TWI673300B - Liquid crystal alignment agent containing a polymer having a blocked isocyanate group, liquid crystal alignment film and liquid crystal display element - Google Patents

Abstract

The present invention provides a liquid crystal alignment agent capable of obtaining a liquid crystal alignment film having functions having various required characteristics, and provides a liquid crystal alignment film and a liquid crystal display element using the liquid crystal alignment agent.

The liquid crystal alignment agent of the present invention contains a polymer having a blocked isocyanate group, and a compound having at least one functional group selected from an amine group and a hydroxyl group in the molecule.

Description

Liquid crystal alignment agent containing polymer having blocked isocyanate group, liquid crystal alignment film and liquid crystal display element

The present invention relates to a liquid crystal alignment film having various functions, a liquid crystal alignment agent containing a polymer having a blocked isocyanate group, a liquid crystal alignment film obtained therefrom, and a liquid crystal display element having the obtained liquid crystal alignment film. .

In the liquid crystal display element, the liquid crystal alignment film plays a role of aligning the liquid crystal in a certain direction. At present, the main liquid crystal alignment films used in industry will be composed of polyimide precursors, namely polyamic acid (also known as polyamide acid), polyamic acid esters, or polyimide solutions. A polyimide-based liquid crystal alignment agent is produced by coating a substrate and forming a film. In addition, when the liquid crystal is aligned in parallel or obliquely with respect to the substrate surface, after film formation, surface stretching treatment is further performed by rubbing. In addition, it is proposed to replace the rubbing treatment by a method of anisotropic photochemical reaction such as polarized ultraviolet light irradiation. In recent years, it is being reviewed for industrialization.

In order to improve the display characteristics of such a liquid crystal display element, the structure and doping of the polyamic acid, polyamic acid ester, or polyimide are changed by Polyacetic acid, polyamidate or polyimide with different characteristics; or adding additives, etc. to improve the alignment or electrical characteristics of the liquid crystal, or control the pretilt angle.

Technology of controlling the pretilt angle by the structure of polyimide In the method of using a diamine with a side chain as part of the polyimide raw material, the pretilt angle can be controlled by using the proportion of the diamine. Therefore, it is relatively easy to set the pretilt angle for the purpose, which can be used to increase Pre-tilt means are used. The side chain structure of the diamine that increases the pretilt angle of the liquid crystal includes, for example, a long-chain alkyl group or a fluoroalkyl group (for example, refer to Patent Document 1), a cyclic group, or a combination of a cyclic group and an alkyl group (for example, refer to Patent Document). 2) A steroid skeleton (for example, refer to Patent Document 3) is known.

In recent years, as liquid crystal display elements are widely used in large screens Compared with conventional LCD TVs or high-definition mobile applications (display parts of digital cameras or mobile phones), the substrates used are larger in size or larger in unevenness. In this case, from the viewpoint of display characteristics, it is required to uniformly coat the liquid crystal alignment film for a large substrate or a step.

In addition, with the advancement of high performance, large area of liquid crystal display devices, power saving of display devices, etc., and use in various environments, characteristics required for liquid crystal alignment films have become severe. In particular, when a liquid crystal alignment agent is applied to a substrate, problems such as poor printing due to precipitation or separation due to long takt time, and problems such as image sticking due to accumulated charge (RDC) become problems, and it is difficult for conventional technologies. Solve both.

In this way, polyimide-based liquid crystal alignment films use various diamine components as part of the raw materials in order to improve desired properties. This is because the desired diamine component cannot be used freely depending on the relationship with other characteristics.

In addition, the special properties of polyimide are high mechanical strength, heat resistance, and solvent resistance, so it can be used as electrical in addition to liquid crystal alignment films. Protective materials and insulating materials in the electronics field are widely used. When used as such materials, the diamine component modified into a raw material of polyimide is also improved, but similarly, the desired diamine component cannot be used freely.

Moreover, it is desired to improve such desired characteristics. The liquid crystal alignment agent containing other polymers such as a (meth) acrylic polymer or a siloxane polymer is not limited to the above-mentioned polyimide-based liquid crystal alignment film. Desired properties.

[Advanced technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2-282726

[Patent Document 2] Japanese Patent Application Laid-Open No. 3-179323

[Patent Document 3] Japanese Unexamined Patent Publication No. 4-281427

The present invention relates to a liquid crystal alignment agent capable of obtaining a liquid crystal alignment film having various characteristics or functions required, a liquid crystal alignment film obtained thereby, and a liquid crystal display element provided with the obtained liquid crystal alignment film.

The present invention is based on the following important techniques.

A liquid crystal alignment agent comprising a polymer having a blocked isocyanate group and a compound having at least one functional group selected from the group consisting of an amine group and a hydroxyl group in a molecule.

2. The liquid crystal alignment agent according to claim 1, wherein the polymer having a blocked isocyanate group is a polymer obtained by polymerizing a monomer represented below.

3. The liquid crystal alignment agent of the above 1, which has a blocked isocyanate The ester-based polymer is a reaction of at least one type of polymer selected from the group consisting of a polyimide precursor and a polyimide polymer of the polyimide precursor and a compound having a blocked isocyanate group. Formed during the formation of the liquid crystal alignment film.

4. The liquid crystal alignment agent of 3 above, which contains polyimide At least one polymer selected from the group consisting of a precursor and a polyimide obtained by subjecting the polyimide precursor to imidization, a compound having a blocked isocyanate group, and a molecule having an amine group and A compound of at least one selected from the group consisting of hydroxyl groups.

