JP2762551B2 - Liquid crystal alignment film and liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a liquid crystal alignment film and a liquid crystal display device using the same, particularly, liquid crystal molecules are aligned with a tilt angle (pretilt angle) with respect to a substrate. The present invention relates to a liquid crystal alignment film for giving a state and a liquid crystal display device.

[Prior Art] There are three types of alignment of liquid crystal molecules in a liquid crystal display element: vertical, horizontal, and inclined. Widely used than before
The alignment of the liquid crystal molecules in the TN type liquid crystal display device was horizontal and the alignment direction of the liquid crystal molecules was parallel to the substrate. Such an alignment state can be exhibited by forming an organic resin film such as polyimide on a substrate and using a liquid crystal alignment film obtained by rubbing the film in one direction. As a liquid crystal element having such a liquid crystal alignment film, there are an optical element such as an optical shutter and a wavelength converter using a nonlinear optical effect, in addition to a display element.

The TN type liquid crystal display element has drawbacks in threshold characteristics, response speed, and the like, and cannot respond to a large-capacity liquid crystal display element, which has been increasingly required in recent years, in terms of performance. Therefore, STN with steep threshold characteristics and excellent contrast, visual characteristics, etc.
Type or SBE type liquid crystal display device was developed (T.
J. Scheffer et al. Appl. Phys. Lett. 45 (10), 1021 (1984)
reference).

In this type of liquid phase display device, the orientation direction of liquid crystal molecules between the upper and lower substrates must be twisted by 180 ° or more. Therefore, the liquid crystal molecules must be oriented at an inclination angle of about 3 ° to 20 ° with respect to the substrate surface.

Also, a liquid crystal display device using a ferroelectric liquid crystal having a higher response speed than that of a TN type or STN type liquid crystal display device has been developed (NAClark et al., Appl. Phys. Lett. 36 (198)
0), 899). Ferroelectric liquid crystals are attracting attention for their high-speed response, and are considered to be used in fields other than display elements, such as application to shutter arrays of optical printers (see Optronics, 64 (1987), p. 97).

As one of the methods for controlling the orientation of a ferroelectric liquid crystal, a method of inclining liquid crystal molecules with respect to a substrate has been proposed (T. Uemura et al., JAPAN DISPLAY'86 Proceedings 464).
(See lecture number 12.3).

In an alignment method of rubbing an organic resin film, which has been used in a conventional TN type liquid crystal display element, an angle (pretilt angle) between liquid crystal molecules and a substrate is about 0 ° to 2 ° at most. With such a small pretilt angle, it is difficult to realize the STN mode or the tilt alignment of the ferroelectric liquid crystal. Thus, TJ Scheffer et al. And T. Uemura et al. Use an obliquely evaporated inorganic film such as silicon oxide to tilt-align liquid crystal molecules. Further, a method of achieving a tilt alignment by a rubbing treatment method by mixing a vertical alignment agent with an organic resin such as polyimide has also been reported (Japanese Patent Application Laid-Open Nos. 62-262828, 62-262829, 62-262829). 297819).

Further, attempts have been made to provide a large pretilt angle using a liquid crystal alignment film obtained by rubbing an organic resin film such as polyimide containing fluorine atoms (Japanese Patent Application Laid-Open No. Sho 62).
-127827, 62-127828, 63-259515, 63-262620
Reference).

[Problem to be Solved by the Invention] The method of forming an inorganic oblique vapor deposition film on a substrate has disadvantages such as requiring a special device such as a vapor deposition device, complicated work, and not suitable for mass production technology. .

On the other hand, in a system in which a vertical alignment agent is mixed with a horizontal alignment agent such as polyimide, there is a problem that the value of the tilt angle of the liquid crystal molecules is unstable or greatly depends on manufacturing conditions such as rubbing. Further, in the conventional fluorinated polyimide, the effect of inducing the pretilt angle of the fluorinated component is small, and it is necessary to copolymerize a large amount of the fluorinated component in order to realize a practically sufficient pretilt angle. In the case of such a polyimide, when other components are copolymerized for the purpose of improving various properties such as improvement in adhesiveness and solvent resistance, it becomes a serious limitation and causes a problem.

