JP7031606B2 - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element using it - Google Patents

Description

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 are widely used as display units for personal computers, mobile phones, smartphones, televisions, and the like. The liquid crystal display element includes, for example, a liquid crystal layer sandwiched between an element substrate and a color filter substrate, a pixel electrode and a common electrode that apply an electric field to the liquid crystal layer, and an alignment film that controls the orientation of liquid crystal molecules in the liquid crystal layer. It is equipped with a thin film transistor (TFT) or the like for switching an electric signal supplied to a pixel electrode. As the driving method of the liquid crystal molecule, 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 an FFS method are known. The horizontal electric field method in which electrodes are formed on only one side of the substrate and an electric field is applied in the direction parallel to the substrate is wider than the conventional vertical electric field method in which a voltage is applied to the electrodes formed on the upper and lower substrates to drive the liquid crystal display. It is known as a liquid crystal display element having a viewing angle characteristic and capable of high-quality display.

Although the transverse electric field type liquid crystal cell has excellent viewing angle characteristics, since there are few electrode portions formed in the substrate, if the voltage holding ratio is low, a sufficient voltage is not applied to the liquid crystal and the display contrast is lowered. Further, if the stability of the liquid crystal orientation is small, the liquid crystal does not return to the initial state when the liquid crystal is driven for a long time, which causes a decrease in contrast and an afterimage. Therefore, the stability of the liquid crystal orientation is important. Furthermore, static electricity is likely to be accumulated in the liquid crystal cell, and charges are accumulated in the liquid crystal cell even when a positive / negative asymmetric voltage generated by driving is applied, and these accumulated charges affect the display as a disorder of liquid crystal orientation or an afterimage. , The display quality of the liquid crystal element is significantly deteriorated. In addition, when the liquid crystal cell is irradiated with backlight light immediately after driving, electric charges are accumulated, afterimages are generated even after driving for a short time, and the size of flicker changes during driving. It will occur.

As a liquid crystal aligning agent having excellent voltage retention and reduced charge accumulation when used in such a transverse electric field type liquid crystal display element, Patent Document 1 describes a specific diamine and an aliphatic tetracarboxylic acid derivative as a heavy weight. A liquid crystal alignment agent containing a polymer obtained by condensation is disclosed. However, as the performance of the liquid crystal display element is improved, the characteristics required for the liquid crystal alignment film are becoming stricter, and it is difficult to fully satisfy all the required characteristics with these conventional techniques.

International Publication WO2004 / 021076 Pamphlet

The present invention provides a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element capable of obtaining a liquid crystal alignment film having excellent voltage retention, quick relaxation of accumulated charges, and less flicker during driving. That is the issue.

但し、Ｒ^１は水素、又は一価の有機基を表し、Ｒ^２は一価の有機基を表し、＊は他の基に結合する部位を示す。ベンゼン環の任意の水素原子は一価の有機基で置換されていてもよい。As a result of diligent studies to solve the above problems, the present inventors have found that various properties can be improved at the same time by introducing a specific structure into the polymer contained in the liquid crystal alignment agent. Completed the invention.
The present invention is based on such findings, and has the following gist.
A liquid crystal alignment agent containing a polymer obtained from a diamine having a structure represented by the following formula (1) and an organic solvent.

However, R ¹ represents hydrogen or a monovalent organic group, R ² represents a monovalent organic group, and * indicates a site to be bonded to another group. Any hydrogen atom on the benzene ring may be substituted with a monovalent organic group.

<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 the structure of the following formula (1) (hereinafter, also referred to as a specific diamine).

In the above formula (1), R ¹ and R ² are as defined above. The monovalent organic group is preferably an alkyl group, an alkenyl group, an alkoxy group, a fluoroalkyl group, a fluoroalkoxy group or a fluoroalkoxy group having 1 to 3 carbon atoms. In particular, R ¹ is preferably a hydrogen atom or a methyl group, and R ² is preferably a methyl group.

The bond position between the carbazole structure and the nitrogen atom in the formula (1) is preferably bonded as in the formula (1-1) from the viewpoint of steric hindrance.

The specific diamine can be represented by, for example, the following formula (1-2), in particular, a diamine represented by the following formula (1-3) is preferable, and further, it is represented by the formula (1-4). Diamines are more preferred.

In the above formula, the definitions of R ¹ and R ² are the same as in the case of the above formula (1), and Q ¹ and Q ² are independently single-bonded or divalent organic groups, that is, Q. ¹ and ^Q2 may have different structures from each other. Further, the ^two Q2s in the equation (1-4) may have different structures from each other. Further, any hydrogen atom of the benzene ring may be substituted with a monovalent organic group as in the case of the above formula (1).

Preferred examples of the specific diamine include diamines represented by the following formulas (2-1), (2-2), or (2-3).

In the above formula, the definitions of R ¹ and R ² are the same as those in the above formula (1), R ³ independently represents a single bond or the structure of the following formula (3), and n is 1 to 3. Represents an integer. Any hydrogen atom on the benzene ring may be substituted with a monovalent organic group.

In the above formula, R ⁴ is derived from single bond, -O-, -COO-, -OCO-,-(CH ₂ ) _l- , -O (CH ₂ ) _m O-, -CONR-, and -NRCO-. It represents the selected divalent organic group and k represents an integer of 1-5. In addition, R represents hydrogen or a monovalent organic group, and l and m represent integers of 1 to 5. As the monovalent organic group, an alkyl group having 1 to 3 carbon atoms is preferable. * ₁ represents a site that binds to a benzene ring in formulas (2-1) to (2-3), and * ₂ represents a site that binds to an amino group in formulas (2-1) to (2-3). Represents a part.
Specific examples include, but are not limited to, the following. Of these, (2-1-1) to (2-1-7) and (2-1-10) to (2-1-17) are preferable from the viewpoint of mitigating the accumulated charge, and (2-1-). 1) to (2-1-7) or (2-1-15) to (2-1-17) are particularly preferable.

<Synthesis method of specific diamine>
Hereinafter, the method for obtaining the diamine described above will be described using 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, a dinitro compound (2-1-N) which is a precursor of the diamine of the above formula (2-1-1) is synthesized, and the nitro group thereof is used. There is a method of reducing.

