JP3252564B2 - Liquid crystal alignment film and liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal alignment film having a polybenzylimide skeleton and a liquid crystal display device provided with the liquid crystal alignment film.

[0002]

2. Description of the Related Art A liquid crystal display element used in a timepiece or a calculator includes a twisted nematic (twisted nematic) structure in which the arrangement direction of nematic liquid crystal molecules is twisted by 90 degrees between a pair of upper and lower electrode substrates. Hereinafter, abbreviated as TN.) Mode is mainly adopted. In addition, a super twisted nematic (hereinafter abbreviated as STN) mode in which the twist angle is increased to 180 to 300 degrees has been developed, and a liquid crystal display element having good display quality even on a large screen can be obtained. Furthermore, in recent years, matrix display, color display, and the like have been performed, so that an MIM (metal-insulating phase-metal) employing an active twisted nematic mode capable of performing ON / OFF of a large number of pixel electrodes. ) Element, TF
The development of T (field-effect thin film transistor) devices has become active.

A problem common to all of these modes is that when the same screen is displayed for a long time and then shifted to another screen, a phenomenon in which the previous image remains as an afterimage occurs. In particular, in order to obtain a high quality liquid crystal display device, it is very important to improve this afterimage phenomenon. The cause of the afterimage phenomenon is caused by the DC component applied to the liquid crystal display element.
It is considered that the electric double layer is generated due to the ionic component of the impurities contained in the liquid crystal on the surface of the alignment film, and the electric charge is biased between the upper and lower substrates, and the difference is considered to be caused by the potential difference caused by keeping the bias stable. . In particular, in the case of a TFT element, the DC component cannot be removed due to the characteristics of the element.
The afterimage phenomenon is more noticeable and more serious than TN and STN. In the TFT mode, a high voltage holding ratio is required to prevent the screen from flickering.

As an alignment film used in such a liquid crystal display device, an organic film such as polyimide or polyamide is mainly used.

[0005]

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There is disclosed a liquid crystal display device provided with a liquid crystal alignment film using a polyimide resin having a repeating unit represented by the following formula. However, in an element provided with a polyimide alignment film obtained using such a polyether compound, an afterimage phenomenon is likely to occur.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide a liquid crystal alignment film and a liquid crystal display device which have no afterimage phenomenon and have excellent voltage holding ratio. .

[0008]

Means for Solving the Problems As a result of intensive research and development, the present inventors have confirmed that the afterimage phenomenon has a correlation with the polarity of the alignment film surface. By using a diamino compound having a specific structure with a small polarity for the polymer used as the alignment film, it is found that a liquid crystal alignment film and a liquid crystal display element having no voltage lag and excellent voltage holding ratio can be obtained. The present invention has been completed.

The content of the present invention will be described in more detail.

[0010]

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A liquid crystal alignment film comprising, as a main component, a polymer having a skeleton represented by the following formula:

2) General formula

[0013]

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A liquid crystal alignment film mainly composed of polyimide having a structural unit represented by the following formula:

3) A polyamic acid obtained by reacting a tetracarboxylic dianhydride represented by the following formula (3) with a diamino compound represented by the following formula (4) in a solvent, and heating the resulting polyamic acid. Item 2. The liquid crystal alignment film according to item 2), which mainly comprises polyimide.

[0016]

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4) A liquid crystal display device comprising the liquid crystal alignment film according to any one of the items 1) to 3).

