JP2019139851A - Light guide plate, surface light source device, display device, and electronic apparatus - Google Patents

Abstract

To inhibit generation of uneven brightness on a light output surface near a light input portion of a light guide plate.SOLUTION: A planar light guide plate has on a side surface thereof a light input surface from which light is inputted, and outputs from a light output surface the light having been inputted from the light input surface. The light guide plate comprises: a plurality of diffuse reflection sections, which are discretely provided on the light output surface and diffusely reflect light; and a plurality of protruding strips, which are provided on a surface opposite to the light output surface and extend in the direction perpendicular to the light input surface when viewed from the normal direction of the opposite surface.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light guide plate, a surface light source device, a display device, and an electronic apparatus.

  In recent years, electronic devices are becoming smaller and thinner. The liquid crystal display device mounted on such an electronic device has a need for a narrower frame and a smaller thickness in order to obtain a larger display area with the same area. For the backlight of the display device, for example, an LED (Light Emitting Diode) that emits white light is used as a light source, and a side light type (also called an edge light system) surface light source device that uses a light guide plate (also called a light guide). Is used.

  The light emitting surface has a lens array in which a plurality of convex structures extending in a straight line are arranged in parallel, the concave structure is disposed on the light reflecting surface, and the concave structure near the corner A light guide plate that has an average height smaller than the average height of the concave structure in the vicinity of the center and that improves the uniformity of emitted light in the surface has been proposed (see Patent Document 1). .

JP 2014-86245 A

  With the acceleration of the enlargement of the screen of the liquid crystal display device, the width of the light-shielding double-sided tape on the light incident side is narrowed in order to cope with the narrowed frame on the light incident side. FIG. 15 is a plan view of the surface light source devices 100 and 200 in the conventional example. The surface light source device 100 includes a light guide plate 101. As viewed from the light output surface side of the light guide plate 101, a light shielding double-sided tape 102 is attached to the outer peripheral portion of the light output surface of the light guide plate 101. The surface light source device 200 includes a light guide plate 201. As viewed from the light output surface side of the light guide plate 201, a light shielding double-sided tape 202 is attached to the outer peripheral portion of the light output surface of the light guide plate 201. A light source 103 is disposed facing the light incident portion of the light guide plate 101, and a light-shielding double-sided tape 102 covers the light source 103. A light source 203 is disposed facing the light incident portion of the light guide plate 201, and a light-shielding double-sided tape 202 covers the light source 203. As shown in FIG. 15, the width of the light shielding double-sided tape 202 on the light incident part side of the light guide plate 201 is smaller than the width of the light shielding double-sided tape 102 on the light incident part side of the light guide plate 101.

  As shown in FIG. 15, in the vicinity of the light incident portion of the light guide plate 201, the front surface of the light source 203 is bright, but since the light amount of the light source 203 is small, there is a dark portion 204 in the diagonal direction of the light source 203. In addition, light and darkness occurs on the light exit surface near the light incident portion of the light guide plate 201. Also in the light guide plate 101, light and darkness is generated on the light exit surface near the light incident portion of the light guide plate 101, but since the width of the light shielding double-sided tape 102 is large, the dark portion on the light exit surface near the light input portion of the light guide plate 101. Is covered with a light-shielding double-sided tape 102. When the width of the light-shielding double-sided tape 202 on the light incident portion side of the light guide plate 201 becomes narrower as in the light guide plate 201, the difference in brightness of the light exit surface near the light incident portion of the light guide plate 201 can be recognized. Therefore, there is a problem that the appearance of the liquid crystal display device is deteriorated.

  In view of such a situation, an object of the present invention is to suppress the occurrence of light and darkness on a light exit surface in the vicinity of a light incident portion of a light guide plate.

  The present invention employs the following means in order to solve the above-described problems. That is, the present invention is a flat light guide plate that has a light incident surface on which light is incident on the side surface and emits light incident from the light incident surface from the light exit surface, and is provided discretely on the light exit surface, A plurality of diffuse reflectors for diffusing and reflecting light; and a plurality of ridges provided on the opposite surface of the light exit surface and extending in a direction perpendicular to the light incident surface when viewed from the normal direction of the opposite surface. A light guide plate provided. According to the light guide plate of the present invention, a plurality of diffuse reflection portions are discretely provided on the light output surface of the light guide plate, and a plurality of ridges are provided on the opposite surface of the light output surface, so that the vicinity of the light incident portion of the light guide plate. Occurrence of light and darkness on the light exit surface can be suppressed.

  In the light guide plate according to the present invention, the plurality of ridges have two or more ridges having different heights. In the light guide plate according to the present invention, the plurality of ridges are arranged on the opposite surface with a certain interval. In the light guide plate according to the present invention, a part of the surfaces of the plurality of diffuse reflection parts is a mirror surface, and another part of the surfaces of the plurality of diffusion reflection parts is a rough surface. In the light guide plate according to the present invention, the roughness of the surfaces of the plurality of diffuse reflection portions increases from the light incident surface side to the surface side facing the light incident surface. In the light guide plate according to the present invention, the plurality of diffuse reflection portions are concave. The light guide plate according to the present invention is provided discretely on the opposite surface, and includes a second diffuse reflection portion that diffuses and reflects light, and the second diffuse reflection portion is disposed between two adjacent ridges. . In the light guide plate according to the present invention, a plurality of ridges are arranged in the vicinity of the light incident surface.

  The surface light source device according to the present invention includes a light guide plate, a light source disposed at a position facing the light incident surface, and a reflection sheet disposed at a position facing the opposite surface. A display device according to the present invention includes a surface light source device and a display panel that receives light emitted from the surface light source device. An electronic apparatus according to the present invention includes a display device.

  According to the present invention, it is possible to suppress the occurrence of light and darkness on the light exit surface in the vicinity of the light incident portion of the light guide plate.

