Lighting devices and display devices

Abstract

To provide a lighting device with improved light extraction efficiency. [Solution] In the lighting device, the first light guide plate comprises a first surface and a second surface, the first surface is provided with a plurality of first protrusions, the second surface is provided with a plurality of second protrusions, each of the plurality of first protrusions has a first base angle, a second base angle and a first vertex angle and has a triangular cross-sectional shape projecting downwards, and each of the plurality of second protrusions has a third base angle, a fourth base angle and a second vertex angle and has a triangular cross-sectional shape projecting upwards, the third base angle is larger than the first base angle.

Description

Technical Field

[0005] , , , , , ,

[0001] Embodiments of the present invention relate to a lighting device and a display device.

Background Art

[0002] A lighting device for illuminating a display panel has been developed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] This embodiment provides a lighting device with improved light extraction efficiency. By providing such a lighting device, it is possible to obtain a display device with high luminance.

Means for Solving the Problems

[0005] A lighting device according to an embodiment includes a first light guide plate having a first side and a second side, a second light guide plate disposed on the first light guide plate and having a third side and a fourth side, a plurality of light source elements provided facing the third side of the second light guide plate, a reflector provided below the first light guide plate, an optical sheet provided on the second light guide plate, and includes the cross-sectional shape of the first light guide plate is a trapezoidal shape with the lower side shorter than the upper side, the cross-sectional shape of the second light guide plate is a trapezoidal shape with the upper side shorter than the lower side, the first light guide plate includes a first surface facing the reflector and a second surface facing the second light guide plate, The first surface is provided with a plurality of first protrusions, The second surface is provided with a plurality of second protrusions, Each of the aforementioned plurality of first protrusions has a first base angle, a second base angle, and a first vertex angle, and has a triangular cross-sectional shape that protrudes downward. Each of the aforementioned multiple second protrusions has a third base angle, a fourth base angle, and a second vertex angle, and has a triangular cross-sectional shape that protrudes upward. The third base angle is greater than the first base angle.

[0006] Furthermore, the lighting device according to one embodiment is A first light guide plate having a first side and a second side, A second light guide plate is placed on the first light guide plate and has a third side and a fourth side, A plurality of light source elements are provided opposite the third side of the second light guide plate, A reflector is provided below the first light guide plate, An optical sheet provided on the second light guide plate, Equipped with, The cross-sectional shape of the first light guide plate is a trapezoidal shape in which the lower side is shorter than the upper side. The cross-sectional shape of the second light guide plate is a trapezoidal shape in which the upper side is shorter than the lower side. The first light guide plate comprises a first surface facing the reflector and a second surface facing the second light guide plate. The first surface is provided with a plurality of first protrusions, The second surface is provided with a plurality of second protrusions, Each of the aforementioned plurality of first protrusions has a first base angle, a second base angle, and a first vertex angle, and has a triangular cross-sectional shape that protrudes downward. Each of the aforementioned multiple second protrusions has a third base angle, a fourth base angle, and a second vertex angle, and has a triangular cross-sectional shape that protrudes upward. The third base angle and the first base angle are equal.

[0007] A lighting device according to one embodiment, A first light guide plate having a first side and a second side, A second light guide plate disposed on the first light guide plate and having a third side and a fourth side; A plurality of light source elements provided opposite to the third side of the second light guide plate; A reflector provided below the first light guide plate; An optical sheet provided on the second light guide plate; Comprising; The cross-sectional shape of the first light guide plate is a trapezoidal shape with the lower side shorter than the upper side; The cross-sectional shape of the second light guide plate is a trapezoidal shape with the upper side shorter than the lower side; The first light guide plate includes a first surface facing the reflector and a second surface facing the second light guide plate; A plurality of first convex portions are provided on the first surface; A plurality of second convex portions are provided on the second surface; Each of the plurality of first convex portions has a first base angle, a second base angle, and a first apex angle, and has a triangular cross-sectional shape protruding downward; Each of the plurality of second convex portions has a third base angle, a fourth base angle, a fifth base angle, a sixth base angle, and a second apex angle, and has a pentagonal cross-sectional shape protruding upward; The fifth base angle is located between the third base angle and the second apex angle; The sixth base angle is located between the fourth base angle and the second apex angle; The third base angle is equal to the first base angle; The fifth base angle is larger than the first base angle.

Brief Description of the Drawings

[0009] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. Note that the disclosure is merely an example, and for those that can be easily conceived by those skilled in the art with appropriate modifications while maintaining the gist of the invention, they are naturally included in the scope of the present invention. Also, for the purpose of making the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual aspect, but this is merely an example and does not limit the interpretation of the present invention. Further, in this specification and each drawing, elements similar to those described above with respect to the previously presented drawings may be denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

[0010] The embodiments described herein are not general in nature, but rather embodiments that illustrate the same or corresponding specific technical features of the present invention. A lighting device according to one embodiment will be described in detail below with reference to the drawings.

[0011] In this embodiment, the first direction X, the second direction Y, and the third direction Z are orthogonal to each other, but they may intersect at angles other than 90 degrees. The direction toward the tip of the arrow in the third direction Z is defined as up or upward, and the direction opposite to the direction toward the tip of the arrow in the third direction Z is defined as down or downward. The first direction X, the second direction Y, and the third direction Z may also be referred to as the X direction, the Y direction, and the Z direction, respectively.

