JP3108967B2 - Method for manufacturing polymer dispersed liquid crystal display element - 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 polymer dispersed liquid crystal display device.

[0002]

2. Description of the Related Art In a polymer-dispersed liquid crystal display device, a liquid crystal is dispersed in a polymer layer in a cell in which a pair of transparent substrates provided with transparent electrodes are joined via a frame-shaped sealing material. And a nematic liquid crystal having a positive dielectric anisotropy is used as the liquid crystal.

In this polymer dispersed liquid crystal display element, display is driven by applying a voltage between the electrodes of both substrates, and the molecules of the liquid crystal in the polymer dispersed liquid crystal layer are in a state where no voltage is applied. It is oriented in various directions, and in this state, light transmitted through the polymer dispersed liquid crystal layer is scattered by the light scattering action of the polymer dispersed liquid crystal layer. When a voltage higher than the threshold voltage of the liquid crystal is applied between the electrodes, the molecules of the liquid crystal are uniformly arranged so as to be perpendicular to the substrate surface, and the transmitted light is hardly affected by the light scattering effect. Transmits through the polymer dispersed liquid crystal layer.

That is, the above-mentioned polymer dispersed liquid crystal display element displays a desired pattern such as a character or a figure by light transmission and scattering. Has the advantage that the screen is brighter than that of the liquid crystal display device.

The above polymer dispersed liquid crystal display device generally comprises
After assembling a cell by joining a pair of transparent substrates, a mixed solution of a polymer and a liquid crystal polymerized by light is sealed in the cell, and the sealed solution is irradiated with ultraviolet light from outside the cell to remove the polymer. It is manufactured by a method of photopolymerization.

As described above, when the solution enclosed in the cell is irradiated with ultraviolet rays, the double bond of the polymer in a monomer or oligomer state is broken and radicalized, and radicals of adjacent polymers are bonded to each other. Since the polymer is polymerized by the polymerization reaction, the polymer and the liquid crystal are phase-separated to form the polymer-dispersed liquid crystal layer.

[0007]

However, the polymer-dispersed liquid crystal display device manufactured by the conventional manufacturing method does not have a uniform structure of the polymer-dispersed liquid crystal layer, and therefore the electro-optical effect of the device is not uniform. It has the problem of becoming.

This is because the polymer is dissolved in the liquid crystal in a monomer or oligomer state, and the above-mentioned radical polymerization reaction is hindered by the liquid crystal.
For this reason, radical bonds between adjacent polymers are broken, or radicals of the same polymer are recombined, and the structure of the formed polymer-dispersed liquid crystal layer becomes uneven.

In general, a radical initiator is added to the above-mentioned mixed solution in order to promote the radicalization of a polymer. However, the radicalization promotion efficiency of the radical initiator is also reduced by the liquid crystal. Is also a factor that hinders the above radical polymerization reaction.

An object of the present invention is to provide a method of manufacturing a polymer dispersed liquid crystal display device capable of obtaining a polymer dispersed liquid crystal display device having a polymer dispersed liquid crystal layer having a uniform structure.

[0011]

According to the method of manufacturing a polymer-dispersed liquid crystal display element of the present invention, a cell is filled with a mixed solution of a polymer and a liquid crystal which undergo a polymerization reaction by light, and the cell is subjected to ultrasonic vibration. The photopolymerization of the polymer is carried out while the polymerization is performed.

[0012]

As described above, when the photopolymerization of the polymer in the solution sealed in the cell is performed while the cell is ultrasonically vibrated, the radical bonding between the polymers is promoted by the stirring effect of the solution by the ultrasonic vibration. In addition, a uniform radical polymerization reaction is caused in the polymer in the entire region of the solution, and a polymer-dispersed liquid crystal layer having a uniform structure can be obtained.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 2 is a cross-sectional view of a polymer-dispersed liquid crystal display device manufactured by the manufacturing method of this embodiment. This polymer-dispersed liquid crystal display device has a pair of transparent substrates provided with transparent electrodes 13 and 14. For example, a polymer-dispersed liquid crystal layer 16 is provided in a cell 10 in which glass substrates 11 and 12 are joined via a frame-shaped sealing material 15.

FIG. 3 is an enlarged cross-sectional view of a part of the polymer-dispersed liquid crystal layer 16. The polymer-dispersed liquid crystal layer 16 has a liquid crystal (having a dielectric anisotropy) in a polymerized transparent polymer 17 layer. (Positive nematic liquid crystal) 18 is mixed in a dispersed state.

FIG. 1 is a manufacturing process diagram showing the manufacturing method of this embodiment. The above-mentioned polymer-dispersed liquid crystal display element is manufactured by the following steps. In FIG. 1, a pair of transparent substrates 1
The transparent electrodes 13 and 14 provided in 1 and 12 are omitted.

