Patent Application
20180143496
The present invention relates to a lighting device, a display device, and a television device.
Liquid crystal panels in liquid crystal display devices such as liquid crystal television devices do not produce light and thus backlight units that are separately prepared lighting units are required. The backlight units are broadly classified into direct types and edge light types based on their mechanisms. To reduce thicknesses of the liquid crystal display devices, edge light type backlight units are preferable.
An edge light type backlight unit includes a light guide plate and a light source board held in a case. The light guide plate includes an end surface that is configured as a light entering surface and one of plate surfaces that is configured as a light exiting surface. The light source board includes a mounting surface on which light sources such as light emitting diodes (LEDs) are mounted. The mounting surface is opposed to the light exiting surface of the light guide plate. In such a backlight unit, uneven brightness may occur in light that exits the light guide plate through the light exiting surface. A technology for suppressing such uneven brightness is required. Patent document 1 discloses a technology for suppressing uneven brightness around positioning protrusions on a light guide plate in a lighting unit that produces planar light.
Patent Document 1: Unexamined Japanese Patent Application Publication No. 2005-302485
In recent years, the demand for a high definition liquid crystal panel or a high color reproducible liquid crystal panel increases. In such a panel, high brightness is required in light that exits from a light guide plate through the light exiting surface in a backlight unit for supplying the light to the liquid crystal panel. Therefore, a large number of light sources are required. To dispose a large number of light sources in a case of the backlight unit, light source boards may be disposed along a light entering surface of the light guide plate.
When the light source boards are disposed along the light entering surface of the light guide plate, a distance between the adjacent light sources on the different light source boards may be larger than a distance between the adjacent light sources mounted on amounting surface of the light source board. When an edge of the light exiting surface of the light guide plate on a light entering surface side is viewed, a section of the edge facing a gap between the adjacent light source boards may be displayed darker than other portions. Namely, a dark spot may appear at the section facing the gap. This may cause uneven brightness in the light that exits from the light guide plate through the light exiting surface.
The present invention was made in view of the above circumstances. An object is to suppress uneven brightness.
The technology described herein relates to a lighting device including light sources, a light guide plate, light source boards, and a light reflecting member. The light guide plate includes at least an end surface configured as a light entering surface through which light rays from the light sources enter and one of plate surfaces configured as a light exiting surface through which the light rays entering through the light entering surface exit. The light source boards include plate surfaces configured as mounting surfaces on which the light sources are mounted. The light source boards are disposed along the light entering surface with the mounting surfaces opposed to the light entering surface. Each mounting surface is one of plate surfaces of each light source board. The light reflecting member has light reflectivity. The light reflecting member is disposed to a section of an edge of the light exiting surface facing a space between the adjacent light source boards on a light entering surface side.
In a lighting device having a configuration in which light source boards are disposed along a light entering surface of a light guide plate, a distance between light sources that are adjacent to each other is larger than an interval of light sources mounting surfaces of light source boards. Therefore, a dark spot may be produced in a section of an edge of a light exiting surface of the light guide plate facing a space between the adjacent light source boards. This may result in uneven brightness in light exiting through the light exiting surface. In the lighting device described earlier, the light rays that have exited the light guide plate through the light exiting surface and reached the light reflecting member are reflected by the light reflecting member to the section of the edge of the light exiting surface of the light guide plate facing the space between the adjacent light source boards on the light entering surface side. The reflected light rays reach the dark spot in the section facing the space and therearound and thus the dark spot can be eliminated. According to the configuration, the uneven brightness resulting from the dark spot is less likely to occur in light exiting the light guide plate through the light exiting surface.
The lighting device may include a frame member including a covering section that covers an edge of the light exiting surface. The light reflecting member may be bonded to an area of the covering section.
If the light reflecting member is disposed on the light exiting surface of the light guide plate, the optical sheet disposed on the light exiting surface may contact the light reflecting member when the optical sheet is thermally expanded. In the configuration described earlier, the light reflecting member is bonded to the covering section of the frame member. Therefore, the light reflecting member is less likely to contact other components.
