JPH0627328A - Illuminator - Google Patents

Abstract

PURPOSE:To attain high luminance uniformity, thinning in thickness, and high luminance by providing a notch of slit shape at the inside of a fitting part between a light conductive plate and a light diffusion sheet or a light reflecting sheet. CONSTITUTION:A diffusion system 5 provided by performing printing or shape giving on the plane 3 opposite the light emitting plane of a transparent plate 1 is formed in thin line shape or dot shape on the plane 3 and has specified distribution for a mirror surface part. A light source 6 is arranged at one plane or confronting two planes of the end face 4 of the transparent plate 1, and a light beam from the light source 6 is introduced to the transparent plate 1. Several sheets of diffusion sheets 7 are piled on the side of a light emitting surface 2 of the plate 1. A light reflecting sheet 9 is arranged at the side of a plane 3 opposite the light emitting plane. One or plural notches 11 of slit shape are provided on the sheet 7 or sheet 9 between or in the neighborhood of two points of fitting parts 8 almost perpendicularly to the line connecting the two points. Therefore, it is possible to prevent the diffusion sheet 7 or the optical reflecting sheet 9 from being broken by decreasing a force in the direction almost perpendicular to the notch 11, i.e., a shearing force applied to the tip part of the notch 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin lighting device.

More specifically, the present invention relates to an illuminating device comprising a rod-shaped light source and a light guide system and used as a backlight for a liquid crystal display or the like.

[0003]

2. Description of the Related Art FIG. 3 shows the structure of a conventional lighting device. The diffusion sheet 7, the light reflection sheet 9 and the transparent plate 1 are shown in FIG.
When they are integrated as described above, they are fastened at the fastening portion 8 by two or more points.

[0004]

However, when the linear expansion coefficient and the hygroscopic expansion coefficient of the transparent plate are larger than those of the light diffusing sheet or the light reflecting sheet, stress is applied to the fastening portion due to temperature change and moisture absorption, and the transparent plate is placed between the fastening points. Warps,
There is a problem in that the fastening portion is damaged and the light emitting surface has uneven brightness. Therefore, the present invention has been made in order to solve such a conventional problem, and an object thereof is to provide a lighting device having high quality such as brightness uniformity.

[0005]

In order to solve the above-mentioned problems, an illumination device according to the present invention comprises a transparent plate provided with a diffusion layer, a rod-shaped light source arranged adjacent to an end face of the transparent plate, and the transparent plate. In a lighting device having a light diffusing sheet or a light reflecting sheet fastened in a dot shape on the light emitting surface or a surface facing the light outgoing surface, a slit is formed inside a fastening portion of the light diffusing sheet or the light reflecting sheet with the light guide plate. It is characterized by having a notch. Further, it is characterized in that slit-like cuts provided in the light diffusion sheet or the light reflection sheet are provided in the vicinity of the respective fastening portions.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a transparent plate 1 is a transparent plate having a substantially rectangular shape and a certain thickness, and at least a light emitting surface 2 and a non-light emitting surface 3, preferably all surfaces are mirror surfaces (smooth surfaces). The transparent plate 1 may be made of any transparent material that absorbs less light and has a refractive index larger than air, but a refractive index of 1.41 or more is particularly desirable, and acrylic resin, polycarbonate resin, polystyrene resin, glass or the like is used. . When the refractive index is 1.41 or more, the critical angle becomes 45 degrees or less, and all the rays incident on the transparent plate 1 can be totally reflected by the mirror surface that is substantially perpendicular to the end surface 4.

A diffusing system 5 is provided on the reflection surface 3 of the transparent plate 1 by printing or adding a shape. The diffusing system 5 is formed in a thin line shape or a dot shape on the reflection surface 3 and has a constant distribution with respect to the mirror surface portion. This is because the light rays incident from the end surface 4 of the transparent plate 1 are totally reflected by the mirror surface portions of the light emitting surface 2 and the non-light emitting surface 3 that are substantially perpendicular to the end surface 4, and travel further in the transparent plate 1 from the end surface 4. On the other hand, it is necessary for the light to reach the diffusing system 5 with a certain probability and a part of the light is emitted from the light emitting surface 2.

It is desirable that all the surfaces constituting the transparent plate 1 are mirror surfaces because the transparent plate 1 is plate-shaped and the other surfaces are small in area with respect to the light emitting surface 2 and the non-light emitting surface 3. However, the probability of light rays staying in the transparent plate 1 is increased due to the effect of total reflection, and as a result, the light emission efficiency is increased. For example, when a substantially rectangular acrylic plate is used as the transparent plate 1, since the critical angle is about 42 degrees, the light rays incident from the end face 4 will come from other than the end face on the opposite side of the end face 4 unless they reach the diffusion system 5. It will not come out.

