MXPA97010081A

MXPA97010081A - Optical alignment composition, alignment coat that uses the same and liquid crystal screen that keeps the alineac layer

Info

Publication number: MXPA97010081A
Application number: MXPA/A/1997/010081A
Authority: MX
Inventors: Yu Hansung; Yu Seonghan
Original assignee: Samsung Display Devices Co Ltd
Priority date: 1996-12-13
Filing date: 1997-12-11
Publication date: 1999-01-11

Abstract

An optical alignment composition is described which includes a first polymer selected from a polymer of the cinnamate series and a polymer from the coumarin series and a second polymer selected from a polyimide having a long chain alkyl group on its side chains and polyimide having an alkyl group at both ends, an alignment layer formed by using it, and a liquid crystal screen having the alignment layer. According to the present invention, the thermal stability of the alignment layer and the characteristic pre-inclination angle of the liquid crystal are improved.

Description

COMPOSITION OF OPTICAL ALIGNMENT, ALIGNMENT LAYER USING THE SAME AND LIQUID CRYSTAL DISPLAY WHICH HAS THE ALIGNMENT LAYER BACKGROUND OF THE INVENTION Field of the invention The present invention relates to a liquid crystal display (LCD) and more particularly to an optical alignment composition containing a first polymer selected from a polymer of the cinnamate series and a polymer from the coumarin series and a second polymer selected from polyimide having a long chain alkyl group on its side chains and polyimide having an alkyl group on both of its ends, an alignment layer formed by using the optical alignment composition and a liquid crystal display having the alignment layer.

Description of the related art. In general, as shown in Figure 1, an LCD has a pair of upper and lower substrates 2 and 2 'spaced apart from each other and opposed to each other. Transparent electrode layers 3 and 3 'are formed on the upper and lower substrates 2 and 2'. Insulating layers 4 and 4 'and alignment layers 5 and 5' are formed sequentially on the transparent electrodes 3 and 3 '. A liquid crystal layer 7 is formed in the space between the upper and lower substrates 2 and 2 '. Polarization plates 1 and 1 'are provided to polarize incoming light and transmission light to the outside of substrates 2 and 2' respectively. REF: 26459 In the LCD that has the structure mentioned above, according to an externally applied voltage, the arrangement of the liquid crystals influenced by the electric field is changed. According to the changed arrangement, the external light introduced to the LCD is shielded or transmitted. The LCD is controlled or activated by such property. In other words, if a voltage is applied to the transparent electrode layers 3 and 3 ', an electric field is formed in the liquid crystal layer 7. Thus, the liquid crystals are driven or controlled in a predetermined direction. The light introduced to the liquid crystals of the LCD is shielded or transmitted according to the activation of the liquid crystals. The functions of the LCD as a visual representation device, this is light transmittance, response time, viewing angle or contrast, are determined by the arrangement characteristics of the liquid crystal molecules. Therefore, a technology to control the alignment of liquid crystal molecules evenly is a very important factor. The state of uniform alignment of the liquid crystals is difficult to carry out only by interposing the liquid crystals between the upper and lower substrates. Thus, as shown in Figure 1, it is a general form the formation of alignment layers 5 and 5 'to align the liquid crystals on the transparent electrode layers 3 and 3'. The alignment layer is conventionally formed by a rubbing method, in which a thin film, made of an organic polymeric material, such as polyimide or polyamide, is cured and then rubbed with a special fabric.