FIG. 1 is a cross-sectional view illustrating an example of a light guide plate. FIG. 2 is a perspective view illustrating an example of a liquid crystal display device. FIG. 3 is a perspective view illustrating the configuration of the surface light source device. FIG. 4 is a cross-sectional view illustrating an example of the light guide plate. FIG. 5 is a bottom view of the light guide plate. FIG. 6 is a side view of the light guide plate. FIG. 7A is an explanatory diagram of a distribution of emitted light of a light guide plate according to a comparative example. FIG. 7B is a plan view of a light guide plate according to a comparative example. FIG. 7C is a bottom view of the light guide plate according to the comparative example. FIG. 7D is an explanatory diagram of the distribution of emitted light from the light guide plate according to the comparative example. FIG. 7E is a plan view of a light guide plate according to a comparative example. FIG. 8A is an explanatory diagram of the distribution of emitted light from the light guide plate according to the embodiment. FIG. 8B is a plan view of the light guide plate according to the embodiment. FIG. 9A is a side view of the light guide plate. FIG. 9B is a side view of the light guide plate. FIG. 10 is an explanatory diagram of the surface of the dot pattern. FIG. 11A is a side view of the light guide plate. FIG. 11B is a side view of the light guide plate. FIG. 12 is a bottom view of the light guide plate. FIG. 13 is a plan view of the light guide plate. FIG. 14A is a diagram illustrating the degree of light and darkness of the light guide plate according to the embodiment and the degree of light and darkness of the light guide plate according to the comparative example. FIG. 14B is a plan view of the light guide plate according to the embodiment. FIG. 14C is a plan view of a light guide plate according to a comparative example. FIG. 15 is a plan view of a conventional surface light source device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment described below shows an example for carrying out the present invention, and the present invention is not limited to a specific configuration described below.

<Application example>
FIG. 1 is a cross-sectional view illustrating an example of the light guide plate 10. The light guide plate 10 has a flat plate shape. The light guide plate 10 has a light incident surface 10A on which light is incident, a light output surface 10B that emits light incident from the light incident surface 10A, and a surface 10C opposite to the light output surface 10B. The light incident surface 10 </ b> A is a part of the side surface of the light guide plate 10. The light exit surface 10B and the opposite surface 10C are orthogonal or substantially orthogonal to the light incident surface 10A. The light exit surface 10B and the opposite surface 10C are parallel. The light guide plate 10 is formed so that the light incident on the light guide plate 10 is guided to the light exit surface 10B so that the entire light exit surface 10B is illuminated. The light that has entered the light guide plate 10 travels through the light guide plate 10 by being totally reflected by the light exit surface 10B and the opposite surface 10C. When light in the light guide plate 10 enters the light exit surface 10B at an incident angle smaller than the critical angle, light is emitted from the light exit surface 10B to the outside of the light guide plate 10.

  As shown in FIG. 1, a plurality of dot patterns 21 are discretely provided on the light exit surface 10B. A plurality of lenticulars 22 are provided on the opposite surface 10C. The lenticular 22 is a ridge extending in a direction perpendicular to the light incident surface 10A when viewed from the normal direction of the opposite surface 10C. By providing the plurality of dot patterns 21 on the light exit surface 10B and providing the lenticular 22 on the opposite surface 10C, it is possible to suppress the occurrence of light and darkness on the light exit surface 10B near the light incident portion of the light guide plate 10.

  In the following embodiments, the “surface light source device” will be described as a backlight unit of a liquid crystal display device. The “surface light source device” may be used for purposes other than the backlight unit, such as a front light disposed on the front surface of a display device using a display panel or electronic paper.

(Configuration of liquid crystal display device)
FIG. 2 is a perspective view illustrating an example of a liquid crystal display device. As shown in FIG. 2, the liquid crystal display device includes a surface light source device 1 disposed as a backlight and a display panel (liquid crystal display) 2 that receives light emitted from the surface light source device 1. The display panel 2 displays an image by applying a voltage to the liquid crystal sandwiched between glass plates and increasing or decreasing the light transmittance. Hereinafter, in the surface light source device 1, the display panel 2 side may be described as the upper surface side, and the opposite surface side thereof may be described as the lower surface side.

(Configuration of surface light source device)
FIG. 3 is a perspective view illustrating the configuration of the surface light source device 1. The surface light source device 1 includes a light guide plate 10, a light source 11, a flexible printed circuit board (hereinafter also referred to as “FPC”) 12, a frame 13, and a fixing member 14. Further, the surface light source device 1 includes a reflection sheet 15 disposed on the lower surface side of the light guide plate 10. Furthermore, the surface light source device 1 includes a diffusion sheet 16, a prism sheet 17, and a light shielding double-sided tape 18 that are sequentially stacked on the upper surface side of the light guide plate 10.

The light guide plate 10 has a substantially flat plate shape and is formed of a translucent material such as polycarbonate resin or polymethyl methacrylate resin. The configuration of the light guide plate 10 will be described later. The light source 11 has a light emitting surface that emits light. A plurality of light sources 11 are mounted on the FPC 12 in a row at regular intervals. The light source 11 is disposed at a position facing the light incident surface 10 </ b> A of the light guide plate 10. The light source 11 is, for example, an LED package, but a light source other than the LED package may be used. The light source 11 may be formed by sealing an LED chip as a light emitting element with a translucent resin (resin layer) containing a phosphor. Alternatively, the phosphor layer may be disposed on the light exit surface 10B of the light guide plate 10 without arranging the phosphor on the LED chip, or the phosphor layer may be disposed on the reflection sheet 15. The light source 11 is driven by power supplied from the FPC 12 and lights up. Note that an LED light source other than white may be used as the light source 11.

