JPS59195624A - 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 using two oriented plastic films with their principal orientation directions in parallel to each other, for the protective cover of polarizing films. 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. One of the two may be raised in birefringency by raising strentching ratio a little or the like, or changed in film thickness by changing an extrusion amt. of the extruder. Each of two polarizing films are applied to each of said plastic films to form two pairs of polarizing plates, with each oriented plastic films inside and the principal orientation directions in parallel to each other to form a liquid crystal display cell by joining the two pairs with adhesive or the like. 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 polarizing plate. More specifically, the present invention relates to a liquid crystal display cell using an oriented plastic film as a protective cover for a polarizing plate.

[Prior art]

BACKGROUND ART Conventionally, a liquid crystal display cell has been known in which two polarizing plates are disposed on both sides of a so-called liquid crystal cell in which a liquid crystal is sealed in a transparent substrate, with their absorption axes perpendicular to each other. A polarizing plate is a polarizing plate with a protective cover pasted on both sides or one side.
Films such as those shown in Japanese Patent No. 344, which are axially stretched and oriented, have been known. However, in such a liquid crystal display cell, no consideration was given to the respective orientations of the protective cover films of the two polarizing plates on both sides, so when the liquid crystal display cell is viewed slightly diagonally,
Strong interference colors appeared on the display surface, significantly detracting from 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 occurs even when using the same method. SUMMARY OF THE INVENTION 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 cells with nine curved 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 polarizing plate is provided using oriented plastic films as protective covers on both sides of the liquid crystal cell, the oriented plastic film inside the two polarizing plates has its main orientation direction. It is characterized by liquid crystal display cells in which the cells are arranged substantially in parallel.

The liquid crystal cell according to the present invention has a liquid crystal sealed between two glass or transparent film substrates, and the liquid crystal may be of a twisted nematic type, a guest host type, or a dynamic scattering type. But, among others, f'
P1-node, hawkmatic type, guest-host type, and dynamic scattering type are used, but among them, twisted nematic type liquid crystal is preferred because it has a large effect of the present invention.

The plastic film in the present invention includes high density polyethylene, low density polyethylene, polyhinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polystyrene, polypropylene, polyester, polycarbonate,
Films such as polyamide, polysulfone, and polyphenylene sulfide are used, and among them, polyester films in which the polyethylene terephthalate component accounts for 80 mol % or more are particularly preferred.

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 present invention requires that the main orientation directions of the two oriented plastic films on the liquid crystal cell side, that is, inside, of the two polarizing plates be substantially parallel. The main orientation direction refers to the direction in which the refractive index is maximum within the plane of the film. If the main orientation directions are perpendicular to each other, the phase difference of the light passing through the two films will be mutually reduced, resulting in light interference and a strong interference color appearing, which is not preferable. In particular, 2
It is not preferable if two sheets of film have the same retardation value, since the disadvantage becomes even 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 appear when the main orientation directions of two films are deviated from parallel, which is not preferable.

In addition, the angle by which the main orientation directions of the nine films are deviated from parallel in the two films is preferably within 5 degrees, and more preferably within 6 degrees.

Thickness of oriented plastic film: 10 to 250 μm
, preferably '1-j20 to 180 μm, more preferably 1
Preferably, the thickness is 0 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 i,;io, 07 to 0.2. 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.

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 the protective cover may be coated with an adhesive or a pressure-sensitive adhesive. These are pasted together to form a polarizing plate. In the present invention, it is necessary that the two protective covers on the liquid crystal cell side, that is, the inner side, be made of the above-mentioned oriented plastic film, and the outer protective cover is not particularly limited. The absorption axis of the polarizing group and the main orientation direction of the oriented plastic film are approximately parallel or perpendicular to each other. Although the absorption axes of the two polarization groups may be parallel or orthogonal, it is preferable that the absorption axes of the two polarization groups are orthogonal because the effect of the present invention is greater.

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 amount of extrusion from an extruder.

Next, a polarizing film was attached to each of these two oriented plastic films to form two sets of polarizing plates, with the oriented plastic film inside.

