TWI847801B - Curable resin composition, laminated structure, cured product and electronic component - Google Patents

Abstract

The present invention relates to providing a curable resin composition having good resolution of the obtained dry coating and low adhesion characteristics even when the cured products after heat curing are stacked and stored in a high temperature environment. The curable resin composition of the present invention is a cured film that can be alkali-developed and exposed and heated. When a dry coating with a thickness of 2 to 100 μm is formed by the curable resin composition, the arithmetic average roughness Ra of the dry coating is less than 0.1 μm and the arithmetic average roughness Ra of the cured film after heat curing of the dry coating becomes 0.1 μm or more and 1 μm or less. The dried coating obtained by the curable resin composition of the present invention has good resolution and has low adhesion properties even when the cured product after thermal curing is stored in a stacked high temperature environment.

Description

Curable resin composition, laminated structure, cured product and electronic component

The present invention relates to a laminated structure of a resin layer formed by the curable resin composition, a cured product thereof, and an electronic component having an insulating film formed by the cured product, and particularly to a curable resin composition that can be alkali developed and forms a cured film by exposure and heat treatment, a laminated structure of a resin layer formed by the curable resin composition, a cured product thereof, and an electronic component having an insulating film formed by the cured product.

In the past, as a protective film for flexible printed wiring boards, a non-photosensitive resin structure formed by applying a thermosetting adhesive to a film such as polyimide can be used. As a method of patterning a non-photosensitive resin structure to form a flexible printed wiring board, there has been a method of punching holes and then hot-pressing the flexible printed wiring board. Alternatively, there is also a method of directly patterning a solvent-soluble thermosetting resin composition on a flexible printed wiring board and then heat-curing it to form a pattern. In particular, polyimide film is used as a preferred material for flexible printed wiring boards because it has flexibility, heat resistance, mechanical properties, and excellent electrical properties (for example, refer to patent document 1). However, in the above-mentioned conventional methods, the shape of the pattern ends may collapse due to resin seepage during coating or hot pressing, making it difficult to form fine patterns required for miniaturization of wiring or miniaturization of chip parts mounted on flexible printed wiring boards. [Prior technical literature] [Patent literature]

[Patent Document 1] WO2012/133665

[Problems solved by the invention]

On the other hand, photosensitive solder resists, which are known as permanent protective films for circuits that can be micro-processed, are also considered to be applicable as covering layers for flexible printed wiring boards. Since photosensitive solder resists can impart flexibility to flexible printed wiring boards, it is necessary to reduce the crosslinking density. Flexible substrates are thin and easily bend, so they often must be stacked in multiple pieces and fixed for storage or transportation. The storage environment is further increased to a high temperature due to the transportation environment. When photosensitive solder resists are used as covering layers, the area of the flexible printed wiring board to be protected becomes wider, so due to the low crosslinking density, the coatings formed on the substrate sometimes adhere to each other.

In recent years, the demand for thinner films has also been increasing in the field of using rigid boards. Not only flexible boards, but also thin boards such as rigid boards with a thickness of 0.1 mm will also cause the phenomenon of adhesion between coatings.

To solve this problem, if the surface roughness of the coating is increased, the surface area to be contacted will be reduced, and adhesion will not occur. However, if a coating with a relatively large surface roughness is patterned by photolithography, halo will be caused on the surface of the coating, and sufficient resolution cannot be obtained.

In view of the above-mentioned problems, the first object of the present invention is to provide a curable resin composition having good resolution of a dried coating film, good softness of a cured product, and low adhesion when stored in a stacked state.

Furthermore, in view of the aforementioned problem, the second purpose of the present invention is to provide a curable resin composition having good developability of the dried coating film, good heat resistance and flexibility of the obtained cured product, and having low adhesion properties when the obtained cured product is stored by stacking. [Means for solving the problem]

The inventors of the present invention have conducted detailed studies to achieve the above-mentioned first purpose. As a result, the present invention has been completed by maintaining a relatively small surface roughness (arithmetic mean roughness) at the time of drying the coating film, and by using a curable resin composition that can increase the surface roughness (arithmetic mean roughness) after thermal curing, thereby obtaining a high resolution of the dried coating film and the softness and low adhesion of the thermally cured film. In addition, for this specification, the so-called resolution means the detail expression of the image obtained when the resin layer composed of the curable resin composition of the present invention is exposed and then developed by alkali.

That is, the first object of the present invention is to provide a curable resin composition that can be alkali developed and form a cured film by exposure and heat treatment. It has been found that when a dry coating film with a thickness of 2 to 100 μm is formed by the above-mentioned curable resin composition, the arithmetic average roughness Ra of the above-mentioned dry coating film is less than 0.1 μm, and the arithmetic average roughness Ra of the cured film after thermal curing of the above-mentioned dry coating film is 0.1 μm or more and 1 μm or less (hereinafter also referred to as the first aspect of the present invention) can be achieved.

In this specification, the so-called resolution refers to the detail representation of an image obtained when a resin layer composed of the curable resin composition of the first aspect of the present invention is pattern-exposed and then developed with alkali.

In the first aspect of the present invention, the curable resin composition is preferably such that when a dry coating having a thickness of 2 to 100 μm is formed from the curable resin composition, the arithmetic average roughness Ra of the dry coating is less than 0.05 μm, and the arithmetic average roughness Ra of the cured film after thermal curing of the dry coating is preferably not less than 0.1 μm and not more than 0.5 μm.

Furthermore, it is preferred that the composition contains (A) an alkali-soluble polyamide imide resin, (B) a photoalkali generator, (C) a thermosetting compound, and (D) a cellulose derivative.

Furthermore, (C) the thermosetting compound is preferably an epoxy resin.

Therefore, the first object of the present invention can be achieved by a laminated structure in which at least one side of a resin layer formed by the curable resin composition of the present invention is supported or protected by a film, a cured product of the curable resin composition of the present invention or the resin layer of the laminated structure of the present invention, and an electronic component having an insulating film formed by the cured product of the present invention.

Furthermore, the inventors of the present invention have conducted detailed studies to achieve the second object and have found that by adding a cellulose derivative to a curable resin composition and mixing a predetermined amount of an alkali-soluble polyimide resin, the adhesion between the obtained cured products is reduced, thereby completing the present invention.

That is, it has been found that the aforementioned second object of the present invention can be achieved by a curable resin composition characterized by containing (A) an alkali-soluble polyamide-imide resin, (B) a photoalkali generator, (C) a thermosetting compound, and (D) a cellulose derivative (hereinafter also referred to as the curable resin composition of the second aspect of the present invention).

Furthermore, the alkali-soluble polyamide imide resin (A) preferably has a carboxyl group, and the alkali-soluble polyamide imide resin (A) more preferably has a carboxyl group and a phenolic hydroxyl group.

Furthermore, the curable resin composition of the second aspect of the present invention preferably further contains (E) an alkali-soluble polyimide resin.

Therefore, (C) the thermosetting compound is preferably an epoxy resin.

Furthermore, the second object of the present invention can be achieved by a cured product obtained from the curable composition of the present invention, and an electronic component having an insulating film formed by the cured product. [Effect of the invention]

According to the first aspect of the curable resin composition of the present invention, the obtained dry coating film has good resolution, and the obtained cured product after heat curing also has good flexibility, and at the same time, when the cured product is stacked and stored in a high temperature environment, it also has low adhesion characteristics. In addition, the dry coating film of the curable composition of the second aspect of the present invention has good developability, and the cured product obtained from the curable composition of the second aspect of the present invention has good heat resistance and flexibility, and at the same time, it has low adhesion characteristics when stacked and stored.

[Embodiments of the invention] <The first aspect of the curable resin composition of the present invention>

The first aspect of the present invention is a hardening resin composition that can be alkali developed and can form a hardened film by exposure and heat treatment. When a dry coating having a thickness of 2 to 100 μm is formed from the hardening resin composition, the arithmetic average roughness Ra of the dry coating is less than 0.1 μm, and the arithmetic average roughness Ra of the cured film after thermal curing of the dry coating is greater than or equal to 0.1 μm and less than or equal to 1 μm.

The first aspect of the present invention is a hardening resin composition that is alkali-developable and is intended to form a hardened film by exposure and heat treatment. The composition comprises a compound (hereinafter referred to as an alkali-soluble compound) containing an alkali-soluble functional group (hereinafter referred to as an alkali-soluble group), (B) a photoalkali generator, and (C) a thermosetting compound.

Among these, (B) the photoalkali generator can function as a catalyst for the addition reaction between the alkali-soluble compound and the (C) thermosetting compound by causing a change in the molecular structure through irradiation with light such as ultraviolet rays or visible light, or by cleavage of the molecule.

Examples of the alkali-soluble compound include compounds having a phenolic hydroxyl group, compounds having a carboxyl group, and compounds having a phenolic hydroxyl group and a carboxyl group. The alkali-soluble compound is preferably the alkali-soluble polyamide imide resin (A) described below. Among them, the alkali-soluble polyamide imide resin (A) preferably has a structure represented by the general formula (1) described below and a structure represented by the general formula (2) described below.

In the first aspect of the present invention, the thickness of the curable resin composition is 2 to 100 μm. From the viewpoint of improving resolution, when a dry coating film of 3 to 80 μm is formed, the arithmetic average roughness Ra of the dry coating film is preferably less than 0.1 μm, preferably less than 0.05 μm, and the arithmetic average roughness Ra of the cured film after thermal curing of the dry coating film is greater than 0.1 μm and less than 1 μm, preferably greater than 0.1 μm and less than 0.5 μm.

