JPH04366914A - Manufacture of liquid crystal cell with diaphragm - Google Patents

Abstract

PURPOSE:To prevent an air bubble from being generated in the liquid crystal cell regardless of heating at the time of the adhesion of the diaphragm. CONSTITUTION:An orientation film which is already rubbed is cleaned and then a substrate is heated at 150-220C for >=2 hours, and residual water and water adsorbed by other constituent materials are removed, so no air bubble is generated in the assembled liquid crystal cell even when the liquid crystal cell is heated almost at 140C as shown in a figure 1 in the subsequent adhering process of the ultrasonic wave diaphragm. Further, no air bubble is generated in the liquid crystal cell even in ultrasonic wave operation endurance.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal cell with a diaphragm.

0002

[Prior Art] Liquid crystal display devices utilize the electro-optic effect of liquid crystals, that is, changes in the optical properties of liquid crystal molecules that occur when an electric field is applied. In addition to being used as display elements, it is also used as anti-glare mirrors in automobiles.

[0003] That is, it is possible to install a liquid crystal sealed in two electrodes on the glass front surface of a mirror, and apply a voltage between the electrodes to make the liquid crystal translucent, thereby obtaining an anti-glare effect of the mirror. It is already known as Japanese Patent Publication No. 48-35384.

On the other hand, in order to remove water droplets that adhere to outside mirrors such as door mirrors and fender mirrors,
In 1983, a device was developed in which a vibrating device using a piezoelectric element was attached to the mirror, and the vibration of the vibrating device vibrated the mirror to atomize and instantly remove water droplets adhering to the reflective surface of the mirror. No. 25658.

[0005]

[Problem to be Solved by the Invention] It is desired to develop a liquid crystal mirror with a raindrop removing function in which a diaphragm is attached for the purpose of removing raindrops that adhere to this liquid crystal anti-glare mirror.The structure is shown in Fig. 3. It is assumed that the

In FIG. 3, two transparent substrates 1a and 1b are arranged to face each other, transparent electrode layers 2a and 2b are respectively deposited on the opposing surfaces, and alignment films 3a and 3b are further applied thereon. is formed. Note that an Al vapor deposition film 7 is formed on the back surface of the transparent substrate 1b, and a protective film 8
covered by.

After the alignment films 3a and 3b have been subjected to an alignment treatment such as rubbing, a particulate spacer 5 made of glass or plastic is interposed to control the gap between the transparent electrode layers 2a and 2b. The peripheral edges of transparent substrates 1a and 1b are adhered with sealant 4 to assemble a liquid crystal cell.

After the liquid crystal 13 is sealed in this liquid crystal cell,
A diaphragm 10 having a piezoelectric element 12 fixed to the back surface with an adhesive 11 for fixing the piezoelectric element is adhered to the back surface of the transparent substrate 1b using an adhesive 9 for fixing the diaphragm.

The manufacturing process after forming the transparent electrode layer of this liquid crystal cell with a diaphragm is as follows. Alignment film printing → alignment film curing → rubbing → cleaning → sealant printing → cell assembly (sealant curing) → liquid crystal injection sealing → ultrasonic diaphragm adhesion. In order to prevent the spacers from moving within the liquid crystal cell due to ultrasonic operation, a method is used in which the spacers are mixed into an alignment agent solution during printing of the alignment film and fixed to the alignment film.

However, when a liquid crystal cell is manufactured by the above process, there is a problem that air bubbles are generated inside the liquid crystal cell in the step of attaching the ultrasonic diaphragm, which hardens the adhesive by heating at 120° C. for 30 minutes. Further, there is a problem in that bubbles are generated within the liquid crystal cell at the initial stage of ultrasonic operation durability.

The present invention has been made to solve the problem of air bubbles occurring in the liquid crystal cell during the manufacturing process of a liquid crystal cell equipped with an ultrasonic diaphragm or during the early stages of ultrasonic operation durability. Another object of the present invention is to provide a method for manufacturing a liquid crystal cell with an ultrasonic diaphragm in which bubbles are not generated within the liquid crystal cell at the initial stage of operation.

