KR101108611B1 - Composition for liquid crystal aligning, liquid crystal aligning film manufactured by the same, and liquid crystal display comprising the same - Google Patents

Abstract

The present invention relates to a liquid crystal display composition, a liquid crystal alignment film prepared therefrom, a method for manufacturing the same, and a liquid crystal display including the liquid crystal alignment film.

The liquid crystal alignment film prepared from the liquid crystal alignment composition according to the present invention not only exhibits an excellent alignment state and can implement excellent pretilt angle, but also excellent electrical properties such as solubility and voltage maintenance ratio (VHR).

Polyamic acid / polyimide, diamine, liquid crystal alignment film

Description

Composition for liquid crystal alignment, liquid crystal alignment film prepared therefrom, and a liquid crystal display including the same.

The present invention relates to a liquid crystal display composition, a liquid crystal alignment film prepared therefrom, a method for manufacturing the same, and a liquid crystal display including the liquid crystal alignment film.

With the development of the display industry, liquid crystal displays provide low driving voltage, high resolution, reduction of monitor volume, and flattening of monitors.

In general, liquid crystal displays induce anisotropy by applying an organic film such as polyimide to two glass substrates and rubbing the surface with a cloth (rubbing), bonding the two substrates in a sandwich form, and then injecting liquid crystals and heat treatment. It includes a liquid crystal cell prepared by. However, in order to realize a good quality liquid crystal display, the liquid crystal should have a constant pre-tilt angle with respect to the surface of the alignment layer. In particular, in the TN (Twisted Nematic) and STN (Super Twisted Nematic) type liquid crystal display, which are widely used in recent years, a pretilt angle of 2 to 10 ° is required. Conventionally, in order to implement such a pretilt angle in a liquid crystal alignment layer, a link ring such as an ester group, an amide group, or an ether group having polarity in a side chain group is introduced.

However, the introduction of such a polarizing ring lowers the voltage holding ratio (VHR) of the liquid crystal display device, and also shows a poor result for the stability of the tilt angle, which is an important factor of long-term reliability.

In addition, a general liquid crystal alignment layer is a polyamic acid or polyimide is mixed or made of a single component, but some components often do not dissolve when re-dissolved using a certain solvent for the precipitated components due to low solubility or staining in the subsequent coating process There is.

Accordingly, the present invention is not only capable of exhibiting an excellent orientation state and realizing excellent pretilt angles, but also providing a liquid crystal alignment composition for preparing a liquid crystal alignment layer having excellent electrical properties such as solubility and voltage maintenance ratio (VHR), which is prepared from the An object of the present invention is to provide a liquid crystal alignment film, a method for manufacturing the same, and a liquid crystal display device including the liquid crystal alignment film.

The present invention provides a polyamic acid comprising a repeating unit represented by the following formula (1).

[Formula 1]

In Chemical Formula 1,

A represents a tetravalent organic group,

B is represented by the following formula (3),

n is an integer of 5 to 200.

The present invention also provides a polyimide comprising a repeating unit represented by the following formula (2).

[Formula 2]

In Chemical Formula 2,

D represents a tetravalent organic group,

E is represented by the following formula (3),

n is an integer of 5 to 200.

(3)

In Chemical Formula 3,

m is an integer from 1 to 11,

Preferably it is an integer of 2 or more.

The present invention provides a liquid crystal alignment composition comprising at least one of a polyamic acid containing a repeating unit represented by the formula (1) and a polyimide containing the repeating unit represented by the formula (2).

The present invention also provides a liquid crystal alignment film prepared from the liquid crystal alignment composition.

In addition, the present invention 1) applying the liquid crystal alignment composition on the surface of the substrate to form a coating film, 2) drying the solvent contained in the coating film, and 3) aligning the dried coating film surface It provides a method for producing a liquid crystal alignment film comprising a.

In addition, the present invention provides a liquid crystal display comprising the liquid crystal alignment film.

The liquid crystal alignment film prepared from the liquid crystal alignment composition according to the present invention not only exhibits an excellent alignment state and can implement excellent pretilt angle, but also excellent electrical properties such as solubility and voltage maintenance ratio (VHR).

