KR20160109191A

KR20160109191A - Manufacturing method of graphite heat-spreading sheet with high graphite content and low thickness

Info

Publication number: KR20160109191A
Application number: KR1020150033185A
Authority: KR
Inventors: 박규남
Original assignee: 리모트솔루션주식회사
Priority date: 2015-03-10
Filing date: 2015-03-10
Publication date: 2016-09-21

Abstract

The present invention relates to a heat radiating sheet for an effective radiation by efficiently dissipating and spreading heat generated from the inside of an electrical device and, more specifically, to a method for manufacturing a high content thin graphite heat radiating sheet, capable of manufacturing a heat radiating sheet with excellent thermal properties by having much higher graphite contents compared with an existing graphite heat radiating sheet and reducing the thickness of a sheet significantly, at the same time by using graphite powder as major thermal conductive materials. According to the present invention, the method for manufacturing a high content thin graphite heat radiating sheet comprises the steps of: (a) manufacturing graphite slurry by mixing graphite powder with binders and solvents; (b) forming a graphite layer by spraying the graphite slurry on the base material; (c) drying the graphite layer by evaporating the solvents from the graphite layer; (d) removing a part or all of the binders contained in the graphite layer by burning the binders; and (e) compressing the graphite layer from which the binders are removed by applying pressure.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a high-content thin graphite heat-

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a thermal radiation sheet for diffusing and effectively dissipating heat generated in electronic devices and the like, and more particularly, to a thermal radiation sheet using graphite powder as a main thermally conductive material, The present invention relates to a process for producing a high-content thin graphite heat-radiating sheet capable of producing a heat-radiating sheet excellent in thermal characteristics by having a content of graphite and capable of significantly reducing the thickness of the sheet.

Generally, in the case of devices included in electronic products, heat is generated during driving, and if the heat generated in the device can not be appropriately discharged to the outside, the performance of the product is deteriorated due to an increase in the internal temperature, Malfunction or system down may occur or the life of the equipment may be reduced and, in severe cases, to failure.

Particularly, in recent years, electronic devices have become multifunctional, high-performance, light-weight and miniaturized, and accordingly, the high integration of electronic devices has been inevitably generated. As a result, the heat generated inside the device is effectively dissipated, Has become a very important technical concern.

Various heat dissipation mechanisms such as a heat sink, a cooling fan, and a heat pipe have been used as a method for solving the above-mentioned heat generation problem. However, since these systems have a considerable volume, they have recently become slimmer and smaller, There is a problem that is not suitable to be applied. Therefore, in recent years, a heat dissipation pad, a heat radiation sheet, a heat dissipation paint, or the like has been widely used as a cooling means mainly in smart phones, tablet PCs, and thin film display products.

Among them, the heat-radiating sheet diffuses the heat of the specific heat-generating portion to the entire sheet to enlarge the overall cooling area to improve the heat-radiating performance. As a heat-dissipating material used in such a heat-radiating sheet, have.

The graphite sheet is produced by processing the peeled natural or artificial graphite (graphite) powder. Generally, the graphite sheet is manufactured by mixing graphite powder with a synthetic resin binder, processing the mixture into a sheet shape, and then drying the mixture. However, in the case of the graphite heat-radiating sheet manufactured in this manner, since the graphite powder is fixed through the binder, it is relatively easy to manufacture and scattering of dust is advantageous. However, since the content of the graphite powder is limited due to the addition of the binder, The heat diffusion effect can not be obtained.

Generally, the content of graphite in the above-mentioned graphite sheet is difficult to exceed 80% by weight of the total sheet. For example, in the heat-releasing sheet disclosed in Korean Patent Publication No. 10-2014-0104757, 5 to 80 parts by weight, and in the heat diffusion sheet disclosed in Korean Patent No. 10-1457914, it is described that graphite is contained in an amount of 30 to 70 wt% and 30 to 70 wt% in forming a graphite layer have.

