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Title:
THERMALLY CONDUCTIVE MOLDED ARTICLE AND PRODUCTION METHOD THEREOF
Document Type and Number:
WIPO Patent Application WO/2019/135178
Kind Code:
A1
Abstract:
A method for producing a thermally conductive molded article includes conforming a film to a mold having a three-dimensional shape to form a first film having substantially the three-dimensional shape; disposing a curable composition containing a thermally conductive material and a (meth)acrylic monomer on the first film; disposing a second film on the curable composition and sandwiching the curable composition between the first and second films; and performing radical polymerization on the (meth)acrylic monomer in the curable composition to form a cured product of the curable composition between the first and second films. The oxygen transmissivity of each of the first and second films is less than 1000 mL/m2·24 h·atm, and the 50% elongation strength of the first film at a temperature of 100°C is not greater than 100 N/25 mm.

Inventors:
UCHIYA, Tomoaki (6-7-29 Kitashinagawa, Shinagawa-ku, Tokyo, 〒141-8684, JP)
TORIUMI, Naoyuki (6-7-29 Kitashinagawa, Shinagawa-ku, Tokyo, 〒141-8684, JP)
Application Number:
IB2019/050027
Publication Date:
July 11, 2019
Filing Date:
January 02, 2019
Export Citation:
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Assignee:
3M INNOVATIVE PROPERTIES COMPANY (3M Center, Post Office Box 33427Saint Paul, Minnesota, 55133-3427, US)
International Classes:
B29C39/10; B32B27/30
Attorney, Agent or Firm:
MOSHREFZADEH, Robert S., et al. (3M Center, Office of Intellectual Property CounselPost Office Box 3342, Saint Paul Minnesota, 55133-3427, US)
Download PDF:
Claims:
Claims:

1. A method for producing a thermally conductive molded article comprising:

preparing a first film having a shape corresponding to a three-dimensional shape of a mold having a three-dimensional shape by disposing a film on the mold so as to conform to the three-dimensional shape of the mold;

disposing a curable composition containing a thermally conductive material and a (meth)acrylic monomer on the first film;

disposing a second film on the curable composition and sandwiching the curable composition between the first and second films; and

performing radical polymerization on the (meth)acrylic monomer in the curable composition to form a cured product of the curable composition between the first and second films;

wherein an oxygen transmissivity of each of the first and second films is less than 1000 mL m2-24 h atm; and an 50% elongation strength of the first film at a temperature of l00°C is not greater than 100 N/25 mm.

2. The method for a thermally conductive molded article according to claim 1, wherein a thickness of the first film is from 3 to 200 pm.

3. The method for a thermally conductive molded article according to claim 1 or 2, wherein a coefficient of dynamic friction of the first film is not greater than 0.7.

4. A thermally conductive molded article comprising:

a resin molding having a first surface with a three-dimensional shape and containing a thermally conductive material and a (meth)acrylic polymer; and

a first film disposed on the first surface of the resin molding so as to conform to the three- dimensional shape;

wherein an oxygen transmissivity of each of the first and second films is less than 1000 mL· m2-24 h atm; and an 50% elongation strength of the first film at a temperature of l00°C is not greater than 100 N/25 mm.

5. The thermally conductive molded article according to claim 4, wherein a thickness of the first film is from 3 to 200 pm.

6. The thermally conductive molded article according to claim 4 or 5, wherein a coefficient of dynamic friction of the first film is not greater than 0.7.

7. The thermally conductive molded article according to any one of claims 4 to 6, further comprising a second film disposed on a surface on an opposite side as the first surface of the resin molding; wherein an oxygen transmissivity of the second film is less than 1000 mL m2-24 h atm.

Description:
THERMALLY CONDUCTIVE MOLDED ARTICLE AND PRODUCTION METHOD

THEREOF

TECHNICAL FIELD

[0001]

The present invention relates to a thermally conductive molded article and a production method thereof.

BACKGROUND ART

[0002]

To efficiently reduce heat generation in a heat-generating part mounted (for example, an automobile battery pack or the like) on an electronic device or the like, the heat dissipation of the heat generating part is enhanced by applying a thermally conductive molded article between the heat generating part and a heat-dissipating part such as a heat sink. Such a thermally conductive molded article is produced, for example, by a method including: forming a composition containing a resin matrix material and a thermally conductive filler; filling tray concavities of a heat-resistant tray having a shape corresponding to a desired shape with the composition; and thermally curing the composition filling the tray concavities (see Patent Document 1).

PRIOR ART DOCUMENTS

Patent Documents

[0003]

Patent Document 1: JP 2016-92227 A

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

[0004]

An object of the present invention is to provide a novel production method for a thermally conductive molded article exhibiting excellent thermal conductivity, and a thermally conductive molded article obtained by the production method.

