TW201406821A - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display device having thereof - Google Patents

Abstract

A liquid crystal alignment agent comprising a polymer (A) is disclosed. The polymer (A) comprises at least 50 wt% of polyamic acid or polyimide, at least 2.5 mole% of frames of compound with phenyl group, and at least 5 mole% of frames of compound with tertiary nitrogen atom. The liquid crystal alignment agent can be employed to form a liquid crystal alignment film with lower residue direct current voltage and lesser image sticking effect.

Description

Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element thereof

The invention relates to a liquid crystal alignment agent and a liquid crystal alignment film and a liquid crystal display element thereof, and particularly relates to a liquid crystal alignment agent with low residual DC voltage and low afterimage characteristics and a liquid crystal prepared thereby Alignment film and liquid crystal display element.

Due to its thinness, power saving and high image quality, liquid crystal display elements have generally replaced traditional cathode ray tube displays and are widely used in home and personal electronic products.

As the image quality of the liquid crystal display element is improved, the liquid crystal alignment film should have the following properties: (1) Image Sticking Effect: If the liquid crystal display element continuously displays the same picture for a long time, the previous image cannot be displayed after the screen is switched. The phenomenon of disappearing immediately and overlapping with a new picture or moving in a meteor shape is called an afterimage phenomenon. (2) Residue Direct Current Voltage: The liquid crystal alignment film adsorbs ionic charges to form a residual DC voltage. Although the mechanism of residual DC voltage and afterimage remains unclear, if the residual DC voltage of the liquid crystal alignment film can be reduced It can also effectively improve the phenomenon of image sticking.

At present, the academic community and the industry have invested a lot of effort in researching the above problems. However, no satisfactory solution has been obtained so far. Therefore, the industry continues to demand a new liquid crystal alignment agent, which can produce a low residual image phenomenon. And low residual DC voltage and other characteristics.

One aspect of the present invention provides a liquid crystal alignment agent comprising a polymer (A), the polymer (A) comprising more than 50% by weight of a polyamic acid or a polyimine, and a polymer (A) a phenolic skeleton containing more than 2.5 mole percent, and a tertiary nitrogen atom skeleton of more than 5 mole percent, wherein the phenolic skeleton is selected from the group consisting of formula (i), formula (ii), and combinations thereof. The structures of formula (i) and formula (ii) are as follows:

In the formula (i), each of Y ₁ to Y ₅ is an independently hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a hydroxyl group (-OH) or -(CH ₂ ) pCF. ₃ , p is an integer from 1 to 5, and at least one of Y ₁ to Y ₅ is a hydroxyl group. In the formula (ii), Z is a single bond, an alkylene group having 1 to 4 carbon atoms, -CO-, -COO- or -O-, and the substituents on the benzene ring are each independently a hydrogen atom and have a carbon number of 1 An alkyl group of 5, an alkoxy group having 1 to 5 carbon atoms, a hydroxyl group, -CF ₃ or -OCF ₃ , and at least one of these substituents is a hydroxyl group.

According to an embodiment of the invention, the polymer (A) skeleton may additionally comprise a phthalate, a guanamine or a quinone. The polymer (A) may also be a quinone imine-proline copolymer, a polyimine or a poly-proline.

According to an embodiment of the present invention, the phenolic skeleton of the polymer (A) and the third a nitrogen atom skeleton selected from a residue of a diamine (a-1) or a diamine (a-2), wherein the diamine (a-1) has a phenol group, and the diamine (a-2) does not have a phenol group And has a three-stage nitrogen atom.

The diamine (a-1) may comprise a structure represented by the formula (I-1) or the formula (I-2):

In the formula (I-1), each of M ₁ to M ₅ is an independently hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a hydroxyl group or -(CH ₂ )pCF ₃ , p is an integer from 1 to 5, and at least one of M ₁ to M ₅ is a hydroxyl group.

In the formula (I-2), Z is a single bond, an alkylene group having 1 to 4 carbon atoms, -CO-, -COO- or -O-; and one of R ₁ to R ₅ is an amine group (-NH _{2 )} One of which is a hydroxyl group, and the rest are each a separate hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a hydroxyl group, -CF ₃ or -OCF ₃ ; R ₆ to R ₁₀ One of them is an amine group, one of which is a hydroxyl group, and the others are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a hydroxyl group, -CF ₃ or -OCF ₃ .

The diamine (a-2) may be a structure represented by the formula (II):

Wherein each of X ₁ to X ₅ is an independently hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms or -(CH ₂ ) _p CF ₃ , and p is an integer of 1 to 5.

The reactant in the formation reaction of the polymer (A) comprises a diamine (a-1), a diamine (a-2), a diamine (a-3), and a tetracarboxylic dianhydride (a-4), of which two The amine (a-3) is a diamine compound other than the diamine (a-1) and the diamine (a-2).

According to an embodiment of the present invention, the diamine (a-3) comprises the formula (a-3-1), the formula (a-3-2), the formula (a-3-3), and the formula (a-3-4). , formula (a-3-5), formula (a-3-6) or formula (a-3-7):

The tetracarboxylic dianhydride (a-4) may contain an alicyclic tetracarboxylic dianhydride or an aromatic tetracarboxylic dianhydride.

