JPH0451202A - Color filter - Google Patents

Abstract

PURPOSE:To obtain a film which does not crack and wrinkle, is less rugged and has excellent flatness by using a photosensitive resin formed by adding a multifunctional photopolymerizable acrylate monter to a photopolymerizable acrylate oligomer having an epoxy group in a part of an acrylate group as a protective film to be formed on the surface of a colored film. CONSTITUTION:Colored layers 2 corresponding to three primary colors of light are formed on a transparent substrate 1. Glass, such as borosilicate glass and synthetic resins, such as polycarbonate and polyethylene terephthalate, are usable as the transparent substrate. The colored layers are formed of color materials, such as dyes and pigments, by a printing method or photolithography method. This color filter is formed by providing the protective film 3 on the surface of the colored layers 2 by a method, such as spin coater, roll coater, spraying or printing and particularly the photosensitive resin formed by adding the multifunctional photopolymerizable acrylate monter to the photopolymerizable acrylate oligomer is used as the protective film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a color filter, and particularly to a color filter used in a color liquid crystal display device.

[Prior Art] In a liquid crystal display device, a liquid crystal substance is sealed between transparent substrates such as glass provided with transparent electrodes with an interval of about 1 to 10 μm, and the liquid crystal is heated at a certain level by a voltage applied between the electrodes. Images are displayed by oriented in the same direction to form transparent and opaque areas.

In a color liquid crystal display device, three color filters of red (R), green (G), and blue (B) corresponding to the three primary colors of light are provided on one of the transparent electrode substrates. R, G is controlled by adjusting the voltage to control the transmission of light through the liquid crystal.
, B by controlling the amount of light transmitted through the three color filters.
Color display is performed by adding color to the primary colors.

In color liquid crystal display devices, transparent substrate, colored layer, protective film
A transparent conductive film is laminated in this order.

The protective film protects the colored layer and also serves as a base material for the transparent conductive film. Many materials can be used as long as they are transparent and can withstand the heat treatment temperatures used in the subsequent color filter manufacturing process, but thermosetting urethane resins, acrylic resins, polyimide resins, and photocuring acrylic resins are particularly suitable. Resin, polyimide resin, etc. are used.

[Problems to be Solved by the Invention] When a thermosetting resin is used as a protective film for a color liquid crystal display device, the protective film is formed over the entire surface of the color filter, so it is necessary to limit the protective film to a predetermined area. This is difficult.

If a protective film is formed on the entire surface of the color filter, sufficient adhesive strength may be required since the color filter and the counter electrode will be bonded to each other through the protective film when the color filter and the counter electrode are glued together. Something happens that you don't get. In addition, if there is a quality problem when inspecting the display quality after gluing the color filter and counter electrode together and it is determined to be a defective product, the liquid crystal sealant can be removed in order to reuse the color filter. Furthermore, when removing the tab by φ, if there is a protective film on the outer periphery of the colored layer, the transparent electrode formed on the color filter will peel off along with the sealant or tab, making it impossible to reuse the color filter. There is also the problem.

Therefore, in order to limit the portions on which the protective film is formed to specific portions, photocurable resins are used, which can easily limit the portions to be cured using a mask. However, photosensitive polyimide resin, which has been conventionally used as a photocurable resin, has high hygroscopicity, lacks corrosion resistance to alkaline solutions used in forming electrodes, etc., and is expensive, making it undesirable for practical use. . Further, conventional photosensitive acrylic resins have poor heat resistance, and when a relatively thick transparent conductive film is formed on a protective film, cracks and wrinkles occur on the color filter.

Furthermore, in order to use it as a color filter for a color liquid crystal display device, transparent electrodes are provided on the protective film of the colored layer to drive the liquid crystal in the portions corresponding to the R, G, and B positions of the colored layer. The issue of flatness of transparent electrodes is particularly important in driving active type liquid crystals in which a transparent electrode is formed on a protective film to act as a counter electrode to a thin film transistor (TPT) formed on a transparent substrate, such as in color television display devices. However, in the case of the STN liquid crystal driving method used in color displays of personal computers, the flatness of the transparent electrode is a major problem.

Furthermore, even when the protective film is limited to the colored layer, the protective film is formed on the wall surface around the colored layer and the transparent substrate adjacent to the wall surface to protect the colored layer. If the adhesive strength between the protective layer and the transparent substrate is not strong enough, the protective layer may peel off from the transparent substrate, or chemicals used in the process of forming transparent electrodes or assembling liquid crystal display devices may leak between the transparent substrate and the protective layer. Penetration may occur and adversely affect the colored layer.