[0012] Furthermore, when referring to "the second member above the first member" and "the second member below the first member," the second member may be in contact with the first member or may be located away from the first member. In the latter case, a third member may be interposed between the first member and the second member. On the other hand, when referring to "the second member above the first member" and "the second member below the first member," the second member is in contact with the first member.

[0013] Furthermore, assuming that there is an observation position for observing the lighting device on the tip side of the arrow in the third direction Z, viewing from this observation position toward the XY plane defined by the first direction X and the second direction Y is called a plan view. Viewing the cross-section of the lighting device in the XZ plane defined by the first direction X and the third direction Z, or in the YZ plane defined by the second direction Y and the third direction Z, is called a cross-sectional view.

[0014] [Embodiment 1] Figure 1 is a perspective view showing a schematic configuration of a display device according to an embodiment. The display device DSP includes a display panel PNL, an illumination device ILD, a drive IC chip ICP for driving the display panel PNL, a flexible circuit board FPC1 for supplying control signals to the display panel PNL, and a flexible circuit board FPC2 for supplying control signals to the illumination device ILD. For example, flexible circuit boards FPC1 and FPC2 may be connected to a control module that controls the operation of the display panel PNL and the illumination device ILD.

[0015] The display panel PNL comprises a substrate SUB1 (array substrate) and a substrate SUB2 (opposing substrate) facing substrate SUB1. The display panel PNL has a display area DA for displaying images. The display panel PNL includes, for example, a plurality of pixels PX arranged in a matrix within the display area DA.

[0016] The ILD lighting device comprises a light source element LS1 and a light guide plate LG facing the substrate SUB1. The light source element LS1 faces one side of the light guide plate LG. Although Figure 1 shows one light source element LS1, multiple light source elements LS1 may be provided.

[0017] In the configuration example shown in Figure 1, substrates SUB1, SUB2, and light guide plate LG have a short side along the first direction X and a long side along the second direction Y, and their shape in plan view is rectangular. However, the shape of substrates SUB1, SUB2, and light guide plate LG is not limited to this, and their shape in plan view may be a square, a circle, or other shape.

[0018] Figure 2 is a plan view showing the schematic configuration of the display device. Figure 3 is a cross-sectional view showing the cross-sectional structure of the display device along the line A1-A2 in Figure 2.

[0019] The display device DSP comprises an illumination device ILD and a display panel PNL. The illumination device ILD comprises a reflector REF, a light guide plate LGL, a light guide plate LGU, an optical sheet OPS, and a light source element LS1. The reflector REF, light guide plate LGL, light guide plate LGU, and optical sheet OPS are stacked in this order. When the light guide plates LGL and LGU are not distinguished, they are referred to as light guide plate LG. The display panel PNL is provided on the illumination device ILD.

[0020] In a plan view, the edges extending along the second direction Y of the light guide plate LGU are denoted as edges GVU1 and GVU2. In Figure 2, the edge on the left side of the paper is defined as edge GVU1, and the edge on the right side of the paper is defined as edge GVU2. The light source element LS1 is positioned opposite edge GVU1 of the light guide plate LGU.

[0021] Although not shown in Figure 2, the edge GVL1 of the light guide plate LGL is located below the edge GVU1 of the light guide plate LGU. The edge GVL2 of the light guide plate LGL is located below the edge GVU2 of the light guide plate LGU.

[0022] The light guide plate LGL has a rectangular shape in plan view and a trapezoidal shape in cross-section, where the lower side is shorter than the upper side. The left side of the trapezoidal shape, side GVL1, extends along the third direction Z. The right side of the trapezoidal shape, side GVL2, extends at an angle with respect to the third direction Z.

[0023] The light guide plate LGU has a rectangular shape in plan view and a trapezoidal shape in cross-section, with the lower side being longer than the upper side. The left side of the trapezoidal shape, side GVU1, extends along the third direction Z. The right side of the trapezoidal shape, side GVU2, extends at an angle with respect to the third direction Z.

[0024] The light source element LS is positioned opposite the edge GVU1 of the light guide plate LGU. Light emitted from the light source element LS is incident on the edge GVU1 of the light guide plate LGU.

[0025] Note that edges GVU1 and GVL1, although referred to as edges, are actually planes parallel to the YZ plane. Edges GVU2 and GVL2 are actually planes inclined at an angle to the YZ plane.

[0026] Multiple protrusions (also called prisms) are provided on the main surfaces of the reflector REF, light guide plate LGL, light guide plate LGU, and optical sheet OPS.

[0027] Figure 4 is a cross-sectional view showing the schematic structure of a comparative example lighting device. The lighting device ILDr shown in Figure 4 comprises a reflector REF, a light guide plate LGL, a light guide plate LGU, a prism sheet PRS, and a light source element LS1. The optical sheet OPS shown in Figure 3 corresponds to the prism sheet PRS shown in Figure 4. However, the configuration of the optical sheet OPS is not limited to this, and it may have optical sheets other than prism sheets.

[0028] Of the main surfaces of the light guide plate LGL, the surface facing the reflector REF is designated as surface BSL. Of the main surfaces of the light guide plate LGL, the surface facing the light guide plate LGU is designated as surface USL. Of the main surfaces of the light guide plate LGU, the surface facing the light guide plate LGL is designated as surface BSU. Of the main surfaces of the light guide plate LGU, the surface facing the prism sheet PRS is designated as surface USU.

