JP2018037257A - Surface light source device and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device capable of improving uniformity of planar illumination light by using both of a light beam penetrating a light emission surface of a light distribution control element and a light beam reflecting the light emission surface, and capable of improving robustness on arrangement of the light distribution control element and a holding substrate or arrangement or the light distribution control element and a light source.SOLUTION: A surface light source device includes: a light source; a holding substrate on a main surface of which the light source is held; a reflector arranged on the main surface side of the holding substrate; a light distribution control element arranged on the main surface side of the holding substrate so as to cover the light source, and configured to change distribution of light emitted from the light source; and a diffuser panel configured to diffuse light emitted from the light distribution control element. The light distribution control element has an installation surface capable of contacting with the reflector. The reflector has a first reflection region, and a second reflection region having lower reflectivity than the first reflection region. The second reflection region is arranged correspondingly to the installation surface of the light distribution control element.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a surface light source device that emits planar light and a liquid crystal display device using the surface light source device.

  The liquid crystal panel included in the liquid crystal display device does not emit light by itself. Therefore, the liquid crystal display device includes a backlight device, that is, a surface light source device on the back side of the liquid crystal panel as a light source for illuminating the liquid crystal panel. One configuration of a backlight device is a direct-type backlight device in which a plurality of light emitting diodes (hereinafter referred to as LEDs) are arranged. In recent years, small, high-efficiency, high-power LEDs have been developed. Therefore, even if the number of installed LEDs used in the backlight device or the number of installed LEDBARs, which are light sources in which a plurality of LEDs are arranged in a row, is reduced, the same brightness as that of the conventional backlight device is calculated. You can get it. Patent Document 1 or Patent Document 2 discloses a backlight device that expands a light beam emitted from an LED by a cylindrical lens and converts it into planar illumination light.

JP 2006-286608 A JP 2014-38697 A

  In the backlight device described in Patent Document 1 or Patent Document 2, when light is transmitted from the cylindrical lens into the air, a part of the light is reflected at the boundary surface between the cylindrical lens and the air. In order to improve the uniformity of the illumination light, it is necessary to use both direct light transmitted through the boundary surface and reflected light reflected at the boundary surface as illumination light. However, the reflected light increases as the divergence angle of the light emitted from the light source is increased. Therefore, it is difficult to suppress a decrease in the amount of light around the irradiation area of the backlight device. In order to improve the uniformity of the illumination light, it is desirable that the light emitted from the light source is incident on the incident surface of the light distribution control element constituted by a cylindrical lens or the like as designed. However, it is difficult to completely eliminate assembly errors and the like in the manufacturing process, and the light distribution control element may not be arranged on the holding substrate as designed.

  The present invention has been made in order to solve the above-described problems, and by using both a light beam transmitted through a light exit surface of a light distribution control element and a light beam reflected by the light distribution surface, the uniformity of planar light is achieved. An object of the present invention is to provide a surface light source device that improves the robustness of the arrangement of the light distribution control element and the holding substrate or the arrangement of the light distribution control element and the light source.

  The surface light source device according to the present invention includes a light source, a holding substrate on which the light source is held on the main surface, a reflector disposed on the main surface side of the holding substrate, and a main surface side of the holding substrate so as to cover the light source. A light distribution control element that changes the light distribution of the light emitted from the light source and a diffusion plate that diffuses the light emitted from the light distribution control element, and the light distribution control element can contact the reflector The reflector includes a first reflection region and a second reflection region having a lower reflectance than the first reflection region, and the second reflection region corresponds to the installation surface of the light distribution control element. Arranged.

  According to the present invention, the uniformity of planar illumination light is improved and the light distribution control element is held by using both the light beam that passes through and reflects the light emission surface of the light distribution control element. It is possible to provide a surface light source device that improves the robustness of the arrangement with the substrate or the arrangement of the light distribution control element and the light source.

3 is a cross-sectional view illustrating a structure of a liquid crystal display device in Embodiment 1. FIG. 3 is a cross-sectional view showing a configuration around a light source included in the surface light source device in Embodiment 1. FIG. It is a figure which shows the holding substrate and reflector which the surface light source device in Embodiment 1 contains. It is a figure which shows the holding substrate and reflector which the surface light source device in Embodiment 1 contains. It is a figure which shows the holding substrate and reflector which the surface light source device in Embodiment 1 contains. It is a figure which shows the reflection part which the surface light source device in Embodiment 1 contains. It is a figure which shows the light ray radiate | emitted from the light source of the surface light source device in a base technology. It is a figure which shows the light ray radiate | emitted from the light source of the surface light source device in a base technology. It is a figure which shows the light ray radiate | emitted from the light source of the surface light source device in a base technology. It is a figure which shows the light ray radiate | emitted from the light source of the surface light source device in Embodiment 1. FIG. It is a figure which shows the light ray radiate | emitted from the light source of the surface light source device in Embodiment 1. FIG. It is a figure which shows the light ray radiate | emitted from the light source of the surface light source device in Embodiment 1. FIG. It is sectional drawing which shows the structure of the light source periphery which the surface light source device in Embodiment 2 contains. It is a figure which shows the holding substrate and reflector which the surface light source device in Embodiment 2 contains.

  Embodiments of a surface light source device and a liquid crystal display device including the surface light source device according to the present invention will be described with reference to the drawings. The liquid crystal display device and the surface light source device shown in each drawing are illustrated based on xyz orthogonal coordinates. A direction perpendicular to the xy plane that is a plane including the x-axis and the y-axis is the z-axis direction.

  In this specification, each direction is defined as follows. For example, when the liquid crystal panel 1 has a rectangular shape, the long side direction of the liquid crystal panel 1 is the x-axis direction, and the short side direction is the y-axis direction. In FIG. 1, the long side direction of the liquid crystal panel 1 is a direction perpendicular to the paper surface, and the short side direction is the left-right direction of the paper surface. When the long side direction of the liquid crystal panel 1 is horizontally arranged and the short side direction is arranged vertically, the x-axis direction is the horizontal direction and the y-axis direction is the vertical direction. In this case, the upper side of the liquid crystal display device 100 is the positive direction of the y axis (+ y axis direction), and the lower side is the negative direction of the y axis (−y axis direction). The direction in which the liquid crystal display device 100 displays an image is the positive direction of the z axis (+ z axis direction), and the opposite direction is the negative direction of the z axis (−z axis direction). The + z-axis direction side is referred to as the display surface side. The −z-axis direction side is referred to as the back surface side. Further, when viewed from the display surface side of the liquid crystal display device 100, the right side is the positive direction of the x axis (+ x axis direction), and the left side is the negative direction of the x axis (−x axis direction). “View from the display surface side” means to look at the −z-axis direction side from the + z-axis direction side.

