JP2011113852A - Surface light source device and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light source device improving utilization efficiency of emission light from a point light source. <P>SOLUTION: A light guide plate 200 has a recess 240 on a side face 231. The light guide plate 200 outputs a light inputted to the recess 240 from a front surface 210 as a planar light. The point light source 100 has a light-emitting body 110 generating the light to be input to the recess 240, and it is arranged in proximity to the recess 240. An opening of the recess 240 is provided on the side face 231 but does not reach the front surface 210. The recess 240 is configured to include a front slope 242, and the front slope 242 is located on the side of the front surface 210 and rising toward the point light source 100. The front slope 242 has a shape capable of refracting the light reaching from the light-emitting body 110 to the front surface 210 via the slope 242 to cause a total reflection at the front surface 210 in a plane passing the light-emitting body 110 and perpendicular to the front surface 210 and the side face 231. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface light source device and a display device.

  In a non-light emitting display device typified by a liquid crystal display device, a backlight unit for illuminating the liquid crystal panel is provided on the back surface of the liquid crystal panel. As such a backlight unit, for example, a structure having a light source, a light guide plate, and a reflection sheet is known.

  More specifically, in the light guide plate, the side surface facing the light source is used as a light incident surface, and one main surface is used as a light output surface. That is, the light emitted from the light source is incident on the side surface of the light guide plate and is emitted as planar output light from the one main surface of the light guide plate. The reflection sheet is provided on the side of the other main surface of the light guide plate, and is used to return light that has escaped from the other main surface back into the light guide plate.

  The backlight unit may have a lens sheet or a diffusion plate on the light exit surface of the light guide plate. The lens sheet is used to improve the luminance by condensing the light emitted from the emission surface within the viewing angle. The diffuser plate is used for uniform brightness.

  As a light source, a line light source such as a cold cathode fluorescent lamp or a point light source such as an LED (Light Emitting Diode) is employed. In recent years, in order to further reduce the thickness and extend the life, many LEDs are being used in place of fluorescent lamps.

  Each LED is a point light source, but by arranging a plurality of LEDs in a row, it can be treated as a linear light source in the same manner as a fluorescent lamp. However, since each LED has directivity, a configuration in which a plurality of LEDs are arranged in a row is likely to cause variations in luminance, in other words, luminance unevenness, as compared with a fluorescent lamp that is a line light source.

  Such luminance variation is considered to be reduced by the techniques disclosed in Patent Documents 1 and 2, for example.

  The light guide plate disclosed in Patent Document 1 has a lens at a position facing the LED. The said lens is comprised by shape | molding the side surface of a light-guide plate in a curved shape. More specifically, the curved shape has a concave shape when viewed from the LED, and has a cylindrical shape extending in the thickness direction of the light guide plate. According to the lens having such a shape, the light of the LED diverges as it enters the light guide plate. By devising the size and shape of the curved shape, the intersection position of the light emission boundary lines of adjacent LEDs can be adjusted. Therefore, by such adjustment, the effective light emitting region on the light exit surface of the light guide plate can be made to emit light with uniform intensity. That is, variation in luminance can be reduced.

  The light guide plate disclosed in Patent Document 2 also has a lens similar to the above, and thereby exhibits the same effect. Patent Document 2 states that the number of LEDs can be reduced. In addition, the light guide plate of Patent Document 2 has a curved shape for reflecting light within the light guide plate, in addition to the position facing the LED.

JP 10-260404 A Japanese Patent No. 4159059

  The curved portion of the light guide plate has a concave shape when viewed from the LED, and has a cylindrical shape extending in the thickness direction of the light guide plate. Moreover, the cylindrical portion reaches the two main surfaces of the light guide plate. That is, the cylindrical portion has a notch shape extending between both main surfaces of the light guide plate.

  For this reason, in the said notch part, the emitted light from LED will leak. For example, even when the light is emitted from the LED, there is light that does not enter the light guide plate because it passes through the upper or lower portion of the notch. Since light that does not enter the light guide plate does not contribute as planar light output from the light guide plate, the presence of such light reduces the light entrance efficiency to the light guide plate, in other words, the use efficiency of the LED light. Will be invited.

  Such a problem may also occur when a point light source other than an LED is employed. Although the backlight unit used in the liquid crystal display device is illustrated here, the above-described problem may occur even in a general surface light source device.

  An object of this invention is to provide the surface light source device which can improve the utilization efficiency of the light radiate | emitted from a point light source.

  Moreover, it aims at providing the display apparatus by which such a surface light source device was employ | adopted.

  In one aspect, the surface light source device according to the present invention has a front surface, a back surface, and a side surface, and has a recess provided with an opening on the side surface, and the light that has entered the recess. A light guide plate that outputs light as planar light from the front surface; and a point light source that includes a light-emitting body that generates light for entering the recess and is disposed in proximity to the recess. The opening does not extend to the front surface, and the recess includes a front side slope that is located on the front side and is raised toward the point light source. A shape capable of refracting light reaching the front surface from the light emitter through the front-side slope on the front surface through the light emitter so as to cause total reflection on the front surface and the side surface. have.

  According to the above configuration, the recess of the light guide plate is not opened on the front surface of the light guide plate, and when the inside of the recess is viewed from the point light source, the front side slope exists on the front side of the light guide plate. For this reason, the emitted light from the point light source does not leak from such an opening, and enters the light guide plate from the front side slope. Therefore, the utilization efficiency of the emitted light from the point light source can be improved.

  Further, it is not necessary to provide a reflection member on the front surface of the light guide plate for reflecting light leaking from the opening and guiding it to the light guide plate. For this reason, low cost is sufficient.

  Further, the front-side inclined surface protrudes toward the point light source and has the above-mentioned unique shape. For this reason, there are the following differences compared to the structure in which the inclined surface sinks in the direction away from the point light source or the structure having a planar shape. That is, among the light emitted from the point light source and transmitted through the front-side inclined surface, the amount of light whose incident angle to the front surface of the light guide plate is equal to or greater than the total reflection critical angle increases. As a result, according to the raised front-side slope, more light can be guided to the center of the light guide plate and used to generate planar light that is output light. Therefore, also from this point, the utilization efficiency of the emitted light from the point light source can be improved.

It is a disassembled perspective view which outlines a surface light source device regarding Embodiment 1 of this invention. It is a figure (top view and sectional view) outlining the surface light source device in the first embodiment. FIG. 5 is a perspective view outlining the depression of the light guide plate in the first embodiment. FIG. 4 is a diagram outlining the optical path of light emitted from a light emitter in the first embodiment. 5 is a graph outlining the correlation between angles α and β in FIG. 4 with respect to the first embodiment. It is a figure which outlines the slope shape of the dent of a light-guide plate, and the optical path of the light which injects into the said slope regarding Embodiment 1. FIG. FIG. 6 is an exploded perspective view outlining a surface light source device in the second embodiment. FIG. 10 is a perspective view outlining a recess of a light guide plate in the second embodiment. It is a figure (top view and sectional drawing) which outlines a surface light source device regarding Embodiment 2. FIG. It is a figure (top view and sectional drawing) which outlines a surface light source device regarding Embodiment 3. FIG. It is a figure (top view and sectional drawing) which outlines a surface light source device regarding Embodiment 4. FIG. It is a figure (top view and sectional drawing) which outlines a surface light source device regarding Embodiment 5. FIG. FIG. 10 is a perspective view outlining the depression of the light guide plate in the fifth embodiment. FIG. 10 is a cross-sectional view outlining a surface light source device according to a sixth embodiment. FIG. 20 is an exploded perspective view outlining a surface light source device with respect to the seventh embodiment. FIG. 10 is a cross-sectional view outlining a surface light source device according to a seventh embodiment. It is a perspective view which outlines a light-guide plate regarding the modification of Embodiment 1-7. FIG. 20 is an exploded perspective view outlining a display device according to an eighth embodiment.

