CA2079469A1 - Process for producing multicolor display - Google Patents

Abstract

ABSTRACT

A color filter is made easily and uniformly employing electrodeposition.
A specific positive type photosensitive resin layer is formed on a transparent electrode formed on a transparent substrate and, then a step for exposing and developing to obtain a desired pattern and a step for forming a desired colored layer by electrodeposition are repeated without peeling of the resin layer.

Description

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DESCRIPTlON

PROCESS FOR PRODUCING M~LTICOLOR DISP~AY

Technical Field The present invention relates to a process for producing a multicolor display used for multi~coloring display elements such as liquid crystal and the like.
Background Art As a method for forming a conventional color ~ilter, there are various methods. Among them, a noticeable method is that employing electrodeposition. For example, in Japanese Patent Kokai No. 61-272720, there is disclosed a method comprising forming an electroconductive layer on a substrate, forming a positive type photosensitive coating thereon, exposing the coating, removing the exposed part and formlng a desired colored layer by electrodeposition. In this method, since the positive type photosensitivc coating is formed, only the exposed part is ideally solubilized in a developer, whereby, Pxposure and development can be repeatedly conducted regarding the remained photosensitive coating.
However, regarding the positive type photosensitive coating, the part which is not subjec~ed to llght is modi~icd by a developer and electrodeposition upon the first development and it becomes impo~sible to subject the remained part to expo~ing and developing treatment again SEP 30 ' 92 4: 56 06 949 0361 Pl:~GE . æ I a ., .

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and, ~herefore, a commercially available quinonediazide can not be used. Accordingly, in this method, it is necessary to provide a peeling step at which all of a positive type photosensitive coating which has been exposed and developed is once peeled off and then the positive type photosensitive coating is formed again. which makes the step complicated.
Further, in Japanese Patent Kokai No. 61-279803, there is also disclosed a method for producing a color filter wherein exposure, development and electrodeposition are repeatedly conducted using a positive type photosensitive composition oontaining quinonedia2ide. In ~his case, quinonediazide is decomposed by a heat and, ~herefore, it can not act as the posi~ive type photosensitive coating after a step for making the second colored layer.
The present invention provi.des a process for producing a multicolor display by which a color filter having a fine colored pattern superior in thin-film uniformi~y is obtained by more simple produc~ion process.
Disclosure of the invention ~ hat is, the present invention provides a process ~or producing a multicolor display which comprises the followirg steps:
(a) a step for forming a transparen~
el.ectroconductive layer on a transparent substrate;
~ b~ a step for forming a positive type photosensitive resin composition comprising a polymer having SEP 30 ~92 4:57 06 949 0361 P~GE.

