JP2016184564A - Surface light source device and liquid crystal display unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device and a liquid crystal display unit capable of efficiently obtaining planar light with simple constitution according to the present invention.SOLUTION: A surface light source device 100 according to the present invention comprises: a laser light source 6 which emits first light; a light guide rod 5 which has a light incidence surface 51 and converts the first light made incident from the light incidence surface 51 into linear light; and a reflection part 4 which is formed in a box shape so as to accommodate the laser light source 6 and light guide rod 5, and has an opening part made open on a side opposed to a bottom surface of the box shape and a reflecting surface for reflecting the linear light inside the box shape. The light incidence surface 51 is an end face in a longer direction of the light guide rod 5, the laser light source 6 is arranged at a position opposed to the light incidence surface 51, and the light guide rod 5 has a light emission part 55, the linear light being reflected by the light emission part 55 and the reflecting surface to be emitted from the opening part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a surface light source device that displays an image on a liquid crystal display element by illuminating the liquid crystal display element from the back surface of the liquid crystal display element, and a liquid crystal display device including the same.

  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 (surface light source device) on the back side of the liquid crystal display element as a light source for illuminating the liquid crystal display element.

  In addition, the liquid crystal display element includes a color filter and displays only red light, green light, and blue light by transmitting only a part of the wavelength of light from a fluorescent lamp that emits white light in a continuous spectrum through the color filter. The color is extracted and expressed. In this way, in the case of obtaining a display color by cutting out only a part of the wavelength band of light from the continuous spectrum light source light, if an attempt is made to increase the color purity of the display color in order to widen the color reproduction range, the liquid crystal display element The transmission wavelength band of the provided color filter must be set narrow. For this reason, when trying to increase the color purity of the display color, there arises a problem that the amount of light transmitted through the color filter is reduced and the luminance is lowered. 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.

  As a light source having a narrow wavelength width, that is, high color purity, there is a laser. The laser has a very excellent monochromaticity and a high light emission efficiency, and thus can provide a high-quality image with a wide color reproduction range and high brightness.

  A laser is a light source that emits light with high color purity and high straightness. A liquid crystal display device requires a surface light source device that emits planar light that illuminates a liquid crystal panel with uniform intensity. Therefore, when a laser is used as the light source of the liquid crystal display device, it is necessary to obtain planar light from laser light having high straightness. Further, in order to use the laser light without waste, it is desired to convert the laser light into planar light with a configuration as simple as possible.

  2. Description of the Related Art Conventionally, in a liquid crystal display device, a technique for obtaining planar light from laser light by using a light guide rod containing a diffusing material and a reflection bar has been disclosed (see, for example, Patent Document 1). When the laser light is incident on the light guide rod containing the diffusing material, it is emitted from the light guide rod as linear light extending in the longitudinal direction of the light guide rod. In addition, a reflection bar is disposed directly above the light guide bar in the direction of the diffusion plate, and light that travels directly in the direction of the diffusion plate among the light emitted from all directions of the light guide bar is reflected by the reflection bar. The laser light reflected by the reflection bar spreads in the arrangement direction of the light guide bars while being reflected in the reflection part surrounded by the reflection surface, and is mixed with the light emitted from the adjacent light guide bars. Further, other laser beams emitted from the light guide bar are mixed with the light emitted from the adjacent light guide bars while being reflected in the reflecting portion. Thereby, it becomes planar light and becomes planar illumination light that illuminates the liquid crystal panel.

  In this way, the laser beam having high rectilinearity is converted into planar light with a simple configuration by the light guide rod containing the diffusing material and the reflection bar that reflects a part of the light emitted from the light guide rod. A surface light source device is realized.

Japanese Patent Application No. 2014-167207

  However, in the surface light source device of Patent Document 1, since a lot of light that goes directly from the light guide rod in the direction of the diffusion plate is reflected by the reflection bar, the number of times of reflection of the laser light in the reflection portion increases, and the efficiency decreases. Reflective sheets used as a reflective surface have an absorption characteristic of several percent. For this reason, an increase in the number of reflections results in a loss and appears in the surface light source device as a decrease in luminance. Therefore, it is desirable that the number of reflections is small.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a surface light source device and a liquid crystal display device capable of efficiently obtaining planar light with a simple configuration. .

  In order to solve the above problems, a surface light source device according to the present invention has a first light source that emits first light, a light incident surface, and linearly transmits the first light incident from the light incident surface. A light guide rod that converts the light into a light, a box shape that can accommodate the first light source and the light guide rod, an opening that opens on the side facing the bottom surface of the box shape, and a linear shape inside the box shape A light incident surface is an end surface in the longitudinal direction of the light guide rod, and the first light source is disposed at a position facing the light incident surface. The light rod has a notch, and the linear light is reflected by the notch and the reflecting surface and emitted from the opening.

  According to the present invention, a surface light source device includes a first light source that emits first light, a light guide surface that has a light incident surface, and converts the first light incident from the light incident surface into linear light. A bar, an opening that opens on the side facing the bottom of the box, and a reflective surface that reflects linear light on the inside of the box The light incident surface is an end surface in the longitudinal direction of the light guide rod, the first light source is disposed at a position facing the light incident surface, and the light guide rod is a notch portion. Since the linear light is reflected by the notch and the reflection surface and emitted from the opening, the planar light can be efficiently obtained with a simple configuration.

