JP6951132B2 - Curable resin composition, laminated structure, cured product thereof and electronic components - Google Patents

Description

The present invention relates to a curable resin composition (hereinafter, also simply referred to as “composition”) useful as an insulating film for electronic components such as flexible printed wiring boards, a laminated structure, a cured product thereof, and electronic components.

In recent years, with the spread of smartphones and tablet terminals, electronic devices have become smaller and thinner, and it has become necessary to reduce the space for electronic components such as circuit boards. Therefore, the applications of flexible printed wiring boards that can be folded and stored have expanded, and flexible printed wiring boards that have higher reliability than ever before are required.

On the other hand, as an insulating film for ensuring the insulation reliability of flexible printed wiring boards, the bent portion (bent portion) is currently covered with a polyimide-based cover having excellent mechanical properties such as heat resistance and flexibility. A mixed loading process using a ray (see, for example, Patent Documents 1 and 2) and a photosensitive resin composition having excellent electrical insulation and solder heat resistance and capable of fine processing is used for the mounting portion (non-bent portion). Widely adopted.

That is, the polyimide-based coverlay is not suitable for fine wiring because it requires processing by die punching. Therefore, it is necessary to partially use an alkali-developed photosensitive resin composition (solder resist) that can be processed by photolithography in the chip mounting portion that requires fine wiring.

Japanese Unexamined Patent Publication No. 62-263692 Japanese Unexamined Patent Publication No. 63-11024

As described above, in the conventional manufacturing process of the flexible printed wiring board, there is no choice but to adopt a mixed loading process of the process of laminating the coverlay and the process of forming the solder resist, and there is a problem that the cost and workability are inferior. rice field.

On the other hand, it has been studied to apply an insulating film as a solder resist or an insulating film as a coverlay as a solder resist and a coverlay of a flexible printed wiring board, but the space of the circuit board is reduced. A material that can sufficiently satisfy the required performance of both the solder resist and the coverlay has not yet been put into practical use.

Therefore, a main object of the present invention is to provide a curable resin composition that satisfies the required performances of both solder resist and coverlay and is excellent in developability (alkali solubility) and heat resistance (solder heat resistance). be.
Another object of the present invention is an insulating film such as a flexible printed wiring board, particularly a curable resin composition suitable for a batch forming process of a bent portion (bent portion) and a mounting portion (non-bent portion), and a laminated structure. An object of the present invention is to provide an electronic component such as a body, a cured product thereof, and a flexible printed wiring board having the cured product as a coverlay or a solder resist, for example.

As a result of diligent studies to solve the above problems, the present inventors have completed the present invention.
That is, the curable resin composition of the present invention is characterized by containing an alkali-soluble polyimide resin, an alkali-soluble resin other than the polyimide resin, core-shell rubber particles, and a curable compound. Is.

In the curable resin composition of the present invention, the alkali-soluble resin other than the polyimide resin is preferably a polyamide-imide resin.

（Ｘ_１は炭素数が２４〜４８のダイマー酸由来の脂肪族ジアミン（ａ）の残基、Ｘ_２はカルボキシル基を有する芳香族ジアミン（ｂ）の残基、Ｙはそれぞれ独立にシクロヘキサン環または芳香環である。） Further, in the curable resin composition of the present invention, it is preferable that the polyamide-imide resin is a resin having a structure represented by the following general formula (1) and a structure represented by the following general formula (2).

(X ₁ is a residue of an aliphatic diamine (a) derived from dimer acid having 24-48 carbon atoms, X ₂ is a residue of an aromatic diamine (b) having a carboxyl group, and Y is an independently cyclohexane ring or Aromatic ring.)

Further, in the curable resin composition of the present invention, the curable compound is preferably an epoxy resin.

Further, the laminated structure of the present invention is a laminated structure having a resin layer (A) and a resin layer (B) laminated on a base material via the resin layer (A).
The resin layer (B) is composed of a curable resin composition containing an alkali-soluble polyimide resin, core-shell rubber particles, and a curable compound, and is composed of a curable resin composition.
The resin layer (A) is characterized by comprising an alkali-developable resin composition containing an alkali-soluble resin and a heat-reactive compound.

Here, the curable resin composition for forming the resin layer (B) preferably further contains an alkali-soluble resin other than the polyimide resin, and the alkali-soluble resin is a polyamide-imide resin. In particular, it is more preferable that the structure has the above-mentioned structure.

Further, the cured product of the present invention is characterized by comprising the curable resin composition or a laminated structure.

Further, the electronic component of the present invention is characterized by having an insulating film made of the cured product.

Here, the electronic component of the present invention has, for example, an insulating film formed by forming a layer of the laminated structure on a flexible printed wiring board, patterning by light irradiation, and collectively forming a pattern with a developing solution. Things can be mentioned.
Further, without using the laminated structure, the resin layer (A) and the resin layer (B) are sequentially formed on the flexible printed wiring board, then patterned by light irradiation, and the patterns are batched with a developing solution. It may have an insulating film formed by the above.
In the present invention, the "pattern" means a cured product in the form of a pattern, that is, an insulating film.

According to the present invention, it is possible to provide a curable resin composition that satisfies the required performances of both the solder resist and the coverlay and is excellent in developability and heat resistance. In addition, an insulating film for electronic components such as flexible printed wiring boards, particularly a curable resin composition suitable for a batch forming process of a bent portion (bent portion) and a mounting portion (non-bent portion), a laminated structure, and its curing. It has become possible to realize an electronic component such as a flexible printed wiring board having a product and a cured product thereof as a protective film such as a coverlay or a solder resist.

It is a process drawing which shows typically the manufacturing method of the flexible printed wiring board which shows an example of the electronic component of this invention. It is a process drawing which shows another example of the manufacturing method of the flexible printed wiring board which shows an example of the electronic component of this invention schematically.

Hereinafter, embodiments of the present invention will be described in detail.
(Curable resin composition)
The curable resin composition of the present invention contains an alkali-soluble polyimide resin, an alkali-soluble resin other than the polyimide resin, core-shell rubber particles, and a curable compound.
With such a configuration, both excellent developability and heat resistance are suitable for insulating film applications of electronic components such as flexible printed wiring boards, and curing that can satisfy the required performance of both solder resist and coverlay, for example. It becomes possible to provide a sex resin composition.

(Alkali-soluble polyimide resin)
The alkali-soluble polyimide resin may be any as long as it contains one or more functional groups of phenolic hydroxyl group and carboxyl group and can be developed with an alkaline solution, and known and commonly used ones are used.
According to this polyimide resin, characteristics such as bending resistance and heat resistance become more excellent.

Examples of such an alkali-soluble polyimide resin include a resin obtained by reacting a carboxylic acid anhydride component with an amine component and / or an isocyanate component. Here, the alkali-soluble group is introduced by using an amine component having a carboxyl group or a phenolic hydroxyl group. Further, the imidization may be carried out by thermal imidization or chemical imidization, or these may be carried out in combination.

