JP2000034693A - Composite sheet and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composite sheet with excellent mechanical strengths, electrical insulation and thermal conductivity by forming into a sheet a mixture of aramid fibrids, aramid flocs and a thermoconductive substance. SOLUTION: This composite sheet is obtained by subjecting a mixture to papermaking process into a sheet form; wherein the mixture is composed of 0-90 wt.% of aramid fibrids such as of poly-m-phenylene isophthalamide, 0-90 wt.% of aramid flocs and 5-100 wt.% of a fibrous thermoconductive substance of anisotropic shape with a specific thermal conductivity of >=10 W/m.Kelvin (e.g. alumina fiber), and the sheet thus produced consists of at least two layers differing in compositional ratio for the above three components from each other and the content of the thermoconductive substance in at least one layer is >=70 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a rotating machine (generator,
The present invention relates to a composite sheet material composed of aramid fibrid and aramid floc used for an electric insulating material of a motor or a transformer or a substrate of a printed wiring board of an electric / electronic device, and a method of manufacturing the same. The present invention relates to a composite sheet material having effective composite properties when applied to an insulating material or a substrate which requires good thermal conductivity at the same time as insulation, and a composite sheet obtained by impregnating and complexing the sheet material with a resin. is there. Further, the present invention relates to a printed wiring board provided with such a composite sheet.

[0002]

2. Description of the Related Art In recent years, as one of the technological development trends of electric power supply-related devices such as electric motors, generators, and transformers, and consumer electric devices such as personal computers and televisions, higher performance such as larger capacity and smaller size has been developed. Have been pursued. At the same time, improving the heat dissipation of these devices is a very important issue. Various means for improving the heat dissipation have been studied and proposed. For example, in order to promote the heat dissipation of the heat generating element in a personal computer (PC), the design arrangement of the element and the substrate, the use of a heat conductive auxiliary material such as a heat sink, a heat radiating grease or a heat radiating cushion sheet, a fan, or a water cooling tube A supplementary device such as a forced cooling device is employed. Also,
Because the substrate material is in direct contact with the heating element,
If the thermal conductivity of the substrate is improved, effects such as an improvement in the reliability of the element brought about by the temperature reduction and an extension of the life of the device can be expected. Therefore, it is necessary to improve and improve the thermal conductivity. However, generally used substrate materials such as a glass cloth-ethoxy resin composite material and a paper-phenol resin composite material are essentially composed of a low heat conductive material, and thus have poor heat dissipation. For the purpose of solving such a problem, it has been conventionally developed to use a substrate material in which an insulating resin is applied / laminated on a metal plate (commonly called a metal core substrate or a metal base substrate).
Proposed.

[0003] However, these conventional metal core substrate materials require complicated processing in the substrate manufacturing process, have poor through-hole properties, and go against the weight reduction of the above-mentioned devices, and the weight of the substrate itself is large. Become. In addition, there are practical problems such as high cost and complicated confirmation of insulation reliability. Therefore, at present, these metal core substrates are limitedly used in a portion where the heating elements are particularly concentrated inside the device. As described above, the above-mentioned conventional electric insulating material or substrate material does not sufficiently satisfy the demands for the thermal conductivity as well as the electrical properties, heat resistance, weight reduction, mechanical strength, processing properties, and manufacturing cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide not only electrical characteristics, heat resistance, weight reduction, mechanical strength, processing characteristics, manufacturing costs, but also total fragrance. It is an object of the present invention to provide a technique capable of obtaining a sheet-like molded product in which a fibrid and a floc of an aromatic polyamide (aramid) and heat conductive particles contributing to improvement of heat radiation characteristics are mixed at a specific composition ratio. Other objects of the present invention are electrical properties, heat resistance, weight reduction, mechanical strength,
An object of the present invention is to provide a method capable of producing a composite sheet having excellent heat conductivity as well as processing characteristics and production cost.

It is an object of the present invention to provide a fully aromatic polyamide (aramid) fibrid and floc, which are excellent in electrical properties, heat resistance, weight reduction, mechanical strength, processing properties, and production cost, as well as thermal conductivity, and heat. It is an object of the present invention to provide a technique capable of obtaining a composite sheet obtained by further impregnating a resin into a sheet-shaped molded product in which conductive particles are mixed at a specific composition ratio. Another object of the present invention is to provide a printed wiring board having improved thermal conductivity by providing such a composite sheet.

