JP7562362B2 - Non-thermoplastic polyimide film, polyimide laminated film, method for producing non-thermoplastic polyimide film, and method for producing polyimide laminated film - Google Patents

Description

The present invention relates to a polyimide laminate film for flexible printed circuit boards that suppresses cracks on the inner walls of vias during the process of forming vias in the polyimide laminate film using a laser, and a method for manufacturing the polyimide laminate film.

Among flexible printed circuit boards (hereafter referred to as FPCs) used in tablets, smartphones, etc., two-layer flexible printed circuit boards (hereafter referred to as two-layer FPCs) using polyimide film are seeing growing demand in the market due to their excellent heat resistance. When manufacturing these FPCs, copper foil is attached to both sides of the polyimide film to create a copper-clad laminate, and there is a process in which holes (vias) are formed in this copper-clad laminate for the purpose of forming circuits, and the inner surface of the vias is copper-plated to ensure electrical continuity between the top and bottom of the laminate.

The via formation process can be done using a through-hole method, in which a drill or laser is used to open a through hole in the copper foil on both sides, or a blind via hole method, in which only the copper foil on one side is etched and the insulating layer is removed with a laser, leaving the copper foil on the other side. The blind via hole method is used frequently, especially for fine FPCs, in order to make effective use of the area.

After the vias are formed, wet desmearing (cleaning with an alkaline potassium permanganate aqueous solution) is often performed to remove and clean the resin residue adhering to the inside of the vias and the copper foil surface. However, residual stress accumulates locally in the laser processing area used to form the vias, and the desmearing process after via formation can cause defects such as cracks and peeling around the vias, which is an issue. Patent Document 1 discloses a method of suppressing defects such as cracks by performing heat treatment after laser processing to reduce residual stress, and Patent Document 2 discloses polyimide with improved resistance to alkaline solutions as a countermeasure against defects, but no process has been found that fundamentally avoids this issue.

JP 2012-186377 A JP 2017-179148 A

The objective of the present invention is to provide a polyimide laminate film that suppresses the occurrence of cracks on the inner walls of vias during the process of forming vias in polyimide laminate film for flexible printed circuit boards using a laser.

It has been discovered that a polyimide laminate film obtained from a mixture of a non-thermoplastic polyimide precursor and a solvent-soluble polyimide can produce a polyimide laminate film that suppresses the occurrence of cracks on the inner wall of a via after a via formation process using a laser. The present invention comprises the following.

[1]. A method for producing a non-thermoplastic polyimide film by imidizing a mixture of a non-thermoplastic polyimide precursor (polyamic acid) and a solvent-soluble polyimide to produce a non-thermoplastic polyimide film, and forming a phase-separated structure in the film having domains of the solvent-soluble polyimide with island structures of 10 μm or less.

[2]. The non-thermoplastic polyimide film according to [1], characterized in that the inflection point temperature of the film obtained from the solvent-soluble polyimide used in the production of the non-thermoplastic polyimide film is 290°C or lower.

[3]. The non-thermoplastic polyimide film according to [1] or [2], characterized in that the weight average molecular weight of the non-thermoplastic polyimide precursor (polyamic acid) used in the production of the non-thermoplastic polyimide film is 150,000 or more.

[4]. The diamine compound used in the solvent-soluble polyimide is 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane, 4,4'-bis[4-(4-amino-2-trifluoromethyl)phenoxy]-octafluorobiphenyl, bis[4-(4-aminophenoxy)phenyl]sulfone, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, bis[4-(3-aminophenoxy)phenyl]sulfon The method for producing a non-thermoplastic polyimide film according to any one of [1] to [3], characterized in that the polyimide film contains one or more compounds selected from the group consisting of 1,1-bis(4-aminophenyl)cyclohexane, 9,9-bis(4-amino-3-fluorophenyl)fluorene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, and 1,4-bis(4-aminophenoxy)benzene.

[5]. The non-thermoplastic polyimide film according to any one of [1] to [4], characterized in that the acid dianhydride used in the solvent-soluble polyimide contains one or more compounds selected from 2,2'-hexafluoropropylidenediphthalic dianhydride, 3,3',4,4'-perfluoroisopropylidenediphthalic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride, and ethylenediaminetetraacetic dianhydride.

[6]. The method for producing a non-thermoplastic polyimide film according to any one of [1] to [5], characterized in that the solvent-soluble polyimide used in the production of the non-thermoplastic polyimide film contains 2,2-bis(4-aminophenoxyphenyl)propane.

[7]. A method for producing a polyimide laminate film, comprising forming a thermoplastic polyimide resin layer on at least one side of a non-thermoplastic polyimide film produced by the method for producing a non-thermoplastic polyimide film according to any one of [1] to [6].

[8]. A non-thermoplastic polyimide film characterized by forming a phase separation structure in the film having domains of solvent-soluble polyimide with island structures of 10 μm or less and domains of non-thermoplastic polyimide with sea structures.

[9]. The non-thermoplastic polyimide film according to [8], characterized in that the inflection point temperature of the film obtained from the solvent-soluble polyimide used in the production of the non-thermoplastic polyimide film is 290°C or lower.

[10]. The non-thermoplastic polyimide film according to [8] or [9], characterized in that the weight average molecular weight of the non-thermoplastic polyimide precursor (polyamic acid) used in the production of the non-thermoplastic polyimide film is 150,000 or more.

[11]. The diamine compound used in the solvent-soluble polyimide is 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane, 4,4'-bis[4-(4-amino-2-trifluoromethyl)phenoxy]-octafluorobiphenyl, bis[4-(4-aminophenoxy)phenyl]sulfone, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, bis[4-(3-aminophenoxy)phenyl]sulfone, The non-thermoplastic polyimide film according to any one of [8] to [10], characterized in that it contains one or more compounds selected from the group consisting of benzene, 1,1-bis(4-aminophenyl)cyclohexane, 9,9-bis(4-amino-3-fluorophenyl)fluorene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, and 1,4-bis(4-aminophenoxy)benzene.

[12]. The non-thermoplastic polyimide film according to any one of [8] to [11], characterized in that the acid dianhydride used in the solvent-soluble polyimide contains one or more compounds selected from 2,2'-hexafluoropropylidenediphthalic dianhydride, 3,3',4,4'-perfluoroisopropylidenediphthalic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride, and ethylenediaminetetraacetic dianhydride.

