Polyimide film and method for producing the same, and metal-clad laminate and method for manufacturing the same

Abstract

To provide polyimide which is excellent in dimensional accuracy at high temperature while securing transparency, a method for producing a polyimide film, and a method for manufacturing a metal-clad laminate.SOLUTION: When a polyimide film is obtained by preparing a mixed solution containing a tetracarboxylic acid anhydride component, a diamine component, and an organic solvent, reacting the mixture and obtaining a solution of a polyamide acid, coating the solution onto a base material, drying the solution and obtaining a resin film, heat treating the resin film and imidizing the resin film, when the polyimide film is obtained by using a solvent containing a predetermined aprotic polar solvent and a predetermined amount of water as the organic solvent contained in the mixed solution, total light transmittance is 85% or more, polyimide having a thermal decomposition temperature (Td0.5) showing decrease in a weight of 0.5% of 460°C or higher is obtained.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyimide film, a method for manufacturing a polyimide film, a metal-clad laminate, and a method for manufacturing a metal-clad laminate, and more particularly to a polyimide film having excellent dimensional accuracy at high temperatures, a metal-clad laminate formed by laminating this polyimide film, a method for manufacturing a polyimide film, and a method for manufacturing a metal-clad laminate using this method. [Background technology]

[0002] Polyimide has excellent heat resistance, mechanical properties, and electrical properties. Polyimide films made from this polyimide are widely used in a variety of applications, including circuit wiring boards such as flexible printed circuits (FPCs).

[0003] Typical known methods for producing polyimide films are the tenter method and the casting method. The tenter method involves casting a solution of a polyimide precursor (polyamic acid) onto a rotating drum, peeling it off as a gel film from the rotating drum, and heating and curing it in a tenter furnace to produce a polyimide film. The casting method involves applying a solution of the polyimide precursor to a supporting substrate such as copper foil, followed by drying and curing the solution by heat treatment to obtain a polyimide film.

[0004] To prepare polyimide, a tetracarboxylic dianhydride is typically reacted with a diamine to form a precursor, polyamic acid. In this state, the precursor is soluble in organic solvents; however, when the precursor is heat-treated at temperatures above 200°C, dehydration and ring closure occurs within the molecule, resulting in an organic solvent-insoluble polyimide. Therefore, whether using the tenter or casting method, a polyimide precursor containing an organic solvent is used, and this is imidized (cured) by heat treatment to prepare the polyimide.

[0005] For example, in COF (Chip on Film) mounting of LCD driver ICs (chips) for LCD monitors, LCD televisions, etc. on FPCs, temperatures of approximately 350 to 400°C are required to bond the FPC and chip. Furthermore, when using thin-film transistors (TFTs) in flexible devices, they are sometimes fabricated on polyimide film, and in this case, the TFT fabrication process can reach temperatures of 400°C. Therefore, it is necessary to suppress thermal shrinkage of polyimides during such high-temperature processing.

[0006] For example, Patent Document 1 describes that annealing a polyimide film obtained using a specific aromatic diamine component and an aromatic acid anhydride component at a temperature of 300°C or higher and 450°C or lower can improve dimensional stability, particularly in the transverse direction (TD) of the film, and can reduce dimensional changes at any position in the transverse direction even during high-temperature processing.

[0007] Furthermore, Patent Document 2 describes that by performing heat treatment under maximum treatment temperature conditions, which are expressed in a temperature range from a temperature 10°C higher to a temperature 10°C lower than the temperature at which the rate of change of the linear expansion coefficient of the polyimide film is 25% or more, for a treatment time of 40 seconds or less, sagging defects that occur during heat treatment are improved, and a polyimide film with low thermal deformation and excellent flatness can be obtained.

[0008] On the other hand, although Patent Document 3 does not directly mention dimensional stability, it does state that in a method for producing a polyimide film by a roll-to-roll method, a polyimide film that is transparent, has low birefringence, and is excellent in optical isotropy can be obtained by annealing the film at 200 to 400°C for 200 to 2000 seconds under a tension of 10 N or less in the machine direction (MD). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-043511 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-116021 [Patent Document 3] Special Publication No. 2014-506204 Summary of the Invention [Problem to be solved by the invention]

[0010] As mentioned above, polyimide films have become indispensable for electronic devices, as exemplified by flexible printed circuit boards (FPCs), and as products become more compact and modularized, they must be able to withstand the temperatures experienced when COFs and TFTs are mounted.

[0011] The present invention has been made in view of these circumstances, and has as its object to provide a polyimide that has excellent dimensional accuracy at high temperatures while ensuring transparency.

[0012] Another object of the present invention is to provide a method for producing a polyimide film, which can provide a polyimide film that has excellent dimensional accuracy at high temperatures while maintaining transparency.

[0013] Furthermore, the present invention provides a method for producing a metal-clad laminate that has excellent dimensional accuracy at high temperatures while maintaining transparency, by utilizing this method for producing a polyimide film. [Means for solving the problem]

[0014] As a result of extensive research aimed at solving the above problems, the present inventors have surprisingly found that when a polyimide is obtained from a mixed solution of a tetracarboxylic acid anhydride component, a diamine component, and an organic solvent, by using a predetermined tetracarboxylic acid anhydride component and a diamine component and allowing the organic solvent to contain water in a predetermined ratio, it is possible to ensure the transparency of the obtained polyimide film and to impart excellent dimensional accuracy at high temperatures, and have completed the present invention.

