JPS59193422A - Liquid crystal display cell - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display cell which is excellent in distinctness and brightness, and also suitable for conversion to a large size and a curved surface, by using an oriented plastic film having a difference of specified retardation value, to which a main orienting direction is orthogonal, for a protective cover of a polarizing plate. CONSTITUTION:In a liquid crystal display cell provided with a polarizing plate which uses a plastic film oriented in both sides of a liquid crystal cell for a protective cover, the plastic film oriented in the inside of these two polarizing plates is constituted so that its main orientation is arranged so as to be roughly orthogonal, and also a difference of a retardation value is >=200mmu. Said main orienting direction signifies a direction in which a refractive index becomes maximum on the surface of the film. This liquid crystal cell is formed by enclosing a liquid crystal between two pieces of glass or transparent film substrates, and as for a liquid crystal, a twisted nematic type, a guest host type, and a dynamic scattering type are used, but especially, the twisted nematic type liquid crystal is desirable.

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. To be more specific, the protective cover of the polarizing plate has 6e
This invention relates to a liquid crystal display cell using a plastic film.

[Prior art]

Conventionally, a one-night display cell has been known in which a so-called liquid crystal cell, in which a liquid crystal is sealed in a transparent substrate, is provided with two polarizing plates on both sides thereof with their absorption axes perpendicular to each other. A polarizing plate is a polarizing film with a protective cover attached to both sides or one side.
Films such as those shown in Publication No. 143344, 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 of the cell. Light interference colors appear and seriously spoil the appearance.

[Purpose of the invention]

In view of this drawback of the prior art, the present inventors carefully examined the orientation of two films and found that the main orientation directions of the films are perpendicular to each other, and the difference in retardation values is 200 mμ or more. The present invention was achieved by discovering that by using a liquid crystal display cell as a display cell, no interference color of light occurs even when the liquid crystal display cell is viewed obliquely. The purpose of the present invention is to
Eliminates the shortcomings of conventional technology and provides excellent clarity and brightness.

Furthermore, the present invention aims to provide a liquid crystal display cell suitable for large-sized and nine-curved surfaces.

[Structure of the invention]

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

In other words, 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 film on the inside of the two polarizing plates has its main orientation. The arrangement is such that the directions are almost orthogonal and the difference in retardation value is 20
It is characterized by having a diameter of 0 mμ or more.

The liquid crystal cell in the present invention is one in which liquid crystal is sealed between two glass or transparent film substrates, and the liquid crystal used may be a twisted symmetric type, a guest host type, or a dynamic scattering type. However, among these, twisted nematic type liquid crystals are preferred because they are highly effective in the present invention.

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

The plastic film may be uniaxially or 211011 oriented, but a uniaxially oriented film is particularly preferred in the present invention. In the present invention, the main orientation directions of the two polarizing plates on the liquid crystal cell side, that is, the two inner oriented plastic films are almost perpendicular to each other, and the difference in retardation value is 200 mμ or more. It needs to be a different film. 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 direction is parallel, it is not preferable because the manufacturing yield of the polarizing plate will be poor and the product will be expensive. The retardation value is the product of the birefringence value of the film and the thickness of the film, and is expressed in units of 9 mμ.

The difference in glue density between two films is 200 mμ.
By doing so, interference colors of light on the liquid crystal display surface can be prevented, and a clear and bright display can be obtained. The preferred range for the difference in retardation values is 400 to 200 DO.
mμ, the most preferable range is 1000 to 10,00
It is 0 mμ. If the difference in the radiance value is too large by one or two degrees, it is not preferable because interference colors of light cannot be prevented or problems such as cracking or curling of the liquid crystal display cell are likely to occur.

The convex self-directed plastic film The thickness is preferably 5011μ, more preferably 20 to 180μ.

More preferably, it is 30 to 120 mμ. Thickness
There is no waist in the cell and it is 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 0.03, more preferably 0.05 to 0.02.

If the birefringence value is too small, the 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, but may be, for example, 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. are laminated 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 film and the main orientation direction of the oriented plastic film are approximately parallel or perpendicular to each other, but it is preferable that the absorption axis of the polarizing film and the main orientation direction of the oriented plastic film are perpendicular to each other, since the effect of the present invention is greater.

