JP2690855B2 - Ink composition for color filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink composition for forming a color filter used in a color liquid crystal display, and more particularly to an ink composition for forming a color filter in intaglio or intaglio offset printing.

[0002]

2. Description of the Related Art The full-color liquid crystal display is rapidly expanding mainly in an active matrix driving system, particularly a thin film transistor (TFT) driving system. In the full-color liquid crystal display, the liquid crystal is driven as an optical shutter with respect to a red, green, and blue transmission filter patterned for each pixel.

Various methods have been proposed for producing a color filter which is a transmission filter of the above three colors of red, green and blue. Broadly classified, (1) pigment dispersion method, (2) dyeing method, There are four methods: (3) electrodeposition method and (4) printing method. Furthermore, for the patterning of the filter, the photolithography method is used in the pigment dispersion method and the dyeing method,
The electrodeposition method also uses the photolithography method when patterning the transparent electrode. Therefore, the patterning method is divided into a photolithography method and a printing method.

Among them, in the photolithography method, a photosensitive photoresist is applied onto a substrate by a spinner or the like, dried to form a patterned resist film, and then a pattern is formed through steps such as exposure, etching and peeling. It is a method of forming. Therefore, there is an advantage that a fine pattern with high dimensional accuracy can be formed, but on the other hand, a large number of steps requires a lot of expensive equipment, and expensive photoresists are discarded by 90% or more in the spin coating step. Therefore, the material cost is also high.

On the other hand, in the printing method, the pattern can be formed by printing once.
The material cost is low because the number of steps is small, and the loss of materials such as ink is small, as it is completed by printing once. for that reason,
The printing method is a very promising method in terms of mass productivity and cost. Problems with the printing method include print dimensional accuracy and surface smoothness. The printing dimensional accuracy has been improved to a practical level by improving the accuracy of the printing press and the accuracy of the printing blanket. Regarding the surface smoothness, various flattening methods have been developed to improve the accuracy.

Therefore, under such circumstances, the development of the optimum ink for forming the color filter by the printing method is being promoted.

[0007]

The characteristics required of the color filter are as follows. (1) Heat resistance Cleaning, drying, transparent electrode formation at the mounting stage on the liquid crystal panel,
At least 25 because it goes through each process of alignment film formation and seal adhesion
It is required that there be no change in color tone, appearance, etc. by heating at 0 ° C for about 1 hour. (2) Chemical resistance Sufficient chemical resistance is required because it is exposed to various chemicals in various cleaning steps and alignment film forming steps at the mounting stage on a liquid crystal panel. (3) Light resistance Since it is often used outdoors, sufficient light resistance is required. (4) Adhesiveness Since various glasses are used as substrates for color filters, the adhesiveness with glass is very important.

On the other hand, the printing ink is required to have the following characteristics. (1) Printability The transfer from the printing plate to the blanket and the transfer from the blanket to the glass substrate are both good, and high dimensional accuracy is required. (2) Pigment dispersibility It is required that the pigment be uniformly and finely dispersed in the ink vehicle.

On the other hand, the conventionally proposed inks for color filter printing do not sufficiently satisfy the above-mentioned characteristics. That is, Japanese Patent Publication No. 5-58466 (Japanese Patent Laid-Open No. 62-54774) discloses an ink composition using an epoxy resin. However, epoxy resins have the advantage of being excellent in adhesiveness and mechanical strength and having very little curing shrinkage, but the acid anhydride used as a curing agent is extremely easy to evaporate in a thin film, so a sufficient cured coating film is formed. Was difficult. Further, the color filter is usually required to have a high surface hardness of 5 to 6H, but even if it is hard with an epoxy resin, only a film having a hardness of about 2 to 3H can be produced, and the heat resistance is not sufficiently satisfactory. .

Japanese Unexamined Patent Publication No. 63-129302 discloses a color filter ink in which an epoxy resin and a melamine resin are used in combination. However, this ink
By mixing the melamine resin, it is said that it is possible to improve the curability and surface hardness, which are the drawbacks when using the epoxy resin alone, and further improve the heat resistance, but by mixing the melamine resin, the curing shrinkage of the coating film It becomes large, it is very difficult to control the thickness of the coating film, and the surface flatness deteriorates. Further, there is a problem that the adhesiveness to a glass substrate, particularly SiO ₂ coated glass, is significantly deteriorated.