[0015] That is, the gist of the present invention is as follows. [1] A polyimide film composed of a polyimide having a tetracarboxylic acid residue derived from a tetracarboxylic acid anhydride component and a diamine residue derived from a diamine component, the polyimide contains an aromatic tetracarboxylic acid residue containing a fluorine atom and / or an aromatic diamine residue containing a fluorine atom, The diamine component contains 50 mol % or more of a diamine compound represented by the following formula (1): [ka] [In formula (1), the substituents X independently represent a hydrogen atom, a fluorine atom, or a monovalent hydrocarbon group or alkoxy group having 1 to 3 carbon atoms which may be substituted with a fluorine atom; m and n independently represent integers of 1 to 4; and the linking group Y represents a divalent group selected from a single bond, -CONH-, or -COO-.] the tetracarboxylic acid anhydride component includes at least one selected from the group consisting of 2,2-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride (6FDA), pyromellitic dianhydride (PMDA), 4,4'-oxydiphthalic dianhydride (ODPA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and p-biphenylenebis(trimellitic acid monoester dihydrate) (BP-TME); A polyimide film characterized by having a total light transmittance of 85% or more and a thermal decomposition temperature (Td0.5) at which a weight loss of 0.5% is achieved of 460°C or more. [2] The polyimide film according to [1], having a coefficient of thermal expansion (CTE) of 25 ppm / K or less. [3] A metal-clad laminate comprising an insulating resin layer consisting of a plurality of polyimide layers and a metal layer laminated on at least one surface of the insulating resin layer, characterized in that the thickest base polyimide layer among the plurality of polyimide layers is the polyimide film described in [1] or [2]. [4] A method for producing a polyimide film, comprising the following steps a to d: a) preparing a mixed solution containing a tetracarboxylic acid anhydride component, a diamine component, and an organic solvent, wherein the tetracarboxylic acid anhydride component and / or the diamine component contains a compound having an aromatic ring containing a fluorine atom; b) reacting the tetracarboxylic acid anhydride component with the diamine component in the mixed solution to obtain a polyamic acid solution; c) applying the polyamic acid solution onto a substrate and drying it to form a resin film of the polyamic acid; d) heat-treating the resin film to imidize the polyamic acid, thereby obtaining a polyimide film; It is equipped with The organic solvent is a mixture of the following components A and B: A) aprotic polar solvents with a boiling point of 200°C or less at 1 atmosphere; B) water; wherein the content of component A measured by gas chromatography is 50% by mass or more, and the content of component B measured by Karl Fischer method is within a range of 300 to 1000 ppm, A method for producing a polyimide film, characterized by obtaining a polyimide film having a total light transmittance of 85% or more and a thermal decomposition temperature (Td0.5) at which a weight loss of 0.5% is achieved of 460°C or more. [5] The method for producing a polyimide film according to [4], wherein the component A is at least one selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide. [6] The method for producing a polyimide film according to [4], wherein the organic solvent is recovered from the solvent vapor generated in the step c or the steps c to d and reused as the organic solvent for the mixed solution. [7] The method for producing a polyimide film according to [4], wherein the organic solvent used in step a is obtained via a step of recovering solvent vapor generated in step c or any one of steps c to d. [8] A method for producing a metal-clad laminate having an insulating resin layer made of a plurality of polyimide layers and a metal layer laminated on at least one surface of the insulating resin layer, comprising: A method for producing a metal-clad laminate, characterized in that, in obtaining a base polyimide layer that is the thickest among the multiple polyimide layers that form the insulating resin layer, the method for producing a polyimide film described in (4) is used, and the heat treatment of the resin film in step d is carried out in a state where it is directly or indirectly laminated on a metal layer, thereby forming the base polyimide layer. [Effects of the Invention]

[0016] According to the present invention, the transparency of the polyimide film can be ensured and dimensional accuracy at high temperatures can be improved. In particular, the polyimide of the present invention, having excellent transparency and dimensional accuracy, is extremely suitable for forming the thickest base polyimide layer among multiple polyimide layers in a metal-clad laminate used to obtain an FPC, which includes an insulating resin layer made of multiple polyimide layers and a metal layer laminated on at least one surface of the insulating resin layer. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described.

[0018] [Polyimide film] The present invention provides a polyimide film composed of a polyimide having tetracarboxylic acid residues derived from a tetracarboxylic acid anhydride component and diamine residues derived from a diamine component, which has a total light transmittance of 85% or more and a thermal decomposition temperature (Td0.5) at which a weight loss of 0.5% is achieved of 460° C. or more. The tetracarboxylic acid residue refers to a tetravalent group derived from a tetracarboxylic acid anhydride, and the diamine residue refers to a divalent group derived from a diamine compound.

[0019] In the present invention, in order to ensure that the polyimide film has a total light transmittance of 85% or more and a thermal decomposition temperature (Td0.5) at which a weight loss of 0.5% is achieved of 460°C or more, the polyimide contains a fluorine atom-containing aromatic tetracarboxylic acid residue and / or a fluorine atom-containing aromatic diamine residue, and the diamine component contains 50 mol % or more, preferably 70 mol % or more, of a diamine compound represented by the following formula (1): [ka] [In formula (1), the substituents X independently represent a monovalent hydrocarbon group or alkoxy group having 1 to 3 carbon atoms which may be substituted with a hydrogen atom or a fluorine atom, m and n independently represent integers of 1 to 4, and the linking group Y represents a divalent group selected from a single bond, -CONH-, or -COO-.]

[0020] The aromatic diamine represented by the above formula (1) has a rigid structure in which a biphenyl skeleton or two phenyl skeletons are linked by -CONH- or -COO-, and therefore easily forms an ordered structure, promoting the in-plane orientation of molecular chains and suppressing an increase in the thermal expansion coefficient of the polyimide film.

[0021] Specific preferred examples of such aromatic diamines include 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-diethyl-4,4'-diaminobiphenyl (m-EB), 2,2'-diethoxy-4,4'-diaminobiphenyl (m-EOB), and 2,2'-dipropoxy-4,4'-diaminobiphenyl (m-EOB). Examples of the diaminobenzanilide include 2,2'-n-propyl-4,4'-diaminobiphenyl (m-POB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), 2,2'-divinyl-4,4'-diaminobiphenyl (VAB), 4,4'-diaminobiphenyl, 4-aminophenyl-4'-aminobenzoate (APAB), 2'-methoxy-4,4'-diaminobenzanilide (MABA), and 4,4'-diaminobenzanilide (DABA).

