JPH08334614A - Color film and liquid crystal display device therefor - Google Patents

Abstract

PURPOSE: To provide a color film for a liquid crystal display device of high display quality capable of accomplishing a bright color display with improved utilization of light, and also capable of accomplishing a gradation display. CONSTITUTION: The color film 1 is constituted of a double refraction film presenting coloring by a polarization interference, also presenting coloring in two or more colors by a variance of a phase difference and where respective colored areas 11 and 12 are distributed in a prescribed pattern state, and the liquid crystal device is provided with the color film 1 outside, or inside a liquid crystal cell. Thus, the light is efficiently used by coloring by the polarization interference, then, the bright color display is accomplished, and also, the gradation display is accomplished by arranging the colored area with a phase difference which is made different in accordance with the display pixel of the liquid crystal device, arranging a phase difference are suitable to a monochromatic display, or a red display etc., and varying display colors by pixels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color film showing a coloring pattern of two or more colors due to polarization interference, and a liquid crystal display device using the same which is excellent in color display quality.

[0002]

2. Description of the Related Art Conventionally, as a colorization technology for liquid crystal displays,
It is known that a birefringent film having a constant retardation is used to cause coloring due to polarization interference. The change in coloring is achieved by controlling the alignment of the liquid crystal by the voltage applied to the liquid crystal cell. The colorization technology of such a method is excellent in light utilization efficiency, and has low light utilization efficiency in the case of colorization by a current mainstream color filter, in particular, display brightness in a low power consumption reflective liquid crystal display device. It is expected to overcome the problems of insufficient display quality due to the shortage.

However, in the conventional product in which coloring is controlled by the above-mentioned applied voltage, the color changes due to a minute voltage difference and it is difficult to perform gradation display, and the quality of black-and-white display is deteriorated so that the phase difference plate is obtained. There is a problem that the display quality is inferior to that of the STN type liquid crystal display device etc.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a liquid crystal display device which is excellent in light utilization efficiency, can achieve bright color display, and can also achieve gradation display, and can obtain a liquid crystal display device having excellent display quality. For development purposes.

[0005]

The present invention shows birefringence in which coloring by polarization interference is shown, and two or more colors are shown due to difference in phase difference, and each colored region is distributed in a predetermined pattern state. Provided is a color film comprising a transparent film and a liquid crystal display device having the color film outside or inside a liquid crystal cell.

[0006]

By the coloring method based on the polarization interference, light can be efficiently used and bright color display can be realized. Further, by distributing the colored regions of two or more colors due to the difference in the phase difference in a predetermined pattern, the colored regions having different phase differences can be arranged according to the display pixels of the liquid crystal device, which is optimal for black and white display or red display. A phase difference region can be arranged, a display color can be changed by a pixel, and gradation display can be achieved.

[0007]

EXAMPLE A color film of the present invention is a birefringent film showing coloring due to polarization interference, and showing two or more colorings due to the difference in retardation, and the respective colored regions being distributed in a predetermined pattern state. Consists of. An example thereof is shown in FIG. Reference numeral 1 is a color film, and 11 and 12 are regions showing different coloring due to different retardation. In addition, 2 is an adhesive layer provided as needed, and 3 is a separator.

The color film of the present invention comprises, for example, a method of partially adhering and superimposing another birefringent film having a different retardation on the base birefringent film, or a cut piece of a different birefringent film. Can be formed by an appropriate method such as a method in which they are connected to each other and covered with a protective film.

A method for producing a color film, which is preferable from the viewpoint of production efficiency, is to partially apply heat above the glass transition temperature to the stretched film to partially reduce the degree of orientation of molecules and to partially cause retardation. A method of making the stretched film different or a method of partially applying a chemical solution capable of dissolving or swelling the stretched film to partially lower the degree of orientation of molecules and partially making the retardation different. According to such a method, it is easy to obtain a color film composed of a continuous monolayer film.

The stretched film, and thus the birefringent film, can be obtained, for example, by stretching a polymer film by an appropriate method such as uniaxial or biaxial. From the viewpoint of controlling the retardation, a stretched film excellent in uniformity of retardation can be preferably used because the molecules are oriented as uniformly as possible. Therefore, any conventional retardation film can be used. As the polymer film forming the stretched film, an appropriate film made of transparent plastic can be used and is not particularly limited.

