JPH0511252A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To allow a sealed liquid crystal to exhibit a large pretilt angle by forming oriented films consisting of the polyimide obtainable from a specific diamine compd. and tetracarboxylic acid or its deriv. on substrates. CONSTITUTION:Transparent electrodes 2a, 2b and the oriented films 3a, 3b are respectively formed in this order on transparent substrates 1a, 1b, by which two sheets of transparent electrode substrates are constituted. Two sheets of the transparent electrode substrates are respectively so disposed that the oriented films 3a, 3b face each other and the ferroelectric liquid crystal 4 is sealed therebetween. The transparent electrodes 2a, 2b are formed to stripe shapes and are so formed that the stripes intersect orthogonally with each other. The oriented films 3a, 3b consist of the polyimide obtd. from at least one kind of the diamine compds. expressed by formula I and at least one kind of the tetracarboxylic acid or its deriv. In the formula I, R<1> to R<8> denote a hydrogen atom or the substituent on a benzene ring; X<1> denotes an oxygen atom or sulfur atom; X<2> denotes an alkylene group; R<9> denotes a hydrogen atom, substd. or unsubstd. alkyl group, etc.

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 having a polyimide alignment film.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal display element used for a display of a clock, a computer, a word processor or the like has a basic structure in which two transparent electrode substrates each having an alignment film on a transparent electrode have an alignment film. Usually, the structure is such that the liquid crystal is placed inside and the liquid crystal is enclosed between them. Such a liquid crystal display device transparent electrode is generally formed on the substrate in the form of a display pattern such as a stripe pattern or a grid pattern, and the alignment film is formed on the transparent electrode and the exposed substrate (other than the display pattern). It is provided by coating or vapor deposition on the entire surface. A liquid crystal display element is manufactured by arranging the two transparent electrode substrates with the alignment films inside and enclosing a liquid crystal therebetween. In general, the alignment film is provided because it is necessary to align the liquid crystals in a certain direction, that is, to align the liquid crystals, and thereby the liquid crystal molecules are aligned.

The mainstream of such a liquid crystal display device is a display in a twisted nematic (TN) mode in which a nematic liquid crystal has a twisted structure. However, this TN type liquid crystal display element is not suitable for high capacity display by high multiplex drive (generally, time division drive used for dot matrix) because the threshold value is not steep. Also, the response speed of the TN type liquid crystal display element is slow,
It has a drawback that it has a limit of milliseconds, which is a big problem when it is used for a television panel or the like that requires high-speed response.

Recently, it has the above-mentioned high-speed responsiveness that responds quickly to changes in the electric field, and responds to the applied electric field to bring about either the first optically stable state or the second optically stable state. Attention has been paid to a ferroelectric liquid crystal which has a property of maintaining its state when no voltage is applied, that is, a memory property (also referred to as bistability). A liquid crystal display device utilizing this has been studied because it can realize high-speed response with a simple structure.

The operating principle of the TN mode utilizes the optical rotatory power of a liquid crystal cell with a twist angle of about 90 degrees. However, if the SBE (super twist birefringence) mode using nematic liquid crystal is used, the steep threshold is achieved. Since the value can be obtained, a large capacity display by high multiplex drive becomes possible. The SBE (super twist birefringence) mode in which such a steep threshold value is obtained utilizes the birefringence of a liquid crystal cell having a twist angle of 180 degrees or more using the above liquid crystal. That is, it is necessary to cause the liquid crystal to be twisted by 180 degrees or more between the upper and lower substrates in the alignment direction. To this end, the liquid crystal molecules are required to have a pretilt angle of 3 to 30 degrees at the substrate electrode interface. Generally, such a pretilt angle is provided by an alignment film. On the other hand, if an alignment film that gives such a pretilt angle is used, generally, the alignment defects of the smectic liquid crystal such as the ferroelectric liquid crystal can be extremely reduced, and the bistability can be improved.

However, when an alignment film made of an organic material such as a polymer, which has been used in the conventional TN mode or the like, is formed on an electrode substrate and subjected to a rubbing treatment, the pretilt angle of the aligned liquid crystal molecules is at most 2 degrees. However, a large value cannot be obtained. Further, when an oblique vapor deposition film such as SiO is used as the alignment film, a large pretilt angle can be obtained, but forming the alignment film by vapor deposition has low mass productivity,
It cannot be said that it is advantageous in manufacturing.

