TWI483968B - Polymer, liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display - Google Patents

Description

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

The present invention relates to a polymer, and more particularly to a polymer containing a specific unit, a liquid crystal alignment agent containing the polymer, a liquid crystal alignment film made of the liquid crystal alignment agent, and a liquid crystal having the foregoing liquid crystal alignment film. Display component.

The operation principle of the liquid crystal display is to change the alignment state of the liquid crystal molecules by using an external electric field, thereby causing the polarization state and direction of the light to change, thereby obtaining a display effect of light and dark contrast. Due to its small size, light weight, low power consumption and good display quality, liquid crystal displays have become the mainstream of flat panel displays in recent years.

As the size of the screen has expanded, liquid crystal display elements having thin filmed transistors (TFTs) in each of the pixels have been developed. When the liquid crystal molecules are placed between a pair of substrates containing electrodes, the alignment of the liquid crystal molecules can be controlled by controlling the electric field due to the difference in the electric attraction rates of the liquid crystals in the parallel and perpendicular directions. On the other hand, since the liquid crystal molecules have birefringence characteristics, the polarization direction of the polarized light can be regulated by the change in the alignment state of the liquid crystal molecules.

In order to allow the liquid crystal molecules to have a uniform tilt angle and a fixed orientation on the substrate, an alignment film is coated on the substrate, and the alignment film is used to control the alignment direction of the liquid crystal molecules and provide The liquid crystal molecules have a stable pretilt angle, and when the applied electric field is turned off, the liquid crystal molecules return to the original arrangement by the anchoring force at the interface with the alignment film and its own elasticity.

At present, a typical method for preparing an alignment film in the industry is to apply an organic film on the surface of a substrate, and the molecules on the surface of the film are oriented by friction or other means, thereby allowing the subsequently placed liquid crystal molecules to be tilted in a fixed direction. The material of the organic film may be selected from the group consisting of polyvinyl alcohol, polyethylene glycol, polyamidamine, polyaminic acid or polyimine, wherein the polyamic acid and the polyimide have excellent thermal stability and good mechanical properties. Electrical and chemical resistance are often used as alignment film materials.

Due to the increasing requirements for the display quality of liquid crystal display elements, the resolution of the image afterimage problem is relatively important. It is known that when a voltage is applied to a display element, the generated ionic charge is adsorbed by the liquid crystal alignment film of the display element, and when the applied voltage is released, the ionic charge is difficult to be detached from the alignment film, thereby causing an internal electric field phenomenon and causing a picture to be generated. Afterimage problem. Recently, many developments of alignment film materials have been intended to improve afterimage problems.

The present invention provides a polymer in which a liquid crystal alignment film made of the polymer has excellent pretilt stability.

The polymer of the present invention comprises at least one unit represented by Formula 1-1 or Formula 1-2: And at least one unit represented by Equation 2, Wherein R ₁ is a tetravalent organic group, R ₂ and R ₄ are each a divalent organic group, and R ₃ is different The divalent organic group, and the unit represented by Formula 1-2 is a unit obtained by dehydration cyclization of the unit represented by Formula 1-1.

In one embodiment of the invention, the above polymer comprises at least one unit represented by Formula 1-1 and at least one unit represented by Formula 1-2.

In one embodiment of the invention, R _{1 is} selected from the following formulas (i) to (iii): Wherein X is selected from the group consisting of -(CF ₃ )C(CF ₃ )-, -(CH ₃ )C(CH ₃ )-, -SO ₂ -, -O-,

In one embodiment of the invention, R ₂ and R ₄ are respectively:

In one embodiment of the present invention, the unit represented by Formula 2 is a unit represented by Formula 2-1: Wherein R ₆ is a trivalent organic group, R ₅ is -CONHP, -OP or -COOP, and P is the group: Wherein A ₁ is a C ₁ -C ₂₀ hydrocarbyl group.