<Embodiment 1>
FIG. 1 shows an exploded perspective view outlining a surface light source device (also referred to as a surface light emitting device) 50 according to Embodiment 1 of the present invention. The surface light source device 50 employs a so-called side light system.

  The surface light source device 50 illustrated in FIG. 1 includes a point light source 100, a light guide plate 200, and reflecting members 300 and 310. 1 illustrates three point light sources 100, the number of point light sources 100 may be one, two, or four or more.

<Light guide plate 200>
First, the light guide plate 200 will be outlined. In the example of FIG. 1, the light guide plate 200 has an outer shape constituted by main surfaces 210 and 220 and side surfaces 231 to 234.

  The main surfaces 210 and 220 are opposed to each other via the inside of the light guide plate 200, and have a plate-shaped front and back relationship. The arrangement direction of the main surfaces 210 and 220 corresponds to the thickness direction (plate thickness direction) of the light guide plate 200. Here, it is assumed that the main surfaces 210 and 220 are formed of a single plane and are parallel to each other.

  Here, a case where the main surfaces 210 and 220 have the same shape and the same size is illustrated. Moreover, although the case where the main surfaces 210 and 220 are rectangular is illustrated, the shape of the main surfaces 210 and 220 may be, for example, a polygon other than a square or a quadrangle, a circle, an ellipse, or the like.

  The main surfaces 210 and 200 are positioned such that corresponding sides of the four sides forming the rectangle (in other words, four edges) are aligned in the thickness direction of the light guide plate 200.

  The side surfaces 231 to 234 are provided for the four sides of the main surfaces 210 and 220, respectively, and connect the corresponding sides of the main surfaces 210 and 220. Since the corresponding sides of the main surfaces 210 and 220 are aligned in the thickness direction of the light guide plate 200 as described above, the side surfaces 231 to 234 are orthogonal to the main surfaces 210 and 220.

  The side surfaces 231 to 234 are sequentially connected in the circumferential direction of the main surfaces 210 and 220 and constitute a frame shape. In this case, the side surfaces 231 and 233 are opposed to each other via the inside of the light guide plate 200, and the side surfaces 232 and 234 are opposed to each other via the inside of the light guide plate 200.

  The number of side surfaces is determined according to the shapes of the main surfaces 210 and 220. For example, when the main surfaces 210 and 220 are polygonal, there are as many side surfaces as the number of sides of the polygon. For example, when the main surfaces 210 and 220 are circular, elliptical, etc., it can be expressed that the number of side surfaces is one. In the case of a circle, an ellipse or the like, a continuous surface surrounding the circumference of the main surfaces 210 and 220 can be referred to as a “side surface” regardless of the shape of the main surfaces 210 and 220.

  The light guide plate 200 has a recess 240 that is open on the side surface 231. In particular, the opening 241 of the recess 240 exists only on the side surface 231 and does not extend into the main surfaces 210 and 220. In the example of FIG. 1, the same three recesses 240 as the number of the point light sources 100 are arranged in the longitudinal direction of the side surface 231, in other words, in the circumferential direction of the main surfaces 210 and 220.

  The openings 241 of the recesses 240 are respectively provided at positions facing the point light source 100. In other words, the point light sources 100 are respectively arranged facing the opening 241. The recess 240 will be described in detail later.

  In the example of FIG. 1, the recess 240 is provided only on the side surface 231, but the recess 240 may be provided on any of the other side surfaces 232 to 234. Moreover, it is also possible to disperse and provide the plurality of recesses 240 on a plurality of the side surfaces 231 to 234.

  Here, the side surface 231 on which the point light source 100 is arranged in the example of FIG. 1 is also referred to as a “light source arrangement surface 231”.

  In addition, the light guide plate 200 scatters the light emitted from the point light source 100 and introduced into the recess 240, and outputs the light from the main surface 210 as planar light. The planar light is used as a backlight of a liquid crystal panel, for example. In view of this point, the main surface 210 is referred to as a “front surface 210”, while the main surface 220 is also referred to as a “back surface 220”.

  The light guide plate 200 can be made of, for example, a transparent acrylic resin or polycarbonate resin. The shape having the recess 240 can be formed by using, for example, an injection molding technique. However, the material and manufacturing method of the light guide plate 200 are not limited to this example.

  Here, the upper part of FIG. 2 illustrates a partially enlarged top view of the surface light source device 50 as viewed from the front surface 210 of the light guide plate. The top view is illustrated around the recess 240. A cross-sectional view taken along line AA in the top view is illustrated in the lower part of FIG. Such a cross section is a plane that passes through the light emitter 110 (described later) of the point light source 100 and is orthogonal to the main surfaces 210 and 220 and the side surface 231. In FIG. 2, the reflection member 300 (see FIG. 1) is not shown. The description will be continued with reference to FIG.

<Point light source 100>
The point light source 100 is disposed close to the recess 240 in a posture in which the light emitting portion (in other words, the light emitting region) faces the recess 240 of the light guide plate 200.

  More specifically, in the point light source 100, the light emitting portion (here, a planar shape is exemplified) is positioned on the same plane as the opening 241 of the recess 240, in other words, on the same plane as the light source arrangement surface 231. Is arranged. Or the point light source 100 is arrange | positioned so that a light emission part may be located in the inside of the dent 240 so that it may be illustrated by FIG.

  An arrangement in which the light emitting portion is located outside the recess 240 is also possible, but according to the above two arrangements, all of the light emitted from the point light source 100 can be introduced into the recess 240.

  The point light source 100 is mounted on a substrate (not shown), for example. In this case, the point light source 100 can be supported at the above-described arrangement position by setting the arrangement position of the mounting substrate.

  Here, the case where the point light source 100 is comprised by an LED element is illustrated. The LED element has an LED chip as the light emitter 110 that generates output light.

  Since the light emitting portion of the LED element is sufficiently smaller than the light emitting portion such as a fluorescent lamp, the LED element is generally referred to as a point light source in comparison with a linear light source such as a fluorescent lamp. However, the LED chip mounted on the LED element is even smaller. For example, in the case of LED light source NS2W123BT_BL manufactured by Nichia Corporation, the light emitting portion has a size of 2.6 mm × 1.5 mm, but the LED chip itself has a size of 0.3 mm square.

  In general, the LED chip that is the light emitter 110 is disposed at the center of the light emitting portion, and this is also the case in the illustrated example. In the illustrated example, the point light source 100 is provided at the center of the recessed opening 241 provided on the light guide plate side surface 231. More specifically, the point light source 100 is arranged such that the light emitter 110 at the center of the point light source 100 is aligned with the center of the opening 241. In FIG. 2, the light emitted from the light emitter 110 corresponding to the LED chip is schematically illustrated by several light rays (see the lines with black arrows).

  For example, the point light source 100 can be configured by an EL element having an EL (Electro Luminescence) light emitter.

<Reflection members 300 and 310>
The reflection members 300 and 310 are sheet-like members or plate-like members configured to include a reflection sheet using, for example, a polyester-based resin.

  The reflection member 300 is disposed close to the light guide plate 200 with its reflection surface directed toward the light source arrangement surface 231 of the light guide plate 200. In addition, it is more preferable that the reflection member 300 is in contact with the light source arrangement surface 231. In the example of FIG. 1, the reflection member 300 is spread so as to cover the entire light source arrangement surface 231 except for the arrangement region of the point light source 100. In this case, the reflecting member 300 is disposed so as to cover the opening 241 of the light guide plate recess 240 together with the point light source 100, in other words, close the opening 241.

  The reflection member 310 is disposed close to the reflection member 310 with the reflection surface facing the light guide plate back surface 220. It is more preferable that the reflecting member 310 is in contact with the back surface 220. In the example of FIG. 1, the reflecting member 310 spreads so as to cover the entire back surface 220.