The present invention has been made in view of the drawbacks of the conventional technology, and has as its object to require a special device and to provide a stable and large tilt alignment without sacrificing other characteristics of the liquid crystal alignment film. It is an object of the present invention to provide a liquid crystal alignment film and a liquid crystal display element which can exhibit the above.

[Means for Solving the Problems] That is, first, the present invention provides a polyimide containing a repeating unit represented by the following general formula (I) and a repeating unit represented by the following general formula (II) as main components. Provided is a liquid crystal alignment film characterized by being formed.

In the formulas (I) and (II), R ¹ represents an alkyl group having 4 to 20 carbon atoms or a fluoroalkyl group. When R ¹ is a fluoroalkyl group, X at that time r represents 0 or 1. When R ¹ is an alkyl group,
X at that time And r represents 1. R ² represents a tetravalent organic residue, and R ³ represents a divalent organic residue. The m / n ratio is between 1/99 and 80/20.

The present invention provides a liquid crystal display device in which a liquid crystal alignment film is provided on a surface of a pair of parallelly arranged transparent electrode substrates sandwiching a liquid crystal, and the surface of the liquid crystal alignment film is rubbed in a certain direction. A liquid crystal display element characterized by using a polyimide containing as a main component a repeating unit represented by the following general formula (I) and a repeating unit represented by the following general formula (II) as a liquid crystal alignment film. provide.

In the formulas (I) and (II), R ¹ represents an alkyl group having 4 to 20 carbon atoms or a fluoroalkyl group. When R ¹ is a fluoroalkyl group, X at that time r represents 0 or 1. When R ¹ is an alkyl group,
X at that time And r represents 1. R ² represents a tetravalent organic residue, and R ³ represents a divalent organic residue. The m / n ratio is between 1/99 and 80/20.

The repeating unit represented by the general formula (I) and the general formula (I
The value of the constitutional ratio m / n of the repeating unit represented by I) is 1/99
~ 80/20. Preferably it is 5/95 to 50/50. When the value of m / n is less than 1/99, it is difficult to obtain a liquid crystal alignment film that provides a large pretilt angle required by the STN method or the like, while the value of m / n exceeds 80/20 In such a case, problems such as instability of the liquid crystal alignment and deterioration of the mechanical or thermal characteristics of the polyimide may occur. M / which can be preferably used to obtain a stable pretilt angle
The value of n is between 5/95 and 50/50.

In the present invention, the polyimide containing the repeating unit represented by the above general formula (I) and the repeating unit represented by the general formula (II) as a main component is a polyimide containing a diamine compound represented by the following general formula (III): General formula (I
One or more of the diamine compounds represented by V) and one or more of the tetracarboxylic dianhydrides represented by the general formula (V) are combined with N, N-dimethylformamide, N, N- By reacting in a polar solvent such as dimethylacetamide, N-methyl-2-pyrrolidone, and γ-butyrolactone, it can be synthesized in the form of a polyamic acid solution as a precursor.

The reaction temperature and time are not particularly limited, but are usually 0 ° C.
By stirring at a temperature of 8080 ° C. for 1 to 10 hours, a polyamic acid solution having an intrinsic viscosity in the range of 0.1 to 4.0 can be adjusted.

Further, such a polyamic acid solution as it is, or by heating to 100 ° C. or more under azeotropic dehydration conditions in the presence of a solvent such as toluene and xylene, to obtain a polyimide solution partially or completely imide ring-closed,
It is possible by appropriately selecting the repeating units of the general formulas (I) and (II).

Further, such an imide ring closure reaction can be carried out in the presence of a ring closure reaction promoting catalyst such as pyridine / acetic anhydride.

H ₂ N-R ³ -NH ₂ (IV) In the above general formulas (III), (IV) and (V), X, R ¹ , R ² , R ³ and r have the same meanings as in the general formulas (I) and (II). .

R ¹ in the general formulas (I) and (III) has 4 to 2 carbon atoms.
It is an alkyl group having 0 or a fluoroalkyl group having 4 to 20 carbon atoms. When the number of carbon atoms is less than 4, the liquid crystal alignment characteristics, particularly the tilt alignment characteristics, are not sufficient. Even when the number of carbon atoms exceeds 20, almost no portion can be obtained in terms of the liquid crystal alignment characteristics.
More preferably, it has 8 to 16 carbon atoms.