[0006]

In order to achieve the above object, the present invention is characterized by the following configuration or method. (1) at least 0-90% by weight of aramid fibrid, 0-90% by weight of aramid floc and 5-10
A composite sheet characterized in that a mixture composed of a thermally conductive material having 0% by weight of an anisotropic shape is formed in a sheet shape. (2) Aramid five in the mixture comprising at least a plurality of sheet layers formed from a mixture composed of aramid fibrid, aramid floc and a thermally conductive material having an anisotropic shape, and forming respective layers. Thermal conduction having at least two or more of the sheet layers, wherein at least one of the sheet layers has a non-isotropic shape, wherein a composition ratio of a lid, an aramid floc and a thermally conductive material having an anisotropic shape is different. A composite sheet characterized in that the content of the active substance is 70% by weight or more.

(3) The composite sheet of (1) or (2) is characterized in that the aramid constituting the composite sheet is polymetaphenylene isophthalamide. (4) The composite sheet according to any one of (1) to (3), wherein the heat conductive substance constituting the composite sheet has an intrinsic thermal conductivity of 10 W /
(MK: meter Kelvin) or more. (5) The composite sheet according to (1) to (4), wherein the heat conductive substance having an anisotropic shape constituting the composite sheet is formed of aluminum oxide, magnesium oxide, boron nitride, aluminum nitride, beryllium oxide. The heat conductive material has at least one selected anisotropic shape. (6) The composite sheet of (1) to (5) is characterized in that the shape of the heat conductive substance having an anisotropic shape constituting the composite sheet is fibrous.

(7) The composite sheet according to any one of (1) to (6), further comprising a resin impregnated therein. (8) The method for producing a composite sheet according to any one of (1) to (7), wherein at least 0 to 90% by weight
Aramid fibrids, 0 to 90% by weight of aramid floc and 5 to 100% by weight of a heat conductive substance having an anisotropic shape are dispersed and mixed in water, and the paper is formed into a sheet shape. And (9) The composite sheet according to any one of (1) to (7), wherein a circuit for transmitting an electric signal is formed on the surface and / or inside of the resin-impregnated composite sheet further impregnated with a resin. It is a printed wiring board characterized by the following.

That is, the main technical problem of the present invention is to select at least three types of aramid fibrid, aramid floc and a heat conductive substance having an anisotropic shape as raw materials for obtaining a composite sheet, By mixing and selecting the composition ratio of the mixture, the electrical properties,
An object of the present invention is to obtain a composite sheet having excellent heat conductivity as well as heat resistance, weight reduction, mechanical strength, processing characteristics, and production cost.

(A) Aramid The aramid used in the present invention means a wholly aromatic polyamide. In terms of chemical structure, it is defined as a linear synthetic polymer in which 60 mol% or more of the bonds connecting the benzene rings are amide groups. Aramids are classified into para-aramids, meta-aramids, and copolymers thereof, depending on the substitution position of the amide group on the benzene ring. Examples of the para-aramid include polyparaphenylene terephthalamide and a copolymer thereof, poly (paraphenylene) -copoly (3,4'diphenyl ether) terephthalamide, and the like. Examples of the meta-aramid include polymetaphenylene isophthalamide and a copolymer thereof. In the present invention, meta-aramid is preferably selected.
Meta-aramid is soluble in general-purpose amide solvents, can be wet-molded and / or dry-molded using a polymer solution as a starting material, has excellent heat-fusibility, and has excellent heat resistance and flame retardancy. There are features such as that. The method for producing meta-aramid is not particularly limited. In general,
A solution polymerization method by a condensation reaction between metaphenylenediamine and isophthalic acid dichloride, a two-stage interfacial polymerization method, and the like can be industrially performed. It should be noted that other components may be copolymerized as long as the properties of the meta-aramid are not impaired.