As a coating type alignment film material capable of obtaining a large pretilt angle, a polyamic acid composition comprising a component having a fluorine atom in at least one of a carboxylic acid anhydride and a diamine (Japanese Patent Laid-Open No. 62-127827),
Also disclosed is an alignment treatment material for a polyimide resin obtained from a diamine, a tetracarboxylic dianhydride and a specific monoamine (JP-A-62-297819). Further, as a ferroelectric liquid crystal alignment film, a polyimide film obtained by using di-4-aminocyclohexylmethane as a base component and an aromatic tetracarboxylic acid anhydride having one or two benzene rings in the skeleton as an acid component ( JP-A-2-
No. 310524), and fluorine-containing polyimide (Japanese Patent Laid-Open No. 3-25418).

However, when the liquid crystal is oriented by using the above-mentioned orientation film, a large pretilt angle cannot always be obtained, and there is a problem that it tends to change depending on post-treatment conditions such as rubbing treatment.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal display device having a polyimide alignment film showing a large pretilt angle.

Another object of the present invention is to provide a liquid crystal display device having a polyimide alignment film suitable for multiplex driving.

[0011]

The above-mentioned object is to provide a substrate on
In a liquid crystal display device in which two transparent electrode substrates in which stripe-shaped or grid-shaped transparent electrodes are stacked, each transparent electrode being placed inside, and liquid crystal enclosed between them, at least one of the transparent electrodes And an alignment film made of polyimide obtained from at least one of the diamine compounds represented by the following general formula (I) and tetracarboxylic acid or its derivative. You can General formula (I)

[Chemical 2] In the above formula, R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ ,
R ⁸ represents a hydrogen atom or a substituent on the benzene ring, which may be the same or different from each other, X ¹ represents an oxygen atom or a sulfur atom, X ² represents an alkylene group,
R ⁹ represents a hydrogen atom, a substituted or unsubstituted alkyl group, or an aryl group.

The general formula (I) will be described in detail below.

R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R
Examples of the substituents on the benzene ring of ⁷ , R ⁸ and specific groups of R ⁹ include methyl group, ethyl group, propyl group, isopropyl group, butyl group, octyl group, dodecyl group, cyclohexyl group, 2- Unsubstituted alkyl groups such as cyclohexylethyl group, trifluoromethyl group, pentafluoroethyl group, heptafluoropropyl group, 2-perfluorooctylethyl group, 4-trifluoromethylcyclohexyl group, 3,4-dichlorocyclohexyl group, 3 -Substituted alkyl group such as trifluoromethylpentyl group, unsubstituted aromatic group such as phenyl group, biphenyl group, naphthyl group, 4-trifluoromethylphenyl group, 3-nonafluorobutylphenyl group, pentafluorophenyl group,
Substituted aromatic groups such as 3,5-dimethylphenyl group and 4-phenoxyphenyl group, carboxamide groups such as halogen, nitrile, acetamide and lauric acid amide, sulfonamide groups such as benzenesulfonic acid amide and butanesulfonic acid amide, N Carbamoyl groups such as-(4-propylphenyl) carbamoyl, N-dodecylcarbamoyl, N-methyl-N-octylcarbamoyl, N-dodecylsulfamoyl, N-phenylsulfamoyl, N-methyl-N- (2- Perfluorohexyl) ethylsulfamoyl and other sulfamoyl groups, methoxy, propoxy, 4-trifluoromethylbutoxy, sec-butoxy and other alkoxy groups, phenoxy, 4-trifluoromethylphenoxy, 3-nonafluorobutylphenoxy and other aryls Oxy group Aralkyloxy groups such as benzyloxy, 3,5-dichlorobenzyloxy and naphthylmethoxy, carbonyloxy groups such as benzoyloxy, cyclohexylcarbonyloxy and tetradecylcarbonyloxy, methoxycarbonyl, isohexyloxycarbonyl, 3-nonafluorobutylphenoxy Examples thereof include oxycarbonyl groups such as carbonyl, and ureido groups such as 1,3-dimethylureido, 3,3-diphenylureido, 3- (4-trifluoromethylcyclohexyl) ureido, and 3-octadecylureido.

