JP2022062784A - Polyimide laminated film - Google Patents

Abstract

To provide a polyimide laminated film which suppresses occurrence of cracks in an inner wall of a via in a step of forming the via on a polyimide laminated film for a flexible printed board using a laser, and a method for producing the same.SOLUTION: There are provided a non-thermoplastic polyimide film forming a phase separation structure having a domain of solvent-soluble polyimide of an island structure of 10 μm or less and a domain of non-thermoplastic polyimide of a sea structure in the film; and a method for producing a non-thermoplastic polyimide film that is obtained by imidizing a mixture of a non-thermoplastic polyimide precursor (polyamic acid) and solvent-soluble polyimide to prepare a non-thermoplastic polyimide film, and forming a phase separation structure having a domain of the solvent-soluble polyimide of an island structure of 10 μm or less in the film.SELECTED DRAWING: None

Description

The present invention relates to a polyimide laminated film and a method for manufacturing a polyimide laminated film that suppress the generation of cracks on the inner wall of a via in a step of forming a via on a polyimide laminated film for a flexible printed substrate by using a laser.

Among the flexible printed wiring boards (hereinafter referred to as FPC) used for tablets, smartphones, etc., the two-layer flexible printed wiring board (hereinafter referred to as two-layer FPC) using a polyimide film is in demand in the market because of its excellent heat resistance. It is expanding. During the production of this FPC, a copper-clad laminate is used by laminating copper foil on both sides of the polyimide film. For the purpose of circuit formation, holes (vias) are formed in the copper-clad laminate, and the inner surface of the via is plated with copper. There is a step of ensuring continuity between the upper and lower layers of the laminated plate.

In the via forming process, a through-hole method is used to make through holes in the copper foil on both sides with a drill or laser, and a branded beer hole method is used in which only the copper foil on one side is etched and the insulating layer is removed with a laser to leave the copper foil on one side. However, especially in fine FPC, the branded via hole method is frequently used in order to effectively use the area.

After forming the via, wet desmear treatment (cleaning with an alkaline potassium permanganate aqueous solution) is often performed for the purpose of removing and cleaning the resin residue adhering to the inside of the via and the surface of the copper foil. However, since residual stress is locally accumulated in the laser-machined part used for via formation, there is a problem that defects such as cracks and peeling occur in the peripheral part of the via in the desmear treatment after via formation. .. Patent Document 1 discloses a method of suppressing the generation of defects such as cracks by performing heat treatment after laser processing to reduce residual stress, and Patent Document 2 discloses polyimide having improved resistance to an alkaline solution as a countermeasure against the generation of defects. However, no process has been found in which this problem does not occur drastically.

Japanese Unexamined Patent Publication No. 2012-186377 Japanese Unexamined Patent Publication No. 2017-179148

It is an object of the present invention to provide a polyimide laminated film that suppresses the generation of cracks on the inner wall of a via in a step of forming a via on a polyimide laminated film for a flexible printed substrate by using a laser.

It has been found that a polyimide laminated film obtained from a mixture of a non-thermoplastic polyimide precursor and a solvent-soluble polyimide can obtain a polyimide laminated film that suppresses the generation of cracks on the inner wall of vias after a via forming step using a laser. .. The present invention comprises the following.

[1]. 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 a domain of a solvent-soluble polyimide having an island structure of 10 μm or less is formed in the film. A method for producing a non-thermoplastic polyimide film obtained by forming a phase-separated structure having a structure.

[2]. The non-thermoplastic polyimide film according to [1], wherein the film obtained from the solvent-soluble polyimide used for producing the non-thermoplastic polyimide film has an inflection temperature of 290 ° C. or lower.

[3]. The non-thermoplastic according to [1] or [2], wherein the non-thermoplastic polyimide precursor (polyamic acid) used for producing the non-thermoplastic polyimide film has a weight average molecular weight of 150,000 or more. Polyimide film.

[4]. The diamine compounds used in the solvent-soluble polyimide are 2,2-bis (4-aminophenyl) hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, and 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, 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. The non-heat according to any one of [1] to [3], which comprises one or more compounds selected from 4-aminophenoxy) biphenyl and 1,4-bis (4-aminophenoxy) benzene. A method for producing a plastic polyimide film.

[5]. The acid dianhydride used for the solvent-soluble polyimide is 2,2'-hexafluoropropyridendiphthalic acid dianhydride, 3,3', 4,4'-perfluoroisopropyridene diphthalic acid dianhydride, 3, 3', 4,4'-diphenylsulfone tetracarboxylic acid dianhydride, 9,9-bis (3,4-dicarboxyphenyl) fluorene dianhydride, dicyclohexyl-3,4,3', 4'-tetracarboxylic The non-thermoplastic polyimide film according to any one of [1] to [4], which comprises one or more compounds selected from acid dianhydride and ethylenediamine tetraacetichydride dianhydride.

[6]. The non-thermoplastic polyimide film according to [1] to [5], wherein the solvent-soluble polyimide used for producing the non-thermoplastic polyimide film contains 2,2-bis (4-aminophenoxyphenyl) propane. Manufacturing method.

[7]. A polyimide laminated film characterized by forming a thermoplastic polyimide resin layer on at least one surface of the non-thermoplastic polyimide film produced by the method for producing a non-thermoplastic polyimide film according to any one of [1] to [6]. Manufacturing method.

[8]. A non-thermoplastic polyimide film comprising a phase-separated structure having a solvent-soluble polyimide domain having an island structure of 10 μm or less and a non-thermoplastic polyimide domain having a sea structure in the film.

[9]. The non-thermoplastic polyimide film according to [8], wherein the film obtained from the solvent-soluble polyimide used for producing the non-thermoplastic polyimide film has an inflection temperature of 290 ° C. or lower.

[10]. The non-thermoplastic according to [8] or [9], wherein the non-thermoplastic polyimide precursor (polyamic acid) used for producing the non-thermoplastic polyimide film has a weight average molecular weight of 150,000 or more. Polyimide film.

