JP2017145431A - Manufacturing method of composite of metal and carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a composite of a metal and a carbon fiber capable of uniformizing physical properties in a plane direction of the composite.SOLUTION: A manufacturing method of a composite of a metal and a carbon fiber has a process for obtaining a coating foil having a carbon fiber layer 11 formed on a surface 10a of a metal foil 10 by coating the surface 10a of the metal foil 10 with a coating liquid 5 containing the carbon fiber, a binder and a solvent for binder with a mixed state by a gravure printing method and drying, a process for forming a laminate with a state that a plurality of coating foils are laminated and a process for conjugation uniformizing the coating foils by heating the laminate with pressuring in a lamination direction of the coating foil. In the process for obtaining the coating foil, the coating liquid 5 is coated by the gravure printing method so that the carbon fiber layer 11 becomes a void state and dried.SELECTED DRAWING: Figure 3A

Description

  The present invention relates to a method for producing a composite material of metal and carbon fiber.

  In the present specification and claims, the term “aluminum” is used to include both pure aluminum and aluminum alloys, unless otherwise specified, and the term “copper” is also specifically indicated. Except in some cases, it is meant to include both pure copper and copper alloys.

  As a metal, for example, a composite material of aluminum and a carbon material has been studied as a material that improves the heat dissipation of aluminum and controls the linear expansion coefficient.

  As a method for producing this composite material, a method of mixing carbon fiber as a carbon material into molten aluminum and stirring and mixing (a molten metal stirring method), a method of pushing molten aluminum into a carbon molded body having voids (a molten metal forging method), Known are a method of mixing aluminum powder and carbon powder and baking under pressure (powder metallurgy method), a method of mixing aluminum powder and carbon powder and extruding (powder extrusion method), and the like.

  However, in these methods, since molten aluminum or aluminum powder is used, the manufacturing operation is complicated and the manufacturing equipment is large.

  Japanese Patent Laid-Open No. 59-76840 (Patent Document 1) discloses that a precursor molded product (prepreg) is manufactured by bonding or bonding inorganic whiskers to a metal surface of a metal thin plate with an organic binder. A method of manufacturing a reinforced metal material by laminating a plurality of layers and heating and pressing them is disclosed.

  Japanese Patent No. 5150905 (Patent Document 2) prepares a coating mixture by mixing carbon fiber with an organic binder and a solvent, and then deposits the coating mixture on a sheet-like or foil-like metal support. Forming a preform foil (coating foil), then stacking multiple preform foils to form a laminate, and then heat-pressing the laminate to integrate the preform foils together with the metal and carbon fiber Discloses a method for producing a metal-based carbon fiber composite material as a composite material.

  Other documents disclosing a method for producing a composite material of metal and carbon fiber include Japanese Patent No. 5145591 (Patent Document 3) and Japanese Patent Application Laid-Open No. 2015-25158 (Patent Document 4).

  In the manufacturing methods disclosed in Patent Documents 2 to 4, a composite material of metal and carbon fiber is obtained, which is integrally joined in a state where a plurality of metal layers and carbon fiber layers are alternately laminated.

JP 59-76840 A Japanese Patent No. 5150905 Japanese Patent No. 5145591 Japanese Patent Laying-Open No. 2015-25158

  Thus, in the method for manufacturing a composite material disclosed in Patent Document 1, if the inorganic whisker layer bonded or adhered to the metal surface of the metal thin plate is too thick, the metal of the metal thin plate is sufficiently contained in the inorganic whisker layer. The strength of the composite material is low because it cannot penetrate and voids are formed in the inorganic whisker layer, and the metal thin plates placed on both sides of the inorganic whisker layer are not joined to each other. It was.

  The composite materials disclosed in Patent Documents 2 to 4 have the following drawbacks.

  Here, in the present specification, in the composite material, a plane perpendicular to the stacking direction of the metal layer and the carbon fiber layer is referred to as a “plane of the composite material”, and the stacking direction of the metal layer and the carbon fiber layer. The vertical plane direction is referred to as “the plane direction of the composite material”.

  In the composite material, when the fiber directions of the carbon fibers in the carbon fiber layer are aligned in one direction within the plane of the composite material, that is, when the carbon fibers are oriented in one direction, the linear expansion coefficient, heat conduction The physical properties of the composite material, such as the rate, greatly differ between the fiber direction of the carbon fiber (that is, the orientation direction of the carbon fiber) in the plane of the composite material and the direction perpendicular thereto. Therefore, there has been a drawback that the composite material is easily distorted when the composite material is heated.

  Therefore, it is conceivable to form a laminate by stacking a plurality of preform foils so that the fiber directions of the carbon fibers are alternately perpendicular.

  However, in this method, the preform foil has to be laminated while taking into account the fiber direction of the carbon fiber, so the lamination work of the preform foil is troublesome. Moreover, the physical properties (eg, linear expansion coefficient) in the oblique direction (eg, 45 ° direction) with respect to the fiber direction of the carbon fiber in the plane of the composite material are the same as the physical properties of the carbon fiber and the direction perpendicular thereto. It was difficult to do.

  The present invention has been made in view of the above-described technical background, and an object of the present invention is to provide a method for producing a composite material of metal and carbon fiber that can achieve uniform physical properties in the planar direction of the composite material. It is in.

  The present invention provides the following means.

[1] A coating liquid containing carbon fiber, a binder, and the binder solvent in a mixed state is applied to the surface of the metal foil by a gravure printing method and dried, so that the carbon fiber is formed on the surface of the metal foil. Obtaining a coated foil with a layer formed;
Forming a laminate in which a plurality of the coating foils are laminated;
Removing the binder from the laminate by heating the laminate, and joining and integrating the coating foil by heating while pressing the laminate in the laminating direction of the coating foil; Comprising
In the step of obtaining the coating foil, a method for producing a composite material of metal and carbon fiber, in which the coating liquid is applied by a gravure printing method so that the carbon fiber layer is in a white state, and is dried.

  The present invention has the following effects.

