JPH06118423A - Production of liquid crystal display element - Google Patents

Abstract

PURPOSE:To accurately and uniformly control the fine cell gap interval of a liquid crystal display element, especially ferroelectric liquid crystal display element to the prescribed value. CONSTITUTION:In the case of realization of prescribed cell gap by applying the sealing medium 4 containing a solvent on the peripheral part of one side substrate 10 of a couple of the substrates 10, and distributing a spacer 6 and adhesive beads 5 on the other side substrate 10, then superposing the couple of the substrate 10 each other, pressurizing and heating, the substrate is maintained at each prescribed temp., that is, the temp. for evaporating the solvent contained in the sealing medium 4, the temp, for curing sealing medium 4 and the temp. for adhering the beads 5, and the pressure to be added to the substrate is maintained in the prescribed range. Preferably, the pressure to be added to the substrate 10 is maintained within a 2.5-3.5kg/cm<2> range.

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 liquid crystal display device. More specifically, the present invention relates to a method for manufacturing a liquid crystal display device having a minute cell gap, which is suitable for a ferroelectric liquid crystal display device.

[0002]

2. Description of the Related Art Conventional liquid crystal display devices such as STN cells and TN cells are mainly driven by multiplex driving in the former case and TFT active matrix driving in the latter case. However, in recent years, further improvement in high-speed response, large screen, and high precision of images have been required for liquid crystal display elements. Attention has been paid to a surface-stabilized ferroelectric liquid crystal display device using a ferroelectric liquid crystal.

Generally, various characteristics such as the response speed of a liquid crystal display device, image contrast, viewing angle, and display uniformity are
It is closely related to the thickness of the liquid crystal layer, that is, the liquid crystal cell gap. This is because the alignment state of liquid crystal molecules strongly depends on the liquid crystal cell gap. In particular, in the case of the ferroelectric liquid crystal, it is desired to control the liquid crystal cell gap to be about 1.40 ± 0.05 μm, which is considerably smaller than that of the conventional STN cell or TN cell.

As described above, in order to control the cell gap of the ferroelectric liquid crystal display device to about 1.5 μm,
Conventionally, a sealant (curing temperature of about 135 ° C.) made of a thermosetting resin containing a solvent is applied to a peripheral portion of one of a pair of glass substrates with a predetermined width, and the other substrate is coated with, for example, Adhesive beads composed of 5 μm diameter silica spacer and 5 μm diameter thermosetting epoxy resin (curing temperature of about 15
(0 ° C) is evenly dispersed, then both substrates are superposed,
A temperature higher than the temperature at which the sealant and the adhesive beads are simultaneously cured by applying a predetermined pressure with a hot press plate, for example, 1
The liquid crystal cell gap is controlled to a predetermined value by heating at 70 to 180 ° C. for about 1 hour.

[0005]

However, in the case of heating a pair of glass substrates under pressure to form a liquid crystal cell as in the prior art, generally, both a sealing agent and adhesive beads exhibiting different curing temperatures are used. Since it is heated at the curing temperature at the same time, air bubbles are created in the sealant, and the adhesive beads are cured before they are sufficiently crushed. Since the pressure applied to the substrate rises, it is difficult to control the cell gap spacing with high accuracy.

The present invention is intended to solve such a problem of the prior art, and makes the minute cell gap interval of a liquid crystal display element, particularly a ferroelectric liquid crystal display element, uniform to a desired value with high accuracy. An object of the present invention is to provide a controllable liquid crystal display device manufacturing method.

[0007]

The present inventor has made it possible to evaporate the solvent contained in the sealant, cure the sealant after solvent evaporation, and cure the adhesive beads within a predetermined pressure range during heating under pressure. It was found that the above-mentioned object can be achieved by carrying out the method independently, and the present invention has been completed.

That is, according to the present invention, a sealing agent containing a solvent is applied to the peripheral portion of one of the pair of substrates, and the spacer and the adhesive beads are sprinkled on the other substrate, and then the pair of substrates is separated from each other. In a method for manufacturing a liquid crystal display device, which comprises a step of forming a liquid crystal cell having a predetermined cell gap by overlapping and pressurizing and heating each other, when superposing and pressing the pair of substrates, The temperature at which the solvent contained in the sealant is evaporated, the temperature at which the sealant is cured, and the temperature at which the adhesive beads are cured are maintained for a predetermined time and the pressure applied to the substrate is within a predetermined range. A method for manufacturing a characteristic liquid crystal display device is provided.

The present invention will be described in detail below.

