Polymer, photosensitive resin composition, photosensitive element, method for forming resist pattern, and method for forming wiring pattern

Abstract

Disclosed is a polymer comprising a structural unit represented by formula (I) and a structural unit having a carboxy group. Also disclosed is a photosensitive resin composition containing a binder resin including the polymer, a photopolymerizable compound, and a photopolymerization initiator. (In formula (I), R1 represents a hydrogen atom or a methyl group and R2 represents an alkyl group, an aryl group, an aralkyl group, or a hydrogen atom.)

Description

Polymer, photosensitive resin composition, photosensitive element, method for forming a resist pattern, and method for forming a wiring pattern

[0001] This disclosure relates to polymers, photosensitive resin compositions, photosensitive elements, methods for forming resist patterns, and methods for forming wiring patterns.

[0002] In the field of printed circuit board manufacturing, photosensitive elements (laminated structures) comprising a photosensitive resin composition and a layer formed on a support film using the photosensitive resin composition (hereinafter sometimes referred to as the "photosensitive layer") are widely used as resist materials for etching or plating processes.

[0003] Printed circuit boards are manufactured using the above-mentioned photosensitive element by, for example, the following procedure. First, the photosensitive layer of the photosensitive element is laminated onto a circuit-forming substrate such as a copper-clad laminate. Next, the photosensitive layer is exposed to light through a mask film or the like to form a photocurable area. At this time, the support film is peeled off before or after exposure. After that, the area of ​​the photosensitive layer other than the photocurable area is removed with a developer to form a resist pattern. Next, the resist pattern is used as a resist and subjected to etching or plating to form a conductor pattern, and finally the photocurable area (resist pattern) of the photosensitive layer is peeled off (removed).

[0004] Patent documents 1 and 2 disclose photosensitive resin compositions that have excellent high resolution as resist materials.

[0005] Japanese Patent Publication No. 2005-122123, Japanese Patent Publication No. 2006-234995

[0006] However, conventional photosensitive resin compositions can experience edge fusion, where the resin leaches out during storage, and there is room for improvement in terms of storage stability.

[0007] Therefore, the main objective of this disclosure is to provide a novel polymer that can improve storage stability while maintaining the resolution of a photosensitive resin composition.

[0008] This disclosure includes the following [1] to

[13] : [1] A polymer comprising a structural unit represented by the following formula (I) and a structural unit having a carboxyl group. [In formula (I), R １ R represents a hydrogen atom or a methyl group. ２[1] represents an alkyl group, an aryl group, an aralkyl group, or a hydrogen atom. [2] The polymer according to [1], wherein the content of the structural unit represented by formula (I) is 5 to 50% by mass based on the total amount of the polymer. [3] A photosensitive resin composition comprising a binder resin containing the polymer according to [1] or [2], a photopolymerizable compound, and a photopolymerization initiator. [4] The photosensitive resin composition according to [3], wherein the photopolymerization initiator comprises a hexaarylbiimidazole compound. [5] The photosensitive resin composition according to [3] or [4], further comprising a sensitizer. [6] The photosensitive resin composition according to any one of [3] to [5], further comprising a photochromic agent. [7] A photosensitive element comprising a support film and a photosensitive layer formed on the support film, wherein the photosensitive layer comprises the photosensitive resin composition according to any one of [3] to [6]. [8] A method for forming a resist pattern, comprising the steps of: forming a photosensitive layer on a substrate using a photosensitive resin composition according to any one of [3] to [6]; irradiating at least a part of the photosensitive layer with an active light to form a photocurable portion; and removing at least a part of the photosensitive layer other than the photocurable portion from the substrate to form a resist pattern. [9] A method for forming a resist pattern, comprising the steps of: forming a photosensitive layer on a substrate using a photosensitive element according to [7]; irradiating at least a part of the photosensitive layer with an active light to form a photocurable portion; and removing at least a part of the photosensitive layer other than the photocurable portion from the substrate to form a resist pattern.

[10] A method for forming a wiring pattern, comprising the step of etching or plating a substrate on which a resist pattern has been formed by the resist pattern forming method according to [8] to form a conductor pattern.

[11] A method for forming a wiring pattern, comprising the step of etching or plating a substrate on which a resist pattern has been formed by the resist pattern forming method according to [9] to form a conductor pattern.

[12] The method for forming a wiring pattern according to

[10] , further comprising the step of removing the photocured portion with an alkaline aqueous solution after the etching or plating process.

[13] The method for forming a wiring pattern according to

[11] , further comprising the step of removing the photocured portion with an alkaline aqueous solution after the etching or plating process.

[0009] According to this disclosure, it is possible to provide a novel polymer, a photosensitive resin composition, a photosensitive element, a method for forming a resist pattern, and a method for forming a wiring pattern that can improve storage stability while maintaining the resolution of the photosensitive resin composition.

[0010] Figure 1 is a schematic cross-sectional view showing one embodiment of a photosensitive element.

[0011] The embodiments of this disclosure will be described in detail below. However, this disclosure is not limited to the embodiments described below.

[0012] In this specification, the term "process" includes not only independent processes but also processes that are indistinguishable from other processes as long as their intended function is achieved. Numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. The term "layer" includes not only structures that form a shape across the entire surface when observed as a plan view, but also structures that form a shape in part. "(meth)acrylic acid" means at least one of "acrylic acid" or its corresponding "methacrylic acid." The same applies to other similar expressions such as (meth)acrylate and (meth)acryloyl.

[0013] In this specification, unless otherwise specified, when there are multiple substances corresponding to each component in the photosensitive resin composition, the amount of each component means the total amount of the multiple substances present in the photosensitive resin composition. In the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. Also, aspects obtained by arbitrarily combining the matters described in this specification are also included in the present disclosure. In this specification, the "solid content" refers to the non-volatile components excluding volatile substances such as water and solvents contained in the photosensitive resin composition. That is, the "solid content" refers to components other than solvents that do not volatilize during the drying of the photosensitive resin composition described later, and includes components that are liquid, syrup-like, and wax-like at room temperature (25°C).

[0014] [Polymer] The polymer according to the present embodiment includes a structural unit represented by the following formula (I) and a structural unit having a carboxy group.

[0015]

[0016] In formula (I), R １ represents a hydrogen atom or a methyl group, and R ２ represents an alkyl group, an aryl group, an aralkyl group, or a hydrogen atom.

[0017] The alkyl group represented by R ２ may have 1 to 20 carbon atoms, 2 to 15 carbon atoms, or 3 to 12 carbon atoms. The alkyl group represented by R ２ may be, for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, or a dodecyl group. The alkyl group represented by R ２ may be linear, branched, or cyclic. The -CH ２ group contained in the alkyl group represented by R ２ may be substituted with a -C(O)- group.

[0018] The aryl group represented by R ２ may have 6 to 20 carbon atoms, 6 to 15 carbon atoms, or 6 to 10 carbon atoms. The aryl group represented by R ２ may be, for example, a phenyl group or a naphthyl group

[0019] R ２ The number of carbon atoms in the aralkyl group represented by R may be 7 to 22, 7 to 15, or 7 to 12. ２ The aralkyl group represented by may be, for example, a benzyl group.

[0020] Examples of monomers that give rise to the structural unit represented by formula (I) include (meth)acrylamide, N-alkyl(meth)acrylamide, N-aryl(meth)acrylamide, and N-aralkyl(meth)acrylamide.

[0021] Examples of N-alkyl(meth)acrylamides include N-isopropyl(meth)acrylamide, N-n-butyl(meth)acrylamide, N-tert-butyl(meth)acrylamide, N-(1,1,3,3-tetramethylbutyl)(meth)acrylamide (N-tert-octyl(meth)acrylamide), N-(1,1-dimethyl-3-oxobutyl)(meth)acrylamide (diacetone(meth)acrylamide), and N-n-dodecyl(meth)acrylamide.

