Patent Application
20100177499
The present invention relates to a lighting device, a display device and a television receiver.
In a display device having non-luminous optical elements as typified by a liquid crystal display device, a backlight device is provided on the backside of a display panel such as a liquid crystal panel, so as to illuminate the display panel (as shown in Patent Document 1, for example).
In order to prevent reduction in luminescent efficiency of light sources attributable to their own heat, Patent Document 1 discloses a technique that provides at least one opening section on a reflective member arranged across a plurality of light sources from a liquid crystal display element, so that the opening section is located to correspond to the orthogonal projection of a light source onto the reflective member, which can be obtained by projecting the light source along a direction perpendicular to the display surface of the liquid crystal display element.
Following recent needs for the growing size and power-saving feature of a liquid crystal display device, problems have been generated in connection with light sources of the liquid crystal display device. Some of them are cited as major problems, which includes problems related to the uneven distribution of brightness, such as unevenness of brightness or visible images of lamps, as well as the problems related to the above-described luminescent efficiency.
In order to obtain homogeneous light sources overcoming the uneven distribution of brightness, for example, Patent Document 2 discloses a technique that provides a number of transmittance regulators having a size equal to or smaller than 500 micrometers, which are arranged on an optical member and in a predetermined pattern of density distribution.
Further, Patent Document 3 discloses a technique that provides a plurality of straight tube lamps arranged substantially parallel and along the horizontal or longitudinal direction of the display screen of a display panel. The intervals between the straight tube lamps are set to be narrower at the central area of the display screen of the display panel and to increase at a constant rate and towards the upper or lower end of the display screen (which is also referred to as an unequal lamp-pitch structure). In general, people pay attention to the center of the screen, and therefore don't mind if the end of the screen has brightness slightly lower than that of the center of the screen. Focusing on this tendency, the technique allows for reduction in number of lamps and therefore in power consumption while maintaining the uniformity in brightness of the surface light source.
However, the existing measures are not adequate to prevent the uneven distribution of brightness, and accordingly, there is an urgent need to develop new technologies in accordance with the growing screen size of a liquid crystal display device. Particularly in the unequal lamp-pitch structure as in Patent Document 3, the brightness distribution on the entire screen is extremely sensitive to the arrangement of lamps. Therefore, the end of the screen may be prone to display unevenness, such as brightness unevenness due to shortage of the light amount attributable to the wide intervals between lamps, or visible images of lamps due to insufficient reflection of the light.
The present invention was made in view of the foregoing circumstances, and an object thereof is to provide a lighting device having a simple construction capable of partially regulating the illumination brightness so as to provide a gentle distribution of illumination brightness. A further object of the present invention is to provide a display device having the lighting device, and to provide a television receiver having the display device.
In order to solve the above problem, a lighting device according to the present invention includes a plurality of linear light sources arranged parallel to one another, and a light reflecting member arranged on the side of the linear light sources that corresponds to the opposite side of the light emitting side. The linear light sources are arranged so that a narrow-interval area where the arrangement interval thereof is relatively narrow and a wide-interval area where the arrangement interval is relatively wide are provided. An opening section is formed on the light reflecting member. The opening section is provided so that the opening ratio as a ratio of the area of the opening section in the entire light reflecting member is higher at an area corresponding to the narrow-interval area, than at an area corresponding to the wide-interval area.
The lighting device, in which the linear light sources are thus arranged so that the narrow-interval area where the arrangement interval is relatively narrow and the wide-interval area where the arrangement interval is relatively wide are provided, can have illumination brightness that is higher at the narrow-interval area side than at the wide-interval area side. Further, the provision of the wide-interval area can lead to reduction in number of linear light sources due to the relatively wide interval, which contributes to cost reduction. In the case of some applications of the lighting device, it is preferable that an area with high illumination brightness is provided partly and separately from an area with low illumination brightness. For example, in the case of a display device that provides display by use of the present lighting device, a bright display may be required on the inner side (or central area) of the display screen while a brighter display is not required on the outer side (or peripheral area) of the display screen. In this case, it is preferable that the narrow-interval area is arranged on the inner side of the display device while the wide-interval area is arranged on the outer side of the display device.