In the present invention, the evaporation of the solvent contained in the sealing agent, the curing of the sealing agent after solvent evaporation, and the curing of the adhesive beads are carried out independently by maintaining the temperature suitable for each for a predetermined time. . For example, the solvent of the sealant is removed by evaporation at 90 ° C, and the sealant is cured at 135 ° C.
Cure the adhesive beads at 150 ° C. Further, if necessary, the heating can be carried out to a temperature of about 180 ° C. to complete the curing. It is preferable that the variation error of the heating temperature be within ± 5%. By setting the temperature steps stepwise in this manner, it is possible to prevent air bubbles from being generated in the sealant and to prevent the adhesive beads from being cured before being sufficiently crushed.

When the sealing agent and the adhesive beads have the same curing temperature, they may be cured at the same temperature at once.

In the present invention, the time for holding at each heating temperature is not particularly limited, but generally 0.5 to 1 hour is preferable.

By the way, when heating is performed by providing several temperature steps stepwise as described above, if the pressurizing condition of the hot press plate is not changed according to the heating state, the pressure applied to the substrate is It changes a lot. For example, if the pressure applied to the substrate is 3.5 kg / cm ² when heated at 90 ° C., the pressure becomes 5.0 kg / cm ² when heated at 135 ° C. due to expansion of the glass substrate, 150 ° C
When heated at ¹ , the pressure becomes 5.7 kg / cm ² , and when heated at 180 ° C., the pressure becomes 7.0 kg / cm ² . As described above, when the pressure applied to the substrate changes greatly, it becomes difficult to control the cell gap distance. Therefore, in the present invention, when the heating is performed stepwise as described above, the pressure applied to the substrate is set within a predetermined range. By heating the substrate under pressure in such a predetermined range, it is possible to manufacture a minute cell gap with high accuracy and high uniformity. The fluctuation range of the pressure is preferably within ± 5% both in the constant temperature heating state and in the temperature rising heating state.

Although the specific pressure range varies depending on the desired cell gap thickness and the like, it is generally preferable to maintain the pressure applied to the substrate within the range of 2.5 to 3.5 kg / cm ² . If it exceeds 3.5 kg / cm ² , the cell gap spacing tends to be smaller than the spacer diameter, and the variation in the gap spacing tends to increase. 2.5k again
If it is less than g / cm ² , the cell gap spacing tends to be larger than the spacer diameter.

There is no particular limitation on the means for maintaining the pressure within the predetermined pressure range, and any means can be adopted as long as the pressure can be maintained within the predetermined pressure range. For example, the liquid crystal display element can be pressed with a hot press plate through a cushioning material such as a silicone rubber sheet. By interposing the cushioning material in this way, it is possible to reduce the influence of irregularities on the surface of the substrate or the press plate.

Although the present invention has been described above, the configuration of other inventions can be the same as the conventional one. For example, a substrate that has been conventionally used as a substrate of a liquid crystal display element can be used, and for example, a substrate on which a transparent electrode or a SiO oblique vapor deposition film is formed can be used. Further, as the sealing agent and the adhesive beads, those similar to the conventional one can be used.

Regarding the sealant, if a sealant having an excessively high viscosity, for example, a sealant having a viscosity of 300 poise is used, the cell gap distance in the vicinity of the sealant application portion tends to be larger than the spacer diameter. If the viscosity of the sealant is too low, the sealant may flow beyond the area to be coated when it is applied to the glass substrate, so it is preferable to use a sealant of 150 to 200 poise.

The liquid crystal cell manufactured in this manner can be filled with liquid crystal by a conventional method to form a liquid crystal display element.

[0019]

In the method of manufacturing a liquid crystal display device according to the present invention, the solvent contained in the sealant is evaporated, the sealant is cured after the solvent is evaporated, and the adhesive beads are cured independently within a predetermined pressure range. It is possible to prevent air bubbles from being generated in the sealant, and to prevent the adhesive beads from being sufficiently crushed and cured before the desired cell gap is achieved.

[0020]

EXAMPLES The present invention will be described in detail below based on examples. In the drawings, the same reference numerals represent the same or equivalent components.

Example 1 Two glass substrates 10 as shown in FIG. 1 in which a transparent electrode layer 2 and a SiO oblique vapor deposition film 3 were laminated on a glass base 1 having a surface roughness of 200 nm were prepared. A sealant 4 (XN-2, which is a one-component thermosetting epoxy resin, is formed on the substrate.
10FA, manufactured by Mitsui Toa Kasei Co., Ltd.) was applied in a pattern as shown in FIG. The viscosity of the sealant 4 was adjusted by adding methyl carbitol, and the viscosity was measured by using MR-3 solid liquid meter manufactured by Rheology Co., Ltd. On the other substrate, as shown in FIG. 3, a liquid crystal spacer spreader (manufactured by Sonocom Co., Ltd.) was used, and adhesive beads 5 of 5 μm in diameter made of a thermosetting epoxy resin were used.
(Trepearl, manufactured by Toray Industries, Inc.) is sprayed at a density of about 30 pieces / mm ² , and a silica spacer 6 having a diameter of 1.6 μm is further sprayed.
(Manufactured by Nippon Shokubai Co., Ltd.) was sprayed at a density of about 250 pieces / mm ² .