<Embodiment 1>
(Configuration of liquid crystal display device)
FIG. 1 is a cross-sectional view schematically showing the configuration of the surface light source device 200 and the configuration of the liquid crystal display device 100 including the surface light source device 200 in the first embodiment. The liquid crystal display device 100 includes a transmissive liquid crystal panel 1 and a surface light source device 200. The liquid crystal display device 100 further includes an optical sheet 2 and an optical sheet 3 between the liquid crystal panel 1 and the surface light source device 200. Further, the diffusion plate 4 is disposed on the light emission surface of the surface light source device 200. That is, the diffusion plate 4 is provided in the opening 53 of the surface light source device 200. The liquid crystal panel 1, the optical sheet 2, the optical sheet 3, the diffusion plate 4, and the surface light source device 200 are sequentially arranged from the + z-axis direction to the -z-axis direction. The liquid crystal panel 1 has a back surface 1 b that faces the surface light source device 200 through the optical sheet 2 and the optical sheet 3. The liquid crystal panel 1 has a display surface 1a on the opposite side of the back surface 1b. The back surface 1b is a surface on the −z axis direction side of the liquid crystal panel 1, and the display surface 1a is a surface on the + z axis direction side thereof. The display surface 1a has a planar rectangular shape. That is, the display surface 1a has a plane that extends in a direction parallel to the xy plane. Further, the short side in the x-axis direction and the long side in the y-axis direction constituting the plane are orthogonal to each other. In addition, the shape of said display surface 1a is an example, Other shapes may be sufficient. The liquid crystal panel 1 includes a liquid crystal layer, and the liquid crystal layer has a planar structure that spreads in a direction parallel to the xy plane.

  The surface light source device 200 emits planar light from the diffusion plate 4 and illuminates the back surface 1 b of the liquid crystal panel 1 through the optical sheet 3 and the optical sheet 2. The optical sheet 3 has a function of directing the traveling direction of light emitted from the diffusion plate 4 in the normal direction with respect to the display surface 1 a of the liquid crystal panel 1. The optical sheet 2 reduces fine unevenness of illumination light and the like, and suppresses optical adverse effects. The liquid crystal panel 1 converts illumination light incident from the back surface 1b into image light. “Image light” refers to light having image information.

(Configuration of surface light source device)
The surface light source device 200 includes a light source 7, a holding substrate 8, a reflector 9 (not shown in FIG. 1), a light distribution control element 6, and a reflector 5. The reflection part 5 is formed in a container shape so as to accommodate the light source 7, the reflector 9, and the light distribution control element 6, and includes a reflection surface 54 and an opening 53. The surface light source device 200 further includes a housing 10. The housing 10 is a member that holds and stores the reflecting portion 5 and the holding substrate 8. The reflector 5 is disposed along the inner wall of the housing 10. The housing 10 reflects the shape of the reflecting portion 5 and has a container shape with an upper surface, that is, the liquid crystal panel 1 side opened. The material which comprises the housing | casing 10 is resin or a metal plate, for example.

  FIG. 2 is an enlarged cross-sectional view of the periphery of the light source 7 of the surface light source device 200. The light source 7 is disposed on the main surface 81 of the holding substrate 8. The main surface 81 is the upper surface of the holding substrate 8 and is, for example, a mounting surface. The surface light source device 200 further includes a reflector 9 on the main surface 81 side of the holding substrate 8. The surface light source device 200 further includes a light distribution control element 6. The light distribution control element 6 is disposed on the main surface 81 side of the holding substrate 8 so as to cover the light source 7. The light distribution control element 6 has an installation surface 63 that can come into contact with the reflector 9. In FIG. 2, the installation surface 63 is in contact with the reflector 9, but is not necessarily in contact, and there is a gap between the installation surface 63 and the reflector 9 or between the installation surface 63 and the main surface 81. It may be provided. Below, the detailed structure of the surface light source device 200 is demonstrated.

(Holding substrate)
FIG. 3 is a plan view of the main surface 81 of the holding substrate 8. In FIG. 3, the light distribution control element 6 is not shown. In the first embodiment, the holding substrate 8 is long in the longitudinal direction of the liquid crystal panel 1 and has a rectangular shape in plan view. The holding substrate 8 has a plate shape. The main surface 81 of the holding substrate 8 includes, for example, a white resist layer or a white silk layer on the resist layer. The main surface 81 has a function of a reflecting surface. As shown in FIG. 2, the holding substrate 8 on which the light source 7, the reflector 9, and the light distribution control element 6 are arranged is held on the bottom surface 10 a of the housing 10. The surface of the holding substrate 8 held on the bottom surface 10 a of the housing 10 is a back surface 82 opposite to the main surface 81. The back surface 82 is a surface on the −z axis side of the holding substrate 8. The back surface 82 transmits heat generated by the light source 7 to the housing 10 via the main surface 81 to radiate heat. Moreover, the surface light source device 200 may enhance the heat radiation effect by providing a heat radiation sheet between the holding substrate 8 and the housing 10, for example.

(light source)
The light source 7 is disposed on the main surface 81 of the holding substrate 8. As shown in FIG. 3, in the first embodiment, a plurality of light sources 7 are arranged in a row on the main surface 81 with a predetermined interval. The arrangement direction is the longitudinal direction of the liquid crystal panel 1, that is, the x-axis direction. Further, as shown in FIG. 2, the back surface 72 that is the surface on the −z-axis side of the light source 7 is in contact with the main surface 81 of the holding substrate 8. Thereby, the light source 7 is held on the holding substrate 8. The light source 7 is supplied with power through the back surface 72. The light source 7 is electrically connected to the holding substrate 8. In the first embodiment, the other surface different from the back surface 72 is a light emitting surface. For example, the surface 71 facing the back surface 72 of the light source 7 is a light emitting surface. Alternatively, for example, when the light source 7 has a rectangular parallelepiped shape, five surfaces different from the back surface 72 are light emitting surfaces.

  The light source 7 is, for example, a solid light source. The solid light source is, for example, a light emitting diode (hereinafter referred to as an LED element). Alternatively, for example, the light source 7 includes an organic electroluminescence light source or a light source that emits light by irradiating excitation light onto a phosphor applied on a flat surface. In the first embodiment, the light source 7 is an LED element.

