WO2015182600A1 - Thermally conductive sheet and production method for thermally conductive sheet - Google Patents

Abstract

This thermally conductive sheet comprises a mesh sheet within a polymer matrix that contains a thermally conductive filler material. The thermally conductive sheet is configured so that a step in which a mesh reinforcing material is coated with a liquid composition can be carried out more efficiently. The ratio of the number of vertical and horizontal filaments that constitute the mesh sheet (13) is configured such that there are 1.05 to 1.56 times as many vertical threads (13a) as horizontal threads (13b). As a result, properties of the thermally conductive sheet (11) such as toughness and thermal conductivity are improved.

Description

Thermally conductive sheet and method for producing thermally conductive sheet

The present invention relates to a thermally conductive sheet used for heat countermeasures such as heat dissipation and cooling of electronic components provided in electronic devices, displays, batteries, and other devices and devices, and a method for manufacturing the same.

An electronic component such as a CPU mounted on the electronic device is a heating element, and a heat radiating body such as a heat sink is mounted for cooling the electronic component. A heat conductive sheet is interposed between the heat generator and the heat radiator to promote heat conduction from the heat generator to the heat radiator.
In a heat conductive sheet, in order to lower the thermal resistance value, which is an index indicating the difficulty of transferring heat, it is required that the followability and adhesion to the heating element and the heat dissipation element are good. From this viewpoint, it is preferable to use a flexible heat conductive sheet. However, when the flexibility of the heat conductive sheet is increased, its adhesiveness is also increased, and it may be difficult to attach the heat conductive sheet to the heating element.
Moreover, since the thermal conductivity improves as the shape of the thermal conductive sheet is thinner, it is preferable to use a thinner thermal conductive sheet from this viewpoint. However, if it is too thin, there is a risk that problems such as elongation, tearing, and wrinkling will occur during the mounting operation, and the handleability will deteriorate.

Japanese Patent Application Laid-Open No. 7-014950 (Patent Document 1) and Japanese Patent Application Laid-Open No. 7-266356 (Patent Document 2) describe a soft rubber or gel-like heat conductive sheet, a glass, metal or resin woven fabric. A heat conductive sheet that contains such a mesh-like reinforcing material and has improved handleability is disclosed. According to such a heat conductive sheet, the tensile strength of the sheet is enhanced by the mesh-like reinforcing material contained, but the handleability is improved, but the sheet thickness is made thinner than before by increasing the tensile strength. There is also an advantage that heat can be transmitted more easily.

Japanese Patent Laid-Open No. 7-014950 JP-A-7-266356

The above-mentioned heat conductive sheet containing a mesh reinforcing material is excellent in reinforcing effect and heat conductivity, but for the production thereof, the liquid before the rubber reinforcing material around the mesh reinforcing material becomes a gel or a gel. It is necessary to go through a step of coating with the composition. This coating process is a process in which a liquid composition is applied on the mesh reinforcement or a mesh reinforcement is immersed in the liquid composition. The opening ratio that is an index of the mesh of the mesh reinforcement is determined. When it is lowered, there is a disadvantage that the liquid composition does not sufficiently enter the opening and voids are generated, thereby increasing the thermal resistance value of the sheet. On the other hand, when the aperture ratio of the mesh-like reinforcing material is increased, there is a disadvantage that the reinforcing effect is insufficient and the tensile strength of the sheet itself is weakened. For this reason, it is necessary to sufficiently impregnate the liquid composition into the mesh reinforcing material having a low aperture ratio, which takes a long time to work, and limits the amount of heat conductive filler added to adjust the liquid composition viscosity low. There were many restrictions.

Therefore, an object of the present invention is to improve the process of coating the mesh reinforcing material with a liquid composition and to produce a heat conductive sheet more efficiently. Another object of the present invention is to obtain a thermally conductive sheet having improved performance such as toughness and thermal conductivity by improving the process of coating the network reinforcing material with a liquid composition.

That is, the following invention is provided.
Regarding the heat conductive sheet having a mesh sheet in a polymer matrix containing a heat conductive filler, the ratio of the length and width of the filaments constituting the mesh sheet is 1.05 to 1. It is a heat conductive sheet characterized by being 56 times.

