TWI864119B - Reusing method of circuit board substrate - Google Patents

Abstract

The present invention provides a method that when there is curing film on the manufacturing substrate of the circuit board, once there is a part of defect on the curing film, the method can remove only the defective part from the substrate. The method can remove all kinds of curing film from the substrate without limitation to the composition of the photosensitive resin. It is a reuse-method of removing part or all of the curing film on the surface of the substrate from the circuit board so as to reuse the substrate again. The curing film is made of cured photosensitive resin composition and the method includes the following steps: step of using at least one ray of active energy ray to produce reactive oxygen species (ROS) or ray which can break the C-C carbon bond to irradiate parts or entire of the curing film under aerobic environment; and step of washing the circuit board with solvent to remove the curing film being irradiated parts.

Description

Method for recycling wiring board substrate

The present invention relates to a method for recycling a wiring board substrate, and more specifically, to a method for recycling the substrate by removing part or all of a cured film formed on the surface of a wiring board.

In order to protect the conductor circuit or prevent solder from adhering to other places other than where soldering is required, a circuit board is manufactured in which a cured film is formed only on the intended part of the surface of the printed wiring substrate. As a method for forming a cured film, a method in which a photosensitive resin composition is applied to a substrate, and after drying, it is exposed and developed to form a cured film only on the intended part of the substrate surface, or a method in which a film having a photosensitive resin layer of a so-called dry film is attached to a substrate, and a cured film is formed only on the intended part of the substrate surface by exposure and development has become the mainstream.

In addition, during the step of forming a cured film on a substrate, certain defects that may cause a decline in product quality may occur. For example, the following defects may occur: poor printing when applying a photosensitive resin composition called solder mask ink to a substrate, positional deviation during exposure, mottled spots, pinholes in the dried coating, mixing of foreign matter, poor printing of marking ink, etc. Such defects in the step of forming a cured film can be easily removed by a developer before exposure. Moreover, even after exposure and development, as long as it is before the coating is cured by heat treatment, the developed coating can be peeled off with an appropriate solvent, and the photosensitive resin composition can be applied to the substrate again and dried, and then exposed and developed to correct the defects. On the other hand, if the developed coating is heat treated to form a cured film, it is difficult to completely peel the cured film from the substrate using a solvent. The reason is that a cross-linked structure is formed due to the cross-linking reaction of the photocurable components contained in the photosensitive resin composition.

When defects such as those described above occur during the step of forming a cured film, discarding the defective product will waste the substrate and reduce the productivity (yield) of the product. Recently, as circuit wiring boards using high value-added substrates have begun to be manufactured, there is a potential demand to reuse the substrate when a defect occurs.

Therefore, a method of reusing a substrate when a defect occurs in the step of forming a cured film has been proposed. For example, Patent Document 1 proposes that when a defect is found on a coating film after development and exposure (before the coating film is cured by heat treatment), the substrate provided with the coating film is immersed in a stripping liquid made from a specific alkaline aqueous solution, and the coating film is stripped from the substrate to reuse the substrate. However, in this method, when a defect is found on a cured coating film that has been cured after exposure and development, the cured coating film cannot be stripped from the substrate. Therefore, various studies have been conducted on stripping liquids that can reuse the substrate even after the coating film after development is cured. For example, Patent Document 2 proposes a method for peeling a cured coating from a substrate even after the coating is cured after development by using a stripping solution prepared from a mixed solution of an alkali metal hydroxide and an aprotic solvent (e.g., N-methylpyrrolidone).

However, in recent years, there has been a demand for further improvement of cured film properties such as adhesion between the substrate and the cured film, and photosensitive resin compositions that are mixed with thermosetting components such as epoxy resins have begun to be used. As a result, it has become increasingly difficult to peel off the cured film with defects from the substrate. Due to this situation, for example, Patent Document 3 proposes that by mixing a curable component derived from a specific polyester into the photosensitive resin composition, the cured film can also be peeled off from the substrate using an alkaline aqueous solution. [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Publication No. 7-115048 [Patent Document 2] Japanese Patent Publication No. 11-145594 [Patent Document 3] Japanese Patent Publication No. 2015-28646

[The problem that the invention wants to solve]

In the method proposed in the above-mentioned Patent Document 2, since the wiring substrate with the cured film formed thereon is immersed in a stripping liquid to remove the cured film, even if a very small part of the cured film is defective, the entire cured film is stripped off, resulting in material waste. For example, if only the cured film at the defective part can be removed, it can be said that the substrate can be effectively reused.

Furthermore, the method for recycling the substrate proposed in Patent Document 3 focuses on the composition of the photosensitive resin composition and makes it easy to peel off the cured film from the substrate by mixing a specific component. However, it is difficult to change the composition in accordance with the general photosensitive resin composition (such as solder resist containing a thermosetting component) that has come into use in recent years, and there is a situation where the method of Patent Document 3 cannot be applied.

Therefore, the purpose of the present invention is to provide a method for removing only the defective cured film from the substrate when a defect is found in a part of the cured film during the manufacture of a wiring substrate having a cured film on the substrate, and the cured film can be removed from the substrate regardless of the composition of the photosensitive resin composition. [Means for Solving the Problem]

In view of the above problem, the inventors of this case have reached the following conclusion: even a cured film formed by curing after exposure and development can be easily peeled off from a substrate using a general solvent by irradiating the cured film with a predetermined active energy ray in the presence of oxygen. The present invention was completed based on the above conclusion. That is, the gist of the present invention is as follows.

[1] A method for recycling a substrate for a wiring board, which is a method for removing part or all of a cured film from a wiring board having a cured film formed on a surface of the substrate and recycling the substrate, wherein the cured film is made of a cured product of a photosensitive resin composition, and the method comprises the following steps: irradiating part or all of the cured film with at least one of active energy rays capable of generating active oxygen or active energy rays capable of cleaving C-C carbon bonds in the presence of oxygen, and washing the substrate on which the cured film is formed with a solvent and removing the portion of the cured film irradiated by the active energy rays from the substrate. [2] The method as described in [1], wherein the cured film is formed by coating a photosensitive resin composition on the substrate and drying to form a dry coating film, or by coating a photosensitive resin composition on a supporting film and drying to form a resin layer, and the dry film is attached in a manner that the substrate and the resin layer are in contact with each other, and then the dry coating film or the resin layer of the dry film is exposed, developed and patterned. [3] The method as described in [1] or [2], wherein the active energy ray includes ionizing radiation having a wavelength of 100 to 255 nm. [4] The method as described in any one of [1] to [3], further comprising the step of heating the wiring substrate from which the cured film has been removed. [5] The method as described in any one of [1] to [4], wherein the solvent is an aprotic polar solvent. [6] The method as described in any one of [1] to [5], wherein the photosensitive resin composition contains (A) a carboxyl group-containing resin, (B) a photopolymerizable monomer, (C) a photopolymerization initiator, and (D) a thermosetting component. [7] The method as described in any one of [1] to [6], wherein at least one of heating and ultraviolet irradiation is performed after the resin layer is exposed and developed and before the cured film is irradiated with active energy rays. [8] The method as described in any one of [1] to [7], wherein the thickness of the cured film is 1 to 1000 μm. [Effect of the Invention]

According to the present invention, even if a cured film is made of a cured product of a photosensitive resin composition, by irradiating the cured film with at least one of active energy rays capable of generating active oxygen or active energy rays capable of cleaving C-C carbon bonds in the presence of oxygen, the cured film can be removed from the substrate regardless of the composition of the photosensitive resin composition. Furthermore, since the active energy rays can be irradiated only to the defective portion of the cured film, when a defect is found in a part of the cured film during the manufacture of a wiring board, only the defective portion of the cured film can be removed from the substrate.

The method for recycling a substrate for a wiring board of the present invention is a method for removing part or all of a cured film from a wiring board having a cured film formed on the surface of the substrate and recycling the substrate, the method comprising the following steps: (1) irradiating part or all of the cured film with at least one of active energy rays capable of generating active oxygen or active energy rays capable of cleaving C-C carbon bonds in the presence of oxygen, and (2) washing the substrate on which the cured film is formed with a solvent and removing the portion of the cured film irradiated by the active energy rays from the substrate.

