TW201625078A - Laminate structure - Google Patents

Abstract

Provided is a structure that satisfies the required performance of an insulating film for a flexible printed wiring board and is suitable for a collective formation process of a bending portion and mounting portion. Further provided is a flexible printed wiring board that has a cured product of the structure as a protective film, e.g. a coverlay or solder resist. Provided are: a laminate structure that has an adhesive layer (A) comprising an alkali-developable resin composition and a protective layer (B) comprising a photosensitive resin composition and being formed upon the adhesive layer (A), wherein the ratio of the film thickness of the adhesive layer (A) to the protective layer (B) is A/B=0.5-50, and the ratio of the development speed (a) of the adhesive layer (A) to the development speed (b) of the protective layer (B) is a/b=1.1-100; and a dry film and flexible printed wiring board using said laminate structure.

Description

Laminated structure

The present invention relates to a laminated structure, and more particularly to a laminated structure having an insulating film for a flexible printed wiring board, and a dry film and a flexible printed wiring board using the same.

In recent years, the popularity of smart phones and tablet terminals has led to a reduction in size and size of electronic devices, which has made it necessary to reduce the size of circuit boards. Therefore, the use of the flexible printed wiring board that can be bent and accommodated is increased, and the reliability of the flexible printed wiring board is higher than ever.

On the other hand, in the insulating film for ensuring the insulation reliability of the flexible printed wiring board, a mixing process is widely used, and the bent portion (bending portion) is made of a polymer having excellent mechanical properties such as heat resistance and flexibility. A bismuth imine is used as a coating film for a substrate (for example, refer to Patent Documents 1 and 2); and a mounting portion (non-bending portion) is a photosensitive resin composition which is excellent in electrical insulating properties and can be finely processed.

In other words, a cover film having a polyimine which is excellent in mechanical properties such as heat resistance and flexibility as a base needs to be punched through a die. It is not suitable for fine wiring. Therefore, it is necessary for the wafer-mounting portion which requires fine wiring to partially use an alkali-developable photosensitive resin composition (solder resist) which can be photolithographically processed.

Prior technical literature Patent literature

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

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

As described above, in the manufacturing process of the flexible printed wiring board, the mixing process of the step of bonding the cover film and the step of forming the solder resist cannot be employed, so that cost and workability are disadvantageous.

In view of this, although the insulating film or the insulating film as a solder resist is applied to both the solder resist and the cover film of the flexible printed wiring board, materials which can fully satisfy the performance requirements of both can be considered. However, it has not yet reached practical use. In particular, in the case of a flexible printed wiring board, it is desired to achieve material having the following characteristics: alkali developability required for an insulating film as a solder resist, and heat resistance required for an insulating film as a cover film. Mechanical properties such as bendability.

The object of the present invention is to provide a structure which can satisfy the performance required as a flexible printed wiring board insulating film and which is applicable even in a single forming process of a bent portion and a mounted portion. In addition, provided with A flexible printed wiring board having a cured product thereof as a protective film (for example, a cover film or a solder resist).

In order to solve the above problems, the present invention is characterized in that the adhesive layer (A) comprising an alkali-developable resin composition and a protective layer composed of a photosensitive resin composition formed on the adhesive layer (A) B), and the ratio of the film thickness of the adhesion layer (A) to the protective layer (B): A/B = 0.5 to 50; the development speed (a) of the adhesion layer (A) and the protective layer (B) The ratio of the developing speed (b): a/b = 1.1 to 100.

In the laminated structure of the present invention, it is preferable that the laminate layer (A) and the protective layer (B) are patterned by light irradiation. Further, the laminated structure of the present invention can be applied to at least one of a bent portion and a non-curved portion of a flexible printed wiring board; specifically, a cover film for a flexible printed wiring board, a solder resist, and At least any of the use of the interlayer insulating material is feasible.

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

Further, in the flexible printed wiring board of the present invention, the laminated structure layer of the present invention is directly formed on the flexible printed wiring board, or the laminated structure layer is formed on the dry film of the present invention; The pattern is formed by irradiation, and the pattern is formed once with the developer to obtain an insulating film. In addition, the "pattern" in the present invention means a cured product of a pattern shape, that is, an insulating film.

According to the present invention, it is possible to realize a laminated structure that satisfies the performance required as a flexible printed wiring board insulating film, and is also applicable to a primary forming process of a bent portion and a mounted portion, and a dry film using the same Flexible printed wiring board.

1‧‧‧Flexible printed wiring substrate

2‧‧‧Bronze circuit

3‧‧‧Next layer

4‧‧‧Protective layer

5‧‧‧ mask

Fig. 1 is a flow chart showing an exemplary example of a method of manufacturing a flexible printed wiring board of the present invention.

Embodiments of the present invention will be described below in detail with reference to the drawings.

(layered structure)

The laminated structure system of the present invention has an adhesive layer (B) composed of an alkali-developable resin composition and a protective layer (B) composed of a photosensitive resin formed on the adhesive layer (A). And the ratio of the film thickness of the adhesive layer (A) and the protective layer (B) is A/B = 0.5 to 50, and the developing speed (a) of the bonding layer (A) and the developing speed of the protective layer (B) The ratio of (b) is a/b=1.1~100.