Since the heat conductive filler is contained in the polymer matrix, even the insulating polymer matrix can be provided with heat conductivity. Moreover, since the polymer sheet has the mesh sheet, the polymer matrix can be reinforced with the mesh sheet.
The ratio of the length and width of the filaments that make up the mesh sheet is 1.05 to 1.56 times that of the warp, so the distance between the warps is narrowed and the mesh between the warps is reduced. can do. Since the interval between the warp yarns is narrow, the reinforcing effect can be enhanced as compared with the case where the interval between the warp yarns is increased. On the other hand, the space between the wefts can be made slightly wider to increase the mesh between the wefts. Since the distance between the wefts is slightly wider than the distance between the warps, it is difficult to inhibit the penetration of the liquid composition, which is a raw material before the polymer matrix is formed, into the network. Therefore, without impairing the reinforcing effect, it is possible to obtain a thermally conductive sheet that easily causes the penetration of the liquid composition and is easy to manufacture.

The thickness of the mesh sheet is 130 μm or less, the filament diameter is 90 μm or less, and the mesh sheet has an opening ratio of 70% or more.
Since the mesh sheet has a thickness of 130 μm or less and the filament has a wire diameter of 90 μm or less, a thin thermal conductive sheet can be obtained. In addition, since the opening ratio of the mesh sheet is set to 70% or more, the liquid composition can easily penetrate between the mesh sheet meshes, and the heat conductive sheet can be easily manufactured.

The mesh sheet has a plain weave structure of resin fibers that are monofilaments, and a heat conductive sheet in which the intersections of the vertical and horizontal filaments are fixed can be obtained.
The structure of the mesh sheet is a monofilament resin fiber plain weave structure, so the resin fiber structure is simple and the liquid composition easily wets the periphery of the resin fiber, and air bubbles enter between the liquid composition and the resin fiber. Hateful. Further, since the intersections of the vertical and horizontal filaments are fixed, the resin fiber is difficult to move, and a mesh sheet having a high reinforcing effect can be obtained.

It can be set as the heat conductive sheet whose specific gravity of a mesh sheet is lighter than the specific gravity of the polymer matrix containing the heat conductive filler.
Because the specific gravity of the mesh sheet is lighter than the specific gravity of the polymer matrix containing the heat conductive filler, when the mesh sheet is submerged with the liquid composition before becoming the polymer matrix, the mesh sheet is contained in the liquid composition. Can emerge. Therefore, if the liquid composition is solidified before it completely emerges, a thermally conductive sheet in which a mesh sheet is contained inside the polymer matrix can be easily produced.

It can be set as the heat conductive sheet in which the longitudinal direction of the warp of the mesh sheet substantially coincides with the longitudinal direction of the sheet.
Since the longitudinal direction of the warp yarn of the mesh sheet is substantially the same as the longitudinal direction of the sheet, the warp yarn that exists at short intervals resists the pulling in the longitudinal direction of the heat conductive sheet, so the tensile strength in the longitudinal direction of the sheet High thermal conductive sheet.

And a method for producing a heat conductive sheet having a mesh sheet in a polymer matrix containing a heat conductive filler, wherein the ratio of the length and width of the filaments constituting the mesh sheet is equal to the warp 1.05 times to 2.00 times, and a liquid composition that is cured to become a polymer matrix containing a thermally conductive filler is applied onto the mesh sheet along the length direction of the warp of the mesh sheet. A method for producing a thermally conductive sheet is provided.

A method for producing a heat conductive sheet having a mesh sheet in a polymer matrix containing a heat conductive filler, wherein the ratio of the length and width of the filaments constituting the mesh sheet is 1. In order to apply a liquid composition, which is a polymer matrix containing a heat conductive filler that is cured from 05 times to 2.00 times, on the mesh sheet along the longitudinal direction of the warp yarn of the mesh sheet, During the coating process, the liquid composition can be easily impregnated into the rectangular mesh of the mesh sheet. Therefore, it is difficult for air bubbles to enter between the mesh sheet and the liquid composition, and it is possible to manufacture a heat conductive sheet with stable quality.