However, when the linear light sources are arranged at intervals of varying length as described above, it is significantly important that the narrow-interval area capable of providing relatively high illumination brightness and the wide-interval area capable of providing relatively low illumination brightness are arranged in a balanced manner. If the illumination brightness differs excessively between the narrow-interval area and the wide-interval area, the entire distribution of illumination brightness may be provided as an uneven distribution, resulting in brightness unevenness in a display device that uses the present lighting device, for example.
According to the present invention, the opening section of the light reflecting member is additionally provided in the above construction having linear light sources arranged at intervals of varying length, so that the opening ratio as a ratio of the area of the opening section in the entire light reflecting member is higher at an area corresponding to the narrow-interval area of the linear light sources, than at an area corresponding to the wide-interval area of the linear light sources.
Some of the lights from the linear light sources are directly oriented to the light emitting side (e.g., to the display panel side). However, the rest may be emitted in directions other than toward the light emitting side, and can be reflected by the light reflecting member to the light emitting side. Both lights collectively provide the illumination brightness.
In view of this, the provision of the opening section on the light reflecting member enables reduction in amount of light to be reflected by the light reflecting member, because the opening section is less prone to reflecting lights from the linear light sources. Consequently, the illumination brightness can be reduced. At the time, the reduction of illumination brightness can be set to be larger at the narrow-interval area of the array of the linear light sources, as a result of setting the opening ratio, i.e., the ratio of the area of the opening section in the entire light reflecting sheet, to be higher at the area corresponding to the narrow-interval area than at the area corresponding to the wide-interval area. Thus, the difference in illumination brightness between the narrow-interval area and the wide-interval area can be reduced. That is, the adjustment of illumination brightness between the narrow-interval area and the wide-interval area of the array of the linear light sources can be achieved by regulating the opening ratio in the light reflecting member. Consequently, the illumination brightness can be gently distributed over the entire lighting device, and thereby display unevenness such as the above-described brightness unevenness can be prevented or suppressed, for example, in a display device that uses the present lighting device.
An embodiment 1 according to the present invention will be explained with reference to
Referring to
Next, the liquid crystal panel 11 and the backlight device 12 of the liquid crystal display device 10 will be explained (See
The liquid crystal panel 11 includes a pair of glass substrates, which are attached to each other so as to face each other while a gap of a predetermined size is kept therebetween. Liquid crystal is sealed between the glass substrates. On one of the glass substrates, components such as switching elements (e.g., TFTs) connected to source wiring lines and gate wiring lines running at right angles to each other, and pixel electrodes connected to the switching elements are provided. On the other of the glass substrates, components such as a counter electrode and a color filter having R, G, and B color sections arranged in a predetermined pattern are provided.
The backlight device 12 is a so-called direct-light type backlight device that includes a plurality of linear light sources (e.g., cold cathode tubes (tubular light sources) 17 as high-pressure discharge tubes, in the present embodiment), which are positioned directly below the back surface of the liquid crystal panel 11 (i.e., the panel surface on the opposite side of the display side), and are arranged along the panel surface.
The backlight device 12 includes a backlight chassis (chassis) 14 having a substantially box-like shape with an opening on its upper side, and a plurality of optical members 15 (e.g., a diffuser plate, a diffusing sheet, a lens sheet and an optical sheet, in order from the lower side of the figure) which are arranged to cover in the opening of the backlight chassis 14. Further included is a frame 16 arranged to hold the optical members 15 on the backlight chassis 14. The backlight chassis 14 contains the cold cathode tubes 17, lamp holders 19 arranged to collectively cover the end portions of the cold cathode tubes 17, and lamp clips (or light source supporting members) 20 arranged to mount and hold the cold cathode tubes 17 on the backlight chassis 14. Note that the optical member 15 side of the cold cathode tubes 17 corresponds to the light emitting side of the backlight device 12.
