JP2018085267A - Surface light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source that improves luminance uniformity and a contrast ratio.SOLUTION: A surface light source comprises a first light guide plate 10 and a second light guide plate 11 oppositely arranged, a prism sheet 15 arranged on the side of the first light guide plate, first light sources 8a and 8b that cause light to enter one side surface and the other side surface of the first light guide plate respectively, second light sources 9a and 9b that cause light to enter one side surface and the other side surface of the second light guide plate respectively, and a light source drive circuit 18 that drives the first light sources and the second light sources. The first light guide plate comprises first optical control parts 16a and 16b that deflect the light from the first light sources in specific directions between the one side surface and the other side surface, and comprises first flat parts 23 in respective regions on the side of the one side surface and the side of the other side surface across arrangement regions of the first optical control parts. The second light guide plate comprises second optical control parts 17a and 17b that deflect the light from the second light sources in specific directions in respective regions overlapping with arrangement regions of the respective first flat parts.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 the surface light source device is described in, for example, Japanese Patent No. 4482286 (Patent Document 1). The backlight unit (surface light source device) described in FIG. 2 of Patent Document 1 has two light guide plates arranged in a stacked manner, and a light source is provided near each of the left and right end surfaces of each light guide plate. The cold cathode tubes are arranged. Each light guide plate is provided with two diffuse reflection layers, and is configured such that light incident from a light source located near each diffuse reflection layer is emitted to the upper surface side of the light guide plate.

  Further, the backlight unit described in FIG. 6 of Patent Document 1 includes two upper light guide plates arranged in the left-right direction at the same height and arranged such that one end surfaces of both are in contact with each other, and these two upper light guide plates There are two lower light guide plates respectively disposed on the lower side, and a light source is disposed on the other end surface of each light guide plate. Each lower light guide plate has a shorter length in the left-right direction than each upper light guide plate, and is arranged close to the other end face side of each upper light guide plate. Each upper light guide plate is provided with one diffuse reflection layer, and each lower light guide plate is also provided with one diffuse reflection layer. These four diffuse reflection layers overlap each other in the vertical direction. It is arranged not to become.

  By the way, in the backlight unit described in FIG. 2 of Patent Document 1, it is assumed that the light emitted from the light source at the closest position is incident on the diffuse reflection layer of each light guide plate. Since part of the light emitted from the light source located far from the diffuse reflection layer also enters, there is room for improvement in that light leakage can occur and the luminance uniformity can be reduced.

  On the other hand, the backlight unit described in FIG. 6 of Patent Document 1 has the disadvantage that the number of light guide plates is increased, resulting in increased assembly man-hours and costs. In addition, dark lines may occur at the joint between the two upper light guide plates. In this regard, an embodiment in which a reflection mirror is provided at the seam has been proposed, but in that case, another disadvantage that a bright line may be generated at the seam by reflected light may occur. Furthermore, on one end face of the lower light guide plate, there is a means to blur the boundary to prevent uneven brightness due to the boundary, but this makes it difficult to cut off the light when the backlight unit partially emits light. The disadvantage that the ratio is reduced can occur.

Japanese Patent No. 4482286

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

[1] A surface light source device according to one aspect of the present invention includes: (a) a first light guide plate and a second light guide plate disposed to face each other; and (b) a prism sheet disposed on the first light guide plate side. (C) a first light source for individually making light incident on one side surface and the other side surface of the first light guide plate; and (d) a second light source for individually making light incident on one side surface and the other side surface of the second light guide plate. And (e) a light source driving circuit for driving the first light source and the second light source, and (f) the first light guide plate is light from the first light source between the one side surface and the other side surface. A first optical control unit that deflects the first optical control unit in a specific direction, and a first flat portion in each of the one side surface side and the other side surface side across the arrangement region of the first optical control unit, and (g ) The second light guide plate applies light from the second light source to each region overlapping with the arrangement region of each first flat portion. A second optical control unit which deflects the directed, is a surface light source device.
[2] A surface light source device according to another aspect of the present invention includes: (a) a first light guide plate and a second light guide plate disposed to face each other; and (b) a prism sheet disposed on the second light guide plate side. (C) a first light source that individually makes light incident on one side surface and the other side surface of the first light guide plate; and (d) a second light source that makes light individually incident on one side surface and the other side surface of the second light guide plate. A light source; and (e) a light source driving circuit for driving the first light source and the second light source, and (f) the first light guide plate from the first light source between the one side surface and the other side surface. And (g) the second light guide plate has a second flat portion in a region overlapping an arrangement region of the first optical control unit, and the second optical control unit deflects the light in a specific direction. In each region located on each of the one side surface side and the other side surface side across the flat region arrangement region, A second optical control unit which deflects the light from the light source to a specific direction, is a surface light source device.

