JP3108963B2 - Manufacturing method of ferroelectric liquid crystal device - Google Patents

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 ferroelectric liquid crystal device.

[0002]

2. Description of the Related Art A ferroelectric liquid crystal device is a device in which a ferroelectric liquid crystal is sealed between a pair of substrates. This ferroelectric liquid crystal device has a memory property of alignment in two directions (stability of alignment state). )
There is a type using a normal ferroelectric liquid crystal having the following characteristics, and a type using a ferroelectric liquid crystal called antiferroelectricity having a memory property of alignment in three directions.

The above-mentioned ferroelectric liquid crystal device has been conventionally manufactured by the manufacturing method shown in FIG. 3 or the manufacturing method shown in FIG.
In addition, the manufacturing method shown in FIG. 3 is not limited to the ferroelectric liquid crystal element,
Widely employed in the production of various liquid crystal elements, the production method shown in FIG. 4 is also employed in the production of a TN type liquid crystal element in which liquid crystal molecules are twisted and aligned.

[0004] The manufacturing method shown in FIG.
Are assembled via a frame-shaped sealing material 13 surrounding the liquid crystal sealed region to assemble a cell 10 having a predetermined substrate gap.
In this method, a liquid crystal LC is injected into a liquid crystal injection hole 13a formed by removing a part of the sealing material 13 into the liquid crystal injection hole 13 and then the liquid crystal injection hole 13a is sealed.
The liquid crystal LC is injected into the chamber 0 by a vacuum injection method in a vacuum chamber (not shown).

In the vacuum injection method, the cell 10 is set in a vacuum tank, the inside of the tank is evacuated to a vacuum state, and then the end face of the cell 10 where the liquid crystal injection port 13a is formed is closed. By immersing the cell in a liquid crystal bath in a liquid crystal dish 14 arranged at the bottom of the cell and raising the pressure in the tank to atmospheric pressure or more in this state, the pressure difference between the inside of the cell 10 and the outside is utilized. This is a method of injecting the liquid crystal LC in the liquid crystal dish 14 into the cell 10. The cell 10 into which the liquid crystal LC has been injected is taken out of the pressure-resistant tank, and the liquid crystal injection port 13a is sealed.

The ferroelectric liquid crystal element is manufactured by this method by heating a liquid crystal (ferroelectric liquid crystal) LC in a liquid crystal dish 14 to a temperature at which a low viscosity state is obtained and injecting the liquid crystal LC into a cell 10. Is being done.

[0007] This is because the ferroelectric liquid crystal currently in practical use is in a smectic phase state at a temperature near room temperature, and both ordinary ferroelectric liquid crystal and antiferroelectric liquid crystal are in a smectic phase state. Since the ferroelectric liquid crystal has a high viscosity, injection into the cell 10 by a vacuum injection method is almost impossible.

For this reason, in the above-mentioned manufacturing method, the viscosity of the ferroelectric liquid crystal LC in the liquid crystal dish 14 is reduced by heating the liquid crystal to a temperature at which it becomes a cholesteric phase, a nematic phase or an isotropic phase. The ferroelectric liquid crystal LC in the state is injected into the cell 10.

The ferroelectric liquid crystal LC injected into the cell 10 by heating to a low viscosity state is returned to the smectic phase state by cooling the cell 10 to around room temperature.

In the manufacturing method shown in FIG. 4, an endless frame-like sealing material 23 surrounding a liquid crystal sealing region is formed on one or both of a pair of substrates 21 and 22 constituting a liquid crystal element. The liquid crystal LC is dropped on the substrate by the amount of the sealing liquid, and then the two substrates 21 and 22 are overlapped with each other via the sealing material 23 and pressed until a predetermined substrate gap is formed. Then, the sealing material 23 is cured in that state. In this method, the two substrates 21 and 22 are joined, and the liquid crystal LC is dropped on the substrate 21 and the two substrates 21 and 22 are joined in a vacuum chamber (not shown).

When a ferroelectric liquid crystal element is manufactured by this method, the liquid crystal (ferroelectric liquid crystal) LC is dropped onto the substrate 21 by heating the liquid crystal LC to a temperature at which the liquid crystal LC has a low viscosity. If the ferroelectric liquid crystal LC is kept in a low viscosity state as described above, the liquid crystal LC dropped on the substrate 21 flows smoothly and spreads when the two substrates 21 and 22 are overlapped and pressed. The liquid crystal LC can be uniformly sealed over the entire liquid crystal sealing area surrounded by the sealing material 23.

