WO2012050290A1

WO2012050290A1 - Heat-dissipating device of liquid crystal display device using rear case

Info

Publication number: WO2012050290A1
Application number: PCT/KR2011/004374
Authority: WO
Inventors: 남동진; 정인수
Original assignee: 주식회사 에이치앤에스솔루션
Priority date: 2010-10-12
Filing date: 2011-06-15
Publication date: 2012-04-19

Abstract

The present invention relates to a heat-dissipating device placed between a backlight unit of a liquid crystal display device having a printed circuit board coupled to the rear surface thereto, and a rear case for accommodating the backlight unit, wherein the heat-dissipating device comprises a heat-conductive pad located between an exothermic element mounted on the printed circuit board, and the rear case, and the heat-dissipating device is characterized by being closely in contact with the surface of the exothermic element and one surface of the rear case, thereby efficiently discharging to the exterior, the heat generated from the exothermic element mounted on the printed circuit board of the liquid crystal display device using the rear case of the liquid crystal display device, enhancing the efficiency of heat-dissipation, and enabling the liquid crystal display device to be slimmer and lighter.

Description

Heat dissipation device for LCD using rear case

The present invention relates to a heat dissipation device of a liquid crystal display device, and more particularly, it is possible to efficiently discharge heat generated from a heating element mounted on a printed circuit board of a liquid crystal display device to the outside by using a rear case of the liquid crystal display device. It relates to a heat dissipation device of a liquid crystal display device using a rear case.

In general, in the case of heat generating elements of electric and electronic products, a heat dissipating device such as a heat sink is mounted on the heat generating elements in order to prevent malfunction of the product due to heat generation. Typically, heat sinks, such as heat sinks, use metals with high thermal conductivity so that the heat generated by the product can be released quickly.

Conventionally, a heat having a structure in which a plurality of heat dissipation fins which are uniformly protruded on the front surface is arranged by heating and melting aluminum, copper, and their alloys at a high temperature, and then extruding them using a mold having a predetermined shape. Sinks have been commonly used. However, manufacturing a heat sink by a method of extrusion molding into a mold has a problem in that a manufacturing process is difficult and a processing cost increases because a separate mold corresponding to the heat sink has to be manufactured in order to manufacture a heat sink having various shapes. In addition, in order to secure required properties such as electrical insulation and oxidation prevention, a separate process such as anodizing has to be performed. In this process, a large amount of acid or basic waste is generated, resulting in additional treatment costs.

Meanwhile, technologies related to cooling devices for electronic products include fin and fan methods, thermoelectric methods, cooling water circulation methods, and heat pipe methods. Heat pipe systems that do not generate noise or vibration, do not require large driving energy, and can be installed in a narrow space, are mainly used. The heat pipe type cooling apparatus includes an evaporation unit in which a refrigerant absorbs heat from a heating element, a condensation unit in which evaporated refrigerant releases heat, and a transfer unit in which a microstructure is formed so that the refrigerant liquefied in the condensation unit moves back to the evaporation unit. Is common.

The movement of the refrigerant in the transfer unit is mainly performed by a capillary pumped loop (CPL) using the surface tension of the refrigerant as a driving force in the microstructure. At this time, it is important that the refrigerant flows continuously from the condenser to the evaporator without dry-out of the surface of the evaporator and the flow of liquid. Therefore, the evaporator and the condenser are separated, and as the distance of the conveying part becomes longer, the design of the microstructure becomes more difficult. However, since the conventional heat spreader for cooling electronics has to be formed in a plurality of layers having a thin plate shape of 1 mm or less in thickness, a lead frame structure that forms upper and lower flow paths in order to transfer the refrigerant using a capillary phenomenon in a long section, that is, There was a problem that the design and manufacture of the microstructure is difficult.

In addition, the conventional heat spreader for cooling electronic products made of metals such as aluminum, copper, iron, zinc, silver, and gold requires a complicated structure in order to reduce the heat generated per unit area to a desired level, and as a result, a large amount of metal is used. The weight and volume of the whole product increases, and the price also increases.

In addition, a device was developed to increase the cooling efficiency by increasing the heat dissipation surface area by using a heat sink made of ceramic material rather than a metal material, and using the characteristic capillary pores of the ceramic material. This lengthened productivity was low, and inefficient in terms of processability, impact resistance, and size and weight of shapes having various and complex structures.

