JP4429259B2 - Surface light source device and display device using the same - Google Patents

Description

  The present invention relates to a surface light source device, in particular, a surface light source device that performs surface light emission using a light source having a small light emitting region such as an LED, and a display device such as a liquid crystal display device, a guide light, and a signboard using the surface light source device.

  Conventionally, in a surface light source device, light sources having a small light emitting area such as LEDs are arranged in an array at a constant pitch so as to face one side surface of a light guide plate, and light from each of these light sources is incident on the light incident surface of the light guide plate. There is a configuration in which surface emission is performed by emitting light from an emission surface orthogonal to the light incident surface.

  In the surface light source device having such a configuration, a plurality of light sources are discretely arranged with respect to the light incident surface of the light guide plate, and the light emission angle of each light source is naturally limited. In the vicinity of the light surface, light portions and dark portions are mixed in the light source arrangement direction, and the light intensity distribution tends to be non-uniform.

  Therefore, in the conventional surface light source device, a stepped shape in which the thickness gradually increases from the light incident surface toward the light incident surface on the light emitting surface located at a position opposite to the light emitting surface that emits light of the light guide plate. In addition, a prism sheet is formed and a reflection sheet is disposed at an outer position facing these prism arrays, and the light incident on the light incident surface of the light guide plate from the light source is guided to the light incident surface to be reflected once here. The reflected light is guided to the light incident surface, diffused by the prism array and the reflection sheet, and the diffused light is emitted to the outside from the light exit surface, thereby reducing the non-uniformity of the light intensity distribution on the light exit surface. The thing of the structure made to do is proposed (for example, refer patent document 1).

  Further, in the above-mentioned Patent Document 1, a diffusion surface is formed in the form opposite to the prism rows on the opposite light exit surface of the light guide plate, and a reflection sheet is provided at an outer position facing the prism rows and the diffusion surfaces. The light incident on the light guide plate from the light source is diffused by the diffusion surface on the way to the anti-incident light surface and emitted to the outside from the light emitting surface, and the reflected light reflected by the anti-light incident surface is reflected to the prism array. A configuration has also been proposed in which non-uniformity in the light intensity distribution on the exit surface is reduced by diffusing the light and the reflection sheet to exit from the exit surface.

JP-T-2005-524194

  By the way, the prior art described in the above-mentioned Patent Document 1 has a non-uniformity in the light intensity distribution on the exit surface by forming a stepped prism array on the light exit surface of the light guide plate. Although it can be reduced, the light intensity distribution is still uneven. That is, in the configuration in which the prism array and the diffusing surface are formed on the side opposite to the exit surface of the light guide plate, the light is diffused by the prism array because both are formed on the same counter exit surface side. It is extremely difficult to adjust the degree of light and the degree of light diffusion by the diffusing surface so that the light intensity distribution on the exit surface becomes uniform, and the boundary between the prism row forming region and the diffusing surface forming region However, the light intensity distribution still tends to be uneven.

  Furthermore, when a step-like prism array whose thickness gradually increases from the light incident surface toward the counter light incident surface is formed, the entire thickness of the light guide plate is increased, and the device can be miniaturized. There is a problem that it is difficult.

  The present invention has been made to solve the above problems, and further reduces the non-uniformity of the light intensity distribution on the light exit surface of the light guide plate without incurring an extra cost. In addition, an object of the present invention is to provide a surface light source device that can be downsized.

  In order to achieve the above object, in the surface light source device of the present invention, the main surface of the light guide plate is formed as an emission surface that emits light, and at least one side surface orthogonal to the emission surface is used as a light incident surface. A surface light source device in which a light source is disposed at an outer position facing the light incident surface, and a reflecting member is disposed at least at an outer position facing the opposite light emitting surface facing the light emitting surface. A first light extraction function for extracting light from the light incident surface side of the light guide plate to the outside in a certain region from the light incident surface toward the light incident surface on the light exit surface of the light guide plate And the second light extraction function unit for diffusing the light from the light incident surface side and the light incident surface side and emitting the light to the outside is formed on the light exit surface of the light guide plate, respectively. In addition, the first light extraction function unit includes a plurality of portions extending along a direction parallel to the light incident surface of the light guide plate. Each prism includes a first inclined surface that propagates light propagated from the light incident surface side toward the anti-light incident surface, and light emitted from the anti-light incident surface side. And a second inclined surface that propagates toward the surface.