MEANS FOR SOLVING THE PROBLEM

[0005]

One aspect of the present invention relates to a method for producing a thermally conductive molded article including: preparing a first film having a shape corresponding to a three-dimensional shape of a mold having a three-dimensional shape by disposing a film on the mold so as to conform to the three- dimensional shape of the mold; disposing a curable composition containing a thermally conductive material and a (meth)acrylic monomer on the first film; disposing a second film on the curable composition and sandwiching the curable composition between the first and second films; and performing radical polymerization on the (meth)acrylic monomer in the curable composition to form a cured product of the curable composition between the first and second films. In the production method described above, the oxygen transmissivity of each of the first and second films is less than 1000 mL/m 2 -24 h atm, and the 50% elongation strength of the first film at a temperature of l00°C is not greater than 100 N/25 mm.

[0006]

In addition, another aspect of the present invention relates to a thermally conductive molded article including: a resin molding having a first surface with a three-dimensional shape and containing a thermally conductive material and a (meth)acrylic polymer; and a first film disposed on the first surface of the resin molding so as to conform to the three-dimensional shape. In the thermally conductive molded article described above, the oxygen transmissivity of the first film is less than 1000 mL/m 2 -24 h atm, and the 50% elongation strength at a temperature of l00°C is not greater than 100 N/25 mm.

EFFECT OF THE INVENTION

[0007]

According to the present invention, it is possible to provide a novel method for producing a thermally conductive molded article exhibiting excellent thermal conductivity, and a thermally conductive molded article obtained by the method.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]

FIGs. 1A-1G are perspective views schematically illustrating different embodiments of a thermally conductive molded article.

FIG. 2 is a cross-sectional view illustrating an embodiment of a thermally conductive molded article.

FIGs. 3A-3H are cross-sectional process diagrams illustrating an embodiment of the production method for a thermally conductive molded article.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009]

Preferred embodiments of the present invention will be described in detail hereinafter with appropriate reference to the drawings as necessary. However, the present invention is not limited to the following embodiments.

[0010]

Thermally conductive molded article The thermally conductive molded article according to this embodiment includes: a resin molding having a first surface with a three-dimensional shape; and a first film disposed on the first surface of the resin molding so as to conform to the three-dimensional shape.

[0011]

The three-dimensional shape can be set appropriately in accordance with the shape of the adherend to which the thermally conductive molded article is applied (for example, a heat-generating part, a heat-dissipating part, or the like). For example, the shape may conform to the surface shape of the adherend, or may be a shape that allows the article to be easily installed at the applied position.

[0012]

The three-dimensional shape is not particularly limited, but at least part of the shape may be a semispherical or semicylindrical shape, for example. A thermally conductive molded article having such a three-dimensional shape facilitates alignment with the applied adherend while sliding, which yields excellent workability. In addition, pressing against the adherend after alignment can deform the three- dimensional shape and secure a contact area.

[0013]

FIGS. 1A to G illustrate specific examples of thermally conductive molded articles having portions with three-dimensional shapes. As illustrated in FIGS. 1A and B, for example, the thermally conductive molded article having a portion with a three-dimensional shape may be semispherical or semicylindrical. In addition, the size, number, location, and the like of the portions having three- dimensional shapes in the thermally conductive molded article can be set appropriately taking into consideration the shape, size, and the like of the part to which the thermally conductive molded article is to be applied. For example, the thermally conductive molded article may have a plurality of portions with three-dimensional shapes - specifically, 2 or more, 3 or more, or 5 or more - portions with three- dimensional shapes, as illustrated in FIGS. 1C to G. In addition, a portion with a semispherical three- dimensional shape and a portion with a semicylindrical three-dimensional shape may both be present in the same thermally conductive molded article.

[0014]

The resin molding contains a thermally conductive material and a (meth)acrylic polymer.

[0015]

The thermally conductive material is a component which substantially imparts thermal conductivity to the resin molding. The thermally conductive material is not particularly limited, but a known thermally conductive filler, for example, may be used.

[0016]

Examples of thermally conductive materials include metal hydrates, metal oxides, metal nitrides, and metal carbides.

[0017]

Examples of metal hydrates include aluminum hydroxide, magnesium hydroxide, barium hydroxide, calcium hydroxide, dawsonite, hydrotalcite, zinc borate, calcium aluminate, and zirconium oxide hydrates. In addition, examples of metal oxides include aluminum oxide, magnesium oxide, beryllium oxide, titanium oxide, zirconium oxide, and zinc oxide. Further, examples of metal nitrides include boron nitride, aluminum nitride, and silicon nitride, and examples of metal carbides include boron carbide, aluminum carbide, and silicon carbide.

