Diffusion sheet, surface light source device and transmission display unit

Abstract

A diffusion sheet capable of unevenness-free, uniform lighting regardless of a screen observing position, a surface light source device and a transmitting display unit. The transmitting display unit (10) comprises an LCD panel (11) and a surface light source device (16) for illuminating the LCD panel (11) from behind. The surface light source device (16) has a plurality of cathode ray tubes (13) arranged side by side. A diffusion sheet (14) and a converging sheet (12) are provided between the cathode ray tubes (13) of the surface light source device (16) and the LCD panel (11). Diffusion lens arrays (141) are formed on the light outgoing side of the diffusion sheet (14). The diffusion lens arrays (141) have a plurality of unit lens (a plurality of sets each consisting of a low unit lens (141a) and a high unit lens (141b) that are arranged are regularly arranged and disposed) each of which forming a shape corresponding to part of an elliptical tube having an elliptical section. The converging sheet (12) has a plurality of unit lenses (121) that are formed along the sheet surface on the cathode ray tube (13) side and have almost trapezoidal sectional shapes. The above arrangement can diffuse lighting lights from the cathode ray tubes (13) of the surface light source device (16) to provide a uniform lighting and converge lighting lights to enhance a light utilization efficiency as a back light.

Description

technical field [0001] The present invention relates to a display device such as a liquid crystal display device, and more particularly to a diffuser plate used for a surface light source device such as a transmissive liquid crystal display device backlighting, a surface light source device, and a transmissive display device using them. Background technique [0002] As a surface light source device for illuminating a transmissive liquid crystal display device or the like from the back, various types of surface light source devices have been proposed and put into practical use. Such surface light source devices are mainly classified into edge light type and direct type according to the method of converting a non-surface light source into a surface light source. [0003] Among them, for example, a direct-type surface light source device is configured by using cathode ray tubes (light-emitting tubes) arranged in parallel to directly introduce light from the back of a tran...

AI Technical Summary

Problems solved by technology

However, in such a conventional direct-type surface light source device, there is a problem that there are too many optical plates required, and the light-converging characteristics are relatively insufficient. In order to compensate for this deficiency, transmissive displays such as LCD panels have been improved. The structure of the part itself, so that the incident light from an oblique direction will not reduce the image quality

However, in this conventional method, there are problems in that the utilization efficiency of light is lowered, and the structure of a transmissive display portion such as an LCD panel becomes complicated, resulting in an increase in cost.

Therefore, especially for the light transmitted after total reflection, it emerges from the plate at a relatively large exit angle, and the exit light spreads in a wider range, and there is a problem that it is difficult to converge the exit light to the required exit angle range.

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