DE4447760C2 - Color layer composition for a chromia display and its use - Google Patents

Description

The present invention relates to a color layer together setting for a chromia display and its use. For example, the composition can be used in one Color layer formation process for the formation of a reduction color layer of an electrochromic (EC) display device.

As shown in FIG. 1, a conventional chromia display, for example an EC display, comprises a first, transparent layer support 1 , a first electrode layer 2 , a reduction color layer 3 , an electrolyte layer 4 , an oxidation color layer 5 , a second, transparent electrodes layer 6 and a second, transparent layer support 7 , the layers being successively laminated. In this EC display, when a current higher than a predetermined limit value is applied between the first electrode layer 2 and the second electrode layer 6 , oxidation and reduction reactions take place in the vicinity of the interfaces between the first electrode layer 2 and the reduction color layer 3 and between the second electrode layer 6 and the oxidation color layer 5 , so that a reversible change in dye-bleaching is obtained.

Tungsten oxide (WO ₃ ) can be used in the EC display for the reduction color layer 3 . Conventional methods for forming the reducing color layer 3 containing WO ₃ include ordinary drying methods such as a sputtering method and an evaporation method, a spin coating method for forming a film using a peroxotungstic acid solution as described in "Applied Physics "No. 61, Vol. 3 (1992) (pp. 226-269), and a dip coating method for forming a film using the same peroxotungstic acid solution. Other known methods for forming the reduction color layer in the EC display include methods using a solution containing an organic W compound as disclosed in Japanese Patent Laid-Open Nos. 56-38379, 61-36292, 61-123691 and 62-112132.

In the publication by CG Grangvist, "Thin Solid Films" 193/194 (1990), pp. 730-441, chapter 4 describes the schematic structure of an EC display. It is said that the optical properties change when the electro-chrome material, such as. B. WO ₃ , with ions, e.g. B. H ⁺ , Li ⁺ , reacted from an electrolyte (IC, IS). Electrochromic systems described further are based on NiO _x H _y and Li _y V ₂ O ₅ . Chapter 5 of this reference also deals with thermochromic coatings based on VO ₂ , VO ₂ substituted with W, Mo, Nb or Re or with VO _x F _y .

From Jpn. Appl. Phys. Vol. 32 (1993), pp. 93-96, a method is known for producing an electrochromic MoO ₃ thin film on an ITO glass substrate. For this purpose, stoichiometric amounts of Li ₂ CO ₃ and MoO ₃ are fused together, and the resulting Li ₂ MoO ₄ is dissolved in H ₂ SO ₄ . This solution is then sprayed onto an ITO glass substrate coated with Cu.

Furthermore, DE-OS 41 25 381 is a method for education known from tungsten oxide films in which a solution of a Akylamine tungstate compound in a solvent containing a contains polar component, applied to a substrate and is then dried.

Furthermore, from US Pat. No. 4,855,161 a method for Ab separation of electrochromic layers known in which a Halide of an electrochromically active transition metal, the is necessarily anhydrous, dissolved in an alcohol and is then applied to a substrate.

In addition, U.S. Patent 4,347,265 discloses a process for Production of an electrochromic layer described in which a metal compound such as tungsten chloride in  an organic solvent such as one Alcohol is dissolved. This solution is transparent Electrode applied and then calcined, whereby one receives an electrochromic layer with tungsten oxide.

However, if a dry process such as atomization or Sputtering process, or the evaporation process is used, a large vacuum device is required to display an EC obtain with large area, reducing manufacturing costs increase. Especially if the atomization or Sputtering can be done using a glass substrate be used, however - because the temperature of the used Layer carrier is increased - no plastic carrier what hinders the lightweight properties of the EC display is.

Even if the spin application process is carried out, the ink layer can only be obtained without increasing the production costs if a substrate of approximately 30 cm ^{2 is} rotated, so that a larger EC display cannot be produced at low costs.

This is how the execution of the diving order process appears Manufacture of a large EC display at a low cost practically feasible. Also appear alongside the dive job do other wet processes like the printing process that Spraying process, the turning or spin application process, etc. to be practically effective.