The catalyst used for the reduction reaction is preferably an activated carbon-supported metal available as a commercially available product, and examples thereof include palladium-activated carbon, platinum-activated carbon, and rhodium-activated carbon. Further, it does not necessarily have to be an activated carbon-supported metal catalyst such as palladium hydroxide, platinum oxide, and Raney nickel. Palladium-activated carbon, which is generally widely used, is preferred because it gives good results.

In order to proceed the reduction reaction more effectively, the reaction may be carried out in the coexistence of activated carbon. At this time, the amount of activated carbon used is not particularly limited, but is preferably in the range of 1 to 30% by mass, more preferably 10 to 20% by mass with respect to the dinitro compound X1. For the same reason, the reaction may be carried out under pressure. In this case, in order to avoid reduction of benzene nuclei, the pressure range is up to 20 atm. The reaction is preferably carried out in the range of up to 10 atm.

The solvent can be used without limitation as long as it is a solvent that does not react with each raw material. For example, aprotonic polar organic solvents (dimethylformamide (DMF), dimethylsulfide (DMSO), dimethylacetate (DMAc), N-methylpyrrolidone (NMP), etc.), ethers (diethyl ether ( _Et2O ), diisopropyl). (I-Pr ₂ O), tetrabutylmethyl ether (TBME), cyclopentylmethyl ether (CPME), tetrahydrofuran (THF), dioxane, etc.); aliphatic hydrocarbons (pentane, hexane, heptane, petroleum ether, etc.); Aromatic hydrocarbons (benzene, toluene, xylene, mesitylene, chlorobenzene, dichlorobenzene, nitrobenzene, tetralin, etc.); Halogen hydrocarbons (chloroform, dichloromethane, carbon tetrachloride, dichloroethane, etc.); Lower fatty acid esters (methyl acetate) , Ethyl acetate, butyl acetate, methyl propionate, etc.); nitriles (nitrile, propionitrile, butyronitrile, etc.); and the like can be used.

These solvents can be appropriately selected in consideration of the susceptibility to reaction and the like, and can be used alone or in combination of two or more. If necessary, the solvent can be dried with a suitable dehydrating agent or desiccant and used as a non-aqueous solvent.
The amount of the solvent used (reaction concentration) is not particularly limited, but is usually 0.1 to 10 times by mass, preferably 0.5 to 30 times by mass, and more preferably 1 to 10 times by mass with respect to the dinitro compound. It is double. The reaction temperature is not particularly limited, but 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 easily synthesized by a known reaction using diiodocarbazole and the corresponding nitrobenzene derivative.

<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 acids, polyamic acid esters, polyimides, polyureas, polyamides, etc., but from the viewpoint of use as a liquid crystal aligning agent, a polyimide precursor having a structural unit represented by the following formula (4), And / or at least one polymer selected from polyimide as an imidized product thereof (hereinafter, also referred to as a specific polymer) is more preferable.

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. R5 is a hydrogen atom or an alkyl group having 1 to ⁵ carbon atoms. ^R5 is preferably a hydrogen atom, a methyl group or an ethyl group from the viewpoint of ease of imidization by heating.
The above X ¹ depends on the degree of required characteristics such as the solubility of the polymer in the solvent, the coatability of the liquid crystal alignment agent, the orientation of the liquid crystal when it is used as a liquid crystal alignment film, the voltage retention rate, and the accumulated charge. It may be appropriately selected, and two or more kinds may be used in the same polymer.
Specific examples of X ¹ include the structures of the formulas (X-1) to (X-46) published on pages 13 to 14 of the International Publication 2015/111968.

Hereinafter, preferred X1s (A- ¹ ) to (A-21) are shown, but the present invention is not limited thereto.

Of the above, (A-1) and (A-2) are particularly preferable from the viewpoint of further improving the rubbing resistance, and (A-4) is particularly preferable from the viewpoint of further improving the relaxation rate of the accumulated charge. A-15) to (A-17) are particularly preferable from the viewpoint of further improving the liquid crystal orientation and the relaxation rate of the accumulated charge.

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

X ² is the same as the definition of X ¹ in the above equation (4). Specific examples of X ² include the same examples as those illustrated in X ¹ of the formula (4), including preferable examples. All of R ⁶ are the same as the definition of R ⁵ in the above formula (4). R ⁷ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Further, it is preferable that at least one of the two ^R7s is a hydrogen atom.
Further, Y ² is a divalent organic group derived from a diamine that does not contain the structure of the formula (1) in the main chain direction, and its structure is not particularly limited. Y ² is appropriately determined according to the degree of required characteristics such as the solubility of the polymer in the solvent, the coatability of the liquid crystal alignment agent, the orientation of the liquid crystal when it is used as a liquid crystal alignment film, the voltage retention rate, and the accumulated charge. It may be selected and two or more kinds may be mixed in the same polymer.

To give a specific example of Y2, the structure of the formula ( ² ) published on page 4 of International Publication 2015/111968 and the formulas (Y-1) to (Y-1) to be published on pages 8-12. Structures of Y-97), (Y-101) to (Y-118); a divalent organic group obtained by removing two amino groups from the formula (2), which is published on page 6 of International Publication 2013/008906. A divalent organic group obtained by removing two amino groups from the formula (1) published on page 8 of International Publication 2015/122413; the formula (3) published on page 8 of International Publication 2015/060360. Structure: A divalent organic group obtained by removing two amino groups from the formula (1) described on page 8 of Japanese Patent Publication No. 2012-173514; the formula published on page 9 of International Publication No. 2010-050523 ( Examples thereof include a divalent organic group obtained by removing two amino groups from A) to (F).
The preferred structure of Y ² is shown below, but the present invention is not limited thereto.

Among the above structures, (B-28), (B-29) and the like are particularly preferable from the viewpoint of further improving the rubbing resistance, and (B-1) to (B-3) and the like are liquid crystal oriented. Particularly preferable from the viewpoint of further improvement, (B-14) to (B-18), (B-27) and the like are particularly preferable from the viewpoint of further improvement of the relaxation rate of the accumulated charge, and (B-26) and the like. Is preferable from the viewpoint of further improving the voltage retention rate.