[0022] Among these, from the viewpoint of simultaneously maintaining transparency and a low thermal expansion coefficient, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB) and 4,4'-diaminobenzanilide (DABA) are more preferred, and 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB) is even more preferred.

[0023] On the other hand, the tetracarboxylic acid anhydride component is at least one selected from the group consisting of 2,2-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride (6FDA), pyromellitic dianhydride (PMDA), 4,4'-oxydiphthalic dianhydride (ODPA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and p-biphenylenebis(trimellitic acid monoester dihydrate) (BP-TME). Preferably, the tetracarboxylic acid anhydride component contains at least one of these components in an amount of 50 mol% or more, more preferably 70 mol% or more.

[0024] Among these, from the viewpoint of simultaneously maintaining transparency and heat resistance, the tetracarboxylic acid anhydride component is preferably 2,2-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride (6FDA), pyromellitic dianhydride (PMDA), or 4,4'-oxydiphthalic dianhydride (ODPA), and more preferably 2,2-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride (6FDA) or pyromellitic dianhydride (PMDA).

[0025] The polyimide constituting the polyimide film of the present invention may contain other diamine residues derived from diamine components other than those mentioned above, as long as the purpose of the present invention is not impaired. However, when other diamine residues are contained, the other diamine residues should account for less than 30 mol %, preferably less than 10 mol %, of the total diamine residues. As such other diamine residues, any of those known as diamine components for polyimides, particularly transparent polyimides, can be used. Specific examples include, but are not limited to, the following:

[0026] That is, examples of other diamine residues include bis[4-(aminophenoxy)phenyl]sulfone (BAPS), 4,6-dimethyl-m-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 2,4-diaminomesitylene, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,5,3',5'-tetramethyl-4,4'-diaminodiphenylmethane, 2,4-toluenediamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4, 4'-Diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2,2-bis(4-aminophenoxyphenyl)propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 1,3-bis (3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, benzidine, 3,3'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 4,4"-diamino-p-terphenyl, 3,3"-diamino-p-terphenyl, bis(p-aminocyclohexyl)methane, bis(p-β-amino-t-butylphenyl)ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminocyclohexyl)methane (aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis(β-amino-t-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 4-(1H,1H,11H-eicosafluoroundecanoxy)-1,3-Diaminobenzene, 4-(1H,1H-perfluoro-1-butanoxy)-1,3-diaminobenzene, 4-(1H,1H-perfluoro-1-heptanoxy)-1,3-diaminobenzene, 4-(1H,1H-perfluoro-1-octanoxy)-1,3-diaminobenzene, 4-pentafluorophenoxy-1,3-diaminobenzene, 4-(2,3,5,6-tetrafluorophenoxy)-1,3-diaminobenzene, 4-(4-fluorophenoxy)-1,3-diaminobenzene, 4-(1H,1H,2H,2H-perfluoro-1- (hexanoxy)-1,3-diaminobenzene, 4-(1H,1H,2H,2H-perfluoro-1-dodecanoxy)-1,3-diaminobenzene, (2,5)-diaminobenzotrifluoride, diaminotetra(trifluoromethyl)benzene, diamino(pentafluoroethyl)benzene, 2,5-diamino(perfluorohexyl)benzene, 2,5-diamino(perfluorobutyl)benzene, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-bis(trifluoromethyl)-4,4'-diaminobiphenyl nyl, octafluorobenzidine, 4,4'-diaminodiphenyl ether, 2,2-bis(4-aminophenyl)hexafluoropropane, 1,3-bis(anilino)hexafluoropropane, 1,4-bis(anilino)octafluorobutane, 1,5-bis(anilino)decafluoropentane, 1,7-bis(anilino)tetradecafluoroheptane, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether, 3,3'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether, 3,3',5,5'- Tetrakis(trifluoromethyl)-4,4'-diaminodiphenyl ether, 3,3'-bis(trifluoromethyl)-4,4'-diaminobenzophenone, 4,4'-diamino-p-terphenyl, 1,4-bis(p-aminophenyl)benzene, p-(4-amino-2-trifluoromethylphenoxy)benzene, bis(aminophenoxy)bis(trifluoromethyl)benzene, bis(aminophenoxy)tetrakis(trifluoromethyl)benzene, 2,2-bis{4-(4-aminophenoxy)phenyl}hexafluoropropane, 2,2-bis{4-(3-aminophenoxy)phenyl}hexafluoropropane, 2,2-bis{4-(2-aminophenoxy)phenyl}hexafluoropropane, 2,2-bis{4-(4-aminophenoxy)-3,5-dimethylphenyl}hexafluoropropane, 2,2-bis{4-(4-aminophenoxy)-3,5-ditrifluoromethylphenyl}hexafluoropropane, 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl, 4,4'-bis(4-amino-3-trifluoromethylphenoxy)biphenyl, 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl Examples of diamine residues include those derived from 4,4'-bis(4-aminophenoxy)diphenyl sulfone, 4,4'-bis(3-amino-5-trifluoromethylphenoxy)diphenyl sulfone, 2,2-bis{4-(4-amino-3-trifluoromethylphenoxy)phenyl}hexafluoropropane, bis{(trifluoromethyl)aminophenoxy}biphenyl, bis[{(trifluoromethyl)aminophenoxy}phenyl]hexafluoropropane, bis{2-[(aminophenoxy)phenyl]hexafluoroisopropyl}benzene, and 4,4'-bis(4-aminophenoxy)octafluorobiphenyl.