Examples of the carboxylic acid anhydride component include tetracarboxylic acid anhydride and tricarboxylic acid anhydride, but the present invention is not limited to these acid anhydrides, and acid anhydride groups that react with amino groups and isocyanate groups and acid anhydride groups and Any compound having a carboxyl group can be used including its derivative. Moreover, these carboxylic acid anhydride components may be used alone or in combination.

As the amine component, diamines such as aliphatic diamines and aromatic diamines, polyvalent amines such as aliphatic polyether amines, diamines having a carboxyl group, diamines having phenolic hydroxyl groups and the like can be used. The amine component is not limited to these amines, but it is necessary to use an amine capable of introducing at least one functional group out of a phenolic hydroxyl group and a carboxyl group. Moreover, these amine components may be used alone or in combination.

As the isocyanate component, aromatic diisocyanates and their isomers and multimers, aliphatic diisocyanates, alicyclic diisocyanates and their isomers and other diisocyanates and other general-purpose diisocyanates can be used. It is not limited. Moreover, these isocyanate components may be used alone or in combination.

In the synthesis of such an alkali-soluble polyimide resin, a known and commonly used organic solvent can be used. As such an organic solvent, there is no problem as long as it is a solvent that does not react with carboxylic acid anhydrides, amines and isocyanates as raw materials and in which these raw materials are dissolved, and the structure thereof is not particularly limited. In particular, since the raw material has high solubility, aprotic solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, and γ-butyrolactone are preferable.

The alkali-soluble polyimide resin as described above has a good balance between the alkali-solubleness (developability) of the polyimide resin and other properties such as the mechanical properties of the cured product of the resin composition containing the polyimide resin. Therefore, the acid value (solid content acid value) is preferably 20 to 200 mgKOH / g, and more preferably 60 to 150 mgKOH / g. Specifically, by setting this acid value to 20 mgKOH / g or more, alkali solubility, that is, developability is improved, and further, the crosslink density with the thermosetting component after light irradiation is increased, so that sufficient development is possible. You can get the contrast. Further, by setting the acid value to 200 mgKOH / g or less, so-called heat fogging in the PEB (POST EXPOSURE BAKE) step after light irradiation, which will be described later, can be suppressed, and the process margin becomes large.

Further, the molecular weight of such an alkali-soluble polyimide resin is preferably 100,000 or less, and more preferably 1,000 to 100,000, in consideration of developability and cured coating film characteristics. It is preferable, and more preferably 2,000 to 50,000. When this molecular weight is 100,000 or less, the alkali solubility of the unexposed portion is increased, and the developability is improved. On the other hand, when the molecular weight is 1,000 or more, sufficient development resistance and cured physical properties can be obtained in the exposed portion after exposure / PEB.

(Alkali-soluble resin other than polyimide resin)
As the alkali-soluble resin, any resin that contains one or more functional groups of phenolic hydroxyl group and carboxyl group and can be developed with an alkaline solution is sufficient, and known and commonly used resins are used. For example, a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, which has been conventionally used for solder resists, can be used.

In particular, an alkali-soluble polyamide-imide resin can be preferably used from the viewpoint of obtaining a resin composition having more excellent properties such as bending resistance and heat resistance without impairing the developability.
By using such an alkali-soluble polyamide-imide resin in combination with the above-mentioned alkali-soluble polyimide resin, it is excellent in heat resistance and low resilience without impairing the developability, and it is low in dielectric and after heating. A curable resin composition having a small warp can be provided.

Here, the blending ratio of the alkali-soluble polyamide-imide resin and the above-mentioned alkali-soluble polyimide resin can be 98: 2 to 50:50 in terms of mass ratio, and 90: 10 to 50: 50: It is preferably 50.

As the alkali-soluble polyamide-imide resin, any known and commonly used one may be used as long as it contains one or more functional groups of a phenolic hydroxyl group and a carboxyl group and can be developed with an alkaline solution.

Such an alkali-soluble polyamide-imide resin is, for example, a resin obtained by reacting a carboxylic acid anhydride component with an amine component to obtain an imidized product, and then reacting the obtained imidized product with an isocyanate component. And so on. Here, the alkali-soluble group is introduced by using an amine component having a carboxyl group or a phenolic hydroxyl group. Further, the imidization may be carried out by thermal imidization or chemical imidization, or these may be carried out in combination.

Examples of the carboxylic acid anhydride component include tetracarboxylic acid anhydride and tricarboxylic acid anhydride, but the present invention is not limited to these acid anhydrides, and acid anhydride groups that react with amino groups and isocyanate groups and acid anhydride groups and Any compound having a carboxyl group can be used including its derivative. Moreover, these carboxylic acid anhydride components may be used alone or in combination.

As the amine component, diamines such as aliphatic diamines and aromatic diamines, polyvalent amines such as aliphatic polyether amines, diamines having a carboxyl group, diamines having phenolic hydroxyl groups and the like can be used. The amine component is not limited to these amines, but it is necessary to use an amine capable of introducing at least one functional group out of a phenolic hydroxyl group and a carboxyl group. Moreover, these amine components may be used alone or in combination.

As the isocyanate component, aromatic diisocyanates and their isomers and multimers, aliphatic diisocyanates, alicyclic diisocyanates and their isomers and other diisocyanates and other general-purpose diisocyanates can be used. It is not limited. Moreover, these isocyanate components may be used alone or in combination.

The alkali-soluble polyamide-imide resin as described above has a good balance between the alkali solubility (developability) of the polyamide-imide resin and other properties such as the mechanical properties of the cured product of the resin composition containing the polyamide-imide resin. The acid value (solid content acid value) is preferably 30 mgKOH / g or more, more preferably 30 mgKOH / g or more and 150 mgKOH / g or less, and 50 mgKOH / g or more and 120 mgKOH / g or less. It is particularly preferable to do so. Specifically, by setting this acid value to 30 mgKOH / g or more, alkali solubility, that is, developability is improved, and further, the crosslink density with the thermosetting component after light irradiation is increased, so that sufficient development is possible. You can get the contrast. Further, by setting the acid value to 150 mgKOH / g or less, so-called heat fogging in the PEB (POST EXPOSURE BAKE) step after light irradiation, which will be described later, can be suppressed, and the process margin becomes large.

In particular, in the present invention, a polyamide-imide resin having a structure represented by the following general formula (1) and a structure represented by the following general formula (2) is more preferable in that the developability is further improved.

Here, X ₁ is a residue of an aliphatic diamine (a) derived from dimer acid having 24 to 48 carbon atoms (also referred to as “dimer diamine (a)” in the present specification). X ₂ is a residue of an aromatic diamine (b) having a carboxyl group (also referred to as “carboxyl group-containing diamine (b)” in the present specification). Y is independently a cyclohexane ring or an aromatic ring.

By including the structure represented by the general formula (1) and the structure represented by the general formula (2), a mild alkaline solution such as a 1.0% by mass aqueous sodium carbonate solution is used. It can be a polyamide-imide resin having excellent alkali solubility, which can also be dissolved. Further, the cured product of the resin composition containing such a polyamide-imide resin can have excellent dielectric properties.