30-SEP-92 17:57 f:iOYRMf~8Pl:~RTNERS PRGE IZ/26 a branched group which i8 unstable to an acid of tert-butyl ester of carboxylic acid or tert-butyl carbonate of phenyl, and a photopolymerization initiator which produces an acid upon exposure on the transpa~ent electroconductive layer ~ c) a step for placing a mask having a desired pattern on the photosensitive resin layer followed by exposure and development to expose the part of the transparent electroconductive layer;
(d) a step for forming a desired colored layer on the exposed transparent electroconductive layer; and (e) a step for repeating the steps ~c) and ~d~
desired times.
As shown in Fig 1 (A), a transparent electroconductive layer is firstly forlned on a substrate 1. The substrate may be anyone which is normally used for a mul~icolor display and examples thereof include glass substrate, plastic substrate and the like. As the transparent electroconductive layer, for example, ~hose containing tin oxide, lndium oxide, antimony oxide and the like as a main component are sui~ably used. The trasparen~
electroconductive layer is ~ormed by an art-known method such as deposition, spattering and the like.
Then, a positive type photosensltive resin layer 3 is for~ed on the electroconductlve layer 2, as shown in Fig 1 IB). The positive type photosensitive resin layer is a photosensitive resin layer which was once applied and it can bc exposed and developed plural times. For example, it is a SEP :20 ~ gz 4: 57 06 949 0361 PflGE . 012 30-5E?-92 17:58 f~)YRI`1R8~PRRTNERS Pf~G~ 1:3/21~
~9`~ g9 positive type photosensitive resin composition comprising a polymer having a branched group which is u~s~able to an acid composed of tert-butyl ester of carboxylic acid or tert-butyl carbonate of phenyl (U.S. ~aten~ No. 4,4~1,628 and Japanese Patent Kokai No. 2-309358). In this case, the polymer having a branched group which is unstable to an acid is a polylner or copolymer of a polymerizable compound having a branched group which is unstable to the above acid. A~
the polymerizable compound having a branched group which is unstable to the acid, for example, there are p-t-butoxycarbonyloxy-~-methylstyrene, p-t-butoxycarbonyloxystyrene, t-butyl-p-vinyl ben20ate, t-butyl-p-isopropenylphenyloxy acetate, t-buty~ methacrylate and the li~e. E~.amples of the monomer which can be copolymerized with the above monomer include monoolefin and diolefin hydrocarbons. The photopolymerizat~on initiator which produces an acid by light irradiation ~exposureJ is generally onium salt, which has been known heretofore.
ay placing a mask 4 having a desired pattern on the positive type photosensitive resin composition (Fig 1 (C)) followed by exposure, it becomes possible to elute off the photosensitive resin composition layer at the exposed part. Then, the photosensitlve resin composition is eluted off with a predetermined eluting solution to ~orm a patterned substrate lPig 1 (D)~. The ~na~k and elution technique are known. The substrate is in the form tha~ the electroconductive layer 2 is exposed at the position which SEP 30 ~92 4:s8 06 949 036l PRGE.013 30-SEP-9Z 17: 58 ROYRI`l~?~PRRTNER5 PRGE 14/26 2~)7~9 must be colo~ed, aa shown in Fig 1 (D). As shown in Fig 1 (E), a colored layer 5 (e.g. red (R)) is formed by conducting electrodeposition in an electrodeposition bath with applying a current through ~he electroconductive layer 2. A synthesl~ed polymer resin used as a membrane-forming component of the electrodeposition bath which is used in this method may be cationic, anionic or amphoionic resin, and examples thereof include various known resins such as acrylic resin, epoxy resin, urethane resin, polybutadiene resin, polyamide resins, carhoxyl group-introduoed polybutadiene, carboxyl group-introduced alkyd resin and the like. ~urther, some synthesi~ed polymer resin having specific ionic character attack on the electroconductive layer 2 and, therefore, it is necessary to select ~embrane-forming components by taking this respect into consideration.
The electrodeposition bath and other details are descrlbed ln Japanese Patent Kokal No. 59-114592, Japanese Patent Application No. 62-46321 by the present inventors et al. ~Japanese Patent Kokai ~o. 63-210901) and the like. The elecrodepositable paint may be any o~ photopolymerizable and thermoset paint.
Then, by placing a positive mask 4 on the colored layer and the positive type photosensitive resin layer which are formed on the substrate 1 ~Fig 1 (F~) followed by exposure, the photosensitive resin composition layer at the exposed par~ is eluted off to obtain a patterned substrate SEP 30 ~92 4:59 06 949 036l PRGE.0l4 30-SEP-92 1 -~: 59 ROYf~ Pf~RTN~i~S PRG~ 15'21~
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(Fig 1 ~G)), according to the same manner as that described above.
~ urther, a colored layer 6 (e~g~ green (G)) is formed by conducting electrodeposition in an electrodeposition bath with applying a current through the electroconductive layer 2, as shown in Fig 1 (H). ~hen, by repeating steps shown in Fig l lF) to Fig 1 (H), a colored layer 7 (e.g. blue (B~) is formed [Fig 1 (I) to Pig 1 (K)].
If necessary, a black matrix may be formed, in addition to blue, red and green colored layers. In this case, the total surface of the substrate wherein the colored layers (~, G and B) and the positive type photosensitive layer are remained is exposed and further eluted to expose the electroconductive layer 2 other than the colored layers (R, G and B) (~ig 1 (L)).
Then, as shown in ~ig 1 (M), a colored layer 8 le.g. black) may be formed by conducting electrodeposition in an electrodeposition bath with applying a current through the electroconductive layer 2. Further, B blac~ matrix may be formed by a method other than electrodeposition method.
According to the production process of the color ~ilter of the present invention, a color filter having a colored layer in any arrangement and shape can be produced, regardless of tho shape of the electroconduc~ive layer.
In the present ~nvention, it is nccessary to design a mask used for the exposure in Figs I ~C), 1 tP) and 1 ~I) by taking arrangement and shape oÇ the desired colored layer SEP 30 ~92 4:59 06 949 0361 P~GE.015 30-SEP-92 1~:59 ROY~M~&PRRTNERS P~GE 16/ZS

