CN106796400A - layered structure - Google Patents

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

layered structure

technical field

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

Background technique

In recent years, with the miniaturization and thinning of electronic equipment brought about by the popularization of smartphones and tablet terminals, it has gradually become necessary to reduce the space of circuit boards. Therefore, the use of flexible printed wiring boards that can be bent and stored is expanding, and the above-mentioned flexible printed wiring boards are also required to have reliability higher than hitherto.

In this regard, at present, as an insulating film for ensuring the insulation reliability of flexible printed circuit boards, polyimide, which has excellent mechanical properties such as heat resistance and flexibility, is widely used as a base for bending parts (flexure parts). A coating process in which a photosensitive resin composition that is excellent in electrical insulation and capable of fine processing is used for the cover layer (for example, refer to Patent Documents 1 and 2) and the mounting portion (non-flexing portion).

That is, a cover layer based on a polyimide having excellent mechanical properties such as heat resistance and flexibility needs to be processed by die pressing, and thus is not suitable for fine wiring. Therefore, it is necessary to partially use an alkali-developing type photosensitive resin composition (soldering resist) that can be processed by photolithography in combination for a chip mounting portion that requires fine wiring.

prior art literature

patent documents

Patent Document 1: Japanese Patent Application Laid-Open No. 62-263692

Patent Document 2: Japanese Patent Application Laid-Open No. 63-110224

Contents of the invention

The problem to be solved by the invention

In this way, in the manufacturing process of the flexible printed circuit board, it is necessary to adopt a mixed process of the process of laminating the cover layer and the process of forming the solder resist layer, and there is a problem of poor cost and operability.

In this regard, the application of an insulating film as a solder resist layer or an insulating film as a cover layer to both the solder resist layer and the cover layer of a flexible printed circuit board has been studied, but materials that can sufficiently satisfy the required performance of both have not yet been developed. Realize practicality. Especially for flexible printed circuit boards, it is necessary to achieve both the alkali developability required for the insulating film as the solder resist layer and the mechanical properties such as heat resistance and flexibility required for the insulating film as the cover layer. raw materials.

Therefore, the object of the present invention is to provide a structure that satisfies the required performance as an insulating film of a flexible printed circuit board, is also suitable for the process of simultaneously forming a bending portion and a mounting portion, and provides a structure having its cured product as a protective film. Films, such as coverlays or solder masks for flexible printed circuit boards.

solutions to problems

In order to solve the aforementioned problems, the present invention is characterized by comprising: an adhesive layer (A) formed of an alkali-developable resin composition; and a protective layer formed on the adhesive layer (A) formed of a photosensitive resin composition. layer (B), the film thickness ratio of the aforementioned adhesive layer (A) to the aforementioned protective layer (B) is A/B=0.5 to 50, and the developing speed (a) of the aforementioned adhesive layer (A) and the aforementioned protective layer (B) The ratio of the developing speed (b) is a/b=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) can be patterned by light irradiation. In addition, the laminated structure of the present invention can be suitably used for at least any of the flexible printed wiring board's flexure and non-flexible sections, specifically, for a flexible printed wiring board's cover layer, solder resist, and The use of at least any one of the interlayer insulating materials is useful.

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

Furthermore, the flexible printed circuit board of the present invention is characterized in that it includes an insulating film in which the layer of the above-mentioned laminated structure of the present invention is directly formed on the flexible printed circuit board, or a layer of the above-mentioned dry film of the present invention is used to form a laminate. The layer of the structure is patterned by light irradiation, and the pattern is formed at one time using a developer.

In addition, in this invention, a "pattern" means the hardened|cured material of a pattern shape, ie, an insulating film.

The effect of the invention

According to the present invention, it is possible to realize a laminated structure that satisfies the required performance of an insulating film as a flexible printed circuit board and is also suitable for a process of simultaneously forming a bending portion and a mounting portion; a dry film using the same; and a flexible printed circuit board.

Description of 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 has an adhesive layer (A) formed of an alkali-developable resin composition, and a protective layer (B) formed of a photosensitive resin composition formed on the adhesive layer (A), The film thickness ratio of the adhesive layer (A) to the protective layer (B) is A/B=0.5 to 50, and the developing speed (a) of the adhesive layer (A) is different from the developing speed of the protective layer (B). The ratio of speed (b) is a/b=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 with excellent heat resistance is used for the protective layer, it is difficult to impart solubility to the resin composition with excellent heat resistance, so the development speed becomes slow, and as a result, patterning occurs. problem that becomes difficult.

In order to solve this problem, the inventors of the present invention focused on the film thickness and developing speed of the protective layer and the adhesive layer and conducted intensive research. The ratios of the developing speeds of the adhesive layers were within the above-mentioned ranges, and the above-mentioned problems could be solved, and the present invention has been accomplished thus far.

That is, it was found that a protective layer using a resin composition having a slow developing speed is laminated on an adhesive layer using a resin composition having a fast developing speed compared with the resin composition of the protective layer, and the ratio of the film thicknesses of the two When the ratios to the developing speed are within the above-mentioned ranges, even if the developing speed of the protective layer is slow, it is difficult to pattern by alkali development, and residues appear, the developing speed of the adhesive layer is also fast, and as a result, both can be completely rinsed, making The development speed of the entire laminated structure is within a realistic range.

