WO2011118845A1

WO2011118845A1 - Polyester resin, and optical materials, films and image display devices using the same

Info

Publication number: WO2011118845A1
Application number: PCT/JP2011/058153
Authority: WO
Inventors: Shinsuke Tokuoka; Yasuhiro Aiki
Original assignee: Fujifilm Corporation
Priority date: 2010-03-26
Filing date: 2011-03-24
Publication date: 2011-09-29
Also published as: TW201139510A; JP2011202129A

Abstract

A polyester resin containing a structure represented by Formula (1) and a structure represented by Formula (2) : wherein R¹¹ to R¹⁴ and R²¹ to R²⁶ represent a hydrogen atom or a substituent; R¹⁵to R¹⁸ represent a substituent; and at least one of R²¹ to R²⁶ represents a substituent.

Description

DESCRIPTION

POLYESTER RESIN, AND OPTICAL MATERIALS, FILMS AND IMAGE DISPLAY DEVICES USING THE SAME

Technical Field

The present invention relates to a polyester resin excellent in melt-molding properties, and excellent in transparency. Moreover, it relates to optical materials and films using the polyester resin, in particular to films that have a suitable glass transition temperature, are easily melt-cast, and have a small coefficient of linear thermal expansion, and to devices for displaying an image using the film.

Background Art

Since inorganic glass materials are excellent in transparency and heat resistance, and have a small optical anisotropy, they are widely used as a transparent material. However, they have such disadvantages that they are hard to be molded, and that they have a large specific gravity and are brittle and, therefore, molded glass products are heavy and easy to break. Due to such disadvantages, in these years, the development of resin materials for replacing inorganic glass materials has energetically carried out.

As resin materials for replacing inorganic glass materials, for example, polymethyl methacrylate, polycarbonate, polyethylene terephthalate , etc. are known. Since these resin materials are light in weight, excellent in mechanical properties, and excellent in processability, recently, they are used in various applications such as lenses and films.

In these years, the replacement of display substrates from glass to resin has been examined, in particular, resin substrates etc. capable of loading ITO (indium tin oxide) are required. Because, the utilization of resin gives various advantages such as weight reduction, shock-resistant properties, thickness reduction, etc. In order to make it possible to replace glass by a resin substrate, a certain degree of heat resistance (roughly from 150°C to 250°C) is necessary. Moreover, when a display substrate is produced while heating a resin, particularly when the resin is annealed after the loading of ITO, it is required that the resin has a low coefficient of linear thermal expansion when it is formed into a film, from the viewpoint of dimensional stability.

On the other hand, when a resin material is used for a film application, it is required that the production by melt-casting is easy from the viewpoint of production cost. Here, if the heat resistance of a resin is improved too much, a high temperature becomes necessary in melt-casting. Moreover, even when the temperature is in a range capable of melt-casting, the production cost required for the heating must be suppressed. Therefore, a resin is strongly desired that has a suitable glass transition temperature (hereinafter, it may also be referred to as Tg) so as to allow itself to be melt-cast at a practical temperature and not to require a high production cost necessary for heating.

Furthermore, when a resin material is used for optical material applications, the transparency, too, must be high.

In order to satisfy both the heat resistance and the low coefficient of linear thermal expansion, there is examined a film having a low coefficient of linear thermal expansion using a resin having a polyallylate structure of an aromatic diol (among others, particularly biphenol) and a dicarboxylic acid (see JP-A 2007-254663). The document also describes various biphenols ( those having a biphenylene skeleton ) and bisphenols as aromatic diols used for the polyallylate. The document also describes in paragraph [0006] that biphenol and bisphenol show different characteristics such that the biphenol exerts adamant properties. However, JP-A 2007-254663 discloses only a solution casting method for producing a polyester film by dissolving a resin in a solvent and performing solution casting. Furthermore, the document discloses specific performances for only an example using a biphenol having substituents at the 2-site and the 2 '-site of the biphenol and a bisphenol as aromatic diol components. That is, the document does not refer to resins obtained when two or more kinds of biphenols having substituents at different sites, in any way.

On the other hand, documents other than JP-A 2007-254663 disclose resins having the polyallylate structure of a biphenol and a dicarboxylic acid, but they do not particularly examine the lowering of the coefficient of linear thermal expansion and melt-casting properties (see, for example, JP-A 10-017658 and JP-A 58-180525) . JP-A 10-017658 discloses a resin having improved electric properties, -solubility in a solvent and storage stability obtained by combining one kind of biphenol and one kind of bisphenol as aromatic diols. Specifically, it discloses examples of resins obtained by combining a 4, 4' -biphenol having such substitution forms as 3, 3' -dimethyl, 3, 3' , 5, 5' -tetramethyl or 2 , 2 ' , 3 , 3 ' , 5 , 5 ' -hexamethyl , respectively, with a bisphenol.

JP-A 58-180525 discloses a resin having an improved heat resistance, strength and hydrolysis resistance obtained by combining one kind of biphenol and one or two kinds of bisphenols as aromatic diols. Specifically, it discloses an example of resin obtained by combining a 4 , 4 ' -biphenol having such substitution form as 3 , 3 ', 5 , 5 ' -tetramethyl with a bisphenol.

However, in the same manner as JP-A 2007-254663, JP-A 10-017658 and JP-A 58-180525 do not refer to the combined use of two or more kinds of biphenols having different sites of substituents .

The present inventors checked whether or not resins disclosed in above-mentioned three Patent Documents satisfied required performances. But, the resin described in JP-A 2007-254663 was unsatisfactory from the viewpoint of production cost. That is, the resin described in JP-A 2007-254663 satisfied to a certain degree both the heat resistance and the lowering of the coefficient of linear thermal expansion of films obtained by using the resin, but polyester resins described in Examples of the document had a high Tg, and were unsatisfactory from the viewpoint of carrying out the melt-casting.

From the examination of the inventors about the resin containing a biphenol having a specified structure described in JP-A 10-017658, it was known that the resin certainly had a good solubility in a solvent, but that it had a too high coefficient of linear thermal expansion to deteriorate the dimensional stability of a polyester resin film in a process where it was laminated with ITO or the like and annealed, thereby leading to performance deterioration of devices for displaying an image to be obtained.

From the examination of the inventors about the resin containing a biphenol having a specified structure described in JP-A 58-180525, it was known that the resin had a too high coefficient of linear thermal expansion to deteriorate the dimensional stability of a polyester resin film in a process where it was laminated with ITO or the like and annealed, thereby leading to performance deterioration of devices for displaying an image to be obtained.

Summary of the Invention

The present inventors studied on the subject of obtaining a resin that satisfies all above-mentioned demanded characteristics. That is, a purpose of the present invention is to provide a polyester resin having an appropriate glass transition temperature for carrying out effective melt-casting, having a low coefficient of linear thermal expansion, and having a good transparency, and optical components and films using the resin. Moreover, a purpose is to provide an image display device using the film.

Detailed Description of the Invention

The present inventors studied hard while paying attention to a combined effect obtained by the use of 4,4' -biphenol having substituents at least 3, 3' , 5, 5' -sites and the introduction of plural_. biphenol units, and, as the result, found that it is possible to lower the coefficient of linear thermal expansion and to give Tg lying around the upper limit capable of melt-casting .

The inventors examined the combined use of 4 , 4 ' -biphenol having substituents at least 3,3' ,5,5' - sites and 4,4' -biphenol having a substituent at another site. Meanwhile, we presumed that, generally, a resin formed by using two or more kinds of copolymerization components having different structures in combination leads to the reduction of intermolecular interaction and to the rise of the coefficient of linear thermal expansion .

However, it was known, surprisingly, that the coefficient of linear thermal expansion is lowered. That is, we found that the above-mentioned combination lowers largely the coefficient of linear thermal expansion as compared with the case where each of biphenols is used singly, while adjusting the Tg in the range capable of melt-casting, to thereby complete the invention.

That is, the inventors found that the above-mentioned purposes are attained by the constitution below.

[1] A polyester resin containing a structure represented by Formula (1) below and a structure represented by Formula (2) :

wherein R to R each independently represents a hydrogen atom or a substituent, and R to R each independently represents a substituent,

wherein R²¹ to R²⁶ each independently represents a hydrogen atom or a substituent, and at least one of R to R represents a substituent .

[2] The polyester resin according to [1], wherein R¹⁵ to R¹⁸ in Formula (1) each independently is a halogen atom, an alkyl group, an aryl group or an alkoxy group.

[3] The polyester resin according to [1], wherein R¹⁵ to R¹⁸ in Formula (1) each independently is a fluorine atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group or a methoxy group.

[4] The polyester resin according to any one of [1] to [3], wherein R²¹ to R²⁶ in Formula (2) each independently is a hydrogen atom, a halogen atom, an alkyl group, an aryl group or an alkoxy group .

[5] The polyester resin according to any one of [1] to [3], wherein R²¹ to R²⁶ in Formula (2) each independently is a hydrogen atom, a fluorine atom, a bromine atom, a chlorine atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group or a methoxy group .