[11]. The diamine compounds used in the solvent-soluble polyimide are 2,2-bis (4-aminophenyl) hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, and 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, 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. The non-heat according to any one of [8] to [10], which comprises one or more compounds selected from 4-aminophenoxy) biphenyl and 1,4-bis (4-aminophenoxy) benzene. Plastic polyimide film.

[12]. The acid dianhydride used in the solvent-soluble polyimide is 2,2'-hexafluoropropyridendiphthalic acid dianhydride, 3,3', 4,4'-perfluoroisopropyridendiphthalic acid dianhydride, 3, 3', 4,4'-diphenylsulfone tetracarboxylic acid dianhydride, 9,9-bis (3,4-dicarboxyphenyl) fluorene dianhydride, dicyclohexyl-3,4,3', 4'-tetracarboxylic The non-thermoplastic polyimide film according to any one of [8] to [11], which comprises one or more compounds selected from acid dianhydride and ethylenediamine tetraacetichydride dianhydride.

[13]. The non-thermoplastic polyimide film according to [8] to [12], wherein the solvent-soluble polyimide used for producing the non-thermoplastic polyimide film contains 2,2-bis (4-aminophenoxyphenyl) propane. ..

[14]. A polyimide laminated film characterized by forming a thermoplastic polyimide resin layer on at least one side of the non-thermoplastic polyimide film according to any one of [8] to [13].

The polyimide laminate obtained by the present invention can provide a flexible printed substrate that suppresses cracks in the inner wall of vias generated in the via forming process by laser processing without making any special change in the film manufacturing process.

It is a figure which shows an example of the optical microscope image used for the actual discrimination concerning 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 a solvent-soluble island structure of 10 μm or less is dissolved in the film. It is found that a non-thermoplastic polyimide film characterized by forming a phase-separated structure having a polyimide domain can obtain a polyimide laminated film that suppresses crack generation on the inner wall of vias after a via forming step using a laser. It came to. The details will be described below.

(About non-thermoplastic polyimide film)
The non-thermoplastic polyimide film used in the polyimide laminated film of the present invention has a phase-separated structure having an island-structured soluble polyimide domain of 10 μm or less and a sea-structured non-thermoplastic polyimide domain in the film. The non-thermoplastic polyimide film is characterized by the above, and the non-thermoplastic polyimide corresponding to the sea structure portion and the polyimide precursor (polyimide acid) are not particularly limited.

(About non-thermoplastic polyimide precursor (polyamic acid))
In particular, as a film material used for a polyimide laminated film for a flexible printed substrate, it is preferable that a rigid structure such as a biphenyl structure or a phenyl structure is contained in a polymer molecule from the viewpoint of dimensional stability and the like. In addition, the biphenyl structure has lower symmetry than the phenyl structure, and the decrease in symmetry of the polymer primary structure hinders the packing of molecules, and the elastic modulus decreases when the polymer softens above a certain temperature. preferable.

Examples of the diamine monomer having a specific biphenyl structure include 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diaminobiphenyl, and 4,4'-diamino-2,2'-dimethyl. Biphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-2,2'-dimethoxybiphenyl, 4,4'-diamino-3,3'-dimethoxybiphenyl, 3,3 ', 5,5'-tetramethylbenzidine, 4,4'-bis (4-aminophenoxy) biphenyl and the like can be exemplified. However, 4,4'-diaminobiphenyl and 4,4'-diamino-3,3'-dimethylbiphenyl are not preferable to be actually used because they are carcinogenic to humans. For practical use, 4,4'-diamino-2,2'-dimethylbiphenyl is particularly preferred.

In addition, of the 100% diamine monomer components constituting the non-thermoplastic polyimide precursor (polyamic acid), the more rigid monomer components, the lower the linear expansion coefficient due to the formation of an aggregated structure, which is effective as a film with excellent dimensional stability. If the content is too large, the linear expansion coefficient of the obtained film becomes too low, which is not preferable, and the optimum content as a film for a flexible printed substrate is preferably 10 to 50 mol%. It is more preferably to 40 mol%, still more preferably 20 to 35 mol%. As the diamine monomer used in addition, aromatic diamine having high heat resistance is preferable. For example, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4'-diamino. Diphenylpropane, 4,4'-diaminodiphenylmethane, benzene, 3,3'-dichlorobenzidine, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 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'-diaminodiphenylN-methylamine, 4,4'-diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3- Examples thereof include diaminobenzene and 1,2-diaminobenzene. The content of the diamine used in addition is preferably 50 to 90 mol%, more preferably 60 to 85 mol%, still more preferably 65 to 80 mol%.

Since the flexibility as a polymer can be adjusted while maintaining high heat resistance, it is preferable to use a combination of 4,4'-diaminodiphenyl ether and para-phenylenediamine, and the content of 4,4'-diaminodiphenyl ether at that time is , 40-70 mol%, more preferably 45-65 mol%, even more preferably 50-65 mol%, and the paraphenylenediamine content is 10-50 mol%. It is preferably present, more preferably 15 to 40 mol%, still more preferably 15 to 30 mol%.

As the acid dianhydride monomer used in the non-thermoplastic polyimide precursor (polyamic acid) of the present invention, aromatic acid dianhydride is preferable from the viewpoint of heat resistance.

For example, pyromellitic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 1,2,5,6 -Naphthalenetetracarboxylic acid dianhydride, 2,2', 3,3'-biphenyltetracarboxylic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 2,2', 3,3'-Benzophenone tetracarboxylic acid dianhydride, 4,4'-oxyphthalic acid dianhydride, 3,4'-oxyphthalic acid dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane Acid dianhydride, 3,4,9,10-perylenetetracarboxylic acid dianhydride, bis (3,4-dicarboxyphenyl) propanoic acid dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ) Ethanic acid dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethaneic acid dianhydride, bis (2,3-dicarboxyphenyl) methaneic acid dianhydride, bis (3,4-dicarboxyphenyl) Carboxylic acid) ethaneic acid dianhydride, oxydiphthalic acid dianhydride, bis (3,4-dicarboxyphenyl) sulfonic acid dianhydride, p-phenylene bis (trimeritic acid monoesteric acid anhydride), ethylene bis (tri) Merit acid monoesteric acid anhydride), bisphenol A bis (trimeric acid monoesteric acid anhydride) and similar substances thereof can be mentioned.

