JP5450216B2 - Thin adhesive heat conductive sheet - Google Patents

Description

  The present invention relates to a thin heat conductive sheet. More specifically, the present invention relates to a thin-walled adhesive heat conductive sheet having excellent heat conductivity and flame retardancy and excellent adhesion to an object to be disposed.

  The heat conductive sheet promotes heat dissipation from a heating element such as an electronic component. In an electric or electronic device, an electronic component serving as a heat source and a member serving as a heat sink such as a heat radiating plate or a housing panel are provided. It is used by being arranged so as to be interposed between them. Therefore, the heat conductive sheet is required to have high flame resistance as well as excellent heat conductivity. In recent years, as electronic devices have become smaller and highly integrated, there is a demand for conversion from silicone resin to non-silicone resin, where the generated siloxane gas causes contact failure of electronic devices. From the viewpoint of improving workability when the heat conductive sheet is mounted on an electronic device, a thin and sticky heat conductive sheet is desired.

  In order to meet such demands, it has been proposed to use acrylic polyurethane resin or acrylic resin instead of silicone resin or rubber (Patent Documents 1 and 2). Patent Document 1 describes that acrylic polyurethane resin has excellent thermal conductivity and well-balanced adhesiveness. Patent Document 2 discloses a multilayer heat conductive sheet containing hydrated metal compounds at a predetermined ratio and laminating acrylic heat conductive sheet layers having different crosslink densities. This multilayer heat conductive sheet does not use a halogen-containing flame retardant, red phosphorus, or silicone resin, has excellent heat conductivity and flame retardancy, and is excellent in handleability and adhesion to an object to be disposed. Have been described.

Japanese Patent Laid-Open No. 2002-030212 JP 2005-354002 A

  As described above, the installation location of the heat conductive sheet on the object to be disposed is between an electronic component that is a heat generation source and a member that is a heat sink such as a housing panel, and efficiently conducts heat from the electronic component to the member. In order to carry out, it is desired that the heat conductive sheet has adhesiveness on both sides, and the electronic component, the heat conductive sheet and the member are arranged as closely as possible. By the way, in general, the installation of the heat conduction sheet on the object is usually performed by first installing the electronic components and then attaching the heat conduction sheet, and finally attaching the housing panel to the heat conduction sheet. It is performed by mounting by fitting or the like. In this case, the heat conductive sheet adhered to the electronic component needs to be able to cope with corrections such as displacement of the position surface at the time of adhesion, while being firmly adhered along the shape of the electronic component. For that purpose, it is necessary that the heat conductive sheet is as thin as possible and is firmly adhered along the shape of the casing panel, and at the same time, it is easily peeled off from the panel at the time of opening and closing for adjustment or repair at the time of joining. Thus, a heat conductive sheet needs to have the intensity | strength which can endure the said operation with adhesiveness. Further, the heat conductive sheet needs to have high flame resistance as described above. In recent years, along with the reduction in weight and thickness of electronic components, it has been required to achieve such various physical requirements with a thin heat conductive sheet.

In the above document 1, a thermal conductive sheet made of an acrylic polyurethane resin obtained by a polymerization reaction of an acrylic oligomer having at least two hydroxyl groups in one molecule and a polyfunctional isocyanate is balanced with excellent thermal conductivity. It has been described that it has adhesiveness. However, there is no description about flame retardancy, and it does not teach how to maintain high flame retardancy without impairing thermal conductivity and adhesiveness when thinned. Moreover, the above-mentioned document 2 includes a multilayer heat conductive sheet containing a hydrated metal compound and a flame retardant, having excellent heat conductivity and flame retardancy, and having excellent handleability and adhesion to an object. Although it is disclosed, since it is a two-layer structure, productivity is difficult, and the resin used is also related to an acrylic resin mainly composed of a monofunctional (meth) acrylic monomer and crosslinked with a triazine skeleton-containing compound. .
Under such circumstances, an object of the present invention is to provide a thin-walled heat conductive sheet mainly composed of an acrylic polyurethane resin having high thermal conductivity and flame retardancy, and excellent adhesion and handling properties with an object to be disposed. It is to provide.

  The present inventor, in a thin heat conductive sheet prepared by adding a non-functional acrylic polymer to a binder resin mainly composed of an acrylic polyurethane resin, containing a heat conductive filler and a flame retardant, The above-mentioned problems have been solved by finding that the tensile strength of the entire heat conductive sheet can be maintained within a predetermined range.