When the arithmetic mean roughness Ra of the dried coating is less than 0.1 μm, the random reflection of the light irradiating the coating during exposure is suppressed, and the resolution becomes good. In addition, after thermal curing, by making the arithmetic mean roughness Ra of the cured film 0.1 μm or more and 1 μm or less, small irregularities are generated on the cured film. Due to the irregularities, the contact area between the cured films stacked and arranged becomes smaller, so that the bonding is reduced.

The phenomenon that the unevenness of the dried coating before thermal curing is small and the unevenness of the cured film after thermal curing becomes larger is considered to be caused by the fact that the curable resin composition of the present invention contains a polymer component having a miscibility with the above-mentioned (C) thermosetting compound or alkali-soluble compound. That is, it is presumed that the polymer component dispersed in the dried coating before thermal curing migrates to the film surface during the thermal curing reaction.

As the polymer component, it is preferred to add (D) a cellulose derivative.

The first aspect of the present invention preferably comprises a curable resin composition comprising (A) an alkali-soluble polyamide-imide resin, (B) a photoalkali generator, (C) a thermosetting compound, and (D) a cellulose derivative.

<The second aspect of the curable resin composition of the present invention> The second aspect of the curable resin composition of the present invention contains (A) an alkali-soluble polyamide imide resin, (B) a photoalkali generator, (C) a thermosetting compound, and (D) a cellulose derivative.

The curable resin composition of the second aspect of the present invention preferably further contains (E) an alkali-soluble polyimide resin.

Therefore, (C) the thermosetting compound is preferably an epoxy resin.

[(A) Alkali-soluble polyamide-imide resin] (A) Alkali-soluble polyamide-imide resin is a preferred example of the above-mentioned alkali-soluble photocurable compound. (A) Alkali-soluble polyamide-imide resin contains an alkali-soluble group (one or more of phenolic hydroxyl group and carboxyl group). The first aspect of the curable resin composition of the present invention preferably contains (A) alkali-soluble polyamide-imide resin, and the second aspect of the present invention preferably contains (A) alkali-soluble polyamide-imide resin.

Examples of such alkaline-soluble polyamide imide resins include resins obtained by reacting a carboxylic acid anhydride component with an amine component to obtain an imide, and then reacting the obtained imide with an isocyanate component. Among them, the alkaline-soluble group can be introduced by using an amine component having a carboxyl group or a phenolic hydroxyl group. In addition, imidization can be carried out by thermal imidization, chemical imidization, or a combination of these.

As the carboxylic anhydride component, tetracarboxylic anhydride or tricarboxylic anhydride can be cited, but it is not limited to these anhydrides. If it is a compound having an anhydride group and a carboxyl group that react with an amine group or an isocyanate group, a compound containing such a derivative can be used. In addition, these carboxylic anhydride components can be used alone or in combination.

As the amine component, diamines such as aliphatic diamines or aromatic diamines, polyvalent amines such as aliphatic polyetheramines, diamines having a carboxyl group, diamines having a phenolic hydroxyl group, etc. can be used. The amine component is not limited to these amines, and it is necessary to use an amine that can introduce at least one functional group of a phenolic hydroxyl group or a carboxyl group. In addition, these amine components can be used alone or in combination.

As the isocyanate component, diisocyanates such as aromatic diisocyanates and their isomers or polymers, aliphatic diisocyanates, alicyclic diisocyanates and their isomers, or other general diisocyanates can be used, but the invention is not limited to these isocyanic acids. In addition, these isocyanate components can be used alone or in combination.

(A) When an alkali-soluble polyamide imide resin is contained in the curable resin composition of the present invention, the acid value (solid content acid value) is preferably 30 mgKOH/g or more, more preferably 30 mgKOH/g to 150 mgKOH/g, and particularly preferably 50 mgKOH/g to 120 mgKOH/g, from the viewpoint of maintaining a good balance between the alkali solubility (developability) of the polyamide imide resin and other properties of the cured product of the resin composition containing the polyamide imide resin. Specifically, when the acid value is set to 30 mgKOH/g or more, the alkali solubility, i.e., the developability becomes good, and the crosslinking density with the heat-curing component after light irradiation becomes high, so that a sufficient development contrast can be obtained. Furthermore, by setting the acid value to 150 mgKOH/g or less, it is possible to suppress excessive heating in the PEB (POST EXPOSURE BAKE) step after light irradiation described later, thereby increasing the process width.

In addition, when considering the developing property and the properties of the cured coating, the molecular weight of the alkali-soluble polyamide-imide resin (A) is preferably 20,000 or less, preferably 1,000 to 17,000, and more preferably 2,000 to 15,000. When the molecular weight is 20,000 or less, the alkali solubility of the unexposed part increases, thereby improving the developing property. On the other hand, when the molecular weight is 1,000 or more, sufficient developing resistance and curing properties can be obtained for the exposed part after the exposure and PEB step.

When the alkali-soluble polyamide imide resin (A) is contained in the curable resin composition of the present invention, it is particularly preferred to use a polyamide imide resin having a structure represented by the following general formula (1) or a structure represented by the following general formula (2) because the developing property is further improved and the flexibility and adhesion are also improved. Furthermore, the structure represented by the following general formula (1) or the structure represented by the following general formula (2) may be contained in not only one molecule of the alkali-soluble polyamide imide resin (A), but also in the alkali-soluble polyamide imide resin (A).

(In general formula (1), _X1 is a residue of an aliphatic diamine (a) (also referred to as "dimer diamine (a)" in the present specification) derived from a dimer acid having 24 to 48 carbon atoms. In general formula (2), _X2 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. In general formulas (1) and (2), Y is independently cyclohexane or an aromatic ring.)

By containing the structure represented by the general formula (1) and the structure represented by the general formula (2), a polyamide imide resin having excellent alkali solubility can be obtained which is soluble even in a mild alkaline solution such as a 1.0 mass % sodium carbonate aqueous solution. In addition, a cured product of a curable resin composition containing the polyamide imide resin can have excellent dielectric properties.

Dimer diamine (a) can be obtained by reductively aminated the carboxyl group in the dimer of an aliphatic unsaturated carboxylic acid having 12 to 24 carbon atoms. That is, the dimer diamine (a) of an aliphatic diamine derived from a dimer acid is obtained by, for example, polymerizing unsaturated fatty acids such as oleic acid and linoleic acid to form a dimer acid, reducing the dimer acid, and then aminated. As such an aliphatic diamine, for example, PRIAMINE 1073, 1074, 1075 (trade name manufactured by Croda Japan) and other commercial products having a carbon number of 36 can be used. The dimer diamine (a) is preferably derived from a dimer acid having 28 to 44 carbon atoms, and is more preferably derived from a dimer acid having 32 to 40 carbon atoms.

Specific examples of the diamine (b) containing a carboxyl group include 3,5-diaminobenzoic acid, 3,4-diaminobenzoic acid, 5,5'-methylenebis(o-aminobenzoic acid), benzidine-3,3'-dicarboxylic acid, etc. The diamine (b) containing a carboxyl group may be composed of one type of compound or a plurality of types of compounds. From the viewpoint of raw material availability, the diamine (b) containing a carboxyl group is preferably one containing 3,5-diaminobenzoic acid or 5,5'-methylenebis(o-aminobenzoic 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. From the viewpoint of good balance between the alkaline solubility of the polyamide imide resin and the mechanical properties of the cured product of the curable resin composition containing the polyamide imide resin, the content (unit: mass %) of the dimer diamine (a) is preferably 20 to 60 mass %, more preferably 30 to 50 mass %. In this specification, the "content of dimer diamine (a)" means the ratio of the amount of dimer diamine (a) charged as one of the raw materials in the production of polyamide imide resin to the mass of the produced polyamide imide resin. Here, "the mass of the produced polyamide imide resin" means the value obtained by subtracting the theoretical amount of water ( _H2O ) generated by imidization and carbonic acid gas ( _CO2 ) generated by imidization from the amount of all raw materials charged to produce the polyamide imide resin.

From the viewpoint of improving the alkaline 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 good balance between the alkaline solubility of the polyamide imide resin and other properties of the cured product of the resin composition containing the polyamide imide resin, such as mechanical properties, the relationship between the amount of the aromatic ring and the cyclohexane ring in the portion represented by Y is such that 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, and even more preferably 90/10 to 98/2.

The method for producing the alkaline-soluble polyamide imide resin (A) is not particularly limited, and the resin can be produced by a conventional method through an imidization step and an amide imidization step.

In the imidization step, an imide compound is obtained by reacting one or two selected from the group consisting of a dimer diamine (a), a carboxyl group-containing diamine (b), and cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride (c) and trimellitic anhydride (d).

The amount of the dimer diamine (a) added is preferably such that the content of the dimer diamine (a) is 20 to 60% by mass, more preferably such that the content of the dimer diamine (a) is 30 to 50% by mass. The content of the dimer diamine (a) is defined as above.

If necessary, the dimer diamine (a) and the carboxyl group-containing diamine (b) may be used together with other diamines. Specific examples of other diamines include 2,2-bis[4-(4-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]sulfone, 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)phenyl] phenoxy)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)diphenyl sulfone, (4,4'-diamino)benzophenone, (3,3'-diamino)benzophenone, (4,4'-diamino Examples of the aromatic diamines include (4,4'-diamino)diphenylmethane, (4,4'-diamino)diphenyl ether, (3,3'-diamino)diphenyl ether, and the like; and examples of the aliphatic diamines include hexamethylenediamine, octamethylenediamine, decamethylenediamine, dodecamethylenediamine, octadecamethylenediamine, 4,4'-methylenebis(cyclohexylamine), isophoronediamine, 1,4-cyclohexanediamine, and norbornenediamine.

