JP2008305664A - Backlight device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight device which can be thinned while maintaining the utilization efficiency of light. <P>SOLUTION: In this backlight device 100, a reflecting sheet 142 and a diffusion sheet 144 of a surface emitter 140 are disposed face to face through an air gap. In this backlight device 100, light is made to enter the air gap from all sides of the surface emitter 140. Thereby, a clearance between the reflective sheet 142 and the diffusion sheet 144 can be made small, and the thickness of the surface emitter 140 can be thereby thinned. As a result, the backlight device 100 can be thinned. In addition, since light is made to enter the air gap from all the sides of the surface emitter 140, light spreads over the whole air gap. Therefore, the uniformity of light can be secured, and light can be efficiently used. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a backlight device.

  In recent years, there has been an increasing demand for thinner displays. Typical examples of thin displays include liquid crystal displays and plasma displays. Among these, in the liquid crystal display, the liquid crystal is used as a shutter for controlling transmission of light from a backlight or the like. In order to improve the display quality in the liquid crystal display, the luminance uniformity is required over the entire surface where the liquid crystal exists.

In order to improve the luminance uniformity, the backlight device generally adopts the following configuration. That is, the backlight device includes a reflection plate that reflects light, a light guide plate disposed on a reflection surface of the reflection plate, and a light source. The light emitted from the light source is incident on the light guide plate from one direction intersecting with an axis passing through the reflector plate and the light guide plate arranged to face each other. The light guide plate has a function of guiding light in the direction from the light incident surface toward the opposite surface. The incident light by this function spreads over the entire light guide plate, so that the light use efficiency is increased. And the light which spread over the whole light-guide plate is reflected by a reflecting plate, and light is light-emitted from the whole surface on the opposite side to the reflecting plate side of a light-guide plate. By arranging the liquid crystal panel in the light emitting direction, the uniformity of the luminance in the liquid crystal panel is improved. Such a backlight device is disclosed in Patent Document 1, for example.
JP-A-4-79102

  Incidentally, in general, the volume occupied by the light guide plate in the liquid crystal display is large. Therefore, it is desired to make the light guide plate thin in order to reduce the thickness of the liquid crystal display. However, generally, the light guide plate is produced by injection molding of acrylic resin or the like. There is a limit to the thinness of the product produced by this injection molding. In addition, with the increase in the size of the light guide plate accompanying the increase in the size of the liquid crystal display, it is further difficult to make the light guide plate produced by injection molding thinner.

  The present invention has been made in view of such points, and an object thereof is to provide a backlight device that can be thinned.

  The backlight device of the present invention includes a surface light emitter having a reflection sheet that reflects light in a direction orthogonal to the surface, a prism sheet that is disposed on the surface of the reflection sheet with a gap therebetween, and a light source. And a light guide member that inputs light into the gap of the surface light emitter in a plurality of directions.

  ADVANTAGE OF THE INVENTION According to this invention, the backlight apparatus which can be reduced in thickness can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiment, the same components are denoted by the same reference numerals, and the description thereof will be omitted because it is duplicated.

  (Embodiment 1)

  FIG. 1 is a diagram illustrating a main configuration of a backlight device according to Embodiment 1 of the present invention. As shown in the figure, the backlight device 100 includes an LED 110, a beam splitter 120, an optical fiber 130, and a surface light emitter 140. The backlight device 100 is mounted on a liquid crystal display device of a mobile terminal, for example.

  The LED 110 is a high-power light source. The beam splitter 120 distributes the light from the LED 110 to a plurality of paths. The optical fiber 130 is a light guide path through which the light distributed by the beam splitter 120 travels.

