Display device and television device

A display device includes a light source, a light guide plate, a chassis, a display panel, a flexible circuit board, a signal transmission circuit board, and a first heat dissipation member. The chassis includes a bottom plate that includes a light source supporting portion and a light guide plate supporting portion. The bottom plate includes a surface on which the light source and the light guide plate are arranged. The flexible circuit board is bent and a portion thereof is opposed to another surface of the light source supporting portion. The signal transmission circuit board is arranged over the other surface. The first heat dissipation member is sandwiched between the light guide plate supporting portion and the flexible circuit board and in contact with the other surface and with the flexible circuit board.

TECHNICAL FIELD

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

BACKGROUND ART

A display device that may be used for a liquid crystal television device is disclosed in Patent Document 1. The display device includes a light source and a light guide plate held by a chassis that is a case of the display device. The liquid crystal panel is arranged on the front of the chassis. A flexible circuit board is connected to a display surface of the liquid crystal panel and bent such that a portion thereof is arranged on the rear of the chassis. In such a display device, heat generated from the light source may be transferred to the rear of the chassis and the portion of the flexible circuit board and then dissipated to the outside of the display device.

RELATED ART DOCUMENT

Patent Document

Problem to be Solved by the Invention

In recent years, demands for liquid crystal panels having high definition such as 2K and 4K panels have been increased. The liquid crystal panel having high definition includes a large number of flexible circuit boards that are connected to an edge of a panel with little gaps to increase the number of image pixels. If the display device disclosed in Patent Document 1 includes a liquid crystal panel having high definition, a portion of the rear of the chassis is covered with a large number of flexible circuit boards and thus heat may remain in an air gap between the portion of the rear of the chassis and the flexible circuit boards. This may degrade heat dissipation performances of the display device for dissipating heat through the chassis.

DISCLOSURE OF THE PRESENT INVENTION

The technology disclosed in this description was made in view of the above circumstances. An object is to reduce or suppress degradation in heat dissipating performance through a chassis.

Means for Solving the Problem

The technology disclosed in this description includes a display device including a light source, a light guide plate, a chassis, a display panel, a flexible circuit board, a signal transmission circuit board, and a first heat dissipation member. The light guide plate includes at least one side surface that is a light entrance surface opposed to the light source. The chassis includes at least a bottom plate that includes a surface on which at least the light source and the light guide plate are arranged. The bottom plate includes a light source supporting portion and a light guide plate supporting portion. The light source supporting portion supports the light source. The light guide plate supporting portion supports the light guide plate. The display panel is arranged over a plate surface of the light guide plate opposite from a plate surface of the light guide plate facing the chassis. The flexible circuit board has flexibility and includes an end connected to the display panel. The flexible circuit board is bent and a portion of the flexible circuit board is opposed to another surface of the light source supporting portion of the bottom plate. The signal transmission circuit board is connected to another end of the flexible circuit board and arranged over the other surface of the light source supporting portion of the bottom plate for transmitting a signal to the flexible circuit board. The first heat dissipation member is sandwiched between the light guide plate supporting portion of the bottom plate and the flexible circuit board and in contact with the other surface of the light guide plate supporting portion of the bottom plate and with the flexible circuit board.

In the above display device, the other surface of the bottom plate of the chassis, that is, a surface of the bottom plate opposite from the surface of the bottom plate facing the light source and the light guide plate, is a surface facing the outside of the chassis. The first heat dissipation member closes an air gap between the surface of the light source supporting portion in the other surface of the bottom plate and the flexible circuit board. According to this configuration, heat transferred to the other surface of the light source supporting portion o of the bottom plate is efficiently transferred to the flexible circuit board through the first heat dissipation member. The heat transferred to the flexible circuit board is dissipated to the outside of the display device through the flexible circuit board. Thus, the heat is less likely to remain in the air gap between the surface of the light source supporting portion of the bottom plate on the other side and the flexible circuit board. That is, the heat does not or is less likely to remain in an air gap between the chassis and the flexible circuit board even though the light source supporting portion of the chassis is a portion to which the heat from the light source is more likely to be transferred. Thus, the performance of the display device for dissipating the heat through the chassis does not or is less likely to degrade even in the display device in which the flexible circuit board covers one of the surfaces of the light source supporting portion facing the outside of the chassis.

The display device may further includes a second heat dissipation member sandwiched between the other surface of the light guide plate supporting portion of the bottom plate and the signal transmission circuit board and in contact with the other surface of the light guide plate supporting portion of the bottom plate and the signal transmission circuit board.

The second heat dissipation member closes an air gap between the surface of the light guide plate supporting portion on the other side of the bottom plate and the signal transmission circuit board so that the heat that transferred to the light guide plate supporting portion of the bottom plate is efficiently transferred to the signal transmission circuit board through the second heat dissipation member. Thus, the heat is less likely to remain in the air gap between the other surface of the light guide plate supporting portion of the bottom plate and the signal transmission circuit board. That is, the heat does not or is less likely to remain in the air gap not only between the light source supporting portion and the flexible circuit board but also between the light guide plate supporting portion of the chassis and the signal transmission circuit board. Thus, the performance of the display device for dissipating the heat through the chassis does not degrade or is less likely to degrade even in the display device in which the flexible circuit board and the signal transmission circuit board cover the one of the surfaces of the chassis facing the outside.

The display device may further includes a circuit board cover and a third heat dissipation member. The circuit board cover may cover a surface of the signal transmission circuit board opposite from a surface of the signal transmission circuit board facing the other surface of the bottom plate. The third heat dissipation member may be sandwiched between the signal transmission circuit board and the circuit board cover and in contact with the signal transmission circuit board and the circuit board cover.

The third heat dissipation member closes an air gap between the signal transmission circuit board and the circuit board cover so that the heat from the signal transmission circuit board is efficiently transferred to the circuit board cover through the third heat dissipation member. Thus, heat is less likely to remain between the signal transmission circuit board and the circuit board cover. With the circuit board cover, the performance of the display device for dissipating the heat while the signal transmission circuit board is protected by the circuit board cover.

The circuit board cover may include an extending portion that extends to the flexible circuit board and covers a portion of the flexible circuit board opposed to the light source supporting portion. The display device may further include a fourth heat dissipation member that is sandwiched between the flexible circuit board and the fourth heat dissipation member and in contact with the flexible circuit board and the fourth heat dissipation member.

With the fourth heat dissipation member, the performance of the display device for dissipating the heat further improves while noises caused by the flexible circuit board is reduced by the extending portion that covers the portion of the flexible board. Furthermore, the extending board supports the flexible circuit board so that the flexible circuit board is less likely to warp. That is, the flexible circuit board remains in contact with the first heat dissipation member properly. Thus, heat dissipation properties of the chassis are further less likely to degrade.

The display device may further includes a light source board and a fifth heat dissipation member. The light source may be mounted to the light source board. The fifth heat dissipation member may include a portion that is sandwiched between the light source board and the chassis and in contact with the light source board and the chassis.

According to this configuration, the heat generated from the light source is efficiently transferred to the chassis through the fifth heat dissipation member. Thus, the performance of the display device for dissipating the heat further improves.

The fifth heat dissipation member may be in contact with surfaces of the light source board.

In comparison to a configuration that the fifth heat dissipation member is only in contact with a single surface of the light source board, the fifth heat dissipation member has a larger area that contacts the light source board. Thus, heat generated from the light source is more likely to propagate to the chassis through the fifth heat dissipation member. Thus, heat dissipation properties of the display device further improve.

