JP2011124026A - Lighting unit, and display device equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent luminance unevenness of a lighting unit and a liquid crystal display device by controlling light emitted in a direction inclined against the normal direction of the outgoing face of a light guide plate to prevent eyeballs and hot spots generated in the vicinity of the light source, without using a prism sheet. <P>SOLUTION: An optical absorber 4 is arranged parallel to an outgoing face 3 between the light source 1 and the effective emission area 10 of the light guide plate 2. This optical absorber 4 absorbs the light with high intensity emitting to the inclined direction against the perpendicular direction of the outgoing face 3. Thereby, without using a prism sheet, a lighting unit and a liquid crystal display device with thin size and without luminance unevenness can be achieved. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a lighting device having a flat light emitting surface and a display device using the same.

  Liquid crystal display devices are widely used in portable devices such as notebook personal computers, mobile phones, PDAs, and electronic dictionaries. Since the liquid crystal panel is a non-self-luminous type, it is necessary to incorporate a flat illumination device on the back of the liquid crystal panel. This type of display device needs to have high illumination light intensity so that it can be seen outdoors during the day. In addition, uniform light emission without unevenness is required to brighten the displayed image. Therefore, it is conventionally known to use a sidelight type illumination device in which a light source is installed on a side surface of a light emitting surface and a prism sheet is disposed above the light emitting surface to control the directivity of light rays. On the other hand, thinning of lighting devices for portable devices has been demanded. For this reason, a side light that does not have a prism sheet, forms a reflecting structure on the light guide plate, reflects light from the light source by the reflecting structure, and emits illumination light with high brightness and no uneven brightness from the light emitting surface. A type of lighting device is known (see, for example, Patent Document 1).

  FIG. 9A is a schematic top view of a conventional lighting device that does not use a prism sheet. The effective light emitting area 10 of the lighting device is the same area as the opening of the rim sheet 7 and is contained in the frame 11. FIG. 9B schematically shows the A-A ′ cross section of FIG. The lighting device includes a light source 1 and a light guide plate 2 disposed on the side of the light source 1. A diffusion plate 5 is disposed on the light exit surface 3 of the light guide plate 2, and a reflection plate 6 is disposed on the back surface of the light guide plate 2. Further, a rim sheet 7 is provided on the diffusion plate 5 around the effective light emitting area 10 of the lighting device. A diffusion plate 5 provided with a light source 1, a light guide plate 2, a reflection plate 6, and a rim sheet 7 is housed in a frame 11.

  Light emitted from the light source 1 disposed on the side surface of the light guide plate 2 is introduced into the light guide plate 2 from the light incident surface. Although not shown, a plurality of reflective structures are formed on the facing surface (back surface) facing the light exit surface 3 of the light guide plate 2. The light confined between the exit surface 3 and the back surface of the light guide plate 2 is reflected by the reflecting structure and is emitted from the exit surface 3 of the light guide plate 2. Therefore, the light confined in the light guide plate 2 can be taken out from the emission surface 3 of the light guide plate 2 by appropriately setting the reflection structure. Further, the reflection plate 6 reflects the light leaked from the back surface of the light guide plate 2 toward the light guide plate 2 again, and prevents a reduction in the intensity of the illumination light taken out from the emission surface 3 of the light guide plate 2.

  FIG. 10 is an enlarged partial sectional view showing the vicinity of the light source 1 of the illumination device shown in FIG. 9B, and shows optical paths 12 and 13 of light emitted from the light source 1. The optical path 12 indicates a light beam that is reflected by the reflecting structure 8 and is emitted in a direction perpendicular to the emission surface 3. The optical path 13 indicates a light beam that is reflected by the rim sheet 7 provided on the diffusion plate 5 and enters the light guide plate 2 from the exit surface. Light (optical path 13) incident from the exit surface 3 or the back surface of the light guide plate 2 is emitted in the direction lying on the perpendicular to the exit surface 3. In addition to this, in the vicinity of the light source 1, there are many light beams emitted in the direction lying with respect to the emission surface 3 (within approximately 30 degrees with respect to the emission surface 3 of the light guide plate 2).

JP 2008-041295 A

  In the conventional illuminating device, many light beams are emitted from the exit surface of the light guide plate in the vicinity of the light source 1 in the direction lying on the exit surface 3 (approximately within 30 degrees with respect to the exit surface 3 of the light guide plate 2). Exists. The light emitted at such an angle causes a phenomenon called “eyeball” or “hot spot” in which the intensity in the vicinity of the light source 1 is higher than that in other parts, and reduces the intensity distribution of the illumination device and the liquid crystal display device. End up.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thin and uniform illuminating device and display device that eliminates the eyeballs and hot spots generated near the light source without using a prism sheet.