(B) Aramid fibrids Aramid fibrids are fine particles of a film made of aramid, and are sometimes called aramid pulp. (A description of Aramid Fibrid is published by
5-11851, Japanese Patent Publication No. 37-5752, etc.).
Since fibrids have papermaking properties like ordinary wood (cellulose) pulp, they can be dispersed in water and then formed into a sheet by a paper machine. In this case, in order to improve the properties such as electrical insulation and mechanical properties, an operation of dispersing the fibrid mass using equipment such as a disintegrator and a beater and reducing the twist of each individual fibrid can be applied. . In this operation, the morphological change of the fibrid can be monitored by the freeness test method (freeness) specified in Japanese Industrial Standard P8121. The preferred freeness in the present invention is in the range of 10 to 300 ml (Canadian freeness). With a fibrid having a freeness greater than this range, the strength and dielectric breakdown voltage of the sheet molded product are not sufficient. On the other hand, even if an attempt is made to obtain a freeness smaller than 10 ml, the utilization efficiency of the input mechanical power is small,
In addition, the processing amount per unit time is often impaired. Further, the fineness of the fibrid is excessively advanced, so that the so-called binder function is reduced. Even if it is attempted to obtain a freeness of less than 10 ml, no remarkable advantage is found.

(C) Aramid floc Aramid floc is a short fiber made of aramid. As such fibers, poly- (metaphenylene isophthalamide) fiber “Nomex (registered trademark)” and poly- (para-metaphenylene isophthalamide) fiber “Kepler (registered trademark)” of E. I. Dupont de Nemours and Company ) ”, Teijin Limited
(Metaphenylene isophthalamide) fiber "CONEX (registered trademark)", poly- (paraphenylene) -copoly (3,4'-diphenylether) terephthalamide fiber "Technola (registered trademark)", Unitika Ltd. Examples thereof include, but are not limited to, phenylene isophthalamide) fiber “Apier (registered trademark)” and Akzo's poly (paraphenylene terephthalamide) fiber “Twaron (registered trademark)”.

The fineness of flocks is 0.1 denier or more and 10
A denier range is preferred. Here, denier is fiber 9
It is a unit expressed in mass (gram) per 000 m. If the fineness is smaller than 0.1 denier, the entanglement in water is increased, and the sheet quality is reduced. on the other hand. If the fineness is more than 10 denier, the diameter of the floc becomes too large, which causes a decrease in the aspect ratio, a decrease in the mechanical reinforcing effect, and a poor uniformity in the sheet, which is not a preferable choice. Flock length (cut length) is 1-50
The range of mm is appropriate. If the length is less than 1 mm, the effect of reinforcing the sheet is reduced. If the length of the flock is more than 50mm, when forming the sheet, the "lock" of the flock
This is not preferable because “binding” is likely to occur and may cause defects. In order to improve convergence, antistatic properties, smoothness, dispersibility in water, and the like, a surface treatment agent can be applied to the floc in advance.

(D) Thermally conductive substance (1) Intrinsic thermal conductivity In the present invention, a thermally conductive substance is defined as having a thermal conductivity of 10%.
W / (mK: meter-Kelvin) or more. Generally, the thermal conductivity of a single crystalline material often shows anisotropy. The value of the thermal conductivity of the thermally conductive substance used in the present invention is the value of the bulk body of the polycrystalline substance. If the thermal conductivity of the thermally conductive substance is smaller than 10 W / (mK), the effect of improving the thermal conductivity of the composite sheet in a state where the resin is impregnated and filled is not sufficient (Polymer Enger).
Sci. 16, 615 and Polymer Comp 7, 125). Ceramics such as aluminum oxide, magnesium oxide, aluminum nitride, and beryllium oxide are exemplified as the electrically insulating substance having an intrinsic thermal conductivity of 10 W / (mK: meter-Kelvin) or more, but are not limited thereto. Absent. It is not necessary to use one kind of these heat conductive substances, and two or more kinds can be used in combination.

(2) Form and Size Restrictions on the form and size of the heat conductive substance that can be used in the present invention depend on the sheet forming method. That is, as will be described later, when the sheet is formed by wet papermaking, the heat conductive substance preferably has an anisotropic shape in order to keep the added heat conductive substance at a good value (retention). Here, the anisotropic shape is a three-dimensional quantity (major axis, minor axis, thickness, length,
Width, etc.) are not the same. The heat conductive material is preferably in the form of a fiber having a large aspect ratio. Here, the aspect ratio is a ratio of the major axis / minor axis of the fibrous particles. In the present invention, the preferable fibrous substance means that the aspect ratio is 20 or more. The size of the fibrous heat conductive material is such that the fiber diameter is 0.1 to 50 μm and the fiber length is 0.0.
A range of 1 mm to 50 mm is preferably selected.

