JP6501157B2 - Surface light source device and display device - Google Patents

Description

  The present invention relates to a surface light source device, and more particularly to a surface light source device capable of reducing light emitted toward a direction largely deviated from the front direction. The present invention also relates to a display device in which the surface light source device is incorporated.

  BACKGROUND A surface light source device that emits light in a plane is widely used, for example, as a backlight incorporated in a liquid crystal display device to illuminate a liquid crystal display panel from the back side. Surface light source devices for liquid crystal display devices can be roughly classified into a direct type in which a light source is disposed immediately below a light guide plate and an edge light type (also referred to as a side light type) in which a light source is disposed to the side of a light guide plate. being classified.

  The edge light type surface light source device has a structural feature that enables thinning of the surface light source device as compared with the direct type surface light source device. From this structural feature, the edge light type surface light source device has been applied mainly to a display device mainly for a notebook type personal computer (hereinafter, also simply referred to as a "note type PC").

  For example, an edge light type surface light source device described in Patent Document 1 includes a light guiding surface including light emitting surfaces and a back surface facing each other, and a light incident surface forming a part of a side surface between the light emitting surface and the back surface. It has a light plate and a light source disposed facing the side of the light guide plate. An optical sheet is disposed to face the light exit surface of the light guide plate, and a plurality of unit prism elements are arranged on the surface of the optical sheet facing the light guide plate.

  In the surface light source device described in Patent Document 1, the light from the light source that has entered the light guide plate from the light entrance surface is guided while being repeatedly reflected between the light exit surface and the back surface, and is extracted from the light exit surface. The unit prism element can change its direction in the front direction.

JP 2004-227934 A

  The light traveling in the light guide plate is not only light that repeats total reflection on the light exit surface and the back surface, but also light whose direction is changed in a direction different from the total reflection direction on the back surface or a reflection sheet after transmitting the back surface. It also includes the light returned again. Light directed in a direction different from such an intended direction is not bent as intended by the unit prism element after being extracted from the light exit surface, and is directed toward a direction greatly inclined with respect to the front direction. The case emitted from the surface light source device can be seen.

  Light emitted toward such a direction largely deviated from the frontal direction causes reflection on an object and a decrease in contrast. In particular, when the liquid crystal display device is used for on-vehicle use, light emitted in a direction largely deviated from the front direction is recognized as being reflected on the front window, which causes a reduction in the productability.

  The present invention has been made in consideration of such points, and provides a surface light source device and a display device capable of reducing light emitted toward a direction largely deviated from the front direction. To aim.

The surface light source device according to the present invention comprises a light exit surface, a back surface opposite to the light exit surface, at least one light entrance surface consisting of a portion of a side surface between the light exit surface and the back surface, and a portion of the side surface. A light guide plate having an opposite surface opposed to the one light incident surface along a first direction;
A light source disposed to face the light incident surface of the light guide plate;
A sheet-like emission angle control layer disposed opposite to the light exit surface of the light guide plate;
A direction which is arranged along the first direction between the emission angle control layer and the light guide plate and which is not parallel to the first direction and which is along the sheet surface of the sheet-like emission angle control layer A plurality of unit optical elements extending along the
The emission angle control layer is
A plurality of first portions arranged along the arrangement direction along the sheet surface of the emission angle control layer, each being not parallel to the arrangement direction and along the sheet surface of the emission angle control layer A plurality of first portions extending longitudinally,
The first portion and a plurality of second portions alternately arranged in the arrangement direction, the plurality of second portions including a light absorbing material that absorbs light;
The surface of the first portion facing the light guide plate has a length W1 along the arrangement direction, and the surface of the second portion facing the light guide plate has a length W2 along the arrangement direction Have
0.30 ≦ W1 / (W1 + W2)
Meet the relationship.

  In the surface light source device according to the present invention, the relationship of W1 / (W1 + W2) <0.96 may be satisfied.

  In the surface light source device according to the present invention, the arrangement direction of the first portion may be along the first direction.

  In the surface light source device according to the present invention, the plurality of unit optical elements may be arranged on a surface facing the light guide plate side of the emission angle control layer. In other words, in the surface light source device according to the present invention, an optical sheet is configured by the emission angle control layer and the plurality of unit optical elements provided on the surface facing the light guide plate side of the emission angle control layer. It may be

  In the surface light source device according to the present invention, the unit optical element includes a light transmitting surface, and a light reflecting surface located closer to the opposite surface than the light transmitting surface along the first direction, At least a portion of the light emitted from the light exit surface of the light guide plate may be transmitted through the light transmission surface of the unit optical element and then totally reflected by the light reflection surface toward the emission angle control layer .

  In the surface light source device according to the present invention, the back surface of the light guide plate includes a plurality of inclined surfaces arranged in the first direction, and each inclined surface has an end located close to the opposite surface. The light emitting device may be inclined with respect to both the normal direction of the emission angle control layer and the first direction so as to be closer to the light output surface than the end located closer to the light surface side.

  A display device according to the present invention includes a surface light source device having any of the features described above, and a liquid crystal display panel disposed to face the surface light source device.

  The display device according to the present invention may be an on-vehicle display device installed in a vehicle, and the arrangement direction may correspond to the vertical direction.

  According to the present invention, the second portion of the emission angle control layer can block the light to be emitted in the direction largely deviated from the front direction, and as a result, the light greatly deviates from the front direction It is possible to reduce the light emitted.

FIG. 1 is a view for explaining an embodiment according to the present invention, and is a cross-sectional view showing a schematic configuration of a display device and a surface light source device. FIG. 2 is a cross-sectional view showing a surface light source device constituting the display shown in FIG. FIG. 3 is a perspective view showing a light guide plate incorporated in the surface light source device of FIG. 1 from the side of the light exit surface. FIG. 4 is a perspective view showing a light guide plate incorporated in the surface light source device of FIG. 1 from the back side. FIG. 5 is a perspective view showing an optical sheet incorporated in the surface light source device of FIG. FIG. 6 is a cross-sectional view of the unit optical element shown in FIG. FIG. 7 is a cross-sectional view showing the emission angle control layer incorporated in the optical sheet shown in FIG. FIG. 8 is a cross-sectional view for explaining the operation of the surface light source device shown in FIG. FIG. 9 is a perspective view showing an example in which the display shown in FIG. 1 is incorporated in a car. FIG. 10 is a perspective view showing a modification of the display shown in FIG. FIG. 11 is a cross-sectional view for explaining the dimensions of the surface light source device according to the embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to the present specification, for the sake of easy illustration and understanding, the scale, the dimensional ratio in the vertical and horizontal directions, etc. are appropriately changed from those of the actual one and exaggerated.

  1 to 11 are views for explaining an embodiment according to the present invention. Among these, FIG. 1 is a cross-sectional view showing a schematic configuration of the display device 10, and FIG. 2 is a cross-sectional view showing a surface light source device 20. 3 and 4 are perspective views showing the light guide plate 30, and FIG. 5 is a perspective view showing the optical sheet 60.

