WO2010032551A1 - Phase difference film, polarizing plate, and liquid crystal display device - Google Patents

Abstract

Disclosed is a phase difference film that, when used as a display device for a long period of time, does not cause a light leakage (an uneven light leakage) during black display.  Also disclosed are a polarizing plate and a liquid crystal display device. The phase difference film comprises an optical film and an optically anisotropic layer comprising a liquid crystal that is aligned and is in a fixed alignment state.  The optical film is characterized in that the phase difference film comprises an acrylic resin (A) and a cellulose ester resin (B) at a mass ratio of 95 : 5 to 30 : 70 in a compatibilized state, the weight average molecular weight Mw of the acrylic resin (A) is not less than 80000 and not more than 1000000, the total degree of substitution (T) of acyl groups in the cellulose ester resin (B) is not less than 2.0 and not more than 3.0, the degree of substitution of an acyl group having 3 to 7 carbon atoms is not less than 1.2 and not more than 3.0, and the weight average molecular weight Mw of the cellulose ester resin (B) is not less than 75000 and not more than 280000.

Description

Retardation film, polarizing plate, liquid crystal display

The present invention relates to a retardation film used in a liquid crystal display device, a polarizing plate having the retardation film, and a liquid crystal display device.

Retardation film with fixed liquid crystal alignment can be used for liquid crystal display devices, etc., but liquid crystal display devices cause unevenness of cloudy light leakage during black display, which is called heat unevenness due to long-term use. This improvement is necessary.

This phenomenon has been found to be improved to some extent by thinning the triacetyl cellulose film that is the support for the retardation film (Patent Document 1), but it has not yet reached a radical solution, and further There was a need for improvement.

The present inventors have found that this cause is due to the wet heat resistance of the retardation film itself, and further to the hygroscopicity of the support of the retardation film.

In general, as an optical film material with low hygroscopicity, polymethyl methacrylate (hereinafter abbreviated as PMMA), which is a representative of acrylic resin, exhibits excellent transparency and dimensional stability in addition to low hygroscopicity. It is suitably used for a film, and is used as a material for a retardation film and its support including derivatives thereof (Patent Documents 2 and 3).

However, the PMMA film has poor heat resistance and has a drawback that its shape changes when used under high-temperature conditions due to heat generation of the backlight, as with a liquid crystal display device, or when used for a long time.

This problem was an important issue not only as a physical property of a single film but also in a polarizing plate and a display device using such a film.

That is, in a liquid crystal display device, with the deformation of the film, the film itself originally fixed to the liquid crystal cell with an adhesive layer or the like may cause light leakage during black display, and further a polarizing plate using the film Curled, causing the entire panel to warp.

The problem due to film deformation is also a problem on the backlight side, but when used at the position on the viewing side surface, the design phase difference changes due to deformation, so the viewing angle changes and the color changes. The problem arises.

Patent Document 4 discloses a technique of mixing a cellulose ester derivative polymer and polymethyl methacrylate or polyvinyl acetate for the purpose of reducing birefringence in order to improve heat resistance.

However, this technique is originally intended to provide an optical compensation film having no phase difference generated by extrusion forming at the time of film forming, and therefore is inferior in versatility as a phase difference film.

In addition, the mixture of the cellulose ester derivative polymer and polymethyl methacrylate was not necessarily versatile in terms of compatibility.

On the other hand, an optical compensation film having a liquid crystal alignment layer was also known as a versatile retardation film, but a cellulose ester film was usually used as its support.

JP 2008-40487 A JP 2003-12859 A JP 2005-146084 A JP 2008-88417 A

Accordingly, the present invention has been made in view of the above problems, and its purpose is to prevent light leakage (light leakage unevenness) during black display when used for a long time as a display device. An object of the present invention is to provide a retardation film having an optical film that has low hygroscopicity, is transparent, has high heat resistance, and has markedly improved brittleness.

Furthermore, it aims at providing the polarizing plate and liquid crystal display device which use this retardation film.

The object of the present invention was achieved by the following means.

1. The acrylic resin (A) and the cellulose ester resin (B) are contained in a mass ratio of 95: 5 to 30:70 and in a compatible state, and the acrylic resin (A) has a weight average molecular weight Mw of 80000 to 1000000. Yes, the total substitution degree (T) of the acyl group of the cellulose ester resin (B) is 2.0 or more and 3.0 or less, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 or more and 3.0. An optical film characterized in that the weight average molecular weight Mw of the cellulose ester resin (B) is 75000 or more and 280000 or less, and an optically anisotropic layer in which the orientation is fixed by aligning liquid crystal Retardation film having.

2. A polarizing plate comprising a polarizer and two polarizing plate protective films sandwiching the polarizer, wherein at least one of the polarizing plate protective films is the retardation film described in 1 above.

3. A liquid crystal display device comprising the retardation film as described in 1 above.

According to the present invention, it is possible to provide a retardation film, a polarizing plate and a liquid crystal display device that do not generate light leakage (light leakage unevenness) during black display when used for a long time as a display device.

It is the figure which showed typically the dope preparation process, casting process, and drying process of the solution casting film forming method used for this invention.

Hereinafter, the present invention will be described in detail.

The retardation film of the present invention is characterized by having a liquid crystal alignment layer for expressing a retardation on an optical film which is a support having improved heat resistance and moisture resistance.

That is, the optical film of the present invention can mix the acrylic resin and the cellulose ester resin within the range of the weight average molecular weight of the present invention with good compatibility. As a result, the liquid crystal alignment layer Since the heat resistance and moisture resistance as a support are improved and each resin has a plastic effect, the amount of plasticizer added can also be reduced, and the adjustment of the retardation developed by the liquid crystal alignment layer is facilitated. It is a thing.

Also, the presence of the liquid crystal alignment layer increases the thermal conductivity, so that the heat conduction to the entire surface of the optical film is made uniform, and the effect of suppressing the occurrence of unevenness is exhibited.

Therefore, the optical film of the present invention can promote liquid crystal alignment when the content of the plasticizer is reduced, and is preferably less than 2% by mass with respect to the resin, and preferably contains no plasticizer.

In the present invention, an alignment film is applied without providing an elution block layer, and a liquid crystal alignment process is performed. More preferably, the surface of the support is subjected to an alignment process so as to function as an alignment film. Can be fixed by a conventional method, and it is excellent in that a target retardation film can be obtained even though the coating layer is reduced.

The reduction of the coating layer can improve the yield of the product and contribute to the cost reduction. When the liquid crystal compound having a vinyl-based reactive group is used on the acrylic resin film of the present invention, the reaction for fixing the alignment of the liquid crystal, in particular. At the same time, the film thickness of the retardation film can be improved, and since the plasticizer contained in the support is also small, there is no elution of the plasticizer during wet heat durability, and a retardation film excellent in stability can be provided.
<Optical film>
The moisture permeability of the optical film of the present invention is achieved by the constitution of acrylic resin (A), cellulose ester resin (B), and in some cases resins other than acrylic resin (A) and cellulose ester resin (B), and other additives. It was done.

The optical film of the present invention initially had a problem with compatibility between resins, but the compatibility problem could be solved by setting the molecular weight range of the present invention and the substitution degree range of cellulose ester.

More specifically, the acrylic resin (A) and the cellulose ester resin are contained in a mass ratio of 95: 5 to 30:70 and in a compatible state, and the weight average molecular weight Mw of the acrylic resin (A) is 80000 to 1000000. The total substitution degree (T) of the acyl group of the cellulose ester resin (B) is 2.0 or more and 3.0 or less, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 or more and 3 0.0 or less, and the weight average molecular weight (Mw) of the cellulose ester resin (B) is from 75,000 to 280000.

Furthermore, the optical film can contain 0.5 to 30% by mass of acrylic particles (C) with respect to the total mass of the resin constituting the film.

<Acrylic resin (A)>
The acrylic resin used in the present invention includes a methacrylic resin. The resin is preferably composed of 50 to 99% by mass of methyl methacrylate units and 1 to 50% by mass of other monomer units copolymerizable therewith.

Examples of other copolymerizable monomers include alkyl methacrylates having 2 to 18 alkyl carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, alkyl acrylates such as acrylic acid and methacrylic acid. Unsaturated group-containing divalent carboxylic acids such as saturated acid, maleic acid, fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, Examples thereof include maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride and the like, and these can be used alone or in combination of two or more monomers.

Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

The acrylic resin (A) used in the optical film of the present invention has a weight average molecular weight (Mw) particularly from the viewpoint of improving brittleness as an optical film and improving transparency when it is compatible with the cellulose ester resin (B). Is 80000 or more. When the weight average molecular weight (Mw) of the acrylic resin (A) is less than 80000, sufficient brittleness improvement cannot be obtained, and compatibility with the cellulose ester resin (B) deteriorates.

The weight average molecular weight (Mw) of the acrylic resin (A) is more preferably in the range of 80,000 to 1,000,000, particularly preferably in the range of 110,000 to 600,000, and in the range of 150,000 to 400,000. Most preferred. Although the upper limit of the weight average molecular weight (Mw) of an acrylic resin (A) is not specifically limited, It is a preferable form that it shall be 1 million or less from a viewpoint on manufacture.

The weight average molecular weight of the acrylic resin of the present invention can be measured by gel permeation chromatography (GPC). The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

The production method of the acrylic resin (A) in the present invention is not particularly limited, and any known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used.

Commercially available acrylic resins can be used as the acrylic resin according to the present invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dialal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. . Two or more acrylic resins can be used in combination.

<Cellulose ester resin (B)>
The cellulose ester resin (B) of the present invention has an acyl group total substitution degree (T) of 2.0 or more, particularly from the viewpoint of transparency when improved in brittleness or compatible with the acrylic resin (A). The substitution degree of an acyl group having 0 to 3 carbon atoms is 1.2 to 3.0, and the substitution degree of an acyl group having 3 to 7 carbon atoms is 2.0 to 3.0. It is preferable.

The cellulose ester resin of the present invention is a cellulose ester resin substituted with an acyl group having 3 to 7 carbon atoms. Specifically, propionyl, butyryl and the like are preferably used, and a propionyl group is particularly preferably used.

The acyl substitution degree of the cellulose ester resin (B) of the present invention is such that the total substitution degree (T) is 2.0 or more and 3.0 or less, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 or more. 3.0 or less is preferable, and the total degree of substitution of acyl groups other than those having 3 to 7 carbon atoms, that is, acetyl groups or acyl groups having 8 or more carbon atoms, is preferably 1.3 or less.

Further, the total substitution degree (T) of the acyl group of the cellulose ester resin (B) is more preferably in the range of 2.5 to 3.0.

In the present invention, the acyl group may be an aliphatic acyl group or an aromatic acyl group. In the case of an aliphatic acyl group, it may be linear or branched and may further have a substituent. The number of carbon atoms of the acyl group in the present invention includes an acyl group substituent.

