JPH06102493A - Production of high polymer dispersion type liquid crystal display element - Google Patents

Abstract

PURPOSE:To prevent the peeling between substrates and a liquid crystal material by the shrinkage, thermal and dynamic impacts, etc., generated at the time of curing of a polymerizable resin material dispersed with the liquid crystal material by curing a compd. and the polymerizable resin material to the state of bonding both. CONSTITUTION:This process for production includes a stage for allowing the compd. having polymerizable functional groups in molecules on the substrates 1, a stage for injecting a material mixture 3 contg. the polymerizable resin material 4 and the liquid crystal material 5 into the spacing between a pair of the substrates 1 and a stage for curing the compd. and the resin material 4 and chemically bonding the compd. and the polymerizable compd. 2. The liquid crystal display element obtd. by the above- mentioned process for production is constituted by dispersing the liquid crystal material 5 into the curable resin in which the curable resin and the liquid crystal material 5 cause a phase sepn. to constitute a supporting medium. The display state of the device is controlled without requiring the orientation treatment of the liquid crystal material and polarizing plates. Further, the compd. and the resin material are chemically bonded so that the substrates 1 and the liquid crystal material 5 have good adhesiveness.

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 dispersion type liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal display element utilizing the electro-optical effect, a liquid crystal element using a liquid crystal material such as a twisted nematic (TN) liquid crystal, a super twisted nematic (STN) liquid crystal or a ferroelectric liquid crystal has been actively used. Is being researched. These liquid crystal display elements are
It requires a polarizing plate and requires an alignment treatment on the liquid crystal material.

On the other hand, there has been proposed a liquid crystal display element which does not have a polarizing plate and which does not require alignment treatment of a liquid crystal material by utilizing scattering. This liquid crystal display element is a polymer-dispersed liquid crystal display element in which a liquid crystal material is dispersed in a polymer serving as a supporting medium, and its transparent or opaque state is electrically controlled by the birefringence of the liquid crystal material. . In this case, since the orientation of the liquid crystal molecules becomes uniform when a voltage is applied, the ordinary refractive index of the liquid crystal material and the refractive index of the polymer match to display a transparent state, and when no voltage is applied, the liquid crystal molecules are The orientation is disturbed to create a light scattering state, resulting in an opaque display. The following methods have been disclosed for manufacturing such a polymer-dispersed liquid crystal display device.

First, Japanese Patent Application Laid-Open No. 58-501631 discloses a method of encapsulating a liquid crystal material in a polymer capsule. However, in this method, since the liquid crystal droplets are independent cells, the driving voltage that causes a change in the orientation of the liquid crystal molecules is high, and the application range is narrow.

In Japanese Patent Laid-Open No. 61-502128, a mixed material composed of a liquid crystal material and a polymerizable resin material is prepared, and the polymerizable resin material is cured by light or heat to form a curable resin and liquid crystal is prepared. A method of depositing to form liquid crystal droplets in a resin is disclosed. However, the obtained liquid crystal display element has a weak adhesive property between the substrate and the liquid crystal material, contracts when the polymerizable compound cures, and receives a thermal shock or mechanical shock between the substrate and the liquid crystal material. There is a drawback that peeling occurs at.

Further, as a method of modifying the surface of the substrate, a method of applying a polymer film on the surface of the substrate and performing orientation treatment is disclosed in Technical Research Report EID91-48 pp11-14 of the Institute of Electronics and Communication Engineers. However, this method also cannot sufficiently increase the adhesive force between the substrate of the liquid crystal display element and the liquid crystal material.

[0007]

As described above, in the conventional polymer-dispersed liquid crystal display element, the liquid crystal material is used for a projector light valve in which the adhesiveness between the substrate and the liquid crystal material is weak and which is particularly susceptible to thermal shock. When the display element is used, the reliability of the product is significantly reduced.

The present invention is intended to solve the above problems, and an object of the present invention is to improve the adhesiveness between a substrate and a liquid crystal material and to provide a polymerizable resin material in which the liquid crystal material is dispersed. It is an object of the present invention to provide a method for producing a polymer-dispersed liquid crystal display device capable of preventing the substrate and the liquid crystal material from being separated from each other due to shrinkage or thermal or mechanical impact that occurs during curing.