[6] The polyester resin according to any one of [1] to [5], containing a structure represented by Formula (3) below:

wherein R to R each independently represents a hydrogen atom or a substituent; X represents a linking group that may have a substituent or may be a part of a ring structure, and, in such case, may be bonded with at least one of R³¹ to R³⁴ to form a ring structure.

[7] The polyester resin according to [6], satisfying Expression (A) below:

0.2 < (a + b)/(a + b + c) < 0.9 (A)

wherein a represents the content ratio (unit: % by mol) of the structure represented by Formula (1) above in the polyester resin; b represents the content ratio (unit: % by mol) of the structure represented by Formula (2) above in the polyester resin; and c represents the content ratio (unit: % by mol) of the structure represented by Formula (3) above in the polyester resin .

[8] The polyester resin according to any one of [1] to [7], containing a structure represented by Formula (4) below: Formula (4)

wherein R⁴¹ each independently represents a substituent; and m represents an integer of 0 to 3.

[9] The polyester resin according to any one of [1] to [8], containing a structure represented by Formula (5) below: Formula (5)

wherein R and R each independently represents a substituent; and n and k each independently represents an integer of 0 to 3. [10] The polyester resin according to any one of [1] to [9], wherein Tg is 170°C to 270°C.

[11] An optical material produced by the polyester resin of any one of [1] to [10] .

[12] A film produced by the polyester resin of any one of [1] to [10] .

[13] The film according to [12] , wherein a coefficient of linear thermal expansion is 40 ppm/K or less.

[14] The film according to [12] or [13], wherein a gas barrier layer is provided.

[15] The film according to any one of [12] to [14], wherein a transparent electroconductive layer is provided.

[16] An image display device using at least one film of [12] to [15] .

According to the present invention, it is possible to provide a polyester resin having an appropriate glass transition temperature for carrying out effective melt-casting, having a low coefficient of linear thermal expansion and having good transparency, films and optical components using the same, and devices for displaying an image using the film. Moreover, the polyester resin of the invention has sufficient heat resistance when a display substrate is produced, particularly when ITO is loaded while heating the resin. Furthermore, the polyester resin of the invention is excellent in transparency in molding, and can favorably be used for optical components, films and devices for displaying an image.

Mode for Carrying Out the Invention

Hereinafter, the polyester resin, the film and the image display device of the invention will be explained in detail. Constitutional elements described below may be explained based on a representative embodiment of the invention, but the invention is not limited to such embodiment. Meanwhile, in the specification, a numerical range represented using "to" means a range including numerical values described before and after "to" as the lower limit value and the upper limit value, respectively .

Polyester resin

The polyester resin of the invention (hereinafter, also referred to as "the resin of the invention") is characterized by containing the structure represented by Formula (1) and the ula (2) be]_ow.

wherein R¹¹ to R¹⁴ each independently represents a hydrogen atom or a substituent; and R¹⁵ to R¹⁸ each independently represents a substituent.

As the result of containing the structure represented by Formula (1) above and the structure represented by Formula (2) above at the same time, the resin of the invention can satisfy at the same time melt-casting characteristics, a low coefficient of linear thermal expansion and transparency.

The resin of the invention is a polyester resin, and, in the resin of the invention, the main chain contains an ester bond. That is, in addition to structures derived from an aromatic diol such as the structure represented by Formula (1) above and the structure represented by Formula (2) above, the resin has a structure derived from a polyvalent carboxylic acid (preferably a dicarboxylic acid) , and has such structure that both are linked by the ester bond.

Hereinafter, the relation between the structure and the function of the resin of the invention will be explained from Formula (1) in order with other structures that are preferably contained .

Structure derived from aromatic diol

(Structure represented by Formula (1))

Formula (1)

In Formula (1) above, R to R each independently represents a hydrogen atom or a substituent; and R¹⁵ to R¹⁸ each independently represents a substituent.

In Formula (1) above, examples of preferable substituents represented by R¹⁵ to R¹⁸ include alkyl groups (preferably having 1 to 10 carbon atoms, such as a methyl group, an ethyl group, an isopropyl group, and tert-butyl group) , halogen atoms (such as a chlorine atom, a bromine atom, and an iodine atom) , aryl groups (preferably having 6 to 20 carbon atoms, such as a phenyl group, a biphenyl group, and a naphthyl group) , alkoxy groups (preferably having 1 to 10 carbon atoms, such as a methoxy group, an ethoxy group, and an isopropoxy group) , acyl groups (preferably having 2 to 10 carbon atoms, such as an acetyl group, a propionyl group, and a butyryl group) , acylamino groups (preferably having 1 to 10 carbon atoms, such as a formylamino group, and an acetylamino group) , a nitro group, a cyano group and groups formed by combining these groups.

R¹⁵ to R¹⁸ are more preferably an alkyl group, a halogen atom, an aryl group, an alkoxy group, a cyano group or a nitro group, particularly preferably a halogen atom, an alkyl group, an aryl group or an alkoxy group, yet particularly preferably a fluorine atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group or a methoxy group, and yet furthermore particularly preferably a fluorine atom, a chlorine atom, a methyl group, an ethyl group, a phenyl group or a methoxy group. A methyl group is preferable from the viewpoint of satisfying all of the solubility in an organic solvent, adjustment of Tg in a range that gives balanced melt-casting characteristics and heat resistance, the coefficient of linear thermal expansion and the transparency.

R¹⁵ to R¹⁸ may be substituents each independently different from one another, or all of them may be the same substituents, and preferably all R¹⁵ to R¹⁸ are the same substituents from the standpoint of raising Tg.

In Formula (1) above, R¹¹ to R¹⁴ each independently represents a hydrogen atom or a substituent. Preferable examples of the substituents represented by R¹¹ to R¹⁴ include the same as preferable substituents represented by R¹⁵ to R¹⁸.

R¹¹ to R¹⁴ are more preferably a hydrogen atom, an alkyl group, a halogen atom, an aryl group, an alkoxy group, a cyano group or a nitro group, particularly preferably a hydrogen atom, a halogen atom or an alkyl group, and yet particularly preferably a hydrogen atom, a fluorine atom, a chlorine atom or a methyl group. From the viewpoint of satisfying all of the solubility in an organic solvent, the adjustment of Tg in a range that gives balanced melt-casting properties and heat resistance, the coefficient of linear thermal expansion and the transparency, R¹¹ to R¹⁴ are preferably a hydrogen atom or a methyl group.

In Formula (1) above, when at least one of R¹¹ to R¹⁴ is an alkyl group, preferably two of these are alkyl groups (preferably methyl groups ) and remaining two are hydrogen atoms . On this occasion, sites of two substituents are preferably R¹¹ and R¹⁴, or R¹² and R¹³. On the other hand, when at least one of R to R is a halogen atom, preferably all halogen atoms are the same (preferably a fluorine atom or a chlorine atom) .

Hereinafter, specific examples of Formula (1) are shown, but structures represented by Formula (1) usable in the invention are not limited to these.

1-1 1-2 1-3

1-10 -11

(Structures represented by Formula (2))

The polyester resin of the invention contains the structure represented by Formula (2) .

wherein R²¹ to R²⁶ each independently represents a hydrogen atom or a substituent; and at least one of R²¹ to R²⁶ represents a substituent Preferable examples of substituents represented by R to R²⁶ include the same as preferable substituents represented by R¹⁵ to R¹⁸ in Formula (1) above.

R²¹ to R²⁶ are more preferably a hydrogen atom, an alkyl group, a halogen atom, an aryl group, an alkoxy group, a cyano group or a nitro group, particularly preferably a hydrogen atom, a halogen atom, an alkyl group, an aryl group or an alkoxy group, more particularly preferably a hydrogen atom, a fluorine atom, a bromine atom, a chlorine atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group or a methoxy group, yet more particularly preferably a hydrogen atom, a methyl group or a phenyl group.

In Formula (2) above, among R²¹ to R²⁶, preferably two are substituents, and remaining four are hydrogen atoms. On this occasion, sites of two substituents are preferably R²¹ and R²⁴, or R²⁵ and R²⁶.

Hereinafter, specific examples of structures represented by Formula (2) are shown, but structures represented by Formula (2) usable in the invention are not limited to these.

2- 19 2-20 2-21

(Structure represented by Formula (3))

As the structure derived from an aromatic diol, in addition to structures derived from biphenols such as structures represented by Formula (1) above and structures represented by Formula (2) above, the resin of the invention may contain a structure derived from another aromatic diol.

As the structure derived from the other aromatic diol that may be contained in the resin of the invention, structures derived from bisphenols are cited, and the polyester resin of the invention preferably contains the structure represented by Formula (3) below.

In Formula (3.), R to R each independently represents a hydrogen atom or a substituent. X represents a linking group that may have a substituent, or may be a part of a ring structure and, on this occasion, may be bonded with at least one of R³¹ to R³⁴ to form a ring structure.

