JPH04109222A - Liquid crystal oriented film and liquid crystal display element - Google Patents

Abstract

PURPOSE:To form the liquid crystal display element without subjecting the element to a high-temp. treating stage by incorporating specific constituting units into the bivalent org. groups in a polyimide material contg. a specific repeating unit. CONSTITUTION:The liquid crystal oriented film contg. the constituting unit expressed by formula II and the constituting unit expressed by formula III in the bivalent org. group in the polyimide material contg. the repeating unit expressed by formula I is used. In the formula I, A denotes a quadrivalent org. group; B denotes a bivalent org. group; R1, R2 denote H or alkyl group. In the formula II, III, m denotes 1 or 2; n denotes 4 to 12 integer. The high pretilt liquid crystal oriented film which is imidized at a low temp. is obtd. in this way and the need for a high-temp. treating stage is eliminated. The stage is thus simplified.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention can be used in fields that require a high pretilt alignment film, such as STN (super twisted nematic) liquid crystal display elements and FLC (ferroelectric liquid crystal display elements). The present invention relates to a liquid crystal alignment film and a liquid crystal display element.

Conventional technology In an STN liquid crystal display device with a twist angle of 180 degrees or more, it is necessary to set the pretilt angle of the liquid crystal from the substrate to 5 degrees or more, preferably about 10 degrees to 30 degrees.

For this reason, the alignment film is one that produces a high pretilt angle (
A variety of high pretilt liquid crystal alignment films have been studied. In JP-A-62-174825, a linear polymer having a fluoroalkyl group is used as an alignment film. However, the polyimide alignment film according to the prior art document requires a high temperature of 250° C. for imidization treatment after the alignment film is formed on the substrate.

Problems to be Solved by the Invention However, the above configuration has problems in that it must go through a high temperature treatment process, making it impossible to simplify the process, and making it impossible to use parts that cannot withstand high temperature treatment.

In view of the above problems, the present invention aims to provide a high pretilt liquid crystal alignment film and a liquid crystal display device that undergo imidization at low temperatures.

Means to solve problems The present invention is general 2N) co c.

-(-N A N-B-L
(1) co c.

(In the formula, A is a tetravalent organic group and B is a divalent organic group.) In a polyimide material containing a repeating unit represented by the formula (wherein A is a tetravalent organic group and B is a divalent organic group), the divalent organic group is a structural unit represented by the formula (n). A liquid crystal alignment film containing a structural unit represented by formula (II) and a liquid crystal display element using the same.

F ”-◎-)-i, (n) -+cH2→-i,
(III)F (In the formula, m is 1 or 2, and n is an integer from 4 to 12.) Function The alignment film of the present invention consists of two structural units. Each of these structural units has an independent function. That is, a structural unit having a fluorinated Hensen ring (II
), the structural unit (I[l) having an alkyl chain can lower the imidization reaction temperature in order to increase the pretilt angle of the liquid crystal.

F Ken-◎-h (Il,) Responsibility CH2-”r-= (
III)F (In the formula, m is 1 or 2, and n is an integer from 4 to 12.) The reason why the pretilt angle becomes high is thought to be due to the water and oil repellent effect of fluorine. Also, the temperature at which the imidization reaction occurs is The reason for the decrease is considered to be that the flexibility of the alkyl chain allows the polymer chain itself to move easily, lowering the activation energy for the imidization reaction.

Example The liquid crystal display element of the present invention will be explained using the drawings.

A liquid crystal 3 is sealed between two substrates 2 whose surfaces having electrodes 1 face each other. A liquid crystal alignment film 4 is formed on the electrode 1 . The periphery of the upper and lower substrates 2 is bonded with a sealing material 5 so that the liquid crystal 3 does not leak from between the substrates 2. Also, the upper and lower boards 2
A spacer 6 is arranged between the substrates 2 in order to keep the distance between the substrates 2 constant.

