TW202003817A - Liquid-crystal alignment agent, liquid-crystal alignment film, and liquid-crystal display element including same - Google Patents

Abstract

Provided are: a liquid-crystal alignment agent capable of giving a liquid-crystal alignment film on which accumulated-charge relaxation is quick and which changes little in accumulated-charge amount upon irradiation by a backlight; a liquid-crystal alignment film; and a liquid-crystal display element. The liquid-crystal alignment agent is characterized by comprising: a polymer obtained from a diamine having a structure represented by formula (1); and an organic solvent. (In formula (1), R1 represents a hydrogen atom or a C1-4 alkyl, alkenyl, alkoxy, fluoroalkyl, fluoroalkenyl, or fluoroalkoxy group, and the two R1 moieties may be the same or different but not both of the R1 moieties are hydrogen atoms; symbol * indicates a site to which another group is bonded; and any hydrogen atom of the benzene rings may have been replaced with a monovalent organic group.).

Description

Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element using the same

The present invention relates to a liquid crystal alignment agent using a novel polymer, a liquid crystal alignment film, and a liquid crystal display element using the same.

Liquid crystal display elements have been widely used as display units for personal computers, mobile phones, smart phones, televisions, etc. The liquid crystal display element includes, for example, a liquid crystal layer sandwiched between the element substrate and the color filter substrate, a pixel electrode and a common electrode that apply an electric field to the liquid crystal layer, an alignment film that controls the alignment of liquid crystal molecules of the liquid crystal layer, and a pair of electrodes supplied to the pixel electrode Thin-film transistors (TFT), etc. for switching of electrical signals. As a driving method of liquid crystal molecules, a vertical electric field method such as a TN method and a VA method, and a horizontal electric field method such as an IPS method and a FFS method are known. The horizontal electric field method of forming electrodes only on one side of the substrate and applying an electric field in a direction parallel to the substrate has a wider viewing angle characteristic than the conventional vertical electric field method of applying voltage to the electrodes formed on the upper and lower substrates to drive the liquid crystal. Known as a liquid crystal display device capable of high-quality display.

Although the liquid crystal cell of the horizontal electric field method has excellent viewing angle characteristics, since there are few electrode portions formed in the substrate, when the voltage retention rate is low, a sufficient voltage cannot be applied to the liquid crystal to lower the display contrast. Moreover, when the stability of the liquid crystal alignment is small, the liquid crystal will not return to the initial state when the liquid crystal is driven for a long time, and it will cause a decrease in contrast or afterimage, so the stability of the liquid crystal alignment is important. Furthermore, static electricity tends to accumulate in the liquid crystal cell. Even if the positive and negative asymmetric voltages generated by the drive are applied, charges will also accumulate in the liquid crystal cell. These accumulated charges cause the liquid crystal alignment disorder or affect the display as a residual image. , Significantly reducing the display quality of the liquid crystal device. In recent years, due to the introduction of HDR (High Dyanmic Range) with the requirement of high contrast, it has become a backlight with higher brightness than before.

Although Patent Document 1 discloses a liquid crystal alignment agent containing a specific structure and compound, it does not describe the resistance to backlight. In addition, although Patent Documents 2 and 3 disclose a liquid crystal alignment agent containing a specific structure, and the backlight of VHR (Voltage Holding Ratio) is also described, it does not mention the accumulated charge, which is difficult to fully satisfy in the prior art. These required characteristics. [Prior Technical Literature]

[Patent Document 1] International Publication Gazette WO2016/063834 [Patent Document 2] International Publication No. WO2014/104015 Specification [Patent Document 3] International Publication No. WO2015/119168 Specification

[Problem to be solved by invention]

An object of the present invention is to provide a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element of a liquid crystal alignment film that can obtain a relaxation of accumulative charges quickly, and the accumulation amount of the backlight charges is unlikely to change even when irradiated. [Means to solve the problem]

(R¹ 表示氫、具有碳數1~4之烷基、烯基、烷氧基、氟烷基、氟烯基或氟烷氧基，2個R¹ 可相同亦可不同，但該等至少一個不為氫，*表示與其他基鍵結之部位，苯環之任意氫原子可經一價有機基取代)。 [發明效果]The present inventors have conducted active research to solve the above-mentioned problems, and found that by introducing a specific structure into the polymer contained in the liquid crystal alignment agent, various characteristics can be simultaneously improved, and the present invention has been completed. The present invention is based on this knowledge, and the following is the gist. A liquid crystal alignment agent characterized by containing a polymer obtained from a diamine having a structure represented by the following formula (1) and an organic solvent,

(R ¹ represents hydrogen, alkyl having 1 to 4 carbons, alkenyl, alkoxy, fluoroalkyl, fluoroalkenyl or fluoroalkoxy, two R ¹ may be the same or different, but these at least One is not hydrogen, * indicates the site of bonding with other groups, any hydrogen atom of the benzene ring may be substituted by a monovalent organic group). [Effect of the invention]

According to the present invention, a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element of a liquid crystal alignment film that can obtain a relaxation of accumulative charges quickly and whose change in the accumulated amount of backlight charge is difficult to change are obtained.

<Specific diamine> The liquid crystal alignment agent of the present invention is a liquid crystal alignment agent containing a novel polymer obtained from a diamine having a structure represented by the following formula (1) (hereinafter referred to as a specific diamine).

In the above formula (1), R ^{1 is} as defined above, but it is preferably an alkyl group having 1 to 5 carbon atoms, particularly preferably a methyl group. The bond between the benzene ring and the nitrogen atom in formula (1) is preferably bonded as in formula (1-1) from the viewpoint of steric hindrance.

The specific diamine is preferably represented by the following formula (1-2), particularly preferably a diamine represented by the following formula (1-3), more preferably a diamine represented by the formula (1-4).

