JP2018198158A - Surface light source device - Google Patents

Abstract

To suppress luminance unevenness of a surface light source device.SOLUTION: A surface light source device 100 includes: first and second light guide plates 10a and 10b; first and second reflection sheets 12a and 12b; first and second light sources 8a and 8b; and a light source drive circuit 19. The first light guide plate has a first optical control portion 16a deflecting light made incident from one side surface in a specified direction to emit it, and a first translucent portion 23a provided on a distal side from the first light source. The second light guide plate has a second translucent portion 23b transmitting the light made incident from the one side surface, and a second optical control portion 16b provided at a distal side from the second light source than the second light guide plate and deflecting the light in the specified direction to emit it. The first light guide plate and the second light guide plate are disposed so as to cause the first reflection sheet and the first optical control portion to overlap with each other, and to cause the second optical control portion and the first translucent portion to overlap with each other, in a lamination direction thereof.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a surface light source device having a light emitting surface that emits light in a planar shape.

  A conventional example of a surface light source device is described in, for example, Japanese Patent No. 4949278 (Patent Document 1). The planar illumination device (surface light source device) described in Patent Document 1 includes a light guide unit configured in a staircase shape by stacking a plurality of transparent substrates having different lengths, and each transparent light guide unit. Each light source has a light source arranged on each substrate and a reflecting member provided on the opposite side of the output surface of each transparent substrate, and each transparent substrate has an optical path conversion for directing light incident from the light source toward the output surface. Means are provided.

  By the way, in the planar illuminating device described in patent document 1, since the transparent substrate from which length differs is comprised in step shape, it irradiates in the edge part of each transparent substrate when it sees from the light-projection surface side. There is room for improvement in that light breaks are likely to occur, and the breaks are visually recognized as dark lines, resulting in uneven brightness. Such luminance unevenness becomes more conspicuous as the luminance of the irradiation light increases.

Japanese Patent No. 4949278

  A specific aspect according to the present invention is to suppress luminance unevenness of a surface light source device and improve contrast.

  A surface light source device according to an aspect of the present invention is a surface light source device that emits light in a planar shape from a light emitting surface, and (a) a first light guide plate and a second light guide plate arranged in a stacked manner, (B) a first light source that causes light to enter from one side surface of the first light guide plate; and (c) a second light source that causes light to enter from one side surface of the second light guide plate on the same side as the first light guide plate. (D) a light source driving circuit for driving the first light source and the second light source, and (e) the first light source on the facing surface on the facing surface side of the first light guide plate with the second light guide plate. A first reflection sheet disposed so as to overlap with a partial region on the near side in a plan view; and (f) a surface of the second light guide plate opposite to the surface facing the first light guide plate. A second reflection sheet disposed so as to overlap the entire surface in plan view, and (g) the first light guide plate includes a front On the other hand, a first optical control unit that deflects light incident from the side surface in a specific direction and emits the light from the first light guide plate, and a first transparent unit provided on a side farther from the first light source than the first optical control unit. (H) the second light guide plate has a second light transmissive portion for propagating light incident from the one side surface, and the second light source more than the second light guide portion. A second optical control unit that is provided on a far side and deflects the light in a specific direction and emits the light from the second light guide plate, and (i) the first light guide plate and the second light guide plate. The light plate is arranged such that, in the stacking direction, the first reflection sheet and the first optical control unit overlap, and the second optical control unit and the first light transmission unit overlap. Device.

  According to the above configuration, it is possible to suppress the uneven brightness of the surface light source device and improve the contrast.

FIG. 1 is a schematic cross-sectional view illustrating a configuration of a surface light source device according to an embodiment. FIG. 2 is a schematic cross-sectional view illustrating a configuration example of the optical control unit. FIG. 3 is a diagram for explaining the behavior (propagation state) of the light emitted from the light source inside the light guide plate. FIG. 4 is a schematic cross-sectional view showing a configuration example of the prism sheet. FIG. 5 is a plan view and a partially enlarged plan view showing the structure of the light-transmitting portion of the light guide plate on the lower layer side. FIG. 6 is a schematic perspective view showing a configuration example of a surface light source device having many light emitting areas. FIG. 7 is a schematic cross-sectional view illustrating a configuration of a surface light source device according to another embodiment. FIG. 8 is a diagram for explaining the behavior (propagation state) inside the light guide plate when the optical control unit is provided on the upper surface side of the light guide plate. FIG. 9 is a schematic cross-sectional view illustrating a configuration of a surface light source device according to another embodiment. FIG. 10 is a schematic cross-sectional view illustrating a configuration of a surface light source device according to another embodiment. FIG. 11 is an enlarged perspective view showing a cutting portion region.

