JP7492836B2 - Polyimide film manufacturing method - Google Patents

Description

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

Polyimide has excellent heat resistance, mechanical properties, and electrical properties. Polyimide films made from this polyimide are used widely for a variety of purposes, including as the base material for circuit boards (also simply called circuit boards) such as flexible printed circuits (FPCs).

Typical methods for producing polyimide films include the tenter method and the cast method. The tenter method involves casting a solution of a polyimide precursor (polyamic acid) onto a rotating drum, peeling it off from the rotating drum in the form of a gel film, and heating and curing it in a tenter furnace to produce a polyimide film (see, for example, Patent Document 1). The cast method involves applying a solution of a polyimide precursor to any supporting substrate such as copper foil, and drying and curing it by heat treatment to obtain a polyimide film (see, for example, Patent Document 2).

To prepare polyimide, a tetracarboxylic dianhydride is usually reacted with a diamine to produce a precursor polyamic acid. In this state, it is soluble in organic solvents, but when it is heat-treated at a high temperature of 200°C or higher, dehydration and ring closure occurs within the molecule, resulting in a polyimide that is insoluble in organic solvents. Therefore, in both the tenter method and the casting method, a polyimide precursor containing an organic solvent is used, and this is heat-treated to imidize (cure) it, thereby preparing polyimide.

Polyimide precursors are often unstable to heat and water, but in order to improve storage stability, it has been proposed to limit the moisture content to 1% by weight or less (see, for example, Patent Document 3).

JP 2000-191806 A JP 2004-322441 A JP 2009-263646 A

The present invention aims to provide an organic solvent that can prepare a polyamic acid solution with high storage stability, regardless of the chemical structure of the polyimide that is ultimately obtained, and that can improve the visibility of the polyimide film (or polyimide layer) obtained when the polyamic acid solution is used to obtain the polyimide film (or polyimide layer). The present invention also aims to provide a method for producing a polyimide film that can suppress an increase in haze and obtain a polyimide film (or polyimide layer) with excellent visibility by using the above organic solvent.

As a result of intensive research to solve the above problems, the present inventors have focused on the fact that the boiling point of the organic solvent forming the mixed solution containing the tetracarboxylic anhydride component and the diamine component affects the haze of the resulting polyimide film or polyimide layer, and have discovered that by appropriately controlling the water content of the organic solvent, the imidization temperature of the polyimide precursor can be increased, thereby reducing the amount of solvent remaining after imidization, and thus suppressing an increase in haze, which has led to the completion of the present invention.

［一般式（１）において、連結基Ｚは単結合若しくは－ＣＯＯ－を示し、Ｙは独立にハロゲン若しくはフェニル基で置換されてもよい炭素数１～３の１価の炭化水素あるいは炭素数１～３のアルコキシ基又は炭素数１～３のパーフルオロアルキル基若しくはアルケニル基を示し、ｎは１～２の整数を示し、ｐ及びｑは独立に０～４の整数を示す。］
（７）下記の工程ａ～ｄ；
ａ）（１）～（３）のいずれか１項に記載の有機溶剤と、テトラカルボン酸無水物成分と、ジアミン成分と、を含有する混合溶液を準備する工程；
ｂ）前記混合溶液中で、前記テトラカルボン酸無水物成分と前記ジアミン成分とを反応させて、ポリアミド酸の溶液を得る工程；
ｃ）基材上に前記ポリアミド酸の溶液を塗布し、乾燥することによって、前記ポリアミド酸の樹脂膜を形成する工程；
ｄ）前記樹脂膜を熱処理し、前記ポリアミド酸をイミド化することによって、ポリイミドフィルムを得る工程；
を備えることを特徴とするポリイミドフィルムの製造方法。
（８）前記工程ｃで発生した溶剤蒸気から有機溶剤を回収して、前記混合溶液の有機溶剤として再利用することを特徴とする請求項７に記載のポリイミドフィルムの製造方法。
（９）前記工程aの有機溶剤が、前記工程ｃで発生した溶剤蒸気を回収する工程を経由して得られたものであることを特徴とする（７）に記載のポリイミドフィルムの製造方法。 That is, the gist of the present invention is as follows.
(1) Components A and B below;
A) an aprotic polar solvent having a boiling point of 200° C. or lower at 1 atmospheric pressure;
B) water;
wherein 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 within the range of 40 to 500 ppm.
(2) The organic solvent according to (1), wherein the component A is at least one selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethylsulfoxide.
(3) The organic solvent according to (1) or (2), which is used for mixing a tetracarboxylic anhydride component and a diamine component and polymerizing them to obtain a polyamic acid.
(4) A mixed solution containing the organic solvent according to any one of (1) to (3), a tetracarboxylic acid anhydride component, and a diamine component.
(5) The mixed solution according to (4), characterized in that, of all monomer components derived from the tetracarboxylic acid anhydride component and the diamine component, monomers having a biphenyl skeleton account for 50 mol % or more.
(6) The mixed solution according to (4) or (5), wherein the diamine component contains 20 mol % or more of a diamine compound represented by the following general formula (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, 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 integers of 0 to 4.]
(7) the following steps a to d;
a) preparing a mixed solution containing the organic solvent according to any one of (1) to (3), a tetracarboxylic acid anhydride component, and a diamine component;
b) reacting the tetracarboxylic anhydride component with the diamine component in the mixed solution to obtain a polyamic acid solution;
c) applying a solution of the polyamic acid onto a substrate and drying the solution 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;
A method for producing a polyimide film, comprising:
(8) The method for producing a polyimide film according to claim 7, further comprising recovering the organic solvent from the solvent vapor generated in the step (c) and reusing the organic solvent as the organic solvent for the mixed solution.
(9) The method for producing a polyimide film according to (7), wherein the organic solvent in the step (a) is obtained via a step of recovering the solvent vapor generated in the step (c).

