JPH0894818A - Color filter and coating liquid to form protective film - Google Patents

Abstract

PURPOSE: To provide a color filter having good surface flatness which is suitable as a color filter for a liquid crystal display and to provide a coating liquid to form a protective film for the filter. CONSTITUTION: In this color filter, a protective layer is formed by applying a coating liquid prepared by the following method. An initial polymer of a melamine resin having proper polymn. degree so as not to render the polymer tacky at room temp. is synthesized in such a manner that the polymer has enough solubility with an org. solvent org. such as ethylcellusolve acetate and ethyl lactate which is to be used for the coating liquid to form the protective film of the color filter. Or, the initial polymer of melamine resin and epoxy compd. having proper polymn. degree is synthesized. The coating liquid essentially consists of the initial polymer above described and an org. solvent having low boiling point and is used to form the protective film for the color filter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color filter having a good surface flatness and a coating liquid for forming a protective film thereof, and is particularly suitable for use as a color filter for liquid crystal display.

[0002]

2. Description of the Related Art Conventionally known color filters for liquid crystal display materials have been proposed by various manufacturing methods such as a dyeing method, a pigment dispersion method, an electrodeposition method and a printing method. Production is carried out.

By the way, in any case, the color filter is provided with a protective film for the purpose of improving the flatness of the surface and protecting it. The surface protective film is required to have optical transparency and sufficient film strength, and is also required to have heat resistance to withstand the step of forming a transparent conductive film on the protective film.

The material for forming the protective layer of the surface protective film and the method for forming the protective layer have been conventionally known, and, for example, those containing glycidyl methacrylate as a main constituent component (Japanese Patent Laid-Open No.
No. 134306), one containing polyimide as a main constituent (JP-A No. 62-163016), one containing a mixture of a melamine resin and an epoxy resin as a main constituent (JP-A-63-131103), and the like. Are known.

Here, the melamine resin is an inexpensive resin that has been known for a long time, and has high film strength, excellent optical transparency, and no yellowing due to heating. It is suitable as a film material, and it is known that its adhesion to a glass substrate is improved by mixing it with an epoxy resin (JP-A-63-131103).
(See the official gazette).

[0006]

By the way, in forming a film using a coating liquid for forming a protective film containing a mixture of the melamine resin and an epoxy resin as a main constituent, a melamine resin and an epoxy compound are combined. There is a problem in that the handleability is poor in that the surface of the coating film is sticky only when the low-boiling organic solvent is removed by evaporation, and the cured coating film is formed only after thermal curing.

[0007] Further, for convenience of manufacturing process, the surface is apparently not dry and sticky at the stage where the coating liquid is applied and the low boiling point organic solvent is removed by evaporation to prevent the adhesion of dust during the handling work. It is considered desirable because it can be done. This does not mean that the curing is completed when the coating solvent is removed by evaporation, but it is necessary to obtain a coating film whose surface is apparently dried and complete the curing in the subsequent heat curing step. I mean.

In view of the above circumstances, the present invention provides protection by using a coating solution for a protective film composed of a melamine / epoxy composition whose surface appears to be dry at the stage where the low boiling point organic solvent is evaporated off after coating. An object of the present invention is to provide a color filter formed by forming a film and a coating liquid for forming a protective film thereof.

[0009]

A first color filter structure according to the present invention for achieving the above object is a color filter having a surface protective layer, wherein the surface protective film is sticky in a solid state at room temperature. It is characterized in that it is formed by coating a solution containing a solvent-soluble melamine resin having a medium degree of polymerization, an epoxy compound and a solvent as main components, and drying and thermosetting.

In the color filter, the compound having a medium degree of polymerization of the melamine resin has an average molecular weight of 1700.
The following low-polymerization degree melamine resin is dissolved in an organic solvent, a polymerization catalyst is added and heated if necessary, and when the polymer is isolated, polymerization is performed up to a degree of polymerization in a solid state without stickiness and completely dissolved in an organic solvent. It is characterized by being a polymerized product.

