TW202024185A - Liquid crystal alignment agent, production method thereof, liquid crystal alignment film, and liquid crystal display element - Google Patents

Abstract

A liquid crystal alignment agent is provided which, even when reducing the light irradiation amount in alignment treatment by the photo-alignment method, enables obtaining excellent afterimage characteristics in an IPS-driven or FFS-driven liquid crystal display element; a production method of the liquid crystal alignment agent, a liquid crystal alignment film obtained therefrom, and a liquid crystal display element provided therewith are also provided. This liquid crystal alignment agent contains a polyimide, which is the imidized product of a polyimide precursor obtained from a polycondensation reaction of: a tetracarboxylic acid component that contains tetracarboxylic dianhydride represented by formula (1), or a derivative thereof; and a diamine component that contains a first diamine represented by formula (3) and a second diamine represented by formula (4). (X1 is a structure represented by formula (X1-1) or (X1-2).) (R3-R12 are independently a hydrogen atom, a halogen atom, an alkyl group of 1-6 carbons, an alkenyl group of 2-6 carbons, an alkynyl group of 2-6 carbons, a monovalent organic group of 1-6 carbons containing a fluorine atom, or a phenyl group, but at least one of R3-R6 is a group in the aforementioned definition other than a hydrogen atom.) (The A2's are independently a halogen atom, a hydroxyl group, an amino group, a thiol group, a nitro group, a phosphate group, or a monovalent organic group of 1-20 carbons, a is an integer 0-4, if there are multiple A2's, then the structure of the A2's may be the same or different.).

Description

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

The present invention relates to a liquid crystal alignment agent, its manufacturing method, a liquid crystal alignment film obtained therefrom, and a liquid crystal display element provided with the liquid crystal alignment film obtained.

Liquid crystal display elements used in liquid crystal televisions, liquid crystal displays, etc. usually have a liquid crystal alignment film for controlling the alignment of liquid crystals in the element. At present, the most popular liquid crystal alignment film in the industry will be formed on the surface of a film made of polyamide acid and/or polyimidated polyimide on an electrode substrate to Cloths such as cotton, nylon, polyester, etc. are made by rubbing in one direction, the so-called rubbing treatment.

The rubbing treatment is an industrially useful method that is simple and excellent in productivity. However, with the high performance, high definition, and large size of liquid crystal display elements, the surface damage of the alignment film caused by the rubbing treatment, the impact of dust, mechanical force or static electricity, and even the unevenness in the alignment treatment surface Various problems are obvious. Instead of the rubbing method, a photo-alignment method that imparts alignment energy to liquid crystals by irradiating polarized ultraviolet rays is known. With the liquid crystal alignment process by the photo-alignment method, it is proposed to use the photoisomerization reaction, the photo-crosslinking reaction and the photolysis reaction.

Patent Document 1 proposes to use a polyimide film having an alicyclic structure such as a cyclobutane ring in the main chain for the photo-alignment method. Compared with the rubbing method, this optical alignment method can be expected to improve the contrast or viewing angle characteristics of liquid crystal display elements in the IPS driving mode or fringe field switching (Fringe Field Switching: FFS) driving mode. A promising liquid crystal alignment processing method has attracted attention.

The liquid crystal alignment film used in the liquid crystal display element of the IPS drive mode or the FFS drive mode, in addition to the excellent basic characteristics of the liquid crystal alignment or electrical characteristics, it also needs the alignment control force to suppress the residual image caused by the long-term drive However, the liquid crystal alignment film obtained by the photo-alignment method has the problem of weaker alignment control force than the liquid crystal alignment film obtained by the rubbing process. In addition, in the liquid crystal alignment film obtained by the photolysis reaction, a method of removing the low molecular weight component generated by the photolysis as a cause of the decrease in the alignment control force by heat treatment or washing treatment is proposed (patent Literature 2).

However, in the manufacture of liquid crystal display elements, as described above, in order to remove low-molecular-weight components, it is necessary to add a heating treatment step or a washing treatment step, which results in an increase in the number of manufacturing steps of the liquid crystal display element. In this regard, even with a small number of steps, a method for manufacturing a liquid crystal alignment film that can suppress image retention due to long-term driving, and does not have an undesirable state due to low molecular weight components (Patent Document 3). [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 9-297313 [Patent Document 2] JP 2011-107266 A [Patent Document 3] WO2018/117239

[The problem to be solved by the invention]

When the alignment treatment is performed by the photo-alignment method, the amount of light irradiation becomes a factor that affects the energy cost or the production speed, so it is better to align the treatment with a smaller amount of irradiation. However, even if it is a liquid crystal alignment agent that can obtain good image retention characteristics, when the light irradiation amount is reduced, there is still a problem of insufficient image retention characteristics.

Therefore, the object of the present invention is to provide a liquid crystal alignment agent that can obtain good residual image characteristics even if the amount of light irradiation in the alignment process caused by the photo-alignment method is reduced, and can obtain good quality and stable liquid crystal alignment performance. The manufacturing method thereof, the liquid crystal alignment film obtained therefrom, and the liquid crystal display element provided with the liquid crystal alignment film obtained. [Means to solve the problem]

In order to achieve the above-mentioned object, the inventors of the present invention conducted careful examination and found that the above-mentioned object can be achieved by the invention of the following requirements. A liquid crystal alignment agent comprising: a tetracarboxylic acid component containing a tetracarboxylic dianhydride represented by the following formula (1) or a derivative thereof, and a first diamine represented by the following formula (3) and the following The polyimide of the polyimide precursor of the polyimide obtained by the polycondensation reaction of the diamine component of the second diamine represented by the formula (4).

