JP4969376B2 - Liquid crystal display equipment - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly to a cooling technique for a liquid crystal display device using a light emitting diode element as a backlight.

In a liquid crystal display, a light emitting diode (LED) as a backlight may be used in order to further increase the luminance (high image quality) and reduce the thickness. Since an LED is a semiconductor light source element, a change in light emission efficiency, a lifetime, and the like are likely to be greatly affected by a temperature change. In order to reduce the influence of such a temperature change, a technique for suitably cooling an LED as a backlight has been conventionally studied.

  For example, in Patent Document 1, air is circulated by a fan through a space between a stripe-shaped protrusion provided on the lower surface of a metal substrate on which light emitting elements (LEDs) are arranged and a guide member fixed to the protrusion. The light-emitting element is air-cooled by this fan.

  Patent Document 2 discloses that the LED is liquid-cooled by using a flat tube, which is a flow path for the cooling coolant, as an LED substrate.

  In Patent Document 3, a space between a wiring board on which a large number of LED chips are mounted and a metal casing is filled with a heat conductive silicone rubber to form a large area heat conduction path, and heat generated by the chips is quickly generated. Discloses that heat is transferred to a metal casing to dissipate heat.

JP 2006-114501 A JP 2006-253205 A JP 2007-42552 A

The technique described in Patent Document 1 is an air cooling method using air as a cooling refrigerant. Since air has a lower heat transfer capacity than liquid refrigerant or the like, in order to obtain the effect of cooling performance in such an air cooling method, it is necessary to significantly increase the amount of air to be ventilated or to lower the temperature of the ventilated air. Therefore, with the air cooling method as described in Patent Document 1, it is difficult to obtain a cooling performance that is commensurate with an increase in the size of the cooling device.

  Patent Document 2 discloses a liquid cooling system, but no consideration is given to the structure of the radiator for radiating the heat of the refrigerant received by the flat tube, and no consideration is given to the miniaturization of the entire cooling device. It has not been.

  Since Patent Document 3 is configured to conduct the heat generated by the LED to the metal casing by the heat conductive silicone rubber, in a liquid crystal display having a large screen and a direct backlight, a large amount of silicone rubber is used. There is a concern that the workability in increasing the weight or repairing the circuit board may be hindered.

  The present invention has been made in view of the above-described problems, and its purpose is to reduce the thickness of the device while increasing the cooling efficiency of the LED in a liquid crystal display device using a light emitting diode (LED) as a backlight. The purpose is to provide a technique for enabling weight reduction.

  In order to achieve the above object, the present invention is characterized by the offense described in the claims.

That is, the present invention includes a liquid crystal display, a circuit board disposed opposite to the back surface of the liquid crystal display, a backlight that is placed on the circuit board and irradiates the liquid crystal display, and a cooling device that cools the backlight. In the liquid crystal display device comprising: the backlight includes a plurality of light emitting diodes, and the heat generated by the light emitting diodes is configured to be conducted to the cooling device disposed on the back surface of the circuit board,
In the cooling device, a heat receiving base body thermally connected to each of the plurality of light emitting diodes and a cover body constitute an internal space through which the refrigerant flows, and the refrigerant is vaporized by injection into the internal space. The heat exchanger and the back surface of the first heat exchanger are opposed to each other, and are formed in an integrated structure on the back housing of the liquid crystal display device, and are vaporized by the first heat exchanger. A second heat exchanger having a planar shape that constitutes an internal space through which the flowed refrigerant flows, and liquefies the vaporized refrigerant by heat transfer from the housing, and the first heat exchanger And the second heat exchanger are connected to each other so that the refrigerant can circulate.

  The first heat exchanger of the cooling device has a planar shape that is substantially equal in size to the liquid crystal display, and thermal connection with the plurality of light emitting diodes is performed on the circuit board. You may carry out through the opening part penetrated corresponding to the diode.

