JPH107906A - Varnish based on polyamide acid, liquid crystal aligned film prepared using said varnish, and liquid crystal display device using said aligned film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a novel varnish based on a polyamide acid which can pro vide a film having excellent electric characteristics, no significant coloring, and excellent transparency by condensing a tetracarboxylic acid dianhydride with a particular diamine. SOLUTION: This varnish comprises: a polyamide acid obtd. by condensing a tetracarboxylic acid dianhydride with a diamine; a partially imidated polyamide acid; and a polyimide, wherein the diamine is composed mainly of bis(aminomethyl)-bicyclo[2,2,1]heptane represented by the formula. The tetracarboxylic acid dianhydride is pref. an aromatic tetracarboxylic acid dianhydride. Another pref. tetracarboxylic acid dianhydride is an aliph. tetracarboxylic acid dianhydride (including an alicyclic tetracarboxylic acid dianhydride). Still another pref. tetracarboxylic acid dianhydride is a siloxane tetracarboxylic acid dianhydride. A liq. crystal aligned film prepd. using the above varnish is still pref.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel polyimide suitable for a liquid crystal alignment film and a color filter substrate, a varnish containing a polyamic acid which is a precursor of the polyimide, and a polyamic acid partially imidized. The present invention relates to a liquid crystal alignment film formed using the varnish, and a liquid crystal display device having the liquid crystal alignment film.

[0002]

2. Description of the Related Art Liquid crystal display devices have characteristics such as low voltage driving, low voltage consumption, thin structure, and light weight, and are used in many fields. In recent years, an active matrix type display device having an active element added to each pixel has been developed. As the active element, a MIM (metal-insulating phase-metal) element, a TF
T (field effect thin film transistor) elements and the like have been used. A common problem with these display devices is that when the same screen is displayed for a long time and then shifted to another screen, the previous screen remains as an afterimage. To obtain a high-quality liquid crystal display device, this afterimage is required. It is important to eliminate the phenomenon. Particularly, in the TFT element, the DC component of the applied voltage cannot be removed due to the characteristics of the element, so that the afterimage is more conspicuous than in a simple matrix type display device, which is a problem. In addition, a high voltage holding ratio is required for a TFT element in order to prevent a screen from flickering. Currently, most of the alignment film materials of the liquid crystal display element are polyimide-based polymers. Typical polymers include polyimides composed of imide bonds, polyamideimides composed of amide bonds and imide bonds, and polyamide imides composed of imide bonds and imide bonds described in JP-A-51-65960. A polyesterimide can be exemplified. Among these polymers, a polyimide alignment film using an aromatic diamine as a diamine component has a drawback that a voltage holding ratio is small and a residual charge is large. Furthermore, when a polyimide film is used as a liquid crystal alignment film, an alignment process is usually performed to rub the surface of the polyimide film.However, depending on a combination of a tetracarboxylic dianhydride and a diamine compound, the polyimide film is removed from the substrate during the alignment process. There is a problem of peeling. In addition to polyimide, polyimide has applications such as a protective film, an insulating film, and a color filter base material. In these applications, uncolored polyimide is preferred, but there is a problem that polyimide is generally liable to be colored yellow.

[0003]

SUMMARY OF THE INVENTION A first object of the present invention is to provide an alignment film which provides a liquid crystal display device having a high voltage holding ratio and a small residual charge. It is possible to provide polyimide with less coloring.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, when producing a polyimide by condensing tetracarboxylic dianhydride and diamine, a diamine represented by the general formula It has been found that the intended purpose can be achieved by using a diamine having bis (aminomethyl) -bicyclo [2.2.1] heptane as a main component represented by (1), and the present invention has been completed. Reached.

