JP2010234556A - Graphite-polyimide laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel laminate by imparting various functions of a graphite sheet to a flexible polyimide film. <P>SOLUTION: The laminate 101 is manufactured by laminating the graphite sheet 3 directly on the polyimide film 2 having at least one thermocompression bondable surface through thermocompression bonding. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laminate of a graphite sheet and a polyimide film.

  Graphite occupies an important position as an industrial material because it has outstanding heat resistance, chemical resistance, high electrical conductivity, etc., and is widely used as a gasket, electrode, heating element, and structural material. Among them, the highly oriented graphite layered sheet material has excellent characteristics as an electric conductor or a heat conductor, has a thin film thickness, and is easy to process and handle. Used.

  Patent Document 1 discloses a composite circuit board in which a polymer film is graphitized on a surface of a resin layer of a flexible substrate in which a conductive layer is laminated on an elastic resin layer, and a graphite layer that exhibits thermal conductivity is laminated. Yes.

Patent Document 2 discloses a graphite composite film in which any one of an adhesive layer, an insulating layer, and a conductive layer is formed on at least one surface of a graphite film obtained by heat-treating a polymer film at a temperature of 2000 ° C. or higher. A graphite composite film characterized in that the density of the graphite film is 1.3 g / cm ³ or more is disclosed.

  Patent Document 3 discloses an invention relating to an electrode for a quantum beam monitor having a monitor target in which a plurality of ribbon-like carbon graphite thin films are arranged in parallel in one direction at predetermined intervals. Graphite is processed using a laser. It describes what you can do.

JP 2002-344095 A JP 2007-261087 A JP 2007-101367 A

  An object of the present invention is to provide a novel laminate in which a graphite sheet and a polyimide film are directly laminated without an adhesive layer, and a novel laminate in which a metal layer is combined.

  The present invention relates to the following matters.

1. A laminate having a polyimide film having at least one surface having thermocompression bonding, and a graphite sheet directly bonded to a part or all of the surface having thermocompression bonding of the polyimide film by thermocompression bonding.

  2. The said polyimide film is a laminated body of said 1 with which the metal layer is laminated | stacked on the one part or all part of at least single side | surface of a polyimide film.

  3. 3. The laminate according to 2 above, wherein the polyimide film has a metal layer laminated on the surface on the opposite side to the bonding of the graphite sheet.

  4). 4. The laminate according to 3 above, comprising at least one of the graphite sheet and the metal layer, and a via hole penetrating the polyimide film.

  5. 5. The laminate according to 4 above, wherein a conductive layer is formed in the via hole, and the graphite sheet and the metal layer are electrically and / or thermally coupled.

  6). 6. The laminate according to 4 or 5 above, wherein a metal plating layer is formed on a part or all of the outside of the graphite sheet.

  7). The laminate according to any one of 1 to 6 above, wherein the graphite sheet has a thickness of 0.2 to 50 µm.

  ADVANTAGE OF THE INVENTION According to this invention, the novel laminated body of a graphite sheet and a polyimide film, and also the novel laminated body compounded with the metal layer can be provided.

  The laminate of the present invention can have various forms, and can be used in various applications. In particular, the heat resistance, chemical resistance, high electrical conductivity, high thermal conductivity, light resistance, weather resistance, radiation resistance, and other functions of the graphite sheet can be imparted to the flexible polyimide film.

It is a figure which shows one example of the laminated body of this invention. It is a figure which shows one example of the laminated body of this invention. It is a figure which shows one example of the laminated body of this invention. It is a figure which shows one example of the laminated body of this invention. It is a figure which shows one example of the laminated body of this invention. It is a figure which shows one example of the laminated body of this invention.

  First, the graphite sheet and polyimide film used in the present invention will be described, and then the laminate of the present invention will be described.

<< Graphite sheet >>
The graphite sheet used in the present invention is not particularly limited. However, in order to impart the advanced functions of graphite to the polyimide film without impairing the flexibility and heat resistance of the polyimide film, the graphite sheet is not brittle and has flexibility and toughness. The thickness of the graphite sheet is, for example, 0.2 μm to 50 μm, more preferably 0.5 μm to 20 μm. Moreover, it is preferable that it has the softness | flexibility and toughness of a grade which is not cracked even if it bends.

  As the graphite sheet, a sheet having a highly developed graphite layer structure, a high crystallinity, and a large crystallite size of graphite is preferable. In particular, a structure in which the graphite network surface is highly oriented so as to be a sheet surface is preferable. Preferably, the crystallite size in the (002) plane direction is 9 nm or more, particularly 10 to 100 nm, and the C-axis lattice constant is 0.68 nm or less, particularly 0.67 nm or less. The crystallinity is preferably 75% or more, more preferably 90% or more, and particularly preferably 95% or more.