The diamino compound used in the liquid crystal alignment film of the present invention, -O -, - SO ₂ - of such polar atoms has no reduce relatively the ratio of imide groups by increasing the molecular weight of the amine , The proportion of the polar component is made as small as possible. For example, 1,1-bis [4
-(4-aminobenzyl) phenyl] cyclohexane,
1,1-bis [4- (4-aminobenzyl) phenyl]
-4-methylcyclohexane, 1,1-bis [4- (4
-Aminobenzyl) phenyl] -4-ethylcyclohexane, 1,1-bis [4- (4-aminobenzyl) phenyl] -4-propylcyclohexane, 1,1-bis [4- (4-aminobenzyl) phenyl] -4-butylcyclohexane, 1,1-bis [4- (4-aminobenzyl) phenyl] -4-pentylcyclohexane,
1-bis [4- (4-aminobenzyl) phenyl] -4
-Hexylcyclohexane, 1,1-bis [4- (4-
Aminobenzyl) phenyl] -4-heptylcyclohexane, 1,1-bis [4- (4-aminobenzyl) phenyl] -4-octylcyclohexane,

1,1-bis [4- (4-amino-3-methylbenzyl) phenyl] -4-methylcyclohexane, 1,1-bis [4- (4-amino-3-methylbenzyl) phenyl]- 4-ethylcyclohexane, 1,1
-Bis [4- (4-amino-3-methylbenzyl) phenyl] -4-propylcyclohexane, 1,1-bis [4- (4-amino-3-methylbenzyl) phenyl]
-4-butylcyclohexane, 1,1-bis [4- (4
-Amino-3-methylbenzyl) phenyl] -4-pentylcyclohexane, 1,1-bis [4- (4-amino-3-methylbenzyl) phenyl] -4-hexylcyclohexane, 1,1-bis [4- (4-amino-3-methylbenzyl) phenyl] -4-heptylcyclohexane, 1,1-bis [4- (4-amino-3-methylbenzyl) phenyl] -4-octylcyclohexane,

1,1-bis [4- (4-aminobenzyl) -3-methylphenyl] -4-methylcyclohexane, 1,1-bis [4- (4-aminobenzyl) -3-
Methylphenyl] -4-ethylcyclohexane, 1,1
-Bis [4- (4-aminobenzyl) -3-methylphenyl] -4-propylcyclohexane, 1,1-bis [4- (4-aminobenzyl) -3-methylphenyl]
-4-butylcyclohexane, 1,1-bis [4- (4
-Aminobenzyl) -3-methylphenyl] -4-pentylcyclohexane, 1,1-bis [4- (4-aminobenzyl) -3-methylphenyl] -4-hexylcyclohexane, 1,1-bis [4- (4-aminobenzyl) -3-methylphenyl] -4-heptylcyclohexane, 1,1-bis [4- (4-aminobenzyl) -3
-Methylphenyl] -4-octylcyclohexane,

1,1-bis [4- (4-aminobenzyl) -2-methylphenyl] -4-methylcyclohexane, 1,1-bis [4- (4-aminobenzyl) -2-
Methylphenyl] -4-ethylcyclohexane, 1,1
-Bis [4- (4-aminobenzyl) -2-methylphenyl] -4-propylcyclohexane, 1,1-bis [4- (4-aminobenzyl) -2-methylphenyl]
-4-butylcyclohexane, 1,1-bis [4- (4
-Aminobenzyl) -2-methylphenyl] -4-pentylcyclohexane, 1,1-bis [4- (4-aminobenzyl) -2-methylphenyl] -4-hexylcyclohexane, 1,1-bis [4- (4-aminobenzyl) -2-methylphenyl] -4-heptylcyclohexane, 1,1-bis [4- (4-aminobenzyl) -2
-Methylphenyl] -4-octylcyclohexane,

1,1-bis [4- (4-amino-3-methylbenzyl) phenyl] cyclohexane, 1,1-bis [4- (4-amino-3-ethylbenzyl) phenyl] cyclohexane, 1,1 -Bis [4- (4-amino-3-propylbenzyl) phenyl] cyclohexane,
1,1-bis [4- (4-amino-3-fluorobenzyl) phenyl] cyclohexane, 1,1-bis [4-
(4-aminobenzyl) -3-methylphenyl] cyclohexane, 1,1-bis [4- (4-aminobenzyl)
-3-Ethylphenyl] cyclohexane, 1,1-bis [4- (4-aminobenzyl) -3-propylphenyl] cyclohexane, 1,1-bis [4- (4-aminobenzyl) -3-fluorophenyl] Cyclohexane,