The method of rubbing is easy to carry out and the process of it is simple. However, materials or small particles such as cellulose can be separated from the fabric used in the rubbing treatment to contaminate the alignment layer. In addition, depending on the material to form the alignment layer, the alignment can not be carried out uniformly. A thin film transistor can be damaged by the static electricity generated during the rubbing treatment. To solve the problems described above, an optical alignment technology has been developed, in which dust, static electricity or other contaminating particles are not generated and cleaning is maintained during the total process. According to such non-destructive alignment method, the polarized light is irradiated on the optical alignment layer, to cause the anisotropic photopolymerization. As a result, the optical alignment layer has an alignment feature, to uniformly align the liquid crystals. The polymer for the optical alignment layer includes polyvinyl carbamate (PVCN) and polyvinylmethoxycinnamate (PVMC). However such polymers have poor thermal stability, although they have excellent optical alignment property. In other words, the thermal stability of an alignment layer depends on the polymer, which depends on a vitreous transmission temperature and the crosslink density. Since the PVCN or the PVMC have a vitreous transition temperature of about 100 ° C or less, in such a way that the post-alignment thermal stability is decreased. Furthermore, it is difficult to form a pre-inclination angle due to a symmetrical structure obtained after the cross-linking reaction.

BRIEF DESCRIPTION OF THE INVENTION To solve the above problem (s), it is an object of the present invention to provide an optical alignment composition having excellent thermal stability and an excellent pre-tilt angle characteristic. It is another object of the present invention to provide an alignment layer formed by using the optical alignment composition. It is still another object of the present invention to provide a liquid crystal display (LCD) having the alignment layer. Therefore to achieve the first object there is provided an optical alignment composition that includes a first polymer, selected from a polymer of the vinylcinnamate series and a polymer from the coumarin series and a second polymer selected from polyimide having an alkyl group (R) in both of its ends and polyimide represented by the formula (1): wherein Ri is selected from the group consisting of cycloalkyl of three to ten (C3-C10) carbon atoms, a cycloalkyl having at least one substituent (G), cycloalkenyl of three to ten (C3-C10) carbon atoms , a cycloalkenyl having at least one substituent and a compound of formula AYB [herein, A and B are each independently selected from the group consisting of an unsubstituted aromatic ring and an aromatic ring (in present, the aromatic ring is a monocyclic ring of six carbon atoms, a bicyclic ring of ten carbon atoms or a tricyclic ring of fourteen carbon atoms) and Y is -O-, carbonyl (C = 0) or -C (R4) (Rd) - (in the present R4 and R5 are each independently selected from the group consisting of hydrogen, alkyl of one to ten carbon atoms and alkyl of one to ten carbon atoms having at least one substituent (G))]; R2 is selected from the group consisting of an unsubstituted aromatic ring, aromatic ring having at least one substituent (G) (herein, the aromatic ring is a monocyclic ring of six carbon atoms, a bicyclic ring of ten atoms carbon or a tricyclic ring of fourteen carbon atoms), a cycloalkyl of three to ten carbon atoms, a cycloalkyl of three to ten carbon atoms having at least one substituent (G), a cycloalkenyl of three to ten atoms of carbon, a cycloalkenyl of three to ten carbon atoms having at least one substituent (G) and a compound having the formula AYB (in the present A, B and Y are as defined above); X1 represents -COO-, -O- or -OCO-; and R3 is an alkyl of three to ten carbon atoms (herein the substituent (G) is selected from the group consisting of alkyl of one to ten carbon atoms, an unsubstituted or substituted aromatic amino, a halide, hydroxyl ( OH), nitro (NO2), cyano (CN), thiocyano (SCN), thiol (SH) and carboxyl (COOH), and mi: m2 is from 1:99 to 20: 80 and mi is a positive integer in which Zero is included Polyimide having an alkyl at both ends is selected from the compounds represented by formula (2): wherein Ri is as defined above, R 4 is selected from the group consisting of an unsubstituted aromatic ring, an aromatic ring having at least one substituent (G) (herein, the aromatic ring is a monocyclic ring of six carbon atoms, a bicyclic ring of ten carbon atoms or a tricyclic ring of fourteen carbon atoms), a cycloalkyl of three to ten carbon atoms, a cycloalkyl of three to ten carbon atoms having at least one substituent ( G), a cycloalkenyl of three to ten carbon atoms, a cycloalkenyl of three to ten carbon atoms having at least one substituent (G) and a compound having the formula A and B (in the present A, B and Y are as defined above), (herein, the substituent (G) is selected from the group consisting of an alkyl of one to ten carbon atoms, an unsubstituted or substituted aromatic amino, a halide, a hydroxyl (OH), a nitro (N02), cyano (CN), thiocyano (SCN), thiol (SH) and carboxyl (COOH), m2 is an integer of 10 at 100 and n2 is an integer from 2 to 9. The second object of the present invention is obtained by an alignment layer including a first polymer selected from a polymer of the cinnamate series and a polymer from the coumarin series and a second polymer selected from polyimide having an alkyl group (R) at both ends thereof and polyimide represented by formula (1). The third object of the present invention is obtained by an LCD having the alignment layer that includes a first polymer selected from a polymer of the cinnamate series and a polymer of the coumarin series and a second polymer selected from polyimide having an alkyl group (R) at both ends thereof and the polyimide represented by the formula (1).

