JP4819389B2 - Backlight unit and liquid crystal display device - Google Patents

Description

  The present invention relates to a backlight unit disposed on the back side of a liquid crystal display panel.

  2. Description of the Related Art As a liquid crystal display device for a computer or a mobile phone, a configuration in which a backlight unit is disposed on the back side of a transmissive liquid crystal panel and light is irradiated from the back is known. In such a liquid crystal display device, since a backlight light source is used in a closed narrow space, heat generated from the light source tends to accumulate and the temperature inside the device tends to rise. When the temperature in the apparatus rises, the brightness of the light source fluctuates and the operating characteristics of other semiconductors and electrical components are degraded, so that heat must be dissipated (see Patent Documents 1 and 2).

  The heat dissipating device described in Patent Document 1 is provided with heat dissipating fins on the back surface of a backlight reflector disposed behind a fluorescent tube, and further forcibly air-cooled by an air cooling fan. Further, the heat dissipating device described in Patent Document 2 cools the display panel by arranging a cooling liquid tube along the fluorescent tube, and connects the cooling liquid tube to a cooling liquid tank provided in a stand to cool the cooling liquid. Is circulated, receives heat with a cooling tube, and dissipates heat with a coolant tank.

Conventionally, fluorescent tubes have been used as light sources for liquid crystal display devices, but in recent years, LEDs that have higher luminance than fluorescent tubes have attracted attention. High-brightness LEDs generate a large amount of heat and reach several W / mm ² , so that even higher heat dissipation performance is required.
Japanese Utility Model Publication No. 6-43625 JP-A-2005-17413

  However, in the heat radiating device described in Patent Documents 1 and 2, the cooling capacity is insufficient when the LED light source is used. Moreover, in the heat dissipating device of Patent Document 1, the operating noise of the cooling fan may become noise, and the operating noise increases when the rotational speed of the fan is increased to improve the heat dissipation performance. On the other hand, the heat dissipating device of Patent Document 2 circulates the coolant, so there is no noise from the cooling fan, but heat is radiated by a stand away from the heat generation source. The cooling capacity is extremely insufficient.

  In view of the above-described technical background, an object of the present invention is to provide a backlight unit that has high luminance with an LED light source and has excellent heat dissipation, and a liquid crystal display device incorporating the backlight unit.

  That is, the backlight unit of the present invention has the configuration described in [1] to [11] below.

[1] In the backlight unit arranged on the back side of the liquid crystal panel,
A plate-type heat radiating portion, an LED light source disposed at a side end of the plate-type heat radiating portion, and a heat receiving portion that receives heat from the LED light source and is connected to the plate-type heat radiating portion. Backlight unit.

  [2] The backlight unit according to [1], wherein the heat receiving unit is a tube having a passage through which a coolant flows.

  [3] The backlight unit according to item 2, wherein the hydraulic equivalent diameter (De) of the passage is 0.2 to 3.1 mm.

  [4] The backlight unit according to 2 or 3 above, wherein the flow rate of the coolant in the passage is 0.05 to 2 m / sec.

  [5] The backlight unit according to any one of items 1 to 4, wherein an energization layer is integrally laminated on the heat receiving portion via an insulating layer, and an LED light source is attached to the energization layer.

  [6] The backlight unit according to any one of [1] to [5], wherein a passage through which a coolant flows is provided in the plate-type heat radiation portion.

  [7] The backlight unit according to any one of [2] to [4] and [6], wherein the passage of the tube and the passage of the plate-type heat radiating portion communicate with each other.

  [8] The backlight unit according to any one of items 1 to 7, wherein a radiation fin is attached to a back surface of the plate-type heat radiation portion.

  [9] The backlight unit according to any one of items 1 to 8, wherein a front surface of the plate-type heat radiating portion is a reflector of an LED light source.

  [10] The backlight unit according to any one of [1] to [9], further including a light guide plate disposed on a front surface side of the plate-type heat radiation portion.

  [11] The method according to any one of the above items 2 to 4, 6, and 7, further comprising a pump that circulates the coolant and a reservoir tank that stores the coolant and communicates with the tube passage or the panel radiator. Backlight unit.

