Backlight device for display device and display device

Abstract

To provide a backlight device for display device and a display device which can suppress the occurrence of luminance unevenness in an image to be displayed when a lens sheet including a lens is moved to a luminance unified sheet in order to change the irradiation direction of light in the direction of being emitted from a light source.SOLUTION: In a backlight device 10 for display device, a plurality of lenses 31 are configured such that at least one of the thickness T and shape becomes different according to the hole diameters D of a plurality of through holes 21 opposite to each other.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a backlight device for a display device and a display device, and more particularly to a backlight device for a display device and a display device that are provided with a lens sheet. [Background technology]

[0002] 2. Description of the Related Art Backlight devices for display devices and display devices each having a lens sheet are known (see, for example, Patent Document 1).

[0003] The above-mentioned Patent Document 1 discloses an illumination device including a light source, a first optical sheet, and a second optical sheet, in which the first optical sheet has an opening through which light passes, and the second optical sheet has a plurality of lens portions of the same size. In Patent Document 1, the illumination device is configured such that the direction of the light emitted from the second optical sheet is changed by moving the second optical sheet, so that the image cannot be seen when viewed from an oblique position relative to the display surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-80755 A Summary of the Invention [Problem to be solved by the invention]

[0005] Although not disclosed in the above Patent Document 1, the size of the hole diameter of the opening (through hole) provided in the first optical sheet (brightness uniformizing sheet) as described above is adjusted according to the position of the light source in order to uniformize the brightness. In addition, by increasing the hole diameter of the opening provided in the first optical sheet, light with a large angle is more likely to pass through the opening. Therefore, if a second optical sheet (lens sheet) as described above including lenses of the same shape and thickness is used for a first optical sheet including openings with different hole diameters, when the second optical sheet is moved, in the part where the hole diameter of the opening is large, the amount of light that does not pass through the center of the lens provided in the second optical sheet increases, and the image becomes blurred. As a result, when the second optical sheet is moved relative to the first optical sheet, there is a problem that unevenness occurs in the entire image displayed depending on the angle at which the image is viewed.

[0006] The present invention has been made to solve the problems described above, and one object of the present invention is to provide a backlight device for a display device and a display device that are capable of suppressing the occurrence of uneven brightness in a displayed image when a lens sheet including lenses is moved relative to a brightness uniformizing sheet to change the irradiation direction of light emitted from a light source. [Means for solving the problem]

[0007] In order to achieve the above object, a backlight device for a display device according to a first aspect of the present invention includes: a light source; a luminance uniformizing sheet arranged to face the light source and including a plurality of through holes for transmitting light emitted from the light source having a plurality of different hole diameters, for uniforming the luminance of light emitted from the light source; and a lens sheet arranged on the opposite side to the light source and including a plurality of lenses arranged to face the plurality of through holes of the luminance uniformizing sheet, the lens sheet being configured to be movable to adjust a width or a direction of a light distribution of light emitted from the light source, the plurality of lenses being arranged to view an image from an oblique position with respect to a display surface within a range of a viewing angle at which the image is viewable. Measure the brightness In order to make the brightness uniform when the light-emitting diode is turned on, the thickness or radius of curvature At least one of the At least one of the thickness of the lenses and the radius of curvature of the lenses is set to be proportional to the diameter of the through holes of the luminance uniformizing sheet.

[0008] In the backlight device for a display device according to the first aspect of the present invention, as described above, the lenses are configured to have at least one of different thicknesses or shapes so that the brightness is uniform when the image is viewed from an oblique position relative to the display surface within the range of viewing angles at which the image can be viewed. By adjusting at least one of the thicknesses or shapes of the lenses, it is possible to suppress an increase in light that does not pass through the center of the lens provided on the lens sheet, thereby suppressing blurring of the image. As a result, when the lens sheet including the lenses is moved relative to the brightness uniformizing sheet to change the irradiation direction of the light emitted from the light source, it is possible to suppress the occurrence of brightness unevenness in the displayed image. In addition, at least one of the thicknesses of the lenses and the radii of curvature of the lenses is set to be proportional to the diameter of the through-holes of the luminance uniforming sheet. With this configuration, when adjusting at least one of the thicknesses of the lenses and the radii of curvature of the lenses, the thickness or the radii of curvature of the lenses can be appropriately changed based on a lens having an appropriate relationship between the size of the through-hole and at least one of the radii of curvature or the thickness of the lens.

[0009] In the backlight device for a display device according to the first aspect, the lenses are preferably configured to have at least one of a thickness and a radius of curvature that differ according to the diameter of the through holes so that the brightness of light passing through the through holes of the brightness uniformizing sheet having different diameters becomes uniform when the image is viewed from an oblique position with respect to the display surface within a range of viewing angles at which the image is viewable. With this configuration, the brightness can be uniformed by setting at least one of the thickness and the radius of curvature of the lenses according to the diameter of the through holes, and therefore the occurrence of unevenness in the displayed image can be easily suppressed.

