Luminaire

Abstract

To provide a technology which enables radiation of high luminance light from an emission surface of a light guide plate in a luminaire.SOLUTION: A luminaire includes: a light source; a light guide plate which includes a side surface for receiving the light from the light source, an emission surface and an inclined surface which is provided between the side surface and the emission surface, whose cross sectional shape is a wedge shape and where the emission surface is arranged on the upper side and the inclined surface is arranged on the lower side; and an optical sheet group provided on the upper side of the emission surface. The optical sheet group includes: a reverse prism sheet arranged on the upper side of the emission surface; a lower side prism sheet arranged on the reverse prism sheet; and an upper side prism sheet arranged on the lower side prism sheet. The reverse prism sheet changes the emission light from the emission surface of the light guide plate to the light in the direction around 45° from the normal direction of the emission surface, and the lower side prism sheet changes the light in the direction around 45°to the light in the normal direction.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present disclosure relates to a lighting device. [Background technology]

[0002] A display device is provided with an illumination device as a backlight device. Proposals regarding backlight devices are found in, for example, Patent Documents 1 to 4. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-73004 [Patent Document 2] International Publication No. 2003 / 040784 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-041015 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-208535 Summary of the Invention [Problem to be solved by the invention]

[0004] Illumination devices used as backlight devices include edge-lit illumination devices and direct-lit illumination devices. In edge-lit illumination devices, it is necessary to irradiate high-intensity light with high efficiency from the light-emitting surface of the light guide plate.

[0005] An object of the present disclosure is to provide a technique that enables a lighting device to emit high-luminance light from the exit surface of a light guide plate.

[0006] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0007] A brief summary of the representative aspects of the present invention is as follows.

[0008] That is, the lighting device A light source and a light guide plate having a wedge-shaped cross section, the light guide plate having a side surface that receives light from a light source, an exit surface, and an inclined surface provided between the side surface and the exit surface, the exit surface being disposed on an upper side and the inclined surface being disposed on a lower side; a group of optical sheets provided above the light exit surface, the optical sheet group includes an inverted prism sheet disposed above the light exit surface, a lower prism sheet disposed on the inverted prism sheet, and an upper prism sheet disposed on the lower prism sheet, the inverse prism sheet has a plurality of first prisms, the plurality of first prisms extending in the x direction and arranged in the y direction, each of the plurality of first prisms having one first side surface, one second side surface, and one first vertex, the first vertex being located on a lower side, the first side surface being located on a side closer to the light source, and the second side surface being located on a side farther from the light source; the lower prism sheet has a plurality of second prisms, the plurality of second prisms extending in the x direction and arranged in the y direction, each of the plurality of second prisms having one third side surface, one fourth side surface, and one second vertex, the second vertex being located on an upper side, the third side surface being located on a side closer to the light source, and the fourth side surface being located on a side farther from the light source; the reverse prism sheet changes the light emitted from the light emitting surface of the light guide plate to light in a direction approximately 45° with respect to the normal direction of the light emitting surface, The lower prism sheet changes the light in the direction of about 45 degrees to light in the normal direction. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a plan view of a display device according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the display device of FIG. [Figure 3] FIG. 3 is a cross-sectional view illustrating a first configuration example of the light guide plate. [Figure 4] FIG. 4 is a cross-sectional view illustrating a second configuration example of the light guide plate. [Figure 5] FIG. 5 is a top view of the light guide plate of FIG. [Figure 6] FIG. 6 is a conceptual diagram illustrating the angular distribution of emitted light when a diffusion sheet is disposed above the emission surface 403 of the light guide plate 40 in FIG. [Figure 7] FIG. 7 is a conceptual diagram illustrating the angular distribution of emitted light when two lens sheets are placed on the diffusion sheet of FIG. [Figure 8] Figure 8 shows the definition of polar angle. [Figure 9] FIG. 9 is a conceptual diagram of a backlight device illustrating the angular distribution of emitted light when the diffusion sheet of FIG. 7 is replaced with an inverted prism sheet. [Figure 10] FIG. 10 is an enlarged view of the inverted prism sheet and two lens sheets in the region R50 in FIG. [Figure 11] FIG. 11 is a diagram illustrating the shape of the first prism when the peak position of the output angle is θ7=70°. [Figure 12] FIG. 12 is a diagram illustrating the shape of the first prism when the peak position of the output angle is θ7=60°. [Figure 13] FIG. 13 is a diagram showing an example of the configuration of a prism when both the first principal ray and the second principal ray are taken into consideration. [Figure 14] FIG. 14 is a schematic diagram illustrating a light guide plate according to a modified example. [Figure 15] FIG. 15 is a diagram illustrating the configuration of the light guide plate of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0011] The disclosure is merely an example, and any appropriate modifications that a person skilled in the art can easily make while maintaining the gist of the invention are naturally included within the scope of the present invention. Furthermore, in order to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention.

