Thermally conductive polyimide film, method for manufacturing the same, metal laminate, electrical and electronic equipment, and flexible printed circuit board

Abstract

The present invention provides a thermally conductive polyimide film with high elongation, a method for manufacturing the same, a metal laminate using the polyimide film, electrical and electronic equipment, and a flexible printed circuit board. [Solution] A thermally conductive polyimide film is used, comprising a polyimide resin (A), a filler (B), and an aliphatic ester compound (C) of pyromellitic acid or trimellitic acid, wherein the aliphatic ester compound (C) contains an aliphatic group having 4 to 12 carbon atoms, and the content of the filler (B) relative to the total volume of the thermally conductive polyimide film is 15% by volume or more.

Description

Technical Field

[0001] The present invention relates to a thermally conductive polyimide film, a method for producing the same, a metal laminate, an electric and electronic device, and a flexible printed circuit board.

Background Art

[0002] In recent years, the demand for miniaturization and weight reduction of electronic devices typified by mobile phones has been increasing. For this reason, flexible printed circuit boards, which are advantageous for miniaturization and weight reduction of such electronic devices, have come to be widely used in the field of electronic technology. Among them, flexible printed circuit boards having a polyimide film as an insulating layer have been widely used conventionally because of their good heat resistance, chemical resistance, etc. Recently, with the improvement of communication speed and computing speed, the amount of arithmetic processing in integrated circuits has increased, resulting in a large amount of heat generation and an increase in the amount of heat generation per unit area. On the other hand, due to the miniaturization of electronic devices, the degree of circuit integration has also increased, and the amount of heat transfer by a metal circuit for transferring heat to a heat dissipation device (heat dissipation fins, heat dissipation sheets, etc.) cannot keep up, and combined with the high-speedization of information processing, the heat dissipation means for heat generated in the device has attracted attention.

[0003] In order to provide a flexible printed circuit board with excellent heat dissipation properties, in addition to heat dissipation from a metal circuit with high thermal conductivity, heat dissipation from the polyimide film constituting the insulating layer, that is, improvement of the thermal conductivity is required.

[0004] As a method for improving the thermal conductivity of a polyimide film, for example, a method using a polyimide film containing a large amount of a high thermal conductivity inorganic filler is known (Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] However, the polyimide films described in these patent documents contain a large amount of inorganic filler, which reduces their strength during the film formation process, making them prone to breakage during the circuit board manufacturing process. Furthermore, the elongation of the resulting polyimide films is not sufficient.

[0007] The present invention has been made in view of the above problems, and aims to provide a thermally conductive polyimide film having a high elongation rate, a method for manufacturing the same, a metal laminate using the polyimide film, electrical and electronic equipment, and a flexible printed circuit board. [Means for solving the problem]

[0008] The inventors of the present invention have discovered that the above problems can be solved by using a polyimide film containing a specific aliphatic ester compound, and have completed the present invention.

[0009] The embodiments of this disclosure relate to the following: thermally conductive polyimide films, methods for manufacturing the same, metal laminates, electrical and electronic equipment, and flexible printed circuit boards.

[0010] [1] Polyimide resin (A) and Filler (B) and, A pyromellitic acid or trimellitic acid aliphatic ester compound (C), A thermally conductive polyimide film containing, The aliphatic ester compound (C) contains an aliphatic group having 4 to 12 carbon atoms, A thermally conductive polyimide film in which the content of the filler (B) relative to the total volume of the thermally conductive polyimide film is 15% by volume or more. [2] The thermally conductive polyimide film according to [1], wherein the aliphatic ester compound (C) contains two or more ester groups per molecule. [3] The thermally conductive polyimide film according to [1] or [2], wherein the aliphatic ester compound (C) comprises at least one selected from the group consisting of trioctyl trimellitate, tributyl trimellitate, tri-2-ethylhexyl trimellitate, trialkyl trimellitate, triisononyl trimellitate, 2-ethylhexyl pyromellitate, and mixed linear alkyl pyromellitate. [4] The thermally conductive polyimide film according to any one of [1] to [3], wherein the filler (B) comprises at least one selected from the group consisting of aluminum oxide, aluminum hydroxide, boron nitride, aluminum nitride, zinc oxide, magnesium oxide, and silica. [5] A thermally conductive polyimide film according to any of [1] to [4], having an elongation rate of 30% or more. [6] A thermally conductive polyimide film according to any of [1] to [5], wherein the thermal conductivity in the thickness direction of the film is 0.7 W / mK or higher. [7] Step 1(A): A step of mixing filler (B), polyamic acid (D), and organic solvent (E) to obtain a polyamic acid-containing mixture (I), Step 1(B): A step of mixing filler (B) and organic solvent (E) to prepare a dispersion, and mixing the dispersion with polyamic acid (D) to obtain a polyamic acid-containing mixture (I), or Process 1(C): Prepared by any of the following steps: mixing filler (B) and organic solvent (E) to prepare a dispersion, and mixing the dispersion during the manufacturing process of polyamic acid (D) to obtain a polyamic acid-containing mixture (I). A step to obtain a polyamic acid-containing mixture (I), Step 2: A step of mixing the polyamic acid-containing mixture (I), an aliphatic ester compound of pyromellitic acid or trimellitic acid (C), and an imidation catalyst and / or a dehydrating agent to obtain a polyamic acid-containing mixture (II), Step 3: A step of forming a film using the polyamic acid-containing mixture (II), A method for producing a thermally conductive polyimide film containing, A method for producing a thermally conductive polyimide film, wherein the aliphatic ester compound (C) contains an aliphatic group having 4 to 12 carbon atoms. [8] The method for producing a thermally conductive polyimide film according to [7], wherein the aliphatic ester compound (C) contains two or more ester groups per molecule. [9] The method for producing a thermally conductive polyimide film according to [7] or [8], wherein the aliphatic ester compound (C) comprises at least one selected from the group consisting of trioctyl trimellitate, tributyl trimellitate, tri-2-ethylhexyl trimellitate, trialkyl trimellitate, triisononyl trimellitate, 2-ethylhexyl pyromellitate, and mixed linear alkyl pyromellitate. A thermally conductive polyimide film as described in any of [1] to [6], A metal layer laminated on one or both sides of the thermally conductive polyimide film, A metal laminate having [a certain characteristic].

