TWI487731B - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display device having the same - Google Patents

Description

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

The present invention relates to a liquid crystal alignment agent and a liquid crystal alignment film and liquid crystal display element produced thereby.

In order to improve the image quality of the liquid crystal display element, the liquid crystal alignment film should have the following properties: (1) good electrical characteristics: low image sticking effect (Image Sticking Effect), high voltage holding ratio, and the like. (2) Good alignment ability: The more uniform the pretilt angle of the liquid crystal molecules, the smaller the difference in steering after the liquid crystal molecules are driven by the electric field, and the image quality of the liquid crystal display element is better. (3) Excellent film property: When the liquid crystal alignment agent is applied to the substrate, no rubbing brush marks and cutting debris are generated. (4) High reliability: In the environment of high temperature and high humidity, the alignment of liquid crystal molecules is not affected.

With the popularization of liquid crystal display elements, consumers are increasingly demanding the imaging quality of liquid crystal display elements, and how to further improve the imaging quality of liquid crystal display elements is a goal of related companies.

An object of the present invention is to provide a liquid crystal alignment agent which has low image sticking property, low pretilt angle variability, excellent brush film property, excellent alignment property and high reliability, and is prepared by using the liquid crystal alignment agent. In turn, it provides excellent and stable image quality.

According to one embodiment of the present invention, there is provided a liquid crystal alignment agent comprising a first polymer, wherein the first polymer is obtained by polymerizing a diamine compound and a tetracarboxylic dianhydride compound. The main chain structure of the first polymer comprises an aromatic group having symmetry and rigidity and a tertiary amine residue, wherein the content of the aforementioned aromatic group is from 30 mole percent to 70 mole percent of the main chain structure of the first polymer.

According to the aforementioned liquid crystal alignment agent, the first polymer is a polyamic acid, a polyamidene, a quinone imine-proline copolymer or a combination thereof. The diamine compound may comprise a first diamine compound and a second diamine compound, wherein the first diamine compound provides the aforementioned tertiary amine residue, and the second diamine compound provides the aforementioned aromatic group. The first diamine compound may be present in an amount from 20 mole percent to 50 mole percent of the diamine compound.

According to the liquid crystal alignment agent described above, the first diamine compound may have a structure as shown in the formula (I-1): (I-1) wherein R ₃ is hydrogen or OH, and R ₁ , R ₂ , R ₄ and R ₅ are each independently hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, OH or (CH ₂ ) _x CF ₃ , and x is an integer from 1 to 5.

The first diamine compound may have a structure as shown in the formula (a-1-1) or the formula (a-1-2):

The second diamine compound may have a structure as shown in the formula (I-2): Wherein d is a single bond, a C 1-4 alkylene group, a C 1-4 fluorine-containing alkyl group, a CO, an oxygen or a phenyl group, an e-systemic single bond, a CO or a phenyl group, S ₁ , Each of S ₂ , S ₃ and S ₄ is independently hydrogen, OH, a halogen group, SO ₂ H, an alkyl group having 1 to 4 carbon atoms or a fluorine-containing alkyl group having 1 to 4 carbon atoms, and each of m and n groups. Is an independent integer from 0 to 3.

According to the liquid crystal alignment agent described above, the tetracarboxylic dianhydride compound may contain a first tetracarboxylic dianhydride compound, and the first tetracarboxylic dianhydride compound provides the aforementioned aromatic group. The first tetracarboxylic dianhydride compound may have a structure as shown in the formula (I-3) or (I-4): Wherein X ₂ has a structure as shown in formula (ii), formula (iii) or formula (iv): T is a single bond, CO, SO, SO ₂ , phenylene or has a structure as shown in formula (i): QJQ (i), wherein J is a phenyl group, a phenyl group, a naphthyl group or a stretching group Benzophenone, Q is oxygen.

According to the liquid crystal alignment agent, the second polymer may be further obtained by polymerizing a diamine compound and a tetracarboxylic dianhydride compound, and the main chain structure of the second polymer comprises symmetry and a rigid aromatic group, the content of the aforementioned aromatic group accounts for 30% of the main chain structure of the second polymer The ratio is up to 70 mole percent, wherein the first polymer is uniformly mixed with the second polymer.

