KR20170070134A - Dry film and flexible printed wiring board - Google Patents

Abstract

Provided is a dry film that satisfies the required performance as an insulating film of a flexible printed wiring board and is suitable for a batch forming process of a bent portion and a mounting portion. Further, there is provided a flexible printed wiring board having the dry film as a protective film, for example, a coverlay or a solder resist. A dry film of a laminated structure in which two or more different resin compositions are laminated and has a glass transition point of at least 100 deg. C and at least 100 deg. C as a cured product, and a flexible printed wiring board using the same.

Description

[0001] DRY FILM AND FLEXIBLE PRINTED WIRING BOARD [0002]

The present invention relates to a dry film and a flexible printed wiring board, and more particularly to a dry film useful as an insulation film of a flexible printed wiring board and a flexible printed wiring board using the dry film.

2. Description of the Related Art In recent years, small-sized circuit boards have become necessary due to the miniaturization of electronic devices due to the spread of smart phones and tablet terminals. As a result, the use of a flexible printed wiring board which can be folded and housed has been expanded, and such a flexible printed wiring board is required to have higher reliability than ever.

On the other hand, a coverlay based on polyimide excellent in mechanical properties such as heat resistance and bending property is used as the insulating film for securing the insulation reliability of the flexible printed wiring board at the bent portion (bent portion) (Refer to documents 1 and 2), and a mixed process using a photosensitive resin composition which is excellent in electric insulation and can be micro-machined is widely adopted in a mounting portion (non-bent portion).

That is, a coverlay based on polyimide excellent in mechanical properties such as heat resistance and bendability is not suitable for fine wiring because it requires machining by die punching. As a result, it has been necessary to partially use an alkali development type photosensitive resin composition (solder resist) capable of being processed by photolithography in a chip mounting portion where fine wiring is required.

Japanese Patent Application Laid-Open No. 62-263692 Japanese Patent Application Laid-Open No. 63-110224

As described above, in the manufacturing process of the flexible printed wiring board, there is a problem in that cost and operability are inferior because the process of combining the coverlay and the solder resist is inevitable.

On the contrary, it has been studied to apply an insulating film as a solder resist or an insulating film as a coverlay to both of a solder resist and a coverlay of a flexible printed wiring board. However, materials that can sufficiently satisfy both required performances have not yet been put to practical use I did not. Particularly, for a flexible printed wiring board, it has been required to realize a material having both alkali development required for an insulating film as a solder resist and mechanical properties such as heat resistance and flexibility required for an insulating film as a coverlay.

It is therefore an object of the present invention to provide a dry film which improves lamination for forming an insulating film of a flexible printed wiring board, satisfies required performance as an insulating film, and is suitable for a process of forming a bending part and a mounting part in a batch, And a flexible printed wiring board having a film as a protective film, for example, a coverlay or a solder resist.

DISCLOSURE OF THE INVENTION As a result of intensive investigations to solve the above problems, the present inventors have found that when a dry film used for a flexible printed wiring board is a laminated structure composed of two or more different resin compositions laminated and a glass transition point Tg) within a predetermined range, the above problems can be solved, and the present invention has been accomplished.

That is, the present invention is characterized in that a dry film of a laminated structure comprising two or more different resin compositions is laminated, and has at least one glass transition point (Tg) of less than 100 캜 and not less than 100 캜 as a cured product.

The dry film of the present invention preferably has at least one glass transition point in the range of 40 to 90 占 폚 and in the range of 110 to 200 占 폚, respectively. It is also preferable that the laminated structure has a two-layer structure. It is also preferable that the laminate structure of the two-layer structure has an adhesive layer (A) comprising an alkali developable resin composition and a protective layer (B) comprising a photosensitive resin composition. Further, it is preferable that the laminated structure can be patterned by light irradiation.

The dry film of the present invention is suitably used for at least one of a bent portion and a non-bent portion of a flexible printed wiring board. Further, the dry film of the present invention is suitably used for the use of at least one of a coverlay, a solder resist and an interlayer insulating material of a flexible printed wiring board. It is preferable that the dry film of the present invention has at least one side supported or protected by a film.

The flexible printed wiring board of the present invention includes an insulating film formed by forming a layer of a laminated structure with the above dry film of the present invention on a flexible printed wiring board and patterning it by light irradiation and collectively forming patterns by a developer .

In the present invention, the term " pattern " means a patterned cured product, that is, an insulating film.

According to the present invention, it is made possible to realize a dry film and a flexible printed wiring board using the same, which satisfies required performance as an insulating film of a flexible printed wiring board and is suitable for a batch forming process of a bent portion and a mounting portion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process diagram schematically showing an example of a manufacturing method of a flexible printed wiring board according to the present invention.
2 shows the dynamic characteristics of the dry film of (a) Example 1, (b) Example 2, (c) Example 3, (d) A graph showing the glass transition point from the results of viscoelasticity measurement (DMA).

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Dry film)

The dry film of the present invention is a dry film of a laminated structure in which two or more different resin compositions are laminated, and the cured product thereof has at least one glass transition point lower than 100 캜 and higher than 100 캜, respectively.

