JP2012048915A - Lighting device, and display device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device which has high utilization efficiency of light by increasing light components in a direction orthogonal to a light emitting surface among light from a light source.SOLUTION: Concave surface forming minute structures 3 are produced on the light emitting surface 4 or an opposed surface opposite to the light emitting surface of a light guide plate 2. The minute structure has a reflecting face for forming an angle of 40-60° against a bottom face and side faces approximately perpendicular to the light emitting surface of the light guide plate, and is arranged in such a manner that the bottom face in relation to the reflecting face to be approximately perpendicular to an optical path connecting between the light source and the minute structure.

Description

  The present invention relates to a display device used for a portable information device such as a mobile phone or a mobile computer, and a lighting device used for the display device.

  The liquid crystal display device includes an illumination device as a light source. As a type of illumination device, an edge light type illumination device is known in which light from a light source is incident from a side surface of a light guide plate and is emitted from an upper surface of the light guide plate (hereinafter referred to as an emission surface).

  Conventionally, in an edge light type illuminating device, in order to improve and equalize the luminance of the illuminating device, a large number of grooves and dot patterns are formed on the exit surface of the light guide plate and the opposite surface to the exit surface. It has been proposed to diffuse light from a light source. A configuration in which a quadrangular pyramid-shaped diffusion pattern is formed on the exit surface or the opposing surface of a light guide plate is widely known for such an illumination device (see, for example, Patent Document 1 and Patent Document 2).

JP 2007-280952 A JP 2008-311210 A

  However, when a quadrangular pyramid-shaped microstructure is used, such as the diffusion patterns disclosed in Patent Document 1 and Patent Document 2, light is transmitted by all the inclined surfaces of the four side surfaces forming the microstructure. It will be reflected. FIG. 7 is a top view schematically showing an illuminating device in which a quadrangular pyramid-shaped microstructure is formed on a light guide plate. Since the light 19 from the light source is incident substantially perpendicular to the base of the light source side slope of the fine structure 3, the light 19 is emitted in a direction perpendicular to the emission surface of the light guide plate. On the other hand, when the light 18 from the light source is reflected by the side surface of the light guide plate 2, it is reflected by another inclined surface (side surface side inclined surface of the light guide plate) of the microstructure 3. At this time, the light 18 is difficult to enter perpendicularly to the bottom of the slope, and the light 18 is diffused without being emitted in a direction perpendicular to the emission surface of the light guide plate. Thus, when the shape of the fine structure is a quadrangular pyramid, the slope other than the light source side slope becomes a diffusion surface, and the utilization efficiency of light from the light source decreases.

  In order to solve the above-described problems, a concave microstructure having a reflecting surface and two side surfaces is provided on the upper surface (outgoing surface) or the lower surface (opposing surface) of the light guide plate of the lighting device. When the virtual surface obtained by extending the surface of the light guide plate is the bottom surface of the fine structure, the reflection surface of the fine structure forms an angle of 40 to 60 degrees with the bottom surface. Further, the two side surfaces of the fine structure are formed substantially perpendicular to the exit surface of the light guide plate. Further, the reflection surface is arranged so that the bottom side is substantially perpendicular to the optical path connecting the light source and the fine structure.

The shape of the fine structure may be a triangular frustum.
The height of the fine structure may be 1 to 10 μm.
Furthermore, the fine structures may be arranged so that the density increases as the distance from the light source increases.

Alternatively, the fine structure may be arranged so that its size increases as the distance from the light source increases.
In the display device of the present invention, a non-self-luminous display element is disposed on the light exit surface of the light guide plate of any one of the above illumination devices.

  According to the configuration of the illumination device of the present invention, among the light from the light source, the light component diffused on the side surface of the fine structure can be reduced, and the light component in the direction perpendicular to the emission surface can be increased. A lighting device with high light utilization efficiency can be realized.

It is sectional drawing which shows typically the structure of the illuminating device by this invention. It is a perspective view which shows typically the microstructure of the illuminating device by this invention. It is sectional drawing which shows typically the microstructure of the illuminating device by this invention. It is a top view which shows typically the structure of the illuminating device by this invention. It is a top view which shows typically the structure of the illuminating device by this invention. It is sectional drawing which shows typically the structure of the display apparatus by this invention. It is an upper view which shows typically the structure of the conventional illuminating device.