Japanese Unexamined Patent Publication (Kokai) No. 63-129303 discloses a color filter ink using a melamine resin. However, melamine resin has the advantage of good heat resistance and high surface hardness, on the other hand, the adhesion to the glass substrate is very poor, the coating film thickness control is difficult because the curing shrinkage of the coating film is large, There is a problem that the surface flatness deteriorates.

Japanese Unexamined Patent Publication (Kokai) No. 1-168775 discloses an ink for a color filter in which a polyester resin and an amino resin are mixed and used. However, while polyester resin is excellent in heat resistance, it has a problem that its adhesiveness to a glass substrate is very poor. Further, since an anionic dye is used as a colorant, there is a problem that heat resistance is poor.

An object of the present invention is to provide an ink composition for a color filter, which is suitable for producing a color filter having well-balanced characteristics such as heat resistance, chemical resistance and adhesiveness. .

[0014]

Means and Actions for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a mixed resin composed of an epoxy resin, a polyester resin and a melamine resin, a solvent and a pigment are contained. The present invention has been completed by discovering a new fact that a color filter produced by a printing method using the prepared ink composition is excellent in various properties such as heat resistance, chemical resistance and adhesiveness. .

That is, the epoxy resin in the above-mentioned mixed resin of the present invention has the advantages that it has high chemical resistance alone, almost no curing shrinkage, and particularly excellent adhesiveness, but the surface hardness is as low as 3H or less. There is.
Further, the melamine resin alone has high heat resistance and chemical resistance, and particularly has a good surface hardness of 6H or more, but has drawbacks that it is inferior in adhesiveness and has large curing shrinkage.
On the other hand, when the epoxy resin and the melamine resin are mixed, although the characteristics are improved, the adhesiveness and curing shrinkage are not sufficient. On the other hand, a polyester resin alone has high chemical resistance and surface hardness and is particularly excellent in heat resistance, but has a drawback that it is inferior in adhesiveness.

On the other hand, when the epoxy resin, the polyester resin and the melamine resin are mixed as in the present invention, all the drawbacks in the case of using each resin alone are solved, and heat resistance, chemical resistance, and It is possible to provide an ink for color filters, which is excellent in all properties such as light resistance, adhesiveness, surface hardness, and curing shrinkage. The mixing ratio of the epoxy resin, the polyester resin and the melamine resin in the present invention is such that the melamine resin is contained in the mixed resin in a proportion of 30 to 70% by weight, and the balance is 30/70 to 70 / of the epoxy resin and the polyester resin. The ratio is 30 (weight ratio).

That is, the melamine resin acts as a crosslinking agent for the epoxy resin and the polyester resin. Therefore, when the addition amount of the melamine resin is less than the above range, the epoxy resin and the polyester resin are not sufficiently crosslinked, and the crosslink density is low, so that sufficient surface hardness cannot be obtained, and heat resistance and chemical resistance are also low. May not be enough. On the other hand, when the amount of the melamine resin added is more than the above range, the adhesiveness to the glass substrate becomes poor, and the curing shrinkage becomes large, so that the flatness of the printing surface is not sufficient.

If the amount of the epoxy resin added exceeds the above range, the heat resistance, surface hardness and cure shrinkage tend to deteriorate. On the other hand, when the amount of the epoxy resin added is less than the above range, the adhesiveness to the glass substrate tends to be poor. When the amount of the polyester resin added exceeds the above range, the heat resistance is improved, but the adhesiveness to glass tends to be lowered.

The resin used in the present invention may be any transparent resin which is basically excellent in heat resistance and has no discoloration. As the epoxy resin, bisphenol type,
Both novolak type and cycloaliphatic type can be used. Polyester resins include saturated polyesters and unsaturated polyesters, but considering heat resistance, chemical resistance, light resistance, etc., saturated polyesters containing saturated dibasic acid ester bonds in the polymer main chain. Preference is given to using polyester resins. Examples of the saturated dibasic acid include phthalic acid, isophthalic acid, terephthalic acid, adipic acid, trimellitic acid, sebacic acid, succinic acid, azelaic acid, hexahydrophthalic acid and acid anhydrides thereof. Further, as the glycol component forming an ester bond with a dibasic acid, for example, ethylene glycol, glycerin, propylene glycol, diethylene glycol,
1,3-butylene glycol, pentaerythritol,
Examples thereof include sorbitol, trimethylolpropane, butenediol, neopentyl glycol and the like. The polyester resin used in the present invention has an acid value of 3 to 5
It is suitable that it is 0, preferably 3 to 15, and especially about 10 to 15. When the acid value becomes large, the water resistance and alkali resistance become poor.