In such a dry film, a resin composition having a glass transition temperature of less than 100 占 폚 exhibits a good adhesion function to a printed wiring board by having at least one glass transition point of less than 100 占 폚 and at least 100 占 폚, respectively, On the other hand, a resin composition having a glass transition temperature of 100 占 폚 or higher of a cured product can satisfactorily exhibit mechanical properties such as heat resistance and flexibility required for an insulating film as a coverlay. In order for the dry film of the present invention to exhibit various properties such as adhesion function and heat resistance, it is preferable that the glass transition point is at least one in the range of 40 to 90 캜 and in the range of 110 to 200 캜, respectively. It is more preferable that the temperature range of the glass transition point is in the range of 45 to 80 ° C on the low temperature side and the range of 120 to 180 ° C on the high temperature side is more preferable. The number of layers of the laminated structure is not limited to two, and may be three or more.

The laminated structure preferably has a two-layer structure, and preferably has an adhesive layer (A) comprising an alkali developable resin composition and a protective layer (B) comprising a photosensitive resin composition, and the laminated structure It is preferable that patterning by light irradiation is possible. This makes it possible to realize a dry film having both of alkali development required for an insulating film as a solder resist and mechanical properties such as heat resistance and flexibility required for an insulating film as a coverlay for a flexible printed wiring board.

Sensitive dry film of the present invention constituting the adhesive layer (A) for the alkali developable resin composition and the protective layer (B) for the photosensitive resin composition will be specifically described below.

In addition, the following examples taken as examples of the components in the resin composition are that these components can be used in order to control the Tg to obtain a high Tg (or low Tg). For example, it is useful to use an imide or an imide precursor in order to form a coating film having a high Tg. In addition, a method of forming a dense crosslinked structure by using a polyfunctional acrylate or a polyfunctional epoxy I think. On the other hand, in order to suppress the Tg to a low level, a resin having a flexible skeleton may be used, or a bifunctional acrylate or monofunctional component may be used.

(Protective layer (B))

If the photosensitive resin composition constituting the protective layer (B) is capable of exhibiting a glass transition point as a cured product of a dry film at 100 占 폚 or higher, preferably 110 to 200 占 폚, more preferably 120 to 180 占 폚, For example, a composition containing a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, a compound having an ethylenically unsaturated bond, a photopolymerization initiator and a thermoreactive compound, which are conventionally used as a solder resist composition, A photosensitive thermosetting resin composition comprising a composition, a carboxyl group-containing resin, a photo-base generator and a heat-reactive compound may be used.

Among them, the protective layer (B) preferably comprises a resin composition comprising an alkali soluble resin having an imide ring or imide precursor skeleton.

In the present invention, an alkali soluble resin having an imide ring or imide precursor skeleton is one 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 introduction of the imide ring or imide precursor skeleton to the alkali soluble resin, a publicly known method can be used. For example, a resin obtained by reacting a carboxylic acid anhydride component with either or both of an amine component and an isocyanate component can be given. The imidization may be performed by thermal imidization, chemical imidization, or both.

Examples of the carboxylic acid anhydride component include tetracarboxylic acid anhydride and tricarboxylic acid anhydride. However, the acid anhydride is not limited to these acid anhydrides, and if it is a compound having an acid anhydride group and a carboxyl group which react with an amino group or an isocyanate group , And derivatives thereof. These carboxylic acid anhydride components may be used alone or in combination.

Examples of the tetracarboxylic acid anhydride include pyromellitic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid Acid dianhydride, 4,4'-oxydiphthalic dianhydride, 1,2,3,4-benzenetetracarboxylic acid dianhydride, 3,3 ", 4,4" -terphenyltetracarboxylic acid dianhydride, 3,3 "', 4,4"' - quinquephenyl tetracarboxylic acid dianhydride, methylene-4,4'-di Phthalic dianhydride, 1,1-ethynylidene-4,4'-diphthalic dianhydride, 2,2-propylidene-4,4'-diphthalic dianhydride, 1,2- Diphthalic acid dianhydride, 1,3-trimethylene-4,4'-diphthalic dianhydride, 1,4-tetramethylene-4,4'-diphthalic dianhydride, 1,5-pentamethylene- -Diphthalic acid dianhydride, thio-4,4'-diphthalic acid dianhydride, sulfonyl-4,4'-diphthalic dianhydride, 1,3-bis (3,4-dicarboxyphenyl) 3,3-tetramethylsiloxane imine Water, 1,3-bis (3,4-dicarboxyphenyl) benzene dianhydride, 1,4-bis (3,4-dicarboxyphenyl) benzene dianhydride, 1,3- Benzene dianhydride, 1,4-bis (3,4-dicarboxyphenoxy) benzene dianhydride, 1,3-bis [2- (3,4-dicarboxyphenyl) Water, 1,4-bis [2- (3,4-dicarboxyphenyl) -2-propyl] benzene dianhydride, bis [3- (3,4-dicarboxyphenoxy) phenyl] methane dianhydride, 3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 3,4,9,10-perylenetetracarboxylic acid dianhydride, 2,3 , 6,7-anthracene tetracarboxylic acid dianhydride, 1,2,7,8-phenanthrene tetracarboxylic acid dianhydride, 1,2,3,4-butanetetracarboxylic acid dianhydride, 1,2, 3,4-cyclobutanetetracarboxylic acid dianhydride, cyclopentanetetracarboxylic acid dianhydride, cyclohexane-1,2,3,4-tetracarboxylic acid dianhydride, 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 1,2-dicarboxylic acid dianhydride, 1,1-ethynylidene-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, 2,2- Diethylene glycol bis (trimellitate anhydride), 1, 2, 3, 4, 5, 6, (Tetramethylene anhydride), 1,5- (pentamethylene) bis (trimellitate anhydride), 1,6- (tetramethylene anhydride) (Hexamethylene) bis (trimellitate anhydride), 1,7- (heptamethylene) bis (trimellitate anhydride), 1,8- (octamethylene) bis (Trimellitate anhydride), 1,10- (decamethylene) bis (trimellitate anhydride), 1,12- (dodecamethylene) bis (trimellitate anhydride) Anhydride), 1,16- (hexadecamethylene) bis (trimellitate anhydride), and 1,18- (octadecamethylene) bis (trimellitate anhydride).