The display device may further include a bezel, a driving component, and a sixth heat dissipation member. The bezel may have a frame-like shape and may be connected to the chassis on the one side. The driving component may be mounted on the flexible circuit board. The driving component may be configured to process the signal from the signal transmission circuit board and transmit a signal that is processed thereby to the display panel for driving the display panel. The sixth heat dissipation member may be sandwiched between the bezel and a portion of the flexible circuit board on which the driving component is mounted and in contact with the bezel and the portion of the flexible circuit board on which the driving component is mounted.

According to the configuration, heat from the driving component is effectively transferred to the bezel via the sixth heat dissipation member and thus heat dissipation properties of the display device improve.

The light source supporting portion of the bottom plate may protrude toward a direction in which the surface of the bottom plate on the other side faces and forma step together with the light guide plate supporting portion.

This configuration is for the light source that is arranged opposite to the light entrance surface of the light guide plate. The light source may require components including a board to mount them, wirings or traces, and connectors and thus the light source may require a space with a height larger than that of a space for the light guide plate. Since the bottom plate of the chassis in includes the light source supporting portion that protrudes to the other side, a space with a sufficient height is provided for the light source. The configuration that the light source supporting portion of the bottom plate protrude to the other side so as to form a step can be represented as that the light guide plate supporting portion is dented toward the liquid crystal panel with respect to the light source supporting portion. In this configuration, it is preferable to arrange the signal transmission circuit board at the light guide plate supporting portion in terms of reduction of overall thickness of the display device. However, to arrange the signal transmission circuit board at the light guide plate supporting portion, it is necessary to bend the flexible circuit board and arrange the flexible circuit board across the step formed by the light guide plate supporting portion. In general, although heat tends to stay in an area in which a flexible circuit board is arranged across a step, the configuration described above includes the first heat dissipation sheet. Thus, heat is less likely to stay in such an area. Namely, such a problem is solved.

The display device may further include a reflection sheet that is in contact with the surface of the bottom plate on the one side.

According to this configuration, reflectivity of the reflection sheet does not degrade or is less likely to degrade in comparison to a configuration that includes a heat dissipation sheet that is arranged between the surface of the bottom plate on the one side and the reflection sheet.

The reflection sheet may be sandwiched between the light guide plate and the surface of the bottom plate on the one side and in contact with the light guide plate and the surface of the bottom plate on the one side.

With the configuration that the reflection sheet is sandwiched between the light guide plate and the chassis, the reflection sheet does not warp or is less likely to warp due to heat.

The flexible circuit board may include a plurality of flexible circuit boards arranged along at least an end of the display panel. The first heat dissipation member may be arranged such that the first heat dissipation member closes an entirety of an air gap between the plurality of the flexible circuit boards and the surface of the bottom plate on the other side.

In a configuration that includes multiple flexible circuit boards, a large portion of the surface of the light source supporting portion of the chassis on the other side is covered with the flexible circuit boards. Therefore, heat is more likely to stay in the air gap between the surface of the chassis on the other side and the flexible circuit boards. According to the above configuration, the first heat dissipation member closes the entirety of the air gap in which heat tends to stay. Therefore, even if multiple flexible circuit boards are arranged, heat dissipation properties of the display device do not or are less likely to degrade. That is, the display device that includes the display panel having a high definition has high heat dissipation properties.

The technologies described in this specification may be applied to a display device including a liquid crystal panel that includes liquid crystals therein. Furthermore, a television device including the display device may be considered as new and advantageous.

Advantageous Effect of the Invention

According to the present invention, heat dissipating performances through the chassis is less likely to be degraded or degradation in heat dissipating performance is reduced.

MODE FOR CARRYING OUT THE INVENTION

A first embodiment will be described with reference to the drawings. A liquid crystal display device (an example of a display device)10according to this embodiment will be described. X-axis, Y-axis and Z-axis may be indicated in the drawings. The axes in each drawing correspond to the respective axes in other drawings. The Y-axis direction corresponds to a vertical direction and the X-axis direction corresponds to a horizontal direction. The Z-axis direction corresponds to a thickness direction (i.e. a front-rear direction). An upper side inFIG. 2corresponds to a front side of the liquid crystal display device10. A lower side inFIG. 2corresponds to a rear side of the liquid crystal display device10.

A television device TV 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 device10is landscape rectangular. The liquid crystal display device10includes a liquid crystal panel11as a display panel and a backlight unit12as an external light source. The liquid crystal panel11and the backlight unit12are collectively held by a bezel13having a frame-like shape. In the liquid crystal display device10, the liquid crystal panel11is fixed such that a display surface11C for displaying images faces the front. The liquid crystal panel11in this embodiment is a high definition panel including a large number of pixels, so-called e a 4K2K panel.

The bezel13is made of metal having high rigidity such as stainless steel. As illustrated inFIGS. 2 and 3, the bezel13includes a bezel frame-shaped portion13A and a bezel peripheral wall portion13B. The bezel frame-shaped portion13A is parallel to the liquid crystal panel11and has a frame-like shape in a plan view. The bezel peripheral wall portion13B extends from peripheral edges of the bezel frame-shaped portion13A toward the rear to have a short box-wall shape. The bezel frame-shaped portion13A extends along an outer portion of the display surface11C of the liquid crystal panel11. Between the bezel frame-shaped portion13A and the liquid crystal panel11, a cushioning member26A is arranged. The bezel frame-shaped portion13A retains the liquid crystal panel11by holding the outer portion of the display surface11C from the front via the cushioning member26A. The bezel peripheral wall portion13B covers a portion of an outer surface of a frame14, which will be described later. The bezel peripheral wall portion13B constitutes a portion of a peripheral exterior of the liquid crystal display device10.

The backlight unit12will be described. As illustrated inFIG. 2, components of the backlight unit12are arranged within space provided between the frame14and a chassis15. The frame14constitutes a front exterior of the backlight unit12. The chassis15constitutes a rear exterior of the backlight unit12. Between the frame14and the chassis15, components including at least a light guide plate18, a reflection sheet21, and LED units LU are arranged. Optical sheets16are arranged on the front side of the light guide plate18. The light guide plate18is sandwiched and held by the frame14and the chassis15. On the front side of the light guide plate18, the liquid crystal panel11and the optical sheets16are arranged in this sequence from the front. The LED units LU in the backlight unit12are arranged in the space between the frame14and the chassis15along edges of a short-dimension of the light guide plate18. Namely, the backlight units12of this embodiment are edge-light type unit. Each component of the backlight unit12will be described next.

The light guide plate18is made of substantially transparent (high transmissivity) synthetic resin (e.g. acrylic resin or polycarbonate such as PMMA) which has a refractive index sufficiently higher than that of the air. As illustrated inFIG. 2, the light guide plate18has a landscape rectangular shape in a plan view similar to the liquid crystal panel11and the optical sheets16, which will be described later. A long-side direction and a short-side direction of a main surface of the light guide plate18correspond to the X-axis direction and the Y-axis direction, respectively. A thickness direction of the light guide plate18that is perpendicular to the main surface of the light guide plate18corresponds to the Z-axis direction. The light guide plate18is held by the chassis15, which will be described later.