According to another embodiment of the present invention, there is provided a liquid crystal alignment film formed of the liquid crystal alignment agent of any of the above.

According to still another embodiment of the present invention, there is provided a liquid crystal display element comprising the liquid crystal alignment film described above.

First polymer (A)

The first polymer (A) is obtained by polymerizing a diamine compound (a) and a tetracarboxylic dianhydride compound (b), and the main chain structure of the first polymer (A) contains a fragrance having symmetry and rigidity. The base and the tertiary amine residue, the aforementioned aromatic group is present in an amount of from 30 mole percent to 70 mole percent of the main chain structure of the first polymer (A), preferably from 40 mole percent to 70 mole percent. The tertiary amine residue may be present in an amount of from 2.5 mole percent to 80 mole percent of the backbone structure of the first polymer (A), preferably from 10 mole percent to 60 mole percent, more preferably 15 mole percent Up to 45 mole percentage.

By the main chain structure of the first polymer (A) having an aromatic group having a symmetry and rigidity of 30 mol% to 70 mol%, the tightness of the polymer stack of the first polymer (A) can be increased and Alignment of the same orientation, which contributes to the excellent release of the alignment film made of the first polymer (A) The ability to accumulate charge and have excellent alignment force.

Since the main chain structure of the first polymer (A) contains a tertiary amine residue, the liquid crystal display element made of the first polymer (A) can have low afterimage characteristics and a low residual DC voltage.

The liquid crystal display element made of the first polymer (A) can have a low afterimage by the main chain structure of the first polymer (A) containing both an aromatic group and a tertiary amine residue having symmetry and rigidity. Characteristics, good alignment and low pretilt variability.

The first polymer (A) may be a polyamic acid, a polyimine, a quinone imine-proline copolymer, or a combination thereof. The above "combination" means that the first polymer (A) may be composed of two or more kinds of polyacrylic acid, polyamidimide, quinoneimine-proline copolymer, and mixed in any ratio, specifically The first polymer (A) may be a mixture of poly-proline and polyimine, and the first polymer (A) may be a mixture of poly-proline and a quinone-proline copolymer. A polymer (A) may be a mixture of a polyimine and a quinone imine-proline copolymer or the first polymer (A) may be a poly phthalic acid, a polyimine, and a quinone imine-guanamine. a mixture of acid copolymers.

The diamine compound (a) may comprise a first diamine compound (a-1) and a second diamine compound (a-2), wherein the first diamine compound (a-1) provides the aforementioned tertiary amine residue The second diamine compound (a-2) provides the aforementioned aromatic group. The diamine compound (a) may further comprise a third diamine compound (a-3), and the third diamine compound (a-3) is a first diamine compound (a-1) and a second diamine compound (a). a diamine compound other than -2). The content of the first diamine compound (a-1) may be from 20 mol% to 50 mol% of the diamine compound (a). Second diamination The content of the compound (a-2) may be from 10 mol% to 80 mol% of the diamine compound (a). The content of the third diamine compound (a-3) may be from 0 mole percent to 30 mole percent of the diamine compound (a).

The tetracarboxylic dianhydride compound (b) may contain the first tetracarboxylic dianhydride compound (b-1), and the first tetracarboxylic dianhydride compound (b-1) provides the aforementioned aromatic group. The tetracarboxylic dianhydride compound (b) may further comprise a second tetracarboxylic dianhydride compound (b-2), and the second tetracarboxylic dianhydride compound (b-2) is a first tetracarboxylic dianhydride compound ( A tetracarboxylic dianhydride compound other than b-1). The content of the first tetracarboxylic dianhydride compound (b-1) is from 10 mol% to 80 mol% of the tetracarboxylic dianhydride compound (b). The content of the second tetracarboxylic dianhydride compound (b-2) is from 10 mol% to 80 mol% of the tetracarboxylic dianhydride compound (b).