In addition, in order to dissipate the heat inside the product, the heat radiators listed above must drill a considerable amount of vent holes in the product casing, which may cause the hot air inside the product to flow to the outside, which may cause system malfunction and failure. There is a problem that there is a high possibility that foreign dust and contaminants that may enter through the vent hole.

Therefore, in order to solve the above problems, there is a recent need for a new heat dissipation device capable of improving the heat dissipation structure and increasing the efficiency of the liquid crystal display device, in which the thickness of the liquid crystal device is required to increase.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the problem to be solved by the present invention is that the heat generated from the heating element mounted on the printed circuit board of the liquid crystal display device can be efficiently discharged to the outside and has become more slim recently. In a thin liquid crystal display device, it is possible to provide a heat dissipation device of a liquid crystal display device using a rear case, which can be miniaturized and lighter than a conventional heat dissipation device.

In order to achieve the above object,

A heat dissipation device disposed between a backlight unit of a liquid crystal display device having a printed circuit board coupled to a rear surface and a rear case accommodating the backlight unit, wherein the heat dissipation device is disposed between the heating element mounted on the printed circuit board and the rear case. And a heat conductive pad positioned thereon, wherein the heat dissipation device is in close contact with a surface of the heat generating element and one surface of the rear case.

Here, the thermally conductive pad is preferably an elastomer pad.

In addition, a non-adhesive layer may be formed on a surface of the thermal conductive pad in contact with the heating element.

The heat dissipation device may further include a thermally conductive sheet positioned between the thermally conductive pad and the rear case.

In addition, the thermally conductive sheet is preferably a graphite sheet.

In addition, an adhesive layer may be formed on a surface of the thermal conductive sheet in contact with the rear case.

In addition, a protective film may be disposed between the graphite sheet and the thermally conductive pad.

In addition, the elastomer pad may be made by mixing hexamethylene diisocyanate, methylene diphenyl isocyanate, isophorone diisocyanate and dibutyl tin dilaurate to the synthesized polyol.

In addition, the elastomer pad may further include an alumina powder and aluminum hydroxide.

The heat dissipation device according to the present invention is provided in close contact with a heat generating element which is electrically operated inside a liquid crystal display device in which a liquid crystal display device, in particular, a light emitting diode (LED) is used as a light source, and controls the liquid crystal display device. The heat dissipation efficiency can be improved by transferring the heat generated from the back case to the rear case, and the thickness can be reduced compared to the existing heat dissipation device, which can help slim down and lighten the liquid crystal display. In addition, by dissipating heat through the rear case, external dust or contaminants may be introduced, which may cause malfunction and failure of the device by minimizing or eliminating the quantity and area of the air vent holes formed in the radiator of the existing LCD. Can significantly reduce the likelihood of

1 is a schematic structural diagram of a backlight unit of a liquid crystal display device in which a light emitting diode is used as a light source.

2 is a schematic cross-sectional view of a heat dissipation device of a liquid crystal display using a rear case according to an embodiment of the present invention.

3 is a schematic cross-sectional view of a heat dissipation device of a liquid crystal display using a rear case according to another embodiment of the present invention.

4 is a schematic cross-sectional view of a heat dissipation device of a conventional liquid crystal display.

Hereinafter, the present invention will be described in more detail with reference to preferred examples. However, these examples are intended to illustrate the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited thereby.

First, a general structure of an edge type backlight unit 100 will be described with reference to FIG. 1. 1 is a view schematically illustrating a structure of a backlight unit 100 of a liquid crystal display device in which a light emitting diode (LED) is used as a light source.

The general edge type backlight unit 100 includes a lower chassis 70, a light emitting diode (LED) 30, a reflective sheet 60, a light guide plate 50, an optical sheet 20, an LCD panel 10, a substrate for attaching an LED ( 40). As shown in FIG. 1, in the general edge type backlight unit 100, the substrate 40 to which the light emitting diodes 30 are coupled is coupled to both sides of the lower chassis 70. In this case, the substrate 40 may be made of metal or FR4.

The reflective sheet 60 and the light guide plate 50 may be accommodated in the lower chassis 70. The light guide plate 50 scatters the linear light emitted from the light emitting diodes 30 to emit the surface light. In this case, not all of the light emitted from the light emitting diode 30 is incident on the light guide plate 50, but is also reflected and lost to the lower portion of the light guide plate 50, and the reflective sheet 60 transmits the light to the light guide plate 50. Let it reflect totally.