The organic solvent of the present invention can ensure storage stability when applied as a solution of polyamic acid, for example, and can suppress imidization of polyamic acid at low temperatures, thereby reducing the amount of solvent remaining 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 deteriorating the physical properties of the polyimide film. Furthermore, since the used organic solvent can be repeatedly reused, the production cost can be significantly reduced, and it is also excellent in terms of the environment, and it is possible to produce with a high yield in continuous production such as a roll-to-roll method, and it has high industrial utility value. Since it is possible to suppress an increase in haze of the polyimide layer when producing a metal-clad laminate, it is possible to suppress diffusion when light is transmitted through the polyimide layer in, for example, an FPC mounting process, and to make the polyimide layer recognizable by a camera.

Next, we will explain the embodiment of the present invention.

[Organic solvent]
The organic solvent of the present embodiment is composed of the following components A and B;
A) an aprotic polar solvent having a boiling point of 200° C. or lower at 1 atmospheric pressure;
B) water;
Contains:

<Component A>
Component A is an aprotic polar solvent having a boiling point of 200° C. or less under 1 atmosphere, but from the viewpoint of compatibility with water and ease of control of water content, the lower limit of the boiling point is preferably 120° C. or more. If the boiling point is 200° C. or less, for example, it is easily released outside the system during the process of imidizing 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 the polyamic acid, and it is considered that if the ratio of the aprotic polar solvent is high compared to the imidization ratio, the aprotic polar solvent functions as a plasticizer, and reconformation of the molecular chain occurs, thereby increasing the haze when the film is made. Therefore, since aprotic polar solvents with a boiling point exceeding 200° C. tend to remain during imidization and the haze increases, the boiling point of the aprotic polar solvent is set to 200° C. or less to suppress the increase in haze.

Specific examples of the aprotic polar solvent, component A, include N,N-dimethylformamide (boiling point: 153°C), N,N-dimethylacetamide (boiling point: 166°C), dimethylsulfoxide (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 controlling the physical properties of the polyamic acid resin film, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethylsulfoxide are preferred, and N,N-dimethylacetamide is more preferred.

The aprotic polar solvent is contained as the main component of the organic solvent of the present invention, and has a concentration of 50% or more as measured by gas chromatography. From the viewpoint of ease of controlling the moisture content, it is preferably 99% or more, more preferably 99.5% or more, and even more preferably 99.99% or more. Note that the percentages indicating the concentrations here represent weight percentages unless otherwise specified.

The organic solvent of the present invention may contain a solvent other than component A. 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.

<Component B>
In the organic solvent of the present invention, the content of water in component B is within the range of 40 to 500 ppm, preferably within the range of 40 to 450 ppm, more preferably within the range of 40 to 400 ppm, as measured by the Karl Fischer method. By controlling the content within such a range, for example, during the process of imidizing polyamic acid, hydrolysis of polyamic acid is unlikely to occur, and the presence of water molecules capable of coordinating with the amide group of polyamic acid makes it easier to inhibit the ring-closing reaction of polyamic acid at low temperatures, which is considered to result in a higher imidization temperature. Therefore, it is considered that the remaining amount of aprotic polar solvent can be reduced as the imidization of polyamic acid progresses, and the increase in haze when the film is formed can be suppressed.