  In the preceding item [1], coating is performed by applying a coating liquid on the surface of the metal foil, forming a laminate in which a plurality of coating foils are laminated, and pressurizing and heating the laminate. By adopting that the foils are joined and integrated, a composite material of metal and carbon fiber can be manufactured at low cost and in large quantities.

  Furthermore, in the step of joining and integrating the coating foil, the thermal conductivity of the resulting composite material can be reliably increased by removing the binder from the laminate.

  Furthermore, in the process of obtaining the coating foil, the carbon fiber layer is formed on the surface of the metal foil by applying the coating liquid by a gravure printing method so that the carbon fiber layer is in a whitened state and drying it. A large number of carbon fibers in each halftone dot are arranged in a substantially annular shape (substantially annual ring shape) around the bubble bleed part formed at the center of the halftone dot in a direction surrounding the bleed part. Such a substantially annular arrangement of carbon fibers is generated in each of a large number of halftone dots present on the surface of the metal foil, and as a result, the degree of orientation of the carbon fibers is reduced over the entire surface of the metal foil. Thereby, the physical properties in the planar direction of the composite material can be made uniform.

  In addition, it is not necessary to consider the fiber direction of the carbon fibers when forming the laminate, and this makes it possible to easily achieve uniform physical properties in the plane direction of the composite material.

FIG. 1 is a flowchart showing a method for manufacturing a composite material of metal and carbon fiber according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a process of obtaining a coating foil. FIG. 3A is a schematic cross-sectional view in the case of this embodiment showing the state of the carbon fiber layer formed on the surface of the strip of metal foil in time series. FIG. 3B is a schematic cross-sectional view in the case of the reference form showing the state of the carbon fiber layer formed on the surface of the strip of metal foil in time series. FIG. 4 is a schematic plan view showing an arrangement state of the carbon fibers in the halftone dots constituting the carbon fiber layer in the present embodiment. FIG. 5 is a schematic view when the strip of the coating foil is cut. FIG. 6 is a schematic side view of a laminate formed by laminating a plurality of coating foils. FIG. 7 is a schematic diagram for explaining a step of sintering and integrating the coating foil. FIG. 8 is a schematic side view of the composite material of the present embodiment obtained by sintering and integrating the coating foil. FIG. 9 is a perspective view of the composite material showing various directions defined by the composite material of the present embodiment (example). FIG. 10 is a photomicrograph of the surface of the strip of coated foil of the example.

  Next, an embodiment of the present invention will be described below with reference to the drawings.

  The manufacturing method of the composite material (composite body) of the metal and carbon fiber which concerns on one Embodiment of this invention, as shown in FIG. 1, process S1 which obtains coating foil, process S2 which forms a laminated body, Step S3 for integrating the coating foil by sintering, and these steps are performed in the order of this description.

  The step S1 of obtaining the coating foil will be described in detail as shown in FIG. 2. When the coating liquid 5 is applied to the surface 10a of the strip 10A of the metal foil 10 by a gravure printing method and dried, a metal is obtained. This is a step of obtaining a strip-shaped strip 14A of the coating foil 14 in which the carbon fiber layer 11 is formed on the surface 10a of the strip 10A of the foil 10. The coating liquid 5 contains the carbon fiber 1, the binder 2, and the binder 2 solvent 3 in a mixed state.

  Step S2 of forming the laminate 15 is a step of forming the laminate 15 in a state where a plurality of coating foils 14 are laminated as shown in FIG.

  As shown in FIG. 7, the step S3 of sintering and integrating the coating foil 14 is performed by heating the laminated body 15 while pressing it in the laminating direction of the coating foil 14 (that is, the thickness direction of the laminated body 15). This is a step of integrating the coating foil 14 by sintering. This process S3 includes process S3a which removes the binder 2 from the laminated body 15 by heating the laminated body 15 (refer FIG. 1).

  In addition, process S3 which sinter-integrates the coating foil 14 is equivalent to the desirable example about the process of joining and integrating the coating foil 14 described in the claim.

  In the composite material 17 obtained in this embodiment, as shown in FIG. 8, the metal layers formed of the metal foil 10 and the carbon fiber layers (shown by dot hatching) 11 mainly composed of a large number of carbon fibers 1 are alternately arranged. In the state where a plurality of layers are laminated, they are sintered and integrated. A part of the metal of the metal foil 10 penetrates into the carbon fiber layer 11.

  Since the composite material 17 contains the carbon fiber 1, the linear expansion coefficient in the planar direction of the composite material 17 is about the middle between metal and ceramic. Therefore, the composite material 17 includes a buffer layer disposed between the insulating ceramic layer and the metal wiring layer in the electronic module insulating substrate such as the power module substrate (this layer is referred to as a “first buffer layer” for convenience of description). And / or preferably used as a material for a buffer layer (this layer is referred to as a “second buffer layer” for convenience of description) disposed between the insulating ceramic layer and the metal cooling layer (including the metal heat dissipation layer). Is possible.

  Furthermore, the composite material 17 can be regarded as a metal matrix composite material reinforced with the carbon fiber 1 and has high heat dissipation and high Young's modulus. Therefore, the composite material 17 can be suitably used as a material for a member that requires high mechanical strength (eg, bending strength).

  Next, each step will be described in detail below.

<Step S1 for obtaining coating foil 14>
The coating liquid 5 used in this step S1 is obtained as follows, for example. As shown in FIG. 2, a large number of carbon fibers 1, a binder 2, and a binder 2 solvent 3 are placed in a mixing container 41, and these are stirred and mixed by a stirring and mixing device 42. Thereby, the coating liquid 5 which contains the carbon fiber 1, the binder 2, and the solvent 3 in the mixed state is prepared. At this time, a dispersing agent, an antifoaming agent, a surface adjusting agent, a viscosity adjusting agent, etc. are also put in the mixing container 41 as needed, and are stirred and mixed together with the carbon fiber 1, the binder 2 and the solvent 3, and the coating solution 5 You may make it contain.

  Specific descriptions of the carbon fiber 1, the binder 2, and the solvent 3 will be described later.