When the cellulose ester resin (B) has an aromatic acyl group as a substituent, the number of substituents X substituted on the aromatic ring is preferably 0 to 5. Also in this case, it is necessary to pay attention so that the degree of substitution of the acyl group having 3 to 7 carbon atoms including the substituent is 1.2 or more and 3.0 or less.

Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

In the cellulose ester resin (B) as described above, a structure having at least one kind of an aliphatic acyl group having 3 to 7 carbon atoms is used as a structure used in the cellulose resin of the present invention.

The substitution degree of the cellulose ester resin (B) according to the present invention is such that the total substitution degree (T) of the acyl group is 2.0 or more and 3.0 or less, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2. It is 3.0 or less.

Further, it is preferable that the total substitution degree of acyl groups other than an acyl group having 3 to 7 carbon atoms, that is, an acetyl group and an acyl group having 8 or more carbon atoms is 1.3 or less.

The cellulose ester resin (B) according to the present invention is preferably at least one selected from cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, and cellulose butyrate, Those having an acyl group having 3 or 4 carbon atoms as a substituent are preferred.

Among these, particularly preferable cellulose ester resins are cellulose acetate propionate and cellulose propionate. These can be synthesized by known methods.

Incidentally, the substitution degree of the acetyl group and the substitution degree of other acyl groups were determined by the method prescribed in ASTM-D817-96.

The weight average molecular weight (Mw) of the cellulose ester resin (B) according to the present invention is 75,000 or more, particularly in the range of 75,000 or more and 300,000 or less from the viewpoint of compatibility with the acrylic resin (A) and improvement of brittleness. It is more preferable that it is in the range of 100,000 or more and 240,000 or less, and that of 160000 or more and 240,000 or less is particularly preferable. The weight average molecular weight was measured according to the method described above.

In the present invention, two or more kinds of cellulose resins can be mixed and used.

In the optical film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) are contained in a mass ratio of 95: 5 to 30:70 and in a compatible state, preferably 95: 5 to 50. : 50, and more preferably 90:10 to 60:40.

In the optical film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) must be contained in a compatible state. The physical properties and quality required for an optical film are achieved by supplementing each other by dissolving different resins.

<Judgment of compatible state>
Whether the acrylic resin (A) and the cellulose ester resin (B) are in a compatible state can be determined from the glass transition temperature Tg.

When both resins are simply mixed, there are two glass transition temperatures for each resin because there is a glass transition temperature for each resin. However, when both resins are compatible, each glass has its own glass transition temperature. The temperature disappears and becomes one glass transition temperature, which becomes the glass transition temperature of the compatible resin.

The glass transition temperature T _g1,2 of the mixture in this compatible state is _expressed by the Gordon-Taylor equation (M. Gordon and JS Taylor, 2 J. of Applied).
Chem. 493-500 (1952)). :
T _g1,2 = (w ₁ T _g1 + Kw ₂ T _g2 ) / (w ₁ + Kw ₂ )
[Where w ₁ and w ₂ are mass fractions of component 1 (acrylic resin (A)) and 2 (cellulose ester resin (B)); T _g1 and T _g2 are component 1 _{And Tg1,2} is the glass transition temperature of the mixture of components 1 and 2; K is a constant related to the free volume of the two resins. ]
The glass transition temperature here is a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer) in which a sample stored for 24 hours in an atmosphere of 23 ° C. and 55% RH is placed in the same atmosphere. Then, it is measured at a rate of temperature increase of 20 ° C./min in a nitrogen stream, and is defined as the midpoint glass transition temperature (Tmg) determined according to JIS K7121 (1987).

The acrylic resin (A) and the cellulose ester resin (B) are each preferably an amorphous resin, and either one may be a crystalline polymer or a partially crystalline polymer. In the present invention, the acrylic resin (A) and the cellulose ester resin (B) are preferably compatible with each other to become an amorphous resin.

In order to make the acrylic resin (A) and the cellulose ester resin (B) of the present invention compatible, it is preferable to conduct a compatibility test in advance and select a compatible resin in advance.

Specifically, for example, a 5% by mass solution of resins (A) and (B) dissolved in 100 ml of methylene chloride is mixed, and the compatibility test is performed by observing the turbidity and the mixed state visually. Can do. If the turbidity is remarkably increased or the two-layer separation state is not visually observed, it can be said that they are compatible. This test makes it possible to easily select a resin.

In the present invention, “containing acrylic resin (A) and cellulose ester resin (B) in a compatible state” means mixing each resin (polymer) and resulting in a compatible state. This means that a state in which a precursor of acrylic resin such as monomer, dimer or oligomer is mixed with cellulose ester resin (B) and then polymerized by polymerization is not included. .

For example, the process of obtaining a mixed resin by mixing a precursor of an acrylic resin such as a monomer, dimer or oligomer with the cellulose ester resin (B) and then polymerizing it is complicated by the polymerization reaction. The resin is difficult to control the reaction, and it is difficult to adjust the molecular weight.

The optical film of the present invention may contain a resin and additives other than acrylic resin (A) and cellulose ester resin (B).

When the resin other than the acrylic resin (A) and the cellulose ester resin (B) is contained, even if the added resin is in a compatible state, it may be simply mixed and dispersed without being compatible.

The total mass of the acrylic resin (A) and the cellulose ester resin (B) in the optical film of the present invention is preferably 55% by mass or more of the optical film, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

When using resins and additives other than the acrylic resin (A) and the cellulose ester resin (B), it is preferable to adjust the addition amount as long as the function of the optical film of the present invention is not impaired.

<Resin other than acrylic resin (A) and cellulose ester resin (B)>
(Acrylic particles (C))
The optical film of the present invention can contain acrylic particles (C) as a resin other than the acrylic resin (A) and the cellulose ester resin (B).

The acrylic particles (C) according to the present invention exist in a mixed / dispersed state without being incompatible in an optical film containing the acrylic resin (A) and the cellulose ester resin (B) in a compatible state.

The acrylic particles (C) are obtained, for example, by collecting a predetermined amount of the produced optical film, dissolving it in a solvent, stirring, and sufficiently dissolving / dispersing it, so that the pore diameter is less than the average particle diameter of the acrylic particles (C). It is preferable that the weight of the insoluble matter filtered and collected using the PTFE membrane filter is 90% by mass or more of the acrylic particles (C) added to the optical film.

The acrylic particles (C) used in the present invention are not particularly limited, but are preferably acrylic particles (C) having a layer structure of two or more layers, particularly the following multilayer structure acrylic granular composite. It is preferable.

The multilayer structure acrylic granular composite is formed by laminating an innermost hard layer polymer, a cross-linked soft layer polymer exhibiting rubber elasticity, and an outermost hard layer polymer from the center to the outer periphery. This refers to a particulate acrylic polymer having a structure.

Examples of commercially available products of such a multilayer structure acrylic granular composite include, for example, METABRENE W-341 (C2), Chemisnow MR-2G (C3), MS-300X (C4) manufactured by Mitsubishi Rayon Co., Ltd. (Soken Chemical ( Co., Ltd.), Kaneka Chemical Co., Ltd. “Kane Ace”, Kureha Chemical Industry Co., Ltd. “Paraloid”, Rohm and Haas Co., Ltd. “Acryloid”, Ganz Kasei Kogyo Co., Ltd. “Staffyroid” and Kuraray Co., Ltd. “Parapet SA” These may be used alone or in combination of two or more.

The optical film of the present invention preferably contains 0.5 to 30% by mass of acrylic particles (C) with respect to the total mass of the resin constituting the film, and is in the range of 1.0 to 15% by mass. It is more preferable to contain.

<Other additives>
In the optical film of the present invention, a plasticizer can be used in combination in order to improve the fluidity and flexibility of the composition. Examples of the plasticizer include phosphoric acid, phthalic acid ester, fatty acid ester, trimellitic acid ester, polyester, and epoxy.

Of these, phosphoric acid-based, polyester-based and phthalic acid ester-based plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate, but are slightly inferior in plasticizing effect and compatibility.

Therefore, it can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

Examples of phosphoric acid plasticizers include triphenyl phosphate (TPP), biphenyl diphenyl phosphate (BDP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), cresyl diphenyl phosphate (CDP), 2-ethylhexyl diphenyl. Phosphate (EHDP), t-butylphenyl diphenyl phosphate (BDP), bis- (t-butylphenyl) phenyl phosphate (BBDP), tris- (t-butylphenyl) phosphate (TBDP), isopropylphenyl diphenyl phosphate (IPP), Bis- (isopropylphenyl) diphenyl phosphate (BIPP), tris- (isopropylphenyl) phosphate (TIPP), and the like. Sulfonyl diphenyl phosphate is preferred.

The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like.

In particular, when adipic acid, phthalic acid, or the like is used, those having excellent plasticizing properties can be obtained. Examples of the glycol include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, and dipropylene. These divalent carboxylic acids and glycols may be used alone or in combination.

The ester plasticizer may be any of ester, oligoester, and polyester types, and the molecular weight is preferably in the range of 100 to 10,000, and preferably in the range of 600 to 3000, which has a large plasticizing effect.

Also, the viscosity of the plasticizer has a correlation with the molecular structure and molecular weight, but in the case of an adipic acid plasticizer, the range of 200 to 5000 MPa · s (25 ° C.) is preferable because of compatibility and plasticization efficiency.

Furthermore, an aromatic terminal polyester plasticizer having an average molecular weight of 1000 or less may be used in combination. It is also preferable to add sugars such as Monopet SB (Daiichi Kogyo Seiyaku Co., Ltd.).

The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the optical film of the present invention, but the plasticizer having a molecular weight of 1000 or less is preferably 2 parts by mass or less.

The optical film of the present invention preferably contains an ultraviolet absorber, and examples of the ultraviolet absorber used include benzotriazole, 2-hydroxybenzophenone, and salicylic acid phenyl ester. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone And benzophenones.

Here, among ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are less likely to volatilize at a high boiling point and are difficult to disperse even during high-temperature molding, so that the weather resistance is effectively improved with a relatively small amount of addition. be able to.

Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis ( Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid Bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] Such as til] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine A hybrid system having both structures can be mentioned, and these can be used alone or in combination of two or more.

Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

Further, the optical film of the present invention has other functions such as an agent for adjusting retardation, various antioxidants and acid scavengers for improving thermal decomposability and thermal coloring during molding. Can also be added. It is also possible to add an antistatic agent to give the optical film antistatic performance.

You may contain particles, such as a mat agent mentioned later, for the handleability of an optical film.
<Physical properties of optical film>
The optical film of the present invention is preferably “an optical film in which ductile fracture does not occur”.