The lighting device may include a frame member including a covering section that covers an edge of the light exiting surface. The light reflecting member may be an area of the covering section painted in white.
In this configuration, the thickness of the light reflecting member is equal to the thickness of the paint. In comparison to a configuration in which the light reflecting member has a sheet shape, the thickness of the light reflecting member is smaller. Therefore, the thickness of the lighting device can be reduced.
The light reflecting member may be bonded to an area of a section of an edge of the light exiting surface on a light entering surface side.
According to the configuration, specific arrangement of the light reflecting member is provided.
The lighting device may include an optical sheet bundle including optical sheets that are disposed in layers on the light exiting surface. The optical sheet that is located at an upper side among the optical sheets may include a protrusion that protrudes toward the light source board at an edge of the optical sheet on a light entering surface side. The light reflecting member may be bonded to the protrusion.
If the light reflecting member is disposed on the light exiting surface of the light guide plate, the optical sheet disposed on the light exiting surface may contact the light reflecting member when the optical sheet is thermally expanded. In the configuration described earlier, the light reflecting member is bonded to the protrusion of the optical sheet. Therefore, the light reflecting member is less likely to contact other components.
The technology described herein relates to a lighting device including light sources, a light guide plate, light source boards, and a light diffusing member. The light guide plate includes at least an end surface configured as a light entering surface through which light rays from the light sources enter and one of plate surfaces configured as a light exiting surface through which the light rays entering through the light entering surface exit. The light source boards include plate surfaces configured as mounting surfaces on which the light sources are mounted. The light source boards are disposed along the light entering surface with the mounting surfaces opposed to the light entering surface. Each mounting surface is one of plate surfaces of each light source board. The light diffusing member has a light diffusing property. The light diffusing member is opposed to a section of an edge of the light exiting surface of the light guide plate facing a space between the adjacent light source boards on a light entering surface side.
In the lighting device, light rays that have exited the light guide plate through the light exiting surface and reached the light diffusing member are diffused by the light diffusing member to the section of the edge of the light exiting surface of the light guide plate facing the space between the adjacent light source boards on the light entering surface side. According to the configuration, brightness in a dark spot produced in the section facing the space and therearound increases and thus a difference in brightness between the dark spot and other sections decreases. Therefore, uneven brightness resulting from the dark spot is less likely to occur in light exiting the light guide plate through the light exiting surface.
The lighting device may include an optical member including optical sheets that are disposed in layers on the light exiting surface. The optical sheets are configured to exert optical effects on light rays exiting from the light exiting surface. At least one of the optical sheets may include a protrusion that protrudes toward the light source board at an edge of the optical sheet on a light entering surface side. The protrusion may be the light diffusing member.
In the above configuration, a portion of the optical sheet is configured as the light diffusing member. Therefore, a separate light diffusing member is not required and thus the part cost can be reduced.
In the lighting device, the light source boards may be made of metal.
A metal light source board delivers higher heat dissipation performance in comparison to a resin light source board; however, a dimension of the metal light source board in an extending direction thereof is smaller than that of the resin light source board. In a large-sized lighting device, a large number of light source boards need to be disposed along a light entering surface of a light guide plate. In the configuration described earlier, even if a large number of light source boards are disposed, uneven brightness resulting from the dark spot in each section of the edge of the light guide plate facing the space between the adjacent light source boards is less likely to occur. Therefore, a large-sized lighting device can be provided while the uneven brightness is reduced and the heat dissipation performance is improved.
The technology described herein relates to a display device including the lighting device described above and a display panel configured to display an image using light supplied by the lighting device. Such a display device is new and advantageous. Furthermore, a television device including the display device described above is new and advantageous.
According to the technology described herein, in an edge light type backlight unit, uneven brightness is less likely to occur in light exiting from the light guide plate.
