Display device

Abstract

To provide a display device which can be improved in display quality and can be downsized.SOLUTION: According to an embodiment, a display device comprises a liquid crystal panel, an illumination device opposing the liquid crystal panel, and an optical sheet disposed between the liquid crystal panel and the illumination device. The illumination device comprises: a plurality of light sources; a first light guide plate having a first side face opposing the plurality of light sources, and a second side face on an opposite side of the first side face; a second light guide plate opposing the first light guide plate and having a third side face; a transparent element that has a first plane coming into contact with the second side face and the third side face, and a second plane positioned on an opposite side of the first plane and inclined relative to the first plane; and a reflection element opposing the second plane.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to a display device. [Background technology]

[0002] In recent years, various liquid crystal display devices have been put to practical use as display devices. For example, there are various demands for liquid crystal display devices applied to head mounted displays (HMDs) worn on the user's head, such as miniaturization and improvement of display quality. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-026905 [Patent Document 2] International Publication No. 2013-161811 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a display device that can improve display quality and be made smaller. [Means for solving the problem]

[0005] According to an embodiment, the display device comprises: The illumination device comprises a liquid crystal panel, an illumination device facing the liquid crystal panel, and an optical sheet arranged between the liquid crystal panel and the illumination device, wherein the illumination device comprises: a first light guide plate having a plurality of light sources, a first side surface facing the plurality of light sources, and a second side surface opposite the first side surface; a second light guide plate facing the first light guide plate and having a third side surface; a transparent element having a first plane in contact with the second side surface and the third side surface, and a second plane located opposite the first plane and inclined with respect to the first plane; and a reflective element facing the second plane.

[0006] According to an embodiment, the display device comprises: a first light guide plate having a first side surface facing the plurality of light sources and a second side surface opposite the first side surface; a second light guide plate having a third side surface; a first plane contacting the second side surface and the third side surface; a second plane located opposite the first plane and inclined with respect to the first plane; a transparent element having an upper surface located between the first plane and the second plane and facing the optical sheet; and a lower surface opposite the upper surface; and a reflective element facing the second plane, wherein the second light guide plate is located between the first light guide plate and the optical sheet, and the width of the lower surface of the transparent element is smaller than the width of the upper surface.

[0007] According to an embodiment, the display device comprises: a first light guide plate having a first side surface facing the first light sources and a second side surface opposite the first side surface; a second light guide plate having a third side surface; a first plane contacting the second side surface and the third side surface; a second plane located opposite the first plane and inclined with respect to the first plane; a transparent element having an upper surface located between the first plane and the second plane and facing the optical sheet; and a lower surface opposite the upper surface; and a reflective element facing the second plane. The first light guide plate is located between the second light guide plate and the optical sheet. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing an example of the appearance of a head-mounted display 1. As shown in FIG. [Figure 2] FIG. 2 is a diagram for explaining the configuration of the display devices DSP1 and DSP2 shown in FIG. [Figure 3] FIG. 3 is a perspective view showing the configuration of the display panel PNL1. [Figure 4] FIG. 4 is a plan view showing an example of the configuration of the illumination device IL1. [Figure 5] FIG. 5 is a cross-sectional view showing an example of the configuration of a display device DSP1 including the illumination device IL1 shown in FIG. [Figure 6] FIG. 6 is a cross-sectional view showing another example of the configuration of the display device DSP1 including the illumination device IL1 shown in FIG. [Figure 7] FIG. 7 is a plan view showing another example of the configuration of the illumination device IL1. [Figure 8] FIG. 8 is a cross-sectional view showing an example of the configuration of a display device DSP1 including the illumination device IL1 shown in FIG. [Figure 9] FIG. 9 is a cross-sectional view showing another example of the configuration of the display device DSP1 including the illumination device IL1 shown in FIG. [Figure 10] FIG. 10 is a plan view showing another example of the configuration of the illumination device IL1. [Figure 11] FIG. 11 is a cross-sectional view showing another example of the configuration of the display device DSP1 including the illumination device IL1 shown in FIG. [Figure 12] FIG. 12 is a plan view showing another example of the configuration of the illumination devices IL1 and IL2. [Figure 13] FIG. 13 is an enlarged plan view of the cutout portion ILC of the illumination device IL1 shown in FIG. [Figure 14] FIG. 14 is a diagram for explaining optimization of the width of the transparent element TE along the first direction X. In FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described with reference to the drawings. It should be noted that the disclosure is merely an example, and the invention is not limited to the contents described in the following embodiments. Modifications that can be easily conceived by a person skilled in the art are naturally included in the scope of the disclosure. For clearer explanation, the size, shape, etc. of each part may be changed from the actual embodiment and shown schematically in the drawings. In multiple drawings, corresponding elements may be given the same reference numerals, and detailed explanations may be omitted.

[0010] In the drawings, mutually orthogonal X, Y, and Z axes are shown as necessary to facilitate understanding. The direction along the X axis is referred to as the first direction X, the direction along the Y axis is referred to as the second direction Y, and the direction along the Z axis is referred to as the third direction Z. Viewing various elements parallel to the third direction Z is called a planar view. The first direction X and the second direction Y are directions parallel to the main surfaces of the substrate included in the display panel or the light guide plate included in the lighting device, and the third direction Z corresponds to the thickness direction of the display device, display panel, and lighting device.