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

As amine components, polyamines such as aliphatic diamines and diamines such as aromatic diamines and aliphatic polyether amines can be used, but the amines are not limited to these amines. These amine components may be used alone or in combination.

Examples of the diamine include benzene nucleus such as p-phenylenediamine (PPD), 1,3-diaminobenzene, 2,4-toluenediamine, 2,5-toluenediamine, 2,6- , Diaminodiphenyl ethers such as 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether and 3,4'-diaminodiphenyl ether, and diaminodiphenyl ethers such as 4,4'-diaminodi 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-diaminodiphenyl ether, Benzene nucleus such as 4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, etc. Two diamines , Benzene nuclei 3 such as 1,3-bis (3-aminophenylsulfide) benzene, 1,3-bis (4-aminophenylsulfide) benzene and 1,4- Biphenyl, 3,3'-bis (4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl , 2,2- Propane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, Aromatic diamine such as benzene nucleus 4 diamine such as propane and 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,2-diaminoethane, 1,3-diaminopropane, , 4-diaminobutane, 1,5-diaminopentane, and 1,6-diaminohexane. Examples of aliphatic polyether amines include ethylene glycol and / or propylene glycol-based polyamines. . Examples of the polyoxyalkylene diamine include polyoxyethylene diamine, polyoxypropylene diamine, and polyoxybutylene diamine. Commercially available products include Zephamine EDR-148, EDR-176, Jeffamine D- 230, D-400, D-2000, D-4000, Jeffamine ED-600, ED-900, ED-2003 and Jeffamine XTJ-542. In addition, an amine having a carboxyl group may be used as described below.

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) Aminophenoxybenzoic acids such as 3,5-bis (4-aminophenoxy) benzoic acid, carboxybiphenyl compounds such as 3,3'-diamino-4,4'-dicarboxybiphenyl, Diamino-4,4'-dicarboxy diphenylmethane, 3,3'-dicarboxy-4,4'-diaminodiphenylmethane, 2,2-bis [ , Carboxy diphenyl alcohols such as 3,3'-diamino-4,4'-dicarboxy diphenyl ether and 4,4'-diamino-3,3'-dicarboxy diphenyl ether Ether compounds, diphenyl sulfone compounds such as 3,3'-diamino-4,4'-dicarboxy diphenyl sulfone and 4,4'-diamino-3,3'-dicarboxy diphenyl sulfone have.

Examples of the isocyanate component include diisocyanates such as aromatic diisocyanates and isomers or isomers thereof, aliphatic diisocyanates, alicyclic diisocyanates and isomers thereof, and other general diisocyanates. However, the diisocyanates are not limited to these isocyanates no. These isocyanate components may be used alone or in combination.

Examples of the diisocyanate include aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, biphenyl diisocyanate, diphenylsulfone diisocyanate and diphenyl ether diisocyanate. Aliphatic diisocyanates such as diisocyanate and its isomers, oligomers, hexamethylene diisocyanate, isophorone diisocyanate and dicyclohexylmethane diisocyanate, alicyclic diisocyanates obtained by hydrogenating aromatic diisocyanates and isomers thereof, And general diisocyanates out of these.

The alkali-soluble resin having an imide ring or imide precursor skeleton as described above may have an amide bond. This may be an amide bond obtained by reacting an isocyanate and a carboxylic acid, or may be obtained by other reactions. Further, it may have a bond including addition and condensation.

The introduction of the imide ring or imide precursor skeleton to the alkali-soluble resin may be carried out using an alkali-soluble polymer, oligomer or monomer having either or both of a carboxyl group and an acid anhydride group for known purpose, The resin may be a resin obtained by reacting a known alkali-soluble resin stream with the above amine / isocyanate, alone or in combination with the above carboxylic acid anhydride component.