In one embodiment of the invention, R ₁ is: And R ₃ is:

In one embodiment of the present invention, the ratio of the unit represented by Formula 1-1 and/or the unit represented by Formula 1-2 in the above polymer is 50% by weight to 99% by weight.

The liquid crystal alignment agent of the present invention includes the above polymer.

The liquid crystal alignment film of the present invention is made of the above liquid crystal alignment agent.

The liquid crystal display element of the present invention includes the above liquid crystal alignment film.

Based on the above, the present invention provides a polymer, a liquid crystal alignment agent made of the polymer, a liquid crystal alignment film, and a liquid crystal display element, wherein the liquid crystal display element exhibits better pretilt stability, film property, and alignment. And the phenomenon of afterimages has also been improved.

The above described features and advantages of the present invention will be more apparent from the following description.

Fig. 1 shows the pretilt angles of the liquid crystal display elements of Experimental Examples 6 to 8.

In the present specification, the range represented by "a value to another value" is a schematic representation that avoids enumerating all the values in the range in the specification. Therefore, the recitation of a particular range of values is intended to include any value in the range of values and the range of values defined by any value in the range of values, as in the specification. This smaller range of values is the same. For example, the range of "content of 10 to 80% by weight" covers the range of "content of 50% by weight to 60% by weight" regardless of whether other values are listed in the specification.

Herein, if a group is not specifically indicated to be substituted, the group may represent a substituted or unsubstituted group. For example, "alkyl" can mean a substituted or unsubstituted alkyl group. Further, when a group crown is described by "C _X ", it means that the main chain of the group has X carbon atoms.

In this context, the structure of a compound is sometimes represented by a skeleton formula. This representation can omit carbon atoms, hydrogen atoms, and carbon-hydrogen bonds. Of course, if the functional group is clearly drawn in the structural formula, the manufacturer will prevail.

A first embodiment of the present invention provides a polymer having at least two units; the first unit is a unit represented by Formula 1-1 or Formula 1-2, and the second unit is represented by Formula 2. unit.

Wherein R ₁ is a tetravalent organic group, R ₂ and R ₄ are each a divalent organic group, and R ₃ is different from The divalent organic group, and the unit represented by Formula 1-2 is a unit obtained by dehydration cyclization of the unit represented by Formula 1-1.

The unit represented by the formula 1-1 may be a product containing a guanamine bond obtained by reacting a diamine having a dihydroxy group and dichloromethane, wherein the guanamine bond is formed by reacting -NH ₂ and -COCl. The diamine having a dihydroxy group may be arbitrarily selected from known compounds, and the restriction condition is that the relative position of the hydroxyl group to the amine group is specified, so that the unit represented by the formula 1-1 can be dehydrated and cyclized, thereby obtaining the formula 1- The unit indicated by 2.

For example, a diamine having a dihydroxy group can be represented by the following formula:

Wherein R ₁ may be selected from the group represented by the following formula (i) to formula (iii): Wherein X is selected from the group consisting of -(CF ₃ )C(CF ₃ )-, -(CH ₃ )C(CH ₃ )-, -SO ₂ -, -O-,

In the above-exemplified diamine having a dihydroxy group, the hydroxyl group is ortho to the amine group, and therefore, the diamine having a dihydroxy group and the dichloro group are reacted to form a unit represented by Formula 1-1, and the unit is The guanamine bond and the hydroxyl group can be further dehydrated and cyclized to form an oxazole structure.

In an embodiment, R ₁ is:

The aforementioned dichloromethane is not particularly limited as long as it can react with a diamine having a dihydroxy group to form a unit of the formula 1-1. In some embodiments, the diterpene chloride may be the following compound:

The method for synthesizing the unit represented by the formula 1-1 is not limited to the above, that is, it is not limited to the reaction of a diamine having a dihydroxy group and dichlorocyanine. For example, it can also be obtained by reacting a diamine having a dihydroxy group and a dianhydride. The reaction of diamines and dianhydrides is well known to those of ordinary skill in the art and will therefore not be further described herein.