[0011] FIG. 1 is a perspective view showing an example of the appearance of a head-mounted display 1. As shown in FIG. The head-mounted display (HMD) 1 is used by being worn on the head of a user USR, for example. The head-mounted display 1 is used to provide the user USR with, for example, virtual reality (VR) or augmented reality (AR). The head mounted display 1 includes a display device DSP1 for the left eye and a display device DSP2 for the right eye. The display device DSP1 is arranged so as to be located in front of the left eye of the user USR when the user USR wears the head mounted display 1 on his / her head. The display device DSP2 is arranged so as to be located in front of the right eye of the user USR when the user USR wears the head mounted display 1 on his / her head. Details will be described later.

[0012] FIG. 2 is a diagram for explaining the configuration of the display devices DSP1 and DSP2 shown in FIG.

[0013] The display device DSP1 includes an illumination device IL1, an optical sheet OS1, and a display panel PNL1. The illumination device IL1 is disposed behind the display panel PNL1 and configured to illuminate the display panel PNL1. A plurality of optical sheets OS1 are disposed between the illumination device IL1 and the display panel PNL1.

[0014] The display device DSP2 includes an illumination device IL2, an optical sheet OS2, and a display panel PNL2. The illumination device IL2 is disposed behind the display panel PNL2 and configured to illuminate the display panel PNL2. A plurality of optical sheets OS2 are disposed between the illumination device IL2 and the display panel PNL2.

[0015] The optical sheets OS1 and OS2 are, for example, prism sheets or diffusion sheets. The display panel PNL1 and the display panel PNL2 are, for example, liquid crystal panels.

[0016] 3 is a perspective view showing the configuration of the display panel PNL1. Note that the display panel PNL1 shown here has the same configuration as the display panel PNL2, and therefore a description of the display panel PNL2 will be omitted.

[0017] The display panel PNL1 includes a first substrate SUB1 and a second substrate SUB2 facing the first substrate SUB1. The display panel PNL1 has a display area DA for displaying an image. In the display area DA, a plurality of pixels PX are arranged in a matrix in a first direction X and a second direction Y.

[0018] A driving IC chip IC for driving the display panel PNL1 and a flexible printed circuit board FPC are mounted on the first substrate SUB1.

[0019] In the example shown in FIG. 3, the first substrate SUB1 and the second substrate SUB2 each have an octagonal shape in a plan view. The shapes of the first substrate SUB1 and the second substrate SUB2 can be considered as rectangles with four corners cut out. Because the shapes of the first substrate SUB1 and the second substrate SUB2 are octagonal, the shape of the display panel PNL1 in a plan view can also be considered as an octagon. However, the shape of the display panel PNL1 is not limited to this. The shape of the display panel PNL1 may be any shape that prevents the display panel PNL1 from hitting the nose of the user USR (i.e., a shape with a cutout portion called a nose cut). For example, the shape of the display panel PNL1 may be any polygon or circle with at least one corner close to the nose of the user USR cut out.

[0020] 4 is a plan view showing an example of the configuration of the illumination device IL1. Note that the illumination device IL1 shown here has the same configuration as the illumination device IL2, and therefore a description of the illumination device IL2 will be omitted.

[0021] The illumination device IL1 includes a plurality of light sources LS, a first light guide plate LG1, a second light guide plate LG2, a transparent element TE, and a reflecting element RE.

[0022] The plurality of light sources LS include a first light source LSR configured to emit red laser light, a second light source LSG configured to emit green laser light, and a third light source LSB configured to emit blue laser light, and are arranged in the second direction Y. In the illustrated example, the number of each of the first light source LSR, second light source LSG, and third light source LSB is one, but there may be more than one of each.

[0023] The first light source LSR, the second light source LSG, and the third light source LSB are, for example, laser diodes (semiconductor lasers). The laser light emitted from each light source has high directivity (or linearity) but includes a diffused component. In one example, the red laser light, the green laser light, and the blue laser light are each linearly polarized light.

[0024] The first light guide plate LG1 is, for example, a glass substrate having a refractive index distribution for forming a plurality of optical waveguides. In a plan view, the first light guide plate LG1 has a first side surface S1 and a second side surface S2 opposite the first side surface S1. The first side surface S1 and the second side surface S2 face each other in a first direction X and both extend along a second direction Y. In the illustrated example, the first side surface S1 and the second side surface S2 are parallel to a YZ plane defined by the second direction Y and the third direction Z.

[0025] The first side surface S1 faces the plurality of light sources LS in the first direction X and corresponds to the light entrance surface of the first light guide plate LG1.

[0026] The first light guide plate LG1 has a base body (low refractive index portion) 10 having a first refractive index, and an optical waveguide (high refractive index portion) 11 having a second refractive index higher than the first refractive index. That is, in the first light guide plate LG1, the base body 10 corresponds to the cladding, and the optical waveguide 11 corresponds to the core. At the interface between the base body 10 and the optical waveguide 11, light that enters the optical waveguide 11 is totally reflected.

[0027] The optical waveguide 11 extends from the first side surface S1 to the second side surface S2 inside the first light guide plate LG1 and branches along the way. The optical waveguide 11 is formed, for example, by irradiating the base body 10 with laser light to change the refractive index of a part of the base body 10.

