MXPA98000235A - Alignment film material for a liquid crystal cell and method for preparing - Google Patents

Abstract

The novel N-substituted aromatic polyamide compound is prepared by introducing the aralkyl group in the N-position of the aromatic polyamide, wherein the derivatives are represented by the formula 1 and are prepared by metallizing the aromatic polyamide, then reacting the metallized polyamide with a aralqui

Description

ALIGNMENT FILM MATERIAL FOR A LIQUID CRYSTAL CELL AND METHOD TO PREPARE IT DESCRIPTION OF THE INVENTION The present invention relates to an alignment film material for liquid crystal cell and a method for preparing the same and, more particularly, to poly-m-phenylene isophthalamide derivatives substituted with N-aralkyls of the formula 1 which produce a pre-thin angle of less than Io when the derivatives are applied as material for an alignment film of the liquid crystal cell, and the method for preparing the same. [Formula l] (wherein, R is an aralkyl group) Generally, a liquid crystal cell comprises two rigid substrates and liquid crystal materials injected therebetween. Also, an electrode is formed on the substrate to apply an electric field to the pixel of the liquid crystal cell, and an alignment film is formed on the transparent film to align the liquid crystal material between the substrates. In order to obtain the electro-optical effect of the liquid crystal cell, uniform alignment of the liquid crystal materials in the liquid crystal cell is needed. There are two types of liquid crystal alignment, one is a homogeneous alignment and the other is a homeotropic alignment. The homeotropic alignment aligns the liquid crystal material vertically relative to the surface of the substrate by depositing SiOx or coating a surfactant such as a silane based on the coupling agent on the substrate. The homogeneous alignment aligns the liquid crystal material substantially horizontally relative to the substrate, and is carried out by a conventional tilting method of silicon dioxide (SiO2), a friction method, and a Langmuir-brodgett method. The friction method is the most commonly used method for aligning liquid crystals, and comprises the steps of coating polyimide to form an organic alignment film on the substrate and rubbing the alignment film mechanically. By the friction process, many micro notches are produced on the surface of the alignment film in the rubbed direction. In this way, when the liquid crystal is placed on the rubbed alignment film, the liquid crystal is aligned due to the micro notches. Generally, the polyimide has been used predominantly as the alignment film material for liquid crystal by the friction method due to its good property of liquid crystal alignment and chemical stability. Additionally, the polyimide is easily printed on the substrate and rubbed. The process for preparing the polyamide alignment film on the substrate comprises the steps of reacting a diamine compound with an acid anhydride in a solvent to produce a solution of polyamic acid; coating a solution of 4-8% of the polyamic acid on a substrate; and baking the substrate in an oven at 180 ° C-300 ° C. The thermoplastic polyimide film obtained by the above process is represented by formula 2. [Formula 2] However, there is a disadvantage in that the method requires annealing process of the coated precursor, polyamic acid, to form a thin polyimide film. Furthermore, the polyimide can not produce a pre-thin angle of less than Io which is required in a liquid crystal cell of IPS mode (Exchanged in plane) recently introduced by a wide viewing angle. Therefore, it is an object of the present invention to provide an alignment film having a small pre-thin angle of less than Io. It is another object of the present invention to provide a new material which is soluble in an organic solvent and forms an alignment film easily. It is further an object of the present invention to provide a new material for forming an alignment film which can be used in the liquid crystal cell of the IPS mode (Flat Exchange). • To achieve the above object, the present invention provides aromatic polyamide substituted with N-aralkyl represented by formula 1, and the process for preparing the same comprising the steps of metallizing an aromatic polyamide and reacting the metallized polyamide with an aralkyl halide . [Formula 1] wherein, R is an aralkyl group. In the following detailed description, only the preferred embodiment of the invention has been shown and described, simply by the form of illustration of the best mode contemplated by the inventor to carry out the invention. As will be carried out, the invention is capable of being modified in several obvious aspects, all without departing from the invention. Therefore, the description is taken into account as illustrative in nature, and not restrictive. The present invention provides aromatic polyamide substituted with N-aralkyl of the following formula 1, and also provides a process for preparing the same comprising the steps of metallizing an aromatic polyamide and reacting the metallized polyamide with an aralkyl halide. [Formula 1] wherein, R is an aralkyl group. The aromatic polyamide is preferably PMIA (poly-m-phenylene isophthalamide). The metallization step is carried out preferably by reacting the poly-m-phenylene isophthalamide with methylsulfinyl carbanion. The aralkyl halide of the group consisting of formulas 3 to 7 is selected.