The primary purpose of this invention is to provide a color filter that does not have a protective film in the areas that are problematic during assembly of the outer periphery of the colored layer, and does not cause cracks or wrinkles on the protective film. The purpose is to form a strong protective film.

A second object of the present invention is to obtain a protective film in which a flat transparent electrode with small irregularities is formed at the same time.

Furthermore, the third purpose is to increase the adhesive strength between the transparent substrate and the protective film to prevent the protective film from peeling off from the periphery and to prevent chemicals, etc. from penetrating between the transparent substrate and the protective film. It is.

[Means for Solving the Problems] As a result of research into means for solving the above-mentioned problems, the present inventors have developed a photopolymerizable acrylate oligomer in which part of the acrylate group is an epoxy group, which has multiple functional groups in one molecule. By using a photosensitive acrylic resin added with a polyfunctional photopolymerizable acrylate monomer having a group, the degree of cross-linking of the resin can be increased to create a rigid and hard film, and a thick transparent electrode can be formed on the protective film. It was discovered that no cracks or wrinkles occur even when the material is heated. At the same time, if a resin with such a composition is used as a protective film, differences in height will occur between the recesses formed between adjacent R, G, and B of the colored layer formed on the transparent substrate, and between the R, G, and H portions. We have discovered that it is possible to obtain a protective film with good flatness with very little unevenness on the surface of the protective film, and to increase the adhesive strength between the transparent substrate and the protective film without treating the transparent substrate. It is something.

The above photopolymerizable acrylate oligomer that can be used for the purpose of the present invention preferably has a molecular weight of about 1000 to 2000, and includes polyester acrylate, epoxy acrylate such as phenol novolac epoxy acrylate, 0-talesol novolac epoxy acrylate, or Polyurethane acrylate, polyether acrylate, oligomer acrylate, alkyd acrylate polyol acrylate, melamine,
Examples include oligomers such as acrylates in which part of the acrylate group is an epoxy group. The ratio of epoxy groups to acrylate groups in the oligomer is set to 10% of the epoxy group in the oligomer as a condition for the resin to be cured by ultraviolet rays.
It is preferable to set it as 40 parts by weight.

When epoxy acrylate is produced by the reaction of glycidyl ether and acrylic acid, it can be produced by leaving the epoxy group in this precursor. An example of such an oligomer is shown below.

H as a polyfunctional photopolymerizable acrylate monomer, 1.4
Examples include butanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, pentaerythritol acrylate, dipentaerythritol hexaacrylate, and the like.

The method for forming the protective film of the present invention is to apply a photosensitive resin prepared by adding a photopolymerization initiator to a photopolymerizable acrylate oligomer and a multifunctional photopolymerizable acrylate monomer onto a colored layer provided on a transparent substrate using a spinner method, a roll method, or the like. After coating by any coating method such as spray method or screen printing method, a mask with a predetermined pattern is placed on it and UV rays are irradiated to cure the necessary areas, and the uncured areas that have not been exposed to UV rays are exposed. By dissolving and removing the resin with a solvent that dissolves it, a protective film of a resin with increased cross-linking, rigidity, and high hardness is formed only in a predetermined area. The obtained protective film has sufficient strength, so even if a thick transparent electrode is formed on the protective film, no cracks or wrinkles will occur.
It is a highly flat film with few irregularities. Furthermore, since it has photosensitivity, it is possible to form a protective film only in a predetermined area by using a photomask.

[Function] The color filter of the present invention uses a photosensitive resin in which a polyfunctional photopolymerizable acrylate monomer is added to a photopolymerizable acrylate oligomer in which some of the acrylate groups are epoxy groups as a protective film formed on the surface of the colored film. Even if a thick transparent electrode is formed on the protective film, no cracks or wrinkles will occur, and at the same time, a film with excellent flatness and little unevenness can be obtained. Furthermore, by arranging a photomask etc. and irradiating ultraviolet rays onto the surface coated with the resin, and dissolving and removing the resin in the areas that have not been irradiated with ultraviolet rays, the adhesive strength with the transparent substrate with a protective film formed only in predetermined areas is increased. A color filter with a protective film is obtained.

