JP2933992B2 - Color filter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a color filter, and more particularly to a color filter used for a color liquid crystal display device.

2. Description of the Related Art A liquid crystal display device has a structure in which a transparent substrate such as a glass provided with a transparent electrode is provided with an interval of about 1 to 10 μm, a liquid crystal substance is sealed therebetween, and the liquid crystal is kept constant by a voltage applied between the electrodes. An image is displayed by orienting in the direction to form a transparent portion and an opaque portion. The color liquid crystal display device has three color filters of red (R), green (G), and blue (B) corresponding to the three primary colors of light on one of the transparent electrode substrates. By controlling the transmission of the light of the liquid crystal by adjusting the amount of light, the amount of light transmitted through the three color filters of R, G, and B is controlled, and color display is performed by adding colors of the three primary colors.

In a color liquid crystal display device, a transparent substrate, a colored layer, a protective film, and a transparent conductive film are laminated in this order. The protective film protects the colored layer and plays a role as a base material of the transparent conductive film. Many materials can be used as long as they are transparent and can withstand the heat treatment temperature in the subsequent color filter manufacturing process. Particularly, a thermosetting urethane resin, an acrylic resin, a polyimide resin, or a photocurable acrylic resin can be used. Resin, polyimide resin and the like are used.

[Problems to be Solved by the Invention] When a thermosetting resin is used as a protective film of a color liquid crystal display device, the protective film is formed on the entire surface of the color filter, so that the protective film is limited to a predetermined region. It is difficult.

When the protective film is formed on the entire surface of the color filter, sufficient adhesion strength is required to bond the counter electrode to the counter electrode through the protective film when the color filter and the counter electrode are bonded with an adhesive. Things that cannot be obtained happen. In addition, when the display quality after laminating the color filter and the transparent electrode is judged to be defective due to a quality problem, the liquid crystal sealant is peeled off in order to reuse the color filter. In addition, when the tab is peeled off, if the outer periphery of the colored layer has a protective film, the transparent electrode formed on the color filter together with the sealant or the tab is also peeled off, and the color filter cannot be reused. There is also.

Therefore, in order to limit the portion on which the protective film is formed to a specific portion, a photocurable resin that is easy to limit the portion to be cured with a mask is also used. However, photosensitive polyimide resins conventionally used as photocurable resins have high hygroscopicity, lack corrosion resistance to alkaline solutions used when forming electrodes, etc., and are expensive and not practically preferred. . Further, the conventional photosensitive acrylic resin has a problem that cracks and wrinkles are generated on a color filter when a relatively thick transparent conductive film is formed on a protective film due to poor heat resistance.

Further, in order to use as a color filter of a color liquid crystal display device, a transparent electrode for driving liquid crystal in a portion corresponding to the position of R, G, B of the colored layer is provided on the protective film of the colored layer. The flatness of the transparent electrode is particularly important when driving an active type liquid crystal, which forms a transparent electrode on the protective film that acts as a counter electrode of a thin film transistor (TFT) formed on a transparent substrate, such as a color television display device. However, in the case of the STN-type liquid crystal driving method used for personal computer color displays, the flatness of the transparent electrode is a major problem.

Further, even when the protective film is limited on the colored layer, when the protective film is formed on the wall around the colored layer and on the transparent substrate adjacent to the wall to protect the colored layer, the transparent portion around the colored layer is protected. If the bonding strength between the substrate and the protective film is not large, the protective layer may be peeled off from the transparent substrate, or the chemicals used in the process of forming the transparent electrode and the process of assembling the liquid crystal display device may be located between the transparent substrate and the protective layer. And penetrates into the colored layer.

The first object of the present invention is to provide a color filter which does not have a protective layer in a problematic portion such as the outer peripheral portion of the colored layer as described above, in which cracks and wrinkles do not occur on the protective film. Further, the object is to form a strong protective film having high heat resistance and high water resistance.

It is a second object of the present invention to obtain a protective film on which a flat transparent electrode with small unevenness is formed at the same time.

