JPH0572537A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display element having uniform film thickness and showing good liquid crystal orientation performance to the liquid crystal molecules without rubbing treatment by consisting the liquid crystal oriented film of the imide compd. of specified polyamic acid. CONSTITUTION:At least a pair of electrode substrates having a liquid crystal oriented film on the surface are disposed while facing to each other, and a liquid crystal is held between these electrode substrates to form the liquid crystal display element. The liquid crystal oriented film consists of the imide compd. of polyamic acid (A) and/or modified polyamic acid (B). The polyamic acid (A) is a polyamic acid expressed by formula I composed a diamine compd. and tetracarboxylic acid. The polyamic acid B is a modified polyamic acid from A and an amine compd. having the hydrocarbon groups of 1-40C. In formula, Z is a poly-nuclear aromatic tetracarboxylic acid residue. The liquid crystal oriented film is the imide compd. of an extended film on water surface or a Langmuir-Blodgett acid.

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 using an electrode substrate having a liquid crystal alignment film.

[0002]

2. Description of the Related Art In a liquid crystal display device utilizing an electro-optical effect driven by the action of an electric field, a liquid crystal alignment film is provided on an electrode substrate in order to uniformly align liquid crystal molecules and obtain good display quality. ing.

As the liquid crystal alignment film, there is an inorganic liquid crystal alignment film in which an electrode film is formed on a glass substrate provided with an inorganic protective layer, and then an inorganic compound such as SiO is formed by oblique vapor deposition. However, since this inorganic liquid crystal alignment film has selectivity for liquid crystal type in liquid crystal alignment, it is difficult to perform good alignment of all liquid crystal compositions. Further, the oblique vapor deposition method requires a vacuum device such as a vapor deposition device, resulting in high manufacturing cost and is not a sufficient formation method from the viewpoint of mass productivity. Due to the above problems in the method of forming the inorganic liquid crystal alignment film, the organic liquid crystal alignment film is currently the mainstream.

As a method for producing this organic liquid crystal alignment film, polyamic acid, polyimide or the like is formed on an electrode substrate by a printing method or a spin coater method, and after thermal imidization or drying to form a polyimide film, the film is formed. A method is known in which a liquid crystal alignment film is obtained by rubbing in one direction with Tetoron or nylon cloth. A pair of electrode substrates, each having a liquid crystal alignment film obtained by such a method on the surface thereof, are arranged so as to face each other to form a liquid crystal display cell, and then a liquid crystal composition is enclosed to manufacture a liquid crystal display element. ing.

[0005]

However, in a conventional liquid crystal display device having an organic liquid crystal alignment film formed thereon, the larger the electrode substrate, the more difficult it is to form a polymer film with a uniform film thickness. Display unevenness may occur due to non-uniformity of the threshold voltage due to the thickness. In addition, when rubbing with a cloth, electrostatic breakdown of the substrate caused by static electricity,
Problems such as defective lighting due to adhesion of dust and scratches on the liquid crystal alignment film have occurred.

[0006]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, have found that the film thickness is uniform, rubbing treatment is not required, and the alignment ability with respect to liquid crystal molecules is high. Has found a liquid crystal display device using an electrode substrate having an excellent liquid crystal alignment film, and arrived at the present invention.

That is, according to the present invention, in a liquid crystal display element in which at least a pair of electrode substrates having a liquid crystal alignment film on the surface are arranged to face each other, and liquid crystal is sandwiched between the electrode substrates, the liquid crystal alignment film is: A liquid crystal display element comprising an imidized product of a polyamic acid (A) and / or a modified polyamic acid (B) described below. Polyamic acid (A): general formula

[0008]

[Chemical 2]

A polyamic acid comprising a diamine compound (1) represented by the formula (wherein Z represents a polynuclear aromatic tetracarboxylic acid residue) and a tetracarboxylic acid (2). Modified polyamic acid (B): A modified polyamic acid comprising (A) and an amine compound (3) having a hydrocarbon group having 1 to 40 carbon atoms.