The liquid crystal alignment film 4 of the present invention is formed on the electrode 1 on the substrate 2. The substrate I may be made of any transparent material such as glass, acrylic resin, polycarbonate resin, etc., but it is preferable to use glass from the viewpoint of environmental resistance. Further, if only one of the two opposing substrates 2 is used, a material that reflects light, such as a silicon wafer or aluminum, may be used. As the electrode 1, a known transparent electrode such as ITO (indium tin oxide) or 5n02 can be used. Also, the electrodes 1 on the two opposing substrates 2
If only one of them is used, a material that reflects light, such as semiconductor silicon or aluminum, can also be used. Furthermore, in order to drive the liquid crystal 3, the electrodes 1 are made into a specific pattern, and the driving transistors and diodes are placed on the substrate 2.
It may be formed on top.

The liquid crystal alignment film 4 of the present invention is made of polyimide, and the general formula (
IV) -(-N1(-CO-A-CO-NH-B-)-(IV
) ROOCC00R2 (wherein A is a tetravalent organic group, B is a divalent organic group R,,R
, represents H or an alkyl group), in which the divalent organic group contains a structural unit represented by formula (n) and a structural unit represented by (III). is used as a precursor and is manufactured by subjecting it to treatments such as heating.

F ---10 → -i, (It) Shin CH2mo
(■)F (in the formula, m is 1 or 2, and n is an integer from 4 to 12).

The borimiadic acid of the present invention usually has the following general formulas (V) and (VI) F H2N+ NN2 (V) HzN-+ctlz→-
rj-NH2(VI)F (in the formula, m is 1 or 2, and n is an integer from 4 to 12).

It is produced by reacting two types of diamines represented by the following with tetracarboxylic acids in an organic solvent. The orientation ratio of diamines (V) and (Vl) determines the ratio of fluorinated aromatics to aliphatics in the final polyimide product. This blending ratio (Vl) is 10% or more in molar ratio7
It is preferably contained in an amount of 0% or less. Aliphatic diamine (VT
) is less than 10%, the imidization reaction temperature becomes high, and when it exceeds 70%, the pretilt angle becomes small, which is unsuitable.

Here, the tetracarboxylic acids include tetracarboxylic acid, tetracarboxylic anhydride, tetracarboxylic dianhydride,
These include tetracarboxylic acid monoalkyl esters, tetracarboxylic acid dialkyl esters, tetracarboxylic acid trialgyl esters, and tetracarboxylic acid tetraalkyl esters.

Tetracarboxylic acids that can be used in the present invention include bilomeri nodonic acid, 3.3',4.4'-biphenyltetracarboxylic acid, 2,3.3',4-tetracarboxybiphenyl, 3.3',4. 4-Tetracarboxybiphenyl ether, 2,3.3'4''-tetracarboxybiphenyl ether, 3゜3',4.4'-tetracarboxybenzophenone, 2.3.3',4'
-Tetracarboxybenzophenone, 2,3,6.7-
Titracarpoxynaphthalene, 1,4,5.7-titracarpoxynaphthalene, 1.2.5.6-titracarpoxynaphthalene, 3.3',4.4'-tetracarboxydiphenylmethane, 2,2'- Bis(3,4-dicarboxyphenyl)propane, 3.3', 4.4'tetracarboxydiphenyl sulfone, 1,2°7.8-tetracarboxyperylene, 2,2-bis(4-(3, 4
-dicarboxyphenoxy)phenyl)propane, 3.
Aromatic tetracarboxylic acids such as 3',4.4°-dimethyldiphenylsilanetetracarboxylic acid, 3.3',4゜4゛-tetraphenylsilanetetracarboxylic acid, butanetetracarboxylic acid, L2,3.4 Examples include aliphatic or alicyclic tetracarboxylic acids such as -cyclobutanetetracarboxylic acid, 1,2,3,4-cyclobencunetetracarboxylic acid, and L2,3,4-furantetracarboxylic acid.

