JPS5981625A - Light diffusing reflector - Google Patents

Abstract

PURPOSE:To obtain an excellent light diffusing reflector plate with improved contrast and a wide angle of field by controlling the total light diffused reflection factor and angle dependency of light diffused reflection factor of the reflector plate of a reflection type liquid-crystal display element. CONSTITUTION:Light 8 incident to a flat plate xy in a (z)-axis direction becomes reflected light 9 parallel to the incidence path partially and the other is reflected at an angle theta to become reflected light 10. The ratio of the total integral intensity of the reflected light 10 other than the reflected light 9 and the intensity of the incident light 8, i.e. total diffused reflection factor is set to >=60% and the intensity ratio of reflected light when the angle dependency of the light diffused reflection factor, i.e. reflection angle is 20 and 35 deg. is 0.40-0.75 when the intensity of the reflected light with a 20 deg. reflection angle is 1; a reflecting layer 13 and a light diffusing layer 14 are provided basically on a base 12 in order and the diffusing layer 14 may be provided on the base serving as the reflecting layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a good light-diffusing reflector for a reflective liquid crystal display element, and more particularly to improving the light-diffusing properties of the light-diffusing reflector.

The structure of a typical reflective liquid crystal display element is, for example, as shown in FIG. A liquid crystal layer 4 is provided in the gap, and a polarizing plate 5 is provided as necessary.
and 5' are arranged as shown in the figure, and a reflecting plate 7 is further provided behind the liquid crystal element with respect to the viewer 6.

These polarizing plates and reflecting plates are generally adhered to the liquid crystal element with an adhesive or the like so that no air layer is formed between the transparent substrate and the polarizing plate or between the polarizing plate and the reflecting plate.

However, in a liquid crystal display cell with the above configuration, the linear reflectance after reflection is high and the diffuse reflectance is low.
The light reflected from the background reflector is not uniform, the contrast between display and non-display areas is low, making it difficult to distinguish between display areas, and the viewing angle is narrow, meaning that the amount of light reflected from the reflector is angle-dependent. However, it has drawbacks such as a limited viewing angle, making it difficult to actually apply it as a display.

Attempts have been made to improve the above-mentioned drawbacks by processing the reflecting plate by sandblasting or the like to impart appropriate light diffusivity, but this is still insufficient.

Reasons for this include, for example, the light diffusivity is small and the reflected light glares, or the light diffusivity is too large and the light intensity of the light source is small, making it too dark to see (and, furthermore, the total light diffuse reflectance Due to its small size, there were various problems such as darkness, and in many cases it could not be said that it had sufficient performance from the standpoint of practical use.

The present inventor has solved the above-mentioned problems by controlling the angle dependence characteristics of the all-party diffuse reflectance and the light diffuse reflectance of the reflector used in a reflective liquid crystal display element, and has created an extremely good light-diffusive reflector. An object of the present invention is to provide a reflective liquid crystal display element incorporating the light diffusive reflector.

The angular dependence of the total 3ffi diffuse reflectance and the light diffuse reflectance referred to herein will be explained with reference to FIG.

The incident light 8 that is perpendicularly incident from the plane XYKz axis direction is the plane x
Depending on the smoothness of the y surface, some of it is reflected along the incident optical path and becomes the reflected light 9, while the other part is reflected as the incident light 8 and θ as shown in 10.
It is reflected at an angle of , and becomes reflected light 10.

Light diffuse reflectance is the intensity of reflected light 100% relative to the intensity of 80% incident light.
This refers to the intensity ratio, which changes depending on θ, and refers to the angular dependence of light diffuse reflectance.

The total diffuse reflectance is the intensity ratio of the total intensity of the incident light 8 and the integrated intensity of all reflected light at an angle to the incident light 8, such as the reflected light 10, excluding the reflected light 9. It is something to take.

In addition, in the present invention, the incident light is 400 to 700 n.
Light in the wavelength range of m was used. Furthermore, to measure the angle dependence of the reflected light, the intensity of the total reflected light when the incident light is perpendicularly incident on the reflector and the reflection angle θ is 20 degrees, and the intensity of the total reflected light when the reflection angle θ is 3 degrees. The ratio with the strength shall be taken.

The structure of the light-diffusing reflector 11 used in the reflective liquid crystal display element of the present invention is as shown in FIG. 6, in which a reflective layer 13 and a light-diffusing layer 14 are sequentially provided on a support 12. As for the basic configuration, if the reflective layer 13 has light diffusivity and performance as a support, only the reflective layer 16 may be used.

For example, a bright aluminum plate treated with a satin finish is extremely effective in the present invention. Therefore, in most cases, a diffusion layer 14 is provided on a support that also serves as a reflection layer, or the reflection layer itself has diffusivity.

As the support, general metal plates such as gold, silver, copper, aluminum, stainless steel, chromium, palladium plates, etc.
Alternatively, plastic sheets or films such as acetyl cellulose may be used. As the reflective layer, a general vapor-deposited film or sheet of metal is used, and as the diffusion layer, a diffusion substance is dispersed in a binder, for example, glass powder or aluminum oxide powder is dispersed in a resin. things are used.

The light diffusive reflector used in the reflective liquid crystal display element of the present invention is not limited to the above-mentioned example, but has a total diffuse reflectance of 60% or more, and furthermore, has an angular dependence of the light diffuse reflectance, that is, a reflection The intensity ratio of the reflected light at the angle 2o0 and the angle 3 is the reflection angle 2
Any material can be used as long as it is 0.40 to 0.75, assuming that the intensity of reflected light at 0° is 1. Further, the strength ratio is preferably 0.45 to 0.70, particularly 0.
．． It is preferably 50 to 0.65. Further, the total diffuse reflectance is preferably 65 inches or more, and particularly preferably 70 inches or more.