The alicyclic tetracarboxylic dianhydride may comprise a structure represented by the formula (a-4-1):

The aromatic tetracarboxylic dianhydride may comprise a structure represented by the formula (a-4-2), the formula (a-4-3) or the formula (a-4-4):

Another aspect of the present invention provides a liquid crystal alignment film formed using the liquid crystal alignment agent described above.

Still another aspect of the present invention provides a liquid crystal display element comprising the liquid crystal alignment film described above.

The liquid crystal alignment film formed by the liquid crystal alignment agent has a low residual DC voltage and low afterimage characteristics, and thus the liquid crystal display element produced by using the liquid crystal alignment film can satisfy the market demand.

Polymer (A)

The polymer (A) contains 50% by weight or more of polyamic acid or polyimine, and the polymer (A) contains a phenol-based skeleton of 2.5 mol% or more, and a tertiary nitrogen atom skeleton of 5 mol% or more. Wherein the phenolic backbone is selected from the group consisting of formula (i), formula (ii), and combinations thereof, and the structures of formulas (i) and (ii) are as follows:

In the formula (i), each of Y ₁ to Y ₅ is an independently hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a hydroxyl group or -(CH ₂ )pCF ₃ , p is An integer from 1 to 5, and at least one of Y ₁ to Y ₅ is a hydroxyl group. In the formula (ii), Z is a single bond, an alkylene group having 1 to 4 carbon atoms, -CO-, -COO- or -O-, and the substituents on the benzene ring are each independently a hydrogen atom and have a carbon number of 1 An alkyl group of 5, an alkoxy group having 1 to 5 carbon atoms, a hydroxyl group, -CF ₃ or -OCF ₃ , and at least one of these substituents is a hydroxyl group.

According to an embodiment of the present invention, the skeleton of the polymer (A) may further comprise a phthalate ester, a guanamine or a quinone ester, and is a dimer block copolymer or a ternary block copolymer. Examples of the diblock copolymer include a phthalic acid-proline copolymer, a quinone imine-quinone copolymer, a phthalic acid-melamine copolymer, and a quinone imine-melamine copolymer. An example of the ternary block copolymer comprises a phthalic acid-guanamine-valerate copolymer, a quinone imine-guanamine-imide ester copolymer.

According to another embodiment of the present invention, the polymer (A) may be a quinone imine-oxime Aminic acid copolymer, polyimide or polylysine.

The above-mentioned "phenol-based skeleton" means a compound having a phenol group, and a part of its structure becomes a part of the structure of the polymer (A) after the polymerization reaction of the polymer (A) is formed, and this partial structure is called " Phenolic skeleton."

The aforementioned "2.5 mol%" means the ratio of the "phenolic skeleton" to the structure of the polymer (A).

The above-mentioned "three-stage nitrogen atom skeleton" means a compound having a tertiary nitrogen atom, and a part of its structure becomes a part of the structure of the polymer (A) after the polymerization reaction of the polymer (A) is formed, and this partial structure This is called the "three-stage nitrogen atom skeleton".

The above "5 mole percentage" means the ratio of the "three-stage nitrogen atom skeleton" to the structure of the polymer (A).

The above-mentioned "binary" means that the polymer of the polymer (A) has two kinds of monomers.

The term "ternary" as used herein means that the polymer of the polymer (A) has three kinds of monomers.

The polymer (A) of the present invention utilizes the synergistic effect of the phenol group provided by the phenol group skeleton and the phenol group of the phenol group skeleton and the tertiary nitrogen of the tertiary nitrogen atom skeleton, so that the liquid crystal alignment agent of the present invention can be utilized. The liquid crystal alignment film produced has characteristics such as low image sticking phenomenon and low residual DC voltage.

The polymer (A) generates a hydrogen bond between the chain polymers constituting the polymer (A) by the phenol group provided by the phenol group skeleton, and the hydrogen bond between the polymers causes the polymer to be tightly packed, and the polymer is lifted. (A) The ability to release accumulated charge.

The "synergy effect of the phenolic group of the phenolic skeleton and the tertiary nitrogen of the tertiary nitrogen atom skeleton", hereinafter referred to as "synergy effect", means that the phenolic skeleton contained in the polymer (A) dissociates from the hydrogen ion. (H ⁺ ) with negative charge, the tertiary nitrogen atom attracts H ⁺ and is positively charged, and the positively charged tertiary nitrogen atom forms a salt-like ionic compound with the negatively charged phenolic skeleton, which can also enhance the chain. The stacking between the polymers accelerates the charge transfer between the polymers or the polymer, thereby improving the conductivity of the polymer, thereby reducing the image sticking phenomenon and reducing the residual DC voltage.

According to an embodiment of the present invention, the phenol-based skeleton and the tertiary nitrogen atom skeleton of the polymer (A) are selected from the group consisting of a residue of a diamine (a-1) or a diamine (a-2), wherein the diamine (a) -1) having a phenol group, the diamine (a-2) having no phenol group and having a tertiary nitrogen atom.

The formation reaction of the polymer (A) may be carried out by using a diamine (a-1), a diamine (a-2), a diamine (a-3), and a tetracarboxylic dianhydride (a-4) as a reactant in an organic solvent. It is obtained by carrying out a polycondensation reaction. The diamine (a-3) is a diamine compound other than the diamine (a-1) and the diamine (a-2). The equivalent ratio of the amine group of the diamine (a-1), the diamine (a-2) and the diamine (a-3) to the acid anhydride group of the tetracarboxylic dianhydride (a-4) may be 0.5:1 to 2:1.