Among these tetracarboxylic acids, aromatic tetracarboxylic acids are preferred, and particularly preferred are pyromellitic acid, 3.3', 4.4'-tetracarboxyhensiphenone, and 2,3.3', 4- Tetracarboxybenzophenone, 233',4'-tetracarboxybiphenyl ether, 3.3',4.4''-biphenyltetracarboxylic acid.

Note that silicone diamine can also be copolymerized to improve adhesion to the substrate.

for example R3R.

H2N (CH2)m-5i-(0-5i)n-(CJ
Iz) n+NH2R3R3 (where m = an integer of 1 to 3, n = an integer of 1 to 20, R3
represents aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic groups. ).

In the present invention, when the mixing ratio of diamic acid and tetracarboxylic acid in the reaction is 1 to 1.1 mol of tetracarboxylic acid per 1 mol of diamine, a polyamide resin with the highest molecular weight and high storage stability can be obtained. The reaction conditions are usually N,N-dimethylformamide,
Diamines are dissolved in an organic solvent such as NN-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide, dimethylsulfoxide, or N-methyl-2-pyrrolidone, and the tetracarboxylic acid is added while stirring the solution. It can be synthesized by adding.

The reaction solvent may be used alone or in combination of two or more. Further, in order to obtain a high molecular weight resin, the solvent should be dehydrated before use.

The reaction temperature is preferably about O'C to 50'C when an acid anhydride is used as the tetracarboxylic acid, and preferably from 40 to 180C when a carboxylic acid or ester is used.

A polyamide resin can be obtained by the method described above. This resin is N,N-dimethylformamide, NN-
dimethylacetamide, NN-diethylformamide,
Since it is easily dissolved in a solvent such as N,N-diethylacetamide, dimethyl sulfoxide, or N-methyl-2-pyrrolidone at room temperature, it can be used by coating it on a substrate in the form of a solution and then drying it.

When the above-mentioned polyamide resin is heated to a temperature of about 70° C., a ring-closing reaction occurs and a polyimide resin can be obtained. Normally, it is preferable for the imidization rate (the rate of reaction progress from polyamic acid to imide) to be close to 100%, but it is also possible to create a film with a controlled imidization rate as necessary by adjusting the heating temperature. be.

More specific examples will be shown below.

(Example 1) 4,4'-diaminooctafluorobiphenyl (3,9 g, 12 [110
1 and diaminododecane (0,6 g, 3 mm
ol) and N-methyl-2-pyrrolidone (
100ml of NMP) was added and dissolved. Pyromellitic anhydride (3,
3g, 15mmo1. ) was added over about 15 minutes. The reaction mixture was further stirred at room temperature for 2 hours. This solution was filtered through a 0.2 μm membrane filter.

This solution was added to a 1.1 m thick Corning #7059
An ITO electrode was sputtered onto a type glass substrate, and the ITO surface of the substrate was spin-coded. Next, add this board to 8
The solvent was removed by heating at 0°C to create a polyamic acid film on the substrate. Furthermore, the substrate was heated at 170°C for 2 hours to create a polyimide film as a liquid crystal alignment film.

At the same time, the infrared absorption spectrum of the polyimide film of the example prepared on NaCL was measured.

In the sample before heating at 170°C, the absorption based on the NH stretching of the amide and the ○H stretching of the carboxylic acid was 3200 CI11-
It was widely seen around 1. In addition, absorption based on CO stretching was observed at 1670 cm-1 and 1712 cm-1. 170
After heating at °C, absorptions due to CO stretching of imidocarbonyl were observed at 1718 cm-1 and 1740 cm-1. The absorption at 1718 cm-1 is the imide ring near the fluorinated biphenyl moiety, and the absorption at 1740C1m-1 is the carbonyl of the imide ring near the aliphatic polyimide. The absorbance of these absorptions was almost the same as that of the sample heated at 250°C. Since it is a copolymer, it is difficult to calculate the imidization rate, but it can be said that it is almost imidized at 170''C.

