JP2013209542A - Thermally conductive fluororesin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermally conductive body composed only of a polytetrafluoroethylene (PTFE)-based resin, having high thermal conductivity in at least one direction, even without filling a filler in order to impart thermal conductivity.SOLUTION: A thermally conductive molded body comprises only polytetrafluoroethylene(PTFE)-based resin, and has ≥0.5 W/m K thermal conductivity in at least one direction, measured by a laser flash method according to ASTM D257.

Description

  The present invention relates to a heat conductive molded body, a heat conductive cut film or sheet obtained from the heat conductive molded body, their use, method of use, and manufacturing method.

  A fluororesin film has advantages such as low dielectric constant, low dielectric loss tangent, and high heat resistance, and is therefore often used as a low dielectric circuit board. In particular, it is often used in electronic devices including semiconductor elements such as LEDs (light emitting diodes) and integrated circuits (ICs and LSIs). However, since fluororesin has low heat conduction characteristics, it stores the heat generated by the semiconductor element, and as a result, the electrical characteristics change due to the thermal stress, resulting in malfunctions and malfunctions of electronic devices. There was a thing.

  As a countermeasure, it is conceivable to dissipate the heat generated as described above to the outside of the apparatus. In the case of imparting thermal conductivity to the fluororesin, there is a method for improving the thermal conductivity characteristics of the substrate by adding a filler with high thermal conductivity such as alumina powder or aluminum nitride powder to the fluororesin. Are known.

  For example, Patent Document 1 substantially includes a step of preparing a plurality of sheet-like molded bodies each composed of a fluororesin containing polytetrafluoroethylene (PTFE), thermally conductive inorganic particles, and a molding aid. A method for producing an insulating heat conductive sheet is disclosed, which includes a step of superposing and rolling the sheet-like molded body and a step of removing the molding aid.

  Patent Document 2 discloses a heat conductive sheet in which a mixture containing scaly graphite and a binder resin is extruded into a sheet shape, and the obtained sheets are laminated and integrated, and then cut into a sheet in the lamination direction. A manufacturing method is disclosed.

  However, the molded products obtained by these production methods are excellent in heat conduction characteristics because a high heat conductive filler is blended in the resin, but the insulation is lowered by the filler, so that There is a risk of adverse effects during use. In addition, in order to achieve high thermal conductivity, it is necessary to blend a large amount of fillers, which deteriorates the more important characteristics as a fluororesin film such as moldability, low dielectric properties, and voltage resistance. Tended to end up.

As an embodiment using a resin other than a fluororesin, for example, a method is known in which molecules of a liquid crystal polymer compound are oriented in a specific direction to develop thermal conductivity.
For example, Patent Document 3 discloses a thermally conductive polymer molded body obtained from a liquid crystalline composition containing a liquid crystalline polymer as a main component, and applying a magnetic field or an electric field to the liquid crystalline composition in a heated and melted state. Thus, there is disclosed a thermally conductive polymer molded body formed such that the thermal conductivity (λ1) is higher than the thermal conductivity (λ2) of the molded body obtained from the liquid crystalline polymer.

  However, since the fluororesin is not a liquid crystalline polymer, the thermal conductivity cannot be improved even if the method disclosed in Patent Document 3 is applied to the fluororesin. Even if it can be applied, the method disclosed in Patent Document 3 requires the alignment of the liquid crystalline polymer with a magnetic field or an electric field, so that there are restrictions on equipment and the cost increases. Problems arise.

On the other hand, a molded body in which the orientation direction of the fluororesin is aligned in an arbitrary direction and a manufacturing method thereof are known.
For example, Patent Document 4 discloses a ring-shaped sealing material formed of uniaxially stretched porous PTFE, wherein the fibril orientation direction of the uniaxially stretched porous PTFE is 10 to 90%. A ring-shaped sealing material characterized by being in the thickness direction of the material is disclosed.

  Patent Document 5 discloses a film containing PTFE, in which the tensile strength of the matrix in at least one direction is at least 25,000 psi, and the tensile strength ratio of the matrix in two orthogonal directions is about 0.25-4. A film having an orientation index of about 50 ° or less and a density of about 2.0 g / cc or less is disclosed.

  And patent document 4 and patent document 5 are also disclosing the molded object which consists only of PTFE. However, nothing is taught about the thermal conductivity of the molded body, and since there are voids (low density) and the molded body does not contain a thermally conductive filler, its thermal conductivity Is presumed to be insufficient for use as a heat conductive member.

  Thus, the molded object which consists only of a fluororesin which has a high heat conductive characteristic is not known.

JP 2010-137562 A JP 2009-66817 A JP 2004-43629 A Japanese Patent Laid-Open No. 10-281291 JP-T-2006-524283

The objects of the present invention are broadly classified as follows.
(1) Only a polytetrafluoroethylene (hereinafter also referred to as “PTFE”) resin having a high thermal conductivity and having a high thermal conductivity in at least one direction even without being filled with a thermally conductive filler. A heat conductive molded body comprising:
(2) To provide a thermally conductive cut film or sheet made of only a PTFE resin, which has high thermal conductivity even if it is not filled with a thermal conductive filler and has high thermal conductivity in at least one direction. .
(3) To provide a suitable use of the heat conductive molded body and the heat conductive cut film or sheet.
(4) To provide a suitable method of use and production method of the heat conductive molded body and the heat conductive cut film or sheet.

  Therefore, as a result of intensive studies to solve the above problems, the present inventor is a molded body made of only a polytetrafluoroethylene (PTFE) resin, and has a thermal conductivity measured by a specific method of at least one. It was found that a heat conductive molded body having a direction of 0.5 W / m · K or more in the direction can solve the problem (1).