The light guide plate18includes two long-side peripheral surfaces that are configured as light entrance surfaces18A and through which rays of light from the LED units enter the light guide plate18. The light guide plate18further includes two main plate surfaces, one of which is a light exit surface18B (a front plate surface) and the other one is an opposite surface18C (a rear plate surface). The light guide plate18is arranged such that the two light entrance surfaces18A are opposed to the respective LED units, the light exit surface18B faces the optical sheets16, and the opposite surface18C faces the reflection sheet21. The light guide plate18has a function of receiving rays of light emitted from the LED units LU to the light guide plate18through the light entrance surface18A, transmitting the rays of light therethrough, and guiding the rays of light toward the optical sheets16so that the rays of light exit the light guide plate18through the light exit surface18B.

The reflection sheet21is a rectangular sheet-like member made of a synthetic resin. The reflection sheet21includes a white surface having a high light reflectivity. A long-side direction and a short-side direction of the reflection sheet21correspond to the X-axis direction and the Y-axis direction, respectively. The reflection sheet21is sandwiched between the light guide plate18and the chassis15and in contact with the light guide plate18and the chassis15. The reflection sheet21is configured to reflect rays of light that travel from the LED units LU or the light guide plate18toward the front surface of the reflection sheet21. The reflection sheet21has a short-side dimension larger than a short-side dimension of the fixing member28. As illustrated inFIG. 3, end portions of the reflection sheet21at ends of the long dimension of the reflection sheet21are located slightly outer than edges of the light entrance surfaces18A of the light guide plate18.

As illustrated inFIG. 2, similar to the light guide plate18and the liquid crystal panel11, each optical sheet16has a landscape rectangular shape in a plan view and has a size (i.e., a short-side dimension and a long-side dimension) slightly smaller than that of the light exit surface18B of the light guide plate18and the liquid crystal panel11in a plan view. Specific examples of the optical sheets16include a diffuser sheet, a lens sheet, and a reflective-type polarizing sheet and any of them are selected as appropriate for the optical sheets16. The optical sheets16that are arranged between the light guide plate18and the liquid crystal panel11are configured to pass light from the light guide plate18, to add specific optical effects to the light, and to direct the light toward the liquid crystal panel11.

As illustrated inFIG. 2, the LED units LU are arranged along the long sides of the light guide plate18, respectively. A long-side dimension of the LED unit LU is substantially the same as the long-side dimension of the light guide plate18. Each LED unit LU includes LEDs (an example of a light source)24and an LED board (an example of a light source board)25. Each of the LEDs24included in the LED units LU includes an LED chip (not illustrated) which is arranged on a board fixed to the LED board25and 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 seals 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 LED24is 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 LED24includes a main light-emitting surface that is an opposite surface (a surface facing the light entrance surface18A of the light guide plate18) from a mounting surface of the LED24which is fixed to the LED board25. Namely, the LED24is a so-called top-surface-emitting type LED.

As illustrated inFIG. 2, the LED board25of the LED unit LU is made of aluminum, which has a heat dissipation property. The LED board25has an elongated plate-like shape that extends in the long-side direction of the chassis15(the X-axis direction) of the light guide plate18. One of plate surfaces of the LED board25is parallel to the X-Z plane, that is, parallel to the light entrance surface18A of the light guide plate18. A long-side dimension of the LED board25(a dimension along the X-axis direction) is substantially the same as the long-side dimension of the light guide plate18(a dimension along the X-axis direction). A short-side dimension of the LED board25(a dimension along the Y-axis direction) is larger than the thickness of the light guide plate18. The LEDs24are surface mounted on an inner surface of the LED board25, that is, a surface of the LED board25facing the light guide plate18(an opposed surface to the light guide plate18). The inner surface is a mounting surface. The LEDs24are arranged in a line (linearly) along the long direction (the X-axis direction) on the mounting surface of the LED board25at a predetermined interval. Metal film (e.g., copper foil) traces (not illustrated) are formed on the mount surface of each LED board25. The traces extend along the X-axis direction and connect the adjacent LEDs24that across the group of the LEDs24. The traces connect the adjacent LEDs24to each other in series. When terminals at ends of the traces are connected to a power board (not illustrated) via wiring members including connectors and electric wires, driving power is supplied to each LED24.

The chassis15constitutes a rear exterior of the liquid crystal display device10. The chassis15is made of a metal plate such as an aluminum plate. As illustrated inFIG. 2, the chassis15has a landscape rectangular and shallow tray-like overall shape that covers substantially an entire area of a rear surface of the liquid crystal display device10. The chassis15includes a bottom plate15A and side plates15B. The bottom plate15A covers the rear of the liquid crystal panel11. The side plates15B extend frontward from long edges of the bottom plate15A, respectively. As illustrated inFIG. 3, the bottom plate15A includes a light guide plate supporting portion15A1and light source supporting portions15A2. The light guide plate supporting portion15A1for supporting the light guide plate18from the rear (from an opposite surface18C side) is a large portion of the bottom plate15A. The light source supporting portions15A2are for supporting the respective LED units LU from the rear. The light source supporting portions15A2protrude from long-side edges of the light guide plate supporting portion15A1toward the rear side of the liquid crystal display device10so as to from steps together with the light guide plate supporting portion15A1, respectively. That is, outer portions of the bottom plate15A along long-sides thereof are the light source supporting portions15A2and a portion of the bottom plate15A between the light source supporting portions15A2is the light guide plate supporting portion15A1(seeFIG. 7). As illustrated inFIG. 3, a short-side dimension of the light guide plate supporting portion15A1is substantially the same as a short-side dimension of the light guide plate18. A dimension of each side plate15B measured along a direction in which the side plate15B extends (a dimension measured along the Z-axis direction) is substantially the same as the sum of a dimension of the light guide plate18measured along the thickness thereof and a dimension of the light source supporting portion15A2measured along a direction in which the light source supporting portion15A2protrudes. The light source supporting portions15A2cover entire back surfaces of the respective LED units LU (a surface opposite from a surface facing a direction in which light from the LEDs24travels).

As illustrated inFIG. 3, heat dissipation sheets HS5are arranged between the respective LED units LU and the chassis15. The heat dissipation sheets HS5are sheets having heat dissipative properties. Each heat dissipation sheet HS5will be referred to as a fifth heat dissipation sheet (an example of a fifth heat dissipation member). A portion of the fifth heat dissipation sheet HS5is sandwiched between the LED board25and the side plate15B of the chassis15. The fifth heat dissipation sheet HS5bends so that another portion of the fifth heat dissipation sheet HS5is sandwiched between the LED board25and the light source supporting portion15A2of the chassis15and in contact with the LED board25and the chassis15. The fifth heat dissipation sheet HS5is arranged in an entire area of the LED board25between the LED board25and the chassis15such that the LED board25is not in contact with the chassis15. If the LED board25is in direct contact with the chassis15, a gap may be created between the LED board25and the chassis15because the LED board25and the chassis15have different linear expansion coefficients. Heat may not be transferred from the LED board25to the chassis15because of the gap. In this embodiment, the fifth heat dissipation sheet HS5is disposed between the LED board25and the chassis15. Therefore, a gap is less likely to be created between the LED board25and the fifth heat dissipation sheet HS5or between the LED board25and the chassis15. Namely, a large amount of the heat generated from the LEDs24when the LEDs24are turned on is effectively transferred from the LED board25to the chassis15through the fifth heat dissipation sheet HS5.

