JPH0895008A - Dispersed liquid crystal display element and its manufacture - Google Patents

Abstract

PURPOSE: To provide a dispersed liquid crystal display element using high- polymer resin as matrix with liquid crystal dispersion and weather resistance combined to control the water solubility of high polymer. CONSTITUTION: For a dispersed liquid crystal display element, a liquid crystal dispersion layer which has dielectric aeolotropic liquid crystals 4 uniformly dispersed in matrix resin 3 formed of high polymer to be made water soluble by forming ammonium salt for alkylamine is provided with transparent electrodes 2, 2' and at least one substrate is held between a pair of transparent substrates 1, 1'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device in which liquid crystal responsive to an electric field or heat is dispersed in a polymer matrix in the form of oil droplets.

[0002]

2. Description of the Related Art A so-called capsule type liquid crystal in which a liquid crystal is wrapped in a polymer material and a method for producing the same have been known.

In JP-A-58-50163 and JP-A-59-226322, a nematic liquid crystal is emulsified and dispersed in a polyvinyl alcohol aqueous solution, and an emulsion dispersion is applied onto a transparent electrode substrate and dried. There is shown a liquid crystal display element which is held between another transparent electrode substrate which will be an opposite electrode and which is applied with an electric field to change the light scattering. However, since it uses an emulsified dispersion of polyvinyl alcohol, it has a high hygroscopic property, and when left in a high-humidity atmosphere for a long time, its electrical resistance decreases, and the electric field required to drive the liquid crystal cannot be applied, or in severe cases. Has the drawback of shorting between the electrodes. Further, there is a drawback that the liquid crystal material is deteriorated by moisture absorption.

Further, Japanese Patent Application Laid-Open No. 63-124025 discloses a dispersion type liquid crystal display device using a matrix resin containing cellulose acetate as a main component. In a matrix resin whose main component is cellulose acetate,
As a method of dispersing the liquid crystal, a uniform solution obtained by dissolving the liquid crystal and the matrix resin in a common solvent is applied onto a substrate having a transparent electrode. The coating liquid is in a uniform transparent state as long as the solvent is sufficiently present, but as the solvent evaporates, the matrix resin and the liquid crystal phase separate to form a cloudy state. When the solvent is almost eliminated, the liquid crystal is dispersed in the matrix resin in the form of oil droplets.

However, it is difficult to control the particle size of the liquid crystal dispersed in the matrix resin because it is a forming method utilizing phase separation from a homogeneously dissolved state. Therefore, when it is used as a liquid crystal display element, There are problems that the contrast is reduced and display unevenness occurs.

Further, in the above method using cellulosic acetate, methylene dichloride as a common solvent,
In order to put it into practical use, the working place is limited and the treatment of volatile solvents is required because organic solvents such as chloroform, acetone, methyl ethyl ketone, methyl acetate, ethyl acetate, benzene, toluene, tetrahydrofuran, dioxane, methanol, ethanol must be used. , There are many problems to be solved such as environmental impact. Furthermore, since the organic solvent is used as the common solvent, there is a problem that the usable substrate material is limited.

The matrix resin as a liquid crystal dispersion medium is required to be physically, thermally and chemically stable. Polyimide is a typical material that can meet such requirements. However, there has been no means for dispersing the liquid crystal in the polyimide until now.

[0008]

The object of the present invention is to solve the above-mentioned problems of the prior art and to uniformly disperse liquid crystals in the form of oil droplets in a water-soluble matrix resin which has both the dispersibility of liquid crystals and the weather resistance. The present invention provides a dispersed liquid crystal display device.

[0009]

The gist of the present invention for achieving the above object is as follows.

(1) A liquid crystal dispersion layer in which a liquid crystal having dielectric anisotropy is uniformly dispersed in a matrix resin composed of a polymer which is made water-soluble by forming an ammonium salt of alkylamine has a transparent electrode. In at least one of the substrates, the dispersion-type liquid crystal display element is sandwiched between a pair of transparent substrates.