In the synthesis of such an alkali-soluble group and an alkali-soluble resin having an imide ring or imide precursor skeleton, an organic solvent for publicly known generations can be used. Such an organic solvent is not particularly limited as long as it is a solvent which does not react with carboxylic acid anhydrides, amines and isocyanates as raw materials, and dissolves these raw materials, and the structure thereof is not particularly limited. Among them, non-proton such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, Sex solvents are preferred.

The alkali soluble resin having an alkali soluble group such as a carboxyl group or an acid anhydride group and an alkali soluble resin having an imide ring or imide precursor skeleton as described above preferably has an acid value of 20 to 200 mgKOH / g in order to cope with the photolithography step, And more preferably 60 to 150 mgKOH / g. When the acid value is not less than 20 mgKOH / g, the solubility in alkali is increased, the developability is improved, and further the degree of crosslinking with the thermosetting component after irradiation is increased, so that sufficient development contrast can be obtained. When the acid value is 200 mgKOH / g or less, so-called thermal blur in the post-exposure bake (PEB) process after light irradiation described later can be suppressed, and the process margin is increased.

The molecular weight of the alkali-soluble resin is preferably 1,000 to 100,000, more preferably 2,000 to 50,000, in view of developability and cured coating film characteristics. When the molecular weight is 1,000 or more, sufficient developing resistance and physical properties can be obtained after exposure and PEB. When the molecular weight is 100,000 or less, the alkali solubility is increased and the developability is improved.

The resin composition comprising an alkali-soluble resin having an imide ring or an imide precursor skeleton contains a photo-base generator and a thermoreactive compound in addition to an alkali-soluble resin in the case of using a photo-base generator, Is used, it contains a photopolymerization initiator and a compound having an ethylenically unsaturated bond in addition to the alkali-soluble resin. As the resin component, a carboxyl group-containing urethane resin, a carboxyl group-containing novolak resin, or the like may be used in combination.

The photobase generator is a compound capable of generating at least one basic substance capable of functioning as a catalyst for the polymerization reaction of the heat-reactive compound described later, when the molecule structure is changed by light irradiation such as ultraviolet rays or visible light, to be. Examples of the basic substance include a secondary amine and a tertiary amine.

Examples of the photobase generator include an? -Amino acetophenone compound, an oxime ester compound, an acyloxyimino group, an N-formylated aromatic amino group, a N-acylated aromatic amino group, a nitrobenzyl carbamate group, And a compound having a substituent such as a carboxylate group and a carboxylate group. Of these, oxime ester compounds and? -Aminoacetophenone compounds are preferable. As the? -amino acetophenone compound, those having at least two nitrogen atoms are particularly preferred.

The? -aminoacetophenone compound has a benzoin ether bond in its molecule, and when subjected to light irradiation, cleavage occurs in the molecule, and a basic substance (amine) is produced which exhibits a curing catalytic action. Specific examples of the? -amino acetophenone compound include 4- (methylthiobenzoyl) -1-benzyl-1-dimethylaminopropane (Irgacure 369, trade name, Methyl-1-morpholinoethane (Irgacure 907, trade name, manufactured by BASF Japan) and 2- (dimethylamino) -2 - [(4- methylphenyl) methyl] -1- [4- Phenyl] -1-butanone (Irgacure 379, trade name, manufactured by BASF Japan), or a solution thereof can be used.

As the oxime ester compound, any compound capable of generating a basic substance by light irradiation can be used. Examples of such oxime ester compounds include CGI-325, Irgacure-OXE01, Irgacure-OXE02 manufactured by BASF Japan, N-1919 and NCI-831 manufactured by Adeka Corporation. Compounds having two oxime ester groups in the molecule described in Japanese Patent No. 4344400 can also be suitably used.

These photobase generators may be used singly or in combination of two or more. The blending amount of the photo-base generator in the resin composition is preferably 0.1 to 40 parts by mass, more preferably 0.1 to 30 parts by mass with respect to 100 parts by mass of the thermally reactive compound. When the amount is not less than 0.1 part by mass, the contrast of the developability of the light irradiation portion / the non-irradiation portion can be satisfactorily obtained. When the amount is 40 parts by mass or less, the properties of the cured product are improved.

The heat-reactive compound is a resin having a functional group capable of a curing reaction by heat, and examples thereof include an epoxy resin and a polyfunctional oxetane compound.

The epoxy resin is a resin having an epoxy group, and any known epoxy resin can be used. Specifically, there may be mentioned a bifunctional epoxy resin having two epoxy groups in the molecule and a polyfunctional epoxy resin having a large number of epoxy groups in the molecule. Further, it may be a hydrogenated bifunctional epoxy compound.

Examples of the epoxy resin include bisphenol A epoxy resin, brominated epoxy resin, novolak epoxy resin, bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, glycidylamine epoxy resin, Hidantoin epoxy resin, Type epoxy resin, trihydroxyphenylmethane type epoxy resin, beccylenol type or biphenol type epoxy resin or a mixture thereof; Bisphenol S type epoxy resin, bisphenol A novolak type epoxy resin, biphenyl novolac type epoxy resin, tetraphenylol ethane type epoxy resin, heterocyclic epoxy resin, diglycidyl phthalate resin, tetraglycidylsilaneoyl ethane resin , Naphthalene group-containing epoxy resin, epoxy resin having dicyclopentadiene skeleton, glycidyl methacrylate copolymer-based epoxy resin, copolymerized epoxy resin of cyclohexylmaleimide and glycidyl methacrylate, and CTBN-modified epoxy resin. .