In the present invention, a part or all of a cured film obtained by curing a photosensitive resin composition formed on a substrate is irradiated with the specific active energy ray, whereby only the portion of the cured film irradiated with the active energy ray can be easily and simply removed with a solvent. That is, even when the photosensitive resin composition contains a crosslinking component such as a photopolymerizable monomer or a thermosetting component such as an epoxy resin, the C-C carbon bonds of the polymer chain constituting the cured film (polymer of the photosensitive resin composition) can be cleaved by irradiating the cured film of the photosensitive resin composition with active energy rays that can generate active oxygen or active energy rays that can cleave C-C carbon bonds in the presence of oxygen, or the C-C carbon bonds of the polymer chain constituting the cured product can be cleaved by active oxygen generated by irradiation with active energy rays. As a result, a part of the cleaved hydrocarbon radicals bonds with oxygen in the presence of oxygen, becomes carbon dioxide, etc., and vaporizes. In addition, the hydrocarbon radicals may re-bond with each other to generate low molecular weight compounds, and a part of these low molecular weight compounds vaporizes. Furthermore, the molecular weight is reduced when the C-C carbon bond in the polymer chain is cleaved, so the cured film itself will also become brittle. Furthermore, even if the polymer chain has a cross-linked structure in the cured film, it can be soluble in the solvent because the C-C carbon bond in the cross-linked part can be cleaved by irradiation with active energy rays or active oxygen. In the previous technology, the focus was on preparing an easily strippable solvent or preparing a photosensitive composition that can obtain a cured film that is easily stripped with a solvent, but the present invention has discovered a completely new method that is different from all previous technologies. According to the present invention, the cured film can be removed from the substrate regardless of the composition of the photosensitive resin composition, and the active energy ray can be irradiated only to the defective part of the cured film. Therefore, when a defect is found in a part of the cured film during the manufacture of the wiring board, only the defective part of the cured film can be removed from the substrate. The steps of the method for recycling the wiring board substrate of the present invention are described below.

[Wiring board] As described above, the present invention provides a method for removing part or all of a cured film from a wiring board having a cured film formed on a substrate surface and reusing the substrate. That is, a method is provided for removing only the cured film having the defect when a defect is found in a part of the cured film during the manufacturing step of forming the cured film on the wiring board. First, a cured film is formed on a substrate to illustrate the wiring board.

As a step of forming a cured film on a substrate to make a wiring board, a method of forming a cured film by curing the coating after exposure and development of the coating can be applied to a printed circuit board formed with a solder mask, etc., without limitation. The following describes a general method of forming a cured film on a substrate.

First, a photosensitive resin composition is coated on a substrate and dried to form a dry coating film, or a photosensitive resin composition is coated on a supporting film and dried to form a dry film having a resin layer, and the dry film is attached in such a manner that the substrate and the resin layer are in contact with each other. Next, the dry coating film or the resin layer of the dry film is exposed and developed to form a cured film on the substrate. When the cured film is formed using the dry film, it is preferred to peel off the supporting film from the resin layer before or after exposure.

<Substrate> As substrates, in addition to printed circuit boards or flexible printed circuit boards with circuits formed in advance using copper, etc., copper-clad multilayer boards of all grades (FR-4, etc.) using materials such as copper-clad multilayer boards for high-frequency circuits, other wafer substrates, metal substrates, polyimide films, polyethylene terephthalate films, polyethylene naphthalate (PEN) films, glass substrates, ceramic substrates, wafer boards, etc., among which the copper-clad multilayer boards for high-frequency circuits are made of phenolic paper (paper phenol), paper epoxy, glass cloth epoxy, glass polyimide, glass cloth/stainless steel epoxy, glass cloth/paper epoxy, synthetic fiber epoxy, fluororesin/polyethylene/polyphenylene oxide, polyphenylene oxide/cyanate, etc. Among them, copper clad laminate is particularly preferred.

Furthermore, when using a copper-clad laminate or the like as a substrate, in order to improve the adhesion between the substrate and the cured film, it is preferred to grind the surface of the copper foil. As grinding, physical grinding such as polishing, frosting, and brushing, chemical grinding such as CZ8101, etc. can be listed. In addition, the arithmetic average surface roughness (Ra) of the copper foil surface after grinding is preferably 50 to 1000nm. According to the method of the present invention, even such a cured film that increases the adhesion of the substrate can be easily removed by a solvent.

<Photosensitive resin composition> The photosensitive resin composition is patterned by exposure and development to form a cured film on a substrate. As such a photosensitive resin composition, for example, conventionally known solder mask inks can be used without limitation. The following is an example of a photosensitive resin composition that is suitable for use in the present invention.

In the present invention, a photosensitive resin composition comprising (A) a carboxyl group-containing resin, (B) a photopolymerizable monomer, (C) a photopolymerization initiator, and (D) a thermosetting component is preferably used.

As the (A) carboxyl-containing resin, various photosensitive resins known in the past having a carboxyl group in the molecule can be used. By making the photosensitive resin composition include the (A) carboxyl-containing resin, the photosensitive resin composition can be given alkaline development property. In particular, a carboxyl-containing photosensitive resin having a (meth)acryl group in the molecule is better in terms of photocurability and development resistance. The (meth)acryl group is preferably derived from acrylic acid or methacrylic acid or a derivative thereof. As specific examples of the (A) carboxyl-containing resin, the following compounds (which may be either an oligomer or a polymer) can be listed. In addition, in this specification, the (meth)acryl group is a general term for acryl group, methacryl group and a mixture thereof, and other similar expressions are the same.

(1) Carboxyl-containing resins obtained by copolymerization of unsaturated carboxylic acids such as (meth)acrylic acid with unsaturated group-containing compounds such as styrene, α-methylstyrene, lower (meth)acrylic acid alkyl esters, isobutylene, etc.

(2) Carboxyl-containing urethane resins obtained by addition polymerization of diisocyanates such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates, aromatic diisocyanates, and diol compounds containing carboxyl groups such as dihydroxymethylpropionic acid and dihydroxymethylbutyric acid, and diol compounds such as polycarbonate polyols, polyether polyols, polyester polyols, polyolefin polyols, acrylic polyols, bisphenol A-based epoxide adduct diols, and compounds having phenolic hydroxyl groups and alcoholic hydroxyl groups.

(3) A carboxyl-containing photosensitive urethane resin obtained by the addition polymerization reaction of a diisocyanate with a (meth)acrylate of a bifunctional epoxy resin such as bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, bixylenol epoxy resin, diphenol epoxy resin or a partially anhydride-modified product thereof, a carboxyl-containing diol compound and a diol compound.

(4) A carboxyl-containing photosensitive urethane resin is prepared by adding a compound having one hydroxyl group and one or more (meth)acryl groups in the molecule, such as a hydroxyalkyl (meth)acrylate, to the synthesis of the resin of (2) or (3) to perform terminal (meth)acrylation.

(5) A carboxyl-containing photosensitive urethane resin is prepared by adding an equimolar reaction product of isophorone diisocyanate and pentaerythritol triacrylate or the like, wherein the compound has one isocyanate group and one or more (meth)acryl groups in the molecule, to the synthesis of the resin of (2) or (3), thereby subjecting the terminal of the compound to (meth)acrylation.

(6) A carboxyl-containing photosensitive resin is prepared by reacting (meth)acrylic acid with a difunctional or higher polyfunctional (solid) epoxy resin to add a diprotic anhydride to the hydroxyl group present in the side chain.

(7) A polyfunctional epoxy resin obtained by epoxidizing the hydroxyl group of a bifunctional (solid) epoxy resin with epichlorohydrin is reacted with (meth)acrylic acid to add a diprotic anhydride to the generated hydroxyl group to produce a carboxyl-containing photosensitive resin.

(8) A dicarboxylic acid such as adipic acid, phthalic acid, or hexahydrophthalic acid is reacted with a bifunctional cyclohexane resin to add a diprotic anhydride such as phthalic anhydride, tetrahydrophthalic anhydride, or hexahydrophthalic anhydride to the resulting primary hydroxyl group to produce a carboxyl-containing polyester resin.

(9) A carboxyl-containing photosensitive resin obtained by reacting an epoxide having a plurality of epoxy groups in one molecule with a compound having at least one alcoholic hydroxyl group and one phenolic hydroxyl group in one molecule such as p-hydroxyphenethyl alcohol and an unsaturated group-containing monocarboxylic acid such as (meth)acrylic acid, and reacting the alcoholic hydroxyl group of the reaction product with a polyacid anhydride such as maleic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, adipic acid, etc.