BRIEF DESCRIPTION OF THE DRAWING The above objects and advantages of the present invention will become more apparent when describing in detail a preferred embodiment thereof with reference to the accompanying drawing in which: Figure 1 is a sectional view of a liquid crystal display in general.

Description of preferred embodiments In the polyimide of formula (1), Ri is preferably selected from the group consisting of: yx? jj, and R selects preferably from the group consisting of: (Here, R3 is an alkyl of three to twenty carbon atoms and is preferably a long chain alkyl of eight to twelve carbon atoms, which is advantageous in the formation of a desired pre-inclination angle). In the polyimide of formula (2), Ri is as defined above, R 4 is selected from the group consisting of: and n2 is an integer from 2 to 9. The present invention is characterized by using an optical alignment composition produced by mixing a heat resistant polyimide having an alkyl group in its extreme or side chain, with a conventional polymer of the series of cinnamate or polymer of the coumarin series, to thereby improve the thermal stability of the alignment and improve a pre-inclination angle by the interaction between the introduced alkyl group and the liquid crystals. In the present invention, it is preferable that the weight ratio of a first polymer selected from a polymer of the cinnamate series and a polymer of the coumarin series, to a second polymer selected from polyimide, having an alkyl group (R) at both ends thereof and the polyimide of formula (1) is between 99: 1 and 80: 20, which is because the optical alignment and thermal stability are superior within this range. The weight average molecular weight of the polyimide represented by the formulas (1) and (2) is from 5x103 to 5x10. The polymer of the cinnamate series series is preferably selected from polyvinylcinnamate, polyvinylmethoxycinnamate and polyimide having a cinnamate group in its side chain and the weight average molecular weight thereof is preferably between 5x103 and 5x105 The polymer of the The coumarin series is preferably selected from the polymers represented by the formulas 3 to 5 and has a portion of coumarin in its side chain and the weight average molecular weight thereof is preferably between 5x103 to 5x105. (5) wherein k is an integer from 20 to 2000. Hereinafter, the methods of manufacturing an optical alignment composition, an alignment layer using it and an LCD (liquid crystal display) having the alignment layer according to the present invention. First we will explain the method to produce the polyimide of formula (1 ). Acid anhydride (A) and a diamine compound (B) are reacted to synthesize a polyamic acid (C). Then the polyamic acid (C) is imidized to synthesize a polyimide (D). [Reaction scheme (1)] The polyimide (D) and the alkyl halide (E) are reacted to synthesize polyimide (F) having an alkyl group on its side chain. At this time, if excess alkyl halide is used, the polyimide having a 100% substitution ratio in the alkyl group, that is, the polyimide where m is zero in the formula (1), can be synthesized. [Reaction scheme (2)] wherein X is selected from the group consisting of chloride (Cl), bromide (Br) iodide (I) and Re is selected from the group consisting of: The soluble polyimide having an alkyl group at its polymeric end is synthesized in the following manner. Acid anhydride (A), a diamide compound (B) and solvent are mixed and 1 to 10% mole of alkylamine is added to the mixture, based on the weight of the acid anhydride. The resulting product is reacted to synthesize a polyamic acid (C) at a temperature of 0 ° C to 25 ° C. Then the polyamic acid (C) is imidized to synthesize the soluble polyimide (G). [Reaction scheme (3)] ÍC) (OR) A polymer selected from polyimide (F) and polyimide (G), produced in the manner described above and a polymer selected from a polymer of the cinnamate series and a polymer from the coumarin series are mixed in a weight ratio of 1 : 99 and 20:80 and mixed with an appropriate solvent to form an optical alignment composition. At this time, the solvent used is N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMA) or methyl cellosolve. The compositions are coated on two glass substrates and then the solvent is dried to form an alignment layer.

