JPH0854631A - Liquid crystal orienting agent - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal orienting agent having a short erasing time of afterimages when voltage is applied on a liquid crystal cell by incorporating a specified polymer material and a powder and specifying the proportions of these. CONSTITUTION:This orienting agent contains 100 pts.wt. of one kind of polymer (polymer A) selected from among polyamic mic acid, polyimide, polyamide imide acid, polyamide imide and polyamide, and 0.01-10 pts.wt. of a powder material (powder B) having <=1X10<3>OMEGA.cm volume specific resistance at 25 deg.C and <=1mum average particle size. The polymer A is a high mol.wt. compd. selected from polyamic acid or the like and a single compd. or combination of these can be used. Further, repeating units of these high mol.wt. compds. may be present at random or in a block state in one molecule. The powder B is a conductive powder showing >1X10<3>OMEGA.cm volume specific resistance at 25 deg.C. When a powder having >1X10<3>OMEGA. volume specific resistance is used, enough improvement in the erasing time of afterimages is not obtd.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a liquid crystal aligning agent.
More specifically, it relates to a liquid crystal aligning agent having a short afterimage erasing time when a voltage is applied to a liquid crystal cell.

[0002]

2. Description of the Related Art Conventionally, a nematic liquid crystal having a positive dielectric anisotropy is sandwiched by a substrate with a transparent electrode having a liquid crystal alignment film made of polyimide or the like, and the long axis of liquid crystal molecules is 90 to 270 between the substrates. A liquid crystal display element having a TN type or STN type liquid crystal cell which is twisted continuously (hereinafter referred to as "TN, STN type display element").
It has been known. The liquid crystal alignment in the TN and STN type display elements is formed by a rubbing-treated liquid crystal alignment film, but when a voltage is applied, ionic charges are adsorbed to the liquid crystal alignment film, and when the voltage is turned off. There is a problem that a sufficient contrast cannot be obtained because of an afterimage. At this time, the time until the afterimage disappears (hereinafter,
It is called "afterimage erasing time". ) Depends on the application etc., but the shorter the better.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal aligning agent having a short afterimage erasing time when a liquid crystal cell voltage is applied.

[0004]

The present invention provides (A) at least one polymer selected from polyamic acid, polyimide, polyamidoimidic acid, polyamideimide and polyamide (hereinafter referred to as "polymer A") 100. Parts by weight, and (B) a powder having a volume resistivity of 1 × 10 ³ Ω · cm or less at 25 ° C. and an average particle diameter of 1 μm or less (hereinafter referred to as “powder B”) 0.01 to. 10 parts by weight,
The present invention provides a liquid crystal aligning agent comprising:

The constituent features of the present invention will be described below. The polymer A is a polymer compound selected from polyamic acid, polyimide, polyamidoimidic acid, polyamideimide and polyamide, and can be used alone or in combination of two or more kinds. Further, repeating units of these polymer compounds may coexist in the same molecule in a random or block form.

As the above polyamic acid, tetracarboxylic acid or its anhydride (hereinafter referred to as "tetracarboxylic acid etc.")
Say. ) And a diamine. Examples of the tetracarboxylic acid and the like include butanetetracarboxylic acid, butanetetracarboxylic dianhydride, cyclobutanetetracarboxylic acid, cyclobutanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid, 2,3,3. Examples thereof include aliphatic, alicyclic and aromatic tetracarboxylic acids such as 5-tricarboxycyclopentyl acetic acid dianhydride, pyromellitic acid and pyromellitic dianhydride, and dianhydrides thereof. Also,
Examples of the diamine include p-phenylenediamine,
Aromatic diamines such as 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, 2,2-bis [4- (4-aminophenoxy) phenyl] propane and 1,5-diaminonaphthalene can be mentioned.

Examples of the polyimide include polymers obtained by imidizing the polyamic acid with heat or the like.
Examples of the polyamidoimidic acid include polymers obtained by reacting a tricarboxylic acid, an anhydride thereof or a halogenated anhydride thereof (hereinafter referred to as “tricarboxylic acid etc.”) with a diamine. Examples of the tricarboxylic acid and the like include trimellitic acid, trimellitic anhydride, and trimellitic anhydride chloride, and examples of the diamine include the same diamines as described above. Examples of the above-mentioned polyamide-imide include polymers obtained by imidizing the above-mentioned polyamide-imide acid by heat or the like. Examples of the polyamide include a polymer obtained by reacting a dicarboxylic acid or a halide thereof (hereinafter referred to as “dicarboxylic acid or the like”) with a diamine. Examples of the dicarboxylic acid and the like include terephthalic acid, terephthalic acid dichloride, isophthalic acid, and isophthalic acid dichloride, and examples of the diamine include the above diamines. Among these, as the polymer A, polyamic acid and polyimide are preferable. The intrinsic viscosity of the polymer A is usually 0.05 to 10 dl / g, preferably 0.05 to obtain a coating film having an appropriate thickness of 0.001 to 1 μm.
~ 5 dl / g.

