JP2015138613A - Surface light source device and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device which suppresses occurrence of color unevenness when using light sources having different characteristics, and a liquid crystal display device.SOLUTION: A surface light source device 200 includes a laser light source 8, an LED light source 7, a laser light diffusion member 6 and a surface light emitting light guide plate 4. The laser light source 8 has a laser light emitting element for emitting a laser beam L8. The LED light source 7 has a plurality of LED elements 71 for emitting an LED beam L7. The laser light diffusion member 6 diffuses and reflects the laser beam L8 emitted from the laser light source 8 at a light diffusion part 62, and spreads a light divergence angle of the laser beam L8 to the divergence angle equal to that of the LED beam L7. The surface light emitting light guide plate 4 has a light incident surface 41c for allowing the beam to enter, allows the laser beam L8 and the LED beam L7 to enter from the light incident surface 41c and converts them to planar light. The optical distance A from a diffusion reflection surface 62a of the light diffusion part 62 to a light incident surface 41a is equal to the optical distance A from a light emitting surface 72 of the LED elements 71 to the light incident surface 41a.

Description

  The present invention relates to a surface light source device having a planar light emitting surface, and a liquid crystal display device having a surface light source device and a liquid crystal panel.

  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 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, backlight devices using blue LEDs as light sources have been widely adopted. The “rear surface” is a surface on the opposite side to the image display direction.

  The light source using the 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. Such an LED is called a white LED. The “blue complementary color” is yellow, which is a color including green and red.

  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 uses this color filter to extract only the red, green, and blue spectral ranges and perform color expression. 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.

  For example, Patent Document 1 proposes a liquid crystal display device that employs a white LED and a monochromatic LED in order to widen the color reproduction range. By using a monochromatic light source, it is possible to improve the color reproducibility of colors that were insufficient with white LEDs.

Japanese Patent Laid-Open No. 2005-56842

  In the liquid crystal display device of Patent Document 1 described above, white LEDs and single color LEDs are alternately arranged on one side surface of the light guide plate. The characteristics as a light source are not significantly different between the white LED and the single color LED. In particular, the light divergence angle is not significantly different. For this reason, even when white LEDs and monochromatic LEDs are alternately arranged, the light guide plate can be designed in substantially the same manner as in the case of only white LEDs. This is because light having the same angular intensity distribution enters the light guide plate. The “angle intensity distribution” is a distribution of light intensity with respect to a light emission angle on a reference surface. Here, the “light emission angle” is the light emission direction. “Light intensity” is the amount of light energy.

  However, when using light sources of a plurality of colors, if the characteristics of these light sources are different, color unevenness will occur if LEDs are arranged alternately on one side of the light guide plate as in Patent Document 1. In particular, when the divergence angles of the light emitted from the light source are different, color unevenness appears. The light incident on the light guide plate travels in the direction facing the incident surface while repeating total reflection. However, due to the fine structure provided on the light guide plate, the condition of total reflection is broken, and the light travels in the direction of the exit surface. The amount of light emitted from the exit surface of the light guide plate is adjusted by the arrangement of the fine structure or the like in accordance with the characteristics of the light source. The microstructure of the light guide plate is mainly provided on the back side with respect to the light exit surface. "Back side" has the same meaning as the back side. At this time, if the divergence angle of the light emitted from the light source is different, the optical path in the light guide plate is different, and the light intensity distribution on the emission surface is different for each light source. The difference in light intensity distribution appears as uneven color.

  A laser is a light source that emits light with a narrow wavelength bandwidth. Color reproducibility can be improved by using a laser. However, a laser is a light source having a very narrow divergence angle, and if LEDs and lasers are alternately arranged on one side of a light guide plate, color unevenness occurs. This is because it is difficult to match the arrangement of the microstructure to both the LED and the laser.

  The present invention has been made in view of the above, and provides a liquid crystal display device in which, when two types of light sources, a laser and an LED, are used, the divergence angle of the laser is widened with a simple configuration and color unevenness is suppressed. The purpose is to do.

  A surface light source device according to the present invention includes a laser light source having a laser light emitting element that emits a laser beam, an LED light source having a plurality of LED elements that emit an LED beam, and the laser beam emitted from the laser light source is diffused by a light diffusion unit. A laser light diffusing member that reflects and expands the divergence angle of the laser beam to a divergence angle equivalent to that of the LED beam; and a light incident surface on which the light beam is incident. The laser beam and the LED beam are incident from the light incident surface. And an optical distance from the diffuse reflection surface of the light diffusing section to the light incident surface is an optical distance from the light emitting surface of the LED element to the light incident surface. be equivalent to.

  According to the present invention, it is possible to suppress the occurrence of color unevenness in a surface light source device using a laser and an LED as a light source.

It is a block diagram which shows roughly an example of a structure of the liquid crystal display device (including surface light source device) concerning Embodiment 1 of this invention. It is a perspective view of the surface light source device of FIG. It is the block diagram which looked at the surface light source device of FIG. 1 from the display surface side. FIG. 2 is a block diagram schematically showing a configuration of a control system of the liquid crystal display device shown in FIG. 1. It is sectional drawing which shows roughly an example of a structure of the liquid crystal display device (including surface light source device) which concerns on Embodiment 2 of this invention. It is the top view which looked at the surface light source device of FIG. 5 from the display surface side. It is a block diagram which shows schematically another structure of the laser diffusion rod of the liquid crystal display device (including surface light source device) concerning Embodiment 2 of this invention. It is a block diagram which shows schematically another structure of the laser diffusion rod of the liquid crystal display device (including surface light source device) concerning Embodiment 2 of this invention.

Embodiment 1 FIG.
A surface light source device 200 and a liquid crystal display device 100 according to Embodiment 1 for carrying out the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram schematically showing an example of the configuration of the liquid crystal display device 100 (including the surface light source device 200) according to the first embodiment. FIG. 2 is a perspective view of the surface light source device 200. FIG. 3 is a configuration diagram of the surface light source device 200 as viewed from the display surface side.

  In order to facilitate the explanation of the figure, xyz coordinates are used. 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 guide plate 4 toward the opposite surface 41d is the positive direction of the x axis (+ x axis direction). That is, the direction from the left to the right 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>
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 is a panel having liquid crystal display elements and forming image light. The liquid crystal panel 1 is a transmissive type panel that transmits light. “Image light” refers to light having image information. Further, the liquid crystal display device 100 can include an optical sheet (first optical sheet) 2. In addition, the liquid crystal display device 100 can 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. 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 surface light source device 200 includes a surface light-emitting light guide plate 4, a laser light diffusion member 6, an LED light source 7, and a laser light source 8. The surface-emitting light guide plate 4 has a thin plate shape. Moreover, the surface light source device 200 can be provided with the light reflection sheet 5 as needed.

  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, an LED light source driving unit (first light source driving unit) 33a, as shown in FIG. A laser light source driving unit (second light source driving unit) 33b is provided. The liquid crystal display element driving unit 32 drives the liquid crystal panel 1. The LED light source driving unit 33a drives the LED light source 7 (described later). The laser light source driving unit 33b drives a laser light source 8 (described later).

  As shown in FIG. 1, the liquid crystal display device 100 includes a liquid crystal panel 1, an optical sheet 2, an optical sheet 3, and a surface light source device 200 in order from the positive direction of the z axis to the negative direction. The components 1, 2, and 3 are plate-shaped. Further, the surface light-emitting light guide plate 4 constituting the surface light source device 200 has a plate shape. For this reason, each component 1, 2, 3, 4 is arrange | positioned at the laminated form. “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 adjacent sides of 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.

  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.

<Configuration of Surface Light Source Device 200>
The surface light source device 200 includes a surface light-emitting light guide plate 4, a laser light diffusion member 6, an LED light source 7, and a laser light source 8. Further, the surface light source device 200 can include the light reflecting sheet 5. In the surface light source device 200, a surface light-emitting light guide plate 4, a light reflection sheet 5, and a laser light diffusion member 6 are arranged in order from the positive direction of the z axis to the negative direction. Further, the surface light source device 200 includes an LED light source 7 on the −x axis side of the surface light emitting light guide plate 4. The LED light source 7 is a light source having, for example, a blue LED element and a phosphor. Further, the surface light source device 200 includes a laser light source 8 on the back side (−z axis side) of the surface light emitting light guide plate 4 and on the + x axis side of the laser light diffusion member 6. In FIG. 1, the surface light source device 200 includes a laser light source 8 on the back side (−z axis side) of the light reflecting sheet 5 and on the + x axis side of the laser light diffusion member 6. The laser light source 8 is, for example, a light source having a laser light emitting element that emits red laser light.