The results of tests carried out by the inventors showed, however, that the wet immersion procedure after pulling up causes wave-like drains in the film, and that this causes unevenness in the reduction color layer caused by drying the resulting film. Especially when the peroxotungstic acid solution is in the dip application method is used, bubbles appear in the film on due to the generation of oxygen, which by the Decomposition reaction of the hydrogen peroxide contained in the solution  is caused, as well as due to the release of the dissolved oxygen in it during diving and pulling up process of the layer support. If the resulting film is dried, occur in the reduction color layer formed Bumps on. This can be confirmed visually. Further become irregularities in the transmittance of the EC display caused during the coloring. Therefore, quality occurs problems arise.

Furthermore, although it causes a uniform film immediately after pulling up the substrate can be the film's heat act in an after treatment step cracks in the reduction paint layer as well Removing the layer. The cracks and peeling lead to contact between the electrolyte layer and the first Electrode layer of the EC display, so that quality problems due to the destruction or detachment of the first Electrode layer are caused. If a large EC display is the bump in or peeling off the reduction color layer is particularly noticeable, and the Usability is then particularly disrupted.

Wet process using a solution which contains organic compound of tungsten has the disadvantage that the preparation of the organic compound is troublesome.

The disadvantages mentioned above do not only apply to EC displays, but also for other chrome displays like thermochromic Ads, photochromic ads, etc., which have a layer of paint have an oxide of at least one of the elements W, Nb, Mo and V included.

Accordingly, there is the object of the present invention in making a new color layer composition available places which to form a reduction color layer of a Chromia indicator can be used and therefore the most reliable Manufacture of a large chromium display at a low cost  enables. In particular, there should be unevenness in the paint layer and the peeling of the paint layer can be prevented.

As a result, more intense, from the inventors to the solution above Problems with trials have been found that the Mixing an organic solvent into a die Color layer forming composition, which is a degradation the surface energy of the film formed causes Prevention of bumps in the film and peeling of the film is effective. It was also found that the organic solvents due to the generation of oxygen can prevent the decomposition of hydrogen peroxide, and that it also prevents dissolved oxygen from being released becomes. It is required that the organic solvent Has compatibility with water because of the substance used includes at least peroxotungstic acid and possibly still Contains niobium oxide, molybdenum oxides and / or vanadium oxide in water is soluble, as well as that by heat treating the film can be evaporated. In so doing, the present invention achieved. It was also found that a color film without Bumps or detachment can be formed under Using a dive application process and by vertical Pulling out the treated object at less Speed.

The present invention thus provides a color layer composition for a chromia display, which

• a) a water-soluble substance that is at least peroxo includes tungstic acid, which may contain niobium oxide, Contains molybdenum oxide and / or vanadium oxide;
• b) water; and
• c) an organic solvent compatible with water includes.

The present invention further provides a color layer composition for a chromia display, which contains as a soluble substance a tungsten oxide-containing compound which is represented by the formula WO ₃ . aNb ₂ O ₅ . bH ₂ O ₂ . cH ₂ O (where a, b and c each represent a positive number) is shown.

The present invention further provides a color coating composition for a chromia display, which contains a peroxotungstic acid solution containing 100 parts by weight of WO ₃ as a soluble substance. aNb ₂ O ₅ . bH ₂ O ₂ . cH ₂ O (wherein a, b and c each represent a positive number), 20 to 120 parts by face of water and 80 to 800 parts by weight of proponol as an organic solvent.

A chrome display with a first, transparent layer carrier, a first, transparent electrode layer, one Reduction color layer, an electrolyte layer, one Oxidation color layer, a second, transparent electrodes layer and a second, transparent substrate, which can be applied successively, by a method below Formation of the reduction color layer on the first, transparent Electrode layer can be produced. The step to education the reduction color layer uses a dip coating process of forming a film on the first, transparent Electrode layer using the above Color layer composition, the vertical Pull-out speed is less than 15 cm / min.

Fig. 1 is a schematic sectional view showing a conventional EC display; and

Fig. 2 to 9 are graphs showing the relationship between the pulling rate and the film thickness, representing on a first electrode layer using a color layer composition of the present invention (with eight different types with different compositions) is formed.