  FIG. 1 is a schematic cross-sectional view illustrating a configuration of a surface light source device according to an embodiment. A surface light source device 100 shown in FIG. 1 emits light in a planar shape from a light emitting surface (light emitting surface), and includes two light sources 8a and 8b, two light guide plates 10a and 10b, two reflecting sheets 12a, 12b, the prism sheet 14, and the light source drive circuit 19 are comprised. This surface light source device 100 emits light toward the upper side in the figure, and its light emission surface is divided into two light emitting areas A01 and A02, and light can be emitted individually for each area. It is configured. In the present embodiment, the upper surface of the prism sheet 14 constitutes a “light emitting surface”. In this embodiment, the light guide plate 10a corresponds to the “first light guide plate”, the light guide plate 10b corresponds to the “second light guide plate”, the optical control unit 16a corresponds to the “first optical control unit”, The optical control unit 16b corresponds to a “second optical control unit”.

  The light source 8a is disposed on the left end side of the light guide plate 10a in the drawing, and makes light incident on a light incident surface that is a side surface on the left end side of the light guide plate 10a. The light source 8b is disposed on the left end side in the drawing of the light guide plate 10b, and makes light incident on a light incident surface that is a side surface on the left end side of the light guide plate 10b. In the present embodiment, the two light sources 8a and 8b are arranged on the left end side which is a common one end side in each of the light guide plates 10a and 10b. In the present embodiment, these light sources 8 a and 8 b are light sources including one or more light emitting elements such as LEDs, and are driven by the light source driving circuit 19.

  The light guide plate 10a guides light incident from the light source 8a and emits the light from a predetermined position to the upper surface side. The light guide plate 10b guides light incident from the light source 8b and emits the light from a predetermined position to the upper surface side. In the present embodiment, each of the light guide plates 10a and 10b is a film-like light guide plate and has substantially the same length in the left-right direction in the figure, and is stacked in the vertical direction in the figure. As such a light guide plate 10a, 10b, what is described in well-known literature, such as Unexamined-Japanese-Patent No. 2015-060765, can be used, for example.

  The light guide plate 10a is disposed at a position closest to the light emitting surface, and has an optical control unit 16a partially disposed on the lower surface side thereof. On the upper surface side of the light guide plate 10a, continuous or discontinuous lenticular patterns having a role (function) for condensing the light emitted from the light guide plate may be formed on the entire surface at equal intervals. A range in which the optical control unit 16a of the light guide plate 10a is formed is associated with the light emitting region A01 described above.

  The light guide plate 10b is disposed at a position relatively far from the light emitting surface as compared with the light guide plate 10a, and has an optical control unit 16b partially disposed on the lower surface side thereof. Specifically, the optical control unit 16b of the light guide plate 10b is provided at a position that does not overlap with the optical control unit 16a of the light guide plate 10a. On the upper surface side of the light guide plate 10b, a continuous or discontinuous lenticular pattern having a role (function) of collecting the light emitted from the light guide plate may be formed on the entire surface at equal intervals. A range in which the optical control unit 16b of the light guide plate 10b is formed is associated with the light emitting region A02 described above.

  The optical control unit 16a is provided on the lower surface of the light guide plate 10a in the drawing. The optical control unit 16a deflects light incident from the light source 8a in a specific direction and emits the light toward the upper surface side of the light guide plate 10a in the drawing, and has a reflection surface formed by a plurality of minute irregularities. Yes. The optical control unit 16b has the same configuration. As illustrated, the optical control unit 16a is disposed at a position relatively close to the light incident surface, and the optical control unit 16b is disposed at a position relatively far from the light incident surface. ing. The light guide plates 10a and 10b are arranged so as not to overlap each other in the respective stacking directions (vertical direction in the figure). In addition, each optical control part 16a, 16b may mutually overlap slightly.