1,1-bis [4- (4-amino-3-ethylbenzyl) phenyl] -4-methylcyclohexane, 1,1-bis [4- (4-amino-3-propylbenzyl) phenyl]- 4-methylcyclohexane, 1,
1-bis [4- (4-amino-3-fluorobenzyl)
Phenyl] -4-methylcyclohexane,

1,1-bis [4- (4-aminobenzyl) -3-ethylphenyl] -4-methylcyclohexane, 1,1-bis [4- (4-aminobenzyl) -3-
Propylphenyl] -4-methylcyclohexane, 1,
1-bis [4- (4-aminobenzyl) -3-fluorophenyl] -4-methylcyclohexane,

1,1-bis [4- (4-amino-3-ethylbenzyl) phenyl] -4-ethylcyclohexane, 1,1-bis [4- (4-amino-3-propylbenzyl) phenyl]- 4-ethylcyclohexane, 1,
1-bis [4- (4-amino-3-fluorobenzyl)
Phenyl] -4-ethylcyclohexane,

1,1-bis [4- (4-aminobenzyl) -3-ethylphenyl] -4-ethylcyclohexane, 1,1-bis [4- (4-aminobenzyl) -3-
Propylphenyl] -4-ethylcyclohexane, 1,
1-bis [4- (4-aminobenzyl) -3-fluorophenyl] -4-ethylcyclohexane,

1,1-bis [4- (4-amino-3-ethylbenzyl) phenyl] -4-propylcyclohexane, 1,1-bis [4- (4-amino-3-propylbenzyl) phenyl]- 4-propylcyclohexane,
1,1-bis [4- (4-amino-3-fluorobenzyl) phenyl] -4-propylcyclohexane,

1,1-bis [4- (4-aminobenzyl) -3-ethylphenyl] -4-propylcyclohexane, 1,1-bis [4- (4-aminobenzyl) -3
-Propylphenyl] -4-propylcyclohexane,
1,1-bis [4- (4-aminobenzyl) -3-fluorophenyl] -4-propylcyclohexane, and the like.

As the tetracarboxylic dianhydride used in the liquid crystal alignment film of the present invention, any of aromatic, aliphatic, and composite systems having both aromatic and aliphatic properties may be used. Although not particularly limited, to illustrate specific names, pyromellitic dianhydride, 3, 3 ', 4, 4'-biphenyltetracarboxylic dianhydride, 2, 2', 3, 3'- Biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 2,3,3 ′ , 4'-benzophenonetetracarboxylic dianhydride, 2,2 ', 3,3'-benzophenonetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4 Dicarboxyphenyl) sulfone dianhydride, 1,2,5,6 naphthalenetetracarboxylic dianhydride, 2,3,6,7 naphthalenetetracarboxylic dianhydride, bis (dicarboxyphenyl) methane dianhydride Anhydride, cyclobutanetetracarboxylic dianhydride, cyclopentane Tetracarboxylic dianhydride, cyclohexanetetracarboxylic dianhydride, dicyclohexanetetracarboxylic dianhydride, dicyclopentanetetracarboxylic dianhydride, bis (dicarboxycyclohexyl) ether dianhydride, bis (dicarboxy Cyclohexyl) sulfone dianhydride, bis (dicarboxycyclohexyl) methane dianhydride,

[0030]

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And the like. Some of these compounds contain isomers, but a mixture of these isomers may be used. Further, it is not necessary to limit the tetracarboxylic dianhydride used in the present invention to the above exemplified compounds.