  Therefore, the illumination device of the present invention is configured as follows. That is, a light source, a light incident surface arranged on the side of the light source and receiving light from the light source, a light guide plate having an output surface for emitting light, and light from the light source formed on the light guide plate. An illuminating device having a reflecting structure that reflects and emits light in a direction perpendicular to the exit surface of the light guide plate. The light absorber is disposed in parallel with the exit surface so as to face the ineffective light emitting area on the light source side. The light emitted from the ineffective light emitting area on the light source side is absorbed by the light absorber, and the light emitted from the effective light emitting area is emitted in a direction perpendicular to the emitting surface. did. That is, it is possible to absorb light emitted from the vicinity of the light source of the light guide plate and lying in the direction lying on the emission surface.

  In addition, a reflection plate is provided below the light guide plate, and a light absorber is provided on the surface of the reflection plate facing the light guide plate.

  Alternatively, a diffusion plate is provided above the light guide plate, and a light absorber is provided on the surface of the diffusion plate facing the light guide plate.

  At this time, you may form a reflective structure in the effective light emission area and non-effective light emission area of a light-guide plate. Further, the reflecting structure may be formed on at least one of the back surface and the exit surface opposite to the exit surface.

  Further, by illuminating the non-self-luminous display element using the illumination device having any one of the above-described structures, a display device having no luminance unevenness on the light source side can be realized.

  According to the configuration of the illuminating device of the present invention, it is possible to reduce the light emitted in the lying direction with respect to the normal of the emitting surface near the light source without using a prism sheet, and the illuminating device is thin and has no unevenness. And a display device can be realized.

It is a longitudinal cross-sectional view which shows the structure of the illuminating device of this invention typically. It is a perspective view which shows typically the structure of the illuminating device of this invention. It is an expanded sectional view which shows a part of structure of the illuminating device of this invention typically. It is a longitudinal cross-sectional view which shows the structure of the illuminating device of this invention typically. It is a longitudinal cross-sectional view which shows the structure of the illuminating device of this invention typically. It is a perspective view which shows typically the structure of the illuminating device of this invention. It is a figure which shows typically the reflective structure formed in the light-guide plate of this invention. It is a longitudinal cross-sectional view which shows typically the structure of the liquid crystal display device of this invention. It is a figure which shows typically the structure of the conventional illuminating device. It is a figure which shows typically the structure of the conventional illuminating device.

  The illumination device of the present invention will be described with reference to the drawings. A cross-sectional configuration of the illumination device is schematically shown in FIG. 1, and a perspective view is schematically shown in FIG. As shown in the drawing, the illumination device has a configuration in which a light guide plate 2 is provided on the side of the light source 1. The light guide plate 2 has a light incident surface that faces the light source 1 and receives light, an light emission surface 3 that emits light, and a back surface opposite to the light emission surface. There is an effective light emitting area 10 on the exit surface 3 of the light guide plate. The effective light emitting area on the exit surface corresponds to a displayable area when a display element is arranged on the lighting device. Here, an area corresponding to the effective light emitting area on the back surface of the light guide plate is also referred to in the same manner, and an area outside the effective light emitting area is referred to as an ineffective issue area. A reflective structure is formed on the back surface or the exit surface of the light guide plate. The reflecting structure reflects light from the light source and emits light in a direction perpendicular to the light emitting surface of the light guide plate. At this time, the reflective structure may be formed not only in the effective issue area but also in the non-effective issue area. Further, a light absorber is disposed in parallel to the light exiting surface of the light guide plate in the ineffective light emitting area on the light source 1 side (that is, the exit surface from the end on the light incident surface side to the boundary of the effective light emitting area). By this light absorber, light emitted from the ineffective light emitting area on the light source side is absorbed. In general, light that enters a light guide plate from a light source is configured to totally reflect and travel in the light guide plate. And if the light guide light collides with a reflective structure, it will reflect and will come out from an output surface. That is, when there is a reflective structure in the non-effective issue area, light is emitted from the non-effective issue area on the emission surface, which hinders uniform brightness control. Thus, without providing a prism sheet on the light guide plate, it is possible to prevent an eyeball or a hot spot generated in the vicinity of the light source and realize an illumination device free from luminance unevenness.