  The translucent portion 23a is a portion sandwiched between the upper and lower surfaces of the light guide plate 10a, has translucency, and is disposed on the light guide plate 10a on the side farther from the light source 8a than the optical control portion 16a. The translucent portion 23b is a portion sandwiched between the upper and lower surfaces of the light guide plate 10b, has translucency, and is disposed closer to the light source 8b than the optical control portion 16b in the light guide plate 10b. . The light transmitting portion 23b functions as a waveguide for guiding light incident on the one side surface of the light guide plate 10b from the light source 8b along the right direction in the drawing to reach the optical control portion 16b. The optical control unit 16b is disposed so as to overlap with the light transmitting unit 23a of the light guide plate 10a in plan view, and the light deflected by the optical control unit 16b and emitted to the upper surface side of the light guide plate 10b in the drawing is the light transmitting unit. The light passes through 23 a and enters the prism sheet 14.

  The reflection sheet 12a is disposed on the lower surface side of the light guide plate 10a so as to overlap with a range in which the optical control unit 16a is provided in plan view. An air layer exists between the reflection sheet 12a and the optical control unit 16a of the light guide plate 10a. Further, the reflection sheet 12b is arranged on the lower surface side of the light guide plate 10b so as to overlap with substantially the entire lower surface of the light guide plate 10b including the range in which the optical control unit 16b is provided in plan view. An air layer exists between the reflection sheet 12b and the optical control unit 16b of the light guide plate 10b.

  The prism sheet 14 has a large number of prism portions on one surface facing the light guide plate 10a, and emits light incident on the one surface from an oblique direction in the normal direction on the other surface. In addition, many prism parts of the prism sheet 14 may be provided in the other surface side which does not oppose the light-guide plate 10a.

  FIG. 2 is a schematic cross-sectional view illustrating a configuration example of the optical control unit. In addition, although illustrated about the optical control part 16a here, it is the same structure also about the other optical control part 16b. As shown in the figure, the optical control unit 16a includes a plurality of prism portions 20a which are convex portions having a triangular cross section provided so as to protrude from the lower surface of the light guide plate 10a. Each prism portion 20a has two inclined surfaces 21a and 22a. In addition, as such an optical control part 16a etc., what is described in well-known literatures, such as patent 5066741, for example, can be used.

  FIG. 3 is a diagram for explaining the behavior (propagation state) of the light emitted from the light source inside the light guide plate. Here, the light guide plate 10a is shown in a simplified manner, and the optical path inside the light guide plate 10a is schematically shown by thin lines. As shown in the drawing, the light emitted to the upper surface of the light guide plate 10a is not obliquely reflected light or diffused light but has a straight traveling property on the upper surface of the light guide plate 10a. The oblique direction is not coincident with the normal direction of the upper surface. The light is deflected at a certain angle and emitted.

  Specifically, the light that has entered the light guide plate 10a from the light source 8a reaches the optical control unit 16a directly or after being reflected from the upper surface of the light guide plate 10a, is reflected by the prism unit 20a, and is incident on the upper or lower surface. Until the angle becomes smaller than a critical angle (for example, 42.2 ° for an acrylic light guide plate), total reflection is repeated in the section where the optical control unit 16a exists, and when the incident angle reaches the critical angle, the upper surface of the light guide plate 10a is repeated. To the side. The emitted light reaches the prism sheet 14.

  The behavior of the light guide plate 10b is basically the same. In the case of the light guide plate 10b, the light incident from the light source 8b is totally reflected in the light transmitting part 23b where the optical control part 16b does not exist, the component whose incident angle θ to the upper surface or the lower surface exceeds the critical angle. The light propagates through the light guide plate 10b repeatedly and reaches the optical control unit 16b. The subsequent behavior is the same as that of the light guide plate 10a.

  When the incident angle θ to the prism portion 20a of the optical control unit 16a is smaller than the critical angle, light is emitted to the air layer, passes through the light guide plate 10a, reaches the reflection sheet 12a, and is reflected by the reflection sheet 12a. Then, the light again passes through the light guide plate 10a and returns to the light guide plate 10a. Similarly, when the incident angle θ to the prism unit 20b of the optical control unit 16b is smaller than the critical angle, light is emitted to the air layer and reaches the reflection sheet 12b, is reflected by the reflection sheet 12b, and is guided again. Return to the light plate 10b.

