JP2002350859A - Liquid crystal alignment film and liquid crystal display element using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alignment film which aligns liquid crystal in a direction different from the rubbing direction by rubbing, does not change the alignment direction even when heat treatment such as annealing treatment is performed and enables the baking at a low temperature, and a liquid crystal display ele ment using the alignment film. SOLUTION: This alignment film is endowed with liquid alignment ability to a direction different from the rubbing direction by the rubbing and consists essentially of one or more kinds of polymer compounds selected from an addition polymerization system polymer compound which has one or more kinds of groups represented by formula (1) as side chains and a polymer compound which has one or more kinds of groups represented by formula (2) as structural units.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal alignment film and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art A liquid crystal display element used in a timepiece or a calculator is obtained by filling a liquid crystal between a pair of upper and lower electrode substrates. In these liquid crystal display elements, in order to function as a display element, it is necessary to orient the liquid crystal inside the element in a predetermined direction. However, since the liquid crystal used here is a rod-shaped molecule, the refractive index differs depending on the direction in which the liquid crystal display element is viewed, and the phenomenon of grayscale inversion and a decrease in the viewing angle occurs. In order to solve this problem, a method has been proposed in which each pixel or each pixel is divided into two and rubbed in different directions. However, this method requires forming a photoresist film after the first rubbing, removing a part of the photoresist film, performing a second rubbing, and removing the remaining photoresist film, which complicates the process. There's a problem.

Therefore, a polymer for aligning the liquid crystal parallel to the rubbing direction and a polymer for aligning the liquid crystal perpendicular to the rubbing direction are provided in a fixed pattern, and the rubbing is performed once so that the alignment is performed. A method of performing the division has been proposed. This method can perform the orientation division more easily. However, polystyrene, which is disclosed in Japanese Patent Application Laid-Open No. 2-77015 and is known as a polymer that orients liquid crystals perpendicular to the rubbing direction, can be used after rubbing. When heated,
The orientation direction changes from a direction perpendicular to the rubbing direction to a direction parallel to the rubbing direction. In particular, after the liquid crystal display device is made, the liquid crystal is heated to an isotropic liquid state, and an annealing process is performed to correct the alignment defects and the like of the liquid crystal display device. There was a problem of doing it. On the other hand, it has been desired that the alignment film can be fired at a low temperature of 120 ° C. to 140 ° C. from the viewpoint of low heat resistance of the color filter and energy saving.

JP-A-1-304424 discloses that a polymer having a ring structure in a side chain is considered as an example of a polymer compound for aligning liquid crystal molecules in a direction perpendicular to a rubbing direction. Including pentane ring, cyclohexane ring, benzene ring, naphthalene ring, furan ring, oxolan ring, dioxolan ring, thiophene ring, pyrrole ring, pyran ring, oxane ring, dioxane ring, pyridine ring, piperidine ring, pyrimidine ring, pyrazine ring, etc. Mentions polymers. However, what is specifically disclosed in this publication is only the high molecular compound having a benzene ring in the side chain among the above, and other polymer compounds are only suggested to be usable. Not just. Japanese Patent Application Laid-Open No. 11-212097 discloses that a polymer having a polyamic acid and / or imide group obtained from 9,9-bis (4-aminophenyl) fluorene and a tetracarboxylic anhydride is used in a rubbing direction. To align liquid crystal molecules in a vertical direction.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to align a liquid crystal in a direction different from the rubbing direction by rubbing and to perform a heat treatment such as an annealing process. Another object of the present invention is to provide an alignment film which does not change its alignment direction and can be fired at a low temperature, and a liquid crystal display device using this alignment film.

[0006]

Means for Solving the Problems As a result of intensive research and development, the present inventors have found that when a polymer compound having a specific structure is rubbed, the liquid crystal is oriented in a direction different from the rubbing direction, and annealing is performed. It has been found that the orientation direction does not change even when a heat treatment such as a treatment is performed, and an orientation film that can be fired at a low temperature can be obtained, and the present invention has been completed.

That is, the present invention has the following configuration. (1) A liquid crystal alignment film provided with a liquid crystal alignment ability in a direction different from the rubbing direction by rubbing, wherein the polymer compound used for the liquid crystal alignment film is a group represented by the following group (1): At least one kind selected from the group consisting of an addition polymerization type polymer compound having at least one kind as a side chain and a polymer compound having at least one kind of a group shown in the following group (2) as a constituent unit; A liquid crystal alignment film comprising a polymer compound containing a polymer compound as a main component and not containing a polymer obtained from a fluorene ring-containing diamine compound and a tetracarboxylic anhydride.