[0005]

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In the present invention, there is no particular limitation on the tetracarboxylic dianhydride used as a raw material for polyimide, and aromatic tetracarboxylic dianhydrides and fatty acids used in the production of various conventionally known polyamides can be used. Aliphatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, tetracarboxylic dianhydride having an alicyclic structure and an aromatic structure in a skeleton structure, an aliphatic structure and a fatty acid in a skeleton structure Any of a tetracarboxylic dianhydride having a cyclic structure and a tetracarboxylic dianhydride having an aromatic structure and an aliphatic structure in a skeleton structure can be used. Further, these tetracarboxylic dianhydrides may have substituents such as halogen, lower alkyl group, lower alkoxy group, and hydroxyl group, and the ring structure may be a heterocyclic ring. Further, as these acid dianhydrides, a single compound may be used, or a plurality of compounds may be used in combination. The following compounds are illustrated as tetracarboxylic dianhydrides.

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'-
Benzophenone tetracarboxylic dianhydride, bis (3,
4-dicarboxyphenyl) sulfone dianhydride, 1,
2,5,6-naphthalenetetracarboxylic dianhydride,
2,3,6,7-naphthalenetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, cyclohexanetetracarboxylic dianhydride, cyclooctanetetracarboxylic dianhydride, Bicyclooctanetetracarboxylic dianhydride, bicyclo [2.2.2] -oct-7-ene 2,
3,5,6-dianhydride, 2,3,5-tricarboxycyclopentylacetic dianhydride, 3,5,6-tricarboxynorbornane-2-acetic anhydride, tetrahydrofurantetracarboxylic dianhydride, butanetetra Carboxylic dianhydride. Further, the following tetracyclic dianhydrides having a complex ring system and tetracarboxylic dianhydrides having a siloxane structure can be used.

[0008]

Embedded image

In the present invention, bis (aminomethyl)
The diamine containing -bicyclo [2.2.1] heptane as a main component refers to a case where the diamine is composed of only bis (aminomethyl) -bicyclo [2.2.1] heptane, and bis (aminomethyl) -bicyclo [ 2.2.1] means the case where heptane and another diamine are used in combination. The bis (aminomethyl) -bicyclo [2.2.1] heptanediamine represented by the general formula (1) used as a main component of the diamine in the present invention is specifically described as 2,5-bis (aminomethyl). ) -Bicyclo [2.2.1] heptane, 2,6-
Bis (aminomethyl) -bicyclo [2.2.1] heptane, 2,3-bis (aminomethyl) -bicyclo [2.
2.1] heptane. These diamines can be used alone, but can also be used as a mixture. In the present invention, as long as the effects of the present invention are not impaired, one or more other diamines can be used in combination with the above bis (aminomethyl) -bicyclo [2.2.1] heptane. Examples of such other diamines are described below, but are not limited thereto.

Ethylenediamine propylenediamine 1,1-bis [4- (4-aminophenoxy) phenyl] cyclohexane, 1,1-bis [4- (4-aminophenoxy) phenyl] -4-methylcyclohexane,
1,1-bis [4- (4-aminophenoxy) phenyl] -4-ethylcyclohexane, 1,1-bis [4-
(4-aminophenoxy) phenyl] -4-npropylcyclohexane, 1,1-bis [4- (4-aminophenoxy) phenyl] -4-nbutylcyclohexane,
1,1-bis [4- (4-aminophenoxy) phenyl] -4-npentylcyclohexane, 1,1-bis [4- (4-aminophenoxy) phenyl] -4-nhexylcyclohexane, 1,1- Bis [4- (4-aminophenoxy) phenyl] -4-nheptylcyclohexane, 1,1-bis [4- (4-aminophenoxy) phenyl] -4-noctylcyclohexane,