In the above color filter, the compound having a medium degree of polymerization of the melamine resin is a polymer obtained by polymerization to a degree of polymerization having a weight average molecular weight of 20,000 to 60,000.

A second color filter structure according to the present invention is a color filter having a surface protective layer,
The surface protective film is formed by applying a solution containing a solvent-soluble melamine resin / epoxy compound having a medium degree of polymerization and a solvent as a main component in a solid state at room temperature without stickiness and drying / thermosetting. It is characterized by

In the above color filter, the compound having a medium degree of polymerization of the melamine resin / epoxy compound is prepared by dissolving a melamine resin having a low degree of polymerization having an average molecular weight of 1700 or less and an epoxy compound in an organic solvent, adding a polymerization catalyst and heating if necessary. However, when the polymer is isolated, the polymer is characterized by being polymerized to a degree of polymerization in a range in which it is solid without stickiness and is completely soluble in an organic solvent.

In the color filter, the melamine resin / epoxy compound having a medium degree of polymerization is a polymer obtained by polymerization to a degree of polymerization having a weight average molecular weight of 20,000 to 60,000.

The color filter is a color filter for a liquid crystal display material.

The composition of the first color filter protective film forming coating solution of the present invention is a protective film forming coating solution for forming a surface protective layer provided on the surface of a color filter, which is in a solid state at room temperature. Is characterized in that it contains a solvent-soluble melamine resin having a medium degree of polymerization, an epoxy compound and a solvent as main components.

The composition of the second color filter protective film forming coating solution of the present invention is a protective film forming coating solution for forming a surface protective layer provided on the surface of a color filter at room temperature. It is characterized in that it contains, as a main component, a solvent-soluble melamine resin / epoxy compound having a medium degree of polymerization and a solvent, which is not sticky in the solid state.

The details of the present invention will be described below.

In the present invention, ethyl cellosolve acetate,
An initial polymerization product of a melamine resin having sufficient solubility in an organic solvent used for a coating solution for a color filter protective film such as ethyl lactate, and having an appropriate degree of polymerization so that it does not become sticky at room temperature, Alternatively, a prepolymer of a melamine resin having an appropriate degree of polymerization and an epoxy compound is synthesized, and a coating liquid containing this and a low-boiling organic solvent as a main constituent is used as a coating liquid for a color filter protective film, To form a protective layer.

Here, a known melamine resin for protecting a color filter has a low degree of polymerization and is in a paste form at room temperature, and its surface after applying a solution mixed with an epoxy compound is sticky. As the melamine resin, a high molecular weight product (for example, a product manufactured by "Nissan Chemical Co., Ltd.": "NR
-200 ", etc.) is also commercially available, and although it is solid at room temperature and is not sticky, it has low solubility in organic solvents commonly used in coating solutions for color filter protective films such as ethyl cellosolve acetate. Since it is impossible to adjust the liquid, in the present invention, the catalyst is added to the paste-like low-polymerization degree melamine resin at room temperature, and by heating for a desired time, it is dissolved clearly in the organic solvent and the solvent is removed. It was decided to use a medium polymer of the melamine resin which later becomes a solid.

The intermediate polymer of the melamine resin can be used as it is as a solvent for the protective film composition solution without isolation from the reaction solvent, but a poor solvent is added to the reaction solution. Alternatively, the intermediate polymer of the melamine resin may be used once isolated.

The above melamine resin polymer is dissolved in an organic solvent together with an epoxy compound, a surfactant and a silane coupling agent are added according to a conventional method, and the mixture is subjected to microfiltration with a membrane filter to obtain a protective film forming composition solution. I was able to adjust. When the obtained solution was applied onto a color filter with a spin coater, a coating film having almost no stickiness could be formed.

