Method for producing polyimide film

Abstract

To provide an organic solvent capable of preparing a solution of a polyamide acid having high storage stability, and capable of improving recognizability of a film when the polyimide film is obtained using the solution of the polyamide acid, and a method for producing the polyimide film capable of obtaining the polyimide film excellent in recognizability by using the organic solvent to suppress an increase of haze.SOLUTION: There is provided an organic solvent containing aprotic polar solvent having a boiling point of 200°C or less under 1 atmosphere and water, having a content of the aprotic polar solvent measured by gas chromatography of 50% or more, and having the content of water measured by the Karl Fischer method of 40-500 ppm. There is also provided a method for producing a polyimide film to obtain a polyimide film using a mixed solution containing this organic solvent, a tetracarboxylic anhydride component, and a diamine component.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an organic solvent useful for producing polyimide or its precursor that can be used as a material such as a circuit board, a mixed solution containing this organic solvent, a tetracarboxylic dianhydride component, and a diamine component, and a method for producing a polyimide film using this mixed solution.

Background Art

[0002] Polyimide has excellent heat resistance, mechanical properties, and electrical properties. The polyimide film using this polyimide is widely used in various applications in addition to being a base material of a circuit wiring board (also simply referred to as a circuit board) typified by a flexible printed circuit board (FPC; Flexible Printed Circuits).

[0003] As methods for producing a polyimide film, typically, a tenter method and a casting method are known. Among these, the tenter method is a method in which a solution of a polyimide precursor (polyamic acid) is cast onto a rotating drum, peeled off from the rotating drum in the state of a gel film, and heated and cured in a tenter furnace to obtain a polyimide film (see, for example, Patent Document 1). Further, the casting method is a method in which a solution of a polyimide precursor is applied to an arbitrary support substrate such as a copper foil, and dried and cured by heat treatment to obtain a polyimide film (see, for example, Patent Document 2).

[0004] In the preparation of polyimide, usually, a tetracarboxylic dianhydride and a diamine are reacted to obtain a polyamic acid as a precursor. In this state, it is soluble in an organic solvent, but when heat-treated at a high temperature of 200 °C or higher, dehydration ring closure occurs within the molecule, resulting in a polyimide that is insoluble in the organic solvent. Therefore, in both the tenter method and the casting method, a polyimide precursor containing an organic solvent is used and heat-treated to be imidized (cured) to prepare polyimide.

[0005] Polyimide precursors are often unstable to heat and water, but from the perspective of improving storage stability, it has been proposed to set the water content to 1% by weight or less (see, for example, Patent Document 3).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide an organic solvent that can prepare a polyamic acid solution with high storage stability regardless of the chemical structure of the finally obtained polyimide, and can improve the visibility of the obtained polyimide film (or polyimide layer) when the polyimide film (or polyimide layer) is obtained using the polyamic acid solution. Furthermore, an object of the present invention is to provide a method for producing a polyimide film that can obtain a polyimide film (or polyimide layer) having excellent visibility by suppressing an increase in haze by using the above organic solvent.

Means for Solving the Problems

[0008] As a result of intensive studies to solve the above problems, the present inventors focused on the fact that the boiling point of an organic solvent that forms a mixed solution containing a tetracarboxylic dianhydride component and a diamine component affects the haze of the obtained polyimide film or polyimide layer, and by appropriately controlling the water content of the organic solvent, it was found that the imidization temperature of the polyimide precursor can be increased to reduce the residual solvent after imidization, and thus the increase in haze can be suppressed, and the present invention has been completed.

[0009] That is, the gist of the present invention is as follows. (1) The following steps a, b, c'; a) The following components A and B; A) An aprotic polar solvent having a boiling point of 200°C or lower under 1 atm; B) Water; Preparing a mixed solution containing an organic solvent in which the content of component A measured by gas chromatography is 50% or more and the content of component B measured by the Karl Fischer method is in the range of 40 to 500 ppm, a tetracarboxylic anhydride component, and a diamine component; b) Reacting the tetracarboxylic anhydride component and the diamine component in the mixed solution to obtain a solution of polyamic acid; c’) Heat-treating the Coated or cast on a substrate containing an organic solvent and heated at 80 to 400 °C for 1 to 60 minutes polyamic acid solution Coated or cast on a substrate containing an organic solvent and heated at 80 to 400 °C for 1 to 60 minutes to imidize and obtain a polyimide film; Comprising A method for producing a polyimide film, characterized in that an organic solvent is recovered from the solvent vapor generated in the step c’ and reused as the organic solvent of the mixed solution. (2) The method for producing a polyimide film according to (1), wherein the component A is at least one selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide. (3) The method for producing a polyimide film according to (1) or (2), characterized in that among all monomer components derived from the tetracarboxylic anhydride component and the diamine component, a monomer having a biphenyl skeleton is contained in an amount of 50 mol% or more. (4) The method for producing a polyimide film according to (1) or (2), characterized in that the diamine component contains 20 mol% or more of a diamine compound represented by the following general formula (1).

Chemical formula

Chemical formula

Advantages of the Invention

[0010] The organic solvent of the present invention can ensure the storage stability when applied as, for example, a solution of polyamic acid, suppress the imidization of polyamic acid at low temperatures, and reduce the amount of residual solvent after imidization. In addition, since the organic solvent of the present invention has a boiling point in a specific range and the water content is controlled, a polyimide film can be produced without degrading the physical properties of the polyimide film. Furthermore, since the used organic solvent can be repeatedly reused, the manufacturing cost can be significantly reduced, and it is excellent in terms of the environment. For example, high-yield production in continuous production such as a roll-to-roll method is possible, and it has high industrial utility value. When manufacturing a metal-clad laminate, the increase in the haze of the polyimide layer can be suppressed. Therefore, for example, when light is transmitted through the polyimide layer in the mounting process of an FPC, diffusion can be suppressed, and a polyimide layer that can be recognized by a camera can be obtained.

Embodiments for Carrying Out the Invention

[0011] Next, embodiments of the present invention will be described.

[0012] [Organic Solvent] The organic solvent of the present embodiment comprises the following components A and B; A) An aprotic polar solvent having a boiling point of 200°C or lower under 1 atm; B) Water; contains.