R ^{1 to} R ⁴ and R ^{5 to} R ⁸ are adjacent to each other and can be bonded to each other to form a benzene ring and a condensed ring. Specific examples thereof include naphthalene, indene, Indane, anthracene, 1,3-dioxaindane, 1,4-dithianaphthalene, indole, benzofuran, quinoline, isoquinoline, benzothiophene, phthalazine, chroman, isochroman, quinoxaline and the like can be mentioned. In this case, the amino group may be on the condensed ring.

Specific examples of the alkylene group for X ² include unsubstituted alkylene groups such as methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene and decylene, and general formula (I
A substituted alkylene group as shown in I) may be mentioned. General formula (II)

[Chemical 3]

In the above formula, R ¹⁰ has the same meaning as R ⁹ and may be substituted at any position of the alkylene chain, but preferably on the carbon atom adjacent to X ¹ and n is 1 or more. Is an integer, and m is an integer of n or less. Furthermore, m is 2
In the above case, R ¹⁰ may be the same or different.

Preferred embodiments of the liquid crystal display device of the present invention are as follows.

In the general formula (I), R ^{1 to} R ⁸ are hydrogen atoms, halogen atoms, substituted or unsubstituted carbon atoms of 1 or more and 1
An alkyl group having 4 or less (linear, branched or alicyclic), a substituted or unsubstituted aromatic group having 6 to 18 carbon atoms is preferable, and a hydrogen atom, a fluorine atom, a trifluoromethyl group, or a carbon number is particularly preferable. It is a linear alkyl group of 1 or more and 4 or less.

In the general formula (I), R ⁹ is a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms (straight chain, branched or alicyclic), a substituted or unsubstituted 6 or more carbon atom 18 The following aromatic groups are preferable, and a hydrogen atom and a linear alkyl group having 1 to 30 carbon atoms are particularly preferable.

In the general formula (I), X ¹ is preferably an oxygen atom.

In the general formula (I), X ² is an unsubstituted alkylene of methylene, ethylene or propylene, and is represented by the general formula (I
Substituted alkylene represented by I) having n of 1 or more and 4 or less and R ¹⁰ having a substituted or unsubstituted alkyl group having 1 or more and 30 or less carbon atoms is preferable, and particularly preferably, in the general formula (II), n is 1 or Substituted alkylene in which m is 1 and R ¹⁰ has 8 to 30 carbon atoms is preferable.

At least one of R ⁹ and R ¹⁰ is preferably a straight chain alkyl group having 12 or more and 20 or less carbon atoms.

The tetracarboxylic acid derivative used in the present invention is preferably a tetracarboxylic acid dianhydride, and examples thereof include the tetracarboxylic acid dianhydrides shown in Table 1.

Table 1 Examples of tetracarboxylic dianhydrides ───────────────────────────────────── Compound number Tetracarboxylic dianhydride A-1 1,2,4,5-benzenetetracarboxylic dianhydride A-2 3,3 ′, 4,4′-diphenyltetracarboxylic dianhydride A-3 3,3 ′, 4,4 ′ -Benzophenone tetracarboxylic acid dianhydride A-4 Bis (3,4-dicarboxyphenyl) ether dianhydride A-5 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride A-5 -6 1,4,5,8-naphthalenetetracarboxylic dianhydride A-7 cyclobutanetetracarboxylic dianhydride A-8 cyclopentanetetracarboxylic dianhydride ───────────── ────────────────────────

Table 2 shows specific examples of the general formula (I) of the present invention, but the present invention is not limited thereto.