[0012] In this embodiment, a liquid crystal display device is disclosed as an example of a display device, which can be used in various devices such as smartphones, tablet terminals, mobile phone terminals, personal computers, television receivers, in-vehicle devices, and game consoles.

[0013] (Embodiment) Fig. 1 is a plan view of a display device according to an embodiment. In Fig. 1, the display device (liquid crystal display device) 1 has a configuration in which a TFT substrate 100 and a counter substrate 200 are bonded with a sealant 16, with liquid crystal sandwiched therebetween. A display area 14 is formed in the area where the TFT substrate 100 and the counter substrate 200 overlap. In the display area 14, scanning lines 11 extend in the horizontal direction (x direction: first direction) and are arranged in the vertical direction (y direction: second direction). Video signal lines 12 extend in the vertical direction and are arranged in the horizontal direction. Pixels 13 are formed in the area surrounded by the scanning lines 11 and the video signal lines 12.

[0014] 1, the portion where the TFT substrate 100 does not overlap with the counter substrate 200 is a terminal region 15. A flexible wiring substrate 17 is connected to the terminal region 15 to supply power and signals to the liquid crystal display panel. A driver IC that drives the liquid crystal display panel is mounted on the flexible wiring substrate 17. In the display device 1, a backlight device 20 is disposed on the back surface of the TFT substrate 100 as an illumination device, as shown in FIG.

[0015] Fig. 2 is a cross-sectional view of the display device of Fig. 1. In the display device 1 of Fig. 2, a backlight device 20 is disposed on the back surface of a liquid crystal display panel 10. The liquid crystal display panel 10 has the following configuration: a counter substrate 200, on which a black matrix and color filters are formed, is disposed opposite a TFT substrate 100, on which pixel electrodes, common electrodes, TFTs, scanning lines, video signal lines, etc. are formed. The TFT substrate 100 and the counter substrate 200 are bonded together at their peripheries with a sealant 16, and liquid crystal 300 is sealed inside.

[0016] The liquid crystal molecules are initially aligned by alignment films formed on the TFT substrate 100 and the counter substrate 200. When a voltage is applied between the pixel electrode and the common electrode, the liquid crystal molecules rotate, and an image is formed by controlling the light from the backlight device 20 for each pixel. Since the liquid crystal 300 can only control polarized light, a lower polarizer 101 is placed below the TFT substrate 100, and only polarized light is incident on the liquid crystal 300. The light modulated by the liquid crystal 300 is analyzed by the upper polarizer 201, and an image is visible.

[0017] 2, the backlight device 20 is disposed on the back surface of the display area 14 of the liquid crystal display panel 10. The backlight device 20 is configured to be able to irradiate the display area 14 of the display panel 10 with backlight. The backlight device 20 includes a light source 30, a light guide plate 40, and a group of optical sheets 50. The light source 30 is disposed on one side of the light guide plate 40, and the group of optical sheets 50 is disposed on the light exit surface of the light guide plate 40.

[0018] The light guide plate 40 in Fig. 2 is made of a transparent resin and serves to properly set the distance between the light source 30 and the liquid crystal display panel 10. The light source 30 is formed, for example, from an LED (light-emitting diode). The light guide plate 40 in Fig. 2 also serves to homogenize the light from the LED, which is a point light source, by reflecting the light incident on the light guide plate 40 at the interface.

[0019] The optical sheet group 50 may include a prism sheet, a diffusion sheet, etc. In addition, to obtain white light using a blue LED or the like as a light source, a color conversion sheet in which phosphors are dispersed in a resin sheet or a sheet using quantum dots may be used. Also, a polarized reflection sheet may be used to improve the efficiency of use of light from the backlight device 20. The type of optical sheet to be used and the number of such optical sheets to be used are determined depending on the display device.

[0020] Fig. 3 is a cross-sectional view illustrating a first configuration example of a light guide plate. Fig. 4 is a cross-sectional view illustrating a second configuration example of a light guide plate. The cross-sectional views of Fig. 3 and Fig. 4 are cross-sectional views of the light guide plate (40A, 40) along the horizontal or vertical direction of the display device 1 of Fig. 1. Fig. 5 is a top view of the light guide plate of Fig. 4.

