JPH05305628A - Orientated sheet and manufacture thereof - Google Patents

Abstract

PURPOSE:To make it possible to easily produce orientated sheet, the direction of the maximum refractive index of which is arbitrary, such as the visual characteristic improving plate of a liquid crystal display unit by a method wherein a block made of uniaxially orientated liquid crystal polymer is sliced into sheet so as to produce the orientated sheet. CONSTITUTION:The orientated sheet concerned is produced by slicing a block made of uniaxially orientated liquid polymer into sheet. In addition, the direction of maximum refractive index of the orientated sheet is set to the direction of the film thickness of the sheet. Further, at the slicing of the liquid crystal polymer block, the slicing is performed so as to set the direction of orientation of the main chain of the liquid crystal polymer to the direction of the film thickness. As the liquid crystal polymer, lyotropic liquid crystal polymer such as p-orientated total aromatic polyamide or the like, thermotropic liquid crystal polymer such as polyethylene terephthalate/para-hydroxybenzoic copolymer or the like, or the like is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oriented sheet which can be widely used for producing electronic materials, optical materials, molecular functional materials and the like in various fields and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a method of producing an oriented sheet, a method of stretching a sheet produced by casting or the like has been generally used. Further, as a method for producing an oriented sheet of a liquid crystal polymer, there is a method of directly obtaining an oriented sheet by injection molding.

[0003]

However, according to the prior art as described above, only an oriented sheet having a maximum refractive index direction in the in-plane direction of the film can be obtained. By the way, in order to improve the viewing angle characteristics of the liquid crystal display element, there are cases where an alignment sheet having a maximum refractive index direction in the film thickness direction is required. Thus, if the maximum refractive index direction of the orientation sheet can be set to any direction, it will be applicable to various applications,
The scope of application is greatly expanded. The present invention provides an oriented sheet and a method for producing the same that solves the above problems.

[0004]

That is, the first aspect of the present invention is to:
A second aspect of the present invention is to provide an alignment sheet comprising a sheet cut out from a block of uniaxially oriented liquid crystal polymer, and a method for producing an alignment sheet characterized by cutting out a block of uniaxially oriented liquid crystal polymer into a sheet shape. It is what According to the present invention, depending on the direction in which a block of uniaxially oriented liquid crystal polymer is cut into a sheet,
It is possible to obtain an oriented sheet in which the maximum refractive index direction is set to an arbitrary direction. The liquid crystal polymer used in the present invention is not particularly limited as long as it is a polymer that exhibits a liquid crystal state when given suitable conditions such as temperature, pressure and admixture with a solvent. However, it should not be a material that normally exhibits a liquid crystal state when the oriented sheet is used. Lyotropic liquid crystal polymers such as, for example, p-oriented wholly aromatic polyamides,
Thermotropic liquid crystal polymers such as polyethylene terephthalate / para-hydroxybenzoic acid copolymer, para-hydroxybenzoic acid / bisphenol / terephthalic acid, para-hydroxybenzoic acid / 6-hydroxy-2-naphthalenecarboxylic acid / terephthalic acid and the like can be mentioned.

A method for producing a block of a uniaxially oriented liquid crystal polymer is not particularly limited, but a method of producing a block by subjecting a liquid crystal polymer to a uniaxial orientation by giving a strong shear stress in a specific direction by injection molding is a preferred embodiment. However, in order for the orientation of the obtained oriented sheet to be uniform, the entire block must be uniformly uniaxially oriented,
It is necessary to take measures such that uniform shear stress is applied to the entire molded body during injection molding, and the block after molding is reoriented.

The method for cutting out the alignment sheet from the block of the liquid crystal polymer and the film thickness of the alignment sheet are not particularly limited, and the film thickness of the alignment sheet is determined according to the intended use. Is selected.

[0007]

EXAMPLES Next, the present invention will be described in more detail based on examples, but it goes without saying that the present invention is not limited to the examples.

Example A 5-inch square block of polyethylene terephthalate / parahydroxybenzoic acid (molar ratio 2: 3) copolymer was prepared by hot injection molding. Next, the liquid crystal polymer main chain alignment direction from the block is in the film thickness direction,
An oriented sheet having a thickness of 100 μm was cut out. The birefringence retardation of the obtained oriented sheet was measured in the film plane,
It was zero. Next, when the orientation sheet was tilted at 45 degrees and the birefringence retardation was measured, a value of 120 nm was obtained. These results show that the liquid crystal polymer in the alignment sheet is perfectly uniaxially aligned in the film thickness direction.

Application Example STN of the oriented sheet and polyarylate obtained in the example
Phase difference compensation film for liquid crystal display device (Kanebuchi Chemical Co., Ltd., F-1100, birefringence phase difference 230 nm, film thickness 1
00 μm) was adhered to prepare a retardation compensation film for STN liquid crystal display device including a viewing angle improving effect. Polarizer,
STN liquid crystal cell having a birefringence phase difference of 800 nm and a twist angle of 240 °, a phase difference compensation film for STN liquid crystal display device including the effect of improving the viewing angle, and finally, a polarizing plate is made into a crossed Nicol to be darkened in an off state. A liquid crystal display element for STN liquid crystal display panel was produced. The change in darkness of the obtained liquid crystal display element in the off state depending on the viewing angle was observed to evaluate the viewing angle characteristics. No change in darkness was observed up to 30 °, and the viewing angle characteristics were better than in the case where only the polyarylate retardation compensation film for STN liquid crystal display element was used.

[0010]

As described above, according to the present invention,
It is possible to produce an oriented sheet having a maximum refractive index direction in an arbitrary direction, and it can be applied to various applications such as a viewing angle characteristic improving plate of a liquid crystal element for improving the viewing angle characteristic of the liquid crystal display element.

Claims (4)

[Claims] 1. An orientation sheet comprising a sheet cut out from a block of uniaxially oriented liquid crystal polymer. 2. The oriented sheet according to claim 1, wherein the maximum refractive index direction is in the film thickness direction of the sheet. 3. A method for producing an oriented sheet, which comprises cutting a block of uniaxially oriented liquid crystal polymer into a sheet. 4. The method according to claim 3, wherein the liquid crystal polymer is cut out so that the main chain alignment direction is the film thickness direction.