JP2007017655A - Member for liquid crystal display element, and the liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a member for liquid crystal display element, capable of reducing large unevenness of a cell gap occurring, when superimposing a glass substrate and a plastic substrate to each other, and to provide a liquid crystal display element that uses the member for liquid crystal display element. <P>SOLUTION: Upon heating and curing a sealing material in the conventional technique, a plastic substrate has a coefficient of thermal expansion larger than that of a glass substrate. Thus, when both substrates are stuck to each other and are cooled up to room temperature, distortions are generated due to differences in the rates of shrinkage, to produce a nonuniform gap. Here, a method is adopted, where the seal material is not heated; moreover, is completely hardened and mechanical strength is secured is employed. That is, a spacer serving concurrently as a liquid crystal outflow-preventing wall is preformed on the plastic substrate by the heating and curing, and thereafter, both substrates are stuck. Then, instantaneous adhesive agent is applied into a microgap between both substrates. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display element member and a liquid crystal display element. More specifically, the present invention relates to a liquid crystal display element member capable of reducing cell gap unevenness generated when a glass substrate and a plastic substrate are overlapped with each other, and a liquid crystal display element using the same.

  The conventional method of manufacturing a liquid crystal display element is a method using a glass substrate, and a large liquid crystal display element or a small-sized liquid crystal display element is manufactured and used for a liquid crystal television, a monitor for a personal computer, a mobile phone, and the like. Yes. When a liquid crystal display element using a glass substrate is dropped, the glass is damaged or heavy, and if it is thinned, there are drawbacks such as cracking during production and inferior mass productivity. For this reason, a liquid crystal display element (hereinafter referred to as a plastic substrate liquid crystal display element) using a plastic substrate which is less likely to be damaged than a glass substrate and which is lightweight is manufactured. Plastic substrate liquid crystal display elements are mass-produced by STN (Super Twisted Nematic) with passive matrix drive, but it is difficult to increase screen size and inferior contrast and high resolution with active matrix drive. There were drawbacks. In recent years, therefore, active matrix drive plastic substrate liquid crystal display elements have been actively developed.

  In order to manufacture an active matrix driving liquid crystal display element, it is necessary to form a TFT element (Thin Film Transistor), an MIM element (Metal Insulator Metal), or the like on a substrate. Currently, glass substrates are mainly used as substrates. However, since it is necessary to pass a high-temperature process for forming TFT elements on a plastic substrate, there is a problem of thermal expansion and contraction of the substrate, making mass production difficult. Therefore, it is considered that a thin and light liquid crystal display element can be easily produced by using a plastic substrate as one substrate and using a conventional TFT element-formed glass substrate on the other side. However, as shown in FIG. 1, the plastic substrate has a higher coefficient of thermal expansion than the glass substrate, and the liquid crystal display produced by the difference in thermal expansion between the two substrates when they are bonded together by a sealing material and thermally cured. There is a problem that one substrate of the element is curved and the cell gap becomes non-uniform.

  An object of the present invention is to provide a member for a liquid crystal display element that can reduce even a large cell gap unevenness generated when a glass substrate and a plastic substrate are overlapped with each other, and a liquid crystal display element using the same.

  Other objects and advantages of the present invention will become apparent from the following description.

As a result of intensive studies to solve the above problems, it has been found that cell gap unevenness can be reduced by using a specific liquid crystal display element member.
That is, the present invention is a liquid crystal display element member and a liquid crystal display element in which a wall / spacer for preventing liquid crystal outflow is formed on a plastic substrate.

  In the liquid crystal display element member of the present invention, since a wall and spacer for preventing liquid crystal outflow are formed on a plastic substrate, a cell gap generated when the glass substrate and the plastic substrate are overlapped with each other is used. Unevenness can be reduced.

Preferred embodiments of the invention

  In the conventional method, when a plastic substrate is used on one side and a glass substrate is used on the other side, a seal is formed between the glass substrate and the plastic substrate, and then the glass substrate and the plastic substrate are overlapped and thermally cured by a spacer included in the sealing material. The cell gap of the seal part is made uniform. However, when the sealing material is heat-cured, the plastic substrate has a larger coefficient of thermal expansion than the glass substrate, so it hardens after the plastic substrate side expands or contracts, so it cools to room temperature after bonding the glass substrate and the plastic substrate together Then, since the plastic substrate side contracts or expands again, distortion occurs, resulting in a cell with a non-uniform gap.

When the sealing material is not heated, a cell having a uniform gap can be produced without causing shrinkage or expansion of the substrate. However, since the heat curing of the sealing material is insufficient, the adhesiveness is weak, and an uncured sealing material may enter the cell and cause a display defect.
Thus, when the liquid crystal display element member of the present invention is used, display defects can be reduced without causing the gap non-uniformity as described above.