  Here, the reflection members 300 and 310 may be either a regular reflection type or a diffuse reflection type, and are appropriately selected. For example, since the diffuse reflection type is generally inexpensive, it contributes to cost reduction. On the other hand, the regular reflection type is suitable when directivity of reflected light is required. Some specular reflection type reflection sheets can obtain a high reflectance by adopting a multilayer film structure.

  Each of the side surfaces 232 to 234 of the light guide plate 200 may be covered with a reflective member similar to the reflective members 300 and 310.

  Further, the reflection member 300 on the light source arrangement surface 231, the reflection member 310 on the light guide plate back surface 220, and the reflection members (not shown) on the light guide plate side surfaces 232 to 234 are separate members as illustrated in FIG. 1. Or a plurality of these may be supplied as an integrated member.

  The reflective members 300 and 310 have a role of returning light transmitted from the light guide plate 200 to the inside of the light guide plate 200. Thereby, the utilization efficiency of light improves. Specifically, the light traveling in the light guide plate 200 can be reflected by the light guide plate surfaces 210, 220, and 231 to 234 without providing the reflecting members 300 and 310. However, transmission also occurs with reflection. Therefore, in order to effectively use such transmitted light, that is, in order to increase the light utilization efficiency, it is preferable to provide the reflecting members 300, 310 and the like.

  The surface light source device 50 may further have an optical member such as a lens sheet or a diffusion plate on the light guide plate front surface 210.

<Light guide plate recess 240>
In FIG. 3, the perspective view which outlines the dent 240 of the light-guide plate 200 is shown. FIG. 3 is a perspective view of the dent 240 from the opening 241 side. The description will be continued with reference to FIG.

  As seen from the top view in FIG. 2 and FIG. 3, the dent 240 is viewed from the light guide plate front surface 210 (or back surface 220) side (in other words, in plan view (also referred to as top view)), It has a curved shape that protrudes away from the point light source 100. More specifically, the shape of the recess 240 in plan view has the opening 241 as a straight edge, and has a curved edge connecting both ends of the straight edge. Here, the curved edge has an arc shape. The arc shape includes not only a part of a regular circle but also a part of an ellipse and a curve that can be identified with these parts.

  Further, as can be seen from FIG. 1 and FIG. 3, the recess 240 has a rectangular shape when viewed from the light source arrangement surface 231 side. That is, the opening 241 of the recess 240 has a quadrangular shape.

  Further, as can be seen from the cross-sectional view in FIG. 2, the recess 240 has an opening 241 as a straight edge when viewed from the side of the light guide plate side 234 (or the side 232). The two raised edges extending from each of the ends toward the inside of the light guide plate and raised toward the straight edge (in other words, the point light source 100), and the ends of the two raised edges are connected. And one straight edge. Since the straight edge on the back side of the recess 240 is shorter than the straight edge corresponding to the opening 241, the former may be referred to as a short straight edge and the latter may be referred to as a long straight edge.

  More specifically, the recess 240 is constituted by a front side slope 242, a back side slope 243, and a side wall surface 244. These three surfaces 242 to 244 are located inside the light guide plate 200.

  The front-side inclined surface 242 is a surface located on the light guide plate front surface 210 side among the three surfaces 242 to 244. The front-side inclined surface 242 extends from the light source arrangement surface 231 (here, from the side where the light source arrangement surface 231 and the front surface 210 are coupled) toward the inside of the light guide plate 200. Further, the front-side inclined surface 242 has a shape protruding to the opening 241 side, in other words, the point light source 100 side.

  The back side inclined surface 243 is a surface located on the light guide plate back surface 220 side among the three surfaces 242 to 244. The back-side inclined surface 243 extends from the light source arrangement surface 231 (here, from the side where the light source arrangement surface 231 and the back surface 220 are coupled) toward the inside of the light guide plate 200. Further, the back-side inclined surface 243 has a shape that protrudes toward the opening 241, in other words, toward the point light source 100.

  These two inclined surfaces 242 and 243 are parallel to the light guide plate main surfaces 210 and 220 (in other words, orthogonal to the thickness direction of the light guide plate 200) and symmetrical with respect to a plane passing through the center of the recessed opening 241. It has a curved shape.

  The inclined surfaces 242 and 243 provide the straight edge and the curved edge as viewed from the light guide plate front surface 210 side. In addition, the inclined surfaces 242 and 243 provide two opposing sides (two sides parallel to the main surfaces 210 and 220) of the rectangular opening 241 when viewed from the light source arrangement surface 231 side. In addition, the inclined surfaces 242 and 243 provide the raised edges when viewed from the light guide plate side surface 234 side.

  Specific examples of the shapes of the inclined surfaces 242 and 243 will be described in detail later.

  The side wall surface 244 is a surface connecting the inclined surfaces 242 and 243. More specifically, the side wall surface 244 is formed between the inclined surfaces 242 and 243 so as to border the inclined surfaces 242 and 243 and to be orthogonal to the main surfaces 210 and 220 except for a portion constituting the opening 241. It extends to.

  The side wall surface 244 has two straight edge portions on the light source arrangement surface 231 and is curved toward the inside of the light guide plate 200. The two straight edges extend in a direction orthogonal to the main surfaces 210 and 220. Further, the curved shape of the side wall surface 244 follows the shape of the curved edge portion of the inclined surfaces 242 and 243.

  The side wall surface 244 provides the curved edge portion when viewed from the light guide plate front surface 210 side. Further, the side wall surface 244 provides two opposite sides (sides other than the two sides provided by the inclined surfaces 242 and 243) of the rectangular opening 241 when viewed from the light source arrangement surface 231 side. Further, the side wall surface 244 provides the short straight edge and the long straight edge when viewed from the light guide plate side 234 side.

  Hereinafter, the shape of the front side slope 242 will be described. Since the back side slope 243 has a shape symmetrical to the front side slope 242 with respect to the predetermined plane as described above, detailed description of the shape of the back side slope 243 is omitted here.

  FIG. 4 is a diagram outlining the optical path of light emitted from the light emitter 110 in the point light source 100. FIG. 4 corresponds to the cross-sectional view in FIG. 2, and shows a plane that passes through the light emitter 110 and is orthogonal to the main surfaces 210 and 220 and the side surface 231. FIG. 4 schematically shows a state in which light emitted from the light emitter 110 enters the light guide plate 200 (see FIG. 2) and is reflected by the front surface 210 of the light guide plate (see FIG. 2). This is typically illustrated with a book of rays (see lines with black arrows).

  Here, the element indicated by reference numeral 245 in FIG. 4 is a virtual plane determined according to the shape of the front side slope 242 (see FIG. 2). More specifically, the plane 245 is a plane (so-called tangential plane) in contact with the front side slope 242 at a certain point on the front side slope 242. The point is arbitrarily selected on the front side slope 242 and a plane 245 is defined for each of the arbitrary points. In FIG. 4, a tangential plane 245 is illustrated at a point where light emitted from the light emitter 110 enters the front-side inclined surface 242.

  Further, in FIG. 4, α is an emission angle of light emitted from the light emitter 110. The emission angle α is defined with respect to the emission front direction, that is, the normal direction of the light source arrangement surface 231 (see FIG. 2) as a reference (α = 0 °).

  Β is an inclination angle of the tangential plane 245 at a point where the light emitted from the light emitter 110 enters the front-side inclined surface 242. The inclination angle β is defined as an angle formed with respect to the front surface 210 (or the back surface 220). The inclination angle β can be grasped as a characteristic value representing the curved surface shape of the front side slope 242.

Θ ₁ and θ ₂ are an incident angle and an outgoing angle (also referred to as a refraction angle) when outgoing light from the light emitter 110 passes through the front-side inclined surface 242. These angles θ ₁ and θ ₂ are defined with reference to the normal direction of the tangent plane 245 at the incident point (that is, the normal direction of the front side slope 242 at the incident point) (θ ₁ , θ ₂ = 0 °). Is done.