  The method for producing such a graphite sheet is not particularly limited, but is preferably a method described in JP-A No. 2002-274827, JP-A No. 2002-308611 and JP-A No. 2007-101367. In the method, a polyimide film carbonized product in which a component imparting high orientation is present or a polyimide film carbonized product having high orientation per se is graphitized by high-temperature heat treatment (2600 ° C. to 3000 ° C.) in an inert atmosphere. By performing this, a highly oriented graphite layered sheet can be obtained. At this time, it is particularly preferable to perform the treatment while applying pressure simultaneously with heating. In addition, a polyimide film carbonized material is obtained by baking a polyimide film at 1000 ° C. to 2000 ° C. in an inert atmosphere.

  Since the graphite sheet obtained by this method has a flexible, strong and flexible layer structure, it has excellent lateral and thermal conductivity, and is suitable as an electrical conductor or a thermal conductor.

  In the present invention, the graphite sheet may be processed after being bonded to the polyimide film, but since the graphite sheet can be easily cut, it is preferable that the graphite sheet is previously cut into a predetermined shape and a predetermined pattern and bonded. .

  << Polyimide film >>

  Although the thickness of a polyimide film is not specifically limited, Preferably it is 1-500 micrometers, More preferably, it is 2-300 micrometers, More preferably, it is 5-200 micrometers, More preferably, it is 7-175 micrometers, Most preferably, it uses 8-100 micrometers. preferable. At least one surface of the polyimide film may be subjected to a surface treatment such as corona discharge treatment, plasma treatment, chemical roughening treatment, or physical roughening treatment.

  As for the polyimide film used in this invention, the surface laminated | stacked with a graphite sheet has thermocompression bonding property. Preferably, the polyimide film has at least a thermocompression bonding polyimide layer (a) that can be directly laminated by pressurizing or heating under pressure with a graphite sheet on one or both sides of the heat-resistant polyimide layer (b). A multilayer polyimide film having two or more layers.

  The polyimide film is a multilayer polyimide film having at least two layers in which a thermocompression bonding polyimide layer (a) and a heat-resistant polyimide layer (b) are directly laminated and integrated using a coextrusion die. Is preferred.

  As the heat-resistant polyimide layer (b), it is preferable to use a heat-resistant polyimide constituting a base film that can be used as a tape material for electronic components such as a printed wiring board, a flexible printed circuit board, a TAB tape, and a COF board. As a specific example, the brand name “UPILEX (S or R)” (manufactured by Ube Industries), the brand name “Kapton” (manufactured by Toray DuPont and DuPont), and the brand name “Apical” (manufactured by Kaneka) The polyimide obtained from the acid component and diamine component which comprise a polyimide film, such as, can be mentioned.

In the thermocompression bonding polyimide film, the heat-resistant polyimide of the heat-resistant polyimide layer (b layer) has at least one of the following characteristics, and has at least two of the following characteristics [1) and 2), 1) And 3), 2) and 3)], particularly those having all of the following characteristics can be used.
1) A single polyimide film having a glass transition temperature of 300 ° C. or higher, preferably a glass transition temperature of 330 ° C. or higher, more preferably unidentifiable.
2) As a single polyimide film, the linear expansion coefficient (50 to 200 ° C.) (MD) is preferably close to the thermal expansion coefficient of a metal layer such as a copper foil laminated on a heat-resistant resin substrate. Is preferably 5 × 10 ^{−6 to} 28 × 10 ⁻⁶ cm / cm / ° C., preferably 9 × 10 ^{−6 to} 20 × 10 ⁻⁶ cm / cm / ° C. is preferably is preferably further ^{12 × 10 -6 ~18 × 10 -6} cm / cm / ℃.
3) As a single polyimide film, a tensile elastic modulus (MD, ASTM-D882) is 300 kg / mm ² or more, preferably 500 kg / mm ² or more, and further 700 kg / mm ² or more.

As the heat-resistant polyimide of the heat-resistant polyimide layer (b),
(1) 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride and 1,4-hydroquinone dibenzoate-3,3 ′, 4,4′-tetracarboxylic acid bis An acid component containing at least one component selected from anhydrides, preferably an acid component containing at least 70 mol% or more, more preferably 80 mol% or more, more preferably 90 mol% or more of these acid components;
(2) As a diamine component, a diamine containing at least one component selected from p-phenylenediamine, 4,4′-diaminodiphenyl ether, m-tolidine and 4,4′-diaminobenzanilide, preferably at least these diamine components A polyimide obtained from a diamine component containing 70 mol% or more, more preferably 80 mol% or more, and more preferably 90 mol% or more can be used.

As an example of a combination of an acid component and a diamine component constituting the heat-resistant polyimide layer (b),
1) 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, p-phenylenediamine or p-phenylenediamine and 4,4-diaminodiphenyl ether,
2) 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride, p-phenylenediamine or p-phenylenediamine and 4,4-diaminodiphenyl ether,
3) pyromellitic dianhydride, p-phenylenediamine and 4,4-diaminodiphenyl ether,
4) What is obtained by using 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine as main components (50 mol% or more in a total of 100 mol%) can be mentioned. These are used as materials for electronic components such as printed wiring boards, flexible printed circuit boards, TAB tapes, etc., have excellent mechanical properties over a wide temperature range, have long-term heat resistance, and hydrolysis resistance It is preferable because it has excellent heat resistance, a high thermal decomposition starting temperature, a small heat shrinkage rate and a small linear expansion coefficient, and excellent flame retardancy.