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

As the photopolymerization initiator, known photopolymerization initiators can be used, and examples thereof include an? -Aminoacetophenone photopolymerization initiator, an acylphosphine oxide photopolymerization initiator, a benzoin compound, an acetophenone compound, an anthraquinone compound, Ketone compounds, benzophenone compounds, tertiary amine compounds and xanthone compounds.

As the compound having an ethylenic unsaturated bond, known compounds can be used, and hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; Mono or diacrylates of glycols such as ethylene glycol, methoxytetraethylene glycol, polyethylene glycol and propylene glycol; Polyhydric alcohols such as hexanediol, trimethylol propane, pentaerythritol, dipentaerythritol, and tris-hydroxyethylisocyanurate, or polyhydric acrylates such as ethylene oxide adducts or propylene oxide adducts thereof; Phenoxy acrylate, bisphenol A diacrylate, and acrylates such as ethylene oxide adducts or propylene oxide adducts of these phenols.

(Adhesive layer (A))

The alkali developable resin composition constituting the adhesive layer (A) is a composition containing a resin which contains at least one functional group selected from the group consisting of a phenolic hydroxyl group, a thiol group and a carboxyl group and which can be developed into an alkali solution, May be any composition as far as the transition point can be expressed at a temperature of less than 100 ° C, preferably 40 to 90 ° C, more preferably 45 to 80 ° C. The photocurable resin composition may also be used as a thermosetting resin composition . Preferably, a resin composition comprising 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 can be used and a known one is used .

Specifically, for example, a photocurable thermosetting resin composition comprising a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, a compound having an ethylenically unsaturated bond, a photopolymerization initiator, and a thermoreactive compound, which has been conventionally used as a solder resist composition . Further, a resin composition containing a carboxyl group-containing urethane resin, a carboxyl group-containing resin, a photo-base generator and a thermosetting component may also be used. Such a resin composition is obtained by subjecting a urethane resin having a carboxyl group and a thermosetting component to an addition reaction by heating after exposure using a base generated from a photo-base generating agent as a catalyst and removing the unexposed portion with an alkali solution, will be.

As the materials constituting the resin composition used for the adhesive layer (A), those used in the protective layer (B) may be used as well as the known materials.

The resin composition used in the adhesive layer (A) and the protective layer (B) may be blended with a publicly known polymer resin for the purpose of improving the flexibility and tackiness of the resulting cured product. Examples of such a polymer resin include cellulose type, polyester type, phenoxy resin type, polyvinyl acetal type, polyvinyl butyral type, polyamide type, polyamideimide type binder polymer, block copolymer and elastomer. One kind of the polymer resin may be used alone, or two or more kinds may be used in combination.

An inorganic filler may be added to the resin composition used in the adhesive layer (A) and the protective layer (B) in order to suppress curing shrinkage of the cured product and to improve properties such as adhesion and hardness. Examples of such inorganic fillers include barium sulfate, amorphous silica, fused silica, spherical silica, talc, clay, magnesium carbonate, calcium carbonate, aluminum oxide, aluminum hydroxide, silicon nitride, aluminum nitride, boron nitride, .

An organic solvent can be used for the resin composition used in the adhesive layer (A) and the protective layer (B) for the production of a resin composition or for viscosity adjustment for application to a substrate or a carrier film. Examples of such organic solvents include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons and petroleum solvents. These organic solvents may be used singly or as a mixture of two or more kinds.

A component such as a colorant, a mercapto compound, an adhesion promoter, an antioxidant, and an ultraviolet absorber may be further added to the resin composition used in the adhesive layer (A) and the protective layer (B). These can be used in the field of electronic materials. It is also possible to appropriately blend known additives such as thickening agents for known additives such as fine silica, hydrotalcite, organic bentonite and montmorillonite, defoaming agents and leveling agents such as silicones, fluorides and polymers, silane coupling agents and rust preventives have.

In the dry film of the present invention, it is preferable that the adhesive layer (A) is thicker than the protective layer (B) in view of the ability to follow the copper circuit.

The dry film of the present invention can be used for at least one of the bent portion and the non-bent portion of the flexible printed wiring board, or preferably both, so that the flexible printed wiring board having sufficient durability against bending can be used as the flexible printed wiring board, Can be obtained while improving. Specifically, the dry film of the present invention can be used for at least one of the coverlay, the solder resist, and the interlayer insulating material of the flexible printed wiring board.

(Manufacturing Method of Flexible Printed Circuit Board)

In the present invention, a layer of a laminated structure of the dry film of the present invention is formed on a flexible printed wiring substrate, patterned by light irradiation, and patterns are collectively formed by a developer to form an insulating film, Can be obtained. In the conventional single layer of the solder resist layer, the characteristics such as flexibility are poor. However, according to the present invention, a dry film of a laminated structure having at least an adhesive layer (A) and a protective layer (B) , A resin composition having a glass transition temperature of less than 100 占 폚 as a cured product exhibits a good adhesion function to a printed wiring board and a glass as a cured product having a glass transition temperature of less than 100 占 폚 and at least two independently at 100 占 폚 or more, The resin composition having a transition temperature of 100 deg. C or higher can exhibit satisfactory mechanical properties such as heat resistance and flexibility required for an insulating film as a coverlay.