[0013] <Component A> Component A is an aprotic polar solvent with a boiling point of 200 °C or lower under 1 atm. However, from the viewpoints of compatibility with water and ease of controlling the water content, those with a lower limit of the boiling point of 120 °C or higher are preferred. If the boiling point is 200 °C or lower, for example, it is likely to be released outside the system during the imidization process of polyamic acid, and the content of the aprotic polar solvent contained in the polyimide film after imidization can be reduced. The remaining amount of the aprotic polar solvent is closely related to the imidization ratio of polyamic acid. If the ratio of the aprotic polar solvent is high relative to the imidization ratio, the aprotic polar solvent functions as a plasticizer, and molecular chain re-conformation occurs, which is considered to increase the haze when forming a film. Therefore, an aprotic polar solvent with a boiling point exceeding 200 °C is likely to remain during imidization, resulting in a high haze. Thus, the boiling point of the aprotic polar solvent is set to 200 °C or lower to suppress the increase in haze.

[0014] Specific examples of the aprotic polar solvent as Component A include, for example, 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), diglyme (boiling point: 162 °C), and the like. Among these, from the viewpoint of ease of controlling the physical properties of the resin film of polyamic acid, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide are preferred, and N,N-dimethylacetamide is more preferred.

[0015] The aprotic polar solvent is contained as a main component of the organic solvent according to the present invention, and the concentration 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 still more preferably 99.99% or more. The % indicating the concentration here represents weight % unless otherwise specified.

[0016] In the organic solvent of the present invention, a solvent other than component A may be included. 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 furthermore, aromatic hydrocarbons such as xylene and toluene may be mixed.

[0017] <Component B> In the organic solvent of the present invention, the water content of component B measured by the Karl Fischer method is in the range of 40 to 500 ppm, preferably in the range of 40 to 450 ppm, and more preferably in the range of 40 to 400 ppm. By controlling within such a range, for example, during the imidization of polyamic acid, hydrolysis of polyamic acid is less likely to occur, and the presence of water molecules that can coordinate to the amide groups of polyamic acid makes it easier to inhibit the ring closure reaction of polyamic acid at low temperatures. As a result, it is considered that the imidization temperature can be increased. For this reason, it is considered that the remaining amount of the aprotic polar solvent can be reduced as the imidization of polyamic acid progresses, and an increase in haze when forming a film can be suppressed.

[0018] The organic solvent of this embodiment is suitably used as a solvent for obtaining a polyamic acid by mixing a tetracarboxylic dianhydride component and a diamine component and polymerizing them, and imidizing the polyamic acid to form a polyimide. That is, the organic solvent according to the present invention, the tetracarboxylic dianhydride component, and the diamine component are contained to form a mixed solution. The organic solvent of such an embodiment is a monomer residue having a biphenyl skeleton with respect to all monomer residues including a tetracarboxylic dianhydride residue derived from the tetracarboxylic dianhydride component and a diamine residue derived from the diamine component (hereinafter sometimes referred to as "biphenyl skeleton-containing residue"). It can be suitably used for the production of a polyimide film having a polyimide layer made of a polyimide having a high ratio.

[0019] Among them, it is preferable that the monomer having a biphenyl skeleton is contained in an amount of 40 mol% or more, more preferably 50 mol% or more, based on all monomer components derived from the tetracarboxylic dianhydride component and the diamine component. That is, the ratio of the biphenyl skeleton-containing residue is preferably 40 mol% or more, more preferably 50 mol% or more, based on all monomer residues derived from all monomer components constituting the polyimide. Here, the "acid anhydride residue" means a tetravalent group derived from a tetracarboxylic dianhydride, and the "diamine residue" means a divalent group derived from a diamine compound.

[0020] A polyimide having a high ratio of biphenyl skeleton-containing residues is likely to form an ordered structure. A polyimide film having a polyimide layer made of such a polyimide is likely to have an increased haze and a decreased visibility. Further, it is considered that the more the residual amount of the aprotic polar solvent in the step of imidizing the polyamic acid, the more easily the ordered structure is formed. For this reason, it is presumed that the aprotic polar solvent functions as a plasticizer and affects the re-conformation of the biphenyl skeleton portion. Therefore, controlling the residual amount of the aprotic polar solvent after imidization is important for controlling the haze of the polyimide film.

[0021] The polyimide layer composed of a polyimide having a high proportion of biphenyl skeleton-containing residues is preferably configured as a polyimide film as the main layer in, for example, the polyimide layer in manufacturing a metal-clad laminate. Here, "main" means having the largest thickness among the plurality of polyimide layers constituting the polyimide film, and preferably having a thickness of 50% or more, more preferably 60% or more, with respect to the total thickness of the polyimide film.

[0022] Also, as shown in the following formula (a), the biphenyl skeleton is a skeleton in which two phenyl groups are singly bonded. Therefore, examples of the biphenyl skeleton-containing residue include a biphenyldiyl group, a biphenyltetrayl group, and the like. The aromatic rings contained in these residues may have any substituent. Typical examples of the biphenyldiyl group include those represented by the following formula (b). Typical examples of the biphenyltetrayl group include those represented by the following formula (c). In the biphenyldiyl group and the biphenyltetrayl group, the bonds in the aromatic ring are not limited to the positions shown in formula (b) and formula (c), and as described above, the aromatic rings contained in these residues may have any substituent.

[0023]

Chemical formula

[0024] The biphenyl skeleton-containing residue is a structure derived from a raw material monomer, and may be derived from a tetracarboxylic dianhydride, may be derived from a diamine compound, or may be derived from both to form a biphenyl skeleton-containing residue.

[0025] As the diamine residue contained in the polyimide, a diamine residue derived from a diamine compound represented by the general formula (1) is preferably mentioned.

[0026]

Chemical formula

[0027] In general formula (1), the linking group Z represents a single bond or -COO-, Y independently represents a monovalent hydrocarbon having 1 to 3 carbon atoms which may be substituted with a halogen or a phenyl group, an alkoxy group having 1 to 3 carbon atoms, a perfluoroalkyl group having 1 to 3 carbon atoms, or an alkenyl group, n represents an integer of 1 to 2, and p and q independently represent an integer of 0 to 4. Here, "independently" means that in the above formula (1), a plurality of substituents Y, integers p, and q may be the same or different.

[0028] The diamine residue derived from the diamine compound represented by general formula (1) (hereinafter, may be referred to as "diamine residue (1)") is likely to form an ordered structure and can enhance dimensional stability. From such a viewpoint, diamine residue (1) is preferably contained in an amount of 20 mol parts or more, preferably in the range of 70 to 99 mol parts, more preferably in the range of 80 to 99 mol parts, based on 100 mol parts of all the diamine residues contained in the polyimide.

[0029] Preferable specific examples of the diamine residue (1) include diamine residues derived from diamine compounds such as 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-diethyl-4,4'-diaminobiphenyl (m-EB), 2,2'-diethoxy-4,4'-diaminobiphenyl (m-EOB), 2,2'-dipropoxy-4,4'-diaminobiphenyl (m-POB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), 2,2'-divinyl-4,4'-diaminobiphenyl (VAB), 4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB). Among these, 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB) is particularly preferable because it is likely to form an ordered structure.

