Patent Application
20120127395
The present invention relates to a lighting device, a display device and a television receiver.
For example, a liquid crystal panel used for a liquid crystal display device such as a liquid crystal television does not emit light, and thus a backlight unit is required as a separate lighting device. The backlight unit is known, which is placed behind the liquid crystal panel (on a side opposite to a display surface side). The backlight unit includes a chassis having an opening on a liquid crystal panel side surface, numerous light sources (for example, LEDs) housed in the chassis as lamps, and an optical member (diffuser and the like) provided in the opening of the chassis and efficiently discharging light emitted from the light sources to the liquid crystal panel side.
When the light sources emit point-like light in the backlight unit, the point-like light is converted into planar light by the optical member to uniform in-plane brightness of illumination light. However, when the point-like light is not sufficiently converted into the planar light, a point lamp image is generated along arrangement of the light sources, which deteriorates display quality of the liquid crystal display device.
In order to suppress generation of the lamp image in the backlight unit, for example, it is desirable that the number of the light sources to be arranged is increased to reduce a distance between the light sources that are adjacent to each other or a diffusivity of the diffuser is increased. However, when the number of the light sources is increased, cost of the backlight unit is increased, and power consumption is also increased. When the diffusivity of the diffuser is increased, brightness cannot be improved, which disadvantageously requires an increase in the number of the light sources at the same time. Then, a known backlight unit suppressing power consumption and generation of a lamp image is disclosed in the following Patent Document 1.
Patent Document 1 describes that a pitch of LEDs arranged in an outer circumferential area of a diffuser is smaller than that in a center area of the diffuser in the backlight device. Thereby, a color tone of the outer circumferential area equivalent to that of the center area can be obtained, and color unevenness and brightness reduction of the outer circumferential area can be prevented.
However, in the device disclosed in Patent Document 1, color unevenness (uneven brightness) may be generated in a portion (the center area in Patent Document 1) having a large pitch.
The present invention was accomplished in view of the above circumstances. It is an object of the present invention to provide a lighting device realizing cost reduction, suppressing of power consumption, and suppressing lamp image generation. It is another object of the present invention to provide a display device including the lighting device. It is still another object of the present invention to provide a television receiver including the display device.
To solve the above problem, a lighting device of the present invention includes a plurality of point light sources, and a chassis housing the point light sources and having an opening through which light from the point light source exits. The point light sources are arranged at relatively small intervals in a light source high-density area and the point light sources are arranged at relatively large intervals in a light source low-density area. The lighting device further includes a diffuser lens configured to diffuse light from the point light sources and the diffuser lens is provided on at least a light exit side of the point light sources arranged at least in the light source low-density area.
Thus, the point light sources are arranged such that the light source high-density area and the light source low-density area are provided. Thereby, the number of the point light sources can be reduced as compared with a case where the light source high-density area is formed over the entire chassis, to realize cost reduction and power saving. Because a distance between the point light sources that are adjacent to each other in the light source low-density area is comparatively larger when the light source low-density area is formed, light from the point light sources is less likely to be mixed with each other. As a result, brightness in a region overlapping with the point light sources is locally increased, which tends to generate a lamp image. In the present invention, the diffuser lens is provided on at least the light exit side of the point light sources arranged in the light source low-density area, to sufficiently diffuse the light emitted from the point light sources. Thereby, after the light emitted from the point light sources is sufficiently mixed with each other also in the light source low-density area, the light is exited as illumination light. Therefore, almost uniform brightness can be obtained over the entire chassis, and the generation of the lamp image can be suppressed.
A first embodiment of the present invention will be described with reference to
First, a configuration of a television receiver TV including a liquid crystal display device 10 will be described.