(10) A carboxyl group-containing photosensitive resin obtained by reacting a reaction product obtained by reacting a compound having a plurality of phenolic hydroxyl groups in one molecule with an alkylene oxide such as ethylene oxide or propylene oxide, reacting the reaction product with an unsaturated group-containing monocarboxylic acid, and reacting a polyacid anhydride with the reaction product.

(11) A carboxyl group-containing photosensitive resin obtained by reacting a compound having a plurality of phenolic hydroxyl groups in one molecule with a cyclic carbonate compound such as ethyl carbonate or propylene carbonate, reacting the reaction product with an unsaturated group-containing monocarboxylic acid, and reacting a polyacid anhydride with the reaction product.

(12) A carboxyl-containing photosensitive resin obtained by further adding a compound having one epoxy group and one or more (meth)acryl groups in one molecule to the resins of (1) to (11).

The carboxyl group-containing resin (A) that can be used in the present invention is not limited to the above-mentioned ones. In addition, the carboxyl group-containing resin (A) listed above can be used alone or in combination of two or more.

The weight average molecular weight of the carboxyl group-containing resin (A) varies depending on the resin skeleton, but is generally in the range of 2,000 to 150,000, preferably in the range of 5,000 to 100,000. By using a carboxyl group-containing resin (A) with a weight average molecular weight of 2,000 or more, the resolution and non-tackiness performance can be improved. In addition, by using a carboxyl group-containing resin (A) with a weight average molecular weight of 150,000 or less, the developing property and storage stability can be improved.

The amount of the carboxyl-containing resin (A) blended is preferably 50 to 90 parts by mass, based on the total amount of the carboxyl-containing resin (A) and the thermosetting component (D) being 100 parts by mass, in terms of solid content. By making the amount of the carboxyl-containing resin (A) blended within the above range, the surface of the coating film changes appropriately over time, and the adhesion to the substrate can be further improved. According to the method of the present invention, even such a cured film with increased adhesion on the substrate can be easily removed by a solvent.

The (B) photopolymerizable monomer contained in the photosensitive resin composition is a monomer having an ethylenically unsaturated double bond. Examples of the (B) photopolymerizable monomer include conventionally used polyester (meth)acrylates, polyether (meth)acrylates, urethane (meth)acrylates, carbonate (meth)acrylates, and epoxy (meth)acrylates. Specifically, alkyl acrylates appropriately selected from 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, etc.; diacrylates of glycols such as ethylene glycol, methoxytetraethylene glycol, polyethylene glycol, propylene glycol, etc.; acrylamides such as N,N-dimethylacrylamide, N-hydroxymethylacrylamide, N,N-dimethylaminopropylacrylamide, etc.; alkyl acrylates such as N,N-dimethylaminoethyl acrylate, N,N-dimethylaminopropyl acrylate, etc.; polyols such as hexylene glycol, trihydroxymethylpropane, pentaerythritol, dipentaerythritol, triisocyanatothiocyanate, etc., or ethylene oxide adducts, propylene oxide adducts, or ε-caprolactone adducts thereof can be used. Acrylates; polyacrylates such as phenoxyacrylate, bisphenol A diacrylate, and ethylene oxide adducts or propylene oxide adducts of such phenols; polyacrylates such as glycidyl ethers such as glyceryl diglycidyl ether, glyceryl triglycidyl ether, trihydroxymethylpropane triglycidyl ether, and triisocyanuric acid triglycidyl ether; not limited to the above, there are also acrylates and melamine acrylates made by directly acrylated polyols such as polyether polyols, polycarbonate diols, hydroxyl-terminated polybutadiene, polyester polyols, etc., or urethane acrylated through diisocyanates, and methacrylates corresponding to the above acrylates. Such (B) photopolymerizable monomers can also be used as reactive diluents.

The following compounds can also be used as (B) photopolymerizable monomers: epoxy acrylate resins obtained by reacting acrylic acid with a multifunctional epoxy resin such as a cresol novolac epoxy resin, and epoxy urethane acrylate compounds obtained by reacting a hydroxy acrylate such as pentaerythritol triacrylate with a half urethane compound of a diisocyanate such as isophorone diisocyanate with respect to the hydroxyl group of the epoxy acrylate resin. Such epoxy acrylate compounds do not reduce the touch drying property but can improve the photocurability.

The amount of the photopolymerizable monomer (B) blended is preferably 10 to 50 parts by mass, more preferably 15 to 45 parts by mass, relative to 100 parts by mass of the carboxyl group-containing resin (A) in terms of solid content. When the amount of the photopolymerizable monomer (B) blended is 10 parts by mass or more, the photocurability of the photosensitive resin composition is improved. When the amount of the photopolymerizable monomer (B) blended is 50 parts by mass or less, the resolution of the cured film can be improved.

In particular, when a carboxyl-containing non-photosensitive resin having no ethylenically unsaturated double bonds is used, (B) a photopolymerizable monomer must be used in combination in order to make the composition photocurable. Therefore, (B) a photopolymerizable monomer is effective.

The (C) photopolymerization initiator included in the photosensitive resin composition is used to make the above-mentioned (A) carboxyl group-containing resin and (B) photopolymerizable monomer react by exposure. As the (C) photopolymerization initiator, any known one can be used. The (C) photopolymerization initiator can be used alone or in combination of two or more.

Specific examples of the photopolymerization initiator (C) include bis-(2,6-dichlorobenzyl)phenylphosphine oxide, bis-(2,6-dichlorobenzyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichlorobenzyl)-4-propylphenylphosphine oxide, bis-(2,6-dichlorobenzyl)-1-naphthylphosphine oxide, bis-(2,6-dimethoxybenzyl)phenylphosphine oxide, bis-(2,6-dichlorobenzyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichlorobenzyl)-4-propylphenylphosphine oxide, bis-(2,6-dichlorobenzyl)-1-naphthylphosphine oxide, bis-(2,6-dimethoxybenzyl)phenylphosphine oxide, Bisacylphosphine oxides such as (2,6-dimethoxybenzyl)-2,4,4-trimethylpentylphosphine, bis-(2,6-dimethoxybenzyl)-2,5-dimethylphenylphosphine oxide, bis-(2,4,6-trimethylbenzyl)-phenylphosphine oxide; 2,6-dimethoxybenzyldiphenylphosphine oxide, 2,6-dichlorobenzyldiphenylphosphine oxide, 2,4,6-trimethylbenzylphenylphosphonic acid methyl esters, 2-methylbenzyldiphenylphosphine oxide, trimethylacetylphenylphosphine isopropyl ester, 2,4,6-trimethylbenzyldiphenylphosphine oxide, etc.; phenyl (2,4,6-trimethylbenzyl)phosphine ethyl ester, 1-hydroxy-cyclohexylphenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, 2-hydroxy-1-{4-[ Hydroxyacetophenones such as 4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl]-2-methyl-propane-1-one and 2-hydroxy-2-methyl-1-phenylpropane-1-one; benzoins such as benzoin, benzyl, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl ether, benzoin n-butyl ether; benzoin alkyl ethers; benzophenone, p-methylbenzophenone, Michler's ketone Benzophenones such as methyl benzophenone, 4,4'-dichlorobenzophenone, 4,4'-bis(diethylamino)benzophenone, acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinyl-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinyl)- Acetophenones such as 2-(4-(4-phenyl)-butanone, 2-(dimethylamino)-2-[(4-methylphenyl)methyl)-1-[4-(4-linolyl)phenyl]-1-butanone and N,N-dimethylaminoacetophenone; thiothione such as 2-ethylthiothione, 2-isopropylthiothione, 2,4-dimethylthiothione, 2,4-diethylthiothione, 2-chlorothiothione, 2,4-diisopropylthiothione; anthraquinone, chloroanthraquinone, 2-methylanthraquinone and 2-ethylanthraquinone anthraquinones such as 2-tert-butylanthraquinone, 1-chloroanthraquinone, 2-amylanthraquinone, and 2-aminoanthraquinone; ketones such as acetophenone dimethyl ketal and benzyl dimethyl ketal; benzoic acid esters such as ethyl 4-dimethylamino benzoate, 2-(dimethylamino)ethyl benzoate, and ethyl p-dimethylbenzoate; 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyl oxime)], ethyl ketone, 1-[9-ethyl-6-(2-methylbenzoyl)-9-[(2-methylbenzoyl)-1-methylamino)-1-methylbenzoyl]- Oxime esters such as bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl)titanium, bis(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(1-pyridin-1-yl)ethyl)phenyl]titanium, etc.; 2-nitrofluorene phenyl disulfide, butyroin, anisyloin ether, azobisisobutyronitrile, tetramethylthiuram disulfide, etc.