[0010] In this case, preferably, at least one of the thickness of the lenses and the radius of curvature of the lenses is set to increase as the diameter of the through-holes of the luminance uniformizing sheet increases. In this configuration, by increasing at least one of the thickness of the lenses and the radius of curvature of the lenses as the diameter of the through-holes of the luminance uniformizing sheet increases, it is possible to effectively suppress an increase in the amount of light that does not pass through the center of the lens, and therefore it is possible to suppress blurring of the image caused by the increase in the size of the through-hole.

[0012] In the backlight device for a display device according to the first aspect, the plurality of lenses are preferably arranged one for each of the plurality of through holes. With this configuration, compared to a case where one lens corresponds to a plurality of through holes having different hole diameters, the size of the through hole can be matched one-to-one with at least one of the thickness or radius of curvature of the lens, making it possible to finely adjust at least one of the thickness or radius of curvature of the lens.

[0013] In the backlight device for a display device according to the first aspect, the plurality of through holes in the luminance uniformizing sheet preferably have hole diameters set according to the distance from the light source. Here, the luminance is greatest directly above the light source, and the luminance decreases as the distance from the light source increases. Therefore, by setting the hole diameter of the through hole directly above the light source to the smallest and increasing the size of the through hole as the distance from the light source increases, it is possible to appropriately adjust the amount of light passing through the through hole and make the luminance uniform.

[0014] In the backlight device for a display device according to the first aspect, the lens sheet is preferably configured to be movable along the direction in which the lenses are arranged. With this configuration, by moving the lens sheet, the focal position moves, and the position at which the light is collected can be moved, so that the direction of the light passing through the lenses can be changed.

[0015] In the aforementioned backlight device for a display device according to the first aspect, the lens sheet is preferably Sheet surface In this configuration, for example, when the position of the display unit and the position of the focal point of the lens are set to coincide with each other, by moving the lens sheet in a direction away from the luminance uniformizing sheet (direction toward the display unit), the position of the focal point of the lens shifts from the position of the display unit, and light is not focused on the display unit, so that the width of the light distribution can be increased.

[0016] The display device according to the second aspect includes a light source, a luminance uniformizing sheet arranged to face the light source and including a plurality of through holes for transmitting the light emitted from the light source having a plurality of different hole diameters, for uniforming the luminance of the light emitted from the light source, a lens sheet arranged on the opposite side to the light source and including a plurality of lenses arranged to face the plurality of through holes of the luminance uniformizing sheet, for adjusting a width or a direction of the light distribution of the light emitted from the light source, and a display unit on which an image is displayed using the light transmitted through the lens sheet, and the plurality of lenses are arranged to view the image from an oblique position with respect to a display surface within a range of a viewing angle at which the image is viewable. Measure the brightness of In order to make the brightness uniform when the light-emitting diode is turned on, the thickness or radius of curvature At least one of the lens sheet is set to be different from the other, and the lens sheet is configured to be movable and arranged on the passenger seat side of the vehicle, and the viewing angle is configured to be adjusted so that the lens sheet cannot be viewed from the driver's seat side. At least one of the thickness of the lenses and the radius of curvature of the lenses is set to be proportional to the diameter of the through holes of the luminance uniformizing sheet.

[0017] In the display device according to the second aspect, as described above, the lenses are configured to have at least one of thickness and shape different depending on the hole diameter of the opposing through holes so that the brightness is uniform when the image is viewed from an oblique position relative to the display surface within the range of viewing angles at which the image can be viewed. By adjusting at least one of the thickness and shape of the lenses, it is possible to suppress an increase in light that does not pass through the center of the lens provided in the lens sheet, and therefore it is possible to suppress blurring of the image. As a result, when the lens sheet including the lenses is moved relative to the brightness uniformizing sheet to change the irradiation direction of the light emitted from the light source, it is possible to suppress the occurrence of brightness unevenness in the image displayed on the display unit. In addition, at least one of the thicknesses of the lenses and the radii of curvature of the lenses is set to be proportional to the diameter of the through-holes of the luminance uniforming sheet. With this configuration, when adjusting at least one of the thicknesses of the lenses and the radii of curvature of the lenses, the thickness or the radii of curvature of the lenses can be appropriately changed based on a lens having an appropriate relationship between the size of the through-hole and at least one of the radii of curvature or the thickness of the lens. Effect of the Invention