Next, the manufacturing method of the present invention will be explained. An unstretched plastic film is made using an extruder and a die. This is stretched uniaxially or biaxially to produce a sheet of oriented plastic film. Next, another oriented plastic film with a retardation value of 200 mμ or more than this film is made. In order to increase the retardation value, the birefringence value may be increased by slightly increasing the stretching ratio, or the birefringence value may be increased by changing the stretching temperature and heat treatment conditions. Alternatively, the retardation value may be increased by increasing the film thickness.

Next, these two oriented plastic films were bonded together with a polarized C film to create a polarizing plate.

This oriented plastic filler is placed inside and overlaid or pasted on the liquid crystal cell with its main orientation direction orthogonal to each other.

Although the present invention is characterized by the liquid crystal display cell as described above, a di9 display cell can be obtained by using the above-mentioned oriented plastic film as a film whose refractive index in six directions is within the following range. Furthermore, it is possible to obtain an excellent liquid crystal display cell that exhibits no interference color even when viewed from a deep angle.

n, +n.

100ro≦-n, ≦+0.05k, n
, -n, ≧0.1 where, nl; refractive index in the main orientation direction n + :
refractive index n in the direction perpendicular to l and n; refractive index in the thickness direction; also, the long side or major axis size of the liquid crystal display cell is 5 cm
When the above conditions are met, an even more excellent liquid crystal display cell can be obtained. A more preferable size is 1 Qcm or more. Further, when the transparent substrate of the liquid crystal cell is flexible, an even more excellent liquid crystal display cell can be obtained by bending the liquid crystal display cell to a curved surface with a radius of curvature of 200 cm or less.

The curved surface allows display patterns 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.

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 is subjected to corona discharge treatment.
Carnivorous) treatment may be applied.

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

The birefringence value is determined by the compensator method using a polarizing microscope. The refractive index is measured using an Atsube refractometer using methylene iodide as a liquid. The retardation value is the product of film thickness and birefringence, Q, and is displayed in mμ.
Used in toys, automobile instrument clusters, 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 with a difference in retardation value of 2 D Omμ or more are used as protective covers for each polarizing plate, and the main orientation directions of the films are orthogonal to each other. 9 Even if the display cell is viewed diagonally by a child, there will be no light interference color, the background will be bright and the display pattern will be clear. In a large display cell or a display cell with a curved surface, the end portion of one display surface is viewed more diagonally, so the effect is even more significant and a liquid crystal display cell suitable for a large display cell with nine curved surfaces can be provided.

The effects of the present invention were determined by making a liquid crystal display cell with a size of 2 cm x 6 cm and observing the display pattern portion under white light when electricity was applied once. A liquid crystal display cell was made by laminating a polarizing film on two oriented plastic films, and then stacking the polarizing film and a twisted matic type liquid crystal cell.

The determination method is to sequentially tilt the liquid crystal display cell in a direction that makes an angle of 45 degrees with the main orientation direction of the oriented plastic film on the surface of the liquid crystal display cell, starting from a position where the liquid crystal display cell is viewed vertically (the viewing angle is 0). We sought a viewing angle that would allow the interference colors of strong light to appear.

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

Example 1 An oriented polyethylene terephthalate film having a thickness of 100 μm was prepared by vertically stretching an unstretched ethylene terephthalate film by 4 times. The film has a birefringence value of 0.12 and a retardation value of 12,000 mμ.
Met. Next, a slightly thick unstretched polyethylene terephthalate film was vertically stretched 45 times to a thickness of 100.
A micro-oriented polyethylene terenotate film was prepared. The extraction force of the film was 1 (the folding value was 0.14, and the retardation value was 14.000 mμ.) These two films were exposed to polarized light with their main orientation direction and the absorption axis of the polarizing film parallel to each other. Making a polarizing plate by pasting films/(
. These were stacked on a liquid crystal cell with the oriented film on the inside and the main orientation directions perpendicular to each other to create a liquid crystal display.

The difference in the 7'-7yon values of the two films was 200-Qmμ, so the liquid crystal display cell was placed at a viewing angle of 60
No interference color appeared even when viewed from 0 or above.