When an aminosilicon compound or a diaminosilicon compound is used for the liquid crystal alignment film of the present invention, the adhesion between the alignment film and the substrate can be improved. As the aminosilicon compound, specifically, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane,
Aminopropyltris (2-methoxyethoxy) silane, 2-aminoethyltrimethoxysilane, 2-aminoethyltriethoxysilane, 2-aminoethylmethyldimethoxysilane, 2-aminoethylmethyldiethoxysilane, 4-aminobutyltrimethoxy Silane, 4-aminophenyltrimethoxysilane, 4-aminophenyltriethoxysilane, 4-aminophenylmethyldimethoxysilane, 4-aminophenylmethyldiethoxysilane, 4-aminophenyltris (2-methoxyethoxy) silane, 3- (4-aminophenyl) propyltrimethoxysilane, 3- (4-aminophenyl) propyltriethoxysilane, 3-aminophenyltrimethoxysilane, 3-aminophenyltriethoxysilane, 3-
(4-aminophenyl) propylmethyldimethoxysilane, 3- (4-aminophenyl) propylmethyldiethoxysilane, 3-aminophenylmethyldimethoxysilane, and 3-aminophenylmethyldiethoxysilane. When these aminosilicon compounds are introduced into a polyimide-based polymer, the content thereof is preferably not more than 50 mol%, preferably not more than 30 mol%, based on the polyimide raw material.

Further, as the diaminosilicon compound,

[0034]

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The following can be mentioned. When a diaminosilicon compound is introduced into a polyimide-based polymer, its content is preferably not more than 50 mol%, and preferably not more than 30 mol%, of the diamino compound as a polyimide raw material.

In order to provide the liquid crystal alignment film of the present invention on a substrate, a polyamic acid obtained by condensation of a tetracarboxylic dianhydride, which is a precursor of polyimide, with a diamino compound is applied to the substrate, followed by heat treatment. And forming a polyimide polymer film on the substrate by dehydration reaction. Specifically, the polyamic acid is dissolved in a solvent such as N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide (DMSO), butyl cellosolve, ethyl carbitol, The solution is adjusted to a 0.1 to 30% by weight solution, preferably 1 to 10% by weight, and this solution is applied on a substrate by a brush coating method, a dipping method, a spin coating method, a spraying method, a printing method, etc. Is formed. After coating, 50-150 ° C, preferably 80-120
After evaporating the solvent at a temperature of 150 ° C., a heat treatment is performed at a temperature of 150 ° C. to 400 ° C., preferably 180 ° C. to 280 ° C., and a dehydration ring closure reaction is performed to provide a polybenzylimide polymer film.
If the surface of the substrate is treated with a silane coupling agent before coating, and a polymer film is formed thereon, the adhesiveness between the polymer film and the substrate can be improved. Thereafter, the coated surface is rubbed in one direction with a cloth or the like to obtain a liquid crystal alignment film.

The substrate used as a liquid crystal display element is usually
An electrode, specifically, a transparent electrode made of ITO (indium oxide-tin oxide) or tin oxide is formed on a substrate. Further, between this electrode and the substrate, alkali elution from the substrate is prevented. Insulating film, color filter,
An undercoat film such as a color filter overcoat may be provided, and an overcoat film such as an insulating film and a color filter film may be provided on the electrode. The configuration of the conventional liquid crystal display element can be used for these electrodes, the undercoat, and other configurations in the liquid crystal cell.

Using the substrate thus formed, cells are formed, liquid crystal is injected, and the injection port is sealed to produce a liquid crystal display device. Alternatively, a liquid crystal display element may be manufactured by spraying liquid crystal on a substrate, then superposing the substrates, and sealing the liquid crystal so that the liquid crystal does not leak. As the liquid crystal to be enclosed, various liquid crystals such as a normal nematic liquid crystal and a liquid crystal to which a dichroic dye is added can be used. The liquid crystal display element of the present invention is characterized in that it has an alignment control film with little afterimage phenomenon, has a high voltage holding ratio, has good liquid crystal orientation, and has a high pretilt as high as polyetherimide-based polyimide. Has horns.