Since the non-thermoplastic polyimide film of the present invention is required to have heat resistance, it is preferable to use 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride and pyromellitic acid dianhydride, in particular. 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride is more preferred because it contains a biphenyl structure. Of the 100% acid dianhydride monomer component constituting the non-thermoplastic polyimide film, the content of 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride is preferably 20 to 60 mol%. It is more preferably 25 to 55 mol%, still more preferably 30 to 50 mol%. When pyromellitic acid dianhydride is contained, the content of pyromellitic acid dianhydride is preferably 40 to 80 mol% in 100% of the acid dianhydride monomer components constituting the non-thermoplastic polyimide film. , 35-75 mol%, more preferably 50-70 mol%.

(Manufacturing of non-thermoplastic polyimide precursor (polyamic acid))
The non-thermoplastic polyimide precursor in the present invention indicates a polyamic acid before imidization, and any known method or a method in which they are combined can be used as a method for producing the polyamic acid. The characteristic of the polymerization method in the production of the non-thermoplastic polyimide precursor lies in the order of addition of the monomers, and various physical properties of the polyimide obtained by controlling the order of addition of the monomers can be controlled. Therefore, in the present invention, any method of adding a monomer may be used for producing a non-thermoplastic polyimide precursor. The following methods can be mentioned as typical polymerization methods.

For example, it can be produced by the following steps (Aa) to (Ab).
(A-a): A step of 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.
(Ab): A step of additionally adding an aromatic diamine having a structure different from that used in the step (Aa). Further, an aromatic acid dianhydride having a structure different from that used in the step (Aa) is added so that the aromatic diamine and the aromatic acid dianhydride in the whole step are substantially equimolar. The process of polymerizing.

Alternatively, it is also possible to obtain a non-thermoplastic polyimide precursor by going through the following steps (B-a) to (B-b).
(BA): Aromatic diamine and aromatic acid dianhydride are reacted in an organic polar solvent with an excess of aromatic acid dianhydride, and a pre-acid anhydride group is provided at both ends. Step of obtaining a polymer, (B-b): A step of additionally adding an aromatic acid anhydride having a structure different from that used in the step (B-a). Further, an aromatic diamine having a structure different from that used in the step (BA) is added and polymerized so that the aromatic diamine and the aromatic acid dianhydride in all the steps are substantially equimolar. Process to do.

Synthetic methods that set the order of addition so that a particular diamine or acid dianhydride is selectively bound to any diamine or acid dianhydride (eg, steps (A)-(Ab)), and (. B-a) to (B-b)) are referred to as sequence polymerization in the present invention. Among the polymers obtained by sequence polymerization, the case where the block component is two is called a diblock copolymer, and the case where the block component is three is called a triblock copolymer. On the other hand, a synthetic method in which the diamine and the acid dianhydride to be bonded are not selected in the order of addition is called random polymerization in the present invention. The polymer obtained by random polymerization is called a random copolymer. In the present invention, as a preferable polymerization method for obtaining a polyimide resin effective for suppressing tearing of a film while maintaining the characteristics as a flexible metal-clad laminate, sequence polymerization is preferable to random polymerization.

The solid content concentration of the precursor to be the non-thermoplastic polyimide film of the present invention is not particularly limited, and is usually obtained at a concentration of 5% by weight to 35% by weight, preferably 10% by weight to 30% by weight. When the concentration is in this range, a polyimide precursor having an appropriate molecular weight can be easily obtained.

A filler may be added to the non-thermoplastic non-thermoplastic polyimide precursor of the present invention for the purpose of improving various properties of the film such as slidability, thermal conductivity, conductivity, corona resistance, and loop stiffness. .. Any filler may be used, and preferred examples thereof 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))
Further, in the non-thermoplastic polyimide precursor used in the present invention, a higher molecular weight is preferable from the viewpoint that it is easier to form a phase-separated structure with the solvent-soluble polyimide and the crack improving effect by stress relaxation is excellent, and the precursor (polyamide) thereof is preferable. The average molecular weight of the acid) is preferably 150,000 or more, more preferably 200,000 or more, when measured in terms of PEG (polyethylene glycol) by GPC.

(About solvent-soluble polyimide)
Further, the diamine and acid dianhydride used for producing the solvent-soluble polyimide corresponding to the island structure in the present invention include the same ones used for the non-thermoplastic polyimide described above, but the island structure has a phase-separated structure. A flexible film is preferable, and the above-mentioned monomer can be used without particular limitation, because it is excellent in alleviating stress applied during processing of a laminated film. 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-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-amino) Phenyl) -2-propyl] benzene, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl, 1 , 4-Bis (4-aminophenoxy) benzene can be exemplified.

In particular, from the viewpoint of excellent stress relaxation, it is preferable to use 2,2-bis (4-aminophenoxyphenyl) propane as a monomer.
Acid dianhydrides used in the production of solvent-soluble polyimides include 2,2'-hexafluoropropyridenediphthalic acid dianhydride, 3,3', 4,4'-perfluoroisopropyridenediphthalic acid dianhydride. , 3,3', 4,4'-diphenylsulfonetetracarboxylic acid dianhydride, 9,9-bis (3,4-dicarboxyphenyl) fluorene dianhydride, dicyclohexyl-3,4,3', 4' -Tetracarboxylic acid dianhydride, ethylenediamine tetraacetichydride dianhydride can be exemplified.

Further, in order to obtain a solvent-soluble polyimide, it is preferable to react with a diamine having a fluorine group in combination with an acid dianhydride (particularly, an aromatic acid dianhydride) because the solubility in a solvent is improved.

Examples of diamines having a fluorine group are 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, etc. Similarly, the acid dianhydride compound preferably contains a fluorine group, and specifically, 2,2'-hexafluoropropyridendiphthalic acid dianhydride, 3,3', 4, Examples thereof include 4'-perfluoroisopropyridendiphthalic acid dianhydride, and the total content of the diamine or acid dianhydride monomer having these fluorine groups in the polymer may be 40 to 90 mol%. It is preferably 60 to 85 mol%, more preferably 65 to 80 mol%.