(Light distribution control element)
The light distribution control element 6 is arranged on the main surface 81 side of the holding substrate 8 so as to cover the light source 7. That is, the light distribution control element 6 is disposed on the + z axis direction side of the light source 7 so as to surround the light source 7. Further, the light distribution control element 6 has an installation surface 63 that can come into contact with the reflector 9. In the first embodiment, the light distribution control element 6 is an optical element having a rod shape along the direction in which the plurality of light sources 7 are arranged. That is, the light distribution control element 6 is a rod-shaped optical element extending in the x-axis direction. For example, the light distribution control element 6 is a cylindrical lens. The cylindrical lens is a lens waiting for a cylindrical refractive surface. The cylindrical lens has a curvature in the first direction and does not have a curvature in the second direction perpendicular to the first direction. Light emitted from the cylindrical lens is condensed or diverged only in one direction. For example, when parallel light is incident on a convex cylindrical lens, the light is condensed into a linear shape. This condensed line is called a focal line. In the first embodiment, the first direction is a direction orthogonal to the direction in which the light sources 7 are arranged, that is, the y-axis direction. The second direction is a direction parallel to the direction in which the light sources 7 are arranged, that is, the x-axis direction.

  As shown in FIG. 2, the light distribution control element 6 includes a light incident surface 61 on which light emitted from the light source 7 is incident. In the present embodiment, the light incident surface 61 extends in the arrangement direction of the light sources 7. The light incident surface 61 is formed as a concave curved surface or plane covering the light source 7. The concave curved surface is, for example, an aspherical surface or a cylindrical surface. The light distribution control element 6 includes a light emission surface 62 from which light incident from the light incident surface 61 is emitted to the outside of the light distribution control element 6. The light emitting surface 62 is located on the opposite side of the light incident surface 61 from the light source 7. That is, the light emitting surface 62 is a surface on the + z-axis direction side of the light distribution control element 6. The light emitting surface 62 includes a convex cylindrical surface having a curvature in a direction orthogonal to the arrangement direction of the light sources 7. That is, the light emitting surface 62 includes a cylindrical surface in the y-axis direction. The optical axis C of the light distribution control element 6 is parallel to the z axis. The “optical axis” is a straight line passing through the center and the focal point, such as a lens or a spherical mirror. When the optical element has a cylindrical surface, it is determined by its cross-sectional shape having a curvature. In the present embodiment, the optical axis C is defined by the shape of the light emitting surface 62 in a plane perpendicular to the direction in which the light sources 7 are arranged, that is, a yz plane perpendicular to the x-axis direction. The light exit surface 62 has an intersection with the optical axis C.

  Further, the light source 7 described above is disposed in a recess formed by the light incident surface 61. The concave portion is a space surrounded by the light incident surface 61 and the main surface 81 of the holding substrate 8. That is, the recess is a space located on the −z axis side with respect to the light incident surface 61. The light source 7 is arranged side by side in the axial direction of the cylinder defined by the cylindrical surface of the light emitting surface 62. The “cylindrical axis” is an axis different from the optical axis C and is an axis parallel to the x-axis. Further, in the first embodiment, the optical axis of the light source 7 coincides with the optical axis C of the light distribution control element 6. For example, the optical axis C of the light distribution control element 6 passes through the center of the light source 7. Alternatively, for example, the optical axis C coincides with the direction with the highest luminous intensity in the light distribution of the light emitted from the light source 7. Alternatively, for example, the optical axis C coincides with the direction of the light distribution angle of 0 degrees in the light distribution curve of the light source 7.

  The light distribution control element 6 of the first embodiment has a rod shape. Therefore, the surface light source device 200 can include the light distribution control elements 6 in a number smaller than the number of the light sources 7 for the plurality of light sources 7 arranged in a line. For example, in the first embodiment, there is one light distribution control element 6. Thus, when the light distribution control element 6 has a rod-like shape, the surface light source device 200 can reduce the number of light distribution control elements 6 used. In addition, the mounting process only needs to fix one light distribution control element 6 to a plurality of light sources 7 arranged in a line, and fixing work such as adhesion is easy.

  Moreover, the rod-shaped light distribution control element 6 can be manufactured by extrusion molding. In the manufacturing method by extrusion molding, the length of the light distribution control element 6 can be freely changed. For example, even when the sizes of the liquid crystal display device 100 are different, it is possible to manufacture the light distribution control element 6 in which only the length is changed using the same mold. Since it is not necessary to change the mold of the light distribution control element 6 in accordance with the increase or decrease in the number of light sources 7, the light distribution control element 6 is highly versatile with respect to changes in the specifications of the surface light source device 200. Further, the surface light source device 200 can adjust the luminance only by changing the number of the light sources 7. Therefore, the surface light source device 200 having the optimal number and arrangement of the light sources 7 can be manufactured.

  The light distribution control element 6 is made of a transparent material, and for example, the transparent material is acrylic resin (PMMA).

  The light distribution control element 6 has a function of changing the light distribution of the light emitted from the light source 7. “Light distribution” refers to the luminous intensity distribution of a light source with respect to space. That is, the spatial distribution of light emitted from the light source. “Luminance” indicates the intensity of light emitted from a light emitter, and is obtained by dividing a light beam passing through a minute solid angle in a certain direction by the minute solid angle. That is, the luminous intensity is a physical quantity representing how much light is emitted from the light source. The light distribution control element 6 has the above-described configuration, thereby condensing or diverging light emitted from the light source 7 on the yz plane.

(Reflector)
As shown in FIG. 2, the reflector 9 is disposed on the main surface 81 side of the holding substrate 8. The reflector 9 includes a first reflection area 91 and a second reflection area 92. In the first embodiment, the first reflection region 91 and the second reflection region 92 are formed on the main surface 81 of the holding substrate 8. In FIG. 2, the installation surface 63 is in contact with the reflector 9, but is not necessarily in contact with it, and a gap may be provided between the installation surface 63 and the reflector 9. The second reflection region 92 is provided so as to correspond to the installation surface 63 included in the light distribution control element 6. The second reflection region 92 faces the installation surface 63. As shown in FIG. 3, the second reflection region 92 has a rectangular shape in plan view, and is provided on both sides of each light source 7. The shape and arrangement are examples, and for example, the second reflection region 92 may have an arc shape as shown in FIG. 4 or an elliptical shape as shown in FIG. .

  The reflectance of the second reflective region 92 is lower than the reflectance of the first reflective region 91. The difference between the reflectance of the first reflective region 91 and the reflectance of the second reflective region 92 is formed, for example, by adjusting the form of the resist layer of the main surface 81, for example, the composition or thickness. Alternatively, for example, the second reflective region 92 may be formed by disposing materials having different reflectivities or unevenness on the surface of the resist layer. Alternatively, for example, the second reflective region may be formed by arranging a sheet-like component having a lower reflectance than the main surface 81 on the main surface 81. In the first embodiment, the first reflection area 91 is the main surface 81 of the holding substrate 8 itself, and the second reflection area 92 is an area formed with a lower reflectance than the main surface 81. The second reflection region 92 may be a region having a light absorption rate (light absorption coefficient) higher than the light absorption rate of the first reflection region 91. In this case, it is desirable that the second reflection region 92 is a complete absorption band in the emission wavelength band of the light source 7.