  As shown in FIG. 1, the display device 10 includes a liquid crystal display panel 15 as a transmissive display unit, and a surface light source device 20 disposed on the back side of the liquid crystal display panel 15 and illuminating the liquid crystal display panel 15 in a plane from the back side. And have. The display device 10 has a display surface 11 for displaying an image. The liquid crystal display panel 15 functions as a shutter that controls transmission or blocking of light from the surface light source device 20 for each pixel, and is configured to display an image on the display surface 11.

  The illustrated liquid crystal display panel 15 is disposed between the upper polarization plate 13 disposed on the light emission side, the lower polarization plate 14 disposed on the light incident side, and the upper polarization plate 13 and the lower polarization plate 14. And a liquid crystal layer cell 12. The polarizing plates 14 and 13 separate linearly incident light into two orthogonal polarization components (P wave and S wave) and vibrate in one direction (direction parallel to the transmission axis) (for example, P wave) And has a function of absorbing a linearly polarized light component (for example, S wave) oscillating in the other direction (parallel to the absorption axis) orthogonal to the one direction.

  An electric field can be applied to the liquid crystal layer 12 in each region forming one pixel. Then, the alignment direction of the liquid crystal molecules in the liquid crystal layer 12 changes depending on the presence or absence of the application of the electric field. As an example, when passing through the liquid crystal layer 12 to which an electric field is applied, the polarization component in the specific direction transmitted through the lower polarizing plate 14 disposed on the light entrance side rotates its polarization direction by 90 °, while When passing through the liquid crystal layer 12 which is not applied, the polarization direction is maintained. In this case, whether the polarized light component vibrating in the specific direction transmitted through the lower polarizing plate 14 is further transmitted through the upper polarizing plate 13 disposed on the light exit side of the lower polarizing plate 14 depending on the presence or absence of the electric field application to the liquid crystal layer 12 Alternatively, it can be controlled to be absorbed by the upper polarizing plate 13 and blocked.

  Thus, in the liquid crystal display panel 15, transmission or blocking of light from the surface light source device 20 can be controlled for each pixel. The details of the liquid crystal display panel 15 are described in various known documents (for example, "flat panel display large dictionary (Tatsuo Uchida, Hiraki Uchiike ed.)" Published by 2001 Industrial Research Association), and here The detailed description above is omitted.

  Next, the surface light source device 20 will be described. The surface light source device 20 has a light emitting surface 21 that emits light in a plane, and in the present embodiment, is used as a device that illuminates the liquid crystal display panel 15 from the back side.

  As shown in FIG. 1, the surface light source device 20 is configured as an edge light type surface light source device, and is disposed on the side of the light guide plate 30 and one side (left side in FIG. 1) of the light guide plate 30. The light source 24 and the optical sheet 60 and the reflection sheet 28 respectively disposed on both sides (the light output side and the back surface side) of the light guide plate 30 are provided. In the illustrated example, the optical sheet 60 is disposed to face the liquid crystal display panel 15, and the light emission surface 21 of the surface light source device 20 is defined by the emission angle control layer 65 of the optical sheet 60.

  The light guide plate 30 has a light emitting surface 31 formed by one main surface on the liquid crystal display panel 15 side, a back surface 32 formed of the other main surface facing the light emitting surface 31, a light emitting surface 31 and a back surface 32 And an extending side surface. Of the side surfaces, one of the two surfaces facing in the first direction d1 defines the light incident surface 33. As shown in FIG. 1, a light source 24 is provided to face the light incident surface 33. Light incident from the light incident surface 33 into the light guide plate 30 is directed to the opposite surface 34 facing the light incident surface 33 along the first direction (light guiding direction) d1, and substantially in the first direction (light guiding direction) d1. The light is guided in the light guide plate 30 along the

  In the illustrated example, the light exit surface 31 of the light guide plate 30 has the same shape as the display surface 11 of the liquid crystal display device 10 and the light emission surface 21 of the surface light source device 20 (in FIG. The shape seen) is formed in a square shape. As a result, the light guide plate 30 is generally configured as a rectangular parallelepiped member having a pair of main surfaces (the light emitting surface 31 and the back surface 32) in which the side in the thickness direction is smaller than the other sides. The side surface defined between the pair of main surfaces includes four surfaces. Similarly, the optical sheet 60 and the reflective sheet 28 are generally configured as rectangular solid members whose sides in the thickness direction are relatively smaller than the other sides.

  The light source 24 may be configured, for example, in various modes such as a fluorescent lamp such as a linear cold cathode tube, a point LED (light emitting diode), an incandescent lamp and the like. In the present embodiment, the light sources 24 are arranged in a line along the longitudinal direction of the light incident surface 33 (in FIG. 1, in the direction orthogonal to the paper surface, ie, the front and back direction of the paper surface) The light emitter 25 is specifically configured by a large number of light emitting diodes (LEDs). 3 and 4 show the arrangement positions of a large number of point light emitters 25 forming the light source 24. As shown in FIG.

  By the way, in the present specification, the “light output side” refers to the light source 24, the light guide plate 30, the output angle control layer 65, the liquid crystal display panel 15, and the components of the display device 10 without going back. 10 is the downstream side (observer side, for example, the upper side of the sheet in FIG. 1) in the traveling direction of light toward the observer, and “light incident side” means the light source 24, the light guide plate 30, and the light emission The angle control layer 65, the liquid crystal display panel 15, and the components of the display device 10 are advanced without going back, and are upstream in the traveling direction of light emitted from the display device 10 toward the observer.

  Moreover, in the present specification, terms such as “sheet”, “film”, “plate” and the like are not distinguished from one another based only on the difference in designation. Thus, for example, "sheet" is a concept that also includes members that may be called films or plates.

  Furthermore, in the present specification, the “sheet surface (plate surface, film surface)” corresponds to the planar direction of the target sheet-like member when the target sheet-like member is viewed generally and globally. Point to the face. In the present embodiment, the plate surface of the light guide plate 30, the sheet surface of the emission angle control layer 65, the sheet surface of the reflective sheet 28, the panel surface of the liquid crystal display panel, the display surface 11 of the display device 10, and the surface light source device The twenty light emitting surfaces 21 are parallel to one another. Furthermore, in the present specification, the normal direction of the sheet-like member refers to the normal direction to the sheet surface of the target sheet-like member. Further, the normal direction nd of the emission angle control layer 65 matches the front direction of the surface light source device 20 and the front direction of the display device 10.

  Moreover, “unit prism”, “unit shape element”, “unit optical element”, and “unit lens” in the present specification exert an optical action such as refraction or reflection on light to determine the traveling direction of the light. It refers to elements that have the function of changing, and they are not distinguished from one another based only on the difference in designation.

  Next, the light guide plate 30 will be described in more detail.

  As well illustrated in FIG. 2, the back surface 32 of the light guide plate 30 has a plurality of inclined surfaces 37 arranged in the first direction d1, a rising surface 38 extending in the normal direction nd of the light guide plate 30, And a connecting surface 39 extending in the plate surface direction of the light plate 30. In the example shown in FIG. 2, the inclined surface 37, the rising surface 38, and the connection surface 39 are repeatedly arranged along the first direction d1. The inclined surfaces 37, the rising surfaces 38, and the connection surfaces 39 extend along the second direction d2 which extends in the plane of the light guide plate 30 so as to intersect the first direction d1. In the present embodiment, the second direction d2 is orthogonal to the first direction d1.