The step of applying the liquid composition provides a method for producing a heat conductive sheet, which is a step of applying the liquid sheet by moving the mesh sheet in the longitudinal direction of the warp to the application position of the liquid composition.
In the process of applying the liquid composition, the mesh sheet is moved in the longitudinal direction of the warp yarn to the application position of the liquid composition and applied. The application position of the composition can be fixed. Therefore, it is a highly productive manufacturing method.

A material having a specific gravity lower than that of the liquid composition can be used for the mesh sheet, and a method for producing a thermally conductive sheet can be provided in which a step of lifting the mesh sheet in the liquid composition after application of the liquid composition is provided.
Using a material having a lower specific gravity than the liquid composition for the mesh sheet, and after applying the liquid composition, provided a step of lifting the mesh sheet in the liquid composition, so if the liquid composition is applied from above the mesh sheet, A mesh sheet floats in the liquid composition, and the liquid composition is solidified in the floated state, whereby a heat conductive sheet containing the mesh sheet can be easily produced.

According to the heat conductive sheet of this invention, it is excellent in heat conductivity and handleability.
Moreover, according to the manufacturing method of the heat conductive sheet of this invention, the heat conductive sheet excellent in heat conductivity and handleability can be manufactured efficiently.

It is a top view which shows the heat conductive sheet of one Embodiment. FIG. 2 is a schematic cross-sectional view taken along line SA-SA in FIG. It is a partial enlarged plan view of a mesh sheet. It is explanatory drawing which shows the coating process of a liquid composition.

The present invention will be described in more detail based on the following embodiments.
In FIG. 1, the top view of the heat conductive sheet 11 is shown. FIG. 2 shows a schematic cross-sectional view thereof. The heat conductive sheet 11 contains a mesh sheet 13 in a polymer matrix 12 containing a heat conductive filler. A polymer matrix 12 is inserted into a lattice-like mesh (through hole) formed in the mesh sheet 13, and a thermally conductive filler is dispersed and contained in the polymer matrix 12 so that heat can be easily transmitted. Therefore, it has thermal conductivity in the thickness direction of the sheet. Therefore, by using the heat conductive sheet 11 between a heat generating body such as an IC or a CPU and a heat radiating body such as a heat sink or a heat pipe, heat transfer from the heat generating body to the heat radiating body can be rapidly advanced. Can do.

The polymer matrix 12 is obtained by curing a liquid or gel rubber or a polymer substrate, and the liquid composition before curing can be composed of a mixed system such as a main agent and a curing agent. Therefore, this liquid composition can contain, for example, an uncrosslinked rubber and a crosslinking agent, or an uncrosslinked rubber containing a crosslinking agent and a crosslinking accelerator. The curing reaction may be room temperature curing or heat curing. If the polymer matrix 12 is silicone rubber, examples thereof include a silicone rubber main component and a curing agent, such as a vinyl group-containing silicone raw rubber and a peroxide. In addition, a diol and a dicarboxylic acid can be used for a polyester-based thermoplastic elastomer or a polyamide-based thermoplastic elastomer, and a diisocyanate and a diol can be used for a polyurethane-based thermoplastic elastomer.

The main agent and the curing agent are distinguished by calling one of at least two components before mixing as the main agent and the other as the curing agent, which may be defined as the main agent or the curing agent. . Therefore, for example, the lower mixing ratio and the lower viscosity can be used as the main agent. Further, the polymer base material may be only the main agent that does not contain a curing agent among these main agents and curing agents. Thus, even if the component which comprises the liquid composition before polymer matrix formation is called a polymer base material, it does not necessarily need to be a high molecular weight of the grade called a general resin or a polymer.

Examples of the thermally conductive filler contained in the polymer matrix 12 include fine powders made of metal, carbon, metal oxide, metal nitride, metal carbide, metal hydroxide, carbon fiber, and the like. Examples of the metal include copper and aluminum. Examples of the carbon include pitch-based carbon fibers, PAN-based carbon fibers, fibers obtained by carbonizing resin fibers, fibers obtained by graphitizing resin fibers, and graphite powder. When voltage resistance is required for the heat conductive sheet, it is preferable to use a heat conductive filler other than metal or carbon.