Embedded image (Any hydrogen atom in these groups may be substituted with alkyl, aryl, halogen or allyl.)

Embedded image (Any hydrogen atom in these groups may be substituted with alkyl, aryl, halogen or allyl.) (2) When the polymer compound has at least one of the groups shown in group (1), The liquid crystal alignment film according to the above (1), wherein the liquid crystal alignment film is at least one polymer compound selected from addition polymerization polymer compounds having a chain. (3) The polymer compound has the formula (1)

Embedded image (Any hydrogen atom in the formula may be substituted with alkyl, aryl, halogen or allyl.) It is characterized by being an addition polymerization type polymer compound having a group represented by a side chain. The liquid crystal alignment film according to the above (2). (4) The polymer compound described above, wherein the polymer compound is at least one polymer compound selected from polymer compounds having at least one of the groups shown in group (2) as a constituent unit. The liquid crystal alignment film according to the item 1). (5) The polymer compound has the formula (2)

Embedded image (Any hydrogen atom in the formula may be substituted with alkyl, aryl, halogen or allyl.) A polymer compound having a group represented by the structural unit as a structural unit, wherein (4) Item). (6) The polymer compound represented by the formula (3)

Embedded image (5) The above-mentioned item (5), which is a polymer compound having a repeating unit represented by the formula (any hydrogen atom in the formula may be substituted with alkyl, aryl, halogen or allyl). The liquid crystal alignment film according to 1. (7) A liquid crystal display device comprising the liquid crystal alignment film according to any one of the above (1) to (6).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An alignment film of the present invention, which is oriented at a low temperature by rubbing and aligning the liquid crystal in a direction different from the rubbing direction, and does not change its alignment direction even if heat treatment such as annealing is performed. Is an addition-polymerized polymer compound having at least one of the groups shown in the following group (1) as a side chain (hereinafter, sometimes referred to as a raw material polymer A) and shown in the following group (2): And at least one polymer compound selected from the group consisting of a polymer compound having at least one type of group as a constituent unit (hereinafter, may be referred to as a raw material polymer B). It is an alignment film. However, it does not include a polymer obtained from a fluorene ring-containing diamine compound and a tetracarboxylic anhydride.

[0009]

Embedded image (Any hydrogen atom in these groups may be substituted with alkyl, aryl, halogen or allyl.)

[0010]

Embedded image (Any hydrogen atom in these groups may be substituted with alkyl, aryl, halogen or allyl.)

The raw material polymer A can be obtained by, for example, addition polymerization of a vinyl derivative having one of the groups shown in the above group (1) as a substituent.
As the monomer capable of addition polymerization, in addition to the vinyl derivative,
A propylene derivative or a butylene derivative having one of the groups shown in group (1) as a substituent can also be used. These monomers may be subjected to addition polymerization alone, or two or more of these monomers may be copolymerized. In addition, as long as the liquid crystal alignment ability in a direction different from the stretching direction added by rubbing is not hindered, one or more of these monomers may be copolymerized with a monomer having no such group. It can be used even if it is united. Specific examples of the raw material polymer A include poly (vinyl imidazole), poly (N-vinyl carbazole), and poly (N-vinyl phthalimide). In order to improve the heat resistance of the alignment film, Poly (N-vinylcarbazole) is preferred.

The high molecular compound (raw material B) having at least one of the groups represented by the above group (2) as a structural unit is a main compound after one of the carbon atoms constituting the ring is polymerized. It can be obtained by polymerizing a compound having a cyclic group having a structure that becomes a part of a chain. The method of polymerizing may be a polycondensation reaction with another compound or a polyaddition reaction. That is, as the raw material polymer B, polymer compounds such as polyester, polycarbonate, polyamide, polyimide, polyurethane, polysulfone, and polyethersulfone can be used. The raw material polymer B may be a polymer compound containing two or more of the groups shown in group (2), and has a liquid crystal alignment ability in a direction different from the stretching direction, which is added by rubbing. As long as it is not hindered, in addition to one or more of these groups, it may have a group other than the group shown in group (2) as a constitutional unit.

From the viewpoint of the stability of orientation and the like, a preferred polymer compound is a polymer compound having, as a constitutional unit, at least one group selected from the following group (3) among the above groups.

Embedded image (Any hydrogen atom in these groups may be substituted with alkyl, aryl, halogen or allyl.)