1 is a perspective view schematically showing an example of a configuration of a liquid crystal display device according to Embodiment 1 of the present invention. It is a schematic diagram which shows schematically the light guide rod and reflection part by Embodiment 1 of this invention. It is a schematic diagram which shows roughly the structure of the light guide bar by Embodiment 1 of this invention. It is a schematic diagram which shows roughly the light extraction part of the light guide rod by Embodiment 1 of this invention. It is a schematic diagram which shows roughly another example of a structure of the light guide bar by Embodiment 1 of this invention. It is a schematic diagram which shows roughly another example of a structure of the light-incidence surface of the light guide bar by Embodiment 1 of this invention. It is a schematic diagram which shows schematically the diffusion member by Embodiment 1 of this invention. It is a perspective view which shows roughly another example of a structure of the liquid crystal display device by Embodiment 1 of this invention. It is a perspective view which shows roughly another example of a structure of the liquid crystal display device by Embodiment 1 of this invention. It is a perspective view which shows roughly another example of a structure of the liquid crystal display device by Embodiment 1 of this invention. It is a schematic diagram which shows roughly another example of the light guide bar by Embodiment 1 of this invention. It is a schematic diagram which shows roughly another example of the shape of the light guide bar by Embodiment 1 of this invention. It is a schematic diagram which shows roughly another example of the shape of the light guide bar by Embodiment 1 of this invention. It is a perspective view which shows roughly an example of a structure of the liquid crystal display device by Embodiment 2 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

<Embodiment 1>
FIG. 1 is a perspective view schematically showing an example of the configuration of a liquid crystal display device 200 according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the liquid crystal display device 200 includes a transmissive liquid crystal panel 1 composed of liquid crystal display elements, an optical sheet 2, and a surface light source device 100. The surface light source device 100 includes a diffusion plate 3, a box-shaped reflection unit 4, a light guide bar 5, and a laser light source 6 (first light source).

  Here, for ease of explanation, the xyz orthogonal coordinate system is defined as follows, and the coordinate axes of the xyz orthogonal coordinate system are also shown in each figure. The long side direction of the display surface of the liquid crystal panel 1 is defined as the x-axis direction (the left-right direction in FIG. 1). The short side direction of the display surface of the liquid crystal panel 1 is defined as the y-axis direction (the depth direction in FIG. 1). A direction perpendicular to the xy plane including the x-axis and the y-axis is taken as a z-axis direction (vertical direction in FIG. 1).

  In FIG. 1, the direction from the side portion 43 of the reflecting portion 4 to the side portion 45 on the opposite side (the direction from the left to the right of the paper surface) is the positive direction of the x axis (+ x axis direction), and the opposite direction. Is the negative direction of the x axis (−x axis direction). Further, in FIG. 1, the direction from the side portion 44 of the reflecting portion 4 toward the side portion 42 on the opposite side (the direction from the front of the paper to the back) is the positive direction of the y axis (+ y axis direction), and the opposite direction. Is the negative direction of the y axis (−y axis direction). Further, in FIG. 1, the direction from the diffusion plate 3 toward the liquid crystal panel 1 (the direction from the bottom to the top of the page) is the positive z-axis direction (+ z-axis direction), and the opposite direction is the negative z-axis direction (− z-axis direction).

  The surface light source device 100 is disposed on the back side (−z-axis direction side) of the liquid crystal panel 1, and transmits light to the back surface of the liquid crystal panel 1 through the optical sheet 2 disposed between the surface light source device 100 and the liquid crystal panel 1. It is a device that illuminates. The liquid crystal panel 1 displays an image when the light emitted from the surface light source device 100 is illuminated on the back surface.

  As shown in FIG. 1, in the liquid crystal display device 200, the liquid crystal panel 1, the optical sheet 2, and the surface light source device 100 are sequentially arranged from the positive direction of the z axis toward the negative direction. The optical sheet 2 has a function of suppressing optical influences such as fine illumination unevenness of illumination light emitted from the surface light source device 100 and a function of directing illumination light toward the back surface of the liquid crystal panel 1.

  The display surface of the liquid crystal panel 1 is a surface on the + z axis side of the liquid crystal panel 1, and a surface (surface on the −z axis side) facing the surface is the back surface of the liquid crystal panel 1. The liquid crystal layer is provided between the display surface and the back surface of the liquid crystal panel 1.

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

  As shown in FIG. 1, the reflecting portion 4 includes a bottom portion 41 (bottom surface) parallel to the xy plane, and a bottom portion 41, a side portion 42, a side portion 43, and a side portion 44 that are in contact with the four sides of the bottom portion 41. And has a box shape having an opening on the side facing the bottom 41 (the side of the diffusion plate 3). More specifically, the side portion 45 is disposed at an end portion of the bottom portion 41 in the + x-axis direction, and the side portion 43 is disposed at a side portion of the bottom portion 41 in the −x-axis direction. The side portion 42 is disposed at the end portion of the bottom portion 41 in the + y axis direction, and the side portion 44 is disposed at the end portion of the bottom portion 41 in the −y axis direction. The + z-axis side facing the bottom 41 is an opening.

  The inner surface of the reflector 4 has a function of reflecting and diffusing light. Here, the inner surface of the reflecting portion 4 is a box-shaped inner surface of the reflecting portion 4. That is, the surface on the + z axis direction side of the bottom portion 41, the surface on the −y axis direction side of the side portion 42, the surface on the + x axis direction side of the side portion 43, and the surface on the + y axis direction side of the side portion 44, The surface on the −x-axis direction side of the side portion 45 is a diffuse reflection surface. This diffuse reflection surface can be configured by, for example, disposing a light reflection sheet based on a resin such as polyethylene terephthalate on the entire inner surface of the reflection portion 4. Moreover, you may comprise a reflective surface by vapor-depositing a metal to the whole inner surface of the reflection part 4. FIG.