In a lighting device and a display device using a light source and a light guide plate, a concave microstructure is formed on either the upper surface or the lower surface of the light guide plate. This fine structure has a reflection surface and two side surfaces. When a virtual surface obtained by extending the surface of the light guide plate is a bottom surface of the fine structure, the reflection surface forms an angle of 40 to 60 degrees with the bottom surface. The two side surfaces are formed substantially perpendicular to the upper surface of the light guide plate, that is, the exit surface. Furthermore, the fine structure is disposed so that the bottom of the reflection surface is substantially perpendicular to the optical path connecting the light source and the fine structure. The shape of the fine structure may be a triangular frustum. With such a configuration, it is possible to reflect light from the light source only on the reflection surface of the fine structure toward the upper surface of the light guide plate, that is, the emission surface direction. Further, the light hitting the side surface of the fine structure enters the light guide plate again without being diffused, and is reflected in the direction of the emission surface by the reflection surface of the other fine structure. Therefore, the light component in the direction perpendicular to the emission surface can be increased, and the light use efficiency from the light source can be increased.
The lighting device and display device of the present invention will be specifically described below with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing the configuration of the illumination device of this embodiment. A light guide plate 2 that guides light emitted from the light source 1 is disposed in front of the light source 1. The light source 1 is disposed to face the incident surface of the light guide plate 2. A plurality of microstructures 3 are formed in a concave shape on a surface opposite to the light exit surface 4 of the light guide plate 2 (hereinafter referred to as an opposing surface). A reflection plate 15 is disposed below the light guide plate 2 on the opposite surface side.

  FIG. 2 is a perspective view schematically showing the configuration of the fine structure 3 of the present embodiment. As shown in the drawing, the microstructure 3 of the present invention has a triangular frustum shape, and is formed of a reflective surface 5, two side surfaces 6, and five surfaces of an upper base 7 and a bottom surface substantially parallel to the emission surface. The In this embodiment, a virtual surface obtained by extending the facing surface of the light guide plate is used as the bottom surface of the fine structure 3. The height of the fine structure 3 is about 1 to 10 μm. The reflecting surface 5 is disposed so as to face the light source 1 and has a function of reflecting light from the light source in a direction perpendicular to the exit surface of the light guide plate. The angle formed between the reflecting surface 5 and the bottom surface is 40 to 60 degrees. The side surface 6 is formed to be substantially perpendicular to the exit surface of the light guide plate.

  FIG. 3 shows another embodiment of the microstructure 3 of this example. As shown in the figure, the fine structure 3 may be formed from a straight line 9 and a curved line 8. By adopting such a shape, the moldability at the time of injection molding is improved, and the difference in shape between the mold and the injection molded product can be reduced.

  Next, the behavior of light in the light guide plate 2 will be described with reference to FIG. Since the light 19 from the light source is incident on the bottom of the slope of the fine structure 3 perpendicularly, it is reflected in the vertical direction with respect to the light guide plate and exits from the exit surface. The light 18 from the light source is reflected by the side surface of the light guide plate 21 and is refracted and incident on the light guide plate again when it hits the side surface of the fine structure 3a. The light that has entered again is reflected in the vertical direction with respect to the light guide plate by the reflecting surface of another fine structure 3b. In this way, by forming the side surface 6 of the fine structure substantially perpendicular to the emission surface, the light hitting the side surface of the fine structure again enters the light guide plate and is reflected by the reflection surface of another fine structure. It is possible to reflect in the direction perpendicular to the exit surface of the light guide plate. For this reason, the light component diffused by the side surface of the microstructure is reduced in the light from the light source, and the light component traveling perpendicular to the exit surface of the light guide plate is increased. Efficiency can be improved.

  Next, the arrangement of the fine structures 3 will be described with reference to FIGS. 5 (a) and 5 (b). FIG. 5A and FIG. 5B are top views schematically showing the configuration of the illumination device of this embodiment.

  As shown in FIG. 5A, a plurality of fine structures 3 are arranged on the opposite surface side of the light guide plate 2. Each fine structure 3 is installed such that its reflection surface faces the light source 1. Further, the fine structure 3 is arranged so that the bottom of the reflection surface 5 is substantially perpendicular to the optical path 10 connecting the light source 1 and each fine structure 3. By arranging the fine structure 3 in this way, the light incident from the light source 1 is reflected by the reflection surface of the fine structure 3 and is emitted in the vertical direction from the emission surface, so that the light use efficiency is maximized. be able to.

  Further, the plurality of fine structures 3 are arranged so that the density increases as the distance from the light source 1 increases. In the light guide plate 2, the closer to the light source 1, the larger the amount of light.