  The FPC 12 is a wiring board that supplies power to the light source 11. The FPC 12 is formed by providing wiring with a conductive foil on a base material that is a flexible insulating film, and bonding a coverlay or resin (photosensitive resin) that is a protective insulating film to the surface. ing. The frame 13 is a frame-shaped member (an example of a “frame body”) having an opening and having four sides. The frame 13 is molded from a polycarbonate resin containing titanium oxide or the like. The frame 13 may have a resin frame and a metal frame. The frame 13 accommodates the light guide plate 10, and the inner peripheral surface of the frame 13 surrounds the side surface of the light guide plate 10. The frame 13 has a high reflectance, and reflects light so that light in the light guide plate 10 does not leak from the side surface of the surface light source device 1. The upper and lower surfaces of the fixing member 14 are adhesive surfaces. The fixing member 14 is, for example, a double-sided adhesive tape. The fixing member 14 is disposed on the lower surface of the FPC 12 or the like. The light guide plate 10 and the FPC 12 are fixed by the fixing member 14, and the FPC 12 and the frame 13 are fixed.

  The reflective sheet 15 is a highly reflective film having a multilayer film structure or a smooth sheet made of a highly reflective white resin sheet or metal foil, so that the light in the light guide plate 10 does not leak from the lower surface of the surface light source device 1. To reflect light. The reflection sheet 15 is disposed at a position facing the opposite surface 10 </ b> C of the light guide plate 10. The diffusion sheet 16 is a translucent resin film, and diffuses the light emitted from the light exit surface 10 </ b> B of the light guide plate 10 to widen the light directivity. The prism sheet 17 is a transparent resin film having a triangular prism-shaped fine pattern formed on the upper surface, condenses the light diffused by the diffusion sheet 16, and the luminance when the surface light source device 1 is viewed from the upper surface side. To raise. The upper and lower surfaces of the light-shielding double-sided tape 18 are adhesive surfaces. The light-shielding double-sided tape 18 is, for example, a black double-sided adhesive tape. The light-shielding double-sided tape 18 has a frame shape, for example, and suppresses light from leaking from the outer peripheral portion of the surface light source device 1.

(Configuration of light guide plate 10)
FIG. 4 is a cross-sectional view illustrating an example of the light guide plate 10. The light guide plate 10 includes a light incident surface 10A on which light is incident, a light output surface 10B that emits light incident from the light incident surface 10A, a surface 10C opposite to the light output surface 10B, and a facing surface 10D that faces the light incident surface 10A. And have. The light incident surface 10 </ b> A and the facing surface 10 </ b> D are part of the side surface of the light guide plate 10. The facing surface 10D is a surface opposite to the light incident surface 10A. The light exit surface 10B and the opposite surface 10C are orthogonal or substantially orthogonal to the light incident surface 10A. The light exit surface 10B and the opposite surface 10C are substantially parallel. The light incident surface 10A and the facing surface 10D are substantially parallel. The light guide plate 10 and the light source 11 are accommodated in the frame 13 so that the light incident surface 10A of the light guide plate 10 and the light emitting surface of the light source 11 face each other. The light guide plate 10 is formed so that the light incident on the light guide plate 10 is guided to the light exit surface 10B so that the entire light exit surface 10B is illuminated. The light that has entered the light guide plate 10 travels through the light guide plate 10 by being totally reflected by the light exit surface 10B and the opposite surface 10C. When light in the light guide plate 10 enters the light exit surface 10B at an incident angle smaller than the critical angle, light is emitted from the light exit surface 10B to the outside of the light guide plate 10.

  The light guide plate 10 may include a light guide plate main body and a light introducing portion that is higher than the height of the light guide plate main body. The light emitted from the light source 11 efficiently enters the light guide plate body from the light introducing portion, and the light use efficiency of the light guide plate 10 is improved. Since the light guide plate main body is thinner than the light introducing portion, the surface light source device 1 is thinned, and the liquid crystal display device including the surface light source device 1 is thinned. However, the light guide plate 10 may have a flat plate shape that does not have a light introducing portion.

  A plurality of dot patterns 21 are discretely provided on the light exit surface 10B. The dot pattern 21 is an example of a diffuse reflection part. The light in the light guide plate 10 strikes the dot pattern 21 provided on the light exit surface 10B and is diffusely reflected. The dot pattern 21 shown in FIG. 4 has a concave shape that is recessed inside the light guide plate 10, but is not limited to this shape, and the dot pattern 21 may be a convex shape that protrudes outside the light guide plate 10. . The concave shape and the convex shape are, for example, a hemispherical shape, a lens shape, a cylindrical shape, a prismatic shape, a conical shape, a pyramid shape, a truncated cone shape, and a truncated pyramid shape.

  When the dot pattern 21 has a convex shape, the dot pattern 21 may be crushed by applying an impact to the light exit surface 10B. When an impact is applied to the light exit surface 10B, the dot pattern 21 is crushed by applying a load to the top of the dot pattern 21. When some of the dot patterns 21 are crushed, a local dark portion is generated on the light exit surface 10B. On the other hand, when the dot pattern 21 has a concave shape, when an impact is applied to the light exit surface 10B, the load applied to the dot pattern 21 is dispersed, and damage to the dot pattern 21 is suppressed. Thus, when the dot pattern 21 has a concave shape, the load resistance of the dot pattern 21 is improved, and the occurrence of a local dark portion on the light exit surface 10B is suppressed.

  A plurality of lenticulars 22 are provided on the opposite surface 10C. FIG. 5 is a bottom view of the light guide plate 10 when viewed from the normal direction of the opposite surface 10 </ b> C of the light guide plate 10. The lenticular 22 is a ridge extending in a direction perpendicular to the light incident surface 10A when viewed from the normal direction of the opposite surface 10C. The lenticular 22 extends from the light incident surface 10A side toward the facing surface 10D side. The plurality of lenticulars 22 are arranged in parallel to each other. The plurality of lenticulars 22 are continuously arranged, and two adjacent lenticulars 22 are connected to each other. Therefore, the plurality of lenticulars 22 are arranged on the opposite surface 10C without any gaps. The lenticular 22 may be formed integrally with the light guide plate 10 manufactured by injection molding.