[13]. The non-thermoplastic polyimide film according to any one of [8] to [12], characterized in that the solvent-soluble polyimide used in the production of the non-thermoplastic polyimide film contains 2,2-bis(4-aminophenoxyphenyl)propane.

[14]. A polyimide laminate film comprising a thermoplastic polyimide resin layer formed on at least one side of the non-thermoplastic polyimide film described in any one of [8] to [13].

The polyimide laminate obtained by the present invention can provide a flexible printed circuit board that suppresses cracks on the inner walls of vias that occur during the via formation process by laser processing, without any special changes to the film manufacturing process.

FIG. 1 is a diagram showing an example of an optical microscope image used for actual discrimination in a hole crack test.

In the present invention, a non-thermoplastic polyimide film is produced by imidizing a mixture of a non-thermoplastic polyimide precursor (polyamic acid) and a solvent-soluble polyimide, and it has been discovered that a polyimide laminate film can be obtained that is characterized by forming a phase-separated structure having domains of solvent-soluble polyimide with island structures of 10 μm or less in the film, and that suppresses the occurrence of cracks on the inner walls of vias after a via formation process using a laser. Details are described below.

(Non-thermoplastic polyimide film)
The non-thermoplastic polyimide film used in the polyimide laminate film of the present invention is a non-thermoplastic polyimide film characterized by forming a phase separation structure having soluble polyimide domains with island structures of 10 μm or less and non-thermoplastic polyimide domains with a sea structure in the film, and the non-thermoplastic polyimide and polyimide precursor (polyamic acid) that constitute this sea structure are not particularly limited.

(Regarding non-thermoplastic polyimide precursors (polyamic acids))
In particular, film materials used for polyimide laminate films for flexible printed circuit boards preferably contain rigid structures such as biphenyl structures and phenyl structures in the polymer molecules from the viewpoint of dimensional stability, etc. Furthermore, biphenyl structures are less symmetrical than phenyl structures, and a decrease in the symmetry of the polymer primary structure inhibits molecular packing, so that the elastic modulus decreases when softened above a certain temperature, making them more preferable from the viewpoint of stress relaxation.

Specific examples of diamine monomers having a biphenyl structure include 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-2,2'-dimethoxybiphenyl, 4,4'-diamino-3,3'-dimethoxybiphenyl, 3,3',5,5'-tetramethylbenzidine, and 4,4'-bis(4-aminophenoxy)biphenyl. However, 4,4'-diaminobiphenyl and 4,4'-diamino-3,3'-dimethylbiphenyl are carcinogenic to humans, so their actual use is not preferred. For practical use, 4,4'-diamino-2,2'-dimethylbiphenyl is particularly preferred.

In addition, out of the 100% diamine monomer components constituting the non-thermoplastic polyimide precursor (polyamic acid), the more rigid monomer components there are, the lower the linear expansion coefficient will be due to the formation of an aggregate structure, and the more effective the film will be in terms of excellent dimensional stability. However, if the content is too high, the linear expansion coefficient of the resulting film will be too low, which is not preferable, and the optimal content for a film for flexible printed circuit boards is preferably 10 to 50 mol%, more preferably 15 to 40 mol%, and even more preferably 20 to 35 mol%. As other diamine monomers to be used, aromatic diamines with high heat resistance are preferred. For example, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, benzidine, 3,3'-dichlorobenzidine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl N-methylamine, 4,4'-diaminodiphenyl Examples of the diamine include N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, and 1,2-diaminobenzene. The content of the other diamines used is preferably 50 to 90 mol%, more preferably 60 to 85 mol%, and even more preferably 65 to 80 mol%.

It is preferable to use a combination of 4,4'-diaminodiphenyl ether and paraphenylenediamine, since this allows the flexibility of the polymer to be adjusted while maintaining high heat resistance. In this case, the content of 4,4'-diaminodiphenyl ether is preferably 40 to 70 mol%, more preferably 45 to 65 mol%, and even more preferably 50 to 65 mol%, and the content of paraphenylenediamine is preferably 10 to 50 mol%, more preferably 15 to 40 mol%, and even more preferably 15 to 30 mol%.

From the viewpoint of heat resistance, aromatic dianhydrides are preferred as the dianhydride monomers used in the non-thermoplastic polyimide precursor (polyamic acid) of the present invention.

For example, pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 4,4'-oxyphthalic dianhydride, 3,4'-oxyphthalic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propanoic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis(3, 4-dicarboxyphenyl)propanoic dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethaneic dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethaneic dianhydride, bis(2,3-dicarboxyphenyl)methaneic dianhydride, bis(3,4-dicarboxyphenyl)ethaneic dianhydride, oxydiphthalic dianhydride, bis(3,4-dicarboxyphenyl)sulfonic dianhydride, p-phenylene bis(trimellitic acid monoester anhydride), ethylene bis(trimellitic acid monoester anhydride), bisphenol A bis(trimellitic acid monoester anhydride) and similar compounds.

Since the non-thermoplastic polyimide film of the present invention requires heat resistance, it is preferable to use 3,3',4,4'-biphenyltetracarboxylic dianhydride or pyromellitic dianhydride, and 3,3',4,4'-biphenyltetracarboxylic dianhydride is even more preferable since it contains a biphenyl structure. Of the 100% acid dianhydride monomer components constituting the non-thermoplastic polyimide film, the 3,3',4,4'-biphenyltetracarboxylic dianhydride content is preferably 20 to 60 mol%, more preferably 25 to 55 mol%, and even more preferably 30 to 50 mol%. When pyromellitic dianhydride is included, of the 100% acid dianhydride monomer components constituting the non-thermoplastic polyimide film, the content of pyromellitic dianhydride is preferably 40 to 80 mol%, more preferably 35 to 75 mol%, and even more preferably 50 to 70 mol%.

(Production of Non-Thermoplastic Polyimide Precursor (Polyamic Acid))
The non-thermoplastic polyimide precursor in the present invention refers to polyamic acid before imidization, and any known method or a combination thereof can be used for its production. The polymerization method for producing the non-thermoplastic polyimide precursor is characterized by the order of addition of the monomers, and the physical properties of the polyimide obtained can be controlled by controlling the order of addition of the monomers. Therefore, any method of adding monomers can be used for producing the non-thermoplastic polyimide precursor in the present invention. Representative polymerization methods include the following methods.