[11] Electrical and electronic equipment using a thermally conductive polyimide film as described in any of [1] to [6].

[12] A flexible printed circuit board using the metal laminate described in

[10] . [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a thermally conductive polyimide film having a high elongation rate, a method for producing the same, a metal laminate using the polyimide film, electrical and electronic equipment, and a flexible printed circuit board. [Modes for carrying out the invention]

[0012] Thermally conductive polyimide film The thermally conductive polyimide film contains a polyimide resin (A), a filler (B), and an aliphatic ester compound (C) of pyromellitic acid or trimellitic acid. The aliphatic ester compound (C) contains an aliphatic group having 4 to 12 carbon atoms. The content of the filler (B) with respect to the total volume of the thermally conductive polyimide film is 15% by volume or more.

[0013] By containing the aliphatic ester compound (C), the thermally conductive polyimide film has a high elongation rate.

[0014] Hereinafter, the essential or optional components contained in the thermally conductive polyimide film will be described.

[0015] <Polyimide resin (A)> The polyimide resin (A) is the matrix resin of the thermally conductive polyimide film. The polyimide resin (A) is obtained by imidizing a polyamic acid (D) using a known imidization means. As the polyamic acid (D) which is a polyimide precursor, a polyamic acid solution is usually used. The concentration of the polyamic acid solution is not particularly limited, and is usually 5% by mass or more and 35% by mass or less, and preferably 10% by mass or more and 30% by mass or less. When the concentration is within this range, a polyamic acid (D) having an appropriate molecular weight and solution viscosity can be obtained.

[0016] Typical methods for adding monomers in the polymerization of polyamic acid (D) include the following: 1) A method of polymerization by dissolving a diamine in an organic solvent (E) and reacting it with substantially equimolar amounts of tetracarboxylic dianhydride; 2) A method of polymerization by reacting tetracarboxylic dianhydride with a diamine compound in an organic solvent (E) to obtain a prepolymer having acid anhydride groups at both ends. Subsequently, polymerization is carried out using diamine such that the tetracarboxylic dianhydride and diamine are substantially equimolar throughout the entire process; 3) A method of polymerization by reacting tetracarboxylic dianhydride with an excess molar amount of diamine in an organic solvent (E) to obtain a prepolymer having amino groups at both ends. Next, a method of polymerization using tetracarboxylic dianhydride after adding diamine and ensuring that the tetracarboxylic dianhydride and diamine are substantially equimolar throughout the entire process; 4) a method of polymerization using diamine after dissolving and / or dispersing tetracarboxylic dianhydride in an organic solvent (E) and ensuring that it is substantially equimolar; 5) a method of polymerization by reacting a substantially equimolar mixture of tetracarboxylic dianhydride and diamine in an organic solvent (E). These methods may be used individually or in combination in part.

[0017] While there are no particular limitations on the order in which the diamine and tetracarboxylic dianhydride, which are the raw materials, are added, it is possible to control the properties of the resulting polyamic acid or polyimide not only by controlling the chemical structure of the raw materials but also by controlling the order in which they are added.

[0018] The above-mentioned substantially equimolar means that, when A moles of tetracarboxylic dianhydride and B moles of diamine are used, the molar ratio calculated as A ÷ B is within the range of 0.90 to 1.10. In particular, it is preferable to control the molar ratio to be between 0.95 and 1.05, as this can improve the molecular weight of polyamic acid (D).

[0019] To control the reaction temperature, it is preferable to carry out the polymerization reaction in a reaction apparatus equipped with a temperature control device, and the temperature in the reaction solution is preferably between 0°C and 60°C, and more preferably between 15°C and 50°C.