Specifically, it is as follows.
The thermal conductive molded article of the present invention is a molded article of a film or sheet made of only a polytetrafluoroethylene (PTFE) resin, and has a thermal conductivity measured by a laser flash method in accordance with ASTM D257 at least in one direction. In the above, it is characterized by being 0.5 W / m · K or more.

From the viewpoint of providing a heat conductive molded body having high thermal conductivity in a desired direction, the heat conductive molded body of the present invention is preferably in the following mode.
The heat conductive molded body of the present invention preferably has a density of 2.1 g / cm ³ or more.

The heat conductive molded body of the present invention is preferably a uniaxially stretched PTFE resin film or sheet laminate.
The heat conductive molded body of the present invention is obtained by laminating a PTFE resin film or sheet that is uniaxially stretched and has a porosity of 30 to 80% so that the stretching directions of the PTFE resin film or sheet coincide with each other. The laminated body is preferably obtained by hot pressing under conditions of a temperature of 350 to 430 ° C., a pressure of 5 to 50 MPa, and a time of 10 minutes to 5 hours.

Furthermore, the present applicant has found that the above problem (2) can be solved by a specific heat conductive cut film or sheet obtained from the heat conductive molded body.
That is, a thermally conductive cut film or sheet (hereinafter also simply referred to as “thermal conductive cut film or sheet”) made of only the PTFE resin of the present invention is uniaxially stretched and has a porosity of 30 to 80%. A film or sheet is laminated so that the stretching directions of the PTFE resin film or sheet coincide with each other, and the obtained laminate is subjected to a temperature of 350 to 430 ° C., a pressure of 5 to 50 MPa, and a time of 10 minutes to 5 hours. It is obtained by heat-pressing to form a column, and then cutting the film or sheet from the column in parallel or perpendicular to the stretching direction of the PTFE resin film or sheet constituting the column. It is characterized by.

Furthermore, the present applicant has found that the heat conductive molded body, the heat conductive cut film, or the sheet is suitable for a heat conductive member, and has found that the problem (3) can be solved.
Furthermore, the present applicant has found that the above problem (4) can also be solved by the following.

  That is, the method of using the heat conductive molded body of the present invention is that the heat conductive laminate is formed of a heating element and a cooling body so that the stretching direction of the PTFE resin film or sheet is in the direction connecting the heating element and the cooling body. It is characterized in that it is joined to.

  The method for using the thermally conductive cut film or sheet of the present invention is to use the heat conductive cut film or sheet as a heating element and the PTFE resin film or sheet so that the stretching direction of the PTFE resin film or sheet is a direction connecting the heating element and the cooling body. It is characterized by being joined to a cooling body.

  The method for producing a heat conductive molded body comprising only the PTFE resin of the present invention is a uniaxially stretched PTFE resin film or sheet having a porosity of 30 to 80%, and the stretching direction of the PTFE resin film or sheet is Lamination is performed so as to match, and the obtained laminate is hot-pressed under conditions of a temperature of 350 to 430 ° C., a pressure of 5 to 50 MPa, and a time of 10 minutes to 5 hours.

  The method for producing a thermally conductive cut film or sheet comprising the PTFE resin of the present invention is obtained by subjecting a PTFE resin film or sheet that is uniaxially stretched and has a porosity of 30 to 80% to the stretching direction of the PTFE resin film or sheet. And the obtained laminate is hot-pressed under the conditions of a temperature of 350 to 430 ° C., a pressure of 5 to 50 MPa, and a time of 10 minutes to 5 hours, and then formed into a column, The film or sheet is cut out from the pillar in parallel or perpendicular to the stretching direction of the stretched film or sheet constituting the film.

  The heat conductive molded article, heat conductive cut film or sheet of the present invention exhibits high heat conductivity in at least one direction even though it is composed of only a PTFE resin not filled with a heat conductive filler. . Moreover, since the heat conductive molded body, the heat conductive cut film or sheet of the present invention is not blended with various fillers including the heat conductive filler, the original properties of the PTFE resin are impaired by the filler. There is nothing. Therefore, the heat conductive molded body, the heat conductive cut film or sheet of the present invention not only has high heat conductivity, but also has excellent dielectric properties, insulating properties, voltage resistance properties, moldability, thin film properties, and flexibility. .

  In the embodiment in which the thermally conductive molded body of the present invention is a molded body in which a uniaxially stretched PTFE resin film or sheet is molded and integrated, the direction in which high thermal conductivity is expressed is the stretching direction of the film or sheet. In the same direction. Therefore, the uniaxially stretched PTFE resin film or sheet is arranged such that the stretching direction is, for example, the in-plane direction or the thickness direction, and the thermal conductivity cut film or sheet having a high thermal conductivity in the in-plane direction or the thickness direction. Can also be provided. A heat conductive molded body having a density equal to or higher than a specific value has higher heat conductivity. Moreover, the heat conductive laminated body obtained through the said specific process is excellent in balance of all the said characteristics including heat conductivity.

  The thermally conductive cut film or sheet obtained through the above specific process has both the above characteristics including excellent thermal conductivity, and has a high thermal conductivity in at least one direction (for example, a planar direction or a thickness direction). To express.

  Since the heat conductive molded body, the heat conductive cut film or the sheet have the above characteristics including excellent heat conductive characteristics, the heat conductive molded body, the heat conductive cut film or the sheet can be suitably used for a heat conductive member and provide a heat conductive member excellent in the above characteristics. be able to.

  In the method of using the heat conductive molded body and the method of using the heat conductive cut film or sheet of the present invention, heat flows from the heating element to the cooling body via the heat conductive molded body, heat conductive cut film or sheet of the present invention. The heat flow can be controlled. Therefore, the above method can efficiently dissipate the heat of the heating element, for example.

  According to the method for producing a heat conductive molded article and the method for producing a heat conductive cut film or sheet of the present invention, the heat conductive molded article, the heat conductive cut film or the sheet can be produced very efficiently.