An inverter board 21 for supplying drive voltage to the cold cathode tubes 17 is mounted to the backlight chassis 14, or specifically, mounted on the opposite side of the cold cathode tubes 17 (i.e., on the opposite side of the light emitting surface). The inverter board 21 includes an inverter circuit that generates a high-frequency voltage for lighting the cold cathode tubes 17.
Each of the cold cathode tubes 17 forms an elongated tubular shape. A number (e.g., sixteen in
The backlight chassis 14 is formed of a metallic plate, and the inner surface thereof is coated with black color. A light reflecting sheet (or a light reflecting member) 40 is provided to form a light reflecting surface, which is arranged on the side of the cold cathode tubes 17 that corresponds to the opposite side of the light emitting side. The backlight chassis 14 thus includes the light reflecting sheet 40, and thereby light from the cold cathode tubes 17 can be reflected to the optical members 15 such as the diffuser plate.
The light reflecting sheet 40 can be formed of a resin sheet having light reflectivity, for example. The light reflectivity thereof is set to be higher than that of the backlight chassis 14. The light reflecting sheet 40 is arranged parallel to the array direction of the cold cathode tubes 17. Referring to
The light reflecting sheet 40 includes through holes 22 provided for insertion of the lamp clips 20, and opening sections (not shown in
The opening sections 50 can be formed in the light reflecting sheet 40 by punching. In the present embodiment, the opening sections 50 are the same in dimension. Referring to
Within each of the rows, the intervals between opening sections 50 adjacently arranged on the same row along the axial direction of the cold cathode tube 17 are set to be constant.
However, the intervals between opening sections 50 adjacently arranged along the axial direction of the cold cathode tubes 17 vary among rows. On the rows located in the area of the light reflecting sheet 40 corresponding to the narrow-interval area 17A (i.e., the area of the light reflecting sheet 40 corresponding to the center of its short side), the opening sections 50 are arranged densely or at relatively small intervals. On the rows located in the areas of the light reflecting sheet 40 corresponding to the wide-interval areas 17B (i.e., the areas of the light reflecting sheet 40 corresponding to the ends of its short side), the opening sections are arranged sparsely or at relatively large intervals. Specifically, the intervals are set to increase gradually from the rows facing the narrow-interval area 17A, toward the rows facing the wide-interval areas 17B. Thus, the opening ratio, i.e., the ratio of the areas of opening sections 50 in the entire light reflecting sheet 40, is set to be higher at the area corresponding to the narrow-interval area 17A, than at the areas corresponding to the wide-interval areas 17B.
The intervals between opening sections 50 adjacently arranged along the array direction of the cold cathode tubes 17 are set as follows. In the area of the light reflecting sheet 40 corresponding to the narrow-interval area 17A (i.e., the area of the light reflecting sheet 40 corresponding to the center of its short side), the opening sections 50 are arranged densely or at relatively small intervals. In the areas of the light reflecting sheet 40 corresponding to the wide-interval areas 17B (i.e., the areas of the light reflecting sheet 40 corresponding to the ends of its short side), the opening sections 50 are arranged sparsely or at relatively large intervals. Specifically, the intervals are set to increase gradually from the area facing the narrow-interval area 17A toward the areas facing the wide-interval areas 17B. Thus, the opening ratio, i.e., the ratio of the areas of opening sections 50 in the entire light reflecting sheet 40, is set to be higher at the area corresponding to the narrow-interval area 17A, than at the areas corresponding to the wide-interval areas 17B.
The television receiver TV thus constructed according to the present embodiment can provide the following operational effects.
