JPH04355432A - Manufacture of display element - Google Patents

Abstract

PURPOSE:To obtain a display element of small display unevenness. CONSTITUTION:A number of substrates 2 laminated on each other through seal materials are provided to be disposed on a table 3 in a reduced pressure chamber 1, and a load cell 7 connected with a changeable pressure cylinder 5 is disposed on it. After reducing the pressure in the reduced pressure chamber 1, the substrate 2 is heated by a heater 9, and the changeable pressurizing cylinder 5 is actuated gradually in following temperature rise of it, thereby the substrates 2 are heat pressed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a display element.

0002

[Prior Art] Display elements include liquid crystal display elements, electrochromic display elements, electrophoretic display elements, etc.
Electrode plates with electrodes formed on a substrate of glass, plastic, etc. are arranged with the electrode surfaces facing each other, the electrode plates are stacked and sealed with a sealing material in between, and an electro-optic medium such as liquid crystal is sealed inside. There is.

[0003] Among these, the liquid crystal display element is the most commonly used display element at present, and is composed of, for example, two electrode plates having transparent electrodes and a sealing material around the electrode plates. contains a liquid crystal.

[0004] In such a liquid crystal display element, after each electrode plate is formed, a sealing material is applied around at least one of the electrode plates, precure is performed by heating, and then the electrode plate is bonded through the sealing material. A liquid crystal cell is formed by stacking them together, heating and pressurizing them to harden the sealing material.

However, low-volatile substances such as gases and monomers generated during the precure of the sealant and the thermocompression bonding process described above cannot be removed sufficiently, and because the gap between the substrates is particularly narrow during the thermocompression bonding process, most of the liquid crystal It will be adsorbed to the alignment control film, etc.

Therefore, even if vacuum degassing is performed before liquid crystal injection, it is not sufficient, and some gases and low-volatile substances remain in the liquid crystal cell, deteriorating the liquid crystal and causing display defects. For this reason, it has been proposed to perform the above thermocompression bonding process under reduced pressure to prevent deterioration of the liquid crystal and display defects.

[0007]

[Problems to be Solved by the Invention] Conventionally, however, in this method, it has been common to immediately apply pressure at an optimal pressure during thermocompression bonding. Therefore, the gap in the liquid crystal cell narrows to almost a predetermined value immediately after pressurization, and gases and reactive components generated from the sealing material cannot be sufficiently exhausted and tend to remain in the cell, causing display unevenness to occur near the sealing material. There was a problem.

An example of a conventional method is shown in cross section in FIG. 1 is a decompression chamber, 2 is a board, in which many pairs of boards are stacked one on top of the other, 4 is an exhaust pipe connected to the exhaust system, and 8 is a pressurizing spring jig that can be pressurized in a fixed manner. It shows. As for the heating means, a heater 9 may be provided inside the decompression chamber as shown in FIG. 2, and heating may be performed using radiant heat, or the heater may be incorporated into the pressurizing spring type jig 8.

According to the conventional method, a plurality of sets of substrates 2 are stacked one on top of the other with the above-mentioned sealing material interposed in between, and after pressurizing the substrates with the pressurizing spring type jig 8, the exhaust system is activated and the decompression chamber is opened. While reducing the pressure inside 1, the substrate 2 was heated.

0010

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and includes a step of overlapping two electrode plates with a sealing material in between so that the electrode surfaces face each other. and a step of raising the temperature of the electrode plate and the sealing material in a reduced pressure atmosphere, and gradually pressurizing and crimping the two electrode plates via the sealing material. It provides:

Typical sealing materials used in the present invention are one-component or two-component epoxy resins. Screen printing methods, dispenser methods, and the like are available as methods for accurately applying this sealing material onto a substrate in a thin and voluminous manner according to the cell shape. In particular, the screen printing method has the advantage of being excellent in mass production.

The method of the present invention will be explained in detail below.

[0013] On the two electrode plates, alignment films are formed, each of which is made of an organic resin film made of polyvinyl alcohol, polyimide, polyamide, etc. whose surfaces are rubbed, or an inorganic film made of diagonally deposited SiO or the like. after that,
A sealing material containing a spacer made of glass beads, glass fibers, organic resin beads, etc. is applied around one substrate, and precure is performed by heating. Spacers made of glass beads, glass fibers, organic resin beads, etc. are scattered on the other substrate.

Next, the electrode surfaces of both substrates are faced to each other,
After overlapping, they are temporarily fixed with an adhesive or the like, and both temporarily fixed substrates are placed in a pressure bonding device.

The crimping device may be of either a batch type or a continuous type. The batch type consists of one chamber, and can change the pressure applied to the substrate in a reduced pressure atmosphere by following the temperature rise curve of heating. On the other hand, the continuous type consists of three chambers, the first chamber is a chamber for preliminary depressurization,
The second chamber is the main decompression chamber, and the third chamber is the buffer chamber. As the substrates are transferred through each room, the substrates can be heated as described above and pressurized in accordance with the temperature rise curve.

An example of a batch-type crimping apparatus is shown in cross-section in FIG. 3 is a surface plate made of a glass plate or a metal plate, 5 is a variable pressure cylinder, 6 is a packing, and 7 is a load cell.