R ¹ may be linear or branched. Examples of the linear alkyl group include n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, and n-butyl. -Dodecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-octadecyl, n-eicosyl and the like. Examples of the branched alkyl group include isobutyl, sec-butyl, tert-butyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-methylpentyl, 2-methylpentyl, Methylpentyl group, 4-methylpentyl group, 1-methylhexyl group, 2-methylhexyl group, 3
-Methylhexyl group, 4-methylhexyl group, 5-methylhexyl group, 1-methylheptyl group, 2-methylheptyl group, 3-methylheptyl group, 4-methylheptyl group, 5-methylheptyl group, 6-methyl Heptyl group, 1
-Methyloctyl group, 2-methyloctyl group, 3-methyloctyl group, 4-methyloctyl group, 5-methyloctyl group, 6-methyloctyl group, 7-methyloctyl group, 1-methylnonyl group, 2-methylnonyl group , 3-methylnonyl, 4-methylnonyl, 5-methylnonyl, 6-methylnonyl, 7-methylnonyl, 8-methylnonyl, 1-methyldecyl, 2-methyldecyl, 3-methyldecyl, 4-methyldecyl 5-methyldecyl group, 6-methyldecyl group, 7-methyldecyl group, 8-methyldecyl group, 9-methyldecyl group, 1-methyldodecyl group, 2-methyldodecyl group, 3-methyldodecyl group, 4-methyldodecyl group, 5 -Methyldecyl group,
6-methyldodecyl group, 7-methyldodecyl group, 8-methyldodecyl group, 9-methyldodecyl group, 10-methyldodecyl group, 11-methyldodecyl group, 1-methyltetradecyl group, 2-methyltetradecyl group, 3-methyldodecyl group Methyltetradecyl group, 4-methyltetradecyl group, 5-methyltetradecyl group, 6-methyltetradecyl group, 7-methyltetradecyl group, 8-methyltetradecyl group, 9-methyltetradecyl group, 10-methyl Tetradecyl group, 11-methyltetradecyl group, 12-methyltetradecyl group, 13-methyltetradecyl group, 1-methylhexadecyl group, 2-methylhexadecyl group, 3-methylhexadecyl group, 4-methylhexa Decyl group, 5-methylhexadecyl group, 6-
Methylhexadecyl group, 7-methylhexadecyl group, 8
-Methylhexadecyl group, 9-methylhexadecyl group,
10-methylhexadecyl group, 11-methylhexadecyl group, 12-methylhexadecyl group, 13-methylhexadecyl group, 14-methylhexadecyl group, 15-methylhexadecyl group, 1-methyloctadecyl group, 2- Methyloctadecyl group, 3-methyloctadecyl group, 4-methyloctadecyl group, 5-methyloctadecyl group, 6-methyloctadecyl group, 7-methyloctadecyl group, 8-methyloctadecyl group, 9-methyloctadecyl group, 10-methyloctadecyl Group, 11-methyloctadecyl group, 12-methyloctadecyl group, 13-methyloctadecyl group, 14-
Methyl octadecyl group, 15-methyl octadecyl group, 16
-Methyloctadecyl group and 17-methyloctadecyl group.

As the fluoroalkyl group, those in which one or more hydrogen atoms of the above alkyl group have been substituted with a fluorine atom can be used. Among these fluoroalkyl groups, particularly preferred ones are heptafluorobutyl group, nonafluoro-tert-butyl group, perfluorobutyl group, octafluoropentyl group, perfluoropentyl group, nonafluorohexyl group, and perfluorohexyl. Group, dodecafluoroheptyl group, tridecafluorohexyl group, perfluoroheptyl group, tridecafluorooctyl group, pentadecafluorooctyl group, perfluorooctyl group, hexafluorononyl group, perfluorononyl group, heptadecafluorodecyl group , Perfluorodecyl group, heneicofluorododecyl group, perfluorododecyl group, pentacosafluorotetradecyl group, perfluorotetradecyl group, perfluoropentadecyl group, perfluorohexadecyl group, Examples thereof include a perfluorooctadecyl group and a perfluoroeicosyl group.