Dimerdiamine (a) can be obtained by reductive amination of the carboxyl group in the dimer of an aliphatic unsaturated carboxylic acid having 12 to 24 carbon atoms. That is, dimer diamine (a), which is an aliphatic diamine derived from dimer acid, can be obtained by polymerizing unsaturated fatty acids such as oleic acid and linoleic acid to obtain dimer acid, reducing the diamine, and then aminating the diamine. .. As such an aliphatic diamine, for example, a commercially available product such as PRIAMINE1073, 1074, 1075 (manufactured by Croda Japan, trade name), which is a diamine having a skeleton having 36 carbon atoms, can be used. The diamine diamine (a) may be preferably derived from a dimer acid having 28 to 44 carbon atoms, and more preferably derived from a dimer acid having 32 to 40 carbon atoms.

Specific examples of the carboxyl group-containing diamine (b) include 3,5-diaminobenzoic acid, 3,4-diaminobenzoic acid, 5,5'-methylenebis (anthranilic acid), benzidine-3,3'-dicarboxylic acid and the like. Can be mentioned. The carboxyl group-containing diamine (b) may be composed of one kind of compound or may be composed of a plurality of kinds of compounds. From the viewpoint of raw material availability, the carboxyl group-containing diamine (b) preferably contains 3,5-diaminobenzoic acid and 5,5'-methylenebis (anthranilic acid).

The relationship between the content of the structure represented by the general formula (1) and the content of the structure represented by the general formula (2) in the polyamide-imide resin is not limited. The content of dimer diamine (a) (unit: mass%) from the viewpoint of improving the balance between the alkali solubility of the polyamide-imide resin and other properties such as the mechanical properties of the cured product of the resin composition containing the polyamide-imide resin. ) Is preferably 20 to 60% by mass, more preferably 30 to 50% by mass. In the present specification, the "content of dimer diamine (a)" refers to the amount of diamine diamine (a) charged as one of the raw materials for producing the polyamide-imide resin of the produced polyamide-imide resin. It means the ratio to the mass. Here, "the mass of the produced polyamide-imide resin", from the charged amounts of all the raw material for producing the polyamide-imide resin, resulting in imidization water (H 2 _O) and carbon dioxide produced by amidation (CO It is the value obtained by subtracting the theoretical amount of _2).

From the viewpoint of increasing the alkali solubility of the polyamide-imide resin, the portion represented by Y in the general formula (1) and the general formula (2) preferably has a cyclohexane ring. From the viewpoint of improving the balance between the alkali solubility of the polyamide-imide resin and other properties such as the mechanical properties of the cured product of the resin composition containing the polyamide-imide resin, the aromatic ring and the cyclohexane ring in the portion indicated by Y above. In terms of the quantitative relationship with, the molar ratio of the cyclohexane ring content to the aromatic ring content is preferably 85/15 to 100/0, more preferably 90/10 to 99/1. It is more preferably 90/10 to 98/2.

ここで、Ｘ_３は、ダイマージアミン（ａ）およびカルボキシル基含有ジアミン（ｂ）以外のジアミン（ｆ）（本明細書において、「他のジアミン（ｆ）」ともいう。）の残基であり、Ｙは、上記一般式（１）および上記一般式（２）と同様に、それぞれ独立に芳香環またはシクロヘキサン環である。他のジアミン（ｆ）は１種類の化合物から構成されていてもよいし、複数種類の化合物から構成されていてもよい。 The polyamide-imide resin may further have a partial structure represented by the following general formula (i).

Here, X ₃ is a residue of a diamine (f) other than the diamine diamine (a) and the carboxyl group-containing diamine (b) (also referred to as “another diamine (f)” in the present specification). Y is an aromatic ring or a cyclohexane ring independently as in the general formula (1) and the general formula (2). The other diamine (f) may be composed of one kind of compound or may be composed of a plurality of kinds of compounds.

Specific examples of other diamines (f) include 2,2-bis [4- (4-aminophenoxy) phenyl] propane, bis [4- (3-aminophenoxy) phenyl] sulfone, and bis [4- (4). -Aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, bis [4- (4-aminophenoxy) phenyl] methane, 4,4'-bis (4) -Aminophenoxy) biphenyl, bis [4- (4-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ketone, 1,3-bis (4-aminophenoxy) benzene, 1,4 -Bis (4-aminophenoxy) benzene, 2,2'-dimethylbiphenyl-4,4'-diamine, 2,2'-bis (trifluoromethyl) biphenyl-4,4'-diamine, 2,6,2 ', 6'-Tetramethyl-4,4'-diamine, 5,5'-dimethyl-2,2'-sulfonyl-biphenyl-4,4'-diamine, 3,3'-dihydroxybiphenyl-4,4' -Diamine, (4,4'-diamino) diphenyl ether, (4,4'-diamino) diphenylsulfone, (4,4'-diamino) benzophenone, (3,3'-diamino) benzophenone, (4,4'- Aromatic diamines such as diamino) diphenylmethane, (4,4'-diamino) diphenyl ether, and (3,3'-diamino) diphenyl ether include hexamethylenediamine, octamethylenediamine, decamethylenediamine, dodecamethylenediamine, octadeca. Examples thereof include aliphatic diamines such as methylene diamine, 4,4'-methylenebis (cyclohexylamine), isophorone diamine, 1,4-cyclohexanediamine and norbornene diamine.

The polyamide-imide resin may have a structure represented by the following general formula (ii).

Here, Z may be an aliphatic group or a group containing an aromatic. When it is an aliphatic group, it may contain an alicyclic group such as a cyclohexane ring. According to the production method described later, Z is a residue of the diisocyanate compound (e).

The method for producing the above-mentioned polyamide-imide resin is not limited, and the polyamide-imide resin can be produced through an imidization step and an amide imidization step using a known and commonly used method.

The imide step comprises dimerdiamine (a), carboxyl group-containing diamine (b), and cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride (c) and trimellitic anhydride (d). One or two selected from the group are reacted to obtain an imidized product (A).

The amount of the diamine diamine (a) charged is preferably an amount in which the content of the diamine diamine (a) is 20 to 60% by mass, and more preferably an amount in which the content of the diamine diamine (a) is 30 to 50% by mass. .. The definition of the content of the diamine diamine (a) is as described above.

If necessary, other diamines (f) may be used together with the diamine diamine (a) and the carboxyl group-containing diamine (b).

From the viewpoint of increasing the alkali solubility of the polyamide-imide resin, it is preferable to use cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride (c) in the imidization step. The molar ratio of the amount of cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride (c) to the amount of trimellitic anhydride (d) used shall be 85/15 to 100/0. Is preferable, 90/10 to 99/1 is more preferable, and 90/10 to 98/2 is even more preferable.