The first embodiment of the present invention will be described with reference to the drawings. In this section, a television device 1 will be described. As illustrated in
The liquid crystal display device 10 has a horizontally-long rectangular overall shape. The liquid crystal display device 10 includes a liquid crystal panel 11 (an example of a display panel) and a backlight unit 12 (an example of a lighting device). The backlight unit 12 is an external light source. The liquid crystal panel 11 and the backlight unit 12 are collectively held by a bezel 13 that has a frame shape. In the liquid crystal display device 10, the liquid crystal panel 11 is held in a position such that a display surface 11C faces the front side and fixed. The display surface 11C is configured to display images. The liquid crystal panel 11 in this embodiment is a high definition panel that includes a larger number of pixels, that is, a so-called 4K2K panel. Namely, the liquid crystal panel 11 is a large-sized panel, for instance, a 32-inch panel.
The bezel 13 is made of metal having high rigidity such as stainless steel. As illustrated in
As illustrated in
On the array substrate 11A, switching components (e.g., TFTs) which are connected to source lines and gate lines that are perpendicular to each other, pixel electrodes connected to the switching components, and an alignment film are disposed. Specifically, on the array substrate 11A, the TFTs and the pixel electrodes are disposed and the gate lines and the source lines are routed in a grid to surround the TFTs and the pixel electrodes. The gate lines and the source lines are connected to gate electrodes and source electrodes, respectively. The pixel electrodes are connected to drain electrodes of the TFTs. On the color filter substrate 11B, color filters, counter electrodes, and an alignment film are disposed. The color filters include red (R), green (G), and blue (B) color portions in predefined arrangement.
As illustrated in
As illustrated in
Next, a configuration of the backlight unit 12 will be described. As illustrated in
The light guide plate 18 is made of substantially transparent synthetic resin (having high light transmissivity) having a refractive index sufficiently higher than that of the air (e.g., acrylic resin such as PMMA or polycarbonate). As illustrated in
The light guide plate 18 is held in a position such that the light entering surfaces 18A are opposed to the LED units 20, the light exiting surface 18B that is a main plate surface (the front plate surface) facing the optical sheet bundle 16, and an opposite surface 18C that is an opposite plate surface from a light exiting surface 18B (the back plate surface) facing the reflection sheet 21, which will be described later. The light guide plate 18 is configured such that the light rays emitted by the LED units 20 enter through the light entering surfaces 18A, travel inside the light guide plate 18, and exit through the light exiting surface 18B. The light guide plate 18 directs the light rays inside the light guide plate 18 toward the optical sheet bundle 16. Although not illustrated, dot patterns are formed on the opposite surface 18C of the light guide plate 18 for reflecting the light rays. The short end surfaces of the light guide plate 18 on the short sides includes recesses 18D in edge positions closer to one of the light entering surfaces 18A. The recesses 18D are recessed inward (toward the middle of the light guide plate 18). Each recess 18D has a rectangular shape in a plan view and extends all the way through the light guide plate 18 in the thickness direction (the Z-axis direction).
The reflection sheet 21 has a rectangular sheet made of synthetic resin and a white surface having high light reflectivity. The reflection sheet 21 is sandwiched between the light guide plate 18 and the chassis 15 with the long direction and the short direction corresponding with the X-axis direction and the Y-axis direction, respectively. The reflection sheet 21 contacts the light guide plate 18 and the chassis 15. The reflection sheet 21 reflects light rays leaking from the LED units 20 or the light guide plate 18 to the surface of the reflection sheet 21.