[0018] According to the present invention, as described above, it is possible to provide a backlight device for a display device and a display device that can suppress the occurrence of uneven brightness in a displayed image when a lens sheet including lenses is moved relative to a brightness uniformizing sheet to change the irradiation direction of light emitted from a light source. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is a schematic diagram showing a state in which a display device is mounted. [Diagram 2] FIG. 1 is a schematic diagram of a structure of a display device. [Diagram 3] 11 is a diagram illustrating a through hole provided in the luminance uniformizing sheet. FIG. [Figure 4] FIG. 2 is a diagram for explaining the arrangement of lenses. [Diagram 5] FIG. 1 is a diagram for explaining a viewing angle. [Figure 6] 11A and 11B are schematic diagrams for explaining movement along the direction in which lenses of the lens sheet are arranged. [Figure 7]11 is a schematic diagram for explaining movement along a direction perpendicular to the direction in which the lenses of the lens sheet are arranged. FIG. [Figure 8] FIG. 13 is a diagram showing a comparative example in which lenses of the same shape are used for through holes of different hole diameters. [Figure 9] 8 is a graph showing the relationship between the angle of the lens shown in FIG. 7 with respect to the display surface and luminance. [Figure 10] 1 is a graph showing an optimum relationship between angle and luminance relative to a lens. [Figure 11] 13 is a graph showing the relationship between the diameter of a through hole and the thickness and radius of curvature of a lens. [Figure 12] FIG. 1 shows a lens with adjusted thickness and radius of curvature. [Figure 13] FIG. 1A is a diagram showing a state in which the center of the lens and the center of the through-hole are aligned in the Y direction, and FIG. 1B is a graph showing the relationship between luminance and the angle with respect to the display surface in the state of FIG. [Figure 14] FIG. 10A shows a state in which the lens has been moved in the X2 direction, and FIG. 10B is a graph showing the relationship between luminance and the angle relative to the display surface in the state of FIG. [Figure 15] FIG. 10A is a diagram showing a state in which the lens has been moved in the Y2 direction, and FIG. 10B is a graph showing the relationship between luminance and the angle with respect to the display surface in the state of FIG. [Figure 16] FIG. 10A shows the state where the lens has been further moved in the Y2 direction, and FIG. 10B is a graph showing the relationship between luminance and the angle with respect to the display surface in the state of FIG. [Figure 17] 13 is a graph showing the relationship between the angle with respect to the display surface and the luminance in the modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] [First embodiment] The configuration of a display device 100 according to an embodiment of the present invention will be described with reference to FIGS.

[0022] As shown in FIG. 1, the display device 100 is mounted on a vehicle 200. The display device 100 is configured to be capable of displaying an image. The vehicle 200 is, for example, an automobile. FIG. 1 shows a simplified view of the interior of the vehicle 200. Note that the left-right direction when a user views the display device 100 from the front side is defined as the X direction, the up-down direction is defined as the Z direction, and the front-rear direction perpendicular to the X direction and the Z direction is defined as the Y direction. FIG. 1 shows an example of an automobile in which a steering wheel is provided on the right side (X2 side).

[0023] The display device 100 is disposed on the passenger seat side in the vehicle 200, and the viewing angle is adjusted so that it is difficult to view from the driver's seat side. In Fig. 1, the X1 side is the passenger seat side and the X2 side is the driver's side, but in the case of a vehicle in which the steering wheel is provided on the left side (X1 side), the X2 side is the passenger seat side and the X1 side is the driver's side.

[0024] As shown in Fig. 2, the display device 100 includes a backlight device 10 for a display device and a display unit 20. The backlight device 10 for a display device includes LED (light emitting diode) light sources 1, a luminance uniformizing sheet 2, a lens sheet 3, a diffusion sheet 4, an LED light source substrate 5, a reflective sheet 6, and a drive unit 7. The LED light sources are an example of the "light source" described in the claims.

[0025] A plurality of LED light sources 1 are arranged on the surface of the LED light source substrate 5 on the Y1 side. The LED light sources 1 are arranged in a lattice pattern on the LED light source substrate 5. The LED light source 1 has a light emitting surface 11 on the Y1 side, and emits light from the light emitting surface 11 toward the Y1 side. The light emitted from the LED light source 1 includes light that travels straight toward the Y1 direction and light that travels obliquely toward the Y1 direction. The light emitted from the LED light source 1 is irradiated onto the luminance uniformizing sheet 2.

[0026] 2, the luminance uniformizing sheet 2 is disposed on the Y1 side of the LED light source 1 so as to face the light emitting surface 11 of the LED light source 1. The shape of the luminance uniformizing sheet 2 is, for example, rectangular or circular. The luminance uniformizing sheet 2 is made of a resin having a property of reflecting light.

[0027] As shown in FIG. 3, the luminance uniformizing sheet 2 includes a plurality of through holes 21 and a reflecting portion 22. The plurality of through holes 21 are configured to penetrate the luminance uniformizing sheet 2 in the thickness direction (Y direction). The plurality of through holes 21 are provided to allow light irradiated from the LED light source 1 (see FIG. 2) to pass through and reach the lens sheet 3. The plurality of through holes 21 are arranged in a lattice pattern along the X direction and the Z direction. Note that FIG. 3 shows a part of the luminance uniformizing sheet 2, and a long hole 72, which will be described later, is located outside the luminance uniformizing sheet 2 of FIG. 3.

[0028] The plurality of through holes 21 includes through holes 21 having the same hole diameter D. The plurality of through holes 21 also includes through holes 21 having a plurality of different hole diameters D. The through holes 21 are set so that their hole diameters D vary according to the distance from the LED light source 1. Specifically, the hole diameter D of the through hole 21a directly above the LED light source 1 is the smallest. The hole diameter D of the through hole 21 located away from the LED light source 1 is set so as to be larger than the hole diameter D of the through hole 21a directly above the LED light source 1. The luminance uniformizing sheet 2 adjusts the amount of light to uniformize the luminance of the light. The hole diameter D of the plurality of through holes 21 refers to the diameter of the through hole 21.