In order to achieve better balance between alkali developability and mechanical properties such as heat resistance and flexibility, the ratio of the aforementioned film thickness is A/B=0.5 to 50, preferably A/B=1.0 to 30, more preferably A/B =2.0-10, Moreover, the ratio of the said developing speed is a/b=1.1-100, Preferably it is a/b=2.0-50, More preferably, it is a/b=3.0-30.

When the ratio of the film thickness is A/B=50 or less, the ratio of the heat-resistant protective layer (B) in the layer thickness of the laminated structure is large, so that the developability is good and sufficient heat resistance can also be obtained. sex. Moreover, since the ratio of the adhesive layer (A) with favorable developability is large when it is A/B=0.5 or more, heat resistance is favorable and patterning by alkali image development is possible.

When the ratio of development speed is a/b=1.1 or more, since the development speed of an adhesive layer (A) becomes relatively fast with respect to the protective layer (B) which development is difficult, patterning by alkali image development is possible. Moreover, when it is a/b=100 or less, the solubility to the aqueous alkali solution of an adhesive layer (A) becomes appropriate, and a pattern shape is stable, Therefore Various characteristics, such as plating resistance, also become favorable.

When developing a laminated structure, the time required to dissolve each layer of the protective layer and the adhesive layer in an alkaline aqueous solution is defined as the developing time [second], and the film thickness of each layer is defined as the film thickness [μm], the developing speed represented by the following formula.

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. For example, a composition containing a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin and having an ethylenically unsaturated bond, which is conventionally used as a solder resist composition, can be used. A photocurable thermosetting resin composition comprising a compound, a photopolymerization initiator and a thermally reactive compound; a photosensitive thermosetting resin composition comprising a carboxyl-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 excellent in heat resistance and toughness.

In the present invention, the alkali-soluble resin having an imide ring or an imide precursor skeleton refers to 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 the introduction of the imide ring or the imide precursor skeleton into the alkali-soluble resin, known and commonly used methods can be used. For example, resin obtained by making a carboxylic anhydride component react with either one or both of an amine component and an isocyanate component is mentioned. Imidation may be performed by thermal imidation, chemical imidation may be performed, and it may manufacture using these in combination.

Among them, the carboxylic anhydride component includes tetracarboxylic anhydride, tricarboxylic anhydride, etc., but is not limited to these anhydrides, and derivatives thereof are included as long as they have an acid anhydride group and a carboxyl group that react with an amino group or an isocyanate group. Can be used inside. In addition, these carboxylic anhydride components can be used individually or in combination.

Examples of tetracarboxylic anhydrides include pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetra Carboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,3",4,4"-terphenyltetracarboxylic dicarboxylic acid anhydride, 3,3'",4,4'"-quaterphenyltetracarboxylic dianhydride, 3,3"",4,4""-pentaphenyltetracarboxylic dianhydride, methylene-4, 4'-Diphthalic dianhydride, 1,1-ethylidene-4,4'-diphthalic dianhydride, 2,2-propylidene-4,4'-diphthalic acid Dianhydride, 1,2-ethylene-4,4'-diphthalic dianhydride, 1,3-trimethylene-4,4'-bisphthalic dianhydride, 1,4-tetra Methylene-4,4'-bisphthalic dianhydride, 1,5-pentamethylene-4,4'-bisphthalic dianhydride, Thio-4,4'-bisphthalic dianhydride Dicarboxylic dianhydride, sulfonyl-4,4'-diphthalic dianhydride, 1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethylsiloxane Alkanedianhydride, 1,3-bis(3,4-dicarboxyphenyl)phthalic anhydride, 1,4-bis(3,4-dicarboxyphenyl)phthalic anhydride, 1,3-bis(3, 4-dicarboxyphenoxy)phthalic anhydride, 1,4-bis(3,4-dicarboxyphenoxy)phthalic anhydride, 1,3-bis[2-(3,4-dicarboxyphenyl) -2-Propyl]phthalic anhydride, 1,4-bis[2-(3,4-dicarboxyphenyl)-2-propyl]phthalic anhydride, bis[3-(3,4-dicarboxyphenyl) Oxy)phenyl]methane dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride Carboxylic dianhydride, 2,3,6,7-anthracene tetracarboxylic dianhydride, 1,2,7,8-phenanthrene tetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride , 1,2,3,4-cyclobutane tetracarboxylic dianhydride, cyclopentane tetracarboxylic dianhydride, cyclohexane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1 ,2,4,5-tetracarboxylic dianhydride, 3,3',4,4'-bicyclohexyltetracarboxylic 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, 1,1-ethylidene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, 2,2-propylidene-4 ,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, ethylene glycol bis(trimellitic dianhydride), 1,2-(ethylene)bis(trimellitic anhydride), 1, 3-(trimethylene)bis(trimellitic anhydride), 1,4-(tetramethylene)bis(trimellitic anhydride), 1,5-(pentamethylene)bis(trimellitic anhydride), 1,6-(hexamethylene Base) 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-(hexadecyl methylene base) bis(trimellitic anhydride), 1,18-(octadecamethylene)bis(trimellitic anhydride), etc.

