Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/20—Graphite
  • C01B32/205—Preparation
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
  • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
  • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets

Definitions

• the present invention relates to polyimide films for graphite sheets, graphite sheets, and methods for producing them.
• Graphite sheets have excellent thermal conductivity, so they are used as heat dissipation materials in various electronic devices such as computers, semiconductor elements mounted in electrical devices, and other heat-generating parts.
• Patent Documents 1 and 2 describe a technique for producing a graphite sheet by heat-treating (graphitizing) a polyimide film.
• An object of one embodiment of the present invention is to provide a polyimide film that can produce a graphite sheet excellent in thermal conductivity, surface properties and flexibility with good productivity.
• the present inventors have completed the present invention as a result of intensive research aimed at solving the above problems.
• one embodiment of the present invention includes the following.
• the anhydride component includes 65 to 100 mol% of pyromellitic dianhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 4 , 4'-oxydiphthalic dianhydride in an amount of 0 to 35 mol%
• the diamine component contains 65 to 100 mol% of 4,4'-diaminodiphenyl ether in 100 mol% of the total amount of the diamine component.
• a step of polymerizing an acid dianhydride component and a diamine component wherein the acid dianhydride component is 65 to 100 mol% of pyromellitic dianhydride in the total amount of 100 mol% of the acid dianhydride component; At least one of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 4,4′-oxydiphthalic dianhydride is contained in an amount of 0 to 35 mol %, and the diamine component is the diamine component.
• the acid dianhydride containing 65 to 100 mol% of 4,4'-diaminodiphenyl ether and 0 to 35 mol% of 2,2-bis[4-(4-aminophenoxy)phenyl]propane in a total amount of 100 mol%.
• graphite sheets are also required to have excellent flexibility in order to be placed in a limited space inside a small electronic device.
• the present inventors have found a polyimide film capable of providing a graphite sheet having excellent thermal conductivity, surface properties and productivity, in particular, a thick polyimide film capable of providing a thick graphite sheet. Intensive studies have been made to provide a polyimide film that can provide a graphite sheet excellent in thermal conductivity, surface properties and productivity even in the case of .
• the orientation of the graphite (graphite layer) in the resulting graphite sheet has the effect of increasing the orientation of the polyimide film for the purpose of improving interlaminar strength, etc.
• Acid anhydrides (PMDA, BPDA, etc.) and/or diamines (ODA, PDA, etc.) with enhancing properties have been employed as raw materials for polyimide films.
• PMDA, BPDA, etc. acid anhydrides
• ODA, PDA, etc. diamines
• the thickness of the graphite layer is increased (the number of graphite layers is increased).
• the polyimide film according to one embodiment of the present invention can moderately remove outgassing during heat treatment. Therefore, deterioration of the surface properties and productivity of the graphite sheet caused by the outgas can be suppressed. Therefore, it can be used particularly preferably for manufacturing thick graphite sheets.
• the present invention in addition to the acid anhydride and / or diamine that has the effect of increasing the orientation of the polyimide film, acid anhydride and / or diamine that has the effect of disturbing the orientation of the polyimide film
• acid anhydride and / or diamine that has the effect of disturbing the orientation of the polyimide film
• outgassing can be removed, but the resulting graphite sheet has excessive disorder in the orientation of the graphite layer, so thermal diffusivity and flexibility are particularly required for the graphite sheet as a heat dissipation member. It was also newly discovered that the physical properties required by the method could not be satisfied.
• the present invention provides an acid anhydride that has the effect of disturbing the orientation of a polyimide film and that can satisfy both the removal of outgassing generated during heat treatment and the physical properties required for a graphite sheet as a heat dissipation member. and/or the amount of diamine used.
• a technique based on such an idea is unprecedented and surprising.
• polyimide film A polyimide film according to one embodiment of the present invention (hereinafter sometimes referred to as the present polyimide film) will be described in detail below.
• the polyimide film for the graphite sheet used in this production method is a polyimide film made from an acid dianhydride component and a diamine component, and the acid dianhydride component is the acid dianhydride component.
• CMDA pyromellitic dianhydride
• BTDA 3,3',4,4'-benzophenonetetracarboxylic dianhydride
• ODPA 4,4'-oxydiphthalic acid
• the diamine component contains 65 to 100 mol% of 4,4'-diaminodiphenyl ether (ODA) in 100 mol% of the total amount of the diamine component.