  According to the present invention, since the first light extraction function unit and the second light extraction function unit are individually provided on the emission surface and the non-emission surface facing each other, two functions are seen from the emission surface side of the light guide plate. The portion has a distance difference in the thickness direction of the light guide plate. For this reason, the light diffused by the first light extraction function unit is not only emitted from the region of the emission surface facing the first light extraction function unit, but also enters the second light extraction function unit and is here. Are diffused and emitted to the outside. Therefore, the light intensity change at the boundary between the formation region of the second light extraction function part and the non-formation region is blurred on the emission surface of the light guide plate. Thereby, the surface light source device in which the nonuniformity of the light intensity distribution on the emission surface is reduced can be stably obtained.

  Further, since the first light extraction function part and the second light extraction function part are formed on different surfaces with the light guide plate interposed therebetween, they can be formed so as to partially overlap each other. For this reason, it becomes possible to further reduce the non-uniformity of the light intensity distribution.

  In particular, the light propagation function of the light guide plate light is maintained if the angle formed by the normal line of the first slope and the light incident surface constituting the first light extraction function unit is set to be greater than 0 degrees and less than 10 degrees. However, since the increase in the thickness direction can be suppressed, the apparatus can be downsized.

Embodiment 1 FIG.
FIG. 1 is an exploded perspective view showing a schematic configuration of a display device according to Embodiment 1 of the present invention, and FIG. 2 is a longitudinal sectional view of the device.

  The display device according to the first embodiment has a surface light source device 1, and a light diffusing sheet 2 and a liquid crystal display element 3 are not shown on the light emission side (upper side in FIG. 1) of the surface light source device 1 or the like. Are arranged in sequence.

The surface light source device 1 includes a flat light guide plate 10 made of a transparent resin such as acrylic resin or polycarbonate resin, and the main surface of the light guide plate 10 faces the light emission surface 11 as a light emission surface 11 that emits light. The surfaces are formed as anti-emission surfaces 12 respectively. Further, one side surface orthogonal to the emission surface 11 of the light guide plate 10 is formed as a light incident surface 13, and a surface opposite to the light incident surface 13 is formed as a counter light incident surface 14.
Here, for convenience of explanation, the direction from the light incident surface 13 of the light guide plate 10 toward the light incident surface 14 is the X axis direction, and is orthogonal to the X axis direction and parallel to the light incident surface 13 and the light incident surface 14. A direction to be performed is a Y-axis direction, and a thickness direction of the light guide plate 10 orthogonal to the X-axis direction and the Y-axis direction is a Z-axis direction.

  A plurality of LEDs 4 as light sources are arranged at a constant pitch at an outer position facing the light incident surface 13 of the light guide plate 10, and the LED substrate 5 that drives these LEDs 4 and the light from each LED 4 Are respectively arranged to reflect the light toward the light incident surface 11 of the light guide plate 10.

  Each of the LEDs 4 emits white light and is held by a plurality of LED substrates 5. Further, the LED 4 is electrically connected to the LED substrate 5, and an electric signal is supplied from the outside through the LED substrate 5. Further, the reflector 6 is for efficiently making the light emitted from the LED 4 incident on the light guide plate 10.

  In addition, reflection sheets 7 and 8 as reflection members are disposed at the outer position of the light exit surface 12 and the outer position of the light incident surface 14 of the light guide plate 10, respectively. These reflection sheets 7 and 8 are for making the light emitted from other than the emission surface 11 of the light guide plate 10 re-enter the light guide plate 10 efficiently.

  The reflector 6 and the reflection sheets 7 and 8 are silver or white and have a high reflectance, specifically 70% or more, more preferably 90% or more. For example, foamed PET or silver It is formed by a vapor deposition film or the like.

  Further, the light exit surface 12 of the light guide plate 10 has a first region in a certain region (region of length L from the light incident surface 13 in the X-axis direction) from the light incident surface 13 toward the light incident surface 14. In addition, the light extraction function unit 151 has a certain area (length M in the X-axis direction from the anti-incident surface 14 to the incident surface 13 on the outgoing surface 11 of the light guide plate 10. The second light extraction function unit 152 is formed in each region. And the 1st light extraction function part 151 and the 2nd light extraction function part 152 are formed so that a part (area | region for length N along an X-axis direction) may mutually overlap on both sides of the light-guide plate 10. FIG. .

  The first light extraction function unit 151 propagates the light from the light incident surface 13 side of the light guide plate 10 toward the anti-incident light surface 14 side and emits light from the anti-incident light surface 14 side. A plurality of prisms 16 extending along a direction (Y-axis direction) parallel to the light incident surface 13 of the light guide plate 10 are continuously formed in the X-axis direction. 16 has a first inclined surface 161 and a second inclined surface 162.