5. The liquid crystal alignment agent of 3 or 4 above, wherein the compound having a blocked isocyanate group is selected from the group consisting of the following (Z-1), (Z-2), (Z-3), and (Z-4) At least 1 (In formulas (Z-1) to (Z-4), R ² represents an organic group in a closed portion, any one of B ₁ to B ₃ represents a methyl group, the other two represent hydrogen, and B ₄ to B ₆ and B ₇ to B ₉ are the same as B ₁ to B ₃ (one of them represents a methyl group, and the other two represent hydrogen).

6. The liquid crystal alignment agent according to any one of 1 to 5, wherein the compound having at least one functional group selected from the group consisting of an amine group and a hydroxyl group in the molecule is 100% by mass relative to the polymer having a blocked isocyanate group Contains 5 to 50% by mass.

7. The liquid crystal alignment agent according to any one of 1 to 6, wherein the compound having at least one functional group selected from the group consisting of an amine group and a hydroxyl group in the molecule is represented by the following formula (2), (In the formula, R represents an amine group or a hydroxyl group, and Y represents an n-valent organic group.)

8. A liquid crystal alignment film characterized by being obtained from the liquid crystal alignment agent according to any one of 1 to 7 above.

9. A liquid crystal display device, comprising the liquid crystal alignment film of the above 8.

According to the present invention, a polymer in a liquid crystal alignment agent is modified by blocking a compound having at least one functional group selected from the group consisting of an amine group and a hydroxyl group in a molecule through a blocked isocyanate group. Liquid crystal alignment agent for freely improving liquid crystal alignment film of various characteristics.

[Mode for Carrying Out the Invention] <Polymer with blocked isocyanate group>

In the present invention, the polymer having a blocked isocyanate group contained in the liquid crystal alignment agent may be the case (A) in which the polymer having a blocked isocyanate group is contained in the liquid crystal alignment agent in advance, or in the stage of obtaining a liquid crystal alignment film, Any one of the cases (B) of forming a polymer having a blocked isocyanate group. These are explained below.

In addition, in the present invention, the blocked isocyanate group means a blocked isocyanate group in which the isocyanate group (-NCO) is blocked with an appropriate protecting group (R ² ), for example, as shown in the following formula (2). In the present invention, the blocked isocyanate group is sintered by heating during the formation of the liquid crystal alignment film, and the protective group (block portion) is thermally dissociated to release a reactive isocyanate group. The generated isocyanate group is one that undergoes a cross-linking reaction with a polymer constituting the liquid crystal alignment film, or reacts with a compound having at least one functional group selected from the group consisting of an amine group and a hydroxyl group in the molecule.

(In formula (2), R ² represents an organic group in a closed portion.)

(A) When a liquid crystal alignment agent contains a polymer having a blocked isocyanate group

At this time, the liquid crystal alignment agent of the present invention contains a polymer having a blocked isocyanate group and a compound having at least one functional group selected from an amine group and a hydroxyl group in the molecule (hereinafter also referred to as a functional monomer).

The polymer having a blocked isocyanate group can be obtained by using a raw material containing various polymers containing a blocked isocyanate group to produce the polymer. For example, when using a polyfluorene imide precursor and a polyfluorene imine obtained by fluorinating the polyfluorene imide precursor as a polymer, any one of tetracarboxylic dianhydride and diamine as raw materials or In both cases, those containing a blocked isocyanate group can be obtained by polymerizing a polyfluorene imine precursor and imidizing it. this In this case, it is preferable to use a diamine containing a blocked isocyanate group from the ease of introducing a blocked isocyanate.

The same applies to the case of other polymers such as a (meth) acrylic polymer and a polysiloxane, and examples thereof include the following acrylic polymers.

<Functional monomer>

The functional single system in the present invention refers to a compound introduced into the backbone of a polymer via a blocked isocyanate group, and therefore is a compound having a site (functional group) that reacts with an isocyanate group, that is, an amine group and / or a hydroxyl group.

The functional single system molecule of the present invention has at least one group selected from an amine group and a hydroxyl group in the molecule, and is represented by the following formula.

(In the formula, R represents an amine group or a hydroxyl group, and Y represents an n-valent organic group.)

In the above formula, specific examples of Y when n is 2 include, for example, divalent organic groups represented by the following formulas (Y-1) to (Y-120). Among them, in order to obtain good liquid crystal alignment, a structure using a highly linear diamine compound as a raw material is preferred. Examples of such Y are (Y-7), (Y-10), (Y-11), (Y-12), (Y-13), (Y-21), ( Y-22), (Y-23), (Y-25), (Y-26), (Y-27), (Y-41), (Y-42), (Y-43), (Y- 44), (Y-45), (Y-46), (Y-48), (Y-61), (Y-63), (Y-64), (Y-65), (Y-66) , (Y-67), (Y-68), (Y-69), (Y-70), (Y-71), (Y-78), (Y-79), (Y-80), ( Y-81), (Y-82), (Y-109), etc.

Liquid crystal alignment film for improving the pretilt angle of liquid crystal In this case, a structure having a side chain having a long-chain alkyl group (for example, an alkyl group having 10 or more carbon atoms), an aromatic ring, an aliphatic ring, a steroid skeleton, or a diamine compound combining these structures as a raw material is preferred. Examples of such Y are (Y-83), (Y-84), (Y-85), (Y-86), (Y-87), (Y-88), (Y-89), (Y -90), (Y-91), (Y-92), (Y-93), (Y-94), (Y-95), (Y-96), (Y-97), (Y-98 ), (Y-99), (Y-100), (Y-101), (Y-102), (Y-103), (Y-104), (Y-105), (Y-106), (Y-107), or (Y-108), etc., but are not limited to these.

When it is desired to improve the electrical characteristics of a liquid crystal display element, for example, There are (Y-31), (Y-40), (Y-64), (Y-65), (Y-66), (Y-67), (Y-109), (Y-110) and so on. In addition, when it is desired to impart photoreactivity to a liquid crystal alignment film, there are, for example, (Y-17), (Y-18), (Y-111), (Y-112), (Y-113), (Y-114) , (Y-115), (Y-116), (Y-117), (Y-118), (Y-119), etc.