Also, when an acid catalyst is added to a paste-like low-polymerization degree melamine resin at room temperature and the melamine / epoxy copolymer is prepared by adding an epoxy compound in advance when heating for a desired time, the same effect is obtained. was gotten.

Further, a commercially available melamine resin is used as a low-polymerization degree melamine resin as a raw material, and a higher alcohol is previously reacted with the melamine resin to obtain a chemical structure in which a part of methoxy groups of the melamine resin is substituted with a higher alkoxy group. Similar effects were obtained when the above melamine resin was synthesized and used.

As the coating method of the protective film forming composition solution, in addition to the spin coating method, any commonly used coating method such as flexographic printing and gravure printing can be used.

The preferred degree of polymerization of the melamine resin medium polymer and the melamine / epoxy medium degree copolymer are preferably in the range of 20,000 to 60,000 in terms of weight average molecular weight. This is not preferable when the weight average molecular weight is 20,000 or less because the surface of the low boiling point organic solvent is sticky when it is evaporated, and when the weight average molecular weight exceeds 60,000, the low boiling point organic solvent This is because they are both unfavorable in that the solubility decreases. Since it is impossible to prove all combinations of the melamine polymer and the epoxy compound used as the raw material, the range of the weight average molecular weight for achieving the object cannot be rigorously defined.

As the melamine resin used as a raw material in the present invention, an ordinary commercially available resin may be used. For example, "Cymel 325", "Cymel 370", "Cymel 701" (made by Mitsui Cyanamide Co., Ltd.) Name) and the like, and examples of the epoxy compound include “Epicoat 1001” and “Epicoat 1002” (above, trade name) manufactured by Yuka Shell Epoxy Co., Ltd., and “Araldite CY-177” manufactured by Ciba Geigy Co., Ltd. , "Araldite CY
-179 "(above, trade name)," EHPE3150 "(trade name) manufactured by Daicel Chemical Industries, Ltd., and the like.

As the catalyst for polymerizing the melamine resin up to the optimum molecular weight, for example, acids such as methanesulfonic acid, toluenesulfonic acid, phosphoric acid, dodecylbenzenesulfonic acid and the like can be used.

In the present invention, it is convenient to use the same solvent as the solvent for adjusting the coating solution described below as the reaction solvent, but in the case of isolating and using the intermediate polymer of the melamine resin, , And other various solvents can be optionally used.

The solvent for adjusting the coating solvent is not particularly limited as long as it has a strong dissolving power and is relatively easy to evaporate. For example, a coating for a color filter protective film such as ethyl cellosolve acetate, carbitol or ethyl lactate. Conventional solvents can be used as the solution.

[0031]

EXAMPLES A preferred embodiment of the present invention will be described below, but the claims of the present invention are not limited to the description of this example.

<Example 1> In a 500 ml three-necked flask, 150 g of "Cymel 325 (trade name)" manufactured by Mitsui Cyanamid Co., Ltd. was used as a low molecular weight melamine resin as a raw material;
As a reaction solvent, ethyl cellosolve acetate 280
g; Dodecylbenzenesulfonic acid 0.9 as a polymerization catalyst
g was taken and reacted at a reaction temperature of 110 ° C. for 4.5 hours while stirring. After cooling, the reaction solution was added dropwise to 2 kg of n-hexane with stirring, and a white precipitate was deposited. This was filtered and dried to obtain 110 g of a solvent-soluble solid melamine resin intermediate polymer. The molecular weight of this product was measured by GPC (gel permeation chromatography) using polystyrene as a standard substance.
It was 2000.

