LIGHTING DEVICE, DISPLAY DEVICE AND TELEVISION DEVICE

A backlight device 12 includes a LED 17, alight guide plate 19 having an end surface as a light entrance surface 19b and a plate surface as a light exit surface 19a, a LED board 18 having a square plate surface that is opposed to the light entrance surface 19b, a board-side connector 22 arranged on the LED board 18, and a heat dissipation member 20. The heat dissipation member 20 has a positioning hole 26 that is through the heat dissipation member 20 and with which the LED board 18 is positioned with respect to the heat dissipation member 20. The heat dissipation member 20 has a hole edge portion around the positioning hole 26 and the hole edge portion includes two sides 26S1, 26S2 constituting a corner portion, and the two sides 26S1, 26S2 are parallel to two sides 18S1, 18S2 of the plate surface of the LED board 18, respectively. The two sides 18S1, 18S2 of the LED board 18 constitute a corner portion of the plate surface of the LED board 18. The positioning hole 26 overlaps the board-side connector 22.

TECHNICAL FIELD

The present invention relates to a lighting device, a display device and a television device.

BACKGROUND ART

In recent years, displays in image display devices, such as television devices, are being shifted from conventional cathode-ray tube displays to thin display panels, such as liquid crystal panels and plasma display panels. With the thin displays, thicknesses of the image display devices can be decreased. Liquid crystal panels used for the liquid crystal display device do not emit light. Therefore, liquid crystal display devices including liquid crystal panels require backlight devices. The backlight devices are classified broadly into a direct type and an edge-light type based on mechanisms. For further reduction in thicknesses of the liquid crystal display devices, the edge-light type backlight devices are more preferable. A backlight device disclosed in Patent Document 1 is known as an example of the kind. A lighting device disclosed in Patent Document 2 is known as a lighting device that improves a heat dissipation property and mechanical strength.

RELATED ART DOCUMENT

Patent Document

Patent Document 2: Japanese Unexamined Patent Application Publication No. 2011-129440

Problem to be Solved by the Invention

In the edge-light type backlight device, light from light sources that are locally arranged in an end portion of the backlight device is guided by the light guide plate to obtain planar exit light. Therefore, if any variation occurs in positional relation of the light sources with respect to the light guide plate, light use efficiency may be decreased or brightness unevenness may occur in the exit light. Especially, as the backlight device becomes thinner, the positional relation of the light sources with respect to the light guide plate tends to be required to be matched at high precision and therefore, it is difficult to deal with the above matters.

DISCLOSURE OF THE PRESENT INVENTION

A technology disclosed herein was made in view of the above circumstances. An object is to improve light use efficiency and reduce occurrence of unevenness in brightness.

Means for Solving the Problem

A technology disclosed herein relates to a lighting device including a light source, alight guide plate having an end surface as a light entrance surface and a plate surface as a light exit surface, a light source board, a power feed relay portion, and a heat dissipation member. Light from the light source enters the light guide plate through the light entrance surface and the light exits the light guide plate through the light exit surface. The light source board has a plate surface where the light source is arranged and that is opposed to the light entrance surface and has a square shape. The power feed relay portion is arranged on the light source board and relays power feed to the light source. The light source board is arranged on the heat dissipation member and the heat dissipation member is configured to dissipate heat generated from the light source. The heat dissipation member has a positioning hole that is through the heat dissipation member and with which the light source board is positioned with respect to the heat dissipation member and the positioning hole corresponds to the power feed relay portion. The heat dissipation member has a hole edge portion around the positioning hole and the hole edge portion includes two sides constituting a corner portion, and the two sides are parallel to two sides of the plate surface of the light source board, respectively. The two sides of the light source board constitute a corner portion of the plate surface of the light source board.

With such a configuration, the light source arranged on the light source board emits light with the power feed relayed by the power feed relay portion. The light emitted from the light source enters the light guide plate through the light entrance surface that faces the light source and travels within the light guide plate and exits the light guide plate through the light exit surface. The light source generates heat according to the light emission. However, the heat from the light source is transmitted to the heat dissipation member via the light source board to be released.

The light source board is mounted on the heat dissipation member so that the two sides constituting one corner portion of the plate surface of the light source board are parallel to the respective two sides constituting one corner portion of the hole edge portion of the positioning hole. Thus, the light source board is mounted on the heat dissipation member so as to be positioned optimally with respect to the heat dissipation member in a direction along the plate surface of the light source board. Accordingly, a mounting error that may be caused between the light source board and the heat dissipation member is decreased and a positional error that may be caused between the light entrance surface and the light source with respect to a direction along the light entrance surface of the light guide plate is decreased. Therefore, the light entrance efficiency of light emitted from the light source and entering the light guide plate through the light entrance surface is improved and brightness unevenness is less likely to be caused in the exit light exiting the light guide plate through the light exit surface. Further, the positioning hole is through the heat dissipation member. Therefore, when the light source board is mounted on the heat dissipation member, the positional relation between the two sides constituting the corner portion of the hole edge portion of the positioning hole and the two sides constituting the corner portion of the plate surface of the light source board can be easily recognized according to light passing through the positioning hole. Accordingly, the light source board is positioned with high accuracy.

As described before, the heat dissipation member has the positioning hole that is therethrough, and the heat dissipation property is deteriorated locally in the portion of the heat dissipation member where the positioning hole is formed. On the light source board that is mounted on the heat dissipation member, the power feed relay portion is arranged on a portion of the light source board corresponding to the positioning hole. Therefore, the light source is arranged not to overlap the positioning hole and the heat generated from the light source can be released effectively via the heat dissipation member even with the positioning hole. The power feed relay portion causes a relatively small amount of heat generation compared to the light source. Therefore, even if the power feed relay portion is arranged to correspond to the positioning hole, the temperature of the light source board is less likely to be increased. Accordingly, the heat dissipation property of the light source is effectively ensured and a space for the power feed relay portion is allocated on the light source board.

The present technology may include following configurations.

(1) The light source board may include an identification portion on the plate surface that is opposed to the heat dissipation member, and the identification portion includes identification information relating to the light source board. The identification portion may be arranged in the positioning hole. The identification portion of the light source board is arranged in the positioning hole that is through the heat dissipation member and the identification portion can be seen through the positioning hole. With such a configuration, even after the light source board is mounted on the heat dissipation member, the identification information of the light source board can be obtained and it is effective for component management. The identification information includes information regarding, for example, a specification (brightness, light flux, chromaticity, chromaticity rank) of the light source board or the light source, a manufacturing number (a manufacturing number, a manufacturing lot number) of the light source board or the light source, a manufactured time of the light source board or the light source (manufactured year, manufactured month, manufactured date), or a manufactured place of the light source board or the light source.

(2) The two sides constituting the corner portion of the hole edge portion of the positioning hole may be positioned on the two sides of the plate surface of the light source board. Accordingly, if the two sides constituting the corner portion of the plate surface of the light source board are not positioned on the respective two sides constituting the corner portion of the hole edge portion of the positioning hole in mounting the light source board on the heat dissipation member, it is recognized that the light source board is not correctly positioned with respect to the heat dissipation member. Therefore, the light source board is positioned with higher accuracy and the light use efficiency is further improved and unevenness in brightness is less likely to be caused.

(3) The hole edge portion of the positioning hole may have a square shape having four corner portions, and three sides constituting off-diagonal two corner portions among the four corner portions may be parallel to three sides constituting off-diagonal two corner portions of the plate surface of the light source board, respectively. With such a configuration, the light source board is mounted on the heat dissipation member so that the three sides constituting off-diagonal two corner portions of plate surface of the light source board are parallel to the respective three sides constituting off-diagonal two corner portions of the hole edge portion of the positioning hole. Accordingly, the light source board is attached to the heat dissipation member with being positioned more effectively with respect to the heat dissipation member along the plate surface of the light source board. Accordingly, a mounting error that may be caused between the light source board and the heat dissipation member can be made smaller and the light entrance efficiency is further improved and unevenness in brightness is less likely to be caused in the exit light exiting the light guide plate through the light exit surface.

(4) One of the three sides constituting the two corner portions of the hole edge portions of the positioning hole may be away from the light source board with a clearance. With such a configuration, the position of the light source board is confirmed according to the determination whether the clearance between at least one of the three sides constituting the two corner portions of the hole edge portion of the positioning hole and the light source board has a constant width over an entire length thereof. Therefore, the position of the light source board is confirmed by using the light passing through the clearance, for example. Accordingly, the light source board is positioned with higher accuracy.