After rubbing the surface of this liquid crystal alignment film, the two substrates were bonded together using a sealant with the alignment film surfaces facing each other and a gap of 2 μm maintained. At this time, the rubbing direction was parallel to the upper and lower substrates. Between these two boards pasted together,
, Merck & Co. ferroelectric liquid crystal ZLI-3654 at 100°
The liquid crystal display element of Example 1 was prepared by injecting C.

In addition, between two substrates that were bonded together using the same manufacturing method with a gap of 16 μm between the substrates, Chisso Petrochemical Co., Ltd.'s Kuson 91 was used.
50 nematic liquid crystal was injected. At this time, the rubbing direction was antiparallel between the upper and lower substrates. This liquid crystal cell was used for pretilt angle measurement.

(Example 2) 4,4′-diaminooctafluorobiphenyl (2.5 g, 7.6 mm) was placed in a round bottom flask with a capacity of 200 ml.
ol and diaminododecane (1.5g, 7.5m
mol), and 100 ml of N-methyl-2-pyrrolidone (NMP) was added thereto and dissolved. Pyromellitic anhydride (3.3g) purified by sublimation while stirring the solution.
, 15 mmol) was added over about 15 minutes. The reaction mixture was further stirred at room temperature for 2 hours. Add this solution to 0.2
It was filtered with a μm membrane filter.

This solution was added to a 1.1 mm thick Corning #7059
An ITO electrode was sputtered onto a type glass substrate, and the ITO surface of the substrate was spin-coded. Next, add this board to 8
The solvent was removed by heating at 0°C to create a polyamic acid film on the substrate. Furthermore, the substrate was heated at 170°C for 2 hours to create a polyimide film as a liquid crystal alignment film. The infrared absorption spectrum of the polyimide heated at 170°C was almost the same as the infrared absorption spectrum of the polyimide heated at 250°C.

After rubbing the surface of this liquid crystal alignment film, the two substrates were bonded together with a sealant with the alignment film surfaces facing each other and a gap of 2 μm maintained. At this time, the rubbing direction was parallel to the upper and lower substrates. Between these two bonded boards, E,
Merck's ferroelectric liquid crystal ZLI-3654 at 100"C
The liquid crystal display element of Example 1 was prepared by injecting the liquid crystal.

In addition, between two substrates that were bonded together using the same manufacturing method with a gap of 16 μm between the substrates, Chisso Petrochemical Co., Ltd.'s Kuson 91 was used.
50 nematic liquid crystal was injected. At this time, the rubbing direction was antiparallel between the upper and lower substrates. This liquid crystal cell was used for pretilt angle measurement.

(Example 3) 4,4'-diaminooctafluorobiphenyl (3.9 g, 12 mmol) was added to a round bottom flask with a capacity of 200 ml.
l and diaminodecane (0.52g, 3.0ml)
1) and add N-methyl-2-pyrrolidone (N
M P ) 100 ml was added and dissolved. Pyromellitic anhydride (3.3 g) purified by sublimation without stirring the solution.
, 15 mmof) was added over approximately 15 minutes. The mixture was further stirred at room temperature for 2 hours to react. This solution is 0.2 μm
filtered through a membrane filter.

This solution was applied to a Corning Co. M; #7 with a thickness of 1.1 mm.
An ITO electrode was sputtered onto a 059 type glass substrate, and the ITO surface of the substrate was spin-coded. Subsequently, this substrate was heated at 80° C. to remove the solvent, and a polyamic acid film was formed on the substrate. Furthermore, the substrate was heated to 170°C for 2 hours.
A polyimide film was prepared as a liquid crystal aligning film by heating for a period of time. The infrared absorption spectrum of the polyimide heated at 170°C was almost the same as the infrared absorption spectrum of the polyimide heated at 250°C.