  The liquid crystal display device of the present invention has the configuration described in [12] below.

  [12] A liquid crystal display device, wherein the backlight unit according to any one of items 1 to 11 is disposed on the back side of the liquid crystal panel.

  According to the backlight unit according to the invention of [1], the heat generated by the LED light source is absorbed by the heat receiving portion and is radiated by the plate-type heat radiating portion having a large area, so that an excellent cooling capacity is obtained.

  According to the invention of [2], further excellent cooling capacity heat radiation performance can be obtained by the coolant flowing through the tube passage.

  According to the inventions [3] and [4], particularly excellent cooling capacity can be obtained.

  According to the invention of [5], the heat generated by the LED light source can be quickly transmitted to the heat receiving section.

  According to the inventions [6], [7] and [8], particularly excellent heat dissipation performance can be obtained.

  According to the invention [9], it is not necessary to separately install a reflector.

  According to the invention [10], light can be reflected to the liquid crystal panel side by the light guide plate. According to the invention of [11], an excellent cooling capacity can be obtained.

  Since the liquid crystal display device according to the invention [12] uses the backlight unit according to any one of the inventions [1] to [11], the heat generated by the LED light source is sufficiently dissipated. Therefore, no heat is trapped in the apparatus. For this reason, even if the liquid crystal display device is used for a long time, the luminance of the light source does not fluctuate, and other semiconductors and electrical components can be operated normally.

  1A and 1B show an embodiment of the backlight unit (1) of the present invention. The backlight unit (1) is disposed on the back side of the liquid crystal panel in the liquid crystal display device.

  The backlight unit (1) is received by a number of LED light sources (10) arranged above and below, the heat receiving units (20) (21) that receive the heat generated by the LED light sources (10), and the heat receiving unit (20). And a light guide plate (2) for guiding the light from the LED light source (10) to the entire surface.

  A number of LED light sources (10) are mounted in a row on the printed circuit board (11), and the printed circuit board (11) is in close contact with the heat receiving part (20) via an adhesive layer such as a heat conductive compound. It is joined. The heat receiving parts (20) and (21) are in close contact with the upper and lower side edges of the plate-type heat radiation part (30) installed on the back side of the light guide plate (2) in the direction in which the upper and lower LED light sources (10) face each other. Attached to the state.

  The heat receiving portion (20) is composed of flat aluminum tubes (22) and (23) having a passage (24) that penetrates in the longitudinal direction and through which the coolant flows. One end of the lower flat tube (22) is connected to the coolant inlet (40).

  The plate-type heat radiating part (30) is formed to have a planar dimension substantially equivalent to that of the liquid crystal panel. The plate-type heat radiating section (30) receives heat by the heat receiving sections (20) and (21) and diffuses the heat-absorbed cooling liquid over a wide area and meanders the pipe sections (31) and (32) through which the cooling liquid flows. As a result, the flow rate of the coolant is increased, and the heat dissipation efficiency is improved. Moreover, the pipe part is formed by two paths on the left and right. The pipe portion (31) of the first path has a lower end connected to the other end of the lower flat tube (22) and an upper end connected to one end of the upper flat tube (23). On the other hand, the pipe portion (32) of the second path has an upper end connected to the other end of the upper flat tube (23) and a lower end connected to the coolant outlet (41). Further, a pump (42) for circulating the coolant and a reservoir tank (43) for storing the coolant are connected between the inlet (40) and the outlet (41). Accordingly, the coolant fed from the inlet (40) by the pump (42) is supplied to the lower flat tube (22), the pipe portion (31) of the first path of the plate-type heat radiating portion (30), the upper flat tube ( 23) and flows in the order of the second path (32) of the plate-type heat radiation part (30), is discharged from the outlet (41), and returns to the reservoir tank (43). While the coolant circulates in this normal path, the heat generated by the LED light source (10) is absorbed by the upper and lower heat receiving portions (20) and further radiated by the plate-type heat radiating portion (30). The LED light source (10) and the backlight unit (1) are cooled by repeating this heat absorption and heat dissipation.