[0029] Let the thickness of the light guide plate LG (length along the third direction Z) be d0. The ray width d1 is the same as the thickness d0 (d1=d0).

[0030] Figure 5 is a cross-sectional view showing a protrusion on the light guide plate LGL. The surface BSL of the light guide plate LGL is provided with a protrusion PRM1 that projects downward (in the opposite direction to the third direction Z). On the other hand, the surface USL of the light guide plate LGL is not provided with a protrusion.

[0031] As described above, the convex portion PRM1 is a convex portion that protrudes downward. Of the base angles of the convex portion PRM1, the angle on the left side of the paper is angle θ11, and the angle on the right side of the paper is angle θ12. The apex angle of the convex portion PRM1 is angle θ13. Angles θ11, θ12, and θ13 may be different. In the example shown in Figure 5, angle θ11 is smaller than angle θ12.

[0032] The light source element LS1 is positioned opposite edge GVU1 of the light guide plate LGU. Light LT emitted from the light source element LS1 enters the light guide plate LGU from the surface including edge GVU1 and travels in a straight line within the light guide plate LGU. When light LT reaches edge GVU2 of the light guide plate LGU, it is reflected downward by edge GVU2. The reflected light LT exits the light guide plate LGU and enters the light guide plate LGL. Let the light that enters the light guide plate LGL be called light LTB. Light LTB that enters the light guide plate LGL is reflected by edge GVL2 of the light guide plate LGL and propagates in the opposite direction to the first direction X. At this time, light LTB that enters the light guide plate LGL propagates in the opposite direction to the first direction X while satisfying the total internal reflection condition between surfaces BSL and USL of the light guide plate LGL.

[0033] Light LT and light LTB propagate through the interior of the light guide plate LGU and the light guide plate LGL, respectively, with a ray width d1. Light LTB, which has a ray width d1, is reflected by the surface BSL of the light guide plate LGL and emitted upward by a protrusion (prism) provided on the surface BSL. This emitted light is called light RL. Light RL is emitted upward from the surface USU of the light guide plate LGU and enters the prism sheet PRS. Light RL is emitted by the prism sheet PRS as light DL along the third direction Z and is further emitted above the illumination device ILD.

[0034] Let angle t1 be the acute angle formed by plane BSU and edge GVU2. Let angle t2 be the acute angle formed by a virtual line extending plane BSL along the first direction X and edge GVL2. Let angle t3 be the angle at which light LTB enters plane BSL. Let angle t4 be the angle formed by plane BSL and light RL.

[0035] However, some light LTB, even when reflected by the surface BSL of the light guide plate LGL, does not exit upward from the surface BSL but undergoes total internal reflection at the surface USL and returns to the light guide plate LGL. After total internal reflection at the surface USL and returning to the interior of the light guide plate LGL, the light LTB undergoes total internal reflection again at the surface BSL. In this way, the light LTB guides light inside the light guide plate LGL. If the amount of light LTB is large, there is a risk that the utilization efficiency of the light LT incident from the light source element LS1 will be reduced.

[0036] The region between the reflection of optical LTB from the surface USL and the further reflection from the surface BSL is defined as the NFR region. In the NFR region, optical LTB with linewidth d1 is not reflected, so the light is not lifted upwards.

[0037] Let LD2 be the distance along the first direction X corresponding to region NFR. Let LL1 be the distance along the first direction X in region RLR where light DL is irradiated. No light irradiation occurs between the right edge of the light guide plate LGU and region NNR adjacent to edge GVU2 where light DL is irradiated. Let LD1 be the distance along the first direction X in region NNR. Let NLR1 be the region located between adjacent regions RLR and not irradiated by light DL. Let LD2 be the distance along the first direction X in region NLR1.

[0038] Distances LL1, LD1, and LD2 are expressed by the following formulas. LL1=d2((1 / tant3)-(1 / tant2)) (Equation 1) LD1=(d2 / tant2)+((d0+d2) / tant4)) (Formula 2) LD2=d2((1 / tant3)+(1 / tant2)) (Equation 3) t3=2t1+2t2−180° (Equation 4) t4=t3+2θ11 (Equation 5)

[0039] For example, let's assume the thickness d0 is 0.54 [mm] (d0=0.54) and the thickness d2 is 1 [mm] (d2=1). Let's assume the angle t1 is 35.25° (t1=35.25°), the angle t2 is 68° (t2=68°), and the angle θ11 is 15° (θ11=15°).

[0040] At this time, from (Equation 1) and (Equation 4), the distance LL1 is 1.60 [mm] (LL1 = 1.60). From (Equation 2), (Equation 4), and (Equation 5), the distance LD1 is 1.42 [mm] (LD1 = 1.42). From (Equation 3) and (Equation 4), the distance LD2 is 2.41 [mm] (LD2 = 2.41).

[0041] In this embodiment, by providing a protrusion (prism) on the surface USL of the light guide plate LGL, it is possible to emit the light LTB guided inside the light guide plate LGL upwards.

[0042] Figure 6 is a cross-sectional view showing the schematic structure of the lighting device of the embodiment. The lighting device ILD shown in Figure 6 differs from the lighting device ILDr shown in Figure 4 in that multiple protrusions PRM2 are provided on the surface USL of the light guide plate LGL. Figure 7 is a cross-sectional view showing the protrusions provided on the light guide plate LGL.