  A diffusion plate 3 is disposed on the + z-axis direction side of the reflection unit 4. The diffusing plate 3 is arranged so as to cover the opening of the reflecting portion 4. The reflecting portion 4 and the diffusing plate 3 form a hollow box shape having a reflecting surface (the inner surface of the reflecting portion 4) and a diffusing surface (a surface in the −z-axis direction of the diffusing plate 3).

  The light guide bar 5 is disposed so as to penetrate the hollow box shape in the x-axis direction, and most of the light guide bar 5 is accommodated in the reflecting portion 4. That is, the reflection part 4 can accommodate the light guide bar 5. Here, the x-axis direction includes the + x-axis direction and the −x-axis direction, and the same applies to the y-axis direction and the z-axis direction.

  FIG. 2 is a cross-sectional view of the inside of the reflecting portion 4 as viewed from the + z-axis direction.

  A plurality of light guide bars 5 are arranged at intervals in the y-axis direction. As shown in FIGS. 1 and 2, the light guide bar 5 is disposed through the side portions 43 and 45. In other words, the light guide bar 5 is held by the reflecting portion 4 in a state where the end portion protrudes outside the reflecting portion 4. Specifically, the side portions 43 and 45 are provided with holes having the same size as or larger than the end portions in the x-axis direction of the light guide bar 5. The positions of the holes through which the light guide bar 5 is inserted in the side portions 43 and 45 are the same coordinate positions on the yz plane. The light guide bar 5 is inserted into a hole provided in the side part 43 and the side part 45 and attached to the reflection part 4.

  The light incident surface 51 of the light guide bar 5 is disposed on the + x axis direction side of the side portion 45. Further, the end surface 52 facing the light incident surface 51 is disposed on the −x axis direction side with respect to the side portion 43. That is, the light incident surface 51 and the end surface 52 of the light guide bar 5 are disposed outside the reflecting portion 4.

  On the + x axis direction side of the light incident surface 51 of the light guide bar 5, the laser light source 6 is disposed with the light emitting portion directed in the −x axis direction. The laser light source 6 has a plurality of laser light emitting elements arranged one-dimensionally in the y-axis direction. The laser light source 6 is composed of a plurality of types of laser light emitting elements that emit light of different colors in order to produce white light. In the first embodiment, the red laser light emitting element 61 that emits red monochromatic light, the green laser light emitting element 62 that emits green monochromatic light, and the blue laser light emitting element 63 that emits blue monochromatic light. Laser light emitting elements are alternately arranged along the y-axis direction.

  The laser light source 6 is disposed on the + x axis direction side with respect to the side portion 45 and at a position facing the light incident surface 51. In other words, the laser light source 6 is disposed outside the reflection unit 4. The laser light source 6 includes a light emitting unit (not shown). The laser light source 6 is disposed with the light emitting portion directed in the −x axis direction, and emits laser light in the −x axis direction.

  In recent years, in many liquid crystal display devices, a white LED (Light Emitting Diode) is adopted as a light source of a backlight unit. White LEDs produce white light with a broad spectrum from blue to red. White LEDs have high luminous efficiency and are effective in reducing power consumption.

  The liquid crystal display element of the liquid crystal display device includes a color filter. The liquid crystal display device performs color expression by taking out only the wavelength ranges of red, green, and blue using a color filter. In the case of a light source having a continuous spectrum with a wide wavelength band such as a white LED, in order to widen the color reproduction range, the transmission wavelength band of light transmitted through the color filter is set narrow, and the color purity of the display color is increased. There is a need. However, if the wavelength band of light transmitted through the color filter is set narrow, the amount of unnecessary light increases. That is, in the liquid crystal display element, the light use efficiency is very poor. This causes a decrease in luminance of the display surface of the liquid crystal display element, and further causes an increase in power consumption of the liquid crystal display device.

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

  Next, the light guide bar 5 will be described.

  As shown in FIGS. 1 and 2, the light guide bars 5 are arranged along the x-axis direction and arranged in a plurality of rows with a predetermined interval in the y-axis direction. In each light guide bar 5, the + x-axis side end surface in the longitudinal direction is the light incident surface 51, and the laser light source 6 (more specifically, the light emitting portion of the laser light source 6) is located at a position facing the light incident surface 51. Has been placed.

  FIG. 3 is a schematic diagram schematically showing the configuration of the light guide rod.

  Laser light L <b> 60 (first light) emitted from the laser light source 6 toward the light incident surface 51 of the light guide bar 5 enters the light guide bar 5 from the light incident surface 51. The laser beam L60 propagates toward the end surface 52 opposite to the light incident surface 51 while being totally reflected at the interface between the light guide bar 5 and the air layer. That is, in FIG. 2, the laser light L60 incident from the light incident surface 51 located on the + x axis side of the light guide bar 5 travels in the −x axis direction inside the light guide bar 5.