As illustrated in
The chassis 15 forms the rear exterior of the liquid crystal display device 10. The chassis 15 is made of metal such as aluminum. As illustrated in
As illustrated in
As illustrated in
The frame 14 is formed in a horizontally-long frame shape similar to the bezel 13 and made of synthetic resin. The frame 14 includes a frame portion 14A and a frame peripheral portion 14B. The frame portion 14A is formed in a substantially frame shape in a plan view and parallel to the liquid crystal panel 11. The frame peripheral portion 14B extends from outer peripheral edge of the frame portion 14A toward the front and the rear sides. The frame peripheral portion 14B has a short tubular shape. The frame portion 14A extends along the edges of the light exiting surface 18B of the light guide plate 18. A section of the frame portion 14A press the farthest section of the edge of the light exiting surface from the front side to hold the light guide plate 18 between the bottom plate 15A of the chassis 15 and the frame portion 14A. The frame portion 14A includes a covering section 14A1 that covers the edges of the light exiting surface 18B and the optical member bundle 16 from the front side (see
The frame peripheral portion 14B includes sections that extend from the outer peripheral edges of the frame portion 14A toward the rear side longer than sections of the frame peripheral portion 14B that extend from the outer peripheral edges toward the front side. The sections that extend toward the rear side are against large areas of the side plates 15B of the chassis 15 and form portions of side exterior of the liquid crystal display device 10. The section of the frame peripheral portion against one of the side plates 15B includes a driver holding recess 14B1 that opens outward and holds the source driver D1 therein (see
As illustrated in
Each LED 24 in each LED unit 20 includes a substrate that is fixed to the LED board 25 and an LED chip (not illustrated) which is enclosed with a resin. The LED chip that is mounted on the substrate is configured to emit light with one kind of main emitting wavelength, specifically, light in a single color of blue. In the resin that encloses the LED chip, phosphors are dispersed. The phosphors emit light in predefined colors when excited by the blue light emitted by the LED chip. According to the configuration, the LED 24 emits white light. Different kinds of phosphors such as yellow phosphors that emit yellow light, green phosphors that emit green light, and red phosphors that emit red light may be used for the phosphors. An appropriate combination of the kinds of the phosphors or a single kind of the phosphors may be used. The LED 24 includes an opposite surface from the surface that is fixed to the LED board 25. The opposite surface is a main light exiting surface and thus the LED 24 is referred to as a top surface light emitting type LED.
The LED boards 25 in the LED units 20 are made of aluminum that has high heat dissipation properties. As illustrated in
The LEDs 24 are mounted on plate surfaces of the LED boards 25 on the inner sides, that is, the plate surfaces facing the light guide plate 18. The plate surfaces are referred to as the mounting surfaces 25A. The LEDs 24 are directly soldered to the mounting surfaces 25A of the LED boards 25 with a light emitting surfaces 24A opposed to the light entering surfaces 18A of the light guide plate 18. The LEDs 24 are arranged in line (linearly) at about equal intervals on the mounting surface 25A of each LED board 25 in the longitudinal direction of the LED board 25 (the X-axis direction). Wiring patterns, which are not illustrated, are formed on the mounting surfaces 25A of the LED boards 25 for supply driving power to the LEDs 24. The wiring patterns are formed from a metal film (a copper foil). As illustrated in
In the backlight unit 12 according to this embodiment, as illustrated in
In the backlight unit 12 according to this embodiment, as illustrated in
In the backlight unit 12 according to this embodiment, the light reflecting members 40 having the light reflectivity are disposed as described earlier. Therefore, light rays that have exited the light guide plate 18 through the light exiting surface 18B and reached the light reflecting members 40 are reflected to the sections of the light exiting surface 18B of the light guide plate 18 on the lighter entering surface 18A sides facing the spaces S1 between the adjacent LED boards 25 by the light reflecting member 40. According to the configuration, the reflected light rays reach the dark sports in the sections facing the spaces S1 and therearound. Therefore, the dark spots in the non-display area and the dark spots in the display area A1 can be eliminated. The dark spots are less likely to be produced in the light exiting the light guide plate 18 through the light exiting surface 18B. Therefore, the uneven brightness resulting from the dark spots are less likely to occur in the image displayed on the display surface 11C of the liquid crystal display panel 11.
