Color filter for low temperature applications

Abstract

A color filter comprising a cured layer of a photosensitive resist composition comprising a highly reactive polyacrylate monomer and a process for the preparation thereof are provided. The color filter is especially useful for low temperature applications such as electrophoretic displays, polymer dispersed liquid crystal displays, OLED devices and the like.

Claims

1. A mixture of two or more different polyacrylate monomers of formula (I) ##STR00020## wherein n is 4; and R.sup.1, R.sup.2, and R.sup.3 are independently from each other H or a group of formula ##STR00021## where R.sup.4 is independently from each other H or methyl; with the proviso that at least three groups of formula (II) are present, and an amount of sorbitol hexaglycerolate hexa(meth)acrylate of 20 to 60% by weight, based on the two or more different polyacrylate monomers of formula (I).

2. The mixture as claimed in claim 1, wherein each R.sup.4 is methyl.

3. The mixture as claimed in claim 1, wherein each R.sup.4 is hydrogen.

4. The mixture as claimed in claim 1, wherein the amount of sorbitol hexaglycerolate hexa(meth)acrylate is from 20 to 50% by weight, based on the two or more different polyacrylate monomers of formula (I).

5. The mixture as claimed in claim 1, wherein the amount of sorbitol hexaglycerolate hexa(meth)acrylate is from 25 to 40% by weight, based on the two or more different polyacrylate monomers of formula (I).

6. The mixture as claimed in claim 1, wherein the amount of sorbitol hexaglycerolate hexa(meth)acrylate is from 25 to 30% by weight, based on the two or more different polyacrylate monomers of formula (I).

7. The mixture as claimed in claim 2, wherein the amount of sorbitol hexaglycerolate hexa(meth)acrylate is from 25 to 30% by weight, based on the two or more different polyacrylate monomers of formula (I).

8. The mixture as claimed in claim 3, wherein the amount of sorbitol hexaglycerolate hexa(meth)acrylate is from 25 to 30% by weight, based on the two or more different polyacrylate monomers of formula (I).

9. The mixture as claimed in claim 1, wherein the mixture consists of the two or more different polyacrylate monomers of formula (I).

10. The mixture as claimed in claim 1, wherein one of the two or more different polyacrylate monomers of formula (I) is sorbitol polyglycerolate polyacrylate.

Description

EXAMPLES

Example 1: Sorbitol Polyglycerolate Polyacrylate

(1) 80 g of sorbitol polyglycidyl ether (0.5 epoxy eq from .sup.1H NMR; EEW 160; ERISYS GE-60/CVC Chemicals), 0.55 g (5 mmol) of tetramethyl ammonium chloride and 110 mg of hydroquinone monomethyl ether are mixed and heated to a temperature of 90 C. 49 g (0.5 moles) of acrylic acid are added dropwise within 2 hours keeping the reaction temperature at 90 C. Then, the mixture is stirred for 4 hours at 90 C. until NMR analysis shows complete conversion. The mixture is cooled to room temperature to give sorbitol polyglycerolate polyacrylate comprising sorbitol hexaglycerolate hexaacrylate as a highly viscous, yellow liquid.

(2) .sup.1H NMR (500 MHz, CDCl.sub.3, ppm): 3.56-3.84 (m, 62H), 4.04 (m, 6H), 4.22 (m, 10H), 4.45 (m, 1H), 5.86 (d, 6H), 6.15 (dd, 6H), 6.42 (d, 6H).

Synthesis of the (Copolymerisable) Polyacrylates

Example 2

(3) 112.5 g of methoxypropyl acetate are degassed with nitrogen for 60 min at room temperature followed by heating to 140 C. under a nitrogen atmosphere. A homogenous blend of 60.0 g of benzyl methacrylate, 14.3 g of methacrylic acid and 0.38 g of di-t-butylperoxide is added dropwise within 1.5 hours keeping the temperature at 135-140 C. Then, the mixture is stirred for 4 hours at 140 C. and cooled to room temperature. The resulting clear viscous polymer solution has a solid content of 37.7 wt % (halogen dryer, 150 C.). The final polymer solution is adjusted to 25 wt % by addition of 91 g of methoxypropyl acetate. The molecular weight of the polymer is determined by GPC (THF): Mn 5.300, Mw 13.700, pdi 2.6. Viscosity (Brookfield, 20 C., 100 rpm): 438 mPas.