Commercially available products of α-aminoacetophenone-based photopolymerization initiators include Omnirad 907, 369, 369E, and 379 manufactured by IGM Resins. Commercially available products of oxyacylphosphine-based photopolymerization initiators include Omnirad TPO H and 819 manufactured by IGM Resins. Commercially available products of oxime ester-based photopolymerization initiators include Irgacure OXE01 and OXE02 manufactured by BASF JAPAN Co., Ltd., N-1919 manufactured by ADEKA Corporation, ADEKA ARKLS NCI-831 and NCI-831E, and TR-PBG-304 manufactured by Changzhou Qiangli Electronic New Materials Co., Ltd.

In addition, carbazole oxime ester compounds described in Japanese Patent Application Publication Nos. 2004-359639, 2005-097141, 2005-220097, 2006-160634, 2008-094770, 2008-509967, 2009-040762, and 2011-80036 can be cited.

The amount of the photopolymerization initiator (C) is preferably 1 to 20 parts by mass relative to 100 parts by mass of the carboxyl group-containing resin (A) in terms of solid content. When the amount is 1 part by mass or more, the photocurability of the photosensitive resin composition becomes good, and the film properties such as chemical resistance also become good. When the amount is 20 parts by mass or less, the effect of reducing outgassing can be obtained, and the light absorption of the surface of the cured film becomes good, and the deep curing property is not easily reduced. It is more preferably 2 to 15 parts by mass.

Furthermore, in the present invention, a photoinitiator or sensitizer may be used in combination with (C) a photopolymerization initiator. Examples of photoinitiators or sensitizers include benzoin compounds, anthraquinone compounds, thioxanthone compounds, ketal compounds, benzophenone compounds, tertiary amine compounds, and oxythionone compounds. Particularly preferred are thioxanthone compounds such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, and 4-isopropylthioxanthone. By including thioxanthone compounds, deep curing properties can be improved. These compounds may also be used as (C) a photopolymerization initiator, but are preferably used in combination with (C) a photopolymerization initiator. Furthermore, the photoinitiator or sensitizer may be used alone or in combination of two or more.

The (C) photopolymerization initiators, photoinitiator aids and sensitizers absorb specific wavelengths, and therefore may reduce the sensitivity depending on the situation, and function as ultraviolet absorbers. However, these components are not only used to increase the sensitivity of the photosensitive resin composition. They can absorb light of specific wavelengths as needed to increase the light reactivity of the surface, making the line shape and opening of the photoresist pattern vertical, conical, or inverted conical, while improving the accuracy of the line width and opening diameter.

The photosensitive resin composition preferably contains (D) a thermosetting component. By containing (D) a thermosetting component, the barrier properties (e.g., etching resistance, etc.) of the cured film in the subsequent step are improved, and at the same time, the resolution and the peeling property can be combined in a high-dimensional manner. As the (D) thermosetting component, any known one can be used. For example, known compounds such as melamine resin, benzoguanidine resin, melamine derivative, benzoguanidine derivative, etc., amino resin, isocyanate compound, blocked isocyanate compound, cyclocarbonate compound, epoxide, oxycyclobutane compound, episulfide resin, dimaleimide, carbodiimide resin, etc. can be used. Particularly preferably, a compound having a plurality of cyclic ether groups or cyclic thioether groups (hereinafter referred to as cyclic (thio)ether groups) in the molecule can be used. These thermosetting components can be used alone or in combination of two or more.

The above-mentioned compound having multiple cyclic (thio) ether groups in the molecule is a compound having multiple 3-, 4- or 5-membered cyclic (thio) ether groups in the molecule, for example: a compound having multiple epoxide groups in the molecule, i.e., a polyfunctional epoxide; a compound having multiple oxycyclobutane groups in the molecule, i.e., a polyfunctional oxycyclobutane compound; a compound having multiple sulfide groups in the molecule, i.e., a cyclosulfide resin, etc.

Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, hydrogenated bisphenol A type epoxy resins, brominated bisphenol A type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A novolac type epoxy resins, biphenyl type epoxy resins, naphthalene type epoxy resins, dicyclopentadiene type epoxy resins, and triphenylmethane type epoxy resins.

Examples of commercially available epoxy resins include JER 828, 806, 807, YX8000, YX8034, and 834 manufactured by Mitsubishi Chemical Co., Ltd.; YD-128, YDF-170, ZX-1059, and ST-3000 manufactured by NIPPON STEEL Chemical & Material Co., Ltd.; EPICLON 830, 835, 840, 850, N-730A, and N-695 manufactured by DIC Corporation; and RE-306 manufactured by Nippon Kayaku Co., Ltd.

Examples of the polyfunctional cyclohexane compound include bis[(3-methyl-3-cyclohexanebutane methoxy)methyl]ether, bis[(3-ethyl-3-cyclohexanebutane methoxy)methyl]ether, 1,4-bis[(3-methyl-3-cyclohexanebutane methoxy)methyl]benzene, 1,4-bis[(3-ethyl-3-cyclohexanebutane methoxy)methyl]benzene, (3-methyl-3-cyclohexanebutane)methyl acrylate, (3-ethyl-3-cyclohexanebutane)methyl acrylate, methacrylate, Examples of polyfunctional cyclohexanes include (3-methyl-3-cyclohexanyl)methyl ester, (3-ethyl-3-cyclohexanyl)methyl methacrylate, and oligomers or copolymers thereof. Examples of polyfunctional cyclohexanes include cyclohexanol and novolac resins, poly(p-hydroxystyrene), cardo-type bisphenols, calixarene, calixresorcinarene, or ethers of resins having hydroxyl groups such as silsesquioxane. Examples of polyfunctional cyclohexanes include copolymers of unsaturated monomers having cyclohexanol rings and (meth)acrylic acid alkyl esters.

Examples of compounds having a plurality of cyclic sulfide groups in the molecule include bisphenol A type cyclic sulfide resins, etc. In addition, cyclic sulfide resins obtained by replacing the oxygen atom of the epoxide group of a novolac type epoxy resin with a sulfur atom by the same synthesis method can also be used.

Examples of the amino resins such as melamine derivatives and benzoguanidine derivatives include hydroxymethylmelamine compounds, hydroxymethylbenzoguanidine compounds, hydroxymethylacetylene urea compounds, and hydroxymethylurea compounds.

A polyisocyanate compound may also be blended as the isocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as 4,4'-diphenylmethane diisocyanate, 2,4-methylenediisocyanate, 2,6-methylenediisocyanate, naphthalene-1,5-diisocyanate, o-isocyanate, m-isocyanate, and 2,4-methylenediisocyanate dimer; tetramethylene diisocyanate, hexamethylene diisocyanate; aliphatic polyisocyanates such as diisocyanate, methylene diisocyanate, trimethylhexamethylene diisocyanate, 4,4-methylenebis(cycloisocyanate hexyl) and isophorone diisocyanate; alicyclic polyisocyanates such as dicycloheptane triisocyanate; and adducts, biuret forms and trimer forms of the isocyanate compounds listed above.

As the blocked isocyanate compound, an addition reaction product of an isocyanate compound and an isocyanate blocking agent can be used. As the isocyanate compound that can react with the isocyanate blocking agent, for example, the above-mentioned polyisocyanate compound can be mentioned. As the isocyanate blocking agent, for example, phenol-based blocking agents; lactam-based blocking agents; active methylene-based blocking agents; alcohol-based blocking agents; oxime-based blocking agents; thiol-based blocking agents; acid amide-based blocking agents; imide-based blocking agents; amine-based blocking agents; imidazole-based blocking agents; imine-based blocking agents, etc. can be mentioned.