Examples of the powder B in the present invention include conductive powders having a volume resistivity of 1 × 10 ³ Ω · cm or less at 25 ° C. When a powder having a density of more than 1 × 10 ³ Ω · cm is used, the afterimage erasing time is not sufficiently improved.

Specific examples of the powder B include Fe and C.
u, Al, W, Mo, Ni, Co, Ta, Nb, Cr,
V, Ti, Zr, Be, U, Th, Au, Ag, Pt,
Metal powder such as Mn, Pb, Zn, Sn and TiO,
VO, NbO, CrO ₂ , MoO ₂ , WO ₂ , ReO ₂ , R
uO ₂ , CsO ₂ , RhO ₂ , IrO ₂ , ReO ₃ , LaT
iO ₃ , SrMoO ₃ , ZnO, SnO ₂ , TiO ₂ , Sb
Metal oxide powders such as ₂ O ₃ can be mentioned. These can be used alone or in combination of two or more.
Among these, the powder B is ZnO, TiO ₂ , Sb ₂
O ₃ , Ni and Au are preferred.

The average particle diameter of the powder B is obtained by number-averaging the longest diameters of the individual particles and is 1 μm or less, preferably 0.
It is 5 μm or less. If the average particle size exceeds 1 μm, short-circuiting between electrodes tends to occur when used as a liquid crystal alignment film in a TN or STN type display element. There is no particular lower limit to the average particle size, but it is usually about 0.001 μm. As the method for obtaining the powder B, for example, a stamp mill method, a ball mill method, a vortex flow mill method, a carding mill method, a granulation method, an impact method,
The spray method, the gas reduction method, the solid reduction method, the thermal decomposition method, the carbonyl method, the hydrogen compound decomposition method, the wet electrolysis method, the dry electrolysis method, the evaporation deposition method, the amalgam method, the intergranular corrosion method and the like can be used.
The shape of the powder B is preferably spherical. Also,
The ratio of the powder B to the polymer A used is that of the polymer A100.
It is 0.01 to 10 parts by weight, preferably 0.01 to 5 parts by weight, based on parts by weight. If the proportion of the powder B is less than 0.01 part by weight, the effect of improving the afterimage erasing time is small, and if it exceeds 10 parts by weight, the liquid crystal alignment becomes insufficient.

For the liquid crystal aligning agent of the present invention, an organic solvent for dissolving the polymer A and dispersing the powder B can be used. Examples of the organic solvent include aprotic type solvents such as γ-butyrolactone, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, tetramethylurea and hexamethylphosphoramide. Polar solvents; phenolic solvents such as m-cresol, xylenol, phenol and halogenated phenols can be mentioned. Of these, γ-butyrolactone, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide and the like are preferable.

As the organic solvent, alcohols, ketones, esters, ethers, halogenated hydrocarbons and hydrocarbons, which are poor solvents of the polymer A, are used.
Can be used together to the extent that does not precipitate. Examples of the poor solvent include methyl alcohol, ethyl alcohol, isopropyl alcohol, cyclohexanol, ethylene glycol, propylene glycol, 1,4-butanediol, triethylene glycol, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate, acetic acid. Ethyl, butyl acetate, diethyl oxalate, diethyl malonate, diethyl ether,
Methyl cellosolve, ethyl cellosolve, ethylene glycol-n-propyl ether, ethylene glycol isopropyl ether, butyl cellosolve, ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, tetrahydrofuran, dichloromethane, 1,2-dichloroethane, 1,4-dichlorobutane , Trichloroethane, chlorobenzene, o-dichlorobenzene, hexane, heptane, octane, benzene, toluene, xylene and the like.

The liquid crystal display device obtained by using the liquid crystal aligning agent of the present invention can be manufactured, for example, by the following method. First, the liquid crystal aligning agent of the present invention is applied to the transparent conductive film side of the substrate provided with the transparent conductive film by a printing method, a roll coater method, a spinner method, or the like, and the temperature is 80 to 200 ° C.
Preferably, the coating film is formed by heating at a temperature of 120 to 200 ° C. This coating film usually has a thickness of 0.001 to 1 μm, preferably 0.005 to 0.5 μm. The formed coating film is made into a liquid crystal alignment film by performing a rubbing treatment with a roll around which a cloth made of synthetic fiber such as nylon is wound.