• BAPP 2,2-bis[4-(4-aminophenoxy)phenyl]propane
• BAPP 2,2-bis[4-(4-aminophenoxy)phenyl]propane
• BTDA 3 ,3′,4,4′-benzophenonetetracarboxylic dianhydride
• ODPA 4,4′-oxydiphthalic dianhydride
• BAPP 2,2-bis[4-(4-aminophenoxy)
• the total content of phenyl]propane (BAPP) is from 1 to 35 mol %.
• the present polyimide film has the above structure, by using the present polyimide film as a raw material, it is possible to provide a graphite sheet excellent in thermal conductivity, surface properties and flexibility with good productivity. That is, the present polyimide film can be suitably used for producing graphite sheets. Therefore, the present polyimide film can also be called a polyimide film for graphite sheets.
• the acid dianhydride component which is the raw material of the present polyimide film, contains 65 to 100 mol% of pyromellitic dianhydride (PMDA) and 3,3',4,4'-benzophenonetetracarboxylic dianhydride. (BTDA) and at least one of 4,4'-oxydiphthalic dianhydride (ODPA) from 0 to 35 mol%.
• the acid dianhydride component may contain only one of BTDA and ODPA, or both of them.
• the acid dianhydride component may contain BTDA and / or ODPA, and does not contain either BTDA or ODPA. It's good.
• the amount of PMDA contained in the acid dianhydride component is 65 mol% or more, preferably 70 mol% or more, relative to 100 mol% of the total amount of the acid dianhydride component, More preferably, it is 80 mol % or more.
• the present polyimide film contains 65 mol % or more of PMDA, it is possible to provide a polyimide film (and a carbonaceous film) having moderate orientation.
• the amount of PMDA contained in the acid dianhydride component may be 85 mol% or more, 90 mol% or more, 95 mol% or more, or 100 mol%. .
• the obtained graphite sheet has good thermal diffusivity and flexibility.
• the acid dianhydride component contains at least one of BTDA and ODPA in an amount of 1 mol % or more, the orientation of the resulting polyimide film (and carbonaceous film) can be moderately disturbed. As a result, a graphite sheet having excellent thermal conductivity, surface properties and flexibility can be provided with high productivity. Further, when the content (total amount) of at least one of BTDA and ODPA in the acid dianhydride component is 35 mol% or less, there is no fear that the orientation of the resulting graphite sheet will be excessively disturbed. Good thermal diffusivity and flexibility of the sheet. In other words, when the content (total amount) of BTDA and ODPA exceeds 35%, the orientation of the resulting graphite sheet is excessively disturbed, and the thermal conductivity and flexibility of the graphite sheet tend to be poor. .
• the content of the other acid dianhydride in the acid dianhydride component, which is the raw material of the present polyimide film, is 35 mol% or less, preferably 20 mol, in 100 mol% of the total amount of the acid dianhydride component. %, more preferably 10 mol % or less, still more preferably 5 mol % or less, even more preferably 1 mol % or less, and particularly preferably 0 mol %. That is, it is particularly preferable that the acid dianhydride component, which is the raw material of the present polyimide film, does not contain other acid dianhydrides.
• the diamine component which is the raw material of the present polyimide film, contains 4,4'-diaminodiphenyl ether (ODA) in an amount of 65 to 100 mol%, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP ) in an amount of 0 to 35 mol %.
• ODA 4,4'-diaminodiphenyl ether
• BAPP 2,2-bis[4-(4-aminophenoxy)phenyl]propane
• the diamine component may or may not contain BAPP.
• the diamine component contains 100 mol % of ODA.
• the dianhydride component contains 65 to 99 mol % of PMDA and 1 to 35 mol of at least one of BTDA and ODPA. % is preferred. With such a configuration, the obtained graphite sheet has good thermal diffusivity and flexibility.
• the content of BAPP is 1 mol% or more, preferably 5 mol% or more, relative to 100 mol% of the total amount of the diamine component. It is preferably 10 mol % or more, more preferably 15 mol % or more.
• the upper limit of the BAPP content is 35 mol% or less, preferably 30 mol% or less, and more preferably 25 mol% or less.
• the present polyimide film may contain other diamines in addition to the ODA and BAPP as diamine components.
• Other diamines include, for example, p-phenylenediamine (PDA), 4,4'-diaminodiphenylmethane, benzidine, 3,3'-dichlorobenzidine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl Sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diamino Diphenylsilane, 4,4'-diminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl
• the content of the other diamine in the diamine component, which is the raw material of the present polyimide film is 35 mol% or less, preferably 20 mol% or less, more preferably 10 mol% in the total amount of 100 mol% of the diamine component. It is mol % or less, more preferably 5 mol % or less, even more preferably 1 mol % or less, and particularly preferably 0 mol %. That is, it is particularly preferable that the diamine component, which is the raw material of the present polyimide film, does not contain other diamines.