From the viewpoint of improving the alkaline solubility of the polyamide imide resin, it is preferred 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) used to the amount of trimellitic anhydride (d) used is preferably 85/15 to 100/0, more preferably 90/10 to 99/1, and even more preferably 90/10 to 98/2.

The relationship between the amount of the diamine compound (specifically, the dimer diamine (a) and the carboxyl group-containing diamine (b) and other diamines used as necessary) used to obtain the imide compound and the amount of the acid anhydride (specifically, one or two selected from the group consisting of cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride (c) and trimellitic anhydride (d)) is not limited. The amount of the acid anhydride used is preferably an amount in which the molar ratio relative to the amount of the diamine compound used is 2.0 to 2.4, and more preferably an amount in which the molar ratio is 2.0 to 2.2.

In the amide imidization step, a diisocyanate compound is reacted with the imide obtained in the above-mentioned imidization step to obtain a polyamide imide resin containing a substance having a structure represented by the general formula (3) described below.

The specific type of the diisocyanate compound is not particularly limited. The diisocyanate compound may be composed of one type of compound or a plurality of types of compounds.

Specific examples of the diisocyanate compound include aromatic diisocyanates such as 4,4′-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, naphthalene-1,5-diisocyanate, o-xylene diisocyanate, m-xylene diisocyanate, and 2,4-terdimer; and aliphatic diisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and norbornene diisocyanate. From the viewpoint of improving both the alkali solubility of the alkali-soluble polyamide imide resin (A) and the light transmittance of the polyamide imide resin, the diisocyanate compound preferably contains an aliphatic isocyanate, and the diisocyanate compound preferably contains an aliphatic isocyanate.

The amount of the diisocyanate compound used in the amidoimidization step is not limited. From the viewpoint of imparting appropriate alkaline solubility to the polyamidoimide resin, the amount of the diisocyanate compound used is preferably 0.3 to 1.0, more preferably 0.4 to 0.95, and particularly preferably 0.50 to 0.90 as a molar ratio to the amount of the diamine compound used to obtain the imide compound.

The polyamide imide resin thus produced contains the following general formula (3): (In the above general formula (3), X is independently a diamine residue (a residue of a diamine compound), Y is independently an aromatic ring or a cyclohexane ring, and Z is a residue of a diisocyanate compound. n is a natural number)

The total amount of the alkali-soluble polyamide imide resin (A) and the alkali-soluble polyamide imide resin (E) described later as an optional component is, for example, 10 parts by mass to 85 parts by mass, preferably 15 parts by mass to 80 parts by mass, and particularly preferably 20 parts by mass to 75 parts by mass, based on 100 parts by mass of the curable resin composition of the present invention.

[(B) Photoalkali generator] The first aspect of the curable resin composition of the present invention preferably contains (A) an alkali-soluble polyamide imide resin (and (E) an alkali-soluble polyamide imide resin as an optional component described later), (C) a thermosetting compound, and (B) a photoalkali generator. The second aspect of the curable resin composition of the present invention contains (B) a photoalkali generator. (B) A photoalkali generator is a compound of one or more alkaline substances that can function as a catalyst for the addition reaction between a polyamide imide resin having a carboxyl group and a thermosetting component by changing its molecular structure or by cleaving its molecules when irradiated with light such as ultraviolet rays or visible light.

Examples of alkaline substances include secondary amines and tertiary amines.

As the photobase generator, for example, there can be mentioned α-aminoacetophenone compounds, oxime ester compounds, or compounds having substituents such as acyloxyimino groups, N-formylated aromatic amine groups, N-acylated aromatic amine groups, nitrobenzylcarbamate groups, and alkoxybenzylcarbamate groups. Among them, oxime ester compounds and α-aminoacetophenone compounds are preferred. As α-aminoacetophenone compounds, those having two or more nitrogen atoms are particularly preferred.

As other photoalkali generators, WPBG-018 (trade name: 9-anthrylmethyl N,N’-diethylcarbamate), WPBG-027 (trade name: (E)-1-[3-(2-hydroxyphenyl)-2-propenoyl]piperidine), WPBG-082 (trade name: guanidinium2-(3-benzoylphenyl)propionate), WPBG-140 (trade name: 1-(anthraquinon-2-yl; 1-(anthraquinone-2-yl))ethyl imidazolecarboxylate), etc. can be used (all manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.). α-Aminoacetophenone compounds have benzoin ether bonds in their molecules. When exposed to light, they cause cracking within the molecule, generating alkaline substances (amines) that act as hardening catalysts.

As specific examples of α-aminoacetophenone compounds, commercially available compounds or solutions such as (4-morpholinobenzoyl)-1-benzyl-1-dimethylaminopropane (Omnirad 369, trade name, manufactured by IGM Resins Co., Ltd.), 4-(methylthiobenzoyl)-1-methyl-1-morpholinoethane (Omnirad 907, trade name, manufactured by IGM Resins Co., Ltd.), and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholino)phenyl]-1-butanone (Omnirad 379, trade name, manufactured by IGM Resins Co., Ltd.) can be used.

As the oxime ester compound, any compound can be used as long as it can generate an alkaline substance by light irradiation. As the oxime ester compound, an oxime ester-based photoalkali generator having a group represented by the following general formula (4) is preferred.

(wherein, _R1 represents a hydrogen atom, an unsubstituted or substituted alkyl group having 1 to 6 carbon atoms, a phenyl group or a phenyl group substituted by a halogen atom, an unsubstituted or substituted alkyl group having 1 to 20 carbon atoms, an alkyl group interrupted by one or more oxygen atoms, a cycloalkyl group having 5 to 8 carbon atoms which is unsubstituted or substituted by an alkyl group having 1 to 6 carbon atoms or a phenyl group, an alkyl group having 2 to 20 carbon atoms which is unsubstituted or substituted by an alkyl group having 1 to 6 carbon atoms or a phenyl group, or a benzoyl group, R ₂ represents an unsubstituted or substituted alkyl group having 1 to 6 carbon atoms, a phenyl group or a phenyl group substituted with a halogen atom, an unsubstituted or substituted alkyl group having 1 to 20 carbon atoms, an alkyl group interrupted by one or more oxygen atoms, a cycloalkyl group having 5 to 8 carbon atoms which is unsubstituted or substituted with an alkyl group having 1 to 6 carbon atoms or a phenyl group, an alkyl group having 2 to 20 carbon atoms which is unsubstituted or substituted with an alkyl group having 1 to 6 carbon atoms or a phenyl group, or a benzoyl group. ) As commercial products of oxime ester-based photobase generators, IRGACURE OXE01 and IRGACURE OXE02 manufactured by BASF Japan, and N-1919 and NCI-831 manufactured by ADEKA can be cited. In addition, compounds having two oxime ester groups in the molecule as described in Patent No. 4344400 can also be used.

Other examples include carbazole oxime ester compounds described in JP-A-2004-359639, JP-A-2005-097141, JP-A-2005-220097, JP-A-2006-160634, JP-A-2008-094770, JP-T-2008-509967, JP-T-2009-040762, and JP-A-2011-80036.

The photoalkali generator may be used alone or in combination of two or more. The amount of the photoalkali generator (B) in the curable resin composition of the present invention is, for example, 0.1 to 40 parts by mass, preferably 0.2 to 20 parts by mass, relative to 100 parts by mass of the alkali-soluble polyamide-imide resin (A), or, when the alkali-soluble polyamide-imide resin is contained, relative to 100 parts by mass of the total amount of the alkali-soluble polyamide-imide resin and the alkali-soluble polyamide-imide resin (A).

When the content is 0.1 parts by mass or more, a good contrast of the developing resistance of the light-irradiated part/the non-irradiated part can be obtained. When the content is 40 parts by mass or less, the properties of the cured product can be improved.

[(C) Thermosetting compound] From the perspective of imparting heat resistance and chemical resistance to the cured product after thermal curing, the first aspect of the curable resin composition of the present invention preferably contains a thermosetting compound (C). The second aspect of the curable resin composition of the present invention contains a thermosetting compound (C).

(C) As the thermosetting compound, known and commonly used thermosetting resins may be used, such as epoxy resins, urethane resins, polyester resins, hydroxyl, amino or carboxyl-containing polyurethanes, polyesters, polycarbonates, polyols, phenoxy resins, acrylic copolymer resins, vinyl resins, oxazine resins, and cyanate resins.

Among them, from the viewpoint of heat resistance and chemical resistance, the (C) thermosetting compound is preferably an epoxy resin.