2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane, 2,2-bis [4
-(4-aminophenoxy) phenyl] pentane, 2,
2-bis [4- (4-aminophenoxy) phenyl] hexane, 2,2-bis [4- (4-aminophenoxy)
Phenyl] heptane, 2,2-bis [4- (4-aminophenoxy) phenyl] octane, 2,2-bis [4-
(4-aminophenoxy) phenyl] nonane, 2,2-
Bis [4- (4-aminophenoxy) phenyl] decane, 2,2-bis [4- (4-aminophenoxy) phenyl] dodecane, 1,1-bis [4- (4-aminobenzyl) phenyl] cyclohexane, 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-npropylcyclohexane, 1,1-bis [4- (4-aminobenzyl) phenyl] -4-nbutylcyclohexane,
1,1-bis [4- (4-aminobenzyl) phenyl]
-4-n pentylcyclohexane, 1,1-bis [4-
(4-aminobenzyl) phenyl] -4-nhexylcyclohexane, 1,1-bis [4- (4-aminobenzyl) phenyl] -4-nheptylcyclohexane, 1,
1-bis [4- (4-aminobenzyl) phenyl] -4
-N octylcyclohexane,

1,1-bis [4- (4-aminobenzyl) phenyl] methane, 4,4'-diaminophenyl ether, 4,4'-diaminodiphenylmeta4,4'-
Diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, 4,4'-di (meth-aminophenoxy) diphenyl sulfone, 4,4 '-(para-aminophenoxy) diphenyl sulfone, ortho-phenylenediamine, meta-phenylene Diamine, para-phenylenediamine, benzidine, 2,2'-
Diaminobenzophenone, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenyl-2,2-propane, 1,5-diaminonaphthalene, 1,8-diaminonaphthalene, 2,2-bis [4- (4- Aminophenoxy) phenyl] hexamethylpropane,

1,4-diaminocyclohexane,
1,4-diaminodicyclohexane, 4,4′-diaminodicyclohexylmethane, 4,4′-diaminodicyclohexylpropane, 2,3-diaminobicyclo [2.
2.1] Heptane, 2,5-diaminobicyclo [2.
2.1] Heptane, 2,6-diaminobicyclo [2.
2.1] Heptane, 2,7-diaminobicyclo [2.
2.1] Heptane, and siloxane-based diamines represented by the following general formula are exemplified.

[0014]

Embedded image

(Wherein, R represents a phenylene group or an alkylene group, R ′ represents an alkyl group or an alkoxy group, and m represents a positive integer). Also, in order to improve the adhesion between the polymer and the substrate,
It is also possible to use a siloxane-based monoamine such as para-aminophenyltrimethoxysilane in combination.

The above tetracarboxylic dianhydride, bis (aminomethyl) -bicyclo [2.2.1] heptane,
And, if necessary, another diamine is subjected to a condensation reaction in an aprotic polar solvent to obtain a polyimide precursor. Such solvents include N-methyl-2-pyrrolidone, dimethylimidazolidinone, N-methylcaprolactam,
N-methylpropionamide, N, N-dimethylformamide, N, N-diethylformamide, γ-
Butyl lactone. It is preferable that the use ratio of the total tetracarboxylic dianhydride to the total diamine is such that the acid and the amine are substantially equivalent, but if it is several% or less, the acid can be used in excess. The polymerization reaction may be carried out according to the conditions usually used for producing a polyimide precursor, and the reaction is carried out for 1 to 10 hours while controlling the reaction temperature to 60 ° C. or lower, preferably 30 ° C. The polyimide precursor solution thus obtained contains a polyamic acid as a main component, and further contains a polyimide and a partially imidized polyamic acid.

In the present invention, the varnish of the present invention can be used by appropriately adding the above-mentioned various solvents to the above-mentioned polyimide precursor solution to adjust the viscosity. Also, for the purpose of improving the applicability to the glass substrate,
Butyl cellosolve, ethyl carbitol, triethylene glycol monomethyl ether, tetraethylene glycol monoalkyl ether, propylene glycol
Solvents such as monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether 3-methoxy, 3-methylbutanol cyclohexanone butyrolactone Ethyl lactate, butyl lactate, diethyl malonate, and dibutyl malonate cyclohexanone can be added. .