A light source 6 is arranged adjacent to the end surface 4 of the transparent plate 1. The light source 6 may be any of a fluorescent tube, an incandescent lamp, linearly arranged light emitting diodes, light introduced by an optical fiber, etc., but a fluorescent tube is suitable depending on conditions such as luminous efficiency, color and handling. The light source 6 is arranged on one surface of the end surface 4 of the transparent plate 1 or on two surfaces facing each other, and a light beam from the light source 6 is guided to the transparent plate 1.

On the light emitting surface 2 side of the transparent plate 1, one or several diffusing sheets 7 are stacked and arranged, and on the side opposite to the light emitting surface 3 a light reflecting sheet 9 is arranged. The diffusing sheet 7 and the light reflecting sheet 9 are arranged with respect to the transparent plate 1 with a slight air layer therebetween, and this air layer is necessary for total reflection due to the critical angle described above. The light reflection sheet 9 has a function of returning the light rays that have been diffused by the diffusing system 5 and then reflected by the light exit surface 2 and passed through the opposite light exit surface 3 to the diffusing sheet 7 side. A reflector sheet 10 is arranged so as to cover the light source 6. The reflector sheet 10 has a function of guiding the light beam from the light source 6 to the end face 4, and is made of a plastic sheet, a molded article, or the like in which white or silver or aluminum is vapor-deposited.

Polycarbonate resin is used for the diffusion sheet 7,
Acrylic resin or the like is used, and one surface has a roughly flat surface and the other surface has a random uneven shape or a double-sided uneven shape. The diffusion sheet 7 has a prism surface,
By combining various diffusing sheets to have a lens effect, the light rays emitted from the light emitting surface 2 are refracted in a direction in which the light rays are distributed substantially perpendicularly to the light emitting surface 2. With this effect, the brightness when viewed from the front can be increased by about 20 to 50% as compared with the case where one normal diffusion sheet is used.

The transparent plate 1, the diffusion sheet 7 and the irregular reflection plate 7
Welding is used to integrate the two. Examples of the welding method include heat welding and ultrasonic welding. In the case of welding at two points as shown in FIG. 3, when the linear expansion coefficient and the hygroscopic expansion coefficient of the transparent plate 1 are larger than those of the diffusion sheet 7 or the light reflection sheet 9, the transparent plate 1 warps or is tightened due to temperature change and moisture absorption. Part 8
However, there is a problem in that the light emitting surface is damaged and the brightness is uneven. Therefore, in the present invention, as shown in FIG. 2 (A), slit-like cuts 11 are formed in the diffusion sheet 7 or the light reflection sheet 9 between two fastening portions 8 or between two fastening portions 8 in the vicinity thereof. One or more were provided almost vertically. The reason why the notch 11 is provided in the vicinity of the fastening portion 8 is to prevent the damage to the diffusion sheet 7 or the light reflection sheet 9 by reducing the force in the direction substantially perpendicular to the notch 11 at the tip end of the notch 11, that is, the shearing force. This effect is
It is more effective that the cut position is closer to the fastening portion 11. Further, if a plurality of cuts 11 are provided, the total deformation amount due to temperature change and moisture absorption can be dispersed to each cut, and the damage of the diffusion sheet 7 or the light reflection sheet 9 can be prevented as described above. Therefore, even if the transparent plate expands due to moisture absorption, the slit-like notch 11 opens to relax the stress applied to the welded portion, that is, the fastening portion 8 as shown in FIG. Can be overcome.

[0013]

According to the present invention, as described above,
A slit-like cut is provided between the welded portions of the light diffusion sheet or the light reflection sheet to avoid obstacles such as warpage of the transparent plate due to temperature changes and differences in elongation due to moisture absorption. As a result, it is possible to provide a thin and high-luminance illuminating device having high luminance uniformity.

In particular, the lighting device of the present invention is useful as a surface lighting device for a liquid crystal display device.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2A is an explanatory view showing the assembling of the present invention. (B) Explanatory drawing which shows the effect of this invention at the time of temperature change and moisture absorption.

FIG. 3 is a perspective view showing a conventional example of a lighting device.

[Explanation of symbols]

 1 ・ ・ ・ Transparent plate 6 ‥‥ Light source 7 ‥‥‥‥‥‥‥‥‥ Diffusion sheet 8 ‥‥‥‥‥

Claims (2)

[Claims] 1. A transparent plate provided with a diffusion layer, a rod-shaped light source disposed adjacent to an end surface of the transparent plate, and a light diffusion sheet fastened in a dot shape on a light emitting surface of the transparent plate or a surface facing the light emitting surface. Alternatively, in the illuminating device having a light reflecting sheet, the illuminating device has a slit-like notch inside a fastening portion of the light diffusing sheet or the light reflecting sheet with the transparent plate. 2. The lighting device according to claim 1, wherein slit-shaped cuts provided in the light diffusion sheet or the light reflection sheet are provided in the vicinity of the respective fastening portions.