The definition of R ^{1 is} the same as the case of the aforementioned formula (1), and Q ¹ and Q ² are independently a single bond or a divalent organic group, that is, Q ¹ and Q ² may have different structures from each other. In addition, the two Q ² in formula (1-4) may have different structures. In addition, any hydrogen atom of the benzene ring may be substituted with a monovalent organic group as in the case of the above formula (1).

As a preferable example of the above-mentioned specific diamine, a diamine represented by the following formula (2-1), (2-2) or (2-3) can be exemplified.

In the above formula, the definition of R ^{1 is} the same as the above formula (1), R ² represents a single bond or a structure represented by the following formula (3), and n represents an integer of 1 to 3. Any hydrogen atom of the benzene ring may be substituted with a monovalent organic group.

In the above formula, R ³ represents a single bond, selected from -O-, -COO-, -OCO-, -(CH ₂ ) _l -, -O(CH ₂ ) _m O-, -CONR- and -NRCO- Bivalent organic group, k represents an integer from 1 to 5. Furthermore, R represents hydrogen or a monovalent organic group, and l and m represent integers from 1 to 5. The monovalent organic group is preferably an alkyl group having 1 to 3 carbon atoms. * ₁ indicates the position bonded to the benzene ring in formula (2-1) to formula (2-3), * ₂ indicates the bond to the amine group in formula (2-1) to formula (2-3) Location.

As specific examples, the following can be exemplified, but not limited to these. Among them, from the viewpoint of mitigating the accumulated charge, it is preferably formula (2-1-1) to formula (2-1-6), formula (2-1-15), formula (2-1-16), based on From the viewpoint of simultaneous solubility, particularly preferred are formula (2-1-1), formula (2-1-2), formula (2-1-15), and formula (2-1-16).

<Synthesis Method of Specific Diamine> The following describes the method of obtaining the specific diamine by taking the diamine of the following formula (2-1-1) as an example.

The method for synthesizing the specific diamine of the present invention is not particularly limited, but for example, the synthesis of the dinitro compound (2-1-N), which is a precursor of the diamine of the above formula (2-1-1), to make the nitrate Radical reduction method.

The catalyst used in the above-mentioned reduction reaction is preferably a commercially available activated carbon-supporting metal, and examples thereof include palladium-activated carbon, platinum-activated carbon, rhodium-activated carbon, and the like. The catalyst may also be palladium hydroxide, platinum oxide, Raney nickel, etc., not necessarily a metal catalyst supported by activated carbon. Palladium-activated carbon, which is generally widely used, is preferred because of good results.

In order to carry out the above reduction reaction more efficiently, the reaction may be carried out in the presence of activated carbon. At this time, the amount of activated carbon used is not particularly limited, but it is preferably in the range of 1 to 30% by mass, more preferably 10 to 20% by mass, relative to the dinitro compound X1. For the same reason, the reaction may be carried out under pressure. In this case, in order to avoid the reduction of the benzene nucleus, the pressure range of at most 20 atm is preferable, and the reaction is preferably carried out in the range of at most 10 atm.

If the solvent is a solvent that does not react with each raw material, it can be used without particular limitation. For example, aprotic polar organic solvents (dimethylformamide (DMF), dimethylsulfoxide (DMSO), dimethylacetate (DMAc), N-methylpyrrolidone (NMP), etc. can be used ), ethers (diethyl ether (Et ₂ O), diisopropyl (i-Pr ₂ O), tetrabutyl methyl ether (TBME), cyclopentyl methyl ether (CPME), tetrahydrofuran (THF), dioxane Alkane, etc.); aliphatic hydrocarbons (pentane, hexane, heptane, petroleum ether, etc.); aromatic hydrocarbons (benzene, toluene, xylene, mesitylene, chlorobenzene, dichlorobenzene, nitrobenzene, Tetrahydronaphthalene, etc.); halogenated hydrocarbons (chloroform, methylene chloride, carbon tetrachloride, dichloroethane, etc.); lower fatty acid esters (methyl acetate, ethyl acetate, butyl acetate, methyl propionate) Etc.); nitriles (acetonitrile, propionitrile, butyronitrile, etc.); etc.

These solvents may be appropriately selected in consideration of the difficulty in causing the reaction, etc., and they may be used alone or in combination of two or more. If necessary, an appropriate dehydrating agent or desiccant may be used to dry the solvent and used as a non-aqueous solvent. The use amount (reaction concentration) of the solvent is not particularly limited, but it is usually 0.1 to 10 mass times, preferably 0.5 to 30 mass times, and more preferably 1 to 10 mass times relative to the dinitro compound. The reaction temperature is not particularly limited, but it is usually in the range of -100°C to the boiling point of the solvent used, preferably -50 to 150°C. The reaction time is usually 0.05 to 350 hours, preferably 0.5 to 100 hours.

The dinitro compound (2-1-N) can be synthesized, for example, using an amine corresponding to 4-bromonitrobenzene according to the following reaction formula by a conventional reaction.

<Specific polymer> The polymer contained in the liquid crystal alignment agent of the present invention is a polymer obtained by using the above-mentioned specific diamine. Specific examples include polyamic acid, polyamic acid ester, polyimide, polyurea, polyamidide, etc., but from the viewpoint of use as a liquid crystal alignment agent, it is more preferable to have the following formula (4) At least one polymer (hereinafter also referred to as a specific polymer) selected from the polyimide precursor of the structural unit shown and/or the polyimide of its imide compound.

In the above formula, X ¹ is a tetravalent organic group derived from a tetracarboxylic acid derivative, and Y ¹ is a divalent organic group derived from a specific diamine. R ⁵ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. From the viewpoint of easy imidization by heating, R ^{5 is} preferably a hydrogen atom, a methyl group or an ethyl group.

The above X ¹ is appropriately selected according to the degree to which the solubility of the polymer in the solvent or the applicability of the liquid crystal alignment agent, the liquid crystal alignment when forming the liquid crystal alignment film, the voltage retention rate, the accumulated charge, etc. become necessary characteristics. Two or more types may be used in the same polymer. If a specific example of X ¹ is illustrated, the structure of formulas (X-1) to (X-46) disclosed in International Publication No. 2015/119168, pages 13 to 14 will be cited.

