JPS5957221A - Production of display element - Google Patents

Abstract

PURPOSE:To perform a hardening process for a sealant under reduced pressure by discharging quickly generated gas to the outside of a cell. CONSTITUTION:A liquid crystal cell 14, a flexible partition wall film 18, and an upper mold 19 are disposed on a lower mold 16, and either of a lower space 24 and an upper space 25 is made reduceable in pressure. A valve 21 is closed and a valve 20 is opened to evacuate the inside of the space 24 by an evacuation pump 17 to maintain said space under -0.2-1kg/cm<2> reduced pressure. The gas such as oxygen, moisture or the like stuck on the electrode surface of the liquid crystal cell is thus discharged. The cell is then heated to 100-200 deg.C or is irradiated with UV light to harden the sealant. If gas is generated from the sealant in this stage, the gas is also discharged to the outside of the cell without sticking on the electrode surface. The valve 20 is closed and the valve 21 are opened upon hardening of the seal to introduce dry air, gaseous N2 or the like, then the pressure reduction in the lower space 24 is released to restore atm. pressure.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a display element.

Display elements include liquid crystal display elements, electrochromic display elements, electrophoretic display elements, etc. Electrode plates with electrodes formed on a substrate such as glass or plastic are arranged with the electrode surfaces facing each other, and the electrode plates are sealed. Some types are stacked and sealed with a material interposed between them, and an electro-optical liquid such as liquid crystal is sealed inside.

Among these, liquid crystal display elements are currently the most commonly used display elements.For example, as shown in Figure 1, two electrode plates (1) having transparent electrodes (4Al, (4B))
, (2) and a sealing material (5), and a liquid crystal (5) is sealed inside.

Such liquid crystal display elements have respective li! Pole plate (1),
(2) is formed, a sealing material is applied to at least one electrode plate, and the sealing material is hardened by applying pressure.

FIGS. 2 and 5 are cross-sectional explanatory views of a device for performing this pressure sealing. Based on Figure 2, (6) is a table for crimping, (7A) and (7B) are cushioning materials to apply force uniformly, and (8) is an air cylinder, etc. for applying force. , (9A) and (9B) are heaters for heating, and inlet (inlet) is a mold for transmitting the force of the air cylinder to the cell (11).

Further, FIG. 5 shows a type of device that pressurizes a cell using a membrane (12), and (12) applies pressure to a cell (11).
This membrane is used to apply pressure to the cell by injecting compressed gas between it and the mold (15), and is connected to a compressed gas source (not shown) at the top of the figure through a pipe. .

The lower table (6) in this case is the same as in Figure 2, and has a 1111 heat heater (9BJ) and a cushioning material (7B) on the top. Although not shown, a mechanism for regulating the vertical position of the upper mold (15) may be provided.

In a cell of a liquid crystal display element used in such a device, an electrode plate having a pair of transparent electrodes and a sealing material printed on at least one of the plates by screen printing or the like is arranged so that the electrode surfaces face each other.

The example shown in FIG. 2 or FIG. 5 is an apparatus used when using a heat-reduced seal, and cells (11) are placed on the cushioning material (7B) on the lower mold (6). Place the mold (10) on the upper part (II!l) with the air cylinder (8), pressurize the lower part, or press down the membrane (12) with pressurized gas.JJ
I + pressure and heat with heaters (9A) and (9B) to harden the sealing material.

In addition, with room-temperature-curing sealants, only pressure is applied at room temperature without heating, and with ultraviolet-curing sealants, conventional sealants are cured by applying pressure and irradiating ultraviolet rays. When sealed using a curing device, water and gas emitted from the sealant are adsorbed on the surface of the electrode plate of the cell into which liquid crystal is injected, and when liquid crystal is later injected and sealed to form a liquid crystal display element. This tends to have an adverse effect on the liquid crystal and shorten its lifespan.

The present invention has been made to prevent such drawbacks, and provides a display device in which a display element is manufactured by overlapping two electrode plates with a sealing material in between so that the electrode surfaces face each other, and hardening the sealing material. This is a method of dipping a display element, in which the step of curing the sealing material is performed under reduced pressure.

According to the manufacturing method of the present invention, since the curing process of the sealing material is performed under reduced pressure, the gas generated as the sealing material hardens is quickly discharged to the outside of the cell, making it difficult for the gas to adhere to the electrode plate, thereby preventing the display element. has a longer lifespan.

Next, the manufacturing method of the present invention will be explained based on a preferred apparatus with reference to the drawings.

