KR101560570B1 - Composition for complex sheet with EMI shielding and absorbing, thermal dissipation and electric insulation, and complex sheet comprising the same - Google Patents

Abstract

The composite sheet including the composition according to the present invention can be used as a composite sheet having a composite function of simultaneously possessing electromagnetic interference (EMI) noise shielding, absorption, heat dissipation and electrical insulation characteristics by including reformed graphite, Sheet. Therefore, unlike the prior art in which a plurality of sheets have to be stacked to provide the above characteristics simultaneously, it is possible to provide a single-layer sheet, which makes it possible to reduce the size and weight of the electronic apparatus or electronic parts while enhancing the stability thereof. .
Further, since the degree of shielding of heat radiation and electromagnetic interference noise can be controlled according to various characteristics required for electronic devices and parts by controlling the mixing ratio of the modified graphite, the magnetic particles and the carbon material, the NFC antenna film, the FPCB, And can be usefully utilized in a variety of electronic and mechanical fields requiring three characteristics such as electronic parts.

Description

TECHNICAL FIELD [0001] The present invention relates to a composition for electromagnetic interference noise shielding and absorption, heat radiation and electrical insulation composite sheets, and a composite sheet comprising the same,

The present invention relates to a composition for a composite sheet having electromagnetic interference (EMI) noise shielding, absorption, heat dissipation and electrical insulation characteristics, and a composite sheet comprising the composite sheet.

BACKGROUND ART [0002] With the recent miniaturization and weight reduction of electronic devices and components, the degree of integration of circuitry mounted on them has been increasing. As the amount of generated electromagnetic waves increases, electromagnetic interference and electromagnetic interference threats are increasing. As a result, the heat generated by the electric devices operating on the basis of electric energy is rising, and the heat problem is highlighted. Therefore, it is necessary to develop a technology capable of simultaneously realizing heat dissipation characteristics that effectively dissipate and dissipate heat generated from the electric element, and that can effectively shield and absorb electromagnetic waves that cause malfunction of the electric element and adversely affect the human body .

Accordingly, there is a problem in that products having two or more sheets, in particular, sheets obtained by laminating a sheet having heat conductive property and a sheet having electromagnetic wave absorbing property are studied, but the processability is poor due to a multilayered structure, In addition, in order to realize the thermal conductivity and the electromagnetic wave absorbing property to the extent required in recent electronic apparatuses, the thickness has to be thickened due to the characteristics of multilayer, which is a problem in that it is not suitable for recent electronic devices seeking miniaturization and weight saving.

Korean Patent Publication No. 10-0741616

An object of the present invention is to provide an integrated type heat dissipation device capable of simultaneously dissipating heat dissipation characteristics that effectively dissipate and dissipate heat generated from an electric device and shielding and absorbing electromagnetic waves that cause malfunction of the electric device, A composition for a composite sheet, and a composite sheet comprising the same.

Embodiments of the present invention provide a composition for a composite sheet comprising a modified graphite, magnetic particles and a carbon material, and a composite sheet comprising the composite sheet.

The composite sheet comprising the composition according to the embodiments of the present invention can be used as a composite sheet containing modified graphite, magnetic particles and carbon material together to provide electromagnetic interference (EMI) noise shielding, absorption, Thereby providing a sheet having a desired function. Therefore, unlike the prior art in which a plurality of sheets have to be stacked to provide the above characteristics simultaneously, it is possible to provide a single-layer sheet, thereby making it possible to reduce the size and weight of the electronic apparatus or electronic parts while enhancing the stability of the applied electronic apparatus or electronic parts. .

Further, since the degree of shielding of heat radiation and electromagnetic interference noise can be adjusted according to various characteristics required for electronic devices and parts by controlling the mixing ratio of the modified graphite, magnetic particles and carbon materials, it is possible to control the NFC antenna film, FPCB single- And can be usefully utilized in a variety of electronic and mechanical fields requiring three characteristics such as electronic parts.

1 is a schematic view showing a composition for a composite sheet comprising a modified graphite (1), a carbon material (2) and magnetic particles (3) according to an embodiment of the present invention.