[0020] In the production of this polyamic acid (D), it is preferable to carry out the polymerization reaction in one step in a single reactor to produce a polyamic acid solution. In order to carry out the polymerization reaction in one step, it is preferable to include a step in which the monomer is dissolved in an organic solvent immediately before being added to the reaction vessel and any foreign matter is removed using a filter or the like to reduce foreign matter and defects in the film, in order to remove insoluble raw materials and foreign matter from the monomer components in the polymerization reaction. Alternatively, it is preferable to include a step in which foreign matter is directly removed by sieving the powder to reduce foreign matter and defects in the film before carrying out the polymerization reaction. The mesh size of the above filter is usually 1 / 2 of the thickness of the obtained film, preferably 1 / 5, and more preferably 1 / 10. This is because if defects caused by insoluble raw materials and foreign matter are present on the surface of the polyimide film, the adhesion between the film and the metal layer will decrease in the metal layer formation step on the polyimide film.

[0021] Furthermore, another method involves carrying out the polymerization reaction in two stages. In this method, a low-viscosity polyamic acid called a prepolymer is polymerized in the first stage, and then a high-viscosity polyamic acid is obtained by adding an organic solvent containing an acidic dianhydride dissolved in an organic solvent. When transitioning from the first stage to the second stage, it is preferable to include a step to remove insoluble raw materials and foreign matter from the prepolymer using a filter or the like to reduce foreign matter and defects in the film. The mesh size of the above filter is usually 1 / 2 of the thickness of the obtained film, preferably 1 / 5, and more preferably 1 / 10. This is because if defects caused by insoluble raw materials and foreign matter are present on the surface of the polyimide film, the adhesion between the film and the metal layer will decrease in the process of forming the metal layer on the polyimide film.

[0022] (Diamine) Examples of the above diamines include o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis(4-amino-3,5-dimethylphenyl)methane, bis(4-amino-3,5-diisopropylphenyl)methane, 3,3'-diaminodiphenyldifluoromethane, 3,4'-diaminodiphenyldifluoromethane, 4,4'-diaminodiphenyldifluoromethane, 3,3'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl ketone, 3,4'-diaminodiphenyl Phenyl ketone, 4,4'-diaminodiphenyl ketone, 2,2-bis(3-aminophenyl)propane, 2,2'-(3,4'-diaminodiphenyl)propane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)hexafluoropropane, 2,2-(3,4'-diaminodiphenyl)hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(3- Minophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 3,3'-(1,4-phenylenebis(1-methylethylidene))bisaniline, 3,4'-(1,4-phenylenebis(1-methylethylidene))bisaniline, 4,4'-(1,4-phenylenebis(1-methylethylidene))bisaniline, 2,2-bis(4-(3-aminophenoxy)phenyl)propane, 2,2-bis(4-(3-aminophenoxy)phenyl)hexafluoropropane, 2,2-Bis(4-(4-aminophenoxy),phenyl)hexafluoropropane, bis(4-(3-aminoenoxy)phenyl) sulfide, bis(4-(4-aminoenoxy)phenyl) sulfide, bis(4-(3-aminoenoxy)phenyl) sulfone, bis(4-(4-aminoenoxy)phenyl) sulfone, aromatic diamines such as 3,5-diaminobenzoic acid, 1,3-bis(aminomethyl)cyclohexane, 2,2-bis(4-aminophenoxyphenyl)propane, 3,3'-dichlorobenzide 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 1,5-diaminonaphthalene, 2,2'-dimethoxy-4,4'-biphenyldiamine, 2,2'-dimethyl-4,4'-biphenyldiamine, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 4,4'-diaminodiphenylpropane, 2,4-bis(β-amino-t-butyl)toluene, bis(p-β-amino-t-butylphenyl) ether, bis(p-β-methyl-δ-aminophenyl)benzene N, bis-p-(1,1-dimethyl-5-amino-pentyl)benzene, 1-isopropyl-2,4-m-phenylenediamine, m-xylylenediamine, p-xylylenediamine, di(p-aminocyclohexyl)methane, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, diaminopropyltetramethylene, 3-methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2- Examples include bis-3-aminopropoxyethane, 2,2-dimethylpropylenediamine, 3-methoxyhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 3-methylheptamethylenediamine, 5-methylnonamethylenediamine, 2,11-diaminododecane, 2,17-diaminoeicosadecane, 1,4-diaminocyclohexane, 1,10-diamino-1,10-dimethyldecane, 1,12-diaminooctadecane, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane. These may be used individually or in combination of two or more. Among these, p-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2'-dimethyl-4,4'-biphenyldiamine and 2,2-bis[4-(4-aminophenoxy)phenyl]propane are preferred.