The amount of the thermosetting component (D) blended is preferably 0.8 to 2.5 mol, more preferably 1.0 to 2.0 mol, of the functional groups of the thermosetting component (D) reacted per 1.0 mol of the carboxyl group contained in the carboxyl group-containing resin (A).

In particular, when an epoxy resin is used as the (D) thermosetting component, the epoxy group of the epoxy resin is preferably 1.0 to 2.0 mol per 1.0 mol of the carboxyl group of the (A) carboxyl group-containing resin. By making it 1 mol or more, it is possible to prevent the carboxyl group from remaining in the cured film, and to obtain good heat resistance, alkali resistance, and electrical insulation. In addition, by making the above-mentioned blending amount 2 mol or less, it is possible to prevent low molecular weight cyclic (thio) ether groups from remaining in the dried coating, and to ensure good strength of the cured film.

The photosensitive resin composition may also contain (E) a heat curing catalyst to promote the curing of the above-mentioned (D) thermosetting component. Examples of the (E) heat curing catalyst include imidazole derivatives such as imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole, amine compounds such as cyanamide, benzyldimethylamine, 4-(dimethylamino)-N,N-dimethylbenzylamine, 4-methoxy-N,N-dimethylbenzylamine, 4-methyl-N,N-dimethylbenzylamine, hydrazide compounds such as dihydrazide adipic acid and dihydrazide sebacic acid, and phosphorus compounds such as triphenylphosphine. In addition, commercially available products include, for example, 2MZ-A, 2MZ-OK, 2PHZ, 2P4BHZ, 2P4MHZ (all trade names of imidazole compounds) manufactured by Shikoku Chemical Industries, Ltd., U-CAT 3513N (trade name of dimethylamine compound), DBU, DBN, U-CAT SA 102 (all bicyclic amidine compounds and salts thereof) manufactured by San-Apro Ltd., and the like.

The compounds are not limited to the above compounds, and any compound can be used as long as it serves as a heat curing catalyst for the epoxy resin or the cyclohexane compound (E), or promotes the reaction between at least one of the epoxy group and the cyclohexane group and the carboxyl group. It can be used alone or in combination of two or more. In addition, S-tria derivatives such as guanidine, ethylguanidine, benzoguanidine, melamine, 2,4-diamino-6-methacryloxyethyl-S-tria, 2-ethylene-2,4-diamino-S-tria, 2-ethylene-4,6-diamino-S-tria, isocyanuric acid adduct, and 2,4-diamino-6-methacryloxyethyl-S-tria, can also be used. It is preferred to use these compounds that also function as adhesion-imparting agents in combination with the (E) heat-curing catalyst.

The above-mentioned (E) heat-curing catalyst may be used alone or in combination of two or more. From the viewpoint of the storage stability of the photosensitive resin composition and the heat resistance of the cured film, the blending amount of the (E) heat-curing catalyst is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 1 part by mass, based on solid content conversion, relative to 100 parts by mass of the (A) carboxyl group-containing resin.

In order to improve the physical strength of the cured film, fillers may be mixed into the photosensitive resin composition as required. As fillers, known inorganic or organic fillers may be used, and barium sulfate, spherical silica, hydrotalcite and talc are particularly preferred. In addition, in order to obtain flame retardancy, metal oxides or metal hydroxides such as aluminum hydroxide may be used as physical pigment fillers.

Among the above-mentioned fillers, spherical silica is preferably used. As the spherical silica, it is preferred to use spherical silica with an average particle size of 1 nm to 100 nm, and the average particle size is more preferably 2 nm to 50 nm. By blending spherical silica having the above-mentioned average particle size, the surface conditions Ra1 and Ra2 of the above-mentioned cured film can also be adjusted. In addition, the average particle size is not only the particle size of the primary particles, but also the average particle size (D50) including the particle size of the secondary particles (agglomerates), which is the D50 value measured by the laser diffraction method. The average particle size can be obtained by using a measuring device (for example, Microtrac MT3300EXII manufactured by MicrotracBEL Corp.) using the laser diffraction method.

In order to improve the dispersibility in the photosensitive resin composition, the filler may be surface treated. By using the surface treated filler, aggregation can be suppressed. The surface treatment method is not particularly limited, and any conventional method may be used. However, it is preferred to treat the surface of the inorganic filler with a surface treatment agent having a curable reactive group, such as a coupling agent having a curable reactive group as an organic group.

As the coupling agent, silane-based, titanium-based, aluminum-based, and aluminum-zirconia-based coupling agents can be used. Among them, silane-based coupling agents are preferred. Examples of the silane coupling agent include vinyl trimethoxysilane, vinyl triethoxysilane, N-(2-aminomethyl)-3-aminopropyl methyl dimethoxysilane, N-(2-aminoethyl)-3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, 3-anilinopropyl trimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl methyl dimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, 3-methacryloyloxypropyl trimethoxysilane, 3-butylenepropyl trimethoxysilane, etc., which can be used alone or in combination. The silane coupling agents are preferably pre-adsorbed on the surface of the filler or immobilized on the surface of the filler by reaction. Here, the treatment amount of the coupling agent is preferably 0.5 to 10 parts by weight relative to 100 parts by weight of the spherical silica.

The photosensitive resin composition may also contain a colorant as required. As the colorant, known colorants such as red, blue, green, and yellow may be used, and any of pigments, dyes, and pigments may also be used. However, from the perspective of reducing environmental burden and having less impact on the human body, a halogen-free colorant is preferred.

Red colorants include monoazo, disazo, azochromatin, benzimidazolone, perylene, diketopyrrolopyrrole, condensed azo, anthraquinone, quinacridone, etc. Specifically, the following are listed with color index (C.I.; issued by The Society of Dyers and Colourists) numbers.

Examples of monoazo red colorants include Pigment Red 1, 2, 3, 4, 5, 6, 8, 9, 12, 14, 15, 16, 17, 21, 22, 23, 31, 32, 112, 114, 146, 147, 151, 170, 184, 187, 188, 193, 210, 245, 253, 258, 266, 267, 268, 269, etc. Examples of disazo red colorants include Pigment Red 37, 38, 41, etc. Examples of monoazo red coloring agents include Pigment Red 48:1, 48:2, 48:3, 48:4, 49:1, 49:2, 50:1, 52:1, 52:2, 53:1, 53:2, 57:1, 58:4, 63:1, 63:2, 64:1, 68, etc. Examples of benzimidazolone red coloring agents include Pigment Red 171, 175, 176, 185, 208, etc. Examples of perylene red coloring agents include Solvent Red 135, 179, Pigment Red 123, 149, 166, 178, 179, 190, 194, 224, etc. Examples of diketopyrrolopyrrole red coloring agents include Pigment Red 254, 255, 264, 270, and 272. Examples of condensed azo red coloring agents include Pigment Red 220, 144, 166, 214, 220, 221, and 242. Examples of anthraquinone red coloring agents include Pigment Red 168, 177, 216, Solvent Red 149, 150, 52, and 207. Examples of quinacridone red coloring agents include Pigment Red 122, 202, 206, 207, and 209.

Blue colorants include phthalocyanine and anthraquinone. Pigment systems include compounds classified as pigments, such as Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, and 60. As dye systems, Solvent Blue 35, 63, 68, 70, 83, 87, 94, 97, 122, 136, 67, and 70 can be used. In addition to the above, metal-substituted or unsubstituted phthalocyanine compounds can also be used.

Examples of yellow colorants include monoazo, disazo, condensed azo, benzimidazolone, isoindolinone, and anthraquinone. For example, anthraquinone yellow colorants include Solvent Yellow 163, Pigment Yellow 24, 108, 193, 147, 199, and 202. Examples of isoindolinone yellow colorants include Pigment Yellow 110, 109, 139, 179, and 185. Examples of condensed azo yellow colorants include Pigment Yellow 93, 94, 95, 128, 155, 166, and 180. Examples of benzimidazolone yellow coloring agents include Pigment Yellow 120, 151, 154, 156, 175, and 181. Examples of monoazo yellow coloring agents include Pigment Yellow 1, 2, 3, 4, 5, 6, 9, 10, 12, 61, 62, 62:1, 65, 73, 74, 75, 97, 100, 104, 105, 111, 116, 167, 168, 169, 182, and 183. Moreover, as the disazo yellow coloring agent, there are Pigment Yellow 12, 13, 14, 16, 17, 55, 63, 81, 83, 87, 126, 127, 152, 170, 172, 174, 176, 188, 198, and the like.

