A light-emitting-diode backlight device includes a light source substrate to which many light-emitting diodes are mounted, and a bottom chassis having the light source substrate mounted to a principal surface side of the bottom chassis. Illumination light from the light-emitting diodes is supplied to a display panel unit. A back-surface side of the bottom chassis is provided with a heat-dissipating unit making uniform a temperature distribution over the entire bottom chassis. The heat-dissipating unit includes a mounting plate, a heat pipe, and a radiating fin. The mounting plate is mounted to at least a high-temperature area of the bottom chassis. The heat pipe is disposed on both the high-temperature area and a low-temperature area, and is mounted to the mounting plate. The radiating fin is mounted to the low-temperature area, and connected to an end of the heat pipe.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese Patent Application JP 2008-064450 filed in the Japanese Patent Office on Mar. 13, 2008, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an LED backlight device in which a many light emitting diodes (LEDs) serve as light sources.

2. Description of the Related Art

An LED backlight device is, for example, assembled to a display panel (such as a liquid display panel), and illumination light emitted from each LED is supplied to a display panel unit, to form a display device. Compared to, for example, a cold cathode fluorescent lamp (CCFL), which is generally used as a light source in a related art, the LED backlight device is provided with many LEDs which are low in cost and which have various characteristics, such as being small in size/being light, having low electrical power consumption, or high luminance, so that image display of high luminance is performed even for a large display device.

In the LED backlight device, improvement in each LED has caused an increase in the luminance and a reduction in an individual heat value. However, by providing the LED backlight device with more LEDs due to an increase in the size of the display device, its overall heat value is also large. In addition, in the LED backlight device, since a light-guiding space, which is externally shielded from light, is formed at a back-surface side of the display panel unit for assembly of the LED backlight device, heat generated from each LED is confined in the light-guiding space in a sealed state. Therefore, the overall temperature is high.

In the LED backlight device, the chromaticity of each LED may become an improper value or the life of each LED may be reduced due to light-emission characteristics of each LED becoming unstable under a high-temperature environment. In the LED backlight device, in particular, a reduction in light-emission efficiency of a red LED under a high-temperature environment is reduced, thereby reducing color reproducibility. The effect of higher temperature in the display device not only gives rise to the aforementioned problems in the LED backlight device, but also gives rise to problems such as reducing the life and deteriorating the characteristics of, for example, an integrated circuit device or electronic components mounted to various circuit unit substrates.

With regard to the problem of the LED backlight device, the applicant has provided heat-dissipating devices. Each of these heat-dissipating devices restricts a rise in temperature of the entire backlight device by efficiently dissipating heat generated from, for example, a circuit block or heat generated from each LED. The heat is efficiently dissipated using a heat pipe having a very high heat conveyance efficiency. (Refer to, for example, Japanese Unexamined Patent Application Publication Nos. 2005-317480 and 2006-58487.)

Each of these heat-dissipating devices of the previous applications is formed by connecting a heat-conveying unit to a heat-dissipating unit. The heat-conveying unit for generating heat is formed by mounting an aluminum heat-dissipating plate to the back surface of a wiring board (on which many LEDs are disposed in lines and are mounted) and by mounting a heat pipe to the heat-dissipating plate. The heat-dissipating unit includes a heat sink and a cooling fan and is disposed at a side of a bottom chassis. In each of the heat-dissipating devices of the previous applications, the heat generated from, for example, each LED is efficiently conveyed to a side by the heat pipe through the heat-dissipating plate, and the heat sink and the cooling fan efficiently dissipate the heat to the outside for efficient cooling. This reduces the overall temperature rise, so that each LED is stably driven.

SUMMARY OF THE INVENTION

In each of the heat-dissipating devices of the previous applications, as mentioned above, the LED backlight device is provided with many LEDs that generate a considerable amount of heat, and the heat conveying unit (including the heat-dissipating plate and the heat pipe) is disposed at the back-surface side of a light-source substrate (on which each LED serving as a heat-generating source is mounted) so as to face a mounting area of each LED. In each of the heat-dissipating devices of the previous applications, the heat generated from the mounting area of each LED (serving as a heat-generating source) is directly conveyed to the heat-dissipating unit for efficient cooling, so that the overall temperature rise is restricted.

In each of the heat-dissipating devices of the previous applications, the generated heat conveyed by the heat pipe is efficiently dissipated to the outside by the heat sink and the cooling fan, which is a large component. In addition, in each of the heat-dissipating devices of the previous applications, many relatively expensive heat pipes, and a heat sink and a cooling fan, which are large, heavy, and expensive, are provided. Therefore, costs, size, and weight are increased.

In the LED backlight device, due to technical progress, as with a circuit block, etc., LEDs having low electrical power consumption characteristics, a long life, high luminance characteristics, etc., and generating a smaller amount of heat have been developed. This makes it possible to reduce the size of the heat-dissipating unit. A reduction in the cost of a main body device (display device) has caused a demand for a considerable reduction in the cost of the LED backlight device. Accordingly, realizing a heat-dissipating unit which is smaller, lighter, and lower in cost is becoming important.