(Inflection temperature of storage elastic modulus of solvent-soluble polyimide)
In the solvent-soluble polyimide corresponding to the island structure of the present invention, the temperature indicated by the change point of the storage elastic modulus in the glass region by the dynamic viscoelasticity measurement (referred to as the E'change point temperature) is when the film laminate is laser-processed. The temperature is preferably 290 ° C. or lower, more preferably 250 ° C. or lower, from the viewpoint of easily relieving the stress in the film generated during the high-temperature cooling. Further, if the temperature is 180 ° C. or lower, the temperature applied when soldering the flexible substrate cannot be withstood and problems such as foaming may occur, which is not preferable.

(Molecular weight of solvent-soluble polyimide)
Further, in the solvent-soluble polyimide used in the present invention, a high molecular weight is preferable from the viewpoint of excellent crack resistance effect by improving the toughness and strength of the resin, but on the other hand, if the molecular weight is too large, it may not dissolve in the solvent, which is optimal. There is a range, and the weight average molecular weight of the solvent-soluble polyimide is preferably 50,000 to 200,000, more preferably 100,000 to 150, when measured in terms of PEG (polyethylene glycol) by GPC. It is preferably 000.

(Non-thermoplastic polyimide film with phase separation structure)
The non-thermoplastic polyimide film of the present invention is characterized by having a phase-separated structure having a domain of a solvent-soluble polyimide having an island structure of 10 μm or less and a domain of a non-thermoplastic polyimide having a sea structure in the film, and is characterized by having a polyimide laminated film. By relaxing the stress remaining in the film due to the heat generated during hole formation by laser processing in the flexible metal-clad laminate manufactured using the polyimide, the generation of cracks after the desmear process can be suppressed.
The size of the solvent-soluble polyimide domain of the island structure is preferably 10 μm or less because if the size is too large, the interface between the sea structure and the island structure is reduced and the generated stress cannot be sufficiently dispersed. It is more preferably 7 μm or less, and further preferably 5 μm or less. The lower limit of the size is preferably 0.3 μm or more from the viewpoint of stress relaxation. In addition, the size of this domain can be observed and measured by general TEM observation.

(Method for manufacturing a non-thermoplastic polyimide film having a phase-separated structure)
The non-thermoplastic polyimide film of the present invention is characterized by forming a phase-separated structure in which a domain of a solvent-soluble polyimide having an island structure of 10 μm or less and a domain of a non-thermoplastic polyimide having a sea structure are formed in the film. The manufacturing method is not particularly limited. In particular, as a simple and uniform method for forming a phase-separated structure in a film, a method obtained by premixing a non-thermoplastic polyimide precursor (polyamic acid) and a solvent-soluble polyimide solution and imidizing the mixture. Can be mentioned.

In this case, the mixing temperature is about −20 ° C. to 50 ° C., preferably 10 ° C. to 45 ° C., more preferably 20 ° C. to 40 ° C. If the temperature is lower than this range, the torque will be too high and it may not be possible to mix uniformly, and if the temperature is high, it will be partially compatible or the precursor will be decomposed. There is a possibility that a simple phase-separated structure cannot be formed.
The mixing time is preferably 3 hours or longer, more preferably 5 hours or longer. 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.

(Manufacturing method of polyimide film)
The method for obtaining the non-thermoplastic polyimide film in 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) A step of reacting an aromatic diamine with an aromatic tetracarboxylic acid 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 a film-forming dope containing the above-mentioned polyimide precursor from a die onto a support to form a resin layer (sometimes referred to as a liquid film).
iii) A step of heating a resin layer on a support to form a self-supporting gel film, and then peeling the gel film from the support.
iv) A step of further heating to imidize the remaining amic acid and drying to obtain a non-thermoplastic polyimide film.

The steps after ii) are roughly classified into a thermal imidization method and a chemical imidization method. The thermal imidization method is a method in which a polyimide precursor solution is cast on a support as a film-forming dope without using a dehydration ring closure agent or the like, and imidization is promoted only by heating. On the other hand, the chemical imidization method is a method of promoting imidization by using a polyimide precursor solution to which at least one of a dehydration ring-closing agent and a catalyst is added as an imidization accelerator as a film-forming dope. Either method may be used, but the chemical imidization method is more productive.

As the dehydration ring closure agent, an acid anhydride typified by acetic anhydride can be preferably used. As the catalyst, tertiary amines such as aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines are preferably used. As the support for spreading the film-forming dope, a glass plate, aluminum foil, an endless stainless belt, a stainless drum, or the like can be preferably used. Heating conditions are set according to the thickness of the finally obtained film and the production rate, and after at least one of partial imidization and drying is performed, the film is peeled off from the support to form a polyimide precursor film (hereinafter referred to as gel film). ) Is obtained. The end of the gel film is fixed to avoid shrinkage during curing, and heat treatment is performed to remove water, a residual solvent, an imidization accelerator, a dehydration ring closure agent, etc. from the gel film, and the remaining amic acid is removed. It is completely imidized to obtain a film containing polyimide. The heating conditions may be appropriately set according to the thickness of the finally obtained film and the production rate.

(Manufacturing of polyimide laminated film)
The polyimide laminated film of the present invention is a polyimide laminated film laminate in which a thermoplastic polyimide resin layer is laminated on at least one surface of the non-thermoplastic polyimide film, and the method for producing the polyimide laminated film is also particularly limited. However, various known methods can be applied. For example, a coextruding die may be used to simultaneously form a multi-layered resin layer containing a polyimide precursor that is a precursor of the non-thermoplastic polyimide film of the present invention and a thermoplastic polyimide precursor that can be an adhesive layer. ..
Further, the precursor of the non-thermoplastic polyimide film of the present invention is synthesized, and the polyimide film obtained by forming a film using the precursor is once recovered, and then another thermoplastic polyimide precursor is newly prepared by coating on the precursor. A resin layer containing the above may be formed. Since imidization requires a very high temperature, when a resin layer other than polyimide is provided, it is preferable to adopt the latter means in order to suppress thermal decomposition. When the thermoplastic polyimide resin layer is provided by coating, a thermoplastic polyimide precursor may be applied and then imidization may be performed, or a thermoplastic polyimide solution capable of forming the thermoplastic polyimide resin layer may be used. It 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 laminated film. The total thickness of the polyimide laminated film of the present invention is preferably 6 to 60 μm. Even within that range, a thinner thickness is preferable from the viewpoint of reducing the weight of the FPC and improving the bendability, for example, 7 to 30 μm is more preferable, and 10 to 25 μm is further preferable.