(2) A liquid crystal having a dielectric anisotropy is dispersed in an aqueous solution of a polymer which has been made water-soluble by reacting with an alkylamine to form an ammonium salt, and is developed into a film.
Dispersion-type liquid crystal in which a film-like liquid crystal dispersion layer that is desorbed from the alkylamine by heating to be substantially water-insoluble is formed between a pair of substrates having a transparent electrode and at least one substrate being transparent. It is in the manufacturing method of the display element.

When a liquid crystal having a positive dielectric anisotropy is used as the liquid crystal having a dielectric anisotropy used in the present invention, light is scattered at the interface between the liquid crystal and the polymer matrix when the voltage is off. It becomes opaque, and when the voltage is on, the liquid crystal aligns in the direction of the electric field and becomes transparent. When a liquid crystal having a negative dielectric anisotropy is used, the contrast opposite to the above is obtained.

When a smectic liquid crystal is used as the liquid crystal, a transparent state is obtained by applying a voltage, and the state is maintained even when the voltage is turned off. When heat is applied to this, it can be used as a so-called thermal writing type display element in which the orientation of the liquid crystal is disturbed and becomes opaque only in the heated portion.

Although not particularly limited, a liquid crystal whose refractive index in the ON state or the OFF state is close to that of the matrix resin is desirable in view of display characteristics.

In order to uniformly disperse a liquid crystal having dielectric anisotropy in a matrix made of a polymer resin which has been made water-soluble by forming an ammonium salt, an aqueous solution of the ammonium salt of the polymer resin described above and a liquid crystal are used. Mix. The liquid crystal is insoluble in water and therefore uniformly dispersed in the form of oil drops.

The above-mentioned dispersion liquid in which the liquid crystal is uniformly dispersed is applied onto a substrate having a transparent electrode formed thereon. As the water, which is the solvent, evaporates, the dispersion is solidified to form a film in which the liquid crystal is uniformly dispersed in the polymer resin in the form of oil droplets.

Next, when the film is heated, the ammonium salt of the polymer resin is decomposed to generate an alkylamine, and the alkylamine evaporates by heating, so that the liquid crystal is uniformly dispersed in the matrix resin in the form of oil droplets. (Liquid crystal dispersion layer) can be obtained. The liquid crystal dispersion layer may be formed on another substrate.

Examples of the monomers giving the matrix resin of the present invention include polyacrylic acid and polyalkyl acrylate derivatives described in Table 9.1 of Polymer Data Handbook, Basic Edition (Polymer Society of Japan, Baifukan, 1986). 1
Mention may be made of maleic acid and its derivatives according to 4.1, chain-polymerizing monomers such as fluoroalkyl maleates and vinyl acetate. Any polymer of these monomers or a polymer containing the monomer as a copolymerization component can be applied to the present invention.

The copolymerizable monomers include acrolein, acrylamide, N, N-dimethylacrylamide, butyl acrylate, butyl methacrylate,
Isopropyl acrylate, propylene, styrene, vinyl acetate, vinyl chloride, vinyl hydroquinone,
Examples thereof include vinylidene chloride, vinylidene cyanide, methyl acrylate, and methyl methacrylate. Also,
A polymer applicable to the present invention can be obtained by introducing a carboxylic acid group by chemical modification even if it is a polymer that does not contain a carboxylic acid group in the monomer during polymerization. Furthermore, esters of polyacrylic acid and polymethacrylic acid can also be used as the target matrix resin material.

Polycondensation type polymers can also be used in the present invention, and examples thereof include polymers having a carboxylic acid group represented by polyamic acid and chitin. In particular, when polyamic acid is applied to the present invention, excellent performance is exhibited. Such polyamic acid is obtained by reacting a diamine or diisocyanate with a tetracarboxylic acid or its derivative. Examples of tetracarboxylic acid derivatives include acid anhydrides and acid chlorides. Particularly, acid anhydrides are preferable in terms of reactivity and by-products.