[0023] (acid dianhydride) Examples of the above tetracarboxylic dianhydrides include pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, and bis(3,4-dicarboxyphenyl) Xyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 3,4,9,10-perylenetetracarboxylic acid dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, benzene-1,2,3,4-tetracarboxylic acid dianhydride, 3,4,3',4'-benzophenonetetracarboxylic acid dianhydride, 2,3,2',3'-benzophenonetetracarboxylic acid dianhydride, 3,3,3',4'-benzophenonetetracarboxylic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalene Tetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,2,4,5-naphthalenetetracarboxylic acid dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride, phenanthrene-1,8,9,10-tetracarboxylic acid dianhydride, pyrazine-2,3,5,6-tetracarboxylic acid dianhydride, thiophene-2,3,5,6-tetracarboxylic acid dianhydride Rubonic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, 3,4,3',4'-biphenyltetracarboxylic acid dianhydride, 2,3,2',3'-biphenyltetracarboxylic acid dianhydride, bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride, bis(3,4-dicarboxyphenyl)methylphenylsilane dianhydride, bis(3,4-dicarboxyphenyl)diphenylsilane dianhydride, 1,4-bis(3,4-dicarboxyphenyldimethylsilyl)benzene dianhydride, 1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-Tetramethyldicyclohexane dianhydride, p-phenylenebis(trimellitate anhydride), ethylenetetracarboxylic acid dianhydride, 1,2,3,4-butanetetracarboxylic acid dianhydride, decahydronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic acid dianhydride, cyclopentane-1,2,3,4-tetracarboxylic acid dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic acid dianhydride, 1,2,3,4-cyclobutanete Dianhydride of racarboxylic acid, bis(exo-bicyclo[2,2,1]heptane-2,3-dicarboxylic acid dianhydride, bicyclo-[2,2,2]-octo-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenyl)phenyl]propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenyl)phenyl]hexafluoropropane dianhydride, 4 ,4'-Bis(3,4-Dicarboxyphenoxy)diphenyl sulfide dianhydride, 1,4-Bis(2-Hydroxyhexafluoroisopropyl)benzenebis(trimellitic anhydride), 1,3-Bis(2-Hydroxyhexafluoroisopropyl)benzenebis(trimellitic anhydride), 5-(2,5-Dioxotetrahydrofuryl)-3-Methyl-3-Cyclohexene-1,2-Dicarboxylic acid dianhydride, Tetrahydrofuran-2,3,4,5-Tetracarboxylic acid dianhydride, 1,2-(Ethylene)bis(Trimellitate anhydride), 1,3-(T Limethylene)bis(trimellitate anhydrous), 1,4-(tetramethylene)bis(trimellitate anhydrous), 1,5-(pentamethylene)bis(trimellitate anhydrous), 1,6-(hexamethylene)bis(trimellitate anhydrous), 1,7-(heptamethylene)bis(trimellitate anhydrous), 1,8-(octamethylene)bis(trimellitate anhydrous), 1,9-(nonamethylene)bis(trimellitate anhydrous), 1,10-(decamethylene)bis(trimellitate anhydrous), 1,12-(dodecamethylene)bis(trimellitate anhydrous), 1,Examples include 16-(hexadecamethylene)bis(trimellitate anhydride) and 1,18-(octadecamethylene)bis(trimellitate anhydride). These may be used individually or in combination of two or more. Among these, 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and 3,3',4,4'-benzophenonetetracarboxylic dianhydride are preferred.

[0024] A particularly preferred structure for polyimide resin (A) is one in which the total tetracarboxylic dianhydride contains 30 to 70 mol% of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 30 to 70 mol% of pyromellitic dianhydride, and the total diamine contains 0 to 60 mol% of p-phenylenediamine and 40 to 100 mol% of 4,4'-diaminodiphenyl ether, which is preferable for increasing thermal conductivity and improving mechanical properties.

[0025] (Organic solvent (E)) As the organic solvent (E), an organic polar solvent is preferred. The organic polar solvent is not particularly limited, but it is required that it does not react with diamines or acidic dianhydrides and can dissolve polyamic acids. Examples of such organic polar solvents include 1-methylpyrrolidone, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, 3-methoxy-NN-dimethylpropanamide, and 3-methoxy-N,N-dibutylpropanamide. These may be used individually or in combination of two or more.

[0026] (Imidization) Polyimides are obtained by a dehydration conversion reaction (dehydration ring-closing reaction) from polyamic acids. Two methods are widely known for this conversion reaction: the thermal curing method, which uses only heat, and the chemical curing method, which uses an imidation catalyst and a dehydrating agent. To improve thermal conductivity, it is desirable to use the thermal curing method. Furthermore, it is preferable to use an imidation catalyst in combination with the polyamic acid precursor to promote thermal imidation and ensure the mechanical strength of the film. In addition, the chemical curing method using an imidation catalyst and a dehydrating agent improves productivity and ensures the mechanical strength of the film. In this case, it is preferable to add the dehydrating agent and imidation catalyst to the polyimide precursor solution immediately before film formation.