  Further, γ is an incident angle when the light transmitted through the front side inclined surface 242 enters the light guide plate front surface 210. The incident angle γ is defined with reference to the normal direction of the light guide plate front surface 210 (γ = 0 °). Note that the angle γ is also a reflection angle when light incident on the front surface 210 is reflected by the front surface 210.

Note that α, β, γ, θ ₁ , and θ ₂ can theoretically take values of 0 ° or more and 90 ° or less, but actually, for example, the upper limit value may be smaller than 90 °. For example, the emission angle α from the light emitter 110 is a value within a predetermined range corresponding to the directivity of the point light source 100. In addition, the range that α can take may affect the range of other angles.

Referring also to the auxiliary line indicated by a broken line in FIG. 4, the following equation (1) is established for a triangle having θ ₁ as _one of the inner angles.

(180 ° −β) + θ ₁ + (90 ° −α) = 180 ° (1)
If this formula (1) is rearranged, formula (2) is obtained.

θ ₁ = β + α−90 ° (2)
Here, when the relative refractive index of the light guide plate 200 with respect to the refractive index of air is n, the following formula (3) is established by the Fresnel formula.

n = sin θ ₁ / sin θ ₂ (3)
Further, the following equation (4) is established for a triangle having γ as one of the inner angles.

γ + θ ₂ + (90 ° −β) = 90 ° (4)
If this formula (4) is rearranged, formula (5) is obtained.

γ = β−θ ₂ (5)
Here, by adjusting the inclination angle β of the tangential plane 245 corresponding to the front-side inclined surface 242, the light beam emitted from the light emitter 110 at the emission angle α can be totally reflected on the light guide plate front surface 210. According to the total reflection on the front surface 210, more light can be guided to the center of the light guide plate and used effectively. In view of this viewpoint, the inclination angle β, that is, the curved surface shape of the front-side inclined surface 242 is defined.

  More specifically, based on the above formulas (2), (3), and (5), the front surface is set so that the incident angle γ on the front surface 210 is equal to or greater than the critical angle (referred to as γc) at which total reflection occurs. An inclination angle β at each point on the side slope 242 (more specifically, each point determined according to the emission angle α) is defined.

  FIG. 5 shows a correlation graph of the angles α and β obtained based on the equations (2), (3), and (5). The characteristic line in the graph shows the case where the angle γ is equal to the total reflection critical angle γc (γ = γc), that is, the angle γ satisfies the total reflection critical condition. Further, this corresponds to the case where the upper region of the characteristic line is γ> γc, and the lower region corresponds to the case where γ <γc. That is, when the angles α and β satisfy the relationship corresponding to the characteristic line and the region above the characteristic line, total reflection can be caused on the front surface 210 of the light guide plate.

  For example, when the emission angle α from the light emitter 110 is 30 °, total reflection occurs when the inclination angle β of the front-side inclined surface 242 is about 13 ° or more. For example, when the inclination angle β of the front side slope 242 is 50 °, total reflection occurs when the emission angle α from the light emitter 110 is about 55 ° or less.

  In view of this point, not only the light emitted from the light emitter 110 but also the light transmitted from the same point on the front side slope 242 including the light emitted from the point shifted from the light emitter 110 can be totally reflected. Is possible.

  However, it may be difficult to cause total reflection over the entire light emitting portion including the light emitter 110. In this case, it is preferable to prioritize the condition for totally reflecting the light emitted from the light emitter 110. This is because the light emitted from the light emitter 110 generally has a larger amount of light than the light emitted from other points, and thus can greatly contribute to the improvement of light utilization efficiency.

  FIG. 6 is a diagram outlining the shape of the front side slope 242 when γ = γc. In FIG. 6, a coordinate system having the origin of the position of the light emitter 110 is applied to the cross-sectional view in FIG. 2 and a plane selected in the same manner as in FIG. 5. In this case, the position of the vertical axis corresponds to the position of the light source arrangement surface 231 (see FIG. 1), in other words, the position of the recessed opening 241 (see FIG. 1). Further, the extending direction of the vertical axis corresponds to the thickness direction of the light guide plate 200, and the extending direction of the horizontal axis corresponds to the depth direction of the recess 240.

  In FIG. 6, a curve with a thick solid line represents a cross-sectional shape of the front side slope 242. A line extending radially from the origin (line with a black arrow) schematically represents an optical path of light emitted from the light emitter 110. Such optical paths are illustrated for exit angles α = 10 °, 20 °, 30 °, 40 °, 50 °, 60 °, 70 °, 80 °. In addition, in order to make the drawing easy to see, the line types representing the light rays are appropriately changed.

  The physical quantity indicated by the vertical axis and the horizontal axis is a length, but in FIG. 6, an arbitrary unit, in other words, a relative value is adopted. For this reason, you may read the scale of a vertical axis | shaft and a horizontal axis, for example applying a millimeter (mm). According to this example, the front side slope 242 illustrated in FIG. 6 extends from the point 3 mm away from the light emitter 110 toward the front side 210 in the thickness direction of the light guide plate into the light guide plate 200, and has a depth of 2. If it continues to a point of 8mm, it will be expressed. In this case, a side wall surface 244 (see FIG. 2) is provided at a point having a depth of 2.8 mm.

  According to FIGS. 5 and 6, the smaller the emission angle α, the smaller the inclination angle β of the front side slope 242. For this reason, the inclination angle β becomes smaller toward the back of the recess 240. Further, the amount of change in the inclination angle β becomes smaller toward the back of the recess 240. Therefore, the gentle inclination continues toward the back of the recess 240.

  The depth dimension of the recess 240 can be determined from various viewpoints. For example, in order to allow more light to enter the front-side inclined surface 242, the depth of the recess 240 is preferably as deep as possible. On the other hand, in order to narrow the frame of the light guide plate 200, it is not preferable that the depth of the recess 240 is too deep. For this reason, for example, it is possible to determine the depth dimension of the dent 240 by comparatively considering both. An example of the dimension obtained as a result is the depth of 2.8 mm.

  Here, FIG. 6 illustrates the case where the incident angle γ to the light guide plate front surface 210 is equal to the total reflection critical angle γc (γ = γc). However, if γ is close to γc, problems such as ringing are likely to occur. It is done. For this reason, it is preferable to set the inclination angle β of the front side inclined surface 242 so that the difference Δγ (= γ−γc) between γ and γc becomes large.

<Effects of surface light source device 50>
According to the above configuration, the recess 240 of the light guide plate 200 is not opened on the front surface 210 of the light guide plate, and when the inside of the recess 240 is viewed from the point light source 100, the front side slope 242 exists on the front 210 side. For this reason, the emitted light from the point light source 100 does not leak from such an opening, and enters the light guide plate 200 from the front side inclined surface 242. Therefore, the utilization efficiency of the emitted light from the point light source 100 can be improved.

  Further, it is not necessary to provide a reflection member on the front surface 210 of the light guide plate for reflecting the light leaking from the opening and guiding it to the light guide plate 200. For this reason, low cost is sufficient.

  Further, since the front-side inclined surface 242 protrudes toward the point light source 100, the following differences are compared with the shape in which the inclined surface 242 sinks in a direction away from the point light source 100 or a planar shape. There is. In other words, among the light emitted from the point light source 100 and transmitted through the front-side inclined surface 242, the amount of light having an angle γ incident on the light guide plate front surface 210 equal to or greater than the total reflection critical angle γc increases. As a result, according to the raised front-side slope 242, more light can be guided to the center of the light guide plate 200 and used to generate planar light that is output light. Therefore, also from this point, the utilization efficiency of the emitted light from the point light source 100 can be improved.