  The gravure coating apparatus 20 (for example, gravure coater) used for coating the coating liquid 5 by the gravure printing method is a direct gravure coating apparatus (for example: direct gravure coater) in detail, and a gravure roll 21 A backup roll 24, a coating liquid pan 26 containing the coating liquid 5, and the like.

  A large number of gravure cells (hereinafter referred to as “cells”) are arranged on the peripheral surface 21 a of the gravure roll 21 in an orderly manner. The backup roll 24 is disposed to face the gravure roll 21.

  The carbon fibers 1 in the coating liquid 5 in the pan 26 are dispersed in the coating liquid 5 so that the fiber directions are random. A part of the circumferential surface 21 a of the gravure roll 21 in the circumferential direction is immersed in the coating liquid 5 in the pan 26.

  In the gravure coating apparatus 20 shown in FIG. 2, the strip 10A of the metal foil 10 unwound from the unwinding roll 27a is between the gravure roll 21 and the backup roll 24, and a drying furnace 28 as a heating and drying apparatus. After passing through the inside at a predetermined feed rate in a substantially horizontal direction, the paper is taken up by a take-up roll 27b.

  The feed direction F of the strip 10A of the metal foil 10 is set to the longitudinal direction of the strip 10A of the metal foil 10, and the direction parallel to the feed direction F is the gravure coating device 20 (more specifically, the gravure coating device). 20 is a coating direction (printing direction) of the coating liquid 5 on the surface 10a of the strip 10A of the metal foil 10 by the gravure roll 21).

  In the present embodiment, the gravure roll 21 is disposed below the strip 10A of the metal foil 10 so as to traverse the strip 10A of the metal foil 10 over the entire width direction, and the backup roll 24 is The strip 10A of the metal foil 10 is arranged on the upper side of the strip 10A of the metal foil 10 so as to traverse the entire width direction. Therefore, the surface 10a of the strip 10A of the metal foil 10 to which the coating solution 5 is applied is the lower surface of the strip 10A of the metal foil 10 in detail.

  In the present invention, the surface 10a of the strip 10A of the metal foil 10 to which the coating solution 5 is applied is not limited to the lower surface of the strip 10A of the metal foil 10, and other examples include The upper surface of the strip 10A of the metal foil 10 may be used.

  The coating liquid 5 is applied when the strip 10 </ b> A of the metal foil 10 passes between the gravure roll 21 and the backup roll 24. That is, by rotating the gravure roll 21, the coating liquid 5 in the pan 26 adheres to the peripheral surface 21 a of the gravure roll 21 and the coating liquid 5 is filled in each cell 22. And the excess coating liquid 5 adhering to the peripheral surface 21a of the gravure roll 21 is scraped off by a doctor blade (scraper) 25, and then the peripheral surface 21a of the gravure roll 21 is the surface 10a of the strip 10A of the metal foil 10. , The coating liquid 5 in the cell 22 is transferred to the surface 10a of the strip 10A of the metal foil 10. As a result, a carbon fiber layer 11 composed of a large number of halftone dots 12 is formed on the entire surface 10a of the strip 10A of the metal foil 10 over the entire surface 10a. Thereby, the strip 14A of the coating foil 14 in which the carbon fiber layer 11 is formed on the surface 10a of the strip 10A of the metal foil 10 is obtained. The halftone dot 12 is made of the coating liquid 5 in the transferred cell 22.

  The rotation direction of the gravure roll 21 is normally set in the same direction as the feed direction F of the strip 10 </ b> A of the metal foil 10. The peripheral speed of the gravure roll 21 is normally set equal to the feed speed of the strip 10 </ b> A of the metal foil 10.

  The drying furnace 28 heats and drys the carbon fiber layer 11 formed on the surface 10a of the strip 10A of the metal foil 10 (that is, the carbon fiber layer 11 of the strip 14A of the coating foil 14), thereby heating the carbon fiber layer 11. Is for evaporating and removing the solvent 3 contained in the carbon fiber layer 11.

  In the gravure roll 21 of the gravure coating apparatus 20, the shape of the cell 22 is cup-shaped, and in particular, it is desirable that the periphery of the cell 22 is substantially closed over the entire circumference. Specifically, the shape of the cell 22 is desirably a lattice type, a pyramid type, a turtle shell type, or a circular type.

  Further, the shape of the bottom surface of the cell 22 is not limited, and may be flat, concave curved surface (eg, concave spherical shape), or concave conical surface (eg, concave pyramid surface). Or a concave conical surface shape).

  Regarding the size of the cell 22, the diameter of a circle inscribed in the mouth shape of the cell 22 (specifically, a circle inscribed in the opening periphery of the cell 22) is set larger than the average fiber length of the carbon fibers 1.

  The carbon fiber 1 can be used as long as it is a fibrous carbon particle, and specifically includes, for example, a PAN-based carbon fiber, a pitch-based carbon fiber, and a carbon nanofiber (eg, vapor-grown carbon fiber, carbon nanotube). One kind of carbon fiber selected from the group or two or more kinds of mixed carbon fibers are used.

  The length of the carbon fiber 1 is not limited, and it is particularly desirable that the average fiber length of the carbon fiber 1 is 1 mm or less.

  The binder 2 gives the carbon fiber 1 adhesion to the surface 10 a of the strip 10 </ b> A of the metal foil 10, whereby the carbon fiber 1 in the carbon fiber layer 11 falls off from the surface 10 a of the strip 10 </ b> A of the metal foil 10. This is to suppress the operation. In the present embodiment, the binder 2 is made of resin.

  Furthermore, when the binder 2 is heated, it easily becomes an organic sintered residue or an amorphous carbide, which becomes a factor of lowering the thermal conductivity of the composite material 17 as a residue of the binder 2. Therefore, it is desirable to use a binder 2 that disappears by decomposition or sublimation without carbonizing at a temperature of 300 ° C. to 550 ° C. in a non-oxidizing atmosphere. As such a binder 2, an acrylic resin, a polyethylene glycol resin, a butylene rubber resin, a phenol resin, a cellulose resin, or the like is preferably used. These binders 2 are generally solid at room temperature.