Examples of the metal oxide include aluminum oxide, magnesium oxide, zinc oxide, iron oxide, and quartz. Examples of the metal nitride include boron nitride and aluminum nitride. In addition, examples of the metal carbide include silicon carbide, and examples of the metal hydroxide include aluminum hydroxide.
Such a heat conductive filler can be oriented in a certain direction in the polymer matrix 12, and is preferable in that the heat conductivity increases in the oriented direction.

The hardness of the polymer matrix 12 containing the heat conductive filler is 5 to 95, preferably a value measured by a Japanese Industrial Standard JIS K-6253 type E hardness meter (hereinafter referred to as “E hardness”). Is 55-90. When the E hardness exceeds 95, sufficient followability to the shape of the heating element or the heat radiating body is not obtained, and the adhesion between the heating element or the heat radiating body and the polymer matrix 12 is reduced, and the heat conductive sheet 11 There is a possibility that the thermal conductivity is lowered. When the E hardness is 90 or less, the polymer matrix 12 follows well along the shape of the heating element and the heat radiating body, so that sufficient adhesion between the heating element and the heat radiating body and the heat conductive sheet 11 is ensured. can do. Furthermore, the flexibility of the heat conductive sheet 11 is secured by the polymer matrix 12 having an E hardness of 90 or less. Therefore, for example, when the heat conductive sheet 11 absorbs an impact applied to the heat generating element to which the heat conductive sheet 11 is attached, the heat generating element can be suitably protected. However, if the E hardness is lower than 5, it is too soft to be stably sandwiched between the heat generator and the heat radiator. The reason why it is preferably 55 to 90 among 5 to 95 is that the adhesiveness on the surface of the heat conductive sheet can be moderately suppressed, and the strength and handleability can be improved.

In addition to the thermally conductive filler, the liquid composition to be the polymer matrix 12 includes various additives for the purpose of enhancing various properties such as productivity, weather resistance, and heat resistance of the thermally conductive sheet 11. Can be used. Examples of such additives include various functional improvers such as plasticizers, reinforcing materials, colorants, heat resistance improvers, coupling agents, flame retardants, adhesives, catalysts, cure retarders, and deterioration inhibitors. It is done.

The viscosity of the liquid composition including the thermally conductive filler is preferably 7000 to 120,000 cP, more preferably 15000 to 65000 cP at 25 ° C. If the viscosity is lower than 7000 cP, the heat conductive filler is not stably dispersed in the liquid composition, and it is difficult to obtain the polymer matrix 12 containing the heat conductive filler uniformly. This is because if the viscosity is higher, the liquid composition does not soak into the openings of the mesh sheet 13 and air bubbles easily enter. Further, if it is in the range of 15000 to 65000 cP, the viscosity is so high that the mesh sheet 13 is sufficiently soaked, and at the same time, the viscosity is such that the heat conductive filler can be filled in a moderately high amount.

The mesh sheet 13 is a sheet formed by weaving filaments (wires) constituting the mesh by plain weaving, twill weaving, satin weaving, tangle weaving, imitation weaving, tatami weaving, or the like, or by laminating filaments without weaving And a mesh-like material including those formed into sheets by knitting filaments.
The shape of the mesh is not limited, and the mesh may be anything from the front side to the back side of the mesh sheet 13. However, it is preferable that the through-hole to be a mesh is formed along the direction perpendicular to the surface of the mesh sheet 13, A plain weave is preferable to a tatami weave in that respect.

Further, the filament constituting the mesh is preferably less overlapped in the direction perpendicular to the mesh sheet 13, and in this respect, plain weave is preferable to imitation weave.
Furthermore, it is preferable that the mesh is regularly formed because it gives uniform heat conduction performance. In this respect, a woven fabric is preferable to a non-woven fabric or a knitted fabric.
And it is the monofilament (single fiber) of the two directions of the warp (warp) 13a and the weft (weft) 13b at the point which can make small the clearance gap where the polymer matrix containing a heat conductive filler does not enter in the vicinity of the intersection of a filament. Most preferably, the mesh sheet 13 shown in FIG. 3 is composed of only filaments and the intersection of the filaments is composed of only one warp and one weft.