On the other hand, a graphite compacted sheet obtained by molding and solidifying a graphite powder directly by pressing with a roll press or the like without using a synthetic resin binder or a pressure-sensitive adhesive as a graphite layer fixing material as described above is known. In the case of such a graphite compression sheet, since the binder is not used or is used in a very small amount, there is an advantage that the graphite sheet is significantly superior to the heat-dissipating sheet of the above-mentioned type and thus has excellent heat diffusion performance. However, since the graphite compressed sheet produced in this manner tends to fall off the graphite powder from the sheet, there is a high risk of short circuit, so that a separate protective film is necessarily required outside, and in particular, the graphite- It is difficult to reduce the thickness of the sheet to a certain thickness or less due to the nature of the production process of directly molding the sheet into a roll press and compression-molding the sheet into a sheet form. It is generally known that the thickness of such a graphite sheet is limited to 20 mu m.

Accordingly, the present invention relates to a method for producing a high-content thin graphite heat-radiating sheet capable of producing a heat-radiating sheet having excellent thermal properties because graphite can be contained in a high content in the production of a graphite heat-radiating sheet using graphite as a main thermally conductive material Which is a technical problem to be solved.

Another object of the present invention is to provide a method of manufacturing a high-content thin graphite heat-radiating sheet capable of significantly reducing the thickness of a sheet, thereby contributing to slimming of the product.

According to an aspect of the present invention, there is provided a method for producing a high-content thin graphite sheet, comprising the steps of: (a) mixing a graphite powder with a binder and a solvent to prepare a graphite slurry; (b) applying the graphite slurry on a substrate to form a graphite layer; (c) evaporating and drying the solvent from the graphite layer; (d) burning out some or all of the binder contained in the graphite layer; (e) applying pressure to the graphite layer from which the binder has been removed to compress the graphite layer.

In the present invention as described above, the substrate may be a thin metal plate, and a copper foil may be preferably used. Further, the base material may be embodied as a release film for temporary support, and this release film may be subsequently removed to produce a graphite sheet composed solely of a pure graphite layer.

According to another principal technical feature of the present invention, in the step (d), by burning part or all of the binder, a lamp for emitting light energy and heat energy is irradiated on the surface of the graphite slurry layer, And when the lamp is a xenon lamp, the advantageous effect of the present invention can be more preferably realized.

According to the method for producing a high-content graphite heat-radiating sheet of the present invention as described above, graphite can be contained in a high content in producing the graphite-heat-radiating sheet, and a heat-radiating sheet having excellent thermal properties can be produced.

Further, according to the method for producing a high-content graphite heat-radiating sheet of the present invention, since the thickness of the sheet can be greatly reduced, the production of a high-content thin graphite heat-radiating sheet which contributes to the slimming of the product and which is also excellent in thermal conductivity in the vertical direction There is an effect that is possible.

Therefore, the heat-radiating sheet produced by the manufacturing method provided by the present invention is expected to provide a better thermal solution by having excellent characteristics in terms of graphite content, thickness, thermal conductivity and the like compared with the existing products.

1 is a view showing one embodiment of a high-content thin graphite heat-radiating sheet in which the present invention is most preferably implemented.
2 is a flowchart showing a method of manufacturing a high-content thin graphite heat-radiating sheet according to a preferred embodiment of the present invention.
FIG. 3A is a photograph of a smartphone with an existing heat-radiating sheet attached thereto, taken by an infrared camera.
FIG. 3B is a photograph of a smartphone with a heat-radiating sheet according to the first embodiment of the present invention taken by an infrared camera. FIG.
FIG. 3C is a photograph of a smartphone with a multifunctional composite sheet according to a third embodiment of the present invention taken by an infrared camera. FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention may be readily understood and practiced by those skilled in the art. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the invention are provided to more fully describe the present invention to those skilled in the art.

1 is a view showing an embodiment of a high-content thin graphite heat-radiating sheet in which the present invention is most preferably implemented. Referring to Fig. 1, a graphite heat- ) And a graphite layer 20 in which the graphite powder is pressed and hardened can be laminated.

In the graphite heat-radiating sheet of the present invention, the base layer 10 may preferably include a thermally conductive material, and more preferably a metal foil. The thin metal substrate layer 10 basically has a function of shielding electromagnetic waves generated from electronic devices, in addition to a function of transferring heat generated from a heat radiation portion of an electronic device such as a smart phone to the outside. Therefore, according to the graphite heat-radiating sheet in which the thin metal plate substrate layer 10 and the graphite layer 20 are stacked as described above, the heat-radiating sheet alone can shield not only the heat conduction but also the electromagnetic wave, It is possible to reduce the number of parts related to heat dissipation, thereby positively affecting the slimming of the product.