Also in this manufacturing method, the ferroelectric liquid crystal LC sealed in a low-viscosity state is assembled by joining the two substrates 21 and 22 to assemble a liquid crystal element, and then cooling the liquid crystal element to near room temperature to obtain a smectic. It is returned to the phase state.

[0013]

However, the manufacturing method shown in FIG. 3 has a disadvantage that it takes time to inject the liquid crystal LC into the cell 10.

This is because the liquid crystal LC is injected into the cell 10 by a vacuum injection method. In the vacuum injection method, the liquid crystal LC is injected into the cell 10 as the liquid crystal LC is injected into the cell 10. Since the pressure difference between the liquid crystal LC and the outside decreases, the flow rate of the liquid crystal LC into the cell 10 gradually decreases, and a considerable time is required until the injection of the liquid crystal LC is completed.

For this reason, the manufacturing method shown in FIG. 3 is inferior in the manufacturing efficiency of the liquid crystal element. Particularly, in manufacturing a large-screen liquid crystal element, the time required for liquid crystal injection is considerably long, and the manufacturing efficiency is greatly reduced. Had the problem that

On the other hand, the manufacturing method shown in FIG.
A liquid crystal LC is dropped on a pair of substrates 21 and 22,
3 can be assembled at the same time, and the liquid crystal element can be assembled and the liquid crystal can be sealed at the same time.
The liquid crystal element can be manufactured much more efficiently than the manufacturing method shown in FIG.

However, in the manufacturing method shown in FIG.
The drop amount of the liquid crystal LC dropped on the liquid crystal element must be strictly controlled in accordance with the liquid crystal sealing amount of the liquid crystal element, that is, the volume of the liquid crystal sealing region when the two substrates 21 and 22 are joined via the sealing material 23. Therefore, there is a problem that it is difficult to control the drop amount of the liquid crystal LC.

In addition, according to this manufacturing method, a ferroelectric liquid crystal element cannot be manufactured with a high yield. This is because vacuum bubbles are formed in the liquid crystal layer when the ferroelectric liquid crystal sealed in the liquid crystal element returns to the smectic phase state.

That is, when a ferroelectric liquid crystal element is manufactured by the manufacturing method shown in FIG. 4, as described above, the ferroelectric liquid crystal LC is heated to a temperature at which it has a low viscosity, and the substrate 2 is heated.
In this manufacturing method, when the liquid crystal element is assembled, the pair of substrates 21 and 22 and the endless frame-shaped sealing material 2 are dropped.
Since the liquid crystal is hermetically sealed in the sealed gap formed by the liquid crystal device 3 and the ferroelectric liquid crystal returned to the smectic phase state by cooling the assembled liquid crystal element, the volume of the liquid crystal expanded by heating is reduced (by cooling). (Contraction to the original volume) and a volume decrease due to the phase change, and a vacuum bubble without liquid crystal is formed in the liquid crystal layer.

If there is a vacuum bubble having no liquid crystal in the liquid crystal layer, the orientation of the liquid crystal is disturbed, and light transmitted through the liquid crystal layer passes through the vacuum bubble without being affected by the polarization action of the liquid crystal. Defective products with display defects.

According to the present invention, a ferroelectric liquid crystal element is dropped on one substrate, and a pair of substrates are joined together to efficiently manufacture a ferroelectric liquid crystal element. Can easily control the drop amount of
In addition, the ferroelectric liquid crystal, which has been heated to a temperature at which it has a low viscosity, returns to the smectic phase state without generating vacuum bubbles in the liquid crystal layer, and a high-quality ferroelectric liquid crystal element without display defects is obtained. It is an object of the present invention to provide a method of manufacturing a ferroelectric liquid crystal element which can be manufactured with a high yield.