It is a third object of the present invention to increase the adhesive strength between the transparent substrate and the protective film to prevent peeling from the periphery of the protective film and to prevent penetration of a drug or the like between the transparent substrate and the protective film. It is.

[Means for Solving the Problems] As a result of studying means for solving the above problems, the present inventors have found that a mixture of a photopolymerizable acrylate oligomer and an epoxy resin has a plurality of functional groups in one molecule. By using a photosensitive acrylic resin to which a polyfunctional photopolymerizable acrylate monomer is added, the degree of cross-linking of the resin can be increased to obtain a rigid and high-hardness film, and even if a thick transparent electrode is formed on the protective film. It was found that cracks and wrinkles did not occur. At the same time, when a resin having such a composition is used as a protective film, a concave portion formed between adjacent R, G, and B of the colored layer formed on the transparent substrate and R, G, and B
It has been found that even if a difference in height occurs in the portion, a protective film having excellent flatness with very few irregularities on the surface of the protective film can be obtained.

As the photopolymerizable acrylate oligomer usable for the purpose of the present invention, those having a molecular weight of about 1,000 to 2,000 are preferable, polyester acrylate or epoxy acrylate such as phenol novolak epoxy acrylate, o-cresol novolak epoxy acrylate, or polyurethane. Examples include acrylate, polyether acrylate, oligomer acrylate, alkyd acrylate, polyol acrylate, melamine acrylate, and the like.

Examples of the epoxy resin include a phenol novolak type epoxy resin or a cresol novolak type epoxy resin having the following structural formula.

Further, as the polyfunctional photopolymerizable acrylate monomer, 1,4 butanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, pentaerythritol triacrylate,
Trimethylolpropane triacrylate, pentaerythritol acrylate, dipentaerythritol hexaacrylate, and the like.

The method for forming a protective film of the present invention comprises adding a polymerization initiator and an epoxy curing agent to a photopolymerizable acrylate oligomer, a phenol novolak type epoxy resin, and a polyfunctional photopolymerizable acrylate monomer on a colored layer provided on a transparent substrate. After applying the photosensitive resin by any coating method such as spinner method, roll method, spray method, screen printing method etc., place a mask with a predetermined pattern drawn and irradiate with ultraviolet light to cure necessary parts Then, only a predetermined region was formed by dissolving and removing the uncured photosensitive resin in a solvent that dissolves the uncured photosensitive resin in an ultraviolet-irradiated portion, thereby forming a protective resin film of a rigid and high-hardness film having a high degree of crosslinking. Things. Since the obtained protective film has sufficient strength, it does not cause cracks or wrinkles even when a thick transparent electrode is formed on the protective film, and has a high level of flatness with few irregularities. Furthermore, since it has photosensitivity, it is possible to form a protective film only in a predetermined region by using an optical mask.

[Function] The color filter of the present invention uses a photosensitive resin obtained by adding a polyfunctional photopolymerizable acrylate monomer to a mixture of a photopolymerizable acrylate oligomer and an epoxy resin as a protective film formed on the surface of a colored film. Therefore, even if a thick transparent electrode is formed on the protective film, cracks and wrinkles do not occur, the heat resistance is excellent, and a film with little unevenness and excellent flatness can be obtained. Further, a color mask having a protective film formed only in a predetermined region can be obtained by disposing a photomask or the like and irradiating the resin-coated surface with ultraviolet rays and dissolving and removing the resin in the unirradiated portions.

[Example] The color filter of the present invention will be described with reference to the drawings. A colored layer 2 corresponding to the three primary colors of light is formed on a transparent substrate 1 as shown in cross section in FIG.

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

The protective film 3 is provided on the surface of the colored layer 2 by a method such as spin coater, roll coater, spraying, printing, etc. In particular, as a protective film, a mixture of a photopolymerizable acrylate oligomer and an epoxy resin is applied to a polyfunctional light-sensitive material. It uses a photosensitive resin to which a polymerizable acrylate monomer is added.

Examples of the photopolymerizable acrylate oligomer include polyester acrylate, epoxy acrylate such as phenol novolak epoxy acrylate, o-cresol novolak epoxy acrylate, and polyurethane acrylate, polyether acrylate, oligomer acrylate, alkyd acrylate, polyol acrylate, melamine acrylate, and the like. be able to.