However, the ratio of the length and width of the filaments constituting the mesh sheet 13 is different, and more specifically, the warp is 1.05 to 1.56 times the weft. Since the warp is 1.05 times or more than the weft, the distance between the wefts can be made wider than the distance between the warps. Therefore, if the liquid composition is applied in the longitudinal direction of the warp, the opening of the mesh sheet 13 (the warp and the weft can be crossed in the flow operation of applying the liquid composition on the mesh sheet 13). It is possible to allow a suitable time for the liquid composition to soak into the mesh. Therefore, the liquid composition can be sufficiently infiltrated into the opening, and the entry of bubbles can be reduced.

On the other hand, if a general mesh sheet having the same ratio of the vertical and horizontal numbers is used, it is not possible to take a sufficient time until the liquid composition enters the opening, bubbles easily enter, and the thermal resistance value. There is a possibility that a high thermal conductive sheet may be produced.
The “mesh” as a unit refers to the number of lines or the number of meshes within 25.4 mm (1 inch). If the density (lines / inch) is 100, it is 100 mesh. Further, the opening and the aperture ratio (spatial ratio) are defined by the following expressions.
Aperture (mm) = (25.4 / number of meshes)-Wire diameter (mm)
Opening ratio (%) = ((opening mm) / (opening mm + wire diameter mm)) ² × 100

The material of the filament constituting the mesh sheet 13 is glass, metal such as iron, copper, brass, stainless steel, aluminum, nickel, polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyamide (PA). And thermoplastic resins such as polyimide (PI).
When the intersection of the mesh sheet 13 is heat-sealed or pressure-bonded, it is preferable to use a thermoplastic resin. Further, when the mesh sheet 13 is made of resin, the mesh sheet 13 may be made of a filament subjected to surface treatment such as corona treatment or UV modification. In addition, when voltage resistance is required for the heat conductive sheet, it is preferable to use a mesh sheet other than metal.

Among these materials, a resin mesh sheet 13 having a specific gravity of 0.90 to 1.40 is preferable. This is because, since the specific gravity of the liquid composition is 1.60 to 5.00, the mesh sheet 13 can be lifted in the liquid composition with the specific gravity described above.

The mesh sheet 13 has a thickness of about 10 μm to 500 μm, an opening size of 200 μm to 1200 μm, and an opening ratio of 40% or more from the viewpoint of maintaining the heat conduction performance of the polymer matrix 12 and handling. It is preferable to use 90% and a wire diameter of about 20 μm to 300 μm.
In order to obtain a thin thermal conductive sheet 11 having a thickness of about 200 μm, it is more preferable that the thickness is 130 μm or less, the filament wire diameter is 90 μm or less, and the mesh intersection is fused to reduce the thickness. Further, it is more preferable that the opening ratio is 70% or more because the liquid composition easily penetrates the opening of the mesh.
In order to increase the aperture ratio, the density of the mesh is preferably less than 100 mesh (less than 100 / inch).

The thickness of the heat conductive sheet 11 is equal to or greater than the thickness of the mesh sheet 13, and is preferably about 0.1 mm to 5 mm. If the thickness exceeds 5 mm, the heat conduction performance may be lowered (heat resistance increases), and if it is less than 0.1 mm, it is difficult to handle even if the mesh sheet 13 is used.