As the substrate, for example, a glass substrate such as float glass or soda glass, or a plastic film transparent substrate such as polyethylene terephthalate, polybutylene terephthalate, polyether sulfone, polycarbonate, polyarylate or norbornene resin can be used. As the transparent conductive film, SnO
₂ NESA film, In ₂ O ₃ —SnO ₂ IT
An O film or the like can be used, and a photo-etching method, a method using a mask in advance, or the like is used for patterning these transparent conductive films.

When applying the liquid crystal aligning agent, in order to further improve the adhesion between the substrate and the transparent conductive film and the coating film, a functional silane-containing compound, titanate or the like is previously applied onto the substrate and the transparent conductive film. You can also do it. The substrates on which the liquid crystal alignment film is formed are made to face each other so that the rubbing directions of the liquid crystal alignment films are orthogonal or antiparallel, and the peripheral portion between the substrates is sealed with a sealant to fill the liquid crystal,
A liquid crystal cell is obtained by sealing the filling hole to form a liquid crystal cell, and laminating polarizing films on both sides of the liquid crystal alignment film so that their polarization directions are the same or orthogonal to the rubbing direction of the liquid crystal alignment film of the substrate. As the sealing agent, for example, a curing agent and an epoxy resin containing aluminum oxide spheres as a spacer can be used.

As the liquid crystal, a nematic type liquid crystal,
Smectic type liquid crystals can be exemplified, and among them, those forming a nematic type liquid crystal layer are preferable, for example, Schiff base type liquid crystal, azoxy type liquid crystal, biphenyl type liquid crystal, phenylcyclohexane type liquid crystal, ester type liquid crystal, terphenyl type liquid crystal. , Biphenylcyclohexane type liquid crystal, pyrimidine type liquid crystal, dioxane type liquid crystal, bicyclooctane type liquid crystal, cubane type liquid crystal and the like are used. In addition to these liquid crystals, for example, cholesteric liquid crystals such as cholesteryl chloride, cholesteryl nonaate and cholesteryl carbonate, and trade names C-15 and CB.
A chiral agent such as that sold as -15 (manufactured by Merck & Co., Inc.) may be added and used. further,
Ferroelectric liquid crystals such as p-decyloxybenzylidene-p-amino-2-methylbutyl cinnamate can also be used.

As the polarizing film used on the outside of the liquid crystal cell, a polarizing film in which a polarizing film called an H film absorbing iodine while sandwiching and stretching polyvinyl alcohol is sandwiched between cellulose acetate protective films, or the H film itself. And a polarizing film made of

[0018]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The afterimage erasing time was measured by visually applying a DC voltage of 10 V to the liquid crystal cell for 2 hours, turning off the voltage, and visually observing the time until the afterimage was erased. The liquid crystal orientation of the liquid crystal display device was judged to be good when a voltage was applied to the liquid crystal cell and no abnormal domain was observed under a microscope. Also,
As for the average particle size of the powder B, the number average particle size of the longest diameter was determined by observation with an electron microscope. Further, the volume resistivity of the powder B was obtained by pressing the powder to prepare a pellet sample and measuring the current value when a DC voltage of 1 V was applied to the pellet sample.

Synthesis of Polymer A; Synthesis Example 1 44.8 g of 2,3,5-tricarboxycyclopentylacetic acid dianhydride and 21.6 g of p-phenylenediamine
Was dissolved in 988 g of N-methyl-2-pyrrolidone and reacted at room temperature for 6 hours. The reaction mixture was then poured into a large excess of methanol to precipitate the reaction product. afterwards,
It was washed with methanol and dried under reduced pressure at 40 ° C. for 15 hours to obtain 60.2 g of a polyamic acid (polymer A-1) having an intrinsic viscosity of 1.44 dl / g.

Synthesis Example 2 Polyamic acid (polymer A-1) 3 obtained in Synthesis Example 1
Dissolve 0.0 g in 570 g of γ-butyrolactone,
1.6 g of pyridine and 16.74 g of acetic anhydride were added, and an imidization reaction was carried out at 120 ° C. for 3 hours. Then
The reaction product solution was precipitated in the same manner as in Synthesis Example 1 to give an intrinsic viscosity of 1.
24.0 g of 35 dl / g polyimide (polymer A-2)
I got Synthetic Example 3 A polyamic acid (polymer A-3) was obtained in the same manner as in Synthetic Example 1 except that diamine was changed to 39.6 g of 4,4′-diaminodiphenylmethane in Synthetic Example 1, and was further synthesized using this. The imidization reaction is carried out in the same manner as in Example 2,
Polyimide with intrinsic viscosity of 1.16 dl / g (polymer A-
4) 22.2 g was obtained.