For X in the general formulas (I) and (III), R ¹
X is a fluoroalkyl group, r represents 0 or 1. X when R ¹ is an alkyl group
Is And r represents 1.

In formulas (I), (II) and (V), R ² forming a tetracarboxylic acid structure is a tetravalent organic residue, preferably a tetravalent aromatic or aliphatic residue. Specific examples of the aromatic tetracarboxylic dianhydride that can be preferably used include aromatic mononuclear compounds such as pyromellitic acid, trifluoromethylpyromellitic acid, bis (trifluoromethyl) pyromellitic acid, and aromatic dinuclear compounds. 3,3'-4,4 '
-Tetracarboxydiphenyl ether, 2,3,3 ', 4'
-Tetracarboxydiphenyl ether, 3,3 ', 4,4'
-Benzophenonetetracarboxylic acid, 2,3,3 ', 4-benzophenonetetracarboxylic acid, 3,3', 4,4'-biphenyltetracarboxylic acid, 2,3,3 ', 4'-biphenyltetracarboxylic acid, 3,3 ', 4,4'-tetracarboxydiphenylmethane, 2,3,6,7-naphthalenetetracarboxylic acid,
4,5,8-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) propane, 2,2-bis (3,4- Dicarboxyphenyl) hexafluoropropane, 3,3 ', 4,4'-tetracarboxydiphenylsulfone, as aromatic tetranuclear
2,2-bis (4- (3,4-dicarboxyphenoxy) phenyl) propane, 2,2-bis (4- (3,4-dicarboxyphenoxy) phenyl) hexafluoropropane, 1,2,
7,8-tetracarboxyperylene and the like can be exemplified.

Specific examples of the tetracarboxylic acid dianhydride containing aliphatic residues R ^2, cyclobutane tetracarboxylic acid, cyclopentane tetracarboxylic acid, cyclohexane tetracarboxylic acid, 1,1,4,4-butane tetracarboxylic acid , 2,2,6,6
Heptanetetracarboxylic acid, dianhydrides such as 3,5,6-tricarboxy-2-carboxymethylnorbornane and 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2 -Dicarboxylic anhydride, bicyclo (2,2,2) -oct-7-ene, 2,3,5,6-
Examples thereof include tetracarboxylic acid.

R ³ in the general formulas (II) and (IV) is a divalent organic residue, preferably a divalent aromatic or aliphatic residue. Specific examples of the diamine compound of the general formula (IV) in which R ³ is a divalent aromatic residue include p-aromatic mononuclear compounds.
Phenylenediamine, m-phenylenediamine, o-phenylenediamine, 2,4-diaminotoluene, 4,6-dimethyl-m-phenylenediamine, 2,4-diaminomesitylene, 4-chloro-m-phenylenediamine, 4-fluoro -M-phenylenediamine, tetrafluoro-p-
Phenylenediamine, tetrafluoro-m-phenylenediamine, tetrafluoro-o-phenylenediamine,
2-nitro-p-phenylenediamine, benzidine as an aromatic binuclear, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4 , 4'-Diaminodiphenylmethane, 3,4'-
Diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,4 '
-Diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3, 3'-diaminobenzophenone, 2,2-bis (4-
Aminophenyl) propane, 2,2-bis (3-aminophenyl) propane, 2,2-bis (4-aminophenyl)
Hexafluoropropane, 2,2-bis (3-aminophenyl) hexafluoropropane, 1,5-diaminonaphthalene, 2,6-diaminaphthalene, 3,3′-dimethylbenzidine, 3,3′-dimethoxybenzidine, 3,3'-dimethyl-4,4'-diaminophenyl ether, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 1,4-bis (4-aminophenoxy) benzene as an aromatic nucleus, 1,3
-Bis (4-aminophenoxy) benze, 1,3-bis (3-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, 4,4'-bis (4-aminophenoxy) diphenylsulfone, 4,4'-bis (3-aminophenoxy) diphenylsulfone, 3,4-bis (4-aminophenoxy)
Diphenylsulfone, 3,4'-bis (3-aminophenoxy) diphenylsulfone, 3,3'-bis (4-aminophenoxy) diphenylsulfone, 3,3'-bis (3-
Aminophenoxy) diphenylsulfone, 2,2-bis (4- (4-aminophenoxy) phenyl) propane,
2,2-bis (4- (3-aminophenoxy) phenyl)
Propane, 2,2-bis (4- (2-aminophenoxy)
Phenyl) propane, 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane, 22-bis (4- (3-aminophenoxy) phenyl) hexafluoropropane, 2,2-bis (4- (2-aminophenoxy) phenyl) hexafluoropropane and the like.