  The tubes (22) and (23) are formed into a fine channel by forming a large number of fine protrusions (25) on the wall surface of the passage (24), and excellent heat dissipation is obtained by increasing the surface area in the passage. Further, in the perforated tube (27) shown in FIG. 2, fine channels are formed by partitioning into a large number of passages (26) in the cross section, and the surface area inside the passage passages is enlarged, so that excellent heat dissipation can be obtained. .

  FIG. 3 shows the hydraulic equivalent diameter (De) and heat of the passages (24) and (26) in the tubes (22), (23) and (27) described above when the power of the pump for injecting the coolant is constant. The figure (graph) which shows the relationship between resistance and pressure loss is shown. The hydraulic equivalent diameter (De) when the cross-sectional area A of the passages (24) and (26) and the wet circumferential length p are calculated as De = 4 A / p. In general, the absolute value of thermal resistance varies depending on the size of the tubes (22), (23), and (27), but the tendency of thermal resistance to change relative to the hydraulic equivalent diameter depends on the size of the tubes (22), (23), and (27). However, it is the same as that of FIG.

  As shown in the figure, when the hydraulic equivalent diameter (De) of the passages (24) and (26) of the tubes (22), (23), and (27) is 0.2 mm or more, the pressure loss becomes small, and when the diameter is 3.1 mm or less Resistance becomes small and high cooling efficiency can be exhibited. For this reason, in the present invention, it is recommended to set the hydraulic equivalent diameter (De) of the passages (24) and (26) in the range of 0.2 to 3.1 mm. Further, the pressure loss is further reduced at 0.25 mm or more, and is further reduced at 0.3 mm or more. Further, the thermal resistance is further reduced at 2 mm or less. Therefore, a particularly preferable hydraulic equivalent diameter (De) is 0.3 to 2 mm.

  The flow rate of the coolant in the passages (24) and (26) is preferably 0.05 to 2 m / sec. If it is less than 0.05 m / sec, sufficient cooling performance cannot be obtained, and if it exceeds 2 m / sec, erosion may occur in the pipe. A particularly preferred flow rate is 0.5 to 1 m / sec.

  Although the manufacturing method of the tube which has the above-mentioned fine channel is not limited, For example, it can manufacture by pre-molding a thin plate to a pipe | tube by a precision extrusion method or a precision type roll process, and brazing a joint. Moreover, as the material for the heat receiving portion, it is possible to recommend a material having high heat conductivity such as aluminum, copper, or an alloy thereof.

  In the present invention, the LED light source and the heat receiving part need only be arranged at the side edge of at least one side of the panel-type heat radiation part, and when only one of the upper, lower, left and right sides is arranged, any two or more sides It is also included in the present invention if it is arranged in the above.

  By the way, the printed circuit board (11) on which the LED light source (10) is mounted generally has an insulating layer laminated on a substrate such as an aluminum plate, and further a conductive layer made of copper foil or the like. In the embodiment described above, the substrate of the printed circuit board (11) and the heat receiving part (20) are bonded to each other through an adhesive layer such as a heat conductive compound, and the generated heat is promptly received by the heat receiving part (20 ) To absorb heat. However, by integrating the printed circuit board (11) and the heat receiving portion (20), the heat transfer can be further improved.

  In the LED substrate (50) shown in FIG. 4, an insulating layer (51) is directly bonded onto a tube (27) serving as a heat receiving portion, and a current-carrying layer (52) having a required circuit shape is further formed on the insulating layer (51). Is a substrate in which these are integrated. The LED light source (10) is mounted on the energization layer (52). In this LED board (50), since there is no board part in the above-mentioned printed circuit board (11) and there is no adhesive layer for joining to the tube (27), the heat generated by the LED light source (10) is directly applied to the tube ( 27) is quickly transmitted to improve heat dissipation efficiency. Moreover, since the tube (27) which is a heat receiving part also serves as a circuit board, the strength as the board is satisfied.

  In the LED substrate (50), the energization layer (52) is a layer made of a conductive material, and for example, copper foil or aluminum foil is used.