  FIG. 4 is a schematic cross-sectional view showing a configuration example of the prism sheet. As shown in the figure, the prism sheet 14 is a triangular prism-shaped convex portion having a substantially triangular cross section and a thickness direction in a direction perpendicular to the paper surface, on one surface side (lower surface in the drawing) facing the light guide plate 10a and the like. A plurality of prism portions 30a are provided. The shape of each prism portion 30a is determined by the radius of ∠OAB, ∠OAC, and arc AC as shown in FIG. In addition to the arc AC, an arbitrary curve such as a straight line, a spline curve, or a parabola may be used. Each prism portion 30a has a slope 31a corresponding to the flange OAB and a slope 32a corresponding to the arc AC. Light emitted from the light guide plates 10a and 10b and obliquely incident on the lower surface of the prism sheet 14 is incident on the inclined surface 31a of each prism portion 30a and refracted, and is totally reflected on the inclined surface 32a. It emits in the line direction. In addition, as such a prism sheet 14, what was described in well-known literature, such as patent 4044511, can be used, for example.

  FIG. 5 is a plan view and a partially enlarged plan view showing the structure of the light transmitting portion 23b of the lower-side light guide plate 10b. A plurality of cut portions (groove portions) 40 are provided in the light transmitting portion 23b of the light guide plate 10b in a direction along the traveling direction of light from the light source 8b. Each cutting part 40 in this example is arrange | positioned at intervals. Specifically, it is preferable that each cutting unit 40 be arranged in correspondence with the interval between unit blocks of the light source 8b (for example, blocks for several light emitting elements). The space | interval of the cutting parts 40 can be about 40 mm, for example.

  Moreover, it is preferable that each cutting part 40 is formed as a groove | channel (hole) penetrated between the upper surface and the lower surface in the thickness direction of the light-guide plate 10b. Thereby, an air layer is arrange | positioned by the predetermined space | interval in the translucent part 23b of the light-guide plate 10b. The faces facing each other across the cutting portion 40 of the light guide plate 10b may be in contact with each other with an air layer interposed therebetween, or may be separated from several μm to several mm.

  Moreover, the junction part 41 is provided between the edge part of the light-guide plate 10b, and each cutting part 40. As shown in FIG. That is, each cutting part 40 does not reach the end part of the light guide plate 10 b, and the end part of the light guide plate 10 b is joined by the joining part 41. The width of the joint portion 41, that is, the distance between the end portion of the light guide plate 10b and each cutting portion 40 is set as appropriate, and is, for example, several mm. By providing such a joint portion 41, the number of steps for assembling the light guide plate 10b when the surface light source device 100 is assembled can be reduced. However, in principle, this joint 41 may be omitted. That is, each cutting part 40 may reach the end of the light guide plate 10b.

  The processing for providing each of the cutting portions 40 and the joining portions 41 can be easily realized by adding a blade to a die used for forming the light guide plate 10b, for example. In this case, for example, a film light guide plate made of polycarbonate is preferably used.

  By providing each of the cut portions 40 as described above in the light transmitting portion 23b of the light guide plate 10b, the light incident on the end portion of the light guide plate 10b from the light source 8b is entirely transmitted between the surfaces defining the cut portions 40. The light propagates through the light guide plate 10b while being reflected. That is, the light incident from the light source 8b is totally reflected between the two adjacent cutting sections 40 and propagates to the optical control section 16b. For this reason, since the incident light propagates without spreading, light utilization efficiency and contrast can be improved.

  Here, it is preferable that a certain distance is provided between each cutting unit 40 and the optical control unit 16b. By appropriately setting this distance W, it is possible to reduce unevenness in luminance. The distance W has a correlation with the thickness of the light guide plate 10b. Specifically, the distance W is preferably 10 times or more the thickness of the light guide plate 10b. For example, if the thickness d of the light guide plate 10b is 300 μm, the effect of reducing luminance unevenness can be obtained by setting the distance W to 3 mm or more. In consideration of both luminance unevenness and contrast, the distance W is preferably set in the range of 15 to 100 times the thickness d of the light guide plate 10b.

  FIG. 6 is a schematic perspective view showing a configuration example of a surface light source device having many light emitting areas. The surface light source device 100 can emit light individually in each of the light emitting areas A01 and A02. That is, the light emitting surface can be divided for each light emitting region to emit light. In addition, since the straightness of light in each light guide plate 10a is high, a plurality of light emitting regions are provided in a direction substantially orthogonal to the main traveling direction of the light emitted from the light source, and the driving is performed using the plurality of light sources. By performing for each block, a larger number of light emitting regions can be caused to emit light individually. A configuration example of a surface light source device that realizes this will be described below.

