JPS62115122A - Liquid injecting method for electrooptic element - Google Patents

Abstract

PURPOSE:To shorten the time required for injecting liquid by decreasing the area where the liquid required for an electrooptic display contacts gas during the time when the gas in a cell is evacuated by the reduction of pressure. CONSTITUTION:The liquid is moved toward a vessel 6 for storage from a vessel 5 for injection and is drawn into the mid-way of a pipeline 7 or the vessel 6 in a stage for discharging the gas in the cell 1 by the pressure reduction. The surface area of the liquid under the reduced pressure in this state is extremely small and the evaporation of a low boiling compd. from the surface is small. The fluctuation of the compsn. of the liquid is extremely little. The liquid is supplied from the vessel 6 into the vessel 5 for injection and the injec tion port of the cell is allowed to contact the liquid filled in the vessel 5 in the stage of injecting the liquid into the cell. The pressure reduction is then released and the injection is completed by utilizing the atm. pressure. The expos ing area of the liquid is made small in this case to quickly execute the injection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a liquid injection method for an electro-optical element, which injects a liquid necessary for electro-optical display into a cell.

[Prior Art 1] A liquid crystal display element has been known as a typical electro-optical element in which a liquid necessary for electro-optical display is injected into a cell.

This liquid crystal display device usually places a cell equipped with an inlet in a reduced pressure chamber, reduces the pressure to a degree of reduced pressure of about 0.01 to 0.0001 torr, exhausts the gas in the cell, and then releases the reduced pressure. Liquid crystal is injected into a narrow gap in a cell using atmospheric pressure differences.

Problems to be Solved by the Invention] This reduced pressure injection method is widely used because liquid crystal can be injected into a narrow gap such as in a liquid crystal cell. However, in recent years, as liquid crystal display elements capable of operating at low temperatures have been developed and used, compositions for low temperature operation have come to be used as liquid crystal compositions.

This liquid crystal composition capable of operating at low temperatures is designed to keep the viscosity of the liquid crystal low even at low temperatures, so it often contains compounds with low boiling points.

When a liquid crystal composition mixed with this low-boiling point compound is injected using the vacuum injection method described above, the low-boiling point compound evaporates under the high vacuum described above, and during repeated injections several times. However, there is a problem in that the composition changes even during one injection depending on the case, and the characteristics of the liquid crystal display element change.

For this reason, attempts have been made to lower the degree of pressure reduction to evacuate the gas inside the cell at around 0.1 torr, but because the degree of pressure reduction is low, it takes time to exhaust the gas inside the cell, reducing production efficiency. There were other problems, such as insufficient gas evacuation and air bubbles remaining inside the cell during injection. Furthermore, although the degree of decompression is low, the liquid crystal is exposed to decompression for a long time, so it lasts longer than in the case of high decompression, but it still has the problem that the composition changes during repeated injections. had.

[Means for Solving the Problems] The present invention has been made to solve these problems, and the periphery of two substrates is sealed with a sealing material except for the injection port to form a cell, and the decompression chamber is closed. The cell is placed in a vacuum chamber, the gas inside the cell is exhausted by reducing the pressure, and the vacuum in the vacuum chamber is released with the inlet of the cell in contact with the liquid necessary for electro-optical display. In a liquid injection method for an electro-optical element in which the liquid is injected into the cell, the exposed area of the liquid is made smaller than the injection period during a period in which the vacuum chamber is depressurized and gas in the cell is exhausted. This is a liquid injection method for an electro-optical element, characterized in that the exposed area of the liquid is increased so that the liquid can be injected during the subsequent injection period.

The injection method of the present invention reduces the area in which the liquid, which is required for electro-optical displays such as liquid crystals, comes into contact with the gas during the period when the gas in the cell is evacuated by reducing the pressure. The evaporation of boiling-point compounds is greatly reduced, and the gas in the cell can be evacuated under high vacuum, so it can be done in a short time, reducing the time required for one injection. , it is possible to suppress fluctuations in the composition of the liquid. Therefore, injection can be continued for a long period of time, and productivity can be greatly improved.