In the liquid crystal display device 10 included in the television receiver TV of the present embodiment, the cold cathode tubes 17 are arranged so that the narrow-interval area 17A where the arrangement interval is relatively narrow and the wide-interval areas 17B where the arrangement interval is relatively wide are provided. Specifically, the narrow-interval area 17A is arranged on the center side of the backlight device 12, while the wide-interval areas 17B are arranged on the end sides of the backlight device 12. According to the construction, the illumination brightness can be higher at the narrow-interval area 17A than at the wide-interval areas 17B, and consequently the liquid crystal display device 10 can have improved visibility at the center of the screen. Further, the provision of the wide-interval areas 17B can lead to reduction in number of cold cathode tubes 17, resulting in cost reduction.
However, it is extremely difficult to arrange the narrow-interval area 17A capable of providing a relatively high illumination brightness and the wide-interval areas 17B capable of providing a relatively low illumination brightness, in a balanced manner. If the illumination brightness differs excessively between the narrow-interval area 17A and the wide-interval areas 17B, the entire distribution of illumination brightness may be provided as an uneven distribution, resulting in brightness unevenness in the liquid crystal display device 10.
In view of this, according to the present embodiment, the opening sections 50 of the light reflecting sheet 40 are additionally provided as regulating means for illumination brightness. Thereby, the opening ratio, i.e., the ratio of the areas of opening sections 50 in the entire light reflecting sheet 40, is set to be higher at the area corresponding to the narrow-interval area 17A, than at the areas corresponding to the wide-interval areas 17B.
The opening sections 50, thus provided on the light reflecting sheet 40, cannot reflect the light from the cold cathode tubes 17. Therefore, the amount of light to be reflected by the light reflecting sheet 40 can be reduced, and consequently the illumination brightness can be reduced. At the time, the reduction of illumination brightness can be set to be larger at the narrow-interval area 17A, as a result of setting the opening ratio, i.e., the ratio of the areas of opening sections 50 in the entire light reflecting sheet 40, to be higher at the area corresponding to the narrow-interval area 17A than at the areas corresponding to the wide-interval areas 17B. Thus, the difference in illumination brightness between the narrow-interval area 17A and the wide-interval areas 17B can be reduced. That is, the adjustment of illumination brightness between the narrow-interval area 17A and the wide-interval areas 17B can be achieved by partially regulating the opening ratio in the light reflecting sheet 40. Consequently, the illumination brightness can be gently distributed over the backlight device 12, and thereby display unevenness such as brightness unevenness in the liquid crystal display device 10 can be prevented or suppressed.
Further, in the present embodiment, the opening sections 50 are arranged so that the intervals between opening sections 50 adjacently arranged along the axial direction of the cold cathode tube 17 are set to be smaller at the area corresponding to the narrow-interval area 17A than at the areas corresponding to the wide-interval areas 17B.
Moreover, the opening sections 50 are arranged so that the intervals between opening sections 50 adjacently arranged along the array direction of cold cathode tubes 17 are set to be smaller at the area corresponding to the narrow-interval area 17A than at the areas corresponding to the wide-interval areas 17B.
According to the construction, a larger number of opening sections 50 can be provided in the area corresponding to the narrow-interval area 17A, compared to those in the areas corresponding to the wide-interval areas 17B. Thus, the opening ratio in the light reflecting sheet 40 is set to be relatively high at the area corresponding to the narrow-interval area 17A. Consequently, the amount of light to be reflected and therefore the illumination brightness can be reduced more greatly at the narrow-interval area 17A, and thereby the illumination brightness can be gently distributed between the narrow-interval area 17A and the wide-interval areas 17B.
The present embodiment includes the backlight chassis 14 formed of a metallic plate, and the light reflectivity of the light reflecting sheet 40 is set to be higher than that of the backlight chassis 14.
Referring to
In the present embodiment, the inner surface of the backlight chassis 14 is coated with black color.