In another embodiment, the equivalent of the acid group of the diamine (a-1), the diamine (a-2) and the diamine (a-3) and the anhydride group of the tetracarboxylic dianhydride (a-4) The ratio can range from 0.7:1 to 1.5:1.

The above-mentioned "residue" means that the diamine (a-1) and the diamine (a-1) participate in the polycondensation reaction of the polymer (A), and the diamine (a-1) and/or the diamine ( Part of the structure of a-2) becomes part of the structure of the polymer (A), and this part of the structure is called "residue".

After the above-mentioned diamine is polycondensed with tetracarboxylic dianhydride (a-4), it can be produced. Poly-proline.

The produced polyamic acid is subjected to partial dehydration ring closure reaction to obtain a quinone imine-proline copolymer. If the ring closure reaction is completely dehydrated, polyimine can be formed.

The poly-proline, poly-imine or quinone-proline copolymer can be formed into a binary or ternary block copolymer, such as hydrazine, by embedding a small amount of an ester bond or a guanamine bond according to actual needs. Amino acid-melamine copolymer, quinone-melamine copolymer, glutamine-valerate copolymer, quinone-quinone copolymer, glutamine-amide-ammonium ester Copolymer or quinone imine-melamine- quinone copolymer or the like. The polymer composed of a single monomer is changed into a copolymer having two or more monomers by an intercalation method to improve the performance of the original polymer, which is well known in the art and will not be described herein.

Diamine (a-1)

The diamine (a-1) may be a structure represented by the formula (I-1) or the formula (I-2):

In the formula (I-1), each of M ₁ to M ₅ is an independently hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a hydroxyl group or -(CH ₂ )pCF ₃ , p is an integer from 1 to 5, and at least one of M ₁ to M ₅ is a hydroxyl group. In the formula (I-2), Z is a single bond, an alkylene group having 1 to 4 carbon atoms, -CO-, -COO- or -O-; and one of R ₁ to R ₅ is an amine group, one of which is a hydroxyl group (-OH), each of which is an independently hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a hydroxyl group, -CF ₃ or -OCF ₃ ; R ₆ to R ₁₀ One is an amine group, one is a hydroxyl group, and the others are each a separate hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a hydroxyl group, -CF ₃ or -OCF ₃ .

In the formula (I-2), the two amine groups are bonded to different benzene rings, and when they are bonded to the same benzene ring, the liquid crystal alignment agent formed by the liquid crystal alignment agent has a large misalignment angle and a decrease in coatability.

According to an embodiment of the present invention, in the formula (I-1), M ₁ , M ₂ , M ₄ and M ₅ are a hydrogen atom, and when M ₃ is a hydroxyl group (-OH), a diamine (a-1-1) can be obtained. ), its structure is as follows:

According to another embodiment of the present invention, Z in the formula (I-2) is a single bond, R ₃ and R ₈ are an amine group, R ₂ and R ₉ are a hydroxyl group, and R ₁ , R ₄ , R ₅ and R _{6 are} R ₇ and R ₁₀ are a hydrogen atom, and a diamine (a-1-2) can be obtained, which has the following structure:

Diamine (a-2)

According to an embodiment of the invention, the diamine (a-2) may be of the formula (II):

Wherein each of X ₁ to X ₅ is an independently hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms or -(CH ₂ ) _p CF ₃ , and p is an integer of 1 to 5.

According to an embodiment of the present invention, when X ₁ to X ₅ in the formula (II) is a hydrogen atom, a diamine (a-2-1) can be obtained, and the structure is as follows:

The main difference between the diamine (a-1) and the diamine (a-2) is that the diamine (a-1) has a phenol group, and the diamine (a-2) has a tertiary nitrogen atom but does not have a phenol group.

Diamine (a-3)

The diamine (a-3) is a diamine compound other than the diamine (a-1) and the diamine (a-2).

According to an embodiment of the present invention, the diamine (a-3) may be a structure represented by the formula (a-3-1) to the formula (a-3-7):

The above diamine (a-3) may be used singly or in combination of two or more kinds without affecting the performance of the liquid crystal alignment film.

Tetracarboxylic dianhydride (a-4)

According to an embodiment of the present invention, the tetracarboxylic dianhydride (a-4) comprises an alicyclic tetracarboxylic dianhydride or an aromatic tetracarboxylic dianhydride.

The alicyclic tetracarboxylic dianhydride may be, but not limited to, the structure represented by the formula (a-4-1), and the aromatic tetracarboxylic dianhydride may be, but not limited to, the formula (a-4-2), the formula (a) -4-3) or the structure shown in formula (a-4-4):

The above tetracarboxylic dianhydride (a-4) may be used singly or in combination of two or more. The tetracarboxylic dianhydride (a-4) can also be used together with other tetracarboxylic dianhydrides without affecting the performance of the liquid crystal alignment film.

When the tetracarboxylic dianhydride (a-4) is used together with the non-aromatic tetracarboxylic dianhydride and the aromatic tetracarboxylic dianhydride, the content of the aromatic tetracarboxylic dianhydride is from 20% by weight to 90% by weight. .