  FIG. 6 is a side view of the light guide plate 10 when viewed from the normal direction of the light incident surface 10 </ b> A of the light guide plate 10. A part of the light guide plate 10 is shown in FIG. The light in the light guide plate 10 strikes the lenticular 22 provided on the opposite surface 10C and is diffusely reflected. The lenticular 22 shown in FIG. 4 to FIG. 6 is a ridge protruding outside the light guide plate 10, but is not limited to this shape, and the lenticular 22 may be a dent recessed inside the light guide plate 10. Good. The cross-sectional shape of the lenticular 22 when viewed from the normal direction of the light incident surface 10A is, for example, a semicircular shape, a semielliptical shape, a square shape, a trapezoidal shape, or the like.

Here, the distribution of the emitted light from the light guide plate 10 according to the embodiment and the distribution of the emitted light from the light guide plate 301 according to the comparative example will be described. FIG. 7A is an explanatory diagram of the distribution of emitted light from the light guide plate 301 according to the comparative example, and is a cross-sectional view of the light guide plate 301. The light guide plate 301 has a light incident surface 301A on which light is incident, a light output surface 301B that emits light incident from the light incident surface 301A, and a surface 301C opposite to the light output surface 301B. The light incident surface 301 </ b> A of the light guide plate 301 and the light emitting surface of the light source 302 face each other, and light enters the light guide plate 301 from the light source 302. The light that has entered the light guide plate 301 travels through the light guide plate 301 by being totally reflected by the light exit surface 301B or the opposite surface 301C. When light in the light guide plate 301 enters the light exit surface 301B at an incident angle smaller than the critical angle, light is emitted from the light exit surface 301B to the outside of the light guide plate 301. A plurality of lenticulars 303 are provided on the light exit surface 301B, and a plurality of dot patterns 304 are provided discretely on the opposite surface 301C. The lenticular 303 is a ridge extending in a direction perpendicular to the light incident surface 301A when viewed from the normal direction of the light exit surface 301B. The light in the light guide plate 301 strikes and reflects the lenticular 303 provided on the light exit surface 301B and diffuses and reflects the dot pattern 304 provided on the opposite surface 301C. A solid arrow A1 in FIG. 7A indicates the traveling direction of the light emitted in the front direction of the light guide plate 301. A dotted arrow A2 in FIG. 7A indicates the traveling direction of the light emitted in the oblique direction of the light source 11. The thickness T1 of the light guide plate 301 is about 0.3 mm, but is not limited to this value. The light beam angle (irradiation angle) of the light source 302 when viewed from the side surface of the light guide plate 301 is an arbitrary value, and is appropriately determined depending on the type of the light source 302, the thickness T1 of the light guide plate 301, and the like.

  In the example of FIG. 7A, the light totally reflected by the opposite surface 301C is emitted from the light exit surface 301B. In the example of FIG. 7A, the light totally reflected by the light exit surface 301B is emitted from the opposite surface 301C. FIG. 7B is a plan view of the light guide plate 301 when viewed from the normal direction of the light exit surface 301B of the light guide plate 301 according to the comparative example. A solid arrow A1 in FIG. 7B indicates the traveling direction of the light emitted in the front direction of the light guide plate 301. A plurality of dot patterns 304 are provided on the opposite surface 301C. In many cases, light emitted in the front direction of the light source 302 strikes the slope of the dot pattern 304 and is diffusely reflected. Since the light emitted in the front direction of the light source 302 is reflected by the opposite surface 301C and emitted from the light output surface 301B, the multi-light quantity region B1 exists in the front direction of the light source 302. The multi-light quantity region B1 is a predetermined region of the light exit surface 301B and is a region where the amount of light emitted from the light exit surface 301B is large. The distance D1 between the light incident surface 301A and the multi-light quantity region B1 is less than about 1 mm, but is not limited to this value. The pitch of the light sources 302 is the sum of the distance between adjacent light sources 302 and the width of the light sources 302.

  FIG. 7C is a bottom view of the light guide plate 301 when viewed from the normal direction of the opposite surface 301C of the light guide plate 301 according to the comparative example. A dotted arrow A2 in FIG. 7C indicates the traveling direction of the light emitted in the oblique direction of the light guide plate 301. A plurality of lenticulars 303 are provided on the light exit surface 301B. The traveling direction of light emitted from the light source 302 in the front direction coincides with the extending direction of the lenticular 303. Therefore, the light emitted in the front direction of the light source 302 is often emitted from the light exit surface 301B without hitting the inclined surface of the lenticular 303, and the amount of light on the opposite surface 301C in the front direction of the light source 302 is small. On the other hand, the light emitted in the oblique direction of the light source 302 often hits the slope of the lenticular 303 and is diffusely reflected. The amount of light on the opposite surface 301 </ b> C in the oblique direction of the light source 302 is large due to the overlap of the light emitted from the adjacent light sources 302. Therefore, the multi-light quantity region B <b> 2 exists in the oblique direction of the light source 302. The multi-light quantity region B2 is a predetermined region on the opposite surface 302C, and is a region where the amount of light emitted from the opposite surface 301C is large. A distance D2 between the light incident surface 301A and the multi-light quantity region B2 is about ½ of the pitch P1 of the light sources 302. The distance until the light emitted in the oblique direction of the light source 302 reaches the opposite surface 301C is longer than the distance until the light emitted in the front direction of the light source 302 reaches the light emission surface 301B. Therefore, the distance D2 is longer than the distance D1. The multi-light area B1 and the multi-light area B2 have the same brightness. The light beam angle of the light source 302 when viewed from the opposite surface 301C is an arbitrary value, and is appropriately determined depending on the type of the light source 302, for example.