] Retardation value of bite example 1 7j): 12,000
Two oriented polyethylene terephthalate films similar to the mμ film were made, and a liquid crystal display cell was made in the same manner as in Example 1 and observed. Since the difference in adhesiveness values between the two films was Omμ, a strong interference color appeared at a viewing angle of 5°.

Comparative Example 2 Two oriented polyethylene terephthalate films were made with different thickness and stretching ratio from Example 1.

I made a liquid crystal display cell. One film has a thickness of 47μ
, the birefringence value is 0.12. ! J Kuchy John value is 564
0 mμ, and the other film each has a thickness of 96 μ,
0.06, 5760 m 7. z, and the difference in their retardation values was 120 mμ.

When the liquid crystal display cell was observed, a strong bright color appeared at a viewing angle of 7.

Example 2 Same as Example 1, only the thickness was changed and the birefringence value was 012.
A liquid crystal display cell was made in the same manner as in Example 1, except that two oriented polyethylene terephthalate films were made, and a polarizing plate was made with the main orientation direction of the film and the absorption axis of the polarizing film at right angles.

One film has a thickness of 100μ and a retardation value of 12000μ, and the other film has a retardation value of 8
0μ, 96DOmμ, and the difference in retardation value was 2400mμ.

No interference color appeared even when the liquid crystal display cell was viewed from a viewing angle of 60 degrees or more.

Examples 6 to 5 By changing the thickness and stretching ratio from Example 1, 2 shown in Table 1 was prepared.
Make a sheet of oriented polyethylene terentalate film,
A liquid crystal display cell was made and observed.

The difference in retardation value between Example 4 and Example 4 is 3.
401 nμ and 680 mμ, and the viewing angle is 20
A slight interference color appeared at 0.45°.

It was at a level with no practical problems. In Example 5, the difference in beam tartness value is 50 Omμ tare and the viewing angle is 60°.
Even with the above, no interference color appeared at all.

Example 6 An unstretched polypropylene film was vertically stretched 9 times (Il
An oriented polypropylene film with a thickness of 100 μm was prepared using L L. The film had a birefringence value fi of 0.03 and a retardation value of 3000 mμ.

On the other hand, as in Example 1, the thickness was 100μ and the birefringence value was 0.
12. An oriented polyethylene terephthalate film with a retardation value of 12,000 mμ was prepared. A liquid crystal display cell was made using these two films in the same manner as in Example 1 and observed. The difference in adhesiveness value between the two films is 900 mμ. Therefore, the viewing angle of the liquid crystal display cell is 6
No interference color appeared even when tilted above 0.

Example 7 Two films similar to those in Example 1 were fabricated to produce a liquid crystal display cell having a convexly curved surface with a display surface size of 5 cm x 12 cm and 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.

Procedural amendments Director of the Patent Office Kazuo Wakasugi 1, Indication of the case, Patent Application No. 68777 of 1982, 2, Name of the invention, liquid crystal display cell 3, Person making the amendment, Relationship to the case, Patent applicant address, Chuo-ku, Tokyo Nihonbashi Nae-cho 2-2-4, date of amendment order 5, number of inventions not increased by amendment 6, “Claims” and “Details of invention 8Ill” of the specification to be amended
Contents of amendment (1) The scope of claims on page 1 of the specification is amended as shown in the attached sheet.

(2) Same page 9th line 5th Correct "birefringence" to "birefringence value".

(Attachment) Claims: In a liquid crystal display cell comprising a polarizing plate using plastic films arranged on both sides of the liquid crystal cell as a protective cover, an oriented plastic film inside the two polarizing plates. A liquid crystal display cell characterized in that its main orientation directions are substantially perpendicular to each other, and the difference in retardation values is 200 mμ or more.

Claims (1)

[Claims] In a liquid crystal display cell comprising a polarizing plate using oriented plastic films as protective covers on both sides of the liquid crystal cell, the self-oriented plastic film of the two polarizing plates is The main self-direction direction is almost perpendicular to each other, and the difference in 1-turdition value is 20.
A liquid crystal display cell characterized by having a particle size of 0 mμ or more.