Method for synthesizing polymer (A)

Hereinafter, the polymer (A) is a ruthenium-proline copolymer, and a preparation method of the polymer (A) will be described in detail.

The diamine (a-1), the diamine (a-2), the diamine (a-3) and the tetracarboxylic dianhydride (a-4) are used as a reactant, and are polymerized in an organic solvent (a-5). The condensation reaction is adjusted depending on the amount of the reaction, and is carried out at a temperature of from 40 ° C to 110 ° C for 1 to 12 hours to obtain a reaction solution containing polylysine.

The ratio of the diamine mixture to the tetracarboxylic dianhydride (a-4) is preferably 1 equivalent of the anhydride group content of the tetracarboxylic dianhydride (a-4) and 0.5 to 2 equivalents of the amine group of the diamine mixture. , 0.7 to 1.5 equivalents is more preferred.

The organic solvent (a-5) is used to dissolve the reactants and products, including dissolution. A preferred organic solvent and an organic solvent having a poor solubility.

The organic solvent having a good solubility includes, but is not limited to, N-methyl-2-pyrrolidone (a-5-1), N,N-dimethylformamide, N,N-dimethylacetamide, N. -methyl caprolactam, dimethyl hydrazine, tetramethyl urea, hexamethylphosphoniumamine, γ-butyrolactone (a-5-2), pyridine, the above organic solvents may be used alone or Mix two or more types at the same time.

The organic solvent having a poor solubility may also be used in combination with the above-mentioned organic solvent having a better solubility, provided that the product quinone imine-proline copolymer is not precipitated. Poorly soluble organic solvents include, but are not limited to, methanol, ethanol (a-5-3), isopropanol, n-butanol, cyclohexanol, ethylene glycol, ethylene glycol methyl ether, ethylene glycol monoethyl Ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethyl ether, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate , tetrahydrofuran, dichloromethane, chloroform, 1,2-dichloroethane, benzene, toluene, xylene, n-hexane, n-heptane, n-octane.

In addition to the organic solvents listed above, an organic solvent which can dissolve the quinone imine-proline copolymer can be used as the organic solvent (a-5).

The above reaction solution containing polylysine is subjected to partial dehydration ring-closure reaction to obtain a reaction solution containing a quinone imine-proline copolymer.

The dehydration ring closure reaction can be carried out by the method (1): direct heating, or the method (2): adding a dehydrating agent (a-6) and a catalyst (a-7).

Method (1): direct heating, the reaction temperature is about 50 ° C ~ 300 ° C, and preferably 100 ° C ~ 250 ° C. When the reaction temperature is lower than 50 ° C, the dehydration ring-closure reaction does not proceed, and if the reaction temperature is too high, the average molecular weight of the produced polymer (A) is extremely low.

Method (2): adding a dehydrating agent (a-6) and a catalyst (a-7), the reaction temperature is about -20 ° C to 150 ° C, and preferably 0 ° C to 120 ° C.

The dehydrating agent (a-6) includes, but is not limited to, an acid anhydride, and an acid anhydride such as acetic anhydride (a-6-1), propionic anhydride, trifluoroacetic anhydride or the like can be used. The amount of the dehydrating agent (a-6) is adjusted depending on the desired dehydration ring-closing ratio, and it is preferably 0.01 to 20 mol per 1 unit of the molybdenum imine-proline copolymer.

The catalyst (a-7) includes, but is not limited to, a tertiary amine such as triethylamine, pyridine (a-7-1), lutidine or the like. The amount of the catalyst (a-7) is adjusted depending on the amount of the dehydrating agent (a-6), and about 0.01 to 10 moles of the catalyst (a-7) is used per 1 mol of the dehydrating agent (a-6).

Finally, the reaction solution of the above-mentioned quinone imine-proline copolymer is poured into a solvent having a poor solubility to obtain a precipitate, and the precipitate is dried under reduced pressure to obtain a quinone imine-guanamine. Acid copolymer. The obtained quinone imine-proline copolymer can be purified one or more times, and the purification step is as follows: the quinone imine-proline copolymer is dissolved in an organic solvent and precipitated with a solvent having poor solubility, and The precipitate was dried under reduced pressure.

When the polymer (A) is a poly-proline, the preparation method is substantially the same as the above reaction, and only the dehydration ring-closure reaction needs to be skipped. When the polymer (A) is a polyimine, the reaction solution of the obtained polyglycolic acid may be subjected to a complete dehydration ring-closure reaction.

Liquid crystal alignment agent

The liquid crystal alignment agent of the present invention comprises the polymer (A) and the organic solvent (B), and optionally contains an additive (C).

The above polymer (A) is dissolved in an organic solvent (B) to form a liquid crystal alignment agent. The temperature at which the liquid crystal alignment agent is prepared is preferably from 0 ° C to 150 ° C, more preferably from 20 ° C to 50 ° C.

The liquid crystal alignment agent can adjust the solid content contained in it according to the viscosity and the volatility, and preferably contains a solid content of 1 wt% to 10 wt%. If the solid content is less than 1% by weight, the thickness of the liquid crystal alignment film after coating is too thin to lower the alignment property, and if the solid content is more than 10% by weight, the coating quality is affected.