FIG. 4 is a cross-sectional view of a preferred apparatus for curing the sealant used in the present invention.

The display element cells (14) arranged in this device include the aforementioned liquid crystal display element cells, electrochromic display element cells, electrophoretic display element cells, etc. A liquid display substance is placed between two electrode plates. Examples include a liquid crystal, a viologen solution, or a display auxiliary substance, such as a propylene carbonate solution in which lithium perchlorate for coloring and decoloring WOsM is dissolved. The following explanation will be based on an example of a cell of a liquid crystal display element.

The two electrode plates of a cell of a liquid crystal display element are usually transparent substrates made of glass, plastic, etc. on which i4 bright electrodes are formed, but one can be made into an opaque substrate as a reflective electrode, or a semiconductor substrate can be used, or five substrates can be used. Although a multilayer cell as described above may be used, and the electrodes may also be two-layer electrodes, this example shows the simplest transparent substrate with one layer of transparent electrodes provided on one surface.

This electrode plate is sealed with the electrode surfaces facing each other, and a heat-curing type, room-temperature curing type, ultraviolet curing type, etc. sealing material is applied to at least one of the electrode plates by screen printing or the like. ing. Of course, a spacer such as glass fiber or alumina particles can be placed in this sealing material and between the electrode plates to regulate the cell gap. It may be given to

In particular, the present invention is useful when a portion of the display surface of the cell that is not filled with liquid crystal is formed by an in-plane seal. This is because in Ichikawa's large cells, there are many areas where no display is performed even within the display surface, and in order to keep the cell gap constant and reduce the amount of liquid crystal filled, a sealant is used to prevent liquid crystal from entering the display surface. The idea is to form a closed space. If such a closed space is formed, if you try to seal it under normal pressure, the pressure will increase and the sealing material will come into contact with the two electrode plates, and the air trapped inside will not be able to escape, so the sealing material will be crushed only in that area. However, there is a problem in that the cell gap widens, resulting in defects such as color unevenness.

The sealing material has a print height of 2 compared to the cell gap after sealing.
It is made more than twice as high and is crushed under pressure.
The height is reduced to the height regulated by a spacer made of glass fiber, alumina particles, etc. that is usually mixed in the sealing material, and it also expands in the width direction, bringing the two electrode plates into close contact, and ensuring that the sealing material is sufficient. If it is not crushed, the cell will swell in that area.

Moreover, in a liquid crystal cell, the cell gap is normally controlled to about ±1 μm, and non-uniformity of the cell gap increases the difficulty of seeing such as color unevenness.

Even in a cell in which such a closed space is formed within the display surface using a sealing material, according to the method of the present invention, the cell can be easily crushed because it is sealed under reduced pressure, and the cell gap can be kept constant.

In addition, cells with such a closed space are not only used in large cells such as those used in military instrument panels as described above, but also in small cells such as those used in digital watches (77), where the button hole is formed on the surface of the cell. It can also be used by forming an inner seal and forming the needle hole after sealing.

Furthermore, on the inner surface of this electrode plate, S i OH is added as necessary.
% At203, ``Sl'' to form an overcoat such as limide! 1., AZ2 (13 etc.) is obliquely deposited.

A known orientation treatment such as rubbing is performed in advance.

A heater (15) for heating such a liquid crystal cell (14)
is placed on the mold (16) in which it is embedded, with a cushioning material (17) interposed therebetween. Above this mold (0), a partition membrane (18) having flexibility and extensibility and an upper mold (19) are placed.

This partition membrane is made of a heat-resistant silicone rubber sheet, a glass fiber-containing rubber sheet, or the like, and may be joined to the mold (19) or may be separated.

This mold (16) is connected to the vacuum pump (17), and a pulp (20) and a pulp for releasing the vacuum (c) are provided in the middle, and the mold (19) is also connected to the vacuum pump. A pulp (22) and a pulp (25) for releasing the reduced pressure are provided.

That is, a liquid crystal cell (14) is placed on the lower mold (16),
A flexible septum membrane (18) is arranged, and the upper mold (Ka) is placed.
The lower space (24) formed by the lower mold and the partition membrane and the upper space (25) formed by the upper mold and the partition membrane can both be depressurized. Moreover, this upper mold presses the partition membrane against the upper surface of the side wall of the lower mold.

Next, the operation will be explained.