After rubbing the surface of this liquid crystal alignment film, the two substrates were bonded together with a sealant with the alignment film surfaces facing each other and a gap of 2 am maintained. At this time, the rubbing direction was parallel to the upper and lower substrates. Between these two bonded boards, E,
Merck's ferroelectric liquid crystal ZLI-3654 at 100"C
The liquid crystal display element of Example 1 was prepared by injecting the liquid crystal.

In addition, between two substrates that were bonded together using the same manufacturing method with a gap of 16 μm between the substrates, Chisso Petrochemical Co., Ltd.'s Kuson 91 was used.
50 nematic liquid crystal was injected. At this time, the rubbing direction was antiparallel between the upper and lower substrates. This liquid crystal cell was used for pretilt angle measurement.

(Example 4) 4,4゛-diaminooctafluorobiphenyl (3.9 g, 12 mmol) was placed in a round bottom flask with a capacity of 200 ml.
and diaminooctane (0.43g, 3.Ozono1
) and N-methyl-2-pyrrolidone (NMP
) 100ml was added and dissolved. Pyromelli nodoic anhydride (3.3 g, purified by sublimation while stirring the solution)
15 mmo+) was added over approximately 15 minutes. The reaction mixture was further stirred at room temperature for 2 hours. This solution was filtered through a 0.2 μm membrane filter.

This solution was mixed with Corning #7059 with a thickness of 1.1 mm.
An ITO electrode was sputtered onto a type glass substrate, and the ITO surface of the substrate was spin-coded. Next, add this board to 8
The solvent was removed by heating at 0°C to create a polyamic acid film on the substrate. Furthermore, the substrate was heated at 170°C for 2 hours to create a polyimide film as a liquid crystal alignment film. The infrared absorption spectrum of the polyimide heated at 1.70''C was almost the same as the infrared absorption spectrum of the polyimide heated at 250°C.

After rubbing the surface of this liquid crystal alignment film, the two substrates were bonded together with a sealant with the alignment film surfaces facing each other and a gap of 2 μm maintained. At this time, the rubbing direction was parallel to the upper and lower substrates. Between these two bonded boards, E,
A liquid crystal display element of Example 1 was prepared by injecting ferroelectric liquid crystal ZLI-3654 manufactured by Merck & Co. at 100°C.

In addition, between two substrates that were bonded together using the same manufacturing method with a gap of 16 μm between the substrates, Chisso Petrochemical Co., Ltd.'s Kuson 91 was used.
50 nematink liquid crystal was injected. At this time, the rubbing direction was antiparallel between the upper and lower substrates. This liquid crystal cell was used for pretilt angle measurement.

(Example 5) 4,4゛-diaminooctafluorobiphenyl (3.9 g, 12 mmol) was placed in a round bottom flask with a capacity of 200 ml.
and diaminobutane (0.26g, 3.Ommol
) and N-methyl-2-pyrrolidone (NM
P) 100ml was added and melted. Pyromellitic anhydride (3.3 g, 1
5 mmol) was added over about 15 minutes. The reaction mixture was further stirred at room temperature for 2 hours. This solution was filtered through a 0.2 μm membrane filter.

Spread this solution to a thickness of 1, 1. A JTO electrode was sputtered on a #7059 type glass substrate made by Corning Co., Ltd., and spin-coding was performed on the JTO-forming surface of the substrate. Subsequently, this substrate was heated at 80"C to remove the solvent and a polyamic acid film was created on the substrate. Furthermore, the substrate was heated at 170°C.
C for 2 hours to create a polyimide film as a liquid crystal alignment film. The infrared absorption spectrum of the polyimide heated at 170°C was almost the same as the infrared absorption spectrum of the polyimide heated at 250°C.