A more preferable polymer compound from the viewpoint of availability of raw materials and the like is a polymer compound having a group represented by the following formula (2) as a constitutional unit, and the following formula (3) A polymer compound having a repeating unit represented by the following is more preferred.

Embedded image

Embedded image (Any hydrogen atom in these formulas may be substituted with alkyl, aryl, halogen or allyl.)

In the present invention, the above-mentioned raw material polymer A and raw material polymer B can be used as a mixture. In addition, various properties related to the alignment film, for example, solvent resistance, liquid crystal resistance,
In order to improve orientation stability, heat resistance, water resistance, adhesion to a substrate, and the like, the above-mentioned raw material polymer A and raw material polymer B are used.
Alternatively, other polymers may be blended and used. Examples of the polymer to be blended include polyester, polycarbonate, polyamide, polyimide, polyvinyl alcohol, polyacrylamide, polyacrylonitrile, polysulfone, and polyethersulfone. However, when blending these polymers, care must be taken not to lose the property of aligning the liquid crystal in a direction different from the rubbing direction. At this time, by utilizing the fact that a polymer having a lower surface energy transfers to the coating film surface, the object of the present invention can be achieved even when the amount of the raw material polymer A or the raw material polymer B is small. Can be. The liquid crystal alignment film of the present invention does not contain a polymer obtained from a fluorene ring-containing diamine compound and a tetracarboxylic anhydride.

The liquid crystal alignment film of the present invention can be formed by applying a solution of the above raw material polymer on a substrate and subjecting the solution to a heat treatment. As solvents, toluene, xylene,
Methyl isobutyl ketone, cyclohexanone, γ-butyrolactone, N-methyl-2-pyrrolidone (NMP),
Dimethylacetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide (DMSO),
Dissolve the raw material polymer using ethylene glycol monobutyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, etc., and prepare a 0.1 to 30% by weight solution. , Preferably in a 1 to 10% by weight solution. Then, this solution is applied on a substrate by a brush coating method, a dipping method, a spin coating method, a spray method, a printing method, or the like to form a coating film. After forming the coating film, the solvent is evaporated at 50 to 140 ° C., preferably 80 to 120 ° C.
A heat treatment is performed at 0 ° C. to form a polymer film. If the surface of the substrate is treated with a silane coupling agent before coating, and a polymer film is formed thereon, the adhesion between the polymer film and the substrate can be improved. The surface of the formed polymer film is rubbed in one direction with a cloth or the like to obtain a liquid crystal alignment film.

The liquid crystal display element of the present invention is a polymer film formed by using the above-mentioned raw material polymer, and is provided with a liquid crystal alignment ability in a direction different from the rubbing direction by rubbing. A liquid crystal display device characterized by using an oriented film. The liquid crystal display device of the present invention is usually manufactured by the following method. That is, an electrode (specifically, a transparent electrode of ITO (indium oxide-tin oxide) or tin oxide) is formed on a substrate such as glass, and the liquid crystal alignment film is provided on the electrode. The two substrates formed in this manner are held at regular intervals with the alignment film inside, and the periphery is sealed with an epoxy resin or the like to form a cell. Thereafter, a liquid crystal is injected into the cell, the injection port is sealed, and the cell is gradually cooled to produce a liquid crystal display element. Or,
A liquid crystal display element may be manufactured by spraying liquid crystal on two substrates on which electrodes and an alignment film are formed and overlapping them, and sealing the liquid crystal so that the liquid crystal does not leak. Further, characters, graphics, color filters, and the like may be printed outside the cell as necessary, or a polarizing plate, a reflector, lighting, and the like may be arranged.

The range of the liquid crystal display device of the present invention includes a merocyanine type, styryl type, azo type, azomethine type, azoxy type, quinophthalone type, anthraquinone type and tetrazine type in the liquid crystal composition used for the display element. Guest-host (G-
H) Mode liquid crystal display device; NCAP prepared by encapsulating nematic liquid crystal; polymer dispersion type liquid crystal display device (PDLCD; typical example: prepared by forming three-dimensional network polymer in liquid crystal). Polymer network liquid crystal display (PNLCD); birefringence control (ECB) mode
And a liquid crystal display element of a dynamic scattering (DS) mode.

[0019]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples described below, the orientation direction was confirmed as follows. First, one polarizing plate whose polarization axis direction is known is placed on the light source. A cell into which a liquid crystal composition containing a dichroic dye has been injected is placed thereon and rotated. At this time, it is possible to know the orientation direction of the liquid crystal by utilizing the fact that when the polarization axis and the major axis of the dye, that is, the major axis direction of the liquid crystal match, it looks colored and when it does not match, it becomes colorless. The liquid crystal composition to be injected into the cell was prepared by adding an anthraquinone dichroic dye to an equivalent mixture of the following compounds.