Examples of the epoxy resin include a phenol novolak type epoxy resin or a cresol novolak type epoxy resin having the following structural formula.

Examples of the polyfunctional photopolymerizable acrylate monomer include 1,4 butanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, pentaerythritol acrylate, dipentane Erythritol hexaacrylate and the like.

In addition, if the photopolymerizable acrylate monomer or oligomer is provided with an acidic group such as a carboxyl group, it can be developed with an alkaline aqueous solution. It is preferable in terms of safety.

Further, benzophenone as an initiator in the photopolymerizable resin, or Irgacure 184, Irgacure 907, Irgacure 651 (all trade names of Ciba-Geigy),
Darocur (Merck company name) etc. solid content ratio 1-3
% May be added.

Furthermore, a photocationic catalyst such as an aryldiazonium salt is added as an epoxy curing agent, but an epoxy curing agent of an amine type is not preferable because it has a problem of yellowing. Particularly preferred compounding ratio (wt%) of the photopolymerizable acrylate oligomer and the polyfunctional photopolymerizable monomer is mixing ratio 1 phenol novolak epoxy acrylate 40% phenol novolak epoxy resin 18% trimethylolpropane triacrylate 17% Dipentaerythritol hexaacrylate 20% Irgacure 184 3% UVE1014 (GE) ... 2% Proportion 2 O-cresol novolak epoxy acrylate 38% Cresol novolac epoxy resin 18% Dipentaerythritol hexaacrylate 38 % Irgacure 184 ... 2% UVE1014 (GE) ... 2% Proportion 3 Polyurethane acrylate ... 35% Phenol novolak epoxy resin ... 13% Dipentaerythritol hexaacrylate ... 48% UVE1014 (GE) ... 2% Il Cure 651 ... 2% Proportion 4 Melamine acrylate ... 70% Phenol novolak type epoxy resin ... 20% Trimethylolpropane triacrylate ... 27% UVE1014 (manufactured by GE) ... 2% Irgacure 184 ... 2% .

After applying the compound of the photocurable resin on the colored layer, a photomask having a predetermined pattern is arranged at a certain distance from the photosensitive resin layer as shown in a cross section in FIG. The resin was cured by irradiation with ultraviolet rays. After irradiation with ultraviolet light, the resist film is developed with an organic solvent such as methylene chloride, dichloroethane, tetrachloroethane, and methyl ethyl ketone, or an alkaline aqueous solution such as sodium hydroxide and potassium hydroxide to dissolve and remove the uncured protective film on the outer periphery of the colored layer. As shown in the cross section in FIG. 3, a color filter in which a protective film 3 of a photocurable resin was formed only on the surface of the colored layer portion 2 could be produced.

An electrode having a display pattern formed 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 protective film on the upper portion of the portion corresponding to the concave portion formed between the adjacent R, G, and B portions of the colored layer and on the portion where the thickness of the colored layer is different. FIG. 4 (A) is a cross-sectional view of a color filter on which a colored layer is formed. There is a space 5 between the R, G, and B portions of the colored layer. A step 6 is formed at the end.
When a protective film is formed on such a colored layer, the surface of the material of the conventional protective film has large irregularities depending on the irregularities on the lower portion and the like, as shown in FIG. However,
In the protective film of the present invention, even if the lower unevenness is large as shown in FIG. 3C, no large unevenness is generated on the surface of the protective film, and the flatness is extremely good. As a result, the flatness of the transparent electrode formed on the protective film is improved.

Further, in the protective film made of the photosensitive resin of the present invention, as a result of the multifunctional photopolymerizable monomer acting as a cross-linking agent, the degree of crosslinking of the resin increases, and when the film hardness is only oligomer,
Pencil hardness from HB to 2H was improved to 4H to 9H, and addition of epoxy resin improved heat resistance, water resistance, and adhesion to a transparent substrate such as glass. As a result, the heat resistance becomes about 250 ° C, and 0.2-0.4μ
Even if a transparent conductive film having a thickness of about m was formed, no cracks or wrinkles occurred in the color filter.