  The first heat exchanger is a heat exchanger having a planar shape substantially equal in size to the liquid crystal display, and absorbing heat generated by the light emitting diodes by vaporization of the refrigerant flowing in the internal space, and The refrigerant injection port connected to the pump for injecting the refrigerant and the first heat exchanger are installed in the first heat exchanger so as to be thermally connected with a size equal to substantially the entire plane of the inner wall surface of the first heat exchanger. A retaining member having an opening for mooring the injected refrigerant in a thin film liquid state, a refrigerant discharge port for discharging the vaporized refrigerant to the second heat exchanger side, and a mooring to the opening And a refrigerant recovery for recovering the falling refrigerant liquid of the refrigerant thin film liquid.

  In addition, the second heat exchanger includes a refrigerant receiving portion disposed in an upper portion of the first heat exchanger, a refrigerant inlet for carrying in the refrigerant liquid vaporized in the refrigerant receiving portion, and the second heat exchanger. The vaporized refrigerant is condensed and liquefied on the inner wall surface by heat transfer from the housing, and is opposed to the inner wall surface of the second heat exchanger, and is rotated and driven by the carry-in pressure of the vaporized refrigerant. You may have a wiper member which scrapes off the liquid refrigerant exposed to the wall surface, and a refrigerant carrying-out port which carries out the liquefied refrigerant to a tank part.

  Furthermore, the first heat exchanger and the second heat exchanger are arranged close to each other so as to face each other, and the first heat exchanger and the second heat exchanger are directly or via an air layer. It is good also as a structure which heat-connects and heat-transmits a part of rising temperature by the condensation of the refrigerant | coolant in a said 2nd heat exchanger to a said 1st heat exchanger.

  According to the present invention configured as described above, an LED backlight mounted on a liquid crystal display device having a large screen can be efficiently cooled, and a highly reliable and thin liquid crystal display device can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a liquid crystal display device according to the present embodiment. The plan view of FIG. 1 is displayed through the liquid crystal display 3 and the diffusion plate 5 for convenience of explanation. In FIG. 1, a liquid crystal display 3 that displays information, a backlight 4 that is arranged in a plane opposite to the back surface of the liquid crystal display 3 and emits light, and a backlight 4 is mounted on the liquid crystal display 3 and a circuit board 6 on which the backlight 4 is disposed.

  A high thermal conductivity member 8 is fixed to the circuit board 6, and the high thermal conductivity member 8 is configured so that heat generated from the backlight 4 is conducted through an opening through the circuit board 6. Further, the liquid crystal display device 1 according to the present embodiment includes a cooling device 7 for cooling the backlight 4, and the cooling device 7 includes a plurality of refrigerant driving members 74 for injecting the refrigerant, the refrigerant A heat receiving member 71 that is a first heat exchanger for vaporizing the refrigerant injected by the drive member 74 and a heat radiating member 72 that is a second heat exchanger for liquefying the vaporized refrigerant are included. The first heat exchanger and the second heat exchanger are connected to each other so that the refrigerant circulates. The backlight 4 is cooled by latent heat due to the phase change of the vaporization and liquefaction of the refrigerant. A wiper member 726 for scraping off the attached refrigerant condensed and exposed by heat conversion is provided inside the heat receiving member 71 as the second heat exchanger. Details of the cooling device 7 will be described later.

  Here, in the present embodiment, the backlight 4 is a backlight 4 made of LEDs in order to improve the luminance of the liquid crystal display 3.

  Next, an example of the configuration of the LED backlight 4 will be described with reference to FIG.

  FIG. 2 is a schematic structural cross-sectional view of a backlight using LEDs in the present embodiment. In FIG. 2, the LED of the backlight 4 has a light emitting diode element 41 and is held on a base 43. The circuit board 6 is provided with wiring (not shown). The LED backlight 4 is fixed to the circuit board 6 with an adhesive or the like at a base portion 431 of a base 43 that holds the light emitting diode element 41. Further, the light emitting diode element 41 and wiring (not shown) attached to the circuit board 6 are electrically connected by, for example, wire bonding 42.

  Here, the base 43 that holds the light emitting diode element 41 includes a reflection portion 432 that reflects the light of the light emitting diode element 41 and a protrusion 433 that protrudes from the opening 61 of the circuit board 6 to the back side of the circuit board 6. Are integrated.

  In the above configuration, the heat generated by the light emitting diode element 41 is transferred to the protruding portion 433 via the base 43.