The diamine compound (a) and the tetracarboxylic dianhydride compound (b) are subjected to a polycondensation reaction in an organic solvent to form a 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 above poly-proline, polyimine or quinone-proline copolymer can be embedded with a small amount of ester bond and guanamine bond to form a binary or ternary block copolymer, such as guanamine. Acid-melamine copolymer, quinone-melamine copolymer, lysine-valerate copolymer, quinone-quinone copolymer, glutamic acid-melamine-proline copolymer Or a quinone imine-guanamine- quinone copolymer or the like. The performance of the original polymer is improved by embedding, which is well known in the art and will not be described herein.

Second polymer (B)

The second polymer (B) is obtained by polymerizing a diamine compound (a) and a tetracarboxylic dianhydride compound (b), and the main chain structure of the second polymer (B) contains a fragrance having symmetry and rigidity. And the content of the aforementioned aromatic group is 30% by mole of the main chain structure of the second polymer (B) to 70% by mole, preferably 40% by mole to 70% by mole.

Thereby, the tightness of the polymer stack of the second polymer (B) and the omnidirectionality of the alignment can be increased, and the alignment film made of the second polymer (B) can have an excellent ability to release the accumulated charge. And has an excellent alignment force.

The second polymer (B) may be a polyamic acid, a polyimine, a quinone imine-proline copolymer or a combination thereof. The above "combination" means that the second polymer (B) may be obtained by mixing two or more kinds of three polymers of polyphthalic acid, polyimine, and quinone-proline copolymer and mixing them in any ratio.

The diamine compound (a) may contain the second diamine compound (a-2), and the second diamine compound (a-2) provides the aforementioned aromatic group. The diamine compound (a) may further comprise a first diamine compound (a-1) and/or a third diamine compound (a-3), wherein the first diamine compound (a-1) provides a tertiary amine The residue, the third diamine compound (a-3) is a diamine compound other than the first diamine compound (a-1) and the second diamine compound (a-2). The content of the first diamine compound (a-1) may be from 0 mole percent to 50 mole percent of the diamine compound (a). The content of the second diamine compound (a-2) may be from 20 mol% to 100 mol% of the diamine compound (a). The content of the third diamine compound (a-3) may be from 0 mol% to 40 mol% of the diamine compound (a).

The tetracarboxylic dianhydride compound (b) may comprise a first tetracarboxylic dianhydride The compound (b-1) and the first tetracarboxylic dianhydride compound (b-1) provide the aforementioned aromatic group. The tetracarboxylic dianhydride compound (b) may further comprise a second tetracarboxylic dianhydride compound (b-2), and the second tetracarboxylic dianhydride compound (b-2) is a first tetracarboxylic dianhydride compound ( A tetracarboxylic dianhydride compound other than b-1). The content of the first tetracarboxylic dianhydride compound (b-1) is from 10 mol% to 80 mol% of the tetracarboxylic dianhydride compound (b). The content of the second tetracarboxylic dianhydride compound (b-2) is from 20 mol% to 80 mol% of the tetracarboxylic dianhydride compound (b).

Other embodiments regarding the second polymer (B) are the same as those of the first polymer (A), and are not described herein.

First diamine compound (a-1)

The first diamine compound (a-1) provides a tertiary amine residue, and the first diamine compound (a-1) may have a structure as shown in the formula (I-1): Wherein R ₃ is hydrogen or OH, and R ₁ , R ₂ , R ₄ and R ₅ are each independently hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, OH or (CH 2 ) _x CF3, x is an integer from 1 to 5.

According to an embodiment of the present invention, the first diamine compound (a-1) may have a structure as shown in the formula (a-1-1) or the formula (a-1-2):

The first diamine compound (a-1) may be used singly or in combination of two or more kinds without affecting the performance of the liquid crystal alignment film.