In a configuration in which a reflection member is disposed on a light exiting surface of a light guide plate, if optical sheets on the light exiting surface thermally is expanded, the optical members may contact the light reflection member. In this embodiment, as described earlier, the light reflecting members 40 are bonded to the section of the frame 14, that is, the covering section 14A1 of the frame 14. Therefore, the light reflecting members 40 are less likely to contact other components due to thermal expansion of the other components.
In general, a metal LED board delivers higher heat dissipation performance in comparison to a resin LED board. However, a length of the metal LED board in an extending direction is smaller than that of the resin LED board. Therefore, in a large-sized backlight unit, a large number of LED boards need to be arranged along a light entering surfaces of a light guide plate. In the backlight unit 12 according to this embodiment, the large number of the LED boards 25 made of aluminum are arranged, the uneven brightness resulting from the dark spots in the sections of the edges of the light guide plate 18 facing the spaces S1 between the adjacent LED boards 25 is less likely to occur. The backlight unit 12 can be increases in size and heat dissipation properties while occurrence of the uneven brightness is reduced.
<First Modification of First Embodiment>
A first modification of the first embodiment will be described with reference to
In this modification, the number of the LED units 120 and the number of the light reflecting members 140 are different from those of the first embodiment. However, the light rays that have exited the light guide plate 18 through the light exiting surface 18B and reached the light reflecting members 140 are reflected by the light reflecting members 140 toward the sections of the edges of the light exiting surface 18B of the light guide plate 18 facing the spaces S2 between the adjacent LED boards 125 on the light entering surface 18A sides. According to the configuration, the light rays reach the dark spots in the sections facing the spaces S2 and therearound and thus not only the dark spots in the non-display area A2 but also the dark spots in the display area A1 can be eliminated. Therefore, the uneven brightness resulting from the dark spots is less likely to occur in the image displayed on the display surface of the display device.
<Second Modification of First Embodiment>
A second modification of the first embodiment will be described. In a backlight unit according to this modification, a covering section of a frame in which the light reflecting members 40 in the first embodiment are disposed is painted in white to configure the entire covering section as a light reflecting member having light reflectivity. Therefore, light reflecting members having a sheet shape are not disposed in the covering section. In this modification, the covering section is painted in white and configured as the light reflecting member. Therefore, the thickness of the light reflecting member is equal to the thickness of the paint. In comparison to the configuration of the first embodiment in which the reflection members having the sheet shape are provided, the thickness of the light reflecting member can be reduced. Therefore, the thickness of the backlight unit can be reduced.
A second embodiment of the present invention will be described with reference to
In this embodiment, the light reflecting members are arranged as described above. Therefore, light rays traveling toward the sections of the light exiting surface 18B of the light guide plate 18 to which the light reflecting members 240 are bonded are reflected by the light reflecting members 240 toward the sections of the light guide plate 18 facing the spaces S3 between the adjacent LED boards 125 and therearound. The reflected light rays reach dark spots in the sections of the edges of the light exiting surface 18 of the light guide plate 18 facing the spaces S3 between the LED boards 25 on the light entering surface 18A sides and therearound. As a result, not only the dark spots in the non-display area A2 of the liquid crystal panel but also the dark spots in the display area A1 can be eliminated. Therefore, the uneven brightness resulting from the dark spots in the image displayed on the display surface of the liquid crystal panel 11 is less likely to occur.
A picture in
A third embodiment will be described with reference to
In the backlight unit 312 according to this embodiment, the protrusion 316D having the light diffusing properties is arranged as described above. Light rays that have exited the light guide plate 18 through the light exiting surface 18B and reach the protrusion 316D are diffused by the protrusion 316D to the section of the light exiting surface 18B of the light guide plate 18 facing the space S4 between the adjacent LED boards 25 on the light entering surface 18A side. The light rays are diffused to the section facing the space S4 and therearound. The brightness in dark spots in the section facing the space S4 and therearound increases and thus the difference in brightness between the dark spots and other areas is reduced. Therefore, dark spots are less likely to be produced in light exiting the light guide plate 18 through the light exiting surface 18B. The uneven brightness resulting from the dark spots is less likely to occur in the image displayed on the display surface of the liquid crystal panel 11.