In the present invention, in the general formula representing the diamine compound (1), the polynuclear aromatic tetracarboxylic acid residue represented by Z is obtained by removing the four carboxyl group moieties from the polynuclear aromatic tetracarboxylic acid. It is a base. Examples of such polynuclear aromatic tetracarboxylic acid include 3,4,9,
Examples thereof include 10-perylene tetracarboxylic acid, 1,2,5,6-naphthalene tetracarboxylic acid, 1,4,5,6-naphthalene tetracarboxylic acid and 2,3,6,7-naphthalene tetracarboxylic acid. Of these, preferred is 3,4,9,10-perylenetetracarboxylic acid. The diamine compound (1) has a chemical structure in which 2 mol of 4,4′-diaminodiphenyl sulfone is dehydrated and condensed with 1 mol of the polynuclear aromatic tetracarboxylic acid. Exemplifying the production method of the diamine compound (1),
A polynuclear aromatic tetracarboxylic acid dianhydride as exemplified above and 4,4′-diaminodiphenyl sulfone are combined with 1
The diamine compound (1) can be obtained by reacting at 80 to 230 ° C. for 1 to 2 hours.

In the present invention, examples of the tetracarboxylic acids (2) include aromatic tetracarboxylic acids [pyromellitic acid, 3,4,9,10-perylenetetracarboxylic acid, 1,2,5,6-naphthalene. Tetracarboxylic acid, 1,4,5,6-naphthalene tetracarboxylic acid,
2,3,6,7-naphthalene tetracarboxylic acid, 2,
2 ', 3,3'-biphenyltetracarboxylic acid, thiophene-2,3,4,5-tetracarboxylic acid, 2,2'-
Bis (3,4-dicarboxyphenyl) propane, bis (3,4-dicarboxyphenyl) ether, bis (3,4-dicarboxyphenyl) methane, 2,2-bis (3,4-dicarboxyphenyl) Propane, 3,
3 ', 4,4'-benzophenone tetracarboxylic acid,
3,3 ′, 4,4′-biphenyltetracarboxylic acid, etc.]; Aliphatic / alicyclic tetracarboxylic acid [butanetetracarboxylic acid, ethanetetracarboxylic acid, cyclobutane-
1,2,3,4-tetracarboxylic acid, cyclopentane-
1,2,3,4-tetracarboxylic acid, etc.]; dianhydrides of these tetracarboxylic acids; compounds in which the carboxyl groups of these tetracarboxylic acids are replaced with acid halide (chloride, bromide, etc.) groups; and these two types The above mixture may be mentioned. Of these, the preferred one is
It is tetracarboxylic dianhydride.

As an example of the method for producing the polyamic acid (A), the diamine compound (1) and the tetracarboxylic acid (2) are added in a polymerization solvent (4) at 0 to 80 ° C. for 1 to 1
The polyamic acid (A) is obtained by stirring for 2 hours and polycondensing. As the above-mentioned polymerization solvent (4),
There is no particular limitation as long as it can dissolve the generated polyamic acid (A). Specific examples of such a polymerization solvent (4) include N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, cresol and phenol.

In the present invention, examples of the alkylamine compound (3) having a hydrocarbon group having 1 to 40 carbon atoms include primary amine compounds [n-butylamine, n-decylamine, n-octylamine, n- Dodecylamine, N-tetradecylamine, n-hexadecylamine, n-octadecylamine, etc.]; secondary amine compound [di-n-butylamine, N-methyl-n-octylamine, N-methyl-n-decylamine, N-methyl-n
-Dodecylamine, N-methyltetradecylamine, N
-Methyl-n-hexadecylamine, N-methyl-n-
Octadecylamine etc.]; tertiary amine compounds [trimethylamine, triethylamine, N, N-dimethyl-
n-octylamine, N, N-dimethyl-n-decylamine, N, N-dimethyl-n-dodecylamine, N, N
-Dimethyl-n-tetradecylamine, N, N-dimethyl-n-octadecylamine, aniline, etc.]; and a mixture of two or more thereof. Among these, preferred are alkylamine compounds having one or more hydrocarbon groups having 10 to 30 carbon atoms.