The frame14has a horizontally-long frame shape similar to the bezel13. The frame14is made of a synthetic resin (e.g. polycarbonate and polyethylene terephthalate). The frame14includes a frame-shaped portion14A and a frame peripheral wall portion14B. The frame-shaped portion14A having a substantially frame-like shape is parallel to the liquid crystal panel11. The frame peripheral wall portion14B extends from outer edges of the frame-like portion14A toward the front and the rear. The frame peripheral wall portion14B has a shallow frame shape. The frame-shaped portion14A extends along an outer portion of the light exit surface18B of the light guide plate18. The frame-shaped portion14A holds down the outer portion of the light exit surface18B from the front and thus the light guide plate18is held between the frame-shaped portion14A and the light guide plate supporting portion15A1. A cushioning member26B is disposed between the frame-shaped portion14A and the liquid crystal panel11. Namely, the frame-shaped portion14A holds down the liquid crystal panel11by applying pressure from a rear surface of the frame-shaped portion14A to the outer portion of the liquid crystal panel11via the cushioning member26B. The frame peripheral wall portion14B includes two portions, one of which extends frontward and the other of which extends rearward from the outer edges of the frame-shaped portion14A. The one of the portions extending rearward has a length longer than the other portion that extends frontward. The portion that extends rearward covers a large portion of the side plates15B of the chassis15and constitutes a portion of the peripheral exterior of the liquid crystal display device10. The portion that extends rearward includes driver holding recesses14B1in each of which a source driver SD, which will be described later, is arranged. Each driver holding recess14B1has an opening on an outer side (an opposite side from a side close to the side plate15B).

Next, configuration of the liquid crystal panel11and configurations for driving the liquid crystal panel11will be described. As illustrated inFIGS. 2 and 3, the liquid crystal panel11has a landscape rectangular shape in a plan view. The liquid crystal panel11is disposed on the optical sheets16. The liquid crystal panel11includes a pair of glass substrates11A,11B and liquid crystals. The substrates11A,11B having high light transmissivity are bonded together with a predetermined gap therebetween and the liquid crystals are sealed between the substrates11A,11B. The substrate on the front corresponds to a CF board11B and the substrate on the rear corresponds to an array board11A. On the array board11A, switching elements (e.g. TFTs), pixel electrodes, and an alignment film are arranged. The switching elements are connected to gate lines and source lines that are arranged perpendicular to each other. The pixel electrodes are connected to the switching elements. On the array board11A, a number of TFTs and a number of pixel electrodes are arranged. Furthermore, gate lines and source lines are arranged in a matrix around the TFTs and the pixel electrodes. The gate lines and the source lines are connected to gate electrodes and source electrodes, respectively. The pixel electrodes are connected to drain electrodes of the TFTs.

On the CF board11B, capacitive lines (auxiliary capacitive lines, storage capacitive lines) are arranged parallel to the gate lines and so as to overlap the pixel electrodes in a plan view. The capacitive lines and the gate lines are alternately arranged in the Y-axis direction. On the CF board11B, color filters, a counter electrode, and an alignment film are arranged. The color filters include red (R), green (G), and blue (B) color portions that are arranged in a predetermined arrangement. The display surface11C of 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 with a frame-like shape (or a picture frame-like shape) and covered by the bezel frame-shaped portion13A of the bezel13. The polarizing plates (not illustrated) are arranged on outer sides of the boards11A and11B.

As illustrated inFIGS. 3 and 6, the array board11A of the pair of boards11A,11B included in the liquid crystal panel11is slightly larger than the CF board11B such that outer edge portions of the array board11A project over outer edge portions of the CF board11B for an entire periphery. Gate terminals connected to the gate lines and the capacitive lines are disposed on one of short outer edge portions of the outer edge portions of the array board11A. Gate flexible circuit boards28having flexibility are connected to the gate terminals, respectively. The gate flexible circuit boards28(six in each short edge portion in this embodiment) are arranged at about equal intervals along the Y-axis direction, that is, a direction along the short edge of the array board11A. The gate flexible circuit boards28project outward over the short edge of the array board11A. Source terminals connected to the source lines are disposed on one of long outer edge portions of the outer edge portions of the array board11A (the one on the right inFIG. 3or on the top inFIG. 6). Source flexible circuit boards (an example of a flexible board)30having flexibility are connected to the source terminals, respectively. The source flexible circuit boards30(twelve of them in this embodiment) are arranged at about equal intervals along the X-axis direction, that is, a direction along the long edge of the array board11A. The source flexible circuit boards30project outward over the long edge of the array board11A.

As illustrated inFIGS. 3 and 6, each of the gate flexible circuit boards28and each of the source flexible circuit boards30includes a film base member made of synthetic resin (e.g., polyimide resin) which has insulating and flexible properties. On rear surfaces of the gate flexible circuit boards28, gate drivers GD for alignment of liquid crystals are mounted, respectively. On rear surfaces of the source flexible circuit boards30, the source drivers SD are mounted, respectively. The gate drivers GD and the source drivers SD project inward from mount surfaces, respectively. Each of the gate drivers GD and the source drivers SD has a horizontally-long rectangular shape. Each of the gate driver GD and the source driver SD is an LSI chip including a drive circuit that is configured to process image-related input signals transmitted from the control circuit board (not illustrated), to generate output signals, and to send the output signals to the liquid crystal panel11.

The length of each source flexible circuit board30along a direction in which the source flexible circuit board30extends is longer than a length of the gate flexible circuit board28along a direction in which the gate flexible circuit board28extends. As illustrated inFIG. 4, the source flexible circuit board30includes an end30A that is connected to the liquid crystal panel11. The source flexible circuit board30is bent such that an end (another end)30B of the source flexible circuit board30opposite from the end30A is arranged at the rear of the bottom plate15A of the chassis15. At the rear of the light guide plate supporting portion15A1of the bottom plate15A, a source circuit board (an example of a signal transmission circuit board)32is disposed (seeFIG. 4). The ends30A of the source flexible circuit boards30are pressure bonded to the respective source terminals formed on the array board11A. The other ends30B of the source flexible circuit boards30are pressure bonded to the source circuit board32via anisotropic conductive films (ACFs). Traces (not illustrated) are formed on inner surfaces of the source flexible circuit boards30(surfaces that face the chassis15). One end of each trace is connected to the corresponding source terminal formed on the liquid crystal panel11. The other end of the trance is connected to the source circuit board32. Each of the source flexible circuit boards30is a single-side mounting type circuit board that includes a single mounting surface on which the traces are formed and the source driver SD is mounted. On the inner surface of the source flexible circuit board30, an insulation coating is formed to cover large portions of the traces except for the ends of the traces. Thus, the trances are insulated.

A middle portion of the trace between the one end and the other end thereof (an intermediate portion) is connected to the source driver SD, which is mounted on the inner surface of the source flexible circuit board30. As illustrated inFIG. 4, the source driver SD is entirely housed in the driver holding recess14B1that is formed in the frame peripheral wall portion14B of the frame14. Specifically, the source driver SD is arranged in the driver holding recess14B1with air gap therebetween. Namely, the source driver SD is not in contact with walls of the driver holding recess14B1. The source flexible circuit boards30that include mounting portions30C on which the respective source drivers SD are mounted may warp when the source drivers SD are brought into contact with the frame peripheral wall portion14B of the frame14. Because the source drivers SD do not contact the frame peripheral wall portion14B of the frame14, the mounting portions30C of the source flexible circuit boards30do not or are less likely to warp. Therefore, an about entire inner surface of the source flexible circuit board30facing the frame peripheral wall portion14B of the frame14is in contact with an outer surface of the frame peripheral wall portion14B.