A picture in
<First Modification of Third Embodiment>
A first modification of the third embodiment will be described with reference to
In the backlight unit 412 according to this modification, all optical sheets in the optical sheet bundle 416 include the protrusions that are on top of each other. In comparison to the fourth embodiment, effects for diffusing the light rays that have reached the protrusions 416D can be improved. The light rays are further diffused by the protrusions 416D to the sections of the edges of the light exiting surface of the light guide plate 18 facing the spaces between the adjacent LED boards 25 on the light entering surface 18A sides and therearound. The brightness in the dark spots in the sections facing the spaces and therearound is further increased. The uneven brightness resulting from the dark spots in the image displayed on the display surface of the liquid crystal panel 11 can be effectively suppressed.
<Second Modification of Third Embodiment>
A first modification of the third embodiment will be described with reference to
According to the configuration, the backlight unit 512 according to this modification can achieve the same effects that are achieved by the backlight unit 12 according to the first embodiment. Light rays that have exited the light guide plate 18 through the light exiting surface 18B and reached the light reflecting member 540 are reflected by the light reflecting member 540 toward the section of the edge of the light exiting surface 18B of the light guide plate 18 facing the space between the adjacent LED boards 25 on the light entering surface 18A side. Dark spots are less likely to be produced in light exiting the light guide plate 18 through the light exiting surface 18B. Therefore, the uneven brightness resulting from the dark spots is less likely to occur in the image displayed on the display surface 11C of the liquid crystal panel 11.
Modifications of the above embodiments will be listed below.
(1) In each of the first embodiment, the modification of the first embodiment, and the second embodiment, the light reflecting member having the sheet shape or the section of the frame configured as the light reflecting member by paining the section in white is provided. However, the configuration is not limited to those in the above embodiments or the modification as long as the light reflecting member has the light reflectivity.
(2) In each of the third embodiment and the modifications of the third embodiment, the optical sheet bundle includes protrusions at the sections of the optical sheet bundle. However, the shapes of the protrusions are not limited to those of the embodiment and the modifications. For instance, protrusions may be formed in a hemisphere shape or a pyramid shape.
(3) In the third embodiment and the first modification of the third embodiment, the protrusions formed at the sections of the optical sheet bundle are configured as the light diffusing members. However, the configuration of the light diffusing members is not limited. For instance, the backlight unit may include a light diffusing member having a sheet shape.
(4) In each of the above embodiments, the long edge surfaces among the end surfaces of the light guide plate are configured as the light entering surfaces and the LED boards are opposed to the light entering surfaces. However, all end surfaces of the light guide plate may be configured as light entering surfaces and LED boards may be disposed to be opposed to the light entering surfaces. In such a configuration, the light reflecting members or light diffusing members may be disposed to be opposed to sections of the edges of the light exiting surface of the light guide plate facing spaces between the adjacent LED boards on the light entering surface sides. According to the configuration, the uneven brightness resulting from the dark spots is less likely to occur in the image displayed on the display surface of the liquid crystal panel.
(5) In each of the above embodiments, the high definition liquid crystal panel is provided. However, the present invention can be applied to display panels that are not high definition display panels. For instance, by applying the present invention to a liquid crystal panel with high color reproducibility, uneven brightness resulting from the dark spots is less likely to occur in an image displayed on the display surface of the liquid crystal panel.
(6) In each of the above embodiment sections, the television device including the cabinets is described. However, the present invention can be applied to television devices without cabinets.
(7) In each of the above embodiment sections, the television device including the high definition liquid crystal panel is described. However, the present invention can be applied to display devices other than the television device.
Embodiments of the present inventions have been described in detail above. However, the embodiments are only examples and not limit claims. Technologies described in the claims include various modification and alteration of the embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-095498 | May 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/063179 | 4/27/2016 | WO | 00 |