[0021] The light guide plate 40A in FIG. 3 has a rectangular cross-sectional shape and includes a first side surface 40A1, a second side surface 40A2 facing the first side surface 40A1, an exit surface 40A3 disposed between the first side surface 40A1 and the second side surface 40A2, and a back surface 40A4 facing the exit surface 40A3. The light source 30 is disposed on the first side surface 40A1 side and configured to emit light toward the first side surface 40A1, which constitutes the entrance surface. Furthermore, the back surface 40A4 of the light guide plate 40A is provided with multiple reflective patterns 40A5 for improved efficiency. In this example, the multiple reflective patterns 40A5 are patterns with triangular cross sections with vertices at the bottom. With this configuration, light emitted from the light source 30 is reflected by the reflective patterns 40A5, for example, as indicated by solid lines, and emitted as light 40AL1 from the exit surface 40A3. 3, for example, as shown by the dotted line, light 40AL2 cannot be emitted from the exit surface 40A3, but is emitted from the second side surface 40A2. That is, the light emitted from the light source 30 experiences a terminal loss at the second side surface 40A2, which serves as the terminal end, and the utilization efficiency of the light emitted from the light source 30 to the exit surface 40A3 decreases.

[0022] Therefore, to improve the utilization efficiency of light emitted from the light guide plate 40 and reduce the weight of the light guide plate 40, a light guide plate 40 with a wedge-shaped cross section, as shown in FIG. 4, is adopted instead of the rectangular light guide plate 40A shown in FIG. 3. The wedge-shaped light guide plate 40 is composed of a side surface 401, an exit surface 403, and a slope 402. The light source 30 is provided on the side surface 401 and is configured to emit light toward the side surface 401, which constitutes the entrance surface. In this example, to improve efficiency, multiple reflective patterns 405 are provided on the slope 402 of the light guide plate 40. In this example, the multiple reflective patterns 405 have a triangular cross section with a vertex 407 on the lower side. As shown in FIG. 5, the multiple reflective patterns 405 extend in the x direction and are arranged in the y direction. The multiple reflective patterns 405 are arranged at a constant pitch (Lp1) so that the intervals Lp1 between the vertices 407 are the same. The plurality of reflective patterns 405 may extend in the y direction and be arranged in the x direction. The light source 30 is composed of a plurality of LEDs 60. The cross-sectional view of the light guide plate 40 taken along line AA in FIG. 5 corresponds to the cross-sectional view in FIG.

[0023] 4, the portion of the light guide plate surrounded by the slope 402 and the dashed line is eliminated compared to the light guide plate 40A in FIG. 3, thereby reducing the volume of the light guide plate 40. This reduces the weight of the light guide plate 40. Furthermore, the propagating light from the light source 30 includes a first exiting light (first principal ray) 40L1 that is reflected by the slope 402 and exits from the exiting surface 403, and a second exiting light (second principal ray) 40L2 that is reflected by the reflecting pattern 405 and exits from the exiting surface 403. As a result, most of the light rays from the light source 30 exit from the exiting surface 403 before reaching the end 406 of the light guide plate 40, so the light guide plate 40 has high light emission efficiency.

[0024] FIG. 6 is a conceptual diagram illustrating the angular distribution of emitted light when a diffusion sheet is placed above the emission surface 403 of the light guide plate 40 in FIG. 4. FIG. 7 is a conceptual diagram illustrating the angular distribution of emitted light when two lens sheets are placed on the diffusion sheet in FIG. 6. FIG. 8 shows the definition of polar angle. In FIG. 8, the polar angle is defined as the angle with respect to the normal direction of the light guide plate 40. Note that even when light is directed in a specific direction, it has a distribution. This is called the luminous intensity distribution characteristic.

[0025] In this example, a case will be described in which a diffusion sheet 51 and lens sheets 52 and 53 are used as the optical sheet group 50. The diffusion sheet 51 has the function of diffusing light incident on the diffusion sheet 51. The lens sheets 52 and 53 have the role of directing light that is emitted at a certain angle with respect to the main surface of the diffusion sheet 51 in the normal direction of the lens sheets 52 and 53. The lens sheets 52 and 53 can also be referred to as the lower prism sheet 52 and the upper prism sheet 53.