That is, the present invention relates to the following (1) to (9).
(1) A binder resin mainly composed of an acrylic polyurethane resin, a non-functional acrylic polymer having a molecular weight of 1000 to 3000, an average particle size of 0.1 to 50 μm, and a relatively small particle size within the range of the average particle size A heat conductive sheet comprising a heat conductive filler and a flame retardant obtained by mixing large particles and small particles , wherein the heat conductive sheet has a thickness of 150 μm to 400 μm and has an adhesive strength. A thin-walled adhesive heat conductive sheet having a flame strength equivalent to V0 or VTM0 of UL-94, which is 0.10 N / 25 mm or more, has a tensile strength of 0.5 MPa or more.
(2) The acrylic polyurethane resin obtained by a reaction of an acrylic polymer having at least two hydroxyl groups in one molecule and a polyfunctional isocyanate having at least two isocyanate groups in one molecule ( The thin-walled adhesive heat conductive sheet described in 1).
(3) The ratio of the acrylic polyurethane resin and the non-functional acrylic polymer is 30 to 90 parts by weight of the non-functional acrylic polymer with respect to 100 parts by weight of the acrylic polymer having a hydroxyl group in the acrylic polyurethane resin (2 ) Thin-walled adhesive heat conductive sheet.
(4) The thin adhesive heat conductive sheet according to any one of (1) to (3), wherein the hardness of the heat conductive sheet is 80 or less in hardness C.
(5) The thin adhesive heat conductive sheet according to any one of (1) to (4), wherein the heat conductive filler of the heat conductive sheet is aluminum hydroxide and / or magnesium hydroxide.
(6) The thin adhesive heat conductive sheet according to any one of (1) to (5), wherein the heat conductivity of the heat conductive sheet is 0.5 W / mK or more.
(7) The thin adhesive heat conductive sheet according to any one of (1) to (6), wherein a tensile strength of the heat conductive sheet is 0.7 MPa or more.
(8) The thin-walled adhesive according to any one of (1) to (7), wherein the flame retardant is at least one non-halogen flame retardant selected from a phosphorus compound, a metal hydroxide, expanded graphite, and a nitrogen compound. Heat conductive sheet.
(9) The thin adhesive heat conductive sheet according to any one of (1) to (8), wherein a release film is provided on one surface or both surfaces of the heat conductive sheet.

  The heat conductive sheet of the present invention is a thin-walled adhesive heat conductive sheet having high heat conductivity and flame retardancy, and excellent adhesion to the object to be placed and handleability. Useful as a medium.

It is a conceptual diagram of the apparatus used for manufacture of the thin adhesive heat conductive sheet of this invention.

The present invention will be specifically described below.
The present invention is a heat conductive sheet containing a binder resin mainly composed of an acrylic polyurethane resin, a non-functional acrylic polymer, a heat conductive filler and a flame retardant, and the thickness of the heat conductive sheet is 100 μm. Thin adhesive heat conductive sheet having a thickness of ˜500 μm, an adhesive strength of 0.10 N / 25 mm or more, a tensile strength of 0.5 MPa or more, and a flame retardancy of UL-94 equivalent to V0 or VTM0 It is related to.

  In the present invention, the acrylic polyurethane resin is a polyaddition of an acrylic polymer having at least two hydroxyl groups in one molecule and a polyfunctional isocyanate having at least two isocyanate groups in one molecule in the presence of a catalyst. It has been reacted. In the acrylic polyurethane resin of the present invention, an acrylic polymer is used as the polyol component. The acrylic polymer refers to both an acrylic polymer and a methacrylic polymer.

Examples of the component of the acrylic polymer include monomers such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate having a hydroxyl group.
Moreover, monomers, such as isooctyl acrylate, 2-ethylhexyl acrylate, n-butyl acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, are mentioned.
Furthermore, monomers such as methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, vinyl acetate may be added as appropriate to adjust the physical properties. These acrylic polymers may be used alone or in combination of two or more.
These monomers can be converted into acrylic polymers by addition polymerization in the usual manner under a catalyst such as a radical. As the acrylic polymer having a hydroxyl group of the present invention, a liquid material having a relatively small molecular weight is preferably used.