In order to pattern using an alkali developer, the resin composition Must have alkali solubility. In the case of the laminated structure, when a resin composition having excellent heat resistance is used for the protective layer, it is difficult to impart solubility to the resin composition excellent in heat resistance, so that the development speed is slow, and as a result, it is difficult to pattern. The problem.

In order to solve this problem, the inventors of the present invention have intensively examined the film thickness and development speed of the protective layer and the adhesive layer, and as a result, found that the ratio of the thickness of the protective layer to the adhesive layer and the development of the protective layer and the adhesive layer are obtained. The above-mentioned problems can be solved by the ratio of the speeds falling within the above ranges, and the present invention is completed.

That is, it was found that a protective layer of a resin composition using a slow development speed was laminated on the adhesive layer using a resin composition which was developed faster than the resin composition of the protective layer, and both were After the ratio of the film thickness ratio and the development speed falls within the above range, even if the development speed of the protective layer is slow and it is difficult to pattern by alkali development, even if the residue appears, the development speed of the adhesive layer is fast, and the result is The two are completely washed away, so that the development speed of the laminated structure as a whole falls within the realization range.

In order to achieve better alkali developability, mechanical properties such as heat resistance and flexibility, the ratio of the film thickness is A/B = 0.5 to 50, preferably A/B = 1.0 to 30, and more preferably A/B. =2.0~10, and the ratio of the development speed is a/b=1.1~100, preferably a/b=2.0~50, more preferably a/b=3.0~30.

When the ratio of the film thickness is A/B=50 or less, the proportion of the protective layer (B) having heat resistance among the layer thicknesses of the laminated structure is large, and The developability is good and sufficient heat resistance can be obtained. In addition, when A/B = 0.5 or more, since the ratio of the adhesive layer (A) which is excellent in developability is large, it is excellent in heat resistance and can be patterned by alkali development.

When the ratio of the developing speed is a/b = 1.1 or more, the development speed of the protective layer (B) and the layer (A) which are difficult to develop is relatively fast, so that it can be patterned by alkali development. In addition, when a/b = 100 or less, the solubility in the aqueous alkali solution of the adhesive layer (A) is appropriate, and the shape of the pattern is stabilized, so that the properties such as plating resistance are also good.

In the development of the laminated structure, the time required for the respective layers of the protective layer and the subsequent layer to be dissolved in the aqueous alkali solution is set as the development time [second], and when the film thickness of each layer is set to the film thickness [μm], the development speed is as follows. Expression.

Development speed [μm/sec] = film thickness [μm] / development time [seconds]

(protection layer (B))

The component of the photosensitive resin composition of the protective layer (B) is not particularly limited. For example, a compound 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 of a photopolymerization initiator and a thermally reactive compound, and a photosensitive thermosetting resin composition containing a carboxyl group-containing resin, a photobase generator, and a heat-reactive compound.

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

The alkali-soluble resin having a quinone imine ring or a quinone imine precursor skeleton in the present invention means an alkali-soluble group having a carboxyl group and an acid anhydride group, and a bismuth imine ring or a quinone imine precursor skeleton. . A conventionally known method can be used to introduce a quinone imine ring or a quinone imine precursor skeleton into the alkali-soluble resin. For example, a resin obtained by reacting a carboxylic anhydride component with any one or both of an amine component and an isocyanate component can be mentioned. The ruthenium imidization can be carried out by thermal imidization, chemical imidation, or the like.

Here, the carboxylic anhydride component may, for example, be a tetracarboxylic acid anhydride or a tricarboxylic acid anhydride, but is not limited to such an acid anhydride, and may be a compound having an acid anhydride group and a carboxyl group which react with an amine group or an isocyanate group. Its derivatives are used. Further, these carboxylic anhydride components may be used singly or in combination.

Examples of the tetracarboxylic anhydride include pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 3,3',4,4'-biphenyltetracarboxylate. Acid dianhydride, 4,4'-oxydiphthalic acid dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,3",4,4"-triphenyltetracarboxylic dianhydride , 3,3''',4,4'''-tetraphenylene tetracarboxylic dianhydride, 3,3''',4,4''''-pentaphenyltetracarboxylic dianhydride , methylene-4,4'-diphthalic acid dianhydride, 1,1-vinylidene-4,4'-diphthalic acid dianhydride, 2,2-propylene-4,4'-di Acid dianhydride, 1,2-extended ethyl-4,4'-dicarboxylic acid dianhydride, 1,3-trimethylene-4,4'-dicarboxylic acid dianhydride, 1,4-tetramethylene -4,4'-diphthalic acid dianhydride, 1,5-pentamethylene-4,4'-diphthalic acid dianhydride, thio-4,4'-diphthalic acid dianhydride, sulfonyl- 4,4'-diphthalic acid dianhydride, 1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethylphosphorane dianhydride, 1,3-double ( 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) Benzene phthalic anhydride, 1,3-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, 1,4-bis[2-(3,4-dicarboxyphenyl) -2-propyl]benzene phthalic anhydride, bis[3-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1, 2,5,6-naphthalenetetracarboxylic dianhydride, 3,4,9,10-decanetetracarboxylic dianhydride, 2,3,6,7-nonanetetracarboxylic dianhydride, 1,2,7,8 - phenanthrenetetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, cyclopentane tetracarboxylic dianhydride, Cyclohexane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, 3,3',4,4'-bicyclohexyl Carboxylic dianhydride, carbonyl-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, methylene-4,4'-bis(cyclohexane-1,2-dicarboxylate Acid) dianhydride, 1,2-extended ethyl-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, 1,1-vinylidene-4,4'-double ( Cyclohexane-1,2-dicarboxylic acid) dianhydride, 2,2-propylene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, ethylene glycol double bias Pyrogallate dianhydride, 1,2-(extended ethyl) bis(trimellitic 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-(heptylene)bis(trimellitic anhydride), 1,8-(octamethylene)bis(trimellitic anhydride), 1,9-(nonamethylene Bis(trimellitic anhydride), 1,10-(decamethylene)bis(trimellitic anhydride), 1,12-(dodecyl)bis(trimellitic anhydride), 1,16-(hexamethylene) bis ( Trimellitic anhydride), 1,18-(octamethylidene)bis (trimellitic anhydride), and the like.

