JP7193783B2 - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element using the same - Google Patents

Description

The present invention relates to a liquid crystal aligning agent, a liquid crystal aligning film obtained from the liquid crystal aligning agent, and a liquid crystal display element using the liquid crystal aligning film.

Liquid crystal display elements used in liquid crystal televisions, liquid crystal displays, etc. are usually provided with a liquid crystal alignment film for controlling the alignment state of liquid crystals.

Currently, the liquid crystal alignment film that is most widely used industrially is a film made of polyamic acid and/or polyimide imidized thereof formed on an electrode substrate. It is produced by performing a so-called rubbing process, which is rubbing in a direction.

The rubbing treatment is a simple, highly productive and industrially useful method. However, along with the high performance, high definition, and large size of liquid crystal display elements, scratches on the surface of the alignment film caused by rubbing, dust generation, mechanical force and static electricity, and furthermore, the alignment processing surface There are various problems such as the non-uniformity of the

As an alternative to the rubbing treatment, there is known a photo-alignment method in which polarized radiation is applied to impart liquid crystal alignment ability. As the liquid crystal alignment treatment by the photo-alignment method, a method using a photo-isomerization reaction, a method using a photo-crosslinking reaction, a method using a photo-decomposition reaction, etc. have been proposed (see Non-Patent Document 1).

Patent Document 1 proposes the use of a polyimide film having an alicyclic structure such as a cyclobutane ring in its main chain for the photo-alignment method.
The photo-alignment method as described above can be produced by an industrially simple manufacturing process as a rubbing-less alignment treatment method. Compared with the liquid crystal alignment film obtained by the rubbing treatment method, the contrast and viewing angle characteristics of the liquid crystal display device can be expected to be improved.

JP-A-9-297313

"Liquid Crystal Photo-Alignment Film" Kidowaki, Ichimura, Functional Materials, November 1997, Vol. 17, No. 11 Pages 13-22

A panel vibration test is sometimes performed as a reliability test of liquid crystal display elements for mobile applications such as smartphones and mobile phones, and for vehicle-mounted displays. In this vibration test, it is required that defects such as bright spots do not occur. In order to obtain a liquid crystal display element free from defects after the vibration test, it is necessary to increase the mechanical strength of the liquid crystal alignment film. As a method for improving the mechanical strength, particularly hardness, of the liquid crystal alignment film, there is a method of adding a cross-linking agent to the liquid crystal alignment agent. However, in the study of the present inventors, when a cross-linking agent is added, although the film hardness of the obtained liquid crystal alignment film is improved, the deterioration of the contrast due to the deterioration of the black luminance of the liquid crystal display element and the afterimage due to long-term AC driving are caused. Turned out to be worse.
Therefore, the present invention provides a liquid crystal display element having high film hardness, capable of suppressing afterimages caused by long-term AC driving that occurs in liquid crystal display elements of the IPS drive system or the FFS drive system, and having good contrast of the liquid crystal display element. A liquid crystal aligning agent, a liquid crystal aligning film obtained from the liquid crystal aligning agent, and a liquid crystal display element having the liquid crystal aligning film.

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, the gist of the present invention is as follows.
1. A liquid crystal aligning agent characterized by containing the following (A) component, (B) component, and an organic solvent.
Component (A): At least one polymer selected from the group consisting of a polyimide precursor having a structural unit of the following formula (1) and an imidized polymer of the polyimide precursor (B) Component: Formula (2) below A compound having two or more structures of

X ₁ is a tetravalent organic group and Y ₁ is a divalent organic group. R ₁ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and A ₁ to A ₂ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or alkenyl having 2 to 10 carbon atoms or an alkynyl group having 2 to 10 carbon atoms.

Z ₁ is an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkynyl group having 2 to 6 carbon atoms. Z ₂ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkynyl group having 2 to 6 carbon atoms. "*" indicates a bond.

By using the liquid crystal aligning agent of the present invention, a liquid crystal alignment film having high film hardness can be obtained. In addition, by using the liquid crystal alignment film of the present invention, a liquid crystal display device with good contrast can be obtained in spite of introducing a cross-linking agent. Furthermore, by using the liquid crystal aligning agent of this invention, it becomes possible to achieve the above-mentioned subject, without deteriorating a liquid crystal aligning property or an electrical property.

The liquid crystal aligning agent of the present invention is characterized by containing the following components (A), (B) and an organic solvent.
Component (A): At least one polymer selected from the group consisting of a polyimide precursor having a structural unit of the following formula (1) and an imidized polymer of the polyimide precursor (B) Component: Formula (2) below A compound having two or more structures of: Each component will be described in detail below.

<(A) Component>
Component (A) contained in the liquid crystal aligning agent of the present invention is at least one polymer selected from the group consisting of a polyimide precursor having a structural unit of the following formula (1) and an imidized polymer of the polyimide precursor. is. The polyimide precursor is not particularly limited as long as it is a polyimide precursor that forms an imide ring by chemical imidization with heating or a catalyst such as polyamic acid or polyamic acid ester. Polyamic acid or polyamic acid ester is more preferable as the polyimide precursor from the viewpoint of facilitating heating or chemical imidization.

X ₁ is a tetravalent organic group and Y ₁ is a divalent organic group. R ₁ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and A ₁ to A ₂ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms. , or an alkynyl group having 2 to 10 carbon atoms.
Specific examples of the alkyl group for R ₁ include methyl, ethyl, propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl and n-pentyl groups. etc. From the viewpoint of ease of imidization by heating, R ₁ is preferably a hydrogen atom or a methyl group.
A ₁ and A ₂ each independently represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms which may have a substituent, or a number of carbon atoms which may have a substituent. 2 to 10 alkynyl groups.
Specific examples of the alkyl group include methyl group, ethyl group, propyl group, butyl group, t-butyl group, hexyl group, octyl group, decyl group, cyclopentyl group, cyclohexyl group and bicyclohexyl group. Examples of the alkenyl group include those in which one or more CH—CH structures present in the above alkyl groups are replaced with a C=C structure, and more specifically, a vinyl group, an allyl group, and a 1-propenyl group. , isopropenyl group, 2-butenyl group, 1,3-butadienyl group, 2-pentenyl group, 2-hexenyl group, cyclopropenyl group, cyclopentenyl group, cyclohexenyl group and the like. Examples of the alkynyl group include those in which one or more CH ₂ —CH ₂ structures present in the above alkyl group are replaced with a C≡C structure. -propynyl group and the like.
In general, introduction of a bulky structure may reduce the reactivity of the amino group and the liquid crystal orientation, so A ₁ and A ₂ are more preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. , a hydrogen atom, a methyl group or an ethyl group are particularly preferred.
Hereinafter, each component that becomes a raw material for forming a polymer will be described in detail.

<Diamine>
The structure of the diamine component used in the liquid crystal aligning agent of the present invention is not particularly limited.
The diamine used for polymerizing the polymer having the structure of formula (1) can be generalized by the following formula (3). Examples of the structure of Y ₁ are as follows (Y-1) to (Y-184).

A _{1 and A 2 in the above formula (3) have the same definitions as A 1 and A 2 in the} above formula (1), including preferred examples.

From the viewpoint of liquid crystal orientation, the structure of Y ₁ is preferably a highly linear structure, and examples thereof include structures represented by the following formulas (4) and (5).

In formulas (4) and (5), A ₁ is a single bond, an ester bond, an amide bond, a thioester bond, or a divalent organic group having 2 to 20 carbon atoms, A ₃ is a hydrogen atom, a halogen atom, hydroxyl group, amino group, thiol group, nitro group, phosphate group, or monovalent organic group having 1 to 20 carbon atoms, a is an integer of 1 to 4, and when a is 2 or more, A ₃ structure may be the same or different. b and c are each independently an integer of 1 to 2;

Specific examples of the structures represented by the formulas (4) and (5) include Y-7, Y-25, Y-26, Y-27, Y-43, Y-44, Y-45, Y-46, Y-48, Y-71, Y-72, Y-73, Y-74, Y-75, Y-76, Y-82, Y-87, Y-88, Y-89, Y- 90, Y-92, Y-93, Y-94, Y-95, Y-96, Y-100, Y-101, Y-102, Y-103, Y-104, Y-105, Y-106, Y-110, Y-111, Y-112, Y-113, Y-115, Y-116, Y-121, Y-122, Y-126, Y-127, Y-128, Y-129, Y- 132, Y-134, Y-153, Y-156, Y-157, Y-158, Y-159, Y-160, Y-161, Y-162, Y-163, Y-164, Y-165, Y-166, Y-167, Y-168, Y-169, and Y-170.

The content of the diamines represented by the above formulas (4) and (5) is preferably 50% or more, more preferably 70% by mole or more, relative to 1 mol of the total diamine component.
From the viewpoint of improving the solubility of the polymer, the structure of Y1 preferably includes _a structure represented by the following formula (6).

In the above formula (6), D is a substituent that replaces a hydrogen atom by heating, and its structure is not limited as long as it has a known structure. A t-butoxycarbonyl group is preferred from the viewpoint of thermal elimination. Specific examples of Y ₁ containing the structure represented by formula (6) include Y-158, Y-159, Y-160, Y-161, Y-162 and Y-163.
The content of the diamine containing the structure of formula (6) is preferably 0 to 50 mol %, more preferably 5 to 30 mol %, relative to 1 mol of the total diamine component.

Among (Y-1) to (Y-184), particularly preferred structures of Y ₁ are as follows.

<Tetracarboxylic acid derivative>
As the tetracarboxylic acid derivative component for producing the polymer having the structural unit of formula (1), which is contained in the liquid crystal aligning agent of the present invention, not only tetracarboxylic dianhydride but also the tetracarboxylic acid Derivatives such as tetracarboxylic acids, tetracarboxylic acid dihalide compounds, tetracarboxylic acid dialkyl ester compounds, or tetracarboxylic acid dialkyl ester dihalide compounds can also be used.

The tetracarboxylic dianhydride or derivative thereof is preferably a photoreactive tetracarboxylic dianhydride or a derivative thereof, and among them, at least selected from tetracarboxylic dianhydrides represented by the following formula (7) It is more preferable to use one.

X ₁ is a tetravalent organic group having an alicyclic structure, and specific examples include the following formulas (X1-1) to (X1-10).

R ₃ to R ₂₃ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, or a carbon atom containing a fluorine atom. It is a monovalent organic group of numbers 1 to 6 or a phenyl group, which may be the same or different. From the viewpoint of liquid crystal orientation, R ₃ to R ₂₃ are preferably a hydrogen atom, a halogen atom, a methyl group, or an ethyl group, more preferably a hydrogen atom or a methyl group. Specific structures of the formula (X1-1) include structures represented by the following formulas (X1-11) to (X1-16). (X1-12) is particularly preferred from the viewpoint of liquid crystal orientation and photoreaction sensitivity.

As the tetracarboxylic dianhydride used in the present invention, a tetracarboxylic dianhydride represented by the following formula (8) and a derivative thereof may be used in addition to the above formula (7).

X2 is a _tetravalent organic group, and its structure is not particularly limited. Specific examples include structures represented by the following formulas (X-9) to (X-42). From the viewpoint of compound availability, the structures of X include X-17, X-25, X-26, X-27, X-28, X-32, X-35, X-37 and X-39. be done. In addition, it is preferable to use a tetracarboxylic dianhydride having an aromatic ring structure from the viewpoint of obtaining a liquid crystal alignment film in which the residual charge accumulated by a DC voltage is quickly relaxed. More preferred are X-27, X-28, X-32, X-35, and X-37.

The tetracarboxylic dianhydride and its derivative, which are raw materials for the polyimide precursor and polyimide according to the present invention, are represented by the above formula (3) with respect to 1 mol of the total tetracarboxylic dianhydride and its derivative. It preferably contains 60 to 100 mol% of tetracarboxylic dianhydride and its derivatives. It is more preferably 80 mol % to 100 mol %, even more preferably 90 mol % to 100 mol %, since a liquid crystal alignment film having good liquid crystal alignment properties can be obtained.
<(B) Component>
The (B) component contained in the liquid crystal aligning agent of the present invention is a compound having two or more structures of the following formula (2).
The structure of component (B) is not particularly limited as long as it contains two or more structures represented by the following formula (2). If the molecular weight is too high, the liquid crystal orientation is affected, so the molecular weight is preferably 2,000 or less, more preferably 1,000 or less.

Z ₁ is an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkynyl group having 2 to 6 carbon atoms. From the viewpoint of liquid crystal orientation, Z1 is preferably _a methyl group or an ethyl group, more preferably a methyl group.
Z ₂ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkynyl group having 2 to 6 carbon atoms. A hydrogen atom is more preferable from the viewpoint of cross-linking reactivity. "*" indicates a bond.
As the component (B), a compound having two or more structures represented by the above formula (2) is preferable, and a compound having three or more structures is more preferable.
Further, the component (B) is preferably a compound having two or more structures represented by the following formula (B1-1).

Z ₁ has the same definition as in formula (2), including preferred examples. Specific examples of component (B) include compounds represented by the following formulas (B-1) to (B-18).

If the component (B) is too large, it will affect the liquid crystal orientation and pretilt angle, and if it is too small, the effect of the present invention cannot be obtained. Therefore, the amount of component (B) added is preferably 0.1 to 30% by mass, more preferably 0.1 to 20% by mass, more preferably 1 to 15% by mass, relative to the polymer of component (A).
<Method for producing polyamic acid ester, polyamic acid and polyimide>
Polyamic acid ester, polyamic acid and polyimide, which are polyimide precursors used in the present invention, can be synthesized by known methods such as those described in International Publication WO2013/157586, for example.

<Liquid crystal aligning agent>
The liquid crystal aligning agent used in the present invention is at least one type of polymer selected from the group consisting of the polyimide precursor which is the component (A) and the imidized polymer of the polyimide precursor (hereinafter referred to as a polymer having a specific structure). and (B) are dissolved in an organic solvent. The weight average molecular weight of the specific structure polymer is preferably 2,000 to 500,000, more preferably 5,000 to 300,000, and still more preferably 10,000 to 100,000. Also, the number average molecular weight is preferably 1,000 to 250,000, more preferably 2,500 to 150,000, still more preferably 5,000 to 50,000.

The concentration of the polymer of the liquid crystal aligning agent used in the present invention can be appropriately changed by setting the thickness of the coating film to be formed. % or more, and preferably 10% by weight or less from the viewpoint of storage stability of the solution.

The organic solvent contained in the liquid crystal aligning agent used in the present invention is not particularly limited as long as it uniformly dissolves the polymer component. Specific examples include N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone, N-vinyl-2-pyrrolidone, dimethylsulfoxide, dimethylsulfone, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, 3-methoxy-N,N-dimethylpropanamide and the like. These may be used singly or in combination of two or more. Moreover, even a solvent that cannot uniformly dissolve the polymer component by itself may be mixed with the above organic solvent as long as the polymer is not precipitated.

The liquid crystal aligning agent used in the present invention may contain, in addition to the organic solvent for dissolving the polymer component, a solvent for improving coating uniformity when the liquid crystal aligning agent is applied to the substrate. . Such a solvent generally has a lower surface tension than the above organic solvent. Specific examples include ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, ethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-butoxy-2-propanol. , 1-phenoxy-2-propanol, propylene glycol monoacetate, propylene glycol diacetate, propylene glycol-1-monomethyl ether-2-acetate, propylene glycol-1-monoethyl ether-2-acetate, butyl cellosolve acetate, dipropylene glycol , 2-(2-ethoxypropoxy)propanol, lactic acid methyl ester, lactic acid ethyl ester, lactic acid n-propyl ester, lactic acid n-butyl ester, lactic acid isoamyl ester and the like. Two or more of these solvents may be used in combination.

In the liquid crystal aligning agent of the present invention, in addition to the above, as long as the effects of the present invention are not impaired, polymers other than the specific polymer, electrical properties such as the dielectric constant and conductivity of the liquid crystal alignment film are changed. Dielectric or conductive material for the purpose, silane coupling agent for the purpose of improving the adhesion between the liquid crystal alignment film and the substrate, cross-linking compound for the purpose of increasing the hardness and density of the film when the liquid crystal alignment film is formed, and An imidization accelerator or the like may be added for the purpose of efficiently advancing the imidization of the polyamic acid when baking the coating film.
<Liquid crystal alignment film>
<Method for producing liquid crystal alignment film>
The liquid crystal aligning film of the present invention is a film obtained by applying the liquid crystal aligning agent to a substrate, drying, and baking. The substrate to which the liquid crystal aligning agent of the present invention is applied is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a silicon nitride substrate, an acrylic substrate, a plastic substrate such as a polycarbonate substrate, or the like can be used. From the viewpoint of process simplification, it is preferable to use a substrate on which an ITO electrode or the like for is formed. In the case of a reflective liquid crystal display element, an opaque material such as a silicon wafer can be used as long as the substrate is only on one side.

Examples of the method for applying the liquid crystal aligning agent of the present invention include a spin coating method, a printing method, an inkjet method, and the like. Any temperature and time can be selected for the drying and baking steps after applying the liquid crystal aligning agent of the present invention. In general, it is dried at 50° C. to 120° C. for 1 minute to 10 minutes in order to sufficiently remove the contained organic solvent, and then calcined at 150° C. to 300° C. for 5 minutes to 120 minutes. The thickness of the coating film after baking is not particularly limited.

A rubbing method, an optical alignment treatment method, etc. are mentioned as a method of aligning the obtained liquid crystal aligning film.
The rubbing process can be performed using an existing rubbing apparatus. The material of the rubbing cloth in this case includes cotton, nylon, rayon, and the like. As the conditions for the rubbing treatment, a rotation speed of 300 to 2,000 rpm, a feed rate of 5 to 100 mm/s, and a pressing amount of 0.1 to 1.0 mm are generally used. After that, the residue generated by the rubbing is removed by ultrasonic cleaning using pure water, alcohol, or the like.

As a specific example of the photo-alignment treatment method, the coating film surface is irradiated with radiation polarized in a certain direction, and in some cases, further heat-treated at a temperature of 150 to 250 ° C. to impart liquid crystal alignment ability. mentioned. As radiation, ultraviolet rays and visible rays having wavelengths of 100 nm to 800 nm can be used. Among them, ultraviolet rays having a wavelength of 100 nm to 400 nm are preferable, and those having a wavelength of 200 nm to 400 nm are particularly preferable. In order to improve liquid crystal orientation, radiation may be applied while heating the coated film substrate at 50 to 250°C. The radiation dose is preferably 1 to 10,000 mJ/cm ² , particularly preferably 100 to 5,000 mJ/cm ² . The liquid crystal alignment film produced as described above can stably orient liquid crystal molecules in a certain direction.

A higher extinction ratio of polarized ultraviolet rays is preferable because higher anisotropy can be imparted. Specifically, the extinction ratio of linearly polarized ultraviolet light is preferably 10:1 or more, more preferably 20:1 or more.

The film irradiated with polarized radiation may then be contact-treated with a solvent containing at least one selected from water and organic solvents.

The solvent used for the contact treatment is not particularly limited as long as it can dissolve the decomposition products produced by light irradiation. Specific examples include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, methyl lactate, diacetone alcohol, 3- methyl methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, and cyclohexyl acetate; Two or more of these solvents may be used in combination.
At least one selected from the group consisting of water, 2-propanol, 1-methoxy-2-propanol and ethyl lactate is more preferable from the viewpoint of versatility and safety. Particularly preferred are water, 2-propanol, and mixed solvents of water and 2-propanol.

In the present invention, the contact treatment between the film irradiated with polarized radiation and the solution containing the organic solvent is a treatment such as immersion treatment or spray treatment, which preferably allows sufficient contact between the film and the liquid. done. Among them, a method of immersing the film in a solution containing an organic solvent for preferably 10 seconds to 1 hour, more preferably 1 to 30 minutes, is preferred. The contact treatment may be carried out at room temperature or with heating, preferably at 10 to 80°C, more preferably at 20 to 50°C. In addition, means for enhancing contact, such as ultrasonic waves, can be applied as necessary.

After the above contact treatment, either or both rinsing with a low boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone, and methyl ethyl ketone, or drying for the purpose of removing the organic solvent in the solution used. may be performed.
Furthermore, the film that has been subjected to contact treatment with a solvent as described above may be heated at 150° C. or higher for the purpose of drying the solvent and reorienting the molecular chains in the film.
The heating temperature is preferably 150 to 300°C. A higher temperature promotes the reorientation of the molecular chains, but if the temperature is too high, the molecular chains may be decomposed. Therefore, the heating temperature is more preferably 180 to 250°C, particularly preferably 200 to 230°C.
If the heating time is too short, the effect of reorientation of the molecular chains may not be obtained, and if it is too long, the molecular chains may be decomposed, so 10 seconds to 30 minutes is preferable, and 1 minute. ~10 minutes is more preferred.

<Liquid crystal display element>
A liquid crystal display element of the present invention is characterized by comprising a liquid crystal alignment film obtained by the method for producing a liquid crystal alignment film.
In the liquid crystal display element of the present invention, after obtaining a substrate with a liquid crystal aligning film from the liquid crystal aligning agent of the present invention by the method for producing a liquid crystal aligning film, a liquid crystal cell is produced by a known method, and the liquid crystal is used. It is used as a display element.

As an example of the method of manufacturing a liquid crystal cell, a liquid crystal display element having a passive matrix structure will be described. A liquid crystal display element having an active matrix structure in which a switching element such as a TFT (Thin Film Transistor) is provided in each pixel portion forming an image display may be used.

First, transparent glass substrates are prepared, a common electrode is provided on one substrate, and a segment electrode is provided on the other substrate. These electrodes can be ITO electrodes, for example, and are patterned so as to display a desired image. Next, an insulating film is provided on each substrate so as to cover the common electrodes and the segment electrodes. The insulating film can be, for example, a film made of SiO ₂ —TiO ₂ formed by a sol-gel method.

Next, the liquid crystal alignment film of the present invention is formed on each substrate. Next, one substrate is overlaid on the other substrate so that the alignment film surfaces face each other, and the periphery is bonded with a sealant. A spacer is usually mixed in the sealing agent in order to control the gap between the substrates. Moreover, it is preferable to spread spacers for controlling the gap between the substrates even in the in-plane portions where the sealant is not provided. A part of the sealant is provided with an opening through which liquid crystal can be filled from the outside.

Next, a liquid crystal material is injected into the space surrounded by the two substrates and the sealant through an opening provided in the sealant. This opening is then sealed with an adhesive. For injection, a vacuum injection method may be used, or a method utilizing capillary action in the atmosphere may be used. Next, a polarizing plate is installed. Specifically, a pair of polarizing plates are attached to the surfaces of the two substrates opposite to the liquid crystal layer. The liquid crystal display device of the present invention is obtained through the above steps.

In the present invention, as the sealing agent, for example, a resin that has a reactive group such as an epoxy group, an acryloyl group, a methacryloyl group, a hydroxyl group, an allyl group, and an acetyl group and is cured by ultraviolet irradiation or heating is used. In particular, it is preferred to use a curable resin system having both epoxy and (meth)acryloyl reactive groups.

The sealant of the present invention may contain an inorganic filler for the purpose of improving adhesion and moisture resistance. The inorganic filler that can be used is not particularly limited, but specific examples include spherical silica, fused silica, crystalline silica, titanium oxide, titanium black, silicon carbide, silicon nitride, boron nitride, calcium carbonate, magnesium carbonate, barium sulfate, Calcium sulfate, mica, talc, clay, alumina, magnesium oxide, zirconium oxide, aluminum hydroxide, calcium silicate, aluminum silicate, lithium aluminum silicate, zirconium silicate, barium titanate, glass fiber, carbon fiber, molybdenum disulfide, asbestos, etc. preferably spherical silica, fused silica, crystalline silica, titanium oxide, titanium black, silicon nitride, boron nitride, calcium carbonate, barium sulfate, calcium sulfate, mica, talc, clay, alumina, aluminum hydroxide, calcium silicate , aluminum silicate. Two or more kinds of the above inorganic fillers may be mixed and used.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these. The abbreviations of the compounds and the methods for measuring each property are as follows.
NMP: N-methyl-2-pyrrolidone GBL: γ-butyrolactone BCS: butyl cellosolve DA-1: 1,2-bis(4-aminophenoxy)ethane DA-2: N-tert-butoxycarbonyl-N-(2-( 4-aminophenyl)ethyl)-N-(4-aminobenzyl)amine DA-3: p-phenylenediamine DA-4: see formula (DA-4) below DA-5: 4,4'diaminodiphenylamine DA-6 : 4,4' diaminodiphenylmethane CA-1: see formula (CA-1) below CA-2: see formula (CA-2) below CA-3: see formula (CA-3) below AD-1: see formula (CA-3) below AD-1) See AD-2: See formula (AD-2) below

[viscosity]
The viscosity of the solution was measured using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.) with a sample volume of 1.1 mL, a cone rotor TE-1 (1°34', R24), and a temperature of 25°C.

[Molecular weight]
The molecular weight was measured with a GPC (normal temperature gel permeation chromatography) device, and the number average molecular weight (Mn and weight average molecular weight (Mw) were calculated as polyethylene glycol and polyethylene oxide conversion values.

GPC apparatus: manufactured by Shodex (GPC-101), column: manufactured by Shodex (KD803, KD805 in series), column temperature: 50 ° C., eluent: N,N-dimethylformamide (as an additive, lithium bromide-water hydrate (LiBr.H ₂ O) 30 mmol/L, phosphoric acid/anhydride crystals (o-phosphoric acid) 30 mmol/L, tetrahydrofuran (THF) 10 mL/L), flow rate: 1.0 mL/min.

Standard samples for creating a calibration curve: TSK standard polyethylene oxide manufactured by Tosoh Corporation (weight average molecular weight (Mw) of about 900,000, 150,000, 100,000, 30,000), and polyethylene glycol manufactured by Polymer Laboratory (peak top molecular weight (Mp) about 12,000, 4,000, 1,000). In order to avoid overlapping of peaks, the measurement was performed by mixing four types of samples of 900,000, 100,000, 12,000, and 1,000, and three types of 150,000, 30,000, and 4,000. Two samples of the mixed sample were measured separately.

<Measurement of imidization rate>
20 mg of polyimide powder was placed in an NMR sample tube (NMR sampling tube standard, φ5 (manufactured by Kusano Kagaku Co., Ltd.)), and deuterated dimethyl sulfoxide (DMSO-d6, 0.05% TMS (tetramethylsilane) mixture) (0. 53 mL) was added and dissolved completely by ultrasonication. This solution was subjected to proton NMR at 500 MHz using an NMR spectrometer (JNW-ECA500) (manufactured by JEOL Datum Co., Ltd.). For the imidization rate, a proton derived from a structure that does not change before and after imidization is determined as a reference proton. It was obtained by the following formula using the integrated value.

Imidation rate (%) = (1-α x/y) x 100
In the above formula, x is the proton peak integrated value derived from the NH group of the amic acid, y is the peak integrated value of the reference proton, and α is one NH group proton of the amic acid in the case of polyamic acid (imidization rate is 0%). is the number ratio of reference protons to

[Production of liquid crystal cell]
A liquid crystal cell having a configuration of a fringe field switching (FFS) mode liquid crystal display element is produced.

First, a substrate with electrodes was prepared. The substrate is a glass substrate having a size of 30 mm×50 mm and a thickness of 0.7 mm. An ITO electrode having a solid pattern is formed as a first layer on the substrate to form a counter electrode. A SiN (silicon nitride) film formed by a CVD method is formed as a second layer on the counter electrode of the first layer. The SiN film of the second layer has a film thickness of 500 nm and functions as an interlayer insulating film. On the SiN film of the second layer, a comb-shaped pixel electrode formed by patterning an ITO film is arranged as a third layer to form two pixels, a first pixel and a second pixel. ing. The size of each pixel is about 10 mm long and about 5 mm wide. At this time, the counter electrode of the first layer and the pixel electrode of the third layer are electrically insulated by the action of the SiN film of the second layer.

The pixel electrode on the third layer has a comb-like shape formed by arranging a plurality of dogleg-shaped electrode elements with a bent central portion. The width of each electrode element in the lateral direction is 3 μm, and the interval between electrode elements is 6 μm. Since the pixel electrode that forms each pixel is configured by arranging a plurality of bent dogleg-shaped electrode elements in the central portion, the shape of each pixel is not rectangular, but in the central portion like the electrode elements. It has a curved shape resembling a bold character. Each pixel is vertically divided by the curved portion in the center, and has a first region above the curved portion and a second region below the curved portion.

Comparing the first region and the second region of each pixel, the formation direction of the electrode elements of the pixel electrodes constituting them is different. That is, when the rubbing direction of the liquid crystal alignment film, which will be described later, is used as a reference, the electrode element of the pixel electrode is formed to form an angle of +10° (clockwise) in the first region of the pixel, and the pixel in the second region of the pixel. The electrode elements of the electrode are formed at an angle of -10° (clockwise). That is, in the first region and the second region of each pixel, the directions of the rotational movement (in-plane switching) of the liquid crystal induced by the voltage application between the pixel electrode and the counter electrode in the plane of the substrate are mutually different. It is configured to be in the opposite direction.

Next, after filtering the liquid crystal aligning agent with a 1.0 μm filter, spin coating was performed on the prepared substrate with electrodes and a glass substrate having a columnar spacer with a height of 4 μm and an ITO film formed on the back surface. applied according to the method. Dry on a hot plate at 80°C for 2 minutes, irradiate the coating film surface with linearly polarized ultraviolet light with a wavelength of 254 nm and an extinction ratio of 10:1 or more through a polarizing plate, and then place it in a hot air circulating oven at 230°C for 20 minutes. Baking was performed to form a coating film having a thickness of 100 nm. The above two substrates are set as a set, a sealant is printed on the substrate, and another substrate is laminated so that the liquid crystal alignment film surfaces face each other and the alignment direction is 0°, and then the sealant is cured. to prepare an empty cell. Liquid crystal MLC-3019 (manufactured by Merck & Co.) was injected into this empty cell by a vacuum injection method, and the injection port was sealed to obtain a liquid crystal cell. After that, the obtained liquid crystal cell was heated at 110° C. for 1 hour and allowed to stand overnight before being used for evaluation.