  The ridge shape of the front side slope 242 is particularly devised as described above. That is, the front side slope 242 passes from the light emitter 110 to the front side slope on the plane that passes through the light emitter 110 and is orthogonal to the main surfaces 21 and 220 and the light source arrangement surface 231 (see the lower view of FIG. 2, FIG. 4 and FIG. 6). The light reaching the front surface 210 through 242 can be refracted so as to cause total reflection at the front surface 210.

  With such a device, it is possible to guide most of the light emitted from the light emitter 110 to the center side of the light guide plate 200 and use it to generate planar light. Therefore, the utilization efficiency of the emitted light from the point light source 100 can be improved. This is because the light emitter 110 such as an LED chip generally has a strong directivity in the emission front direction (range where the emission angle is small). That is, a large amount of light is emitted toward the front direction of emission, and according to the above shape, this can be used effectively.

  In addition, the recess 240 does not open on the back surface 220 of the light guide plate, and when the inside of the recess 240 is viewed from the point light source 100, a back side inclined surface 243 exists on the back surface 220 side. Since the back side slope 243 is configured in the same manner as the front side slope 242, the same effect as the front side slope 242 is achieved.

  Further, according to the curved shape of the recess 240, more specifically, according to the side wall surface 244 having the curved shape, the lens light source (diverging action) caused by the curved shape causes the light from the point light source 100 to come out. It is possible to spread the light uniformly. For this reason, luminance unevenness of the planar light emitted from the light guide plate front surface 210 can be reduced. In addition, since the illumination range per point light source can be expanded, for example, the number of point light sources 100 can be reduced to reduce the cost.

<Embodiment 2>
FIG. 7 shows an exploded perspective view outlining the surface light source device 50B according to the second embodiment. The surface light source device 50B illustrated in FIG. 7 is basically the same as the surface light source device 50 (see FIG. 1) described above except that the light source plate 200B is used instead of the light guide plate 200 (see FIG. 1). It is configured.

<Light guide plate 200B>
In general, the light guide plate 200B illustrated in FIG. 7 is cut out from the light guide plate 200 (see FIG. 1) on the back side slope 243 (see FIG. 2) side by a plane parallel to the light guide plate main surfaces 210 and 220. It can be grasped as a part obtained.

  More specifically, the light guide plate 200B is basically configured in the same manner as the light guide plate 200 described above except that the light guide plate 200B has a recess 240B instead of the recess 240 (see FIG. 1). FIG. 8 is a perspective view of the light guide plate 200B as viewed from the back surface 220 side. Further, FIG. 9 shows a top view and a cross-sectional view shown in the same manner as FIG. In FIG. 9, the reflection member 300 (see FIG. 1) is not shown.

  The recess 240 </ b> B is provided in the vicinity of the coupling portion between the side surface 231 (that is, the light source arrangement surface 231) and the back surface 220, and opens on both the side surface 231 and the back surface 220. That is, the opening 241 </ b> B of the recess 240 </ b> B extends over the side surface 231 and the back surface 220. However, the opening 241B does not reach the front surface 210.

  Here, a portion of the opening 241B that exists on the side surface 231 is referred to as the “side opening 241B1” of the opening 241B or the recess 240B. In addition, the portion of the opening 241B that exists on the back surface 220 is referred to as the “back surface opening 241B2” of the opening 241B or the recess 240B.

  The recess 240 </ b> B is configured by the aforementioned front side slope 242 and side wall surface 244. However, the side wall surface 244 reaches the back surface 220. That is, the side wall surface 244 connects the front side slope 242 and the back surface 220. Further, when the side wall surface 244 reaches the back surface 220, a back surface opening 241B2 of the opening 241B is configured.

  The side opening 241B1 has a rectangular shape as in the case where the above-described opening 241 (see FIGS. 1 to 3) is viewed from the side 231. The rear opening 241B2 has a curved shape, similar to the case where the above-described opening 241 (see FIGS. 1 to 3) is viewed from the front surface 210.

<Point light source 100>
The point light source 100 is basically configured and arranged in the same manner as in the first embodiment. However, the point light source 100 is arrange | positioned in the position nearest to the back surface 220 among the side surface opening part 241B1 of the dent 240B in the example of FIG. 7 and FIG. In other words, the point light source 100 is arranged with its lower end (that is, the end side on the light guide plate rear surface 220 side) aligned with the position of the light guide plate rear surface 220.

<Reflection members 300 and 310>
The reflecting member 300 is basically configured and arranged in the same manner as in the first embodiment. However, since the arrangement positions of the point light sources 100 with respect to the recessed openings 241 and 241B are different in the surface light source devices 50 and 50B, the shape of the reflecting member 300 is deformed according to the difference. However, the point that the reflecting member 300 is provided so as to cover the side opening 241B1 of the recess 240B together with the point light source 100 is common to the surface light source devices 50 and 50B.

  The reflection member 310 is basically configured and arranged in the same manner as in the first embodiment. In particular, as shown in FIG. 9, the reflective member 310 is disposed close to the rear opening 241B2 and covers the opening 241B2 (in other words, is closed).

  Thereby, the light leakage from the back surface opening 241B2 can be prevented. In addition, the light that has traveled to the rear opening 241B2 can be reflected by the reflecting member 310 to enter the light guide plate 200. Therefore, the utilization efficiency of the emitted light from the point light source 100 can be improved. According to such a viewpoint, it is preferable that at least a portion covering the recess 240B in the reflecting member 310 is a regular reflection type. This is because loss due to reflection can be suppressed.

<Effects of surface light source device 50B>
According to the surface light source device 50 </ b> B, the same effects as those of the surface light source device 50 can be obtained with respect to the configuration common to the surface light source device 50.

  In particular, according to the above configuration, the recessed opening 241 </ b> B of the light guide plate 200 </ b> B extends over the side surface 231 and the back surface 220. For this reason, compared with the light guide plate 200 described above (see FIGS. 1 to 3), that is, compared with the structure in which the recessed opening 241 exists only on the side surface 231, there are the following advantages.

  When the light guide plates 200 and 200B are manufactured by using an injection molding technique, the molding die for the light guide plate 200B has a shape in which the material can easily flow and the molded product can be easily taken out. For this reason, workability can be improved and manufacturing costs can be reduced.

  Further, according to the light guide plate 200B, it is possible to reduce the plate thickness necessary for providing the back side inclined surface 243 (see FIGS. 2 and 3). For example, when the dimensions of the front-side inclined surface 242 and the side wall surface 244 are the same between the light guide plates 200 and 200B, the light guide plate 200B can be about half as thick as the light guide plate 200. Therefore, reduction in thickness, weight, and material cost can be achieved.

<Embodiment 3>
FIG. 10 shows a top view and a cross-sectional view outlining the surface light source device 50C according to the third embodiment. FIG. 10 is illustrated similarly to FIGS. The surface light source device 50C illustrated in FIG. 10 is basically the same as the surface light source device 50 (see FIG. 1) described above except that the light source plate 200C is used instead of the light guide plate 200 (see FIG. 1). It is configured. In addition, illustration of the reflection member 300 (refer FIG. 1) is abbreviate | omitted in FIG.

  The light guide plate 200C illustrated in FIG. 10 is basically configured in the same manner as the light guide plate 200 described above except that it has a recess 240C instead of the recess 240 (see FIG. 1).

  The recess 240 </ b> C is configured by directly connecting the front-side slope 242 and the back-side slope 243 described above, and does not have the side wall surface 244 (see FIG. 2). The recess 240 </ b> C opens only on the side surface 231, and does not open on the main surfaces 210 and 220, similarly to the above-described recess 240 (see FIG. 1).

  According to the light guide plate 200 </ b> C, the recess 240 </ b> C is configured not to include a surface on which light emitted from the light emitter 110 in a direction parallel to the main surfaces 21 and 220 is vertically incident.