(E) Wet Papermaking The production of the composite sheet of the present invention is not particularly limited, and can be carried out by generally used papermaking methods, equipment and techniques. Above all, it is better to use a fluid such as water as the transport medium in the sheet raw material process, to improve the dispersibility of the raw material, to improve the uniformity of the sheet, and to adjust the basis weight (sheet mass per 1 m ² ) of the sheet that can be manufactured. The wet papermaking method is preferred because of its superiority such as easiness.

In the wet papermaking method using water, a single or mixture aqueous slurry containing at least aramid fibrid, aramid floc and heat conductive particles is sent to a paper machine and dispersed, and then dewatered and squeezed. A method of winding the sheet as a sheet by performing a drying operation is common. Fourdrinier, circular net,
An inclined paper machine and a combination paper machine combining these can be used. In the case of production with a combination paper machine, a composite sheet composed of a plurality of paper layers can be obtained by forming and joining together slurries having different mixing ratios. In papermaking, additives such as a dispersibility improver, an antifoaming agent, and a paper strength enhancer can be used as needed. In addition, other fibrous components (eg, glass fiber, polyester fiber, para-type aramid fiber,
Cellulose fibers, etc.). Aramid fibrid has excellent properties as a binder, so that it can efficiently supplement aramid floc and other additional components, and has a good stock yield that constitutes the composite sheet of the present invention.

The composite sheet obtained by the wet papermaking method can be improved in density and mechanical strength by hot pressing at a high temperature and a high pressure between a pair of flat plates or a metal roll. The condition of the heat pressure is, for example, a temperature of 10 when using a metal roll.
Examples are 0 to 350 degrees and a linear pressure of 50 to 300 kg / cm, but the present invention is not limited to these. It is also possible to simply press at room temperature without adding a heating operation. A plurality of sheets can be stacked during hot pressing. Considering the mechanical strength of the composite sheet, the thermal conductivity after resin impregnation, etc., the amount of each component in the composite sheet is 0% to 90% by weight of aramid fibrids and 0% by weight of aramid floc. % To 90% by weight, for the heat conductive material,
It is from 5% by weight to 100% by weight.

When the composition ratio of aramid fibrid and aramid floc is out of the above range, the mechanical properties of the composite sheet become insufficient or a problem arises in terms of development of thermal conductivity. On the other hand, when the content of the thermally conductive substance is less than 5%, the resulting composite sheet has poor thermal conductivity. Particularly preferred ranges are 5% to 30% by weight of aramid fibrids and 5% by weight of aramid floc.
30% by weight, and 30% by weight for the heat conductive substance.
90% by weight. Within the above range, a composite sheet having a multilayer structure using at least two or more composite sheet materials in which the weight ratios of the respective components of aramid fibrid, aramid floc, and a heat conductive substance are different from each other is also provided by the present invention. This is within the scope of the invention. In this case, it is preferable that the weight percentage of the thermally conductive substance in at least one of these layer structures is 70% or more. When the weight percent of the heat conductive substance is less than 70%, the expected effect on the thermal conductivity in the in-plane direction after resin impregnation, which will be described later, is difficult to exert.

As a method for producing a composite sheet having a structure in which a plurality of composite sheet materials having different raw material mixing ratios are laminated, in addition to the above-described laminating, a method of laminating at the time of hot pressing and an adhesive are used. Any method such as a method of bonding together can be adopted. Further, the composite sheet can be backed with a sheet material such as glass cloth or alumina fiber cloth for the purpose of mechanical reinforcement.

(F) Resin-impregnated composite sheet The present invention also relates to a resin sheet impregnated with a resin which is further impregnated with a base material of a composite sheet formed from a mixture comprising the aramid fibrid, aramid floc and a heat conductive substance. It is characterized by obtaining a resin-impregnated composite sheet as described above. That is, in many cases, the composite sheet contains a large amount of voids therein and thus has a large heat insulating effect, and as a result, the effect of improving the potential thermal conductivity of the heat conductive substance is hardly exhibited.
Therefore, it is preferable to remove the voids by a resin impregnation operation. Here, as a simple measure for quantifying the resin impregnation property, Gurley air permeability described in JIS P8117 can be used. In the present invention, the preferable range of Gurley air permeability is, for example, 100,000 seconds or less, more preferably 10,000 seconds or less, and further preferably 1000 seconds or less.

