JPS59195623A - Liquid crystal display cell - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display cell superior in sharpness and brightness and suitable for size enlargement and formation of a curved face by making parallel the principal orientation directions of two oriented plastic films interposing liquid crystals. CONSTITUTION:An unstretched plastic film is formed by using an extruder and a die, and the film is stretched uni- or bi-axially to obtain two oriented films. A transparent electrically conductive film is deposited on each film by sputtering, and subjected to patterning and orientation processing. Then, a cell is formed by holding said two films with their principal orientation directions kept in parallel, and using a sealing material, spacers, etc., and sealing in liquid crystal. Each of two polarizing films are applied to each of said plastic films with its absorption axis in parallel or rectangular to the principal orientation axis of the plastic film in contact with said polarizing film, and the two polarizing films are arranged with each absorption axis in parallel or rectangular to each other. High density PE, low density PE, PVC, and polyphenylene sulfide films, etc. are usable for said plastic film, and above all, a polyester film having >=80mol% polyethylene terephthalate component is preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a liquid crystal display cell using a plastic film as a constituent material. To be more specific, 2
This invention relates to a liquid crystal display cell in which a liquid crystal is sealed between sheets of plastic film and a polarizing film is provided on the outside thereof.

[Prior art]

BACKGROUND ART Conventionally, a liquid crystal display cell has been known in which a liquid crystal is sealed between two oriented plastic films, and two polarizing films are placed on the outside thereof with their absorption axes perpendicular to each other. As the oriented plastic film, a film stretched in one direction as shown in, for example, Japanese Unexamined Patent Publication No. 57'-173816 has been used. Also.

The stretching direction, that is, the orientation direction of such a plastic film and the absorption axis of the polarizing plate may be parallel or perpendicular9.
For example, it was known from Japanese Patent Laid-Open No. 56-97318. However, in such liquid crystal display cells, no consideration was given to the combination of orientations of the two plastic films on both sides sandwiching the liquid crystal. Light interference colors appeared, significantly spoiling its appearance.

[Purpose of the invention]

In view of this shortcoming of the conventional technology, the present inventors have made extensive studies on the orientation of two films, and have created a liquid crystal display cell in which the main orientation directions of the films are parallel, so that the liquid crystal display cell can be viewed diagonally. The present invention was achieved by discovering that no interference color of light is produced even when using the same method. An object of the present invention is to eliminate the drawbacks of the prior art and to provide a liquid crystal display cell that is excellent in clarity and brightness and is suitable for large-sized and monocurved surfaces.

[Structure of the invention]

The present invention has the following configuration to achieve the above object.

That is, in a liquid crystal display cell in which a liquid crystal is sealed between two oriented plastic films and a polarizing film is provided on the outside, the main orientation directions of the two oriented plastic films are approximately parallel to each other. It is characterized by a liquid crystal display cell arranged in.

The plastic film used in the present invention includes films of high-density polyethylene, low-density polyethylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polystyrene, polypropylene, polyester, polycarbonate, polyamide, polysulfone, polyphenylene sulfide, and the like. However, particularly preferred is a polyester film in which the polyethylene terephthalate component accounts for 80 moles or more.

The plastic film may be uniaxially or biaxially oriented, but a uniaxially oriented film that is oriented only in the vertical or horizontal direction is particularly preferred in the present invention.

The liquid crystals used are twisted nematic types, guest-host types, and dynamic scattering types.

Among them, twisted nematic type liquid crystals are preferred because they are highly effective in the present invention. The liquid crystal is sandwiched and sealed between the two plastic films.

The polarizing film is not particularly limited;9 For example, it may be a uniaxially stretched film of polyvinyl alcohol adsorbed with an iodine dye or a dichroic dye, and may be formed on the non-liquid crystal side of the oriented plastic film. It is pasted together with adhesive or glue.

A so-called polarizing plate sandwiched with a protective film such as a cellulose triacetate film or a polyester film may also be used. Although the absorption axes of the two polarizing films may be parallel or orthogonal, it is preferable that the absorption axes of the two polarizing films be orthogonal because the effect of the present invention is greater.

The present invention requires that the two oriented plastic films sandwiching the liquid crystal be arranged so that their main orientation directions are substantially parallel. The main orientation direction refers to the direction in which the refractive index is maximum within the plane of the film. When the two films are arranged so that the main orientation directions of both films are perpendicular to each other.

This is undesirable because the phase difference between the light passing through the two films is mutually reduced, resulting in light interference and the appearance of strong interference colors. In particular, it is not preferable if the two films have the same turbulence value, since this disadvantage becomes more noticeable. If the two films have different adhesive tarpsion values, the interference color will be slightly reduced, but this is not preferable because it will complicate the manufacturing process of the liquid crystal display cell since two types of films are required. The retardation value is the product of the film's thickness and birefringence value. Furthermore, interference colors will appear even if the main orientation directions of two films are deviated from parallel, which is undesirable.

The angle at which the main orientation directions of the two films deviate from parallel is preferably within ε, more preferably within 6.

The thickness of the oriented plastic film is 10 to 250 μm
, preferably 20 to 180 μm, more preferably 30 to 120 μm. If the thickness is too thin, the cells will not have elasticity and will be difficult to handle. Also, if it is too thick, the display pattern will cast a shadow, which is undesirable. The thicknesses of the two films may be the same or different. Further, the birefringence value of the film is preferably 0.03 to 0.06, more preferably 0.07 to 0.02.
It is desirable that If the birefringence value is too small, the 9 display pattern tends to be colored, and if it is too large, the cell tends to break, which is not preferable. The birefringence values of the two films may be the same or different.