Specific examples of Y when n is 1 in the compound represented by the above formula include, for example, a monovalent organic group represented by the following formula or [Y-1] to [Y-120] The structure and the like in which a bond is bonded to a hydrogen atom are not limited thereto.

Moreover, in the compound represented by the above formula, specific examples of Y when n is 3 or more include, for example, a trivalent or more organic group represented by the following formula or hydrogen atoms of [Y-1] to [Y-120] are removed The latter structure is not limited thereto. In this specification, Me is a methyl group.

(B) In the case where a liquid crystal alignment film is obtained, a polymer having a blocked isocyanate group is formed

The liquid crystal alignment agent of the present invention at this time contains a polymer forming a liquid crystal alignment film, a compound having a blocked isocyanate group (hereinafter simply referred to as a blocked isocyanate compound), and the above-mentioned functional monomer.

Here, the polymer forming the liquid crystal alignment film refers to a poly (meth) acrylic polymer in addition to a poly (imide) precursor and a poly (imide) obtained by subjecting the poly (imide) precursor to fluorination. Polymers, silicone polymers, etc. Among them, from the easiness of introduction of a site reacting with an isocyanate group, the characteristics of the liquid crystal alignment film, and the like, it is preferable to use a polyimide precursor and a polyimide obtained by subjecting the polyimide precursor to fluorenimization. A polymer of at least one selected from the group of hydrazone.

The polyimide precursor is a polyamidic acid obtained by reacting a tetracarboxylic acid derivative component and a diamine component, and the polyimide is a polyimide obtained by subjecting the polyimide to a polyimide.

Next, polyimide precursors, polyimide, and compounds having blocked isocyanate groups will be described.

<Polyimide precursor>

The polyimide precursor contained in the liquid crystal alignment agent of the present invention refers to a polyamic acid and / or a polyamic acid ester, and has a structural unit represented by the following formula (1).

In the formula (1), R ₁ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. A ₁ and A ₂ are each independently a hydrogen atom or an alkyl group, alkenyl group and alkynyl group having 1 to 10 carbon atoms which may have a substituent.

In formula (1), R ₁ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, preferably 1 to 2 carbon atoms. As the number of carbon atoms in the alkyl group increases, the temperature of the polyimide increases. Therefore, R _{1 is} particularly preferably a methyl group from the viewpoint that fluorene imidization can be easily performed by heat.

In the formula (1), A ₁ and A ₂ are each independently a hydrogen atom, or an alkyl group, alkenyl group, alkynyl group, or aliphatic ring group having 1 to 12 carbon atoms which may have a substituent. Specific examples of the alkyl group include methyl, ethyl, propyl, butyl, t-butyl, hexyl, octyl, and decyl. The alkenyl group is, for example, one or more of the CH-CH structures existing in the alkyl group are replaced with a C = C structure. More specifically, there are, for example, vinyl, allyl, 1-propenyl, and isopropene. Group, 2-butenyl, 1,3-butadienyl, 2-pentenyl, 2-hexenyl, cyclopropenyl, cyclopentenyl, cyclohexenyl, and the like. The alkynyl group includes, for example, one or more of the CH ₂ -CH ₂ structures existing in the alkyl group are replaced by a C≡C structure. More specifically, there are, for example, ethynyl, 1-propynyl, and 2-propane. Alkynyl, etc. Specific examples of the aliphatic cyclic group include cyclopentyl, cyclohexyl, and dicyclohexyl.

The above-mentioned alkyl group, alkenyl group, and alkynyl group may have a substituent as long as the carbon number thereof is 1 to 10, or may form a ring structure through the substituent. In addition, the formation of a ring structure through a substituent means that the substituents are bonded to each other or a portion of the parent skeleton to form a ring structure.

Examples of the substituent include a halogen group, a hydroxyl group, a thiol group, a nitro group, an aryl group, an organic oxy group, an organic thio group, an organic silyl group, a fluorenyl group, an ester group, a thioester group, a phosphate group, a fluorenyl group, Alkyl, alkenyl, alkynyl.

Examples of the halogen group of the substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the aryl group of the substituent include a phenyl group. This aryl group may be further substituted with the aforementioned other substituents. The organic group of the substituent may have a structure represented by OR, for example. The organic thio group of the substituent may have a structure represented by -SR, for example. The organosilyl group having a substituent may have a structure represented by, for example, -Si- (R) ₃ . The fluorenyl group as a substituent may have a structure represented by -C (O) -R, for example. The ester group of the substituent may be, for example, a structure represented by -C (O) OR or -OC (O) -R. The thioester group of the substituent may have a structure represented by, for example, -C (S) OR or -OC (S) -R.

The phosphate group of the substituent may have a structure represented by, for example, -OP (O)-(OR) ₂ . The amido group of the substituent may be represented by, for example, -C (O) NH ₂ or -C (O) NHR, -NHC (O) R, -C (O) N (R) ₂ , -NRC (O) R structure. These Rs may be the same or different, and examples thereof include the aforementioned alkyl, alkenyl, alkynyl, aryl, and the like. These R may be further substituted with the aforementioned substituents.

Specific examples of the organic oxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, and an octyloxy group.

Specific examples of the organic thio group include methylthio, ethylthio, propylthio, butylthio, pentylthio, hexylthio, heptylthio, and octylthio.

Specific examples of the organic silyl group include trimethylsilyl, triethylsilyl, tripropylsilyl, tributylsilyl, tripentylsilyl, trihexylsilyl, pentyldimethylsilyl, and hexyl. Dimethylsilyl, etc.