The organic solvent of the present embodiment is preferably used as a solvent used for mixing and polymerizing a tetracarboxylic anhydride component and a diamine component to obtain a polyamic acid, and imidizing the polyamic acid to obtain a polyimide. That is, a mixed solution is formed by containing the organic solvent of the present invention, a tetracarboxylic anhydride component, and a diamine component, and such an organic solvent of the present embodiment can be preferably used for producing a polyimide film having a polyimide layer made of a polyimide having a high ratio of monomer residues having a biphenyl skeleton (hereinafter, sometimes referred to as "biphenyl skeleton-containing residues") to the total monomer residues consisting of tetracarboxylic anhydride residues derived from the tetracarboxylic anhydride component and diamine residues derived from the diamine component.

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

Polyimides with a high proportion of biphenyl skeleton-containing residues tend to form an ordered structure, and polyimide films having a polyimide layer made of such polyimides tend to have increased haze and reduced visibility. It is also believed that the greater the amount of aprotic polar solvent remaining in the process of imidizing polyamic acid, the more likely it is that an ordered structure will form. The reason for this is believed to be that the aprotic polar solvent functions as a plasticizer, influencing the reconformation of the biphenyl skeleton portion. For this reason, controlling the amount of aprotic polar solvent remaining after imidization is important in controlling the haze of the polyimide film.

The polyimide layer made of polyimide with a high ratio of biphenyl skeleton-containing residues preferably constitutes a polyimide film as a main layer in, for example, a polyimide layer for manufacturing a metal-clad laminate. Here, "main" means that it has the greatest thickness among the multiple polyimide layers constituting the polyimide film, and preferably has a thickness of 50% or more, more preferably 60% or more of the total thickness of the polyimide film.

The biphenyl skeleton is a skeleton in which two phenyl groups are single-bonded, as shown in the following formula (a). Therefore, examples of biphenyl skeleton-containing residues include a biphenyldiyl group and a biphenyltetrayl group. The aromatic rings contained in these residues may have any substituent.
Representative examples of biphenyldiyl groups include those represented by the following formula (b). Representative examples of biphenyltetrayl groups 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 formulas (b) and (c), and as described above, the aromatic rings contained in these residues may have any substituent.

The biphenyl skeleton-containing residue is a structure derived from the raw material monomer, and may be derived from a tetracarboxylic acid anhydride or a diamine compound, or the biphenyl skeleton-containing residue may be derived from both.

Preferred examples of the diamine residue contained in the polyimide include diamine residues derived from a diamine compound represented by general formula (1).

In general formula (1), the linking group Z represents a single bond or -COO-, Y 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, 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 represent independently an integer of 0 to 4. Here, "independently" means that in the above formula (1), the multiple substituents Y and the integers p and q may be the same or different.

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

Specific examples of preferred diamine residues (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, and 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB). Among these, 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB) is particularly preferred because it is easy to form an ordered structure.

In addition, in order to reduce the elastic modulus of the polyimide film and improve the elongation and 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).

In the above formula (2) and formula (3), R ₅ , R ₆ , R ₇ and R ₈ each independently represent a halogen atom, an alkyl group or 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-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -CO-, -COO-, -SO ₂ -, -NH- or -NHCO-; X ₁ and X ₂ each independently represent a divalent group selected from a _single bond, -O-, -S-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -CO-, -COO-, -SO ₂ -, -NH- or -NHCO-; Except for the case where both of ₂ are single bonds, j, k, l and m independently represent an integer of 0 to 4.
In addition, "independently" means that in one or both of the above formulas (2) and (3), the multiple linking groups X, the linking groups _X1 and _X2 , the multiple substituents _R5 , _R6 , _R7 , and _R8 , and further the integers j, k, l, and m may be the same or different.

The diamine residues represented by general formulas (2) and (3) have a flexible site, and therefore can impart flexibility to the polyimide. Here, since the diamine residue represented by general formula (3) has four benzene rings, it is preferable that the terminal group bonded to the benzene ring is in the para position in order to suppress an increase in the coefficient of thermal expansion (CTE). In addition, from the viewpoint of suppressing an increase in the coefficient of thermal expansion (CTE) while imparting flexibility to the polyimide, it is preferable that the diamine residues represented by general formulas (2) and (3) are contained in a range of preferably 2 to 30 molar parts per 100 molar parts of all diamine residues contained in the polyimide.

The diamine residue represented by formula (2) is preferably one in which at least one of m, n and o is 0, and preferred examples of groups R ₅ , R ₆ and R ₇ include an alkyl group having 1 to 4 carbon atoms which may be substituted with a halogen atom, an alkoxy group having 1 to 3 carbon atoms, or an alkenyl group having 2 to 3 carbon atoms. In formula (2), preferred examples of the linking group X include -O-, -S-, -CH ₂ -, -CH(CH ₃ )-, -SO ₂ - and -CO-. Preferred 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.