12 g of the intermediate polymer of melamine resin from the above white precipitate, 8 g of "Epicoat 1004" manufactured by Yuka Shell Epoxy Co., Ltd. were added to ethyl cellosolve acetate 79.
Dissolve in 5 g and add 0.5 g of silane coupling agent “KBM-602 (trade name)” manufactured by Shin-Etsu Silicon Co., Ltd. and 0.1 g of surfactant “FC-430 (trade name)” manufactured by Sumitomo 3M Co., Ltd. A coating solution for a color filter protective film was prepared by applying a spin coat method onto a color filter having a color stripe formed on a glass substrate. The color filter used was a printing machine "Ekter CL600" manufactured by Koyosha.
(Trade name) ”using an ink having the following composition in which an organic pigment is dispersed in an epoxy-melamine resin (see Japanese Patent Application No. 5-25746 previously proposed by the applicant):
Stripes of about 90 μm each of red, blue and green were printed on a glass substrate at a pitch of 270 μm. <Preparation of Ink (For Red Ink)> The following composition was bound with three rolls to prepare a red ink.・ High viscosity vehicle 37.5g ・ Low viscosity vehicle 37.5g ・ Pigment Chromophtal red (Ciba Geigy) 20g Symuler Fast Yellow 4181 (Dainippon Ink and Chemicals) 5
g ・ Silane coupling agent KBM602 (manufactured by Shin-Etsu Silicone Co., Ltd.) 0.2% by weight ・ Paratoluenesulfonic acid 40% IPA solution 0.1% by weight <Ink adjustment (for blue ink)> Three of the following compounds A blue ink was prepared by binding with a roll.・ High viscosity vehicle 37.5g ・ Low viscosity vehicle 37.5g ・ Pigment Lionol Blue ES (Toyo Ink) 8.0g Hostaperm Violet RL (Hoechst) 2.4g ・ Silane coupling agent KBM602 (Shin-Etsu Silicone) 0 .2 wt% -Paratoluenesulfonic acid 40% IPA solution 0.1 wt% <Adjustment of ink (in the case of green ink)> The following composition was bound with three rolls to produce a green ink.・ High viscosity vehicle 37.5g ・ Low viscosity vehicle 37.5g ・ Pigment Fastogen agzreen S (manufactured by Dainippon Ink and Chemicals) 17.0g Symuler Fast Yellow 4181 (manufactured by Dainippon Ink and Chemicals) 3.0g ・ Silane coupling agent KBM602 (manufactured by Shin-Etsu Silicone Co., Ltd.) 0.2% by weight • Paratoluenesulfonic acid 40% IPA solution 0.1% by weight

The color filter protective film applied by the above spin coating method showed no stickiness in a finger touch test, and was 230
The surface height of the protective film after the heat treatment at 1 ° C. for 1 hour was “5H” in the pencil hardness test. In addition, a transparent electrode (ITO
When a film was formed, no wrinkles or cracks were found on the color filter and the transparent electrode.

Example 2 In a 500 ml three-necked flask, 150 g of "Cymel 325 (trade name)" manufactured by Mitsui Cyanamid Co., Ltd. was used as a low molecular weight melamine resin as a raw material.
As an epoxy compound, 24 g of "Epicoat 1004 (trade name)" manufactured by Yuka Cielepoki Co., Ltd., 280 g of ethyl cellosolve acetate as a reaction solvent; 0.3 g of dodecylbenzene sulfonic acid as a polymerization catalyst are taken, and the reaction temperature is 115 ° C. at 3 ° C. The reaction was carried out for 5 hours. After standing to cool, the reaction solution was added dropwise to 2 kg of diisopropyl ether while stirring, and a white precipitate was deposited. This was filtered and dried to obtain 90 g of a solvent-soluble solid melamine resin / epoxy resin copolymerization initial compound. The molecular weight of this product was measured by GPC (gel permeation chromatography) using polystyrene as a standard substance, and the weight average molecular weight was 59400.

Copolymerization of melamine resin / epoxy resin from the white precipitate 20 g of the initial compound was dissolved in 79.5 g of ethyl cellosolve acetate, and 0.5 g of silane coupling agent "KBM-602" manufactured by Shin-Etsu Silicon Co., Ltd., Sumitomo Surfactant "FC-430 (trade name)" manufactured by 3M Co. 0.
1 g was added to prepare a coating solution for a color filter protective film, which was coated on the same color filter as in Example 1 by a flexo method.