Specific examples of the diamine compound of the general formula (IV) in which R ³ is an aliphatic group include 1,4-diaminobutane, 1,6-diaminohexane, 1,8-diaminooctane, and 1,12-diaminododecane , 1,4-diaminocyclohexane, bis (4-
Aminocyclohexyl) methane, bis (4-amino-2)
-Methylcyclohexyl) methane, bis (4-amino-
3-methylcyclohexyl) methane, 1,3-bis (3-
Aminopropyl) tetramethyldisiloxane and the like. A diamine compound in which R ³ is an aromatic aliphatic residue can also be preferably used, and specific examples of such a compound include p-xylylenediamine, m-metaxylylenediamine and the like.

The above-mentioned polyamic acid or polyimide solution is applied to a liquid crystal display element substrate, that is, a transparent electrode substrate, using a polymer concentration of 0.01 to 40% by weight, preferably 0.1 to 20% by weight, using a printing method, a spinner method, It can be performed by a technique such as a dip method or a spray method. The solvent used is
There is no particular limitation as long as it dissolves the polyamic acid or polyimide, but specific examples of preferably usable solvents include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, γ -Butyrolactone and the like. These can be used alone or in combination with other solvents. In particular, methyl cellosolve and butyl cellosolve,
By mixing an appropriate amount of a poor solvent for polyimide such as ethyl carbitol or ethyl cellose acetate with the above solvent, the applicability of the polyimide precursor solution to the glass substrate may be significantly improved.

By applying the polyamic acid solution to the substrate and then heating at 100 ° C. to 400 ° C., preferably 200 ° C. to 300 ° C., a corresponding polyimide film is obtained. By subjecting this to a rubbing treatment by a method known to those skilled in the art, a liquid crystal alignment film capable of aligning liquid crystal molecules with a stable pretilt angle is obtained. A similar heat treatment is performed when a polyimide solution partially or completely imide-closed is used, but in this case, a polyimide film can be obtained at a lower temperature, that is, 150 ° C. to 250 ° C.

The structure of the liquid crystal display device of the present invention is not particularly limited, and a known structure can be used. In general, a segment electrode made of a transparent conductive film such as an indium oxide or tin oxide film is provided on two glass or film substrates, and a liquid crystal alignment film is formed thereon by a conventional method, and the liquid crystal is sandwiched with these materials. A structure in which a portion is sealed with a sealant and a polarizing plate is disposed on both sides thereof can also be used.

The liquid crystal alignment film of the present invention is effectively used for a display element such as a liquid crystal display element, but is also effectively used for an optical element such as an optical shutter and a wavelength converter using a nonlinear optical effect in addition to the display element. It can be used.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

 The measurement of the pretilt angle in the embodiment is based on the magnetic field capacity null method.
(T.J.Sheffer et al., J. Appl.Phys.48
(5), 1783- (1977)).

Example 1 3.94 g (0.0197 mol) of 4,4-diaminodiphenyl ether and 4- (1H, 1H, 2H, 2H-perfluorodecyloxy)
1.25 g (0.0022 mol) of 1,3-diaminobenzene was dissolved in 89.78 g of N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) and cooled in an ice water bath. To this, 4.78 g (0.0219 mol) of pyromellitic dianhydride was added little by little. The mixture was stirred for 1 hour in an ice-water bath and then for 2 hours at room temperature to obtain a 10% by weight NMP solution of polyamic acid. The obtained polyamic acid solution was cast on a glass plate to form a coating, and this was heated at 100 ° C. for 1 hour and then at 250 ° C. for 3 hours to imidize it, thereby producing a polyimide film. As a result of measuring an IR spectrum of this film, absorption by the imide ring in 1780 and 720 cm ^-1, C to 1260-1200Cm ^-1
Absorption by a -F bond was observed.