  In this case, the first inclined surface 161 propagates the light propagated from the light incident surface 13 side toward the anti-light incident surface 14, and the second inclined surface 162 has propagated from the anti-light incident surface 14 side. The transmitted light is propagated toward the exit surface 11. For this reason, α is set to be larger than 0 degree and 10 degrees or less (0 degree <α ≦ 10 degrees), where α is an angle formed by the first inclined surface 161 and the normal line of the light incident surface 13. Yes. Further, if the angle formed between the normal line of the light incident surface 13 and the second inclined surface 162 is γ, γ is set to be in the range of 45 degrees to 90 degrees (45 degrees ≦ γ ≦ 90 degrees). ing. The reason for setting the angles α and γ will be described in detail later.

  In addition, the second light extraction function unit 152 is for diffusing the light respectively propagated from the light incident surface 13 side and the counter light incident surface 14 side of the light guide plate 10 and emitting them to the outside. In, it is formed by a random rough surface. In particular, in a region overlapping each other with the first light extraction function unit 151 and the light guide plate 10 interposed therebetween, the degree of light diffusion along the X-axis direction is formed to change according to the distance. That is, the surface is rough on the side opposite to the light incident surface 14, and the surface roughness becomes finer and closer to the mirror surface as the light incident surface 13 is approached.

  The liquid crystal display element 3 includes a colored layer, a light-shielding layer, a thin film transistor (hereinafter referred to as TFT) serving as a switching element, a TFT array substrate on which electrodes and wiring such as pixel electrodes are formed, and a counter electrode. Substrate, spacer for holding two substrates at equal intervals, sealing material for bonding the two substrates, sealing material for sealing after injecting liquid crystal between the two substrates, giving initial alignment to the liquid crystal It is comprised by the orientation film and the polarizing plate etc. which polarize light. In addition, since this structure is an existing one as the liquid crystal display element 3, detailed description is omitted here.

Next, the behavior of light introduced into the light guide plate 10 will be described with reference to FIGS.
Here, first, the behavior of light propagating from the light incident surface 13 side of the light guide plate 10 toward the counter light incident surface 14 side (hereinafter referred to as incident light) will be described.

  The light beam emitted from the LED 4 enters the light incident surface 13 of the light guide plate 10 directly or via the reflector 6 and propagates toward the counter light incident surface 14 side. When this incoming light reaches the first inclined surface 161 of the first light extraction function unit 151, as shown by a solid line in FIG.

  Assuming that the angle formed between the normal line of the exit surface 11 and the incident light is β, β decreases as the angle α formed between the normal line of the light incident surface 13 and the first inclined surface 161 increases, and β is critical. If the angle is less than or equal to the angle, the light can not be immediately emitted from the emission surface 11 in the non-formation region of the second light extraction function part 152 of the light guide plate 10 and propagate toward the light incident surface 14 side. The light intensity distribution in the axial direction cannot be kept uniform.

  Therefore, in the first embodiment, in order to propagate most of the incident light toward the side opposite to the light incident surface 14, the angle α formed by the first inclined surface 161 and the normal line of the light incident surface 13 as described above. In this example, α is set such that 0 degree <α ≦ 10 degrees, more preferably 0 degree <α ≦ 3 degrees. Thereby, the 1st inclined surface 161 functions as a surface which propagates without taking out outside with respect to incident light. In addition, when the angle α formed by the normal line of the light incident surface 13 and the first inclined surface 161 is set in a range of 0 ° <α ≦ 10 °, the light incident plate 10 is maintained with a substantially constant thickness. Since most of the incident light incident from the surface 13 can be propagated to the anti-incident light surface 14 side, it is advantageous in reducing the size of the surface light source device 1.

  Moreover, since the 2nd inclined surface 162 inclines in the reverse direction with the 1st inclined surface 161, as shown to the incoming light which reached this 2nd inclined surface 162 as shown with a dashed-dotted line in Fig.3 (a), Here, the light is totally reflected and further propagates toward the non-light-incident surface 14 without exiting from the exit surface 11.

  Further, the incoming light is totally reflected by the exit surface 11 and the counter-exit surface 12 of the light guide plate 10 and travels toward the counter-incident surface 14, but the second light extraction formed on the output surface 11 side of the light guide plate 10. Part of the incoming light reaching the function unit 152 is diffused by the second light extraction function unit 152. Then, the incident light that has become the critical angle or less by this diffusion is emitted from the light guide plate 10 to the outside. Further, a part of the incident light having a critical angle or less at the counter-exiting surface 12 of the light guide plate 10 exits from the counter-exiting surface 12 but is reflected by the reflection sheet 7 and returned to the light guide plate 10 again. Thereafter, the light is emitted from the emission surface 11 to the outside.