The applied color filter protective film was free from stickiness in a finger touch test, and the surface height of the protective film after heat treatment at 230 ° C. for 1 hour was “6H” in a pencil hardness test.
Met. When a transparent electrode (ITO film) was formed on this color filter by heating at 200 ° C., no wrinkles or cracks were found on the color filter and the transparent electrode.

[0038]

As described above in connection with the embodiments, according to the present invention, it has a sufficient solubility in the organic solvent used for the coating solution for the color filter protective film, and is self-sustaining at room temperature. Prepolymer of melamine resin having a suitable degree of polymerization to prevent stickiness, or synthesize a prepolymer of an epoxy compound with a melamine resin having a suitable degree of polymerization, and a low boiling point organic solvent as a main component The coating liquid used as a coating liquid for a color filter protective film is applied to the surface of the color filter to form a protective layer, so that the curing of the coating film is not completed when the coating solvent is removed by evaporation. Regardless, it is possible to obtain a coating film whose surface is apparently dry and which is not sticky, and only after the subsequent heat curing step is the curing completed to form a cured coating film. It is possible. Therefore, according to the present invention, the surface is not apparently dry and sticky at the stage where the coating liquid is applied and the organic solvent having a low boiling point is removed by evaporation, and it is possible to prevent the adhesion of dust during the handling work. .

Claims (9)

[Claims] 1. A color filter having a surface protective layer, wherein the surface protective film is mainly composed of a solvent-soluble melamine resin having a medium degree of polymerization, an epoxy compound and a solvent. A color filter characterized by being formed by applying a solution as a component and drying and thermosetting. 2. The color filter according to claim 1, wherein the melamine resin having a medium degree of polymerization has a low degree of melamine resin having an average molecular weight of 1700 or less dissolved in an organic solvent, and a polymerization catalyst is added to heat the polymer. A color filter characterized in that, when the polymer is isolated, it is a polymer that is polymerized to a degree of polymerization in a range in which it is solid without stickiness and is completely soluble in an organic solvent. 3. The color filter according to claim 1, wherein the melamine resin having a medium degree of polymerization has a weight average molecular weight of 20,000 to 60,000. The color filter to use. 4. A color filter having a surface protective layer, wherein the surface protective film is mainly composed of a solvent-soluble melamine resin / epoxy compound having a medium degree of polymerization and a solvent in a solid state at room temperature without stickiness. A color filter characterized by being formed by applying a solution as a component and drying and thermosetting. 5. The color filter according to claim 4, wherein the melamine resin / epoxy compound having a medium degree of polymerization has a low polymerization degree melamine resin having an average molecular weight of 1700 or less and an epoxy compound, and is polymerized. A color filter characterized in that it is a polymer obtained by polymerizing to a degree of polymerization in a solid state without stickiness when the polymer is isolated by adding a catalyst and heating as needed to completely isolate the polymer. 6. The color filter according to claim 4 or 5, wherein the melamine resin / epoxy compound having a medium degree of polymerization has a weight average molecular weight of 20,000 to 60,000. Is a color filter. 7. A color filter, wherein the color filter according to claim 1 is a color filter for a liquid crystal display material. 8. A coating solution for forming a protective film for forming a surface protective layer provided on the surface of a color filter, which is a solvent-soluble melamine resin having a medium degree of polymerization in a solid state at room temperature without stickiness. A coating liquid for forming a protective film of a color filter, which comprises an epoxy compound and a solvent as main components. 9. A coating solution for forming a protective film for forming a surface protective layer provided on the surface of a color filter, which is a solvent-soluble melamine resin / epoxy compound in a solid state in a solid state at room temperature. A coating liquid for forming a protective film of a color filter, which comprises a polymerization degree compound and a solvent as main components.