(5) Two of the three sides constituting the two corner portions of the hole edge portion of the positioning hole may be opposed to each other. One of the two sides may be away from the light source board with the clearance, and another one of the two sides may be positioned on one of the three sides constituting the two corner portions of the plate surface of the light source board. With such a configuration, when the light source board is mounted on the heat dissipation member, the light source board is positioned with respect to the heat dissipation member with higher accuracy in the following manner. The light source board is positioned to keep the clearance between one of the two opposed sides among the three sides constituting the two corner portions of the hole edge portion of the positioning hole and the light source board to have a constant width over an entire length thereof. Further, the light source board is positioned such that the other side is positioned on one of the three sides constituting the two corner portions of the plate surface of the light source board.

(6) The plate surface of the light source board may have a rectangular shape and have a short-side direction that matches a thickness direction of the light guide plate and a long-side direction that matches a direction perpendicular to the thickness direction of the light guide plate. The light source may include light sources that are arranged on the light source board along the long-side direction and each of the light sources may not overlap the positioning hole. With such a configuration, since the light sources are arranged on the light source board so as not to overlap the positioning hole, heat from the light sources are released substantially evenly via the heat dissipation member. Accordingly, the thermal environment around the light sources is stable and the light emission efficiency of each light source is equalized and the unevenness in brightness is further less likely to be caused.

(7) The light source board may include light source boards that are arranged linearly along the long-side direction and mounted on the heat dissipation member. With this configuration, the light source boards are positioned with respect to the heat dissipation member by the positioning hole and the light source boards are positioned with respect to each other. Accordingly, difference in the amount of rays of light emitted from each of the light sources mounted on the light source boards and entering the light guide plate through the light entrance surface is less likely to be caused and unevenness in brightness is further less likely to be caused.

(8) The power feed relay portion may be arranged on the light source board to be opposed to an end portion of the light guide plate. With this configuration, since no light source is arranged on the portion of the light source board where the power feed relay portion is arranged, dark portions having a smaller amount of incident light may be caused on opposed portions of the light entrance surface of the light guide plate. However, since the power feed relay portion is arranged on the portion of the light source board opposed to the end portion of the light guide plate, dark portions are less likely to be caused in the most part of the middle portion of the light guide plate. Accordingly, the unevenness in brightness is further less likely to be caused.

(9) The lighting device may further include a casing member. The casing member may include a light guide plate support portion configured to support a plate surface of the light guide plate opposite from the light exit surface, and a heat dissipation member mount portion where the heat dissipation member is mounted. With such a configuration, the plate surface that is an opposite surface from the light exit surface of the light guide plate is supported by the light guide plate support portion of the casing member and the heat dissipation member where the light source board is mounted is mounted on the heat dissipation member mount portion of the casing member. Accordingly, the light guide plate and the light source are maintained in the optimal positions via the casing member.

(10) The hole edge portion of the positioning hole may include at least two positioning pieces that are parallel to the respective two sides constituting the corner portion thereof and the positioning pieces may contact the light source board. Accordingly, at least two positioning pieces that are provided on the hole edge portion of the positioning hole are in contact with the light source board so that the light source board is positioned easily and precisely. This improves workability and the LED board118is positioned with higher accuracy.

Next, to solve the above problems, a display device according to the present technology includes the above lighting device and a display panel displaying with using light from the lighting device.

Such a display device includes the lighting device supplying light to the display panel has improved light use efficiency and less occurrence of unevenness in brightness, and therefore, the display having excellent display quality is achieved.

The display panel may be a liquid crystal panel. The display device as a liquid crystal display device has a variety of applications, such as a television display or a personal-computer display. In particular, it is suitable for a large screen display.

Advantageous Effect of the Invention

According to the technology disclosed herein, light usage efficiency is improved and unevenness in brightness is less likely to occur.

MODE FOR CARRYING OUT THE INVENTION

First Embodiment

A first embodiment will be described with reference toFIGS. 1 to 12. According to this embodiment, a liquid crystal display device10will be described. X-axis, Y-axis and Z-axis are indicated in some drawings. The axes in each drawing correspond to the respective axes in other drawings. An upper side inFIGS. 4 and 5corresponds to a front-surface side and a lower side inFIGS. 4 and 5corresponds to a rear-surface side.

As illustrated inFIG. 1, a television device TV according to this embodiment includes the liquid crystal display device10, front and rear cabinets Ca and Cb that hold the liquid crystal display device10therebetween, a power source P, a tuner T, and a stand S. An overall shape of the liquid crystal display device (a display device)10is landscape rectangular (longitudinal). The liquid crystal display device10is held in a vertical position. As illustrated inFIG. 2, the liquid crystal display device10includes a liquid crystal panel11as a display panel and a backlight unit (a lighting device)12as an external light source. The liquid crystal panel11and the backlight unit12are held with a bezel13having a frame-like shape.

As illustrated inFIG. 2, the liquid crystal panel has a landscape rectangular shape (rectangular and longitudinal) in a plan view and includes a pair of glass substrates and liquid crystals. The substrates having high light transmissivity are bonded together with a predetermined clearance therebetween. The liquid crystals are sealed between the substrates. On one of the substrates (an array substrate), switching components (e.g., TFTs), pixel electrodes, and an alignment film are arranged. The switching components are connected to source lines and gate lines that are perpendicular to each other. The pixel electrodes are connected to the switching components. On the other substrate (a CF substrate), a color filter, common electrodes, and an alignment film are arranged. The color filter has color sections such as R (red), G (green) and B (blue) color sections that are arranged in a predetermined pattern. The liquid crystal panel11includes a display area and a non-display area. The display area is an inner area of a screen in which images are displayed. The non-display area is an outer area of the screen around the display area and has a frame-like shape. Polarizing plates are arranged on outer sides of the substrates.

Next, the backlight unit12will be described in detail. As illustrated inFIG. 2, the backlight unit12includes a chassis (a casing member)14, optical members15, and a frame (a holding member)16. The chassis14having a substantially tray-like shape includes a light exit portion14cthat opens to the front side (a liquid crystal panel11side). The optical members15cover the light exit portion14cof the chassis14. The frame16holds down a light guide plate19, which will be described later, from the front side. LEDs (Light Emitting Diodes)17provided as light sources, an LED board (light source board)18on which the LEDs17are mounted, a heat dissipation member20to which the LED board18is attached, and a light guide plate19are arranged in the chassis14. The light guide plate19is configured to guide light from the LEDs17and directs the light toward the optical members15(the liquid crystal panel11, the light exit side). The LED board18is arranged at one of long-side end portions (on a front side inFIG. 2or a left side inFIG. 3) of the backlight unit12, and accordingly, the LEDs17mounted on the LED board18are located locally close to one of long-side end portions of the liquid crystal panel11. The backlight unit12according to this embodiment is so-called a single-edge-light type (or a side-light type) backlight. Hereinafter, components of the backlight unit12will be described in detail.

The chassis14is made of a metal plate having good heat conductivity such as an aluminum plate and an electrolytic zinc-coated steel sheet (SECC). As illustrated inFIGS. 2 to 4, the chassis14includes a bottom plate14ahaving a landscape rectangular shape similar to the liquid crystal panel11and side plates14bextending from an outer end of each side (a pair of long sides and a pair of short sides) of the bottom plate14a. A long-side direction and a short-side direction of the chassis14(the bottom plate14a) correspond to the X-axis direction (the horizontal direction) and the Y-axis direction (the vertical direction), respectively. Most part of the bottom plate14ais a light guide plate support portion14a1that supports the light guide plate19from a rear-surface side (an opposite side from the light exit surface19aside). An end part of the bottom plate14aon the LED board18side is a step portion14a2that projects to the rear-surface side to form a step. The step portion14a2and the side plate (a heat dissipation member mount portion)14bthat is continuously provided from an end of the step portion14a2constitute an LED container21where the LEDs17, the LED board18, and the heat dissipation member20are arranged. The bezel13is fixed to the side plate14bwith screws having the frame16in between.

As illustrated inFIG. 2, similar to the liquid crystal panel11and the chassis14, the optical members15have a landscape rectangular shape in a plan view. The optical members15are placed on a front surface (a light exit side surface) of the light guide plate19and located between the liquid crystal panel11and the light guide plate19. Light receives predetermined optical effects while passing through the optical members15and exits toward the liquid crystal panel11. The optical members15include multiple sheet-like members (three sheets in this embodiment) which are overlaid with each other. Each optical member15may be selected from a diffuser sheet, a lens sheet, and a reflecting type polarizing sheet, whatever is appropriate.

As illustrated inFIGS. 2 and 4, the frame16has a frame shape extending along outer edge portions of the light guide plate19and holds down substantially the entire edge portions of the light guide plate19from the front side. The frame16is made of synthetic resin. A front surface of the frame16may be in black so as to have light blocking properties. The frame16receives outer edge portions of the liquid crystal panel11from the rear-surface side.