As the polyamic acid of the diamine and the acid anhydride derivative, those described in JP-A-61-181829 can be mentioned.

Considering the color characteristics and brightness of the display, it is desirable that the polyimide has no absorption in the visible region. Such a polyimide can be easily synthesized by using an aliphatic diamine or its derivative and an aliphatic dianhydride or its derivative as raw material monomers. Fluorinated diamine or its derivative and fluorinated dianhydride or its derivative can be similarly synthesized.

The method of dispersing the liquid crystal having dielectric anisotropy in the polyamic acid is as follows. The polyamic acid and the alkylamine are mixed to react the polyamic acid and the alkylamine to form an ammonium salt, which is water-soluble. To give a uniform aqueous solution. Liquid crystal is mixed with this.

The alkylamine used in the present invention may be any one that reacts with a carboxylic acid to change the solubility of the matrix resin. In order to obtain water solubility, it is generally desirable that the alkylamine compound has 12 or less carbon atoms. Examples of such alkylamine compounds include tertiary aliphatic amines having 12 or less carbon atoms, secondary aliphatic amines, and the like. Furthermore, 2-dimethylaminoethanol,
2-diethylaminoethanol, 2-methylaminodiethanol, 2-dimethyl-3-butanone, 2-diethylaminoacetone, N-methylaminodiethanol, N-
Methylaminoethanol, 2,2-aminodiethanol, 3-diethylamino-1-propanol, aminocyclohexanone and the like are preferable from the viewpoint of solution stability. Further, the alkylamine preferably has a boiling point of 120 ° C. or lower in order to evaporate after the film is formed.

As the ammonium salt, it is preferable to form a polycarboxylic acid ammonium salt.

The liquid crystal is uniformly dispersed in the form of oil droplets in the aqueous solution of the ammonium salt of polyamic acid and alkylamine. When this dispersion is applied onto a substrate having a transparent electrode, the dispersion solidifies as water as a solvent evaporates, and a film in which liquid crystals are dispersed in uniform particles is formed. When this film is heated, the ammonium salt decomposes,
The generated alkylamine evaporates to obtain a film in which liquid crystal is dispersed in polyamic acid.

By further adjusting the heating temperature,
Polyamic acid can be dehydrated and ring-closed to form a polyimide. The imide ring-closing temperature at this time is lower than the imide ring-closing temperature of a normal polyamic acid, and imidization can be achieved at 100 to 150 ° C. It is considered that this is because the presence of the alkylamine promotes imide ring closure.

Polyimide is a matrix resin having high decomposition temperature and glass transition temperature and excellent thermal stability. Also,
Polyimide has a lower hygroscopic rate than conventional matrix resins such as polyvinyl alcohol, excellent moisture resistance, is chemically stable, and is not easily attacked by ordinary organic solvents. Further, since polyimide is stable against sunlight and has a property of absorbing ultraviolet rays in particular, it is effective in preventing decomposition of liquid crystal due to ultraviolet rays.

FIG. 1 shows a schematic sectional view of the dispersion type liquid crystal display device of the present invention. The substrate 1 is made of glass, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyether sulfone, triacetic acid film, polymethylmethacrylate, polystyrene, etc., on which a transparent electrode 2 made of a metal or a metal oxide is provided by vapor deposition, sputtering or the like. Is used. The above pair of substrates 1, 1 '
Then, the dispersion type liquid crystal display device is obtained by holding the matrix resin 3 in which the liquid crystal 4 is uniformly dispersed.

[0030]

The present invention is made water-soluble by forming an ammonium salt by the reaction of a polymer with a specific alkylamine, and the liquid crystal is dispersed in the aqueous solution, and this is applied to form a film and heated. By doing so, the ammonium salt is decomposed, and the produced amine compound is evaporated and volatilized. By doing so, it is possible to provide a liquid crystal dispersion type display element having excellent moisture resistance.

Further, this display element has excellent display characteristics because uniform liquid crystal particles are uniformly dispersed in a matrix made of a polymer resin.

