JP2017091984A - Surface light source device and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device which has a wide color region and excellent uniformity.SOLUTION: A surface light source device 200 includes: a plurality of laser light emitting elements 81, 82, 83 for emitting light of different colors; a light guide member 6 having a first light incident surface 61a and a first light emission surface 61b; a surface light emitting light guide plate 4 having a second light incident surface 41c and a second light emission surface 41a; and a reflection film 5. The light guide member 6 mixes colors of the light emitted by the plurality of laser light emitting elements 81, 82, 83 entering from the first light incident surface 61a and emits it from the first light emission surface 61b. The reflection film 5 is arranged opposing to the surface coming into contact with the second light emission surface 41a of the surface light emitting light guide plate 4, and in the reflectance of the reflection film 5, the reflectance of the light whose wavelength is relatively small in the light of different colors is larger than the reflectance of the light whose wavelength is relatively large.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a surface light source device and a liquid crystal display device.

  The liquid crystal display element included in the liquid crystal display device does not emit light by itself. For this reason, the liquid crystal display device includes a backlight device (also referred to as a surface light source device) on the back surface of the liquid crystal display element as a light source for illuminating the liquid crystal display element. In recent years, as the performance of blue light emitting diodes (hereinafter referred to as LEDs (Light Emitting Diodes)) has dramatically improved, surface light source devices using blue LEDs as light sources have been widely adopted. Here, the “rear surface” is a surface opposite to the surface on the liquid crystal display element that displays an image.

  A light source using a blue LED has a blue LED element and a phosphor. This phosphor absorbs light emitted from the blue LED and emits light that is a complementary color of blue. An LED that emits white light (white LED) can be obtained by combining the blue LED and the phosphor. Here, the “blue complementary color” is a color including green and red, which is yellow.

  White LEDs have high electrical-light conversion efficiency and are effective in reducing power consumption. However, on the other hand, white LEDs have the problem that their wavelength bandwidth is wide and the color reproduction range is narrow. The liquid crystal display device includes a color filter inside the liquid crystal display element. The liquid crystal display device performs color expression by extracting only the red, green, or blue spectral range by using the color filter. A light source having a continuous spectrum with a wide wavelength bandwidth such as a white LED needs to increase the color purity of the display color of the color filter in order to widen the color reproduction range. That is, the wavelength band that transmits the color filter is set narrow. However, if the wavelength band that passes through the color filter is set narrow, the light utilization efficiency decreases. This is because the amount of unnecessary light that is not used for image display of the liquid crystal display element increases.

  In order to extend the color reproduction range while minimizing light loss due to the color filter, it is necessary to employ a light source that emits light with a narrow wavelength bandwidth. That is, it is necessary to employ a light source that emits light with high color purity.

  Laser light-emitting elements emit light with a narrower wavelength bandwidth and higher color purity than LEDs. Further, when a laser light emitting element is used as a light source, a light source having only independent spectral ranges for red, green and blue can be used, and color reproducibility can be improved. However, in order to construct a surface light source device using a plurality of light sources having independent spectral bands, it is necessary to uniformly mix the light emitted from each light source in the surface light source device.

  As a method of the surface light source device, a sidelight method in which a light source is arranged along the side end surface of the surface light-emitting light guide plate is widely adopted. Such backlight devices have so far been required to be thin, have high brightness, and uniformity of brightness, but in recent years, with the increase in definition of liquid crystal display panels, the uniformity of the color tone of emitted light has been improved. The demand for improvement is also increasing.

  Therefore, in the liquid crystal display device of Patent Document 1, by reflecting only the blue component of the light leaking from the side end face of the light guide plate and making it incident on the light guide plate again, the color on the end face side facing the light entrance face is reflected. The occurrence of unevenness is suppressed.

JP 2012-94283 A

  When light sources having independent spectral bands for red, green, and blue are used in order to widen the color reproduction range, color unevenness is obtained only by returning only the blue component to the light guide plate and reusing it as in Patent Document 1 described above. It is not necessarily sufficient to correct the above.

  The present invention has been made to solve the above-described problems, and is a surface light source device including a light source having a plurality of independent narrow spectral bands and having a wide color gamut and excellent uniformity. The purpose is to provide a device.

  A surface light source device according to the present invention includes a plurality of laser light emitting elements that emit light of different colors, a light guide member having a first light incident surface and a first light emitting surface, and a second light incident surface. A light-emitting plate having a second light exit surface, and a reflective film, wherein the light guide member mixes light emitted from a plurality of laser light-emitting elements incident from the first light incident surface to mix the light. The light emitted from the first light emitting surface is incident on the second light incident surface of the surface light-emitting light guide plate, and the surface light-emitting light guide plate has the second light incident surface. The incident light from the light is converted into planar light and emitted from the second light emitting surface, and the reflective film is disposed to face the surface in contact with the second light emitting surface of the surface light emitting light guide plate. In the reflectance, the reflectance of light having a relatively small wavelength in light of different colors is larger than the reflectance of light having a relatively large wavelength.

  In the surface light source device according to the present invention, a reflective film having a reflectance characteristic for correcting a difference in internal absorptance is disposed so as to face a surface in contact with the second light emitting surface of the surface emitting light guide plate. Here, the reflectance characteristic that corrects the difference in internal absorptance is a characteristic in which the reflectance of light having a relatively small wavelength is larger than the reflectance of light having a relatively large wavelength in laser beams of a plurality of colors. . Accordingly, even when a plurality of laser light emitting elements that emit light of different colors are provided as a light source, a surface light source device that emits planar light with excellent color uniformity and a wide color gamut can be obtained. Is possible.