A liquid crystal display cell is made by stacking or bonding liquid crystal cells with their main orientation directions parallel to each other.

The present invention is characterized by the liquid crystal display cell as described above, but the display cell may be further modified by using the oriented plastic film as a film whose refractive index in six directions is within the following range. An excellent liquid crystal display cell with no interference colors even when viewed from a deep angle can be obtained.

−〇〇3≦Nia! n, ≦+0.05.

and In+”!≧0.1 Here, 1n+; refractive index in the main orientation direction.

n,; refractive index in the direction perpendicular to n and n;

n,; refractive index in the thickness direction. , Also, set the long side or major axis size of the liquid crystal display cell to 5 cm.
When the above conditions are met, an even more excellent liquid crystal display cell can be obtained. The most preferred size is 110 cm or less. Further, when the transparent substrate of the liquid crystal cell is flexible, an even better liquid crystal display cell can be obtained when the liquid crystal display cell is curved to a radius of curvature of 200 cm or less. 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 cm 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 a mount. 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 the product of the film thickness and 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 described above, the present invention is a liquid crystal display cell in which two oriented plastic films whose main orientation directions are parallel are used as a protective cover for a polarizing plate.

No interference colors appear even when viewing the display cell from an angle.

The background becomes brighter and the display pattern becomes clearer. In a large display cell or a curved display cell, the edges of the display section are viewed more diagonally.

The effect is even more remarkable, and a liquid crystal display cell suitable for large-sized and nine-curved surfaces can be provided.

The effect of the present invention is that the size of one display surface is 2 cm x 6 cm.
A liquid crystal display cell was prepared and the display pattern portion was observed under white light when electricity was applied twice, and the judgment was made. The liquid crystal display cell is
A polarizing plate was made by pasting a polarizing film on two oriented plastic films, and a twisted nematic type liquid crystal cell was stacked on this polarizing plate.

The determination method is to sequentially tilt the liquid crystal display cell from a vertical viewing position (this is the viewing angle O) in a direction that makes an angle of 45° with the main orientation direction of the oriented plastic film on the surface of the liquid crystal display cell. The viewing angle at which the interference color of light appears 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 six directions is n, -1·71. n,=1
59, n = 1.50, the main alignment direction was the n direction, and the birefringence value was 0.12. This 2
Two strands of polarizing plates were made by pasting polarizing films onto two sheets of film. Regarding the main orientation direction of the film and the absorption axis of the polarizing film, 1#i was parallel to each other and one set was perpendicular to each other. A liquid crystal display cell was made by stacking these polarizing plates on a liquid crystal cell with the orientation film inside and the main orientation direction parallel. Even when the liquid crystal display cell was tilted to a viewing angle of 60° or more, no interference color appeared on the display surface.

Comparative Example 1 The same two films as in Example 1 were used. A polarizing plate was made with the main orientation direction of the film and the absorption axis of the polarizing film parallel to each other, and the polarizing plate was stacked on the liquid crystal cell with the main orientation directions perpendicular to each other. I created a display cell. A strong interference color appeared on the display surface at a viewing angle of 5.

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 - 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.

Kazuo Wakasugi, Commissioner of the Japan Patent Office (Monday, Showa)2, Name of the invention Liquid crystal display cell4, Date of amendment order Voluntary5, No number of inventions increased by amendment6, Details of invention F in Mei 1 that is the subject of the amendment Column 7 of Explanation J, contents of amendment (1) Details t11 Page 3, lines 12 to 14 “Twisted...” is used among others.
Delete.

(2) Same, page 5, line 4 "I deviation" is corrected as "misalignment".

(3) Same, page 7, line 11 Correct it by saying, ``Put the cells into one cell.''

(4) Same, 9th true line 2 Correct [N1~Takedoshi] to [N1~Liquid].

Claims (1)

[Claims] In a liquid crystal display cell in which polarizing plates using oriented plastic films as protective covers are provided on both sides of the liquid crystal cell, the oriented plastic films inside the two polarizing plates have their main orientation direction approximately A liquid crystal display cell characterized by being arranged in parallel.