In the following, the preferred (A-1) to (A-21) of X1 are shown, but not limited to these.

Among the above, from the viewpoint of further improving the film hardness, particularly preferred are (A-1) and (A-2), from the viewpoint of further increasing the relaxation speed of the accumulated charge, particularly preferred are (A-4), based on further improving the liquid crystal From the viewpoint of the alignment and the relaxation speed of the accumulated charge, particularly preferred are (A-15) to (A-17).

<Other structural units> In addition to the structural unit represented by the formula (4), the polyimide precursor may have a structural unit represented by the following formula (5).

X ² has the same definition as X ¹ in the aforementioned formula (4). As a specific example of X ² , the same as those exemplified by X ¹ of formula (4), which is also included as a preferred example, can be exemplified. R ⁶ has the same definition as R ⁵ in the aforementioned formula (4). R ⁷ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Furthermore, it is preferred that at least one of the two R ⁷ is a hydrogen atom.

In addition, Y ² is derived from the divalent organic group of the diamine which does not contain the structure represented by Formula (1) in the main chain direction, and the structure thereof is not particularly limited. Y ² is appropriately selected according to the degree of necessary properties such as the solubility of the polymer in the solvent or the applicability of the liquid crystal alignment agent, the liquid crystal alignment property, voltage retention rate, accumulated charge, etc. when the liquid crystal alignment film is formed, in the same polymerization Two or more types may be mixed in the substance.

If a specific example of Y ² is illustrated, the structure of the formula (2) disclosed on page 4 of International Publication No. 2015/119168 and the formulas (Y-1) to (Y disclosed on pages 8 to 12) -97), (Y-101)~(Y-118) structure; divalent organic group with two amine groups removed from formula (2) disclosed in page 6 of International Publication No. 2013/008906; International The divalent organic group in which two amine groups are removed from the formula (1) disclosed in page 8 of Open Publication No. 2015/122413; the formula (3) disclosed in page 8 of International Publication No. 2015/060360 Structure; divalent organic group with two amine groups removed from formula (1) disclosed in page 8 of Japanese International Publication No. 2012-173514; self-disclosed page 9 of International Publication No. 2010-050523 Formulas (A)~(F) remove two divalent organic groups such as amine groups.

The following shows the formula (B-1) to formula (B-20) of the preferred structure of Y ² , but the present invention is not limited to these.

In the above structure, from the viewpoint of more improving the film hardness, (B-28) and (B-29) are particularly preferable, and from the viewpoint of more improving the liquid crystal alignment, particularly preferably are (B-1) to (B-3) , Based on the viewpoint of increasing the relaxation speed of the accumulated charge, particularly preferably (B-14) to (B-18), (B-27), and from the viewpoint of more improving the voltage retention rate, (B-26) .

When the formula polyimide precursor contains structural units represented by formula (5) in addition to the structural units represented by formula (4), the structural units represented by formula (4) are relative to formula (4) and formula (5) ) Is preferably 10 mol% or more, more preferably 20 mol% or more, and particularly preferably 30 mol% or more. The molecular weight of the polyimide precursor used in the present invention, based on the weight average molecular weight (Mw), is preferably 2,000 to 500,000, more preferably 5,000 to 300,000, and still more preferably 10,000 to 100,000.

<Polyimide> The polyimide in the specific polymer is obtained by ring-closing the polyimide precursor represented by formula (4) and formula (5). In this case, the rate of acyl imidization does not have to be 100%, and can be arbitrarily adjusted according to the use or purpose. As a method for imidizing the polyimide precursor imidate, a known method can be used. It is simpler to add chemical chemical imidization of alkaline catalyst to the solution of polyimide precursor. Chemical imidization can be carried out at a relatively low temperature, and it is preferable because the molecular weight of the polymer is not likely to be reduced during the imidization step.

The chemical imidization can be carried out by stirring the polyimide precursor in an organic solvent in the presence of an alkaline catalyst. As the organic solvent, the solvent used in the aforementioned polymerization reaction can be used. Examples of the alkaline catalyst include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Among them, triethylamine is preferable because it has sufficient basicity to make the reaction proceed. The temperature during the amide imidization reaction is -20°C to 140°C, preferably 0°C to 100°C, and the reaction time is preferably 1 to 100 hours. The amount of the alkaline catalyst is 0.5 to 30 mole times of the amide group, preferably 2 to 20 mole times. The amidation rate of the resulting polymer can be controlled by adjusting the amount of catalyst, temperature, reaction time, etc. Since the catalyst added remains in the solution after the amide imidization reaction, it is preferable to recover the obtained amide imidized polymer by the following means and re-dissolve it with an organic solvent to make the liquid crystal alignment agent of the invention.

Since the catalyst added in the solution of the polyimide precursor after the imidization reaction remains, it is preferable to recover the resulting imidized polymer by the following means and re-dissolve it with an organic solvent to make The liquid crystal alignment agent of the present invention. The polyimide solution obtained as described above is poured into a weak solvent with sufficient stirring to precipitate a polymer. After several precipitations and washing with a weak solvent, the powder of purified polyimide can be obtained at room temperature or by heating and drying. The weak solvent is not particularly limited, and examples thereof include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, and benzene.

<Liquid crystal alignment agent> The liquid crystal alignment agent of the present invention contains a specific polymer, but may contain two or more specific polymers with different structures. In addition to the specific polymer, other polymers may be contained. Examples of the type of the other polymer include polyamic acid, polyimide, polyamic acid ester, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivative, polycondensation Aldehydes, polystyrene or its derivatives, poly(styrene-phenylmaleimide) derivatives, poly(meth)acrylates, etc. It may also contain a polyimide selected from the polyimide precursor represented by the above formula (5) and/or the polyimide polyimide which is imidized with the polyimide precursor.