[0043] As shown in Figure 7, the light guide plate LGL is provided with not only the convex portion PRM1 on surface BSL but also the convex portion PRM2 on surface USL. The convex portion PRM2 is a convex portion that protrudes upward. Of the base angles of the convex portion PRM2, the angle on the left side of the paper is angle θ21, and the angle on the right side of the paper is angle θ22. The apex angle of the convex portion PRM2 is angle θ23. Angle θ21, angle θ22, and angle θ23 may be different. In the example shown in Figure 7, angle θ21 is greater than angle θ22. Also, angle θ21 of the convex portion PRM2 is greater than angle θ11 of the convex portion PRM1. Angle θ23 of the convex portion PRM2 is greater than angle θ13 of the convex portion PRM1.

[0044] As shown in Figure 6, and similarly as in Figure 4, the light LT emitted from the light source element LS1 is incident on the light guide plate LGU from the plane containing edge GVU1 and propagates within the light guide plate LGU. The light LT that reaches edge GVU2 of the light guide plate LGU is reflected downward by the plane containing edge GVU2. The reflected light LT is emitted from the light guide plate LGU and incident on the light guide plate LGL. The light LTB incident on the light guide plate LGL is reflected by the plane containing edge GVL2 of the light guide plate LGL and propagates in the opposite direction to the first direction X.

[0045] Light LTB reflected from the surface BSL of the light guide plate LGL is emitted upward by a protrusion (prism) provided on the surface BSL. The emitted light RL is then emitted from the surface USU of the light guide plate LGU and incident on the prism sheet PRS. Light RL is then emitted upward by the prism sheet PRS as light DL along the third direction Z, and is further emitted above the illumination device ILD.

[0046] As explained in Figure 4, there is optical LTB that does not exit upward from the surface BSL but is reflected by the surface USL and returns to the light guide plate LGL. After the optical LTB undergoes total internal reflection at the surface USL and returns to the inside of the light guide plate LGL, it undergoes total internal reflection again at the surface BSL. The optical LTB reflected at the surface BSL propagates toward the surface USL.

[0047] The light LTB that reaches the surface USL is emitted upward by the protrusion PRM2 provided on the surface USL. This emitted light is called light RAL. Light RAL is emitted from the surface USU of the light guide plate LGU and incident on the prism sheet PRS. Light RAL is emitted by the prism sheet PRS as light DAL along the third direction Z and is further emitted upward above the illumination device ILD.

[0048] In the example shown in Figure 6, a region NFR also exists. However, because a protrusion PRM2 is provided on the surface USL, the optical LTB is emitted upward in region PRR1 of the surface USL. This makes it possible to efficiently extract the optical LTB propagating through the light guide plate LGL.

[0049] The region irradiated by optical DAL is defined as region RAR. The distance along the first direction X in region RAR is defined as distance LL2. The region located between the regions irradiated by optical DL and optical DAL, and not irradiated by optical DL and optical DAL, is defined as region NLR2. The distance along the first direction X in region NLR2 is defined as distance LD3.

[0050] The distance LL2 is expressed by the following formula. LL2=d2((1 / tant3)-(1 / tant4)) (Equation 6)

[0051] Similar to Figure 4, in Figure 6, for example, let's assume that thickness d0 is 0.54 [mm] (d0=0.54) and thickness d2 is 1 [mm] (d2=1). Let angle t1 be 35.25° (t1=35.25°), angle t2 be 68° (t2=68°), and angle θ11 be 15° (θ11=15°). Let angle θ21 be 78.5° (θ21=78.5°).

[0052] At this time, from (Equation 1) and (Equation 4), the distance LL1 is 1.60 [mm] (LL1 = 1.60). From (Equation 4), (Equation 5), and (Equation 6), the distance LL2 is 1.34 "mm" (LL2 = 1.34).

[0053] In the example shown in Figure 6, a portion of region RAR overlaps with region RLR. However, the embodiments are not limited to this. Region RAR may not overlap with region RLR and may be positioned separately. Alternatively, the entirety of region RAR may overlap with region RLR. The positional relationship between region RLR and region RAR can be controlled by changing the angles of edges GVU2 and GVL2 with respect to the XY plane, angles θ21, θ22, and θ23 of the convex portion PRM2, and the refractive indices of light guide plates LGU and LGL.

[0054] According to this embodiment, a lighting device with improved light extraction efficiency can be obtained. By equipping such a lighting device, it is possible to obtain a display device with high brightness.

[0055] <Configuration Example 1> Figure 8 is a cross-sectional view showing another configuration example of the lighting device in the embodiment. The configuration example shown in Figure 8 differs from the configuration example shown in Figure 6 in that it has a convex portion (prism) that reflects light downwards. Figure 9 is a cross-sectional view showing the convex portion provided on the light guide plate LGL.

[0056] As shown in Figure 9, the light guide plate LGL is provided with not only a convex portion PRM1 on surface BSL but also a convex portion PRM3 on surface USL. The convex portion PRM3 is a convex portion that protrudes upward. Of the base angles of the convex portion PRM3, the left side of the paper is denoted as angle θ31, and the right side of the paper is denoted as angle θ32. The apex angle of the convex portion PRM3 is denoted as angle θ33. Angles θ31, θ32, and θ33 may be different. In the example shown in Figure 9, angle θ31 is smaller than angle θ32.