[0027] (Imidation catalyst) An imidation catalyst is a component that promotes the dehydration and cyclization of polyamic acids. Examples of imidation catalysts include aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines. Of these, nitrogen-containing heterocyclic compounds such as triethylamine, pyridine, imidazole, benzimidazole, isoquinoline, quinoline, lutidine, and pyridine compounds with alkyl groups substituted at the β and / or γ positions are preferred. In particular, pyridine, isoquinoline, imidazole, and pyridine compounds with alkyl groups substituted at the β and / or γ positions are preferred. More specifically, it is preferable to use one or more imidation catalysts selected from isoquinoline, β-picoline, 3,5-lutidine, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 4-ethyl-2-methylimidazole, and 1-methyl-4-ethylimidazole. The content of the imidation catalyst relative to the polyamic acid depends on the structural formula of the polyamic acid, but the ratio of moles of imidation catalyst to moles of amide groups in the polyamic acid is preferably 10 to 0.01, and more preferably 5 to 0.1.

[0028] (Dehydrating agent) The dehydrating agent is a dehydrating cyclization agent for polyamic acids. Suitable dehydrating cyclization agents include, for example, aliphatic anhydrides, aromatic anhydrides, N,N'-dialkylcarbodiimides, lower aliphatic halides, halogenated lower aliphatic anhydrides, arylsulfonic acid dihalides, thionyl halides, or mixtures of two or more of these. Among these, aliphatic anhydrides and aromatic anhydrides work more favorably. Acetic anhydride is particularly preferred. The amount of dehydrating agent relative to the polyamic acid depends on the structural formula of the polyamic acid, but the ratio of moles of dehydrating agent to moles of amide groups in the polyamic acid is preferably 10 to 0.01, and more preferably 5 to 0.5. In this case, a reaction retarder such as acetylacetone may be used in combination.

[0029] <Filler (B)> As filler (B), a filler with high thermal conductivity is preferred, and it is preferable that it contains at least one selected from the group consisting of aluminum oxide, aluminum hydroxide, boron nitride, aluminum nitride, zinc oxide, magnesium oxide, and silica. Among these, boron nitride, aluminum oxide, and zinc oxide are preferred for improving thermal conductivity. The shape of filler (B) is not particularly limited and may be spherical, plate-shaped, needle-shaped, etc.

[0030] The average particle size of filler (B) is preferably 0.3 μm or more and 50 μm or less, and more preferably 0.5 μm or more and 40 μm or less. Using particles with an average particle size of 0.3 μm or more and 50 μm or less is preferable because it makes it easier to uniformly disperse the particles inside the polyimide film, increases the probability of contact between particles, and improves thermal conductivity. Furthermore, it is preferable because the improved dispersibility inside the resin improves the toughness of the polyimide film. In the present invention, the average particle size is the median diameter (D50) measured by dynamic light scattering.

[0031] The content of filler (B) relative to the total volume of the thermally conductive polyimide film is 15% by volume or more, preferably 15% to 90% by volume, and more preferably 20% to 70% by volume.

[0032] <Aliphatic ester compounds (C)> The aliphatic group (C) of the aliphatic ester compound has 4 to 12 carbon atoms, preferably 6 to 10. The aliphatic group preferably includes at least one selected from the group consisting of alkyl groups and cycloalkyl groups. Among these, the inclusion of an alkyl group is preferred.

[0033] From the viewpoint of obtaining a thermally conductive polyimide film with high elongation, the aliphatic ester compound (C) preferably contains two or more ester groups per molecule, and more preferably contains three or more ester groups per molecule.

[0034] The aliphatic ester compound (C) preferably includes at least one selected from the group consisting of trioctyl trimellitate, tributyl trimellitate, tri-2-ethylhexyl trimellitate, trialkyl trimellitate, triisononyl trimellitate, 2-ethylhexyl pyromellitate, and mixed linear alkyl pyromellitate. Among these, tri-2-ethylhexyl trimellitate, 2-ethylhexyl pyromellitate, and mixed linear alkyl pyromellitate are preferred because they do not volatilize during the manufacturing process of the polyimide film and remain partially inside the film, improving the film's properties.

[0035] The amount of aliphatic ester compound (C) added to the total mass of the thermally conductive polyimide film is not particularly limited, but it is preferably 0.1% to 5% by mass, and more preferably 0.2% to 4.0% by mass for improving the film's properties.

[0036] (Other ingredients) The thermally conductive polyimide film may contain components other than the polyimide resin (A), filler (B), and aliphatic ester compound (C) described above (hereinafter also referred to as "other components"), as long as the effects of the present invention are not impaired. Examples of other components include antioxidants, light stabilizers, flame retardants, antistatic agents, heat stabilizers, ultraviolet absorbers, or inorganic fillers, metal powders, or various reinforcing agents. These other components may be used individually or in combination of two or more.