  The surface-emitting light guide plate 4 has a plate shape. The surface emitting light guide plate 4 has a light emitting surface 41a, a back surface 41b, a light incident surface 41c, and an end surface 41d. The 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 surface and the back surface of the plate-shaped surface-emitting light-guiding plate 4. That is, it is a plate-shaped side surface. The front surface and the back surface are surfaces parallel to the xy plane. The light incident from the light incident surface 41a is emitted from the light emitting surface 41a which is the surface.

  A micro optical element 42 is formed on the back surface 41 b of the surface emitting light guide plate 4. The light incident from the light incident surface 41a 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 light incident surface 41c.

  The light reflecting sheet 5 is disposed on the back surface 41 b side of the surface emitting light guide plate 4. The light reflecting sheet 5 is disposed on the surface side of the light reflecting sheet 5. 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 light reflecting sheet 5 reflects the light emitted from the back surface 41b side toward the 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 diffusing member 6 has a function of guiding the laser light L8 emitted from the laser light source 8 to the light incident surface 41c. The laser light diffusion member 6 has a light incident surface 61a, a light guide part 61d, and a reflection part 61e. The reflection part 61e has the light-diffusion part 62 and the light-projection surface 61b. Moreover, the reflection part 61e can have the inclined surface 61c.

  The light guide 61d has a plate shape. The light incident surface 61a is formed on one end surface having a plate shape. The light guide unit 61d is arranged to be inclined with respect to the xy plane so as to rotate clockwise as viewed from the −y axis direction. That is, the light guide portion 61 d is disposed so as to be inclined so that the light incident surface 61 a is separated from the surface light-emitting light guide plate 4. The light incident surface 61a is formed at the end portion in the + x-axis direction of the light guide portion 61d. The light diffusing unit 62 is disposed on the −x axis direction side of the light guide unit 61d. The light that travels in the −x-axis direction in the light guide portion 61 d reaches the light diffusion portion 62. The light reflected by the diffuse reflection surface 62a of the light diffusion portion 62 reaches the light exit surface 61b. In the following description, “reflecting on the diffuse reflection surface 62a of the light diffusion portion 62” is referred to as “reflecting on the light diffusion portion 62”. The light guide part 61d is inclined so that the light traveling through the light guide part 61d is reflected by the light diffusion part 62 and emitted from the light exit surface 61b.

  The “diffuse reflection surface” is a reflection surface formed on the surface of ink or the like when, for example, ink that reflects light is used for the light diffusion portion 62. Further, for example, the light diffusing portion 62 is formed of a layer (light transmissive layer) that does not diffuse light and transmits the light as it is, and a reflective film. After the light is transmitted through the light transmissive layer, it is reflected by the reflective film, When the light passes through the light transmission layer again and enters the reflection portion 61e of the laser light diffusing member 6, it is the reflection surface of the reflection film. In addition, for example, the light diffusing unit 62 is formed of a light diffusing layer (light diffusing layer) and a reflecting film, and after the light has passed through the light diffusing layer, the light is reflected by the reflecting film, and again the light diffusing layer. Is the light emission surface (surface on the reflection portion 61e side) of the light diffusion layer when the light is transmitted through and enters the reflection portion 61e of the laser light diffusion member 6. That is, it is a surface on which diffused light is formed when entering from the light diffusion part 62 to the reflection part 61e of the laser light diffusion member 6.

  The light diffusing unit 62 is a plane parallel to the yz plane. The light exit surface 61b is also a surface parallel to the yz plane. The light emission surface 61 b is disposed to face the light diffusion portion 62. Further, the light emitting surface 61 b is disposed so as to face the light incident surface 41 c of the surface emitting light guide plate 4. The length of the light emitting surface 61b in the z-axis direction is set to be equal to or shorter than the length of the light incident surface 41c in the z-axis direction. This is because the light emitted from the light emitting surface 61b efficiently enters the light incident surface 41c.

  The slope 61c is a surface that connects the light diffusion portion 62 and the light emitting surface 61b. The inclined surface 61c is inclined with respect to the xy plane so as to rotate counterclockwise when viewed from the -y axis direction. That is, the inclined surface 61c is arranged so that the optical path of light spreads in the + x axis direction. This is because the light diffused and reflected by the light diffusing unit 62 is totally reflected by the inclined surface 61c and efficiently guided to the light incident surface 41c. “Diffuse reflection” means to diffuse and reflect.

  The laser light source 8 is disposed to face the light incident surface 61a. The laser light L8 travels in the light guide portion 61d from the back surface 41b side of the surface emitting light guide plate 4 and reaches the light diffusion portion 62. The laser beam L8 is incident on the light diffusion unit 62 from a direction inclined in the −z axis direction with respect to the x axis. The laser beam L8 is reflected by the light diffusion unit 62 and travels in the + x axis direction. The laser beam L8 is diffused by the light diffusion unit 62. For this reason, the laser beam L8 reflected by the light diffusing unit 62 has an angular intensity distribution of a Lambert distribution with a full width at half maximum of 120 degrees on a plane parallel to the xy plane and a plane parallel to the zx plane. . The “angular intensity distribution” represents the intensity of light with respect to the traveling direction of light as a distribution. The traveling direction of light is represented by an angle. The “divergence angle” is a light spread angle. The laser beam L8 having a Lambertian distribution is incident on the light incident surface 41c. The “Lambert distribution” is a light distribution when completely diffused. That is, the distribution is such that the luminance of the light emitting surface is constant regardless of the viewing direction.

  The light emitting surface 61b is disposed to face the light incident surface 41c. A slope 61c is formed between the light diffusion portion 62 and the light exit surface 61b. The slope 61c is inclined according to the divergence angle of the laser light L8 having a Lambertian distribution.

<Comparison between LED light source 7 and laser light source 8>
More specifically, the LED light source 7 employs a blue-green LED in which a package including a single-color LED element that emits blue light is filled with a green phosphor that absorbs the blue light and emits green light. Light source. A blue-green LED is a simple and small-sized LED that can be applied to a display, and has lower power consumption and higher output than a single-color LED that emits green light or a laser that emits green light.

  For this reason, by combining the LED light source 7 having a blue LED element and a green phosphor and the laser light source 8 that emits red laser light, it has a wider color reproduction range and lower power consumption than before. A liquid crystal display device can be obtained. Note that the LED light source 7 may include, for example, a blue LED element that emits blue light and a green LED element. However, when this LED (blue LED element and green LED element) is adopted as the LED light source 7, a power saving effect is obtained as compared with the case where a blue-green LED (blue LED element and green phosphor) is adopted as the LED light source 7. Inferior.

  In general, humans are highly sensitive to red color differences. For this reason, the difference in wavelength bandwidth in red is perceived as a significant difference by human vision than the difference in wavelength bandwidth of other colors. Here, “difference in wavelength bandwidth” refers to a difference in color purity. A white LED used as a light source in a conventional liquid crystal display device has a small amount of energy of a red spectrum particularly in a band from 600 nm to 700 nm. That is, when a color filter with a narrow wavelength bandwidth is used to increase the color purity in the wavelength range from 630 nm to 640 nm, which is preferable as pure red, the amount of transmitted light is reduced, the light use efficiency is lowered, and the luminance is lowered. .

  On the other hand, the laser light emitting element has a narrower wavelength bandwidth than the white LED and can obtain light with high color purity. In addition, by using a laser as the light source, it is possible to suppress loss of light amount in the color filter and increase the light utilization efficiency.

  The liquid crystal display device 100 and the surface light source device 200 according to the first embodiment cause red light to be emitted by the laser light source 8 having high monochromaticity among the three primary colors of light. As a result, the effect of reducing the power consumption and improving the color purity is significantly improved as compared with the case of emitting light of other colors with a laser light source.

  In a liquid crystal display device using a conventional white LED as a light source, the wavelength bandwidth of red light emitted from the white LED is wider than the wavelength bandwidth of red light by the laser light emitting element. Therefore, in the conventional liquid crystal display device, a part of red light is transmitted through the green filter, so that the green color purity is also lowered. The spectrum of light transmitted through the green filter is adjacent to the spectrum of red light. In the liquid crystal display device 100 and the surface light source device 200 according to the first embodiment, the red color purity is increased by using the red laser light source 8. Moreover, since the red light quantity which permeate | transmits a green filter is reduced by using the red laser light source 8, green color purity improves.

  Here, the LED light source 7 has been described as an LED light source that emits blue-green light, and the laser light source 8 has been described as a laser light source that emits red light. However, the configuration of the present invention is not limited to this. For example, the LED light source 7 can be composed of an LED element that emits green light, and the laser light source 9 can be composed of a laser light emitting element that emits red light and a laser light emitting element that emits blue light. Further, for example, the LED light source 7 can be constituted by an LED element that emits red light and an LED element that emits green light, and the laser light source 8 can be constituted by a laser light emitting element that emits blue light.

  In addition, when using a red laser light emitting element for the laser light source 8, compared with the case where a blue laser light emitting element is used, in the reduction of power consumption and the improvement of a color purity, the remarkable difference with the conventional liquid crystal display device. Can be shown.