[0018]

The present invention will be described below with reference to examples and comparative examples. Preparation of cell: Spinner (100
Apply varnish using 0 rpm for 10 seconds)
After drying at 80 ° C. for 5 minutes, baking was performed at 200 ° C. for 90 minutes. The varnish-coated surface was rubbed with a rubbing device and subjected to an orientation treatment to prepare an anti-parallel cell having a gap of 7 μm with the coated surface facing inward. A liquid crystal (liquid crystal for TFT: FB-01: manufactured by Chisso Corporation) was injected into the cell, and the injection port was sealed. Thereafter, the cell was subjected to isotropic treatment at 120 ° C. for 50 minutes and allowed to cool to room temperature. Evaluation of orientation: The cells prepared as described above were arranged with polarizing plates above and below the substrate, and the orientation was visually observed.

Evaluation of electrical characteristics: (1) Residual charge: An alternating current of 25 mV and 1 KHZ is applied to the liquid crystal cell, and a DC triangular wave (hereinafter simply referred to as DC voltage) having a frequency of 0.0036 HZ is superimposed on the AC. The voltage is swept in the range of -10 V to +10 V, and the change in the capacitance of the cell is measured. The width of the hysteresis (voltage difference) of the electric capacitance of the cell generated in the going and returning of the sweep was defined as the residual charge. The specific calculation method is shown in FIG. 1, and the calculation was performed by the following equation. Residual charge = (| α1−α2 | + | α3−α4 |) / 2 (2) Voltage holding ratio; measured by the circuit shown in FIG. A gate signal of a rectangular wave (Vs) having a pulse width of 69 μs, a frequency of 60 Hz, and a wave height of ± 4.5 V is applied to the source electrode, and a change in the generated drain voltage is read by an oscilloscope.
The drain voltage (Vd) shows a positive value after the positive signal is applied to the source until the next negative rectangular wave is applied, and at the time when the negative signal is applied, the drain voltage (Vd) becomes a negative value. Flip to When the voltage holding ratio of the cell is 100%, Vd keeps a constant value as shown by the dotted line in FIG. 3, but when the voltage holding ratio is small, it gradually decreases as shown by the solid line. The relative value (%) between the measured integral value of Vd (= hatched portion) and the integral value when the voltage did not decrease at all was displayed as the voltage holding ratio. Coloring: Using a spectrophotometer, measure the transmittance in the visible region of a varnish with a polymer concentration of 16% by weight at a cell thickness of 10 mm,
Table 1 shows the values of the transmittance (%) at 400 nm.

Example 1 1) Production of mother liquor 1 In a separable flask, under a nitrogen atmosphere, 2,5 (2,2
6) -bis (aminomethyl-bicyclo [2.2.1] heptane 2.0159 g of N-methylpyrrolidone (NM
P) 2.899 g of pyromellitic acid in 26.250 g solution
After adding 0 g and stirring at room temperature for 8 hours, 0.0850 g of para-aminophenyltrimethoxysilane was added and further reacted at room temperature for 2 hours to obtain a mother liquor 1 having a polymer content of 16% by weight. According to GPC, the polymer of the mother liquor 1 thus obtained had a weight average molecular weight of about 63,000. 2) Preparation of Varnish 1 0.963 g of mother liquor 1 and 1.563 g of NMP and BC
2.500 g was added to prepare Varnish 1 having the following composition. Polymer concentration 3.0% NMP 47.0% Butyl cellosolve 50.0% 3) Test result In the cell prepared using this varnish 1, it was confirmed that the liquid crystal was uniformly aligned. Table 1 shows the test results of the residual charge and the voltage holding ratio of this cell.