The composition of the polyamic acid solution obtained as described above has a composition ratio m / n of the repeating unit represented by the general formula (I) and the repeating unit represented by the general formula (II) of 10 /.
Equivalent to 90.

Then, this solution was diluted with a mixed solvent of NMP and butyl cellosolve (hereinafter abbreviated as BC) so as to become a 3% by weight solution. The ratio of NMP to BC in the diluted solution is by weight.
7: 3. This solution was applied to a glass substrate (30 mm × 33 mm) on which a transparent electrode made of an indium tin oxide film (so-called ITO film) was formed using a spinner. Thereafter, a heat treatment was carried out at 80 ° C. for 15 minutes and then at 250 ° C. for 1 hour to form a polyimide film. The coating was then rubbed with a nylon cloth. A rubbing machine RM-300H manufactured by EHC was used for the rubbing treatment. The rotation speed of the rubbing roller was 800 rpm, and the moving speed of the substrate was 100 mm / sec. After that, the cell was assembled so that the rubbing direction was antiparallel with the 8 μm spacer interposed, and the liquid crystal (ZLI-2293, Merck
(Manufactured by the company) was injected to produce a liquid crystal display device. When the pretilt angle of this device was measured, it was 5.1 ° and the orientation state was good.

Further, the liquid crystal display element was heated at 100 ° C. for 1 hour, allowed to cool to room temperature, and the pretild angle was measured again.
At 5.1 °, there was no change from before the heat treatment, and no disturbance in the orientation occurred.

Example 2 A rubbing treatment was performed in exactly the same manner as in Example 1 except that a polyimide film was formed on a glass substrate and the moving speed of the substrate was changed to 20 mm per second, and the cell was assembled in exactly the same manner as in Example 1. However, the pretilt angle did not change at 5.1 °,
The orientation was also good. The rubbing strength at this time is approximately five times that of the first embodiment. When the same heat treatment as in Example 1 was performed, the pretilt angle was 5.1 °, and no disorder in the orientation occurred.

From this result, it was confirmed that the polyimide in this example gave a very stable tilt orientation.

Example 3 0.0197 mol of 4,4'-diaminodiphenyl ether was added to 0.0
The polyamic acid solution was prepared in the same manner as in Example 1 except that 0.0022 mol of 4- (1H, 1H, 2H, 2H-perfluorodecyloxy) -1,3-diaminobenzene was changed to 0.0044 mol. It was adjusted. The composition ratio m / n of the repeating unit is 20/80. Using this solution, a liquid crystal display device similar to that of Example 1 was produced. The pretilt angle was 7.0 ° and the liquid crystal alignment was good.

Example 4 N, N-dimethylacetamide (hereinafter abbreviated as DMAC)
As a solvent, pyromellitic dianhydride 0.0119 mol, 4,
4'-diaminodiphenyl ether, 0.0107 mol and 4- (1H, 1H, 2H, 2H-perfluorodecyloxy) -1,3-
0.0012 mol of diaminobenzene was stirred at 0 ° C. for 1 hour and then at room temperature for 2 hours to obtain a 10% by weight DMCA solution of polyamic acid. The composition ratio m / n of the repeating unit is 10/90. This solution was diluted to 3% by weight with DMAC and BC. The weight ratio of DMAC to BC after dilution was 7: 3. afterwards,
A liquid crystal display device was manufactured in the same manner as in Example 1, and the measured tilt angle was 48 °.

Example 5 3.94 g (0.0197 mol) of 4,4'-diaminodiphenyl ether and 4-hexadecyloxy-1,3-diaminobenzene
0.76 g (0.0022 mol) was dissolved in 85 g of MMP and cooled in an ice-water bath. Add 4.78 g (0.0219 g) of pyromellitic dianhydride
Mol) was added in small portions. Stir in an ice water bath for 1 hour and then at room temperature for 2 hours.
A P solution was obtained.

This polyamic acid solution was treated in the same manner as in Example 1 to produce a liquid crystal display device. As a result, the pretilt angle was 6.0 ° and the orientation was good.