  An LED element and a laser light emitting element are light sources having different characteristics. When these light sources are used together in a surface light source device, it is necessary to take into account the difference in the angular intensity distribution and the light emission efficiency of the light emitted from each light source. As will be described later, the angular intensity distribution of emitted light is greatly different between the LED element and the laser light emitting element.

  When light sources that emit light having different angular intensity distributions are used, a difference occurs in the spatial intensity distribution of light for each color emitted from the surface light-emitting light guide plate. For this reason, color irregularities appear on the display surface 1a of the liquid crystal display element. That is, the light intensity unevenness of each color appears as color unevenness when the light of each color is mixed to generate white. The light intensity unevenness is also called luminance unevenness.

  In a side-light type surface light source device using a surface-emitting light guide plate, in order to prevent color unevenness by using together light sources that emit light having different angular intensity distributions, the light emitted from the respective light sources It is necessary to shape the light so as to have the same angular intensity distribution before reaching the light incident surface of the light plate.

  In the first embodiment, the angle intensity distribution of the light emitted from the LED light source 7 and the angle intensity distribution of the light emitted from the laser light source 8 are equivalent on the light incident surface 41 c of the surface light-emitting light guide plate 4. Have means.

<LED light source 7>
First, the LED light source 7 will be described.
The LED light source 7 has a plurality of LED elements 71 one-dimensionally arranged in a line in the y-axis direction. FIG. 2 is a perspective view showing a part of the surface light source device 200. FIG. 3 is a configuration diagram of the surface light source device 200 as viewed from the + z-axis direction. The LED light source 7 shown in FIGS. 2 and 3 has three LED elements 71. As shown in FIGS. 2 and 3, the light emitting portion of the LED light source 7 is disposed to face the light incident surface 41 a of the surface light emitting light guide plate 4. The light emitting part of the LED light source 7 is a surface that emits the LED light L7 of each LED element. The plurality of LED elements are arranged along one end surface which is the light incident surface 41a. That is, the plurality of LED elements are arranged to face the light incident surface 41a.

  The LED light source 7 emits a blue-green LED beam L7. This blue-green light has peaks at, for example, 450 nm and 530 nm. The blue-green light has a continuous spectrum in the band from 420 nm to 580 nm. Further, the LED light source 7 has an angular intensity distribution of a Lambertian distribution with a full width at half maximum of 120 degrees on a plane parallel to the xy plane and a plane parallel to the zx plane. Here, “full width at half maximum” refers to an angle (full angle) in a direction in which the light intensity reaches 50% of the peak with respect to the direction in which the light intensity peaks.

<Laser light source 8>
Next, the laser light source 8 will be described.
The laser light source 8 is a laser light emitting element that emits a red laser beam L8. As shown in FIG. 2, the laser light source 8 has one laser light emitting element. In this case, the laser light source 8 is a laser light emitting element. When the laser light source 8 has a plurality of laser light emitting elements, the plurality of laser light emitting elements are collectively referred to as a laser light source 8.

  The red laser beam L8 is, for example, light having a light intensity peak at a wavelength of 640 nm. The wavelength width of the laser beam L8 is 1 nm in full width at half maximum. That is, the spectral width of the laser beam L8 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.

  The divergence angle of the laser beam L8 is 40 degrees in full width at half maximum in the fast axis direction (the direction in which the divergence angle is large). The divergence angle of the laser beam L8 is 10 degrees in full width at half maximum in the slow axis direction (direction in which the divergence angle is small). Here, the “fast axis direction” refers to a direction in which the divergence angle of the laser beam L8 is large. The “slow axis direction” refers to a direction in which the divergence angle of the laser beam L8 is small. The fast axis direction is a direction perpendicular to the slow axis direction. The “full width at half maximum” refers to a width up to an angle (full angle) in a direction in which the light intensity reaches 50% of the peak with respect to the direction in which the light intensity reaches a peak.

  The laser light source 8 in the surface light source device 200 is arranged so that the fast axis direction is parallel to the width direction (y-axis direction) of the laser diffusion member 6. The laser light source 8 is disposed so that the fast axis direction of the laser light emitting element is parallel to the y-axis direction. That is, the laser light source 8 is disposed so that the fast axis direction of the laser light emitting element is parallel to the direction of the long side of the light incident surface 61a having a rectangular shape.

  The laser light source 8 is arranged so that the slow axis direction is parallel to the height direction (z-axis direction) of the laser diffusion member 6. The laser light source 8 is arranged so that the slow axis direction of the laser light emitting element is parallel to the thickness direction (z-axis direction) of the laser light diffusion member 6. That is, the laser light source 8 is arranged so that the slow axis direction of the laser light emitting element is parallel to the direction of the short side of the light incident surface 61a having a rectangular shape.

  Further, the light emitting portion of the laser light source 8 is disposed so as to face a light incident surface 61 a (described later) of the laser diffusing member 6. The light emitting part of the laser light source 8 is a surface that emits a laser beam L8 of each laser light emitting element.

<Laser light diffusion member 6>
Next, the laser light diffusing member 6 will be described in detail.
The laser light diffusing member 6 is disposed on the back surface 41 b side of the surface emitting light guide plate 4. When the surface light source device 200 includes the light reflection sheet 5, the laser light diffusion member 6 is disposed on the back surface side (−z-axis direction side) of the light reflection sheet 5. That is, the light reflecting sheet 5 is disposed between the surface light emitting light guide plate 4 and the laser light diffusing member 6.

  The laser light diffusing member 6 is made of a transparent material. For example, acrylic resin (PMMA) or the like is used as the material of the laser light diffusion member 6. The light diffusing portion 62 of the laser light diffusing member 6 is a surface parallel to the yz plane of FIG. The light diffusing unit 62 is disposed to face a light incident surface 41c (described later) of the surface light-emitting light guide plate 4. The light emitting surface 61b of the laser light diffusing member 6 is a surface parallel to the yz plane of FIG. The light emitting surface 61b is disposed to face a light incident surface 41c (described later) of the surface light-emitting light guide plate 4.

  The light guide portion 61d is disposed so as to be inclined with respect to the xy plane so that the light incident surface 61a is disposed in the −z-axis direction with respect to the reflecting portion 61e.

  As shown in FIG. 2, the laser light source 8 has one laser element. Therefore, the plate-shaped light guide part 61d has a trapezoidal shape. The upper base having a short trapezoidal shape forms one side of the light incident surface 61a. The shape of the light guide portion 61d has a trapezoidal shape in which the side in the y-axis direction of the light incident surface 61a is a short side of the bottom. The long bottom of the trapezoidal shape forms one side of the reflecting portion 61e. As shown in FIG. 2, the light guide portion 61 d has a long y-axis direction length from the light incident surface 61 a toward the light diffusion portion 62. That is, as the laser beam L8 spreads due to its divergence angle, the width of the light guide portion 61d in the y-axis direction increases.

  As described above, the angular intensity distribution in the fast axis direction of the laser beam L8 is larger than the angular intensity distribution in the slow axis direction. That is, the laser light source 8 is arranged so that the fast axis direction of the laser light emitting element is parallel to the y-axis direction. As a result, the laser beam L8 can travel in the laser light diffusing member 6 while spreading in the y-axis direction.

  Further, the laser light source 8 is arranged so that the slow axis direction of the laser light emitting element is parallel to the thickness direction of the laser light diffusing member 6. The thickness direction of the laser light diffusion member 6 is the direction of the short side of the light incident surface 61a having a rectangular shape. Thereby, the laser beam L8 can go straight through the laser light diffusion member 6 while maintaining the directivity. And the fall of the reflection efficiency in the light-diffusion part 62 of the laser-light-diffusion member 6 is suppressed, and the laser beam L8 can be guided efficiently.

As shown in FIG. 1, the reflection portion 61 e is disposed at the end portion in the −x-axis direction of the light guide portion 61 d. That is, the light diffusing unit 62 and the light emitting surface 61b are disposed at the end portion in the −x-axis direction of the light guide unit 61d. As shown in FIGS. 2 and 3, the reflection part 61 e is divided and arranged in the y-axis direction. The reflection part 61e has a plurality of reflection parts 61e ₁ , 61e ₂ , 61e ₃ cut along a plane parallel to the zx plane.

In FIG. 2, the reflective portion 61e ₁ , the reflective portion 61e ₂ and the reflective portion 61e ₃ are arranged in this order from the + y axis direction to the −y axis direction. Of the + y-axis direction reflecting portion 61e _1, LED elements 71a are arranged. In the y-axis direction, between the reflective portion 61e ₁ and the reflecting portion 61e _2, LED elements 71b are arranged. Then, in the y-axis direction, between the reflective portion 61e ₂ and the reflecting portion 61e _3, LED element 71c is disposed.