Example 2 1) Production of mother liquor 2 In a separable flask under a nitrogen atmosphere, 2,5 (2,2)
6) To a solution of 3.465 g of -bis (aminomethyl-bicyclo [2.2.1] heptane in 42.000 g of NMP,
After adding 4.4498 g of butanetetracarboxylic dianhydride and reacting by stirring at room temperature for 8 hours, 0.1437 g of paraaminophenyltrimethoxysilane was added and further reacted at room temperature for 2 hours to obtain a polymer content of 16%. % Mother liquor 2 was obtained. According to GPC, the mother liquor 2 thus obtained
Of the polymer had a weight average molecular weight of about 69,000. 2) Preparation of Varnish 2 NMP and BC were added to the mother liquor 2 to prepare a varnish 2 having the following composition. Polymer concentration 3.0% NMP 47.0% Butyl cellosolve 50.0% 3) Test result In the cell prepared using this varnish 2, it was confirmed that the liquid crystal was uniformly aligned. Table 1 shows the test results of the residual charge and the voltage holding ratio of this cell.

Example 3 1) Production of mother liquor 3 In a separable flask under a nitrogen atmosphere, 2,5 (2,2
6) To a solution of 2.2840 g of -bis (aminomethyl-bicyclo [2.2.1] heptane in 28.000 g of NMP,
After adding 2.9500 g of cyclobutanoic acid dianhydride and stirring at room temperature for 8 hours to react, 0.1437 g of paraaminophenyltrimethoxysilane was added and further reacted at room temperature for 2 hours to obtain a polymer having a polymer content of 16%. Mother liquor 3 was obtained. According to GPC, the polymer of the mother liquor 3 thus obtained had a weight average molecular weight of about 85,000. 2) Preparation of Varnish 3 NMP and BC were added to the mother liquor 3 to prepare a varnish 3 having the following composition. Polymer concentration: 3.0% NMP: 47.0% Butyl cellosolve: 50.0% 3) Test results In the cell prepared using the varnish 3, it was confirmed that the liquid crystal was uniformly aligned. Table 1 shows the test results of the residual charge and the voltage holding ratio of this cell.

Comparative Example 1 1) Preparation of mother liquor 4 Pyromellit was added to a solution of 5.1407 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane in 42.000 g of NMP in a separable flask under a nitrogen atmosphere. After adding 2.7778 g of acid and reacting by stirring at room temperature for 8 hours, 0.0815 g of paraaminophenyltrimethoxysilane was added and further reacted at room temperature for 2 hours to obtain a mother liquor 4 having a polymer content of 16%. I got According to GPC, the polymer of the mother liquor 4 thus obtained had a weight average molecular weight of about 89,000. 2) Preparation of varnish 4 NMP and BC were added to the mother liquor 4 to prepare a varnish 4 having the following composition. Polymer concentration 3.0% NMP 47.0% Butyl cellosolve 50.0% 3) Test results In the cell made using this varnish 4, the liquid crystal was uniformly aligned. Table 1 shows the test results of the residual charge and the voltage holding ratio of this cell.

Comparative Example 2 1) Preparation of mother liquor 5 In a separable flask under a nitrogen atmosphere, a solution of 5.1858 g of NMP of 5.1858 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane in a solution of 42.000 g of NMP was prepared. Then, 2.6061 g of butanoic dianhydride was added, and the mixture was stirred and reacted at room temperature for 8 hours. Then, 0.0822 g of paraaminophenyltrimethoxysilane was added, and the mixture was further reacted at room temperature for 2 hours to obtain a polymer content of 16%. Mother liquor 5 was obtained. According to GPC, the polymer of the mother liquor 5 thus obtained had a weight average molecular weight of about 98,000. 2) Preparation of Varnish 5 NMP and BC were added to the mother liquor 5 to prepare a varnish 5 having the following composition. Polymer concentration 3.0% NMP 47.0% Butyl cellosolve 50.0% 3) Test results In the cell made using this varnish 5, the liquid crystal was uniformly aligned. Table 1 shows the test results of the residual charge and the voltage holding ratio of this cell.