Further, in order to suppress the warp of the polyimide laminated film, it is preferable that both sides of the non-thermoplastic polyimide layer are thermoplastic polyimide layers. When the thermoplastic polyimide layer is formed on only one side of the non-thermoplastic polyimide layer, the film may warp due to the asymmetric structure when the imidization reaction of the thermoplastic polyimide layer is allowed to proceed. 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 on both sides is based on the thickness of the thick thermoplastic polyimide layer, and the thickness of the other is 40% or more, 100. If it is% or less, there is no problem with the film shape.

The thickness ratio of the non-thermoplastic polyimide layer to the thermoplastic polyimide layer of 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 of the non-thermoplastic polyimide layer and the thermoplastic polyimide layer even if there are a plurality of layers, and the non-thermoplastic polyimide layer has a large number of layers. It is preferable not to exceed the thickness.

(Flexible metal-clad laminate)
By laminating a metal foil on at least one side of the polyimide laminated film, it is possible to manufacture a flexible metal-clad laminate. The method for producing the flexible metal-clad laminate is not particularly limited, and various known methods can be applied. For example, continuous processing by a thermal roll laminating device having a pair or more of metal rolls or a double belt press (DBP) can be used. The specific configuration of the means for performing the thermal laminating is not particularly limited, but a protective material is arranged between the pressure surface and the metal leaf in order to improve the appearance of the obtained laminated board. It is also preferable.

Means of casting a multilayer organic solvent solution containing a solution of at least one of a thermoplastic polyimide precursor and a non-thermoplastic polyimide precursor on a metal foil can also be used. The means for casting the organic solvent solution containing the polyimide precursor on the 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 the polyimide resin layer is provided as a plurality of layers such as when the thermoplastic polyimide resin layer and the non-thermoplastic polyimide film in the present invention are provided, or when a resin layer other than the polyimide is also provided, the above casting and heating steps are repeated a plurality of times, or both. A means of forming a multi-layered cast layer by extrusion or continuous casting and heating at one time is preferably used. By this means, a flexible metal-clad laminate is obtained as soon as imidization is completed. When the metal foils are provided on both sides of the resin layer, the metal foils may be attached to the resin layer surface on the opposite side by heating and pressurizing. The metal foil is not particularly limited, and any metal foil can be used. For example, copper, stainless steel, nickel, aluminum, alloys of these metals, and the like can be preferably used. Further, in a general metal-clad laminate, copper such as rolled copper and electrolytic copper is often used, but it can also be used in the present invention.

Further, as the metal foil, one having various characteristics such as surface treatment and surface roughness can be selected according to the purpose. Further, the surface of the metal foil may be coated with a rust preventive layer, a heat resistant layer or an adhesive layer. The thickness of the metal foil is not particularly limited, and may be any thickness as long as it can exhibit sufficient functions according to its use.

(Beer forming process by laser processing)
In the production of flexible substrates, when vias are formed on a copper-clad laminate by laser processing, the processed parts are irradiated with a laser to penetrate the substrate and remove only through holes (TH), copper foil on the upper surface, and polyimide resin. Indovia holes (BVH) can be formed. A known type of laser 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. As for TH, a method of directly drilling a through hole is also widely used.

On the other hand, desmear treatment is performed for the purpose of removing resin waste generated during processing, but a swelling step consisting of an alkaline aqueous solution or a solution containing an organic solvent, and a crude composition consisting of an alkaline aqueous solution such as sodium permanganate or potassium permanganate. A wet desmear treatment consisting of a conversion step and a neutralization step is generally used. Cracks in the inner wall of the hole that occur during processing of the copper-clad laminate using the polyimide laminated film of the present invention often occur in the inner wall of the hole after the desmear treatment, and the swelling time and roughening time in the desmear treatment are lengthened. Then, cracks are likely to occur. Also, after the desmear treatment, the inside of the hole is metal-plated to form vias. The general metal plating is not particularly limited, but a plating layer having a desired thickness may be formed only by electrolytic copper plating, or a desired thickness may be formed by thinning the electrolytic copper plating layer and then electrolytic copper plating. A thick plating layer may be formed.

(Hole crack test: crack evaluation method)
Cracks generated on the inner wall of the via in FPC manufacturing are usually detected by visual inspection or the like after FPC manufacturing. The present inventors conducted a hole crack test in which a test piece was cut out from a long flexible metal-clad laminate used as a material, and cracks generated in the inner wall of the hole were evaluated at the stage where laser processing and desmear processing in the via forming process were performed. By doing so, it was found that the occurrence of cracks on the inner wall of the via can be easily evaluated in the FPC manufacturing process.

In this evaluation method, the copper foil of the test piece after the desmear treatment 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 a cross Nicol. It was confirmed in combination with the observation with a polarizing microscope that when a crack occurs on the inner wall of the via, it is detected as a light leak.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the Examples.

(Inflection temperature evaluation)
Using DM6100 manufactured by SII Nanotechnology, dynamic viscoelasticity was measured in an air atmosphere, and the storage elastic modulus at each temperature and the turning point temperature were measured.
Sample measurement range; width 9 mm, distance between grippers; 20 mm
Measurement temperature range; 0 ° C to 440 ° C
Temperature rise rate; 3 ° C / min
Strain amplitude; 10 μm
Measurement frequency; 1Hz, 5Hz, 10Hz
Minimum tension / compressive force; 100 mN
Tension / compression gain; 1.5
Initial force amplitude; 100 mN

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

(TEM observation)
The film used for observation was embedded in resin, and an ultrathin section was created with an ultramicrotome (UCT manufactured by Leica). Using a transmission electron microscope (TEM, manufactured by Hitachi High-Technologies Corporation, H-7650), the presence or absence of a sea-island structure and the domain size were measured from a TEM image at a magnification of 40,000 under the condition of an acceleration voltage of 100 kV.