  The inclined surface 37 is an element for adjusting the traveling direction of the light guided in the light guide plate 30 along the first direction d 1 and extracting the light from the light guide plate 30. As shown in FIG. 2, each inclined surface 37 is closer to the light exit surface 31 than the end E2 closer to the light incident surface 33, with the end E1 located closer to the opposite surface 34, It is inclined with respect to the normal direction nd and the first direction d1. In other words, each inclined surface 37 approaches the light output surface 31 along the normal direction nd of the light guide plate 30 as it goes from the light incident surface 33 to the opposite surface 34 side, It is inclined with respect to both of the 1 directions d1. In particular, in the cross section shown in FIG. 2, assuming that the inclined surface 37 forms an angle with the first direction d1 as the inclination angle θ, the inclination angles θ of the plurality of inclined surfaces 37 are equal to one another.

  The rising surface 38 is a surface which is not expected to exert an optical action on the light guided in the light guide plate 30, and the connection surface 39 is a surface which is not parallel to the inclined surface 37 and The light guided in the light plate 30 has an optical action different from that of the inclined surface 37. The connection surface 39 in the present embodiment is parallel to the plate surface of the light guide plate 30.

  According to such a light guide plate 30, among light repeating reflection between the light exit surface 31 and the back surface 32, the light reflected by the connection surface 39 has an incident angle at the time of incidence on the light exit surface 31 thereafter. With respect to the light that is maintained and reflected by the inclined surface 37, the incident angle when it subsequently enters the light exit surface 31 decreases. When the incident angle to the light exit surface 31 becomes less than the total reflection critical angle by the reflection at the inclined surface 37, this light is emitted from the light exit surface 31 of the light guide plate 30.

  In particular, in the present embodiment, the distribution of the inclined surface 37 and the connection surface 39 in the back surface 32 changes along the first direction d1 which is the light guide direction. By adjusting the distribution of the inclined surface 37 and the connection surface 39 along the first direction d1, the distribution of the amount of light emitted from the light guide plate 30 along the first direction d1 can be adjusted. In the example shown in FIG. 2, as the incident surface 33 approaches the opposite surface 34 along the first direction d1, the ratio of the inclined surface 37 in the back surface 32 increases. According to such a configuration, the emission of light from the light guide plate 30 is promoted in a region separated from the incident surface 33 along the light guide direction, and the amount of emitted light decreases as it is separated from the incident surface 33. Can be effectively prevented.

  Next, the configuration of the light exit surface 31 of the light guide plate 30 will be described. Unit prisms 50 are arranged on the light exit surface 31 of the light guide plate 30. The plurality of unit prisms 50 are arranged in the arrangement direction (left and right direction in FIG. 3) which intersects the first direction d1 and is parallel to the plate surface of the light guide plate 30. Each unit prism 50 linearly extends in the plane of the light guide plate 30 in a direction intersecting the arrangement direction.

  In particular, in the present embodiment, as shown in FIG. 3, the plurality of unit prisms 50 are arranged without gaps in the second direction (arrangement direction) d2 orthogonal to the first direction d1. Therefore, the light exit surface 31 of the light guide plate 30 is configured as the inclined surfaces 35 and 36 formed by the surface of the unit prism 50. Each unit prism 50 is formed in a columnar shape, and has the same cross-sectional shape along the longitudinal direction.

  Next, the cross-sectional shape of each unit prism 50 in a cross section parallel to both the arrangement direction (second direction) d2 of the unit optical elements and the normal direction to the plate surface of the light guide plate 30 will be described. As understood from FIG. 4, the cross-sectional shape of each unit prism 50 in the cross section is a shape that tapers toward the light output side. That is, in the cross section, the width of the unit prism 50 parallel to the plate surface of the light guide plate 30 becomes smaller along with the normal direction of the light guide plate 30 as it is separated from the back surface 32.

  Here, the dimensions of the light guide plate 30 may be set as follows, as an example. For example, the thickness of the light guide plate 30 can be 0.3 mm to 6 mm. In addition, the length or width of the unit prism 50 in the second direction d2 can be 10 μm to 500 μm.

  The light guide plate 30 configured as described above can be manufactured by forming the inclined surface 37 and the unit prism 50 on a base material, or by extrusion. Various materials can be used as the material of the light guide plate 30. However, materials widely used as materials for optical sheets to be incorporated in display devices, and having excellent mechanical properties, optical properties, stability, processability, etc., as well as inexpensively available materials, such as acrylic resin, polystyrene, polycarbonate A transparent resin mainly composed of one or more of polyethylene terephthalate, polyacrylonitrile and the like, and a reactive resin of epoxy acrylate and urethane acrylate (ionizing radiation curable resin and the like) may be suitably used. In addition, a diffusive component having a function of diffusing light can be added to the light guide plate 30 as needed. The diffusion component is, for example, using particles made of a transparent material such as silica (silicon dioxide), alumina (aluminum oxide), acrylic resin, polycarbonate resin, silicone resin, etc. having an average particle diameter of about 0.5 to 100 μm. Can.

  When manufacturing the light guide plate 30 by curing the ionizing radiation curable resin on the base material, the sheet-like land portion to be positioned between the unit prism 50 and the base material together with the unit prism 50 is used as a base It may be formed on a material. In this case, it is possible to use, as a base material, a plate made of a resin material which is extrusion-molded together with the light diffusing particles. On the other hand, the light guide plate 30 manufactured by extrusion molding can be formed as an integral body.

  Returning to FIG. 2, the reflective sheet 28 is disposed to face the back surface 32 of the light guide plate 30. The reflection sheet 28 is a member for reflecting the light leaked from the back surface 32 of the light guide plate 30 and returning the light back into the light guide plate 30. The reflection sheet 28 is formed of a white scattering reflection layer, a sheet made of a material having high reflectance such as metal, a sheet including a thin film (for example, a metal thin film) made of a material having high reflectance as a surface layer, etc. obtain. The reflection on the reflection sheet 28 may be regular reflection (specular reflection) or diffuse reflection. When the reflection on the reflection sheet 28 is diffuse reflection, the diffuse reflection may be isotropic diffuse reflection or anisotropic diffuse reflection.

  Next, the optical sheet 60 disposed to face the light exit surface 31 of the light guide plate 30 will be described. The optical sheet 60 is for changing the traveling direction of the light that has entered from the light entrance side, emitting the light from the light exit side, and controlling the emission direction of the emitted light. As shown in FIG. 5, the optical sheet 60 is formed on a sheet-like emission angle control layer 65 disposed on the light exit surface 31 side of the light guide plate 30 and a surface 65 a facing the light guide plate 30 side of the emission angle control layer 65. And a plurality of unit optical elements 70 arranged.

