KR102015915B1

KR102015915B1 - Heat discharging sheet and method for manufacturing the same

Info

Publication number: KR102015915B1
Application number: KR1020130078355A
Authority: KR
Inventors: 변나미; 이동욱; 이성국
Original assignee: 엘지전자 주식회사
Priority date: 2013-07-04
Filing date: 2013-07-04
Publication date: 2019-08-29
Also published as: KR20150005755A

Abstract

The present invention relates to a heat dissipation sheet, and more particularly, to a heat dissipation sheet using graphene and a method of manufacturing the same. The present invention, the heat dissipation sheet, the heat dissipation layer having a first surface and a second surface, and containing graphene and inorganic particles; An adhesive layer on the first surface of the heat dissipation layer; And a protective layer on the second surface of the heat dissipation layer.

Description

Heat dissipation sheet and method for manufacturing the same {Heat discharging sheet and method for manufacturing the same}

The present invention relates to a heat dissipation sheet, and more particularly, to a heat dissipation sheet using graphene and a method of manufacturing the same.

Materials composed of carbon atoms include fullerene, carbon nanotube, graphene and graphite. Of these, graphene is a structure in which carbon atoms are composed of a single atom in a two-dimensional plane.

In particular, graphene is not only very stable and excellent in electrical, mechanical and chemical properties, but also as a good conducting material, it can move electrons much faster than silicon and carry a much larger current than copper. The discovery of the separation method has been proved through experiments, and many studies have been conducted to date.

Such graphene can be formed in a large area, and has attracted attention as a basic material of electronic circuits because it has electrical, mechanical and chemical stability as well as excellent conductivity.

In addition, the graphene generally can change the electrical characteristics according to the crystal orientation of the graphene of a given thickness, so that the user can express the electrical characteristics in the selection direction, and thus can easily design the device. Therefore, graphene may be effectively used for carbon-based electrical or electromagnetic devices.

As such, graphene may be applied to a heat radiating material that emits heat because it has excellent thermal conductivity.

It is an object of the present invention to provide a heat dissipation sheet and a method of manufacturing the same, which can effectively transfer and release heat generated from a heat source.

In addition, it is an object of the present invention to provide a heat dissipation sheet and a method of manufacturing the same, which can improve thermal conductivity in a vertical direction.

As a first aspect for achieving the above technical problem, a heat dissipation sheet comprising: a heat dissipation layer having a first side and a second side, and including graphene and inorganic particles; An adhesive layer on the first surface of the heat dissipation layer; And a protective layer on the second surface of the heat dissipation layer.

Here, in the heat dissipation layer, inorganic particles may be distributed between the laminated structures of graphene.

At this time, the content of the inorganic particles is 0.5 to 50 wt%, the content of graphene may be 50 to 99.5% wt%.

Meanwhile, at least one of the adhesive layer and the protective layer may include a heat conductive material.

Such a thermally conductive material may include at least one of graphene, an inorganic material, a metal, and graphite.

Herein, the inorganic particles may include at least one of h-BN, SiC, AlN, Al ₂ O ₃ , SiO _2, and MgO.

As a second aspect for achieving the above technical problem, a method for producing a heat dissipation sheet, comprising: preparing an inorganic particle and a graphene material; Preparing a dispersion solution by dispersing the inorganic particles and the graphene material in a solution; And drying and rolling the dispersion solution.

Here, the rolling after drying the dispersion solution may include filtering the dispersion solution using a sieve.

Meanwhile, the drying and rolling of the dispersion solution may include coating the dispersion solution on a substrate; Drying the coating; And rolling the coating together with the substrate.

The present invention has the following effects.

First, the heat dissipation sheet of the present invention is attached to a heat source so that the heat generated from the heat source can be efficiently released.

Specifically, the heat dissipation layer included in the heat dissipation sheet is attached to the heat source by the adhesive layer to release heat generated from the heat source, wherein the pressure-sensitive adhesive layer is attached to the heat source to transfer heat generated from the heat source to the heat dissipation layer. Can be.

The heat dissipation layer can dissipate heat, particularly in the lateral direction, and can more efficiently dissipate heat generated from the heat source.

The graphene included in the heat dissipation layer has excellent thermal conductivity in the horizontal direction, and inorganic particles located between the graphenes may be connected to each other so as to form a thermal conductivity through each layer of graphene.