  The light guide bar 5 is made of, for example, a transparent material. The light guide bar 5 is, for example, a quadrangular columnar bar of about 5 mm square. Here, as the transparent material, for example, acrylic resin (Polymethyl methacrylate: PMMA) or the like is employed. A plurality of light extraction portions 55 (notches) are arranged on the side surfaces 53 and 54 in the y-axis direction of the light guide bar 5. The laser beam L60 propagates through the light guide bar 5 while being totally reflected at the interface between the light guide bar 5 and the air layer. At this time, when the laser beam L60 enters the light extraction unit 55, the traveling direction of the incident laser beam L60 changes. When the traveling direction of the laser beam L60 changes, the laser beam L60 includes light that does not satisfy the total reflection condition at the interface between the surface of the light guide bar 5 and the air layer. The laser beam L60 that does not satisfy the total reflection condition is emitted from the side surface 53 or the side surface 54 of the light guide bar 5.

  FIG. 4 is a schematic diagram schematically showing the light extraction portion 55 of the light guide bar 5.

  As shown in FIG. 4, the light extraction portion 55 has a shape in which the side surfaces 53 and 54 of the light guide bar 5 are cut out into a prism shape. This prism shape is a triangle with the side surface 53 (or side surface 54) as the base. That is, the cross section of the light extraction portion 55 in the xy plane is a triangle. The details of the prism shape will be described using the nth light extraction portion 55 (n) in the x-axis direction from the light incident end face 51 side of the light guide rod 5 shown in FIG. The triangular shape of the light extraction portion 55 (n) is two sides 55A (n) and 55B (n) inclined with respect to the side surface 53 (or side surface 54) of the light guide bar 5, and the side surface 53 (or side surface 54). The angle 55θa (n) between the side 55A (n) and the angle 55θb (n) between the side surface 53 (or side surface 54) and the side 55B (n) are formed. Here, the side 55A (n) and the angle 55θa (n) are the angle and the side on the + x axis side, and the side 55B (n) and the angle 55θb (n) are the angle and the side on the −x axis side.

  The angle 55θa (n) and the angle 55θb (n) have an arbitrary angle in a range of 0 ° to 90 °, and have an arbitrary length of the side 55A (n), the side 55B (n), and the side surface 53 (or the side surface). 54) to form a triangular shape.

  The light guide bar 5 also has the same light extraction portion 55 on the side surface 54 as the light extraction portion 55 on the side surface 53. That is, the light extraction portion 55 is arranged so as to be line-symmetric with respect to the x-axis direction as the central axis at any location on the side surfaces 53 and 54.

  As shown in FIG. 3, the laser beam L <b> 60 is incident from the light incident surface 51 of the light guide bar 5 and travels inside the light guide bar 5 toward the end surface 52. In the middle of the process, the light that does not satisfy the total reflection condition among the light incident on the light extraction unit 55 is emitted from the side surfaces 53 and 54 in the y-axis direction. A plurality of light extraction portions 55 are arranged along the x-axis direction. In the first embodiment, for example, the light extraction portion 55 is arranged so that the arrangement interval becomes narrower from the light incident surface 51 toward the end surface 52 that is the opposite surface. The In this way, by controlling the arrangement interval of the light extraction portions 55, the intensity in the x-axis direction of the laser light L60 emitted from the light guide bar 5 can be adjusted.

  For example, as illustrated in FIG. 5, the light guide bar 5 may have a shape in which a cross section in the longitudinal direction (x-axis direction) becomes narrower from the light incident surface 51 toward the end surface 52. In this way, by making the shape narrower from the light incident surface 51 toward the end surface 52, it is possible to increase the chance of reflection by the side surfaces 53 and 54 even on the end surface 52 side where the light is reduced. The amount of light that reaches can be increased and light can be used effectively.

  The reflector 7 is disposed on the end surface 52 of the light guide bar 5. The reflector 7 is a mirror that reflects specularly or a reflection sheet that diffusely reflects. The laser light L60 that propagates through the light guide bar 5 and reaches the end face 52 is reflected by the reflector 7 and becomes light that travels in the + x-axis direction through the light guide bar 5.

  The laser light L60 emitted from the light guide bar 5 becomes linear light extending in the x-axis direction. The linear light emitted from the light guide bar 5 spreads in the reflecting portion 4 while spreading mainly in the y-axis direction. Further, the light that reaches each surface, which is the reflecting surface in the reflecting portion 4, is reflected and propagates in the reflecting portion 4 while changing the traveling direction. Similarly, the light emitted from the adjacent light guide rod 5 also propagates in the reflecting portion 4. At this time, the light emitted from each light guide bar 5 is spatially overlapped in the process of propagating through the reflecting portion 4.

  In the first embodiment, the laser light source 6 includes red laser light emitting elements 61, green laser light emitting elements 62, and blue laser light emitting elements 63 arranged alternately. Each laser light emitting element is provided with a corresponding light guide bar 5. In other words, each laser beam emitted from the light guide bar 5 in the reflection unit 4 is red linear light, green linear light, and blue linear light. The laser light emitted from each light guide bar 5 is spatially overlapped in the process of spreading while being reflected in the reflecting portion 4, and red, green, and blue light are mixed. The light traveling in the + z-axis direction after being reflected by the bottom portion 41 and the side portions 42, 43, 44, 45 which are the reflecting surfaces in the reflecting portion 4 is diffused by the diffusion plate 3. The light diffused by the diffusing plate 3 and emitted in the + z-axis direction is mixed with red, green, and blue light, and becomes planar white light having a uniform luminance distribution in the xy plane. The laser beam L60 emitted from the diffusion plate 3 passes through the optical sheet 2 and irradiates the back surface of the liquid crystal panel 1.

