JPH03245121A - Liquid crystal panel - Google Patents

Abstract

PURPOSE:To make improvement in optical characteristics and electric field responsiveness by bringing a liquid crystal layer and electrodes into tight contact with each other by photosetting adhesion. CONSTITUTION:The liquid crystal panel 2 is inserted with the liquid crystal layer 22, which is formed by dispersing the liquid crystal 23a into a transparent resin 23b, between a pair of the electrodes 21a and 21b facing each other. At least one of the electrodes 21a, 21b is transparent. An adhesive layer 24 consisting of a UV curing resin is formed between the liquid crystal layer 22 and the electrode 21b. The adhesive layer 24 adheres securely and tightly to both so that the electrode 21b and the liquid crystal layer 22 are securely and tightly fitted to each other. Namely, the adhesion between the liquid crystal layer and the electrodes improves and the easy production without via press welding under heating is possible if the liquid crystal layer and the electrodes are tightly adhered to each other by the photosetting adhesion. The sepn. and flocculation of the liquid crystal decrease, the optical characteristics improve and electric field responsiveness is excellent in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal panel used in optical shutters and the like.

[Conventional technology]

Conventionally, as a liquid crystal panel, there is a liquid crystal panel as shown in FIG. 3, for example. This liquid crystal panel 1 has a structure in which a liquid crystal layer made of transparent resin 12 and liquid crystal 13 is inserted between a pair of opposing electrodes 11a and llb. The liquid crystal layer is formed by finely dispersing liquid crystal 13 having an electro-optical effect in a transparent resin 12, and at least one of the electrodes 11a11b is transparent.

Such liquid crystal panels utilize the fact that the refractive index of the liquid crystal changes by applying or removing voltage between the electrodes, which changes the amount of light transmitted, and is combined with materials such as glass. It is used as window materials, blinds, and video screens that can be made transparent or opaque.

Examples of methods for manufacturing the liquid crystal panel include methods (1), (2), and (2) below.

■ Disperse granular microcapsules containing liquid crystals in transparent resin to form a liquid crystal layer and create a liquid crystal panel.

■ Heat and harden a mixture of transparent resin and liquid crystal to form a liquid crystal layer and produce a liquid crystal panel.

■ A liquid crystal layer is formed by drying and evaporating the solvent from a dispersion of transparent resin and liquid crystal in a solvent, thereby producing a liquid crystal panel.

However, in either method, after forming the liquid crystal layer, it is necessary to bring electrodes into close contact with the front and back surfaces of the liquid crystal layer to form a liquid crystal panel.

At this time, various methods can be considered for bringing the liquid crystal layer into close contact with the electrodes, but usually methods such as applying an adhesive or heat-pressing in an autoclave are adopted.

[Problem to be solved by the invention]

However, liquid crystal panels obtained using conventional methods have low electric field response due to poor adhesion between the liquid crystal layer and electrodes.
Further, when using a method of heat-pressing, there is a problem that separation or aggregation of liquid crystals causes haze (turbidity) in the liquid crystal layer, resulting in deterioration of optical properties.

In view of these circumstances, it is an object of the present invention to provide a liquid crystal panel that has good adhesion between a liquid crystal layer and electrodes and can be easily manufactured without heat-pressing.

[Means for Solving the Problems] In order to solve the above problems, a liquid crystal panel according to the present invention includes a liquid crystal panel in which liquid crystal is dispersed in a transparent resin between a pair of opposing electrodes, at least one of which is transparent. In a liquid crystal panel having a structure in which a liquid crystal layer is inserted, the liquid crystal layer and the electrode are in close contact with each other by photocurable adhesive.The electrode used in this invention is not particularly limited. For example, conductive 1tFJ made of tin and indium oxide (ITO) can be deposited on a substrate by vacuum evaporation, sputtering, or sol-gel method.
Examples include those that have been formed. The base material for such an electrode is not particularly limited, but glass, plastic film, etc. are preferable. Specifically, in the case of glass,
Examples include soda glass and borosilicate glass, and, in the case of plastic films, polyethylene terephthalate and acrylic films. The resistance value required for this electrode is not particularly limited, as long as it functions as an electrode, and usually, it may be in the range of 0 to several hundreds of ohms. In the present invention, the electrode on at least one side of the liquid crystal panel may be transparent, for example, transparent to ultraviolet rays or visible light. That is, the electrodes on one side may be transparent and the electrodes on the other side may be made of an opaque material such as metal such as aluminum, gold, nickel, or copper. It works not on the light but on the reflected light.

