JPH06202118A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To provide a liquid crystal element using polymer liquid crystal oriented films having small residual charges or a high voltage holding rate. CONSTITUTION:The material for the oriented film of this liquid crystal element using polymer oriented films essentially contains a polyimide precursor as the main component and at least a compd. selected from the following group as the second component compounded by 0.01-10wt.%. They are an alkylester polycarylate, alkylester polymethacrylate, copolymer of them, polyoxyethylene glycol di(meth)acrylate, and polyoxypropylene glycol di(meth)acrylate. In the obtd. liquid crystal element, while improving and maintaining the voltage holding rate, residual charges can be decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention shows a liquid crystal display cell using a polymer type alignment film such as polyimide as an alignment film for controlling the alignment of liquid crystal, which shows improved electric characteristics and display characteristics with few defects. And a liquid crystal element having

[0002]

2. Description of the Related Art Liquid crystal display devices are used as various display devices for watches, calculators, TVs, word processors, personal computers, etc. due to their characteristics such as low voltage driving, low power consumption, and thin display device. And, in the future, it is going to expand its usage more and more. Behind it, the substrate, the spacer,
Various technologies such as light source, driving technology, liquid crystal material, display method, sealant, color filter, electrode technology, alignment film, etc. have been developed. It becomes an element. However, various problems still remain, and even in the field of alignment films,
There are various problems such as applicability of the alignment film (occurrence of repellency, generation of craters, etc.), tilt angle size, tilt angle stability, uneven alignment, and deterioration of display characteristics due to inclusion of foreign matter. In addition, the electrical characteristics of the liquid crystal element have a problem such as occurrence of a burn-in phenomenon that is considered to be caused by the magnitude of the residual charge of the element, or flickering of the screen or deterioration of contrast due to a decrease in voltage holding ratio. .

As a method for increasing the voltage holding ratio of the liquid crystal display element, there are methods such as studying the basic skeleton of tetracarboxylic acid or diamine which is a raw material of polyimide, or reducing impurities in the alignment film. It is also said that the voltage holding ratio changes depending on the difference in the imidization ratio of polyimide. At present, generally, the improvement of the voltage holding ratio is mainly dependent on the improvement of the liquid crystal material, but the improvement of the liquid crystal material alone has not sufficiently solved the problem.

Further, the method for improving the residual charge is also being improved by improving the liquid crystal material, but like the voltage holding rate, it has not been improved to a sufficient range. It is said that the residual charge of the liquid crystal element varies depending on the type of the alignment film, but the relationship between the molecular structure of polyimide and the residual charge is not well known.

[0005]

As is clear from the above, the object of the present invention is to provide a liquid crystal device using a polymer liquid crystal alignment film such as polyimide, in which the residual charge of the device is small or the voltage holding ratio is low. It is to provide a liquid crystal element having high cost.

The present invention provides a liquid crystal device using a polymer-based alignment film, which is a polymer of alkyl acrylate and alkyl methacrylate, and copolymers thereof, polyoxyethylene glycol mono- and diacrylates, and polyacrylates. Oxyethylene glycol mono-
And dimethacrylate, polyoxypropylene glycol mono- and diacrylates, and polyoxypropylene glycol mono- and dimethacrylates, ethylene glycol diacrylates and dimethacrylates, and propylene glycol diacrylates and dimethacrylates. As a second component, at least one compound is added in a weight ratio of 0.01 to the polyimide precursor material as the main component.
It is a liquid crystal element obtained by using an alignment film material containing 10%.

The liquid crystal element of the present invention is characterized by the liquid crystal alignment film. The alignment film is manufactured by the same procedure as the alignment film using a normal polyimide material, but the alignment film material is characterized in that it contains the second component in the form of a varnish. That is, in the varnish, the compound as the second component, with respect to the polyimide precursor component as the main component,
A uniform substance containing 0.01 to 10%, preferably 0.05 to 2.0% is uniformly applied to the electrode surface by means such as spin coating, and then subjected to heat treatment, rubbing treatment, etc. A substrate provided with an alignment film can be obtained. A liquid crystal element is assembled using the substrate thus obtained according to a usual method.