When the polyimide precursor contains a structural unit represented by the formula (5) in addition to the structural unit represented by the formula (4), the structural unit represented by the formula (4) is the structural unit represented by the formula (4). It is preferably 10 mol% or more, more preferably 20 mol% or more, and particularly preferably 30 mol% or more with respect to the total of the formula (5).
The molecular weight of the polyimide precursor used in the present invention is preferably 2,000 to 500,000, more preferably 5,000 to 300,000, still more preferably 10,000 to 100, in terms of weight average molecular weight (Mw). It is 000.

<Polyimide>
The polyimide among the specific polymers is obtained by ring-closing the polyimide precursors represented by the formulas (4) and (5). The imidization rate in this case does not necessarily have to be 100%, and can be arbitrarily adjusted according to the intended use and purpose.
As a method for imidizing the polyimide precursor, a known method can be used. Chemical imidization by adding a basic catalyst to the solution of the polyimide precursor is convenient. Chemical imidization is preferable because the imidization reaction proceeds at a relatively low temperature and the molecular weight of the polymer is unlikely to decrease during the imidization process.
Chemical imidization can be performed by stirring the polyimide precursor in an organic solvent in the presence of a basic catalyst. As the organic solvent, the solvent used in the above-mentioned polymerization reaction can be used. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine and the like. Of these, triethylamine is preferable because it has sufficient basicity to allow the reaction to proceed.

The temperature at which the imidization reaction is carried out is −20 to 140 ° C., preferably 0 to 100 ° C., and the reaction time is preferably 1 to 100 hours. The amount of the basic catalyst is 0.5 to 30 mol times, preferably 2 to 20 mol times, that of the amic acid ester group. The imidization rate of the obtained polymer can be controlled by adjusting the amount of catalyst, temperature, reaction time and the like. Since the added catalyst and the like remain in the solution after the imidization reaction, the obtained imidized polymer is recovered by the means described below and redissolved in an organic solvent to orient the liquid crystal of the present invention. It is preferable to use it as an agent.

Since the added catalyst and the like remain in the solution after the imidization reaction of the polyimide precursor, the obtained imidized polymer is recovered by the means described below and redissolved in an organic solvent. It is preferable to use the liquid crystal alignment agent of the present invention.
The polyimide solution obtained as described above can precipitate a polymer by injecting it into a poor solvent with good stirring. Precipitation is carried out several times, and after washing with a poor solvent, it can be dried at room temperature or by heating to obtain a purified polyimide powder.
Examples of the poor solvent include, but are not limited to, methanol, acetone, hexane, butyl cellsolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene and the like.

<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 having different structures as long as the effects described in the present invention are exhibited. Further, in addition to the specific polymer, other polymers may be contained. Other types of polymers include polyamic acid, polyimide, polyamic acid ester, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivative, polyacetal, polystyrene or its derivative, poly (styrene-phenylmaleimide) derivative, and poly (meth). ) Acrylate and the like can be mentioned. Further, it may contain a polyimide precursor represented by the above formula (5) and / or a polyimide selected from a polyimide obtained by imidizing the polyimide precursor.

When the liquid crystal alignment agent of the present invention contains other polymers, the ratio of the specific polymer to the total polymer components is preferably 5% by mass or more, more preferably 5 to 95% by mass.
The liquid crystal alignment agent is used for producing a liquid crystal alignment film, and generally takes the form of a coating liquid from the viewpoint of forming a uniform thin film. The liquid crystal alignment agent of the present invention is also preferably a coating liquid containing the above-mentioned polymer component and an organic solvent for dissolving the polymer component. At that time, the concentration of the polymer in the liquid crystal alignment agent 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, and from the viewpoint of storage stability of the solution, it is preferably 10% by mass or less. A particularly preferable concentration of the polymer is 2 to 8% by mass.

The organic solvent contained in the liquid crystal alignment agent is not particularly limited as long as the polymer component is uniformly dissolved. Specific examples thereof include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethyl. -Imidazoridinone, methylethylketone, cyclohexanone, cyclopentanone and the like can be mentioned. Of these, it is preferable to use N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, or γ-butyrolactone.
As the organic solvent contained in the liquid crystal alignment agent, a mixed solvent is used in which a solvent that improves the coatability when the liquid crystal alignment agent is applied and the surface smoothness of the coating film is used in addition to the above-mentioned solvent. This is common, and such a mixed solvent is preferably used in the liquid crystal alignment agent of the present invention. Specific examples of the organic solvent used in combination are given below, but the present invention is not limited to these examples.

For example, ethanol, isopropyl alcohol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol, tert-Pentyl alcohol, 3-methyl-2-butanol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol , 2-Heptanol, 3-Heptanol, 1-Octanol, 2-Octanol, 2-Ethylene-1-hexanol, Cyclohexanol, 1-Methylcyclohexanol, 2-Methylcyclohexanol, 3-Methylcyclohexanol, 1,2- Ethylene diol, 1,2-propanediol, 1,3-propanediol, 1,2-butane diol, 1,3-butane diol, 1,4-butane diol, 2,3-butane diol, 1,5-pentane Dire, 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-Butoxyetan, 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-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene 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- ( Butoxyethoxy) 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, ethylene glycol monoethyl ether acetate, ethylene glycol mono Butyl ether acetate, ethylene glycol monoacetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2- (2-ethoxyethoxy) ethyl acetate, diethylene glycol acetate, triethylene glycol, tri Ethylene glycol monomethyl ether, triethylene glycol monoethyl ether, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate , 3-ethoxypropionic acid methyl ethyl, 3-methoxypropionic acid ethyl, 3-ethoxypropionic acid, 3-methoxypropionic acid, 3-methoxypropionic acid propyl, 3-methoxypropionic acid butyl, lactic acid methyl ester, lactic acid ethyl ester, Examples thereof include lactic acid n-propyl ester, lactic acid n-butyl ester, lactic acid isoamyl ester, and solvents represented by the following formulas [D-1] to [D-3].