  The unit optical element 70 is an optical element that directs the light extracted from the light exit surface 31 of the light guide plate 30 in the front direction. As shown in FIG. 5, the plurality of unit optical elements 70 are arranged along the first direction d1. Each unit optical element 70 is nonparallel to the first direction d 1 and linearly extends in a direction along the sheet surface of the sheet-like emission angle control layer 65. In particular, in the example shown in FIG. 5, the longitudinal direction of each unit optical element 70 is parallel to the second direction d 2 orthogonal to the first direction d 1 in the sheet surface of the emission angle control sheet 65.

  In the present embodiment, each unit optical element 70 is formed in a columnar shape, and has the same cross-sectional shape along the longitudinal direction. Furthermore, the plurality of unit optical elements 70 are arranged without any gap on the surface 65 a facing the light guide plate 30 side of the emission angle control layer 65 along the first direction d1.

  As well illustrated in FIG. 5, each unit optical element 70 is provided with a light transmitting surface 71 and a light reflecting surface disposed opposite to each other along a first direction d1 which is an arrangement direction of the unit optical elements 70. It has 72. The light transmission surface 71 of each unit optical element 70 is located on one side in the first direction (the left side in FIGS. 1 and 2), and the light reflection surface 72 is on the other side in the first direction (FIGS. It is located on the right side of the page 2). More specifically, the light transmission surface 71 of each unit optical element 70 is located on the side of the light source 24 in the first direction d1 and faces one side in the first direction d1. The light reflecting surface 72 of each unit optical element 70 is located on the side away from the light source 24 in the first direction d1, and faces the other side in the first direction d1. As described later, the light transmission surface 71 mainly travels into the light guide plate 30 from the light source 24 disposed on one side in the first direction d1, and light emitted from the light guide plate 30 enters the optical sheet 60 thereafter. Act as an entrance surface for On the other hand, the light reflecting surface 72 has a function of reflecting the light incident on the optical sheet 60 and correcting the light path of the light.

  As well shown in FIG. 5, the light transmitting surface 71 and the light reflecting surface 72 respectively extend from the emission angle control layer 65 side and are connected to each other. The proximal end 75 b of the unit optical element 70 is defined at a position where the light transmitting surface 71 and the light reflecting surface 72 most approach the emission angle control layer 65. Further, at the position where the light transmitting surface 71 and the light reflecting surface 72 are connected to each other, the tip end portion 75 a of the unit optical element 70 which protrudes most to the light guide plate 30 side from the emission angle control layer 65 is defined.

  A cross section of the unit optical element 70 is shown in FIG. In the cross section shown in FIG. 6, the cross-sectional shape of each unit optical element 70 is a shape that tapers toward the light incident side (the light guide plate side). That is, in the cross section shown in FIG. 6, the length of the unit optical element 70 along the first direction d1 becomes smaller as it is separated from the output angle control layer 65 along the normal direction nd of the output angle control layer 65. Go.

  In the present embodiment, at least one unit, where the light reflection surface 72 forming a part of the outer contour of the unit optical element 70 in the cross section shown in FIG. The inclination angle φ of the optical element 70 is not constant in the light reflection surface 72. As shown in FIG. 6, the inclination angle φ changes so as to increase from the tip end 75 a of the unit optical element 70 to the base end 75 b in the light reflecting surface 72. According to such a unit optical element 70, the base end of the light reflecting surface 72 where the relatively rising light L61 advancing in the direction in which the inclination angle with respect to the front direction nd is relatively small is mainly incident Excellent light collecting function both in the area on the 75b side and in the area on the tip 75a side where the relatively flat light L62 traveling in the direction in which the inclination angle with respect to the front direction nd becomes very large is mainly incident Can be secured.

  As a specific configuration, in the cross section shown in FIG. 6, the inclination angle φ with respect to the first direction d1 is gradually increased from the side of the distal end 75 a of the unit optical element 70 toward the side of the proximal end 75 b. It includes a plurality of element surfaces 73 arranged. In the illustrated embodiment, the contour of the light reflecting surface 72 of the unit optical element 70 is formed in a broken line or in a shape obtained by chamfering the corner of the broken line. In the illustrated example, the light reflecting surface 72 includes a first element surface 73a defining the tip 75a, and a second element surface 73b adjacent to the first element surface 73a from the side of the emission angle control layer 65; have. The inclination angle φb of the second element surface 73b is larger than the inclination angle φa of the first element surface 73a.

  Next, with reference to FIG. 7, the emission angle control layer 65 supporting the plurality of unit optical elements 70 will be described. FIG. 7 is a cross-sectional view of the emission angle control layer 65. As shown in FIG. The emission angle control layer 65 is provided to reduce the light emitted from the surface light source device 20 in the front direction of the surface light source device 20, ie, the direction largely deviated from the normal direction nd of the emission angle control layer 65. There is. As shown in FIG. 7, the emission angle control layer 65 includes a plurality of first portions 66 and a plurality of second portions arranged alternately repeatedly along the arrangement direction pd along the sheet surface of the emission angle control layer 65. It has 67. In the example shown in FIG. 7, the plurality of first portions 66 are configured the same as one another, and the plurality of second portions 67 are also configured the same as one another. However, the plurality of first portions 66 may not be identical to each other as long as the effects according to the present embodiment can be achieved, and the plurality of second portions 67 may not be identical to each other. Further, in the example shown in FIG. 7, the arrangement direction Pd is parallel to the first direction d1, but is not limited to such an example, and the arrangement direction pd is not parallel to the first direction d1. May be

  Each first portion 66 and each second portion 67 have a longitudinal direction ld extending in the sheet surface of the emission angle control layer 65 and intersecting the arrangement direction pd (see FIG. 5). In addition, the emission angle control layer 65 further includes a sheet-like land layer 68 which is a layer stacked on the first portion 66 and the second portion 67. The land layer 68 is integrally formed with the first portion 66, and forms a main body portion 69 together with the first portion 66. In other words, the emission angle control layer 65 has the main body portion 69 formed by arranging the plurality of grooves 69a having the longitudinal direction ld in the arrangement direction pd, and the second portions 67 are respectively formed in the plurality of grooves 69a of the main body portion 69. Is arranged. The portion of the main body 69 between adjacent grooves 69 a defines a first portion 66.

  As shown in FIG. 7, in particular, the second portion 67 disposed in the groove 69a has a bottom surface 67a forming a surface facing the light guide plate 30 and a top surface 67d forming a surface facing the liquid crystal display panel 15; A first side surface 67b and a second side surface 67c extend between the end of the bottom surface 67a and the end of the top surface 67d.

  The bottom surface 67a and the top surface 67d face each other at an interval in the normal direction nd, and the first side face 67b and the second side face 67c face each other at an interval in the first direction d1. In particular, the first side surface 67b is disposed on the light incident surface 33 side in the first direction d1, and the second side surface 67c is disposed on the opposite surface 34 side in the first direction d1.

  In the present embodiment, the first side surface 67 b and the second side surface 67 c are inclined with respect to the bottom surface 67 a and extend from the bottom surface 67 a toward the light output side. In particular, in the example shown in FIG. 7, an angle α1 formed by the first side surface 67b with respect to the bottom surface 67a is smaller than an angle α2 formed by the second side surface 67c with respect to the bottom surface 67a.