  Thus, the incoming light that has propagated through the light guide plate 10 and reached the anti-incident light surface 14 is reflected by the anti-incident light surface 14 or is emitted to the outside from the anti-incident light surface 14. The emitted light is reflected by the reflection sheet 8 and returned to the light guide plate 10 again, and becomes light that propagates in the light guide plate 10 from the anti-light incident surface 14 toward the light incident surface 13.

  Next, the behavior of light propagating from the light incident surface 14 of the light guide plate 10 toward the light incident surface 13 (hereinafter referred to as return light) will be described.

  When the return light propagating from the light incident surface 14 toward the light incident surface 13 reaches the second light extraction function unit 152 in the propagation process, a part of the return light is totally reflected and further propagated, while the remaining light is propagated. The return light is diffused by the second light extraction function unit 152 and extracted outside as described above.

  Further, the return light further propagated in the light guide plate 10 reaches the first light extraction function unit 151. A part of the return light reaches the second inclined surface 162 of the first light extraction function unit 151 as shown by a solid line in FIG. In order to allow the return light that has reached the second inclined surface 162 to be emitted from the emission surface 11 of the light guide plate 10, the normal line of the emission surface 11 is obtained by transmitting or totally reflecting the second inclined surface 162. It is necessary to make the angle β formed by the return light with respect to be less than the critical angle.

  Here, in order to transmit the second inclined surface 162, the angle γ formed by the second inclined surface 162 and the normal line of the light incident surface 13 is set large, and the second inclined surface 162 is substantially parallel to the light incident surface 13. In order to make most of the light totally reflected by the second inclined surface 162 reach the emission surface 11 so that β ≦ critical angle, the same applies. , Γ may be set as large as possible. For this reason, in this example, γ is set to be in the range of 45 ° to 90 ° (45 ° ≦ γ ≦ 90 °), more preferably approximately 80 °.

  In addition, since the first inclined surface 161 is inclined in the opposite direction to the second inclined surface 162, the return light that has reached the first inclined surface 161 is, as indicated by the alternate long and short dash line in FIG. Since the light is totally reflected by the one inclined surface 161, the light is not emitted from the light emission surface 11, and is further propagated toward the light incident surface 13 side.

  Next, the relationship with the light intensity distribution when the incident light and return light in the light guide plate 10 are emitted from the emission surface 11 will be described with reference to FIG. FIG. 4 shows a light intensity distribution along the X-axis direction on the exit surface 11 of the light guide plate 10.

  When attention is paid to the incident light propagating from the light incident surface 13 toward the counter light incident surface 14, the incident light is emitted mainly by the action of the second light extraction function unit 152. That is, the first light extraction function unit 151 only has a function of totally reflecting the incoming light and propagating it to the anti-light-incident surface 14 side. Therefore, as shown in FIG. In the predetermined section K from the light incident surface 13, the incident light is not extracted to the outside, and the incident light is extracted to the outside from the emission surface 11 of the region M where the second light extraction function unit 152 is formed. Therefore, incoming light from the discretely arranged LEDs 4 are mixed in the process of propagating through the light guide plate 10 until reaching the second light extraction function unit 152, and the light intensity distribution in the Y-axis direction is uniform. After being improved, the light is taken out from the second light extraction function unit 152.

  On the other hand, paying attention to the return light reflected by the anti-light-incident surface 14 and the reflection sheet 8, the return light is emitted to the outside of the emission surface 11 by the action of the second light extraction function unit 152 and the first light extraction. The light is emitted to the outside of the emission surface 11 also by the function of the function unit 151. For this reason, light is emitted from the entire light guide plate 10 as shown by the solid line in FIG. In this case, since light is mixed in the process of reaching from the light incident surface 13 to the counter light incident surface 14, the light intensity distribution in the Y-axis direction is extracted to the outside in a state where the light intensity distribution in the Y-axis direction is increased. . In FIG. 4B, symbol I1 is the intensity of the return light extracted outside by the action of the first light extraction function unit 151, and I2 is the intensity of the return light extracted outside by the action of the second light extraction function part 152. Indicates strength.

  Therefore, the light intensity distribution in the X-axis direction when both incoming light and return light in the light guide plate 10 are emitted from the emission surface 11 overlaps the distribution of FIG. 4A and the distribution of FIG. 4B. In addition, the distribution is as shown in FIG.

  In this case, with respect to the second light extraction function unit 152, the overall roughness along the X-axis direction in which the incident light and the return light emitted from the emission surface 11 are superimposed is adjusted by adjusting the average roughness and the average interval of the unevenness. The light intensity distribution is made as flat as possible.