Examples of the tricarboxylic acid anhydride include benzenetricarboxylic anhydride and hydrogenated trimellitic anhydride.

As the amine component, an aliphatic diamine or an aromatic two can be used. A polyamine such as a diamine such as an amine or an aliphatic polyether amine, but is not limited to such an amine. Further, these amine components may be used singly or in combination.

Examples of the diamine include p-phenylenediamine (PPD), 1,3-phenylenediamine, 2,4-toluenediamine, 2,5-toluenediamine, and 2,6-toluene. a monophenylphosphine diamine such as an amine, a diamine group such as 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether or 3,4'-diaminodiphenyl ether Phenyl 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'-diamine Diphenyl nuclear diamine such as diphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 1,3-bis(3-aminophenyl sulfide) benzene, 1,3-double (4-aminophenyl sulfide) benzene, 1,4-bis(4-aminophenyl sulfide) benzene, etc., triphenyl nucleodiamine, 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)phenyl]propane An aromatic diamine such as tetraphenyl nuclear diamine; 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diamine An aliphatic diamine such as pentane or 1,6-diaminohexane. Examples of the aliphatic polyether amines include ethylene glycol (and/or) propylene glycol-based polyamines. Further, an amine having a carboxyl group as described below can also be used.

Examples of the amine having a carboxyl group include diaminobenzoic acid such as 3,5-diaminobenzoic acid, 2,5-diaminobenzoic acid or 3,4-diaminobenzoic acid, and 3, 5-bis(3-aminophenoxy)benzoic acid, 3,5-bis(4-amino group Aminophenoxybenzoic acid such as phenoxy)benzoic acid, carboxylbiphenyl compound such as 3,3'-diamino-4,4'-dicarboxybiphenyl, and 3,3'-diamine 4-,4'-dicarboxydiphenylmethane, 3,3'-dicarboxy-4,4'-diaminodiphenylmethane, 2,2-bis[4-amino-3-carboxybenzene a carboxydiphenylalkane such as propane, 3,3'-diamino-4,4'-dicarboxydiphenyl ether, 4,4'-diamino-3,3'-dicarboxydiphenyl a carboxydiphenyl ether compound such as ether, 3,3'-diamino-4,4'-dicarboxydiphenylanthracene, 4,4'-diamino-3,3'-dicarboxydiphenylanthracene A diphenyl hydrazine compound or the like.

As the isocyanate component, an aromatic diisocyanate and an isomer or a polymer thereof, a diisocyanate such as an aliphatic diisocyanate, an alicyclic diisocyanate or an isomer thereof, or other general-purpose diisocyanate can be used. However, it is not limited to such an isocyanate. Further, these isocyanate components may be used singly or in combination.

Examples of the diisocyanate include 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, decyl diisocyanate, biphenyl diisocyanate, diphenyl sulfonium diisocyanate, and diphenyl group. An aromatic diisocyanate such as an ether diisocyanate and an aliphatic diisocyanate such as an isomer, a polymer, a hexamethylene diisocyanate, an isophorone diisocyanate or a dicyclohexylmethane diisocyanate, or a hydrogenated aromatic Alicyclic diisocyanates and isomers of diisocyanates, or other general purpose diisocyanates.

The alkali-soluble resin having a quinone ring or a quinone imine precursor skeleton as described above may also contain a guanamine bond. It may also be a guanamine bond obtained by reacting an isocyanate with a carboxylic acid, or may be obtained by other reactions. again It may have a bond formed by other additions and condensations.

Further, in the introduction of the quinone imine ring or the quinone imine precursor skeleton of the alkali-soluble resin, an alkali-soluble polymer having a carboxyl group or an acid anhydride group or both, and an oligosaccharide are conventionally used. The polymer or the monomer may be, for example, a resin obtained by reacting the above-mentioned alkali-soluble resin alone or in combination with the above-mentioned carboxylic anhydride component and reacting with the above amine/isocyanate.

As the synthesis of such an alkali-soluble resin having an alkali-soluble group and a quinone imine ring or a quinone imine precursor skeleton, a well-known organic solvent can be used. The organic solvent is not particularly limited as long as it does not react with a carboxylic acid anhydride, an amine or an isocyanate of a raw material, and can dissolve such a raw material. The structure is not particularly limited. Among them, because of the high solubility of the raw materials, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl alum, An aprotic solvent such as γ-butyrolactone is preferred.