• the lower limit of the total content of the BTDA, the ODPA and the BAPP with respect to the total amount of 200 mol% of the acid dianhydride component and the diamine component is 1 mol% or more, preferably It is 5 mol % or more, more preferably 10 mol % or more, and still more preferably 15 mol % or more.
• the upper limit of the total content of BTDA, ODPA and BAPP is 35 mol % or less, preferably 30 mol % or less, and more preferably 25 mol % or less.
• This polyimide film is a polyimide film made from substantially equimolar amounts of the acid dianhydride component and the diamine component as raw materials.
• substantially equimolar amounts means that the ratio of molar amounts of two or more different substances (for example, an acid dianhydride component and a diamine component) is from 100:98 to 100:102. It is intended to be within the range, preferably 100:100.
• containing 0 to 35 mol% of at least one of BTDA and ODPA in the total amount of 100 mol% of the acid dianhydride component means "the acid dianhydride component and the diamine component It can also be said that at least one of BTDA and ODPA is contained in an amount of 0 to 35 mol% relative to the total amount of 200 mol%. It can also be said that "0 to 35 mol% of BAPP is contained with respect to 200 mol% of the total amount of the acid dianhydride component and the diamine component".
• the total content of the BTDA, the ODPA and the BAPP with respect to 200 mol% of the total amount of the acid dianhydride component and the diamine component is the content of BTDA and ODPA in the acid dianhydride component and the content of BAPP in the diamine component.
• the present polyimide film may contain inorganic particles (filler).
• inorganic particles filler
• the lower limit of the content of the inorganic particles in the present polyimide film is preferably 0.01% by weight or more, more preferably 0.02% by weight, and even more preferably 0.03% by weight.
• the upper limit of the inorganic particle content is preferably 0.30% by weight, more preferably 0.20% by weight, and even more preferably 0.15% by weight.
• Inorganic particles that the present polyimide film may contain include calcium carbonate (CaCO 3 ), silica, calcium hydrogen phosphate (CaHPO 4 ), calcium phosphate (Ca 2 P 2 O 7 ), and the like.
• phosphorus-containing inorganic particles such as calcium hydrogen phosphate and calcium phosphate are preferred.
• the average particle size of the inorganic particles that the present polyimide film may contain is not particularly limited, it is preferably more than 1.5 ⁇ m, more preferably 1.8 ⁇ m or more.
• the average particle size of inorganic particles is intended to be the volume average particle size, and the inorganic particles dispersed in dimethylformamide are measured using a microtrac particle size distribution analyzer MT3000II. is.
• the thickness of the present polyimide film is preferably 80 ⁇ m to 200 ⁇ m, more preferably 90 ⁇ m to 180 ⁇ m, even more preferably 100 ⁇ m to 160 ⁇ m, even more preferably 110 ⁇ m to 140 ⁇ m, and 115 ⁇ m to 135 ⁇ m. is particularly preferred. If the thickness of the polyimide film is within the above range, it is possible to provide a graphite sheet having a more excellent thermal diffusivity.
• the lower limit of the thickness of the polyimide film according to one embodiment of the present invention is preferably 80 ⁇ m or more, more preferably 90 ⁇ m or more, further preferably 100 ⁇ m or more, and more preferably 110 ⁇ m or more. It is preferably 115 ⁇ m or more, and particularly preferably 115 ⁇ m or more.
• the upper limit of the thickness of the polyimide film is preferably 200 ⁇ m or less, more preferably 180 ⁇ m or less, even more preferably 160 ⁇ m or less, even more preferably 140 ⁇ m or less, and 135 ⁇ m or less. It is particularly preferred to have
• the problem with conventional polyimide films is that when the thickness of the polyimide film is increased (e.g., 80 ⁇ m or more in thickness) in order to provide a thick graphite sheet, the resulting graphite sheet has poor surface properties and productivity.
• the present polyimide film can provide a thick graphite sheet with excellent surface properties with good productivity. That is, the present polyimide film can be suitably used as a thick polyimide film.
• the method for producing a polyimide film according to one embodiment of the present invention (hereinafter sometimes referred to as the method for producing the present polyimide film) is not particularly limited, but for example, a method having the following steps i) to iv) is preferable.
• Polymerization of the acid dianhydride component and the diamine component detailed in the Polyimide film> section (as raw materials) is not particularly limited as long as a polyamic acid can be obtained, for example, the following polymerization methods (1) to (5) can be preferably used.