Embedded image

Example 1 Poly (9-vinylcarbazole) (manufactured by Aldrich, Mw. 1100000, Tg 200 ° C.) was dissolved in a mixed solvent of N-methyl-2-pyrrolidone-ethylene glycol monobutyl ether (volume ratio 1/1). A solution having a polymer concentration of 3% was obtained. This solution was applied by a spin coating method (spinner method) on an ITO electrode on a transparent glass substrate provided with an ITO electrode on one side. Rotation condition is 1000 rpm
m, 15 seconds. After coating, the coating is dried at 60 ° C. for 5 minutes, and then heat-treated at 140 ° C. for 60 minutes to obtain a film thickness of about 60 n.
m was obtained. Another substrate was prepared in exactly the same manner, and the resin film surfaces of these two substrates were each subjected to rubbing treatment to form a liquid crystal alignment film, and were bonded together via a 20 μm spacer so that the rubbing directions coincided. A cell was prepared, and the above liquid crystal composition was injected. Observation of the orientation direction of the liquid crystal in the cell thus formed revealed that the liquid crystal was oriented in a direction perpendicular to the rubbing direction. After the cell was annealed at 120 ° C. for 60 minutes, the orientation of the liquid crystal was observed. As a result, the liquid crystal was oriented in the direction perpendicular to the rubbing direction as before the annealing.

Example 2 9,500 was placed in a 500 ml three-necked flask equipped with a stirrer.
3.0 g of 9-bis (hydroxyphenyl) fluorene,
0.7 g of sodium hydroxide, 1.0 g of tetrabutylammonium bromide and 100 ml of water
Stirred for 0 minutes. A solution of 1.56 g of adipoyl dichloride in 30 ml of 1,2-dichloroethane was added thereto, and the mixture was vigorously stirred for 15 minutes. Loose stirring, heptane 100ml
Was added to precipitate a polymer, and a liquid component was removed by filtration. Next, the obtained solid component was transferred to a beaker, added with 100 ml of water, stirred, washed, filtered, and dried. (Yield 3.9 g) Using the polyester thus obtained, a cell was prepared in the same manner as in Example 1. When the above liquid crystal composition was injected into the cell and the alignment direction of the liquid crystal was observed, the liquid crystal was aligned in a direction perpendicular to the rubbing direction. After the cell was annealed at 120 ° C. for 60 minutes, the orientation of the liquid crystal was observed. As a result, the liquid crystal was oriented in the direction perpendicular to the rubbing direction as before the annealing.

Example 3 In a 100 ml three-necked flask equipped with a stirrer, a thermometer, a mantle heater, a condenser and a dropping funnel, 3.0 g of 9,9-bis (hydroxyphenyl) fluorene and 0.1 g of 1,6-hexanediol were added. 26 g, 3 ml of pyridine and 15 ml of 1,2-dichloroethane were added, and the temperature was raised to 80 ° C. while stirring. A solution of 1.16 g of bis (trichloromethyl) carbonate in 8 ml of 1,2-dichloroethane was added dropwise over 10 minutes, and the mixture was stirred at the same temperature for 3 hours. After cooling, 15 ml of 1,2-dichloroethane was added, and the mixture was reprecipitated in 400 ml of methanol. The precipitated polymer was collected by filtration, placed in a 200 ml eggplant flask, added with 100 ml of methanol, and refluxed for 1 hour. The polymer was filtered off again and dried. (Yield 3.2 g) Using the polycarbonate thus synthesized, Example 1
A cell was created in the same manner as. The dye-containing liquid crystal was injected into the cell, and the alignment direction of the liquid crystal was observed. As a result, the liquid crystal was aligned in a direction perpendicular to the rubbing direction. After the cell was annealed at 120 ° C. for 60 minutes, the orientation of the liquid crystal was observed. As a result, the liquid crystal was oriented in the direction perpendicular to the rubbing direction as before the annealing.

Comparative Example 1 Polystyrene (manufactured by Aldrich, Mw. 280000, Tg) was used instead of poly (9-vinylcarbazole).
A cell was prepared in the same manner as in Example 1 except that the temperature was 100 ° C.), and the above-described liquid crystal composition was injected. Observation of the orientation direction of the liquid crystal in the cell thus formed revealed that the liquid crystal was oriented in a direction perpendicular to the rubbing direction. This cell is
After annealing at 120 ° C. for 60 minutes, the alignment direction of the liquid crystal was observed. As a result, the liquid crystal was aligned in a direction parallel to the rubbing direction, unlike before the annealing.