As used herein, the term " modified graphite "refers to graphite in which an insulating layer is coated through physical and chemical treatments to change electrical conductivity characteristics of graphite to electrical insulation.

In the present specification, the term "composite sheet" means a sheet having a plurality of functions at the same time.

Embodiments of the present invention provide a composition for a composite sheet comprising a modified graphite, magnetic particles and a carbon material. 1 schematically shows a composition for a composite sheet comprising a modified graphite (1), a carbon material (2) and magnetic particles (3) according to an embodiment of the present invention.

According to embodiments of the present invention, the modified graphite is a surface treated with graphite, which is a hydrophobic surface, and then coated with a thin film of silica (SiO2) by a sol-gel method. Specifically, the modified graphite is, for example, a core-shell structure of a core coated with a sol-gel method and a thin film of a silica coating layer surrounding the core. Conventional graphite has a high thermal conductivity, but it has a limitation that it can not be used as a heat-dissipating material in an application field requiring electrical insulation because of its excellent electric conductivity. However, in the modified graphite according to an embodiment of the present invention, the hydrophobic interface having a low reactivity is converted into a hydrophilic state through the surface modification treatment, and then the thin film silica is coated by the sol-gel method to add the electrical insulation property by the silica . That is, the modified graphite has high electrical conductivity and high electrical conductivity, but it has electrical insulating properties that do not allow electricity to flow. Thus, the modified graphite can provide excellent heat dissipation performance and electrical insulation when applied to electronic devices and the like. Thin film silica coated on the outer surface of the modified graphite may cause peeling of the coating layer when the thickness is very low and may block the heat transfer when it is thick. Therefore, when the mass ratio of the graphite to the graphite in the synthesis is 100 wt%, the relative silica precursor The mass ratio is preferably 10 to 40% by weight.

In one embodiment, the silica coating can be accomplished through emulsifier-free emulsion polymerization and sol-gel processes. Specifically, a mixed solution in which alcohol, water, and a vinyl-based suspension are mixed is prepared, silane, which is a precursor of silica, is added to the mixed solution, and when silane is introduced into the mixed solution, phase separation by precipitation is performed, The reformed graphite particles are added to the precipitate to induce a sol-gel reaction between the reformed graphite particles and the precipitate, thereby coating silica on the surface of the modified graphite particles. After the spherical silica seed is formed, a coating film is formed.

In one embodiment, the modified graphite has an average particle size of 1 to 50 m, more specifically 5 to 45 m. If the particle size is less than the above range, the thermal conductivity and heat dissipation will be lowered. If the particle size of the modified graphite is twice the particle size of the original graphite, the number of interfaces with the polymer is 1/2, But it is difficult to be filmed.

In one embodiment, the magnetic particles absorb electromagnetic waves generated from electronic devices or components, thereby preventing interference of electromagnetic waves and electromagnetic interference, and shielding electromagnetic interference noise. The magnetic particles included in the composition may include soft magnetic metal alloy particles or ferrite magnetic particles. The soft magnetic metal alloy particles may include a metal alloy that can be quickly magnetized when a magnetic field is applied from the outside, and can realize an action or effect of absorbing and removing electromagnetic noise of a specific frequency on the composite sheet. Specific examples of such magnetic particles include iron-chromium-silicon alloys, iron-chromium alloys, iron-silicon-aluminum alloys, iron-silicon alloys, nickel-iron alloys, carbonyl iron, nickel-zinc alloys and manganese- And at least one magnetic powder selected from the group consisting of the above-mentioned magnetic powders. In one embodiment, the average particle size of the magnetic particles is from 1 to 100 mu m.

In one embodiment, since the carbon material has battery conductivity, effective electromagnetic shielding by electromagnetic shielding of electromagnetic waves generated from electronic devices or parts becomes possible. The carbon material included in the composition may be at least one selected from the group consisting of graphite, carbon black, carbon nanotube, carbon fiber and graphene. Particularly, a material having an aspect ritio of less than 100 is excluded because it is difficult to improve the mechanical strength. The carbon nanotubes may be at least one selected from single wall carbon nanotubes (SWNTs), double wall carbon nanotubes (DWNTs), and multiwall carbon nanotubes (MWNTs).