In order to reliably provide the light reflectivity of the light reflecting sheet 40 higher than that of the backlight chassis 14, the backlight chassis 14 is thus coated with black color as regulating means for the light reflectivity of the backlight chassis 14. Consequently, the backlight chassis 14 can have a lower light reflectivity or more greatly differ in light reflectivity from the light reflecting sheet 40. Consequently, the opening sections 50 can function as regulators for illumination brightness, more effectively.
In the present embodiment, the light reflecting sheet 40 includes the through holes 22 provided for insertion of the lamp clips 20, and the opening sections 50 provided for regulating the light reflectivity. The through holes 22 and the opening sections 50 both have a circular shape, but differ in planar dimension from each other.
When the through holes 22 and the opening sections 50 are thus provided to differ in planar dimension (or in size) from each other, the through holes 22 and the opening sections 50 are distinguishable, and therefore confusion therebetween can be prevented at the time of assembly of the backlight device 12. Thereby, the manufacturing process may be simplified.
Further, in the present embodiment, the opening sections 50 are formed on the light reflecting sheet 40 by punching. The opening sections 50 can be thus formed by a simple method, as designed.
Next, an embodiment 2 of the present invention will be explained with reference to
In the above embodiment 1, the arrangement of the opening sections 50 is determined based on the difference in illumination brightness between the narrow-interval area 17A and the wide-interval areas 17B. In the present embodiment, the arrangement of opening sections 51 is determined further based on the difference in illumination brightness due to voltage difference among areas of cold cathode tubes 17. The other constructions are similar to the above embodiment 1. Therefore, the same parts as the above embodiment are designated by the same symbols, and redundant explanations are omitted.
An inverter board 21 for supplying drive voltage to the cold cathode tubes 17 is mounted on one side of the backlight chassis 14 corresponding to a long-side-directional end thereof, so that the drive voltage from the inverter board 21 is applied to one end portion of each cold cathode tube 17. Therefore, one end side of each cold cathode tube 17, to which the drive voltage is applied, is provided as an area subjected to high voltage (i.e., a high voltage area 30A), while the other end side is provided as an area subjected to low voltage (i.e., a low voltage area 30B).
Referring to
In each row, the intervals between opening sections 51 adjacently arranged on the same row along the axial direction of the cold cathode tube 17 are set to vary depending on the position. Specifically, the intervals between opening sections 51 located in areas corresponding to the high voltage areas 30A are relatively small, while the intervals between opening sections 51 located in areas corresponding to the low voltage areas 30B are relatively large.
The arrangement of the opening sections 51 along the array direction of the cold cathode tubes 17, that is, intervals between opening sections 51 in the area corresponding to the narrow-interval area 17A and in the areas corresponding to the wide-interval areas 17B, are set in a similar manner to that of the above embodiment 1.
As explained above, according to the present embodiment, the opening sections 51 are provided so that the opening ratio as the ratio of the areas of opening sections 51 in the entire light reflecting sheet 41 is higher at the areas corresponding to the high voltage areas 30A of the cold cathode tubes 17, than at the areas corresponding to the low voltage areas 30B.
The unevenness in illumination brightness of the backlight device 14 can be caused not only by the balanced arrangement of the narrow-interval area 17A and the wide-interval areas 17B, but also by voltage difference among areas of the cold cathode tubes 17. That is, the brightness of cold cathode tubes 17 as linear light sources may be higher at the high voltage areas 30A of the cold cathode tubes 17, than at the low voltage areas 30B.
In view of this, the opening ratio, i.e., the ratio of the areas of opening sections 51 in the entire light reflecting sheet 41, is set to be higher at the areas corresponding to the high voltage areas 30A of the cold cathode tubes 17, than at the areas corresponding to the low voltage areas 30B, as described above.
Thereby, the amount of light to be reflected and therefore illumination brightness can be reduced more greatly at the high voltage areas 30A where the illumination brightness is relatively high in comparison with that at the low voltage areas 30B. Thus, the difference in illumination brightness between the high voltage areas 30A and the low voltage areas 30B can be reduced. Consequently, the illumination brightness can be provided to be gentle in the entire distribution.