  That is, according to the manufacturing method described above, a large-scale apparatus for applying a magnetic field, an electric field, or the like is not required, and a heat conductive molded body having excellent characteristics such as the thermal conductivity, a heat conduction cut-out, and the like by a simple method. A film or sheet can be produced. Furthermore, according to the manufacturing method described above, components such as various fillers are not necessarily required in the manufacturing process of the heat conductive molded body and the heat conductive cut film or sheet finally made of only the PTFE resin, and only the PTFE resin is used. It is also possible to produce the heat conductive molded body, heat conductive cut film or sheet as a raw material, and the cost performance is very high.

  In particular, according to the method for producing a thermally conductive cut film or sheet, a thermally conductive cut film or sheet having a high thermal conductivity in a desired direction can be obtained.

Thermally conductive molded body obtained by laminating and molding uniaxially stretched PTFE resin film or sheet so that the stretching directions coincide, thermal conductive cut film or sheet obtained from the thermally conductive molded body, and production process thereof FIG. It is a figure which shows the photograph of the SEM observation (Apparatus: S-3400N (made by Hitachi High-Technologies Corporation), magnification: 5000 times) of the uniaxially stretched PTFE resin sheet.

Hereinafter, the best mode of the present invention will be described in detail.
Various characteristic values described below are values measured at normal pressure (about 1.013 MPa) and normal temperature (about 25 ° C.) unless otherwise specified.

1. Thermally conductive molded body, thermally conductive cut film or sheet, and their production method The thermally conductive molded body of the present invention consists of a tetrafluoropolyethylene (PTFE) resin alone.

  In this specification, PTFE-based resin refers to PTFE resin and PTFE resin mixed with an appropriate amount of modified PTFE resin. The modified PTFE resin means a resin of a copolymer of PTFE and a comonomer capable of copolymerization with PTFE. Examples of the comonomer that can be copolymerized with PTFE include hexafluoropropylene, vinylidene fluoride, perfluorovinyl ether, chlorotrifluoroethylene, and the like, and it is preferable to use 1% by weight or less based on PTFE.

  Since the heat conductive molded body of the present invention is made only of PTFE resin and does not contain a filler, the original properties of the PTFE resin are not impaired by the filler. Therefore, for example, the heat conductive filler is filled in the fluororesin molded body like the conventional heat conductive fluororesin molded body, so that the dielectric properties, insulation characteristics, high voltage resistance characteristics, molding of the fluororesin molded body As a result, there will be no adverse effects such as deterioration in properties, thin film properties, flexibility and the like as compared with PTFE resin. Moreover, the heat conductive molded object of this invention is excellent in the heat conductivity of at least one direction so that it may explain in full detail behind.

The thermally conductive cut film or sheet of the present invention is obtained by cutting the heat conductive molded body.
Hereinafter, the heat conductive molded body and the heat conductive cut film or sheet of the present invention will be described together with their production methods.

[Uniaxially stretched PTFE resin film or sheet (PTFE resin uniaxially stretched film or sheet)]
The PTFE resin used for the heat conductive molded body of the present invention may be produced, for example, according to a conventional method, or may be a commercially available product.

As the PTFE resin, fine powder of unfired or semi-fired PTFE can be suitably used.
When a uniaxially stretched PTFE resin film or sheet (hereinafter also referred to as “PTFE resin uniaxially stretched film or sheet”) is used for the heat conductive molded body, PTFE resin is obtained by, for example, paste extrusion. For example, a uniaxially stretched resin film or sheet can be used.

  The PTFE resin film or sheet can be molded, for example, by mixing the above PTFE resin with a lubricating aid such as solvent naphtha, white oil, liquid paraffin, etc., if necessary, followed by paste extrusion. Preferably, the method further includes a step of rolling the obtained paste and a step of removing the lubricating aid by drying or the like.

The stretching is usually performed under the conditions of a stretching temperature of 200 to 420 ° C., preferably 320 to 380 ° C., and a stretching speed of 10 to 600% / second, preferably 50 to 400% / second.
The draw ratio is usually 1.1 to 20 times, preferably 1.5 to 10 times.

By performing uniaxial stretching of the PTFE resin film or sheet under the above conditions, the porosity is usually 30 to 80%, preferably the porosity is in the above range, and the density measured by Archimedes method is 0. A PTFE-based resin uniaxially stretched film or sheet of 4 to 1.5 g / cm ³ is obtained.

  When using a commercial product as the above-mentioned PTFE-based resin uniaxially stretched film or sheet, for example, “sa-PTFE series” manufactured by Nippon Valqua Industries, Ltd., “Poreflon (registered trademark) membrane” manufactured by Sumitomo Electric Industries, Ltd. Series "," expanded PTFE series "manufactured by WL Gore and Associates, Inc. can be used.

  As shown in FIG. 1, the PTFE resin film or sheet has a fibrous structure in a part of the PTFE resin film or sheet as shown in FIG. In this specification, the fibrous structure is referred to as “fibril”, and the phenomenon in which fibrils are generated in a PTFE resin film or sheet is referred to as fibrillation. It is inferred that this fibrillation aligns molecular chains or / and crystals in a specific direction in the fibril, and as a result, improves the expression and heat conduction characteristics of the heat conduction molded body in a specific direction. Is done. Such specific heat conduction characteristics are presumed to be more pronounced as the degree of crystallinity is higher and the degree of molecular chain or / and crystal orientation is higher. The PTFE resin film or sheet stretched under the above stretching conditions has a higher degree of molecular chain or / and crystal orientation, and the film strength or sheet strength is also maintained.

  When heat-treating a PTFE-based resin film or sheet in which fibrils have occurred, it is possible to maintain high thermal conductivity by adjusting the thermal history so that the crystal structure formed by the fibrils does not change significantly. It is preferable from the viewpoint.