As a tricarboxylic anhydride, trimellitic anhydride, a nucleohydrogenated trimellitic anhydride, etc. are mentioned, for example.

As the amine component, diamines such as aliphatic diamine and aromatic diamine, and polyamines such as aliphatic polyetheramine can be used, but are not limited to these amines. In addition, these amine components can be used individually or in combination.

Examples of diamines include p-phenylenediamine (PPD), 1,3-diaminobenzene, 2,4-toluenediamine, 2,5-toluenediamine, 2,6-toluenediamine, etc. 1 Diamines with a benzene nucleus, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether and other diaminodiphenyl ethers, 4,4 '-Diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3 '-Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diamino Diamines with 2 benzene nuclei such as diphenyl sulfide, 1,3-bis(3-aminophenyl sulfide)benzene, 1,3-bis(4-aminophenyl sulfide)benzene, 1,4- Diamines with 3 benzene nuclei such as bis(4-aminophenylsulfide)benzene, 3,3'-bis(3-aminophenoxy)biphenyl, 3,3'-bis(4-aminophenoxy ) biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 2,2-bis[3-(3-aminophenoxy)phenyl]propane, 2,2-bis[3- (4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy) Aromatic diamines such as diamines with 4 benzene nuclei such as phenyl]propane, 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diamino Examples of aliphatic diamines such as pentane and 1,6-diaminohexane, and aliphatic polyetheramines include ethylene glycol and/or propylene glycol-based polyamines, and the like. In addition, as described below, an amine having a carboxyl group can 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; 3,5-bis(3 -aminophenoxy)benzoic acid, 3,5-bis(4-aminophenoxy)benzoic acid and other aminophenoxybenzoic acids; 3,3'-diamino-4,4'-dicarboxybiphenyl Equal carboxybiphenyl compounds; 3,3'-diamino-4,4'-dicarboxydiphenylmethane, 3,3'-dicarboxy-4,4'-diaminodiphenylmethane, 2,2 -Carboxydiphenyl alkanes such as bis[4-amino-3-carboxyphenyl]propane; 3,3'-diamino-4,4'-dicarboxydiphenyl ether, 4,4'-diamino-3 ,3'-dicarboxydiphenyl ether and other carboxydiphenyl ether compounds; 3,3'-diamino-4,4'-dicarboxydiphenyl sulfone, 4,4'-diamino-3,3'-di Diphenylsulfone compounds such as carboxyldiphenylsulfone, etc.

As the isocyanate component, diisocyanates such as aromatic diisocyanates and their isomers and polymers, aliphatic diisocyanates, alicyclic diisocyanates and their isomers, and other general-purpose diisocyanates can be used. It is not limited to these isocyanates. In addition, these isocyanate components can be used individually or in combination.

Examples of diisocyanate include: 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, biphenyl diisocyanate, diphenyl sulfone diisocyanate, diphenyl ether Aromatic diisocyanate such as diisocyanate and its isomers, polymers, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate and other aliphatic diisocyanate; or aromatic diisocyanate Hydrogenated alicyclic diisocyanates and isomers, 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. It may be an amide bond obtained by reacting an isocyanate and a carboxylic acid, or may be an amide bond obtained by another reaction. Furthermore, it may have a bond formed by other addition and condensation.

In addition, for the introduction of imide ring or imide precursor skeleton into the alkali-soluble resin, known and commonly used alkali-soluble polymers having either or both of carboxyl groups and acid anhydride groups, low Polymers and monomers are, for example, resins obtained by reacting these well-known and commonly used alkali-soluble resins alone or in combination with the above-mentioned carboxylic anhydride components and the above-mentioned amines/isocyanates.

In the synthesis of such an alkali-soluble resin having an alkali-soluble group and an imide ring or an imide precursor skeleton, known and commonly used organic solvents can be used. As the above-mentioned organic solvent, there is no problem as long as it does not react with carboxylic acid anhydrides, amines, and isocyanates as raw materials and can dissolve these raw materials, and its structure is not particularly limited. Among them, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, γ - Aprotic solvents such as 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 200 mgKOH/g in order to cope with the photolithography process. , More preferably 60 to 150 mgKOH/g. When the acid value is 20 mgKOH/g or more, the solubility to alkali increases, the developability becomes favorable, and the degree of crosslinking with the thermosetting component after light irradiation becomes high, so that sufficient development contrast can be obtained. In addition, when the acid value is 200 mgKOH/g or less, so-called thermal fogging in the PEB (POST EXPOSURE BAKE) process after light irradiation described later can be suppressed, and the process margin (process margin) becomes large. .

In addition, the molecular weight of the alkali-soluble resin is preferably 1,000 to 100,000, and more preferably 2,000 to 50,000, in consideration of developability and cured coating film properties. When the molecular weight is 1000 or more, sufficient development resistance and cured product properties can be obtained after exposure and PEB. Moreover, when molecular weight is 100000 or less, alkali solubility increases and developability improves.