The inventor et al. have repeatedly conducted keen examinations on the LED backlight device. The results have made us focus attention on the fact that, regardless of the size, a particular portion of a bottom chassis (that is, a slightly upward portion of a central area of the bottom chassis) becomes a high-temperature area, and peripheral areas close to respective corners become relatively low-temperature areas, so that, overall, a temperature distribution in a driving state (turned on state) of each LED is not uniform. In the LED backlight device, heat generated from each LED, an electronic component of a circuit block, etc., causes convection to occur in the interior of the LED backlight device. This causes hot air to flow to the central area, as a result of which the central area becomes a high-temperature area. In addition, in the LED backlight device, natural heat dissipation occurs at the peripheral areas facing the outside, thereby restricting a rise in temperature, as a result of which the peripheral areas become areas having relatively low temperatures. Further, in the LED backlight device, the heat is dissipated in two directions, in particular, at the corners, so the temperature of the low-temperature areas is further reduced.

In the LED backlight device, for achieving uniform color reproducibility over an entire screen, the color temperature of the many LEDs needs to be uniform overall. In the related LED backlight device, heat is efficiently dissipated directly from the areas where the LEDs (serving as heat-generating sources) are mounted, to restrict an overall temperature rise. In addition, in the LED backlight device, it is possible to make the temperature distribution uniform over the entire LED backlight device by reducing differences between the temperature distribution at the central area and the temperature distribution at the peripheral areas.

Accordingly, it is desirable to provide an LED backlight device which is reduced in cost and which can achieve uniform color reproducibility over an entire screen, by efficiently dissipating heat in accordance with temperature distribution variations using a simple heat dissipation structure.

According to an embodiment of the present invention, there is provided a light-emitting-diode backlight device including a light source substrate to which many light-emitting diodes are mounted, and a bottom chassis having the light source substrate mounted to a principal surface side of the bottom chassis. Illumination light emitted from each of the light-emitting diodes at the light source substrate is supplied to a display panel unit. In the light-emitting diode backlight device, a back-surface side of the bottom chassis is provided with heat-dissipating means which makes uniform a temperature distribution over the entire bottom chassis. In addition, in the light-emitting-diode backlight device, the heat-dissipating means includes a mounting plate, a heat pipe, and a radiating fin, the mounting plate being mounted to at least, for example, a central area corresponding to a high-temperature area of the bottom chassis, the heat pipe being disposed on both the high-temperature area and, for example, a peripheral area corresponding to a low-temperature area of the bottom chassis and being mounted to the mounting plate, the radiating fin being mounted to the low-temperature area and being connected to an end of the heat pipe.

In the LED backlight device, heat is efficiently conveyed from, for example, the central area (which becomes the high-temperature area of the bottom chassis due to concentration of the heat resulting from internal convection caused by the heat generated from, for example, an electronic component and the many LEDs) to, for example, the peripheral area (which becomes, for example, the low-temperature area) through the mounting plate and the heat pipe. The heat is dissipated from a radiating fin having high heat-dissipation efficiency and provided at the low-temperature area, to cool the high-temperature area. In the LED backlight device, the heat-dissipating means performs partial heat dissipation on a most effective portion. Therefore, the number of heat pipes is reduced, and a cooling fan and a heat sink, which are large and expensive, are not required. Consequently, a predetermined heat-dissipation operation is performed with only the radiating fin having high heat-dissipation efficiency and being low in cost. As a result, in the LED backlight device, the temperature distribution variations are reduced, so that, overall, the color temperature of each LED is made uniform, thereby allowing an image to be displayed with high color reproducibility.

According to the LED backlight device of the embodiment of the present invention, heat is efficiently conveyed from the high-temperature area to the low-temperature area of the bottom chassis through the mounting plate and the heat pipe, and the heat is efficiently dissipated from the radiating fin at the low-temperature area, to reduce the temperature distribution variations. This causes the color temperature of each LED to become uniform overall, so that an image can be displayed with high color reproducibility. According to the LED backlight device, even if the number of heat pipes is reduced and the heat pipe is thin and light, the heat is efficiently dissipated by the heat-dissipating means including the radiating fin having high heat-dissipation efficiency. Therefore, it is possible to considerably reduce costs, and make the LED backlight device thinner and lighter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A large liquid crystal color display device (hereunder simply referred to as the “liquid crystal display device”)2including an LED backlight unit (hereunder simply referred to as the “backlight unit”)1as an LED backlight device according to an embodiment of the present invention will be described in detail with reference to the drawings. The liquid crystal display device2is used in, for example, a television receiver or various display monitor devices. As shown inFIG. 1, in the liquid crystal display device2, a front chassis (bezel)4is assembled to a front-surface side of a liquid crystal panel unit3, and the backlight unit1(which supplies illumination light) is assembled to a back-surface side of liquid crystal panel unit3.