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into considesation.
Example ~he following Examples further illustrate the present invention in detail but are not to be construed to limit the scope thereoÇ.
Reference Exam~le l Preparation of positive type photosensitive resin composition To 50 9 of xylene containing 2.0 9 of azobisisobutyronitrile, 65.0 9 of t-butyl methacrylate, 20.0 g of butyl acrylate and 20.0 9 of methyl methacrylate were added and ~he mixture was heated with stirring in a nitrogen flow at 60C for 10 hours. After cooling, the reaction product was diluted with tetrahydrofuran and rinsed with petroleum ether/methanol. The resulting polym~r ~93.0 9, yield of 93 ~) had a weight-average molecular weight ~GPC) of 22,000 The polymer waa dissolved in tetrahydrofuran so that an amount of a solid material becomes 20 ~ by weight and, further, triphenylsulfoni~m hexafluoroantimonate was added to the polymer in an amount of 20 % by weight to obtain a positive type photosensitive resin composition.
Reference Example 2 Preparation of cationic photo~ensitive electrodepositable resin ~ompositlon for ~orming color filter SEP 30 '9Z 5:00 06 949 0361 P~GE.016 313-SEP-92 18:~0 f~o`~ &PRRTNER5 PRGE 17/ZEi ~7~

Blue Green Red ~lack Catio~ic photosensitive 99S.0 99S.O 995.O 992.5 electrodepositable resin composition Phthalocyanine blue S.0 Phthalocyanine green - S.~ - -Azo metal salt red piqment - - 5.O
Carbon black - - - 7.5 'rotal amount lOOO.O lOOO.O lOOO.O lOOO.O

A ca~ionic photosensitive resin composition comprising 80 parts by weight of an organic polymer binder (weight-average molecular weight of 70,000) wherein each compound obtained by the equimolar reaction of N,N-diethylaminoethyl methacrylate, styrene, ethyl acrylate and p-hydroxybenzoic acid with glycidyl acrylate was copolymerized each other in a molar ratio of 3:2:4:1, 0.5 parts by weight of 2,2-dimethoxy-2-phenylacetophenone and 14.5 parts by weight of trimethylolpropane triacrylate was diluted with ethylene glycol monobutyl ether 50 that a ~olatile content becomes 00 ~ and neutrali~ed with 0.5 equivalent ace~ic acid and, then, the volatile content was adjusted to 10 ~ with deionized water.
To ~he electrodepositable resin composition thus ~repared, a pigment was formulated as described below to for~ cationic electrodepositable solu~ions o three colors.
Example 1 SEP 30 ' 92 S: 00 06 949 0361 P~GE . 017 30-SEP-9Z 18:00 f~OYf:lM~&PflRTN~RS Pf~Gc l9/Z6 ` ~7~3 ~5~
g According to the same manner as that of a conventional techni~ue, a trasparent electroconductive memhrane 2 of ITO (indium tin oxide) compound was formed on a ~lass substrate 1. A po~itive type photosen3itive resin composit~on of Reference Example 1 was applied on the transparent electroconductive membrane 2 using a spinner ~ollowed by drying to form a positive type photose~sitive resin composition layer 3 on the transparent elec~roconductive membrane.
Then, it was exposed to a high pressure mercury lamp through a mask having a predetermined pattern and heated at lOO~C for ~ minutes. Afte~ developing with an al~ali solution, a salt was formed at the exposed part to elute off, which resulted in exposure of the surÇace Oe the ~ransparent electroconductive layer 2. Then, the substrate 1 wherein the transparent electroconductive layer 2 was exposed was immersed in an electrodeposition bath of a red cationic photosensitive electrodepositable resin composition and a direct current of 5 volt was applied for 30 seconds using a transparent conductive layer as a negative electrode. ~hereaf~er, the substrate was taken out and sufficiently rinsed with water. In this case, the electrodepositable composltion was not deposited onto the pos~tive type photosensitive resin composltion on the ~ransparent electroconductive me~brane and was removed by rinoing wi~h water. However, ~ polymer deposited on the e~ectrode to which an electric current was applied beco~e SEP 30 ' 9Z 5: 01 06 949 0361 PRGE . 019 .