The diamine residue represented by formula (3) is preferably one in which at least one of m, n, o and p is 0, and preferred examples of groups R ₅ , R ₆ , R ₇ and R ₈ include an alkyl group having 1 to 4 carbon atoms which may be substituted with a halogen atom, an alkoxy group having 1 to 3 carbon atoms, or an alkenyl group having 2 to 3 carbon atoms. In formula (3), preferred examples of linking groups X ₁ and X ₂ include a single bond, -O-, -S-, -CH ₂ -, -CH(CH ₃ )-, -SO ₂ - or -CO-. However, from the viewpoint of imparting a bending portion, cases in which both linking groups X ₁ and X ₂ are single bonds are excluded. Preferred specific examples of the diamine residue represented by 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.

Among the diamine residues represented by general formula (2), the diamine residue derived from 1,3-bis(4-aminophenoxy)benzene (TPE-R) (sometimes referred to as "TPE-R residue") is particularly preferred, and among the diamine residues represented by general formula (3), the diamine residue derived from 2,2'-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) (sometimes referred to as "BAPP residue") is particularly preferred. TPE-R residues and BAPP residues have flexible sites, so 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 is expected to have the effect of reducing the imide group concentration of the polyimide and suppressing the moisture absorption of the polyimide film.

Other diamine residues contained in 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'-[1,3-phenylenebis(1-methylethylidene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β- Examples of diamine residues derived from aromatic diamine compounds such as 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, and piperazine.

The tetracarboxylic acid residue contained in the polyimide is not particularly limited, but for example, a tetracarboxylic acid residue derived from pyromellitic dianhydride (PMDA) (hereinafter also referred to as PMDA residue) and a tetracarboxylic acid residue derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) (hereinafter also referred to as BPDA residue) are preferred. These tetracarboxylic acid residues tend to form an ordered structure. In addition, the PMDA residue is a residue that plays a role in controlling the thermal expansion coefficient and the glass transition temperature. Furthermore, since the BPDA residue has no polar group and a relatively large molecular weight among tetracarboxylic acid residues, it is expected to have the effect of lowering the imide group concentration of the polyimide and suppressing the moisture absorption of the polyimide film. From this perspective, the total amount of the PMDA residue and/or the BPDA residue is preferably 50 molar parts or more, more preferably in the range of 50 to 100 molar parts, and most preferably in the range of 70 to 100 molar parts, relative to 100 molar parts of all tetracarboxylic acid residues contained in the polyimide.

Other tetracarboxylic acid residues contained in polyimide include, for example, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 2,2',3,3'-, 2,3,3',4'- or 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3',3,4'-diphenylethertetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, 3,3'',4,4''-, 2,3,3 2,2-bis(2,3- or 3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3- or 3,4-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-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic 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 acid dianhydride, 2,3,8,9-, 3,4,9,10-, 4,5,10,11- or 5,6,11,12-perylene-tetracarboxylic acid dianhydride, cyclopentane-1,2,3,4-tetracarboxylic acid dianhydride, pyrazine-2,3,5,6-tetracarboxylic acid dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic acid dianhydride, thiophene-2,3,4,5-tetracarboxylic acid dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, and other aromatic tetracarboxylic acid dianhydrides are included.

In polyimide, the thermal expansion coefficient, storage modulus, tensile modulus, etc. can be controlled by selecting the types of the tetracarboxylic acid residues and diamine residues, or the molar ratios of two or more types of tetracarboxylic acid residues or diamine residues. In addition, when a polyimide has multiple structural units, they may exist as blocks or randomly, but from the viewpoint of suppressing in-plane variations, they are preferably present randomly.

[Method of manufacturing 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 an organic solvent according to the present invention, a tetracarboxylic acid anhydride component, and a diamine component;
b) reacting the tetracarboxylic anhydride component with the diamine component in the mixed solution to obtain a polyamic acid solution;
c) applying a solution of the polyamic acid onto a substrate and drying the solution to form a resin film of the polyamic acid;
d) heat-treating the resin film to imidize the polyamic acid to obtain a polyimide film;
It can be provided with:

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

<Step b>
In step b, for example, a tetracarboxylic anhydride and a diamine compound are dissolved in an organic solvent in approximately equimolar amounts and stirred for 30 minutes to 24 hours at a temperature in the range of 0 to 100° C. 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% by mass, preferably 10 to 20% by mass.

The viscosity of the polyamic acid solution is preferably within 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 operations using a coater, etc.