[0030] Further, in order to lower the elastic modulus of the polyimide film and improve elongation, bending resistance, etc., it is preferable that the polyimide contains at least one diamine residue selected from the group consisting of diamine residues represented by the following general formulas (2) and (3).

[0031]

Chemical formula

[0032] In the above formulas (2) and (3), R5, R6, R7, and R8 each independently represent a halogen atom or an alkyl group, an alkoxy group which may be substituted with a halogen atom having 1 to 4 carbon atoms, or an alkenyl group having 1 to 4 carbon atoms, X independently represents a divalent group selected from -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -CO-, -COO-, -SO2-, -NH-, or -NHCO-, and X1 and X2 each independently represent a divalent group selected from a single bond, -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -CO-, -COO-, -SO2-, -NH-, or -NHCO-, provided that the case where both X1 and X2 are single bonds is excluded, and j, k, l, and m each independently represent an integer of 0 to 4. Note that "independently" means that in one or both of the above formulas (2) and (3), a plurality of linking groups X, linking groups X1 and X2, a plurality of substituents R5, R6, R7, R8, and further, the integers j, k, l, m may be the same or different.

[0033] The diamine residues represented by general formulas (2) and (3) have flexible sites, so flexibility can be imparted to the polyimide. Here, since the diamine residue represented by general formula (3) has four benzene rings, in order to suppress an increase in the coefficient of thermal expansion (CTE), it is preferable that the terminal groups bonded to the benzene rings are in the para position. Further, from the viewpoint of suppressing an increase in the coefficient of thermal expansion (CTE) while imparting flexibility to the polyimide, the diamine residues represented by general formulas (2) and (3) are preferably contained in the range of 2 to 30 mol parts with respect to 100 mol parts of all the diamine residues contained in the polyimide.

[0034] Among the diamine residues represented by general formula (2), it is preferable that one or more of m, n, and o are 0. Further, preferable examples of the groups R5, R6, and R7 include an alkyl group which may be substituted with a halogen atom having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or an alkenyl group having 2 to 3 carbon atoms. In general formula (2), preferable examples of the linking group X include -O-, -S-, -CH2-, -CH(CH3)-, -SO2-, or -CO-. Preferable specific examples of the diamine residue represented by general formula (2) include diamine residues derived from diamine compounds such as 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,4-bis(4-aminophenoxy)benzene (TPE-Q), bis(4-aminophenoxy)-2,5-di-tert-butylbenzene (DTBAB), 4,4-bis(4-aminophenoxy)benzophenone (BAPK), 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, and 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene.

[0035] The diamine residue represented by the general formula (3) is preferably one in which one or more of m, n, o, and p are 0. Preferred examples of the groups R5, R6, R7, and R8 include an alkyl group which may be substituted with a halogen atom having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or an alkenyl group having 2 to 3 carbon atoms. In the general formula (3), preferred examples of the linking groups X1 and X2 include a single bond, -O-, -S-, -CH2-, -CH(CH3)-, -SO2-, or -CO-. However, from the viewpoint of imparting a bent site, both of the linking groups X1 and X2 being a single bond are excluded. Preferred specific examples of the diamine residue represented by the general formula (3) include diamine residues derived from diamine compounds such as 4,4'-bis(4-aminophenoxy)biphenyl (BAPB), 2,2'-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2'-bis[4-(4-aminophenoxy)phenyl]ether (BAPE), and bis[4-(4-aminophenoxy)phenyl]sulfone.

[0036] Among the diamine residues represented by the general formula (2), a diamine residue derived from 1,3-bis(4-aminophenoxy)benzene (TPE-R) (which may be referred to as a "TPE-R residue") is particularly preferred. Among the diamine residues represented by the general formula (3), a diamine residue derived from 2,2'-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) (which may be referred to as a "BAPP residue") is particularly preferred. Since the TPE-R residue and the BAPP residue have a flexible site, they can reduce the elastic modulus of the polyimide film and impart flexibility. In addition, since the BAPP residue has a large molecular weight, it can be expected to have an effect of reducing the imide group concentration of the polyimide and suppressing the moisture absorption of the polyimide film.

[0037] Other diamine residues contained in the polyimide include, for example, m-phenylenediamine (m-PDA), 4,4'-diaminodiphenyl ether (4,4'-DAPE), 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl methane, 3,3'-diaminodiphenyl methane, 3,4'-diaminodiphenyl methane, 4,4'-diaminodiphenyl propane, 3,3'-diaminodiphenyl propane, 3,4'-diaminodiphenyl propane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)biphenyl, bis[1-(3-aminophenoxy)]biphenyl, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)]benzophenone, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane, 3,3’-dimethyl-4,4’-diaminobiphenyl, 4,4’-methylenedi-o-toluidine, 4,4’-methylenedi-2,6-xylidine, 4,4’-methylene-2,6-diethylaniline, 3,3’-diaminodiphenylethane, 3,3’-diaminobiphenyl, 3,3’-dimethoxybenzidine, 3,3''-diamino-p-terphenyl, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline, 4,4'-[1,Diamine residues derived from aromatic diamine compounds such as 3-phenylenebis(1-methylethylidene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-t-butylphenyl)ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-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, etc. are included.

[0038] The tetracarboxylic acid residues contained in the polyimide are not particularly limited. For example, tetracarboxylic acid residues derived from pyromellitic dianhydride (PMDA) (hereinafter also referred to as PMDA residues), and tetracarboxylic acid residues derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) (hereinafter also referred to as BPDA residues) are preferably mentioned. These tetracarboxylic acid residues are likely to form an ordered structure. In addition, the PMDA residue is a residue that plays a role in controlling the coefficient of thermal expansion and the glass transition temperature. Furthermore, since the BPDA residue has no polar group and has a relatively large molecular weight among the tetracarboxylic acid residues, it can also be expected to reduce the imide group concentration of the polyimide and suppress the moisture absorption of the polyimide film. From such a viewpoint, the total amount of the PMDA residue and / or the BPDA residue is preferably 50 mole parts or more, more preferably in the range of 50 to 100 mole parts, and most preferably in the range of 70 to 100 mole parts with respect to 100 mole parts of all the tetracarboxylic acid residues contained in the polyimide.