• a method of dissolving a diamine component in an organic solvent (organic polar solvent) and reacting the diamine component with a substantially equimolar amount of an acid dianhydride component for polymerization is a method of dissolving a diamine component in an organic solvent (organic polar solvent) and reacting the diamine component with a substantially equimolar amount of an acid dianhydride component for polymerization.
• a specific example of the method (2) is to synthesize a prepolymer having the acid dianhydride at both ends using a diamine component and an acid dianhydride component, and add the diamine component used in the synthesis of the prepolymer to the prepolymer.
• a method of synthesizing a polyamic acid by reacting a diamine component having the same composition as or a diamine component having a different composition.
• the diamine component to be reacted with the prepolymer may have the same composition as the diamine component used to synthesize the prepolymer, or may have a different composition.
• a diamine component is added in an amount substantially equimolar to the acid dianhydride component to obtain an acid dianhydride.
• a method of polymerizing by reacting a mixture of an acid dianhydride component and a diamine component in substantially equimolar amounts in an organic solvent.
• step i) in the present method for producing a polyimide film can be expressed as follows: a step of polymerizing an acid dianhydride component and a diamine component, wherein the acid dianhydride component is the 65 to 100 mol% of pyromellitic dianhydride (PMDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 4 , 4'-oxydiphthalic dianhydride (ODPA) in an amount of 0 to 35 mol%, and the diamine component is 4,4'-diaminodiphenyl ether (ODA) in the total amount of 100 mol% of the diamine component.
• PMDA pyromellitic dianhydride
• BTDA 3,3′,4,4′-benzophenonetetracarboxylic dianhydride
• ODPA 4'-oxydiphthalic dianhydride
• the diamine component is 4,4'-diaminodiphenyl
• BAPP 2,2-bis[4-(4-aminophenoxy)phenyl]propane
• BAPP 2,2-bis[4-(4-aminophenoxy)phenyl]propane
• the total amount of the acid dianhydride component and the diamine component is 200 the 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), the 4,4′-oxydiphthalic dianhydride (ODPA) and the 2,2-bis[4- The total content of (4-aminophenoxy)phenyl]propane (BAPP) is 1-35 mol%.
• BTDA 3,3′,4,4′-benzophenonetetracarboxylic dianhydride
• ODPA 4,4′-oxydiphthalic dianhydride
• BAPP 2,2-bis[4- The total content of (4-aminophenoxy)phenyl]propane
• a preferred method for producing the present polyimide film can be expressed as follows: including a step of polymerizing an acid dianhydride component and a diamine component, wherein the acid dianhydride component is the acid dianhydride 65 to 100 mol% of pyromellitic dianhydride (PMDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4′- 0 to 35 mol% of at least one of oxydiphthalic dianhydride (ODPA), and the diamine component contains 65 to 100 mol% of 4,4'-diaminodiphenyl ether (ODA) in the total amount of 100 mol% of the diamine component.
• the acid dianhydride component is the acid dianhydride 65 to 100 mol% of pyromellitic dianhydride (PMDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4′- 0 to
• BAPP 2,2-bis[4-(4-aminophenoxy)phenyl]propane
• BAPP 2,2-bis[4-(4-aminophenoxy)phenyl]propane
• BTDA 3,3′,4,4′-benzophenonetetracarboxylic dianhydride
• ODPA 4,4′-oxydiphthalic dianhydride
• BAPP 2,2-bis[4-(4-amino A method for producing a polyimide film, wherein the total content of phenoxy)phenyl]propane (BAPP) is 1-35 mol%.
• step i) in the method for producing the present polyimide film are described in ⁇ 2.
• Polyimide film> section can be incorporated as appropriate.
• the steps ii) to iv) in the present method for producing a polyimide film are steps of imidizing the polyamic acid solution to obtain a polyimide film.
• the method for imidizing the polyamic acid includes, for example, (i) a thermal imidization method in which a polyamic acid solution is heated to imidize without using an imidization accelerator, or , (ii) polyamic acid, a dehydrating agent (a dehydrating ring-closing agent) typified by acid dianhydrides such as acetic anhydride, and/or tertiary amines typified by picoline, quinoline, isoquinoline, pyridine, etc.
• a chemical imidization method of imidizing polyamic acid by adding an imidization accelerator such as a catalyst and heating a polyamic acid solution containing the imidization accelerator can be used.
• the resulting polyimide film has a small coefficient of linear expansion, a high elastic modulus, a tendency to increase birefringence, and can be rapidly graphitized at a relatively low temperature, so that a high-quality graphite sheet can be obtained. Therefore, the chemical imidization method is preferred. In particular, it is preferable to use a dehydrating agent and an imidization accelerator in combination, because the resulting polyimide film can have a smaller linear expansion coefficient, a larger elastic modulus, and a larger birefringence. In addition, since the imidization reaction proceeds more rapidly in the chemical imidization method, the imidization reaction can be completed in a short time in the heat treatment, and is an industrially advantageous method with excellent productivity.
