JPH1152386A - Liquid crystal orienting film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a thick film with high transparency by using a three- dimensional crosslinking resin to form a film and giving liquid crystal orientating ability to the film by rubbing. SOLUTION: The liquid crystal orienting film is produced by dissolving a three-dimensional crosslinking resin in an org. solvent to prepare a liquid crystal orienting film material, applying the obtd. material on a substrate, and successively subjecting to predrying, hardening and rubbing treatment. As for the three-dimensional crosslinking resin, a resin containing glycidylacrylate (including glycidyl methacrylate) and its hardening agent is used. As for the hardening agent, at least one compd. selected from trimellitic acid anhydride, 2,4- diaminoazobenzene, 4,4'-diaminostilbene and magneson is used. The rubbing treatment is carried out by using a roller with a nylon or rayon cloth wound and rubbing the surface of the orienting film. Thereby, orientation of liquid crystal molecules is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal alignment film used for a liquid crystal display device.

[0002]

2. Description of the Related Art In general, a liquid crystal alignment film is used for a liquid crystal display device, and aligns liquid crystal molecules in a certain direction.
That is, it is provided because it needs to be oriented.
Liquid crystal display elements have traditionally been used for watches, calculators, computers,
It is used for liquid crystal displays (LCD) such as word processors. As a basic structure of a liquid crystal display element, it is common that two substrates having an alignment film provided on a transparent electrode are arranged with the alignment film inside, and a liquid crystal is sealed between them. Such a liquid crystal display device includes a twisted nematic (TN) mode in which a nematic liquid crystal has a twisted structure and a super twisted nematic (S).
Display in the TN) mode is known. As the driving of the liquid crystal display element, a matrix display in which electrodes are formed in a display pattern such as a stripe shape or a grid shape on a substrate, and a device using a thin film transistor (TFT) are known. Something comparable to a normal CRT has been realized. Market requirements for LCDs include large screens, wide viewing angles, high definition, high brightness, high contrast, lightweight and thin, low power consumption, low price, and the like. Among them, in order to achieve high brightness and high contrast, it is necessary to increase the light use efficiency. Therefore, it is desired to minimize the absorption of light by each member of the LCD.
LCDs with the same brightness if light absorption can be suppressed
In this case, the brightness of the backlight can be reduced to reduce power consumption.

[0003]

A polyimide resin is usually used for the alignment film. However, many polyimide resins have an absorption in the visible light region and are colored or have insufficient transmittance, and the quality of the liquid crystal display device is poor. Leads to a drop. Insufficiency of coloring or transmittance becomes remarkable when the alignment film is thick, so that the alignment film is usually a thin film of 0.1 μm or less. It has been made as a result of intensive studies to make the three-dimensional crosslinked resin of the present invention suitable for use as an alignment film.
The present invention also aims at not only using the three-dimensionally crosslinked resin as the OC but also as the alignment film in consideration of the fact that the overcoat layer (OC) also serves as the alignment film. This is the result of intensive studies. That is, a three-dimensional crosslinked resin capable of aligning the liquid crystal by rubbing is used as the alignment film.

[0004]

Means for Solving the Problems The liquid crystal alignment film of the present invention comprises:
A liquid crystal alignment film made of a three-dimensionally crosslinked (cross-linked) resin and provided with liquid crystal alignment ability by rubbing. As the three-dimensional crosslinked resin, glycidyl acrylate (including glycidyl methacrylate) and a resin containing a curing agent thereof can be used. As the curing agent, trimellitic anhydride, 2,4-
At least one selected from diaminoazobenzene, 4,4'-diaminostilbene and magneson is used.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The liquid crystal alignment film of the present invention is
It is formed on an electrode substrate such as a glass plate on which a transparent electrode such as ITO (Indium Tin Oxide) is provided, and a pair thereof is arranged to face each other, and a liquid crystal is sandwiched between the electrode substrates to form a liquid crystal sandwiching substrate. . In this case, the liquid crystal alignment film formed on one electrode substrate of the liquid crystal sandwiching substrate does not have to be the liquid crystal alignment film of the present invention. In addition, a liquid crystal display element having a liquid crystal holding substrate can be obtained by a known method using the liquid crystal holding substrate. The thickness of the liquid crystal alignment film of the present invention is desirably 5 μm or less. The thickness of the liquid crystal alignment film used in the present invention is 0.1.
1-3 μm is more desirable. The rotation speed of the spin coater is desirably 500 to 5000 rpm. The rotation speed of the spin coater is more desirably 500 to 2000 rpm. Drying after spin coating can be performed using a hot plate that is generally widely used. The temperature of the hot plate used for leveling is 30 ° C to 130 ° C.
Is desirable. The temperature of the hot plate used for leveling is more preferably from 30C to 80C.

The three-dimensionally crosslinked (crosslinked) resin undergoes a curing reaction at an appropriate temperature. In this curing reaction, by selecting appropriate conditions, the degree of crosslinking can be appropriately adjusted. For example, at 100 ° C. or higher, particularly 120 ° C. or higher, an appropriate curing accelerator or the like can be used as necessary.

