JP5854625B2 - Light source device - Google Patents

Description

The present invention relates to a light source device .

A liquid crystal display device including a liquid crystal display panel and a backlight unit that illuminates the liquid crystal display panel has been proposed. The backlight unit is a light source device, and includes an edge light type in which a light guide plate is disposed on the back surface of the liquid crystal display panel, and a light source is disposed on one side of the light guide plate, and a diffusion plate is disposed on the back surface of the liquid crystal display panel. There is a direct type in which a light source is arranged on the back surface of the diffusion plate.

  An edge-light type liquid crystal display device has a light source arranged at a position facing one side of a light guide plate made of a synthetic resin plate having a thickness of several millimeters, and light incident from one side of the light guide plate is placed on one side. Emits light from the front. The direct type liquid crystal display device has a substrate on which a plurality of light sources arranged in a grid pattern are mounted on the back surface of a diffusion plate made of a synthetic resin plate having a thickness of several millimeters. The emitted light is emitted on the entire surface of the diffusion plate.

  In the direct type liquid crystal display device, the light source is on the back surface of the diffusion plate, and a sufficient space is required between the diffusion plate and the light source in order to uniformly emit light on the entire surface of the diffusion plate. On the other hand, the edge light type liquid crystal display device can be thinned because the light source is disposed around the light guide plate.

  Further, for the liquid crystal display device, widening the color gamut and increasing the contrast are also important issues as other issues different from the problem of thinning. An RGB backlight unit that widens the color gamut using light emitting diodes (LEDs) corresponding to the three primary colors red (R), green (G), and blue (B) has been proposed. Yes. Further, a local dimming technique has been proposed in which LEDs are two-dimensionally arranged and the luminance distribution is changed according to a video signal.

  The RGB backlight unit can have a wider color gamut than a backlight unit using white LEDs. The local dimming technique is a technique for achieving high contrast by partially driving an LED with a video signal and turning on a backlight only in an area where luminance is necessary. In order to apply the local dimming technique, it is desirable to have a light source directly under the displayed image. Therefore, the direct type backlight unit is structurally suitable for the local dimming technology. However, as described above, it is difficult to reduce the thickness of the direct type backlight unit, and the compatibility between the reduction in thickness and the increase in contrast is a contradictory requirement.

  Patent Document 1 includes a plurality of light-emitting surfaces that emit light incident from one side surface and a light guide plate having a non-light-emitting surface, and a light output surface of an arbitrary light guide plate and a non-out-going surface of another light guide plate. Disclosed is a display device that is arranged in a row. Further, Patent Document 2 includes a plurality of light guide plates arranged in a state where the side surfaces face each other, and a plurality of point light sources arranged on the side surfaces of the light guide plates, respectively, for simultaneously entering light into the plurality of light guide plates. A backlight unit is provided.

JP 2010-113239 A JP 2009-272251 A

  FIG. 8 is a cross-sectional view of a display device disclosed in Patent Document 1. The display device 80 has a configuration in which optical sheets 87b and a diffusion plate 87a are arranged on the back surface of the display panel 88, and a plurality of light guide plates 81 are juxtaposed thereunder. The LED 82 is mounted on the electric circuit board 84, and the light guide plate 81 is disposed so as to guide the light emitted from the LED 84 in the surface direction of the diffusion plate 87a. A reflector 83 is disposed so as to reflect the emitted light. The light guide plate 81 includes a light incident surface 81a on which light emitted from the LED 84 is incident, and a light output surface 81b that irradiates light incident on the light incident surface 81a in a direction substantially orthogonal to the light incident surface 81a. The light guide plate 81 includes a non-light-emitting surface 81c that is continuous with the light-emitting surface 81b and a reflecting plate 86.

  FIG. 9 is a partially enlarged view of the backlight unit disclosed in Patent Document 2. As shown in FIG. The backlight unit 90 includes a large number of light guide plates 91 and a large number of LEDs 92 that function as light sources. Each light guide plate 91 is formed in a square shape, has a square light exit surface 91a, and four side surfaces 91b, and is formed of a transparent synthetic resin. A large number of light guide plates 91 are arranged in a grid pattern with the side surfaces 91b in surface contact. Each corner of each light guide plate 91 is cut out in an arc shape to form a recess 93. By combining the corners of the four light guide plates 91, a substantially circular through hole 94 is defined by the recess 93. The LED 92 is disposed at the center of the through hole 94, and light from the LED 22 enters the concave portions 93 of the four light guide plates 91 simultaneously.