但是，式(1)中，X₁ 為下述式(X1-1)或(X1-2)表示之結構。

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

但是，式(X1-1)、(X1-2)中，R₃ ~R₁₂ 各自獨立為氫原子、鹵素原子、碳數1~6之烷基、碳數2~6之烯基、碳數2~6之炔基、含有氟原子之碳數1~6之1價有機基、或苯基，R₃ ~R₆ 之至少1個為上述定義中之氫原子以外之基團。

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 with 1 to 6 carbons, an alkenyl group with 2 to 6 carbons, and 2-6 alkynyl groups, fluorine atoms-containing monovalent organic groups with 1 to 6 carbon atoms, or phenyl groups, at least one of R ₃ to R ₆ is a group other than the hydrogen atom in the above definition.

但是，式(3)、(4)中，A₂ 各自獨立為鹵素原子、羥基、胺基、硫醇基、硝基、磷酸基、或碳數1~20之1價有機基，a為0~4之整數，A₂ 複數存在時，A₂ 之結構可相同或不同。 [發明效果]

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 with 1 to 20 carbon atoms, and a is 0 An integer of ~4, when A _{2 is} plural, the structure of A ₂ can be the same or different. [Invention Effect]

With the liquid crystal alignment agent of the present invention, the amount of light irradiation can be greatly reduced, and a liquid crystal alignment film with good residual image characteristics can be obtained. In addition, the liquid crystal alignment film obtained from the liquid crystal alignment agent of the present invention has a high yield in the manufacture of liquid crystal panels, and can reduce the residual image caused by AC driving in the liquid crystal display element of the IPS driving mode or FFS driving mode ( Afterimage), a liquid crystal display device of IPS driving method or FFS driving method with excellent afterimage characteristics can be obtained. [The form of implementing the invention]

The liquid crystal alignment agent of the present invention is characterized by containing: a tetracarboxylic acid component containing a tetracarboxylic dianhydride or its derivative having a specific structure (hereinafter also referred to as a tetracarboxylic acid component) and a tetracarboxylic acid component containing two types of specific structures The polyimide of the polyimide (hereinafter also referred to as a specific polymer) of the polyimide obtained by the polycondensation reaction of the diamine component of the diamine (hereinafter also referred to as the diamine component).

＜Specific polymers＞ The specific polymer used in the present invention is a polyimide of a polyimide precursor with a specific structure. The polyimide precursor is not particularly limited if it is a polyimide precursor that is chemically imidized by heating or a catalyst to form an imine ring. From the viewpoint of easiness to perform the imidization or chemical imidization by heating, the polyimide precursor is preferably polyimide acid or polyimide ester.

The imidization rate of the polyimide is not particularly limited, and is preferably 10-100%, more preferably 50-100%, and still more preferably 50-80%. Each component of the raw material for obtaining the above-mentioned specific polymer is described in detail below.

＜Tetracarboxylic acid component＞ The tetracarboxylic acid component used in the polymerization of the specific polymer used in the liquid crystal alignment agent of the present invention is not only tetracarboxylic dianhydride, but also derivatives of tetracarboxylic acid, tetracarboxylic acid dihalide, and tetracarboxylic acid Dialkyl ester, or dialkyl tetracarboxylic acid dihalide.

The above-mentioned tetracarboxylic dianhydride or its derivative is preferably represented by the following formula (1).

但是X₁ 為下述式(X1-1)或(X1-2)表示的結構。

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

但是R₃ ~R₁₂ 各自獨立為氫原子、鹵素原子、碳數1~6之烷基、碳數2~6之烯基、碳數2~6之炔基、含有氟原子之碳數1~6之1價有機基、或苯基。又，R₃ ~R₆ 之至少1個為上述定義中之氫原子以外的基團。

However, R ₃ ~ R ₁₂ are each independently a hydrogen atom, a halogen atom, an alkyl group with 1 to 6 carbons, an alkenyl group with 2 to 6 carbons, an alkynyl group with 2 to 6 carbons, and a fluorine atom-containing carbon number from 1 to 6 is a monovalent organic group, or a phenyl group. In addition, at least one of R ₃ to R ₆ is a group other than the 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 selected from the following formulas (X1-1-1) to (X1-1-5), particularly preferred It is the following formula (X1-1-1). The tetracarboxylic dianhydride represented by the formula (1) or its derivative can also be used in combination of two or more kinds.

The use ratio of the tetracarboxylic dianhydride or its derivatives represented by the above formula (1) is preferably 50 mol% or more, more preferably 70% relative to 1 mol of the all tetracarboxylic acid component used in the specific polymer Mole% or more, and more preferably 80 mole% or more.

In addition, the tetracarboxylic acid component used in the polymerization of the specific polymer described in the present invention includes, in addition to the tetracarboxylic dianhydride represented by the above formula (1) or its derivatives, the tetracarboxylic acid represented by the following formula (2) In the case of acid dianhydride or its derivatives, it is more preferable from the viewpoint of suppressing bright spots or liquid crystal alignment due to decomposition products.