In particular, in the case of a graphite heat-radiating sheet, the thermal diffusion characteristics in the horizontal plane direction are excellent, while the thermal conductivity in the vertical direction is somewhat deteriorated. However, when the metal foils are stacked together as described above, Is spread rapidly to the metal thin plate substrate layer 10 while being uniformly diffused over the entire surface area of the sheet, so that heat conduction efficiency and heat dissipation characteristics are greatly improved in the vertical and horizontal directions as a whole.

Copper foil may be used for the thin metal substrate layer 10, and other types of thermally conductive metals such as aluminum or nickel or alloys thereof may be used. The thickness of the metal thin plate substrate layer 10 may be 5 占 퐉 or more and 250 占 퐉 or less, more preferably 10 占 퐉 to 120 占 퐉. When the thickness of the metal foil used as the base layer 10 is 10 μm or less, the thermal conductivity is lowered. When the thickness is 120 μm or more, the thickness of the metal foil is rather thick.

1 shows a heat radiation sheet in which a graphite layer 20 is laminated on a base layer 10 as a preferred embodiment of the present invention. However, in the manufacturing method of the present invention, The present invention is applicable to the production of a graphite heat-radiating sheet which is removed only and consists solely of the graphite layer 20. That is, the base layer 10 may be implemented as a release film as an application for temporarily holding the graphite slurry by temporarily supporting the graphite slurry during the production of the graphite sheet, After the layer 20 is finally cured, the graphite sheet composed of only the pure graphite layer can be produced by peeling off. As the material of the release film, for example, a PET film may be used, and a release film of another material capable of performing the functions described above may be used according to a selection of a person skilled in the art.

1, a graphite layer 20 may be laminated on the substrate layer 10. The graphite layer 20 may be formed on the graphite layer 20, as shown in FIG. According to the graphite sheet according to the present invention, the base layer 10 and the graphite layer 20 are laminated and bonded together without separate adhesion means or material. On the base layer 10, graphite The method of forming the layer 20 to produce the graphite heat-radiating sheet 1 will be described later in detail.

The graphite layer 20 is made of graphite powder as a thermal diffusion and conductive material. Natural graphite and artificial graphite can be used as the graphite, and graphite (graphite) in various forms such as expanded graphite, spheroid graphite, graphite graphite, graphene and carbon nanotube can be selected and used have. In the following embodiments, description will be made on the basis of manufacturing a graphite heat-radiating sheet using artificial graphite powder.

In the present invention, there is no particular limitation on the size of the graphite powder, but it is preferable that the graphite powder has an average particle size of 5 to 15 mu m. If the average particle size is less than 5 탆, an excessive amount of solvent may be added during mixing with the binder in the course of producing the sheet, and dispersion and heat conduction characteristics may be deteriorated. If the average particle size exceeds 15 탆, surface scratching may occur and the surface may become coarse without uniform coating. This is because the thermal conductivity of the graphite sheet 1 of the present invention and the factor .

In the present invention, the average density of the graphite powder may be 1.6 to 2.0 g / cm 3 and the porosity may be 5 to 10%. When the average density and the porosity are less than the above-mentioned reference values, the initial viscosity of the mixture may be increased during mixing of the graphite powder with the binder and the solvent to produce a slurry, which may not be uniformly dispersed. On the other hand, if the average density and the porosity exceed the above-mentioned reference value, the internal pores of the graphite powder may be developed. In this case, since the solvent gradually permeates into the pores during the production of the graphite powder mixed slurry, There is a problem that the viscosity of the mixed slurry may rapidly increase after the stirring is completed.

In the method for manufacturing a graphite sheet according to the present invention, a binder is included to bind the graphite powder of the graphite layer 20 and fix it in a predetermined sheet shape. In the present invention, the binder is used for primarily fixing the graphite powder in the process of manufacturing the heat-radiating sheet, and a part or the whole of the binder is fixed to the combustion / There is a feature to be removed. Therefore, the graphite heat-radiating sheet manufactured according to the manufacturing method of the present invention can contain graphite in a high amount as compared with the conventional graphite heat-radiating sheet having the graphite powder bonded with a binder, and also has the advantage of reducing the thickness of the sheet do.

