JPS62917A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To form a uniform liq. crystal orienting film having high orienting properties at a low temp. by using polyamidoimide having repeating units represented by a prescribed structural formula. CONSTITUTION:Anhydrous trimellitic acid chloride and diamine are brought into polycondensation-ring opening addition reaction by soln. polymn. at a low temp., and the resulting polyamic acid is imidated by heat treatment to produce polyamidoimide represented by general formula I. The polyamidoimide has high solubility in various solvents. When a stable soln. prepd. by dissolving the polyamidoimide in a solvent such as dimethylformamide or N-methyl-2- pyrrolidone is applied to a transparent, electrically conductive substrate, a uniform liq. crystal orienting film having high orienting properties is obtd. The concn. of the soln. is about 0.1-1wt% and the thickness of the film is about 500-2,000Angstrom . Since the film can be removed by dissolution in a conventional org. solvent, necessary etching can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal display device, and particularly to improvements in its liquid crystal alignment film.

A variety of transparent conductive substrates with alignment films are used in Jubei Enfeng liquid crystal display elements, and since the alignment film has a great effect on the display quality of the liquid crystal display element, much effort has been put into the 68 shots. It is directed towards.

Conventionally, as an alignment film material for horizontally aligning liquid crystals,
It is known to use a polymer film such as polyimide, for example, polypyromellitimide or polyimide isoindoquinazolinedione.

However, since polyimide as mentioned above is soluble during etching, in order to form a film on a substrate, its precursor polyamic acid (a ring-opened form of polyimide) is applied in the form of a solution, and then cyclized after heating. It is necessary to make it into a polyimide structure. In this case, the heating cyclization requires 250 to 30
Since a high temperature of 0° C. or higher is required, there are problems such as deformation of the glass substrate and the need for special heating equipment. In recent years, active matrix liquid crystal display devices using thin film transistor arrays have been attracting attention in order to increase display capacity. However, since thin film transistor arrays are susceptible to deterioration at high temperatures, it is difficult to use the polyimide as an alignment film. It is difficult. In addition, liquid crystal display elements using plastic substrates have also been developed, but in the case of plastic substrates, the heat resistance is poor, so it is difficult to apply the above-mentioned polyimide as an alignment film. In this case, the precursor polyamic acid is unstable, so it has a short pot life.

TECHNICAL FIELD The present invention relates to a liquid crystal display element capable of forming a liquid crystal alignment film at low temperatures and a method for manufacturing the same.

Monthly 1Bγ extinction.

The liquid crystal display element of the present invention is a liquid crystal display element having a liquid crystal alignment film on a substrate, in which the liquid crystal alignment film has a general formula (I) [wherein the ratio of n and m is arbitrary, and Ar is ( R1)a
(R") p (R3) It is characterized by containing polyamideimide as a main component having a repeating unit represented by an integer of 4].

The present invention will be explained in more detail below.

The polyamide-imide of the present invention can be produced, for example, by subjecting trimellitic anhydride chloride and diamine to a polycondensation ring-opening addition reaction using a low-temperature solution polymerization method according to the reaction formula below to obtain a polyamic acid, which is then further heat-treated to imidize it. It can be synthesized by

The polyamideimide represented by the general formula (I) has high solvent solubility itself, unlike conventional polyimides,
For example, it can be dissolved in various solvents such as N-methyl-2-pyrrolidone, dimethylformamide, dimethylsulfoxide, and dimethylacetamide to give stable polyamideimide solutions. Such a polyamide-imide solution has high manufacturability and can be easily coated onto a transparent conductive substrate to form an alignment film, and the resulting alignment film is uniform and has high orientation. . Furthermore, the polyamide-imide used in the present invention has a long pot life, and when stored in powder or solution form, maintains its excellent performance even after storage for 2 months to over 1 year.

The appropriate thickness of the polyamide-imide alignment film is about 100 to 5000, preferably 500 to 2000.The alignment film is made of cotton cloth or nylon flocked fabric.

Orientation treatment can be performed by rubbing with a polyester flocked cloth or the like.

The polyamide-imide alignment film of the present invention has excellent homogeneous alignment with respect to liquid crystal.

Examples of liquid crystals include thin-base liquid crystals.

Examples include azoxy liquid crystal, biphenyl liquid crystal, phenylcyclohexane liquid crystal, ester liquid crystal, pyrimidine liquid crystal, terphenyl liquid crystal, and biphenylcyclohexane liquid crystal. These liquid crystals are used alone or usually as a mixture. Furthermore, cholesteric liquid crystals such as cholesteryl chloride, cholesteryl nonaate, and cholesteryl carbonate, chiral nematic liquid crystals such as those sold by British Drug House under the trade names C-15 and CB-15, etc. may be attached. , an ionic dopant such as a tetraalkylammonium salt, etc. can also be added.