Diamine compound (B) used to obtain the imidized product (A) (specifically, diamine diamine (a) and carboxyl group-containing diamine (b) and other diamines (f) used as needed. The group consisting of the amount of acid anhydride (C) (specifically, cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydrous (c) and trimellitic anhydride (d)). The relationship with the amount of one or two selected from) is not limited. The amount of the acid anhydride (C) used is preferably such that the molar ratio to the amount of the diamine compound (B) used is 2.0 or more and 2.4 or less, and the molar ratio is 2.0 or more and 2. It is more preferable that the amount is 2 or less.

In the amidimidization step, the imidized product (A) obtained in the above imidization step is reacted with the diisocyanate compound (e) to obtain a polyamide-imide resin containing a substance having a structure represented by the following general formula (3). ..

The specific type of the diisocyanate compound (e) is not limited. The diisocyanate compound (e) may be composed of one kind of compound or may be composed of a plurality of kinds of compounds.

Specific examples of the diisocyanate compound (e) include 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, naphthalene-1,5-diisocyanate, o-xylylene diisocyanate, m. Aromatic diisocyanates such as -xylylene diisocyanate and 2,4-tolylene diisocyanate; aliphatic diisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate and norbornene diisocyanate can be mentioned. From the viewpoint of improving both the alkali solubility of the polyamide-imide resin and the light transmittance of the polyamide-imide resin, the diisocyanate compound (e) preferably contains an aliphatic isocyanate, and the diisocyanate compound (e) is an aliphatic isocyanate. Is more preferable.

The amount of the diisocyanate compound (e) used in the amidimidization step is not limited. From the viewpoint of imparting appropriate alkali solubility to the polyamide-imide resin, the amount of the diisocyanate compound (e) used is 0. It is preferably 3 or more and 1.0 or less, more preferably 0.4 or more and 0.95 or less, and particularly preferably 0.50 or more and 0.90 or less.

The polyamide-imide resin produced in this manner contains a substance having a structure represented by the following general formula (3).

In the above general formula (3), X is an independently diamine residue (residue of diamine compound (B)), Y is independently an aromatic ring or cyclohexane ring, and Z is a residue of diisocyanate compound (e). .. n is a natural number.

(Core shell rubber particles)
The core-shell rubber particles constituting the curable resin composition of the present invention have a function of improving the flexibility of the core-shell rubber particles without reducing the adhesion.
The core-shell rubber particles refer to a rubber material having a multi-layer structure composed of core layers having different compositions and one or more shell layers covering the core layers. As will be described later, the core-shell rubber particles are composed of a core layer made of a material having excellent flexibility and a shell layer made of a material having an excellent affinity for other components. Dispersibility is improved while achieving the above-mentioned.
According to the characteristic combination configuration of the present invention in which such core-shell rubber particles are blended, it has excellent flexibility without cracks or the like occurring in an excessive bending test even in a state of being heat-treated such as reflow. It is possible to exert a unique effect of being able to provide a cured product, which is not found in the prior art.

As the constituent material of the core layer, a material having excellent flexibility is used. Specific examples thereof include silicone-based elastomers, butadiene-based elastomers, styrene-based elastomers, acrylic-based elastomers, polyolefin-based elastomers, and silicone / acrylic-based composite elastomers.

On the other hand, as a constituent material of the shell layer, a material having an excellent affinity for other components is used. For example, when the curable resin composition contains an epoxy resin, it is preferable to use core-shell rubber particles having a shell layer made of a material having excellent affinity for the epoxy resin. More preferably, it is an acrylic resin or an epoxy resin.

From the viewpoint of storage stability, such core-shell rubber particles preferably have a curable reactive group on the surface, and the curable reactive group is a photocurable reactive group even if it is a thermosetting reactive group. You may. Further, the core-shell rubber particles may have two or more types of curable reactive groups.

Examples of the thermosetting reactive group include a hydroxyl group, a carboxyl group, an isocyanate group, an imino group, an epoxy group, an oxetanyl group, a mercapto group, a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, an ethoxyethyl group and an oxazoline group. .. More preferably, it is an epoxy group.

Examples of the photocurable reactive group include a vinyl group, a styryl group, a methacrylic group, an acrylic group and the like. A methacrylic group or an acrylic group is preferable because the reactivity becomes appropriate even when the filler content is large.

Here, the method for introducing the curable reactive group onto the surface of the core-shell rubber particles is not particularly limited, and a known and commonly used method can be used. For example, when a shell layer is formed around the core layer, a material having a curable reactive group different from the functional group for polymerizing with the core layer is polymerized on the core layer as a constituent material of the shell layer. Can be introduced.

Examples of commercially available core-shell rubber particles include Paraloid ELX2655 manufactured by Roam and Hearth Co., Ltd., XER-91 manufactured by Nippon Synthetic Rubber Co., Ltd., and the like.

In the curable resin composition of the present invention, it is preferable that the core-shell rubber particles have an average particle size of 2 μm or less because they are excellent in crack resistance. More preferably, it is 0.01 to 1 μm. In the present specification, the average particle size is a value of D50 measured using a Microtrack particle size analyzer manufactured by Nikkiso Co., Ltd.

In the curable resin composition of the present invention, the content of the core-shell rubber particles is preferably 1 to 30% by mass per organic component in the solid content in the composition. When it is 1% by mass or more, it is preferable in that it is excellent in crack resistance. On the other hand, when it is 30% by mass or less, it is preferable in that it is excellent in printability and developability. More preferably, it is 3 to 20% by mass. Further, the curable resin composition of the present invention may contain core-shell rubber particles having a curable reactive group and core-shell rubber particles not having the curable reactive group. Here, the organic component means all solid components other than inorganic components such as fillers.

(Curable compound)
The curable resin composition of the present invention further contains a curable compound. As the curable compound, a known and commonly used compound having a functional group capable of a curing reaction by heat or light is used. Examples thereof include a thermosetting compound having a functional group capable of a curing reaction by heat such as a cyclic (thio) ether group, and a photocurable compound capable of a curing reaction by light such as an ethylenically unsaturated double bond group. Of these, it is preferable to use a thermosetting compound, particularly an epoxy resin.

Examples of this epoxy resin include bisphenol A type epoxy resin, brominated epoxy resin, novolak type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, glycidylamine type epoxy resin, hidden in type epoxy resin, and alicyclic type. Epoxy resin, trihydroxyphenylmethane type epoxy resin, bixyleneol type or biphenol type epoxy resin or a mixture thereof; bisphenol S type epoxy resin, bisphenol A novolac type epoxy resin, heterocyclic epoxy resin, biphenyl novolac type epoxy resin, naphthalene Examples thereof include a group-containing epoxy resin and an epoxy resin having a dicyclopentadiene skeleton.

In particular, when a thermosetting compound is used, the thermosetting compound has an equivalent ratio with an alkali-soluble resin (polyimide resin, polyamide-imide resin, etc.) (alkali-soluble group such as carboxyl group: heat such as epoxy group). The curable group) is preferably blended in a ratio of 1: 0.1 to 1:10. With such a blending ratio, the developability is improved and a fine pattern can be easily formed. The equivalent ratio is more preferably 1: 0.2 to 1: 5.