After rubbing the surface of this liquid crystal alignment film, the two substrates were bonded together with a sealant with the alignment film surfaces facing each other and a gap of 2 μm maintained. At this time, the rubbing direction was parallel to the upper and lower substrates. Between these two bonded boards, E,
Merck's ferroelectric liquid crystal ZLI-3654 at 100°C
The liquid crystal display element of Example 1 was prepared by injecting the liquid crystal.

In addition, Nisso Petrochemical's Rixon 9-50 nematic liquid crystal was injected between two substrates that were bonded together using the same manufacturing method with the distance between the substrates maintained at 16 μm. At this time, the rubbing direction was antiparallel between the upper and lower substrates. This liquid crystal cell was used for pretilt angle measurement.

(Example 6) 1.4-diaminotetrafluorobenzene (2.2 g, 12 mmol) and diaminododecane (0.6 g, 3.0 mmol) were placed in a round bottom flask with a capacity of 200+nl.
) and N-methyl-2-pyrrolidone (NM
P) 100n+I was added and melted. Pyromellitic anhydride (3.3g) purified by sublimation while stirring the solution.
, 15 mmol) was added over about 15 minutes. The mixture was further stirred at room temperature for 2 hours to react. Add this solution to 0.2μ
It was filtered with a membrane filter of 1.0 m.

This solution was added to a 1.1 mm thick Corning Co., Ltd. W: #70
ITO electrodes were sputtered on a type 59 glass substrate, and the TTO-forming surface of the substrate was spin-coded. Subsequently, this substrate was heated at 80"C to remove the solvent and a polyamic acid film was created on the substrate.The substrate was further heated at 170"C for 2 hours to create a polyimide film as a liquid crystal alignment film. The infrared absorption spectrum of polyimide heated at 'C was almost the same as the infrared absorption spectrum of polyimide heated at 250°C.

After rubbing the surface of this liquid crystal alignment film, the two substrates were bonded together with a sealant with the alignment film surfaces facing each other and a gap of 2 μm maintained. At this time, the rubbing direction was parallel to the upper and lower substrates. Between these two bonded boards, E,
Merck's ferroelectric liquid crystal ZLI-3654 at 100"C
The liquid crystal display element of Example 1 was prepared by injecting the liquid crystal.

In addition, between two substrates that were bonded together using the same manufacturing method with a gap of 16 μm between the substrates, Chisso Petrochemical Co., Ltd.'s Kuson 91 was used.
50 nematic liquid crystal was injected. At this time, the rubbing direction was antiparallel between the upper and lower substrates. This liquid crystal cell was used for pretilt angle measurement.

(Example 7) 1,4-diaminotetrafluorobenzene (2.2 g, 12 mmol) and diaminodecane (1.5 g, 3.0 mmol) were placed in a round bottom flask with a capacity of 200 ml, and N-)Li was added thereto. -2-Pyrrolide: / (N
MP) was added and dissolved. Pyromellitic anhydride (3.3 g, purified by sublimation while stirring the solution)
15 mmol) was added over about 15 minutes. The reaction mixture was further stirred at room temperature for 2 hours. This solution was filtered through a 0.2 μm membrane filter.

This solution was added to a 1.1 mm thick Corning #705
An ITO electrode was sputtered on a Type 9 glass substrate, and the ITO surface of the substrate was spin-coded. Subsequently, this substrate was heated at 80'C to remove the solvent and form a polyamic acid film on the substrate. Furthermore, the substrate was heated at 170°C for 2 hours to create a polyimide film as a liquid crystal alignment film. The infrared absorption spectrum of the polyimide heated at 170°C was almost the same as the infrared absorption spectrum of the polyimide heated at 250°C.

After rubbing the surface of this liquid crystal alignment film, the two substrates were bonded together with a sealant with the alignment film surfaces facing each other and a gap of 2 μm maintained. At this time, the rubbing direction was parallel to the upper and lower substrates. Between these two bonded boards, E,
Ferroelectric liquid crystal Zlj-3654 manufactured by Merck & Co., Ltd. at 100°C
The liquid crystal display element of Example 1 was prepared by injecting the liquid crystal.