(Hole crack test)
12 μm electrolytic copper foil (3EC-M3S-HTE, manufactured by Mitsui Metals) was placed on both sides of the polyimide film laminates obtained in Examples and Comparative Examples, and further as protective films on both sides of the copper foil (Apical 125 NPI; Kaneka). A flexible metal-clad laminate was obtained by thermal laminating under the conditions of a laminating temperature of 360 ° C., a laminating pressure of 265 N / cm (27 kgf / cm), and a laminating speed of 1.0 m / min. Next, a flexible metal-clad laminate was cut into a size of 5.0 cm × 20.0 cm square, and a blind via hole having a diameter of 100 μm was laser-processed using a UV-YAG laser by the process shown in Table 2. 10 rows of patterns were formed, 10 vertically at 1 mm intervals for each condition (100 each). After laser processing, desmear treatment was performed by the process shown in Table 3.

After removing the copper foil by etching, the copper foil was observed under a cross Nicol at a magnification of 200 times with a polarizing microscope. Light leaking through the hole was regarded as a crack. Those with a weak degree of light leakage that could not be determined were classified by cutting the hole cross section and observing at a higher magnification with an electron microscope or the like to determine whether or not it was a crack. FIG. 1 shows an example of an optical microscope image used for actual discrimination. After observing 100 pieces, the ratio of cracks was determined as a percentage.

(Synthesis of non-thermoplastic polyamic acid (polyimide precursor))
(Synthesis Example 1)
Add 334.13 g of N, N-dimethylformamide (hereinafter, DMF) and 17.70 g of 4,4'-diaminodiphenyl ether (hereinafter, ODA) to a glass flask having a capacity of 2000 ml, and add 3,3 while stirring in a nitrogen atmosphere. 18.01 g of', 4,4'-biphenyltetracarboxylic acid dianhydride (hereinafter, BPDA) was gradually added. After visually confirming that BPDA was dissolved, 7.79 g of pyromellitic acid dianhydride (hereinafter referred to as PMDA) was gradually added. After visually confirming that PMDA had dissolved, stirring was performed for 30 minutes. Then, 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, 0.46 g of PMDA was adjusted to a solid content concentration of 7.2%, gradually added to the above reaction solution, and added when the viscosity at 23 ° C. reached 2500 poisons. A non-thermoplastic polyimide precursor A was obtained. The average weight molecular weight at this time was 156,000.

(Synthesis Example 2)
DMF334.13 g and ODA 17.70 g were added to a glass flask having a capacity of 2000 ml, and BPDA 18.01 g was gradually added while stirring under a nitrogen atmosphere. After visually confirming that BPDA was dissolved, 7.79 g of PMDA was gradually added. After visually confirming that PMDA had dissolved, stirring was performed for 30 minutes. Then, 5.78 g of m-TB was added, 7.11 g of PDA was added, and then 11.85 g of PMDA was added, and the mixture was stirred for 30 minutes. Finally, 0.46 g of PMDA was adjusted to a solid content concentration of 7.2%, gradually added to the above reaction solution, and added when the viscosity at 23 ° C. reached 8000 poise. A non-thermoplastic polyimide precursor B was obtained. The average weight molecular weight at this time was 251,000.

(Synthesis Example 3)
To a glass flask having a capacity of 2000 ml, add DMF334.13 g, ODA 5.27 g, 2,2'-bis [4- (4-aminophenoxy) phenyl] propane (hereinafter, BAPP) 16.20 g, and add under a nitrogen atmosphere. 7.17 g of PMDA was gradually added while stirring with. After visually confirming the dissolution of PMDA, 8.48 g of benzophenone tetracarboxylic dianhydride (hereinafter referred to as BTDA) was added, and the mixture was stirred for 30 minutes. Then, 3.76 g of PDA was added, and then 15.32 g of PMDA was added, and the mixture was stirred for 30 minutes. Finally, a solution prepared by dissolving 0.46 g of PMDA in DMF so as to have a solid content concentration of 7.2% is gradually added to the above reaction solution, and the viscosity at 23 ° C. is 2500 poisons. When it reached, the addition was stopped 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 are added to a glass flask having a capacity of 2000 ml, and 77.01 g of 2,2'-hexafluoropropyridene diphthalic acid dianhydride (hereinafter referred to as 6FDA) is added while stirring under a nitrogen atmosphere. Gradually added. After visually confirming that 6FDA was dissolved, stirring was performed for 30 minutes. Finally, the DMF solution was adjusted to a solid content concentration of 7.2% with 2.22 g of 6FDA, and this solution was gradually added to the above reaction solution to reach a viscosity of 2000 poise at 23 ° C. At this point, the addition was stopped, and 158.4 g of N, N-dimethylformamide, 40.66 g of pyridine, and 53.5 g of anhydrous acetic acid were sequentially added to the flask, and the mixture was stirred for 3 hours while heating at 90 ° C. After returning to room temperature, 2000 mL of isopropyl alcohol was put into the flask, and the precipitate was recovered. Further, the washing was carried out three times with 1000 mL liter of isopropyl alcohol, and the obtained precipitate was dried under reduced pressure at 80 ° C. for 20 hours to obtain a solvent-soluble polyimide D. The weight average molecular weight at this time 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 6FABP) are added to a glass flask having a capacity of 2000 ml, and nitrogen is added. 51.000 g of BPDA was gradually added while stirring under the atmosphere. After visually confirming that BPDA was dissolved, stirring was performed for 30 minutes. Finally, 1.47 g of BPDA was adjusted to a solid content concentration of 7.2%, and this solution was gradually added to the above reaction solution, and the viscosity at 23 ° C. reached 2000 poise. At this point, the addition was stopped, and 158.4 g of N, N-dimethylformamide, 40.66 g of pyridine, and 53.5 g of anhydrous acetic acid were sequentially added to the flask, and the mixture was stirred for 3 hours while heating at 90 ° C. After returning to room temperature, 2000 mL of isopropyl alcohol was put into the flask, and the precipitate was recovered. Further, the washing was carried out three times with 1000 mL liter of isopropyl alcohol, and the obtained precipitate was dried under reduced pressure at 80 ° C. for 20 hours to obtain a solvent-soluble polyimide E. The weight average molecular weight at this time was 120,500.