Organic solvent (B)

The organic solvent (B) includes, but is not limited to, N-methyl-2-pyrrolidone (a-5-1), N,N-dimethylformamide, N,N-dimethylacetamide, N- Methyl caprolactam, dimethyl hydrazine, γ-butyrolactone (a-5-2), γ-butyrolactam, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, B Glycol mono-n-propyl ether, ethylene glycol monobutyl ether, and the like. The above solvents may be used in combination of two or more. In addition to the above-exemplified solvents, as long as the quinone imine-proline copolymer can be dissolved, it can be used as the organic solvent (B).

Additive (C)

The liquid crystal alignment agent may optionally comprise an additive (C) which may be an organic oxime (oxyl) alkane compound (C-1) or an epoxy compound (C-2).

Organic oxime (oxygen) alkane compound (C-1)

The content of the organic oxime (oxyl) alkane compound (C-1) in the liquid crystal alignment agent, The adhesion of the liquid crystal alignment film to the surface of the substrate can be improved without affecting the characteristics required for the liquid crystal alignment film. When the content of the organic oxime (oxygen) alkane compound (C-1) is too large, the formed liquid crystal alignment film is liable to cause poor alignment, and if the content of the organic oxime (oxygen) alkane compound (C-1) is too small, The formed liquid crystal alignment film is liable to cause a phenomenon of poor brushing and excessive dusting. Therefore, the liquid crystal alignment agent of the present invention contains 100 parts by weight based on the total weight of the polymer (A), and the content of the organic oxime (oxyl) alkane compound (C-1) is preferably 0.01 to 5 parts by weight, more preferably 0.1. ~3 parts by weight.

Epoxy compound (C-2)

The content of the epoxy compound (C-2) in the liquid crystal alignment agent can improve the adhesion of the liquid crystal alignment film to the surface of the substrate without affecting the characteristics required for the liquid crystal alignment film. When the content of the epoxy compound (C-2) is too large, the formed liquid crystal alignment film is liable to cause poor alignment. If the content of the epoxy compound (C-2) is too small, the formed liquid crystal alignment film is liable to cause brushing failure. Excessive phenomenon with powder. Therefore, the liquid crystal alignment agent of the present invention contains 100 parts by weight of the total weight of the polymer (A), and the epoxy compound (C-2) content is preferably 0.01 to 3 parts by weight, more preferably 0.1 to 2 parts by weight. .

Liquid crystal alignment film

The liquid crystal alignment agent of the present invention is applied onto a glass substrate having a patterned transparent conductive film to form a coating layer, and the coating method includes, but is not limited to, a roll coating method, a spin coating method, and a printing method, and the coating method is For the sake of abuse, we will not repeat them here.

Then, the coating layer is heated and baked to form a liquid crystal alignment of the coating layer. membrane. The purpose of the heat baking is to remove the organic solvent (B) in the liquid crystal alignment agent, and to promote the dehydration ring closure reaction of the polyamic acid contained in the polymer (A). The heating and baking temperature may be 80 ° C to 300 ° C, more preferably 100 ° C to 240 ° C. The thickness of the liquid crystal alignment film formed is preferably 0.005 to 0.5 μm.

The liquid crystal alignment film can be further directionally rubbed by a roller wound with a nylon or cotton fiber cloth, so that the liquid crystal alignment film has an alignment property with respect to the liquid crystal molecules.

Liquid crystal display element

First, a sealant is coated on a substrate having the liquid crystal alignment film, and a spacer is sprayed on another substrate having the liquid crystal alignment film, and then the liquid crystal alignment film substrates are vertically or mutually parallel to each other in a brush film direction. Finally, liquid crystal is injected into the gap between the two substrates, and the injection hole is sealed to form a liquid crystal display element.

evaluation method Viscosity measurement of liquid crystal alignment agent

The viscosity (η _ln ) of the liquid crystal alignment agent of the present invention is obtained by dissolving a liquid crystal alignment agent comprising a polymer (A), a solvent (B) and an additive (C) in N-methyl-2-pyrrolidone from the following formula (1). In the solvent (a-5-1), a solution having a concentration of 0.5 g/100 ml was prepared, and the viscosity of the solution was measured at 30 °C.

Determination of residual image phenomenon of liquid crystal display elements

Determine the penetration and power of a specific position of the liquid crystal display element before charging Pressure change curve, then after charging at 10V DC for 6 hours at room temperature or 60 degrees (high temperature), measure the transmittance and voltage curve of the same specific position again, and the voltage corresponding to the penetration of 50% before charging For the reference, compare the change in the penetration of a specific position before and after charging at this voltage, and then divide the change in the penetration by the penetration before the voltage is charged, and the percentage is expressed as a percentage, and the variation is less than 2 % is judged to be excellent, and less than 5% is judged to be excellent, more than 5% is judged to be medium, and more than 10% is judged to be poor.

Residual DC voltage of liquid crystal display element

A voltage of 5 V was applied to the liquid crystal display element for 3600 seconds, followed by a discharge of 1 second, and finally the residual DC voltage value at the 600th second was recorded.