The alkali-soluble resin having an alkali-soluble group such as a carboxyl group or an acid anhydride group and a quinone imine ring or a quinone imine precursor skeleton as described above has an acid value of 20 to 200 mgKOH/g in order to correspond to the photolithography step. Preferably, it is preferably 60 to 150 mgKOH/g. When the acid value is 20 mgKOH/g or more, the solubility in alkali is increased, and the developability is improved. Further, since the degree of crosslinking with the heat-curing component after light irradiation is high, sufficient development contrast can be obtained. Moreover, when the acid value is 200 mgKOH/g or less, so-called hot mist can be suppressed in the PEB (POST EXPOSURE BAKE) step after light irradiation described later, and the process margin can be increased.

Further, the molecular weight of the alkali-soluble resin is preferably from 1,000 to 100,000 by mass average molecular weight, and more preferably from 2,000 to 50,000, in consideration of developability and film properties. When the molecular weight is 1,000 or more, sufficient development resistance and cured physical properties can be obtained after exposure and PEB. Further, when the molecular weight is 100,000 or less, the alkali solubility is increased, and the developability is improved.

a resin composition containing an alkali-soluble resin having a quinone ring or a quinone imine precursor skeleton, and a photobase generator, in addition to an alkali-soluble resin, a photobase generator and a heat-reactive compound; When a photopolymerization initiator is used, a photopolymerization initiator and a compound having an ethylenically unsaturated bond are contained in addition to the alkali-soluble resin. Further, as the resin component, a carboxyl group-containing urethane resin or a carboxyl group-containing novolac resin may be used in combination.

A photobase generator is a compound which undergoes light irradiation by ultraviolet light, visible light or the like to change its molecular structure, or molecularly cleaves to form more than one basicity of a polymerization catalyst function which can be used as a thermally reactive compound to be described later. substance. Examples of the basic substance include a secondary amine and a tertiary amine.

Examples of the photobase generator include an α-aminoacetophenone compound, an oxime ester compound, or an anthracene imino group, an N-methylated aromatic amine group, and an N-methylated aromatic group. A compound such as a substituent of a group such as a group of aminino group, a benzylidene urethane group or an alkoxybenzyl amide group, and the like, and an oxime ester compound or an α-aminoacetophenone compound is preferred. The α-aminoacetophenone compound is particularly preferably one having two or more nitrogen atoms.

The α-aminoacetophenone compound has a benzoin ether bond in the molecule, and undergoes cleavage inside the molecule after being irradiated with light to form a basic substance (amine) which acts as a sclering catalyst. As a specific example of the α-aminoacetophenone compound, (4-morpholinylbenzylidene)-1-benzyl-1-dimethylaminopropane (IRGACURE 369, trade name, BASF JAPAN) can be used. , 4-(methylthiobenzimidyl)-1-methyl-1-morpholinylethane (IRGACURE 907, trade name, manufactured by BASF JAPAN) or 2-(dimethylamino) -2-[(4-Methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone (IRGACURE 379, trade name, manufactured by BASF JAPAN Co., Ltd.) Commercially available compounds or solutions thereof.

As the oxime ester compound, any compound which can form a basic substance via light irradiation can be used. Examples of the oxime ester compound include CGI-325, IRGACURE-OXE01, IRGACURE-OXE02 manufactured by BASF JAPAN Co., Ltd., N-1919, NCI-831 manufactured by ADEKA Co., Ltd., and the like. Further, as described in Japanese Patent No. 4344400, a compound having two oxime ester groups in the molecule can also be suitably used.

These photobase generators may be used alone or in combination of two or more. The amount of the photobase generator 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 part by mass or more, a good contrast of the development resistance of the light-irradiated portion/unirradiated portion can be obtained. Moreover, when it is 40 mass parts or less, the hardening property improves.

Thermally reactive compounds have a hardening reaction due to heat Examples of the functional group-containing resin include an epoxy resin and a polyfunctional oxetane compound.

The above epoxy resin is an epoxy group-containing resin, and any well-known epoxy resin can be used. Specific examples thereof include a difunctional epoxy resin having two epoxy groups in the molecule, and a polyfunctional epoxy resin having a large amount of epoxy groups in the molecule. Further, it may be a hydrogenated difunctional epoxy compound.

Examples of the epoxy resin include bisphenol A epoxy resin, brominated epoxy resin, novolac epoxy resin, bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, and epoxy resin. Propylamine type epoxy resin, intramethylene urea type epoxy resin, alicyclic epoxy resin, trihydroxyphenylmethane type epoxy resin, bixylenol type or biphenol type epoxy resin or the like Bisphenol S type epoxy resin, bisphenol A novolak type epoxy resin, tetraphenol ethane type epoxy resin, heterocyclic epoxy resin, diepoxypropyl phthalate resin, tetraglycol A xylenol ethane resin, an epoxy resin containing a naphthyl group, an epoxy resin having a dicyclopentadiene skeleton, a glycidyl methacrylate copolymer epoxy resin, a cyclohexyl maleimide and a Copolymer epoxy resin based on glycidyl acrylate, CTBN modified epoxy resin, and the like.

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

The amount of the thermally reactive compound to be added is preferably from 1:0.1 to 1:10 in terms of the equivalent ratio of the alkali-soluble resin (the alkali-soluble group such as a carboxyl group to a thermally reactive group such as an epoxy group). With such a ratio The range can be such that the development is good and the fine pattern is easily formed. The above equivalent ratio is preferably from 1:0.2 to 1:5.