In the liquid crystal display device2, the liquid crystal panel unit3and the backlight unit1are assembled to each other in a stacked state through a middle chassis5, and the stacked member is assembled to a bottom chassis7. Further, the resulting stacked structure is covered to assemble outer peripheral edges thereof to a back cabinet8, which abuts upon the bezel4. In the liquid crystal display device2, a circuit board15(seeFIG. 3) is mounted to a back-surface side of the bottom chassis7. In addition, although not described in detail, the back cabinet8is provided with a heat-dissipation slit or an opening allowing, for example, an operating section of a control box or a connector unit to face the outside. The connector unit is used to connect a power supply cord, an antenna cable, or an external connection cable. The bezel4and the back cabinet8constitute an exterior portion of the liquid crystal display device2.

In the liquid crystal display device2, the circuit board15includes, for example, a power-supply circuit unit, or a control circuit unit, or a transmission-reception circuit unit or a driving circuit unit. Although not shown, the liquid crystal display device2is set at, for example, a floor surface by assembling its bottom portion to a stand having an appropriate structure through a stay. A pair of left and right built-in speaker units is also assembled to the liquid crystal display device2on respective left and right sides of the liquid crystal panel unit3.

In the liquid crystal panel unit3, as is well known, a non image display area and an effective display area are provided. The non image display area is provided when an outer peripheral area having a predetermined width and extending along an outer peripheral portion of the liquid crystal panel unit3is defined as an electrode draw-out area. An area surrounded by the non image display area is the image effective display area. In the liquid crystal panel unit3, a frame3A (which holds the structural members in a stacked state) is fitted to the outer peripheral area thereof, and is secured to a front frame disposed at a bezel-4side, and the image effective display area is made to face the outside, so that the frame3A surrounds an outer periphery of the image effective display area.

In the liquid crystal panel unit3, as is well known, a space between a first glass substrate and a second glass substrate is filled with liquid crystals. The first glass substrate and the second glass substrate are kept at a predetermined from each other by, for example, a spacer bead so as to oppose each other. In addition, in the liquid crystal panel unit3, a stripe-like transparent electrode, an insulation film, and an alignment film are formed on the inner surface of the first glass substrate; and color filters for three primary colors of light, an overcoat layer, a stripe-like transparent electrode, and an alignment film are formed on the inner surface of the second glass substrate. Further, in the liquid crystal panel unit3, a deflection film and a retardation film are joined to the surface of each of the first and second glass substrates.

In the liquid crystal panel unit3, driving voltages are applied to the liquid crystals through each of the transparent electrodes from a driving control unit9mounted to the bottom chassis7(described later), to change the orientations of liquid crystal molecules. This changes light transmittance of illumination light supplied from the backlight unit1. In addition, in the liquid crystal panel unit3, the alignment films (formed of polyimide) are disposed horizontally with the liquid crystal molecules being defined as an interface. The deflection films and the retardation films cause wavelength characteristics to become achromatic characteristics and whitening characteristics. The color filters, which can provide a full-color image, are used to display, for example, a color image. Obviously, the liquid crystal panel unit3is not limited to that having the above-described structure.

The backlight unit1includes a light-guiding unit. The light-guiding unit efficiently supplies illumination light emitted from each LED11, mounted to a light source substrate6(described later), to the liquid crystal panel unit3. As shown inFIG. 2, a plurality of stud members10(provided on the bottom chassis7) are abutted upon the light-guiding unit to make it oppose and to keep it at a predetermined distance from the bottom chassis7over the entire surface of the back-surface-side of the liquid crystal panel unit3, and to form a light-guiding space between the backlight unit1and the bottom chassis7.

The light-guiding unit includes, for example, an optical sheet member12, a diffusion plate13, and a reflecting sheet14, which are assembled to each other in a stacked state. In the light-guiding unit, the size of the reflecting sheet14is substantially the same as the size of the liquid crystal panel unit3. As shown inFIG. 2, each LED11faces the interior of the light-guiding space through an opening. This makes it possible to prevent leakage of the illumination light emitted from each LED11to the surroundings, and to reflect and efficiently supply the illumination light to the diffusion plate13.

In the light-guiding unit, with the diffusion plate13diffusing the illumination light over the entire surface thereof, the illumination light is supplied to the optical sheet member12. In addition, in the light-guiding unit, the optical sheet member12performs a predetermined optical operation on the supplied illumination light, to supply the resulting illumination light to the liquid crystal panel unit3. The optical sheet member12is formed by stacking upon each other, for example, an optical sheet member which separates the illumination light into an orthogonal component and an optical sheet member which prevents coloring or widens a viewing angle by compensating for a phase difference of the illumination light, or a reflecting sheet member and a diffusion sheet member (which diffuses the illumination light). The optical sheet member12is not limited to the stacked structure of the aforementioned optical sheet members. For example, another optical sheet member may include, for example, two light diffusion sheets having a luminance increasing film, a retardation film, or prism sheet interposed therebetween. The light-guiding unit diffuses the illumination light over the entire surface thereof, to supply the illumination light having a substantially uniform luminance to the liquid crystal panel unit3.