For example, it can be produced by the following steps (Aa) to (Ab).
(Aa): A process for reacting an aromatic diamine with an aromatic acid dianhydride in an organic polar solvent with an excess of the aromatic diamine to obtain a prepolymer having amino groups at both ends.
(A-b): A step of adding an aromatic diamine having a structure different from that used in step (A-a), and further adding an aromatic acid dianhydride having a structure different from that used in step (A-a) so that the aromatic diamine and aromatic acid dianhydride are substantially equimolar in all steps, to polymerize.

Alternatively, it is also possible to obtain a non-thermoplastic polyimide precursor through the following steps (Ba) to (Bb).
(B-a): a step of reacting an aromatic diamine with an aromatic acid dianhydride in an organic polar solvent in a state where the aromatic acid dianhydride is in excess to obtain a prepolymer having acid anhydride groups at both ends, (B-b): a step of additionally adding an aromatic acid dianhydride having a structure different from that used in step (B-a), and further adding an aromatic diamine having a structure different from that used in step (B-a) so that the aromatic diamine and aromatic acid dianhydride are substantially equimolar in all steps, and polymerizing the resultant.

In the present invention, a synthesis method in which the order of addition is set so that a specific diamine or dianhydride is selectively bonded to any diamine or dianhydride (for example, steps (A-a) to (A-b) and (B-a) to (B-b)) is called sequence polymerization. Among the polymers obtained by sequence polymerization, those with two block components are called diblock copolymers, and those with three block components are called triblock copolymers. In contrast, in the present invention, a synthesis method in which the order of addition of the diamine and dianhydride to be bonded is not selected is called random polymerization. A polymer obtained by random polymerization is called a random copolymer. In the present invention, sequence polymerization is preferable to random polymerization as a polymerization method for obtaining a polyimide resin that is effective in suppressing film tearing while maintaining the properties as a flexible metal-clad laminate.

The solids concentration of the precursor that will become the non-thermoplastic polyimide film of the present invention is not particularly limited, and is usually obtained at a concentration of 5% to 35% by weight, preferably 10% to 30% by weight. A polyimide precursor with an appropriate molecular weight is easily obtained when the concentration is within this range.

A filler can be added to the non-thermoplastic non-thermoplastic polyimide precursor of the present invention for the purpose of improving various film properties such as sliding properties, thermal conductivity, electrical conductivity, corona resistance, and loop stiffness. Any filler can be used, but preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica.

(Molecular Weight of Non-Thermoplastic Polyimide Precursor (Polyamic Acid))
In addition, in the non-thermoplastic polyimide precursor used in the present invention, a higher molecular weight is preferable from the viewpoints of facilitating the formation of a phase-separated structure with the solvent-soluble polyimide and of being excellent in the effect of improving cracks by stress relaxation. The average molecular weight of the precursor (polyamic acid) is preferably 150,000 or more, more preferably 200,000 or more, as measured by GPC in terms of PEG (polyethylene glycol).

(Solvent-soluble polyimide)
The diamines and acid dianhydrides used in the production of the solvent-soluble polyimide having an island structure in the present invention may be the same as those used in the non-thermoplastic polyimide described above. However, a flexible film is preferred because it forms a phase-separated structure as an island structure and is particularly excellent in mitigating stress applied during processing of the laminated film, and the monomers described above are not particularly limited and may be used. For example, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane, 4,4'-bis[4-(4-amino-2-trifluoromethyl)phenoxy]-octafluorobiphenyl, bis[4-(4-aminophenoxy)phenyl]sulfone, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, bis[4-(3 ... Examples of the 4-aminophenyl-2-[4-aminophenoxy)phenyl]sulfone, 1,1-bis(4-aminophenyl)cyclohexane, 9,9-bis(4-amino-3-fluorophenyl)fluorene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, and 1,4-bis(4-aminophenoxy)benzene.

In particular, from the viewpoint of excellent stress relaxation, it is preferable to use 2,2-bis(4-aminophenoxyphenyl)propane as the monomer.
Examples of the acid dianhydride used in the production of the solvent-soluble polyimide include 2,2'-hexafluoropropylidenediphthalic dianhydride, 3,3',4,4'-perfluoroisopropylidenediphthalic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride, and ethylenediaminetetraacetic dianhydride.

In order to make the polyimide soluble in a solvent, it is preferable to react a diamine having a fluorine group with an acid dianhydride (especially an aromatic acid dianhydride) in combination, as this improves the solubility in the solvent.

Examples of diamines having fluorine groups include 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane, and 4,4'-bis[4-(4-amino-2-trifluoromethyl)phenoxy]-octafluorobiphenyl. Similarly, dianhydride compounds containing fluorine groups are preferred, specifically 2,2'-hexafluoropropylidenediphthalic dianhydride and 3,3',4,4'-perfluoroisopropylidenediphthalic dianhydride. In the polymer, the total content of diamines or dianhydride monomers having fluorine groups is preferably 40 to 90 mol%, more preferably 60 to 85 mol%, and even more preferably 65 to 80 mol%.

(Inflection point temperature of storage modulus of solvent-soluble polyimide)
In the solvent-soluble polyimide having the island structure of the present invention, the temperature at which the storage modulus in the glass region is inflection-point measured by dynamic viscoelasticity measurement (referred to as the E' inflection-point temperature) is, from the viewpoint of easily relaxing the stress in the film that occurs when cooling the high heat generated during laser processing of the film laminate, preferably 290° C. or less, and more preferably 250° C. or less. Moreover, if it is 180° C. or less, it is not preferable because it cannot withstand the temperature applied during solder mounting on a flexible substrate, and there is a risk of problems such as foaming occurring.

(Molecular weight of solvent-soluble polyimide)
In the solvent-soluble polyimide used in the present invention, a higher molecular weight is preferred from the viewpoint of excellent crack resistance due to improved toughness and strength of the resin. On the other hand, if the molecular weight is too large, the polyimide may not dissolve in the solvent, so there is an optimum range. The weight average molecular weight of the solvent-soluble polyimide measured by GPC in terms of PEG (polyethylene glycol) is preferably 50,000 to 200,000, and more preferably 100,000 to 150,000.