The color layer composition of the present invention contains a water-soluble substance, of at least peroxotungstic acid  which optionally includes niobium oxide, molybdenum oxide and / or contains vanadium oxide;

Water to dissolve or disperse (absorb) the soluble As well as an organic compatible with water Solvent. The organic solvent reduces the Surface energy of the film formed and thus prevented effective bumps as well as the peeling of the paint layer. The organic solvents compatible with water does not affect the dissolution of the solute in Water and is evaporated by heat treating the film.

Preferred examples of the solute are tungsten oxide-containing compounds represented by the following formula:
WHERE ₃ . aNb ₂ O ₅ . bH ₂ O ₂ . cH ₂ O (where a, b and c are positive numbers, respectively).

Of these compounds, preference is given to those in which a, b and c each represent a positive number. The connections are heteropolyacids obtained by treating tungsten and Niobium metal powder or metal compounds with hydrogen peroxide can be obtained. The connection is subsequently called Denoted "peroxotungstic acid". Although a solution to that Peroxotungstic acid due to the hydrogen it contains Peroxide easily creates bubbles, which can be done with water compatible, organic solvents caused by the decomposition of the Hydrogen peroxide causes generation of oxygen prevent, and it can also prevent dissolved Oxygen is released.

In the composition according to the invention, water and a organic solvent used as solvent. Examples of organic solvents include methanol, ethanol, Propanol, 2-ethoxyethanol and dimethylformamide. Of these Solvents are preferred propanol and 2-ethoxyethanol. The Amount of the present in the composition according to the invention solute is 50% by weight or less, preferably  20 to 30 wt .-%, based on the total amount of the combinations settlement.

The amount of the organic solvent used is 80 Parts by weight or more, preferably 80 to 800 parts by weight, based on 100 parts by weight of the dissolved substance.

A preferred color layer composition according to the present invention comprises 100 parts by weight of WO ₃ . aNb ₂ O ₅ . bH ₂ O ₂ . cH ₂ O (where a, b and c each represent a positive number) as a solute, not more than 120 parts by weight, preferably 20 to 120 parts by weight, water and at least 80 parts by weight, preferably 80 to 800 parts by weight, propanol as an organic solvent. The use of the composition can particularly effectively prevent unevenness in the color layer and the peeling of the color layer.

The color layer composition of the present invention is used in a part of the reduction color layer formation step as a step for manufacturing an EC display using the dip coating method. A film is formed on a first, transparent electrode layer using a peroxotungstic acid solution. The solvent is removed from the film by heat treatment to form a reducing color layer which is WO ₃ . aNb ₂ O ₅ . bH ₂ O ₂ . Contains CH ₂ O (where a, b and c each represent a positive number) as a solute.

As a result of the tests carried out by the inventors it became clear that unevenness in the reduction color layer occur due to a wavy flow of the film after the pulling the substrate vertically out of the peroxotungsten acid solution under the conditions of a low solution concentration (also a low viscosity) and one high pull-up speed, what the attachment of a large Solution set caused.  

Under the conditions of high concentration and high Pull-up speed, resulting in the formation of a thick film leads to cracks in the reduction ink layer. It seems to crack due to an increase in film thickness Increasing the film's internal tension during the heat treatment can occur. This easily leads to the replacement of the Films.

Accordingly, it is to prevent the generation of bumps and effective in preventing detachment that the conc tration of the soluble substance in the color layer Composition less than 50% by weight, preferably 20 to 30% by weight, and that is the vertical pull-up speed is less than 15 cm / min, preferably 10 cm / min.

Examples

Although the present invention with reference to a Example and test examples are explained in more detail, the present invention is not limited to these examples limited.

Preparation of the color layer composition

The EC display shown in FIG. 1 as an example of a chromia display was manufactured using an example of the reducing color layer composition. The EC display is characterized by the reduction color layer composition and thus has the same appearance as a conventional display.