[0018]

These thermally conductive materials are ordinarily added in a particulate state. Note that the amount (filling amount) of the thermally conductive material to be added can be increased by using relatively large particle size group having an average particle size from 10 to 100 pm and a relatively small particle size group having an average particle size of less than 10 pm in combination. Note that the average particle size refers to the particle size with an integrated value of 50% in the particle size distribution determined by laser diffraction/scattering.

[0019]

The thermally conductive material (thermally conductive filler) may be surface -treated with a surface treatment agent such as a silane coupling agent, a titanate coupling agent, or a fatty acid. Use of a thermally conductive material that has been subjected to such surface treatment can enhances the strength (for example, the tensile strength) of the thermally conductive molded article. In addition, the surface treatment described above is preferable from the perspective of the production process in that the effect of reducing the viscosity of the curable composition described below is substantial. Note that although surface treatment may be performed on the thermally conductive material in advance, the effect of surface treatment can also be achieved by adding a coupling agent or a surface treatment agent to the curable composition described below together with the thermally conductive material.

[0020]

The content of the thermally conductive material in the resin molding is preferably from 55 to 95 vol% and more preferably from 65 to 85 vol% on the basis of the total amount of the resin molding.

When the content of the thermally conductive material is within the range described above, sufficient thermal conductivity can be achieved, and it is possible to prevent difficulties in production as a result of the resin molding becoming brittle due to an excessively large amount of the thermally conductive material. This makes it possible to easily obtain a thermally conductive molded article having sufficient strength and flexibility.

[0021]

A (meth)acrylic polymer is a polymer obtained by polymerizing a monomer component including a (meth)acrylic monomer. As described below, polymerization can be performed by radical

polymerization. Here,“(meth)acrylic monomers” refer to acrylic monomers such as acrylic acids and acrylic acid esters and/or methacrylic monomers such as methacrylic acids and methacrylic acid esters. That is, a (meth)acrylic polymer may be considered a polymer that is obtained by polymerizing a monomer component including at least one type of monomer selected from the group consisting of acrylic monomers and methacrylic monomers.

[0022] The (meth)acrylic monomer is not particularly limited as long as it is a typical monomer that is used to form a (meth)acrylic polymer. In addition, one type of (meth)acrylic monomer may be used alone, or two or more types thereof may be used in combination.

[0023]

The monomer component described above preferably contains at least a monofunctional

(meth)acrylic monomer as a (meth)acrylic monomer. Note that a monofunctional (meth)acrylic monomer is a monomer having one (meth)acryloyl group.

[0024]

Examples of monofunctional (meth)acrylic monomers include (meth)acrybc acids, alkyl (meth)acrylates, aryl (meth)acrylates, (meth)acrylamides, epoxy acrylates, and urethane acrylates.

[0025]

Of these, an alkyl (meth)acrylate having an alkyl group having from 12 to 20 carbons is preferable as a monofunctional (meth)acrylic monomer. Note that here, the alkyl group may be a chain like, branched, or cyclic group.

[0026]

In addition, two or more types of alkyl (meth)acrylates having different numbers of carbons are preferably used as monofunctional (meth)acrylic monomers. In this case, the flexibility of the resulting resin molding can be appropriately adjusted in accordance with the application thereof by adjusting the content of each alkyl (meth)acrylate.

[0027]

The monomer component described above may further contain a polyfunctional (meth)acrylic monomer as a (meth)acrylic monomer. Note that a polyfunctional (meth)acrylic monomer is a monomer having two or more (meth)acryloyl groups. When the monomer component contains a polyfunctional (meth)acrylic monomer, the (meth)acrylic polymer assumes a crosslinked structure, and the strength of the resin molding is therefore enhanced.

[0028]

Examples of polyfunctional (meth)acrylic monomers include difunctional (meth)acrylic monomers such as l,6-hexanediol di(meth)acrylate, l,4-butanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, poly(butanediol) di(meth)acrylate, 1,3- butylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, triisopropylene glycol

di(meth)acrylate, polyethylene glycol di(meth)acrylate, and bisphenol A di(meth)acrylate; trifunctional (meth)acrylic monomers such as trimethylol propane tri(meth)acrylate, pentaerithritol monohydroxy tri(meth)acrylate, and trimethylol propane triethoxy tri(meth)acrylate; tetrafunctional (meth)acrylic monomers such as pentaerithritol tetra(meth)acrylate and di-trimethylol propane tetra(meth)acrylate; and pentafunctional (meth)acrylic monomers such as dipentaerithritol (monohydroxy) penta(meth)acrylate.