[0022] Examples of N-aryl(meth)acrylamides include N-phenyl(meth)acrylamide and N-naphthyl(meth)acrylamide.

[0023] Examples of N-aralkyl(meth)acrylamides include N-benzyl(meth)acrylamide.

[0024] The polymer according to this embodiment, by containing the structural unit represented by formula (I), can improve storage stability while maintaining resolution when used as a photosensitive resin composition. The inventors believe that this effect is due to pseudo-high molecular weight formation occurring through intermolecular interactions via hydrogen bonds.

[0025] Furthermore, the polymer according to this embodiment can control its viscosity by utilizing the interaction between amide groups through hydrogen bonding, and therefore tends to exhibit excellent conformability.

[0026] The content of the structural unit represented by formula (I) in the polymer may be 5 to 50% by mass, based on the total amount of polymer. The content of the structural unit represented by formula (I) may be 6% or more by mass, 7% or more by mass, or 8% or more by mass, from the viewpoint of further improving resolution and storage stability. The content of the structural unit represented by formula (I) may be 45% or less by mass, 40% or less by mass, 35% or less by mass, 30% or less by mass, 25% or less by mass, or 20% or less by mass, from the viewpoint of increasing the solubility of the polymer in alkaline aqueous solutions.

[0027] The polymer according to this embodiment contains structural units having carboxyl groups from the viewpoint of alkali developability. The content of structural units having carboxyl groups may be 10 to 45% by mass, 15 to 40% by mass, or 20 to 35% by mass, based on the total amount of polymer, in order to improve alkali developability in a balanced manner. When the content of structural units having carboxyl groups is 10% by mass or more, alkali developability tends to be further improved, and when it is 45% by mass or less, alkali resistance tends to be more superior.

[0028] Examples of monomers that provide structural units having a carboxyl group include (meth)acrylic acid, α-bromoacrylic acid, α-chloroacrylic acid, β-furyl(meth)acrylic acid, β-styryl(meth)acrylic acid, maleic acid, maleic anhydride, monomethyl maleate, monoethyl maleate, monoisopropyl maleate, fumaric acid, cinnamic acid, α-cyanocinnamic acid, itaconic acid, crotonic acid, and propiolic acid. The polymer according to this embodiment may contain structural units derived from (meth)acrylic acid in order to further improve alkali developability.

[0029] The polymer according to this embodiment may further contain structural units derived from styrene or styrene derivatives from the viewpoint of adhesion and peelability. Styrene derivatives are polymerizable compounds in which a hydrogen atom at the α-position or aromatic ring of styrene is substituted. Examples of styrene derivatives include vinyltoluene, α-methylstyrene, p-methylstyrene, and p-ethylstyrene.

[0030] The content of structural units derived from styrene or styrene derivatives in the polymer may be 20-60% by mass, 25-55% by mass, or 30-50% by mass, based on the total amount of polymer. When the content of structural units derived from styrene or styrene derivatives is 20% by mass or more, adhesion tends to improve, and when it is 60% by mass or less, the size of the peeling fragments during development can be suppressed, and the time required for peeling tends to be reduced.

[0031] The polymer according to this embodiment may further contain structural units derived from benzyl (meth)acrylate or a benzyl (meth)acrylate derivative, from the viewpoint of resolution and aspect ratio. Examples of benzyl (meth)acrylate derivatives include 4-methylbenzyl (meth)acrylate. From the viewpoint of improving resolution, the content of structural units derived from benzyl (meth)acrylate or a benzyl (meth)acrylate derivative in the polymer may be 5 to 40% by mass, 8 to 30% by mass, or 10 to 25% by mass, based on the total amount of the polymer.

[0032] The polymer according to this embodiment may further contain structural units derived from alkyl (meth)acrylate esters from the viewpoint of improving plasticity. Examples of alkyl (meth)acrylate esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate.

[0033] The weight average molecular weight (Mw) of the polymer may be 5000 or more, 8000 or more, 10000 or more, 12000 or more, or 15000 or more from the viewpoint of improving resolution. The Mw of the polymer may be 60000 or less, 55000 or less, 50000 or less, 45000 or less, or 40000 or less from the viewpoint of better developability. Mw can be measured by gel permeation chromatography (GPC) using a calibration curve of standard polystyrene.

[0034] The polymer can be obtained, for example, by polymerizing monomers by radical polymerization using a solution polymerization method. More specifically, it can be obtained by polymerizing a monomer containing a monomer that gives a structural unit represented by formula (I) and a monomer that gives a structural unit having a carboxy group in a solvent.

[0035] The solvent can be appropriately selected from organic solvents generally used in the field of radical polymerization. Examples of the solvent include aromatic hydrocarbons such as toluene, xylene, and benzene; aliphatic hydrocarbons such as hexane and heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; ketones such as methyl ethyl ketone and methyl isobutyl ketone; alcohols or glycols such as ethylene glycol, propylene glycol, and dipropylene glycol; glycol ethers such as methyl cellosolve, 2-butoxyethanol, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether; and known organic solvents such as glycol esters such as ethylene glycol diacetate and propylene glycol monomethyl ether acetate. The amount of the solvent used can be appropriately set according to the type of monomer, reaction conditions, solid content concentration, etc.

[0036] When polymerizing the monomer, a chain transfer agent may be added as necessary. Examples of the chain transfer agent include monofunctional thiol compounds such as n-dodecyl mercaptan and β-mercaptopropionic acid; bifunctional thiol compounds such as mercapto-modified polysiloxane at both ends; and side-chain polyfunctional mercapto-modified polysiloxane with a mercapto-modified side chain. The blending amount of the chain transfer agent can be appropriately set according to the type of monomer, reaction conditions, etc., and is not particularly limited, but may be 0.01 to 3% by mass based on the total amount of the monomer.

[0037] When polymerizing the monomer, a thermal radical generator may be added as necessary. Examples of the thermal radical generator include azo compounds such as 2,2'-azobis(isobutyronitrile), 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl-2,2'-azobis(2-methylpropionate). The blending amount of the thermal radical generator can be appropriately set according to the type of monomer, reaction conditions, etc., and is not particularly limited, but may be 0.01% by mass or more or 0.05% by mass or more, and may be 10% by mass or less, 5% by mass or less, or 1% by mass or less based on the total amount of the monomer.

[0038] The polymerization temperature may be 60 to 100°C or 70 to 100°C. The polymerization time may be 1 to 15 hours or 5 to 10 hours.

[0039] [Photosensitive resin composition] The photosensitive resin composition according to this embodiment contains (A) a binder resin (hereinafter sometimes referred to as the "(A) component"), (B) a photopolymerizable compound (hereinafter sometimes referred to as the "(B) component"), and (C) a photopolymerization initiator (hereinafter sometimes referred to as the "(C) component"). Hereinafter, each component that the photosensitive resin composition may contain will be described in detail.

[0040] (A) Component: Binder resin Component (A) includes a polymer having the above-described specific structure (hereinafter sometimes referred to as "(A1) component"). By including (A) component (A1), the storage stability of the photosensitive resin composition (photosensitive layer) can be improved while maintaining its resolution. Component (A1) may consist of only one type of resin, or it may consist of two or more types of resins.

[0041] Component (A) may further contain resins other than component (A1). Examples of such resins include alkali-soluble resins having phenolic hydroxyl groups. Examples of resins having phenolic hydroxyl groups include polyhydroxystyrene; hydroxystyrene-based resins such as copolymers containing hydroxystyrene as monomer units; phenolic resins; polybenzoxazole precursors such as poly(hydroxyamide); poly(hydroxyphenylene) ethers; and polynaphthol.