In the present invention, the binder may be made of, for example, an acrylic resin, a urethane resin, or a silicone resin. Other synthetic resin binders or other binders commonly used in the art may be used. In the present invention, when the binder and the graphite powder are stirred, the composition ratio may be 80 to 90% by weight of the graphite powder and 10 to 20% by weight of the binder. According to a main technical feature of the present invention, after the graphite powder is added to / agitated in the binder to form the graphite layer 20, the binder is partially or wholly burned and removed using a xenon lamp and other means, In the final sheet product formed through such a process, the graphite layer 20 may contain 85 to 99 parts by weight of graphite powder based on 100 parts by weight of the graphite layer 20 from which the solvent and the binder have been removed.

In forming the graphite layer 20, a solvent is further added to dissolve the binder to obtain a fluid adhesive. The solvent may include at least one of ethanol, methanol, Methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), toluene, Lt; / RTI > The solvent can be evaporated and removed during the drying of the graphite heat-radiating sheet 1 of the present invention.

Further, in the formation of the graphite layer 20, a dispersing agent may be further added to suitably disperse the graphite powder and the binder so as to exhibit a uniform distribution. The dispersant may be, for example, an adsorbent such as a surfactant, a polymer substance, a peptizer, and the like. If the dispersion agent is used for the purpose of uniform dispersion of a material and aggregation of mixed particles as described above in the art, There is no limitation.

In the production of the graphite layer 20, a hardener and a flame retardant may be added as needed. The hardener may be included to improve the hardness of the graphite layer 20 and may include, for example, an organic peroxide, an isocyanate, an azo dyes, an amine, Amidazole-based, and urethane-based curing agents can be selected and used. However, the curing agent is not limited thereto, and may include various materials capable of improving the strength of the graphite layer 20.

The flame retardant is also referred to as a flame retardant and may be added for the purpose of preventing combustion due to overheating of the graphite layer 20 and suppressing the generation of noxious gas during combustion. The flame retardant may be selected from the group consisting of aluminum hydroxide (AlOH3), magnesium hydroxide (MgOH2) or phosphorus flame retardant.

Further, although not shown in the drawing, the graphite heat-radiating sheet 1 of the present invention may further include a protective film (not shown). The protective film protects the surface of the graphite layer 20 and functions to prevent the graphite powder from leaking out and scattering dust. The material of the protective film includes at least one of polyethylene (PE), polyethylene phthalate (PET), polypropylene (PP), polyimide (PI), polycarbonate (PC), and polycarbonate can do.

Since the graphite heat-radiating sheet of the present invention as described above can be manufactured with a very thin thickness, it can be very preferably used as a rear heat-radiating pad of an electronic product such as a smart phone, where slimming of the product is important. In addition, the graphite heat-radiating sheet of the present invention can be processed and used in various forms such as a gasket and a mold packing, and can be subjected to a pressure-sensitive adhesive treatment using appropriate means commonly known in the art to provide a variety of conductive adhesive tape and heat- It is possible to apply it to the form.

Hereinafter, a method of manufacturing the graphite heat-radiating sheet of the present invention will be described in detail.

A method for producing a high-content graphite heat-radiating sheet provided by the present invention relates to a method for producing a graphite heat-radiating sheet using graphite powder as a main thermally conductive material, the basic process comprising the steps of: (a) mixing the graphite powder with a binder and a solvent Mixing the mixture to prepare a graphite slurry; (b) applying the graphite slurry on a substrate to form a graphite layer; (c) evaporating and drying the solvent from the graphite layer; (d) burning out all or a part of the binder contained in the graphite layer; (e) applying pressure to the graphite layer from which the binder has been removed and compressing the graphite layer.

FIG. 2 is a flow chart showing a method of manufacturing a graphite heat-radiating sheet according to a preferred embodiment of the present invention. Referring to FIG. 2, the method of manufacturing the graphite heat-radiating sheet of the present invention will be described step by step.