  In FIG. 2, one light absorber 4 is provided, but it can be divided. FIG. 6 shows a configuration in which the light absorber 4 is divided and arranged so as to correspond to the light source 1. Here, the light absorber 4 has a rectangular shape, but is not limited to this shape as long as it does not deteriorate the light shielding performance. One light absorber 4 may be arranged for one light source, or a plurality of light absorbers 4 may be arranged for one light source. 1 and 2, the light absorber is disposed above the light guide plate, but the same effect can be expected even if it is provided below the light guide plate.

  In addition, a display device of the present invention includes a non-self-luminous display element and the illumination device having the above-described configuration that irradiates light to the display element. Thereby, the brightness nonuniformity which generate | occur | produces in the side by which the light source is arrange | positioned can be prevented.

  Hereinafter, the present invention will be specifically described with reference to the drawings.

  The lighting device of the first embodiment will be described with reference to FIG. FIG. 3 is a schematic diagram showing a cross-sectional configuration of the illumination device, and shows an enlarged portion on the light source side. In the figure, an optical path of light emitted from the light source 1 is illustrated. As shown in the drawing, the light guide plate 2 has a flat plate shape, has a light incident surface, an output surface 3, and a back surface opposite to the output surface 3, and has a light source 1 on the side so as to face the light incident surface. Is arranged. The light guide plate 2 has an effective light emitting area 10, and light emitted from this area contributes to pixel display of the display element. On the emission surface 3 of the light guide plate 2 outside the effective light emitting area 10, the light absorber 4 is disposed so as to be substantially parallel to the emission surface 3 of the light guide plate 2. That is, the light absorber is disposed on the exit surface in the ineffective light emitting area on the light source side. A reflective plate 6 is provided behind the light guide plate 2 so as to face the back surface.

  The optical path of the light emitted from the light source 1 will be described with reference to FIG. An optical path 12 indicates light emitted from the effective light emitting area 10 of the emission surface 3. That is, the light emitted from the light source 1 is reflected by the reflecting structure 8 formed on the back surface of the light guide plate, and is emitted from the emission surface 3 of the light guide plate 2 in a direction perpendicular to the emission surface 3. On the other hand, between the light source 1 and the effective light emitting area 10 of the light guide plate 2, that is, from the ineffective light emitting area on the light source side, as shown by the optical path 13, the light is not emitted in the direction perpendicular to the emitting surface 3 It is easy to emit at an angle (within approximately 30 degrees with respect to the emission surface 3). Therefore, eyeballs and hot spots are generated. As shown in FIG. 3, by providing the light absorber 4 on the exit surface of the non-effective light emitting area on the light source 1 side, the light emitted in the direction lying on the exit surface 3 is absorbed, and there is no unevenness. Can be realized.

  Moreover, the illuminating device of the structure which has arrange | positioned the diffuser plate above the output surface 3 of the light-guide plate 2 is typically shown in FIG. At this time, the light absorber 4 is disposed on the lower surface of the diffusion plate 5 so as to face the light guide plate 2. Further, as illustrated, the light absorber 4 can be formed on the diffusion plate 5. According to such a configuration, since the alignment can be performed with the outer dimensions of the light guide plate 2 and the diffusion plate 5, the positions of the light absorber 4 and the light guide plate 2 can be easily aligned. A black tape may be attached to the diffusion plate 5 to form the light absorber 4, or black ink may be printed on the diffusion plate 5. It is desirable to use non-glossy material for both black tape and black ink.

  FIG. 5 is a longitudinal sectional view schematically showing the illumination device of the present embodiment. In this embodiment, a light absorber is provided behind the light guide plate. That is, in this embodiment, the light absorber 4 is provided on the upper surface of the reflection plate 6 provided below the light guide plate 2 so as to face the light guide plate 2. That is, among the light incident on the reflecting plate 6 from above, a lot of light in the sleeping direction is present in a portion corresponding to the ineffective light emitting area on the light source side. Therefore, the light absorber 4 is provided in that portion. The same effect as Example 1 will be produced. Further, as shown in the figure, the light absorber 4 can be formed on the reflection plate 6. According to such a configuration, the light guide plate 2 and the reflection plate 6 can be aligned with each other according to the external dimensions, so that the positions of the light absorber 4 and the light guide plate 2 can be easily aligned. A black tape may be attached to the reflecting plate 6 as a light absorber, or black ink may be printed on the reflecting plate 6. It is desirable to use non-glossy material for both black tape and black ink.