Specific examples of epoxy resins include bisphenol A type epoxy resins such as jER828 manufactured by Mitsubishi Chemical Corporation, EHPE3150 manufactured by Daicel Chemical Industries, Ltd., EPICLON840 manufactured by DIC Corporation, EpotohtoYD-011 manufactured by Nippon Steel Chemical & Materials Corporation, D.E.R.317 manufactured by Dow/Chemicals Corporation, and SumiepoxyESA-011 manufactured by Sumitomo Chemical Co., Ltd. (all trade names); jERYL903 manufactured by Mitsubishi Chemical Corporation, and EPICLON840 manufactured by DIC Corporation. LON152, Epotohto YDB-400 manufactured by Nippon Steel Chemical & Materials Co., Ltd., D.E.R.542 manufactured by Dow/Chemicals Co., Ltd., Sumiepoxy ESB-400 manufactured by Sumitomo Chemical Co., Ltd. (all trade names) brominated epoxy resins; jER152 manufactured by Mitsubishi Chemical Co., Ltd., D.E.N.431 manufactured by Dow/Chemicals Co., Ltd., EPICLON manufactured by DIC Corporation N-730, Epotohto YDCN-701 manufactured by Nippon Steel Chemicals & Materials, EPPN-201 manufactured by Nippon Kayaku, Sumiepoxy ESCN-195X manufactured by Sumitomo Chemical (all trade names) phenolic varnish type epoxy resins; EPICLON 830 manufactured by DIC Corporation, jER807 manufactured by Mitsubishi Chemical Corporation, Epotohto YDF-170, YDF-175, YDF- 2004, etc. (all trade names) bisphenol F type epoxy resins; Epotohto ST-2004 (trade name) and other hydrogenated bisphenol A type epoxy resins manufactured by Nippon Steel Chemical & Materials Co., Ltd.; jER604 manufactured by Mitsubishi Chemical Co., Ltd., Epotohto YH-434 manufactured by Nippon Steel Chemical & Materials Co., Ltd., Sumiepoxy ELM-120 manufactured by Sumitomo Chemical Co., Ltd. (all trade names) glycerylamine type epoxy resins; hydantoin type epoxy resins; Daicel Chemical Industries, Ltd. CELLOXIDE2021 and other (all trade names) manufactured by Japan Chemical Industry Co., Ltd.; trihydroxyphenylmethane type epoxy resins such as EPPN-501 and other (all trade names) manufactured by Japan Chemical Industry Co., Ltd.; bis(xylenol) type or bisphenol type epoxy resins such as YL-6056, YX-4000, YL-6121 (all trade names) manufactured by Mitsubishi Chemical Co., Ltd. or mixtures thereof; EBPS-200 manufactured by Japan Chemical Industry Co., Ltd., EPX-30, D Bisphenol S type epoxy resins such as EXA-1514 (trade name) manufactured by IC Corporation; bisphenol A novolac type epoxy resins such as jER157S (trade name) manufactured by Mitsubishi Chemical Corporation; hybrid epoxy resins such as TEPIC manufactured by Nissan Chemical Corporation (all trade names); biphenyl novolac type epoxy resins; naphthyl-containing epoxy resins such as ESN-190 manufactured by Nippon Steel Chemicals & Materials Co., Ltd. and HP-4032 manufactured by DIC Corporation; epoxy resins having a dicyclopentadiene skeleton such as HP-7200 manufactured by DIC Corporation, etc.

(C) The thermosetting compound may be added in any amount, but when (A) the alkali-soluble polyamide imide resin is contained, it is preferably added in an equivalent ratio (alkali-soluble group: thermosetting group such as epoxy group) of 1:0.1 to 1:10 to the alkali-soluble polyamide imide resin.

[(D) Cellulose derivative] The first aspect of the curable resin composition of the present invention preferably contains a (D) cellulose derivative as a polymer component having different solubility with the above-mentioned (C) thermosetting compound or alkali-soluble photocurable compound, and the second aspect of the curable resin composition of the present invention contains a (D) cellulose derivative. When the (D) cellulose derivative is contained in the curable resin composition of the present invention, it is preferably soluble in an organic solvent and has a high glass transition temperature (Tg). Examples of the (D) cellulose derivative include cellulose ethers, carboxymethyl cellulose, cellulose esters, etc. as described below.

Examples of the cellulose ether include ethyl cellulose and hydroxy alkyl cellulose. Examples of the sales product of ethyl cellulose include Etocell (registered trademark) 4, Etocell 7, Etocell 10, Etocell 14, Etocell 20, Etocell 45, Etocell 70, Etocell 100, Etocell 200, and Etocell 300 (all trade names manufactured by Dow Chemicals). Examples of the sales product of hydroxy alkyl cellulose include Metros SM, Metros 60 SH, Metros 65 SH, Metros 90 SH, Metros SEB, and Metros SNB (all trade names manufactured by Shin-Etsu Chemical Co., Ltd.).

In addition, as commercial products of carboxymethylcellulose, CMCAB-641-0.2 (a trade name manufactured by Eastman Chemical Company), Sunrose F, Sunrose A, Sunrose P, Sunrose S, and Sunrose B (all trade names manufactured by Nippon Paper Industries, Ltd.) can be cited.

A more preferred cellulose derivative is a cellulose ester in which the hydroxyl group of cellulose is esterified with an organic acid. Specifically, the following formula (5) can be cited: (In formula (5), R ₁ , R ₂ and R ₃ are each independently hydrogen or acyl, or in formula (6) (In formula (6), R ₄ is hydrogen or methyl, R ₅ is hydrogen, methyl, ethyl or glycidyl.), at least one of R ₁ , R ₂ and R ₃ is hydrogen, and n is an integer greater than 1, the upper limit of which is limited by the molecular weight described below).

The cellulose ester represented by the above formula (5) has an acyl group content in the range of more than 0 and less than 60 wt %, preferably in the range of 5 to 55 wt %, based on the acyl group content of the cellulose resin.

For the cellulose ester represented by the above formula (5), the content of hydroxyl groups relative to the cellulose resin is 0-6wt%, the content of acetyl groups as acyl groups is 0-40wt%, the content of propionyl groups and/or butyryl groups is 0-55wt%, and the content of the groups represented by the formula (6) is preferably in the range of 0-20wt%. The so-called "wt%" here means the weight % of hydrogen, acyl groups or groups represented by the formula (6) relative to the weight of the cellulose.

As the commercial products of such cellulose esters, cellulose acetate includes CA-398-3, CA-398-6, CA-398-10, CA-398-30, CA-394-60S, etc., and cellulose acetate butyrate includes CAB-551-0.01, CAB-551-0.2, CAB-553-0.4, CAB-531-1, CAB-500-5, CAB-3 81-0.1, CAB-381-0.5, CAB-381-2, CAB-381-20, CAB-381-20BP, CAB-321-0.1, CAB-171-15, etc. As cellulose acetate propionate, CAP-504-0.2, CAP-482-0.5, CAP-482-20 (the above cellulose derivatives are all trade names made by Eastman Chemical Company) etc. Among these, cellulose acetate butyrate and cellulose acetate propionate are preferred from the perspective of solubility in solvents. Furthermore, the above-mentioned cellulose acetate or cellulose acetate butyrate, cellulose acetate propionate, in the presence of an oxidizing agent such as benzoyl peroxide, is reacted with (meth)acrylic acid, (meth)acrylic acid methyl, (meth)acrylic acid ethyl, (meth)acrylic acid glycidyl, etc., to obtain a cellulose derivative containing a group represented by formula (6). By using a cellulose derivative containing a group represented by formula (6), the adhesion evaluation result can be improved.

(D) The number average molecular weight of the cellulose derivative is not particularly limited, but is preferably 5,000 to 500,000, more preferably 10,000 to 100,000, and even more preferably 10,000 to 30,000. When the molecular weight is within the above range, the adhesion is small, that is, the adhesion evaluation result becomes good, and the viscosity of the curable resin composition becomes an appropriate range.

The glass transition temperature Tg referred to in this specification is the glass transition temperature measured by the method described in "5.17.5 DSC method" of JIS C 6481:1996 using thermomechanical analysis (DSC).

If the cellulose derivative used in the present invention is derived from natural materials, it is preferred from the perspective of fossil fuel depletion. In addition, the starting materials of the cellulose derivative used in the present invention can also be made from recycled products such as recycled paper pulp, which can also provide a better composition from the perspective of reducing _CO2 .

(D) The cellulose derivative can be used alone or in combination of two or more. The amount of the cellulose derivative (D) relative to 100 parts by mass of the alkali-soluble polyamide-imide resin (and the alkali-soluble polyamide-imide resin of the optional component described below) is, for example, 0.5 parts by mass to 20 parts by mass, preferably 1 part by mass to 15 parts by mass, and more preferably 4 parts by mass to 10 parts by mass. In the above range, at the time of drying the coating, the surface roughness (arithmetic mean roughness Ra) can be less than 0.1μm, the adhesion is small, that is, the evaluation result of adhesion becomes good, and the viscosity of the curable resin composition becomes an appropriate range. This is considered to be because the (A) alkali-soluble polyamide imide resin, (C) thermosetting compound and (D) cellulose derivative have good compatibility before thermal curing, and the polymer component exists in a dispersed manner in the dry coating. In addition, it is considered that the polymer component existing in a dispersed manner in the dry coating after thermal curing moves to the film surface during the thermal curing reaction, and the surface roughness (arithmetic mean roughness Ra) of the cured film after thermal curing becomes larger due to the dry coating before thermal curing. If the number average molecular weight and the compounding amount of the (D) cellulose derivative are set within the above range, the surface roughness (arithmetic mean roughness Ra) after curing can also be 0.1μm or more and 1μm or less.

[(E) Alkali-soluble polyimide resin] From the viewpoint of heat resistance, the curable resin composition of the present invention preferably contains (E) alkali-soluble polyimide resin.

(E) Alkali-soluble polyimide resin has an alkali-soluble functional group (hereinafter also referred to as an alkali-soluble group). The so-called alkali-soluble functional group is a functional group that allows the curable resin composition of the present invention to be developed in an alkaline solution, for example, a carboxyl group and a phenolic hydroxyl group.

Examples of such alkaline-soluble polyimide resins (E) include resins obtained by reacting carboxylic anhydride components with amine components and/or isocyanate components. The alkaline-soluble group can be introduced by using an amine component having a carboxyl group or a phenolic hydroxyl group. The imidization can be carried out by thermal imidization or chemical imidization, or by combining these methods.