Specific examples of the fluorenyl group include formamyl, acetamyl, propionyl, butylamyl, isobutylamyl, pentamyl, isoamyl, and benzamyl.

The alkyl group, alkenyl group, alkynyl group, and aryl group of the substituent are the same as those of the aforementioned alkyl group, alkenyl group, alkynyl group, and aryl group, respectively. These alkyl and olefins Group, alkynyl group, and aryl group may be further substituted with the aforementioned other substituents.

Generally speaking, when a bulky structure is introduced, the reactivity of the amine group or the alignment of the liquid crystal may be reduced. A ₁ and A _{2 are more} preferably a hydrogen atom or a carbon number of 1 to 5 which may have a substituent. Alkyl is particularly preferably a hydrogen atom, methyl or ethyl.

In the above formula (1), when X ₁ is a tetravalent organic group, the structure is not particularly limited, and two or more kinds may be mixed. When specific examples of X _{1 are to} be displayed, for example, X-1 to X-46 and the like are shown below. Among them, in terms of the availability of monomers, X _{1 is} preferably X-1, X-2, X-3, X-4, X-5, X-6, X-8, X-16, X- 19. X-21, X-25, X-26, X-27, X-28 or X-32.

In the above formula, Y ₁ is a divalent organic group, and two or more kinds may be mixed. When the structure of a specific example of Y ₁ is to be displayed, for example, Y-1 to Y-106 are shown below, but they are not limited thereto. Among these, from the viewpoint of the reactivity of the diamine and the solubility of the polymer, it is more preferable to use Y-7, Y-8, Y-13, Y-18, Y-19, Y-42, and Y- 43, Diamines of the structure Y-45, Y-55, Y-59, Y-74, Y-78, Y-79, Y-80, Y-81, Y-82.

Polyimide precursor used in liquid crystal alignment agent of the present invention Among them, polyimide precursors having a structure suitable for performing a cross-linking reaction with a compound having a blocked isocyanate group are preferred. Specifically, a polyimide precursor having at least one of an amine group and a hydroxyl group is preferred. Moreover, the polyfluorene imide precursor polymer has many carboxylic acid groups. It is clear that the compound having a blocked isocyanate group is rich in reactivity, so it is preferable as the first aspect of the present invention.

In addition, in the polyfluorene imide contained in the liquid crystal alignment agent of the present invention, the dehydration ring closure ratio (fluorine imidization ratio) of the amino acid group is not necessarily 100%, and can be arbitrarily adjusted according to the purpose or purpose.

<Manufacturing method of polyimide>

In the case of obtaining a polyimide by using a polyimide of a polyimide precursor, the method of subjecting the polyimide to amidation is, for example, a method of heat-imidizing the polyimide solution directly, The catalyst is imidized by adding a catalyst to the polyamic acid solution.

The temperature at which the polyamidoacid is subjected to thermal hydrazone imidization in a solution is 100 ° C to 400 ° C, preferably 120 ° C to 250 ° C, and water generated by the hydrazone imidization reaction is excluded from the system. It is better to carry out thermal ammonium imidization at the same time.

The catalyst of polyamic acid / imidization is performed by adding a basic catalyst and an acid anhydride to a polyamic acid solution, and stirring can be performed at -20 to 250 ° C, preferably 0 to 180 ° C. The amount of the alkaline catalyst is 0.5 to 30 mol times of the amino acid group, preferably 2 to 20 mol times, and the amount of the acid anhydride is 1 to 50 mol times of the amino acid group, preferably 3 to 30 mol times. 30 mol times.

Examples of the basic catalyst used for the above catalyst 醯 imidization include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Among them, pyridine has a moderate basicity for carrying out the reaction, so it is preferred.

Examples of the acid anhydride used in the above catalyst fluorination include acetic anhydride, trimellitic anhydride, pyromellitic dianhydride, and the like. Of which acetic anhydride is used In this case, purification at the end of the reaction becomes easy, which is preferable. The rate of ammonium imidization using catalyst ammonium imidization can be controlled by adjusting the amount of catalyst, reaction temperature, and reaction time.

<Blocked isocyanate compound>

The type and structure of the blocked isocyanate compound in the present invention are not particularly limited as long as it is the compound having a blocked isocyanate group. The blocked isocyanate compound can be obtained, for example, by using a suitable blocking agent for a compound having an isocyanate group in the molecule.

Examples of blocking agents include alcohols such as methanol, ethanol, isopropanol, n-butanol, 2-ethylhexanol, 2-N, N-dimethylaminoethanol, 2-ethoxyethanol, and cyclohexanol. Phenols, phenols, o-nitrophenols, p-chlorophenols, o-, m- or p-cresols, phenols such as ε-caprolactam, ε-caprolactam, acetone oximes, etc. , Methyl ethyl ketoxime, methyl isobutyl ketoxime, cyclohexanone oxime, acetophenone oxime, benzophenone oxime, etc., pyrazole, 3,5-dimethylpyrazole, 3 -Pyrazoles such as methylpyrazole, thiols such as dodecanethiol, and benzenethiol.

The blocked isocyanate compound is a person who generates thermal dissociation of the blocked portion under high temperature conditions such as heating and firing temperature during the formation of the liquid crystal alignment film, and performs cross-linking reaction through the isocyanate group, but does not preserve the low temperature state of the liquid crystal alignment agent. Crosslinking by an isocyanate group is preferred. In order to achieve such thermal reactivity, the temperature of the thermal dissociation of the blocked portion of the blocked isocyanate compound is very high compared to the storage of the liquid crystal alignment agent, such as 50 ° C to 230 ° C, and more preferably 100. ℃ ~ 180 ℃.