<Step c and step d>
The solution of polyamic acid obtained in step b is applied onto a substrate, and then dried and imidized (or cured) by heat treatment. The heat treatment is generally preferably performed by heating for 1 to 60 minutes at a temperature of 80 to 400° C. In this case, in order to advance the imidization of polyamic acid, heat treatment for evaporating the organic solvent that dissolves or is mixed with the polyamic acid and heat treatment for releasing the organic solvent coordinated to the polyamic acid to the outside of the system are required.

After forming the polyamic acid resin film in step c, it may be imidized on the substrate, or the resin film may be peeled off from the substrate and imidized. In addition, when the polyimide film is a polyimide film consisting of multiple polyimide layers, the manufacturing method may be, for example, a method in which a solution of polyamic acid is repeatedly applied and dried on the substrate multiple times, followed by imidization (hereinafter, the casting method), or a method in which polyamic acid is simultaneously applied and dried in a multi-layer laminated state by multi-layer extrusion, followed by imidization (hereinafter, the multi-layer extrusion method).

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 polyamic acid resin film is imidized while fixed to the substrate, it is possible to suppress changes in the expansion and contraction of the polyimide layer during the imidization process and maintain the thickness and dimensional accuracy of the polyimide film.

<Substrate>
The substrate used in step c is used for the purpose of reinforcing the polyimide film (or polyimide layer) and for the purpose of suppressing the expansion and contraction change of the polyimide film to maintain dimensional accuracy. The substrate is the object to 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. In order to obtain productivity, it is efficient to use a roll or an endless belt form that allows continuous production. Furthermore, from the viewpoint of more significantly improving the dimensional accuracy of the polyimide film, the supporting substrate is preferably a long roll.

Materials for the substrate include heat-resistant materials such as metals, ceramics, resins, and carbon, but metals are preferred from the viewpoint of thermal conductivity and flexibility. Therefore, examples of the substrate 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 used as an insulating layer of a circuit wiring board and the substrate is used as a wiring layer of a circuit wiring board, the substrate is preferably copper foil or copper alloy foil. In addition, when the polyimide film is to be peeled off from the substrate for use, a smooth stainless steel belt or stainless steel drum can be suitably used as the substrate.

The thickness of the metal foil as the substrate is preferably within the range of 5 to 35 μm, and more preferably within 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 during the manufacturing process of the laminate, and defects such as wrinkles will be more likely to occur. In addition, the surfaces of these metal foils may be subjected to chemical or mechanical surface treatments to improve adhesion, etc., or chemical surface treatments for rust prevention.

<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 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 thus recovered is reused as the organic solvent in step a.

Methods for recovering and reusing solvent vapor are not particularly limited, but include, for example, 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, and an absorption method using water. In addition, general solvent recovery equipment can be used, such as a multi-effect steam type solvent recovery equipment, a heat pump type solvent recovery equipment, a heat pump type multi-effect concentrator, and an evaporation concentrator.

From the viewpoints that the solvent vapor is hydrophilic and easily dissolves in water, has a higher boiling point than water and a lower vapor pressure than water, so evaporates more easily than water, and does not have an azeotropic point with water, it is preferable that the process of recovering the solvent from the solvent vapor includes a process of dissolving the water-soluble substance 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 the outside. The thermal energy used is preferably the heat of the solvent vapor, but if the solvent vapor is at a low temperature, heat from a heater or the like may be used. The concentrated recovered liquid may be treated with an acid, an alkali, activated carbon, or the like as necessary.

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

When using an organic solvent containing recycled solvent, it is preferable that 50% by volume or more of the raw organic solvent is recycled solvent. By making the ratio of recycled solvent to the raw organic solvent 50% by volume or more, the cost merit is increased.

The following examples are provided to more specifically explain the features of the present invention. However, the scope of the present invention is not limited to these examples. In the following examples, unless otherwise specified, the various measurements and evaluations were performed as follows.

[Evaluation of moisture content]
The water content of the recycled solvent was measured using a Karl Fischer water content meter (trace water content meter AQ-300, manufactured by Hiranuma Sangyo Co., Ltd.).

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

[Viscosity measurement]
The viscosity was measured at 25° C. 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 the value was read when the viscosity stabilized 2 minutes after the start of the measurement.

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

[Evaluation of Haze]
The haze was measured by the method described in ASTM D 1003 using a haze measuring device (turbidity meter: Nippon Denshoku Industries Co., Ltd., product name: NDH5000) on a polyimide film having a size of 5 cm x 5 cm.

[Measurement of coefficient of thermal expansion (CTE)]
A polyimide film measuring 3 mm (coating width direction) x 20 mm (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, product name: 4000SA), and then held at that temperature for 10 minutes. The film was then cooled at a rate of 5°C/min to determine the average thermal expansion coefficient (thermal expansion coefficient) from 250°C to 100°C.