  When the PTFE resin is uniaxially stretched under the above stretching conditions, the PTFE resin uniaxially stretched film or sheet obtained here is laminated and molded and integrated as described below to produce a thermally conductive molded body. Furthermore, it becomes easy to control the thermal conductivity, density, porosity and the like of the molded body to the ranges described below.

The thickness of the PTFE-based resin uniaxially stretched film or sheet is usually from 0.01 to 5 mm, preferably from 0.05 to 1 mm, from the viewpoints of film strength, ease of the stretching process, and the like.
As described above, a PTFE-based resin uniaxially stretched film or sheet suitable for use in the heat conductive molded article of the present invention can be produced.

  In addition, since it is only necessary to finally obtain a heat conductive molded body made only of PTFE-based resin, any additive that can be finally removed can be added at the time of manufacturing the PTFE-based resin or during uniaxial stretching of the PTFE-based resin. May be. The above additives may be removed all at once in the final stage of manufacturing the heat conductive molded body, or partly removed several times during the manufacturing stage of the heat conductive molded body. It may be removed completely.

[Heat conductive molded body]
In the PTFE resin uniaxially stretched film or sheet obtained as described above, fibrils are formed by uniaxial stretching, and the PTFE resin uniaxially stretched film or sheet has a thermal conductivity of 0.01 to 0.00. It is about 1 W / m · K, which is insufficient for use in, for example, radiating the heat inside the electronic device to the outside of the device. This is because the PTFE resin is partially fibrillated by uniaxial stretching to increase the porosity of the obtained PTFE resin uniaxially stretched film or sheet (for example, 30 to 80%) and to reduce the density (for example, 0). .4 to 1.5 g / cm ³ ).

  Therefore, in the present invention, a predetermined number of PTFE-based resin uniaxially stretched films or sheets are laminated, and for example, by adjusting the pressing conditions when molding and integrating, the density and porosity are controlled within the ranges described below. A heat conductive molded body having excellent heat conductivity in a specific direction is manufactured.

Hereinafter, the aspect which integrates the said shaping | molding by pressure molding is explained in full detail as a specific example.
In such an embodiment, the heat conductive molded body of the present invention is obtained by laminating a predetermined number of the above-mentioned PTFE resin uniaxially stretched films or sheets and molding and integrating them by pressure molding (preferably hot pressing).

  As described above, when pressure molding is performed, the voids in the molded body can be reduced to improve the density, and the thermal conductivity of the molded body can be improved. That is, in order to further improve the thermal conductivity of the obtained molded body, it is desirable to reduce the porosity of the molded body and increase the density so as to fall within the range described later. Further, the pressure molding is desirably performed at a temperature (for example, 350 to 430 ° C.) within the PTFE firing temperature range. By performing pressure molding at such a temperature, the porosity can be efficiently reduced and the density can be increased.

Hereinafter, the aspect which laminates | stacks the said PTFE type resin uniaxially stretched film or sheet | seat, and then performs pressure molding is further explained in full detail, referring FIG.
First, a predetermined number of the PTFE resin uniaxially stretched films or sheets are prepared and laminated. At this time, the PTFE-based resin uniaxially stretched film or sheet may be cut into a predetermined size and used as necessary.

  The number of PTFE-based resin uniaxially stretched films or sheets to be laminated depends on the thickness and physical properties of the target heat conductive molded body, the shape and physical properties of the film or sheet cut out from the heat conductive molded body, but usually 10 or more, preferably Is about 20 to 5000 sheets (the total thickness here is usually 10 mm or more, preferably about 50 to 1000 mm). Further, from the viewpoint of increasing the area of the cut film or sheet obtained from the heat conductive molded body and increasing the strength of the cut film or sheet, a total thickness of about 100 to 1000 mm is desirable.

  The method of stacking the PTFE resin uniaxially stretched films or sheets in the uniaxially stretched direction when laminating the PTFE resin uniaxially stretched films or sheets is not particularly limited as long as the object of the present invention is not impaired.

Here, by laminating each PTFE-based resin uniaxially stretched film or sheet as described below, a heat conductive molded body having high thermal conductivity in the stretching direction can be produced.
For example, as shown in FIG. 1, when a PTFE-based resin uniaxially stretched film or sheet is laminated so that the stretching direction coincides, a heat conductive molded body having high thermal conductivity in the stretching direction is laminated by other lamination methods. Compared to the above, it can be efficiently produced with a smaller number of PTFE-based resin uniaxially stretched films or sheets (unidirectional heat-conductive molded article).

  For example, when PTFE-based resin uniaxially stretched films or sheets are laminated alternately or in any order so that the uniaxially stretched directions intersect, a heat conductive molded body having high thermal conductivity in two directions can be produced. (Bidirectional heat conductive molded body).

  It is also possible to produce a heat conductive molded body having a high thermal conductivity in three or more directions so that the stretching direction of the PTFE resin uniaxially stretched film or sheet is shifted by a certain angle.

  When using the same PTFE-based resin uniaxially stretched film or sheet, the unidirectional heat conductive molded body is bi-directional from the viewpoint of providing a heat conductive laminate having a direction in which higher heat conductivity is expressed with a smaller number of sheets. It is more preferable than a heat conductive molded body.

  In the laminated structure as described above, a PTFE-based resin uniaxially stretched film or sheet is laminated on a compression mold for supporting a PTFE-based resin uniaxially stretched film or sheet that is subjected to pressure during lamination integration. At this time, when the PTFE-based resin uniaxially stretched film or sheet is a continuous film or sheet, it may be cut to an appropriate size before lamination. The number of laminated PTFE resin uniaxially stretched films or sheets is as described above. Subsequently, the PTFE resin uniaxially stretched film or sheet is molded and integrated (here, pressure bonding) by applying a pressure of 5 to 50 MPa at 350 to 430 ° C., preferably 350 to 400 ° C., and treating for 10 minutes to 5 hours. It can be performed. The pressure is usually applied perpendicular to the in-plane direction of the laminated PTFE-based resin uniaxially stretched film or sheet. In general, the molding and integration are performed in a shorter time as the temperature is higher. When the PTFE resin uniaxially stretched film or sheet is pressure-bonded under such conditions, the PTFE resin uniaxially stretched film or sheet does not suffer from the disadvantage that the porosity cannot be sufficiently reduced or the density cannot be sufficiently increased. Can be crimped.