(Diffusion plate)
As shown in FIG. 1, the diffusion plate 4 is disposed so as to cover the opening 53. The diffusion plate 4 is disposed on the light emission surface of the surface light source device 200. That is, the diffusing plate 4 is disposed on the + z axis side with respect to the reflecting portion 5. The diffusion plate 4 has, for example, a thin plate shape. Alternatively, for example, the diffusion plate 4 is in the form of a sheet. Alternatively, the diffusion plate 4 may include a transparent substrate and a diffusion film formed on the transparent substrate.

  The diffuser plate 4 diffuses the transmitted light. “Diffusion” means spreading. That is, light is scattered. In the following description, for example, “the light beam reaches the diffusion plate 4” is described. As described above, the diffusing plate 4 is disposed in the opening 53 of the reflecting portion 5. Therefore, the expression “the light beam reaches the diffusion plate 4” can be rephrased as “the light beam reaches the opening 53”. Further, the opening 53 or the diffusing plate 4 functions as a light emitting surface of the surface light source device 200. For this reason, the expression “the light beam reaches the diffusion plate 4” can be rephrased as “the light beam reaches the light emitting surface of the surface light source device 200”.

(Reflection part)
As shown in FIG. 1, the surface light source device 200 includes a reflecting unit 5. The reflector 5 has a container shape that can accommodate the light source 7, the reflector 9, and the light distribution control element 6. FIG. 6 is a plan view of the surface light source device 200. In FIG. 6, the diffusion plate 4 is not shown. As shown in FIGS. 1 and 6, the reflecting portion 5 includes a bottom surface 51 and four side surfaces 52 (side surfaces 52 a, 52 b, 52 c, 52 d) connected to the bottom surface 51. That is, the reflection unit 5 includes five surfaces. In the surface of the bottom surface 51, the light source 7 and the light distribution control element 6 held on the holding substrate 8 are arranged. The reflection unit 5 further includes a reflection surface 54 and an opening 53. The opening 53 of the reflection unit 5 is disposed on the side opposite to the bottom surface 51. The bottom surface 51 has a rectangular shape smaller than the rectangular shape of the diffusion plate 4. The bottom surface 51 is arranged in parallel with the diffusion plate 4, that is, in parallel with the light emitting surface. The side surface 52 connects the outer periphery of the bottom surface 51 and the outer periphery of the diffusion plate 4. That is, the four side surfaces 52 are inclined from the outer periphery of the bottom surface 51 toward the outer periphery of the diffusion plate 4.

  Hereinafter, the shape of the reflecting portion 5 will be described with reference to the xyz coordinate axes. Of the four side surfaces 52, the two side surfaces 52a and the side surfaces 52b connected to the sides parallel to the x-axis direction of the bottom surface 51 are inclined so that the distance between them increases toward the + z-axis direction. That is, the side surface 52a on the + y-axis direction side is inclined in the counterclockwise direction with respect to the yz plane as viewed from the −x-axis direction, with the connection portion with the bottom surface 51 as the center. Further, the side surface 52b on the −y-axis direction side is inclined in the clockwise direction with respect to the yz plane as viewed from the −x-axis direction, with the connection portion with the bottom surface 51 as the center. Of the four side surfaces 52, the two side surfaces 52c and the side surfaces 52d connected to the sides parallel to the y direction of the bottom surface 51 are also inclined so that the distance between them increases toward the + z-axis direction. That is, the side surface 52c on the −x axis direction side is inclined in the counterclockwise direction with respect to the zx plane as viewed from the −y axis direction, with the connection portion with the bottom surface 51 as the center. Further, the side surface 52d on the + x-axis direction side is inclined in the clockwise direction with respect to the zx plane as viewed from the −y-axis direction, with the connection portion with the bottom surface 51 being the center. An opening 53 is formed in the + z-axis direction facing the bottom surface 51 of the reflecting portion 5. The reflection part 5 and the diffusing plate 4 constitute a hollow container shape. In addition, as shown in FIG. 2, a part of the reflector 5 is sandwiched between the light distribution control element 6 and the housing 10 at positions on both sides of the holding substrate 8.

  As shown in FIGS. 1 and 2, the inner side of the reflecting portion 5 is a reflecting surface 54. That is, the inside of the reflecting portion 5 is a member that reflects light. The reflection part 5 is a reflection sheet which is a sheet-like member, for example. The reflection surface 54 of the reflection unit 5 may be a diffuse reflection surface, for example. The reflecting portion 5 is, for example, a light reflecting sheet based on a resin such as polyethylene terephthalate or a light reflecting sheet obtained by depositing metal on the surface of the substrate.

(Prerequisite technology related to light distribution control elements)
Prior to describing the operation and effect of the surface light source device 200 according to the first embodiment, the prerequisite technology of the present invention will be described. In addition, this base technology shows the surface light source device which is not provided with the reflector 9 as an example. FIG. 7 is a cross-sectional view of the periphery of the light source 7 of the surface light source device according to the base technology. FIG. 7 includes an illustration of a light ray 73a that is part of a light ray that is emitted from the light source 7 toward the + z-axis direction and spreads only in the yz plane. The light beam 73 a is a light beam emitted from the light source 7 at a narrow angle with respect to the optical axis C. The light beam 73 a emitted from the light source 7 is refracted at the light incident surface 61 and enters the light distribution control element 6. According to Snell's law, when a medium having a small refractive index is incident on a medium having a large refractive index, the refraction angle of the light beam is smaller than the incident angle. In addition, when a medium having a high refractive index is incident on a medium having a low refractive index, the refraction angle of the light beam is larger than the incident angle. When the light distribution control element 6 is made of acrylic resin, the light beam 73a is refracted to the −y axis direction side at the light incident surface 61 as shown in FIG. The light beam 73 a travels inside the light distribution control element 6 and reaches the light emitting surface 62. The light ray 73a is refracted in the direction in which the angle with respect to the optical axis C is further increased, that is, the −y axis direction side, by the light emitting surface 62 having a convex shape. FIG. 8 is a plan view of the light distribution control element 6 and is a diagram in which the xy plane is observed from the + z-axis side. FIG. 8 includes an illustration of a portion of the light rays 73 b emitted from the light source 7. The light ray 73b is a light ray that has a wider angle with respect to the optical axis C than the light ray 73a among light rays that are emitted from the light source 7 and spread only on the yz plane. The light beam spreading only on the yz plane means a light beam spreading only in the vertical direction in FIG. As shown in FIGS. 7 and 8, the light distribution control element 6 diverges the light emitted from the light source 7. The light beam 73 a or 73 b emitted from the light distribution control element 6 reaches the diffusion plate 4. Although illustration of each light beam is omitted, a part of the light beam that has reached the diffusion plate 4 shown in FIG. 1 is reflected and travels in the container-like space of the reflection unit 5. The light beam is reflected by the bottom surface 51 or the side surface 52 of the reflecting portion 5 and reaches the diffusion plate 4 again. The light is diffused while passing through the diffusion plate 4. And the light which permeate | transmitted the diffusion plate 4 turns into planar illumination light which has uniformity. The illumination light is applied to the back surface 1 b of the liquid crystal panel 1 through the optical sheet 3 and the optical sheet 2.