Second diamine compound (a-2)

The second diamine compound (a-2) provides an aromatic group having symmetry and rigidity, and the second diamine compound (a-2) may have a structure as shown in the formula (I-2): Wherein d is a single bond, a C 1-4 alkylene group, a C 1-4 fluorine-containing alkyl group, a CO, an oxygen or a phenyl group, an e-systemic single bond, a CO or a phenyl group, S ₁ , Each of S ₂ , S ₃ and S ₄ is independently hydrogen, OH, a halogen group, SO ₂ H, an alkyl group having 1 to 4 carbon atoms or a fluorine-containing alkyl group having 1 to 4 carbon atoms, and each of m and n is Independent 0~3 integer.

According to an embodiment of the present invention, the second diamine compound (a-2) may have the formula (a-2-1), the formula (a-2-2), the formula (a-2-3) or the formula (a) -2-4) One of the structures shown:

(a-2-1), (a-2-2),

The second diamine compound (a-2) may be used singly or in combination of two or more kinds without affecting the performance of the liquid crystal alignment film.

Third diamine compound (a-3)

The third diamine compound (a-3) is a diamine compound other than the first diamine compound (a-1) and the second diamine compound (a-2). According to an embodiment of the present invention, the third diamine compound (a-3) may have, but is not limited to, the formula (a-3-1), the formula (a-3-2), the formula (a-3-3) or One of the structures shown in formula (a-3-4):

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

First tetracarboxylic dianhydride compound (b-1)

The first tetracarboxylic dianhydride compound (b-1) provides an aromatic group having symmetry and rigidity, and the first tetracarboxylic dianhydride compound (b-1) may have the formula (I-3) or (I- 4) One of the structures shown: Wherein X ₂ has a structure as shown in formula (ii), formula (iii) or formula (iv): T is a single bond, CO, SO, SO ₂ , phenylene or has a structure as shown in formula (i): QJQ (i), wherein J is a phenyl group, a phenyl group, a naphthyl group or a stretching group Benzophenone, Q is oxygen.

According to an embodiment of the present invention, the first tetracarboxylic dianhydride compound (b-1) may have a formula (b-1-1), a formula (b-1-2) or a formula (b-1-3). Show one structure:

The first tetracarboxylic dianhydride compound (b-1) may be used singly or in combination of two or more kinds without affecting the performance of the liquid crystal alignment film.

Second tetracarboxylic dianhydride compound (b-2)

The second tetracarboxylic dianhydride compound (b-2) is a tetracarboxylic dianhydride compound other than the first tetracarboxylic dianhydride compound (b-1). According to an embodiment of the present invention, the second tetracarboxylic dianhydride compound (b-2) may have, but is not limited to, the formula (b-2-1), the formula (b-2-2) or the formula (b-2- 3) One of the structures shown:

The second tetracarboxylic dianhydride compound (b-2) may be used singly or in combination of two or more kinds without affecting the performance of the liquid crystal alignment film.

Method for synthesizing first polymer (A)

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

The diamine compound (a) and the tetracarboxylic dianhydride compound (b) are used as a reactant, and a polycondensation reaction is carried out in an organic solvent, and the temperature is carried out at a temperature of 40 ° C to 110 ° C for 1 to 12 hours to obtain a The reaction solution of polylysine may be elastically adjusted depending on the amount of the reactants and the temperature and time of the polymerization.

The ratio of the diamine compound (a) to the tetracarboxylic dianhydride compound (b), the anhydride group content of the tetracarboxylic dianhydride compound (b) is 1 equivalent, and the amine of the diamine compound (a) The base is preferably from 0.5 to 2 equivalents, more preferably from 0.7 to 1.5 equivalents.

The organic solvent is used to dissolve the reactants and products, and can be distinguished into an organic solvent having a good solubility and an organic solvent having a poor solubility depending on the solubility of the organic solvent to the reactants and the product.

Preferred organic solvents include, but are not limited to, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-isopropyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl caprolactam, dimethyl hydrazine, tetramethyl urea, hexamethylphosphonium, γ-butyrolactone or pyridine, the above organic solvent can be It can be used alone or in combination of two or more.

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, isopropanol, n-butanol, cyclohexanol, ethylene glycol, ethylene glycol methyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl Ether, ethylene glycol dimethyl ether, B 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 an organic solvent.