In addition, the length from the end of the long side direction (y-axis direction) of the reflection part 61e can be made equal to the length of the light incident surface 41c of the surface light-emitting light guide plate 4 in the y-axis direction. In Figure 2, a length from the surface of the + y-direction side of the reflecting portion 61e ₁ to a surface of the -y direction side of the reflecting portion 61e _3. In this case, the LED element 71 is disposed only between the adjacent reflecting portions 61e. That is, as the LED element 71a of FIG. 2, can not be arranged in the + y direction side of the reflecting portion 61e _1.

Alternatively, the length from the end in the long side direction (y-axis direction) of the reflecting portion 61 e can be made shorter than the length in the y-axis direction of the light incident surface 41 c of the surface light-emitting light-guiding plate 4. In this case, the LED element 71 can be disposed outside the reflecting portion 61e disposed at the end in the y-axis direction. That is, it is possible arrangement, in the + y direction side of the reflecting portion 61e ₁ as LED elements 71a of FIG.

  The light diffusion part 62 is formed in the reflection part 61e. As shown in FIG. 2, the light diffusing unit 62 is formed on the end side facing the light incident surface 61a of the light guide unit 61d. The light diffusion part 62 is formed in parallel to the yz plane. The light diffusing unit 62 is disposed at a position facing the light incident surface 41 c of the surface light-emitting light guide plate 4.

  Moreover, the light diffusion part 62 is discontinuously arranged in the y-axis direction. As described above, the LED light source 7 has a plurality of LED elements 71. The LED elements 71 are arranged side by side in the y-axis direction. The light diffusion parts 62 and the LED elements 71 of the LED light source 7 are alternately arranged in the y-axis direction. That is, the light diffusion part 62 is disposed between the LED elements.

  And as shown in FIG. 3, the optical distance from the light-diffusion part 62 to the light-incidence surface 41c is equal to the optical distance from the light emission part of the LED light source 7 to the light-incidence surface 41c. The optical distance is the distance A. Further, the direction in which the light from the light diffusing unit 62 is reflected and the direction in which the light from the LED light source 7 is emitted are the same direction.

  As described above, the LED element 71 has a very wide angular intensity distribution. On the other hand, the laser light emitting element has a very narrow angular intensity distribution. When these light sources having different divergence angles are incident on the same surface-emitting light guide plate 4, how light travels in the surface-emitting light guide plate 4 varies depending on the divergence angle. For this reason, the surface intensity distributions of the laser beam L8 and the LED beam L7 on the light emitting surface 41a of the surface emitting light guide plate 4 are different.

  This difference in the surface intensity distribution becomes uneven color and is visually recognized by the observer. Therefore, when the surface light-emitting device is configured with the light beams L7 and L8 of the light sources 7 and 8 having different angular intensity distributions by the single surface light-emitting light guide plate 4, the light beams L7 and L8 of the light sources 7 and 8 are surface-emitting. Before entering the light guide plate 4, it is necessary to make the angular intensity distributions of the light beams L7 and L8 equal.

  As described above, the angular intensity distribution of the LED element 71 is a Lambertian distribution. In order to make the divergence angle of the laser light emitting element equal to the divergence angle of the LED element 71, the laser light L8 needs to be completely diffused light. In the first embodiment, the light diffusing unit 62 is provided in order to widen the divergence angle of the laser beam L8 to the divergence angle of the completely diffused light. The light diffusing unit 62 is a surface on which a white coating is applied so as to perform complete diffuse reflection. The white coating is, for example, a white coating such as barium sulfate used for coating the inside of the integrating sphere.

  The laser beam L8 completely diffused and reflected by the light diffusing unit 62 becomes light having a divergence angle equivalent to that of the LED beam L7, and proceeds toward the light incident surface 41c of the surface light-emitting light guide plate 4. Further, as described above, the light emitting surface 72 of the LED light source 7 and the diffuse reflection surface 62a of the light diffusing portion 62 have the same optical distance A to the light incident surface 41c of the surface light emitting light guide plate 4. That is, after the light having the same divergence angle propagates by the same optical distance A, it reaches the light incident surface 41 c of the surface light-emitting light guide plate 4. Further, the direction in which the light from the light diffusing unit 62 is reflected and the direction in which the light from the LED light source 7 is emitted are the same direction. Therefore, both the LED light L7 and the laser light L8 travel in the same state in the surface emitting light guide plate 4.

  In FIG. 3, the light emitting surface 72 of the LED light source 7 is shown as the light emitting surface of the package of the LED element 71. This is because the light emitting portion of the package of the LED element 71 is normally processed to diffuse light. However, when the light emitting part of the package of the LED element 71 is transparent, the light emitting surface 72 can be the light emitting surface of the LED element 71 itself. For example, when adopting a configuration in which the LED light L7 is guided to the vicinity of the light diffusion unit 62 using an optical fiber or the like, an emission surface of the optical fiber or the like that guides the LED light L7 is set as the light emitting surface 72. Can do.

<Surface emitting light guide plate 4>
Next, the surface emitting light guide plate 4 will be described in detail.
As described above, the surface-emitting light guide plate 4 has the light emitting surface 41a, the back surface 41b, the light incident surface 41c, and the end surface 41d. The light emission surface 41a is a 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 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 between the optical sheet 3 and the light reflecting sheet 5. “Lamination” is the stacking of layers. That is, the sheet-like optical sheet 3 and the light reflecting sheet 5 and the plate-like surface light-emitting light guide plate 4 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 light emission surface 41a is arranged in parallel to the display surface 1a. Further, the back surface 41b is arranged in parallel to the display surface 1a.

  The 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 light incident surface 41c is an end surface on the −x side. The end surface 41d is an end surface on the + x side. The end surface 41d is disposed to face the light incident surface 41c.

  The LED light beam L7 emitted from the LED light source 9 is incident from the light incident surface 41c. Further, laser light L8 emitted from the light emitting surface 61b of the laser light diffusing member 6 is also incident from the light incident surface 41c.

  A micro optical element 42 is 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 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 light emitting 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 the micro optical element 42 has a function of reflecting the LED light L7 and the laser light L8 serving as the illumination light L44 in the + z-axis direction and emitting the light toward the back surface 1b of the liquid crystal panel 1. good. 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 LED light beam L7 and the laser light beam L8 after entering from the light incident surface 41c. The micro optical elements 42 are arranged from coarse to dense from the light incident surface 41a toward the opposing end surface 41d. Thereby, the amount of light emitted from the light incident surface 41c is uniform in the x-axis direction, and planar light with high uniformity can be formed.

<Light reflecting sheet 5>
Next, the light reflection sheet 5 will be described.
The light reflecting sheet 5 is disposed to face the back surface 41 b of the surface light emitting light guide plate 4. The light reflecting sheet 5 is disposed in parallel with the display surface 1 a of the liquid crystal panel 1. The light reflecting sheet 5 is formed of, for example, a sheet that reflects light based on a resin such as polyethylene terephthalate. Further, the light reflecting sheet 5 may be a sheet that reflects light obtained by depositing metal on the surface of the substrate. As described above, the light reflecting sheet 5 reflects the light emitted from the back surface 41b side toward the 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 light reflecting sheet 5 may have a plate shape as long as it has a function of reflecting light emitted from the back surface 41b side toward the light emitting surface 41a side (+ z-axis direction).

<Behavior of rays L7 and L8>
Next, the behavior of the LED light L7 and the laser light L8 will be described.
The laser light source 8 emits laser light L8 in the −x axis direction. Laser light L8 emitted from the laser light source 8 enters the laser light diffusion member 6 from the light incident surface 61a. The incident laser beam L8 travels while being totally reflected in the light guide portion 61d. The laser beam L8 travels in the −x axis direction within the light guide portion 61d. The laser beam L8 enters the laser light diffusing member 6 from the light incident surface 61a and travels toward the light diffusing portion 62. That is, the laser beam L8 travels toward the light diffusion unit 62 in the light guide unit 61d.

  The laser beam L8 reaches the light diffusion unit 62 from the −z-axis direction in the + x-axis direction. That is, the laser beam L8 reaches the light diffusion portion 62 at an inclined angle. The laser beam L8 that has reached the light diffusion portion 62 is diffusely reflected and becomes light having a wide divergence angle. The laser beam L8 that has become a light having a wide divergence angle is emitted from the light emitting surface 61b of the laser light diffusing member 6. The laser beam L8 emitted from the light emitting surface 61b of the laser light diffusing member 6 travels toward the light incident surface 41c of the surface emitting light guide plate 4.

  The LED light source 7 emits an LED light beam L7 in the + x axis direction. That is, the LED light source 7 emits the LED light beam L7 toward the light incident surface 41c. The LED light beam L7 emitted from the LED light source 7 travels toward the light incident surface 41c of the surface emitting light guide plate 4. The LED light beam L7 travels toward the light incident surface 41c without passing through an optical element or the like.