  According to the above configuration, the luminance uniformity and contrast ratio of the surface light source device can be improved.

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 diagram illustrating an example of an optical simulation result assuming a surface light source device having the configuration of the present embodiment. FIG. 6 is a diagram illustrating an example of an optical simulation result assuming a surface light source device having the configuration of the present embodiment. FIG. 7 is a schematic perspective view illustrating a configuration example of a surface light source device having many light emitting regions. FIG. 8 is a schematic cross-sectional view illustrating a configuration of a surface light source device according to another embodiment. FIG. 9 is a schematic cross-sectional view illustrating a configuration of a surface light source device according to another embodiment.

  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 has a light emitting surface that emits light in a planar shape, and includes four light sources 8a, 8b, 9a, 9b, two light guide plates 10, 11, three reflecting sheets 12, 13, 14, a prism sheet 15, and a light source driving circuit 18. This surface light source device 100 emits light upward in the figure, and its light emitting surface is divided into four light emitting areas A01, A02, A03, A04, and light is individually emitted for each area. It is configured to be injectable.

  The light source 8 a is disposed on the left end side in the drawing of the light guide plate 10, and makes light incident on a light incident surface that is a side surface on the left end side of the light guide plate 10. The light source 8 b is disposed on the right end side of the light guide plate 10 in the drawing, and makes light incident on a light incident surface that is a side surface of the right end portion of the light guide plate 10. The light source 9 a is disposed on the left end side in the drawing of the light guide plate 11, and makes light incident on a light incident surface that is a side surface on the left end side of the light guide plate 11. The light source 9 b is disposed on the right end side in the drawing of the light guide plate 11, and makes light incident on a light incident surface that is a side surface on the right end side of the light guide plate 11. In the present embodiment, these light sources 8 a, 8 b, 9 a, and 9 b are light sources configured to include one or more light emitting elements such as LEDs, and are driven by the light source driving circuit 18. The light sources 8a and 8b correspond to “first light sources”, and the light sources 9a and 9b correspond to “second light sources”.

  The light guide plate 10 guides light incident from the light sources 8a and 8b and emits the light to the upper surface side. Similarly, the light guide plate 11 guides light incident from the light sources 9a and 9b and emits it to the upper surface side. In this embodiment, each light guide plate 10 and 11 is a film-form light guide plate. As the detailed structure of such a light guide plate, for example, those described in publicly known documents such as JP-A-2015-060765 can be used. The light guide plate 10 corresponds to a “first light guide plate”, and the light guide plate 11 corresponds to a “second light guide plate”.

  The light guide plate 10 has two optical control units 16a and 16b on the center side in the left-right direction in the figure, and a left end side (left side) and a region where the optical control units 16a and 16b are arranged. Each has a flat portion (translucent portion) 23 on the right end side (right side surface side). The two optical control units 16a and 16b correspond to “first optical control unit”, and the flat portion 23 corresponds to “first flat portion”.

  Each of the optical control units 16a and 16b is provided on the lower surface of the light guide plate 10 in the drawing. The optical control unit 16a reflects the light incident from the light source 8a and emits it to the upper surface side of the light guide plate 10 in the figure, and has a reflection surface formed by a plurality of minute irregularities. Similarly, the optical control unit 16b reflects light incident from the light source 8b and emits it to the upper surface side of the light guide plate 10 in the drawing, and has a reflection surface formed by a plurality of minute irregularities. .

  Each flat portion 23 is a portion sandwiched between flat upper and lower surfaces of the light guide plate 10 and has translucency. These flat portions 23 are used to transmit light emitted from the light guide plate 11 disposed below the light guide plate 10 and to enter the prism sheet 15. Each flat portion 23 also functions as a waveguide for causing light incident from each light source 8a, 8b to reach each optical control portion 16a, 16b.