  The polyfunctional isocyanate to be polyaddition-reacted with the above-mentioned acrylic polymer for forming an acrylic polyurethane resin is an isocyanate compound having two or more isocyanate groups in the molecule, such as tetramethylene-1,4-diisocyanate. Aliphatic isocyanates such as hexamethylene diisocyanate; alicyclic isocyanates such as cyclohexane-1,3-diisocyanate, cyclohexylmethane-4,4-diisocyanate; tolylene-2,4-diisocyanate, diphenylmethane-4,4-diisocyanate, etc. Aromatic diisocyanate compounds can be mentioned. These isocyanate compounds may be monomers or dimers or more.

The polyaddition reaction between the acrylic polymer and the polyfunctional isocyanate is carried out in the presence of a suitable catalyst. As the catalyst used here, for example, organometallic catalysts such as dibutyltin dilaurate and lead octenoate and amine-based catalysts such as triethylenediamine and normal methylmorpholine are used, and are not particularly limited. The polyaddition reaction can be carried out in the presence of a catalyst in the presence of a catalyst in accordance with a polymerization method generally used in the production of a polyurethane resin, using an acrylic polymer and a polyfunctional isocyanate as starting materials. it can.
In the present invention, the reaction between the acrylic polymer, which is the main component of the binder resin, and the polyfunctional isocyanate can be performed before mixing the non-functional acrylic polymer, heat conductive filler and flame retardant described later, Usually, it is performed after mixing these compounds.

  Introduction of a hydroxyl group into an acrylic polymer can be performed by using a polymerization initiator having a hydroxyl group or a polymerization chain transfer agent in addition to using the monomer having a hydroxyl group. In addition, the ratio of the isocyanate group in the polyfunctional isocyanate with respect to the hydroxyl group in the acrylic polymer is appropriately determined depending on the target acrylic polyurethane resin.

In the present invention, the acrylic polymer serving as a precursor of the acrylic polyurethane resin constituting the binder resin has a hydroxyl group content (OHV: mgKOH / g) of 20 to 80, preferably 40 to 60, and a molecular weight. (Mw) is preferably 3000 to 10000, preferably 5000 to 8000.
By adopting such a configuration, the acrylic polymer having a hydroxyl group reacts with isocyanate and is suitably used as the binder resin of the present invention, and the present invention as an adhesive heat conductive sheet in which a heat conductive agent or a flame retardant is mixed. Can achieve the purpose.

As an acrylic polymer used as a precursor of such an acrylic polyurethane resin, Alhon (ARUFON: manufactured by Toagosei Co., Ltd.) UH2000 series and Actflow (produced by Soken Chemical Co., Ltd.) UT series can be suitably used as commercial products. .
In order to obtain an acrylic polymer suitable for the present invention, it is preferable to adjust these products (grades) by appropriately blending two or more of them.

In the present invention, the non-functional acrylic polymer is an acrylic polymer having no functional group such as a hydroxyl group in the molecule, and a liquid polymer having a molecular weight of 1000 to 3000 is preferably used.
The non-functional acrylic polymer serves as a kind of plasticizer and imparts moderate flexibility to the sheet and also serves to impart tackiness.
One of the features of the present invention is the combination of an acrylic polyurethane as a binder resin and a non-functional acrylic polymer. Even when other plasticizers such as tricresyl phosphate and phthalates generally used as plasticizers are used, the plasticizer bleeds at 120 ° C., so the flexibility and the adhesiveness are poor. Cannot be achieved.

Examples of the components of the non-functional acrylic polymer include methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, n-butyl acrylate, methoxyethyl (meth) acrylate, and ethoxyethyl (meth). And monomers such as acrylate.
These acrylic polymers may be used alone or in combination of two or more. These monomers can be converted into acrylic polymers by addition polymerization in the usual manner under a catalyst such as a radical. As the non-functional acrylic polymer of the present invention, a liquid material having a relatively small molecular weight is preferably used.

As such a non-functional acrylic polymer, Alphon (ARUFON: manufactured by Toagosei Co., Ltd.) UP-1000 series can be suitably used as a commercially available product.
In order to control the hardness and tensile strength of the binder resin, these products can be used by appropriately mixing two or three or more different product numbers.