The transparent resin constituting the liquid crystal layer is not particularly limited.
Any ordinary material may be used, but one with good liquid crystal dispersibility is preferred.

The liquid crystal to be dispersed in the transparent resin is not particularly limited, and includes, for example, nematic, smectic, and cholesteric types, but nematic type is preferred because it has excellent responsiveness to electric fields. The electro-optical effect exhibited by nematic liquid crystals is, for example, known as birefringence, which is due to the optical properties of the molecules that make up the liquid crystal. That is, it has two different refractive indices no % n l. The difference between n and nl indicates the birefringence Δn, which is a measure of the change in refractive index when the liquid crystal is subjected to an electric field and molecules are aligned. In other words, the larger Δn is, the greater the change between when an electric field is applied and when it is not applied.

When manufacturing liquid crystal panels, it is preferable to use materials with relatively large Δn and chemical and optical stability.
Noph chlorine type, benzoic acid ester type, biphenyl type, cyclohexanecarboxylic acid ester type, phenylcyclohexane type, pyrimidine type, etc. are known, but biphenyl type and phenylcyclohexane type are generally used from a practical standpoint. It is a type of thing. These things are
It has good chemical and optical stability and high birefringence.

The weight ratio when dispersing the above-mentioned liquid crystal in the transparent resin is not particularly limited, but it is usually as follows:
It is desirable that the liquid crystal content ranges from 10% to 90%. If the liquid crystal content is less than 10%, sufficient light diffusivity cannot be obtained, whereas if the liquid crystal content exceeds 90%,
Because the amount of resin is insufficient, it may become impossible to form a desired liquid crystal layer.

The method of dispersing the liquid crystal in the transparent resin is not particularly limited, and may be carried out using an ordinary stirrer or the like. Further, if necessary, a solvent or a dispersant such as a surfactant may be added to control the dispersibility. However, when a solvent is added, it is necessary to sufficiently evaporate the solvent by reducing pressure or heating prior to curing. If the solvent remains in the cured resin, the light diffusivity of the liquid crystal panel may be significantly reduced.

Examples of the photocurable resin used for adhesion in the present invention include ultraviolet curable resins.

Specific examples include photoinitiators by polymerization type. Radical polymerization types include unsaturated polyesters, acrylate resins such as epoxy acrylates, urethane acrylates, polyester acrylates, and silicone acrylates. , benzophenone, benzoin ether, acetophenone, etc.

Radical addition types include polythiol, polyene, and spiran resins, and photoinitiators include benzophenone. The cationic polymerization type includes epoxy resins, etc., and its photoinitiators include Lewis acids such as Lewis acid diazonium salts, Lewis acid sulfonium salts, and Lewis acid iodonium salts. Further, acid-curing type resins include ξ-noalkynd resins, and photoinitiators thereof include p-benzoylbenzyl chloride. However, the photocurable resin used in this invention may be a visible light curable resin other than the above, and is not particularly limited.

In short, without causing thermal damage to the liquid crystal layer,
Any material may be used as long as it has a resin composition containing a photoinitiator that is cured by light transmitted through the electrode, and is transparent in the cured state. As conventionally, this resin may itself become an RFC component of the liquid crystal layer.

The thickness of the adhesive layer is not particularly limited, but if it is set in the range of several microns to several tens of microns, an adhesive effect can be obtained without affecting the optical properties of the liquid crystal panel.

As described above, in the liquid crystal panel according to the present invention, the liquid crystal layer itself, which is formed by dispersing liquid crystal in the transparent resin, may have a photocurable adhesive ability and strongly adhere to the electrodes.

The method for producing a liquid crystal panel having the above configuration is not particularly limited, but for example, a film is produced from a mixture of polymethyl methacrylate, polyvinyl chloride, etc. and liquid crystal by a solvent casting method, and the film is applied to electrodes. or il! After dispersing the liquid crystal in a commonly used transparent paint and applying it to the electrode to form a coating film, a photocurable resin is further applied on top of this film or coating, and the other layer is coated. Examples include a method of curing the material in close contact with the electrode.

The method of applying the photocurable resin or the transparent resin in which liquid crystal is dispersed as an adhesive layer onto the electrode is not particularly limited, but any commonly used method may be used, such as spray method, bar coater method, dipping method, etc. Any method such as the law may be used.

When applying these resins, paints, inks, etc. are preferable because they are easy to handle. When the resin is a photocurable resin, additives such as a photopolymerization accelerator, a chain transfer agent, a stabilizer, and an adhesion promoter may be appropriately added in addition to the photoinitiator.