[0028] The multiple optical waveguides 11 include an optical waveguide 11R (shown by a dotted line in FIG. 4) having an end facing the first light source LSR, an optical waveguide 11G (shown by a solid line in FIG. 4) having an end facing the second light source LSG, and an optical waveguide 11B (shown by a dashed line in FIG. 4) having an end facing the third light source LSB. For example, the optical waveguide 11R corresponds to the first optical waveguide, the optical waveguide 11G corresponds to the second optical waveguide, and the optical waveguide 11B corresponds to the third optical waveguide. The optical waveguide 11R propagates red laser light, the optical waveguide 11G propagates green laser light, and the optical waveguide 11B propagates blue laser light.

[0029] For example, focusing on the optical waveguide 11R, the optical waveguide 11R has one end facing the first light source LSR on the first side surface S1, and has multiple ends on the second side surface S2 side. On the second side surface S2 side, the end of the optical waveguide 11R, the end of the optical waveguide 11G, and the end of the optical waveguide 11B are aligned in the second direction Y.

[0030] In the illustrated example, the ends of the optical waveguides 11R, 11G, and 11B face the first light source LSR, the second light source LSG, and the third light source LSB, but optical fibers may be installed between the ends of the optical waveguides 11R, 11G, and 11B and the first light source LSR, the second light source LSG, and the third light source LSB to optically couple them to each other.

[0031] The second light guide plate LG2 faces the first light guide plate LG1 in the third direction Z and is made of, for example, a resin material or a glass material. In a plan view, the second light guide plate LG2 has a third side surface S3. The third side surface S3 extends along the second direction Y and overlaps the second side surface S2 in the third direction Z. In the illustrated example, the third side surface S3 is parallel to the YZ plane.

[0032] The transparent element TE faces the first light guide plate LG1 and the second light guide plate LG2 in the first direction X and is formed, for example, from a resin material. When the red laser light, the green laser light, and the blue laser light are each linearly polarized, the transparent element TE is desirably formed from a polymer with almost zero refractive index anisotropy in order to maintain the polarization state. That is, the transparent element TE has an isotropic refractive index. That is, in the transparent element TE, the orientation birefringence due to stretching orientation is almost zero, and the photoelastic birefringence due to stress deformation is almost zero. From a similar perspective, it is also desirably that the second light guide plate LG2 is formed from a polymer with almost zero refractive index anisotropy, similar to the transparent element TE. Furthermore, although the transparent element TE and the second light guide plate LG2 can be formed from glass, it is desirably formed from a polymer in terms of weight reduction, etc.

[0033] The transparent element TE has a first plane F1. The first plane F1 extends along the second direction Y and is parallel to the YZ plane. The first plane F1 is in contact with the second side surface S2 and the third side surface S3, and is preferably adhered to the second side surface S2 and the third side surface S3. The adhesive that adheres the first plane F1 and the second side surface S2, and the first plane F1 and the third side surface S3 to each other is preferably transparent and made of a material having a refractive index equivalent to that of the transparent element TE, the first light guide plate LG1, and the second light guide plate LG2.

[0034] The transparent element TE also has a second plane F2 opposite to the first plane F1. The second plane F2 extends along the second direction Y, but is tilted with respect to the first plane F1 as described below, and is not parallel to the YZ plane.

[0035] The reflective element RE faces the second plane F2 in the first direction X. The reflective element RE is, for example, a reflective layer formed on the second plane F2. The reflective layer here may be a thin film formed directly on the second plane F2, or a reflective sheet adhered to the second plane F2.

[0036] The display panel PNL1 indicated by the two-dot chain line faces the illumination device IL1 in the third direction Z.

[0037] Fig. 5 is a cross-sectional view showing an example of the configuration of a display device DSP1 including the illumination device IL1 shown in Fig. 4. The display device DSP1 includes a display panel PNL1 that is a liquid crystal panel, an illumination device IL1, and an optical sheet OS1.

[0038] In addition to the first substrate SUB1 and second substrate SUB2 described above, the display panel PNL1 further includes a sealant SL, a liquid crystal layer LC, a first polarizer PL1, and a second polarizer PL2. The first substrate SUB1 and the second substrate SUB2 face each other in the third direction Z and are bonded to each other by the sealant SL. The liquid crystal layer LC is held between the first substrate SUB1 and the second substrate SUB2 and is sealed by the sealant SL. The first substrate SUB1 includes signal lines, scanning lines, switching elements, pixel electrodes, etc., which will not be described in detail. A common electrode shared by multiple pixels may be arranged on either the first substrate SUB1 or the second substrate SUB2.

[0039] The first polarizer PL1 is disposed on the lower surface of the first substrate SUB1, and the second polarizer PL2 is disposed on the upper surface of the second substrate SUB2. The polarization axes of the first polarizer PL1 and the second polarizer PL2 are, for example, perpendicular to each other.

[0040] In the lighting device IL1, the first light guide plate LG1 has a main surface M1 and a main surface M2 opposite to the main surface M1. The main surfaces M1 and M2 face each other in the third direction Z and are parallel to each other. The main surfaces M1 and M2 are parallel to the XY plane defined by the first direction X and the second direction Y. In other words, the first light guide plate LG1 has a constant thickness T1 along the third direction Z from the first side surface S1 to the second side surface S2.