When using a photobase generator in a resin composition containing an alkali-soluble resin having an imide ring or an imide precursor skeleton, it usually contains a photobase generator and a heat-reactive compound in addition to the alkali-soluble resin. In the case of the photopolymerization initiator, in addition to the alkali-soluble resin, a photopolymerization initiator and a compound having an ethylenically unsaturated bond are contained. In addition, as the resin component, a carboxyl group-containing polyurethane resin, a carboxyl group-containing novolak resin, or the like can be used in combination.

The photobase generator is a compound whose molecular structure is changed or molecularly cleaved by irradiation with light such as ultraviolet rays or visible light to generate one or more basic substances that can function as catalysts for polymerization reactions of thermally reactive compounds described later. As a basic substance, a secondary amine and a tertiary amine are mentioned, for example.

Examples of photobase generators include: α-aminoacetophenone compounds; oxime ester compounds; Compounds with substituents such as base carbamate group, alkoxybenzyl carbamate group, etc. Among them, oxime ester compounds and α-aminoacetophenone compounds are preferable. As the α-aminoacetophenone compound, one having two or more nitrogen atoms is particularly preferable.

The α-aminoacetophenone compound has a benzoin ether bond in its molecule, and when it is irradiated by light, it is cleaved in the molecule to generate a basic substance (amine) that exerts a curing catalytic effect. As a specific example of the α-aminoacetophenone compound, (4-morpholinobenzoyl)-1-benzyl-1-dimethylaminopropane (IRGACURE 369, trade name, manufactured by BASF JAPAN LTD.) can be used , 4-(methylthiobenzoyl)-1-methyl-1-morpholinoethane (IRGACURE 907, trade name, manufactured by BASFJAPAN LTD.), 2-(dimethylamino)-2-[( Commercially available compounds such as 4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone (IRGACURE 379, trade name, manufactured by BASF JAPAN LTD.), or its solution.

As the oxime ester compound, any compound can be used as long as it generates a basic substance by light irradiation. As a commercial item of the said oxime ester compound, CGI-325 by BASF JAPAN LTD., Irgacure OXE01, Irgacure OXE02, N-1919 by ADEKA CORPORATION, NCI-831 etc. are mentioned. In addition, a compound having two oxime ester groups in the molecule described in Japanese Patent No. 4344400 can also be preferably used.

Such a photobase generator may be used individually by 1 type, and may use it in combination of 2 or more types. The compounding quantity of the photobase generator in a resin composition becomes like this with respect to 100 mass parts of heat reactive compounds, Preferably it is 0.1-40 mass parts, More preferably, it is 0.1-30 mass parts. When it is 0.1 mass part or more, the contrast of the image development resistance of a light irradiation part / a non-irradiation part can be acquired favorably. Moreover, when it is 40 mass parts or less, hardened|cured material characteristic improves.

The heat-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 above-mentioned epoxy resin is a resin having an epoxy group, and any known resin can be used arbitrarily. Specifically, a bifunctional epoxy resin having two epoxy groups in a molecule, a polyfunctional epoxy resin having a plurality of epoxy groups in a molecule, and the like are mentioned. In addition, hydrogenated bifunctional epoxy compounds may also be used.

Examples of the above-mentioned epoxy resin include bisphenol A epoxy resin, brominated epoxy resin, novolak epoxy resin, bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, glycidol Amine type epoxy resin, hydantoin type epoxy resin, alicyclic epoxy resin, trishydroxyphenylmethane type epoxy resin, bixylenol type epoxy resin or biphenol type epoxy resin or their Mixture; bisphenol S type epoxy resin, bisphenol A novolak type epoxy resin, tetrahydroxyphenylethane type epoxy resin, heterocyclic epoxy resin, diglycidyl phthalate resin, tetraglycidyl Glyceryl xylenol ethane resin, naphthyl-containing epoxy resin, epoxy resin with dicyclopentadiene skeleton, glycidyl methacrylate copolymerized epoxy resin, cyclohexylmaleimide and methacrylic acid Glycidyl ester copolymerized epoxy resin, CTBN modified epoxy resin, etc.

These epoxy resins may be used alone or in combination of two or more.

As the compounding quantity of the said heat reactive compound, it is preferable that the equivalent ratio (alkali-soluble group, such as a carboxyl group: heat reactive group, such as an epoxy group) with alkali-soluble resin is 1:0.1-1:10. By setting it as the range of such a compounding ratio, image development becomes favorable, and a fine pattern can be formed easily. The said equivalent ratio is more preferably 1:0.2-1:5.

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

In addition, as the compound having an ethylenically unsaturated bond, known compounds can be used, including: hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; ethylene glycol, methoxytetraethylene glycol, etc. monoacrylates or diacrylates of diols such as alcohol, polyethylene glycol, and propylene glycol; Polyacrylic acid esters such as ethylene oxide adducts or propylene oxide adducts; phenoxy acrylate, bisphenol A diacrylate, and ethylene oxide adducts or propylene oxide adducts of these phenols Acrylic esters, etc.