As illustrated inFIGS. 2 and 4, each of the LEDs17includes an LED chip that is arranged on a board fixed on the LED board18and sealed with resin. The LED chip mounted on the board has one main light emission wavelength. Specifically, the LED chip that emits light in a single color of blue is used. The resin that reals the LED chip contains phosphors dispersed therein. The phosphors emit light in a predetermined color when excited by blue light emitted from the LED chip. Overall color of light emitted from the LED17is white. The phosphors may be selected, as appropriate, from yellow phosphors that emit yellow light, green phosphors that emit green light, and red phosphors that emit red light. The phosphors may be used in combination of the above phosphors. The LED17includes a main light-emitting surface17athat is opposite from a mount surface of the LED17on which the LED board18is mounted. Namely, the LED17is a top-surface-emitting type LED. Each LED includes the light-emitting surface17ahaving a landscape rectangular front view shape and an optical axis LA (a direction in which light having highest light emission intensity is directed) at substantially a center thereof. The optical axis LA is represented by a dashed-dotted line inFIG. 4.

As illustrated inFIGS. 2 to 4, the LED board18has an elongated plate-like shape extending in the long-side direction (the X-axis direction) of the chassis14and the light guide plate19. The LED board18is arranged in the LED container21of the chassis14such that plate surfaces of the LED board18are parallel to the X-Z plane, i.e., perpendicular to plate surfaces of the liquid crystal panel11and the light guide plate19(the optical members15). Namely, the long-side direction and the short-side direction of the LED board18correspond to the X-axis direction (a direction that is perpendicular to a plate thickness direction of the light guide plate19and parallel to the light entrance surface19b) and the Z-axis direction (a plate thickness direction of the light guide plate19), respectively. The LED board18is arranged such that a plate surface thereof (a mount surface18a) facing the inner side is opposed to one of the long side end surfaces (the light entrance surface19b) of the light guide plate19to have a certain clearance therebetween in the Y-axis direction. Therefore, the direction in which the LEDs17, the LED board18, and the light guide plate19are arranged substantially matches the Y-axis direction. The LED board18has a length dimension that is approximately a half of the long-side dimension of the light guide plate19. Two LED boards18are arranged to correspond to a heat dissipation member20, which will be described later. Namely, the two LED boards18are arranged linearly such that the long side direction of each LED board18matches each other (FIG. 3).

As illustrated inFIGS. 6,9, and10, the plate surface of the LED board18is a landscape rectangular front or rear view shape. The plate surface of the LED board18includes a pair of first sides18S1and a pair of second sides18S2. The first sides18S1constitute long sides parallel to the X-axis direction (the long-side direction of the light entrance surface19b) and the second sides18S2constitute short sides parallel to the Z-axis direction (the short-side direction of the light entrance surface19b). Each of four corner portions of the plate surface of the LED board18is formed by the respective first sides18S1and the respective second sides18S2that cross each other to forma right angle.

As illustrated inFIGS. 6 and 9, the LED board18includes a mount surface18aon which the LEDs17are surface-mounted. The mount surface18ais one of the plate surfaces that faces an inner side, namely, a surface of the LED board18that faces the light guide plate19(a surface opposite the light guide plate19). The LEDs17are arranged apart from each other in a line (i.e., linearly) on the mount surface18aof the LED board18along the long-side direction of the LED board18(the X-axis direction). In other words, multiple LEDs17are arranged at intervals in each of the long-side end portions of the backlight unit12along the long-side direction. A metal-film trace (not illustrated), such as a copper-foil trace, is formed on the mount surface18aof each LED board18. The metal-film trace extends in the X-axis direction and crosses over a group of the LEDs17so as to connect the adjacent LEDs17in series. Further, a board-side connector (a power feed relay portion)22that relays power feed to the LEDs17is mounted at an end portion of the trace on the mount surface of the LED board18. The LEDs17and the board-side connector22are mounted on only one plate surface of the LED board18and such an LED board18is an LED board of a one-side mounting type. The board-side connector22is arranged on one of two end portions of the length dimension of the LED board18, that is, a portion of the LED board18adjacent to an end portion of the long-side dimension of each of the chassis14and the light guide plate19. Therefore, each of the board-side connectors22that are arranged on the respective two LED boards18is arranged adjacent to each of the LED board18side two corners of the chassis14and the light guide plate19. The two board-side connectors22are arranged to be opposed to two end portions of the long-side dimension of the light guide plate19. The board-side connector22is a low-heat-generating member that causes a relatively small amount of heat generation according to current applying compared to the LED17. The LED17is a high-heat-generating member that causes a relatively treat amount of heat generation according to current applying. A substrate of the LED board18is made of metal similar to the chassis14and the trace (not illustrated), which is described before, is formed on the surface of the substrate having an insulation layer therebetween. An insulating material such as ceramics may be used as the material for the substrate of the LED board18.

A line-side connector24is arranged at an end of a relay line (a line member)23that is connected to an external LED drive circuit, which is not illustrated. As illustrated inFIG. 5, the line-side connector24is fitted to the board-side connector22from the front side along the Z-axis direction (a plate thickness direction of the light guide plate19) and connected to the board-side connector22. The board-side connector22has a recessed shape and the line-side connector24has a convex shape. The board-side connector22and the line-side connector24are fitted to each other to establish electric connection. Accordingly, the driving power is supplied from the external LED drive circuit to each LED17on the LED board18.

As illustrated inFIG. 10, an identification portion25including identification information of each LED board18is provided on an outer side surface of the LED board18, that is, a plate surface (a surface opposed to a heat dissipation member20) facing an opposite side from the light guide plate19side (a heat dissipation member20side). The identification portion25includes a film-shaped base member and a bar code25aprinted thereon and the identification portion25is bonded to a plate surface of the LED board18with an adhesive that is coated over a bonding surface of the base member that faces the LED board18. The bar code25aincludes identification information of each LED board18. The identification information includes information relating to, for example, a specification (brightness, light flux, chromaticity, chromaticity rank) of each LED board18or each LED17, a manufacturing number (a manufacturing number, a manufacturing lot number) of each LED board18or each LED17, a manufactured time of each LED board18or each LED17(manufactured year, manufactured month, manufactured date), or a manufactured place of each LED board18or each LED17. The identification portion25is provided on one of two end portions of the length dimension of the LED board18, that is, provided adjacent to an end portion of the long-side dimension of each of the chassis14and the light guide plate19. Therefore, the two identification portions25provided on the respective two LED boards18are arranged adjacent to two LED-board18-side corners of the chassis14and the light guide plate19. Each identification portion25is arranged to overlap each board-side connector22seen from the front side or the rear side. In other words, the identification portion25is arranged to hold the LED board18with the board-side connector22from two sides with respect to a plate thickness direction.

The light guide plate19is made of substantially transparent (high transmissivity) synthetic resin (e.g. acrylic resin or polycarbonate such as PMMA) that has a refractive index sufficiently higher than that of the air. As illustrated inFIGS. 2 and 3, the light guide plate19has a landscape rectangular shape in a plan view similar to the liquid crystal panel11and the bottom plate14aof the chassis14. A main surface of the light guide plate19faces and is parallel to each plate surface of the liquid crystal panel11and the optical member15. A long-side direction and a short-side direction of the main surface of the light guide plate19correspond to the X-axis direction and the Y-axis direction, respectively. A thickness direction of the light guide plate19that is perpendicular to the main surface of the light guide plate19corresponds to the Z-axis direction. As illustrated inFIG. 4, the light guide plate19is arranged on a rear-surface side of the liquid crystal panel11the optical member15within the chassis14. One of long-side end surfaces of the outer peripheral surface of the light guide plate19(a lower side surface inFIG. 3, a left side surface inFIG. 4) is opposed to the LED board18that is arranged in one long-side end portion of the chassis14and the LEDs17mounted thereon. Therefore, a direction in which the LEDs17(the LED board18) and the light guide plate19are arranged matches the Y-axis direction (the vertical direction) and a direction in which the optical member15(the liquid crystal panel11) and the light guide plate19are arranged matches the Z-axis direction, and the directions are perpendicular to each other. The light guide plate19is configured to guide the light, which is emitted from the LEDs17and directed along the Y-axis direction and enters the light guide plate19through the long-side end surface, toward the optical member15(the front side, the light exit side) and exits the light guide plate19through the main surface.