[0026] In the case of the wedge-shaped light guide plate 40, the angle of the emitted light 40L11 based on the light (first reflected light, first principal ray 40L1) reflected by the inclined wedge surface 402 is larger with respect to the normal direction of the emission surface 403 of the light guide plate 40 than the angle of the emitted light 40L21 based on the light (second reflected light, second principal ray 40L2) reflected by the reflection pattern 405. Therefore, in the case of the diffusion sheet 51 (see FIG. 6) disposed above the emission surface 403 of the light guide plate 40, even if two lens sheets 52 and 53 are disposed above the diffusion sheet 51 as shown in FIG. 7, the position of the peak brightness cannot be shifted to the normal direction of the emission surface 403 (vertical direction, the front direction of the display area 14). Therefore, the angular distribution of the emitted light 40L31 emitted from the emission surface 501 of the optical sheet group 50 becomes asymmetric, resulting in a problem of reduced brightness in the vertical (front) direction.

[0027] 8, because the angle of emitted light 40L11 with respect to the normal direction of emission surface 403 of light guide plate 40 (angle with the Z direction) is large, the angular distribution in the y direction of emitted light 40L31 emitted from emission surface 501 of optical sheet group 50 becomes asymmetric, and the luminance in the normal direction in the y direction becomes low. In other words, although the light intensity is high when the polar angle is zero, the polar angle of emitted light 40L31 is not zero, and therefore the light distribution angle characteristics of emitted light 40L31 cannot be said to be high, and the light intensity also decreases.

[0028] Fig. 9 is a conceptual diagram of a backlight device illustrating the angular distribution of emitted light when the diffusion sheet in Fig. 7 is replaced with an inverted prism sheet. Fig. 10 is an enlarged view of the inverted prism sheet and two lens sheets in region R50 in Fig. 9.

[0029] As shown in FIG. 9, in a backlight device 20 serving as an illumination device, an inverted prism sheet 55 is disposed above the exit surface 403 of a light guide plate 40. A lower prism sheet 52 is disposed above the inverted prism sheet 55. An upper prism sheet 53 is disposed above the lower prism sheet 52. The light guide plate 40 may be formed of a transparent resin such as acrylic or polycarbonate, or glass. In FIG. 10, a first prism 551 and a second prism 521 are made of acrylic resin, and a substrate 559 of the first prism 551 and a substrate 529 of the second prism 521 are made of PET (polyethylene terephthalate) resin.

[0030] As shown in FIG. 10 , the inverse prism sheet 55 has a plurality of first prisms 551 each having a vertex 552 on its lower side. The plurality of first prisms 551 extend, for example, in the x direction and are arranged in the y direction. Therefore, the inverse prism sheet 55 can be described as a film in which a plurality of linear prisms (first prisms 551) serving as optical elements are formed in an array. Each of the plurality of first prisms 551 has a first side surface 554, a second side surface 555, and a vertex (first vertex) 552, and is configured in the shape of an inverted triangle with the first vertex 552 on its lower side. The first side surface 554 is located closer to the light source 30, and the second side surface 555 is located farther from the light source 30. The inverse prism sheet 55 is a film comprising an array of optical elements that has peak brightness around 45° and reduces light rays at angles of 60° or greater. That is, the inverse prism sheet 55 has the function of changing the output angle of the light emitted from the light guide plate 40 in the vertical (propagation) direction to approximately 45°.

[0031] The lower lens sheet 52 has a function of changing the output angle of light emitted from the inverse prism sheet 55 in the vertical (propagation) direction to an angle in the normal direction. As shown in FIG. 10 , the lower lens sheet 52 has a plurality of second prisms 521 each having a vertex 522 on its upper side. Like the plurality of second prisms 521, the plurality of second prisms 521 extend, for example, in the x direction and are arranged in the y direction. Therefore, the lower lens sheet 52 can be considered a film in which a plurality of linear prisms (second prisms 521) serving as optical elements are formed in an array. Each of the plurality of second prisms 521 has one first side surface (third side surface) 524, one second side surface (fourth side surface) 525, and one vertex (second vertex) 522, forming a triangular shape with the vertex 522 on its upper side. The first side surface 524 is disposed closer to the light source 30, and the second side surface 525 is disposed farther from the light source 30.

[0032] The upper lens sheet 52 functions to increase brightness by narrowing the horizontal emission angle distribution and increasing the normal light density. Although not shown, the upper lens sheet 52, like the lower lens sheet 52, has multiple third prisms with an apex on the upper side. The upper lens sheet 52 can be described as a film on which multiple linear prisms (third prisms) serving as optical elements are formed in an array. Unlike the multiple second prisms 521, which extend in the x direction and are aligned in the y direction, the multiple third prisms extend in the y direction and are aligned in the x direction. In other words, the multiple third prisms are configured to intersect or intersect with the multiple second prisms 521 in a plan view. Each of the multiple third prisms has one first side (eighth side), one second side (ninth side), and one vertex (fourth vertex), forming a triangular shape with the vertex (fourth vertex) on the upper side.