Hereinafter, the present invention will be described in more detail.

The present invention provides a polyamic acid represented by Chemical Formula 1.

In another aspect, the present invention provides a polyimide represented by the formula (2).

The present invention provides a liquid crystal alignment composition comprising at least one of a polyamic acid containing a repeating unit represented by the formula (1) and a polyimide containing the repeating unit represented by the formula (2).

In Formula 1 and Formula 2, A and D are tetravalent organic groups, and are preferably selected from the group consisting of the following structural formulas.

Y ₁ , Y ₂ and Y ₃ are each independently or simultaneously a direct bond, -O-, -CO-, -S-, -SO _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -CONH,-(CH ₂ ) n _1- , -O (CH ₂ ) n ₂ O-, -COO (CH ₂ ) n ₃ OCO- and halogen,

Where n ₁ , n ₂ And n ₃ are each independently an integer of 1 to 5.

In Chemical Formulas 1 and 2, B and E are represented by the following Chemical Formula 3.

(3)

The structure of Formula 3 is connected to two different aromatic carbon, it characterized in that it comprises a quaternary carbon at the point where the ring structure starts.

M is an integer of 1-11, Preferably it is an integer of 2 or more.

When m is less than 1, the solubility is excellent, but the ring structure is too small to form a desired pretilt angle, and thus the image quality may be degraded when Tw (Twist Nematic) liquid crystals are driven. Because of the stability, the ring structure is folded, so the effect of improving the pretilt angle is not so great.

The polyamic acid and polyimide of the present invention include a group containing an aromatic and aliphatic ring structure represented by Formula 3 in the side chain, and is generally generated by introducing a long alkyl group into the side chain structure for application to a TN alignment layer. It improves the result of decreasing solubility by increasing hydrophobicity and free volume, showing excellent solubility, and due to stereochemistry with aromatic and aliphatic ring structure, proper pretilt angle required in TN (Twist Nematic) alignment layer It may represent, and may have electrical characteristics such as a voltage maintenance ratio (VHR).

The polyimide containing the repeating unit represented by Formula 2 may be prepared by imidizing a polyamic acid including the repeating unit represented by Formula 1.

By adding an acetic anhydride and a pyridine base to the polyamic acid solution by imidizing the polyamic acid, and then heated to a temperature of 50 to 100 ℃ imidized by a chemical reaction, or by applying a polyamic acid solution to the substrate, Thermal imidation may be performed on an oven or a hot plate at 100 ° C. to 250 ° C., but is not limited thereto.

The number average molecular weight (Mn) of the polyamic acid or polyimide is preferably 5,000 to 200,000 g / mol. When the molecular weight of the polyamic acid or polyimide is less than 5,000 g / mol, the coating properties are poor, and when the polyamic acid or polyimide exceeds 200,000 g / mol, it is difficult to implement a stable coating process because the viscosity is too high when preparing the coating solution.

The polyamic acid or polyimide according to the present invention may be prepared from a dianhydride compound represented by Formula 4 and a diamine compound represented by Formula 5 below. Other reaction conditions may use methods known in the art.

[Formula 4]

In Formula 4, X ₁ is the same as the definition of A in Formula 1.

[Chemical Formula 5]

Here, m is as defined in the formula (3).

Specifically, in the method for producing the polyamic acid or polyimide, at least one of the diamine compounds represented by the formula (5) is dissolved in a solvent, and at least one of the dianhydride compounds represented by the formula (4) is added to the solution. Can be prepared by reacting. The reaction of the diamine compound and dianhydride compound is preferably carried out at 0 to 5 ℃ for 12 to 36 hours. At this time, it is advantageous to mix the dianhydride compound and the diamine compound in a molar ratio of 1: 0.9 to 1: 1.1 to achieve desirable molecular weight, mechanical properties and viscosity.

The method for producing the polyamic acid or polyimide may be used by further adding other diamine compounds and dianhydride compounds in addition to the above-described types.

For example, the polyamic acid or polyimide according to the present invention is a polyamic acid comprising a repeating unit represented by the following formula (6) by additionally adding one or more diamine compounds in addition to the diamine compound represented by the formula (5) in the manufacturing method To provide a polyimide comprising a repeating unit represented by the formula (7), but is not limited to the following structure.