  FIG.5 (b) is a figure which shows typically another embodiment of the illuminating device of a present Example. In the present embodiment, the fine structure 3 is arranged so that its size increases as the distance from the light source 1 increases. By arranging in this way, the light incident from the light source 1 can be uniformly emitted from the emission surface 4 of the light guide plate 2 as in the configuration shown in FIG. Further, the fine structures 3 may be arranged so that both the density and the size increase as the distance from the light source 1 increases.

  FIG. 6 is a cross-sectional view schematically showing the display device of this example. The display device of the present embodiment has a configuration in which the liquid crystal display element 16 is disposed above the lighting device 17 described in the first embodiment, and the liquid crystal display element 16 is irradiated by the lighting device 17.

  The liquid crystal display element 16 is formed by the liquid crystal panel 12 and the polarizing plate 11 attached to the upper and lower surfaces of the liquid crystal panel 12. Although not shown, the liquid crystal panel 12 has a liquid crystal layer sealed in a gap between two glass substrates with a sealing material. An illumination device 17 is installed below the liquid crystal display element 16 and irradiates illumination light from the back surface of the liquid crystal display element 16. The illuminating device 17 includes a light source 1, a light guide plate 2 disposed on the side of the light source 1, a reflection plate 15 installed on the back surface of the light guide plate 2, a diffusion plate 14 installed on the exit surface of the light guide plate 2, A rim sheet 13 is provided. A fine structure 3 is formed on the light guide plate 2 in the same manner as shown in the first embodiment.

  In each of the above-described embodiments, the fine structure is formed in a concave shape on the opposing surface, but the fine structure may be formed in a concave shape on the output surface. In that case, a reflecting plate is disposed below the light guide plate. Thereby, the light from the light source is reflected by the reflecting surface of the fine structure, and when it is emitted from the opposing surface, it is reflected by the reflecting plate, returns to the light guide plate, and can be emitted from the emitting surface.

  In each of the above-described embodiments, the shape of the fine structure is a triangular frustum, but it may be a triangular pyramid. However, the triangular frustum can improve the reliability in molding.

  Further, the light source 1 of each of the above-described embodiments is a point light source, and a side view type white LED is assumed. However, a top view type white LED or a bullet type white LED has a color other than white. It doesn't matter. As a white LED, a blue LED with a yellow phosphor potted may be used. Further, as the light guide plate 2, a molded product of a transparent resin such as COP (cycloolefin polymer), PMMA, or PC may be used.

  The illumination device and the display device according to the present invention can be applied to display devices such as a mobile phone and a digital camera.

DESCRIPTION OF SYMBOLS 1 Light source 2 Light-guide plate 3 Fine structure 4 Output surface 5 Reflective surface 6 Side surface 7 Upper bottom 8 Curve 9 Straight line 10 Optical path 11 Polarizing plate 12 Liquid crystal panel 13 Rim sheet 14 Diffuser plate 15 Reflector plate 16 Liquid crystal display element 17 Illuminating device 18, 19 Light from light source

Claims (6)

A light source;
A light guide plate that makes light from the light source incident from a side surface and exits from an upper surface;
A concave microstructure formed on either the upper surface or the lower surface of the light guide plate;
The microstructure has a reflective surface that forms an angle of 40 to 60 degrees with respect to the bottom surface, and two side surfaces that are substantially perpendicular to the top surface,
An illumination device, wherein the bottom surface of the reflecting surface is disposed so as to be substantially perpendicular to an optical path connecting the light source and the fine structure.   The illumination device according to claim 1, wherein a shape of the fine structure is a triangular frustum.   The lighting device according to claim 1, wherein the fine structure has a height of 1 to 10 μm.   The illumination device according to any one of claims 1 to 3, wherein the fine structures are arranged so that the density increases as the distance from the light source increases.   The illumination device according to any one of claims 1 to 3, wherein the fine structure is arranged so that the size thereof increases as the distance from the light source increases. A light source;
A light guide plate that makes light from the light source incident from a side surface and exits from an upper surface;
A concave microstructure formed on either the upper surface or the lower surface of the light guide plate;
A non-self-luminous display element disposed above the light guide plate;
The microstructure has a reflective surface that forms an angle of 40 to 60 degrees with respect to the bottom surface, and two side surfaces that are substantially perpendicular to the top surface,
A display device, wherein the bottom surface of the reflecting surface is arranged so as to be substantially perpendicular to an optical path connecting the light source and the fine structure.

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