Blocked isocyanate compound It is particularly preferred to be a blocked isocyanate compound having three or more blocked isocyanate groups in one molecule. This compound is obtained, for example, from a compound having three or more isocyanate groups in one molecule by applying an appropriate blocking agent as described above.

Specific examples of the compound having three or more blocked isocyanate groups in one molecule include compounds represented by the following formulae (Z-1) to (Z-4).

(In formulae (Z-1) to (Z-4), R ² represents an organic group in a closed portion.

In the formula (Z-3), any one of B ₁ to B ₃ represents a methyl group, and the other two represent hydrogen. In B ₄ to B ₆ and B ₇ to B ₉ , similarly to B ₁ to B ₃ , any one represents a methyl group, and the other two represent hydrogen. )

When the liquid crystal alignment agent of the present invention contains a blocked isocyanate compound, the blocked isocyanate compound may be used singly or in combination of two or more kinds.

In addition, the blocked isocyanate compound is contained in a liquid crystal alignment agent at a ratio of 0.5 to 50% by mass, preferably 5 to 40% by mass, with respect to at least one polymer selected from the polyimide precursor and the polyimide. .

<Liquid crystal alignment agent>

The liquid crystal alignment agent of the present invention contains a resin component for a liquid crystal alignment film that forms a resin film, and an organic solvent that dissolves the resin component.

The liquid crystal alignment agent of this invention contains the said polymer which has the said blocked isocyanate group as a said resin component (henceforth the polymer of this invention).

All of the above resin components may be the polymer of the present invention, and a polymer other than the polymer of the present invention may be mixed. The content of the polymer of the present invention in the liquid crystal alignment agent is preferably 5% by mass or more, and more preferably 10% by mass or more.

The polymer other than the polymer of the present invention includes, for example, a polyimide precursor represented by the above formula (1) and / or a polyimide obtained by subjecting the polyimide precursor to a polyimide.

The organic solvent contained in the liquid crystal alignment agent to dissolve the resin component is not particularly limited. Specific examples include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, Dimethyl sulfene, γ-butyrolactone, etc. These organic solvents become good solvents with high resin solubility.

In addition to the above good solvents, in order to improve the coating of liquid crystal alignment agents Uniformity of cloth, weak solvent with low solubility of polymer is preferred. In the present invention, preferred weak solvents include, for example, ethylcellosolvin, butylcellosolvin, ethylcarbitol, butylcarbitol, diethylene glycol diethyl ether, diethylene glycol monoethyl ether, and diethyl ether. Glycol monobutyl ether, ethyl carbitol acetate, ethylene glycol, ethylene glycol monohexyl ether, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1- Butoxy-2-propanol, 1-phenoxy-2-propanol, propylene glycol monoacetate, propylene glycol diacetate, propylene glycol-1-monomethyl ether-2-acetate, propylene glycol-1- Monoethyl ether-2-acetate, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, 4-hydroxy-4-methyl-2-pentanone, 2- (2-ethoxypropoxy) propane Alcohol, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, isoamyl lactate.

This weak solvent becomes a weak solvent with low solubility of the resin. The organic solvent contained in the solvent-based liquid crystal alignment treatment agent is preferably 5 to 60% by mass, and more preferably 10 to 50% by mass.

The concentration of the resin component in the liquid crystal alignment agent of the present invention can be appropriately adjusted according to the thickness of the liquid crystal alignment film to be obtained and the device used for coating the liquid crystal alignment treatment agent. The general resin concentration of the liquid crystal alignment agent is, for example, 1 to 20% by mass, and preferably 2 to 10% by mass.

The liquid crystal alignment agent of the present invention may contain components other than the above. Examples include a functional compound or an epoxy group-containing compound for improving the adhesion between the liquid crystal alignment film and the substrate, and a fluorine-based boundary for improving the flatness of the coating film. Surfactants, polysiloxane surfactants, non-ionic surfactants, etc.

When the compound containing a functional silane or an epoxy group is contained, the content is 100 parts by mass relative to the resin component, preferably 0.1 to 30 parts by mass, more preferably 1 to 20 parts by mass, and particularly preferably 1 ~ 10 parts by mass.

When the surfactant is contained, the content is preferably 0.01 to 2 parts by mass, and more preferably 0.01 to 1 part by mass based on 100 parts by mass of the resin component.

<Liquid crystal alignment film and liquid crystal display element>

The liquid crystal alignment agent of the present invention is coated on a substrate, and after firing, it is subjected to alignment treatment by rubbing treatment or light irradiation, or a part of vertical alignment applications, etc., without alignment treatment, it can be used as a liquid crystal alignment film.

The application method of the liquid crystal alignment agent of the present invention is not particularly limited, and it is generally applied by screen printing, letterpress printing, offset printing, inkjet method, or the like. Other methods of using the coating liquid include a dipping method, a roll coating method, a slit coating method, a rotation method, and the like, and these can be used depending on the purpose. After being coated on the substrate by such methods, the solvent is evaporated by heating means such as a hot plate to form a coating film.

The firing after applying the liquid crystal alignment agent can be performed at any temperature of 100 to 300 ° C, but it is preferably 150 ° C to 250 ° C. For this firing, a hot plate, a heat cycle type oven, or an IR (infrared) type oven can be used.

For the rubbing treatment, raw silk cloth, nylon cloth, cotton cloth and the like can be used. The liquid crystal alignment film for vertical alignment is difficult to obtain a uniform alignment state by rubbing treatment. Therefore, when used as a liquid crystal alignment agent for vertical alignment, it is better not to use friction.