As illustrated in
Next, the liquid crystal panel 11 and the backlight unit 12 included in the liquid crystal display device 10 will be described (see
The liquid crystal panel (display panel) 11 is configured such that a pair of glass substrates is bonded together with a predetermined gap therebetween and liquid crystal is sealed between the glass substrates. On one of the glass substrates, switching components (for example, TFTs) connected to source lines and gate lines which are perpendicular to each other, pixel electrodes connected to the switching components, and an alignment film and the like are provided. On the other substrate, color filters having color sections such as R (red), G (green) and B (blue) color sections arranged in a predetermined pattern, counter electrodes, and an alignment film and the like are provided. Polarizing plates 11a, 11b are attached to outer surfaces of the substrates (see
As illustrated in
The chassis 14 is made of metal. The chassis 14 is formed in a substantially shallow box shape through sheet metal forming. As illustrated in
The LED board 81 is laid on an inner surface of the bottom plate 30 of the chassis 14. The LED board 81 has a reflection sheet 82 laid on a light exit side surface, that is, a surface facing the diffuser 15a, and a plurality of LED light sources 80 surrounded by the reflection sheet 82, that is, provided so as to exposed from openings 82a (see
The LED light sources 80 emit white color light. For example, three kinds of red, green, and blue LED chips (not shown) may be face-mounted. Alternatively, the LED light sources 80 may be obtained by combining a blue LED chip with a yellow fluorescent material. As illustrated in
The low density side LED light sources 80a of the LED light sources 80 are covered with diffuser lenses 24 for diffusing lights emitted from the low density side LED light sources 80a. The high density side LED light sources 80b are not covered with the diffuser lenses 24. The diffuser lens 24 is formed of a transparent member (for example, acrylic and polycarbonate) having a refractive index higher than that of air. The diffuser lens 24 functions to refract light emitted from each LED light source 80a to diffuse the light. The diffuser lens 24 has a circular shape in a plan view, and the LED light source 80a is provided at a center thereof. As illustrated in
The diffuser lens 24 has a recess (light entrance side recess) 24D having a substantially conical shape formed in a lower surface (LED light source 80a side) thereof by denting a place located immediately above the LED light source 80a to the front side (upper side of
The reflection sheet 82 formed on the LED board 81 is made of a synthetic resin, and has a surface having white color that provides excellent light reflectivity. The reflection sheet 82 is provided along an inner surface of the bottom plate 30 of the chassis 14 to cover the almost entire chassis 14. The light emitted from the LEDs 80 can be reflected to the diffuser 15a side by the reflection sheet 82.
As illustrated in
The optical sheet set 15 including the diffuser (optical member, optical diffusing member) 15a and the optical sheets 15b is provided on the opening side 14b of the chassis 14. The diffuser 15a includes a plate-like member made of a synthetic resin and light scattering particles dispersed in the plate-like member. The diffuser 15a has a function for diffusing point light emitted from the LED light sources 80 as the point light sources and also has a function for reflecting the light emitted from the LED light sources 80.
The diffuser 15a has an optical sheet 15b thereon. The optical sheet 15b is obtained by laminating a diffusion sheet, a lens sheet, and a reflection type polarizing plate in this order from the diffuser 15a side. The optical sheet 15b has a function for converting light emitted from the LED light source 80 and passed through the diffuser 15a into planar light. The optical sheet 15b has the liquid crystal panel 11 placed on the upper surface side thereof. The optical sheet 15b is sandwiched between the diffuser 15a and the liquid crystal panel 11.
The light reflection function of the diffuser 15a and a forming aspect of the light reflection portion will be described with reference to
The diffuser 15a has light reflection portions 50 forming a white dot pattern provided on a surface facing the LED light sources 80. In the present embodiment, each dot of the light reflection portions 50 has a round shape. The dot pattern of the light reflection portions 50 is formed by printing paste containing metal oxide (titanium oxide and the like), for example, on the surface of the diffuser 15a. Preferable printing means are screen printing and inkjet printing and the like.