[Formula 3] [Formula 4] [Formula 5] [Formula 6] [Formula 7] wherein, X is a halogen atom such as Cl and Br, and Z is H, CH3, CN, OCH3, or CF3. More preferably, the aralkyl group is a benzyl group. The process for preparing N-substituted aralkyl of aromatic polyamide of the formula 1 will be described in detail. Firstly, the carbanion of methylsulfinyl is prepared by reacting sodium hydride (NaH) with dimethyl sulfoxide (DMSO). Then, as shown in reaction formula 1, PMIA, an aromatic polyamide material, is metallized with the methylsulfinyl carbanion for 5-6 hours. Then, the metallized PMIA is reacted with an aralkyl halide for 12-16 hours, such that the N-position of an amide group of the metallized PMIA backbone is replaced by the aralkyl group. As a result, the PMIA substituted with N-aralkyl of the present invention is prepared. [Reaction formula 1] Wherein, R is an aralkyl group, and X is Cl or Br. The above reaction is carried out with a high substitution ratio of above 85%, and a high yield of 78% even though it has a reaction of polymerization. The PMIA substituted with N-aralkyl is analyzed by an analyzer element, an NMR and an IR. PMIA substituted with N-aralkyl is soluble in an organic solvent such as NMP (N-methyl-2-pyrrolidone), DMSO (dimethyl sulfoxide), THF (tetrahydrofuran) and benzyl alcohol, although unsubstituted PMIA is insoluble in the organic solvent. In addition, a liquid crystal cell is manufactured after forming the alignment film with the derivatives. That is, an alignment film is formed on a substrate by coating the derivative and the NMP solution, and baking the substrate at about 150-180 ° C for 1 hour to obtain an alignment film. Then, the alignment film is rubbed with rayon roll. The substrate is assembled with another substrate, and the liquid crystal is injected between them. Therefore, the liquid crystal is aligned in order with a pre-thin angle of less than 1 °. Observing the cell with a polarization microscope, it is shown that the pre-inclined angle is substantially less than Io. For example, the pre-inclined angle is 0.5 ° -l ° if the benzyl group is introduced as the aralkyl group, and the pre-inclined angle is appropriate for a liquid crystal cell of the IPS mode. Therefore, a liquid crystal cell having a wide viewing angle is manufactured by adapting the alignment film of this invention. The derivatives of this invention are soluble in an organic solvent such as NMP, THF, DMSO, and benzyl alcohol. Also, the alignment film formed with the derivative provides a small pre-thin angle of less than Io, so it can be used in a liquid crystal cell of IPS mode which provides a wide angle of view. In this description, only the preferred embodiment of the invention is shown and described, but, as mentioned hereinabove, it is understood that the invention is capable of being used in various other combinations and environments and is capable of change or modification within range. of the concepts of the invention as expressed herein,

Claims (14)

CLAIMS 1. A method for preparing aromatic polyamide substituted with N-aralkyl of the following formula, the method characterized in that it comprises the steps of: Metallizing an aromatic polyamide; and Reacting the metallized polyamide with an aralkyl halide. (wherein, R is an aralkyl group) 2. The method according to claim 1, characterized in that the aromatic polyamide is poly-m-phenylene isophthalamide. 3. The method according to claim 1, characterized in that the aralkyl halide is selected from the group consisting of the compounds of the following formulas 3-7:
1. [Formula 3] X-CH2-H? ~ ~ Z [Formula 4]
2. [Formula 5]
3. [Formula 6] ? -cH2 ~ O0 [Formula 7]
4. Four . The method according to claim 3, characterized in that the alkyl halide is a benzyl halide.
5. 5 . A method for manufacturing an alignment film of the liquid crystal cell, the method characterized in that it comprises the steps of: Metallizing an aromatic polyamide; Reacting the polyamide with an aralkyl halide to produce an aromatic polyamide substituted with N-aralkyl of the formula 1; Melting the aromatic polyamide substituted with N-aralkyl in an organic solvent to produce an alignment solution; Coating the alignment solution on a substrate; and Rub the substrate [Formula 1]
6. Wherein, R is an aralkyl group 6. The method according to claim 5, characterized in that the aromatic polyamide is poly-m-phenylene isophthalamide. The method according to claim 5, characterized in that the aralkyl halide is selected from the group consisting of the compounds of the following formulas 3-7:
7. [Formula 3]
8. X-CH2 -O '
9. [Formula 6] ? -cH!? Q Q [Formula 7]
10. ? -CHí "Ü" GH3 Where, X is Cl, or Br, Z is H, CH3, CN, OCH3, or CF3. 8. The method according to claim 5, characterized in that the aralkyl halide is a benzyl halide. 9. The method according to claim 5, characterized in that the organic solvent is selected from the group consisting of NMP, DMPSO, THF, and benzyl alcohol. 10. The method of compliance with the claim 5, characterized in that the alignment film of the liquid crystal cell produces a pre-inclined angle from below
11. 11. An alignment material for a liquid crystal cell of aromatic polyamide substituted with N-aralkyl of the following formula. Wherein, R is an aralkyl group. The alignment material according to claim 11, characterized in that the R aralkyl group is produced from the group consisting of the compounds of the following formulas 3-7: [Formula 3] [Formula 4] [Formula 5] [Formula 6] ? -cH2? Q-0 [Formula 7] X - CH2? \ J- CHJ Where, X is Cl or Br, Z is H, CH3, CN, OCH3, or CF3. 13. The alignment material according to claim 11, characterized in that the aralkyl group is a benzyl group. 14. An alignment film formed with the alignment material according to claims 11 to 13, characterized in that the film produces a pre-inclined angle below Io.