[0029] The reflecting portion 22 is a portion of the luminance uniformizing sheet 2 where the multiple through holes 21 are not provided. Since the light from the LED light source 1 is irradiated while being diffused radially, a part of the light from the LED light source 1 is transmitted through the through holes 21 and a part of the light is reflected by the reflecting portion 22. A part of the light irradiated from the LED light source 1 is reflected by the reflecting portion 22 and reaches the reflective sheet 6.

[0030] 2, the lens sheet 3 is disposed on the display unit 20 side (Y1 side) opposite the LED light source 1 so as to face the luminance uniformizing sheet 2. The lens sheet 3 is formed of a resin that transmits light. The lens sheet 3 is, for example, rectangular or circular. The lengths of the lens sheet 3 in the X direction and the Z direction are the same as the lengths of the luminance uniformizing sheet 2 in the X direction and the Z direction, respectively.

[0031] As shown in FIG. 4, the lens sheet 3 has a plurality of lenses 31. The plurality of lenses 31 are provided for each of the plurality of through holes 21 of the luminance uniformizing sheet 2. Although the plurality of lenses 31 are illustrated in FIG. 4 as having the same shape, the plurality of lenses 31 have different shapes and thicknesses T according to the plurality of through holes 21 of the luminance uniformizing sheet 2 so that the luminance is uniform when an image displayed on the display surface is viewed from an oblique position relative to the display surface within a range of viewing angles at which the image can be viewed. The light transmitted through the plurality of lenses 31 reaches the diffusion sheet 4. The plurality of lenses 31 are arranged side by side in the X direction and the Z direction. The plurality of lenses 31 are arranged in a lattice pattern in the same manner as the arrangement of the through holes 21. The plurality of lenses 31 are convex lenses.

[0032] As shown in FIG. 5, the display device 100 can be viewed by the user P from a position A1 (front) which is a position of 0 degrees with respect to the display surface 20a (origin O). The display device 100 can also be viewed by the user P from positions A2 and A3 which are oblique to the display surface 20a (positions at angles θ1 and θ2 with respect to the display surface 20a). The positions A2 and A3 are variable. Here, the angle range from angle θ1 to angle θ2 when A2 and A3 are the limit positions where they can be viewed from an oblique position with respect to the display surface 20a is called the range of viewing angles. θ1 is a negative value, and θ2 is a positive value. The lens sheet 3 has different shapes and thicknesses T according to the multiple through holes 21 of the luminance uniformizing sheet 2 so that the luminance is uniform when an image is viewed from an oblique position with respect to the display surface 20a within the range of viewing angles.

[0033] As shown in FIG. 2, the diffusion sheet 4 is disposed on the display unit 20 side (Y1 side) of the lens sheet 3 so as to face the lens sheet 3. The diffusion sheet 4 is made of resin. The diffusion sheet 4 is, for example, rectangular or circular. The diffusion sheet 4 scatters light that has passed through the lens sheet 3. The light diffused by the diffusion sheet 4 reaches the display unit 20. The lengths of the diffusion sheet 4 in the X direction and the Z direction are the same as the lengths of the lens sheet 3 in the X direction and the Z direction, respectively.

[0034] The LED light source board 5 is provided on the opposite side to the light emitting surface 11 of the LED light source 1. The LED light source board 5 is a printed circuit board. The LED light source board 5 is provided with a circuit to which the LED light sources 1 are electrically connected.

[0035] The reflective sheet 6 is disposed on the Y1 side of the LED light source substrate 5. The reflective sheet 6 has openings that correspond to the positions of the LED light sources 1. The reflective sheet 6 is made of resin. The reflective sheet 6 is configured to reflect light reflected by the reflective portion 22 of the luminance uniformizing sheet 2. The light reflected by the reflective sheet 6 passes through the through-holes 21 or is repeatedly reflected between the reflective portion 22 and the reflective sheet 6. By repeatedly reflecting between the reflective portion 22 and the reflective sheet 6, the light is diffused over a wide range.

[0036] As shown in FIG. 6, the driving unit 7 moves the lens sheet 3 in the direction in which the lenses 31 are arranged (X direction and Z direction). The driving unit 7 includes a motor 71. The driving unit 7 includes long holes 72 provided in the luminance uniforming sheet 2 and the lens sheet 3, and a fixture 73 inserted into the long hole 72. The driving unit 7 is configured to move the lens sheet 3 in the X direction using the driving force of the motor 71 and stop the movement at a position where the fixture 73 contacts one end of the long hole 72 on the X1 side. The driving unit 7 is also configured to move the lens sheet 3 in the X direction using the driving force of the motor 71 and stop the movement at a position where the fixture 73 contacts one end of the long hole 72 on the X1 side or the X2 side, and reciprocates the lens sheet in the X direction. Note that the through hole 21 is omitted in FIG. 6. The fixture 73 is, for example, a screw or a pin.