[0009]

The method for producing a polymer-dispersed liquid crystal display device according to the present invention comprises a pair of substrates, at least one of which is transparent, facing each other, and a polymerizable functional group in the inner surface of each substrate. And a step of injecting a mixed material containing a polymerizable resin material and a liquid crystal material into a gap between the pair of substrates, and curing the compound and the polymerizable resin material into a state in which they are bound to each other. Including the step of
Thereby, the above object is achieved.

In a preferred embodiment, the above compound is a polymerizable compound.

In a preferred embodiment, the polymerizable compound is a monomer.

In a preferred embodiment, the compound is a silane coupling agent.

[0013]

The method for producing a polymer-dispersed liquid crystal display device according to the present invention comprises a step of allowing a compound having a polymerizable functional group in its molecule to exist on a substrate, and a polymerizable resin material and a liquid crystal material in a gap between a pair of substrates. And a step of curing the compound and the resin material and chemically bonding the compound and the polymerizable compound. The liquid crystal display device obtained by this manufacturing method has a configuration in which the liquid crystal material is dispersed in the curable resin that serves as a support medium by phase separation of the curable resin and the liquid crystal material, and requires alignment treatment of the liquid crystal material and a polarizing plate. You can control the display state without doing.
When a voltage is applied, the orientation of the liquid crystal molecules becomes uniform and the ordinary refractive index of the liquid crystal material and the refractive index of the polymer match to display a transparent state.When no voltage is applied, the orientation of the liquid crystal molecules is disturbed. Creates a light-scattering state, resulting in an opaque display. Further, the compound and the resin material are chemically bonded to each other, so that the substrate and the liquid crystal material have good adhesiveness.

[0014]

First, the basic contents of the present invention will be described.

The method for producing a polymer-dispersed liquid crystal display device of the present invention comprises a step of allowing a compound containing a polymerizable functional group in its molecule to exist on a substrate, and a mixed material containing a polymerizable resin material and a liquid crystal material. The method includes the steps of injecting into the gap between the pair of substrates and curing the compound and the resin material into a state in which they are bound to each other.

The step of allowing a compound having a polymerizable functional group in the molecule to exist on the substrate includes (a) a polymerizable compound such as a monomer, an oligomer or a polymer having a polymerizable functional group in the molecule of a pair of substrates. Examples thereof include a method of coating on two opposing surfaces, and a method of treating (b) two opposing surfaces of a pair of substrates with a silane coupling agent having a polymerizable functional group in the molecule.

In the method (a), examples of the polymerizable compound include photocurable and thermosetting compounds. Further, a compound having the same type of polymerizability as the polymerizable resin material used in the subsequent step can be used.

The photocurable compound has 3 carbon atoms.
Examples thereof include monomers having the above long-chain alkyl groups or aryl groups, and oligomers and polymers having a large molecular weight that are difficult to dissolve in the liquid crystal material before the curing step. Examples of the monomer include isobutyl acrylate, stearyl acrylate, lauryl acrylate, isoamyl acrylate, n-butyl methacrylate, n-lauryl methacrylate, tridecyl methacrylate, 2-ethylhexyl acrylate, n-stearyl methacrylate, cyclohexyl methacrylate, benzyl. Acrylic esters such as methacrylate and 2-phenoxyethyl methacrylate,
Acrylate and methacrylate, bisphenol A dimethacrylate, bisphenol A diacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol methacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, etc. Polyfunctional compounds of 2,2,3,4,4,4-hexafluorobutyl methacrylate, 2,2,3,4,4,4-hexachlorobutyl methacrylate, 2,2,3,3-tetrafluoropropyl Halogenation of methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, perfluorooctylethyl methacrylate, perchlorooctylethyl methacrylate, perfluorooctylethyl acrylate, perchlorooctylethyl acrylate, etc., especially salts It may be mentioned and fluorinated monomers. Further, examples of the oligomer and polymer include urethane acrylate and acrylate and methacrylate derivatives of polyethylene glycol. These compounds may be used alone or in combination of two or more. Further, a monomer, an oligomer and a polymer may be mixed and used, if necessary.