[0029] The content of the polyfunctional (meth)acrylic monomer in the monomer component described above is preferably from 0.01 to 5 parts by mass per 100 parts by mass of the monofunctional

(meth)acrylic monomer. When the content is within such a range, the effect of enhancing the strength of the resin molding by means of a crosslinked structure can be achieved sufficiently, and decreases in flexibility due to excessive crosslinking can be avoided, and thereby a thermally conductive molded article having high flexibility can be obtained.

[0030]

The content of the (meth)acrylic polymer in the resin molding is preferably from 0.05 to 30 mass% and more preferably from 0.5 to 15 mass% on the basis of the total amount of the resin molding.

[0031]

The resin molding may contain components other than those described above. For example, the resin molding may contain additives such as antioxidants, tackifiers, plasticizers, flame retardants, flame retardant promoters, anti-settling agents, thickeners, thixotropic agents such as ultrafme powdered silica, surfactants, antifoam agents, colorants, antistatic agents, and metal deactivators. One type of these additives may be used alone, or two or more types thereof may be used in combination.

[0032]

In the thermally conductive molded article according to this embodiment, the oxygen

transmissivity of the first film needs to be less than 1000 mL/m 2 -24 h atm. When the oxygen

transmissivity of the first film is less than 1000 mL/m 2 -24 h atm, it is possible to prevent radical polymerization from being inhibited by oxygen when producing a (meth)acrylic polymer by performing radical polymerization on a (meth)acrylic monomer in the production of the thermally conductive molded article described below. From such a perspective, the oxygen transmissivity of the first film is preferably not greater than 200 mL/m 2 -24 h atm, more preferably not greater than 150 mL/m 2 -24 h atm, and even more preferably not greater than 100 mL/m 2 -24 h atm. The lower limit of the oxygen transmissivity of the first film is not particularly limited but may be, for example, not less than 0.01 mL/m 2 -24 h atm. Note that in this specification, oxygen transmissivity refers to the oxygen transmissivity measured using an OX- TRAN Model 2/21 oxygen transmission rate tester available from MOCON. Note that when the oxygen transmissivity exceeds 200 mL/m 2 -24 h atm, measurements are performed by masking some of the test cells.

[0033]

In addition, the 50% elongation strength of the first film at a temperature of l00°C needs to be not greater than 100 N/25 mm. When the 50% elongation strength of the first film at a temperature of l00°C is not greater than 100 N/25 mm, the flexibility of the first film can be sufficiently secured, and conformity to the mold can be kept high in the production of the thermally conductive molded article described below. From such a perspective, the 50% elongation strength of the first film at a temperature of l00°C may be, for example, not greater than 50 N/25 mm or not greater than 25 N/25 mm. Note that in this specification, the 50% elongation strength at a temperature of l00°C refers to the elongation strength measured by the method according to ISO 527-3 (JIS K 7172: 1999). [0034]

The coefficient of dynamic friction of the first film is preferably not greater than 0.7, more preferably not greater than 0.5, and even more preferably not greater than 0.3 from the perspective of imparting the excellent sliding properties of the first film and thereby enhancing the workability when applying the thermally conductive molded article to an adherend. The lower limit of the coefficient of dynamic friction of the first film is not particularly limited but may be, for example, not less than 0.05. Note that in this specification, the coefficient of dynamic friction refers to a value measured as the coefficient of dynamic friction with respect to copper based on the method according to ISO 8295: 1995 (JIS K 7125: 1999). Specifically, this refers to a value measured under conditions with a load of 200 g and a tension rate of 100 mm/min when a copper foil is attached to the bottom surface of a weight using double-sided adhesive tape (ST-416 available from 3M Japan Limited).

[0035]

Examples of the first film that may be suitably used in the thermally conductive molded article according to this embodiment include films containing at least one type selected from the group consisting of polyvinyl alcohol, ethylene -vinyl alcohol copolymers (EVOH), polyvinylidene fluoride (PVDF), polyacrylonitrile, biaxially stretched polyethylene terephthalate (biaxially stretched PET), unstretched nylon, and unstretched PET. Of these, from the perspective of the deep drawability, sliding properties, releasability from the resin molding, and releasability from a second film described below, a film containing at least one type selected from the group consisting of EVOH, PVDF, and unstretched nylon is preferable, and a film containing EVOH is more preferably a multilayer film.

[0036]

The thickness of the first film can be set appropriately within a range that does not significantly diminish the effect of the present invention in accordance with the application of the thermally conductive molded article and the type of the film. The thickness of the first film may be, for example, from 3 to 200 pm, from 5 to 150 pm, or from 10 to 130 pm. When the thickness of the first film is within the range described above, the oxygen transmissivity and strength can be sufficiently ensured, and heat resistance can be reduced, and thus moldability can also be ensured.