Furthermore, when a silane coupling agent is applied to a transparent substrate or added to the resin composition before the application of the resin composition, the adhesive strength is increased by using many commercially available silane coupling agents. Although it is possible, it is particularly preferable to use γ- (2aminoethyl) aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane and the like.

Example 1 Red, green, and blue pigments are dispersed in a photosensitive resin in the composition ratios shown in Table 1 to produce red, green, and blue colored photosensitive resins.

The substrate is a 1.1 mm thick glass substrate (Asahi Glass Co., Ltd. A
L material) after thoroughly washing.

A red photosensitive resin is applied thereon to a thickness of 1.2 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. Then, a red relief image was formed in a region where a red pixel was to be formed, and was cured by heating at 150 ° C. for 30 minutes.

By repeating the same process, a green relief pixel was formed in a region where a green pixel was to be formed, and a blue relief pixel was formed in a region where a blue pixel was to be formed, thereby forming a colored layer.

Subsequently, as a photocurable acrylate oligomer, o-
Cresol novolak epoxy acrylate (molecular weight 15
35 to 100 parts by weight of a cresol novolak type epoxy resin, and 50 parts by weight of dipentaerythritol hexaacrylate (DPHA manufactured by Nippon Kayaku Co., Ltd.) as a polyfunctional polymerizable monomer. A mixture prepared by mixing 2 parts by weight of Irgacure (manufactured by Ciba Geigy) as a polymerization initiator and 2 parts by weight of UVE1014 (manufactured by General Electric) as an epoxy curing agent was dissolved in 200 parts by weight of ethyl cellosolve acetate. , Its solution 10g
Was applied on the colored layer with a spin coater to a thickness of 2.0 μm. A photomask is placed at a distance of 100 μm from the coating film, and 2.0K
Ultra-high pressure mercury lamp of W applies ultraviolet light only on colored layer
Irradiated for 0 seconds. Subsequently, it was immersed in a developing solution composed of 1,1,2,2-tetrachloroethane at a temperature of 25 ° C. for 1 minute to remove only the uncured portion of the coating film.

The hardness of the obtained protective film was equivalent to a pencil hardness of 7H.

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

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

The color filter obtained had sufficient heat resistance without any abnormality even when heated at 250 ° C. for 1 hour.

Example 2 (a) 50 parts by weight of o-cresol novolak epoxy acrylate (molecular weight: 1500 to 2000) and 50 parts by weight of dipentaerythritol hexaacrylate (DPHA manufactured by Nippon Kayaku Co., Ltd.)
Parts by weight and further mixed with 2 parts by weight of Irgacure (manufactured by Ciba Geigy Co., Ltd.) as a polymerization initiator; (b) a film formed of the resin of Example 1, (c) a silane cup A 0.1% solution of γ- (2aminoethyl) aminopropyltrimethoxysilane (SH6020 manufactured by Toray Silicone Co., Ltd.) as a ring agent is applied to a glass substrate, dried, and then coated with the resin of Example 1 to form. The adhesive strength of the applied film was evaluated by a board test (JIS standard) as shown in Table 2 for the obtained film and (d) a film formed by applying the resin of Example 1 to which a silane coupling agent was added. became. The base test for each coating film was performed on a transparent substrate (Corning 7059).
After applying and drying the resin to a thickness of 1.0 to 1.5 μm,
Exposure was performed for 10 seconds with a 20.KW ultra-high pressure mercury lamp to cure the coated film, and the coated film was immersed together with the substrate in boiling water for 60 minutes.

Comparative Example 1 Thermosetting acrylate trade name JS as material for protective film
A protective film was formed in the same manner as in Example, except that S181 (manufactured by Nippon Synthetic Rubber Co., Ltd.) was used, and that the curing of the protective film was heated at 180 ° C. for 1 hour.

The hardness of the obtained protective film was equivalent to a pencil hardness of HB to 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. The unevenness was 0.2 μm to 0.7 μm, and the heat resistance temperature was 200 ° C.