[0039]

EXAMPLES In the following application examples and application comparative examples, the degree of the afterimage phenomenon was measured by the CV curve method. The CV curve method uses a liquid crystal cell with 25 mV and 1 kHz.
Is applied, and a DC triangular wave having a frequency of 0.0036 Hz (hereinafter referred to as DC voltage) is weighed.
In this method, the capacitance C that changes by sweeping the C voltage in the range of -10 V to 10 V is recorded. When the DC voltage is swept to the positive side (0 → 10V), the capacitance increases. Next, when the voltage is swept to the negative side (10 → 0 V), the capacitance becomes small. When the voltage is swept from 0 to the negative side (0 → −10 V), the capacitance increases again, and when the voltage is swept to the positive side (−10 → 0 V), the capacitance also decreases. The waveform after repeating this for several cycles is as shown in FIG. When the bias of the charge is generated on the surface of the liquid crystal alignment film and the bias is stabilized, a hysteresis curve is drawn on both the positive side and the negative side of the voltage. For the residual charge, two tangent lines are drawn on the CV curve on both the positive side and the negative side, and the intersections (α _{1 to} α ₄ ) of these with the capacitance (C ₀ ) when the DC voltage is 0 are obtained. , The positive side is | α ₁ −α ₂ |, and the negative side is | α ₃ −α ₄ |. Then, the average voltage difference between them, ie, (| α ₁ −α ₂₎ | + | Α ₃ −
α ₄ |) / 2. This value is, if the thickness of the liquid crystal cell and the thickness of the alignment film are the same,
This is a parameter for stabilizing the charge bias. That is, the use of an alignment film having a small residual charge can reduce the afterimage phenomenon.

The voltage holding ratio was measured by a circuit as shown in FIG. The measuring method is as follows: gate pulse width 69 μs, frequency 60
The drain (V _D ) changed by applying a rectangular wave (V _S ) having a pulse height of 4.5 Hz to the source was read from an oscilloscope. For example, when a positive square wave is applied to the source, the drain (V _D ) shows a positive value until the next negative square wave is applied. if,
When the retention is 100%, V _D shown in FIG. 3 takes a rectangular trajectory represented by a dotted line, but usually V _D takes a solid trajectory gradually approaching zero. Therefore, the measured area of the orbit (the area surrounded by V = 0 and the orbit), that is, the hatched portion was calculated, and this was performed four times to obtain the average value. The area where the voltage did not decrease at all was defined as 100%, and the relative value of the measured area was defined as the voltage holding ratio (%). The measurement of the pretilt angle was performed using a crystal rotation method.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Example 1 50 g of dehydrated and purified N-methyl-2-pyrrolidone was added to a 200 ml four-necked flask equipped with a stirrer, a thermometer, a condenser and a nitrogen purging apparatus, and then 1,1-bis [4-
(4-aminobenzyl) phenyl] cyclohexane7.
43 g was charged and dissolved by stirring. This was cooled to 13 ° C., and 3.69 g of pyromellitic dianhydride was added all at once, and a stirring reaction was performed while cooling. One hour later, 0.11 g of para-aminophenyltrimethoxysilane was added, and the mixture was stirred and reacted at 20 ° C. for 1 hour. Thereafter, the reaction solution was treated with N-methyl-2-
By diluting with 51.1 g of pyrrolidone (NMP), a clear solution of 10% by weight of polyamic acid was obtained. The viscosity of this solution at 25 ° C. was 1870 centipoise. A 1: 1 mixed solution of butyl cellosolve and NMP was added to the solution to dilute it to 3% by weight.
Coating was performed on a transparent glass substrate provided with electrodes by a spin coating method (spinner method). The rotation conditions were 5000 rpm and 15 seconds. After the coating was dried at 100 ° C. for 10 minutes, the temperature was raised to 200 ° C. in an oven for 1 hour, and heat treatment was performed at 200 ° C. for 90 minutes to obtain a film thickness of about 600 Å polybenzylimide. The coating surfaces of the two substrates on which the polybenzylimide film was formed were each subjected to a rubbing treatment to form a liquid crystal alignment film, and a liquid crystal cell having a cell thickness of 6 microns was assembled so that the rubbing directions were parallel and opposed to each other. The liquid crystal FB01 for TFT manufactured was enclosed. After the encapsulation, an isotropic treatment was performed at 120 ° C. for 30 minutes, and the resultant was gradually cooled to room temperature to obtain a liquid crystal element. For the measurement of the pretilt angle, a liquid crystal cell having a cell thickness of 20 μm and containing a liquid crystal ZLI-1132 manufactured by Merck was prepared in the same manner. The orientation of the liquid crystal element was good, and the pretilt angle of the liquid crystal measured by the crystal rotation method was 7.
3 degrees. Also, the residual charge of this cell was 0.2 at 25 ° C.
06V, the retention was 97.4%.