(Non-thermoplastic polyimide film having phase separation structure)
The non-thermoplastic polyimide film of the present invention is characterized by having a phase-separated structure having solvent-soluble polyimide domains with island structures of 10 μm or less and non-thermoplastic polyimide domains with sea structures in the film, and can suppress the occurrence of cracks after a desmearing process by mitigating the stress remaining in the film due to the heat generated during hole formation by laser processing in a flexible metal-clad laminate produced using the polyimide laminate film.
The domain size of the island-structured solvent-soluble polyimide is preferably 10 μm or less, more preferably 7 μm or less, and even more preferably 5 μm or less, because if the size is too large, the interface between the sea structure and the island structure becomes small and the generated stress cannot be sufficiently dispersed. The lower limit of the size is preferably 0.3 μm or more from the viewpoint of stress relaxation. The domain size can be observed and measured by general TEM observation.

(Method for producing a non-thermoplastic polyimide film having a phase-separated structure)
The non-thermoplastic polyimide film of the present invention is characterized in that it has a phase-separated structure having a solvent-soluble polyimide domain with an island structure of 10 μm or less and a non-thermoplastic polyimide domain with a sea structure in the film, and the method for producing the film is not particularly limited. In particular, a method for easily forming a uniform phase-separated structure in the film includes a method in which a non-thermoplastic polyimide precursor (polyamic acid) and a solvent-soluble polyimide solution are mixed in advance and the mixture is imidized.

In this case, the mixing temperature is about −20° C. to 50° C., preferably 10° C. to 45° C., and more preferably 20° C. to 40° C. If the temperature is lower than this range, the torque may become too high and uniform mixing may not be possible, and if the temperature is higher, there is a possibility that a uniform phase-separated structure cannot be formed, for example, due to partial compatibility or decomposition of the precursor.
The mixing time is preferably 3 hours or more, more preferably 5 hours or more. If the mixing time is too short, the polyimide precursor may not be uniformly dispersed and a phase-separated structure may not be formed, which is not preferable.

(Method of manufacturing polyimide film)
The method for obtaining the non-thermoplastic polyimide film of the present invention is not particularly limited, and various known methods can be applied. For example, it is preferable to include the following steps i) to iv):
i) reacting an aromatic diamine with an aromatic tetracarboxylic dianhydride in an organic solvent to obtain a mixture of a non-thermoplastic polyimide precursor and a solvent-soluble polyimide solution;
ii) a step of casting the film-forming dope containing the polyimide precursor from a die onto a support to form a resin layer (which may also be referred to as a liquid film);
iii) heating the resin layer on the support to form a self-supporting gel film, and then peeling the gel film off the support;
iv) A step of further heating to convert the remaining amic acid into an imidized form and drying to obtain a non-thermoplastic polyimide film.

ii) The steps after this can be broadly divided into thermal imidization and chemical imidization. Thermal imidization is a method in which a polyimide precursor solution is cast onto a support as a film-forming dope without using a dehydrating ring-closing agent, and the imidization proceeds only by heating. On the other hand, chemical imidization is a method in which at least one of a dehydrating ring-closing agent and a catalyst is added to a polyimide precursor solution as an imidization promoter, and the resulting solution is used as a film-forming dope to promote imidization. Either method can be used, but chemical imidization is more productive.

As the dehydration ring-closing agent, an acid anhydride such as acetic anhydride can be suitably used. As the catalyst, a tertiary amine such as an aliphatic tertiary amine, an aromatic tertiary amine, or a heterocyclic tertiary amine can be suitably used. As the support for casting the film-forming dope, a glass plate, an aluminum foil, an endless stainless steel belt, a stainless steel drum, or the like can be suitably used. The heating conditions are set according to the thickness and production speed of the final film to be obtained, and at least one of partial imidization and drying is performed, and then the film is peeled off from the support to obtain a polyimide precursor film (hereinafter referred to as a gel film). The ends of the gel film are fixed to avoid shrinkage during curing, and the film is heated to remove water, residual solvent, imidization promoter, dehydration ring-closing agent, etc. from the gel film, and the remaining amic acid is completely imidized to obtain a film containing polyimide. The heating conditions can be set appropriately according to the thickness and production speed of the final film to be obtained.

(Production of polyimide laminated film)
The polyimide laminate film of the present invention is a polyimide laminate film laminate obtained by laminating a thermoplastic polyimide resin layer on at least one side of the non-thermoplastic polyimide film, and the method for producing the polyimide laminate film is not particularly limited, and various known methods can be applied. For example, a co-extrusion die may be used to simultaneously form multiple resin layers containing a polyimide precursor, which is a precursor of the non-thermoplastic polyimide film of the present invention, and a thermoplastic polyimide precursor that can be an adhesive layer.
In addition, a precursor of the non-thermoplastic polyimide film of the present invention may be synthesized, and the polyimide film obtained by forming the precursor into a film using the precursor may be collected, and then a resin layer containing another thermoplastic polyimide precursor may be formed on the polyimide film by coating or the like. Since a very high temperature is required for imidization, when a resin layer other than polyimide is provided, it is preferable to adopt the latter method in order to suppress thermal decomposition. In addition, when a thermoplastic polyimide resin layer is provided by coating, a thermoplastic polyimide precursor may be applied and then imidized, or a thermoplastic polyimide solution capable of forming a thermoplastic polyimide resin layer may be applied and dried. It is also possible to perform various surface treatments such as corona treatment and plasma treatment on the outermost surface of the polyimide laminate film. The thickness of the entire polyimide laminate film of the present invention is preferably 6 to 60 μm. Even within this range, a thinner thickness is preferable from the viewpoint of reducing the weight of the FPC and improving the foldability, for example, 7 to 30 μm is more preferable, and 10 to 25 μm is even more preferable.

In addition, in order to suppress warping of the polyimide laminate film, it is preferable that both sides of the non-thermoplastic polyimide layer are thermoplastic polyimide layers. If a thermoplastic polyimide layer is formed on only one side of the non-thermoplastic polyimide layer, the film may warp when the imidization reaction of the thermoplastic polyimide layer is allowed to proceed due to an asymmetric structure. The thickness of the thermoplastic polyimide layers on both sides of the non-thermoplastic polyimide layer is preferably 1 to 15 μm, and the difference in thickness between the two sides is based on the thickness of the thick thermoplastic polyimide layer, and as long as the thickness of the other side is 40% or more and 100% or less, there is no problem with the film shape.

