Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2001-07-31
2004-01-20
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S280100, C430S281100, C430S283100
Reexamination Certificate
active
06680158
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radiation-sensitive resin composition for spacer used in liquid crystal display (LCD) or touch panel, and more particularly to a radiation-sensitive resin composition for spacer, which resin composition provides good aging stability, and good spacer properties such as good surface smoothness or no undercut, good heat resistance and good chemical resistance and which resin composition can be developed by alkaline developer solution.
2. Description of the Related Art
It has been known that glass bead spacers or plastic bead spacers are often used to distribute in-between the two pieces of glass to maintain a given cell gap of LCD. Due to the random dispersion manner, the beads distributed by this known way are often spread on the red (R), green (G) and blue (B) pixel elements, leading to a scattering effect of the incident light, which in turn resulting in a decreasing contrast of the LCD.
In view of the problem of the decreasing contrast of LCD caused by the light scattering effect in the prior art, one of the major objects of the present invention is to provide a method to prepare spacers made from radiation-sensitive resin composition by photolithography. After development, the radiation-sensitive resin spacers prepared according to the present invention form dot type or stripe type spacers on the substrate (glass) plate and spread in the area beyond the R, G, and B pixel elements, therefore the problem of decreasing contrast caused by the light scattering can be dissolved. Furthermore, the spacers prepared according to the present invention provide good controllability of spacer thickness, good controllability for the cell gap between the two pieces of glass, and significantly improved LCD precision, all of which have extreme importance to the high resolution LCD.
In the manufacture process of LCD, there are three ways for the formation of radiation-sensitive resin spacers and alignment layer as follows:
1. coating the alignment layer after the formation of the radiation-sensitive resin spacers, then rubbing;
2. coating the alignment layer and rubbing, then forming the radiation-sensitive resin spacers; and
3. coating the alignment layer followed by forming the radiation-sensitive resin spacers, then finally rubbing.
In the above methods 1 and 3, rubbing comes after the formation of the radiation-sensitive resin spacers, which often leads to the rub-off of the spacers thus resulting in a poor display quality. In the method 2, because the alignment layer coating is performed prior to the formation of the spacers, swelling and dissolution of the alignment layer and scum deposition on the alignment layer occur, which cause abnormal alignment of the liquid crystals. The problems of poor surface smoothness, high undercut, poor heat and poor chemical resistance of the spacers, which were usually occurred in prior art, caused deformation of spacer and poor display quality of LCD. On the other hand, the viscosity of radiation-sensitive resin composition is apt to increase with increasing storage time, which resulted in production problems.
SUMMARY OF THE INVENTION
The object of the present invention is to avoid the poor display quality problem of the LCD mentioned above, the further object of the present invention is to provide a radiation-sensitive resin composition with good aging stability and to provide improved surface smoothness, heat resistance, chemical resistance and decreasing or no undercut for the radiation-sensitive resin spacers.
For the above-described objects, the radiation-sensitive resin composition for LCD spacers according to the present invention is such a radiation-sensitive resin composition for spacers, which is provided to meet the above-mentioned requirements and can be developed by alkaline developer solutions.
BRIEF DESCRIPTION OF THE TABLES
The preferred embodiments according the present invention will be set forth in details thereinafter in illustration with the aid of the following figures and tables, wherein:
Table 1 shows the synthesis examples of copolymer [A] and their molecular weight distribution in the embodiments;
Table 2 shows formulations in Examples 1-5 and Comparative Examples 1-8 and the contents of residual unsaturated carboxylic acid monomer; and
Table 3 shows the evaluation results for the spacers made from the radiation-sensitive resin compositions obtained in Examples 1-5 and Comparative Examples 1-8 of the embodiments according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The radiation-sensitive resin composition for LCD spacers according to the present invention comprises of [A], a copolymer comprising (a1) unsaturated carboxylic acid monomer derivative unit, (a2) epoxy-containing unsaturated monomer derivative unit, and optionally (a3) copolymerizable unsaturated monomer derivative unit other than the above monomer derivative units (a1) and (a2); [B] an addition polymerizable compound having at least one ethylenically unsaturated double bond; [C] a radiation-sensitive initiator; and [D] a solvent.
The compositions of the present invention will be described in details thereafter.
[A] Units of the Copolymer [A]
The copolymer [A] according to the present invention is obtained by free radical polymerization reaction of (a1) unsaturated carboxylic acid monomer, (a2) epoxy-containing unsaturated monomer, and (a3) optionally, copolymerizable unsaturated monomer other than the above monomer (a1) and (a2) in the presence of a solvent and an initiator, wherein:
The content of the unsaturated carboxylic acid monomer derivative unit (a1) is in the range of 5 wt %-50 wt %, preferably in the range of 15 wt %-40 wt %. When it is less than 5 wt %, the solubility of the obtained radiation sensitive resin composition in an alkali developer solution is liable to lower which results in poor developing property. On the other hand, when it is more than 56 wt %, the solubility of which becomes too high, and the developing property is poor. The unsaturated carboxylic acid monomer for (a1) can be exemplified as follows: unsaturated monocarboxylic acid monomers, such as acrylic acid, methacrylic acid, crotonic acid, &agr;-chloroacrylic acid, ethylacrylic acid and cinnamic acid; unsaturated dicarboxylic acid(anhydrides) monomers, such as maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, and mesaconic acid and anhydrides thereof; and unsaturated polycarboxylic acid(anhydrides) having a valence of 3 or more. Among these, acrylic acid and methacrylic acid are preferred. The unsaturated carboxylic acid monomers can be used alone or in admixture of two or more.
The content of the epoxy-containing unsaturated monomer derivative unit (a2) is in the range of 10 wt %-70 wt %; preferably in the range of 20 wt %-50 wt %. When it is less than 10 wt %, the heat resistance and chemical resistance of the radiation sensitive resin composition are poor; when it is more than 70 wt %, the solubility of the obtained radiation sensitive resin composition in an alkali developer solution is liable to lower and the developing property is poor. The epoxy-containing unsaturated monomer for (a2) can be exemplified as follows: glycidyl acrylate, glycidyl methacrylate, glycidyl &agr;-ethylacrylate, 3,4-epoxybutyl acrylate, 6,7-epoxyheptyl methacrylate, 6,7-epoxyheptyl &agr;-ethylacrylate, o-vinylbenzylglycidylether, m-vinylbenzylglycidylether, p-vinylbenzylglycidylether; among these, glycidyl methacrylate, 6,7-epoxyheptyl methacrylate, o-vinylbenzylglycidylether, m-vinylbenzylglycidylether and p-vinylbenzylglycidylether are preferred. The epoxy-containing unsaturated monomers can be used alone or in admixture of two or more.
The content of the copolymerizable unsaturated monomer derivative unit (a3) is in the range of 0 wt %-70 wt %, preferably in the range of 10 wt %-60 wt %, more preferably 15 wt %-50 wt %. When it is more than 70
Baxter Janet
Chi Mei Corporation
Walke Amanda C.
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