Examples of thermosetting compounds include bisphenol A type epoxy compounds, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, hexahydrobisphenol A diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, Phthalic acid diglycidyl ester, triglycidyl isocyanate,
Tetotaglycidyl metaxylenediamine and the like. These monomers may be used alone or in combination of two or more kinds. In addition, chlorinated and fluorinated polymers or oligomers may be mixed with these monomers, if necessary.

In the above method (a), examples of the method for applying the polymerizable compound onto the substrate include a spin coating method, a bar coating method and a screen printing method. Examples of the solvent that dissolves the polymerizable compound include general organic solvents such as γ-butyrolactone, methyl ethyl ketone, tetrahydrofuran, alcohols (n-butanol, ethanol), and n-hexane. The amount of the solvent used is preferably twice or more the weight ratio of the polymerizable compound. The thickness of the coating film formed on the substrate may be adjusted depending on the coating conditions and the concentration of the solvent that dissolves the polymerizable compound.
The range is preferably 2 μm. When the film thickness is less than 100 Å, it is difficult to uniformly apply the coating solution on the substrates, and when the film thickness exceeds 2 μm, the coating films formed on the pair of substrates contact each other. As a result, a part of the gap between the substrates is filled with the polymerizable compound, which is not preferable. After forming the coating film, the hardness of the coating film is further improved by partially curing the polymerizable compound.

In the above method (b), the substrate and the silane coupling agent are chemically bonded via the polymerizable functional group, and the liquid crystal material is further dispersed in the silane coupling agent after this treatment. Since it is chemically bonded to the polymerizable resin material, peeling between the substrate and the liquid crystal material can be prevented more effectively. In this case, examples of the polymerizable functional group include an acryloxy group having an unsaturated bond, a methacryloxy group, a vinyl group and an epoxy group. Examples of the silane coupling agent having such a polymerizable functional group in the molecule include vinyltrichlorosilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane, vinyl-tris- (β-methoxyethoxy) silane, etc. can be used. The silane coupling agent formed on a substrate preferably has a thickness of 1 μm or less. . After treating the substrate by the method (b), the method (a) may be further used.

In order to inject the mixed material composed of the polymerizable resin material and the liquid crystal material into the gap between the pair of substrates, the polymerizable resin material, the liquid crystal material and the polymerization initiator are uniformly mixed and then this mixed material is added. It may be injected into the gap between the substrates. Further, it is preferable that the above-mentioned mixed material is a material that can cure only a polymerizable resin material into a curable resin and can cause phase separation of a liquid crystal material and a curable resin. The polymerizable resin material and the liquid crystal material are mixed at a mixing ratio of 50/50 to 5/95.

The above-mentioned polymerizable resin material is a substance that is converted into a curable resin and finally forms a polymer matrix that supports liquid crystal droplets. In particular, when the TFT is driven, the liquid crystal material is required to have electrical insulation, so that the specific resistance of the polymerizable resin material in the uncured state is 1 × 10 ¹² ohm · c.
m or more is required. Examples of the polymerizable resin material include the same compounds as the above-mentioned polymerizable compounds.

The liquid crystal material is preferably an organic mixture that exhibits a liquid crystal state at around room temperature, although it depends on the application. For example, a nematic liquid crystal (two-frequency driving liquid crystal, Δε).
A liquid crystal of <0), a cholesteric liquid crystal (particularly, a liquid crystal having a selective reflection property for visible light), a smectic liquid crystal (ferroelectric liquid crystal), a discotic liquid crystal, or the like can be used.
These liquid crystal materials may be used as a mixture of two or more kinds, and in particular, nematic liquid crystal or nematic liquid crystal to which cholesteric liquid crystal is added is preferable in view of its characteristics. Further, a liquid crystal material excellent in resistance to a chemical reaction such as a polymerization reaction due to light or heat performed in a later step is particularly preferable,
For example, a liquid crystal material having functional groups such as fluorine and chlorine in the liquid crystal can be used. As a concrete liquid crystal material, ZLI-
4801-000, ZLI-4801-001, ZLI-4792 and the like.