  The solvent 3 is desirably one that dissolves the binder 2 at room temperature, and water, alcohol solvents, hydrocarbon solvents, ester solvents, ether solvents, and the like are preferably used.

  The coating liquid 5 preferably contains the carbon fiber 1 and the binder 2 in a mass ratio of 75:25 to 99.5: 0.5. In this case, the carbon fiber 1 can be reliably attached to the surface 10a of the strip 10A of the metal foil 10 in the step S1 of obtaining the coating foil 14, and the binder 2 is surely attached in the step S3a of removing the binder 2. Can be eliminated. It is particularly desirable that the coating liquid 5 contains the carbon fiber 1 and the binder 2 in a mass ratio of 80:20 to 99: 1.

In the step S1 of obtaining the coating foil 14, the coating amount of the coating liquid 5 on the surface 10a of the strip 10A of the metal foil 10 is not limited. For example, the carbon fiber 1 included in the carbon fiber layer 11 is not limited. The coating amount is set to 40 g / m ² or less (preferably 30 g / m ² or less).

  Further, the coating liquid 5 is applied to the surface 10 a of the strip 10 </ b> A of the metal foil 10 so that the volume of the carbon fiber 1 in the obtained composite 17 is 50% or less with respect to the total volume of the composite 17. In this way, the metal of the metal foil 10 can be reliably infiltrated into the carbon fiber layer 11 in the step S3 of sintering and integrating the coating foil 14, and the coating foil 14 can be securely and firmly Sintering can be integrated.

  Furthermore, when the metal foil 10 is an aluminum foil, the volume of the carbon fiber 1 is desirably 10% or more with respect to the total volume of the composite material 17, and thereby the thermal conductivity of the composite material 17 is 250 W / ( m · K) or more, and can be reliably differentiated from the thermal conductivity of aluminum (about 225 W / (m · K)).

  Here, when the composite material 17 is used as the material of the first buffer layer of the insulating substrate described above, the linear expansion coefficient in the planar direction of the composite material 17 is equal to the linear expansion coefficient of the insulating ceramic layer and the metal wiring layer (example: It is desirable to set the ratio of the volume of the metal foil 10 and the volume of the carbon fiber 1 so as to be an intermediate value between the linear expansion coefficient of the aluminum wiring layer and the copper wiring layer. When the composite material 17 is used as the material of the second buffer layer of the insulating substrate described above, the linear expansion coefficient in the planar direction of the composite material 17 is equal to the linear expansion coefficient of the insulating ceramic layer and the metal cooling layer (eg, aluminum). It is desirable to set the ratio of the volume of the metal foil 10 and the volume of the carbon fiber 1 so as to be an intermediate value between the linear expansion coefficient of the cooling layer and the copper cooling layer.

In the case where the metal foil 10 is an aluminum foil, for example, the linear expansion coefficient in the planar direction of the composite material 17 is used as a ceramic (aluminum nitride, alumina, silicon carbide, etc.) wire often used as a material for the insulating ceramic layer. An expansion coefficient (eg, about 3 × 10 ⁻⁶ / K to about 5 × 10 ⁻⁶ / K) and a linear expansion coefficient (about 23 × 10 ⁻⁶ / K) of aluminum often used as a material for the metal cooling layer; In order to obtain an intermediate value (approximately 10 × 10 ⁻⁶ / K to approximately 16 × 10 ⁻⁶ / K), the volume of the carbon fiber 1 is set in a range of 30% to 60% with respect to the total volume of the composite material 17. It is desirable to set.

  The metal foil 10 (the strip 10A of the metal foil 10) is not limited to that material as long as it can withstand coating. In particular, the metal foil 10 is desirably at least one of an aluminum foil and a copper foil. The reason is that the composite material 17 having a high thermal conductivity can be obtained with certainty.

  When the metal foil 10 is an aluminum foil, the material of the aluminum foil is not limited, and A1000 series, A3000 series, A6000 series, and the like are used. In general, the material of the aluminum foil is appropriately selected from a plurality of types of aluminum materials so that the physical properties (thermal conductivity, linear expansion coefficient, strength, etc.) of the obtained composite material 17 are set to desired values.

  When the metal foil 10 is a copper foil, the type and material of the copper foil are not limited, and an electrolytic copper foil, a rolled copper foil, and the like are used. In general, the material of the copper foil is appropriately selected from a plurality of types of copper materials so that the physical properties of the obtained composite material 17 are set to desired values.

  The thickness of the metal foil 10 is not limited, and the thickness of the metal foil 10 can be selected so that the physical properties of the obtained composite material 17 become a desired set value.

  Here, since the thinnest thickness of the commercially available metal foil 10 (eg, aluminum foil, copper foil) is 6 μm, the lower limit of the thickness of the metal foil 10 is 6 μm. It is particularly desirable in that it is readily available. The upper limit of the thickness of the metal foil 10 is usually 100 μm, and is preferably about 50 μm.

  The carbon fiber layer 11 is dried when the strip 14A of the coating foil 14 passes through the drying furnace 28 as shown in FIG. That is, when the strip 14A of the coating foil 14 passes through the drying furnace 28, the carbon fiber layer 11 is heated and dried by the drying furnace 28, whereby the solvent 3 contained in the carbon fiber layer 11 is changed to the carbon fiber layer. 11 and the binder 2 contained in the carbon fiber layer 11 is cured. Thereafter, the strip material 14A of the coating foil 14 is wound around the winding roll 27b.

  The drying conditions are not limited as long as the solvent 3 contained in the carbon fiber layer 11 can be removed from the carbon fiber layer 11 by evaporation. Usually, the drying temperature is 60 ° C. to 250 ° C. and the drying time is 1 min to A drying condition of 120 min is applicable.

  Here, in this embodiment, in the process S1 of obtaining the coating foil 14, the coating liquid 5 is applied by a gravure printing method using the gravure coating apparatus 20 so that the carbon fiber layer 11 is in a white-out state, It needs to be dried. This step S1 will be described below with reference to FIGS. 3A and 3B.

  FIG. 3A is a schematic cross-sectional view in the case of this embodiment showing the state of the carbon fiber layer 11 formed on the surface 10a of the strip 10A of the metal foil 10 in time series.