First, the reducing color layer composition (peroxo tungstic acid solution) was obtained. For this, 0.18 mol of tungsten powder and 0.015 mol of niobium carbide powder were dissolved in 200 ml of 15% aqueous hydrogen peroxide solution. The resulting solution was then dried under reduced pressure to obtain a powder 10 from WO ₃ . 0.041Nb ₂ O ₅ . 6H ₂ O ₂ . 3H ₂ O (hereinafter referred to as "IPA powder") to synthesize. The IPA powder was dissolved in pure water. The solution thus formed contained 100 parts by weight of the IPA powder as a solute and 24 parts by weight of water.

The solution was diluted with n-propanol to make a peroxowolf to obtain ramic acid solution containing the IPA powder. The resulting peroxotungstic acid solution contained 100% by weight parts of the IPA powder as a solute, 24 parts by weight Water and 230 parts by weight of n-propanol.

Production of the EC display

The EC display was manufactured by the following method: A transparent PET (polyethylene terephthalate) resin film (5 cm × 5 cm) was used as the first and second transparent layer supports 1 and 7 . ITO (indium tin oxide (In ₂ O ₃ .SnO ₂ )) was deposited on the surfaces of the first and second transparent substrates 1 and 7 to form the ITO-containing first (and second electrode layers 2 and 6 , respectively. In this way a first ITO multi-film containing the first transparent support and the first electrode layer 2 , and a second ITO multi-film containing the second transparent support 7 and the second electrode layer 6 were obtained.

The first ITO film was then in the peroxotungstic acid solution submerged and then vertical at a pull-up speed pulled up to 10 cm / min. In this way, a film was made the dive order method made. No wave-like drains in this case occurred in the film after it was pulled out.

The first ITO film on which the IPA film was formed was then subjected to a heat treatment at 120 ° C. for one hour to remove moisture from the IPA film to form a reducing color layer 3 , WO ₃ . 0,041Nb ₂ O ₅ contained, to be formed on the first electrode layer. 2 Neither unevenness, crack formation nor detachment occurred in the reduction ink layer 3 .

The first ITO film provided with the color layer 3 was dissolved in a solution of LiCF ₃ SO ₃ . Pro pylene carbonate (PC) dipped to Li-ion in the WO ₃ . 0.041Nb ₂ O ₅ to inject.

In the meantime, Prussian blue, (Fe ³⁺ [Fe ²⁺ (CN) ₆ ^4- ]) was applied to the second electrode layer 6 of the second ITO film washed with alkali by an electrolytic process to form an oxidation color layer 5 , which the Prussian blue film contained to form.

An electrolytic solution was prepared by dissolving a carrier salt (LiCF ₃ SO ₄ ) and a photopolymerization initiator (2,2-dimethoxy-2-phenylacetophenone) in polyethylene oxide and applied to the oxidation color layer 5 of the second ITO film. The reduction color layer 3 of the first ITO Films and the electrolyte solution on the second ITO film were bonded, then irradiated with ultraviolet rays (UV) to cure the electrolyte solution to form an electrolyte layer 4 from the electrolyte solution.

It was confirmed that the EC display thus obtained showed outstanding, reversible staining-bleaching changes achieved.

Accordingly, the reducing color layer composition (Peroxotungstic acid solution) of the present invention after Example of the appearance of unevenness and detachment of the Reduction paint layer by the dip application process is effectively prevented, so that the reliable Manufacture of a large EC display at a low cost is made possible.

Test 1

An optimal composition range of the reduction color layer Composition (peroxotungstic acid solution) was determined. First, an IPA powder was synthesized by the same Procedure as used in the example above. The IPA Powder was then dissolved in pure water to make each  Solutions A to G together with those shown in Table 1 to receive settlements in parts by weight.