When the liquid crystal alignment agent of the present invention contains other polymers, the ratio of the specific polymer to all polymer components is preferably 5% by mass or more, and more preferably 5 to 95% by mass. Liquid crystal alignment agents are used to make liquid crystal alignment films. From the viewpoint of forming a uniform thin film, the form of a coating liquid is generally adopted. The liquid crystal alignment agent of the present invention is also preferably a coating liquid containing the aforementioned polymer component and an organic solvent in which the polymer component is dissolved. At this time, the polymer concentration in the liquid crystal alignment agent can be appropriately changed according to the setting of 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, and from the viewpoint of storage stability of the solution, it is preferably 10% by mass or less. The best polymer concentration is 2-8% by mass.

The organic solvent contained in the liquid crystal alignment agent is not particularly limited if it can uniformly dissolve the polymer components. To cite specific examples, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidine Ketone, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, etc. Among them, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone or γ-butyrolactone is preferably used.

In addition, the organic solvent contained in the liquid crystal alignment agent can be generally used in addition to the above-mentioned solvents, and a mixed solvent of a solvent which can improve the coating property or the smoothness of the coating film surface when the liquid crystal alignment agent is applied in combination, the liquid crystal alignment of the present invention These mixed solvents are also preferably used in the agent. Specific examples of the organic solvent used in combination are as follows, but not limited to these examples. Examples include ethanol, isopropanol, 1-butanol, 2-butanol, isobutanol, tertiary butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1 -Butanol, isoamyl alcohol, tertiary amyl alcohol, 3-methyl-2-butanol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol Alcohol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, cyclohexanol , 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 1,2-ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butane Glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 2- Ethyl-1,3-hexanediol, dipropyl ether, dibutyl ether, dihexyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1,2 -Butoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, 4-hydroxy-4-methyl-2-pentanone, diethylene glycol methyl ethyl ether, diethylene glycol Dibutyl ether, 2-pentanone, 3-pentanone, 2-hexanone, 2-heptanone, 4-heptanone, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethyl acetate Butyl butyl ester, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propyl carbonate, ethyl carbonate, 2-(methoxymethoxy) ethanol, Ethylene glycol monobutyl ether, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, 2-(hexyloxy) ethanol, furfuryl alcohol, diethylene glycol, propylene glycol, propylene glycol monobutyl ether, 1-(butoxy) Ethoxy) propanol, propylene glycol monomethyl ether acetate, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate Ester, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monoacetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol Alcohol monobutyl ether acetate, 2-(2-ethoxyethoxy) ethyl acetate, diethylene glycol acetate, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol mono Ether, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, 3- Ethoxypropionic acid methyl ethyl ester, 3-methoxypropionic acid ethyl ester, 3-ethoxypropionic acid, 3-methoxypropionic acid, 3-methoxypropionic acid propyl ester, 3-methoxypropionic acid Butyl propionate, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, isoamyl lactate, solvents represented by the following formulas [D-1] to [D-3], etc.

In formula [D-1], D ¹ represents a C 1-3 alkyl group, in formula [D-2], D ² represents a C 1-3 alkyl group, in formula [D-3], D ³ It represents an alkyl group having 1 to 4 carbon atoms. Among them, 1-hexanol, cyclohexanol, 1,2-ethylene glycol, 1,2-propylene glycol, propylene glycol monobutyl ether, diethylene glycol diethyl ether, 4-hydroxy-4-methyl-2- Pentanone, ethylene glycol monobutyl ether or dipropylene glycol dimethyl ether. The type and content of these solvents are appropriately selected according to the application device, application conditions, application environment, etc. of the liquid crystal alignment agent.

The liquid crystal alignment agent of the present invention may additionally contain components other than the polymer component and the organic solvent. Examples of these additional components include adhesion aids for improving the adhesion between the liquid crystal alignment film and the substrate or the adhesion between the liquid crystal alignment film and the sealing material, crosslinking agents for improving the strength of the liquid crystal alignment film, Dielectrics or conductive materials used to adjust the dielectric constant or resistance of the liquid crystal alignment film. As specific examples of these additional components, there are various disclosures in the conventional literature on liquid crystal alignment agents, but if an example is shown, the example is International Publication No. 2015/060357, page 53 [0105] to page 55 Page [0116] reveals the ingredients.

<Liquid crystal alignment film> The liquid crystal alignment film of the present invention is obtained from the liquid crystal alignment agent of the present invention described above. An example of a method for obtaining a liquid crystal alignment film from a liquid crystal alignment agent is to apply a liquid crystal alignment agent in the form of a coating liquid on a substrate, dry and fire the film to be implemented by a rubbing treatment method or an optical alignment treatment method Alignment processing method. The substrate to which the liquid crystal alignment agent is applied is not particularly limited if it is a substrate with high transparency, and a glass substrate, a silicon nitride substrate, a plastic substrate such as an acrylic substrate or a polycarbonate substrate, etc. can be used. In this case, when using a substrate formed with an ITO electrode or the like for driving liquid crystal, it is preferable from the viewpoint of simplifying the manufacturing process. In addition, in a reflective liquid crystal display element, if it is a substrate on only one side, an opaque substance such as a silicon wafer may be used, and in this case, an electrode such as aluminum may be used to reflect light.

The coating method of the liquid crystal alignment agent is not particularly limited, and the industry generally includes screen printing method, gravure printing method, flexographic printing method, inkjet method and the like. As other coating methods, there are a dipping method, a roll coating method, a slit coating method, a spin coating method, a spray method, etc., and these can be used depending on the purpose. After the liquid crystal alignment agent is applied on the substrate, the solvent can be evaporated and fired by heating means such as a hot plate, a thermal cycle oven, and an IR (infrared) oven. Any temperature and time can be selected for the drying and firing steps after applying the liquid crystal alignment agent. Generally, in order to fully remove the contained solvent, for example, firing at 50 to 120°C for 1 to 10 minutes, followed by firing at 150 to 300°C for 5 to 120 minutes.