A known photopolymerization initiator can be used as the photopolymerization initiator, and examples thereof include an α-aminoacetophenone photopolymerization initiator, a mercaptophosphine oxide photopolymerization initiator, and a benzoin compound. An acetophenone compound, an onion compound, a thioxanthone compound, a ketal compound, a benzophenone compound, a tertiary amine compound, and a oxonone compound.

Further, as the compound having an ethylenically unsaturated bond, a well-known compound, a hydroxyalkyl acrylate such as 2-hydroxyethyl acrylate or 2-hydroxypropyl acrylate; ethylene glycol or methoxy group can be used. a mono- or diacrylate of glycol such as ethylene glycol, polyethylene glycol or propylene glycol; hexanediol, trimethylolpropane, pentaerythritol, dipentaerythritol, tris-hydroxyethyl isocyanurate, etc. a polyhydric alcohol or a polyacrylate of such an ethylene oxide adduct or a propylene oxide adduct; a phenoxy acrylate, a bisphenol A diacrylate, and the phenolic epoxy B An acrylate or the like such as an alkane adduct or a propylene oxide adduct.

(Next layer (A))

The alkali-developable resin composition constituting the adhesive layer (A) may be any composition containing the following resin, and both the photocurable resin composition and the thermosetting resin composition may be used: phenolic hydroxyl group, sulfur A resin which is one or more functional groups of an alcohol group and a carboxyl group and which can be developed in an alkali solution. Preferred examples include 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 having two or more thiol groups. As the resin composition of the compound, a conventionally known one can be used.

Specifically, for example, a photocurable thermosetting resin composition which is 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, and photopolymerization Starting agent, and heat reactive compound. Further, a resin composition comprising a carboxyl group-containing urethane resin, a carboxyl group-containing resin, a photobase generator, and a thermosetting component can also be used. In the resin composition, a base formed by a photobase generator is used as a catalyst, and a urethane resin having a carboxyl group and a thermosetting component are subjected to an addition reaction by heating after exposure, and the unexposed portion can be made by using a base. The solution was removed for development.

As the various materials constituting the resin composition for the adhesive layer (A), those used for the protective layer (B) can be similarly used, except that a conventionally known one can be used.

The resin composition used for the above-mentioned adhesive layer (A) and the protective layer (B) can be blended with a conventional polymer resin for the purpose of improving the flexibility and dryness of the cured product. Examples of such a polymer resin include cellulose-based, polyester-based, phenoxy resin-based polymers, polyvinyl acetal-based, polyvinyl butyral-based, polyamid-based, and polyamidimide. Adhesive polymers, block copolymers, elastomers, and the like. These polymer resins may be used alone or in combination of two or more.

Further, in order to suppress the curing shrinkage of the cured product and to improve the properties such as adhesion and hardness, an inorganic filler may be blended in the resin composition used for the adhesive layer (A) and the protective layer (B). Examples of such an inorganic filler include barium sulfate, amorphous ceria, molten ceria, and spherical dioxygen. Plutonium, talc, clay, magnesium carbonate, calcium carbonate, aluminum oxide, aluminum hydroxide, tantalum nitride, aluminum nitride, boron nitride, Newcastle diatomaceous earth, and the like.

For the preparation of the resin composition and the viscosity adjustment when applied to the substrate and the carrier film, an organic solvent can be used for the resin composition used in the adhesive layer (A) and the protective layer (B). Examples of such an organic solvent include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, and petroleum solvents. These organic solvents may be used singly or in combination of two or more.

In the resin composition used in the adhesive layer (A) and the protective layer (B), a colorant, a mercapto compound, an adhesion promoter, an antioxidant, an ultraviolet absorber, and the like may be further blended as needed. A well-known object in the field of electronic materials. In addition, a conventionally known tackifier such as fine cerium oxide, hydrotalcite, organic bentonite, or montmorillonite, a defoaming agent such as a polyfluorene-based system, a fluorine-based polymer, or a polymer, and a leveling agent may be appropriately formulated. A well-known additive such as a decane coupling agent or a rust inhibitor.

In the laminated structure of the present invention, the adhesion layer (A) is preferably thicker than the protective layer (B) from the viewpoint of traceability to the copper circuit.

The laminated structure system of the present invention can be used for at least one of a curved portion and a non-curved portion of the flexible printed wiring board, and is preferably used for both, thereby providing sufficient durability for bending. The flexible printed wiring board improves both cost and workability. Specifically, the laminated structure system of the present invention can be used as at least one of a cover film, a solder resist, and an interlayer insulating material of a flexible printed wiring board.

(Method of Manufacturing Flexible Printed Wiring Board)

In the present invention, the laminated structure layer is formed directly or through a dry film on a flexible printed wiring substrate, and then patterned by light irradiation, and then patterned by forming a pattern once by a developer. A film can be used to obtain a flexible printed wiring board. Although the characteristics such as the bendability of the single layer of the solder resist layer are not good in the past, the laminated structure formed by the adhesive layer (A) and the protective layer (B) is formed according to the present invention, and the film thickness of the protective layer and the adhesive layer is formed. The ratio of the ratio of the protective layer and the development speed of the adhesive layer falls within the above range, and the alkali developability and the mechanical properties such as heat resistance and flexibility can be satisfactorily combined.