As an example of the method for producing the modified polyamic acid (B), the modified polyamic acid (B) is obtained by reacting the polyamic acid (A) and the amine compound (3) with stirring at room temperature. Be done. At this time, when an excessively small amount of the amine compound (3) is reacted with the carboxyl group of the polyamic acid (A), a mixture of the polyamic acid (A) and the modified polyamic acid (B) is produced, but it is used as it is. May be. Further, when an excess amount of the amine compound (3) is reacted with the carboxyl group of the polyamic acid (A), the amine compound remains in the modified polyamic acid, which may affect the display characteristics of the liquid crystal display device and the liquid crystal itself. It is not preferable because it is given. The amount of the amine compound (3) used is based on the carboxyl group of the polyamic acid (A).
Usually 0.01 to 2.5 molar equivalents, preferably 0.1 to 2.5
An amount that provides 2.0 molar equivalents may be used.

In the present invention, the polyamic acid (A)
The modified polyamic acid (B) and the modified polyamic acid (B) may be used alone, or may be used as a mixture in any ratio.
Furthermore, if necessary, the film-forming polymer compound (C) may be used in combination with the polyamic acid (A) and / or the modified polyamic acid (B). The film-forming polymer compound (C) is not particularly limited as long as it is soluble in the developing solvent described below. To illustrate this,
Fluorine resin, urea resin, melamine resin, phenol resin, silicon resin, epoxy resin, alkyd resin, urethane resin, resorcin resin, furan resin, polyester, polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polystyrene, poly Ether imide, polyamide imide, polyamide, polyvinyl pyrrolidone, polyvinyl butyrate, polysulfone, polycarbonate, polyacetal, polyethylene, polypropylene, cellulosic resin, natural rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, polybutadiene, polyisoprene and the like. .. Also, two or more of these may be used in combination. These film-forming polymer compounds (C) are used to form the polyamic acid (A) and / or the modified polyamic acid (B), particularly when formed into a film by a method such as the water surface development method described below.
It may be used in combination when it is necessary to enhance the film-forming property and film strength.

In the present invention, the polyamic acid (A)
And / or the modified polyamic acid (B) and, if necessary, the film-forming polymer compound (C) used in combination, as a method for forming a film, a brush coating method, a dipping method, a spin coating method, a printing method, vapor deposition. Any known method such as a method, a water surface development method, a Langmuir-Blodgett method, or the like can be used. The film may be formed by a brush coating method, a dipping method, a spin coating method, a printing method, etc., and imidized, and then subjected to a rubbing treatment to obtain a liquid crystal display element, but it is easy to produce a uniform polymer film, and a rubbing treatment is required. Since the molecular alignment of the liquid crystal alignment film can be controlled without doing so, the Langumuir-Blodgett method (hereinafter referred to as LB)
(Abbreviated as “method”), or a water surface development method, which is a technology obtained by industrializing the LB method. Of these, the water surface development method is particularly preferable because continuous film formation is possible.

In the water surface development method, the polyamic acid (A) is used.
And / or the modified polyamic acid (B) and, if necessary, a film-forming polymer compound (C) used in combination with a developing solvent are dissolved in a polymer solution to continuously develop the polymer solution on the water surface, and to spread in the developing direction. The film can be formed by volatilizing the developing solvent to form a polymer film and continuously winding it. With this water surface development method, a polymer film having a desired film thickness within the range of 50 to 3000 angstroms can be formed at one time. Further, in the LB method, the same polymer solution as in the case of the above-mentioned water surface expansion method is expanded on the water surface, and then the developing solvent is volatilized to form a polymer film while being compressed at a constant surface pressure,
By transferring to a support, a film can be formed at the monolayer level. According to the LB method, a monomolecular film having a thickness of about 5 Å can be formed, and by laminating the monomolecular film, an arbitrary film thickness can be obtained.

Polyimide is generally said to be a relatively rigid polymer because of its structure. Since the polyamic acid (A) and / or the modified polyamic acid (B) according to the present invention has a polynuclear aromatic residue in the molecule, in addition to the arrangement in the one-dimensional direction, the arrangement in the two-dimensional (planar) direction I think it will be possible. In order to realize this, the polyamic acid (A) and / or the modified polyamic acid (B) according to the present invention is combined with a water surface development method or an LB method to form a film, thereby obtaining a polymer film having a planar molecular orientation. The liquid crystal molecules are aligned along this alignment direction without rubbing.