  In the illustrated example, the bottom surface 67a, the top surface 67d, the first side surface 67b and the second side surface 67c are formed as flat surfaces, and the second portion 67 has a trapezoidal shape in the cross section shown in FIG. However, the cross-sectional shape of the second portion 67 does not have to be trapezoidal, and may have various shapes. For example, the cross-sectional shape of the second portion 67 may be triangular, or one or more corners of the triangle, for example, an angle separated from the bottom surface 67a may be chamfered.

  On the other hand, the first portion 66 includes a bottom surface 66 a that forms a surface facing the light guide plate 30. The bottom surface 66 a of the first portion 66 extends between the bottom surfaces 67 a of two adjacent second portions 67. Therefore, the bottom surface 66 a of the first portion 66 and the bottom surface 67 a of the second portion 67 define a surface 65 a facing the light guide plate 30 side of the emission angle control layer 65.

In the present embodiment, the bottom surface 66a forming the surface of the first portion 66 facing the light guide plate 30 has a length W1 along the arrangement direction pd, and the surface facing the light guide plate 30 of the second portion 67 The bottom surface 67a has a length W2 along the arrangement direction pd. The length W1 of the bottom surface 66a and the length W2 of the bottom surface 67a are determined to satisfy the following relational expression (1).
0.30 ≦ W1 / (W1 + W2) <0.96. (1)
As understood from FIG. 7, the equation (1) is an index indicating the aperture ratio in the emission angle control layer (louver layer) 65.

  If the length W1 of the bottom surface 66a is different among the plurality of first portions 66, or if the length W2 of the bottom surface 67a is different among the plurality of second portions 67, may the expression (1) be satisfied? Can be determined as follows. First, a test area of 2.0 mm × 2.0 mm is extracted from the emission angle control layer 65. According to the inventors of the present invention, if a test area of 2.0 mm × 2.0 mm is extracted from the result of considering the size and arrangement pitch of the first portion 66 and the second portion 67, the bottom surface 66a of the first portion 66 is obtained. It has been found that the length W1 and the length W2 of the bottom surface 67a of the second portion 67 are sufficiently large to be determined.

  Next, the length W1 of the bottom surface 66a of all the first portions 66 in the test area and the length W2 of the bottom surfaces 67a of all the second portions 67 are measured, and the average value W1 'of the length W1 and the length W2 The average value W2 'of the is calculated. The obtained average value W1 'and the average value W2' are regarded as W1 and W2 in the expression (1), and the satisfiability of the expression (1) is judged.

  The second portion 67 is formed by dispersing a light absorbing material 67m that absorbs light in the resin material that forms the main portion. When the second portion 67 includes the light absorbing material 67m, it is possible to absorb the light entering the second portion 67. The light absorbing material 67m may have a function of absorbing visible light, and may be made of, for example, a pigment such as carbon black, graphite, metal salt such as black iron oxide, pigment, or dye.

  In addition, the resin material forming the main part of the second portion 67 is made of a material having a smaller refractive index than the resin material forming the main body portion 69 including the first portion 66. For this reason, at the boundary between the first portion 66 and the second portion 67, a reflective interface 65x having a refractive index difference is formed.

  According to the reflection interface 65x, the light L71 having a large incident angle to the first side surface 67b or the second side surface 67c can be reflected by the reflection interface 65x and directed in the front direction. On the other hand, the light L72 having a small incident angle to the first side surface 67b or the second side surface 67c enters the second portion 67. The light L72 entering the second portion 67 is absorbed by the light absorbing material 67m.

  Next, the operation of the display device 10 configured as described above will be described.

  First, as shown in FIG. 2, the lights L 21 and L 22 emitted by the light emitters 25 constituting the light source 24 enter the light guide plate 30 through the light incident surface 33. The lights L21 and L22 incident on the light guide plate 30 are repeatedly reflected at the light emitting surface 31 and the back surface 32 of the light guide plate 30, and in particular, the total reflection is repeated due to the difference in refractive index between the material of the light guide plate 30 and air. It will be lighted up.

  As shown in FIG. 2, the back surface 32 of the light guide plate 30 has an inclined surface 37 inclined so as to approach the light exit surface 31 as it goes from the light incident surface 33 to the opposite surface 34. The inclined surface 37 is connected via the rising surface 38 and the connecting surface 39. Among them, the upper surface 38 extends in the normal direction nd. Therefore, most of the light L21 and L22 traveling in the light guide plate 30 from the side of the light incident surface 33 to the side of the opposite surface 34 is the inclined surface 37 or the connection surface without entering the rising surface 38 of the back surface 32. It will be reflected at 39. And when it reflects on the inclined surface 37 of the back surfaces 32, the advancing direction of the said light L21, L22 in the cross section shown by FIG. 2 increases the inclination angle with respect to the 1st direction d1. That is, when the light is reflected by the inclined surface 37 of the back surface 32, the incident angles of the light L21 and L22 to the light exit surface 31 and the back surface 32 become smaller. Therefore, the incident angles of the lights L21 and L22 traveling in the light guide plate 30 to the light output surface 31 and the back surface 32 become gradually smaller by one or more reflections on the inclined surface 37 of the back surface 32. When the incident angle to the light exit surface 31 and the back surface 32 is less than the total reflection critical angle, the light L21 and L22 can be emitted from the light exit surface 31 or the back surface 32 of the light guide plate 30. Among these, the light emitted from the back surface 32 is reflected by the reflection sheet 28 disposed on the back surface of the light guide plate 30 and returned to the inside of the light guide plate 30 again.

  On the other hand, the lights L 21 and L 22 emitted from the light guide plate 30 through the light exit surface 31 are refracted at the surface of the unit prism 50 forming the light exit surface 31. The light L21 and L22 traveling in a direction inclined in the second direction d2 with respect to the normal direction nd due to this refraction narrows down the traveling direction of the transmitted light in the normal direction nd side with respect to the components along the second direction d2. Be That is, the light emission side unit optical element 50 acts to improve the luminance in the front direction with respect to the light component along the second direction d2 orthogonal to the light guide direction.

  The lights L21 and L22 emitted from the light guide plate 30 then enter the optical sheet 60. As described above, the optical sheet 60 has unit optical elements 70 that project toward the light guide plate 30. As well illustrated in FIG. 5, the longitudinal direction of the unit optical element 70 is parallel to a second direction d2 orthogonal to the light guide direction (first direction) d1 by the light guide plate 30.

  As a result, the lights L21 and L22 emitted by the light source 24 and directed to the optical sheet 60 through the light guide plate 30 are transmitted through the first prism surface 71 of the unit optical element 70 located on the light incident surface 33 side. Incident to. As shown in FIG. 2, the lights L21 and L22 are then totally reflected by the second prism surface 72 of the unit optical element 70 located on the opposite surface 34 side to change the traveling direction. More specifically, in the cross section shown in FIG. 2, the light L21 and L22 traveling in the direction inclined from the normal direction nd of the light guide plate 30 has its traveling direction due to total reflection at the second prism surface 72 of the unit optical element 70. It bends so that the angle made with respect to the normal direction nd becomes small. With such an action, the unit optical element 70 can narrow down the traveling direction of the transmitted light to the normal direction nd for the light component along the first direction (light guiding direction) d1. That is, the unit optical element 70 acts to improve the brightness in the front direction with respect to the component of light along the first direction d1.