As the melamine resin, for example, methylated melamine, butylated melamine, mixed etherified melamine thereof, guanamine resin, melamine alkyd resin and the like can be used, but coating properties, heat resistance, high solidification, etc. can be used. From the viewpoint, it is preferable to use methylated melamine. Examples of the solvent used in the present invention include cetyl alcohol, stearyl alcohol, oleyl alcohol, octyl alcohol, decyl alcohol, lauryl alcohol, tridecyl alcohol (tridecanol), n-butyl alcohol, cyclohexyl alcohol, 2-methylcyclohexyl. Higher boiling alcohols such as alcohols or mixtures of C ₁₀ -C ₁₅ alkyl alcohols; alkyls such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, butyl carbitol, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate. Ether; Aromatic hydrocarbons such as toluene, xylene, tetralin; Cyclohexanone, methylcyclohexanone, iso Ron, although ketones such as diacetone alcohol and the like, is not limited to, printability (ink transfer properties, etc.) may be appropriately selected in consideration of workability. When using higher alcohols, consider the drying and fluidity of the ink,
Alcohols or esters such as butyl carbitol (diethylene glycol monobutyl ether), butyl cellosolve, ethyl carbitol, butyl cellosolve acetate, butyl carbitol acetate, and terpineol, which dry faster than this, may be used in combination. The amount of the solvent added may be appropriately determined in consideration of the solubility or dispersibility of the components such as the mixed resin used, workability, printability, etc., and is usually 5 to 80% by weight with respect to the total amount of the ink,
It is preferably about 15 to 50% by weight.

The pigment usable in the present invention is preferably an organic pigment having good heat resistance, spectral characteristics, chemical resistance and dispersibility. Further, the particle size of the pigment greatly affects the dispersibility, and the use of a pigment having a large particle size may adversely affect the spectral characteristics, flatness, etc. Therefore, it is preferable to use a pigment having a particle size as small as possible.
Specifically, in the primary particle size at a practical level, 80% or more of the entire particles have a particle size of 1 μm or less, especially 0.3 μm.
It is preferable to use an organic pigment having a size of m or less.

The organic pigments contained in the color filter ink include red pigments, green pigments and blue pigments as basic pigments, and complementary color pigments such as yellow pigments and violet pigments for adjusting spectral characteristics. . The pigments that can be used in the present invention in terms of heat resistance, spectral characteristics, chemical resistance, dispersibility, etc. are shown below by color index numbers. (1) Red pigment 19, 38, 43, 88, 122,
123, 144, 149, 166, 168, 177, 1
78,179,185,208,216,226 (2) Green pigment 7,36 (3) Blue pigment 15: 1, 15: 3, 15: 4, 1
5: 6,16,22,29,60 (4) Yellow pigment 81,83,97,108,10
9,110,137,138,139,153,15
4,166,168,185 (5) Violet pigment 19,23,29,30,3
7,88 Further, pigments other than the above can be used as long as they are useful in terms of heat resistance, spectral characteristics, chemical resistance, dispersibility and the like.

The amount of pigment added is usually 5 to 5 with respect to the total amount.
0% by weight, preferably about 10 to 30% by weight. Further, in the present invention, an extender pigment may be added for the purpose of adjusting printability, particularly the transition shape and film thickness. Examples of extender pigments include silicon oxide, barium sulfate, and calcium carbonate, which have a small primary particle size and high transparency and a relatively small refractive index. The amount of the extender pigment added is 2 to 50% by weight, preferably 5 to 50% by weight based on the total amount.
It is about 30% by weight.