As illustrated inFIG. 6, the source circuit board32has an elongated shape along the X-axis direction. The source circuit board32is arranged in an area of the light guide plate supporting portion15A1adjacent to one of the light source supporting portions15A2(seeFIG. 4). A plate surface of the source circuit board32is parallel to the X-Y plane, namely, parallel to the bottom plate15A of the chassis15. The source flexible circuit boards30inFIG. 6is in a state before being bent. The source circuit board32includes a plate-like base member made of synthetic resin. Metal traces are formed on the base member. Terminals are connected to at least portions of the metal traces and the terminals are connected to the source flexible circuit boards30.

As illustrated inFIG. 4, a heat dissipation sheet HS2having heat dissipation properties is arranged between the bottom plate15A of the chassis15and the source circuit board32. The heat dissipation sheet HS2will be referred to as a second heat dissipation sheet (an example of a second heat dissipation member) HS2hereinafter. The second heat dissipation sheet HS2is sandwiched between the bottom plate15A of the chassis15and the source circuit board32and in contact with the bottom plate15A and the source circuit board32. That is, the second heat dissipation sheet HS2closes an entire air gap between the source circuit board32and the bottom plate15A of the chassis15. Thus, heat transferred from the LED board25to the light guide plate supporting portion15A1of the bottom plate15A of the chassis15is effectively transferred from the light guide plate supporting portion15A1to the source circuit board32via the second heat dissipation sheet HS2.

A circuit board cover34is disposed over an outer surface of the source circuit board32(i.e., a surface opposite from a surface that faces the second heat dissipation sheet HS2). The circuit board cover34covers an entire plate surface of the source circuit board32. The circuit board cover34has a plate-like shape and arranged such that plate surfaces thereof are parallel to the X-Y plate, that is, parallel to the plate surface of the source circuit board32. One of the plate surfaces of the circuit board cover34on the outer side (an opposite surface from a surface facing the source circuit board32) is exposed to the outside of the liquid crystal display device10. The circuit board cover34that covers the outer surface of the source circuit board32is a protector for protecting the source circuit board32from external objects. The circuit board cover34is arranged substantially on the same level with the rear surface of the light source supporting portion15A2of the bottom plate15A of the chassis15(a position in the Z-axis direction).

As illustrated inFIG. 4, a heat dissipation sheet HS3having heat dissipation properties is arranged between the source circuit board32and the circuit board cover34. The heat dissipation sheet HS3will be referred to as a third heat dissipation sheet (an example of a third heat dissipation member) HS3hereinafter. The third heat dissipation sheet HS3is sandwiched between the source circuit board32and the circuit board cover34and in contact with the source circuit board32and the circuit board cover34. That is, the third heat dissipation sheet HS3closes an entire air gap between the source circuit board32and the circuit board cover34. Thus, heat transferred from the light guide plate supporting portion15A1of the bottom plate15A of the chassis15to the source circuit board32is effectively transferred from the light guide plate supporting portion15A1to the circuit board cover34via the third heat dissipation sheet HS3. Then, the heat transferred to the circuit board cover34is dissipated to the outside of the liquid crystal display device10.

As illustrated inFIG. 4, a heat dissipation sheet HS1having heat dissipation properties is arranged between a portion of each source flexible circuit board30and the light source supporting portion15A2. The portion of the source flexible circuit board30is opposed to the rear surface of the light source supporting portion15A2. The heat dissipation sheet HS1sheet will be referred to as a first heat dissipation sheet (an example of a first heat dissipation member) HS1hereinafter. The first heat dissipation sheet HS1has an elongated shape along the X-axis direction similar to the source circuit board32. The first heat dissipation sheet HS1is sandwiched between the source flexible circuit boards30and the bottom plate15A of the chassis15and in contact with the source flexible circuit boards30and the bottom plate15A. That is, the first heat dissipation sheet HS1closes an air gap between the source flexible circuit boards30and the bottom plate15A of the chassis15. Thus, heat transferred from the LED board25to the light source supporting portion15A2of the bottom plate15A of the chassis15is effectively transferred from the light source supporting portion15A2to the source flexible circuit boards30. Then, the heat transferred to the source flexible circuit boards30is dissipated to the outside of the liquid crystal display device10through the source flexible circuit boards30.

Each of the heat dissipation sheets HS1, HS2, HS3, and HS5may be made of graphite. Each of the heat dissipation sheets HS1, HS2, HS3, and HS5includes adhesive surfaces. Each of the heat dissipation sheets HS1, HS2, HS3, and HS5is sandwiched between the respective components with the adhesive surfaces stuck to the components. With this configuration, positions of the heat dissipation sheets HS1, HS2, HS3, and HS5are less likely to change. The thicknesses of the heat dissipation sheets HS1, HS2, HS3, and HS5may be altered as appropriate according to the thicknesses or arrangement of the source circuit board32and the LED boards25. The second heat dissipation sheet HS2and the third heat dissipation sheet HS3may be made of materials having insulation properties to reduce or suppress short circuit.

Paths in which the heat is transferred in the liquid crystal display device10of this embodiment will be described. A large amount of heat generated from one of the LED boards25supported by the light source supporting portion15A2close to the source flexible circuit boards30is transferred to the corresponding side plate15B and the light source supporting portion15A2of the bottom plate15A of the chassis15via the fifth heat dissipation sheet HS5. A proportion of the heat transferred to the light source supporting portion15A2close to the source flexible circuit boards30is transferred to the light guide plate supporting portion15A1of the bottom plate15A of the chassis15. The rest of the heat is effectively transferred to the source flexible circuit boards30via the first heat dissipation sheet HS1and then dissipated to the outside of the liquid crystal display device10through the source flexible circuit boards30. The heat transferred to the light guide plate supporting portion15A1is effectively transferred from the light guide plate supporting portion15A1to the circuit board cover34through the second heat dissipation sheet HS2, the source circuit board32, the third heat dissipation sheet HS3in this sequence and dissipated to the outside of the liquid crystal display device10through the circuit board cover34.

The source flexible circuit boards30are connected to one of the long edge portions of the liquid crystal panel11. Namely, one of the light source supporting portions15A2of the bottom plate15A of the chassis15different from the one close to the source flexible circuit boards30is exposed to the outside of the liquid crystal display device10(seeFIGS. 5 and 7). Furthermore, the light guide plate supporting portion15A1of the bottom plate15A of the chassis15includes a portion that is not opposed to the source circuit board32. The rear surface of the portion not opposed to the source circuit board32is exposed to the outside of the liquid crystal display device10(seeFIGS. 5 and 7). With this configuration, a large part of heat generated from one of the LED boards25supported by the light source supporting portion15A2on the other side from the side close to the source flexible circuit boards30is transferred to the chassis15via the fifth heat dissipation sheet HS5. The heat that is transferred to the chassis15is dissipated to the outside of the liquid crystal display device10directly from the bottom plate15A of the chassis15.

The source drivers SD are not in contact with the respective driver holding recesses14B1. Therefore, a large part of heat produced from the source drivers SD transferred to the mounting portions30C of the source flexible circuit boards30on which the respective source drivers SD are mounted. As illustrated inFIG. 4, the mounting portions30C are exposed to the outside of the liquid crystal display device10. Thus, heat that transferred from the source drivers SD to the mounting portions30C are dissipated to the outside of the liquid crystal display device10through the mounting portions30C.