  The surface light emitter 140 receives light guided by the optical fiber 130. The surface light emitter 140 includes a reflection sheet 142, a diffusion sheet 144, a prism sheet 146, and a support frame 148. The reflection sheet 142, the diffusion sheet 144, and the prism sheet 146 are all rectangular and have the same size. In order to support these sheet groups, the surface formed by two specific orthogonal sides in the support frame 148 has the same shape as the sheet group. The surface light emitter 140 configured as described above has a hexahedral shape in which each surface is rectangular. Hereinafter, the surface on the reflecting sheet 142 side of the surface light emitter 140 may be referred to as a “lower surface”, the surface on the prism sheet 146 side as an “upper surface”, and the other surfaces as “side surfaces”.

  The reflection sheet 142 is subjected to surface processing so as to reflect light coming from a direction substantially parallel to the surface in a direction orthogonal to the surface.

  The diffusion sheet 144 is disposed on the surface of the reflection sheet 142 that reflects the light while maintaining a certain separation distance. That is, a gap (empty layer) exists between the diffusion sheet 144 and the reflection sheet 142. The diffusion sheet 144 transmits and diffuses incident light.

  The prism sheet 146 outputs the traveling direction of the incident light in accordance with the direction orthogonal to the light emitting surface. The prism sheet 146 is disposed on the surface of the diffusion sheet 144 opposite to the reflection sheet 142 side. The prism sheet 146 includes a lower prism sheet 1461 and an upper prism sheet 1462. The lower prism sheet 1461 and the upper prism sheet 1462 are disposed in the order of the lower prism sheet 1461 and the upper prism sheet 1462 from the diffusion sheet 144 side.

  The support frame 148 supports the reflection sheet 142, the diffusion sheet 144, and the prism sheet 146. The support frame 148 surrounds the reflection sheet 142, the diffusion sheet 144, and the prism sheet 146. The support frame 148 holds the sheet group in a state where the reflection sheet 142, the diffusion sheet 144, and the prism sheet 146 are laminated. Further, an opening for inserting and fixing the optical fiber 130 is provided on the side surface of the support frame 148 (corresponding to the side surface of the surface light emitter 140) at a position corresponding to the gap in the stacking direction. . Here, the openings are provided on all four side surfaces of the support frame 148.

  Next, the light emission principle in the backlight device 100 having the above configuration will be described.

  Light emitted from the LED 110 is distributed to a plurality of paths by the beam splitter 120. The plurality of distributed lights are respectively guided to the surface light emitter 140 by the plurality of optical fibers 130. Since the optical fiber 130 is connected to the four surfaces of the surface light emitter 140, light enters the gap of the surface light emitter 140 from four directions. In this way, light spreads uniformly over the entire gap of the surface light emitter 140. That is, the light is efficiently used.

  Here, the backlight device 100 of the present embodiment does not have a light guide plate formed by injection between the reflection sheet 142 and the diffusion sheet 144. An empty layer exists instead of the light guide plate. Compared with the light guide plate, the degree of freedom of the thickness of the empty layer (that is, corresponding to the separation distance between the reflection sheet 142 and the diffusion sheet 144) is high. Therefore, by forming a gap between the reflection sheet 142 and the diffusion sheet 144, the thickness of the surface light emitter 140 can be reduced. As a result, the backlight device 100 can also be thinned.

  The light incident on the gap is reflected on the surface of the reflection sheet 142 in a direction perpendicular to the surface (direction of the diffusion sheet 144). The reflected light passes through the diffusion sheet 144. Here, as described above, since the light spreads over the entire gap, the reflected light is uniformly incident on the entire diffusion sheet 144. Therefore, the light may enter the prism sheet 146 without passing through the diffusion sheet 144. However, the uniformity of the light transmitted through the diffusion sheet 144 is further increased by the diffusion sheet 144 being interposed.

  The light diffused by the diffusion sheet 144 and increased in uniformity is incident on the prism sheet 146. The traveling direction of the light incident on the prism sheet 146 is matched with the direction orthogonal to the light emitting surface in the prism sheet 146. Therefore, the light emitted from the prism sheet 146 is incident from a direction orthogonal to the incident surface of the liquid crystal panel. Thus, efficient use of light in the liquid crystal panel can be achieved.