(Photopolymerization initiator)
When the curable resin composition of the present invention is a photosensitive resin composition, it is preferable that the curable resin composition further contains a photopolymerization initiator. As the photopolymerization initiator, known and commonly used ones can be used, and in particular, when the curable resin composition of the present invention is applied to the PEB step after light irradiation described later, it can be used as a photobase generator. It is preferable to use a photopolymerization initiator that also has a function. In this PEB step, a photopolymerization initiator and a photobase generator may be used in combination.

The photopolymerization initiator, which also has a function as a photobase generator, is a thermocurable compound which is a curable compound when the molecular structure is changed by irradiation with light such as ultraviolet rays or visible light or when the molecule is cleaved. A compound that produces one or more basic substances that can function as a catalyst for a polymerization reaction. Examples of the basic substance include secondary amines and tertiary amines.
Examples of the photopolymerization initiator having a function as such a photobase generator include an α-aminoacetophenone compound, an oxime ester compound, an acyloxyimino group, an N-formylated aromatic amino group, and an N-acylated aromatic. Examples thereof include compounds having a substituent such as a group amino group, a nitrobenzyl carbamate group and an alcoholoxybenzyl carbamate group. Of these, an oxime ester compound and an α-aminoacetophenone compound are preferable, and an oxime ester compound is more preferable. As the α-aminoacetophenone compound, those having two or more nitrogen atoms are particularly preferable.

The α-aminoacetophenone compound may have a benzoin ether bond in the molecule, and when irradiated with light, cleavage occurs in the molecule to generate a basic substance (amine) that acts as a curing catalyst.

As the oxime ester compound, any compound that produces a basic substance by light irradiation can be used.

Such a photopolymerization initiator may be used alone or in combination of two or more. The blending amount of the photopolymerization initiator in the resin composition is preferably 0.1 to 40 parts by mass, more preferably 0.3 to 15 parts by mass, based on 100 parts by mass of the total amount of the alkali-soluble resin. Is. When the amount is 0.1 parts by mass or more, the contrast of development resistance of the light-irradiated portion / non-irradiated portion can be obtained satisfactorily. Further, when the amount is 40 parts by mass or less, the characteristics of the cured product are improved.

The curable resin composition of the present invention may further contain the following components, if necessary.

(Polymer resin)
In the curable resin composition of the present invention, a known and commonly used polymer resin can be blended for the purpose of improving the flexibility and touch-drying property of the obtained cured product.
Examples of such polymer resins include cellulose-based, polyester-based, phenoxy-resin-based polymers, polyvinyl acetal-based, polyvinyl butyral-based, polyamide-based, polyamide-imide-based binder polymers, and elastomers. This polymer resin may be used alone or in combination of two or more.

(Inorganic filler)
In the curable resin composition of the present invention, an inorganic filler can be blended in order to suppress curing shrinkage of the cured product and improve properties such as adhesion and hardness.
Examples of such inorganic fillers include barium sulfate, amorphous silica, molten silica, spherical silica, talc, clay, magnesium carbonate, calcium carbonate, aluminum oxide, aluminum hydroxide, silicon nitride, aluminum nitride, and boron nitride. Neuburg Siricious Earth and the like can be mentioned.

(Colorant)
The curable resin composition of the present invention can be blended with known and commonly used colorants such as red, blue, green, yellow, white and black.
The colorant may be any of pigments, dyes and pigments.

(Organic solvent)
The curable resin composition of the present invention can contain an organic solvent for preparing the resin composition and for adjusting the viscosity for coating on a base material or a carrier film.
Examples of such an organic solvent include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, petroleum solvents and the like. Such an organic solvent may be used alone or as a mixture of two or more.

(Other ingredients)
The curable resin composition of the present invention can further contain components such as a mercapto compound, an adhesion accelerator, a thermosetting catalyst, an antioxidant, and an ultraviolet absorber, if necessary. As these, known and commonly used ones can be used.
In addition, known and commonly used thickeners such as fine silica, hydrotalcite, organic bentonite, and montmorillonite, antifoaming agents such as silicone-based, fluorine-based, and polymer-based and / or leveling agents, silane coupling agents, and rust preventives. Known and commonly used additives such as, etc. can be blended.

The curable resin composition of the present invention having the structure as described above includes a resin layer (A) and a resin layer (B) laminated on a flexible printed wiring board via the resin layer (A), which will be described later. , Can be suitably used for forming the resin layer (B) in the laminated structure having.

(Laminated structure)
The laminated structure of the present invention has a resin layer (A) and a resin layer (B) laminated on a base material such as a flexible printed wiring board via the resin layer (A). Here, in the laminated structure of the present invention, the resin layer (A) and the resin layer (B) substantially function as an adhesive layer and a protective layer, respectively. In the laminated structure of the present invention, the resin layer (B) is composed of a curable resin composition containing an alkali-soluble polyimide resin, core-shell rubber particles, and a curable compound, and the resin layer (A) is It is characterized in that it comprises an alkali-developable resin composition containing an alkali-soluble resin and a thermosetting compound.

In the present invention, the resin layer (B) on the upper layer side of the laminated structure in which the two resin layers are laminated is made of the curable resin composition, so that the resin layer (B) has excellent developability and heat resistance. In particular, it is possible to obtain a laminated structure having excellent flexibility after solder reflow. If the resin layer (A) on the lower layer side of the laminated structure contains the core-shell rubber particles, the adhesion may be lowered, but the resin layer (B) on the upper layer side is cured as described above containing the core-shell rubber particles. By using the sex resin composition, the effect of improving the flexibility of the core-shell rubber particles can be obtained without lowering the adhesion. Therefore, in the present invention, it is preferable that the resin layer (A) does not contain core-shell rubber particles.

[Resin layer (A)]
(Alkaline developing type resin composition)
The alkali-developable resin composition constituting the resin layer (A) is thermally reactive with an alkali-soluble resin that contains one or more functional groups of phenolic hydroxyl groups and carboxyl groups and can be developed with an alkaline solution. Any composition containing a compound may be used. Preferred examples thereof include a resin composition containing an alkali-soluble resin such as a compound having a phenolic hydroxyl group, a compound having a carboxyl group, a compound having a phenolic hydroxyl group and a carboxyl group, and a heat-reactive compound, which are known and commonly used. Is used.

For example, a resin composition containing a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, a compound having an ethylenically unsaturated bond, and a heat-reactive compound, which have been conventionally used as solder resist compositions, can be mentioned.

Here, a known and commonly used compound is used as the carboxyl group-containing resin or the carboxyl group-containing photosensitive resin, and the compound having an ethylenically unsaturated bond, and the cyclic (thio) ether is used as the heat-reactive compound. A known and commonly used compound having a functional group capable of a curing reaction by heat such as a group is used.

Such a resin layer (A) may or may not contain a photopolymerization initiator, but the photopolymerization initiator used when the photopolymerization initiator is contained includes the above-mentioned curable resin composition. Examples thereof include the same photopolymerization initiators used in the products.