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 above-mentioned dehydration ring closure reaction is a conventional technique and will not be described herein.

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

Method for synthesizing second polymer (B)

The synthesis method of the second polymer (B) is substantially the same as the synthesis method of the first polymer (A), and the difference is only in the difference of the reactants, and will not be described herein.

Liquid crystal alignment agent

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

The weight ratio of the first polymer (A) to the second polymer (B) ranges from 5/95 to 95/5.

The first polymer (A) and the second polymer (B) are dissolved in an organic solvent to form a liquid crystal alignment agent. Preparation of liquid crystal alignment agent It 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 therein according to the viscosity and the volatility, and preferably contains a solid content of 1% by weight to 10% by weight. 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 ability, and if the solid content is more than 10% by weight, the coating quality is affected.

The aforementioned organic solvent (C) includes, but is not limited to, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-isopropyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl caprolactam, dimethyl hydrazine, γ-butyrolactone, γ-butyrolactam, ethylene glycol monomethyl ether, ethylene glycol Monoethyl ether, ethylene glycol mono-n-propyl ether or ethylene glycol monobutyl ether. The above solvents may be used in combination of two or more. In addition to the solvents listed above, both the first polymer (A) and the second polymer (B) are soluble.

The liquid crystal alignment agent may optionally contain an additive, and the additive may be an organic oxime (oxy) alkane compound or an epoxy compound. It is conventional to use an organic oxime compound and an epoxy compound as a liquid crystal alignment agent. I will not repeat them here.

Liquid crystal alignment film

The method for forming a liquid crystal alignment film comprises the steps of: first, applying a liquid crystal alignment agent of the present invention onto a glass substrate having a patterned transparent conductive film to form a coating layer, including but not limited to a roll coating method, The spin coating method and the printing method are conventional, and will not be described herein.

Next, the coating layer is baked by heating to form a coating layer of the liquid crystal alignment film. The purpose of heating baking is to remove the organic solvent in the liquid crystal alignment agent. And the poly-proline acid contained in the first polymer (A) and the second polymer (B) is subjected to a dehydration ring closure reaction. 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.

Finally, the directional friction is performed by a roller wound with a nylon or cotton fiber cloth, so that the liquid crystal alignment film has an alignment ability to the liquid crystal molecules.

Liquid crystal display element

The method of forming a liquid crystal display element comprises the steps of: first applying a sealant on a glass substrate having the liquid crystal alignment film, and spraying a spacer on another glass substrate having the liquid crystal alignment film.

Next, the two glass substrates having the liquid crystal alignment film described above are combined in such a manner that the brush directions of the films are perpendicular to each other or parallel to each other.

Finally, liquid crystal is injected into the gap between the two glass substrates, and the injection holes are sealed to form a liquid crystal display element.

Polymer quality measurement method

(1) Dehydration ring closure ratio (imidization ratio): The first polymer (A) or the second polymer (B) is dried under reduced pressure at room temperature, and the dried solid is continuously dissolved in the deuterated solution. In dimethyl hydrazine, tetramethyl decane was used as a reference material, and the imidization ratio was calculated from the formula by ¹ H-NMR: imidization ratio (%) = (1-K1/(K2 × α) x 100%, where K1 is the peak area derived from the proton of the NH group (10 ppm), K2 is the peak area derived from other protons, and α is the other proton relative to the first polymer (A) or the second polymerization The ratio of the number of protons of the NH group of the precursor (B) precursor (polyglycolic acid).

(B) Polymer molecular weight measurement: manufactured by Waters The GPC (gel permeation chromatography) apparatus was used to measure the weight average molecular weight by converting the time of passage of polystyrene to DMF containing lithium bromide and phosphoric acid as a rinsing liquid at a column temperature of 35 °C.