[0022]

According to a method of manufacturing a ferroelectric liquid crystal element of the present invention, at least one of a pair of substrates has a frame shape surrounding a liquid crystal enclosing region and at least a part of the inside and outside of the liquid crystal enclosing region. A ferroelectric liquid crystal heated to a temperature at which it becomes a low-viscosity state is dropped onto one of the pair of substrates slightly larger than the sealing amount, on a sealing material provided with a communication port for communicating the liquid crystal. Then, after the pair of substrates are overlapped with each other via the sealing material and pressed until a predetermined substrate gap is reached, the sealing material is cured in this state to join the pair of substrates, and thereafter, The communication port is sealed after cooling the ferroelectric liquid crystal to a temperature at which the ferroelectric liquid crystal enters a smectic phase state in a tank at a pressure higher than the atmospheric pressure.

[0023]

According to the present invention, the ferroelectric liquid crystal is dropped on one of the substrates and the pair of substrates is joined to each other, so that the assembling of the liquid crystal element and the enclosing of the liquid crystal can be performed simultaneously.
Therefore, a ferroelectric liquid crystal element can be manufactured efficiently.

In the present invention, since the frame-like sealing material for joining the pair of substrates is provided with a communication port for communicating between the inside and the outside of the liquid crystal enclosing region surrounded by the sealing material, the liquid crystal is formed on the substrate. Even if the amount of dripping is large, excess liquid crystal can be released to the communication port when assembling the liquid crystal element,
Therefore, it is not necessary to strictly control the amount of the liquid crystal to be dropped according to the amount of the liquid crystal, and the amount of the liquid crystal can be easily controlled.

Further, in the present invention, the above-mentioned communication port is provided in the sealing material, and the ferroelectric liquid crystal heated to a temperature at which a low viscosity state is obtained is dropped slightly more than the sealed amount. After the assembly, the cooling for returning the ferroelectric liquid crystal to the smectic phase state is performed in a tank at a pressure higher than the atmospheric pressure. Then, the liquid crystal pushed out to the communication port of the sealing material at the time of assembling the liquid crystal element is pushed back into the element by the pressure in the tank, and the volume of the liquid crystal is reduced. For this reason, the ferroelectric liquid crystal heated to a temperature at which the liquid crystal becomes low in viscosity can be returned to the smectic phase without causing vacuum bubbles in the liquid crystal layer.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a perspective view showing a method of manufacturing a ferroelectric liquid crystal element, in which a ferroelectric liquid crystal is dropped on a substrate to assemble the liquid crystal element and a state in which the ferroelectric liquid crystal in the liquid crystal element is returned to a smectic phase state. FIG. 2 is a sectional view of the manufactured ferroelectric liquid crystal device.

First, the structure of the ferroelectric liquid crystal device shown in FIG. 2 will be described. In this ferroelectric liquid crystal element, a pair of transparent substrates 31 and 32 made of glass or the like are joined via a frame-shaped sealing material 33 surrounding a liquid crystal sealing region.
A ferroelectric liquid crystal (ordinary ferroelectric liquid crystal or antiferroelectric liquid crystal) LC is sealed in a gap surrounded by the sealing material 33 between the two substrates. Respectively have transparent electrodes 3 for applying an electric field to the liquid crystal layer.
4, 35, and alignment films 36, 37 for aligning molecules of the ferroelectric liquid crystal LC in a predetermined direction.

The frame-shaped sealing material 33 is formed in a shape in which a part of the frame side corresponding to one edge of the liquid crystal element is omitted. The missing portion is provided as a communication port 33a for communicating the inside and outside of the liquid crystal sealed area surrounded by the sealing material 33 during the manufacture of the liquid crystal element. Is sealed by.

Next, a method of manufacturing the ferroelectric liquid crystal device will be described with reference to FIG. Note that, in FIG.
The transparent electrodes 34 and 35 on 32 and the alignment films 36 and 37 are omitted.

First, the transparent electrodes 34 and 35 and the alignment film 3
6, 37, on one of the substrates 31, 32, for example, on the lower substrate 31 in FIG.
A photo-curable resin is printed by a screen printing method to form a sealing material 33 which is formed in a frame shape surrounding the liquid crystal sealing area and partially provided with a communication port 33a for communicating the inside and outside of the liquid crystal sealing area.