  FIG. 9 is a view showing a cross section around the light source 7 of the surface light source device that does not include the reflector 9. The surface light source device shown in FIG. 9 shows a state where an error has occurred in the arrangement position of the light distribution control element 6 with respect to the holding substrate 8. That is, there is a gap 64 between the light distribution control element 6 and the holding substrate 8. Since the light source 7 is mounted on the holding substrate 8, the displacement of the light distribution control element 6 relative to the holding substrate 8 means that the positional relationship between the light distribution control element 6 and the light source 7 is also displaced. When the gap 64 is generated between the light distribution control element 6 and the holding substrate 8, a part of the light rays 73 e out of the light emitted from the light source 7 enters the gap 64. The light beam 73 e is reflected by, for example, the main surface 81 of the holding substrate 8 and enters from the installation surface 63 of the light distribution control element 6. Then, the light beam 73 e is emitted from the light emission surface 62 of the light distribution control element 6. In this case, the relationship between the curvature of the incident installation surface 63 and the curvature of the light exit surface 62 is a function that functions as a convex lens. Therefore, the light beam 73e emitted from the light emitting surface 62 is collected and a focal line is generated. Further, the focal line is formed on the irradiated surface (for example, on the diffusion plate 4 or the back surface 1b) depending on the relationship between the curvature of the installation surface 63 and the curvature of the light emitting surface 62. Thus, if an error occurs in the arrangement position of the light distribution control element 6 with respect to the holding substrate 8, the uniformity of the illumination light decreases. Even if the arrangement position of each member constituting the surface light source device varies, it is preferable that the light distribution on the irradiated surface is uniform.

(Action of reflector)
In order to solve the problem included in the above-mentioned base technology, that is, the reduction in the uniformity of illumination light due to the displacement of the light distribution control element 6, the surface light source device 200 according to the present invention includes a second reflection as shown in FIG. Region 92 is included. The second reflection region 92 faces the installation surface 63. In FIG. 2, the installation surface 63 is in contact with the reflector 9, particularly the second reflection region 92. On the other hand, as shown in FIG. 10, a gap 64 may be provided between the installation surface 63 and the reflector 9. For example, the gap 64 is formed by shifting the installation position of the light distribution control element 6 in the + z-axis direction in the manufacturing process of the surface light source device 200. The light beam 73 f emitted from the light source 7 and incident on the gap 64 is incident on the second reflection region 92. Since the reflectivity of the second reflection region 92 is lower than that of the surrounding first reflection region 91, the light ray 73f hardly reflects. As a result, light rays passing through the optical path that causes the above-mentioned focal line are reduced as compared with the case where the second reflection region 92 is not installed. In addition, when the light absorption rate (light absorption coefficient) of the second reflection region 92 is higher than the light absorption rate of the first reflection region 91, light rays that pass through an optical path that causes a focal line are further reduced. .

(effect)
In the surface light source device 200 of the first embodiment, the second reflection region 92 is provided in the region on the main surface 81 where the light beam enters when the installation position of the light distribution control element 6 is shifted in the + z-axis direction. Yes. Therefore, the surface light source device 200 can reduce light rays that cause nonuniform brightness distribution on the irradiated surface. That is, with respect to the installation position of the light distribution control element 6 with respect to the holding substrate 8, the surface light source device 200 has a larger allowable positional deviation than the conventional configuration. That is, the surface light source device 200 can improve its robustness.

  In summary, the surface light source device 200 according to the first embodiment includes the light source 7, the holding substrate 8 on which the light source 7 is held on the main surface 81, and the reflector disposed on the main surface 81 side of the holding substrate 8. 9, a light distribution control element 6 that is disposed on the main surface 81 side of the holding substrate 8 so as to cover the light source 7, changes the light distribution of the light emitted from the light source 7, and the light emitted from the light distribution control element 6 And a diffusion plate 4 to be diffused. The light distribution control element 6 has an installation surface 63 that can come into contact with the reflector 9. The reflector 9 includes a first reflection area 91 and a second reflection area 92 having a lower reflectance than the first reflection area 91. The second reflection region 92 is disposed corresponding to the installation surface 63 of the light distribution control element 6. With the configuration as described above, the surface light source device 200 uses the light beam transmitted through the light output surface 62 of the light distribution control element 6 and the light beam reflected by the light output surface 62 to make the planar light uniformity. Can be improved. Furthermore, the surface light source device 200 can improve the robustness regarding the arrangement position of the light distribution control element 6 with respect to the holding substrate 8. The surface light source device 200 emits planar light having a highly uniform luminance distribution. Therefore, the surface light source device 200 can be used as, for example, a lighting device used for room lighting, in addition to the backlight of the liquid crystal display device 100. The surface light source device 200 can also be used for an advertisement display device that illuminates a photograph or the like from the back side, for example.

  Further, the light absorption rate of the second reflection region 92 of the surface light source device 200 according to the first embodiment is higher than the light absorption rate of the first reflection region 91. With such a configuration, an error occurs in the installation position of the light distribution control element 6, and even if the gap 64 is formed between the main surface 81 of the holding substrate 8 and the light distribution control element 6, the gap The light beam that has entered 64 is incident on the second reflection region 92 that has a higher light absorption rate than the first reflection region 91. The light ray incident on the second reflection region 92 is absorbed and hardly reflected. As a result, the surface light source device 200 can reduce the generation of focal lines. That is, the surface light source device 200 can improve the robustness regarding the arrangement position of the light distribution control element 6 with respect to the holding substrate 8. The surface light source device 200 can emit planar light having a highly uniform luminance distribution.

  In addition, the second reflection region 92 of the surface light source device 200 according to the first embodiment includes a rectangular shape, an arc shape, or an elliptical shape in the plan view of the holding substrate 8. With such a configuration, the surface light source device 200 can have an optimal arrangement of the second reflection regions 92 in accordance with the specifications and arrangement form of the light source 7. Therefore, the surface light source device 200 can reduce the generation of focal lines.