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 Bisaniline-P: 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene (manufactured by Mitsui Chemicals Fine Co., Ltd., product name: Bisaniline-P)
DMAc: N,N-dimethylacetamide DMF: N,N-dimethylformamide

[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 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 the reaction vessel, and the mixture was 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 the mixture was stirred at room temperature for 3 hours to carry out a polymerization reaction, thereby obtaining a polyamic acid solution a-1. The viscosity of the polyamic acid solution a-1 was 34,900 cps. The viscosity when stored for 20 days at 23°C and 50% RH was 30,100 cps.

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

[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 new 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 the reaction vessel, and the mixture was 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 the mixture was stirred at room temperature for 3 hours to carry out a polymerization reaction, thereby obtaining a polyamic acid solution a-2. The viscosity of the polyamic acid solution a-2 was 32,700 cps. The viscosity when stored for 20 days at 23°C and 50% RH was 28,900 cps.

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

[Synthesis Example 5]
18.71 parts by mass of BAPP (0.046 mol parts) and a new DMF (water content 15 wt ppm, purity 99.9% or more) in an amount that makes the solid content concentration after polymerization 12% by weight are charged into a reaction vessel, and dissolved by stirring at room temperature. Next, 10.09 parts by mass of PMDA (0.046 mol parts) are added, and then polymerization reaction is performed by continuing stirring at room temperature for 3 hours, to obtain polyamic acid solution c-2. The viscosity of polyamic acid solution c-2 is 1,600 cps.

[Production Example 1]
The polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly applied to 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 was 2.5 μm, and then heated and dried at 130 ° C. to remove the solvent. Next, the polyamic acid solution a-1 prepared in Synthesis Example 1 was uniformly applied on the dried polyamic acid solution c so that the thickness after curing was 20 μm, and then heated and dried at 130 ° C. to remove the solvent. Furthermore, the polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly applied on the dried polyamic acid solution a-1 so that the thickness after curing was 2.5 μm, and then heated and dried at 130 ° C. to remove the solvent. At this time, the above process used for applying and heating the polyamic acid solution c-1, the polyamic acid solution a-1 and the polyamic acid solution c-1 was defined as the first heat treatment process. Thereafter, the second heat treatment step was performed by increasing the temperature from 160°C to 360°C to imidize the laminate, thereby obtaining a copper-clad laminate 1 consisting of a multi-layer polyimide resin layer having a thickness of 25 μm. The copper foil of the obtained copper-clad laminate A-1 was removed by etching using an aqueous ferric chloride solution to prepare a multi-layer polyimide film A-1. The haze of this multi-layer polyimide film A-1 was 75.30%, and the CTE was 21 ppm/K.

(Solvent recovery and regeneration process)
The solvent vapor generated in the first heat treatment step was dissolved in water by gas-liquid contact to obtain a solvent recovery liquid, and then the solvent and water were separated 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).

[Production Example 2]
The polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly applied to 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 was 2.5 μm, and then heated and dried 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 was 20 μm, and then heated and dried at 130 ° C. to remove the solvent. Furthermore, 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 was 2.5 μm, and then heated and dried at 130 ° C. to remove the solvent. At this time, the above process used for applying and heating the polyamic acid solution c-1, polyamic acid solution b-1 and polyamic acid solution c-1 was defined as the first heat treatment process. Thereafter, the second heat treatment step was performed by increasing the temperature from 160°C to 360°C to imidize the laminate, thereby obtaining a copper-clad laminate B-1 consisting of a multi-layer polyimide resin layer having a thickness of 25 μm. The copper foil of the obtained copper-clad laminate B-1 was removed by etching using an aqueous ferric chloride solution to prepare a multi-layer polyimide film B-1. The haze of this multi-layer polyimide film B-1 was 81.83%, and the CTE was 23 ppm/K.

The solvent vapor generated in the first heat treatment step was dissolved by gas-liquid contact with water to obtain a solvent recovery liquid in the same manner as in Production Example 1, and then separated into the solvent and water by distillation to obtain regenerated DMAc 2. In addition, the same production as in Production Example 2 was carried out twice, and the solvent vapor generated in the first heat treatment step was recovered and separated from water to obtain regenerated DMAc 3 and regenerated DMAc 4.
The purity and water content of the regenerated DMAc thus obtained were measured, and the results are shown in Table 1.