In addition, the resin layer (A) can contain other components similar to those of the curable resin composition, such as a polymer resin, an inorganic filler, a colorant, and an organic solvent.

[Resin layer (B)]
The curable resin composition constituting the resin layer (B) is characterized by containing an alkali-soluble polyimide resin, core-shell rubber particles, and a curable compound.

Here, as the alkali-soluble polyimide resin, core-shell rubber particles, and curable compound, the same resins, particles, and compounds as those constituting the curable resin composition of the present invention can be used.
The curable resin composition constituting the resin layer (B) is preferably an alkali-soluble resin other than the polyimide resin, more preferably a polyamide-imide resin, and further preferably a structure represented by the general formula (1). And a polyamide-imide resin having a structure represented by the general formula (2). With such a configuration, it is possible to obtain a resin composition having more excellent properties such as bending resistance and heat resistance without impairing the developability.

Since the laminated structure of the present invention is excellent in flexibility, it can be used for at least one of a bent portion and a non-bent portion of an electronic component such as a flexible printed wiring board, and further, for example, a flexible printed wiring board. It can be used for at least one of a coverlay, a solder resist and an interlayer insulating material.

The laminated structure of the present invention having the structure as described above is preferably used as a dry film in which at least one side thereof is supported or protected by a film.

(Dry film)
The dry film of the present invention can be produced, for example, as follows. That is, first, on the carrier film (support film), the curable resin composition constituting the resin layer (B) and the alkali-developable resin composition constituting the resin layer (A) are each diluted with an organic solvent. The viscosity is adjusted to an appropriate level, and the resin is sequentially applied by a known method such as a comma coater according to a conventional method. Then, usually, by drying at a temperature of 50 to 130 ° C. for 1 to 30 minutes, a dry film in which a coating film of the resin layer (B) and the resin layer (A) is formed on the carrier film can be produced. A peelable cover film (protective film) can be further laminated on the dry film for the purpose of preventing dust from adhering to the surface of the coating film. As the carrier film and the cover film, a conventionally known plastic film can be appropriately used, and the cover film may be smaller than the adhesive force between the resin layer and the carrier film when the cover film is peeled off. preferable. The thickness of the carrier film and the cover film is not particularly limited, but is generally selected as appropriate in the range of 10 to 150 μm.

(Cured product)
The cured product of the present invention is obtained by curing the above-mentioned curable resin composition of the present invention or the laminated structure of the present invention.

(Electronic components)
The curable resin composition and the laminated structure of the present invention as described above can be effectively used for electronic components such as flexible printed wiring boards. Specifically, it has an insulating film formed by forming a layer of the curable resin composition or the laminated structure of the present invention on a flexible printed wiring board, patterning by light irradiation, and forming a pattern with a developing solution. Flexible printed wiring boards and the like can be mentioned.
Hereinafter, a method for manufacturing a flexible printed wiring board will be specifically described as an example of electronic components.

(Manufacturing method of flexible printed wiring board)
The flexible printed wiring board using the laminated structure of the present invention can be manufactured, for example, according to the procedure shown in the process diagram of FIG. That is, a step of forming a layer of the laminated structure of the present invention on a flexible printed wiring base material on which a conductor circuit is formed (lamination step), and a step of irradiating the layer of the laminated structure with active energy rays in a pattern (exposure). A manufacturing method including a step (step) and a step (development step) of forming a layer of the patterned laminated structure by alkaline developing the layer of the laminated structure. Further, if necessary, after alkaline development, further photocuring or thermosetting (post-cure process) is performed to completely cure the layer of the laminated structure, and a highly reliable flexible printed wiring board can be obtained. ..

Further, the flexible printed wiring board using the laminated structure of the present invention can be manufactured, for example, according to the procedure shown in the process diagram of FIG. That is, a step of forming a layer of the laminated structure of the present invention on a flexible printed wiring base material on which a conductor circuit is formed (lamination step), and a step of irradiating the layer of the laminated structure with active energy rays in a pattern (exposure). Step), a step of heating the layer of the laminated structure (heating (PEB) step), and a step of alkaline-developing the layer of the laminated structure to form a layer of the patterned laminated structure (development step). ) Is included in the manufacturing method. Further, if necessary, after alkaline development, further photocuring or thermosetting (post-cure process) is performed to completely cure the layer of the laminated structure, and a highly reliable flexible printed wiring board can be obtained. ..

Hereinafter, each step in FIG. 1 or 2 will be described in more detail.
[Laminating process]
In this step, the flexible printed wiring base material 1 on which the conductor circuit 2 is formed has a resin layer 3 (resin layer (A)) of an alkali-developable resin composition containing an alkali-soluble resin and the like, and a resin layer 3 on the resin layer 3. , A laminated structure composed of the resin layer 4 (resin layer (B)) of the photosensitive thermosetting resin composition is formed. Here, each resin layer constituting the laminated structure forms the resin layers 3 and 4 by, for example, sequentially applying and drying the resin composition constituting the resin layers 3 and 4 to the wiring base material 1. Alternatively, the resin composition constituting the resin layers 3 and 4 in the form of a dry film having a two-layer structure may be formed by laminating the wiring base material 1.

The resin composition may be applied to the wiring substrate by a known method such as a blade coater, a lip coater, a comma coater, or a film coater. In addition, the drying method uses a hot air circulation type drying furnace, IR furnace, hot plate, convection oven, etc., which is equipped with a heat source of the heating method using steam, and the hot air in the dryer is brought into countercurrent contact, and is supported by the nozzle. A known method such as a method of spraying on the body may be used.

[Exposure process]
In this step, the photopolymerization initiator contained in the resin layer 4 is activated in a negative pattern by irradiation with active energy rays, and the exposed portion is cured. In the case of a composition using the PEB step described later, a photopolymerization initiator or a photobase generator having a function as a photobase generator is activated in a negative pattern to generate a base.
As the exposure machine used in this step, a direct drawing device, an exposure machine equipped with a metal halide lamp, or the like can be used. The mask for patterned exposure is a negative type mask.

As the active energy ray used for exposure, it is preferable to use laser light or scattered light having a maximum wavelength in the range of 350 to 450 nm. By setting the maximum wavelength in this range, the photopolymerization initiator can be activated efficiently. The exposure amount varies depending on the film thickness and the like, but can be ^{, for example, 50 to 1500 mJ / cm 2.}

[PEB process]
In this step, after the exposure, the exposed portion is cured by heating the resin layer. By this step, a base generated in the exposure step of the resin layer (B) composed of a photopolymerization initiator having a function as a photobase generator or a composition in which the photopolymerization initiator and the photobase generator are used in combination. Therefore, the resin layer (B) can be cured to a deep part. The heating temperature is, for example, 80 to 140 ° C. The heating time is, for example, 1 to 100 minutes. Since the curing of the resin composition in the present invention is, for example, a ring-opening reaction of the epoxy resin by a thermal reaction, strain and curing shrinkage can be suppressed as compared with the case where curing proceeds by a photoradical reaction.