  The surface light source device 200 according to the first embodiment further includes a plurality of light sources 7 arranged in a row on the main surface 81 of the holding substrate 8. The light distribution control element 6 has a rod shape along the arrangement direction of the plurality of light sources 7. The light distribution control element 6 includes a light emitting surface 62 including a convex cylindrical surface having a curvature in the short direction of the rod shape, and a concave shape extending in the longitudinal direction of the rod shape and covering the plurality of light sources 7. And a light incident surface 61 including a curved surface or a flat surface. With such a configuration, the surface light source device 200 can include the light distribution control elements 6 that are fewer than the number of the light sources 7. That is, the surface light source device 200 can reduce the number of light distribution control elements 6 used. In addition, the mounting process only requires fixing a smaller number of light distribution control elements 6 than the number of light sources 7 to the plurality of light sources 7 arranged in a row, and the mounting operation is easy. Furthermore, the rod-shaped light distribution control element 6 can be manufactured by extrusion molding, and the manufacturing cost of the surface light source device 200 can be reduced.

  In addition, the surface light source device 200 according to the first embodiment further includes the reflection unit 5. The reflection unit 5 includes an opening 53 in which the diffusion plate 4 is installed and a reflection surface 54. The reflection unit 5 has a container shape that can accommodate the light source 7, the reflector 9, and the light distribution control element 6. The reflective surface 54 is disposed inside the container shape and reflects light emitted from the light distribution control element 6. The opening 53 emits the light emitted from the light distribution control element 6 and the light reflected by the reflecting surface 54 via the diffusion plate 4. With such a configuration, the surface light source device 200 can emit planar light with further improved uniformity.

  The liquid crystal display device 100 according to the first embodiment includes the surface light source device 200 and the liquid crystal panel 1. The liquid crystal panel 1 receives planar light emitted from the diffusion plate 4 of the surface light source device 200, converts the light into image light, and emits the image light. With such a configuration, the liquid crystal display device 100 can illuminate the liquid crystal panel 1 with the surface light source device 200 whose uniformity is improved as compared with the related art. As a result, the liquid crystal display device 100 can achieve higher video quality than before.

(Modifications and effects of light distribution control elements)
When a light ray enters a medium having a high refractive index into a medium having a low refractive index, total reflection can occur at the boundary surface of the medium. For example, when the material of the light distribution control element 6 is acrylic resin (PMMA) having a refractive index of 1.49, and the medium on the emission side, that is, the container-like space of the reflection unit 5 is air, the light is incident on the light emission surface 62. Light rays having an angle greater than 42.1 ° satisfy the total reflection condition. As a result, the light beam is reflected on the light emitting surface 62 toward the holding substrate 8 or the reflecting portion 5. That is, the light beam is reflected in the −z axis direction. By designing the shape of the light incident surface 61 and the shape of the light exit surface 62 so that the incident angle is 42.1 ° or less for light rays propagating only on the yz plane, Can be avoided. As a result, the light beam can be spread from the light exit surface 62 toward the diffusion plate 4.

  FIG. 11 is a cross-sectional view of the periphery of the light source 7 of the surface light source device. Unlike the light ray 73a shown in FIG. 7, the light ray 73c shown in FIG. 11 also has an angle component that spreads in the x-axis direction, that is, a vector component in the x-axis direction. FIG. 12 is a plan view of the light distribution control element 6 and is a diagram in which the xy plane is observed from the + z-axis side. FIG. 12 includes an illustration of some light rays 73 d emitted from the light source 7. The light ray 73d has a vector component in the x-axis direction. In addition, the light ray having an angle component spreading in the x-axis direction means a light ray spreading in an oblique direction or parallel to the x-axis in FIG. The light ray 73c shown in FIG. 11 and the light ray 73d shown in FIG. 12 have a larger incident angle with respect to the light exit surface 62 than the light ray 73a propagating only on the yz plane shown in FIG. This is because the vector component in the x-axis direction is combined with the incident angle with respect to the light exit surface 62. Therefore, a light beam having a large vector component in the x-axis direction easily satisfies the total reflection condition on the light exit surface 62.

  The light beam 73 c totally reflected by the light emitting surface 62 proceeds in the −z-axis direction, and a part thereof is refracted at the bottom surface or a part of the side surface of the light distribution control element 6 and reaches the reflecting portion 5. Although illustration is omitted, the light rays that have reached the reflecting portion 5 are diffusely reflected, and some of the light rays enter the light distribution control element 6 again, and the other light rays reach the diffusion plate 4. The light beam incident on the inside of the light distribution control element 6 is refracted and emitted by the light output surface 62. The light beam emitted from the light emitting surface 62 reaches the diffusion plate 4. A part of the light beam totally reflected by the light emitting surface 62 reaches the main surface 81 of the holding substrate 8. The light beam is reflected by the main surface 81 and enters the light distribution control element 6 again. Then, the light beam is refracted by the light emitting surface 62 of the light distribution control element 6 and reaches the diffusion plate 4.

  As described above, the light beam emitted from the light source 7 and reaching the diffusion plate 4 can be divided into two components, that is, a direct light component and a reflected light component. The direct light component is a light beam that reaches the diffusion plate 4 directly after being refracted by the light distribution control element 6 among the light beams emitted from the light source 7. The reflected light component is a light beam that reaches the diffusion plate 4 after being totally reflected inside the light distribution control element 6 and then diffusely reflected by the reflecting portion 5. Since the reflected light component includes the influence of diffuse reflection by the reflecting portion 5, it is difficult to control the spatial luminance distribution by the light distribution control element 6. The surface light source device 200 needs to control the light distribution including the reflected light component in order to efficiently use the light emitted from the light source 7. The surface light source device 200 preferably controls the direct light component and the reflected light component with the light distribution control element 6 in order to obtain illumination light having a uniform luminance distribution on the light exit surface. For example, it is necessary for the light distribution control element 6 to perform control such that the distribution of the direct light component is made non-uniform in accordance with the distribution of the reflected light component.

  In the first embodiment, the light distribution control element 6 is an optical element having a rod shape and arranged so as to cover the plurality of light sources 7. However, the light distribution control element 6 is not limited to a rod-shaped optical element. The surface light source device 200 according to the present invention has the same effect as that of the first embodiment even if one light distribution control element is attached to one light source. However, in a surface light source device including individual light distribution control elements for each light source, the number of light distribution control elements used increases. Moreover, in the manufacturing process, it is necessary to fix each light distribution control element (lens) to each light source, and the number of processes increases.