但是X₂ 為選自下述式(X2-1)~(X2-6)。

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

其中，X₂ 較佳為上述式(X2-1)、(X2-5)、或(X2-6)，特佳為式(X2-1)。式(2)表示之四羧酸二酐及其衍生物也可混合2種以上使用。

Among them, X _{2 is} preferably the above formula (X2-1), (X2-5), or (X2-6), and particularly preferably is the formula (X2-1). The tetracarboxylic dianhydride represented by formula (2) and its derivatives can also be used in combination of two or more types.

The use ratio of the tetracarboxylic dianhydride or its derivatives represented by the above formula (2) is preferably 1 to 30 mol% relative to 1 mol of the all tetracarboxylic acid component used in the specific polymer, and more preferably 10~30%, more preferably 10~20%.

The tetracarboxylic dianhydride and its derivatives used in the polymerization of the specific polymer of the present invention may also contain tetracarboxylic dianhydrides or their derivatives other than the above formulas (1) and (2).

＜Diamine＞ The diamine component used in the polymerization of the specific polymer used in the liquid crystal alignment agent of the present invention includes a first diamine selected from at least one of the diamines represented by the following formula (3) and, selected from the following formulas (4) The second diamine which is at least one of the diamines indicated.

但是A₂ 為鹵素原子、羥基、胺基、硫醇基、硝基、磷酸基、或碳數1~20之1價有機基，a為0~4之整數，A₂ 複數存在時，A₂ 之結構可相同或不同。

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 with 1 to 20 carbons, a is an integer of 0 to 4, and when A ₂ exists in plural, A ₂ The structure can be the same or different.

式(3)表示之第1二胺的含量係相對於特定聚合物所使用的全二胺成分，較佳為10~50莫耳%，更佳為10~30莫耳%。Preferred specific examples of the first diamine represented by the formula (3) are listed below, but the present invention is not limited to these.

The content of the first diamine represented by the formula (3) is relative to the total diamine component used in the specific polymer, and is preferably 10-50 mol%, more preferably 10-30 mol%.

式(4)表示之第2二胺之含量係相對於特定聚合物所使用的全二胺成分，較佳為10~50莫耳%，更佳為10~40莫耳%。Preferred specific examples of the second diamine represented by formula (4) are listed below, but the present invention is not limited to these.

The content of the second diamine represented by the formula (4) is relative to the full diamine component used in the specific polymer, and is preferably 10-50 mol%, more preferably 10-40 mol%.

The diamine used for the polymerization of the specific polymer contained in the liquid crystal alignment agent of the present invention may also include diamines other than the above formulas (3) and (4) (hereinafter also referred to as other diamines). The following is an example of other diamines, but the present invention is not limited to these.

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-aminophenyl)ethane, 1,3-bis(4-aminophenyl)propane, 1,4-bis(4-aminophenyl) Yl)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)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, bis(2-(4-aminophenoxy)ethyl)ether, 4-amino-4'-(2-(4-amine (Phenoxy) ethoxy) biphenyl, 2,2'-dimethyl-4,4'-diamino biphenyl, 3,3'-dimethyl-4,4'-diamino biphenyl Benzene, 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, etc.

Among the above, it is preferable to include 1,2-bis(4-aminophenoxy)ethane from the viewpoint of liquid crystal alignment. The content of 1,2-bis(4-aminophenoxy)ethane is preferably 10-40 mol% relative to the total diamine component used in the specific polymer.

但是Y₁ 為含有下述式(6)之結構的2價有機基。In addition, when the solvent solubility of polyimide is improved or the liquid crystal alignment agent of the present invention contains polymers other than the specific polymer, the specific polymer component becomes easy to be localized (unevenly distributed) near the surface layer of the liquid crystal alignment film From the viewpoint of, as other diamines, it is preferable to use at least one of the diamines represented by the following formula (5).

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

但是D表示藉由加熱脫離，置換為氫原子的保護基，*表示與其他結構之連接處。D之較佳的結構，可列舉t-丁氧基羰基。 以下列舉式(5)表示之二胺之較佳的具體例，但是不限定於此等者。又，下述結構中之Boc表示t-丁氧基羰基。

However, D represents a protective group that is removed by heating and replaced with a hydrogen atom, and * represents the connection point with other structures. A preferable structure of D includes t-butoxycarbonyl. Preferred specific examples of the diamine represented by formula (5) are listed below, but they are not limited to these. In addition, Boc in the following structure represents t-butoxycarbonyl.

The preferred content when using the diamine represented by the formula (5) is 5-30 mol% of the diamine represented by the formula (5) relative to the total diamine component used in the specific polymer.

＜Production method of polyamide ester, polyamide acid and polyimide＞ The polyimide precursor of the polyimide used in the present invention, the polyimide acid, and the polyimide of the polyimide precursor of these polyimide precursors can be synthesized by conventional methods. As an example, the method described in WO2013/157586 can be cited. 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. In addition, 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 alignment agent＞ The liquid crystal alignment agent of the present invention is a composition containing the above-mentioned specific polymer and an organic solvent, and may also contain two or more specific polymers with different structures. In addition, the liquid crystal alignment agent of the present invention may contain a polymer other than the specific polymer (hereinafter also referred to as a second polymer) or various additives. When the liquid crystal alignment agent of the present invention contains the second polymer, the ratio of the specific polymer to the total polymer component is preferably 5 mass% or more, and as an example, 5 to 95 mass% can be cited.