  As described above, according to the present embodiment, in the backlight device 100, the reflection sheet 142 and the diffusion sheet 144 of the surface light emitter 140 are arranged to face each other with a gap. By doing so, the distance between the reflection sheet 142 and the diffusion sheet 144 can be reduced, so that the thickness of the surface light emitter 140 can be reduced. As a result, the backlight device 100 can be thinned.

  In the backlight device 100, light is incident on the gap from all the side surfaces of the surface light emitter 140. By doing so, light spreads throughout the gap. For this reason, the uniformity of light is ensured and the light can be used efficiently. As a result, power consumption in the backlight device 100 can be reduced.

  In the above description, light is incident from all four side surfaces of the surface light emitter 140. However, it is sufficient that light is incident from at least two surfaces, so that the light is sufficiently spread over the entire gap. In short, it is sufficient that light is input into the gap of the surface light emitter 140 from a plurality of directions.

(Embodiment 2)
FIG. 2 is a diagram showing a main configuration of the backlight device according to Embodiment 2 of the present invention. As shown in the figure, the backlight device 200 is filled with a light-transmitting synthetic resin between the reflection sheet 142 and the diffusion sheet 144. That is, in the backlight device 200, a synthetic resin is filled in a portion that is a gap in the backlight device 100 of the first embodiment.

  The filling of the synthetic resin is performed after the same configuration as that of the backlight device 100 is formed. That is, after the distance between the reflection sheet 142 and the diffusion sheet 144 is shortened to prepare a thin empty layer in advance, the gap is filled with the synthetic resin. Thus, a thin synthetic resin layer is formed. A synthetic resin having a light guiding function for guiding light is selected. By doing so, the backlight device 200 can be provided with a layer having the same function as the light guide plate used in the prior art.

  As described above, according to the present embodiment, in the backlight device 200, the gap between the reflection sheet 142 and the diffusion sheet 144 is filled with the synthetic resin. By doing so, it is possible to form a layer having the same function as the light guide plate while maintaining the thinness of the surface light emitter 140.

(Embodiment 3)
As shown in FIG. 3, the backlight device 300 according to the third embodiment includes a polarization beam splitter 310 that separates the light from the LED 110 into a first polarization and a second polarization whose deflection plane is orthogonal to the first polarization, and the deflection beam splitter 310. A half-wave plate 320 provided at the output stage of the first polarization and rotating the deflection surface of the first polarization by 90 degrees, and polarization-maintaining light guided while holding both the first and second polarization deflection surfaces It has a fiber 330 and a surface light emitter 340 to which the light guided by the polarization maintaining optical fiber 330 is input.

  The surface light emitter 340 has the same configuration as a conventional general surface light emitter. That is, the surface light emitter 340 includes a reflection sheet 342, a light guide plate 344 disposed on the surface of the reflection sheet 342, and a diffusion sheet disposed on the surface of the light guide plate 344 opposite to the reflection sheet 342 side. 346 and a prism sheet 348 disposed on the surface of the diffusion sheet 346 opposite to the reflection sheet 342 side. The prism sheet 348 includes a lower prism sheet 3481 and an upper prism sheet 3482.

  Next, the light emission principle in the backlight device 300 having the above configuration will be described.

  The light emitted from the LED 110 is separated by the polarization beam splitter 310 into first polarized light and second polarized light whose polarization plane is orthogonal to the first polarized light. The separated first polarized light and second polarized light are respectively output to a plurality of different paths. Only the first polarized light passes through the half-wave plate 320. The polarization plane of the first polarized light is rotated 90 degrees by the half-wave plate 320. Therefore, the deflection surface of the first polarization after passing through the half-wave plate 320 coincides with the deflection surface of the second polarization.