  Further, the return light propagating in the light guide plate 10 is extracted as the distance from the anti-incident light surface 14 increases, and the amount of propagation light decreases. For this reason, as shown by the broken line in FIG. 4B, the light intensity of the emitted light decreases as the return light approaches the light incident surface 13. Therefore, the first light extraction function unit 151 is adjusted so that the light receiving area of the second reflecting surface gradually increases as the distance from the light incident surface 14 increases. More specifically, for example, the Z axis direction of the prism 16 is adjusted. By adjusting the height so as to approach the light incident surface 13 gradually, the overall light intensity distribution along the X-axis direction of the return light emitted from the emission surface 11 is made as flat as possible.

  In the first embodiment, since the first light extraction function unit 151 and the second light extraction function unit 152 are provided on different surfaces of the light guide plate 10, the light is diffused by the first light extraction function unit 151. In addition to being emitted from the region of the emission surface 11 where the second light extraction function part 152 is not formed, the light also enters the second light extraction function part 152 and is diffused and emitted to the outside. The Therefore, on the emission surface 11 of the light guide plate 10, the light intensity change in the X-axis direction and the Y-axis direction at the boundary between the formation region of the second light extraction function unit 152 and the non-formation region is blurred. Brightness / darkness unevenness generated in the switching unit between the light extraction function unit 151 and the second light extraction function unit 152 can be reduced.

  Furthermore, in this Embodiment 1, since the area | region N which the 1st light extraction function part 151 and the 2nd light extraction function part 152 overlap is provided seeing from the output surface 11 side, in this overlap area | region N, The surface roughness of the second light extraction function unit 152 on the side opposite to the light incident surface 14 is rough, and the closer to the light incident surface 13, the smaller the surface roughness and the closer to the mirror surface. By adjusting so as to change according to the distance along the direction of the light incident surface 14 from 13, the occurrence of brightness unevenness occurring in the overlapping region N of the first light extraction function unit 151 and the second light extraction function unit 152 is reduced. Further reduction can be achieved.

  In addition, since the 1st light extraction function part 151 comprised by the some prism 16 has few light diffusion effects with respect to the output surface 11 compared with the 2nd light extraction function part 152, when controlling light intensity distribution appropriately. High accuracy is required. For this reason, since the first light extraction function unit 151 can be a factor of reducing the yield of the product, it is desirable to reduce the region L in which the first light extraction function unit 151 is formed in order to obtain a stable good product. For example, it is preferable to be within 3 times the arrangement pitch of the LEDs 4 and preferably within 1 times. Further, for example, by combining a technique such as providing a prism row for diffusing light from the LEDs 4 on the light incident surface 13 of the light guide plate 10, the formation region L of the first light extraction function unit 151 can be further reduced. preferable.

  In this way, the light extracted outside from the exit surface 11 of the light guide plate 10 in a state where the light intensity distribution in the X-axis direction and the Y-axis direction has increased uniformity is diffused by the light diffusion sheet 2 and further The uniformity is increased and the liquid crystal display element 3 is incident. In the liquid crystal display element 3, the liquid crystal layer is aligned by turning on or off a voltage by a switching element (not shown), so that the light incident on the liquid crystal display element 3 is modulated according to the video signal, and each color of red, green, or blue is changed. indicate.

Embodiment 2. FIG.
FIG. 5 is a longitudinal sectional view of the display device according to the second embodiment of the present invention, and the same or corresponding parts as those in the first embodiment shown in FIGS.

  The feature of the second embodiment is that both side surfaces facing each other across the light guide plate 10 are formed as light incident surfaces 13L and 13R, and the LEDs 4L and 4R are arranged at outer positions facing the light incident surfaces 13L and 13R. Each is arranged. For this reason, no reflection sheet is provided at positions outside the light incident surfaces 13L and 13R of the light guide plate 10. In addition, a second light extraction function part 152 is formed on the light emission surface 11 of the light guide plate 10 over substantially the entire area, and at the positions near the LEDs 4L and 4R on the side opposite to the light emission surface 12 facing the light emission surface 11, respectively. First light extraction function portions 151L and 151R are formed.

  The prisms 16L and 16R constituting the first light extraction function units 151L and 151R include the first inclined surfaces 161L and 161R and the second inclined surfaces 162L and 162R. In this case, the first inclined surface 161L, 116R and the light incident surfaces 13L, 13R are formed to have an angle of 0 degrees, and the second inclined surfaces 162L, 162R and the light incident surfaces 13L, 13R have a normal angle of 90 degrees. Has been.

  Next, focusing on the light emitted from the LED 4L located on the left side in FIG. In this case, when viewed from the LED 4L located on the left side, the light incident surface 13R on the side facing the light incident surface 13L of the light guide plate 10 is the anti-light incident surface.