[0057] In Configuration Example 1, the convex parts PRM1 and PRM3 are arranged in a symmetrical relationship with respect to the first direction X. The angle θ11 of convex part PRM1 and the angle θ31 of convex part PRM3 are equal. The angle θ12 of convex part PRM1 and the angle θ32 of convex part PRM3 are equal. The angle θ13 of convex part PRM1 and the angle θ33 of convex part PRM3 are equal.

[0058] Region PRR1 shown in Figure 6 is designated as Region PRR2 in Figure 8. The optical LTB that reaches Region PRR2 is emitted downward by the protrusion PRM3 provided in Region PRR2. This downward emitted light is designated as optical RBL. Optical RBL is incident on Region NFR.

[0059] As explained in Figure 4, the NFR region is a region where optical LTB with a ray width d1 does not occur. In Figure 8, optical RBL also occurs in the NFR region. Optical RBL is emitted upward by a protrusion PRM1 provided in the NFR region (surface BSL). This upward emitted light is called optical RCL.

[0060] Light RCL, like light RL, is emitted upward from the surface USU of the light guide plate LGU and incident on the prism sheet PRS. Light RCL is then emitted upward from the prism sheet PRS as light DBL along the third direction Z, and is further emitted above the illumination device ILD.

[0061] In Configuration Example 1, the protrusion PRM3 provided on the surface USL reflects the light LTB propagating through the light guide plate LGL downward. The light RBL reflected downward is emitted upward by the protrusion PRM1 provided on the surface BSL. Furthermore, it is emitted upward from the illumination device ILD as light DBL. This makes it possible to efficiently extract the light LTB propagating through the light guide plate LGL.

[0062] The region illuminated by optical DBL is defined as region RBR. The distance along the first direction X in region RBR is defined as distance LL3. The region located between the regions illuminated by optical DL and optical DBL, and not illuminated by optical DL or optical DBL, is defined as region NLR3. The distance along the first direction X in region NLR3 is defined as distance LD4.

[0063] The distance LL3 is expressed by the following formula. LL3=d2((1 / tant3)-(1 / tant4)) (Equation 7)

[0064] Similar to Figure 4, in Figure 8, for example, let's assume that thickness d0 is 0.54 [mm] (d0=0.54) and thickness d2 is 1 [mm] (d2=1). Let angle t1 be 35.25° (t1=35.25°), angle t2 be 68° (t2=68°), and angle θ11 be 15° (θ11=15°). Let angle θ31 be 15° (θ31=15°).

[0065] At this time, from (Equation 1) and (Equation 4), the distance LL1 is 1.60 [mm] (LL1 = 1.60). From (Equation 4), (Equation 5), and (Equation 7), the distance LL3 is 1.34 [mm] (LL3 = 1.34).

[0066] In the example shown in Figure 8, a portion of region RBR overlaps with region RLR. However, the embodiments are not limited to this. Region RBR may not overlap with region RLR and may be positioned separately. Alternatively, the entirety of region RBR may overlap with region RLR. The positional relationship between region RLR and region RBR can be controlled by changing the angles of edges GVU2 and GVL2 with respect to the XY plane, angles θ21, θ22, and θ23 of the convex portion PRM2, and the refractive indices of light guide plates LGU and LGL.

[0067] Configuration Example 1 allows for the creation of a lighting device with improved light extraction efficiency. By incorporating such a lighting device, it is possible to obtain a display device with high brightness.

[0068] <Configuration Example 2> Figure 10 is a cross-sectional view showing another configuration example of the lighting device in the embodiment. The configuration example shown in Figure 10 differs from the configuration example shown in Figure 6 in that it has a convex portion (prism) that reflects light downwards and a convex portion (prism) that emits light upwards. Figure 11 is a cross-sectional view showing a convex portion provided on the light guide plate LGL.

[0069] As shown in Figure 11, the light guide plate LGL is provided with a protrusion PRM1 on surface BSL and a protrusion PRM4 on surface USL. The protrusion PRM4 is a protrusion that projects upward. The cross-sectional shape of the protrusion PRM4 is a pentagon shape, like two triangles stacked on top of each other.

[0070] Of the base angles of the convex PRM4, the left-hand corner on the plane of the paper is designated as angle θ41, and the right-hand corner is designated as angle θ42. The apex angle of the convex PRM4 is designated as angle θ43. The angle located between angles θ41 and θ43 is designated as angle θ44. The angle located between angles θ42 and θ43 is designated as angle θ45. Angles θ41, θ42, θ43, θ44, and θ45 may be different.

[0071] Angles θ41 and θ11 may be the same. Angles θ42 and θ12 may be the same. By having such angles θ41 and θ42, the convex PRM4, like the convex PRM3, can reflect optical LTB and produce optical RBL that is emitted downwards.

[0072] The angle θ44 only needs to be greater than the angle θ11. By having such an angle θ44, the convex PRM4 can obtain optical RAL that is emitted upward from the optical LTB, similar to the convex PRM2.