[0042] The content of component (A) may be 30 to 90 parts by mass, 40 to 85 parts by mass, or 50 to 80 parts by mass per 100 parts by mass of the total amount of components (A) and (B). When the content of component (A) is within this range, the strength of the photo-cured portion of the photosensitive layer tends to be better.

[0043] (B) Component: Photopolymerizable compound Component (B) is a compound having a functional group with an ethylenically unsaturated bond, such as a vinyl group, allyl group, propargyl group, butenyl group, ethynyl group, phenylethynyl group, maleimide group, nadiimide group, or (meth)acryloyl group, as a functional group that exhibits photopolymerization. Component (B) is not particularly limited as long as it is a compound having one or more ethylenically unsaturated groups. The functional group that exhibits photopolymerization may be a (meth)acryloyl group. Component (B) may be used alone or in combination of two or more.

[0044] Examples of photopolymerizable compounds having one ethylenically unsaturated group include (meth)acrylic acid, alkyl (meth)acrylate esters, and phthalic acid compounds.

[0045] Examples of alkyl (meth)acrylate esters include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and hydroxyethyl (meth)acrylate.

[0046] Component (B) may contain a phthalate compound from the viewpoint of suitably improving resolution, adhesion, and resist shape. Examples of phthalate compounds include γ-chloro-β-hydroxypropyl-β'-(meth)acryloyloxyethyl-o-phthalate (also known as 3-chloro-2-hydroxypropyl-2-(meth)acryloyloxyethyl phthalate), β-hydroxyethyl-β'-(meth)acryloyloxyethyl-o-phthalate, and β-hydroxypropyl-β'-(meth)acryloyloxyethyl-o-phthalate.

[0047] Examples of photopolymerizable compounds having two ethylenically unsaturated groups include polyethylene glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, polypropylene glycol di(meth)acrylate, 2,2-bis(4-(meth)acryloxypolyethoxypolypropoxyphenyl)propane, bisphenol A diglycidyl ether di(meth)acrylate, and alkylene oxide-modified bisphenol A di(meth)acrylate.

[0048] Component (B) may contain alkylene oxide-modified bisphenol A di(meth)acrylate from the viewpoint of improving alkaline developability and resolution. Examples of alkylene oxide-modified bisphenol A di(meth)acrylate include 2,2-bis(4-((meth)acryloxypolyethoxy)phenyl)propane(EO-modified bisphenol A dimethacrylate), 2,2-bis(4-((meth)acryloxypolypropoxy)phenyl)propane(PO-modified bisphenol A dimethacrylate), 2,2-bis(4-((meth)acryloxypolybutoxy)phenyl)propane(BO-modified bisphenol A dimethacrylate), and 2,2-bis(4-((meth)acryloxypolyethoxypolypropoxy)phenyl)propane(EO,PO-modified bisphenol A dimethacrylate).

[0049] In this specification, "EO modified" means having a block structure of ethylene oxide (EO) groups, "PO modified" means having a block structure of propylene oxide (PO) groups, and "BO modified" means having a block structure of butylene oxide (BO) groups.

[0050] Examples of photopolymerizable compounds having three or more ethylenically unsaturated groups include (meth)acrylates having a trimethylolpropane-derived skeleton such as trimethylolpropane tri(meth)acrylate; (meth)acrylates having a tetramethylolmethane-derived skeleton such as tetramethylolmethane tri(meth)acrylate and tetramethylolmethane tetra(meth)acrylate; (meth)acrylates having a pentaerythritol-derived skeleton such as pentaerythritol tri(meth)acrylate and pentaerythritol tetra(meth)acrylate; (meth)acrylates having a dipentaerythritol-derived skeleton such as dipentaerythritol penta(meth)acrylate and dipentaerythritol hexa(meth)acrylate; (meth)acrylates having a ditrimethylolpropane-derived skeleton such as ditrimethylolpropane tetra(meth)acrylate; and (meth)acrylates having a diglycerin-derived skeleton. Among these, from the viewpoint of improving chemical resistance after curing (exposure) and increasing the difference in developer resistance between the exposed and unexposed areas, the photopolymerizable compound having three or more ethylenically unsaturated groups may be a (meth)acrylate compound having a skeleton derived from dipentaerythritol, or it may be dipentaerythritol penta(meth)acrylate.

[0051] From the viewpoint of improving the alkali developability of the unexposed portion of the photosensitive resin composition and improving the adhesive strength of the exposed portion, component (B) may contain a photopolymerizable compound having an ethylenically unsaturated group and an acid-modified group. Examples of the acidic group to be modified include a carboxyl group, a sulfo group, and a phenolic hydroxyl group. Among these, the acidic group to be modified may be a carboxyl group.

[0052] Examples of photopolymerizable compounds having ethylenically unsaturated groups and acidic groups include styrene-maleic acid resins and acid-modified vinyl group-containing epoxy derivatives.

[0053] Styrene-maleic acid resins are hydroxyethyl (meth)acrylate-modified products of styrene-maleic anhydride copolymers. Acid-modified vinyl group-containing epoxy derivatives are compounds obtained by reacting a compound obtained by modifying an epoxy resin with a vinyl group-containing organic acid with a saturated or unsaturated group-containing polybasic acid anhydride.

[0054] The epoxy resin is not particularly limited as long as it is a compound having two or more epoxy groups. Examples of epoxy resins include glycidyl ether type epoxy resins, glycidylamine type epoxy resins, and glycidyl ester type epoxy resins. Among these, the epoxy resin may be a bisphenol novolac type epoxy resin or a bisphenol F novolac type epoxy resin from the viewpoint of reliability when mounted on semiconductor chips.

[0055] The vinyl group-containing organic acid is not particularly limited and may be a vinyl group-containing monocarboxylic acid. Examples of vinyl group-containing monocarboxylic acids include acrylic acid derivatives such as acrylic acid, acrylic acid dimers, methacrylic acid, β-furfurylacrylic acid, β-styrylacrylic acid, cinnamic acid, crotonic acid, and α-cyanocinnamic acid; semi-ester compounds which are reaction products of hydroxyl group-containing acrylates and dibasic acid anhydrides; and semi-ester compounds which are reaction products of vinyl group-containing monoglycidyl ethers or vinyl group-containing monoglycidyl esters and dibasic acid anhydrides.

[0056] Examples of photopolymerizable compounds having an α,β-unsaturated carbonyl group include α,β-unsaturated carboxylic acid esters of polyhydric alcohols, (meth)acrylates having a urethane bond, bisphenol-type (meth)acrylates, nonylphenoxypolyethylene oxyacrylates, α,β-unsaturated carboxylic acid adducts of glycidyl group-containing compounds, and alkyl (meth)acrylates.

[0057] Examples of α,β-unsaturated carboxylic acid esters of polyhydric alcohols include polyethylene glycol di(meth)acrylate having 2 to 14 ethylene groups, polypropylene glycol di(meth)acrylate having 2 to 14 propylene groups, polyethylene / polypropylene glycol di(meth)acrylate having 2 to 14 ethylene groups and 2 to 14 propylene groups, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, PO-modified trimethylolpropane tri(meth)acrylate, EO,PO-modified trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, and (meth)acrylate compounds having a skeleton derived from dipentaerythritol or pentaerythritol.

[0058] Component (B) may contain polyalkylene glycol di(meth)acrylate from the viewpoint of improving the flexibility of the resist pattern. The polyalkylene glycol di(meth)acrylate may have at least one of an EO group and a PO group, or it may have both an EO group and a PO group. In a polyalkylene glycol di(meth)acrylate having both an EO group and a PO group, the EO group and the PO group may be present in a continuous, block-like manner or randomly. The PO group may be either an oxy-n-propylene group or an oxyisopropylene group. In the case of a (poly)oxyisopropylene group, the secondary carbon of the propylene group may be bonded to an oxygen atom, or the primary carbon may be bonded to an oxygen atom.