Subsequently, linear polarized light (wavelength 300-400 nm) is irradiated to perform a photoreaction. Then, the two substrates are sealed with a predetermined space that is maintained when using a separator, to thereby form an empty cell. After this liquid crystals are injected into the empty cell to complete an LCD. Hereinafter, the present invention will be described with reference to various embodiments, but the invention is not limited thereto.

Example 1 3,3 ', 4,4'-benzophenone tetracarboxylic acid (H) and 3,5-diaminobenzoic acid (I) are reacted to synthesize a compound (J) and then the compound (J) is dehydrated to obtain a compound (K). [Reaction scheme (4)] (H) (I) (J) The compound (K) is reacted with propyl bromide and pyridine to obtain a polyimide (L). [Reaction scheme (5)] 0. 02 g. of the polyimide (L) and 0.18 g. of polyvinylcinnamate are dissolved in 10 g of NMP. Then, the resulting product is coated by centrifugation on two glass substrates and dried at a temperature of about 100 ° C for 1 hour to form an alignment layer. Then linear polarized light (wavelength: approximately 300 - 400 nm) is irradiated to the alignment layer, a lamp is used of high pressure mercury having a light intensity of about 10 mw-cm2 to perform a photoreaction for about 5 min. An empty cell is fabricated by sealing two glass substrates, where the alignment layer is formed. An LCD is completed by injecting liquid crystals into the empty cell.

Example 2 With the exception of octyl bromide which is used in place of propyl bromide, the same process is carried out as described in example 1.

Example 3 With the exception of dodecyium bromide which is used in place of propyl bromide, the same process is carried out as described in example 1.

Example 4 3. 22 g of 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride and 1.80 g of 4,4'-diaminodiphenyl ether are mixed in NMP and then 0.28 g of undecylamine (CH 3 (CH 2)? oNH2) to synthesize a polyamic acid through a series of reactions. Subsequently, the polyamic acid is dehydrated to obtain a polyimide. Then, 0.02 g of the polyimide are mixed with 0.18 g. of polyvinylcinnamate (Aldrichi Chemical Company Inc.) and 10 g of NMP to form an alignment composition, which is then adjusted, such that it has a suitable viscosity and then coated by centrifugation on two glass substrates, wherein an ITO electrode layer is respectively coated. Subsequently, the resulting product is dried at a temperature of about 100 ° C for 1 hour to form an alignment layer. Then linear polarized light of approximately 300-400 nm wavelength is irradiated to the alignment layer, to perform a photoreaction for about 5 minutes. An empty cell is produced by sealing the two obtained glass substrates, while maintaining the space of a predetermined width between two glass substrates when using a separator. An LCD is completed by injecting liquid crystals into the empty cell.

Example 5 With the exception that 0.04 g of polyimide manufactured in example 1 and 0.16 g of polyvinylcinnamate are used, an LCD is manufactured in the same manner as described in example 1.

