JPH05341128A - Illumination light guide plate for liquid crystal display and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an illumination light guide plate for a liquid crystal display, of which display is bright and in which the number of parts is reduced and which can be manufactured stably. CONSTITUTION:In an illumination light guide plate for a liquid crystal device, a light guide plate is made of the high molecular emulsion, which is composed of the transparent polymer A11 as the main component and the micelled polymer B12 for scattering the light and the AB graft polymer or the AB block polymer as the surface active agent. The transparent polymer A11 as the main component and the polymer B12 incompatible with the polymer A are dissolved in the common solvent, and the solvent is eliminated after the distribution to form a high molecular emulsion pellet having a micell at an appropriate diameter, and thereafter, injection molding or extrusion molding is performed to form a light guide plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate for illuminating a liquid crystal display device which has a bright display and a small number of parts and is excellent in manufacturing stability.

[0002]

2. Description of the Related Art Generally, a liquid crystal display device has a structure in which a cold cathode fluorescent discharge lamp is placed on a side surface, a light guide plate guides light to the back surface, and the liquid crystal display panel is irradiated with the light through a reflection plate and a diffusion plate. Is. To ensure in-plane uniformity of brightness, a reflective pattern with a density distribution is printed on the back surface of the light guide plate, and at least three parts other than the illumination lamp are used to achieve low power, high brightness, and in-plane homogeneity. It was possible to achieve a good balance of thinness and lightness. In order to increase the light utilization efficiency and reduce the number of parts, a method of forming a total reflection layer on the lower surface by incorporating transparent fine particles for light scattering in the light guide plate in a distributed manner (Sho 58-46447) has been proposed. Has been presented. Also, a method using a milky white light scatterer (Japanese Patent Publication No. 3-729).
68) is also presented.

Recently, a milky-white high-brightness light-scattering transmitter capable of controlling a scattering angle by forming a microphase-separated structure with a copolymer having a heterogeneous structure and a blended polymer has been reported (Proceedings of the Polymer Society of Japan, Vol. 41, No. 3 (1992) IL27).

[0004]

In the illumination of the conventional liquid crystal display device, it is necessary to use at least three parts of a light guide plate, a reflection plate, and a diffusion plate in addition to the illumination lamp, and the light utilization efficiency cannot be increased so much. There were challenges. Ideally, all the functions should be integrated into the light guide plate in order to increase the light utilization efficiency and to reduce the manufacturing cost.

The previously proposed method of mixing transparent fine particles for light scattering in a light guide plate so as to have a distribution is extremely difficult to control in manufacturing. In addition, the method of forming a micro phase-separated structure with a copolymer having a non-uniform structure and a blended polymer easily changes the phase structure when heated to obtain the shape of the light guide plate, and thus, the light guide plate can be used in a mass production process. It was impossible to guarantee the function.

Therefore, the present invention solves such a problem, and an object thereof is to provide a light guide plate for illumination of a liquid crystal display device which is excellent in brightness and homogeneity and has a small number of parts, and its manufacturing stability. It provides a manufacturing method.

[0007]

The above object is to provide a light guide plate for illumination of a liquid crystal display device provided with an illumination lamp, wherein the light guide plate is a transparent polymer A as a main component, and a light-scattering micellar polymer B. It is achieved by being a polymer emulsion composed of an AB graft polymer or an AB block polymer which is a surfactant. The light guide plate for illumination of the liquid crystal display device includes a transparent polymer A as a main component, a polymer B incompatible with A, an AB graft polymer or an AB.
It can be manufactured by dissolving a block polymer in a common solvent, removing the solvent after dispersion to prepare a polymer emulsion pellet having micelles having an appropriate diameter, and molding the shape of the light guide plate by injection molding or hot drawing.

[0008]

【Example】

(Example 1) Polymethylmethacrylate (PMMA) 80
% By weight, polystyrene (PS) 19.5% by weight, PMM
0.5% by weight of the A-PS-PMMA block polymer was dissolved in butyl acetate, stirred and dispersed, and the solvent was removed to give PMM.
A pellet containing A as a main component was prepared. PMMA-PS
-PMMA block polymer is localized at the interface as a surfactant to stabilize PS micelles having an average particle size of 0.3 μm,
A polymeric emulsion was formed. A light guide plate was formed by extrusion into a flat plate, and aluminum was deposited on the back surface to form a reflective layer. A schematic cross-sectional view of the light guide plate thus manufactured is shown in FIG. Average particle size 0.3 μm
The PS micelles of were uniformly dispersed in the same state as in the raw material pellets.

The scattering angle of the light emitted from the light guide plate and the in-plane brightness distribution can be controlled by the refractive index of the micelles, the particle size distribution, the density distribution and the like. If the phase-separated structure of the raw material pellets is maintained after molding as in this embodiment, the material design can be facilitated and the characteristics of the light guide plate can be managed as designed.
The light incident on the side surface of the light guide plate from the illumination lamp causes almost no absorption loss and is emitted almost vertically from the surface due to diffraction at the micelle interface. The brightness uniformity on the surface was 90% or more.

FIG. 2 shows a schematic sectional view of a liquid crystal display device using the light guide plate thus manufactured. In FIG. 2, 21 is a liquid crystal panel, 22 is a light guide plate, and 23 is an illumination lamp. The brightness on the display surface was improved from 60 candelas to 80 candelas as compared with the conventional backlight using the same illumination lamp. We were able to achieve a bright and easy-to-see display with little variation between individuals. Also, the reliability of heat, humidity, light resistance, etc. was sufficient.