[Formula 6]

[Formula 7]

In Chemical Formulas 6 and 7,

A, B, D and E are as defined in Formula 1 and Formula 2,

It is preferable that n: k is 5: 95-50: 50 by molar ratio.

L ₁ and L ₂ are divalent organic groups, and are preferably selected from the group consisting of the following structural formulas.

Z ₁ , Z ₂ and Z ₃ are each independently or simultaneously a direct bond, -O-, -CO-, -S-, -SO _2- , -C (CH ₃ ) _2- , -CONH,-(CH ₂ ) m _1- , -O (CH ₂ ) m ₂ O-, -COO (CH ₂ ) m ₃ OCO-, -CONCO- and halogen, wherein m ₁ , m ₂ and m ₃ Are each independently an integer of 1 to 5.

The present invention also provides a liquid crystal alignment composition comprising at least one of the polyamic acid represented by the formula (1) and the polyimide represented by the formula (2).

In the liquid crystal alignment composition including the polyamic acid and the polyimide, the weight ratio of the polyamic acid and the polyimide is preferably 90:10 to 30:70.

The composition for liquid crystal alignment according to the present invention may be prepared by dissolving at least one of the polyamic acid and polyimide in a solvent.

Solid content concentration of the polyamic acid and / or polyimide is selected in consideration of the molecular weight, viscosity, volatility, and the like of the polyamic acid or polyimide represented by the formula (1) or (2), achieves the desired liquid crystal alignment effect, preferred coating properties In order to have an appropriate viscosity so as to have a preferably selected in the range of 1 to 20% by weight based on the total weight of the liquid crystal alignment composition.

The solvent includes cyclopentanone, cyclohexanone, N-methylpyrrolidone, DMF (Dimethylformamide), acetamide, gamma butyrolactone, or a mixture thereof, but is not limited thereto. .

In addition, solvents such as 2-butoxyethanol, ethylene glycol monoethyl ether acetate, ethylene glycol monoisopropyl ether or ethylene glycol monomethyl ether in order to avoid film thickness uniformity and printing defects after coating treatment Can be used in combination with the solvents exemplified above.

The temperature at the time of dissolving the said polyamic acid and / or polyimide in a solvent is 0-100 degreeC, More preferably, it is 15-70 degreeC.

The liquid crystal alignment composition according to the present invention may further include conventional solvents, additives, polyimides, or polyamic acids known in the art.

The present invention also provides a liquid crystal alignment film prepared from the liquid crystal alignment composition.

Method for producing a liquid crystal alignment film according to the present invention,

1) coating the liquid crystal alignment composition on the surface of the substrate to form a coating film,

2) drying the solvent contained in the coating film, and

3) orientation treatment of the dried coating film surface

It includes.

The composition for liquid crystal alignment of step 1) may be applied onto the surface of the substrate formed by patterning a transparent conductive film or a metal electrode using a method such as a roll coater method, a spinner method, a printing method, an inkjet spraying method, or a slit nozzle method. .

In addition, at the time of application | coating of the composition for liquid crystal aligning, in order to further improve adhesiveness with the surface of a board | substrate, a transparent conductive film, and a metal electrode, a functional silane containing compound, a functional fluoro containing compound, or a functional titanium containing compound is previously board | substrate. It may be applied to.

In the step 2), the drying may be performed by heating the coating or vacuum evaporation.

In the step 2), the drying of the solvent is carried out for 10 to 60 minutes at 100 to 300 ℃, preferably 170 to 250 ℃ in the case of a liquid crystal alignment composition comprising a polyamic acid and at the same time to imidize the polyamic acid It may be dried, and in the case of a liquid crystal alignment composition including polyimide, it may be performed at 100 to 300 ° C., preferably at 170 to 230 ° C. for 10 to 60 minutes.

In step 3), an alignment capability for orienting the liquid crystal molecules may be imparted to the coating film by physically contacting the rubbing fiber such as nylon or rayon to the dried coating film obtained in step 2).

It is preferable that the film thickness of the final coating film formed by such a series of processes is 50-200 nm, and in order to play a role in a display apparatus, the range of 70-150 nm is more preferable.