Table 1

Solution A was diluted with the amounts of n-propanol shown in Table 2 to obtain the No. 1 to No. 10 peroxotungstic acid solutions. Table 2 also shows the relationship between the pulling-up speed (cm / min) and the state of the reducing ink layer when each of the peroxotungstic acid solutions No. 1 to No. 10 was used in the dip coating process. The other conditions were the same as those used in the example (the same applies below). In Table 2, the symbol O indicates that an excellent reduction ink layer was formed, a Δ indicates that strong blistering occurred in the reduction ink layer, a ▲ indicates that bumps occurred in the reduction ink layer, and an X indicates that detachment of the Reduction paint layer occurred (the same applies here). Fig. 2 shows the relationship between the pull-up speed (cm / min) and the thickness of the reducing ink layer (µm) when some of the peroxotungstic acid solutions were used in the dip coating process.

Table 2

Solution B was made with the amounts of n-propanol shown in Table 3 diluted to the peroxotungstic acid solutions No. 11 to No. 17 to obtain. The table also shows the relationship between the pull-up speed (cm / min) and the condition of the Reduction color layer when each of the peroxotungstic acid solutions # 11 through # 17 was used in the dip application process.

Fig. 3 shows the relationship between the pulling-up speed (cm / min) and the thickness of the reducing ink layer (µm) when some of the peroxotungstic acid solutions were used in the dipping process.

Table 3

Solution C was made with the amounts of n-propanol shown in Table 4 diluted to the peroxotungstic acid solutions (No. 18 to No. 27 to obtain. Table 4 also shows the relationship between the pull-up speed (cm / min) and the condition of the Reduction color layer when each of the peroxotungstic acid solutions No. 18 to No. 27 was used in the dip application process.

Fig. 4 shows the relationship between the pull-up speed (cm / min) and the thickness of the reducing ink layer (µm) when some of the peroxotungstic acid solutions were used in the dipping process.

Table 4

Solution D was made with the amounts of n-propanol shown in Table 5 diluted to the peroxotungstic acid solutions No. 28 to No. 37 to obtain. Table 5 also shows the relationship between the pull-up speed (cm / min) and the condition of the Reduction color layer when each of the peroxotungstic acid solutions No. 28 to No. 37 was used in the dip application process.

Fig. 5 shows the relationship between the pulling-up speed (cm / min) and the thickness of the reducing ink layer (µm) when some of the peroxotungstic acid solutions were used in the dipping process.

Table 5

Solution E was made with the amounts of n-propanol shown in Table 6 diluted to the peroxotungstic acid solutions No. 38 to No. 47 receive. Table 6 also shows the relationship between the Hoisting speed (cm / min) and the condition of the Reduction color layer when each of the peroxotungstic acid solutions # 38 to # 47 was used in the dip application process.

Fig. 6 shows the relationship between the pulling-up speed (cm / min) and the thickness of the reducing ink layer (µm) when some of the peroxotungstic acid solutions were used in the dipping process.

Table 6

Solution F was made with the amounts of n-propanol shown in Table 7 diluted to the peroxotungstic acid solutions No. 48 to No. 57 to obtain. Table 7 also shows the relationship between the pull-up speed (cm / min) and the condition of the Reduction color layer when each of the peroxotungstic acid solutions # 48 to # 57 was used in the dip application process.

Fig. 7 shows the relationship between the pulling-up speed (cm / min) and the thickness of the reducing ink layer (µm) when some of the peroxotungstic acid solutions were used in the dipping process.

Table 7

Solution G was made with the amounts of n-propanol shown in Table 8 diluted to the peroxotungstic acid solutions No. 58 to No. 67 to obtain. Table 8 also shows the relationship between the pull-up speed (cm / min) and the condition of the Reduction color layer when each of the peroxotungstic acid solutions # 58 to # 67 was used in the dip application process.  

Fig. 8 shows the relationship between the pulling-up speed (cm / min) and the thickness of the reducing ink layer (µm) when some of the peroxotungstic acid solutions were used in the dipping process.

Table 8

As can be seen from Tables 2 to 8 and Figs. 2 to 8, a peroxotungstic acid solution containing 100 parts by weight of IPA powder, not more than 120 parts by weight of water and not less than 80 parts by weight of n-propanol as an organic solvent may have bumps in the reducing color layer and effectively prevent detachment of the reduction ink layer. It has also been found that the peroxotungstic acid solution, which contains 100 parts by weight of IPA powder, 20 to 120 parts by weight of water and 80 to 800 parts by weight of propanol as the organic solvent, can effectively prevent unevenness in and detachment of the reducing ink layer.