  The lights L 21 and L 22 directed in the front direction by the unit optical element 70 are directed to the emission angle control layer 65. As described above, the emission angle control layer 65 has the plurality of first portions 66 and the plurality of second portions 67 alternately and repeatedly arranged along the arrangement direction pd, and the second portion 67 is a light absorbing material. Includes 67m. In this case, of the light L21 and L22 bent by the unit optical element 70, the light traveling in the second portion 67 is absorbed by the light absorbing material 67m contained in the second portion 67. The light traveling in the first portion 66 is transmitted through the first portion 66 and travels toward the liquid crystal display panel 15.

  However, the light traveling in the light guide plate 30 is not only light L21 and L22 repeating total reflection on the light exit surface 31 and the back surface 32, but also light whose direction is changed in a direction different from the total reflection direction on the back surface 32. It also includes light that has been transmitted through the back surface 32 and returned again by the reflection sheet 28. In FIG. 8, such light is shown to be incident on the optical sheet 60. As shown in FIG. 8, the lights L81 and L82 directed in directions different from such an intended direction are not bent as intended in the unit optical element 70 after being extracted from the light exit surface 31, The light enters the emission angle control layer 65 with a large inclination with respect to the normal direction nd.

  As shown in FIG. 8, in the emission angle control layer 65, since the plurality of first portions 66 and the plurality of second portions 67 are alternately and repeatedly arranged along the arrangement direction pd, the normal direction nd is The highly inclined light beams L81 and L82 enter the second portion 67 directly or via the first portion 66. When light L81 directed to the second portion 67 via the first portion 66 is incident on the reflection interface 65x at a total reflection critical angle or more, the light L81 is totally reflected at the reflection interface 65x and narrowed in the normal direction nd. Thereafter, the totally reflected light L81 travels toward the liquid crystal display panel 15. On the other hand, when light L82 traveling toward the second portion 67 via the first portion 66 is incident on the reflective interface 65x at a total reflection critical angle less than the critical angle, the light L82 enters the second portion 67 and is absorbed by the light absorbing material 67m. Further, light directly incident on the second portion 67 is also absorbed by the light absorbing material 67 m in the second portion 67. In any case, the light L81 and L82 emitted in the direction different from the intended direction from the light guide plate 30 is reflected or absorbed by the emission angle control layer 65, and the light emitting surface 21 with respect to the normal direction nd It is not emitted toward the direction of the large inclination.

  The light transmitted through the emission angle control layer 65 then enters the lower polarizing plate 14 of the liquid crystal display panel 15. The lower polarizing plate 14 transmits light of a polarized light component oscillating in one direction of two orthogonal polarized light components (P wave and S wave). The light of one polarization component transmitted through the lower polarizing plate 14 is selectively transmitted through the upper polarizing plate 13 according to the state of the electric field application to each pixel. In this manner, by selectively transmitting the light from the surface light source device 20 for each pixel by the liquid crystal display panel 15, the observer of the liquid crystal display device 10 can observe an image.

  As described above, according to the present embodiment, at least one light entrance surface 33 is composed of the light exit surface 31, the back surface 32 facing the light exit surface 31, and a part of the side surface between the light exit surface 31 and the back surface 32. And a light guide plate 30 having a part of the side surface and an opposite surface 34 facing the one light entrance surface 33 along the first direction d1, and disposed to face the light entrance surface 33 of the light guide plate 30 The light source 24, the sheet-like emission angle control layer 65 disposed on the light emission surface 31 side of the light guide plate 30, and the emission angle control layer 65 and the light guide plate 30 are arranged along the first direction d1; And a plurality of unit optical elements 70, each of which is non-parallel to the first direction d1 and extends along the sheet surface of the sheet-like emission angle control layer 65, and the emission angle control layer 65 The arrangement direction pd along the sheet surface of the emission angle control layer 65 A plurality of first portions 66 arranged, each being non-parallel to the arrangement direction pd and extending in the longitudinal direction ld along the sheet surface of the emission angle control layer 65; A first portion 66 and a plurality of second portions 67 alternately arranged in the arrangement direction pd, and having a plurality of second portions 67 including a light absorbing material 67m that absorbs light. According to such a configuration, the light L81 and L82 emitted in the direction different from the intended direction from the light guide plate 30 is reflected or absorbed by the second portion 67 of the emission angle control layer 65, and the emission angle control It becomes difficult to be released from the layer 65 in the direction greatly inclined with respect to the normal direction nd. Therefore, it is possible to reduce the light emitted from the surface light source device 20 in the direction largely deviated from the front direction.

  Furthermore, in the present embodiment, the length W1 of the bottom surface 66a and the length W2 of the bottom surface 67a are determined so as to satisfy the relationship of 0.30 ≦ W1 / (W1 + W2). As described above, the light beams L21 and L22 deflected by the unit optical element 70 are narrowed in the direction of travel toward the normal direction nd. From this, the lights L21 and L22 deflected by the unit optical element 70 are incident on the emission angle control layer 65 from the direction substantially in the normal direction nd. In this case, which one of the first portion 66 and the second portion 67 the light from the unit optical element 70 passes through is determined by the first portion 66 and the first portion 66 occupying the surface 65 a facing the light guide plate 30 of the emission angle control layer 65. It will depend on the ratio of 2 parts 67.

  That is, the ratio of the first portion 66 to the surface 65a of the emission angle control layer 65 facing the light guide plate 30 increases, that is, the length W1 of the bottom surface 66a of the first portion 66 and the bottom surface 67a of the second portion 67 As the value of W1 / (W1 + W2) defined by the length W2 is larger, the light from the unit optical element 70 is more easily incident on the first portion 66. As the ratio of light incident on the first portion 66 increases, the ratio of light transmitted through the emission angle control layer 65 increases, and the utilization efficiency of light from the light guide plate 30 increases.

  Conversely, as the ratio of the second portion 67 to the surface 65a of the emission angle control layer 65 facing the light guide plate 30 increases, that is, as the value of W1 / (W1 + W2) decreases, the light from the unit optical element 70 It becomes easy to enter the second portion 67. As the ratio of the light incident on the second portion 67 increases, the light is absorbed by the light absorbing material 67m, and the utilization efficiency of the light from the light guide plate 30 decreases.

  That is, by determining the length W1 of the bottom surface 66a and the length W2 of the bottom surface 67a so as to satisfy the relationship of 0.30 ≦ W1 / (W1 + W2), the utilization efficiency of light expected for the surface light source device 20 The function of reducing the light emitted in the direction largely deviated from the front direction by the emission angle control layer 65 can be effectively exhibited while maintaining

  Further, according to the present embodiment, the relationship of W1 / (W1 + W2) <0.96 is satisfied, and the second portion 67 is disposed in each of the grooves 69a formed in the main body portion 69. When the above relational expression is satisfied, it is possible to form a plurality of grooves 69a in the main body 69 using an industrial production process while maintaining the optical function by the above-described emission angle control layer 65. Therefore, the emission angle control layer 65 maintaining the above-described optical function can be efficiently manufactured, and can be provided at a competitive price in the market.