In addition, colorants such as purple, orange, brown, black, and white may also be added. Specifically, the colorants include Pigment Black 1, 6, 7, 8, 9, 10, 11, 12, 13, 18, 20, 25, 26, 28, 29, 30, 31, 32, Pigment Violet 19, 23, 29, 32, 36, 38, 42, Solvent Violet 13, 36, C.I. Pigment Orange 1, 5, 13, 14, 16, 17, 24, 34, 36, 38, 40, 43, 46, 49, 51, 61, 63, 64, 71, 73, Pigment Brown 23, 25, carbon black, and titanium oxide.

The amount of the colorant blended in the photosensitive resin composition is not particularly limited, but is preferably 0.1 to 5 mass % of the total amount of the photosensitive resin composition.

The photosensitive resin composition of the present invention may also contain an organic solvent from the viewpoint of ease of preparation and coating properties. As the organic solvent, ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; glycol ethers such as thiourea, methylthiourea, butylthiourea, carbitol, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, diethylene glycol monomethyl ether acetate, and tripropylene glycol monomethyl ether; esters such as ethyl acetate, butyl acetate, butyl lactate, thiourea acetate, butylthiourea acetate, carbitol acetate, butyl carbitol acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and propylene carbonate; aliphatic hydrocarbons such as octane and decane; petroleum-based solvents such as petroleum ether, petroleum naphtha, and solvent naphtha, and the like, which are known and commonly used organic solvents. These organic solvents may be used alone or in combination of two or more.

The amount of the organic solvent blended in the photosensitive resin composition can be appropriately changed according to the components constituting the photosensitive resin composition. For example, in terms of solid content, it can be set to 30 to 300 parts by mass relative to 100 parts by mass of the carboxyl group-containing resin (A).

The photosensitive resin composition of the present invention may further be blended with elastomers, silane compounds, urethane catalysts, catalytic agents, adhesion promoters, block copolymers, chain transfer agents, polymerization inhibitors, copper inhibitors, antioxidants, rust inhibitors, organic bentonite, microcrystalline kaolinite and other viscosity enhancers, polysilicone-based, fluorine-based, polymer-based defoamers and leveling agents, and flame retardants such as phosphonates, phosphate derivatives, phosphorus compounds such as nitrogen-phosphorus compounds, etc. as needed. These components may be those known in the field of electronic materials.

The photosensitive resin composition of the present invention can be used in a dry film state or in a liquid state. When used in a liquid state, it can be a single liquid or a two-liquid or more liquid state.

<Dry film> In the present invention, the photosensitive resin composition may be formed into a dry film having a supporting film and a resin layer made of the photosensitive resin composition formed on the supporting film. Here, the supporting film in the present invention means at least the supporting film that is in contact with the resin layer side of the dry film when laminated on the substrate. The supporting film may also be peeled off from the curable resin layer in a step after lamination. When the dry film is formed, the photosensitive resin composition of the present invention can be diluted with an organic solvent to adjust the viscosity to a suitable level, and then coated on a support film to a uniform thickness using a notch wheel coating device, a doctor blade coating device, a lip coater, a rod coater, a squeeze coater, a reverse coater, a transfer roll coating device, a gravure coater, a spray coating device, etc., and then dried at a temperature of 50 to 130° C. for 1 to 30 minutes to obtain a thin film. There is no particular restriction on the coating film thickness. Generally speaking, the film thickness after drying is appropriately selected within the range of 1 to 150 μm, preferably 10 to 60 μm.

The supporting film is not particularly limited, and known ones can be used. For example, films made of thermoplastic resins such as polyester films such as polyethylene terephthalate and polyethylene naphthalate, polyimide films, polyamide-imide films, polypropylene films, and polystyrene films are suitable. Among these, polyester films are preferred from the viewpoints of heat resistance, mechanical strength, and handling properties. In addition, laminates of these films can also be used as supporting films.

From the viewpoint of improving mechanical strength, the thermoplastic resin film is preferably a film stretched in a uniaxial direction or a biaxial direction.

The thickness of the supporting film is not particularly limited, and may be, for example, 10 μm to 150 μm.

After forming the resin layer of the photosensitive resin composition of the present invention on the support film, a peelable protective (covering) film is preferably deposited on the surface of the resin layer for the purpose of preventing dust and the like from adhering to the surface of the resin layer. Here, the protective film in the present invention means that when being deposited on the substrate in contact with the resin layer side of the dry film and integrally formed, it is peeled off from the resin layer before deposition. As the peelable protective film, for example, polyethylene film, polytetrafluoroethylene film, polypropylene film, surface-treated paper, etc. can be used, as long as the adhesion between the resin layer and the protective film is smaller than the adhesion between the resin layer and the supporting film when the protective film is peeled off.

The thickness of the protective film is not particularly limited, and may be, for example, 10 μm to 150 μm.

The above-mentioned photosensitive resin composition is adjusted to a viscosity suitable for the coating method using the above-mentioned organic solvent, and after being coated on a substrate by a method such as dip coating, shower coating, roll coating, rod coating, screen printing, curtain coating, etc., the organic solvent contained in the composition is volatilized and dried (temporarily dried) at a temperature of 60 to 100° C., thereby forming a non-sticky resin layer. In addition, when the photosensitive resin composition contains an organic solvent, it is preferably volatilized and dried after coating the photosensitive resin composition. Volatile drying can be performed using a hot air circulation drying oven, an IR (infrared) oven, a heating plate, a convection oven, etc. (using a heat source that heats the air with steam to allow the hot air in the dryer to contact in countercurrent and blowing from the nozzle to the support).

On the other hand, when a dry film is used, the dry film is bonded to the substrate by a lamination device or the like so that the resin layer contacts the substrate, and then the support film is peeled off before or after the exposure step described below, thereby forming a resin layer on the substrate. Furthermore, when a dry film having a protective film is used, the protective film is peeled off from the dry film and then bonded to the substrate. The bonding of the dry film to the substrate is preferably performed under pressure and heat using a vacuum lamination device or the like. By using such a vacuum lamination device, when using a substrate on which a circuit is formed, even if the surface of the circuit substrate has bumps and depressions, bubbles will not be mixed in because the dry film is in close contact with the circuit substrate, and the filling effect of the recessed portions on the substrate surface is also improved. The pressurization condition is preferably about 0.1 to 2.0 MPa, and the heating condition is preferably 40 to 120°C.

After forming a dry coating of a photosensitive resin composition on a substrate or using a dry film to form a resin layer, selective exposure is performed by active energy radiation through a mask formed with a predetermined pattern, and the unexposed portion is developed by a dilute alkaline aqueous solution (e.g., a 0.3 to 3 mass % sodium carbonate aqueous solution) to form a pattern of a cured product. In the case of a dry film, after exposure, the support film is peeled off from the dry film and developed, thereby forming a patterned cured product on the substrate. In addition, as long as it is within the range that does not damage the characteristics, the support film can also be peeled off from the dry film before exposure, and the exposed resin layer can be exposed and developed.

Furthermore, in the present invention, after the above exposure and development, and before the following irradiation of active energy rays, the developed resin layer may be subjected to at least one of heating and ultraviolet irradiation. For example, the resin layer formed by exposure and development is cured by heat (100 to 220°C) or light irradiation, or by both heat curing and light irradiation for final finishing curing (formal curing), thereby forming a cured film with excellent properties such as adhesion and hardness. According to the method of the present invention, even such a cured film with increased adhesion on the substrate can be easily removed by a solvent.

As an exposure machine for irradiating the above-mentioned active energy ray, any device equipped with a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halogen lamp, a mercury short arc lamp, etc., and irradiating ultraviolet rays in the range of 350 to 450 nm can be used. Furthermore, a direct drawing device (for example, a laser direct imaging device that uses CAD data from a computer to directly draw an image by laser) can also be used. The lamp light source or laser light source of the direct drawing machine can be one with a maximum wavelength in the range of 350 to 450 nm. The exposure amount used to form an image varies depending on the film thickness, etc., but can generally be set in the range of ¹⁰ to 1000 mJ/cm2, preferably 20 to 800 mJ/ ^cm2 . In addition, the active energy ray here is different from the active energy ray that can generate active oxygen or the active energy ray that can cleave CC carbon bonds in the presence of oxygen in terms of wavelength. In addition, in the presence of oxygen means that the oxygen flow rate in the gas environment is at least 0.2 sccm or more, generally 0.5 sccm or more.