In addition, between two substrates that were bonded together using the same manufacturing method with a gap of 16 μm between the substrates, Chisso Petrochemical Co., Ltd.'s Kuson 91 was used.
50 Nemateink liquid crystals were injected. At this time, the rubbing direction was antiparallel between the upper and lower substrates. This liquid crystal cell was used for pretilt angle measurement.

(Comparative example) 4,4゛-diaminooctafluorobiphenyl (4.9 g) was placed in a round bottom flask with a capacity of 200 m1, and N
-Methyl-2-pyrrolidone (NMP) room was added and dissolved. While stirring the solution, pyromellitic anhydride (3.3 g) purified by sublimation was added over about 15 minutes.

The reaction mixture was further stirred at room temperature for 2 hours.

This solution was filtered through a 0.2 μm membrane filter.

This solution was mixed with Corning #7059 with a thickness of 1.1.
An ITO electrode was sputtered onto a type glass substrate, and the ITO surface of the substrate was spin-coded. Next, add this board to 8
The solvent was removed by heating at 0°C to create a polyamic acid film on the substrate. Furthermore, the substrate was heated at 170°C for 2 hours to create a polyimide film as a liquid crystal alignment film.

When we measured the infrared absorption spectrum of this film, we found that
Under this heating condition of 170°C, the imidization rate was about 65%. Assuming that 100% imidization has progressed in the polyimide film of the comparative example heated at 250°C, the imidization rate is the absorbance of imide carbonyl at this time/absorbance of stretching vibration of benzene ring. It was calculated as the value divided by the absorbance of imidocarnyl of the sample/the absorbance of the stretching vibration of the benzene ring. The polyimide of the comparative example was not sufficiently imidized by heating at 170°C.

(Pretilt angle measurement and cell evaluation) The pretilt angles of the examples and comparative examples of the present invention were measured using a magnetic field capacitance method. In addition, observation of ferroelectric liquid crystal display elements using a polarizing microscope under crossed nicols revealed that
The degree of zigzag defects was investigated. The results are shown in the table. In all Examples, a pretilt angle of 5 degrees or more, which is a sufficient pretilt angle, was obtained. In addition, almost no zigzag defects were observed, and the orientation was good.

Effects of the Invention According to the present invention, a high pre-tilt liquid crystal alignment film that is imidized at a relatively low temperature of 170°C is provided, and by using this liquid crystal alignment film, a liquid crystal display element can be created without going through a high temperature treatment process. be able to. This is particularly effective in manufacturing color liquid crystal display elements that use parts such as color filters that cannot withstand a 250°C process.

[Brief explanation of drawings]

The figure is a cross-sectional view of one embodiment of a liquid crystal display element using the liquid crystal alignment film of the present invention. 1...electrode, 2...substrate, 3...
...Liquid crystal, 4...Liquid crystal alignment film, Seal material, 6...Spacer. Name of agent: Patent attorney Haruaki Ogata and 2 others 71 & 2-4

Claims (3)

[Claims] (1) General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) Contains a repeating unit represented by (in the formula, A represents a tetravalent organic group and B represents a divalent organic group) A liquid crystal aligning film characterized in that the divalent organic group contains a structural unit represented by formula (II) and a structural unit represented by formula (III) in a polyimide material. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (II) (III) (In the formula, m represents 1 or 2, and n represents an integer from 4 to 12). (2) The liquid crystal aligning film according to claim (1), characterized in that the structural unit represented by formula (III) is contained in an amount of 10% or more. (3) In a liquid crystal display element in which a liquid crystal is sandwiched between a pair of substrates having electrodes on the surfaces in contact with the liquid crystal, at least the substrate is made of a polyimide material represented by formula (I) and has a divalent organic group. The structural unit shown by formula (II) and the formula (
A liquid crystal display element comprising a polyimide material containing the structural unit represented by III) as a liquid crystal alignment film.