It is sectional drawing of the surface light source device which concerns on Embodiment 1. FIG. 1 is an exploded perspective view of a surface light source device according to Embodiment 1. FIG. 1 is a plan view of a surface light source device according to Embodiment 1. FIG. 1 is a block diagram of a surface light source device according to Embodiment 1. FIG. It is a figure which shows the light emission characteristic of the laser light emitting element with which the surface light source device which concerns on Embodiment 1 is equipped. It is a figure which shows the reflective characteristic of the reflective sheet for end surfaces with which the surface light source device which concerns on Embodiment 1 is equipped. It is sectional drawing of the surface light source device which concerns on Embodiment 2. FIG. 6 is an exploded perspective view of a surface light source device according to Embodiment 2. FIG.

<Embodiment 1>
FIG. 1 is a cross-sectional view of the surface light source device 200 and the liquid crystal display device 100 according to the first embodiment. FIG. 2 is an exploded perspective view of the surface light source device 200 and the liquid crystal display device 100. FIG. 3 is a plan view of the surface light source device 200 as viewed from the back side.

  In the first embodiment, xyz coordinates are used to facilitate the description of the drawing. The x-axis is the left-right direction when viewed from the display surface side of the liquid crystal display device 100. The + x axis direction is the right side, and the −x axis direction is the left side. The y axis is the vertical direction of the liquid crystal display device 100. The + y axis direction is the upper side, and the −y axis direction is the lower side. The z axis is the front-rear direction when viewed from the display surface side of the liquid crystal display device 100. The + z axis direction is the near side, and the −z axis direction is the far side. The “front side” is the display surface side of the liquid crystal display device 100. The “back side” is the back side (back side) of the liquid crystal display device 100. In FIG. 1, the direction perpendicular to the paper surface is the y-axis direction. In FIG. 1, the direction from the light incident surface 41c of the surface light-emitting light-guiding plate 4 toward the opposing surface (end surface 41d) is the positive direction of the x axis (+ x axis direction). That is, the direction from the right to the left in FIG. 1 is the + x axis direction. The direction from the bottom to the top of FIG. 1 is the positive direction of the z axis.

<Configuration of Liquid Crystal Display Device 100>
As shown in FIG. 1, the liquid crystal display device 100 includes a liquid crystal panel 1 and a surface light source device 200. The liquid crystal panel 1 has a liquid crystal display element and is a panel that forms image light. The liquid crystal panel 1 is a transmissive panel that transmits light. “Image light” refers to light having image information. Further, the liquid crystal display device 100 may include an optical sheet (first optical sheet) 2. Further, the liquid crystal display device 100 may include an optical sheet (second optical sheet) 3. The surface light source device 200 irradiates the back surface 1b (described later) of the liquid crystal panel 1 with light. As shown in FIG. 1, the light emitted from the surface light source device 200 passes through the optical sheets 3 and 2 and reaches the back surface 1 b of the liquid crystal panel 1.

  The optical sheet 2 has a function of directing transmitted illumination light L44 (described later) toward the back surface 1b of the liquid crystal panel 1. The optical sheet 3 has a function of suppressing optical influences such as fine illumination unevenness of the illumination light L44.

  As shown in FIG. 1, the liquid crystal display device 100 includes a liquid crystal panel 1, optical sheets 2 and 3, and a surface light source device 200 in order from the positive direction of the z axis to the negative direction. The liquid crystal panel 1 and the optical sheets 2 and 3 have a plate shape. Further, the surface light-emitting light guide plate 4 constituting the surface light source device 200 has a plate shape. For this reason, the liquid crystal panel 1, the optical sheets 2 and 3, and the surface light source device 200 are arranged in a stacked manner. “Lamination” is the stacking of layers.

  The liquid crystal panel 1 has a display surface 1a on the surface on the + z axis side. The liquid crystal panel 1 has a back surface 1b on the surface on the −z axis side. The liquid crystal panel 1 has a liquid crystal layer (not shown) between the display surface 1a and the back surface 1b. The display surface 1a of the liquid crystal panel 1 is a surface parallel to the xy plane. The liquid crystal layer of the liquid crystal panel 1 has a planar structure spreading in a direction parallel to the xy plane.

  The display surface 1a of the liquid crystal panel 1 is usually rectangular, and two sides that are adjacent to each other in contact with the display surface 1a are orthogonal to each other. In the first embodiment, the long side of the liquid crystal panel 1 is parallel to the x-axis. The short side of the liquid crystal panel 1 is parallel to the y axis. In the first embodiment, the display surface 1a of the liquid crystal panel 1 is described as a rectangle, but the shape of the display surface 1a of the liquid crystal panel 1 is not limited to this, and may be another shape.

  Although not shown in FIG. 1, the liquid crystal display device 100 includes a control unit 31, a liquid crystal display element driving unit 32, and a laser light source driving unit 33, as shown in FIG. The liquid crystal display element driving unit 32 drives the liquid crystal panel 1. The laser light source driving unit 33 drives laser light emitting elements 81, 82, and 83 (described later).

<Configuration of Surface Light Source Device 200>
The surface light source device 200 includes a plurality of laser light emitting elements 81, 82, 83, a light guide member 6, a surface light emitting light guide plate 4, and a reflective film 5. Further, the surface light source device 200 may include a back reflection sheet 7 as necessary.