Furthermore, according to the present invention, since the matrix surface is flat, it is possible to provide a highly reliable liquid crystal dispersion type display element which is easy to adhere and adhere to a substrate and has excellent display characteristics.

[0033]

EXAMPLES The present invention will be described with reference to examples.

Example 1 A solution having the following composition was prepared.

Poly (acrylic acid-co-methyl methacrylate): 6.0 parts by weight Triethylamine: 3.0 parts by weight Water: 100.0 parts by weight Liquid crystal (ZLI-2359: manufactured by Merck Ltd.): 15.0 parts by weight The above solution was applied on a polyethylene terephthalate film having a thickness of 100 μm, which was obtained by vapor-depositing indium-tin oxide as a transparent conductive film, to a dry film thickness of 8 μm, and heated at 80 ° C. for 10 minutes and at 100 ° C. for 10 minutes. did.
A polyethylene terephthalate film having the transparent conductive film formed thereon was laminated on the coating film to prepare a dispersion type liquid crystal display device.

The above liquid crystal display device has a light transmittance of 5% when measured without applying a voltage between the upper and lower electrodes,
Further, the transmittance when measured by applying a voltage of 60 V was 75%, and a large contrast was obtained depending on the presence or absence of voltage application.

Further, this liquid crystal display device was tested at 50 ° C. and 90% R
After leaving it in the H atmosphere for 96 hours, returning it to the atmosphere of 25 ° C. and 40% RH, and measuring the transmittance with and without the voltage application after 1 hour, it was found that the moisture resistance was excellent as the initial value. Do you get it.

Example 2 A solution having the following composition was prepared.

Polyamic acid synthesized from biphenyltetracarboxylic dianhydride and paraxylylenediamine: 6.5 parts by weight Triethylamine: 3.0 parts by weight Water: 55.0 parts by weight Liquid crystal (ZLI-1289: manufactured by Merck Ltd.) ) 15.0 parts by weight The above solution is applied on a polyethylene terephthalate film having a thickness of 100 μm, which is obtained by vapor-depositing indium-tin oxide as a transparent conductive film, so that the dry film thickness is 8 μm, and the temperature is 80 ° C. for 10 minutes. , Heated at 120 ° C. for 10 minutes.
A dispersion type liquid crystal display device was produced by the same method as in Example 1.

The liquid crystal display device had a light transmittance of 5% when the voltage was zero, and a light transmittance of 70% when a voltage of 60 V was applied, and showed a large contrast depending on whether or not a voltage was applied.

The above liquid crystal display device was tested at 50 ° C. and 90% R
After leaving it in the H atmosphere for 96 hours, returning it to the atmosphere of 25 ° C. and 40% RH, and measuring the transmittance with and without the voltage application after 1 hour, it shows that the moisture resistance is the same as the initial value. I understood.

Example 3 A solution having the following composition was prepared.

Polyamic acid synthesized from biphenyltetracarboxylic acid dianhydride and paraxylylenediamine: 6.5 parts by weight Triethylamine: 3.0 parts by weight Water: 55.0 parts by weight Liquid crystal (ZLI-4850: manufactured by Merck Ltd.) ) 15.0 parts by weight The above solution was applied on a polyethylene terephthalate film having a thickness of 100 μm and a transparent conductive film of indium-tin oxide to a dry film thickness of 8 μm.
Heated at 0 ° C for 10 minutes and 120 ° C for 10 minutes. A dispersion type liquid crystal display device was produced by the same method as in Example 1.

The liquid crystal display device has a light transmittance of 75% when the voltage is zero, and a light transmittance of 10% when a voltage of 60 V is applied.
A large contrast was exhibited depending on whether or not a voltage was applied.

96 in an atmosphere of 50 ° C. and 90% RH
After leaving it for 25 hours, return it to the atmosphere of 25 ° C, 40% RH, and
When the transmittance was measured after a lapse of time with and without the voltage applied, it was found that the moisture resistance was excellent, being the same as the initial value.

Comparative Example 1 A solution having the following composition was prepared.