On the other hand, the lower chassis 70 may be provided with a printed circuit board formed with a circuit portion including a drive driver. The printed circuit board is equipped with various heating elements that are electrically operated inside the liquid crystal display device and control the liquid crystal display device. This heating element has a recent increase in heat generation in accordance with the trend of high integration. It is emerging.

4 is a schematic cross-sectional view of a heat dissipation device of a conventional liquid crystal display device, and the heat dissipation device 120 is mounted on a printed circuit board 110 coupled to a rear surface of the backlight unit 100 of the liquid crystal display device. For heat dissipation, the heat generating element 120 is configured by attaching a heat sink 150 made of aluminum or ceramic. The heat sink 150 is installed to be spaced apart from the rear case 200 that accommodates the backlight unit 100 coupled to the rear surface of the printed circuit board 110. In addition, a thermally conductive acrylic foam tape 155 is disposed between the heat generating element 120 and the heat sink 150 to strengthen the adhesive force while maintaining the thermal conductivity.

That is, the heat dissipation device of the conventional liquid crystal display device uses a method of attaching a heat sink to a heat generating element, transferring heat generated by the heat generating element to the heat sink by conduction, and releasing heat by convection in the heat sink. However, the heat dissipation device of the conventional liquid crystal display device is limited in heat dissipation area by the heat sink area, and furthermore, the gap between the rear case and the heat sink becomes narrower in view of the trend of the liquid crystal display device becoming more slim recently. As a result, smooth natural convection is hindered and the heat dissipation performance is reduced.

In order to solve this problem, as shown in FIG. 100 is a heat dissipation device disposed between the rear case 200 to accommodate the backlight unit 100, the thermal conductivity is located between the heating element 120 mounted on the printed circuit board 110 and the rear case. It includes a pad 130, the heat dissipating device is in close contact with the surface of the heat generating element 120 and one surface of the rear case 200. Here, one surface of the rear case refers to a surface facing the backlight unit 100 of both surfaces of the rear case.

As described above, since the heat dissipation device of the liquid crystal display according to the exemplary embodiment of the present invention utilizes the rear case 200 of the liquid crystal display as a heat sink, the heat dissipation performance of the heat sink can be maximized by maximizing the heat dissipation area of the heat sink.

The rear case 200 is generally preferably made of a metal having good thermal conductivity, and may be a galvanized steel sheet that is commonly used as a case material.

The thermal conductive pad is installed to be in contact with the surface of the heat generating element 120 to effectively transfer heat from the heat generating element 120 to the rear case 200 of the liquid crystal display device. The heat conductive pad is thermally conductive to a polymer material such as silicone, urethane, and acryl. Substances, for example, metal powders such as aluminum, zinc, nickel, copper, calcium, potassium, iron, silver, zinc, gold, oxides and hydrates or metal salts thereof, carbon nanotubes, carbon black, silicon carbide, graphite, and nitride It can be prepared by mixing boron, aluminum nitride and the like.

Preferably, the thermal conductive pad 130 is an elastomer pad having good thermal conductivity and adhesion for smooth heat transfer from the heat generating element 120 to the rear case 200 functioning as a heat sink.

Elastomeric pads as thermally conductive pads can solve the disadvantages of thermally conductive silicone pads that have conventionally been used as heat transfer materials. In other words, when the silicon pad is attached to the substrate or the heating element, oil may leak little by little in the silicon pad as time elapses, which may adversely affect the electrical conductivity of the substrate. In addition, the silicon pad has a limit in the strength of the self-adhesiveness, so if more adhesive force is required, there is a need for a separate adhesive treatment.

The elastomer pad according to the present invention solves the drawbacks of the above-described thermally conductive silicone pads, and does not have oil leakage over time, and has an advantage of superior self-adhesiveness compared to the silicone pads, so that the elastomer pad is closely adhered to the rear case 200. Can be combined.

The elastomer pad may be prepared by mixing hexamethylene diisocyanate, methylene diphenyl isocyanate, isophorone diisocyanate and dibutyl tin dilaurate to the synthesized polyol, or further comprising alumina powder and aluminum hydroxide. Can be. Detailed description of the manufacturing method of the elastomer pad will be described later.

On the other hand, a non-adhesive layer 125 may be formed on one side of the elastomer pad, that is, the surface in contact with the heat generating element 120, which is made of no adhesive force or very weakly to be provided with the heat generating element 120. Tally can be easily done.