  FIG. 3B is a schematic cross-sectional view in the case of the reference form showing the state of the carbon fiber layer 111 formed on the surface 110a of the strip 110A of the metal foil 110 in time series. The case of the reference form means a case where the coating liquid 5 is applied by a gravure printing method and dried so that the carbon fiber layer 111 is not whitened.

  3A (a) and FIG. 3B (a) are schematic cross-sectional views of portions of cells 22 and 122 on the peripheral surfaces of gravure rolls 21 and 121 of the gravure coating apparatus, respectively.

  FIGS. 3A (b) and 3B (b) are schematic cross-sectional views showing a state in which the coating liquid 5 is filled in the cells 22 and 122, respectively.

  3A (c) and FIG. 3B (c) are schematic cross-sectional views in a state where the peripheral surfaces of the gravure rolls 21 and 121 are in contact with the surfaces 10a and 110a of the strips 10A and 110A of the metal foils 10 and 110, respectively. is there.

  3A (d) and FIG. 3B (d) show carbon fibers by transferring the coating liquid 5 in the cells 22 and 122 to the surfaces 10a and 110a of the strips 10A and 110A of the metal foils 10 and 110, respectively. It is a schematic sectional drawing in the state where layers 11 and 111 were formed. In these drawings, the strips 10A and 110A of the metal foils 10 and 110 are shown upside down.

  3A (e1) to (e3) are schematic cross sections of an initial state, a middle state, and a late state, respectively, in which the carbon fiber layer 11 on the surface 10a of the strip 10A of the metal foil 10 is heated and dried in the case of the embodiment. FIG. FIG. 3B (e) is a schematic cross-sectional view showing a state in which the carbon fiber layer 111 on the surface 110a of the strip 110A of the metal foil 110 is heated and dried in the case of the reference embodiment.

  First, the case of the reference form shown in FIG. 3B (that is, the case where the coating liquid 5 is applied by a gravure printing method and dried so that the carbon fiber layer 110 is not whitened) will be described below.

  3B (a) and (b), in the state where the coating liquid 5 is filled in the cell 122 of the gravure roll 121, the surface of the coating liquid 5 in the cell 122 is flat and the cell The surface of the partition wall 123a is substantially flush with the surface 123a. In this state, as shown in FIG. 3B (c), the peripheral surface of the gravure roll 121 (more specifically, the surface 123a of the cell partition wall 123) abuts on the surface 110a of the strip 110A of the metal foil 110 to apply the coating in each cell 122. When the working liquid 5 is transferred, a carbon fiber layer 111 composed of a large number of halftone dots 112 is formed on the surface 110a of the strip 110A of the metal foil 110 as shown in FIG. 3B (d). The halftone dot 112 is made of the coating liquid 5 in the transferred cell 122 as described above, and contains a large number of carbon fibers (not shown), a binder, and a solvent. Then, the carbon fiber layer 111 is heated and dried in a drying furnace, whereby the solvent is removed by evaporation from the carbon fiber layer 111 and the binder in the carbon fiber layer 111 is cured. In this drying step, as shown in FIG. 3B (e), the shape of each halftone dot 112 constituting the carbon fiber layer 111 is hardly changed, and the carbon fiber layer 111 is not in a blank state.

  Next, the case of the present embodiment shown in FIG. 3A (that is, the case where the coating liquid 5 is applied by the gravure printing method so that the carbon fiber layer 11 is in a white state and dried) will be described below. .

  In order to ensure that the carbon fiber layer 11 is in a blank state, it is desirable to set the cell 22 of the gravure roll 21 to be large and / or to set the viscosity of the coating solution 5 to be small.

  Therefore, as shown in FIG. 3A (a), a gravure roll 21 having a large opening diameter of each cell 22 (more specifically, a diameter of a circle inscribed in the opening periphery of each cell 22) is used as the gravure roll. Then, as shown in FIG. 3A (b), the coating liquid 5 having a small viscosity is filled in each cell 22 of the gravure roll 21, so that the surface of the coating liquid 5 in each cell 22 is the center thereof. The part is in a recessed state.

  In this state, when the peripheral surface of the gravure roll 21 (more specifically, the surface 23a of the cell partition wall 23) abuts on the surface 10a of the strip 10A of the metal foil 10, as shown in FIG. Bubbles 13 are generated between the center of the surface of the coating liquid 5 and the surface 10a of the strip 10A of the metal foil 10. Then, when the coating liquid 5 in each cell 22 is transferred to the surface 10a of the strip 10A of the metal foil 10, each halftone dot on the surface 10a of the strip 10A of the metal foil 10 is shown in FIG. 12 is a state in which the bubble 13 is involved in the central portion of the contact portion between the metal foil 10 and the surface 10a of the strip 10A.

  When the carbon fiber layer 11 is heated and dried in this state, as shown in FIG. 3A (e1), the solvent is evaporated and removed from the carbon fiber layer 11, and the bubbles 13 in each halftone dot 12 are repelled to cause each halftone dot 12 to appear. A concave bubble-repelling portion 13a is formed at the center of the surface. As the carbon fiber layer 11 is heated and dried, as shown in FIG. 3A (e2), the bubble-repelling portion 13a of each halftone dot 12 has a large number of carbon fibers (not shown) in the halftone dot 12 from the center of the halftone dot 12. 3) (e3) is pushed outward and finally spreads, and as shown in FIG. 3A (e3), finally, a substantially circular bubble splashing portion 13a is formed at the center of each halftone dot 12. As a result, as shown in FIG. 4, a large number of carbon fibers 1 in each halftone dot 12 are surrounded by the bubble splashing portion 13a (that is, the outer peripheral portion of the halftone dot 12) in a direction surrounding the bubble splashing portion 13a (that is, They are arranged in a substantially annular shape (substantially annual ring shape) in the circumferential direction of the halftone dots 12. And the binder in each halftone dot 12 hardens | cures in this arrangement | sequence state.