Although the film thickness of the liquid crystal alignment film after firing is not particularly limited, when it is too thin, the reliability of the liquid crystal display element may decrease, so it is preferably 5 to 300 nm, more preferably 10 to 200 nm. The liquid crystal alignment film of the present invention is preferably used 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 is particularly useful as a liquid crystal alignment film of a liquid crystal display element of an FFS method.

<Liquid crystal display element> The liquid crystal display device of the present invention obtains a substrate with a liquid crystal alignment film obtained from the above liquid crystal alignment agent, and then produces a liquid crystal cell by a known method, and uses the liquid crystal cell as an element. An example of a method for manufacturing a liquid crystal cell is described by taking a passive matrix structured liquid crystal display device as an example. Alternatively, a liquid crystal display element of an active matrix structure in which a switching element such as a TFT (Thin Film Transistor) is provided on each pixel portion constituting an image display.

Specifically, a substrate made of transparent glass is prepared, a common electrode is provided on one of the substrates, and a segmented electrode is provided on the other substrate. These electrodes can be, for example, ITO electrodes, and can be patterned in a desired image display manner. 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 a film made of SiO ₂ -TiO ₂ formed by the solution gel method. Next, a liquid crystal alignment film is formed on each substrate under the aforementioned conditions.

Next, for example, an ultraviolet curable sealing material is arranged on a specific part of one of the two substrates on which the liquid crystal alignment film is formed, and then liquid crystal is arranged on a specific number of places on the liquid crystal alignment film surface, so that the liquid crystal alignment film pairs After the other substrate is bonded in the same direction and the liquid crystal is pressed and pushed in front of the liquid crystal alignment film, the substrate is irradiated with ultraviolet rays to harden the sealing material to obtain liquid crystal cells. In addition, as a step after forming the liquid crystal alignment film on the substrate, when arranging the sealing material on a specific part of a substrate, an opening portion that can be filled with liquid crystal from the outside is provided in advance, and the substrate is bonded after the liquid crystal is not arranged. The opening of the sealing material is filled with liquid crystal material in the liquid crystal cell. Secondly, the opening is sealed with an adhesive to obtain a liquid crystal cell. The injection of the liquid crystal material may be a vacuum injection method or a method using capillary phenomenon in the atmosphere.

In any of the above methods, in order to ensure the space filled with the liquid crystal material in the liquid crystal cells, it is preferable to provide columnar protrusions on a substrate, or spread spacers on a substrate, or mix spacers in the sealing material, or the like The combination of other means. Examples of the liquid crystal material include nematic liquid crystals and smectic liquid crystals, among which nematic liquid crystals are preferred, and either a positive liquid crystal material or a negative liquid crystal material may be used. Next, configure the polarizer. Specifically, it is preferable to attach a pair of polarizing plates to the surfaces of the two substrates opposite to the liquid crystal layer.

In addition, as long as the liquid crystal alignment agent of the present invention is used, the liquid crystal alignment film and liquid crystal display element of the present invention are not limited to the above description, and may be produced by other conventional methods. The steps from the liquid crystal alignment agent to obtaining the liquid crystal display element are disclosed in, for example, paragraphs 0074 to 19 on page 17 of page 17 of Japanese Patent Application Laid-Open No. 2015-135393 and the like. [Example]

Hereinafter, specific examples and the like of the present invention will be specifically described, but the present invention is not limited to those examples. The abbreviations of compounds and solvents are as follows. NMP: N-methyl-2-pyrrolidone GBL: γ-butyrolactone BCS: Butyl Cellosolve DA-1~DA-9: Compounds of the following structural formula CA-1, CA-2: compounds of the following structural formula AD-1: 3-glycidoxypropyltriethoxysilane AD-2, AD-3: compounds of the following structural formula

<Viscosity> The viscosity of the polymer solution was measured using an E-type viscometer TVE-22H (manufactured by Toki Industries Co., Ltd.), a sample volume of 1.1 mL, a conical rotor TE-1 (1°34', R24), and a temperature of 25°C.

＜Determination of Amidation Rate＞ The rate of polyimidization of polyimide is determined as follows. 30 mg of polyimide powder was put into an NMR (nuclear magnetic resonance) sample tube (NMR sampling tube standard, φ5, manufactured by Kusano Scientific Corporation), and 0.53 ml of deuterated dimethyl sulfoxide (DMSO-d6, 0.05% by mass) was added TMS (Tetramethylsilane)), apply ultrasound to completely dissolve. This solution was measured for a 500 MHz proton NMR with an NMR measuring machine (JNW-ECA500, manufactured by JEOL DATUM Corporation). The rate of amide imidization is determined based on protons derived from the structure that has not changed before and after amide imidization as the reference protons. The peak integral value of the proton and the NH derived from amide acid appearing near 9.5 ppm to 10.0 ppm are used. The integrated value of the peak proton peak is calculated by the following formula. Acetylimidization rate (%) = (1-α・x/y)×100 In the above formula, x is the peak integral value of the proton derived from the NH group of the amidic acid, y is the peak integral value of the reference proton, and the reference protons are the alpha protonic acid (the imidization rate is 0%). The number is relative to the ratio of one NH matrix of amide acid.