  The light emitted from the LED 4L enters the light guide plate 10 from the light incident surface 13L. This light propagates toward the other light incident surface 13R side while repeating total reflection between the first inclined surface 161L constituting the first light extraction function unit 151L and the emission surface 11. Since light mixing proceeds in this propagation process, the uniformity of the light in the Y-axis direction increases.

  Part of the light reaching the second light extraction function unit 152 formed on the light exit surface 11 side of the light guide plate 10 in the propagation process is diffused by the second light extraction function unit 152. Then, the incoming light that has become below the critical angle by this diffusion is emitted to the outside of the light guide plate 10.

  Further, the light that has reached the second inclined surface 162R configuring the first light extraction function unit 151R on the right side is emitted to the outside from the light guide plate 10, but is reflected by the reflection sheet 7 and returned to the light guide plate 10 again. Thereafter, the light is emitted from the emission surface 11. The light that has reached the first inclined surface 161R is totally reflected and propagated toward the other light incident surface 13R.

  In this way, the light emitted from the left LED 4L propagates through the light guide plate 10 and is on the light exit surface 11 side of the light guide plate 10 by the action of the second light extraction function unit 152 and the right first light extraction function unit 151R. Is taken out from the outside. Similarly, the light emitted from the LED 4R located on the right side propagates through the light guide plate 10 and is emitted from the light guide plate 10 by the action of the second light extraction function unit 152 and the left first light extraction function unit 151L. It is taken out from the surface 11 side.

  In the case of the configuration of the second embodiment, the light incident on the light guide plate 10 from each of the LEDs 4L and 4R is not sufficiently propagated in the light guide plate 10, and each input is performed by the action of the second light extraction function unit 152. If the light is extracted from the light exit surface 11 near the light surfaces 13L and 13R to the outside, the light mixing is not sufficiently advanced, so that not only the Y-axis direction but also the light intensity distribution along the X-axis direction becomes uneven. Become.

Therefore, in the second embodiment, the surface roughness becomes closer to the light incident surfaces 13L, 13R, for example, so that the light diffusion function of the second light extraction function unit 152 in the vicinity of the light incident surfaces 13L, 13R becomes weaker. The diffusion function of the second light extraction function unit 152 is adjusted by, for example, forming it so as to be close to a mirror surface. In this example, the second light extraction function unit 152 is formed on substantially the entire surface of the emission surface 11 of the light guide plate 10, so that the second light extraction function unit 152 is uniform so that the light intensity distribution on the emission surface 11 is uniform. It is easy to adjust the diffusion function.
Since other configurations and operational effects are the same as those of the first embodiment, detailed description thereof is omitted here.

Embodiment 3 FIG.
FIG. 6 is a longitudinal sectional view of the display device according to the third embodiment of the present invention, and the same or corresponding parts as those in the first embodiment shown in FIGS.

  The third embodiment is characterized in that, on the side of the light exiting surface 12 of the light guide plate 10, a third region extends from the light incident surface 14 to a predetermined region (a region corresponding to a length J in the X-axis direction from the light incident surface 14). A light extraction function unit 153 is provided. The third light extraction function unit 153 extracts incident light from the light incident surface 13 side of the light guide plate 10 to the outside from the light emission surface 11 and directs return light from the counter light incident surface 14 toward the light incident surface 13. A plurality of prisms 17 extending along a direction (Y-axis direction) parallel to the light incident surface 13 of the light guide plate 10 are continuously formed in the X-axis direction. Has a first inclined surface 171 and a second inclined surface 172.

  The first inclined surface 171 propagates the return light propagated from the side opposite to the light incident surface 14 toward the light incident surface 13 side, and the second inclined surface 172 is propagated from the light incident surface 13 side. The incoming light is propagated toward the exit surface 11. Therefore, in order to efficiently propagate the return light to the light incident surface 13 side, if the angle formed by the first inclined surface 171 and the normal line of the anti-light incident surface 14 is δ, δ is greater than 0 degree and less than 10 degrees. It is preferable to set so that (0 degree <δ ≦ 10 degrees). In addition, when the incident light is efficiently extracted from the exit surface 11 side to the outside, if the angle formed by the second inclined surface 172 and the normal line of the non-incident light surface 14 is ε, ε is 45 degrees or more and 90 degrees. It is preferable to set so as to be in the following range (45 degrees ≦ ε ≦ 90 degrees).