[0033] As explained in FIG. 4, in the case of a wedge-shaped light guide plate 40 having a plurality of reflection patterns 405, when the output angle distribution is a combination of two distributions (40L1, 40L2), the average value of the two peak angles is taken as the chief ray (output light 40L11) in the following explanation.

[0034] 10 , for example, output light 40L11 emitted from output surface 403 of light guide plate 40 enters first prism 551 from first side surface 554 of first prism 551, is reflected by second side surface 555 of first prism 551, and is emitted from output surface 556 of first prism 551. Light L2 emitted from output surface 556 of first prism 551 has an angle (angle with the Z direction) of approximately 45° (near 45°) with respect to the normal direction of output surface 403 of light guide plate 40 (or output surface 556 of first prism 551). Light L2 then enters incident surface 526 of lower lens sheet 52, enters second side surface 525 of second prism 521, and is refracted and emitted from second side surface 525. The outgoing light 40L41 emitted from the exit surface (second side surface 525) of the second prism 521 of the lower lens sheet 52 changes the exit angle in the vertical (propagation) direction of the light emitted from the inverted prism sheet 55 to an angle in the normal direction to the exit surface 403 of the light guide plate 40 (or the exit surface 556 of the first prism 551).Then, the outgoing light 40L41 is emitted from the exit surface 501 of the optical sheet group 50.

[0035] The emitted light 40L41 is supplied to the display area 14 of the display panel 10 as backlight.

[0036] The polar angle in the y direction of the outgoing light 40L41 emitted from the exit surface 501 of the optical sheet group 50 is zero degrees, so the light intensity of the outgoing light 40L41 is high. In addition, since a wedge-shaped light guide plate 40 is used, light can be emitted from the exit surface 403 of the light guide plate 40 with high efficiency.

[0037] Next, the shape of first prism 551 will be described with reference to Fig. 11. Fig. 11 is a diagram illustrating the shape of first prism 551. Note that in the wedge-shaped light guide plate 40, when the output angle distribution is a combination of two distributions (40L1, 40L2), the average value of the two peak angles will be considered as the chief ray (output light 40L11) in the following description.

[0038] In FIG. 11 , angle θ1 indicates the angle of emergence of the chief ray 40L11 from the light guide plate 40. The chief ray 40L11 is incident on the first side surface 554 of the first prism 551 at a right angle. Angle θ2 is the angle between the normal passing through the apex angle 552 of the first prism 551 and the first side surface 554. Angle θ3 is the angle between the normal passing through the apex angle 552 of the first prism 551 and the second side surface 555. Angle θ4 is the angle of incidence of the chief ray 40L11 on the second side surface 555, or the angle of reflection of the chief ray 40L11 reflected by the second side surface 555. Angle θ5 is the angle of incidence of the chief ray 40L11 reflected by the second side surface 555 on the exit surface 556 of the inverted prism sheet 55. Angle θ6 is the angle of emergence of chief ray 40L11 from emergent surface 556 of inverse prism sheet 55. The refractive index n1 of the medium of light guide plate 40 and the refractive index n0 of air are set to 1. The refractive index n1 is set to 1.59, for example.

[0039] From the above relationship, the following is obtained: θ2=90-θ1 θ4=θ1-θ3 θ5=θ3-θ4=θ3-(θ1-θ3)=2×θ3-θ1 n1×sinθ5=n0×sinθ6 n1×sin(2×θ3-θ1)=n0×sin45° Since we want the emission angle θ6 from the optical element array film to be 45° (θ6=45°), if θ1 is known, θ2 and θ3 can be found.

[0040] (The average value of the peak position of the emission angle of the light guide plate 40 is θ1=70°) When the average value of the peak positions of the emission angles from light guide plate 40 is θ1 = 70°, θ2 = 20°, θ3 = 48.2°, and the apex angle of vertex 552 is θ2 + θ3 = 68.2°. In this case, angle θ20 between first side surface 554 and emission surface 556 is 70° (θ20 = 70°). Angle θ21 between second side surface 555 and emission surface 556 is 41.8° (θ21 = 41.8°). This triangular prism is called Pri1.

[0041] As a result, when the emission angle distribution is a combination of two distributions (first chief ray 40L1 and second chief ray 40L2), a prism Pri1 can be configured in which the average value of the two peak angles is taken into consideration as the average value of the peak position of the emission angle of the chief ray (40L11). By configuring an inverted prism sheet 55 based on this prism Pri1, an edge-light type lighting device can be configured that can irradiate light emitted from the emission surface of the light guide plate 40 with high efficiency and high brightness.