[0037] As shown in FIG. 7, the driving unit 7 moves the lens sheet 3 in a direction (Y direction) perpendicular to the direction in which the lenses 31 are arranged (X direction and Z direction). The driving unit 7 includes a motor 71a for moving the lens sheet 3 in the direction in which the lenses 31 are arranged (X direction) and in a direction (Y direction) perpendicular to the direction in which the lenses 31 are arranged (X direction and Z direction). The ball screw 74 rotates in response to the rotation of the motor 71a, and the lens sheet 3 fixed to the bearing 75 moves back and forth in the Y direction. Specifically, the diffusion sheet 4 and the lens sheet 3 are spaced apart, and the lens sheet 3 repeatedly moves toward and away from the diffusion sheet 4. The driving unit 7 is configured to stop the lens sheet 3 at a predetermined position by controlling the number of rotations of the motor 71a.

[0038] As shown in FIG. 2, the surface on the Y1 side of the display unit 20 is the display surface 20a. The display surface 20a is a surface on which an image is displayed. The display unit 20 includes a polarizing plate, a liquid crystal cell, and a color filter, which are not shown in the figure. The display unit 20 changes the orientation of the liquid crystal molecules by applying a voltage to the liquid crystal cell, and adjusts the brightness by changing the light transmittance by combining the orientation of the liquid crystal molecules and the polarizing plate. The color filter includes a red color filter, a blue color filter, and a green color filter. The polarizing plate and the liquid crystal cell adjust the amount of light transmitted through each color filter, thereby adjusting the color.

[0039] (How to set lens thickness and curvature radius) A method for setting at least one of the thickness T and the radius of curvature R of a plurality of lenses 31 will be described with reference to Figs. 8 and 9. Figs. 8(A) to 8(C) show a comparative example in which lenses 31 having the same shape and thickness T are used in through holes 21 having different diameters. The diameter of through hole 21 in Fig. 8(A) is d1, the diameter of through hole 21 in Fig. 8(B) is d2, the diameter of through hole 21 in Fig. 8(C) is d3, and d1 <d2<d3とする。

[0040] FIG. 9 shows an example of the relationship between the angle to the lens 31 and the brightness ratio when d1 is 0.2 mm, d2 is 0.3 mm, and d3 is 0.4 mm. In the graph of FIG. 8, the angle to the lens 31 (the angle represented by θ1 or θ2 in FIG. 4) is plotted on the horizontal axis, and the angle when viewed from the front at the position A1 is set to 0, the angle θ1 when viewed obliquely from a position shifted toward the X1 side from the front is shown as a negative value, and the angle θ2 when viewed obliquely from a position shifted toward the X2 side from the front is shown as a positive value. In addition, the vertical axis shows the brightness value ratio when the brightness ratio of each lens 31 when viewed from the Y1 side is set to 100 as a reference. In addition, the graph when the hole diameter d1 is 0.2 mm is shown by a solid line, the graph when the hole diameter d2 is 0.3 mm is shown by a dashed line, and the graph when the hole diameter d3 is 0.4 mm is shown by a dashed line.

[0041] When the hole diameter d1 is 0.2 mm, the brightness ratio is 100 when the angle is within the range of -10 degrees to 10 degrees. In other words, this indicates that even when viewed obliquely from a position of 10 degrees relative to the lens 31 (position A1 where θ1=-10 or position A2 where θ=+10 in FIG. 4), the image can be clearly seen as when viewed from the front.

[0042] When the hole diameter d2 is 0.3 mm, the brightness ratio is 100 when the angle is within the range of -3 degrees to 3 degrees. In other words, this indicates that even when viewed obliquely from a position of 3 degrees relative to the lens 31 (position A1 where θ1=-3 or position A2 where θ=+3 in FIG. 4), the image can be clearly seen as when viewed from the front.

[0043] When the hole diameter d3 is 0.2 mm and the angle is 0 degrees, the brightness ratio is 100. This indicates that the image can be clearly seen when viewed from the front of the lens 31 (position A1 in the figure).

[0044] From the above, when the shape and thickness T of lens 31 are constant, the range of angles at which the image can be clearly seen and the amount of change in luminance per unit angle change differ depending on the hole diameter D of through-hole 21. Therefore, when lenses 31 having the same shape and thickness T are placed in through-holes 21 with different hole diameters D, uneven luminance occurs in the displayed image according to the distribution of hole diameters D when viewed obliquely.

[0045] Therefore, in this embodiment, the shape and thickness T of lens 31 are set according to the hole diameter D of through-hole 21. A method for setting thickness T and radius of curvature R of lens 31 will be described with reference to Figs.

[0046] The inventors of the present application performed a simulation based on the graph of FIG. 9 so as to obtain a graph as shown in FIG. 10 in which the luminance value for each unit angle is uniform.