These inorganic particles can significantly improve the vertical thermal conductivity than that of graphene alone by using heat transfer by phonons.

That is, if there is an interlayer gap of graphene, heat transfer by phonon may not be easy, and thus inorganic particles may act as an interlayer heat transfer material to facilitate heat transfer by phonon.

Therefore, the thermal conductivity in the horizontal direction and the vertical direction can be greatly improved.

1 is a cross-sectional view showing an example of a heat dissipation sheet using graphene.
2 is a cross-sectional view showing another example of a heat dissipation sheet using graphene.
3 is a schematic diagram illustrating a state in which a heat dissipation sheet is attached to a heat source to release heat.
4 is a schematic view showing an example of applying a heat radiation sheet.
5 is a schematic view showing an example in which a heat dissipation sheet is used for a solar cell as a heat source.
6 is a schematic view showing an example in which the heat dissipation sheet is used in a light emitting diode illumination device as a heat source.
7-10 is a schematic diagram which shows the process of manufacturing the heat radiation layer of a heat radiation sheet.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

While the invention allows for various modifications and variations, specific embodiments thereof are illustrated by way of example in the drawings and will be described in detail below. However, it is not intended to be exhaustive or to limit the invention to the precise forms disclosed, but rather the invention includes all modifications, equivalents, and alternatives consistent with the spirit of the invention as defined by the claims.

When an element such as a layer, region or substrate is referred to as being on another component "on", it will be understood that it may be directly on another element or there may be an intermediate element in between. .

Although the terms first, second, etc. may be used to describe various elements, components, regions, layers, and / or regions, such elements, components, regions, layers, and / or regions It will be understood that it should not be limited by these terms.

1 is a cross-sectional view showing an example of a heat radiation sheet.

As shown in FIG. 1, the heat dissipation sheet 100 is provided with a heat dissipation layer 10 having a first face 13 and a second face 14. The heat dissipation layer 10 may have a property of transferring or dissipating heat.

The heat dissipation layer 10 may include graphene 11 and inorganic particles 12.

Here, the graphene 11 forms a two-dimensional layered structure, and the inorganic particles 12 may be distributed between the graphenes 11 forming the layered structure.

That is, the inorganic particles 12 may be distributed between the stacked structures of the graphene 11.

At this time, since the heat dissipation layer 10 mainly has thermal conductivity, graphene 11 having excellent thermal conductivity may be used as a main material.

The graphene 11 has excellent thermal conductivity, but as mentioned above, the graphene has a layered anisotropic arrangement and thus has excellent thermal conductivity in the horizontal direction, but may have low thermal conductivity in the vertical direction. .

However, the inorganic particles 12 having isotropic thermal conductivity may be distributed between the stacked structures of the graphene 11 to improve thermal conductivity in the vertical direction.

For this property, the content of the inorganic particles 12 may be 0.5 to 50 wt%, and the content of graphene 11 may be 50 to 99.5 wt%.

The heat dissipation layer 10 may have a thickness of 5 to 100 μm, and the graphene 11 may be stacked to achieve such a thickness, and the inorganic particles 12 may be disposed between the graphenes 11. .

Meanwhile, the adhesive layer 20 attached to the heat source 200 (see FIG. 3) may be located on the first surface 13 of the heat dissipation layer 10.

The adhesive layer 20 may serve to effectively transfer heat generated from the heat source to the heat dissipating layer 10 while minimizing the gap between the heat source and the adhesion characteristic with the heat source.

The matrix of the adhesive layer 20 may mainly use a polymer-based material, but is not limited thereto.

When a polymer material is used as a matrix of the adhesive layer 20, various polymer resins such as polyurethane resins, epoxy resins, acrylic resins, and polymer resins may be used.

Here, the adhesive layer 20 may have a thickness ranging from several tens of nm to several hundred μm, and may have a thickness of 5 to 100 μm for effective release of heat and adhesion to a heat source.

In more detail, when the adhesion layer 20 has a thickness of 5-20 micrometers, an optimal effect can be exhibited.

In addition, a protective layer 30 for protecting the heat dissipating layer 10 may be disposed on the second surface 14 of the heat dissipating layer 10.

The protective layer 30 may be formed by coating on the heat dissipation layer 10 to prevent the falling of the material constituting the heat dissipation layer 10.

However, in addition to these fall prevention characteristics, the spinning characteristics can be improved. In some cases, the insulating properties can be improved.