  As an acid component capable of obtaining the heat-resistant polyimide of the heat-resistant polyimide layer (b), 2,3,3 ′, 4′-biphenyltetra is not limited to the above-described acid component as long as the characteristics of the present invention are not impaired. Carboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfide Dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane Anhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis [(3,4-dicarboxy Feno ) Phenyl] propane dianhydride, it is possible to use an acid dianhydride component, such as.

  As a diamine component capable of obtaining the heat-resistant polyimide of the heat-resistant polyimide layer (b), m-phenylene diamine, 3,4′-diaminodiphenyl ether, as long as the characteristics of the present invention are not impaired in addition to the diamine component shown above. 3,3′-diaminodiphenylsulfide, 3,4′-diaminodiphenylsulfide, 4,4′-diaminodiphenylsulfide, 3,3′-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfone, 4,4 ′ -Diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4'- Diaminodiphenylmethane, 2,2-di (3-amino Phenyl) propane, 2,2-di (4-aminophenyl) propane, can be used diamine component, such as.

  If the thermocompression bonding polyimide layer (a layer) is a known polyimide having a property capable of thermocompression bonding with a copper foil or a property capable of thermocompression bonding under pressure, it is used for thermocompression bonding with a graphite sheet in the present invention. be able to.

  The thermocompression bonding polyimide of the thermocompression bonding polyimide layer (a layer) is preferably a polyimide having thermocompression bonding that can be bonded to graphite and copper foil at a temperature of not less than the glass transition temperature of the thermocompression bonding polyimide and not more than 400 ° C. It is.

The thermocompression bonding polyimide layer (a layer) of the thermocompression bonding polyimide film further has at least one of the following characteristics, at least two of the following characteristics [1) and 2), 1) and 3), 2) and 3)], having at least three of the following characteristics [1), 2), 3), 1), 3), 4), 2), 3) and 4 ), 1), 2), 4), etc.], particularly those having all the following characteristics can be used.
1) The thermocompression bonding polyimide layer (a layer) has a peel strength of 0.7 N / mm or more between copper foil and a layer, or copper foil and thermocompression bonding polyimide film, and after heat treatment at 150 ° C. for 168 hours. A polyimide having a peel strength retention of 90% or more, more preferably 95% or more, particularly 100% or more.
2) The glass transition temperature is 130 to 330 ° C.
3) The tensile elastic modulus is 100 to 700 Kg / mm ² .
4) The linear expansion coefficient (50 to 200 ° C.) (MD) is 13 to 30 × 10 ⁻⁶ cm / cm / ° C.

The thermocompression bonding polyimide of the thermocompression bonding polyimide layer (a layer)
(1) 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 3,3 ′ , 4,4′-benzophenonetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfide dianhydride, bis (3,4- Dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride and 1,4-hydroquinone dibenzoate An acid component containing at least one component selected from acid dianhydrides such as −3,3 ′, 4,4′-tetracarboxylic dianhydride, preferably at least 70 mol% of these acid components; Preferably 80 mol% or more, more preferably an acid component comprising 90 mol% or more,
(2) As the diamine component, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 3,3 '-Diaminobenzophenone, 4,4'-bis (3-aminophenoxy) biphenyl, 4,4'-bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4 -(4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl Sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] Ter, bis [4- (4-aminophenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] It is obtained from a diamine containing at least one component selected from diamines such as propane, preferably a diamine component containing these diamine components at least 70 mol% or more, more preferably 80 mol% or more, more preferably 90 mol% or more. Polyimide or the like can be used.

As an example of a combination of an acid component and a diamine component that can obtain a polyimide of a thermocompression bonding polyimide layer (a layer),
(1) At least one component selected from 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride acid dianhydride An acid component containing seeds, preferably an acid component containing at least 70 mol% or more, more preferably 80 mol% or more, more preferably 90 mol% or more of these acid components;
(2) As the diamine component, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene 4,4′-bis (3-aminophenoxy) biphenyl, bis [4 -(3-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4 A diamine containing at least one component selected from diamines such as-(4-aminophenoxy) phenyl] propane, preferably at least 70 mol%, more preferably 80 mol% or more, more preferably 90 mol, of these diamine components. The polyimide etc. which are obtained from the diamine component which contains% or more can be used.

  As a diamine component capable of obtaining a polyimide of the thermocompression bonding polyimide layer (a layer), m-phenylenediamine and 3,4′-diaminodiphenyl ether are used as long as the properties of the present invention are not impaired in addition to the diamine component shown above. 3,3′-diaminodiphenylsulfide, 3,4′-diaminodiphenylsulfide, 4,4′-diaminodiphenylsulfide, 3,3′-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfone, 4,4 ′ -Diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4'- Diaminodiphenylmethane, 2,2-di (3-amino Eniru) propane, 2,2-di (4-aminophenyl) propane, can be used diamine component, such as.