  FIG. 8 is a cross-sectional view schematically showing the liquid crystal display device of this example. In this embodiment, the liquid crystal display element 17 is irradiated by the illumination device 16. The liquid crystal panel 15 has a configuration in which a liquid crystal layer (not shown) is sealed with a sealing material in a gap between two glass substrates. A liquid crystal display element 17 is configured by attaching polarizing plates 14 to the upper and lower surfaces of the liquid crystal panel 15. An illumination device 16 is installed below the liquid crystal display element 17 and irradiates illumination light from the back surface of the liquid crystal display element 17. The illumination device 16 includes a light source 1, a light guide plate 2 disposed on the side of the light source 1, a diffusion plate 5 installed on the back surface of the light guide plate 1, a reflection plate 6 installed on the exit surface of the light guide plate 1, A rim sheet 7 is provided, and a light absorber 4 is arranged in a non-effective light emitting area on the light source 1 side in parallel with the exit surface of the light guide plate 2. In addition, the arrangement | positioning location of the light absorber 4 is not restricted to this, The structure demonstrated in each above-mentioned Example can be used.

  Moreover, LED can be illustrated as the light source 1 used in the above-mentioned Examples 1-3. For the light guide plate 2, a light-transmitting plastic material such as acrylic (PMMA), polycarbonate (PC), or cycloolefin polymer (COP) or glass can be used.

  Further, in each of the above-described embodiments, the reflective structure 8 is formed on the back surface of the light guide plate. However, as long as it has a function of reflecting light from the light source 1 in a direction perpendicular to the emission surface 3 of the light guide plate 2. It may be formed on the exit surface 3 of the light guide plate 2 or on both the exit surface 3 and the back surface. FIG. 7 is a top view and a perspective view illustrating the shape of the reflective structure 8. The reflective structure 8 shown in FIG. 7A has a shape composed of two rectangles. The reflection structure 8 shown in FIG. 7B has a quadrangular pyramid shape, and the reflection structure 8 shown in FIG. 7C has a triangular pyramid shape. These reflecting structures 8 include a reflecting surface 18 that reflects light from the light source. Regardless of which shape is used, unevenness in luminance of the lighting device can be prevented by arranging the reflecting structure 8 so that the bottom of the reflecting surface 18 is approximately 90 degrees with respect to the optical path of the light from the light source 1. Can do. The reflective structure 8 is formed with a size of several μm to several hundred μm, and is not limited to the illustrated shape.

DESCRIPTION OF SYMBOLS 1 Light source 2 Light-guide plate 3 Output surface 4 Light absorber 5 Diffuser plate 6 Reflector plate 7 Rim sheet 8 Reflective structure 10 Effective light emission area 11 Frame 12 Light beam 13 Light beam 14 Polarizer 15 Liquid crystal panel 16 Illumination device 17 Liquid crystal display element 18 Reflective surface

Claims (9)

A light source;
A light guide plate disposed on the side of the light source and having a light incident surface on which light from the light source is incident, and an output surface that emits light;
A reflective structure that is formed on the light guide plate and reflects light from the light source to emit light in a direction perpendicular to an exit surface of the light guide plate;
Comprising a light absorber disposed parallel to the exit surface;
The exit surface has an effective light emitting area that emits effective light to the irradiated object, and an ineffective light emitting area outside thereof,
By providing the light absorber so as to face the non-effective light emitting area on the light source side, light emitted from the non-effective light emitting area on the light source side is absorbed by the light absorber. The light emitted from the effective light emitting area is emitted in a direction perpendicular to the emission surface.   The lighting device according to claim 1, further comprising: a reflecting plate disposed below the light guide plate, wherein the light absorber is provided on a surface of the reflecting plate facing the light guide plate.   The lighting device according to claim 1, further comprising: a diffusion plate disposed above the light guide plate, wherein the light absorber is provided on a surface of the diffusion plate facing the light guide plate.   The lighting device according to claim 2, wherein the light absorber is formed by printing black ink.   The lighting device according to claim 2 or 3, wherein the light absorber is formed by applying a black tape.   6. The light source according to claim 1, wherein a plurality of the light sources are present, and the light absorber is divided and provided so as to correspond to each of the plurality of light sources. Lighting device.   The lighting device according to claim 1, wherein the reflective structure is formed in the effective light emitting area and the ineffective light emitting area of the light guide plate.   The lighting device according to claim 1, wherein the reflective structure is formed on a back surface opposite to the light exit surface.   A display device comprising: the illuminating device having the configuration described in any one of claims 1 to 8; and a non-self-luminous display element disposed above an emission surface of the illuminating device.

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