Also, according to embodiments of the present invention, the composition may include 30 to 80 parts by weight of modified graphite, 40 to 80 parts by weight of magnetic particles and 1 to 5 parts by weight of carbonaceous material, more specifically 40 to 80 parts by weight 50 to 80 parts by weight of magnetic particles and 1 to 3 parts by weight of carbon material. When the modified graphite powder is filled in an amount exceeding 80 parts by weight, it is difficult to prepare a sheet because the powder arrangement is difficult. When the amount of the modified graphite powder is less than 30 parts by weight, the heat radiation effect is remarkably decreased. In addition, when the content of the magnetic particles is more than 80 parts by weight, the frequency band is shifted to a lower frequency band than the mobile communication frequency band, and powder arrangement in the polymer resin is difficult. When it is filled to less than 50 parts by weight, the electromagnetic wave absorbing ability is deteriorated and deviates from the permeability target of the invention. In addition, when the carbon material content is more than 3 parts by weight, it is difficult to disperse the carbon material, so that it can not be made into a sheet. When the carbon material content is less than 1 part by weight, shielding efficiency is significantly lowered, do.

According to embodiments of the present invention, the composition may include 30 to 80% by weight, more specifically 50 to 80% by weight, based on the total weight of the composition, of a filler composed of modified graphite, magnetic particles and carbon material. If the amount is more than 80% by weight, sheet formation is difficult, while if it is less than 30% by weight, sheet workability is excellent, but heat radiation, electromagnetic wave shielding and absorption performance are deteriorated and the function as a composite sheet is deteriorated.

In addition, the composition according to embodiments of the present invention further comprises a binder resin. The binder resin includes at least one of a thermoplastic resin and a thermosetting resin, and may further include at least one of a curing agent, a curing accelerator, and a binder-based material. The thermoplastic resin may be selected from the group consisting of an acrylate copolymer, a polystyrene, a polyester, a polyimide, a polyetherimide, a polyamide, a polyurethane and a polyphenylene ether. The thermosetting resin may be a thermosetting silicone rubber compound , One-component thermosetting silicone binder, two-component thermosetting silicone binder, acrylic resin, epoxy resin and urethane resin. In one embodiment, the composition for a composite sheet may contain 20 to 50 wt%, preferably 20 wt%, of the binder resin based on the total weight of the composition.

Embodiments of the present invention provide a composite sheet comprising the composition for a composite sheet as described above. The composite sheet as described above can provide excellent heat dissipation, electromagnetic interference noise shielding, absorption, and electrical insulation characteristics of a single layer, a thermal conductivity of 1.0 W / mK or more, a shielding efficiency of 50 dB or more, and a permeability of 30 H / m or more.

In one embodiment, the composite sheet comprises mixing reformed graphite and magnetic particles, adding a carbonaceous material to the mixture to produce a filler mixture; And a composite sheet prepared by mixing the prepared filler with a binder resin and then using a hot press method, a tape casting method, a vacuum extrusion method, or a vacuum molding casting method. Further, in one embodiment, the composite sheet may have a thickness of 0.1 to 1.0 mm. If the thickness exceeds the above range, it is difficult to realize appropriate electromagnetic wave shielding, absorption, and heat radiation performance. If the thickness is less than the above range, it may be a limitation in application to electronic devices and it is difficult to reduce the weight of the product.

Hereinafter, the present invention will be described with reference to the following examples and test examples. The examples and the test examples are for illustrating the present invention in more detail, and the scope of the present invention is not limited to the range of the following examples. In addition, the comparative example described below is described only for the purpose of comparison with the embodiments, and is not described as a conventional technique. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit of the invention.

[Manufacturing Example]

Examples and comparative examples according to the embodiments of the present invention were respectively prepared by the following methods and compositions of Table 1.