[0047] In the case of the graph shown in FIG. 10, the inventors of the present application found that the hole diameter D of the luminance uniforming sheet 2 and the radius of curvature R and the thickness T of the lens 31 are in a proportional relationship as shown in FIG. 11. In the graph of FIG. 11, the hole diameter D of the luminance uniforming sheet 2 is plotted on the horizontal axis, and the radius of curvature R of the lens 31 or the thickness T of the lens 31 is plotted on the vertical axis. Then, based on the graph of FIG. 11, the radius of curvature R of the lens 31 or the thickness T of the lens 31 was changed as shown in FIG. 12. In FIG. 12, the lens 31 provided in the through hole 21 with a hole diameter D of 0.2 mm and the lens 31 provided in the through hole 21 with a hole diameter D of 0.3 mm were adjusted to be smaller so as to approximate the graph of the hole diameter D of 0.4 mm shown in FIG. Specifically, it can be seen from the graph of Fig. 11 that the ratio of the thickness T of the lens 31 when the hole diameter D is 0.4 mm to the thickness T of the lens 31 when the hole diameter D is 0.3 mm is 1.1 mm to 0.9 mm. Therefore, the thickness T of the lens 31 was set so that the relationship between the thickness T of the lens 31 when the hole diameter is 0.4 mm and the thickness T of the lens 31 when the hole diameter is 0.3 mm is 1.1 mm to 0.9 mm. Figs. 12(A) and 12(B) show lenses 31 in which the thickness T and the radius of curvature R of the lenses 31 in Figs. 8(B) and 8(C) are reduced, respectively.

[0048] (Change the direction and width of light distribution) Changes in the light distribution direction and width will be described with reference to Fig. 13 to Fig. 16. Note that in Fig. 13 to Fig. 16, light is represented by dashed lines. For the sake of explanation, three wavy lines are used to represent light. One lens 31 will be described.

[0049] As shown in Fig. 13(A), when the center C1 of the through-hole 21, the center C2 of the lens 31, and the focal point F of the lens 31 are aligned in a straight line in the Y direction, the optical axis extends in the Y direction, and the light distribution direction is linear along the 0 degree line as shown in Fig. 13(B). In Fig. 13(B), the radial distance from the origin represents the ratio of luminance values, and the rotation direction around the origin represents the angle in the X direction. In Fig. 12, the focal point is adjusted to be located at a position where it reaches the diffusion sheet 4.

[0050] As shown in Fig. 14(A), when the lens sheet 3 is moved in the X2 direction in which the lenses 31 are arranged, the position of the center C2 of the lens 31 and the position of the focal point F move in the X2 direction. As the position of the focal point F shifts in the X2 direction, the position where the light is concentrated moves toward the X2 side compared to the case of Fig. 13(A). As a result, the direction of the light distribution is changed to a straight line extending in an oblique direction as shown in Fig. 14(B). In the case of Fig. 14, the luminance value of X1 is low, and it becomes difficult to view the image of the display device 100 from the X1 side.

[0051] As shown in Fig. 15(A), when the lens 31 is moved in the Y1 direction away from the luminance uniformizing sheet 2 among the directions (Y directions) perpendicular to the direction in which the lenses 31 are arranged, the focal position of the lens 31 moves in the perpendicular direction, and the viewing angle is widened. Specifically, by arranging the diffusion sheet 4 in the same position as in Fig. 13, the position of the diffusion sheet 4 and the position of the focal point F do not match, and the range where the luminance is maximum without focusing at the position of the diffusion sheet 4 is widened. As a result, the width of the light distribution is widened as shown in Fig. 15(B).

[0052] As shown in Fig. 16(A), when the lens 31 is further moved from the position shown in Fig. 15(A) in the direction Y1 away from the luminance uniformizing sheet 2 in the direction (Y direction) perpendicular to the direction in which the lenses 31 are arranged, the focal position of the lens 31 moves in the perpendicular direction, so that the viewing angle is further widened. Specifically, by disposing the diffusion sheet 4 in the same position as in Fig. 13, the position of the diffusion sheet 4 and the position of the focal point F do not match, and the range where the luminance is maximum without light collection at the position of the diffusion sheet 4 is further widened. As a result, the width of the light distribution is further widened as shown in Fig. 16(B).

[0053] (Effects of this embodiment) In this embodiment, the following effects can be obtained.

[0054] In this embodiment, as described above, the lenses 31 are configured to have at least one of the thickness T or shape different depending on the hole diameter D of the opposing through holes 21 so that the luminance is uniform when the image is viewed from an oblique position with respect to the display surface 20a within the range of the viewing angle at which the image can be viewed. By adjusting at least one of the thickness T or shape of the lenses 31, it is possible to suppress an increase in light that does not pass through the center of the lenses 31 provided in the lens sheet 3, and therefore it is possible to suppress blurring of the image. As a result, when the lens sheet 3 including the lenses 31 is moved relative to the luminance uniformizing sheet 2 to change the irradiation direction of the light emitted from the light source 1, it is possible to suppress the occurrence of unevenness in the displayed image.

[0055] Furthermore, in this embodiment, as described above, the lenses 31 are configured so that at least one of the thickness T and the radius of curvature R is different according to the hole diameter D of the plurality of through holes 21 so that the luminance of light passing through the through holes 21 of the luminance uniformizing sheet 2 having different hole diameters is uniform when the image is viewed from an oblique position with respect to the display surface 20a within the range of viewing angles at which the image is visible. As a result, by setting at least one of the thickness T and the radius of curvature R of the plurality of lenses 31 according to the hole diameter D of the plurality of through holes 21, the luminance can be uniformed, and therefore, the occurrence of unevenness in the displayed image can be easily suppressed.