The liquid crystal cell of the present invention can be produced by a common method, and the production method is not particularly limited. Generally, for example, a sealant can be applied to a glass substrate having a liquid crystal alignment film formed on at least one of the substrates, and the spacers can be dispersed at a certain distance, and then the two substrates can be bonded to harden the sealant. A method of producing a liquid crystal cell by emptying the cell, and then injecting liquid crystal from the liquid crystal injection port under a vacuum, and closing the injection port; or a method of dropping liquid crystal on a substrate with dispersed spacers, and then bonding two substrates to make a liquid crystal cell Wait. The liquid crystal system can be used in combination with fluorine-based liquid crystals or cyano-based liquid crystals having positive and negative dielectric anisotropy.

As described above, the liquid crystal alignment film obtained from the liquid crystal alignment agent of the present invention can impart a large pretilt angle to the liquid crystal, and can be used as a liquid crystal alignment film for various purposes.

The following specifically describes the present invention, but the present invention is not limited to these embodiments.

[Example]

The abbreviations used in the examples are as follows.

(Methacrylic monomer)

MOI-BM: 2- (0- [1'-methylideneamino] carboxyamino) ethyl methacrylate (manufactured by Showa Denko, karenz MOI-BM)

(Tetracarboxylic dianhydride)

CBDA: 1,2,3,4-cyclobutane tetracarboxylic dianhydride

(Diamine)

DBA: 3,5-diaminobenzoic acid

(Compound with amine group)

(Hydroxy compound)

(Compound with blocked isocyanate)

TAKENATE B-882N (manufactured by Mitsui Chemicals)

(Organic solvents)

NMP: N-methyl-2-pyrrolidone

BCS: Butyl Cellulose

DMF: N, N’-dimethylformamide

THF: tetrahydrofuran

(Polymerization initiator)

AIBN: 2,2’-azobisisobutyronitrile

<Measurement of molecular weight of polymer>

The molecular weight of the polymer in the synthesis example was measured using a room temperature gel permeation chromatography (GPC) device (SSC-7200, manufactured by Shodex Co., Ltd. (KD-803, KD-805), manufactured by Senshu Scientific Corporation) as follows.

Column temperature: 50 ℃

Eluent: DMF (additive: 30mmol / L of lithium bromide-hydrate (LiBr‧H ₂ O), 30mmol / L of phosphoric acid · anhydrous crystal (o-phosphoric acid), 10ml / L of tetrahydrofuran (THF))

Flow rate: 1.0mL / min

Production of standard samples for calibration lines: TSK standard polyethylene oxide (weight average molecular weight approximately 9 million, 150,000, 100,000, 30,000) manufactured by TOSOH company and polyethylene glycol (wave top molecular weight (Mp) approximately produced by Polymer Laboratories) 12,000, 4,000, 1,000).

<Synthesis example 1>

MOI-BM (15.56 g, 30.0 mmol) was dissolved in NMP (142.3 g), and a 6-minute diaphragm pump was used for 6 minutes. After degassing, add AIBN (0.246 g, 2.0 mmol) and degas for 6 minutes. Then, it was made to react at 60 degreeC for 30 hours, and the methacrylate polymer solution was obtained. BC (105.4 g) was added to this polymer solution and diluted to 6% by mass, and the liquid crystal alignment agent (A) was obtained by stirring at room temperature for 5 hours. This polymer had a number average molecular weight of 14,000 and a weight average molecular weight of 55,000.

<Synthesis example 2>

CBDA (3.88 g, 20.0 mmol) and DBA (3.04 g, 20.0 mol) were mixed in NMP (27.7 g) and reacted at room temperature for 20 hours to obtain a polyamic acid solution. NMP (45.0g) and BCS (34.6g) were added to this polyamic acid solution and diluted to 6 mass%, and the liquid crystal alignment agent (B) was obtained by stirring at room temperature for 5 hours. This polyamic acid had a number average molecular weight of 15,000 and a weight average molecular weight of 34,000.

<Example 1>

With respect to 10.0 g of the liquid crystal alignment agent (A) obtained in Synthesis Example 1, 60 mg of DA-1 (10% by mass with respect to the solid content) was added, and the mixture was stirred at room temperature for 3 hours to dissolve the liquid crystal alignment agent (A1).

In addition, after a liquid crystal cell was produced under the following conditions, the tilt angle was measured and the liquid crystal alignment was evaluated.

[Production of liquid crystal cell (VA mode)]

The liquid crystal alignment agent (A1) obtained in Example 1 was spin-coated on The ITO surface of the glass substrate with a transparent electrode made of an ITO film was dried on a hot plate at 80 ° C for 90 seconds, and then fired in a hot air circulation oven at 200 ° C for 30 minutes to form a liquid crystal alignment film with a thickness of 100 nm.

Two sheets of the substrate were prepared, and a 6 μm bead spacer was spread on a liquid crystal alignment film of one of the substrates, and then a sealant (XN-1500T manufactured by Kyoritsu Chemical Co., Ltd.) was printed thereon. Next, the liquid crystal alignment faces of the two substrates were pressure-bonded, and the sealant was thermally cured at 150 ° C for 105 minutes. A negative type liquid crystal (MLC-6608, manufactured by Merck, Inc.) was injected into this empty cell by a reduced-pressure injection method to prepare a liquid crystal cell.

[Evaluation of pretilt angle]

The measurement of the pretilt angle of the liquid crystal cell was measured using a Mueller matrix using "AxoScan" manufactured by Axo Metrix.

"Evaluation of liquid crystal cell alignment"

After the liquid crystal cell was produced, the cell was observed with a polarizing microscope. If there was no misalignment such as flow alignment or light transmission, the alignment was evaluated as good.

<Example 2>

Based on 10.0 g of the liquid crystal alignment agent (A) obtained in Synthesis Example 1, 60 mg of DA-2 (10% by mass with respect to the solid content) was added, and the liquid crystal alignment agent (A2) was prepared by stirring at room temperature for 3 hours. After preparing a liquid crystal cell in the same manner as in Example 1, the tilt angle was measured and the alignment was evaluated.