As the carboxylic anhydride component, tetracarboxylic anhydride or tricarboxylic anhydride can be cited, but it is not limited to these anhydrides. Any compound having an anhydride group and a carboxyl group that react with an amine group or an isocyanate group can be used, and derivatives thereof can be used. In addition, these carboxylic anhydride components can be used alone or in combination.

As the amine component, diamines such as aliphatic diamines or aromatic diamines, polyvalent amines such as aliphatic polyetheramines, diamines having a carboxyl group, and diamines having a phenolic hydroxyl group can be used. The amine component is not limited to these amines, but an amine that can introduce at least one functional group of a phenolic hydroxyl group or a carboxyl group must be used. In addition, these amine components can be used alone or in combination.

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

For the synthesis of such (E) alkaline-soluble polyimide resin, a known and commonly used organic solvent can be used. As the organic solvent, any solvent that does not react with carboxylic anhydrides, amines, and isocyanates of the raw materials and can dissolve these raw materials will not cause any problem, and the structure is not particularly limited. In particular, from the viewpoint of high solubility of the raw materials, aprotic solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, and γ-butyrolactone are used.

(E) The alkali-soluble polyimide resin preferably has a carboxyl group as an alkali-soluble group, and particularly preferably has both a carboxyl group and a phenolic hydroxyl group as an alkali-soluble group.

(E) Alkali-soluble polyimide resin: From the viewpoint of achieving a good balance between the alkaline solubility (developability) of the polyimide resin and other properties such as mechanical properties of the cured product of the curable resin composition containing the polyimide resin, the acid value (solid content acid value) is preferably 20 to 200 mgKOH/g, and particularly preferably 60 to 150 mgKOH/g.

In addition, the molecular weight of the alkaline-soluble polyimide resin is preferably 100,000 or less, more preferably 1,000 to 100,000, and even more preferably 2,000 to 50,000, in consideration of the developing property and the cured coating properties.

When (E) an alkali-soluble polyimide resin is added, from the viewpoint of improving heat resistance and developing properties, the mass ratio of the (A) alkali-soluble polyamide-imide resin to the (E) alkali-soluble polyimide resin can be set to 98:2 to 50:50, preferably 95:5 to 50:50, and more preferably 95:5 to 70:30.

The following components may be further added to the curable resin composition of the present invention as necessary.

[Polymer resin] The curable resin composition of the present invention may be added with a known polymer resin for the purpose of improving the flexibility and dryness to touch of the obtained cured product. Examples of such polymer resins include polyester-based, phenoxy resin-based polymers, polyvinyl acetal-based, polyvinyl butyral-based, polyamide-based polymers, and elastomers. Such polymer resins may be used alone or in combination of two or more.

[Inorganic filler] In order to suppress the curing shrinkage of the cured product and improve the properties such as adhesion and hardness in the curable resin composition of the present invention, an inorganic filler can be added. 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, Newburgh siliceous clay, etc.

[Colorant] The curable resin composition of the present invention may be added with a commonly used colorant such as red, orange, blue, green, yellow, white, or black. The colorant may be any of a pigment, a dye, or a pigment.

[Organic solvent] An organic solvent may be added to the curable resin composition of the present invention when preparing the resin composition or adjusting the viscosity of the coating on a substrate or carrier film. Examples of such organic solvents include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, and petroleum-based solvents. Such organic solvents may be used alone or as a mixture of two or more.

[Other ingredients] The curable resin composition of the present invention may further contain alkyl compounds, adhesion promoters, antioxidants, ultraviolet absorbers and other ingredients as necessary. These ingredients may be those commonly used.

Furthermore, known conventional additives such as finely powdered silica, hydrotalcite, organic bentonite, montmorillonite, etc., silicone-based, fluorine-based, polymer-based defoaming agents and/or leveling agents, silane coupling agents, rust-proofing agents, etc. may be added.

<Laminated structure> The laminated structure of the present invention is a structure in which at least one side of a resin layer formed by the curable resin composition of the present invention is supported or protected by a film.

The resin layer may be a single layer or a laminated structure having two or more resin layers. When a laminated structure having two or more resin layers is set, for example, a resin layer formed by the curable resin composition of the present invention may be laminated, or a resin layer formed by the curable resin composition of the present invention and a resin layer not formed by the curable resin composition of the present invention may be laminated.

In the case of the latter laminated structure, the laminated structure is, for example, a resin layer (A) disposed on a substrate such as a flexible printed wiring board, and a resin layer (B) disposed on the resin layer (A), wherein at least one side of the resin layer is supported or protected by a film. The resin layer (A) may be, for example, composed of an alkali-developable resin composition containing an alkali-soluble resin and a heat-reactive compound.

The above-mentioned laminated structure can be produced, for example, as follows.

That is, first, on a carrier film (support film), the curable resin composition of the present invention constituting the resin layer is diluted with an organic solvent and adjusted to an appropriate viscosity, and then applied according to a conventional method using a notch wheel coater or other known methods. When the resin layer has a laminated structure, the applied resin composition is replaced, or the coating operation is repeated without replacement. After drying at a temperature of 50 to 130°C for 1 to 30 minutes, a dry coating film of the resin layer in the B stage state (semi-hardened state) is formed on the carrier film, and the laminated structure of the present invention can be manufactured. The resin layer of the laminated structure is a so-called dry film. On the dry film, a peelable film (protective film) can be further laminated for the purpose of preventing dust from adhering to the surface of the dry coating film. As the carrier film and the coating, conventionally known plastic films can be used. For the coating, when peeling the coating, the one with the smaller adhesion between the resin layer and the carrier film is preferred. There is no particular restriction on the thickness of the carrier film and the coating, and generally, a range of 10 to 150 μm can be appropriately selected.

<Hardened product> The cured product of the present invention is obtained by hardening the curable resin composition of the present invention or the resin layer of the laminated structure of the present invention.

<Electronic components> The curable resin composition of the present invention and the resin layer of the laminated structure of the present invention can be used, for example, for electronic components such as flexible printed wiring boards. Specifically, a flexible printed wiring board, etc. can be cited as a cured product having an insulating film formed by patterning in a developer after forming a layer of the curable resin composition of the present invention or a resin layer of the laminated structure on a flexible printed wiring substrate, patterning by light irradiation, and forming a pattern.

The following is a detailed description of the method for manufacturing a flexible printed wiring board.

<Method for manufacturing a flexible printed wiring board> An example of manufacturing a flexible printed wiring board using the curable resin composition of the present invention or the resin layer of the laminated structure of the present invention is shown below. That is, the manufacturing method includes the steps of coating the curable resin composition of the present invention on a flexible printed wiring substrate forming a conductive circuit, or bonding the resin layer of the laminated structure of the present invention to form a resin layer (layer forming step), irradiating the resin layer with active energy rays in a patterned shape (exposure step), and performing alkaline development on the exposed resin layer to form a patterned resin layer image (development step). Furthermore, after alkaline development, if necessary, light curing or heat curing (post-curing step) is further performed to completely cure the resin layer and form a cured film to obtain a highly reliable and flexible printed wiring board.

Furthermore, the production of a flexible printed wiring board using the curable resin composition of the present invention or the resin layer of the laminate structure of the present invention may also be carried out according to other procedures. That is, the manufacturing method includes the steps of coating the curable resin composition of the present invention on a flexible printed wiring substrate forming a conductive circuit, or bonding the resin layer of the laminated structure of the present invention to form a resin layer (layer forming step), irradiating the resin layer with active energy rays in a patterned shape (exposure step), heating the exposed resin layer (heating (PEB) step), and subjecting the heated resin layer to alkali development to form a patterned resin layer image (development step). Furthermore, after alkaline development is performed as necessary, light curing or heat curing (post-curing step) is further performed to completely cure the resin layer to form a cured film, thereby obtaining a highly reliable and flexible printed wiring board. [Example]

The present invention is specifically described below with reference to the following examples, but the present invention is not limited to these examples. In addition, unless otherwise specified, "parts" means parts by mass of solid components.

((A) Synthesis of alkaline-soluble polyamide imide resin) [Synthesis Example 1] In a four-mouth 300 mL flask equipped with a nitrogen inlet tube, a thermometer, and a stirrer, 28.61 g (0.052 mol) of an aliphatic diamine derived from a dimer acid having 36 carbon atoms (manufactured by Croda Japan, product name PRIAMINE1075) as a dimer diamine (a), 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 anhydride (c) and 3.07 g (0.016 mol) of trimellitic anhydride (d) were added and kept at room temperature for 30 minutes. 30 g of toluene was further added, and the temperature was raised to 160°C. After removing the water produced together with the toluene, the mixture was kept for 3 hours and cooled to room temperature to obtain a solution containing an imide.

14.30 g (0.068 mol) of trimethylhexamethylene diisocyanate as a diisocyanate compound was added to the solution containing the obtained imide compound, and the solution was kept at 160° C. for 32 hours, and then diluted with 21.4 g of cyclohexanone to obtain a solution (A-1) containing an alkaline-soluble polyamide imide resin (A). 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 content of the dimer diamine (a) of 40.0% by mass.

[Synthesis Example 2] In a four-mouth 300 mL flask equipped with a nitrogen inlet tube, a thermometer, and a stirrer, 29.49 g (0.054 mol) of an aliphatic diamine (manufactured by Croda Japan, product name PRIAMINE1075) derived from a dimer acid having 36 carbon atoms as the dimer diamine (a), 4.02 g (0.026 mol) of 3,5-diaminobenzoic acid as the carboxyl group-containing diamine (b), and 73.5 g of γ-butyrolactone were charged and dissolved at room temperature.