After the above-described process, it is possible to obtain a liquid crystal alignment film having a liquid crystal alignment ability stable to external thermal, physical, and chemical impact.

In addition, the present invention provides a liquid crystal display comprising the liquid crystal alignment film.

The liquid crystal display can be manufactured according to conventional methods known in the art. For one embodiment thereof, one of the two glass substrates with the photoreaction with the liquid crystal alignment layer according to the present invention is applied to the end of the glass substrate by applying a photoreactive adhesive containing a ball spacer to the other one, The glass substrates are bonded together, and only the portion to which the adhesive is applied is irradiated with ultraviolet rays to bond the cells. After the liquid crystal is injected into the completed cell and heat treated, the liquid crystal cell is completed.

In fact, the liquid crystal display of the present invention having the liquid crystal alignment film In addition to exhibiting excellent orientation and excellent pretilt angle, electrical characteristics such as voltage holding ratio (VHR) are also excellent. In particular, the liquid crystal alignment film according to the present invention is preferably used as a TN type liquid crystal display alignment film by showing a pretilt angle suitable for TN (Twisted Nematic) type liquid crystal display rather than IPS type and VA type liquid crystal display.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are merely provided to more easily understand the present invention, and the scope of the present invention is not limited thereto.

Manufacturing example  One: Diamine Monomeric  synthesis

After reacting the aliphatic ketone as described above with an excess of aniline and aniline HCl salt at 120 ^° C. for 18 hours, the desired compound was separated using a column separation tube, and then DA-BCy10 (m = 5) and DA-BCy12 (m = 7). ) And DA-BCy16 (m = 11). Each of the DA-BCy10 (m = 5), DA-BCy12 (m = 7) and DA-BCy16 (m = 11) compounds prepared above was identified using ¹ H and ¹³ C NMR.

DA-BCy10: ¹ H NMR δ 0.85 2H, δ 1.19-1.31 17H, δ 4.74 4H, δ 6.41 4H, δ 6.75 4H

DA-BCy12: ¹ H NMR δ 0.85 2H, δ 1.19-1.31 21H, δ 4.74 4H, δ 6.41 4H, δ 6.75 4H

DA-BCy16: ¹ H NMR δ 0.85 2H, δ 1.19-1.31 29H, δ 4.74 4H, δ 6.41 4H, δ 6.75 4H

Example  One : Polyamic acid  Preparation of Resin and Liquid Crystal Alignment Composition

7.6 g (80 mmol) of methylene diamine (MDA) and 1 g (10 mmol) of para-phenylene diamine (p-PDA) and 1 g (10 mmol) of DA-BCy12 prepared in the above were dissolved in 390 g of NMP at room temperature. 16.4 g (70 mmol) of cyclobutanetetracarboxylic dianhydride (CBDA) and 7.8 g (30 mmol) of pyromellitic dianhydride (PMDA) were added thereto, followed by stirring at room temperature for 12 hours to prepare a polyamic acid resin.

NMP 44 g and 39 g of 2-butoxyethanol were added to and diluted with the obtained polyamic acid resin, and then passed through a 0.2 mm filter to remove impurities to prepare a liquid crystal alignment composition.

As a result of confirming the molecular weight of the filtered polyamic acid resin through GPC, the number average molecular weight (Mn) was 32,000 and the weight average molecular weight (Mw) was 49,000.

Example  2 : Preparation of Polyimide Resin and Liquid Crystal Alignment Composition

61 g of acetic anhydride and 28 g of pyridine were added to the polyamic acid prepared in Example 1 and reacted at 50 ^° C. for 3 hours. It was dropped in methanol to precipitate and filtered to obtain a yellow polyimide resin. This was dissolved in 12.5 g of NMP and 3.13 g of 2-butoxy ethanol and passed through a 0.2 mm filter to prepare a composition for liquid crystal alignment of 6 wt%.

Example  3 : Polyamic acid  Preparation of Resin and Liquid Crystal Alignment Composition

Polyamic acid was prepared in the same manner as in Example 1, except that 1 g of DA-BCy10 was used instead of DA-BCy12.