FIG. 7D is an explanatory diagram of the distribution of emitted light from the light guide plate 301 according to the comparative example, and is a cross-sectional view of the light guide plate 301. As shown in FIG. 7D, the reflection sheet 305 is disposed to face the opposite surface 301C. FIG. 7E is a plan view of the light guide plate 301 according to the comparative example. A solid line arrow A1 in FIGS. 7D and 7E indicates the traveling direction of the light emitted in the front direction of the light guide plate 301. A dotted arrow A2 in FIGS. 7D and 7E indicates the traveling direction of the light emitted in the oblique direction of the light guide plate 301. The multi-light quantity region B1 in FIG. 7E is the same as the multi-light quantity region B1 in FIG. 7B. The distance D1 in FIG. 7E is the same as the distance D1 in FIG. 7B. In many cases, the light emitted in the oblique direction of the light source 302 strikes the slope of the lenticular 303 and is diffusely reflected. The light emitted in the oblique direction of the light source 302 is reflected by the light exit surface 301 </ b> B and the reflection sheet 305. Due to the overlap of the light emitted from the adjacent light sources 302, the amount of light on the light exit surface 301B in the oblique direction of the light source 302 is large. For this reason, the multi-light quantity region B <b> 3 exists in the oblique direction of the light source 302. The multi-light quantity region B3 is a predetermined region on the light exit surface 302B, and is a region where the amount of light emitted from the light exit surface 301B is large. The multi-light area B1 and the multi-light area B3 have the same brightness.

  The distance D3 between the light incident surface 301A and the multi-light quantity region B3 is about 1 mm or more, but is not limited to this value. The distance until the light emitted in the oblique direction of the light source 302 is reflected once and reaches the light exit surface 301B is the distance until the light emitted in the front direction of the light source 302 is reflected twice and reaches the light exit surface 301B. Longer than the distance. The light emitted in the front direction of the light source 302 is reflected once and emitted from the light exit surface 301B. The light emitted in the oblique direction of the light source 302 is reflected twice and emitted from the light exit surface 301B. Therefore, the distance D3 is longer than the distance D1. Therefore, a region with a small amount of light exists between the adjacent multi-light amount regions B1, and a portion with a small amount of light exists between the adjacent multi-light amount regions B3. In this way, light and darkness is generated on the light exit surface 301 </ b> B in the vicinity of the light incident portion of the light guide plate 301.

  FIG. 8A is an explanatory diagram of the distribution of emitted light from the light guide plate 10 according to the embodiment, and is a cross-sectional view of the light guide plate 10. The light source 11 is disposed to face the light incident surface 10A, and the reflection sheet 15 is disposed to face the opposite surface 10C. An arrow A3 in FIG. 8A indicates the traveling direction of the light emitted in the front direction of the light source 11. An arrow A4 in FIG. 8A indicates the traveling direction of the light emitted in the oblique direction of the light source 11. The thickness T2 of the light guide plate 10 is about 0.3 mm, but is not limited to this value. The light beam angle (irradiation angle) of the light source 11 when viewed from the side surface of the light guide plate 10 is an arbitrary value, and is appropriately determined depending on, for example, the type of the light source 11 and the thickness T2 of the light guide plate 10.

  FIG. 8B is a plan view of the light guide plate 10 when viewed from the normal direction of the light exit surface 10B of the light guide plate 10 according to the embodiment. A plurality of dot patterns 21 are provided on the light exit surface 10B. In many cases, the light emitted in the front direction of the light source 11 strikes the slope of the dot pattern 21 and is diffusely reflected. The light emitted in the front direction of the light source 11 is reflected by the light exit surface 10B and emitted from the opposite surface 10C. Since the light emitted from the opposite surface 10 </ b> C is reflected by the reflection sheet 15 and emitted from the light exit surface 10 </ b> B, the multi-light quantity region B <b> 4 exists in the front direction of the light source 11. The multi-light quantity region B4 is a predetermined region of the light exit surface 10B, and is a region where the amount of light emitted from the light exit surface 10B is large. A distance D4 between the light incident surface 10A and the multi-light quantity region B4 is about ½ of the pitch P2 of the light sources 11. The pitch of the light sources 11 is the sum of the distance between the adjacent light sources 11 and the width of the light sources 11.

  A plurality of lenticulars 22 are provided on the opposite surface 10C. The traveling direction of light emitted from the light source 11 in the front direction coincides with the extending direction of the lenticular 22. The traveling direction of light emitted from the light source 11 in an oblique direction intersects with the extending direction of the lenticular 22. Therefore, the light emitted in the oblique direction of the light source 11 is reflected by the opposite surface 10C when it hits the slope of the lenticular 22, and is emitted from the light exit surface 10B. Due to the overlap of the light emitted from the adjacent light sources 11, the amount of light on the light exit surface 10 </ b> B in the oblique direction of the light sources 11 is large. Therefore, the multi-light quantity region B <b> 5 exists in the oblique direction of the light source 11. The multi-light quantity region B5 is a predetermined region of the light exit surface 10B, and is a region where the amount of light emitted from the light exit surface 10B is large.

  A distance D5 between the light incident surface 10A and the multi-light quantity region B5 is about ½ of the pitch P2 of the light sources 11. The light emitted in the front direction of the light source 11 is reflected twice and emitted from the light exit surface 10B. The light emitted in the oblique direction of the light source 11 is reflected once and emitted from the light exit surface 10B. Since the distance D4 and the distance D5 are substantially equal, the multi-light quantity region B5 exists between the two multi-light quantity areas B4, and the multi-light quantity area B4 exists between the two multi-light quantity areas B5. That is, the multi-light quantity region B4 and the multi-light quantity region B5 are arranged so as to be alternately repeated in a direction orthogonal to the direction from the light incident surface 10A side toward the opposing surface 10D side. In this way, the difference in brightness of the light exit surface 10B in the vicinity of the light incident portion of the light guide plate 10 is suppressed.