Here, the ductile fracture is a fracture that occurs due to a stress that is greater than the strength of a certain material, and is defined as a fracture that involves significant elongation or drawing of the material before the final fracture.

In the present invention, whether or not it is an “optical film that does not cause ductile fracture” is determined by whether or not the film is broken even when a large stress is applied such that the film is folded in two under an atmosphere of 23 ° C. and 55% RH. It shall be evaluated by not being seen.

In the present invention, if the tension softening point in an atmosphere of 23 ° C. and 55% RH is 105 ° C. to 145 ° C., it can be judged that sufficient heat resistance is exhibited. In particular, it is more preferable to control at 110 ° C. to 130 ° C.

Also, from the viewpoint of heat resistance, the optical film preferably has a glass transition temperature (Tg) of 110 ° C. or higher. More preferably, it is 120 ° C. or higher. Especially preferably, it is 150 degreeC or more.

Haze value (turbidity) is used as an index for judging the transparency of the optical film in the present invention. In particular, liquid crystal display devices used outdoors are required to have sufficient brightness and high contrast even in a bright place. Therefore, the haze value is required to be 1.0% or less, and 0.5% or less. More preferably.

According to the optical film of the present invention containing the acrylic resin (A) and the cellulose ester resin (B), high transparency can be obtained, but when using acrylic particles for the purpose of improving another physical property. By increasing the refractive index difference between the resin (acrylic resin (A) and cellulose ester resin (B)) and the acrylic particles (C), an increase in haze value can be prevented.

In addition, since the surface roughness also affects the haze value as surface haze, the particle diameter and addition amount of acrylic particles (C) should be suppressed within the above range, and the surface roughness of the film contact portion during film formation should be reduced. Is also effective.

In addition, the optical film of the present invention preferably has a defect with a diameter of 5 μm or more in the film plane of 1 piece / 10 cm square or less. More preferably, it is 0.5 piece / 10 cm square or less, more preferably 0.1 piece / 10 cm square or less.

The optical film of the present invention preferably has a breaking elongation in at least one direction of 10% or more, more preferably 20% or more in the measurement based on JIS-K7127-1999.

The thickness of the optical film of the present invention is preferably 20 μm or more. More preferably, it is 30 μm or more.

The optical film of the present invention preferably has a total light transmittance of 90% or more, more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%.

The optical film of the present invention can be particularly preferably used as a polarizing plate protective film for a large-sized liquid crystal display device or a liquid crystal display device for outdoor use as long as the above physical properties are satisfied.

Such a physical property is that the optical film contains the acrylic resin (A) and the cellulose ester resin (B) in a mass ratio of 95: 5 to 30:70, and the weight average molecular weight Mw of the acrylic resin (A) is 80000. The total substitution degree (T) of the acyl group of the cellulose ester resin (B) is 2.00 to 3.00, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 or more and 3.0. The weight average molecular weight (Mw) is 75000 or more.
<Method for producing optical film>
Hereinafter, the preferable film forming method of the optical film of the present invention will be described.

1) Dissolution step In an organic solvent mainly composed of a good solvent for the acrylic resin (A) and the cellulose ester resin (B), the acrylic resin (A), the cellulose ester resin (B), and optionally acrylic particles ( C), a step of dissolving other additives while stirring to form a dope, or the acrylic resin (A) and cellulose ester resin (B) solutions, optionally with acrylic particle (C) solutions and other additive solutions Are mixed to form a dope which is a main solution.

For dissolving the acrylic resin (A) and the cellulose ester resin (B), a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544 Various dissolution methods such as a method of performing a cooling dissolution method as described in JP-A-9-95557 or JP-A-9-95538, a method of performing at a high pressure as described in JP-A-11-21379, and the like. Although it can be used, a method in which pressure is applied at a temperature equal to or higher than the boiling point of the main solvent is particularly preferable.

The acrylic resin (A) and cellulose ester resin (B) in the dope are preferably in the range of 15 to 45% by mass in total. After the additive is added to the dope during or after dissolution, the dope is dissolved and dispersed, filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

For filtration, it is preferable to use a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml.

In this method, the aggregate remaining at the time of particle dispersion and the aggregate generated when the main dope is added are aggregated by using a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. Can only be removed. In the main dope, the concentration of particles is sufficiently thinner than that of the additive solution, so that the aggregates do not stick together during filtration and the filtration pressure does not increase suddenly.

If necessary, remove large agglomerates from the acrylic particle charging pot with a filter and feed it to the stock pot. Thereafter, the acrylic particle additive liquid is added from the stock kettle to the main dope dissolving kettle.

After that, the main dope solution is filtered with a main filter, and an ultraviolet absorber additive solution is further added in-line thereto.

In many cases, the main dope may contain about 10 to 50% by weight of recycled material. The return material may contain acrylic particles. In that case, it is preferable to control the addition amount of the acrylic particle addition liquid in accordance with the addition amount of the return material.

The additive liquid containing acrylic particles preferably contains 0.5 to 10% by mass of acrylic particles, more preferably 1 to 10% by mass, and more preferably 1 to 5% by mass. Most preferably.

If it is within the above range, the additive solution is preferable because it has a low viscosity and is easy to handle and can be easily added to the main dope.

The return material is a product obtained by finely pulverizing the optical film, which is generated when the optical film is formed, and is obtained by cutting off both sides of the film, or by using an optical film original that has been speculated out due to scratches, etc. .

In addition, acrylic resin, cellulose ester resin, and in some cases, acrylic particles kneaded into pellets can be preferably used.

2) Casting process An endless metal belt, such as a stainless steel belt or a rotating metal drum, which supports the dope is fed to a pressure die through a liquid feed pump (for example, a pressurized metering gear pump) and supported infinitely. This is a step of casting a dope from a pressure die slit to a casting position on the body.

¡Pressure dies that can adjust the slit shape of the die base and make the film thickness uniform are preferred. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

3) Solvent evaporation step In this step, the web (the dope is cast on the casting support and the formed dope film is called a web) is heated on the casting support to evaporate the solvent.

To evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. High efficiency and preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or heat by means such as infrared rays.

From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds.

4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

The temperature at the peeling position on the metal support is preferably 10 to 40 ° C, more preferably 11 to 30 ° C.

The amount of residual solvent at the time of peeling of the web on the metal support at the time of peeling is preferably 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. If the web is peeled off at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be lost, and slippage and vertical stripes are likely to occur due to the peeling tension. The amount of solvent is determined.

The amount of residual solvent in the web is defined by the following formula.

Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

The peeling tension at the time of peeling the metal support and the film is usually 196 to 245 N / m. However, if wrinkles easily occur at the time of peeling, it is preferable to peel with a tension of 190 N / m or less. It is preferable to peel at a minimum tension of ˜166.6 N / m, and then peel at a minimum tension of ˜137.2 N / m, and particularly preferable to peel at a minimum tension of ˜100 N / m.

In the present invention, the temperature at the peeling position on the metal support is preferably −50 to 40 ° C., more preferably 10 to 40 ° C., and most preferably 15 to 30 ° C.

5) Drying and stretching step After peeling, a drying device 35 that alternately conveys the web through a plurality of rolls arranged in the drying device and / or a tenter stretching device 34 that clips and conveys both ends of the web with a clip are used. And dry the web.

The drying means is generally to blow hot air on both sides of the web, but there is also a means to heat by applying microwaves instead of wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of residual solvent. Throughout, drying is generally performed at 40-250 ° C. In particular, drying at 40 to 160 ° C. is preferable.

When using a tenter stretching apparatus, it is preferable to use an apparatus that can independently control the film gripping length (distance from the start of gripping to the end of gripping) left and right by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

It is also preferable to provide a neutral zone between different temperature zones so that each zone does not cause interference.

The stretching operation may be performed in multiple stages, and it is also preferable to perform biaxial stretching in the casting direction and the width direction. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise.

In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, for example, the following stretching steps are possible.

-Stretch in the casting direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction-Stretch in the width direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension. The preferred draw ratio for simultaneous biaxial stretching can be in the range of x1.01 to x1.5 in both the width direction and the longitudinal direction.

When the tenter is used, the amount of residual solvent in the web is preferably 20 to 100% by mass at the start of the tenter, and drying is preferably performed while the tenter is applied until the amount of residual solvent in the web is 10% by mass or less. More preferably, it is 5% by mass or less.

When performing the tenter, the drying temperature is preferably 30 to 160 ° C., more preferably 50 to 150 ° C., and most preferably 70 to 140 ° C.

In the tenter process, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film. The temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, and within ± 2 ° C. Is more preferable, and within ± 1 ° C. is most preferable.

6) Winding step This is a step of winding the optical film by the winder 37 after the residual solvent amount in the web is 2% by mass or less, and the dimensional stability is achieved by setting the residual solvent amount to 0.4% by mass or less. A film having good properties can be obtained. It is particularly preferable to wind up at 0.00 to 0.10% by mass.

As a winding method, a generally used one may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc., and these may be used properly.

The optical film of the present invention is preferably a long film. Specifically, the optical film has a thickness of about 100 m to 5000 m, and is usually in the form of a roll. The film width is preferably 1.3 to 4 m, more preferably 1.4 to 2 m.

The film thickness of the optical film of the present invention is not particularly limited, but when used for a polarizing plate protective film, it is preferably 20 to 200 μm, more preferably 25 to 100 μm, and more preferably 30 to 80 μm. Particularly preferred.
<Retardation film having optically anisotropic layer by liquid crystal alignment layer on optical film>
The retardation film of the present invention has at least one optically anisotropic layer formed from a liquid crystalline compound according to a target liquid crystal system. The optically anisotropic layer may be formed directly on the surface of the optical film described above, or may be formed on the layer or film by forming an intermediate layer or an alignment film on the optical film.

It is also possible to produce a retardation film having an optically anisotropic layer by transferring a liquid crystalline compound layer formed on another substrate onto an optical film using an adhesive, an adhesive or the like. It is.

Examples of the liquid crystalline compound used for forming the optically anisotropic layer include a rod-like liquid crystalline compound and a discotic liquid crystalline compound (hereinafter, the discotic liquid crystalline compound may be referred to as a “discotic liquid crystalline compound”). .

The rod-like liquid crystal compound and the discotic liquid crystal compound may be a high-molecular liquid crystal or a low-molecular liquid crystal.

In addition, the compound finally contained in the optically anisotropic layer no longer needs to exhibit liquid crystallinity. For example, when a low-molecular liquid crystalline compound is used for the production of the optically anisotropic layer, In the process of forming the isotropic layer, the compound may be cross-linked and fixed and no longer exhibits liquid crystallinity.

<Optically anisotropic layer with fixed orientation by vertically aligning rod-like liquid crystal>
The optically anisotropic layer of the present invention preferably has the following characteristics.