[0073] The triangular shape formed by angles θ43, θ44, and θ45 may be the same as the triangular cross-sectional shape of the convex PRM2 shown in Figure 7. The virtual triangular shape including angles θ41 and θ42 may be the same as the triangular cross-sectional shape of the convex PRM3 shown in Figure 9.

[0074] In Figure 11, the positions where optical RAL is emitted upward by the convex PRM4 and where optical RBL is emitted downward by the convex PRM4 are shown as different locations. However, as shown in Figure 10, since optical LTB has a line width d1, optical RAL and optical RBL are emitted upward and downward, respectively, from the same position.

[0075] In Figure 10, region PRR3 is designated as region PRR1, which is shown in Figure 6. From the light LTB that reaches region PRR3, the convex portion PRM4 provided in region PRR3 generates light RAL that is emitted upward and light RBL that is emitted downward.

[0076] Light RAL enters the light guide plate LGU and exits from the surface USU of the light guide plate LGU. Light RAL enters the prism sheet PRS. Light RAL is then emitted by the prism sheet PRS as light DAL along the third direction Z, and is further emitted above the illumination device ILD.

[0077] The optical RBL is emitted downward by the convex PRM4, and then emitted upward as optical RCL by the convex PRM1 provided on the surface BSL.

[0078] The RCL light is emitted upward from the surface USU of the light guide plate LGU and incident on the prism sheet PRS. The RCL light is then emitted upward from the prism sheet PRS as a DBL light along the third direction Z, and further emitted above the illumination device ILD.

[0079] In Configuration Example 2, the protrusion PRM4 provided on the surface USL reflects the light LTB propagating through the light guide plate LGL upwards and downwards. The light RAL emitted upwards is emitted from the illumination device ILD as light DAL. The light RBL reflected downwards is emitted upwards by the protrusion PRM1 provided on the surface BSL. Furthermore, it is emitted upwards from the illumination device ILD as light DBL. This makes it possible to efficiently extract the light LTB propagating through the light guide plate LGL.

[0080] Distances LL1, LL2, and LL3 are set as described above. Distance LD5 is the distance along the first direction X of region NLR4, which is located between the regions illuminated by optical DL and optical DBL and is not illuminated by optical DL, optical DAL, and optical DBL.

[0081] Similar to Figure 4, in Figure 10, for example, let the thickness d0 be 0.54 [mm] (d0=0.54) and the thickness d2 be 1 [mm] (d2=1). Let the angle t1 be 35.25° (t1=35.25°), the angle t2 be 68° (t2=68°), and the angle θ11 be 15° (θ11=15°). Let the angle θ44 be 78.5° (θ21=78.5°). Let the angle θ41 be 15° (θ31=15°).

[0082] At this time, from (Equation 1) and (Equation 4), the distance LL1 is 1.60 [mm] (LL1 = 1.60). From (Equation 4), (Equation 5), and (Equation 6), the distance LL2 is 1.34 "mm" (LL2 = 1.34). From (Equation 4), (Equation 5), and (Equation 7), the distance LL3 is 1.34 [mm] (LL3 = 1.34).

[0083] In the example shown in Figure 10, a portion of region RAR overlaps with region RLR. A portion of region RBR overlaps with region RAR. However, the embodiments are not limited to these. Region RAR may not overlap with region RLR and may be located separately. Alternatively, the entirety of region RAR may overlap with region RLR. Region RBR may not overlap with region RAR and may be located separately. Alternatively, the entirety of region RBR may overlap with region RAR.

[0084] By changing the angles of edges GVU2 and GVL2 with respect to the XY plane, the angles θ41, θ42, θ43, θ44, and θ45 of the convex PRM4, and the refractive indices of light guide plates LGU and LGL, it is possible to control the positional relationship between regions RLR, RAR, and RBR.

[0085] Configuration Example 2 allows for the creation of a lighting device with improved light extraction efficiency. By incorporating such a lighting device, it is possible to obtain a display device with high brightness.

[0086] <Configuration Example 3> Figure 12 is a plan view illustrating an example of an application of the lighting device. The display device DSP shown in Figure 12 includes a lighting device ILDh for the left eye and a lighting device ILDh for the right eye.

[0087] The left eye illumination device ILDh has a similar configuration to the illumination device ILD shown in Figure 2. In Figure 12, the illumination device ILDh comprises a light guide plate LGUh and a plurality of light source elements LS1h. In a plan view, the edges of the light guide plate LGUh extending along the second direction Y are denoted as edges GVU1h and GVU2h. In Figure 12, the edge on the left side of the paper is edge GVU1h, and the edge on the right side of the paper is edge GVU2h. The light source elements LS1h are positioned opposite the edge GVU1h of the light guide plate LGUh.

[0088] The illumination device ILDm for the right eye is positioned symmetrically to the illumination device ILDh with respect to the second direction Y. As shown in Figure 12, the illumination device ILDm comprises a light guide plate LGUm and a plurality of light source elements LS1m. In a plan view, the edges of the light guide plate LGUm extending along the second direction Y are denoted as edges GVU1m and GVU2m. In Figure 12, the edge on the right side of the paper is edge GVU1m, and the edge on the left side of the paper is edge GVU2h. The light source element LS1h is provided at a position opposite edge GVU1h of the light guide plate LGUh.