0012

[Means for Solving the Problems] The inventors believed that the cause of bubbles in liquid crystal cells is insufficient degassing of empty cells and sealed liquid crystals. Therefore, we investigated the effects of ultrasonic degassing of empty cells after cell assembly. However, even if an empty cell is ultrasonically degassed and the deaeration time is sufficiently extended when liquid crystal is injected, air bubbles are generated due to the heating when the ultrasonic diaphragm is assembled, and the cause of air bubbles forming in the liquid crystal cell is It was found that the empty cell and the enclosed liquid crystal were not insufficiently degassed.

[0013] Therefore, as a result of further investigation into causes other than insufficient deaeration, we found that air bubbles were generated due to heating at about 140°C, and it was found that it was due to residual moisture during the process, that is, insufficient drying of the washing water after rubbing. It was determined that the cause of this was residual or adsorbed moisture, that is, moisture that had been adsorbed in each component material in advance.

Based on this knowledge, the present inventors conducted further research and found that after cleaning after rubbing, the substrate was
The present invention was completed based on the discovery that these residual moisture and adsorbed moisture can be removed by heating at 50 to 220°C for 2 hours or more.

The method for manufacturing a liquid crystal cell with a diaphragm according to the present invention includes a step of applying a transparent electrode layer to opposing surfaces of a pair of transparent substrates, forming an alignment layer on the surface of the transparent electrode layer, and rubbing. a step of cleaning the rubbed alignment film; a step of heat-treating the substrate at 150 to 220° C. for 2 hours or more; and bonding the substrate together after applying a sealant to the peripheral edge of the substrate. The gist of the method is to include a step of assembling a cell, a step of injecting and sealing liquid crystal into the liquid crystal cell, and a step of bonding a diaphragm to the substrate.

A glass plate or a transparent plastic plate is used as the transparent substrate. If necessary, a polarizing plate is superimposed on the outer surface when two substrates are superimposed. Furthermore, when the liquid crystal cell is used as a liquid crystal anti-glare mirror or the like, it is necessary to form a metal vapor deposited film such as aluminum on one of the transparent substrates to form a reflecting plate.

As the transparent electrode, a thin film of a metal oxide such as tin oxide or indium oxide is generally used. The transparent electrode layers can be formed on opposing surfaces of the substrate by a spray method, a vacuum evaporation method, or a high frequency sputtering method. The electrode configuration can be applied not only to segment electrodes and fixed pattern electrodes but also to matrix electrodes.

The present invention is applied to a liquid crystal cell in which an alignment film is formed by a rubbing method. Forming an alignment film using the rubbing method involves applying an aqueous solution of polyimide or polyvinyl alcohol to form a thin alignment film on the surface of the substrate, and then rubbing the surface in one direction with a cloth (rubbing) to obtain alignment. .

[0019] Furthermore, in the case of a liquid crystal cell with an ultrasonic diaphragm,
In order to prevent the spacers from moving within the liquid crystal cell due to ultrasonic operation, a method is used in which the spacers are mixed into an alignment agent solution during printing of the alignment film, and the spacers are fixed to the alignment film.

The sealing agent seals the periphery of the liquid crystal cell, and an organic adhesive such as a thermosetting epoxy adhesive is used as the sealing agent. The liquid crystal cell assembled by heat curing the sealant after bonding the substrates is vacuum degassed before injection of the liquid crystal.

[0021]

[Operation] A transparent electrode layer is formed on the transparent substrates by a step of applying the transparent electrode layers to opposing surfaces of a pair of transparent substrates. By forming an alignment layer on the surface of the transparent electrode layer and performing a rubbing treatment, an alignment film that aligns liquid crystal molecules in a desired direction is formed.

[0022] In the step of cleaning the alignment film that has been subjected to the rubbing treatment, the rubbing residue is removed, and the generation of domains (color unevenness) due to the rubbing residue is prevented. The step of heating the substrate at 150 to 220° C. for 2 hours or more removes moisture remaining in the alignment film cleaning step and moisture adsorbed on other constituent materials.