(Synthesis Example 1)

Synthesis of Compound [1] DA-1 (50.0 g, 234 mmol) was fed into tetrahydrofuran (500 g) and dimethylformamide (125 g), and trifluoroacetic anhydride (103 g) was added dropwise over 1 hour under ice cooling. After the dropwise addition, the mixture was stirred at room temperature for 30 minutes. After distilling off most of the tetrahydrofuran under reduced pressure, ethyl acetate (300 mL) was added, and the solution was washed with a saturated sodium bicarbonate aqueous solution (250 mL) three times, washed with saturated saline (250 mL), and then dehydrated with sodium sulfate. The filtrate was concentrated to obtain compound [1] (yield: 76.5 g, yield: 81%, blue-white crystals). 1H-NMR(400MHz, DMSO-d6, δppm): 11.16(s,2H), 7.57(d,4H, J=9.2Hz), 7.04(d,4H, J=9.2Hz), 3.26(s, 3H)

Synthesis of Compound [2] To acetonitrile (300 g), compound [1] (76.5 g, 189 mmol), potassium carbonate (78.4 g) and methane iodide (80.5 g) were added, and the mixture was stirred at room temperature for 68 hours. The crystals were filtered out by filtration and dried to obtain the compound [2] (yield: 83.3 g, crude yield: 102%, blue-white crystals). Compound [2] was directly subjected to the following steps as a crude product. 1H-NMR(400MHz, DMSO-d6, δppm): 7.35(d,4H, J=8.8Hz), 7.09 (d,4H, J=8.8Hz), 3.32(s, 3H), 3.27(s,6H)

Synthesis of compound [3] Compound [2] (83.3g) and potassium carbonate (52.2g) were added to methanol (416g) and pure water (208g), and it stirred at 70 degreeC for 2 hours. After distilling off about 70% of methanol under reduced pressure, pure water (300 g) and ethyl acetate (400 g) were added, and the organic layer was extracted by liquid separation. The liquid was washed with pure water (200 g), dehydrated with sodium sulfate, and the crude product was obtained by concentrating the filtrate. Isopropyl alcohol (168g) was added to the crude product, and after complete dissolution at 75°C, it was cooled and filtered to dry the filtrate to obtain compound [3] (yield: 27.0g, yield: 59% (as compound [1] For reference), gray crystals). 1H-NMR(400MHz, DMSO-d6, δppm): 6.69(d,4H, J=8.8 Hz), 6.45 (d,4H, J=8.8Hz), 5.22-5.19(m,2H), 3.02(s, 3H), 2.62(d,6H, J=5.2Hz)

Synthesis of Compound [4] To NMP (350g), add compound [3] (35.0g), 4-bromonitrobenzene (61.5g), potassium phosphate (92.3g), palladium acetate (0.65g) and bis[2-(diphenyl Phosphonoyl)phenyl] ether (1.56 g), stirred at 100°C for 2 hours. After cooling the reaction liquid, it was poured into pure water (1400 g), stirred at room temperature, and then filtered. The filtrate was washed with a mixed solvent of pure water (175 g) and ethyl acetate (350 g). After filtration, the slurry was washed with methanol (350 g), filtered, and the filtrate was dried to obtain a crude product. To this crude product, dimethylformamide (235 g) was added, and after stirring at 100°C, methanol (336 g) was added, cooled and filtered, and the filtered substance was dried. Dimethylformamide (230g) was added again and stirred at 100°C. Methanol (336g) was added to the filtrate filtered while hot, cooled and filtered. The filtered material was washed with methanol (200 g) and dried to obtain compound [4] (yield: 56.7 g, yield: 81%, yellowish-colored crystal). 1H-NMR(400MHz, DMSO-d6, δppm): 8.06(d,4H, J=9.6 Hz), 7.25 (d,4H, J=8.8Hz), 7.17(d,4H, J=8.8Hz), 6.76 (d,4H, J=9.6Hz), 3.37(s, 6H), 3.34(s,3H)

Synthesis of [DA-2] In dimethylformamide (360g), feed compound [4] (36.0g, 74.5mmol) and 5% palladium on carbon (3.6g) in an autoclave under 0.4MPa hydrogen environment at 40℃ Stir for 12 hours. After the catalyst was hot filtered at 80°C, the total internal weight was 189 g by concentration under reduced pressure. After completely dissolved at 100°C, methanol (220g) was added to precipitate crystals, which were stirred at room temperature, filtered and dried to obtain compound [DA-2] (yield: 23.5g, yield: 74%, light brown crystals) . 1H-NMR (400MHz, DMSO-d6, δppm): 6.77 (d, 4H, J=8.8 Hz), 6.74 (d, 4H, J=9.2Hz), 6.62 (d, 4H, J=9.2Hz), 6.54 (d,4H, J=8.8Hz), 4.88(br, 4H), 3.08(s,3H), 3.07(s,6H)

(Synthesis Example 2) In a 50mL eggplant-shaped bottle with a stirring device and a nitrogen introduction tube, measure DA-2 2.03g (4.8mmol), DA-3 0.96g (4.8mmol) and DA-4 0.72g (2.4mmol), add NMP 35.0g, dissolve while stirring with nitrogen. CA-1 3.22g (10.9mmol) was added to this diamine solution while stirring under ice cooling, and further 15.0g of NMP was added, followed by stirring at 70°C for 11 hours under a nitrogen atmosphere to obtain a polymer solution A-1 (viscosity: 390mPa· s).

(Synthesis Example 3) In a 50mL eggplant-shaped bottle with a stirring device and a nitrogen introduction tube, measure DA-1 1.02g (4.8mmol), DA-3 0.96g (4.8mmol) and DA-4 0.72g (2.4mmol), add NMP 30.5g, stir while dissolving by feeding nitrogen. CA-1 3.39g (11.5mmol) was added to this diamine solution while stirring under ice cooling, and 13.1g of NMP was further added, followed by stirring at 70°C for 5 hours under a nitrogen atmosphere to obtain a polymer solution B-1 (viscosity: 420mPa· s).

(Synthesis Example 4) In a 100mL eggplant-shaped bottle with a stirring device and a nitrogen introduction tube, measure DA-3 1.67g (8.4mmol), DA-4 1.25g (4.2mmol) and DA-5 3.54g (5.24mmol), add NMP 63.3g, stirring and dissolving while feeding nitrogen. CA-1 5.98g (20.3mmol) was added to this diamine solution while stirring under ice cooling, and 27.1g of NMP was further added, followed by stirring at 70°C for 10 hours under a nitrogen atmosphere to obtain a polymer solution B-2 (viscosity: 500mPa· s).