[0056] Furthermore, in this embodiment, as described above, at least one of the thickness T of the lenses 31 and the radius of curvature R of the lenses 31 is set to increase as the hole diameter D of the through-holes 21 of the luminance uniformizing sheet 2 increases. As a result, by increasing at least one of the thickness T of the lenses 31 and the radius of curvature R of the lenses 31 as the hole diameter D of the through-holes 21 of the luminance uniformizing sheet 2 increases, it is possible to effectively suppress an increase in the amount of light that does not pass through the center of the lenses 31, and therefore it is possible to suppress blurring of an image caused by an increase in the size of the through-hole 21.

[0057] Furthermore, in this embodiment, as described above, at least one of the thickness T of the lenses 31 and the radius of curvature R of the lenses 31 is set to be proportional to the hole diameter D of the through-holes 21 of the luminance uniformizing sheet 2. As a result, when adjusting at least one of the thickness T of the lenses 31 and the radius of curvature R of the lenses 31, the thickness T or the radius of curvature R of the lenses 31 can be appropriately changed based on the lens 31 having an appropriate relationship between the size of the through-hole 21 and at least one of the radius of curvature R or the thickness T of the lens 31.

[0058] In this embodiment, as described above, the lenses 31 are arranged one by one for each of the through holes 21. This allows a one-to-one correspondence between the size of the through hole 21 and at least one of the thickness T or the radius of curvature R of the lens 31, compared to a case in which one lens 31 corresponds to a plurality of through holes 21 having different hole diameters D, and therefore at least one of the thickness T or the radius of curvature R of the lens 31 can be finely adjusted.

[0059] In this embodiment, as described above, the size of the hole diameter D of the multiple through holes 21 in the luminance uniformizing sheet 2 is set according to the distance from the LED light source 1. Here, the luminance is greatest directly above the LED light source 1, and the luminance decreases as the distance from the LED light source 1 increases. Therefore, by setting the hole diameter D of the through hole 21a directly above the LED light source 1 to a minimum and increasing the size of the through hole 21 as the distance from the LED light source 1 increases, the amount of light passing through the through hole 21 can be appropriately adjusted to make the luminance uniform.

[0060] In this embodiment, as described above, the lens sheet 3 is configured to be movable along the direction in which the lenses 31 are arranged. As a result, by moving the lens sheet 3, the focal position moves, and the position at which the light is collected can be moved, so that the direction of the light passing through the lenses 31 can be changed.

[0061] Furthermore, in this embodiment, as described above, the lens sheet 3 is configured to be movable along a direction perpendicular to the direction in which the lenses 31 are arranged. As a result, for example, when the position of the display unit 20 and the position of the focal point of the lens 31 are set to coincide with each other, by moving the lens sheet 3 in a direction away from the luminance uniformizing sheet 2 (direction toward the display unit 20), the position of the focal point F of the lens 31 shifts from the position of the display unit 20, and light is not condensed at the display unit 20, so that the width of the light distribution can be widened.

[0062] In addition, in this embodiment, as described above, the lenses 31 are configured to have at least one of the thickness T or shape different depending on the hole diameter D of the opposing through holes 21 so that the luminance is uniform when the image is viewed from an oblique position with respect to the display surface 20a within the range of the viewing angle at which the image can be viewed. By adjusting at least one of the thickness T or shape of the lenses 31, it is possible to suppress an increase in light that does not pass through the center of the lens 31 provided in the lens sheet 3, and therefore it is possible to suppress blurring of the image. As a result, when the lens sheet 3 including the lenses 31 is moved relative to the luminance uniformizing sheet 2 to change the irradiation direction of the light emitted from the light source 1, it is possible to suppress the occurrence of unevenness in the image displayed on the display unit 20.

[0063] [Variations] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the description of the embodiments above, and further includes all modifications (variations) within the meaning and scope of the claims.

[0064] For example, in the above embodiment, the lens thickness and the radius of curvature are changed, but the present invention is not limited to this. For example, only one of the lens thickness and the radius of curvature may be changed.

[0065] In the above embodiment, the thickness and the radius of curvature of the lens are changed, but the present invention is not limited to this. For example, something other than the thickness and the radius of curvature of the lens may be changed.

[0066] In the above embodiment, the lens thickness and the radius of curvature are reduced, but the present invention is not limited to this. For example, something other than the lens thickness and the radius of curvature may be increased. In that case, the graph in FIG. 9 is set as the graph in FIG. 17.

[0067] In the above embodiment, the display device includes a reflective sheet, but the present invention is not limited to this. For example, the display device does not need to include a reflective sheet.

[0068] In addition, in the above embodiment, the lens is a convex lens, but the present invention is not limited to this. For example, the lens may be a concave lens.

[0069] In the above embodiment, the lens thickness and the curvature radius of the multiple lenses are adjusted to be small, but the present invention is not limited to this. For example, the lens thickness and the curvature radius of the multiple lenses may be adjusted to be large.

[0070] In the above embodiment, the vehicle is an automobile, but the present invention is not limited to this. For example, the vehicle may be a train or a human-powered vehicle.