Since the heat conductive molded body of the present invention is composed only of PTFE-based resin, it is excellent in dielectric characteristics, insulation characteristics, and withstand voltage characteristics.
From the viewpoint of achieving high thermal conductivity, in a unidirectional thermal conductive molded body, the PTFE resin uniaxially stretched film or sheet is laminated so that the deviation in the stretching direction is within a range of about 0 to 10 ° as a whole. The number of PTFE resin uniaxially stretched films or sheets in the PTFE resin uniaxially stretched film or sheet assembly is 95 to 100% when the total number of PTFE resin uniaxially stretched films or sheets is 100%. Is preferable, and 100% is particularly preferable.

  In the case of a thermally conductive molded body having high thermal conductivity in a plurality of directions, the axial displacement of the PTFE resin uniaxially stretched film or sheet in the thermally conductive molded body is independently 0 to 0 in each direction. The number of PTFE resin uniaxially stretched films or sheets in a group of PTFE resin uniaxially stretched films or sheets laminated so as to be within a range of about 10 ° is 100% of the total number of PTFE resin uniaxially stretched films or sheets. Is preferably 95 to 100%, particularly preferably 100%.

Here, in each set, the stretching directions of the PTFE-based resin uniaxially stretched film or sheet are treated as being the same.
The shape of the heat conductive molded body of the present invention is not particularly limited as long as the object of the present invention is not impaired. For example, a film, a sheet, a polyhedron (for example, a tetrahedron, a pentahedron, a hexahedron, etc.), a column ( For example, shapes such as a triangular prism, a quadrangular prism (cube, rectangular parallelepiped, etc.), a pentagonal prism, a polygonal column such as a hexagonal column, a cylinder, etc., a ring, a cylinder, and the like can be given.

  In order to obtain the heat conductive molded body having the above shape, for example, a film or sheet having a shape capable of forming a desired shape is laminated (for example, a circular film or sheet is laminated if it is a cylinder), or a desired shape is formed. Using a crimping device having a mold capable of producing a heat conductive molded body, or by cutting out a heat conductive molded body having an arbitrary shape with a microtome, a planer, etc., or cutting with a cutter blade, etc., the desired heat conductive molded body is obtained. By processing into a shape or punching with a mold having a desired shape, a heat conductive molded body having the above-described shape can be produced.

  For example, when the heat conduction molded body is used as a cylinder, if the PTFE resin uniaxially stretched film or sheet fibril is laminated so that the major axis direction of the fibril is perpendicular to the cylinder axis, In addition, a molded article having excellent thermal conductivity in the perpendicular direction can be produced.

  Moreover, you may shape | mold the PTFE resin sheet molded object of arbitrary shapes by punching in the shape of a cylinder so that the long-axis direction of the fibril of a PTFE-type resin uniaxially stretched film or sheet may face a desired direction.

  Thus, according to the present invention, it is possible to provide a heat conductive molded body having high heat conductivity in at least one direction regardless of the shape. For example, when applied to an electronic device or the like, In many cases, it is easy to utilize the direction of high thermal conductivity of the molded body regardless of the shape.

  Among these shapes, the heat conduction cut film or sheet described in detail below is easy to apply to electronic devices, particularly electronic devices including semiconductor elements such as LEDs (light emitting diodes) and integrated circuits (IC and LSI), It is preferable from the viewpoint of easy utilization of the direction of thermal conductivity.

[Heat conduction cut film or sheet]
In order to obtain a cut film or sheet from the heat conductive molded article of the present invention, for example, the molded article is obtained by cutting into a film or sheet using a cutting means such as a microtome or a planer.

Furthermore, a cut film or sheet having a high thermal conductivity in at least one direction can be produced by the following method.
For example, a PTFE resin uniaxially stretched film or sheet is laminated and molded so that the stretching direction is aligned, and a heat conductive molded body (unidirectional heat conductive molded body) of a pillar is formed. For example, by using a cutting means (cutting means) such as a microtome or planer, a blade is applied in parallel or perpendicular to the stretching direction, and the film or sheet is cut out from the column, so that the stretching direction is a surface. A heat conduction cut film or sheet arranged in the direction, or a heat conduction cut film or sheet in which the stretching direction is arranged in the thickness direction can be obtained (FIG. 1). The heat conduction cut film or sheet thus obtained has extremely high heat conduction characteristics in the surface direction or thickness direction because molecular chains or / and crystals are oriented by stretching in the surface direction or thickness direction. It is considered excellent.

  The heat conduction cut film or sheet thus obtained has molecular chains or / and crystal directions aligned in one direction, and has a direction with higher heat conductivity than an embodiment using a bi-directional heat conductive molded body described later. It is more preferable than the heat conduction cut-out film or sheet obtained by using the bi-directional heat conductive molded body described later in that it is considered to have.