The resin impregnation is an operation of permeating a liquid, a solution, and a solid resin in a fluid state into a sheet formed of a mixture composed of at least aramid fibrid aramid floc and a heat conductive substance. It is. Specifically, varnish, liquid resin, after dipping or coating the resin in a fluid state such as latex, if necessary, drying, pre-curing and then hot-pressing between heated plates, thermoplastic resin Examples include a method in which the sheet and the composite sheet are stacked and then pressed between the heated flat plates at a temperature equal to or higher than the flow temperature of the thermoplastic resin, a method in which a hot-melt type thermosetting resin sheet and the composite sheet are stacked and pressed, and the like. However, it is a matter of course that the invention is not limited to these.
Further, instead of the heating flat plate, a heating / pressing device such as a metal-metal roll or a metal-resin roll can be used.

Examples of the resin usable for impregnation include epoxy resin, xylene resin, guanamine resin, diallyl phthalate resin, vinyl ester resin, phenol resin, unsaturated polyester resin, polyimide resin, polyurethane resin, maleic resin, melamine resin, urea Resin, thermosetting resin such as silicone resin, polyethylene terephthalate resin, vinyl chloride resin, polyethylene resin, coumarone resin, ketone resin, vinyl acetate resin, phenoxy resin, butadiene resin, fluorine resin, vinylidene fluoride resin, polyacetal resin , Polyamide resin, polycarbonate resin, polyarylate resin, polyamideimide resin, polyetherimide resin, polyetheretherketone resin, polyethylene resin, polyethylene oxide resin, polysulfo Resins, polyethersulfone resins,
Thermoplastic resins such as polyparamethylstyrene resin, polyvinyl alcohol resin, polyvinyl ether resin, polyvinyl formal resin, polyphenylene ether resin, polyphenylene sulfide resin, polybutylene terephthalate resin, polypropylene resin, polymethylpentene resin, and liquid crystal polymer Examples can be given but are not limited to these. When these resins are dissolved in a solvent and impregnated, a heat conductive substance can be added for the purpose of further improving heat dissipation. In this case, it is not necessary that the shape of the heat conductive substance is fibrous. When adding a heat conductive substance to a solvent and co-impregnating it, sedimentation and separation of these particles may occur with the lapse of time. can do. The amount of resin impregnation is an important control item that affects the thermal conductivity of the composite sheet after impregnation. The amount of resin impregnation is preferably adjusted so that the volume fraction of the thermally conductive substance in the resin-impregnated composite sheet becomes 5% or more, and a large amount of unimpregnated voids (voids) does not remain.

The thermal conductivity of the resin-impregnated composite sheet is improved by the effect of the thermally conductive substance. The thermal conductivity of the resin-impregnated composite sheet is determined by the thickness (z) direction and the surface (X-
Y) Both directions are improved, but when the composite sheet is prepared by wet papermaking, the thermal conductivity in the plane direction tends to be improved. When such characteristics are exhibited, an effect of transferring heat from the heating element in the plane direction can be expected. Further, the composite sheet of the present invention can be used not only as a single substance, but also as a laminated composite with an existing material such as a glass cloth-epoxy resin composite or a paper-phenol resin composite. In addition, it can be used as an insulating layer of a rigid substrate material such as an aluminum plate, an iron plate, an enamel plate, and a glass plate.