• the support used in step ii) is not dissolved by the solution containing the polyimide, and is particularly a support that can withstand the heating required for drying the laminate.
• a glass plate, an aluminum foil, an endless stainless steel belt, a stainless steel drum, etc. can be suitably used.
• the heating conditions are set according to the thickness of the finally obtained polyimide film and the production rate, and the mixed solution layer (polyamic acid solution) coated on the support is subjected to After performing at least one of partial imidization and drying, this is a step of obtaining (peeling) a gel film from the support.
• the gel film (the gel film obtained in the step iii) is heat-treated by fixing the ends of the gel film (the gel film obtained in the step iii) while avoiding shrinkage during curing. , Water, residual solvent, imidization accelerator, etc. are removed, and the remaining amic acid (amic acid that is not imidized) is completely imidized to obtain a polyimide-containing film (polyimide film). .
• the heating conditions in the iv) step may be appropriately set according to the thickness of the film to be finally obtained and the production rate.
• the method of drying the mixed solution layer and the gel film in the iii) step and the iv) step is not particularly limited.
• a method of heating by treatment can be mentioned.
• the drying temperature (heating temperature) in the drying step is not particularly limited as long as a gel film or polyimide film can be obtained. It may be 400°C to 500°C.
• Graphite sheet> In one embodiment of the invention, there is provided a graphite sheet comprising the polyimide film as a raw material. It can also be said that the graphite sheet according to one embodiment of the present invention (hereinafter referred to as the present graphite sheet) is a graphite sheet obtained by heat-treating the present polyimide film. Since the present graphite sheet contains the present polyimide film as a raw material, it is excellent in thermal conductivity, surface properties, flexibility and productivity.
• the graphite sheet refers to both a graphite sheet before being subjected to the rolling process described later (graphite sheet before rolling) and a graphite sheet after being subjected to the rolling process (graphite sheet after rolling). is intended, unless otherwise specified, graphite sheets after rolling are intended.
• the thermal conductivity of the graphite sheet can be evaluated by the thermal diffusivity of the graphite sheet (graphite sheet after rolling).
• the thermal diffusivity of the present graphite sheet is preferably 5.0 cm 2 /s or more, more preferably 5.5 cm 2 /s or more, further preferably 6.0 m 2 /s or more, It is more preferably 6.5 cm 2 /s or more, and particularly preferably 7.0 cm 2 /s or more.
• a graphite sheet having a thermal diffusivity of 5.0 cm 2 /s or more has excellent thermal conductivity.
• the surface properties of the graphite sheet can be evaluated based on surface peeling of the graphite sheet (graphite sheet before rolling). That is, in the present specification, a graphite sheet with excellent surface properties means a graphite sheet with no (almost no) surface peeling. A specific method for evaluating the surface peeling of the graphite sheet is as described in Examples described later.
• This graphite sheet (graphite sheet after rolling) has excellent flexibility. Therefore, it can be arranged in a limited space such as inside a small electronic device.
• a specific method for evaluating the flexibility of the graphite sheet is as described in Examples described later.
• the productivity of the graphite sheet is defined as the ratio of the thickness of the raw material polyimide film to the thickness of the resulting graphite sheet (graphite sheet before rolling) (thickness of graphite sheet before rolling/thickness of polyimide film). It can be evaluated based on the thickness (hereinafter referred to as "GS thickness/PI thickness"). If the GS thickness/PI thickness is greater than a certain value (for example, more than 3.0), especially in the case of winding, the amount of graphite sheet before rolling that can be handled at one time is limited, resulting in poor productivity. .
• a certain value for example, more than 3.0
• the smaller the GS thickness/PI thickness the larger the amount of the graphite sheet that can be handled at one time, that is, the more excellent the productivity. Specifically, if the GS thickness/PI thickness is 3.0 or less, it can be evaluated that the graphite sheet has excellent productivity.
• the GS thickness/PI thickness is preferably 2.5 or less, more preferably 2.0 or less, even more preferably 1.5 or less, and even more preferably 1.0 or less.
• the lower limit of the thickness of the present graphite sheet is preferably 45 ⁇ m or more, more preferably 50 ⁇ m or more, and even more preferably 55 ⁇ m or more.
• the upper limit of the thickness of the graphite sheet after rolling is preferably 110 ⁇ m or less, more preferably 105 ⁇ m or less. If the thickness of the graphite sheet after rolling is 45 ⁇ m or more, it has sufficient heat dissipation effect for electronic equipment, and if it is 110 ⁇ m or less, it can be installed in thin electronic equipment with little space. have advantages.