  9A and 9B are side views of the light guide plate 10 when viewed from the normal direction of the light incident surface 10A of the light guide plate 10. FIG. 9A and 9B show part of the light guide plate 10. The reflection sheet 15 is disposed to face the opposite surface 10C. In the example of the light guide plate 10 of FIG. 9A, one type of lenticular 22 is provided on the opposite surface 10C. In the example of the light guide plate 10 in FIG. 9B, two types of lenticulars 22 are provided on the opposite surface 10C. In the example of the light guide plate 10 in FIG. 9B, a large-sized lenticular 22A and a small-sized lenticular 22B are provided on the opposite surface 10C.

  In the example of the light guide plate 10 in FIG. 9A, since the lenticulars 22 of the same size are provided on the opposite surface 10C, all the lenticulars 22 are in contact with the reflection sheet 15, and the adhesion of the reflection sheet 15 to the opposite surface 10C. Is expensive. When the light in the light guide plate 10 hits the portion where the opposite surface 10C and the reflection sheet 15 are in close contact, the light is transmitted through the reflection sheet 15 without being diffusely reflected. Therefore, as the adhesion of the reflection sheet 15 to the opposite surface 10C increases, the transmitted light of the reflection sheet 15 increases, the light amount of the light exit surface 10B decreases, and the luminance efficiency of the light guide plate 10 decreases.

  In the example of the light guide plate 10 in FIG. 9B, two types of lenticulars 22 having different heights are provided on the opposite surface 10C, and the lenticulars 22A are discontinuously arranged on the opposite surface 10C. In the example of the light guide plate 10 in FIG. 9B, a plurality of second size lenticulars 22B are arranged between two first size lenticulars 22A. Therefore, the plurality of lenticulars 22A are arranged on the opposite surface 10C in parallel with each other with a certain interval. A plurality of lenticulars 22B are arranged on the opposite surface 10C in a row. The height of the lenticular 22A is higher than the height of the small lenticular 22B. Therefore, the lenticular 22 </ b> A contacts the reflection sheet 15, but the lenticular 22 </ b> B does not contact the reflection sheet 15. Thereby, the adhesiveness of the reflective sheet 15 with respect to 10 C of opposite surfaces falls. Therefore, the transmitted light of the reflection sheet 15 is reduced, the light amount of the light exit surface 10B is increased, and the luminance efficiency of the light guide plate 10 is improved. Two or more types of lenticulars 22 having different heights may be provided on the opposite surface 10C.

  The surface light source device 1 according to the embodiment may include the light guide plate 10 in FIG. 9A or the light guide plate 10 in FIG. 9B. In the example of the light guide plate 10 in FIG. 9B, the space between the opposite surface 10 </ b> C and the reflection sheet 15 provides a space, thereby reducing the adhesion of the reflection sheet 15 to the opposite surface 10 </ b> C. In the example of the light guide plate 10 of FIG. 9A, a spacer is disposed between the opposite surface 10C and the reflection sheet 15, and a space is provided between the opposite surface 10C and the reflection sheet 15, so that the reflection sheet 15 with respect to the opposite surface 10C. You may reduce the adhesiveness of.

  The surface of the dot pattern 21 may be a mirror surface, a fine rough surface, or a rough surface. FIG. 10 is an explanatory diagram of the surface of the dot pattern 21. As shown in FIG. 10, when the surface of the dot pattern 21 is a mirror surface, the reflectivity of the dot pattern 21 is high, and the light hitting the dot pattern 21 is often reflected without being diffused. Therefore, when the surface of the dot pattern 21 is a mirror surface, the luminance efficiency of the light guide plate 10 is reduced. When the surface of the dot pattern 21 is a mirror surface, the arithmetic average roughness (Ra) of the surface of the dot pattern 21 is, for example, about 0.1 μm, but is not limited to this value. As shown in FIG. 10, when the surface of the dot pattern 21 is rough, the dot pattern 21 has low reflectivity, and the light hitting the dot pattern 21 often diffuses without being reflected. Therefore, when the surface of the dot pattern 21 is a rough surface, the luminance efficiency of the light guide plate 10 is improved. When the surface of the dot pattern 21 is a rough surface, the arithmetic average roughness (Ra) of the surface of the dot pattern 21 is, for example, about 0.3 μm, but is not limited to this value.

As shown in FIG. 10, when the surface of the dot pattern 21 is a fine rough surface, the dot pattern 21 has appropriate diffusibility and reflectivity. When the surface of the dot pattern 21 is a rough surface, the arithmetic average roughness (Ra) of the surface of the dot pattern 21 is, for example, about 0.2 μm, but is not limited to this value. The luminance efficiency of the light guide plate 10 when the surface of the dot pattern 21 is a fine rough surface is higher than when the surface of the dot pattern 21 is a mirror surface, and is lower than when the surface of the dot pattern 21 is a rough surface. In order to suppress a phenomenon in which only one dot appears to shine (dot appearance), the surface of the dot pattern 21 is preferably a fine rough surface, and the surface of the dot pattern 21 is more preferably a mirror surface. In order to suppress the chromaticity shift, the surface of the dot pattern 21 is preferably a fine rough surface, and the surface of the dot pattern 21 is more preferably a mirror surface. Further, the surface of the lenticular 22 may be a mirror surface, a fine rough surface, or a rough surface. Further, the surface of the dot pattern 23 may be a mirror surface, a fine rough surface, or a rough surface.