  The polyimide of the heat-resistant polyimide layer (b layer) and the polyimide of the thermocompression bonding polyimide layer (a layer) can be synthesized by a known method, such as random polymerization, block polymerization, or a plurality of polyimide precursor solutions or polyimides in advance. This is achieved by any method in which a solution is synthesized and the plurality of solutions are mixed and then mixed under reaction conditions to obtain a homogeneous solution.

  The polyimide of the heat-resistant polyimide layer (b layer) and the polyimide of the thermocompression bonding polyimide layer (a layer) have an acid component and a diamine component in an organic solvent of about 100 ° C. or lower, further 80 ° C. or lower, and further 0 to 60 A polyimide precursor solution is prepared by reacting at a temperature of 20 ° C., particularly at a temperature of 20 to 60 ° C. for about 0.2 to 60 hours, and this polyimide precursor solution is used as a dope solution to form a thin film of the dope solution And it can manufacture by evaporating and removing a solvent from the thin film, and imidating a polyimide precursor.

  Moreover, in the polyimide which is excellent in solubility, the polyimide precursor solution is heated to 150 to 250 ° C., or an imidizing agent is added and reacted at a temperature of 150 ° C. or less, particularly 15 to 50 ° C., to imide cyclization. Thereafter, the solvent is evaporated or precipitated in a poor solvent to obtain a powder. Thereafter, the powder can be dissolved in an organic solution to obtain an organic solvent solution of polyimide.

  In carrying out the polymerization reaction of the polyimide precursor solution, the concentration of all monomers in the organic polar solvent may be appropriately selected according to the purpose of use or the purpose of production. For example, the polyimide of the heat-resistant polyimide layer (b layer) In the precursor solution, the concentration of all monomers in the organic polar solvent is preferably 5 to 40% by mass, more preferably 6 to 35% by mass, and particularly preferably 10 to 30% by mass. It is preferable that the polyimide precursor solution of the thermocompression bonding polyimide layer (a layer) has a ratio in which the concentration of all monomers in the organic polar solvent is 1 to 15% by mass, particularly 2 to 8% by mass.

  In carrying out the polymerization reaction of the polyimide precursor solution, the solution viscosity may be appropriately selected according to the purpose of use (coating, casting, etc.) and the purpose of production. The polyamic (polyimide precursor) acid solution is 30 From the viewpoint of workability in handling this polyamic acid solution, the rotational viscosity measured at ° C is about 0.1 to 5000 poise, particularly 0.5 to 2000 poise, more preferably about 1 to 2000 poise. preferable. Therefore, it is desirable to carry out the polymerization reaction to such an extent that the produced polyamic acid exhibits the above viscosity.

  The thermocompression bonding polyimide layer (a layer) can be used by producing a polyimide precursor solution by the above-described method, newly adding an organic solvent, and diluting it.

  The polyimide of the heat-resistant polyimide layer (b layer) and the polyimide of the thermocompression bonding polyimide layer (a layer) are approximately equimolar amounts of the diamine component and tetracarboxylic dianhydride, the diamine component is in a slightly excessive amount, or the acid component. A slightly excessive amount can be reacted in an organic solvent to obtain a polyimide precursor solution (which may be partially imidized as long as a uniform solution state is maintained).

  The polyimide of the heat-resistant polyimide layer (b layer) and the polyimide of the thermocompression bonding polyimide layer (a layer) are dicarboxylic anhydrides, for example, phthalic anhydride and its substitutes, hexahydrophthalic anhydride to seal the amine terminal. In particular, it can be synthesized by adding phthalic anhydride, such as an acid and a substituted product thereof, succinic anhydride and a substituted product thereof.

  The polyimide of the heat resistant polyimide layer (b layer) and the polyimide of the thermocompression bonding polyimide layer (a layer) are used in an organic solvent in which the amount of diamine (as the number of moles of amino group) is the total number of moles of acid anhydride (tetra Ratio of acid dianhydride and dicarboxylic acid anhydride as the total moles as acid anhydride groups) of 0.95 to 1.05, especially 0.98 to 1.02, of which 0.99 to 1 in particular .01 is preferred. When the dicarboxylic acid anhydride is used, each component can be reacted at a ratio of 0.05 or less as a ratio of the tetracarboxylic dianhydride to the molar amount of the acid anhydride group.

  For the purpose of limiting the gelation of the polyimide precursor, a phosphorus stabilizer such as triphenyl phosphite, triphenyl phosphate, etc. is in the range of 0.01 to 1% with respect to the solid content (polymer) concentration during polyamic acid polymerization. Can be added.

  For the purpose of promoting imidization, a basic organic compound can be added to the dope solution. For example, imidazole, 2-imidazole, 1,2-dimethylimidazole, 2-phenylimidazole, benzimidazole, isoquinoline, substituted pyridine and the like also use 0.05 to 10% by weight, particularly 0. It can be used at a ratio of 1 to 2% by weight. Since these form a polyimide film at a relatively low temperature, they can be used to avoid insufficient imidization.