In the formula [D-1], D ¹ represents an alkyl group having 1 to 3 carbon atoms, and in the formula [D-2], D ² represents an alkyl group having 1 to 3 carbon atoms, and the formula [D-3]. Among them, D ³ represents an alkyl group having 1 to 4 carbon atoms. Among them, 1-hexanol, cyclohexanol, 1,2-ethanediol, 1,2-propanediol, propylene glycol monobutyl ether, diethylene glycol diethyl ether, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monobutyl ether or Dipropylene glycol dimethyl ether is preferred. The type and content of such a solvent are appropriately selected depending on the coating device for the liquid crystal alignment agent, coating conditions, coating environment, and the like.

The liquid crystal alignment agent of the present invention may additionally contain a component other than the polymer component and the organic solvent. Such additional components include an adhesion aid for enhancing the adhesion between the liquid crystal alignment film and the substrate and the adhesion between the liquid crystal alignment film and the sealing material, a cross-linking agent for increasing the strength of the liquid crystal alignment film, and a liquid crystal alignment. Examples thereof include a dielectric and a conductive substance for adjusting the dielectric constant and electric resistance of the film. Specific examples of these additional components are as disclosed in various known literatures on liquid crystal alignment agents. To give an example thereof, see pages 53 [0105] to 55 of International Publication No. 2015/060357 [ 0116] and the like.

<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. To give an example of a method of obtaining a liquid crystal alignment film from a liquid crystal alignment agent, a liquid crystal alignment agent in the form of a coating liquid is applied to a substrate, dried, and fired. The obtained film is subjected to a rubbing treatment method or a photoalignment treatment method. There is a method of performing orientation treatment with.
The substrate to which the liquid crystal alignment agent is applied is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a silicon nitride substrate, a plastic substrate such as an acrylic substrate or a polycarbonate substrate, or the like can be used. At that time, it is preferable to use a substrate on which an ITO electrode or the like for driving the liquid crystal is formed, from the viewpoint of simplifying the process. Further, in the reflective liquid crystal display element, if only one side of the substrate is used, an opaque object such as a silicon wafer can be used, and in this case, a material that reflects light such as aluminum can also be used for the electrode.

The method for applying the liquid crystal alignment agent is not particularly limited, but industrially, screen printing, offset printing, flexographic printing, inkjet method and the like are common. Other coating methods include a dip method, a roll coater method, a slit coater method, a spinner method, a spray method, and the like, and these may be used depending on the purpose.
After applying the liquid crystal alignment agent on the substrate, the solvent is evaporated and fired by a heating means such as a hot plate, a heat circulation type oven, or an IR (infrared) type oven. Any temperature and time can be selected for the drying and firing steps after applying the liquid crystal alignment agent. Usually, in order to sufficiently remove the contained solvent, a condition of firing at 50 to 120 ° C. for 1 to 10 minutes and then firing at 150 to 300 ° C. for 5 to 120 minutes can be mentioned.

The thickness of the liquid crystal alignment film after firing is not particularly limited, but if it is too thin, the reliability of the liquid crystal display element may decrease, so it is preferably 5 to 300 nm, and more preferably 10 to 200 nm.
The liquid crystal alignment film of the present invention is suitable as a liquid crystal alignment film for a horizontal electric field type liquid crystal display element such as an IPS method or an FFS method, and is particularly useful as a liquid crystal alignment film for an FFS type liquid crystal display element.

<Liquid crystal display element>
In the liquid crystal display element of the present invention, after obtaining a substrate with a liquid crystal alignment film obtained from the liquid crystal alignment agent, a liquid crystal cell is produced by a known method, and the liquid crystal cell is used as an element.
As an example of a method for manufacturing a liquid crystal cell, a liquid crystal display element having a passive matrix structure will be described as an example. It should be noted that a liquid crystal display element having an active matrix structure in which a switching element such as a TFT (Thin Film Transistor) is provided in each pixel portion constituting the image display may be used.

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

Next, for example, an ultraviolet curable sealing material was placed at a predetermined place on one of the two substrates on which the liquid crystal alignment film was formed, and liquid crystal was further placed at a predetermined number of places on the liquid crystal alignment film surface. After that, the liquid crystal is spread on the front surface of the liquid crystal alignment film by adhering and crimping the other substrate so that the liquid crystal alignment film faces each other, and then irradiating the entire surface of the substrate with ultraviolet rays to cure the liquid crystal. Get a cell.
Alternatively, as a step after forming the liquid crystal alignment film on the substrate, when arranging the sealing material at a predetermined place on one of the substrates, an opening capable of filling the liquid crystal from the outside is provided to provide the liquid crystal. After the substrates are bonded together without being arranged, the liquid crystal material is injected into the liquid crystal cell through the opening provided in the sealing material, and then the opening is sealed with an adhesive to obtain a liquid crystal cell. The liquid crystal material may be injected by a vacuum injection method or a method using a capillary phenomenon in the atmosphere.

In any of the above methods, in order to secure a space for filling the liquid crystal material in the liquid crystal cell, a columnar protrusion is provided on one substrate, a spacer is sprayed on one substrate, or a sealing material is used. It is preferable to take measures such as mixing spacers in the liquid crystal display or combining them.
Examples of the liquid crystal material include nematic liquid crystal and smectic liquid crystal, and among them, nematic liquid crystal is preferable, and either positive type liquid crystal material or negative type liquid crystal material may be used. Next, the polarizing plate is installed. Specifically, it is preferable to attach a pair of polarizing plates to the surfaces of the two substrates opposite to the liquid crystal layer.

The liquid crystal alignment film and the liquid crystal display element of the present invention are not limited to the above description as long as the liquid crystal alignment agent of the present invention is used, and may be manufactured by other known methods. good. The process of obtaining a liquid crystal display element from a liquid crystal alignment agent is disclosed in, for example, paragraphs 0074 to 19 on page 17 of Japanese Patent Application Laid-Open No. 2015-135393 (Japanese Patent Laid-Open No. 2015-135393).