The non-adhesive layer 125 may be a polymer film such as PET, PE, PP, or the like, and may be formed by coating a silane compound, such as a polymer and an inorganic material, such as acrylic and urethane, which have no adhesive force, on an elastomer pad. In this case, the type of adhesive such as acrylic, silicone adhesive, and the like, the amount of additives thereof, the coating thickness, and the like may be appropriately adjusted to suitably adjust the non-tackiness of the non-adhesive layer.

On the other hand, as shown in Figure 3 as another embodiment of the heat dissipation device according to the present invention, in order to efficiently transfer the heat generated from the heating element 120 to a larger area rather than a predetermined portion of the rear case 200 The thermally conductive sheet 140 having a good horizontal thermal conductivity may be further used. Such materials may be graphite sheets, carbon sheets, metal plates such as aluminum, copper, silver, gold or magnesium, or thermally conductive sheets made of silicon, urethane, or acryl, but more preferably, workability, workability and economy. It is good to use this good graphite sheet.

When the graphite sheet is used as the thermal conductive sheet 140, the protective film 135 may be disposed between the thermal conductive pad 130 and the graphite sheet to prevent the graphite sheet from being broken. The protective film 135 is preferably a PET film, and in order to provide adhesion with the graphite sheet and the thermally conductive pad, an adhesive layer made of acryl, silicon, or the like may be formed on one or both surfaces.

One side of the thermal conductive sheet 140 having a good horizontal thermal conductivity (the surface facing the rear case) forms an adhesive layer 145 made of acrylic, silicon, or the like, so that the thermal conductive sheet is easily adhered to the rear case. Preferably, the other side (the side facing the thermal conductive pad) covers a polymer film such as PET, PE, PP, etc., which is not adhesive, or a silane compound, which is a polymer and inorganic material such as acrylic or urethane, which is made of adhesive. It is preferable to coat.

As described above, the reason for using the thermally conductive sheet 140 having a good horizontal thermal conductivity is to further lower the surface temperature of the rear case serving as a heat sink. In general, the surface temperature of the electronics case is prescribed to be below a certain temperature (45 ℃), which is to increase the reliability of the product so that consumers do not feel the heat when contacted with the electronics.

Accordingly, the heat dissipation device according to another embodiment of the present invention is formed by attaching a thermally conductive sheet having a good horizontal thermal conductivity to a rear case wider than an area of a thermally conductive pad used for effectively transferring heat generated from the heat generating element. . Accordingly, the heat transferred to the rear case is widely distributed in the horizontal direction, thereby suppressing high radiation of heat only in one portion of the rear case, and at the same time, the heat dissipation area is expanded, and as a result, the heat dissipation effect can be further increased.

Experimental Example

The heat dissipation device according to the present invention was mounted on the liquid crystal display, and the surface temperature of the heat generating element and the rear case were measured to compare the heat dissipation performance with the conventional heat dissipation device. The size of the heating element mounted on the printed circuit board used in the experiment was 25mmX25mm, and after driving the video for 12 hours through the liquid crystal display, the temperature of the heating element and the temperature of the rear case at the position closest to the heating element. Was measured.

-Synthesis of polyols

Into a 1000 ml four-necked flask equipped with a cooling condenser, 320 g of adipic acid, 250 g of 1,4-butanediol, and 15 g of ethylene glycol were added thereto, and a temperature was slowly increased while stirring the mantle heater by stirring the stirring rod and the stirrer. Condensation polymerization was carried out at 150-160 ° C. for 8 hours to proceed with esterification, and the condensed water generated at this time was separated from the flask through a condenser. When the production rate of the condensed water started to slow down, a small amount of the sample was removed to measure the acid value, and when the acid value was 80 or less, the temperature was raised to 210 ° C and the reaction was further performed for 5 hours while measuring the acid value every hour. The color of the synthesized polyol was the same as Gardner colori swatch 2, and the acid value was 43.

Preparation of Elastomeric Pads

To 300 g of the polyol synthesized above, 35 g of hexamethylene diisocyanate, 15 g of methylene diphenyl isocyanate, 5 g of isophorone diisocyanate and 2 g of dibutyl tin dilaurate were added and mixed. Here, as a filler to help heat transfer, an average particle diameter of 10 μm alumina powder 200 g, an average particle diameter of 5 μm alumina powder 150 g, an average particle diameter of 2 μm alumina powder 100 g, and aluminum hydroxide 600 g were added and stirred for 1 hour. The elastomer slurry obtained by stirring was coated on a PET film with a thickness of 5 mm and then cured at 120 ° C. for 15 minutes to prepare an elastomer pad.