  The light guide plate 11 has two optical control units 17a and 17b on the left end side and the right end side in the left-right direction in the figure, and is a region sandwiched between regions where the optical control units 17a and 17b are arranged. The flat portion 24 is provided in a region overlapping the region where the optical control units 16a and 16b are disposed. The two optical control units 17a and 17b correspond to the “second optical control unit”, and the flat portion 24 corresponds to the “second flat portion”.

  Each optical control unit 17a, 17b is provided on the lower surface of the light guide plate 11 in the drawing. The optical control unit 17a reflects light incident from the light source 9a and emits it to the upper surface side of the light guide plate 11 in the figure, and has a reflection surface formed by a plurality of minute irregularities. Similarly, the optical control unit 17b reflects light incident from the light source 9b and emits it to the upper surface side of the light guide plate 11 in the figure, and has a reflection surface formed by a plurality of minute irregularities. .

  The flat part (translucent part) 24 is a part sandwiched between the flat upper and lower surfaces of the light guide plate 11 and has translucency.

  The reflection sheet 12 is disposed on the lower surface side of the light guide plate 10 so as to overlap the optical control units 16a and 16b provided on the light guide plate 10 in plan view. An air layer exists between the reflection sheet 12 and the optical control units 16 a and 16 b of the light guide plate 10.

  The reflection sheet 13 is arranged on the lower surface side of the light guide plate 11 so as to overlap the optical control unit 17a provided on the light guide plate 11 in plan view. Similarly, the reflection sheet 14 is disposed on the lower surface side of the light guide plate 11 so as to overlap the optical control unit 17b provided on the light guide plate 11 in plan view. There is an air layer between the reflection sheets 13 and 14 and the optical control units 17 a and 17 b of the light guide plate 11.

  The prism sheet 15 has a large number of prism portions on one surface facing the light guide plate 10, and emits light incident on the one surface from an oblique direction in the normal direction on the other surface.

  FIG. 2 is a schematic cross-sectional view illustrating a configuration example of the optical control unit. As illustrated, the optical control unit 16a and the optical control unit 16b have a symmetrical shape with a certain reference position a (for example, the center of the light guide plate 10 in the left-right direction in the figure) interposed therebetween. In addition, although the example of a structure of each optical control part 16a, 16b provided in the light-guide plate 10 is shown here, similarly about each optical control part 17a, 17b provided in the light-guide plate 11, it sandwiches a certain reference position. It has a symmetrical shape.

  The optical control unit 16a includes a plurality of prism portions 20a which are convex portions having a triangular cross section provided on the lower surface of the light guide plate 10 in the drawing. Each prism portion 20a has two inclined surfaces 21a and 22a. Similarly, the optical control part 16b is comprised including the some prism part 20b which is a convex part of the cross-sectional triangle shape provided in the lower surface in the figure of the light-guide plate 10. As shown in FIG. Each prism portion 20b has two inclined surfaces 21b and 22b. In addition, about detailed structures, such as such an optical control part 16a, what was described in well-known literatures, such as patent 5066741, can be used, for example.

  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 10 and the reflection sheet 12 are partially shown, and the optical path inside the light guide plate 10 is schematically shown by thin lines. Although the light incident on the light guide plate 10 from the light source 8a will be described here, the behavior is the same for the light incident on the light guide plate 10 from the light source 8b and the light incident on the light guide plate 11 from the light source 9a or 9b. .

  The light that has entered the light guide plate 10 from the light source 8a is reflected by the prism portion 20a and is emitted to the upper surface side of the light guide plate 10. The light transmitted through the prism portion 20 a is reflected by the lower reflection sheet 12, returns to the prism portion 20 a, and is emitted to the upper surface side of the light guide plate 10. The light emitted to the upper surface of the light guide plate 10 is deflected to the upper surface of the light guide plate 10 at a constant angle and emitted as light having straightness rather than diffusely reflected light or diffused light. In addition, since the optical control unit 16 a does not exist in each flat part 23, the light incident on these flat parts 23 propagates by repeating total reflection inside the light guide plate 10.

  FIG. 4 is a schematic cross-sectional view showing a configuration example of the prism sheet. As shown in the figure, the prism sheet 15 is a triangular prism-shaped convex portion on one surface (lower surface in the drawing) facing the light guide plate 10, each having a substantially triangular cross section and having a thickness direction perpendicular to the paper surface. A plurality of prism portions 30a and 30b are provided. The shape of each prism portion 30a, 30b 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. Each prism portion 30b has a slope 31b corresponding to the flange OAB and a slope 32b corresponding to the arc AC.