[0039] Examples of other tetracarboxylic acid residues contained in the polyimide include 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 2,2',3,3'-, 2,3,3',4'- or 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3',3,4'-diphenyl ether tetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl) ether dianhydride, 3,3'',4,4''-, 2,3,3'',4''- or 2,2'',3,3''-p-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3- or 3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3- or 3.Tetracarboxylic acid residues derived from aromatic tetracarboxylic dianhydrides such as 4-dicarboxyphenyl)methane dianhydride, bis(2,3- or 3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3- or 3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-, 1,2,6,7- or 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,3,6,7-anthracene tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2,6- or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-(or 1,4,5,8-)tetrachloronaphthalene-1,4,5,8-(or 2,3,6,7-)tetracarboxylic dianhydride, 2,3,8,9-, 3,4,9,10-, 4,5,10,11- or 5,6,11,12-perylene-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, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, etc. are mentioned.

[0040] In the polyimide, by selecting the types of the above tetracarboxylic acid residues and diamine residues, and the respective molar ratios when applying two or more types of tetracarboxylic acid residues or diamine residues, the coefficient of thermal expansion, storage elastic modulus, tensile elastic modulus, etc. can be controlled. Further, when having a plurality of structural units of the polyimide, they may be present as blocks or randomly, but from the viewpoint of suppressing in-plane variations, it is preferably present randomly.

[0041] [Method for producing polyimide film] The method for producing a polyimide film according to this embodiment includes the following steps a to d; a) A step of preparing a mixed solution containing an organic solvent according to the present invention, a tetracarboxylic dianhydride component, and a diamine component; b) A step of reacting the tetracarboxylic dianhydride component and the diamine component in the mixed solution to obtain a solution of polyamic acid; c) A step of forming a resin film of the polyamic acid by applying and drying the solution of the polyamic acid on a substrate; d) A step of obtaining a polyimide film by heat-treating the resin film to imidize the polyamic acid; can be provided. Note that the following steps a, b, c'; a) A step of preparing a mixed solution containing an organic solvent according to the present invention, a tetracarboxylic dianhydride component, and a diamine component; b) A step of reacting the tetracarboxylic dianhydride component and the diamine component in the mixed solution to obtain a solution of polyamic acid; c') A step of obtaining a polyimide film by heat-treating and imidizing the polyamic acid solution; may be provided.

[0042] <Step a> The organic solvent used in step a contains the components A and B.

[0043] <Step b> In step b, for example, a tetracarboxylic dianhydride and a diamine compound are dissolved in an organic solvent in approximately equimolar amounts and stirred and polymerized at a temperature in the range of 0 to 100°C for 30 minutes to 24 hours to obtain a solution of polyamic acid. In the reaction, the reaction components are dissolved so that the resulting polyamic acid is in the range of 5 to 30% by mass, preferably 10 to 20% by mass, in the solvent.

[0044] 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 thickness unevenness and streaks are likely to occur in the film during the coating operation using a coater or the like.

[0045] <Process c and Process d> The solution of polyamic acid obtained in Process b is coated on a substrate and then dried and imidized (or cured) by a subsequent heat treatment. As the heat treatment method, generally, for example, heat treatment such as heating at a temperature in the range of 80 to 400 °C for a time in the range of 1 to 60 minutes is preferably employed. At that time, in order to advance the imidization of polyamic acid, heat treatment for evaporating the organic solvent that dissolves or mixes and heat treatment for releasing the organic solvent coordinated to polyamic acid out of the system are required.

[0046] After forming the polyamic acid resin film in Process c, it may be imidized on the substrate, or the resin film may be peeled off from the substrate and then imidized. Further, when the polyimide film is a polyimide film composed of a plurality of polyimide layers, as an aspect of the manufacturing method, for example, a method of repeating the application and drying of the polyamic acid solution on the substrate a plurality of times and then performing imidization (hereinafter, the casting method), a method of applying and drying while laminating the polyamic acid in multiple layers simultaneously by multi-layer extrusion and then performing imidization (hereinafter, the multi-layer extrusion method), etc. can be mentioned.

[0047] Regardless of whether the polyimide film is a single layer or a plurality of layers, it is preferable to complete the imidization of polyamic acid on the substrate. Since the polyamic acid resin film is imidized in a state fixed to the substrate, the expansion and contraction changes of the polyimide layer in the imidization process can be suppressed, and the thickness and dimensional accuracy of the polyimide film can be maintained.

[0048] <Substrate> Regarding the base material used in Process C, it is used for the purpose of reinforcing the polyimide film (or polyimide layer) and suppressing the expansion and contraction changes of the polyimide film to maintain dimensional accuracy. Further, the base material is the object to which the solution of polyamic acid is applied, and shapes such as cut sheet form, roll form or endless belt form can be used. In order to obtain productivity, it is efficient to adopt a roll form or an endless belt form and make it a form that enables continuous production. Furthermore, from the viewpoint of more significantly expressing the effect of improving the dimensional accuracy of the polyimide film, the support base material is preferably a long-sized roll form.

[0049] Examples of the material of the base material include those with heat resistance such as metal, ceramics, resin, and carbon. From the viewpoints of thermal conductivity and flexibility, metal is preferred. Therefore, examples of the base material include metal films 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 and alloy foils thereof. When the polyimide film is applied as the insulating layer of the circuit wiring board and the base material is applied as the wiring layer of the circuit wiring board, the base material is preferably copper foil or copper alloy foil. Further, when the polyimide film is peeled off from the base material and used, as the base material, a smooth stainless steel belt, a stainless steel drum, etc. can be preferably used.

[0050] The thickness of the metal foil as the base material is preferably in the range of, for example, 5 to 35 μm, and more preferably in the range of 9 to 18 μm. When the metal foil is thicker than 35 μm, the flexibility and bendability of the laminate composed of the polyimide layer and the metal foil layer deteriorate. On the other hand, when the metal foil is thinner than 5 μm, it becomes difficult to adjust the tension, etc. in the manufacturing process of the laminate, and defects such as wrinkles are likely to occur. Further, these metal foils may be subjected to chemical or mechanical surface treatment on their surfaces for the purpose of improving the adhesive force, etc., or may be subjected to chemical surface treatment for the purpose of rust prevention.

[0051] <Recovery and Reuse of Organic Solvents> It is preferable to have a step of recovering the organic solvent from the solvent vapor generated in step c. The recovery of the organic solvent is carried out by recovering the organic solvent from the solvent vapor generated by drying after applying 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 thus recovered is reused as the organic solvent in step a.

[0052] The method of recovering and reusing the solvent vapor is not particularly limited. For example, a cooling method, an adsorption method using a solid adsorbent such as activated carbon or zeolite, an adsorption method using a liquid non-volatile solvent, an absorption method using water, etc. can be mentioned. Also, 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 type concentration device, an evaporation concentration device, etc.