  The plurality of laser light emitting elements 81, 82, 83 emit light beams L81, L82, L83 of different colors. The light guide member 6 has a first light incident surface 61a and a first light emitting surface 61b. The surface-emitting light guide plate 4 has a second light incident surface 41c and a second light emitting surface 41a.

  The light guide member 6 mixes the light beams L81, L82, and L83 emitted from the plurality of laser light emitting elements 81, 82, and 83 that are incident from the first light incident surface 61a to produce the first light emitting surface 61b as the mixed color light L70. Exits from. The light emitted from the first light emitting surface 61b is incident on the second light incident surface 41c of the surface light-emitting light guide plate 4. The surface emitting light guide plate 4 converts the mixed color light L70 incident from the second light incident surface 41c into planar light (illumination light L44) and emits the light from the second light emitting surface 41a.

  The reflection film 5 is provided on the surface of the end surface reflection sheet 50. That is, the reflective film 5 is disposed so as to face the surface (that is, the end surface 41 d) that is in contact with the second light emitting surface 41 a of the surface emitting light guide plate 4. The reflective film 5 has a reflection characteristic in which the reflectance of light having a relatively small wavelength is larger than the reflectance of light having a relatively large wavelength. The reflective film 5 has the same rectangular shape as the end surface 41 d of the surface light-emitting light guide plate 4.

  In the surface light source device 200, the surface light-emitting light guide plate 4 and the back reflection sheet 7 are disposed in order from the positive direction of the z-axis to the negative direction. Further, in the surface light source device 200, laser light emitting elements 81, 82, and 83 are disposed on the −x axis side (back side) of the surface emitting light guide plate 4.

  The surface-emitting light guide plate 4 has a plate shape. The surface-emitting light guide plate 4 has a second light emitting surface 41a, a back surface 41b, a second light incident surface 41c, and an end surface 41d. The second light incident surface 41 c of the surface emitting light guide plate 4 is formed on one end surface of the surface emitting light guide plate 4. The “end face” is a face of a cut surface that is formed when a thick object is cut. Here, it is a surface that connects the second light exit surface 41a and the back surface 41b of the plate-shaped surface-emitting light guide plate 4. That is, it is a plate-shaped side surface. The second light exit surface 41a and the back surface 41b are surfaces parallel to the xy plane. The light incident from the second light incident surface 41c is emitted as planar light from the second light emitting surface 41a.

  A plurality of micro optical elements 42 are formed on the back surface 41 b of the surface emitting light guide plate 4. The light incident from the second light incident surface 41c travels in the x-axis direction while satisfying the total reflection condition. However, among the light incident on the micro optical element 42, there is light that does not satisfy the total reflection condition. The light that does not satisfy the total reflection condition is emitted from the second light emission surface 41a.

  The end surface reflection sheet 50 is disposed on the end surface 41 d side facing the second light incident surface 41 c of the surface light emitting light guide plate 4. In addition, the reflective film 5 is disposed on the surface of the reflective sheet for end surface 50 that faces the end surface 41 d of the surface light-emitting light guide plate 4.

  In the light guide member 6, the light beams L81, L82, and L83 emitted from the laser light emitting elements 81, 82, and 83 are incident on the first light incident surface 61a of the light guide member 6, and the first light emitting surface. The light exits from 61b. The first light exit surface 61b of the light guide member 6 and the second light incident surface 41c of the surface light-emitting light guide plate 4 are disposed to face each other.

  The back reflection sheet 7 is disposed on the back surface 41 b side of the surface light-emitting light guide plate 4. Further, the back reflection sheet 7 is arranged with the surface side (reflection surface side) of the back reflection sheet 7 facing the surface light-emitting light guide plate 4. The light that does not satisfy the total reflection condition by the micro optical element 42 is also emitted from the back surface 41b side. The back light reflecting sheet 7 reflects the light emitted from the back surface 41b side of the surface light-emitting light guide plate 4 toward the second light emitting surface 41a side (+ z-axis direction). Thereby, the light incident on the surface light-emitting light guide plate 4 can be efficiently emitted to the liquid crystal panel 1 side.

  The laser light emitting elements 81, 82, 83 are arranged to face the first light incident surface 61 a of the light guide member 6. Light rays L81, L82, and L83 incident from the first light incident surface 61a of the light guide member 6 travel through the light guide member 6 while satisfying the condition of total reflection, and reach the first light output surface 61b. The light beams L <b> 81, L <b> 82, and L <b> 83 are mixed in the process of traveling inside the light guide member 6 and become mixed color light L <b> 70 (white light). The mixed color light L70 emitted from the first light emitting surface 61b of the light guide member 6 is incident on the second light incident surface 41c of the surface emitting light guide plate 4. The mixed color light L70 propagates in the surface emitting light guide plate 4 while being totally reflected, but the light beam that has entered the micro optical element 42 in the course of propagation and does not satisfy the conditions for total reflection is emitted from the second light emitting surface 41a. To do. The light beam that has reached the end surface 41 d of the surface light-emitting light guide plate 4 is diffusely reflected by the reflective film 5 provided on the end surface reflection sheet 50 and returns to the inside of the surface light-emitting light guide plate 4 again. “Diffuse reflection” means to diffuse and reflect.

<Laser light emitting device>
The laser light emitting elements 81, 82, and 83 emit red, green, and blue laser beams L81, L82, and L83, respectively. As shown in FIG. 3, the surface light source device 200 may include a plurality of laser light emitting elements 81, 82, and 83.