  The arithmetic average roughness (Ra) of the surface of the dot pattern 21 may increase from the light incident surface 10A side toward the opposing surface 10D side. For example, the surface of the plurality of dot patterns 21 arranged within a predetermined distance from the light incident surface 10A is a mirror surface, and the surface of the plurality of dot patterns 21 arranged at a predetermined distance or more away from the light incident surface 10A is a rough surface. It may be. Since the surface of the plurality of dot patterns 21 arranged within a predetermined distance from the light incident surface 10A is a mirror surface, the reflectivity of the light emitting surface 10B in a region within the predetermined distance from the light incident surface 10A is improved. Since the surface of the plurality of dot patterns 21 arranged at a predetermined distance or more away from the light incident surface 10A is a fine surface, the diffusibility of the light emitting surface 10B in a region away from the light incident surface 10A by a predetermined distance or more is improved. . Thereby, the light emitted in the front direction of the light source 11 is reflected twice and easily emitted from the light exit surface 10B (see FIG. 8A).

  FIG. 11A is a side view of the light guide plate 10 when viewed from the normal direction of the light incident surface 10 </ b> A of the light guide plate 10. FIG. 11A shows a part of the light guide plate 10. The reflection sheet 15 is disposed to face the opposite surface 10C. In the example of the light guide plate 10 in FIG. 11A, a large lenticular 22A, a small lenticular 22B, and a dot pattern 23 are provided on the opposite surface 10C. A plurality of lenticulars 22 </ b> A are arranged on the opposite surface 10 </ b> C so as to be arranged in parallel to each other with a certain interval. In addition, a plurality of lenticulars 22B are arranged on the opposite surface 10C in parallel with each other at a certain interval. A plurality of dot patterns 23 are discretely provided on the opposite surface 10C. The dot pattern 23 is an example of a second diffuse reflection unit. In the example of the light guide plate 10 in FIG. 11A, a dot pattern 23 is disposed between two adjacent lenticulars 22B. The dot pattern 23 shown in FIG. 11A is a convex shape that protrudes to the outside of the light guide plate 10, but is not limited to this shape, and the dot pattern 23 may be a concave shape that is recessed inside the light guide plate 10. . The concave shape and the convex shape are, for example, a hemispherical shape, a lens shape, a cylindrical shape, a prismatic shape, a conical shape, a pyramid shape, a truncated cone shape, and a truncated pyramid shape. By arranging the dot pattern 23 between the two lenticulars 22B, the luminance of the light emitted from the light exit surface 10B can be adjusted, and the uniformity of the brightness of the light emitted from the light exit surface 10B can be improved.

As shown in FIG. 11A, when the dot pattern 23 has a convex shape, the plurality of dot patterns 23 may have different heights, or the plurality of dot patterns 23 may have the same height. . Further, a plurality of dot patterns 23 having a first height, a plurality of dot patterns 23 having a second height, and a plurality of dot patterns 23 having a third height are provided on the opposite surface 10C. Also good. The first height, the second height, and the third height are different from each other. By adjusting the height of the dot pattern 23, the brightness of the light emitted from the light exit surface 10B can be adjusted, and the uniformity of the brightness of the light emitted from the light exit surface 10B can be improved. The height of the dot pattern 23 is lower than the height of the lenticular 22A. The dot pattern 23 is not in contact with the reflection sheet 15 because the height of the dot pattern 23 is lower than the height of the lenticular 22A. Therefore, damage to the dot pattern 23 when a load is applied to the opposite surface 10C is suppressed. The height of the dot pattern 23 may be higher than the height of the lenticular 22B, or may be lower than the height of the lenticular 22B. Further, when the dot pattern 23 has a concave shape, the depths of the plurality of dot patterns may be different from each other.

  When the dot pattern 23 has a concave shape, the depths of the plurality of dot patterns 23 may be different from each other, or the depths of the plurality of dot patterns 23 may be the same. Also, a plurality of dot patterns 23 having a first depth, a plurality of dot patterns 23 having a second depth, and a plurality of dot patterns 23 having a third depth are provided on the opposite surface 10C. Also good. The first depth, the second depth, and the third depth are different depths. By adjusting the depth of the dot pattern 23, the brightness of the light emitted from the light exit surface 10B can be adjusted, and the uniformity of the brightness of the light emitted from the light exit surface 10B can be improved.

  FIG. 11B is a side view of the light guide plate 10 when viewed from the normal direction of the light incident surface 10 </ b> A of the light guide plate 10. FIG. 11B shows a part of the light guide plate 10. The reflection sheet 15 is disposed to face the opposite surface 10C. As shown in FIG. 11B, a plane 24 may be provided between adjacent lenticulars 22 among the plurality of lenticulars 22. In the example of the light guide plate 10 in FIG. 11B, a plurality of lenticulars 22 are arranged on the opposite surface 10 </ b> C so as to be arranged in parallel to each other with a certain interval. Thereby, the adhesiveness of the reflective sheet 15 with respect to 10 C of opposite surfaces falls. Therefore, the transmitted light of the reflection sheet 15 is reduced, the light amount of the light exit surface 10B is increased, and the luminance efficiency of the light guide plate 10 is improved.

  FIG. 12 is a bottom view of the light guide plate 10. In the example of the light guide plate 10 of FIG. 12, a plurality of lenticulars 22 are provided on the opposite surface 10C. As shown in FIG. 12, a plurality of lenticulars 22 are arranged in the vicinity of the light incident surface 10A. For example, a plurality of lenticulars 22 may be arranged in the vicinity of the light incident surface 10 </ b> A and in the oblique direction of the light source 11. The oblique direction of the light source 11 is a direction orthogonal to the extending direction of the line connecting adjacent light sources 11. As shown in FIG. 15, since there are dark portions 204 in the oblique direction of the light source 203, a plurality of lenticulars 22 may be arranged only in the oblique direction of the light source 11 with respect to the opposite surface 10C. . By disposing a plurality of lenticulars 22 in the vicinity of the light incident surface 10A and in the oblique direction of the light source 11, a difference in brightness between the light exit surface 10B near the light incident portion of the light guide plate 10 is suppressed.