The thickness of the liquid crystal alignment film of the liquid crystal display device of the present invention is usually 5 to 3000 angstrom, preferably 5
It is 0 to 1000 angstroms.

As the developing solvent in the water surface developing method or the LB method, a solvent for dissolving the polyamic acid (A) and / or the modified polyamic acid (B) and, if necessary, the film-forming polymer compound (C) used in combination is dissolved. It is sufficient if it is not particularly limited. Examples of such developing solvents include organic solvents that are incompatible with water [aliphatic hydrocarbons such as hexane, heptane, and octane; aromatic hydrocarbons such as benzene, toluene, and xylene; dichloromethane,
Halogenated hydrocarbons such as dichloroethane and carbon tetrachloride; alicyclic alcohols such as cyclohexanol]; water-compatible organic solvents [N-methylpyrrolidone,
Amide compounds such as N, N-dimethylacetamide, N, N-dimethylformamide, tetramethylurea, N-methylcaprolactam and hexamethylphosphoramide;
Sulfoxide compounds such as dimethyl sulfoxide and dimethyl sulfolane; cyclic ethers such as tetrahydrofuran, dioxane and butyrolactone, lactone compounds and the like]; and mixtures of two or more thereof.

In the water surface spreading method, when the polymer solution is difficult to spontaneously spread, a spreading aid may be added to the polymer solution. Examples of development aids include aliphatic, alicyclic or aromatic ketones, esters, alcohols, amines, aldehydes, ethers, peroxides and mixtures of two or more thereof.

Further, in the water surface spreading method, a surfactant may be added to the polymer solution in order to improve the spreading property of the polymer solution. The surfactant is not particularly limited as long as it can be used in the water surface development method,
Preferred are nonionic or anionic surfactants.

In the LB method, distilled water or ion-exchanged water is usually used for the lower aqueous phase, but in some cases, monovalent ions such as potassium ion, sodium ion, calcium ion, barium ion and cadmium ion are added to the lower aqueous phase. Also, polyvalent inorganic ions and polymer ions such as polydimethyldiallylammonium salt and sodium polyacrylate may coexist.

In the present invention, the electrode substrate is not particularly limited, and is a glass substrate on which a transparent electrode such as SnO ₂ , In ₂ O ₃ —SnO ₂ or In ₂ O ₃ is formed; a color filter is provided on the transparent electrode. The formed glass substrate; a plastics substrate such as polyester; a glass substrate on which thin film transistors, thin film diodes and the like are formed; a silicone wafer and the like.

The liquid crystal alignment film according to the present invention can be directly formed on the electrode substrate as described above, but SiO ₂ , Al ₂ O ₃ , T as an inorganic insulating film is formed on the upper or lower layer of the electrode.
It is also possible to form the liquid crystal alignment film on a film provided with a film such as iO ₂ . Further, in order to enhance the adhesion between the liquid crystal alignment film and the electrode substrate, a silane coupling agent [for example, 3-
Aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3
-Ureidopropyltriethoxysilane and N-triethoxysilylpropyl-triethylenetriamine] may be used. Further, one or more titanate compounds [eg, isopropyltriisostearoyl titanate, bis (triethanolamine) diisopropyl titanate and diisopropyl dilauryl titanate] may be used.

As a method for laminating the polymer film formed by the method as exemplified above on the electrode substrate, the polymer film on the water surface may be directly laminated, or the polymer film may be previously supported. You may use the method of transferring what was laminated | stacked on the film (polyethylene terephthalate etc.) to an electrode substrate. The polymer film formed on the electrode substrate may be either a single layer or a multi-layer. In the case of a multi-layer, the moisture adhering to the transferred polymer film is completely removed before the next layer is laminated. It is desirable to do.