First, as shown in FIG. 1A, a pair of transparent substrates 11 and 12 are joined via a sealing material 15 to assemble a cell 10. At one side of the cell 10, a solution injection port 15a formed by partially removing the sealing material 15 is provided.

Next, as shown in FIG. 1B, a mixed solution A of a polymer and a liquid crystal polymerized by light is injected into the cell 10 by a vacuum injection method. Note that a radical initiator for accelerating the radicalization of the polymer is added to the mixed solution A. Injecting the mixed solution A, as in the conventional vacuum injection method, after setting the cell 10 in a vacuum tank (not shown) and reducing the pressure in the tank to a vacuum state, the injection port 15a of the cell 10 is Then, the pressure in the tank is increased to atmospheric pressure or a slightly higher pressure.

In this way, the mixed solution A is placed in the cell 10
After injection into the cell, first, as shown in FIG. 1 (c), the injection port 15a is sealed with a sealing material 15b made of a room temperature polymerizable or thermopolymerizable resin, and then sealed in the cell 10. The polymer of the solution A is photopolymerized.

This photopolymerization is carried out as shown in FIG.
The cell 10 is immersed in the vibration medium 22 in the vibration tank 20 to which the ultrasonic vibrator 21 is attached, and the ultrasonic vibrator 21 is vibrated. The irradiation is performed by irradiating the cell 10 with ultraviolet UV from above the vibration tank 20 while oscillating the sound wave. In addition,
As the vibration medium 22 in the vibration tank 20, a transparent liquid inert to ultraviolet rays, for example, IPA (iso-propyl alcohol) or the like is used.

When the solution A in the cell 10 is irradiated with the ultraviolet rays UV as described above, the double bonds of the polymer in a monomer or oligomer state are broken to form radicals, and radicals of adjacent polymers are bonded to each other. Since the polymer is polymerized by the radical polymerization reaction, the polymer 17
And the liquid crystal 18 are phase-separated to form the polymer dispersed liquid crystal layer 16 shown in FIG.

In this case, the radical polymerization reaction between the polymers is hindered by the liquid crystal. However, when the photopolymerization is performed while the cell 10 is vibrated by ultrasonic vibration, the radical polymerization between the polymers is caused by the stirring effect of the solution A by the ultrasonic vibration. Bonding is promoted, and conversely, the inhibitory effect of the liquid crystal on the radical polymerization reaction is reduced, and adjacent polymers are favorably radical-bonded, and the efficiency of radicalization promotion by the radical initiator added to the solution A is also improved. It is promoted by the ultrasonic stirring effect.

For this reason, the rate at which radical bonds between adjacent macromolecules are broken or radicals of the same macromolecule are recombined is reduced. By causing a polymerization reaction, the polymer-dispersed liquid crystal layer 16 having a uniform structure can be obtained.

Therefore, according to the above manufacturing method, it is possible to obtain a polymer-dispersed liquid crystal display element having a uniform structure of the polymer-dispersed liquid crystal layer 16 having a uniform structure and a good display quality without display unevenness. it can.

In the above embodiment, the mixed solution A was sealed in the cell 10 by the vacuum injection method, but the mixed solution A was joined to the pair of substrates 11 and 12 via the sealing material 15. When assembling the cell 10 by using the method, the mixed solution A may be sealed in the cell 10 by dropping the mixed solution A onto one of the substrates.

[0026]

According to the manufacturing method of the present invention, after a mixed solution of a polymer and a liquid crystal polymerized by light is sealed in a cell, the polymer is photopolymerized while ultrasonically oscillating the cell. Therefore, a polymer-dispersed liquid crystal display device having a polymer-dispersed liquid crystal layer having a uniform structure can be obtained.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a polymer-dispersed liquid crystal display device showing one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a polymer dispersed liquid crystal display device.

FIG. 3 is an enlarged sectional view of a part of a polymer-dispersed liquid crystal layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Cell 11, 12 ... Substrate 13, 14 ... Electrode 15 ... Sealing material 15a ... Solution injection port 15b ... Sealing material 16 ... Polymer dispersed liquid crystal layer 17 ... Polymer 18 ... Liquid crystal A ... Mixing of polymer and liquid crystal solution

Claims (1)

(57) [Claims] A polymer-dispersed liquid crystal layer in which liquid crystals are mixed in a dispersed state in a polymer layer is provided in a cell in which a pair of transparent substrates provided with transparent electrodes are joined via a frame-shaped sealing material. A method for producing a polymer-dispersed liquid crystal display device, comprising: filling a mixed solution of a polymer and a liquid crystal polymerizable by light in the cell, and then photopolymerizing the polymer while ultrasonically vibrating the cell. A method for producing a polymer-dispersed liquid crystal display device, comprising: