KR20210045393A - Liquid crystal aligning agent, its manufacturing method, liquid crystal aligning film, and liquid crystal display element - Google Patents

Abstract

(단, X₁ 은 하기 식 (X1-1) 또는 (X1-2) 로 나타내는 구조이다.) (단, R₃ ∼ R₁₂ 는, 각각 독립적으로, 수소 원자, 할로겐 원자, 탄소수 1 ∼ 6 의 알킬기, 탄소수 2 ∼ 6 의 알케닐기, 탄소수 2 ∼ 6 의 알키닐기, 불소 원자를 함유하는 탄소수 1 ∼ 6 의 1 가의 유기기, 또는 페닐기이지만, R₃ ∼ R₆ 중 적어도 하나는 상기 정의 중의 수소 원자 이외의 기이다.) (단, A₂ 는, 각각 독립적으로 할로겐 원자, 하이드록실기, 아미노기, 티올기, 니트로기, 인산기, 또는 탄소수 1 ∼ 20 의 1 가의 유기기이고, a 는 0 ∼ 4 의 정수이고, A₂ 가 복수 존재하는 경우, A₂ 의 구조는 동일해도 되고 상이해도 된다.)Even if the amount of light irradiation in the alignment treatment by the photo-alignment method is reduced, a liquid crystal aligning agent that obtains good afterimage characteristics in a liquid crystal display element of an IPS driving method or an FFS driving method, a manufacturing method thereof, a liquid crystal alignment film obtained therefrom, It provides a liquid crystal display device to be provided. A tetracarboxylic acid component containing a tetracarboxylic dianhydride represented by the following formula (1) or a derivative thereof, a first diamine represented by the following formula (3), and a second diamine represented by the following formula (4) are included. A liquid crystal aligning agent containing a polyimide which is an imidized product of a polyimide precursor obtained from the polycondensation reaction of the diamine component to be described.

(However, X ₁ is a structure represented by the following formula (X1-1) or (X1-2).) (However, R ₃ to R ₁₂ are each independently a hydrogen atom, a halogen atom, or a C 1 to C 6 Although an alkyl group, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group, _{at least one of R 3} to R ₆ is hydrogen in the above definition. It is a group other than an atom.) (However, A ₂ is each independently a halogen atom, a hydroxyl group, an amino group, a thiol group, a nitro group, a phosphoric acid group, or a monovalent organic group having 1 to 20 carbon atoms, and a is 0 to It is an integer of 4, and when multiple _{A 2 exists, the structure of A 2} may be the same or different.)

Description

Liquid crystal aligning agent, its manufacturing method, liquid crystal aligning film, and liquid crystal display element

The present invention relates to a liquid crystal display device comprising a liquid crystal aligning agent, a method for producing the same, a liquid crystal aligning film obtained therefrom, and a liquid crystal aligning film obtained therefrom.

In a liquid crystal display element used for a liquid crystal television, a liquid crystal display, or the like, a liquid crystal alignment film for controlling an arrangement state of liquid crystals is usually formed in the element. Currently, the most popular liquid crystal alignment film in the industry is a treatment in which the surface of a film made of polyamic acid formed on an electrode substrate and/or a polyimide imidized therein is rubbed in one direction with a cloth such as cotton, nylon, or polyester. It is manufactured by performing a so-called rubbing treatment.

The rubbing treatment is an industrially useful method that is simple and excellent in productivity. However, along with the high performance, high definition, and large size of the liquid crystal display, various problems such as scratches and dust on the surface of the alignment film generated in the rubbing treatment, influences due to mechanical strength or static electricity, and furthermore, in-plane non-uniformity of the alignment treatment. Is becoming clear. As a method instead of the rubbing treatment, a photo-alignment method in which a liquid crystal alignment ability is imparted by irradiating polarized ultraviolet rays is known. As for the liquid crystal alignment treatment by the photo-alignment method, a photo-isomerization reaction, a photo-crosslinking reaction, and a photodecomposition reaction have been proposed.

In Patent Document 1, it is proposed to use a polyimide film having an alicyclic structure such as a cyclobutane ring in the main chain in the photoalignment method. This optical alignment method is a promising liquid crystal because the obtained liquid crystal alignment film can be expected to improve the contrast and viewing angle characteristics of a liquid crystal display device of an IPS driving method or a fringe field switching (hereinafter, FFS) driving method, as compared with the rubbing treatment method. It attracted attention as an orientation treatment method.

In addition to basic characteristics such as excellent liquid crystal alignment and electrical characteristics, the liquid crystal alignment film used in the IPS driving method or the FFS driving method liquid crystal display element requires an alignment regulating force to suppress afterimages caused by long-term driving. The liquid crystal aligning film obtained by the alignment method has a problem that the alignment regulating force is weak compared with the liquid crystal aligning film obtained by rubbing treatment. And, in the liquid crystal aligning film obtained by using the photodecomposition reaction, it is said that the low molecular weight component produced|generated by photodecomposition becomes the cause of lowering the orientation regulating power, and the method of removing this low molecular weight component by heat treatment or washing treatment It has been proposed (Patent Document 2).

However, in the manufacture of a liquid crystal display element, in order to remove a low molecular weight component in the above manner, it is necessary to add a heat treatment process or a washing treatment process, which leads to an increase in the manufacturing process of the liquid crystal display element. On the other hand, a method for producing a liquid crystal alignment film has been proposed that can suppress an afterimage due to long-term driving even with a small number of steps, and does not have a problem caused by a low molecular weight component (Patent Document 3).

Japanese Unexamined Patent Application Publication No. Hei 9-297313 Japanese Unexamined Patent Publication No. 2011-107266 WO2018/117239

In the case of performing the alignment treatment by the photo-alignment method, since the irradiation amount of light becomes a factor affecting the energy cost and production speed, it is preferable that the alignment treatment can be performed with a small amount of irradiation. However, even if it is a liquid crystal aligning agent from which good afterimage characteristics are obtained, there existed a problem that the afterimage characteristic is insufficient when the light irradiation amount is reduced.

Therefore, an object of the present invention is a liquid crystal aligning agent in which a good afterimage property can be obtained even if the amount of light irradiation in the alignment treatment by the photo-alignment method is reduced, and a stable liquid crystal alignment ability with good quality is obtained, a method for producing the same, and the obtained It exists in providing a liquid crystal display element provided with a liquid crystal aligning film and the obtained liquid crystal aligning film.

In order to achieve the above object, the inventors of the present invention have repeatedly studied and found that the above object can be achieved by the invention of the following summary.

A tetracarboxylic acid component containing a tetracarboxylic dianhydride represented by the following formula (1) or a derivative thereof, a first diamine represented by the following formula (3), and a second diamine represented by the following formula (4) are included. A liquid crystal aligning agent containing a polyimide which is an imidized product of a polyimide precursor obtained from the polycondensation reaction of the diamine component to be described.

[Formula 1]

However, in formula (1), X ₁ is a structure represented by the following formula (X1-1) or (X1-2).

[Formula 2]

However, in formulas (X1-1) and (X1-2), R ₃ to R ₁₂ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, and 2 Although it is an alkynyl group of to 6, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group, _{at least one of R 3} to R ₆ is a group other than a hydrogen atom in the above definition.

[Formula 3]

However, in formulas (3) and (4), A ₂ is each independently a halogen atom, a hydroxyl group, an amino group, a thiol group, a nitro group, a phosphoric acid group, or a monovalent organic group having 1 to 20 carbon atoms, and a is It is an integer of 0-4, and when multiple _{A 2 exists, the structure of A 2} may be the same or different.

With the liquid crystal aligning agent of the present invention, a significant reduction in the amount of light irradiation is possible, and a liquid crystal aligning film having good afterimage characteristics can be obtained. In addition, the liquid crystal aligning film obtained from the liquid crystal aligning agent of the present invention has a high yield in manufacturing a liquid crystal panel, and can reduce afterimages caused by alternating current driving generated in a liquid crystal display element of an IPS drive method or an FFS drive method. , A liquid crystal display device of an IPS driving method or an FFS driving method having excellent afterimage characteristics can be obtained.

The liquid crystal aligning agent of the present invention has a tetracarboxylic acid component (hereinafter, also referred to as a tetracarboxylic acid component) containing tetracarboxylic dianhydride or a derivative thereof having a specific structure and two types of specific structures. It is characterized by containing a polyimide (hereinafter, also referred to as a specific polymer), which is an imidized product of a polyimide precursor obtained from a polycondensation reaction of a diamine-containing diamine component (hereinafter, also referred to as a diamine component).

<Specific polymer>

The specific polymer used in the present invention is a polyimide which is an imidized product of a polyimide precursor having a specific structure. The polyimide precursor is not particularly limited as long as it is a polyimide precursor that forms an imide ring by heating or chemical imidization by a catalyst. From the viewpoint that imidation by heating or chemical imidation easily proceeds, polyamic acid or polyamic acid ester is preferable as the polyimide precursor.

Although the imidation ratio of a polyimide is not specifically limited, 10-100% is preferable, 50-100% is more preferable, and 50-80% is still more preferable.

Hereinafter, each component used as a raw material for obtaining the specific polymer will be described in detail.

<Tetracarboxylic acid component>

As the tetracarboxylic acid component used for polymerization of the specific polymer used in the liquid crystal aligning agent of the present invention, not only tetracarboxylic dianhydride but also its derivatives, such as tetracarboxylic acid, tetracarboxylic acid dihalide, and tetracarboxyl An acid dialkyl ester or a tetracarboxylic acid dialkyl ester dihalide can also be used.

It is preferable that the said tetracarboxylic dianhydride or its derivative is represented by following formula (1).

[Formula 4]

However, X ₁ is a structure represented by the following formula (X1-1) or (X1-2).

[Formula 5]

However, R ₃ to R ₁₂ are each independently 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, and 1 to 6 carbon atoms containing a fluorine atom. It is a monovalent organic group or a phenyl group of. In addition, _{at least one of R 3} to R ₆ is a group other than a hydrogen atom in the above definition.

From the viewpoint of liquid crystal orientation, X ₁ is preferably the above formula (X1-1), more preferably at least one paper selected from the following formulas (X1-1-1) to (X1-1-5), and the following Formula (X1-1-1) is particularly preferred. Tetracarboxylic dianhydride represented by formula (1) or a derivative thereof may be used in combination of two or more.

[Formula 6]

The ratio of the tetracarboxylic dianhydride represented by the above formula (1) or a derivative thereof is preferably 50 mol% or more, more preferably 70 mol% or more with respect to 1 mol of all tetracarboxylic acid components used in the specific polymer. It is preferable, and 80 mol% or more is more preferable.

In addition, the tetracarboxylic acid component used for polymerization of the specific polymer described in the present invention is a tetracarboxylic acid represented by the following formula (2) in addition to the tetracarboxylic dianhydride represented by the above formula (1) or a derivative thereof. When it contains dianhydride or its derivative, it is more preferable from the viewpoint of suppression of a bright point by a decomposition product and liquid crystal orientation.

[Formula 7]

However, X ₂ is selected from the following formulas (X2-1) to (X2-6).

[Formula 8]

Among them, X ₂ is preferably the above formula (X2-1), (X2-5), or (X2-6), and particularly preferably the formula (X2-1). Tetracarboxylic dianhydride represented by formula (2) and its derivatives may be used in combination of two or more.

The ratio of use of the tetracarboxylic dianhydride represented by the above formula (2) or a derivative thereof is preferably 1 to 30 mol%, and 10 to 30% based on 1 mol of all tetracarboxylic acid components used in the specific polymer. It is more preferable and 10-20% is still more preferable.

The tetracarboxylic dianhydride and its derivative used for polymerization of the specific polymer described in the present invention may contain tetracarboxylic dianhydride or a derivative thereof other than the above formulas (1) and (2).

<Diamine>

The diamine component used for polymerization of the specific polymer used in the liquid crystal aligning agent of the present invention is selected from at least one first diamine selected from diamines represented by the following formula (3) and diamines represented by the following formula (4). It contains at least one type of second diamine.

[Formula 9]

However, A ₂ is a halogen atom, a hydroxyl group, an amino group, a thiol group, a nitro group, a phosphoric acid group, or a monovalent organic group having 1 to 20 carbon atoms, a is an integer of 0 to 4, and a _{plurality of A 2} is present. In the case, _{the structure of A 2} may be the same or different.

Although preferable specific examples of the 1st diamine represented by Formula (3) are given below, this invention is not limited to these.

[Formula 10]

The content of the first diamine represented by the formula (3) is preferably 10 to 50 mol%, and more preferably 10 to 30 mol% with respect to all the diamine components used in the specific polymer.

Although preferable specific examples of the 2nd diamine represented by Formula (4) are given below, this invention is not limited to these.

[Formula 11]

The content of the second diamine represented by the formula (4) is preferably 10 to 50 mol%, and more preferably 10 to 40 mol% with respect to all diamine components used in the specific polymer.

The diamine used for polymerization of the specific polymer contained in the liquid crystal aligning agent of the present invention may contain diamines other than the above formulas (3) and (4) (hereinafter, also referred to as other diamines).

Examples of other diamines are given below, but the present invention is not limited thereto.

m-phenylenediamine, 4-(2-(methylamino)ethyl)aniline, 3,5-diaminobenzoic acid, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 4 ,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 1,2-bis(4-amino Phenyl)ethane, 1,3-bis(4-aminophenyl)propane, 1,4-bis(4-aminophenyl)butane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis( 4-aminophenoxy)benzene, 1,2-bis(4-aminophenoxy)ethane, 1,2-bis(4-amino-2-methylphenoxy)ethane, 1,3-bis(4-aminophenoxy) Si) propane, 1,4-bis(4-aminophenoxy)butane, 1,5-bis(4-aminophenoxy)pentane, 1,6-bis(4-aminophenoxy)hexane, 4-(2 -(4-aminophenoxy)ethoxy)-3-fluoroaniline, di(2-(4-aminophenoxy)ethyl) ether, 4-amino-4'-(2-(4-aminophenoxy) Ethoxy)biphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 1,4-diaminonaphthalene, 1, 5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,7-diaminonaphthalene, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, 2,2'-bis[4 -(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis(4-aminophenyl)propane, 1,3-bis(4-aminophenethyl)urea, and the like.

Among the above, it is preferable to contain 1,2-bis(4-aminophenoxy)ethane from the viewpoint of liquid crystal alignment. The content of 1,2-bis(4-aminophenoxy)ethane is more preferably 10 to 40 mol% based on all diamine components used in the specific polymer.

In addition, from the viewpoint of improving the solvent solubility of the polyimide or from the viewpoint that when a polymer other than a specific polymer is contained in the liquid crystal aligning agent of the present invention, the specific polymer component is easily distributed in the vicinity of the surface layer of the liquid crystal aligning film. It is preferable to use at least 1 type of diamines represented by formula (5).

[Formula 12]

However, Y ₁ is a divalent organic group containing the structure of the following formula (6).

[Formula 13]

However, D represents a protecting group that is desorbed by heating and substituted with a hydrogen atom, and * represents a connection point with another structure. As a preferable structure of D, a t-butoxycarbonyl group is mentioned.

Below, although a preferable specific example of the diamine represented by Formula (5) is given, it is not limited to these. In addition, Boc in the following structure represents a t-butoxycarbonyl group.

[Formula 14]

As for the preferable content when using the diamine represented by formula (5), the diamine represented by formula (5) is 5 to 30 mol% with respect to all the diamine components used in the specific polymer.

<Production method of polyamic acid ester, polyamic acid, and polyimide>

The polyamic acid ester, the polyamic acid, and the imidized product of these polyimide precursors, which are polyimide precursors used in the present invention, can be synthesized by a known method. As an example, the method described in WO2013/157586 is mentioned.

The molecular weight of the specific polymer is not particularly limited as long as it can form a good coating film. For example, the weight average molecular weight (also referred to as Mw) is preferably 2,000 to 500,000, more preferably 5,000 to 300,000, and still more preferably 10,000 to 100,000. Further, the number average molecular weight (also referred to as Mn) is preferably 1,000 to 250,000, more preferably 2,500 to 150,000, and still more preferably 5,000 to 50,000.

<Liquid crystal aligning agent>

The liquid crystal aligning agent of this invention is a composition containing the said specific polymer and an organic solvent, and may contain 2 or more types of specific polymers of different structures. Moreover, the liquid crystal aligning agent of this invention may contain a polymer other than a specific polymer (it is also called 2nd polymer hereafter) and various additives.

When the liquid crystal aligning agent of this invention contains a 2nd polymer, it is preferable that the ratio of a specific polymer to all polymer components is 5 mass% or more, and 5 to 95 mass% is mentioned as an example.

As the second polymer, polyamic acid, polyimide, polyamic acid ester, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivative, polyacetal, polystyrene or its derivative, poly(styrene-phenylmaleimide) derivative , Poly(meth)acrylate, etc. are mentioned.

Particularly, a polyamic acid (hereinafter, also referred to as a second polyamic acid) obtained from a tetracarboxylic dianhydride component and a diamine component is preferable as the second polymer.

The compound represented by the following formula (7) is mentioned as a tetracarboxylic dianhydride component for obtaining a 2nd polyamic acid.

[Formula 15]

However, in formula (7), A is a tetravalent organic group, Preferably it is a C4-C30 tetravalent organic group. Below, although a preferable structure of A is shown, this invention is not limited to these.

[Formula 16]

[Formula 17]

Among the above structures, (A-1) and (A-2) are preferable from the viewpoint of further improvement in photoalignment, and (A-4) is preferable from the viewpoint of improving the relaxation rate of accumulated charge, and (A-15 ) To (A-17) and the like are preferable from the viewpoint of further improvement in liquid crystal alignment and improvement in the relaxation rate of the accumulated charge. As the tetracarboxylic dianhydride component for obtaining the second polyamic acid, two or more types of tetracarboxylic dianhydride may be used in combination.

As the diamine component for obtaining the second polyamic acid, the diamine represented by the formula (3), the diamine represented by the formula (4), and other diamines exemplified above may be mentioned.

Moreover, it is preferable to use at least 1 type of diamines represented by following formula (8) from a viewpoint of improvement of the relaxation rate of accumulated electric charges. As the diamine component for obtaining the second polyamic acid, two or more types of diamines may be used in combination.

[Formula 18]

In formula (8), Y ₂ is a divalent organic group having a nitrogen atom bonded to an aromatic group or having a nitrogen-containing aromatic heterocycle.

Below, although a preferable _{structure of Y 2} is shown, this invention is not limited to these.

[Formula 19]

The molecular weight of the second polyamic acid is not particularly limited, but, for example, Mw is 2,000 to 500,000, preferably 5,000 to 300,000, and more preferably 10,000 to 100,000. Moreover, Mn is 1,000-250,000, Preferably, it is 2,500-150,000, More preferably, it is 5,000-50,000.

The concentration of the polymer in the liquid crystal aligning agent of the present invention can be appropriately changed according to the setting of the thickness of the coating film to be formed, but it is preferably 1% by mass or more from the viewpoint of forming a uniform and defect-free coating film. It is preferable to set it as 10 mass% or less from the point of storage stability. A particularly preferable concentration of the polymer is 2 to 8% by mass.

The organic solvent contained in the liquid crystal aligning agent of the present invention is not particularly limited as long as the polymer component is uniformly dissolved. For specific examples, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrroly Don, N-methylcaprolactam, 2-pyrrolidone, N-vinyl-2-pyrrolidone, dimethylsulfoxide, dimethylsulfone, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, 3- And methoxy-N,N-dimethylpropanamide. These may be used alone or in combination of two or more. Moreover, even if it is a solvent in which the polymer component cannot be dissolved uniformly by itself, it may be mixed with the above organic solvent as long as the polymer is not precipitated.

In addition to the organic solvent for dissolving the polymer component, the liquid crystal aligning agent of the present invention may contain a solvent for improving the uniformity of the coating film when the liquid crystal aligning agent is applied to a substrate. As such a solvent, generally, a solvent having a lower surface tension than the organic solvent is used. Specific examples thereof 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, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, isoamyl lactate Ester, etc. are mentioned. These solvents may be used in combination of two or more.

In the liquid crystal aligning agent of the present invention, in addition to the above, a dielectric or conductive material for the purpose of changing electrical properties such as dielectric constant and conductivity of the liquid crystal aligning film, a silane coupling agent for improving the adhesion between the liquid crystal aligning film and the substrate, and a liquid crystal aligning film are used. You may add a crosslinkable compound for the purpose of increasing the hardness and density of the film at the time, and further, an imidation accelerator for the purpose of efficiently advancing the imidation of the polyamic acid when firing the coating film.

<Method of producing a liquid crystal alignment film>

The method for producing a liquid crystal aligning film using the liquid crystal aligning agent of the present invention is not particularly limited, but the excellent properties of the liquid crystal aligning agent of the present invention can be more effectively exhibited by producing by the steps (A) to (D) shown below. have.

Process (A): The process of applying the liquid crystal aligning agent of this invention on a board|substrate.

Step (B): A step of heating the applied liquid crystal aligning agent at a temperature at which thermal imidization does not substantially proceed to obtain a film.

Step (C): A step of irradiating polarized ultraviolet rays to the film obtained in step (B).

Step (D): A step of firing the film obtained in step (C) at a temperature of 100°C or higher and higher than that of step (B).

Hereinafter, each process of (A)-(D) is demonstrated in more detail.

<Step (A)>

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 substrate having high transparency, and a plastic substrate such as an acrylic substrate or a polycarbonate substrate may be used together with a glass substrate and a silicon nitride substrate. In that case, the use of a substrate on which an ITO electrode or the like for driving the liquid crystal is formed is preferable from the viewpoint of simplification of the process. In addition, in a reflective liquid crystal display device, if only one substrate is used, an opaque material such as a silicon wafer can be used, and a material that reflects light such as aluminum can also be used for the electrode in this case.

The method of applying the liquid crystal aligning agent is not particularly limited, but a method of performing by screen printing, offset printing, flexo printing, inkjet method, or the like is common. Other coating methods include a dip method, a roll coater method, a slit coater method, a spinner method, a spray method, and the like, and may be used depending on the purpose.

<Step (B)>

Step (B) is a step of forming a film by heating the liquid crystal aligning agent applied on the substrate under conditions in which thermal imidization does not substantially proceed. After applying the liquid crystal aligning agent on the substrate, the solvent is evaporated by a heating means such as a hot plate, a heat circulation type oven, or an IR (infrared ray) type oven to form a film. In this step, as long as the organic solvent contained in the liquid crystal aligning agent can be removed under conditions in which thermal imidization does not substantially proceed, an arbitrary temperature and time can be selected. Usually, in order to sufficiently remove the contained solvent, it is preferable to heat at 50 to 150°C for 1 to 10 minutes, and more preferably at 50 to 120°C for 1 to 5 minutes.

<Step (C)>

Step (C) is a step of irradiating polarized ultraviolet rays to the film obtained in step (B). As an ultraviolet ray, it is preferable to have a wavelength of 200-400 nm, Especially, it is more preferable to have a wavelength of 200-300 nm. In order to improve the liquid crystal aligning property, you may irradiate an ultraviolet-ray while heating the board|substrate coated with the liquid crystal aligning agent at 50-250 degreeC. The irradiation amount of the ultraviolet rays is, for example, 1 to 2,000 mJ/cm 2, preferably 10 to 1,000 mJ/cm 2, and more preferably 100 to 600 mJ/cm 2. Further, the polarized ultraviolet rays are preferable because the higher the extinction ratio, the higher the anisotropy can be imparted. Specifically, the extinction ratio of the ultraviolet rays polarized in a straight line is preferably 10:1 or more, and more preferably 20:1 or more.

<Step (D)>

Step (D) is a step of firing the film irradiated with ultraviolet rays in step (C). Specifically, it is a step of firing at a temperature of 100°C or higher and higher than the temperature heated in the step (B). The firing temperature is not particularly limited as long as it is 100°C or higher and higher than the heating temperature in step (B), but is preferably 150 to 300°C, more preferably 150 to 250°C, and still more preferably 200 to 250°C. . The firing time is preferably 5 to 120 minutes, more preferably 5 to 60 minutes, and still more preferably 5 to 30 minutes. When the thickness of the liquid crystal aligning film after firing is too thin, the reliability of the liquid crystal display element may be lowered. Therefore, 5 to 300 nm is preferable, and 10 to 200 nm is more preferable.

The liquid crystal aligning film of this invention is preferable as a liquid crystal aligning film of a horizontal electric field type liquid crystal display element, such as an IPS method and an FFS method, and is especially useful as a liquid crystal aligning film of a liquid crystal display element of an FFS method. The liquid crystal display element is produced by producing a liquid crystal cell by a known method after obtaining a substrate with a liquid crystal aligning film obtained from the liquid crystal aligning agent of the present invention, and using the liquid crystal cell.

As an example of a method for manufacturing a liquid crystal cell, a liquid crystal display device having a passive matrix structure will be described as an example. Further, it may be a liquid crystal display element having an active matrix structure in which a switching element such as a TFT (Thin Film Transistor) is formed in each pixel portion constituting an image display.

Specifically, a transparent glass substrate is prepared, a common electrode is formed on one substrate, and a segment electrode is formed on the other substrate. These electrodes can be used as ITO electrodes, for example, and are patterned so as to display a desired image. Next, on each substrate, an insulating film is formed by covering the common electrode and the segment electrode. The insulating film can be, for example, a film of _{SiO 2} -TiO _{2 formed by a sol-gel method.}

Next, a liquid crystal aligning film is formed on each substrate, and the other substrate is superposed on one substrate so that the liquid crystal aligning film surfaces of each other face each other, and the periphery is adhered with a sealing agent. In order to control the gap between the substrates in the sealing agent, it is usually preferable to mix a spacer. In addition, it is preferable to spread a spacer for controlling the gap of the substrate even in the in-plane portion where the sealing agent is not formed. A part of the sealing agent is provided with an opening in which liquid crystal can be filled from the outside. Subsequently, a liquid crystal material is injected into the space surrounded by the two substrates and the sealing agent through the opening formed in the sealing agent, and after that, the opening is sealed with an adhesive. For the injection, a vacuum injection method may be used, or a method using a capillary phenomenon in the atmosphere may be used. As the liquid crystal material, either a positive liquid crystal material or a negative liquid crystal material may be used. Next, a polarizing plate is installed. Specifically, a pair of polarizing plates is affixed to the surface of the two substrates on the opposite side to the liquid crystal layer.

As described above, according to the liquid crystal aligning agent of the present invention, it is possible to suppress an afterimage caused by long-term AC driving that occurs in a liquid crystal display device of an IPS driving method or an FFS driving method, and a bright spot generated by the remaining low molecular weight compounds There is no such problem, and it is possible to obtain a liquid crystal aligning film that can be manufactured in a smaller number of steps than before.

Example

Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is limited to these and is not interpreted.

The symbol of the compound below and the measuring method of each characteristic are as follows. In addition, the numerical values and units in the following are all based on mass unless otherwise noted.

NMP: N-methyl-2-pyrrolidone, GBL: γ-butyrolactone,

BCS: Butyl Cellosolve,

[Formula 20]

However, in the above formula, Boc represents a t-butoxycarbonyl group.

[Formula 21]

[Viscosity]

Using the E-type viscometer TVE-22H (manufactured by Toki Industries, Ltd.), the samples were measured at 1.1 ml of sample amount, cone rotor TE-1 (1° 34', R24) and a temperature of 25°C.

[Molecular Weight]

It measured using a GPC (normal temperature gel permeation chromatography) apparatus, and Mn and Mw were calculated as polyethylene glycol and polyethylene oxide conversion values.

GPC apparatus: Shodex company make (GPC-101), column: Shodex company make (KD803, KD805 serial), column temperature: 50°C, eluent: N,N-dimethylformamide (as additive, lithium bromide-hydrate (LiBr H ₂ O) is 30 mmol/L, phosphoric acid/anhydrous crystal (o-phosphoric acid) is 30 mmol/L, tetrahydrofuran (THF) is 10 mL/L), flow rate: 1.0 mL/min

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

<Measurement of imidation rate>

20 mg of the polyimide powder was put into an NMR sample tube (NMR sampling tube standard, φ5 (manufactured by Kusano Scientific Co., Ltd.)), and deuterated dimethyl sulfoxide (DMSO-d6, 0.05% TMS (tetramethylsilane) mixture) (0.53 ml) Was added, and ultrasonic waves were applied to dissolve completely. A 500 MHz proton NMR was measured for this solution with an NMR measuring device (JNW-ECA500) (manufactured by Nippon Electronics Datum). For the imidation rate, a proton derived from a structure that does not change before and after imidation is determined as a reference proton, and the peak integrated value of this proton and the proton peak derived from the NH group of the amic acid appearing in the vicinity of 9.5 ppm to 10.0 ppm. It was calculated|required by the following formula using the value.

Imidation rate (%) = (1-α·x/y) × 100

In the above formula, x is the integrated value of the proton peak derived from the NH group of the amic acid, y is the integrated value of the peak of the reference proton, and α is the integrated value of the amic acid in the case of polyamic acid (imidation ratio is 0%). It is the ratio of the number of reference protons to one NH group proton.

[Configuration of FFS driving liquid crystal cell]

The liquid crystal cell for the fringe field switching (FFS) mode is a first glass substrate on which a FOP (Finger on Plate) electrode layer composed of a planar common electrode-insulation layer-comb-shaped pixel electrode is formed on the surface. And, a second glass substrate having a columnar spacer having a height of 4 µm on the surface and an ITO film for preventing static electricity on the rear surface thereof was formed as one set. The pixel electrode has a comb-tooth shape in which a plurality of electrode elements having a width of 3 μm in which the central portion is bent at an inner angle of 160° are parallel to each other at an interval of 6 μm, and one pixel includes a plurality of electrode elements. It has a first area and a second area as a boundary between a line connecting the bent portion.

In addition, the liquid crystal alignment film formed on the first glass substrate is subjected to alignment treatment so that the direction of equally dividing the inner angle of the pixel bent portion and the alignment direction of the liquid crystal are orthogonal, and the liquid crystal alignment film formed on the second glass substrate is when a liquid crystal cell is manufactured. The alignment treatment is performed so that the alignment direction of the liquid crystal on the first substrate and the alignment direction of the liquid crystal on the second substrate coincide.

A liquid crystal aligning agent filtered through a filter having a pore diameter of 1.0 µm was applied to each surface of the one set of glass substrates by spin coat coating, and dried on a hot plate at 80° C. for 2 minutes. Thereafter, a predetermined amount of ultraviolet rays having a wavelength of 254 nm linearly polarized with an extinction ratio of 26:1 through a polarizing plate were irradiated on the coating surface, followed by firing in a 230°C hot air circulation oven for 30 minutes, and a film thickness of 100 nm. A substrate with a liquid crystal alignment film was obtained.

Next, a sealing agent was printed on one side of the glass substrate to which the liquid crystal alignment layer was attached, and the other substrate was bonded to face the liquid crystal alignment layer, and the sealing agent was cured to prepare an empty cell. Liquid crystal MLC-3019 (manufactured by Merck) was injected into this empty cell by a vacuum injection method, and the injection port was sealed to obtain an FFS-driven liquid crystal cell. After that, the obtained liquid crystal cell was heated at 120° C. for 1 hour and left to stand overnight, and then the afterimage characteristics were evaluated.

[Afterimage evaluation by long-term AC drive]

To the FFS-driven liquid crystal cell manufactured above, an AC voltage of ±5 V was applied for 120 hours at a frequency of 60 Hz in a constant temperature environment at 60°C. After that, the pixel electrode and the counter electrode of the liquid crystal cell were short-circuited, and left as it is at room temperature for one day.

With respect to the liquid crystal cell subjected to the above treatment, the deviation of the alignment direction of the liquid crystal in the first region of the pixel and the alignment direction of the liquid crystal in the second region in the state where no voltage was applied was calculated as an angle.

Specifically, a liquid crystal cell is provided between two polarizing plates arranged so that the polarization axes are perpendicular to each other, the backlight is turned on, and the arrangement angle of the liquid crystal cell is adjusted so that the transmitted light intensity of the first region of the pixel is the smallest, and then the pixel The rotation angle required when the liquid crystal cell was rotated so that the transmitted light intensity in the second region of was the smallest was obtained.

It can be said that the afterimage characteristic by long-term AC drive is better as the value of this rotation angle is small. When the value of the angle Δ of the liquid crystal cell was 0.1° or less, it was evaluated as "good".

Synthesis examples of polyamic acid and polyimide are shown below.

<Synthesis Example 1>

In a 300 ml four-necked flask with a stirring device and a nitrogen inlet tube, DA-1 was 5.86 g (24.0 mmol), DA-2 was 1.73 g (16.0 mmol), and DA-3 was 5.53 g (24.0 m). Mol) and DA-4 were weighed and taken 3.79 g (16.0 mmol), and 197.2 g of NMP were added, followed by stirring and dissolving while sending nitrogen. While stirring this diamine solution, 14.88 g (66.4 mmol) of CA-1 and 3.00 g (12.0 mmol) of CA-2 were added, followed by stirring at 40° C. for 24 hours, and polyamic acid solution (A-1) (viscosity : 425 mPa·s) was obtained. Mn of the polyamic acid was 11000 and Mw was 29000.

<Synthesis Examples 2 to 6>

The polyamic acid solution (A-2) shown in Table 1 below was carried out in the same manner as in Synthesis Example 1 except that the diamine component, the tetracarboxylic acid component, and NMP shown in Table 1 below were used, and further carried out at the reaction temperature. (A-4), (B-1), and (B-2) were obtained. The viscosity and Mn/Mw of the obtained polyamic acid are shown in Table 1 below.

In addition, all the concentrations of the polyamic acid in the polyamic acid solution obtained in Synthesis Examples 1 to 6 were 15% by mass.

<Synthesis Example 7>

100 g of the obtained polyamic acid solution (A-1) was taken into a 300 ml four-neck flask equipped with a stirring device and a nitrogen introduction tube, 50 g of NMP was added, and the mixture was stirred for 30 minutes. To the obtained polyamic acid solution, 17.60 g of acetic anhydride and 5.50 g of pyridine were added, followed by heating at 50° C. for 3 hours to perform chemical imidization.

The obtained reaction solution was poured into 600 mL of methanol while stirring, and the precipitated precipitate was collected by filtration, and the resin powder was washed by performing the same operation twice, and then dried at 60° C. for 12 hours to obtain a polyimide resin powder. . The imidation ratio of this polyimide resin powder was 73 %, Mn = 12600 and Mw = 33900. 3.60 g of the obtained polyimide resin powder was taken in a 100 ml Erlenmeyer flask, 26.4 g of NMP was added so that the solid content concentration was 12%, stirred at 70°C for 24 hours to dissolve, and a polyimide solution (A-1-PI) was obtained. (See Table 2 below).

In addition, in Table 2, the concentration (mass %) in the imidation condition represents the polymer concentration in the solution in the imidation reaction.

<Synthesis Examples 8 to 10>

Polyimide solutions (A-2-PI) to (A-4-PI) shown in Table 2 below by performing a chemical imidation operation in the same manner as in Synthesis Example 7 except that acetic anhydride and pyridine shown in Table 2 below were used. Got it. The imidation ratio of the obtained polyimide and Mn/Mw are shown in Table 2 below.

<Example 1>

4.0 g of the 12 mass% polyimide solution (A-1-PI) obtained in Synthesis Example 7 and 4.8 g of the 15 mass% polyamic acid solution (B-1) obtained in Synthesis Example 5 were taken in a 50 ml Erlenmeyer flask, NMP 3.24 g, GBL 3.96 g, and BCS 4.00 g were added, and it mixed at 25 degreeC for 8 hours, and the liquid crystal aligning agent (1) was obtained (refer to following Table 3). Abnormalities such as turbidity and precipitation were not seen in this liquid crystal aligning agent, and it was confirmed that it was a uniform solution.

In addition, in Table 3, A/B shows the mass% ratio of a polyimide solution/polyamic acid solution, and solid content ratio (mass %) shows the content ratio of a polymer in a liquid crystal aligning agent.

<Examples 2 to 4, Comparative Example 1>

Except having used the polyamic acid solution and the polyimide solution shown in following Table 3, it carried out similarly to Example 1, and obtained the liquid crystal aligning agent (2)-(5). Abnormalities such as turbidity and precipitation were not seen in these liquid crystal aligning agents, and it was confirmed that it was a uniform solution.

<Example 11>

The afterimage characteristics were evaluated according to the above-described [evaluation of afterimages by long-term AC drive]. That is, after filtering the liquid crystal aligning agent (1) obtained in Example 1 with a filter having a pore diameter of 1.0 µm, a glass substrate having a prepared substrate with the electrode and a columnar spacer having a height of 4 µm on which an ITO film is formed on the back surface On, it was applied by spin coat application. After drying for 5 minutes on a hot plate at 80°C, through a polarizing plate on the coating surface, irradiation with ultraviolet rays having a linearly polarized wavelength of 254 nm with an extinction ratio of 26:1, and then calcined for 30 minutes in a 230°C hot air circulation type oven, This attached substrate was obtained.

Using the obtained two substrates as one set, a sealing agent is printed on the substrate, and the other substrate is adhered with the liquid crystal alignment film face facing each other so that the alignment direction is 0°, and then the sealing agent is cured to empty. The cell was prepared. Liquid crystal MLC-3019 (manufactured by Merck) was injected into this empty cell by a vacuum injection method, and the injection port was sealed to obtain an FFS-driven liquid crystal cell. Thereafter, the obtained liquid crystal cell was heated at 120° C. for 1 hour, left to stand overnight, and an afterimage evaluation by long-term AC drive was performed.

The value (°) of the angle Δ of this liquid crystal cell after long-term AC drive is as shown in Table 4 below, that is, the value of the angle Δ of the liquid crystal cell at 0.15 J/cm 2, where the irradiation amount of ultraviolet rays is It was 0.08°, the value of the angle Δ of the liquid crystal cell at 0.20 J/cm 2 was 0.09°, and the value of the angle Δ of the liquid crystal cell at 0.25 J/cm 2 was 0.09°. In all, since the minimum value of the angle Δ was less than 0.10°, good liquid crystal alignment was obtained according to the liquid crystal aligning agent (1).

<Examples 12 to 14 and Comparative Example 11>

In place of the liquid crystal aligning agent (1), in Examples 12 to 14 and Comparative Example 11, except having used each of the liquid crystal aligning agents shown in Table 4 below, an FFS-driven liquid crystal cell was produced in the same manner as in Example 11, , After-image evaluation by long-term AC drive was performed.

For each of Examples 12 to 14 and Comparative Example 11, the value (°) of the angle Δ of the liquid crystal cell after long-term AC drive for each irradiation amount of different ultraviolet rays is shown in Table 4.

As shown in Table 4, in Examples 11 to 14, the angle Δ is the best with a small amount of polarized ultraviolet rays irradiation of 200 mJ/cm 2 or less for giving an angle Δ (deg.) of 0.1° or less. It can be seen that because of such a good afterimage characteristic, it is excellent in shortening the production time of the liquid crystal display device.

Industrial applicability

The liquid crystal aligning agent of this invention is useful for formation of a liquid crystal aligning film in a wide range of liquid crystal display elements, such as an IPS drive method and an FFS drive method.

In addition, the entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2018-154228 for which it applied on August 20, 2018 are cited here, and taken as an indication of the specification of the present invention.

Claims (13)

A tetracarboxylic acid component containing a tetracarboxylic dianhydride represented by the following formula (1) or a derivative thereof, a first diamine represented by the following formula (3), and a second diamine represented by the following formula (4) are included. A liquid crystal aligning agent containing a polyimide which is an imidized product of a polyimide precursor obtained from the polycondensation reaction of the diamine component to be described.

(However, X ₁ is a structure represented by the following formula (X1-1) or (X1-2).)

(However, R ₃ to R ₁₂ are each independently 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 1 carbon number containing a fluorine atom. Although it is a monovalent organic group of to 6 or a phenyl group, _{at least one of R 3} to R ₆ is a group other than a hydrogen atom in the above definition.)

(However, A ₂ is each independently a halogen atom, a hydroxyl group, an amino group, a thiol group, a nitro group, a phosphoric acid group, or a monovalent organic group having 1 to 20 carbon atoms, a is an integer of 0 to 4, and A ₂ When a plurality of is present, _{the structure of A 2} may be the same or different.) The method of claim 1,
_{The liquid crystal aligning agent in which X 1} in said formula (1) is at least 1 type selected from following formula (X1-1-1)-(X1-1-5).

The method according to claim 1 or 2,
The liquid crystal aligning agent which 1st diamine represented by said formula (3) is a diamine represented by a following formula.

The method according to any one of claims 1 to 3,
The liquid crystal aligning agent in which 1st diamine represented by said formula (4) is a diamine represented by a following formula.

The method according to any one of claims 1 to 4,
The liquid crystal aligning agent in which 10-50 mol% of 1st diamine represented by said formula (3) is contained with respect to the said diamine component. The method according to any one of claims 1 to 5,
The liquid crystal aligning agent in which 10-50 mol% of 2nd diamine represented by said formula (4) is contained with respect to the said diamine component. The method according to any one of claims 1 to 6,
The liquid crystal aligning agent in which the said tetracarboxylic acid component further contains tetracarboxylic dianhydride represented by following formula (2) or its derivative.

(However, X ₂ is a structure selected from the following formulas (X2-1) to (X2-6).)

The method of claim 7,
The liquid crystal aligning agent in which the tetracarboxylic dianhydride represented by said formula (2) or its derivative is contained in 1 to 30 mol% with respect to a tetracarboxylic acid component. A liquid crystal aligning film obtained using the liquid crystal aligning agent in any one of Claims 1-8. A liquid crystal display device comprising the liquid crystal aligning film according to claim 9. The manufacturing method of a liquid crystal aligning film which has the process of following process (A), process (B), process (C), and process (D).
Process (A): The process of applying the liquid crystal aligning agent in any one of Claims 1-8 on a board|substrate.
Step (B): A step of heating the applied liquid crystal aligning agent under conditions in which thermal imidization does not substantially proceed to obtain a film.
Step (C): A step of irradiating polarized ultraviolet rays to the film obtained in step (B).
Step (D): A step of firing the film obtained in step (C) at a temperature of 100°C or higher and higher than step (B). The method of claim 11,
In the said step (B), the manufacturing method of a liquid crystal aligning film heated at 50 degreeC-150 degreeC. The method of claim 11 or 12,
In the said process (D), the manufacturing method of the liquid crystal aligning film which fires the said film at 150-300 degreeC.