[0059] Examples of commercially available polyalkylene glycol di(meth)acrylates include FA-023M, FA-024M (manufactured by Resonaq Corporation), and NK Ester 9PG (manufactured by Shin Nakamura Chemical Industry Co., Ltd.).

[0060] Component (B) may include a (meth)acrylate having a urethane bond, from the viewpoint of improving the flexibility of the resist pattern. Examples of (meth)acrylates having a urethane bond include addition products of a (meth)acrylic monomer having an OH group at the β position and a diisocyanate (isophorone diisocyanate, 2,6-toluene diisocyanate, 2,4-toluene diisocyanate, 1,6-hexamethylene diisocyanate, etc.), tris((meth)acryloxytetraethylene glycol isocyanate) hexamethylene isocyanurate, EO-modified urethane di(meth)acrylate, and EO,PO-modified urethane di(meth)acrylate.

[0061] Examples of commercially available EO-modified urethane di(meth)acrylate include UA-11 and UA-21EB (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.). Examples of commercially available EO,PO-modified urethane di(meth)acrylate include UA-13 (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.).

[0062] Component (B) may contain a (meth)acrylate compound having a skeleton derived from dipentaerythritol or pentaerythritol, from the viewpoint of facilitating the formation of thick resist patterns and improving resolution and adhesion in a balanced manner. The (meth)acrylate compound having a skeleton derived from dipentaerythritol or pentaerythritol may have four or more (meth)acryloyl groups and may be dipentaerythritol penta(meth)acrylate or dipentaerythritol hexa(meth)acrylate.

[0063] Component (B) may contain a bisphenol-type (meth)acrylate, or a bisphenol A-type (meth)acrylate, from the viewpoint of further improving resolution and peelability after curing. Examples of bisphenol A-type (meth)acrylates include 2,2-bis(4-((meth)acryloxypolyethoxy)phenyl)propane (EO-modified bisphenol A dimethacrylate), 2,2-bis(4-((meth)acryloxypolypropoxy)phenyl)propane (PO-modified bisphenol A dimethacrylate), 2,2-bis(4-((meth)acryloxypolybutoxy)phenyl)propane (BO-modified bisphenol A dimethacrylate), and 2,2-bis(4-((meth)acryloxypolyethoxypolypropoxy)phenyl)propane (EO,PO-modified bisphenol A dimethacrylate). Among these, component (B) may be 2,2-bis(4-(meth)acryloxypolyethoxy)phenyl)propane (EO-modified bisphenol A dimethacrylate) from the viewpoint of further improving resolution and pattern formation.

[0064] Commercially available bisphenol A (meth)acrylate products include BPE-200, BPE-500 (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), FA-321M (manufactured by Resonaq Corporation), and BP-2EM (manufactured by Kyoeisha Chemical Co., Ltd.).

[0065] Examples of nonylphenoxypolyethylene oxyacrylates include nonylphenoxytetraethylene oxyacrylate, nonylphenoxypentaethylene oxyacrylate, nonylphenoxyhexaethylene oxyacrylate, nonylphenoxyheptaethylene oxyacrylate, nonylphenoxyoctaethylene oxyacrylate, nonylphenoxynonaethylene oxyacrylate, nonylphenoxydecaethylene oxyacrylate, and nonylphenoxyundaethylene oxyacrylate.

[0066] The content of component (B) may be 10 to 70 parts by mass, 15 to 60 parts by mass, or 20 to 50 parts by mass per 100 parts by mass of the total amount of components (A) and (B). When the content of component (B) is within this range, the strength of the photo-cured portion of the photosensitive layer tends to be better.

[0067] Component (A) and component (B) may be the main components of the photosensitive resin composition. The total content of component (A) and component (B) may be, for example, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, and 99% by mass or less, based on the total amount of the photosensitive resin composition.

[0068] (C) Component: Photopolymerization initiator The (C) component is not particularly limited as long as it is a component that can polymerize the (B) component, and can be appropriately selected from commonly used photopolymerization initiators. The (C) component can be used alone or in combination of two or more types.

[0069] Examples of component (C) include photopolymerization initiators such as acylphosphine oxides, oxime esters, aromatic ketones, quinones, alkylphenones, imidazoles, acridines, phenylglycines, and coumarins.

[0070] As component (C), a hexaarylbiimidazole compound, an acridine compound, or an imidazole compound may be used to improve sensitivity and resolution in a balanced manner.

[0071] Examples of hexaarylbiimidazole compounds include 2-(o-chlorophenyl)-4,5-diphenylbiimidazole, 2,2',5-tris-(o-chlorophenyl)-4-(3,4-dimethoxyphenyl)-4',5'-diphenylbiimidazole, 2,4-bis-(o-chlorophenyl)-5-(3,4-dimethoxyphenyl)-diphenylbiimidazole, 2,4,5-tris-(o-chlorophenyl)-diphenylbiimidazole, and 2-(o-chlorophenyl)-bis-4,5-(3,4-dimethoxyphenyl)-biimidazole. Examples include 2,2'-bis-(2-fluorophenyl)-4,4',5,5'-tetrakis-(3-methoxyphenyl)-biimidazole, 2,2'-bis-(2,3-difluorophenyl)-4,4',5,5'-tetrakis-(3-methoxyphenyl)-biimidazole, 2,2'-bis-(2,4-difluorophenyl)-4,4',5,5'-tetrakis-(3-methoxyphenyl)-biimidazole, and 2,2'-bis-(2,5-difluorophenyl)-4,4',5,5'-tetrakis-(3-methoxyphenyl)-biimidazole.

[0072] Among these, the hexaarylbiimidazole compound may be a 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer from the viewpoint of sensitivity and adhesion. As a 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2-biimidazole is commercially available from Hodogaya Chemical Co., Ltd. under the product name "B-CIM".

[0073] Examples of acridine compounds include 9-phenylacridine, 9-(p-methylphenyl)acridine, 9-(m-methylphenyl)acridine, 9-(p-chlorophenyl)acridine, 9-(m-chlorophenyl)acridine, 9-aminoacridine, 9-dimethylaminoacridine, 9-diethylaminoacridine, 9-pentylaminoacridine, 1,2-bis(9-acridinyl)ethane, 1,4-bis(9-acridinyl)butane, 1,6-bis(9-acridinyl)hexane, and 1,8-bis(9-acridinyl) Examples include lysinyl octane, 1,10-bis(9-acridinyl)decane, 1,12-bis(9-acridinyl)dodecane, 1,14-bis(9-acridinyl)tetradecane, 1,16-bis(9-acridinyl)hexadecane, 1,18-bis(9-acridinyl)octadecane, 1,20-bis(9-acridinyl)eicosane, 1,3-bis(9-acridinyl)-2-oxapropane, 1,3-bis(9-acridinyl)-2-thiapropane, and 1,5-bis(9-acridinyl)-3-thiapentane.

[0074] Examples of imidazole compounds include 2-(o-chlorophenyl)-4,5-diphenylbiimidazole, 2,2',5-tris-(o-chlorophenyl)-4-(3,4-dimethoxyphenyl)-4',5'-diphenylbiimidazole, 2,4-bis-(o-chlorophenyl)-5-(3,4-dimethoxyphenyl)-diphenylbiimidazole, 2,4,5-tris-(o-chlorophenyl)-diphenylbiimidazole, 2-(o-chlorophenyl)-bis-4,5-(3,4-dimethoxyphenyl)-biimidazole, and 2,2'- Examples include bis-(2-fluorophenyl)-4,4',5,5'-tetrakis-(3-methoxyphenyl)-biimidazole, 2,2'-bis-(2,3-difluorophenyl)-4,4',5,5'-tetrakis-(3-methoxyphenyl)-biimidazole, 2,2'-bis-(2,4-difluorophenyl)-4,4',5,5'-tetrakis-(3-methoxyphenyl)-biimidazole, and 2,2'-bis-(2,5-difluorophenyl)-4,4',5,5'-tetrakis-(3-methoxyphenyl)-biimidazole.

