JPH06242322A - Surface light source device - Google Patents

Abstract

PURPOSE:To uniform the distribution of luminance on a light emitting face even by a surface light source device having a wide light emitting face by increasing the diameters of hollow particles mixed into a light guiding body in accordance with a distance separated from the light source. CONSTITUTION:The diameters of all light transmissive hollow powdery bodies 5 mixed into the light guiding body 1 are <=1mum and the powdery bodies 5 are mixed so that the diameters are reduced in accordance with a distance approached the light source 2 and increased in accordance with a distance separated from the light source and distribution density is reduced in accordance with a distance approached the light source 2 and increased in accordance with the distance separated from the light source 2. Thus a difference in the quantity of projected light on the projection face 1a of the light guiding body between a part near to the light source 2 and a part far from the light source 2 is removed by mixing the light transmissive hollow powdery bodies 5. Consequently the surface light source device having extremely uniform luminance distribution can be provided changing both the diameters and distribution density of hollow particles mixed into the light guiding body and setting up the diameters of the hollow particles to <=10mum, preferably <=1mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source device using a light guide.

[0002]

2. Description of the Related Art FIG. 2 shows a structure of a conventional surface light source device using a light guide body. In the light guide body 1, bubbles 6 are mixed in a diffused state, and the bubbles 6 are formed. The distribution close to the light source 2 is sparse, and the distribution becomes denser as the distance from the light source 2 increases. The light emitted from the light source 2 enters the light guide body 1 through the incident end face 1a of the light guide body, and is diffused by hitting the light-transmissive bubbles 6 while being transmitted through the light guide body 1. Is diffused by being reflected by an inner surface of the light guide 1 or by a reflection sheet 4 arranged on the side facing the light exit surface 1a of the light guide, and emitted from the light exit surface 1a of the light guide, and By passing through the diffusion sheet 3 arranged on the emission surface 1a of the light guide, the light is further diffused and becomes a uniform surface light source.

[0003]

However, even with the above-mentioned surface light source device, the luminance distribution is not uniform over the entire light emitting surface. The brightness on the light emitting surface close to the light source 2 is inevitably high, and the brightness on the light emitting surface decreases as the distance from the light source 2 increases. Particularly, in the case of a surface light source device having a large light emitting surface area, the difference in the distance from the light source 2 between the portion close to the light source 2 and the portion far from the light source 2 becomes large, and therefore the difference in luminance between the high luminance portion and the low luminance portion Has grown.

An object of the present invention is to provide a surface light source device having a wide light emitting surface, in which the luminance distribution on the light emitting surface is uniform.

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, the diameter of hollow particles mixed in a light guide body is made smaller as the distance from the light source is smaller and becomes larger as the distance from the light source is increased. Solves the above-mentioned problem by making the density closer to the light source and making the density closer to the light source.

[0006]

[Function] When the diameter of the hollow particles mixed in the light guide body is increased, the probability that the light entering the light guide body hits the hollow particles increases, and the light hitting the large diameter hollow particles becomes the small diameter hollow particles. It is more diffuse than the light it strikes. Therefore, more light is emitted from the emission surface of the light guide. However, it was found from an experiment that, when the diameter of the hollow particles is larger than 10 μm, only the hollow particles are extremely bright when viewed from the exit surface side of the light guide. Further experiment shows that the diameter of hollow particles is about 1μ
It was found that about m has the highest light diffusion effect.

When the diameter of the hollow particles is larger than 10 μm, only the hollow particles become extremely bright and the uneven brightness on the emission surface of the light guide cannot be reduced. Not only is the diameter of the light guide changed, but the density of the hollow particles inside the light guide is also changed, so that the brightness on the exit surface of the light guide is further changed. The higher the density of the hollow particles in the light guide, the higher the probability that light entering the light guide will hit the hollow particles,
The light incident on the light guide is more diffused, the brightness on the exit surface of the light guide increases in the vicinity thereof, and conversely, if the distribution density of hollow particles is low, the light incident on the light guide is more The probability of hitting the hollow particles decreases, and the amount of light emitted from the emission surface of the light guide decreases.

[0008]

EXAMPLE An example in which a permeable hollow powder body is used as the hollow particles will be described with reference to FIG. FIG. 1 is a diagram showing an example of the configuration of a surface light source device according to the present invention. 1
Is a light guide made of a transparent material, 2 is a linear light source arranged in the vicinity of the light guide 1, 3 is a diffusion sheet arranged on the exit surface 1a of the light guide, and 4 is a light guide. The reflection sheet 5 arranged on the side of the body facing the emission surface 1 a is the light guide body 1.
It is a light-transmissive hollow powder body mixed in a large number.