<Example 3>

Based on 10.0 g of the liquid crystal alignment agent (A) obtained in Synthesis Example 1, 60 mg of DA-3 (10% by mass relative to the solid content) was added, and the mixture was stirred at room temperature for 3 hours to be dissolved to prepare a liquid crystal alignment agent (A3). After preparing a liquid crystal cell in the same manner as in Example 1, the tilt angle was measured and the alignment was evaluated.

<Example 4>

Based on 10.0 g of the liquid crystal alignment agent (A) obtained in Synthesis Example 1, 60 mg of DA-4 (10% by mass relative to the solid content) was added, and the liquid crystal alignment agent (A4) was prepared by stirring at room temperature for 3 hours. After preparing a liquid crystal cell in the same manner as in Example 1, the tilt angle was measured and the alignment was evaluated.

[Production of liquid crystal cell (photo-alignment VA mode)]

The liquid crystal alignment agent (A4) obtained in Example 4 was spin-coated on the ITO surface of a glass substrate with a transparent electrode made of an ITO film, dried on a hot plate at 80 ° C for 90 seconds, and then subjected to a hot air circulation method at 200 ° C. The oven was fired for 30 minutes to form a liquid crystal alignment film with a thickness of 100 nm.

This substrate was irradiated with linearly polarized UV 0 to 100 mJ at 313 nm at an irradiation intensity of 11.0 mW / cm ² . The direction of the incident light is inclined by 40 ° with respect to the normal direction of the substrate. Linearly polarized UV is modulated by the ultraviolet light of a high-pressure mercury lamp after passing through a bandpass filter at 313nm and then by a 313nm polarizer.

Two sheets of the substrate were prepared, and a 6 μm bead spacer was spread on a liquid crystal alignment film of one of the substrates, and then a sealant (XN-1500T manufactured by Kyoritsu Chemical Co., Ltd.) was printed thereon. Next, the liquid crystal of the two substrates was made. The alignment face is pressed and bonded so that the projection direction of the linearly polarized UV optical axis of each substrate becomes antiparallel, and the sealant is thermally hardened at 150 ° C for 105 minutes. A positive type liquid crystal (MLC-6608, manufactured by Merck, Inc.) was injected into the empty cell by a reduced pressure injection method to prepare a liquid crystal cell.

[Evaluation of pretilt angle]

The pretilt angle was measured in the same manner as in Example 1.

"Confirmation of liquid crystal cell alignment"

After the liquid crystal cell is manufactured, the liquid crystal is driven with an AC voltage of AC = 8Vp-p, and the cell is observed with a polarizing microscope. There is no misalignment such as flow alignment or light transmission, and the uniaxial alignment is displayed. .

<Example 5>

With respect to 10.0 g of the liquid crystal alignment agent (A) obtained in Synthesis Example 1, 60 mg of DA-5 (10% by mass with respect to the solid content) was added, and the liquid crystal alignment agent (A5) was prepared by stirring at room temperature for 3 hours. After preparing a liquid crystal cell in the same manner as in Example 4, the tilt angle was measured and the alignment was evaluated.

<Example 6>

Based on 10.0 g of the liquid crystal alignment agent (A) obtained in Synthesis Example 1, 60 mg of DA-6 (10% by mass relative to the solid content) was added, and the liquid crystal alignment agent (A6) was prepared by stirring at room temperature for 3 hours. After preparing a liquid crystal cell in the same manner as in Example 4, the tilt angle was measured and the alignment was evaluated.

<Example 7>

Based on 10.0 g of the liquid crystal alignment agent (A) obtained in Synthesis Example 1, 60 mg of DA-7 (10% by mass relative to the solid content) was added, and the liquid crystal alignment agent (A7) was prepared by stirring at room temperature for 3 hours. After preparing a liquid crystal cell in the same manner as in Example 4, the tilt angle was measured and the alignment was evaluated.

<Example 8>

60 mg of DA-8 (10% by mass relative to the solid content) was added to 10.0 g of the liquid crystal alignment agent (A) obtained in Synthesis Example 1, and the liquid crystal alignment agent (A8) was prepared by stirring at room temperature for 3 hours. After preparing a liquid crystal cell in the same manner as in Example 4, the tilt angle was measured and the alignment was evaluated.

<Example 9>

60 mg of DA-9 (30% by mass relative to the solid content) was added to 10.0 g of the liquid crystal alignment agent (A) obtained in Synthesis Example 1, and the liquid crystal alignment agent (A9) was prepared by stirring at room temperature for 3 hours. After producing a liquid crystal cell under the following conditions, the tilt angle was measured and the liquid crystal alignment was evaluated.

[Production of liquid crystal cell (IPS mode)]

The liquid crystal alignment agent (A9) obtained in Example 9 was spin-coated on the ITO surface of a glass substrate with a transparent electrode made of an ITO film, dried on a hot plate at 80 ° C for 90 seconds, and then subjected to a hot air circulation method at 200 ° C. The oven was fired for 30 minutes to form a liquid crystal alignment film with a thickness of 100 nm.

This substrate was irradiated with linearly polarized light UV0 to 1000 mJ at 313 nm at an irradiation intensity of 11.0 mW / cm ^-2 . The direction of the incident light is the normal direction of the substrate. Linearly polarized UV light is modulated by a high-pressure mercury lamp through a 313 nm band-pass filter and then a 313 nm polarizer.