Incidentally, examples of the polymer film include polycarbonate-based polymers, polyester-based polymers such as polyarylate and polyethylene terephthalate,
Polyimide-based polymer, polysulfone-based polymer, polyethersulfone-based polymer, polystyrene-based polymer, polyolefin-based polymer such as polyethylene and polypropylene, polyvinyl alcohol-based polymer, cellulose acetate-based polymer, polyvinyl chloride-based polymer , A film made of a thermoplastic polymer such as polymethylmethacrylate polymer. Further, a film made of a liquid crystal polymer can also be used.

In the above, the operation of lowering the degree of molecular orientation in the stretched film can be carried out by a method of applying heat above the glass transition temperature (heat deformation temperature) or a method of applying a chemical solution capable of dissolving or swelling. . There is no particular limitation on the method of applying heat or the method of applying the chemical solution, such as a heating method via a heat source or a heat applying method via electric discharge, or an application method such as an organic solvent capable of dissolving or swelling the stretched film. It is possible to employ an appropriate method of, and it is also possible to use both methods of applying heat and applying the chemical solution.

From the viewpoint of efficient formation of a pattern, particularly a fine pattern, which is composed of a region in which the phase difference is changed due to a decrease in the degree of molecular orientation, an appropriate heating type or chemical liquid ejecting type such as a thermal transfer type printer or an ink jet type printer is used. A method of applying heat or applying a chemical solution with a printer is preferable. Also, a desired pattern such as a fine pattern can be efficiently formed by a heating method using a laser beam, a press heating method such as a stamp method, or a method of applying a chemical by a mask method, a printing method, or the like.

The region in which the degree of molecular orientation is lowered to change the phase difference may be a region of a desired pattern, or a region other than the desired pattern, that is, a region of the desired pattern is stretched originally. A region remaining in the film in the degree of molecular orientation and other than the pattern may be a region in which the degree of molecular orientation is lowered. The latter operation of lowering the degree of molecular orientation can be performed by, for example, a method of masking a target pattern region with a resist or the like and treating with heat or a chemical solution.

In the color film of the present invention, coloring due to polarization interference of two or more colors appears due to the difference in retardation within a retardation range where coloring due to polarization interference occurs, especially within a retardation range of 300 to 700 nm. Therefore, it is formed so as to have two or more types of retardation regions, and the respective colored regions are distributed in a predetermined pattern state. As a result, it is possible to arrange a predetermined retardation region, and thus a predetermined colored region, in a pattern corresponding to display pixels in a liquid crystal display device or the like. Although the number of colors due to the difference in phase difference is arbitrary, it is generally 10 colors or less, preferably 8 colors or less, and particularly 2 to 5 colors.

The distribution pattern of the colored regions described above can be appropriately determined according to the purpose of use of the color film of the liquid crystal display device to which it is applied. For example, a pattern conforming to a color filter such as a stripe pattern or a checkered pattern can be used. can give. The size of each colored region in the pattern can also be appropriately determined according to the purpose of use of the color film.

A pattern having a size corresponding to the color filter can be easily formed by a measure according to the method of forming the color film, such as the adjustment of the resolution of the thermal transfer printer and the adjustment of the mask size. In the present invention, 1 /
It is easy to form a minute area of about 1000 to 1/100 mm ² .

When forming regions having different retardations by the method of reducing the degree of molecular orientation described above, the retardation can be controlled by a degree of reducing the degree of molecular orientation. The degree of decrease in the degree of molecular orientation is controlled by controlling the amount of heat by adjusting the heating temperature or heating time, the method of controlling the degree of dissolution or swelling by adjusting the solubility or swelling degree according to the type of drug, or the processing time. And the like.

The color film of the present invention can be put to practical use as one sheet or a laminate of two or more sheets of the same or different color films. By stacking by a method of changing the crossing state of the optical axes or the like, the distribution state of the phase difference, that is, the coloring state can be changed.

The thickness of the color film is appropriately determined on the basis of the retardation value (product of difference in refractive index of birefringence and thickness) which forms a desired colored state by polarization interference. In general, the thickness of the monolayer film is 500 μm or less, preferably 5 to 300 μm.

The color film of the present invention can be preferably used for colorization of a liquid crystal display device, but may be used as it is in practical use, or a surface formed of a film or a resin coat for the purpose of protecting a coloring pattern or the like. A protective layer may be provided. Further, as illustrated in FIG. 1, the adhesive layer 2 for the purpose of adhering to an adherend or the like may be attached in advance.

The adhesive layer may be provided on one side or both sides of the color film. For forming the adhesive layer, an appropriate adhesive substance such as a rubber-based adhesive, an acrylic-based adhesive, a silicone-based adhesive or a polyvinyl ether-based adhesive can be used. From the viewpoint of preventing the change of the coloring pattern and the like, those which do not require a high temperature process or a long period of time during curing or drying are preferable. The adhesive layer is preferably covered with a separator 3 for the purpose of preventing contamination and the like until it is put into practical use as illustrated in FIG.