Comparative Example With the exception that 0.2 g of polyvinylcinnamate (Aldrichi Chemical Company Inc.) and 10 g of NMP are used as the optical alignment composition, an LCD is manufactured in the same manner as described in example 1. In the LCD produced in examples 1-5 and the comparative example, the pre-inclination angle of the liquid crystal and the thermal stability of the alignment layer are measured. In the present, the pre-inclination angle was measured at using a method of crystal rotation and thermal stability was measured by raising the temperature to 180 ° C, while maintaining the resulting product as it is for a predetermined time at that temperature, decreasing the temperature to the temperature environment and then the state of the alignment layer is inspected, depending on the change in temperatures through a polarization film. As a result of the measurement, in the LCD manufactured according to example 1-5, considering the fact that the alignment state of the alignment layer was not changed even when the temperature was increased to 180 ° C, it is appreciated that the Thermal stability was very excellent. Also, the pre-inclination angle of the liquid crystal was increased to 15 °. Specifically, as in the cases of Examples 2 and 3, where a polymer having a long chain alkyl group was used, the pre-inclination angle was improved more markedly. However, in the case of the LCD manufactured according to the comparative example, the alignment property was excellent, but the thermal stability was poor, that is, the alignment layer was deformed at a temperature of approximately 70 ° C and the angle of pre-inclination was approximately 0o. According to the present invention, the thermal stability of the alignment layer and the characteristic of the pre-inclination angle of the liquid crystal are improved. It is noted that, in relation to this date, the best method known to the applicant, to carry out the aforementioned invention is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following