  Here, in order to widen the color gamut, which is an important issue for the liquid crystal display device, when an LED that emits light of each of the three primary colors is applied to the conventional technology, there are the following problems. A problem in the case where an LED that emits red (R), green (G), and blue (B) light is used as the LED 82 included in the display device illustrated in FIG. 8 will be described. In this case, the LEDs 82 are arranged in a row in a direction perpendicular to the cross section of the display device in FIG. 8 so as to face the light incident surface 81 a of the light guide plate 81. Here, in order to emit white light from the light exit surface 81b, the RGB colors emitted from the respective LEDs 82 must be sufficiently mixed. Since each RGB light that has entered from the light incident surface 81a has a diffusion angle that is a characteristic of the LED 82, a sufficient light guide distance is required to mix the RGB colors. That is, the light guide plate 81 needs to have a large outer size in order to take a sufficient light guide distance to mix the RGB colors.

  Moreover, when using LED which light-emits red (R), green (G), and blue (B) light for LED92 with which the backlight unit shown in FIG. 9 is provided, there exist the following problems. In this case, the LEDs 92 disposed at the four corners of the light guide plate 91 need to be configured by LEDs that emit red (R), green (G), green (G), and blue (B) colors, respectively. The light emitted from the four LEDs 92 enters the light guide plate 91 from the concave portion 93, is mixed in the light guide plate 91, and exits from the light exit surface 91a as white light.

  At this time, in order to change the amount of white light from the light exit surface 91a of the independent light guide plate 91 for each light guide plate 91 by applying local dimming technology, the light guide plate 91 adjacent to the light guide plate 91 is used. It is necessary to enter a light amount different from the amount of light that enters the light. In the application example of this backlight unit, the light emitted from one LED 92 enters the four light guide plates 91 at the same time. Therefore, if a white monochromatic LED is used, a local dimming technique is possible. However, since this application example uses LEDs that emit RGB independent colors, each LED is incident on a plurality of light guide plates, so that the color balance is lost. As a result, it is difficult to apply the local dimming technique.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light source device that is thin and has a wide color gamut and a high contrast.

A light source device according to an embodiment of the present invention includes a light exit surface , a bottom surface facing the light exit surface, a side surface, and a plurality of light incident portions provided in the vicinity of an end portion of the bottom surface, and the side surfaces are mutually connected. A plurality of light guide plates disposed in opposition to each other, provided in the vicinity of the plurality of light incident portions , a plurality of light sources including a red light source, a green light source, and a blue light source, and provided on the bottom surface, the light color mixing inside the light guide plate is reflected on the light exit surface side, Ru and a reflecting portion for exiting the light from the light exit surface. Wherein the plurality of such light entering from the light input portion is mixed within the light guide plate is provided with recesses for diffusing light to said input light. The recess includes a first recess having a first bottom surface disposed on the side surface side, and a second recess having a second bottom surface disposed on a center side of the light guide plate, and the first bottom surface includes the first bottom surface 2 closer to the light source than the bottom surface.

  According to the present invention, it is possible to provide a backlight unit that is thin and can achieve a wide color gamut and high contrast.

It is a figure which shows an example of the whole structure of a liquid crystal display device. It is an example of principal part sectional drawing of a liquid crystal display device and a backlight unit. It is a figure explaining the structure of the light-guide plate with which a backlight unit is provided. It is a figure which shows the arrangement | positioning relationship between the light-guide plate and LED of a backlight unit. It is a reverse view of a light-guide plate. It is a figure explaining the structure of the light-guide plate with which a backlight unit is provided. It is a figure explaining the structure of the light-guide plate with which a backlight unit is provided. FIG. 11 is a cross-sectional view of a display device disclosed in Patent Document 1. It is the elements on larger scale of the backlight unit which patent document 2 discloses.

FIG. 1 is an exploded perspective view of the liquid crystal display device according to the first embodiment, and shows an example of the entire configuration of the liquid crystal display device. The backlight unit 10 is a light source device that illuminates from the back surface of the liquid crystal display device 11. FIG. 2 is an example of a cross-sectional view of main parts of the liquid crystal display device and the backlight unit shown in FIG. FIG. 3 is a diagram illustrating a configuration of a light guide plate included in the backlight unit.