[0027] Similarly, the polyimide constituting the polyimide film of the present invention may contain tetracarboxylic acid residues derived from tetracarboxylic acid anhydrides other than those mentioned above, as long as the object of the present invention is not impaired. However, when other tetracarboxylic acid residues are contained, the content of these residues is less than 30 mol%, preferably less than 10 mol%, based on the total tetracarboxylic acid residues. As such other tetracarboxylic acid residues, any of those known as tetracarboxylic acid anhydride components of polyimides, particularly transparent polyimides, can be used. Specific examples include, but are not limited to, the following:

[0028] That is, examples of other tetracarboxylic acid residues include 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 2,3,3',4'-benzophenonetetracarboxylic dianhydride, naphthalene-1,2,5,6-tetracarboxylic dianhydride, naphthalene-1,2,4,5-tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, naphthalene-1,2,6,7-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexacarboxylic acid dianhydride, and 4,8-dimethyl-1,2,3,5,6,7-hexacarboxylic acid dianhydride. hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 1,4,5,8-tetrachloronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,2',3,3'- Biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3'',4,4''-p-terphenyltetracarboxylic dianhydride, 2,2'',3,3''-p-terphenyltetracarboxylic dianhydride, 2,3,3'',4''-p-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride Bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, perylene-2,3,8,9-tetracarboxylic dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, perylene-4,5,10,11-tetracarboxylic dianhydride, perylene-5,6,11,12-tetracarboxylic dianhydride, phenanthrene-1,2,7,8-tetracarboxylic dianhydride, phenanthrene-1,2,6,7-tetracarboxylic dianhydride, phenanthrene-1,2,9,10-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, (trifluoromethyl)pyromellitic dianhydride, di(trifluoromethyl)pyromellitic dianhydride, di(heptafluoropropyl)pyromellitic dianhydride, pentafluoromethyl Fluoroethyl pyromellitic dianhydride, Bis{3,5-di(trifluoromethyl)phenoxy}pyromellitic dianhydride, 5,5'-bis(trifluoromethyl)-3,3',4,4'-tetracarboxybiphenyl dianhydride, 2,2',5,5'-tetrakis(trifluoromethyl)-3,3',4,4'-tetracarboxybiphenyl dianhydride, 5,5'-bis(trifluoromethyl)-3,3',4,4'-tetracarboxydiphenyl ether dianhydride, 5,5'-bis(trifluoromethyl)-3,3',4,4' -Tetracarboxybenzophenone dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}benzene dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}trifluoromethylbenzene dianhydride, bis(dicarboxyphenoxy)trifluoromethylbenzene dianhydride, bis(dicarboxyphenoxy)bis(trifluoromethyl)benzene dianhydride, bis(dicarboxyphenoxy)tetrakis(trifluoromethyl)benzene dianhydride, 2,2-bis{(4-(3,4-dicarboxyphenoxy) bis(trifluoromethyl)dicarboxyphenoxy}biphenyl dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}bis(trifluoromethyl)biphenyl dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}diphenyl ether dianhydride, bis(dicarboxyphenoxy)bis(trifluoromethyl)biphenyl dianhydride, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, fluorenylidenebisphthalic anhydride, 1,2,4,Examples include acid anhydride residues derived from 5-cyclohexanetetracarboxylic dianhydride.

[0029] The polyimide film of the present invention has a total light transmittance of 85% or more, preferably 87% or more, and a thermal decomposition temperature (Td0.5) at which a weight loss of 0.5% is achieved of 460°C or more, preferably 480°C or more. These values ​​are for a 20 μm-thick polyimide film, as shown in the examples described below. The thermal decomposition temperature (Td0.5) at which a weight loss of 0.5% is achieved is the temperature at which a weight loss of 0.5% is achieved based on the weight at 200°C when the film is heated from 30°C to 550°C at a rate of 10°C / min in a nitrogen atmosphere.

[0030] In addition to the above, the polyimide film of the present invention preferably has a coefficient of thermal expansion (CTE) of 30 ppm / K or less, more preferably 25 ppm / K or less, when made into a polyimide film.

[0031] The polyimide film of the present invention is not particularly limited in its application, but it can be suitably used for circuit wiring substrates such as flexible printed wiring boards (FPCs). In particular, it is extremely suitable for forming the base polyimide layer, which is the thickest of the multiple polyimide layers constituting a metal-clad laminate used to obtain a flexible printed wiring board.

[0032] That is, a metal-clad laminate generally comprises an insulating resin layer composed of multiple polyimide layers and a metal layer laminated on at least one surface of the insulating resin layer. The insulating resin layer, composed of multiple polyimide layers, is laminated on a metal layer such as copper foil via a thermoplastic polyimide that serves as an adhesive layer, followed by a polyimide layer composed of a non-thermoplastic polyimide that serves as a base layer (base film). Furthermore, a polyimide layer composed of a thermoplastic or non-thermoplastic polyimide that forms a top layer may also be laminated on the base layer. Of these, the base layer has the greatest thickness and is composed of a polyimide that has excellent dimensional stability and heat resistance. Furthermore, to suppress warping of the metal-clad laminate, a polyimide film with a reduced coefficient of thermal expansion (CTE) is used. Therefore, the polyimide film according to the present invention is extremely suitable for forming the base layer of a metal-clad laminate.

[0033] [Manufacturing method of polyimide film] The method for producing a polyimide film according to the present embodiment includes the following steps a to d: a) preparing a mixed solution containing a tetracarboxylic acid anhydride component, a diamine component, and an organic solvent, wherein the tetracarboxylic acid anhydride component and / or the diamine component contains a compound having an aromatic ring containing a fluorine atom; b) reacting the tetracarboxylic acid anhydride component with the diamine component in the mixed solution to obtain a polyamic acid solution; c) applying the polyamic acid solution onto a substrate and drying it to form a resin film of the polyamic acid; d) heat-treating the resin film to imidize the polyamic acid, thereby obtaining a polyimide film; It can be equipped with:

[0034] -Process a- Here, the organic solvent used in step a contains the following components A and B. A) aprotic polar solvents with a boiling point of 200°C or less at 1 atmosphere; B) water;

[0035] <Ingredient A> Of these, component A is an aprotic polar solvent with a boiling point of 200°C or less at 1 atmosphere. However, a lower limit of the boiling point of 120°C or more is preferred due to compatibility with water and ease of control of water content. A boiling point of 200°C or less facilitates release of the aprotic polar solvent from the system during the imidization process of polyamic acid, for example, thereby reducing the amount of aprotic polar solvent contained in the imidized polyimide film. In particular, component B has a lower boiling point than component A, and evaporates first, swelling the polymer chains that form the film and creating an evaporation route, facilitating the evaporation of component A and facilitating its removal. Furthermore, the amount of remaining aprotic polar solvent is closely related to the imidization rate of polyamic acid. It is believed that if the aprotic polar solvent ratio is high relative to the imidization rate, the aprotic polar solvent functions as a plasticizer, causing molecular chain reconformation, resulting in increased haze when the film is formed. Therefore, since aprotic polar solvents with a boiling point exceeding 200°C tend to remain during imidization, resulting in high haze, the increase in haze can be suppressed by setting the boiling point of the aprotic polar solvent to 200°C or less.