The above-mentioned polymerization initiator is a polymerization initiator such as a photocurable catalyst or a thermosetting catalyst. Examples of photocurable catalysts include Irugacure 184, 651, 907 and Darocure 1173, 11
16, 2959, etc. can be used, and as the thermosetting catalyst, BPO, t-
Peroxide compounds such as butyl peroxide, AIBN
Radical generators such as ethylamine, n-butylamine,
Amine compounds such as benzylamine, diethylenetriamine, tetramethylenepentamine, mensendiamine and diaminodiphenylmethane can be used. Further, the addition amount of the above-mentioned polymerization initiator is 0.1 to 20% by weight with respect to the total mixed material.
Is preferred.

In order to cure the compound containing the polymerizable functional group in the molecule and the polymerizable resin material in a state in which they are bound to each other, a polymerization reaction of the compound and the resin material is performed. In this case, the polymerization reaction is preferably a photo-curing reaction (irradiation with ultraviolet rays) or a heat-curing reaction (providing heat). Through this step, the resin material forms a polymer matrix in the liquid crystal material, and the substrate and the liquid crystal material have good adhesiveness.

Next, the present invention will be described based on examples.

Example 1 FIG. 1 is a sectional view showing a polymer dispersed liquid crystal display device of this example. A liquid crystal display device was manufactured by the method described below.

First, a transparent conductive film made of ITO (a mixture of indium oxide and tin oxide) was formed on one surface of two PET films (thickness 100 μm, manufactured by Toray) as the substrate 1 to a thickness of 500 Å, A urethane acrylate ELE530 dissolved in γ-butyrolactone as the polymerizable compound 2 was spin-coated thereon.
0 (manufactured by Nippon Kayaku Co., Ltd.) was applied to a thickness of 800 Å to form a coating film. These two substrates 1 were heated at a temperature of 120 ° C. to evaporate γ-butyrolactone.

Next, two substrates 1 were positioned so that the surfaces on which the coating films were formed faced each other, and a liquid crystal cell was formed with a 12 μm spacer (product name Micropearl, manufactured by Sekisui Chemical Co., Ltd.) interposed therebetween. . Then, as the polymerizable resin material 4, 0.1 g of trimethylolpropane trimethacrylate and 2-
0.9 g of ethylhexyl acrylate, 4 g of ZLI-4792 (manufactured by Merck) as a liquid crystal material 5, and 0.03 g of a photocurable catalyst Irgacure 184 (manufactured by Ciba Geigy) are uniformly mixed to prepare a mixed material 3, and this mixture is prepared. Material 3 was injected into the liquid crystal cell. This is a high pressure mercury lamp (20m
Under the condition of W / cm ² , 365 nm), the polymerizable compound 2 and the polymerizable resin material 4 were subjected to photocuring reaction by irradiation with ultraviolet rays for 2 minutes to be converted into a photocurable resin. At this time, the polymerizable compound 2 and the resin material 4 are chemically bonded to each other so that the substrate 1 and the liquid crystal material 5 are bonded to each other. Then, the liquid crystal display element of this example was obtained through a predetermined process.

In order to examine the adhesiveness between the substrate 1 and the liquid crystal material 5 of the obtained liquid crystal display element, evaluation was carried out by the following method. That is, one side of the prepared liquid crystal cell 20 × 40 mm square was fixed, and the other side was bent vertically at a rate of 3 times / minute for 1 hour, and was bent 45 ° to the left and right respectively, so that the substrate and the liquid crystal material were separated from each other. I checked. Further, by measuring the voltage value V ₉₀ when the light transmittance of the liquid crystal material 5 when a voltage is applied shows a change amount of 90% with respect to the maximum change amount, the electro-optical property of the liquid crystal material is measured. The characteristics were evaluated. The results are shown in Table 1. According to this, it is understood that in the liquid crystal display element of the present embodiment, peeling between the substrate 1 and the liquid crystal material 5 does not occur due to repeated bending, and these two have good adhesiveness. It was also found that the electro-optical characteristics were not affected.

(Comparative Example 1) A liquid crystal display device was prepared in the same manner as in Example 1 except that the substrate was not coated with urethane acrylate, and evaluated in the same manner as in Example 1. The results are shown in Table 1. This liquid crystal display element was repeatedly bent, and peeling occurred between the substrate and the liquid crystal material.