The unit represented by Formula 2 may be a unit obtained by reacting a diamine with any one of dichlorobenzene, as long as the "diamine" is different from the "diamine having a dihydroxy group" described above; in other words, as long as R ₃ is different The divalent organic group can be. Here, specific examples of dioxonium chloride may be the same as those enumerated in the preceding paragraph.

In some embodiments, the unit represented by Formula 2 may be a unit represented by Formula 2-1:

That is, the unit represented by Formula 2 is a unit obtained by reacting a diamine and dichloromethane represented by the following formula: Wherein R ₆ is a trivalent organic group, R ₅ is -CONHP, -OP or -COOP, and P is the following group: Wherein A ₁ is a C ₁ -C ₂₀ hydrocarbyl group.

In these embodiments, the unit represented by Formula 2 is a unit having a branch, and if a polymer containing the unit is used as a component of a liquid crystal alignment agent, liquid crystal molecules can be adjusted by adjusting the ratio of the unit in the polymer. Pretilt angle.

In an embodiment, the unit represented by Equation 2 may be of the following structure:

In some embodiments, the polymer of the first embodiment may include both the unit represented by Formula 1-1, the unit represented by Formula 1-2, and the unit represented by Formula 2. At this time, the ratio of the unit represented by Formula 1-1 and the unit represented by Formula 1-2 in the polymer is 50% by weight to 99% by weight.

A second embodiment of the present invention proposes a liquid crystal alignment agent comprising the polymer of the first embodiment dissolved in a solvent. Further, the liquid crystal alignment agent may further contain polyamic acid, polyimine, polylysine-polyimine, polyamine or a mixture thereof. Hereinafter, each component in the liquid crystal alignment agent will be described. However, the preparation of polylysine, polyimine, poly-proline-polyimine, polyamidamine or mixtures thereof and other possible components of liquid crystal alignment agents are within the prior art in the art. The skilled person can make appropriate changes and choices based on his or her knowledge, not limited to the following.

The following is an example of the synthesis of polyimine-polyamide.

Polyimine-polyproline can be obtained by reacting a tetracarboxylic dianhydride with a diamine, wherein the ratio of the two is preferably an amine of a diamine when the anhydride group content of the tetracarboxylic dianhydride is 1 equivalent. The base is 0.5 equivalents to 2 equivalents; more preferably, the amine group of the diamine is 0.7 to 1.5 equivalents when the acid anhydride group content of the tetracarboxylic dianhydride is 1 equivalent.

The synthesis of polyimine-polyamide is carried out in an organic solvent. The organic solvent used is classified into an organic solvent having a solubility and a poor solubility for polyimine-polyamide. Correct The organic solvent having a good solubility in polyimine-polyamide is, for example, N-methyl-2-pyrrolidone, N-isopropyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-propyl. -2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylcaprolactam, dimethyl hydrazine, tetramethyl urea, hexamethyl Phosphoniumamine, γ-butyrolactone, pyridine, etc., and the above solvents may be used in combination of two or more.

A solvent having a poor solubility of polyimine-polyamide may also be used in combination with the aforementioned organic solvent, and its use is limited to that the polyimine-polyglycine is not separated. Solvents with poor solubility include methanol, ethanol, isopropanol, n-butanol, cyclohexanol, ethylene glycol, ethylene glycol methyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene Alcohol 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, and the like.

The formation of polyimine-polyamide requires a dehydration ring closure reaction, and the dehydration ring closure reaction can be carried out by (1) direct heating dehydration ring closure, or (2) addition of a dehydrating agent and a catalyst to carry out a dehydration ring closure reaction.

Method (1): heating dehydration ring-closing reaction temperature is preferably 50 ° C ~ 300 ° C, and more preferably 100 ° C ~ 250 ° C. When the reaction temperature is lower than 50 ° C, the dehydration ring closure reaction does not proceed.