As illustrated inFIG. 4, the light guide plate19has plate surfaces one of which faces the front side (a surface opposite the liquid crystal panel11and the optical member15) and is a light exit surface19a. Light exits the light guide plate19through the light exit surface19atoward the optical member15and the liquid crystal panel11. The light guide plate19includes outer peripheral end surfaces that are adjacent to the plate surfaces of the light guide plate19and the outer peripheral end surfaces include two long-side end surfaces thereof each extend in the X-axis direction (the direction in which the LEDs17are arranged, the long-side direction of the LED board18). One of the long-side end surfaces on a left side inFIG. 4(on a lower side inFIG. 3) is opposite the LEDs17(the LED boards18) with a predetermined space therebetween and serves as a light entrance surface19bthrough which light from the LEDs17enters the light guide plate19. The light entrance surface19bis parallel to the main surface of the LED board18(the X-Z plane) and substantially perpendicular to the light exit surface19a. The light guide plate19includes recesses19dat respective end portions of the length dimension of the light entrance surface19b(in the X-axis direction). The board-side connector22on each LED board18that is opposed to the light entrance surface19bis fitted to the recess19d. An arrangement direction in which the LEDs17and the light entrance surface19bare arranged matches the Y-axis direction and parallel to the light exit surface19a.

As illustrated inFIG. 4, a reflection sheet R is arranged on one of the plate surfaces of the light guide plate19, that is, a plate surface19copposite to the light exit surface19aso as to cover an entire area of the plate surface. Light that travels within the light guide plate19is reflected by the reflection sheet R to be directed toward the front side. The reflection sheet R is arranged between a light guide plate support portion14a1of the bottom plate14aincluded in the chassis14and the light guide plate19. The light guide plate19is supported by the light guide plate support portion14a1of the chassis from the rear-surface side with the reflection sheet R therebetween. The reflection sheet R is arranged such that an end thereof on a side of the light entrance surface19bof the light guide plate protrudes outwardly than the light entrance surface19b, that is, closer to the LEDs17and light that travels from the LEDs17is reflected by the protruded portion. Accordingly, light entrance efficiency of light entering the light guide plate19through the light entrance surface19bis improved. A scattering portion (not illustrated) is patterned on one of the light exit surface19aand the opposite plate surface19cof the light guide plate19or a surface of the reflection sheet R so as to have a predetermined plane distribution. The scattering portion scatters light within the light guide plate19. Accordingly, the light exiting the light guide plate19through the light exit surface19ahas an even distribution within a plane.

As illustrated inFIGS. 3 and 6, similar to the LED board18, the heat dissipation member20has a rectangular plate-like shape extending along the long-side direction (the X-axis direction) of the chassis14and the light guide plate19. The heat dissipation member20is arranged in the LED container21included in the chassis14such that a plate surface thereof is parallel to the plate surface of the LED board18. A long-side direction, a short-side direction, and a thickness direction of the heat dissipation member20correspond to the X-axis direction (a direction that is perpendicular to the plate thickness direction of the light guide plate19and parallel to the light entrance surface19b), the Z-axis direction (the plate thickness direction of the light guide plate19), and the Y-axis direction (the direction in which the LEDs17and the light guide plate19are arranged), respectively. The thickness direction is perpendicular to the plate surface of the heat dissipation member20. The heat dissipation member20has a length dimension (a long-side dimension) that is substantially equal to the long-side dimension of the light guide plate19and is approximately twice as the length dimension of the LED board18. The heat dissipation member20has a width dimension (a short-side dimension) that is greater than the width dimension of the LED board18and is substantially equal to a height dimension of the side plate14bincluded in the LED container21.

As illustrated inFIGS. 3 and 7, two LED boards18are arranged linearly in the X-axis direction on the plate surface of the heat dissipation member20facing an inner side (the light guide plate19side). The plate surface of the heat dissipation member20facing an outer side (the opposite side from the light guide plate19side) is attached to the side plate14bincluded in the LED container21of the chassis14. Namely, the heat dissipation member20is sandwiched between the LED boards18and the side plate14bof the LED container21and in contact with both of them. The heat dissipation member20is made of metal having high thermal conductivity, such as aluminum. If heat generated by the LEDs17according to the current applying is transferred to the heat dissipation member20via the LED board18, the heat dissipation member20dissipates the heat from a surface thereof and transfers the heat to the side plate14bof the chassis so that the heat from the LEDs17is effectively released. Accordingly, high light emission efficiency of the LEDs17is maintained and the LED17has a long life-span. The heat dissipation member20is closely fixed to the side plate14bof the chassis14with mounting means such as an adhesive, a double-sided tape, or screws.

According to the present embodiment, as illustrated inFIGS. 6,7, and11, the heat dissipation member20has positioning through holes26with which the LED board18is positioned with respect to the plate surface direction thereof. The heat dissipation member20has two positioning holes26at respective two end portions of the length dimension thereof (the X-axis direction). Namely, the number of the positioning holes26is same as the number of the LED boards18and each of the LED boards18is positioned independently from each other. Each of the positioning holes26is located to correspond to a part of each LED board18seen from a front side or a rear side. When mounting the LED board18on the heat dissipation member20, an operator recognizes the mounting position of each LED board18based on positional relation between the sides18S1,18S2of each LED board18.

Specifically, as illustrated inFIGS. 3,6, and7, the heat dissipation member20has the positioning holes26in the two end portions of the length dimension thereof, that is, in the portions opposed to the respective two end portions of the length dimension of the light guide plate19. Each of the positioning holes26overlaps the end portion of each LED board18with a front view or a side view. As illustrated inFIGS. 7 and 11, the positioning hole26has a substantially quadrate shape with a front view or a rear view and has four corner portions. The heat dissipation member20has a hole edge portion around the positioning hole26and the hole edge portion includes a pair of first sides26s1that are parallel to the X-axis direction (the long-side direction of the heat dissipation member20and the LED board18) and a pair of second sides26S2that are parallel to the Z-axis direction (the short-side direction of the heat dissipation member20and the LED board18). Each of the four corner portions included in the hole edge portion of the positioning hole26is formed by the first side26S1and the second side26S2crossing each other and forms a substantially right angle. Therefore, the first sides26S1of the hole edge portion of the positioning hole26are parallel to the respective first sides18S1of the LED board18and the second sides26S2of the hole edge portion are parallel to the respective second sides18S2of the LED board18.

As illustrated inFIG. 7, when the LED board18is attached to the heat dissipation member20, the LED board18is correctly positioned in a correct position with respect to the heat dissipation member20in the Z-axis direction so that a rear-surface side one of the first sides26S1of the hole edge portion of the positioning hole26is positioned on and overlaps a rear-surface side one of the first sides18S1of the LED board18(so that light does not leak from a clearance between the first sides18S1,26S1on the rear-surface side). Accordingly, the optical axis LA of light from each LED17corresponds to a middle position of the light guide plate19with respect to the plate thickness direction. Therefore, light entrance efficiency of light emitted from each LED17and entering the light guide plate19bthrough the light entrance surface19bbecomes optimal. On the other hand, when the LED board18is attached to the heat dissipation member20, the LED board18is correctly positioned in a correct position with respect to the heat dissipation member20in the X-axis direction so that one of the second sides26S2of the hole edge portion of the positioning hole26closer to an end of the heat dissipation member20is positioned on and overlaps one of the second sides1852closer to an end of the heat dissipation member20(on an end opposite to the adjacent LED board18side) (so that light does not leak from a clearance between the second sides18S2,26S2). With the above configuration, the LEDs17that are arranged on end portions of the respective LED boards18and in a middle portion of the light guide plate19(the LEDs17that are mounted on different LED boards18and adjacent to each other) are arranged with a distance therebetween and the distance is substantially equal to each interval between other LEDs17. Accordingly, the amount of the light exiting the middle portion of the long-side dimension of the light guide plate19is less likely to be excessive or too small compared to the amount of the light exiting other portions of the light guide plate19. Further, with the above configuration, on each of the LED boards18, the board-side connector22and the LED17that is adjacent to the board-side connector22are positioned with respect to the end portions of the light guide plate19in the X-axis direction. Therefore, brightness unevenness is less likely to be caused in the end portions of the long-side dimension of the light guide plate19.

As illustrated inFIG. 7, the length of each of the sides26S2of the hole edge portion of the positioning hole26is slightly greater than a width dimension of the LED board18and the length of each of the sides26S1is slightly smaller than a long-side dimension of the board-side connector21. With such a configuration, when the rear-surface side first side18S1of the LED board18is positioned on and overlaps the rear-surface side first side26S1of the hole edge portion of the positioning hole26, the front-surface side first side26S1of the hole edge portion and the front-surface side first side18S1of the LED board18are parallel to each other and have a certain clearance C therebetween. The clearance C constitutes a slit having a constant width over its entire length if the LED board18is positioned correctly without being tilted with respect to the positioning hole26. Therefore, an operator can recognize the mount position of the LED board18with high accuracy based on the light passing through the clearance C. As described before, an end portion of the plate surface of the LED board18has three sides18S1,18S2that form two corner portions that are off-diagonal, and the hole edge portion of the positioning hole26has three sides26S1,26S2that form two corner portions that are off-diagonal and adjacent to the end of the heat dissipation member20. Based on the positional relation between the three sides18S1,18S2and the three sides26S1,26S2, the operator can easily see whether the mounting position of the LED board18with respect to the light entrance surface20is optimal.