In the backlight unit1, the light source substrate6is divided into a plurality of substrate portions in accordance with the size of the liquid crystal panel unit3. A first principal surface6A facing the liquid crystal panel unit3is provided with, for example, many LEDs11and an input-output connector (not shown). The LEDs11include an appropriate combination of red LEDs11R, green LEDs11G, and blue LEDs11B. The first principal surface6A of the light source substrate6is provided with many LED mounting lands (not shown) in a predetermined arrangement. The LEDs11are mounted to the LED mounting lands, respectively. Although not shown in detail, a second principal surface6B of the light source substrate6is provided with, for example, predetermined wiring patterns and lands to mount various electronic components thereto. Driving circuit boards15A for the LEDs11are mounted on the respective substrate portions.

In the backlight unit1, a driving voltage is applied to each LED11from its corresponding driving circuit, so that each LED11emits illumination light, which is supplied to the light-guiding unit through the light-guiding space. In addition, in the backlight unit1, as shown inFIG. 2, the red LEDs11R, the green. LEDs11G, and the blue LEDs11B are mounted in an annular arrangement to the light source substrate6. However, the arrangement is obviously not limited thereto. In addition, the number of LEDs11to be mounted is appropriately set in accordance with the size of the liquid crystal panel unit3.

In the liquid crystal display device2, the bottom chassis7(which supports each structural component, such as the backlight unit1and the liquid crystal panel unit3, and which constitutes a mechanical structure) is formed of, for example, a light aluminum sheet plate having good thermal conductivity, good mechanical processability, and mechanical rigidity, or a metallic material having characteristics that are equivalent thereto. Although not described in detail, the bottom chassis7is supported at a central portion thereof through the stay with reference to the studs, and is positioned and secured at its upper-side portion to an upper frame portion of the bezel4through a top bracket member.

In the bottom chassis7, as mentioned above, a first principal surface7A (constituting the surface of mounting the backlight unit1) is provided with the many stud members10and has the light source substrate6of the backlight unit1mounted thereto. When the light source substrate6is secured to appropriate locations of the bottom chassis7with, for example, a plurality of metallic setscrews, the bottom chassis7is firmly mounted to the light source substrate6, and heat is transmitted from the light source substrate6. As shown inFIG. 3, the circuit boards15, such as various control circuit boards or electronic-component mounting boards having mounted thereto, for example, various switches or various connectors (such as an external connection connector or a power supply connector), are mounted to the bottom chassis7.

In the liquid crystal display device2, as mentioned above, the liquid crystal panel unit3has an electrode draw-out area having, many draw-out electrodes along the upper edge and the lower edge thereof, so that, through the draw-out electrodes, input-output signals (driving voltages) output from the driving control unit9are transmitted and received. Therefore, in the liquid crystal display device2, the driving control unit9is mounted to the bottom chassis7so as to oppose a portion of an upper edge or a lower edge near the electrode draw-out area of the liquid crystal panel unit3, thereby shortening the wiring portions to restrict, for example, superimposed noise at the wiring portions. In addition, in the liquid crystal display device2, higher performance of the liquid crystal panel unit3, such as controlling a residual image, has caused the driving control unit9to increase in size, thereby increasing heating value. Therefore, efficient heat dissipation of the driving control unit9whose setting position, along with the heating value of the LEDs11, is limited is becoming important.

In the liquid crystal display device2, internal convection occurs due to heat generated from, for example, the driving control unit, the electronic components mounted to the circuit boards15, or the LEDs11mounted to the light source substrate6of the backlight unit1, as a result of which the heat is concentrated at a central area H of the bottom chassis7, thereby causing the central area H to become a high-temperature area. In the liquid crystal display device2, natural heat dissipation occurs at, for example, a left peripheral area LL or a right peripheral area LR (hereunder simply referred to as the “peripheral areas L”) to restrict a rise in temperature, so that these peripheral areas L become low-temperature areas. The peripheral areas LL and LR face the outer portion of the bottom chassis7. In the liquid crystal display device2, as mentioned above, this phenomenon occurs in common regardless of the size thereof.

In the liquid crystal display device2, although, particularly speaking, a range depends upon the heating value, the difference between the temperatures of the peripheral areas L and the central area H of the bottom chassis7is, for example, approximately 20° C. for a 46-inch size. In the backlight unit1, heat is efficiently dissipated from the central area H by providing heat-dissipating units16(described in detail later) at the bottom chassis7, so that, overall, the temperature distribution variations are reduced. As a result, overall, the color temperature of each LED11is made uniform, so that it is possible to display an image with high color reproducibility. In the backlight unit1, the overall internal temperature of the bottom chassis7is also reduced by efficient dissipation of heat from the central area H by the heat-dissipating units16, so that the characteristics of the LEDs11and the various electronic components are stabilized, and the lives thereof are increased.