  As shown in the figure, in each halftone dot 12, a carbon bubble 1 is formed at the center of the halftone dot 12, so that almost no carbon fiber 1 is present, and a large number of carbon fibers 1 are air bubbles. Since the bubbles are arranged in a substantially annular shape in the direction surrounding the repelling part 13a around the repelling part 13a, when the halftone dot 12 is magnified and observed with a microscope, the halftone dot 12 looks like Baumkuchen.

  The opening diameter of each cell 22 is about several millimeters, and the diameter of the bubble-repelling portion 13a of the halftone dot 12 is slightly smaller than or equal to the opening diameter of the cell 22. Then, on the surface 10a of the strip 10A of the metal foil 10, a large number of carbon fibers 1 in the halftone dots 12 are arranged in a substantially annular shape around the bubble repellency portion 13a for each of the large number of halftone dots 12. Therefore, the carbon fibers 1 are arranged so as to form a large number of small polka dots on the entire surface 10a of the strip 10A of the metal foil 10 (see an example described later and FIG. 10). As a result, the degree of orientation of the carbon fibers 1 is reduced over the entire surface 10a of the strip 10A of the metal foil 10.

  Then, the strip 14A of the coating foil 14 comes out of the drying furnace 28 in such an orientation state of the carbon fibers 1 and is wound around the winding roll 27b.

<Step S2 of Forming Laminate 15>
In step S <b> 2 for forming the laminated body 15, as shown in FIG. 5, the strip material 14 </ b> A of the coating foil 14 unwound from the winding roll 27 b is cut into a predetermined shape by a cutting machine 29. As a result, a plurality of coating foils 14 having a predetermined shape (eg, substantially rectangular shape) are cut out from the strip 14A of the coating foil 14. And as shown in FIG. 6, the laminated body 15 of the state by which the coating foil 14 was laminated | stacked by forming a plurality of coating foils 14 is formed. Alternatively, although not shown, even when a strip 14A of the coating foil 14 unwound from the winding roll 27b is wound into a roll shape, a laminate in which a plurality of coating foils 14 are stacked is formed. good.

  Although the cutting method of the strip 14A of the coating foil 14 is not limited, it is desirable that the strip can be cut without damaging the coated surface of the strip 14A of the coating foil 14.

  The laminated body 15 thus formed is used as a preform (sintered material).

  The number of coating foils 14 to be stacked is not limited, and is set according to the desired thickness of the composite material 17, for example, 5 to 1000 sheets.

<Step S3 of sintering and integrating the coating foil 14>
In step S3 for integrating the coating foil 14 by sintering, as shown in FIG. 7, the laminate 15 is disposed in a sintering chamber 31 of a sintering apparatus (joining apparatus) 30 such as a pressure heating sintering apparatus. The laminate 15 is heated at a predetermined sintering temperature while being pressed in the lamination direction of the coating foil 14 (that is, the thickness direction of the laminate 15) in a predetermined sintering atmosphere by the sintering device 30. The laminated body 15 is sintered, that is, the coating foil 14 is sintered and integrated. Thereby, as shown in FIG. 8, the composite material 17 of this embodiment is obtained.

  In this step S3, the laminate 15 is pressurized and heated, so that the carbon fiber layer 11 is compressed in the thickness direction, and a part of the metal of the metal foil 10 penetrates into the carbon fiber layer 11 to form carbon. The fine voids (for example, the gaps between the carbon fibers 1 in the carbon fiber layer 11) existing in the fiber layer 11 are filled, and the voids substantially disappear. Thereby, the density of the composite material 17 obtained can be 95% or more of the theoretical density of the composite material 17.

  The theoretical density of the composite material 17 is the density of the composite material 17 when the composite material 17 is formed only of the metal of the metal foil 10 and the carbon fiber 1 and there is no void inside the composite material 17. Means.

  As the sintering apparatus 30, a hot press apparatus, a discharge plasma sintering apparatus, etc. are used suitably. When using a hot press apparatus, sintering is performed by vacuum hot press or hot press with nitrogen replacement.

  The pressurization to the laminated body 15 is performed by, for example, pressing the laminated body 15 with a pair of punches 32 and 32 provided in the sintering apparatus 30.

  The sintering atmosphere is preferably a non-oxidizing atmosphere. The non-oxidizing atmosphere includes an inert gas atmosphere (eg, nitrogen gas atmosphere, argon gas atmosphere), a vacuum atmosphere, and the like.

  The sintering temperature means a temperature at which the coating foil 14 is sintered and integrated (joined and integrated). Specifically, the sintering temperature is set to a temperature equal to or lower than the melting point of the metal of the metal foil 10, and in particular, set to a temperature between the melting point of the metal of the metal foil 10 and a temperature about 50 ° C. lower than the melting point. It is desirable that the coating foil 14 can be sintered and integrated reliably and reliably. When the metal foil 10 is, for example, an aluminum foil, the sintering temperature is desirably set in the range of 550 ° C to 620 ° C.

  The pressure applied to the stacked body 15 is not limited, and may be a pressure that lightly presses the stacked body 15. Furthermore, since the fluidity of the metal of the metal foil 10 may be improved when the laminate 15 is pressurized when heated to the laminate 15, the metal of the metal foil 10 is removed from the laminate 15 by the pressurization to the laminate 15. It is particularly desirable to pressurize with a pressing force that does not flow out, or pressurize the laminated body 15 in a mold (not shown) so that the metal of the metal foil 10 does not flow out of the laminated body 15.

  If the coating foil 14 is sintered and integrated with a gap remaining between the coating foils 14, the gap portion becomes an internal defect of the composite material 17. Therefore, in order to suppress the occurrence of this defect, it is desirable to pressurize the laminate 15 as a sintering atmosphere in a vacuum atmosphere and / or pressurize the laminate 15 in the mold.

  In this embodiment, the decomposition temperature of the binder 2 is lower than the sintering temperature, and the step S3a for removing the binder 2 is the initial stage of the laminate 15 in the step S3 for sintering and integrating the coating foil 14 by the sintering device 30. This is performed by the sintering apparatus 30 while heating from about room temperature as the temperature to the sintering temperature.