[0075] The content of component (C) may be 0.1 to 15 parts by mass, 0.5 to 10 parts by mass, or 1 to 8 parts by mass per 100 parts by mass of the total amount of components (A) and (B). When the content of component (C) is 0.1 parts by mass or more, the photosensitivity, resolution, and adhesion tend to improve, and when it is 10 parts by mass or less, the resist pattern formation properties tend to be superior.

[0076] (D) Component: Sensitizer The photosensitive resin composition according to this embodiment may further contain a sensitizer (hereinafter sometimes referred to as "(D) component"). By containing component (D) in the photosensitive resin composition, when exposed to light having a peak within a specific wavelength range, a maximum absorption can be provided near that specific wavelength range, thereby increasing the sensitivity of the photosensitive resin composition. Component (D) can be used alone or in combination of two or more types.

[0077] Examples of component (D) include dialkylaminobenzophenone compounds, pyrazoline compounds, anthracene compounds, coumarin compounds, xanthone compounds, thioxanthone compounds, oxazole compounds, benzoxazole compounds, thiazole compounds, benzothiazole compounds, triazole compounds, stilbene compounds, triazine compounds, thiophene compounds, naphthalimide compounds, triarylamine compounds, and aminoacridine compounds. Component (D) may also contain dialkylaminobenzophenone compounds from the viewpoint of further improving resolution.

[0078] Examples of dialkylaminobenzophenone compounds include 4,4'-bis(dimethylamino)benzophenone and 4,4'-bis(diethylamino)benzophenone.

[0079] The content of component (D) may be 0.01 to 5 parts by mass, 0.01 to 1 part by mass, or 0.01 to 0.2 parts by mass per 100 parts by mass of the total amount of components (A) and (B).

[0080] (E) Component: Photochromic agent. The photosensitive resin composition may further contain a photochromic agent (hereinafter sometimes referred to as "(E) component") to enhance the sensitivity of the photosensitive resin composition. The photochromic agent may be an amine compound. Examples of photochromic agents include tribromophenylsulfone, leucocrystal violet, diphenylamine, benzylamine, triphenylamine, diethylaniline, and o-chloroaniline.

[0081] Other Components The photosensitive resin composition according to this embodiment may further contain additives as needed, such as polymerization inhibitors, dyes, adhesion promoters, thermal color inhibitors, plasticizers, pigments, fillers, defoamers, flame retardants, leveling agents, release accelerators, antioxidants, fragrances, imaging agents, and thermal crosslinking agents. These additives can be used individually or in combination of two or more.

[0082] Examples of polymerization inhibitors include catechol compounds (such as 4-tert-butylcatechol) and hindered amines (such as 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl).

[0083] Examples of dyes include malachite green, Victoria pure blue, brilliant green, and methyl violet.

[0084] Examples of adhesion-imparting agents include triazoles (benzotriazole, tolyltriazole, carboxybenzotriazole, 1-hydroxybenzotriazole, etc.), imidazoles (1H-imidazole, 2-methylimidazole, 2-undecylimidazole, 2-ethyl-4-methylimidazole, etc.), and tetrazoles (1H-tetrazole, 5-amino-1H-tetrazole, 5,5'-azobis-1H-tetrazole, 1-methyl-5-mercapto-1H-tetrazole, 1-phenyl-5-mercapto-1H-tetrazole, etc.).

[0085] The photosensitive resin composition can be dissolved in solvents such as methanol, ethanol, acetone, methyl ethyl ketone, methyl cellosolve, ethyl cellosolve, toluene, N,N-dimethylformamide, propylene glycol monomethyl ether, or a mixture thereof, as needed, to prepare a solution with a solid content of about 30 to 60% by mass.

[0086] [Photosensitive Element] Figure 1 is a schematic cross-sectional view showing one embodiment of a photosensitive element. The photosensitive element 1 according to this embodiment comprises a support film 2 and a photosensitive layer 3 formed on the support film 2, the photosensitive layer 3 containing the above-mentioned photosensitive resin composition. The photosensitive element 1 may also include other layers, such as a protective layer 4, which may be provided as needed. When using the photosensitive element according to this embodiment, the photosensitive layer may be laminated onto a substrate and then exposed without peeling off the support film.

[0087] Examples of support films include polyester films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene-2,6-naphthalate (PEN), as well as polyolefin films such as polypropylene and polyethylene. Among these, PET film may be used as the support film because it is readily available and has excellent handling properties in the manufacturing process (especially in terms of heat resistance, thermal shrinkage rate, and breaking strength).

[0088] The haze of the support film may be 0.01 to 1.0% or 0.01 to 0.5%. A haze of 0.01% or more tends to make the support film itself easier to manufacture, while a haze of 1.0% or less tends to reduce the minute defects that may occur in the resist pattern. "Haze" means the degree of cloudiness. In this specification, haze refers to the value measured using a commercially available cloudiness meter (turbidimeter) in accordance with the method specified in JIS K7136:2000. Haze can be measured with a commercially available turbidimeter such as the NDH-5000 (manufactured by Nippon Denshoku Industries Co., Ltd.).

[0089] The thickness of the support film may be 1 to 100 μm, 5 to 60 μm, 10 to 50 μm, 10 to 40 μm, 10 to 30 μm, or 10 to 25 μm. When the thickness of the support film is 1 μm or more, it tends to suppress tearing of the support film when peeling it off. Also, when the thickness of the support film is 100 μm or less, it is possible to suppress a decrease in resolution when exposure is performed through the support film.

[0090] The photosensitive element may further include a protective layer as needed. The protective layer may be a film such that the adhesive force between the photosensitive layer and the protective layer is less than the adhesive force between the photosensitive layer and the support film, or a low-fisheye film may be used. Specifically, examples include those that can be used as the support film mentioned above. From the viewpoint of release from the photosensitive layer, it may be a polyethylene film.

[0091] The thickness of the protective layer varies depending on the application, but may be 1 to 100 μm, 5 to 50 μm, 5 to 30 μm, or 15 to 30 μm. A protective layer thickness of 1 μm or more tends to suppress tearing of the protective layer when it is peeled off, while a protective layer thickness of 100 μm or less tends to be cost-effective.

[0092] A photosensitive element can be manufactured, for example, as follows: a solution of a photosensitive resin composition (coating solution) is applied to a support film to form a coating layer, and this coating is dried to form a photosensitive layer. Then, the side of the photosensitive layer opposite to the support film is covered with a protective layer to obtain a photosensitive element comprising a support film, a photosensitive layer formed on the support film, and a protective layer laminated on the photosensitive layer.

[0093] The coating solution can be applied to the support film by known methods such as roll coating, comma coating, gravure coating, air knife coating, die coating, and bar coating.

[0094] The drying of the coating layer is not particularly limited as long as at least a portion of the organic solvent can be removed from the coating layer. Drying conditions may be, for example, 70 to 150°C for 5 to 30 minutes. After drying, the amount of residual solvent in the photosensitive layer may be 2% by mass or less, from the viewpoint of preventing solvent diffusion in subsequent processes.

[0095] The thickness of the photosensitive layer in a photosensitive element can be appropriately selected depending on the application, but the thickness after drying may be 1 to 100 μm, 5 to 50 μm, or 10 to 40 μm. A thickness of 1 μm or more facilitates industrial coating and improves productivity. A thickness of 100 μm or less improves adhesion and resolution.

[0096] The transmittance of the photosensitive layer to ultraviolet light at a wavelength of 365 nm may be 5-75%, 7-60%, or 10-40%. A transmittance of 5% or higher tends to improve adhesion, while a transmittance of 75% or lower tends to improve resolution. The transmittance can be measured using a UV spectrometer.