Synthetic Example 4 Intrinsic viscosity 1.26 dl / g was carried out in the same manner as in Synthetic Example 1 except that 39.22 g of cyclobutanetetracarboxylic dianhydride was used as the tetracarboxylic dianhydride.
50.5 g of the polyamic acid (polymer A-5) was obtained. Synthesis Example 5 A polyamic acid having an intrinsic viscosity of 1.66 dl / g (polymer A) was prepared in the same manner as in Synthesis Example 1 except that the tetracarboxylic dianhydride was changed to 43.6 g of pyromellitic dianhydride. -6) 60.5 g was obtained.

Synthesis Example 6 40.6 g of terephthalic acid dichloride and 2,2-bis [4- (4-aminophenoxy) phenyl] propane 8
2.0 g was dissolved in 988 g of N-methyl-2-pyrrolidone, 40 g of pyridine was added, and the mixture was reacted at room temperature for 6 hours. The reaction mixture was then poured into a large excess of methanol,
The reaction product was precipitated. Then, it was washed with methanol and dried under reduced pressure at 40 ° C. for 15 hours to obtain an intrinsic viscosity of 1.
49 dl / g polyamide (polymer A-7) 110.2
g was obtained. Synthesis Example 7 42.0 g of trimellitic anhydride chloride and 82.0 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane were dissolved in 988 g of N-methyl-2-pyrrolidone, and 40 g of pyridine was added. The reaction was carried out at room temperature for 6 hours. The reaction mixture was then poured into a large excess of methanol to precipitate the reaction product. Then, it was washed with methanol and dried under reduced pressure at 40 ° C. for 15 hours to give a polyamidoimidic acid having an intrinsic viscosity of 1.49 dl / g (polymer A-
8) 111.2 g was obtained.

Example 1 Polyamic acid (polymer A-1) 5 obtained in Synthesis Example 1
g was dissolved in N-methyl-2-pyrrolidone, and then Zn having an average particle diameter of 0.02 μm and a volume resistivity of 80 Ω · cm was used.
0.1 g of O powder was added and sufficiently dispersed to obtain a solution having a solid content concentration of 4% by weight. This solution was filtered with a filter having a pore size of 1 μm to prepare a liquid crystal aligning agent solution. This solution was applied to a transparent electrode surface on a glass substrate with a transparent electrode made of an ITO film using a printer for applying a liquid crystal alignment film, and the temperature was 180 ° C.
And dried for 1 hour to form a coating film having a dry film thickness of 0.05 μm. A rubbing machine (manufactured by Iinuma Gauge Co., Ltd.) having a roll in which a rayon cloth is wrapped around this coating film;
RLN-9 type), the rotation speed of the roll is 500 rpm,
The rubbing process was performed at a moving speed of the stage of 1 cm / sec.

Next, an epoxy resin adhesive containing aluminum oxide spheres having a diameter of 17 μm was screen-printed on the outer edges of the pair of rubbing-treated substrates having the liquid crystal alignment film, and then the pair of substrates was placed on the liquid crystal alignment film surface. And the rubbing directions were orthogonal to each other, and they were stacked and pressure-bonded to cure the adhesive. After filling the nematic liquid crystal (ZLI-1565 manufactured by Merck & Co., Inc.) through the liquid crystal injection hole between the pair of substrates thus manufactured,
The liquid crystal injection port was sealed with an epoxy adhesive. A polarizing film was attached to both outer surfaces of the substrate so that the polarization direction of the polarizing film coincided with the rubbing direction of the liquid crystal alignment film of each substrate, to manufacture a liquid crystal display element. The alignment of the liquid crystal was good. When the afterimage erasing time after applying the DC voltage of 10 V for 2 hours was measured, it was as short as 0.3 sec.

Examples 2 to 12 In Example 1, the polymers (A) obtained in Synthesis Examples 2 to 7 were used.
-1 to A-8) and a powder B shown in Table 1 were used to prepare a liquid crystal aligning agent, and a liquid crystal cell was prepared in the same manner as in Example 1. The liquid crystal orientation of the obtained liquid crystal cell and the afterimage erasing time of the liquid crystal cell were measured.