  The LED light source 7 is disposed at a position facing the light incident surface 41c. Further, the light diffusion part 62 is disposed at a position facing the light incident surface 41c. The LED light sources 7 are arranged side by side in the y-axis direction. Further, the light diffusion parts 62 are arranged side by side in the y-axis direction. The LED light sources 7 and the light diffusion parts 62 of the laser light diffusion member 6 are alternately arranged in the y-axis direction. That is, the LED light beam L7 emitted from the LED light source 7 and the laser light beam L8 after being diffusely reflected by the light diffusion portion 62 of the laser light diffusion member 6 are alternately positioned in the y-axis direction.

  The LED light beam L7 has a Lambertian angular intensity distribution. Further, the laser beam L8 after being diffusely reflected by the light diffusing unit 62 also has an angular intensity distribution of Lambertian distribution. For this reason, the LED light beam L7 and the laser light beam L8 spatially overlap with adjacent light beams before reaching the light incident surface 41c. That is, the LED light beam L7 and the laser light beam L8 overlap spatially before reaching the light incident surface 41c. The “adjacent light beams” are the LED light beam L7 emitted from one LED element 71 included in the LED light source 7 and the laser light beam L8 diffusely reflected from the light diffusion part 62 located next to the LED element 71. . Then, the spatially overlapping LED beam L7 and laser beam L8 become a white beam L9 and travel in the surface light-emitting light guide plate 4.

  Many of the light rays L9 incident from the light incident surface 41c of the surface light-emitting light guide plate 4 travel in the + x-axis direction while being totally reflected at the interface between the surface light-emitting light guide plate 4 and the air layer. The “interface between the surface emitting light guide plate 4 and the air layer” refers to a surface on the light emitting surface 41a side and a surface on the back surface 41b side. Further, part of the light beam L9 enters the micro optical element 42 in the process of repeating total reflection. The light beam L9 incident on the micro optical element 42 changes its traveling direction when reflected by the curved surface of the micro optical element 42. The light beam L9 whose traveling direction has changed includes a light beam that does 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 from the light emitting surface 41a of the surface light-emitting light guide plate 4 toward the back surface 1b of the liquid crystal panel 1 as illumination light L44. The illumination light L44 is emitted in the + z-axis direction from the 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, among the light rays L <b> 9 that travel inside the surface 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 emitting light guide plate 4. The light emitted from the back surface 41b is reflected by the light reflecting sheet 5, and becomes light traveling in the + z-axis direction. That is, the light beam L9 reflected by the light reflecting sheet 5 becomes the illumination light L44. Then, the light beam L <b> 9 reflected by the light reflecting sheet 5 illuminates the back surface 1 b of the liquid crystal panel 1.

  The LED light source 7 is a light source including an LED element 71 having a relatively wide divergence angle. On the other hand, the laser light source 8 is a light source including a laser light emitting element having a relatively narrow divergence angle. That is, the divergence angle of the laser light emitting element is narrower than the divergence angle of the LED element 71. For this reason, in order to generate uniform planar light, it is necessary to widen the divergence angle of the laser light emitting element. It is necessary to make the divergence angle of the laser light emitting element equal to the divergence angle of the LED element 71.

  As a method of expanding the divergence angle of the laser beam L8, for example, a method of refracting light using a structure such as a prism or a cylindrical can be considered. Further, a method of refracting light using a diffusion sheet containing minute beads can be considered. However, when refraction at the time of transmitting such light is used, it is difficult to bend the light greatly with a simple configuration. That is, it is difficult to make the divergence angle of the highly directional laser beam L8 close to the divergence angle of the LED beam L7 having a Lambertian distribution in a configuration that transmits light.

  In order to expand the divergence angle of the laser beam L8 to the very wide divergence angle of the LED beam L7 emitted from the LED element 71 using refraction when transmitting light, a complicated configuration is required. In the first embodiment, diffuse reflection is used as a simple configuration that extends a very narrow divergence angle of the laser light emitting element to a very wide divergence angle of the LED element 71. Reflection can greatly bend light that has traveled compared to refraction. In the first embodiment, the light diffusion portion 62 is provided with a diffuse reflection surface (diffuse reflection surface 62 a). Then, by diffusing and reflecting the laser beam L8, the divergence angle of the laser beam L8 can be easily expanded to be equal to the divergence angle of the LED element 71.

<Control of the liquid crystal display device 100>
Here, 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. Moreover, the control part 31 produces | generates the LED light source control signal 36a, and sends it to the LED light source drive part 33a. The control unit 31 also generates a laser light source control signal 36b and sends it to the laser light source driving unit 33b.

  The LED light source control signal 36 a 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. The laser light source control signal 36b 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.

  Upon receiving the liquid crystal display element control signal 35, the liquid crystal display element driving unit 32 drives the liquid crystal display element 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 the position. 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 LED light source control signal 36a, the LED light source driving unit 33a drives the LED light source 7 based on the received signal. Similarly, upon receiving the laser light source control signal 36b, the laser light source driving unit 33b drives the laser light source 8 based on the received signal.

  The control unit 31 individually controls the LED light source driving unit 33a and the laser light source driving unit 33b. In this case, the control unit 31 can easily adjust the ratio between the amount of blue-green light emitted from the LED light source 7 and the amount of red light emitted from the laser light source 8. That is, the control unit 31 adjusts the light emission amount of the LED light source 7 and the light emission amount of the laser light source 8 based on the ratio of the light intensity of each color necessary for displaying the video signal 34. Thereby, the liquid crystal display device 100 and the surface light source device 200 can reduce power consumption.

  In the first embodiment, the laser light source 8 is arranged so that the fast axis direction of the laser light emitting element is parallel to the direction of the long side of the light incident surface 61a having a rectangular shape. However, the arrangement direction of the laser light source 8 is not limited to this. Depending on the size (dimension in the y-axis direction and the dimension in the x-axis direction) and the thickness (dimension in the z-axis direction) of the laser light diffusing member 6, the laser light diffusing member 6 can be arranged in an optimal and efficient direction. However, normally, the light guide 61d of the laser light diffusing member 6 has a thin plate shape. For this reason, the light use efficiency can be improved by arranging the fast axis direction and the slow axis direction of the laser light emitting element as described in the first embodiment.

  Further, the laser light emitting element constituting the laser light source 8 has been described as one. However, the first embodiment is not limited to this. A plurality of laser light emitting elements may be arranged side by side in the y-axis direction. That is, a plurality of laser light emitting elements may be arranged side by side in the long side direction of the light incident surface 61a having a rectangular shape.

  In this case, for example, the same number of laser light diffusion members 6 as the laser light emitting elements can be arranged. That is, a plurality of laser light emitting elements and one laser light diffusion member 6 can be arranged as a set.

A plurality of laser light emitting elements may be arranged side by side on the light incident surface 61 a of one laser light diffusing member 6. In this case, the light guide 61d has a rectangular shape instead of a trapezoidal shape. Then, at a position corresponding to the y-axis direction of the position of the reflecting portion _{61e 1, 61e 2, 61e 3} , it is possible to arrange the laser light emitting element. With such an arrangement of the laser light emitting elements, the light use efficiency can be improved. In other words, it is possible to reach between the reflective portion _{61e 1, 61e 2, 61e 3} , to reduce the amount of laser beam L8 which is not incident into the reflective portion _{61e 1, 61e 2, 61e 3} .

  In the first embodiment, the example in which the three reflection portions 61e exist in one laser light diffusion member 6 has been described. That is, the example in which the three light emitting surfaces 61b exist in one laser light diffusion member 6 has been described. However, the present invention is not limited to the three light exit surfaces 61b (reflecting portions 61e). What is necessary is just the structure by which the light-projection surface 61b (reflective part 61e) of the laser-light-diffusion member 6 is arrange | positioned between the LED elements 71. FIG. That is, the number of light emitting surfaces 61 b (reflecting portions 61 e) of one laser light diffusing member 6 is optimally designed from the number of LED elements 71 arranged.

  Further, the number of the light emitting surfaces 61b (reflecting portions 61e) can be determined from the amount of the laser beam L8 emitted from one light emitting surface 61b. The amount (light intensity) of the laser beam L8 emitted from one light emitting surface 61b is an amount that becomes white when mixed with the amount (light intensity) of the LED beam L7 emitted from one LED light source 7. is there. Note that the laser light emitting element is more expensive than the LED element 71. For this reason, it is desirable to set the number of laser light emitting elements as small as possible.

  In the case of using a plurality of light sources as in the liquid crystal display device 100, in addition to luminance unevenness, suppression of color unevenness is also an important issue. In order to suppress the color unevenness, it is necessary to have the same divergence angle when each light enters the surface light-emitting light guide plate 4.