[0041] The optical waveguides 11R, 11G, and 11B are formed in layers in different layers (heights) of the first light guide plate LG1 in the third direction Z without intersecting with one another. Moreover, the optical waveguides 11R, 11G, and 11B are not bent in the third direction Z. In the illustrated example, the optical waveguides 11R, 11G, and 11B are arranged in this order from top to bottom, but the optical waveguides 11R, 11G, and 11B may be arranged in an order different from that shown in FIG. 5. Furthermore, in the illustrated example, only one each of the optical waveguides 11R, 11G, and 11B is shown, but multiple each of the optical waveguides 11R, 11G, and 11B may be formed in layers.

[0042] The second light guide plate LG2 is disposed between the first light guide plate LG1 and the optical sheet OS1 in the third direction Z. The second light guide plate LG2 has a main surface M3 and a main surface M4 opposite to the main surface M3. The main surfaces M3 and M4 face each other in the third direction Z. The main surface M3 faces the main surface M2 in the third direction Z and has a plurality of minute protrusions (prisms). The main surface M4 is parallel to the XY plane. The second light guide plate LG2 also has a substantially constant thickness T2 along the third direction Z. In one example, the thickness T2 is greater than the thickness T1.

[0043] In the illustrated example, the reflecting sheet RS is disposed between the main surface M2 and the main surface M3 in the third direction Z.

[0044] The optical sheet OS1 is disposed between the second light guide plate LG2 and the display panel PNL1 in the third direction Z. The optical sheet OS1 includes, for example, a prism sheet PS and a diffusion sheet DS. The prism sheet PS has the function of appropriately converging and refracting the illumination light emitted from the lighting device IL1. The diffusion sheet DS has the function of appropriately diffusing the illumination light that has passed through the prism sheet PS.

[0045] The transparent element TE has a trapezoidal cross section in the XZ plane defined by the first direction X and the third direction Z. In addition to the first plane F1 and the second plane F2, the transparent element TE has an upper surface TS facing the optical sheet OS1 and a lower surface BS opposite the upper surface TS. The upper surface TS and the lower surface BS face each other in the third direction Z and are parallel to each other. The upper surface TS and the lower surface BS are parallel to, for example, the XY plane. The first plane F1 and the second plane F2 face each other in the first direction X and are non-parallel to each other. As described above, the first plane F1 is in contact with the second side surface S2 and the third side surface S3. The second plane F2 is covered with the reflective element RE.

[0046] The width W1 of the transparent element TE between the first light guide plate LG1 and the reflection element RE is smaller than the width W2 of the transparent element TE between the second light guide plate LG2 and the reflection element RE (W1 < W2). Here, the width of the transparent element TE is the length parallel to the first direction X from the first plane F1 to the second plane F2. In the illustrated example, the width of the lower surface BS is shown as an example of the width W1, and the width of the upper surface TS is shown as an example of the width W2. And in the transparent element TE, the width from the first plane F1 to the second plane F2 gradually increases from the lower surface BS toward the upper surface TS.

[0047] From another perspective, in the transparent element TE, when the angle formed by the lower surface BS and the first plane F1 is θ1, and the angle formed by the lower surface BS and the second plane F2 is θ2, the angle θ2 is larger than the angle θ1 (θ1 < θ2). In one example, the angle θ1 is a right angle, and the angle θ2 is an obtuse angle.

[0048] In such a display device DSP1, the laser light emitted from the light source LS enters the first light guide plate LG1 and spreads in the X - Y plane while passing through any one of the optical waveguides 11R, 11G, 11B. Then, the red laser light, green laser light, and blue laser light are appropriately mixed when propagating through the base body 10 from the end of each optical waveguide to the second side surface S2. The principal ray MB forming the luminance center of the laser light and the diffused light ray DB diffused from the principal ray MB enter the transparent element TE after passing through the first light guide plate LG1, are reflected by the reflection element RE, and then enter the second light guide plate LG2. In the figure, the principal ray MB is indicated by a solid arrow, and the diffused light ray DB is indicated by a dashed arrow.

[0049] The laser light incident on the second light guide plate LG2 travels while being totally reflected by the main surfaces M3 and M4. For example, the reflected light that deviates from the total reflection condition in the prism of the main surface M3 exits from the main surface M4 to form illumination light.

[0050] Illumination light emitted from the illumination device IL1 passes through the prism sheet PS and the diffusion sheet DS, and at least a portion of it passes through the first polarizer PL1. From the viewpoint of suppressing absorption of the illumination light by the first polarizer PL1, it is desirable that the laser light emitted from the light source LS is linearly polarized light parallel to the transmission axis of the first polarizer PL1. At least a portion of the illumination light that passes through the first polarizer PL1 is modulated in the liquid crystal layer LC and converted into display light. At least a portion of the display light passes through the second polarizer PL2 to form a display image.

[0051] Here, the display device DSP1 configured with the illumination device IL1, the optical sheet OS1, and the display panel PNL1 has been described, but the display device DSP2 has the same configuration as the display device DSP1, and therefore description thereof will be omitted.

[0052] The display device described above includes a first light guide plate LG1 that propagates light emitted from a light source LS while diffusing it in-plane and mixes light of different colors, a second light guide plate LG2 that faces the first light guide plate LG1 in the thickness direction, and a transparent element TE and a reflective element RE that guide the light propagated by the first light guide plate LG1 to the second light guide plate LG2. This makes it possible to shorten the approach distance for sufficiently mixing light of different colors in a plan view, thereby enabling the device to be made more compact and suppressing uneven brightness and color of the illumination light, thereby improving display quality.