The light reflection portion 50 has a light reflectance of 80% in a surface facing the LED light source 80. The light reflection portion 50 has a light reflectance relatively greater than a light reflectance of 30% in a surface of the diffuser 15a itself. In this context, in the present embodiment, the light reflectance of each material is represented by an average light reflectance inside the measurement diameter measured with an LAV of CM-3700d (measurement diameter φ of 25.4 mm) manufactured by Konica Minolta. The light reflectance of the light reflection portion 50 is a value obtained by forming the light reflection portion 50 over an entire surface of a glass substrate and measuring the surface based on the above measuring means. The light reflectance of the light reflection portion 50 is preferably 80% or greater, and more preferably 90% or greater. Thus, as the light reflectance of the light reflection portion 50 is higher, the reflection degree can be controlled precisely and accurately according to an aspect of the dot pattern (the number of dots and the area of each dot and the like).
In the present embodiment, the light reflection portion 50 is provided in at least a region overlapping with the light source low-density area LL in the diffuser 15a. Particularly, the light reflection portion 50 is formed in a position overlapping with the low density side LED light source 80a in a plan view. As illustrated in
The configuration of the liquid crystal display device included in the television receiver TV of the first embodiment has been described above. Operations and effects exhibited by the configuration will then be described.
First, in the present embodiment, the backlight unit 12 has the plurality of point LED light sources 80 (80a, 80b). The LED light sources 80 (80a, 80b) are arranged such that the light source high-density area LH where the arrangement interval thereof is relatively small and the light source low-density area LL where the arrangement interval is relatively large are provided. Thus, the LED light sources 80 are arranged in the light source high-density area LH and the light source low-density area LL. Thereby, the number of the LED light sources 80 can be reduced as compared with a case where the light source high-density area LH is formed over the entire chassis 14, to enable realization of cost reduction and power saving.
Because the distance between the LED light sources 80, 80 (80a, 80a) that are adjacent to each other in the light source low-density area LL is comparatively large when the light source low-density area LL is formed, light emitted from the LED light sources 80 (80a) is likely to reach the diffuser 15a without mixing the light with each other. As a result, brightness in the region overlapping with the LED light sources 80 (80a) in the diffuser 15a is locally increased, which tends to generate a lamp image. In the present embodiment, the diffuser lenses 24 are provided on at least the light exit side of the LED light sources 80a belonging to the light source low-density area LL in the LED light sources 80, to sufficiently diffuse the light emitted from the LED light sources 80a. Thereby, after the light emitted from the LED light sources 80a is sufficiently mixed with each other also in the light source low-density area LL, the light reaches the diffuser 15a. Therefore, almost uniform brightness can be obtained over the entire chassis 14, and the generation of the lamp image is suppressed.
The diffuser lens 24 has a circular shape in a plan view. Thereby, because the light from the LED light sources 80 (80a) is almost uniformly diffused at 360 degrees by the diffuser lenses 24, the generation of the lamp image can further be suppressed.
The diffuser lens 24 includes the light entrance surface facing each LED light source 80 (80a) and receiving light from each LED light source 80 (80a). The light entrance surface includes the recess 24D formed in the position overlapping with each LED light source 80 (80a). The recess 24D has the side wall inclined so as to face each LED light source 80 (80a). According to such a configuration, the light emitted from the LED light sources 80 (80a) mostly enters the recess 24D of each diffuser lens 24. In this context, the recess 24D has the side wall inclined so as to face each LED light source 80 (80a). Therefore, the light entering the recess 24D reaches the side wall, and can be refracted into the diffuser lens 24 at a wide angle (that is, toward the outer side from the inner side of the diffuser lenses 24) through the side wall. Thereby, the local increase in brightness in the region overlapping with the LED light sources 80 (80a) in the diffuser lens 24 can be suppressed, and the generation of the lamp image can further be suppressed.