Next, 31.71 g (0.160 mol) of cyclohexane-1,2,4-tricarboxylic anhydride (c) and 1.54 g (0.008 mol) of trimellitic anhydride (d) were added and kept at room temperature for 30 minutes. 30 g of toluene was further added, the temperature was raised to 160°C, water produced together with toluene was removed, and the mixture was kept for 3 hours. After cooling to room temperature, a solution containing an imide was obtained.

Into the solution containing the obtained imide compound, 6.90 g (0.033 mol) of trimethylhexamethylene diisocyanate and 8.61 g (0.033 mol) of dicyclohexylmethane diisocyanate as diisocyanate compounds were added, and the mixture was kept at 160°C for 32 hours, and then diluted with 36.8 g of cyclohexanone to obtain a solution (A-2) containing (A) alkaline-soluble polyamide imide resin. The obtained polyamide imide resin had a mass average molecular weight Mw of 5840, a solid content of 40.4% by mass, an acid value of 62 mgKOH/g, and a content of dimer diamine (a) of 40.1% by mass.

[Synthesis Example 3] In a four-necked 300 mL flask equipped with a nitrogen inlet tube, a thermometer, and a stirrer, 6.98 g of 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, 3.80 g of 3,5-diaminobenzoic acid, 8.21 g of polyether diamine (manufactured by Huntsman, product name Erastamin RT1000, molecular weight 1025.64), and 86.49 g of γ-butyrolactone were charged and dissolved at room temperature.

Next, 17.84 g of cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride and 2.88 g of trimellitic anhydride were added and kept at room temperature for 30 minutes. 30 g of toluene was further added and the temperature was raised to 160° C. After removing the water produced together with the toluene, the mixture was kept for 3 hours and cooled to room temperature to obtain an imide solution.

Into the obtained imide solution, 9.61 g of trimellitic anhydride and 17.45 g of trimethyl hexamethylene diisocyanate were added and kept at 160°C for 32 hours. Thus, a carboxyl-containing (A) alkaline-soluble polyamide imide resin solution (A-3) was obtained. The solid content was 40.1% by mass and the acid value was 83 mgKOH/g.

((E) Synthesis of alkaline-soluble polyimide resin) [Synthesis Example 4] In a separable three-necked flask equipped with a stirrer, a nitrogen inlet tube, a distillation ring, and a cooling ring, 22.4 g of 3,3'-diamino-4,4'-dihydroxydiphenylsulfone, 8.2 g of 2,2'-bis[4-(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 were added, and stirred at 100 rpm for 4 hours at room temperature under a nitrogen environment. Next, add 20g of toluene, distill off toluene and water in a silica bath at 180°C and 150rpm while stirring for 4 hours to obtain a polyimide resin solution (PI-1) with phenolic hydroxyl and carboxyl groups.

The obtained resin (solid content) had an acid value of 18 mgKOH, a Mw of 10,000, and a hydroxyl equivalent of 390.

((D) Synthesis of cellulose derivatives) [Synthesis Example 5] In a flask equipped with a stirrer, a thermometer, and a reflux cooler, 64 g of methyl ethyl ketone and 16 g of CAB-553-0.4 (cellulose acetate derivative, manufactured by Eastman Chemical Company) were placed and stirred at 75°C for 1 hour. Next, a mixture of 15 g of methyl methacrylate and 1 g of benzoyl peroxide was added dropwise over 3 hours. After the addition was completed, a mixture of 0.5 g of benzoyl peroxide and 5 g of methyl ethyl ketone was added dropwise over 1 hour while maintaining 75°C. The mixture was stirred for 3 hours at 75°C and then cooled. 61 g of methyl ethyl ketone was added to the mixture and stirred to obtain a resin solution (CA-1). Moreover, the heating residue of resin solution CA-1 is 20.0 mass %.

[Synthesis Example 6] In a flask equipped with a stirrer, a thermometer, and a reflux cooler, 64 g of methyl ethyl ketone and 16 g of CAB-553-0.4 (cellulose acetate derivative, manufactured by Eastman Chemical Company) were placed and stirred at 75°C for 1 hour. Next, a mixture of 15 g of glycidyl methacrylate and 1 g of benzoyl peroxide was added dropwise over 3 hours. After the addition was completed, a mixture of 0.5 g of benzoyl peroxide and 5 g of methyl ethyl ketone was added dropwise over 1 hour while maintaining 75°C. The mixture was stirred for 3 hours at 75°C and then cooled. 61 g of methyl ethyl ketone was added to the mixture and stirred to obtain a resin solution (CA-2). The heated residue of resin solution CA-2 is 20.0 mass %.

[Examples of the first embodiment of the hardening resin composition of the present invention] <1-1. Preparation of hardening resin compositions of Examples 1-1 to 1-12 and Comparative Examples 1-1 to 1-3> According to the composition shown in Table 1 below, the materials of the hardening resin compositions of Examples 1-1 to 1-12 and Comparative Examples 1-1 to 1-3 are added, pre-mixed with a stirrer, and then kneaded with a three-roll mill to adjust the hardening resin compositions to form the resin layer. In addition, the values in Table 1 represent the mass fraction of the solid component unless otherwise specified.

For each of the aforementioned curable resin compositions, as shown below, a resin layer (dried coating) in the B-stage state (semi-cured state) of each curable resin composition was formed, and the resolution was evaluated. And as described later, for a flexible wiring board having a resin layer in the B-stage state (semi-cured state) and a flexible wiring board having a cured product of the resin layer, the surface roughness of each coating in the B-stage state (semi-cured state)/after thermal curing was evaluated. Therefore, for the flexible wiring board having a cured product of the resin layer, its heat resistance (soldering heat resistance), gold plating resistance (chemical resistance), flexibility and adhesion were also evaluated. The results are shown in Table 1.

<1-2. Formation of resin layer> A flexible printed wiring substrate with a copper circuit of 18 μm in thickness was prepared and pre-treated using CZ-8100 of MEC. Subsequently, the pre-treated flexible printed wiring substrate was coated with each of the curable resin compositions obtained in Examples 1-1 to 1-12 and Comparative Examples 1-1 to 1-3 until the film thickness after drying became the film thickness described in Table 1. Subsequently, after drying at 90°C for 30 minutes in a hot air circulation drying oven, a resin layer (dried coating) in the B stage state (semi-cured state) was formed.

<1-3. Preparation of evaluation substrate> For each flexible printed wiring substrate on which the resin layer is formed as described above, the uncured resin layer is first exposed to a pattern at 300mJ/ ^cm2 through a negative mask using an exposure device equipped with a metal halogen lamp (HMW-680-GW20: manufactured by Oak Manufacturing) to form an opening with a diameter of 200μm. After that, a PEB step is performed at 90℃ for 30 minutes, and then development (30℃, 0.2MPa, 1 mass% _{Na2CO3 aqueous} solution) is performed for 60 seconds. By heat curing at 150℃×60 minutes, a flexible printed wiring substrate (evaluation substrate) with a cured resin layer (cured coating) is produced.

<1-4. Evaluation of surface roughness> The arithmetic average surface roughness Ra of the resin layer (dried coating) in the B-stage state (semi-cured state) formed on the flexible printed wiring substrate as described in <1-2. Formation of resin layer>, or the resin layer on the evaluation substrate after heat curing prepared as described in <1-3. Preparation of evaluation substrate>, was measured. The measured value is the average value of any five points in the observation range of 100×100μm. For the measurement of the arithmetic average surface roughness Ra, a shape measurement laser microscope (VK-X100 manufactured by Keyence Corporation) was used. After starting the shape measurement laser microscope (same as VK-X100) body (control unit) and VK observation application (VK-H1VX manufactured by KEYENCE Co., Ltd.), load the support film with the intermediate layer to be measured on the x-y stage (the surface with the intermediate layer is the upper part). Rotate the lens rotation of the microscope unit (VK-X110 manufactured by KEYENCE Co., Ltd.), select the object lens with a magnification of 10 times, and use the image observation mode of the VK observation application (same as VK-H1VX) to roughly adjust the focus and brightness. Operate the x-y stage and adjust the part to be measured on the sample surface to move to the center of the screen. Replace the 10x object lens with a 100x lens, and use the auto focus function of the image observation mode of the VK observation application (same as VK-H1VX) to focus on the sample surface. Select the simple mode of the shape measurement tab of the VK observation application (same as VK-H1VX), press the measurement start button, measure the surface shape of the sample, and obtain a surface image film. Start the VK analysis application (VK-H1XA manufactured by KEYENCE Co., Ltd.), display the obtained surface image film, and perform tilt correction.

In addition, the observation measurement range (horizontally) in the measurement of the surface shape of the sample is 100μm×100μm. Display the line roughness window, select JIS B 0601-1994 in the parameter setting area, select the horizontal line from the measurement line button, display the horizontal line at any location in the surface image, and press the OK button to obtain the numerical value of the arithmetic average surface roughness Ra. And further display the horizontal line at 4 different locations in the surface image, and obtain the numerical value of each arithmetic average surface roughness Ra. Calculate the average of the 5 values obtained as the arithmetic average surface roughness Ra value of each resin layer surface.