Examples of such additives include photopolymerization accelerators such as amines, chain transfer agents such as mercaptans, stabilizers such as chelating agents, organic acids, and acrylates having carboxyl groups; Examples of adhesion promoters include, but are not limited to, surfactants, solvents, adhesives, pulling agents, acids, and the like.

The thickness of the liquid crystal layer, that is, the gear between the electrodes, can be set using a spacer.For example, a film of constant thickness can be inserted between the edges, or
Alternatively, glass or resin beads of a similar particle size may be mixed in the resin solution.

In this way, a liquid crystal panel can be obtained by irradiating light onto a laminate in which a transparent resin film in which liquid crystal is dispersed and an adhesive layer are formed between opposing electrodes. It is desirable to remove air bubbles by reducing the pressure.

In addition, the light irradiation device for photocuring may be one that is commonly used. For example, in the case of ultraviolet irradiation, several tens of W/
A device equipped with a high-pressure mercury lamp or a metal halide lamp such as CJ is sufficient. The energy irradiated to the object to be cured is greatly affected by the distance between the lamp and the object to be cured, so it must be determined according to the type of resin, but in general, if used within the range of 10 to 20 am, However, in order to reduce the thermal energy from the lamp, a cold mirror, filter, etc. may be used.

[For production]

When the liquid crystal layer and the electrodes are brought into close contact with each other by photocurable adhesive, the adhesion between the liquid crystal layer and the electrodes is improved, and it is possible to easily manufacture the liquid crystal layer without using heat and pressure bonding.

〔Example〕

The present invention will be explained in detail below based on examples.

Note that this invention is not limited to the following examples.

FIG. 1(a) shows a first embodiment. As shown in the figure, this liquid crystal panel 2 has an I pair of electrodes 21a and 21b facing each other.
It has a structure in which a liquid crystal layer 22 in which liquid crystal 23a is dispersed in transparent resin 23b is inserted between them. Electrodes 21a, 2
At least one of 1b is transparent. liquid crystal layer 2
2 and the electrode 21b, an adhesive Jii 24 made of ultraviolet curing resin is formed. This adhesive layer 24 firmly adheres both the electrode 21b and the liquid crystal layer 22.
are strongly attached to each other.

FIG. 1(b) shows a second embodiment. This liquid crystal panel 3 has a liquid crystal 33 between a pair of opposing electrodes 31a and 31b.
A liquid crystal layer 32 formed by dispersing a in a transparent resin 33b
It has a structure in which is inserted. Electrodes 31a, 3
At least one of 1b is transparent. The transparent resin 33b is made of ultraviolet curing resin, and the liquid crystal layer 3
The liquid crystal layer 32 and the electrodes 31a, 31b are strongly adhered to each other by the 2 itself exhibiting a photocurable adhesive function.
Since the liquid crystal 33a is embedded in the crosslinked structure of the cured transparent resin 32, the liquid crystal panel 3 has improved light scattering properties and haze. ＞・In the case of a panel having an adhesive function, it is manufactured as shown in FIG. 2 fat to C1. First, as shown in figure (al), the electrode 41a
A mixture of ultraviolet curing resin and liquid crystal is applied to the surface of the substrate to form a film 45 of a predetermined thickness.Next, as shown in Figure (b), a transparent electrode 41b is laminated on the film 45. Then, ultraviolet rays are irradiated from the transparent electrode 41b side using the lamp A. After the irradiation, the resin is cured to form a liquid crystal layer 46 as shown in FIG.

Next, more specific examples of the present invention will be described together with comparative examples.

Example 1 - A cyanobiphenyl liquid crystal (Merck Japan, E- 60% by weight of 44>
The mixture was added and thoroughly stirred with a stirrer to prepare a resin solution. T
Conductive glass with a conductive film made of TO (indium-tin oxide) (100mX 100mX 1.1 tm
, resistance value 200Ω) was coated with the resin solution using a bar coater. As gear material, 25w thick PET (
A polyethylene terephthalate (polyethylene terephthalate) film was placed on the edge, and conductive glass was further layered on this coated surface. After sufficiently degassing by reducing the pressure, it was cured by irradiation with ultraviolet rays to produce a liquid crystal panel. The amount of ultraviolet rays irradiated at this time was approximately 90
It was 0 mJ/-.

Example 2 - A liquid crystal panel was produced in the same manner as in Example 1, except that biphenylcyclohexane liquid crystal (manufactured by Merck Japan, ZLI-1840) was used instead of cyanobiphenyl liquid crystal. did.