Considering the procedure for manufacturing the alignment film, it is desirable that the second component is soluble in the varnish, and therefore, a liquid substance per se is preferably used. Even non-liquid compounds are preferably used in the present invention as the second component as long as they are soluble in varnish and can be mixed uniformly. If the mixing ratio of the compound as the second component is less than 0.01% by weight with respect to the polyimide precursor component, the residual charge in the obtained device is not sufficiently reduced, which is not suitable. Also,
If the mixing ratio of the second component exceeds 10% by weight, the cloth may be contaminated during rubbing, or the tilt angle of the obtained liquid crystal element may be decreased, which is not preferable either.

As the second component, ethylene oxide such as polyoxyethylene glycol or polyoxypropylene glycol, or mono- or diacrylate, mono- or dimethacrylate of diol obtained by ring-opening polymerization of propylene oxide is preferably used. . The diol portion in these is preferably ethylene oxide or propylene oxide having a degree of polymerization of 1 to 18, and a degree of polymerization of 3
The thing of 10 is more preferably used.

As the second component, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-methacrylate. A homopolymer or copolymer such as ethylhexyl is also preferably used.
Examples of these materials include a series of commercially available polyflow surfactants (trade name, manufactured by Kyoeisha Co., Ltd.).

The polyimide precursor component in the present invention is
It is obtained from a tetracarboxylic dianhydride and a diamine compound exemplified below, or from a mixture of these acid anhydrides and a diamine compound. Examples of the tetracarboxylic acid as a raw material include 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 ′
-Benzophenone tetracarboxylic dianhydride, 2,
2 ', 3,3'-benzophenone tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,2, Examples thereof include 5,6-naphthalenetetracarboxylic dianhydride and 2,3,6,7-naphthalenetetracarboxylic dianhydride.

The following compounds can be mentioned as the diamine compound. Examples of the alicyclic diamine include 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, 4,4′-diaminodicyclohexylmethane, 4,
4'-diamino-3,3'-dimethyldicyclohexylmethane, and isophoronediamine. Examples of carbocyclic aromatic diamines are o-, m- and p-phenylenediamine, diaminotoluenes (eg 2,4-diaminotoluene), 1,4-diamino-2-methoxybenzene, 2,5. -Diaminoxylenes, 1,3-diamino-4-chlorobenzene, 1,4-diamino-2,5-dichlorobenzene, 1,4-diamino-4-isopropylbenzene, N, N'-diphenyl-1, 4-phenylenediamine, 4,4'-diaminodiphenyl-2,2-propane, 4,4'-diaminodiphenylmethane, 2,
2'-diaminostilbene, 4,4'-diaminostilbene, 4,4'-diaminodiphenyl ether, 4,
4'-diphenyl thioether, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminobenzoic acid phenyl ester,
2,2'-diaminobenzophenone, 4,4'-diaminobenzyl, 4- (4'-aminophenyl) aniline,
Bis (4-aminophenyl) phosphine oxide, bis (4-aminophenyl) methylphosphine oxide, bis (3-aminophenyl) methylsulfine oxide,
Bis (4-aminophenyl) phenylphosphine oxide, bis (4-aminophenyl) cyclohexylphosphine oxide, N, N'-bis (4-aminophenyl)
-N-phenylamine, N, N-bis (4-aminophenyl) -N-methylamine, 4,4'-diaminodiphenylurea, 1,8-diaminonaphthalene, 1,5-diaminonaphthalene, 1,5- Diaminoanthraquinone, diaminofluoranthene, bis (4-aminophenyl) diethylsilane, bis (4-aminophenyl) dimethylsilane, bis (4-aminophenyl) tetramethyldisiloxane, 3,4′-diaminodiphenyl ether, benzidine, 2,2'-dimethylbenzidine, 2,2-bis [4,-(4-aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] sulfone, 4,4'-bis ( 4-aminophenoxy) biphenyl, 2,2-bis [4- (4-aminophenoxy)
Phenyl] hexafluoropropane, 1,4-bis (4-
Aminophenoxybenzene, 1,3-bis (4-aminophenoxybenzene.