[0037] ≪Method for manufacturing thermally conductive polyimide film≫ The method for producing the aforementioned thermally conductive polyimide film will be described below. A method for manufacturing a thermally conductive polyimide film is: Step 1 (A): A step of mixing filler (B), polyamic acid (D), and organic solvent (E) to obtain a polyamic acid-containing mixture (I), or Step 1(B): A step of mixing filler (B) and organic solvent (E) to prepare a dispersion, and mixing the dispersion with polyamic acid (D) to obtain a polyamic acid-containing mixture (I), or Process 1(C): Prepared by any of the following steps: mixing filler (B) and organic solvent (E) to prepare a dispersion, and mixing the dispersion during the manufacturing process of polyamic acid (D) to obtain a polyamic acid-containing mixture (I). A step to obtain a polyamic acid-containing mixture (I), Step 2: A step of mixing the above polyamic acid-containing mixture (I), an aliphatic ester compound of pyromellitic acid or trimellitic acid (C), and an imidation catalyst and / or a dehydrating agent to obtain a polyamic acid-containing mixture (II), Step 3: A step of forming a film using the above polyamic acid-containing mixture (II), Includes. The above aliphatic ester compound (C) contains an aliphatic group having 4 to 12 carbon atoms.

[0038] In step 2, by using an aliphatic ester compound (C), a thermally conductive polyimide film can be manufactured without the film breaking during the film formation process, and the resulting thermally conductive polyimide film has a high elongation rate.

[0039] The filler (B), polyamic acid (D), organic solvent (E), aliphatic ester compound (C), and imidation catalyst and dehydrating agent used in each of the above processes are the same as those described in the section on "Thermally Conductive Polyimide Film" above.

[0040] The polyamic acid-containing mixture (I) in step 1 and the polyamic acid-containing mixture (II) in step 2 are prepared by mixing or dispersing the above components in a conventional manner. Examples of equipment that can be used when mixing or dispersing the above components include dissolvers, homogenizers, roll mills, bead mills, planetary mixers, dispersers, high-pressure jet dispersers, ultrasonic dispersers, etc. After uniformly mixing the above components, the resulting mixture may be further filtered using a mesh, membrane filter, etc.

[0041] A method for forming the film in step 3 includes, for example, the steps of: applying a polyamic acid-containing mixture (II) from a slitted die onto a support such as a drum or endless belt to form a film, and obtaining a self-supporting gel film by heating and drying it on the support at 200 degrees Celsius or below for 1 to 20 minutes; peeling the gel film from the support, then fixing both ends of the film, and then gradually or stepwise heating to 100 degrees Celsius to 600 degrees Celsius to promote imidation, and after slow cooling, removing the fixings at the ends to obtain a polyimide film.

[0042] <Physical properties of thermally conductive polyimide films> (Growth rate) From the viewpoint of suitability for use as a flexible printed circuit board or heat dissipation member, the elongation of the thermally conductive polyimide film is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more.

[0043] (Thermal conductivity) From the viewpoint of suitability for use as a flexible printed circuit board, the thermal conductivity of the thermally conductive polyimide film is preferably 0.7 W / mK or higher in the thickness direction of the film.

[0044] <Applications of thermally conductive polyimide films> As mentioned above, thermally conductive polyimide films have a high elongation rate. For this reason, they can be suitably used as in flexible printed circuit boards, heat dissipation components, metal laminates, electrical and electronic equipment, motor coil insulated wires, and insulated wires for flat cables.

[0045] ≪Metal Laminates≫ The metal laminate of this embodiment comprises the aforementioned thermally conductive polyimide film and A metal layer laminated on one or both sides of the above-mentioned thermally conductive polyimide film, It holds.

[0046] The method for forming the metal laminate is not particularly limited, and examples include the following methods. A metal laminate is fabricated by directly forming a metal layer on the surface of the above-mentioned thermally conductive polyimide film using the PVD method, and then laminating a base metal onto the resulting metal laminate, and then laminating a metal layer onto the polyimide film surface by electroplating copper sulfate without using an adhesive. The PVD method referred to here includes various metal deposition methods such as vacuum heating deposition, electron ion beam deposition (EB deposition), ion plating, sputtering, plasma ion deposition, and CVD. Suitable base metals include precious metals, alkaline earth metals, transition metals (e.g., copper, cobalt, nickel, chromium, titanium, etc.), or alloys of these metals. Furthermore, the metal laminate in the present invention may be a metal laminate formed by bonding a metal foil with an adhesive. The above metal laminate can be suitably used in electrical and electronic equipment applications such as flexible wiring boards, COF base films, TAB tapes, and high-density recording media base films. As adhesives, for example, epoxy resins, polyamide resins, phenolic resins, acrylic resins, polyimide resins, rubber-based resins, etc., can be used, either individually or in various mixed proportions with a solvent, and additives such as curing agents and curing accelerators can be added as needed.