  The insulating layer (51) is made of an insulating material that can be directly bonded to the tube (27). Specifically, an insulating resin or an insulating resin composition in which a thermally conductive filler is blended with the insulating resin can be recommended. These resin-based insulating layers are harder to break than ceramics, and a large-area substrate can be manufactured.

  As the insulating resin, a resin having excellent heat resistance and a low coefficient of thermal expansion, being in close contact with a metal tube and excellent in adhesiveness is preferable. An epoxy resin or a polyimide resin can be recommended as a resin that satisfies these conditions.

Further, by using an insulating resin composition in which a heat conductive filler is blended with the insulating resin, the heat conductivity of the insulating layer can be increased, and the heat dissipation performance can be improved. The thermally conductive filler is preferably an insulator having a high thermal conductivity, preferably a metal oxide or a metal nitride, specifically, SiO ₂ , Al ₂ O ₃ , BeO, MgO, Si ₃ N ₄ , Examples include BN and AlN. These heat conductive fillers may be used alone or in combination of any plural kinds. The heat conductive filler has a higher thermal conductivity of the insulating layer (51) as the content in the resin composition increases, and is preferably 40 to 90% by volume. If it is less than 40% by volume, the effect of improving the thermal conductivity is poor, and if it exceeds 90% by volume, the adhesion to the flat tube is lowered and the heat dissipation performance is lowered. A particularly preferred content is 60 to 80% by volume. The particle size of the heat conductive filler is preferably 10 to 40 μm.

  The thickness of the insulating layer (51) is preferably 0.01 to 0.5 mm in any of the above two types.

  The above-described joining of the tube (27), the insulating layer (51), and the energizing layer (52) is appropriately performed by a known method such as hot pressing. For example, a case where a thermosetting resin is used as the insulating resin of the insulating layer (51) will be described as an example.The conductive layer (52), the insulating layer (51), and the tube (27) are stacked and pressed. , Heat. By this hot pressing, the insulating layer (51) is cured and joined to the tube (27) and the energizing layer (52), and these are integrated.

  In the plate-type heat radiation portion having the coolant passage, the passage route can be set arbitrarily. In the backlight unit (60) illustrated in FIG. 5, the plate-type heat radiating section (62) has a large number of pipe sections (through the vertical direction) that communicate with the upper heat receiver (61) and the lower heat receiver (63). 64), and the coolant is on the upper heat receiver (61) -plate-type heat radiation part (62) -lower heat receiver (63) -plate-type heat radiation part (62) -upper heat receiver (61), and so on. The U-turn is repeatedly circulated between the upper and lower heat receiving portions (61) and (63). As shown in FIGS. 1A and 5, the heat receiving portion (20) (20) (21) (61) (63) and the plate-type heat radiating portion (30) (62) are connected to each other to connect the flow path. 21) The heat absorbed by (61) and (63) can be efficiently dissipated by the plate-type heat dissipating sections (30) and (62). In addition, this invention is not limited to the thing in which the channel | path of the plate-type heat radiation part and the channel | path of the heat receiving part were connected, and the one flow path was formed, and the several flow path may be formed.

  In the plate-type heat radiating portion, it is preferable to meander the coolant passage and lengthen the entire length of the passage in order to improve the heat radiation performance. In order to reduce the channel resistance, a parallel flow circuit is preferable. Further, the LED light source may be attached to the side end portion of one plate-type heat radiating portion, and the heat receiving portion and the plate-type heat radiating portion may be formed substantially integrally.

  Moreover, the shape and manufacturing method of the plate-type heat radiation part having the coolant passage are not limited. For example, a roll bond panel in which a metal flat plate is pressure-bonded by roll bonding and a pipe portion is formed, and a pipe-on-sheet in which a separately manufactured pipe is joined on the flat plate can be exemplified. In addition, as a material for the plate-type heat radiation portion, a highly heat-conductive material such as aluminum, copper, or an alloy thereof can be recommended.