Test 2

Other organic solvents for the reduction color layer composition (peroxotungstic acid solution) were examined. First, IPA powder was synthesized by the same method as used in the example. The so synthesized Powder was dissolved in pure water to make solution B with the composition shown in Table 1 in parts by weight receive.  

Solution B was diluted with the amounts of 2-ethoxyethanol shown in Table 9 to obtain the No. 68 to No. 77 peroxotungstic acid solutions. Table 9 also shows the relationship between the pulling-up speed (cm / min) and the state of the reduction ink layer when each of the peroxotungstic acid solutions No. 68 to No. 77 was used in the dip coating process. Fig. 9 shows the relationship between the pulling-up speed (cm / min) and the thickness of the reducing ink layer (µm) when some of the peroxotungstic acid solutions were used in the dip coating process.

Table 9

From Table 9 and Fig. 9 it is easy to understand that 2-ethoxyethanol can be used as the organic solvent. Although dimethylformamide can be used as an organic solvent, the tests performed by the inventors showed that dimethylformamide is difficult to use because the compositions containing dimethylformamide produced precipitates of the IPA powder within several hours.

Although the wet dipping method was used to coat the composition in the above example and tests 1 and 2, the composition of the invention can be applied to other wet methods. However, when a wet filming process is carried out, an EC display can only be manufactured without significantly increasing the manufacturing cost if a substrate of about 30 cm ^{2 is} rotated, and difficulties usually arise in producing larger EC displays at a low cost.

Although the above example and tests 1 and 2 are each the same refer to an EC display as a chromia display is the Application of the composition according to the invention not to EC Ads are limited, and the composition can be different Chromium displays such as thermochromic displays, photochromic Displays etc. are used which have a reduction layer have an oxide of at least one of the elements W, Nb, Mo and V included.

As described above, the color layer composition is for a chromia display according to the present invention as in the following, respective claims, and the Composition can consequently the appearance of bumps and prevent peeling of the color layer, which is caused by a Wet process like the dip application process was made.

The use of this composition thus improves the Customs of the wet process like the dipping job process and allows the reliable production of a large one Chromium display at low cost.

Claims (8)

1. Color layer composition for a chromia display, which

• a) a water-soluble substance which includes at least peroxotungstic acid, which optionally contains niobium oxide, molybdenum oxide and / or vanadium oxide;
• b) water; and
• c) comprises a water-compatible organic solvent.

2. Color layer composition for a chromia display after Claim 1, wherein the organic solvent c) a Is a compound consisting of methanol, ethanol, propanol, Group consisting of 2-ethoxyethanol and dimethylformamide is selected. 3. The color layer composition for a chromia display according to claim 1, wherein the water-soluble substance a) is a peroxotungstic acid which contains niobium oxide and is represented by WO ₃ . aNb ₂ O ₅ . bH ₂ O ₂ . cH ₂ O, where a, b, and c are each a positive number. 4. Color layer composition for a chromia display after Claim 1, wherein the concentration of the water soluble Substance a) is 50% by weight or less.   5. Color layer composition for a chromia display after Claim 1, wherein the concentration of the water soluble Substance a) is 20 to 30 wt .-%. 6. The color layer composition for a chromia display according to claim 1, comprising a peroxotungstic acid solution containing 100 parts by weight of WO ₃ . aNb ₂ O ₅ . bH ₂ O ₂ . cH ₂ O, where a, b and c are each a positive number, contains not more than 120 parts by weight of water and not less than 80 parts by weight of propanol as an organic solvent. 7. A color layer composition for a chromia display according to claim 1, comprising a peroxotungstic acid solution containing 100 parts by weight of WO ₃ . aNb ₂ O ₅ . bH ₂ O2. cH ₂ O, in which a, b and c are each a positive number, contains 20 to 120 parts by weight of water and 80 to 180 parts by weight of propanol as an organic solvent. 8. Use of the color layer composition according to one of the Claims 1 to 7 for an electrochromic display.