  In addition, the two-way heat conductive molded body may be parallel to or parallel to both the two stretching directions by a cutting means (cutting means) such as a microtome or a planer so that the heat conductive molded body has a desired thickness. Heat in which the two stretching directions are aligned in the plane direction by cutting the film or sheet from the pillar by applying a blade so that it is parallel to one of the stretching directions and perpendicular to either It is possible to obtain a conductive cut film or sheet, or a heat conductive cut film or sheet in which either one of the two stretching directions is oriented parallel to the surface direction, and either the MD direction or the TD direction is oriented vertically. The heat conduction cut film or sheet thus obtained has the fibrils produced by the above stretching in the plane direction or the thickness direction, so the heat conduction cut film or sheet in which the two stretching directions are oriented in the plane direction. Is excellent in thermal conductivity in the stretching direction in two directions in the plane direction, one of the two stretching directions is oriented parallel to the plane direction, and one of the two stretching directions is oriented vertically. A film or sheet is excellent in thermal conductivity in the surface direction and thickness direction.

  The heat conduction cut film or sheet obtained in this way is higher than the heat conduction cut film or sheet obtained using the unidirectional heat conductive molded body in that it has a high heat conductivity in two directions as well as in one direction. preferable.

  As described above, a heat conductive molded body, a heat conductive cut film, or a sheet having a high thermal conductivity in at least one direction can be manufactured by a layer configuration and a stacking direction at the time of stacking, a molding method to a desired shape, and the like. it can.

  As long as the object of the present invention is not impaired, for example, another heat conductive film or sheet excellent in heat conductivity may be laminated on the heat conductive molded body, the heat conductive cut film, or the sheet. From the viewpoint of providing a heat conductive molded article having excellent dielectric properties, insulating characteristics, and voltage resistance characteristics, it is preferable to use the above heat conductive laminated molded article, heat conductive cut film or sheet alone.

  In addition, the heat conductive molded body and the heat conductive cut film or sheet of the present invention are superior in terms of insulation characteristics and voltage resistance characteristics compared to a liquid crystalline polymer compound sheet produced by applying an electric field or a magnetic field. is there.

2. [Physical properties of thermally conductive molded body, thermally conductive cut film or sheet]
<Thermal conductivity>
The heat conductive molded body of the present invention and the heat conductive cut film or sheet obtained therefrom have a thermal conductivity measured by a laser flash method in accordance with ASTM D257 of at least one direction, usually 0.5 W / m · K. As mentioned above, Preferably it is 0.5-2.0 W / m * K.

  In addition, the unidirectional heat conductive molded body, which is an embodiment of the heat conductive molded body of the present invention, and the heat conductive cut film or sheet obtained from the heat conductive molded body are heat conduction in the stretching direction measured by a laser flash method in accordance with ASTM D257. The rate is usually 0.5 W / m · K or more, preferably 0.5 to 2.0 W / m · K, and the thermal conductivity in the direction perpendicular to the stretching direction is usually 0.05 to 0.3 W / K. m · K.

  The bi-directional heat conductive molded body, which is an embodiment of the heat conductive molded body of the present invention, and the heat conductive cut film or sheet obtained therefrom have a unidirectional heat conductivity measured by a laser flash method in accordance with ASTM D257. The thermal conductivity in the other direction is usually 0.3 to 1.5 W / m · K.

In solving the problem of the present invention, the heat conductive molded body may have a heat conductivity of at least one direction of usually 0.5 to 1.5 W / m · K.
When the thermal conductivity is in such a range, it is preferable from the viewpoint of excellent heat dissipation characteristics of the thermal conductive molded body.

  The thermal conductivity can be achieved, for example, by stretching a PTFE resin film or sheet, laminating the obtained PTFE resin uniaxially stretched film or sheet, and press molding as described above.

  Hereinafter, it demonstrates in detail, referring the photograph (FIG. 2) of the SEM observation (Apparatus: S-3400N (made by Hitachi High-Technologies Corporation), magnification: 5000 times) of a PTFE-based resin uniaxially stretched film or sheet. .

  As shown in FIG. 2, fibrils are generated along the stretching direction of the PTFE-based resin uniaxially stretched film or sheet. The PTFE-based resin uniaxially stretched film or sheet exhibits high thermal conductivity in the stretching direction, in other words, in the long axis direction of the fibril. This is presumably because fibrils are formed in the PTFE resin by stretching, and the molecular chain direction is oriented in the stretching direction at this time to produce crystal orientation, and heat is easily conducted along this crystal orientation. .

  And, since the stretched film or sheet having such fibrils is laminated and molded and integrated as described above, a molded body having a density and porosity that exhibits excellent thermal conductivity is obtained. It is presumed that a molded article having a high thermal conductivity can be obtained.

In any case, the thermal conductivity of the heat conductive molded body, the heat conductive film or the sheet can be controlled by the stretching conditions, lamination, and hot press conditions.
From the viewpoint of thermal conductivity, a unidirectional thermal conductive molded body having a high degree of fibrils or molecular chains or / and crystal orientations oriented in one direction is obtained by diffusing fibrils or molecular chains or / and crystal orientations in two directions. This is preferable from the viewpoint of having a direction having a higher thermal conductivity than the directional heat conductive molded body.

<Density and porosity>
The density measured by the Archimedes method is preferably 2.1 g / cm ³ or more for the heat conductive molded article and the heat conductive cut film or sheet of the present invention. The upper limit that the density can take is usually 2.2 g / cm ³ . When the density is in such a range, it is preferable from the viewpoint of providing a heat conductive molded article having excellent dielectric characteristics, insulating characteristics, and high voltage resistance characteristics.

  The porosity of the heat conductive molded body, the heat conductive cut film or the sheet of the present invention is preferably 0 to 5%, more preferably 0 to 2%. Here, “porosity (%) = (true density of PTFE resin−density of thermally conductive cut sheet) ÷ true density of PTFE resin”. When the porosity is in such a range, it is preferable from the viewpoint of providing a heat conductive molded article having excellent heat conduction characteristics, insulation characteristics, and high withstand voltage characteristics.

  The density and porosity of the heat conductive molded body, heat conductive cut film or sheet of the present invention are factors that affect the heat conductivity, and when they are outside the above range, particularly when the density is too low or When the porosity is excessive, the thermal conductivity tends to decrease and the range is not satisfied.