0 ≦ Ro ≦ 10
−500 ≦ Rt ≦ −100
The optically anisotropic layer of the present invention is obtained by applying a liquid crystal material or a liquid crystal solution directly on an optical film cellulose ester film or on an intermediate layer, drying and heat-treating (also referred to as an alignment treatment), and curing with ultraviolet rays or heat. The liquid crystal alignment is fixed by polymerization or the like, and has a retardation layer of rod-like liquid crystal aligned in the vertical direction.

Here, “orienting in the vertical direction” means that the rod-like liquid crystal is within a range of 70 to 90 ° (the vertical direction is 90 °) with respect to the film surface serving as a support.

The rod-like liquid crystal may be oriented obliquely or the orientation angle may be gradually changed. The range is preferably from 80 to 90 °.

The retardation layer of the present invention is a retardation layer made of rod-like liquid crystal aligned in the vertical direction with Ro in the range of 0 to 10 nm and Rt in the range of −500 to −100 nm. Further, Ro is more preferably in the range of 0 to 5 nm. The phase difference of the phase difference of the layer on which the liquid crystal alignment is fixed on these supports can be measured using AxoScan manufactured by Opto Science Co., Ltd.

When forming a retardation layer by aligning rod-shaped liquid crystals, an alignment film coated with a vertical alignment agent that aligns the so-called liquid crystal material in the vertical direction is used, and the liquid crystal material is vertically aligned and then fixed. be able to.

When the liquid crystal material itself is aligned in the vertical direction at the air interface, the alignment regulating force extends to the interface opposite to the air interface, and the alignment film is not particularly necessary, and this is also preferable from the viewpoint of simplifying the configuration. preferable.

As a specific method for vertically aligning the liquid crystal material, an alignment film composed of a cross-linked product of a block polymer composition containing a (meth) acrylic block polymer described in JP-A-2005-148473 and the like is used. Known methods such as a method of using, a method of using a vertical alignment film described in JP 2005-265889 A, and a method of using an air interface vertical alignment agent can be used.

In order to make the retardation layer in the above range, it is preferable to control the orientation of the rod-like liquid crystal layer, the film thickness control, the temperature during UV curing, the tilt angle control, and the pretilt angle at the support / air interface.

The liquid crystal layer is formed by curing a liquid crystal material capable of forming a liquid crystal phase at a predetermined temperature with a predetermined liquid crystal regularity. The upper limit of the temperature showing the liquid crystal phase is not particularly limited as long as the cellulose ester film of the base material is not damaged.

Specifically, from the viewpoint of easy control of the process temperature and maintenance of dimensional accuracy, 120 ° C. or lower is preferable, and a liquid crystal material that becomes a liquid crystal phase at a temperature of 100 ° C. or lower is more preferably used. On the other hand, the lower limit of the temperature showing the liquid crystal phase can be said to be a temperature at which the liquid crystal material can maintain the alignment state when used as a polarizing plate.

As the liquid crystal material used for the retardation layer of the present invention, a polymerizable liquid crystal material is preferably used. The polymerizable liquid crystal material can be used by being polymerized by irradiating with predetermined actinic radiation. In the polymerized state, the vertical alignment state is fixed.

As the polymerizable liquid crystal material, any of a polymerizable liquid crystal monomer, a polymerizable liquid crystal oligomer, and a polymerizable liquid crystal polymer can be used, and they can also be mixed with each other.

Among the above, a polymerizable liquid crystal monomer is preferably used as the polymerizable liquid crystal material because of its high sensitivity during alignment and easy vertical alignment.

Specific examples of the polymerizable liquid crystal monomer include a rod-like liquid crystal compound (I) represented by the following general formula (1) and a rod-like liquid crystal compound (II) represented by the following general formula (2). be able to. As the compound (I), two or more compounds included in the general formula (1) can be mixed and used. Similarly, the compound (II) is included in the general formula (2). Two or more kinds of compounds may be mixed and used. In addition, one or more compounds (I) and one or more compounds (II) can be used in combination.

In the general formula (1) representing the compound (I), R1 and R2 each represent hydrogen or a methyl group, but it is preferable that both R1 and R2 are hydrogen because of the wide temperature range showing the liquid crystal phase.

X may be hydrogen, chlorine, bromine, iodine, an alkyl group having 1 to 4 carbon atoms, a methoxy group, a cyano group, or a nitro group, but is preferably a chlorine or methyl group.

In addition, a and b indicating the chain length of the (meth) acryloyloxy group at both ends of the molecular chain of the compound (I) and the alkylene group as a spacer with the aromatic ring are each independently an arbitrary integer in the range of 2 to 12. However, it is preferably in the range of 4 to 10, more preferably in the range of 6 to 9.

In addition to the above, in the present invention, conventionally known materials can be appropriately selected and used as the polymerizable liquid crystal oligomer and the polymerizable liquid crystal polymer.

For example, as a polymerizable rod-like liquid crystal compound, Makromol. Chem. , 190, 2255 (1989), Advanced Materials, Volume 5, 107 (1993), US Pat. Nos. 4,683,327, 5,622,648, and 5770107, International Publication WO95 / 22586. No. 95/24455, No. 97/00600, No. 98/23580, No. 98/52905, JP-A-1-272551, JP-A-6-16616, and JP-A-7-110469. 11-80081, JP 2001-328773, JP 2004-240188, JP 2005-99236, JP 2005-99237, JP 2005-121827, JP It is possible to use a compound described in, for example, 2002-30042 Kill.

As commercially available compounds, UCL-018 (manufactured by Dainippon Ink & Chemicals, Inc.), Palio Color LC242 (manufactured by BASF Corporation), and the like can be used.

In the present invention, in addition to the polymerizable liquid crystal material, a photopolymerization initiator is used as necessary. When polymerizing a polymerizable liquid crystal material by electron beam irradiation, a photopolymerization initiator may not be necessary. However, in the case of curing by, for example, ultraviolet (UV) irradiation, which is generally used, photopolymerization is usually performed. An initiator is used to promote polymerization.

Photopolymerization initiators include benzyl (also called bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoyl benzoic acid, methyl benzoyl benzoate, 4-benzoyl-4'-methyldiphenyl sulfide, benzyl methyl ketal, dimethylamino Methylbenzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3′-dimethyl-4-methoxybenzophenone, methylobenzoyl formate, 2-methyl-1- (4 -(Methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 1- (4-dodecylphenyl) -2 Hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2- Examples include methylpropan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, or 1-chloro-4-propoxythioxanthone. it can.

The addition amount of the photopolymerization initiator is generally preferably from 0.01% to 20%, more preferably from 0.1% to 10%, and even more preferably from 0.5% to 5%. Can be added to the polymerizable liquid crystal material of the present invention.

In addition to the photopolymerization initiator, a sensitizer can be added as long as the object of the present invention is not impaired.

The film thickness of the liquid crystal layer in the present invention is preferably in the range of 0.1 μm to 10 μm, and more preferably in the range of 0.2 to 5 μm.

A polymerizable liquid crystal material is prepared by using a composition for forming a liquid crystal layer by blending a photopolymerization initiator, a sensitizer, etc., if necessary, and coating on a substrate to form a liquid crystal layer forming layer. To do.

As a method of forming a layer in which the orientation of liquid crystal is fixed, for example, a method in which a dry film or the like is formed in advance and a layer in which the orientation of liquid crystal is fixed is laminated on a substrate, or a liquid crystal composition is dissolved. Alternatively, it is possible to use a method of melting and coating on a substrate, but in the present invention, a liquid crystal composition is added with a solvent and a coating composition in which other components are dissolved is used. It is preferable to form a layer in which the orientation of the liquid crystal is fixed by coating on the substrate and removing the solvent. This is simple in terms of process as compared with other methods.

The solvent is not particularly limited as long as it is a solvent capable of dissolving the above-described polymerizable liquid crystal material and the like and does not deteriorate the properties of the transparent resin film. Specifically, benzene, Hydrocarbons such as toluene, xylene, n-butylbenzene, diethylbenzene, tetralin; ethers such as methoxybenzene, 1,2-dimethoxybenzene, diethylene glycol dimethyl ether; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, or 2,4- Ketones such as pentanedione; ethyl acetate, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, or γ-butyrolactone Ters; Amide solvents such as 2-pyrrolidone, N-methyl-2-pyrrolidone, dimethylformamide, or dimethylacetamide; chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, tritrichloroethylene, tetrachloroethylene, chlorobenzene, or orthodichlorobenzene Halogen solvents such as t-butyl alcohol, diacetone alcohol, glycerin, monoacetin, ethylene glycol, triethylene glycol, hexylene glycol, ethylene glycol monomethyl ether, ethyl cellosolve, or butyl cellosolve; phenols, One or more of phenols such as parachlorophenol can be used.

If only a single kind of solvent is used, the solubility of the polymerizable liquid crystal material or the like may be insufficient, or the substrate may be eroded as described above. However, this inconvenience can be avoided by using a mixture of two or more solvents.

Of the above-mentioned solvents, preferred as a single solvent are a hydrocarbon solvent and a glycol monoether acetate solvent, and a preferred mixed solvent is a mixed system of ethers or ketones and glycols. It is.

The concentration of the solution depends on the solubility of the polymerizable liquid crystal material or the like and the film thickness of the liquid crystal layer to be produced, but cannot be defined unconditionally, but is usually preferably 1% to 60%, more preferably 3% to It is adjusted within the range of 40%.

In the composition for forming a liquid crystal layer used in the present invention, compounds other than those described above can be added within a range not impairing the object of the present invention.

Examples of compounds that can be added include polyester (meth) acrylate obtained by reacting (meth) acrylic acid with a polyester prepolymer obtained by condensing polyhydric alcohol and monobasic acid or polybasic acid; A polyurethane (meth) acrylate obtained by reacting a compound having two isocyanate groups with each other and then reacting the reaction product with (meth) acrylic acid; bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak Type epoxy resin, polycarboxylic acid polyglycidyl ester, polyol polyglycidyl ether, aliphatic or cycloaliphatic epoxy resin, amine epoxy resin, triphenolmethane type epoxy resin, dihydroxybenzene type epoxy resin and the like (meth) A A photopolymerizable compound such as epoxy (meth) acrylate obtained by reacting rilic acid, or a photopolymerizable liquid crystal compound having an acryl group or a methacryl group, an onium salt described in JP-A-2007-45993, and a fluorine compound. Acrylate polymers and the like.

The amount of these compounds added to the composition for forming a liquid crystal layer of the present invention is selected within a range that does not impair the purpose of the present invention, and is generally 40% by mass or less of the composition for forming a liquid crystal layer of the present invention. It is preferable that there is, more preferably 20% by mass or less.

The addition of these compounds improves the curability of the liquid crystal material in the present invention, increases the mechanical strength of the resulting liquid crystal layer, and improves its stability.

