CN106796400B

CN106796400B - Laminated structure

Info

Publication number: CN106796400B
Application number: CN201580055745.0A
Authority: CN
Inventors: 宫部英和; 小池直之; 林亮; 横山裕
Original assignee: Taiyo Ink Mfg Co Ltd
Current assignee: Taiyo Holdings Co Ltd
Priority date: 2014-10-14
Filing date: 2015-10-13
Publication date: 2020-11-03
Anticipated expiration: 2035-10-13
Also published as: WO2016060137A1; KR20170069260A; JP6374521B2; TW201625078A; KR101959648B1; TWI685281B; CN106796400A; JPWO2016060137A1

Abstract

Provided is a structure which can satisfy the performance required as an insulating film of a flexible printed wiring board and is suitable for a process of simultaneously forming a bending portion and a mounting portion. Also disclosed is a flexible printed wiring board which is provided with such a cured product as a protective film, for example, a cover layer or a solder resist layer. A laminated structure body, a dry film and a flexible printed circuit board using the same, the laminated structure body having: the adhesive layer (A) is formed by an alkali developable resin composition, and the protective layer (B) is formed by a photosensitive resin composition on the adhesive layer (A), wherein the ratio of the film thickness of the adhesive layer (A) to the film thickness of the protective layer (B) is 0.5-50, and the ratio of the developing speed (a) of the adhesive layer (A) to the developing speed (B) of the protective layer (B) is 1.1-100.

Description

Laminated structure

Technical Field

The present invention relates to a laminated structure, and more particularly, to a laminated structure useful as an insulating film of a flexible printed circuit board, a dry film using the same, and a flexible printed circuit board.

Background

In recent years, with the miniaturization and thinning of electronic devices due to the spread of smart phones and tablet terminals, there is a growing need for a smaller space for a circuit board. Therefore, the flexible printed circuit board which can be stored in a bent state has been used in a wide range of applications, and the flexible printed circuit board also has been required to have a reliability as high as that of the conventional flexible printed circuit board.

In contrast, a hybrid process has been widely used in which a cover layer made of polyimide having excellent mechanical properties such as heat resistance and flexibility is used for a bending portion (flexible portion) (see, for example, patent documents 1 and 2), and a photosensitive resin composition having excellent electrical insulation properties and capable of being finely processed is used for a mounting portion (non-flexible portion) as an insulating film for ensuring insulation reliability of a flexible printed circuit board.

That is, a cover layer having a polyimide substrate excellent in mechanical properties such as heat resistance and flexibility requires processing by die pressing, and is therefore not suitable for fine wiring. Therefore, for a chip mounting portion requiring fine wiring, it is necessary to partially use an alkali development type photosensitive resin composition (solder resist) which can be processed by photolithography.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 62-263692

Patent document 2: japanese laid-open patent publication No. 63-110224

Disclosure of Invention

Problems to be solved by the invention

In this way, in the manufacturing process of the flexible printed circuit board, a mixed mounting process of a step of attaching the cover layer and a step of forming the solder resist layer has to be adopted, and there is a problem that the cost and the workability are poor.

In contrast, although it has been studied to apply an insulating film as a solder resist layer or an insulating film as a coverlay layer to both a solder resist layer and a coverlay layer of a flexible printed circuit board, a material that can sufficiently satisfy both required performances has not been put to practical use. In particular, for flexible printed wiring boards, there is a demand for materials that have both alkali developability required for insulating films as solder resists and mechanical properties such as heat resistance and flexibility required for insulating films as coverlays.

Accordingly, an object of the present invention is to provide a structure which satisfies the required performance as an insulating film of a flexible printed wiring board, is suitable for a process of simultaneously forming a bending portion and a mounting portion, and further provides a flexible printed wiring board including a cured product thereof as a protective film, for example, a cover layer or a solder resist layer.

Means for solving the problems

In order to solve the above problem, the present invention is characterized by comprising: the adhesive layer (A) is formed by an alkali developable resin composition, and the protective layer (B) is formed by a photosensitive resin composition on the adhesive layer (A), wherein the ratio of the film thickness of the adhesive layer (A) to the film thickness of the protective layer (B) is 0.5-50, and the ratio of the developing speed (a) of the adhesive layer (A) to the developing speed (B) of the protective layer (B) is 1.1-100.

In the laminated structure of the present invention, it is preferable that both the adhesive layer (a) and the protective layer (B) be patterned by light irradiation. In addition, the laminated structure of the present invention is useful for at least any one of a flexible portion and a non-flexible portion of a flexible printed circuit board, and more specifically, for at least any one of a cover lay layer, a solder resist layer, and an interlayer insulating material of a flexible printed circuit board.

In addition, the dry film of the present invention is characterized in that at least one surface of the laminate structure of the present invention is supported or protected by a film.

Further, the flexible printed wiring board of the present invention is characterized by comprising an insulating film formed by forming the layer of the laminated structure of the present invention directly on a flexible printed wiring board or by forming the layer of the laminated structure with the dry film of the present invention, patterning the layer by light irradiation, and forming a pattern at a time with a developer.

In the present invention, the term "pattern" refers to a pattern-like cured product, i.e., an insulating film.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a laminated structure can be realized which satisfies the performance required as an insulating film of a flexible printed circuit board and is also suitable for a process of simultaneously forming a bent portion and a mounting portion; and a dry film using the same; and, a flexible printed circuit board.

Drawings

Fig. 1 is a process diagram schematically showing an example of a method for manufacturing a flexible printed wiring board according to the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(laminated Structure)

The laminated structure of the present invention comprises: the adhesive layer (A) is formed by an alkali developable resin composition, and the protective layer (B) is formed by a photosensitive resin composition on the adhesive layer (A), wherein the ratio of the film thickness of the adhesive layer (A) to the film thickness of the protective layer (B) is 0.5-50, and the ratio of the developing speed (a) of the adhesive layer (A) to the developing speed (B) of the protective layer (B) is 1.1-100.