  In the first embodiment, the light extraction portions 55 of the light guide bar 5 are provided on both end faces (opposing faces) in the y-axis direction. Therefore, the laser light L60 emitted from the light guide bar 5 spreads in the y-axis direction and easily overlaps with the laser light L60 emitted from the adjacent light guide bar 5.

  For example, a semiconductor laser is used for the laser light emitting element constituting the laser light source 6. Due to its structure, the semiconductor laser has a fast axis direction with a large divergence angle and a slow axis direction with a small divergence angle perpendicular to the fast axis direction. In the first embodiment, the fast axis direction is parallel to the laser light emitting element arrangement direction (y-axis direction), and the slow axis direction is parallel to the thickness direction (z-axis direction) of the surface light source device 100. The laser light emitting elements are arranged so that By arranging so that the fast axis direction is parallel to the arrangement direction (y-axis direction) of the laser light emitting elements, light is incident on the light extraction portion 55 existing near the light incident surface 51 of the light guide bar 5. It is easy, and the light is sufficiently emitted even on the + x axis side (near the light incident surface) of the reflector 4, and more uniform linear light can be obtained. Further, since the laser light L60 emitted from the light guide bar 5 spreads in the y-axis direction, the light emitted from the adjacent light guide bar 5 is easily mixed in the reflection part 4, and the thickness (z Axial direction) can be reduced. However, the arrangement direction of the laser light emitting elements is not limited to the above.

  Although it has been described that the light extraction portion 55 of the light guide bar 5 is arranged so that the interval decreases from the light incident surface 51 toward the end surface 52, the present invention is not limited to this. For example, when the light extraction portions 55 are densely arranged near the light incident surface 51 of the light guide bar 5, a lot of laser light L <b> 60 is emitted from the light guide rod 5 by the light extraction portions 55 near the light incident surface 51, and the end surface 52. The laser beam L60 reaching the vicinity is lost. That is, the intensity of the light emitted from the light guide bar 5 is high in the vicinity of the light incident surface 51 and low on the end surface 52 side, and has an uneven distribution in the x-axis direction. On the other hand, when the light extraction portion 55 is eliminated or made small in number on the light incident surface 51 side and is closely arranged in the vicinity of the end surface 52, the light emitted from the light guide rod 5 is low in the vicinity of the light incident surface 51, and the end surface 52 side is low. Get higher. Thus, by changing the arrangement interval of the light extraction portions 55, the intensity distribution in the x-axis direction of the laser light L60 emitted from the light guide bar 5 can be controlled. That is, the arrangement of the light extraction unit 55 can be changed to obtain an arbitrary intensity distribution.

  Further, it is not necessary that all the light extraction portions 55 of the light guide bar 5 have the same shape. The light extraction unit 55 can change the length of the sides 55A (n) and 55B (n) and the angles 55θa (n) and 55θb (n) depending on the arrangement position. The distribution of the emitted light emitted from the light guide rod 5 varies depending on the length of the sides 55A (n) and 55B (n) and the angles 55θa (n) and 55θb (n).

  From the above, the laser light L60 becomes linear light extending in the longitudinal direction (x-axis direction) of the light guide bar 5 by the light guide bar 5. Further, the linear light is adjacent to the light extraction part 55 of the light guide bar 5 by being reflected by the reflection surface in the reflection part 4 while spreading in the arrangement direction (y-axis direction) of the light guide bars 5. It overlaps with the light emitted from the light guide bar 5 and becomes planar light that illuminates the back surface of the liquid crystal panel 1.

  The light incident surface 51 of the light guide bar 5 may have a diffusion portion 511. The diffusion unit 511 is a cylindrical surface extending in the y-axis direction as shown in FIG. 6, for example. Since the light incident surface 51 includes the diffusion portion 511, the divergence angle of the laser light can be widened. Since the laser light emitting element has a small divergence angle, a propagation distance is required until the laser light emitting element sufficiently spreads in the yz plane in the light guide bar 5 after entering the light guide bar 5. If the spread of the laser light is small on the yz plane in the light guide bar 5, light reaching the light extraction portion 55 is reduced in the vicinity of the light incident surface 51, and the light incident surface 51 side becomes dark. Therefore, by providing the diffusing portion 511 on the light incident surface 51 of the light guide bar 5, the divergence angle of the laser light can be widened to shorten the propagation distance until it is sufficiently spread in the yz plane. The surface 51 side can be brightened. In FIG. 6, the diffusion portion 511 is a cylindrical surface extending in the y-axis direction, but is not limited thereto, and may be a cylindrical surface extending in the x-axis direction. In addition to the cylindrical shape, the diffusing portion 511 may have a shape for widening the divergence angle such as a prism shape or blasting. In addition, as shown in FIG. 7, the diffusing member 8 may be disposed between the light incident surface 51 of the light guide bar 5 and the exit surface of the laser light source 6. The diffusion member 8 can be realized by a diffusion sheet or a prism sheet.

  In the first embodiment, the laser light source 6 is disposed on the side surface on one side (+ x axis side) of the liquid crystal panel 1, but the present invention is not limited to this arrangement. For example, as shown in FIG. 8, the laser light source 6 may be arranged on the end surfaces of both sides (+ x axis side, −x axis side) of the liquid crystal panel 1. At this time, the light guide rods 5 may be arranged so that the light incident surfaces 51 and the end surfaces 52 alternate along the y-axis direction on each side. By arranging in this way, the number of laser light sources 6 can be increased.