The polyester resin of the invention preferably has the structure represented by Formula (3) above in addition to components of the linear structure represented by Formulae (1) and (2) above, from the viewpoint of satisfying both melt-casting properties and a low coefficient of linear thermal expansion, and, furthermore, improving drawing properties , in particular breaking elongation.

Examples of preferable R³¹ to R³⁸ in Formula (3) include a hydrogen atom, alkyl groups (preferably having 1 to 10 carbon atoms, such as a methyl group, an ethyl group, an isopropyl group and tert-butyl group) , halogen atoms (such as a chlorine atom, a bromine atom and an iodine atom) , aryl groups (preferably having 6 to 20 carbon atoms, such as a phenyl group, a biphenyl group and a naphthyl group) , alkoxy groups (preferably having 1 to 10 carbon atoms, such as a methoxy group, an ethoxy group and an isopropoxy group) , acyl groups (preferably having 2 to 10 carbon atoms, such as an acetyl group, a propionyl group and a butyryl group) , acylamino groups (preferably having 1 to 10 carbon atoms, such as a formylamino group and an acetylamino group) , a nitro group, a cyano group, etc. More preferable are a hydrogen atom, an alkyl group, a halogen atom, an aryl group, an alkoxy group and a nitro group, and particularly preferable are a hydrogen atom, an alkyl group and a halogen atom.

In Formula (3), X represents a bivalent linking group. Examples of X include an alkylene group, an alkylidene group, a perfluoroalkylidene group, an oxygen atom, a sulfur atom, a ketone group, a sulfonyl group, -NR' - (R' is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms), and -CO-NH- . Moreover, X may be a part of a ring structure, which means that X itself may be a linking group contains a ring or X may form a fused ring with either one of, or both of benzene rings linked to both sides of X with at least one of R³¹ to R³ . Examples of the linking groups in which X itself contains a ring include a fluorene ring, an indanedione ring, an indanone ring, an indene ring, an indane ring, a tetralone ring, an anthrone ring, a cyclohexane ring, a cyclopentane ring, a chroman ring, a 2 , 3-dihydrobenzofuran ring, an indoline ring, a tetrahydropyran ring, a tetrahydrofuran ring, a dioxane ring, etc. Among these, X is preferably an alkylidene group, an oxygen atom, a sulfur atom, a ketone group, an amino group or a sulfonyl group, and particularly preferably is isopropylidene or an oxygen atom.

Furthermore, the structure represented by Formula (3) above is more preferably a structure that is relatively bendable (bendable component) , that is, in the structure of benzene ring-X-benzene ring, it is preferable that X itself does not contain a ring, and, in particular, the structure represented by Formula (3) above such as a p-phenylene group does not form a linear component ( terphenylene linear structure) , from the viewpoint of satisfying both melt-casting properties and low coefficient of linear thermal expansion, and furthermore improving drawing properties and, in particular, breaking elongation .

In Formula (3), bonding positions of two oxygen atom linking groups may be arbitrary in the benzene ring. Of these, linking positions of two oxygen atom linking groups are preferably the 4-site and the 4 '-site of the benzene rings.

Hereinafter, specific examples of structures represented by Formula (3) will be shown, but structures represented by Formula (3) usable in the invention are not limited to these.

(3-22)

Structures derived from divalent carboxylic acids

(Structures represented by Formula (4))

In the polyester resin of the invention, preferably an aromatic diol and a divalent carboxylic acid are linked by an ester bond. No particular limitation is imposed on the divalent carboxylic acid, but preferably the resin of the invention contains at least a structure represented by Formula (4) below, from the viewpoint of lowering the coefficient of linear thermal expansion .

Formula (4)

wherein R each independently represents a substituent; and m represents an integer of 0 to 3.

The range of preferable substituents represented by R⁴¹ is the same as that of preferable substituents represented by R¹¹ to R¹⁸ above.

m represents an integer of 0 to 3, is preferably 0 to 2, more preferably 0 or 1, and particularly preferably 0.

As structures derived from other divalent carboxylic acids, the polyester resin of the invention preferably also has a structure represented by Formula (5) below and/or a structure represented by Formula (6) below, in addition to the structure represented by Formula (4) above, and preferably has either one of the structure represented by Formula (5) below and the structure represented by Formula (6) below.

(Structure represented by Formula (5))

The polyester resin of the invention preferably contains the structure represented by Formula (5) below, from the viewpoint of fine adjustment in such direction as rising Tg, and more improving melt-casting properties.

Formula (5)

wherein R and R each independently represents a substituent; and n and k each independently represents an integer of 0 to 3.

In Formula (5), examples of preferable substituents represented by R⁵¹ and R⁵² include alkyl groups (preferably having 1 to 10 carbon atoms, such as a methyl group, an ethyl group, an isopropyl group, and a tert-butyl group) , halogen atoms (such as a chlorine atom, a bromine atom, and an iodine atom) , aryl groups (preferably having 6 to 20 carbon atoms, such as a phenyl group, a biphenyl group, and a naphthyl group) , alkoxy groups (preferably having 1 to 10 carbon atoms, such as a methoxy group, an ethoxy group, and an isopropoxy group) , acyl groups (preferably having 2 to 10 carbon atoms, such as an acetyl group, a propionyl group, and a butyryl group) , acylamino groups (preferably having 1 to 10 carbon atoms, such as a formylamino group, and an acetylamino group) , a nitro group, a cyano group, etc. More preferable are an alkyl group, a halogen atom, an aryl group, an alkoxy group and a nitro group, particularly preferable are an alkyl group and a halogen atom.

In Formula (5) , a carbonyl group may link with any carbon in the naphthalene ring, and two carbonyl groups may link with one ring. With regard to the linking position of the carbonyl group, preferably one is bonded to the 2-site or the 3-site, and one is bonded to the 6-site or the 7 -site, and more preferably each one is bonded to the 2-site and the 6-site.

n and k each independently represents an integer of 0 to

3, wherein n is preferably an integer of 0 to 2, and k is preferably an integer of 0 to 2.

Hereinafter, specific examples of structures represented by Formula (5) will be shown, but structures represented by Formula (5) usable in the invention are not limited to these.

(Structure represented by Formula (6))

The polyester resin of the invention preferably contains a structure represented by Formula (6).

Formula (6)

In Formula (6) above, R to R each independently represents a hydrogen atom or a substituent. Preferable substituents represented by R to R are the same as preferable substituents represented by R¹¹ to R¹⁸. R⁶¹ to R⁶⁴ are preferably hydrogen atoms. (Other structures)

As structures derived from aromatic diols or divalent carboxylic acids, the polyester resin of the invention may have structures other than structures represented by Formulae (1) to (6) above only if they do not run contrary to the gist of the invention. Meanwhile, in the specification, structures derived from aromatic diols include, for example, the structure represented by Formula (1) above, the structure represented by Formula (2) above, the structure represented by Formula (3) above, etc. In the specification, structures derived from dicarboxylic acids include, for example, the structure represented by Formula (4) above, the structure represented by Formula (5) above, the structure represented by Formula (6) above, etc.

In addition to the ester bond, the resin of the invention may contain therein an ether bond, a carbonate bond, a sulfone bond, a ketone bond, an imide bond, an amide bond, an urethane bond or an urea bond in one kind or in plural kinds. As other structures forming these bonds, there can be cited known structures that are known to be incorporated into a polyester resin, if only they do not run contrary to the gist of the invention .

(Ratio of respective structures in resin)

In the polyester resin of the invention, the aromatic diol component preferably satisfies Expression (A) below from the standpoint of lowering the coefficient of linear thermal expansion .

0.2 < (a + b)/(a + b + c) < 0.9 (A)

In particular, when X is a dimethyl-substituted carbon atom, the range (a + b)/(a + b + c) ( 0.2 tends to make it possible to lower the coefficient of linear thermal expansion, preferably. The lower limit value of (a + b) / (a + b + c) is preferably 0.4 or more, and particularly preferably 0.5 or more .

The upper limit value of (a + b) / (a + b + c) is preferably 0.9 or less, more preferably 0.8 or less, and particularly preferably 0.75 or less, from the viewpoint of transparency and drawing properties.

On the other hand,, such knowledge was obtained empirically that, in the polyester resin of the invention, the relation of the structure derived from a biphenol and structures represented by Formula (4) or (5) (preferably structures derived from terephthalic acid) satisfying Expression (B) below is also preferable from the viewpoint of lowering the coefficient of linear thermal expansion.

A + B + 0.5 x D + 0.5 x E > 80 (B)

wherein A represents the content ratio (unit: % by mol) of structures derived from aromatic diols represented by Formula (1) above relative to the whole structures derived from aromatic diols contained in the polyester resin, B represents the content ratio (unit: % by mol) of structures derived from aromatic diols represented by Formula (2) above relative to the whole structures derived from aromatic diols contained in the polyester resin, D represents the content ratio (unit: %bymol) of structures derived from dicarboxylic acids represented by Formula (4) above relative to the whole structures derived from dicarboxylic acids contained in the polyester resin, and E represents the content ratio (unit: % by mol) of structures having linking positions at the 2-site and the 6-site among structures 'derived from dicarboxylic acids represented by Formula (5) above relative to the whole structures derived from dicarboxylic acids contained in the polyester resin.