Example 6: 0.02 mol of pyromellitic dianhydride, 0.0152 mol of 3,3'-diaminodiphenyl ether, 4- (1H, 1H, 2H, 2H-
Perfluorodecyloxy) -1,3-diaminobenzene 0.0
04 mol and 0.0008 mol of 1,3-bis (3-aminopropyl) tetramethyldisiloxane in an NMP solvent at room temperature
After reacting for a time, a 15% by weight solution of polyamide was obtained. The composition ratio m / n of the polymerization repeating unit is 20/80. This solution
After dilution with NMP and BC to 7.5% by weight (NMP: BC = 7: 3), it was applied by a printing method to a glass substrate (30 mm × 33 mm) on which a transparent conductive film was formed. Thereafter, a liquid crystal display device was prepared in the same manner as in Example 1, and the pretilt angle was measured.

Example 7 Pyromellitic dianhydride 0.1 mol, 2,2-bis (4-
(4-aminophenoxy) phenylpropane 0.076 mol), 4- (1H, 1H, 2H, 2H-perfluorodecyloxy)
0.02 mol of 1,3-diaminobenzene and 1,3-bis (3
A polyamic acid solution was prepared by reacting 0.004 mol of (-aminopropyl) tetramethyldisiloxane in an NMP solvent at 40 ° C for 3 hours. The composition ratio m / n of the polymerization repeating unit is 20 /
80. This solution was diluted to 7.5% by weight with NMP and BC (NMP:
(BC = 7: 3), and then applied to a glass substrate (30 mm × 33 mm) on which a transparent conductive film was formed by a printing method. Hereinafter, in the same manner as in Example 2, a liquid crystal display element was manufactured, and the pretilt angle was measured. When this liquid crystal display element was heated to 100 ° C. and then cooled to room temperature, the pretilt angle was 7.0 ° and the liquid crystal alignment state was good.

Example 8 0.02-mol of 2,2-bis (4- (4-aminophenoxy) phenylpropane is 0.05 mol, and 4- (1H, 1H, 2H, 2H-perfluorodecyloxy) -1,3-diaminobenzene is 0.02 mol.
A polyamic acid solution was prepared in exactly the same manner as in Example 7, except that the mole was changed to 0.05 mole. The composition ratio m / n of the polymerization repeating unit is 50/50. Thereafter, the same processing as in Example 7 was performed to produce a liquid crystal display element, and the pretilt angle was measured.
It was 11 ゜.

Comparative Example 1 Using NMP as a solvent, 0.0219 mol of pyromellitic dianhydride and 0.0219 mol of 4,4′-diaminodiphenyl ether were stirred at 0 ° C. for 1 hour and then at room temperature for 2 hours to obtain 10% by weight of the obtained polyamic acid. An NMP solution was prepared. When the pretilt angle was measured, it was almost 0 °.

Example 9 4- (1H, 1H, 2H, 2H-perfluorodecyloxy) -1,3
A polyamic acid solution was prepared in the same manner as in Example 1 except that 0.0022 mol of diaminobenzene was changed to 0.0022 mol of N-hexadecyloxy-3,5-diaminobenzamide.
Using this solution, a crystal display element similar to that of Example 1 or Example 2 was produced, and the pretilt angle was measured. As a result, the pretilt angle was 4.9 ° when the moving speed of the substrate was 100 mm / sec, and 4.9 ° when the moving speed of the substrate was 20 mm / sec. The liquid crystal orientation was good in each case, and the pretilt angle was not affected by the rubbing strength.

Comparative Example 2 4- (1H, 1H, 2H, 2H-perfluorodecyloxy) -1,3
0.0022 mol of diaminobenzene is added to 1,3-diamino-4-
Except that it was changed to 0.0022 mol of hexadecyloxybenzene,
A polyamic acid solution was prepared in the same manner as in Example 1, and a liquid crystal display device similar to that in Examples 1 and 2 was prepared using this solution, and the pretilt angle was measured. As a result, the difference between the pretilt angles when the moving speed of the substrate was 100 mm / sec and 20 mm / sec was 1.0 °.