  Next, the blending ratio of the acrylic polyurethane resin and the non-functional acrylic polymer will be described. The mixing ratio of the acrylic polyurethane resin and the non-functional acrylic polymer constituting the heat conductive sheet of the present invention is appropriately changed depending on the required tensile strength and adhesive strength, but generally has a hydroxyl group in the acrylic polyurethane resin. The addition amount of the non-functional acrylic polymer is 20 to 100 parts by weight, preferably 30 to 90 parts by weight with respect to 100 parts by weight of the acrylic polymer (hereinafter also referred to as “hydroxyl group-containing acrylic polymer”). If the addition amount of the non-functional acrylic polymer is less than 20 parts by weight, the strength of the heat conductive sheet increases, but the sheet becomes hard and the heat conductivity decreases. On the other hand, when the amount exceeds 100 parts by weight, the thermal conductivity of the heat conductive sheet increases, but the strength of the sheet decreases and handling becomes difficult.

  The binder resin mainly composed of the acrylic polyurethane resin of the present invention refers to containing an acrylic polyurethane resin as a main component, for example, other compounds and resins such as a pressure-sensitive adhesive to further provide adhesiveness. Can be added as appropriate without departing from the object and effects of the present invention.

Next, examples of the thermally conductive filler used in the present invention include metals such as aluminum, copper and silver, metal oxides such as alumina and magnesia, metal hydroxides such as aluminum hydroxide and magnesium hydroxide. , One or a mixture of two or more selected from nitrides such as aluminum nitride, boron nitride and silicon nitride, and carbon nanotubes. Examples of the shape include substances such as powder, fiber, needle, flake, and sphere. Among these, metal hydroxides are preferably used, and aluminum hydroxide and magnesium hydroxide are particularly preferably used.
In the present invention, when a metal oxide or metal hydroxide is used as the thermally conductive filler, the average particle diameter is preferably 0.1 to 50 μm, and generally, in order to increase the packing density, Within the range of the average particle diameter, a relatively large particle and a small particle are mixed and used. The addition amount is 300 to 700 parts by weight, preferably 400 to 600 parts by weight, based on 100 parts by weight of the hydroxyl group-containing acrylic polymer. If the addition amount is small, the heat conduction efficiency is deteriorated, and if it is too large, the flexibility is reduced.
The adhesive thermal conductive sheet has a thermal conductivity of 0.5 W / mK or more, preferably 1.0 W / mK, from the viewpoint of heat dissipation efficiency from the object to be arranged.

In the present invention, the flame retardant is preferably a flame retardant containing substantially no halogen (sometimes referred to as a “non-halogen flame retardant”), and conventionally used metal water such as aluminum hydroxide and magnesium hydroxide. Oxides and other non-halogen flame retardants can be used.
Among the non-halogen flame retardants, the metal hydroxide is particularly preferably aluminum hydroxide or magnesium hydroxide, and these hydroxides have the effects of both the heat conductive filler and the flame retardant. It is useful in the present invention.
Examples of other non-halogen flame retardants include phosphorus compounds, expanded graphite, polyphenylene ether, and triazine skeleton-containing compounds. Of these other non-halogen flame retardants, the most preferable ones are those that exhibit a flame-retardant effect. Examples of the phosphorus compound include phosphate esters, aromatic condensed phosphate esters, and ammonium polyphosphates. Of these, ammonium polyphosphates are preferably used. In addition, these flame retardants can also be used individually or in combination of 2 or more types.
The content of the flame retardant is 10 to 60 parts by weight, preferably 20 to 40 parts by weight with respect to 100 parts by weight of the hydroxyl group-containing acrylic polymer. If the content is less than 10 parts by weight, the desired flame retardant effect cannot be obtained. If it exceeds the part, the thermal conductivity is impaired.

  In addition, the heat conductive sheet of the present invention is a concept including a heat conductive film, and is used at a thickness of 100 μm to 500 μm, preferably 200 μm to 400 μm. In such a thin-walled heat conductive sheet, the amount of the heat conductive filler and flame retardant added is limited, and in order to reduce the thickness while maintaining a balance between heat conductivity and flame retardancy, If the thickness is not 100 μm or more, the desired thermal conductivity and flame retardancy cannot be obtained.

  The adhesive heat conductive sheet of this invention concerns on the heat conductive sheet whose adhesive force is 0.10 N / 25mm or more. Preferably, the adhesive strength is 0.20 N / 25 mm or more. If the adhesive strength is less than 0.10 N / 25 mm, the adhesiveness to the housing is small and the sheet may fall off.