Example 2 50 g of dehydrated and purified N-methyl-2-pyrrolidone was added to a 200 ml four-necked flask equipped with a stirrer, a thermometer, a condenser and a nitrogen purge device, and then 1,1-bis [4-
(4-aminobenzyl) phenyl] cyclohexane7.
43 g was charged and dissolved by stirring. This was cooled to 13 ° C. and methylcyclobutanetetracarboxylic dianhydride 3.68 was obtained.
g at a time and agitation reaction was performed while cooling. One hour later, p-aminophenyltrimethoxysilane 0.33
g was added and the mixture was stirred and reacted at 20 ° C. for 1 hour. Thereafter, the reaction solution was treated with 53.0 g of N-methyl-2-pyrrolidone (NMP).
Then, a clear solution of 10% by weight of polyamic acid was obtained. The viscosity of this solution at 25 ° C. is 10
It was 4.5 centipoise. After a 7: 3 mixed solution of butyl cellosolve and NMP was added to the solution to dilute it to 3% by weight, the solution was applied on a transparent glass substrate provided with an ITO electrode on one side by a spin coating method (spinner method). The rotation conditions were 3000 rpm for 15 seconds. 10 at 100 degrees after coating
After drying for a minute, the temperature was raised to 200 ° C. in an oven for 1 hour, and heat treatment was performed at 200 ° C. for 90 minutes to obtain a film thickness of about 600 Å polybenzylimide.
Rubbing treatment is applied to each of the coating surfaces of the two substrates on which the polybenzylimide film is formed to form a liquid crystal alignment film, and a liquid crystal cell having a cell thickness of 6 μm is assembled so that the rubbing directions are parallel and opposed to each other. LCD F for TFT
B01 was enclosed. After the encapsulation, an isotropic treatment was performed at 120 ° C. for 30 minutes, and the resultant was gradually cooled to room temperature to obtain a liquid crystal device. The pretilt angle was measured using a liquid crystal Z manufactured by Merck.
A liquid crystal cell having a cell thickness of 20 microns and containing LI-1132 was prepared in the same manner. The orientation of the liquid crystal element was good, and the pretilt angle of the liquid crystal measured by a crystal rotation method was 3.1 degrees. The residual charge of this cell is 0.01 V at 25 ° C., and the voltage holding ratio is 97.
3%.