The heterocyclic diamines include 2,6-diaminopyridine, 2,4-diaminopyridine and 2,4-
Diamino-s-triazine, 2,7-diaminodibenzofuran, 2,7-diaminocarbazole, 3,7-diaminophenothiazine, 2,5-diamino-1,3,4-
Thiadiazole, 2,4-diamino-6-phenyl-s
-Triazine.

As examples of the aliphatic diamine, dimethyldiamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, 2,2-dimethylpropylenediamine. , 2,5-dimethylhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 4,4
-Dimethylheptamethylenediamine, 3-methylheptamethylenediamine, 3-methoxyheptamethylenediamine, 5-methylnonamethylenediamine, 2,11-diaminododecane, 1,12-diaminooctadecane, 1,
2-bis (3-aminopropoxy) ethane, N, N'-
Dimethylethylenediamine, N, N'-diethyl-1,
3-diaminopropane, N, N'-dimethyl-1,6-
Diaminohexane etc. can be mentioned.

As the solvent for the polyimide-based alignment film material, N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide (DMSO), dimethylsulfate, sulfolane, butyrolactone are used. , Cresol,
Phenol, halogenated phenol, cyclohexanone, dioxane, tetrahydrofuran and the like are preferably used.

The device of the present invention comprises a pair of electrodes obtained by uniformly mixing the above-mentioned compound as a second component with a varnish containing these polyimide materials and applying the compound by a usual means such as a spinner or a printing method. It is an object that can be assembled using a substrate. Even in an alignment film material containing an organic polymer material such as polyvinyl alcohol as a main component in place of the polyimide-based material in the present invention, the same effect as the present invention can be obtained by containing the compound used as the second component in the present invention. Can be expected.

[0017]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the following examples and comparative examples, percentages mean weight percentages. In the example, the residual charge is measured by sweeping a direct current of 0 to 20 V applied to the liquid crystal element and drawing a hysteresis curve between the voltage and the capacitance. And the difference in voltage at the intersection was determined as the residual charge (see FIG. 1). The voltage difference appears on the plus side and the minus side, but in the following examples, it is represented by the average value thereof. The leak voltage ratio is measured at 60 μs on the liquid crystal element.
When a DC voltage of 4.5 V is applied during the period, the change in the voltage of the element (capacitance) until 1/60 s is obtained as the area (V · s), and the voltage drop is not within 1/60 s The ratio of the area corresponding to the voltage drop to the area was expressed as a leakage voltage rate in%. In the following examples, as a liquid crystal material to be sealed in a liquid crystal cell, a liquid crystal composition composed of equal weights of compounds represented by the following three formulas was used.

[0018]

[Chemical 1]

Example 1 A solution of a polyamic acid containing a diamine compound represented by the following formula and a commercially available pyromellitic acid as main components (polyamic acid concentration 7.0%) was prepared. A mixed solvent of butyl cellosolve and N-methyl-2-pyrrolidone was used as the solvent.

[0020]

[Chemical 2]

A varnish prepared by mixing 0.7% of a compound represented by the following formula with polyamic acid was prepared in this solution, and a glass substrate having a transparent electrode was coated with an aligning agent using a spinner. After drying for 1 minute, baking was performed at 200 ° C. for 90 minutes, and then alignment treatment was performed by rubbing. A liquid crystal cell having a cell thickness of 6 μm was assembled using the two substrates.
The above liquid crystal composition was sealed in this cell and the residual charge and the leakage voltage ratio were measured. The residual charge is expressed as a ratio to the value obtained for a cell prepared by using a varnish containing no compound (shown in Comparative Example 1 below), and the result is the leakage voltage ratio measured at 25 ° C. and 60 ° C. The results are shown in Table 1.

[0022]

[Chemical 3]

[0023]

[Table 1]

Comparative Example 1 A liquid crystal cell was assembled in the same manner as in Example 1 except that the second component was not added to the polyamic acid solution prepared in Example 1. The same liquid crystal composition was filled in this cell, and its characteristics were measured in the same manner as in Example 1 and the results are shown in Table 1.

