Light diffusing plate and lighting device using it

Abstract

A light diffusion plate (2a) with an optical element array (1, 1′) integrally formed on the front and back, and a box-shaped light reflection plate ( 3) Constructing a direct-type lighting device, thereby providing a light-diffusing plate and a thin direct-type lighting device having the light-diffusing plate, which can eliminate brightness unevenness (uniform brightness) in the number of light sources (distance between light sources) at a practical level ) and achieve high brightness (exhibiting the same brightness as when laminating conventional prism sheets).

Description

technical field [0001] 0001 [0002] The present invention relates to a light diffuser formed by integrally forming an array of optical elements on the front and back, and a direct lighting device configured by placing the light diffuser on a box-shaped light reflection plate provided with a light source inside. . Background technique [0003] 0002 [0004] Conventionally, in order to eliminate the light shadow of the light source (fluorescent tube) of the backlight unit in a liquid crystal display with a large screen, firstly, a light diffusion plate is provided. [0005] The light diffusion plate is required to have the property of dispersing the transmitted light over a wide angle in the traveling direction. [0006] In addition, in order to project transmitted light with high brightness on the entire surface of the liquid crystal module, a light diffusion plate is usually used as a support, and at least one prism sheet is interposed between the light diffusion plate a...

AI Technical Summary

Problems solved by technology

[0010] However, in the assembly process of the liquid crystal backlight, there is a problem that the prism sheet must be assembled with two other optical functional films (light diffusing film, polarized light separation film, etc.) according to different situations, so the process is long and difficult. Complicated, the cost of these optical functional films including prism sheets increases, resulting in decreased productivity

Therefore, the problem is that the brightness unevenness is serious when emitting light, and the light emission is uneven.

Among them, in the case where the concavo-convex pattern is an optical element array composed of V-shaped groove prisms with a cross-sectional apex angle of 90°, there is a problem that as the position from the center between the light sources approaches to the position directly above the light source, due to the Total reflection characteristics, the incident light cannot exit (transmit) from the exit surface, on the contrary, it is reflected to the light source side, the brightness is extremely reduced, the darkest is directly above the light source, and the luminescence is uneven, which is difficult to be practical

[0013] In addition, there is also an attempt to form a linear Fresnel lens on the surface (for example, refer to Patent Document 3), but there is a problem that in the case of a linear light source such as a cold cathode tube, although the viewing angle dependence is high, the front brightness is high. And uniform, but when viewed from an oblique direction, the brightness will be extremely reduced, but the shadow of the light source is very obvious

However, although thinning can be achieved with this method, it is difficult to achieve weight reduction due to the use of multiple light guide plates

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