[Example: To explain the color filter of the present invention with reference to drawings,
As shown in cross section in FIG. 1, colored layers 2 corresponding to the three primary colors of light are formed on a transparent substrate 1.

The transparent substrate can be made of glass such as borosilicate glass, or synthetic resin such as polycarbonate or polyethylene terephthalate. Further, the colored layer is formed by using a coloring material such as a dye or pigment by a printing method or a photolithography method.

A protective film 3 is provided on the surface of the colored layer 2 by a method such as a spin coater roll coater, spraying, or printing, and in particular, a polyfunctional photopolymerizable acrylate monomer is added to a photopolymerizable acrylate oligomer as a protective film. It uses photosensitive resin.

Examples of photopolymerizable acrylate oligomers in which part of the acrylate groups are epoxy groups include polyester acrylates, epoxy acrylates such as phenol novolac epoxy acrylate, 0-cresol novolac epoxy acrylate, polyurethane acrylates, polyether acrylates, oligomer acrylates, and alkyds. Examples of polyfunctional photopolymerizable acrylate monomers include acrylate, polyol acrylate, and melamine acrylate. Examples of polyfunctional photopolymerizable acrylate monomers include 1,4-butanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, and pentaerythritol triacrylate. , trimethylolpropane triacrylate,
Examples include pentaerythritol acrylate and dipentaerythritol hexaacrylate.

In addition, when a photopolymerizable acrylate monomer or oligomer has an acidic group such as a carboxyl group, it becomes possible to develop it with an alkaline aqueous solution, which is easier to handle and waste liquid treatment than development with an organic solvent, and is economical and efficient. Favorable from the standpoint of safety.

Furthermore, as an initiator in the photopolymerizable resin, benzophenone, Irgacure 184, Irgacure 907
, Irgacar-651 (all brand names of Ciba Geigy), Darocure (trade name of Merli), etc. may be added in an amount of about 1 to 3% solid content.

A particularly suitable blending ratio (weight % -) of the photopolymerizable acrylate oligomer and the polyfunctional photopolymerizable monomer is blending ratio 1: 60% phenol novolak epoxy acrylate in which about 30% of the acrylate groups are epoxy groups, 60% trimethylolpropane triacrylate ...17% dipentaerythritol hexaacrylate...20
% Irgacure 184... 3% Blending ratio 2 ○-Cresol novolac eboxy acrylate with approximately 30% of acrylate groups being epoxy groups...60% Dipentaerythritol hexaacrylate...38% Irgacure 184... 2% blending ratio 3 Polyurethane acrylate with epoxy groups accounting for approximately 30% of the acrylate groups...50% dipentaerythritol hexaacrylate...48% Irgacure 651...2% blending ratio 4 Approximately 30% of the acrylate groups Melamine acrylate with epoxy group as %: 70% Trimethylolpropane triacrylate: 27% Irgacure 184: 2%, etc.

After applying the photocurable resin formulation on the colored layer, the second
As shown in the cross section in the figure, a photomask 4 with a predetermined pattern drawn on it was placed at a certain distance from the photosensitive resin layer, and the resin was cured by irradiating ultraviolet rays.After irradiating with ultraviolet rays, methylene chloride, The uncured protective film on the outer periphery of the colored layer is dissolved and removed by development with an organic solvent such as dichloroethane, tetrachloroethane, methyl ethyl ketone, etc. or an alkali aqueous solution such as sodium hydroxide or potassium hydroxide, and the cross section is shown in Figure 3. As shown, it was possible to create a color filter in which the protective film 3 of photocurable resin was formed only on the surface of the colored layer portion 2.

An electrode formed with a display pattern made of a transparent conductive film was provided on the protective film of the color filter thus prepared.

The unevenness of the lower portion is reflected on the upper protective film of the portion corresponding to the recess formed between the adjacent R, G, and B portions of the colored layer and the portion of the colored layer having a different thickness. FIG. 4(A) shows a cross-sectional view of a color filter with a colored layer formed thereon. There is a space 5 between the RlG and B portions of the colored layer, and there is a height difference in R, G, and B. A step 6 has occurred. When a protective film is formed on such a colored layer, the conventional protective film material has large surface irregularities corresponding to the unevenness of the lower part, as shown in FIG. However, in the protective film of the present invention, even if the lower part has large irregularities as shown in FIG. As a result, the flatness of the transparent electrode formed on the protective film also becomes good.