  That is, in the step S3 of integrating the coating foil 14 by sintering, the laminate 15 in the middle of heating the laminate 15 by the sintering device 30 so that the temperature of the laminate 15 rises from about room temperature to the sintering temperature. When the temperature is the decomposition temperature of the binder 2, the binder 2 is decomposed and removed from the laminate 15 (specifically, the carbon fiber layer 11 of each coating foil 14 of the laminate 15).

  The binder removal method will be specifically described as follows.

  When the laminate 15 is sintered in a vacuum atmosphere, for example, the binder 2 can be reliably secured by setting the heating rate when heating the laminate 15 from approximately room temperature to the sintering temperature to 50 ° C./min or less. It can be decomposed and removed. Here, when the total amount of the binder 2 contained in the laminate 15 is large, or when the size of the laminate 15 is large, the temperature is raised when the temperature of the laminate 15 is the decomposition temperature of the binder 2. It is possible to surely remove the binder 2 by once stopping or slowing the heating rate.

  Thus, the number of manufacturing steps of the composite material 17 is reduced by performing the step S3a for removing the binder 2 while heating the laminate 15 in the step S3 for sintering and integrating the coating foil 14 to the sintering temperature. The composite material 17 can be easily manufactured.

  In addition, this invention does not exclude that process S3a which removes binder 2 is performed independently from process S3 which sinter-integrates the coating foil 14 with the sintering apparatus 30 (joining integration). In this case, the step S3a for removing the binder 2 may be performed after the step S2 for forming the laminated body 15 and before the step S3 for sintering and integrating (joining integration) the coating foil 14. desirable.

  The manufacturing method of the composite material 17 of this embodiment has the following advantages.

  In the process S1 of obtaining the coating foil 14, the coating liquid 5 is applied by the gravure printing method using the gravure coating apparatus 20 so that the carbon fiber layer 11 is in a white-out state, and is dried. On the surface 10a of the strip 10A of the metal foil 10, a large number of carbon fibers 1 in each halftone dot 12 constituting the carbon fiber layer 11 have a halftone dot 12 as shown in FIG. 3A (e3) and FIG. The air bubbles formed in the center are arranged in a substantially annular shape (substantially annual ring shape) around the repelling portion 13a in a direction surrounding the repelling portion 13a. Such a substantially annular arrangement of the carbon fibers 1 is generated in each of a large number of halftone dots 12 existing on the surface 10 a of the strip 10 </ b> A of the metal foil 10. As a result, the fiber direction of the carbon fiber 1 becomes messy on the entire surface 10a of the strip 10A of the metal foil 10, and the degree of orientation of the carbon fiber 1 decreases. Therefore, the physical properties (thermal conductivity, linear expansion coefficient, strength, etc.) in the planar direction of the composite material 17 can be made uniform.

  In addition, it is not necessary to consider the fiber direction of the carbon fiber 1 when forming the laminate 15, thereby making it possible to easily equalize the physical properties of the composite material 17 in the planar direction.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention.

  In the present invention, the metal foil to which the coating solution is applied in the step of obtaining the coating foil is preferably a strip of metal foil as shown in the above embodiment, but is not limited thereto. Instead, for example, it may be a metal foil that is not in the form of a strip (eg, a substantially rectangular metal foil having preset length dimensions and width dimensions).

  Next, specific examples and comparative examples of the present invention are shown below. However, the present invention is not limited to the examples shown below.

<Example>
In this example, a composite material of aluminum and carbon fiber was produced by the following procedure.

  Carbon fiber having an average fiber length of 150 μm and average fiber diameter of 10 μm (Nippon Graphite Fiber Co., Ltd .: XN-100) and polyethylene oxide having an average molecular weight of 700,000 as a binder (manufactured by Meisei Chemical Industry Co., Ltd .: Alcox (registered trademark)) ) A 3% by mass aqueous solution of E-45), methanol as a solvent, water, a dispersant, and a surface conditioner were mixed with stirring to prepare a coating solution. The mass of the binder contained in the coating liquid was 3% in terms of solid content with respect to the mass of the carbon fiber. The viscosity of the coating solution was 300 mPa · s at 25 ° C.

The coating solution was applied to the entire surface of the strip of aluminum foil (material: A1N30) having a thickness of 20 μm and a width of 280 mm by a gravure printing method using a gravure coater. A strip of coated foil having a carbon fiber layer formed on the surface of the strip was obtained. The strip of the coating foil was passed through a drying furnace and dried by heating to evaporate and remove the solvent from the carbon fiber layer. The coating amount of the carbon fiber contained in the carbon fiber layer after removing the solvent from the carbon fiber layer was 30 g / m ² .

  The mesh on the peripheral surface of the gravure roll provided in the gravure coater used for coating was # 15, and the cell shape was a lattice type.

  FIG. 10 is a photomicrograph of the surface of the strip of coated foil thus obtained. On the surface of the strip of metal foil, a large number of carbon fibers in each halftone dot constituting the carbon fiber layer are in a direction surrounding the bubble repellency around the bubble crease formed at the center of the halftone dot. The carbon fibers were arranged in a substantially annular shape (substantially annual ring shape), and such a substantially annular arrangement of carbon fibers occurred in each of a large number of halftone dots existing on the surface of the strip of metal foil.

  Subsequently, the strip of the coating foil was cut into a square shape (its dimensions: 50 mm long × 50 mm wide), whereby a plurality of square coated foils were cut out from the strip of the coating foil. And the laminated body was formed by laminating | stacking 200 coating foil.

  Next, the laminate is sintered by heating at a predetermined sintering temperature while pressing the laminate in the laminating direction of the coating foil in a vacuum atmosphere by a discharge plasma sintering apparatus as a pressure heating sintering apparatus. That is, the coating foil was sintered and integrated, thereby obtaining a composite material of aluminum and carbon fiber. The thickness of the composite material was 4 mm.

  The sintering conditions applied to this sintering were a sintering temperature of 550 ° C., a sintering temperature holding time (sintering time) of 3 h, and a degree of vacuum of 5 Pa.