  Next, the configuration of the backlight and its cooling will be described. FIG. 3 is a schematic configuration diagram showing the relationship between the circuit board on which the LED is placed and the heat receiving member of the cooling device in the present embodiment. In FIG. 3, the circuit board 6 has a planar shape substantially equal to the planar shape of the liquid crystal display 3, and a plurality of LEDs are arranged in a matrix in the vertical and horizontal directions. The number of LEDs necessary for uniformly irradiating the liquid crystal display 3 with a desired luminance is arranged. A heat receiving member 71 of a cooling device 7 to be described later is disposed on the other plane side opposite to the plane on which the LED of the circuit board 6 is placed, and the heat receiving member 71 is the LED protruding from the opening 61 of the circuit board 6. Each protrusion 433 is thermally connected (hereinafter referred to as thermal connection). The thermal connection between each projecting portion 433 and the heat receiving member 71 of the cooling device 7 is not damaged by the displacement of the projecting position when the LED is placed on the circuit board 6 or the warp deformation of the circuit board 6. It is desirable that the two members are fixed to each other via an adhesive high thermal conductive member 8.

  The cooling device 7 configured as described above will be described in detail. FIG. 4 is a schematic configuration diagram of an example of the cooling device 7 that cools the backlight according to the present embodiment. First, the configuration of the cooling device 7 will be described with reference to FIG. The cooling device 7 includes a heat receiving member 71 that absorbs heat generated by the LED by the refrigerant, a heat radiating member 72 that dissipates and condenses the heat of the refrigerant that has risen in temperature due to heat absorption in the heat receiving member 71, and a tank 73 that stores the refrigerant. And a refrigerant driving member 74 that injects the refrigerant to the heat receiving member 71 and a pipe 75 group (751, 752, 753) in which the refrigerant is circulated between the members (71, 72, 73). .

  That is, in the cooling device 7 according to the present embodiment, the heat receiving member 71 operates as a first heat exchanger for vaporizing the mist refrigerant injected from the refrigerant driving member 74, and the heat radiating member 72 It is configured to operate as a second heat exchange for cooling and condensing (liquefying) the refrigerant vaporized by the first heat exchanger.

  In the present embodiment, the heat receiving member 71 as the first heat exchanger is disposed opposite to the circuit board 6 as a planar shape having a size substantially equal to the planar shape of the liquid crystal display 3, and each of the protrusions 433 of the LEDs described above. The heat receiving base body 711 and the heat receiving cover body 712 that are thermally connected to each other form a sealed space inside. Further, the heat receiving member 71 has a refrigerant injection port 713 for injecting and flowing in the refrigerant on the lower end side, and a refrigerant discharge port 714 for discharging the refrigerant on the upper end side. Further, in the internal space through which the refrigerant flows, a planar liquid retaining member 715 provided with openings on all the planes for temporarily mooring the injected refrigerant as a thin film liquid state is provided in the heat receiving base body 711. Installed close to the inner wall with the same size. Here, the opening of the liquid retaining member 715 has a wire mesh structure or a flat plate structure having a large number of openings. Further, when the amount of refrigerant moored at the opening increases, the refrigerant liquid drops from the liquid retaining member 715 and is returned to the tank 73 connected by the liquid return port 716 and the pipe 751.

  The heat radiating member 72, which is the second heat exchanger, has a planar shape having a sealed space through which the refrigerant flows. The flat surface has one flat surface 721 as the housing 2 and the other opposing flat surface 722 as the heat receiving member 71. In addition, they are arranged on the back side of the heat receiving member 71 in a state where they are in contact with each other or are in close proximity (described in a close state in the drawing). On the upper side of the heat radiating member 72, a refrigerant receiving space 723 is provided. The refrigerant receiving space 723 has a refrigerant inlet 724 for carrying the refrigerant from the heat receiving member 71, and a refrigerant outlet 725 for discharging the refrigerant at the lower end of the sealed space. Furthermore, a wiper member 726 is provided on the inner wall surface of the flat surface 721 on the housing 2 side of the internal sealed space through which the refrigerant flows to scrape off the adhering refrigerant condensed and exposed by heat conversion.