Two sheets of the substrate were prepared, and a 6 μm bead spacer was spread on a liquid crystal alignment film of one of the substrates, and then a sealant (XN-1500T manufactured by Kyoritsu Chemical Co., Ltd.) was printed thereon. Next, the liquid crystal alignment faces of the two substrates were faced, and then the projection direction of the optical axis of the linearly polarized UV of each substrate was anti-parallel, and the sealant was thermally cured at 150 ° C for 105 minutes. A positive type liquid crystal (MLC-2014, manufactured by Merck, Inc.) was injected into the empty cell by a reduced pressure injection method to prepare a liquid crystal cell.

[Evaluation of pretilt angle]

The pretilt angle was measured in the same manner as in Example 1.

[Evaluation of liquid crystal cell alignment]

The alignment was evaluated in the same manner as in Example 1.

<Example 10>

60 mg of MA-1 (10% by mass relative to solid content) was added to 10.0 g of the liquid crystal alignment agent (A) obtained in Synthesis Example 1, and the liquid crystal alignment agent (A10) was prepared by stirring at room temperature for 3 hours. After preparing a liquid crystal cell in the same manner as in Example 4, the tilt angle was measured and the alignment was evaluated.

<Example 11>

Based on 10.0 g of the liquid crystal alignment agent (A) obtained in Synthesis Example 1, added 60 mg of HM-1 (30% by mass with respect to solid content) was stirred at room temperature for 3 hours to be dissolved to prepare a liquid crystal alignment agent (A11). After preparing a liquid crystal cell in the same manner as in Example 9, the tilt angle was measured and the alignment was evaluated.

<Example 12>

With respect to 10.0 g of the liquid crystal alignment agent (A) obtained in Synthesis Example 1, 60 mg of HM-2 (30% by mass relative to the solid content) was added, and the mixture was stirred at room temperature for 3 hours to dissolve the liquid crystal alignment agent (A12). After preparing a liquid crystal cell in the same manner as in Example 9, the tilt angle was measured and the alignment was evaluated.

<Comparative example 1>

Using the liquid crystal alignment agent (A) obtained in Synthesis Example 1, a liquid crystal cell was produced in the same manner as in Example 1, and the alignment was evaluated.

<Example 13>

Based on 10.0 g of the liquid crystal alignment agent (B) obtained in Synthesis Example 2, 120 mg of DA-4 (20% by mass relative to the solid content) and TAKENATE B-882N (180mg) (30% by mass relative to the solid content) were added, After stirring at room temperature for 3 hours to dissolve, a liquid crystal alignment agent (B1) was prepared. After preparing a liquid crystal cell in the same manner as in Example 4, the tilt angle was measured and the alignment was evaluated.

<Comparative example 2>

Using the liquid crystal alignment agent (B) obtained in Synthesis Example 2, a liquid crystal cell was produced in the same manner as in Example 1, and the alignment was evaluated.

As described in Examples 1 to 3, it was confirmed that by adding an amine compound having a vertical alignment energy to a polymer having a blocked isocyanate, it can be used as a vertical alignment agent.

In addition, as in Examples 4-8 and 10, it was confirmed that an amine compound having photoreactivity and vertical alignment energy can be used as a photo-alignment film for VA mode.

In addition, as in Examples 9, 11, and 12, it was confirmed that a photoreactive group that exhibits photoalignment energy can be used as a photoalignment film for horizontal alignment.

[Industrial availability]

The liquid crystal alignment agent of the present invention can relatively freely form a liquid crystal alignment film that improves various characteristics, and therefore can be widely used in liquid crystal display elements that meet various requirements.

In addition, the entire contents of the specification, scope of patent application, drawings, and abstract of Japanese Patent Application No. 2013-73825 filed on March 29, 2013 are incorporated herein by reference for disclosure of the specification of the present invention.

Claims (6)

A liquid crystal alignment agent comprising a polymer having a blocked isocyanate group and a compound having at least one functional group selected from the group consisting of an amine group and a hydroxyl group in the molecule, wherein the aforementioned polymer having a blocked isocyanate group is A polymer obtained by polymerizing a monomer shown below, A liquid crystal alignment agent characterized by containing a polymer having a blocked isocyanate group and a compound having at least one functional group selected from the group consisting of an amine group and a hydroxyl group in the molecule, wherein the polymer having a blocked isocyanate group is obtained by Reaction of at least one type of polymer selected from the group consisting of polyimide precursors and polyimide polymers of the polyimide precursors and compounds having blocked isocyanate groups, when a liquid crystal alignment film is formed It is a polymer containing at least one selected from the group consisting of a polyimide precursor and a polyimide obtained by subjecting the polyimide precursor to polyimide, and having a blocked isocyanate group. The compound having at least one functional group selected from the group consisting of an amine group and a hydroxyl group in the molecule, and the compound having a blocked isocyanate group are the following (Z-1), (Z-2), ( Z-3) and (Z-4) at least one selected from the group, (In formulas (Z-1) to (Z-4), R ² represents an organic group in a closed portion, any one of B ₁ to B ₃ represents a methyl group, the other two represent hydrogen, B ₄ to B ₆ and B ₇ to B ₉ are also the same as B ₁ to B ₃ (one of them represents a methyl group, and the other two represent hydrogen). For example, the liquid crystal alignment agent of claim 1 or 2, wherein the compound having at least one functional group selected from the group consisting of an amine group and a hydroxyl group in the molecule is 100% by mass relative to the polymer having a blocked isocyanate group, and contains 5 Mass% to 50% by mass. For example, the liquid crystal alignment agent according to claim 1 or 2, wherein the compound having at least one functional group selected from the group consisting of an amine group and a hydroxyl group in the molecule is represented by the following formula (2), (In the formula, R represents an amine group or a hydroxyl group, and Y represents an n-valent organic group.) A liquid crystal alignment film is characterized by being obtained from the liquid crystal alignment agent according to any one of claims 1 to 4. A liquid crystal display element having a liquid crystal alignment film as claimed in claim 5.