Dehydration ring closure ratio (imidization ratio)

The polymer (A) or the liquid crystal alignment agent is dried under reduced pressure at room temperature, and the dried solid is continuously dissolved in the deuterated dimethyl hydrazine, using tetramethyl decane as a reference substance, by ¹ H-NMR measurement, imidization ratio obtained from the following formula (2): imidization ratio (%) = (1-A ¹ /A ² × α) × 100 (2)

A ¹ : Peak area (10 ppm) derived from the proton of the NH group.

A ² : Peak area derived from other protons.

α: the ratio of the number of other protons to the protons of the NH group of the polylysine in the polymer (A).

experiment one: Synthesis Example Polymer A-1 (A-1-1~A-1-6), A-2 (A-2-1~A-2-5) and Comparative Example Polymer A-3 (A-3- 1), A-4 (A-4-1, A-4-2) synthesis method

Diamine (a-1, a-2, a-3) and tetracarboxylic dianhydride (a-4) are sequentially added to N-methyl-2-pyrrolidone according to the ratios shown in Tables 1 to 2 In (a-5-1), a solution having a solid content of 20% by weight is prepared and reacted at 40 ° C for 5 to 6 hours to obtain a solution containing poly-proline. After the polyproline solution is diluted, an appropriate ratio of pyridine (a-7-1) and acetic anhydride (a-6-1) is added, and the dehydration ring-closing reaction is carried out at 100 to 110 ° C for 3 to 4 hours to form a solution containing a ruthenium-proline copolymer, the solution containing the copolymer is precipitated into ethanol (a-5-3), and is purified by washing with ethanol (a-5-3), and finally collected. The solid was dried under reduced pressure to obtain a polymer (A) having the intrinsic viscosity and imidization ratio shown in Tables 1 and 2.

Experimental methods of Examples 1 to 9 and Comparative Examples 1' to 2':

A fixed ratio of polymer (A-1) and polymer (A-2) and polymer (A-3) and polymer (A-4) were dissolved in γ-butyrolactone (a-5-2). a solution having a solid content of 6 wt% in a mixed solvent of N-methyl-2-pyrrolidone (a-5-1), and filtered through a filter having a diameter of 1 μm, and the collected filtrate is the liquid crystal of the present invention. An aligning agent.

The liquid crystal alignment agent of the present invention was applied onto a glass substrate by a roller printer, and dried on a hot plate at 200 ° C for 20 minutes to form a film having a thickness of 0.08 μm. The film was oriented at a roller speed of 1000 (rev/min), a platform moving speed of 60 (mm/sec), and a press-in amount of 0.4 m.

Taking a substrate-coated sealant having the liquid crystal alignment film, spraying the spacer on another substrate having the liquid crystal alignment film, and then vertically combining the two liquid crystal alignment film substrates with each other in the brush film direction, and finally on the two substrates Liquid crystal (ZLI-4792 liquid crystal manufactured by Merck Ltd.) was injected into the gap, and the injection holes were sealed to form a liquid crystal display element.

The obtained liquid crystal display element was evaluated for room temperature afterimage characteristics, high temperature afterimage characteristics, and residual DC voltage. The evaluation results are shown in Table 3.

In Examples 1 to 9, in the synthesis of the polymer (A), the diamine (a-1), the diamine (a-2), and the diamine (a-3) were used together, while the comparative examples 1' and 2' were used. Only the diamine (a-3) was used, and the room temperature afterimage characteristics of the liquid crystal display elements obtained in Comparative Examples 1' and 2' were poor in medium and high temperature image sticking characteristics, and the residual DC voltage was 345 mV and 420 mV, Comparative Example 1 The evaluation results of ', 2' are worse than those of Examples 1 to 9. Therefore, the present invention is based on diamine (a-1) and diamine (a-2). The phenol group provided, and the synergistic effect of the phenol group and the tertiary nitrogen atom, can improve the image sticking characteristics of the liquid crystal display element and obtain a low residual DC voltage.

In Examples 1, 8, and 9, the content of the diamine (a-1-1) was gradually increased, wherein the content of the diamine (a-1-1) of Example 1 was the lowest, and the residual DC voltage was 81 mV. Most preferred, while the diamine (a-1-1) of Example 9 has the highest content, but has the worst residual image at room temperature and the highest residual DC voltage. Therefore, the amount of the diamine (a-1-1) used is within a certain range, and the use of the residual DC voltage of the liquid crystal display element is caused by the absence of the use of Comparative Examples 1', 2', or the use of excess as in Examples 8 and 9. The height and the residual image characteristics are deteriorated, and the amount of the diamine (a-1-1) used is preferably 30% by weight or less, more preferably 15% by weight or less based on the total amount of the diamine.

In Examples 1 to 4, the diamine used and the tetracarboxylic dianhydride (a-4) were the same, and the difference was mainly in the imidization ratio, and the imidization ratio of Example 1 was 70%. The imidization ratio of Example 4 is 0%, and when the imidization ratio is lowered, the high-temperature afterimage characteristics are remarkably improved, and the residual DC voltage is lowered.