  Next, the heat conductive sheet of the present invention needs to have a tensile strength of 0.5 MPa or more, preferably 0.7 MPa or more, more preferably 1.0 MPa or more. If the tensile strength of the thermal conductive sheet is less than 0.5 MPa, not only may there be a risk of breakage when the release sheet described later is peeled off, but the pasted or pasted product as a product will be modified / Breaking occurs when adjusting.

  Further, the heat conductive sheet of the present invention has a hardness of preferably 80 or less, more preferably 75 or less, as measured by hardness C. If the hardness C exceeds 80, a problem occurs in the adhesion.

  In addition, the adhesive heat conductive sheet of this invention is normally used as what stuck the peeling film on the single side | surface or both surfaces. Examples of the release film include stretched polypropylene (OPP), polyethylene terephthalate (PET), paper, and the like. Among these, PET is preferably used. In addition, the thickness of a peeling sheet is 10-75 micrometers normally.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In addition, the physical property evaluation of the adhesive heat conductive sheet was based on the following method.

(1) Thermal conductivity (unit: W / mK)
Measured according to ASTM D5470.
(2) Adhesive strength (unit: N / 25mm)
The measurement was performed according to JIS Z0237.
(3) Tensile strength (unit: MPa)
The measurement was performed according to JIS K6251.
(4) Flame retardancy For sheets having a film thickness of 250 μm or more, measurement was performed based on the UL-94V combustion test. On the other hand, for a sheet having a film thickness of less than 250 μm, since the sample melted and measurement based on the UL-94V combustion test was not possible, it was evaluated by the VTM test under the following conditions to determine whether it was VTM0.
1) V test (vertical combustion test): A sample having a width of 13 mm and a length of 125 mm was subjected to flame contact for 10 seconds × 2 times.
2) VTM test (thin material check test): A sample having a width of 50 mm and a length of 200 mm was wound into a cylinder and flame-contacted for 3 seconds × 2 times.
(5) Hardness C
The measurement was performed according to JIS K7312.

Examples 1-5
(1) Preparation of coating liquid As a prepolymer component of the binder resin, a liquid hydroxyl group-containing acrylic polymer, Alphon UH-2032 (manufactured by Toa Gosei Chemical Co., Ltd., Mw: 2000, OH value: 110) and UH-2000 ( Mw: 11000, OH value: 20), and Alphon UP-1021 (manufactured by Toa Gosei Chemical Co., Ltd. (Mw: 1600, not including OH group)) was used as the non-functional acrylic polymer. Here, OH value shows the content rate (unit: mgKOH / g) of the hydroxyl group as a functional group. These acrylic polymers were further blended with an isocyanate, a reaction catalyst, a heat conductive filler and a flame retardant to prepare a coating solution. Table 1 shows the blending ratio (in terms of solids) of each component in each example. The blending ratio was set such that the total amount of the hydroxyl group-containing acrylic polymer was 100 parts by weight, and the amount of the non-functional acrylic polymer and other components was set.
As the thermally conductive filler, a mixture of aluminum hydroxide having a particle size of 40 μm and 1 μm aluminum hydroxide in a weight ratio of 8: 2 was used (for example, in Example 1, the particle size was 40 μm aluminum hydroxide: 384 parts by weight, aluminum hydroxide having a particle diameter of 1 μm: 93 parts by weight). Moreover, ammonium polyphosphate was used as a flame retardant.

  First, predetermined amounts of the binder resin, the heat conductive filler, and the flame retardant were placed in a mixing container and stirred and mixed with a planetary stirrer. Next, isocyanate (trade name; Takenate (registered trademark) D127N, manufactured by Mitsui Chemicals Polyurethane Co., Ltd.) and a reaction catalyst (dibutyltin dilaurate) are added as a resin curing agent, and 4 wt% of the total amount of the formulation as an organic solvent. Methyl ethyl ketone was added, the pressure was reduced, and the mixture was stirred until it was uniform while degassing to prepare a coating solution.