Method (2): adding a dehydrating agent and a catalyst for dehydration ring-closing reaction temperature is preferably -20 ° C ~ 150 ° C, and more preferably 0 ° C ~ 120 ° C. As the dehydrating agent, an acid anhydride such as acetic anhydride, propionic anhydride, trifluoroacetic anhydride or the like can be used. The amount of the dehydrating agent depends on the desired closed-loop ratio, and it is preferably 0.01 mol to 20 mol per 1 mol of the polyimine-polyglycine reproducing unit. The catalyst may use a tertiary amine such as triethylamine, pyridine, lutidine or the like, and the amount of the catalyst is preferably from 0.01 mol to 10 mol per 1 mol of the dehydrating agent.

Polyimine-polyproline is purified by pouring a polyimine-polyamide solution into a large amount of solvent with poor solubility to obtain a precipitate, which is then dried under reduced pressure. To polyimine-polyamide. The polyimine-polyamide acid is dissolved in an organic solvent and precipitated with a poorly soluble solvent. This step is carried out one or more times to purify the polyimine-polyamide. Finally, the polyimine-polyamide is dissolved in a solvent having a better solubility.

The organic solvent contained in the liquid crystal alignment agent includes N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylcaprolactam, and Methyl hydrazine, γ-butyrolactone, γ-butyrolactam, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol monobutyl ether Etc., the above solvents may be used in combination of two or more.

In addition to the foregoing components, the liquid crystal alignment agent may contain other components such as an organic oxime (oxy) alkane compound or an epoxy compound.

The organic oxime (oxy)alkyl compound is not particularly limited and may, for example, be aminopropyltrimethoxydecane, aminopropyltriethyldecane, vinylmethylnonane or N-(2-aminoethyl)- 3-aminopropylmethyldimethoxydecane, N-(2-aminoethyl)-3-aminopropyltrimethoxydecane, vinyltriethoxydecane, 3-methylpropene oxime Oxypropyltrimethoxydecane, 3-glycidoxypropyltrimethoxydecane, 3-glycidoxypropylmethyldimethoxydecane, 2-(3,4-epoxy ring Alkenyl)trimethoxydecane, 3-ureidopropyltrimethoxydecane, 3-ureidopropyltriethoxydecane, N-ethoxycarbonyl-3-aminopropyltrimethoxydecane, N-ethoxycarbonyl-3-aminopropyltriethoxyamine decane, N-triethoxycarbenylpropyltriethylamine, N-trimethoxymethylidenepropyltriazine A triamine, N-bis(oxyethylidene)-3-aminopropyltrimethoxydecane, N-bis(oxyethylidene)-3-aminopropyltriethyldecane, and the like. The content of the above organic oxime (oxy) alkane compound in the liquid crystal alignment agent should be balanced between "does not affect the properties required for the original alignment film" and "improve the brush film properties of the alignment film"; If the content of the organic hydrazine (oxy) alkane compound is too large, the formed alignment film is liable to cause poor alignment; if the content of the organic sulfonium (oxy) alkane compound in the alignment agent is too small, the formed alignment film is liable to cause a bad film defect. Excessive dusting. Therefore, the content of the organic hydrazine (oxy) alkane compound of the liquid crystal alignment agent is relative to the alignment agent The weight of all the polymers is preferably 0.01 to 5% by weight, more preferably 0.1 to 3% by weight.