In the liquid crystal display device2, as mentioned above, the central area H of the bottom chassis7becomes a high-temperature area due to concentration of heat resulting from internal convection. However, even corresponding areas of the circuit boards15and the driving control unit9(having, for example, electronic components having high heating values mounted thereto) partly become high-temperature areas. In the backlight unit1, the heat-dissipating units16(described later) can partly dissipate the heat of these high-temperature areas in addition to dissipating the heat of the central area H.

In the backlight unit1, as shown inFIG. 3, the heat-dissipating units16include a plurality of mounting plates17, heat pipes18, and a left radiating fin19L and a right radiating fin19R (hereunder generically referred to as the “radiating fins19”), all of which are mounted to the second principal surface7B of the bottom chassis7. Pairs of left and right heat-dissipating units16L and16R (hereunder generically referred to as the “heat-dissipating units16”) are disposed on the left and the right sides of the central area H. As described in detail below, in the heat-dissipating units16, the heat pipes18are mounted to the respective mounting plates17, and ends of the heat pipes18are connected to the radiating fins19. Heat conveyed by each heat pipe18is dissipated by each radiating fin19.

Similarly to the aforementioned bottom chassis7, each mounting plate17of the heat-dissipating units16is formed of an extruded aluminum component, made of an aluminum material having high thermal conductivity, or a metallic material having an equivalent characteristic. Each mounting plate17has a horizontally long, rectangular shape having a length extending from the central portion to the peripheral portions of the bottom chassis7. Each mounting plate17may be formed of, for example, an aluminum alloy, a magnesium alloy, a silver alloy, or a copper material. Each mounting plate17may be formed by an appropriate processing method, such as a sheet-metal processing method, a pressing method, or a cutting-out method. As shown inFIG. 3, the mounting plates17are each secured at a plurality of locations to the bottom chassis7with metallic setscrews, and are mounted horizontally and parallel to each other on the left and right peripheral areas L (LL, LR), respectively, from the central area H.

Each heat pipe18in close contact with the principal surface is mounted to its corresponding mounting plate17. As is well known, each heat pipe18has a pipe body made of a material, such as copper, having high thermal conductivity. An inside wall of each pipe body is provided with a capillary structure (wick). The interior of each pipe body in a substantially vacuous state is filled with operating fluid. Each heat pipe18is used as a member that efficiently conducts heat in a heat-dissipation structure including various electronic devices. In addition, each heat pipe18conducts heat with high efficiency by repeating an operation of discharging heat by evaporating working liquid at a high-temperature side, moving the resulting gas towards a low-temperature side, and liquefying the resulting gas at the low-temperature side, and an operation of moving the resulting liquid again towards the high-temperature side by capillary phenomenon in the wick. Even if the temperature difference is on the order of ±1° C., each heat pipe18can conduct heat.

In the heat-dissipating units16, the radiating fins19are formed by assembling many rectangular plates to respective fin mounting plates20(formed of, for example, aluminum sheet metal) as shown inFIG. 4. The many fins are formed by punching an aluminum sheet metal (having characteristics equivalent to those of the bottom chassis7and the mounting plates17) by, for example, a pressing operation. Although not described in detail, the many radiating fins19are assembled and integrated to the fin mounting plates20on the principal surface at one end so as to oppose each other and so as to be disposed apart from each other by a predetermined distance in a thickness direction thereof. When the radiating fins19are stacked upon each other by a simple processing operation, the radiating fins19have an overall larger surface area and provide good heat-dissipation characteristics compared to those of an aluminum sheet metal product or an aluminum die-cast product having a large thickness.

The radiating fins19each dissipate heat by conveying the heat from the central area H of the bottom chassis7by the mounting plates17and the heat pipes18. The thickness and pitch of each of the fins19are determined on the basis of a required heat-dissipation amount. The relationship between a maximum temperature (° C.) of heat-dissipation amount and thickness (mm) when the height of each of the fins19is constant is as shown inFIG. 5A. Similarly, the relationship between the maximum temperature (° C.) of heat-dissipation heating value and pitch (mm) when the height of each of fins19is constant is as shown inFIG. 5B. As is clear from these graphs, for the radiating fins19, it is effective to use fins whose thickness becomes larger as the maximum temperature of heat-dissipation heating value is increased. In addition, it is desirable to use fins disposed at a certain pitch. When the thickness of each of the radiating fins19is increased, the weight thereof is increased, and when the pitch between the radiating fins19is increased, the overall size of the radiating fins19is increased. Therefore, these values are optimally set in accordance with the required heat-dissipation heating value.