Table 2 Specific examples of general formula (I) of the present invention ─────────────────────────────────── ── Compound number Example compound name B-1 N- (4-aminophenyl) -2- (4-aminophenoxy) tetradecane amide B-2 N- (3-aminophenyl) -2- (4-aminophenoxy) tetradecane amide B- 3 N- (2-aminophenyl) -2- (4-aminophenoxy) tetradecane amide B-4 N- (2-aminophenyl) -2- (3-aminophenoxy) tetradecane amide B-5 N -(4-Aminophenyl) -2- (4-aminophenoxy) do decanamide B-6 N- (3-aminophenyl) -2- (4-aminophenoxy) do decanamide B-7 N- (2-aminophenyl ) -2- (4-Aminophenoxy) dodecane amide B-8 N- (4-aminophenyl) -2- (4-aminophenoxy) hexadecane amide B-9 N- (3-amino Phenyl) -2- (4-aminophenoxy) hexadecane amide B-10 N- (2-aminophenyl) -2- (4-aminophenoxy) hexadecane amide B-11 N- (2-aminophenyl) -2- ( 3-Aminophenoxy) hexadecaneamide B-12 N- (3-aminophenyl) -2- (3-aminophenoxy) hexadecaneamide B-13 N- (4-aminophenyl) -2- (3-aminophenoxy) hexa Xadecane amide B-14 N- (2-aminophenyl) -2- (2-aminophenoxy) hexadecaneamide B-15 N- (4-aminophenyl) -2- (2-aminophenoxy) hexadecaneamide B-16 N- (3-Aminophenyl) -2- (2-aminophenoxy) hexadecane amide B-17 N-tetra Syl-N- (4-aminophenyl) -2- (4-aminophenoxy) ethanamide B-18 N-hexadecyl-N- (4-aminophenyl) -2- (4-aminophenoxy) ethanamide B-19 N-octadecyl-N- (3-aminophenyl) -2- (4-aminophenylthio) ethanamide B-20 N-eicosyl-N- (2-aminophenyl) -2- (4-aminophenylthio) ethanamide B -21 N-tetradecyl-N- (4-aminophenyl) -2- (4-aminophenoxy) decanamide B-22 N- (4-trifluoromethylbenzyl) -N- (3-aminophenyl) -2- (4-Aminophenyl) ethanamide B-23 N-tetradecyl-N- (3-aminophenyl) -2- (4-aminophenylthio) p Pionamide B-24 N-methyl-N- (3-aminophenyl) -2- (4-aminophenylthio) hexadecanamide B-25 N- (4-aminoindan-6-yl) -2- (4-aminonaphthoxy) ) Docosanamide B-26 N- (4-aminophenyl) -4- (8-aminochroman-6-yloxy) -2-octylbutanamide B-27 N- (2,3-dichloro-4-aminophenyl)- 5- (2-trifluoromethyl-4-aminophenoxy) -4-hexadecyl pentanamide B-28 N-methyl-N- (3-propyl-4-aminophenyl) -6- (3-phenyl-5- Aminophenoxy) -2-propylhexanamide B-29 N- (3-aminophenyl) -2- (4-aminophenoxy) butanamide B- 0 N- (2-aminophenyl) -5- (4-aminophenoxy) pentanamide B-31 N- (2-perfluorooctylethyl) -N- (3-aminophenyl) -2- (4-aminophenyl) Thio) hexanamide B-32 N-perfluoroisohexylmethyl- (4-aminophenoxy) -2- (4-trifluoromethylphenyl)-(5-aminonaphthoxy) ethanamide B-33 N-perfluorohexyl-N -(3-Aminophenyl) -2- (3-aminophenoxy) ethanamide ────────────────────────────────── ───

A preferred structure of the liquid crystal display device obtained by the manufacturing method of the present invention will be described. FIG. 1 shows a cross-sectional view of an example of the liquid crystal display element of the present invention.

On the transparent substrates 1a and 1b, the transparent electrodes 2a,
2b and alignment films 3a and 3b are stacked in this order to form two transparent electrode substrates. An insulating layer may be interposed between the transparent electrode and the alignment film, if necessary. The two transparent electrode substrates are arranged so that the alignment films 3a and 3b face each other, and the ferroelectric liquid crystal 4 is enclosed between them. The transparent electrodes 2a and 2b are formed on the transparent substrates 1a and 1b, respectively, in the form of a striped display pattern.

As described above, the transparent electrodes 2a and 2b are formed in stripes, and the stripes are formed so as to be orthogonal to each other. This allows matrix display. Further, the transparent electrode may be formed in a stripe shape only on one side. Further, it is not necessary to have both alignment films, and only one may be provided.