Hereinafter, the value on the left side of Expression (B) above, that is, A + B + 0.5 ^χ D + 0.5 ^χ E is also referred to as the amount of linear components.

The meaning of the Expression (B) of the amount of linear components as a numerical expression relates to the coefficient of linear thermal expansion of films obtained by uniaxial drawing .

The value of the amount of linear components, that is, the left side of Expression (B) above is more preferably 80 to 120, and particularly preferably 90 to 120.

In the polyester resin of the invention, the weight of the structure represented by Formula (4) above (preferably a structure derived from terephthalic acid) is preferably greater than the weight of the structure represented by Formula (6) above (preferably a structure derived from isophthalic acid) .

The weight ratio of the structure represented by Formula (4) above and the structure represented by Formula (6) above is preferably 55:45^'to 85:15, more preferably 55:45 to 75:25, and particularly preferably 60:40 to 75:25. When the weight ratio of the structure represented by Formula (4) above and the structure represented by Formula (6) above is 55:45 to 85:15, the coefficient of linear thermal expansion becomes low, preferably .

In particular, when the weight ratio of the structure represented by Formula (4) above and the structure represented by Formula (6) above is 55: 45 or more , the coefficient of linear thermal expansion becomes small, preferably, and when it is 85:15 or less, the melting temperature does not become too high to make the melting easy, and films obtained after the melting hardly tends to become clouded, preferably.

On the other hand, in the polyester resin of the invention, when the weight of the structure represented by Formula (4) above is less than or equal to the weight of the structure represented by Formula (6) above, it is also preferable that the sum of the content ratio of the structure represented by Formula (1) above and the content ratio of the structure represented by Formula (2) above is high.

In the resin of the invention, relative to the whole structures derived from aromatic diols, the content ratio of the structure represented by Formula (1) is preferably 10 to 99% by mol, more preferably 20 to 90% by mol, and particularly preferably 30 to 85% by mol.

In the resin of the invention, relative to the whole structures derived from aromatic diols, the content ratio of the structure represented by Formula (2) is preferably 10 to 99% by mol, more preferably 10 to 80% by mol, and particularly preferably 10 to 60% by mol.

In the resin of the invention, relative to the whole structures derived from aromatic diols, the content ratio of the structure represented by Formula (3) is preferably 10 to 80% by mol, more preferably 10 to 70% by mol, and particularly preferably 15 to 65% by mol.

In the resin of the invention, relative to the whole structures derived from dicarboxylic acids, the content ratio of the structure represented by Formula (4) is preferably 20 to 99% by mol, more preferably 30 to 95% by mol, and particularly preferably 40 to 95% by mol.

In the resin of the invention, relative to the whole structures derived from dicarboxylic acids, the content ratio of the structure represented by Formula (5) is preferably 0 to 90% by mol, more preferably 0 to 70% by mol, and particularly preferably 1 to 50% by mol.

In the resin of the invention, relative to the whole structures derived from dicarboxylic acids, the content ratio of the structure represented by Formula (6) is preferably 0 to 90% by mol, more preferably 0 to 70% by mol, and particularly preferably 1 to 50% by mol.

(Method for producing resin)

The resin of the invention can generally be synthesized using a biphenol derivative, a dicarboxylic acid and/or a derivative thereof as monomers. Moreover, it may be synthesized as a copolymer using, preferably, a bisphenol derivative or the like.

As general methods for synthesizing a biphenol derivative having a substituent, methods described in Macromolecules, 1996, 29, pp 3727-3735, or Sen-i Kagaku Zassi (Journal of Fiber Chemistry) vol. 84, No. 2 (1963) pp 143-145 are cited.

A dicarboxylic acid derivative can be synthesized by a method similar to the method of introducing a substituent into dialkylnaphthalene and oxidizing the alkyl group. Examples of general methods for introducing a substituent into dialkylnaphthalene include methods described in Journal of Organic Chemistry, 2003, 68(22), pp 8373-8378; Heteroatom Chemistry, 2001, 12(4), pp 287-292; Journal of the Chemical Society, Perkin Transactions 1 : Organic and Bio-Organic Chemistry, 1981, (3) pp 746-750; or Journal of the Chemical Society [Section] D: Chemical Communications, (24), p 1487, 1969.

As a general method for oxidizing an alkyl group as a substituent in naphthalene, the method described in Journal of organic Chemistry, 50(22), pp 4211-4218, 1985 is cited.

As a general method for synthesizing polyallylate using the above-mentioned monomer, the method described in Shin Kobunshi Jikken Gaku 3, Kobunshi no Gosei/Hanno (2) (New Course of Polymer Experiment 3, Synthesis/reaction of Polymer (2)), KYORITSU SHUPPAN, (Section 87 to Section 95) is cited. No particular limitation is imposed on the order of adding respective monomers in the synthesis, and all of the monomer components may be added at the same time, or only a biphenol and a bisphenol may be synthesized first and then a dicarboxylic acid derivative may be synthesized.

Moreover, the synthesis may be carried out by a solution polymerization in which a divalent carboxylic acid halide and a divalent phenol are reacted in an organic solvent, or by a melt polycondensation in which a divalent carboxylic acid and a divalent phenol are reacted in the presence of diallyl carbonate or acetic anhydride.

(Specific examples of resins)

Hereinafter, specific examples of the polyester resins of the invention will be shown, but polyester resin usable in the invention are not limited to these. Meanwhile, in P-l to P-9, numerals written at lower right of a parenthesis represent % by mol of respective structures.

f ^^yCO^ fOKy^o s)-

(Characteristics of resins)

The weight average molecular weight of the resin of the invention is preferably 10,000 to 5,000,000, more preferably 15,000 to 1,000,000, and particularly preferably 20,000 to 500, 000.

The resin of the invention is formed as a copolymer, and the copolymerization system thereof may be random copolymerization, block copolymerization, or other polymerization systems.

The glass transition temperature (Tg) of the resin of the invention preferably lies in a range suitable for melt-casting. Specifically, it is preferably 170°C to 270°C, more preferably 180°C to 260°C, and particularly preferably 190°C to 260°C. Tg of the resin of the invention in this range can furthermore enhance the transparency of films to be obtained. Moreover, Tg of 170°C or more can enhance the dimensional stability in carrying out the process of laminating ITO (process with heating) when the resin of the invention is used as an optical film, and enhance the performance of the image display device of the invention.

(Solubility)

The resin of the invention may be subjected to solution casting, and, in such a case, it is soluble preferably in a solvent such as methylene chloride, chloroform or tetrahydrofuran, particularly preferably in methylene chloride having a low boiling point.

The resin of the invention is useful, for example, for optical materials, films of the invention to be described later, etc. Preferable examples of the optical materials include optical films such as a polarizing plate protective film, a retardation film, an antireflection film and an electromagnetic wave-shielding film, a pickup lens, a microlens array, a light guide plate, an optical fiber, an optical waveguide, etc.

Film

(Method for producing film)

The resin of the invention can be used as a film. As methods for producing the film of the invention, the use of a solution casting method or an extrusion molding (melt molding) method is preferable, and the use of the extrusion molding method is more preferable from the standpoint of convenience of equipment.

With regard to casting and drying methods in the solution casting method, there are descriptions in US Patent Nos . 2336310, 2367603, 2492078, 2492977, 2492978, 2607704, 2739069 and 2739070, GB Patent Nos. 640731 and 736892, JP-B 45-4554, JP-B 49-5614, JP-A 60-176834, JP-A 60-203430 and JP-A 62-115035.

With regard to the extrusion molding method, methods known in the field may be employed, and no particular limitation is imposed.

With regard to manufacturing equipment, manufacturing equipment known in the filed may be employed. But, manufacturing equipment employable in the invention is not limited to these.

In the extrusion molding method, although not particularly limited, a resin composition containing the resin of the invention etc. is preferably molded once in a shape of pellets prior to the film formation. When it is molded in a shape of pellets, it is preferable that, firstly, the resin composition is molten and kneaded with a kneader, taken out in a shape of noodle, and cut to thereby prepare the resin composition in a shape of pellets.

In addition to the resin of the invention, the resin composition may contain a stabilizer such as a coloring inhibitor, and other additives that do not function contrary to the gist of the invention.

The temperature of the melt kneading is preferably 250°C to 350°C, more preferably 260°C to 350°C, and particularly preferably 270°C to 340°C.

Next, a film is preferably formed by introducing the pellet-shaped resin composition into a melt extrusion machine, feeding the resin composition to a die disposed at the outlet of the melt extrusion machine, melt extruding the resin composition from the die, extruding the same onto cast rolls, and then stripping off the cast material.