  The light traveling in the light guide plate 200C in parallel with the front surface 210, for example, is perpendicularly incident on the side surface 233 (see FIG. 1) opposite to the side surface 231 having the recess 240C and exits from the light guide plate 200C as it is.

  However, according to the above configuration, it is possible to prevent the light emitted from the light emitter 110 from traveling in parallel with the front surface 210 in the light guide plate 200C. For this reason, the light which escapes from 200 C of light guide plates as mentioned above can be reduced. Therefore, the utilization efficiency of the emitted light from the point light source 100 can be improved.

  Here, in the light guide plate 200 </ b> C, a coupling edge between the front side slope 242 and the back side slope 243 exists on a plane that passes through the light emitter 110 and is parallel to the main surfaces 210 and 220. However, the area of the connecting edge is extremely small compared to the total area of both surfaces 242 and 243. For this reason, it can be understood that the light emitted from the light emitter 110 is substantially incident on both surfaces 242 and 243.

  In view of this point of view, it is possible to grasp that the front-side slope 242 or the back-side slope 243 is provided in the light guide plate 200C in a direction parallel to the main surfaces 210 and 220 when viewed from the light emitter 110. is there.

  In this case, light emitted in a direction parallel to the front surface 210 from the light emitter 110 is incident on the front-side slope 242 or the back-side slope 243 and travels toward the front surface 210 or the back surface 220. And it repeats reflection with the front surface 210 and the back surface 220, and propagates to the center side of the light guide plate 200C. For this reason, it is possible to guide more light to the center side of the light guide plate and use it to generate planar light. Therefore, the utilization efficiency of the emitted light from the point light source 100 can be improved.

  According to the surface light source device 50C, the same effects as those of the surface light source devices 50 and 50B can be obtained with respect to the configuration common to the surface light source devices 50 and 50B.

<Embodiment 4>
FIG. 11 shows a top view and a sectional view outlining the surface light source device 50D according to the fourth embodiment. FIG. 11 is illustrated similarly to FIGS. The surface light source device 50D illustrated in FIG. 11 has the above-described surface light source device 50B (see FIGS. 7 to 9) except that the light source plate 200D is provided instead of the light guide plate 200B (see FIGS. 7 to 9). It is configured in the same way. In addition, illustration of the reflection member 300 (refer FIG. 7) is abbreviate | omitted in FIG.

  The light guide plate 200D illustrated in FIG. 11 is basically configured in the same manner as the light guide plate 200B described above except that it has a recess 240D instead of the recess 240B (see FIGS. 7 to 9). ing.

  The recess 240 </ b> D opens across the side surface 231 and the back surface 220, and does not open on the front surface 210, similar to the above-described recess 240 </ b> B. Further, the recess 240D illustrated in FIG. 11 includes a front-side inclined surface 242 and a side wall surface 244 in the same manner as the above-described recess 240B.

  However, as can be seen with reference to FIGS. 11 and 9, the recess 240D is deeper than the recess 240B. That is, the front side slope 242 extends longer.

  Further, in the recess 240B of FIG. 9, the side wall surface 244 is positioned in front of the light emitter 110, whereas in the recess 240D of FIG. 11, the front slope 242 is positioned in front of the light emitter 110.

  In the case of the dent 240 </ b> B in FIG. 9, light emitted from the light emitter 110 in a direction parallel to the light guide plate main surfaces 210 and 220 is incident on the side wall surface 244. Since the side wall surface 244 is orthogonal to the main surfaces 210 and 220, the light incident on the side wall surface 244 travels toward the side surface 233 (see FIG. 7) without being refracted to the front surface 210 side or the back surface 220 side. Further, since the side surface 233 is also orthogonal to the main surfaces 210 and 220, the light incident on the side wall surface 244 passes through the side surface 233 as it is. For this reason, it is not used as the output light of the surface light source device 50B.

  On the other hand, in the case of the dent 240D in FIG. 11, a front-side inclined surface 242 exists in a direction parallel to the main surfaces 210 and 220 when viewed from the light emitter 110. In other words, the recess 240D is configured without including a surface on which light emitted from the light emitter 110 in a direction parallel to the main surfaces 210 and 220 is perpendicularly incident. For this reason, the same effect as the light guide plate 200C according to the third embodiment can be obtained.

  That is, it is possible to prevent the light emitted from the light emitter 110 from traveling in parallel with the front surface 210 in the light guide plate 200D. For this reason, the light which escapes from light-guide plate 200D can be reduced, and light utilization efficiency can be improved.

  Further, light emitted from the light emitter 110 in a direction parallel to the front surface 210 is incident on the front surface side slope 242 and travels toward the front surface 210 side. And it repeats reflection with the front surface 210 and the back surface 220, and propagates to the center side of light-guide plate 200D. Thereby, the light utilization efficiency can be improved.

  Note that the positional relationship between the light emitter 110 and the front-side inclined surface 242 can be applied to other surface light source devices 50 and the like. The positional relationship can also be applied to the positional relationship between the light emitter 110 and the back-side inclined surface 243.

  According to the surface light source device 50D, the same effects as those of the surface light source devices 50, 50B, and 50C can be obtained with respect to the configuration common to the surface light source devices 50, 50B, and 50C.

<Embodiment 5>
FIG. 12 shows a top view and a sectional view outlining the surface light source device 50E according to the fifth embodiment. Note that FIG. 12 is illustrated in the same manner as FIGS. The surface light source device 50E illustrated in FIG. 12 has the above-described surface light source device 50B (see FIGS. 7 to 9) except that the light source plate 200E is used instead of the light guide plate 200B (see FIGS. 7 to 9). It is configured in the same way. In addition, illustration of the reflection member 300 (refer FIG. 7) is abbreviate | omitted in FIG.

  The light guide plate 200E illustrated in FIG. 12 is basically configured in the same manner as the light guide plate 200B described above except that it has a recess 240E instead of the recess 240B (see FIGS. 7 to 9). ing.

  Here, FIG. 13 shows a perspective view outlining the recess 240E. FIG. 13 is a perspective view of the dent 240E from the back side of the dent 240E.

  The recess 240E opens over the side surface 231 and the back surface 220, and does not open on the front surface 210, like the above described recess 240B.

  Further, the recess 240E includes the above-described front side slope 242 and a side wall surface 244E instead of the side wall surface 244. The front-side inclined surface 242 has a substantially trapezoidal shape according to the shape of the side wall surface 244E, which will be described later, when viewed from the light guide plate front surface 210. For this reason, the shape of the recess 240E viewed from the light guide plate front surface 210 is substantially trapezoidal.

  The side wall surface 244E is a surface that connects the front-side slope 242 and the back surface 220 in the same manner as the side wall surface 244 described above. The side wall surface 244E includes three surfaces 246, 247, and 248 corresponding to the substantially trapezoidal short side portion and the two oblique side portions. The long side portion of the substantially trapezoidal shape corresponds to the end side of the front side slope 242 on the side surface 231, in other words, the side opening 241 </ b> B <b> 1 of the recess 240 </ b> E configured to include the end side.

  The short side equivalent surface 246 is located in front of the side opening 241B1, in other words, in front of the point light source 100. The short side equivalent surface 246 is configured by a prism surface in which a plurality of prism columns are arranged in a planar shape. Each prism column extends in a direction orthogonal to the main surfaces 210 and 220. For this reason, the light incident on the prism surface 246 is scattered and spreads in a plane parallel to the main surfaces 210 and 220.

  Although a triangular prism is illustrated in FIGS. 12 and 13, for example, a semi-cylindrical prism may be employed. The shape of the prism may be properly used in consideration of, for example, the scattering angle. Note that the examples of FIGS. 12 and 13 do not limit the size, number, etc. of the prisms.