[0042] (When only the first principal ray 40L1 from the inclined surface 402 of the light guide plate 40 is considered: the peak position of the emission angle is θ1=70°) In this case, θ1 = 70°, and the calculation results are the same as those above, so a duplicated explanation will be omitted. In this case, in FIG. 11, the chief ray 40L11 is changed to the first chief ray 40L1. This allows for the construction of a prism Pri1 that takes into account the emission angle of the first chief ray 40L1. By constructing an inverted prism sheet 55 based on this prism Pri1, an edge-light type lighting device can be constructed that can irradiate light emitted from the emission surface of the light guide plate 40 with high efficiency and high brightness.

[0043] (When both the first principal ray 40L1 from the inclined surface 402 of the light guide plate 40 and the second principal ray 40L2 from the pattern 405 of the light guide plate 40 are considered) 1) In the case of the first principal ray 40L1 from the inclined surface 402 of the light guide plate 40, θ1=70°, and the calculation results are the same as those above, so a duplicated explanation will be omitted.

[0044] 2) The peak position of the emission angle of the second principal ray 40L2 from the pattern 405 is θ7=60°. Fig. 12 is a diagram illustrating the shape of the first prism when the peak position of the emission angle is θ7=60°.

[0045] 12, angle θ7 indicates the emission angle of second chief ray 40L2 from light guide plate 40. Second chief ray 40L2 is incident on first side surface 554 of first prism 551 at an angle obtained by subtracting angle θ8 from the right angle (the normal direction to first side surface 554). Angle θ9 is the angle at which second chief ray 40L2 incident on first side surface 554 at angle θ8 is refracted.

[0046] Angle θ2 is the angle between the normal passing through apex angle 552 of first prism 551 and first side surface 554 (θ2 = 20°). Angle θ23 between first side surface 554 and exit surface 556 is 70° (θ23 = 70°). This is because it is assumed that first chief ray 40L1 is incident on first side surface 554 of first prism 551 at a right angle, so angle θ2 is 20° and angle θ23 is 70° (θ20 = θ23 = 70°). Angle θ24 is the angle between second side surface 555 and exit surface 556. Angle θ10 is the angle between the normal passing through apex angle 552 of first prism 551 and second side surface 555.

[0047] The angle θ11 is the angle of incidence of the second chief ray 40L2 on the second side surface 555, or the angle of reflection of the second chief ray 40L2 reflected by the second side surface 555. The angle θ12 is the angle of incidence of the second chief ray 40L2 reflected by the second side surface 555 on the exit surface 556 of the inverse prism sheet 55. The angle θ6 is the angle of emission of the second chief ray 40L2 from the exit surface 556 of the inverse prism sheet 55 (θ6=45°). The refractive index n1 of the medium of the light guide plate 40 and the refractive index n0 of air are set to 1. The refractive index n1 is, for example, n1=1.59.

[0048] The second chief ray 40L2 emitted from the light guide plate 40 at an emission angle of θ7 is incident on the first side surface 554 at an angle obtained by subtracting the angle θ8 from the normal direction (right angle) of the first side surface 554, and is refracted at an angle θ9 at the first side surface 554. Thereafter, the second chief ray 40L2 is reflected by the second side surface 555 and is emitted from the emission surface 556 of the inverse prism sheet 55 at an angle θ6.

[0049] From the above relationship, the following is obtained: θ8=90-(θ2+θ7): θ2 and θ7 are known, so θ8 is a constant n0×sinθ8=n1×sinθ9 θ9=sin^-1(sinθ8 / n1):Since θ8 is substituted, θ9 is also a constant θ11=90-(θ2+θ9+θ10): Since θ2 and θ9 are known, θ11 is a variable of θ10 θ12=θ10-θ11:Since θ11 is substituted, θ12 is the variable of θ10 n1×sinθ12=n0×sinθ6:By substituting θ12, θ10 can be found.

[0050] From the above calculations, we can see that θ2 = 20°, θ10 = 45.1°, θ23 = 70°, and angle θ24 = 44.9°.

[0051] Here, second side surface 555 of first prism 551 when the peak position of the output angle is θ7=60° is referred to as third side surface (seventh side surface) 557. In addition, this triangular prism is referred to as Pri2.

[0052] Therefore, when both the first principal ray 40L1 and the second principal ray 40L2 are taken into consideration, the prism Pri3 can be configured as shown in Fig. 13. Fig. 13 is a diagram showing an example of the configuration of a prism when both the first principal ray and the second principal ray are taken into consideration.