That is, the protective layer 30 may have a characteristic that heat transferred through the heat dissipation layer 10 can be effectively radiated to the outside.

The protective layer 30 may mainly use a polymer-based material, but is not limited thereto.

When the polymer material is used as the protective layer 30, various polymer resins such as polyurethane resin, epoxy resin, acrylic resin, polymer resin, PET, PT, and the like may be used.

As such, the protective layer 30 may have a thickness in the range of several tens of nm to several hundred μm in consideration of the protection of the heat dissipating layer 10 and the radiation of heat to the outside, and for effective heat release and adhesion to a heat source. The thickness may be 5-100 μm.

More specifically, when the protective layer 30 has a thickness of 5 to 20 μm, an optimal effect can be exhibited.

On the other hand, as shown in Figure 2, in order to improve the thermal conductivity, at least one of the adhesive layer 20 and the protective layer 30 may include a thermal conductive material (21, 31).

When the heat conductive material 21 is included in the adhesive layer 20, heat generated from the heat source may be more effectively transmitted to the heat dissipating layer 10 through the adhesive layer 20.

The thermally conductive material 21 may include at least one of graphene, an inorganic material, a metal, and graphite.

In more detail, such a thermally conductive material 21 may include, in addition to graphene, metals such as Cu and Al, inorganic materials such as BN, AiN, Al ₂ O ₃ and MgO, graphite, in addition to carbon It may include a carbon nano tube (CNT).

As such, when the heat conductive material 21 is included in the adhesive layer 20, the heat conductive material 21 may be mixed with the polymer material constituting the adhesive layer 20 in a weight ratio of 10 to 90 wt%. have.

In addition, the thermal conductive material 31 may also be included in the protective layer 30, and the thermal conductive material 31 may further improve the conductivity of heat through the protective layer 30.

Accordingly, the heat conductive material 31 included in the protective layer 30 may allow heat to be more effectively released through the protective layer 20 or heat exchange with the outside.

The same matters as the heat conductive material 21 included in the adhesive layer 20 may be applied to the heat conductive material 31.

3 schematically shows a state in which a heat radiating sheet is attached to a heat source and heat is released.

As mentioned above, the heat dissipation sheet 100 may be attached to the heat source 200 to efficiently discharge the heat generated from the heat source 200.

The heat dissipation layer 10 including the graphene 11 and the inorganic particles 12 is attached to the heat source 200 to release heat generated from the heat source 200, wherein the adhesive layer 20 is a heat source ( Attached to 200 may allow heat generated from the heat source 200 to be effectively transferred to the heat dissipation layer 10.

As mentioned above, graphene 11 is a material in which carbon atoms are composed of a single layer of hexagonal structure, and is rich in pi electrons on a flat side, and thus is excellent in thermal conductivity and electrical conductivity.

Since the graphene 11 has a very high thermal conductivity of about 3000 to 5000 W / mK, the graphene 11 can effectively dissipate heat transferred from the heat source through the heat dissipation layer 10, and in particular, to be released laterally. Can be.

Graphene 11 is manufactured by stacking and compressing powder obtained from graphene oxide, so that it has an anisotropic arrangement, so that the thermal conductivity in the horizontal direction is 300 to 1000 W / mK, which is very good but the relatively low thermal conductivity in the vertical direction. (2 to 5 W / mk).

At this time, the inorganic particles 12 located between the graphene 11 may be connected to each other so that the thermal conductivity is achieved through each layer of the graphene 11, thereby achieving a structure, thus, the thermal conductivity in the vertical direction is greatly improved Can be.

The inorganic particles 12 may be greatly improved in the thermal conductivity in the vertical direction by the heat transfer phenomenon by the phonon (negative).

That is, if there is an interlayer gap of the graphene 11, heat transfer by phonons is not easy, and thus the inorganic particles 12 may act as interlayer heat transfer materials to facilitate heat transfer by phonons. .

By the connection structure of the inorganic particles 12 and the graphene 11, the thermal conductivity in the vertical direction may be improved by several to several tens of W / mK.

As the inorganic particles 12, h-BN, SiC, AlN, Al ₂ O ₃ , SiO ₂ , MgO, and the like may be used, but is not limited thereto.

Among them, h-BN (hexagonal boron nitride) has a thermal conductivity of approximately 600 W / mK, and SiC has a thermal conductivity of 7 to 12 W / mK. In addition, AlN, Al ₂ O ₃ and MgO have thermal conductivity of 19, 24 to 35 and 45 to 60 W / mK, respectively.