In order to perform patterning using an alkali developing solution, the resin composition needs to have alkali solubility. In the case of a laminated structure, if a resin composition having excellent heat resistance is used for the protective layer, it is difficult to impart solubility to the resin composition having excellent heat resistance, and therefore, the development speed is slowed, and as a result, patterning becomes difficult.

The present inventors have made extensive studies with attention paid to the film thicknesses and developing speeds of the protective layer and the adhesive layer in order to solve the above problems, and as a result, have found that the above problems can be solved by setting the ratio of the film thicknesses of the protective layer and the adhesive layer and the ratio of the developing speeds of the protective layer and the adhesive layer to the above ranges, respectively, and have completed the present invention.

Namely, it was found that: when a protective layer using a resin composition having a slower developing speed is laminated on an adhesive layer using a resin composition having a faster developing speed than the resin composition of the protective layer, and the ratio of the film thicknesses of the protective layer and the ratio of the developing speeds of the protective layer and the adhesive layer are set to the above ranges, the developing speed of the adhesive layer is increased even if the developing speed of the protective layer is slow and patterning by alkali development is difficult and residues are generated, and as a result, both layers can be completely washed away, and the developing speed of the entire laminated structure can be set within a realistic range.

In order to achieve a more satisfactory combination of alkali developability, heat resistance, flexibility and other mechanical properties, the film thickness ratio is 0.5 to 50, preferably 1.0 to 30, more preferably 2.0 to 10, and the development rate ratio is 1.1 to 100, preferably 2.0 to 50, more preferably 3.0 to 30.

When the ratio of the film thickness is 50 or less, the ratio of the heat-resistant protective layer (B) in the layer thickness of the laminated structure is large, and therefore, the developing property is good and sufficient heat resistance can be obtained. When a/B is 0.5 or more, the ratio of the adhesive layer (a) having good developability is large, and thus, the adhesive layer has good heat resistance and can be patterned by alkali development.

When the ratio of the developing speed is 1.1 or more, the developing speed of the adhesive layer (a) becomes relatively faster than that of the protective layer (B) which is difficult to develop, and thus patterning can be performed by alkali development. When a/b is 100 or less, the adhesive layer (a) has appropriate solubility in an alkaline aqueous solution and a stable pattern shape, and thus has good various properties such as plating resistance.

When the laminated structure is developed, the developing speed is represented by the following formula, where the time required for dissolving each of the protective layer and the adhesive layer in an alkaline aqueous solution is defined as the developing time [ sec ] and the film thickness of each layer is defined as the film thickness [ μm ].

Developing speed [ μm/sec ] - [ film thickness [ μm ]/developing time [ sec ]

(protective layer (B))

The composition of the photosensitive resin composition of the protective layer (B) is not particularly limited, and for example, a photocurable thermosetting resin composition containing a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, a compound having an ethylenically unsaturated bond, a photopolymerization initiator, and a thermally reactive compound, which have been conventionally used as a solder resist composition, can be used; a photosensitive thermosetting resin composition comprising a carboxyl group-containing resin, a photobase generator and a thermally reactive compound.

Among them, the protective layer (B) is preferably formed of a resin composition containing an alkali-soluble resin having an imide ring or an imide precursor skeleton, which is excellent in heat resistance and toughness.

In the present invention, the alkali-soluble resin having an imide ring or an imide precursor skeleton means a resin having an alkali-soluble group such as a carboxyl group or an acid anhydride group and an imide ring or an imide precursor skeleton. For introducing the imide ring or the imide precursor skeleton into the alkali-soluble resin, a known and commonly used method can be used. Examples thereof include: a resin obtained by reacting a carboxylic acid anhydride component with either or both of an amine component and an isocyanate component. The imidization may be performed by thermal imidization, may be performed by chemical imidization, or may be performed by using these in combination.

Among them, examples of the carboxylic anhydride component include: tetracarboxylic anhydride, tricarboxylic anhydride, etc., but are not limited to these anhydrides, and any derivatives thereof may be used as long as they are compounds having an acid anhydride group and a carboxyl group which react with an amino group and an isocyanate group. These carboxylic anhydride components may be used alone or in combination.