[0053] 4 and 5, the first light guide plate LG1 has a branched optical waveguide 11. Therefore, the light emitted from the light source LS is appropriately distributed within the surface of the first light guide plate LG1. Therefore, even when the number of light sources is small, uneven brightness and color of the illumination light can be suppressed, and costs can be reduced.

[0054] Next, other configuration examples will be described. Note that the same components as those in the above configuration examples will be given the same reference numerals and the description thereof will be omitted.

[0055] FIG. 6 is a cross-sectional view showing another configuration example of the display device DSP1 including the lighting device IL1 shown in FIG. 4.

[0056] The configuration example shown in FIG. 6 is different from the configuration example shown in FIG. 5 in that the top and bottom of the lighting device IL1 are inverted. That is, the first light guide plate LG1 is disposed between the second light guide plate LG2 and the optical sheet OS1 in the third direction Z.

[0057] The main surface M1 of the first light guide plate LG1 faces the optical sheet OS1, and the main surface M2 faces the main surface M3 of the second light guide plate LG2. The main surface M4 faces the reflection sheet RS.

[0058] The transparent element TE has a trapezoidal cross section in the X-Z plane. The transparent element TE has a first plane F1, a second plane F2, an upper surface TS on the side facing the optical sheet OS1, and a lower surface BS on the side opposite to the upper surface TS. The upper surface TS and the lower surface BS face each other in the third direction Z and are parallel to each other. These upper surface TS and lower surface BS are, for example, parallel to the X-Y plane. The first plane F1 and the second plane F2 face each other in the first direction X and are non-parallel to each other. The first plane F1 is in contact with the second side surface S2 and the third side surface S3. The second plane F2 is covered with the reflection element RE.

[0059] The width W1 of the transparent element TE between the first light guide plate LG1 and the reflection element RE is smaller than the width W2 of the transparent element TE between the second light guide plate LG2 and the reflection element RE (W1 < W2). In the illustrated example, the width of the upper surface TS is shown as an example of the width W1, and the width of the lower surface BS is shown as an example of the width W2. And in the transparent element TE, the width from the first plane F1 to the second plane F2 gradually decreases as it goes from the lower surface BS to the upper surface TS.

[0060] From another viewpoint, in the transparent element TE, when the angle formed by the lower surface BS and the first plane F1 is θ1 and the angle formed by the lower surface BS and the second plane F2 is θ2, the angle θ2 is smaller than the angle θ1 (θ2 < θ1). In one example, the angle θ1 is a right angle and the angle θ2 is an acute angle.

[0061] In this display device DSP1, laser light emitted from the light source LS enters the first light guide plate LG1 and spreads in the XY plane while passing through one of the optical waveguides 11R, 11G, and 11B. The red, green, and blue laser lights are mixed appropriately as they propagate through the base body 10 from the end of each optical waveguide to the second side surface S2. After passing through the first light guide plate LG1, the chief ray MB and the diffused ray DB of the laser light enter the transparent element TE, are reflected by the reflecting element RE, and then enter the second light guide plate LG2. In the figure, the chief ray MB is indicated by a solid arrow, and the diffused ray DB is indicated by a dashed arrow.

[0062] The laser light incident on the second light guide plate LG2 travels while being totally reflected by the main surfaces M3 and M4, and for example, reflected light that does not meet the total reflection conditions at the prism on the main surface M4 is emitted from the main surface M3, passes through the first light guide plate LG1, and forms illumination light.

[0063] According to this configuration example, the same effects as those of the above configuration example can be obtained. In addition, as shown by the dashed arrows in Fig. 6, the light rays that are incident on the second light guide plate LG2 and then reflected by the prism are closer to the third side surface S3 than in the configuration example shown in Fig. 5. This allows the display area of the display panel PNL1 to be expanded to a position closer to the third side surface S3. In other words, the width of the frame of the display device DSP can be reduced.

[0064] 7 is a plan view showing another example of the configuration of the illumination device IL1. Note that the illumination device IL1 shown here has the same configuration as the illumination device IL2, and therefore a description of the illumination device IL2 will be omitted.

[0065] The illumination device IL1 includes a plurality of light sources LS, a first light guide plate LG1, a second light guide plate LG2, a transparent element TE, and a reflecting element RE. 7 differs from the configuration example shown in Fig. 4 in that a greater number of light sources LS are arranged in the second direction Y. In addition, in the configuration example shown in the figure, the first light guide plate LG1 does not have a refractive index distribution for forming an optical waveguide.

[0066] The plurality of light sources LS include a plurality of first light sources LSR configured to emit red laser light, a plurality of second light sources LSG configured to emit green laser light, and a plurality of third light sources LSB configured to emit blue laser light, and are arranged in a second direction Y.

[0067] The red laser light emitted from the first light source LSR, the green laser light emitted from the second light source LSG, and the blue laser light emitted from the third light source LSB are, for example, linearly polarized light.

[0068] The first light guide plate LG1 and the second light guide plate LG2 are made of, for example, a resin material or a glass material. The transparent element TE is made of, for example, a resin material. When the red laser light, the green laser light, and the blue laser light are each linearly polarized, from the viewpoint of maintaining the polarization state, it is desirable that the first light guide plate LG1, the second light guide plate LG2, and the transparent element TE be made of a polymer with the above-mentioned refractive index anisotropy being almost zero. Also, from the viewpoint of weight reduction, it is desirable that the first light guide plate LG1, the second light guide plate LG2, and the transparent element TE be made of a polymer.