Further, the color film of the present invention can be put to practical use as a laminated polarizing plate composed of a laminate with a polarizing plate. The laminated polarizing plate is illustrated in FIG. 4 is a polarizing plate. By using a laminated polarizing plate, it is possible to facilitate the assembly of a liquid crystal display device and the like.

As the polarizing plate, an appropriate one can be used without any particular limitation. Generally, a film made of a hydrophilic polymer such as polyvinyl alcohol is treated with a dichroic dye such as iodine and stretched, or a plastic film such as polyvinyl chloride is oriented with polyene. And a polarizing film covered with a sealing film for protection.

The liquid crystal display device using the color film of the present invention can be formed by disposing the color film outside or inside the liquid crystal cell. Examples thereof are shown in FIGS. 3 and 4. 5 is a liquid crystal cell. The liquid crystal cell is not particularly limited. Therefore, any known liquid crystal cell such as STN type can be used, and also a reflective type liquid crystal cell can be used.

When the color film is arranged outside the liquid crystal cell, it is arranged inside the polarizing plate on the viewing side. When the color film is arranged inside the liquid crystal cell, a color film made of a material that withstands liquid crystal is used and is usually arranged on the visible side of the liquid crystal cell. In that case,
It is also possible to use a color film as a cell substrate of a liquid crystal cell.

Example 1 A polycarbonate film having a thickness of 60 μm was stretched 1.7 times at 155 ° C. and heated through a thermal transfer printer at a heat quantity of 0.4 mj / dot at 0.1 mm intervals,
A striped pattern was applied to obtain a two-color color film. The retardation value (Δnd) characteristic of this color film is shown in FIG. The portion where Δnd is small is the heat-treated portion.

Example 2 Using NRZ (trade name, manufactured by Nitto Denko Corporation) as a birefringent film, heat treatment was carried out in the same manner as in Example 1 to obtain a two-color type color film. The change in retardation value of this color film was in accordance with Example 1.

Example 3 The same stretched film as in Example 1 was passed through a thermal transfer printer at a heat quantity of 0.4 mj / dot and 0.3 mj / dot to give a thickness of 0.1 mm.
By heating in a predetermined order at intervals, a stripe pattern was applied to obtain a three-color color film. The retardation value (Δnd) characteristic of this color film is shown in FIG.
It was shown to. The minimum portion of Δnd is the portion subjected to heat treatment with a heat amount of 0.4 mj / dot, and the middle portion of Δnd of about 520 nm is the portion subjected to heat treatment with a heat amount of 0.3 mj / dot.

[0030]

According to the color film of the present invention, light can be efficiently utilized by coloring due to polarization interference, a bright color display can be realized, and colored regions having different phase differences can be arranged according to display pixels of a liquid crystal device. Thus, a phase difference region suitable for black-and-white display or red display can be arranged, and the display color can be changed depending on the pixel, so that gradation display can be achieved. Therefore, it is possible to obtain a liquid crystal display device having excellent display quality in which light color utilization and gradation display are achieved with excellent light utilization efficiency.

[Brief description of drawings]

1 is a sectional view of an example of a color film.

FIG. 2 is a sectional view of an example of a laminated polarizing plate.

FIG. 3 is a sectional view of an example of a liquid crystal display device.

FIG. 4 is a cross-sectional view of another liquid crystal display device example.

FIG. 5 is a graph showing retardation in the color film of Example 1.

FIG. 6 is a graph showing retardation of the color film of Example 3.

[Explanation of symbols]

 1: Color film 11, 12: Region showing different coloring due to different retardation 2: Adhesive layer 4: Polarizing plate 5: Liquid crystal cell

Claims (5)

[Claims] 1. A birefringent film which exhibits coloring due to polarization interference and which exhibits two or more colors due to the difference in retardation, and each colored region of which is distributed in a predetermined pattern state. Color film to do. 2. The color film according to claim 1, wherein the birefringent film is a stretched film showing a difference in retardation based on a difference in the degree of molecular orientation. 3. An adhesive layer on one side or both sides
Or the color film according to item 2. 4. A laminated polarizing plate comprising a laminated body of the color film according to claim 1 and a polarizing plate. 5. A liquid crystal display device comprising the color film according to any one of claims 1 to 3 outside or inside a liquid crystal cell.