In addition, when injecting, the liquid can be supplied to an injection container, which is a normal injection device, using a liquid supply device, so the resident process can be the same as the conventional process, and the cell can also be It also has the advantage that conventional products can be used as is.

The electro-optical device of the present invention includes a liquid crystal display device, an electrochromic display device, an electrophoretic display device, etc., and the periphery of two substrates is sealed with a sealing material to form a cell, and a space between the substrates of the cell is formed. Any device that produces an electro-optical display by injecting a liquid into the liquid may be used. Of course, three or more substrates may be used to inject liquid into two or more gaps.

An electrode is formed on at least one of the two substrates constituting this cell, and if necessary, an electro-optic material such as an electrochromic substance, an insulating or alignment film such as polyimide, polyamide, silica, titanium oxide, etc. Materials, color filters, and other elements and films required for various types of electro-optical devices are formed and laminated.

In the present invention, when a liquid necessary for electro-optical display is injected into such a cell, the pressure of the liquid is reduced during the period in which gas such as air or inert gas is exhausted from the cell by the reduced pressure. The surface area of the liquid is enlarged and the inlet of the cell is brought into injectable contact with the liquid so that as little surface area as possible is exposed, and conventional injection methods can be easily applied during injection.

[Effect] Next, explanation will be given with reference to the drawings.

FIG. 1 is a sectional view showing a preferred example of an apparatus used in the injection method of the present invention.

In FIG. 1, (1) is an electro-optic display cell, (2A
), (2B) is a substrate made of glass, plastic, etc., (3)
is a liquid necessary for electro-optical displays such as liquid crystals and electrolytes, (4
) is the cell injection port, (5) is the injection container, (6)
(7) is a conduit connecting the injection container and the storage container, and (8) is the float of the storage container.

FIG. 2 is a schematic cross-sectional view illustrating the pressure reduction step and injection step of the present invention, in which (A) shows the state of the liquid when the gas in the cell is being exhausted by pressure reduction, and (B) ) shows the state of the liquid when it is injected into the cell.

During the step (A) of evacuating the gas in the cell by reducing the pressure, the liquid is moved from the injection container to the storage container, and as shown in this figure, the liquid is moved from the injection container to the storage container. drawn into the container. In this state, even under reduced pressure, the surface area of the liquid is extremely small, so evaporation of low-boiling compounds from the surface is small, and fluctuations in the composition of the liquid are extremely small.

In this step, the degree of pressure reduction is high and can be reduced to 0.01 torr or less, particularly about 0.001 torr or less, so that the gas inside the cell can be exhausted in a short time and the inside of the cell can be made into a high vacuum.

Next, in step (B), which is the step of injecting the liquid, the liquid is supplied from the storage container to the injection container, and the injection port of the cell is brought into contact with the liquid filled in the injection container. to release the reduced pressure and complete the injection using the atmospheric pressure difference.

In this case, since the inside of the cell is under high vacuum, there is a very low possibility that bubbles will remain when the liquid is injected, and the injection can be carried out in a short time. Further, when this liquid is supplied to an injection container, the liquid is exposed to a high reduced pressure, but since the time is short, the composition is hardly affected.

Furthermore, in order to reduce this effect, it is necessary to apply a slight pressure, for example 0.1 torr, just before supplying the liquid to the injection container.
After reducing the degree of vacuum to a certain extent, the liquid can be filled into an injection container and brought into contact with the injection port of the cell for injection.

This is because even if the degree of decompression is lowered to a certain degree just before injection, the cell is only connected to the outside air through a narrow injection port, so the degree of decompression inside the cell does not decrease rapidly, but rather decreases after a short delay. This is because by lowering the pressure and immediately drawing the liquid into the injection container and injecting with the injection ports touching, there is little risk that the degree of vacuum inside the cell will drop significantly and bubbles will remain in the cell after injection. .

The container for this injection is one in which the liquid is removed or its surface area is reduced during evacuation by reduced pressure, and any container that allows the liquid to come into contact with the injection port of the cell at the time of injection is usually used. It may be a rectangular box-shaped container with an open section, and may be designed in consideration of the shape of the cell into which the injection is to be made.