No particular limitation is imposed on the melt extrusion machine, and known melt extrusion machines may be used, including, for example, a melt extrusion machine . Among these, a twin screw extrusion machine is preferable. No particular limitation is imposed on the shape of the die, and known dies are usable, including a T die, a hanger coat die, etc. The use of the hanger coat die is preferable. The temperature of the resin composition in the melt extrusion machine is preferably 250°C to 350°C, more preferably 260°C to 350°C, and particularly preferably 270°C to 340°C. -

No particular limitation is imposed on the time of melt kneading.

No particular limitation is imposed on the casting roll, and known casting rolls may be used. The temperature of the casting roll is not particularly limited.

The film of the invention can also be drawn. As the drawing method, known methods are usable. The drawing can be carried out by a roll uniaxial drawing method, a tenter uniaxial drawing method, a simultaneous biaxial drawing method, a sequential biaxial drawing method, an inflation method, or a rolling method, described, for example, in JP-A 62-115035, JP-A 4-152125, JP-A 4-284211, JP-A 4-298310 or JP-A 11-48271. Hereinafter, the drawing will be explained while taking a drawing method that uses a tenter as an example.

The drawing of films is carried out under the condition of ordinary temperature or with heating. Films may be drawn either by a uniaxial drawing or a biaxial drawing, but the biaxial drawing is preferable. Films can be drawn by a treatment in drying, which is particularly effective when the solvent remains. For example, by adjusting the speed of convey rollers of a film so that the winding speed of the film becomes larger than the stripping speed of the film, the film is drawn. A film can also be drawn by conveying it while holding the both ends in the width direction with a tenter and enlarging gradually the interval of the tenter. Moreover, it is also possible to draw a film after the drying using a drawing machine (preferably a uniaxial drawing using a long drawing machine) . The draw ratio of a film (ratio of an increased length relative to the original length) is preferably 0.5 to 300%, more preferably 1 to 200%, and particularly preferably 1 to 100%.

The drawing rate is preferably 5 %/min to 1000 %/min, and more preferably 10 %/min to 500 %/min. The drawing is preferably carried out by a heat roll or/and radiant heat source (such as an IR heater), or warm air. Moreover, in order to enhance the evenness of temperatures, a constant-temperature bath may be provided.

On the basis of glass transition temperature of the resin of the invention, the drawing temperature is preferably (Tg - 100°C) to (Tg + 25°C) , more preferably (Tg - 80°C) to (Tg + 20°C) , and particularly preferably (Tg - 70°C) to (Tg + 15°C) .

The film of the invention may be heat-treated after the drawing. On the basis of the glass transition temperature Tg, the heat treatment temperature is preferably (Tg - 100°C) to (Tg + 25°C), more preferably (Tg - 80°C) to (Tg + 20°C) , and particularly preferably (Tg - 70°C) to (Tg + 15°C) . The heat treatment can relax the contraction stress by the drawing, and reduce the contraction in heating.

(Physical properties of film)

The film of the invention preferably shows the maximum point in the change of the length measured by thermomechanical analysis at the glass transition temperature (Tg) or more. Here, the thermomechanical analysis means an analytical method defined in JIS K7197. And, "shows the maximum point in the change of the length measured by thermomechanical analysis" means a behavior in the case where the length contracts, and then expands, and again contracts.

The film of the invention preferably has a light transmittance of 50% or more at 400 nm in terms of the thickness of 100 μπι. The light transmittance in this range gives such advantage that a material closely contacted to the film can be seen through the film. The light transmittance is more preferably 70 to 100%, furthermore preferably 75% to 100%, and particularly preferably 80 to 100%.

In the film of the invention, the coefficient of linear thermal expansion (CTE) is preferably 40 ppm/K or less, more preferably 30 ppm/K or less, furthermore preferably 20 ppm/K or less, and particularly preferably 15 ppm/K or less, in any portion in the plane. The CTE of 40 ppm/K or less gives such advantage that, when an inorganic thin film is laminated over the film, the generation of cracks and the warp of the film caused by the difference in expansion rates can be suppressed in heating .

The coefficient of linear thermal expansion in the invention is a value defined in the temperature range of 25°C to (Tg - 30°C) .

The coefficient of linear thermal expansion of the film of the invention is preferably the value as described above, and is preferably the value as described above in both temperature-rise process and temperature-fall process. Moreover, the difference between the CET in the temperature-rise process and the CTE in the temperature-fall process is preferably 20 ppm/K or less, more preferably 10 ppm/K or less, and particularly preferably 5 ppm/K or less. The difference between the CET in the temperature-rise process and the CTE in the temperature-fall process that is 20 ppm/K or less gives such advantage that the deformation magnitude is small before and after the heat treatment of the temperature-rise or the temperature-fall.

(Breaking elongation)

The film of the invention preferably has a breaking elongation of 10% or more, from the viewpoint of drawing properties. The breaking elongation is more preferably 15% or more, and particularly preferably 20% or more.

(Functional layer)

The film of the invention may have another layer on the surface thereof corresponding to the application. Or, for the purpose of enhancing the adherence with another part, the surface of the film may be subjected to such treatment as saponification, a corona treatment, a flame treatment or a glow discharge treatment. Furthermore, the surface of the film may be provided with an anchor layer.

-Gas barrier layer- In order to suppress a gas permeability, the film of the invention may also be laminated with a gas barrier layer on at least one side. Examples of preferable gas barrier layers include films formed from a metal oxide of one kind or two or more kinds of metals selected from the group consisting of silicon, aluminum, magnesium, zinc, zirconium, titanium, yttrium and tantalum as a main component, a metal nitride of silicon, aluminum and boron, or a mixture thereof . Among these, favorable is a film formed from a metal oxide containing a silicon oxide having an oxygen atom number relative to a silicon atom number in such a ratio as 1.5 to 2.0 as a main component, from the viewpoint of gas barrier properties, transparency, surface flatness, bending properties, film stress, cost, etc. These gas barrier layers constituted of an inorganic compound can be produced by a gas phase deposition method in which the material is deposited from a gas phase to thereby form a film, including, for example, a sputtering method, a vacuum evaporation method, an ion plating method, a plasma CVD method, a Cat-CVD method, etc. Among these, preferable are the sputtering method and the Cat-CVD method capable of giving particularly superior gas barrier properties. In providing the gas barrier layer, the temperature may be raised to 50°C to 250°C.

The thickness of the gas barrier layer is preferably 10 to 300 nm, and more preferably 30 to 200 nm.

The gas barrier layer may be provided on either the same side or the opposite side of a transparent electroconductive layer to be described later.

With regard to the gas barrier performance of the film of the invention, a water vapor permeability measured at 40°C and relative humidity 90% is preferably 0 to 5 g/m²*day, more preferably 0 to 3 g/m²*day, and furthermore preferably 0 to 2 g/m²«day. An oxygen permeability measured at 40°C and relative humidity 90% is preferably 0 to 1 ml/m²«day«atm (0 to 1 * 10⁵ ml/m²«day«Pa) , more preferably 0 to 0.7 ml/m²«day*atm (0 to 0.7 x 10⁵ ml/m²«day»Pa) , and furthermore preferably 0 to 0.5 ml/m²»day»atm (0 to 0.5 * 10⁵ ml /m²«day«Pa ) . For example, when the film is used for organic EL display devices or liquid crystal display devices, the gas barrier performance in the range above can substantially eliminate the deterioration of EL elements due to water vapor and oxygen, preferably.

For the purpose of improving the gas barrier performance, a defect compensation layer is preferably formed adjacent to the gas barrier layer. As the defect compensation layer, for example, (1) an inorganic oxide layer produced by using a sol-gel method as described in US Patent No. 6171663 or JP-A 2003-94572, or (2) an organic material layer as described in US Patent No. 6413645, can be employed. These defect compensation layers can be formed by a method in which the raw material is evaporated under vacuum and then cured by ultraviolet ray or electron beam, or by a method in which the raw material is coated, and then cured by heating, electron beam, ultraviolet ray etc. When the defect compensation layer is formed by a coating system, conventional various coating methods can be employed, including, for example, a spray coat method, a spin coat method, a bar coat method, etc.

For the purpose of giving chemical resistance, the film of the invention may be provided with an inorganic barrier layer, an organic barrier layer, an organic-inorganic hybrid layer, or the like. -Transparent electroconductive layer-

The film of the invention may be laminate with a transparent electroconductive layer on at least one side thereof. As the transparent electroconductive layer, a known metal film, metal oxide film, or the like may be applied. Among these, preferable is the use of a metal oxide film excellent in transparency, electroconducti ity and mechanical properties as the transparent electroconductive layer. Examples of the metal oxide films include films of metal oxide such as indium oxide, cadmium oxide and tin oxide into which tin, tellurium, cadmium, molybdenum, tungsten, fluorine, zinc or germanium is added as an impurity; and films of metal oxide such as zinc oxide and titanium oxide into which aluminum is added as an impurity. Among these, a thin film of indium oxide mainly consisting of tin oxide and containing zinc oxide in 2 to 15% by mass is excellent in transparency and electroconductivity, and is used preferably.