As described above, in the liquid crystal display device10according to this embodiment, the first heat dissipation sheet HS1closes the air gap between the rear surface of the light source supporting portion15A2of the bottom plate15A and the source flexible circuit boards30. Thus, the heat transferred to the rear surface of the light source supporting portion15A2of the bottom plate15A is effectively dissipated to the source flexible circuit boards30via the first heat dissipation sheet HS1. The heat transferred to the source flexible circuit boards30is dissipated to the outside of the liquid crystal display device10through the source flexible circuit boards30. Therefore, the heat is less likely to remain in the air gap between the rear surface of the light source supporting portion15A2of the bottom plate15A and the source flexible circuit boards30. Although the heat is more likely to be transferred to the light source supporting portion15A2of the bottom plate15A of the chassis15, the heat does not or is less likely to remain in the air gap between the light source supporting portion15A2of the bottom plate15A and the source flexible circuit boards30. Even though the liquid crystal display device10includes the light source supporting portion15A2including the outer surface covered with the source flexible circuit boards30, the performance of the liquid crystal display device10for dissipating the heat through the chassis15does not or is less likely to degrade.

In this embodiment, the second heat dissipation sheet HS2is sandwiched between the rear surface of the light guide plate supporting portion15A1of the bottom plate15A and the source circuit board32and in contact with the rear surface of the light guide plate supporting portion15A1of the bottom plate15A and the source circuit board32. According to this configuration, the second heat dissipation sheet HS2closes the air gap between the rear surface of the light guide plate supporting portion15A1of the bottom plate15A and the source circuit board32. Therefore, the heat transferred to the rear surface of the light guide plate supporting portion15A1of the bottom plate15A is effectively transferred to the source circuit board32by the second heat dissipation sheet HS2. Namely, the heat is less likely to remain in the air gap between the rear surface of the light guide plate supporting portion15A1of the bottom plate15A and the source circuit board32. Since the heat does not or is less likely to remain in the air gap between the light guide plate supporting portion15A1of the chassis15and the source circuit board32, the performance of the liquid crystal display device10for dissipating the heat through the chassis15does not or is less likely to degrade.

In this embodiment, the circuit board cover34covers the rear surface of the source circuit board32. The third heat dissipation sheet HS3is sandwiched between the source circuit board32and the circuit board cover34and in contact with the source circuit board32and the circuit board cover34. The third heat dissipation sheet HS3closes the air gap between the source circuit board32and the circuit board cover34. According to this configuration, the third heat dissipation sheet HS3effectively transfers the heat generated by the source circuit board32to the circuit board cover34. Thus, the heat is less likely to remain in the air gap between the source circuit board32and the circuit board cover34. Namely, the performance of the liquid crystal display device10for dissipating the heat through the circuit board cover34improves while the source circuit board32is protected by the circuit board cover34.

Each of the fifth heat dissipation sheets HS5is sandwiched between the chassis15and the corresponding LED board25, which include the LEDs24, and in contact with the chassis15and the corresponding LED board25. Furthermore, each of the fifth heat dissipation sheets HS5is in contact with several surfaces of the corresponding LED board25. According to this configuration, the fifth heat dissipation sheets HS5effectively transfer the heat generated by the LED boards25to the chassis15. Thus, the performance of the liquid crystal display device10for dissipating the heat improves.

The light source supporting portions15A2of the bottom plate15A of the chassis15project rearward and form steps together with the light guide plate supporting portion15A1, respectively. This configuration is for the LEDs24that are arranged opposite to the light entrance surfaces18A of the light guide plate18. The LEDs24may require components including the LED boards25on which the LEDs24are mounted, traces or patterns, and connectors. Thus, a space for holding the LEDs24may require a vertical dimension larger than that of a space for holding the light guide plate18. Since the bottom plate15A of the chassis15in this embodiment includes the light source supporting portions15A2that project rearward, the space has a vertical dimension sufficient for holding the LEDs24. Furthermore, because the light source supporting portions15A2of the bottom plate15A project rearward so as to form steps, the light guide plate supporting portion15A1is dented toward the liquid crystal panel11with respect to the light source supporting portions15A2. In this configuration, it is preferable to arrange the source circuit board32in the light guide plate supporting portion15A1for reducing an overall thickness of the liquid crystal display device10. However, to arrange the source circuit board32in the light guide plate supporting portion15A1, the source flexible circuit boards30need to be bent to cross over the step formed by the light guide plate supporting portion15A1. In general, heat tends to remain in an area in which a source flexible circuit board is bent to cross over a step. With the first heat dissipation sheet HS1, the problem that the heat remains in such an area can be resolved.

In this embodiment, the traces are formed on only a single surface of each LED board25because the LED board25is made of aluminum, namely, metal. Therefore, in comparison to the LED board25made of nonmetallic materials, the LED board25made of metal needs a larger plate surface. The bottom plate15A of the chassis15of this embodiment has the shape as described earlier. According to the chassis15having such a shape, the LED boards25are easily arranged in areas of the chassis15in which the LED boards25overlap the respective light source supporting portions15A2in the plan view. Furthermore, portions of the chassis15in which the light guide plate supporting portions15A1overlap in a plan view have a relatively smaller thickness.

In this embodiment, the reflection sheet21is arranged so as to be in contact with the front surface of the bottom plate15A of the chassis15and the opposite surface18C of the light guide plate18. If the reflection sheet21is arranged to be in contact with a heat dissipation sheet, the reflection sheet21may warp due to heat that is transferred to the heat dissipation sheet and thus reflectivity of the reflection sheet21may degrade. In contrast, since this embodiment includes the reflection sheet21that is not in contact with the heat dissipation sheet, the reflectivity of the reflection sheet21does not degrade or is less likely to degrade in comparison to a configuration that includes a heat dissipation sheet that is arranged between the front surface of the bottom plate15A and the reflection sheet21.

The reflection sheet21is sandwiched between the bottom plate15A of the chassis15and the light guide plate18and in contact with the bottom plate15A and the light guide plate18. According to this configuration, warping of the reflection sheet21due to heat is effectively reduced or suppressed.

The first heat dissipation sheet HS1of this embodiment closes the entire air gap between the source flexible circuit boards30and the rear surface of the light source supporting portion15A2of the chassis15. Since the liquid crystal panel11of this embodiment has a high definition, the source flexible circuit boards30are arranged close to each other along the long-side end of the liquid crystal panel11(along the X-axis direction). Furthermore, the source flexible circuit boards30cover a large portion of the rear surface of the light source supporting portion15A2. If the liquid crystal display device10includes the liquid crystal panel11having a particularly high definition, the distance between the adjacent source flexible circuit boards30further decreases as the size of the display surface11C decreases. If the liquid crystal display device10includes a further high definition display, power consumption for turning on the LEDs24and for driving the source drivers SD increase and thus larger heat energy is produced in comparison to the liquid crystal display device10that does not include the liquid crystal panel11having a high definition. If the first heat dissipation sheet HS1is not arranged, the heat is more likely to remain in an air gap between the source flexible circuit boards30and the rear surface of the light source supporting portion15A2. In contrast, the first heat dissipation sheet HS1of this embodiment closes the entirety of the air gap. According to this configuration, even though the source flexible circuit boards30are arranged close to one another, heat dissipation properties of the liquid crystal display device10does not degrade or is less likely to degrade. Namely, the liquid crystal display device10that includes the liquid crystal panel11having a high definition has high heat dissipation properties.

A second embodiment will be described with reference to the drawings. The second embodiment includes a circuit board cover134having configurations different from that of the first embodiment. Furthermore, the second embodiment includes a fourth heat dissipation sheet HS4which is not included in the first embodiment. Other configurations are similar to the first embodiment. Similar configurations, operations, and effects to the first embodiment will not be described. InFIG. 8, portions indicated by numerals including the reference numerals inFIG. 4with100added thereto have the same configurations as the portions indicated by the respective reference numerals in the first embodiment.