The liquid crystal display element of the present invention is provided with the above-mentioned alignment film 3a.
And 3b are formed from a polyimide using the diamine compound of the general formula (I) as a diamine component.
By using this alignment film, it is possible to align the liquid crystal, particularly the ferroelectric liquid crystal, with a large pretilt angle which can be obtained only by the alignment film formed by oblique vapor deposition of SiO 2.

The liquid crystal display element of the present invention is not limited to the one shown in FIG. 1, but all the modes which are carried out for a normal liquid crystal display element such as using a spacer are possible. In particular, the gap between both alignment films (that is, the layer thickness of the liquid crystal layer)
It is preferred that a spacer be used to ensure As the spacer, glass fiber, glass
Beads, plastic beads, metal oxide particles such as alumina and silica are used. The particle size of the spacer is
Depending on the liquid crystal used, alignment film material, setting of the gap, particles used as spacers, etc., 1.2
Generally, it is from 6 μm to 6 μm.

The liquid crystal display device of the present invention can be manufactured, for example, as follows.

Examples of the transparent substrate of the present invention include glass such as float glass having good smoothness, polyester such as polyethylene terephthalate and polybutylene terephthalate, epoxy resin, phenol resin, polyimide, polycarbonate, polysulfone, polyether sulfone, Heat-resistant resins such as polyetherimide, acetyl cellulose, polyamino acid ester, aromatic polyamide,
Examples thereof include plastic films formed from polystyrene, polyacrylic acid ester, polymethacrylic acid ester, vinyl-based polymers such as polyacrylamide, polyethylene and polypropylene, fluorine-containing resins such as polyvinylidene fluoride and modified products thereof.

On the above-mentioned substrate, transparent electrodes having a stripe-shaped or lattice-shaped display pattern are formed by a conventional method. As the transparent electrode, for example, indium oxide (I
Examples thereof include n ₂ O ₃ ), tin oxide (SnO ₂ ), and ITO (indium tin oxide).

A color filter and a protective layer may be formed in this order on the surface of the substrate. The alignment film of the present invention is formed on the transparent electrode (and the substrate), for example, as described below.

The polyimide alignment film of the present invention can be produced by various production methods, but is preferably a polyamic acid obtained from at least one diamine compound represented by the general formula (I) and a tetracarboxylic acid derivative. It can be obtained by dehydration condensation of some or all of the above.

Regarding the production of the above polyamic acid, the molar ratio of the diamine compound to the tetracarboxylic acid derivative may be any ratio, but preferably, the diamine compound / tetracarboxylic acid derivative (mol number / mol number) is 0.50 to 2 .0
Within the range, and particularly preferably 0.83 to 1.2.

In the alignment film of the present invention, a polyamic acid synthesized from a diamine compound represented by the general formula (I) and the tetracarboxylic acid derivative is dissolved in a solvent to prepare a coating liquid for forming an alignment film, It is formed by coating this on a substrate, drying it, and heat-treating it to form a polyimide film partially or entirely.

Synthesis Examples 1 to 3 of the diamine represented by the above general formula (I) are shown below.

Synthesis Example 1 Synthesis of B-6 2.76 g (0.02 mol) of 3-nitroaniline and 2.4 g (0.03 mol) of pyridine in acetonitrile (50
ml) solution was slowly added with 7.11 g (0.02 mol) of 2- (4-nitrophenoxy) -dodecanoic acid chloride, reacted at room temperature for 3 hours, and then poured into water to obtain N- (3′-). 7.55 g (0.5%) of crystals of nitrophenyl) -2- (4-nitrophenoxy) -dodecanoic acid amide.
(0165 mol) was obtained. Then, this N- (3′-nitrophenyl) -2- (4-nitrophenoxy) -dodecanoic acid amide was added with 20 g of reduced iron and 1.2 g of ammonium chloride.
g, 8 g of water, and 50 ml of isopropyl alcohol to reduce N- (3′-aminophenyl) -2.
-(4-aminophenoxy) -dodecanoic acid amide (B-
5 g of crude crystals of 6) were obtained. Moreover, what refine | purified this crude crystal by column chromatography (silica gel-ethyl acetate) was made into the raw material for polyamic acid synthesis.