  The liquid crystal display device 100 according to the first embodiment uses a blue-green LED light source 7 and a red laser light source 8. That is, the liquid crystal display device 100 uses light sources of a plurality of colors. In addition, the angular intensity distribution between the LED light source 7 and the laser light source 8 is greatly different. The LED light beam L7 emitted from the LED light source 7 has a wide angular intensity distribution. The laser beam L8 emitted from the laser light source 8 has high directivity and a narrow angular intensity distribution.

  In the surface light source device 200 according to the first embodiment, the divergence angle of the laser light source 8 is greatly widened by using the light diffusion portion 62 of the laser light diffusion member 6 as diffuse reflection. Further, the diffuse reflection surface 62 a of the light diffusion portion 62 and the light emitting surface 72 of the LED light source 7 are arranged at the same optical distance A from the light incident surface 41 c of the surface light emitting light guide plate 4. Thereby, the light incident on the surface light-emitting light guide plate 4 becomes light having the same spread (divergence angle) for both the LED light beam L7 and the laser light beam L8. Therefore, it is possible to suppress color unevenness caused by a difference in divergence angles of light emitted from different light sources.

  As described above, the laser beam L8 becomes light having a divergence angle equivalent to that of the LED beam 7 and reaches the light incident surface 41c of the surface-emitting light guide plate 4. For this reason, the arrangement | positioning of the micro optical element 42 of the surface emitting light-guide plate 4 can employ | adopt the design generally used using the normal LED light source. That is, since the surface emitting light guide plate 4 for the LED light source can be employed, it is not necessary to employ a special surface emitting light guide plate 4.

  Further, the diffuse reflection surface 62 a of the light diffusion portion 62 and the light emitting surface 72 of the LED light source 7 are arranged at the same optical distance A from the light incident surface 41 c of the surface light emitting light guide plate 4. Thereby, for example, even when the surface light-emitting light guide plate 4 expands and contracts in the x-axis direction due to thermal expansion or moisture absorption, there is no change in the conditions when the LED light beam L7 and the laser light beam L8 enter the surface light-emitting light guide plate 4. . For this reason, generation | occurrence | production of color unevenness can be suppressed.

  The surface light source device 200 has a wider color reproduction range than a conventional surface light source device using a white LED light source. In addition, the surface light source device 200 can achieve brightness equivalent to that of a surface light source device using only a conventional LED light source with lower power consumption than a surface light source device using only a monochromatic LED light source or a laser light source. That is, the surface light source device 200 has a wide color reproduction range and can suppress power consumption.

  Moreover, the liquid crystal display device 100 can have a wider color reproduction range than the liquid crystal display device using only the conventional LED light source by including the surface light source device 200. In addition, the liquid crystal display device 100 can reduce power consumption.

  The surface light source device 200 includes a laser light source 8, an LED light source 7, a laser light diffusing member 6, and a surface light emitting light guide plate 4. The laser light source 8 has a laser light emitting element that emits a laser beam L8. The LED light source 7 includes a plurality of LED elements 71 that emit LED light L7. The laser light diffusing member 6 diffuses and reflects the laser beam L8 emitted from the laser light source 8 by the light diffusing unit 62, and widens the divergence angle of the laser beam L8 to the divergence angle equivalent to the LED beam L7. The surface light-emitting light guide plate 4 has a light incident surface 41c on which a light beam is incident. The laser light L8 and the LED light beam L7 are incident from the light incident surface 41c and converted into planar light. The optical distance A from the diffuse reflection surface 62a of the light diffusion portion 62 to the light incident surface 41a is equal to the optical distance A from the light emitting surface 72 of the LED element 71 to the light incident surface 41a.

  The traveling direction of the laser beam L8 diffusely reflected by the light diffusing unit 62 is the same as the traveling direction of the LED beam L7 emitted from the light emitting surface 72 of the LED element 71.

  The diffuse reflection surface 62a and the light emitting surface 72 are alternately arranged along the light incident surface 41c.

Embodiment 2. FIG.
A surface light source device 201 and a liquid crystal display device 101 according to a second embodiment for carrying out the present invention will be described with reference to FIGS. The second embodiment is different in that a laser light diffusion rod 9 is used instead of the laser light diffusion member 6 of the first embodiment. Further, the second embodiment differs from the first embodiment in the arrangement position of the laser light source 8 due to the use of the laser light diffusing rod 9. Except for these two points, 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. Constituent elements similar to those of the first embodiment are the liquid crystal panel 1, the optical sheets 2 and 3, the surface emitting light guide plate 4, the light reflecting sheet 5, the LED light source 7 and the laser light source 8. Further, although the names and symbols are different, the light diffusion unit 92 has the same light diffusion surface as the light diffusion unit 62. For this reason, the description of the light diffusing unit 62 described in the first embodiment is applied to the description of the light diffusing unit 92 of the second embodiment.

  FIG. 5 is a configuration diagram schematically showing an example of the configuration of the liquid crystal display device 101 (including the surface light source device 201) according to the second embodiment. FIG. 5 is a diagram viewed from the −y axis side. FIG. 6 is a configuration diagram of the surface light source device 201 according to Embodiment 2 as viewed from the display surface side (+ z axis side). In order to facilitate the explanation of the figure, the same xyz coordinates as in the first embodiment are used.

<Configuration of laser light diffusing rod 9 and behavior of light beams L7 and L8>
The configuration of the laser light diffusing rod 9 and the behavior of the light beams L7 and L8 will be described.
The laser light diffusing rod 9 is disposed between the light incident surface 41 a of the surface emitting light guide plate 4 and the LED light source 7. In FIG. 5, the laser light diffusing rod 9 is disposed on the −x axis direction side of the light incident surface 41 a of the surface emitting light guide plate 4. Further, the laser light diffusing rod 9 is disposed on the + x axis direction side of the LED light source 7 of the surface light-emitting light guide plate 4.

  The laser light diffusing rod 9 is a columnar part. A “column” is a columnar space figure having two planar figures as a bottom face. Surfaces other than the bottom of the column are called side surfaces. The distance between the two bottom surfaces of the column is called height.

  The laser light diffusing rod 9 is made of a transparent material. The laser light diffusion rod 9 is, for example, a prism having a cross section of 2 × 2 mm in the zx plane. The surface corresponding to the bottom surface of the laser light diffusing rod 9 is a surface parallel to the zx plane. The laser light diffusing rod 9 has a light incident surface 91a, a light emitting surface 91b, and a light diffusing portion 92. The light incident surface 91 a is provided on a surface corresponding to the bottom surface of the laser light diffusion rod 9. The light emitting surface 91 b and the light diffusing portion 92 are provided on the surface corresponding to the side surface of the laser light diffusing rod 9. The light incident surface 91a of the laser light diffusing rod 9 is a surface parallel to the zx plane. The light diffusion portion 92 of the laser light diffusion rod 9 is a surface parallel to the yz plane. The light emitting surface 91b of the laser light diffusing rod 9 is a surface parallel to the yz plane. The light emitting surface 91b is disposed to face the light incident surface 41c of the surface emitting light guide plate 4. The side surface 91c of the laser light diffusing rod 9 is a surface parallel to the yz plane. The side surface 91c is a surface facing the light emitting surface 91b. The side surface 91c is located on the −x axis direction side of the light emitting surface 91b. The light diffusion portion 92 is located on the −x axis direction side of the light exit surface 91b.

  As shown in FIG. 6, the light diffusion portion 92 of the laser light diffusion portion 9 is formed on a part of the side surface 91c. The light diffusing unit 92 is, for example, a portion provided with a white coating that diffuses and reflects light. The light diffusing unit 92 is disposed between the LED elements 71 constituting the LED light source 7. The LED element 71 is disposed to face the side surface 91c. The LED elements 71 are arranged side by side in the y-axis direction. The light diffusing unit 92 is provided between the LED elements 71 arranged side by side.

  The LED element 71 has a very wide angular intensity distribution. On the other hand, laser light emitting elements have a very narrow angular intensity distribution. When light emitted from light sources having different divergence angles enters the same surface emitting light guide plate 4, the angular intensity distribution of each light is made equal before each light enters the surface emitting light guide plate 4. There is a need to do.

  The angular intensity distribution of the LED element 71 is a Lambertian distribution. In order to make the divergence angle of the laser light emitting element equal to that of the LED element 71, the laser beam L8 needs to be Lambertian light. In the second embodiment, the light diffusing unit 92 is provided in order to change the divergence angle of the laser beam L8 to light having a Lambertian distribution. The light diffusing portion 92 is a portion where a white coating that diffuses and reflects is applied to the side surface 91c. The white coating is, for example, a white coating such as barium sulfate used for coating the inside of the integrating sphere.

  The laser light source 8 is disposed to face the light incident surface 91a of the laser light diffusing rod 9. The light incident surface 91 a is formed on the bottom surface of the laser light diffusing rod 9. In FIG. 6, the light incident surface 91a is formed on one bottom surface. However, the light incident surface 91a may be formed on two bottom surfaces.