[0097] The form of the photosensitive element is not particularly limited. The form of the photosensitive element may be, for example, a sheet, or it may be wound in a roll on a core. When wound in a roll, the support film may be wound on the outside. Examples of the core include plastics such as polyethylene resin, polypropylene resin, polystyrene resin, polyvinyl chloride resin, or ABS resin (acrylonitrile-butadiene-styrene copolymer).

[0098] An end separator may be installed on the end face of the roll-shaped photosensitive element for end face protection, or a moisture-proof end separator may be installed to prevent edge fusion (resin seepage). The photosensitive element may be wrapped and packaged in a black sheet with low moisture permeability.

[0099] Photosensitive elements can be suitably used, for example, in the resist pattern formation method described later. In particular, from the viewpoint of resolution, photosensitive elements are suitable for application in manufacturing methods that form conductive patterns by plating.

[0100] [Method for forming a resist pattern] The method for forming a resist pattern according to this embodiment comprises: (i) forming a photosensitive layer on a substrate using the photosensitive resin composition or the photosensitive element (photosensitive layer formation step); (ii) irradiating at least a part (a predetermined part) of the photosensitive layer with active light to form a photocured portion (exposure step); and (iii) removing at least a part other than the photocured portion from the substrate to form a resist pattern (development step). The method for forming a resist pattern according to this embodiment may include other steps as needed. The resist pattern can also be called a photocured pattern of the photosensitive resin composition or a relief pattern. The method for forming a resist pattern can also be called a method for manufacturing a substrate with a resist pattern.

[0101] (i) Photosensitive layer formation process As a method for forming a photosensitive layer on a substrate, for example, the photosensitive resin composition may be applied and dried, or the protective layer may be removed from the photosensitive element and then the photosensitive layer of the photosensitive element may be pressed onto the substrate while heating. When a photosensitive element is used, a laminate is obtained in which the substrate, the photosensitive layer and the support film are stacked in order. The substrate is not particularly limited, but typically examples include a circuit forming substrate having an insulating layer and a conductive layer formed on the insulating layer, or a die pad (lead frame substrate) such as an alloy substrate.

[0102] When a photosensitive element is used, the photosensitive layer formation process is preferably carried out under reduced pressure from the viewpoint of adhesion and conformability. Heating of the photosensitive layer and / or substrate during pressing may be carried out at a temperature of 70 to 130°C. Pressing should be done at approximately 0.1 to 1.0 MPa (1 to 10 kgf / cm). ２ The process may be carried out with a pressure of a certain degree, but these conditions are selected as appropriate as needed. Note that if the photosensitive layer is heated to 70-130°C, preheating the substrate is not necessary; however, preheating the substrate can be performed to further improve adhesion and conformability.

[0103] (ii) Exposure process In the exposure process, an active light is irradiated onto at least a portion of the photosensitive layer formed on the substrate, causing the irradiated portion to photocur and form a latent image. At this time, if a support film is present on the photosensitive layer, if the support film is transparent to the active light, the active light can be irradiated through the support film. However, if the support film is light-shielding, the support film is removed before irradiating the photosensitive layer with the active light.

[0104] One exposure method is to irradiate an active light image-like pattern through a negative or positive mask pattern called artwork (mask exposure method). Alternatively, exposure methods that irradiate an active light image-like pattern using projection exposure, or direct drawing exposure methods such as LDI (Laser Direct Imaging) exposure or DLP (Digital Light Processing) exposure may be employed.

[0105] A known light source can be used for the active light ray. Examples of active light ray sources include carbon arc lamps, mercury vapor arc lamps, high-pressure mercury lamps, xenon lamps, gas lasers (argon lasers, etc.), solid-state lasers (YAG lasers, etc.), semiconductor lasers, etc., which effectively emit ultraviolet or visible light.

[0106] (iii) Development process In the development process, at least a portion of the photosensitive layer other than the photocured portion is removed from the substrate, thereby forming a resist pattern on the substrate.

[0107] If a support film is present on the photosensitive layer, the support film is removed before removing (developing) the areas other than the photocured area (unexposed areas). There are two development methods: wet development and dry development, with wet development being more widely used.

[0108] In the case of wet development, development is carried out using a developer solution corresponding to the photosensitive resin composition and a known development method. Examples of development methods include the dip method, paddle method, spray method, brushing, slashing, scrubbing, and agitation immersion. From the viewpoint of improving resolution, the development method may also be a high-pressure spray method. Two or more of these development methods may also be combined.

[0109] The composition of the developer is appropriately selected according to the composition of the photosensitive resin composition described above. Examples of developers include alkaline aqueous solutions and organic solvent developers.

[0110] From the viewpoint of safety, stability, and ease of use, the developer may be an alkaline aqueous solution. Examples of bases in alkaline aqueous solutions include alkali hydroxides such as lithium, sodium, or potassium hydroxides; alkali carbonates such as lithium, sodium, potassium, or ammonium carbonates and bicarbonates; alkali metal phosphates such as potassium phosphate and sodium phosphate; alkali metal pyrophosphates such as sodium pyrophosphate and potassium pyrophosphate; borax, sodium metasilicate, tetramethylammonium hydroxide, ethanolamine, ethylenediamine, diethylenetriamine, 2-amino-2-hydroxymethyl-1,3-propanediol, 1,3-diaminopropanol-2, and morpholine.

[0111] Examples of alkaline aqueous solutions include dilute solutions of 0.1 to 5% by mass of sodium carbonate, dilute solutions of 0.1 to 5% by mass of potassium carbonate, dilute solutions of 0.1 to 5% by mass of sodium hydroxide, and dilute solutions of 0.1 to 5% by mass of sodium tetraborate. The pH of the alkaline aqueous solution may be in the range of 9 to 14, and its temperature can be adjusted according to the alkaline developability of the photosensitive layer. The alkaline aqueous solution may contain, for example, a surfactant, an antifoaming agent, and a small amount of organic solvent to promote development.

[0112] Examples of organic solvents used in alkaline aqueous solutions include acetone, ethyl acetate, alkoxyethanol having an alkoxy group with 1 to 4 carbon atoms, ethyl alcohol, isopropyl alcohol, butyl alcohol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether.

[0113] Examples of organic solvents used in organic solvent developers include 1,1,1-trichloroethane, N-methyl-2-pyrrolidone, N,N-dimethylformamide, cyclohexanone, methyl isobutyl ketone, and γ-butyrolactone. To prevent ignition, water may be added to these organic solvents to form an organic solvent developer. The amount of water added may be in the range of 1 to 20% by mass.

[0114] In the resist pattern formation method of this embodiment, after removing the uncured portion in the development step, heating at 60 to 250°C or 0.2 to 10 J / cm is performed as necessary. ２ The system may also include a step to further harden the resist pattern by performing exposure.

[0115] [Method for forming wiring patterns] The method for forming wiring patterns according to this embodiment includes the step of forming a conductor pattern by etching or plating a substrate on which a resist pattern has been formed by the resist pattern forming method described above. The method for forming wiring patterns may further include the step of removing the photocured portion with an alkaline aqueous solution after the etching or plating process.

[0116] In the plating process, a resist pattern formed on the substrate is used as a mask, and the conductive layer provided on the substrate is plated. After the plating process, the resist is removed by removing the resist pattern as described later, and the conductive layer that was covered by this resist may be further etched to form a conductive pattern. Examples of plating processes include electrolytic plating and electroless plating. The plating process may be electroless plating.

[0117] In the etching process, a resist pattern formed on the substrate is used as a mask to etch away the conductive layer provided on the substrate, thereby forming a conductive pattern. The etching method is appropriately selected depending on the conductive layer to be removed. Examples of etching solutions include cupric chloride solution, ferric chloride solution, alkaline etching solution, and hydrogen peroxide-based etching solution.

