Light diffusion plate and direct type backlight unit

Abstract

A light diffusion plate for a direct-lit backlight unit is provided which is capable of inhibiting generation of defects in production, and which is superior in mechanical strength even if being formed to be thin. The light diffusion plate for a direct-lit backlight unit includes a resin matrix, and a diffusion agent dispersed in the resin matrix, in which a principal component of the resin matrixis a polycarbonate resin, a ratio Mw / Mn of a polystyrene equivalent weight average molecular weight Mw to a number average molecular weight Mn of the polycarbonate resin, as determined by gel permeation chromatography is no less than 1.8 and no greater than 3.2, and the weight average molecular weight Mw of the polycarbonate resin is no less than 3.0*104 and no greater than 6.5*104. The light diffusion plate has an average thickness of preferably no less than 0.1 mm and no greater than 1.0 mm.

Description

technical field [0001] The present invention relates to a light diffusion plate and a directly under-type backlight unit. Background technique [0002] LEDs are used as backlights for liquid crystal display devices. Two types of backlights using LEDs are known, an edge type and a direct type. The edge type backlight is a backlight in which LEDs are linearly arranged above and below the screen or left and right, and the direct backlight is a backlight in which LEDs are arranged two-dimensionally on the entire surface behind the screen. The edge-type backlight does not need to arrange LEDs on the back of the screen, so it can reduce the thickness of the liquid crystal display device. On the other hand, the direct type backlight requires space for disposing LEDs on the back of the screen, but high brightness can be obtained by using a large number of LEDs. [0003] Conventionally, direct type backlights have been adopted for large liquid crystal display devices, but as LEDs ...

AI Technical Summary

Problems solved by technology

[0006] On the other hand, in the molding of the light diffusing plate, in order to ensure the fluidity of the forming material, when the molding temperature of the light diffusing plate is set high unavoidably, the inner part of the light diffusing plate is generated from undissolved There is a possibility that the optical characteristics of the light diffusion plate will be reduced due to defects such as material and deterioration

It is considered to separate these defects using a gel-like foreign matter removal filter in a state where the forming material of the light diffusion plate is dissolved, but it is difficult to selectively separate only the defects because the light diffusion plate contains a diffusing agent