As shown inFIG. 4, each fin mounting plate20includes a member that integrally forms the central portion of each fin, and a member that integrally forms the top end and the bottom end of the fin stacked body and that constitutes a mounting member to the bottom chassis7. This reduces the weight of each fin mounting plate20. Since each fin mounting plate20also properly conducts heat from the bottom chassis7due to its material characteristics, it may be formed of, for example, an integrated member or a member that is L-shaped in cross section and that can be assembled to two sides of the fin stacked body. Although not described in detail, the radiating fins19are provided with fitting holes whose axial lines are aligned with respect to each other while the fins are integrated to the fin mounting plates20. The heat pipes18whose ends are tightly fitted to the fitting holes extend through these fitting holes to orthogonally connect the heat pipes18thereto.

As shown inFIGS. 3 and 4, in the heat-dissipating units16, the mounting plates17are arranged in a height direction and mounted horizontally at the second principal surface7B of the bottom chassis7so that, at the central portion of the bottom chassis7, ends of the mounting plates17oppose each other and so that the mounting plates17extend from the central area H to the left peripheral area LL and the right peripheral area LR (hereunder simply refereed to as the “peripheral areas L”). That is, in the heat-dissipating units16, the heat pipes18are disposed on the second principal surface7B of the bottom chassis7so as to be provided at the central area H and the left and right peripheral areas L through the respective mounting plates17. In the heat-dissipating units16, the left and right fin mounting plates20oppose and are mounted to the second principal surface7B of the bottom chassis7on the left and right peripheral areas L, provided on respective sides of the central area H, in the height direction. That is, the heat-dissipating units16are disposed on the left and right peripheral areas L of the second principal surface7B of the bottom chassis7while the radiating fins19, mounted to the fin mounting plates20, are arranged in the height direction and are stacked upon each other.

As mentioned above, the heat-dissipating units16having the above-described structure effectively dissipate heat from the central area H of the bottom chassis7whose temperature becomes high due to the concentration of the heat generated by convection resulting from the heat generated from the circuit boards15or the driving control unit9, or the many LEDs11. In each of the heat-dissipating units16, the heat is conveyed from one end of each heat pipe18through the corresponding mounting plate17from the central area H of the hot bottom chassis7. In addition, in each of the heat-dissipating units16, each heat pipe18evaporates the operating liquid at one end thereof to which the heat has been conducted, and causes the resulting gas to move towards the other end, to efficiently convey the heat.

In the heat-dissipating units16, the heat pipes18conduct the heat from the central area H to the peripheral areas L of the bottom chassis7, and the radiating fins19, connected to the ends of the heat pipes18at the peripheral areas L, dissipate the heat. In addition, in the heat-dissipating units16, the heat conveyed from the heat pipes18is efficiently dissipated from the surfaces of the radiating fins19. In addition, in the heat-dissipating units16, the heat pipes18efficiently convey heat from the central area H to the peripheral areas L, and cool the central area H, so that the temperature distribution over the entire bottom chassis7is made uniform.

In the heat-dissipating units16, as mentioned above, the radiating fins19, superimposed upon each other and disposed in the height direction, are disposed at the peripheral areas L of the bottom chassis7. In the heat-dissipating units16, the radiating fins19are disposed along the direction of convention of the hot air generated in the liquid crystal display device2, so that even the hot air is efficiently dissipated.

As mentioned above, the driving control unit9of the liquid crystal panel unit3is disposed at the bottom chassis7so as to oppose the top edge of the central area H. In the heat-dissipating units16, the mounting plates17and the heat pipes18extend below the driving control unit9, and the radiating fins19are disposed in the left and right peripheral areas L so as to surround the mounting plates17and the heat pipes18. Therefore, in the heat-dissipating units16, the diffusion of the heat generated from the driving control unit9to the interior of the device is restricted. The heat-dissipating units16cool the bottom chassis7when the driving control unit9is directly connected to the bottom chassis7through, for example, a heat conduction structure of a heat-dissipation sheet.

In the liquid crystal display device2, as mentioned above, the backlight unit1is assembled to the back surface side of the liquid crystal panel unit3. In addition, in the liquid crystal display device2, the backlight unit1is assembled to the first principal surface7A of the bottom chassis7, and the heat-dissipating units16are provided at the second principal surface7B of the bottom chassis7. Further, in the liquid crystal display device2, as described above, the heat-dissipating units16include the mounting plates17(mounted to the central area H and the lateral peripheral areas L), the heat pipes18(mounted to the respective mounting plates17), and the many radiating fins19(mounted to the peripheral areas L of the bottom chassis7through the fin mounting plates20, connected to the ends of the heat pipes18; and stacked upon each other and integrated to the fin mounting plates20).