Example 3 50 g of dehydrated and purified N-methyl-2-pyrrolidone was placed in a 200 ml four-necked flask equipped with a stirrer, a thermometer, a condenser and a nitrogen purging apparatus.
8.36 g of bis [4- (4-aminobenzyl) phenyl] -4-butylcyclohexane was charged and dissolved by stirring.
This is cooled to 13 ° C. and pyromellitic dianhydride 3.6
9 g was added at a time, and a stirring reaction was performed while cooling. After one hour, 0.1 mg of para-aminophenyltrimethoxysilane
1 g was added, and the mixture was stirred and reacted at 20 ° C. for 1 hour. afterwards,
The reaction solution was treated with N-methyl-2-pyrrolidone (NMP) 59.
By diluting with 4 g, a clear solution of 10% by weight of polyamic acid was obtained. The viscosity of this solution at 25 ° C. was 1540 centipoise. A 1: 1 mixed solution of butyl cellosolve and NMP was added to this solution to dilute the polyamic acid to 3% by weight, and then applied on a transparent glass substrate provided with an ITO electrode on one side by a spin coating method (spinner method). . The rotation conditions were 5000 rpm and 15 seconds.
After the coating was dried at 100 ° C. for 10 minutes, the temperature was raised to 200 ° C. in an oven for 1 hour, and heat treatment was performed at 200 ° C. for 90 minutes to obtain a film thickness of about 600 Å polybenzylimide. The coating surfaces of the two substrates on which the polybenzylimide film was formed were each subjected to a rubbing treatment to form a liquid crystal alignment film, and a liquid crystal cell having a cell thickness of 6 microns was assembled so that the rubbing directions were parallel and opposed to each other. The liquid crystal FB01 for TFT manufactured was enclosed. 120 after encapsulation
The liquid crystal device was obtained by performing isotropic treatment at 30 ° C. for 30 minutes and gradually cooling to room temperature. The pretilt angle was measured by measuring the cell thickness 2 with the liquid crystal ZLI-1132 manufactured by Merck.
A 0 micron liquid crystal cell was made in a similar manner. The orientation of the liquid crystal element was good, and the pretilt angle of the liquid crystal measured by a crystal rotation method was 5.0 degrees. The residual charge of this cell was 0.07 at 25 ° C.
V, the retention was 95.6%.

Comparative Example 1 8.06 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane and pyromellitic dianhydride
36 g and para-aminophenyltrimethoxysilane 0.1
1 g was polymerized to obtain a polyamic acid solution. The solution was diluted with a 1: 1 mixed solution of butyl cellosolve and NMP to 3% by weight, and then applied to a transparent glass substrate provided with an ITO electrode on one side by a spin coating method (spinner method). The rotation conditions were 3000 rpm for 15 seconds. After the coating was dried at 100 ° C. for 10 minutes, the temperature was raised to 200 ° C. in an oven for 1 hour, and heat treatment was performed at 200 ° C. for 90 minutes to obtain a film thickness of about 600 Å polyetherimide. The coating surfaces of the two substrates on which the polyetherimide film was formed were each subjected to rubbing treatment to form a liquid crystal alignment film, and a liquid crystal cell having a cell thickness of 6 microns was assembled so that the rubbing directions were parallel and opposed to each other. The liquid crystal FB01 for TFT manufactured was enclosed. 3 at 120 ° C after encapsulation
The liquid crystal device was obtained by performing isotropic treatment for 0 minutes and gradually cooling to room temperature. For the measurement of the pretilt angle, a liquid crystal cell having a cell thickness of 20 μm and containing a liquid crystal ZLI-1132 manufactured by Merck was prepared in the same manner. The orientation of the liquid crystal element was good, and the pretilt angle of the liquid crystal measured by a crystal rotation method was 3.7 degrees.
The residual charge of this cell was 0.20 at 25 ° C., and the voltage holding ratio was 90.0%.

Comparative Example 2 8.06 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 3.92 g of methylcyclobutanetetracarboxylic dianhydride and 0.11 g of paraaminophenyltrimethoxysilane were polymerized. Thus, a polyamic acid solution was obtained. The solution was mixed with butyl cellosolve and NMP 7:
3 and diluted to 3% by weight.
It was applied to a transparent glass substrate provided with a TO electrode by a spin coating method (spinner method). Rotation condition is 5000 rpm, 15
Seconds. After drying at 100 ° C. for 10 minutes after coating, the temperature was raised to 200 ° C. in an oven for 1 hour,
A heat treatment was performed at 90 ° C. for 90 minutes to obtain a polyetherimide having a thickness of about 600 Å. The coating surfaces of the two substrates on which the polyetherimide film was formed were each subjected to rubbing treatment to form a liquid crystal alignment film, and a liquid crystal cell having a cell thickness of 6 microns was assembled so that the rubbing directions were parallel and opposed to each other. The liquid crystal FB01 for TFT manufactured was enclosed. After the encapsulation, an isotropic treatment was performed at 120 ° C. for 30 minutes, and the resultant was gradually cooled to room temperature to obtain a liquid crystal element. For the measurement of the pretilt angle, a liquid crystal cell having a cell thickness of 20 μm and containing a liquid crystal ZLI-1132 manufactured by Merck was prepared in the same manner. The orientation of the liquid crystal element was good, and the pretilt angle of the liquid crystal measured by a crystal rotation method was 1.5 degrees. The residual charge of this cell is 25
The temperature was 0.15 and the voltage holding ratio was 89.0%.