[0037]

In addition, the first film may be formed from a single layer or from two or more layers. When the first film is formed from two or more layers, at least one of the layers may have the properties of the first film according to this embodiment, or all of the layers may have the properties of the first film according to this embodiment. When the first film is formed from two or more layers, each of the layers may be laminated via an adhesive layer or the like as necessary.

[0038]

The thermally conductive molded article according to this embodiment may further include a second film disposed on a surface on the opposite side as the first surface of the resin molding described above. FIG. 2 is a cross-sectional view illustrating an embodiment of a thermally conductive molded article. As illustrated in FIG. 2, a thermally conductive molded article 100 includes a first film 1, a second film 2, and a resin molding 3, and the resin molding 3 has a first surface 3a with a three-dimensional shape and a surface 3b on the opposite side as the first surface. The first film 1 is disposed so as to conform to the three-dimensional shape of the first surface 3a of the resin molding 3, and the second film 2 is disposed on the surface 3b on the opposite side as the first surface of the resin molding 3.

[0039]

When the thermally conductive molded article further includes the second film 2, the oxygen transmissivity of the second film 2 is less than 1000 mL/m 2 -24 h atm. When the oxygen permeability of the second film 2 is less than 1000 mL/m 2 -24 h atm, it is possible to more effectively prevent radical polymerization from being inhibited by oxygen when producing a (meth)acrylic polymer by performing radical polymerization on a (meth)acrylic monomer in the production of the thermally conductive molded article described below. From such a perspective, the oxygen permeability of the second film 2 is preferably not greater than 200 mL/m 2 -24 h atm, more preferably not greater than 150 mL/m 2 -24 h atm, and even more preferably not greater than 100 mL/m 2 -24 h atm. The lower limit of the oxygen permeability of the second film 2 is not particularly limited but may be, for example, not less than 0.01 mL/m 2 -24 h atm.

[0040]

Examples of such a second film include films containing at least one type selected from the group consisting of polyvinyl alcohol, ethylene -vinyl alcohol copolymers (EVOH), polyvinylidene fluoride (PVDF), polyacrylonitrile, biaxially stretched polyethylene terephthalate (biaxially stretched PET), biaxially stretched polyethylene naphthalate (biaxially stretched PEN), unstretched nylon, and unstretched PET. Of these, from the perspective of more sufficiently controlling releasability from the resin molding, releasability from the first film, and the oxygen transmissivity, a film containing at least one type selected from the group consisting of biaxially stretched PET, biaxially stretched PEN, and unstretched nylon is preferable. Note that, as described below, when the thermally conductive molded article is used after the second film is peeled, a release agent such as silicone may be applied to a surface on the side of the second film to which the curable composition comes into contact from the perspective of facilitating peeling.

[0041]

The thickness of the second film 2 can be set appropriately within a range that does not significantly diminish the effect of the present invention in accordance with the application of the thermally conductive molded article 100 and the type of the film. The thickness of the second film 2 may be, for example, from 5 to 200 pm, from 10 to 100 pm, or from 20 to 75 pm.

[0042]

In addition, the second film may be formed from a single layer or from two or more layers. When the second film is formed from two or more layers, at least one of the layers may have the properties of the second film according to this embodiment, or all of the layers may have the properties of the second film according to this embodiment. When the second film is formed from two or more layers, each of the layers may be laminated via an adhesive layer or the like as necessary. [0043]

In addition, the thermally conductive molded article 100 may include a reinforcing substrate (not illustrated) such as a knit fabric, a woven fabric, or a nonwoven fabric between the second film 2 and the resin molding 3 or within the resin molding 3. Provision of the reinforcing substrate reduces the stretchability in the planar direction of the thermally conductive molded article 100, and reduces the risk of causing problems such as cracking when peeling off the thermally conductive molded article from the mold, which makes it possible to enhance handleability. Of these, a nonwoven fabric is preferable in that it exhibits excellent impregnating capacity in the curable resin composition described below. Glass, vinylon, aramid, nylon, polyolefins, polyesters, acrylics, and the like can be used as the material of the reinforcing substrate, but glass is preferable in that flame retardance can also be imparted. The thickness of the reinforcing substrate may be, for example, not less than 20 pm or not less than 40 pm and may be, for example, not greater than 0.2 mm or not greater than 0.1 mm.

[0044]

<Method for producing thermally conductive molded article>

Next, the method for producing the thermally conductive molded article described above will be described. The method for producing a thermally conductive molded article according to this embodiment includes: preparing a first film having a shape corresponding to a three-dimensional shape of a mold having a three-dimensional shape by disposing a film on the mold so as to conform to the three- dimensional shape of the mold (first step); disposing a curable composition containing a thermally conductive material and a (meth)acrylic monomer on the first film (second step); disposing a second film on the curable composition and sandwiching the curable composition between the first and second films (third step); and performing radical polymerization on the (meth)acrylic monomer in the curable composition to form a cured product of the curable composition between the first and second films (fourth step).