[0053] From the viewpoint that the solvent vapor is hydrophilic, easily soluble in water, has a higher boiling point than water, a smaller vapor pressure than water, and thus is more easily evaporated than water and does not have an azeotropic point with water, the step of recovering the solvent from the solvent vapor preferably includes a step of dissolving the water-soluble substances contained in the solvent vapor in water. The recovered liquid can be concentrated by evaporating water with a high vapor pressure by the thermal energy supplied from the outside. It is preferable to utilize the heat of the solvent vapor for the thermal energy, but when the solvent vapor is at a low temperature, the heat from a heater or the like may be utilized. The concentrated recovered liquid may be subjected to acid treatment, alkali treatment, activated carbon treatment, etc. as necessary.

[0054] Also, the concentrated recovered liquid can be regenerated and reused as the raw material organic solvent in step a by purification such as distillation.

[0055] When using an organic solvent containing the reused solvent, it is preferable that 50% by volume or more of the raw material organic solvent is the reused solvent. By setting the ratio of the reused solvent in the raw material organic solvent to 50% by volume or more, the cost merit increases.

Examples

[0056] Examples are shown below to more specifically explain the features of the present invention. However, the scope of the present invention is not limited to the examples. In the following examples, unless otherwise specified, various measurements and evaluations are as follows.

[0057] [Evaluation of moisture content] The moisture content of the regenerated solvent was measured using a Karl Fischer moisture measuring device (micro moisture measuring device AQ-300, manufactured by Hiranuma Sangyo Co., Ltd.).

[0058] [Measurement of solvent purity] The solvent purity was measured using a gas chromatograph (column: G-100). It is the value expressed as a percentage of the main peak area of the solvent in the total peak area obtained.

[0059] [Measurement of viscosity] The viscosity at 25°C was measured using an E-type viscometer (manufactured by Brookfield, product name; DV-II+Pro). The rotation speed was set so that the torque was 10% to 90%, and after 2 minutes from the start of the measurement, the value when the viscosity became stable was read.

[0060] [Measurement of surface roughness of copper foil] The surface roughness of the copper foil was measured using an AFM (manufactured by Bruker AXS, product name; Dimension Icon type SPM), a probe (manufactured by Bruker AXS, product name; TESPA (NCHV), tip radius of curvature 10 nm, spring constant 42 N / m) in tapping mode over a range of 80 μm × 80 μm on the copper foil surface, and the ten-point average roughness (Rzjis) was determined.

[0061] [Evaluation of haze] Using a haze measuring device (turbidimeter: manufactured by Nippon Denshoku Industries Co., Ltd., product name; NDH5000), for a polyimide film with a size of 5 cm × 5 cm, the measurement was carried out according to the measurement method described in ASTM D 1003.

[0062] [Measurement of coefficient of thermal expansion (CTE)] A polyimide film with a size of 3 mm (in the coating width direction) × 20 mm (in the coating length direction) was heated from 30 °C to 260 °C at a constant heating rate while applying a load of 5.0 g using a thermomechanical analyzer (manufactured by Bruker, trade name: 4000SA), then held at that temperature for 10 minutes, and then cooled at a rate of 5 °C / min. The average coefficient of thermal expansion (coefficient of thermal expansion) from 250 °C to 100 °C was determined.

[0063] The abbreviations used in the examples and reference examples represent the following compounds. PMDA: Pyromellitic dianhydride BPDA: 3,3',4,4'-Biphenyltetracarboxylic dianhydride m-TB: 2,2'-Dimethyl-4,4'-diaminobiphenyl TPE-Q: 1,4-Bis(4-aminophenoxy)benzene BAPP: 2,2-Bis[4-(4-aminophenoxy)phenyl]propane Bis-aniline-P: 1,4-Bis[2-(4-aminophenyl)-2-propyl]benzene (manufactured by Mitsui Chemicals Fine Inc., trade name: Bis-aniline-P) DMAc: N,N-Dimethylacetamide DMF: N,N-Dimethylformamide

[0064] [Synthesis Example 1] 14.20 parts by mass of m-TB (0.067 mol parts), 3.45 parts by mass of TPE-Q (0.012 mol parts), and a new product of DMAc (water content 10 wt ppm, purity 99.9% or more) in an amount such that the solid content concentration after polymerization was 15 wt% were charged into a reaction vessel and stirred at room temperature to dissolve. Next, 12.66 parts by mass of PMDA (0.058 mol parts) and 5.69 parts by mass of BPDA (0.019 mol parts) were added, and then the polymerization reaction was continued by stirring at room temperature for 3 hours to obtain a polyamic acid solution a-1. The viscosity of the polyamic acid solution a-1 was 34,900 cps. Also, the viscosity when stored at 23 °C and 50% RH for 20 days was 30,100 cps.

[0065] [Synthesis Example 2] 14.49 parts by mass of m-TB (0.068 mol parts), 1.11 parts by mass of TPE-Q (0.004 mol parts), 1.31 parts by mass of bisaniline-P (0.004 mol parts), and a novel DMAc (water content 10 wt ppm, purity 99.9% or more) in an amount such that the solid content concentration after polymerization is 15% by weight were charged into a reaction vessel, and stirred at room temperature to dissolve. Next, 8.13 parts by mass of PMDA (0.037 mol parts) and 10.97 parts by mass of BPDA (0.037 mol parts) were added, and then the polymerization reaction was continued by stirring at room temperature for 3 hours to obtain a polyamic acid solution b-1. The viscosity of the polyamic acid solution b-1 was 35,500 cps. Also, the viscosity when stored at 23 °C and 50% RH for 20 days was 32,800 cps.

[0066] [Synthesis Example 3] 14.20 parts by mass of m-TB (0.067 mol parts), 3.45 parts by mass of TPE-Q (0.012 mol parts), and a novel DMF (water content 15 wt ppm, purity 99.9% or more) in an amount such that the solid content concentration after polymerization is 15% by weight were charged into a reaction vessel, and stirred at room temperature to dissolve. Next, 12.66 parts by mass of PMDA (0.058 mol parts) and 5.69 parts by mass of BPDA (0.019 mol parts) were added, and then the polymerization reaction was continued by stirring at room temperature for 3 hours to obtain a polyamic acid solution a-2. The viscosity of the polyamic acid solution a-2 was 32,700 cps. Also, the viscosity when stored at 23 °C and 50% RH for 20 days was 28,900 cps.