As illustrated inFIG. 7, the positioning hole26with the above configuration is provided to overlap the board-side connector22over its entire area with a front view or a rear view. The board-side connector22is provided on one end portion of the length dimension of the LED board18. Therefore, all of the LEDs17mounted on the LED board18do not overlap the positioning hole26with a front view or a rear view. In other words, the board-side connector22overlaps the positioning hole26with respect to the X-axis direction and all the LEDs17are offset from the positioning hole26and do not overlap the positioning hole26with respect to the X-axis direction. The heat dissipation member20has the positioning hole26therethrough and a heat dissipation property is likely to be deteriorated locally in the portion having the positioning hole26. If the LED is arranged to overlap the positioning hole26, heat from the overlapped LED is less likely to be dissipated. This may reduce the heat dissipation efficiency of the whole LED board. Further, difference in temperature of the overlapped LED and temperature of other non-overlapped LEDs is caused and this may cause difference in the chromaticity of the emission light and the emission light amount. With the above configuration including the positioning holes26, heat from each LED17is effectively dissipated. More in detail, heat generated form each LED17according to current applying is transferred evenly to the heat dissipation member20via the LED board18. The LED board18effectively dissipates the heat as a whole and difference in temperatures of the LEDs17is less likely to be caused. Accordingly, the chromaticity of light emitted from each LED17and the amount of light emitted from each LED17are averaged and brightness unevenness or color unevenness is less likely to be caused. The board-side connector22is a low-heat-generating member that causes a relatively small amount of heat generation compared to the LED17. Therefore, even if the board-side connector22is arranged to overlap the positioning hole26, a temperature of the LED board18is less likely to be increased.

As illustrated inFIG. 8, the identification portion25provided on the plate surface of the LED board18facing the outer side is located in the positioning hole26and surrounded by the sides26S1,26S2of the hole edge portion. Therefore, when the heat dissipation member20with the LED board18attached thereto is seen from the rear side, the bar code25aprinted on the identification portion25can be seen through the positioning hole26. Accordingly, the LED board18where the heat dissipation member20is attached is effective for easy management.

The configuration is described and operations will be described next. If the power of the liquid crystal display device10with the above configuration is turned on, driving of the liquid crystal panel11is controlled by a control circuit, which is not illustrated, and driving power is supplied from an LED drive circuit, which is not illustrated, to each of the LEDs17on the LED board18to control the driving. The light emitted from each LED17is guided by the light guide plate19to be irradiated to the liquid crystal panel11via the optical member15, and thus a certain image is displayed on the liquid crystal panel11. Hereinafter, operations of the backlight device12will be described in detail.

If each LED17is lit on, the light emitted from each LED17enters the light guide plate19through the light entrance surface19b, as illustrated inFIG. 4. A certain space is provided between the LEDs17and the light entrance surface19band the space is covered with an extended portion of the reflection sheet R from the rear-surface side. Therefore, the light emitted from the LED17reflects off the extended portion to be directed toward the light entrance surface19b. Accordingly, the light entrance efficiency of light entering the light guide plate19through the light entrance surface19bis improved. The light entering the light guide plate19through the light entrance surface19bis fully reflected at a boundary face between the light guide plate19and an external air layer or reflected by the reflection sheet R and travels within the light guide plate19and is reflected with scattered by a scattering portion. Accordingly, the light has the angles of incidence with respect to the light exit surface19awhich do not exceed the critical angle and the exiting of light from the light guide plate19through the light exit surface19ais accelerated.

The light entrance efficiency of light emitted from the LED17and entering the light guide plate19through the light entrance surface19band the brightness distribution of light exiting the light guide plate19through the light exit surface19avary according to the positional relation between the light entrance surface19bof the light guide plate19and the LEDs17. Specifically, if the optical axis LA of light from the LED17matches a middle position of the plate-thickness dimension of the light guide plate19(in the Z-axis direction), the light from the LED17enters the light guide plate19through the light entrance surface19bmost effectively (the light entrance efficiency is maximized). If the optical axis does not match the middle position and is positioned closer to the front-surface side or the rear-surface side with respect to the Z-axis direction, the light entrance efficiency is likely to be lowered as the offset amount becomes greater. Especially, as the plate thickness of the light guide plate19becomes smaller, the variation amount of the light entrance efficiency with respect to the offset amount is increased and high positional accuracy is likely to be required. On the other hand, among the LEDs17that are arranged on each LED board18, if the two LEDs17that are arranged on the respective end portions of each LED board18are located to have a substantially equal distance from the respective two end portions of the long-side dimension of the light entrance surface19b, the emission light is even within a plane of the light exit surface19aof the light guide plate19. If the two LEDs17are located with different distances from the respective two end portions of the light entrance surface19b, the amount of exit light from the light guide plate19through one of the two end portions of the long-side dimension of the light exit surface19amay be excessive or too small and this may cause unevenness in the exit light. Further, if the distance with respect to the X-axis direction between the adjacent LEDs17that are mounted on the respective different LED boards18is substantially equal to each interval between other LEDs17, exit light becomes even within a plane of the light exit surface of the light guide plate19. If the distance is different from the interval, the amount of exit light from the light guide plate19through the middle portion of the long-side dimension of the light exit surface19amay be excessive or too small and this may cause unevenness in the exit light.

According to the present embodiment, when the LED board18is attached to the heat dissipation member20in the manufacturing process, the LED board18is attached in a correct position with reference to the positioning hole26that is through the heat dissipation member20. Therefore, a mounting error that may be caused between the LED board18and the heat dissipation member20is possibly decreased. Accordingly, the positional error that may be caused between the light entrance surface19band the LEDs17in a direction along the light entrance surface19bof the light guide plate19is less likely to be caused. This improves light entrance efficiency of light emitted from LED17and entering the light guide plate19through the light entrance surface19band brightness unevenness is less likely to be caused in the exit light exiting the light guide plate19through the light exit surface19a.

In the mounting operation, when a plate surface of the LED board18facing an outer side is attached to a plate surface of the heat dissipation member20facing an inner side, the LED board18is positioned with respect to the positioning hole26as follows. As illustrated inFIG. 6, the end portion of the plate surface of the LED board18has three sides18S1,18S2that form two corner portions that are off-diagonal, and the hole edge portion of the positioning hole26has three sides26S1,26S2that form two corner portions that are off-diagonal and adjacent to the end of the heat dissipation member20. The three sides18S1,18S2are parallel to the respective three sides26S1,26S2. More specifically, for example, if the position of the LED board18is shifted diagonally downward right with respect to the positioning hole26, as illustrated in the left portion inFIG. 12, the LED board18is moved diagonally upward left so that the rear-surface side first side18S1of the plate surface of the LED board18is positioned on and overlaps the rear-surface side first side26S1of the hole edge portion of the positioning hole26and the left-side second side18S2of the plate surface of the LED board18is positioned on and overlaps the left-side second side26S2of the hole edge portion of the positioning hole26. If a slight positional error is caused when the sides18S1,18S2are positioned on the sides26S1,26S2, respectively, light leaks through the positioning hole26. Therefore, the positional error is easily found. Accordingly, the sides18S1,18S2and the sides26S1,26S2are positioned with respect to each other with high positioning accuracy. Further, it is confirmed whether the clearance C between the front-surface side first side18S1of the plate surface of the LED board18and the front-surface side first side18S1of the hole edge portion of the positioning hole26has a constant width over an entire length thereof. If the width of the clearance C is not constant, it is easily recognized that the width of the clearance C is not constant based on the light leaking through the clearance C and the positioning accuracy is improved. Accordingly, as illustrated by a dashed two-dotted line inFIG. 12, the LED board18is positioned in the correct position with respect to the heat dissipation member20with high accuracy. If the LED board18is shifted diagonally upward right with respect to the positioning hole26as illustrated in the right portion inFIG. 12, the LED board18is moved diagonally downward left inFIG. 12so that the side18S1is positioned on and overlaps the side26S1and the side18S2is positioned on and overlaps the side26S2. Accordingly, the LED board18is positioned in the correct position with respect to the heat dissipation member26.