  For the purpose of stabilizing the adhesive strength, an organoaluminum compound, an inorganic aluminum compound, or an organotin compound may be added to the polyamic acid solution for thermocompression bonding polyimide. For example, aluminum hydroxide, aluminum triacetylacetonate or the like can be added in an amount of 1 ppm or more, particularly 1 to 1000 ppm as an aluminum metal with respect to the polyamic acid.

  Organic solvents used for the production of polyamic acid are N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide, N- Examples include methyl caprolactam and cresols. These organic solvents may be used alone or in combination of two or more.

  The polyimide film having thermocompression bonding property is preferably formed by (i) coextrusion-casting film forming method (also simply referred to as multilayer extrusion method) and heat-resistant polyimide layer (b layer) dope solution and thermocompression bonding property. A method of obtaining a multilayer polyimide film by laminating a dope solution of a polyimide layer (a layer), drying and imidizing, (ii) or applying a dope solution of a heat-resistant polyimide layer (b layer) on a support, The dry self-supporting film (gel film) can be obtained by applying a dope solution of a thermocompression bonding polyimide layer (a layer) on one side or both sides and drying and imidizing to obtain a multilayer polyimide film.

  The coextrusion method can be performed by a known method, and for example, a method described in JP-A-3-180343 (Japanese Patent Publication No. 7-102661) can be used.

  An example of the production of a three-layer thermocompression bonding polyimide film having thermocompression bonding on both sides is shown.

  The heat-resistant polyimide layer (b layer) has a thickness of 4 to 3 by co-extrusion of a polyamic acid solution for the heat-resistant polyimide layer (b layer) and a polyamic acid solution for the thermocompression bonding polyimide layer (a layer). Supply to a three-layer extrusion die so that the total thickness of thermocompression-bondable polyimide layers (a layer) on both sides is 3 to 10 μm at 45 μm, cast on a support, and this is stainless steel mirror surface, belt surface, etc. It is possible to obtain a polyimide film A which is a self-supporting film which is cast-coated on the surface of the substrate and made into a semi-cured state or a dried state before 100 to 200 ° C.

  When the cast film is processed at a high temperature exceeding 200 ° C., the self-supporting polyimide film A tends to cause defects such as a decrease in adhesiveness in the production of a polyimide film having thermocompression bonding. This semi-cured state or an earlier state means that it is in a self-supporting state by heating and / or chemical imidization.

  The resulting self-supporting polyimide film A has a temperature not higher than the glass transition temperature (Tg) of the thermocompression bonding polyimide layer (a layer) and lower than the temperature at which deterioration occurs, preferably a temperature of 250 to 420 ° C. (surface (Surface temperature measured with a thermometer) (preferably heated at this temperature for 0.1 to 60 minutes), dried and imidized, and thermocompression-bonded on both sides of the heat-resistant polyimide layer (b layer) A polyimide film in which a heat-resistant polyimide layer (b layer) having a polyimide layer (a layer) and a thermocompression bonding polyimide layer (a layer) are laminated and integrated can be produced.

  The polyimide film A of the obtained self-supporting film preferably has about 20 to 60% by mass, particularly preferably 30 to 50% by mass of the solvent and generated water remaining, and the self-supporting film is heated to the drying temperature. When heating, it is preferable to raise the temperature within a relatively short time, for example, a temperature increase rate of 10 ° C./min or more is suitable. By increasing the tension applied to the self-supporting film at the time of drying, the linear expansion coefficient of the finally obtained polyimide film A can be reduced.

  Then, following the above-described drying step, at least a pair of both end edges of the self-supporting film is continuously or intermittently fixed with a fixing device or the like that can be moved together with the self-supporting film. Higher than the above drying temperature, and preferably at a high temperature in the range of 200 to 550 ° C., particularly preferably in the range of 300 to 500 ° C., preferably 1 to 100 minutes, in particular 1 to 10 minutes. The support film is dried and heat-treated, and the solvent is preferably removed from the self-support film so that the content of volatile substances composed of an organic solvent and product water in the finally obtained polyimide film is 1% by weight or less. The polyimide film which has the thermocompression bonding on both sides by sufficiently imidizing the polymer constituting the film It can be formed.

  Examples of the fixing device for the self-supporting film include, for example, a belt-like or chain-like one provided with a large number of pins or gripping tools at equal intervals, and the length of the solidified film supplied continuously or intermittently. A device that can be installed in a pair along both side edges in the direction and can fix the film while moving the film continuously or intermittently with the movement of the film is suitable. The solidified film fixing device can stretch or shrink the film being heat-treated in the width direction or the longitudinal direction at an appropriate elongation or contraction rate (particularly preferably about 0.5 to 5%). It may be a device.

  The polyimide film having thermocompression bonding on both sides produced in the above step is preferably at a temperature of 100 to 400 ° C. under a low tension or no tension of preferably 4N or less, particularly preferably 3N or less. Can be made into a polyimide film having thermocompression bonding on both surfaces particularly excellent in dimensional stability when heat-treated for 0.1 to 30 minutes. Moreover, the manufactured polyimide film which has thermocompression bonding on both surfaces can be wound up in a roll shape by an appropriate known method.