  The first polarized light and the second polarized light whose polarization surfaces are combined in this way are respectively guided to the surface light emitter 340 by the plurality of polarization maintaining optical fibers 330. The polarization maintaining optical fiber 330 can guide light while maintaining the deflection surface. Therefore, when the light is incident on the surface light emitter 340, the polarization planes of the first polarization and the second polarization are the same.

  Light incident on the light guide plate 344 of the surface light emitter 340 passes through the diffusion sheet 346 and the prism sheet 348 and is input to the liquid crystal panel.

  Here, even if white light is incident on the liquid crystal panel, only one of the orthogonally polarized light is transmitted due to the influence of the polarizing plate of the liquid crystal panel or the liquid crystal itself. That is, one of the orthogonal polarizations is wasted. However, the backlight device 300 according to the present embodiment divides light into first polarized light and second polarized light whose deflection surfaces are orthogonal to each other, and passes one of the obtained first polarized light and second polarized light through the half-wave plate 320. Thus, the light incident on the surface light emitter 340 is converted into light having one deflection surface. The light having one deflection surface is incident on the liquid crystal panel via the surface light emitter 340. Therefore, if the deflection surface of light incident on the liquid crystal panel via the surface light emitter 340 is aligned with the direction of high light transmission of the liquid crystal panel, light can be used very efficiently.

  As described above, according to the present embodiment, the backlight device 300 includes the polarization beam splitter 310 that separates the light into the first polarized light and the second polarized light whose polarization plane is orthogonal thereto, and the polarization plane of the first polarization. A half-wave plate 320 rotated 90 degrees was provided. By doing so, it is possible to form light having one deflection surface. For this reason, it is possible to realize a backlight device that can increase the light utilization efficiency particularly when mounted on a liquid crystal display device.

  In the above description, the configuration of the surface light emitter 340 is a configuration generally used conventionally. However, the polarization beam splitter 310 and the half-wave plate 320 of the present embodiment can also be applied to the backlight device 100 and the backlight device 200 of the first and second embodiments. That is, in the backlight device 100 (200), the polarization beam splitter 310 and the half-wave plate 320 are applied instead of the beam splitter 120.

  The backlight device of the present invention is useful as a device that can be made thin while maintaining the light use efficiency.

The figure by which the main structures of the backlight apparatus which concerns on Embodiment 1 of this invention are shown The figure by which the main structures of the backlight apparatus which concerns on Embodiment 2 are shown. The figure which shows the main structures of the backlight apparatus which concerns on Embodiment 3. FIG.

Explanation of symbols

100, 200, 300 Backlight device 110 LED
DESCRIPTION OF SYMBOLS 120 Beam splitter 130 Optical fiber 140,340 Surface light emitter 142,342 Reflection sheet 144,346 Diffusion sheet 146,348 Prism sheet 148 Support frame 310 Polarization beam splitter 320 Half wavelength plate 330 Polarization holding optical fiber 344 Light guide plate 348 Prism Sheet

Claims (6)

A surface light emitter having a reflection sheet that reflects light in a direction orthogonal to the surface, and a prism sheet that is disposed opposite to the surface of the reflection sheet via a gap;
A light guide member that makes light emitted from a light source enter the gap of the surface light emitter in a plurality of directions;
A backlight device comprising:   2. The backlight according to claim 1, wherein the surface light emitter further includes a support frame that surrounds the gap together with the reflective sheet and the prism sheet, and a synthetic resin having translucency filled in the gap. apparatus. A polarization splitter that separates light incident on the light guide member into first polarized light and second polarized light having a deflection plane orthogonal thereto;
A half-wave plate for rotating the deflecting surface of the first polarized light by 90 degrees;
The backlight device according to any one of claims 1 and 2.   A liquid crystal display device comprising the backlight device according to claim 1.   A portable terminal device comprising the liquid crystal display device according to claim 4. A step of disposing a reflecting sheet that reflects light in a direction perpendicular to the surface and a prism sheet through a gap;
Filling the gap with a synthetic resin having translucency;
A method for producing a surface light emitter comprising:

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