Example 1

As shown in FIG. 2, the elastomer pad manufactured by the above-described process is embossed on a surface of a rear case made of a galvanized steel sheet of a liquid crystal display device using a light emitting diode as a light source, having a size of 35 mm × 35 mm × 4.5 mm. The surface of the attached elastomer pad was coated with a 20 μm-thick PET film so as to be in close contact with a heating element mounted on a printed circuit board.

Example 2

As shown in FIG. 3, in Example 1, 0.5 mm thick single-sided acrylic adhesive graphite sheet was cut to a size of 70 mm × 70 mm on one surface of a rear case made of a galvanized steel sheet, and the graphite sheet was cut thereon. To prevent breakage, a composition coated with a 20 μm thick single-sided acrylic adhesive PET film was added.

Comparative Example 1

As shown in FIG. 4, a heat sink made of aluminum 35 mm × 35 mm × 1 mm, having a 0.25 mm thick thermally conductive acrylic foam tape attached thereto, was mounted on a heating element mounted on a printed circuit board.

Comparative Example 2

Instead of an aluminum heat sink in Comparative Example 1, a ceramic heat sink having a size of 35 mm × 35 mm × 2 mm was mounted.

Comparative Example 3

In Comparative Example 1, a heat sink made of aluminum having a size of 35 mm × 35 mm × 1 mm was not mounted.

Temperature measurement result

The temperature of the heating element and the temperature of the rear case according to Examples 1 and 2 and Comparative Examples 1 and 2 are as follows.

Table 1

	Heating element temperature (℃)	Rear case temperature (℃)
Example 1	61.2	43.3
Example 2	58.4	40.7
Comparative Example 1	76.9	44.5
Comparative Example 2	78.8	44.8
Comparative Example 3	89.7	55.0

Based on the temperature measurement results of the embodiments and comparative examples, it can be seen that the heat dissipation device according to Examples 1 and 2 has better heat dissipation performance than the heat dissipation device according to Comparative Examples 1, 2 and 3.

Although Comparative Examples 1 and 2, which are conventionally used, the rear case temperature does not deviate from the reference value (45 ° C.), but was measured to be relatively high in comparison with Examples 1 and 2 in the temperature of the heating element. Therefore, as the chips having high processing capacity are gradually integrated and developed, it is inevitable that the heat generation temperature of the heat generating element is continuously increased. Therefore, the continuous use of the conventional heat dissipating devices such as Comparative Examples 1 and 2 for the liquid crystal display device in the future Will be inappropriate. That is, since the heat dissipation device according to the present invention utilizes the rear case as a heat sink, it can be said that it is very effective in coping with the heat dissipation problem of the liquid crystal display device which is continuously integrated, ultra-light and ultra slim.

All simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims

A heat dissipation device disposed between a backlight unit of a liquid crystal display device having a printed circuit board coupled to a rear surface and a rear case accommodating the backlight unit,

The heat dissipation device includes a thermally conductive pad positioned between the heating element mounted on the printed circuit board and the rear case.

And the heat dissipating device is in close contact with the surface of the heat generating element and one surface of the rear case.
The method of claim 1,

The heat conductive pad is a heat radiation device of the liquid crystal display device using a rear case, characterized in that the elastomer pad.
The method of claim 1,

And a non-adhesive layer is formed on a surface of the thermally conductive pad in contact with the heat generating element.
The method of claim 1,

The heat dissipating device may further include a heat conductive sheet positioned between the heat conductive pad and the rear case.
The method of claim 4, wherein

The heat conductive sheet is a heat dissipation device of a liquid crystal display device using a rear case, characterized in that the graphite sheet.
The method of claim 4, wherein

And a pressure-sensitive adhesive layer is formed on a surface of the thermally conductive sheet in contact with the rear case.
The method of claim 5,

A heat dissipation device of a liquid crystal display device using a rear case, characterized in that a protective film is disposed between the graphite sheet and the thermal conductive pad.
The method of claim 2,

The elastomer pad is a heat dissipation device of a liquid crystal display device using a rear case, characterized in that the polyol synthesized, hexamethylene diisocyanate, methylene diphenyl isocyanate, isophorone diisocyanate and dibutyl tin dilaurate.
The method of claim 8,

The elastomer pad is a heat dissipation device of a liquid crystal display device using a rear case, characterized in that it further comprises an alumina powder and aluminum hydroxide.