(Synthesis Example 5) In a 3L four-necked flask equipped with a stirring device and a nitrogen introduction tube, measure DA-6 17.3g (159mmol), DA-7 58.6g (240mmol), DA-8 76.8g (240mmol) and diamine DA-9 54.6g (160mmol), 2458g of NMP was added, and dissolved while stirring with nitrogen gas. This diamine solution was added with 171 g (764 mmol) of CA-2 while stirring under ice cooling, and further NMP was added to make the solid content concentration 12% by mass, and stirred at 40° C. for 20 hours to obtain a polyamic acid solution (viscosity: 426 mPa・S). 2250 g of this polyamic acid solution was taken, and after adding 750 g of NMP, 171 g of acetic anhydride and 35.4 g of pyridine were added, and the reaction was carried out at 55° C. for 3 hours. The reaction solution was taken up in 9620 g of methanol, and the resulting precipitate was filtered. The precipitate was washed with methanol and dried under reduced pressure at 60°C to obtain polyimide powder. The polyimide had an imidization rate of 66%. NMP 440g and GBL 440g were added to 120g of obtained polyimide powders, and it stirred at 70 degreeC for 20 hours, and it melt|dissolved and obtained the polymer solution C-1.

(Examples 1, 2) and (Comparative Examples 1, 2) For the solution obtained by mixing the polymer solutions obtained in Synthesis Examples 2 to 5 in such a manner that the ratio of polymer-1 and polymer-2 shown in Table 1 below is as shown in Table 1 below , Add NMP, GBL, BCS, GBL solution containing 1% by weight of AD-1, NMP solution containing 10% by weight of AD-2, and AD-3 while stirring, and then stir at room temperature for 2 hours, thereby obtaining an example Liquid crystal alignment agents for 1, 2 and Comparative Examples 1 and 2.

Using the liquid crystal alignment agent obtained above, an FFS-driven liquid crystal cell was fabricated in the following order, and the backlight accumulation resistance of DC accumulation was evaluated. [Composition of liquid crystal cell driven by FFS] The liquid crystal cell used in the Fringe Field Switching (FFS) mode will be formed on the surface with a FOP (Finger on Plate, finger-shaped plate) formed by a common electrode-insulating layer-comb-shaped pixel electrode in the shape of a plane The first glass substrate of the electrode layer and the second glass substrate having a columnar spacer with a height of 4 μm on the surface and a ITO film formed on the back surface to prevent charging are set as a set. The pixel electrode has a comb shape in which a 3 μm-wide electrode element bent at an inner angle of 160° at a central portion is arranged in parallel with a gap of 6 μm, and one pixel has a line connecting the bent portions of the multiple electrode elements as It has a first area and a second area. Furthermore, the liquid crystal alignment film formed on the first glass substrate is subjected to alignment treatment so that the direction that bisects the inner angle of the pixel bending portion is orthogonal to the alignment direction of the liquid crystal, and the liquid crystal alignment film formed on the second glass substrate is processed The alignment process makes the alignment direction of the liquid crystal on the first substrate coincide with the alignment direction of the liquid crystal on the second substrate when manufacturing the liquid crystal cell.

[Production of LCD Cells] On the surface of each of the above-mentioned glass substrates, the liquid crystal alignment agent filtered by a filter with a pore size of 1.0 μm was spin-coated and dried on a hot plate at 80° C. for 2 minutes. Subsequently, the coating film surface was irradiated with a specific amount of polarizing plate interposed and a linear polarization with an extinction ratio of 26:1 at a wavelength of 254 nm, followed by baking in a hot air circulating oven at 230°C for 30 minutes to obtain a film thickness of 100 nm The substrate of the liquid crystal alignment film. Next, a sealant is printed on one of the glass substrates with a liquid crystal alignment film in the above group, and the other substrate is bonded with the liquid crystal alignment film facing each other, and the sealant is hardened to make cells. The liquid crystal MLC-3019 (manufactured by MERCK) was injected into the hollow cell by a reduced pressure injection method, and the injection port was sealed to obtain an FFS-driven liquid crystal cell. Subsequently, the obtained liquid crystal cell was heated at 120° C. for 1 hour, and after being left overnight, the afterimage characteristic evaluation was performed. The liquid crystal alignment of the liquid crystal cell has no defects, and the liquid crystal alignment state is good.

[Backlight aging resistance of DC accumulation] The liquid crystal cell is arranged between two polarizing plates arranged in such a way that the polarizing axis is orthogonal, so that the pixel electrode and the counter electrode are short-circuited to the same potential, and the LED backlight is illuminated from below the two polarizing plates, so that Adjust the angle of the liquid crystal cell in the way that the brightness of the LED backlight transmitted light measured on the 2 polarizing plates is minimum. Next, while applying an AC voltage with a frequency of 30 Hz to the liquid crystal cell, the V-T curve (voltage-transmittance curve) was measured, and an AC voltage with a relative transmittance of 23% or 100% was calculated as the driving voltage. The liquid crystal cell was heated to 60°C, and a rectangular wave of 20 mV was applied at a frequency of 1 kHz for 30 minutes. Subsequently, an AC drive with a relative transmittance of 100% was applied for 30 minutes, during which the minimum offset voltage value was measured every 3 minutes, and the amount of change from the start of measurement to 30 minutes was calculated as the initial DC cumulative amount.

Furthermore, it was left on the LED backlight panel for 24 hours, and the minimum offset voltage value was measured using the same method as described above as the accumulated DC amount after aging. The smaller the difference between the accumulated amount and the initial DC accumulated amount, the better the backlight aging resistance. For the liquid crystal display elements using the liquid crystal alignment agents of Examples 1 and 2 and Comparative Examples 1 and 2, the evaluation results of the DC accumulation amount as described above are shown in Table 2 below.

In the liquid crystal display device using the liquid crystal alignment agent of Examples 1 and 2 of the present invention, the change in the accumulated DC amount after backlight irradiation was small, and it was determined that the backlight aging resistance was good.