Examples of the tetracarboxylic anhydride include: pyromellitic dianhydride, 3 ', 4,4 ' -benzophenonetetracarboxylic dianhydride, 3 ', 4,4 ' -biphenyltetracarboxylic dianhydride, 4,4 ' -oxydiphthalic dianhydride, 1,2,3, 4-benzenetetracarboxylic dianhydride, 3 ', 4,4 ' -terphenyltetracarboxylic dianhydride, 3 ', 4,4 ' -quaterphenyltetracarboxylic dianhydride, 3 ', 4,4 ' -pentabiphenyltetracarboxylic dianhydride, methylene-4, 4 ' -bisphthalic dianhydride, 1-ethylidene-4, 4 ' -bisphthalic dianhydride, 2-propylidene-4, 4 ' -bisphthalic dianhydride, 1, 2-ethylidene-4, 4 ' -bisphthalic dianhydride, 1, 3-trimethylene-4, 4 ' -biphthalic dianhydride, 1, 4-tetramethylene-4, 4 ' -biphthalic dianhydride, 1, 5-pentamethylene-4, 4 ' -biphthalic dianhydride, thio-4, 4 ' -biphthalic dianhydride, sulfonyl-4, 4 ' -biphthalic dianhydride, 1, 3-bis (3, 4-dicarboxyphenyl) -1,1,3, 3-tetramethylsiloxane dianhydride, 1, 3-bis (3, 4-dicarboxyphenyl) benzene dianhydride, 1, 4-bis (3, 4-dicarboxyphenyl) benzene dianhydride, 1, 3-bis (3, 4-dicarboxyphenoxy) benzene dianhydride, 1, 4-bis (3, 4-dicarboxyphenoxy) benzene dianhydride, 1, 3-bis [ 2- (3, 4-dicarboxyphenyl) -2-propyl ] benzene dianhydride, 1, 4-bis [ 2- (3, 4-dicarboxyphenyl) -2-propyl ] benzene dianhydride, bis [ 3- (3, 4-dicarboxyphenoxy) phenyl ] methane dianhydride, 2,3,6, 7-naphthalenetetracarboxylic dianhydride, 1,2,5, 6-naphthalenetetracarboxylic dianhydride, 3,4,9, 10-perylenetetracarboxylic dianhydride, 2,3,6, 7-anthracenetetracarboxylic dianhydride, 1,2,7, 8-phenanthrenetetracarboxylic dianhydride, 1,2,3, 4-butanetetracarboxylic dianhydride, 1,2,3, 4-cyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, cyclohexane-1, 2,3, 4-tetracarboxylic dianhydride, Cyclohexane-1, 2,4, 5-tetracarboxylic dianhydride, 3 ', 4,4 ' -dicyclohexyltetracarboxylic dianhydride, carbonyl-4, 4 ' -bis (cyclohexane-1, 2-dicarboxylic acid) dianhydride, methylene-4, 4 ' -bis (cyclohexane-1, 2-dicarboxylic acid) dianhydride, 1, 2-ethylene-4, 4 ' -bis (cyclohexane-1, 2-dicarboxylic acid) dianhydride, 1-ethylidene-4, 4 ' -bis (cyclohexane-1, 2-dicarboxylic acid) dianhydride, 2-propylidene-4, 4 ' -bis (cyclohexane-1, 2-dicarboxylic acid) dianhydride, ethylene glycol bis (trimellitic acid dianhydride), 1,2- (ethylene) bis (trimellitic acid anhydride), 1,3- (trimethylene) bis (trimellitic anhydride), 1,4- (tetramethylene) bis (trimellitic anhydride), 1,5- (pentamethylene) bis (trimellitic anhydride), 1,6- (hexamethylene) bis (trimellitic anhydride), 1,7- (heptamethylene) bis (trimellitic anhydride), 1,8- (octamethylene) bis (trimellitic anhydride), 1,9- (nonamethylene) bis (trimellitic anhydride), 1,10- (decamethylene) bis (trimellitic anhydride), 1,12- (dodecamethylene) bis (trimellitic anhydride), 1,16- (hexadecamethylene) bis (trimellitic anhydride), 1,18- (octadecamethylene) bis (trimellitic anhydride), and the like.

Examples of the tricarboxylic acid anhydride include: trimellitic anhydride, nuclear hydrogenated trimellitic anhydride, and the like.

As amine components, it is possible to use: diamines such as aliphatic diamines and aromatic diamines; and polyamines such as aliphatic polyether amines, but are not limited to these amines. In addition, these amine components may be used alone or in combination.

Examples of the diamine include: p-phenylenediamine (PPD), 1, 3-diaminobenzene, 2, 4-tolylenediamine, 1-nucleus-containing diamines such as 2, 5-tolylenediamine and 2, 6-tolylenediamine, diaminodiphenyl ethers such as 4,4 ' -diaminodiphenyl ether, 3 ' -diaminodiphenyl ether and 3,4 ' -diaminodiphenyl ether, diaminodiphenyl ethers such as 4,4 ' -diaminodiphenylmethane, 3 ' -dimethyl-4, 4 ' -diaminobiphenyl, 2 ' -dimethyl-4, 4 ' -diaminobiphenyl, 3 ' -diaminodiphenyl ether, 3,4 ' -diaminodiphenyl ether, 4 ' -diaminodiphenyl ether, 3 ' -diaminodiphenyl sulfide, 3,4 ' -diaminodiphenyl sulfide and other 2-nucleus-containing diamines, such as p-phenylenediamine, 1, 3-diaminobenzene, 2, 4-tolylenediamine, 2, 5-tolylenediamine and 2, 6-tolyl, Aromatic diamines such as 3-nucleus diamines including 1, 3-bis (3-aminophenylsulfide) benzene, 1, 3-bis (4-aminophenylsulfide) benzene and 1, 4-bis (4-aminophenylsulfide) benzene, 3 ' -bis (3-aminophenoxy) biphenyl, 3 ' -bis (4-aminophenoxy) biphenyl, 4 ' -bis (3-aminophenoxy) biphenyl, 2-bis [ 3- (3-aminophenoxy) phenyl ] propane, 2-bis [ 3- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2-bis [4- (4-aminophenoxy) phenyl ] propane and the like, Aliphatic diamines such as 1, 2-diaminoethane, 1, 3-diaminopropane, 1, 4-diaminobutane, 1, 5-diaminopentane and 1, 6-diaminohexane, and examples of the aliphatic polyether amines include: and ethylene glycol and/or propylene glycol based polyamines. In addition, as described below, an amine having a carboxyl group may also be used.

Examples of the amine having a carboxyl group include: diaminobenzoic acids such as 3, 5-diaminobenzoic acid, 2, 5-diaminobenzoic acid, and 3, 4-diaminobenzoic acid; aminophenoxybenzoic acids such as 3, 5-bis (3-aminophenoxy) benzoic acid and 3, 5-bis (4-aminophenoxy) benzoic acid; carboxybiphenyl compounds such as 3,3 '-diamino-4, 4' -dicarboxybiphenyl; carboxydiphenylalkanes such as 3,3 '-diamino-4, 4' -dicarboxydiphenylmethane, 3 '-dicarboxydiphenyl-4, 4' -diaminodiphenylmethane and 2, 2-bis [ 4-amino-3-carboxyphenyl ] propane; carboxyl diphenyl ether compounds such as 3,3 '-diamino-4, 4' -dicarboxydiphenyl ether and 4,4 '-diamino-3, 3' -dicarboxydiphenyl ether; and diphenyl sulfone compounds such as 3,3 '-diamino-4, 4' -dicarboxydiphenyl sulfone and 4,4 '-diamino-3, 3' -dicarboxydiphenyl sulfone.

As the isocyanate component, there can be used: diisocyanates such as aromatic diisocyanates and isomers, polymers thereof, aliphatic diisocyanates, alicyclic diisocyanates and isomers thereof, and other general-purpose diisocyanates, but are not limited to these isocyanates. In addition, these isocyanate components may be used alone or in combination.