[Production Example 3]
The polyamic acid solution c-2 prepared in Synthesis Example 5 was uniformly applied to 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 was 2.5 μm, and then heated and dried 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-2 so that the thickness after curing was 20 μm, and then heated and dried at 130 ° C. to remove the solvent. Furthermore, the polyamic acid solution c-2 prepared in Synthesis Example 5 was uniformly applied on the dried polyamic acid solution a-2 so that the thickness after curing was 2.5 μm, and then heated and dried at 130 ° C. to remove the solvent. At this time, the above process used for applying and heating the polyamic acid solution c-2, polyamic acid solution a-2 and polyamic acid solution c-2 was defined as the first heat treatment process. Thereafter, the second heat treatment step was performed by increasing the temperature from 160°C to 360°C to imidize the laminate, thereby obtaining a copper-clad laminate A-2 consisting of a multi-layer polyimide resin layer having a thickness of 25 μm. The copper foil of the obtained copper-clad laminate A-2 was removed by etching using an aqueous ferric chloride solution to prepare a multi-layer polyimide film A-2. The haze of this multi-layer polyimide film A-2 was 72.16%, and the CTE was 20 ppm/K.

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

[Production Example 4]
The polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly applied to 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 was 2.5 μm, and then heated and dried 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 was 20 μm, and then heated and dried at 130 ° C. to remove the solvent. Furthermore, 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 was 2.5 μm, and then heated and dried at 130 ° C. to remove the solvent. At this time, the above process used for applying and heating the polyamic acid solution c-1, the polyamic acid solution a-2, and the polyamic acid solution c-1 was defined as the first heat treatment process. Thereafter, the second heat treatment step was performed by increasing the temperature from 160°C to 360°C to imidize the laminate, thereby obtaining a copper-clad laminate A-3 consisting of a multi-layer polyimide resin layer having a thickness of 25 μm. The copper foil of the obtained copper-clad laminate A-3 was removed by etching using an aqueous ferric chloride solution to prepare a multi-layer polyimide film A-3. The haze of this multi-layer polyimide film A-3 was 72.52%, and the CTE was 20 ppm/K.

The solvent vapor generated in the first heat treatment step was dissolved in water by gas-liquid contact in the same manner as in Production Example 1 to obtain a solvent recovery liquid, and then the solvent and water were separated 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).

[Example 1]
14.20 parts by mass of m-TB (0.067 mol parts) and 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 is 15% by weight were added to the reaction vessel, and the mixture was 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 the mixture was stirred at room temperature for 3 hours to carry out a polymerization reaction, thereby obtaining a polyamic acid solution a-3. The viscosity of the polyamic acid solution a-3 was 31,200 cps. The viscosity when stored for 20 days at 23 ° C. and 50% RH was 26,500 cps.

Next, the polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly applied to 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 was 2.5 μm, and then heated and dried at 130 ° C. to remove the solvent. Next, the polyamic acid solution a-3 was uniformly applied 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. Furthermore, the polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly applied on the dried polyamic acid solution a-3 so that the thickness after curing was 2.5 μm, and then heated and dried at 130 ° C. to remove the solvent. Then, a second heat treatment process was performed in which the temperature was raised from 160 ° C. to 360 ° C. to imidize, and a copper-clad laminate A-3 consisting of a multi-layer polyimide resin layer having a thickness of 25 μm was obtained. The copper foil of the obtained copper-clad laminate A-3 was etched away using an aqueous ferric chloride solution to prepare a multi-layer polyimide film A-3, which had a haze of 71.78% and a CTE of 21 ppm/K.

[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. The viscosity after storage for 20 days at 23° C. and 50% RH was 19,100 cps. The haze of the multilayer polyimide film A-4 was 65.20%, and the CTE was 22 ppm/K.

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

[Example 4]
Except for changing the DMAc used to recycled DMF1 and changing the polyamic acid solution c-1 to polyamic acid solution c-2, the same procedure as in Example 1 was followed to obtain polyamic acid solution a-6, copper-clad laminate A-6, and multilayer polyimide film A-6.
The viscosity of the obtained polyamic acid solution a-6 was 26,100 cps. The viscosity after storage for 20 days at 23° C. and 50% RH was 13,700 cps. The haze of the multilayer polyimide film A-6 was 60.08%, and the CTE was 21 ppm/K.

[Example 5]
Into the reaction vessel, 14.49 parts by mass of m-TB (0.068 mol), 1.11 parts by mass of TPE-Q (0.004 mol), and 1.31 parts by mass of bisaniline-P (0.004 mol) and an amount of regenerated DMAc2 such that the solid content concentration after polymerization becomes 15% by weight were charged and dissolved by stirring at room temperature. Next, 8.13 parts by mass of PMDA (0.037 mol) and 10.97 parts by mass of BPDA (0.037 mol) were added, and the polymerization reaction was carried out by continuing 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. The viscosity when stored for 20 days at 23 ° C. and 50% RH was 22,500 cps.