In addition, the entire contents of Japanese Patent Application No. 2018-074928, patent application scope, drawings and abstract filed on April 9, 2018 are incorporated herein by reference, and are incorporated herein as the disclosure of the specification of the present invention.

Claims (15)

A liquid crystal alignment agent characterized by containing a polymer obtained from a diamine having a structure represented by the following formula (1) and an organic solvent,

(R ¹ represents hydrogen, alkyl having 1 to 4 carbons, alkenyl, alkoxy, fluoroalkyl, fluoroalkenyl or fluoroalkoxy, two R ¹ may be the same or different, but these at least One is not hydrogen, * indicates the site of bonding with other groups, any hydrogen atom of the benzene ring may be substituted by a monovalent organic group). The liquid crystal alignment agent according to claim 1, wherein the aforementioned polymer is a polyimide precursor selected from a polycondensate of a polycondensate of diamine and tetracarboxylic dianhydride having the structure represented by the aforementioned formula (1) and its imide At least one polymer in the group of polyimide compounds. If the liquid crystal alignment agent of claim 1 or 2, wherein the aforementioned diamine is represented by the following formula (2-1), formula (2-2) or formula (2-3),

(The definition of R ^{1 is} the same as the above formula (1), R ² represents a single bond or a structure represented by the following formula (3), n represents an integer of 1 to 3, and any hydrogen atom of the benzene ring may be substituted by a monovalent organic group ),

(R ³ represents a single bond, a divalent organic selected from -O-, -COO-, -OCO-, -(CH ₂ ) _l -, -O(CH ₂ ) _m O-, -CONR-, and -NRCO- Group, k represents an integer from 1 to 5, R represents hydrogen or a monovalent organic group, l and m represent integers from 1 to 5, * ₁ represents the benzene ring in formula (2-1) to formula (2-3) For the bonding part, * ₂ indicates the bonding part with the amine group in formula (2-1) to formula (2-3)). If the liquid crystal alignment agent of claim 2 or 3, wherein the aforementioned polyimide precursor is represented by the following formula (4),

(X ¹ is a tetravalent organic group derived from a tetracarboxylic acid derivative, Y ¹ is a divalent organic group derived from a diamine having the structure represented by the aforementioned formula (1), and R ⁵ is a hydrogen atom or carbon number 1 ~5 alkyl). The liquid crystal alignment agent according to claim 4, wherein in the aforementioned formula (4), X ¹ is at least one selected from the group consisting of the following (A-1) to (A-21),

. The liquid crystal alignment agent according to claim 4 or 5, wherein the aforementioned polymer having the structural unit represented by formula (4) contains 10 mol% or more of all polymers contained in the liquid crystal alignment agent. The liquid crystal alignment agent according to any one of claims 1 to 6, wherein the aforementioned organic solvent contains at least one selected from the group consisting of 4-hydroxy-4-methyl-2-pentanone and diethylene glycol diethyl ether. A liquid crystal alignment film obtained from the liquid crystal alignment agent according to any one of claims 1 to 7. A liquid crystal display element comprising the liquid crystal alignment film according to claim 8. The liquid crystal display element of claim 9, wherein the liquid crystal display element is driven by a transverse electric field. A polymer selected from the group consisting of polyimide precursors of polycondensates of diamines and tetracarboxylic dianhydrides having the structure represented by the following formula (1) and polyimide compounds of their imide compounds In groups,

(R ¹ represents hydrogen, alkyl having 1 to 4 carbons, alkenyl, alkoxy, fluoroalkyl, fluoroalkenyl or fluoroalkoxy, two R ¹ may be the same or different, but these at least One is not hydrogen, * indicates the site of bonding with other groups, any hydrogen atom of the benzene ring may be substituted by a monovalent organic group). The polymer according to claim 11, wherein the above diamine is represented by the following formula (2-1), formula (2-2) or formula (2-3),

(The definition of R ^{1 is} the same as the above formula (1), R ² represents a single bond or a structure represented by the following formula (3), n represents an integer of 1 to 3, and any hydrogen atom of the benzene ring may be substituted by a monovalent organic group ),

(R ³ represents a single bond, a divalent organic selected from -O-, -COO-, -OCO-, -(CH ₂ ) _l -, -O(CH ₂ ) _m O-, -CONR-, and -NRCO- Group, k represents an integer from 1 to 5, R represents hydrogen or a monovalent organic group, l and m represent integers from 1 to 5, * ₁ represents the benzene ring in formula (2-1) to formula (2-3) For the bonding part, * ₂ indicates the bonding part with the amine group in formula (2-1) to formula (2-3)). The polymer according to claim 11 or 12, wherein the aforementioned polyimide precursor is represented by the following formula (4),

(X ¹ is a tetravalent organic group derived from a tetracarboxylic acid derivative, Y ¹ is a divalent organic group derived from a diamine represented by the aforementioned formula (1), R ⁵ is a hydrogen atom or a carbon number of 1 to 5 alkyl). The polymer according to claim 13, wherein in the aforementioned formula (6), X ¹ is at least one selected from the group consisting of the following (A-1) to (A-21),

. A diamine represented by formula (2-1), formula (2-2) or formula (2-3),

(The definition of R ^{1 is} the same as the above formula (1), R ² represents a single bond or a structure represented by the following formula (3), n represents an integer of 1 to 3, and any hydrogen atom of the benzene ring may be substituted by a monovalent organic group ),

(R ³ represents a single bond, a divalent organic selected from -O-, -COO-, -OCO-, -(CH ₂ ) _l -, -O(CH ₂ ) _m O-, -CONR-, and -NRCO- Group (k, l, and m represent integers from 1 to 5), R represents hydrogen or a monovalent organic group, * ₁ represents the site bonded to the benzene ring in formula (2-1) to formula (2-3), * ₂ represents the part bonded to the amine group in formula (2-1) to formula (2-3)).