The thickness ratio of the non-thermoplastic polyimide layer and the thermoplastic polyimide layer in the multilayer polyimide film is preferably 55/45 to 95/5 in terms of controlling the linear expansion coefficient of the multilayer polyimide film. This ratio is the ratio of the total thickness of each, even if the non-thermoplastic polyimide layer and the thermoplastic polyimide layer are multiple layers, and it is preferable that the thickness does not exceed the thickness of the non-thermoplastic polyimide layer even if the number of thermoplastic polyimide layers is increased.

(Flexible metal clad laminate)
A flexible metal-clad laminate can be produced by laminating a metal foil on at least one side of a polyimide laminate film. The method for producing a flexible metal-clad laminate is not particularly limited, and various known methods can be applied. For example, a continuous process using a hot roll laminator having one or more pairs of metal rolls or a double belt press (DBP) can be used. The specific configuration of the means for carrying out the hot lamination is not particularly limited, but it is also preferable to place a protective material between the pressing surface and the metal foil in order to improve the appearance of the resulting laminate.

A means of casting a multi-layer organic solvent solution containing at least one of a thermoplastic polyimide precursor or a non-thermoplastic polyimide precursor on a metal foil can also be used. The means of casting an organic solvent solution containing a polyimide precursor on a metal foil is not particularly limited, and conventionally known means such as a die coater, a comma coater (registered trademark), a reverse coater, and a knife coater can be used. When a polyimide resin layer is provided in multiple layers, such as when the thermoplastic polyimide resin layer and a non-thermoplastic polyimide film in the present invention are included, or when a resin layer other than polyimide is also provided, the above-mentioned casting and heating steps are repeated multiple times, or a means of forming multiple cast layers by co-extrusion or continuous casting and heating them at once is preferably used. In this means, a flexible metal-clad laminate is obtained at the same time as the imidization is completed. When providing metal foil on both sides of the resin layer, the metal foil may be laminated on the opposite resin layer surface by heating and pressing. The metal foil is not particularly limited, and any metal foil can be used. For example, copper, stainless steel, nickel, aluminum, and alloys of these metals can be preferably used. In addition, copper such as rolled copper and electrolytic copper is often used in general metal-clad laminates, and it can also be used in the present invention.

Metal foils with various properties, such as surface treatment and surface roughness, can be selected according to the purpose. Furthermore, the surface of the metal foil may be coated with an anti-rust layer, a heat-resistant layer, or an adhesive layer. There are no particular limitations on the thickness of the metal foil, and it is sufficient if the thickness can provide sufficient functionality depending on the application.

(Via formation process using laser processing)
In manufacturing flexible boards, when vias are formed in a copper-clad laminate by laser processing, a laser can be irradiated to the processing area to penetrate the board and form a through hole (TH) or a blind via hole (BVH) by removing only the copper foil and polyimide resin on the top surface. Known types of lasers can be used. Short wavelength lasers such as UV-YAG lasers and excimer lasers are preferable because they show a very high absorption rate for both resin and copper and can be processed. For THs, a method of directly drilling a through hole is also widely used.

On the other hand, a desmear process is performed to remove resin debris generated during processing. A wet desmear process is generally used, which includes a swelling process using an aqueous alkaline solution or a solution containing an organic solvent, a roughening process using an aqueous alkaline solution such as sodium permanganate or potassium permanganate, and a neutralization process. Cracks on the inner wall of a hole that occur during processing of a copper-clad laminate using the polyimide laminate film of the present invention often occur on the inner wall of the hole after the desmear process, and cracks are more likely to occur if the swelling time and roughening time in the desmear process are extended. In addition, a via is formed by metal plating the inside of the hole after the desmear process. There are no particular limitations on the general metal plating, but a plating layer of the desired thickness may be formed only by electroless copper plating, or a plating layer of the desired thickness may be formed by electrolytic copper plating after thinning the electroless copper plating layer.

(Hole crack test: Crack evaluation method)
Cracks occurring on the inner wall of a via during FPC manufacturing are usually detected after FPC manufacturing by visual inspection, etc. The present inventors have found that the occurrence of cracks on the inner wall of a via during the FPC manufacturing process can be easily evaluated by cutting a test piece from a long flexible metal-clad laminate as a material and conducting a hole crack test to evaluate cracks occurring on the inner wall of a hole at the stage of performing the via formation process from laser processing to desmearing.

In this evaluation method, the copper foil of the test piece after desmearing is removed by etching, and the presence or absence of cracks on the inner wall of the via can be confirmed by observing with a polarizing microscope under crossed Nicols. By combining this with polarizing microscope observation, it was confirmed that if cracks occur on the inner wall of the via, they are detected as light leakage.

The present invention will be described in detail below with reference to examples, but is not limited to these examples.

(Inflection point temperature evaluation)
The dynamic viscoelasticity was measured in an air atmosphere using DM6100 manufactured by SII Nano Technology Co., Ltd., and the storage modulus and inflection point temperature at each temperature were measured.
Sample measurement range: width 9 mm, gripping distance: 20 mm
Measurement temperature range: 0℃ to 440℃
Temperature rise rate: 3°C/min
Strain amplitude: 10 μm
Measurement frequency: 1Hz, 5Hz, 10Hz
Minimum tension/compression force: 100 mN
Tension/Compression Gain: 1.5
Initial force amplitude: 100 mN

(Molecular Weight Measurement)
The weight average molecular weight (Mw) was evaluated under the following conditions.

(TEM Observation)
The films used for observation were embedded in resin, and ultrathin sections were prepared using an ultramicrotome (Leica UCT). Using a transmission electron microscope (TEM, Hitachi High-Technologies Corporation, H-7650), the presence or absence of sea-island structures and the domain size were measured from TEM images at 40,000x magnification under conditions of an accelerating voltage of 100 kV.