  Further, the front surface of the plate-type heat radiating portion (10) can be used as a reflecting plate, and it is not necessary to install a reflecting plate separately. If necessary, surface treatment such as white coating is performed in order to reflect light uniformly. The back surface is preferably subjected to anodizing treatment or coating for increasing the heat emissivity.

  Furthermore, in the plate type heat radiating part (10), as a means for improving the heat radiating performance, a heat radiating fin (33) is attached to the back of the plate type heat radiating part (30) (FIG. 6) or an air cooling fan (not shown) ) Is optional. The air cooling fan preferably has a rotation speed that does not cause excessive noise.

  As the light guide plate (2), a well-known one can be arbitrarily used, and an example is one in which light reflecting dots are printed on a resin plate. In the backlight unit of the present invention, the light guide plate is not an essential constituent element, and the backlight unit can be configured by an LED light source, a heat receiving unit, and a panel-type heat radiation unit without the light guide plate.

  The liquid crystal display device of the present invention has the above-described backlight unit of the present invention disposed on the back side of a liquid crystal panel. In this liquid crystal display device, heat generated by the LED light source is sufficiently dissipated, so that heat does not accumulate in the device. For this reason, even if the liquid crystal display device is used for a long time, the luminance of the light source does not fluctuate, and other semiconductors and electrical components can be operated normally.

  Since the backlight unit of the present invention has excellent heat dissipation performance, it can be used by being incorporated in liquid crystal display devices of various electronic devices such as computers and mobile phones.

It is a perspective view which shows one Embodiment of the backlight unit of this invention. It is the 1B-1B sectional view taken on the line in FIG. 1A. It is sectional drawing which shows the heat receiving part and LED light source which consist of a perforated tube. It is a graph which shows the relationship of a hydraulic equivalent diameter, thermal resistance, and pressure loss in the flow path of a tube. It is sectional drawing which shows the board | substrate for LED and an LED light source. It is a figure which shows typically another cooling fluid flow path in a backlight unit. It is a perspective view which shows a panel type thermal radiation part and a thermal radiation fin.

Explanation of symbols

1, 60 ... Backlight unit 2 ... Light guide plate
10 ... LED light source
11 ... Printed circuit board
20,21… Heat receiving part
22,23,27… Tube (heat receiving part)
24 ... Aisle
30 ... Plate type heat radiation part
31,32 ... Aisle
50 ... LED substrate
51… Insulating layer
52… Conducting layer

Claims (9)

In the backlight unit arranged on the back side of the liquid crystal panel,
A plate-type heat radiating portion; an LED light source disposed at a side end of the plate-type heat radiating portion; and a heat receiving portion that receives heat in contact with the LED light source and is connected to the plate type heat radiating portion.
The heat receiving portion is a tube having a passageway through which cooling fluid flows, the plate-type heat dissipation unit passage coolant flows are provided, and through a passage of the passage and the plate-type heat radiating portion of the tube communicates, A backlight unit, wherein a number of fine protrusions are formed on the inner wall surface of the passage of the tube .   The backlight unit according to claim 1, wherein a hydraulic equivalent diameter (De) of the passage is 0.2 to 3.1 mm.   The backlight unit according to claim 1 or 2, wherein a flow rate of the coolant in the passage is 0.05 to 2 m / sec.   The backlight unit according to any one of claims 1 to 3, wherein an energization layer is integrally laminated on the heat receiving portion via an insulating layer, and an LED light source is attached to the energization layer.   The backlight unit according to any one of claims 1 to 4, wherein a radiation fin is attached to a back surface of the plate-type heat radiation portion.   The backlight unit according to any one of claims 1 to 5, wherein a front surface of the plate-type heat radiation portion is a reflector of an LED light source.   The backlight unit of any one of Claims 1-6 provided with the light-guide plate arrange | positioned at the front side of the said plate-type thermal radiation part.   The backlight unit according to any one of claims 1 to 3, further comprising: a pump that circulates the coolant and a reservoir tank that stores the coolant, and communicates with the tube passage or the panel radiator.   A liquid crystal display device comprising the backlight unit according to claim 1 disposed on the back side of the liquid crystal panel.

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