Comparative Example 3 1) Production of mother liquor 6 In a separable flask, under a nitrogen atmosphere, 3.7378 g of 4,4'-diaminophenyl ether was added.
To the 000 g solution was added 4.1408 g of pyromellitic acid, and the mixture was stirred and reacted at room temperature for 8 hours. Then, 0.1215 g of paraaminophenyltrimethoxysilane was added, and the mixture was further reacted at room temperature for 2 hours to obtain a polymer content of 16%. % Mother liquor 6 was obtained. According to GPC, the thus obtained mother liquor 6
The polymer had a weight average molecular weight of about 105,000. 2) Preparation of varnish 6 NMP and BC were added to the mother liquor 6 to prepare a varnish 6 having the following composition. Polymer concentration 3.0% NMP 47.0% Butyl cellosolve 50.0% 3) Test results In the cell made using this varnish 6, the liquid crystal was uniformly aligned. Table 1 shows the test results of the residual charge and the voltage holding ratio of this cell.

Comparative Example 4 1) Preparation of mother liquor 7 Bicyclo [2.2.1] heptane-2,5-diamine was added to diamine in a separable flask under a nitrogen atmosphere.
To a solution of 6900 g of NMP 84.111 g, pyromellitic acid 10.010 g was added, and the mixture was stirred at room temperature for 8 hours to react. Then, paraaminophenyltrimethoxysilane 0.2940 g was added, and the mixture was further reacted at room temperature for 2 hours. A mother liquor 7 having a polymer content of 16% was obtained. The varnish thus obtained had a weight average molecular weight of about 8.5 determined by GPC.
It was 10,000. 2) Preparation of Varnish 7 NMP and BC were added to the mother liquor 7 to prepare a varnish 7 having the following composition. Polymer concentration 3.0% NMP 47.0% Butyl cellosolve 50.0% 3) Preparation of cell A varnish 7 was applied to the substrate and baked in the same manner as in Example 1, but rubbing was performed. Since the film was peeled off from the substrate, the electrical characteristics of the cell could not be evaluated. In the polyamide used in the varnish of the present invention, -CH2 of -CH2-NH2 group of raw material diamine is used.
-The part seems to be acting favorably against the external force of rubbing.

[0027]

[Table 1]

[0028]

The liquid crystal alignment film prepared using the varnish of the present invention has a high voltage holding ratio by using bis (aminomethyl) -bicyclo [2.2.1] heptane as the diamine component of the polyamide. A liquid crystal display device having a very small residual charge could be produced. This is particularly suitable as an alignment film for a TFT display element, which is strictly required in terms of electric characteristics. Further, by using the varnish of the present invention, a colorless and transparent polyimide film can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for measuring a residual charge.

FIG. 2 is a diagram showing a method for measuring a voltage holding ratio.

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[Procedure amendment]

[Submission date] August 27, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for measuring a residual charge.

FIG. 2 is a diagram showing a method for measuring a voltage holding ratio.

FIG. 3 is a diagram showing a method for measuring a voltage holding ratio.

Claims (6)

[Claims] 1. A varnish containing a polyamic acid obtained by condensing a tetracarboxylic dianhydride and a diamine, a partially imidized polyamic acid, and a polyimide, wherein the diamine is represented by the general formula (1): A varnish characterized by being a diamine containing bis (aminomethyl) -bicyclo [2.2.1] heptane as a main component. Embedded image 2. The varnish according to claim 1, wherein the tetracarboxylic dianhydride is an aromatic tetracarboxylic dianhydride. 3. The varnish according to claim 1, wherein the tetracarboxylic dianhydride is an aliphatic (including alicyclic) tetracarboxylic dianhydride. 4. The varnish according to claim 1, wherein the tetracarboxylic dianhydride is a siloxane-based tetracarboxylic dianhydride. 5. A liquid crystal alignment film produced using the varnish according to claim 1. 6. A liquid crystal display device having the liquid crystal alignment film according to claim 5.