(Example 2) Polymethyl acrylate (PM
A) 70% by weight, PS 29.7% by weight, and 0.3% by weight of a polymer having PMA and PS in the graft chain were dissolved in toluene by heating, and dispersed by stirring and removing the solvent to prepare pellets containing PMA as a main component. .. The PMA-PS graft polymer is localized at the interface as a surfactant and has an average particle size of 0.8.
The μm PS micelles were stabilized to form a polymer emulsion. A light guide plate was formed by injection molding into a wedge shape having fine uneven surfaces, and aluminum was deposited on the back surface to form a reflective layer. A schematic cross-sectional view of the light guide plate thus manufactured is shown in FIG. Average particle size 0.
8 μm PS micelles were uniformly dispersed in the same state as in the raw material pellets.

The scattering angle of the light emitted from the light guide plate and the in-plane brightness distribution can be controlled by the refractive index of the micelles, the particle size distribution, the density distribution and the like. The light incident on the thick side surface of the wedge-shaped light guide plate from the illumination lamp is emitted with an angular distribution having a maximum value in the vertical direction due to diffraction at the micelle interface and diffuse reflection by the surface. The brightness uniformity on the surface is 9
It was 0% or more.

In the liquid crystal display device using the light guide plate thus manufactured, the brightness on the display surface is improved from 50 candela to 70 candela, as compared with the conventional backlight using the same illumination lamp. We were able to achieve a bright and easy-to-see display with little variation between individuals. Also, the reliability of heat, humidity, light resistance, etc. was sufficient.

Example 3 Polymethylmethacrylate (P
MMA) 90% by weight, polyvinyl acetate (PVAc) 9.
Pellets containing PMMA as a main component were prepared by dissolving 8% by weight and 0.2% by weight of a polymer having PMMA and PVAc in a graft chain in methyl ethyl ketone, dispersing by stirring and removing the solvent. PMMA-PVAc graft polymer is localized at the interface as a surfactant and has an average particle size of 0.15 μm.
The PVAc micelles of Example 1 were stabilized to form a polymer emulsion. A light guide plate was formed into a U shape by injection molding, and aluminum was deposited on the back surface to form a reflective layer. A schematic cross-sectional view of the light guide plate thus manufactured is shown in FIG. PVAc micelles having an average particle diameter of 0.15 μm were uniformly dispersed in the same state as in the raw material pellets.

The scattering angle of the light emitted from the light guide plate and the in-plane brightness distribution can be controlled by the refractive index of the micelles, the particle size distribution, the density distribution and the like. Light incident on the thick side surface of the U-shaped light guide plate from the two illumination lamps arranged on both sides is emitted from the surface in a substantially vertical direction due to diffraction at the micelle interface. The brightness uniformity on the surface was 90% or more.

In the liquid crystal display device using the light guide plate thus manufactured, the brightness on the display surface is improved from 70 candela to 90 candela, as compared with the conventional backlight using the same illumination lamp. We were able to achieve a bright and easy-to-see display with little variation between individuals. Also, the reliability of heat, humidity, light resistance, etc. was sufficient.

[0017]

As described above, according to the present invention, in the illuminating light guide plate of the liquid crystal display device having the illuminating lamp, the light guide plate is made into the transparent polymer A as the main component and the micelle for light scattering. By using a polymer emulsion composed of polymer B and an AB graft polymer or an AB block polymer which is a surfactant, it is possible to illuminate a liquid crystal display device having excellent brightness and homogeneity and a small number of parts.

Further, in the light guide plate for illumination of the liquid crystal display device, a transparent polymer A as a main component, a polymer B incompatible with A, and an AB graft polymer or an AB block polymer are dissolved in a common solvent and dispersed. After the solvent was removed to prepare polymer emulsion pellets having micelles with a proper diameter, the light guide plate was molded by injection molding or extrusion molding, which enabled stable manufacture. Since it was possible to reduce the number of components of the lighting, it was possible to improve the utilization efficiency of light and reduce the manufacturing cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing the concept of a light guide plate in Example 1 of the present invention.

FIG. 2 is a cross-sectional view schematically showing the concept of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 3 is a sectional view schematically showing the concept of a light guide plate in Example 2 of the present invention.

FIG. 4 is a sectional view schematically showing the concept of a light guide plate in Example 3 of the present invention.

[Explanation of symbols]

 11 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥・ ・ ・ ‥ Indicator lamp 31 ‥‥‥‥‥‥

Claims (5)

[Claims] 1. A light guide plate for illumination of a liquid crystal display device provided with an illumination lamp, wherein the light guide plate is a transparent polymer A containing a main component.
A light-guiding plate for illumination of a liquid crystal display device, which is a polymer emulsion comprising a micelle polymer B for light scattering and an AB graft polymer or an AB block polymer as a surfactant. 2. The illumination light guide plate of a liquid crystal display device according to claim 1, wherein the illumination light guide plate of the liquid crystal display device has a wedge shape or a U shape. 3. The light guide plate for illumination of a liquid crystal display device according to claim 1, wherein a metal layer for total reflection is formed on the back surface of the light guide plate for illumination of the liquid crystal display device. 4. The light guide plate for illumination of a liquid crystal display device according to claim 1, wherein the light guide plate for illumination of the liquid crystal display device is provided with a fine uneven surface for scattering light. 5. A transparent polymer A as a main component in the manufacture of a light guide plate for illumination of a liquid crystal display device equipped with an illumination lamp,
Polymer B, which is incompatible with, and AB graft polymer or AB block polymer are dissolved in a common solvent, and after dispersion, the solvent is removed to prepare polymer emulsion pellets having micelles of appropriate diameter, and injection molding or extrusion molding is performed. A method for manufacturing a light guide plate for illumination of a liquid crystal display device, characterized in that the light guide plate is formed into a shape of a light guide plate.