  As shown in the figure, each prism portion 30a and each prism portion 30b have a symmetrical shape with a certain reference position b (for example, the center of the prism sheet 15 in the left-right direction in the figure) interposed therebetween. The portion where each prism portion 30a, which is the left portion of the prism sheet 15, is associated with the light emitting areas A01 and A02 described above. The light emitted from the light guide plates 10 and 11 is incident on the inclined surface 31a of each prism portion 30a, refracted, totally reflected by the inclined surface 32a, and emitted in the normal direction of the upper surface of the prism sheet 15. Similarly, the portion where each prism portion 30b, which is the right portion of the prism sheet 15 in the drawing, is associated with the light emitting areas A03 and A04 described above. The light emitted from the light guide plates 10 and 11 is incident on the inclined surface 31b of each prism portion 30b and refracted, totally reflected by the inclined surface 32b, and emitted in the normal direction of the upper surface of the prism sheet 15. In addition, about the detailed structure of such a prism sheet 15, what is described in well-known literatures, such as patent 4044511, can be used, for example.

  5 and 6 are diagrams illustrating an example of an optical simulation result assuming a surface light source device having the configuration of the present embodiment. FIG. 5A is a diagram showing the luminance when all the four light emitting regions emit light, and FIG. 5B is a diagram showing the luminance when the two light emitting regions A02 and A03 are made to emit light. FIG. 5C is a diagram showing the luminance when the two light emitting areas A01 and A04 are caused to emit light. FIGS. 6A to 6D are diagrams showing the luminance when the four light emitting regions A01, A02, A03, and A04 are individually emitted. As shown in each figure, it can be seen that even when light is emitted separately for each light emitting region, the contrast ratio for each light emitting region is good without being affected by leakage light. In addition, there is no need to divide the light guide plate for each light emitting region, and there is no problem of uneven brightness at the boundary due to the joint between the light guide plates or the installation of the reflecting mirror. It turns out that the brightness | luminance when light-emitting a region can be made more uniform.

  As described above, the surface light source device 100 of the present embodiment can individually emit light in the light emitting areas A01, A02, A03, and A04. That is, the light emitting surface can be divided for each light emitting region to emit light. In addition, since the light guide plates 10 and 11 have high linearity of light, a plurality of light emitting areas are provided in a direction substantially orthogonal to the main traveling direction of the light emitted from the light source, and the light sources are used to drive them. By performing for each block, more light emitting regions can be made to emit light individually. A configuration example of a surface light source device that realizes this will be described below.

  FIG. 7 is a schematic perspective view illustrating a configuration example of a surface light source device having many light emitting regions. The illustrated surface light source device 100a is arranged at both ends of the light guide plates 10 and 11 arranged in the y direction, which is the vertical direction in the drawing, in the z direction (longitudinal direction of both left and right side surfaces) in the drawing. Light sources 8 a, 8 b, 9 a, 9 b made up of light emitting elements arranged along a large number are used. The structure of each light guide plate 10 and 11 is the same as the above, and reflection sheets 12, 13 and 14 are provided on the lower surface side of each light guide plate 10 and 11, respectively. The prism sheet 15 is not shown in the drawing, but is actually disposed on the upper surface side of the light guide plate 10.

  In the illustrated example, for each of the light sources 8a, 8b, 9a, and 9b, four light emitting elements 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 (the horizontal direction in the figure), the four light emitting areas 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, 8b, 9a, and 9b in the front block in the figure individually emits light, thereby causing the light emitting areas A01, A02, A03, and A04 to emit light individually. Can do. Since such blocks are provided in m rows in the depth direction (z direction), the light emitting areas A11, A12, A13, A14, the light emitting areas A21, A22, A23, A24,..., The light emitting areas Am1, Am2, Am3, Am4 can be made to emit light individually. In other words, in the illustrated example, 4 × m light emitting regions can be made 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. 8 is a schematic cross-sectional view illustrating a configuration of a surface light source device according to another embodiment. The surface light source device 100b shown here is mainly different from the surface light source device 100 shown in FIG. 1 described above in that the vertical relationship between the light guide plate 10 and the light guide plate 11 is changed. With the replacement of the light guide plates 10 and 11, the positions of the light sources 8a, 8b, 9a, and 9b are also switched, and the positions of the reflection sheets 12, 13, and 14 are also switched. In this surface light source device 100 b, light emitted from the light guide plate 10 through the flat portion 24 passes through the flat portion 24 of the light guide plate 11 and enters the prism sheet 15. Even with such a configuration, the same effect as the surface light source device 100 having the configuration shown in FIG. 1 can be obtained. In the surface light source device 100b of this embodiment, as shown in FIG. 9, the horizontal width of the lower light guide plate 10c may be shortened corresponding to the arrangement range of the optical control units 16a and 16c. . In the surface light source device 100c of this embodiment, since the flat portion is omitted and the light sources 8a and 8b and the optical control units 16a and 16b are closer to each other, an effect of increasing the central luminance of the light emitting surface can be obtained.