These two glass substrates are precisely stacked, and the heat press plate 7 as shown in FIG.
It was clamped through the plate and a pressure of 2.5 to 3.5 kg / cm ² was applied. While maintaining this pressure, first 0.5 at 90 ℃
The solvent contained in the sealant was removed by evaporation by heating for 1 hour to 1 hour. Further, the temperature was raised to 130 ° C., and the sealing agent was cured by heating at this temperature for 0.5 hour to 1 hour. The temperature was further raised to 150 ° C. and heated at this temperature for 0.5 to 1 hour to cure the adhesive beads. Finally, the temperature was raised to 180 ° C., and heating was performed at this temperature for 0.5 hour to 1 hour. Then, the liquid crystal cell was manufactured by naturally cooling to room temperature while maintaining the above-mentioned pressure.

The cell gap of the obtained liquid crystal cell was measured using an MS-200 film thickness measuring instrument (manufactured by Otsuka Electronics Co., Ltd.) utilizing light interference, and the average cell gap was 1.615 μm. Deviation to 0.004 μm
Met. FIG. 5 shows the cell gap distribution of this example. As is clear from this figure, it can be seen that a highly accurate and highly uniform cell gap is realized in the liquid crystal cell.

Examples 2 to 4 and Comparative Examples 1 to 4 Liquid crystal cells were manufactured according to Example 1 except that the pressure applied to the pair of glass substrates was kept constant as shown in Table 1. The cell gap of the obtained liquid crystal cell was measured in the same manner as in Example 1. The results are shown in Table 1. As is clear from Table 1, the pressure is 2.5 to 3.5 kg / c.
It can be seen that the cell gap with high accuracy and high uniformity can be realized by keeping the cell gap within the range of m ² .

[0025]

[Table 1] Pressure (kg / cm ² ) Average cell gap (μm) Example 2 2.5 1.605 3 2.9 1.584 4 3.4 1.616 Comparative Example 1 1.7 1.712 2 2.4 1.650 3 3.6 1.505 4 17.1 1.335

[0026]

According to the present invention, the minute cell gap of a liquid crystal display element, particularly a ferroelectric liquid crystal display element, can be accurately and uniformly controlled to a desired value.

[Brief description of drawings]

FIG. 1 is a sectional view of a glass substrate used in the present invention.

FIG. 2 is a diagram showing a pattern of a sealant applied on a glass substrate.

FIG. 3 is a view showing a sprayed state of adhesive beads and spacers on a glass substrate.

FIG. 4 is an explanatory diagram of a state in which a pair of glass substrates is heated under pressure with a hot press plate.

FIG. 5 is a three-dimensional distribution curve of liquid crystal cell gap intervals of the liquid crystal display device obtained by the present invention.

[Explanation of symbols]

 1 Glass Base 2 Transparent Electrode 3 SiO Orthorhombic Vapor Deposition Film 4 Sealant 5 Adhesive Beads 6 Silica Spacer 7 Hot Press Plate 8 Silicon Rubber 10 Glass Substrate

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Akio Yasuda 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (3)

[Claims] 1. A pair of substrates is coated with a sealant containing a solvent on the periphery of one substrate, and the other substrate is sprayed with spacers and adhesive beads, and then the pair of substrates are superposed on each other. In a method of manufacturing a liquid crystal display device, which comprises a step of forming a liquid crystal cell having a predetermined cell gap by heating under pressure, when a pair of substrates are superposed and heated under pressure, a sealing agent is contained. A liquid crystal which is maintained at a temperature for evaporating the stored solvent, a temperature for curing the sealant, and a temperature for curing the adhesive beads for a predetermined period of time so that the pressure applied to the substrate is within a predetermined range. Display element manufacturing method. 2. The method for producing a liquid crystal display device according to claim 1, wherein the pressurization is performed at 2.5 to 3.5 Kg / cm ² . 3. The method for producing a liquid crystal display element according to claim 1, wherein the liquid crystal cell is pressurized and heated by a hot press plate through a buffer material in order to maintain the pressure condition within a predetermined range.