[0045]

FIGs. 3A-3H are cross-sectional process diagrams illustrating an embodiment of the method for producing a thermally conductive molded article. Each step will be described hereinafter with reference to the drawings as necessary.

[0046]

First step

The first step is a step of preparing a first film having a shape corresponding to the three- dimensional shape of a mold by disposing a film on the mold so as to conform to the three-dimensional shape of the mold. Examples of the method for preparing a first film having a three-dimensional shape conforming to a mold include vacuum heat-compression, vacuum molding, and film insert molding.

[0047]

A specific method of vacuum heat-compression will be described illustratively hereinafter. First, a mold 20 having a prescribed three-dimensional shape such as that illustrated in FIG. 3A is prepared. As illustrated in FIG. 3B, an exemplary vacuum heat-compression device 30 includes a first vacuum chamber 31 and a second vacuum chamber 32 in the vertical direction, and a jig for setting a first film 10 to be attached to the mold 20 is provided between the upper and lower vacuum chambers. In addition, a partition plate 34 and a pedestal 33 are installed on an elevating platform 35 (not illustrated) that can be raised and lowered vertically in the first vacuum chamber 31 on the lower side, and the mold 20 is set on this pedestal 33. A commercially available product such as a two-sided vacuum molding device (available from Fu-se Vacuum Forming), for example, can be used as such a vacuum heat-compression device 30.

[0048]

As illustrated in FIG. 3B, the first film 10 is first set between the upper and lower vacuum chambers in a state in which the first vacuum chamber 31 and the second vacuum chamber 31 of the vacuum heat-compression device 30 are opened to atmospheric pressure. The mold 20 is set on the pedestal 33 in the first vacuum chamber 31.

[0049]

Next, as illustrated in FIG. 3C, the first vacuum chamber 31 and the second vacuum chamber 32 are closed and respectively depressurized to form a vacuum inside each chamber. The first film 10 is heated thereafter or simultaneously with the pulling of a vacuum. Next, as illustrated in FIG. 3D, the elevating platform 35 is raised so as to press the mold 20 up to the second vacuum chamber 32. Heating is performed with a lamp heater (not illustrated) incorporated into the roof portion of the second vacuum chamber 32, for example. The heating temperature is not particularly limited but is ordinarily not lower than 50°C or not lower than l30°C and not higher than l80°C or not higher than l60°C. The degree of vacuum in the reduced-pressure atmosphere may be, for example, not greater than 0.10 atm, not greater than 0.05 atm, or not greater than 0.01 atm, defining atmospheric pressure as 1 atm.

[0050]

The heated first film 10 is pressed against the surface of the mold 20 and stretched. After or simultaneously with stretching, as illustrated in FIG. 3E, the inside of the second vacuum chamber 32 is pressurized to an appropriate pressure (for example 1 atm to 3 atm). The first film 10 that is heated by a pressure difference adheres to the exposed surface of the mold 20 and stretches while conforming to the three-dimensional shape of the exposed surface to form a covering in a coating in which the film is peelably attached to the surface of the mold 20. After depressurization and heating are performed in the state of FIG. 3C, the inside of the second vacuum chamber 32 may also be pressurized directly and the exposed surface of the mold 20 may be covered with the first film 10.

[0051]

The upper and lower first and second vacuum chambers 31 and 32 are then once again opened to atmospheric pressure, and the mold 20 covered with the first film 10 is removed. As illustrated in FIG.

3F, the edges of the first film 10 adhering to the surface of the mold 20 can be trimmed to obtain an integrated product 40 including the first film 10 and the mold 20. Note that a method for performing the second step using the integrated product 40 will be described hereinafter, but in this embodiment, the second step may also be performed using the first film 10 molded into a three-dimensional shape after the mold 20 is peeled from the integrated product 40. [0052]

Second step

The second step is a step of disposing a curable composition containing a thermally conductive material and a (meth)acrylic monomer on the first film. An example of the second step will be described hereinafter using at least some of FIGs. 3A-3H.

[0053]

As illustrated in FIG. 3G, hollow portions 11 of the integrated product 40 are filled with a curable composition containing a thermally conductive material and a (meth)acrylic monomer, and after flattening treatment is performed using a blade or the like as necessary, the curable composition is disposed by forming filling parts 12. At the time of the filling of the curable composition, although not particularly limited, it is preferable to apply a degassed product to prevent the immixing of air.

[0054]

Third step

The third step is a step of disposing a second film on the curable composition and sandwiching the curable composition between the first and second films.