  On the other hand, the surface light source device 200 described in the first embodiment can be provided with a smaller number of light distribution control elements 6 than the number of the light sources 7 for the plurality of light sources 7 arranged in a row. For example, the number of rod-shaped light distribution control elements 6 may be one. Thus, the surface light source device 200 can reduce the number of light distribution control elements 6 used. In addition, the mounting process only needs to fix one light distribution control element 6 to a plurality of light sources 7 arranged in a line, and fixing work such as adhesion is easy.

  Further, as the light distribution control element, an optical element that requires positioning in the x direction or the y direction with respect to the light source, such as a lens array in which a plurality of lenses are arranged on the xy plane, can be considered. However, as the number of light sources increases or decreases, it is necessary to change the size of the optical element that covers these light sources. That is, it is necessary to change the mold for manufacturing the optical element by increasing or decreasing the number of light sources. Therefore, such an optical element has low versatility with respect to a change in specifications of the surface light source device.

  On the other hand, since the light distribution control element 6 according to the first embodiment has a rod-like shape, it can be manufactured by extrusion molding. In the manufacturing method by extrusion molding, the length of the light distribution control element 6 can be freely changed. For example, even when the sizes of the liquid crystal display device 100 are different, it is possible to manufacture the light distribution control element 6 in which only the length is adjusted using the same mold. Since it is not necessary to change the mold of the light distribution control element 6 in accordance with the increase or decrease in the number of light sources 7, the light distribution control element 6 is highly versatile with respect to changes in the specifications of the surface light source device 200. The luminance of the surface light source device 200 can be adjusted by simply changing the number of the light sources 7. Therefore, the surface light source device 200 having the optimal number and arrangement of the light sources 7 can be manufactured.

  In the first embodiment, the light distribution control element 6 is a transparent material, but may be a material including a diffusing material. The light rays that have entered the light distribution control element 6 are diffused by the diffusing material and change the traveling direction. The traveling direction of the light beam traveling inside the light distribution control element 6 is changed in a random direction. The light beam whose traveling direction has been changed reaches the light emitting surface 62 of the light distribution control element 6. The light emitted from the light emitting surface 62 of the light distribution control element 6 can irradiate a wide range.

  In addition, a minute uneven shape may be formed on the light incident surface 61 or the light emitting surface 62 of the light distribution control element 6. The uneven shape does not necessarily need to be formed in the entire area of the light incident surface 61 and the light emitting surface 62. For example, the uneven shape may be formed only on the light incident surface 61. Further, for example, the concavo-convex shape may be formed only in a partial region of the light emitting surface 62. In other words, the uneven shape may be provided in a partial region of the light incident surface 61 or the light emitting surface 62. Further, the uneven shape does not need to have the same roughness in all regions. For example, the uneven shape of the light incident surface 61 may be smaller than the uneven shape of the light emitting surface 62.

  The direction of travel of light rays incident on the concavo-convex shape changes randomly. Therefore, the light distribution control element 6 having a concavo-convex shape can relax the bright line. The “bright line” is a region having a high luminance formed in a linear shape on the light emission surface (the diffusion plate 4) of the surface light source device 200. Further, the uneven shape can alleviate luminance unevenness on the light emitting surface (the diffuser plate 4) of the surface light source device 200, which is generated by arranging a plurality of light sources 7 side by side. That is, the uneven shape can alleviate the difference between the bright part and the dark part. Further, due to the uneven shape, the light distribution control element 6 can distribute and irradiate light over a wide range.

  However, the degree of light diffusion due to the diffusing material or the uneven shape needs to be smaller than the degree of light refraction at the light incident surface 61 and the light emitting surface 62. This is because, when light scattering due to the diffusing material or the concavo-convex shape becomes dominant, it is difficult to refract the light as designed and distribute the light on the light incident surface 61 and the light emitting surface 62 of the light distribution control element 6. Because it becomes. The light distribution is directed to the light emitting surface of the surface light source device 200, that is, the diffusion plate 4 by refraction depending on the shape of the light distribution control element 6. Therefore, when the effect of light diffusion due to the diffusing material or the uneven shape increases, the luminance near the position where the light source 7 is arranged is high, and the luminance may decrease as the distance from the light source increases.

<Embodiment 2>
The surface light source device 201 and the liquid crystal display device including the surface light source device 201 in the second embodiment will be described. Note that the description of the same configuration and operation as in the first embodiment will be omitted.

  FIG. 13 is a cross-sectional view showing a configuration around the light source 7 of the surface light source device 201 according to the second embodiment. The surface light source device 201 includes a first reflection region 91 between the light distribution control element 6 and the holding substrate 8. FIG. 14A is a plan view of the main surface 81 of the holding substrate 8, and FIG. 14B is a plan view of the first reflection region 91. FIG. 13 described above shows a cross section taken along the line A-A ′ of FIG.

  Similar to the first embodiment, the second reflection region 92 is formed on the main surface 81 of the holding substrate 8 and is disposed corresponding to the installation surface 63 of the light distribution control element 6. The reflectance of the second reflection region 92 is formed lower than that of the main surface 81, for example. The second reflection region 92 has a rectangular shape in plan view, and is provided on both sides of each light source 7. The shape and arrangement are examples. For example, the second reflection region 92 may have an arc shape as shown in FIG. 4 or an ellipse shape as shown in FIG. Also good.

  As shown in FIG. 13, the first reflection region 91 is disposed between the light distribution control element 6 and the holding substrate 8. The first reflection area 91 is arranged closer to the installation surface 63 side of the light distribution control element 6 than the second reflection area 92. In the second embodiment, a part of the first reflection region 91 is stacked on the second reflection region 92. As shown in FIG. 14B and FIG. 13, the first reflection region 91 includes a plurality of openings 93. The opening 93 is arranged corresponding to the position of the second reflection region 92. In the second embodiment, the outer shape of the first reflection region 91 in plan view has a strip shape. The first reflection area 91 is, for example, a reflection sheet. The shape of the opening 93 in the first reflection region 91 is appropriately formed corresponding to the planar shape of the second reflection region 92. Further, the first reflection area 91 does not have to cover the main surface 81 except for the second reflection area 92 and the light source 7. That is, in the second embodiment, a part of the main surface 81 of the holding substrate 8 is covered with the first reflection region 91. Further, in the second embodiment, the reflectance of the first reflection region 91 is higher than the reflectance of the second reflection region 92 and the reflectance of the main surface 81 of the holding substrate 8.

  A light beam 73 g emitted from the light source 7 and traveling to the opening 93 enters the second reflection region 92. Since the reflectivity is lower than that of the surrounding first reflection region 91 and main surface 81, the light beam is hardly reflected. As a result, light rays that pass through the optical path that causes the above-mentioned focal line are reduced as compared with the case where the second reflection region 92 is not formed.