In the following, in an example of the method for producing the flexible printed wiring board of the present invention from the laminated structure of the present invention, both the layer (A) and the protective layer (B) contain a photobase generator and a thermally reactive compound. The case of the resin composition is explained based on the step diagram shown in FIG. In addition, photocuring thermosetting using a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, a compound having an ethylenically unsaturated bond, a photopolymerization initiator, and a heat-reactive compound, which are conventionally used as a solder resist composition, is used. In the case of the resin composition, the same steps as the solder resist can be employed.

[Lamination step]

The lamination step is a step of forming the laminated structure of the present invention on a substrate. The lamination step in FIG. 1 is a state in which a laminated structure formed by the adhesive layer 3 and the protective layer 4 is formed on the flexible printed wiring substrate 1 on which the copper circuit 2 has been formed, and the adhesive layer 3 is made of a base. A composition of a developing resin composition.

Here, each layer constituting the laminated structure, for example, a method in which the resin composition constituting the adhesive layer 3 and the protective layer 4 is sequentially applied and dried on a substrate to directly form the adhesive layer 3 and the protective layer 4 Or the resin composition constituting the adhesive layer 3 and the protective layer 4 is formed by sequentially laminating the resin composition on the substrate in a dry film form. Further, it may be formed by a method in which a laminated structure having a dry film form of a two-layer structure is laminated on a substrate. In this case, at least one side of the laminated structure is supported or protected by a film. As the film to be used, a plastic film which can be peeled off from the laminated structure can be used. Although the thickness of the film is not particularly limited, it is generally selected in the range of 10 to 150 μm. From the viewpoint of film strength, the interfaces between the layers may also be fused.

The method of applying the resin composition to the substrate may be a well-known method such as a knife coater, a lip coater, a comma coater, or a film coater. Further, the drying method is a method using a hot air circulating drying oven, an IR furnace, a heating plate, a convection oven, or the like, which has a heat source such as a steam heating method, and a reverse flow of the hot air in the dryer, and a nozzle sprayed support. The method can be a well-known method.

Here, the substrate is a flexible printed wiring substrate in which a circuit has been formed in advance. Further, in order to obtain effects other than the intended effect, an additional layer may be provided between the adhesive layer 3 and the protective layer 4.

[Light irradiation step]

The light irradiation step is a step of activating the photobase generating agent contained in the resin composition by light irradiation to the negative pattern shape, and curing the light irradiation portion. In the light irradiation step, the mask 5 is placed on the protective layer 4, and the negative pattern is irradiated with light to activate the photobase generator contained in the resin composition to harden the light irradiation portion. .

In this step, the photobase generator is not stabilized by the alkali generated in the light-irradiating portion, and an alkaline substance derived from a photobase generator (hereinafter sometimes simply referred to as "base") is generated. The resulting base causes the photobase generator to become unstable and the base to be regenerated. By generating a base in this manner and chemically proliferating to the depth of each layer, it is considered that it can be sufficiently hardened to the depth of each layer. In the subsequent thermal hardening, since the alkali is used as an addition reaction catalyst for the alkali-developable resin and the thermally reactive compound, an addition reaction is also performed, so that each layer in the light-irradiating portion is sufficiently thermally hardened. To the deeper level. Since the hardening of the resin composition in this case is, for example, a ring-opening reaction of an epoxy by thermal reaction, strain or hardening shrinkage can be suppressed more than in the case of photoreaction.

As a light irradiation machine used for light irradiation, a direct drawing device (for example, a laser direct imaging device that directly draws an image by laser from CAD data of a computer) and a light of a metal halide lamp can be used. An irradiation machine, a light irradiation machine equipped with a (super) high-pressure mercury lamp, a light irradiation machine equipped with a mercury short-arc lamp, or a direct drawing device using an ultraviolet lamp such as a (ultra) high-pressure mercury lamp. The mask-shaped light-illuminating mask is a negative mask.

As the active energy ray system, it is preferred to use laser light or scattered light having a maximum wavelength in the range of 350 to 410 nm. By allowing the maximum wavelength to fall within this range, the photobase generator can be efficiently activated. As long as the laser light of this range is used, the type of laser can be either a gas laser or a solid laser. Further, while the light irradiation amount different lines depending on the film thickness and the like, but is generally 100 ~ 1500mJ / cm ^2, preferably in the range of 300 ~ 1500mJ / cm ² in.

[heating step]

The heating step means that the light-irradiating portion is hardened by heating, and can be hardened to a depth by the alkali generated in the light-irradiating step. This heating step is a step of curing the light irradiation portion by heating the adhesive layer 3 and the protective layer 4 after the light irradiation step, and is referred to as a "PEB (POST EXPOSURE BAKE) step". According to this, each layer is sufficiently hardened to a deep point by the alkali generated in the light irradiation step, whereby a pattern layer having excellent curing properties can be obtained.

For example, the heating step is preferably performed at a temperature lower than a heat generation start temperature or a heat generation peak temperature of the unexposed resin composition, and higher than a heat generation start temperature or a heat generation peak temperature of the resin composition which has been irradiated with light. By heating in this way, only the light irradiation portion can be selectively hardened.

The heating temperature at this time is thermally hardened by the light-irradiating portion in the resin composition, but the temperature at which the unirradiated portion is not thermally cured is preferable. The heating temperature is, for example, 80 to 140 ° C, and the heating temperature is set to 80 ° C or higher, whereby the light-irradiating portion can be sufficiently cured. On the other hand, by setting the heating temperature to 140 ° C or lower, only the light irradiation portion can be selectively cured. The heating time is, for example, 10 to 100 minutes. The heating method is the same as the above drying method. Further, since no alkali is generated from the photobase generating agent in the unirradiated portion, thermal hardening is suppressed.