Any method may be usable as a method for forming the transparent electroconductive layer, only if the method can form the intended film. For example, suitable methods include a vapor phase deposition method for forming a film by depositing a material or materials from a vapor phase, etc. such as a sputtering method, a vacuum evaporation method, an ion plating method, a plasma CVD method, and a Cat-CVD method. The film can be formed by methods described in Japanese Patent No. 3400324, JP-A 2002-322561 or JP-A 2002-361774. Among these, the sputtering method is preferable from the viewpoint of capable of obtaining particularly excellent electroconductivity and transparency.

The degree of vacuum in the sputtering method, the vacuum evaporation method, the ion plating method, or the plasma CVD method is preferably 0.133 mPa to 6.65 Pa, and more preferably 0.665 mPa to 1.33 Pa . Prior to the formation of the transparent electroconductive layer, the base film is preferably subjected to such surface treatment as a plasma treatment (inverse sputtering) or a corona treatment. The temperature may be raised to 50°C to 200°C in the process of providing the transparent electroconductive layer.

The thickness of the transparent electroconductive layer thus obtained is preferably 20 to 500 nm, and more preferably 50 to 300 nm.

The surface electric resistance of the transparent electroconductive layer measured at 25°C and relative humidity 60% is preferably 0.1 to 200 Ω/D, more preferably 0.1 to 100 Ω/D, and furthermore preferably 0.5 to 60 Ω/D. The light transmittance of the transparent electroconductive layer is ■ preferably 80% or more, more preferably 83% or more, furthermore preferably 85% or more.

Image display device

The film of the invention as explained above can be used for image display devices. The kind of image display devices is not particularly limited, and includes conventionally known devices. The film of the invention can be used as a substrate for producing flat panel display devices excellent in display quality. Examples of the flat panel display devices include those that utilize liquid crystal, plasma, organic electroluminescence (EL) , inorganic electroluminescence, fluorescent display tube, light-emitting diode, field emission type, etc. In addition to these, the film can be used as the substrate replacing a glass substrate conventionally used in display systems using a glass substrate. Furthermore, the film of the invention is applicable to such applications as solar cells and touch panels, in addition to flat panel display devices. It can be applied, for example, to touch panels described in JP-A 5-127822, JP-A 2002-48913 or the like.

Over the film of the invention, a thin film transistor (TFT) can be formed. TFT can be formed by known methods as disclosed in JP-A 11-102867, JP-T 10-512104 or JP-A 2001-68681. Furthermore, these substrates may have color filters for color display. The color filter may be formed by any method, and the formation by means of photolithography is preferable.

The TFT to be formed in the invention may be an amorphous silicon TFT, or a polycrystalline silicon TFT. For the polycrstallization of amorphous silicon, preferably used is an annealing method by laser exposure.

As a method for forming a silicon film of the semiconductor layer of TFT, a sputtering method, a plasma CVD method, an ICP-CVD method, and a Cat-CVD method are cited, and preferable is the sputtering method. The formation by the sputtering method can reduce the concentration of hydrogen in the silicon thin film and prevent the detachment of the silicon layer due to the laser exposure for polycristalization .

Over the film of the invention, the plasma CVD can form a pure silicon thin film, an impurity-containing silicon thin film, a silicon nitride thin film, a silicon oxide thin film, etc. The substrate temperature on this occasion is preferably 250°C or less.

For pixel electrodes, ITO or IZO can be formed by the sputtering method. The temperature of heat treatment for lowering the resistivity is preferably 250°C or less.

TFT formed in the invention may have any structure such as a channel etching type, an etching stopper type, a top gate type or a bottom gate type.

When the film of the invention is used as a substrate for such application as liquid crystal display devices, in order to attain optical uniformity, the resin composition constituting the film is preferably in an amorphous polymer state. Furthermore, for the purpose of controlling the retardation (Re) and the wavelength dispersion thereof, it is possible to combine a resin that is different in the sign of intrinsic birefringence, or to combine a resin having larger (or smaller) wavelength dispersion.

From the viewpoint of controlling the retardation (Re), or improving a gas permeability or mechanical properties, the film of the invention is preferably combined and laminated etc. with a different kind of resin composition. No particular limitation is imposed on the combination of a different kind of resin composition, and any of aforementioned resin compositions is usable.

Liquid crystal display devices of a reflective mode generally have such constitution, in the order from the bottom, as a lower substrate, a reflective electrode, a lower alignment film, a liquid crystal layer, an upper alignment film, a transparent electrode, an upper substrate, a λ/4 plate, and a polarizing film. Of these, the film of the invention can be used as the transparent electrode and/or the upper substrate. In the case of color display, preferably a color filter layer is furthermore formed between the reflective electrode and the lower alignment film, or between the upper alignment film and the transparent electrode.

Liquid crystal display devices of a transmissive mode generally have such constitution, from the bottom in the order, as a backlight, a polarizing plate, a λ/4 plate, a lower transparent electrode, a lower alignment film, a liquid crystal layer, an upper alignment film, an upper transparent electrode, an upper substrate, aλ/4plate, and a polarizing film. Of these, the film of the invention can be used as the upper transparent electrode and/or the upper substrate. In the case of color display, preferably a color filter layer is furthermore arranged between the lower transparent electrode and the lower alignment film, or between the upper alignment film and the transparent electrode.

No particular limitation is imposed on the kind of liquid crystal layers (liquid crystal cells), and various display modes are proposed, such as TN (Twisted Nematic) , IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-ferroelectric Liquid Crystal), OCB (Optically Compensated Bend) , STN ( Super Twisted Nematic) , VA (Vertically Aligned) , and HAN (Hybrid Aligned Nematic) . Moreover, a display mode obtained by orientation-dividing the above-described display mode is proposed. The film of the invention is also used effectively for liquid crystal display devices of such display modes. It is effectively used for any liquid crystal display device of a transmissive mode, reflective mode or semi-transmissive mode.

Liquid crystal cells and liquid crystal display devices are described in JP-A 2-176625, JP-B 7-69536, MVA (SID97, Digest of tech. Papers (Preprint) 28 (1997) 845), SID99, Digest of tech . Papers (Preprint) 30 (1999) 206), JP-A 11-258605, SURVAIVAL (Monthly DISPLAY, Vol. 6, No. 3 (1999) 14), PVA (Asia Display 98, Proc. of the-18th-Inter . Display res. Conf. (Preprint) (1998) 383),^' Para-A (LCD/PDP International 99), DDVA (SID98, Digest of tech. Papers (Preprint) 29 (1998) 838), EOC (SID98, Digest of tech. Papers (Preprint) 29 (1998) 319), PSHA (SID98, Digest of tech. Papers (Preprint) 29 (1998) 1081), RFFMH (Asia Display 98, Proc. of the-18th-Inter . Displayres. Conf. (Preprint) (1998) 375), HMD (SID98, Digest of tech. Papers (Preprint) 29 (1998) 702), JP-A 10-123478, WO 98/48320, Japanese Patent No. 3022477, and WO 00/65384, etc.

The film of the invention can favorably used for an organic EL display application. Specific layer constitutions of organic EL display devices include anode/light-emitting layer/transparent cathode, anode/light-emitting layer/electron-transporting layer/transparent cathode, anode/hole-transporting layer/light-emitting layer/electron-transporting layer/transparent cathode, anode/hole-transporting layer/light-emitting layer/transparent cathode, anode/light-emitting layer/electron-transporting 1ayer/electron-in ecting layer/transparent cathode, anode/hole-injecting layer/hole-transporting layer/light-emitting layer/electron-transporting layer/electron-inj ecting layer/transparent cathode, etc.

Organic EL display devices capable of using the film of the invention can give light emission by applying a direct current (an alternating current component may be contained if necessary) voltage (ordinary 2 to 40 V) , or a direct current between the anode and the cathode. For driving these light emitting elements, for example, methods described in JP-A 2-148687, JP-A 6-301355, JP-A 5-29080, JP-A 7-134558, JP-A 8-234685, JP-A 8-241047, US Patent Nos . 5828429 and 6023308, Japanese Patent No. 2784615, or the like can be utilized.

For full color display, organic EL display devices may use any of a color filter system, a three-color independent luminescence system, a color conversion system, etc.

Liquid crystal display devices and organic EL display devices may be driven either a passive matrix system or an active matrix system.

The film of the invention can be used as optical films, retardation films, polarizing plate-protecting films, transparent electroconductive films, substrates for display devices, substrates for flexible displays, substrates for flat panel displays, substrates for solar cells, substrates for touch panels, substrates for flexible circuits, optical disc-protecting films, etc.

Examples

Hereinafter, the feature of the present invention will be explained more specifically with the citation of Examples. The material, usage amount, percentage, treatment content, treatment procedure etc. shown in Examples below can appropriately changed only if the change does not cause the deviation from the gist of the invention. Accordingly, the scope of the invention should not be construed in a limited way by specific examples shown below.