The diffuser lens 24 has the light exit surface from which light entering from each LED light source 80 (80a) exits. The light exit surface includes the light exit side recess 24E recessed to the LED light source 80 (80a) side formed in the position overlapping with each LED light source 80 (80a). The amount of light reaching from the LED light sources 80 (80a) in the region overlapping with the LED light sources 80 (80a) in the light exit surface is likely to be increased as compared with that in the other region, which is likely to locally increase brightness. Then, the light exit side recess 24E is formed in the position overlapping with the LED light sources 80 (80a) in the light exit surface. Therefore, the light from the LED light sources 80 (80a) can be refracted at a wide angle by the light exit side recess 34E, or the light from the LED light sources 80 (80a) can be partially reflected. Thereby, the local increase in brightness in the region overlapping with the LED light sources 80 (80a) in the light exit surface can be suppressed, and the generation of the lamp image can further be suppressed.
In the present embodiment, the diffuser 15a includes the light reflection portion 50 formed in the position overlapping with each LED light source 80 (80a) in a plan view. Therefore, because the light emitted from the LED light sources 80 (80a) certainly reaches the light reflection portions 50, and can be reflected to the chassis 14 side by the light reflection portion 50 while the light is mixed with each other, the generation of the lamp image can further be suppressed.
The light reflection portion 50 has a planarly viewed area greater than a planarly viewed area of each LED light source 80 (80a). Therefore, because the light emitted from the LED light sources 80 (80a) can be certainly reflected by the light reflection portion 50, the generation of the lamp image can further be suppressed.
The light reflection portion 50 is formed such that the light reflectance of the diffuser 15a is the greatest in the region overlapping with the light source low-density area LL in the diffuser 15a. Because the light from the LED light sources 80 (80a) can be most reflected in the region overlapping with the light source low-density area LL where the lamp image tends to be generated in the diffuser 15a in this case, the light from the LED light sources 80 (80a) can be likely to be mixed with each other, and the generation of the lamp image can be suitably suppressed.
The diffuser 15a includes the light reflection portion 50 is formed on the surface facing each LED light source 80 (80a). Therefore, because the light reaching the diffuser 15a from the LED light sources 80 (80a) can be certainly reflected, the generation of the lamp image can be suppressed.
The light reflection portion 50 is formed by subjecting the diffuser 15a to print processing. Therefore, the form of the pattern of the light reflection portion 50 can be suitably designed, and the pattern of the light reflection portion 50 can be easily formed as designed.
The chassis 14 includes the light source high-density area LH formed in the center area thereof. Thereby, brightness in the center area of the irradiation surface of the backlight unit 12 is improved. As a result, high brightness in the center area of the display screen is achieved also in the liquid crystal display device 10. Because human eyes usually pay attention to the center area of the display screen, good visibility can be obtained by achieving the high brightness in the center area of the display screen.
The light source high-density area LH has an area smaller than an area of the light source low-density area LL. The light source high-density area LH has the area smaller than the area of the light source low-density area LL, and thereby the number of the LED light sources 80 can further be reduced.
As described above, the first embodiment of the present invention has been illustrated. However, the present invention is not limited to the above embodiment. A modification of a distribution mode of the light reflection portions 50 illustrated in
The diffuser 15a in the present modification includes the light reflection portions 50 provided in at least positions facing the LED light sources 80 in not only the position overlapping with the light source low-density area LL but also the position overlapping with the light source high-density area LH as illustrated in
Such a modification can reduce the number of the LED light sources 80 while securing brightness in the center area of the backlight unit 12, and realizes cost reduction. Particularly because the light reflection portions 50 are formed in the outer edge portion in which the number of the LED light sources 80 is reduced, generation of uneven brightness is suppressed. The generation of the uneven brightness in the center area is also suppressed by partially forming the light reflection portions 50 also in the center area.
Next, a second embodiment of the present invention will be described with reference to
In a liquid crystal display device 10 included in a television receiver TV of the second embodiment, the light reflection portions 50 are omitted from the backlight unit 12 of the first embodiment, and the others are the same as those of the first embodiment. The same constituent parts as those of the above first embodiment are indicated by the same symbols without repeating overlapping descriptions.