(Adhesive layer (A))

As the alkali-developable resin composition constituting the adhesive layer (A), any composition may be used as long as it contains one or more functional groups of phenolic hydroxyl group, thiol group, and carboxyl group and can be developed with an alkali solution. Using a photocurable resin composition, a thermosetting resin composition can also be used. Preferable examples include a resin composition containing a compound having two 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 two or more thiol groups, and known and commonly used ones can be used.

Specifically, for example, a photocurable thermosetting resin composition conventionally used as a solder resist composition, the photocurable thermosetting resin composition comprising: a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, having an ethylenically unsaturated bond compounds, photopolymerization initiators and thermally reactive compounds. In addition, a resin composition containing a carboxyl group-containing polyurethane resin, a carboxyl group-containing resin, a photobase generator, and a thermosetting component can also be used. The above-mentioned resin composition is a composition as follows: the base generated by the photobase generator is used as a catalyst, the polyurethane resin having a carboxyl group and the thermosetting component are subjected to an addition reaction by heating after exposure, and the unexposed part is removed by an alkaline solution. This can be visualized.

As each material constituting the resin composition used in the adhesive layer (A), in addition to using known and commonly used materials, the materials used in the above-mentioned protective layer (B) can also be used in the same manner.

In the resin composition used for the above-mentioned adhesive layer (A) and protective layer (B), in order to improve the flexibility and dry-to-touch properties of the obtained cured product, a known and commonly used polymer resin may be compounded. Such polymer resins include cellulose-based, polyester-based, phenoxy resin-based polymers, polyvinyl acetal-based, polyvinyl butyral-based, polyamide-based, polyamide imide Amine-based binder polymers, block copolymers, elastomers, etc. These polymer resins may be used alone or in combination of two or more.

In addition, an inorganic filler may be compounded in the resin composition used for the adhesive layer (A) and the protective layer (B) in order to suppress curing shrinkage of the cured product and improve properties such as adhesiveness and hardness. Examples of such inorganic fillers include barium sulfate, amorphous silica, fused silica, spherical silica, talc, clay, magnesium carbonate, calcium carbonate, aluminum oxide, aluminum hydroxide, nitrided Silicon, Aluminum Nitride, Boron Nitride, Neuberger Silica, etc.

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 coating on a base material or a carrier film. Examples of such organic solvents include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, petroleum-based solvents, and the like. Such organic solvents may be used alone or as a mixture of two or more.

In the resin composition used for the adhesive layer (A) and the protective layer (B), components such as a colorant, a mercapto compound, an adhesion promoter, an antioxidant, and an ultraviolet absorber may be further compounded as necessary. As these components, known and commonly used ones in the field of electronic materials can be used. In addition, it can be properly compounded: micropowdered silica, hydrotalcite, organic bentonite, montmorillonite and other commonly used thickeners, silicone-based, fluorine-based, polymer-based defoamers, leveling agents, silanes, etc. Well-known and commonly used additives such as coupling agents and rust inhibitors.

In the multilayer structure of the present invention, the adhesive layer (A) is preferably thicker than the protective layer (B) from the viewpoint of followability to the copper circuit.

The laminated structure of the present invention can be used in at least any one of the flexible portion and the non-flexible portion of the flexible printed circuit board, preferably in both, thereby obtaining a flexible material having sufficient durability against bending. printed circuit boards and improve cost and operability. Specifically, the multilayer structure of the present invention can be used for at least any one of a cover layer, a solder resist layer, and an interlayer insulating material of a flexible printed wiring board.

(Manufacturing method of flexible printed circuit board)

In the present invention, the layer of the above-mentioned laminated structure is formed directly or via a dry film on the flexible printed circuit base material, patterned by light irradiation, and an insulating film is formed by patterning with a developer at one time, thereby obtaining a flexible printed circuit board. . The single layer of the conventional solder resist layer has poor properties such as flexibility, but according to the present invention, a laminated structure composed of the adhesive layer (A) and the protective layer (B) is produced, and the protective layer and the adhesive layer are separated. The ratio of the film thickness and the ratio of the developing speeds of the protective layer and the adhesive layer are within the above-mentioned ranges, and alkali developability, heat resistance, and mechanical properties such as flexibility can be satisfactorily compatible.

Hereinafter, regarding an example of the method for producing the flexible printed circuit board of the present invention from the laminated structure of the present invention, a compound containing a photobase generator and a thermally reactive compound is used for both the adhesive layer (A) and the protective layer (B). The case of the resin composition will be described based on the process chart shown in FIG. 1 . It should be noted that, in the case of photocuring using a conventional solder resist composition containing a carboxyl group-containing resin or carboxyl group-containing photosensitive resin, a compound having an ethylenically unsaturated bond, a photopolymerization initiator, and a heat-reactive compound, In the case of a permanent thermosetting resin composition, the same process as that for the solder resist layer can be employed.

[Stacking process]

The lamination step is a step of forming the multilayer structure of the present invention on a base material. The lamination process in FIG. 1 shows a state in which a laminated structure consisting of an adhesive layer 3 and a protective layer 4 formed of an alkali-developing type resin is formed on a flexible printed circuit substrate 1 on which a copper circuit 2 is formed. The composition is formed.