Synthesis Example 2 Synthesis of B-3 Performed in the same manner as in Synthesis Example 1 except that 2-nitroaniline was used as the aniline compound and 2- (4-nitrophenoxy) -myristic acid chloride was used as the carboxylic acid chloride compound. , N- (2'-aminophenyl) -2- (4
-Aminophenoxy) -myristic acid amide (B-3)
Was obtained in an amount of 6.5 g.

Synthesis Example 3 Synthesis of B-10 Synthesis Example 1 except that 2-nitroaniline was used as the aniline compound and 2- (4-nitrophenoxy) -hexadecanoic acid chloride was used as the carboxylic acid chloride compound.
N- (2'-aminophenyl) -2-
(4-Aminophenoxy) -hexadecanoic acid amide (B
-10) was obtained.

Synthesis examples 4 to 7 of polyamic acid are shown below.

Synthesis Example 4 Polyamic Acid; Synthesis of C-1 A solution of the dicarboxylic acid compound B-6 (1.985 g, 0.005 mol) in N-methyl-2-pyrrolidone (27.68 g) was added to the tetracarboxylic acid diamine A-1. Anhydrous 1.09 g (0.0
(05 mol) was added and stirred at room temperature for 6 hours to obtain a 10 wt% polyamic acid; C-1 solution.

Synthesis Example 5 Synthesis of polyamic acid; C-2 The procedure of Synthesis Example 4 was repeated except that B-3 was used as the diamine compound.

Synthesis Example 6 Synthesis of Polyamic Acid; C-3 The procedure of Synthesis Example 4 was repeated except that B-10 was used as the diamine compound.

Synthesis Example 7 Polyamic acids C-4 to C-20 were obtained according to Synthesis Examples 4 to 6. This is shown in Table 3. Table 1 Synthesis of polyamic acid Polyamic acid Diamine acid anhydride Diamine / acid anhydride (molar ratio) C-4 B-5 A-1 1/1 C-5 B-8 A-1 1 / 1.1 C-6 B-10 A-1 1.1 / 1 C-7 B-14 A-1 1/1 C-8 B-15 A-1 1/1 C-9 B-16 A-1 1.2 / 1 C -10 B-18 A-1 1/1 C-11 B-22 A-1 1 / 1.15 C-12 B-24 A-1 1/1 C-13 B-28 A-2 1/1 C -14 B-29 A-3 1/1 C-15 B-31 A-1 1/1 C-16 B-32 A-2 1/1 C-17 B-33 A-3 1/1 C-18 aB-8 bB-22 A-1 (a / b = 0.5 / 0.5) / 1 C-19 B-16 cA-1 dA-2 1 / (c / d = 0.5 / 0.5) C-20 aB-8 bB -22 cA-1 dA-2 (a / b = 0.5 / 0.5) / (c / d = 0.5 / 0.5)

As the coating solution for forming an alignment film, the polyamic acid solution obtained above or the polyamic acid obtained by reprecipitation or the like can be used as a suitable solution such as pyridine, N-methyl-2-pyrrolidone, dioxane, THF or a glycol derivative. A solution dissolved in a solvent can be prepared. This coating solution contains
In addition to the above components, other polymer such as high molecular weight polymer and organic metal may be added for the purpose of increasing the adhesion to the substrate or adjusting the viscosity of the coating liquid.

The coating liquid for forming an alignment film is coated on the transparent electrode and the exposed substrate by a spin coater or the like, and at room temperature to 150 ° C. under normal pressure or reduced pressure for 1 to 120 minutes (preferably 80 to 120 ° C.). At 10-80 minutes). Next, the coating film is heat-treated at 150 to 300 ° C. under normal pressure or reduced pressure for 0.5 to 3 hours. Heating is the latter one
Only heating at 50 to 300 ° C. for 0.5 to 3 hours is sufficient.
As a result, a polyimide alignment film is formed.

The thickness of the obtained alignment film is 10 to 800 nm, preferably 20 to 100 nm, although it depends on the type of liquid crystal and the alignment film used.

The alignment film provided on the transparent electrode substrate (and protective layer) is preferably rubbed with a synthetic fiber such as nylon, polyester or polyacrylonitrile, or a natural fiber such as cotton or wool.