As the second polymer, polyamide, polyimide, polyamide, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivatives, polyacetal, polyamide Styrene or its derivatives, poly(styrene-phenylmaleimide) derivatives, poly(meth)acrylate, etc. In particular, a polyamide obtained from a tetracarboxylic dianhydride component and a diamine component (hereinafter also referred to as a second polyamide) is preferable as the second polymer.

The tetracarboxylic dianhydride component for obtaining the second polyamide acid includes a compound represented by the following formula (7).

但是式(7)中，A為4價有機基，較佳為碳數4~30之4價有機基。以下表示較佳之A的結構，但是本發明不限定於此等者。

However, in formula (7), A is a tetravalent organic group, preferably a tetravalent organic group with 4 to 30 carbon atoms. The structure of a preferable A is shown below, but the present invention is not limited to these.

Among the above structures, from the viewpoint of further improving the photo-alignment properties, (A-1) and (A-2) are preferable, and from the viewpoint of increasing the relaxation speed of the accumulated charge, (A-4 ), from the viewpoint of further improving the alignment of the liquid crystal and increasing the relaxation speed of the accumulated charge, (A-15) to (A-17), etc. are preferred. The tetracarboxylic dianhydride component for the second polyamide acid is obtained, and two or more types of tetracarboxylic dianhydride may be used in combination.

The diamine component for obtaining the second polyamide acid includes the diamine represented by the aforementioned formula (3), the diamine represented by the aforementioned formula (4), and the other diamines exemplified above. Furthermore, from the viewpoint of increasing the rate of relaxation of the accumulated charge, it is preferable to use at least one of the diamines represented by the following formula (8). To obtain the diamine component for the second polyamide acid, two or more types of diamines may be used in combination.

式(8)中，Y₂ 為具有鍵結於芳香族基的氮原子或含氮芳香族雜環之2價有機基。 以下表示較佳之Y₂ 的結構，但是本發明不限定於此等者。

In formula (8), Y ₂ is a divalent organic group having a nitrogen atom or a nitrogen-containing aromatic heterocyclic ring bonded to an aromatic group. The following shows a preferable structure of Y ₂ , but the present invention is not limited to these.

The molecular weight of the second polyamide is not particularly limited. For example, Mw is 2,000 to 500,000, preferably 5,000 to 300,000, and more preferably 10,000 to 100,000. In addition, Mn is 1,000 to 250,000, preferably 2,500 to 150,000, and more preferably 5,000 to 50,000.

The concentration of the polymer in the liquid crystal alignment agent of the present invention can be appropriately changed by setting the thickness of the coating film to be formed. From the viewpoint of forming a uniform and defect-free coating film, it is preferably 1% by mass or more. From the viewpoint of storage stability of the solution, it is preferably 10% by mass or less. The concentration of the particularly preferred polymer is 2-8% by mass.

The organic solvent contained in the liquid crystal alignment agent of the present invention is not particularly limited as long as the polymer component is uniformly dissolved. If this specific example is cited, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone , N-ethyl-2-pyrrolidone, N-methylcaprolactone, 2-pyrrolidone, N-vinyl-2-pyrrolidone, dimethyl sulfide, dimethyl sulfide, γ-butyrolactone, 1 , 3-Dimethyl-imidazolinone, 3-methoxy-N,N-dimethylpropaneamide, etc. These can be used alone or in combination of two or more. Moreover, even if it is a solvent which cannot dissolve a polymer component uniformly, it can mix with the said organic solvent in the range where a polymer does not precipitate.

In addition to the organic solvent for dissolving the polymer component, the liquid crystal alignment agent of the present invention may also contain a solvent for improving the uniformity of the coating film when the liquid crystal alignment agent is applied to the substrate. This solvent generally uses a solvent with a lower surface tension than the above-mentioned organic solvent. Specific examples thereof include ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, ethylene glycol, 1-methoxy-2-propane Alcohol, 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, ethyl lactate, n-propyl lactate, n-butyl lactate, isoamyl lactate, etc. Two kinds of these solvents can be used in combination.

In the liquid crystal alignment agent of the present invention, in addition to the above, a dielectric or conductive material for the purpose of changing the dielectric constant or electrical properties of the liquid crystal alignment film can also be added to improve the adhesion between the liquid crystal alignment film and the substrate. Silane coupling agent for the purpose of use, cross-linking compound for the purpose of improving the hardness or density of the film when forming the liquid crystal alignment film, and the purpose of efficiently performing the imidization of polyamide acid when the coating film is fired The imidization accelerator, etc.

<Method for manufacturing liquid crystal alignment film> The manufacturing method of the liquid crystal alignment film using the liquid crystal alignment agent of the present invention is not particularly limited. It is manufactured through the steps (A) ~ (D) shown below, whereby the liquid crystal alignment agent of the present invention can be used more effectively Excellent characteristics. Step (A): the step of coating the liquid crystal alignment agent of the present invention on the substrate, Step (B): a step of heating the coated liquid crystal alignment agent at a temperature at which thermal imidization is not substantially performed to obtain a film, Step (C): a step of irradiating the film obtained in step (B) with polarized ultraviolet rays, Step (D): A step of firing the film obtained in step (C) at 100°C or higher and a higher temperature than step (B).