  The loss on heating of the self-supporting film is a value obtained by drying the film to be measured at 420 ° C. for 20 minutes and calculating from the following formula from the weight W1 before drying and the weight W2 after drying.

Heat loss (mass%) = {(W1-W2) / W1} × 100
Moreover, the imidation ratio of said self-supporting film can be calculated | required by the method using the Karl Fischer moisture meter of Unexamined-Japanese-Patent No. 9-316199.

  In the self-supporting film, if necessary, fine inorganic or organic additives can be blended in the inside or the surface layer. Examples of inorganic additives include particulate or flat inorganic fillers. Examples of the organic additive include polyimide particles and thermosetting resin particles. The usage amount and shape (size, aspect ratio) are preferably selected according to the purpose of use.

  The heat treatment can be performed using various known devices such as a hot stove and an infrared heating furnace.

  As described above, a polyimide film suitable for the present invention can be produced.

<< Graphite, polyimide, (metal layer) laminate >>
In the laminate of the present invention, as shown in FIG. 1, a graphite sheet 3 and a polyimide film 2 are directly bonded to form a laminate 101.

  In FIG. 1, the graphite sheet 3 is bonded to one side of the polyimide film 2, but may be bonded to both sides. Further, the graphite sheet may be bonded to the entire surface of one side or both sides of the polyimide film, or may be bonded to cover a part of one side or both sides. In general, as shown in FIG. 1, a graphite sheet cut into a predetermined shape according to the purpose is bonded to a predetermined portion of a polyimide film. The surface of the polyimide film to which the graphite sheet is bonded is a thermocompression bonding polyimide layer as described above.

  Specifically, the bonding of the graphite sheet and the polyimide film can be performed by using a heating and pressing apparatus, and the heating conditions and pressing conditions are preferably selected appropriately depending on the materials used, and can be laminated continuously or batchwise. There is no particular limitation.

  Thermocompression bonding under pressure in a temperature range from 20 ° C to 400 ° C higher than the glass transition temperature of the thermocompression bonding polyimide constituting the polyimide film, particularly in a temperature range from 30 ° C higher than the glass transition temperature to 400 ° C. It is preferable to do.

  The polyimide film may be preheated before thermocompression bonding. When preheating, a preheater such as a hot air supply device or an infrared heater may be used. When creating a laminate of a graphite sheet and a polyimide film as a continuous sheet, a roll laminating apparatus, a double belt press apparatus, or the like can also be used.

  Moreover, in the case of lamination | stacking, you may interpose a protective material (namely, two protective materials) between the press surface of a pressurization apparatus, a polyimide film, and a graphite sheet. The protective material is preferably non-thermocompressible and has good surface smoothness, such as metal foil, particularly copper foil, stainless steel foil, aluminum foil, high heat-resistant polyimide film (Ube Industries, Upilex S), etc. Preferably mentioned.

  In the laminate of the present invention, a metal layer may be laminated on a part of at least one surface of the polyimide film. The material and shape of the metal layer can be selected according to the purpose. A metal layer is a copper layer used as wiring as a typical example. Although the thickness of a metal layer does not have a restriction | limiting in particular, In the case of a copper layer, thickness is about 1-100 micrometers, for example. The metal layer may be on the same side as the graphite sheet of the polyimide film or on the opposite side.

  In one typical application example, as shown in FIG. 2, a graphite sheet 3 is bonded to one side of a polyimide film 2 and a metal layer (especially a copper layer 4) is provided on the opposite side.

  Various methods can be adopted as a method for producing a laminate having a graphite sheet and a metal layer on the surface of the polyimide film, but a copper-clad laminate in which a copper layer is laminated on one side or both sides of a polyimide film. Since the substrate is readily available, it is convenient to use a copper clad laminate substrate.

  For example, when a polyimide film has thermocompression polyimide layers on both sides and a copper layer is laminated on one side, a graphite sheet can be laminated on the opposite side of the copper layer by thermocompression. Also, when the polyimide film has a thermocompression-bonded polyimide layer on both sides and a copper layer is laminated on both sides (double-sided copper-clad substrate), at least a part of the copper layer on one side is removed by etching, A graphite sheet can be laminated on the exposed polyimide film surface by thermocompression bonding.

  The laminate of the present invention may have a via hole. The via hole may be either a through hole or a non-through hole (blind hole or recess). A conductive layer (for example, a plating layer) may be formed in the via hole so that both surfaces of the polyimide film are conductive.

  FIG. 3 shows an example of a stacked body having a via hole. In the laminated body 103 of this figure, the graphite sheet 3 is bonded together on one side of the polyimide film 2, and the metal layer 4 (for example, copper foil) is provided on the opposite side. The via hole 10 a is a blind hole, penetrates the graphite sheet 3, penetrates the polyimide film 2, and reaches the metal layer 4. The via hole 10b is also a blind hole, penetrates the metal layer 4 from the metal layer 4 side, penetrates the polyimide film 2 and reaches the graphite sheet 3. The via hole 10 c is a through hole, and is formed through the graphite sheet 3, the polyimide film 2 and the metal layer 4.