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

(Inflection temperature of solvent-soluble polyimide)
DMF (30 g) was added to the solvent-soluble polyimides D and E (60 g) obtained in the above synthesis examples 4 and 5, and the mixture was stirred and defoamed, and cast and coated on an aluminum foil using a comma coater. After heating this resin film at 120 ° C. x 3 minutes, the self-supporting gel film is peeled off from the aluminum foil, fixed to a metal fixing frame, and dried at 250 ° C. x 1 minute, 300 ° C. x 200 seconds. A polyimide film having a thickness of 20 μm was obtained.

Further, the inflection temperature of the storage elastic coefficient was measured by the above-mentioned DMA measurement, and the inflection temperature of the polyimide film obtained from the solvent-soluble polyimide D was 218 ° C., and the inflection temperature was obtained from the solvent-soluble polyimide precursor E. It was found that the inflection temperature of the polyimide film was 207 ° C.

(Example 1)
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 in a 500 mL separable flask at room temperature under a nitrogen atmosphere. The mixture was stirred and mixed for 5 hours using a stirring blade to obtain a precursor mixture. To this precursor mixture was added 32.5 g of a curing agent consisting of acetic anhydride / isoquinoline / DMF (weight ratio 11.48 / 3.40 / 18.18), and the mixture was stirred and defoamed at a temperature of 0 ° C. or lower. It was applied onto the aluminum foil using a comma coater. After heating this resin film at 115 ° C. × 100 seconds, the self-supporting gel film is peeled off from the aluminum foil and fixed to a metal fixing frame, and imidized at 250 ° C. × 15 seconds and 350 ° C. × 79 seconds. A polyimide film having a thickness of 12.5 μm was obtained.

TEM observation of the cross section of the obtained film was performed to confirm that it was a polyimide film having a phase-separated structure having a domain having a size of 3.8 μm at the maximum, and this film was fixed to a metal fixing frame. When it was heated at 450 ° C. for 2 minutes, it retained its morphology, confirming that it was non-thermoplastic.

Next, a solution obtained by diluting the thermoplastic polyimide precursor F obtained in Synthesis Example 6 with DMF so as to have a solid content concentration of 8% by weight was obtained on a non-thermoplastic polyimide film having a phase-separated structure. The non-thermoplastic polyimide film was applied to both sides so that the final one-sided thickness was 3 μm. Then, it heated at 120 degreeC for 2 minutes. Subsequently, it was heated and imidized at 350 ° C. for 15 seconds to obtain a polyimide laminated film.

(Example 2)
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 in a 500 mL separable flask at room temperature under a nitrogen atmosphere. The mixture was stirred and mixed for 5 hours using a stirring blade to obtain a precursor mixture. To this precursor mixture was added 32.5 g of a curing agent consisting of acetic anhydride / isoquinoline / DMF (weight ratio 11.48 / 3.40 / 18.18), and the mixture was stirred and defoamed at a temperature of 0 ° C. or lower. It was applied onto the aluminum foil using a comma coater. After heating this resin film at 115 ° C. × 100 seconds, the self-supporting gel film is peeled off from the aluminum foil and fixed to a metal fixing frame, and imidized at 250 ° C. × 15 seconds and 350 ° C. × 79 seconds. A polyimide film having a thickness of 12.5 μm was obtained.

TEM observation of the cross section of the obtained film was performed to confirm that it was a polyimide film having a phase-separated structure having a domain having a maximum size of 4.6 μm of thermoplastic polyimide, and this film was fixed to a metal fixing frame. When it was heated at 450 ° C. for 2 minutes, it retained its morphology, confirming that it was non-thermoplastic.

Next, a solution obtained by diluting the thermoplastic polyimide precursor F obtained in Synthesis Example 6 with DMF so as to have a solid content concentration of 8% by weight was obtained on a non-thermoplastic polyimide film having a phase-separated structure. The non-thermoplastic polyimide film was applied to both sides so that the final one-sided thickness was 3 μm. Then, it heated at 120 degreeC for 2 minutes. Subsequently, it was heated and imidized at 350 ° C. for 15 seconds to obtain a polyimide laminated film.

(Example 3)
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 in a 500 mL separable flask at room temperature under a nitrogen atmosphere. The mixture was stirred and mixed for 5 hours using a stirring blade to obtain a precursor mixture. To this precursor mixture was added 32.5 g of a curing agent consisting of acetic anhydride / isoquinoline / DMF (weight ratio 11.48 / 3.40 / 18.18), and the mixture was stirred and defoamed at a temperature of 0 ° C. or lower. It was applied onto the aluminum foil using a comma coater. After heating this resin film at 115 ° C. × 100 seconds, the self-supporting gel film is peeled off from the aluminum foil and fixed to a metal fixing frame, and imidized at 250 ° C. × 15 seconds and 350 ° C. × 79 seconds. A polyimide film having a thickness of 12.5 μm was obtained.

TEM observation of the obtained cross section of the film was performed to confirm that it was a polyimide film having a phase-separated structure having a domain having a maximum size of 1.3 μm of thermoplastic polyimide, and this film was fixed to a metal fixing frame. When it was heated at 450 ° C. for 2 minutes, it retained its morphology, confirming that it was non-thermoplastic.