<1-5. Evaluation of resolution> For the resin layer (dried coating) in the B-stage state (semi-cured state) formed on the flexible printed wiring substrate as described in <1-2. Formation of resin layer>, the arithmetic average roughness Ra of each dried coating was measured as described in <1-4. Evaluation of surface roughness>. The dried coatings of each embodiment, comparative example 1-1 and comparative example 1-3 did not reach 0.1μm. The arithmetic average roughness Ra of the dried coating of comparative example 1-2 was 0.1 or more. For each of these dry coatings, firstly, a metal halogen lamp-mounted exposure device (HMW-680-GW20: manufactured by Oak Manufacturing) was used to perform pattern exposure through a negative mask at 300 mJ/ ^cm2 to form openings with diameters of 150 μm and 200 μm. The substrate with the exposed resin layer was heated at 90°C for 30 minutes.

After that, the substrate was immersed in a 1 mass % sodium carbonate aqueous solution at 30°C and developed for 1 minute. The state of pattern formation was observed and the resolution was evaluated. The evaluation criteria are as follows.

◎: The opening pattern of 150μm is well formed. ○: The opening pattern of 200μm is well formed, but the opening pattern of 150μm is slightly poor. ×: Although the unexposed part shows developability, the opening pattern of 200μm is poorly formed (the resolution is insufficient).

<1-6. Evaluation of heat resistance (soldering heat resistance)> For the evaluation substrate prepared as described in <1-3. Preparation of evaluation substrate>, apply rosin-based flux, immerse in a soldering tank pre-set at 260°C for 20 seconds (10 seconds x 2 times), observe the expansion and peeling of the hardened coating, and evaluate the heat resistance (soldering heat resistance). The evaluation criteria are as follows.

◎: No expansion or peeling occurred even after dipping for 10 seconds × 2 times. ○: No expansion or peeling occurred even after dipping for 10 seconds × 1 time, but peeling occurred after dipping for the second time. ×: Swelling or peeling occurred after dipping for 10 seconds × 1 time.

<1-7. Evaluation of gold plating resistance (chemical resistance)> Use the evaluation substrate described in <1-3. Preparation of evaluation substrate> to make the evaluation, and perform the evaluation using the following method.

For evaluation of the substrate, a commercially available electroless nickel plating bath and electroless gold plating bath were used to apply nickel 5μm and gold 0.05μm plating at 80-90°C, and the substrate and hardened coating were observed to evaluate the gold plating resistance (chemical resistance). The evaluation criteria are as follows.

○: No penetration between the substrate and the cured coating. △: Penetration was observed between the substrate and the cured coating. ×: Part of the cured coating peeled off.

<1-8. Flexibility (MIT test)> Each evaluation substrate prepared as described in <1-3. Preparation of evaluation substrate> was used as a test piece, and the MIT folding fatigue tester D type (manufactured by Toyo Seiki Seisaku-sho) was used to perform the MIT test in accordance with JIS P8115 using the film as paper to evaluate the bendability. Specifically, as shown in Figure 1, the test piece 1 was mounted on the device, and under the load state of load F (0.5kgf), the test piece 1 was placed vertically on the clamp 2, and the bending angle α was 135 degrees, and the speed was 175cpm. The number of reciprocating bends (times) was measured until fracture. In addition, the test environment was set at 25°C and the curvature radius was set at R=0.38mm. The evaluation criteria are as follows.

◎: After bending more than 200 times, no cracks occurred in the hardened coating at the bends. ○: After bending 170 to 199 times, no cracks occurred. △: After bending 150 to 169 times, no cracks occurred. ×: Cracks occurred when the number of bends was less than 149 times.

<1-9. Adhesion> For the resin layer in the B stage state (semi-cured state) on each flexible printed wiring substrate on which the resin layer was formed as described in <1-2. Formation of resin layer>, when the arithmetic average roughness Ra of each dried coating was measured as described in <1-4. Evaluation of surface roughness>, the dried coating of each embodiment, comparative example 1-1 and comparative example 1-3 did not reach 0.1 μm. The arithmetic average roughness Ra of the dried coating of comparative example 1-2 was 0.1 or more. For each of these dry coatings, solid exposure was first performed through a negative mask at 300 mJ/ ^cm2 using an exposure device equipped with a metal halogen lamp (HMW-680-GW20: manufactured by Oak Manufacturing). After a PEB step at 90°C for 30 minutes, development (30°C, 0.2 MPa, 1 mass% _{Na2CO3 aqueous} solution) was performed for 60 seconds, and thermal curing was performed at 150°C for 60 minutes to produce a flexible printed wiring board (evaluation board) with a cured coating. The arithmetic average roughness Ra of each dried coating was measured as described in <1-4. Evaluation of surface roughness>. The dried coatings of Examples, Comparative Examples 1-2 and 1-3 were 0.1 μm or more and 1 μm or less. The arithmetic average roughness Ra of the dried coating of Comparative Example 1-1 was less than 0.1.

The obtained evaluation substrates were cut into squares with a side of 2 cm and 10 pieces were stacked. They were then placed at 20, 30, 40, and 60°C for 72 hours to check for adhesion. The evaluation criteria are as follows.

◎: No adhesion at 60℃ ○: No adhesion below 40℃, but slight adhesion at 60℃ △: No adhesion below 30℃, but adhesion above 40℃ ×: No adhesion at any temperature

The details of the ingredients in Table 1 are shown below.

A-1: A polyamide imide resin-containing solution prepared by [Synthesis Example 1] of the above ((A) Synthesis of alkali-soluble polyamide imide resin) A-2: A polyamide imide resin-containing solution prepared by [Synthesis Example 2] of the above ((A) Synthesis of alkali-soluble polyamide imide resin) A-3: A polyamide imide resin-containing solution prepared by [Synthesis Example 3] of the above ((A) Synthesis of alkali-soluble polyamide imide resin) PI-1: Alkali-soluble polyimide resin solution prepared by [Synthesis Example 4] of the above ((E) Synthesis of alkali-soluble polyimide resin) P7-532: Polyurethane acrylate, acid value 47mgKOH/g (manufactured by Kyoei Chemical Co., Ltd.) IRGACURE OXE02: Oxime-based photopolymerization initiator (manufactured by BASF) CAB-553-0.4: Cellulose acetate derivative, number average molecular weight 20,000, 20wt% DPM solution (manufactured by Eastman Chemical Co., Ltd.) (The numbers in Table 1 represent the mass fraction of the solid content of the 20wt% DPM solution) CAB-504-0.2: Cellulose acetate derivative, number average molecular weight 15,000, 20wt% DPM solution (manufactured by Eastman Chemical Co., Ltd.) (The numbers in Table 1 represent the mass fraction of the solid content of the 20wt% DPM solution) JER828: Bisphenol A type epoxy resin, epoxy equivalent 190, mass average molecular weight 380 (Mitsubishi Chemical Co., Ltd.) B-30: Barium sulfate (Sakai Chemical Industry Co., Ltd.)

As shown in Table 1, it can be seen from the comparison between the Examples and the Comparative Examples that the alkali-developable, 2-100 μm thick dry coating formed by the curable resin composition that forms a cured film by exposure and heat treatment has an arithmetic average roughness Ra of less than 0.1 μm, and when the arithmetic average roughness Ra of the cured film after heat curing of the dry coating is 0.1 μm or more and 1 μm or less, the formed resin layer (dry coating) has excellent resolution, and not only the heat resistance, gold plating resistance, and flexibility of the cured coating (cured product) after heat curing are excellent, but also it is confirmed that the bonding after high temperature storage is small.

Furthermore, from the comparison between Examples 1-1, 1-2, 1-4, 1-9 to 1-11 and Examples 1-3, 1-5 to 1-8, and 1-12, it can be seen that when the film thickness of the dry coating is set to 3 μm or more and 80 μm or less, and the arithmetic average roughness Ra of the dry coating is set to less than 0.05 μm, when the ratio of the arithmetic average roughness Ra of the cured film after thermal curing to the arithmetic average roughness Ra of the dry coating (arithmetic average roughness Ra of the cured film after thermal curing/arithmetic average roughness Ra of the dry coating) is 6 or more, the resolution of the formed resin layer (dry coating) is greatly improved, and the adhesion of the cured coating film (cured product) after thermal curing after high temperature storage is further reduced.

[Examples of the second embodiment of the hardening resin composition of the present invention] <2-1. Preparation of hardening resin compositions of Examples 2-1 to 2-8 and Comparative Examples 2-1 to 2-2> According to the composition shown in Table 2 below, the materials of the hardening resin compositions of Examples 2-1 to 2-8 and Comparative Examples 2-1 to 2-2 are added, pre-mixed with a stirrer, and then kneaded with a three-roll mixer to prepare each hardening resin composition to form a resin layer. In addition, the values in Table 2 are the mass percentages of the solid components unless otherwise specified.

For each of the above-mentioned curable resin compositions, a resin layer (dried coating) in the B stage state (semi-cured state) of each curable resin composition was formed as shown below, and the developability (alkali solubility) was evaluated. And as described later, a flexible printed wiring board having the cured product of the resin layer was formed, and the heat resistance (soldering heat resistance), gold plating resistance (chemical resistance), flexibility and adhesion were evaluated. The results are shown in Table 2.

<2-2. Formation of resin layer> A flexible printed wiring substrate with a copper circuit of 18 μm thickness was prepared and pre-treated using CZ-8100 of MEC. Subsequently, the pre-treated flexible printed wiring substrate was coated with each of the curable resin compositions obtained in Examples 2-1 to 2-8 and Comparative Examples 2-1 to 2-2 so that the film thickness after drying was 30 μm. Subsequently, the substrate was dried at 90°C for 30 minutes in a hot air circulation drying oven to form a resin layer (dried coating) in the B stage state (semi-cured state).