In addition, a surfactant or the like can be added to the composition for forming a liquid crystal layer containing a solvent in order to facilitate coating.

Examples of surfactants that can be added include cationic surfactants such as imidazoline, quaternary ammonium salts, alkylamine oxides, polyamine derivatives; polyoxyethylene-polyoxypropylene condensates, primary or secondary Alcohol ethoxylates, alkylphenol ethoxylates, polyethylene glycol and esters thereof, sodium lauryl sulfate, ammonium lauryl sulfate, lauryl sulfate amines, alkyl-substituted aromatic sulfonates, alkyl phosphates, aliphatic or aromatic sulfonic acid formalin condensates, etc. Anionic surfactants such as: amphoteric surfactants such as laurylamidopropylbetaine and laurylaminoacetic acid betaine; non-ionic surfactants such as polyethylene glycol fatty acid esters and polyoxyethylene alkylamine Surfactants: perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyltrimethylammonium salts, oligomers containing perfluoroalkyl groups / hydrophilic groups, perfluoroalkyls / lipophiles Fluorosurfactants such as a group-containing oligomer perfluoroalkyl group-containing urethane can be used.

The amount of surfactant added depends on the type of surfactant, the type of liquid crystal material, the type of solvent, and the type of alignment film on which the solution is applied. 10 ppm to 10% by mass is preferable, more preferably 100 ppm to 5% by mass, and still more preferably 0.1 to 1% by mass.

As a method for coating the composition for forming a liquid crystal layer, a spin coating method, a roll coating method, a printing method, a dip pulling method, a die coating method, a casting method, a bar coating method, a blade coating method, a spray coating method, a gravure coating method , Reverse coating method or extrusion coating method.

The method for removing the solvent after coating the liquid crystal layer forming composition is performed by, for example, air drying, heat removal, or reduced pressure removal, or a combination of these. By removing the solvent, a layer in which the alignment of the liquid crystal is fixed is formed.

In the step of curing the polymerizable liquid crystal material, energy for curing the polymerizable liquid crystal material is given, and thermal energy may be used, but it is usually performed by irradiation with ionizing radiation capable of causing polymerization.

If necessary, a polymerization initiator may be contained in the polymerizable liquid crystal material. The ionizing radiation is not particularly limited as long as it is a radiation capable of polymerizing the polymerizable liquid crystal material. Usually, ultraviolet light or visible light is used from the viewpoint of the ease of the apparatus, and the wavelength is Light having a wavelength of 150 to 500 nm is preferable, ultraviolet light having a wavelength of 300 to 400 nm is more preferable, and ultraviolet light having a wavelength of 300 to 400 nm is more preferable.

In the present invention, a method of performing radical polymerization by irradiating ultraviolet rays (UV) as actinic radiation and generating radicals from the polymerization initiator with ultraviolet rays is preferable. Since the method using UV as the actinic radiation is an already established technique, it can be easily applied to the present invention including the polymerization initiator to be used.

As a light source for irradiating ultraviolet rays, a low-pressure mercury lamp (sterilization lamp, fluorescent chemical lamp, black light), a high-pressure discharge lamp (high-pressure mercury lamp, metal halide lamp), or a short arc discharge lamp (ultra-high-pressure mercury lamp, xenon) Lamp, mercury xenon lamp) and the like.

Among these, use of metal halide lamps, xenon lamps, high-pressure mercury lamps, etc. is recommended. The irradiation intensity may be appropriately adjusted depending on the composition of the polymerizable liquid crystal material used for forming the layer in which the alignment of the liquid crystal is fixed and the amount of the photopolymerization initiator.

The alignment fixing step by irradiation with actinic radiation may be performed under the processing temperature in the above-described step of forming the liquid crystal layer forming layer, that is, the temperature condition in which the polymerizable liquid crystal material becomes a liquid crystal phase, and the temperature at which the liquid crystal phase becomes a liquid crystal phase. It may be performed at a lower temperature.

(Middle layer)
An intermediate layer can be provided between the optically anisotropic layer in which the cellulose ester film of the present invention and the rod-like liquid crystal are vertically aligned to fix the alignment.

The intermediate layer of the present invention is made of a transparent resin. The transparent resin is preferably a binder polymer having a saturated hydrocarbon chain or a polyether chain as a main chain, and more preferably a binder polymer having a saturated hydrocarbon chain as a main chain.

Particularly preferred is a resin that cures through a crosslinking reaction or the like by irradiation with active rays such as ultraviolet rays or electron beams, or a mixed composition of a crosslinking agent and a resin having a reactive site.

Examples of the curable resin include UV curable urethane acrylate resins, UV curable polyester acrylate resins, UV curable epoxy acrylate resins, UV curable polyol acrylate resins, and UV curable epoxy resins. A type acrylate resin is preferably used.

The UV curable urethane acrylate resin generally contains 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate (hereinafter referred to as acrylate as methacrylate) obtained by reacting a polyester polyol with an isocyanate monomer or a prepolymer. It is easily obtained by reacting an acrylate monomer having a hydroxyl group such as 2-hydroxypropyl acrylate.

For example, those described in JP-A-59-151110 can be used. For example, a mixture of 100 parts of purple light UV-7510B (manufactured by Nippon Synthetic Chemical Co., Ltd.), 100 parts of Unidic 17-806 (manufactured by Dainippon Ink Co., Ltd.) and 1 part of coronate L (manufactured by Nippon Polyurethane Co., Ltd.) Preferably used.

Examples of UV curable polyester acrylate resins include those that are easily formed by reacting polyester polyols with 2-hydroxyethyl acrylate and 2-hydroxy acrylate monomers, generally as disclosed in JP-A-59-151112. Those described in the publication can be used.

Specific examples of the ultraviolet curable epoxy acrylate resin include those produced by reacting epoxy acrylate with an oligomer, a reactive diluent and a photopolymerization initiator added thereto. Those described in Japanese Patent No. 105738 can be used.

Specific examples of UV curable polyol acrylate resins include trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, alkyl-modified dipentaerythritol pentaacrylate, etc. Can be mentioned.

Specific examples of photopolymerization initiators for these curable resins include benzoin and its derivatives, acetophenone, benzophenone, hydroxybenzophenone, Michler's ketone, α-amyloxime ester, thioxanthone, and derivatives thereof. You may use with a photosensitizer.

Further, when using an epoxy acrylate photopolymerization initiator, a sensitizer such as n-butylamine, triethylamine, or tri-n-butylphosphine can be used.

The photopolymerization initiator or photosensitizer used in the curable resin composition is 0.1 to 25 parts by weight, preferably 1 to 15 parts by weight, based on 100 parts by weight of the composition.

Examples of the mixed composition of the crosslinking agent and the resin having a reactive site according to the present invention include polyvinyl alcohol and glyoxal, gelatin and glyoxal, and the like.

The intermediate layer may contain a fluorine-acrylic copolymer resin. The fluorine-acrylic copolymer resin is a copolymer resin comprising a fluorine monomer and an acrylic monomer, and a block copolymer comprising a fluorine monomer segment and an acrylic monomer segment is particularly preferred.

The intermediate layer of the present invention may be two or more layers.

(Method for producing intermediate layer)
For the intermediate layer, a coating composition for forming the intermediate layer containing the retardation increasing agent of the present invention is applied using a known method such as a gravure coater, dip coater, reverse coater, wire bar coater, die coater, and ink jet method. It is preferable that after coating on a support, it is dried by heating and UV-cured.

The coating amount is suitably 0.1 to 40 μm, preferably 0.5 to 30 μm, as the wet film thickness.

The dry film thickness is 0.01 to 1 μm, preferably 0.02 to 0.7 μm.

As the light source for the UV curing treatment, any light source that generates ultraviolet rays can be used without limitation. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used.

The irradiation conditions vary depending on individual lamps, irradiation of active rays, usually 5 ~ 500mJ / cm ^2, preferably 5 ~ 150mJ / cm ^2.

Further, when irradiating active rays, it is preferably performed while applying tension in the film transport direction, more preferably while applying tension in the width direction. The tension to be applied is preferably 30 to 300 N / m.

The method for applying tension is not particularly limited, and tension may be applied in the conveying direction on the back roll, or tension may be applied in the width direction or biaxial direction by a tenter. This makes it possible to obtain a film having further excellent flatness.

The coating composition for forming the intermediate layer may contain a solvent. Examples of the organic solvent contained in the coating composition include hydrocarbons (toluene, xylene), alcohols (methanol, ethanol, isopropanol, butanol, cyclohexanol), and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone). , Esters (methyl acetate, ethyl acetate, methyl lactate), glycol ethers, and other organic solvents may be appropriately selected or mixed for use.

As the organic solvent, propylene glycol monoalkyl ether (1 to 4 carbon atoms of the alkyl group) or propylene glycol monoalkyl ether acetate (1 to 4 carbon atoms of the alkyl group) is preferable. The content of the organic solvent is preferably 5 to 80% by mass in the coating composition.

<Optically anisotropic layer in which orientation is fixed by aligning discotic liquid crystalline compounds>
Examples of discotic liquid crystalline compounds include C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994), azacrown type and phenylacetylene type macrocycles are included.

The discotic liquid crystalline compound exhibits liquid crystallinity with a structure in which a linear alkyl group, an alkoxy group or a substituted benzoyloxy group is radially substituted as a side chain of the mother nucleus with respect to the mother nucleus at the center of the molecule. Also included are compounds. The molecule or the assembly of molecules is preferably a compound having rotational symmetry and imparting a certain orientation.

When an optically anisotropic layer is formed from a liquid crystalline compound, the compound finally contained in the optically anisotropic layer no longer needs to exhibit liquid crystallinity. For example, a low-molecular discotic liquid crystalline compound has a group that reacts with heat or light, and the group reacts with heat or light to polymerize or crosslink to increase the molecular weight. When a layer is formed, the compound contained in the optically anisotropic layer may no longer have liquid crystallinity.

Preferred examples of the discotic liquid crystalline compound are described in JP-A-8-50206. The polymerization of discotic liquid crystalline compounds is described in JP-A-8-27284.

In order to fix the discotic liquid crystalline compound by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline compound.

However, if the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, it is preferable to introduce a linking group between the discotic core and the polymerizable group.

In the present invention, in the optically anisotropic layer, the molecules of the discotic compound are fixed in an oriented state. The orientation average direction of the molecular symmetry axis of the liquid crystalline compound at the interface on the retardation film side is substantially 45 ° with respect to the in-plane slow axis of the retardation film.

In this specification, “substantially 45 °” means an angle in the range of 45 ° ± 5 °, preferably 42 to 48 °, more preferably 43 to 47 °.

The orientation average direction of the molecular symmetry axis of the liquid crystal compound can be generally adjusted by selecting a material of the liquid crystal compound or the alignment film or by selecting a rubbing treatment method.