Claims

Claims 1. An optical alignment composition characterized in that it comprises a first polymer selected from a polymer of the cinnamate series and a polymer from the coumarin series and a second polymer selected from polyi having an alkyl (R) group on both of its ends and polyi represented by the formula (1): wherein Ri is selected from the group consisting of C3-C10, wherein R1 is selected from the group consisting of 3 to 10 carbon atoms, a cycloalkyl having at least one substituent (G), 3-adoalkenyl 10 carbon atoms, a cycloalkenyl having at least one substituent and a compound of formula AYB [in present A and B are each independently selected from the group consisting of an unsubstituted aromatic ring and an aromatic ring (here, the aromatic ring is a monocyclic ring of six carbon atoms, a bicyclic ring of ten carbon atoms or a tricyclic ring of fourteen carbon atoms) and Y is -O, carbonyl (C = O) or - C (R4) (R5) - (here, R and R5 are each independently selected from the group consisting of hydrogen, alkyl of 1 to 10 carbon atoms and alkyl of 1 to 10 carbon atoms which has at least one substituent (G))]; R2 is selected from the group consisting of an unsubstituted aromatic ring, aromatic ring having at least one substituent (G) (herein, the aromatic ring is a monocyclic ring of six carbon atoms) carbon, a bicyclic ring of ten carbon atoms or a tricyclic ring of fourteen carbon atoms), a cycloalkyl of 3 to 10 carbon atoms, a cycloalkyl of 3 to 10 carbon atoms having at least one substituent (G) , a cycloalkenyl of 3 to 10 carbon atoms, a cloalkenyl of 3 to 10 carbon atoms having at least one substituent (G) and a compound having the formula A and B (in the present, A, B and Y are as are defined above); Xi represents -COO-, -O-, or -OCO-; and R3 is an alkyl of 3 to 10 carbon atoms (herein, the substituent (G) is selected from the group consisting of alkyl of 1 to 10 carbon atoms, an unsubstituted or substituted aromatic amino, a halide, hydroxyl (OH), nitro (N02), cyano (CN), thiocyano (SCN), thiol (SH) and carboxyl (COOH), and m1: n2 is from 1:99 to 20:80 and m ^ is a positive integer in which includes the zero.
2. The optical alignment composition according to claim 1, characterized in that the polyi having an alkyl group at both ends thereof is selected from the compounds represented by the formula (2): (2) wherein R1 is as defined in claim 1, R4 is selected from the group consisting of an unsubstituted aromatic ring, an aromatic ring having at least one substituent (G) (herein, the aromatic ring is a monocyclic ring of six carbon atoms, a bicyclic ring of ten atoms carbon or a tricyclic ring of fourteen carbon atoms), a cidoalkyl of 3 to 10 carbon atoms, a cycloalkyl of 3 to 10 carbon atoms having at least one substituent (G), a cydoalkenyl of 3 to 10 carbon atoms, carbon, a cycloalkenyl of 3 to 10 carbon atoms having at least one substituent (G) and a compound having the formula A and B (herein, A, B and Y are as defined above), (herein the substituent (G) is selected from the group consisting of an alkyl of 1 to 10 carbon atoms, an unsubstituted or substituted aromatic amino, a halide, a hydroxyl (OH), a nitro (N02), cyano (CN), thiocyano (SCN), thiol (SH) and carboxyl groups (COOH)), m2 is an integer from 10 to 100 and m2 n2 is an integer from 2 to 9.
3. The optical alignment composition according to claim 1, characterized in that, in the formula (1) Ri is selected from the group consisting of: R2 preferably selects from the group consisting of: Y (herein, R3 is an alkyl of 3 to 20 carbon atoms).
4. The optical aligning composition according to claim 1, characterized in that, in the formula (2), R4 is selected from the group consisting of: and n2 is an integer from 2 to 19.
5. The optical alignment composition according to claim 1, characterized in that the weight ratio of the first polymer to the second polymer is between 99: 1 and 80:20.
6. The optical alignment composition according to claim 1, characterized in that the polymer of the dnamate series is selected from the group consisting of polyvinylnamate, polyvinylmethoxycinnamate and polyimide having a cinnamate group in its side chain.
7. The optical alignment composition according to claim 1, characterized in that the polymer of the coumarin series is selected from the polymers represented by the formula (3) to (5) and having a coumarin component in its side chain: (S) where k is an integer from 20 to 2000.
8. The optical alignment composition according to claim 1, characterized in that, in the formula (1), rrt? It is zero.
9. The optical alignment composition according to claim 1, characterized in that the weight average molecular weight of the second polymer is between 5x103 and 5x105.
10. The optical alignment composition according to claim 1, characterized in that the weight average molecular weight of the polymer of the cinnamate series or the polymer of the coumarin series is 5x103 and 5x105.