The steps (A) ~ (D) are explained in more detail below. <Step (A)> The substrate to which the liquid crystal alignment agent of the present invention is applied is not particularly limited as long as it is a highly transparent substrate, and plastic substrates such as glass substrates, silicon nitride substrates, acrylic substrates, or polycarbonate substrates can be used. In this case, from the viewpoint of simplification of the steps, it is preferable to use a substrate formed with ITO electrodes for driving liquid crystals. In addition, in the case of a reflective liquid crystal display element, if it is a single-sided substrate, an opaque material such as a silicon wafer may be used. In this case, a material that reflects light such as aluminum may also be used for the electrode. The coating method of the liquid crystal alignment agent is not particularly limited, and is generally a method performed by screen printing, offset printing, relief printing, or inkjet method. Other coating methods include immersion method, roll coating method, slit coating method, spin coating method, spray method, etc., and these methods can be used according to the purpose.

<Step (B)> Step (B) is a step of heating the liquid crystal alignment agent coated on the substrate to form a film under the condition that thermal imidization is not substantially performed. After the liquid crystal alignment agent is coated on the substrate, the solvent is evaporated to form a film by heating means such as a hot plate, a thermal cycle oven, an IR (infrared) oven, etc. In this step, if the organic solvent contained in the liquid crystal alignment agent can be removed under the condition that the thermal imidization is not substantially performed, any temperature and time can be selected. Generally, in order to sufficiently remove the contained solvent, heating at 50 to 150°C for 1 to 10 minutes is preferred, and heating at 50 to 120°C for 1 to 5 minutes is more preferred.

<Step (C)> Step (C) is a step of irradiating the film obtained in step (B) with polarized ultraviolet rays. Ultraviolet rays are preferably those having a wavelength of 200 to 400 nm, and among them, those having a wavelength of 200 to 300 nm are more preferred. In order to improve the liquid crystal alignment, the substrate coated with the liquid crystal alignment agent can also be irradiated with ultraviolet rays while being heated at 50-250°C. The irradiation amount of the aforementioned 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 . In addition, the higher the extinction ratio of polarized ultraviolet rays is, the higher the anisotropy can be imparted, which is preferable. Specifically, the extinction ratio of linearly polarized ultraviolet rays 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, the step of firing is performed at 100°C or higher and at a temperature higher than the temperature heated in step (B). If the firing temperature is 100°C or higher and higher than the heating temperature of step (B), it is not particularly limited, preferably 150 to 300°C, more preferably 150 to 250°C, and even 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. If the thickness of the liquid crystal alignment film after firing is too thin, the reliability of the liquid crystal display element may be reduced, so it is preferably 5 to 300 nm, more preferably 10 to 200 nm.

The liquid crystal alignment film of the present invention is suitable as a liquid crystal alignment film of a liquid crystal display element of a transverse electric field method such as an IPS method or an FFS method, and particularly can be used as a liquid crystal alignment film of a liquid crystal display element of the FFS method. The liquid crystal display element is obtained by obtaining a substrate with a liquid crystal alignment film obtained from the liquid crystal alignment agent of the present invention, and then a liquid crystal cell is fabricated using a known method, and the unit cell is used for fabrication.

As an example of the manufacturing method of the unit cell, a passive matrix structure liquid crystal display element is taken as an example for description. Alternatively, it may be a liquid crystal display element of an active matrix structure in which switching elements such as TFT (Thin Film Transistor) are provided in each pixel portion constituting the image display.

Specifically, a transparent glass substrate is prepared, a common electrode is provided on one of the substrates, and a segment electrode is provided on the other substrate. These electrodes can be used as ITO electrodes, for example, and can be patterned in such a way that a desired image can be displayed. Next, an insulating film is provided on each substrate so as to cover the common electrode and the segment electrode. The insulating film may be, for example, a SiO ₂ -TiO ₂ film formed by a sol-gel method.

Next, a liquid crystal alignment film is formed on each substrate, and one of the substrates is overlapped with the other substrate so that the liquid crystal alignment film faces each other, and the periphery is bonded with a sealant. In order to control the gap between the substrates, the sealant is usually preferably mixed into the spacer in advance. In addition, it is also preferable to pre-spread spacers for substrate gap control on the in-plane portion where the sealant is not provided. A part of the sealant is provided with an opening that can be filled with liquid crystal from the outside. then. Through the opening provided in the sealant, the liquid crystal material is injected into the space surrounded by the two substrates and the sealant, and then the opening is closed with the adhesive. When injecting, either a vacuum injection method or a method that uses capillary phenomenon in the atmosphere can be used. The liquid crystal material can be either a positive liquid crystal material or a negative liquid crystal material. Next, proceed to install the polarizing plate. Specifically, a pair of polarizing plates are stuck on the surface of the two substrates on the opposite side to the liquid crystal layer.

As mentioned above, according to the liquid crystal alignment agent of the present invention, it is possible to suppress the residual image caused by long-term AC driving that occurs in the liquid crystal display element of the IPS driving method or the FFS driving method, and there is no residual image caused by low molecular weight compounds. The occurrence of bright spots and other undesirable conditions, and a liquid crystal alignment film that can be manufactured in fewer steps than before.