Example 3

(4) 101.6 g of methoxypropyl acetate are degassed with nitrogen for 60 min at room temperature followed by heating to 140 C. under a nitrogen atmosphere. A homogenous blend of 48.4 g of benzyl methacylate, 11.5 g of methacrylic acid and 0.61 g of di-tt-butylperoxide is added dropwise within 1.5 hours keeping the temperature at 135-140 C. Then, the mixture is stirred for 4 hours at 140 C. and cooled to room temperature. The resulting clear viscous polymer solution has a solid content of 35.1 wt % (halogen dryer, 150 C.). The final polymer solution is adjusted to 25 wt % by addition of 58 g of methoxypropyl acetate. The molecular weight of the polymer is determined by GPC (THF): Mn 5.300, Mw 12.500, pdi 2.4. Viscosity (Brookfield, 20 C., 100 rpm): 249 mPas.

Example 4: Functionalization of the Polymer of Example 2

(5) 70 g of the polymer mixture obtained in Example 2 (25 wt % solids) are degassed for 60 min at room temperature followed by heating to 130 C. under a nitrogen atmosphere. During the heating phase, 0.03 g of tetramethyl ammonium chloride and a few crystals (ca 10 mg) of 4-hydroxy-2,2,6,6-tetramethyl piperidine-1-oxyl are added to the polymer mixture. At 130 C., a solution of 1.25 g of glycidyl methacrylate in 2.5 g of methoxypropyl acetate is added dropwise within 45 min keeping the temperature at 130 C. Then, the mixture is stirred for 4 hours at 130 C. and cooled to room temperature. The resulting slightly yellowish polymer solution has a solid content of 24.5 wt % (halogen dryer, 150 C.). Viscosity (Brookfield, 20 C., 100 rpm): 245 mPas.

Example 5: Functionalization of the Polymer of Example 3

(6) 84 g of the polymer mixture obtained in Example 3 (25 wt % solids) are degassed with nitrogen for 60 min at room temperature followed by heating to 130 C. under a nitrogen atmosphere. During the heating phase, 0.04 g of tetramethyl ammonium chloride and a few crystals (ca 10 mg) of 4-hydroxy-2,2,6,6-tetramethyl piperidine-1-oxyl are added to the polymer mixture. At 130 C., a solution of 1.50 g of glycidyl methacrylate in 3.0 g of methoxypropyl acetate is added dropwise within 45 min keeping the temperature at 130 C. Then, the mixture is stirred for 4 hours at 130 C. and cooled to room temperature. The resulting slightly yellowish polymer solution has a solid content of 24.1 wt % (halogen dryer, 150 C.). Viscosity (Brookfield, 20 C., 100 rpm): 151 mPas.

Application Examples: Color Filters Applications

Example 6

(7) 1.5 g of IRGAPHOR Red BK-CF (C.I. Pigment Red 254; Ciba), 0.6 g of Ajisper PB 821 (a pigment dispersing agent; Ajinomoto Japan), 7.65 g of propyl glycol monomethyl ether acetate (PGMEA) and 4.0 g of the polymer obtained in Example 2 are mixed under stirring. 30 g of zirconium oxide beads (0.5 mm) are added, and the mixture is shaken in a Skandex for about 15 hours. Then, the dispersion and the beads are separated by sieving.