The polymer film formed on the electrode substrate may be imidized by a chemical method or a physical method. As a chemical method, the substrate on which the polymer film is bonded is dipped in an acid anhydride, and the polyamic acid (A) and / or the modified polyamic acid (B) in the polymer film are ring-closed to imidize the substrate. The obtained film is obtained. At this time, the reaction is promoted by adding a tertiary amine such as triethylamine or pyridine. Further, a solvent can be added if necessary. A solvent that dissolves polyamic acid or modified polyamic acid cannot be used. In this case, the ring closing temperature needs to be about 20 to 70 ° C. For example, acetic anhydride: pyridine: benzene (1:
With the 1: 3) mixture, the reaction is completed at 40 ° C. in about 1 hour. In addition, as a physical method, an imidized film is obtained by heating and baking a substrate to which the above-mentioned polymer film is bonded, usually at 100 to 400 ° C. The heating and firing temperature is preferably 150 to 250 for protecting the electrode substrate.
It is good to carry out at ℃. The heating time is usually 1 minute to 12 hours, preferably 10 minutes to 6 hours.

As described above, since the polyimide film formed on the surface of the electrode substrate emits fluorescence, by measuring the dichroic ratio and the secondary orientation coefficient of this polyimide film by a conventionally known method, It can be easily confirmed that the liquid crystal alignment ability is good.

Examples of the liquid crystal in the present invention include nematic liquid crystal, cholesteric liquid crystal, smectic liquid crystal and ferroelectric liquid crystal. The liquid crystal display device of the present invention includes a liquid crystal display device using a ferroelectric liquid crystal, a liquid crystal display device by active matrix driving, a super twisted nematic type liquid crystal display device, a twisted nematic type liquid crystal display device, and a guest-type liquid crystal display device.
It is useful as a wide range of liquid crystal display elements such as liquid crystal display elements by the host system. Furthermore, the liquid crystal display device of the present invention is useful in a wide range of applications from the fields of calculators and watches to color televisions, word processors, personal computers and the like.

[0030]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 The following structural formula

[0032]

[Chemical 3]

A polyamic acid was obtained by polycondensing a diamine having a perylene ring emitting fluorescence in the molecule and 3,4,3 ', 4'-biphenyltetracarboxylic dianhydride (each equivalent). Then, using dimethylformamide / acetophenone (1: 1) as a developing solvent, a concentration of 2 was obtained.
% Polymer solution was prepared.

Next, this polymer solution was used to form a film in a water surface development film forming apparatus as shown in FIG. In FIG. 1, 1
Is a metering pump, 2 is a supply port, 3 is a water tank, 4 is a water surface, 5 is a polymer film, 6 is a transfer roller, 7 is a film-shaped substrate, 8
Represents a weir. The polymer solution was discharged from the supply port (2) onto the water surface (4) in the water tank (3) by the metering pump (1) in the water surface development film forming apparatus of FIG. The polymer film (5) was formed by spontaneously developing into The polymer film (5) thus produced was transferred by directly contacting the electrode substrate previously attached on the film-shaped substrate (7) with the transfer roller (6).

After the water content of the electrode substrate to which this polymer film was transferred was removed by drying, it was imidized at 200 ° C. for 4 hours to obtain an electrode substrate on which polyimide was formed. The film thickness of the polymer film formed on the electrode substrate was about 130 Å. The formation of the imide ring was confirmed by the infrared absorption spectrum due to the carbonyl group at 1720 cm ^-1 . Subsequently, a liquid crystal display element as shown in FIG. 2 was created. In FIG. 2, 9 is an electrode substrate, 10 is a transparent electrode, 1
1 is a liquid crystal alignment film, 12 is a spacer, 13 is a liquid crystal, 14
Is a sealant, and 15 is a deflector. The liquid crystal alignment films (11) on the upper and lower electrode substrates (9) are arranged so that the film forming directions are orthogonal to each other. Also, between the electrode substrates,
A 10 μm alumina spacer (11) is interposed. A phenylcyclohexane nematic liquid crystal (13) is injected between the electrode substrates, and the liquid crystal injection port is sealed with an epoxy resin. Further, each deflection plate (15) is attached so that its deflection axis is in the same direction as the film forming direction of the liquid crystal alignment film. As a result of driving using this liquid crystal display element, no uneven alignment was observed and uniform alignment was exhibited. In addition, no short circuit between electrodes and no lighting failure due to electrode destruction were observed.