  The oblique side portion equivalent surfaces 247 and 248 are surfaces that connect the short side portion equivalent surface 246 and the light guide plate side surface 231, and are configured as flat surfaces here. The end sides of the oblique side equivalent surfaces 247 and 248 on the side surface 231 together with the end side of the front side slope 242 on the side surface 231 constitute a side surface opening 241B1.

  The hypotenuse equivalent surfaces 247 and 248 face the direction of the side opening 241B1. For this reason, the light emitted from the point light source 100 also enters the oblique side equivalent surfaces 247 and 248 and travels in the light guide plate 200 in the direction corresponding to the incident angle.

  The side wall surface 244E can also spread the light emitted from the point light source 100 uniformly. For this reason, luminance unevenness of the planar light emitted from the light guide plate front surface 210 can be reduced. Here, according to the prism surface 246, compared with the curved side wall surface 244 described above, the effect of spreading the light uniformly is great. Therefore, a high luminance unevenness reducing effect can be obtained.

  Further, similarly to the curved side wall surface 244 described above, the illumination range per point light source can be widened. For example, the number of point light sources 100 can be reduced to reduce the cost.

  The selection of which one of the side wall surface 244E having the prism surface 246 and the curved side wall surface 244 is adopted may be determined based on, for example, specifications (the size of the side surface 231, the number of point light sources 100, etc.). .

  The side wall surface 244E having the prism surface 246 can also be applied to other surface light source devices 50 and the like.

  In addition, according to the surface light source device 50E, the same effects as those of the surface light source devices 50, 50B to 50D can be obtained with respect to the configuration common to the surface light source devices 50 and 50B to 50D.

<Embodiment 6>
FIG. 14 is a cross-sectional view outlining the surface light source device 50F according to the sixth embodiment. 14 is illustrated in the same manner as the cross-sectional views of FIGS. The surface light source device 50F illustrated in FIG. 14 has the above-described surface light source device 50B (see FIGS. 7 to 9) except that the light source plate 200F is used instead of the light guide plate 200B (see FIGS. 7 to 9). It is configured in the same way. In FIG. 14, the reflection member 300 (see FIG. 7) is not shown.

  The light guide plate 200F is configured in the same manner as the light guide plate 200B (see FIG. 9) described above, except that it has a front surface 210F instead of the front surface 210 (see FIG. 9). The front surface 210F has a shape in which a portion near the dent 240B is inclined on the front surface 210.

  More specifically, the front surface 210F includes a first portion 212 corresponding to the above-described front surface 210 and a second portion 212 near the recess 240B. The first portion 211 is an output light extraction surface and is parallel to the back surface 220.

  The second portion 212 is a portion of the front surface 210 </ b> F that is reached by the light emitted from the light emitter 110 and transmitted through the front-side slope 242. In the example of FIG. 14, the second portion 212 is continuous with the first portion 211, and is inclined toward the back surface 220 in comparison with the first portion 212.

  For this reason, the incident angle γ of light transmitted from the light emitter 110 through the front-side inclined surface 242 and incident on the second portion 212 is equal to the incident angle γ of light incident on the above-described front surface 210 (see FIG. 9) in the same optical path. Compared to

  Therefore, it is possible to cause total reflection in the optical path where total reflection did not occur on the front surface 210 described above. This makes it possible to increase the amount of light that causes total reflection. As a result, the utilization efficiency of the emitted light from the point light source 100 can be improved.

  In addition, regarding the optical path in which total reflection occurs also on the front surface 210 described above, the difference Δγ (= γ−γc) between the incident angle γ to the front surface 210F and the total reflection critical angle γc can be increased. Therefore, the above-described problems such as ringing can be further suppressed. As a result, the brightness of the planar light can be stabilized.

  The light guide plate front surface 210F can also be applied to other light guide plates 200 and the like.

  In addition, according to the surface light source device 50F, the effect similar to the surface light source device 50, 50B-50E is acquired about the structure which is common with the surface light source device 50, 50B-50E.

<Embodiment 7>
FIG. 15 is an exploded perspective view outlining the surface light source device 50G according to the seventh embodiment. FIG. 16 is a sectional view outlining the surface light source device 50G. FIG. 16 is shown similarly to the cross-sectional views of FIGS.

  The surface light source device 50G illustrated in FIGS. 15 and 16 is similar to the surface light source device 50B (see FIG. 7) described above except that the reflective member 310G is used instead of the reflective member 310 (see FIG. 7). It is configured. In FIG. 16, the reflection member 300 (see FIG. 15) is not shown.

  The reflection member 310G includes diffuse reflection portions 311 and 313 and a regular reflection portion 312. These three portions 311 to 313 are arranged in this order from the light source arrangement surface 231 side toward the opposite side surface 233 side.

  As shown in FIG. 16, the diffuse reflection part 311 and the regular reflection part 312 overlap the back opening 241B2 of the recess 240B, but the diffuse reflection part 313 does not overlap the recess 240B. In particular, the arrangement range of the diffuse reflection part 311 and the regular reflection part 312 is determined as follows.

  That is, the diffuse reflection unit 311 has a condition that the light emitted from the light emitter 110 toward the reflection member 310G reaches the front-side slope 242 when the light is regularly reflected by the reflection member 310G (light 121 in FIG. 16). (See below).

  On the other hand, the specular reflection unit 312 has a condition that the light emitted from the light emitter 110 toward the reflection member 310G reaches the side wall surface 244 when the light is regularly reflected by the reflection member 310G (the light 122 in FIG. Reference)).

  The arrangement range of the diffuse reflection part 311 is set for the following reason. As described above, the shape of the front side slope 242 is determined based on the light (see the light 120 in FIG. 16) that is directly incident on the front side slope 242 from the light emitter 121. In addition, the reflected light 121 that follows the optical path indicated by the above conditions has a smaller incident angle on the front-side inclined surface 242 than the direct light 120 from the light emitter 110. For this reason, the reflected light 121 may pass through the light guide plate front surface 210 without causing total reflection. Then, since the reflected light 121 does not propagate to the center side of the light guide plate 200B, it is not used as the planar output light.

  On the other hand, the light quantity of the reflected light 121 that follows the optical path can be reduced by providing the diffuse reflection part 311 in the arrangement range and scattering the light incident on the part 311. Alternatively, it is possible not to follow the optical path.

  Further, light traveling in various directions is obtained by scattering at the diffuse reflection portion 311, and light that causes total reflection at the front surface 210 may be included therein. For example, there may be included light incident on the front side slope 242 at an incident angle causing total reflection at the front surface 210. Alternatively, light that enters from the side wall surface 244 and causes total reflection at the front surface 210 may be included. Alternatively, there is a case where light that enters the front side slope 242 or the side wall surface 244 after being repeatedly reflected in the recess 240B and causes total reflection on the front surface 210 may be generated.

  Thus, from the viewpoint of effectively using light that is not used as the planar output light, the arrangement range of the diffuse reflector 311 is set. In other words, the use efficiency of light can be improved by adopting the diffuse reflection part 311.

  On the other hand, the arrangement range of the regular reflection portion 312 is set for the following reason. The light emitted from the light emitter 110 includes light that enters the side wall surface 244 after being repeatedly reflected in the recess 240B. However, it is preferable that the reflection by the reflecting member is small. This is because, in general, the reflectance of the reflecting member is not 100%, so that loss occurs due to reflection.

  That is, the arrangement range of the regular reflection portion 312 is set from the viewpoint of securing the optical path of light that can reach the side wall surface 244 by one regular reflection. In other words, the light utilization efficiency can be improved by adopting the regular reflection portion 312.

  In the example of FIGS. 15 and 16, the diffuse reflector 311 has a strip shape that passes through a plurality of portions to be diffusely reflected. On the other hand, you may comprise the diffuse reflection part 311 for every part which should be diffusely reflected. The same applies to the regular reflection portion 312.