Examples of the diisocyanate include: aromatic diisocyanates such as 4, 4' -diphenylmethane diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, biphenyl diisocyanate, diphenylsulfone diisocyanate, and diphenylether diisocyanate, and aliphatic diisocyanates such as isomers, polymers, hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate thereof; or alicyclic diisocyanates and isomers obtained by hydrogenating aromatic diisocyanates, or other general-purpose diisocyanates.

The alkali-soluble resin having an imide ring or an imide precursor skeleton described above may have an amide bond. The amide bond may be an amide bond obtained by reacting an isocyanate with a carboxylic acid, or an amide bond obtained by another reaction. Further, the polymer may have a bond formed by other addition and condensation.

In addition, as the imide ring or imide precursor skeleton introduced into the alkali-soluble resin, there can be used a publicly known and commonly used alkali-soluble polymer, oligomer, or monomer having either or both of a carboxyl group and an acid anhydride group, and for example, a resin obtained by reacting these publicly known and commonly used alkali-soluble resins with the above-mentioned amine/isocyanate alone or in combination with the above-mentioned carboxylic acid anhydride component.

In the synthesis of such an alkali-soluble resin having an alkali-soluble group and an imide ring or an imide precursor skeleton, a known and commonly used organic solvent can be used. The organic solvent is not particularly limited in structure as long as it does not react with the carboxylic acid anhydride, amine, or isocyanate as the raw material and can dissolve the raw material. Among them, from the viewpoint of high solubility of the raw materials, preferred are: aprotic solvents such as N, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, and γ -butyrolactone.

The alkali-soluble resin having an alkali-soluble group such as a carboxyl group or an acid anhydride group and an imide ring or an imide precursor skeleton described above preferably has an acid value of 20 to 200mgKOH/g, more preferably 60 to 150mgKOH/g, in order to cope with the photolithography step. When the acid value is 20mgKOH/g or more, solubility to alkali increases, and developability becomes good, and further, the degree of crosslinking with a thermosetting component after light irradiation becomes high, and therefore, sufficient development contrast can be obtained. When the acid value is 200mgKOH/g or less, so-called thermal fogging in a POST exposure bake (POST exposure bake) step of PEB after light irradiation, which will be described later, can be suppressed, and a process margin (process margin) can be increased.

The molecular weight of the alkali-soluble resin is preferably 1000 to 100000, more preferably 2000 to 50000, in view of developability and cured coating properties. When the molecular weight is 1000 or more, sufficient development resistance and curing properties can be obtained after exposure to light and PEB. When the molecular weight is 100000 or less, the alkali solubility increases and the developability improves.

When the photobase generator is used for the resin composition containing the alkali-soluble resin having an imide ring or an imide precursor skeleton, the photobase generator and the thermally reactive compound are generally contained in addition to the alkali-soluble resin, and when the photopolymerization initiator is used, the photopolymerization initiator and the compound having an ethylenically unsaturated bond are contained in addition to the alkali-soluble resin. In addition, as the resin component, a carboxyl group-containing urethane resin, a carboxyl group-containing novolac resin, or the like may be used in combination.

The photobase generator is a compound that generates 1 or more basic substances that function as a catalyst for a polymerization reaction of a thermally reactive compound to be described later by changing a molecular structure or cleaving molecules thereof by irradiation with light such as ultraviolet light or visible light. Examples of the basic substance include: secondary amines, tertiary amines.

Examples of the photobase generator include: an alpha-aminoacetophenone compound; an oxime ester compound; and compounds having a substituent such as acyloxyimino group, N-formylated aromatic amino group, N-acylated aromatic amino group, nitrobenzylcarbamate group, alkoxybenzylcarbamate group, and the like. Among them, oxime ester compounds and α -aminoacetophenone compounds are preferable. As the α -aminoacetophenone compound, a compound having 2 or more nitrogen atoms is particularly preferable.

The molecules of the alpha-amino acetophenone compound have benzoin ether bonds, and when the alpha-amino acetophenone compound is irradiated by light, intramolecular cracking occurs to generate an alkaline substance (amine) which plays a role in curing catalysis. As specific examples of the α -aminoacetophenone compound, there can be used: commercially available compounds such as (4-morpholinobenzoyl) -1-benzyl-1-dimethylaminopropane (IRGACURE 369, trade name, manufactured by BASF japanld., inc.), 4- (methylthiobenzoyl) -1-methyl-1-morpholinoethane (IRGACURE 907, trade name, manufactured by BASF JAPAN ltd., inc.), 2- (dimethylamino) -2- [ (4-methylphenyl) methyl ] -1- [4- (4-morpholino) phenyl ] -1-butanone (IRGACURE 379, trade name, manufactured by BASF JAPAN ltd., inc.), and solutions thereof.

The oxime ester compound may be any compound that generates a basic substance by light irradiation. Examples of the oxime ester compound include commercially available products such as: CGI-325 manufactured by BASF JAPAN LTD, IRGACURE OXE01, IRGACURE OXE02, N-1919 manufactured by ADEKA CORPORATION, NCI-831, and the like. Further, a compound having 2 oxime ester groups in the molecule as described in Japanese patent No. 4344400 can also be preferably used.

Such photobase generators may be used alone in 1 kind, or in combination of 2 or more kinds. The amount of the photobase generator to be blended in the resin composition is preferably 0.1 to 40 parts by mass, more preferably 0.1 to 30 parts by mass, per 100 parts by mass of the thermally reactive compound. When the amount is 0.1 parts by mass or more, the contrast of the development resistance of the irradiated portion/non-irradiated portion can be favorably obtained. When the amount is 40 parts by mass or less, the properties of the cured product are improved.

The thermally reactive compound is a resin having a functional group capable of undergoing a curing reaction by heat, and examples thereof include: epoxy resins, polyfunctional oxetane compounds, and the like.