The backlight unit 12 employed for the second embodiment has the LED light sources 80 provided on the LED board 81. The LED light sources 80 are arranged on the LED board 81 such that the light source high-density area LH where the arrangement interval of the LED light sources 80 is relatively small is formed in the center area (that is, the center area of the chassis 14) of the LED board 81, and the light source low-density area LL where the arrangement interval of the LED light sources 80 is relatively large is formed on the outer edge portion (that is, the outer edge portion of the chassis 14) of the LED board 81. The area of the light source high-density area LH located in the center area of the LED board 81 is smaller than the area of the light source low-density area LL located in the outer edge portion of the LED board 81. The LED light sources provided in the light source high-density area LH are illustrated as high density side LED light sources 80b. The LED light sources provided in the light source low-density area LL are illustrated as low density side LED light sources 80a.
Similarly to the first embodiment, the low density side LED light sources 80a of the LED light sources 80 are covered with diffuser lenses 24 diffusing light emitted from the low density side LED light sources 80a. The high density side LED light sources 80b are not covered with the diffuser lenses 24. The diffuser lens 24 is formed of a transparent member (for example, acrylic and polycarbonate) having a refractive index higher than that of air. The diffuser lens 24 functions to refract light emitted from each LED light source 80a to diffuse the light. The diffuser lens 24 has a circular shape in a plan view, and the LED light source 80a is provided at a center thereof. The diffuser lens 24 is provided so as to cover the front side of the LED light source 80a. The diffuser lens 24 includes a base portion 24A having a circular plate shape in a plan view and a flat spherical portion 24B having a flat semi-spherical shape. Three leg parts 28 are provided so as to protrude from a peripheral part of the diffuser lens 24. The three leg parts 28 are arranged at approximately equal intervals (intervals of about 120 degrees) from a center part of the diffuser lens 24 in a plan view. For example, the leg parts 28 are fixed to the LED board 81 by an adhesive or a thermosetting resin.
In the present embodiment, the light reflection portion 50 is not formed on the diffuser 15a unlike the first embodiment. That is, the diffuser lenses 24 cover the LED light sources 80a, as means for suppressing uneven brightness of the LED light sources 80a configured to have a low density such that the arrangement interval of the light sources is large. However, the light reflection portion 50 as means for suppressing uneven brightness is not formed on the diffuser 15a. In this case, uneven brightness caused by the LED light sources 80a of the light source low-density area LL can be suppressed by the diffuser lenses 24 depending on the arrangement interval of the light sources.
As describe above, the embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments described in the above description and the drawings. The following embodiments are also included in the technical scope of the present invention, for example.
(1) The above embodiments using the LED which is a kind of point light source as the light source have been illustrated. However, other kind of point light source such as a glow lamp is also used in the present invention.
(2) Each dot of the dot pattern constituting the light reflection portion has been formed into a round shape in the above embodiments. However, the shape of each dot is not limited thereto. Optional shapes such as a polygonal shape, for example, a rectangular shape can be selected.
(3) In the above embodiment, the optical sheet set obtained by combining the diffuser with the diffuser sheet, the lens sheet, and the reflecting type polarizing plate is exemplified. However, for example, an optical sheet obtained by laminating two diffusers can also be employed.
(4) The light reflection portions are formed on the surface of the diffuser facing the light source in the above embodiments. However, the light reflection portions may be formed on the surface of the diffuser opposite to the light source.
(5) The configuration in which the light source high-density area is formed in the center area of the bottom plate of the chassis has been illustrated in the above embodiments. However, the configuration can be suitably changed according to the amount of light of the light source and the operating condition of the backlight unit and the like. For example, the light source high-density area is formed in a part of the end area in addition to the center area of the bottom plate.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-155530 | Jun 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/058286 | 5/17/2010 | WO | 00 | 12/16/2011 |