When performing etching on a substrate having a polyamide-imide alignment film used in the present invention to form necessary parts such as an electrode lead-out part and a seal forming part, the polyamide-imide alignment film is Since it can be eluted using an organic solvent, the required etching can be carried out safely by a simple method such as photolithography.

The liquid crystal alignment film of the present invention can be produced, for example, by condensing and imidizing monomers in advance to form polyamide-imide and applying this solution on a substrate (first method), or by using a solution containing polyamic acid as a polyamide-imide precursor. It can be obtained by coating a polyamide-imide film on a substrate and then cyclizing it to form a polyamide-imide film (second method).

In the first method, first, a trimellitic acid derivative of the following general formula (I1) and a general formula (m) or (I'l) are used as monomers.
/) with an aromatic diamine to form polyamide-imide through low-temperature solution polymerization, and this is dissolved in a suitable solvent to obtain a polyamide-imide solution.

o.

[In the formula, X is a halogen atom, X,,X.

are both oxygen atoms or each is a halogen atom. ] [In the formula, R1, R'', Q, and p represent the following R
', R'': halogen atom or lower alkyl group, P: integer from 1 to 4] (R')X (R')V [In the formula, R', R', x+ytz represent R' , R': halogen atom or lower alkyl group
is suitable, preferably 0.1 to 1% by weight.Additives such as other resins can also be added to this solution as required. Next.

This solution is applied by conventionally known methods such as spin cord, roller coating, spray coating, and dipping.
Then, it is heated to remove the solvent to form a polyamide-imide alignment film. When drying a polyamide-imide solution by heating, the heating temperature depends on the boiling point and vapor pressure of the solvent used. - In the case of dimethylformamide (DMF), a temperature of 100 to 150°C is sufficient, and by specifying the type of solvent, heating drying can be performed at extremely low temperatures. Such low-temperature heating and drying can prevent damage and deterioration of the substrate.

The type of liquid crystal substrate used in the present invention is not limited.

In addition to glass substrates, plastic films such as polyester, polyethersulfone, polysulfone, and acetyl cellulose, substrates on which semiconductor elements such as thin film transistor arrays are formed, silicon wafers, and the like can be advantageously used.

In the second method, a trimellitic acid derivative of general formula (n),
A precursor solution is obtained by dissolving a condensate (polyamic #) with an aromatic diamine of general formula (■■) or (rV).

This solution is then applied onto the substrate. The coating method is the same as the first method.

The concentration of the solution depends on the solvent used and the application method, but
For example, when coating with a spin code using N,N-dimethylformamide as a solvent, 2 to 5 vt%
A concentration of about 10% is preferable.

Next, the solvent is dried from this precursor coating film.

After removal, the precursor is ring-closed and imidized by heat treatment to form a polyamide-imide alignment film.

A heat treatment temperature of 120 to 150°C is sufficient, preferably 130 to 150°C. According to this heating temperature,
It is possible to sufficiently suppress damage to plastic substrates and active matrix substrates.

Further, according to the present invention, a liquid crystal alignment film having high alignment performance can be obtained, and the display quality and reliability of a liquid crystal display element can be improved.

In addition, polyamideimide, which is the main component of the alignment film of the present invention, is soluble in solvents, so the alignment film can be formed by a process of applying a solution and drying. Even substrates with poor heat resistance can be satisfactorily applied.

Synthesis Example 1 4.4'-diaminodiphenyl ether 6.01K (0
,03 mol) was dissolved in 75 mQ of dimethylacetanilide, and while cooling with water, 32 g (0.03 mol) of trimellitic anhydride alitro was added, and the mixture was reacted at room temperature for 3 hours. The obtained solution was poured into water, and the polyamic acid was collected by filtration and dried under reduced pressure. Next, this polyamide acid was heated under reduced pressure at 150°C for 1 hour and at 180°C for 3 hours to obtain polyamideimide.

Logarithmic viscosity 71inh=0.52 (DMF, 5g/
dQ, 30℃) Infrared absorption spectrum: 1775.1
720.1670°720co+-1 Synthesis Example 2 Polyamide was produced in the same manner as in Synthesis Example 1 except that 5.85 g of 4,4'-diaminodiphenylmethane was used instead of 4,4'-diaminodiphenyl ether. I got imide.

r) inh=0.55 Infrared absorption spectrum: 1775.1720.167
0°720c+o-1 Synthesis Example 3 4.4'-diaminodiphenyl ether 6.01g (0
,03 mol) was dissolved in dimethylacetanilide 7SmQ, and while cooling with water, 6.32 g (0.03 mol) of trimellitic anhydride chloride was added, and the mixture was reacted at room temperature for 3 hours. The obtained solution was poured into water, and the polyamic acid was collected by filtration and dried under reduced pressure. Next, this polyamic acid was heated under reduced pressure at 150°C for 1 hour and at 180°C for 3 hours to obtain a polyamic acid.