[development step]

The developing step is to remove the unirradiated portion by alkali development to form a negative pattern layer. The developing step in Fig. 1 shows a step of removing the unirradiated portion and forming a negative pattern layer by developing the adhesive layer 3 and the protective layer 4 with an aqueous alkaline solution. As the developing method, a well-known method such as a dipping method, a bathing method, a spraying method, or a brushing method can be used. Further, as the developer, an alkali such as potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium citrate, ammonia or ethanolamine, or a base such as tetramethylammonium hydroxide aqueous solution (TMAH) can be used. An aqueous solution or a mixture of these.

[Second light irradiation step]

Preferably, after the developing step, the step of including the second light irradiation is preferred. This second light irradiation step is a step of irradiating ultraviolet rays as needed in order to activate the residual photobase generator which has not been activated in the pattern layer of the light irradiation step and to generate a base. The ultraviolet light wavelength and the light irradiation amount (exposure amount) in the second light irradiation step may be the same as or different from the light irradiation step described above. Light irradiation amount (exposure amount) based, for example, 150 ~ 2000mJ / cm ^2.

[thermal hardening step]

After the developing step, a thermal hardening step further including thermal hardening (post hardening) is preferred. This heat hardening step is a step of thermally hardening (post-hardening) required for the pattern layer to be sufficiently thermally hardened. In the case where both the second light irradiation step and the heat hardening step are performed after the development step, it is preferred that the heat hardening step is performed after the second light irradiation step.

In the thermal hardening step, the pattern layer is sufficiently thermally cured by the alkali generated by the photobase generator by the light irradiation step or the light irradiation step and the second light irradiation step. Since the unheated portion has been removed at the time point of the heat hardening step, the heat hardening step can be performed at a temperature higher than the hardening reaction starting temperature of the unirradiated resin composition, whereby the patterned layer can be sufficiently thermally hardened. The heating temperature is, for example, 150 ° C or higher.

Example

The invention will be described in more detail below using examples.

(Synthesis Example 1)

<Synthesis of alkali-soluble resin having a quinone ring>

In a separable three-necked flask equipped with a stirrer, a nitrogen introduction tube, a fractionation ring and a cooling ring, 12.5 g of 3,5-diaminobenzoic acid and 2,2'-bis[4-(4-aminobenzene) were added. 8.2 g of oxy)phenyl]propane, 30 g of NMP, 30 g of γ-butyrolactone, 27.9 g of 4,4′-oxydiphthalic anhydride, 3.8 g of benzenetricarboxylic anhydride, and stirred at room temperature and 100 rpm under a nitrogen atmosphere. 4 hours. Then, 20 g of toluene was added, and toluene and water were distilled off at a bath temperature of 180 ° C and 150 rpm while stirring for 4 hours to obtain an alkali-soluble resin solution containing a quinone ring. Thereafter, γ-butyrolactone was added so that the solid content became 30% by mass. The obtained resin solution had a solid content of 86 mg KOH/g and Mw 10000.

(Synthesis Example 2)

<Synthesis of carboxyl group-containing urethane resin>

A polycarbonate diol derived from 1,5-pentanediol and 1,6-hexanediol is placed in a reaction vessel equipped with a stirring device, a thermometer, and a condenser (Asahi Kasei Chemical Co., Ltd., T5650J, number The average molecular weight was 800) 2400 g (3 moles), dimethylglycolic acid 603 g (4.5 moles), and 238 g (2.6 moles) of 2-hydroxyethyl acrylate as a monohydroxy compound. Next, 1887 g (8.5 mol) of isophorone diisocyanate as a polyisocyanate was placed, stirred and heated to 60 ° C, and then stopped, and then heated again at the temperature in the reaction vessel, and continuously stirred at 80 ° C. It was confirmed by infrared absorption spectrum that the absorption spectrum (2280 cm ^-1 ) of the isocyanate group had disappeared and the reaction was terminated. Thereafter, carbitol acetate was added so that the solid content became 50% by mass, and the obtained carboxyl group-containing urethane resin had a solid content of 50 mg KOH/g.

<Preparation of resin composition constituting each layer>

The materials described in the examples and the comparative examples were prepared according to the blending methods described in the following Tables 1 and 2, and pre-mixed with a stirrer, and then kneaded by a three-roll honing machine to prepare an adhesive layer and protect the laminate. The resin composition of the layer. The values in the table are parts by mass unless otherwise specified.

<Formation of layer (A)>

A flexible printed wiring substrate having a circuit having a copper thickness of 18 μm was prepared and pretreated by using CB-801Y manufactured by MEC Corporation. Then, on the flexible printed wiring substrate which has been subjected to the pretreatment, each of the adhesive layers is applied so that the film thickness after drying becomes the film thickness shown in the following Tables 1 and 2. The resin composition. Thereafter, it was dried at 80 ° C / 30 minutes in a hot air circulating drying oven to form an adhesive layer (A) composed of a resin composition. Further, in Comparative Example 1, no adhesion layer was formed.