[0071] In the above embodiment, the luminance uniformizing sheet and the lens sheet are the same size, but the present invention is not limited to this. The luminance uniformizing sheet and the lens sheet may be different in size.

[0072] In the above embodiment, the moving mechanism includes a motor, but the present invention is not limited to this. The moving element may include a piezoelectric element.

[0073] In the above embodiment, the movement mechanism includes the long hole, the screw, and the ball shaft, but the present invention is not limited to this. For example, the movement mechanism may include other members.

[0074] In the above embodiment, the driving unit moves the lens sheet in the direction in which the lenses are arranged (X direction) and in the direction (Y direction) perpendicular to the directions in which the lenses are arranged (X direction and Z direction), but the present invention is not limited to this. For example, the driving unit may be configured to move the lens sheet only in the direction in which the lenses are arranged (X direction).

[0075] In the above embodiment, the driving unit moves the lens sheet in the X2 direction, but the present invention is not limited to this. For example, the driving unit may be configured to move the lens sheet in the X1 direction.

[0076] In the above embodiment, the driving unit moves the lens sheet in a direction away from the luminance uniformization sheet, but the present invention is not limited to this. For example, the driving unit may be configured to move the lens sheet in a direction toward the luminance uniformization sheet.

[0077] In the above embodiment, the display device includes a drive unit, but the present invention is not limited to this. For example, the drive unit does not have to include a drive unit.

[0078] In the above embodiment, a lens is disposed in each of the through holes of the luminance uniformizing sheet, but the present invention is not limited to this. For example, one lens may be provided for a plurality of through holes of the luminance uniformizing sheet. [Explanation of symbols]

[0079] 1 LED light source (light source) 2. Luminance uniformity sheet 3 Lens sheet 4 Diffusion Sheet 10. Backlight device for display device 20 Display section 21, 21a through hole 31 Lens 100 display device 200 vehicles D Pore diameter R radius of curvature T Thickness

Claims

1. A light source; a brightness uniformizing sheet arranged to face the light source and including a plurality of through holes having a plurality of different hole diameters for transmitting the light emitted from the light source, for uniforming the brightness of the light emitted from the light source; a lens sheet that is movable to adjust a width or a direction of a light distribution of light irradiated from the light source, the lens sheet including a plurality of lenses that are arranged on the opposite side of the light source and facing the plurality of through holes of the luminance uniformizing sheet; the plurality of lenses are configured to have at least one of a thickness or a radius of curvature different from one another in accordance with diameters of the plurality of opposed through holes so that the luminance of an image is uniform when measured from an oblique position with respect to a display surface within a range of viewing angles at which the image is visible; A backlight device for a display device, wherein at least one of the thicknesses of the plurality of lenses and the radii of curvature of the plurality of lenses is set to be proportional to the size of the hole diameters of the plurality of through holes in the luminance uniformizing sheet.

2. 2. The backlight device for a display device as described in claim 1, wherein the plurality of lenses are configured to have at least one of a thickness and a radius of curvature that differ depending on the hole diameters of the plurality of through holes so that the brightness of light passing through the through holes of the brightness uniformizing sheet having different hole diameters is uniform when the image is viewed from an oblique position with respect to the display surface within a range of viewing angles at which the image is visible.

3. 3. The backlight device for a display device according to claim 2, wherein at least one of the thickness of the plurality of lenses and the radius of curvature of the plurality of lenses is set to increase as the hole diameter of the plurality of through holes in the luminance uniformizing sheet increases.

4. 4. The backlight device for a display device according to claim 1, wherein the plurality of lenses are arranged one for each of the plurality of through holes.

5. 5. The backlight device for a display device according to claim 1, wherein the plurality of through holes of the luminance uniformizing sheet have a hole diameter set according to a distance from the light source.

6. 6. The backlight device for a display device according to claim 1, wherein the lens sheet is configured to be movable along a direction in which the lenses are arranged.

7. 7. The backlight device for a display device according to claim 6, wherein the lens sheet is configured to be movable along a direction perpendicular to a surface of the lens sheet.

8. A light source; a brightness uniformizing sheet arranged to face the light source and including a plurality of through holes having a plurality of different hole diameters for transmitting the light emitted from the light source, for uniforming the brightness of the light emitted from the light source; a lens sheet including a plurality of lenses arranged on the opposite side of the light source and facing the plurality of through holes of the luminance uniformizing sheet, the lens sheet being configured to be movable in order to adjust a width or a direction of a light distribution of light irradiated from the light source; a display unit on which an image is displayed using light transmitted through the lens sheet, the plurality of lenses are set to have at least one of a thickness or a radius of curvature different from one another in accordance with diameters of the plurality of opposed through holes so that the luminance of an image is uniform when measured from an oblique position with respect to a display surface within a range of viewing angles at which the image is visible; at least one of a thickness of the plurality of lenses and a radius of curvature of the plurality of lenses is set to be proportional to a diameter of the plurality of through holes of the luminance uniformizing sheet; A display device that is arranged on the passenger seat side of a vehicle and has a viewing angle that is adjusted so that it cannot be viewed from the driver's seat side.

Images