A liquid crystal display device110according to the second embodiment includes the circuit board cover134. As illustrated inFIG. 8, an end of the circuit board cover134closer to the first heat dissipation sheet HS1is sloped toward the first heat dissipation sheet H1and bent over a portion of a source flexible circuit board130opposite a light source supporting portion115A2. A portion of the end extending along the light source supporting portion115A2will be referred to as an extending portion134A hereinafter. Between the extending portion134A and portions of the source flexible circuit boards130opposed to the light source supporting portion115A2, the heat dissipation sheet HS4having heat dissipation properties is arranged. The heat dissipation sheet HS4will be referred to as the fourth heat dissipation sheet HS4(an example of a fourth heat dissipation member) hereinafter. The fourth heat dissipation sheet HS4is sandwiched between the extending portion134A and the portions of the source flexible circuit boards130opposed to the light source supporting portion115A2and in contact with the extending portion134A and the portions of the source flexible circuit boards130opposed to the light source supporting portion115A2. The fourth heat dissipation sheet HS4closes an entire air gap between the extending portion134A and the portions of the source flexible circuit boards130opposed to the light source supporting portion115A2. With this configuration, heat transferred to one of the light source supporting portions115A2close to the source flexible circuit boards30is effectively transferred to the extending portion134A of the circuit board cover134from the first heat dissipation sheet HS1, the source flexible circuit boards30, the fourth heat dissipation sheet HS4in this sequence. Then, the heat transferred to the extending portion134A of the circuit board cover134is dissipated to the outside of the liquid crystal display device110therethrough.

As described above, in the liquid crystal display device110, the portions of the source flexible circuit boards130opposed to the light source supporting portion115A2are covered with the extending portion134A of the circuit board cover134. With the heat dissipation sheet HS4, the performance of the circuit board cover134improves while noise from the source flexible circuit boards130decreases. The portions of the source flexible circuit boards130opposed to the light source supporting portion115A2are supported by the extending portion134A via the fourth heat dissipation sheet HS4. That is, the source flexible circuit boards130are less likely to warp and thus the source flexible circuit boards130preferably remain in contact with the first heat dissipation sheet HS1. According to this configuration, heat is more likely to be transferred from the light source supporting portion115A2to the source flexible circuit boards130via the first heat dissipation sheet HS1. Thus, the performance of the liquid crystal display device110for dissipating the heat through the chassis115does not or is less likely to degrade.

A third embodiment will be described with reference to the drawings. In the third embodiment, configurations of a circuit board cover234, the thickness of the second heat dissipation sheet HS2, and the thickness of the third heat dissipation sheet HS3are different from those in the second embodiment. Other configurations are similar to the first and second embodiments. Similar configurations, operations, and effects to the first and second embodiments will not be described. InFIG. 9, portions indicated by numerals including the reference numerals inFIG. 4with200added thereto have the same configurations as the portions indicated by the respective reference numerals in the first embodiment.

As illustrated inFIG. 9, in a liquid crystal display device210, the second heat dissipation sheet HS2and the third heat dissipation sheet HS3each have a thickness larger than those in the first and second embodiments. The rear surface of the third heat dissipation sheet HS3is at the same level with the rear surface of the fourth heat dissipation sheet HS4(the position in the Z-axis direction). An end of the circuit board cover234closer to the first heat dissipation sheet HS1extends in linear over the first heat dissipation sheet HS1without slope or bend so as to cover portions of source flexible circuit boards230opposed to a light source supporting portion215A2. The end of the circuit board cover234extending in linear will be referred to as an extending portion234A. That is, the circuit board cover234including the extending portion234A has a flat plate surface. According to this configuration, during production of the liquid crystal display device210, mountability of the circuit board cover234to the third heat dissipation sheet HS3and the fourth heat dissipation sheet HS4improves. Furthermore, in comparison to the circuit board cover134of the second embodiment, the cost of processing the circuit board cover234during production reduces.

A fourth embodiment will be described with reference to the drawings. The fourth embodiment differs from the first embodiment in that the fourth embodiment includes a sixth heat dissipation sheet HS6. Other configurations are similar to the first embodiment. Similar configurations, operations, and effects to the first embodiment will not be described. InFIG. 10, portions indicated by numerals including the reference numerals inFIG. 4with300added thereto have the same configurations as the portions indicated by the respective reference numerals in the first embodiment.

As illustrated inFIG. 10, in a liquid crystal display device310according to the fourth embodiment, a bezel peripheral wall portion313B of a bezel313extends rearward such that the bezel peripheral wall portion313B covers substantially an entire area of a frame peripheral wall portion314B of a frame314. The heat dissipation sheet HS6that is a sheet having heat dissipation properties is arranged between the bezel peripheral wall portion313B of the bezel313and mounting portions330C of source flexible circuit boards330. The heat dissipation sheet HS6is referred to as the sixth heat dissipation sheet (an example of a sixth heat dissipation sheet) HS6. The sixth heat dissipation sheet HS6is sandwiched between the mounting portions330C and the bezel peripheral wall portion313B and in contact with the mounting portions330C and the bezel peripheral wall portion313B. The source drivers SD generate heat during driving and the heat is transferred to the mounting portions330C. The sixth heat dissipation sheet HS6effectively transfers the heat to the bezel peripheral wall portion313B and thus the heat is dissipated to the outside of the liquid crystal display device310through the bezel peripheral wall portion313B.

As described above, a large part of the heat generated from the source drivers SD is dissipated to the outside of the liquid crystal display device310through the bezel peripheral wall portion313B and thus the performance of the liquid crystal display device310for dissipating the heat improves. In contrast, a large proportion of the heat generated from LED boards325is transferred to a bottom plate315A of a chassis315and then dissipated to the outside of the liquid crystal display device310through outer surfaces of portions of the source flexible circuit boards330opposed to a light source supporting portion315A2and an outer surface of a circuit board cover334. That is, the heat generated by the source drivers SD is separated from the heat generated by the LED board325. Therefore, the heat is sufficiently dissipated through the bottom plate315A of the chassis315(the rear side of the liquid crystal display device310) in comparison to a configuration that a large part of heat from the source drivers SD and a large part of heat from the LED board325are transferred to the bottom plate315A of the chassis315and a large part of heat is gathered to the bottom plate315A of the chassis315. Thus, the performance of the liquid crystal display device310for dissipating the heat improves.

A fifth embodiment will be described with reference to the drawings. The fifth embodiment includes a source circuit board432, the arrangement of which differs from the first embodiment. Furthermore, the fifth embodiment includes source flexible circuit boards430, the length of each of which differs from that in the first embodiment. Other configurations are similar to the first embodiment. Similar configurations, operations, and effects to the first embodiment will not be described. InFIG. 11, portions indicated by numerals including the reference numerals inFIG. 4with400added thereto have the same configurations as the portions indicated by the respective reference numerals in the first embodiment.