The epoxy resin is a resin having an epoxy group, and any known resin can be used. Specifically, there may be mentioned: a 2-functional epoxy resin having 2 epoxy groups in the molecule, a polyfunctional epoxy resin having a plurality of epoxy groups in the molecule, and the like. The epoxy compound may be a hydrogenated 2-functional epoxy compound.

Examples of the epoxy resin include: bisphenol a type epoxy resin, brominated epoxy resin, novolac type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol a type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin, alicyclic epoxy resin, trihydroxyphenyl methane type epoxy resin, bixylenol type epoxy resin or biphenol type epoxy resin or a mixture thereof; bisphenol S type epoxy resins, bisphenol a novolac type epoxy resins, tetrahydroxyphenyl ethane type epoxy resins, heterocyclic epoxy resins, phthalic acid diglycidyl ester resins, tetraglycidyl xylenol ethane resins, naphthyl-containing epoxy resins, epoxy resins having a dicyclopentadiene skeleton, glycidyl methacrylate copolymer epoxy resins, epoxy resins copolymerized from cyclohexylmaleimide and glycidyl methacrylate, CTBN-modified epoxy resins, and the like.

These epoxy resins may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

The amount of the thermally reactive compound to be blended is preferably 1:0.1 to 1:10 in terms of equivalent ratio to the alkali-soluble resin (alkali-soluble group such as carboxyl group: thermally reactive group such as epoxy group). By setting the compounding ratio in such a range, development becomes favorable, and a fine pattern can be easily formed. The equivalent ratio is more preferably 1:0.2 to 1: 5.

As the photopolymerization initiator, known photopolymerization initiators can be used, and examples thereof include: α -aminoacetophenone-based photopolymerization initiator, acylphosphine oxide-based photopolymerization initiator, benzoin compound, acetophenone compound, anthraquinone compound, thioxanthone compound, ketal compound, benzophenone compound, tertiary amine compound, xanthone compound, and the like.

As the compound having an ethylenically unsaturated bond, known compounds can be used, and examples thereof include: hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; monoacrylates or diacrylates of glycols such as ethylene glycol, methoxyethylene glycol, polyethylene glycol, and propylene glycol; polyhydric alcohols such as hexanediol, trimethylolpropane, pentaerythritol, dipentaerythritol, and trishydroxyethyl isocyanurate, and polyvalent acrylates such as ethylene oxide adducts and propylene oxide adducts thereof; acrylic esters such as phenoxy acrylate, bisphenol a diacrylate, and ethylene oxide adducts and propylene oxide adducts of these phenols.

(adhesive layer (A))

As the alkali developable resin composition constituting the adhesive layer (a), any composition may be used as long as it contains a resin that contains 1 or more functional groups among a phenolic hydroxyl group, a thiol group, and a carboxyl group and is developable with an alkali solution, and a photocurable resin composition or a thermosetting resin composition may be used. Preferably, the resin composition contains a compound having 2 or more phenolic hydroxyl groups, a carboxyl group-containing resin, a compound having a phenolic hydroxyl group and a carboxyl group, and a compound having 2 or more thiol groups, and known and commonly used compounds can be used.

Specifically, for example, a photocurable thermosetting resin composition conventionally used as a solder resist composition, which comprises: a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, a compound having an ethylenically unsaturated bond, a photopolymerization initiator, and a thermally reactive compound. In addition, a resin composition containing a carboxyl group-containing urethane resin, a carboxyl group-containing resin, a photobase generator, and a thermosetting component may also be used. The resin composition is as follows: the polyurethane resin having a carboxyl group and the thermosetting component are subjected to an addition reaction by heating after exposure using a base generated from the photobase generator as a catalyst, and an unexposed portion is removed by an alkali solution, whereby development can be performed.

As each material constituting the resin composition used for the adhesive layer (a), a known and commonly used material can be used, and the material used for the protective layer (B) can be similarly used.

The resin composition used for the adhesive layer (a) and the protective layer (B) may contain a known and commonly used polymer resin in order to improve flexibility and dry-to-touch properties of the resulting cured product. Examples of such a polymer resin include: cellulose-based, polyester-based, phenoxy resin-based, polyvinyl acetal-based, polyvinyl butyral-based, polyamide-based, polyamideimide-based binder polymers, block copolymers, elastomers, and the like. The polymer resin may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

In the resin composition used for the adhesive layer (a) and the protective layer (B), an inorganic filler may be blended in order to suppress curing shrinkage of a cured product and improve properties such as adhesion and hardness. Examples of such inorganic fillers include: barium sulfate, amorphous silica, fused silica, spherical silica, talc, clay, magnesium carbonate, calcium carbonate, alumina, aluminum hydroxide, silicon nitride, aluminum nitride, boron nitride, Nojenberg silica, and the like.

In the resin composition used for the adhesive layer (a) and the protective layer (B), an organic solvent may be used for preparing the resin composition and for adjusting the viscosity for application to a substrate or a carrier film. Examples of such organic solvents include: ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, petroleum solvents, and the like. Such organic solvents may be used alone in 1 kind, or may be used in the form of a mixture of 2 or more kinds.

The resin composition used for the adhesive layer (a) and the protective layer (B) may further contain, if necessary, components such as a colorant, a mercapto compound, an adhesion promoter, an antioxidant, and an ultraviolet absorber. The components may be those commonly used in the field of electronic materials. In addition, it is possible to suitably compound: known and commonly used additives such as a thickener such as fine powder silica, hydrotalcite, organobentonite, and montmorillonite, a defoaming agent such as silicone-based, fluorine-based, and polymer-based ones, a leveling agent, a silane coupling agent, and a rust preventive.

In the laminated structure of the present invention, the adhesive layer (a) is preferably thicker than the protective layer (B) from the viewpoint of conformability to copper circuits.

The laminated structure of the present invention can be used for at least one of a flexible portion and a non-flexible portion of a flexible printed wiring board, and preferably both of them, and thus a flexible printed wiring board having sufficient durability against bending can be obtained and cost performance and workability can be improved. Specifically, the laminated structure of the present invention can be used for at least one of a cover lay layer, a solder resist layer, and an interlayer insulating material of a flexible printed circuit board.