NMP 44 g and 39 g of 2-butoxyethanol were added to and diluted with the obtained polyamic acid resin, and then passed through a 0.2 mm filter to remove impurities to prepare a liquid crystal alignment composition.

As a result of confirming the molecular weight of the filtered polyamic acid resin through GPC, the number average molecular weight (Mn) was 28,000, the weight average molecular weight (Mw) was 36,000.

Example  4 : Preparation of Polyimide Resin and Liquid Crystal Alignment Composition

61 g of acetic anhydride and 28 g of pyridine were added to the polyamic acid prepared in Example 3 and reacted at 50 ^° C. for 3 hours. It was dropped in methanol to precipitate and filtered to obtain a yellow polyimide resin. This was dissolved in 12.5 g of NMP and 3.13 g of 2-butoxy ethanol and passed through a 0.2 mm filter to prepare a composition for liquid crystal alignment of 6 wt%.

Example  5 : Polyamic acid  Preparation of Resin and Liquid Crystal Alignment Composition

Polyamic acid was prepared in the same manner as in Example 1, except that 1 g of DA-BCy16 was used instead of DA-BCy12.

NMP 44 g and 39 g of 2-butoxyethanol were added to and diluted with the obtained polyamic acid resin, and then passed through a 0.2 mm filter to remove impurities to prepare a liquid crystal alignment composition.

As a result of confirming the molecular weight of the filtered polyamic acid resin through GPC, the number average molecular weight (Mn) was 30,500 and the weight average molecular weight (Mw) was 42,100.

Example  6 : Preparation of Polyimide Resin and Liquid Crystal Alignment Composition

61 g of acetic anhydride and 28 g of pyridine were added to the polyamic acid prepared in Example 5 and reacted at 50 ^° C. for 3 hours. It was dropped in methanol to precipitate and filtered to obtain a yellow polyimide resin. This was dissolved in 12.5 g of NMP and 3.13 g of 2-butoxy ethanol and passed through a 0.2 mm filter to prepare a composition for liquid crystal alignment of 6 wt%.

Comparative Production Example  One : Diamine  Preparation of the compound DA - EsC12 )

Comparative Production Example  2 : Diamine  Preparation of the compound DA - EsbPh )

Comparative example  One : Polyamic acid  Preparation of Resin and Composition for Liquid Crystal Alignment

7.6 g (80 mmol) of methylene diamine (MDA) and 1 g (10 mmol) of para-phenylene diamine (p-PDA) and 3.2 g (10 mmol) of DA-EsC12 prepared in Comparative Preparation Example 1 were added to 390 g of NMP. After melting at room temperature, 16.4 g (70 mmol) of cyclobutanetetracarboxylic dianhydride (CBDA) and 7.8 g (30 mmol) of pyromellitic dianhydride (PMDA) were added thereto, followed by stirring at room temperature for 12 hours to prepare a polyamic acid resin. Prepared.

NMP 44 g and 39 g of 2-butoxyethanol were added to and diluted with the obtained polyamic acid resin, and then passed through a 0.2 mm filter to remove impurities to prepare a liquid crystal alignment composition.

The molecular weight of the filtered polyamic acid resin was confirmed by GPC, and the number average molecular weight (Mn) was 33,500 and the weight average molecular weight (Mw) was 47,000.

Comparative example  2 : Preparation of Polyimide Resin and Preparation of Liquid Crystal Alignment Composition

61 g of acetic anhydride and 28 g of pyridine were added to the polyamic acid prepared in Comparative Example 1 and reacted at 50 ^° C. for 3 hours. It was dropped in methanol to precipitate and filtered to obtain a yellow polyimide resin. This was dissolved in 12.5 g of NMP and 3.13 g of 2-butoxy ethanol, and then passed through a 0.2 mm filter to prepare a composition for liquid crystal alignment of 6 wt%.

Comparative example  3 : Polyamic acid  Preparation of Resin and Composition for Liquid Crystal Alignment

A polyamic acid was prepared in the same manner as in Example 1, except that DA-Es-bPh 3.0g prepared in Comparative Preparation Example 2 was used instead of DA-EsC12 in Example 1.