As illustrated inFIG. 11, in a liquid crystal display device410according to the fifth embodiment, the source circuit board432is arranged so as to cover a rear surface of alight source supporting portion415A2of a bottom plate415A of a chassis415, namely, the source circuit board432is not arranged on a rear surface of a light guide plate supporting portion415A1of the bottom plate415A of the chassis415. A seventh heat dissipation sheet HS7is arranged between the source circuit board432and the light source supporting portion415A2of the bottom plate415A covered with the source circuit board432. The seventh heat dissipation sheet HS7is in contact with the source circuit board432and the light source supporting portion415A2of the bottom plate415A. The seventh heat dissipation sheet HS7closes an entire air gap between the source circuit board432and the light source supporting portion415A2of the bottom plate415A covered with the source circuit board432. The length of each source flexible circuit board430measured from an end portion430A that is connected to a liquid crystal panel11is shorter than that of the first embodiment. Another end portion430B of the source flexible circuit board430is connected to the source circuit board432. On the outer side of the source circuit board432, a circuit board cover434is arranged so as to cover an entire plate surface of the source circuit board432similar to the first embodiment. The third heat dissipation sheet HS3is sandwiched between the source circuit board432and the circuit board cover434and in contact with the source circuit board432and the circuit board cover434.

According to the above configuration, the heat transferred to the light source supporting portion415A2of the bottom plate415A opposed to the source circuit board432is transferred to the circuit board cover434via the seventh heat dissipation sheet HS7, the source circuit board432, and the third heat dissipation sheet HS3in this sequence. The heat is dissipated to the outside of the liquid crystal display device410through the circuit board cover434. The heat that is transferred to portions of the bottom plate415A other than the light source supporting portion415A2opposed to the source circuit board432is directly dissipated to the outside of the liquid crystal display device410through the bottom plate415A. In this embodiment, the thickness of the liquid crystal display device410increases at a portion thereof including the light source supporting portion415A2because the seventh heat dissipation sheet HS7, the source circuit board432, the third heat dissipation sheet HS3, and the circuit board cover434are arranged on the rear side of the light source supporting portion415A2. However, if there is no restrictions to the thickness of the liquid crystal display device410, the heat dissipation properties of the liquid crystal display device410increase even in such a configuration.

A sixth embodiment will be described with reference to the drawings. The sixth embodiment includes a chassis515, configurations of a bottom plate515A of which are different from those of the first embodiment. Other configurations are similar to the first embodiment. Similar configurations, operations, and effects to the first embodiment will not be described. InFIG. 12, portions indicated by numerals including the reference numerals inFIG. 4with500added thereto have the same configurations as the portions indicated by the respective reference numerals in the first embodiment.

As illustrated inFIG. 12, in a liquid crystal display device510according to the sixth embodiment, the bottom plate515A of the chassis has a flat plate-like shape. Namely, the bottom plate515A does not have steps. LED boards525of this embodiment are made of non-metallic material. Each LED board525has a dimension measured along a short-side direction thereof (i.e. a dimension measured along the Z-axis direction) smaller than that of the first or fifth embodiment. The LED board525is arranged within the chassis515. Even with such a configuration, the first heat dissipation sheet HS1effectively transfers the heat that is transferred to the rear surface of the light source supporting portion515A2of the bottom plate515A to the source flexible circuit boards530. The source flexible circuit boards530dissipate heat to the outside of the liquid crystal display device510therethrough. Therefore, heat is less likely to stay in the air gap between the chassis515and the source flexible circuit boards530. Namely, of the performance for dissipating the heat through the chassis515does not or is less likely to degrade.

Modifications of the above embodiments will be described below.

(1) In each of the above embodiments, the first heat dissipation sheet is a single sheet having an elongated shape. However, the shape and the number of the first heat dissipation sheet are not limited thereto. Multiple first heat dissipation sheets may be arranged between the source flexible circuit boards and the bottom plate such that the first heat dissipation sheets overlap the respective source flexible circuit boards.

(2) In each of the above embodiments, the first heat dissipation sheet is arranged only between the light source supporting portion of the bottom plate of the chassis and the source flexible circuit boards. However, a portion of the first heat dissipation sheet may extend to the rear surface of the light guide plate supporting portion of the bottom plate or the outer surface of the side plate of the chassis.

(3) Each of the above embodiments includes the circuit board cover for covering the source circuit board. However, the circuit board cover and the third heat dissipation sheet may be omitted. In such a case, an outer surface of the source circuit board may be exposed to the outside of the liquid crystal display device and thus heat transferred to the source circuit board may be directly dissipated to the outside of the liquid crystal display device through the source circuit board.

(4) In each of the second and third embodiments, the source flexible circuit boards are covered with the circuit board cover. However, if the first heat dissipation sheet is used as a cushioning member to connect the source flexible circuit boards to the bottom plate of the chassis, the fourth heat dissipation sheet may be omitted.

(5) In each of the above embodiments, the source drivers are arranged in the respective driver holding recesses formed in the frame peripheral wall portion of the frame. However, the frame peripheral wall portion may not include the driver holding recesses and the source drivers may be in contact with the frame peripheral wall portion. Even in such a case, if an embodiment includes the configurations included in the fourth embodiment, heat generated from the source drivers may be effectively transferred to the bezel via the sixth heat dissipation sheet and dissipated to the outside of the liquid crystal display device.

(6) In each of the above embodiments, the frame between the source drivers and the side plate of the chassis is made of polycarbonate or polyethylene terephthalate; however, the material thereof is not limited thereto. For example, the frame may be made of polystyrene (thermal conductivity: 2.4 to 3.3 (10-4 cal/sec/° C.·cm)), which has a thermal conductivity lower than polycarbonate (thermal conductivity: 4.6 (10-4 cal/sec/° C.·cm)) and polyethylene terephthalate (thermal conductivity: 3.63 (10-4 cal/sec/° C.·cm)). If not only the heat generated from the LED board but also the heat generated from the source drivers are transferred to the chassis, the life of the LEDs may shorten due to an increase in temperature of the LED, or the light guide plate may warp and the optical sheet may wrinkle and warp due to an increase in temperature inside the chassis. With the frame having a lower thermal conductivity, the heat generated from the source drivers is less likely to be transferred to the chassis. Thus such problems do not occur or are less likely to occur.

(7) In each of the above embodiments, the side plate of the chassis is in contact with the frame peripheral wall portion while the source drivers are arranged in the driver holding recesses formed in the frame peripheral wall portion. However, configurations between the source drivers and the side plate of the chassis are not limited thereto. For example, thermal blocking members made of urethane may be arranged in a part or an entire area between the source driver and the side plate of the chassis (e.g. the side plate of the chassis and the frame peripheral wall portion, or the bottom portions of the driver holding recesses). If not only heat generated from the LED board but also heat generated from the source drivers are transferred to the chassis, the life of the LEDs may decrease due to an increase in temperature of the LED, the light guide plate may warp, and the optical sheet may wrinkle and warp due to an increase in temperature inside the chassis. With thermal blocking members, the heat generated by the source drivers is not or is less likely to be transferred to the chassis in comparison to each of the above described embodiments. Thus such problems do not occur or are less likely to occur.

(8) In each of the above embodiments, the television device includes the cabinets. However, the present invention may be applied to television devices without cabinets.

(9) In each of the above embodiments, the liquid crystal panel has high definition. However, the present invention may be applied to liquid crystal panels that do not have high definition.

(10) In each of the above embodiments, the television device includes the liquid crystal panel having high definition. However, the present invention may be applied to display devices other than television devices.

The technical elements described in this specification and the drawings may be used independently or in combination to achieve the technical benefits. The combinations are not limited to those in original claims. With the technologies described in this specification and the drawings, multiple objects may be accomplished at the same time. However, the technical benefits can be achieved by accomplishing even only one of the objects.

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