  For example, as shown in FIG. 9, the laser light sources 6 may be arranged on both side surfaces, and two light guide bars 5 may be arranged along the x-axis direction. That is, the light guide bar 5 of FIG. 9 is about half as long as FIGS. When the light guide 5 is divided in this manner, when the liquid crystal display device 200 has a particularly large size, warpage of the light guide 5 that occurs during manufacturing is long. Therefore, manufacturability is improved.

  For example, as shown in FIG. 10, laser light sources 6 are arranged on both side surfaces, and both end surfaces of the light guide bar 5 are light incident surfaces, and laser light is incident from both end surfaces of one light guide bar 5. Also good. At this time, in order to make the laser beam L60 emitted from the light guide bar 5 uniform in the x-axis direction, the light extraction part 55 of the light guide bar 5 becomes farther away from the laser light sources 6 on both sides as shown in FIG. It arrange | positions so that a space | interval may become narrow.

  In FIGS. 1, 8, 9, and 10, the laser light source 6 is disposed in the y-axis direction with respect to the side surface of the liquid crystal panel 1, but is not limited to the arrangement in this direction. The laser light source 6 may be disposed laterally on the upper and lower end surfaces of the liquid crystal panel 1. That is, the laser light source 6 is disposed along the x-axis direction so as to face the side portions 42 and 44 of the reflecting portion 4, and the laser light source 6 disposed at a position facing the side portion 42 is moved in the −y-axis direction. The laser light source 6 disposed at a position facing the side portion 44 emits a laser beam L60 in the + y axis direction. At this time, the light guide bar 5 is disposed so as to penetrate the side portions 42 and 44 of the reflecting portion 4.

  The laser light source 6 emits heat by emitting light. The heat generated by the light emission of the laser light source 6 warms the air around the laser light source 6, but the warmed air rises in the upper direction of the liquid crystal panel 1 (+ z axis direction). In the laser light emitting element, the amount of emitted light and the wavelength easily change depending on the temperature. Therefore, by arranging the laser light source 6 on the lower side of the liquid crystal panel 1, the temperature rise around the laser light source 6 can be suppressed. In addition, by arranging the laser light sources 6 in a row on the lower side (−z-axis direction) of the liquid crystal display device 200, it is possible to prevent a temperature difference from occurring between the laser light emitting elements constituting the laser light source 6. Variation in light emission due to temperature rise of each laser light emitting element can be suppressed.

  In the first embodiment, the light guide bar 5 is, for example, a square columnar bar of about 5 mm square. However, the light guide bar 5 is not limited to this. For example, a light guide bar 500 having a triangular cross section as shown in FIG. 12 or a light guide bar 501 having a trapezoidal cross section as shown in FIG. 13 may be used. At this time, it is desirable that the two surfaces on which the light extraction portion 55 is disposed are surfaces including two sides inclined at the same angle with respect to the bottom surface. As shown in FIGS. 12 and 13, by arranging the light extraction portion 55 on the inclined surface, the traveling direction of the laser light L60 emitted from the light extraction portion 55 changes. For example, depending on the inclination of the surface, the laser light L60 becomes light that actively proceeds in the −z-axis direction. Since the light traveling in the −z-axis direction is immediately reflected by the bottom surface of the reflecting portion 4, the spread of the emitted light in the y-axis direction becomes narrow. The spread in the y-axis direction of the laser light L60 emitted from the light guide bar 5 is determined by the arrangement interval of the laser light emitting elements and the distance from the bottom 41 of the reflecting portion 4 to the diffusion plate 3. Therefore, it is necessary to design an appropriate cross-sectional shape of the light guide bar 5 according to the required spread of the laser light L60 in the y-axis direction, and the cross-sectional shape of the light guide bar 5 according to the first embodiment is It is not limited.

  Moreover, although the light extraction part 55 of the light guide bar 5 was demonstrated as a prism shape, it is not restricted to this. For example, a cylindrical shape may be used instead of the prism shape. The light extraction part 55 of the light guide bar 5 only needs to be arranged on two side surfaces facing in the direction in which light is to be spread, and the shape thereof is not limited, in view of performance (emitted light distribution) and manufacturability. Determined.

  In the first embodiment, the red laser light emitting element 61, the green laser light emitting element 62, and the blue laser light emitting element 63 are described as being alternately arranged. However, the arrangement is not limited to this. Considering characteristics such as the luminous efficiency of the laser light emitting elements of each color, the number of laser light emitting elements of each color necessary for obtaining the target brightness as the surface light source device 100 is determined, and the arrangement is also determined accordingly.

  Moreover, although the case where the laser light source 6 was used was demonstrated in this Embodiment 1, it does not restrict to this. For example, a red LED, a blue LED, and a green LED may be used as the light source. However, the divergence angle (angular intensity distribution) of the emitted light is greatly different between the LED element and the laser light emitting element. Specifically, LED light has a larger divergence angle than laser light. That is, LED light has a larger spread of emitted light than laser light. For this reason, the LED light generates more light that cannot enter the light guide bar 5 when entering the light guide bar 5 than the laser light. The light incident surface 51 of the light source and the light guide bar 5 is disposed outside the reflecting portion 4, and the light that could not enter the light guide bar 5 is not used as it is in the surface light source device 100 and is lost. In addition, the lost light becomes stray light, which may cause a decrease in contrast of the surface light source device 100. Therefore, in the first embodiment, it is desirable to use a light source with a small divergence angle as the light source.