<2-3. Evaluation of substrate preparation> For the resin layer (dry coating) in the B stage state (semi-cured state) on each flexible printed wiring substrate on which the resin layer is formed as described above, first use an exposure device equipped with a metal halogen lamp (HMW-680-GW20: manufactured by Oak Manufacturing) to perform pattern exposure at 300mJ/ ^cm2 through a negative mask until an opening with a diameter of 200μm is formed. Thereafter, a PEB step was performed at 90°C for 30 minutes, followed by 60 seconds of development (30°C, 0.2 MPa, ₁ mass% _Na2CO3 aqueous solution), and thermal curing was performed at 150°C for 60 minutes to produce a flexible printed wiring board (evaluation board) having a cured resin layer (cured coating film).

<2-4. Evaluation of Development Property (Alkali Solubility)> For the resin layer (dried coating) in the B-stage state (semi-cured state) formed on the flexible printed wiring substrate as described in <2-2. Formation of Resin Layer>, firstly, an exposure device equipped with a metal halogen lamp (HMW-680-GW20: manufactured by Oak Manufacturing) was used to perform pattern exposure at 300mJ/ ^cm2 through a negative mask to form an opening with a diameter of 200μm. The substrate with the exposed resin layer was heat treated at 90℃ for 30 minutes.

The substrate was then immersed in a 1 mass % sodium carbonate aqueous solution at 30°C and developed for 1 minute. The state of pattern formation was observed and the developability (alkali solubility) was evaluated. The evaluation criteria are as follows.

○: The exposed part shows resistance to development, the unexposed part shows development, and the pattern formation is good. ×: The unexposed part shows development, but the resolution pattern formation is poor (the resolution is insufficient).

<2-5. Evaluation of heat resistance (soldering heat resistance)> For the evaluation substrate prepared as described in <2-3. Preparation of evaluation substrate>, rosin-based flux was applied, and the substrate was immersed in a soldering tank preset at 260°C for 20 seconds (10 seconds × 2 times). The expansion and peeling of the hardened coating film were observed to evaluate the heat resistance (soldering heat resistance). The evaluation criteria are as follows. ◎: No expansion and peeling even after immersion for 10 seconds × 2 times. ○: No expansion and peeling even after immersion for 10 seconds × 1 time, but peeling occurred in the second immersion. ×: Swelling and peeling occurred when immersion was performed for 10 seconds × 1 time.

<2-6. Evaluation of gold plating resistance (chemical resistance)> Use the evaluation substrate prepared as described in <2-3. Preparation of evaluation substrate> and perform the evaluation according to the following method.

For the evaluation substrate, a commercially available electroless nickel plating bath and electroless gold plating bath were used to apply nickel 5μm and gold 0.05μm plating at 80-90°C, and the substrate and hardened coating were observed to evaluate the gold plating resistance (chemical resistance). The evaluation criteria are as follows.

○: There is no penetration between the substrate and the hardened coating. △: Penetration between the substrate and the hardened coating was confirmed. ×: Peeling occurred on part of the hardened coating.

<2-7. Flexibility (MIT test)> Each evaluation substrate prepared as described in <2-3. Preparation of evaluation substrate> was used as a test piece, and the MIT folding fatigue tester D type (manufactured by Toyo Seiki Seisaku-sho) was used to perform the MIT test in accordance with JIS P8115 using the film as paper to evaluate the bendability. Specifically, as shown in Figure 1, the test piece 1 was mounted on the device, and under the load F (0.5kgf), the test piece 1 was placed vertically on the clamp 2, and the bending angle α was 135 degrees. The speed was set at 175cpm and the number of reciprocating bends was measured until fracture. In addition, the test environment was set at 25°C and the curvature radius was set at R=0.38mm. The evaluation criteria are as follows.

◎: After bending more than 200 times, no cracks occurred in the hardened coating at the bends. ○: After bending 170 to 199 times, no cracks occurred. △: After bending 150 to 169 times, no cracks occurred. ×: Cracks occurred when the number of bends was less than 149 times.

<2-8. Adhesion> For the resin layer (dry coating) in the B stage state (semi-cured state) on each flexible printed wiring substrate formed as described in <2-2. Formation of resin layer>, first, a solid exposure at 300mJ/ ^cm2 was performed through a negative mask using an exposure device equipped with a metal halogen lamp (HMW-680-GW20: manufactured by Oak Manufacturing). Thereafter, after a PEB step at 90°C for 30 minutes, development (30°C, 0.2 MPa, 1 mass% _{Na2CO3 aqueous} solution) was performed for 60 seconds, and thermal curing was performed at 150°C for 60 minutes to produce a flexible printed wiring board (evaluation board) having a cured resin layer (cured coating film).

The obtained evaluation substrates were cut into squares with a side of 2 cm and 10 pieces were stacked. They were then placed at 20, 30, 40, and 60°C for 72 hours to check for adhesion. The evaluation criteria are as follows.

◎: No adhesion at 60℃ ○: No adhesion below 40℃, but slight adhesion at 60℃ △: No adhesion below 30℃, but adhesion above 40℃ ×: No adhesion at any temperature

The details of the ingredients in Table 2-1 are shown below.

PI-1: Alkali-soluble polyimide resin solution produced in [Synthesis Example 4] of the above ((E) Synthesis of alkali-soluble polyimide resin) A-3: Polyamide-imide resin-containing solution produced in [Synthesis Example 3] of the above ((A) Synthesis of alkali-soluble polyamide-imide resin) A-1: Polyamide-imide resin-containing solution produced in [Synthesis Example 1] of the above ((A) Synthesis of alkali-soluble polyamide-imide resin) P7-532: Polyurethane acrylate, acid value 47 mgKOH/g (manufactured by Kyoeisha Chemical Co., Ltd.) IRGACURE OXE02: Oxime-based photoalkali generator (manufactured by BASF) CAB-553-0.4: Cellulose acetate derivative, number average molecular weight 20,000, 20wt% DPM solution (manufactured by Eastman Chemical Company) (the numbers in Table 2 represent the mass fraction of the solid content of the 20wt% DPM solution) CAB-504-0.2: Cellulose acetate derivative, number average molecular weight 15,000, 20wt% DPM solution (manufactured by Eastman Chemical Company) (the numbers in Table 2 represent the mass fraction of the solid content of the 20wt% DPM solution) CA-1: CAB-553-0.4 denatured with methyl methacrylate produced in [Synthesis Example 5] of ((D) Synthesis of cellulose derivatives), number average molecular weight 24,000, 20wt% MEK solution (the numbers in Table 2 represent the mass fraction of the solid content of the 20wt% MEK solution) CA-2: CAB-553-0.4 denatured with glycidyl methacrylate produced in [Synthesis Example 6] of ((D) Synthesis of cellulose derivatives), number average molecular weight 25,000, 20wt% MEK solution (the parts in Table 2 represent the mass parts of the solid content of the 20wt% MEK solution) jER828: Bisphenol A type epoxy resin, epoxy equivalent 190, mass average molecular weight 380 (manufactured by Mitsubishi Chemical Corporation)

As shown in Table 2, by comparing the examples with the comparative examples, it can be seen that since the curable resin composition contains (A) alkali-soluble polyamide imide resin, (C) thermosetting compound and (B) photoalkali generator, as well as (D) cellulose derivative, the resin layer formed has good developability, and the cured resin layer has excellent heat resistance, gold plating resistance and flexibility, and it is confirmed that the adhesion is small.

Furthermore, from the comparison between Examples 2-1 to 2-2 and Examples 2-3 to 2-8, it can be seen that when the amount of the (A) alkali-soluble polyamide imide resin added is greater than that of the (E) alkali-soluble polyamide imide resin, the heat resistance can be further improved. Furthermore, from the comparison between Examples 2-3 and Examples 2-7 to 2-8, it can be seen that when the (D) cellulose derivative containing a group represented by formula (6) is used, the adhesion can be further reduced, that is, it can be seen that the adhesion evaluation result is good. Furthermore, from the comparison between Example 2-3 and Example 2-6, it can be seen that the use of polyamide imide resins having the structure represented by formula (1) and the structure represented by formula (2) as (A) alkaline-soluble polyamide imide resin can also improve the softness and adhesion.

[Fig. 1] is a diagram illustrating an MIT test performed using an evaluation substrate produced in the embodiment as a test piece.

Claims (7)

A curable resin composition, characterized by containing (A) an alkali-soluble polyamide-imide resin, (B) a photobase generator, (C) a thermosetting compound, (D) a cellulose derivative, and (E) an alkali-soluble polyamide-imide resin, wherein the number average molecular weight of the cellulose derivative (D) is 5,000 to 500,000, and the amount of the cellulose derivative (D) is not less than 0.5 parts by mass and not more than 20 parts by mass relative to 100 parts by mass of the alkali-soluble polyamide-imide resin (A). The curable resin composition of claim 1, wherein the aforementioned (A) alkali-soluble polyamide imide resin has a carboxyl group. The curable resin composition of claim 2, wherein the aforementioned (A) alkali-soluble polyamide imide resin has a carboxyl group and a phenolic hydroxyl group. The curable resin composition of claim 1, wherein the aforementioned (C) thermosetting compound is an epoxy resin. A laminated structure, wherein at least one side of a resin layer formed by a hardening resin composition as claimed in claim 1 is supported or protected by a film. A hardened material obtained from a hardening resin composition as in claim 1 or a resin layer as in claim 5. An electronic component characterized by having an insulating film formed by a hardened material as described in claim 6.

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