[0069] The reflective element RE is, for example, a reflective layer formed on the second plane F2. The reflective layer here may be a thin film formed directly on the second plane F2, or a reflective sheet adhered to the second plane F2.

[0070] The display panel PNL1 indicated by the two-dot chain line faces the illumination device IL1 in the third direction Z.

[0071] FIG. 8 is a cross-sectional view showing an example of the configuration of a display device DSP1 including the illumination device IL1 shown in FIG.

[0072] The display panel PNL1 includes a first substrate SUB1, a second substrate SUB2, a sealing material SL, a liquid crystal layer LC, a first polarizing plate PL1, and a second polarizing plate PL2.

[0073] The lighting device IL1 includes a light source LS, a first light guide plate LG1, a second light guide plate LG2, a transparent element TE, and a reflection element RE. The second light guide plate LG2 is disposed between the first light guide plate LG1 and an optical sheet OS1. Also, a reflection sheet RS is disposed between the first light guide plate LG1 and the second light guide plate LG2.

[0074] The transparent element TE has a trapezoidal cross section in the X-Z plane defined by the first direction X and the third direction Z. The transparent element TE has a first plane F1, a second plane F2, an upper surface TS on the side facing the optical sheet OS1, and a lower surface BS on the side opposite to the upper surface TS. The upper surface TS and the lower surface BS face each other in the third direction Z and are parallel to each other. These upper surface TS and lower surface BS are, for example, parallel to the X-Y plane. The first plane F1 and the second plane F2 face each other in the first direction X and are non-parallel to each other. The first plane F1 is in contact with the second side surface S2 and the third side surface S3. The second plane F2 is covered with the reflection element RE.

[0075] The width W1 of the transparent element TE between the first light guide plate LG1 and the reflection element RE is smaller than the width W2 of the transparent element TE between the second light guide plate LG2 and the reflection element RE (W1 < W2). In the illustrated example, the width of the lower surface BS is shown as an example of the width W1, and the width of the upper surface TS is shown as an example of the width W2. And the width of the transparent element TE gradually increases from the lower surface BS toward the upper surface TS.

[0076] From another perspective, in the transparent element TE, the angle θ1 formed by the lower surface BS and the first plane F1 is smaller than the angle θ2 formed by the lower surface BS and the second plane F2 (θ1 < θ2). In one example, the angle θ1 is a right angle and the angle θ2 is an obtuse angle.

[0077] Even in such a configuration example, the same effects as those of the above configuration example can be obtained.

[0078] FIG. 9 is a cross-sectional view showing another configuration example of the display device DSP1 including the lighting device IL1 shown in FIG. 7.

[0079] The configuration example shown in FIG. 9 is different from the configuration example shown in FIG. 8 in that the top and bottom of the lighting device IL1 are inverted. That is, the first light guide plate LG1 is disposed between the second light guide plate LG2 and the optical sheet OS1 in the third direction Z.

[0080] The main surface M1 of the first light guide plate LG1 faces the optical sheet OS1, and the main surface M2 faces the main surface M3 of the second light guide plate LG2. The main surface M4 faces the reflection sheet RS.

[0081] The transparent element TE has a trapezoidal cross section in the X-Z plane. The width W1 of the transparent element TE between the first light guide plate LG1 and the reflection element RE is smaller than the width W2 of the transparent element TE between the second light guide plate LG2 and the reflection element RE (W1 < W2). In the illustrated example, the width of the upper surface TS is shown as an example of the width W1, and the width of the lower surface BS is shown as an example of the width W2. And in the transparent element TE, the width from the first plane F1 to the second plane F2 gradually decreases as going from the lower surface BS to the upper surface TS.

[0082] From another perspective, in the transparent element TE, when the angle formed by the lower surface BS and the first plane F1 is θ1 and the angle formed by the lower surface BS and the second plane F2 is θ2, the angle θ2 is smaller than the angle θ1 (θ2 < θ1). In one example, the angle θ1 is a right angle and the angle θ2 is an acute angle.

[0083] Even in such a configuration example, the same effects as those of the above configuration example can be obtained.

[0084] FIG. 10 is a plan view showing another configuration example of the lighting device IL1. Note that the lighting device IL1 shown here is configured in the same manner as the lighting device IL2, and the description of the lighting device IL2 is omitted.

[0085] The illumination device IL1 includes a plurality of light sources LS, a first light guide plate LG1, a second light guide plate LG2, a transparent element TE, and a reflecting element RE. The configuration example shown in Fig. 10 differs from the configuration example shown in Fig. 7 in that the reflective element RE is a reflector in which a reflective layer is formed on the surface of a metal body or a block. Such a reflective element RE is arranged to face the transparent element TE in the first direction X. Note that the reflective element RE may be bonded to the transparent element TE, or may face the transparent element TE via an air layer.

[0086] FIG. 11 is a cross-sectional view showing another example of the configuration of the display device DSP1 including the illumination device IL1 shown in FIG. The configuration example shown in Fig. 11 is obtained by replacing the reflecting element RE formed as a reflective layer (thin film) with a reflecting element RE formed as a metal body or a reflector in the configuration example shown in Fig. 8. Note that the reflecting element RE formed as a metal body or a reflector can also be applied to the configuration examples shown in Fig. 5, Fig. 6, and Fig. 9.