The polyimide alignment film of the present invention thus formed allows liquid crystals to be aligned with a large pretilt angle. This polyimide alignment film is characterized by using a diamine compound represented by the above general formula (I) as a diamine component of polyimide.

A transparent substrate manufactured as described above,
Two transparent electrode substrates composed of a transparent electrode and an alignment film are made to face each other with their alignment films inside so as to form a cell. The size of this gap, that is, the cell gap is preferably about 0.5 μm to 6 μm.

Next, the following liquid crystal (preferably ferroelectric liquid crystal) is injected into this cell, sealed and then slowly cooled to prepare a liquid crystal display element.

The liquid crystal used in the present invention is preferably a liquid crystal that can be used in the SBE mode or a ferroelectric liquid crystal, but a ferroelectric liquid crystal is particularly preferable.

The liquid crystal having ferroelectricity is specifically a chiral smectic C phase (SmC ^* ) and H phase (Sm
H ^* ), I phase (SmI ^* ), J phase (SmJ ^* ), K phase (SmK ^* ), G phase (SmG ^* ) or F phase (Sm)
It is a liquid crystal having F ^* ). For example, all known ferroelectric liquid crystals as described in "High-speed liquid crystal technology" (published by CMC) p. 127-161 can be used in the present invention.

Specific liquid crystal compositions include CS-1018, CS-1023, CS- manufactured by Chisso Corporation.
1025, CS-1026, DO manufactured by Roddick Co., Ltd.
F0004, DOF0006, DOF0008, ZLI-4237-000, ZLI-4237- manufactured by Merck & Co., Inc.
100, ZLI-4654-100, ZLI-2293
And so on. There is no problem even if a dichroic dye, a viscosity reducing agent, or the like which dissolves in the liquid crystal is added to these liquid crystals.

The liquid crystal display device thus obtained is
The enclosed liquid crystal can be aligned with a large pretilt angle. The pretilt angle of the liquid crystal is preferably 3 to 90 degrees, and particularly preferably 5 to 40 degrees.

In the liquid crystal display element manufactured as described above, polarizing plates may be provided on both substrates of the cell depending on the purpose of use. An insulating layer, a color filter, a protective layer, etc. may be provided between the transparent electrode and the alignment film. Further, the liquid crystal display device of the present invention may be provided with a structure such as a reflection plate and a retardation plate, which are provided in a conventional liquid crystal display device, depending on the purpose of use.

[0060]

EXAMPLES Examples of the present invention will be described below. However, the present invention is not limited to this embodiment.

Example 1 Transparent electrodes of indium-tin oxide (ITO) were formed in stripes (electrode width: 100 μm, gap between electrodes: 15 μm) on two 1.1 mm thick glass substrates. ..

On the two glass substrates with transparent electrodes,
An insulating layer having a layer thickness of 100 nm was formed by depositing SiO 2.

On the above-mentioned insulating layer, a coating liquid dissolved in 3 parts by weight of C-1 polyamic acid and 97 parts by weight of N, N-dimethylacetamide was applied by a spinner.

The conditions of the spinner are 2500 rpm.
m., time 30 seconds. After coating, the polyimide alignment film was formed by drying at 180 ° C. for 1 hour.

Both surfaces of this coating film were rubbed with a nylon raised cloth, and two glass plates were placed so that the rubbing surfaces were inside and the rubbing directions were antiparallel and the electrode patterns were orthogonal. A cell having a cell gap of 3 μm was prepared by stacking with a 3 μm spacer interposed therebetween. Liquid crystal ZLI-2293 manufactured by Merck Ltd. is placed in this cell.
It was injected at 00 ° C and gradually cooled to room temperature at a rate of about 2 ° C / min.

The pretilt angle of the obtained liquid crystal display device was measured by a crystal rotation method using a polarizing microscope manufactured by Nikon Corporation, and it was 18.5 °.

Example 2 A liquid crystal display device was manufactured in the same manner as in Example 1 except that C-2 polyamic acid was used as the polyamic acid.

When the pretilt angle of the obtained liquid crystal display device was measured in the same manner as in Example 1, it was 37.5 °.