Example 2 A liquid crystal cell was assembled in the same manner as in Example 1 except that the second component added to the polyamic acid solution was replaced with the compound of the following formula, and its characteristics were measured in the same manner. The obtained results are shown in Example 1.
The results are shown in Table 1.

[0026]

[Chemical 4]

Example 3 The compound added to the polyamic acid solution as the second component was replaced with Polyflow 7 (trade name, manufactured by Kyoeisha Co., Ltd.), which is a commercially available surfactant which is a copolymer of acrylic acid ester and methacrylic acid ester. A liquid crystal cell was prepared in the same manner as in Example 1 except for the above. The same liquid crystal composition was enclosed in this cell and the characteristics of the cell were measured. The obtained results are shown in Table 1 together with the results of Example 1 and Example 2.

Example 4 A liquid crystal cell was prepared in the same manner as in Example 1 except that Polyflow 90 (trade name, manufactured by Kyoeisha Co., Ltd.) was used as the second component. The characteristics of this cell were measured in the same manner and are shown in Table 1 together with the results of Examples 1 to 3.

Example 5 The polyamic acid used in Example 1 was Polyflow 95 (trade name, manufactured by Kyoeisha Co., Ltd.), which is a copolymer of acrylic acid ester and methacrylic acid ester, in various mixing ratios as the second component. Five types of substrates were prepared using the varnish prepared by mixing with the above, and the cells were assembled using each of them. The production of the substrate and the assembling of the cell were performed in the same manner as in Example 1. A cell similar to that of Comparative Example 1 was assembled and used as a control. A liquid crystal cell was prepared by filling the above liquid crystal composition in each of these cells, and the residual charge was measured in the same manner as in Example 1. Table 2 shows the mixing ratio of the compound as the second component and the measurement results.

[0030]

[Table 2]

[0031]

As shown in the above Examples and Comparative Examples, the liquid crystal device of the present invention can reduce the residual charge without improving or lowering the voltage holding ratio. This is due to the improvement of the material of the varnish for forming the alignment film.

[0032]

[Brief description of drawings]

FIG. 1 is a hysteresis curve obtained when measuring a residual charge in Example 1, in which an auxiliary line is entered for calculation.

FIG. 2 is an infrared spectrum of the residue obtained by distilling off the solvent from Polyflow 7 under reduced pressure.

FIG. 3: Infrared spectrum of Polyflow 90.

FIG. 4 is a residual N obtained by distilling off the solvent from Polyflow 7 under reduced pressure.
MR spectrum.

FIG. 5: NMR spectrum of Polyflow 90.

Claims (4)

[Claims] 1. A liquid crystal device using a polymer-based alignment film, which comprises: polyacrylic acid alkyl ester, polymethacrylic acid alkyl ester, acrylic acid alkyl ester / methacrylic acid alkyl ester copolymer, polyoxyethylene glycol diacrylate, polyoxy. At least one compound selected from the group consisting of ethylene glycol dimethacrylate, polyoxypropylene glycol diacrylate, polyoxypropylene glycol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate and propylene glycol dimethacrylate. As the second component, an alignment film material containing 0.01 to 10% by weight with respect to the polyimide precursor material as the main component is used. Liquid crystal element obtained by 2. A polymer which is a liquid at room temperature, wherein the second component polymer is at least one liquid selected from polyoxyethylene diacrylate, polyoxyethylene dimethacrylate, polyoxypropylene diacrylate and polyoxypropylene dimethacrylate. The liquid crystal element according to claim 1, which is 3. The second component compound is a liquid at room temperature selected from at least one selected from polyacrylic acid alkyl ester, polymethacrylic acid alkyl ester, and acrylic acid alkyl ester / polymethacrylic acid alkyl ester copolymer. The liquid crystal device according to claim 1, which is a polymer. 4. A liquid crystal device obtained by using an alignment film material containing a second component polymer in a weight ratio of 0.05 to 2% with respect to a polyimide precursor material.