(2) Coating process Next, the coating method is demonstrated, referring FIG.
An adhesive heat conductive sheet was prepared using a coating apparatus (manufactured by Hirano Techseed Co., Ltd., comma direct coater; model number TM-MC). A PET film having a thickness of 50 μm wound around a feed roll was used as a release film serving as a support material for the heat conductive sheet of this example.
The release film (PET film) was fed from the feed roll 1 to the back roll 2 of the coating machine, and the coating liquid was placed thereon, and the gap between the PET film and the comma head 3 was adjusted to 400 μm and coated uniformly. . Then, the volatile matter is evaporated under conditions of a temperature of 60 ° C. and a passing time of 10 minutes, and the coating sheet having a resin dry film is passed through the guide rolls 6 and 7 and from the delivery roll 10 to the laminator roll 8. The film was taken up on a take-up roll 9 together with the release film (PET film) supplied to. The coated sheet is further accommodated in a dryer (not shown) together with the wound roll, and the resin film on the release film is completely cured under the conditions of a temperature of 80 ° C. for 60 minutes. An adhesive heat conductive sheet was obtained. The film thickness of this heat conductive sheet was 250 μm (350 μm including the peelable film). In addition, the adhesive heat conductive sheet cut | judged to the predetermined length required for each test was used for the test piece used for the verification test of a present Example. The blending ratios and test results are shown in Table 1 and Table 2, respectively.
All of the obtained heat conductive sheets had an adhesive strength of 0.20 N / 25 mm or more, and the thermal conductivity and the tensile strength satisfied the object of the present invention. The flame retardancy was also equivalent to V0.

Example 6
In the adjustment of the coating liquid of Example 1 (1), a mixture of aluminum hydroxide having a particle size of 40 μm and magnesium hydroxide having a particle size of 1 μm in a weight ratio of 8: 2 as a heat conductive filler. A coating solution was prepared in the same manner as in Example 1 except that it was used.
This coating solution was carried out in the same manner as (2) coating treatment in Example 1 to obtain an adhesive heat conductive sheet. The total film thickness of this heat conductive sheet was 250 μm (including the peelable film, 350 μm). The blending ratio of the coating liquid and the test results of the obtained heat conductive sheet are shown in Table 1 and Table 2, respectively.
Even when the thermally conductive filler was used in combination with aluminum hydroxide and magnesium hydroxide, the same results as in Example 1 were obtained.

Comparative Example 1
In the preparation of the coating liquid of Example 1 (1), 636 parts by weight of aluminum oxide having a particle diameter of 70 μm and 153 parts by weight of aluminum oxide having a particle diameter of 1 μm (weight ratio of 8: 2) were used as the heat conductive filler. The ratio was set to the same volume as in the case of aluminum hydroxide in Example 1.) The coating solution was prepared in the same manner as in Example 1 except that the mixture was used.
This coating solution was carried out in the same manner as (2) coating treatment in Example 1 to obtain an adhesive heat conductive sheet. The total film thickness of this heat conductive sheet was 250 μm (including the peelable film, 350 μm). The blending ratio of the coating liquid and the test results of the obtained heat conductive sheet are shown in Table 1 and Table 2, respectively.
Each of the obtained heat conductive sheets had an adhesive strength of 0.20 N / 25 mm or more, and the thermal conductivity and tensile strength satisfied the object of the present invention, but the flame retardancy was equivalent to V2. Yes, it did not reach the object of the present invention.
Comparative Example 2
In the adjustment of the coating liquid of Example 1 (1), a coating liquid was prepared in the same manner as in Example 1 except that the non-functional acrylic polymer was not used.
This coating solution was carried out in the same manner as (2) coating treatment in Example 1 to obtain an adhesive heat conductive sheet. The total film thickness of this heat conductive sheet was 250 μm (including the peelable film, 350 μm). The blending ratio of the coating liquid and the test results of the obtained heat conductive sheet are shown in Table 1 and Table 2, respectively. The obtained heat conductive sheet had high hardness and the adhesive strength did not satisfy the object of the present invention.

Comparative Example 3
In Example 1, it replaced with the non-functional acrylic polymer (UP-1021), and except having used the tricresyl phosphate (TCP) (made by the 8th Chemical Industry Co., Ltd.) which is a plasticizer, Adjustment was performed and an adhesive heat conductive sheet was produced. The total film thickness of this heat conductive sheet was 250 μm (including the peelable film, 350 μm). The blending ratio and test results are shown in Table 1 and Table 2. As a reliability test, thermal conductivity, tensile strength, elongation (%), and hardness after holding at 120 ° C. were evaluated.