[0036] Specific examples of the aprotic polar solvent, component A, include N,N-dimethylformamide (boiling point: 153°C), N,N-dimethylacetamide (boiling point: 166°C), dimethyl sulfoxide (boiling point: 189°C), N,N-diethylacetamide (boiling point: 168°C), 2-butanone (boiling point: 79°C), N-methylcaprolactam (boiling point: 106°C), cyclohexanone (boiling point: 155°C), dioxane (boiling point: 101°C), tetrahydrofuran (boiling point: 66°C), and diglyme (boiling point: 162°C). Among these, from the viewpoint of ease of control of the physical properties of the polyamic acid resin film, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide are preferred, and N,N-dimethylacetamide is more preferred.

[0037] The aprotic polar solvent is contained as a main component of the organic solvent according to the present invention, and its concentration as measured by gas chromatography is 50% or more. From the viewpoint of ease of controlling the water content, it is preferably 99% or more, more preferably 99.5% or more, and even more preferably 99.9% or more. Here, "%" indicating the concentration represents "% by weight" unless otherwise specified.

[0038] The organic solvent of the present invention may contain a solvent other than Component A (and Component B). Examples of such solvents other than Component A include N-methyl-2-pyrrolidone, hexamethylphosphoramide, dimethyl sulfate, triglyme, cresol, etc. Two or more of these solvents may be mixed, and aromatic hydrocarbons such as xylene and toluene may also be mixed.

[0039] <Component B> In the organic solvent of the present invention, the content of water as component B, as measured by the Karl Fischer method, is within the range of 300 to 1000 ppm, preferably 500 to 800 ppm, and more preferably 550 to 700 ppm. By controlling the content within such a range, the organic solvent is easily removed due to the swelling effect of component A, and as a result, the amount of solvent remaining after imidization can be reduced as much as possible, and as described above, a polyimide film can be obtained whose thermal decomposition temperature (Td0.5) at which a weight loss of 0.5% is achieved is 460°C or higher.

[0040] The organic solvent of this embodiment is preferably used as a solvent for mixing a tetracarboxylic anhydride component and a diamine component, polymerizing them to obtain a polyamic acid, and imidizing the polyamic acid to form a polyimide. That is, a mixed solution is formed containing the organic solvent of the present invention, the tetracarboxylic anhydride component, and the diamine component. In this case, the tetracarboxylic anhydride component and the diamine component for obtaining the polyimide of the present invention, as described above in [Polyimide Film], can be preferably used.

[0041] -Process b- In step b, for example, a tetracarboxylic acid anhydride and a diamine compound are dissolved in an organic solvent in approximately equimolar amounts and stirred at a temperature in the range of 0 to 100°C for 30 minutes to 24 hours to cause a polymerization reaction, thereby obtaining a polyamic acid solution. In the reaction, the reaction components are dissolved in the solvent so that the resulting polyamic acid is in the range of 5 to 30 mass %, preferably 10 to 20 mass %, of the solvent.

[0042] The viscosity of the polyamic acid solution is preferably in the range of 500 cps to 100,000 cps. If it is outside this range, defects such as uneven thickness and streaks are likely to occur in the film during coating using a coater or the like.

[0043] -Process c- -Process d- The polyamic acid solution obtained in step b is applied to a substrate, followed by drying and imidization (or curing) by heat treatment. A suitable heat treatment method is generally heating at a temperature in the range of 80 to 400°C for a time in the range of 1 to 60 minutes. To promote imidization of the polyamic acid, two heat treatments are required: one for evaporating the organic solvent that dissolves or is mixed with the polyamic acid, and the other for releasing the organic solvent coordinated to the polyamic acid out of the system.

[0044] After forming the polyamic acid resin film in step c, imidization may be carried out on the substrate, or the resin film may be peeled off from the substrate and then imidized. When the polyimide film is a polyimide film consisting of multiple polyimide layers, examples of its production method include a method in which a polyamic acid solution is repeatedly applied to a substrate and dried, followed by imidization (hereinafter referred to as a casting method), and a method in which multiple layers of polyamic acid are simultaneously applied and dried by multilayer extrusion, followed by imidization (hereinafter referred to as a multilayer extrusion method).

[0045] Whether the polyimide film is a single layer or multiple layers, it is preferable to complete the imidization of the polyamic acid on the substrate. Since the imidization is performed while the polyamic acid resin film is fixed to the substrate, the expansion and contraction changes of the polyimide layer during the imidization process can be suppressed, and the thickness and dimensional accuracy of the polyimide film can be maintained.

[0046] <Base material> The substrate used in step c is used for the purposes of reinforcing the polyimide film (or polyimide layer) and suppressing changes in expansion and contraction of the polyimide film to maintain dimensional accuracy. The substrate is the target onto which the polyamic acid solution is applied, and can be in the form of a cut sheet, a roll, an endless belt, or the like. To achieve productivity, it is efficient to use a roll or endless belt form that allows for continuous production. Furthermore, from the viewpoint of achieving a greater effect of improving the dimensional accuracy of the polyimide film, the supporting substrate is preferably in the form of a long roll.