The diameters of the light-transmissive hollow powder bodies 5 mixed in the light guide body 1 are all 1 μm or less, and the diameter becomes smaller as it gets closer to the light source 2 and becomes larger as it gets away from the light source 2. Has been done. Further, the distribution density of the light-transmissive hollow powder body 5 is sparser as it is closer to the light source 2, and is mixed so as to become denser as it goes away from the light source 2. By mixing the light-transmissive hollow powder body 5 in this way, the difference in the amount of light emitted from the light exit surface 1a of the light guide between the portion near the light source 2 and the portion far from the light source 2 is eliminated.

By changing both the diameter and the distribution density of the light-transmitting hollow powder body 5, it is possible to reduce the brightness unevenness on the exit surface 1a of the light guide body as compared with the conventional case. By setting the diameter of the light-transmitting hollow powder body 5 to 1 μm or less, the diameter of the light-transmitting hollow powder body 5 is increased more than necessary, and the diffusion effect of the light-transmitting hollow powder body 5 is reduced. In addition, the distribution density of the light-transmissive hollow powder body 5 cannot be increased, and the amount of light emitted from the light exit surface 1a of the light guide can be increased more effectively, and a part of the light exit surface 1a can be obtained. You can only prevent it from becoming extremely bright locally.

In the above embodiments, only the surface light source device in which one light source is arranged on one side of the rectangular light guide 1 has been described, but the present invention is not limited to this. For a surface light source device in which light sources are arranged on a large number of sides, a surface light source device using the light exit surface 1a, or a light guide body 1 in which the surface opposite to the light exit surface 1a is recessed in a mortar. Can be adapted.

When the exit surface 1a of the light guide used in the surface light source device has a small area, the diameter of the light-transmissive hollow powder body 5 may be 10 μm or less. If the diameter of the light-transmissive hollow powder body 5 is too small, it is difficult to control the dimensions, and therefore the diameter of the light-transmissive hollow powder body 5 is not made smaller than necessary. Further, by providing a pattern on the surface of the light guide opposite to the emission surface 1a for reducing the uneven brightness on the emission surface 1a due to printing or unevenness, the uneven brightness on the emission surface 1a is reduced. By reducing to some extent, the diameter range of the light-transmitting hollow powder body 5 is 10 μm.
It may be as follows.

Further, instead of the light-transmitting hollow powder body 5, when the light guide 1 is molded, a foaming substance is mixed into a synthetic resin for molding the light guide 1 and heat is applied. Therefore, hollow particles may be formed in the light guide body 1 by foaming.

Further, instead of the light-transmitting hollow powder body 5, bubbles may be mixed in the light guide body 1 so that both the diameter and the distribution density are changed. Depending on the case, even if the outer periphery is coated with a reflective substance to diffusely reflect the light, particles or the like may be mixed so that both the diameter and the distribution density are changed. Good.

[0015]

According to the present invention, by changing both the diameter and the distribution density of the hollow particles mixed in the light guide body, and further making the diameter of the hollow particles 10 μm or less, preferably 1 μm or less, extremely uniform brightness can be obtained. A surface light source device having a distribution can be realized.
However, if the diameter of the hollow particles is 10 μm or more, only the hollow particles become extremely bright, which causes uneven brightness of the surface light source device, which is not preferable.

[Brief description of drawings]

FIG. 1 is a side view showing an example of the configuration of a surface light source device according to the present invention.

FIG. 2 is a side view showing an example of the configuration of a conventional surface light source device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light guide body 1a Emission surface 2 Light source 3 Diffusion sheet 4 Reflection sheet 5 Hollow powder body

Claims (4)

[Claims] 1. A light guide body made of a transparent material, a linear light source arranged near an end face of the light guide body, a diffusion sheet arranged on an emission surface of the light guide body, and the conductive sheet. A reflecting sheet disposed on the side opposite to the emission surface of the light body, and hollow particles mixed in the light guide body so that the distribution density becomes closer to the light source and becomes denser as the distance from the light source increases. In the surface light source device, all the hollow particles have a diameter within a range of 10 μm or less, and the hollow particles nearer to the light source have a smaller diameter, and the hollow particles have a larger diameter as the distance from the light source increases. Surface light source device. 2. The surface light source device according to claim 1, wherein the hollow particles are light-transmissive hollow powder bodies. 3. The surface light source device according to claim 1, wherein the hollow particles are foams. 4. The surface light source device according to claim 1, wherein the hollow particles are bubbles.