(Synthesis of polymer)

-Synthesis of exemplified compound P-l-

Into a 300 ml three-neck flask provided with a stirrer, 10.56 g of 3, 3' , 5, 5' -tetramethyl-4 , 4' -bishydroxybiphenyl, 4.68 g of 3, 3' -dimethyl-4 , 4 ' -bishydroxybiphenyl, 9.96 g of bisphenol A, 360 mg of sodium hydrosulfite, 1600 mg of tetra-n-butylammonium chloride, 390 ml of methylene chloride, and 450 ml of distilled water were thrown, which were stirred and dissolved under nitrogen flow. To the solution, a solution of 17.8 g of terephthaloyl chloride and 5.36 g of 2 , 6-naphthalene dicarboxylic acid chloride dissolved in 180 ml of methylene chloride was added.

Furthermore, a mixed liquid of 114 ml of a 2 mol/L aqueous sodium hydroxide solution and 30 ml of water was dropped at 15°C to 20°C over 1 hr. After the dropping, the liquid was stirred for 3 hr, and then the reaction liquid was removed to a 3-litter three-neck flask, to which 1.8 ml of acetic acid and 1800 ml of ethyl acetate were added slowly. After filtering, obtained polymer powders were washed sequentially with 1 L of ethyl acetate, 1 L of water, and 1 L of methanol and dried, thereby giving 36.4 g of the exemplified compound P-l.

As the result of GPC (THF solvent; in terms of polystyrene,

HLC-8120GPC manufactured by Tosoh Corporation) measurement, the weight average molecular weight was 105000. The obtained polymer was dissolved in methylene chloride and flow-cast over a glass plate, and then dried, thereby giving a film having a thickness of 100 μπι. For the film, the glass transition temperature was measured using TMA8310 (Thermo Plus series, manufactured by Rigaku Corporation), which was 257°C.

-Synthesis of exemplified compounds P-2 to P-9, comparative polymer 2-

The procedure in the synthesis of exemplified compound P-1 was repeated except that the component and/or weight thereof was changed, thereby giving the aforementioned exemplified compounds and the comparative polymer having the structure to be described later. Respective polyester resins obtained had glass transition temperatures as listed in Table 1 below. Meanwhile, a structure derived from isophthalic acid was introduced using isophthaloyl chloride.

-Synthesis of comparative polymer 1-

As a comparative polymer 1, a polymer having a structure described below, which is described in JP-A 58-180525 Example 8, was synthesized.

-Synthesis of comparative polymers 3 to 7-

As comparative polymers 3 to 7, polymers having structures described below respectively, which are described in JP-A 10-17658 Example 5, 8, 6, 10 or 3, were synthesized. Meanwhile, in comparative example polymers 3, 4, 6 and 7, the structure represented by Formula (2) in the specification is a structure derived from a bisphenol C skeleton.

Comparative polymer 1

Comparative polymer 2

Comparative polymer 3

Comparative polymer 4

Comparative polymer 5

Comparative polymer 6

Comparative polymer 7

Formation of film

Example 1

(Formation, drawing and heat treatment of film)

The exemplified compound P-1 was kneaded with a small scale kneading machine (trade name: MiniLab, manufactured by Haake) having a preset temperature of 350°C for 10 min, which was taken out in a noodle shape and cut with a nipper, thereby giving a resin composition in a pellet shape.

The resin composition in a pellet shape thus formed was melt-extruded from a hanger die using a twin screw melt extrusion machine having temperatures adjusted from 280°C (inlet temperature) to 330°C (outlet temperature), which was extruded over a casting roll having a preset temperature of 120°C and then stripped off, thereby forming a film.

The film was cut out in a size of 120 mm x 120 mm, which was drawn by a simultaneous two-axis drawing machine. The drawing condition in a first stage was set as follows: interval between chucks 100 mm (both longitudinally and laterally) , resin temperature 250°C, draw rate 100 mm/min, draw length 40 mm (draw ratio 40% both longitudinally and laterally) . After the drawing, the film was heated to 240°C in a state held in the two-axis drawing machine until the stress became approximately constant. After that, the film was cooled down to a temperature of 100°C or less, which was taken out of the two-axis drawing machine. The drawn film was set to a metal square frame having inner sides of 120 mm, which was heat-treated under nitrogen atmosphere at 230°C for 24 hr, thereby giving a drawn film of Example 1.

Examples 2 to 9, Comparative Examples 1 to 7

The operation in Example 1 was repeated except that exemplified compounds P-2 to P-9 and comparative polymers 1 to 7, respectively, were used, thereby forming two-axis drawn films. Meanwhile, Comparative Example 1 had a high Tg to make the melt-casting difficult , and, therefore, a film was obtained by melt press film forming. However, the film showed a poor breaking elongation and a drawn film could not be formed.

Tg of respective film samples were measured at a temperature rising rate of 10 °C/min in nitrogen using a differential scanning calorimeter (DSC6200, manufactured by Seiko) . <Coefficient of linear thermal expansion>

A film sample (19 mm ^χ 5 mm) was formed and TMA (TMA8310, manufactured by Rigaku Corporation) was used for the measurement. The measurement rate was set to be 3 °C/min. Three samples were measured, and the average thereof was used. The measurement was carried out in the temperature range of 25°C to 300°C, and the coefficient of linear thermal expansion was calculated in the range of 25°C to 200°C in temperature rising. But, for samples having a glass transition temperature of 200°C or less, it was calculated in the temperature range of 25°C to 150°C.

Films thus obtained were visually observed, and the decision below was carried out for evaluating the transparency.

O: transparency is good, and the light transmittance at

400 nm is 70% or more in terms of the thickness of 100 μπι X: white turbidity is remarkable and heterogeneous

The weight average molecular weight was obtained while comparing with a polystyrene molecular weight standard product by GPC measurement in terms of polystyrene using N-methyl pyrrolidone as a solvent, using "HLC-8120GPC" manufactured by Tosoh Corporation.

The film thus obtained was dissolve in methylene chloride so as to give the concentration of 5% by mass, and the decision below was carried out for evaluating solubility. O: completely dissolved and transparent X: insoluble or cloudy

Obtained results are given in Table 1.

Table 1

As shown in Table 1, it was known that films in Examples 1 to 9 had Tg lying in a range that is suitable for melt-casting, dimensional stability lying in a range that does not deteriorate in a heating process when ITO is to be laminated, show a small value of the coefficient of linear thermal expansion, and have high transparency and good solubility in methylene chloride.

Comparative Example 1 was contrasted with Example 2, and the film in Comparative Example 1 that used a resin containing only the structure shown by Formula (1) above as the structure derived from aromatic diol had high Tg and could not be melt-cast, and, in addition, had a poor solubility in methylene chloride. In contrast, it was known that the film in Example 2 that used the resin containing both the structure shown by Formula (1) above as the case for Comparative Example 1 and the structure shown by Formula (2) above as the structure derived from an aromatic diol could lower Tg to a range suitable for the melt-casting and, furthermore, improve the solubility in methylene chloride.

Comparative Examples 2 and 3 were contrasted with Example 8 and each had a structure derived from terephthalic acid and a structure derived from isophthalic acid in 50 : 50 (molar ratio) as the structure derived from dicarboxylic acid. Moreover, each had the structure shown by Formula (3) above in 50% by mol as the structure derived from the aromatic diol. With regard to the remaining 50% by mol of the structure derived from an aromatic diol, Comparative Example 2 used a single system of 50% by mol of the structure shown by Formula (1) above, which showed such comparatively high coefficient of linear thermal expansion as 42 ppm/K. With regard to the remaining 50% by mol of the structure derived from an aromatic diol, Comparative Example 3 used a single system of 50% by mol of the structure shown by Formula (2) above, which showed such comparatively high coefficient of linear thermal expansion as 41 ppm/K in the same manner as in Comparative Example 2. In contrast, Example 8 used a combined system of the structure shown by Formula (1) above in 30% by mol and the structure shown by Formula (2) above in 20% by mol, which could lower the coefficient of linear thermal expansion down to 32 ppm/k that largely fell below the average value of Comparative Examples 2 and 3.

Moreover, it was known that films in Examples had improved properties as compared with films in Comparative Examples 3 to 7 that used polymers described in Examples 5, 8, 6, 10 and 3, respectively, of JP-A 10-17658. Specifically, it was possible to lower largely the value of the coefficient of linear thermal expansion, and to raise the glass transition temperature, thereby giving a high heat resistance.

Examples 101 to 109, Comparative Examples 102 to 107

1. Formation of gas barrier layer

Both sides of films in Examples 1 to 9 and Comparative Examples 2 to 7 were subjected to sputtering by a DC magnetron sputtering method, using Si0₂ as a target under an Ar atmosphere in a vacuum of 500 Pa with an output power of 5 kW, thereby giving films with a gas barrier layer of Examples 101 to 109, and Comparative Examples 102 to 107, respectively. The obtained gas barrier layer had a thickness of 60 nm. The moisture permeability at 40°C and relative humidity 90% was 0.1 g/m²*day or less.