[0047] The substrate material may be a heat-resistant material such as metal, ceramic, resin, or carbon, but metal is preferred from the viewpoint of thermal conductivity and flexibility. Therefore, the substrate may be a metal film, such as copper foil, aluminum foil, stainless steel foil, iron foil, silver foil, gold foil, zinc foil, indium foil, tin foil, zirconium foil, tantalum foil, titanium foil, cobalt foil, or an alloy foil thereof. When the polyimide film is used as an insulating layer of a circuit wiring board and the substrate is used as a wiring layer of the circuit wiring board, the substrate is preferably copper foil or a copper alloy foil. Furthermore, when the polyimide film is used by peeling it from the substrate, a smooth stainless steel belt or a stainless steel drum can be suitably used as the substrate.

[0048] The thickness of the metal foil as a substrate is, for example, preferably in the range of 5 to 35 μm, more preferably in the range of 9 to 18 μm. If the metal foil is thicker than 35 μm, the flexibility and foldability of the laminate consisting of the polyimide layer and the metal foil layer will be poor. On the other hand, if the metal foil is thinner than 5 μm, it will be difficult to adjust the tension and the like during the manufacturing process of the laminate, and defects such as wrinkles will be more likely to occur. Furthermore, these metal foils may be subjected to a chemical or mechanical surface treatment on their surfaces to improve adhesive strength, etc., or a chemical surface treatment for rust prevention.

[0049] <Recovery and reuse of organic solvents> The present invention preferably includes a step of recovering the organic solvent from the solvent vapor generated in step c or steps c to d. The organic solvent is recovered by recovering the organic solvent from the solvent vapor generated by drying after coating the polyamic acid solution, but the organic solvent may also be recovered from the solvent vapor generated in the heat treatment step of step d. The solvent recovered in this manner is reused as the organic solvent in step a.

[0050] The method for recovering and reusing the solvent vapor is not particularly limited, but examples thereof include a cooling method, an adsorption method using a solid adsorbent such as activated carbon or zeolite, an adsorption method using a liquid, hardly volatile solvent, an absorption method using water, etc. In addition, a general solvent recovery device can be used, such as a multi-effect steam type solvent recovery device, a heat pump type solvent recovery device, a heat pump type multi-effect concentrator, an evaporation concentrator, etc.

[0051] The solvent vapor is hydrophilic and easily soluble in water, and because there is a difference in boiling point between water and the organic solvent and the solvent vapor does not have an azeotropic point with water, the step of recovering the solvent from the solvent vapor preferably includes a step of dissolving water-soluble substances contained in the solvent vapor in water. The recovered liquid can be concentrated by evaporating water with high vapor pressure using thermal energy supplied from an external source. The thermal energy preferably utilizes the heat of the solvent vapor, but if the solvent vapor is at a low temperature, heat from a heater or the like may also be used. The concentrated recovered liquid may be treated with an acid, an alkali, activated carbon, or the like, as needed.

[0052] The concentrated recovered liquid can be regenerated and reused as the raw organic solvent in step a by purification such as distillation.

[0053] When using an organic solvent containing a recycled solvent, it is preferable that the recycled solvent accounts for 50% by volume or more of the raw organic solvent. By making the ratio of recycled solvent to the raw organic solvent 50% by volume or more, cost benefits are increased.

[0054] The method for producing a polyimide film including these steps a to d can also be applied to the production of the metal-clad laminate described above. That is, to obtain the thickest base polyimide layer among the multiple polyimide layers that form the insulating resin layer in the metal-clad laminate, for example, a polyamic acid resin film that forms the base polyimide layer may be applied to a substrate on which a polyamic acid resin film for forming an adhesive layer on a copper foil has been applied, and then dried to form the polyamic acid resin film, and subsequently, the resin film may be heat-treated in step d to form a base polyimide layer made of a predetermined polyimide film.

[0055] By carrying out the above steps a to d using a predetermined organic solvent, a polyimide film can be obtained that has a total light transmittance of 85% or more and a thermal decomposition temperature (Td0.5) at which a weight loss of 0.5% is achieved of 460°C or more. [Example]

[0056] The present embodiment will be specifically described below with reference to examples, but the present embodiment is not limited to the scope of these examples. In the following examples, various measurements and evaluations were performed as follows unless otherwise specified.

[0057] [Calculation of total light transmittance (TT)] After removing the support (copper foil), a test piece of 50 mm in the machine direction (MD) × 50 mm in the width direction (TD) of the film was cut from the polyimide layer (hereinafter referred to as polyimide film). The total light transmittance (TT) was measured in accordance with JIS K 7136 using a HAZE METER NDH500 manufactured by Nippon Denshoku Industries Co., Ltd.

[0058] [Viscosity measurement] The viscosity of the polyamic acid solution obtained in the synthesis example was measured at 25°C using a cone-plate viscometer equipped with a thermostatic water bath (manufactured by Tokimec Co., Ltd.).

[0059] [Measurement of glass transition temperature (Tg)] The dynamic viscoelasticity of a polyimide film (5 mm x 22.6 mm) was measured using a dynamic thermomechanical analyzer while the temperature was raised from 20°C to 350°C at a rate of 5°C / min, and the glass transition temperature (Tan δ maximum value: °C) was determined.

[0060] [Measurement of thermal decomposition temperature (Td0.5)] (Polyimide film) A polyimide film weighing 10 to 20 mg was heated in a nitrogen atmosphere from 30°C to 550°C at a constant rate (10°C / min) using a thermogravimetric analyzer (TG) TG / DTA6200 manufactured by Seiko Corporation, and the weight change was measured. The temperature at which the weight loss rate was 0.5%, based on the weight at 200°C, was defined as the thermal decomposition temperature (Td0.5).

[0061] [Measurement of coefficient of thermal expansion (CTE)] A test piece of 3 mm MD x 15 mm TD was heated from 30°C to 200°C at a heating rate of 10°C / min while applying a load of 5.0 g in a thermomechanical analysis (TMA) device, and then cooled from 180°C to 100°C. The thermal expansion coefficient was measured from the elongation (linear expansion) during cooling.

[0062] [Tensile strength measurement] Using a tensile tester, Strograph VG1F (manufactured by TOYOSEIKI), a tensile test was performed on a polyimide film test sample (size 10 mm x 110 mm) at a speed of 10 mm / min under a load of 100 N to determine the tensile strength, tensile modulus, and tensile elongation (elongation at break).