NMP 44 g and 39 g of 2-butoxyethanol were added to and diluted with the obtained polyamic acid resin, and then passed through a 0.2 mm filter to remove impurities to prepare a liquid crystal alignment composition.

As a result of confirming the molecular weight of the filtered polyamic acid resin through GPC, the number average molecular weight (Mn) was 33,500 and the weight average molecular weight (Mw) was 46,100.

Comparative example  4 : Preparation of Polyimide Resin and Preparation of Liquid Crystal Alignment Composition

61 g of acetic anhydride and 28 g of pyridine were added to the polyamic acid prepared in Comparative Example 3 and reacted at 50 ^° C. for 3 hours. It was dropped in methanol to precipitate and filtered to obtain a yellow polyimide resin. This was dissolved in 12.5 g of NMP and 3.13 g of 2-butoxy ethanol and passed through a 0.2 mm filter to prepare a composition for liquid crystal alignment of 6 wt%.

Experimental Example

Examples 1 to 6 above And liquid crystal alignment characteristics of the liquid crystal alignment composition prepared in Comparative Examples 1 to 4 was carried out as follows. The liquid crystal alignment composition was spin-coated on an ITO glass substrate, and then heated at 100 ° C. for 2 minutes and at 230 ° C. for 60 minutes to obtain a polyimide thin film having a thickness of 70 to 100 nm, which was rubbed using a cylindrical roll wound with a rayon cloth. . After rubbing the two glass substrates are placed in parallel with each other in the rubbing direction, they are bonded together using a UV curing agent impregnated with a 4.5 mm ball space, and then a nematic liquid crystal is injected into the cell to form a liquid crystal cell. Prepared.

Cell orientation characteristic evaluation

The cell orientation characteristic was judged to be good if the obtained cell was not unbalanced in orientation through visual observation and polarization microscopy under a polarization system. The results are shown in Table 1 below.

Pretilt  bracket( pre - tilt angle )

In the pretilt angle measurement, the pretilt angle of the obtained liquid crystal cell was measured by a crystal rotation method. The results are shown in Table 1 below.

Solubility Assessment

Solubility evaluation was carried out to precipitate the polyamic acid or polyimide prepared in methanol to obtain a solid content, and then the solid content was again added to a polar solvent (NMP, DMAc (dimethyl acetamide), GBL (gamma-butyrolactone) used as an alignment layer solvent. Dissolving was used The results of the evaluation observed with the naked eye are shown in Table 1 below.

Electrical property evaluation

Electrical characteristics were evaluated by measuring the voltage holding ratio (VHR). Voltage retention ratio was measured after applying a voltage of 5V, 60 Hz at room temperature and high temperature (60 ℃) conditions. The results are shown in Table 1 below.

 [Table 1]

Claims (15)

Polyamic acid containing a repeating unit represented by the formula (1); [Formula 1]

In Chemical Formula 1, A represents a tetravalent organic group, B is represented by the following formula (3), n is an integer from 5 to 200, (3)

In Chemical Formula 3, m is an integer of 2-11. The polyamic acid of claim 1, wherein A in Formula 1 is selected from the group consisting of the following structural formulas;

Y ₁ and Y ₂ are each independently or simultaneously a direct bond, -O-, -CO-, -S-, -SO _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -CONH,-(CH ₂ ) n _1- , -O (CH ₂ ) n ₂ O-, -COO (CH ₂ ) n ₃ OCO- and halogen, Here, n ₁ , n ₂ and n ₃ are each independently an integer of 1 to 5. The method according to claim 1, wherein the polyamic acid is a polyamic acid, characterized in that the compound containing a repeating unit represented by the formula (6); [Formula 6]

In Chemical Formula 6, A is a tetravalent organic group, It is selected from the group which consists of following structural formulas,

B is represented by the following formula (3), (3)

In Chemical Formula 3, m is an integer from 2 to 11, n: k is 5:95 to 50:50 in molar ratio, L ₁ is a divalent organic group, and is selected from the group consisting of the following structural formulas,