An example of the manufacturing method of the heat conductive sheet 11 is demonstrated.
As a raw material to be cured to become the polymer matrix 12, a liquid composition prepared by adding a heat conductive filler and, if necessary, various additives to the main agent and the curing agent and mixing them with a stirrer is prepared.
Next, as shown in FIG. 4, the liquid composition 14 is applied along the longitudinal direction of the warp yarns of the mesh sheet 13 by passing the raw material with the mesh sheet 13 placed on the film sheet 1 through the roll coater 2. To do. In this coating process, the liquid composition 14 enters the openings (through holes) of the mesh sheet 13, and the mesh sheet 13 having a low specific gravity rises in the liquid composition 14 having a high specific gravity.
The liquid composition 14 may be applied by gravure coating, roll coating, knife coating, comma coating, lip coating, die coating, dipping, or the like. Alternatively, the mesh sheet 13 may be placed in a mold to form a liquid. A method in which the composition 14 is injected and integrally molded may be used.

Then, before the mesh sheet 13 is completely lifted up to the surface of the liquid composition 14, the liquid composition is cured by applying an appropriate curing means such as ultraviolet irradiation or heating, and the mesh sheet 13 is placed in the polymer matrix 12. The contained large-area heat conductive sheet is obtained. In the coating of the liquid composition, the mesh sheet has a mesh spread in the direction of travel of the original fabric, so that the liquid composition can be easily penetrated into the mesh.
The obtained heat conductive sheet is cut into a size suitable for the size of the heat generating body and the heat radiating body to be applied to obtain the heat conductive sheet 11 having a desired size.

It is preferable to cut the roll-shaped heat conductive sheet so that the longitudinal direction of the heat conductive sheet 11 and the length direction of the warp are substantially in the same direction. This is because the heat conductive sheet 11 is easily pulled in the longitudinal direction of the heat conductive sheet 11 during the mounting operation, and thus the heat conductive sheet 11 having high tensile strength in the longitudinal direction can be obtained.
Moreover, it is one of the preferable aspects to cut | disconnect a heat conductive sheet of a large area shape in the direction which cross | intersects with respect to each length direction of the warp of a mesh sheet, and a weft. This is because the warp yarn and the weft yarn cross each other in the cutting direction, so that the heat conductive sheet 11 having high tensile strength can be obtained in any direction.

In addition, in the said manufacturing process of the heat conductive sheet 11, if the process of laminating | stacking a protective film after hardening of the liquid composition 14 is provided in the surface at the side which apply | coated the liquid composition 14, a heat conductive sheet will be used as a film. Since it can protect by pinching | interposing between the sheet | seat 2 and a protective film, it is preferable. However, it is preferable to avoid the step of laminating a protective film before the liquid composition 14 is cured. When the liquid composition 14 is covered with a protective film and then cured, a skin layer in which the density of the heat conductive filler is reduced is formed at the interface between the liquid composition 14 and the protective film. It is because there is a possibility that it becomes worse and flammable.

Experimental Example 1 : As a liquid composition to be a polymer matrix, a mixture having a viscosity of 60000 cP in which aluminum oxide and aluminum hydroxide as heat conductive fillers and a curing catalyst were blended in liquid silicone rubber was used. Further, as the mesh sheet, a plain weave intersection fusion mesh composed of polyester monofilaments having a density of warp 78 mesh and weft 50 mesh, a wire diameter of 86 μm and a thickness of 130 μm was used.

A mesh sheet was placed on a PET film as a release sheet, and the liquid composition was applied along the longitudinal direction of the warp yarn of the mesh sheet using a coater on the mesh sheet. And the liquid composition was heat-hardened with the far-infrared heating furnace, and the heat conductive sheet was obtained.
In this thermally conductive sheet, a polymer matrix spreads above and below the mesh sheet, and the polymer matrix penetrated through the openings. Although the back surface of the heat conductive sheet was observed, no bubbles were found in the polymer matrix. The withstand voltage (dielectric breakdown voltage) also cleared 5.0 kV and was sufficient.

Experimental Example 2 : As a liquid composition to be a polymer matrix, a mixture having a viscosity of 60000 cp in which aluminum oxide and aluminum hydroxide, which are thermally conductive fillers, and a curing catalyst were blended in liquid silicone rubber was used. In addition, a plain weave intersection fusion mesh made of polyester monofilament having a density of warp 60 mesh and weft 40 mesh, a wire diameter of 72 μm and a thickness of 100 μm was used for the mesh sheet. And the heat conductive sheet was obtained like Example 1 except having applied the liquid composition so that thickness might be set to 200 micrometers.
In this thermally conductive sheet, a polymer matrix spreads above and below the mesh sheet, and the polymer matrix penetrated through the openings. Although the back surface of the heat conductive sheet was observed, no bubbles were found in the polymer matrix. The withstand voltage was sufficient.