Evaluation method of liquid crystal display element

(1) Judgment of image sticking phenomenon: The liquid crystal display element which has been injected into the liquid crystal (ZLI-4792) is used as a basis for determining the image sticking phenomenon by measuring the brightness value before and after charging and calculating the percentage change of the brightness. Specifically, the transmittance and the voltage change curve of the specific position of the liquid crystal display element are first measured under the pass voltage, and the voltage value V1 when the transmittance is 50% is obtained, and the liquid crystal display element is driven by the voltage value V1 for 10 minutes and then recorded. After the brightness value K3, the liquid crystal display element is charged with the alternating current of 10 volts for 4 hours, the liquid crystal display element is driven again by the voltage value V1 for 10 minutes, and the brightness value K4 is recorded. The calculation formula of the brightness change percentage is: (|K3-K4 |/K3)×100%, if the percentage change of brightness is less than 5%, it is better to judge the residual image phenomenon, 5%~10% judges that the residual image phenomenon is medium, and more than 10% determines that the residual image phenomenon is poor.

(2) Residual DC voltage: A voltage of 5 V was applied to the liquid crystal display element into which the liquid crystal (ZLI-4792) was injected and maintained for 3600 seconds, followed by discharging for 1 second, and finally the residual DC voltage value at the 600th second was recorded.

(III) Voltage holding ratio: The voltage holding ratio in the liquid crystal display element was measured by applying a direct current of 5 V to a liquid crystal display element of a liquid crystal (ZLI-4792) at a frequency of 60 ° C at a temperature of 60 ° C for 60 sec.

(4) Pre-tilt variability: The liquid crystal display element that has been injected into the liquid crystal (ZLI-4792) is measured by the crystallization rotation method (the measurement machine is Autronic TBA-107), and the pretilt angle variation is calculated according to the measurement result. degree. Specifically, firstly, the pretilt angle of nine points in the plane of the liquid crystal display element is measured and the average value K5 is obtained, and the pretilt angle of nine points on the edge of the liquid crystal display element is measured and the average value K6 is obtained, and the absolute difference between K5 and K6 is obtained. As the pretilt angle variability, the smaller the pretilt angle variability, the higher the stability of the pretilt angle. The above “in-plane” means that the distance from the frame glue is more than 0.51 cm, and the above “edge” means the distance from the frame glue is less than 0.5 cm. At the office.

(5) Brush film property: The liquid crystal alignment agent is applied on a tin indium oxide (ITO) substrate by spin coating, and baked in an oven, and the rotation speed is 1000 rpm, and the platform moving speed is 60 mm/sec. The amount of the film was 0.4 mm, and the film was oriented 10 times. The surface of the liquid crystal alignment film after the brush film was visually observed under a polarizing microscope (POM) at 10 times, and the brushless film was judged to be excellent. Debris less than 10 is preferred.

(6) Reliability: The liquid crystal display element that has been injected into the liquid crystal (ZLI-4792) is placed in a temperature of 121 ° C, humidity of 100% and 2 atmospheres for 24 hours, and the liquid crystal display element is observed under a polarizing microscope at 5 times. The liquid crystal array was abnormal, and no abnormality was judged as OK, and liquid crystal alignment abnormality (LC domain) was judged as NG.

(7) Alignment coefficient: the liquid crystal alignment agent is applied to the tin indium oxide substrate by spin coating, and baked in an oven, and the rotation speed is 1000 rpm, the platform moving speed is 60 mm/sec, and the pressing amount is Oriented brushing at 0.2 mm. Continued measurement by ellipsometer, the incident light angle is 50 degrees, and the incident light wavelength is 633 nm. When the alignment direction of the alignment film is parallel to the direction of the incident linearly polarized light S, the phase difference between the P wave and the S wave of the reflected ellipsometry can be obtained. for Δmax; conversely, when the alignment direction of the alignment film is parallel to the direction of the incident linearly polarized light P, the phase difference between the P wave and the S wave of the reflected ellipsometric light is Δmin. The subtraction of the two is the alignment coefficient D?.

(8) Orientation: The liquid crystal display element which has been injected into the liquid crystal (ZLI-4792) is placed between two mutually perpendicular polarizing plates, and the presence or absence of the liquid crystal alignment abnormality is visually observed. No abnormality determination is preferable, and light leakage occurs. Abnormalities such as liquid crystal wash marks are judged to be poor.