[0055]

FIG. 3G illustrates a configuration in which a second film 13 is further applied to the filling portions 12 formed in the step described above. In this mode, an integrated product 50 can be obtained by disposing the second film 13 so as to cover the first film 10 and the filling portions 12. Note that in the third step, when a reinforcing substrate such as a nonwoven fabric is disposed between the filling portions 12 and the second film 13, the reinforcing substrate may be applied to the top of the second film 13 and may be disposed so that the reinforcing substrate and the filling portions 12 are in contact with one another, for example, and when the reinforcing substrate is disposed inside the filling portions 12, the curable composition may be impregnated with the reinforcing substrate in advance.

[0056]

Fourth step

The fourth step is a step of performing radical polymerization on the (meth)acrylic monomer in the curable composition to form a cured product (resin molding) l2a of the curable composition between the first film 10 and the second film 13. As a result, an integrated product 50a including the cured product (resin molding) l2a of the curable composition is obtained.

[0057]

Radical polymerization may be performed, for example, by UV ray polymerization, electron beam polymerization, g-ray irradiation polymerization, ionization beam irradiation polymerization, or the like. UV ray polymerization can be performed, for example, by filling the hollow portions 11 described above with a curable composition containing an appropriate amount of a photopolymerization initiator to form the filling portions 12 and then irradiating the composition with UV rays. Note that when polymerization is performed using a particle energy beam, as in electron beam polymerization, a polymerization initiator is ordinarily unnecessary. [0058]

Examples of photopolymerization initiators include benzoin ethers such as benzoin ethyl ether and benzoin isopropyl ether; substituted acetophenones such as anisoin ethyl ether, anisoin isopropyl ether, Michler’ ketone (4,4’-tetramethyldiaminobenzophenone), 2,2’-dimethoxy-2-phenylacetophenone (for example, trade name: KB-l (available from Sartomer), trade name: Irgacure 651 (available from Ciba Specialty Chemicals)), and 2,2-diethoxyacetophenone; substituted a-ketols such as 2 -methyl-2 - hydroxypropiophenone; aromatic sulfonyl chlorides such as 2-naphthalene sulfonyl chloride; optically active oxime compounds such as l-phenone-l,l-propanedione-2-(ethoxycarbonyl)oxime; and acyl phosphine oxide compounds such as bis(2,4,6-trimethylbenzoyl)-2,4,4-trimethyl-pentylphosphine oxide and 2,4,6-trimethylbenzoyl-diphenyl-phosphinoxide. Note that one type of the photopolymerization initiators described above may be used alone, or two or more types thereof may be used in combination.

[0059]

The content of the photopolymerization initiator compounded with the curable composition is not particularly limited but is ordinarily from 0.05 to 2.0 parts by mass per 100 parts by mass of the aforementioned monomer component such as a (meth)acrylic monomer.

[0060]

After the integrated product 50a obtained via the fourth step is optionally cooled, it may be removed from the mold 20 to obtain a thermally conductive molded article 60 such as that illustrated in FIG. 3H. Note that the first film 10 and/or the second film 13 may be removed as necessary and may be punched out to appropriate sizes to obtain separate thermally conductive molded articles having three- dimensional shapes. When the first film 10 is used as a product without being removed, there is an advantage in that the sliding properties on the surface of the first film 10 or the strength of the product increases when pressed into a gap of a battery or the like.

[0061]

A thermally conductive molded article obtained by the production method according to this embodiment can be used in vehicles, lithium ion batteries (for example, lithium ion battery packs for automobiles), household electronic appliances, computer equipment, and the like. For example, the thermally conductive molded article may be disposed so as to fill a gap between heat-generating parts such as IC chip and heat-dissipating parts such as a heat sink or a heating pipe and used as a heat- dissipating member capable of efficiently transmitting heat generated from heat-generating parts to the heat-dissipating parts. In particular, since the size and shape of the thermally conductive molded article according to this embodiment can be designed freely, the thermally conductive molded article can be used, for example, as a substitute for a potting material for a circuit board or for a heat-generating part with a complex shape such as a coil.

EXAMPFES

[0062] The present invention will be described more specifically below using examples, but the present invention is not intended to be limited to the examples.

[0063]

The abbreviations and details of each component used in the examples will be described hereinafter.

[0064]

Preparation of curable composition>

Each component shown in Table 1 was charged into a planetary mixer at the compounding ratio (mass ratio) shown in Table 1 and degassed and mixed by kneading for 30 minutes at reduced pressure (0.01 MPa) to obtain a curable composition. Note that in the curable composition described below, the volume ratio of the thermally conductive filler was 67.4 vol%.