  As described above, the second inclined surface 172 of the third light extraction function unit 153 can extract light to the outside from the emission surface 11 opposed to the second inclined surface 172, so that the second light extraction function unit 152 has the light incident surface 13. Further, it is formed only in a certain region K separated from the light incident surface 14. However, the second light extraction function unit 152 and the third light extraction function unit 153 partially overlap each other in the X axis direction with the light guide plate 10 interposed therebetween so as not to cause uneven brightness in the X axis direction. .

Next, the behavior of light introduced into the light guide plate 10 will be described.
Incident light that has exited the LED 4 and entered the light guide plate 10 is directed toward the counter-incident surface 14 while repeating total reflection between the first inclined surface 161 and the exit surface 11 constituting the first light extraction function unit 151. And the mixing of light in the Y-axis direction proceeds.

  Then, the incident light that has reached the second inclined surface 172 constituting the third light extraction function unit 153 is reflected by the reflection sheet 7 when transmitted and is incident on the light guide plate 10 again to be emitted from the output surface 11 to the outside. It is taken out. The incoming light totally reflected by the second inclined surface 172 is taken out of the light guide plate 10 by reaching the outgoing surface 11 at an angle that is equal to or smaller than the critical angle. Incoming light that has reached the first inclined surface 171 is totally reflected and propagates toward the anti-light-entering surface 14.

  The light that reaches the anti-incident light surface 14 and is reflected by the anti-incident light surface 14 or the light that is reflected by the reflection sheet 8 and enters the light guide plate 10 again from the anti-incident light surface 14 is returned as the third light. Propagating to the light incident surface 13 side while repeating total reflection between the first inclined surface 171 and the emission surface 11 constituting the functional unit 153, as in the first embodiment, the first light extraction functional unit 151 The light is extracted from the light guide plate 10 by the action.

  Here, when attention is paid to the light intensity distribution in the case where the incoming light and the return light in the light guide plate 10 are emitted from the emission surface 11, the light propagating in the light guide plate 10 is naturally extracted as the light is extracted. It will gradually decrease. Therefore, the light intensity of the return light when reaching the first light extraction function portion 151 is smaller than the light intensity of the incoming light when reaching the third light extraction function portion 153.

Therefore, in the third embodiment, the light receiving area of the second inclined surface 162 constituting the first light extraction function portion 151 is larger than that of the second inclined surface 172 constituting the third light extraction function portion 153. Specifically, for example, the height of the prism 16 of the first light extraction function unit 151 in the Z-axis direction is higher than the height of the prism 17 of the third light extraction function unit 153. Thus, the overall light intensity distribution along the X-axis direction of the return light emitted from the emission surface 11 is made as flat as possible.
Since other configurations and operational effects are the same as those of the first embodiment, detailed description thereof is omitted here.

  In the third embodiment, in order to adjust the light intensity distribution, the prism of the first light extraction function unit 151 is compared with the pitch of the prism 17 of the third light extraction function unit 153 as shown in FIG. Alternatively, the pitch of 16 may be reduced, or the shape of the prisms 16 and 17 may be changed between the first light extraction function unit 151 and the third light extraction function unit 153.

Regarding the above-described first to third embodiments, the following modifications and application examples can be considered.
(1) In the above-described first to third embodiments, the white LEDs 4, 4L, and 4R are applied as the light source. However, the present invention is not limited to this. For example, a plurality of LEDs having different emission colors are used as the light source. Further, a rod-like light source such as CCFL may be used.

(2) In the first and third embodiments described above, the reflective sheet 8 is disposed on the side surface of the light guide plate 10 so as to face the side surface of the light guide plate 10. May be directly adhered, or a reflective function may be provided directly by printing or vapor deposition on the side surface of the light guide plate 10.

(3) In the first to third embodiments described above, the second light extraction function unit 152 having the diffusion function is configured by directly forming a random rough surface on the emission surface 11, but is not limited thereto. For example, it is possible to perform white dot printing or form a microsphere to have a diffusion function.

(4) In the first to third embodiments, the first light extraction function units 151, 151R, and 151L are configured by providing a plurality of rows of prisms 16, 16L, and 16R having a triangular cross section. For example, as shown in FIG. 8, the cross section may be trapezoidal, and a flat portion is provided between the prisms 16, 16L, 16R. The cross-sectional shape may be a curved surface or the like as long as it has a function of efficiently extracting incoming light and return light to the outside of the light guide plate 10.

(5) In the first to third embodiments described above, the light diffusion sheet 2 is disposed facing the light exit surface 11 side of the light guide plate 10. However, the light diffusion sheet 2 is limited to such a light diffusion sheet 2. Instead, for example, a prism sheet or a polarizing reflection sheet may be used, and these sheets may be used in combination. In particular, it is preferable to use an optical sheet having a function of returning a part of light to the light guide plate 10 side, such as a prism sheet or a polarizing reflection sheet, since light mixing is further promoted and light uniformity is improved.