Example 3 A liquid crystal display device was manufactured in the same manner as in Example 1 except that C-3 polyamic acid was used as the polyamic acid.

The pretilt angle of the obtained liquid crystal display device was measured in the same manner as in Example 1, and it was 30 °.

Example 4 In Example 1, when rubbing with a nylon raised fabric, the rubbing direction was changed from anti-parallel to the same direction with each rubbing surface facing inward, and the spacer was set to 3
Change from μm to 2 μm, and change the liquid crystal to ZL made by Merck.
Ferroelectric liquid crystal CS- manufactured by Chisso Corporation from I-2293
A liquid crystal display device was manufactured in the same manner as in Example 1 except that the number was changed to 1023.

When the alignment state of the obtained liquid crystal display element was observed, a good alignment state without zigzag defects was obtained. Further, when the above liquid crystal display device was driven by multiplex, good contrast was obtained.

Example 5 In Example 4, the liquid crystal was a ferroelectric liquid crystal CS-1023.
To liquid crystal compositions shown in Table 4 below [phase transition temperature (° C) C
^* 58.0A83.4N ^* 89.3Iso], except that the liquid crystal display element was manufactured in the same manner as in Example 4. Table 4 Liquid crystal composition ──────────────────────────────────── Compound composition ratio (wt%) 5- Heptyl-2- (4-octyloxyphenyl) 11 pyrimidine 5-nonyl-2- (4-octyloxyphenyl) 11 pyrimidine 5-heptyl-2- (4-nonyloxyphenyl) 11 pyrimidine 5-octyl-2- ( 4-octyloxyphenyl) 22 pyrimidine 5-hexyl-2- (4-pentylbiphenylyl-4′-) 8 pyrimidine 5-heptyl-2- (4-pentylbiphenylyl-4′-) 8 pyrimidine 5-octyl- 2- (4-heptylbiphenylyl-4′-) 8 pyrimidine 5-nonyloxy-2- (4-heptylphenyl) pyrimidine 15 5-octyl-2- [4-((2S) -2-ph Oro 5 octyloxy) phenyl] pyrimidine 5-((2S) -2-methylbutyl) -2- (4-heptyl 1 biphenylyl-4 ′-) pyrimidine ───────────────── ─────────────────────

When the alignment state of the obtained liquid crystal display device was observed, a good alignment state without zigzag defects was obtained. Further, when the above liquid crystal display device was driven by multiplex, good contrast was obtained.

Examples 6 to 24 In Example 4, C shown in Table 1 as the polyamic acid.
A liquid crystal display device was manufactured in the same manner as in Example 4 except that polyamic acids of −2 to C-20 were used.

When the alignment state of all the obtained liquid crystal display elements was observed, a good alignment state without zigzag defects was obtained. Further, when the above liquid crystal display device was driven by multiplex, good contrast was obtained in all cases.

[0077]

INDUSTRIAL APPLICABILITY As shown in the above examples, in the liquid crystal display element of the present invention, the diamine compound of the present invention represented by the general formula (I) is used as an alignment film for aligning the enclosed liquid crystal. By using at least one of the polyimides obtained by using as an amine component, the liquid crystal can be aligned with a large pretilt angle that can be obtained only by the alignment film formed by oblique vapor deposition of SiO, and alignment defects are almost eliminated. However, it is possible to obtain an improved bistability. Furthermore, the alignment film of the present invention can be formed by coating, which is advantageous in manufacturing.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a configuration example of a liquid crystal display element of the present invention.

[Explanation of symbols]

 1a, 1b: transparent substrate 3a, 3b: alignment film 4: liquid crystal

Claims (1)

Claim: What is claimed is: 1. At least one substrate comprises a polyimide obtained from at least one diamine compound represented by the following general formula (I) and at least one tetracarboxylic acid or a derivative thereof. A liquid crystal display device having an alignment film formed thereon. General formula (I): In the above formula, R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ ,
R ⁸ represents a hydrogen atom or a substituent on the benzene ring, which may be the same or different from each other, X ¹ represents an oxygen atom or a sulfur atom, X ² represents an alkylene group,
R ⁹ represents a hydrogen atom, a substituted or unsubstituted alkyl group, or an aryl group.