Synthesis of first polymer (A), second polymer (B) and other polymers

The diamine compound (a) and the tetracarboxylic dianhydride compound (b) are sequentially added to N-methyl-2-pyrrolidone in a ratio shown in Table 1 and Table 2 to prepare a solid content of 25 parts by weight. The solution of % is reacted at 40 ° C for 5-6 hours to obtain poly-proline. After the polyproline solution is diluted, an appropriate ratio of pyridine and acetic anhydride is added, and the dehydration/cyclization reaction is carried out at 100 to 110 ° C for 3 to 4 hours, and the solution is used for precipitation in ethanol and ethanol. Purification and purification, finally collecting the solid and drying under reduced pressure to obtain the polymers shown in Tables 1 and 2, wherein A1 to A8 belong to the first polymer (A), and B1 to B5 belong to the second polymer (B). A1~a3 and b1~b2 belong to other polymers.

Liquid crystal display elements of Examples 1 to 13 and Comparative Examples 1' to 4'

The first polymer A1~A8, the second polymer B1~B5, the other polymers a1~a3 and b1~b2 are dissolved in γ-butyrolactone and N-methyl-2- according to the ratio shown in Table 3. A solution having a solid content of 6 wt% was prepared in a pyrrolidone mixed solvent, and filtered through a filter having a diameter of 1 μm. The collected filtrates were liquid crystal alignment agents used in Examples 1 to 13 and Comparative Examples 1' to 4'. .

The liquid crystal alignment agent obtained above was applied onto a glass substrate by a roller printer, and dried on a hot plate at 220 ° C for 20 minutes to form a film having a thickness of 0.08 μm. The film was subjected to directional rubbing at a roller rotation speed of 1000 rpm, a table moving speed of 60 mm/sec, and a press-in amount of 0.4 mm.

Applying a sealant to the glass substrate having the liquid crystal alignment film, and spraying the spacer on the glass substrate of the other liquid crystal alignment film. The two glass substrates having the liquid crystal alignment film are successively combined in such a manner that the brush directions are perpendicular to each other, and liquid crystal (ZLI-4792) is injected into the gap between the two glass substrates, and the injection holes are sealed to form a liquid crystal display element.

The obtained liquid crystal display element was subjected to evaluation of residual image characteristics, residual DC voltage, voltage holding ratio, pretilt angle variability, brush film property, alignment coefficient (D?), alignment property, and reliability, and the evaluation results are shown in Table 3. .

In Table 3, in the evaluation results of the residual DC voltage and the voltage holding ratio, Examples 1 to 13 performed in a similar manner to Comparative Examples 1' to 4'. Among the evaluation results of the residual image characteristics, Examples 1 to 13 are preferred, and Comparative Examples 1' to 4' are medium or poor, and the evaluation results of Comparative Examples 1' to 4' are inferior to Examples 1 to 13, showing The liquid crystal display element of the invention has good electrical characteristics and can provide good image quality.

In the evaluation results of the pretilt variability, Examples 1 to 13 are 0.1 to 0.2, and Comparative Examples 1' to 4' are 0.5 to 0.6 and both are higher than Examples 1 to 13, showing the in-plane of the liquid crystal display element of the present invention. The difference in pretilt angle from the edge is minimal, providing a stable alignment capability.

Among the evaluation results of the brushing property, the examples 1 to 13 are excellent, and in the comparative example 1' to 4', only the comparative example 1' is excellent, and other comparative examples are preferable, showing that the liquid crystal display element of the present invention has excellent properties. Brush film.

Among the evaluation results of the alignment coefficient (D△), Examples 1 to 13 are 3.6 to 4.8, and in Comparative Example 1' to 4', only 4.4 of Comparative Example 4' is comparable to Examples 1 to 13, and other control examples are far away. It is lower than Examples 1 to 13. Among the evaluation results of the alignment, Examples 1 to 13 were preferred, and in Comparative Examples 1' to 4', only Comparative Example 4' was preferable, and the other Comparative Examples were inferior to Examples 1 to 13. The liquid crystal display element of the present invention is shown to provide good alignment capability.