A liquid crystal cell is assembled by applying a sealant to the peripheral edges of the substrates and then bonding the substrates together. By the step of injecting and sealing liquid crystal into the liquid crystal cell,
Liquid crystal is filled into the liquid crystal cell. By the step of bonding the diaphragm to the substrate, the diaphragm can be bonded to the liquid crystal cell without generating bubbles in the liquid crystal cell. In addition, no bubbles are generated even after ultrasonic operation.

After the step of drying the substrate at 150 to 220°C for 2 hours or more, immediately store the substrate in a desiccator and dry it for 2 hours.
It is preferable to assemble the liquid crystal cell within 4 hours. Otherwise, moisture in the air will be adsorbed and bubbles will be generated.

The heating temperature of the substrate is set to 150 to 220°C because if the heating temperature is less than 150°C, residual moisture and adsorbed moisture cannot be removed sufficiently, and if the heating temperature exceeds 220°C, it will be used as a spacer. This is because it exceeds the heat resistance temperature of polystyrene beads.

[0026]

[Example] Examples of the present invention will be explained while comparing with comparative examples to clarify the effects of the present invention. FIG. 3 is a cross-sectional view of a liquid crystal cell with an ultrasonic diaphragm used in this example, and its structure is as already described in paragraphs 0006 to 0008.

(Example 1) Two transparent substrates 1a and 1
A curved glass plate with a radius of curvature of 1800 mm and a thickness of 0.7 mm was used for b, and transparent electrode layers 2a and 2b each made of ITO (indium tin oxide) and having a thickness of 400 Å were deposited on opposing surfaces. The alignment films 3a and 3b were formed by applying a polyimide solution and drying and curing it at 300° C. for 1 hour to form a film having a thickness of 1500 Å. Note that the transparent substrate 1
A 1200 Å thick Al vapor deposited film 7 was formed on the back surface of the semiconductor device b, and covered with a protective film 8.

Polystyrene beads with a diameter of 8 μm are used for the spacers 5. After applying a polyimide solution to the substrate 1b and before drying, the spacers 5 are sprinkled on the substrate 1b and the polyimide is dried and hardened. It was fixed to the substrate 1b via.

Cleaning of the alignment films 3a and 3b after the rubbing treatment was carried out by ultrasonic pure water cleaning. After cleaning, the substrate was not heated at all, heated at 100℃ for 2 hours,
Heating was performed at three levels, including heating at 50° C. for 2 hours, and immediately after drying, the mixture was cooled in a desiccator.

Subsequently, an epoxy sealant 4 is printed on the peripheral edges of the transparent substrates 1a and 1b to seal the substrates 1a and 1b.
A liquid crystal cell was assembled by superimposing the sealing material 4 on top of each other and curing it by heating at 180° C. for 75 minutes to harden the sealing material 4.

After injecting and sealing the liquid crystal 13 into the assembled liquid crystal cell, it was heated for 2 hours at the temperature shown in Table 1, and the generation of bubbles in the liquid crystal cell was investigated, and the number of bubbles generated for three samples was calculated. Shown in 1.

[0032]

[Table 1]

As is clear from Table 1, Sample No. 1, which is a comparative example, did not heat the substrate at all after cleaning. In samples 1 to 6, bubbles were generated in the liquid crystal cell when the liquid crystal cell heating temperature reached 140°C. In addition, Sample No. 1, which is a comparative example, had a heating temperature of 100° C. for the substrate after cleaning. In samples 7 to 12, bubbles were generated in the liquid crystal cell when the liquid crystal cell heating temperature reached 150°C.

On the other hand, Sample No. 1, which is an example of the present invention, was prepared by heating the substrate to 150° C. after cleaning. In Samples Nos. 13 to 18, even when the liquid crystal cell heating temperature reached 150° C., no bubbles were generated within the liquid crystal cell, confirming the effect of the present invention.