  According to each embodiment as described above, a surface light source device with improved luminance uniformity and contrast ratio 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.

100, 100a, 100b, 100c: surface light source device 8a, 8b, 9a, 9b: light source 10, 10c, 11: light guide plate 12, 13, 14: reflection sheet 15: prism sheet 16a, 16b, 17a, 17b: optical control Part 18: Light source drive circuit 20a, 20b: Prism part 21a, 22a, 21b, 22b: Slope 23, 24: Flat part 30a, 30b: Prism part 31a, 31b, 32a, 32b: Slope

Claims (8)

A first light guide plate and a second light guide plate disposed to face each other;
A prism sheet disposed on the first light guide plate side;
A first light source for individually making light incident on one side surface and the other side surface of the first light guide plate;
A second light source for individually making light incident on one side surface and the other side surface of the second light guide plate;
A light source driving circuit for driving the first light source and the second light source;
Including
The first light guide plate includes a first optical control unit that deflects light from the first light source in a specific direction between the one side surface and the other side surface, and sandwiches an arrangement region of the first optical control unit. It has a first flat portion in each region on the one side surface side and the other side surface side,
The second light guide plate has a second optical control unit that deflects light from the second light source in a specific direction in each region overlapping with an arrangement region of each first flat part.
Surface light source device. The second light guide plate has a second flat portion in a region overlapping the arrangement region of the first optical control unit,
The surface light source device according to claim 1. A first light guide plate and a second light guide plate disposed to face each other;
A prism sheet disposed on the second light guide plate side;
A first light source for individually making light incident on one side surface and the other side surface of the first light guide plate;
A second light source for individually making light incident on one side surface and the other side surface of the second light guide plate;
A light source driving circuit for driving the first light source and the second light source;
Including
The first light guide plate has a first optical control unit that deflects light from the first light source in a specific direction between the one side surface and the other side surface,
The second light guide plate has a second flat portion in a region overlapping the arrangement region of the first optical control unit, and each of the one side surface side and the other side surface side of the second flat portion with the arrangement region of the second flat portion interposed therebetween. A second optical control unit for deflecting light from the second light source in a specific direction in each region located at
Surface light source device. The first light guide plate has a first flat portion in each of the one side surface side and the other side surface side across the arrangement region of the first optical control unit,
The surface light source device according to claim 3. The first optical control unit has a symmetrical shape with a reference position between the one side surface and the other side surface sandwiched, and deflects light in different specific directions in each region sandwiching the reference position. ,
The surface light source device according to claim 1. The second optical control unit has a symmetrical shape across a reference position between the one side surface and the other side surface, and deflects light in different directions in each region across the reference position.
The surface light source device according to claim 1. The prism sheet emits light incident on one surface side from an oblique direction in the normal direction on the other surface side,
The surface light source device according to claim 1. The first light source has a plurality of first light emitting elements arranged along each longitudinal direction of the one side surface and the other side surface of the first light guide plate,
The second light source has a plurality of second light emitting elements arranged along each longitudinal direction of the one side surface and the other side surface of the second light guide plate,
The light source driving device sets, for each of the plurality of first light emitting elements, a block including one or more first light emitting elements on each of the one side surface and the other side surface of the first light guide plate. In addition to controlling turning off, for each of the plurality of second light emitting elements, a block including one or more second light emitting elements is set on each of the one side surface and the other side surface of the second light guide plate, and the light is turned on and off for each block. Control,
The surface light source device according to claim 1.