The ink composition of the present invention is mixed with a predetermined amount of the mixed resin, solvent, pigment, etc., and dispersed and kneaded using a three-roll mill or the like to improve the dispersibility of the pigment. In order to further improve the dispersibility of the pigment, it is preferable to sufficiently wet the pigment in advance with a planetary mixer or the like before kneading with three rolls. Alternatively, the pigment powder itself may be made into a fine powder by a ball mill or the like. Further, an organic derivative of the pigment, for example, a phthalocyanine copper derivative, or a surfactant, for example, an anionic, cationic, or nonionic surfactant may be added to prevent the pigment from reaggregating. Examples of the anionic surfactant include carboxylic acid salts, sulfuric acid ester salts and sulfonic acid salts. Examples of cationic surfactants include primary to tertiary amine salts. As the nonionic surfactant, for example, ether type (polyoxyethylene alkyl ether etc.), ester type (glycerin ester etc.), ether ester type (polyoxyethylene ether of glycerin ester,
Examples include sorbitan ester polyoxyethylene ether). Among these, it is preferable to use an anionic or cationic surfactant from the viewpoint of dispersibility, but alkali metal (potassium, sodium, etc.) significantly deteriorates the life of the liquid crystal, and therefore a nonionic surfactant is used. Preference is given to using.

The surface of the pigment may be pretreated with a silane coupling agent or a titanium coupling agent in order to improve the wettability between the resin and the pigment. In any case, the proportion of the pigment particles having a particle size of 1 μm or less, preferably 0.3 μm or less is preferably 80% or more of the whole.

[0026]

【Example】

Examples 1 to 13 and Comparative Examples 1 to 6 Various inks having different mixing ratios of epoxy resin, polyester resin and melamine resin were prepared. Table 1 shows the basic composition of each red, green and blue ink.
It is as follows.

[0027]

[Table 1]

The components used are as follows. (1) Resin (1-1) Epoxy resin: Epicoat 1007 (produced by Yuka Shell Co., Ltd., bisphenol A type epoxy resin) (1-2) Melamine resin: Sumimar M100C (produced by Sumitomo Chemical Co., Ltd., methylated melamine) ) (1-3) Polyester resin: Phthalic anhydride, isophthalic acid and neopentyl glycol are charged into a reaction vessel,
Add an appropriate amount of oleyl alcohol as a solvent, and add 200
Polyester resin with acid value 10 polymerized by heating and stirring at ℃ for 2 hours (2) Pigment (2-1) Red pigment: HOSTPERM SCARLET GO (Red No.168 manufactured by Hoechst) and PALIOTOL YELLOW L1820 (BASF) ,
Yellow No. 139) and 3: 1 in a ratio of 3: 1.

(2-2) Green pigment: HELIOGEN GREEN D8
734DD (BASF, Green No.7) and PALIOTOL YELLOW L18
20 (BASF Corp., Green No. 739) was mixed and used at a ratio of 5: 1. (2-3) Blue pigment: HELIOGEN BLUE D7072DD (BASF
Blue No. 15: 3) manufactured by K.K. and VIOLET B (Violet No. 23 manufactured by Ciba-Geigy) were mixed at a ratio of 4: 1 and used. (3) Solvent: 20 wt% of butyl carbitol in oleyl alcohol
The mixture was used in the ratio of. (4) An extender barium sulfate (BF-1 manufactured by Sakai Chemical Co., Ltd.) was used.

A predetermined pigment, a solvent, and an extender pigment are added to the resin in the predetermined amounts shown in Table 1, and the mixture is sufficiently stirred by a stirrer, and then the pigment particles are sufficiently dispersed by using a three-roll mill. The meat was kneaded until fine, and red, green, and blue inks were obtained. The amounts (parts by weight) of the epoxy resin, polyester resin and melamine resin used at that time are shown in Tables 2 and 3.

In Comparative Example 1, since epoxy resin alone does not cure, 4-methylhexahydrophthalic anhydride was added as a curing agent in an amount of 86 parts by weight based on 100 parts by weight of the epoxy resin. A color filter was printed using each of the obtained inks. As the flatbed printing machine, Ekter 600CL manufactured by Koyosha Co., Ltd. was used. The offset blanket is ST800 manufactured by Sumitomo Rubber Industries, Ltd.
(Thickness 1.9 mm) was used. This has a very polished surface (surface roughness Rz = 1 μm).
The glass is the substrate Nippon Sheet Glass Co., Ltd. soda lime glass (surface SiO ₂ immersion treatment products, thickness 1.1m
m) was used. A waterless planographic plate manufactured by Toray Industries, Inc. is used as a plate, and stripes having a width of 100 μm are arranged at a pitch of 300 μm.
Red, green and blue patterns were printed in order.
After printing, it was heated and cured in a clean oven at 220 ° C. for 1 hour.