Among them, for each layer constituting the laminated structure, for example, the resin composition constituting the adhesive layer 3 and the protective layer 4 can be coated on the base material in sequence and dried to form the adhesive layer 3 and the protective layer 4 directly. or by making the resin compositions constituting the adhesive layer 3 and the protective layer 4 into dry films and sequentially laminating them on the base material. In addition, it can also be formed by a method of laminating a laminated structure in the form of a dry film having a two-layer structure on a base material. At this time, at least one surface of the laminated structure may be supported or protected with a film. As the film to be used, a plastic film that can be peeled off from the laminated structure can be used. There is no particular limitation on the thickness of the film, but it is generally suitably selected within the range of 10 to 150 μm. From the viewpoint of coating film strength, the interface between the layers may also be fused.

The method of applying the resin composition to the substrate may be a known method such as a knife coater, a lip coater, a comma coater, or a film coater. In addition, the drying method can be a method of using a hot air circulation drying furnace, an IR furnace, a hot plate, a convection oven, etc., which has a heat source using a steam heating method, and making the hot air in the dryer convectively contact; and blowing it to the support through a nozzle known methods such as body methods.

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

[Light irradiation process]

The photoirradiation step is a step of curing the photoirradiated portion by activating the photobase generator contained in the resin composition by photoirradiation in a negative pattern form. In this light irradiation process, the mask 5 is arrange|positioned on the protective layer 4, and light irradiation is performed in negative pattern form, the photobase generator contained in a resin composition is activated, and the light irradiation part is hardened.

In this step, the photobase generator is destabilized due to the base generated at the light irradiation part, and a basic substance (hereinafter, sometimes simply referred to as "base") is generated from the photobase generator, and the photobase is destabilized due to the generated base. The base generator is destabilized, thereby generating a base. It is considered that by generating a base in this way and chemically proliferating to the deep part of each layer, it is considered that the solidification can be sufficiently carried out to the deep part of each layer. In the subsequent thermosetting, the alkali functions as a catalyst for the addition reaction between the alkali-developable resin and the heat-reactive compound, and the addition reaction proceeds. Therefore, in the light-irradiated part, each layer is sufficiently thermoset to the deep part. The curing of the resin composition at this time is, for example, a ring-opening reaction of epoxy by thermal reaction, and therefore, strain and cure shrinkage can be suppressed compared to the case of proceeding by photoreaction.

As a light irradiation machine used in light irradiation, a direct drawing device (for example, a laser direct imaging device that directly draws an image with a laser from CAD data from a computer), a light irradiation machine equipped with a metal halide lamp, a light irradiation machine equipped with ( Ultra) high pressure mercury lamp light irradiation machine, light irradiation machine equipped with mercury short arc lamp, or direct drawing device using ultraviolet lamp such as (ultra) high pressure mercury lamp. The mask for patterned light irradiation is a negative mask.

As the active energy ray, it is preferable to use a laser beam or scattered light having a maximum wavelength in the range of 350 to 410 nm. By setting the maximum wavelength into this range, the photobase generator can be efficiently activated. As long as a laser beam within this range is used, the type of laser light may be either a gas laser or a solid-state laser. In addition, the amount of light irradiation varies depending on the film thickness and the like, but can be generally set within a range of 100 to 1500 mJ/cm ² , preferably within a range of 300 to 1500 mJ/cm ² .

[Heating process]

In the heating step, the light-irradiated portion is cured by heating, and it can be hardened to a deep portion by alkali generated in the light-irradiating step. This heating step is a step of curing the light-irradiated portion by heating the adhesive layer 3 and the protective layer 4 after the light irradiation step, and is called a so-called PEB (POST EXPOSURE BAKE) step. Thereby, each layer is fully hardened to the deep part by the alkali produced|generated in a light irradiation process, and the patterned layer excellent in hardening characteristic can be obtained.

For example, in the heating step, heating is preferably performed at a temperature lower than the exothermic onset temperature or exothermic peak temperature of the unirradiated resin composition and higher than the exothermic onset temperature or exothermic peak temperature of the light-irradiated resin composition. Only the photoirradiated portion can be selectively cured by heating in this way.

Among them, the heating temperature at this time is preferably a temperature at which the light-irradiated portion of the resin composition is thermally cured, but the non-irradiated portion is not thermally cured. The heating temperature is, for example, 80 to 140°C. By making heating temperature 80 degreeC or more, a light irradiation part can fully harden|cure. On the other hand, only the light irradiation part can be selectively hardened by making heating temperature 140 degreeC or less. The heating time is, for example, 10 to 100 minutes. The heating method is the same as the above drying method. In addition, since the base originating in a photobase generator does not generate|occur|produce in a non-irradiation part, thermal hardening was suppressed.

[Development process]

In the development step, the non-irradiated portion is removed by alkali development to form a negative pattern layer. The developing step in FIG. 1 shows a step of developing the adhesive layer 3 and the protective layer 4 with an alkaline aqueous solution, removing unirradiated portions, and forming a negative pattern layer. As a developing method, well-known methods, such as a dipping method, a shower method, a spray method, and a brushing method, can be utilized. In addition, as the developer, potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia, amines such as ethanolamine, aqueous alkali solutions such as tetramethylammonium hydroxide (TMAH) or the like can be used. their mixture.