[Example]

Examples are given below to explain the present invention more specifically, but the present invention is not limited to these to be interpreted. The abbreviations of the following compounds and the measurement methods of each characteristic are as follows. In addition, the following numerical values and units are all based on quality unless otherwise specified. NMP: N-methyl-2-pyrrolidone, GBL: γ-butyrolactone, BCS: Butyl cellosolve,

但是上述式中，Boc表示t-丁氧基羰基。

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

[Viscosity] The measurement was performed 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] Measured using a GPC (normal temperature gel permeation chromatography) device, and calculated Mn and Mw as polyethylene glycol and polyethylene oxide conversion values. GPC device: manufactured by Shodex (GPC-101), column: manufactured by Shodex (KD803 and KD805 in series), column temperature: 50°C, lysate: N,N-dimethylformamide (as an additive, Lithium bromide-hydrate (LiBr･H ₂ O) is 30mmol/L, phosphoric acid･anhydrous crystal (o-phosphoric acid) is 30mmol/L, tetrahydrofuran (THF) is 10ml/L), flow rate: 1.0ml/min Standard sample: TSK standard polyethylene oxide manufactured by Tosoh Corporation (weight average molecular weight (Mw)) approximately 900,000, 150,000, 100,000, 30,000), and polyethylene glycol manufactured by Polymer Laboratories (peak top molecular weight (Mp) approximately 12,000) , 4,000, 1,000). During the measurement, in order to avoid overlapping of peaks, two samples were measured in which 4 types of samples of 900,000, 100,000, 12,000, and 1,000 were mixed, and 2 samples of 3 types of samples of 150,000, 30,000, and 4,000 were mixed.

＜Determination of imidization rate＞ Put 20 mg of polyimide powder into the NMR sample tube (standard NMR sample tube, ϕ5 (manufactured by Kusano Science)), and add deuterated dimethyl sulfide (DMSO-d6, 0.05% TMS (tetramethyl silane) ) Mixed product) (0.53ml), apply ultrasonic wave to completely dissolve. This solution was measured for 500 MHz proton NMR using an NMR measuring machine (JNW-ECA500) (manufactured by JEOL datum). The rate of imidization is determined by taking the protons from the unchanged structure before and after imidization as the reference protons, using the peak integral value of this proton and the NH group from the amidic acid appearing near 9.5 ppm to 10.0 ppm The proton peak integral value of is obtained by the following formula. The imidization rate (%)=(1-α･x/y)×100 In the above formula, x is the peak integral value of the proton from the NH group of the amide acid, y is the peak integral value of the reference proton, and α is the reference proton relative to the reference proton when the polyamide acid (the imidization rate is 0%) The ratio of the number of NH protons of amide acid.

[Construction of FFS driving unit cell] The unit cell system used in Fringe Field Switching (FFS) mode will have the first FOP (Finger on Plate) electrode layer formed by a common electrode in a planar shape-an insulating layer-a pixel electrode in the shape of a comb tooth on the surface. 1 A glass substrate and a second glass substrate with a columnar spacer with a height of 4 μm on the surface and an antistatic ITO film formed on the back as a set. The above-mentioned pixel electrode has a 3μm wide electrode element whose central part is bent at an internal angle of 160°, and a plurality of comb teeth are arranged in parallel at intervals of 6μm. One pixel is bounded by the line connecting the curved parts of the plurality of electrode elements , Has a first area and a second area. In addition, the liquid crystal alignment film formed on the first glass substrate is oriented so that the direction in which the inner corner of the pixel bending part is equally divided is orthogonal to the alignment direction of the liquid crystal, and the liquid crystal alignment film formed on the second glass substrate is produced In the case of a unit cell, the alignment treatment is performed in such a way that the alignment direction of the liquid crystal on the first substrate is consistent with the alignment direction of the liquid crystal on the second substrate.

On each surface of the above-mentioned set of glass substrates, the liquid crystal alignment agent filtered with a filter with a pore size of 1.0 μm was coated with a spin coater, and dried on a hot plate at 80° C. for 2 minutes. Then, the coated film surface is irradiated with a specific amount of ultraviolet light with a wavelength of 254nm after linear polarization with an extinction ratio of 26:1 through a polarizing plate, and then fired in a hot air circulation oven at 230°C for 30 minutes to obtain a film with a thickness of 100nm. Substrate with liquid crystal alignment film. Next, a sealant is printed on one of the above-mentioned set of glass substrates with a liquid crystal alignment film, and the other substrate is bonded so that the liquid crystal alignment film faces face each other, and the sealant is hardened to form an empty cell. Liquid crystal MLC-3019 (manufactured by Merck) was injected into this empty cell by a reduced pressure injection method, and the injection port was closed to obtain an FFS drive cell. Then, the obtained unit cell was heated at 120°C for 1 hour and left overnight, and then the afterimage characteristics were evaluated.

[Evaluation of residual image caused by long-term AC drive] For the FFS drive cell fabricated above, an AC voltage with a frequency of 60 Hz and ±5V is applied for 120 hours in a constant temperature environment of 60°C. Then, the state was made to short-circuit the pixel electrode and the counter electrode of the cell, and the state was maintained at room temperature for one day. Regarding the cell subjected to the above-mentioned processing, the deviation between the alignment direction of the liquid crystal in the first area of the pixel in the state where the voltage is not applied and the alignment direction of the liquid crystal in the second area is calculated as an angle. Specifically, the following is obtained: a unit cell is set between two polarizing plates arranged so that the polarization axis is orthogonal, the backlight is turned on, and the arrangement angle of the unit cell is adjusted to make the transmitted light intensity of the first area of the pixel Be the smallest, and secondly, rotate the unit cell so that the intensity of the transmitted light in the second area of the pixel becomes the minimum rotation angle. The afterimage characteristics caused by long-term AC driving can be said to be that the smaller the value of the rotation angle, the better. When the value of the angle Δ of the unit cell is 0.1° or less, it is evaluated as "good".