In the present invention, for example, in the case of producing an optical compensation film for the OCB method, an alignment film for forming an optically anisotropic layer is produced by rubbing treatment and rubbed in a direction of 45 ° with respect to the slow axis of the retardation film. By processing, an optically anisotropic layer in which the orientation average direction of the molecular symmetry axis of the liquid crystalline compound at least at the cellulose acylate film interface is 45 ° with respect to the slow axis of the cellulose acylate film is formed. Can do.

For example, the retardation film of the present invention can be continuously produced by using the long retardation film of the present invention whose slow axis is perpendicular to the longitudinal direction.

The plasticizer, surfactant and polymerizable monomer used together with the liquid crystal compound are compatible with the discotic liquid crystal compound and may change the tilt angle of the liquid crystal compound or do not inhibit the alignment. preferable.

Polymerizable monomers (eg, compounds having a vinyl group, vinyloxy group, acryloyl group and methacryloyl group) are preferred. The amount of the above compound added is generally in the range of 1 to 50% by mass and preferably in the range of 5 to 30% by mass with respect to the liquid crystal compound.

In addition, when a monomer having 4 or more polymerizable reactive functional groups is mixed and used, adhesion between the alignment film and the optically anisotropic layer can be improved.

When a discotic liquid crystalline compound is used as the liquid crystalline compound, it is preferable to use a polymer that has a certain degree of compatibility with the discotic liquid crystalline compound and can change the tilt angle of the discotic liquid crystalline compound.

Examples of polymers include cellulose esters. In order not to inhibit the orientation of the discotic liquid crystalline compound, the amount of the polymer added is preferably in the range of 0.1 to 10% by mass, preferably 0.1 to 8% by mass with respect to the discotic liquid crystalline compound. % Is more preferable, and a range of 0.1 to 5% by mass is more preferable.

The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystal compound is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.

In the present invention, the above-mentioned “other” optically anisotropic layer has at least in-plane optical anisotropy. The in-plane retardation Re of the optically anisotropic layer is preferably 3 to 300 nm, more preferably 5 to 200 nm, and even more preferably 10 to 100 nm.

The retardation Rt in the thickness direction of the optically anisotropic layer is preferably 20 to 400 nm, and more preferably 50 to 200 nm. The thickness of the optically anisotropic layer is preferably from 0.1 to 20 μm, more preferably from 0.5 to 15 μm, and even more preferably from 1 to 10 μm.

(Alignment film)
The retardation film of the present invention may have an alignment film between the support and the optically anisotropic layer. In addition, the alignment film is used only when the optically anisotropic layer is prepared, and after the optically anisotropic layer is formed on the alignment film, only the optically anisotropic layer is used as the retardation film (support) of the present invention. ) May be transferred onto.

In the present invention, the alignment film is preferably a layer made of a crosslinked polymer. The polymer used for the alignment film may be either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent.

The alignment film is formed by reacting a polymer having a functional group or a polymer having a functional group introduced therein with light, heat, pH change, or the like; or a cross-linking agent that is a compound having high reaction activity Can be formed by introducing a linking group derived from a cross-linking agent between polymers to cross-link between the polymers.

The alignment film composed of a crosslinked polymer can be usually formed by applying a coating liquid containing the polymer or a mixture of a polymer and a crosslinking agent on a support, followed by heating or the like.

In the rubbing process described later, it is preferable to increase the degree of crosslinking in order to suppress the dust generation of the alignment film. A value (1- (Ma / Mb)) obtained by subtracting 1 from the ratio (Ma / Mb) of the amount (Ma) of the crosslinking agent remaining after crosslinking to the amount (Mb) of the crosslinking agent added to the coating solution. When Mb)) is defined as the degree of crosslinking, the degree of crosslinking is preferably 50 to 100%, more preferably 65 to 100%, and even more preferably 75 to 100%.
<Preparation of polarizing plate>
The polarizing plate of the present invention comprises a polarizer and two polarizing plate protective films sandwiching the polarizer, and at least one of the polarizing plate protective films is the retardation film described above. .

The polarizer of the present invention is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol polarizing film, which is dyed iodine on a polyvinyl alcohol film. And dyed dichroic dyes.

The polarizer is formed by forming a polyvinyl alcohol aqueous solution into a film and dyeing the film by uniaxial stretching or dyeing or uniaxially stretching, and then performing a durability treatment with a boron compound.

The optical film of the present invention is adhered to the polarizer with an adhesive or the like. As an adhesive used for the adhesive layer, an adhesive having a storage elastic modulus at 25 ° C. in the range of 1.0 × 10 ⁴ Pa to 1.0 × 10 ⁹ Pa in at least a part of the adhesive layer is used. Preferably, a curable pressure-sensitive adhesive that forms a high molecular weight body or a crosslinked structure by various chemical reactions after the pressure-sensitive adhesive is applied and bonded is suitably used.

Specific examples include, for example, urethane adhesives, epoxy adhesives, aqueous polymer-isocyanate adhesives, curable adhesives such as thermosetting acrylic adhesives, moisture-curing urethane adhesives, polyether methacrylate types, Examples include anaerobic pressure-sensitive adhesives such as ester-based methacrylate type and oxidized polyether methacrylate, cyanoacrylate-based instantaneous pressure-sensitive adhesives, and acrylate-peroxide-based two-component instantaneous pressure-sensitive adhesives.

The above-mentioned pressure-sensitive adhesive may be a one-component type or a type in which two or more components are mixed before use.

The above-mentioned pressure-sensitive adhesive may be a solvent system using an organic solvent as a medium, or an aqueous system such as an emulsion type, a colloidal dispersion type, or an aqueous solution type that is a medium containing water as a main component. It may be a solvent type. The concentration of the pressure-sensitive adhesive liquid may be appropriately determined depending on the film thickness after adhesion, the coating method, the coating conditions, and the like, and is usually 0.1 to 50% by mass.

In the retardation film of the present invention, the film surface opposite to the optically anisotropic layer to which the aligned liquid crystal layer is fixed is saponified by a usual method, and then adhered to the polarizer with a polyvinyl alcohol-based adhesive. .

Even if the retardation film of the present invention is used on the other surface, it is preferable to bond another polarizing plate protective film.

For example, commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC8UX-RHA, KC8UX-RHA, KC8UX KC4UXW-RHA-NC, manufactured by Konica Minolta Opto Co., Ltd.) is also preferably used.

The retardation film may be bonded to the polarizer at the same time, or may be bonded in a roll state with a so-called roll-to-roll.
<Liquid crystal display device>
The polarizing plate of the present invention is bonded to a liquid crystal cell via the adhesive layer or the like. In that case, the polarizing plate of this invention is bonded by the visual recognition side of a liquid crystal cell, and also the bonding surface with a liquid crystal cell is a cellulose-ester film (b) side.

The polarizing plate according to the present invention includes a reflective type, a transmissive type, a transflective type LCD or a TN type, an STN type, an OCB type, a HAN type, a VA type (PVA type, MVA type), an IPS type (including an FFS type), and the like. It is preferably used in various drive LCDs. In particular, in a large-screen display device having a screen of 30 or more, especially 30 to 54, there is no white spot at the periphery of the screen and the effect is maintained for a long time.

<Preparation of optical films 1 to 51>
<Preparation of acrylic resin>
The following acrylic resins A1-A7 and MS1,2 were prepared by known methods.

A1: Monomer mass ratio (MMA: MA = 98: 2), Mw 70000
A2: monomer mass ratio (MMA: MA = 97: 3), Mw 160000
A3: monomer mass ratio (MMA: MA = 97: 3), Mw350,000
A4: monomer mass ratio (MMA: MA = 97: 3), Mw550,000
A5: monomer mass ratio (MMA: MA = 97: 3), Mw 800000
A6: monomer mass ratio (MMA: MA = 97: 3), Mw 930,000
A7: monomer mass ratio (MMA: MA = 94: 6), Mw1100000
MS1: monomer mass ratio (MMA: ST = 60: 40), Mw100,000
MS2: monomer mass ratio (MMA: ST = 40: 60), Mw100,000
MMA: Methyl methacrylate MA: Methyl acrylate ST: Styrene (Synthesis of A8)
First, a methyl methacrylate / acrylamide copolymer suspension was prepared as follows.

Methyl methacrylate 20 parts by weight Acrylamide 80 parts by weight Potassium persulfate 0.3 part by weight Ion-exchanged water 1500 parts by weight The above is charged into the reactor and the reactor is replaced with nitrogen gas. The reaction was allowed to proceed at 70 ° C. until converted to. The obtained aqueous solution was used as a suspending agent. A solution in which 0.05 part by mass of the above suspending agent is dissolved in 165 parts by mass of ion-exchanged water is supplied to a stainless steel autoclave having a capacity of 5 liters and equipped with a baffle and a foudra-type stirring blade, and the system is filled with nitrogen gas. It stirred at 400 rpm, replacing.

Next, a mixed substance having the following charge composition was added while stirring the reaction system.

Methacrylic acid 27 parts by weight Methyl methacrylate 73 parts by weight t-dodecyl mercaptan 1.2 parts by weight 2,2′-azobisisobutyronitrile 0.4 part by weight The temperature was raised to 70 ° C. and the internal temperature was 70 ° C. The time at which the polymerization was reached was set as the polymerization start time, and the polymerization was continued for 180 minutes.

Thereafter, the reaction system was cooled, the polymer was separated, washed, and dried according to the usual method to obtain a bead-shaped copolymer. The polymerization rate of this copolymer was 97%, and the weight average molecular weight was 130,000.

0.2% by mass of an additive (NaOCH ₃ ) is blended in this copolymer, and nitrogen is added at 10 L / L from the hopper using a twin-screw extruder (TEX30, Nippon Steel Co., Ltd., L / D = 44.5). While purging with a minute amount, an intramolecular cyclization reaction was performed at a screw rotation speed of 100 rpm, a raw material supply rate of 5 kg / hour, and a cylinder temperature of 290 ° C. to produce pellets, which were then vacuum-dried at 80 ° C. for 8 hours for acrylic resin A8 Got. The weight average molecular weight (Mw) of the acrylic resin A8 was 130,000, and Tg was 140 ° C.

In the optical film sample 48, * 1 was used as the acrylic resin (A). This is the same as the acrylic resin described in Example 1 of Patent Document 3 (Japanese Patent Application Laid-Open No. 2005-146084). ) To (0070) and prepared as 1A in Patent Document 3. The weight average molecular weight of the acrylic resin of * 1 according to Patent Document 3 was 244000.

In the optical film sample 50, Acrypet V (manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 105000) is used as the acrylic resin (A) * 2, and as a blend material of the cellulose ester resin (B), Patent Document 5 ( JP, 2008-88417) A blend material described in Example 5 (10% by mass of DOP added) was used.