First, modified graphite and magnetic particles were added and dry-kneaded for 30 minutes, and then the carbon material powder was added to the mixture and dry-kneaded again for 20 minutes to prepare a filler mixture. The prepared filler and the polymeric binder resin were mixed and kneaded for 30 minutes using a kneader, and then a composite sheet was produced using a hot press method, a tape casting method, a vacuum extrusion method, or a vacuum molding casting method . The modified graphite is a graphite of 5 to 45 μm having a core-shell structure of a thin-film silica coating layer. The magnetic particles are plate-shaped particles having a powder size of 1 to 100 μm and Fe-Si of 80% (MWNT) having an aspect ratio of 1000 or more was used as the carbon material.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 filling Modified graphite 80 47 80 17 80 77 80 100 80 97 80 0 Magnetic particle
(Fe-Si-Cr) 50 80 20 0 0 100 Carbon material
(Carbon nanotubes) 3 3 3 0 3 0 Binder resin
(Polyurethane) 20 20 20 20 20 20 Total (% by weight) 100 100 100 100 100 100

[Test Example 1]

The following experiments were conducted to compare the thermal conductivity, the electromagnetic wave shielding ratio and the magnetic permeability of the examples and comparative examples prepared above.

Thermal conductivity was measured by the hot wire method according to ASTM E1461 method, and the electromagnetic wave shielding ratio was measured using ASTM D4935-10 method using Agilent's E5071B network analyzer. The permeability was measured using the Agilent E4991A RF Impedance Analyzer by the short coaxial measurement method of KS C 6031 method. The results are shown in Table 2 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Thermal conductivity (W / mK) 3 One 7.5 10 9 0.5 Electromagnetic Shielding Rate (dB) 50 70 80 20 90 0 Permeability (H / m) 55 70 30 0 0 80

As shown in Table 2, Comparative Example 1 shows heat dissipation characteristics, Comparative Example 2 shows shielding and heat dissipation properties, and Comparative Example 3 shows only electromagnetic wave absorption properties, whereas Examples 1 to 3 according to the embodiments of the present invention Heat radiation characteristics, shielding efficiency, and absorption ratio. In Example 1-3, the heat dissipation characteristics, the shielding efficiency, and the degree of absorption differed according to the mixing ratio of the modified graphite, the magnetic particles, and the carbon material. Specifically, Example 2 having the highest magnetic particle content showed the highest electromagnetic wave absorption characteristic, and Example 3 having the highest modified graphite content showed the best heat radiation characteristic. This means that a composite sheet can be constructed by designing the application portion according to the proper mixing ratio of the filler.

[Test Example 2]

The following experiments were conducted to compare the sheet formability and performance according to the mixing ratio of the filler (modified graphite, magnetic particles and carbon material) and the binder resin of the examples and comparative examples prepared above.

Examples 4 to 9 used in the experiments were prepared by the same conditions and methods as those of the above-mentioned preparation examples except for the composition of each component. The mixing ratios of the modified graphite, the magnetic particles and the carbon material included in the fillers of Examples 4 to 9 were all 77: 20: 3, and the contents of the filler and the binder resin are shown in Table 3 below.

Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 filling
(Modified graphite: magnetic particles: carbon material = 77: 20: 3) 10 30 50 70 80 90 Binder resin
(Polyurethane) 90 70 50 30 20 10 Total (% by weight) 100 100 100 100 100 100

In order to compare the processability, the thermal conductivity, the electromagnetic wave shielding ratio and the magnetic permeability of the above Examples 4-9, the following experiments were conducted.

Processability refers to the degree to which the sheet is processed during sheet production. The characteristic thermal conductivity was measured by the hot wire method according to ASTM E1461 method, and the electromagnetic wave shielding ratio was measured using ASTM D4935-10 method using Agilent's E5071B network analyzer. The permeability was measured using the Agilent E4991A RF Impedance Analyzer by the short coaxial measurement method of KS C 6031 method. The results are shown in Table 4 below. [Excellent (⊚), good (◯), normal (△), unsatisfactory (X)

Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Processability ◎ ◎ ◎ ◎ ○ X Thermal conductivity (W / mK) 0.5 2.0 5.2 7.0 7.5 - Electromagnetic Shielding Rate (dB) 5 20 55 70 80 - Permeability (H / m) 2 7 13 20 30 -

As shown in Table 4, when the filler (modified graphite, magnetic particles and carbon material) was contained in an amount of 50 to 80% by weight based on the total composition for the composite sheet, the processability, thermal conductivity and electromagnetic shielding ratio were excellent. Was the best when the weight ratio was 80:20. On the other hand, when the weight of the filler is more than 80 wt%, the processability is very low and the sheet is difficult to form. When the filler weight is less than 50 wt%, the sheet workability is excellent but the thermal conductivity and electromagnetic wave shielding ratio are low.