[0118] After etching or plating, the resist pattern on the substrate may be removed. The resist pattern can be removed, for example, by using an aqueous solution that is even more strongly alkaline than the alkaline aqueous solution used in the development step. Examples of strongly alkaline aqueous solutions include 1 to 10% by mass sodium hydroxide aqueous solution and 1 to 10% by mass potassium hydroxide aqueous solution. The resist pattern may also be removed using a strongly alkaline aqueous solution at 45 to 65°C.

[0119] After plating and removing the resist pattern, the conductive layer covered with the resist can be further etched to form a conductive pattern, thereby manufacturing the desired printed circuit board. The etching method used in this process is appropriately selected depending on the conductive layer to be removed. For example, the etching solution described above can be applied.

[0120] The wiring pattern formation method according to this embodiment is applicable not only to the manufacture of single-layer printed circuit boards but also to the manufacture of multi-layer printed circuit boards, and furthermore, to the manufacture of printed circuit boards having small-diameter through-holes.

[0121] The present disclosure will be described below in detail based on examples, but the present disclosure is not limited thereto.

[0122] [Synthesis of Polymers] (Example 1-1) Solution X1 was prepared by adding styrene (monomer 1), benzyl methacrylate (monomer 2), methacrylic acid (monomer 3), N-tert-butylacrylamide (acrylamide 1), methyl cellosolve (solvent 1), and toluene (solvent 2) to a flask equipped with a stirrer, reflux condenser, thermometer, dropping funnel, and nitrogen inlet tube. Separately, Solution X2 was prepared by adding methyl cellosolve (solvent 1) and toluene (solvent 2) to 2,2'-azobis (isobutyronitrile) (polymerization initiator). The amounts of each component (in g) are shown in Table 1. Note that the amount of solvent 1 (in g) shown in Table 1 is the total amount of solvent 1 in solution X1 and solvent 1 in solution X2, and the amount of solvent 2 (in g) shown in Table 1 is the total amount of solvent 2 in solution X1 and solvent 2 in solution X2. Solution X1 was heated to 70°C under a nitrogen atmosphere while stirring, and solution X2 was added dropwise to the flask over 30 minutes. Then, the mixture was stirred at 75°C for 90 minutes, at 85°C for 2 hours, and at 95°C for 2 hours, and the reaction mixture was cooled to room temperature (25°C, the same applies below). After removing the toluene from the reaction mixture under reduced pressure, the residue was added to water, and the precipitate was collected and dried to obtain polymer A1-1.

[0123] (Comparative Example 1-1) Polymer a1-1 was obtained in the same manner as in Example 1-1, except that each component was used in the amounts (unit: g) shown in Table 1.

[0124] (Examples 2-1 to 2-7 and Comparative Examples 2-1, 2-2) Solution Y1 was prepared by adding styrene (monomer 1), benzyl methacrylate (monomer 2), methacrylic acid (monomer 3), hydroxyethyl methacrylate (monomer 4), N-tert-butylacrylamide (acrylamide 1), N-n-butylacrylamide (acrylamide 2), N-(1,1,3,3-tetramethylbutyl)acrylamide (acrylamide 3), diacetone acrylamide (acrylamide 4), 2-ethylhexyl-β-mercaptopropionic acid (chain transfer agent), toluene (solvent 2), and 1-methoxy-2-propanol (solvent 3) to a flask equipped with a stirrer, reflux condenser, thermometer, dropping funnel, and nitrogen inlet tube. Table 2 shows the amounts (in g) of each component. Note that the amount (in g) of solvent 2 shown in Table 2 is the total amount of solvent 2 in solution Y1 and solvent 2 in solution Y2, and the amount (in g) of solvent 3 shown in Table 2 is the total amount of solvent 3 in solution Y1 and solvent 3 in solution Y2. Solution Y1 was heated to 70°C while stirring under a nitrogen atmosphere, and solution Y2 was added dropwise to the flask over 30 minutes. Then, the mixture was stirred at 75°C for 90 minutes, at 85°C for 2 hours, and at 95°C for 2 hours, and the reaction mixture was cooled to room temperature. After removing toluene from the reaction mixture under reduced pressure, the residue was added to water, and the precipitate was collected and dried to obtain polymers A2-1 to A2-7 and polymers a2-1 and a2-2.

[0125] The polymer's Mw was measured by gel permeation chromatography (GPC) and derived by conversion using a calibration curve for standard polystyrene. The calibration curve was approximated by a cubic universal calibration curve according to JIS K 7252-2 (2016), using a five-sample set of standard polystyrene (PStQuick MP-H, PStQuick B (manufactured by Tosoh Corporation)). The GPC conditions are shown below.

[0126] (GPC conditions) Pump, detector: HLC-8320 (Tosoh Corporation) Column: TSKgel SuperMultipore HZ-M (3 tubes) (Tosoh Corporation) Eluent: Tetrahydrofuran (THF) Measurement temperature: 40°C Flow rate: 0.35 mL / min

[0127]

[0128]

[0129] [Preparation of Photosensitive Resin Compositions] (Example 3-1 and Comparative Example 3-1) (Examples 4-1 to 4-7 and Comparative Examples 4-1 and 4-2) The photosensitive resin compositions of Example 3-1 and Comparative Example 3-1, and Examples 4-1 to 4-7 and Comparative Examples 4-1 and 4-2 were prepared by mixing each component in the amounts (unit: parts by mass) shown in Table 3 with 60 parts by mass of each polymer (solid content) as component (A).

[0130] The details of each component shown in Table 3 are as follows: (B) Ingredients: Photopolymerizable compounds B-1: EO-modified bisphenol A dimethacrylate (manufactured by Resonaq Corporation, product name: FA-321M) B-2: EO-modified bisphenol A dimethacrylate (manufactured by Kyoeisha Chemical Co., Ltd., product name: BP-2EM) B-3: EO-modified polypropylene glycol dimethacrylate (manufactured by Resonaq Corporation, product name: FA-024M) (C) Ingredients: Photopolymerization initiator C-1: 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenylbiimidazole (manufactured by Hodogaya Chemical Co., Ltd., product name: B-CIM) (D) Ingredients: Sensitizer D-1: 4,4'-bis(diethylamino)benzophenone (manufactured by Hodogaya Chemical Co., Ltd.) (E) Ingredients: Photochromic agent E-1: Leucocrystal violet (manufactured by Yamada Chemical Co., Ltd.) Other ingredients / polymerization inhibitors F-1: 4-tert-butylcatechol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) - Dye G-1: Malachite green (manufactured by Osaka Organic Chemical Industry Co., Ltd.) - Adhesion agent H-1: Benzotriazole derivative (manufactured by Sanwa Chemicals Co., Ltd., product name: SF-808H) Solvent I-1: Toluene I-2: Methanol I-3: Acetone

[0131]

[0132] [Photosensitive Element] A photosensitive resin composition was applied to a 25 μm thick PET film (Teijin Film Solutions Limited (now Toyobo Co., Ltd.), product name: G2) (support film), and dried in a 100°C hot air convection dryer for 4 minutes to form a photosensitive layer with a thickness of 25 μm after drying. A polypropylene film (Tamapoly Co., Ltd., product name: NF-13) (protective layer) was laminated onto this photosensitive layer to obtain a photosensitive element in which the support film, photosensitive layer, and protective layer were laminated in this order.

[0133] [Evaluation] The following evaluations were performed using a photosensitive element. The results are shown in Tables 4 and 5.

[0134] <Stickiness> After heating the photosensitive element to 30°C, the protective film was removed and the presence or absence of stickiness on the surface of the photosensitive layer was checked.