Although this figure shows an example in which only one injection container is provided to simplify the explanation, in reality, a larger number of containers are connected and used by a conduit.

In addition, the mechanism for transferring liquid between an injection container and a storage container is not limited to the method of moving the liquid by moving a float up and down as shown in the figure. The heights of the liquid may be matched by changing the relative positions of the injection container and the storage container, as long as the liquid is supplied or removed from the injection container.

In the present invention, by adopting such a configuration, the gas inside the cell can be exhausted under high reduced pressure, the gas can be exhausted within a short period of time, and the volatilization of highly volatile compounds with low boiling points in liquid crystals etc. is reduced. , it is possible to minimize the compositional fluctuation of a liquid containing a large amount of low linkage point compounds, and it is possible to work continuously for a long time, resulting in good productivity.

Note that the present invention is not limited to this example, and can be applied in various ways as long as it has means for supplying liquid crystal to the injection container and removing liquid crystal from the injection container.

[Example] Example 1 6 wt% of low boiling point high volatility liquid crystal as injection liquid
Using the liquid crystal composition containing IO as a container for injection
Set up 4 rectangular containers of X 190m5, 3hmφ and height as storage containers? The injection container and the storage container are connected to each other by a flexible conduit with a diameter of 5 m connected to the bottom of the container, and the storage container is equipped with a 1-bottom moving mechanism. has been established. A float was not placed or placed in the liquid L portion of this storage container to prevent the liquid crystal composition from being exposed to reduced pressure.

The liquid crystal composition was injected into the liquid crystal cell using this injection device.

FIG. 3 is a graph showing the degree of pressure reduction in this example. First, the liquid crystal composition is drawn into the pipe by lowering the position of the storage container, and the liquid crystal composition is evacuated with a powerful vacuum pump to 0.0 O
1 torr, then maintain that state for 15 minutes to exhaust the gas inside the cell, and then raise the position of the storage container to supply the liquid crystal composition to the injection container through the conduit, and then release the liquid crystal composition into the injection container. When the liquid crystal composition was brought into contact with the inlet, the reduced pressure was released, and the injection was completed over 110 minutes, the injection was completed completely without any air bubbles remaining in the cell.

During this period of depressurization, the liquid crystal composition has an area of approximately 78 II 112, which corresponds to the cross-sectional area of a four-tree pipe, and when the float is not placed in the storage container, the cross-sectional area of the storage container is added to approximately 785 m + *2 It will be exposed to reduced pressure, but even when no float is placed in the storage container, this is the surface area of the injection container of 7600 wm.
It was only about 1/10 of 2.

As described above, in the injection method of the present invention, one injection takes about 30 minutes, and even if the injection operation is performed 20 times in succession, the reduction due to volatilization of the low boiling point liquid crystal is about 0.8 wt% ( (10 wt% of low boiling point components).

Comparative Example 1 For comparison, a conventional method of injection without using a storage container was carried out.

In this example, since a storage container was not used, the liquid crystal composition was injected in the same manner as in Example 1, except that the liquid crystal composition was supplied to the injection container and held during the vacuum.

As a result, the injection was complete, but because the liquid crystal composition was exposed to high vacuum on the surface of the injection container, the low boiling point liquid crystal decreased by 0.8 wt% even after just one injection. , a large compositional variation occurred, and therefore stable injection could not be performed even once. Comparative Example 2 As another comparative example, a method of injection under reduced pressure was carried out.

FIG. 4 is a graph showing the degree of pressure reduction in Comparative Example 2. In this comparative example, injection was carried out in the same manner as in the example except that the degree of pressure reduction and the holding time were changed.

In this example, in order to prevent the low-boiling-point liquid crystal of the liquid crystal composition from volatilizing, we gradually evacuated the liquid crystal using a vacuum pump and 0.1
torr, then held that state for 30 minutes to exhaust the gas inside the cell, and then brought the liquid crystal composition into contact with the injection port of the cell to release the reduced pressure and complete the injection over about 12 minutes. Complete injection was possible with no air bubbles remaining inside.

In this example, the degree of vacuum in the cell was low, so it took time to exhaust the gas in the cell, and the injection also took more time than in Example 1 because the degree of vacuum in the cell was low.