[0053] As shown in FIG. 13, prism Pri3 is constructed by combining Pri1 described in FIG. 11 and Pri2 described in FIG. 12. When θ7=60°, the second principal ray 40L2 is emitted upward compared to the first principal ray 40L1, so Pri2 is positioned above Pri1. Therefore, the second side surface 555 of Pri1 and the third side surface (seventh side surface) 557 of Pri2 are not connected in a straight line but at an angle of 176.9°. In other words, the composite side surfaces (555, 557) of prism Pri3 are outwardly convex. In other words, in the composite side surfaces (555, 557) of prism Pri3, the seventh side surface 557 is connected to the second side surface 555 so that the second side surface 555 is located between the first vertex 552 and the seventh side surface 557.

[0054] As a result, a prism Pri3 that takes into account both the first principal ray 40L1 and the second principal ray 40L2 can be configured. By configuring the reverse prism sheet 55 based on this prism Pri3, an edge light type illumination device that can irradiate the light (the first principal ray 40L1 and the second principal ray 40L2) emitted from the light emitting surface of the light guide plate 40 with high efficiency and high luminance can be configured.

[0055] (Modified Example) Next, a modified example of the light guide plate 40 will be described using FIGS. 14 and 15. FIG. 14 is a schematic diagram for explaining the light guide plate according to the modified example. FIG. 15 is a diagram for explaining the configuration of the light guide plate of FIG. 14.

[0056] The light guide plate 40B in FIG. 14 is different from the light guide plates 40 in FIGS. 4, 5, and 9 in that the size of the plurality of reflection patterns 405 provided on the inclined surface 402 is such that the cross-sectional shape of the reflection pattern 405 is small for the reflection pattern 405 closer to the light source 30, and the cross-sectional shape of the reflection pattern 405 gradually increases as it moves away from the light source 30 (LED 60). That is, in a plan view, if the width Ly of the reflection pattern that is closer to the light source 30 is Ly1, the widths (Ly2, Ly3, Ly4, Ly5) of the reflection pattern 405 increase as it moves away from the light source 30, and the relationship Ly1 < Ly2 < Ly3 < Ly4 < Ly5 holds. This is because the light hitting the reflection pattern 405 is strong on the side near the light source 30, so the reflection pattern 405 is made small, and the light hitting the reflection pattern 405 is weak on the side far from the light source 30, so the reflection pattern 405 is made large to adjust the luminance distribution (screen uniformity). The shapes of the plurality of patterns 405 themselves are triangular and all have the same shape.

[0057] Next, light guide plate 40B will be described in more detail with reference to Fig. 15. Each of the plurality of reflection patterns 405 has a first side surface (fifth side surface) 408, a second side surface (sixth side surface) 409, a vertex (third vertex) 407, and a triangular cross section with vertex 407 on the lower side, with part of slope 402 as the bottom surface. First side surface 408 is disposed on the side closer to light source 30, and second side surface 409 is disposed on the side farther from light source 30. In reflection pattern 405, angle θ30 between first side surface 408 and the bottom surface is set to, for example, 70°, angle θ31 between second side surface 409 and the bottom surface is set to, for example, 20°, and apex angle θ32 of vertex 407 is set to, for example, 90°.

[0058] The height Lz of the side surface 401 of the light guide plate 40B is, for example, 0.7 mm. The length Ly of the exit surface 403 of the light guide plate 40B in the y direction is, for example, 50 mm. The length Lx of the exit surface 403 of the light guide plate 40B in the x direction is, for example, 50 mm. The angle θ35 of the inclined surface 402 from the horizontal or the angle θ35 of the end 406 of the light guide plate 40B is, for example, 0.7°.

[0059] The light guide plate 40B according to the modified example can adjust the luminance distribution (screen uniformity) of the light (first chief ray 40L1, second chief ray 40L2) emitted from the exit surface 403. This makes it possible to make the luminance distribution of the backlight irradiating the display area 14 of the display panel 10 uniform.

[0060] Therefore, by changing the light guide plate 40 of the backlight device 20 described in Figures 9 to 13 to the light guide plate 40B, it is possible to adjust the brightness distribution (screen uniformity) of the light emitted from the light guide plate 40 (first chief ray 40L1, second chief ray 40L2), and to configure an edge-light type lighting device that can irradiate the emitted light (first chief ray 40L1, second chief ray 40L2) with high efficiency and high brightness.

[0061] All lighting devices that can be implemented by a person skilled in the art by appropriately modifying the design of the lighting device described above as an embodiment of the present disclosure also fall within the scope of the present disclosure, as long as they include the gist of the present disclosure.