The LED board18is positioned with respect to the heat dissipation member20, as described above. Accordingly, the optical axis LA of light from the LED17corresponds to the middle position of the plate thickness dimension of the light entrance surface19b(in the Z-axis direction), as illustrated inFIG. 4. Further, as illustrated inFIG. 3, the LEDs17are arranged in the X-axis direction, and two LEDs17that are arranged at two ends are spaced from the respective two end portions of the long-side dimension of the light entrance surface19bwith a substantially equal distance. Further, the distance between the adjacent LEDs17each of which is mounted on a different LED board18is substantially equal to the interval between other LEDs17. Accordingly, the light entrance efficiency of light emitted from each LED17and entering the light guide plate19through the light entrance surface19is maximized and unevenness in brightness is less likely to be caused in the exit light within a surface plane of the light exit surface19a. Therefore, display quality of images displayed on the liquid crystal panel11is improved. Further, the two LED boards18are positioned independently from each other by the corresponding positioning hole26. Therefore, a positional error is less likely to be caused between the adjacent LED boards18with respect to the X-axis direction and the Z-axis direction.

If each LED17is lit on to use the liquid crystal display device10, heat is generated from each LED17. The heat generated from each LED17is transferred to the heat dissipation member20via the LED board18. The heat dissipation member20dissipates the heat therefrom and transfers the heat to the side plate14bto effectively release the heat. The heat dissipation member20has the positioning hole26therethrough and a heat dissipation property is likely to be deteriorated locally in the portion having the positioning hole26. The LED board18is attached to the heat dissipation member20so that the board-side connector22overlaps the positioning hole26and all the LEDs17do not overlap the positioning hole26. Therefore, the heat from each LED17is effectively released by the heat dissipation member20even with the positioning holes26. Further, since all the LEDs17do not overlap the positioning hole26, difference in temperatures of the LEDS is less likely to be caused and the chromaticity of the emission light and the emission light amount from each LED17are maintained to be even. Accordingly, brightness unevenness or color unevenness is less likely to be caused in the exit light exiting from the light guide plate19through the light exit surface19a. This further improves display quality of images displayed on the liquid crystal panel11.

As is described before, according to the present embodiment, the backlight device (the lighting device)12includes the LED (light source)17, the light guide plate19, the LED board (light source board)18, the board-side connector (power feed relay portion)22, and the heat dissipation member20. The light guide plate19includes the light entrance surface19bon an end surface thereof and includes the light exit surface19aon a plate surface thereof. The light entrance surface19bis opposed to the LEDs17and light from the LEDs17enters the light guide plate19via the light entrance surface19b. The light exits the light guide plate19through the light exit surface19a. The LEDs17are arranged on the LED board18and the LED board18has a square plate surface that is opposed to the light entrance surface19b. The board-side connector22is mounted on the LED board18and relays power feed to the LEDs17. The LED boards18aare amounted on the heat dissipation member20and the heat dissipation member20dissipates the heat from the LEDs17. The heat dissipation member20has the positioning holes26that are through the heat dissipation member20and with which the LED board18is positioned with respect to the heat dissipation member20. The hole edge portion around the positioning hole26has at least one corner portion that is formed by the two sides26S1,26S2. The heat dissipation member20is arranged so that the sides26S1,26S2are parallel to the respective two sides18S1,18S2that form one corner portion of the plate surface of the LED board18and so that the positioning hole26corresponds to the board-side connector22.

With such a configuration, the LED17mounted on the LED board18emits light with the power feed relayed by the board-side connector22. The light emitted from the LED17enters the light guide plate19through the light entrance surface19bthat faces the LED17and travels within the light guide plate19and exits the light guide plate19through the light exit surface19a. The LED17generates heat according to the light emission. However, the heat from the LED17is transmitted to the heat dissipation member20via the LED board18to be released.

The LED board18is attached to the heat dissipation member20so that the two sides18S1,18S2that form one corner portion of the plate surface of the LED board18are parallel to the respective two sides26S1,26S2that form one corner portion of the hole edge portion of the positioning hole26. Thus, the LED board18is attached to the heat dissipation member20so as to be positioned optimally with respect to the heat dissipation member20in a direction along the plate surface of the LED board18. Accordingly, a mounting error that may be caused between the LED board18and the heat dissipation member20is decreased and a positional error that may be caused between the light entrance surface19band the LEDs17with respect to a direction along the light entrance surface19bof the light guide plate19is decreased. Therefore, the light entrance efficiency of light emitted from the LED17and entering the light guide plate19through the light entrance surface19bis improved and brightness unevenness is less likely to be caused in the exit light exiting the light guide plate19through the light exit surface19a. Further, the positioning hole26is through the heat dissipation member20. Therefore, when the LED board18is attached to the heat dissipation member20, the positional relation between the two sides26S1,26S2that form the corner portion of the hole edge portion of the positioning hole26and the two sides18S1,18S2that form the corner portion of the plate surface of the LED board18can be easily recognized according to light passing through the positioning hole26. Accordingly, the LED board18is positioned with high accuracy.

As described before, the heat dissipation member20has the positioning hole26being therethrough, and the heat dissipation property is deteriorated locally in the portion of the heat dissipation member20where the positioning hole is formed. On the LED board18that is attached to the heat dissipation member20, the board-side connector22is arranged on a portion of the LED board18corresponding to the positioning hole26. Therefore, the LEDs17are arranged not to overlap the positioning hole26and the heat generated from the LEDs17can be released effectively via the heat dissipation member20even having the positioning holes26. The board-side connector22causes a relatively small amount of heat generation compared to the LED17. Therefore, even if the board-side connector22is arranged to correspond to the positioning hole26, the temperature of the LED board18is less likely to be increased. Accordingly, the heat dissipation property of the LED17is effectively ensured and a space for the board-side connector22is allocated on the LED board18.

The LED board18has the identification portion25including identification information of each LED board18on the plate surface thereof facing the heat dissipation member20side. The identification portion25is arranged in the positioning hole26. The identification portion25of the LED board18is arranged in the positioning hole26that is through the heat dissipation member20and the identification portion25can be seen through the positioning hole26. With such a configuration, even after the LED board18is attached to the heat dissipation member20, the identification information of the LED board18can be obtained and it is effective for component management. The identification information includes information regarding, for example, a specification (brightness, light flux, chromaticity, chromaticity rank) of each LED board18or each LED17, a manufacturing number (a manufacturing number, a manufacturing lot number) of each LED board18or each LED17, a manufactured time of each LED board18or each LED17(manufactured year, manufactured month, manufactured date), or a manufactured place of each LED board18or each LED17.

The two sides26S1,26S2that form the corner portion of the hole edge portion of the positioning hole26are positioned on and overlap the respective two sides18S1,18S2that form the corner portion of the plate surface of the LED board18. Accordingly, if the two sides18S1,18S2that form the corner portion of the plate surface of the LED board18are not positioned on the respective two sides26S1,26S2that form the corner portion of the hole edge portion of the positioning hole26in attaching the LED board18to the heat dissipation member20, it is recognized that the LED board18is not correctly positioned with respect to the heat dissipation member20. Therefore, the LED board18is positioned with higher accuracy and the light use efficiency is further improved and unevenness in brightness is less likely to be caused.

The hole edge portion of the positioning hole26has a square shape having four corner portions. The positioning hole26has three sides26S1,26S2forming off-diagonal two corner portions and the LED board18has three sides18S1,18S2forming off-diagonal two corner portions, and the three sides18S1,18S2are parallel to the respective three sides26S1,26S2. Thus, the LED board18is attached to the heat dissipation member20so that the three sides18S1,18S2forming off-diagonal two corner portions of plate surface of the LED board18are parallel to the respective three sides26S1,26S2forming off-diagonal two corner portions of the hole edge portion of the positioning hole26. Accordingly, the LED board18is attached to the heat dissipation member20with being positioned more effectively with respect to the heat dissipation member20along the plate surface of the LED board18. Accordingly, a mounting error that may be caused between the LED board18and the heat dissipation member20can be made smaller and the light entrance efficiency is further improved and unevenness in brightness is less likely to be caused in the exit light exiting the light guide plate19through the light exit surface19a.

The positioning hole26is formed to have the clearance C between at least one side26S1of the three sides26S1,26S2that form the two corner portions of the hole edge portion and the LED board18. With such a configuration, the position of the LED board18is confirmed according to the determination whether the clearance C between at least one side26S1of the three sides26S1,26S2that form the two corner portions of the hole edge portion of the positioning hole26and the LED board18has a constant width over an entire length thereof. Therefore, the position of the LED board18is confirmed by using the light passing through the clearance, for example. Accordingly, the LED board18is positioned with higher accuracy.