[Black Luminance Evaluation]
The above-mentioned liquid crystal cell is placed between two polarizing plates arranged so that the polarization axes are orthogonal to each other, and the backlight is turned on with no voltage applied. Adjusted the placement angle of After that, the luminance of transmitted light (black luminance) was measured with a luminance meter (SR-UL2 manufactured by TOPCON) with no voltage applied.

[Evaluation of pencil hardness]
A sample for pencil hardness evaluation was prepared as follows. A liquid crystal aligning agent was applied to an ITO substrate of 30 mm×40 mm by spin coating. Dry on a hot plate at 80°C for 2 minutes, irradiate the coating film surface with linearly polarized ultraviolet light with a wavelength of 254 nm and an extinction ratio of 10:1 or more through a polarizing plate, and then place it in a hot air circulating oven at 230°C for 20 minutes. Firing was performed to obtain a substrate with a liquid crystal alignment film. This substrate was measured by a pencil hardness test method (JIS K5400).

<Synthesis Example 1>
In a 100 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 3.91 g (16.0 mmol) of DA-1, 2.19 g (6.41 mmol) of DA-2, and 0.519 g of DA-3 ( 4.80 mmol), 1.54 g (4.81 mmol) of DA-4, and 46.2 g of NMP were added and dissolved by stirring while sending nitrogen. While stirring this diamine solution, 5.70 g (25.4 mmol) of CA-1 and 1.20 g (4.80 mmol) of CA-2 were added, and 39% of NMP was added so that the solid content concentration was 15% by mass. 1 g was added and stirred at 40° C. for 24 hours to obtain a polyamic acid solution (A) (viscosity: 450 mPa·s). The molecular weight of polyamic acid was Mn=11200 and Mw=26900.

<Synthesis Example 2>
Take 5.10 g (25.6 mmol) of DA-5 and 1.27 g (6.41 mmol) of DA-6 in a 100 mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, and add 36.1 g of NMP. The solution was dissolved by stirring while blowing nitrogen. While stirring this diamine solution, 4.00 g (16.0 mmol) of CA-2 and 4.42 g (15.0 mmol) of CA-3 were added, and 47% of NMP was added so that the solid content concentration was 15% by mass. 7 g was added and stirred at 50° C. for 24 hours to obtain a polyamic acid solution (B) (viscosity: 904 mPa·s). The molecular weight of the polyamic acid was Mn=14600 and Mw=37500.

<Synthesis Example 3>
30 g of the obtained polyamic acid solution (A) was placed in a 100 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 15.0 g of NMP was added, and the mixture was stirred for 30 minutes. To the obtained polyamic acid solution, 4.89 g of acetic anhydride and 1.51 g of pyridine were added and heated at 50° C. for 2 hours and 30 minutes for chemical imidization. The resulting reaction solution was poured into 154 mL of methanol with stirring, and the deposited precipitate was collected by filtration and washed three times with 154 mL of methanol. Polyimide resin powder (A) was obtained by drying the obtained resin powder at 60° C. for 12 hours. The imidization rate of this polyimide resin powder was 64%, Mn=9900, and Mw=20000.

<Synthesis Example 4>
Take 3.00 g of the polyimide resin powder (A) obtained in Synthesis Example 3 in a 100 mL Erlenmeyer flask, add 22.0 g of NMP so that the solid content concentration is 12%, and stir at 70 ° C. for 24 hours to dissolve. A polyimide solution (A) was obtained.

<Example 1>
3.80 g of the polyimide solution (A) obtained in Synthesis Example 4 and 4.56 g of the polyamic acid solution (B) obtained in Synthesis Example 2 were placed in a 100 mL Erlenmeyer flask, and 0.114 g of AD-1 and 1 of NMP were added. .64 g, 6.00 g of GBL, and 4.00 g of BCS were added and stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent (1). Abnormality, such as turbidity and precipitation, was not seen by this liquid crystal aligning agent, and it was confirmed that it is a uniform solution.

<Comparative Example 1>
3.80 g of the polyimide solution (A) obtained in Synthesis Example 4 and 4.56 g of the polyamic acid solution (B) obtained in Synthesis Example 2 were placed in a 100 mL Erlenmeyer flask, and 1.64 g of NMP and 6.00 g of GBL were added. , and 4.00 g of BCS were added and stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent (2). Abnormality, such as turbidity and precipitation, was not seen by this liquid crystal aligning agent, and it was confirmed that it is a uniform solution.