• the density of the graphite sheet (graphite sheet after rolling) is preferably 1.20 g/cm 3 or more, more preferably 1.40 g/cm 3 or more, and 1.60 g/cm 3 or more. It is more preferably 3 or more, more preferably 1.80 g/cm 3 or more. Although the upper limit of the density is not particularly determined, the graphite sheet is usually 2.26 g/cm 3 or less. If the graphite sheet has a density of 1.60 g/cm 3 or more, the graphite sheet has the advantage of exhibiting an excellent heat dissipation effect.
• a method for producing a graphite sheet according to one embodiment of the present invention includes a step of heat-treating a polyimide film for a graphite sheet at 2400° C.
• the polyimide film for is a polyimide film made from an acid dianhydride component and a diamine component as raw materials, and the acid dianhydride component is the acid dianhydride component in a total amount of 100 mol%, pyromellit 65 to 100 mol% of an acid dianhydride, and 0 to 35 mol% of at least one of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 4,4′-oxydiphthalic dianhydride and the diamine component contains 65 to 100 mol% of 4,4′-diaminodiphenyl ether and 0 mol% of 2,2-bis[4-(4-aminophenoxy)phenyl]propane in 100 mol% of the total amount of the diamine component.
• the present graphite sheet manufacturing method includes a step of heat-treating the present polyimide film at 2400° C. or higher.
• the present graphite sheet that is, a graphite sheet excellent in thermal conductivity, surface properties and flexibility can be provided with high productivity.
• the polyimide film used in the present graphite sheet manufacturing method the above ⁇ 2. Polyimide Film> section is incorporated as appropriate.
• the method for producing the present graphite sheet is not particularly limited as long as it includes a step of heat-treating a specific polyimide film (the present polyimide film) at 2400 ° C. or higher, but the polyimide film is heat-treated in an inert gas atmosphere or under reduced pressure. It is preferably a so-called polymer thermal decomposition method.
• the present graphite sheet manufacturing method includes a carbonization step of preheating a polyimide film at a temperature of about 1000° C. to obtain a carbonized polyimide film, and a carbonized polyimide film produced in the carbonization step. is heat-treated (heated) at a temperature of 2400° C. or higher to graphitize, and a rolling step of rolling this.
• the carbonization step and the graphitization step may be performed continuously, or after the carbonization step is completed, the graphitization step alone may be performed separately.
• the method for manufacturing the present graphite sheet will be described in detail, taking as an example a method including a carbonization process, a graphitization process, and a rolling process.
• the carbonization step is a step of heat-treating the polyimide film to a temperature of about 1000° C. to carbonize (carbonize) the polyimide film.
• the carbonization method of the polyimide film in the carbonization step is not particularly limited.
• a rectangular polyimide film may be carbonized while being laminated with a graphite sheet, or a roll-shaped polyimide film may be carbonized as it is in a roll.
• the film may be unwound from a roll-shaped polyimide film and carbonized continuously.
• the carbonization step is preferably performed under a vacuum atmosphere, under reduced pressure, or in an inert gas, and nitrogen is preferably used as the inert gas.
• the carbonized polyimide film obtained by the carbonization process may be called a carbonaceous film.
• a carbonaceous film obtained by carbonizing the present polyimide film has a somewhat disturbed orientation, similar to the present polyimide film.
• a carbonaceous film having a somewhat disturbed orientation can easily release outgas in the graphitization step described later, and can suppress foaming of a graphite sheet obtained by heat-treating (graphitizing) the carbonaceous film. , a graphite sheet having excellent surface properties and flexibility can be provided.
• the graphitization step is a step of heat-treating the carbonaceous film obtained in the carbonization step at a temperature of 2400° C. or higher to graphitize the carbonaceous film.
• the graphitization step can also be said to be a step of heat-treating a carbonaceous film to obtain a graphite sheet (graphite sheet before rolling).
• the temperature (maximum temperature) at which the carbonaceous film obtained in the carbonization step is heat-treated is preferably, for example, 2400° C. or higher, 2600° C. or higher, 2800° C. or higher, 2900° C. or higher, or 3000° C. or higher. .
• the upper limit of the maximum temperature is not particularly limited, it is preferably 3300° C. or less, more preferably 3200° C. or less.
• the temperature (maximum temperature) when heat-treating the carbonaceous film obtained in the carbonization step is 2400°C or higher, there is an advantage that the obtained graphite sheet has a good thermal diffusivity. If it is below, there is an advantage that the sublimation of the graphite member in the graphitization furnace can be suppressed.