Example 4 Poly (bisphenol A carbonate) (manufactured by Aldrich, Mw. 64000, Tg 150 ° C.) was used in place of poly (9-vinylcarbazole).
A glass substrate having an alignment film formed thereon was obtained in the same manner as in Example 1. Further, a glass substrate on which an alignment film was formed in the same manner as in Example 1 was obtained using the polymer obtained in Example 3. A cell having a thickness of 0.02 mm was assembled from these two types of substrates such that the rubbing directions were aligned and the alignment film was on the inside, and the above liquid crystal composition was injected. Outside the cell, the rubbing direction and the polarization axis are aligned on the poly (bisphenol A carbonate) alignment film side, and the rubbing direction and the polarization axis are orthogonal on the polymer alignment film side obtained in Example 3. When a polarizing plate was placed in such a manner that a voltage of 10 V was applied, white display changed to black display. That is, switching of liquid crystal molecules was observed.

[0025]

According to the present invention, the rubbing imparts the liquid crystal alignment ability in a direction different from the rubbing direction, and the alignment direction does not change even when a heat treatment such as an annealing treatment is performed. A film and a liquid crystal display device using the alignment film are provided. The liquid crystal alignment film of the present invention,
In order to align the liquid crystal in a direction different from the rubbing direction,
By forming a coating film on the substrate in a fixed pattern together with a polymer for aligning the liquid crystal parallel to the rubbing direction, and performing the rubbing once, the orientation division can be easily performed. In addition, since the orientation direction does not change even when heat treatment such as annealing is performed, it can be suitably used as an orientation film. In addition, since it can be fired at a low temperature of 120 ° C. to 140 ° C., it can be used even if the heat resistance of the color filter is low, and is advantageous from the viewpoint of energy saving.
In addition, it can be suitably used for a recording material, a polarizing element, an optical compensator, a light control element, and the like.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Nobuyuki Otsuka 5-1 Okawa, Kanazawa-ku, Yokohama-shi, Kanagawa Chisso Yokohama Research Laboratory F-term (reference) 2H090 HB07Y HB10Y HD15 MB01 4F071 AA37 AA43 AA50 AA53 AA54 AA60 AA64 AF35 AH12 AH16 BA02 BB02 BC02 4J002 AA072 BJ001 CF132 CF142 CG022 CK022 CL002 CM042 CN032

Claims (7)

[Claims] 1. A liquid crystal alignment film provided with a liquid crystal alignment ability in a direction different from the rubbing direction by rubbing, wherein a polymer compound used for the liquid crystal alignment film is shown in the following group (1). Addition-polymerized polymer compound having at least one type of group as a side chain and the following group (2)
And at least one polymer compound selected from the group consisting of a polymer compound having at least one of the groups shown as constituent units, and a fluorene ring-containing diamine compound and a tetracarboxylic anhydride. A liquid crystal alignment film, which is a polymer compound containing no polymer. Embedded image (Any hydrogen atom in these groups may be substituted with alkyl, aryl, halogen or allyl.) (Any hydrogen atom in these groups may be substituted with alkyl, aryl, halogen or allyl.) 2. The polymer compound is at least one polymer compound selected from addition polymerization polymer compounds having at least one group represented by group (1) as a side chain. The liquid crystal alignment film according to claim 1, wherein 3. A polymer compound represented by the formula (1): (Any hydrogen atom in the formula may be substituted with alkyl, aryl, halogen or allyl.) It is characterized by being an addition polymerization type polymer compound having a group represented by a side chain. The liquid crystal alignment film according to claim 2. 4. The polymer compound is at least one polymer compound selected from polymer compounds having at least one group represented by group (2) as a constituent unit. The liquid crystal alignment film according to claim 1. 5. The polymer compound represented by the formula (2): 5. A polymer compound having a group represented by the formula (wherein any hydrogen atom in the formula may be substituted with alkyl, aryl, halogen or allyl) as a constituent unit. The liquid crystal alignment film according to 1. 6. The polymer compound represented by the formula (3): 6. A polymer compound having a repeating unit represented by the formula (any hydrogen atom in the formula may be substituted with alkyl, aryl, halogen or allyl). Liquid crystal alignment film. 7. A liquid crystal display device comprising the liquid crystal alignment film according to claim 1.