[0025]

Since the composite sheet obtained by the present invention is composed of an aramid material having excellent heat resistance and a heat conductive substance, not only heat resistance, chemical resistance and flame retardancy but also electrical characteristics are obtained. And excellent thermal conductivity. Also, since the aramid material is contained in an appropriate amount, the mechanical properties are good and the processing properties are good. Selecting a heat conductive material having a specific shape facilitates sheet formation. By removing the voids by impregnating the composite sheet with a resin, a resin-impregnated composite sheet having excellent heat conductivity can be obtained. Therefore, the composite sheet according to the present invention can be effectively used for a wide range of uses such as insulating materials and substrate materials for electrical and electronic equipment.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments (examples) of the present invention will be described in detail. These examples explain and supplement the gist of the present invention and do not limit the present invention in any way. In the examples, “%” means “% by weight”. (Measurement method) The measured values were evaluated by the following methods. (1) Measurement of the basis weight and thickness of the sheet The measurement was performed according to JIS C2111. (2) Dielectric breakdown voltage This was performed based on ASTM D-149. (3) Tensile strength and elongation The test was performed based on ASTM D-828. (4) Thermal conductivity The thermal conductivity in the direction of thickness was measured using a rapid thermal conductivity meter manufactured by Kyoto Electronics Industry Co., Ltd., and using foamed polyurethane, quartz, silicone rubber, and epoxy resin as standard substances. It was measured by the film method. The thermal conductivity in the in-plane direction was similarly measured by a film method for a test piece cut into a strip shape and joined so that the original test piece was arranged in the thickness direction. (5) Air permeability Implemented in accordance with JIS P8117. The porosity of the paper was evaluated by the time (unit: second) required for 100 cc of air to pass.

Examples 1 and 2 The composite sheet of the present invention and a method for producing the same will be described. In Examples 1 and 2, poly (metaphenyleneisophthalamide) (abbreviated as meta-aramid) is obtained by a method using a wet precipitator composed of a combination of a stator and a rotor described in Japanese Patent Publication No. 52-151624. ) Was manufactured. This was continuously processed in a beater to adjust the Canadian Standard Freeness (CSF) to 105 ml.

On the other hand, Du Pont's meta-aramid fiber "Nomex (registered trademark)" was cut into a length of 6 mm to obtain a papermaking raw material (flock). The fineness (denier) of this floc was 2. On the other hand, alumina fiber “Arsen (registered trademark)” manufactured by Denki Kagaku Kogyo Co., Ltd.
The slurry was prepared by finely pulverizing bulk B97NL1 in water. These fibrid, floc and alumina fibers were mixed at the compounding ratio of each example shown in Table 1 to prepare a composite sheet by a wet papermaking method. Table 1 shows the main characteristic values of the composite sheet thus obtained.

[0029]

[Table 1]

The composite sheet obtained in Example 1 was impregnated with an epoxy resin “Epiform (registered trademark)” by Somar Co., Ltd., and laminated and pressed at 120 ° C. for 15 minutes to produce a resin-impregnated composite sheet. The thermal conductivity in the thickness direction of the resin-impregnated composite sheet was 1.0 W / (mK).

Examples 3 and 4 In the same manner as in Examples 1 and 2, the same fibrid, floc and alumina fibers used in Examples 1 and 2 were used, and the mixing ratio of each component was changed. The composite sheets of Examples 3 and 4 shown in Table 2 were produced. Table 2 shows the main characteristics of the obtained composite sheet.

[0032]

[Table 2]

A resin-impregnated composite sheet was prepared from the composite sheet obtained in Example 3 in the same manner as in Examples 1 and 2. The thermal conductivity in the thickness direction of the resin-impregnated composite sheet was 1.1 W / (mK).

Example 5 A composite prepared by using the same fibrid, floc and heat conductive material stock materials as used in the above-described embodiment at the mixing ratio shown in Table 3 and using the same method as in the above-described embodiment. 2 body sheets
A laminated composite sheet was prepared. Table 3 shows the main characteristics of the obtained composite sheet having a multilayer structure.

[0035]

[Table 3]

In the multilayer composite sheet obtained in Example 5,
"Epicoat (registered trademark)" manufactured by Yuka Shell Epoxy Co., Ltd.
815 "and" Epomate (registered trademark) B002 "in 2:
The mixture at a weight ratio of 1 was impregnated. This is 13
The resin was impregnated at 0 ° C for 15 minutes to obtain a resin-impregnated composite sheet.
The thermal conductivity in the thickness direction of this resin-impregnated composite sheet is 0.5.
It was 9 W / (mK).