11. An optical aligning layer, characterized in that it comprises a first polymer selected from a polymer of the cinnamate series and a polymer from the coumarin series and a second polyimide polymer having an alkyl group (R) at both its ends and a polyimide represented by formula (1): (1) wherein Ri is selected from the group consisting of C3-C10, wherein R1 is selected from the group consisting of cidoalkyl of 3 to 10 carbon atoms, a cidoalkyl having at least one substituent (G), cycloalkenyl of 3 to 10 carbon atoms, a cycloalkenyl having at least one substituent and a compound of formula AYB [in present A and B are each independently selected from the group consisting of an unsubstituted aromatic ring and an aromatic ring (here, the aromatic ring is a monocyclic ring of six carbon atoms, a bicyclic ring of ten carbon atoms or a tricyclic ring of fourteen carbon atoms) and Y is -O, carbonyl (C = 0) or - C (R4) (Rs) - (here, R and R5 are each independently selected from the group consisting of hydrogen, alkyl of 1 to 10 carbon atoms and alkyl of 1 to 10 carbon atoms which has at least one substituent (G))]; R2 is selected from the group consisting of a ring unsubstituted aromatic ring, aromatic ring having at least one substituent (G) (in the present, the aromatic ring is a monocyclic ring of six carbon atoms, a bicyclic ring of ten carbon atoms or a tricyclic ring of fourteen carbon atoms) carbon), a cycloalkyl of 3 to 10 carbon atoms, a cycloalkyl of 3 to 10 carbon atoms having at least one substituent (G), a cycloalkenyl of 3 to 10 carbon atoms, a cycloalkenyl of 3 to 10 atoms carbon having at least one substituent (G) and a compound having the formula AYB (herein, A, B and Y are as defined above); Xi represents -COO-, -O-, or -OCO-; and R3 is an alkyl of 3 to 10 carbon atoms (herein, the substituent (G) is selected from the group consisting of alkyl of 1 to 10 carbon atoms, an unsubstituted or substituted aromatic amino, a halide, hydroxyl (OH), nitro (N02), cyano (CN), thiodan (SCN), thiol (SH) and carboxyl (COOH); and m?: N2 is from 1:99 to 20:80 and mi is a positive integer in which includes the zero.
12. The optical alignment layer according to claim 11, characterized in that the polyimide having an alkyl group at both ends thereof is selected from the compounds represented by the formula (2): (2) wherein R1 is as defined in claim 1, R4 is selected from the group consisting of an unsubstituted aromatic ring, an aromatic ring having at least one substituent (G) (here, the aromatic ring is a monocyclic ring of six carbon atoms, a bicyclic ring of ten carbon atoms or a tricyclic ring of fourteen carbon atoms), a cycloalkyl of 3 to 10 carbon atoms, a cidoalkyl of 3 to 10 carbon atoms having at least one substituent (G), a cycloalkenyl of 3 to 10 carbon atoms, a cycloalkenyl of 3 to 10 carbon atoms having at least one carbon atom substituent (G) and a compound having the formula AYB (herein, A, B and Y are as defined above), (herein the substituent (G) is selected from the group consisting of an alkyl of 1 to 10 carbon atoms, an unsubstituted or substituted aromatic amino, a halide, a hydroxyl (OH), a nitro (N02), aano (CN), thiocyano (SCN), thiol (SH) and carboxyl groups (COOH)), m2 is an integer from 10 to 100 and m2 n2 is an integer from 2 to 9.
13. The optical alignment layer according to claim 11, characterized in that in the formula (1), Ri is selected from the group consisting of: R2 preferably selects from the group consisting of (herein, R3 is an alkyl of 3 to 20 carbon atoms).
14. The optical alignment layer according to claim 11, characterized in that, in the formula (2), R4 is selected from the group consisting of: and n2 is an integer from 2 to 19.
15. The optical alignment layer according to claim 11, characterized in that the weight ratio of the first polymer to the second polymer is between 99: 1 and 80: 20.
16. The optical alignment layer according to claim 11, characterized in that the polymer of the cinnamate series is selected from the group consisting of polyvinylnanenamate, polyvinylmethoxycinnamate and polyimide having a cinnamate group in its side chain.
17. The optical alignment layer according to claim 11, characterized in that the polymer of the coumarin series is selected from the polymers represented by the formulas (3) to (5) and having a coumarin component in its side chain: (5) where k is an integer from 20 to 2000.
18. The optical alignment layer according to claim 11, characterized in that, in the formula (1), mi is zero.
19. The optical alignment layer according to claim 11, characterized in that the average molecular weight of the second polymer is 5x103 and 5x105.
20. The optical alignment layer according to claim 11, characterized in that the weight average molecular weight of the polymer of the cinnamate series or the polymer of the coumarin series is between 5x103 and 5x103