The epoxy compound is not particularly limited, and examples thereof include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, and 1,6-hexanediol diglycidyl ether. Ether, glycerol diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, 1,3,5,6-tetraglycidyl-2,4-hexanediol, N,N,N ' , N ' -tetraglycidyl-m-phenylene, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N ' ,N ' -tetraglycidyl -4,4 '- diamino diphenyl methane, 3- (N- -N- allyl-glycidyl) aminopropyl trimethoxy Silane, 3- (N, N- diglycidyl Aminopropyltrimethoxydecane. The content of the above epoxy compound in the liquid crystal alignment agent should be balanced between "does not affect the characteristics required for the original alignment film" and "improve the brush film properties of the alignment film"; if the content of the epoxy compound in the alignment agent Too much, the formed alignment film is liable to cause poor alignment; if the content of the epoxy compound in the alignment agent is too small, the formed alignment film is liable to cause a problem of poor brushing and excessive powdering. Therefore, the concentration of the epoxy compound of the liquid crystal alignment agent of the present invention is preferably 0.01 to 3% by weight based on the total weight of the alignment agent, and particularly preferably 0.1 to 2% by weight.

A third embodiment of the present invention proposes a liquid crystal alignment film which is made of the liquid crystal alignment agent of the second embodiment. Specifically, the liquid crystal alignment agent of the second embodiment is applied onto a substrate and heated to form a film, that is, the liquid crystal alignment film of the third embodiment. Here, if the solid content of the liquid crystal alignment agent is less than 1% by weight, the applied alignment film thickness may be too thin to lower the liquid crystal alignment property; if the solid content of the liquid crystal alignment agent is more than 10% by weight, the coating may be affected. quality. In view of the above factors, the solid content of the liquid crystal alignment agent of the second embodiment is preferably from 1 to 10% by weight.

A fourth embodiment of the present invention provides a liquid crystal display element which can be obtained by the following method:

(1) The liquid crystal alignment agent of the second embodiment is applied onto a glass substrate having a patterned transparent conductive film by a roll coating method, a spin coating method, or a printing method, followed by baking by heating The film is formed afterwards. The main purpose of the heating baking is to remove the organic solvent in the liquid crystal alignment agent and to promote the dehydration ring-closing reaction of the poly-proline moiety and the unit represented by the formula 1-1, and the heating baking temperature is 80 ° C ~ 300 ° C, 100 ° C ~ 240 ° C is the best. The thickness of the film formed is preferably from 0.005 μm to 0.5 μm.

(2) The formed film is subjected to directional rubbing by a roller wound with a nylon or cotton fiber cloth, and this step enables the alignment film to provide liquid crystal molecular alignment.

(3) taking the substrate of the liquid crystal alignment film, applying a sealant thereon, spraying the spacer on the substrate of the other liquid crystal alignment film, and continuing to orient the liquid crystal alignment film substrates to each other perpendicularly or mutually The liquid crystal display elements are formed by combining liquid crystals in a gap and injecting liquid crystals into the gaps and sealing the injection holes.

<experiment>

The invention will be described more specifically hereinafter with reference to the embodiments. Although the following examples are described, the materials used, the amounts and ratios thereof, the processing details, the processing flow, and the like can be appropriately changed without departing from the scope of the invention. Therefore, the present invention should not be construed restrictively according to the embodiments described below.

Table 1 presents various compounds used as starting materials in the examples, wherein D1, D2 are specific examples of dichlorosilane; D3, D4 are specific examples of tetracarboxylic dianhydride; and D5 is specific to diamine having dihydroxyl groups. Examples; D6 to D9 are specific examples of diamines.

Synthesis of polymer A1~A9: Diamine and dioxonium chloride compound were added to N-methyl-2-pyrrolidone according to the molar ratio shown in Table 2, and pyridine neutralizer was added to prepare a solid content of 20% by weight. %The solution. The polymer A1~A9 can be obtained by reacting at room temperature for 4 hours to 5 hours. The reaction solution was poured into a mixed solvent of ethanol/water to conduct precipitation, and purified by washing with water and methanol. Finally, the solid was collected and dried under reduced pressure. The solid was dissolved in N-methyl-2-pyrrolidone to prepare a solution having a solid content of 15% by weight to facilitate subsequent testing.