[0067] [Synthesis Example 4] 18.71 parts by mass of BAPP (0.046 mol parts) and a novel DMAc (water content 10 wt ppm, purity 99.9% or more) in an amount such that the solid content concentration after polymerization is 12% by weight were charged into a reaction vessel, and stirred at room temperature to dissolve. Next, 10.09 parts by mass of PMDA (0.046 mol parts) were added, and then the polymerization reaction was continued by stirring at room temperature for 3 hours to obtain a polyamic acid solution c-1. The viscosity of the polyamic acid solution c-1 was 2,100 cps.

[0068] [Synthesis Example 5] 18.71 parts by mass of BAPP (0.046 mole parts) and an amount of a new product of DMF (water content 15 wt ppm, purity 99.9% or more) such that the solid content concentration after polymerization becomes 12% by weight were charged into a reaction vessel, and stirred at room temperature to dissolve. Next, 10.09 parts by mass of PMDA (0.046 mole parts) was added, and then stirring was continued at room temperature for 3 hours to conduct a polymerization reaction, obtaining a polyamic acid solution c-2. The viscosity of the polyamic acid solution c-2 was 1,600 cps.

[0069] [Production Example 1] The polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly applied onto one side of a long rolled copper foil (Rzjis = 0.88 μm) having a thickness of 18 μm and a width of 1,080 mm so that the thickness after curing would be 2.5 μm, and then heat-dried at 130° C. to remove the solvent. Next, the polyamic acid solution a-1 prepared in Synthesis Example 1 was uniformly applied onto the dried polyamic acid solution c so that the thickness after curing would be 20 μm, and then heat-dried at 130° C. to remove the solvent. Further, the polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly applied onto the dried polyamic acid solution a-1 so that the thickness after curing would be 2.5 μm, and then heat-dried at 130° C. to remove the solvent. At this time, the above steps of applying and heat-treating the polyamic acid solution c-1, the polyamic acid solution a-1, and the polyamic acid solution c-1 were defined as the first heat treatment step. Then, a second heat treatment step of raising the temperature from 160° C. to 360° C. for imidization was obtained, and a copper-clad laminate 1 composed of a multilayer polyimide resin layer with a thickness of 25 μm was obtained. For the obtained copper-clad laminate A-1, the copper foil was etched and removed using an aqueous ferric chloride solution to prepare a multilayer polyimide film A-1. The haze of this multilayer polyimide film A-1 was 75.30% and the CTE was 21 ppm / K.

[0070] (Step of recovering and regenerating the solvent) At this time, the solvent vapor generated in the first heat treatment step was brought into gas-liquid contact with water and dissolved to obtain a solvent recovery liquid, and then separated into a solvent and water by distillation to obtain regenerated DMAc1. At this time, the purity of the regenerated DMAc1 was 99.99 (%) and the water content was 41 (wt ppm).

[0071] [Production Example 2] On one side of a long rolled copper foil (Rzjis = 0.88 μm) with a thickness of 18 μm and a width of 1,080 mm, the polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly applied so that the thickness after curing would be 2.5 μm. Then, it was dried by heating at 130°C to remove the solvent. Next, the polyamic acid solution b-1 prepared in Synthesis Example 2 was uniformly applied on the dried polyamic acid solution c-1 so that the thickness after curing would be 20 μm. Then, it was dried by heating at 130°C to remove the solvent. Further, the polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly applied on the dried polyamic acid solution b-1 so that the thickness after curing would be 2.5 μm. Then, it was dried by heating at 130°C to remove the solvent. At this time, the above steps of applying and heat-treating the polyamic acid solution c-1, the polyamic acid solution b-1, and the polyamic acid solution c-1 were used as the first heat treatment step. Then, a second heat treatment step of raising the temperature from 160°C to 360°C for imidization was obtained, and a copper-clad laminate B-1 composed of a multilayer polyimide resin layer with a thickness of 25 μm was obtained. For the obtained copper-clad laminate B-1, the copper foil was etched and removed using an aqueous solution of ferric chloride to prepare a multilayer polyimide film B-1. The haze of this multilayer polyimide film B-1 was 81.83% and the CTE was 23 ppm / K.

[0072] Regarding the solvent vapor generated in the first heat treatment step, similar to Production Example 1, it was brought into gas-liquid contact with water and dissolved to obtain a solvent recovery liquid, and then separated into a solvent and water by distillation to obtain regenerated DMAc2. Also, the same production as in Production Example 2 was carried out twice. At that time, regarding the solvent vapor generated in the first heat treatment step, recovery and separation from water were carried out to obtain regenerated DMAc3 and regenerated DMAc4. Table 1 shows the results of measuring the purity and water content of the regenerated DMAc obtained at this time.

[0073]

Table 1

[0074] [Production Example 3] On one side of a long strip of rolled copper foil (Rzjis = 0.88 μm) with a thickness of 18 μm and a width of 1,080 mm, the polyamic acid solution c-2 prepared in Synthesis Example 5 was uniformly coated so that the thickness after curing would be 2.5 μm. Then, it was heated and dried at 130 °C to remove the solvent. Next, the polyamic acid solution a-2 prepared in Synthesis Example 3 was uniformly coated on the dried polyamic acid solution c-2 so that the thickness after curing would be 20 μm. Then, it was heated and dried at 130 °C to remove the solvent. Further, the polyamic acid solution c-2 prepared in Synthesis Example 5 was uniformly coated on the dried polyamic acid solution a-2 so that the thickness after curing would be 2.5 μm. Then, it was heated and dried at 130 °C to remove the solvent. At this time, the above steps of coating and heat treatment using the polyamic acid solution c-2, the polyamic acid solution a-2, and the polyamic acid solution c-2 were taken as the first heat treatment step. Then, a second heat treatment step of raising the temperature from 160 °C to 360 °C for imidization was obtained, and a copper-clad laminate A-2 composed of a multilayer polyimide resin layer with a thickness of 25 μm was obtained. Regarding the obtained copper-clad laminate A-2, the copper foil was etched and removed using an aqueous ferric chloride solution to prepare a multilayer polyimide film A-2. The haze of this multilayer polyimide film A-2 was 72.16%, and the CTE was 20 ppm / K.

[0075] Regarding the solvent vapor generated in the first heat treatment step, in the same manner as in Production Example 1, it was brought into gas-liquid contact with water and dissolved to obtain a solvent recovery liquid, and then it was separated into a solvent and water by distillation to obtain recycled DMF1. At this time, the purity of the recycled DMF1 was 99.98 (%) and the water content was 246 (wt ppm).