Next, as shown in FIG. 1A, the pair of substrates 31, 32 is carried into a vacuum chamber 41, and the vacuum chamber 4
1, one of the substrates, for example, the sealing material 3
The ferroelectric liquid crystal LC previously heated to a low viscosity state (a temperature at which the ferroelectric liquid crystal becomes a cholesteric phase, a nematic phase, or an isotropic phase) is placed on the substrate 31 on which the substrate 3 is formed. The liquid is dropped slightly more than the liquid crystal filling amount of the liquid crystal element. The liquid crystal L
C is dropped near the center of the liquid crystal sealed area.

Next, in the vacuum chamber 41, the substrate 31 on which the ferroelectric liquid crystal LC is dropped and the other substrate 32 are overlapped with each other via the sealing material 33.
32 is pressed by a pressing means (not shown) until a predetermined substrate gap is reached.

When the two substrates 21 and 22 are overlaid and pressed as described above, the ferroelectric liquid crystal LC dripped near the center of the liquid crystal sealed area is pushed by the two substrates 21 and 22 and surrounded by the sealing material 23. The surplus liquid crystal LC flows uniformly and spreads over the entire liquid crystal sealed area, and the excess liquid crystal LC is pushed out to the communication port 33 a of the sealing material 33. At this time, since the ferroelectric liquid crystal LC is heated to a temperature at which the liquid crystal becomes in a low viscosity state,
The liquid crystal LC flows and spreads smoothly.

After pressing both substrates 31 and 32 to a predetermined substrate gap, the sealing material (photo-curable resin) 33 is irradiated with ultraviolet light while maintaining the pressed state. Is cured, and the two substrates 31 and 32
Are assembled via the sealing material 33 to assemble a liquid crystal element.

After assembling the liquid crystal element in this way,
The liquid crystal element is taken out of the vacuum chamber 41 and transferred to a pressure chamber 42 as shown in FIG. 1 (b). Liquid crystalline LC is returned to the smectic phase state. The step of returning the ferroelectric liquid crystal LC in the pressure tank 42 to the smectic phase state is performed in the following procedure.

First, the liquid crystal element is heated to a temperature at which the ferroelectric liquid crystal LC maintains a low viscosity state, and an inert gas (for example, nitrogen gas) is fed into the pressurizing tank 42 while maintaining this temperature. The pressure in the tank is slightly higher than the atmospheric pressure.

As described above, when the pressure in the pressurizing tank 42 is increased while the liquid crystal element is heated, the excess liquid crystal extruded into the communication port 33a of the sealing material 33 at the time of assembling the liquid crystal element causes the excess liquid crystal to be generated by the pressure in the tank. The liquid crystal LC in the liquid crystal element
Is filled with a higher pressure than the regular filling amount, and a filling defect caused when the liquid crystal LC does not completely reach the liquid crystal filling region at the time of assembling the liquid crystal element is eliminated.

Next, the liquid crystal element is cooled to a temperature (usually room temperature) at which the ferroelectric liquid crystal LC enters a smectic phase state while maintaining the pressure in the pressurizing tank 42 higher than the atmospheric pressure. The dielectric liquid crystal LC is returned to the smectic phase state.

In this case, the liquid crystal LC, which has been expanded by being heated to a temperature at which it has a low viscosity, contracts with cooling and phase change. At the same time, when assembling the liquid crystal element, the liquid crystal LC pushed out to the communication port 33a of the sealing material 33 is pushed back into the element by the pressure in the pressure tank 42, and the liquid crystal LC
Is compensated for, so that no vacuum bubbles are generated in the liquid crystal layer when the ferroelectric liquid crystal LC is returned to the smectic phase state.

Thereafter, the liquid crystal cell is taken out of the pressurizing tank 42, and the communication port 33a is closed with the sealing resin 3 as shown in FIG.
8 to complete a ferroelectric liquid crystal device. Note that a photo-curable resin is used for the sealing resin 38, for example.

As described above, in the method of manufacturing a ferroelectric liquid crystal element, the ferroelectric liquid crystal LC is dropped on one substrate 31 and the pair of substrates 31 and 32 are joined. According to the manufacturing method, the assembling of the liquid crystal element and the enclosing of the liquid crystal can be performed at the same time, so that the ferroelectric liquid crystal element can be manufactured efficiently.