Hereinafter, the present invention will be specifically described with reference to examples and the like. The interpretation of the present invention is not limited to these examples. The abbreviations of raw materials and the method for evaluating characteristics in the following are as follows.

<Organic solvent>
NMP: N-methyl-2-pyrrolidone, NEP: N-ethyl-2-pyrrolidone GBL: γ-butyrolactone, BCS: butyl cellosolve PB: propylene glycol monobutyl ether DME: dipropylene glycol dimethyl ether DAA: 4-hydroxy-4-methyl- 2-Pentanone DEDG: Diethylene glycol diethyl ether DIBK: 2,6-dimethyl-4-heptanone, DIPE: Diisopropyl ether DIBC: 2,6-dimethyl-4-heptanol, Pd / C: Palladium carbon DMSO: Dimethylsulfoxide, THF: Tetrahydrofuran

<Additives>
LS-4668: 3-glycidoxypropyltriethoxysilane <crosslinking agent>

In the specification, Boc indicates a group represented by the following.

( ¹ Measurement of 1 H-NMR)
Equipment: Varian NMR system 400NB (400MHz) (manufactured by Varian), and JMTC-500 / 54 / SS (500MHz) (manufactured by JEOL)
Measuring solvent: CDCl ₃ (deuterated chloroform), DMSO-d ₆ (deuterated dimethyl sulfoxide)
Reference material: TMS (tetramethylsilane) (δ: 0.0 ppm, ¹ H) and CDCl ₃ (δ: 77.0 ppm, ¹³ C)

(Imidization rate)
20 mg of polyimide powder is placed in an NMR sample tube (NMR sampling tube standard, φ5 (manufactured by Kusano Kagaku Co., Ltd.)), and deuterated dimethyl sulfoxide (DMSO-d6, 0.05% TMS (tetramethylsilane) mixture) is added to 0. 53 ml was added and ultrasonically applied to completely dissolve. This solution was measured for proton NMR at 500 MHz with an NMR measuring machine (JNW-ECA500, manufactured by JEOL Datum). The imidization rate is determined by using a proton derived from a structure that does not change before and after imidization as a reference proton, and the peak integrated value of this proton and the proton peak derived from the NH group of amic acid appearing in the vicinity of 9.5 ppm to 10.0 ppm. It was calculated by the following formula using the integrated value.
Imidization rate (%) = (1-α · x / y) × 100
In the above formula, x is the integrated proton peak value derived from the NH group of amic acid, y is the integrated peak value of the reference proton, and α is one NH group proton of the amic acid in the case of polyamic acid (imidization rate is 0%). It is the number ratio of the reference protons to.

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

(Molecular weight)
GPC device: Tetrahydrofuran (GPC-101), Column: Tetrahydrofuran (series of KD803, KD805), Column temperature: 50 ° C., Eluent: N, N-dimethylformamide (lithium bromide-water as an additive) Japanese product (LiBr · H2O) is 30 mmol / L (liter), phosphoric acid / anhydrous crystal (o-phosphoric acid) is 30 mmol / L, tetrahydrofuran (THF) is 10 ml / L), flow velocity: 1.0 ml / min.
Standard sample for preparing a calibration curve: TSK standard polyethylene oxide manufactured by Tosoh (weight average molecular weight (Mw); about 900,000, 150,000, 100,000 and 30,000), and polyethylene glycol manufactured by Polymer Laboratory (Peak Top). Molecular weight (Mp); about 12,000, 4,000 and 1,000).

<Synthesis of diamine compound (DA-1)>

In a 1 L (liter) four-necked flask, 3,6-diiodocarbazole (50.0 g, 119 mmol), potassium hydroxide (10.4 g, 214 mmol), and tetrahydrofuran (300 g) were charged and methyl iodide at room temperature. (30.4 g, 178 mmol) was added dropwise, and the mixture was stirred for 12 hours. After confirming the completion of the reaction by HPLC (High Performance Liquid Chromatography), the salt was filtered and the reaction solution was concentrated to a double amount. Then 2-propanol (300 g) was added, and the mixture was stirred under ice-cooling for 1 hour. The precipitated crystals were filtered under reduced pressure, washed with 2-propanol (100 g), and then dried to obtain powder crystals (1) (yield 46.3 g, yield 90%).
1H-NMR (DMSO-d ₆ ): 8.60-8.62 (2H, m), 7.74-7.77 (2H, dd), 7.46-7.49 (2H, m), 3 .84 (3H, s)

Compound (1) (40.0 g, 92 mmol), N-methyl-4-nitroaniline (33.5 g, 220 mmol), and copper iodide (3.5 g, 18 mmol), phosphate in a 1 L four-necked flask. Potassium (58.6 g, 276 mmol) was added and nitrogen substitution was performed. Degassed dimethylformamide (280 g) and tetramethylethylenediamine (4.3 g, 37 mmol) were charged under a nitrogen atmosphere, and the mixture was stirred at 140 ° C. for 24 hours. After confirming the completion of the reaction by HPLC (high performance liquid chromatography), the salt was filtered, 2-propanol (800 g) was added, and the mixture was stirred under ice-cooling for 1 hour. The obtained crude crystals were washed with hot repulp with acetonitrile (200 g), washed with 2-propanol (100 g), and then dried to obtain powder crystals (2) (yield 27 g, yield 60%). ).
1H-NMR (DMSO-d ₆ ): 8.17 (2H, d), 8.01-8.06 (4H, m), 7.77 (2H, d), 7.41-7.45 (2H) , Dd), 6.68-6.73 (4H, m), 3.97 (3H, s), 3.46 (6H, s)

A mixture of compound (2) (30 g, 62 mmol), 5% by mass Pd / C (50% water-containing type), characteristic Shirasagi activated carbon (3.0 g), and dimethylformamide (240 g) was placed at 60 ° C. under hydrogen pressurization conditions. Was stirred for 12 hours. After completion of the reaction, the catalyst was filtered, concentrated, methanol (300 g) was added, and the mixture was stirred at 5 ° C. for 1 hour. The precipitated crystals were filtered under reduced pressure, washed with methanol (50 g), and then dried to obtain powder crystals (DA-1) (yield 24 g, yield 92%).
1H-NMR (DMSO-d ₆ ): 7.54 (2H, d), 7.33 (2H, d), 6.91-6.94 (2H, dd), 6.72-6.75 (4H) , M), 6.51-6.55 (4H, m), 4.77 (4H, s), 3.75 (3H, s), 3.18 (6H, s)