As a result, in Comparative Example 2@c) injection method, one injection time took about 52 minutes, which was about 1.8 times as long as in Example 1, and the composition variation of the liquid crystal composition was However, by performing the injection operation three times in succession, the decrease due to volatilization of the liquid crystal at the low temperature point was about 0.8%, which was better than in Example 1 of the present invention. Compared to this, the number of consecutive injections was short, and the productivity was low.

Example 2 Liquid crystal was injected using the same device as in Example 1, except for Nigai, in which the liquid was made movable by a float on the -L part of a storage container for storing liquid. ,
Similar results to Example 1 were obtained.

[Effects of the Invention] The injection method of the present invention reduces the area in which the liquid required for electro-optical display comes into contact with the gas during the period when the pressure is reduced and the gas in the cell is exhausted, and the liquid has a low boiling point. Evaporation of the compound is significantly reduced. Therefore, it is possible to maintain a high vacuum inside the vacuum chamber, and because the gas in the cell is evacuated under a high vacuum, it can be evacuated in a short time.Also, because the cell is in a high vacuum, liquid injection can also be done quickly. This reduces both the time required to reduce the pressure and exhaust the gas in the cell, and the time required to release the reduced pressure and inject the liquid into the cell.While reducing the time required for one injection, Since fluctuations in the composition of the liquid can be suppressed, injection can be continued over a long period of time, and productivity can be significantly improved.

In addition, except for moving the liquid between the injection container and the storage container, injection can be performed under the same conditions as conventional injection under high vacuum, so there is no loss of workability, and when injecting, the liquid is normally The injection process can be carried out by supplying it to an injection container which is an injection device, so the injection process can be performed in the same manner as a conventional process, and there is also the advantage that the conventional cell can be used as is.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an injection device used in the injection method of the present invention. FIG. 2 is a cross-sectional explanatory view showing the injection process of the present invention,
(A) shows the exhaust process by reducing the pressure, and (B) shows the injection process by releasing the reduced pressure. FIG. 3 is a graph showing the reduced pressure state of the injection method according to the embodiment of the present invention. FIG. 4 is a graph showing the reduced pressure state of the injection method of the comparative example. l: Electro-optical display cells 2A, 2B: Substrate 3: Liquid necessary for electro-optical display 4: Inlet 5: Container for injection 6: Container for storage 7: Conduit 8: Float complex 11; 71' Proverb 20 (A) (B) Flute 4 figure Hajime 3z

Claims (4)

[Claims] (1) Construct a cell by sealing the periphery of the two substrates with a sealing material except for the injection port, place the cell in a vacuum chamber, and exhaust the gas inside the cell by reducing the pressure to create an electro-optical display. In a liquid injection method for an electro-optical element, in which the vacuum in the vacuum chamber is released while the injection port of the cell is in contact with the necessary liquid, and the liquid is injected into the cell, the pressure in the vacuum chamber is reduced. During the period when the gas in the cell is being evacuated, the exposed area of the liquid is made smaller than the injection period, and then during the injection period, the exposed area of the liquid is made larger so that the liquid can be injected. A liquid injection method for an electro-optical element, which is characterized by: (2) A container for injecting liquid necessary for electro-optical display and a container for storing the liquid are used, and during the period when the gas in the cell is being exhausted, the liquid is not stored in the container for injection. without supplying
A liquid injection method for an electro-optical element according to claim 1, wherein the liquid is supplied from the storage container into the injection container immediately before the injection step. (3) The container for injecting the liquid necessary for electro-optical display and the container for storing the liquid are connected by a pipe, and during the period when the gas in the cell is being evacuated, the liquid is injected into the cell. During the injection period, the liquid is supplied from the pipe into the injection container and injected into the cell, thereby exhausting the gas in the cell. 3. The liquid injection method for an electro-optical element according to claim 2, wherein the exposed area of the liquid is made smaller during the injection period than during the injection period. (4) A liquid injection method for an electro-optical element according to any one of claims 1 to 3, wherein the liquid necessary for electro-optic display is a liquid crystal.