(Hole crack test)
A 12 μm electrolytic copper foil (3EC-M3S-HTE, Mitsui Metal) was placed on both sides of the polyimide film laminate obtained in the examples and comparative examples, and a protective film (Apical 125NPI; Kaneka, thickness 125 μm) was used on both sides of the copper foil, and thermal lamination was performed under the conditions of lamination temperature 360 ° C., lamination pressure 265 N / cm (27 kgf / cm), and lamination speed 1.0 m / min to obtain a flexible metal-clad laminate. Next, the flexible metal-clad laminate was cut into a size of 5.0 cm x 20.0 cm square, and a blind via hole with a diameter of 100 μm was laser processed using a UV-YAG laser by the process of Table 2. A pattern of 10 rows of 10 pieces each was formed at 1 mm intervals for each condition (100 pieces each). After laser processing, desmearing was performed by the process of Table 3.

After removing the copper foil by etching, the specimens were observed under a polarizing microscope at a magnification of 200 times under crossed Nicols. Holes where light was leaking were considered to be cracks. For specimens where the degree of light leakage was too weak to be judged, the cross section of the hole was cut and observed under a higher magnification such as an electron microscope to determine whether or not it was a crack and classified. Figure 1 shows an example of an optical microscope image used for the actual discrimination. After observing 100 specimens, the ratio of cracks that occurred was calculated as a percentage.

(Synthesis of non-thermoplastic polyamic acid (polyimide precursor))
(Synthesis Example 1)
334.13 g of N,N-dimethylformamide (hereinafter, DMF) and 17.70 g of 4,4'-diaminodiphenyl ether (hereinafter, ODA) were added to a glass flask with a capacity of 2000 ml, and 18.01 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter, BPDA) was gradually added while stirring under a nitrogen atmosphere. After visually confirming that BPDA had dissolved, 7.79 g of pyromellitic dianhydride (hereinafter, PMDA) was gradually added. After visually confirming that PMDA had dissolved, stirring was performed for 30 minutes. Thereafter, 5.78 g of 4'-diamino-2,2'-dimethylbiphenyl (hereinafter, m-TB) was added, 7.11 g of p-phenylenediamine (hereinafter, PDA) was added, and then 11.85 g of PMDA was added and stirred for 30 minutes. Finally, a DMF solution containing 0.46 g of PMDA was prepared so that the solid content concentration was 7.2%, and the solution was gradually added to the reaction solution. When the viscosity at 23° C. reached 2,500 poise, the addition was stopped to obtain a non-thermoplastic polyimide precursor A. The weight-average molecular weight at this time was 156,000.

(Synthesis Example 2)
334.13g of DMF and 17.70g of ODA were added to a glass flask with a capacity of 2000ml, and 18.01g of BPDA was gradually added while stirring under a nitrogen atmosphere. After visually confirming that BPDA had dissolved, 7.79g of PMDA was gradually added. After visually confirming that PMDA had dissolved, stirring was performed for 30 minutes. Then, 5.78g of m-TB was added, 7.11g of PDA was added, and then 11.85g of PMDA was added, and stirring was performed for 30 minutes. Finally, 0.46g of PMDA was adjusted to a DMF solution with a solid content concentration of 7.2%, and gradually added to the above reaction solution, and the addition was stopped when the viscosity at 23°C reached 8000 poise, to obtain a non-thermoplastic polyimide precursor B. The average weight molecular weight at this time was 251,000.

(Synthesis Example 3)
A 2000 ml glass flask was charged with 334.13 g of DMF, 5.27 g of ODA, and 16.20 g of 2,2'-bis[4-(4-aminophenoxy)phenyl]propane (hereinafter, BAPP), and 7.17 g of PMDA was gradually added while stirring under a nitrogen atmosphere. After visually confirming the dissolution of PMDA, 8.48 g of benzophenonetetracarboxylic dianhydride (hereinafter, BTDA) was added and stirred for 30 minutes. Then, 3.76 g of PDA was added, followed by 15.32 g of PMDA, and stirred for 30 minutes. Finally, a solution was prepared by dissolving 0.46 g of PMDA in DMF to a solid content concentration of 7.2%, and this solution was gradually added to the above reaction solution, and the addition was stopped when the viscosity at 23°C reached 2500 poise, to obtain a non-thermoplastic polyimide precursor C. The average weight molecular weight at this time was 159,000.

(Synthesis of Solvent-Soluble Polyimide)
(Synthesis Example 4)
673.24 g of DMF and 71.83 g of BAPP were added to a 2000 ml glass flask, and 77.01 g of 2,2'-hexafluoropropylidenediphthalic dianhydride (hereinafter 6FDA) was gradually added while stirring under a nitrogen atmosphere. After visually confirming that 6FDA had dissolved, stirring was performed for 30 minutes. Finally, a DMF solution was prepared so that 2.22 g of 6FDA had a solid content concentration of 7.2%, and this solution was gradually added to the above reaction solution. When the viscosity at 23 ° C. reached 2000 poise, the addition was stopped, and further 158.4 g of N,N-dimethylformamide, 40.66 g of pyridine, and 53.5 g of acetic anhydride were sequentially added to the flask, and the mixture was stirred for 3 hours while heating to 90 ° C. After returning to room temperature, 2000 mL of isopropyl alcohol was added to the flask, and the precipitate was collected. The precipitate was then washed three times with 1000 mL of isopropyl alcohol, and the precipitate was dried under reduced pressure at 80° C. for 20 hours to obtain a solvent-soluble polyimide D. The weight average molecular weight of the polyimide D was 131,000.

(Synthesis Example 5)
673.24 g of DMF and 74.94 g of 4,4'-bis[4-(4-amino-2-trifluoromethyl)phenoxy]-octafluorobiphenyl (hereinafter 6FAPB) were added to a glass flask with a capacity of 2000 ml, and 51.00 g of BPDA was gradually added while stirring under a nitrogen atmosphere. After visually confirming that BPDA had dissolved, stirring was performed for 30 minutes. Finally, a DMF solution was prepared so that 1.47 g of BPDA had a solid content concentration of 7.2%, and this solution was gradually added to the above reaction solution. When the viscosity at 23 ° C. reached 2000 poise, the addition was stopped, and 158.4 g of N,N-dimethylformamide, 40.66 g of pyridine, and 53.5 g of acetic anhydride were sequentially added to the flask, and the mixture was stirred for 3 hours while heating to 90 ° C. After returning to room temperature, 2000 mL of isopropyl alcohol was added to the flask, and the precipitate was collected. The precipitate was then washed three times with 1000 mL of isopropyl alcohol, and the precipitate was dried under reduced pressure at 80° C. for 20 hours to obtain a solvent-soluble polyimide E. The weight average molecular weight of the polyimide E was 120,500.