[Synthesis Example 1]
DA-1 (2.53 g, 6.0 mmol) is added to a 100 mL four-necked flask equipped with a stirrer and a nitrogen introduction tube, then NMP (30.0 g) is added, and the mixture is stirred and dissolved while sending nitrogen. I let you. While stirring this solution, CA-1 (0.87 g, 4.0 mmol), CA-2 (1.08 g, 5.5 mmol), and NMP (9.0 g) were added, and then under 50 ° C. conditions. A polyamic acid solution (PAA-A1) was obtained by stirring with the mixture for 12 hours. The viscosity of this polyamic acid solution was 350 mPa · s. The number average molecular weight (Mn) of this polyamic acid was 1608, and the weight average molecular weight (Mw) was 51878.

[Synthesis Examples 2 to 6]
The polyamic acid solutions (PAA-A2) to (PAA-A4) and the polyamic acid were carried out in the same manner as in Synthesis Example 1 except that the diamine component, the tetracarboxylic acid component and the solvent shown in Table 1 were used. Solutions (PAA-B1) to (PAA-B5) were obtained.
Table 2 shows the viscosities of the polyamic acid solutions obtained in Synthesis Examples 1 to 6 and the Mn and Mw of the polyamic acids.

[Synthesis Example 10]
DA-6 (4.03 g, 16.5 mmol), DA-7 (3.59 g, 9.0 mmol), and DA-8 (2.) in a 200 mL four-necked flask with a stirrer and a nitrogen inlet tube. After adding 51 g, 4.5 mmol), NMP (74.0 g) was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this solution, CA-4 (4.37 g, 19.5 mmol) and NMP (9.0) g were added, and the mixture was stirred under 40 ° C. conditions for 3 hours. Then, CA-2 (1.71 g, 8.7 mmol) and NMP (9.0 g) were added at 25 ° C., and the mixture was further stirred for 12 hours to obtain a polyamic acid solution. The viscosity of this polyamic acid solution was 480 mPa · s, Mn = 10,660 of this polyamic acid, and Mw = 20,512.

80.0 g of this polyamic acid solution was taken, 20.0 g of NMP was added, 6.8 g of acetic anhydride and 1.8 g of pyridine were added, and the mixture was reacted at 50 ° C. for 3 hours. This reaction solution was added to 434.4 g of methanol with stirring, and the precipitated precipitate was separated by filtration. The precipitate was washed with methanol and dried under reduced pressure at 60 ° C. to obtain a polyimide powder. The imidization rate of this polyimide was 75%. A polyimide solution (SPI-B6) was obtained by adding 80.0 g of NMP to 20.0 g of the obtained polyimide powder and stirring at 70 ° C. for 20 hours to dissolve the powder.

[Synthesis Example 11]
DA-9 (17.30 g, 159.98 mmol), DA-5 (58.63 g, 240.0 mmol), DA-10 (76.89 g,) in a 3 L four-necked flask with a stirrer and nitrogen inlet tube. 240.0 mmol) and DA-11 (54.63 g, 159.99 mmol) were weighed, NMP (2458.13 g) was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution, CA-4 (171.27 g, 764.02 mmol) was added, NMP was further added so that the solid content concentration became 12% by mass, and the mixture was stirred at 40 ° C. for 20 hours. A solution of polyamic acid (PAA-4) was obtained. The viscosity of this polyamic acid solution was 426 mPa · s, Mn = 12,380 of this polyamic acid, and Mw = 33,250.

2250.0 g of this polyamic acid solution was taken, 750.0 g of NMP was added, 171.1 g of acetic anhydride and 35.4 g of pyridine were added, and the mixture was reacted at 55 ° C. for 3 hours. This reaction solution was poured into 9619.2 g of methanol, and the resulting precipitate was filtered off. This precipitate was washed with methanol and dried under reduced pressure at 60 ° C. to obtain a polyimide powder. The imidization rate of this polyimide was 66%. A polyimide solution (SPI-B7) was obtained by adding 880.0 g of NMP to 120.0 g of the obtained polyimide powder and stirring at 70 ° C. for 20 hours to dissolve it.

[Examples 1 to 13] and [Comparative Examples 1 to 6]
The solvent and the additive were stirred while stirring the polyamic acid solutions obtained in Synthesis Examples 1 to 9 and the polyimide solutions obtained in Synthesis Examples 10 and 11 so as to have the compositions shown in Tables 3 and 4, respectively. Was added, and the mixture was further stirred at room temperature for 2 hours to obtain liquid crystal alignment agents of Examples 1 to 13 and Comparative Examples 1 to 6.
In Tables 3 and 4, * 1 and * 2 indicate the content (addition) amount (parts by mass) with respect to 100 parts by mass of all the polymers, and * 3 indicates the use of a solvent with respect to 100 parts by mass of the liquid crystal alignment agent. Indicates the amount (parts by mass).

<Manufacturing of liquid crystal display element by rubbing method>
A glass substrate with an electrode having a size of 30 mm in length × 35 mm in width and a thickness of 0.7 mm was prepared. An IZO electrode having a solid pattern, which constitutes a counter electrode as a first layer, is formed on the substrate. A SiN (silicon nitride) film formed by a CVD method is formed as a second layer on the counter electrode of the first layer. The film thickness of the SiN film of the second layer is 500 nm, and it functions as an interlayer insulating film. A comb-shaped pixel electrode formed by patterning an IZO film as a third layer is arranged on the SiN film of the second layer to form two pixels, a first pixel and a second pixel. ing. The size of each pixel is 10 mm in length and about 5 mm in width. At this time, the counter electrode of the first layer and the pixel electrode of the third layer are electrically insulated by the action of the SiN film of the second layer.