In addition, in the protective film made of the photosensitive resin of the present invention, the polyfunctional photopolymerizable monomer acts as a crosslinking agent, and as a result, the degree of crosslinking of the resin increases, and the hardness of the film is HB to 2H on a pencil hardness when only the oligomer is used. The score improved to 4H to 9H. As a result, the heat resistance was about 250''C, and even when a transparent conductive film with a thickness of about 0.2 to 0.4 μm was formed on the protective film, no cranks or wrinkles occurred in the color filter.

Furthermore, it is possible to increase the adhesive strength by using many commercially available silane coupling agents that are applied to the transparent substrate or added to the resin before applying the resin. , especially γ-(2
aminoethyl) aminopropyltrimethoxysilane,
It is preferable to use γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and the like.

Example 1 Red, green, and blue colored photosensitive resins were prepared by dispersing red, green, and blue pigments in a photosensitive resin in the composition ratios shown in Table 1, respectively.

Part 1 table (Unit: Weight%) The board has a thickness of 1 1n+m glass substrate (co Nin 7059 material made by Gug.) is thoroughly cleaned before use.

On top of that, red photosensitive resin was applied to a film thickness of 12 μm, then dried in an oven at a temperature of 70°C for 30 minutes, exposed using a mercury lamp, and spray developed with water for 1 minute. A red relief image is formed in the area where the red pixel is to be formed, and the same process is repeated by heating and curing at 150° C. for 30 minutes to form a green relief pixel in the area where the green pixel is to be formed, A colored layer was formed by forming blue relief pixels in areas where blue pixels were to be formed.

Next, as a photocurable acrylate oligomer, 0-cresol novolacrylic epoxy acrylate (molecular weight 1500-20
00) as a polyfunctional polymerizable polymer, dipentaerythritol hexaacrylate (Nippon Kayaku ■
A mixture of 50 parts by weight of D P HA (manufactured by D P HA) and 2 parts by weight of Irgacure (manufactured by Ciba Geigy) as a photopolymerization initiator was dissolved in 200 parts by weight of ethyl cellosolve acetate. Coat it on the colored layer to a thickness of 2.0 μm using a spin coater using Log L. Place a photomask at a distance of 50 μm from the coated film and use a proximity aligner. 2. OK
1.1.2.2 Only the colored layer was irradiated with ultraviolet rays for 10 seconds using a W ultra-high pressure mercury lamp.
- Only the uncured portion of the coating film was removed by immersing it in a developer consisting of tetrachloroethane for 1 minute.

Next, sputtering is performed on the formed protective film.
An ITO film (composite film of indium oxide and tin oxide) having a thickness of 0.4 μm was coated.

When the flatness of the transparent electrode layer was measured using a probe film thickness meter, the unevenness was as small as 0.01 μm-0.05 pm, and the flatness was good.

In addition, the obtained color filter showed no abnormality even when heated to 250°C and had sufficient heat resistance.Asahi Example 2 Same as Example 1 except that the epoxy group of the acrylate oligomer was replaced with an acrylate group. γ-(2-aminoethyl)aminopropyltrimethoxysilane (Toshii Silicone T8!SH6) was used as a silane coupling agent.
A trap formed by applying a 0.1% solution of 020) to a glass substrate, drying it, and subsequently applying the resin of Example 1. Regarding the film formed from the resin of Example 1 to which a silane coupling agent was added, Based on the adhesion strength of the coating film @ test (JI
Table 2 shows the result of evaluation according to S standard).

The substrate eye test for each coating film was conducted on a transparent substrate (Corning ■7).
059 material) to a thickness of 10 to 15 μm and dried, 2. 1 with OKW's ultra-high mercury lamp
The coating film was cured by exposure for 0 seconds, and the coating film was further immersed together with the substrate in boiling water for 60 minutes.

The protective film of the present invention and the protective film treated with a silane coupling agent had excellent properties in terms of adhesive strength, and no change in properties occurred in terms of transparency or light transmission properties.

Table 2 Comparative Example 1 A protective film was formed in the same manner as in the example except that no polyfunctional photopolymerizable monomer was added.

The hardness of the obtained protective film corresponded to the pencil hardness of HB to 2H.