<Formation of protective layer (B)>

In the above-mentioned adhesive layer (A), the resin composition for each protective layer was applied so that the film thickness after drying became the film thickness shown by the following Table 1 and Table 2. Thereafter, it was dried at 80 ° C / 30 minutes in a hot air circulating drying oven to form a protective layer (B) composed of a resin composition.

Next, the total film thickness of the 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 development speed>

Each resin composition was applied onto a flexible printed wiring substrate on which a circuit having a copper thickness of 18 μm was formed, and dried in a hot air circulating drying oven at 80 ° C / 30 minutes. Thereafter, the substrate was immersed in an aqueous solution of sodium carbonate at 30 ° C in an amount of ‧1% by mass, and the time until the coating film was dissolved was measured. When the time until the coating film is dissolved is set to the development time [second] and the film thickness is set to the film thickness [μm], the development speed is expressed by the following formula.

Development speed [μm/sec] = film thickness [μm] / development time [sec].

<Alkali developability, solder heat resistance, and gold plating resistance>

The base material having the laminated structure obtained as described above was irradiated with a negative pattern shape by an HMW 680GW (metal halide lamp, scattered light) manufactured by ORC Co., Ltd. at an exposure amount of 500 mJ/cm ² . Heating treatment at 90 ° C for 60 minutes was then carried out. Thereafter, the substrate was immersed in an aqueous solution of sodium carbonate at 30 ° C in an amount of ‧1% by mass for 3 minutes, and the alkali developability was evaluated. The evaluation was performed visually and evaluated using the following criteria.

○: No residue development

×: There is development residue

Subsequently, heat treatment was performed at 150 ° C for 60 minutes using a hot air circulating drying oven to obtain a cured coating film having a pattern shape. For the obtained hardened coating film, a rosin-based flux was applied to the evaluation substrate, and immersed in a solder bath set at 260 ° C for 20 seconds (10 seconds × 2 times), and the flux was washed with isopropyl alcohol. Thereafter, the peeling test was carried out using a cellophane adhesive tape, and the following criteria were evaluated for swelling, peeling, discoloration, and the like.

○: No change found at all

×: The person who has expanded or peeled off

Moreover, the obtained hardened coating film was plated with an electroless nickel plating bath and an electroless gold plating bath of a commercial product at 80 to 90 ° C, nickel 5 μm, and gold 0.05 μm. The plated evaluation substrate was visually evaluated for the presence or absence of plating penetration.

○: no penetration

×: An infiltrant was confirmed between the substrate and the coating film.

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

*5: Dicyclopentadiene type epoxy resin (made by DIC) ※6: Bisphenol A type epoxy resin (molecular weight: 400) (Mitsubishi Chemical Co., Ltd.) ※7: 肟-type photobase generator (manufactured by BASF JAPAN Co., Ltd.) *8: 2-(Dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]- 1-Butyl ketone (manufactured by BASF JAPAN Co., Ltd.) *9: bisphenol F-type acid-modified epoxy acrylate (manufactured by Nippon Kayaku Co., Ltd.) *10: Barium sulfate (manufactured by Nippon Chemical Co., Ltd.)

As is clear from the evaluation results shown in Tables 1 and 2 above, it was confirmed that the flexible printed wiring board of the example exhibited good developability and heat resistance. On the other hand, it is understood that Comparative Example 1 is composed only of a protective layer having a resin composition of a quinone ring, and therefore has good heat resistance, but developability is not good, and development using a general sodium carbonate is impossible. Further, in Comparative Example 2, since the adhesion layer was thin, and the ratio of the thickness of the adhesion layer to the protective layer was Although it is out of the range of the present invention, although the heat resistance is good, the developability is deteriorated as a result. Further, in Comparative Example 3, since the ratio of the film thickness of the adhesive layer to the protective layer was still out of the range of the present invention, the developability was good, but the heat resistance was deteriorated. In Comparative Example 4, although the ratio of the film thickness is within the range of the present invention, since the developing speed of the adhesive layer and the protective layer is the same, the ratio of the developing speed of both is out of the range of the present invention, so that the developing property is changed. difference. In Comparative Example 5, since the ratio of the developing speed was out of the range of the present invention, the developability was good, but the heat resistance was deteriorated.

1‧‧‧Flexible printed wiring substrate

2‧‧‧Bronze circuit

3‧‧‧Next layer

4‧‧‧Protective layer

5‧‧‧ mask

Claims (6)

A laminated structure characterized by having an adhesive layer (A) composed of an alkali-developable resin composition and a photosensitive resin composition formed on the adhesive layer (A) The ratio of the film thickness of the adhesive layer (A) to the protective layer (B) is A/B = 0.5 to 50, and the development speed (a) of the adhesive layer (A) and the development speed of the protective layer (B) The ratio of (b) is a/b=1.1~100. The laminate structure of claim 1, wherein the adhesive layer (A) and the protective layer (B) are patterned by light irradiation. The laminated structure according to claim 1 is used for at least one of a bent portion and a non-bent portion of the flexible printed wiring board. The laminated structure according to claim 1, which is used for at least one of a coating layer of a flexible printed wiring board, a solder resist, and an interlayer insulating material. 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. A flexible printed wiring board comprising: an insulating film formed by directly forming a layer of the laminated structure according to any one of claims 1 to 4 on a flexible printed wiring board, or After forming a layer of the laminated structure by the dry film of the claim 5, the pattern is formed by light irradiation, and the insulating film is formed by patterning the developing solution once.