(a) Graphite Slurry Compounding

In step S110, a step of pre-mixing the graphite powder with a binder and a solvent and, if necessary, with a dispersant, a hardener and a flame retardant may be carried out. The graphite powder, the binder, the curing agent, the dispersant, the flame retardant and the mixture of the solvent may be pre-mixed using a pre-mixer. At this time, the content of the graphite powder may be in the range of 80 to 90 parts by weight based on 100 parts by weight of the entire mixture including the graphite powder, the binder, the curing agent and the dispersing agent. Since the solvent evaporates during the drying of the graphite heat-radiating sheet, the solvent is excluded from the total weight portion. This step may optionally be carried out to improve the initial dispersion flow prior to the full dispersion of the graphite mixture.

In step S120, a step of dispersing the pre-mixed mixture to produce a graphite slurry is executed. This step is a step of producing a fluid slurry for sheet molding, wherein the graphite slurry can be produced using a dispersing machine. The graphite slurry may be dispersed through a variety of dispersing equipment well known in the art, preferably a basket mill may be used.

In step S130, a step of filtering the graphite slurry may be further performed. This step can be carried out to remove foreign matter contained in the graphite slurry, or to remove particles exceeding the reference particle size. Particles or particles exceeding the reference particle size affect the quality of the product in the molding step (casting), so it is necessary to pre-filter. For example, the reference granularity may be 100 mesh. The graphite slurry filtration can be carried out using a filter or various slurry filtration devices.

(b) Graphite Layer formation

In step S140, a step of applying a graphite slurry prepared as described above on a substrate to form a graphite layer is performed. In the manufacturing method of the present invention, a thin metal plate may be preferably used as the substrate, and a copper foil may be most preferably used.

A copper plate is supplied to a production line through a roll on which a copper foil is wound, and a graphite layer is formed by applying the flowable graphite slurry mixture prepared in the previous step onto the copper foil. Examples of the slurry coating method include various coating methods such as a comma coating, a gravure coating, a slot die coating, a calendar coating, a roll coating, and a cast coating, and preferably a comma coating can be applied.

When molding in the comma coating method, the graphite slurry applied on the copper foil substrate is cut by the comma blade to adjust the reference thickness while passing the comma roll. In this case, it is preferable to coat the substrate by about 40% or more higher than the design standard thickness in anticipation of the decrease of the coating thickness due to the evaporation of the solvent and the burning of the binder after drying. The graphite slurry thus coated on the substrate constitutes a graphite layer after drying. The reference thickness of the graphite layer may be 5 탆 or more and 200 탆 or less.

On the other hand, in the manufacturing process described above as a preferred embodiment, a copper foil is used as a base material. The copper foil constitutes one layer of the graphite heat-radiating sheet of the present invention and functions as a heat conduction layer and also as an electromagnetic wave shielding layer . However, instead of constituting a single layer of the graphite heat-radiating sheet, the above-described substrate may be constituted of a plastic release film such that the graphite slurry can be temporarily supported in the manufacturing process to maintain the sheet shape and can be removed at the time of sheet production. Thus, when a release film is used as the substrate, the final product to be processed becomes a heat-radiating sheet composed only of a graphite layer. In addition, the substrate as such a role may be a plate-like fixed base block or a sliding base instead of the release film.

(c) Drying of the sheet - solvent evaporation

In step S150, a step of drying the graphite heat-radiating sheet may be executed. This step is carried out to remove the solvent contained in the graphite layer (see Fig. 1, 20) of the graphite heat-radiating sheet. The graphite heat-radiating sheet having the graphite layer (see Fig. 1) formed by applying the graphite slurry onto the base material (see Fig. 1) 10 is dried in a drying chamber (for example, oven or the like) can do. For example, the reference temperature may be 50 ° C to 110 ° C.

Further, according to a preferred embodiment of the present invention, the graphite heat-radiating sheet can be sequentially dried in a plurality of drying zones having different reference temperature ranges. For example, the temperature of the drying chamber inlet (first section) is at room temperature, the temperature of the middle section (second section) is 50 to 70 ° C, the temperature of the outlet (third section) is 70 to 90 ° C, The sheet can be dried by sequentially passing the sheet from a zone having a low temperature to a zone having a high temperature. In addition, the drying time for each section is set so that the drying time of each section having different temperatures, such as 5 minutes for the first section, 10 minutes for the second section, 5 minutes for the third section, You may.