Z ₁ , Z ₂ and Z ₃ are each independently or simultaneously a direct bond, -O-, -CO-, -S-, -SO _2- , -C (CH ₃ ) _2- , -CONH,-(CH ₂ ) m _1- , -O (CH ₂ ) m ₂ O-, -COO (CH ₂ ) m ₃ OCO-, -CONCO- and halogen, wherein m ₁ , m ₂ and m ₃ Are each independently an integer of 1 to 5. Polyimide containing a repeating unit represented by the formula (2); [Formula 2]

In Chemical Formula 2, D represents a tetravalent organic group, E is represented by the following formula (3), n is an integer from 5 to 200, (3)

In Chemical Formula 3, m is an integer of 2-11. The polyimide of claim 4, wherein D in Formula 2 is selected from the group consisting of the following structural formulas;

Y ₁ and Y ₂ are each independently or simultaneously a direct bond, -O-, -CO-, -S-, -SO _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -CONH,-(CH ₂ ) n _1- , -O (CH ₂ ) n ₂ O-, -COO (CH ₂ ) n ₃ OCO- and halogen, Here, n ₁ , n ₂ and n ₃ are each independently an integer of 1 to 5. The method according to claim 4, wherein the polyimide is a polyimide, characterized in that the compound containing a repeating unit represented by the formula (7); [Formula 7]

In Chemical Formula 7, D is a tetravalent organic group, and is selected from the group consisting of the following structural formulas,

E is represented by the following formula (3), (3)

In Chemical Formula 3, m is an integer from 2 to 11, n: k is 5:95 to 50:50 in molar ratio, L ₂ is a divalent organic group, and is selected from the group consisting of the following structural formulas,

Z ₁ , Z ₂ and Z ₃ are each independently or simultaneously a direct bond, -O-, -CO-, -S-, -SO _2- , -C (CH ₃ ) _2- , -CONH,-(CH ₂ ) m _1- , -O (CH ₂ ) m ₂ O-, -COO (CH ₂ ) m ₃ OCO-, -CONCO- and halogen, wherein m ₁ , m ₂ and m ₃ Are each independently an integer of 1 to 5. A composition for liquid crystal alignment comprising at least one of a polyamic acid including a repeating unit represented by Formula 1 and a polyimide including a repeating unit represented by Formula 2 below; [Formula 1]

[Formula 2]

In Chemical Formula 1 and Chemical Formula 2, A and D represent tetravalent organic groups, B and E are represented by the following formula (3), n is an integer from 5 to 200, (3)

In Chemical Formula 3, m is an integer of 1-11. The liquid crystal alignment composition of claim 7, wherein A and D of Formula 1 and Formula 2 are selected from the group consisting of the following structural formulas;

Y ₁ and Y ₂ are each independently or simultaneously a direct bond, -O-, -CO-, -S-, -SO _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -CONH, -CCH ₂ ) n _1- , -O (CH ₂ ) n ₂ O-, -COO (CH ₂ ) n ₃ OCO- and halogen; Where n ₁ , n ₂ And n ₃ are each independently an integer of 1 to 5. The liquid crystal alignment composition of claim 7, wherein the polyamic acid or polyimide has a number average molecular weight of 5,000 to 200,000 g / mol. The liquid crystal alignment composition of claim 7, wherein the solid content concentration of the polyamic acid and / or polyimide is 1 to 20 wt% based on the total weight of the liquid crystal alignment composition. The liquid crystal alignment composition of claim 7, wherein a weight ratio of the polyamic acid and the polyimide is 90:10 to 30:70. 1) forming a coating film by applying the liquid crystal alignment composition of any one of claims 7 to 11 on the substrate surface, 2) drying the solvent contained in the coating film, and 3) orientation treatment of the dried coating film surface Method for producing a liquid crystal alignment film comprising a. A liquid crystal alignment film containing the polyimide of the formula (2). [Formula 2]

In Chemical Formula 2, D represents a tetravalent organic group, E represents a divalent organic group, includes a group represented by the following formula (3), n is an integer from 5 to 200, (3)

In Chemical Formula 3, m is an integer of 1-11. The liquid crystal alignment film of claim 13, wherein the liquid crystal alignment film has a thickness of 50 to 200 nm. A liquid crystal display comprising the liquid crystal alignment film of claim 13.