[0063] [Moisture content measurement] The water content of the solvent was measured using a Karl Fischer moisture meter (coulometric titration method) <mkc-710m>Measurements were carried out using a meter (manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

[0064] [Polyimide film formability] When a polyimide layer (polyimide film) was obtained from the polyamic acid varnish by heat treatment, if there were no bubbles within the film and the polyimide film had a clean appearance, it was marked as "○", and if there were bubbles visible on the surface, the viscosity was too high to be applied uniformly, or the film was brittle, it was marked as "×".

[0065] The abbreviations used in the examples represent the following compounds. TFMB: 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl BAPS: Bis[4-(aminophenoxy)phenyl]sulfone m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-bis(4-aminophenoxy)benzene PMDA: Pyromellitic dianhydride 6FDA: 2,2-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride DMAc(I): N,N-dimethylacetamide DMAc(II): N,N-dimethylacetamide recycled with superheated steam

[0066] Of the above, the solvent DMAc (I) was a commercially available product (purity 99.0% or higher) manufactured by Kanto Chemical Co., Inc., which was opened and stored with the lid closed at 23°C for one week before use, and had the water content shown in Table 1. DMAc (II) was a recycled product obtained from Reference Example 1 described later, and also had the water content shown in Table 1.

[0067] [Table 1]

[0068] Synthesis Example 1 To synthesize polyamic acid solution varnish 1, the solvent DMAc (II) was added to a 200 ml separable flask under a nitrogen stream to a solids concentration of 15% by mass, and the diamine component, acid anhydride component, and molar ratio of resin composition A shown in Table 2 were added and dissolved while stirring at room temperature. The solution was then stirred at room temperature for 20 hours to carry out a polymerization reaction, producing a viscous polyamic acid solution varnish 1. The viscosity was 11,271 cP.

[0069] Synthesis Example 2 To synthesize polyamic acid solution varnish 2, the solvent DMAc (I) was added to a 200 ml separable flask under a nitrogen stream to a solids concentration of 15% by mass, and the diamine component, acid anhydride component, and molar ratio of resin composition A shown in Table 2 were added and dissolved while stirring at room temperature. The solution was then stirred at room temperature for 20 hours to carry out a polymerization reaction, producing a viscous polyamic acid solution varnish 2. The viscosity was 23059 cP.

[0070] Synthesis Example 3 To synthesize polyamic acid solution varnish 3, the solvent DMAc (I) was added to a 200 ml separable flask under a nitrogen stream to a solids concentration of 15% by mass, and the diamine component, acid anhydride component, and molar ratio of resin composition B shown in Table 2 were added and dissolved while stirring at room temperature. The solution was then stirred at room temperature for 20 hours to carry out a polymerization reaction, producing a viscous polyamic acid solution varnish 3. The viscosity was 37,465 cP.

[0071] Synthesis Example 4 To synthesize polyamic acid solution varnish 4, the solvent DMAc (I) was added to a 200 ml separable flask under a nitrogen stream to a solids concentration of 15% by mass, and the diamine component, acid anhydride component, and molar ratio of resin composition C shown in Table 2 were added and dissolved while stirring at room temperature. The solution was then stirred at room temperature for 20 hours to carry out a polymerization reaction, producing a viscous polyamic acid solution varnish 4. The viscosity was 221,000 cP.

[0072] [Table 2]

[0073] [Reference example 1] The polyamic acid solution varnish 4 prepared in Synthesis Example 4 was uniformly applied to one side of a long copper foil I (electrolytic copper foil, manufactured by Mitsui Mining & Smelting Co., Ltd., product name: CF-T49A-DS-HD2 foil, thickness: 12 μm) having a thickness of 12 μm, and a width of 12 μm, so that the thickness after curing would be 2.5 μm. The coating was then dried by heating at 120° C. to remove the solvent. Next, the polyamic acid solution varnish 3 prepared in Synthesis Example 3 was uniformly applied onto the dried polyamic acid solution varnish 4 so that the thickness after curing would be 20 μm, and then the coating was dried by heating at 130° C. to remove the solvent. Furthermore, polyamic acid solution varnish 4 prepared in Synthesis Example 4 was uniformly applied onto the dried polyamic acid solution varnish 3 so that the thickness after curing would be 2.5 μm, and then the coating was dried by heating at 130° C. to remove the solvent. In this case, the above process used for applying and heating polyamic acid solution varnish 4, polyamic acid solution varnish 3, and polyamic acid solution varnish 4 was defined as the first heat treatment process.

[0074] Thereafter, a second heat treatment step was performed in which the temperature was raised from 130° C. to 360° C. to effect imidization, thereby obtaining a copper clad laminate consisting of multiple polyimide resin layers with a thickness of 25 μm.

[0075] (Process for recovering and regenerating solvent) The solvent vapor generated in the first and second heat treatment steps was dissolved in water by gas-liquid contact to obtain a solvent recovery liquid, which was then separated into the solvent and water by distillation to obtain DMAc (II), which had a water content of 575 (ppm by mass) as described above.

[0076] Example 1 Polyamic acid varnish 1 was uniformly applied to copper foil I (electrolytic copper foil, manufactured by Mitsui Mining & Smelting Co., Ltd., product name: CF-T49A-DS-HD2 foil, thickness: 12 μm) to a thickness of 20 μm after curing, and then heated and dried at 70 to 120°C for 3 minutes to remove the solvent. Next, a stepwise heat treatment was performed from 130 to 360°C, and imidization was completed within 10 minutes, forming (film-forming) a 20 μm-thick insulating resin layer consisting of polyimide layer 1a, and metal-clad laminate 1A (referred to as "metal-clad laminate" in the table) was obtained.