  1 and 2, the liquid crystal display device 11 is configured by installing a liquid crystal panel 8 in a backlight unit 10 and holding the liquid crystal panel 8 with a frame-like frame 9. The backlight unit 10 includes a reflector 3 laid on an electric circuit board 4 on which an LED 2 that is a point light source is mounted. The backlight unit 10 includes a plurality of light guide plates 1, optical sheets 6, and a panel holding member 7. The backlight unit 10 includes a case 5 that houses the electric circuit board 4 to the panel holding member 7.

  A connector 4a is mounted on the back surface of the electric circuit board 4 and can be connected to another electric circuit board. In order to use the local dimming technique, the liquid crystal display device 11 includes a light emission amount adjustment substrate 12 as another electric circuit substrate. The light emission amount adjustment substrate 12 functions as an adjustment unit that adjusts the light emission amount from the point light source (LED) of the light guide plate included in the backlight unit 10 for each point light source. The case 5 has a through hole 5a through which the connector 4a passes. The electric circuit board 4 is provided with a connector and a harness (not shown) for supplying power to the circuit board and various signals.

  As shown in FIGS. 1 to 3A, the backlight unit 10 includes a plurality of independent light guide plates 1 and a plurality of LEDs 2 that function as point light sources. Each light guide plate 1 has a rectangular shape and is formed in a square shape in this embodiment, and has a light exit surface 1a and four side surfaces 1b. The light guide plate 1 is formed of, for example, a transparent or translucent synthetic resin, and light emitted from the LED 2 is transmitted and diffused. Each of the multiple light guide plates 1 is arranged in a state where the side surface 1b is adjacent to and faces the side surface 1b of the other light guide plate 1, and is juxtaposed in a grid pattern. Further, the light exit surfaces 1a of the many light guide plates 1 are juxtaposed in the same plane. These light guide plates 1 are arranged so as to cover the effective display area of the liquid crystal panel 8.

  In other words, the light guide plate 1 includes a light exit surface 1a, a side surface 1b, a bottom surface facing the light exit surface 1a, and a light incident portion, and is disposed with the side surfaces 1b facing each other. The light incident part causes light emitted from the LED 2 to enter the light guide plate 1. The light incident portion is provided in the vicinity of the end portion of the bottom surface of the light guide plate 1. In this example, the light incident portion is provided in the vicinity of the apex of the square bottom surface. In this embodiment, the LED 2 emits light in the thickness direction of the light guide plate 1.

  With reference to FIG. 3 (B) thru | or 5, the light guide path | route and diffusion of the light which entered the light guide plate are demonstrated. FIG. 3B is a cross-sectional view taken along the line AA in FIG. 3A and shows a cross section of the light guide plate. FIG. 4 is a plan view showing the positional relationship between the light guide plate and the LEDs of the backlight unit. FIG. 5 is a rear view of the light guide plate.

  As shown in FIG. 3B, the side surface 1b is inclined so that the area of the light exit surface is smaller than the area of the bottom surface. Further, as shown in FIG. 4, one red LED 2R, one blue LED 2B, and two green LEDs 2G are arranged on the bottom surface near the four corners of the square light guide plate 1. The light guide plate 1 produces white light by mixing these four LED lights. 3B and 5, recesses 1 f are formed in the vicinity of the four corners of the light guide plate 1. The recess 1 f constitutes a light incident part that allows light emitted from the LED to enter the light guide plate 1. Each of the LEDs 2R to 2G shown in FIG. 4 is provided in the vicinity of the light incident portion of one corresponding light guide plate, and light of R, G, or B color is incident on the light incident on one corresponding light guide plate. It is a plurality of point light sources that emit light to the side. The light source group including the LEDs 2R to 2G emits all the colors R, G, and B.

  The recess 1f diffuses the incident light so that light emitted from the LED and incident from the light incident portion is mixed in the light guide plate. Specifically, the recess 1f diffuses the light so that a part of the light emitted from the LED and incident is reflected at least on the side surface 1b.

3B, the recess 1f has a hole shape formed from the bottom surface of the light guide plate 1 toward the light exit surface 1a. Specifically, the recess 1f includes a first recess having an inclined surface 1e and a second recess having a cylindrical side surface 1c and an inclined surface 1d. In FIG. 5, the outer side of the recess 1f is an inclined surface 1e (that is, a first recess) when the light guide plate is viewed from the vertical direction, and the inner side is an inclined surface 1d (that is, the second recess) when the light guide plate is viewed from the vertical direction. ). It is desirable that the center of the circle of the recess 1f in FIG. The inclined surface 1e is a surface that guides light incident from the LED in the direction of the side surface 1b. The cylindrical side surface 1c has a cylindrical shape. The cylindrical side surface 1c is a surface that guides the incident light so that the light is reflected by the light exit surface. The inclined surfaces 1d and 1e are inclined in the LED direction toward the center of the cylindrical shape.