(d) Binder burning

According to the manufacturing method of the present invention, after the graphite heat-radiating sheet having the graphite layer formed as described above is firstly dried, a step (step S160) of removing a part (or all) of the binder that has coupled the graphite powders in the graphite layer Which corresponds to a characteristic configuration distinguished from the prior art in the present invention.

That is, according to the present invention, not only the solvent is evaporated and removed from the graphite layer, but the binder binder according to this step also includes a step of burning a certain amount by burning.

In this step, the step of burning and removing the binder as described above can be performed by a method of locally intensely applying locally strong heat to the graphite layer to burn and carbonize the binder. Therefore, in order to burn and carbonize the binder as described above, a heating means capable of heating the graphite layer at a predetermined temperature or higher should be provided. In this process, the temperature may be set to a temperature of 300 to 400 ° C Lt; / RTI >

In the present invention, a lamp for emitting light energy can be preferably used as the heating means. By irradiating the lamp close to the surface of the graphite layer, the light energy and the heat energy of the lamp surface are heated to burn the binder . That is, if the entire sheet is heated to a temperature higher than the burning temperature of the binder in a drying chamber or the like, the sheet may be overheated as a whole, and bubbles may be generated and expanded excessively, thereby deteriorating the quality of the sheet. It is preferable that the sheet is moved while locally intensively heating the surface of the sheet, and the binder is sequentially burned.

In addition, according to the embodiment of the present invention, a xenon lamp may be preferably used as the lamp, and a halogen lamp or an infrared lamp may be used for the same purpose. As a result of the tests conducted by the present inventors, it has been confirmed that when the graphite layer is irradiated with a xenon lamp, the heat conduction characteristics of the heat-radiating sheet are superior to those of other types of lamps or heating means. When using a xenon lamp, the output is 250 to 400 watts, and the lamp can be irradiated 3 to 10 times per second, spaced 10 to 30 mm from the graphite layer. At this time, the irradiation time per each cycle may be 5 to 15 ms.

According to the present process, the binder can remove about 50 to 95% of the initial content, and the incineration amount of the binder can be controlled through the lamp output and irradiation time. In the above embodiment, a lamp, particularly a xenon lamp, has been described as a preferable example of a means for locally heating a sheet for burning a binder. However, in addition to this, a binder may be incinerated by directly contacting or indirectly heating the surface of the sheet A variety of heating means may be used.

Further, in the above-described embodiment, in burning the binder, it is more preferable to locally heat the sheet rather than to heat the sheet as a whole. However, when the substrate is heated entirely (e.g., heated in a high temperature furnace) And does not mean to exclude the burning and incineration of the binder. That is, the main technical feature of the present invention is that the graphite powder is fixed with a binder at the initial stage of sheet production, and then the binder is burnt and removed, whereby a graphite heat-radiating sheet having a high graphite content and a high thickness compression ratio is possible It is to be understood that the difference between the heating method and the range is obviously included in the technical content of the present invention unless the technical idea of the present invention is satisfied.

(e) Graphite Layer compression

When the binder is incinerated through the irradiation of a xenon lamp as described above, the binder is partially removed from the graphite layer. Therefore, after the incineration, the graphite layer does not change much in terms of external volume, but significant voids are generated between the graphite powders . In the inner particle state, each graphite powder is in a very loosely bonded state without being in close contact with each other.

According to the present invention, a step of compressing and compressing the graphite sheet is performed in a state where the graphite powders are loosely coupled as described above (S170). That is, by pressing the graphite heat-radiating sheet in this step, voids between the graphite powder constituting the graphite layer can be reduced to increase the density and reduce the thickness, and as a result, the thermal diffusing performance of the heat-radiating sheet can be improved.

In particular, according to the main technical features of the present invention, the residual voids remaining after the binder is incinerated in the graphite layer are present in a considerable volume of free space, so that when the graphite sheet is pressed by this process, The graphite particles are compressed tightly while disappearing, and a considerably large compression ratio is exhibited in the thickness of the sheet.

Therefore, according to the manufacturing method of the present invention as described above, it is possible to realize a graphite content which is much higher than that of the conventional binder-coupled graphite heat-radiating sheet, and also the thickness of the sheet can be greatly reduced.