  The refrigerant discharge port 714 of the heat receiving member 71 and the refrigerant carry-in port 724 of the heat dissipation member 72 are connected by a pipe 752. The refrigerant discharge port 725 of the heat radiating member 72 and the tank 73 for storing the refrigerant are connected by a pipe (not shown) or an integral configuration so that the refrigerant can flow. Further, a refrigerant drive member 74 that injects the refrigerant toward the inner wall surface of the heat receiving base body 711 is connected to the refrigerant injection port 713 of the heat receiving member 71. The tank 73 and the refrigerant driving member 74 are connected by a pipe 753.

  Next, the operation and action of the cooling device 7 in the above structure will be described. In the liquid crystal display device 1, the backlight 4 is an LED as described above in order to improve the information display performance of the liquid crystal display 3, but the light emitting diode element 41 has a very high temperature dependency.

  In this embodiment, in order to suppress a decrease in light emission efficiency due to a temperature rise of the light emitting diode element 41, the cooling device 7 cools the LED by using a phase change of a refrigerant having a good cooling efficiency. is there.

  The heat generated by each light-emitting diode element 41 is first thermally conducted to the protruding portion 433 of the LED base 43, and is transferred to the heat receiving base body 711 of the heat receiving member 71 of the cooling device 7 thermally connected to the protruding portion 433. The The heat receiving base body 711 is preferably formed of a metal material such as a copper material or an aluminum material having a good thermal conductivity, but has the same area as the large-screen liquid crystal display 3, so that it is as much as possible from the viewpoint of weight. It is desirable to use a thin plate.

  In the sealed space of the heat receiving member 71, the liquid retaining member 715 is installed with a slight gap facing the inner wall surface of the heat receiving base body 711. The refrigerant driving member 74 sprays the refrigerant liquid in the form of a mist toward the inner wall of the heat receiving base body 711. In addition, a plurality of refrigerant driving members 74 are installed at a predetermined interval so as to inject the refrigerant liquid onto the heat receiving base body 711 on average. In FIG. 4, the refrigerant driving member 74 is disposed on the lower end side of the heat receiving base body 711, but in order to absorb the heat by more uniformly injecting the refrigerant in the heat receiving base body 711, Needless to say, they may be arranged on both the lower end side and the lateral side.

  The refrigerant injected to the heat receiving base body 711 by the refrigerant driving member 74 is vaporized at the heat receiving temperature of the heat receiving base body 711, and the LED is cooled by the latent heat of vaporization. Here, the refrigerant that has not been vaporized by a part of the injected refrigerant diffuses the refrigerant into a thin film state by a capillary phenomenon in a slight gap between the heat receiving base body 711 and the liquid retaining member 715, and is caused by surface tension at the opening. Will be moored. The moored refrigerant is vaporized by heat transfer from the heat receiving base body 711. The LED is cooled by cooling the heat receiving base body 711 by the latent heat of vaporization.

  On the other hand, the vaporized refrigerant expands in volume and is radiated from the opening due to an increase in pressure, and is transferred from the refrigerant discharge port 714 to the heat radiating member 72 side.

  Conversely, when the temperature of the LED and the heat receiving base body 711 is lowered, the amount of refrigerant vaporized is suppressed, and in the state where a large amount of refrigerant is moored in the liquid retaining member 715, the refrigerant is removed from the liquid retaining member 715. The liquid is dropped and flows through the pipe 751 from the liquid return port 716 and is returned to the tank 73.

  Here, in order to obtain vaporization latent heat for cooling the heat generation of the LED to a desired temperature, it is necessary to vaporize a predetermined amount of the refrigerant. In order to increase the vaporization amount of the refrigerant, the saturated vaporization amount in the sealed space is increased. Since the saturated vaporization amount increases as the temperature of the sealed space increases, in this embodiment, the heat receiving member 71 is sealed. It is set as the structure (it mentions later for details) which raises the temperature of space.

  The refrigerant that is vaporized in the opening of the heat receiving base body 711 and the liquid retaining member 715 in the sealed space of the heat receiving member 71 causes volume expansion and increases the pressure in the sealed space. The vaporized refrigerant is radiated from the opening of the liquid retaining member 715 due to an increase in pressure, and is transferred from the refrigerant discharge port 714 to the refrigerant receiving space 723 from the refrigerant carry-in port 724 of the heat radiating member 72 via the pipe 752 by the pump action. Is done.