[0047] Insulated wires The insulated wire of this embodiment is an insulated wire in which the aforementioned thermally conductive polyimide film is heat-fused to a copper metal body made of copper metal in the shape of a coil or flat cable, via an adhesive selected from a fluororesin material, meta-aramid resin, silicone resin, etc., which has heat-sealing properties. [Examples]

[0048] The present invention will be described more specifically below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0049] The abbreviations for the raw materials and solvents used in the preparation of polyamic acid solutions in the examples and comparative examples are shown below. DMF: N,N-dimethylformamide ODA: 4,4'-diaminodiphenyl ether p-PDA: Paraphenylenediamine BPDA: 3,3',4,4'-biphenyltetracarboxylic acid dianhydride PMDA: Pyromellitic dianhydride

[0050] In the examples and comparative examples, B1 was used as the filler (B) as described below. B1: Boron nitride (Particle size distribution measured using a particle size distribution analyzer (Microtrac MT3300EXII, manufactured by Microtrac Corporation), D50: 0.9 μm)

[0051] In the examples and comparative examples, the following C1 to C5 were used as aliphatic ester compounds. Of these, C1 to C3 correspond to aliphatic ester compound (C). C1: Tri-2-ethylhexyl trimellitate (manufactured by Tokyo Chemical Industry Co., Ltd.) C2: 2-ethylhexyl pyromellicate (product name "Adekasizer UL80", manufactured by Adeka) C3: Pyromellitic acid mixed linear alkyl ester (C8, C10) (product name "Adeka Sizer UL100", manufactured by Adeka Corporation) C4: Dibutyl phthalate C5: Dioctyl adipate

[0052] <Fabrication of thermally conductive polyimide films> [Examples 1-7 and Comparative Examples 1-3] (Example 1) In a 2000 ml separable flask, 744 g of DMF was added, and 52.88 g (0.264 mol) of ODA and 7.14 g (0.066 mol) of p-PDA were added and dissolved. Then, 48.56 g (0.165 mol) of BPDA and 36.00 g (0.165 mol) of PMDA were added in the same ratio and in that order, and polymerization was carried out to synthesize a polyamic acid solution. To this polyamic acid solution, 102.95 g of B1 and 330 g of DMF were added, and while heating to 50°C, the mixture was finely dispersed in a homogenizer to prepare a boron nitride-dispersed polyamic acid solution (BN-dispersed PA solution). To 70 g of BN-dispersed PA solution (total solid content of boron nitride and polyamic acid: 13.11 g), 1.33 g of isoquinoline, 0.066 g of 1,2-dimethylimidazole, 0.0928 g of C1 (0.7 wt% relative to the total solid content of boron nitride and polyamic acid), and 2.76 g of DMF were added. The mixture was then mixed and degassed, and cast onto a release PET film to a final film thickness of 40 μm. After drying in a 70°C oven for 500 seconds, it was peeled off and fixed to a 30 cm x 30 cm metal frame. After heating in a 160°C oven for 90 seconds, a 250°C oven for 90 seconds, a 300°C oven for 180 seconds, and a 380°C oven for 60 seconds, it was removed from the frame to produce a thermally conductive polyimide film. In this study, the ratio of moles of the imidation catalyst (total of isoquinoline and 1,2-dimethylimidazole) to the number of moles of amide groups in the polyamic acid is 0.32. The content (volume %) of filler B1 is 2.2 g / cm³, based on the density of the filler. 3 The density of the polyimide resin is 1.4 g / cm³. 3 When calculated using this method, the result is 31% by volume.

[0053] (Example 2) A thermally conductive polyimide film was prepared using the same method as in Example 1, except that 0.1199 g of C1 (0.91 wt% relative to the total solid content of boron nitride and polyamic acid) was added.

[0054] (Example 3) A thermally conductive polyimide film was prepared using the same method as in Example 1, except that 0.0388 g of C2 (0.30 wt% relative to the total solid content of boron nitride and polyamic acid) was added.

[0055] (Example 4) A thermally conductive polyimide film was prepared using the same method as in Example 1, except that 0.1408 g of C2 (1.07 wt% relative to the total solid content of boron nitride and polyamic acid) was added.

[0056] (Example 5) A thermally conductive polyimide film was prepared using the same method as in Example 1, except that 0.0421 g of C3 (0.32 wt% relative to the total solid content of boron nitride and polyamic acid) was added.

[0057] (Example 6) A thermally conductive polyimide film was prepared using the same method as in Example 1, except that 0.2377 g of C3 (1.82 wt% relative to the total solid content of boron nitride and polyamic acid) was added.

[0058] (Example 7) A thermally conductive polyimide film was prepared using the same method as in Example 1, except that 0.4520 g of C3 (3.45 wt% relative to the total solid content of boron nitride and polyamic acid) was added.

[0059] (Comparative Example 1) A thermally conductive polyimide film was prepared using the same method as in Example 1, except that C1 was not added.

[0060] (Comparative Example 2) A thermally conductive polyimide film was prepared using the same method as in Example 1, except that 0.1201 g of C4 (0.91 wt% relative to the total solid content of boron nitride and polyamic acid) was added as an aliphatic ester compound.