While the liquid crystal display device2is operating as a result of supplying electrical power to each portion thereof, heat is generated from, for example, various electronic components, mounted to the driving control unit9and the circuit boards15, and each LED11, mounted to the light source substrate6. This causes the internal temperature to rise. In addition, in the liquid crystal display device2, heat is concentrated at the central area H of the bottom chassis7resulting from convection of hot air caused by the heat generated from each of the aforementioned portions in the interior of the liquid crystal display device2. This causes the central area H to become a high-temperature area. In addition, natural heat dissipation from the peripheral areas L (which are closer to the outer side) become low-temperature areas. Therefore, temperature distribution variations occur.

In the liquid crystal display device2, as described above, the heat-dissipating units16efficiently convey heat from the central area H to the peripheral areas L of the bottom chassis7by the mounting plates17and the heat pipes18. In addition, the heat is dissipated from each of the radiating fins19at the peripheral areas L. In addition, in the liquid crystal display device2, the difference between the temperature of the peripheral areas L and that of the central area H of the bottom chassis7is reduced by the heat-dissipating units16, to cause the temperature to be uniform, and to reduce the overall temperature.

In the liquid crystal display device2, this reduces changes in the characteristics of the LEDs11of the backlight unit1, to stably and efficiently supply illumination light to the entire liquid crystal panel unit3. Therefore, in the liquid crystal display device2, it is possible to display an image with high color reproducibility by making uniform the color temperature in the liquid crystal panel unit3. In addition, in the liquid crystal display device2, each LED11, each electronic component, etc., are operated stably and have increased lives.

FIG. 6shows results of actual measurements of temperature distributions of respective areas for an experimental model30in which the heat-dissipating units16having the above-described structure are mounted. In the experimental model30, pairs of left and right units31including mounting plates17and heat pipes18are disposed vertically in two levels so as to be situated slightly above a central area H of a bottom chassis7, and lateral ends of the heat pipes18are connected to dispose a pair of left and right radiating fins19in peripheral areas L. The results of the actual measurements of the temperatures of the respective portions in the experimental model30show that, at the central area H, the temperature of the portion where each upper unit31U is disposed is 53.4° C., the temperature of the portion where each lower unit31L is disposed is 55.8° C., and the temperatures of the portions where the units31are not disposed from the lower units31L to the lower portion of the experimental model30are 59.4° C., 59.6° C., and 51.5° C.

The results of actual measurements of the temperatures of portions of radiating fins19in peripheral areas L in the experimental model30show that the temperature of the portion opposing each upper unit31U is 53.9° C., the temperature of the portion opposing each lower unit31L is 57.3° C., and the temperatures of the portions opposing the measured portions of the central area H and where the units31are not disposed are 57.3° C., 54.4° C., and 49.3° C. Further, the results of actual measurements of the temperatures of portions opposing the measured portions along outer peripheral edges of the experimental model30are 47.7° C., 51.8° C., 51.2° C., 51.5° C., and 43.0° C. As is clear from the aforementioned actual measurement results, in the experimental model30, it is confirmed that, by providing the heat-dissipating units16, the temperature difference range is approximately ±10° C. over the entire bottom chassis7, so that the central area H is cooled and the heat at the central area H and that at the peripheral areas are made uniform.

In the heat-dissipating units16of the liquid crystal display device2, the number of mounting plates17and heat pipes18, and the size and the number of the radiating fins19are optimally set on the basis of, for example, simulation results. In all of these cases, in the liquid crystal display device2, the heat-dissipating units16dissipate heat at the central area H, and make uniform the heat of the entire device.

In the above-described embodiment, in the heat-dissipating units16, the mounting plates17, to which the heat pipes18are mounted, and the fin mounting plates20, to which the radiating fins19are mounted, are separate members; and these separate members are independently mounted to the bottom chassis7. In the heat-dissipating units16, such a structure makes it possible to mount the mounting plates17and the radiating fins19to the bottom chassis7by adjusting the positions of the mounting plates17and the radiating fins19with respect to the bottom chassis7on the basis of the optimal conditions based on the simulation results. The present invention is obviously not limited to such a structure.

InFIG. 7, in a heat-dissipating unit40according to a second embodiment of the present invention, for example, two heat pipes41U and41L are used, and are mounted to mounting plates42U and42L by mounting brackets43, respectively. Radiating fins45L and45R (hereunder simply referred to as the “radiating fins45”) are disposed at the heat pipes41U and41L on respective sides of a central area H of a bottom chassis7. The two heat pipes41U and41L have lengths extending towards a left peripheral area LL and a right peripheral area LR. Since, in the heat-dissipating unit40, these structural members are equivalent to the structural members of the above-described heat-dissipating units16, they will not be described in detail below.