[0089] As shown in Figure 12, for example, light emitted from the light source element LS1h (corresponding to optical LT) and light reflected from the edges GVU2h of the light guide plate LGUh and GVL2h of the light guide plate LGLh and then emitted upward (corresponding to optical DL, optical DAL, and optical DBL) are combined. As a result, a bright region RAh and a dark region RKh are generated in the light guide plate LGUh. The width of the bright region RAh is narrower the closer it is to the light source element LS1h. The width of the bright region RAh increases as it moves away from the light source element LS1h.

[0090] Similarly, the light emitted from the light source element LS1m and the light reflected by the edges GVU2m of the light guide plate LGUm and GVL2m of the light guide plate LGLm, and then emitted upward, are combined. As a result, a bright region RAm and a dark region RKm are created in the light guide plate LGUm. The width of the bright region RAm is narrower the closer it is to the light source element LS1m. The width of the bright region RAm increases as it moves away from the light source element LS1m.

[0091] Figure 13 is a cross-sectional view showing the cross-sectional structure of the display device along line B1-B2 in Figure 12. The display device DSP comprises an illumination device ILDh, a display panel PNLh, an illumination device ILDm, and a display panel PNLm. The display panel PNLh is mounted on the illumination device ILDh. The display panel PNLm is mounted on the illumination device ILDm.

[0092] The lighting device ILDh and display panel PNLh have the same configuration as the lighting device ILD and display panel PNL shown in Figure 3. The lighting device ILDm and display panel PNLm are positioned symmetrically to the lighting device ILDh and display panel PNLh with respect to the YZ plane.

[0093] The lighting device ILDh comprises a reflector REFh, a light guide plate LGLh, a light guide plate LGUh, an optical sheet OPSh, and a light source element LS1h. The reflector REFh, light guide plate LGLh, light guide plate LGUh, and optical sheet OPSh are stacked in this order.

[0094] The light guide plate LGUh has sides GVU1h and GVU2h. Side GVU1h is located on the left side of the paper and faces the light source element LS1h. Side GVU2h is located on the right side of the paper and faces side GVU2m of the light guide plate LGUm.

[0095] The light guide plate LGLh has sides GVL1h and GVL2h. Side GVL1h is located on the left side of the paper and is positioned to coincide with side GVU1h of light guide plate LGUh along the third direction Z. Side GVL2h is located on the right side of the paper and is opposite side GVL2m of light guide plate LGLm.

[0096] The ILDm lighting device comprises a reflector REFm, a light guide plate LGLm, a light guide plate LGUm, an optical sheet OPSm, and a light source element LS1m. The reflector REFm, light guide plate LGLm, light guide plate LGUm, and optical sheet OPSm are stacked in this order.

[0097] The light guide plate LGUm has sides GVU1m and GVU2m. Side GVU1m is located on the right side of the paper and faces the light source element LS1m. Side GVU2m is located on the left side of the paper and faces side GVU2h of the light guide plate LGUh.

[0098] The light guide plate LGLm has sides GVL1m and GVL2m. Side GVL1m is located on the right side of the paper and is positioned to coincide with side GVU1m of light guide plate LGUm along the third direction Z. Side GVL2m is located on the left side of the paper and is opposite side GVL2h of light guide plate LGLh.

[0099] The cross-sectional shapes of the light guide plates LGLh and LGLm are trapezoidal, with the lower side being shorter than the upper side. The cross-sectional shapes of the light guide plates LGUh and LGUm are trapezoidal, with the upper side being shorter than the lower side.

[0100] ILDh and ILDm may use the ILD described above. That is, the light guide plates LGLh and LGLm are provided with protrusions PRM2, PRM3, or PRM4. More specifically, the ILDh including the light guide plate LGLh may use the same configuration as the ILD described above. On the other hand, the ILDm including the light guide plate LGLm may have a configuration that is symmetrical with respect to the YZ plane to the ILD described above.

[0101] Figure 14 is a perspective view showing an example of the appearance of a display device according to Configuration Example 3. In Configuration Example 3, the display device DSP includes a head-mounted display (HMD) that is worn on the user's head. Such a display device DSP is used to provide, for example, virtual reality (VR) to the user USR wearing the display device DSP on their head.

[0102] Display panels PNLh and PNLm are positioned so as to be in front of the left and right eyes of the user USR when the user USR is wearing the display device DSP on their head.

[0103] As described above, by equipping the device with a lighting system that has high light extraction efficiency, it is possible to obtain a display device with high brightness.

[0104] In this disclosure, the light guide plate LGL and the light guide plate LGU are also referred to as the first light guide plate and the second light guide plate, or the lower light guide plate and the upper light guide plate, respectively. The edges GVL1 and GVL2 of the light guide plate LGL are also referred to as the first edge and the second edge, respectively. The edges GVU1 and GVU2 of the light guide plate LGU are also referred to as the third edge and the fourth edge, respectively.

[0105] The surface BSL of the light guide plate LGL is called the first surface, and the surface USL is called the second surface. The convex part PRM1 is called the first convex part, and the convex parts PRM2, PRM3, or PRM4 are called the second convex parts. The cross-sectional shape of the convex part PRM1 is triangular. The angles θ11, θ12, and θ13 of the convex part PRM1 are called the first base angle, the second base angle, and the first vertex angle, respectively.

[0106] The cross-sectional shapes of protrusions PRM2 and PRM3 are triangular. The cross-sectional shape of protrusion PRM4 is pentagonal. In other words, the cross-sectional shape of protrusions PRM2, PRM3, or PRM4 is polygonal.