Note that the samples that were not washed after the rubbing treatment were similarly heated at 150° C. for 2 hours after the liquid crystal cell was assembled, and the generation of bubbles was investigated. As a result, 1 out of 5 bubbles was observed in the samples that were not heated after rubbing, but not 1 out of 5 bubbles in the samples that were heated to 150°C after rubbing. . However, in all liquid crystal cells, domains due to rubbing residue were observed, and it was found that the cleaning treatment after rubbing could not be omitted.

(Example 2) Using the same substrates 1a and 1b as in Example 1, transparent electrode layers 2a and 2b were deposited on opposing surfaces of the substrates 1a and 1b in the same manner as in Example 1. Further, alignment films 3a and 3b were formed in the same manner as in Example 1, and after the rubbing treatment, cleaning was performed by ultrasonic pure water cleaning.

After cleaning, the substrate is heat-treated at a temperature between 80 and 240°C, and after assembling the liquid crystal cell and injecting and sealing the liquid crystal, heating is performed at 150°C for 2 hours, and every 5 samples are heated. The number of bubbles generated was investigated, and the results are shown in FIG.

As shown in FIG. 1, 1 to 5 bubbles were generated when the substrate was heated at a temperature of 80 to 140°C. However, when the heat treatment temperature of the substrate was 150° C. or higher, no bubbles were observed at all, confirming the effect of the present invention.

(Example 3) Using the same substrates 1a and 1b as in Example 1, transparent electrode layers 2a and 2b were deposited on opposing surfaces of the substrates 1a and 1b in the same manner as in Example 1. Further, alignment films 3a and 3b similar to those in Example 1 were formed, and after the rubbing treatment, cleaning was performed by ultrasonic pure water cleaning.

After the cleaned substrates were heat-treated at 150° C. for 2 hours, they were divided into those to be left in the air and those to be stored in a desiccator, and the time from heat treatment to cell assembly was varied. The number of bubbles generated when heating was performed at 150° C. for 2 hours was investigated. The results obtained are shown in Figure 2.

As shown in FIG. 2, bubbles were generated in the samples left in the atmosphere for 24 hours or more. Furthermore, bubbles were generated in the samples stored in the desiccator after 36 hours or more. From this result, it was found that it is preferable to store the substrate in a desiccator after heat treatment and assemble the cell within 24 hours.

[0042]

Effects of the Invention As explained above, the method for manufacturing a liquid crystal cell with a diaphragm according to the present invention is characterized in that after cleaning the rubbed alignment film, the substrate is heat-treated at 150 to 220°C for 2 hours or more. Since residual moisture and moisture adsorbed to other constituent materials are removed in the alignment film cleaning process, the assembled liquid crystal cell is heated to around 140°C in the subsequent ultrasonic diaphragm bonding process. No bubbles are generated within the liquid crystal cell even when heated to high temperatures. Furthermore, no air bubbles are generated within the liquid crystal cell even during ultrasonic operation and durability.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the heat treatment temperature of a substrate and the number of bubbles generated in a liquid crystal cell.

FIG. 2 is a diagram showing the time required to assemble the liquid crystal cell after heat treatment of the substrate and the number of bubbles generated in the liquid crystal cell.

FIG. 3 is a cross-sectional view of a liquid crystal cell with a diaphragm.

[Explanation of symbols]

1a and 1b substrate
2a and 2b transparent electrode layers 3a and 3b alignment film 4
Sealant 5 Spacer
7 Al film 10 Vibration plate
12 Piezoelectric element 13 Liquid crystal

Claims (1)

[Claims] 1. A step of applying a transparent electrode layer to opposing surfaces of a pair of substrates, at least one of which is transparent, a step of forming an alignment layer on the surface of the transparent electrode layer and subjecting it to a rubbing treatment, and a step of applying a rubbing treatment to the substrate. a step of cleaning the alignment film, a step of heat-treating the substrate at 150 to 220° C. for 2 hours or more, a step of applying a sealant to the periphery of the substrate and then bonding the substrate to assemble the liquid crystal cell, and a step of assembling the liquid crystal cell. 1. A method for manufacturing a liquid crystal cell with a diaphragm, comprising the steps of: injecting and sealing a liquid crystal into the substrate; and bonding a diaphragm to the substrate.