The mounting plate42U of the heat-dissipating unit40is formed with a horizontally long rectangular shape that is slightly longer than the heat pipe41U, and has fin mounting portions42U1and42U2at respective ends thereof. The mounting plate42L of the heat-dissipating unit40is also formed with a horizontally long rectangular shape having a length that is equal to the length of the mounting plate42U, and has fin mounting portions42L1and42L2at respective ends thereof as shown inFIG. 7. The fin mounting portions42L1and42L2have widths that are slightly larger than the widths of the radiating fins45and are bent into L shapes. In the heat-dissipating unit40, a mounting structure for mounting the radiating fins45to the bottom chassis7includes fin mounting plates44and the mounting plates42U and42L. The fin mounting plates44secure the upper portions in the height direction of the radiating fins45L and45R. The upper end portions of the radiating fins45L and45R are mounted to the bottom chassis7through the fin mounting plates44.

The radiating fins45L and45R are mounted to the bottom chassis7through the mounting plate42U by connecting intermediate portions of the radiating fins45L and45R to ends of the heat pipe41U, opposing fitting holes (not shown), and by securing the portions of the radiating fin45to the fin mounting portions42U1and42U2of the mounting plate42U. The radiating fins45are mounted to the bottom chassis7through the mounting plate42L by connecting lower end portions of the radiating fins45L and45R to ends of the heat pipe41L, opposing fitting holes (not shown), and by securing the lower end portions to the fin mounting portions42L1and42L2of the mounting plate42L.

In the heat-dissipating unit40having the above-described structure, as described above, the mounting plates42U and42L serve as mounting members for mounting the heat pipes41U and41L and the radiating fins45thereto, so that the number of components and the number of mounting operations are reduced, and handling is facilitated. In addition, in the heat-dissipating unit40, each structural member previously integrated to each other in a separate step is supplied, to mount each structural member to the bottom chassis7. This reduces the occurrence of, for example, bending of the heat pipes41in, for example, a conveyance step. Further, in the heat-dissipating unit40, it is possible for the above-described mounting plates42U and42L to be integrated to the fin mounting plates44and to form the mounting members for mounting thereto the heat pipes41and the radiating fins45into substantially H shapes, though the heat-dissipating unit40will be slightly larger as a whole.

InFIG. 8, a heat-dissipating unit50according to a third embodiment of the present invention is applied to, for example, a liquid crystal display device in which a driving control unit9is disposed so as to oppose a portion along a lower edge of a central portion near an electrode draw-out area of a liquid crystal panel unit3. In the liquid crystal display device, as mentioned above, a large amount of heat is generated from each LED11, electronic components, of circuit boards15, etc., as well as the high-performance driving control unit9. In the liquid crystal display device, the temperature of a central area H of a bottom chassis7becomes even higher when heat generated from the driving control unit9is directly radiated. In the liquid crystal display device, the heat-dissipating unit50efficiently dissipates heat at the central area H of the bottom chassis7to make uniform the temperature distribution over the entire bottom chassis7.

In the liquid crystal display device, the driving control unit9is connected to the bottom chassis7(not shown) through, for example, a heat conveying unit, such as a heat-dissipating sheet. In addition, the heat-dissipating unit50of the liquid crystal display device is disposed on a second principal surface7B of the bottom chassis7so that, a plurality of heat pipes52, mounted to mounting plates51, are arranged and disposed horizontally in a central area H and peripheral areas LL and LR. Heat is conveyed from the high-temperature central area H to the low-temperature peripheral areas LL and LR. Even in the heat-dissipating unit50, radiating fins53in which a plurality of rectangular plates are stacked upon each other in the thickness direction and integrally formed are used. The rectangular plates are formed by punching an aluminum sheet metal by, for example, a pressing operation.

The radiating fins53are used as mounting members used as the mounting plates51of the heat pipes52. Each radiating fin53disposed in the height direction is arranged so as to be positioned at the lower portion of the central area H and so as to oppose the driving control unit9. The radiating fins53are connected to the heat pipes52by passing them through fitting holes (not shown), formed in the radiating fins53so as to extend therethrough in the thickness direction. Since these structural members of the heat-dissipating unit50are equivalent to the structural members of the heat-dissipating unit16, the structural members of the heat-dissipating unit50will not be described in detail.

The heat-dissipating unit50having the above-described structure includes the mounting plates51, the heat pipes52, and the radiating fins53. These structural members are mounted to the bottom chassis7so as to be disposed at the lower portion of the central area H, and so as to surround the driving control unit9connected to the bottom chassis7through a heat coupling unit. In the heat-dissipating unit50, heat is conveyed from the central area H to the peripheral areas LL and LR by the mounting plates51and the heat pipes52. In addition, in the central area H, heat generated from the driving control unit9is dissipated by the radiating fins53. Therefore, in the heat-dissipating unit50, heat concentration at the central area H is restricted, to stably operate, for example, electronic components of the circuit boards15and the driving control unit9, and to stably drive each LED11, so that color reproducibility is increased overall.

The present invention is not limited to the liquid crystal television1discussed in the aforementioned embodiment, so that, obviously, the present invention is also applicable to various panel display monitor devices.