[0107] The angles θ21, θ22, and θ23 of the convex PRM2 are referred to as the third base angle, the fourth base angle, and the second vertex angle, respectively. The angles θ31, θ32, and θ33 of the convex PRM3 are referred to as the third base angle, the fourth base angle, and the second vertex angle, respectively. The angles θ41, θ42, θ43, θ44, and θ4 of the convex PRM4 are referred to as the third base angle, the fourth base angle, the second vertex angle, the fifth base angle, and the sixth base angle, respectively.

[0108] However, the ordinal numbers assigned to the sides and angles are not limited to those mentioned above. Different ordinal numbers may be assigned as needed.

[0109] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0110] BSL...plane, BSU...plane, DAL...light, DBL...light, DSP...display device, GVL1...edge, GVL2...edge, GVU1...edge, GVU2...edge, ILD...lighting device, LGL...light guide plate, LGU...light guide plate, LS1...light source element, LT...light, LTB...light, PRM1...protrusion, PRM2...protrusion, PRM3...protrusion, PRM4...protrusion, PRR1...region, PRR2...region, RAL...light, RBL...light, RCL...light, USL...plane, USU...plane, d1...ray width.

Claims

1. A first light guide plate having a first side and a second side, A second light guide plate is placed on the first light guide plate and has a third side and a fourth side, A plurality of light source elements are provided opposite the third side of the second light guide plate, A reflector is provided below the first light guide plate, An optical sheet provided on the second light guide plate, Equipped with, The cross-sectional shape of the first light guide plate is a trapezoidal shape in which the lower side is shorter than the upper side. The cross-sectional shape of the second light guide plate is a trapezoidal shape in which the upper side is shorter than the lower side. The first light guide plate comprises a first surface facing the reflector and a second surface facing the second light guide plate. The first surface is provided with a plurality of first protrusions, The second surface is provided with a plurality of second protrusions, Each of the plurality of first protrusions has a first base angle, a second base angle, and a first vertex angle, and has a triangular cross-sectional shape that protrudes downward. Each of the aforementioned multiple second protrusions has a third base angle, a fourth base angle, and a second vertex angle, and has a triangular cross-sectional shape that protrudes upward. A lighting device in which the third base angle is larger than the first base angle.

2. The lighting device according to claim 1, wherein the second vertex angle is greater than the first vertex angle.

3. The lighting device according to claim 1, A display panel is provided on the aforementioned lighting device, A display device equipped with the following features.

4. A first light guide plate having a first side and a second side, A second light guide plate is placed on the first light guide plate and has a third side and a fourth side, A plurality of light source elements are provided opposite the third side of the second light guide plate, A reflector is provided below the first light guide plate, An optical sheet provided on the second light guide plate, Equipped with, The cross-sectional shape of the first light guide plate is a trapezoidal shape in which the lower side is shorter than the upper side. The cross-sectional shape of the second light guide plate is a trapezoidal shape in which the upper side is shorter than the lower side. The first light guide plate comprises a first surface facing the reflector and a second surface facing the second light guide plate. The first surface is provided with a plurality of first protrusions, The second surface is provided with a plurality of second protrusions, Each of the plurality of first protrusions has a first base angle, a second base angle, and a first vertex angle, and has a triangular cross-sectional shape that protrudes downward. Each of the aforementioned multiple second protrusions has a third base angle, a fourth base angle, and a second vertex angle, and has a triangular cross-sectional shape that protrudes upward. A lighting device in which the third base angle and the first base angle are equal.

5. The fourth base angle and the second base angle are equal, The lighting device according to claim 4, wherein the second vertex angle and the first vertex angle are equal.

6. The lighting device according to claim 4, A display panel is provided on the aforementioned lighting device, A display device equipped with the following features.

7. A first light guide plate having a first side and a second side, A second light guide plate is placed on the first light guide plate and has a third side and a fourth side, A plurality of light source elements are provided opposite the third side of the second light guide plate, A reflector is provided below the first light guide plate, An optical sheet provided on the second light guide plate, Equipped with, The cross-sectional shape of the first light guide plate is a trapezoidal shape in which the lower side is shorter than the upper side. The cross-sectional shape of the second light guide plate is a trapezoidal shape in which the upper side is shorter than the lower side. The first light guide plate comprises a first surface facing the reflector and a second surface facing the second light guide plate. The first surface is provided with a plurality of first protrusions, The second surface is provided with a plurality of second protrusions, Each of the plurality of first protrusions has a first base angle, a second base angle, and a first vertex angle, and has a triangular cross-sectional shape that protrudes downward. Each of the aforementioned multiple second protrusions has a third base angle, a fourth base angle, a fifth base angle, a sixth base angle, and a second vertex angle, and has a pentagonal cross-sectional shape that protrudes upward. The fifth base angle is located between the third base angle and the second vertex angle, The sixth base angle is located between the fourth base angle and the second vertex angle, Equal to the third base angle and the first base angle, A lighting device in which the fifth base angle is larger than the first base angle.

8. The lighting device according to claim 7, wherein the fourth base angle and the second base angle are equal.

9. The lighting device according to claim 7, A display panel is provided on the aforementioned lighting device, A display device equipped with the following features.

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