Experimental Example 3 : The same procedure as in Experimental Example 1 was performed except that a plain weave intersection fused mesh made of polyester single fiber having a density of warp 50 mesh, weft 35 mesh, wire diameter 89 μm and thickness 130 μm was used for the mesh sheet. A thermally conductive sheet was obtained.
In this thermally conductive sheet, a polymer matrix spreads above and below the mesh sheet, and the polymer matrix penetrated through the openings. Although the back surface of the heat conductive sheet was observed, no bubbles were found in the polymer matrix. The withstand voltage was sufficient.

Experimental Example 4 : As the mesh sheet, a plain weave intersection fused mesh made of polyester monofilaments having a density of warp 40 mesh and weft 38 mesh, a wire diameter of 89 μm and a thickness of 130 μm was used. The composition of the liquid composition and the coating method were the same as in Experimental Example 1.
In this thermally conductive sheet, a polymer matrix spreads above and below the mesh sheet, and the polymer matrix penetrated through the openings. In addition, bubbles were not mixed in the polymer matrix.

Experimental Example 5 : As the mesh sheet, a plain-weave intersection fused mesh made of polyester monofilament having a density of warp 54 mesh and weft 30 mesh, a wire diameter of 89 μm and a thickness of 130 μm was used. The composition of the liquid composition and the coating method were the same as in Experimental Example 1.
In this thermally conductive sheet, a polymer matrix spreads above and below the mesh sheet, and the polymer matrix penetrated through the openings. Although the back surface of the heat conductive sheet was observed, no bubbles were found in the polymer matrix. The withstand voltage was sufficient. However, the tensile strength of the heat conductive sheet has become weak at 10 MPa in the lateral direction of the sheet.

Experimental Example 6 A heat conductive sheet was obtained in the same manner as in Experimental Example 1 except that the liquid composition was applied along the length direction of the weft yarn of the mesh sheet.
In this thermally conductive sheet, a polymer matrix spreads above and below the mesh sheet, and the polymer matrix penetrated through the openings. When the back surface of the heat conductive sheet was observed, a mixture of bubbles was seen in part. In addition, the withstand voltage could not clear 3.0 kV, and did not satisfy the required characteristics of withstand voltage.

Experimental Example 7 : As the mesh sheet, a plain weave intersection fusion mesh made of polyester monofilament having a warp and weft density of 30 mesh, a wire diameter of 70 μm and a thickness of 100 μm was used. And the heat conductive sheet was obtained like Example 1 except having applied the liquid composition so that thickness might be set to 200 micrometers.
The obtained heat conductive sheet had a low tensile strength in both the longitudinal direction and the transverse direction of the sheet, and the handleability was poor.

Experimental Example 8 : As the mesh sheet, a plain weave intersection fused mesh made of polyester single fibers having a warp and weft density of 50 mesh, a wire diameter of 50 μm and a thickness of 77 μm was used. And the heat conductive sheet was obtained like Example 1 except having applied the liquid composition so that thickness might be set to 180 micrometers.
The obtained heat conductive sheet had a tensile strength as low as 10 MPa in both the longitudinal and lateral directions of the sheet, and the handleability was poor.

Experimental Example 9 : As the mesh sheet, a plain weave intersection fusion mesh made of polyester monofilament having a density of warp and weft of 100 mesh, a wire diameter of 48 μm and a thickness of 80 μm was used. And the heat conductive sheet was obtained like Example 1 except having applied the liquid composition so that thickness might be set to 180 micrometers.
Although the obtained heat conductive sheet had high tensile strength, the liquid composition was poorly infiltrated because of the small opening ratio, and pinholes were generated in the sheet. Moreover, the withstand voltage was inferior.
If there are bubbles in the heat conductive sheet, a thin portion is locally generated, so that the voltage resistance is considered to be weak. In addition, because of the large number of meshes, flame retardancy “V-0” could not be obtained.