(6) In the above-described first to third embodiments, the liquid crystal display element 3 is used as the display element. However, the present invention is not limited to this, and for example, a light-transmitting object in which an arbitrary pattern or character is drawn. A display panel having a function may be used as the display element.

(7) Furthermore, the present invention is not limited to the configurations of the first to third embodiments, and various modifications can be made without departing from the spirit of the present invention.

It is a disassembled perspective view of the display apparatus in Embodiment 1 of this invention. It is a longitudinal cross-sectional view of the display apparatus in Embodiment 1 of this invention. It is a fragmentary sectional view of the display apparatus in Embodiment 1 of this invention. It is a characteristic view which shows the light intensity distribution along the X-axis direction in the light emission surface of the surface light source device which comprises the display apparatus in Embodiment 1 of this invention. It is a longitudinal cross-sectional view of the display apparatus in Embodiment 2 of this invention. It is a longitudinal cross-sectional view of the display apparatus in Embodiment 3 of this invention. It is a longitudinal cross-sectional view which shows the modification of the surface light source device which comprises the display apparatus in Embodiment 3 of this invention. It is a longitudinal cross-sectional view which shows the modification of the 1st light extraction function part of the surface light source device of this invention.

Explanation of symbols

1 surface light source device, 2 light diffusion sheet, 3 liquid crystal display element,
4,4L, 4R LED (light source), 5,5L, 5R LED substrate,
6, 6L, 6R Refractor, 7, 8 Reflective sheet (reflective member), 10 Light guide plate,
11 exit surface, 12 counter-exit surface, 13, 13L, 13R light incident surface, 14 anti-incident surface,
151 First light extraction function unit, 152 Second light extraction function unit, 153 Third light extraction function unit,
16, 16L, 16R prism, 161, 161L, 161R first inclined surface,
162, 162L, 162R second inclined surface, 17 prism, 171 first inclined surface,
172 Second inclined surface.

Claims (8)

The main surface of the light guide plate is formed as an exit surface for emitting light, and at least one side surface orthogonal to the exit surface is used as an entrance surface, and a light source is disposed at an outer position facing the entrance surface, Further, the light source device is provided with a reflection member at least at an outer position facing the opposite exit surface facing the exit surface, and the opposite exit surface of the light guide plate is connected to the entrance surface. A first light extraction function unit for extracting light from the light incident surface side of the light guide plate to the outside in a certain region toward the light incident surface, and the light incident surface on the light exit surface of the light guide plate. A second light extraction function unit for diffusing both the light from the surface side and the non-incident light surface side and emitting the light to the outside is formed, and the first light extraction function unit is configured to receive light from the light guide plate. It consists of a plurality of prisms that extend along a direction parallel to the surface, and each prism propagates from the light incident surface side. A first inclined surface that propagates light that has been transmitted toward the anti-incident light surface, and a second inclined surface that propagates light that has been propagated from the anti-incident light surface toward the exit surface, A surface light source device. 2. The surface light source device according to claim 1, wherein the first light extraction function part and the second light extraction function part are formed so as to partially overlap each other with the light guide plate interposed therebetween. The angle formed by the first inclined surface of the prism constituting the first light extraction function unit and the normal line of the light incident surface is set to be greater than 0 degree and less than or equal to 10 degrees. Item 3. A surface light source device according to item 1 or 2. A third light extraction function unit for extracting light from the light incident surface side of the light guide plate to the outside is formed in a certain region from the light incident surface toward the light incident surface on the opposite light exit surface of the light guide plate. The third light extraction function unit is composed of a plurality of prisms extending in a direction parallel to the anti-incident light surface of the light guide plate, and each prism has light propagated from the anti-incident surface side. A first inclined surface that propagates toward the light incident surface; and a second inclined surface that propagates light propagated from the light incident surface toward the exit surface. Item 2. A surface light source device according to Item 1. 5. The surface light source device according to claim 4, wherein the third light extraction function unit and the second light extraction function unit are formed so as to partially overlap each other with the light guide plate interposed therebetween. The angle formed by the first inclined surface of the prism constituting the third light extraction function unit and the normal line of the anti-incident surface is set to be greater than 0 degree and less than or equal to 10 degrees. The surface light source device according to claim 4 or 5. The surface light source device according to any one of claims 1 to 6, wherein the second light extraction function unit is formed so that a degree of light diffusion changes along a light propagation direction. . A display device comprising the surface light source device according to claim 1, wherein a liquid crystal display element is provided on an emission surface side of the device.

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