  As shown in FIG. 6, the laser light source 8 emits a laser beam L8 in the + y-axis direction. Most of the laser beam L8 incident from the light incident surface 91a proceeds in the + y-axis direction while being totally reflected at the interface between the laser beam diffusion rod 9 and the air layer. The y-axis direction is the height direction of the laser light diffusing rod 9. The “interface between the laser light diffusing rod 9 and the air layer” refers to a side surface including the light emitting surface 91b and the side surface 91c.

  A part of the laser beam L8 enters the light diffusion portion 92 in the process of repeating total reflection. The laser beam L8 incident on the light diffusion portion 92 is diffused and reflected by the diffusion reflection surface 92a of the light diffusion portion 92 and emitted from the light emission surface 91b. The laser beam L8 emitted from the light emitting surface 91b travels in the + x axis direction. Then, the laser beam L8 emitted from the light emitting surface 91b travels toward the light incident surface 41c of the surface emitting light guide plate 4. In the following, “reflecting by the diffuse reflection surface 92a of the light diffusion portion 92” is referred to as “reflecting by the light diffusion portion 92”.

  The “diffuse reflection surface” is a reflection surface formed on the surface of ink or the like when, for example, ink that reflects light is used for the light diffusion portion 92. Further, for example, the light diffusing portion 92 is formed of a layer (light transmissive layer) that directly transmits light without diffusing (light transmissive layer) and a reflective film, and after the light passes through the light transmissive layer, is reflected by the reflective film, When the light passes through the light transmission layer again and enters the laser light diffusion rod 9, it is the reflection surface of the reflection film. In addition, for example, the light diffusing portion 92 is formed of a light diffusing layer (light diffusing layer) and a reflecting film, and after the light has passed through the light diffusing layer, the light is reflected by the reflecting film, and again the light diffusing layer. Is the light emitting surface of the light diffusing layer (the surface on the laser light diffusing rod 9 side). That is, it is a surface on which diffused light is formed when it enters the laser light diffusion rod 9 from the light diffusion portion 92.

  The light diffusing unit 92 is disposed on the side surface 91c. The width of the light diffusing unit 92 in the y-axis direction varies depending on the position in the y-axis direction. That is, the width of the light diffusing unit 92 in the y-axis direction increases as the distance from the light incident surface 91a increases. The width of the light diffusing unit 92 is designed so that the amount of light diffusely reflected by each light diffusing unit 92 is equal.

  In order to make the amount of light diffusely reflected by each light diffusing portion 92 equal, for example, the concentration of ink used for coating may be changed according to the position, instead of the width of the light diffusing portion 92. . That is, it is important that the light diffusing unit 92 is designed so that the amount of light diffusely reflected by the light diffusing unit 92 is equal.

  The laser light source 8 is arranged so that the fast axis direction is parallel to the x-axis direction. The laser light source 8 is arranged so that the slow axis direction is parallel to the z axis direction. This is because the light diffusing portion 92 is located on the side surface 91c in the -x-axis direction, so that the fast axis direction (the direction in which the divergence angle is large) of the laser light source 8 is the x-axis direction. That is, a large amount of light is incident on the light diffusion portion 92 and diffusely reflected, thereby improving the light utilization efficiency.

  However, the arrangement direction of the laser light source 8 in the second embodiment is not limited to this. Depending on the shape of the laser light diffusing rod 9, the fast axis or the slow axis can be arranged in an optimal direction with good light utilization efficiency. Here, the “shape” is the size of the laser light diffusing rod 9 in the y-axis direction, the x-axis direction, or the z-axis direction. However, since the laser light diffusing rod 9 is usually made of a thin column, the light utilization efficiency can be improved by arranging the fast axis or the slow axis as described above.

  The optical distance A between the diffuse reflection surface 92 a of the light diffusion portion 92 of the laser light diffusion rod 9 and the light emitting surface 72 of the LED light source 7 is equal to the light incident surface 41 c of the surface light emitting light guide plate 4. The direction in which the light from the light diffusing unit 92 is reflected and the direction in which the light from the LED light source 7 is emitted are the same direction. Therefore, after light having the same divergence angle travels by the same optical distance A, it reaches the light incident surface 41 c of the surface light-emitting light guide plate 4. For this reason, each of the light beams L7 and L8 travels similarly in the surface emitting light guide plate 4.

  As in the first embodiment, in FIG. 6, the light emitting surface 72 of the LED light source 7 is shown as the light emitting surface of the package of the LED element 71. This is because the light emitting portion of the package of the LED element 71 is normally processed to diffuse light. However, when the light emitting part of the package of the LED element 71 is transparent, the light emitting surface 72 can be the light emitting surface of the LED element 71 itself. For example, when adopting a configuration in which the LED light L7 is guided to the vicinity of the light diffusion portion 92 using an optical fiber or the like, an emission surface of the optical fiber or the like that guides the LED light L7 is set as the light emitting surface 72. Can do.

  Moreover, in FIG. 6, in order to provide a gap between the package of the LED element 71 and the side surface 91c, a concave portion is provided on the side surface 91c. This is because the LED element 71 is normally fixed to a component different from the laser light diffusion rod 9. When the LED element 71 package is disposed in contact with the side surface 91c, this recess is not necessary.

  In the second embodiment, the prismatic laser light diffusion rod 9 is shown. Further, the laser light source 8 was arranged so that the laser beam L8 was incident from the bottom surface on the -y axis side. By adopting such a configuration, even when different light sources of the LED light source 7 and the laser light source 8 are used, it is possible to realize the liquid crystal display device 101 that suppresses uneven color with a simple configuration.

  In the second embodiment, the size of the laser light diffusing rod 9 has been described as a prism having a cross section of 2 × 2 mm in the xz plane. However, the shape is not limited to this. The optimum size of the laser light diffusing rod 9 can be designed according to the design as the liquid crystal display device, the size of the LED light source 7, the size of the laser light source 8, or the utilization efficiency of the laser beam L8.

  However, the light beams (LED light beam L7 and laser light beam L8) emitted from the laser light diffusion rod 9 are incident on the surface light-emitting light guide plate 4. For this reason, the dimension of the light emitting surface 91 b of the laser light diffusing rod 9 in the z-axis direction is made equal to the thickness of the surface emitting light guide plate 4. Alternatively, the dimension of the light emitting surface 91 b of the laser light diffusing rod 9 in the z-axis direction is made thinner than the thickness of the surface emitting light guide plate 4. Thereby, light loss can be suppressed and light can be guided from the laser light diffusing rod 9 to the surface emitting light guide plate 4.

<Modification>
A modification of the laser light diffusing rod 9 will be described.
The laser light diffusing rod 9 may have a shape as shown in FIG. FIG. 7 is a configuration diagram schematically showing another configuration of the laser light diffusing rod. FIG. 8 is a configuration diagram schematically showing another configuration of the laser light diffusing rod. FIG. 7 is a view of the LED light source 7 and the laser light diffusing rod 97 viewed from the −x-axis direction side. FIG. 8 is a view of the LED light source 7 and the laser light diffusing rod 98 viewed from the −x-axis direction side.

First, the laser light diffusion rod 97 will be described.
The laser beam diffusion rod 97 in FIG. 7 has an L shape in which a light guide portion 93 and an inclined surface 91d are added to the laser beam diffusion rod 9. The laser light source 8 is disposed in the −z-axis direction of the light guide portion 93 of the laser light diffusion rod 97. The light incident surface 97 a is formed at the end of the light guide portion 93 in the −z-axis direction. The laser light source 8 is disposed to face the light incident surface 97a.

  The laser light source 8 emits a laser beam L8 toward the + z axis direction. The laser beam L8 emitted in the + z-axis direction enters the laser light diffusion rod 97 from the light incident surface 97a. The laser beam L8 incident on the laser beam diffusing rod 97 travels in the + z-axis direction inside the light guide unit 93. The laser beam L8 that has traveled in the + z-axis direction inside the light guide section 93 is reflected by the inclined surface 91d, and the traveling direction can be changed to the + y-axis direction. Some of the laser beams L8 that have traveled in the + y-axis direction are incident on the light diffusion portion 92. The light incident on the light diffusing unit 92 is diffusely reflected and proceeds in the + x-axis direction. The diffusely reflected laser beam L8 is emitted from the light emitting surface 91b. The laser beam L8 emitted from the light emitting surface 91b travels in the + x-axis direction and reaches the light incident surface 41c of the surface emitting light guide plate 4.

  The light guide portion 93 of the L-shaped laser beam diffusing rod 97 extends to the back side (−z-axis direction) of the surface light emitting device 201. By setting it as such a shape, the LED light source 7 and the laser light source 8 can be arrange | positioned separately. That is, by making it difficult for the heat generated by the LED light source 7 to be transmitted to the laser light source 8, the temperature of the laser light source 8 can be kept appropriate.