Examples 201 to 209 and Comparative Examples 202 to 207 2. Formation of transparent electroconductive layer

To one side of films provided with the gas barrier layer in Examples 101 to 109 and Comparative Examples 102 to 107, a transparent electroconductive layer constituted of an ITO film having a thickness of 140 nm was provided by the DC magnetron sputtering method using ITO (ln₂0₃95% by mass, Sn0₂ 5% by mass) as the target under an Ar atmosphere in a vacuum of 0.665 Pa with an output power of 5 kW with heating to 100°C, thereby giving films of Examples 201 to 209 and Comparative Examples 202 to 207, respectively. Each of films in Examples 201 to 209 and Comparative Examples 202 to 207 had a moisture permeability of 0.1 g/m²«day or less at 40°C and relative humidity 90%, and had an oxygen permeability of 0.1 ml/m²»day«atm or less at 40°C and relative humidity 90%. Each of ITO layers had a surface electric resistance of 30 Ω/D at 25°C and relative humidity 60%.

The change of gas barrier properties, or the change of gas barrier properties and surface electric resistance were measured for films in Examples 101 to 109 and Comparative Examples 102 to 107 provided with the gas barrier layer, and for films in Examples 201 to 209 and Comparative Examples 202 to 207 provided with the gas barrier film and the transparent electroconductive layer before and after a heat treatment to obtain the change thereof.

The_, heat treatment was carried out under such conditions as under nitrogen, temperature rise from room temperature to 160°C, retainment at 160°C for 2 hr, and cooling to room temperature .

Before and after the heat treatment, films of the invention in Examples 101 to 109 and 201 to 209 showed no change of both gas barrier properties and surface electric resistance, but films in Comparative Examples 102 to 107 and 202 to 207 showed deterioration of both properties . This is caused by the reduced difference of expansions of films of the invention between the inorganic layer due to a small coefficient of linear thermal expansion.

Examples 301 to 309 and Comparative Examples 302 to 307 <Formation and evaluation of organic EL element>

Films of the invention in Examples 201 to 209, and films in Comparative Examples 202 to 207 provided with the transparent electroconductive layer were used, respectively, for forming organic EL element samples.

To the transparent electrode layer of films in Examples 201 to 209 and Comparative Examples 202 to 207 for which the transparent electroconductive layer had been formed as described above, a lead wire of aluminum was connected, thereby forming a laminated structure. Over the surface of the transparent electrode, an aqueous dispersion liquid of polyethylenedioxy thiophene/polystyrene sulfonic acid (Baytron P: solid content 1.3% by mass, manufactured by BAYER) was spin-coated, which was dried in vacuum at 150°C for 2 hr, thereby forming a hole-transporting organic thin layer having a thickness of 100 nm. The product was denoted by X.

On the other hand, over one surface of a temporary substrate constituted of polyether sulfone having a thickness of 188 μπι (SUMILITE FS-1300, manufactured by Sumitomo Bakelite Co., Ltd.), a coating liquid for a luminescent organic thin layer was coated using a spin coater and dried at room temperature, thereby forming a luminescent organic thin layer having a thickness of 13 nm over the temporary substrate. The product was denoted by a transfer material Y.

(Composition)

· Polyvinyl carbazole (Mw = 63000, manufactured by Aldrich) : 40 parts by mass

• Tris (2-phenylpyridine) iridium complex (ortho-metalated complex) : 1 part by mass

• Dichloroethane : 3200 parts by mass

The luminescent organic thin layer side of the transfer material Y was overlapped on the upper surface of the organic thin layer of the substrate X, which was heated and pressed with a pair of heat rollers at 160°C, 0.3 MPa and 0.05 m/min, and the temporary substrate was stripped off to thereby form a luminescent organic thin layer over the upper surface of the substrate X. The product was denoted by XY .

On one surface of a polyimide film having a thickness of

50 um (UPILEX-50S, manufactured by Ube Industries, Ltd.) cut out in 25 mm square, a patterned mask for evaporation (mask for giving a luminescent area of 5 mm * 5 mm) was arranged, and Al was evaporated in a reduced pressure atmosphere of about 0.1 mPa, thereby forming an electrode having a thickness of 0.3 μπι. AI₂O₃ was deposited in a thickness of 3 nm in the same pattern as the Al layer by DC magnetron sputtering using an A1₂0₃ target. To the Al electrode, a lead wire of aluminum was connected, thereby forming a laminated structure. Over the obtained laminated structure, a coating liquid for an electron-transporting organic thin layer having a composition shown below was coated with a spin coater, which was vacuum-dried at 80°C for 2 hr, thereby forming an electron-transporting organic thin layer having a thickness of 15 nm. The product was denoted by Z. (Composition)

• Polyvinyl butyral 2000L (Mw = 2000, manufactured by Denki Kagaku Kogyo K.K.): 10 parts by mass

• 1-butanol: 3500 parts by mass

• Electron-transporting compound having a structure shown below: 20 parts by mass

Electron-transporting compound The substrate XY and the substrate Z were overlapped so that electrodes faced to each other with the luminescent organic layer arranged between the electrodes, which was heated and pressed to be laminated using a pair of heat rollers at 160°C and0.3MPa, and 0.05 m/min, thereby giving an organic EL element sample .

To the obtained organic EL element sample, a direct current was applied using a source measure unit Model 2400 (manufactured by Toyo Tec Co., Ltd). It was confirmed that samples formed by using films of the invention in Examples 201 to 209 produced luminescence . On the other hand, samples formed by using films in Comparative Examples 202 to 207 produced luminescence for a moment, but stopped the luminescence immediately .

This is resulted from that the films of the invention in

Examples 201 to 209 have a small coefficient of linear thermal expansion not to generate cracks in the inorganic layer by heating in the process for forming the samples, but that films in Comparative Examples 202 to 207 have a large coefficient of linear thermal expansion to generate cracks in the inorganic layer by the heating.

The resin of the invention has a glass transition temperature appropriate when carrying out effective melt-casting, a low coefficient of linear thermal expansion, a high transparency, and a good solubility in methylene chloride . Moreover, the film using the resin shows a small coefficient of linear thermal expansion, and, therefore, it can be used as the gas barrier film, the transparent electrode, and the substrate for image display devices.

Claims

1. A polyester resin containing a structure represented by Formula (1) below and a structure represented by Formula (2) below:

wherein R¹¹ to R¹⁴ each independently represents a hydrogen atom or a substituent, and R¹⁵ to R¹⁸ each independently represents a substituent,

wherein R²¹ to R²⁶ each independently represents a hydrogen atom or a substituent, and at least one of R²¹ to R²⁶ represents a substituent .

2. The polyester resin according to Claim 1, wherein R¹⁵ to R¹⁸ in Formula (1) each independently is a halogen atom, an alkyl group, an aryl group or an alkoxy group.

3. The polyester resin according to Claim 1, wherein R¹⁵ to R¹⁸ in Formula (1) each independently is a fluorine atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group or a methoxy group.

4. The polyester resin according to any one of Claims 1 to 3, wherein R²¹ to R²⁶ in Formula (2) each independently is a hydrogen atom, a halogen atom, an alkyl group, an aryl group or an alkoxy group.

5. The polyester resin according to any one of Claims 1 to 3, wherein R²¹ to R²⁶ in Formula (2) each independently is a hydrogen atom, a fluorine atom, a bromine atom, a chlorine atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group or a methoxy group.

6. The polyester resin according to any one of Claims 1 to 5, containing a structure represented by Formula (3) below:

7. The polyester resin according to Claim 6, satisfying

Expression (A) below:

0.2 < (a + b)/(a + b + c) < 0.9 (A)

wherein a represents the content ratio (unit: % by mol) of the structure represented by Formula (1) in the polyester resin; b represents the content ratio (unit: % by mol) of the structure represented by Formula (2) in the polyester resin; and c represents the content ratio (unit: % by mol) of the structure represented by Formula (3) in the polyester resin.

8. The polyester resin according to any one of Claims 1 to 7, containing a structure represented by Formula (4) below: Formula (4)

9. The polyester resin according to any one of Claims 1 to 8, containing a structure represented by Formula (5-) below: Formula (5)

10. The polyester resin according to any one of Claims

1 to 9, wherein Tg is 170°C to 270°C.

11. An optical material produced by the polyester resin of any one of Claims 1 to 10.

12. A film produced by the polyester resin of any one of Claims 1 to 10.

13. The film according to Claim 12, wherein a coefficient of linear thermal expansion is 40 ppm/K or less.

14. The film according to Claim 12 or 13, wherein a gas barrier layer is provided.

15. The film according to any one of Claims 12 to 14, wherein a transparent electroconductive layer is provided.

16. An image display device using at least one film of any one of Claims 12 to 15.