Comparative Example 3 4- (1H, 1H, 2H, 2H-perfluorodecyloxy) -1,3
A polyamic acid solution was prepared in the same manner as in Example 1 except that 0.0022 mol of -diaminobenzene was changed to 0.0022 mol of hexadecyl 3,5-diaminobenzoate, and the same procedure as in Examples 1 and 2 was performed using this solution. As a result, a display element was prepared, and the pretilt angle was measured. As a result, the difference between the pretilt angles when the moving speed of the substrate was 100 mm / sec and 20 mm / sec was 1.2 °.

Comparative Example 4 4- (1H, 1H, 2H, 2H-perfluorodecyloxy) 1,3-
A polyamic acid solution was prepared in the same manner as in Example 1 except that 0.0022 mol of diaminobenzene was changed to 0.0022 mol of 3.5-diaminophenylhexadecyl ketone, and a liquid crystal similar to that of Examples 1 and 2 was prepared using this solution. A display element was manufactured, and a pretilt angle was measured. As a result, the difference between the pretilt angles when the moving speed of the substrate was 100 mm / sec and 20 mm / sec was 1.2 °.

Comparative Example 5 4- (1H, 1H, 2H, 2H-perfluorodecyloxy) -1,3
0.0022 mol of diaminobenzene to 1,3-diamino-5
A polyamic acid solution was prepared in the same manner as in Example 1 except that the hexadecylbenzene was changed to 0.0022 mol, and a crystal display element similar to that in Examples 1 and 2 was prepared using this solution, and the pretilt angle was adjusted. It was measured. As a result, the difference between the pretilt angles when the moving speed of the substrate was 100 mm / sec and 20 mm / sec was 1.5 °.

[Effect of the Invention] In the present invention, since the liquid crystal alignment film is made of a specific polyimide, it is possible to obtain a stable tilted alignment having a large pretilt angle without using a special device. This allows
It is possible to economically fabricate a liquid crystal display device that requires tilted alignment of liquid crystal molecules as in the STN mode.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-312332 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1/1339-1/1337 530

Claims (7)

(57) [Claims] 1. A liquid crystal alignment film formed of a polyimide containing a repeating unit represented by the following general formula (I) and a repeating unit represented by the following general formula (II) as a main component. In the formulas (I) and (II), R ¹ represents an alkyl group having 4 to 20 carbon atoms or a fluoroalkyl group. When R ¹ is a fluoroalkyl group, X at that time r represents 0 or 1. When R ¹ is an alkyl group,
X at that time And r represents 1, R ² represents a tetravalent organic residue, and R ³ represents a divalent organic residue. The m / n ratio is between 1/99 and 80/20. 2. The liquid crystal alignment film according to claim 1, wherein R ¹ in the general formula (I) is a fluoroalkyl group having 4 to 20 carbon atoms. 3. The liquid crystal alignment film according to claim 1, wherein R ² in the general formula (I) is a tetravalent aromatic residue and / or a tetravalent aliphatic residue. 4. The liquid crystal according to claim 1, wherein the ratio m / n of the repeating unit represented by the general formula (I) to the repeating unit represented by the general formula (II) is 5/95 to 50/50. Alignment film. 5. A liquid crystal display device comprising: a liquid crystal alignment film provided on a surface of a pair of parallel transparent electrode substrates sandwiching a liquid crystal; and rubbing the surface of the liquid crystal alignment film in a predetermined direction. A liquid crystal display device comprising, as a film, a polyimide containing, as a main component, a repeating unit represented by the following general formula (I) and a repeating unit represented by the following general formula (II). In the formulas (I) and (II), R ¹ represents an alkyl group having 4 to 20 carbon atoms or a fluoroalkyl group. When R ¹ is a fluoroalkyl group, X at that time r represents 0 or 1. When R ¹ is an alkyl group,
X at that time And r represents 1. R ² represents a tetravalent organic residue, and R ³ represents a divalent organic residue. The m / n ratio is between 1/99 and 80/20. 6. The liquid crystal display device according to claim 5, wherein R ¹ in the general formula (I) is a fluoroalkyl group having 4 to 20 carbon atoms. 7. The liquid crystal according to claim 5, wherein the ratio m / n of the repeating unit represented by the general formula (I) to the repeating unit represented by the general formula (II) is 5/95 to 50/50. Display element.