Next, the polyamic acid solution c prepared in Synthesis Example 4 was uniformly applied to 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 was 2.5 μm, and then heated and dried at 130 ° C. to remove the solvent. Next, the polyamic acid solution b-2 was uniformly applied on the dried polyamic acid solution c so that the thickness after curing was 20 μm, and then heated and dried at 130 ° C. to remove the solvent. Furthermore, the polyamic acid solution c prepared in Synthesis Example 4 was uniformly applied on the dried polyamic acid solution b-2 so that the thickness after curing was 2.5 μm, and then heated and dried at 130 ° C. to remove the solvent. Then, a second heat treatment process was performed in which the temperature was raised from 160 ° C. to 360 ° C. to imidize, and a copper-clad laminate B-2 consisting of a multi-layer polyimide resin layer having a thickness of 25 μm was obtained. The copper foil of the obtained copper-clad laminate B-2 was etched away using an aqueous ferric chloride solution to prepare a multi-layer polyimide film B-2, which had a haze of 78.67% and a CTE of 23 ppm/K.

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

Next, the polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly applied to 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 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 applied 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. Furthermore, the polyamic acid solution c-1 prepared in Synthesis Example 4 was uniformly applied 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. Then, a second heat treatment process was performed in which the temperature was raised from 160 ° C. to 360 ° C. to imidize, and a copper-clad laminate A-7 consisting of a multi-layer polyimide resin layer having a thickness of 25 μm was obtained. The copper foil of the obtained copper-clad laminate A-7 was etched away using an aqueous ferric chloride solution to prepare a multi-layer polyimide film A-7, which had a haze of 63.87% and a CTE of 21 ppm/K.

[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. The viscosity after storage for 20 days at 23° C. and 50% RH was 9,100 cps. The haze of the multilayer polyimide film A-8 was 59.55% and the CTE was 23 ppm/K.

[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. The viscosity after storage for 20 days at 23° C. and 50% RH was 9,800 cps. The haze of the multilayer polyimide film B-3 was 72.22%, and the CTE was 24 ppm/K.

Although the embodiment of the present invention has been described in detail above for the purpose of illustration, the present invention is not limited to the above embodiment, and various modifications are possible.

Claims (8)

The following steps a to d:
a) components A and B below;
A) an aprotic polar solvent having a boiling point of 200° C. or lower at 1 atmospheric pressure;
B) water;
preparing a mixed solution containing an organic solvent having a content of component A of 50% or more as measured by gas chromatography and a content of component B of 40 to 500 ppm as measured by a Karl Fischer method, a tetracarboxylic anhydride component, and a diamine component;
b) reacting the tetracarboxylic anhydride component with the diamine component in the mixed solution to obtain a polyamic acid solution;
c) applying a solution of the polyamic acid onto a substrate and drying the solution 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;
Equipped with
A method for producing a polyimide film, comprising recovering an organic solvent from the solvent vapor generated in the step (c) and reusing the organic solvent as the organic solvent for the mixed solution. 2. The method for producing a polyimide film according to claim 1, wherein the component A is at least one selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethylsulfoxide. 3. The method for producing a polyimide film according to claim 1, wherein the total monomer components derived from the tetracarboxylic anhydride component and the diamine component contain monomers having a biphenyl skeleton in an amount of 50 mol % or more. 3. The method for producing a polyimide film according to claim 1, wherein the diamine component contains 20 mol % or more of a diamine compound represented by the following general formula (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, 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 integers of 0 to 4.] The following steps a to d:
a) components A and B below;
A) an aprotic polar solvent having a boiling point of 200° C. or lower at 1 atmospheric pressure;
B) Water;
preparing a mixed solution containing an organic solvent having a content of component A of 50% or more as measured by gas chromatography and a content of component B of 40 to 500 ppm as measured by a Karl Fischer method, a tetracarboxylic anhydride component, and a diamine component;
b) reacting the tetracarboxylic anhydride component with the diamine component in the mixed solution to obtain a polyamic acid solution;
c) applying a solution of the polyamic acid onto a substrate and drying the solution 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;
Equipped with
2. A method for producing a polyimide film, wherein the organic solvent in the step (a) is obtained via a step of recovering the solvent vapor generated in the 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 dimethylsulfoxide. 7. The method for producing a polyimide film according to claim 5, wherein the total monomer components derived from the tetracarboxylic anhydride component and the diamine component contain monomers having a biphenyl skeleton in an amount of 50 mol % or more. 7. The method for producing a polyimide film according to claim 5, wherein the diamine component contains 20 mol % or more of a diamine compound represented by the following general formula (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, 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 integers of 0 to 4.]