In this manufacturing method, the frame-like sealing material 33 joining the pair of substrates 31 and 32 is provided with the communication port 33a for communicating the inside and outside of the liquid crystal sealing area surrounded by the sealing material 33. , Liquid crystal LC on substrate 31
Even if the amount of the liquid crystal LC is large, excess liquid crystal can be released from the communication port 33a at the time of assembling the liquid crystal element. Therefore, it is not necessary to strictly control the amount of the liquid crystal LC to be dropped according to the amount of the liquid crystal. Therefore, it is easy to control the drop amount.

Further, in this manufacturing method, the sealing material 33
In addition to the above, the communication port 33a is provided, and the ferroelectric liquid crystal LC heated to a temperature at which a low-viscosity state is obtained is dropped slightly more than the sealing amount, and further performed after assembling the liquid crystal element. Since the cooling for returning the liquid crystal LC to the smectic phase state is performed in the pressurized tank 42 in which the pressure is higher than the atmospheric pressure, even if the volume of the liquid crystal LC is reduced by cooling, the liquid crystal element The liquid crystal LC pushed out to the communication port 33a of the sealing material 33 at the time of assembling is pushed back into the element by the pressure in the tank, and the liquid crystal L
The volume decrease of C is compensated.

For this reason, the ferroelectric liquid crystal LC heated to the temperature at which the viscosity becomes low can be returned to the smectic phase state without generating vacuum bubbles in the liquid crystal layer. A high quality ferroelectric liquid crystal element can be manufactured with good yield.

In the above embodiment, the process of assembling the liquid crystal element by dropping the ferroelectric liquid crystal LC on the substrate 31 is performed in the vacuum chamber 41, and the ferroelectric liquid crystal LC in the assembled liquid crystal element is converted into the smectic phase. Although the step of returning to the state is performed in the pressurized tank 42, these steps may be performed in the same tank by controlling the internal pressure.

In the above embodiment, the pair of substrates 31 and
32 is formed on one of the substrates 31, and the sealing material 33 is formed on a pair of substrates 31 and 3.
2, and the communication port 33a provided in the sealing material 33 may be provided not only in one place but also in a plurality of places.

[0047]

According to the manufacturing method of the present invention, a ferroelectric liquid crystal element is efficiently manufactured by dropping a ferroelectric liquid crystal on one substrate and joining a pair of substrates. In addition, the amount of liquid crystal dropped onto the substrate can be easily controlled, and the ferroelectric liquid crystal, which has been heated to a temperature at which it has a low viscosity, does not cause vacuum bubbles in the liquid crystal layer. By returning to the smectic phase state, a high-quality ferroelectric liquid crystal element free from display defects can be manufactured with high yield. it can.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of the present invention in a state where a ferroelectric liquid crystal is dropped on a substrate to assemble a liquid crystal element and a state where the ferroelectric liquid crystal in the liquid crystal element is returned to a smectic phase state.

FIG. 2 is a sectional view of a ferroelectric liquid crystal element.

FIG. 3 is a diagram showing a conventional method for manufacturing a liquid crystal element.

FIG. 4 is a diagram showing another conventional method for manufacturing a liquid crystal element.

[Explanation of symbols]

 31, 32: substrate 33: sealing material 33a: communication port 34, 35: electrode 36, 37: alignment film 38: sealing resin LC: ferroelectric liquid crystal 41: vacuum tank 42: pressurizing tank

Claims (1)

(57) [Claims] 1. A method of manufacturing a ferroelectric liquid crystal element in which a ferroelectric liquid crystal is sealed between a pair of substrates, wherein at least one of the pair of substrates has a frame shape surrounding a liquid crystal sealing region and at least one of the substrates. A sealing material provided with a communication port communicating the inside and outside of the liquid crystal sealed area is formed in a part, and a ferroelectric liquid crystal heated to a temperature at which a low viscosity state is formed on one of the pair of substrates. After dripping slightly more than the sealing amount, the pair of substrates are overlapped with each other via the sealing material and pressed until a predetermined substrate gap is reached, and then the sealing material is cured in that state and the pair of substrates is cured. Bonding the substrates, and thereafter cooling the ferroelectric liquid crystal to a temperature at which the ferroelectric liquid crystal enters a smectic phase state in a tank at a pressure higher than the atmospheric pressure, and sealing the communication port. Dielectric liquid crystal element Production method.