  In the reflecting portion 4, the side portions 42, 43, 44, and 45 may be inclined (relative to the xy plane) with respect to the bottom portion 41 that is parallel to the xy plane. With this configuration, the laser light L60 incident on the inclined side portions 42, 43, 44, and 45 is reflected in the + z-axis direction, so that the peripheral portion of the display surface of the liquid crystal panel 1 can be brightened. . Further, by providing the inclined side portions 43 and 45, the laser light source 6 can be disposed on the back side (−z-axis direction side) of the diffusion plate 3. Thereby, a narrow bezel becomes possible.

  Here, arranging the laser light source 6 on the back side of the diffusion plate 3 means that the laser light source 6 is arranged so as not to protrude outside the end surface of the diffusion plate 3 in the x-axis direction. Alternatively, the laser light source 6 is arranged so as to protrude only partially outside the end surface of the diffusion plate 3 in the x-axis direction. That is, the reflection unit 4 can accommodate the laser light source 6.

  As described above, in the surface light source device 100 according to the first embodiment, the laser light L60 emitted from the laser light source 6 is converted by the light guide bar 5 into linear light extending in the longitudinal direction of the light guide bar 5. . The linear laser beam L60 is mixed with the adjacent laser beam L60 inside the reflection unit 4 while spreading in the arrangement direction of the laser light source by the light extraction unit 55 of the light guide bar 5, and becomes light directed toward the diffusion plate 3. . The laser light L60 emitted from the diffusing plate 3 is further mixed in color to become illumination light with a uniform surface distribution, and irradiates the liquid crystal panel 1.

  The liquid crystal display device 200 includes the surface light source device 100 and the liquid crystal panel 1 that displays an image when the light from the surface light source device 100 is illuminated. Since the light emitted from the laser light source 6 can be guided without waste by the light guide rod 5, the light utilization efficiency is increased and a high-quality image can be displayed. Also, such high-quality image display can be realized with a simple structure. A laser light source is employed as the light source. Since the laser light source has a narrower wavelength bandwidth than that of the white LED light source and can obtain light with high color purity, a wider color reproduction range than that of a surface light source device including a conventional white LED light source can be obtained. Further, since a laser light source is employed as the light source, loss of light amount in the color filter can be suppressed and light utilization efficiency can be increased.

<Embodiment 2>
FIG. 14 is a perspective view schematically showing an example of the configuration of the liquid crystal display device 201 according to the second embodiment.

  As shown in FIG. 14, the liquid crystal display device 201 includes a liquid crystal panel 1, an optical sheet 2, and a surface light source device 101. The surface light source device 101 includes a light guide bar 5 and an LED light source 9 (second light source) in a hollow box constituted by the reflection unit 4 and the diffusion plate 3, and a laser light source 16 outside the reflection unit 4. It has.

  The liquid crystal display device 201 of the second embodiment has the same configuration as the liquid crystal display device 200 of the first embodiment except for the LED light source 9 and the laser light source 16. That is, the liquid crystal display device 201 is different from the liquid crystal display device 200 in that it has two types of light sources, the LED light source 9 and the laser light source 16. In addition, the same code | symbol is attached | subjected to the component same as the component of Embodiment 1, and the detailed description is abbreviate | omitted.

  Currently, white LEDs are widely used as light sources for liquid crystal display devices. White LEDs produce white light with a broad spectrum from blue to red. This white LED has high luminous efficiency and is effective in reducing power consumption.

  As described above, the liquid crystal display element of the liquid crystal display device includes a color filter. The liquid crystal display device performs color expression by extracting only the red, green, and blue wavelength ranges by using the color filter. In the case of a light source having a continuous spectrum with a wide wavelength bandwidth, such as a white LED, in order to widen the color reproduction range, the transmission wavelength band of the light transmitted through the color filter is set narrow, and the color purity of the display color is increased. There is a need. However, the amount of unnecessary light increases by narrowing the wavelength band of the light transmitted through the color filter. That is, in the liquid crystal display element, the light use efficiency is very poor. This becomes a factor that causes a decrease in luminance of the display surface of the liquid crystal display element and an increase in power consumption of the liquid crystal display device.

  The liquid crystal display device 201 according to the second embodiment has a wide color reproduction range and low power consumption. Therefore, the LED light source 9 and the laser light source 16 are provided as light sources. The LED light source 9 has a blue LED and a phosphor. Specifically, the LED light source 9 is a light source in which a package including a blue LED chip that emits blue light is filled with a green phosphor that absorbs the blue light and emits green light. The laser light source 16 has only a laser light emitting element that emits red light.

  Humans are highly sensitive to red color differences. Therefore, the difference in wavelength bandwidth in red is felt as a more prominent difference in human vision. Here, the difference in wavelength bandwidth is a difference in color purity. Conventionally, a white LED used as a light source in a liquid crystal display device has a small amount of energy in a red spectrum particularly in a 600 nm to 700 nm band. That is, if a color filter having a narrow wavelength band width is used to increase the color purity in a wavelength range of 630 to 640 nm, which is preferable as pure red, the amount of transmitted light is extremely reduced, and the light use efficiency is lowered. Therefore, there arises a problem that the luminance is remarkably lowered.