  The surface of the dot pattern 21 may be a spiral pattern using nanostructures. FIG. 13 is a plan view of the light guide plate 10. FIG. 13 shows a part of the light guide plate 10. As shown in FIG. 13, when viewed from the normal direction of the light exit surface 10 </ b> B, spiral irregularities may be formed on the surface of the dot pattern 21. The surface of the dot pattern 21 may be processed into a fine rough surface or a rough surface by forming spiral irregularities on the surface of the dot pattern 21.

  FIG. 14A is a diagram illustrating the degree of light and darkness of the light guide plate 10 according to the embodiment and the degree of light and darkness of the light guide plate 301 according to the comparative example. FIG. 14B is a plan view of the light guide plate 10 according to the embodiment. FIG. 14C is a plan view of the light guide plate 301 according to the comparative example. A solid line E1 in FIG. 14A indicates the degree of light and darkness of the light guide plate 10 according to the embodiment, and indicates the degree of light and darkness at the location indicated by the dotted line AA in FIG. 14B. A dotted line E2 in FIG. 14A indicates the brightness level of the light guide plate 301 according to the comparative example, and indicates the brightness level of the portion indicated by the dotted line BB in FIG. 14C. An alternate long and short dash line E3 in FIG. 14A indicates the brightness of the light guide plate 301 according to the comparative example, and indicates the brightness of the portion indicated by the dotted line CC in FIG. 14C. The distance F1 between the light incident surface 10A and the dotted line AA in FIG. 14B is the same as the distance F2 between the light incident surface 301A and the dotted line BB in FIG. 14C. The distance F3 between the light incident surface 301A and the dotted line CC in FIG. 14C is longer than the distance F2. A difference F4 between the distance F3 and the distance F2 is about 1.4 mm.

  The undulation of the solid line E1 in FIG. 14A is small. Accordingly, the difference in brightness of the light exit surface 10B at the location indicated by the dotted line AA in FIG. 14B is small, and the occurrence of light and darkness on the light exit surface 10B is suppressed. The undulation of the dotted line E2 in FIG. 14A is large. Therefore, the difference in brightness of the light exit surface 301B at the location indicated by the dotted line BB in FIG. 14C is large. The undulation of the solid line E1 in FIG. 14A and the undulation of the solid line E1 in FIG. 14A are approximately the same. The difference in brightness of the light exit surface 10B at the location indicated by the dotted line AA in FIG. 14B is approximately the same as the brightness difference of the light exit surface 301B at the location indicated by the dotted line CC in FIG. 14C. Therefore, according to the light guide plate 10 according to the embodiment, the width of the light-shielding double-sided tape 18 on the light incident part side of the light guide plate 10 can be reduced by about 1.4 mm. That is, since the difference in brightness of the light exit surface 10B near the light incident portion of the light guide plate 10 is suppressed, even if the width of the light shielding double-sided tape 18 is reduced by about 1.4 mm, the surface light source device 1 and the liquid crystal display device Appearance does not deteriorate.

  Further, such a display device can be mounted on various electronic devices. As an electronic device provided with such a display device, a smart phone, a digital camera, a tablet terminal, an electronic book, a wearable device, a car navigation device, an electronic dictionary, an electronic advertisement board, etc. can be illustrated. Such an electronic device can be reduced in size and thickness, and can be expected to provide an excellent quality display.

DESCRIPTION OF SYMBOLS 1 Surface light source device 2 Display panel 10 Light guide plate 11 Light source 12 FPC
13 Frame 14 Fixing member 15 Reflective sheet 16 Diffusion sheet 17 Prism sheet 18 Light-shielding double-sided tape 21, 23 Dot patterns 22, 22A, 22B Lenticular

Claims (11)

A light guide plate having a light incident surface on which light is incident on a side surface and emitting light incident from the light incident surface from a light exit surface,
A plurality of diffuse reflectors that are discretely provided on the light exit surface and diffusely reflect light;
A plurality of ridges provided on the opposite surface of the light exit surface and extending in a direction perpendicular to the light incident surface as seen from the normal direction of the opposite surface;
A light guide plate comprising: The plurality of ridges have two or more types of ridges having different heights.
The light guide plate according to claim 1. A plurality of the ridges are arranged on the opposite surface at a certain interval,
The light guide plate according to claim 1 or 2. The surface of some of the plurality of diffuse reflection portions is a mirror surface, and the other part of the surface of the plurality of diffusion reflection portions is a rough surface.
The light guide plate according to any one of claims 1 to 3. From the light incident surface side toward the surface facing the light incident surface, the surface roughness of the plurality of diffuse reflection portions increases.
The light guide plate according to any one of claims 1 to 4. The plurality of diffuse reflection portions are concave.
The light guide plate according to any one of claims 1 to 5. A second diffuse reflector that is discretely provided on the opposite surface and diffuses and reflects light;
The second diffuse reflection portion is disposed between two adjacent ridges,
The light guide plate according to any one of claims 1 to 6. A plurality of the ridges are disposed in the vicinity of the light incident surface,
The light guide plate according to any one of claims 1 to 7. The light guide plate according to any one of claims 1 to 8,
A light source disposed at a position facing the light incident surface;
A reflective sheet disposed at a position facing the opposite surface;
A surface light source device comprising: A surface light source device according to claim 9,
A display panel that receives light emitted from the surface light source device;
A display device comprising:   An electronic apparatus comprising the display device according to claim 10.

Images