[0135] <Followability 1> Ten layers of photosensitive material, obtained by peeling off the protective and support films of the photosensitive element, were stacked and laminated at 80°C and 0.4 MPa for 20 seconds to prepare an evaluation sample (thickness: approximately 250 μm). An 8 mm diameter sample stage was set up in a viscoelasticity measuring device (product name: ARES G2, manufactured by TA Instruments). After setting the evaluation sample on the sample stage, the complex viscosity was measured while heating from 30°C to 160°C at a heating rate of 5°C / min. The followability was evaluated based on the complex viscosity at 105°C. If the complex viscosity at 105°C was less than 500 Pa·s, it was evaluated as having excellent followability and was evaluated as "A", and if it was 500 Pa·s or more, it was evaluated as "B". When the complex viscosity at 105°C is low, the resin can follow the recesses of the circuit board, etc., and it can be said that it has excellent followability.

[0136] <Followability 2> (Preparation of Laminate) A copper-clad laminate (manufactured by Resonac Co., Ltd., product name: MCL-E-67) was prepared by laminating copper foil (thickness 35 μm) on both sides of a glass fiber reinforced epoxy resin layer. A photoresist pattern with a line width / space width of 100 μm / 100 μm was formed on one copper surface of the copper-clad laminate, and then it was immersed in an etching solution. Next, the photoresist was removed, and grooves with a width of 100 μm, a spacing of 100 μm, and a depth of 15 μm were formed in the copper-clad laminate.

[0137] A photosensitive element was laminated onto the copper surface of a copper-clad laminate on a grooved surface of the laminate. Lamination was performed using a 110°C heat roll, removing the protective layer while applying a pressing pressure of 0.4 MPa and a roll speed of 1.0 m / min. In this way, a laminate was obtained in which the copper-clad laminate, the photosensitive layer, and the support film were laminated in this order.

[0138] (Observation of voids) Using an ultraviolet exposure machine (Mikasa Corporation, product name: MA-20) equipped with a photomask having a rectangular pattern with a line width / space width of 100 μm / 100 μm, the photomask pattern and groove direction are perpendicular to the support film surface of the laminate, and exposure is performed at 10 mJ / cm². ２ Ultraviolet light was irradiated onto the surface. Illuminance was measured using an ultraviolet illuminometer (Ushio Inc., product name: UIT-150) fitted with a 365 nm probe. After exposure, the support film was peeled off, and the unexposed areas were removed by spraying a 1% by mass sodium carbonate aqueous solution onto the photosensitive layer at 30°C for 90 seconds (development process). After development, the presence or absence of voids between the photosensitive layer and the grooves of the copper-clad laminate was observed using a scanning electron microscope (Hitachi High-Tech Corporation, product name: SU1510). If no voids were observed, the surface was evaluated as having excellent conformability as "A," and if voids were observed, it was evaluated as "B."

[0139] <Resolution> (Preparation of Laminate) A copper-clad laminate (manufactured by Resonaq Corporation, product name: MCL-E679) was prepared by laminating copper foil (18 μm thick) that had been treated with CZ roughening on both sides of a glass fiber reinforced epoxy resin layer. The photosensitive layer of the photosensitive element was laminated onto the copper-clad laminate that had been treated with CZ roughening at 60°C and a pressure of 0.4 MPa to obtain a laminate in which the copper-clad laminate, the photosensitive layer, and the support film were laminated in this order.

[0140] (Resolution Evaluation) Using an ultraviolet exposure machine (Mikasa Corporation, product name: MA-20) equipped with a photomask on which five rectangular patterns with a line width / space width ratio of 1:1 were formed, the support film surface of the laminate was exposed at 10 mJ / cm². ２ Ultraviolet light was applied. Illuminance was measured using an ultraviolet illuminometer (Ushio Inc., product name: UIT-150) fitted with a 365 nm probe. After exposure, the support film was peeled off, and the unexposed areas were removed by spraying a 1% by mass sodium carbonate aqueous solution onto the photosensitive layer at 30°C for 90 seconds (development process). The pattern of the photoresist after development was checked, and the smallest line width that could be resolved properly was recorded. The smaller the smallest line width (for example, the line width / space width is 8 μm:8 μm or less), the better the resolution. (Rectangular pattern with line width / space width of 1:1 (unit: μm)) 100:100, 80:80, 60:60, 40:40, 30:30, 20:20, 15:15, 10:10, 8:8, 7:7, 6:6, 5:5, 4:4, 3:3, 2:2, 1:1

[0141] <Storage Stability> An evaluation sample was prepared by stacking 10 photosensitive elements cut into 20 mm squares. The evaluation sample was placed in a constant temperature and humidity chamber, a weight was placed on top of the sample, and it was stored in a constant temperature and humidity chamber at 40°C and 50% for 70 hours. The mass loss rate (%) of the evaluation sample was measured based on the following formula. The smaller the mass loss rate (%) of the evaluation sample (for example, less than 2.0%), the less resin seepage there is, and the better the storage stability. Mass loss rate (%) = [(Mass of evaluation sample before storage - Mass of evaluation sample after storage) / (Mass of evaluation sample before storage)] × 100

[0142]

[0143]

[0144] As shown in Tables 4 and 5, the photosensitive resin compositions of the examples containing the specified polymer exhibited excellent resolution and storage stability, whereas the photosensitive resin compositions of the comparative examples not containing the specified polymer lacked sufficient resolution and storage stability in at least one of these properties. The photosensitive resin compositions of the examples were non-sticky and also exhibited excellent conformability, indicating that the specified polymer can impart these properties. These results confirm that the polymer of this disclosure can improve the storage stability of the photosensitive resin composition while maintaining its resolution.

[0145] 1...Photosensitive element, 2...Support film, 3...Photosensitive layer, 4...Protective layer.

Claims

1. A polymer comprising a structural unit represented by the following formula (I) and a structural unit having a carboxyl group. [In formula (I), R １ R represents a hydrogen atom or a methyl group. ２ [This represents an alkyl group, aryl group, aralkyl group, or hydrogen atom.] 2. The polymer according to claim 1, wherein the content of the structural unit represented by formula (I) is 5 to 50% by mass based on the total amount of the polymer.

3. A photosensitive resin composition comprising a binder resin containing the polymer described in claim 1 or 2, a photopolymerizable compound, and a photopolymerization initiator.

4. The photosensitive resin composition according to claim 3, wherein the photopolymerization initiator comprises a hexaarylbiimidazole compound.

5. The photosensitive resin composition according to claim 3, further comprising a sensitizer.

6. The photosensitive resin composition according to claim 3, further comprising a photochromic agent.

7. A photosensitive element comprising a support film and a photosensitive layer formed on the support film, wherein the photosensitive layer contains the photosensitive resin composition described in claim 3.

8. A method for forming a resist pattern, comprising: forming a photosensitive layer on a substrate using the photosensitive resin composition described in claim 3; irradiating at least a portion of the photosensitive layer with an active light to form a photocurable portion; and removing at least a portion of the photosensitive layer other than the photocurable portion from the substrate to form a resist pattern.

9. A method for forming a resist pattern, comprising: forming a photosensitive layer on a substrate using the photosensitive element described in claim 7; irradiating at least a portion of the photosensitive layer with an active light to form a photocurable portion; and removing at least a portion of the photosensitive layer other than the photocurable portion from the substrate to form a resist pattern.

10. A method for forming a wiring pattern, comprising the step of etching or plating a substrate on which a resist pattern has been formed by the resist pattern forming method described in claim 8 to form a conductor pattern.

11. A method for forming a wiring pattern, comprising the step of etching or plating a substrate on which a resist pattern has been formed by the resist pattern forming method described in claim 9 to form a conductor pattern.

12. The method for forming a wiring pattern according to claim 10, further comprising the step of removing the photocured portion with an alkaline aqueous solution after the etching or plating process.

13. The method for forming a wiring pattern according to claim 11, further comprising the step of removing the photocured portion with an alkaline aqueous solution after the etching or plating process.

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