Subsequently, an ITO film was coated on the protective film in the same manner as in the example, but wrinkles occurred in the 0.15 μm ITO film. In addition, the unevenness is 0.1 μm to 0.5 μm, and the heat resistance temperature is 220°C.
A protective film was formed in the same manner as in the example except that 5181 (manufactured by Japan Synthetic Rubber Co., Ltd.) was used and the protective film was cured by heating at 180° C. for 1 hour.

The hardness of the obtained protective film corresponded to the pencil hardness of HB or 4H.Subsequently, an ITO film was coated on the protective film in the same manner as in the example, but wrinkles occurred in the 0.1 μm ITO film. .

In addition, the unevenness is 0.2 μm to 0.7 μm, and the heat resistant temperature is 2
It was 00℃.

Comparative Example 3 Thermosetting epoxy resin as material for protective film, trade name C
A protective film was formed in the same manner as in the example except that Z-003 (manufactured by Yasan Kagaku) was used and the protective film was cured by heating at 180° C. for 1 hour.

The hardness of the obtained protective film corresponded to a pencil hardness of HB or 2H.

Subsequently, an ITO film was coated on the protective film in the same manner as in the example, but wrinkles occurred in the 0.1 μm ITO film.

Moreover, the unevenness was 0.2 μm to 0.7 μm, and the heat resistance temperature was 200° C. or lower.

Comparative Example 4 Silicone resin, trade name TDAIH, as material for protective film
(manufactured by Catalysts Kasei Co., Ltd.) and the curing of the protective film was
A protective film was formed in the same manner as in the example except that heating was performed at 80° C. for 1 hour.

The hardness of the obtained protective film corresponded to the pencil hardness of 3H to 9H, and the heat resistance temperature was also good at 250°C or higher, but when the To film was coated on the protective film in the same manner as in the example,
0. Cracks occurred in the ITO film with a thickness of 2 μm or more, and the unevenness was 02 μm to 07 μm.

[Effects of the Invention] Since the color filter of the present invention does not have a protective film on the outer periphery of the colored layer, sufficient adhesive strength can be obtained when the color filter and the counter electrode are bonded together. Furthermore, since the color filter is reused, the protective film will not be peeled off together with the sealant L tab when the sealant and tab are peeled off.

Furthermore, as the resin for the protective film is a photopolymerizable acrylate oligomer in which some of the acrylate groups are epoxy groups and a multifunctional photopolymerizable monomer is added, the resin has a high degree of cross-linking and is rigid and hard. Even if a thick transparent conductive film is formed on the protective film, no wrinkles or cracks will occur, and a protective film with little unevenness and excellent flatness can be obtained. The transparent film has extremely excellent flatness, and also has extremely high adhesion strength to the transparent substrate, making it possible to produce color filters of excellent quality.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the color filter of the present invention coated with uncured resin, Figure 2 is a cross-sectional diagram showing the placement of a photomask and exposure to ultraviolet light, and Figure 3 is a completed book. Figure 4 is a cross-sectional view of the color filter of the invention, showing the unevenness of the protective film: transparent substrate 1, colored layer 2,
Protective film...3, Photomask...4, Space...5,
Level difference/6 Applicant Dai Nippon Printing Co., Ltd.

Claims (6)

[Claims] (1) A mixed system in which a colored layer is formed on a transparent substrate, and a photopolymerizable acrylate oligomer in which some acrylate groups of the epoxy acrylate are epoxy groups and a polyfunctional photopolymerizable acrylate monomer having two or more functionalities are formed on the top surface of the colored layer. A color filter characterized in that a resin consisting of the following is applied onto the colored layer and cured by ultraviolet rays to form a protective film. (2) The color filter according to claim 1, wherein the epoxy group of the acrylate is one in which a portion of the epoxy group of a precursor of the epoxy acrylate remains. (3) In the resin, only the resin in a predetermined area of the color filter is cured with ultraviolet light through a mask, etc., and the uncured resin is dissolved and removed using a solution that is compatible with the resin in the uncured part, and the predetermined area is removed. Claim 1 in which a protective film is formed only on
3. The color filter according to claim 2. (4) The photopolymerizable acrylate oligomer or monomer contains an acid anhydride, and the uncured portion is dissolved and removed in an alkaline aqueous solution to form a protective film only in a predetermined area of the color filter. 2. The color filter according to any one of 2. (5) The color filter according to any one of claims 1 to 4, wherein the resin is applied after applying a silane coupling agent onto a transparent substrate. (6) The color filter according to any one of claims 1 to 4, wherein the resin is coated with a silane coupling agent added thereto.