The positioning hole26is formed to have the clearance C between the LED board18and one side26S1of the opposed two sides26S1among the three sides26S1,26S2that form the two corner portions of the hole edge portion. Further, the other side26S1is positioned on and overlaps the one side18S1of the three sides18S1,18S2that form the two corner portions of the plate surface of the LED board18. With such a configuration, when the LED board18is attached to the heat dissipation member20, the LED board18is positioned with respect to the heat dissipation member20with higher accuracy in the following manner. The LED board18is positioned to keep the clearance C between one side26S1of the two opposed sides26S1among the three sides26S1,26S2that form the two corner portions of the hole edge portion of the positioning hole26and the LED board18to have a constant width over an entire length thereof. Further, the LED board18is positioned such that the other side26S1is positioned on and overlaps one side18S1among the three sides18S1,18S2that form the two corner portions of the plate surface of the LED board18.

The LED board18has a rectangular plate surface and the short-side direction thereof matches the plate thickness direction of the light guide plate19and the long-side direction thereof is orthogonal to the plate thickness direction of the light guide plate19. The LEDs17are arranged on the LED board18along the long-side direction so as not to overlap the positioning holes26. With such a configuration, since the LEDs17are arranged on the LED board18so as not to overlap the positioning holes26, heat from the LEDs17are released substantially evenly via the heat dissipation member20. Accordingly, the thermal environment around the LEDs17is stable and the light emission efficiency of each LED17is equalized and the unevenness in brightness is further less likely to be caused.

The LED boards18are attached to the heat dissipation member20so as to be linearly arranged along the long-side direction. With this configuration, the LED boards18are positioned with respect to the heat dissipation member20by the positioning holes26and the LED boards18are positioned with respect to each other. Accordingly, difference in the amount of rays of light emitted from each of the LEDs17mounted on the LED boards18and entering the light guide plate19through the light entrance surface19bis less likely to be caused and unevenness in brightness is further less likely to be caused.

The board-side connector22is arranged on a portion of the LED board18opposed to each end portion of the light guide plate10. With this configuration, since no LED17is arranged on the portions of the LED boards18where the board-side connectors22are arranged, dark portions having a smaller amount of incident light may be caused on opposed portions of the light entrance surface19bof the light guide plate19. However, since the board-side connectors22are arranged on the respective portions of the LED boards18opposed to the end portions of the light guide plate19, dark portions are less likely to be caused in the most part of the middle portion of the light guide plate19. Accordingly, the unevenness in brightness is further less likely to be caused.

The chassis (a casing member)14includes the light guide plate support portion14a1and the side plate (dissipation member mount portion)14b. The light guide plate support portion14a1supports the plate surface19cthat is an opposite surface from the light exit surface19aof the light guide plate19. The heat dissipation member20is attached to the sideplate14b. With such a configuration, the plate surface19cthat is an opposite surface from the light exit surface19aof the light guide plate19is supported by the light guide plate support portion14a1of the chassis14and the heat dissipation member20where the LED boards18are attached is mounted on the side plate14bof the chassis14. Accordingly, the light guide plate19and the LEDs17are maintained in the optimal positions via the chassis14.

Second Embodiment

A second embodiment will be described with reference toFIGS. 13 to 15. In the second embodiment, a positioning piece27is provided on the hole edge portion of a positioning hole126in a heat dissipation member120. The constructions, functions, and effects similar to those of the first embodiment will not be described.

According to the present embodiment, as illustrated inFIGS. 13 and 14, the heat dissipation member120integrally includes the positioning piece27at a hole edge portion of the positioning hole126. The positioning piece27is directly in contact with a LED board118to position the LED board118. The positioning piece27is provided on each of a first side126S1and a second side126s2that form a corner portion of the hole edge portion of the positioning hole126and a total of two positioning pieces27are provided. Specifically, one of the two positioning pieces27projects and is curved from the rear-surface side first side126S1of the hole edge portion of the positioning hole126toward a LED board118. An inner surface of the positioning piece27facing inside of the positioning hole126is parallel to the first side126S1(the X-axis direction). The other one of the positioning pieces27projects and is curved from the second side126S2of the hole edge portion of the positioning hole126toward the LED board118. The second side126S2is located on a side closer to the heat dissipation member120. An inner surface of the other positioning piece27facing the inside of the positioning hole126is parallel to the second side126S2(the Z-axis direction).

As illustrated inFIG. 15, when the LED board118is attached to the heat dissipation member120, the positioning-hole126side second side118S2of the plate surface of the LED board118is set to be in contact with the inner surface of the one positioning piece27and the rear-surface side first side118S1of the plate surface of the LED board118is set to be in contact with the inner surface of the other positioning piece27. Accordingly, each first side118S1and each second side118S2of the plate surface of the LED board118are parallel to each first side126S1and each second side126S2of the hole edge portion of the positioning hole126, respectively. Further, the LED board118is positioned with respect to the heat dissipation member120along the plate surface thereof with high accuracy.

As described before, according to the present embodiment, at least two positioning pieces27are provided on the hole edge portion of the positioning hole126so as to be parallel to the two sides126S1,12652that form the corner portion, respectively. The positioning pieces27are in contact with the LED board118. Accordingly, at least two positioning pieces27that are provided on the hole edge portion of the positioning hole126are in contact with the LED board118so that the LED board118is positioned easily and precisely. This improves workability and the LED board118is positioned with higher accuracy.

Third Embodiment

A third embodiment will be described with reference toFIG. 16. In the third embodiment, two clearances C1, C2are provided between a positioning hole226and a LED board218. The constructions, functions, and effects similar to those of the first embodiment will not be described.

According to the present embodiment, as illustrated inFIG. 16, the positioning hole226has the clearances C1, C2between two first sides226S1of the hole edge portion and two first sides218S1of the plate surface of the LED board218, respectively. The positioning hole226has a Z-axis dimension opening width greater than the one of the positioning hole according to the first embodiment, and each of the clearances C1, C2between the positioning hole226and the LED board218has an equal width. With such a configuration, the LED board218is attached to a heat dissipation member220so that each of the first sides226S1of the plate surface of the LED board218is set to be parallel to each of the first sides226S1of the hole edge portion of the positioning hole226and the two clearances C1, C2has an equal width. Accordingly, the LED board218is positioned with respect to the heat dissipation member220in the Z-axis direction with high accuracy.

Fourth Embodiment

A fourth embodiment will be described with reference toFIG. 17. In the fourth embodiment, unlike the third embodiment, no clearance is provided between a positioning hole326and a LED board318. The constructions, functions, and effects similar to those of the first embodiment will not be described.

According to the present embodiment, as illustrated inFIG. 17, the positioning hole326is formed so that two first sides326S1of the hole edge portion and two first sides318S1of a plate surface of a LED board318are positioned in lien with each other so as not to have any clearance therebetween. The positioning hole326has a Z-axis opening width dimension that is substantially same as a width dimension of the LED board318. With such a configuration, the LED board318is attached to a heat dissipation member320so that each of the first sides326S1of the plate surface of the LED board318is set to be parallel to and positioned on each of the first sides326S1of the hole edge portion of the positioning hole326. If any clearance is generated between any of the first sides326S1,326S1, it is confirmed that the position of the LED board318and the heat dissipation member320is shifted from the correct position. Therefore, the LED board318is positioned with respect to the heat dissipation member320in the Z-axis direction with high accuracy.

Fifth Embodiment

A fifth embodiment will be described with reference toFIG. 18orFIG. 19. In the fifth embodiment, a heat dissipation member420has a different shape from the one in the above embodiments. The constructions, functions, and effects similar to those of the first embodiment will not be described.

According to the present embodiment, as illustrated inFIGS. 18 and 19, the heat dissipation member420is formed to be bent at a substantially right angle so as to follow the shape of a side plate414band a step portion414a2included in a LED container421of a chassis414. The heat dissipation member420includes a LED board mounting portion28that extends along the side plate414band a bottom portion29that extends along the step portion414a2. The heat dissipation member420has positioning holes426on respective two end portions of the longitudinal dimension (the X-axis direction) of the LED board mounting portion28where the LED board418is mounted. The positioning holes426are through the LED board mounting portion28. The bottom portion29extends from a rear-surface side end of the LED board mounting portion28inwardly, that is, toward the LED board418and a light guide plate419and supports the light guide plate419and the reflection sheet R from the rear-surface side. Accordingly, a contact area between the heat dissipation member420and the chassis414is increased by the area of the bottom portion29. Therefore, the heat is effectively transmitted from the heat dissipation member420to the chassis414and this improves a heat dissipation property.

Sixth Embodiment

A sixth embodiment will be described with reference toFIG. 20. In the sixth embodiment, a heat dissipation member520has a different shape from the one in the fifth embodiment. The constructions, functions, and effects similar to those of the first embodiment will not be described.