Liquid Crystal Display Element Member An example of the liquid crystal display element member of the present invention is shown in FIG. A cell gap forming spacer (hereinafter referred to as spacer A) is formed on a plastic substrate on which electrodes are formed, and a spacer / liquid crystal outflow prevention wall (hereinafter referred to as spacer B) is formed on the outer periphery. Among these, the spacer A is not necessarily formed when the spherical spacer is dispersed, but in order to inject liquid crystal by an ODF (One Drop Filling) method or to reduce the step of dispersing the spherical spacer. Is preferably formed.

Spacer A and Spacer B
Examples of the spacer A and spacer B include spacers formed by photolithography. When forming a spacer by photolithography, for example, a photosensitive resin mainly composed of a polyimide resin, an epoxy resin, an acrylic resin, a urethane resin, a polyester resin, a polyolefin resin, or a phenol novolac resin is used. it can.
The spacer A is formed to make the thickness of the liquid crystal layer uniform. The height is preferably 1 μm to 20 μm. The distance between the spacers A is preferably 1 mm or less in order to keep the cell gap uniform. The shape is, for example, a hemispherical shape, a cylindrical shape, or a prismatic shape, but is not limited thereto.

  As with the spacer A, the spacer B is formed in order to make the thickness of the liquid crystal layer uniform. Further, it is provided on the outer periphery of the cell and also serves as a wall that prevents the liquid crystal from flowing out of the cell. The height of the spacer B is preferably 1 μm to 20 μm. In the case where a single spacer B is provided, the width of the spacer B is preferably 0.8 in order to prevent intrusion of a substance that has an unfavorable influence on the liquid crystal display element from the outside of the cell, for example, water, and prevent the outflow of liquid crystal. 1 mm or more. In the case where a plurality of spacers B are provided in parallel, the width of the spacer B is not limited because the entry of substances from the outside of the cell and the outflow of liquid crystal hardly occur.

Plastic substrate Examples of plastic substrates that can be used in the present invention include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, triacetyl cellulose, polyamide, polyimide, polymethyl methacrylate, polycycloolefin, cycloolefin copolymer, cross-linked epoxy resin, and cross-linked epoxy resin. Examples include substrates made of type acrylic resin, cross-linked silicone resin, unsaturated polyester, polysulfone, polyethersulfone, polycarbonate, polyarylate, and the like. It is not limited to these.

Glass Substrate As a glass substrate that can be used in the present invention, an alkali-free glass excellent in chemical resistance and heat resistance while avoiding alkali elution from glass can be mentioned as a preferable one. It is not limited to these.

As the alignment film , for example, an organic film of a polymer material such as polyimide, polyamic acid, polyamide, or polyvinyl alcohol can be used. The film thickness is preferably 50 to 5,000 mm, more preferably 100 to 3,000 mm.

Example 1
(Preparation of liquid crystal display element member A)
A substrate on which ITO was formed as a transparent electrode on a plastic film having a film thickness of 200 μm and a length of 300 mm using polyethersulfone (glass transition temperature 223 ° C.) as a base was washed with pure water. Thereafter, an acrylic resin photospacer forming agent was applied by spin coating, and prebaked on a hot plate at 80 ° C. for 3 minutes to form a coating film. Using a pattern mask, ultraviolet rays having an intensity at 365 nm of 10 mW / cm ² were irradiated for 30 seconds. The ultraviolet irradiation at this time was performed in an oxygen atmosphere (under air). After developing for 1 minute at 25 ° C. with a 1.0% by weight aqueous solution of N-methylpiperidine, it was rinsed with pure water for 1 minute. By these operations, unnecessary portions were removed, and 10 μm × 10 μm spacers A were formed in a lattice shape at intervals of 300 μm. Further, as shown in FIG. 2, a 1 mm wide spacer / liquid crystal outflow prevention wall spacer B was formed on the outer periphery. It was cured by heating at 180 ° C. for 60 minutes in an oven to obtain a spacer pattern having a height of 6 μm. Thus, a liquid crystal display element A (FIG. 2) was produced.

(Production of liquid crystal display element)
Fabrication of upper substrate After liquid crystal display element member A is washed with pure water, a liquid crystal aligning agent is applied using a printing machine for applying a liquid crystal alignment film and dried in an oven at 180 ° C. for 20 minutes to form ITO. A coated film having a dry average film thickness of 600 mm was formed on the finished surface. Using a rubbing machine having a roll in which a rayon cloth is wound around this coating film, the rubbing treatment was performed at a rotation speed of the roll of 400 rpm, a stage moving speed of 30 mm / sec, and a hair foot pushing length of 0.4 mm, followed by washing with water. Then, it dried for 10 minutes on 120 degreeC oven.

Production of Lower Substrate Using a glass substrate having a thickness of 0.7 mm on which ITO having a thickness of 600 mm was formed, an orientation film was formed and an orientation treatment was performed in the same manner as the upper substrate to obtain a lower substrate.