As a developing method, an immersion method, a shower method, a spray method, a brush method, etc. can be used, and as a developer, an alkaline aqueous solution of potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia, amines, etc. can be used.

The thickness of the formed cured film can be appropriately set according to the purpose of the wiring substrate, but it is preferably in the range of 1 to 1000μm. If the cured film is too thick, it will take time to remove the cured film as described below. In addition, the method for confirming whether a cured film is formed can be confirmed by the following method. That is, in an environment of 25℃50%RH, a cloth containing isopropyl alcohol (IPA) is placed on the surface of the cured film, and a load of 500g is placed on it. After standing for 1 minute, the cloth is peeled off, and the state where the surface of the cloth in contact with the cured film is not attached to all or part of the curable resin layer is judged as a cured state.

The cured film formed on the substrate in the above manner is in close contact with the substrate. The degree of close contact between the substrate and the cured film varies depending on the surface state of the substrate on which the cured film is provided, the composition of the photosensitive resin composition, and the curing conditions, but the peeling strength measured according to the copper-clad laminate test method of JIS-C-6481 and the peeling strength measurement method (specimen width 10 mm, 90° direction, speed 50 mm/min) is preferably 3 N/cm or more, and more preferably 5 N/cm or more. In addition, the upper limit is preferably 10 N/cm or less. According to the method of the present invention, even if the close contact between the substrate and the cured film is high, the cured film can be easily removed by a solvent.

[Active energy ray irradiation step] The cured film obtained in the above manner may have defects depending on the situation. For example, the following defects may occur: poor printing when applying a photosensitive resin composition such as solder mask ink to a substrate, positional deviation during exposure, mottled spots, pinholes in the dried coating, mixing of foreign matter, poor printing of marking ink, etc. Even in such a case, according to the method of the present invention, only the cured film with defects can be peeled off from the substrate and the substrate can be reused.

The active energy ray used in the present invention is at least one of active energy ray capable of generating active oxygen or active energy ray capable of cleaving C-C carbon bonds in the presence of oxygen. Preferably, ionizing radiation with a wavelength of 100 to 255 nm can be used. If ionizing radiation with a wavelength of 100 to 255 nm is irradiated in the presence of oxygen, part of the oxygen molecules in the gas environment will become active oxygen (including ozone). The C-C carbon bonds of the polymer chain constituting the cured product are cleaved by the active oxygen. As a result, a part of the cleaved hydrocarbon radicals bond with oxygen, become carbon dioxide, etc., and vaporize. In addition, hydrocarbon radicals may also re-bond with each other to generate low molecular weight compounds, and a part of these low molecular weight compounds will vaporize. In addition, ionizing radiation with a wavelength of 100 to 255 nm has higher energy than C-C carbon binding energy, so it can break down the polymer chains that constitute the cured film and reduce their molecular weight. As a result, the residue (hydrocarbons that remain without vaporization) remaining on the substrate can be easily removed by solvents.

As a device capable of irradiating ionizing radiation with a wavelength of 100 to 255 nm, for example, there can be mentioned a UV ozone cleaner (the distance from the UV lamp source to the irradiation surface is 1 cm, type: low-pressure mercury lamp (fused quartz), shape: high-density high-output grid lamp, UV intensity: 28 mW/cm ² ), etc. Furthermore, when the ionizing radiation is UV, its intensity is preferably 3 to 50 mW/cm ² .

[Step of removing the cured film] Then, the substrate on which the cured film is formed is cleaned with a solvent, and the cured film on the portion irradiated with the active energy ray is removed from the substrate. As a method for cleaning the cured film on the substrate, an immersion method, a spray method, a method using a blade, etc. can be used. In particular, when only the cured film on a defective portion is to be removed, a spray method, etc. is preferably used.

As the solvent, various organic solvents can be used. Among them, if the influence on the manufactured wiring board is considered, it is appropriate to use aprotic polar solvents. As aprotic polar solvents, there can be listed: N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, tetramethylurea, 1,3-dimethyl-2-imidazolidinone, dimethylpropylurea, dimethylsulfoxide, γ-butyrolactone, β-propiolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, etc. These components can be used alone or in combination of two or more. Among these components, N-methylpyrrolidone can be preferably used.

Even when the residue on the surface of the substrate is cleaned with a solvent, a very small amount of residue may remain on the substrate. Therefore, in the method of the present invention, it is preferred to heat the wiring substrate after removing the cured film. The heating temperature is preferably in the range of 80 to 200°C, and more preferably in the range of 100 to 150°C.

The method of the present invention can be used when manufacturing electronic components such as printed circuit boards. Regardless of the composition of the photosensitive resin composition, the cured film can be removed from the substrate, so it is particularly useful when using a high value-added substrate. In addition, the active energy ray can be irradiated only to the defective parts of the cured film. Therefore, when manufacturing a wiring board, if a defect is found in a part of the cured film, only the defective part of the cured film can be removed from the substrate, which can improve production efficiency (yield).

The following embodiments and comparative examples are provided to specifically illustrate the present invention, but the present invention is not limited to the following embodiments. In addition, the following "parts" and "%" are all based on mass unless otherwise specified.

[Preparation of photosensitive resin composition] First, prepare the photosensitive resin composition. The photosensitive resin composition comprises 13 parts (in terms of solid content) of the following carboxyl group-containing resin varnish 1, 30 parts (in terms of solid content) of the following carboxyl group-containing resin varnish 2, 4 parts of 2,4,6-trimethylbenzyldiphenylphosphine oxide (Omnirad TPO H, manufactured by IGM Resins) as a photopolymerization initiator, 11 parts of tricyclodecane dimethanol diacrylate (A-DCP, manufactured by Shin-Nakamura Industries Co., Ltd.) as a photopolymerizable monomer, 27 parts of bisphenol A type epoxy resin (jER 828, manufactured by Mitsubishi Chemical Co., Ltd.) as a thermosetting component, and 0.3 parts of imidazole epoxy resin curing agent (CUREZOL 1000) as a thermosetting catalyst. 1B2PZ, manufactured by Shikoku Chemical Co., Ltd.) was mixed and pre-mixed with a stirrer and then kneaded with a three-roll mill to prepare a photosensitive resin composition.

<Carboxyl-containing resin varnish 1> In a high pressure autoclave equipped with a thermometer, a nitrogen and oxirane inlet device, and a stirring device, 119.4 g of phenolic varnish type cresol resin (manufactured by Aica Kogyo Company, Limited, trade name "Shonol CRG951", OH equivalent: 119.4), 1.19 g of potassium hydroxide, and 119.4 g of toluene were placed, and nitrogen substitution was performed in the system while stirring, and the temperature was raised. Then, 63.8 g of propylene oxide was slowly dripped in, and the reaction was carried out at 125 to 132°C and 0 to 4.8 kg/ ^cm2 for 16 hours. After cooling to room temperature, 1.56 g of 89% phosphoric acid was added to the reaction solution to neutralize potassium hydroxide, and an propylene oxide reaction solution of a novolac type cresol resin having a non-volatile content of 62.1% and a hydroxyl value of 182.2 g/eq. was obtained. The average amount of alkylene oxide adduct added to 1 equivalent of phenolic hydroxyl group was 1.08 mol. Next, 293.0 g of the obtained phenolic varnish type cresol resin epoxy alkylene oxide reaction solution, 43.2 g of acrylic acid, 11.53 g of methanesulfonic acid, 0.18 g of toluene and 252.9 g of toluene were placed in a reactor equipped with a stirrer, a thermometer and a blowpipe, and air was blown in at a rate of 10 ml/min. The mixture was stirred and reacted at 110°C for 12 hours. The water generated by the reaction was distilled off as an azeotropic mixture with toluene to produce 12.6 g of water. After that, the mixture was cooled to room temperature, and the obtained reaction solution was neutralized with 35.35 g of a 15% sodium hydroxide aqueous solution, and then washed with water. After that, toluene was replaced with 118.1 g of diethylene glycol monoethyl ether acetate and distilled off using an evaporator to obtain a novolac type acrylate resin solution. Next, 332.5 g of the obtained novolac type acrylate resin solution and 1.22 g of triphenylphosphine were placed in a reactor equipped with a stirrer, a thermometer and a blowpipe, and air was blown in at a rate of 10 ml/min. While stirring, 60.8 g of tetrahydrophthalic anhydride was slowly added and reacted at 95 to 101°C for 6 hours. In this way, a resin solution of a carboxyl-containing photosensitive resin with a solid acid value of 88 mgKOH/g, a solid content of 71%, and a weight average molecular weight of 2,000 was obtained. This was referred to as carboxyl-containing resin varnish 1.