The following shows synthesis examples of polyamide acid and polyimide. ＜Synthesis example 1＞ In a 300mL four-necked flask with a stirring device and a nitrogen inlet tube, weigh DA-1 (5.86g, 24.0mmol), DA-2 (1.73g, 16.0mmol), DA-3 (5.53g, 24.0mmol) ) And DA-4 (3.79 g, 16.0 mmol), add 197.2 g of NMP, and stir to dissolve while feeding nitrogen. While stirring the diamine solution, CA-1 (14.88 g, 66.4 mmol) and CA-2 (3.00 g, 12.0 mmol) were added, and stirred at 40°C for 24 hours to obtain a polyamide acid solution (A-1) (Viscosity: 425 mPa･s). The Mn of polyamic acid is 11,000, and the Mw is 29,000.

＜Synthesis example 2~6＞ Except that the diamine component, tetracarboxylic acid component, and NMP shown in Table 1 below were used, and the reaction temperature was used, the same procedure was performed as in Synthesis Example 1, thereby obtaining the polyamide acid solution shown in Table 1 below. (A-2)~(A-4), (B-1), and (B-2). The viscosity and Mn/Mw of the obtained polyamide acid are shown in Table 1 below. In addition, the concentration of polyamic acid in the polyamic acid solution obtained in Synthesis Examples 1 to 6 was 15% by mass.

＜Synthesis example 7＞ In a 300 mL four-necked flask with a stirring device and a nitrogen inlet tube, weigh 100 g of the obtained polyamide acid solution (A-1), add 50 g of NMP, and stir for 30 minutes. To the obtained polyamide acid solution, 17.60 g of acetic anhydride and 5.50 g of pyridine were added, and the mixture was heated at 50°C for 3 hours to perform chemical imidization. The resulting reaction solution was poured into 600 ml of methanol while stirring, the precipitated precipitate was filtered, and the same operation was performed twice to wash the resin powder, and then dried at 60°C for 12 hours to obtain a polyimide resin powder. The polyimide resin powder has an imidization rate of 73%, with Mn=12600 and Mw=33900. Weigh 3.60 g of the obtained polyimide resin powder in a 100 ml Erlenmeyer flask, add 26.4 g of NMP so that the solid content concentration becomes 12%, stir at 70°C for 24 hours to dissolve, and obtain a polyimide solution (A-1 -PI) (refer to Table 2 below). In addition, in Table 2, the concentration (mass %) in the imidization conditions represents the polymer concentration in the solution of the imidization reaction.

＜Synthesis example 8~10＞ Except for using the acetic anhydride and pyridine shown in Table 2 below, the chemical imidization operation was performed in the same manner as in Synthesis Example 7, thereby obtaining the polyimide solution (A-2-PI) shown in Table 2 below. ~(A-4-PI). The imidization rate and Mn/Mw of the obtained polyimide are shown in Table 2 below.

<Example 1> In a 50 ml Erlenmeyer flask, weigh 4.0 g of the 12% by mass polyimide solution (A-1-PI) obtained in Synthesis Example 7 and the 15% by mass polyimide solution (B-PI) obtained in Synthesis Example 5 1) 4.8 g, NMP 3.24 g, GBL 3.96 g, and BCS 4.00 g are added, and mixed at 25° C. for 8 hours to obtain a liquid crystal alignment agent (1) (refer to Table 3 below). No abnormalities such as turbidity or precipitation were observed in this liquid crystal alignment agent, and it was confirmed that it was a uniform solution. In addition, in Table 3, A/B represents the mass% ratio of the polyimide solution/polyamide acid solution, and the solid content ratio (mass %) represents the content ratio of the polymer in the liquid crystal alignment agent.

<Examples 2 to 4, Comparative Example 1> Except for using the polyamide acid solution and the polyimide solution shown in Table 3 below, the same procedure as in Example 1 was carried out to obtain liquid crystal alignment agents (2) to (5). No abnormalities such as turbidity or precipitation were observed in these liquid crystal alignment agents, and they were confirmed to be uniform solutions.