The liquid crystal alignment film material contains the three-dimensionally crosslinked resin, and is preferably a material obtained by dissolving the three-dimensionally crosslinked resin in an organic solvent (varnish).
The three-dimensional crosslinked resin is applied with a thermosetting resin and a curing agent dissolved in an appropriate organic solvent, and the organic solvent is evaporated,
Further, it can be formed on a substrate by causing a curing reaction. Examples of the organic solvent include toluene, xylene, cellosolve acetate, butyl cellosolve acetate, methyl cellosolve, ethyl diglycol acetate, diethylene glycol dimethyl ether,
Ethylene glycol diacetate, propylene glycol monomethyl ether acetate, γ-butyrolactone, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, hexamethylphosphoramide, phenol, m- There are cresol, chlorobenzene, and the like, and two or more kinds may be used as a mixture as long as they are compatible with each other. The selection of the organic solvent to be used is determined in consideration of the solubility of the three-dimensional crosslinked resin. Further, it can be prepared by diluting a thermosetting resin and a curing agent in separate organic solvents and mixing them before use. In such a case, the determination is made in consideration of the compatibility of each organic solvent and the solubility of each solute.

[0008] In addition to the three-dimensionally crosslinked resin, additives can be used in the liquid crystal alignment film material. Examples of the additives used herein include benzophenones such as benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, Michler's ketone, chloroacetophenone, diethoxyacetophenone, 4-phenoxydichloroacetophenone and 4-benzophenone. t-butyldichloroacetophenone, 2
-Hydroxy-2-methyl-1-phenylpropane-1
Acetophenones such as -one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1- (4-methylthiophenyl) -morpholinopropan-1-one, Benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl methyl ketal, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, 2,4- Thioxansones such as diethylthioxanthone and isopropylthioxanthone, dimethyl 2,2′-azobisisobutyrate, 1,1′-azobis- (cyclohexane-1-carbonitrile),
Azo compounds such as 2,2'-azobis (2,4-dimethylvaleronitrile), azobisisobutyronitrile, and 2,2'-azobis- (4-methoxy-2,4-dimethylvaleronitrile); 2,2-bis- ( (4-stearylamino) phenoxyphenyl) propane, 2,2-
Bis-((4-laurylamino) phenoxyphenyl)
There are compounds having a long aliphatic chain such as propane, and these may be used in combination of two or more. The amount of the additive used is 0.01 to 60% by weight based on the weight of the polyimide resin or polyamic acid resin in the liquid crystal alignment film material. If the amount is less than 0.01% by weight, the effect of changing the pretilt is small, and if it is more than 60% by weight, there is a problem in reliability and the like.

The liquid crystal alignment film material is prepared by, for example, applying a three-dimensionally crosslinked resin raw material liquid onto an appropriate substrate such as a glass substrate on which a transparent electrode such as ITO (Indium Tin Oxide) is formed in advance, and sequentially preparing the liquid. After drying and main curing, a three-dimensional crosslinked resin layer is obtained. As a coating method, a method such as a spin coating method, a dipping method, a printing method, and a spraying method is used. Predrying temperature is 30 to 150 ° C, preferably 30 to 100 ° C
Is selected in the range. The time is between 10 seconds and 5 minutes. The curing temperature is 80 to 250 ° C, preferably 150 to 2 ° C.
The temperature is selected within the range of 30 ° C., but the temperature is not lower than the temperature at which the curing reaction of the three-dimensional crosslinked resin proceeds to such an extent that there is no practical problem. For this purpose, the temperature is preferably 150 ° C. or higher, particularly preferably 180 ° C. or higher. The heating time is preferably 1 minute to 6 hours,
In particular, 1 minute to 3 hours are preferable. In order to improve the adhesion between the substrate and the three-dimensionally crosslinked resin, a coupling agent such as a silane coupling agent or a titanium coupling agent may be used.

The liquid crystal alignment film is manufactured by applying the liquid crystal alignment film material to a substrate, sequentially performing preliminary drying and main curing, and then performing a rubbing treatment. The rubbing treatment is a treatment of rubbing the surface of the alignment film using a roller wrapped with a cloth made of nylon or rayon, whereby the alignment of liquid crystal molecules is obtained.

[0011]

【Example】

Examples 1 to 9 A polymer containing glycidyl methacrylate was diluted with an organic solvent to prepare a stock solution (first solution) for a composition for a liquid crystal alignment film.
Next, trimellitic anhydride was diluted with an organic solvent to prepare a stock solution (second solution) for a composition for a liquid crystal alignment film. Further, the reactive additive was diluted with an organic solvent to prepare a stock solution (third solution) for a composition for a liquid crystal alignment film. Cellosolve acetate and propylene glycol monomethyl ether acetate were used for diluting the first and second liquids, and N, N- was used for diluting the third liquid.
Dimethylacetamide was used. Table 1 shows the types of reactive additives used in the third liquid. These stock solutions were mixed as shown in Table 2 to prepare a liquid crystal alignment film composition solution. Here, the equivalent ratio of the reactive functional groups of the second liquid and the third liquid to the epoxy equivalent of the first liquid is shown. For example, in the case of the second liquid (carboxyl group + twice the acid anhydride group) / epoxy group = 1, the equivalent ratio was set to 1.