  The red laser beam L81 is, for example, light having a light intensity peak at a wavelength of 630 nm. The wavelength width of the laser beam L81 is 1 nm in full width at half maximum. That is, the spectral width of the laser beam L81 is extremely narrow compared to the spectral width of light emitted from a single-color LED element or light emitted from an LED element using a phosphor. Here, “full width at half maximum” refers to a wavelength width at which the light intensity is 50% of the maximum intensity with respect to the wavelength at which the light intensity is maximum. An example of the spectrum of laser light is shown in FIG.

  The green laser beam L82 is light having a light intensity peak at a wavelength of 530 nm, for example. The wavelength width of the laser beam L82 is 1 nm in full width at half maximum. The blue laser beam L83 is light having a light intensity peak at a wavelength of 465 nm, for example. The wavelength width of the laser beam L83 is 1 nm in full width at half maximum.

  The light emitting portions of the laser light emitting elements 81, 82, 83 are arranged to face the first light incident surface 61 a of the light guide member 6. Here, the light emitting portion is a surface that emits the laser beams L81, L82, and L83 of the laser light emitting elements 81, 82, and 83.

<Light guide member>
The light guide member 6 is disposed so that the first light incident surface 61a comes to the back surface 41b side of the surface light emitting light guide plate 4. Further, when the surface light source device 200 includes the back reflection sheet 7, the laser light guide member 6 has the first light incident surface 61 a on the back side (−z-axis direction side) of the back reflection sheet 7. Placed in.

  The light guide member 6 is made of a transparent material. For example, acrylic resin (PMMA) or the like is used as the material of the light guide member 6. As shown in FIGS. 1 and 2, the first light exit surface 61 b of the light guide member 6 is disposed to face the second light incident surface 41 c of the surface light-emitting light guide plate 4. Further, as shown in FIG. 3, the first light incident surface 61a of the light guide member 6 overlaps the surface (back surface 41b) facing the second light emitting surface 41a of the surface light-emitting light guide plate 4 in plan view. Are arranged as follows.

<Surface emitting light guide plate>
As described above, the surface-emitting light guide plate 4 has the second light emitting surface 41a, the back surface 41b, the second light incident surface 41c, and the end surface 41d. The second light emitting surface 41a is a main surface of the surface light emitting light guide plate 4 on the liquid crystal panel 1 side (+ z axis side). The back surface 41 b is a surface facing the second light emitting surface 41 a of the surface light-emitting light guide plate 4. That is, the back surface 41 b is a surface on the −z axis side of the surface-emitting light guide plate 4.

  The surface-emitting light guide plate 4 is made of a transparent material. For example, the material of the surface emitting light guide plate 4 is an acrylic resin (for example, PMMA). The surface-emitting light guide plate 4 is a plate-shaped member. The surface-emitting light guide plate 4 is a plate-shaped member having a thickness of 3 mm, for example. The surface emitting light guide plate 4 is laminated and disposed between the optical sheet 3 and the back reflection sheet 7. “Lamination” is the stacking of layers. That is, the sheet-like optical sheet 3, the plate-like surface light-emitting light-guiding plate 4, and the back reflection sheet 7 are arranged so as to be stacked. The surface emitting light guide plate 4 is disposed in parallel to the display surface 1 a of the liquid crystal panel 1. That is, the second light emission surface 41a is disposed in parallel to the display surface 1a. Further, the back surface 41b is arranged in parallel to the display surface 1a.

  The second light incident surface 41 c is formed on one end surface of the surface emitting light guide plate 4. Further, the end surface 41 d is formed on one end surface of the surface light-emitting light guide plate 4. The second light incident surface 41c is an end surface on the −x side. The end surface 41d is an end surface on the + x side. That is, the end surface 41d is a surface facing the second light incident surface 41c. Laser beams L81, L82, and L83 emitted from the first light emitting surface 61b of the light guide member 6 are incident from the second light incident surface 41c of the surface emitting light guide plate 4.

  A plurality of micro optical elements 42 are provided on the back surface 41 b of the surface emitting light guide plate 4. The micro optical element 42 has a hemispherical convex shape (convex lens shape) protruding in the −z-axis direction. That is, the micro optical element 42 protrudes from the back surface 41b to the side opposite to the second light emitting surface 41a. Further, the micro optical elements 42 are arranged at different arrangement densities depending on the position on the back surface 41b (on the xy plane) of the surface emitting light guide plate 4. Here, the “arrangement density” refers to the number of the micro optical elements 42 per unit area or the size of the micro optical elements 42. That is, the arrangement density is a ratio of the micro optical elements 42 per unit area.

  The in-plane luminance distribution of illumination light L44 (described later) can be controlled by changing the arrangement density of the micro optical elements 42. That is, the micro optical element 42 is arranged so that the spatial intensity distribution of the illumination light L44 emitted from the second light emission surface 41a is uniform. The “in-plane luminance distribution” refers to a distribution indicating the level of luminance with respect to a position represented in two dimensions on an arbitrary plane. Here, “in-plane” means within the display surface 1 a of the liquid crystal panel 1.

  Here, although the micro optical element 42 has a convex lens shape, it is not limited to this. The micro optical element 42 may have another shape as long as it has a function of reflecting the mixed color light L70 serving as the illumination light L44 in the + z-axis direction and emitting it toward the back surface 1b of the liquid crystal panel 1. For example, a prism shape or a random uneven pattern can be used as another shape of the micro optical element 42. For example, the micro optical element 42 may be white dot printing.