The conditions and test results for the above Experimental Examples 1 to 9 are summarized in Table 1 below.

In Table 1, “mesh” describes (number of warp yarns) / (number of weft yarns) per inch.
“Opening ratio” indicates the opening ratio of a mesh sheet between wefts having a large value.
“Tensile strength” is measured by cutting the thermal conductive sheet of each experimental example into the shape of a test piece for a tensile test along the warp direction or the weft direction of the mesh sheet, and performing a tensile test according to JIS K6251. did.

“Flame retardancy” was evaluated by a combustion test (UL94) established by Under Writers Laboratories Inc., USA.
The heat conductive sheet of each experimental example was cut into the size of a test piece (length 127 mm × width 12.7 mm) and held in a fixing clamp so that the longitudinal direction of the test piece was in the vertical direction. After 10 seconds of indirect flame, the combustion time of each specimen was recorded away from the flame. In addition, the retention time (glowing time) of the fire type after the second flame contact and the presence / absence of a dripping material that ignites the absorbent cotton disposed below the test piece were recorded. The above operation was performed for each test piece as a set of 5 times. Then, based on the criteria shown in the following Table 2, pass / fail for “V-0” or “V-1” was determined. Note that this flame retardancy criterion indicates that “V-0” has higher flame retardancy than “V-1”.

“Withstand voltage” is based on JIS C2110, with a test piece sandwiched between cylindrical electrodes having a diameter of 2.5 mm, and using a withstand voltage tester (TOS8650, manufactured by Kikusui Electronics Co., Ltd.), a predetermined voltage (3 kV, When 4 kV and 5 kV) were applied for 180 seconds, it was observed whether or not there was energization due to destruction of the heat conductive sheet. The case where there was no energization was “clear”, and the case where there was energization was “x”.

1 Film sheet 2 Roll coater (coating roll)
DESCRIPTION OF SYMBOLS 11 Thermal conductive sheet 12 Polymer matrix 13 Mesh sheet 13a Warp 13b Weft 14 Liquid composition

Claims (8)

1. In a thermally conductive sheet having a mesh sheet in a polymer matrix containing a thermally conductive filler,
   A heat conductive sheet characterized in that the ratio of the number of filaments constituting the mesh sheet is 1.05 to 1.56 times that of the warp.
2. The thermally conductive sheet according to claim 1, wherein the thickness of the mesh sheet is 130 µm or less, the filament has a wire diameter of 90 µm or less, and the mesh sheet has an aperture ratio of 70% or more.
3. The heat conductive sheet according to claim 1 or 2, wherein the mesh sheet has a plain weave structure of resin fibers which are monofilaments, and the intersections of the vertical and horizontal filaments are fixed.
4. The heat conductive sheet according to any one of claims 1 to 3, wherein the specific gravity of the mesh sheet is lighter than the specific gravity of the polymer matrix containing the heat conductive filler.
5. The heat conductive sheet according to any one of claims 1 to 4, wherein a length direction of warp yarns of the mesh sheet substantially coincides with a longitudinal direction of the sheet.
6. A method for producing a thermally conductive sheet having a mesh sheet in a polymer matrix containing a thermally conductive filler,
   The ratio of the length and width of the filaments constituting the mesh sheet is 1.05 to 2.00 times that of the warp with respect to the weft,
   A method for producing a heat conductive sheet, wherein a liquid composition that is cured and becomes a polymer matrix containing a heat conductive filler is applied onto the mesh sheet along the longitudinal direction of the warp of the mesh sheet.
7. The method for producing a thermally conductive sheet according to claim 6, wherein the step of applying the liquid composition is a step of applying the mesh sheet by moving the mesh sheet in the longitudinal direction of the warp yarn with respect to the application position of the liquid composition. .
8. The heat conductive sheet according to claim 6 or 7, wherein a material having a lower specific gravity than the liquid composition is used for the mesh sheet, and a step of lifting the mesh sheet in the liquid composition is provided after the liquid composition is applied. Production method.

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