(Synthesis of Thermoplastic Polyimide)
(Synthesis Example 6)
In a 2000 ml glass flask, 673.24 g of DMF and 71.83 g of BAPP were added, and 7.72 g of BPDA was gradually added while stirring under a nitrogen atmosphere. After visually confirming that BPDA had dissolved, 31.30 g of PMDA was added, and the mixture was stirred for 30 minutes. Finally, a solution was prepared by dissolving 1.15 g of PMDA in DMF to a solid content concentration of 7.2%, and this solution was gradually added to the reaction solution, and the addition was stopped when the viscosity at 23 ° C. reached 300 poise, to obtain a thermoplastic polyimide precursor F.

(Inflection point temperature of solvent-soluble polyimide)
DMF (30 g) was added to the solvent-soluble polyimides D and E (60 g) obtained in Synthesis Examples 4 and 5, and the mixture was stirred and degassed, and cast onto an aluminum foil using a comma coater. The resin film was heated at 120°C for 3 minutes, and then the self-supporting gel film was peeled off from the aluminum foil and fixed to a metal frame, and dried at 250°C for 1 minute and 300°C for 200 seconds to obtain a polyimide film having a thickness of 20 μm.

The inflection point temperature of the storage modulus was also measured using the DMA measurement described above, and it was found that the inflection point temperature of the polyimide film obtained from solvent-soluble polyimide D was 218°C, and the inflection point temperature of the polyimide film obtained from solvent-soluble polyimide precursor E was 207°C.

Example 1
In a 500 mL separable flask, the non-thermoplastic polyimide precursor A (55 g) obtained in Synthesis Example 1 and the solvent-soluble polyimide solution D (11 g) obtained in Synthesis Example 4 were placed, and stirred and mixed for 5 hours at room temperature under a nitrogen atmosphere using a stirring blade to obtain a precursor mixture. 32.5 g of a curing agent consisting of acetic anhydride/isoquinoline/DMF (weight ratio 11.48/3.40/18.18) was added to this precursor mixture, and the mixture was stirred and degassed at a temperature below 0°C, and then coated on aluminum foil using a comma coater. After heating this resin film at 115°C x 100 seconds, the self-supporting gel film was peeled off from the aluminum foil and fixed to a metal fixing frame, and imidized at 250°C x 15 seconds and 350°C x 79 seconds to obtain a polyimide film with a thickness of 12.5 μm.

TEM observation of the cross section of the obtained film confirmed that it was a polyimide film with a phase-separated structure with domains of thermoplastic polyimide up to 3.8 μm in size. Furthermore, when this film was fixed to a metal frame and heated at 450°C for 2 minutes, it retained its shape, confirming that it was non-thermoplastic.

Next, a solution of the thermoplastic polyimide precursor F obtained in Synthesis Example 6 diluted with DMF to a solid content concentration of 8% by weight was applied to both sides of the non-thermoplastic polyimide film having a phase separation structure obtained above so that the final thickness on one side was 3 μm. After that, it was heated at 120°C for 2 minutes. Next, it was heated and imidized at 350°C for 15 seconds to obtain a polyimide laminate film.

Example 2
In a 500 mL separable flask, the non-thermoplastic polyimide precursor B (55 g) obtained in Synthesis Example 2 and the solvent-soluble polyimide solution D (11 g) obtained in Synthesis Example 4 were placed, and stirred and mixed for 5 hours at room temperature under a nitrogen atmosphere using a stirring blade to obtain a precursor mixture. 32.5 g of a curing agent consisting of acetic anhydride/isoquinoline/DMF (weight ratio 11.48/3.40/18.18) was added to this precursor mixture, and the mixture was stirred and degassed at a temperature below 0°C, and then coated on aluminum foil using a comma coater. After heating this resin film at 115°C x 100 seconds, the self-supporting gel film was peeled off from the aluminum foil and fixed to a metal fixing frame, and imidized at 250°C x 15 seconds and 350°C x 79 seconds to obtain a polyimide film with a thickness of 12.5 μm.

TEM observation of the cross section of the obtained film confirmed that it was a polyimide film with a phase-separated structure with domains of thermoplastic polyimide up to 4.6 μm in size. Furthermore, when this film was fixed to a metal frame and heated at 450°C for 2 minutes, it retained its shape, confirming that it was non-thermoplastic.

Next, a solution of the thermoplastic polyimide precursor F obtained in Synthesis Example 6 diluted with DMF to a solid content concentration of 8% by weight was applied to both sides of the non-thermoplastic polyimide film having a phase separation structure obtained above so that the final thickness on one side was 3 μm. After that, it was heated at 120°C for 2 minutes. Next, it was heated and imidized at 350°C for 15 seconds to obtain a polyimide laminate film.

Example 3
In a 500 mL separable flask, the non-thermoplastic polyimide precursor B (55 g) obtained in Synthesis Example 1 and the solvent-soluble polyimide solution E (11 g) obtained in Synthesis Example 5 were placed, and stirred and mixed for 5 hours at room temperature under a nitrogen atmosphere using a stirring blade to obtain a precursor mixture. 32.5 g of a curing agent consisting of acetic anhydride/isoquinoline/DMF (weight ratio 11.48/3.40/18.18) was added to this precursor mixture, and the mixture was stirred and degassed at a temperature below 0°C, and then coated on aluminum foil using a comma coater. After heating this resin film at 115°C x 100 seconds, the self-supporting gel film was peeled off from the aluminum foil and fixed to a metal fixing frame, and imidized at 250°C x 15 seconds and 350°C x 79 seconds to obtain a polyimide film with a thickness of 12.5 μm.

TEM observation of the cross section of the obtained film confirmed that it was a polyimide film with a phase-separated structure with domains of thermoplastic polyimide up to 1.3 μm in size. Furthermore, when this film was fixed to a metal frame and heated at 450°C for 2 minutes, it retained its shape, confirming that it was non-thermoplastic.

Next, a solution of the thermoplastic polyimide precursor F obtained in Synthesis Example 6 diluted with DMF to a solid content concentration of 8% by weight was applied to both sides of the non-thermoplastic polyimide film having a phase separation structure obtained above so that the final thickness on one side was 3 μm. After that, it was heated at 120°C for 2 minutes. Next, it was heated and imidized at 350°C for 15 seconds to obtain a polyimide laminate film.