• the graphitization step is performed under reduced pressure or in an inert gas, and argon or helium can be suitably used as the inert gas.
• a rectangular carbonaceous film may be graphitized in a state of being laminated with a graphite sheet, or a roll-shaped carbonaceous film may be graphitized as it is in a roll. may be drawn out and graphitized continuously.
• the rolling step is a step of rolling the graphite sheet obtained by the graphitization step (graphite sheet before rolling).
• the rolling process can be said to be a process of obtaining a graphite sheet after rolling, and can also be said to be a compression process.
• the graphite sheet before rolling is in a foamed state due to the influence of outgassing generated in the graphitization process, and may have an excessive thickness unsuitable for practical use. The thickness can be adjusted and flexibility can be imparted.
• the method of rolling the graphite sheet is not particularly limited, and examples thereof include a method of rolling using metal rolls or the like.
• the rolling step may be performed while the manufactured graphite sheet is cooled to room temperature, or may be performed continuously with the graphitization step.
• the diamine component contains 65 to 100 mol% of 4,4'-diaminodiphenyl ether and 0 to 35 mol of 2,2-bis[4-(4-aminophenoxy)phenyl]propane in 100 mol% of the total amount of the diamine component.
• the acid dianhydride component contains 100 mol% of pyromellitic dianhydride, and the diamine component contains 65 to 99 mol% of 4,4'-diaminodiphenyl ether, 2,2-bis[4- The polyimide film for a graphite sheet according to [1], containing 1 to 35 mol% of (4-aminophenoxy)phenyl]propane.
• [7] including a step of heat-treating a polyimide film for a graphite sheet to 2400° C. or higher, wherein the polyimide film for the graphite sheet is a polyimide film made from an acid dianhydride component and a diamine component,
• the acid dianhydride component contains 65 to 100 mol% of pyromellitic dianhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride in the total amount of 100 mol% of the acid dianhydride component.
• the acid dianhydride component contains 100 mol% of pyromellitic dianhydride, and the diamine component contains 65 to 99 mol% of 4,4'-diaminodiphenyl ether, 2,2-bis[4- The method for producing a graphite sheet according to [7], containing 1 to 35 mol% of (4-aminophenoxy)phenyl]propane.
• the diamine component is 65 to 100 mol% of 4,4'-diaminodiphenyl ether and 0 to 35 mol% of 2,2-bis[4-(4-aminophenoxy)phenyl]propane in 100 mol% of the total amount of the diamine component, and the acid
• the 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, the 4,4′-oxydiphthalic dianhydride and the 2 relative to 200 mol % of the total amount of the dianhydride component and the diamine component ,2-bis[4-(4-aminophenoxy)phenyl]propane content is 1 to 35 mol%.
• the thickness of the graphite sheet before rolling was measured by the following method.
• the thickness of the graphite sheet was measured at four corners and one central point using a Mitutoyo micrometer.
• the "central point” refers to the position of the intersection of diagonal lines drawn from the four measurement points at each corner of the obtained graphite sheet to the diagonal measurement points.
• the average value of the thickness measurement values obtained at a total of five locations was taken as the thickness of the graphite sheet before rolling. Note that the four corners mean the vertices of a rectangular graphite sheet before rolling, which is the object of measurement.
• the evaluation criteria were as follows. A (excellent): No surface peeling was observed on the entire graphite sheet, and even if the surface of the graphite sheet was touched with a hand, graphite powder did not adhere to the hand. B (acceptable): No peeling of the surface was observed on the entire graphite sheet, but when the surface of the graphite sheet was touched with a hand, graphite powder adhered to the hand. C (slightly unsatisfactory): Surface peeling is observed in part of the graphite sheet. D (Poor): Surface peeling is observed over the entire graphite sheet, and the sheet-like shape cannot be maintained.
• the evaluation criteria were as follows. A (excellent): GS thickness / PI thickness is 1.0 or less B (pass): GS thickness / PI thickness is over 1.0, 3.0 or less C (poor): GS thickness / PI thickness is over 3.0 .
• the thickness of the graphite sheet after rolling was measured by the following method.
• the thickness of the graphite sheet was measured at four corners and one central point using a Mitutoyo micrometer.
• the "central point” refers to the position of the intersection of diagonal lines drawn from the four measurement points at each corner of the obtained graphite sheet to the diagonal measurement points.
• the average value of the thickness measurement values obtained at a total of five locations was taken as the thickness of the graphite sheet after rolling. It should be noted that the four corners are intended to be the vertices when the rolled graphite sheet to be measured is rectangular.