<Example 11> The afterimage characteristics were evaluated in accordance with the above-mentioned [Evaluation of image retention due to long-term AC driving]. That is, the liquid crystal alignment agent (1) obtained in Example 1 was filtered with a filter with a pore size of 1.0 μm, and then applied to the prepared substrate with electrode and the back surface of the ITO film with a height of 4 μm by spin coating. The glass substrate of the columnar spacer. After drying for 5 minutes on a hot plate at 80°C, the coating surface is irradiated with ultraviolet rays with a wavelength of 254nm after linear polarization with an extinction ratio of 26:1 through a polarizing plate, and then burned in a hot air circulating oven at 230°C for 30 minutes. To obtain a substrate with a liquid crystal alignment film. The two substrates obtained above are used as a set, and a sealant is printed on the substrate, and the other substrate is bonded so that the liquid crystal alignment film faces face each other and the alignment direction becomes 0°, and the sealant is cured to produce empty cells . Liquid crystal MLC-3019 (manufactured by Merck) was injected into this empty cell by a reduced pressure injection method, and the injection port was closed to obtain an FFS drive cell. Then, the obtained unit cell was heated at 120° C. for 1 hour and left overnight to evaluate the afterimage caused by long-term AC driving. The value (°) of the angle Δ of the unit cell after long-term AC driving is shown in Table 4 below, that is, the value of the angle Δ of the unit cell when the ultraviolet radiation is 0.15J/cm ² is 0.08°. The value of the angle Δ of the unit cell at 0.20 J/cm ² is 0.09°, and the value of the angle Δ of the unit cell at 0.25 J/cm ² is 0.09°. Since the minimum value of the angle Δ is less than 0.10°, a good liquid crystal alignment can be obtained according to the liquid crystal alignment agent (1).

<Examples 12 to 14 and Comparative Example 11> Except that in Examples 12 to 14 and Comparative Example 11, the respective liquid crystal alignment agents shown in Table 4 below were used instead of the liquid crystal alignment agent (1), the same method as in Example 11 was used to fabricate FFS drive cells , Implement the afterimage evaluation caused by long-term AC drive. Regarding each of Examples 12 to 14 and Comparative Example 11, the value (°) of the angle Δ of the unit cell after long-term AC driving for each different ultraviolet irradiation amount is shown in Table 4.

As shown in Table 4, in Examples 11-14, the angle Δ (deg.) was also set to give a small amount of polarized ultraviolet irradiation with an ultraviolet irradiation amount of 0.1° or less of 200 mJ/cm ² or less, and the angle Δ was the best. In view of this good afterimage characteristic, it is found that the production time of the liquid crystal display element is shortened as excellent. [Industrial availability]

The liquid crystal alignment agent of the present invention is useful for forming a liquid crystal alignment film in a wide range of liquid crystal display devices such as IPS driving mode or FFS driving mode. In addition, all the contents of the specification, scope of patent application, drawings, and abstract of Japanese Patent Application No. 2018-154228 filed on August 20, 2018 are cited here as disclosure of the specification of the present invention.

Claims (13)

A liquid crystal alignment agent comprising: a tetracarboxylic acid component containing a tetracarboxylic dianhydride represented by the following formula (1) or a derivative thereof, and a first diamine represented by the following formula (3) and the following The polyimide of the polyimide precursor of the polyimide obtained by the polycondensation reaction of the diamine component of the second diamine represented by the formula (4),

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

(However, R ₃ ~ R ₁₂ are each independently a hydrogen atom, a halogen atom, an alkyl group with 1 to 6 carbons, an alkenyl group with 2 to 6 carbons, an alkynyl group with 2 to 6 carbons, and a carbon number 1 containing fluorine atoms. ~6 monovalent organic group or phenyl group, at least one of R ₃ ~R ₆ is a group other than the 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 with 1 to 20 carbons, a is an integer of 0 to 4, and when A ₂ exists in plural , The structure of A ₂ can be the same or different). The liquid crystal alignment agent of claim 1, wherein X ₁ in the aforementioned formula (1) is at least one selected from the following formulas (X1-1-1)~(X1-1-5),

. The liquid crystal alignment agent of claim 1 or 2, wherein the first diamine represented by the aforementioned formula (3) is a diamine represented by the following formula,

. The liquid crystal alignment agent of any one of claims 1 to 3, wherein the first diamine represented by the aforementioned formula (4) is a diamine represented by the following formula,

. The liquid crystal alignment agent according to any one of claims 1 to 4, wherein the first diamine represented by the aforementioned formula (3) contains 10-50 mol% relative to the aforementioned diamine component. The liquid crystal alignment agent according to any one of claims 1 to 5, wherein the second diamine represented by the aforementioned formula (4) contains 10-50 mol% relative to the aforementioned diamine component. The liquid crystal alignment agent of any one of claims 1 to 6, wherein the aforementioned tetracarboxylic acid component further contains a tetracarboxylic dianhydride represented by the following formula (2) or a derivative thereof,

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

. The liquid crystal alignment agent of claim 7, wherein the tetracarboxylic dianhydride represented by the aforementioned formula (2) or its derivative contains 1-30 mol% relative to the tetracarboxylic acid component. A liquid crystal alignment film, which is obtained by using the liquid crystal alignment agent according to any one of claims 1 to 8. A liquid crystal display element provided with the liquid crystal alignment film of claim 9. A method for manufacturing a liquid crystal alignment film, which has the following steps (A), step (B), step (C) and step (D), Step (A): the step of coating the liquid crystal alignment agent of any one of claims 1 to 8 on the substrate, Step (B): the step of heating the coated liquid crystal alignment agent under substantially no thermal imidization conditions to obtain a film, Step (C): a step of irradiating the film obtained in step (B) with polarized ultraviolet rays, Step (D): A step of firing the film obtained in step (C) at 100°C or higher and a higher temperature than step (B). The method for manufacturing a liquid crystal alignment film of claim 11, wherein in the above step (B), heating is performed at 50°C to 150°C. The method for manufacturing a liquid crystal alignment film of claim 11 or 12, wherein in the step (D), the film is fired at 150 to 300°C.