An example of a method for producing the flexible printed wiring board of the present invention from the dry film of the present invention will be described below with reference to both of the adhesive layer (A) and the protective layer (B) constituting the dry film, The case where a resin composition containing a thermally reactive compound is used will be described based on a process chart shown in Fig. When a photo-curable thermosetting resin composition containing a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, a compound having an ethylenically unsaturated bond, a photopolymerization initiator and a thermoreactive compound, which has been conventionally used as a solder resist composition, is used , The same process as that of the solder resist can be performed.

[Lamination step]

The lamination step is a step of forming a laminated structure of the dry film of the present invention on a substrate. 1, a lamination structure including an adhesive layer 3 including an alkali developing resin composition and a protective layer 4 is formed on a flexible printed wiring board 1 on which a copper circuit 2 is formed State.

Here, each layer constituting the laminated structure can be formed by a method of laminating a resin composition constituting the adhesive layer 3 and the protective layer 4 in the form of a dry film of the present invention to a substrate. In this case, at least one side of the laminated structure may be supported or protected by a film. As the film to be used, a peelable plastic film can be used from the laminated structure. The thickness of the film is not particularly limited, but is generally appropriately selected in the range of 10 to 150 mu m. From the viewpoint of coating film strength, the interface between the respective layers may be affinity.

The method of applying the resin composition to the substrate is preferably a known method such as a blade coater, a lip coater, a comma coater, and a film coater. The drying method includes a method in which hot air circulation type drying furnace, IR, hot plate, convection oven, or the like, which is provided with a heat source of steam heating method, is used to countercurrent hot air in the dryer, And a method of performing the above method.

In the present invention, the reason why the dry film has at least two-layer structure is that it can be suitably used in various lamination methods as well as whether it is possible to laminate with the vacuum laminator shown in the following examples. In a vacuum laminator used in a printed wiring board or the like, a PET film is often used for transportation. In this case, since the upper limit of the heating temperature to be applied is about 120 deg. C, the use of a resin softened at a lower temperature is preferable.

In lamination, it is necessary to flow the resin sufficiently until fine circuitry or high aspect ratio circuits are used. Therefore, it is necessary to sufficiently soften the resin in a laminate under atmospheric pressure in a roll type laminator or the like. Therefore, it is preferable to use a heat-resistant resin having a high softening point to achieve a laminate-free state in a dry film because of the difficulty of such lamination. In the dry film of the present invention, mechanical properties such as heat resistance and bendability can be achieved in the protective layer 4 by using a component that flows by heating on the side of the adhesive layer 3 in contact with the substrate (circuit).

Here, the substrate is a flexible printed wiring substrate formed in advance. Further, an additional layer may be provided between the adhesive layer 3 and the protective layer 4 in order to obtain another effect in addition to the desired effect.

[Light irradiation step]

The light irradiation step is a step of activating the photo base generating agent contained in the resin composition in the form of a negative pattern and curing the light irradiation part by light irradiation. In this light irradiation step, the mask 5 is disposed on the protective layer 4, and light irradiation is performed on the pattern of a negative pattern to activate the photo base generating agent contained in the resin composition to cure the light irradiation portion.

In this step, the base generated in the light irradiating unit destabilizes the photochemical base, so that a basic substance (hereinafter sometimes abbreviated as "base") is generated from the photochemical base, and the photocatalytic activity I am destabilized, and more bases occur. It is considered that bases are generated in this manner and chemically propagated to the core of each layer, so that the core of each layer can be sufficiently cured. In the subsequent thermal curing, the base acts as a catalyst for the addition reaction between the alkali developable resin and the heat-reactive compound, and the addition reaction proceeds, so that the light-irradiated portion is sufficiently thermally cured to the core of each layer. The curing of the resin composition in this case is a ring-opening reaction of epoxy by, for example, a thermal reaction, so that deformation and curing shrinkage can be suppressed as compared with the case where the resin composition proceeds through a photoreaction.

Examples of the light irradiator used for the light irradiation include a direct drawing apparatus (for example, a laser direct imaging apparatus for directly drawing an image with a laser by CAD data from a computer), an optical irradiator equipped with a metal halide lamp, A light irradiator equipped with a lamp, a light irradiator equipped with a mercury short arc lamp, or a direct drawing apparatus using an ultraviolet lamp such as a (second) high pressure mercury lamp can be used. The mask for light use on the pattern is a negative type mask.

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

[Heating process]

The heating process cures the light irradiated portion by heating, and can be hardened to the deep portion by the base generated in the light irradiation process. 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 a process called a so-called PEB EXPOSURE BAKE (PEB) process. As a result, it is possible to sufficiently cure each layer to the deep portion with a base generated in the light irradiation step, and to obtain a pattern layer having excellent curing characteristics.