The pixel electrode of the third layer has a comb-like shape formed by arranging a plurality of “dogleg” -shaped electrode elements having a bent central portion (FIG. 3 of Japanese Patent Application Laid-Open No. 2014-77745). reference). The width of each electrode element in the lateral direction is 3 μm, and the distance between the electrode elements is 6 μm. Since the pixel electrodes forming each pixel are configured by arranging a plurality of bent "dogleg" shaped electrode elements in the central portion, the shape of each pixel is not rectangular, but is centered like the electrode elements. It has a shape similar to a bold "dogleg" that bends at a part. Then, each pixel is divided into upper and lower parts with a bent portion in the center as a boundary, and has a first region on the upper side and a second region on the lower side of the bent portion.

Comparing the first region and the second region of each pixel, the forming directions of the electrode elements of the pixel electrodes constituting them are different. That is, when the rubbing direction of the liquid crystal alignment film described later is used as a reference, the electrode elements of the pixel electrodes are formed so as to form an angle (clockwise) of + 10 ° in the first region of the pixel, and the pixel is formed in the second region of the pixel. The electrode elements of the electrodes are formed so as to form an angle of −10 ° (clockwise). Further, in the first region and the second region of each pixel, the directions of the rotation operation (inplane switching) of the liquid crystal in the substrate surface induced by the voltage application between the pixel electrode and the counter electrode are mutual. It is configured to be in the opposite direction.

Next, after filtering the liquid crystal alignment agent with a filter having a pore size of 1.0 μm, an ITO film is formed on the back surface of the substrate with electrodes as a facing substrate, and a glass substrate having a columnar spacer having a height of 4 μm is formed. Each was spin coated. Then, it was dried on a hot plate at 80 ° C. for 5 minutes and then fired at 230 ° C. for 20 minutes to obtain a polyimide film having a film thickness of 60 nm on each substrate. The polyimide film surface is rubbed with a rayon cloth under the conditions of a roll diameter of 120 mm, a roller rotation speed of 500 rpm, a stage moving speed of 30 mm / sec, and a rubbing cloth pushing pressure of 0.3 mm, and then in pure water for 1 minute. Ultrasonic irradiation was performed and the mixture was dried at 80 ° C. for 10 minutes.

Using the above two types of substrates with a liquid crystal alignment film, they were combined so that their rubbing directions were antiparallel, and the surroundings were sealed leaving the liquid crystal injection port, to produce an empty cell with a cell gap of 3.8 μm. .. A liquid crystal (MLC-3019 manufactured by Merck) was vacuum-injected into this empty cell at room temperature, and then the injection port was sealed to obtain an anti-parallel oriented liquid crystal cell. The obtained liquid crystal cell constitutes an FFS mode liquid crystal display element. Then, the liquid crystal cell was heated at 120 ° C. for 1 hour, left overnight, and then used for evaluation.

<Evaluation of afterimage erasure time>
The liquid crystal cell produced above is installed between two polarizing plates arranged so that the polarization axes are orthogonal to each other, and the LED backlight is turned on in a state where no voltage is applied so that the brightness of the transmitted light is minimized. In addition, the arrangement angle of the liquid crystal cell was adjusted. Next, the VT curve (voltage-transmittance curve) was measured while applying an AC voltage having a frequency of 30 Hz to the liquid crystal cell, and the AC voltage having a relative transmittance of 23% was calculated as the drive voltage.
In the afterimage evaluation, an AC voltage having a frequency of 30 Hz having a relative transmittance of 23% was applied to drive the liquid crystal cell, and at the same time, a DC voltage of 1 V was applied to drive the liquid crystal cell for 30 minutes. After that, the applied DC voltage value was set to 0 V, only the application of the DC voltage was stopped, and the vehicle was driven for another 15 minutes in that state.

In the afterimage evaluation, the time during which the relative transmittance decreased to 30% or less was quantified from the time when the application of the DC voltage was started until 30 minutes had elapsed. When the relative transmittance decreased to 30% or less within 5 minutes, it was evaluated as “◯”, and when it was within 6 to 30 minutes, it was evaluated as “Δ”. When it took 30 minutes or more for the relative transmittance to decrease to 30% or less, the afterimage could not be erased and evaluated as "x". Then, the afterimage evaluation according to the above-mentioned method was performed under the temperature condition in which the temperature of the liquid crystal cell was 23 ° C.

<Evaluation of flicker shift that occurs immediately after the start of driving>
The liquid crystal cell produced above is installed between two polarizing plates arranged so that the polarization axes are orthogonal to each other, and the LED backlight is turned on in a state where no voltage is applied so that the brightness of the transmitted light is minimized. In addition, the arrangement angle of the liquid crystal cell was adjusted. Next, the VT curve (voltage-transmittance curve) was measured while applying an AC voltage having a frequency of 30 Hz to the liquid crystal cell, and the AC voltage having a relative transmittance of 23% was calculated as the drive voltage.

In the measurement of the flicker level, the LED backlight that has been turned on is turned off and left for 72 hours, then the LED backlight is turned on again, and the relative transmission rate becomes 23% at the same time as the backlight starts turning on at a frequency of 30 Hz. The AC voltage was applied and the liquid crystal cell was driven for 60 minutes to track the flicker amplitude. The flicker amplitude is a data acquisition / data logger switch unit 34970A (Agilent technologies) in which the transmitted light of the LED backlight that has passed through the two polarizing plates and the liquid crystal cell between them is connected via a photodiode and an IV conversion amplifier. I read it with (manufactured by the company). The flicker level was calculated by the following formula.
Flicker level (%) = {flicker amplitude / (2 × z)} × 100

In the above formula, z is a value read by the data acquisition / data logger switch unit 34970A of the brightness when driven by an AC voltage having a frequency of 30 Hz at which the relative transmittance is 23%.
The evaluation of the flicker level is defined as "○" when the flicker level is maintained at less than 3% from the time when the LED backlight is turned on and the application of the AC voltage is started until 60 minutes have passed. went. When the flicker level reached 3% or more in 60 minutes, it was defined as "x" and evaluated.
The evaluation of the flicker level according to the above method was performed under the temperature condition of the liquid crystal cell at a temperature of 23 ° C.

