Optical sheet and backlight unit using the same

Abstract

Provided are an optical sheet having specifically high optical function, especially light diffusion function, the light angulating function to the normal direction and its control function, and a backlight unit using the same. The invention is an optical sheet which has a light reflective sheet substrate on its surface, and a plurality of light guide holes penetrating from the top face of the substrate to the lower face and having a light outlet part on the top face side and a light inlet part at the lower side. The area ratio (S1 / S2) of the average area (S1) of the light outlet part relative to the average area (S2) of the light inlet part is from 1 to 10000, the stuffing rate of the light outlet part is from 70% to 100 %. The average thickness of the substrate is preferably from 5[mu]m to 5mm, and the average area (S1) of the light outlet part is preferably from 25[mu]m2 to 25mm2.

Description

Technical field [0001] The present invention relates to an optical sheet with optical functions such as light diffusion and angle change of light in the normal direction, and particularly to an optical sheet suitable for a backlight unit for a liquid crystal display device and a backlight unit using the optical sheet. Background technique [0002] The liquid crystal display device is generally a backlight method in which a liquid crystal layer is irradiated from the back side, and an edge-light type (side-light type), direct-type, or other backlight unit is installed on the lower surface of the liquid crystal layer. The edge-light type backlight unit 70 is generally as Figure 11a As shown, it is provided with a rod-shaped light source 71 as a light source, a rectangular plate-shaped light guide plate 72 whose ends are arranged along the light source 71, and a plurality of optical sheets 73 laminated on the surface side of the light guide plate 72 . This optical sheet 73 has spec...

AI Technical Summary

Problems solved by technology

[0006] However, the optical functions of this microlens sheet, such as light collection, light diffusion, and angle change to the normal direction, depend on the surface shape and refractive index, so there is a certain limit in the improvement of functions.

Especially for direct-lit backlights, when the light diffusion function of the optical sheet is not sufficient, the elimination effect of the lamp image (lamp image) is small, and there is a problem that the lamp image appears on the surface of the LCD screen.

Therefore, in the conventional backlight unit 70, although it is expensive and difficult to handle, it is necessary to have a plurality of optical sheets.

In the case of having a plurality of optical sheets in this way, there is a disadvantage that the brightness of the liquid crystal display device is lowered, and it also hinders the thinning of the backlight unit.

Also, in order to control the emission direction of the light, the surface shape of the microlens must be adjusted, but this adjustment and the control of the emission direction through this adjustment are technically not easy.

Images