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insoluble to water and, therefore, it could not be removed by rinsing with water. After rinsing and drying, a colored polymer layer having good transparency was formed on the transparent electrode.
Then, the substrate was exposed to a hish pressur~
mercury lamp through a mask 4 having shifted pattern and heated at lOOaC for 3 minutes. After developing with an alkali solution, the surface of the transparent conductive membrane 2 was exposed, similarly~ Then, the substrate 1, wherein the transparent electroconductive layer 2 was exposed and the red colored layer was formed, was im~ersed in an elec~rodeposition bath of a green cationic photosensitive electrodepositable resin composition and a direct current of 5 volt was applied for 45 seconds using the ~ransparent conductive layer as a negative electrode.
Thereaf~er, the substrate was taken out and sufficiently rinsed with water. In this case, a green electrodepositable composition was not deposited onto the positive type photosensitive resin composition and a red colored layer on the transparent conductive membrane and was removed by rinsing with water. After rinsing and drying, a green polymer membrane having good transparency was ~ormed.
Purther, the substrate was exposed through a mask 4 having a shifted pattern, heated and developed and, then, a bl~le electrodepositable composition was deposited b~
applying a direot current of 5 volt for 30 seconds. Af~er rinsing and drying, a blue poly~er membrane was formed, SEP 30 92 5:02 z6 949 0361 PRGE 0l9 3~3-SEP-9Z 18:02 ROYR~16B.Pf~RTNERS Pf~G._ Z0/26 - 11 2 ~ 7 S ~ 6 ~

similarly.
The total surface of the substrate wherein the remainder of the positive type photosensitive resin composition as well as red, green and blue colored layers wer~ formed was exposed to a high pressure mercury lamp.
Ater developing ~ith an alkali solution, the positive type photosensitive resin composition was eluted except the colored layer, which results in exposure Gf surface of the ~ransparent conductive membrane 4.
Then, black color electrodeposition was conducted by applying a direct current of 3 volt for 20 seconds.
After rinsing and drying, a black colored layer was formed between the gap of the red, green and blue colored filter~.
Pinally, the total surface of the red, green and blue colored membranes formed on the transparent substrate was exposed at 200 mJ/cm2 to cure the membranes.
The film thickness of the colored membrane was 2.0 microns.
Effect of the invention According to the present invention, a color filter can be formed only by forming a positive type photosensitive resin layer on a transparent electrode one time and, therefore, an inconvenient process such as peeling o resist is not required.
Purther, it becomes possible to form various colored filter having uniorm film thickness and, there~ore, color shading due to distribution of fil~ ~hickness is SEP 30 ' 92 5: 02 06 949 0:361 P~GE . 0Z0 30-SEP-92 18:0Z ROYRMR&PRRTNERS PRGE Zl/25 ~"~ 2~'7~9 eliminated, which requltq in excellent display image.
Further, a transparent electrode exposed by developinq a photosensitive reQin layer is always flesh and is free from stain, and for~ation of a colored layer by electrodeposition also acts, advantageously.
~rief explanation of dra~inqs Pigs 1 IA) to 1 ~M) are flow sheets illustrating the process for producing a color filter of the present invention.

SEP 30 '92 5:03 06 949 0361 PRGE.021

Claims (4)

CLAIM

1. A process for producing a multicolor display which comprises the following steps:
(a) a step for forming a transparent electroconductive layer on a transparent substrate;
(b) a step for forming a positive type photosensitive resin composition comprising a polymer having a branched group which is unstable to an acid of tert-butyl ester of carboxylic acid or tert-butyl carbonate of phenyl, and a photopolymerization initiator which produces an acid upon exposure on the transparent electroconductive layer;
(c) a step for placing a mask having a desired pattern on the photosensitive resin layer followed by exposure and development to expose the part of the transparent electroconductive layer;
(d) a step for forming a desired colored layer on the exposed transparent electroconductive layer; and (e) a step for repeating the steps (c) and (d) desired times.

2. The process according to claim 1, wherein red, green and blue colored patterns are formed in a coloring step (d) by electrodeposition.

3. The process according to claim 2, wherein a black matrix is present between the gap of red, green and blue colored patterns.

4. The process according to claim 3, wherein a black matrix is also formed by repeating the steps (c) and (d).