Among the evaluation results of the reliability, Examples 1 to 13 were all OK, and in Comparative Examples 1' to 4', only Comparative Example 4' was OK, and the other comparative examples were NG and not in Examples 1 to 13. It is shown that the liquid crystal display element of the present invention is not easily affected by the high temperature and high humidity of the external environment, and has a long service life and can provide stable image quality.

In summary, the liquid crystal alignment agent prepared by the first polymer (A) of the invention can make the liquid crystal display element have low afterimage characteristics, low pretilt angle variability, excellent brush film property and excellent alignment. Sexuality and high reliability provide a stable and good quality.

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 (12)

A liquid crystal alignment agent comprising: a first polymer obtained by polymerizing a diamine compound and a tetracarboxylic dianhydride compound, the main chain structure of the first polymer comprising: an aromatic group, The aryl group is present in an amount of from 30 mole percent to 70 mole percent of the backbone structure of the first polymer, and the aryl group has symmetry and rigidity; and a tertiary amine residue. The liquid crystal alignment agent of claim 1, wherein the first polymer is a polyamic acid, a polyamidene, a quinone imine-proline copolymer, or a combination thereof. The liquid crystal alignment agent of claim 1, wherein the diamine compound comprises a first diamine compound and a second diamine compound, wherein the first diamine compound provides the tertiary amine residue, the second An amine compound provides the aryl group. The liquid crystal alignment agent of claim 3, wherein the first diamine compound is present in an amount of from 20 mole percent to 50 mole percent of the diamine compound. The liquid crystal alignment agent of claim 3, wherein the first diamine compound has a structure as shown in the formula (I-1): Wherein R ₃ is hydrogen or OH, and R ₁ , R ₂ , R ₄ and R ₅ are each independently hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, OH or (CH ₂ ) _x CF ₃ , and the x is an integer from 1 to 5. The liquid crystal alignment agent of claim 5, wherein the first diamine compound has a structure as shown in the formula (a-1-1) or the formula (a-1-2): The liquid crystal alignment agent of claim 3, wherein the second diamine compound has a structure as shown in the formula (I-2): (I-2) wherein the d is a single bond, an alkylene group having 1 to 4 carbon atoms, a fluorine-containing alkyl group having 1 to 4 carbon atoms, CO, oxygen or a phenyl group, and the e is a single bond, CO or a phenyl group, wherein S ₁ , the S ₂ , the S ₃ and the S ₄ system are each independently hydrogen, OH, a halogen group, SO ₂ H, an alkyl group having 1 to 4 carbon atoms or a carbon number of 1 to 4; A fluorine-containing alkyl group, and an integer of 0 to 3 in which m and each of the n-systems are independent. The liquid crystal alignment agent of claim 1, wherein the tetracarboxylic dianhydride compound comprises a first tetracarboxylic dianhydride compound, and the first tetracarboxylic dianhydride compound provides the aromatic group. The liquid crystal alignment agent of claim 8, wherein the first tetracarboxylic dianhydride compound has a structure represented by the formula (I-3) or (I-4): Wherein X ₂ has a structure as shown in formula (ii), formula (iii) or formula (iv) Wherein T is a single bond, CO, SO, SO ₂ , a phenylene group or a structure having the formula (i): QJQ (i), wherein the J is a phenyl group, a phenyl group, a naphthene a benzophenone group and the Q is oxygen. The liquid crystal alignment agent of claim 1, further comprising: a second polymer obtained by polymerizing a diamine compound and a tetracarboxylic dianhydride compound, and a main chain structure of the second polymer Including: an aromatic group having a content of 30 mole percent to 70 mole percent of the main chain structure of the second polymer, and the aromatic group having symmetry and rigidity; wherein the first polymer and the second The polymer is uniformly mixed. A liquid crystal alignment film formed of the liquid crystal alignment agent according to any one of claims 1 to 10. A liquid crystal display element comprising the liquid crystal alignment film of claim 11.