  The laser light-emitting element has a wavelength or a light emission amount that varies greatly according to a temperature change as compared with the LED element. Therefore, it is necessary to keep the temperature of the laser light emitting element at an appropriate temperature. However, when the LED element is disposed near the laser light emitting element, the temperature of the laser light emitting element also rises due to heat generated from the LED element. The laser light emitting element and the LED element are desirably arranged separately.

  By using the L-shaped laser light diffusion rod 97 as shown in FIG. 7, the laser light emitting element (laser light source 8) and the LED element 71 can be arranged apart from each other. And it becomes easy to control the temperature of a laser light emitting element (laser light source 8) to appropriate temperature. Further, the laser light diffusing rod 97 shown in FIG. 7 has a smaller number of light incident surfaces and light emitting surfaces than the configuration of a laser light diffusing rod 98 and a light guide rod 94 described later. Loss can be reduced. In the laser light diffusing rod 97, the laser light source 8 is arranged at a position away from the LED light source 7 as compared with the configuration of the laser light diffusing rod 9 shown in FIGS.

Next, the laser light diffusing rod 98 will be described.
The laser light diffusing rod 98 shown in FIG. 8 uses the light guide portion 93 of FIG. 7 as another component (light guide rod 94). The laser beam diffusion rod 98 shown in FIG. 8 has an inclined surface 91d. The inclined surface 91d is formed at the end of the laser light diffusing rod 98 in the -y axis direction. A light guide rod 94 is disposed in the −z-axis direction of the inclined surface 91d. The light guide rod 94 has a light incident surface 94a and a light exit surface 94b parallel to the xy plane. The light guide rod 94 has a columnar shape in which one bottom surface (−z-axis direction side) serves as a light incident surface 94a and the other bottom surface (+ z-axis direction side) serves as a light emitting surface 94b.

  The laser light source 8 is disposed to face the light incident surface 94a. The laser light source 8 emits a laser beam L8 in the + z axis direction. The laser beam L8 is incident on the light guide rod 94 from the light incident surface 94a. The light incident surface 94 a is located at the end of the light guide rod 94 on the −z axis direction side. The laser beam L8 travels in the + z-axis direction while totally reflecting the inside of the light guide rod 94. The laser beam L8 is emitted from the light emitting surface 94b. The light emitting surface 94b is located on the + z-axis direction side of the light guide rod 94.

  The laser beam L8 emitted from the light emitting surface 94b travels in the + z axis direction. The laser beam L8 emitted from the light emitting surface 94b is incident on the laser light diffusing rod 98 from the light incident surface 98a of the laser light diffusing rod 98. The laser beam L8 incident on the laser beam diffusing rod 98 is reflected by the inclined surface 91d, and the traveling direction is changed in the + y-axis direction. Some of the laser beams L8 that have traveled in the + y-axis direction are incident on the light diffusion portion 92. The laser beam L8 incident on the light diffusion portion 92 is diffusely reflected and proceeds in the + x-axis direction. The diffusely reflected laser beam L8 is emitted from the light emitting surface 91b, and the laser beam L8 emitted from the light emitting surface 91b travels in the + x-axis direction. The laser beam L8 emitted from the light emitting surface 91b enters the surface emitting light guide plate 4.

  Since the light incident surfaces of the laser light diffusing rods 97 and 98 are at positions different from the light incident surface 91a of the laser light diffusing rod 9, the description is given with different reference numerals 97a and 98a. On the other hand, the light exit surfaces of the laser light diffusing rods 97 and 98 are located at the same position as the light exit surface 91b of the laser light diffusing rod 9, and therefore are described as the same reference numeral 91b. In view of the productivity of the laser light diffusing rod 9, etc., as shown in FIG. 8, the light guide rod 94 may be a separate component.

  The configuration shown in FIG. 8 is effective when the inclined surface 91d is subjected to mirror processing or the like. On the slope 91d, a part of the laser beam L8 may pass through the slope 91d without satisfying the total reflection condition. In order to eliminate this transmitted light, it is conceivable to perform mirror processing on the inclined surface 91d. However, for example, when mirror processing is performed on the inclined surface 91d, part of the light hitting the inclined surface 91d may become light traveling in the -z-axis direction. At this time, in the L-shaped configuration of FIG. 7, the light traveling in the −z-axis direction travels directly through the light guide portion 93 in the −z-axis direction and returns to the laser light source 8. The light that returns to the laser light source 8 is called “return light”. This return light is light that is not used for illumination. That is, the light use efficiency is reduced. In addition, the return light causes the life of the laser light source to be shortened.

  Similarly, in the configuration illustrated in FIG. 8, the light is reflected by the mirror-processed inclined surface 91 d and proceeds in the −z-axis direction. However, part of the light traveling in the −z-axis direction is totally reflected by the surface of the inclined surface 91d located in the −z-axis direction. The “surface located in the −z-axis direction of the inclined surface 91d” is the light incident surface 98a or the same surface in the vicinity thereof. The totally reflected light travels in the y-axis direction through the laser light diffusing rod 9, and is then emitted from the light emitting surface 91b toward the surface light-emitting light guide plate 4. With the configuration shown in FIG. 8, it is possible to reduce the return light and suppress a decrease in light use efficiency.

  Although the configuration of the second embodiment is different from that of the first embodiment, the same effects as those of the first embodiment can be obtained.

  The laser light diffusing member (laser light diffusing rod) 9 has a columnar shape, the laser beam L8 is incident from a surface corresponding to the bottom surface of the columnar shape, and the light diffusing portion 92 corresponds to a side surface of the columnar shape. Formed on the surface.

  In each of the above-described embodiments, there are cases where terms such as “parallel” or “vertical” are used to indicate the positional relationship between components or the shape of the components. These represent that a range that takes into account manufacturing tolerances and assembly variations is included. For this reason, when the description showing the positional relationship between the parts or the shape of the part is included in the claims, it indicates that the range including a manufacturing tolerance or an assembly variation is taken into consideration.

  In addition, although embodiment of this invention was described as mentioned above, this invention is not limited to these embodiment.

DESCRIPTION OF SYMBOLS 1 Liquid crystal panel, 1a Display surface, 1b Back surface, 2 1st optical sheet, 3 2nd optical sheet, 4 surface light-emitting light-guide plate, 41a Light output surface, 41b Back surface, 41c Light incident surface, 41d Opposite surface, 42 Micro optics Element, 5 Light reflecting sheet, 6 Laser light diffusing member, 61a Light incident surface, 61b Light emitting surface, 61c Slope, 61d Light guide portion, 61e Reflecting portion, 62, 92 Light diffusing portion, 62a, 92a Diffusing reflecting surface, 7 LED light source, 71 LED element, 72 light emitting surface, 8 laser light source, 9 laser light diffusing rod, 91a light incident surface, 91b light emitting surface, 91c end surface, 91d slope, 93 light guide, 94 light guide rod, 100, 101 Liquid crystal display device, 200, 201 surface light source device, 31 control unit, 32 liquid crystal display element driving unit, 33 light Drive unit, 33a LED light source driving section, 33b a laser light source driving unit, 34 a video signal, 35 a liquid crystal display element control signals, 36a LED light source control signal, 36b laser light source control signal, L7 LED light L8 laser, L44 illumination light.

Claims (6)

A laser light source having a laser light emitting element for emitting a laser beam;
An LED light source having a plurality of LED elements emitting LED light;
A laser light diffusing member that diffuses and reflects the laser beam emitted from the laser light source at a light diffusing unit and expands the divergence angle of the laser beam to a divergence angle equivalent to the LED beam;
A surface emitting light guide plate having a light incident surface on which a light beam is incident, and converting the laser beam and the LED beam from the light incident surface into a planar light,
The surface light source device, wherein an optical distance from the diffuse reflection surface of the light diffusion portion to the light incident surface is equal to an optical distance from the light emitting surface of the LED element to the light incident surface.   2. The surface light source device according to claim 1, wherein a traveling direction of the laser beam diffusely reflected by the light diffusing unit is the same as a traveling direction of the LED beam emitted from a light emitting surface of the LED element.   The surface light source device according to claim 1, wherein the diffuse reflection surface and the light emitting surface are alternately disposed along the light incident surface. The laser light diffusing member has a columnar shape,
The laser beam is incident from a surface corresponding to the bottom surface of the columnar shape,
The surface light source device according to any one of claims 1 to 3, wherein the light diffusion portion is formed on a surface corresponding to the side surface of the columnar shape.   5. The surface light source device according to claim 4, wherein an area of the diffuse reflection surface is different depending on a distance from a position where the laser beam is incident on the laser light diffusion member. The surface light source device according to any one of claims 1 to 5,
A liquid crystal display device comprising a liquid crystal panel for forming image light.

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