  The adhesive heat conductive sheet of Comparative Example 3 using TCP instead of the non-functional acrylic polymer satisfies the requirements for the adhesive heat conductive sheet of the present invention in terms of initial adhesive strength and tensile strength (Table 2). However, the heat conductive sheet kept at 120 ° C. for 100 hours has deteriorated physical properties, particularly increases in hardness and decreases the flexibility of the sheet, and cannot be used as a product. When the surface of the heat conductive sheet of Comparative Example 3 after 100 hours at 120 ° C. was observed, TCP bleeding was clearly confirmed.

Example 7
In the adjustment of the coating liquid of Example 1 (1), the amount of the hydroxyl group-containing acrylic polymer used was the same as in Example 1 except that Alphon UH-2032 was 70 parts by weight and UH-2000 was 30 parts by weight. The coating solution was adjusted.
This coating solution was carried out in the same manner as (2) coating treatment in Example 1 to obtain an adhesive heat conductive sheet. The blending ratio of the coating liquid and the test results of the obtained heat conductive sheet are shown in Table 3 and Table 4, respectively.

Example 8
In the adjustment of the coating liquid of Example 1 (1), the amount of the hydroxyl group-containing acrylic polymer used was the same as in Example 1 except that Alphon UH-2032 was 30 parts by weight and UH-2000 was 70 parts by weight. The coating solution was adjusted.
This coating solution was carried out in the same manner as (2) coating treatment in Example 1 to obtain an adhesive heat conductive sheet. The blending ratio of the coating liquid and the test results of the obtained heat conductive sheet are shown in Table 3 and Table 4, respectively.

Example 9
Using the (1) coating liquid of Example 1, (2) coating treatment was performed to obtain heat conductive sheets having different film thicknesses. Flame retardancy evaluation of each obtained sheet was performed. Table 5 shows the sheet thickness and flame retardancy evaluation.

According to the present invention, there is provided a thin adhesive heat conductive sheet having excellent heat conductivity and flame retardancy and excellent adhesion to an object to be disposed. The sheet | seat of this invention consists of non-silicone-type resin, and can be conveniently used as a heat conductive sheet of an electronic device.

DESCRIPTION OF SYMBOLS 1 Sending roll 2 Back roll 3 Comma head 4 Drying furnace 5 Guide roll 6 Guide roll 7 Guide roll 8 Laminator roll 9 Winding roll 10 Sending roll

Claims (9)

Binder resin mainly composed of acrylic polyurethane resin, non-functional acrylic polymer having a molecular weight of 1000 to 3000, particles having an average particle size of 0.1 to 50 μm and a relatively large particle size within the range of the average particle size And a heat conductive sheet containing a small particle and a flame retardant, wherein the heat conductive sheet has a thickness of 150 μm to 400 μm and an adhesive strength of 0.10 N. / 25 mm or more, a tensile strength is 0.5 MPa or more, and the flame-retardant property in UL-94 is equivalent to V0 or VTM0.   The acrylic polyurethane resin is obtained by a reaction of an acrylic polymer having at least two hydroxyl groups in one molecule and a polyfunctional isocyanate having at least two isocyanate groups in one molecule. Thin-walled adhesive heat conductive sheet.   The ratio of the acrylic polyurethane resin and the non-functional acrylic polymer is 30 to 90 parts by weight of the non-functional acrylic polymer with respect to 100 parts by weight of the acrylic polymer having a hydroxyl group in the acrylic polyurethane resin. Thin adhesive heat conductive sheet. The thin adhesive heat conductive sheet according to any one of claims 1 to 3 , wherein the heat conductive sheet has a hardness C of 80 or less.   The thin adhesive heat conductive sheet according to any one of claims 1 to 4, wherein the heat conductive filler of the heat conductive sheet is aluminum hydroxide and / or magnesium hydroxide.   The thin adhesive heat conductive sheet according to any one of claims 1 to 5, wherein the heat conductivity of the heat conductive sheet is 0.5 W / mK or more.   The thin adhesive heat conductive sheet according to any one of claims 1 to 6, wherein the heat conductive sheet has a tensile strength of 0.7 MPa or more.   The thin adhesive heat conductive sheet according to any one of claims 1 to 7, wherein the flame retardant is at least one non-halogen flame retardant selected from phosphorus compounds, metal hydroxides, expanded graphite and nitrogen compounds.   The thin adhesive heat conductive sheet according to any one of claims 1 to 8, further comprising a release film on one side or both sides of the heat conductive sheet.

Images