- Example 3 Polyvinyl chloride (manufactured by Nacalai Tesque, polymerization degree 1020)
A resin solution was prepared by adding the liquid crystal used in Example 1 to a 6% by weight solution (solvent: tetrahydrofuran) so that the content thereof was 60% by weight. This solution was prepared in Example 1.
The liquid crystal layer was applied onto the same conductive glass using a bar coater and dried under reduced pressure to produce a liquid crystal layer having a thickness of 20 nm. The urethane acrylate added with 1% by weight of the photoinitiator used in Example 1 was applied as an adhesive layer to the electrode surface of one of the conductive glasses to a thickness of approximately 5 nm using a bar coater, and this was applied to the previously prepared liquid crystal. After layering and degassing under reduced pressure, ultraviolet rays (approximately 900
mJ/aJ) was irradiated to cure the adhesive layer, and a liquid crystal panel was produced.

Example 4 A liquid crystal panel was prepared in the same manner as in Example 3, except that biphenylcyclohexane liquid crystal (manufactured by Merck Japan, ZLI-1840) was used instead of cyanobiphenyl liquid crystal. Created.

Example 5 - Insulating polyester ink (manufactured by Acheson Japan, solid content 3)
0%), the liquid crystal used in Example 1 was added to the liquid crystal whose content was 60f.
A solution was prepared by adding fi in an amount of %. This solution was applied onto the same conductive glass as in Example 1 using a bar coater, and dried by heating at 70° C. for 30 minutes to form a liquid crystal layer with a thickness of 20 nm. After that, a liquid crystal panel was produced by forming an adhesive layer and irradiating ultraviolet rays in the same manner as in Example 3. Example 6 In Example 5, a biphenylcyclohexane liquid crystal was used instead of the cyanobiphenyl liquid crystal as the liquid crystal. A liquid crystal panel was produced in the same manner as in Example 5 except that ZLI-1840 (manufactured by Merck Japan) was used.

Comparative Example 1 A liquid crystal panel was produced in the same manner as in Example 3, except that the liquid crystal layer and the electrodes were heat-pressed at about 90° C. without forming an adhesive layer.

Comparative Example 2 A liquid crystal panel was produced in the same manner as in Example 4, except that the liquid crystal layer and the electrodes were heat-pressed at about 90° C. without forming an adhesive layer.

Comparative Example 3 A liquid crystal panel was produced in the same manner as in Example 5, except that the liquid crystal layer and the electrodes were heat-pressed at about 90° C. without forming an adhesive layer.

Comparative Example 4 A liquid crystal panel was produced in the same manner as in Example 6, except that the liquid crystal layer and the electrodes were heat-pressed at about 90° C. without forming an adhesive layer.

Regarding the liquid crystal panels obtained in Examples 1 to 6 and Comparative Examples 1 to 4, the adhesion between the liquid crystal layer and the electrode layer was examined using an adhesion tester and a tape peeling method. Both panels were superior to the comparative examples.

In addition, for the liquid crystal panels of these Examples and Comparative Examples, the diffuse transmittance under normal conditions and the diffuse transmittance when an AC voltage of 30 V was applied were measured with a spectrophotometer needle, and with a measuring device using a photodiode array. The electric field response speed was measured. The results are shown first.

Figure 1 (0) 3゛\ (b) As shown in Table 1, the liquid crystal panels according to the examples, which have excellent adhesion between the liquid crystal layer and the electrodes, have better optical properties and It can be seen that the electric field response is improved.

〔Effect of the invention〕

The liquid crystal panel according to the present invention has good adhesion between the liquid crystal layer and the electrodes, and therefore has excellent electric field response. This LCD panel is also manufactured without heat and pressure bonding, so
Separation and aggregation of liquid crystals are reduced, resulting in improved optical properties.

[Brief explanation of drawings]

Fig. 1fa) is a side sectional view showing the first embodiment of the invention;
Figure 2 (al to fc) is a schematic explanatory diagram showing the method of manufacturing the liquid crystal panel of the second embodiment of the present invention in order of steps, and Figure 3 is a side sectional view showing the second embodiment. FIG. 3 is a side sectional view showing a conventional example. 2.3.4...Liquid crystal panel 21a, 21b, 31a
, 31b, 41a, 4lb--electrode 23a,
33a...Liquid crystal 23b, 33b...Transparent resin 2
232.46...Liquid crystal layer

Claims (1)

[Claims] 1. In a liquid crystal panel having a structure in which a liquid crystal layer made of liquid crystal dispersed in a transparent resin is inserted between a pair of opposing electrodes, at least one of which is transparent, the liquid crystal layer and the electrode are bonded with photocurable adhesive. A liquid crystal panel characterized by being in close contact with each other.