For example, the heating step is preferably performed at a temperature lower than the heat generation starting temperature or the exothermic peak temperature of the resin composition not irradiated and higher than the heat generation initiation temperature or exothermic peak temperature of the irradiated resin composition. By heating in this manner, only the irradiated portion can be selectively cured.

Here, it is preferable that the heating temperature at this time be a temperature at which the 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 占 폚. By setting the heating temperature at 80 占 폚 or higher, the irradiated portion can be sufficiently cured. On the other hand, by setting the heating temperature at 140 占 폚 or lower, only the irradiated portion can be selectively cured. The heating time is, for example, 10 to 100 minutes. The heating method is the same as the above-mentioned drying method. In the non-irradiated portion, since no base is generated from the photo-base generating agent, thermal curing is suppressed.

[Development process]

In the developing step, the unexposed portion is removed by alkali development to form a negative pattern layer. The developing process shown in Fig. 1 shows a step of developing the adhesive layer 3 and the protective layer 4 with an alkaline aqueous solution to remove the unexposed portions to form a negative pattern layer. As the developing method, a known method such as a dipping method, a shower method, a spray method, and a brush method can be used. Examples of the developing solution include amines such as potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia and ethanolamine, imidazoles such as 2-methylimidazole, aqueous solution of tetramethylammonium hydroxide (TMAH) , Or a mixed solution thereof may be used.

[Second light irradiation step]

After the development step, it is preferable to include a second light irradiation step. This second light irradiation step is a step of irradiating ultraviolet rays according to the purpose in order to activate the remaining photoacid generators that are not activated in the pattern layer of the light irradiation step and generate bases. The wavelength of the ultraviolet light and the light irradiation amount (exposure amount) in the second light irradiation step may be the same as or different from the above light irradiation step. The light irradiation amount (exposure amount) is, for example, 150 to 2000 mJ / cm 2.

[Thermal curing process]

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

The thermal curing process sufficiently thermally cures the pattern layer by a light irradiation step or a base generated from a photo base generating agent by a light irradiation step and a second light irradiation step. Since the non-irradiated portion has already been removed at the time of the thermosetting step, the thermosetting step can be carried out at a temperature not lower than the curing reaction initiation temperature of the uncured resin composition. Thereby, the pattern layer can be sufficiently thermally cured. The heating temperature is, for example, 150 DEG C or more.

Example

Hereinafter, the present invention will be described in more detail with reference to examples.

(Synthesis Example 1)

≪ Synthesis of alkali soluble resin having imide ring >

12.5 g of 3,5-diaminobenzoic acid, 4.0 g of polyether diamine (Jeffamine D230 manufactured by HUNTSMAN CO., LTD.) And 30 g of NMP were placed in a separable three-necked flask equipped with a stirrer, 30 g of? -butyrolactone, 27.9 g of 4,4'-oxydiphthalic anhydride and 3.8 g of trimellitic anhydride, and the mixture was stirred at 100 rpm for 4 hours at room temperature under a nitrogen atmosphere. Subsequently, 20 g of toluene was added, and the mixture was stirred for 4 hours while distilling toluene and water at a silicon bath temperature of 180 캜 at 150 rpm to obtain an alkali-soluble resin solution having an imide ring. Thereafter,? -Butyrolactone was added so that the solid content was 30 mass%. The obtained resin solution had a solid content of 117 mgKOH / g and a Mw of 10,000.

(Synthesis Example 2)

<Synthesis of carboxyl group-containing urethane resin>

A polycarbonate diol (T5650J, number average molecular weight 800, manufactured by Asahi Kasei Chemicals Co., Ltd.) derived from 1,5-pentanediol and 1,6-hexanediol was added to a reaction vessel equipped with a stirrer, a thermometer and a condenser (4.5 moles) of dimethylol propionic acid and 238 g (2.6 moles) of 2-hydroxyethyl acrylate as a monohydroxyl compound. Subsequently, 1887 g (8.5 mol) of isophorone diisocyanate as a polyisocyanate was added, and the mixture was heated to 60 캜 with stirring and stopped. When the temperature in the reaction vessel started to decrease, stirring was continued at 80 캜, The absorption spectrum (2280 cm ^-1 ) of the isocyanate group in the infrared absorption spectrum was confirmed to be lost, and the reaction was terminated. Thereafter, carbitol acetate was added so that the solid content was 50 mass%. The acid value of the solid content of the obtained carboxyl group-containing urethane resin was 50 mgKOH / g.

&Lt; Production of Resin Composition Constituting Each Layer >

The materials described in the examples and the comparative examples were each compounded in accordance with the formulation shown in the following Table 1, preliminarily mixed with a stirrer, and then kneaded with a three roll mill to prepare a resin composition constituting the adhesive layer and the protective layer. The values in the table are parts by mass unless otherwise specified.