On the other hand, in this step, equipment such as a rolling press equipped with a pressing roller can be used to press the graphite heat-radiating sheet. However, the present invention is not limited to this, and various equipment capable of compressing the sheet can be used.

When the graphite sheet is manufactured according to the above-described process, the surface of the graphite sheet may be adhered to the surface by a bonding means (pressure-sensitive adhesive, double-sided tape or the like) or a polymer protective film (using PET, PAN coating or the like), it is possible to facilitate the production, assembly, or use of the heat-radiating sheet of the present invention. The heat-radiating sheet of the present invention can be applied to electronic parts such as a smart phone, a panel, a case and the like, and can be secondarily processed in the form of a gasket or a molding packing, and can be used in various fields in various fields.

Hereinafter, the results of experiments and evaluations through various examples will be presented and described in order to confirm the improvement of the thermal characteristics and performance of the graphite heat-radiating sheet according to the present invention described above. It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory only and are not to be construed as limiting the scope of the invention.

Example

Example 1: Using copper foil as substrate

The graphite used in this example used artificial graphite powder having an average particle size of 7 mu m. To 100 parts by weight of the graphite, 15.3 parts by weight of acrylic adhesive as a binder, 20.6 parts by weight of ethyl acetate as a solvent, 0.2 parts by weight of a curing agent, And 0.2 part by weight of a dispersant were mixed and dispersed uniformly with a basket mill to prepare a graphite slurry. The graphite slurry mixture was coated on one side of a copper foil having a thickness of 40 占 퐉 to a thickness of 30 占 퐉 by a comma coating method to form a graphite layer. Then, the solvent was volatilized for 8 minutes while raising the temperature to 80 占 폚 to 120 占 폚 .

Thereafter, a xenon lamp having an output of 250 W was irradiated for 100 ms per irradiation site at a height of 25 mm from the graphite layer to incinerate the binder to a certain extent. The thus-produced graphite heat-radiating sheet was continuously passed through five compression rollers The graphite heat-radiating sheet was prepared so that the final thickness of the graphite layer was 15 mu m.

Example 2: Removing the substrate Graphite Layered Heat-resistant sheet Produce

A graphite heat-radiating sheet having a thickness of 15 탆 was produced by the same composition and method as in Example 1 except that a PET release film having a thickness of 50 탆 was used as a base material. The release film used as the base material was removed after production of the heat-radiating sheet to produce a heat-radiating sheet composed of only the graphite layer.

Comparative Example

Comparative Example One: Graphite Powder as a binder Combined Heat-radiating sheet

A graphite heat-radiating sheet was produced by the same composition and method as in Example 1 except that the step of irradiating the xenon lamp in Example 1 was performed.

Comparative Example 2: Graphite Powder compacted Graphite Compression sheet

Artificial graphite powder having an average particle size of 7 mu m as in Example 1 was charged into a compression roller press through a hopper to prepare a graphite compressed sheet compression-molded to a thickness of 20 mu m. A small amount of an acrylic adhesive as a binder was added in an amount of 1.5 parts by weight based on 100 parts by weight of graphite.

Experimental Example

< Experimental Example One: Example 1 and Comparative Example 1 with Thermal conductivity comparison>

In order to compare the thermal performance of the graphite heat-radiating sheet (Example 1) produced by the present invention and the conventional graphite heat-radiating sheet (Comparative Example 1), a test was performed to measure the thermal conductivity in the horizontal plane direction. The test method was measured by a laser flash method, and the measurement results are shown in Table 1 below.

division Graphite layer thickness (탆) Thermal conductivity (W / Mk) Example 1 15 725 Comparative Example 1 20 630

As shown in Table 1, in Example 1 of the present invention, which was subjected to the xenon lamp irradiation process, the thickness of the sheet was drastically reduced as compared with Comparative Example 1, Can be confirmed. Accordingly, it can be seen that the present invention of burning a binder by a xenon lamp or the like over a certain range through compression molding after the above experiment has a significant effect in reducing the sheet thickness and improving the thermal properties.