<Carboxyl-containing resin varnish 2> In a flask equipped with a stirrer, a thermometer and a condenser, 848.8 g of γ-butyrolactone, 57.5 g (0.23 mol) of MDI (diphenylmethane diisocyanate), 59.4 g (0.225 mol) of DMBPDI (4,4'-diisocyanate-3,3'-dimethyl-1,1'-biphenyl) and TMA ( 67.2g (0.35 mol) of trimellitic anhydride) and 29.7g (0.15 mol) of TMA-H (cyclohexane-1,3,4-tricarboxylic acid-3,4-anhydride) were stirred while paying attention to the heat, and the temperature was raised to 80°C, and it took 1 hour to dissolve and react at this temperature. After further raising the temperature to 160°C for 2 hours, it was reacted at this temperature for 5 hours. The reaction was carried out while bubbling carbon dioxide, and the system became a brown transparent liquid. In this way, a solution of a carboxyl-containing amide imide resin (resin composition in which the resin is dissolved in γ-butyrolactone) with a viscosity of 7Pa･s at 25°C and a solid content of 17% and an acid value of 5.3 (KOHmg/g) was obtained. The solid acid value of the resin was 31.2 (KOH mg/g) and the weight average molecular weight was 34,000. This was designated as carboxyl group-containing resin varnish 2.

The surface of a FR-4 copper-clad laminate (100 mm × 150 mm × 0.8 mm, double-sided copper foil, the thickness of the copper foil on both sides is 18 μm) was chemically polished by CZ8101 manufactured by MEC Co., Ltd. so that the arithmetic mean surface roughness (Ra) was 400 nm, and the photosensitive resin composition obtained in the above manner was applied to the entire surface of the chemically polished substrate by screen printing so that the film thickness after drying was 20 to 25 μm, dried at 80°C for 30 minutes, and cooled to room temperature.

Next, the coating was irradiated with ultraviolet light of 365nm wavelength at an exposure amount of 1,000mJ/cm2 in an atmospheric environment using a metal halogen lamp through a mask having a line pattern of L/S=100/100, 80/80, 60/60, 40/40, 20/20, 10/10, ^7/7 , 5/5, 4/4, 3/3, 2/2, 1/1 (units are all μm), and then developed for 180 seconds using a 30°C, 1wt% _{Na2CO3 aqueous} solution to form a cured film. Whether a cured film is formed is determined by placing a fabric containing isopropyl alcohol (IPA) on the surface of the cured film in an environment of 25°C and 50% RH, placing a load of 500g on it, leaving it for 1 minute, and then peeling off the fabric. The state of not adhering all or part of the resin layer to the surface of the fabric in contact with the cured film is judged. In addition, it is confirmed that the peeling strength of the formed cured film measured in accordance with the copper-clad laminate test method and the peeling strength measurement method of JIS-C-6481 (specimen width 10mm, 90° direction, speed 50mm/min) is 3N/cm or more and 10N/cm or less.

[Example 1] Prepare two substrates on which the cured films obtained in the above manner are formed. For one of the substrates on which the cured films are formed, use a UV ozone cleaner (the distance from the UV lamp light source to the irradiated surface is 1 cm, type: low-pressure mercury lamp (fused quartz), shape: high-density high-output grid-type lamp, UV intensity: 28 mW/cm ² ), and irradiate the entire surface of the cured film ^formation surface with active energy rays of wavelength 185nm (10%) + 254nm (90%) in the presence of oxygen (in an atmosphere with an oxygen flow rate of 0.5 sccm) at an exposure amount of 25.2 J/cm 2. For the other substrate on which the cured film is formed, irradiate the active energy rays through a light-shielding mask in the same conditions as above in a manner that only the line pattern is irradiated. Next, for the substrates with a cured film formed on the entire surface after irradiation, the substrates were immersed in N-methylpyrrolidone solvent, left at 55°C for 20 minutes, and then the solvent was removed. Also, for the substrates with a cured film formed on the partially irradiated surface, N-methylpyrrolidone solvent was dropped onto the substrates where the active energy rays were irradiated, left at 55°C for 20 minutes, and then the solvent was removed. The resulting substrates were visually checked, and the cured films at the active energy ray irradiated locations were completely removed in all the substrates.

[Comparative Example 1] Except that the active energy ray was not irradiated with a low-pressure mercury lamp, two substrates with cured films were treated with N-methylpyrrolidone solvent in the same manner as in Example 1. The obtained substrates were visually checked and the cured films were not peeled off from the substrates in all the substrates.

[Comparative Example 2] Except that the irradiation of active energy rays with a low-pressure mercury lamp was changed from oxygen presence (in an atmospheric environment) to nitrogen environment, two substrates with cured films formed thereon were treated with N-methylpyrrolidone solvent in the same manner as in Example 1. The obtained substrates were visually checked, and the results showed that in all substrates, although the cured film of the portion irradiated with active energy rays was partially peeled off from the substrate, it was not completely peeled off from the substrate, and the cured film still remained. From the experimental results of Example 1 and Comparative Examples 1 and 2, it can be seen that by irradiating with active energy rays in the presence of oxygen, the cured film can be effectively peeled off.

[Comparative Example 3] Two substrates with cured films formed thereon were treated with N-methylpyrrolidone solvent in the same manner as in Example 1, except that the active energy ray (main wavelength 365 nm) irradiated by a UV conveyor (ORC MANUFACTURING CO., LTD. Model: QRM-2082, UV intensity: 80 mW/cm ² ) was changed from a low-pressure mercury lamp to a high-pressure mercury lamp. The obtained substrates were visually checked, and it was found that in all substrates, although the cured film of the portion irradiated with active energy ray was partially peeled off from the substrate, it was not completely peeled off from the substrate, and the cured film still remained. From the experimental results of Example 1 and Comparative Example 3, it can be seen that under the ultraviolet irradiation of the high-pressure mercury lamp, no active oxygen is generated and the CC carbon bond is not cleaved.

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Claims (7)

A method for recycling a substrate for a wiring board, which is a method for removing part or all of a cured film from a wiring board having a cured film formed on the surface of the substrate and recycling the substrate, wherein the cured film is made of a cured product of a photosensitive resin composition, and the method comprises the following steps: irradiating part or all of the cured film with at least one of active energy rays capable of generating active oxygen or active energy rays capable of cleaving C-C carbon bonds in the presence of oxygen, and washing the substrate on which the cured film is formed with a solvent and removing the part of the cured film irradiated by the active energy rays from the substrate, wherein the solvent is a non-protonic polar solvent. The method as described in claim 1, wherein the cured film is formed by coating a photosensitive resin composition on the substrate and drying to form a dry coating film, or by coating a photosensitive resin composition on a supporting film and drying to form a resin layer, and the substrate and the resin layer are bonded to the dry film in a manner that the substrate and the resin layer are in contact with each other, and then the dry coating film or the resin layer of the dry film is exposed, developed and patterned. The method as described in claim 1, wherein the active energy ray comprises ionizing radiation having a wavelength of 100 to 255 nm. The method as described in claim 1 further includes the step of heating the wiring substrate from which the cured film has been removed. The method as described in claim 1, wherein the photosensitive resin composition contains (A) a carboxyl-containing resin, (B) a photopolymerizable monomer, (C) a photopolymerization initiator, and (D) a thermosetting component. The method as described in claim 5, wherein at least one of heating and ultraviolet irradiation is performed after the resin layer is exposed and developed and before the cured film is irradiated with active energy rays. A method as described in any one of claims 1 to 6, wherein the thickness of the cured film is 1 to 1000 μm.