Table 1 Types of reactive additives ----------------------------------------------- No. Reactive additives --------- Reactive additive 1,2,4-diaminoazobenzene Reactive additive 2,4,4'-diaminostilbene Reactive additive 3 Magneson --------------------------------------------------

Table 2 Composition Solution for Liquid Crystal Alignment Films --------------------------------------------------------------------------- Examples Equivalent ratio of the second liquid Equivalent ratio of the third liquid Type of additive Concentration ---------------------------------------------- −−− Example 1 10 −− Example 2 0 1 Reactive additive 1 20% Example 3 0.5 0.5 Reactive additive 1 20% Example 4 11 Reactive additive 1 20% Example 5 1 0.2 Reactive additive 1 20% Example 6 0.5 0.5 Reactive additive 2 10% Example 7 1 1 Reactive additive 2 10% Example 8 0.5 0.0. 5 Reactive Additive 3 10% Example 9 1 0.2 Reactive Additive 3 10% −−−−−−−−−−−−−−−−−−−−−−−−−−−−− −−−−−−−−−

The composition solution for a liquid crystal alignment film is spin-coated on two glass substrates with ITO transparent electrodes, heated at 70 ° C. for 1 minute to evaporate the solvent to form a resin film on the substrate, and then heated in an oven. It was cured by heating at 200 ° C. for 1 hour. Next, the resin coating surface was rubbed with the indentation amount of 0.4 mm under the conditions shown in Table 3. The substrate was subjected to ultrasonic cleaning in pure water at 60 ° C and 170 ° C in an oven as shown in Table 3.
For a predetermined time. Next, the two substrates are combined with the resin coating layers facing each other so that the rubbing directions are antiparallel, and the periphery is sealed with a thermosetting sealant, and the test space is set so that the gap is about 5 μm. The cell was assembled and heated at 150 ° C. for 1 hour in an oven to cure the sealant. Liquid crystal ZLI-4792 (trade name, manufactured by Merck) was sealed in the test empty cell at room temperature to form a liquid crystal cell. The liquid crystal cell was observed through a polarizing plate to evaluate the orientation of the liquid crystal. The evaluation results of the liquid crystal orientation are shown in Table 3 as ○ when uniform orientation was exhibited uniformly in one direction, × when defects occurred or the orientation direction was different depending on the location, and △ in the middle between them. It was shown to. Further, the liquid crystal cell was heated in an oven at 130 ° C. for 1 hour and then gradually cooled to perform an aging treatment, and the liquid crystal orientation was evaluated again. In each case, a good liquid crystal alignment was obtained after the aging treatment.

Table 3 Results of Evaluation of Liquid Crystal Alignment ------------------------------------------ Rubbing conditions Washing Drying Conditions Liquid crystal orientation Alignment film Roller Table Conditions Example Rotation speed Moving speed Number of times Time Aging treatment (rpm) (mm / min) (° C) (min) Before and after --- --- --- ------ −−−−−−−−−−−−−−−−−−−−−−− Example 1 600 140 1 No washing No drying ○ ○ Example 1 600 280 1 Ultrasonic 170 10 △ ○ Example 1 400 600 2 No washing No drying ○ ○ Example 1 400 600 2 Ultrasonic 170 10 △ ○ Example 1 400 600 5 Ultrasonic 170 10 ○ ○ Example 2 600 140 1 No cleaning No drying × ○ Example 3 400 600 2 No washing No drying ○ ○ Example 4 600 140 1 No cleaning No drying ○ ○ Example 5 400 600 2 No cleaning No drying ○ ○ Example 6 600 140 1 No cleaning No drying △ ○ Example 7 600 140 1 No cleaning No drying × ○ Example 8 600 140 1 No washing No drying ○ ○ Example 9 600 140 1 No washing No drying ○ ○ −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− −−−−−

[0016]

The liquid crystal alignment film of the present invention is a three-dimensionally crosslinked product and is not a polyimide resin conventionally used for an alignment film, so that it has high transparency and can easily form a thick film. is there.

Claims (3)

[Claims] 1. A liquid crystal alignment film made of a three-dimensional crosslinked resin and provided with liquid crystal alignment ability by rubbing. 2. The liquid crystal alignment film according to claim 1, wherein the three-dimensional crosslinked resin is a resin containing glycidyl acrylate and a curing agent thereof. 3. A curing agent comprising trimellitic anhydride, 2,4
3. The liquid crystal alignment film according to claim 2, which is at least one selected from -diaminoazobenzene, 4,4'-diaminostilbene and magneson.