  Further, according to the present embodiment, the plurality of unit optical elements 70 are arranged on the surface 65 a facing the light guide plate 30 side of the emission angle control layer 65. In this case, since the emission angle control layer 65 and the unit optical element 70 can be handled integrally, handling is excellent.

  Further, according to the present embodiment, the arrangement direction pd is along the first direction d1. In this case, light that is largely inclined in the first direction d1 from the normal direction nd can be blocked by the emission angle control layer 65.

  Further, according to the present embodiment, the back surface 32 of the light guide plate 30 includes a plurality of inclined surfaces 37 arranged in the first direction d1, and each inclined surface 37 is an end located close to the opposite surface 34 The part E1 is inclined with respect to both the normal direction nd of the output angle control layer 65 and the first direction d1 so that the part E1 approaches the light output surface 31 more than the end E2 located closer to the light input surface 33 side. ing. In this case, light that is repeatedly reflected between the light exit surface 31 and the back surface 32 and guided in the light guide plate 30 is directed from the light exit surface 31 of the light guide plate 30 in a direction inclined with respect to the normal direction nd. It becomes easy to take out.

  In addition, according to the present embodiment, the unit optical element 70 includes the light transmitting surface 71 and the light reflecting surface 72 located closer to the opposite surface 34 than the light transmitting surface 71 along the first direction d1. And at least a part of the light emitted from the light exit surface 31 of the light guide plate 30 is transmitted through the light transmission surface 71 of the unit optical element 70 and then totally reflected by the light reflection surface 72 to be an exit angle control layer 65. There is light going to. In this case, light directed from the light exit surface 31 of the light guide plate 30 in a direction inclined with respect to the normal direction nd is totally reflected by the unit optical element 70 and narrowed in the normal direction nd. For this reason, the lights L21 and L22 deflected by the unit optical element 70 are more likely to be incident on the emission angle control layer 65 from the direction approximately normal to the normal direction nd. Therefore, by adjusting the value of W1 / (W1 + W2), it was intended to use light efficiently and to have a function to reduce the light emitted toward the direction largely deviated from the front direction by the emission angle control layer 65. It becomes easy to adjust to the street.

  Next, an example in which the display device 10 shown in FIG. 1 is applied to the vehicle 1 will be described with reference to FIG. FIG. 9 is a perspective view showing an example in which the display device 10 is incorporated into the instrument panel 3 of a car. In addition, the instrument panel 3 is a generic term including parts called instruments of a driver's seat, a dashboard, and a center console. In the example shown in FIG. 9, the arrangement direction pd parallel to the first direction d1 corresponds to the vertical direction, and the light incident surface 33 and the light source 24 positioned on one side in the first direction d1 are positioned downward in the vertical direction. The opposite surface 34 located on the other side in the first direction d1 is located above in the vertical direction.

  If the output angle control layer 65 is not provided in the display device 10, light directed from the display device 10 to a direction greatly inclined upward with respect to the normal direction nd is incident on the front window 2 and is reflected. Will be observed by the driver etc. In this respect, in the example shown in FIG. 9, since the emission angle control layer 65 is provided in the display device 10, the direction toward the other side (upper side) in the first direction d1 with respect to the normal direction nd It is possible to block the light that is to be emitted by the emission angle control layer 65 and to be observed as a reflection.

«Modification»
Note that various modifications can be made to the embodiment described above. Hereinafter, an example of a modification will be described with reference to the drawings. In the following description and the drawings used in the following description, with respect to parts that can be configured in the same manner as the above-described embodiment, the same reference numerals as those used for the corresponding parts in the above-described embodiment are used. Duplicate descriptions will be omitted.

  In the embodiment described above, as shown in FIG. 7, an example in which the cross-sectional shape of the second portion 67 is a trapezoidal shape is shown, but the present invention is not limited to such an example. The cross-sectional shape of the second portion 67 is arbitrary as long as light L21 and L22 incident on the emission angle control layer 65 from the normal direction nd after being deflected by the unit optical element 70 can be transmitted with high transmittance. The shape of can be adopted.

  In addition, in the display device 10 according to the above-described embodiment, the reflective polarizing layer 80 may be further provided. FIG. 10 shows an example in which the reflective polarizing layer 80 is provided in the display device 10. In the example shown in FIG. 10, the reflective polarizing layer 80 is disposed between the emission angle control layer 65 and the plurality of unit optical elements 70, and the optical sheet 60 is combined with the emission angle control layer 65 and the plurality of unit optical elements 70. Configured. The reflection type polarization layer 80 shown in FIG. 10 is bonded to the output angle control layer 65 at the surface on the light output side, and is bonded to a film in which a plurality of unit optical elements 70 are formed on the surface on the light input side. As a specific example of the reflective polarizing layer 80, for example, DBEF series manufactured by Sumitomo 3M can be mentioned.

  The reflective polarizing layer 80 transmits a linearly polarized light component (for example, P wave) that vibrates in the direction to be transmitted by the lower polarizing plate 14, and in a direction different from the direction to be transmitted by the lower polarizing plate 14. It has a function of reflecting oscillating linearly polarized light components (for example, S waves). The light reflected by the reflective polarizing layer 80 is returned to the light guide plate 30 side, and is reflected again by the surface of each layer constituting the surface light source device 20. The light reflected again on the surface of each layer is changed in vibration direction upon reflection, and is returned to the reflective polarizing layer 80 again. Part of the light returned to the reflective polarizing layer 80 is transmitted through the reflective polarizing layer 80, and the other part is reflected again.

  In this manner, the reflective polarizing layer 80 repeatedly reflects, in the surface light source device 20, a linearly polarized light component that vibrates in a direction different from the direction to be transmitted by the lower polarizing plate 14. Thereby, the polarization direction of the linearly polarized light component vibrating in a direction different from the direction to be transmitted by the lower polarizing plate 14 is changed, and as a result, the linearly polarized light component vibrating in the direction to be transmitted by the lower polarizing plate 14 Increase the amount of light. As a result, more light from the light guide plate 30 can be transmitted through the lower polarizing plate 14, and the luminance of the light emitted from the display surface 11 of the display device 10 can be improved.