  The surface light source device 100a shown in FIG. 6 is in the depth direction in the figure on one side surface provided on the left side in the figure of the two light guide plates 10a and 10b arranged in the y direction which is the vertical direction in the figure. Light sources 8a and 8b composed of a plurality of light emitting elements arranged along the z direction (longitudinal direction of the left side surface) are used. The configuration of each light guide plate 10a, 10b is the same as described above. Although not shown for the sake of convenience, reflection sheets 12a and 12b are disposed on the lower surface side of each light guide plate 10a and the like, and a prism sheet 14 is disposed on the upper surface side of the light guide plate 10a. The light source drive circuit 19 is also connected to each light source 8a and the like, although not shown.

  In the example shown in the figure, for each light guide plate 10a, 10b, four light emitting elements for each of the light sources 8a, 8b associated with each light guide plate 10a, 10b are set as one block, and the light emitting elements are controlled to be turned on and off for each block. Further, as described above, in the x direction (left and right direction in the figure), two light emitting regions can be made to emit light individually for each block. Therefore, for example, each of the four light emitting elements in each of the light sources 8a and 8b in the front block in the figure is caused to emit light individually, whereby the light emitting areas A01 and A02 can be caused to emit light individually. Since such blocks are provided in m rows in the depth direction (z direction), 2 × m light emitting regions can be caused to emit light individually. Note that the number of light emitting elements assigned to each block is not limited to four. For example, it may be one, and in that case, a more finely divided light emitting region can be provided.

  FIG. 7 is a schematic cross-sectional view illustrating a configuration of a surface light source device according to another embodiment. In comparison with the surface light source device 100 shown in FIG. 1, only the arrangement of the light guide plate 10b is different. Since other configurations are common, detailed description of each configuration is omitted by attaching the same reference numerals. In the surface light source device 100b shown in FIG. 7, the optical control unit 16b is provided on the upper surface side of the light guide plate 10b, that is, on the side close to the light guide plate 10a.

  FIG. 8 is a diagram for explaining the behavior (propagation state) inside the light guide plate when the optical control unit is provided on the upper surface side of the light guide plate. Here, the light guide plate 10b is shown in a simplified manner, and the optical path inside the light guide plate 10b is schematically shown by thin lines. As shown in the drawing, the light emitted to the upper surface of the light guide plate 10b is not obliquely reflected light or diffused light but has a straight traveling property on the upper surface of the light guide plate 10b. The oblique direction does not coincide with the normal direction of the upper surface. The light is deflected at a certain angle and emitted.

  Specifically, the light that has entered the light guide plate 10b from the light source 8b and reached the optical control unit 16b is in a section where the optical control unit 16b exists until the incident angle on the prism unit 20b becomes smaller than the critical angle. Total reflection is repeated, and when the incident angle reaches the critical angle, the light is emitted to the upper surface side of the light guide plate 10b. The emitted light reaches the prism sheet 14. When the incident angle θ on the lower surface of the light guide plate 10b is smaller than the critical angle, light is emitted to the air layer, reflected by the reflection sheet 12b, and returned to the light guide plate 10b again.

  According to such a configuration, since the optical control unit 16b of the light guide plate 10b is closer to the upper light guide plate 10a, it is possible to improve the appearance when the surface light source device 100b is fully lit.

  According to each embodiment as described above, a surface light source device in which luminance uniformity is improved by suppressing luminance unevenness can be obtained.

  Note that the present invention is not limited to the contents of the above-described embodiment, and various modifications can be made within the scope of the gist of the present invention. For example, the light emitting elements constituting each light source are not limited to the above-described LEDs. Further, the number of laminated light guide plates is not limited to the above two. Further, the prism sheet used as the optical path adjusting plate in the surface light source device of the above-described embodiment may be replaced with a light diffusing plate.

  In addition, the plurality of cutting portions in the above-described embodiment are effective even when applied to a surface light source device that uses only one light guide plate. Specific examples thereof will be described below.