[0061] (Comparative Example 3) In Comparative Example 2, a thermally conductive polyimide film was prepared using the same method as in Comparative Example 2, except that C5 was added instead of C4.

[0062] <Rating> The thermal conductivity and elongation of the polyimide films obtained from Examples 1-7 and Comparative Examples 1-3 were measured according to the following method. The results are shown in Table 1.

[0063] (Thermal conductivity) A 10mm x 10mm sample was cut from each polyimide film and measured using a resin material thermal resistance measuring device manufactured by Hitachi Technology & Services, Ltd. at a sample temperature of 50°C and a pressurized pressure of 50 N / cm². 2 Once the thermal resistance value became constant, the thermal conductivity was calculated.

[0064] (Growth rate) Five strips of 5mm x 100mm film were cut from each polyimide film. These strips were then gripped with a 20mm distance between the chucks and subjected to a tensile test at a tensile speed of 10mm / min using a Shimadzu Corporation EZ Test (model EZ-SX) compact desktop testing machine. The maximum elongation during this test was defined as the elongation rate.

[0065] [Table 1]

[0066] From the results in Table 1, it can be seen that the thermally conductive polyimides of Examples 1 to 7, which contain aliphatic ester compound (C), have higher thermal conductivity and higher elongation compared to the thermally conductive polyimide film of Comparative Example 1, which does not contain aliphatic ester compound (C), and the thermally conductive polyimide films of Comparative Examples 2 and 3, which contain aliphatic ester compounds that do not fall under the category of aliphatic ester compound (C).

Claims

1. Polyimide resin (A) and Filler (B) and, A pyromellitic acid or trimellitic acid aliphatic ester compound (C), A thermally conductive polyimide film containing, The aliphatic ester compound (C) contains an aliphatic group having 4 to 12 carbon atoms, A thermally conductive polyimide film in which the content of the filler (B) relative to the total volume of the thermally conductive polyimide film is 15% by volume or more.

2. The thermally conductive polyimide film according to claim 1, wherein the aliphatic ester compound (C) contains two or more ester groups per molecule.

3. The thermally conductive polyimide film according to claim 1 or 2, wherein the aliphatic ester compound (C) comprises at least one selected from the group consisting of trioctyl trimellitate, tributyl trimellitate, tri-2-ethylhexyl trimellitate, trialkyl trimellitate, triisononyl trimellitate, 2-ethylhexyl pyromellitate, and mixed linear alkyl pyromellitate.

4. The thermally conductive polyimide film according to claim 1 or 2, wherein the filler (B) comprises at least one selected from the group consisting of aluminum oxide, aluminum hydroxide, boron nitride, aluminum nitride, zinc oxide, magnesium oxide, and silica.

5. A thermally conductive polyimide film according to claim 1 or 2, wherein the elongation rate is 30% or more.

6. A thermally conductive polyimide film according to claim 1 or 2, wherein the thermal conductivity in the thickness direction of the film is 0.7 W / mK or more.

7. Step 1 (A): A step of mixing filler (B), polyamic acid (D), and organic solvent (E) to obtain a polyamic acid-containing mixture (I), or Step 1 (B): A step of mixing filler (B) and organic solvent (E) to prepare a dispersion, and mixing the dispersion with polyamic acid (D) to obtain a polyamic acid-containing mixture (I), or Process 1 (C): Prepared by any of the following steps: mixing filler (B) and organic solvent (E) to prepare a dispersion, and mixing the dispersion during the manufacturing process of polyamic acid (D) to obtain a polyamic acid-containing mixture (I). A step to obtain a polyamic acid-containing mixture (I), Step 2: A step of mixing the polyamic acid-containing mixture (I), an aliphatic ester compound of pyromellitic acid or trimellitic acid (C), and an imidation catalyst and / or a dehydrating agent to obtain a polyamic acid-containing mixture (II), Step 3: A step of forming a film using the polyamic acid-containing mixture (II), A method for producing a thermally conductive polyimide film containing, A method for producing a thermally conductive polyimide film, wherein the aliphatic ester compound (C) contains an aliphatic group having 4 to 12 carbon atoms.

8. The method for producing a thermally conductive polyimide film according to claim 7, wherein the aliphatic ester compound (C) contains two or more ester groups per molecule.

9. The method for producing a thermally conductive polyimide film according to claim 7 or 8, wherein the aliphatic ester compound (C) comprises at least one selected from the group consisting of trioctyl trimellitate, tributyl trimellitate, tri-2-ethylhexyl trimellitate, trialkyl trimellitate, triisononyl trimellitate, 2-ethylhexyl pyromellitate, and mixed linear alkyl pyromellitate.

10. A thermally conductive polyimide film according to claim 1 or 2, A metal layer laminated on one or both sides of the thermally conductive polyimide film, A metal laminate having [a certain characteristic].

11. Electrical and electronic equipment using the thermally conductive polyimide film according to claim 1 or 2.

12. A flexible printed circuit board using the metal laminate described in claim 10.

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