  FIG. 4 shows an example of a laminate in which a conductive layer is formed in a via hole. The laminated body 104 in this figure is an example in which the conductive layer 5 is formed inside each via hole 10a, 10b, 10c of the laminated body shown in FIG. 3 and the conductors on both sides of the polyimide film are bonded. The conductive layer 5 is formed of a material having excellent electrical and / or thermal conductivity. In the case of electrical coupling, a material having the same electrical conductivity as that of a metal is selected, and a metal layer (for example, a known copper plating layer) is preferably used. When the conductive layer 5 is intended to be thermally coupled, it is formed of a material having a thermal conductivity higher than that of at least polyimide. When the conductive layer is formed of metal, both electrical and thermal coupling is achieved.

  The conductive layer 5 may be formed by filling a via hole. When the conductive layer 5 is a copper plating layer, a part or all of the surface of the metal layer 4 and / or the surface of the graphite sheet 3 may be plated like a laminated body 105 shown in FIG.

  In addition, the metal layer 4 and the graphite sheet can have various patterns, and when flexibility is particularly required for the graphite sheet 3 portion, the polyimide of the graphite sheet 3 can be obtained as a laminate 106 shown in FIG. It is also preferable that the film backside portion 6 has a portion where the metal layer 4 is not present.

  A known method can be employed for forming the via hole. Laser processing is preferred because the polyimide film and the graphite sheet are extremely thin. Examples of the laser include a UV-YAG laser (for example, wavelength 355 nm), an excimer laser, and an infrared YAG laser (for example, wavelength 1.1 μm).

  Also, any of the three types of via holes 10a, 10b, and 10c shown in FIG. 3 can be created by controlling the laser output and the processing time. The diameter of the via hole can be set as appropriate, but is generally about 5 to 500 μm, preferably about 20 to 60 μm.

  A known method can also be adopted for forming the conductive layer 5 in the via hole. For example, a conductive film is formed in the via hole by the risertron DSP process of Ebara Eugene, and after degreasing and washing, electrolytic copper plating is performed to a thickness of about 2 to 30 μm, for example, in a copper sulfate plating bath.

  The metal layer (and the layer formed by electrolytic plating) can have various patterns such as wiring, and can be formed by a known etching technique. Also, a plating layer can be formed on the graphite sheet. The plating layer on the graphite sheet can be removed, for example, by etching or patterning without damaging the graphite sheet.

  The laminate of the present invention can have various forms, and can be used in various applications. In particular, the heat resistance, chemical resistance, high electrical conductivity, high thermal conductivity, light resistance, weather resistance, radiation resistance, and other functions of the graphite sheet can be imparted to the flexible polyimide film.

  Therefore, a laminate in which a polyimide film and a graphite sheet are simply laminated includes a heat resistant sheet, a chemical resistant sheet, an electrically conductive sheet, a thermally conductive sheet, a light resistant sheet, a weather resistant sheet, a radiation resistant sheet, and others. Can be used as a target sheet.

  Further, a laminate having a metal layer, particularly a copper layer, can be used as, for example, a flexible wiring board or a flexible electrode in the electric / electronic field. In that case, a graphite sheet part can be used, for example as a heat sink or a heat dissipation path, as a conductor or a conductive path, or as a part having other functions.

  Various electronic / electrical elements and electronic / electrical devices can be mounted on the metal layer. As an example, when the metal layer (copper layer) and the graphite sheet are bonded by the conductive layer as described above, the graphite sheet functions as a heat dissipation plate or a heat dissipation path, Heat generation can be dissipated from the back side of the film. The graphite sheet and the polyimide film are extremely thin and flexible, so that they can be incorporated into a narrow and complicated space.

  Furthermore, on the polyimide film, in addition to the metal layer, a semiconductor layer, an organic or inorganic functional material, etc., for various purposes, a single layer or a multilayer structure (each layer is a layer covering the entire surface, It may be formed in a pattern shape that covers only a part). A material or device having a novel structure is realized in combination with the function of the graphite sheet.

  Hereinafter, the laminate of the present invention will be specifically described with reference to examples.

[Reference Example 1] (Production of graphite sheet)
A polyimide film manufactured by Ube Industries, Ltd. (product name: UPILEX 7.5SN, film thickness 7.5 μm) is sandwiched between air-permeable carbon sheets in a nitrogen gas stream at a rate of 10 ° C./min. The temperature was raised from 1 ° C. to 1400 ° C. and held at 1400 ° C. for 120 minutes. The obtained carbonized film was laminated and set one by one with a breathable carbon sheet in a graphitization hot press capable of uniaxial pressing. The temperature was raised at a rate of 10 to 20 ° C./min in an argon gas atmosphere, maintained at 3000 ° C. under a pressure treatment condition of 3 MPa for 90 minutes, and then cooled in the furnace while gradually reducing the pressure. The appearance of the obtained film was smooth and grayish. This graphite film was not brittle and had flexibility.