< Experimental Example 2: Example 2 and Comparative Example 2>

A heat radiation sheet (Example 2) made of the present invention and made of a graphite layer without a copper foil layer (Example 2) and a graphite compression sheet (Comparative Example 2) using a conventional compression molding method were subjected to a test for measuring the horizontal direction thermal conductivity Respectively. The test method was measured by the same laser flash method as in Example 1, and the measurement results thereof are shown in Table 2 below.

division Graphite layer thickness (탆) Thermal conductivity (W / Mk) Example 2 15 375 Comparative Example 2 20 380

As shown in Table 2, it can be seen that the heat-radiating sheet manufactured according to Example 2 of the present invention is not significantly different in thermal conductivity from the conventional pure graphite sheet. On the other hand, from the viewpoint of the sheet thickness, it is practically difficult to manufacture the conventional pure graphite compact sheet to a thickness of 20 μm or less, but according to the present invention, it becomes possible to produce a graphite sheet with a thickness of 15 μm. Therefore, the graphite heat-radiating sheet manufactured by the process of the present invention through the above-described test examples has a thermal performance comparable to that of a conventional pure graphite sheet while having a thin thickness, so that the graphite heat- Able to know.

< Experimental Example 3: Comparison of heat dissipation performance with existing sheet>

In order to compare the heat dissipation performance of the conventional heat dissipation sheet and the graphite heat dissipation sheet according to the embodiment of the present invention, a conventional heat dissipation sheet and a graphite heat dissipation sheet according to the present invention are mounted on a battery And the same moving image was reproduced for 30 minutes, and then the surface temperature was photographed using a thermal imaging camera (FLIR E40).

FIG. 3A is a photograph of a smartphone with an existing heat-radiating sheet attached thereto, taken by using an infrared camera. The conventional heat radiating sheet photographed in Fig. 6A is composed of a graphite sheet (20 mu m) and a copper foil sheet (40 mu m), and they were bonded using a double-sided tape (5 mu m). In this figure, it can be seen that the maximum temperature of the smartphone is measured at 39.7 ° C.

FIG. 3B is a photograph of a smartphone with a graphite heat-radiating sheet according to the first embodiment of the present invention taken by a thermal imaging camera. The graphite heat-radiating sheet photographed in this drawing was produced by molding a graphite layer (15 mu m) on a copper foil sheet (40 mu m). Referring to this figure, the maximum temperature of the smartphone was measured at 39.7 ° C. The thickness of the graphite layer constituting the conventional heat radiation sheet shown in Fig. 6A is 20 mu m, while the graphite layer of the graphite sheet according to the embodiment of the present invention exhibits approximately the same performance .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, the same is by way of illustration and example only and is not to be taken by way of limitations in the spirit and scope of the invention as defined by the appended claims. And it is to be understood that such modified embodiments also fall within the scope of the present invention defined by the appended claims.

1: Graphite heat-radiating sheet of the present invention
10: substrate layer
20: graphite layer

Claims

(a) mixing the graphite powder with a binder and a solvent to prepare a graphite slurry;
(b) applying the graphite slurry on a substrate to form a graphite layer;
(c) evaporating and drying the solvent from the graphite layer;
(d) removing a part or all of the binder contained in the graphite layer;
(e) applying pressure to the graphite layer from which the binder has been removed to compress the graphite layer;
Wherein the graphite sheet is formed of a sheet material.

The process for producing a graphite heat-radiating sheet according to claim 1, wherein the substrate is a metal thin plate.

The process for producing a graphite heat-radiating sheet according to claim 2, wherein the substrate is a copper foil.

The method of claim 1, wherein the step (d) comprises irradiating a surface of the graphite layer with a lamp that emits light energy and thermal energy to burn the binder.

5. The method of claim 4, wherein the lamp is a xenon lamp.

6. The method of claim 5, wherein the output of the xenon lamp is 250 to 400 watts.

7. The method of claim 6, wherein the xenon lamp is irradiated 3 to 10 times per second at a distance of 10 to 30 mm from the graphite layer, and the irradiation time per each cycle is 5 to 15 ms.

The process for producing a high-content graphite heat-radiating sheet according to claim 1, wherein the substrate is a removable release film.

The method of claim 1, wherein the graphite powder is contained in an amount of 85 to 99 parts by weight based on 100 parts by weight of the graphite layer from which the solvent and the binder have been removed by the steps (c) and (d) By weight based on the total weight of the graphite sheet.