Polyvinyl alcohol: 6.0 parts by weight Water: 100.0 parts by weight Liquid crystal (ZLI-2359: manufactured by Merck Ltd.): 15.0 parts by weight The above solution is vapor-deposited with an indium-tin oxide as a transparent conductive film. It was coated on a polyethylene terephthalate film having a thickness of 100 μm so as to have a dry film thickness of 8 μm, and heated at 80 ° C. for 10 minutes and at 100 ° C. for 10 minutes.
A dispersion type liquid crystal display device was produced by the same method as in Example 1.

The liquid crystal display device had a light transmittance of 5% when the voltage was zero and a light transmittance of 75% when a voltage of 60 V was applied, and showed a large contrast depending on whether or not a voltage was applied.

However, in an atmosphere of 50 ° C. and 90% RH, 9
After leaving it for 6 hours, return it to the atmosphere of 25 ° C and 40% RH,
The light transmittance measured after 1 hour was 5% at a voltage of 0 V and 6%.
It can be seen that the contrast is significantly reduced at 40% at 0V.

Comparative Example 2 An attempt was made to prepare a solution having the following composition. Poly (acrylic acid-co-methyl methacrylate)
Was not soluble in water and could not be prepared.

Poly (acrylic acid-co-methyl methacrylate): 6.0 parts by weight Water: 100.0 parts by weight Liquid crystal (ZLI-2359): 15.0 parts by weight

[0052]

According to the present invention, uniform liquid crystal particles are uniformly dispersed in a matrix made of a polymer resin, and since the matrix surface is flat, it is easy to adhere and bond with a substrate, and the liquid crystal The matrix resin layer in which is dispersed does not deteriorate even if left in an atmosphere of high temperature and high humidity, and a highly reliable dispersion liquid crystal display element can be provided.

Further, the display element has a good contrast, and no bleeding out of the dispersed liquid crystal due to aging is observed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a dispersion type liquid crystal display element of the present invention.

[Explanation of symbols]

1, 1 '... substrate, 2, 2' ... transparent electrode, 3 ... matrix resin layer, 4 ... liquid crystal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisao Yokokura 7-1, 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Yasushi Iwaka 7-chome, Omika-cho, Hitachi-shi, Ibaraki No. 1-1 Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Hiroshi Sasaki No. 1-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Akio Takahashi Hitachi City, Ibaraki Prefecture 7-1-1 Omika-cho, Hitachi, Ltd. Hitachi Research Laboratory

Claims (7)

[Claims] 1. A liquid crystal dispersion layer in which a liquid crystal having dielectric anisotropy is uniformly dispersed in a matrix resin composed of a polymer which is made water-soluble by forming an ammonium salt of alkylamine, and has a transparent electrode. A dispersion type liquid crystal display element, wherein at least one substrate is sandwiched between a pair of transparent substrates. 2. The dispersion type liquid crystal display element according to claim 1, wherein the matrix resin is composed of a resin containing polyimide. 3. The dispersion type liquid crystal display device according to claim 1, wherein the ammonium salt is a polycarboxylic acid ammonium salt. 4. A liquid crystal having a dielectric anisotropy is dispersed in an aqueous solution of a polymer which has been made water-soluble by forming an ammonium salt by reacting with an alkylamine to develop the liquid crystal into a film and heat the alkylamine. A film-type liquid crystal dispersion layer that is desorbed to be substantially water-insoluble, and is formed between a pair of substrates having a transparent electrode and at least one substrate being transparent. Manufacturing method. 5. The method for producing a dispersion type liquid crystal display device according to claim 4, wherein the polymer contains a polyamic acid. 6. The alkylamine has 12 or less carbon atoms,
Alternatively, it is a secondary or tertiary alkylamine having a boiling point of 120 ° C. or lower, and the method for producing a dispersion type liquid crystal display device according to claim 4 or 5. 7. The method for producing a dispersion type liquid crystal display device according to claim 4, wherein the ammonium salt is a polycarboxylic acid ammonium salt.