Further, in the present embodiment, the opening sections 51 are arranged so that the intervals between opening sections 51 adjacently arranged along the axial direction of the cold cathode tube 17 are set to be smaller at the high voltage areas 30A than at the low voltage areas 30B.
According to the construction, a larger number of opening sections 51 can be provided in the areas corresponding to the high voltage areas 30A, compared to those in the areas corresponding to the low voltage areas 30B. Thus, the opening ratio in the light reflecting sheet 41 is set to be relatively high at the areas corresponding to the high voltage areas 30A. Consequently, the amount of light to be reflected and therefore the illumination brightness can be reduced more greatly at the high voltage areas 30A, and thereby the illumination brightness can be gently distributed between the high voltage areas 30A and the low voltage areas 30B.
Moreover, in the present embodiment, the opening sections 51 are arranged so that the intervals between opening sections 51 adjacently arranged along the array direction of cold cathode tubes 17 are set to be smaller at the narrow-interval area 17A than at the wide-interval areas 17B.
According to the construction, a larger number of opening sections 51 can be provided in the area corresponding to the narrow-interval area 17A, compared to those in the areas corresponding to the wide-interval areas 17B. Thus, the opening ratio in the light reflecting sheet 41 is set to be relatively high at the area corresponding to the narrow-interval area 17A. Consequently, the amount of light to be reflected and therefore the illumination brightness can be reduced more greatly at the narrow-interval area 17A, and thereby the illumination brightness can be gently distributed between the narrow-interval area 17A and the wide-interval areas 17B.
According to the present embodiment, the backlight device 12 includes a light reflecting sheet 42 having opening sections 51 as described above. Thereby, the illumination brightness can be gently distributed over the backlight device 12, and consequently display unevenness such as brightness unevenness in the liquid crystal display device 10 can be prevented or suppressed.
Next, an embodiment 3 of the present invention will be explained with reference to
Referring to
The opening sections 52 having the same planar dimension are arranged in a row along the long-side direction of the light reflecting sheet 42 (or along the axial direction of the cold cathode tube 17).
A plurality (e.g., nine in
The intervals between opening sections 52 adjacently arranged along the array direction of the cold cathode tubes 17 are set as follows. In the areas of the light reflecting sheet 42 corresponding to the high voltage areas 30A (i.e., the upper area of the light reflecting sheet 42 in
As explained above, according to the present embodiment, the opening sections 52 are provided so that those located in the area corresponding to the narrow-interval area 17A of the cold cathode tubes 17 are larger in planar dimension, than those located in the areas corresponding to wide-interval areas 17B.
When the opening sections 52 located in the area corresponding to the narrow-interval area 17A are thus provided to be larger in planar dimension (or in size) than those located in the areas corresponding to the wide-interval areas 17B, the opening ratio in the light reflecting sheet 42 can be relatively high at the area corresponding to the narrow-interval area 17A. Consequently, the amount of light to be reflected and therefore the illumination brightness can be reduced more greatly at the narrow-interval area 17A, and thereby the illumination brightness can be gently distributed between the narrow-interval area 17A and the wide-interval areas 17B.
Further, in the present embodiment, the opening sections 52 are arranged so that the intervals between opening sections 52 adjacently arranged along the array direction of cold cathode tubes 17 are set to be smaller at the high voltage areas 30A of the cold cathode tubes 17 than at the low voltage areas 30B.
According to the construction, a larger number of opening sections 52 can be provided in the areas corresponding to the high voltage areas 30A, compared to those in the areas corresponding to the low voltage areas 30B. Thus, the opening ratio in the light reflecting member is set to be relatively high at the areas corresponding to the high voltage areas 30A. Consequently, the amount of light to be reflected and therefore the illumination brightness can be reduced more greatly at the high voltage areas 30A, and thereby the illumination brightness can be gently distributed between the high voltage areas 30A and the low voltage areas 30B.