[Development process]
In this step, the unexposed portion is removed by alkaline development to form a negative patterned insulating film, for example, a coverlay and a solder resist. As the developing method, a known method such as dipping can be used. As the developing solution, sodium carbonate, potassium carbonate, potassium hydroxide, amines, imidazoles such as 2-methylimidazole, an alkaline aqueous solution such as tetramethylammonium hydroxide aqueous solution (TMAH), or a mixed solution thereof may be used. Can be used.

[Post-cure process]
After the developing step, the insulating film may be further irradiated with light, or may be heated at, for example, 150 ° C. or higher.

Hereinafter, the present invention will be described in more detail with reference to Examples, Reference Examples and Comparative Examples, but the present invention is not limited to these Examples, Reference Examples and Comparative Examples.

(Synthesis Example 1)
Aliphatic diamine (manufactured by Claude Japan, product name PRIAMINE 1075) 28 derived from dimer acid having 36 carbon atoms as diamine diamine (a) in a four-necked 300 mL flask equipped with a nitrogen gas introduction tube, a thermometer, and a stirrer. .61 g (0.052 mol), 4.26 g (0.028 mol) of 3,5-diaminobenzoic acid as a carboxyl group-containing diamine (b), and 85.8 g of γ-butyrolactone were charged and dissolved at room temperature.

Next, 30.12 g (0.152 mol) of cyclohexane-1,2,4-tricarboxylic acid anhydride (c) and 3.07 g (0.016 mol) of trimellitic anhydride (d) were charged, and 30 minutes at room temperature. Retained. Further, 30 g of toluene was charged, the temperature was raised to 160 ° C. to remove water generated together with toluene, and the mixture was held for 3 hours and cooled to room temperature to obtain a solution containing an imidized product.

14.30 g (0.068 mol) of trimethylhexamethylene diisocyanate as the diisocyanate compound (e) was charged into the obtained imidized solution, kept at a temperature of 160 ° C. for 32 hours, and diluted with 21.4 g of cyclohexanone. A solution (A-1) containing a polyamide-imide resin was obtained. The obtained polyamide-imide resin had a mass average molecular weight Mw of 5250, a solid content of 41.5% by mass, an acid value of 63 mgKOH / g, and a diamine diamine (a) content of 40.0% by mass.

(Synthesis Example 2: Synthesis of a polyimide resin solution having an imide ring, a phenolic hydroxyl group and a carboxyl group)
3,3'-diamino-4,4'-dihydroxydiphenylsulfone 22.4 g, 2,2'-bis [4] in a separable three-necked flask equipped with a stirrer, nitrogen introduction pipe, distillate ring, and cooling ring. Add 8.2 g of-(4-aminophenoxy) phenyl] propane, 30 g of NMP, 30 g of γ-butyrolactone, 27.9 g of 4,4'-oxydiphthalic anhydride, and 3.8 g of trimellitic anhydride. The mixture was stirred at room temperature and 100 rpm for 4 hours under a nitrogen atmosphere. Next, 20 g of toluene was added, and the mixture was stirred for 4 hours while distilling off toluene and water at a silicon bath temperature of 180 ° C. and 150 rpm to obtain a polyimide resin solution (PI-1) having a phenolic hydroxyl group and a carboxyl group.
The acid value of the obtained resin (solid content) was 18 mgKOH, Mw was 10,000, and the hydroxyl group equivalent was 390.

(Examples 1 and 2, Reference Examples 1 to 3 and Comparative Examples 1 and 2)
According to the composition of the components shown in Table 1, the materials described in Examples 1, 2, Reference Examples 1 to 3, and Comparative Examples 1 and 2, respectively, were blended, premixed with a stirrer, and kneaded with a three-roll mill. A resin composition for forming each resin layer was prepared. Unless otherwise specified, the values in the table are parts by mass of solid content.

＊１）アルカリ溶解性樹脂１（ＰＩ−１）：合成例２
＊２）アルカリ溶解性樹脂２：カルボキシル基含有エポキシアクリレートＺＡＲ−１０３５（酸価９８ｍｇＫＯＨ／ｇ、日本化薬社製）
＊３）ポリアミドイミド含有溶液（Ａ−１）：合成例１
＊４）オキシム系光重合開始剤：ＩＲＧＡＣＵＲＥ ＯＸＥ０２（ＢＡＳＦ社製）
＊５）エポキシ樹脂：ビスフェノールＡ型エポキシ樹脂Ｅ８２８，エポキシ当量１９０，質量平均分子量３８０（三菱化学（株）製）
＊６）コアシェルポリマー１：パラロイドＥＸＬ−２６５５（ロームアンドハーツ社製）＊７）コアシェルポリマー２：スタフィロイドＡＣ−３３５５（ガンツ化成社製）
＊８）コアシェルポリマーからなるマスターバッチ１：（「アラルダイト（登録商標）」ＭＹ７２１：７５質量％／コアシェルポリマー粒子Ａ（体積平均粒子径：１００ｎｍ、コア部分：ブタジエン／スチレン共重合ポリマー［Ｔｇ：−２５℃］、シェル部分：メタクリル酸メチル／グリシジルメタクリレート／スチレン共重合ポリマー）：２５質量％のマスターバッチ），なお、コアシェルポリマー粒子Ａは特開２００５−２４８１０９号公報記載の方法で合成した。但し、ブタジエン／スチレンの比率を５０質量％／５０質量％とした。また、ブタジエン−スチレンゴムラテックスを製造後、このブタジエン−スチレンゴムラテックス１００質量％に対して、メタクリル酸メチル／グリシジルメタクリレート／スチレンを５質量％／５質量％／５質量％の比率で添加し、グラフト重合した。
＊９）アクリレート樹脂：エトキシ化ビスフェノールＡジメタクリレートＢＰＥ−９００（新中村化学（株）製）

* 1) Alkali-soluble resin 1 (PI-1): Synthesis Example 2
* 2) Alkali-soluble resin 2: Carboxyl group-containing epoxy acrylate ZAR-1035 (acid value 98 mgKOH / g, manufactured by Nippon Kayaku Co., Ltd.)
* 3) Polyamideimide-containing solution (A-1): Synthesis Example 1
* 4) Oxime-based photopolymerization initiator: IRGACURE OXE02 (manufactured by BASF)
* 5) Epoxy resin: Bisphenol A type epoxy resin E828, epoxy equivalent 190, mass average molecular weight 380 (manufactured by Mitsubishi Chemical Corporation)
* 6) Coreshell polymer 1: Paraloid EXL-2655 (manufactured by Roam and Hearts) * 7) Coreshell polymer 2: Staphyroid AC-3355 (manufactured by Ganz Kasei)
* 8) Master batch 1: made of core-shell polymer ("Araldite (registered trademark)" MY721: 75% by mass / core-shell polymer particle A (volume average particle size: 100 nm, core portion: butadiene / styrene copolymer polymer [Tg:-] 25 ° C.], shell portion: methyl methacrylate / glycidyl methacrylate / styrene copolymer polymer): 25% by mass master batch), and core-shell polymer particles A were synthesized by the method described in JP-A-2005-248109. However, the ratio of butadiene / styrene was set to 50% by mass / 50% by mass. Further, after producing the butadiene-styrene rubber latex, methyl methacrylate / glycidyl methacrylate / styrene was added at a ratio of 5% by mass / 5% by mass / 5% by mass to 100% by mass of the butadiene-styrene rubber latex. Graft polymerization was performed.
* 9) Acrylate resin: Ethoxybisphenol A dimethacrylate BPE-900 (manufactured by Shin-Nakamura Chemical Co., Ltd.)