  The inclined surface 1d is farther from the LED than the inclined surface 1e. A dotted line arrow in FIG. 3B indicates a locus of light emitted from the LED. The light emitted from the green LED 22G enters the cylindrical side surface 1c and the inclined surface 1e in the inner direction of the light guide plate 1. The light incident on the cylindrical side surface 1 c is refracted on the side surface and guided toward the center of the light guide plate 1. The light incident on the inclined surface 1 d is totally reflected by the side surface 1 b and the light exit surface 1 a and guided toward the center of the light guide plate 1. On the other hand, the light incident on the inclined surface 1 e is refracted in a direction nearly perpendicular to the light exit surface 1 a and enters the light guide plate 1. A part of the light incident on the light guide plate 1 is totally reflected by the side surface 1 b and the light exit surface 1 a and guided to the center direction of the light guide plate 1. Further, part of the light incident on the light guide plate 1 is totally reflected by the side surface 1 b, the inclined surface 1 d, and the light exit surface 1 a, and is guided toward the center of the light guide plate 1. The inclined surface 1d also reflects the light guided by the inclined surface 1e.

  The light guided in the central direction of the light guide plate 1 reaches the bottom surface 1h, is diffusely reflected in the direction of the light exit surface 1a on the reflection surface 1g that is a part of the bottom surface 1h, and is irradiated from the light exit surface 1a. The reflective surface 1g has a fine shape such as white printing, a dot pattern, or a microlens. That is, the reflection surface 1g is provided on the bottom surface and functions as a reflection unit that reflects light mixed in the light guide plate to the light output surface side and emits the light from the light output surface.

  As described above, in the backlight unit of this embodiment, the LEDs 22R, 22G, and 22B having different colors are arranged near the four corners of the light guide plate 1. And since each light is spread | diffused and mixed in the center direction of the light-guide plate 1 with the shape of the recessed part 1f, it becomes possible to take out white light. In addition, the entire light guide plate 1 can cover the light guide distance for mixing different colors. Therefore, it is possible to reduce the size of the light guide plate. Furthermore, since a set of R, G, and B LEDs corresponds to one light guide plate, the luminance can be controlled for each light guide plate, and therefore, a local dimming technique can be employed. That is, according to the present embodiment, it is possible to provide a backlight that is thin and can achieve a wide color gamut and high contrast.

  Next, Example 2 will be described. The overall configuration of the liquid crystal display device of Example 2 is the same as the overall configuration of the liquid crystal display device shown in FIG. FIG. 6 is a diagram illustrating the configuration of the light guide plate included in the backlight unit of the liquid crystal display device according to the second embodiment. FIG. 6A shows the arrangement relationship between the light guide plate and the LEDs. FIG. 6B is a rear view of the light guide plate.

  The light guide plate 21 has a regular triangular shape. In the vicinity of the apex, an LED is mounted on the substrate. That is, the red LED 22 </ b> R, the green LED 22 </ b> G, and the blue LED 22 </ b> B are mounted near the apex of the light guide plate 21. Similar to the light guide plate 1 shown in FIG. 3B, the side surface of the light guide plate 21 is inclined at a predetermined angle.

  On the bottom surface 21h of the light guide plate 21, a concave portion 21f and a reflective surface 21g are arranged near the apex of the regular triangle. The recess 21f is the same as the recess 1f shown in FIG. That is, the recess 21f has a cylindrical hole shape, and two inclined surfaces are formed inside. The light emitted from each LED is refracted inside the recess 21f and guided to the center of the light guide plate 21 as indicated by the dotted arrow in FIG. In the light guide plate 21, light emitted from each of the red LED 22R, the green LED 22G, and the blue LED 22B is mixed. The mixed light is diffusely reflected by the reflecting surface 21g and irradiated as white light from the light exiting surface 21a. The reflective surface 21g has a diffusing structure such as a dot pattern by printing, a microlens pattern, or the like. The shapes of the light exit surface and the bottom surface of the light guide plate are not limited to regular triangles, and may be arbitrary polygons.