  The diffuse reflection part 311 can be formed, for example, by sticking a diffuse reflection sheet to a predetermined substrate. The regular reflection part 312 and the diffuse reflection part 313 can be formed similarly.

  Alternatively, a diffuse reflection sheet or a diffuse reflection plate may be prepared as a base material, and a regular reflection sheet constituting the regular reflection unit 312 may be stuck on the diffuse reflection sheet or the like. According to this, the three parts 311 to 312 can be collectively formed only by pasting the regular reflection sheet. Further, since the diffuse reflection member is less expensive, the reflection member 310G can be provided at a low cost.

  By the way, the diffuse reflection part 313 which does not overlap the recess 240B can be changed to a regular reflection region. In this case, the adjacent regions 312 and 313 are both regular reflection portions. For this reason, for example, the reflection member 310G is easily manufactured by preparing a regular reflection sheet or a regular reflection plate as a base material and sticking the reflection sheet for the diffuse reflection portion 311 on the regular reflection sheet or the like. Can do.

  The reflective member 310G can also be applied to other surface light source devices 50D and the like.

  Note that, according to the surface light source device 50G, the same effects as those of the surface light source devices 50, 50B to 50F can be obtained with respect to the configuration common to the surface light source devices 50 and 50B to 50F.

<Modification of Embodiments 1-7>
In FIG. 17, the perspective view which outlines the light-guide plate 200H which concerns on the modification of Embodiment 1-7 is shown. The light guide plate 200H illustrated in FIG. 17 is compared with the light guide plate 200 described above (see FIGS. 1 to 3).

  That is, in the light guide plate 200 described above, the opening 241 of the recess 240 extends over the entire thickness direction of the light guide plate 200. In other words, there is no plate thickness on the upper side (in other words, on the front surface 210 side) of the side portion formed by the edge of the front-side slope 242 in the opening 241. Similarly, no plate thickness exists on the lower side (in other words, on the back surface 220 side) of the opening portion 241 formed by the edge of the back-side inclined surface 243.

  On the other hand, in the light guide plate 200H in FIG. 17, there are plate thicknesses on the upper side and the lower side of the side portion constituting the opening 241. It is also possible to adopt a structure in which the plate thickness exists only on either the upper side or the lower side of the side portion.

  The other light guide plates 200B to 200F can be configured in the same manner.

  Even if the light guide plate having the structure according to this modification including the light guide plate 200H is employed instead of the light guide plate 200 and the like, the various effects described above can be obtained.

<Eighth embodiment>
The surface light source device 50 itself can be used as, for example, a main lighting device or an illumination lighting device. The surface light source device 50 and the like can be used in combination with other various members. In the eighth embodiment, a display device will be described as an application example of the surface light source device 50 and the like. FIG. 18 is an exploded perspective view outlining the display device 60 according to the eighth embodiment.

  The display device 60 includes a surface light source device 50 and an image providing unit 62 that provides an image to be displayed. In FIG. 18, the surface light source device 50 and the image providing unit 62 are simply illustrated. It is also possible to employ the surface light source device 50B or the like. The image providing means 62 is disposed on the front surface 210 side of the light guide plate 200 (see FIG. 1) of the surface light source device 50.

  With this configuration, the display device 60 can illuminate the image provided by the image providing unit 62 with the planar light emitted from the light guide plate front surface 210. That is, the display device 60 uses the surface light source device 50 as a backlight unit.

  The image providing means 62 can be implemented by, for example, a liquid crystal panel, more specifically, a transmissive or transflective liquid crystal panel. In this case, the display device 60 is generally called a liquid crystal display device. According to the liquid crystal panel, both a moving image and a still image can be provided as a display image.

  Alternatively, the image providing unit 62 can be implemented by, for example, a plate-like member or a sheet-like member on which an image is drawn in advance. A transparent or translucent member is selected as the plate-like or sheet-like member.

  More specifically, when the content of the drawn image is an advertisement, the display device 60 is generally called an advertisement display device. When the content of the drawn image is various types of guidance, the display device 60 is generally called a guidance display device, a guidance display device, or the like. When the display image is drawn and fixed in advance, a still image is provided as the display image.

  Note that the “image” includes pictures, characters, and the like, and includes information that is widely perceivable by the eye. The “image” includes a moving image and a still image as described above.

  According to the above configuration, various effects exhibited by the surface light source device 50 and the like are also exhibited in the display device 60.

  50, 50B to 50G surface light source device, 60 display device, 62 image providing means, 100 point light source, 110 illuminant, 200, 200B to 200F, 200H light guide plate, 210, 210F front surface, 211 first part, 212 second part , 220 Back surface, 231 to 234 Side surface, 240, 240B to 240E Recess, 241, 241B opening, 241B1 Side surface opening, 241B2 Back surface opening, 242 Front side slope, 243 Back side slope, 244, 244E Side wall surface, 246 Prism Surface, 300, 310, 310G Reflective member, 311, 313 Diffuse reflection part, 312 Regular reflection part.

Claims (10)

A light guide plate having a front surface, a back surface, and a side surface, and having a recess provided with an opening on the side surface, and outputting light incident on the recess as planar light from the front surface; ,
A light source that generates light for entering the recess, and a point light source disposed close to the recess,
The opening of the recess does not reach the front surface,
The dent is
It is configured to include a front side slope that is located on the front side and is raised to the point light source side,
The front-side slope refracts light that reaches the front surface from the light emitter through the front-side slope in the plane that passes through the light emitter and is orthogonal to the front surface and the side surface. A surface light source device having a shape that can be made to occur. The surface light source device according to claim 1,
The opening of the recess does not reach the back surface of the light guide plate,
The dent is
It further includes a back side slope that is located on the back side and is raised to the point light source side,
The back side inclined surface refracts light that reaches the back surface from the light emitter through the back side inclined surface in the plane that passes through the light emitter and is orthogonal to the back surface and the side surface. A surface light source device having a shape that can be made to occur. The surface light source device according to claim 1 or 2,
The opening of the recess extends across the side and the back;
The surface light source device is
The surface light source device further provided with the reflection member arrange | positioned covering the back surface opening part which is a part opened in the said back surface among the said opening parts. The surface light source device according to any one of claims 1 to 3,
The said dent is a surface light source device comprised without including the surface where the light radiate | emitted from the said light-emitting body in the direction parallel to the said front surface enters perpendicularly. The surface light source device according to claim 4,
The surface light source device, wherein the front-side slope or the back-side slope is provided in a direction parallel to the front surface when viewed from the light emitter. The surface light source device according to any one of claims 3 to 5,
The dent is
Extending in a direction orthogonal to the back surface, further comprising a side wall surface connected to the back surface and the front side slope,
The reflective member is
Provided in a range that satisfies the condition of reaching the front-side slope when the light emitted from the light emitter toward the reflecting member is regularly reflected by the reflecting member;
A surface light source including a regular reflection portion provided in a range satisfying a condition of reaching the side wall surface when light emitted from the light emitter toward the reflection member is regularly reflected by the reflection member. apparatus. The surface light source device according to any one of claims 1 to 6,
The surface light source device, wherein the front surface has a portion inclined toward the back surface within a range where light emitted from the light emitter and transmitted through the front-side inclined surface reaches. The surface light source device according to any one of claims 1 to 7,
The surface light source device, wherein when viewed from the front side, the recess has a curved shape protruding in a direction away from the point light source. The surface light source device according to any one of claims 1 to 7,
The dent is
It is located in front of the point light source, and a plurality of prism pillars are arranged in a planar shape, further comprising a prism surface,
A surface light source device in which each of the plurality of prism pillars extends in a direction orthogonal to the front surface. A surface light source device according to any one of claims 1 to 9,
Means for providing an image to be displayed, comprising image providing means disposed on the front side of the light guide plate provided in the surface light source device;
The display device capable of illuminating the image provided by the image providing means with the planar light emitted from the front surface of the light guide plate.

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