The light diffusing and reflecting plate used in the reflective liquid crystal display element of the present invention has a structure in which the reflective layer 13 is a plate or foil made of aluminum, silver, chromium, etc., and the diffusing layer 14 is made of glass, or the above-mentioned reflective layer. There are forms such as structures in which the surface thereof is chemically or physically treated to make it diffusible.

The reflective liquid crystal display element of the present invention is an excellent display element whose display area is bright and uniform during operation and is extremely easy to see. The present invention will be specifically described below with reference to Examples.

Example 1 A light diffusing and reflecting plate was made by applying a paint made of fine powder of barium sulfate and EBOKI 7 as a medium to a thickness of 80 μm on the surface of a commercially available corrosion-resistant aluminum plate that had been subjected to matte treatment. As a result of testing by incorporating the device into a FE type (field effect type) liquid crystal cell, the brightness of the display section and the uniformity of the brightness were extremely excellent.

The optical properties of the light diffuser reflector are that the total light diffuse reflectance is 71%.
, the angle dependence of the light reflectance is 1:o. It became 55.

Example 2 A light diffuser reflector made by depositing silver on a commercially available acetyl cellulose film with a matte surface had a total diffuse reflectance of 77 cm, and the angle dependence of the light reflectance was 1:0.62.
The light diffusing and reflecting plate obtained a visual evaluation equivalent to that of Example 1.

Example 6 A light diffuser and reflector made of a commercially available bright aluminum plate with a 120μ thick plastic screen made of polyethylene placed had a total diffuse reflectance of 68 inches and an angular dependence of the light reflectance of 1:0.48. It became.

Good binding was obtained in visual evaluation obtained by incorporating it into an FE type liquid crystal cell.

Example 4 Precipitated barium sulfate 25wt (@ epoxy resin 75wt
(≠) and spread it on the mirror surface of aluminum foil to a thickness of 10 μm.
A liquid crystal cell using a light diffuser and reflector made by coating and heating and solidifying has an extremely high total diffusivity of 71 cm and an angle dependence of light reflectance of 1:0.52, making it very effective for display areas. The color and brightness contrast with the reflective surface of the background increases,
The viewing angle was also greatly expanded, and the angle dependence of the light reflectance was also suitable for the present invention.

Example 5 A light diffusing and reflecting plate made by mixing 15 wt (%) of white pigment rutile titanium oxide and 85 wt (%) of epoxy, coating the mixture on a sandblasted aluminum plate to a thickness of 5 μm, and heating and solidifying the mixture. The liquid crystal cell using the above obtained the same characteristics as in Example 5.

Example 6 A reflective plate was created by mixing 30 wt (%) of calcium stearate powder and 70 wt of acrylic resin (LfQ), forming a flat plate with a thickness of 20 μm, and depositing scissors on the flat plate. The liquid crystal cell produced in Example 5 produced the same effect as in Example 5.

Example 7 Commercially available polyethylene pellets [“Hizex J210
0" (trade name) Mitsui Petrochemical Co., Ltd.] is left in a heating furnace kept at 170℃ and melted on a 12/1 thick aluminum foil, leaving the film as it is to have a film thickness of 250μ. Attach it in a sandwich-like manner by sandwiching it from both sides with frosted glass, keep it for about 1 hour, then take it out, leave it to cool at room temperature of 25 cm and 5 degrees Celsius, solidify it, remove it from the glass frame, and attach it to the light diffusing and reflecting plate. When this light diffuser and reflector is incorporated into a field-effect liquid crystal cell and measured, the contrast between the color and brightness of the display area and the reflective area increases, and the viewing angle is widened. It is an excellent reflective liquid crystal display element that has a high light diffusion reflectance and is suitable for the present invention.

Example 8 Commercially available polypropylene pellet [Mitsui Noblen JH
H-G” (product name), Mitsui Chemicals, Ltd.] at 180℃
After melting by heating to 25cm, let it cool and solidify at room temperature of 5℃ to produce a sheet-like glass diffuser plate with a thickness of 200μ, and deposit silver on one side of the diffuser plate to diffuse and reflect light. Created a board.

When the above-mentioned light diffusing and reflecting plate was incorporated into a field-effect liquid crystal cell and measured, the degree of increase in contrast between the color and brightness of the display part and the reflection part, and the broadening of the viewing angle were different from those in Example 8. ``I got the same results.''

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an example of a reflective liquid crystal display element, FIG. 2 is an explanatory diagram of light diffuse reflectance and total light diffuse reflectance, and FIG. 6 is a diagram showing a configuration example of a light diffuse reflector. . 1.1'--Transparent substrate, 2, 2'--Transparent electrode, 6...Spacer, 4--Liquid crystal layer, 5.5'--... Polarizing plate, 7...Reflecting plate, 8
...Incident light, 9.10...Reflected light, 11.
...Light diffusing and reflecting plate, 12...Support, 16.
...Reflection layer, 141...Diffusion layer. Applicant Canon Co., Ltd.

Claims (1)

[Claims] It has a metal reflective film and a light diffusing member, and its optical properties are a reflection angle of 35° when the reflection angle is 2000 and the intensity of the reflection source is 1.
A light diffusing reflector having a characteristic that the intensity of reflected light is 0.40 to 0.75.