[0087] Next, the lighting devices IL1 and IL2 having a cutout portion called a nose cut will be described.

[0088] FIG. 12 is a plan view showing another example of the configuration of the illumination devices IL1 and IL2.

[0089] The lighting devices IL1 and IL2 are aligned in the first direction X and arranged symmetrically with respect to the user's nose NS, which is indicated by a dashed line. Each of the lighting devices IL1 and IL2 has a cutout ILC to avoid contact with the nose NS. The configuration of the lighting devices IL1 and IL2, other than the cutout ILC, is the same as the configuration example shown in FIGS. 10 and 11. Below, the lighting device IL1 will be described, and a description of the lighting device IL2 will be omitted.

[0090] The outer edge REE of the reflecting element RE is formed to follow the contour of the nose NS, extends linearly in the second direction Y, and extends obliquely at the cutout ILC. The second side surface S2 and the third side surface S3 extend linearly in the second direction Y and are formed in a stepped shape at the cutout ILC. The transparent element TE is interposed between the reflecting element RE and the second side surface S2 and the third side surface S3. The cutout ILC of the lighting device IL1 will be described in more detail below.

[0091] FIG. 13 is an enlarged plan view of the cutout portion ILC of the illumination device IL1 shown in FIG.

[0092] Each of the second side surface S2 and the third side surface S3 includes at least a first linear portion LN1, a second linear portion LN2 that is closer to the first side surface S1 than the first linear portion LN1, and a third linear portion LN3 that connects the first linear portion LN1 and the second linear portion LN2. The first linear portion LN1 is longer than the second linear portion LN2. The first linear portion LN1 and the second linear portion LN2 are parallel to each other and, in the illustrated example, both extend in the second direction Y. In addition, in the illustrated example, the third linear portion LN3 extends in the first direction X.

[0093] The transparent element TE is disposed between the first straight line portion LN1 and the reflecting element RE, and is also disposed between the second straight line portion LN2 and the reflecting element RE. A part of the third straight line portion LN3 faces the reflecting element RE in the second direction Y without the transparent element TE therebetween.

[0094] As described above, the set of transparent element TE and reflective element RE guides laser light emitted from the light source LS along the first direction X from the first light guide plate LG1 to the second light guide plate LG2. On the other hand, if the transparent element TE is disposed between the third straight line portion LN3 and the reflective element RE, the light emitted from the first light guide plate LG1, spreading obliquely with respect to the first direction X within the XY plane, will be guided to the second light guide plate LG2 along the second direction Y, which may cause brightness unevenness at the cutout portion ILC. For this reason, as shown in the figure, by separating the transparent element TE between the first straight line portion LN1 and the reflective element RE from the transparent element TE between the second straight line portion LN2 and the reflective element RE and not disposing the transparent element TE between the third straight line portion LN3 and the reflective element RE, brightness unevenness at the cutout portion ILC can be suppressed.

[0095] The above-described cutout portion ILC can also be applied to the configuration examples shown in FIGS.

[0096] FIG. 14 is a diagram for explaining optimization of the width of the transparent element TE along the first direction X. In FIG.

[0097] In the XZ plane, the chief ray MB is parallel to the first direction X, and the diffused ray DB is inclined at an angle Δθ with respect to the chief ray MB. Here, we consider the conditions under which all of the chief ray MB and the diffused ray DB are guided from the first light guide plate LG1 to the second light guide plate LG2.

[0098] In the second light guide plate LG2, when the chief ray MB forms an angle θ with the first direction X, the diffused ray DB forms an angle (θ-Δθ) with the first direction X. In this case, in the transparent element TE, the second plane F2 is inclined at an angle θ / 2 with respect to the first plane F1 that is parallel to the third direction Z.

[0099] In order for the diffused light ray DB to be reflected near the intersection of the bottom surface BS and the second plane F2 in the transparent element TE and then enter the second light guide plate LG2 above the intersection of the main surface M3 and the third side surface S3 (towards the main surface M4), the following relational expression holds: Dz≦Wx*tan(θ-Δθ) (1)

[0100] Here, Dz is the distance along the third direction Z between the main surface M1 of the first light guide plate LG1 and the main surface M3 of the second light guide plate LG2, and Wx is the minimum width of the transparent element TE along the first direction X (the width of the bottom surface BS in the illustrated example). The angle θ is set to, for example, 26.5° so that the light guided into the second light guide plate LG2 is most efficiently emitted from the second light guide plate LG2.

[0101] By setting the width Wx so as to satisfy this relationship, all of the chief ray MB and the diffused ray DB are guided from the first light guide plate LG1 to the second light guide plate LG2, and a decrease in the light utilization efficiency is suppressed.

[0102] According to the embodiment described above, it is possible to provide a display device that can improve display quality and be made smaller.