In Examples 1, 5 and 7, the amount of the tetracarboxylic dianhydride (a-4-1) of Example 1 and the tetracarboxylic dianhydride (a-4-2) were the same, and the tetracarboxylic acid of Example 5 was used. The amount of the anhydride (a-4-1) used was higher than that of the tetracarboxylic dianhydride (a-4-2), while the example 7 completely used the tetracarboxylic dianhydride (a-4-1). It can be seen that when an alicyclic tetracarboxylic dianhydride (such as tetracarboxylic dianhydride (a-4-1)) is substituted for an aromatic tetracarboxylic dianhydride (such as tetracarboxylic dianhydride (a-4-2)) ), the residual image characteristics at room temperature will deteriorate and the residual DC power will increase. Therefore, in the tetracarboxylic dianhydride (a-4), the aromatic tetracarboxylic dianhydride has a better evaluation result in a specific addition amount, and generally contains 20% by weight to 90% by weight of the aromatic tetracarboxylic acid II. Anhydride is preferred.

Experiment 2: Synthesis Examples Polymer A-5 (A-5-1), A-6 (A-6-1~A-6-4) and Comparative Polymer A-7 (A-7-1), A-8 Synthesis method of (A-8-1, A-8-3)

The diamine (a-1, a-2, a-3) and the tetracarboxylic dianhydride (a-4) are sequentially added to N-methyl-2-pyrrolidone according to the ratios shown in Tables 4 to 5 In (a-5-1), a solution having a solid content of 25 wt% is prepared and reacted at 40 ° C for 5 to 6 hours to obtain a solution containing polylysine. After the polyproline solution is diluted, an appropriate ratio of pyridine (a-7-1) and acetic anhydride (a-6-1) is added, and the dehydration ring-closing reaction is carried out at 100 to 110 ° C for 3 to 4 hours to form a solution containing a ruthenium-proline copolymer, the solution containing the copolymer is poured into ethanol (a-5-3) for precipitation, and is purified by washing with ethanol (a-5-3), and finally collected. The solid was dried under reduced pressure to give a polymer (A) having an intrinsic viscosity and imidization ratio shown in Tables 4 and 5.

Experimental methods of Examples 10 to 16 and Comparative Examples 3' to 5':

According to Table 6, each of the examples and the comparative examples were obtained by dissolving the two polymers (A) in the ratio shown in Table 6 in γ-butyrolactone (a-5-2) and N-methyl. In a mixed solvent of 2-pyrrolidone (a-5-1), a solution having a solid content of 6 wt% was prepared and filtered through a filter having a diameter of 1 μm, and the collected filtrate was the liquid crystal alignment agent of the present invention.

The liquid crystal alignment agent of the present invention was applied onto a glass substrate by a roller printer, and dried on a hot plate at 200 ° C for 20 minutes to form a film having a thickness of 0.08 μm. The film was oriented at a roller speed of 1000 (rev/min), a platform moving speed of 60 (mm/sec), and a press-in amount of 0.4 m.

Taking a substrate coated sealant having the liquid crystal alignment film, spraying a spacer on another substrate having the liquid crystal alignment film, and then aligning the two liquid crystals The film substrates were vertically combined with each other in the direction of the brush film, and finally liquid crystal (ZLI-4792 liquid crystal manufactured by Merck Ltd.) was injected into the gap between the two substrates, and the injection holes were sealed to form a liquid crystal display element.

The obtained liquid crystal display element was evaluated for room temperature afterimage characteristics, high temperature afterimage characteristics, and residual DC voltage. The evaluation results are shown in Table 6.

Example 13 and Comparative Example 3', the only difference is that the latter replaces the diamine (a-1-2) with a diamine (a-2-1), that is, the comparative example 3' uses only a diamine (a-2). -1), diamine (a-3-6), and without using diamine (a-1-2), the residual DC voltage of Comparative Example 3' was significantly higher. Therefore, the present invention simultaneously uses three kinds of diamines as the reactant of the polymer (A), the phenol group provided by the diamine (a-1), the diamine (a-2), and the phenol group and the tertiary nitrogen atom. The synergistic effect can reduce the residual DC voltage of the liquid crystal display element.

In Examples 10, 11, 13, and 14, three kinds of diamines were used as the reactant of the polymer (A), and the residual image characteristics obtained were excellent and excellent, and the residual DC was obtained. The voltage is 19 to 48, indicating that both the diamine (a-1-2) and the diamine (a-2-1) are used together, and a small amount of the diamine (a-3-6) is added to obtain good afterimage characteristics. Lower residual DC voltage.

Comparative Examples 11 and 12, the difference being that the latter replaces the partial diamine (a-2-1) of Example 11 with a diamine (a-3-5), that is, the diamine (a) in Example 12. -2-1) The proportion of the whole diamine decreases, and the ratio of diamine (a-3) to the overall diamine increases. At this time, the room temperature and high temperature residual image characteristics are better, and the residual DC voltage is 19mV. It rose to 165.9mV. Comparative Examples 14, 15 and 16, in Example 15, substituting the diamine (a-3-2) for the partial diamine (a-2-1) of Example 14, the residual image properties at room temperature and high temperature were In the excellent change, the residual DC voltage rises from 31mV to 217.8mV. In Example 16, the partial diamine (a-2-1) in Example 14 was replaced by a diamine (a-3-5), and the residual image voltage was changed from 31 mV to 203.8 mV. . It can be seen from the above comparison that the ratio of the diamine (a-3) to the overall diamine is not too high, otherwise the room temperature and high temperature residual image characteristics of the liquid crystal display element are deteriorated, and the residual DC voltage is increased.