Comparative Example 2 Thermosetting epoxy resin as a material for protective film, trade name
A protective film was formed in the same manner as in Example, except that CZ-003 (manufactured by Nissan Chemical Industries, Ltd.) was used, and that the curing of the protective film was heated at 180 ° C. for 1 hour.

The hardness of the obtained protective film was equivalent to HB or 2H of pencil hardness.

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

Comparative Example 3 Silicone resin, trade name TDA1H as material for protective film
(Catalyst Kasei Co., Ltd.) and hardening of the protective film
A protective film was formed in the same manner as in Example except that heating was performed at 0 ° C. for 1 hour.

The hardness of the obtained protective film was equivalent to a pencil hardness of 3H or 9H, and the heat-resistant temperature was as good as 250 ° C or more.However, when the ITO film was coated on the protective film in the same manner as in the example, 0.2 μm
Cracks occur in the above ITO film, and irregularities
0.7 μm.

[Effect 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, a sufficient adhesive strength can be obtained when the color filter and the counter electrode are bonded together. Further, in order to reuse the color filter, the protective film is not peeled off together with the sealant and the tab when the sealant and the tab are peeled off.

Furthermore, as a resin for the protective film, a mixture of a photopolymerizable acrylate oligomer and an epoxy resin to which a polyfunctional photopolymerizable monomer is added is used, so that the resin has a high degree of crosslinking, and a rigid and hard film can be obtained. Even if a thick transparent conductive film is formed on the protective film, no wrinkles or cracks are generated, the heat resistance is excellent, and a protective film with little unevenness and excellent flatness can be obtained. The transparent conductive film thus obtained is extremely excellent in flatness, and a color filter having excellent quality can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state where an uncured resin is applied to a color filter of the present invention, FIG. 2 is a cross-sectional view for explaining exposure of ultraviolet rays by disposing a photomask, and FIG. FIG. 4 is a cross-sectional view of the color filter of the present invention, and FIG. Transparent substrate ... 1, colored layer ... 2, protective film ... 3, photomask ... 4, space ... 5, step ... 6

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02B 5/20-5/28 G02F 1/1335

Claims (6)

(57) [Claims] 1. A color filter having a protective film on a colored layer formed on a transparent substrate, wherein a mixture of a photopolymerizable acrylate oligomer and an epoxy resin is mixed with a bifunctional or higher polyfunctional photopolymerizable acrylate monomer. A resin composition containing 37 to 48 parts by weight of the epoxy resin based on 100 parts by weight of the photopolymerizable acrylate oligomer, coated on the colored resin, and cured by ultraviolet light to form a protective film. Characteristic color filter. 2. A color filter having a protective film on a colored layer formed on a transparent substrate, wherein a colored layer is formed on a transparent substrate, and a mixture of a photopolymerizable acrylate oligomer and an epoxy resin is formed on the upper surface thereof. A mixed system of a polyfunctional photopolymerizable acrylate monomer having a functionality of not less than 15 to 27 parts by weight based on 100 parts by weight of the photopolymerizable acrylate oligomer and the bifunctional or more polyfunctional photopolymerizable acrylate monomer. A color filter, wherein a resin composition containing a resin is applied on the colored layer and cured by ultraviolet rays to form a protective film. 3. The method according to claim 1, wherein only the resin composition in a predetermined area of the color filter is ultraviolet-cured via a mask or the like, and the uncured resin is a solution compatible with the resin composition in the uncured portion. The color filter according to claim 1, wherein the composition is dissolved and removed, and a protective film is formed only on a predetermined inner region. 4. The photopolymerizable acrylate oligomer or monomer contains an acid anhydride, an uncured portion is dissolved and removed with an aqueous alkali solution, and a protective film is formed only in a predetermined region of the color filter. The color filter according to any one of claims 1 to 3, wherein 5. The color filter according to claim 1, wherein said resin composition is applied after applying a silane coupling agent on a transparent substrate. 6. The color filter according to claim 1, wherein a silane coupling agent is added to said resin composition and applied.