  In the second embodiment, the light distribution control element 6 is disposed on the reflector 9, particularly in contact with the first reflection region 91, but the surface light source device 201 includes the light distribution control element 6 and the first light distribution control element 6. An air gap (not shown) may be provided between the reflective area 91 and the reflective area 91. Note that the gap is generated when the light distribution control element 6 is shifted in the + z-axis direction as in the first embodiment. The light beam emitted from the light source 7 and incident on the gap enters the second reflection region 92 corresponding to the position of the opening 93. Since the reflectance is lower than that of the surrounding first reflection region 91, the light beam is hardly reflected. As a result, the light beam passing through the optical path in which the above-mentioned focal line is generated is reduced as compared with the case where the reflector 9 is not formed.

  Further, in the surface light source device 201 provided with the first reflection region 91, the light beam that has been reflected by the main surface 81 conventionally is reflected by the first reflection region 91. The reflectance of the first reflection region 91 is higher than that of the main surface 81 of the holding substrate 8. Therefore, the surface light source device 201 can improve the light use efficiency compared to the case where the first reflection region 91 is not provided. In addition, the distribution of the irradiated surface can be adjusted by changing the size and shape of the opening 93 of the first reflection region 91.

  The surface light source device 201 includes the first reflection region 91 and the reflection unit 5 separately, but they may be an integral part. For example, the first reflection region 91 or the reflection portion 5 may be bent at the end of the holding substrate 8 so that the first reflection region 91 and the reflection portion 5 are connected. Even with such a surface light source device, the same effect can be obtained, for example, no focal line is generated. Furthermore, such a surface light source device can reduce the number of components.

(effect)
In summary, the first reflection region 91 of the surface light source device 201 according to the second embodiment is arranged closer to the installation surface 63 of the light distribution control element 6 than the second reflection region 92. The first reflection region 91 has an opening 93 corresponding to the second reflection region 92. The second reflection region 92 faces the installation surface 63 of the light distribution control element 6 through the opening 93 of the first reflection region 91. With the above configuration, the surface light source device 201 improves the robustness in the positional relationship between the light distribution control element 6 and the holding substrate 8. The surface light source device 200 can emit planar light having a highly uniform luminance distribution. In addition, it is not necessary to form both the first reflection area 91 and the second reflection area 92 on the main surface 81 of the holding substrate 8, and only the first reflection area 91 such as a sheet is covered on the second reflection area 92. The reflector 9 can be formed. In addition, the surface light source device 201 can adjust the distribution of the irradiated surface according to the size and shape of the opening 93 of the first reflection region 91.

  Further, the reflection surface 54 of the reflection unit 5 included in the surface light source device 201 according to the second embodiment may be integrated with the first reflection region 91 of the reflector 9. With such a configuration, the surface light source device 201 can reduce the number of components of the reflector 9.

(Modification of Embodiment 2)
In the second embodiment, the example in which the second reflection region 92 is formed on the main surface 81 of the holding substrate 8 has been described. The second reflection region 92 may be the main surface 81 of the holding substrate 8 itself. In this case, the reflectance of the first reflection region 91 is formed to be higher than the reflectance of the main surface 81 of the holding substrate 8. That is, the reflectance of the second reflective region 92 is lower than the reflectance of the first reflective region 91. With the configuration as described above, the surface light source device 201 does not need to newly provide the second reflection region 92 on the main surface 81 of the holding substrate 8. Therefore, the cost of the surface light source device 201 can be reduced.

  In each of the embodiments described above, terms such as “parallel” and “vertical” are used to indicate the positional relationship between parts or the shape of the parts. These include ranges that take into account manufacturing tolerances and assembly variations. For this reason, the description of the positional relationship between the components or the shape of the components within the scope of claims includes a range that takes into account manufacturing tolerances or assembly variations.

  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. Although the present invention has been described in detail, the above description is illustrative in all aspects, and the present invention is not limited thereto. It is understood that countless variations that are not illustrated can be envisaged without departing from the scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 Liquid crystal panel, 4 Diffuser plate, 5 Reflection part, 53 Opening part, 54 Reflection surface, 6 Light distribution control element, 61 Light incident surface, 62 Light output surface, 63 Installation surface, 64 Air gap, 7 Light source, 8 Holding substrate, 81 main surface, 9 reflector, 91 first reflection region, 92 second reflection region, 93 aperture, 100 liquid crystal display device, 200 surface light source device, C optical axis.

Claims (8)

A light source;
A holding substrate on which the light source is held on the main surface;
A reflector disposed on the main surface side of the holding substrate;
A light distribution control element that is arranged on the main surface side of the holding substrate so as to cover the light source, and changes a light distribution of light emitted from the light source;
A diffusion plate for diffusing the light emitted from the light distribution control element;
The light distribution control element has an installation surface capable of contacting the reflector,
The reflector includes a first reflection region and a second reflection region having a lower reflectance than the first reflection region,
The surface light source device, wherein the second reflection region is disposed corresponding to the installation surface of the light distribution control element. The first reflection region is disposed closer to the installation surface of the light distribution control element than the second reflection region, and has an opening corresponding to the second reflection region,
2. The surface light source device according to claim 1, wherein the second reflection region is opposed to the installation surface of the light distribution control element through the opening of the first reflection region.   The surface light source device according to claim 1, wherein a light absorption rate of the second reflection region is higher than a light absorption rate of the first reflection region.   The surface light source device according to any one of claims 1 to 3, wherein the second reflection region includes a rectangular shape, an arc shape, or an elliptical shape in a plan view of the holding substrate. A plurality of the light sources arranged in a row on the main surface of the holding substrate;
The light distribution control element has a rod-like shape along an arrangement direction of the plurality of light sources, and includes a light emitting surface including a convex cylindrical surface having a curvature in a short direction of the rod-like shape, and the rod-like shape 5. The surface light source device according to claim 1, further comprising: a light incident surface including a concave curved surface or a flat surface extending in the longitudinal direction of the shape and covering the plurality of light sources. A reflection portion including an opening in which the diffusion plate is installed and a reflection surface, and having a container shape capable of accommodating the light source, the reflector, and the light distribution control element;
The reflective surface is disposed inside the container shape, reflects light emitted from the light distribution control element,
6. The surface light source device according to claim 1, wherein the opening emits light emitted from the light distribution control element and light reflected by the reflection surface through the diffusion plate. 7. .   The surface light source device according to claim 6, wherein the reflection surface of the reflection unit is integrated with the first reflection region of the reflector. A surface light source device according to any one of claims 1 to 7,
A liquid crystal display device comprising: a liquid crystal panel that receives planar light emitted from the diffusion plate of the surface light source device, converts the light into image light, and emits the image light.

Images