Therefore, the inorganic particles 12 may be configured by selecting a material having the thermal conductivity according to the application target of the heat dissipation sheet 100, and in some cases, the materials may be mixed.

On the other hand, as mentioned above, in the case where the heat transfer material 21 is included in the adhesive layer 20, since the heat conductivity of the heat transfer material 21 is excellent, the heat generated from the heat source 200 is more effectively the heat dissipation layer ( 10) can be delivered.

The heat dissipation layer 10 may emit heat, particularly in the lateral direction, so that the heat generated from the heat source 200 may be discharged more effectively.

In this case, the heat transferred to the protective layer 30 may be discharged to the outside through the protective layer 30.

In addition, when the heat transfer material 31 is included in the protective layer 30, the heat transfer material 31 is excellent in thermal conductivity, and thus can be effectively released through the protective layer 30.

In addition, the heat exchange action from the outside air through the protective layer 30 may also occur.

In general, although the oxide layer is included in the adhesive layer 20 and the protective layer 30 to improve thermal conductivity, the oxide filler is heavy and low in thermal conductivity, so that a high content must be added to improve the thermal conductivity to a certain degree. Therefore, there was a problem that is difficult to apply to a product having a thickness of about several tens of micrometers.

However, the adhesive layer 20 or the protective layer 30 including the heat transfer materials 21 and 31 described above may transmit or radiate heat more effectively without this problem.

In FIG. 4, as an example of applying the heat dissipation sheet, an example in which the heat dissipation sheet 100 is used in an application such as a TV (TV) using a flat panel display is shown.

In FIG. 4, the heat dissipation sheet 100 is attached to the driving unit 200 as a heat source, and the display panel 300 is positioned on the heat dissipation sheet 100.

The driving unit 200 is usually provided with a metal frame such as an aluminum (SUS) frame, the heat radiation sheet 100 may be attached to such a metal frame.

The metal frame has a characteristic that heat generated in the driving unit 200 does not spread well in a horizontal direction but transmits heat in a traveling direction. Therefore, heat transmitted from the driving unit 200 may be spread through the heat dissipation sheet 100 in the horizontal direction to be discharged.

In the configuration as shown in FIG. 4, heat may be emitted from the heat dissipation sheet 100 toward the display panel 300 without releasing heat.

In this case, the heat emitted from the display panel 300 may also be released through the heat dissipation sheet 100.

Meanwhile, as illustrated in FIGS. 5 and 6, the heat dissipation sheet 100 may be used in solar cells and light emitting diode lighting devices.

In FIG. 5, an example in which the heat dissipation sheet 100 described above is used in a solar cell as the heat source 200 is illustrated.

The solar cell has a solar cell 210 is provided between the lower arm member 220 and the upper buffer member 230, the solar cell 210 is the light introduced through the transparent substrate 240 Is converted into electrical energy.

The conversion process of energy in which light energy is converted into electrical energy is limited in efficiency, and a certain amount of such energy may be released as heat.

Therefore, it is important to effectively dissipate such heat, and by attaching the heat dissipation sheet 100 to the lower side of the lower buffer member 220, heat generated in the energy conversion process may cause the heat dissipation sheet 100 to be discharged. It is to be effectively released through.

In FIG. 6, the heat radiating sheet is shown the example used for a light emitting diode illumination device.

The use of light emitting diodes is increasing rapidly, and in particular, it is being applied as a lamp that can replace a lamp such as a fluorescent lamp and an incandescent lamp and a lighting device using the same.

Such a light emitting diode has a role of converting electrical energy into light energy as opposed to a solar cell, and even in this case, the energy conversion process is limited in efficiency, so that a certain amount of energy may be emitted as heat.

Therefore, it may be important to effectively dissipate heat emitted from the LED package 250 by attaching the heat dissipation sheet 100 to the lower side of the LED package 250 used in the LED lighting apparatus.

This is because the life of the light emitting diode chip can be extended by the release of heat, and the overall heat generated in the lighting device can be reduced.

The light emitting diode package 250 is mounted to the case 260, and the lens portion 270 and the light guide portion 280 is provided on the light emitting diode package 250, so that heat is hardly emitted to the front side. to be.

Therefore, the heat dissipation sheet 100 may be provided by thermally connecting the lower side of the LED package 250.