  In particular, in the example shown in FIG. 10, a plurality of unit optical elements 70 are arrayed on the light entrance side of the reflective polarizing layer 80. In this case, the light reflected by the reflective polarizing layer 80 returns to the unit optical element 70, but the traveling direction can be changed in various directions according to the position where it is incident on the unit optical element 70. When the light whose direction is changed in these various directions is reflected on the surface of each layer constituting the surface light source device 20 and returns to the reflective polarizing layer 80 again, the light transmitted through the reflective polarizing layer 80 is The traveling direction is also various directions. As a result, light directed to these various directions functions to improve the viewing angle of light exiting the display 10.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

  As described below, surface light source devices according to Examples 1 to 3 and Comparative Example 1 were designed, and simulations were performed on the utilization efficiency of light. The surface light source device is configured the same as the one embodiment described above with reference to FIGS. That is, the surface light source device includes the light source, the light guide plate, and the optical sheet. The light guide plate is configured in the same manner as the above-described one embodiment described with reference to FIGS. The reflective layer and the light source used were those incorporated in a commercially available liquid crystal display device. The reflective layer, the optical sheet, and the light source are common to the surface light source devices.

  The optical sheet of the surface light source device according to each example and the comparative example is configured the same as the above-described one embodiment described with reference to FIGS. However, in the optical sheet according to each example and comparative example, the value of the relational expression W1 / (W1 + W2) of the length W1 of the first portion and the length W2 of the second portion which are components of the emission angle control layer is changed did.

  The main dimensions of each component are as shown in FIG. First, for the light guide plate, the inclination angle θ formed by the inclined surface on the back surface with respect to the first direction is 2.3 °, the pitch Pm of adjacent inclined surfaces is 150 μm, and the length along the first direction of the inclined surface Lm was changed in order between 30 μm and 90 μm. Next, for the unit optical element, the angle β formed by the light transmitting surface with respect to the first direction is 58.3 °, and the first element surface of the light reflecting surface located closer to the tip end with respect to the first direction The angle φa formed is 56.0 °, and the angle φb formed by the second element surface of the light reflecting surface located closer to the base end portion with respect to the first direction is 58.5 °. Further, the pitch Pn of adjacent unit optical elements is 18 μm.

  In addition, the light source was disposed adjacent to the light incident surface, and no gap was observed between the light source and the light incident surface. Furthermore, the reflective sheet was also disposed adjacent to the back surface, and no gap was observed between the reflective sheet and the back surface.

The length W1 along the arrangement direction of the surface facing the light guide plate side of the first part and the length W2 along the arrangement direction of the surface facing the light guide plate side of the second part are shown in Table 1 It is street.

(Evaluation results)
In the surface light source device according to each of the examples and the comparative examples designed in this manner, light was made incident on the light guide plate from the light source. In the column of “use efficiency of light” in Table 1, the use efficiency of light is exhibited to an extent comparable to that of the surface light source device used in the market, and the use efficiency of light expected for the surface light source device is When obtained, it is ◎, and the utilization efficiency of light is slightly lower than that of the surface light source device used in the market, but it is expected when the utilization efficiency of light expected for the surface light source device is obtained It was evaluated as x when the light utilization efficiency was not obtained.

  Also, in the column of “Function to block light largely deviated from the front direction” in Table 1, when the function to block light largely deviated from the front direction is obtained as expected, it is marked as “O” and as expected. When it did not obtain, it was set as x.

  Moreover, in the column of “cost” in Table 1, when the emission angle control layer is repeatedly shaped, a case is considered in which a result is obtained that it can be shaped stably and efficiently (with a high yield). In the case of a result that is considered to have a possibility that the yield might decrease, it was set as Δ.

  As shown in Table 1, in each of the surface light source devices according to Examples 1 to 3 and Comparative Example 1, the function of blocking light largely deviated from the front direction was obtained as expected. Moreover, in the surface light source device which concerns on Examples 1-3, the utilization efficiency of the light anticipated by the surface light source device was obtained. On the other hand, in the surface light source device according to Comparative Example 1, the utilization efficiency of light expected for the surface light source device was not obtained.

  However, when the value of W1 / (W1 + W2) is 0.96 or more, there is a possibility that the yield may be reduced when the light guide plate is repeatedly formed. For this reason, in the surface light source device according to the first embodiment, although the utilization efficiency of light expected for the surface light source device can be obtained, the cost is evaluated as Δ.

Reference Signs List 1 vehicle 2 front window 10 display device 15 liquid crystal display panel 20 surface light source device 24 light source 28 reflective layer 30 light guide plate 31 light emitting surface 32 rear surface 33 light receiving surface 34 opposite surface 37 inclined surface 50 unit prism 60 optical sheet 61 light emitting surface 62 Light surface 65 Output angle control layer 65a Surface 65x facing the light guide side Reflective interface 66 First portion 66a Surface 67 facing the light guide side of the first portion 67 Second portion 67a Surface (bottom side) facing the light guide side of the second portion
67 m light absorbing material 70 unit optical element 71 light transmitting surface 72 light reflecting surface d1 first direction pd arrangement direction ld longitudinal direction

Claims (8)

A light exit surface, a back surface opposite to the light exit surface, at least one light entrance surface consisting of a portion of a side surface between the light exit surface and the back surface, and a portion of the side surface along the first direction A light guide plate having an opposite surface opposite to the two light incident surfaces;
A light source disposed to face the light incident surface of the light guide plate;
A sheet-like emission angle control layer disposed opposite to the light exit surface of the light guide plate;
A direction which is arranged along the first direction between the emission angle control layer and the light guide plate and which is not parallel to the first direction and which is along the sheet surface of the sheet-like emission angle control layer A plurality of unit optical elements extending along the
Equipped with
The emission angle control layer is
A plurality of first portions arranged along the arrangement direction along the sheet surface of the emission angle control layer, each being not parallel to the arrangement direction and along the sheet surface of the emission angle control layer A plurality of first portions extending longitudinally,
The first portion and a plurality of second portions alternately arranged in the arrangement direction, the plurality of second portions including a light absorbing material that absorbs light;
The surface of the first portion facing the light guide plate has a length W1 along the arrangement direction, and the surface of the second portion facing the light guide plate has a length W2 along the arrangement direction Have
0.30 ≦ W1 / (W1 + W2)
A surface light source device that satisfies the relationship of W1 / (W1 + W2) <0.96
The surface light source device according to claim 1, which satisfies the following relationship:   The surface light source device according to claim 1, wherein the arrangement direction of the first portion is along the first direction.   The surface light source device according to any one of claims 1 to 3, wherein the plurality of unit optical elements are arranged on a surface facing the light guide plate side of the emission angle control layer. The unit optical element includes a light transmitting surface, and a light reflecting surface located closer to the opposite surface than the light transmitting surface along the first direction,
At least a part of light emitted from the light exit surface of the light guide plate is transmitted through the light transmission surface of the unit optical element, totally reflected by the light reflection surface, and travels to the emission angle control layer. The surface light source device according to any one of 1 to 4. The back surface of the light guide plate includes a plurality of inclined surfaces arranged in the first direction,
Each inclined surface is normal to the emission angle control layer such that an end located closer to the opposite surface is closer to the light exit surface than an end located closer to the light incident surface side. The surface light source device according to any one of claims 1 to 5, wherein the surface light source device is inclined with respect to both the first direction and the first direction. A surface light source device according to any one of claims 1 to 6,
A display device comprising: a liquid crystal display panel disposed to face the surface light source device. The display device is an on-vehicle display device installed in a vehicle,
The display device according to claim 7, wherein the arrangement direction corresponds to the vertical direction.

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