Examples 6 and 7 In Example 6, the same fibrid, floc and alumina fibers used in the previous example were used, and a combination papermaking method different from the wet papermaking method used in the aforementioned example was used. Using a press, the mixed stock shown in Table 4 was prepared, and three-layer composite sheets having different constituent ratios of the constituent stocks were produced. As Example 7, a composite sheet obtained by hot-pressing the composite sheet having the three-layer structure prepared in Example 6 was produced. Table 4 shows the main properties of the obtained composite sheet.

[0038]

[Table 4]

The composite sheet obtained in Example 6 was subjected to a resin impregnation operation. First, a resin solution was prepared by adding a curing agent dicyandiamide, a curing accelerator EMI-24, and a dissolution aid methylcellosolve to "Epicoat (registered trademark) E5046B80" manufactured by Yuka Shell Epoxy Co., Ltd. This was impregnated into the composite sheet of Example 6 and then dried at 130 ° C. for 8 minutes. Next, five resin-impregnated composite sheets were laminated, and heated and pressed at 170 ° C. for 60 minutes using a flat plate press to produce a five-layer laminated composite sheet material. The weight fraction of the epoxy resin in the laminated composite sheet material was calculated to be 35%. The density of the laminated composite sheet material was 1.70 g / cm ³ , and the thermal conductivity in the thickness direction was 1 W / (mK). On the other hand, this laminated composite sheet material was bonded in the thickness direction to produce a rectangular parallelepiped. A sample from which the thermal conductivity in the plane direction (XY direction) could be measured was cut out from the rectangular parallelepiped, and the thermal conductivity in the plane direction was measured to be 0.9 W / (mK). As a comparison, when the thermal conductivity in the thickness direction of the glass cloth-epoxy composite plate was measured, it was 0.6 W / (mK), and the effect of improving the thermal conductivity in the plane direction according to the present invention was confirmed. Similarly, the hot-pressed paper obtained in Example 7 is subjected to a resin impregnation operation and a laminating hot-pressing, and is a resin-impregnated composite sheet having a density of 1.65 g / cm ³ and a thermal conductivity in the thickness direction of 1.1 W / (mK). I got
As described above, the present invention has been specifically described based on the embodiments (examples). However, it is needless to say that the present invention is not limited to the above embodiments and can be variously modified without departing from the gist thereof. Nor.

Claims (9)

[Claims] 1. A mixture comprising at least 0 to 90% by weight of aramid fibrid, 0 to 90% by weight of aramid floc and 5 to 100% by weight of a thermally conductive material having an anisotropic shape is formed into a sheet. A composite sheet, wherein the composite sheet is formed. 2. The mixture comprising at least an aramid fibrid, an aramid floc and a plurality of sheet layers formed from a mixture composed of a heat conductive substance having an anisotropic shape, wherein each of the layers forms a respective layer. Aramid fibrid, aramid floc, and a heat conductive material having an anisotropic shape have different composition ratios. At least two or more of the sheet layers have at least one anisotropic shape. A composite sheet having a heat conductive substance content of 70% by weight or more. 3. The composite sheet according to claim 1, wherein the aramid constituting the composite sheet is polymetaphenylene isophthalamide. 4. The composite sheet according to claim 1, wherein the heat conductive substance constituting the composite sheet has an intrinsic thermal conductivity of 10 W / (mK: meter-Kelvin) or more. . 5. A heat conductive material having an anisotropic shape constituting said composite sheet is at least one anisotropic shape selected from aluminum oxide, magnesium oxide, boron nitride, aluminum nitride and beryllium oxide. The composite sheet according to any one of claims 1 to 4, wherein the composite sheet is a heat conductive material having: 6. The composite sheet according to claim 1, wherein the shape of the heat conductive substance having an anisotropic shape constituting the composite sheet is fibrous. 7. A resin-impregnated composite sheet, wherein the composite sheet according to claim 1 is further impregnated with a resin. 8. The method for producing a composite sheet according to claim 1, wherein at least 0 to 90% by weight of aramid fibrid, 0 to 90% by weight of aramid floc and 5 to 100% by weight. % Of a thermally conductive substance having a non-isotropic shape in water by mixing and dispersing in water, followed by papermaking and shaping into a sheet shape. 9. A composite sheet according to claim 1, wherein a circuit for transmitting an electric signal is formed on the surface and / or inside of the resin-impregnated composite sheet further impregnated with a resin. And printed wiring board.