Production of liquid crystal display element In order to form a twisted nematic (TN) type liquid crystal cell, the upper substrate and the lower substrate are overlapped with each other at an angle of 90 ° (FIG. 3) while being pressure-bonded at 25 ° C. Then, an adhesive (Aron Alpha manufactured by Toagosei Co., Ltd.) was applied to the outer periphery of the cell and cured. Next, after filling a nematic liquid crystal (MLC-6221, manufactured by Merck & Co., Inc.) from the liquid crystal injection port, the liquid crystal injection port was sealed with an acrylic photo-curing adhesive. A liquid crystal display element (FIG. 4) was produced by laminating polarizing plates so as to be crossed Nicols up and down.

(Evaluation of liquid crystal display elements)
A voltage of 3 V (rectangular wave 60 Hz) was applied at 23 ° C., and it was confirmed whether display unevenness was observed in the cell. As shown in the schematic diagram 5, a uniform black display was obtained. The cell gap at the center of the cell was measured using a pretilt measurement system PAS-301 (manufactured by ELISICON). It was 6 μm.

Example 2
A liquid crystal display device was produced in the same manner as in Example 2 except that an acrylic photocuring agent was applied to the outer periphery of the cell at 25 ° C. instead of the adhesive of Example 1 and photocured. As shown in the schematic diagram 5, a uniform black display was obtained. The cell gap at the center of the cell was 6 μm.

Comparative Example 1
(Preparation of liquid crystal display element member B)
A liquid crystal display member B (FIG. 6) was prepared in the same manner as in Example 1 except that the spacer / liquid crystal outflow prevention wall was not formed.

(Production of liquid crystal display element)
Production of Upper Substrate An upper substrate was produced in the same manner as in Example 1 except that the liquid crystal display member B was used instead of the liquid crystal display member A.

Fabrication of lower substrate Using a glass substrate having a thickness of 0.7 mm on which ITO having a thickness of 600 mm is formed, an alignment film is formed and oriented in the same manner as the upper substrate, and an epoxy resin adhesive containing aluminum oxide spheres having a diameter of 6 μm. Was applied as a sealing material to form a lower substrate. In order to form a twisted nematic (TN) type liquid crystal cell, the upper substrate and the lower substrate are stacked so that they face each other at an angle of 90 ° (FIG. 3), and the sealing material is cured by pressure bonding at 150 ° C. for 90 minutes. I let you. Next, after filling a nematic liquid crystal (MLC-6221, manufactured by Merck & Co., Inc.) from the liquid crystal injection port, the liquid crystal injection port was sealed with an acrylic photo-curing adhesive. A liquid crystal display element was prepared by laminating polarizing plates so as to be crossed Nicols up and down.

(Evaluation of liquid crystal display elements)
Evaluation was performed in the same manner as in Example 1, and the display state was non-uniform display with white display at the center and black display at the periphery as shown in FIG. The cell gap at the center of the cell was 10 μm.
In Examples 1 and 2, it can be seen that a uniform display can be obtained, and a cell gap due to the spacer is generated. In the comparative example, the display is non-uniform, and it can be seen that the cell gap (6 μm) due to the spacer does not appear and the gap remains wide.

It is a schematic diagram for demonstrating the conventional board | substrate bonding method. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram for explaining a liquid crystal display element member A of the present invention (upper is a plan view, and lower is a side sectional view). FIG. 3 is an explanatory diagram illustrating the overlapping direction of the upper substrate and the lower substrate in the liquid crystal display element of Example 1. 3 is a schematic diagram of a liquid crystal display element of Example 1. FIG. 6 is a schematic diagram illustrating a display state of liquid crystal display elements of Example 1 and Example 2. FIG. FIG. 4 is a schematic diagram for explaining a liquid crystal display element member B (top is a plan view, and bottom is a side sectional view). 6 is a schematic diagram showing a display state of a liquid crystal display element of Comparative Example 1. FIG.

Explanation of symbols

1 Plastic substrate 2 Spherical spacer 3 Sealing material 4 Glass substrate 5 Wall and spacer (Spacer B)
6 Spacer (Spacer A)
7 ITO electrode 8 Liquid crystal display element A
9 Adhesive 10 Alignment film 11 Liquid crystal layer

Claims (4)

A member for a liquid crystal display element, wherein a wall and spacer for preventing outflow of liquid crystal are formed on a plastic substrate. A member for a liquid crystal display element, wherein a spacer and a wall and spacer for preventing liquid crystal outflow are formed on a plastic substrate. A liquid crystal display element produced by bonding an opposing substrate to an adhesive layer formed on the outside of the wall and spacer of the liquid crystal display element member according to claim 1. The liquid crystal display element according to claim 3, wherein the opposite substrate according to claim 3 is a glass substrate.