Comparative Example 3 3.46 g of 4,4 ′ diaminophenyl ether, 4.36 g of pyromellitic dianhydride and 0.11 g of paraaminophenyltrimethoxysilane were polymerized to obtain a polyamic acid solution. The solution was mixed with butyl cellosolve and NMP 1:
After adding the mixed solution of Example 1 and diluting it to 3% by weight,
It was applied to a transparent glass substrate provided with a TO electrode by a spin coating method (spinner method). Rotation conditions are 3000 rpm, 15
Seconds. After drying at 100 ° C. for 10 minutes after coating, the temperature was raised to 200 ° C. in an oven for 1 hour,
Heat treatment was performed at 90 ° C. for 90 minutes to obtain a film thickness of about 600 Å polyetherimide. The coating surfaces of the two substrates on which the polyetherimide film was formed were each subjected to rubbing treatment to form a liquid crystal alignment film, and a liquid crystal cell having a cell thickness of 6 microns was assembled so that the rubbing directions were parallel and opposed to each other. The liquid crystal FB01 for TFT manufactured was enclosed.
After the encapsulation, an isotropic treatment was performed at 120 ° C. for 30 minutes, and the resultant was gradually cooled to room temperature to obtain a liquid crystal element. For the measurement of the pretilt angle, a liquid crystal cell having a cell thickness of 20 μm and containing a liquid crystal ZLI-1132 manufactured by Merck was prepared in the same manner. The orientation of the liquid crystal element was good, and the pretilt angle of the liquid crystal measured by a crystal rotation method was 0.5 degrees. The residual charge of this cell is 25
The temperature was 0.90, and the voltage holding ratio was 78.0%.

[0047]

The liquid crystal alignment film of the present invention can be easily formed into a liquid crystal alignment film having a uniform and high pretilt angle over the entire substrate having a wide display area required for an STN liquid crystal display element by ordinary rubbing treatment. . In addition, a liquid crystal display device using the liquid crystal alignment film is of high quality with no afterimage phenomenon and excellent in voltage holding ratio. This is thought to be caused by the phenylcyclohexane ring of the starting diamino compound and the alkyl group bonded thereto.

[0048]

[Brief description of the drawings]

FIG. 1 is a diagram showing a CV hysteresis curve.

FIG. 2 is a circuit diagram used for measuring a voltage holding ratio.

FIG. 3 shows the relationship between V _S and the gate pulse width being 69 μs and 60
Hz, and a rectangular wave having a wave height of ± 4.5 V. V _D is a waveform read from an oscilloscope by applying V _S to the source of the circuit shown in FIG.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/1337 520 G02F 1/1337 525

Claims (4)

(57) [Claims] 1. A compound of the general formula A liquid crystal alignment film comprising, as a main component, a polymer having a skeleton represented by a long chain in a molecular chain. 2. A compound of the general formula A liquid crystal alignment film mainly containing polyimide having a structural unit represented by: 3. A polyamic acid obtained by reacting a tetracarboxylic dianhydride represented by the following formula (3) with a diamino compound represented by the following formula (4) in a solvent: 3. A polyimide containing a polyimide as a main component.
The liquid crystal alignment film as described in the above. Embedded image 4. A liquid crystal display device comprising the liquid crystal alignment film according to claim 1.