  The arrangement density of the micro optical elements 42 is designed according to the angular intensity distribution of the mixed color light L70 after entering from the second light incident surface 41c. The micro optical elements 42 are arranged from coarse to dense from the second light incident surface 41c toward the opposing end surface 41d. Thereby, the amount of light emitted from the second light emitting surface 41a is uniform in the x-axis direction, and planar light with high uniformity can be formed.

<Reflection sheet for end face>
The end surface reflection sheet 50 is disposed to face the end surface 41 d of the surface light-emitting light guide plate 4. A reflective film 5 is provided on the surface on the end surface 41 d side of the surface light-emitting light-guiding plate 4 of the reflection sheet for end surface 50. The reflective film 5 is formed of, for example, a sheet that reflects light using a resin such as polyethylene terephthalate as a base material. Moreover, the reflective film 5 may be a deposited film obtained by depositing a metal material, a dielectric, or the like in a single layer or a plurality of layers on the surface of the reflection sheet 50 for an end face. The surface of the end surface reflection sheet 50 on which the reflective film 5 is provided is attached to the end surface 41 d of the surface light-emitting light-guiding plate 4 with an adhesive such as a double-sided tape having a high transmittance. As described above, the reflective film 5 diffusely reflects the light emitted from the end surface 41d toward the light incident surface 41c (−x axis direction). Thereby, the light incident on the surface light-emitting light guide plate 4 can be efficiently emitted to the liquid crystal panel 1 side.

  An example of the relative spectral reflectance of the reflective film 5 is shown in FIG. As shown in FIG. 6, the reflective film 5 in the present embodiment has a reflectance peak (maximum value) in a blue component (wavelength of 460 nm or more and 470 nm or less) band. Further, the reflectance of the green component (wavelength of 525 nm or more and 535 nm or less) is lower than that of the blue component. Further, the reflectance of the red component (wavelength of 630 nm to 640 nm) is lower than that of the green component.

  Light that is incident from the second light incident surface 41 c of the surface light-emitting light guide plate 4 and is emitted from the end surface 41 d is attenuated by internal absorption while propagating through the surface light-emitting light guide plate 4. Since the internal absorptance of light on the short wavelength side is high, the light emitted from the end face 41d has relatively high intensity on the long wavelength side. When a light source having a narrow wavelength band such as a laser light emitting element is used, the intensity difference due to internal absorption becomes significant. Therefore, when light of all colors is diffused and reflected from the end surface 41d with the same reflectance and reused, a part of the illumination light L44 emitted from the second light emission surface 41a of the surface light-emitting light guide plate 4 ( Color unevenness occurs in the vicinity of the end face 41d).

  In the present embodiment, for example, the reflection film 5 having the relative spectral reflectance shown in FIG. 6 is used to eliminate the imbalance between the blue component, the green component, and the red component generated by the internal absorption of the surface light-emitting light guide plate 4. Can do. Moreover, by providing the reflective film 5, the light emitted from the end face 41d can be used efficiently.

<Reflection sheet for the back>
The back reflection sheet 7 is disposed to face the back surface 41 b of the surface light emitting light guide plate 4. The back reflection sheet 7 is arranged in parallel with the display surface 1 a of the liquid crystal panel 1. The back reflection sheet 7 is formed of, for example, a sheet that reflects light using a resin such as polyethylene terephthalate as a base material. Further, the back reflection sheet 7 may be a sheet in which a metal is coated on the surface of the substrate by vapor deposition. As described above, the back reflection sheet 7 reflects the light emitted from the back surface 41b toward the second light exit surface 41a (+ z-axis direction). Thereby, the light incident on the surface light-emitting light guide plate 4 can be efficiently emitted to the liquid crystal panel 1 side. The back reflection sheet 7 may be plate-shaped as long as it has a function of reflecting light emitted from the back surface 41b toward the second light exit surface 41a (+ z-axis direction).

<Laser beam behavior>
The behavior of the laser beams L81, L82, and L83 emitted from the laser light emitting elements 81, 82, and 83 will be described. Laser beams L81, L82, and L83 emitted from the laser light emitting elements 81, 82, and 83 enter the light guide member 6 from the first light incident surface 61a. The laser beams L81, L82, and L83 are repeatedly reflected a plurality of times while propagating through the light guide member 6, and spatially overlap before reaching the first light emitting surface 61b to become white mixed light L70. The mixed color light L70 enters the surface light-emitting light guide plate 4 from the second light incident surface 41c.

  The mixed light L70 incident from the second light incident surface 41c of the surface light-emitting light guide plate 4 proceeds in the + x-axis direction while repeating total reflection at the interface between the surface light-emitting light guide plate 4 and the air layer. The “interface between the surface light-emitting light-guiding plate 4 and the air layer” refers to the interface between the surface on the second light emitting surface 41 a side or the surface on the back surface 41 b side and the air layer. Further, part of the mixed color light L70 enters the micro optical element 42 in the process of repeating total reflection. The mixed color light L70 incident on the micro optical element 42 changes its traveling direction when reflected by the curved surface of the micro optical element 42. The mixed color light L70 whose traveling direction has changed includes light rays that do not satisfy the total reflection condition at the interface between the surface of the surface light-emitting light guide plate 4 and the air layer. A light beam that does not satisfy the total reflection condition (a light beam traveling in the + z-axis direction) is emitted as illumination light L44 from the second light emission surface 41a of the surface light-emitting light guide plate 4 toward the back surface 1b of the liquid crystal panel 1. The illumination light L44 is emitted in the + z-axis direction from the second light emission surface 41a as planar light. At this time, the illumination light L44 is planar light having a uniform spatial intensity distribution in the xy plane. The emission direction of the illumination light L44 is a direction perpendicular to the xy plane. The illumination light L44 becomes white planar light with high uniformity of spatial intensity distribution in the xy plane.