[0076] [Production Example 4] On one side of a long rolled copper foil (Rzjis = 0.88 μm) with a thickness of 18 μm and a width of 1,080 mm, the polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly applied so that the thickness after curing would be 2.5 μm. Then, it was dried by heating at 130°C to remove the solvent. Next, the polyamic acid solution a-2 prepared in Synthesis Example 3 was uniformly applied on the dried polyamic acid solution c-1 so that the thickness after curing would be 20 μm. Then, it was dried by heating at 130°C to remove the solvent. Further, the polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly applied on the dried polyamic acid solution a-2 so that the thickness after curing would be 2.5 μm. Then, it was dried by heating at 130°C to remove the solvent. At this time, the above steps of applying and heat-treating the polyamic acid solution c-1, the polyamic acid solution a-2, and the polyamic acid solution c-1 were used as the first heat treatment step. Then, a second heat treatment step of heating from 160°C to 360°C for imidization was obtained, and a copper-clad laminate A-3 composed of a multilayer polyimide resin layer with a thickness of 25 μm was obtained. For the obtained copper-clad laminate A-3, the copper foil was etched and removed using an aqueous solution of ferric chloride to prepare a multilayer polyimide film A-3. The haze of this multilayer polyimide film A-3 was 72.52% and the CTE was 20 ppm / K.

[0077] Regarding the solvent vapor generated in the first heat treatment step, in the same manner as in Production Example 1, it was brought into gas-liquid contact with water and dissolved to obtain a solvent recovery liquid, and then separated into a solvent and water by distillation to obtain a regenerated DMF / DMAc mixed solution 1. At this time, the purity of the regenerated DMF / DMAc mixed solution 1 was 99.98 (%) and the water content was 121 (wt ppm).

[0078] [Example 1] 14.20 parts by mass of m-TB (0.067 mol parts), 3.45 parts by mass of TPE-Q (0.012 mol parts), and an amount of recycled DMAc1 such that the solid content concentration after polymerization was 15% by weight were charged into a reaction vessel and stirred at room temperature to dissolve. Next, 12.66 parts by mass of PMDA (0.058 mol parts) and 5.69 parts by mass of BPDA (0.019 mol parts) were added, and then the polymerization reaction was continued by stirring at room temperature for 3 hours to obtain a polyamic acid solution a-3. The viscosity of the polyamic acid solution a-3 was 31,200 cps. Also, the viscosity when stored at 23 °C and 50% RH for 20 days was 26,500 cps.

[0079] Next, the polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly coated on one side of a long rolled copper foil (Rzjis = 0.88 μm) with a thickness of 18 μm and a width of 1,080 mm so that the thickness after curing was 2.5 μm, and then dried by heating at 130 °C to remove the solvent. Next, the polyamic acid solution a-3 was uniformly coated on the dried polyamic acid solution c-1 so that the thickness after curing was 20 μm, and then dried by heating at 130 °C to remove the solvent. Further, the polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly coated on the dried polyamic acid solution a-3 so that the thickness after curing was 2.5 μm, and then dried by heating at 130 °C to remove the solvent. Thereafter, a second heat treatment step of imidization was obtained by raising the temperature from 160 °C to 360 °C, and a copper-clad laminate A-3 composed of a multilayer polyimide resin layer with a thickness of 25 μm was obtained. For the obtained copper-clad laminate A-3, the copper foil was etched and removed using an aqueous solution of ferric chloride to prepare a multilayer polyimide film A-3. The haze of this multilayer polyimide film A-3 was 71.78% and the CTE was 21 ppm / K.

[0080] [Example 2] A polyamic acid solution a-4, a copper-clad laminate A-4, and a multilayer polyimide film A-4 were obtained in the same manner as in Example 1 except that the DMAc used was changed to recycled DMAc2. The viscosity of the obtained polyamic acid solution a-4 was 28,700 cps. Also, the viscosity when stored at 23°C and 50% RH for 20 days was 19,100 cps. The haze of the multilayer polyimide film A-4 was 65.20%, and the CTE was 22 ppm / K.

[0081] [Example 3] A polyamic acid solution a-5, a copper-clad laminate A-5, and a multilayer polyimide film A-5 were obtained in the same manner as in Example 1, except that the DMAc used was changed to regenerated DMAc3. The viscosity of the obtained polyamic acid solution a-5 was 26,500 cps. Also, the viscosity when stored at 23°C and 50% RH for 20 days was 15,500 cps. The haze of the multilayer polyimide film A-5 was 61.71%, and the CTE was 22 ppm / K.

[0082] [Example 4] A polyamic acid solution a-6, a copper-clad laminate A-6, and a multilayer polyimide film A-6 were obtained in the same manner as in Example 1, except that the DMAc used was changed to regenerated DMF1 and the polyamic acid solution c-1 was changed to polyamic acid solution c-2. The viscosity of the obtained polyamic acid solution a-6 was 26,100 cps. Also, the viscosity when stored at 23°C and 50% RH for 20 days was 13,700 cps. The haze of the multilayer polyimide film A-6 was 60.08%, and the CTE was 21 ppm / K.

[0083] [Example 5] 14.49 parts by mass of m-TB (0.068 mol parts), 1.11 parts by mass of TPE-Q (0.004 mol parts), 1.31 parts by mass of bisaniline-P (0.004 mol parts), and an amount of recycled DMAc2 such that the solid content concentration after polymerization becomes 15% by weight were charged into a reaction vessel and stirred at room temperature to dissolve. Next, 8.13 parts by mass of PMDA (0.037 mol parts) and 10.97 parts by mass of BPDA (0.037 mol parts) were added, and then the polymerization reaction was continued by stirring at room temperature for 3 hours to obtain a polyamic acid solution b-2. The viscosity of the polyamic acid solution b-2 was 29,900 cps. Also, the viscosity when stored at 23°C and 50% RH for 20 days was 22,500 cps.

[0084] Next, the polyamic acid solution c prepared in Synthesis Example 4 was uniformly coated on one side of a long rolled copper foil (Rzjis = 0.88 μm) with a thickness of 18 μm and a width of 1,080 mm so that the thickness after curing would be 2.5 μm, and then heated and dried at 130°C to remove the solvent. Next, the polyamic acid solution b-2 was uniformly coated on the dried polyamic acid solution c so that the thickness after curing would be 20 μm, and then heated and dried at 130°C to remove the solvent. Further, the polyamic acid solution c prepared in Synthesis Example 4 was uniformly coated on the dried polyamic acid solution b-2 so that the thickness after curing would be 2.5 μm, and then heated and dried at 130°C to remove the solvent. Then, a second heat treatment step of raising the temperature from 160°C to 360°C for imidization was obtained, and a copper-clad laminate B-2 composed of a multilayer polyimide resin layer with a thickness of 25 μm was obtained. For the obtained copper-clad laminate B-2, the copper foil was etched and removed using an aqueous ferric chloride solution to prepare a multilayer polyimide film B-2. The haze of this multilayer polyimide film B-2 was 78.67% and the CTE was 23 ppm / K.