  The vaporized refrigerant transferred from the heat receiving member 71 is transferred to the heat radiating member 72 arranged to face the housing 2. The vaporized refrigerant is heat generated from the casing 2 on the plane 721 in a plane space formed by the plane 721 that transfers the outside air temperature from the casing 2 of the heat radiating member 72 and the plane 722 that faces the heat receiving member 71. It is condensed and liquefied by transmission. At this time, heat is radiated by the liquefied latent heat, and the refrigerant becomes a low-temperature refrigerant liquid. The condensed refrigerant liquid is transferred to the tank 73 from the refrigerant outlet 725.

  In a conventional liquid cooling type cooling device that circulates a refrigerant liquid, when the temperature of the refrigerant liquid that is heat-converted by the outside air temperature cannot be reduced, the heat absorption amount of the refrigerant liquid that is received from the heating element is reduced and the heat is reduced. It becomes a cooling device with poor conversion efficiency. However, in the cooling device according to the present embodiment, that is, the cooling device of the latent heat method based on the phase change of the refrigerant, the refrigerant temperature after the condensation does not need to be greatly reduced, and the temperature is lowered to such an extent that the refrigerant is not revaporized. It is circulated and driven in the refrigerant liquid state. That is, this means that the flat surface 722 of the heat dissipating member 72 through which the refrigerant liquid flows is also in a slightly high temperature state as heat is transferred by the refrigerant liquid. Arranging the flat surface 722 in the vicinity of or in contact with the heat receiving member 71 affects the heat receiving member 71 with a slightly high temperature state of the flat surface 722 and increases the temperature of the internal space of the heat receiving member 71. . This increases the amount of saturated vaporization in the internal space.

  The arrangement of the heat receiving member 71 and the heat radiating member 72 close to each other can be said to be possible because it is based on a heat exchange method using latent heat due to the phase change of the refrigerant. This makes it possible to construct a thin liquid crystal display device 1 by arranging both heat exchangers in a planar shape and close to each other back to back.

  In the embodiment, the heat receiving member 71, the heat radiating member 72, and the housing 2 are each configured by a dedicated plate member and arranged back to back, but one flat surface 721 of the heat radiating member 72 and the housing 2 And the other flat surface 722 of the heat radiating member 72 and the cover body 712 of the heat receiving member 71 may be configured as a common member, or only one of them may be configured in common. With these configurations, the assembly of the members is slightly complicated, but it is possible to reduce the thickness, reduce the weight, and improve the cooling efficiency.

  Here, in order to smoothly transfer the refrigerant, the vaporized refrigerant transferred from the refrigerant carry-in port 724 of the heat radiating member 72 is close to a saturated state and may be liquefied by a slight temperature change. 723 has an inclined surface for transferring the liquid to the lower part. Moreover, it is preferable that a reverse flow preventing member (not shown) is attached to the refrigerant carry-in port 724 of the heat radiating member 72 so that the vaporized refrigerant does not flow backward.

  Further, since the heat dissipating member 72 is a thin flat-shaped sealed space, the exposed refrigerant liquid easily adheres to the inner wall surfaces of the flat surfaces 721 and 722 of the heat dissipating member 72. Therefore, in order to promote the condensing action, it is preferable to provide a wiper member 726 that scrapes off the liquefied refrigerant adhering to the inner surface of the wall surface. The wiper member 726 is configured to be rotatable like a windmill as shown in FIG. Since the wiper member 726 according to the present embodiment does not require a large rotational force or rotational speed, it can be rotated by increasing the pressure of the vaporized refrigerant. Of course, a method of controlling the rotational drive while detecting the amount of exposure by installing a rotational drive device may be adopted.

  The refrigerant liquid liquefied and dissipated in the heat radiating member 72 is passed through a tank 73 disposed below the heat radiating member 72, and the refrigerant stored in the tank 73 is jetted onto the heat receiving member 71 by the refrigerant driving member 74. The refrigerant is circulated and driven.

  Note that a member that transfers heat generated by the light emitting diode element 41 to the cooling device 7 is a protrusion 433 of the base 43 of the light emitting diode element 41. However, heat is transferred between the base 43 and the cooling device 7 via a heat conductor made of a material having good heat conductivity such as a printed wiring board formed on a circuit board, for example. Also good.