[0077] The copper foil was removed from the single-sided metal-clad laminate 1A obtained by etching using an aqueous ferric chloride solution to prepare a polyimide film 1a. The total light transmittance (TT), coefficient of thermal expansion (CTE), and thermal decomposition temperature (Td0.5) of the polyimide film 1a were determined. Table 3 shows the film-forming conditions for the polyimide film according to Example 1. <1> Table 4 also shows the single-sided metal-clad laminate according to Example 1 together with the results of these measurements.

[0078] [Table 3]

[0079] [Table 4]

[0080] Comparative Examples 1 to 3 Single-sided metal-clad laminates 2A, 3B, and 4C were prepared in the same manner as in Example 1, except that the organic solvent and polyamic acid solution having the polyimide (PI) composition shown in Table 4 were used, and polyimide films 2a (Comparative Example 1), 3b (Comparative Example 2), and 4c (Comparative Example 3) were obtained, respectively. In this case, polyamic acid varnish was applied to a copper foil, dried to remove the solvent, and then heat-treated to complete the imidization. Regarding the film-forming conditions for obtaining the polyimide film, in Comparative Example 1, the same film-forming conditions as in Example 1 were used. <1> For Comparative Examples 2 and 3, the film formation conditions shown in Table 3 were used. <2> The obtained polyimide films 2a, 3b, and 4c were evaluated in the same manner as in Example 1. The results are shown in Table 4.

[0081] As shown in Table 4, in Comparative Example 3, when the polyamic acid varnish applied to the copper foil was heat-treated, the viscosity was too high, and therefore a uniform polyimide film could not be formed normally.

[0082] On the other hand, although polyimide films could be formed in Example 1 and Comparative Examples 1 and 2, the polyimide film according to Comparative Example 2 did not achieve a total light transmittance of 85% and did not achieve a sufficient thermal decomposition temperature (Td0.5).Furthermore, the polyimide film according to Comparative Example 1 had a total light transmittance of 85% or more, but the thermal decomposition temperature (Td0.5) was slightly below 460°C.

[0083] In contrast, the polyimide film of Example 1 achieved a total light transmittance of 85% or more and a thermal decomposition temperature (Td0.5) of 460°C or more. Compared to Comparative Example 1, the film formation conditions and polyimide composition were the same, but Example 1 used a different organic solvent. It is believed that this difference is reflected in the results.

[0084] As described above, according to the present invention, the transparency of the polyimide film can be ensured and the dimensional accuracy at high temperatures can be improved.

Claims

1. A polyimide film comprising a polyimide having a tetracarboxylic acid residue derived from a tetracarboxylic acid anhydride component and a diamine residue derived from a diamine component, the polyimide contains an aromatic tetracarboxylic acid residue containing a fluorine atom and / or an aromatic diamine residue containing a fluorine atom, The diamine component contains 50 mol % or more of a diamine compound represented by the following formula (1): 【Chemical 1】 [In formula (1), the substituents X independently represent a monovalent hydrocarbon group or alkoxy group having 1 to 3 carbon atoms which may be substituted with a hydrogen atom or a fluorine atom; m and n independently represent integers of 1 to 4; and the linking group Y represents a divalent group selected from a single bond, -CONH-, or -COO-.] the tetracarboxylic acid anhydride component comprises at least one selected from the group consisting of 2,2-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride (6FDA), pyromellitic dianhydride (PMDA), 4,4'-oxydiphthalic dianhydride (ODPA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and p-biphenylenebis(trimellitic acid monoester dihydrate) (BP-TME); A polyimide film characterized by having a total light transmittance of 85% or more and a thermal decomposition temperature (Td0.5) at which a weight loss of 0.5% occurs of 460°C or more.

2. 2. The polyimide film according to claim 1, having a coefficient of thermal expansion (CTE) of 25 ppm / K or less.

3. A metal-clad laminate comprising an insulating resin layer made of a plurality of polyimide layers and a metal layer laminated on at least one surface of the insulating resin layer, 3. A metal-clad laminate, wherein the thickest base polyimide layer among the plurality of polyimide layers is the polyimide film according to claim 1.

4. A method for producing a polyimide film, comprising the following steps a to d: a) preparing a mixed solution containing a tetracarboxylic acid anhydride component, a diamine component, and an organic solvent, wherein the tetracarboxylic acid anhydride component and / or the diamine component contains a compound having an aromatic ring containing a fluorine atom; b) reacting the tetracarboxylic acid anhydride component with the diamine component in the mixed solution to obtain a polyamic acid solution; c) applying the polyamic acid solution onto a substrate and drying it to form a resin film of the polyamic acid; d) heat-treating the resin film to imidize the polyamic acid, thereby obtaining a polyimide film; It is equipped with The organic solvent is selected from the group consisting of the following components A and B: A) an aprotic polar solvent having a boiling point of 200°C or less under 1 atmosphere; B) water; wherein the content of component A measured by gas chromatography is 50% by mass or more, and the content of component B measured by the Karl Fischer method is within a range of 300 to 1000 ppm, A method for producing a polyimide film, characterized by obtaining a polyimide film having a total light transmittance of 85% or more and a thermal decomposition temperature (Td0.5) at which a weight loss of 0.5% is achieved of 460°C or more.

5. 5. The method for producing a polyimide film according to claim 4, wherein the component A is at least one selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

6. 5. The method for producing a polyimide film according to claim 4, wherein the organic solvent is recovered from the solvent vapor generated in the step c or the steps c to d and reused as the organic solvent for the mixed solution.

7. 5. The method for producing a polyimide film according to claim 4, wherein the organic solvent in the step (a) is obtained via a step of recovering solvent vapor generated in the step (c) or the steps (c) to (d).

8. A method for producing a metal-clad laminate including an insulating resin layer made of a plurality of polyimide layers and a metal layer laminated on at least one surface of the insulating resin layer, comprising:

10. A method for producing a metal-clad laminate, comprising: forming a base polyimide layer having the thickest thickness among the plurality of polyimide layers forming the insulating resin layer, using the method for producing a polyimide film according to claim 4; and performing the heat treatment of the resin film in step d in a state in which the resin film is directly or indirectly laminated on a metal layer, thereby forming the base polyimide layer.

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