[0085] [Example 6] 14.49 parts by mass of m-TB (0.068 mol parts), 1.11 parts by mass of TPE-Q (0.004 mol parts), 1.31 parts by mass of bisaniline-P (0.004 mol parts) and an amount of recycled DMF / DMAc mixed solution 1 such that the solid content concentration after polymerization becomes 15% by weight were charged into a reaction vessel and stirred at room temperature for dissolution. Next, 8.13 parts by mass of PMDA (0.037 mol parts) and 10.97 parts by mass of BPDA (0.037 mol parts) were added, and then the polymerization reaction was continued by stirring at room temperature for 3 hours to obtain a polyamic acid solution a-7. The viscosity of the polyamic acid solution a-7 was 25,900 cps. Also, the viscosity when stored at 23°C and 50% RH for 20 days was 17,700 cps.

[0086] Next, the polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly coated on one side of a long rolled copper foil (Rzjis = 0.88 μm) with a thickness of 18 μm and a width of 1,080 mm so that the thickness after curing was 2.5 μm, and then heated and dried at 130°C to remove the solvent. Next, the polyamic acid solution a-7 was uniformly coated on the dried polyamic acid solution c-1 so that the thickness after curing was 20 μm, and then heated and dried at 130°C to remove the solvent. Further, the polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly coated on the dried polyamic acid solution a-7 so that the thickness after curing was 2.5 μm, and then heated and dried at 130°C to remove the solvent. Thereafter, a second heat treatment step of raising the temperature from 160°C to 360°C for imidization was obtained, and a copper-clad laminate A-7 composed of a multilayer polyimide resin layer with a thickness of 25 μm was obtained. Regarding the obtained copper-clad laminate A-7, the copper foil was etched and removed using an aqueous solution of ferric chloride to prepare a multilayer polyimide film A-7. The haze of this multilayer polyimide film A-7 was 63.87% and the CTE was 21 ppm / K.

[0087] [Reference Example 1] A polyamic acid solution a-8, a copper-clad laminate A-7, and a multilayer polyimide film A-8 were obtained in the same manner as in Example 1 except that the DMAc used was changed to recycled DMAc4. The viscosity of the obtained polyamic acid solution a-7 was 21,900 cps. Also, the viscosity when stored at 23°C and 50% RH for 20 days was 9,100 cps. The haze of the multilayer polyimide film A-8 was 59.55% and the CTE was 23 ppm / K.

[0088] [Reference Example 2] A polyamic acid solution b-3, a copper-clad laminate B-3, and a multilayer polyimide film B-3 were obtained in the same manner as in Example 5, except that the DMAc used was changed to recycled DMAc4. The viscosity of the obtained polyamic acid solution b-3 was 22,100 cps. Also, the viscosity when stored at 23°C and 50% RH for 20 days was 9,800 cps. The haze of the multilayer polyimide film B-3 was 72.22% and the CTE was 24 ppm / K.

[0089] As described above, the embodiments of the present invention have been described in detail for illustrative purposes, but the present invention is not limited to the above embodiments and various modifications are possible.

Claims

1. The following steps a, b, c'; a) The following components A and B; A) An aprotic polar solvent having a boiling point of 200 °C or lower under 1 atm; B) Water; Preparing a mixed solution containing an organic solvent in which the content of component A measured by gas chromatography is 50% or more and the content of component B measured by the Karl Fischer method is in the range of 40 to 500 ppm, a tetracarboxylic dianhydride component, and a diamine component; b) Reacting the tetracarboxylic dianhydride component and the diamine component in the mixed solution to obtain a solution of polyamic acid; c') Coating or casting the polyamic acid solution containing the organic solvent on a substrate and subjecting it to heat treatment at 80 to 400 °C for 1 to 60 minutes to imidize it to obtain a polyimide film; comprising A method for producing a polyimide film, characterized in that an organic solvent is recovered from the solvent vapor generated in step c' and reused as the organic solvent of the mixed solution.

2. The method for producing a polyimide film according to claim 1, wherein component A is at least one selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

3. The method for producing a polyimide film according to claim 1 or 2, characterized in that among all monomer components derived from the tetracarboxylic dianhydride component and the diamine component, a monomer having a biphenyl skeleton is contained in an amount of 50 mol% or more.

4. The method for producing a polyimide film according to claim 1 or 2, characterized in that the diamine component contains 20 mol% or more of a diamine compound represented by the following general formula (1). 【Chemical 1】 [In general formula (1), the linking group Z represents a single bond or -COO-, Y independently represents a monovalent hydrocarbon having 1 to 3 carbon atoms which may be substituted with a halogen or a phenyl group, an alkoxy group having 1 to 3 carbon atoms, a perfluoroalkyl group having 1 to 3 carbon atoms, or an alkenyl group, n represents an integer of 1 to 2, and p and q independently represent an integer of 0 to 4.]

5. The following steps a, b, c'; a) The following components A and B; A) An aprotic polar solvent having a boiling point of 200 °C or lower under 1 atm; B) Water; containing the component A, the content of the component A measured by gas chromatography being 50% or more, and the content of the component B measured by the Karl Fischer method being in the range of 40 to 500 ppm, and preparing a mixed solution containing a tetracarboxylic anhydride component and a diamine component; b) reacting the tetracarboxylic anhydride component and the diamine component in the mixed solution to obtain a solution of polyamic acid; c') applying or casting the polyamic acid solution containing the organic solvent onto a substrate and heat-treating at 80 to 400 °C for 1 to 60 minutes to effect imidization to obtain a polyimide film; comprising; A method for producing a polyimide film, characterized in that the organic solvent in step a is obtained via a step of recovering the solvent vapor generated in step c'.

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

7. The method for producing a polyimide film according to claim 5 or 6, characterized in that among all the monomer components derived from the tetracarboxylic anhydride component and the diamine component, the monomer having a biphenyl skeleton is contained in an amount of 50 mol% or more.

8. The method for producing a polyimide film according to claim 5 or 6, characterized in that the diamine component contains 20 mol% or more of a diamine compound represented by the following general formula (1). [Chemical Formula 2] [In the general formula (1), the linking group Z represents a single bond or -COO-, Y independently represents a monovalent hydrocarbon having 1 to 3 carbon atoms which may be substituted with a halogen or a phenyl group, or an alkoxy group having 1 to 3 carbon atoms, or a perfluoroalkyl group or alkenyl group having 1 to 3 carbon atoms, n represents an integer of 1 to 2, and p and q independently represent an integer of 0 to 4.]

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