[Second light irradiation process]

After the image development step, it is preferable to include a second light irradiation step. This 2nd light irradiation process is a process of irradiating ultraviolet rays as needed in order to activate the photobase generator which remained in the pattern layer which was not activated in the light irradiation process, and generate|occur|produce a base. The wavelength and light irradiation amount (exposure amount) of the ultraviolet-ray in a 2nd light irradiation process may be the same as that of the said light irradiation process, and may differ. The amount of light irradiation (exposure amount) is, for example, 150 to 2000 mJ/cm ² .

[Heat curing process]

After the development step, it is preferable to further include a thermal curing (post-curing) step. This thermal curing step is a step of performing thermal curing (post-curing) as necessary in order to sufficiently thermally cure the pattern layer. After the image development step, when both the second light irradiation step and the thermosetting step are performed, the thermosetting step is preferably performed after the second light irradiation step.

In this thermal curing step, the pattern layer is sufficiently thermally cured using the base generated from the photobase generator in the light irradiation step, or the light irradiation step and the second light irradiation step. At the time of the thermal curing step, since the unirradiated portion has already been removed, the thermal curing step can 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 fully thermally cured. The heating temperature is, for example, 150° C. or higher.

Example

Hereinafter, the present invention will be further described in detail using examples.

(Synthesis Example 1)

<Synthesis of Alkali-Soluble Resin Having an Imide Ring>

In a detachable three-necked flask equipped with a stirrer, a nitrogen inlet tube, a split tube and a condenser tube, add 12.5 g of 3,5-diaminobenzoic acid, 2,2'-bis[4-(4-aminophenoxy 8.2 g of ) phenyl] propane, 30 g of NMP, 30 g of γ-butyrolactone, 27.9 g of 4,4′-oxydiphthalic anhydride, and 3.8 g of trimellitic anhydride were stirred at 100 rpm for 4 hours under a nitrogen atmosphere at room temperature. Next, 20 g of toluene was added, and the mixture was stirred for 4 hours while distilling off toluene and water at a silicon bath temperature of 180° C. and 150 rpm to obtain an alkali-soluble resin solution containing an imide ring. Then, γ-butyrolactone was added so that the solid content would become 30% by mass. The solid content acid value of the obtained resin solution was 86 mgKOH/g, and Mw was 10000.

(Synthesis Example 2)

<Synthesis of carboxyl group-containing polyurethane resin>

In a reaction vessel equipped with a stirring device, a thermometer and a condenser, polycarbonate diol derived from 1,5-pentanediol and 1,6-hexanediol (manufactured by Asahi Kasei Chemicals Corporation, T5650J, number average molecular weight 800 ) 2400 g (3 mol), 603 g (4.5 mol) of dimethylolpropionic acid, and 238 g (2.6 mol) of 2-hydroxyethyl acrylate as a monohydroxy compound. Next, 1887 g (8.5 moles) of isophorone diisocyanate as a polyisocyanate was put in, heated to 60° C. and stopped while stirring, and reheated when the temperature in the reaction vessel began to drop, and continued stirring at 80° C. It was confirmed by the absorption spectrum that the absorption spectrum (2280 cm ^-1 ) of the isocyanate group disappeared, and the reaction was terminated. Then, carbitol acetate was added so that the solid content would become 50% by mass. The acid value of the solid content of the obtained carboxyl group-containing polyurethane resin was 50 mgKOH/g.

<Preparation of Resin Composition Constituting Each Layer>

According to the formulations shown in the following Tables 1 and 2, the materials shown in the examples and comparative examples were mixed respectively, and after pre-mixing with a mixer, kneading was carried out with a three-roll mill to prepare the adhesive layer and the protective layer. resin composition. The values in the table are parts by mass unless otherwise stated.

<Formation of Adhesive Layer (A)>

A circuit-formed flexible printed circuit substrate having a copper thickness of 18 μm was prepared, and pre-treated using CB-801Y manufactured by Mec Corporation. Then, the resin composition for each adhesive layer was apply|coated so that the film thickness after drying might become the film thickness shown in following Table 1 and Table 2 on the preprocessed flexible printed circuit base material. Then, it dried at 80 degreeC/30 minutes in the hot-air circulation type drying oven, and formed the adhesive layer (A) which consists of a resin composition. In addition, regarding the comparative example 1, the adhesive layer was not formed.

<Formation of protective layer (B)>

The resin composition for each protective layer was apply|coated on the said adhesive layer (A) so that the film thickness after drying might become the film thickness shown in Table 1 and Table 2 below. Then, it dried at 80 degreeC/30 minutes in the hot-air circulation type drying oven, and formed the protective layer (B) which consists of a resin composition.

The total sum of the film thicknesses 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 apply|coated on the flexible printed circuit base material in which the circuit was formed with copper thickness 18 micrometers, and it dried at 80 degreeC/30 minutes in the hot-air circulation type drying oven. Then, the base material was immersed in 30 degreeC and 1 mass % sodium carbonate aqueous solution, and the time until the coating film melt|dissolved was measured. When the time until the coating film dissolves is defined as the developing time [second], and the film thickness is defined as the film thickness [μm], the developing speed is represented by the following formula.