  Further, in the step of sintering and integrating the coating foil in this way, the binder was removed from the laminate while heating the laminate from room temperature to the sintering temperature.

  The obtained composite material is in a state in which a plurality of aluminum layers and carbon fiber layers formed from aluminum foil are alternately laminated, and the aluminum sufficiently penetrates into the carbon fiber layer so that the carbon fiber layer There were almost no voids inside, and the density of the composite material was 99% of the theoretical density of the composite material.

Moreover, the thermal conductivity and the linear expansion coefficient in the length direction A, the width direction B, and the thickness direction C of the composite material 17 were measured (see FIG. 9). As a result, the thermal conductivity in the longitudinal direction A of the composite material 17 is 280 W / (m · K), the linear expansion coefficient is 6 × 10 ⁻⁶ / K, and the thermal conductivity in the width direction B of the composite material 17 is 280 W / (m · K), the linear expansion coefficient is 6 × 10 ⁻⁶ / K, the thermal conductivity in the thickness direction C of the composite 17 is 105 W / (m · K), and the linear expansion coefficient is 22 × 10. ^-6 / K. Therefore, the thermal conductivity in the length direction A and the thermal conductivity in the width direction B of the composite material 17 were equal to each other.

  Here, as shown in FIG. 9, the length direction A of the composite material 17 described above is a direction parallel to the coating direction P of the coating liquid on the surface of the strip of metal foil by the gravure coater, The width direction B of the composite material is a direction perpendicular to the length direction A of the composite material in the plane of the composite material 17. The thickness direction C of the composite material 17 coincides with the lamination direction of the coating foil.

<Comparative example>
In this comparative example, a composite material of aluminum and carbon fiber was manufactured by the following procedure.

  Carbon fiber having an average fiber length of 150 μm and an average fiber diameter of 10 μm (Nippon Graphite Fiber Co., Ltd .: XN-100) and polyethylene oxide having an average molecular weight of 700,000 as a binder (manufactured by Meisei Chemical Industry Co., Ltd .: Alcox) ) A 3 mass% aqueous solution of E-45), methanol as a solvent, water, a dispersant, and a surface conditioner were mixed with stirring, thereby preparing a coating solution. The mass of the binder contained in the coating liquid was 3% in terms of solid content with respect to the mass of the carbon fiber. The viscosity of the coating solution was 1000 mPa · s at 25 ° C.

The coating solution was applied to the entire surface of the strip of aluminum foil (material: A1N30) having a thickness of 20 μm and a width of 280 mm by a gravure printing method using a gravure coater. A strip of coated foil having a carbon fiber layer formed on the surface of the strip was obtained. The strip of the coating foil was passed through a drying furnace and dried by heating to evaporate and remove the solvent from the carbon fiber layer. The coating amount of the carbon fiber contained in the carbon fiber layer after removing the solvent from the carbon fiber layer was 30 g / m ² .

  The mesh on the peripheral surface of the gravure roll provided in the gravure coater used for coating was # 15, and the cell shape was a lattice type.

  Subsequently, the strip of the coating foil was cut into a square shape (its dimensions: 50 mm long × 50 mm wide), whereby a plurality of square coated foils were cut out from the strip of the coating foil. And the laminated body was formed by laminating | stacking 200 coating foil.

  Next, the laminate is sintered at a predetermined sintering temperature while being pressed in the laminating direction of the coating foil in a vacuum atmosphere by a discharge plasma sintering apparatus, that is, the coating foil is sintered integrally. Thus, a composite material of aluminum and carbon fiber was obtained. The thickness of the composite material was 4 mm.

  The sintering conditions applied to this sintering were a sintering temperature of 550 ° C., a sintering temperature holding time (sintering time) of 3 h, and a degree of vacuum of 5 Pa.

  Further, in the step of sintering and integrating the coating foil in this way, the binder was removed from the laminate while heating the laminate from room temperature to the sintering temperature.

  The obtained composite material is in a state in which a plurality of aluminum layers and carbon fiber layers formed from aluminum foil are alternately laminated, and the aluminum sufficiently penetrates into the carbon fiber layer so that the carbon fiber layer There were almost no voids inside, and the density of the composite material was 99% of the theoretical density of the composite material.

Moreover, the thermal conductivity and the linear expansion coefficient in the length direction A, the width direction B, and the thickness direction C of the composite material were measured (see FIG. 9). As a result, the thermal conductivity in the longitudinal direction A of the composite material is 280 W / (m · K), the linear expansion coefficient is 6 × 10 ⁻⁶ / K, and the thermal conductivity in the width direction B of the composite material is 275 W / (M · K), the linear expansion coefficient is 6 × 10 ⁻⁶ / K, the thermal conductivity in the thickness direction C of the composite is 100 W / (m · K), and the linear expansion coefficient is 22 × 10 ⁻⁶ / K. K. Therefore, the thermal conductivity in the length direction A and the thermal conductivity in the width direction B of the composite material were slightly different.

  The present invention is applicable to a method for producing a composite material of metal and carbon fiber.

1: Carbon fiber 2: Binder 3: Solvent 5: Coating liquid 10: Metal foil 10A: Metal foil strip 11: Carbon fiber layer 12: Halftone dot 13: Bubble 13a: Bubble repellency 14: Coating foil 14A: Coating foil strip 15: Laminate 17: Composite material of metal and carbon fiber 20: Gravure coating device 21: Gravure roll 22: Cell 28: Drying furnace 30: Sintering device

Claims (1)

A carbon fiber layer is formed on the surface of the metal foil by applying a coating liquid containing carbon fiber, a binder and the binder solvent in a mixed state on the surface of the metal foil by a gravure printing method and drying the coating liquid. Obtaining a coated foil,
Forming a laminate in which a plurality of the coating foils are laminated;
Removing the binder from the laminate by heating the laminate, and joining and integrating the coating foil by heating while pressing the laminate in the laminating direction of the coating foil; Comprising
In the step of obtaining the coating foil, a method for producing a composite material of metal and carbon fiber, in which the coating liquid is applied by a gravure printing method so that the carbon fiber layer is in a white state, and is dried.