  Here, in the mixed color light L <b> 70 traveling inside the surface light-emitting light guide plate 4, there is light that travels in the −z-axis direction by being emitted from the back surface 41 b of the surface light-emitting light guide plate 4. The light emitted from the back surface 41b is reflected by the back reflection sheet 7 and becomes light traveling in the + z-axis direction. That is, the mixed color light L70 reflected by the back reflection sheet 7 becomes illumination light L44. Then, the mixed color light L70 reflected by the back reflection sheet 7 and becomes the illumination light L44 illuminates the back surface 1b of the liquid crystal panel 1.

  Further, in the mixed color light L <b> 70 traveling in the surface light-emitting light guide plate 4, there is light that is emitted from the end surface 41 d of the surface light-emitting light guide plate 4 and travels in the + x-axis direction. The light emitted from the end face 41d is diffusely reflected by the reflective film 5 provided on the end face reflection sheet 50 and becomes light traveling in the −x-axis direction. That is, the light diffusely reflected by the reflective film 5 is incident again on the surface emitting light guide plate 4 and reused.

<Control of liquid crystal display device>
An operation until an image is displayed on the liquid crystal panel 1 in the liquid crystal display device 100 will be described. FIG. 4 is a block diagram schematically showing the configuration of the control system of the liquid crystal display device 100. As shown in FIG. 4, a video signal 34 is input to the control unit 31 provided in the liquid crystal display device 100. The control unit 31 generates a liquid crystal display element control signal 35 and sends it to the liquid crystal display element driving unit 32. Further, the control unit 31 generates a laser light source control signal 36 and sends it to the laser light source driving unit 33. The laser light source control signal 36 is generated according to the ratio of the light intensity of each color required for displaying the video signal 34 input to the control unit 31.

  When receiving the liquid crystal display element control signal 35, the liquid crystal display element driving unit 32 drives the liquid crystal panel 1 based on the received signal. That is, the liquid crystal display element driving unit 32 sends an electric signal (liquid crystal display element control signal 35) to the liquid crystal panel 1 to change the light transmittance in each pixel. Specifically, the liquid crystal display element driving unit 32 changes the orientation of the liquid crystal by changing the voltage applied to the liquid crystal layer, and rotates the polarization direction of the light transmitted through each pixel. The amount of light transmitted through the polarization direction is controlled by a polarizing plate provided behind the liquid crystal layer. The brightness and color of the image are changed by changing the light transmittance. Upon receiving the laser light source control signal 36, the laser light source driving unit 33 drives each of the laser light emitting elements 81, 82, 83 based on this.

  The control unit 31, the crystal display element driving unit 32, and the laser light source driving unit 33 are realized by a processing circuit. Even if the processing circuit is dedicated hardware, a CPU that executes a program stored in the memory (Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, DSP) It may be.

  When the processing circuit is dedicated hardware, the processing circuit corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

  When the processing circuit is a CPU, the functions of the control unit 31, the liquid crystal display element driving unit 32, and the laser light source driving unit 33 are realized by software, firmware, or a combination of software and firmware. Software and firmware are described as programs and stored in a memory. The processing circuit reads out and executes the program stored in the memory, thereby realizing the functions of the control unit 31, the crystal display element driving unit 32, and the laser light source driving unit 33. It can also be said that this program causes a computer to execute the procedures and methods of the control unit 31, the crystal display element driving unit 32, and the laser light source driving unit 33. Here, the memory corresponds to, for example, a nonvolatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, or EEPROM, a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD, or the like. To do.

  In addition, about the function of the control part 31, the liquid crystal display element drive part 32, and the laser light source drive part 33, a part may be implement | achieved by exclusive hardware and a part may be implement | achieved by software or firmware.

<Effect>
The surface light source device 200 according to the first embodiment has a plurality of laser light emitting elements 81, 82, and 83 that emit light of different colors, a first light incident surface 61a, and a first light emitting surface 61b. The light guide plate 6 includes a member 6, a surface light-emitting light guide plate 4 having a second light incident surface 41c and a second light output surface 41a, and a reflective film 5. The light guide member 6 has a first light incident surface 61a. The light emitted from the plurality of laser light emitting elements 81, 82, and 83 incident from is mixed and emitted from the first light emitting surface 61 b, and the second light incident surface 41 c of the surface emitting light guide plate 4 has the second light incident surface 41 c The light emitted from the light emitting surface 41a is incident, and the surface light-emitting light guide plate 4 converts the light incident from the second light incident surface 41c into planar light (illumination light L44) and converts it to the second light emitting surface 41a. The reflective film 5 is a surface in contact with the second light output surface 41a of the surface light-emitting light guide plate 4 (ie, Disposed opposite to the face 41d), the reflectance of the reflective film 5, the reflectance of light relatively wavelength is small in the different colors of light is greater than the reflectance of a relatively wavelength greater light.