[0033]

[Table 1]

In Table 1, ○ and × mean the following: ○: No change ×: Peeling occurs.

(Embodiment 2) This embodiment is the same as Embodiment 1.
Description will be made with reference to FIG.

A substrate similar to the substrate 1 of Example 1 was used and a coating film made of a polymerizable compound was formed in the same manner as in Example 1. Next, a liquid crystal cell was formed in the same manner as in Example 1,
And 0.2 g of trimethylolpropane trimethacrylate and 0.48 g of 2-ethylhexyl acrylate as a polymerizable resin material, and FA-108 as a liquid crystal material.
(Kyoeisha Yushi) 0.32 g and ZLI-4792
4 g (manufactured by Merck) and 0.03 g of the photocurable catalyst Irgacure 184 (manufactured by Ciba Geigy) were uniformly mixed to prepare a mixed material, and this mixed material was injected into the liquid crystal cell. This is a high pressure mercury lamp (20 mW / cm ² , 365 nm)
The resulting polymerizable compound and the resin material were subjected to photocuring reaction by irradiating with ultraviolet rays for 2 minutes under a light to obtain a photocurable resin.
At this time, the polymerizable compound and the resin material were chemically bonded and the substrate and the liquid crystal material were bonded. Then, the liquid crystal display element of this example was obtained through a predetermined process. This liquid crystal display element
No peeling occurred between the substrate and the liquid crystal material even after repeated bending.

(Comparative Example 2) A liquid crystal display device was prepared in the same manner as in Example 2 except that urethane acrylate was not applied to the substrate. The obtained liquid crystal display element was in a state in which it could not be used as a display element because a large number of tree-like delaminations were observed between the substrate and the liquid crystal material due to repeated bending.

Example 3 The substrate of Example 1 was flint glass (Nippon Sheet Glass, whose surface was treated with a transparent conductive film made of ITO (thickness: 500 Å).
Thickness of 1.1 mm), and γ-
A 1% ethanol solution of methacryloxypropyltrimethoxysilane was applied and dried at 120 ° C. for 1 hour. After that, the same steps as in Example 2 were performed to obtain a liquid crystal display element of this example. In this liquid crystal display element, no peeling was observed between the substrate and the liquid crystal material.

The polymer-dispersed liquid crystal display device obtained by the manufacturing method of the present invention is used for a flat panel display device such as a projection television and a personal computer, a display plate utilizing a shutter effect, a window, a door, a wall and the like. be able to.

[0040]

According to the method for producing a polymer dispersion type liquid crystal display element of the present invention, the substrate is also protected from shrinkage, thermal or mechanical impact that occurs when the polymerizable resin material in which the liquid crystal material is dispersed is cured. There is no peeling between the liquid crystal material and the liquid crystal material, and a liquid crystal display element having good adhesion between the substrate and the liquid crystal material can be obtained, and further, the reliability as a display element can be dramatically improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a method for manufacturing a polymer-dispersed liquid crystal display element according to Embodiment 1 of the present invention.

[Explanation of symbols]

 1 substrate 2 polymerizable compound 3 mixed material 4 polymerizable resin material 5 liquid crystal material

Claims (5)

[Claims] 1. A step of facing a pair of substrates, at least one of which is transparent, and allowing a compound containing a polymerizable functional group in the molecule to exist on the inner surface of each substrate, and a polymerizable resin in the gap between the pair of substrates. A method for producing a polymer-dispersed liquid crystal display device, which comprises a step of injecting a mixed material containing a material and a liquid crystal material, and a step of curing the compound and the polymerizable resin material to a state in which they are bound to each other. 2. The method for producing a polymer dispersed liquid crystal display device according to claim 1, wherein the compound is a polymerizable compound. 3. The method for producing a polymer-dispersed liquid crystal display device according to claim 2, wherein the polymerizable compound is a monomer. 4. The method for producing a polymer dispersed liquid crystal display device according to claim 1, wherein the compound is a silane coupling agent. 5. The method for producing a polymer dispersed liquid crystal display device according to claim 1, wherein the substrate is previously treated with a silane coupling agent before the compound is present on the inner surface of the substrate. .