  Next, Example 3 will be described. The overall configuration of the liquid crystal display device of Example 3 is the same as the overall configuration of the liquid crystal display device shown in FIG. The backlight unit included in the liquid crystal display device according to the third embodiment has a feature that the LED emits light in parallel with the substrate mounting surface. FIG. 7 is a diagram illustrating the configuration of the light guide plate included in the backlight unit of the liquid crystal display device according to the third embodiment. FIG. 7A is an enlarged perspective view of the light guide plate. FIG. 7B is a cross-sectional view taken along the line AA in FIG. 7A and shows a cross section of the light guide plate.

  As shown in FIG. 7A, light guide plates 31 are arranged in a plurality of columns and rows on the electric circuit board 34. The shape of the light guide plate 31 is a square. A light exit surface 31 a is provided on the side facing the electric circuit board 34, and the light exit surface 31 emits the light guided into the light guide plate 31. On the electric circuit board 34 in the vicinity of the four corners of the light guide plate 31, red LEDs 32R, green LEDs 32G, and blue LEDs 32B are arranged. That is, one red LED 32R and one blue LED 32B and two green LEDs 32G are arranged for one light guide plate.

  As shown in FIG. 7B, each of the LEDs 32R, 32G, and 32B is disposed inside the recess 31f of the light guide plate 31. The LEDs 32R, 32G, and 32B are side-emitting types, and irradiate light in a direction parallel to the mounting surface of the electric circuit board 34. That is, each LED emits light in a direction perpendicular to the thickness direction of the light guide plate 31. Specifically, each LED irradiates light to the light incident surface 31c provided in the concave portion 31f constituting the corresponding light incident portion. Light emitted from the LED enters the light guide plate 31 from the light incident surface 31c. The light incident surface 31 c guides light toward the center of the light guide plate 34. That is, the light incident surface 31c is a surface that guides the light so that the light incident from the LED is reflected by at least the light exit surface 31a.

  Since the light emitted from each LED is emitted toward the center of the light guide plate 34, the light is mixed and becomes white light inside the light guide plate 31. The white light is diffusely reflected by a reflection pattern (not shown) provided on the bottom surface of the light guide plate 34 and is emitted from the light exit surface 31a. As the shape of the light guide plate 31, any polygonal shape can be adopted. According to this embodiment, a backlight unit using a side-emitting LED can be thinned, and a wide color gamut and high contrast can be achieved.

(Other examples)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed. In this case, the program and the storage medium storing the program constitute the present invention.

DESCRIPTION OF SYMBOLS 1 Light guide plate 1b Side surface 1f Recessed part 1g Diffusion part 1h Bottom face 2G Green LED
4 Electric circuit board

Claims (8)

A plurality of light guide plates, each including a light exit surface, a bottom surface facing the light exit surface, a side surface, and a plurality of light incident portions provided in the vicinity of an end of the bottom surface, and disposed with the side surfaces facing each other. When,
A plurality of light sources provided in the vicinity of the plurality of light incident portions, including a red light source, a green light source, and a blue light source;
A reflecting portion provided on the bottom surface, reflecting light mixed in the light guide plate toward the light exit surface, and emitting the light from the light exit surface;
The concave portions provided in each of the plurality of light incident portions have first bottom surfaces arranged on the side surfaces so that light incident from the plurality of light incident portions is mixed in the light guide plate. 1 recess and a second recess having a second bottom surface disposed on the center side of the light guide plate,
The first bottom surface is closer to the light source than the second bottom surface . The bottom surface has an area larger than the area of the light exit surface ;
The light source device according to claim 1, wherein the side surface is inclined with respect to the light exit surface and the bottom surface. The light source device according to claim 1, wherein the second recess has a cylindrical surface on a center side of the light guide plate. The first bottom surface and the second bottom surface are inclined so as to approach the bottom surface toward a boundary between the first concave portion and the second concave portion. The light source device described. The shape of the light exit surface and the bottom surface is a polygon,
The light source device according to any one of claims 1 to 4, wherein the light incident portion is provided in the vicinity of an apex of the bottom surface. The light exit surface and the bottom surface are rectangular.
The plurality of light sources corresponding to the plurality of light incident portions provided at the four corners of the bottom surface include one red light source, one blue light source, and two green light sources. The light source device according to claim 5, wherein: The light exit surface and the bottom surface are triangular.
The plurality of light sources corresponding to the plurality of light incident portions provided at the three corners of the bottom surface include one red light source, one blue light source, and one green light source. The light source device according to claim 5, wherein: 8. The light source device according to claim 1, further comprising an adjusting unit configured to adjust a light emission amount of each of the plurality of light sources that emit light entering each light guide plate.

Images