After placing the liquid crystal cell and arranging the partition membrane (181 and mold (19)), the pulp (21) is closed, the pulp (20) is opened and the air is evacuated by the vacuum pump (17), and the space below is (24
) is placed under a reduced pressure of -0.2 to -1 kq/cm". As a result, gases such as oxygen and moisture attached to the electrode surface of the liquid crystal cell are also exhausted. Then, the heater (15)
The sealing material is cured by heating to 0 to 200°C or by irradiating ultraviolet rays from an ultraviolet irradiation source. Gas may also be generated from the sealing material when it hardens, but since it is under reduced pressure, it is discharged outside the cell and does not adhere to the electrode surface.

At this time, if necessary, the pressurizing force can be increased by introducing pressurized gas into the upper space (25).

Alternatively, the upper mold (19) may not be used, and only the partition membrane (1B) and the lower mold (16) may be used.

Note that heating often takes time, so it is preferable to preheat the mold before placing the liquid crystal cell.

After the seal has hardened, the pulp (20) is closed, the pulp (21) is opened and dry air, N, gas, etc. are introduced to release the reduced pressure in the lower four spaces (24) and return it to atmospheric pressure.

The pulp (20) may be closed with the space (24) in a constant reduced pressure state and the reduced pressure pump may be stopped, or the reduced pressure may be continued or intermittent.

Father, when using the device shown in Figure 4, bulp (20), (
22) and close the valves (21) and (25) to reduce the pressure, and after reducing the pressure in both the upper and lower spaces (24) and (25), close the pulp (22) and close the valve. (25)
The pressurizing force on the liquid crystal cell can be adjusted to the desired value by opening it slightly and changing the degree of vacuum in the upper space.

By using a device using a partition membrane (18) and a mold (16) as shown in Fig. 4, it is not necessary to change the mold (10) depending on the shape and size of the cell as in the device shown in Fig. 2. There is no need for a mechanism to generate a large pressurizing force in a large cell, and a mechanism to receive and support it, and only a decompression chamber is required, and it is easy to apply force uniformly.

Compared to the device shown in Fig. 5, the mechanism is simple as it does not require pressurized gas.

After forming a liquid crystal cell in this way, a liquid crystal material such as a nematic liquid crystal or a freesteric liquid crystal to which dichroic dyes, optically active substances, etc. have been added as necessary is injected.
Seal the inlet.

Next, if necessary, polarizing plates, color polarizing plates, reflectors, color filters, % wavelength plates, light guide plates, etc. are laminated, and non-glare treatment is applied, and letters, numbers, figures, etc. are printed, etc., to form a liquid crystal display element. EXAMPLE The surface of a glass substrate with transparent electrodes formed thereon was subjected to a rubbing treatment, and a thermosetting epoxy resin was printed on one substrate by screen printing, and the electrodes were aligned so that the electrode surfaces faced each other. Using the apparatus shown in the figure, it was placed on the lower mold (16), which had been heated to 150° C., with a cushioning material (26) interposed therebetween.

Next, a silicone rubber sheet with a thickness of 1 inch is placed on top of it as a partition membrane, and a mold (16) is formed using a presser frame corresponding to the mold (19).
) side wall J:, close the valve (21),
Open the pulp (20) and make the space (24) -06h9/
The pressure was reduced to C- and held for 10 minutes, then the pulp (20) was closed, the valve (21) was opened and N gas was introduced to return the pressure to atmospheric pressure, the partition membrane and the holding frame were removed, and the liquid crystal cell was taken out. Ta.

The sealing material of this liquid crystal cell spreads extremely uniformly,
The cell gap was also kept almost constant, and a sealing condition equivalent to that of the conventional 11-pressure sealing method was obtained.

In the above example, we have only explained the case of a liquid crystal cell, and moreover, only the case of a single liquid crystal cell, but it can also be applied to electrochromic cells, electrophoretic cells, etc. It can be used in a normal mass production method in which the method is later cut and separated, and in a method for manufacturing a multilayer cell in which two or more liquid crystal layers are formed using five or more electrode plates, and various applications are possible in the future.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display element. 2 and 5 are cross-sectional views of a conventional pressurizing device for curing sealing material. FIG. 4 is a sectional view of a pressurizing device suitable for curing the sealing material of the present invention. Mold 16.19 Decompression tube 17 Partition membrane 1B

Claims (1)

[Claims] (1) In a display element manufacturing method in which a display element is manufactured by overlapping two electrode plates with a sealant in between so that the electrode surfaces face each other and curing the sealant, the step of curing the sealant is A method for manufacturing a display element characterized by performing the process under reduced pressure.