  Laser beams of a plurality of colors propagating through the surface emitting light guide plate 4 are attenuated by internal absorption. Since the internal absorptance is high for light on the short wavelength side, color unevenness is likely to occur in the planar light on the end face of the surface light-emitting light guide plate 4 (the face in contact with the second light emitting face 41a). In the first embodiment, the reflective film 5 having the reflectance characteristic for correcting the difference in internal absorptance is arranged so as to face the end face of the surface light-emitting light guide plate 4. Here, the reflectance characteristic that corrects the difference in internal absorptance refers to the reflectance of light having a relatively small wavelength and the reflectance of light having a relatively large wavelength in light of different colors (plural colors of laser beams). It is a larger characteristic. As a result, even when a plurality of laser light emitting elements 81, 82, and 83 that emit light of different colors as light sources are provided, color unevenness is suppressed, and white planar light with excellent uniformity in a wide color gamut is emitted. The surface light source device 200 can be obtained.

  In the surface light source device 200 according to the first embodiment, the second light emitting surface 41 a is the main surface of the surface light emitting light guide plate 4, and the second light incident surface 41 c is the main surface of the surface light emitting light guide plate 4. The reflective film 5 is an end surface that is in contact with the surface, and is disposed to face a surface (that is, the end surface 41d) that faces the second light incident surface 41c.

  In the surface light-emitting light-guiding plate 4, the difference in the intensity of each color light due to the difference in internal absorptance is the largest on the end surface (that is, the end surface 41 d) facing the light incident surface (that is, the second light incident surface 41 c). Therefore, by disposing the reflective film 5 so as to face the end surface 41d, it is possible to effectively suppress the color unevenness of the planar light.

  In the surface light source device 200 according to the first embodiment, the plurality of laser light emitting elements 81, 82, 83 emit a blue light, a laser light emitting element 81 that emits blue light, a laser light emitting element 82 that emits green light, and a red light. This is a laser light emitting element 83.

  Therefore, by forming a light source with the laser light emitting elements 81, 82, and 83 of blue light, green light, and red light, they can be mixed to obtain white light.

  In the surface light source device 200 according to the first embodiment, the reflective film 5 has a reflectance peak in the blue light wavelength band, and the reflectance of the green light wavelength band is the reflectance of the blue light wavelength band. The reflectance of the red light wavelength band is smaller than the reflectance of the green light wavelength band.

  Therefore, regarding the reflectance characteristics of the reflective film 5, a peak of reflectance is set in the wavelength band of blue light having the largest attenuation due to internal absorption, and the reflectance of green light having the second largest attenuation due to internal absorption is next to blue light. Is set smaller than the reflectance of blue light, and the reflectance of red light having the second largest attenuation due to internal absorption is set smaller than the reflectance of green light. As a result, even when a plurality of laser light emitting elements 81, 82, and 83 that emit light of different colors as light sources are provided, it is possible to correct a difference in attenuation rate due to internal absorption of the surface light emitting light guide plate 4.

  In the surface light source device 200 according to the first embodiment, blue light is light having a wavelength of 460 nm to 470 nm, green light is light having a wavelength of 525 nm to 535 nm, and red light is 630 nm to 640 nm. Light having the following wavelengths.

  Therefore, regarding the reflectance characteristics of the reflective film 5, the peak of reflectance is set in the wavelength band of 460 nm or more and 470 nm or less, and the reflectance of the wavelength band of 525 nm or more and 535 nm or less is higher than the reflectance of the wavelength band of 460 nm or more and 470 nm or less. The reflectance is set to be small, and the reflectance in the wavelength band of 630 nm to 640 nm is set to be smaller than the reflectance of the wavelength band of 525 nm to 535 nm. Thereby, it becomes possible to correct the difference in attenuation rate due to internal absorption of the surface light-emitting light guide plate 4.

  In the surface light source device 200 according to the first embodiment, the reflective film 5 is provided as a member different from the surface light-emitting light guide plate 4.

  Accordingly, by providing the reflective film 5 as a separate member from the surface light-emitting light guide plate 4, the reflective film 5 can be easily opposed to the end surface 4 d of the surface light-emitting light guide plate 4 without processing the surface light-emitting light guide plate 4. It is possible to arrange in

  Further, in the surface light source device 200 according to the first embodiment, the first light incident surface 61a of the light guide member 6 is a surface facing the second light emitting surface 41a of the surface light emitting light guide plate 4 (that is, the back surface 41b). And overlap in plan view.

  Therefore, by arranging the first light incident surface 61a of the light guide member 6 on the back surface 41b side of the surface emitting light guide plate 4, the plurality of laser light emitting elements 81, 82, 83 are arranged on the back surface 41b side of the surface emitting light guide plate 4. It becomes possible to arrange in. Thereby, since the member arrange | positioned by planar view around the 2nd light-projection surface 41a decreases, the frame frame of the surface light source device 200 is possible.

<Embodiment 2>
FIG. 7 is a cross-sectional view of the surface light source device 201 and the liquid crystal display device 101 according to the second embodiment when viewed from the −y axis side. FIG. 8 is an exploded perspective view of the surface light source device 201 and the liquid crystal display device 101. In order to facilitate the explanation of the figure, the same xyz coordinates as in the first embodiment are used.