(method of manufacturing Flexible printed Circuit Board)

In the present invention, a layer of the above laminated structure is formed directly or via a dry film on a flexible printed circuit substrate, and patterned by light irradiation, and a developing solution is used to form a pattern at a time to form an insulating film, thereby obtaining a flexible printed circuit board. In the case of the laminated structure comprising the adhesive layer (a) and the protective layer (B), the ratio of the film thicknesses of the protective layer and the adhesive layer and the ratio of the developing rates of the protective layer and the adhesive layer are respectively set within the above ranges, and therefore, the present invention can satisfactorily achieve both of alkali developability, heat resistance, and mechanical properties such as flexibility.

Hereinafter, an example of the method for producing the flexible printed wiring board of the present invention from the laminated structure of the present invention will be described based on the process diagram shown in fig. 1, in the case where the resin composition containing the photobase generator and the thermally reactive compound is used for both the adhesive layer (a) and the protective layer (B). When a photocurable thermosetting resin composition containing a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, a compound having an ethylenically unsaturated bond, a photopolymerization initiator, and a thermally reactive compound, which is used as a conventional solder resist composition, is used, the same steps as those for a solder resist layer can be employed.

[ laminating Process ]

The lamination step is a step of forming the laminated structure of the present invention on a base material. The laminating step in fig. 1 shows a state in which a laminated structure composed of an adhesive layer 3 and a protective layer 4 is formed on a flexible printed circuit substrate 1 on which a copper circuit 2 is formed, and the adhesive layer 3 is formed of an alkali-developable resin composition.

Among them, each layer constituting the laminated structure can be formed directly by, for example, a method of applying resin compositions constituting the adhesive layer 3 and the protective layer 4 in this order on a base material and drying the resin compositions; or by sequentially laminating the resin compositions constituting the adhesive layer 3 and the protective layer 4 in the form of dry films on the base material. Alternatively, the laminate may be formed by laminating a dry film-type laminate structure having a 2-layer structure on a substrate. At this time, at least one surface of the laminated structure may be supported or protected by a thin film. As the film to be used, a plastic film peelable from a laminated structure can be used. The thickness of the thin film is not particularly limited, but is usually suitably selected within the range of 10 to 150 μm. The interfaces between the layers may also be fused from the viewpoint of the strength of the coating film.

The method for coating the substrate with the resin composition may be any known method such as a blade coater, a lip coater, a comma coater, or a film coater. The drying method may be a method of bringing hot air in a dryer into convective contact with each other by using a device having a heat source using a heating method of steam, such as a hot air circulation drying furnace, an IR furnace, a hot plate, or a convection oven; and a method of blowing the gas to the support body through the nozzle.

The substrate is a flexible printed circuit substrate on which a circuit is formed in advance. In addition, a further layer may be provided between the adhesive layer 3 and the protective layer 4 in order to obtain other effects than the desired effects.

[ light irradiation Process ]

The light irradiation step is as follows: the photobase generator contained in the resin composition is activated by light irradiation in a negative pattern, thereby curing the irradiated portion. In this light irradiation step, a mask 5 is disposed on the protective layer 4, and light irradiation is performed in a negative pattern shape to activate the photobase generator contained in the resin composition, thereby curing the light irradiated portion.

In this step, the photobase generator is destabilized by the base generated in the light irradiation section, and a basic substance (hereinafter, may be simply referred to as "base") is generated from the photobase generator. It is considered that by generating the alkali in this manner and chemically growing the alkali to the deep part of each layer, sufficient curing to the deep part of each layer can be achieved. In the subsequent thermal curing, since the alkali acts as a catalyst for the addition reaction of the alkali-developable resin and the thermally reactive compound and the addition reaction proceeds, the layers are thermally cured sufficiently to the deep part in the light irradiation part. In this case, the curing of the resin composition is, for example, a ring-opening reaction of epoxy by a thermal reaction, and therefore, strain and curing shrinkage can be suppressed as compared with the case of proceeding by a photoreaction.

As a light irradiator used for light irradiation, a direct drawing device (for example, a laser direct imaging device which directly draws an image with a laser beam by CAD data from a computer), a light irradiator equipped with a metal halide lamp, a light irradiator equipped with a (ultra) high-pressure mercury lamp, a light irradiator equipped with a mercury short-arc lamp, or a direct drawing device using an ultraviolet lamp such as a (ultra) high-pressure mercury lamp can be used. The mask for pattern-like light irradiation is a negative mask.

As the active energy ray, a laser beam or scattered light having a maximum wavelength in the range of 350 to 410nm is preferably used. By setting the maximum wavelength to this range, the photobase generator can be efficiently activated. The laser beam in this range may be used, and the laser type may be gas laser or solid laser. The amount of light irradiation varies depending on the film thickness, and can be usually set to 100 to 1500mJ/cm²Preferably 300 to 1500mJ/cm²Within the range of (1).

[ heating Process ]

In the heating step, the light-irradiated portion is cured by heating, and the light-irradiated portion can be cured to a deep portion by the alkali generated in the light-irradiating step. This heating step is a step of heating the adhesive layer 3 and the protective layer 4 after the light irradiation step to cure the light-irradiated portion, and is a step called a so-called PEB (POST EXPOSURE BAKE) step. Thus, the respective layers are sufficiently cured to the deep part by the alkali generated in the light irradiation step, and a pattern layer having excellent curing properties can be obtained.

For example, in the heating step, the heating is preferably performed at a temperature lower than the heat release starting temperature or the heat release peak temperature of the resin composition that has not been irradiated and higher than the heat release starting temperature or the heat release peak temperature of the resin composition that has been irradiated with light. By thus heating, only the light irradiation portion can be selectively cured.