In addition, the relationship between the density and the porosity in the PTFE-based resin uniaxially stretched film or sheet, the heat conductive molded article of the present invention, the heat conductive cut film or sheet can be expressed as follows.
Density of PTFE-based resin uniaxially stretched film or sheet, thermally conductive molded body, thermally conductive cut-out film or sheet (molded body density)
= Density of PTFE resin (material density) x (1-porosity)
Since the density and porosity of the heat conductive molded article, heat conductive cut film or sheet of the present invention are related to the fibrils produced by the above stretching, the heat conductive molded article, and the heat conductive molded article, as well as the heat conductivity. The density and porosity of the thermally conductive cut film or sheet obtained from the body depend on, for example, the stretching conditions of the PTFE resin film or sheet, the pressure molding conditions of a laminate in which the PTFE resin uniaxially stretched film or sheet is laminated, etc. It can control within the said range.

<Volume specific resistivity>
The heat conductive molded body, heat conductive cut film or sheet of the present invention has a volume resistivity determined by volume resistivity measured according to ASTM D257, preferably 10 ¹⁴ Ω · cm or more. When the volume resistivity is in such a range, it is preferable from the viewpoint of providing a heat conductive molded body having excellent insulation characteristics and voltage resistance characteristics. The volume resistivity may exceed the measurement limit (about 10 ¹⁸ Ω · cm) of existing measuring devices.

  When trying to obtain a PTFE resin molded body having high heat conductivity by blending a PTFE resin with a heat conductive filler as in the past, avoid a decrease in volume resistivity due to the effect of the filler. However, in the heat conduction molded article, heat conduction cut film or sheet of the present invention, such a filler is not added, and since there are very few voids inside, the volume resistivity inherent in the PTFE resin is not obtained. It is possible to maintain high thermal conductivity.

3. Use of heat conductive molded body, heat conductive cut film or sheet The heat conductive molded body, heat conductive cut film or sheet of the present invention is interposed between a heat generator such as an electronic component and a heat sink such as a heat sink or heat pipe. Therefore, it is suitable for effective heat conduction between the two. Further, when the temperature of the heating element is higher than the ambient temperature, the cooling body may be air. Since the heat conductive molded body of the present invention has high thermal conductivity, low dielectric constant, and excellent voltage resistance, the heat conductive molded body of the present invention can be used for mobile phones, circuit boards, digital home appliances, and automobile electrical components. Since there is no need to intervene an insulating film separately in the application used for such an electrically charged portion, it can be used directly for such a portion.

  The heat conductive molded body, heat conductive cut film or sheet of the present invention is not only excellent in thin film properties and flexibility, but also has a desired shape that generates heat conduction in a desired direction. As a heat-dissipating sheet for efficiently transferring heat to the part, it can also be suitably used for lighting fixtures and optical modules.

  Since the heat conductive molded body, the heat conductive cut film or sheet of the present invention is a molded body made of only a PTFE-based resin, not only in the field of electrical equipment, but also in the field of precision machinery, It can be suitably used in the fields of medical equipment / instruments / materials, food equipment / packaging materials.

  Moreover, the heat conductive molded object, heat conductive cut film, or sheet | seat of this invention can also be used for the use of an electret member using the high electrical charging retention. The fact that the thermally conductive molded body, thermally conductive cut film or sheet of the present invention is suitable for use as an electret member is characterized by PTFE crystal orientation, that is, a characteristic charge retention performance (high charge) by controlling the distribution of crystal parts and amorphous parts. It is presumed that the retention rate, charge distribution control, etc.) are also shown.

4). Method of using thermally conductive molded body, thermally conductive cut film or sheet The thermally conductive molded body, thermally conductive cut film or sheet of the present invention is a molecular chain or / and derived from the fibril structure of a PTFE resin uniaxially stretched film or sheet. Crystal orientation occurs in the major axis direction (stretching direction) of the fibrils, and heat is conducted specifically in this orientation direction. Therefore, the heat conductive molded body, or the heat conductive cut film or sheet is used as the heating element and the cooling body so that the stretching direction of the PTFE resin uniaxially stretched film or sheet is the direction connecting the heating element and the cooling body. If used by joining, it is possible to dissipate heat generated in the heating element in a desired direction.

  When the temperature of the heating element is higher than the ambient temperature, the cooling element may be air (that is, the cooling element may be allowed to cool in an air atmosphere). Is preferable because of its high heat dissipation efficiency. When heat is dissipated in the air atmosphere, it is preferable to incorporate it with a fan or the like because the amount of air movement is forcibly increased and the heat dissipating efficiency is increased.

Examples of the heating element include an electronic device and a lighting device including a semiconductor element, and among these, an electronic device including a semiconductor element is preferable from the viewpoint of insulation.
Examples of the cooling body include a heat sink and various cooling devices.

  For example, a container containing a cooling medium such as cooling water, a hydrocarbon refrigerant such as ethylene glycol, or a cooling gas may be installed in the cooling body, or the cooling medium may be circulated through a pipe or the like. Alternatively, a cooling device or the like may be incorporated.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail, referring an Example, this invention is not limited to these Examples at all. Unless otherwise specified, the pressure condition is normal pressure (about 1.013 MPa).

[Example 1]
<Manufacture of heat conductive molded body and heat conductive cut sheet using PTFE uniaxially stretched sheet>
PTFE resin uniaxially stretched film (Sa-PTFE ^™ (density 0.78 g / cm ³ , porosity 64%, thickness 0.20 mm, uniaxially stretched product) manufactured by Nippon Valqua Industries Co., Ltd.) with a size of 50 × 50 mm, 400 sheets are punched out, all 400 sheets are laminated so that the stretching direction is aligned, put into a 50 × 50 mm size mold, and hot-pressed at 410 ° C. and 15 MPa for 1 hour to form a 20 mm-thick rectangular heat conductive molded body. Molded.