Next, a solution obtained by diluting the thermoplastic polyimide precursor F obtained in Synthesis Example 6 with DMF so as to have a solid content concentration of 8% by weight was obtained on a non-thermoplastic polyimide film having a phase-separated structure. The non-thermoplastic polyimide film was applied to both sides so that the final one-sided thickness was 3 μm. Then, it heated at 120 degreeC for 2 minutes. Subsequently, it was heated and imidized at 350 ° C. for 15 seconds to obtain a polyimide laminated 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 composed of acetic anhydride / isoquinoline / DMF (weight ratio 11.48 / 3.40 / 18.18) was added. The mixture was stirred and defoamed at a temperature of 0 ° C. or lower, and applied onto the aluminum foil using a comma coater. After heating this resin film at 115 ° C. × 100 seconds, the self-supporting gel film is peeled off from the aluminum foil and fixed to a metal fixing frame, and imidized at 250 ° C. × 15 seconds and 350 ° C. × 79 seconds. A polyimide film having a thickness of 12.5 μm was obtained. Further, when this film was fixed to a metal fixing frame and heated at 450 ° C. for 2 minutes, the morphology was maintained, confirming that the film was non-thermoplastic.

Next, the obtained non-thermoplastic polyimide film was diluted with DMF so that the thermoplastic polyimide precursor F obtained in Synthesis Example 6 had a solid content concentration of 8% by weight, and the solution was added to the obtained non-thermoplastic polyimide film. The plastic polyimide film was coated on both sides so that the final one-sided thickness was 3 μm. Then, it heated at 120 degreeC for 2 minutes. Subsequently, it was heated and imidized at 350 ° C. for 15 seconds to obtain a polyimide laminated film.

(Comparative Example 2)
In Comparative Example 1 above, a polyimide laminate was prepared by the same method 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. Obtained.

(Evaluation results)
Using the polyimide laminated films obtained in Examples 1 to 3 and Comparative Examples 1 and 2, the presence or absence of a sea-island structure and the domain size of the island structure in the non-thermoplastic film by TEM observation were measured, and hole cracks were obtained by the above method. The results of the test are shown in Table 4.

The polyimide laminated film obtained by the present invention can provide a flexible printed substrate in which cracks on the inner wall of vias generated in the via forming step by laser processing are suppressed.

Claims (14)

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 a domain of a solvent-soluble polyimide having an island structure of 10 μm or less is formed in the film. A method for producing a non-thermoplastic polyimide film obtained by forming a phase-separated structure having a structure. The non-thermoplastic polyimide film according to claim 1, wherein the film obtained from the solvent-soluble polyimide used for producing the non-thermoplastic polyimide film has an inflection temperature of 290 ° C. or lower. The non-thermoplastic polyimide film according to claim 1 or 2, wherein the non-thermoplastic polyimide precursor (polyamic acid) used for producing the non-thermoplastic polyimide film has a weight average molecular weight of 150,000 or more. .. The diamine compounds used in the solvent-soluble polyimide are 2,2-bis (4-aminophenyl) hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, and 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, 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 ( The non-thermoplastic polyimide according to any one of claims 1 to 3, which comprises one or more compounds selected from 4-aminophenoxy) biphenyl and 1,4-bis (4-aminophenoxy) benzene. How to make a film. The acid dianhydride used for the solvent-soluble polyimide is 2,2'-hexafluoropropyridendiphthalic acid dianhydride, 3,3', 4,4'-perfluoroisopropyridene diphthalic acid dianhydride, 3, 3', 4,4'-diphenylsulfone tetracarboxylic acid dianhydride, 9,9-bis (3,4-dicarboxyphenyl) fluorene dianhydride, dicyclohexyl-3,4,3', 4'-tetracarboxylic The non-thermoplastic polyimide film according to any one of claims 1 to 4, which comprises one or more compounds selected from acid dianhydride and ethylenediamine tetraacetichydride dianhydride. The production of the non-thermoplastic polyimide film according to claim 1 to 5, wherein the solvent-soluble polyimide used for producing the non-thermoplastic polyimide film contains 2,2-bis (4-aminophenoxyphenyl) propane. Method. Production of a polyimide laminated film characterized by forming a thermoplastic polyimide resin layer on at least one side of the non-thermoplastic polyimide film produced by the method for producing a non-thermoplastic polyimide film according to any one of claims 1 to 6. Method. A non-thermoplastic polyimide film comprising a phase-separated structure having a solvent-soluble polyimide domain having an island structure of 10 μm or less and a non-thermoplastic polyimide domain having a sea structure in the film. The non-thermoplastic polyimide film according to claim 8, wherein the film obtained from the solvent-soluble polyimide used for producing the non-thermoplastic polyimide film has an inflection temperature of 290 ° C. or lower. The non-thermoplastic polyimide film according to claim 8 or 9, wherein the non-thermoplastic polyimide precursor (polyamic acid) used for producing the non-thermoplastic polyimide film has a weight average molecular weight of 150,000 or more. .. The diamine compounds used in the solvent-soluble polyimide are 2,2-bis (4-aminophenyl) hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, and 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, 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 ( The non-thermoplastic polyimide according to any one of claims 8 to 10, which comprises one or more compounds selected from 4-aminophenoxy) biphenyl and 1,4-bis (4-aminophenoxy) benzene. the film. The acid dianhydride used for the solvent-soluble polyimide is 2,2'-hexafluoropropyridendiphthalic acid dianhydride, 3,3', 4,4'-perfluoroisopropyridene diphthalic acid dianhydride, 3, 3', 4,4'-diphenylsulfone tetracarboxylic acid dianhydride, 9,9-bis (3,4-dicarboxyphenyl) fluorene dianhydride, dicyclohexyl-3,4,3', 4'-tetracarboxylic The non-thermoplastic polyimide film according to any one of claims 8 to 11, which comprises one or more compounds selected from acid dianhydride and ethylenediamine tetraacetichydride dianhydride. The non-thermoplastic polyimide film according to claims 8 to 12, wherein the solvent-soluble polyimide used for producing the non-thermoplastic polyimide film contains 2,2-bis (4-aminophenoxyphenyl) propane. A polyimide laminated film comprising forming a thermoplastic polyimide resin layer on at least one side of the non-thermoplastic polyimide film according to any one of claims 8 to 13.

Images