In addition, the following commercially available acrylic resins were used.

Dianar BR80 (Mitsubishi Rayon Co., Ltd.) Mw95000
Dianar BR83 (Mitsubishi Rayon Co., Ltd.) Mw40000
Dianar BR85 (Mitsubishi Rayon Co., Ltd.) Mw280000
Dianar BR88 (manufactured by Mitsubishi Rayon Co., Ltd.) Mw 480000
80N (Asahi Kasei Chemicals Corporation) Mw100,000
The ratio of the MMA unit in the molecule in the commercially available acrylic resin was 90% by mass or more and 99% by mass or less.

<Preparation of optical film 1>
(Dope solution composition 1)
Dianal BR85 (manufactured by Mitsubishi Rayon Co., Ltd.) 70 parts by mass Cellulose ester (cellulose acetate propionate acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, Mw = 200000 )
30 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass The above composition was sufficiently dissolved while heating to prepare a dope solution.

The dope solution was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 162 N / m.

The solvent was evaporated from the peeled acrylic resin web at 35 ° C., slit to 1.6 m width, and then dried at a drying temperature of 135 ° C. while stretching 1.1 times in the width direction with a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 10% by mass.

After stretching with a tenter, relaxation was performed at 130 ° C. for 5 minutes, and then drying was completed while transporting a drying zone at 120 ° C. and 140 ° C. with many rolls, slitting to a width of 1.5 m, and a width of 10 mm at both ends of the film A knurling process having a height of 5 μm was performed, and the film was wound around a core having an initial tension of 220 N / m and a final tension of 110 N / m, and an inner diameter of 15.24 cm.

The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.1 times.

The residual solvent amount of the optical film 1 shown in Table 1 was 0.1% by mass, the film thickness was 60 μm, and the winding length was 4000 m.

<Preparation of optical films 2 to 50>
Optical films 2 to 50 were prepared in the same manner as in the production of optical film 1 except that the types and composition ratios of acrylic resin (A) and cellulose ester resin (B) were changed as shown in Tables 1 and 2. Was made.

The acyl groups of the cellulose ester resins shown in Tables 1 and 2 are as follows: ac is an acetyl group, pr is a propionyl group, bu is a butyryl group, pen is a pentanoyl group, bz is a benzoyl group, hep is a heptanoyl group, and oct is Octanoyl group, ph represents a phthalyl group.

Since the retardation of the optical films 1 to 51 was almost zero, the retardation as the retardation film was adjusted by the thickness of the liquid crystal alignment layer which is an optically anisotropic layer.
<Optical Film 51 (Comparative Example) Solvent Selection Comparative Example>
(Dope composition liquid 51)
Dianal BR85 (manufactured by Mitsubishi Rayon Co., Ltd.) 70 parts by mass Cellulose ester (cellulose acetate propionate acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, Mw = 200000 )
30 parts by mass Methylene chloride 140 parts by mass Toluene 200 parts by mass The above dope composition liquid 51 was produced in the same manner as in the production of the optical film 1 to produce an optical film 51. In addition, toluene is a poor solvent with respect to a cellulose ester.

The glass transition temperatures of the produced optical films 1 to 51 were measured using a differential scanning calorimeter (DSC-7 model manufactured by Perkin Elmer).

The optical film 51 has peaks at two locations of T _g1 : 105 ° C. and T _g2 : 145 ° C., and the acrylic resin (A) and the cellulose ester resin (B) exist in an incompatible state. I understood. For the optical films 1 to 50, two Tg were not observed and were not in an incompatible state.

<Production of retardation film: Production of optically anisotropic layer on optical film>
<Preparation of retardation film a1>
The optical film 1 was sandwiched between two metal rolls having a surface of 140 ° C., and the peripheral speed ratio of the two rolls was set to 0.8 to convey between the rolls for surface treatment. When the phase difference was measured after the surface treatment, the in-plane phase difference was not changed.
(Coating liquid a)
The following discotic liquid crystalline compound 1 41.01 parts by mass Ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 4.06 parts by mass Cellulose acetate butyrate (CAB551-0.2 Yeast) Man Chemical Co., Ltd.) 0.17 parts by weight Cellulose acetate butyrate (CAB531-1 Eastman Chemical Co., Ltd.) 0.06 parts by weight Compound I-51 0.10 parts by weight Photopolymerization initiator (Irgacure 907, Ciba (Made by Japan)
1.35 parts by mass Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 0.45 parts by mass Fluoroaliphatic group-containing polymer The following compound P-2 Mw = 15000
0.27 parts by mass

The optically anisotropic layer composition was dissolved in methyl isobutyl ketone (MIBK) to obtain a coating liquid a having a specific gravity of 0.920.

Using a slot die, the coating liquid a was applied at 5.4 ml / m ² on the optical film 1 subjected to the surface treatment in the previous period, and heated at 125 ° C. for 2 minutes. Next, UV irradiation was performed for 1 minute using a 120 W / cm high-pressure mercury lamp at 100 ° C. to polymerize the discotic liquid crystalline compound.

Thereafter, the mixture was allowed to cool to room temperature and observed under crossed nicols, and it was confirmed that the liquid crystal was aligned. Thus, the retardation film a1 in which the liquid crystal was aligned without performing the rubbing treatment was produced.

The optical properties of the retardation film a1 were measured using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments). When the measurement angle was changed with the film in-plane coasting axis as the tilt axis, it was confirmed that the phase difference value had a non-zero minimum value at 20 °.

The minimum value of the retardation film was 10 nm at Ro = 26 and an inclination angle of 30 °.

<Creation of retardation films a2 to a51>
Using the optical films 2 to 51, retardation films a2 to a51 were produced in the same manner as the retardation film a1. Since the retardation of the optical films 1 to 51 was almost zero, the retardation as the retardation film was adjusted by the thickness of the liquid crystal alignment layer, which is an optically anisotropic layer, as described below.

<Preparation of retardation film ax1>
Arranged between superconducting magnets, adjusted the distance between the magnets so that the magnetic field strength is 1T in the vertical direction, and then applied to the optical film 1 in the same manner as the retardation film a1 except that the coating amount is 6.5 ml. The coating solution a was applied, treated between the prepared magnets at 120 ° C. for 1 minute, and then irradiated with ultraviolet rays while being placed between the magnets. Thus, retardation film ax1 was produced.

Measurement was performed using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments) with the in-plane slow axis as the tilt axis, and the in-plane phase difference Ro = 0.2 and the thickness phase difference Rt. = 240 nm retardation film, and it was confirmed that the angle formed by the optical axis and the normal direction of the retardation film was less than 5 degrees.

<Preparation of retardation film b1>
(Coating solution b)
The following rod-shaped liquid crystal compound 3.8 parts by mass Photopolymerization initiator (Irgacure 907, manufactured by Ciba Japan Co., Ltd.)
0.11 parts by mass Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 0.038 parts by mass Onium salt 1 0.076 parts by mass Polymer AP-1 0.015 parts by mass MIBK 9.2 parts by mass This coating liquid b was applied to the optical film 1 at 6.7 ml / m ² with a wire bar.

This was affixed to a metal frame and heated in a constant temperature bath at 80 ° C. for 2 minutes to align the rod-like liquid crystal compound. Next, UV irradiation was performed at 60 ° C. with a 120 W / cm high-pressure mercury lamp for 20 seconds to crosslink the rod-like liquid crystal compound, and then allowed to cool to room temperature to prepare a retardation film b1.

When an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments) was used to measure the in-plane slow axis as the tilt axis, Ro = 0 nm, Rt = -280 nm, and the optical axis It was confirmed that the angle formed by the normal direction of the retardation film is less than 5 degrees.

<Preparation of retardation film bx1>
The coating liquid b was applied to the optical film 1 and dried, and the film normal line and the magnetic field were 38 ° C. in the magnetic field generator used in ax 1 in a state where the coating liquid b was applied to the optical film 1 and dried and kept at 80 ° C. The film was placed at an angle and held for 1 minute, and then allowed to cool to 50 ° C. and cured with ultraviolet rays to produce a retardation film bx1 having an inclined optical axis.

When optical properties were measured using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments), a retardation film with Ro = 5 nm and an optical axis inclined by about 38 ° was obtained.

<Preparation of retardation film c1>
The optical film 1 was subjected to corona discharge treatment, and an alignment film coating solution having the following composition was coated on the surface with a wire bar. After drying with warm air of 60 ° C. for 60 seconds and further with warm air of 100 ° C. for 120 seconds, rubbing treatment was performed to form an alignment film.
(Alignment film coating solution)
The following modified polyvinyl alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde 0.5 parts by weight

(Coating liquid c)
Discotic liquid crystalline compound 1 91 parts by mass Ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 9 parts by mass Photopolymerization initiator (Irgacure 907, manufactured by Ciba Japan Co., Ltd.)
3 parts by mass Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 1 part by mass 0.4 parts by mass of the following fluoropolymer A 212 parts by mass of methyl ethyl ketone

The coating liquid c having the above composition was applied to the prepared alignment film by 8.5 g / m ² using a wire bar. The conveyance speed of the film was 20 m / min. The solvent was dried in the step of continuously heating from room temperature to 80 ° C., and then heated in a drying zone at 120 ° C. for 90 seconds to align the molecules of the discotic liquid crystalline compound.

Subsequently, the temperature of the film is maintained at 90 ° C., UV light is irradiated at 500 mJ / cm ² using a high-pressure mercury lamp, the orientation of the discotic molecules is fixed, and an optically anisotropic layer is formed. A retardation film c1 was produced.

An optical birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments Co., Ltd.) is used to remove the optically anisotropic layer formed from the produced retardation film c1 using a discotic liquid crystalline compound. Characteristics were measured.

Ro = 0 nm measured at a wavelength of 590 nm, and Rt = 195 nm. It is confirmed that an optically anisotropic layer in which discotic liquid crystal molecules are aligned substantially horizontally with respect to the film surface is formed, and the angle formed by the optical axis and the normal direction of the retardation film is less than 5 degrees. It was.

<Preparation of retardation film d1>
The surface of the optical film 1 was subjected to corona discharge treatment, and SiO was obliquely deposited on the corona discharge treatment surface to form a SiO alignment film. On this alignment film, the following coating liquid d was applied by spin coating (1600 rpm) and dried to form a discotic liquid crystal layer.
(Coating solution d)
Discotic liquid crystal compound 1 1.8 parts by mass Photopolymerization initiator (Irgacure 907, manufactured by Ciba Japan Co., Ltd.)
0.06 parts by mass Methyl ethyl ketone 13.2 parts by mass Another optical film 1 provided with an SiO alignment film prepared in the same manner as above except that no discotic liquid crystal layer was formed was prepared. The discotic liquid crystal layer was overlaid so that the alignment film of the film and the discotic liquid crystal layer were in contact with each other.