A large number of the above-mentioned temporarily fixed substrates 2 are placed on top of each other on the surface plate 3 in the decompression chamber 1, and a load cell 7 connected to the variable pressure cylinder 5 is placed thereon. 1 and is connected to the variable pressure cylinder 5, but a packing 6 is provided to keep the part where it passes through airtight. Once both substrates are placed, the exhaust system is activated to evacuate and reduce the pressure inside the decompression chamber 1. This reduced pressure state is 10-
It is 1 Torr or less, preferably 10 −2 Torr or less. In a continuous crimping device, the pressure in the pre-decompression chamber is 20 Torr or less, preferably 10 Torr or less, and the main vacuum chamber is 10-1 Torr or less, preferably 10-2T.
orr or less.

Next, the substrate 2 is gradually heated by the heater 9 in the vacuum chamber. The temperature increase state of the substrate can be measured in advance and estimated based on time, or the temperature can be directly measured using a thermocouple or a radiation thermometer. The present invention is characterized in that the temperature of the electrode plate, etc. is raised, and the electrode plate is gradually pressurized and crimped through the sealing material as the temperature rises.

In the present invention, the preferable relationship between pressing force and temperature rise is 0.2 kg/cm2, 10
0.4kg/cm2 at 0℃, 0.6kg/cm2 at 120℃
m2, about 0.8 kg/cm2 at 150 to 180°C. The variable pressure cylinder 5 may be of various types such as pneumatic pressure and hydraulic pressure.

[0020] By doing as described above, gas generated from the sealing material and reaction products can be discharged to the outside of the cell without remaining on the alignment control film or the like. After the electrode plates are crimped to form an empty cell, liquid crystal is injected and the injection hole is sealed to form a liquid crystal cell.

[0021] The substrate used in the present invention usually has a transparent electrode made of indium tin oxide (ITO), tin oxide, etc., and if necessary, a low resistance lead made of chromium, aluminum, etc. is formed thereon. An undercoat film such as an insulating film, a deflection film, a color filter film, etc. for the purpose of preventing alkali elution from the substrate may be formed under the substrate.

Further, an overcoat film such as an insulating film, a color filter film, a light transmission prevention film, or a base treatment film for improving the adhesion of the polyimide liquid crystal aligning film may be formed on the electrode. Further, these electrodes may have a two-layer structure with an insulating film interposed therebetween, or an active element such as a thin film transistor (TFT) or a nonlinear resistance element may be formed. For these electrodes, undercoat, overcoat, and other cell configurations, conventional configurations of liquid crystal display elements can be used. As the liquid crystal to be injected, in addition to ordinary nematic liquid crystal, various liquid crystals such as dichroic dye-added liquid crystal and ferroelectric liquid crystal can be used.

[0023] If necessary, letters, figures, a light transmission prevention film or a color filter may be printed on the outer surface of the cell thus manufactured, a non-reflection amount of light may be formed, a polarizing film may be laminated, A reflecting plate, a light guide plate, lighting, etc. may be arranged.

[0024]

[Example] As a first substrate, ITO transparent electrodes provided on a glass substrate were patterned into stripes,
An insulating film made of SiO2 for preventing short circuits was formed by vapor deposition, a polyimide overcoat was spin-coated thereon, and this was rubbed to form a substrate on which an alignment control film was formed.

[0025] As a second substrate, an ITO transparent electrode provided on a glass substrate was patterned into a stripe shape perpendicular to the first substrate, and an insulating film made of SiO2 for short circuit prevention was formed by vapor deposition. Thereafter, a polyimide overcoat was spin-coated on this, and this was rubbed to create a substrate on which an alignment control film was formed.

A one-component epoxy resin was prepared at a weight ratio of epoxy resin and glass bead spacer of 10:0.2, and thoroughly kneaded. Then, this was printed around the first substrate using a screen printing method. On the other hand, a mixture of glass beads and glass fibers was sprinkled as spacers on the second substrate.

[0027] Pre-curing the first substrate under heating and reduced pressure;
Overlapping the first and second substrates with their electrode surfaces facing each other,
After temporarily bonding with instant adhesive, a plurality of such pairs of substrates were stacked on top of each other and placed in a pressure bonding device as shown in FIG. After reducing the pressure in the decompression chamber to 5.0 x 10-3 Torr, the heater and variable pressure cylinder were activated to
0.2kg/cm2 up to ℃, 0.4kg/cm2 at 100℃
cm2, 0.6 kg/cm2 at 120℃, 0.8kg/cm2 at 150℃ or higher, and finally 200
Heat and pressure bonding was carried out at ℃.

A nematic liquid crystal having positive dielectric anisotropy was injected into the empty liquid crystal cell thus obtained, and the injection port was sealed. Polarizing plates were arranged on both sides of this liquid crystal cell so that the polarization axes were parallel to each other to form a liquid crystal display element. The obtained liquid crystal display element had good appearance with little display unevenness.

[0029]

According to the present invention, in a method for manufacturing a display element, a sealing material is cured under reduced pressure, and when thermocompression bonding of a substrate is performed, the pressure applied to the substrate is increased to follow the temperature rise curve of the substrate. This allows gas and reaction products generated from the sealing material to be forcibly discharged, making it possible to suppress the occurrence of display unevenness centered around the seal.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a crimping device according to the method of the present invention.

[Figure 2]
Cross-sectional view of a conventional crimping device

[Explanation of symbols]

1　Decompression chamber 2 Board 3 Surface plate 4 Exhaust pipe 5 Variable pressure cylinder 9 Heater

Claims (1)

[Claims] Claim 1: A step of stacking two electrode plates with a sealing material in between so that the electrode surfaces face each other, and raising the temperature of the electrode plates and the sealing material in a reduced pressure atmosphere, and gradually removing the sealing material. 1. A method for manufacturing a display element, comprising the step of pressurizing and crimping two electrode plates with each other in between.