The printed matter obtained was evaluated for heat resistance, chemical resistance, adhesiveness, surface hardness, cure shrinkage, and printability. The results are also shown in Tables 2 and 3. The test methods and evaluation criteria are as follows. (1) Heat resistance The printed matter was heat-treated in an oven at 250 ° C. for 1 hour, the color difference ΔE before and after the treatment was determined, and evaluated according to the following criteria.

(Evaluation) (ΔE) ◎ 0 to 1 ○ 1 to 3 Δ 3 to 5 × 5 or more (2) Chemical resistance Each printed product was dipped in the liquid shown below for a predetermined time, and the color difference ΔE before and after the dipping The number of liquids having a value of 3 or more was examined.

(A) N-methyl-2-pyrrolidone 25 ° C.
Soak for 30 minutes (b) Isopropyl alcohol at 25 ° C for 1 hour (c) 10% hydrochloric acid at 25 ° C for 1 hour (d) 5% aqueous sodium hydroxide solution at 25 ° C for 1 hour (e) Butyl acetate at 25 ° C Immersion for 1 hour (f) Acetone, 30 minutes at 25 ° C (g) Butyrolactone, 1 hour at 40 ° C (h) Boiling water, 1 hour Immersion criteria are as follows.

(Evaluation) (Number of ΔE ≧ 3) ◎ 0 ○ 1 △ 2 to 3 × 3 or more (3) Adhesiveness Commercially available in accordance with the cross-cut tape method described in JIS K 5400. Adhesive tape in a grid pattern (vertical 10 pieces / cm, horizontal 1
(010 lines / cm) was adhered to a printed matter and peeled off, and the number of peeled pieces was examined and evaluated according to the following criteria.

(Evaluation) (Peeling Number) ◎ 0/100 ○ 1 to 5/100 Δ 6 to 10/100 × 10/100 to 30/100 × × 30/100 to 100/100 (4) Surface Hardness JIS K The hardness was measured based on the pencil scratch value described in 5400 and evaluated according to the following criteria.

(Evaluation) (Hardness) ◎ 6H or more ○ 4-5H △ 2-3H × 1H or less (5) Curing shrinkage The rate of change in volumetric shrinkage before and after curing was measured and evaluated according to the following criteria. .

(Evaluation) (Change rate of volumetric shrinkage ratio) ◎ 0 to 5% ○ 5 to 10% △ 10 to 30% × 30% or more (5) Printability Visual observation of shape and transferability during printing The following criteria were evaluated.

(Evaluation) (Shape and transferability during printing) ◎ Very good ○ Good △ Bad × Very bad

[0040]

[Table 2]

[0041]

[Table 3]

From the results of these tests, the inks of the examples in which the epoxy resin, the polyester resin and the melamine resin are mixed have various characteristics required for a color filter, while one of these resins is used. Or 2
It can be seen that the ink of the comparative example in which only the seed is blended is not sufficiently satisfactory in various properties. Particularly, as in Examples 1 to 3, 9, 10, 12, and 13, the proportion of the melamine resin in the mixed resin is 30 to 70% by weight, and the ratio of the epoxy resin to the polyester resin is 30/70 to 70 /.
When it is 30, it has very high characteristics in a well-balanced manner.

[0043]

EFFECTS OF THE INVENTION According to the ink composition of the present invention, by containing a mixed resin composed of an epoxy resin, a polyester resin and a melamine resin, a solvent and a pigment, heat resistance, chemical resistance, adhesiveness, etc. There is an effect that it is possible to obtain a color filter having all of the above-mentioned various characteristics.

Particularly, the melamine resin in the mixed resin is 30 to
When the content was 70% by weight and the balance was 30/70 to 70/30 (weight ratio) of the epoxy resin and the polyester resin, the above-mentioned properties were well balanced for a color filter. An ink is obtained. Further, when an organic pigment having a particle size of 80% or more and 1 μm or less is used as the pigment, spectral characteristics and flatness are improved.

Claims (3)

(57) [Claims] 1. An ink composition for a color filter comprising a mixed resin composed of an epoxy resin, a polyester resin and a melamine resin, a solvent, and a pigment. 2. A melamine resin in the mixed resin is 30 to 7
The color filter ink composition according to claim 1, wherein the ink composition is contained in an amount of 0% by weight, and the rest is 30/70 to 70/30 (weight ratio) of an epoxy resin and a polyester resin. 3. The ink composition for a color filter according to claim 1, wherein 80% or more of the entire pigment is an organic pigment having a particle size of 1 μm or less.