Optical sheet, surface light source device, and transmissive image display device

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet capable of making printed dots formed on the rear face hard to be seen from the front side, as well as a surface light source device and a transmission-type image display device equipped with the same.SOLUTION: The optical sheet 30 formed of translucent resin includes: a side face 33 to make light incident from a light source 22; an emitting face which is formed in a direction crossing the side face and from which planar light is emitted; a rear face opposed to the emitting face; the printed dots which is printed on the rear face and which reflects the light incident from the side face to an emitting face side; and a plurality of protruding parts which are formed on the emitting face, can emit the light incident from the side face, is extended in one direction, and is arranged in parallel in a direction orthogonal to the one direction. The protruding parts are constituted so as to satisfy an equation (1): H×T / P≥0.23, wherein P is a spacing (μm) between neighboring protruding parts, H is a height (μm) of the protruding parts, and T is a thickness (mm) of the sheet.

Description

technical field [0001] The present invention relates to an optical sheet, a surface light source device, and a transmissive image display device that emit light incident from a side surface of the sheet from an emission surface formed in a direction intersecting the side surface. Background technique [0002] As a backlight used as a surface light source device for a liquid crystal display (transmission type image display device), light sources such as cold cathode tubes and LEDs are arranged in parallel on the back side of the light diffusion plate, and the light incident from the back of the light diffusion plate is directed to the front. Direct type with side emission; and edge light type with light sources such as cold cathode tubes and LEDs arranged on the side of a transparent plate, that is, a light guide plate, and emitting light from the side of the light guide plate to the front side. In the past, as a backlight, from the viewpoint of improving brightness, the dire...

AI Technical Summary

Problems solved by technology

If the size of the display is increased, the output power of the light source needs to be increased, so there is a problem that it is easy to see the printed dots printed on the light guide plate from the screen (image display surface)

Furthermore, due to the increase in the size of the display, it is necessary to greatly change the level (gradation) of the dot diameter, so there is a tendency that the dot with a smaller diameter near the light source is easier to see

In addition, if the thinning of the display is promoted, the thinning of the light guide plate will be promoted, and the trend of making the printed dots easier to see will be further strengthened.

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