The obtained laminate was heated to 180 ° C., cooled to room temperature, irradiated with ultraviolet rays to fix the orientation, and a retardation film d1 was produced.

The film thickness of the liquid crystal cured layer peeled from the optical film 1 of the produced retardation film d1 was 2.1 μm.

The optical properties of the liquid crystal cured layer were measured using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments). When measured at a wavelength of 590 nm, Ro = 95 nm and Rt = −45 nm, and it was confirmed that the angle formed by the optical axis and the retardation film surface was less than 5 degrees.

<Preparation of retardation film e1>
Reaction obtained by polycondensation at 270 ° C. for 12 hours in a nitrogen atmosphere using 50 mmol of terephthalic acid, 50 mmol of 2,6-naphthalenedicarboxylic acid, 40 mmol of methylhydroquinone diacetate, 60 mmol of catechol diacetate and 60 mg of N-methylimidazole The product was dissolved in tetrachloroethane and purified with methanol to obtain 14.6 g of a liquid crystalline polyester. It has a nematic phase as a liquid crystal phase, an isotropic phase-liquid crystal phase transition temperature of 250 ° C. or higher, and a glass transition temperature of 112 ° C.
(Coating solution e)
Liquid crystalline polyester 20 parts by weight N-methyl-2-pyrrolidone 80 parts by weight Coating solution e is applied onto a rubbed polyimide film (trade name “Kapton”, manufactured by DuPont) with a bar coater, and the solvent is removed by drying. Then, a nematic alignment structure was formed by heat treatment at 210 ° C. for 20 minutes.

After the heat treatment, the nematic alignment structure was fixed by cooling to room temperature, and an optically anisotropic layer having an actual film thickness of 1.1 μm uniformly aligned on the polyimide film was obtained.

A commercially available UV curable adhesive (UV-3400, manufactured by Toagosei Co., Ltd.) was applied as an adhesive layer 1 on the optically anisotropic layer (surface opposite to the polyimide film) to a thickness of 5 μm. The adhesive layer 1 was cured by UV irradiation of about 600 mJ.

Thereafter, the polyimide film is peeled off, and a commercially available UV curable adhesive (UV-3400) is applied as an adhesive layer 2 to a thickness of 5 μm on the optically anisotropic layer, and the optical film 1 is applied thereon. The retardation film e1 was obtained by laminating and curing the adhesive layer 2 by UV irradiation of about 600 mJ.

When the optical characteristics of the liquid crystal cured layer were measured using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments) with the in-plane fast axis as the tilt axis, Ro = 104 nm and tilt angle 48 The phase difference became a maximum value at °, and the maximum value was 138 °.

<Preparation of retardation film f1>
The optical film 1 was subjected to corona discharge treatment, and the alignment film used for the retardation film c1 was applied to the surface subjected to the corona discharge treatment with a wire bar. After drying with warm air of 60 ° C. for 60 seconds and further with warm air of 100 ° C. for 120 seconds, rubbing treatment was performed to form an alignment film.

On this alignment film, a coating solution f having the following composition is applied using a bar coater, dried and heated (alignment aging), and further irradiated with ultraviolet rays to form an optically anisotropic layer having a thickness of 2.1 μm. Formed.

The optical characteristics were measured using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments). When measured at a wavelength of 590 nm, Ro = 238 nm and Rt = 119 nm, and it was confirmed that the optical axis was in the plane of the retardation film.
(Coating solution f)
Rod-like liquid crystal compound N49 14.5 parts by mass The following sensitizer 0.15 parts by mass The following polymerization initiator 0.29 parts by mass Methyl ethyl ketone 85.06 parts by mass

<Preparation of retardation film df1>
The retardation film d1 is rubbed, the coating solution f is coated and dried using a bar coater, heated (orientation aging), and further irradiated with ultraviolet rays to form an optically anisotropic layer having a thickness of 1.6 μm. A retardation film df1 was produced.

When this was measured using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments) with the in-plane slow axis as the tilt axis, Ro = 178 nm, Rt = 75 nm, It was confirmed that the axis was tilted 25 ° from the film normal.

<Preparation of retardation film fb1>
The coating liquid b was applied to the retardation film f1 and dried to prepare a retardation film fb1. Ro = 238 nm and Rt = −25 nm.

For comparison, a retardation film in which the coating liquids a to fb were applied to a comparative optical film was prepared in the same manner as the above-described retardation film preparation method.

The obtained optical films a1 to a51 were evaluated as follows.

(Haze: Transparency evaluation)
With respect to each of the produced film samples, one film sample was measured according to JIS K-7136 using a haze meter (NDH2000 type, manufactured by Nippon Denshoku Industries Co., Ltd.).

(Tension softening point: heat resistance evaluation)
A sample conditioned for 24 hours in an air-conditioned room at 23 ° C. and 55% RH was cut out at 120 mm (length) × 10 mm (width) under the same conditions, and 10 N using a Tensilon tester (ORIENTEC, RTC-1225A). The temperature was continuously increased at a rate of temperature increase of 30 ° C./min while pulling with a tension of 30 ° C., and the temperature at the time of 9 N was measured three times, and the average was obtained.

(Ductile fracture: brittleness evaluation)
A sample conditioned for 24 hours in an air-conditioned room at 23 ° C. and 55% RH was cut out at 100 mm (length) × 10 mm (width) under the same conditions, with a radius of curvature of 0 mm and a bending angle of 180 ° at the center in the vertical direction. Then, the film was folded once in a mountain fold and a valley fold so that the films were exactly overlapped, and this evaluation was measured three times and evaluated as follows. In addition, breaking of evaluation here represents having broken into two or more pieces.

○: Cannot be folded 3 times ×: Can be folded at least 1 out of 3 times (Film deformation: heat resistance evaluation for long-term use)
Each optical film was left in an atmosphere of 90 ° C. and DRY (relative humidity 5% RH or less) for 1000 hours, and then the degree of film deformation was visually observed and evaluated according to the following criteria.

○: No deformation of the film Δ: Deformation of the film is recognized ×: Remarkable deformation of the film is recognized (Dimensional change with respect to humidity change: evaluation of moisture resistance)
In the casting direction of the produced optical film, two marks (crosses) were attached and treated at 60 ° C. and 90% RH for 1000 hours, and the distance between the mark (cross) before and after treatment was measured with an optical microscope. Evaluation was made according to the following criteria.

Dimensional change rate (%) = [(W1-W1 ′) / a1] × 100
In the formula, W1 represents a distance before heat treatment, and W1 ′ represents a distance after heat treatment.

○: Less than 0.3% Δ: 0.3% or more, less than 0.5% ×: 0.5% or more (Film appearance: production suitability evaluation)
About the produced optical film, the film external appearance was evaluated visually and evaluated according to the following references | standards.

◯: Very smooth flatness Δ: Slightly creased, wrinkled, or step can be confirmed ×: Clearly creased, creased, or step can be confirmed Tables 3 and 4 show the results of the above evaluation.

<Production of polarizing plate and liquid crystal display device>
<Preparation of polarizing plate>
A polarizing plate PL using the retardation film prepared above as a polarizing plate protective film was prepared as follows.

A 120-μm-thick long roll polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched in the transport direction 5 times at 50 ° C. to produce a polarizer.

Next, the retardation film a1 was subjected to corona treatment using an acrylic adhesive on one side of the polarizer, and then bonded.

Furthermore, Konica Minolta Op KC8UX-2MW manufactured by Konica Minolta Opto Co., Ltd., which had been subjected to alkali saponification treatment, was bonded to the other surface of the polarizer and dried to prepare a polarizing plate PL-a1.

According to this method, other polarizing plates were produced in the same manner. The relationship between the in-plane slow axis of the retardation film and the absorption axis of the polarizer is as follows (indicated by the code of the coating solution).

a: orthogonal ax: orthogonal bx: parallel d: parallel e: orthogonal df: orthogonal fb: orthogonal Note that b and c are polarized light because the in-plane slow axis direction does not affect the performance of the liquid crystal display device. The angle is not taken into account when making the plate.
<Production of liquid crystal display device and evaluation of unevenness>
Evaluation as a liquid crystal display device provided with the retardation film of the present invention is a 100-hour endurance test in an environment of 60 ° C. and 95% RH, and the display is black with the backlight turned on immediately after taking out from the endurance test. The state of unevenness was observed after 2 hours and 24 hours. The evaluation criteria are as follows.

×: Strong unevenness occurs on the entire surface △: Strong unevenness occurs on the corner (or edge) ○: Very weak unevenness occurs on the entire surface (not clear)
A: No occurrence of unevenness <Liquid crystal display device used>
The retardation film of the present invention was bonded to the position as shown in Table 5 so that it was on the liquid crystal cell side. Unless otherwise specified, the absorption axis of the polarizer is set in the same direction as the polarizing plate originally provided, and the retardation is adjusted to a value obtained by combining the polarizing plate originally attached and the retardation film, respectively. did.

As the liquid crystal display device, the VA liquid crystal cell is a 32-inch liquid crystal television “BRAVIA” KDL-32J5000 manufactured by Sony Corporation, the IPS liquid crystal cell is a VIERA (TH-32LZ80) manufactured by Matsushita Electric Industrial Co., Ltd., and the TN liquid crystal cell is A liquid crystal display (LCD-A176G) manufactured by IO Data Equipment Co., Ltd. was used.

The results are shown in Table 5.

The polarizing plate and the liquid crystal display device produced using the retardation film of the present invention showed excellent characteristics in unevenness.

DESCRIPTION OF SYMBOLS 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock tank 5, 14 Liquid feed pump 8, 16 Conduit 10 Ultraviolet absorber charging pot 20 Merge pipe 21 Mixer 30 Die 31 Metal support 32 Web 33 Peeling position 34 Tenter device 35 Roll dryer 41 Particle charging vessel 42 Stock tank 43 Pump 44 Filter

Claims (3)

1. The acrylic resin (A) and the cellulose ester resin (B) are contained in a mass ratio of 95: 5 to 30:70 and in a compatible state, and the acrylic resin (A) has a weight average molecular weight Mw of 80000 to 1000000. Yes, the total substitution degree (T) of the acyl group of the cellulose ester resin (B) is 2.0 or more and 3.0 or less, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 or more and 3.0. An optical film, wherein the cellulose ester resin (B) has a weight average molecular weight Mw of 75,000 or more and 280000 or less, and an optically anisotropic layer in which liquid crystal is aligned and the alignment is fixed. Retardation film having.
2. A polarizing plate comprising a polarizer and two polarizing plate protective films sandwiching the polarizer, wherein at least one of the polarizing plate protective films is the retardation film according to claim 1.
3. A liquid crystal display device comprising the retardation film according to claim 1.

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