In Comparative Examples 3', 4', and 5', all of the diamines (a-1-2) were not used, and the room temperature image retention characteristics were only good and medium, and the high temperature afterimage characteristics were only poor, and the residual DC voltage was Compared with Examples 10, 11, 13, and 14, the phenol group provided by the diamine (a-1) and the diamine (a-2), and the phenol group and the third are also high. The synergistic effect of the nitrogen atom can improve the image sticking characteristics of the liquid crystal display element and obtain a low residual DC voltage.

The present invention provides a phenol group by reacting a polymer (A) comprising at least 2.5 mole percent of a phenolic backbone and at least 5 mole percent of a tertiary nitrogen atom skeleton during the reaction to form the polymer (A). Skeleton combination The phenolic group possessed by the substance, and the synergistic effect produced by the phenol group and the tertiary nitrogen atom providing the skeleton of the tertiary nitrogen atom, so that the liquid crystal display element made of the polymer (A) has good afterimage characteristics and Low residual DC voltage.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and modified without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

Claims (14)

A liquid crystal alignment agent comprising: a polymer (A) comprising more than 50% by weight of polyamic acid or polyimine, and the polymer (A) comprising a phenol-based skeleton of 2.5 mol% or more, and a tertiary nitrogen atom skeleton having a molar percentage of 5 or more, wherein the phenolic skeleton is selected from the group consisting of formula (i), formula (ii), and combinations thereof, and formula (i) and formula (ii) The structure is as follows: In the formula (i), each of Y ₁ to Y ₅ is an independently hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a hydroxyl group (-OH) or -(CH ₂ ) pCF. ₃ , the p is an integer of 1 to 5, and at least one of the Y ₁ to Y ₅ is a hydroxyl group; in the formula (ii), Z is a single bond, an alkylene group having 1 to 4 carbon atoms, -CO-, - The COO- or -O-; substituents on the benzene ring are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a hydroxyl group, -CF ₃ or -OCF ₃ , And at least one of the substituents is a hydroxyl group. The liquid crystal alignment agent of claim 1, wherein the polymer (A) The backbone further comprises a phthalate, a guanamine or a quinone. The liquid crystal aligning agent of claim 1, wherein the polymer (A) is a quinone imine-proline copolymer, a polyimine or a poly phthalic acid. The liquid crystal alignment agent of claim 1, wherein the phenolic skeleton and the tertiary nitrogen atom skeleton are selected from the group consisting of a residue of a diamine (a-1) and a diamine (a-2), wherein the diamine (a) -1) having a phenol group, the diamine (a-2) having no phenol group and having a tertiary nitrogen atom. The liquid crystal alignment agent of claim 4, wherein the diamine (a-1) comprises the formula (I-1) or the formula (I-2): In the formula (I-1), each of M ₁ to M ₅ is an independently hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a hydroxyl group or -(CH ₂ )pCF ₃ , The p is an integer of 1 to 5, and at least one of the M ₁ to M ₅ is a hydroxyl group; in the formula (I-2), Z is a single bond, an alkylene group having 1 to 4 carbon atoms, -CO-, - One of COO- or -O-; R ₁ to R ₅ is an amine group (-NH ₂ ), one of which is a hydroxyl group, and the others are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, and a carbon number of 1 Alkoxy group to 5, hydroxy group, -CF ₃ or -OCF ₃ ; one of R ₆ to R ₁₀ is an amine group, one is a hydroxyl group, and the others are each independently a hydrogen atom and a carbon number of 1 to 5 Alkoxy group having 1 to 5 carbon atoms, a hydroxyl group, -CF ₃ or -OCF ₃ . The liquid crystal alignment agent of claim 4, wherein the diamine (a-2) is a structure represented by the formula (II): Wherein X ₁ to X ₅ are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms or -(CH ₂ )pCF ₃ , and p is an integer of 1 to 5. The liquid crystal alignment agent of claim 4, wherein the reactant in the formation reaction of the polymer (A) comprises the diamine (a-1), the diamine (a-2), and the diamine (a-3) And a tetracarboxylic dianhydride (a-4), wherein the diamine (a-3) is a diamine compound other than the diamine (a-1) and the diamine (a-2). The liquid crystal alignment agent of claim 7, wherein the diamine (a-3) comprises the formula (a-3-1), the formula (a-3-2), the formula (a-3-3), and the formula (a-). 3-4), formula (a-3-5), formula (a-3-6) or formula (a-3-7): The liquid crystal alignment agent of claim 7, wherein the tetracarboxylic dianhydride (a-4) comprises an alicyclic tetracarboxylic dianhydride or an aromatic tetracarboxylic dianhydride. The liquid crystal alignment agent of claim 9, wherein the alicyclic tetracarboxylic dianhydride comprises the structure represented by the formula (a-4-1): The liquid crystal alignment agent of claim 9, wherein the aromatic tetracarboxylic dianhydride comprises a structure represented by the formula (a-4-2), the formula (a-4-3) or the formula (a-4-4): The liquid crystal alignment agent of claim 9, wherein the tetracarboxylic dianhydride (a-4) comprises 20% by weight to 90% by weight of the aromatic tetracarboxylic dianhydride. A liquid crystal alignment film formed of the liquid crystal alignment agent according to any one of claims 1 to 12. A liquid crystal display element comprising the liquid crystal alignment film of claim 13.