  The surface light source device 201 according to the second embodiment does not include the end surface reflection sheet 50 according to the first embodiment, and the reflection film 5 is integrally provided on the end surface 41 d of the surface light-emitting light guide plate 4. Except this point, the configuration is the same as that of the first embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Components similar to those in the first embodiment are the liquid crystal panel 1, the optical sheets 2 and 3, the light guide member 6, the back reflection sheet 7, and the laser light emitting elements 81, 82, and 83.

<End surface 41d of surface-emitting light guide plate 4>
The end face 41d of the surface emitting light guide plate 4 will be described. A reflection film 5 is coated on the end surface 41 d of the surface light-emitting light guide plate 4. The characteristic of the relative spectral reflectance of the reflective film 5 is the same as that of the first embodiment (FIG. 5). As in the first embodiment, the mixed color light L70 that has reached the end surface 41d of the surface light-emitting light guide plate 4 is reflected with a high reflectance in the order of the blue component, the green component, and the red component, and then enters the surface light-emitting light guide plate 4 again. Thereby, the difference of the attenuation factor by the internal absorption of the surface light-emitting light guide plate 4 is corrected.

  Although the second embodiment is different from the first embodiment in that the reflective film 5 is integrally disposed on the end surface 41d of the surface light-emitting light guide plate 4, the same effect as the first embodiment can be obtained.

<Effect>
In the surface light source device 201 in the present embodiment, the reflective film 5 is integrally provided on the surface (that is, the end surface 41 d) in contact with the second light emitting surface 41 a of the surface emitting light guide plate 4.

  Therefore, by providing the reflective film 5 integrally with the end surface 41d of the surface light-emitting light guide plate 4, it is possible to more efficiently reflect the light reaching the end surface 41d. Therefore, it is possible to obtain the surface light source device 201 that emits high-quality white planar light with suppressed color unevenness.

  In the first embodiment described above, the liquid crystal display device 100 includes the surface light source device 200 and the liquid crystal panel 1 that displays an image using light irradiated by the surface light source device 200. In the second embodiment described above, the liquid crystal display device 101 includes the surface light source device 201 and the liquid crystal panel 1 that displays an image using the light emitted by the surface light source device 201.

  Therefore, according to the liquid crystal display devices 100 and 101 in the first and second embodiments, it is possible to suppress color unevenness and display image light having a wide color gamut and excellent color reproducibility.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  DESCRIPTION OF SYMBOLS 1 Liquid crystal panel, 1a Display surface, 1b back surface, 1st optical sheet, 3rd optical sheet, 4 surface light-emitting light-guide plate, 41a 2nd light-projection surface, 41b back surface, 41c 2nd light-incidence surface, 41d end face, 42 micro-optical element, 5 reflecting film, 50 end face reflecting sheet, 6 light guide member, 61a first light incident face, 61b first light emitting face, 7 back reflecting sheet, 81, 82, 83 Laser light emitting element, 100, 101 liquid crystal display device, 200, 201 surface light source device, 31 control unit, 32 liquid crystal display element driving unit, 33 laser light source driving unit, 34 video signal, 35 liquid crystal display element control signal, 36 laser light source control Signal, L70 mixed color light, L81, L82, L83 light, L44 illumination light.

Claims (9)

A plurality of laser light emitting elements emitting light of different colors;
A light guide member having a first light incident surface and a first light exit surface;
A surface emitting light guide plate having a second light incident surface and a second light emitting surface;
A reflective film;
With
The light guide member mixes the light emitted from the plurality of laser light emitting elements incident from the first light incident surface and emits the light from the first light output surface,
Light emitted from the first light emitting surface is incident on the second light incident surface of the surface light-emitting light guide plate,
The surface-emitting light guide plate converts light incident from the second light incident surface into planar light and emits the light from the second light emitting surface.
The reflective film is disposed to face a surface in contact with the second light emitting surface of the surface-emitting light guide plate,
In the reflectance of the reflective film, the reflectance of light having a relatively small wavelength in the light of the different color is larger than the reflectance of light having a relatively large wavelength,
Surface light source device. The second light exit surface is a main surface of the surface-emitting light guide plate,
The second light incident surface is an end surface in contact with the main surface of the surface-emitting light guide plate,
The reflective film is disposed to face a surface facing the second light incident surface;
The surface light source device according to claim 1. The plurality of laser light emitting elements are a laser light emitting element that emits blue light, a laser light emitting element that emits green light, and a laser light emitting element that emits red light.
The surface light source device according to claim 1. The reflective film has a reflectance peak in the wavelength band of the blue light, the reflectance of the wavelength band of the green light is smaller than the reflectance of the wavelength band of the blue light, and the reflectance of the wavelength band of the red light is The reflectance is smaller than the reflectance of the green light wavelength band,
The surface light source device according to claim 3. The blue light is light having a wavelength of 460 nm or more and 470 nm or less,
The green light is light having a wavelength of 525 nm or more and 535 nm or less,
The red light is light having a wavelength of 630 nm to 640 nm.
The surface light source device according to claim 3 or 4. The reflective film is provided as a separate member from the surface-emitting light guide plate.
The surface light source device according to any one of claims 1 to 5. The reflective film is integrally provided on a surface in contact with the second light emitting surface of the surface light-emitting light guide plate.
The surface light source device according to any one of claims 1 to 5. The first light incident surface of the light guide member overlaps with a surface of the surface-emitting light guide plate facing the second light output surface in plan view.
The surface light source device according to any one of claims 1 to 7. A surface light source device according to any one of claims 1 to 8,
A liquid crystal panel for displaying an image using light irradiated by the surface light source device;
Comprising
Liquid crystal display device.

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