• the thermal diffusivity of the graphite sheet after rolling was measured by the following method.
• a sample of a graphite sheet after rolling cut into a square of 30 mm ⁇ 30 mm was measured using a "Thermo Wave Analyzer TA3" manufactured by Bethel Co., Ltd. under the conditions of an atmosphere of 25 ° C. and a frequency of 75 Hz to determine the thermal diffusivity. was obtained by measuring
• the sample was prepared by punching out the center portion of the graphite sheet after rolling, which is the object of measurement, with a Thomson blade.
• the “central portion” means the central portion of the rolled graphite sheet in the width direction and also in the longitudinal direction.
• the mixed solution layer on the aluminum foil was dried using a hot air oven and a far infrared heater.
• the drying conditions are as follows. First, the mixed solution layer on the aluminum foil was dried in a hot air oven at 120° C. for 400 seconds to form a self-supporting gel film. The gel film was peeled off from the aluminum foil and fixed to the frame. Further, the gel film was heated stepwise in a hot air oven at 120°C for 50 seconds, 275°C for 66 seconds, 400°C for 70 seconds, 450°C for 85 seconds, and a far infrared heater at 460°C for 35 seconds. and dried to produce a polyimide film (A) having a thickness of 125 ⁇ m.
• the laminate was placed in a carbonization device (a carbonization device manufactured by Kurata Giken Co., Ltd.) (inside a heating space).
• the heating space in the carbonization apparatus in which the laminate was installed was heated to 600° C. at a heating rate of 0.4° C./min, and then held at 600° C. for 1 hour.
• the heating space in the carbonization device is heated to 1000° C. at a heating rate of 0.4° C./min, and then the laminate (polyimide film in the laminate) is heat-treated (carbonized) at 1000° C. for 30 minutes. to obtain a carbonaceous film.
• the obtained carbonaceous film was cooled to room temperature (23°C) and formed into a roll having an inner diameter of 100 mm to obtain a roll of carbonaceous film.
• the carbonaceous film roll is placed on the hearth of a graphitization furnace (graphitization furnace manufactured by Kurata Giken Co., Ltd.) so that the width direction is vertical.
• the temperature was raised to 2900°C (maximum graphitization temperature) at a heating rate of 2°C/min under an argon atmosphere, and then held at 2900°C for 30 minutes to obtain a graphitized film (graphite sheet before rolling). was made.
• the thickness, surface properties, and productivity of the obtained graphite sheet before rolling were measured and evaluated. Table 1 shows the results.
• the resulting graphitized film was cooled to room temperature and rolled by a 2-ton precision roll press (clearance type) manufactured by Thank Metal Co., Ltd. to obtain a graphite sheet (graphite sheet after rolling).
• the thickness, thermal diffusivity, density and flexibility of the graphite sheet obtained after rolling were measured and evaluated. Table 1 shows the results.
• Examples 1 to 13, Comparative Examples 1 to 3 A polyimide film was prepared and heated in the same manner as in Comparative Example 1, except that the composition and amount of the acid dianhydride component and/or diamine component added were changed to the compositions and amounts shown in Table 1. It was processed to produce graphite sheets. The physical properties of the produced graphite sheet were measured and evaluated in the same manner as in Comparative Example 1. Table 1 shows the results.
• Example 14-18 The composition of the acid dianhydride component and / or the diamine component and the amount of addition thereof were changed to the composition and amount shown in Table 1, and the thickness of the polyimide film was set to the thickness shown in Table 1.
• Comparative A polyimide film was prepared in the same manner as in Example 1 and heat-treated to prepare a graphite sheet. In addition, the film-forming time of the polyimide film and the heating time in the graphitization step were adjusted in proportion to the thickness.
• the film forming time (drying time) of the polyimide film and the heating time in the graphitization process are reduced by 0.001. It was set to 64 (80/125) times the length.
• the physical properties of the produced graphite sheet were measured and evaluated in the same manner as in Comparative Example 1. Table 1 shows the results.
• the thermal diffusivity after rolling is excellent, the flexibility is excellent, and the density is high. That is, according to the polyimide film according to one embodiment of the present invention, it was shown that a graphite sheet excellent in thermal conductivity, surface properties and flexibility can be obtained with good productivity. In addition, it was shown that the graphite sheet has a sufficiently thin thickness before rolling, so that it is excellent in productivity and density.
• a graphite sheet containing the polyimide film according to one embodiment of the present invention as a raw material is excellent in thermal conductivity, surface properties and flexibility, and therefore can be suitably used as a heat dissipation member for electronic devices, particularly thin electronic devices. .

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