  The thickness was 2.2 μm, and X-ray wide angle scattering was measured in both transmission and reflection modes. As a result, it was confirmed that the graphite crystals were oriented and grown in the film surface direction. The graphite crystal had a C-axis lattice constant of 0.6698 nm and a crystallinity of 90% or more. From the analysis of X-ray scattering, the crystallite size was 10 nm or more in both the a-axis and c-axis directions of the crystal.

The graphite sheet was measured according to the following method.
(1) Film thickness The film thickness was measured by cross-sectional observation with a commercially available contact micrometer and a scanning electron microscope.
(2) C-axis lattice constant The C-axis lattice constant of the graphite crystal was determined from the spacing of the (002) plane.
(3) Crystallinity The crystallinity of the graphite film was measured by the Rrand method by measuring the X-ray diffraction using the graphite film as a powder.
(4) Crystallite size The crystallite size was determined from the half width of the peaks on the (002) plane and the (101) plane according to the Sheller formula.

[Example 1]
A single-sided copper-clad laminate (Upicel N, manufactured by Ube Nitto Kasei Co., Ltd.) in which a 9 μm-thick copper foil was laminated on one side of a polyimide film with a thickness of 25 μm was prepared. This polyimide film has a thermocompression bonding polyimide layer on both sides of a heat resistant polyimide layer.

  The graphite sheet produced in Reference Example 1 was cut into 1 cm × 5 cm, and was overlaid on the polyimide surface of the copper-clad laminate, and kept under vacuum at a pressure of 5.0 MPa and a temperature of 330 ° C. for 5 minutes. When observed down to room temperature, the graphite sheet was strongly adhered to the polyimide film surface. The obtained laminate was flexible.

[Example 2]
A double-sided copper-clad laminate (manufactured by Ube Nitto Kasei Co., Ltd., Yupicel N) in which a 9 μm thick copper foil was laminated on both sides of a 25 μm thick polyimide film was prepared. This polyimide film has a thermocompression bonding polyimide layer on both sides of a heat resistant polyimide layer.

  The copper layer on one side of the double-sided copper-clad laminate was removed by etching to expose the polyimide surface. A graphite sheet (1 cm × 5 cm) was superposed on the exposed polyimide film surface and bonded in the same manner as in Example 1. In the obtained laminate, the graphite sheet was strongly adhered to the polyimide film surface. The obtained laminate was flexible.

Example 3
Using the UV-YAG laser (wavelength 355 nm), the blind via hole (10a in FIG. 3) reaching the copper foil surface from the graphite sheet, and the blind reaching the graphite sheet surface from the copper foil to the laminate produced in Example 1 Three types of via holes (through holes 10b in FIG. 3) and through holes / via holes penetrating all of the graphite sheet, polyimide film and copper foil were formed. The pore diameter was about 30 μm.

  When each via hole was observed with a microscope, the target via hole was formed, and no peeling occurred at either the interface between the graphite sheet and the polyimide film or the interface between the polyimide film and the copper foil.

Example 4
The laminate in which via holes were produced by laser processing in Example 3 was plated as follows. First, a conductive film was formed by a risertron DPS (direct plating system) process manufactured by Ebara Eugene, and a conductive film was formed in the hole, on the graphite sheet, and on the copper foil. After degreasing and pickling, electrolytic copper plating was performed by feeding power from the copper foil side of the laminate at a current density of ² A / dm ² at 25 ° C. for 30 minutes using a thin copper foil as a cathode electrode in a copper sulfate plating bath.

  As a result, a 20 μm copper plating layer was formed on the graphite sheet. A copper plating layer was also formed in the via hole, and the copper foil and the graphite sheet on both sides of the polyimide film were electrically connected and were also thermally coupled.

  ADVANTAGE OF THE INVENTION According to this invention, the novel laminated body of a graphite sheet and a polyimide film, and also the novel laminated body compounded with the metal layer can be provided.

2 Polyimide film 3 Graphite sheet 4 Metal layer (copper layer)
5 Conductive layer 6 Polyimide film back side portion 10a, 10b, 10c without metal layer Via hole 101, 102, 103, 104, 105, 106 Laminate

Claims (7)

A laminate having a polyimide film having at least one surface having thermocompression bonding, and a graphite sheet directly bonded to a part or all of the surface having thermocompression bonding of the polyimide film by thermocompression bonding.   The said polyimide film is a laminated body of Claim 1 by which the metal layer is laminated | stacked on the one part or all part of the polyimide film at least.   The laminate according to claim 2, wherein the polyimide film has a metal layer laminated on the surface opposite to the side where the graphite sheets are bonded.   The laminate according to claim 3, further comprising at least one of the graphite sheet and the metal layer, and a via hole penetrating the polyimide film.   The laminate according to claim 4, wherein a conductive layer is formed in the via hole, and the graphite sheet and the metal layer are electrically and / or thermally coupled.   The laminate according to claim 4 or 5, wherein a metal plating layer is formed on a part or all of the outside of the graphite sheet.   The laminate according to any one of claims 1 to 6, wherein the graphite sheet has a thickness of 0.2 to 50 µm.

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