[0103] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0104] DSP: Display device PNL1, PNL2: Display panel IL1, IL2: Lighting device LS...Light source LSR...1st light source LSG...2nd light source LSB...3rd light source LG1...First light guide plate M1, M2...Main surface S1...First side S2...Second side 10...Base body 11...Optical waveguide 11R...First optical waveguide 11G...Second optical waveguide 11B...Third optical waveguide LG2…Second light guide plate M3, M4…Main surface S3…Third side TE…Transparent element F1…1st plane F2…2nd plane BS…Bottom surface TS…Top surface RE...reflection element

Claims

1. An LCD panel, an illumination device facing the liquid crystal panel; an optical sheet disposed between the liquid crystal panel and the lighting device, The lighting device includes: Multiple light sources; a first light guide plate having a first side surface facing the plurality of light sources and a second side surface opposite to the first side surface; a second light guide plate facing the first light guide plate and having a third side surface; a transparent element having a first plane that contacts the second side surface and the third side surface, and a second plane that is located opposite the first plane and is inclined relative to the first plane; a reflecting element facing the second plane, Display device.

2. The first light guide plate is a glass substrate having a base body having a first refractive index and a plurality of optical waveguides extending from the first side surface to the second side surface inside the base body and branching midway, the optical waveguides having a second refractive index higher than the first refractive index, and has a constant thickness from the first side surface to the second side surface. The display device according to claim 1 .

3. the plurality of light sources include a first light source configured to emit red laser light, a second light source configured to emit green laser light, and a third light source configured to emit blue laser light; the plurality of optical waveguides include a first optical waveguide for propagating the red laser light, a second optical waveguide for propagating the green laser light, and a third optical waveguide for propagating the blue laser light; the first optical waveguide, the second optical waveguide, and the third optical waveguide are positioned in layers in a thickness direction of the first light guide plate without intersecting each other, and are not bent in the thickness direction. The display device according to claim 2 .

4. the red laser light, the green laser light, and the blue laser light are each linearly polarized light, the transparent element is formed of a polymer having a refractive index anisotropy of approximately zero; The display device according to claim 3 .

5. the second light guide plate is formed of a polymer having almost zero refractive index anisotropy; The display device according to claim 4 .

6. the plurality of light sources include a first light source configured to emit red laser light, a second light source configured to emit green laser light, and a third light source configured to emit blue laser light; the red laser light, the green laser light, and the blue laser light are each linearly polarized light, the first light guide plate is formed of a polymer having almost zero refractive index anisotropy; The display device according to claim 1 .

7. the transparent element is formed of a polymer having a refractive index anisotropy of approximately zero; The display device according to claim 6.

8. the second light guide plate is formed of a polymer having almost zero refractive index anisotropy; The display device according to claim 7 .

9. the second light guide plate is disposed between the first light guide plate and the optical sheet; The display device according to claim 1 .

10. the first light guide plate is disposed between the second light guide plate and the liquid crystal panel; The display device according to claim 1 .

11. the reflective element is a reflective layer formed on the second plane; The display device according to claim 1 .

12. The reflective element is a metal body or a reflective body having a reflective layer formed on the surface of a block. The display device according to claim 1 .

13. Each of the second side surface and the third side surface includes, in a plan view, a first linear portion, a second linear portion closer to the first side surface than the first linear portion, and a third linear portion connecting the first linear portion and the second linear portion. The display device according to claim 1 .

14. the transparent element is disposed between the first linear portion and the reflective element and between the second linear portion and the reflective element; The display device according to claim 13.

15. An LCD panel, an illumination device facing the liquid crystal panel; an optical sheet disposed between the liquid crystal panel and the lighting device, The lighting device includes: Multiple light sources; a first light guide plate having a first side surface facing the plurality of light sources and a second side surface opposite to the first side surface; a second light guide plate having a third side surface; a transparent element having a first plane in contact with the second side surface and the third side surface, a second plane located opposite to the first plane and inclined relative to the first plane, an upper surface located between the first plane and the second plane and facing the optical sheet, and a lower surface opposite to the upper surface; a reflecting element facing the second plane, the second light guide plate is disposed between the first light guide plate and the optical sheet; In the transparent element, the width of the lower surface is smaller than the width of the upper surface. Display device.

16. the first light guide plate is a glass substrate having a refractive index distribution for forming a plurality of optical waveguides; the transparent element and the second light guide plate are formed of a polymer having a refractive index anisotropy of approximately zero; The display device according to claim 15.

17. the first light guide plate, the transparent element, and the second light guide plate are formed of a polymer having a refractive index anisotropy of approximately zero; The display device according to claim 15.

18. An LCD panel, an illumination device facing the liquid crystal panel; an optical sheet disposed between the liquid crystal panel and the lighting device, The lighting device includes: Multiple light sources; a first light guide plate having a first side surface facing the plurality of light sources and a second side surface opposite to the first side surface; a second light guide plate having a third side surface; a transparent element having a first plane in contact with the second side surface and the third side surface, a second plane located opposite to the first plane and inclined relative to the first plane, an upper surface located between the first plane and the second plane and facing the optical sheet, and a lower surface opposite to the upper surface; a reflecting element facing the second plane, the first light guide plate is disposed between the second light guide plate and the liquid crystal panel, In the transparent element, the width of the lower surface is greater than the width of the upper surface. Display device.

19. the first light guide plate is a glass substrate having a refractive index distribution for forming a plurality of optical waveguides; the transparent element and the second light guide plate are formed of a polymer having a refractive index anisotropy of approximately zero; 19. The display device according to claim 18.

20. the first light guide plate, the transparent element, and the second light guide plate are formed of a polymer having a refractive index anisotropy of approximately zero; 19. The display device according to claim 18.

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