The heating temperature in this case is preferably a temperature at which the irradiated portion of the resin composition is thermally cured, but the unirradiated portion is not thermally cured. The heating temperature is, for example, 80 to 140 ℃. By setting the heating temperature to 80 ℃ or higher, the light irradiation part can be sufficiently cured. On the other hand, by setting the heating temperature to 140 ℃ or lower, only the light irradiation part can be selectively cured. The heating time is, for example, 10 to 100 minutes. The heating method is the same as the above-described drying method. In addition, since alkali derived from the photobase generator is not generated in the non-irradiated portion, thermosetting is suppressed.

[ developing Process ]

In the developing step, the non-irradiated portion is removed by alkali development to form a negative pattern layer. The developing step in fig. 1 is a step of developing the adhesive layer 3 and the protective layer 4 with an aqueous alkali solution to remove the non-irradiated portion and form a negative pattern layer. As the developing method, known methods such as a dipping method, a shower method, a spray method, and a brush method can be used. As the developer, an alkaline aqueous solution such as an amine, e.g., potassium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia, ethanolamine, etc., a tetramethylammonium hydroxide aqueous solution (TMAH), etc., or a mixture thereof can be used.

[ 2 nd light irradiation step ]

After the developing step, a 2 nd light irradiation step is preferably included. The 2 nd light irradiation step is a step of irradiating ultraviolet rays as necessary so as to activate the photobase generator remaining in the pattern layer in the light irradiation step without being activated and to generate a base. The wavelength and the light irradiation amount (exposure amount) of the ultraviolet ray in the 2 nd light irradiation step may be the same as or different from those in the above light irradiation step. The amount of light irradiation (exposure amount) is, for example, 150 to 2000mJ/cm²。

[ Heat curing Process ]

After the development step, a thermal curing (post-curing) step is preferably further included. The thermosetting step is a step of performing thermosetting (post-curing) as necessary in order to sufficiently thermally cure the pattern layer. When the 2 nd light irradiation step and the thermosetting step are both performed after the development step, the thermosetting step is preferably performed after the 2 nd light irradiation step.

In the thermosetting step, the pattern layer is thermally cured sufficiently by the alkali generated from the photobase generator in the light irradiation step or in the light irradiation step and the 2 nd light irradiation step. At the time of the thermosetting step, since the non-irradiated portion is already removed, the thermosetting step may be performed at a temperature equal to or higher than the curing reaction start temperature of the non-irradiated resin composition. Thereby, the pattern layer can be sufficiently thermally cured. The heating temperature is, for example, 150 ℃ or higher.

Examples

The present invention will be described in further detail below with reference to examples.

(Synthesis example 1)

< Synthesis of alkali-soluble resin having imide Ring >

In a separable three-necked flask equipped with a stirrer, a nitrogen inlet tube, a bypass tube and a condenser, 12.5g of 3, 5-diaminobenzoic acid, 8.2g of 2,2 '-bis [4- (4-aminophenoxy) phenyl ] propane, 30g of NMP30g, 30g of gamma-butyrolactone, 27.9g of 4, 4' -oxydiphthalic anhydride and 3.8g of trimellitic anhydride were charged, and the mixture was stirred at 100rpm for 4 hours at room temperature under a nitrogen atmosphere. Subsequently, 20g of toluene was added thereto, and the mixture was stirred at a silicon bath temperature of 180 ℃ and 150rpm for 4 hours while removing toluene and water by distillation to obtain an alkali-soluble resin solution containing an imide ring. Then, γ -butyrolactone was added so that the solid content became 30 mass%. The resin solution thus obtained had an acid value of the solid content of 86mgKOH/g and Mw of 10000.

(Synthesis example 2)

< Synthesis of carboxyl group-containing polyurethane resin >

Into a reaction vessel equipped with a stirrer, a thermometer and a condenser were charged 2400g (3 moles) of a polycarbonate diol derived from 1, 5-pentanediol and 1, 6-hexanediol (manufactured by Asahi Kasei Chemicals Corporation, T5650J, number average molecular weight 800), 603g (4.5 moles) of dimethylolpropionic acid, and 2-hydroxyethylacrylate as a monohydroxy compound238g (2.6 mol) of ester. Subsequently, 1887g (8.5 mol) of isophorone diisocyanate as a polyisocyanate was charged, the mixture was heated to 60 ℃ while stirring, and then, the mixture was heated again at a point at which the temperature in the reaction vessel started to decrease, and the stirring was continued at 80 ℃ to confirm the absorption spectrum (2280 cm) of the isocyanate group by infrared absorption spectrum^-1) The reaction was terminated after disappearance. Next, carbitol acetate was added so that the solid content became 50 mass%. The solid content of the resulting carboxyl group-containing polyurethane resin had an acid value of 50 mgKOH/g.

< preparation of resin composition for Forming layers >

The materials shown in examples and comparative examples were compounded according to the formulations shown in tables 1 and 2 below, premixed with a stirrer, and kneaded with a three-roll mill to prepare resin compositions constituting the adhesive layer and the protective layer. The values in the table are parts by mass unless otherwise specified.

< formation of adhesive layer (A) >

A flexible printed circuit substrate having a copper thickness of 18 μm and formed with a circuit was prepared and subjected to pretreatment using CB-801Y manufactured by Mec Corporation. Then, the resin compositions for the respective adhesive layers were applied to the flexible printed circuit substrate subjected to the pretreatment so that the film thickness after drying became the film thickness shown in tables 1 and 2 below. Then, the resultant was dried at 80 ℃ for 30 minutes in a hot air circulation drying furnace to form an adhesive layer (A) made of the resin composition. In comparative example 1, no adhesive layer was formed.

< formation of protective layer (B) >

The resin compositions for the respective protective layers were applied to the adhesive layer (a) so that the film thickness after drying became the film thickness shown in tables 1 and 2 below. Then, the resultant was dried at 80 ℃ for 30 minutes in a hot air circulation drying furnace to form a protective layer (B) made of the resin composition.

The total thickness of the adhesive layer (A) and the protective layer (B) was 20 μm.

< measurement of film thickness >

The film thickness was measured using a micrometer MDC-25MX manufactured by Mitutoyo corporation.