Synthesis of polymer B1~B3: Diamine and tetracarboxylic dianhydride were added to N-methyl-2-pyrrolidone according to the molar ratio shown in Table 2 to prepare a solution having a solid content of 20% by weight. After reacting at room temperature for 4 to 5 hours, γ-butyrolactone is added to dilute to obtain a polyaminic acid solution.

- Evaluation of liquid crystal display elements -

According to the ratio shown in Table 3, the polymers A1 to A6 and the polymers B1 to B3 were taken and dissolved in a mixed solvent of γ-butyrolactone and N-methyl-2-pyrrolidone to prepare a solid content of 6% by weight. The solution was filtered through a filter having a diameter of 1 μm, and the collected filtrate was a liquid crystal alignment agent. Each of the liquid crystal alignment agents was coated on a glass substrate by a roller printer, and dried on a hot plate at 220 ° C for 30 minutes to form a liquid crystal alignment film having a thickness of 0.08 μm. Then, the film is rotated at a speed of 1000 (rev/min), the moving speed of the platform is 60 (mm/sec), and the pressing amount is 0.4. Oriented friction in micrometers.

And applying a sealant on the substrate coated with the liquid crystal alignment film, spraying the spacer on the substrate of the other liquid crystal alignment film, and continuously combining the two liquid crystal alignment film substrates so that the brush directions of the liquid crystal are perpendicular to each other, and Liquid crystal (ZLI-4792, Merck) was injected into the gap, and the injection hole was sealed to form a liquid crystal display element.

The obtained liquid crystal display element was evaluated for pretilt stability, brushing property, alignment property, and determination of image sticking phenomenon. The evaluation results are shown in Table 3.

evaluation standard:

(1) Determination of oxazole structure

The liquid crystal alignment agent was spin-coated on a glass substrate, baked on a hot plate at 85 ° C for 2 minutes, and then baked in an oven at 220 ° C for 30 minutes, and then the polymer film was scraped for FTIR analysis, and the characteristic peak of 1240 cm ^{-1 was obtained} . It was determined whether the polymer was cyclized to an oxazole structure.

(2) Pretilt stability

The liquid crystal display element to which the liquid crystal (ZLI-4792) was injected was measured by a crystal rotation method. A total of nine points are measured on the surface of the liquid crystal cell, and the difference between the maximum value and the minimum value is calculated. The difference between the two is less than 0.1%, and the difference between 0.1% and 0.2% is judged to be medium, and greater than 0.2% is judged to be inferior.

(3) Brush film properties

The liquid crystal alignment agent was coated on the ITO substrate by a spin coating method, and baked through an oven, and then oriented at a rotation speed of 1000 (rev/min), a table moving speed of 60 (mm/sec), and a pressing amount of 0.4 mm. The film was brushed and the surface after the brush film was observed through a polarizing microscope. No brush marks and chip marks were observed to be excellent, and it was observed that the brush marks and chips were judged to be inferior.

(4) Orientation

Measurement conditions: The liquid crystal cell was placed in an environment of a temperature of 121 ° C, a humidity of 100%, and a pressure of 2 atm, and deteriorated after 24 hours, and it was observed by a polarizing optical microscope whether or not the liquid crystal was abnormally arranged. no The liquid crystal alignment abnormality is judged to be excellent, the abnormal arrangement area is less than 10, and the abnormal arrangement area is greater than 10, and it is judged to be inferior.

(5) Determination of residual phenomenon

Measurement conditions: Measure the transmittance and voltage change at a specific position of the liquid crystal cell, and obtain the voltage (V _50% ) at a transmittance of _50% . After driving the liquid crystal cell for a few minutes, the brightness value is recorded, and then the liquid crystal is recorded. After charging the cartridge (10V AC) for 30 minutes, the liquid crystal cell was driven again at V _50% , the brightness value after 10 minutes was measured, and the difference in brightness variation before and after charging was calculated and expressed as a percentage. The amount of change is less than 0.5%, which is judged to be excellent, 0.5% to 1% is judged to be medium, and more than 1% is judged to be inferior.