&Lt; Preparation of dry film &

The resin composition constituting the protective layer obtained above was coated on the carrier film so that the film thickness after drying was 10 占 퐉. Thereafter, it was dried in a hot-air circulation type drying oven at 90 DEG C for 30 minutes to form a protective layer (B). The resin composition constituting the adhesive layer obtained above was coated on the surface of the protective layer (B) so as to have a thickness of 25 mu m after drying. Thereafter, the film was dried in a hot-air circulation type drying oven at 90 DEG C for 30 minutes to form an adhesive layer (A), and a dry film was produced.

&Lt; Measurement of glass transition point >

The dry film obtained above was laminated on a PTFE film with CVP-300 manufactured by Nichigo Moton Co., Ltd. and light-irradiated with HMW680GW (metal halide lamp, scattered light) manufactured by ORC Co., Ltd. in a negative pattern at an exposure dose of 500 mJ / cm2. Subsequently, heat treatment was performed at 90 占 폚 for 60 minutes. Subsequently, the substrate was immersed in an aqueous sodium carbonate solution at 30 占 폚 占 1 mass%, and developed for 3 minutes. Subsequently, heat treatment was performed at 150 占 폚 for 60 minutes using a hot air circulation type drying furnace to obtain a patterned cured coating film. Using the obtained cured coating film, the glass transition point as a cured product was determined from dynamic viscoelasticity measurement (DMA) under the following conditions.

Measuring temperature: -30 to 300 ° C

Heating rate: 5 ° C / min

<Lamination Property>

The dry film obtained above was laminated on the substrate with CVP-300 manufactured by Nichigo Morton Co., Ltd. under the following conditions to confirm the presence or absence of voids between the substrate and the dry film.

Laminate temperature: 60 ° C

Vacuum: 4 hPa, 30 sec.

Laminate: 0.3 Pa, 25 sec.

○: No gap

×: With gap

<Alkali developing property and solder heat resistance>

The base material provided with the dry film obtained above was irradiated with HMW680GW (metal halide lamp, scattered light) manufactured by ORC Co., Ltd. in a negative patterned state at an exposure amount of 500 mJ / cm 2. Subsequently, heat treatment was performed at 90 占 폚 for 60 minutes. Subsequently, the substrate was immersed in an aqueous sodium carbonate solution at 30 占 폚 占 1 mass% and development was carried out for 3 minutes to evaluate the alkali developability.

○: Possible to develop alkali

?: Possible to develop alkali but with a little residue

X: With development residue

Subsequently, heat treatment was performed at 150 캜 for 60 minutes using a hot-air circulation type drying furnace to obtain a patterned cured coating film. A rosin-based flux was applied to the obtained cured coating film and immersed in a solder bath set at 260 占 폚 for 20 seconds (10 seconds × 2 times), the flux was washed with isopropyl alcohol, A peeling test using a tape was conducted, and the expansion, peeling, and discoloration of the resist layer were evaluated according to the following criteria.

○: No change is recognized at all

X: With swelling and peeling

The obtained results are shown in Table 1 below.

* 1: The resin of Synthesis Example 1

* 2: The resin of Synthesis Example 2

* 3: Trimethylol propane EO-modified triacrylate (manufactured by Doagosei Co., Ltd.)

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

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

※ 6: Oxime type photobase generator (manufactured by BASF Japan)

* 7: 2- (dimethylamino) -2 - [(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-

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

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

As is clear from the evaluation results shown in the above Table 1, the flexible printed wiring boards of Examples 1 to 3 using the dry film satisfying the glass transition point Tg1 of less than 100 DEG C and the glass transition point Tg2 of 100 DEG C or more, Has good alkali developing property, laminate property and solder heat resistance. On the other hand, in Comparative Example 1 in which Tg2 is not satisfied, the solder heat resistance is poor. Further, in Comparative Example 2 which does not have an adhesive layer and shows Tg only at Tg2, the alkali developability and lamination properties are poor. Also, in Comparative Example 3 having no protective layer and showing Tg only at Tg1, the solder heat resistance was poor.

1: Flexible printed wiring board
2: copper circuit
3: Adhesive layer
4: Protective layer
5: Mask

Claims (9)

A dry film of a laminated structure comprising two or more different resin compositions laminated, wherein the dry film has a glass transition point of at least 100 deg. C and at least 100 deg. C as a cured product. The dry film according to claim 1, wherein the glass transition point is at least one each in the range of 40 to 90 占 폚 and in the range of 110 to 200 占 폚. The dry film according to claim 1, wherein the laminated structure has a two-layer structure. The dry film according to claim 3, wherein the laminated structure of the two-layer structure has an adhesive layer (A) comprising an alkali developable resin composition and a protective layer (B) comprising a photosensitive resin composition. The dry film according to claim 1, wherein the laminated structure is patternable by light irradiation. The dry film according to claim 1, wherein the dry film is used for at least one of a bent portion and a non-bent portion of the flexible printed wiring board. The dry film according to claim 1, wherein the dry film is used for at least one of a coverlay, a solder resist, and an interlayer insulating material of a flexible printed wiring board. The dry film according to claim 1, wherein at least one side is supported or protected by a film. An insulating film is formed on a flexible printed wiring board by forming a layer of a laminated structure using the dry film as described in any one of claims 1 to 8, patterning it by light irradiation, and collecting patterns by a developer And the flexible printed wiring board.

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