< measurement of developing speed >

Each resin composition was applied to a flexible printed circuit substrate having a copper thickness of 18 μm and formed with a circuit, and dried in a hot air circulation type drying oven at 80 ℃/30 minutes. Then, the substrate was immersed in a 1 mass% aqueous solution of sodium carbonate at 30 ℃ and the time until the coating film was dissolved was measured. The developing speed is represented by the following formula, where the time until the coating film is dissolved is defined as the developing time [ second ] and the film thickness is defined as the film thickness [ μm ].

Developing speed [ μm/sec ] - [ film thickness [ μm ]/developing time [ sec ]

< alkali developability, solder Heat resistance, and gold plating resistance >

The substrate having the obtained laminated structure was subjected to HMW680GW (metal halide lamp, scattered light) made by ORC CORPORATION, and the exposure amount was 500mJ/cm²The light irradiation is performed in a negative pattern. Subsequently, heat treatment was performed at 90 ℃ for 60 minutes. Then, the substrate was immersed in a 1 mass% aqueous solution of sodium carbonate at 30 ℃ and developed for 3 minutes, and the alkali developability was evaluated. The evaluation was performed visually and evaluated according to the following criteria.

O: can be developed without residue

X: with development residues

Subsequently, the resultant was heat-treated at 150 ℃ for 60 minutes in a hot air circulation drying furnace to obtain a pattern-like cured coating film. The obtained cured coating film was coated with rosin-based flux on the evaluation substrate, immersed in a solder bath set at 260 ℃ in advance for 20 seconds (10 seconds × 2 times), cleaned with isopropyl alcohol, and then subjected to a peel test using a transparent tape, and expansion, peeling, and discoloration of the resist layer were evaluated according to the following criteria.

O: no change at all was confirmed

X: with swelling, peeling

The cured coating film obtained was plated using commercially available electroless nickel plating baths and electroless gold plating baths at 80 to 90 ℃ under conditions of nickel 5 μm and gold 0.05 μm. The plated evaluation substrate was visually evaluated for the presence or absence of plating penetration.

O: without infiltration

X: penetration was confirmed between the substrate and the coating film

The results are shown in tables 1 and 2 below.

[ Table 1]

In addition, the method is as follows: synthesis of the resin of example 1

In addition, 2: synthesis of the resin of example 2

And (2) in color: carboxyl group-containing novolak resin (acid value 104mgKOH/g, Bis A/phenol novolak resin)

In addition, 4: ethoxylated bisphenol A dimethacrylate (manufactured by Xinzhongcun chemical industry Co., Ltd.)

In addition, the method is as follows: dicyclopentadiene type epoxy resin (DIC Co., Ltd.)

In addition, 6: bisphenol A type epoxy resin (molecular weight 400) (Mitsubishi chemical corporation)

In addition, the color is 7: oxime photobase generators (BASF JAPAN LTD. manufactured)

In addition, the color is 8: 2- (dimethylamino) -2- [ (4-methylphenyl) methyl ] -1- [4- (4-morpholinyl) phenyl ] -1-butanone (manufactured by BASF JAPAN LTD., Ltd.)

In addition, the color is 9: bisphenol F type acid-modified epoxy acrylate (manufactured by Nippon Kabushiki Kaisha)

In addition, the color is 10: barium sulfate (made by Sakai chemical industry Co., Ltd.)

[ Table 2]

As is apparent from the evaluation results shown in tables 1 and 2 above: the flexible printed circuit board of the example showed good developability and heat resistance. In contrast, it is known that: comparative example 1 is composed only of a protective layer of a resin composition having an imide ring, and therefore, although good in heat resistance, poor in developability, and cannot be developed with ordinary sodium carbonate. In comparative example 2, the adhesive layer was thin, and the ratio of the film thicknesses of the adhesive layer and the protective layer deviated from the range of the present invention, so that the heat resistance was good, but the developability was still poor as a result. Further, in comparative example 3, since the ratio of the film thicknesses of the adhesive layer and the protective layer deviates from the range of the present invention, the heat resistance was poor although the developability was good. In comparative example 4, although the ratio of the film thickness was within the range of the present invention, the developing speeds of the adhesive layer and the protective layer were the same, and the ratio of the developing speeds of the adhesive layer and the protective layer was out of the range of the present invention, and as a result, the developability was still poor. In comparative example 5, the ratio of the developing speed was out of the range of the present invention, and therefore, the developability was good, but as a result, the heat resistance was poor.

Description of the reference numerals

1 Flexible printed Circuit substrate

2 copper circuit

3 adhesive layer

4 protective layer

5 mask

Claims

1. A laminated structure body is characterized by comprising: an adhesive layer (A) formed from an alkali-developable thermosetting resin composition containing an alkali-developable resin containing 1 or more functional groups selected from a phenolic hydroxyl group, a thiol group and a carboxyl group and a heat-reactive compound, and a protective layer (B) formed on the adhesive layer (A) and formed from a photosensitive thermosetting resin composition containing an alkali-soluble resin having an imide ring or an imide precursor skeleton and a heat-reactive compound,

the ratio of the film thickness of the adhesive layer (A) to the film thickness of the protective layer (B) is 0.5 to 50,

the ratio of the developing speed (a) of the adhesive layer (A) to the developing speed (B) of the protective layer (B) is 1.1 to 100.

2. The laminated structure body according to claim 1, wherein the adhesive layer (a) and the protective layer (B) are each patternable by light irradiation.

3. The laminated structure body according to claim 1, which is used for at least any one of a flexible portion and a non-flexible portion of a flexible printed circuit board.

4. The laminated structure body according to claim 1, for use in at least any one of a cover layer, a solder resist layer and an interlayer insulating material of a flexible printed circuit board.

5. A dry film characterized in that at least one surface of the laminate structure according to any one of claims 1 to 4 is supported or protected by a film.

6. A flexible printed wiring board comprising an insulating film obtained by forming a layer of the laminated structure according to any one of claims 1 to 4 directly or a layer of the laminated structure formed from the dry film according to claim 5 on a flexible printed wiring board, patterning the layer by light irradiation, and forming a pattern at a time by a developing solution.