<Evaluation result>
Tables 4 to 4 show the evaluation results of the afterimage erasing time and the flicker shift that occurs immediately after the start of driving for the liquid crystal display elements using the liquid crystal alignment agents of Examples 1 to 3 and 5 and Comparative Examples 1 to 6. It is shown in Table 7.
In Tables 5 to 8, * 1 indicates the content (parts by mass) of each polymer with respect to 100 parts by mass of all the polymers.

表５～表８に見られるように、実施例１～３、５の液晶配向剤を使用する液晶表示素子は、蓄積電荷の緩和が早く、かつ駆動開始直後に起こるフリッカーシフトが起こりにくいことが判る。

As can be seen in Tables 5 to 8, in the liquid crystal display elements using the liquid crystal alignment agents of Examples 1 to 3 and 5, the accumulated charge is quickly relaxed and the flicker shift that occurs immediately after the start of driving is unlikely to occur. I understand.

<Manufacturing of liquid crystal display element by optical orientation method>
After filtering the liquid crystal alignment agent with a filter having a pore size of 1.0 μm, an ITO film is formed on the back surface of the prepared substrate with electrodes as a facing substrate, and a glass substrate having a columnar spacer having a height of 4 μm is formed. Each was spin coated. Then, it was dried on a hot plate at 80 ° C. for 5 minutes and then fired at 230 ° C. for 20 minutes to obtain a polyimide film on each substrate as a coating film having a film thickness of 100 nm. This coating film surface was irradiated with 300 mJ / cm ² of ultraviolet rays having a wavelength of 254 nm, which was linearly polarized with an extinction ratio of 26: 1 via a polarizing plate.

This substrate was fired at 230 ° C. for 20 minutes to obtain a substrate with a liquid crystal alignment film. The above two substrates are made into a set, a sealant is printed on the substrate, and the other substrate is bonded so that the liquid crystal alignment film surfaces face each other and the orientation direction is 0 °, and then the sealant is applied. It was cured to prepare an empty cell. A liquid crystal display (MLC-3019 manufactured by Merck) was vacuum-injected into this empty cell at room temperature by a vacuum injection method, and the injection port was sealed to obtain an FFS-driven liquid crystal cell. Then, the obtained liquid crystal cell was heated at 120 ° C. for 1 hour, left overnight, and then used for each evaluation.

<Evaluation of afterimage erasure time>
As in the case of the liquid crystal display element by the rubbing method, the afterimage was evaluated using the optical system of the liquid crystal display element by the optical orientation method produced above.
<Evaluation of flicker level immediately after driving>
As in the case of the liquid crystal display element by the rubbing method, the afterimage was evaluated using the optical system of the liquid crystal display element by the optical orientation method produced above.

<Evaluation result>
Table 9 shows the results of the evaluation of the afterimage erasing time and the evaluation of the flicker level immediately after driving with respect to the liquid crystal display element using the liquid crystal alignment agent obtained in Examples 3, 4, 13 and Comparative Example 6. Shown in. In Table 9, * 1 indicates the content (parts by mass) of each polymer with respect to 100 parts by mass of all the polymers.

As can be seen in Table 9, it can be seen that in the liquid crystal display element using the liquid crystal alignment agents of Examples 3, 4 and 13, the accumulated charge is quickly relaxed and the flicker shift that occurs immediately after the start of driving is unlikely to occur.

The liquid crystal alignment agent of the present invention is widely used for a liquid crystal display element of a longitudinal electric field system such as a TN system or a VA system, particularly a horizontal electric field system such as an IPS system or an FFS system.
The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2016-243735 filed on December 15, 2016 are cited here as the disclosure of the specification of the present invention. , Incorporate.

Claims (9)

A liquid crystal alignment agent containing a polymer obtained from a diamine represented by the following formula (2-1), formula (2-2), or formula (2-3) and an organic solvent.

However, R ¹ represents a hydrogen or a monovalent organic group, R ² represents a monovalent organic group, and R ³ represents a single bond or a structure represented by the following formula (3) independently of each other. , N represent an integer of 1 to 3. Any hydrogen atom on the benzene ring may be substituted with a monovalent organic group.

However, R ⁴ is selected from single bond, -O-, -COO-, -OCO-,-(CH ₂ ) _l- , -O (CH ₂ ) _m O-, -CONR-, and -NRCO-. It represents a divalent organic group, and k represents an integer of 1 to 5. However, R represents hydrogen or a monovalent organic group, and l and m represent integers of 1 to 5. * ₁ represents a site that binds to a benzene ring in formulas (2-1) to (2-3), and * ₂ represents a site that binds to an amino group in formulas (2-1) to (2-3). Represents a part. A polyimide precursor in which the polymer is a polycondensate of a diamine represented by the formula (2-1), the formula (2-2), or the formula (2-3) and a tetracarboxylic acid dianhydride and a polyimide precursor. The liquid crystal alignment agent according to claim 1, which is at least one polymer selected from the group consisting of polyimide as an imidized product. The liquid crystal alignment agent according to claim 2 , wherein the polyimide precursor is represented by the following formula (4).

However, X ¹ represents a tetravalent organic group derived from a tetracarboxylic acid derivative, and Y ¹ is a diamine represented by the above formula (2-1), formula (2-2), or formula (2-3). Represents a divalent organic group derived from, and R ⁵ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. The liquid crystal orientation according to claim 3 , wherein in the formula (4), X ¹ represents at least one structure selected from the group consisting of the structures represented by the following (A-1) to (A-21). Agent.

The liquid crystal alignment agent according to claim 3 or 4 , wherein the polymer having the structural unit represented by the formula (4) is contained in an amount of 10 mol% or more based on the total polymer contained in the liquid crystal alignment agent. The liquid crystal alignment agent according to any one of claims 1 to 5 , wherein the 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 6 . A liquid crystal display element comprising the liquid crystal alignment film according to claim 7 . The liquid crystal display element according to claim 8, wherein the liquid crystal display element is a transverse electric field drive system.