In the present embodiment, the light reflecting sheet 42 includes the through holes 23 provided for insertion of the lamp clips 20, and the opening sections 52 provided for regulating the light reflectivity. Each through hole 23 has a square shape, while each opening section 52 has a circular shape.
When the through holes 23 and the opening sections 52 are thus provided to differ in shape from each other, the through holes 23 and the opening sections 52 are readily distinguishable, and therefore confusion therebetween can be prevented at the time of assembly of the backlight device 12. Thereby, the manufacturing process may be simplified.
According to the present embodiment, the backlight device 12 includes a light reflecting sheet 42 having opening sections 52 as described above. Thereby, the illumination brightness can be gently distributed over the backlight device 12, and consequently display unevenness such as brightness unevenness in the liquid crystal display device 10 can be prevented or suppressed.
Next, an embodiment 4 of the present invention will be explained with reference to
Referring to
The opening sections 53 are arranged in a row along the long-side direction of the light reflecting sheet 43 (or along the axial direction of the cold cathode tube 17). In the areas of the light reflecting sheet 43 corresponding to the high voltage areas 30A (i.e., the upper area of the light reflecting sheet 43 in
A plurality (e.g., seven in
The intervals between opening sections 53 adjacently arranged along the array direction of the cold cathode tubes 17 are set as follows. In the area of the light reflecting sheet 43 corresponding to the narrow-interval area 17A (i.e., the area of the light reflecting sheet 43 corresponding to the center of its short side), the opening sections 53 are arranged densely or at relatively small intervals. In the areas of the light reflecting sheet 43 corresponding to the wide-interval areas 17B (i.e., the areas of the light reflecting sheet 43 corresponding to the ends of its short side), the opening sections 53 are arranged sparsely or at relatively large intervals. Specifically, the intervals are set to increase gradually from the area corresponding to the narrow-interval area 17A, toward the areas corresponding to the wide-interval areas 17B. Thus, the opening ratio, i.e., the ratio of the areas of opening sections 53 in the entire light reflecting sheet 43, is set to be higher at the area corresponding to the narrow-interval area 17A, than at the areas corresponding to the wide-interval areas 17B.
As explained above, according to the present embodiment, the opening sections 53 are provided so that those located in the areas corresponding to the high voltage areas 30A of the cold cathode tubes 17 are larger in planar dimension (or in size), than those located in the areas corresponding to low voltage areas 30B. Thereby, the opening ratio in the light reflecting sheet 43 can be relatively high at the areas corresponding to the high voltage areas 30A. Consequently, the amount of light to be reflected and therefore the illumination brightness can be reduced more greatly at the high voltage areas 30A, and thereby the illumination brightness can be gently distributed between the high voltage areas 30A and the low voltage areas 30B.
Further, in the present embodiment, the opening sections 53 are arranged so that the intervals between opening sections 53 adjacently arranged along the array direction of cold cathode tubes are set to be smaller at the area corresponding to the narrow-interval area 17A than at the areas corresponding to the wide-interval areas 17B.
According to the construction, a larger number of opening sections 53 can be provided in the area corresponding to the narrow-interval area 17A, compared to those in the areas corresponding to the wide-interval areas 17B. Thus, the opening ratio in the light reflecting sheet 43 is set to be relatively high at the area corresponding to the narrow-interval area 17A. Consequently, the amount of light to be reflected and therefore the illumination brightness can be reduced more greatly at the narrow-interval area 17A, and thereby the illumination brightness can be gently distributed between the narrow-interval area 17A and the wide-interval areas 17B.
Moreover, in the present embodiment, the opening sections 53 are arranged in parallel lines, so as to form a regular arrangement. Thereby, the illumination brightness can be regulated with improved accuracy.