The two oriented plastic films may be a combination of different types of films, such as a polyester film and a polypropylene film, but from the viewpoint of temperature and humidity stability of the liquid crystal display cell, it is preferable to use a combination of the same types of films, such as a polyester film and a polyester film. preferable.

Next, the manufacturing method of the present invention will be explained. First, an unstretched plastic film is made using an extruder and a die. This is stretched uniaxially or biaxially to produce two oriented plastic films. One of these may be a film whose birefringence value is increased by slightly increasing the stretching ratio, or a film whose thickness is changed by changing the extrusion amount of the two extruders. After each transparent conductive film was deposited by sputtering, patterned, and subjected to alignment treatment, etc., the transparent conductive surface was turned inside.

The sealing material is applied while keeping the main orientation directions of the two films parallel.
A cell is made using gap material, etc., and liquid crystal is sealed in it. Next, a polarizing film is attached so that the absorption axis of the polarizing film is parallel to or perpendicular to the main orientation direction of the oriented plastic film in contact with it. The two polarizing films are provided so that their absorption axes are parallel or orthogonal.

2. The present invention is characterized by the above-mentioned liquid crystal display cell, but the above-mentioned oriented plastic film is
By using a film having a refractive index in the lateral direction within the following range, it is possible to obtain an excellent liquid crystal display cell in which no interference color appears even when the 9 display cell is viewed from a deeper angle.

and n, -n, ≧01 Here, horse: refractive index in the main orientation direction.

n2: refractive index in the direction perpendicular to nl and n3.

n3: refractive index in the thickness direction.

Also, the long side or major axis size of the liquid crystal display cell is 5 em
When the above is done, an even more excellent liquid crystal display cell can be obtained. A more preferable size is 10 cm or more. Further, when the liquid crystal display cell is bent to have a curved surface with a radius of curvature of 2 oocm or less, an even more excellent liquid crystal display cell can be obtained. The curved surface allows the display pattern to be viewed from different directions, and the liquid crystal display cell can be incorporated into narrow and curved spaces. A more preferable range of the radius of curvature is 100 cm or less, and an even more preferable range is 50(4) or less.

Inert inorganic particles in oriented plastic film.

It may also contain ultraviolet absorbers, dyes, pigments, antistatic agents, and the like. The surface of the film may be subjected to corona discharge treatment or anchor coating treatment.

The characteristic values of the present invention are determined by the following measurement method.

The refractive index is measured with an Atsube refractometer using methylene iodide as the mounting liquid. The main orientation direction is the direction in which the refractive index is maximum within the plane of the film. The birefringence value is determined by the compensator method using a polarizing microscope. The retardation value is calculated by multiplying the film thickness by the birefringence value.

The liquid crystal display cell of the present invention can be used in watches, calculators, toys with display screens, automobile instrument panels, televisions, computer terminal displays, telephone displays, etc.

〔Effect of the invention〕

As mentioned above in 2, the present invention is a liquid crystal display cell in which the main orientation directions of the two oriented plastic films sandwiching the liquid crystal are parallel, so even if the display cell is viewed from an angle, the interference color of light is not visible. The background will be brighter and the displayed pattern will be clearer. In a large display cell or a display cell with a curved surface, the end portions of the nine display surfaces are viewed more obliquely, so the effect is even more remarkable, and a liquid crystal display cell suitable for large-sized display cells with nine curved surfaces can be provided.

The effects of the present invention were determined by making a liquid crystal display cell with a display surface size of 2 Ljn x 6 and observing the display pattern portion under white light when electricity was applied once. A liquid crystal display cell is made by sputtering a transparent conductive film onto two oriented plastic films, then patterning and aligning them to encapsulate twisted nematic liquid crystal, and pasting polarizing films on both sides with their absorption axes perpendicular to each other. I made it by combining it. The determination method is based on the main orientation direction of the oriented plastic film on the surface of the liquid crystal display cell.
The liquid crystal display cell was sequentially tilted in a direction forming an angle of 45° from a vertical viewing position (this is defined as the viewing angle O), and a viewing angle at which the interference color of strong light was observed was determined.

Next, embodiments of the present invention will be described based on Examples.

Example 1 Unstretched polyethylene terephthalate film vertically 4
Two oriented polyethylene terephthalate films each having a thickness of 100 μm were made by stretching the film twice.

The refractive index of the film in 6 directions is n, -1,71, n2=1
．． 59°n3-1.50, and the main orientation direction is nl
In the direction of , the birefringence value was 012. A liquid crystal display cell was made with the main orientation directions of the two films parallel to each other and observed. Even when the liquid crystal display cell was tilted to a viewing angle of 60 degrees or more, no interference color appeared at all.

Comparative Example 1 A liquid crystal display cell was produced in the same manner as in Example 1 except that the same two films as in Example 1 were used and their main orientation directions were orthogonal. Strong interference colors appeared on the display surface at a viewing angle of 5 degrees.

Example 2 A liquid crystal display cell was produced in the same manner as in Example 1 except that the display surface size was 5 cm x 12 cm and the shape was curved into a convex shape with a radius of curvature of 50 cm. Even when this liquid crystal display cell was viewed from an angle, there was no interference color, and a clear display pattern with a bright background was obtained.

Claims (1)

[Claims] In a liquid crystal display cell in which a liquid crystal is sealed between two oriented plastic films and a polarizing film is provided on the outside thereof, the two oriented plastic films are
A liquid crystal display cell characterized in that its main orientation directions are arranged substantially parallel to each other.