21. A liquid crystal display (LCD), characterized in that it comprises a first polymer selected from a polymer of the cinnamate series and a polymer from the coumarin series and a second polymer selected from polyimide having an alkyl (R) group on both of its ends and a polyimide represented by the formula (1): (1) wherein Ri is selected from the group consisting of C3-C10, wherein R1 is selected from the group consisting of cycloalkyl of 3 to 10 carbon atoms, a cydoalkyl having at least one substituent (G), cycloalkenyl of 3 to 10 carbon atoms, a cycloalkenyl having at least one substituent and a compound of formula AYB [in present A and B are each independently selected from the group consisting of an unsubstituted aromatic ring and an aromatic ring (here, the aromatic ring is a ring monocyclic of six carbon atoms, a bicyclic ring of ten carbon atoms or a tricyclic ring of fourteen carbon atoms) and Y is -O, carbonyl (C = 0) or -C (R4) (R5) - (in the present, R4 and R5 are each independently selected from the group consisting of hydrogen, alkyl of 1 to 10 carbon atoms and alkyl of 1 to 10 carbon atoms having at least one substituent (G))]; R2 is selected from the group consisting of an unsubstituted aromatic ring, aromatic ring having at least one substituent (G) (here, the aromatic ring is a monocyclic ring of six carbon atoms, a bicyclic ring of ten atoms of carbon or a tricyclic ring of fourteen carbon atoms), a cycloalkyl of 3 to 10 carbon atoms, a cycloalkyl of 3 to 10 carbon atoms having at least one substituent (G), a cydoalkenyl of 3 to 10 atoms of carbon, a C3-C10 alkylcarbonyl having at least one substituent (G) and a compound having the formula AYB (herein, A, B and Y are as defined above); X1 represents -COO-, -O-, or -OCO-; and R3 is an alkyl of 3 to 10 carbon atoms (herein, the substituent (G) is selected from the group consisting of alkyl of 1 to 10 carbon atoms, an unsubstituted or substituted aromatic amino, a halide, hydroxyl (OH), nitro (N02), cyano (CN), thiocyano (SCN), thiol (SH) and carboxyl (COOH); and m?: N2 is from 1:99 to 20:80 and mi is a positive integer in which includes the zero.
22. The liquid crystal display (LCD) according to claim 21, characterized in that the polyimide having an alkyl group at both ends is selected from the compounds represented by the formula (2): (2) wherein Ri is as defined in claim 1, R4 is selected from the group consisting of an unsubstituted aromatic ring, an aromatic ring having at least one substituent (G) (herein, the aromatic ring is a monocyclic ring of six carbon atoms, a bicyclic ring of ten carbon atoms or a tricyclic ring of fourteen carbon atoms), a cycloalkyl of 3 to 10 carbon atoms, a cycloalkyl of 3 to 10 carbon atoms having at least one substituent (G), a cycloalkenyl of 3 to 10 carbon atoms, a cycloalkenyl of 3 to 10 carbon atoms having at least one substituent (G) and a compound having the formula AYB (herein , A, B and Y are as defined above), (hereby the substituent (G) is selected from the group consisting of an alkyl of 1 to 10 carbon atoms, an unsubstituted or substituted aromatic amino, a halide, a hydroxyl (OH), a nitro (N02), cyano (CN), thioc iano (SCN), thiol (SH) and carboxyl groups (COOH)), m2 is an integer from 10 to 100 and m2 n2 is an integer from 2 to 9.
23. The liquid crystal display (LCD) according to claim 21, characterized in that, in the formula (1), Ri is selected from the group consisting of: x and R2 preferably selects from the group consisting of: (herein, R3 is an alkyl of 3 to 20 carbon atoms).
24. The liquid crystal display (LCD) according to claim 21, characterized in that, in the formula (2), R4 is selected from the group consisting of: and n2 is an integer from 2 to 19.
25. The liquid crystal display (LCD) according to claim 21, characterized in that the weight ratio of the first polymer to the second polymer is between 99: 1 and 80:20.
26. The liquid crystal display (LCD) according to claim 21, characterized in that the polymer of the dnamate series is selected from the group consisting of polyvinyl cinnamate, polyvinylmethoxydnamate and polyimide having a cinnamate group in its side chain.
27. The liquid crystal display (LCD) according to claim 21, characterized in that the polymer of the coumarin series is selected from the polymers represented by the formula (3) to (5) and having a coumarin component in its chain lateral: (5) where k is an integer from 20 to 2000.
28. The liquid crystal display (LCD) according to claim 21, characterized in that, in the formula (1), mi is zero.
29. The liquid crystal display (LCD) according to claim 21, characterized in that the weight average molecular weight of the second polymer is between 5x103 and 5x105.
30. The liquid crystal display (LCD) according to claim 21, characterized in that the weight average molecular weight of the polymer of the cinnamate series or the polymer of the coumarin series is 5x103 and 5x105.