  With the above-described configuration, it is possible to provide a thin liquid crystal display device with high reliability while mounting an efficient cooling device that is thin with respect to heat generation of the LED backlight.

1 is a schematic configuration diagram of a liquid crystal display device according to an embodiment of the present invention. Schematic structural sectional view of a backlight using LEDs according to the present embodiment It is a schematic block diagram which shows the relationship between the circuit board which mounted LED in this invention, and the heat receiving member of a cooling device. FIG. 2 is a schematic configuration diagram illustrating an example of a cooling device. An exploded perspective view of the refrigerant wiper member 726 according to the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display apparatus 2 ... Housing | casing 3 ... Liquid crystal display 4 ... Backlight 5 ... Diffusion plate 6 ... Circuit board 7 ... Cooling device 8 ... High thermal conductivity member 71 ... 1st heat exchanger (heat receiving member)
72 ... Second heat exchanger (heat radiating member)

Claims (5)

In a liquid crystal display device comprising: a liquid crystal display; a circuit board disposed opposite to the back surface of the liquid crystal display; a backlight placed on the circuit board to irradiate the liquid crystal display; and a cooling device for cooling the backlight. ,
The backlight includes a plurality of light emitting diodes,
The heat generation of the light emitting diode is configured to be thermally conducted to the cooling device disposed on the back surface of the circuit board,
The cooling device is
A heat-receiving base body thermally connected to each of the plurality of light emitting diodes and a cover body constitute an internal space through which the refrigerant flows, and a first heat exchanger that vaporizes the refrigerant by injection into the internal space; ,
The refrigerant vaporized by the first heat exchanger is disposed so as to face the back side of the first heat exchanger, and is formed in an integrated structure in the back housing of the liquid crystal display device. A second heat exchanger having a planar shape that constitutes an internal space to flow and liquefyes the vaporized refrigerant by heat transfer from the housing;
The liquid crystal display device, wherein the first heat exchanger and the second heat exchanger are connected to each other so that the refrigerant can be circulated. The liquid crystal display device according to claim 1.
The first heat exchanger of the cooling device has a planar shape that is substantially equal in size to the liquid crystal display, and thermal connection with the plurality of light emitting diodes is performed on the circuit board. A liquid crystal display device characterized in that the liquid crystal display device is performed through an opening penetrating the diode. The liquid crystal display device according to claim 1.
The first heat exchanger is a heat exchanger that absorbs heat generated by the light-emitting diode by vaporization of a refrigerant flowing in an internal space, and
A refrigerant injection port connected to a pump for injecting the refrigerant;
Inside the first heat exchanger, an opening that is installed in thermal connection with a size equal to substantially the entire plane of the inner wall surface of the first heat exchanger, and anchors the injected refrigerant in a thin film liquid state. A liquid retaining member having an eye;
A refrigerant discharge port for discharging the vaporized refrigerant to the second heat exchanger side;
A refrigerant recovery port for recovering the falling refrigerant liquid of the refrigerant thin film moored at the opening;
A liquid crystal display device comprising: The liquid crystal display device according to claim 1.
The second heat exchanger includes a refrigerant receiving unit disposed in an upper part of the first heat exchanger;
A refrigerant carry-in port for carrying the vaporized refrigerant liquid into the refrigerant receiving unit;
The carried vaporized refrigerant is condensed and liquefied on the inner wall surface by heat transfer from the housing, and is installed opposite to the inner wall surface of the second heat exchanger, and is rotated by the carried-in pressure of the vaporized refrigerant. A wiper member that scrapes off the liquid refrigerant exposed on the inner wall surface by driving;
A refrigerant outlet for carrying out the liquefied refrigerant to the tank;
A liquid crystal display device comprising: The liquid crystal display device according to claim 1,
The first heat exchanger and the second heat exchanger are disposed in close proximity to each other, and the first heat exchanger and the second heat exchanger are thermally connected directly or via an air layer. The liquid crystal display device is characterized in that a part of the rising temperature due to the condensation of the refrigerant in the second heat exchanger is transferred to the first heat exchanger.

Images