(8) 7.0 g of the resulting dispersion are mixed with 0.51 g of sorbitol polyglycerolate polyacrylate obtained in Example 1 and 3.5 g of PGMEA, followed by adding 0.14 g of IRGAPHOR OXE02 (a photoinitiator; Ciba). The mixture is shaken for 1 hour. The mixture is spin coated on a cleaned and dried polyester substrate for 30 sec with 1000 rpm and dried on a hot plate for 2 min at 65 C. The dried film is exposed with UV light through a photo mask (Karl Sss Mirror mask aligner, MA 6) for about 15 sec. The non-exposed film is washed away with a 0.05% solution of potassium hydroxide in water with 0.25% of a surfactant, rinsed with water and dried on a spin coater for 30 sec at 2000 rpm. A well defined red pixel pattern is obtained.

Example 7

(9) 1.65 g of Heliogen Green CF 9365 (C.I. Pigment Green 36; BASF) and 0.85 g of CROMOPHTAL Yellow LA 2 (C.I. Pigment Yellow 150; Ciba), 7.4 g of PGMEA and 4.0 g of the polymer obtained in Example 2 are mixed under stirring. 30 g of zirconium oxide beads (0.5 mm) are added, and the mixture is shaken in a Skandex for about 15 hours. Then, the dispersion and the beads are separated by sieving.

(10) 7.0 g of the resulting dispersion are mixed with 0.94 g of sorbitol polyglycerolate polyacrylate obtained in Example 1, 1.17 g of the polymer obtained in Example 2 and 5.4 g of PGMEA, followed by adding 0.16 g of IRGAPHOR OXE02 (a photoinitiator). The mixture is shaken for 1 hour.

(11) The mixture is spin coated on the coated substrate obtained in Example 6 with 1000 rpm for 30 sec and dried at 65 C. for 2 min on a hot plate. The dried film is exposed with UV light through a photo mask (Karl Sass Mirror mask aligner, MA 6) for about 26 sec. The non-exposed film is washed according to Example 6.

Example 8

(12) 1.44 g of C.I. Pigment Blue 15.6, 0.03 g of SOLSPERSE5000 (a pigment derivative), 0.03 g of SOLSPERSE 12,000 (a pigment derivative), 8.3 g of PGMEA and 4.0 g of the polymer obtained in Example 2 are mixed under stirring. 30 g of zirconium oxide beads (0.5 mm) are added, and the mixture is shaken in a Skandex for about 15 hours. Then, the dispersion and the beads are separated by sieving.

(13) 7.0 g of the resulting dispersion are mixed with 0.83 g of sorbitol polyglycerolate polyacrylate obtained in Example 1, 1.22 g of the polymer obtained in Example 2 and 4.5 g of PGMEA, followed by adding 0.11 g of IRGAPHOR OXE02 (a photoinitiator). The mixture is shaken for 1 hour.

(14) The mixture is spin coated on the coated substrate obtained in Example 7 with 1000 rpm for 30 sec and dried at 65 C. for 2 min on a hot plate. The dried film is exposed with UV light through a photo mask (Karl Sass Mirror mask aligner, MA 6) for 50 sec. The non-exposed film is washed according to Example 6.

(15) The results of Examples 6 to 8 show a precise formed pixel pattern with a delta structure of three color pixels (R, G and B) with sizes of about 100150 m.sup.2. The distance between the pixels is 10-20 m. No deterioration of the pattern can be observed.

Examples 6a to 8A

(16) Examples 6 to 8 are repeated on a glass substrate. The same good results with regard to adhesion are achieved as in Examples 6 to 8.

Example 6B

(17) 1.5 g of IRGAPHOR Red BK-CF (C.I. Pigment Red 254; Ciba), 0.6 g of Ajisper PB 821 (a pigment dispersing agent; Ajinomoto Japan), 7.65 g of propyl glycol monomethyl ether acetate (PGMEA) and 4.0 g of the polymer obtained in Example 4 are mixed under stirring. 30 g of zirconium oxide beads (0.5 mm) are added, and the mixture is shaken in a Skandex for about 15 hours. Then, the dispersion and the beads are separated by sieving.