<Comparative Example 2>
3.80 g of the polyimide solution (A) obtained in Synthesis Example 4 and 4.56 g of the polyamic acid solution (B) obtained in Synthesis Example 2 were placed in a 100 mL Erlenmeyer flask, and 0.114 g of AD-2 and 1 of NMP were added. .64 g, 6.00 g of GBL, and 4.00 g of BCS were added and stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent (1). Abnormality, such as turbidity and precipitation, was not seen by this liquid crystal aligning agent, and it was confirmed that it is a uniform solution.
<Example 2>
After filtering the liquid crystal aligning agent (1) obtained in Example 1 with a 1.0 μm filter, it has a columnar spacer with a height of 4 μm and an ITO film formed on the back surface of the prepared substrate with electrodes. It was applied to a glass substrate by a spin coating method. After drying on a hot plate at 80°C for 2 minutes, the coating film surface was irradiated with 0.25 J/cm ² of linearly polarized ultraviolet light with a wavelength of 254 nm and an extinction ratio of 26:1 through a polarizing plate, followed by hot air circulation at 230°C. Baking was performed in an oven for 20 minutes to obtain a substrate with a liquid crystal alignment film having a film thickness of 100 nm.
The obtained two substrates are set as a set, a sealing agent is printed on the substrate, and another substrate is laminated so that the liquid crystal alignment film surfaces face each other and the alignment direction is 0°, and then sealed. An empty cell was produced by curing the agent. Liquid crystal MLC-3019 (manufactured by Merck & Co.) was injected into this empty cell by a vacuum injection method, and the injection port was sealed to obtain a liquid crystal cell. After that, the obtained liquid crystal cell was heated at 110° C. for 1 hour, left overnight, and then evaluated for black luminance. The luminance of transmitted light of this liquid crystal cell was 27 cd/m ² with no voltage applied.

<Comparative Examples 3-4>
A liquid crystal cell was produced in the same manner as in Example 2, except that the liquid crystal aligning agent shown in Table 1 was used instead of the liquid crystal aligning agent (1), and black luminance was evaluated. Table 1 shows the brightness of the transmitted light of each obtained liquid crystal cell with no voltage applied.

<Example 3>
After filtering the liquid crystal aligning agent (1) obtained in Example 1 with a 1.0 μm filter, it has a columnar spacer with a height of 4 μm and an ITO film formed on the back surface of the prepared substrate with electrodes. It was applied to a glass substrate by a spin coating method. After drying on a hot plate at 80°C for 2 minutes, the coating film surface was irradiated with 0.25 J/cm ² of linearly polarized ultraviolet light with a wavelength of 254 nm and an extinction ratio of 26:1 through a polarizing plate, followed by hot air circulation at 230°C. Baking was performed in an oven for 20 minutes to obtain a substrate with a liquid crystal alignment film having a film thickness of 100 nm. As a result of measuring the hardness of this substrate by a pencil hardness test method (JIS K5400), it was 3H.

<Comparative Examples 5-6>
A sample for a pencil hardness test was prepared in the same manner as in Example 3, except that the liquid crystal aligning agent shown in Table 2 was used instead of the liquid crystal aligning agent (1). Table 2 shows the evaluation results of each pencil hardness test.

Claims (10)

A liquid crystal aligning agent containing the following (A) component, (B) component, and an organic solvent.
Component (A): at least one polymer selected from the group consisting of a polyimide precursor having a structural unit of the following formula (1) and an imidized polymer of the polyimide precursor (B) Component: the following formula (B1- 1) is a compound having two or more structures represented by

X ₁ is a tetravalent organic group having an alicyclic structure , and Y ₁ is at least one divalent organic group selected from structures represented by the following formulas (4) and (5) . R ₁ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, A ₁ to A ₂ are each independently a hydrogen atom or an optionally substituted alkyl group having 1 to 10 carbon atoms, It is an alkenyl group having 2 to 10 carbon atoms or an alkynyl group having 2 to 10 carbon atoms.

Z ₁ is an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkynyl group having 2 to 6 carbon atoms. "*" indicates a bond.

A ₁ is a single bond, an ester bond, an amide bond, a thioester bond, or a divalent organic group having 2 to 20 carbon atoms, and A ₃ is a hydrogen atom, a halogen atom, a hydroxyl group, an amino group, a thiol group, a nitro group, a phosphate group, or a monovalent organic group having 1 to 20 carbon atoms, a is an integer of 1 to 4, and when a is 2 or more, the structure of A ₃ may be the same or different. b and c are each independently an integer of 1 to 2; 2. The liquid crystal aligning agent according to claim 1, wherein the component (B) is contained in an amount of 0.1 to 20% by mass based on the polymer. 3. The liquid crystal aligning agent according to claim 1, wherein component (B) is at least one selected from the following formulas (B-1) and (B-2).

4. The liquid crystal aligning agent according to any one of claims 1 to 3 , wherein X ₁ in formula (1) is at least one selected from the structures of formulas (X-1) to (X-10) below.

R ₃ to R ₂₃ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, or a carbon atom containing a fluorine atom. It is a monovalent organic group of numbers 1 to 6 or a phenyl group, which may be the same or different. 5. The liquid crystal aligning agent according to any one of claims 1 to 4 , wherein X1 is at least _one structure selected from the structures represented by the following formulas (X1-11) to (X1-16).

6. The liquid crystal aligning agent according to any one of claims 1 to 5 , wherein X1 is at least _one selected from the following formulas (X1-11) and (X1-12).

7. The liquid crystal aligning agent according to any one of claims 1 to 6 , wherein Y ₁ is at least one selected from the following formulas (Y1-1) to (Y1-23).

A liquid crystal alignment film obtained from the liquid crystal alignment agent according to claim 1 . A liquid crystal display device comprising the liquid crystal alignment film according to claim 8 . A lateral electric field driven liquid crystal display device comprising the liquid crystal alignment film according to claim 8 .