(Comparative Example 1)
To the non-thermoplastic polyimide precursor C (65 g) obtained in Synthesis Example 3, 32.5 g of a curing agent consisting of acetic anhydride/isoquinoline/DMF (weight ratio 11.48/3.40/18.18) was added, stirred and degassed at a temperature below 0 ° C, and applied onto aluminum foil using a comma coater. After heating this resin film at 115 ° C x 100 seconds, the self-supporting gel film was peeled off from the aluminum foil and fixed to a metal fixing frame, and imidized at 250 ° C x 15 seconds and 350 ° C x 79 seconds to obtain a polyimide film with a thickness of 12.5 μm. In addition, this film was fixed to a metal fixing frame and heated at 450 ° C for 2 minutes, and the shape was maintained, confirming that it was non-thermoplastic.

Next, a solution of the thermoplastic polyimide precursor F obtained in Synthesis Example 6 diluted with DMF to a solid content concentration of 8% by weight was applied to both sides of the non-thermoplastic polyimide film obtained above so that the final thickness on one side was 3 μm. After that, it was heated at 120°C for 2 minutes. Next, it was heated and imidized at 350°C for 15 seconds to obtain a polyimide laminate film.

(Comparative Example 2)
A polyimide laminate was obtained in the same manner as in Comparative Example 1, except that the non-thermoplastic polyimide precursor A obtained in Synthesis Example 1 was used instead of the non-thermoplastic polyimide precursor C obtained in Synthesis Example 3.

(Evaluation Results)
The polyimide laminate films obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were used to measure the presence or absence of a sea-island structure in the non-thermoplastic film and the domain size of the island structure by TEM observation, and the hole crack test was performed by the above-mentioned method. The results are shown in Table 4.

The polyimide laminate film obtained by the present invention can provide a flexible printed circuit board that suppresses cracks on the inner walls of vias that occur during the via formation process by laser processing.

Claims (12)

A method for producing a non-thermoplastic polyimide film, comprising the steps of: imidizing a mixture of a non-thermoplastic polyimide precursor (polyamic acid) and a solvent-soluble polyimide to produce a non-thermoplastic polyimide film; and forming a phase-separated structure in the film having domains of solvent-soluble polyimide with island structures of 10 μm or less, the method comprising the steps of:
The solvent-soluble polyimide is soluble in N,N-dimethylformamide;
The solvent-soluble polyimide has an inflection point temperature of storage elastic modulus of 290° C. or lower . 2. The method for producing a non-thermoplastic polyimide film according to claim 1 , wherein the non-thermoplastic polyimide precursor (polyamic acid) has a weight average molecular weight of 150,000 or more. The diamine compound used in the solvent-soluble polyimide is 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane, 4,4'-bis[4-(4-amino-2-trifluoromethyl)phenoxy]-octafluorobiphenyl, bis[4-(4-aminophenoxy)phenyl]sulfone, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, bis[4-(3-aminophenoxy)phenyl] The method for producing a non-thermoplastic polyimide film according to claim 1 or 2, characterized in that the polyimide film contains one or more compounds selected from the group consisting of sulfone, 1,1-bis(4-aminophenyl)cyclohexane, 9,9-bis(4-amino-3-fluorophenyl)fluorene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, and 1,4 -bis(4-aminophenoxy)benzene. The method for producing a non-thermoplastic polyimide film according to any one of claims 1 to 3, characterized in that the acid dianhydride used in the solvent-soluble polyimide contains one or more compounds selected from 2,2'-hexafluoropropylidenediphthalic dianhydride, 3,3',4,4'-perfluoroisopropylidenediphthalic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl) fluorene dianhydride, dicyclohexyl-3,4,3', 4' -tetracarboxylic dianhydride, and ethylenediaminetetraacetic dianhydride. 5. The method for producing a non-thermoplastic polyimide film according to claim 1, wherein the solvent- soluble polyimide contains 2,2-bis(4-aminophenoxyphenyl)propane. A method for producing a polyimide laminate film, comprising forming a thermoplastic polyimide resin layer on at least one surface of a non-thermoplastic polyimide film produced by the method for producing a non-thermoplastic polyimide film according to any one of claims 1 to 5 . A non-thermoplastic polyimide film having a phase separation structure formed therein, the phase separation structure having domains of a solvent-soluble polyimide having an island structure of 10 μm or less and domains of a non-thermoplastic polyimide having a sea structure ,
The solvent-soluble polyimide is soluble in N,N-dimethylformamide;
The non-thermoplastic polyimide film, wherein the solvent-soluble polyimide has an inflection point temperature of storage elastic modulus of 290° C. or lower . 8. The non-thermoplastic polyimide film according to claim 7 , wherein the weight average molecular weight of the non-thermoplastic polyimide precursor (polyamic acid) is 150,000 or more. The diamine compound used in the solvent-soluble polyimide is 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane, 4,4'-bis[4-(4-amino-2-trifluoromethyl)phenoxy]-octafluorobiphenyl, bis[4-(4-aminophenoxy)phenyl]sulfone, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, bis[4-(3-aminophenoxy)phenyl]sulfone, 9. The non-thermoplastic polyimide film according to claim 7 or 8, which contains one or more compounds selected from the group consisting of 4-aminophenyl]sulfone, 1,1-bis(4-aminophenyl)cyclohexane, 9,9-bis(4-amino-3-fluorophenyl)fluorene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, and 1,4-bis(4-aminophenoxy)benzene. 10. The non-thermoplastic polyimide film according to any one of claims 7 to 9, characterized in that the acid dianhydride used in the solvent-soluble polyimide contains one or more compounds selected from the group consisting of 2,2'-hexafluoropropylidenediphthalic dianhydride, 3,3',4,4'-perfluoroisopropylidenediphthalic dianhydride, 3,3 ', 4,4' -diphenylsulfonetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride, and ethylenediaminetetraacetic dianhydride. 11. The non-thermoplastic polyimide film according to claim 7 , wherein the solvent- soluble polyimide contains 2,2-bis(4-aminophenoxyphenyl)propane. A polyimide laminate film comprising the non-thermoplastic polyimide film according to any one of claims 7 to 11 and a thermoplastic polyimide resin layer formed on at least one surface of the non-thermoplastic polyimide film.