[0062] Within the scope of the concept of the present disclosure, a person skilled in the art may conceive of various modifications and alterations, and it is understood that these modifications and alterations also fall within the scope of the present disclosure. For example, to the above-described embodiments, a person skilled in the art may appropriately add, delete, or change the design of components, or add, omit, or change the conditions of steps, and these modifications are also included within the scope of the present disclosure as long as they include the gist of the present disclosure.

[0063] Furthermore, other effects and advantages brought about by the aspects described in this embodiment that are clear from the description in this specification or that can be appropriately thought of by a person skilled in the art are naturally understood to be brought about by the present invention.

[0064] Various disclosures can be formed by appropriately combining multiple components disclosed in the above embodiments. For example, some components may be omitted from all components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0065] 20: lighting device (backlight device), 30: light source, 40: light guide plate, 50: group of optical sheets, 55: inverted prism sheet, 52: lower prism sheet, 53: upper prism sheet, 551: first prism, 521: second prism.

Claims

1. A light source and a light guide plate having a wedge-shaped cross section, the light guide plate having a side surface that receives light from a light source, an exit surface, and an inclined surface provided between the side surface and the exit surface, the exit surface being disposed on an upper side and the inclined surface being disposed on a lower side; a group of optical sheets provided above the light exit surface, the optical sheet group includes an inverted prism sheet disposed above the light exit surface, a lower prism sheet disposed on the inverted prism sheet, and an upper prism sheet disposed on the lower prism sheet, the inverse prism sheet has a plurality of first prisms, the plurality of first prisms extending in the x direction and arranged in the y direction, each of the plurality of first prisms having one first side surface, one second side surface, and one first vertex, the first vertex being located on a lower side, the first side surface being located on a side closer to the light source, and the second side surface being located on a side farther from the light source; the lower prism sheet has a plurality of second prisms, the plurality of second prisms extending in the x direction and arranged in the y direction, each of the plurality of second prisms having one third side surface, one fourth side surface, and one second vertex, the second vertex being located on an upper side, the third side surface being located on a side closer to the light source, and the fourth side surface being located on a side farther from the light source; the reverse prism sheet changes the direction of light emitted from the exit surface of the light guide plate to light at an angle of approximately 45° with respect to the normal direction of the exit surface, The lower prism sheet changes the light in the direction of about 45° to light in the normal direction. Lighting equipment.

2. 2. The lighting device according to claim 1, An illumination device in which the first side of each of the plurality of first prisms of the inverted prism sheet is configured so that the angle of incidence of the light emitted from the exit surface of the light guide plate to the first side is a right angle, and the light incident from the first side is reflected by the second side and then emitted from the inverted prism sheet as light in a direction approximately 45°.

3. 3. The lighting device according to claim 2, an angle of the light emitted from the exit surface of the light guide plate with respect to a normal direction of the exit surface is 70°.

4. 4. The lighting device according to claim 3, The light emitted from the light exit surface of the light guide plate includes a first principal ray based on reflection of the light from the light source by the inclined surface of the light guide plate.

5. 5. The lighting device according to claim 4, The light emitted from the inverted prism sheet in a direction near 45° is incident on the lower prism sheet, refracted at the fourth side surface, and emitted as the light in the normal direction.

6. 6. The lighting device according to claim 5, the inclined surface of the light guide plate has a plurality of reflective patterns; each of the plurality of reflection patterns has one fifth side, one sixth side, and one third vertex, the third vertex being disposed on a lower side, the fifth side being disposed on a side closer to the light source, and the sixth side being disposed on a side farther from the light source; The light emitted from the exit surface of the light guide plate is the first chief ray; a second chief ray based on reflection by the sixth side surface of each of the plurality of reflection patterns of the light from the light source.

7. 7. The lighting device according to claim 6, an angle of the second principal ray with respect to a normal direction of the exit surface of the light guide plate is 60°.

8. 8. The lighting device according to claim 7, each of the plurality of first prisms of the inverse prism sheet includes a seventh side face; the seventh side surface is connected to the second side surface such that the second side surface is disposed between the first vertex and the seventh side surface; The second principal ray is incident on the first side surface, refracted, reflected by the seventh side surface, and emitted from the reverse prism sheet as the light in a direction of approximately 45°.

9. 9. The lighting device according to claim 8, In the plurality of reflection patterns, the cross-sectional shape of the reflection pattern on the side closer to the light source is made smaller, and the cross-sectional shape of the reflection pattern on the side farther from the light source is made larger.

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