  The obtained heat conductive molded body was cut in a direction perpendicular to the stretching direction to obtain a heat conductive cut sheet composed only of a PTFE resin having a thickness of 50 μm whose heat conduction direction was the thickness direction of the sheet.

<Evaluation of various physical properties of heat conduction sheet>
(1) Thermal conductivity The thermal conductivity of the thermally conductive cut sheet was measured by a laser flash method in accordance with ASTM D257.

(2) Volume resistivity The volume resistivity of the heat conduction cut sheet was determined by measurement according to ASTM D257.
(3) Density, Density porosity thermal conduction cut sheet was determined by a known Archimedes method.

The porosity of the thermally conductive cut sheet was calculated based on the following formula (1).
Porosity (%) =
(True density of PTFE resin−density of thermally conductive cut sheet) ÷ true density of PTFE resin (1)
(The units of “true density of PTFE resin” and “density of thermally conductive cut sheet” in the formula are both “g / cm ³ ”. Also, “true density of PTFE resin” is 2.17 g / cm ^3. .)
The results are shown in Table 1.

[Comparative Example 1]
A PTFE resin (polyflon PTFE M12 manufactured by Daikin Industries, Ltd.) was compression molded at a pressure of 20 MPa, and then molded in an electric furnace at 380 ° C. for 3 hours to obtain a molded body. A non-stretched sheet having a thickness of 50 μm was prepared from the obtained molded body by applying a planer, and various physical properties were measured in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
In Example 1, a molded body was produced in the same manner as in Example 1 except that the hot press conditions were 300 ° C. and 5 MPa for 1 hour. The obtained molded product had peeling between the surfaces, and the laminate was not sufficiently integrated. Therefore, measurement of various characteristics of the molded body was not performed. Further, a heat conductive molded body and a heat conductive film or sheet could not be obtained from the molded body.

  The thermally conductive molded body, thermally conductive cut film or sheet according to the present invention is a film or sheet for improving adhesion as well as improving heat conduction efficiency by being sandwiched between a heat generating member and a heat radiating member. Can be suitably used.

DESCRIPTION OF SYMBOLS 1 Uniaxial film or sheet | seat of PTFE-type resin 2 Stretching direction 3 Pressure molding machine provided with a compression die 4 Thermal conductive molding 5 Plane 6 Thermal conductive cut film or sheet

Claims (10)

It is a molded body consisting only of polytetrafluoroethylene-based resin,
A thermal conductive molded article having a thermal conductivity of 0.5 W / m · K or more in at least one direction measured by a laser flash method in accordance with ASTM D257. The heat conductive molded object of Claim 1 whose density is 2.1 g / cm < ³ > or more.   The heat conductive molded article according to claim 1 or 2, wherein the molded article is a uniaxially stretched polytetrafluoroethylene resin film or sheet laminate. A polytetrafluoroethylene-based resin film or sheet that is uniaxially stretched and has a porosity of 30 to 80% is laminated so that the stretching directions of the polytetrafluoroethylene-based resin film or sheet match,
The heat conductive molded object in any one of Claims 1-3 obtained by heat-pressing the obtained laminated body on the conditions of the temperature of 350-430 degreeC, the pressure of 5-50 MPa, and time 10 minutes-5 hours. A polytetrafluoroethylene-based resin film or sheet that is uniaxially stretched and has a porosity of 30 to 80% is laminated so that the stretching directions of the polytetrafluoroethylene-based resin film or sheet match,
The obtained laminate was hot-pressed under conditions of a temperature of 350 to 430 ° C., a pressure of 5 to 50 MPa, and a time of 10 minutes to 5 hours, and formed into a pillar body,
Next, a polytetrafluoroethylene resin obtained by cutting out the film or sheet from the pillar in parallel or perpendicular to the stretching direction of the polytetrafluoroethylene resin film or sheet constituting the pillar. Heat-conducting cut film or sheet consisting only of   The heat conductive molded object according to any one of claims 1 to 4, or the heat conductive cut-out film or sheet according to claim 5, which is used for a heat conductive member.   The heat conductive molded body is joined to the heat generating body and the cooling body so that the stretching direction of the polytetrafluoroethylene-based resin film or sheet constituting the heat conductive molded body is a direction connecting the heat generating body and the cooling body. The usage method of the heat conductive molded object in any one of Claims 2-4.   The heat conductive cut film or sheet is heated and cooled so that the stretching direction of the polytetrafluoroethylene-based resin film or sheet constituting the heat conductive cut film or sheet is a direction connecting the heat generating body and the cooling body. The method for using a thermally conductive cut film or sheet according to claim 5 or 6, which is bonded to a body. A polytetrafluoroethylene-based resin film or sheet that is uniaxially stretched and has a porosity of 30 to 80% is laminated so that the stretching directions of the polytetrafluoroethylene-based resin film or sheet match,
The manufacturing method of the heat conductive molded object which consists only of polytetrafluoroethylene-type resin which heat-presses the obtained laminated body on the conditions of the temperature of 350-430 degreeC, the pressure of 5-50 MPa, and time 10 minutes-5 hours. A polytetrafluoroethylene-based resin film or sheet that is uniaxially stretched and has a porosity of 30 to 80% is laminated so that the stretching directions of the polytetrafluoroethylene-based resin film or sheet match,
The obtained laminate was hot-pressed under conditions of a temperature of 350 to 430 ° C., a pressure of 5 to 50 MPa, and a time of 10 minutes to 5 hours, and formed into a pillar body,
Subsequently, the film or sheet is cut out from the column body in parallel or perpendicular to the stretching direction of the polytetrafluoroethylene resin film or sheet constituting the column body, and only the polytetrafluoroethylene resin is formed. A method for producing a thermally conductive cut film or sheet.