<Formation of resin layer (A)>
A flexible printed wiring board on which a circuit having a copper thickness of 18 μm was formed was prepared, and pretreatment was performed using CZ-8100 manufactured by MEC. Then, the resin compositions constituting the resin layers (A) obtained in Examples 1, Reference Examples 1 to 3 and Comparative Examples 1 and 2 were dried on the pretreated flexible printed wiring board. It was applied so that the film thickness was 25 μm. Then, it was dried in a hot air circulation type drying oven at 90 ° C./30 minutes to form a resin layer (A).

<Formation of resin layer (B)>
On the resin layer (A) formed above, a film after drying the resin compositions constituting each of the resin layers (B) obtained in Examples 1, Reference Examples 1 to 3 and Comparative Examples 1 and 2, respectively. It was applied so that the thickness was 10 μm. Then, it was dried in a hot air circulation type drying oven at 90 ° C./30 minutes to form a resin layer (B).

In this way, an uncured laminated structure composed of the resin layer (A) and the resin layer (B) described in Example 1, Reference Examples 1 to 3 and Comparative Examples 1 and 2 is formed on the flexible printed wiring board. bottom.

<Developability (alkali solubility)>
For the uncured laminated structure on each flexible printed wiring substrate on which the laminated structure was formed as described above, first, an exposure device (HMW-680-GW20) equipped with a metal halide lamp was used, and 500 mJ was passed through a negative mask. The pattern was exposed so as to form an opening having a diameter of 200 μm at / cm ^2. The substrate having the uncured laminated structure after exposure was heat-treated at 90 ° C. for 30 minutes. Then, the substrate was immersed in a 1% by mass sodium carbonate aqueous solution at 30 ° C. and developed for 1 minute to evaluate whether or not a 200 μm opening pattern could be formed. The evaluation criteria are as follows.
◯: The exposed part shows the development resistance, the unexposed part shows the developability, and the pattern formation is good.
Δ: The unexposed area shows developability, but the development resistance of the exposed area is insufficient and pattern formation is not possible.
X: Pattern formation is not possible because the unexposed area does not dissolve in the developer.

<Heat resistance>
For the uncured laminated structure on each flexible printed wiring substrate on which the laminated structure was formed as described above, first, an exposure device (HMW-680-GW20) equipped with a metal halide lamp was used, and 500 mJ was passed through a negative mask. The pattern was exposed so as to form an opening having a diameter of 200 μm at / cm ^2. Then, the PEB step was carried out at 90 ° C. for 30 minutes, then development (30 ° C., 0.2 MPa, 1 mass% Na ₂ CO ₃ aqueous solution) was carried out for 60 seconds, and the mixture was thermally cured at 150 ° C. for 60 minutes. A flexible printed wiring board (evaluation board) on which a laminated structure was formed was produced. A rosin-based flux was applied to this evaluation substrate, and the substrate was immersed in a solder bath set at 260 ° C. for 20 seconds (10 seconds x 2 times) to evaluate the swelling and peeling of the cured coating film. The evaluation criteria are as follows.
◯: There was no swelling or peeling even after immersion for 10 seconds × 2 times.
X: When immersed for 10 seconds × 1 time, swelling and peeling occurred, and the adhesion was insufficient.

<Flexibility (bending test after 260 ° C solder reflow)>
The bendability of the test piece, which was passed through the evaluation substrate three times in a reflow oven set to a maximum of 260 ° C. in advance, was evaluated by the following test method.
The test piece is bent 180 ° so that the cured coating film is on the outside, sandwiched between two flat plates, loaded with a load G (1 kg standard weight) for 10 seconds, folded, and then subjected to an optical microscope. The number of times before cracks were recorded was set as one cycle of checking whether or not cracks were generated in the cured coating film portion of the bent portion. The evaluation criteria are as follows.
⊚: Bend 20 times or more.
◯: Bending 10 times or more and less than 20 times.
Δ: Bending 5 times or more and less than 10 times.
X: Bending less than 5 times.

The results of these evaluations are shown in Table 2.

As is clear from the evaluation results shown in the above table, in the laminated structure of each Example and Reference Example, in addition to excellent developability and heat resistance, good flexibility is obtained even after solder reflow. It was confirmed that.

Next, with respect to the resin composition constituting the resin layer (B) of Example 2, the same as the formation of the resin layer (B) on the flexible printed wiring board on which the circuit having a copper thickness of 18 μm is formed. A coating film was formed. The obtained coating film was evaluated for the above-mentioned resolution, heat resistance, and flexibility. The evaluation results are shown in Table 3.

1 Flexible printed wiring board 2 Conductor circuit 3 Resin layer 4 Resin layer 5 Mask

Claims (4)

It contains an alkali-soluble polyimide resin, an alkali-soluble resin other than the polyimide resin, core-shell rubber particles, and a curable compound.
A curable resin composition, wherein the alkali-soluble resin other than the polyimide resin is a polyamide-imide resin having a structure represented by the following general formula (1) and a structure represented by the following general formula (2). ..

(X ₁ is a residue of an aliphatic diamine (a) derived from dimer acid having 24-48 carbon atoms, X ₂ is a residue of an aromatic diamine (b) having a carboxyl group, and Y is an independently cyclohexane ring or Aromatic ring.) Product resin layer (A), the resin layer on the resin layer (A) and (B), made, the resin layer (B) is, that will be laminated on the base material through the resin layer (A) It is a layered structure
The resin layer (B) is composed of a curable resin composition containing an alkali-soluble polyimide resin, an alkali-soluble resin other than the polyimide resin, core-shell rubber particles, and a curable compound.
The alkali-soluble resin other than the polyimide resin is a polyamide-imide resin having a structure represented by the following general formula (1) and a structure represented by the following general formula (2), and
A laminated structure in which the resin layer (A) is made of an alkali-developable resin composition containing an alkali-soluble resin and a heat-reactive compound.

(X ₁ is a residue of an aliphatic diamine (a) derived from dimer acid having 24-48 carbon atoms, X ₂ is a residue of an aromatic diamine (b) having a carboxyl group, and Y is an independently cyclohexane ring or Aromatic ring.) A cured resin composition according to claim 1, or a cured product obtained by curing the laminated structure according to claim 2. An electronic component having an insulating film made of the cured product according to claim 3.

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