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

<Alkali Developability, Resistance to Soldering Heat, and Gold Plating Resistance>

The substrate having the above-obtained laminated structure was irradiated with light in a negative pattern at an exposure amount of 500 mJ/cm ² using HMW680GW (metal halide lamp, scattered light) manufactured by ORC CORPORATION. Next, heat treatment was performed at 90° C. for 60 minutes. Then, the base material was immersed in 30 degreeC and 1 mass % sodium carbonate aqueous solution, and image development was performed for 3 minutes, and the possibility of alkali developability was evaluated. The evaluation was performed visually, and was evaluated according to the following criteria.

○: Developed without residue

×: There is developing residue

Next, it heat-processed at 150 degreeC/60 minutes using the hot-air circulation type drying furnace, and obtained the patterned cured coating film. The obtained cured coating film was coated with rosin-based flux on the evaluation base material, dipped in a solder bath set at 260°C for 20 seconds (10 seconds x 2 times), and washed with isopropyl alcohol. A peeling test using a cellophane tape was performed, and the swelling, peeling, and discoloration of the resist layer were evaluated in accordance with the following criteria.

○: No change is confirmed at all

×: There is swelling and peeling

Moreover, the obtained cured coating film was plated on conditions of 80-90 degreeC, nickel 5 micrometers, and gold 0.05 micrometers using the commercially available electroless nickel plating bath and electroless gold plating bath. In the plated evaluation base material, the presence or absence of plating penetration was evaluated visually.

○: No penetration

×: Penetration was confirmed between the substrate and the coating film

The obtained results are shown in Table 1 and Table 2 below.

[Table 1]

*1: Resin of Synthesis Example 1

*2: Resin of Synthesis Example 2

※3: Carboxyl group-containing novolak resin (acid value 104mgKOH/g, Bis A/phenol novolak resin)

*4: Ethoxylated bisphenol A dimethacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.)

*5: Dicyclopentadiene-type epoxy resin (manufactured by DIC Corporation)

*6: Bisphenol A type epoxy resin (molecular weight 400) (manufactured by Mitsubishi Chemical Corporation)

*7: Oxime photobase generator (manufactured by BASF JAPAN LTD.)

※8: 2-(Dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone (BASF JAPAN LTD.)

*9: Bisphenol F acid-modified epoxy acrylate (manufactured by Nippon Kayaku Co., Ltd.)

*10: Barium sulfate (manufactured by Sakai Chemical Industry Co., Ltd.)

[Table 2]

From the evaluation results shown in Table 1 and Table 2, it was clearly confirmed that the flexible printed wiring boards of Examples showed good developability and heat resistance. On the other hand, it can be seen that Comparative Example 1 is constituted only of the protective layer of the resin composition having an imide ring, so although the heat resistance is good, the developability is poor, and it cannot be developed using ordinary sodium carbonate. In addition, in Comparative Example 2, the adhesive layer was thin, and the ratio of the thickness of the adhesive layer to the protective layer deviated from the range of the present invention. Therefore, although the heat resistance was good, the result was still poor in developability. Furthermore, in Comparative Example 3, since the film thickness ratio of the adhesive layer and the protective layer deviated from the range of the present invention, the developability was good, but as a result, the heat resistance was still poor. In Comparative Example 4, although the ratio of the film thickness is within the scope of the present invention, the development speed of the adhesive layer and the protective layer are the same, and the ratio of the two development speeds deviates from the scope of the present invention, so the result is still relatively low in developability. Difference. In Comparative Example 5, since the ratio of the developing speed deviated from the range of the present invention, the developability was good, but as a result, the heat resistance was inferior.

Explanation of reference signs

1 Flexible printed circuit substrate

2 copper circuit

3 adhesive layer

4 layers of protection

5 masks

Claims (6)

1. A laminated structure, characterized in that it has: an adhesive layer (A) formed of an alkali-developable resin composition, and a photosensitive resin composition formed on the adhesive layer (A). protective layer (B), The film thickness ratio of the adhesive layer (A) to the protective layer (B) is A/B=0.5-50, The ratio of the developing speed (a) of the adhesive layer (A) to the developing speed (b) of the protective layer (B) is a/b=1.1-100. 2. The laminated structure according to claim 1, wherein both the adhesive layer (A) and the protective layer (B) can be patterned by light irradiation. 3. The laminated structure according to claim 1, which is used for at least any one of a flexure portion and a non-flexure portion of a flexible printed circuit board. 4. The laminated structure according to claim 1, which is used for 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 side of the laminated structure according to any one of claims 1 to 4 is supported or protected by a film. 6. A flexible printed circuit board, characterized in that it is provided with an insulating film, and the insulating film is a layer in which the laminated structure according to any one of claims 1 to 4 is directly formed on the flexible printed circuit board, or is formed by The dry film according to claim 5 forms a layer of a laminated structure, is patterned by light irradiation, and is obtained by forming a pattern at one time with a developer.