In this case, since the LED package 250 is often provided with a heat sink on the lower side, the heat radiation sheet 100 may be directly attached to the heat sink.

On the other hand, in addition to any place where heat can be generated, the heat dissipation sheet 100 may be attached to any place.

As such, the heat dissipation layer 10 of the heat dissipation sheet 100 including the graphene 11 and the inorganic particles 12 may be manufactured using a dispersion solution of the inorganic particles 12 and the graphene material.

Hereinafter, a manufacturing process of the heat radiation layer 10 of the heat radiation sheet 100 will be described in detail with reference to FIGS. 7 to 10.

First, as shown in FIG. 7, the graphene material 11a and the inorganic particles 12 are prepared and dispersed in a solution contained in the container 40 to prepare a dispersion solution 50.

As mentioned above, the graphene material 11a may be manufactured by reducing graphene oxide.

Graphene oxide refers to a state in which carbon particles are oxidized by an acid. Graphene oxide can usually be prepared by oxidizing graphite with a strong acid such as sulfuric acid. In some cases, materials containing sulfuric acid and hydrogen peroxide can be used for oxidation.

Graphite has a plate-like structure, which is oxidized when a strong acid is added to the graphite. Graphite oxide is graphene oxide prepared in a chemically small particle state.

Graphene oxide has a non-conductive non-conductor properties and thermal conductivity of several tens of W / mK, it is possible to effectively transfer the heat generated from the heat source.

As described above, such graphene oxide may be made of the graphene material 11a through a reduction process.

Meanwhile, the graphene material 11a or the inorganic particles 12 may be used as the heat transfer materials 21 and 31 included in the adhesive layer 20 and the protective layer 30.

Next, the heat dissipation layer 10 may be manufactured by drying and rolling the dispersion solution 50 in which the graphene material 11a and the inorganic particles 12 dispersed in the above process are dried.

The process of manufacturing the membrane by drying the dispersion solution 50 is as follows, it is possible in two ways.

First, as shown in FIG. 8, a process of fabricating the film 51 by coating the substrate 60 with the dispersion solution 50 in which the graphene material 11a and the inorganic particles 12 are produced is dispersed. Do this.

Alternatively, as shown in FIG. 9, the membrane 51 can be produced by filtering the dispersion solution 50 in which the graphene material 11a and the inorganic particles 12 are dispersed using the cloth 70. have.

In this manner, after the film 51 is prepared using the dispersion solution 50, as shown in FIG. 10, the heat dissipation layer 10 can be produced by rolling using a pair of rollers.

In this rolling process, the graphene material 11a and the inorganic particles 12 are mixed with each other to form a structure in which the inorganic particles 12 are distributed between layers between the multilayer structures of the graphene 11.

When the adhesive layer 20 and the protective layer 30 are attached or directly formed on the first and second surfaces of the heat dissipation layer 10 manufactured in the above process, the heat dissipation sheet 100 as shown in FIG. Will be able to produce.

On the other hand, the embodiments of the present invention disclosed in the specification and drawings are merely presented specific examples for clarity and are not intended to limit the scope of the present invention. It is apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be carried out in addition to the embodiments disclosed herein.

10: heat radiation layer 11: graphene
12: inorganic particles 13: first page
14: 2nd surface 20: adhesion layer
21: heat transfer material 30: protective layer
31: heat transfer material 100: heat dissipation sheet
200: heat source, driver 300: display panel

Claims

In the heat dissipation sheet,
Inorganic particles having a first surface and a second surface and having an isotropic thermal conductivity between the graphene having a laminated structure in a layered anisotropic arrangement and the graphene laminated structure and thermally connecting the laminated structure of the graphene A heat dissipation layer comprising;
An adhesive layer on the first surface of the heat dissipation layer; And
And a protective layer on the second surface of the heat dissipation layer.

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The heat dissipation sheet according to claim 1, wherein the content of the inorganic particles is 0.5 to 50 wt%, and the content of the graphene is 50 to 99.5% wt%.

The heat dissipation sheet according to claim 1, wherein at least one of the adhesive layer and the protective layer includes a heat conductive material.

The heat dissipation sheet according to claim 4, wherein the heat conductive material includes at least one of graphene, an inorganic material, a metal, and graphite.

The heat dissipation sheet according to claim 1, wherein the inorganic particles include at least one of h-BN, SiC, AlN, Al ₂ O ₃ , SiO _2, and MgO.

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