  On the other hand, the laser light-emitting element has a narrow wavelength bandwidth and can obtain light of high color purity without losing light. Among the three primary colors, in particular, the effect of reducing power consumption and the improvement of color purity by making red light a laser light emitting element having very high monochromaticity are great. In the liquid crystal display device 201 of the second embodiment, the laser light source 16 employs a light source that emits red light.

  As shown in FIG. 14, the blue-green LED light sources 9 are two-dimensionally arranged on the bottom 41 parallel to the xy plane of the reflector 4. The blue-green light (second light) emitted from the LED light source 9 is spatially overlapped with the light emitted from the adjacent LED light source 9 inside the reflection unit 4. Further, the LED light is mixed with the linear red laser light emitted from the light guide rod 5 inside the reflecting portion 4 to become white light. Further, the mixed white light is diffused by the diffusion plate 3 and irradiates the back surface of the liquid crystal display panel 1 as planar light having a uniform intensity distribution in the xy plane.

  In order for the LED light emitted from the LED light source 9 to be uniform planar light, for example, an optical member such as a lens or a light guide may be added to the LED light source 9. Further, the LED light source 9 may be disposed directly below the light guide bar 5 (−z-axis direction).

  In the second embodiment, the case where the laser light source 16 that emits red light and the LED light source 9 that emits blue-green light are used has been described. However, the present invention is not limited to this. For example, the laser light source 16 may be configured by a laser light emitting element that emits red light and blue light, and the LED light source 9 may be configured by an LED element that emits green light. Further, for example, the laser light source 16 may be configured by a laser light emitting element that emits blue light, and the LED light source 9 may be configured by an LED element that emits red light and green light. The light emitted from the LED light source 9 and the light emitted from the laser light source 16 may be a combination that is mixed and turns white. That is, the light emission color of the LED light source 9 and the light emission color of the laser light source 16 may be a complementary color. However, as described above, since humans are highly sensitive to red color differences, it is noticeable that adopting only a red laser light source is significantly different from conventional liquid crystal display devices than adopting only a blue laser light source. Can be shown.

  The second embodiment can employ the same configuration as that of the first embodiment except that the LED light source 9 and the laser light source 16 are employed. In this case, the same effect can be obtained.

  From the above, according to the second embodiment, by adopting the laser light source 16 and the LED light source 9, it is possible to obtain planar light with high light use efficiency and high spatial light intensity distribution. It becomes possible. The liquid crystal display device 201 including the surface light source device 101 can provide a high-quality image with a wide color reproduction range and reduced luminance unevenness. In the second embodiment, the light guide bar 5 and the LED light source 9 are disposed inside the reflection unit 4 on the back side of the liquid crystal display panel 1. For this reason, the bezel can be narrowed. Furthermore, the red color is composed of laser elements and the blue-green color is composed of LED elements, so that both the color reproduction range and low power consumption, both of which have been the problems of conventional liquid crystal display devices, can be achieved. An apparatus can be provided.

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

  DESCRIPTION OF SYMBOLS 1 Liquid crystal panel, 2 Optical sheet, 3 Diffusing plate, 4 Reflection part, 5 Light guide rod, 6 Laser light source, 7 Reflector, 8 Diffusing member, 9 LED light source, 41 Bottom part, 42-45 side part, 51 Light incident surface , 52 end face, 53, 54 side face, 55 light extraction part, 61 red laser light emitting element, 62 green laser light emitting element, 63 blue laser light emitting element, 100 surface light source device, 200 liquid crystal display device, 500, 501 light guide bar, 511 Diffusion part.

Claims (10)

A first light source that emits first light;
A light guide rod that has a light incident surface and converts the first light incident from the light incident surface into linear light;
The first light source and the light guide rod are formed in a box shape so as to be accommodated, an opening that opens on a side facing the bottom surface of the box shape, and the linear light is reflected on the inner side of the box shape. A reflective portion having a reflective surface;
With
The light incident surface is an end surface in the longitudinal direction of the light guide rod,
The first light source is disposed at a position facing the light incident surface,
The light guide bar has a notch,
2. The surface light source device according to claim 1, wherein the linear light is reflected by the notch and the reflecting surface and is emitted from the opening. The light guide rod is held by the reflecting portion in a state in which an end protrudes to the outside,
The surface light source device according to claim 1, wherein the first light source and the light incident surface are disposed outside the reflecting portion.   3. The surface light source device according to claim 1, wherein the light guide bar is a surface facing in the longitudinal direction of the light guide bar and has the cutout portion at each of the opposed positions. 4. . The light guide bar is disposed in a direction parallel to the bottom surface,
4. The surface light source device according to claim 1, wherein the linear light is emitted in a direction parallel to the bottom surface after being reflected by the cutout portion. 5. .   5. The light guide bar according to claim 1, wherein the light guide bar has a diffusion part that diffuses the first light incident from the first light source on the light incident surface. 6. The surface light source device described.   The diffusing member for diffusing the first light emitted from the first light source is further provided between the first light source and the incident surface. 2. A surface light source device according to item 1. A second light source disposed on the bottom surface and emitting a second light with a wider divergence angle than the first light source;
The surface light source device according to claim 1, wherein the second light source is reflected by the reflection surface and emitted from the opening.   The surface light source device according to claim 7, wherein the second light source is an LED light source.   The surface light source device according to claim 1, wherein the first light source is a laser light source. A surface light source device according to any one of claims 1 to 9,
A liquid crystal panel that displays an image by being irradiated with light from the surface light source device;
A liquid crystal display device comprising:

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