Comparative Example Polyamic acid (Polymer A-6) 5 obtained in Synthesis Example 5
A liquid crystal cell was prepared in the same manner as in Example 1 except that g was dissolved in N-methyl-2-pyrrolidone, a liquid crystal aligning agent solution having a solid content concentration of 4% by weight was used, and the powder B was not mixed. It was As a result, the orientation of the liquid crystal was good, but the afterimage erasing time was 15 sec, and it took a considerable time to erase the afterimage. Table 1 shows the results of Examples 1 to 13 and Comparative Example.

[0027]

[Table 1]

[0028]

According to the present invention, a liquid crystal aligning agent having a short afterimage erasing time when a voltage is applied to a liquid crystal cell can be obtained. The reason for this is not clear, but it is considered that the charges accumulated on the liquid crystal alignment film are canceled by the addition of the conductive powder through the electrodes.

By using the liquid crystal aligning agent of the present invention, it is possible to obtain a liquid crystal aligning film having a short afterimage erasing time when a voltage is applied to the liquid crystal cell and having a good liquid crystal orientation. Further, a liquid crystal display device having a liquid crystal alignment film formed by using the liquid crystal aligning agent of the present invention can be selected by selecting a liquid crystal to be used, and thus SH (Super
Homeotropic), ferroelectric, and antiferroelectric liquid crystal display devices can also be suitably used. Furthermore, a liquid crystal display device having an alignment film formed by using the liquid crystal aligning agent of the present invention is excellent in liquid crystal alignment and reliability and can be effectively used in various devices. For example, desktop calculators, wrist watches, clocks, and coefficients. It is used for display devices such as display boards, word processors, personal computers, and liquid crystal televisions.

Next, preferred embodiments of the present invention will be listed. 1) Polymer A 100 parts by weight and powder B 0.01 to 10
A liquid crystal aligning agent, which is characterized by containing by weight. 2) A liquid crystal aligning agent containing 100 parts by weight of polymer A and 0.01 to 5 parts by weight of powder B. 3) The liquid crystal aligning agent according to 1), wherein the polymer A is a polyamic acid or a polyimide. 4) Powder B is Zn having an average particle size of 0.001 to 0.5 μm
The liquid crystal aligning agent according to 1) above, which is at least one selected from O, TiO ₂ , Sb ₂ O ₃ , Ni and Au. Remarks: 4) A liquid crystal aligning agent prepared by further dissolving the polymer A in an organic solvent capable of dissolving in the above 1) so as to have a solid content concentration of 0.1 to 15% by weight. 5) The liquid crystal compound according to 4) above, wherein the polymer A is a polyamic acid or a polyimide. 6) Powder B is Zn having an average particle size of 0.005 to 0.5 μm
O, and a _{TiO 2, Sb 2 O 3,} Ni, one or several of the powder selected from Au, said containing and 0.1-5 parts by weight relative to the polymer A100 parts 5) The liquid crystal aligning agent described. Comparative Example 2 Polyamic acid (Polymer A-6) 5 obtained in Synthesis Example 5
g was dissolved in N-methyl-2-pyrrolidone, 0.6 g of ZnO particles having an average particle diameter of 0.02 μm was added and sufficiently dispersed to obtain a solution having a solid content concentration of 4% by weight, except that a liquid crystal aligning agent was used. A liquid crystal cell was manufactured in the same manner as in Example 1. In this comparative example in which the powder B was blended in an amount exceeding the range of the present invention, the afterimage erasing time was as good as 0.4 sec, but the alignment property of the liquid crystal was poor. Comparative Example 3 Polyamic acid (Polymer A-6) 5 obtained in Synthesis Example 5
A liquid crystal cell was produced in the same manner as in Example 1 except that 0.1 g of ZnO particles having an average particle size of 1.5 μm and 0.1 g of ZnO particles were used as a liquid crystal aligning agent and filtered through a filter of 2 μm. In this comparative example in which the average particle diameter of the powder B is larger than the range of the present invention, the liquid crystal orientation was good, but a short circuit occurred between the electrodes of the liquid crystal cell.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Bessho 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd.

Claims (1)

[Claims] (A) 100 parts by weight of at least one polymer selected from (A) polyamic acid, polyimide, polyamidoimidic acid, polyamideimide and polyamide, and (B) 1 × 10 ³ Ω · cm or less at 25 ° C. Powder having a volume resistivity and an average particle diameter of 1 μm or less 0.01 to
A liquid crystal aligning agent containing 10 parts by weight.