According to the present embodiment, as illustrated inFIG. 20, the heat dissipation member520includes a LED board mounting portion528and a bottom plate portion529. The bottom plate portion529extends from a rear-surface side end of the LED board mounting portion528outward, that is, toward an opposite side from a LED board518side. With such a configuration, the bottom plate portion529of the heat dissipation member520is attached to a step portion of a LED container included in the chassis, which is not illustrated.

Seventh Embodiment

A seventh embodiment will be described with reference toFIG. 21. In the sixth embodiment, the number of LED boards618attached to a heat dissipation member620differs from that in the above embodiments. The constructions, functions, and effects similar to those of the first embodiment will not be described.

According to the present embodiment, as illustrated inFIG. 21, the heat dissipation member520includes only one LED board618. The LED board618has a length dimension that is substantially equal to a long-side dimension of a light guide plate619. Only one positioning hole626is formed in one end of the heat dissipation member620to be therethrough. The positioning hole626is formed to overlap a board-side connector622.

Eighth Embodiment

An eighth embodiment will be described with reference toFIG. 22orFIG. 23. In the eighth embodiment, a positioning hole has a different shape from the one in the above embodiments. The constructions, functions, and effects similar to those of the first embodiment will not be described.

According to the present embodiment, as illustrated inFIG. 22, the positioning hole726is a substantially right-angled elongated thin slit having a substantially L-shape seen from a front side or a rear side. A hole edge portion of the positioning hole726includes two horizontal first sides72651that are parallel to the X-axis direction and two vertical second sides726S2that are parallel to the Z-axis direction. As illustrated inFIG. 23, a LED board718is attached to a heat dissipation member720so that a second side718S2of the LED board718is positioned on and overlaps the second side726S2of the hole edge portion of the positioning hole726, and the second side726S2is the one closer to the end of the heat dissipation member720. Further, the LED board718is attached to the heat dissipation member720so that a rear-surface side first side718S1of the LED board718is positioned on and overlaps a front-surface side first side726S1of the hole edge portion of the positioning hole726. The LED board718is attached to the heat dissipation member720so as to have a clearance C between the rear-surface side first side718S1of the LED board718and the rear-surface side first side726S1of the hole edge portion of the positioning hole726. The clearance C has a constant width over its entire length. With such a configuration, the LED board718is positioned with respect to the heat dissipation member720in the X-axis direction and the Z-axis direction with high accuracy.

Ninth Embodiment

A ninth embodiment will be described with reference toFIG. 24orFIG. 25. In the ninth embodiment, a device does not include a heat dissipation member. The constructions, functions, and effects similar to those of the first embodiment will not be described.

According to the present embodiment, as illustrated inFIGS. 24 and 25, a LED board818is directly mounted on a chassis814without having the heat dissipation member that is included in the first embodiment. The LED board818is mounted directly on a side plate814bof a LED container821included in the chassis814. Heat generated from LEDs817according to current applying is transferred to the side plate814bvia the LED board818and released via a chassis814. According to the present embodiment, the chassis814constitutes a heat dissipation member that dissipates heat from the LEDs817. The side plate814bof a LED container821included in the chassis814has positioning holes826therethrough. The LED board818is positioned with respect to the chassis814by the positioning holes826. The constructions, functions, and effects of the positioning holes826are similar to those of the first embodiment.

Other Embodiments

The present invention is not limited to the above embodiments explained in the above description and the drawings. The technology described herein may include the following embodiments.

(1) In the above embodiments (except for the eighth embodiment), each of the hole edge portion of the square positioning hole and the LED board having a square plate surface has three sides that form two corner portions that are off-diagonal. The LED board is positioned with respect to the heat dissipation member by using the three sides. However, the LED board may be positioned with respect to the heat dissipation member using respective two sides that form one corner portion of each of the hole edge portion of the square positioning hole and the square plate surface of the LED board.

(2) In the above embodiments, the hole edge portion of the positioning hole and the plate surface of the LED board have second sides that are parallel to the Z-axis direction, and the second sides overlap each other. However, the LED board may be attached to the heat dissipation member so as to have a clearance between the two sides. In such a configuration, the LED board and the heat dissipation member may have a clearance between the first sides thereof that are parallel to the Z-axis direction and may have clearances between all the corresponding sides thereof.

(3) In the first embodiment, the LED board is attached to the heat dissipation member so as to have a clearance between the front-side first sides of the opening edge portion of the positioning hole and the plate surface of the LED board. However, the clearance may be provided between the rear-surface side first sides, and the LED board and the heat dissipation member may be positioned so that the front-side first sides overlap each other.

(4) In the eighth embodiment, the LED board and the heat dissipation member are positioned so have a clearance between the rear-surface side first side of the opening edge portion of the substantially L-shaped positioning hole and the rear-surface side first side of the plate surface of the LED board. However, the LED board and the heat dissipation member may be positioned so that the rear-surface side first sides may overlap each other and any clearance is provided between the LED board and the positioning hole. Alternatively, the LED board and the heat dissipation member may be positioned to have a clearance between the second sides.

(5) In the second embodiment, each of the first side and the second end of the hole edge portion of the positioning hole has the positioning piece. The positioning piece may be provided on the two first sides of the hole edge portion of the positioning hole and the second side that is close to the heat dissipation member and the total of three positioning pieces may be provided.

(6) In the second embodiment, each of the first side and the second end of the hole edge portion of the positioning hole has the positioning piece. The positioning pieces may be provided on each of the first side and the second side.

(7) In the above embodiments, the number of the positioning holes in the heat dissipation member is equal to the number of the LED boards that are attached to the heat dissipation member. The number of the positioning holes may not be equal to the number of the LED boards. For example, one LED board may be positioned by positioning holes or LED boards may be positioned by one positioning hole.

(8) In the above embodiments, the positioning hole has a square shape or a substantially L-shape seen from a front side or a rear side. The positioning hole may have any other shapes. For example, the positioning hole may have a horizontally long rectangular shape, a vertically long rectangular shape, a triangular shape, a trapezoidal shape, a pentagon shape or other polygonal shapes.

(9) In the above embodiments, the positioning hole is positioned to overlap the board-side connector with an substantially entire area thereof seen from a front side or a rear side. The positioning hole may be positioned to overlap a part of the board-side connector (for example, a half or one third of the board-side connector).

(10) In the above embodiments, the board-side connector is mounted on the mount surface of the LED board where the LEDs are mounted. The board-side connector may be mounted on a plate surface that is opposite from the mount surface of the LED board. In such a configuration, the board-side connector may be effectively arranged through the positioning hole.

(11) In the above embodiments, the LED board is attached to the heat dissipation member with an adhesive or a double-sided tape. The LED board may be attached to the heat dissipation member with screws or rivets.

(12) In the above embodiments, an example of the identification portion provided on the LED board includes a printed bar code. Examples of the identification portion include a two-dimensional codes, characters, numbers that may be printed.

(13) In the above embodiments, the LED board is attached to the heat dissipation member or the chassis. The LED board may be attached to a component other than the heat dissipation member or the chassis.

(14) In the above embodiments, one or two LED boards are arranged along the light entrance surface of the light guide plate. Three or more LED boards may be arranged along the light entrance surface of the light guide plate.

(15) In the above embodiments, the LED board is arranged to face a long-side end surface of the light guide plate. The LED board may be arranged to face a short-side end surface of the light guide plate.

(16) Other than the configuration of (15), the LED boards may be arranged to face the respective long-side end surfaces of the light guide plate or arranged to face the respective short-side end surfaces of the light guide plate.

(17) Other than the configurations of (15) and (16), the LED boards may be arranged to face any three end surfaces of the light guide plate, respectively or arranged to face all the four end surfaces of the light guide plate, respectively.

(18) In the above embodiments, the color filter of the liquid crystal panel includes the color portions of three colors including red (R), green (G), and blue (B). However, the color filter may include color portions of four colors or more.

(19) In the above embodiments, the LEDs are used as the light source. However, other light sources such as an organic EL diode may be used as the light source.

(20) In the above embodiments, the TFTs are used as switching components of the liquid crystal display device. However, the technology described herein may be applied to liquid crystal display devices including a liquid crystal display panel using switching components other than TFTs (e.g., thin film diodes (TFDs)). Furthermore, the technology may be applied to a liquid crystal display device including a black-and-white liquid crystal display panel other than a liquid crystal display device including a color liquid crystal display panel.

(21) In the above embodiments, the liquid crystal display device includes the liquid crystal panel as the display panel. However, the technology described herein may be applied to display devices including other kinds of display panels.

(22) In the above embodiments, the television device includes the tuner. However, the technology can be applied to display devices without including a tuner. Specifically, the technology can be applied to liquid crystal display devices that are used as digital signage or electronic black boards.

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