[Test Example 3]

The following experiments were conducted to compare the electrical insulation and withstand voltage strength performance of modified graphite used in embodiments of the present invention.

Example 10 and Comparative Example 4 used in the experiment were prepared by the same conditions and methods as those of the above-mentioned production example except for each component and its composition. The compositions of Example 10 and Comparative Example 4 are shown in Table 5 below.

At this time, the sheet resistance was measured using Agilent 4339B high resistance meter. The withstand voltage strength was measured using a Zentech 9027A withstand voltage tester.

Modification
Graphite Graphite Magnetic particle Carbon material Binder resin Sheet resistance
(Ω / sq) Withstanding voltage strength
(kV / mm) Example 1 77 - 20 3 20 10 ¹³ 2.5 80 Comparative Example 1 - 77 20 3 20 10 ⁵ 0.3 80

(Unit: wt%)

As shown in Table 5, when the modified graphite was used, the sheet resistance and the withstand voltage were higher by about 10 ⁸ times and about 8.5 times higher, respectively. This means that the modified graphite has a remarkable effect on the electrical insulation and also improves the withstand voltage strength of the composite sheet containing the modified graphite.

1: Modified graphite
2: Carbon material
3: magnetic particles

Claims (11)

A composition for a composite sheet comprising a modified graphite, magnetic particles, a binder resin and a carbon material,
The modified graphite has a shell structure of a graphite core and a thin film silica coating layer surrounding it,
Wherein the modified graphite, the magnetic particles and the carbon material are contained in an amount of 50 to 80% by weight based on the total weight of the composition. The method of claim 1, wherein the modified graphite uses after the surface treatment of silica precursor to the hydrophobic graphite surface gel (sol-gel) method as would a coating of silica (Silica, SiO ₂₎ with a thin film,
Wherein 10 to 40 parts by weight of a silica precursor is used per 100 parts by weight of the modified graphite. 3. The method of claim 2 wherein the magnetic particles are selected from the group consisting of iron-chromium-silicon alloys, iron-chromium alloys, iron-silicon-aluminum alloys, iron-silicon alloys, nickel- Zinc alloy, and a magnetic powder comprising at least one selected from the group consisting of zinc and a zinc alloy. The composition for a composite sheet according to claim 2, wherein the carbon material is at least one selected from the group consisting of graphite, carbon black, carbon nanotube, carbon fiber and graphene. The composition for a composite sheet according to claim 4, wherein the carbon nanotubes are at least one selected from single wall carbon nanotubes (SWNTs), double wall carbon nanotubes (DWNTs) and multiwall carbon nanotubes (MWNTs). The composition for a composite sheet according to claim 2, wherein the composition comprises 40 to 80 parts by weight of modified graphite, 50 to 80 parts by weight of magnetic particles, and 1 to 3 parts by weight of carbon material. delete delete 3. The method of claim 2, wherein the binder resin comprises at least one thermoplastic resin selected from the group consisting of an acrylate copolymer, polystyrene, polyester, polyimide, polyetherimide, polyamide, polyurethane and polyphenylene ether; And at least one thermosetting resin selected from the group consisting of a thermosetting silicone rubber compound, a one-component thermosetting silicone binder, a two-component thermosetting silicone binder, an acrylic resin, an epoxy resin and a urethane resin. A composite sheet comprising the composition for a composite sheet according to any one of claims 1 to 6 or 9. The composite sheet according to claim 10, wherein the thickness of the composite sheet is 0.1 to 1.0 mm.

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