[0065]

[Table 1]

[0066]

Each of the abbreviations shown in Table 1 has the following meanings

[0067]

((meth)acrylic monomers).

LA: Lauryl acrylate

ISTA: Isostearyl acrylate

HDDA: l,6-Hexanediol diacrylate

[0068]

Photopolymerization initiator

IRGACURE819: available from BASF, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide

[0069]

Plasticizer

T10: available from Kao Corporation, trimellitate-based plasticizer, Trimex T-10 [0070]

Antioxidants

IRGACURE: available from BASF, pentaerithritol tetrakis(3-(3,5-di-tert-butyl-4- hydroxyphenyl)propionate)

AO503:“Adekastab AO503” available from ADEKA, ditridecylthiodipropionate

[0071]

Thermally conductive fillers

B53: available from Nippon Light Metal, aluminum hydroxide (average particle size: 50 pm) BF083: available from Nippon Light Metal, aluminum hydroxide (average particle size: 8 pm)

[0072]

Dispersant

BYK-145: available from Byk-Chemie Japan, DISPERBYK-145 wet dispersant

[0073]

Fabrication of thermally conductive molded article

Each film shown in Table 2 was prepared, and as illustrated in FIG. 3B, a two-sided vacuum molding device (available from Fu-se Vacuum Forming) was used as a vacuum heat-compression device 30 to fix the film to the top of a resin mold 20 placed inside the vacuum heat-compression device 30. The heating conditions were set so that the surface temperature of the film was l20°C, and an integrated product 40 such as that illustrated in FIG. 3F was fabricated by laminating the heated film on the surface of the mold 20 so that no air was incorporated in accordance with a procedure such as that illustrated in FIGS. 3C to 3E described above. The conformance of the film was confirmed visually. Here, the mold 20 has a shape so that a semicylindrical three-dimensional shape of 23.5 mm x 90.0 mm x 4.0 mm can be obtained, as illustrated in FIG. 3F. The respective characteristics of the films that were used are shown in Table 2.

[0074]

[Table 2]

[0075]

Note that films A to I in Table 2 are as follows.

Film A: Sperren 35E-LL (available from Ube Films, 3-layer film of PE/EVOH/LLDPE, wherein each film is laminated via an adhesive resin)

Film B: Sperren 35E-LL (available from Ube Films, 3-layer film of PE/EVOH/LLDPE, wherein each film is laminated via an adhesive resin)

Film C: Hitron BX (available from Tamapoly Co., Ltd., polyacrylonitrile film)

Film D: Diamiron C (available from Mitsubishi Chemical Corporation, vinylidene chloride- coated unstretched nylon-6 film)

Film E: Diamiron MF F001 (available from Mitsubishi Chemical Corporation, 3-layer film of PP/EVOH/PP, wherein each film is laminated via an adhesive resin)

Film F: Diamiron MF V442 (available from Mitsubishi Chemical Corporation, 4-layer film of EVOH/Nylon/PP/LLDPH, wherein some layers are laminated via an adhesive resin)

Film G: UB-OB (available from Tamapoly Co., Ltd., straight-chain low-density polyethylene film)

Film H: V-l (available from Tamapoly Co., Ltd., low-density polyethylene film)

Film I: Emblet S50 (available from Unitika Ltd., PET film)

[0076]

The hollow portions 11 of the integrated product 40 were filled with the curable composition obtained above, and a second film 13 (polyester film liner, available from Teijin Film Solutions Limited, trade name“Purex A50”, thickness: 50 pm, oxygen transmissivity: 16) was then laminated on the filled curable composition so that no air was incorporated. An integrated product 50 was fabricated by applying a rubber roller to the top of the second film 13 so that the second film 13 adhered uniformly to the mold 20. The acrylic monomer contained in the curable composition was polymerized by performing UV irradiation for 15 minutes using a black light lamp from a distance of 5.5 cm from the second film 13 side of the integrated product 50 (irradiation conditions: UV-A (wavelength: 315 to 380 nm), 7.46 mW/cm 2 ), and the thermally conductive molded article 60 was then removed from the mold 20.

[0077]

<Curing state of thermally conductive molded article>

The first film was peeled from the resulting thermally conductive molded article, and the curing state of the curable composition was confirmed visually and by touching with the fingers. When polymerization was inhibited, the uncured curable composition remained faintly on the top portion of the thermally conductive molded article and on the film surface, resulting in cloudiness, whereas when polymerization was not inhibited, the film remained transparent. In addition, when polymerization was not inhibited, the presence of tackiness on the surface of the thermally conductive molded article was confirmed by touching the surface with the fingers.

[Reference Numerals]

[0078]

1 First film

2 Second film

3 Resin molded article

3a First surface

3b Surface on opposite side as first surface

100 Thermally conductive molded article