According to the present embodiment, the backlight device 12 includes a light reflecting sheet 43 having opening sections 53 as described above. Thereby, the illumination brightness can be gently distributed over the backlight device 12, and consequently display unevenness such as brightness unevenness in the liquid crystal display device 10 can be prevented or suppressed.
Shown above are embodiments of the present invention. However, the present invention is not limited to the embodiments explained in the above description made with reference to the drawings. The following embodiments may be included in the technical scope of the present invention, for example.
(1) In the above embodiments, the narrow-interval area is positioned in the array direction of the cold cathode tubes so as to be on the center side, while the wide-interval areas are positioned in the array direction of the cold cathode tubes so as to be on the end sides. However, a narrow-interval area and a wide interval area may be located at any position.
Particularly in the case that a lighting device of the present invention is used for a display device, it is preferable that a narrow-interval area is positioned in the array direction of cold cathode tubes so as to be on the inner side of a wide-interval area, because the display device is required to have relatively high brightness at the center of the screen.
(2) In the above embodiments, the opening sections having circular shapes are arranged in parallel lines (to form an in-line arrangement of circular holes). However, the shapes and arrangement of opening sections are not limited to this configuration. For example, on a light reflecting sheet 60, referring to
(3) In the above embodiments, the opening sections on a light reflecting sheet have the same shape. However, opening sections having different shapes may be provided on a light reflecting sheet.
(4) In the above embodiments, the opening sections are formed by punching. However, the opening sections may be formed by any forming means, as long as they can be formed as designed. For example, a cutting plotter can be used as forming means.
(5) In the above embodiments, the opening sections are arranged in rows along the axial direction of cold cathode tubes. However, opening sections may be irregularly arranged. The irregular arrangement is particularly suitable as means for achieving a small interval between adjacent opening sections in the area corresponding to the narrow-interval area.
(6) In the above embodiments, the backlight chassis is coated with black color. However, any color such as gray or a similar color can be used as a coating color, as long as it is unlikely to reflect light. Alternatively, a member with black, gray or a similar color may be arranged between the backlight chassis and the light reflecting sheet.
(7) In the above embodiments, the backlight chassis is coated with black color. However, this construction may lead to an excessively large difference in brightness between the opening sections and the ordinary portions surrounding the opening sections (or areas not including opening sections). In this case, the opening sections may be visible when the lighting device of the present invention is used for a display device. In view of this, the backlight chassis can be coated with white or a similar color, as long as the light reflectivity thereof does not exceed that of the light reflecting sheet. Alternatively, a transparent member or a member with white or a similar color may be arranged between the backlight chassis and the light reflecting sheet.
(8) In the above embodiments, the backlight chassis is formed of a metallic plate. However, it may be formed by resin molding.
(9) In the above embodiments, cold cathode tubes are used as light sources. However, the present invention can include a construction in which another type of light sources such as hot cathode tubes is used, for example.
(10) In the above embodiments, TFTs are used as switching elements of the liquid crystal display device. However, the present invention can be applied to a liquid crystal display device that uses another type of switching elements than TFTs (e.g., thin-film diodes (TFDs)). Further, the present invention can be applied to a liquid crystal display device for monochrome display, as well as a liquid crystal display device capable of color display.
(11) In the above embodiments, a backlight device of a liquid crystal display device is shown as a lighting device. However, the present invention can be applied to other kinds of lighting devices such as a lighting device for interior lighting or a backlight device for illuminating a still image including an advertising image.
Moreover, although a liquid crystal display device is shown as a display device in the above embodiments, the present invention can be applied to other types of display devices than a liquid crystal type, which use a backlight device.
(12) A television receiver having a liquid crystal panel is shown in the above embodiments. However, the present invention can be applied to a television receiver that uses another type of display panel than the liquid crystal panel.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-176330 | Jul 2007 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/055409 | 3/24/2008 | WO | 00 | 12/24/2009 |