  FIG. 9 is a schematic cross-sectional view illustrating a configuration of a surface light source device according to another embodiment. In comparison with the surface light source device 100 shown in FIG. 1 described above, the light source 8a, the light guide plate 10a, and the reflection sheet 12a are omitted, and the cut portion region 42 is provided at the end of the light guide plate 10b on the side close to the light source 8b. And the point which provided the reflective sheet 12c differs. Since other configurations are common, detailed description of each configuration is omitted by attaching the same reference numerals. The cutting portion region 42 in the surface light source device 100c shown in FIG. 9 is a region where the plurality of cutting portions 40 and the joint portions 41 (see FIG. 5) described above are provided. Moreover, the reflection sheet 12c is provided in the range which overlaps the cutting part area | region 42 in the upper surface side of the light-guide plate 10b. Since the cut portion region 42 is sandwiched between the reflective sheet 12c and the lower reflective sheet 12b, light leakage from the cut portion region 42 can be prevented. According to such a configuration, the straightness of light incident from each light source 8b can be improved, and the contrast when the light emitting area is switched for each light source 8b can be improved (see FIG. 6).

  FIG. 10 is a schematic cross-sectional view illustrating a configuration of a surface light source device according to another embodiment. 9 is different from the surface light source device shown in FIG. 9 only in that the cut portion region and the reflection sheet are provided in a curved manner. Since other configurations are common, detailed description of each configuration is omitted by attaching the same reference numerals. The cut portion region 42 in the surface light source device 100d shown in FIG. 10 is provided with a 180 ° curve in a circular arc shape as shown in the drawing, and an end portion thereof is disposed below the light guide plate 10b. Accordingly, the light source 8b is also arranged below the light guide plate 10b. The reflection sheet 12 d is also provided in an arc shape corresponding to the curvature of the cutting part region 42. In order to obtain such a light guide plate 10b, for example, a film light guide plate using a polycarbonate base material is preferably used. FIG. 11 is an enlarged perspective view showing the cutting portion region 42. As illustrated, each cutting portion 40 of the cutting portion region 42 is provided so as to be curved along the cutting portion region 42. According to such a configuration, a surface light source device suitable for a liquid crystal display device with a narrow frame can be obtained.

DESCRIPTION OF SYMBOLS 100: Surface light source device 8a, 8b: Light source 10a, 10b: Light guide plate 12a, 12b: Reflection sheet 14: Prism sheet 16a, 16b: Optical control part 19: Light source drive circuit 20a, 20b: Prism part 21a, 22a: Slope 23a , 23b: Translucent part 30a: Prism part 31a, 32a: Slope

Claims (6)

A surface light source device that emits light in a planar shape from a light emitting surface,
A first light guide plate and a second light guide plate arranged in a stacked manner;
A first light source for allowing light to enter from one side surface of the first light guide plate;
A second light source for allowing light to enter from one side surface of the second light guide plate on the same side as the first light guide plate;
A light source driving circuit for driving the first light source and the second light source;
A first reflection sheet disposed so as to overlap with a partial region of the first surface of the first light guide plate facing the second light guide plate on a side near the first light source of the second surface;
A second reflection sheet disposed on the opposite surface of the second light guide plate to the surface opposite to the first light guide plate so as to overlap substantially the entire opposite surface in plan view;
Including
The first light guide plate has a first optical control unit that deflects light incident from the one side surface in a specific direction and emits the light from the first light guide plate, and is farther from the first light source than the first optical control unit. A first translucent part provided on the side,
The second light guide plate is provided on a side farther from the second light source than the second light guide part and a second light transmitting part for propagating light incident from the one side surface, and directs the light in a specific direction. A second optical control unit that deflects and emits the light from the second light guide plate,
In the stacking direction of the first light guide plate and the second light guide plate, the first reflection sheet and the first optical control unit overlap, and the second optical control unit and the first light transmission unit are Arranged to overlap,
Surface light source device. The second light guide plate further includes a plurality of cutting portions provided in the second light transmitting portion.
The surface light source device according to claim 1. The plurality of cutting portions are arranged with a predetermined distance between each one end side and the second optical control unit,
The surface light source device according to claim 2. The second light guide plate further includes a joint provided between the one side surface and each of the plurality of cut portions.
The surface light source device according to claim 2. The first light guide plate is disposed closer to the light exit surface than the second light guide plate;
The surface light source device according to claim 1. Each of the first light source and the second light source has a plurality of light emitting elements,
The light source driving device sets a block including one or more light emitting elements among the plurality of light emitting elements for each of the first light source and the second light source, and turns on and off the light emitting elements for each of the blocks. Control,
The surface light source device according to claim 1.

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