Example 2 The same diamine as in Example 1 and 0.5 mol% based on it.
3,4,3 ', 4'-biphenyltetracarboxylic dianhydride was polycondensed with a mixture of 4,4'-diaminodiphenyl ether to give a polyamic acid, which was then modified with dimethylhexadecylamine. The acid was obtained. Dimethylacetamide / benzene (1:
It melt | dissolved in 1) and created the polymer solution of concentration 0.5%.
Next, the polyamic acid composition was formed into a film by the LB method. Specifically, pure water was used as an aqueous phase and spread on the water surface at a water temperature of 10 ° C., the surface pressure was increased to 12.5 mN / m, and a monomolecular film was formed on the water surface. The occupied area is 1.35 nm ^2.
It was / unit. While keeping the surface pressure constant, vertically move the electrode substrate (9) vertically to the water surface at 10 mm / min.
Then, dipping was performed to form a monolayer cumulative film of two layers.
By repeating this operation, a 98-layer cumulative film was formed.
After water content of the electrode substrate (9) on which the polymer film is formed is removed by drying, acetic anhydride: pyridine: benzene (1: 1:
3) Immersion was carried out by immersing the mixture in 30 ° C. for 1 hour. The formation of the imide ring was confirmed by the infrared absorption spectrum due to the carbonyl group at 1720 cm ^-1 . The film thickness when washed with pure water and dried was about 400 Å. Since the liquid crystal alignment film emits fluorescence,
When the alignment state was measured by the fluorescence polarization measurement method, the secondary alignment coefficient of the liquid crystal alignment film (with respect to the pulling up direction of the LB film) was about 0.6. (When the secondary orientation coefficient is 1.0 with respect to the pulling direction, the state is a perfect orientation, and 0.5
In the case of, a non-oriented state is shown. )

A liquid crystal display device was prepared in the same manner as in Example 1 except that this electrode substrate was used and that azomethine nematic liquid crystal was used as the liquid crystal. Similar to Example 1, this liquid crystal display element did not show uneven alignment, showed uniform alignment, and did not show any short circuit between electrodes or defective lighting due to electrode destruction.

[0038]

The liquid crystal display device of the present invention has a liquid crystal alignment film capable of favorably aligning the liquid crystal composition without rubbing treatment. Therefore, the surface of the liquid crystal alignment film is not contaminated without destroying the electrodes and the thin film transistors due to the generation of static electricity. Furthermore, when the liquid crystal alignment film is formed by the water surface development method, a uniform polymer film having an arbitrary film thickness of about 50 Å or more can be formed by one treatment. Therefore, the liquid crystal display element of the present invention has the liquid crystal alignment film excellent in mass productivity without deteriorating the display quality.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a water surface development film forming apparatus for forming a film of the composition in Example 1.

FIG. 2 is a basic configuration diagram (cross-sectional view) of a liquid crystal display element in Examples 1 and 2.

[Explanation of symbols]

 1 Metering Pump 2 Supply Port 3 Water Tank 4 Water Surface 5 Polymer Film 6 Transfer Roller 7 Film Base Material 8 Weir 9 Electrode Substrate 10 Transparent Electrode 11 Liquid Crystal Alignment Film 12 Spacer 13 Liquid Crystal 14 Sealant 15 Deflection Plate

Claims (2)

[Claims] 1. In a liquid crystal display device in which at least a pair of electrode substrates having a liquid crystal alignment film on their surfaces are disposed so as to face each other, and a liquid crystal is sandwiched between the electrode substrates, the liquid crystal alignment film has the following polyamic acid ( A liquid crystal display device comprising an imidized product of A) and / or the modified polyamic acid (B) described below. Polyamic acid (A): general formula: (In the formula, Z represents a polynuclear aromatic tetracarboxylic acid residue.) A polyamic acid comprising a diamine compound (1) and a tetracarboxylic acid (2). Modified polyamic acid (B): A modified polyamic acid comprising (A) and an amine compound (3) having a hydrocarbon group having 1 to 40 carbon atoms. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal alignment film is an imidized product of a water surface development film or a Langmuir-Blodgett film.