As can be seen from Table 3, if the polymer in the liquid crystal alignment agent contains an oxazole structure (Experimental Example 1 to Experimental Example 5 and Comparative Example 1), the liquid crystal display element exhibits better pretilt stability, brushing property, and Orientation, and the afterimage phenomenon is also improved. This may be due to the good planarity of the oxazole structure (positive help for pretilt stability and alignment) and the lower resistivity (accelerated charge release, which in turn improves image sticking).

Further, in Comparative Example 1, the polymer component of the liquid crystal alignment agent was obtained by mixing the polymer A4 and the polymer B1, wherein the polymer A4 was obtained by polymerizing the monomer D1 and the monomer D5. That is, the polymer A4 is completely composed of the unit represented by the formula 1-1. However, when the liquid crystal alignment film and the liquid crystal display element are made of the polymer A4 and the polymer B1 (polyphthalic acid-polyimine), the various properties are still inferior to those of the liquid crystal display elements of Experimental Examples 1 to 5. It was thus confirmed that the polymer of the present invention having both units at the same time exhibited a preferable effect.

Further, the applicant also prepared the liquid crystal display elements of Experimental Examples 6 to 8 in the same manner as described above using the polymers A7 to A9, and measured the pretilt angle thereof. The results are presented in Figure 1. As can be seen from Fig. 1, the relative content of the unit represented by Formula 2 in the polymer of the present invention is very effective for adjusting the pretilt angle of the liquid crystal molecules.

In summary, the present invention provides a polymer, a liquid crystal alignment agent made of the polymer, a liquid crystal alignment film, and a liquid crystal display element, wherein the liquid crystal display element exhibits better pretilt stability, film properties, and alignment. Sex, and the phenomenon of afterimages is also improved.

Although the present invention has been described above by way of examples, it is not intended to limit the invention. Any changes and modifications may be made without departing from the spirit and scope of the invention. Therefore, the scope of protection of this application is subject to the definition of the scope of the patent application attached.

Claims (10)

A polymer comprising: at least one unit represented by Formula 1-1 or Formula 1-2: And at least one unit represented by Equation 2, Wherein R ₁ is a tetravalent organic group, R ₂ and R ₄ are each a divalent organic group, and R ₃ is different The divalent organic group, and the unit represented by Formula 1-2 is a unit obtained by dehydration cyclization of the unit represented by Formula 1-1. The polymer of claim 1, which comprises at least one unit represented by Formula 1-1 and at least one unit represented by Formula 1-2. The polymer application patentable scope of item 1, wherein at least one unit represented by Formula 1-1 or Formula _1-2, R ₁ is selected from the following formulas (i) ~ formula (iii): Wherein X is selected from the group consisting of -(CF ₃ )C(CF ₃ )-, -(CH ₃ )C(CH ₃ )-, -SO ₂ -, -O-, The polymer according to claim 1, wherein at least one of R ₂ and R ₄ in the unit represented by Formula 1-1 or Formula 1-2 is independently selected from the following structures: The polymer according to claim 1, wherein at least one unit represented by Formula 2 is a unit represented by Formula 2-1: Wherein R ₆ is a trivalent organic group, R ₅ is -CONHP, -OP or -COOP, and P is the group: Wherein A ₁ is a C ₁ -C ₂₀ hydrocarbyl group. The polymer according to claim 1, wherein at least one of the units represented by Formula 1-1 or Formula 1-2 and Formula 2, R ₁ is: And R ₃ is: The polymer according to claim 1, wherein the unit represented by the formula 1-1 and/or the formula 1-2 accounts for 50% by weight to 99% by weight of the polymer. A liquid crystal alignment agent comprising the polymer according to any one of claims 1 to 7. A liquid crystal alignment film produced by the liquid crystal alignment agent according to claim 8 of the patent application. A liquid crystal display element comprising the liquid crystal alignment film according to claim 9 of the patent application.