(18) 7.0 g of the resulting dispersion are mixed with 0.51 g of sorbitol polyglycerolate obtained in Example 1 and 3.5 g of PGMEA, followed by adding 0.14 g of IRGAPHOR OXE02 (a photoinitiator; Ciba). The mixture is shaken for 1 hour.

(19) The mixture is spin coated on a cleaned and dried polyester substrate for 30 sec with 1000 rpm and dried on a hot plate for 2 min at 65 C. The dried film is exposed with UV light through a photo mask (Karl Sass Mirror mask aligner, MA 6) for about 15 sec. The non-exposed film is washed away with a 0.05% solution of potassium hydroxide in water with 0.25% of a surfactant, rinsed with water and dried on a spin coater for 30 sec at 2000 rpm.

Examples 7B and 8B

(20) Example 6B is repeated twice and Irgaphor Red BK-CF is replaced by a mixture of 1.65 g Heliogen Green 9365 (CA. Pigment Green 36, BASF) and 0.85 g of Cromophtal Yellow LY2 (CA. Pigment Yellow 150, Ciba) in Example 7B and by 1.44 g of Pigment Blue 15:6, 0.03 g of SOLSPERSE5000 and SOLSPERSE 12,000 (two pigment derivatives) in Example 8B.

(21) The green layer is aligned on the red substrate of Example 6B and the blue layer is aligned on the red and green layer of examples 6B and 7B.

(22) Exposure times with the Karl Su{umlaut over (s)}s MA 6 mask aligner are 20 sec for the green layer and 30 sec for the blue layer.

Examples 6C to 8C

(23) Examples 6B to 8B are repeated on a glass substrate. The same good results with regard to adhesion are achieved as in Examples 6B to 8B. The results of Examples 6C to 8C show a precise formed pixel pattern with a delta structure of three color pixels (R, G and B) with sizes of about 100150 m.sup.2. The distance between the pixels is 10-20 m.

(24) The result is a well defined three color filter with very good adhesion properties both on polyester and glass substrates.

(25) The developing step of Example 7C is observed after various periods: after 20, 40, 60, 80, 100 and 120 sec. After 60 seconds a precise pixel is developed.

Comparative Example 9

(26) Example 8 is repeated with the exception that glycerol 1,3-diglycerolate diacrylate (GDDA) instead of sorbitol polyglycerolate polyacrylate and a generic binder (copolymer of about 20 mol % of methacrylic acid and about 80 mol % of benzyl methacrylate) instead of the polymer obtained in Example 2 are used.

(27) The material is applied as a single component material on a glass substrate and a polyester substrate with a resolution testing mask. Adhesion loss of almost all details can be observed.

Example 10

(28) Example 8 is repeated.

(29) The material is applied as a single component material on a glass substrate and a polyester substrate with a resolution testing mask. Adhesion loss is much less in comparison to the coated material of Comparative Example 9 and small details (small lines etc.) are even visible.

Example 11

(30) Example 8 is repeated with the exception that the functionalized polymer obtained in Example 4 instead of the polymer obtained in Example 2 is used.

(31) The material is applied as a single component material on a glass substrate and a polyester substrate with a resolution testing mask.

(32) Adhesion is significantly improved in comparison to the material of Comparative Example 9, and even very small details (e.g. digits) are visible.

(33) In order to check the adhesion and undercut during development under very severe conditions, much stronger than normal, a resolution testing mask is used in Comparative Example 9 and Examples 10 and 11. This mask enables showing specific details of 10 m going down to 1.5 m which are much smaller than in a standard pixel design for conventional color filter of 5 to 6 inch (12.7 to 15.24 cm).

(34) The adhesion quality of the layers in Example 10 and 11 is significantly improved in comparison to the layer obtained in Comparative Example 9. On the glass substrate of Comparative Example 9 most of the small details are lifted off during the development which can be found elsewhere on the glass substrate.

(35) The same improved results are obtained for the coated polyester substrates.