η1nh=0.52 Infrared absorption spectrum: 1775.1720.167
0°720cm-1 Synthesis Example 4 Polyamic acid was produced in the same manner as in Synthesis Example 1, except that 5.85 g of 4,4'-diaminodiphenylmethane was used instead of 4,4'-diaminodiphenyl ether. Obtained.

77 inh = 0.55 Infrared absorption spectrum: 1775.1720.167
0°720cm-1 Example 1 The polyamideimide obtained in Synthesis Example 1 was diluted with N,N-
It was dissolved in dimethylformamide to obtain a riboriamideimide solution with a concentration of 2%. These solutions were coated on a glass substrate having a transparent conductive film of indium oxide-tin oxide by a spin code method, and then heated at 120°C for 15 minutes to
By heating for 30 minutes at °C to evaporate the solvent,
A uniform polyamide-imide coating was obtained.

Next, this polyamide-imide film was subjected to a rubbing treatment to form an alignment film, and then a heat resistance test was conducted at 150° C. for 24 hours. The two substrates obtained in this way were stacked with a 10 μm spacer in between so that the alignment axes were perpendicular to each other, and epoxy adhesive was pasted as a sealant, and biphenyl liquid crystal (BD) 1
E-8), manufactured by Co., Ltd., was sealed therein to create a C-stained nematic type liquid crystal-filled cell. The liquid crystal-filled cell obtained in this way showed good alignment without any alignment defects such as reverse domains, and even when compared with a liquid crystal-filled cell similarly prepared without conducting a heat resistance test, the alignment No difference was observed in the properties, and it was confirmed that they exhibited excellent high-temperature durability. Furthermore, it was confirmed that a liquid crystal-filled cell produced in the same manner using the polyamide-imide obtained in Synthesis Example 2 also exhibited excellent orientation and high-temperature durability.

Example 2 A liquid crystal-filled cell was produced in the same manner as in Example 1, except that phenylcyclohexane liquid crystal (manufactured by E-Merck, ZLI-1285) was used as the liquid crystal. This product also showed excellent orientation similar to Example 1.

Example 3 A liquid crystal-filled cell was produced in the same manner as in Example 1, except that a polyester (PET) film with a transparent conductive film was used as the substrate. This cell too.

Similar to Example 1, excellent orientation was exhibited.

Example 4 The polyamic acid obtained in Synthesis Example 3 was dissolved in N,N-dimethylformamide to obtain a polyamic acid solution having a concentration of 2% by weight. This solution was coated on a glass substrate having a transparent conductive film of indium oxide-tin oxide by a spin code method, and then heated at 120°C for 15 minutes and at 150°C for 30 minutes.
A uniform polyamide-imide coating was obtained by heating for a minute.

Next, this polyamide-imide film was subjected to a rubbing treatment to form an alignment film, and then a heat resistance test was conducted at 150° C. for 24 hours. The two substrates obtained in this way were stacked with a 10 μm spacer in between so that the orientation axes were perpendicular to each other, and were bonded together using an epoxy adhesive as a sealant.
E-8) manufactured by DH Co., Ltd. was sealed to create a twinstead nematic type liquid crystal-filled cell. The thus obtained liquid crystal-filled cell showed good alignment without any alignment defects such as reverse domains, and compared with a liquid crystal-filled cell similarly prepared without conducting a heat resistance test, it showed good alignment. No difference was observed in the orientation, and it was confirmed that they exhibited excellent high-temperature durability. Furthermore, it was confirmed that a liquid crystal cell produced in the same manner using the polyamideimide obtained in Synthesis Example 4 also exhibited excellent orientation and high-temperature durability.

Example 5 A liquid crystal-filled cell was prepared in the same manner as in Example 4, except that a phenylcyclohexane liquid crystal (manufactured by ε-Mark, ZLI-1285) was used as the liquid crystal.

This product also showed excellent orientation similar to Example 4.

Example 6 A liquid crystal-filled cell was produced in the same manner as in Example 4 except that a polyester (PET) film with a transparent conductive film was used as the substrate. This cell also showed excellent orientation similar to Example 4.

Claims (1)

[Claims] 1. In a liquid crystal display element having a liquid crystal alignment film on a substrate, the liquid crystal alignment film has a general formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) [In the formula, n and The ratio with m is arbitrary, and Ar represents ▲There are mathematical formulas, chemical formulas, tables, etc.▼ and/or ▲There are mathematical formulas, chemical formulas, tables, etc.▼. R^1, R^2, R^3, R_4: z representing a halogen atom or lower alkyl group: an integer of 1 to 5 l, p, x, y: an integer of 1 to 4] Having a repeating unit represented by A liquid crystal display element characterized by containing polyamideimide as a main component.