Photosensitive resin composition, dry film, cured product, and printed wiring board

Abstract

[Problem] To provide a photosensitive resin composition containing an acylphosphine oxide photopolymerization initiator that improves deep curability during exposure, wherein the insulation reliability of a cured product of the composition is good. [Solution] In a photosensitive resin composition containing a carboxyl group-containing resin, a photopolymerization initiator, and a thermosetting component, an acylphosphine oxide photopolymerization initiator having a specific structure is used as the photopolymerization initiator.

Description

Photosensitive resin composition, dry film, cured product, and printed circuit board

[0001] The present invention relates to a photosensitive resin composition, and more particularly to a photosensitive resin composition suitably used for forming an insulating layer. Furthermore, the present invention relates to a dry film having a resin layer formed from the photosensitive resin composition, a cured product of the resin layer of the photosensitive resin composition or the dry film, and a printed circuit board comprising the cured product.

[0002] With the recent trend towards miniaturization, lightness, and thinness of electronic devices, and the resulting increase in the precision and density of printed circuit boards, the mainstream method for forming the solder resist layer is now photosolder resist.

[0003] On the other hand, photopolymerization initiators are generally used to form solder resist layers using photosolder resists, and the appropriate photopolymerization initiator is selected and used depending on the composition of the photosensitive resin composition for forming the solder resist layer. There are various types of photopolymerization initiators, but among them, acylphosphine oxide-based photopolymerization initiators have a so-called photobleaching function, which allows for good curing of the deeper parts of the photosensitive resin composition. Photobleaching refers to the process when a photosensitive resin composition containing a photopolymerization initiator is exposed to light, and the photopolymerization initiator absorbs light in a specific wavelength range, generating radicals. The generation of radicals changes the structure, causing it to no longer absorb light in that wavelength range (making it easier to transmit light in that wavelength range during exposure). Therefore, because the photopolymerization initiator has such a photobleaching function, when a resin layer formed from a photosensitive resin composition is exposed, the exposure light can sufficiently reach the deeper parts, improving the deep curing properties of the resin layer. A typical example of an acylphosphine oxide-based photopolymerization initiator is (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide) (TPO), which is widely used today. For example, Patent Document 1 proposes a photosensitive resin composition in which a film can be formed by blending a specific resin, an acylphosphine oxide-based photopolymerization initiator, and a hydrogen abstraction-type photopolymerization initiator into a photosensitive resin composition, and an electrical insulating layer can be produced by exposing this film to light and then heat-curing it, and the film can be sufficiently cured to its depths.

[0004] On the other hand, there is still room for improvement in the insulation reliability of solder resist layers formed using acylphosphine oxide-based photopolymerization initiators with photobleaching capabilities. In particular, improving the insulation reliability of solder resist layers in fine wiring remains a technical challenge.

[0005] International Publication No. 2020 / 045024

[0006] Under these circumstances, when using an acylphosphine oxide-based photopolymerization initiator that can improve the deep curing properties when a photosensitive resin composition is exposed to light, a technical challenge exists in further improving the insulation reliability of the cured product of the photosensitive resin composition.

[0007] Therefore, the present invention aims to provide a photosensitive resin composition containing an acylphosphine oxide-based photopolymerization initiator that can improve deep curing properties during exposure, and further provides a photosensitive resin composition in which the cured product (i.e., the insulating layer) has good insulating reliability. Furthermore, another object of the present invention is to provide a dry film having a resin layer formed from such a photosensitive resin composition, a cured product of the resin layer of the photosensitive resin composition or the dry film, and a printed circuit board comprising the cured product.

[0008] As a result of diligent research, the present inventors have found that the above-mentioned problems can be solved by using an acylphosphine oxide-based photopolymerization initiator having a specific structure as the photopolymerization initiator in a photosensitive resin composition containing a carboxyl group-containing resin, a photopolymerization initiator, and a thermosetting component, and have completed the present invention. In other words, the gist of the present invention is as follows.

[0009] [1] A carboxyl group-containing resin, a photopolymerization initiator, and a thermosetting component, wherein the photopolymerization initiator is of the following general formula (I): [In the formula, R １ and R ２ Each independently represents an aryl group having 7 to 20 carbon atoms, which may be substituted with at least one of an alkyl group, an alkoxy group, and a phenyl group, or an arylcarbonyl group having 7 to 20 carbon atoms, which may be substituted with at least one of an alkyl group and an alkoxy group, R ３[1] A photosensitive resin composition characterized by being a compound having a substructure represented by [1], wherein [1] represents an aryl group having 7 to 20 carbon atoms, which may be substituted with a phenyl group or at least one of an alkyl group and an alkoxy group. [2] The photosensitive resin composition according to [1], wherein the carboxyl group-containing resin comprises a carboxyl group-containing resin obtained from a phenol compound as a starting material. [3] A dry film having a first film and a resin layer formed from the photosensitive resin composition according to [1] or [2] laminated on at least one surface of the first film. [4] A cured product obtained by curing the resin layer of the photosensitive resin composition according to [1] or [2], or the dry film according to [3]. [5] A printed circuit board comprising the cured product according to [4].

[0010] According to the present invention, it is possible to provide a photosensitive resin composition containing an acylphosphine oxide-based photopolymerization initiator that can improve deep curing properties during exposure, and further provides a photosensitive resin composition in which the cured product (i.e., insulating layer) has good insulating reliability. Furthermore, according to the present invention, it is possible to provide a dry film having a resin layer formed from such a photosensitive resin composition, a cured product of the resin layer of the photosensitive resin composition or the dry film, and a printed wiring board equipped with the cured product.

[0011] [Photosensitive Resin Composition] According to one aspect of the present invention, a photosensitive resin composition (hereinafter also referred to as "the photosensitive resin composition of the present invention") is provided. The photosensitive resin composition of the present invention can be suitably used for forming an insulating layer in printed circuit boards and the like. In particular, the photosensitive resin composition of the present invention contains an acylphosphine oxide-based photopolymerization initiator that can improve deep curing properties during exposure, and therefore has good deep curing properties. As a result, when a photosensitive resin composition layer is formed on a substrate and exposed, a cured product (i.e., an insulating layer) with good adhesion to the substrate can be formed. Furthermore, by using a compound having a specific structure as a photopolymerization initiator, the photosensitive resin composition of the present invention can form a cured product with good insulation reliability, particularly crack resistance and HAST (Highly Accelerated Stress Test System) resistance.

[0012] The photosensitive resin composition of the present invention contains a carboxyl group-containing resin, a photopolymerization initiator, and a thermosetting component as essential components. The components of the photosensitive resin composition of the present invention will be described in detail below. Note that commercially available components may be used, or components may be synthesized as appropriate.

[0013] (Carboxyl Group-Containing Resin) The photosensitive resin composition of the present invention contains a carboxyl group-containing resin. Various conventionally known resins having carboxyl groups in their molecules can be used as the carboxyl group-containing resin. By including a carboxyl group-containing resin in the photosensitive resin composition of the present invention, alkali developability can be imparted to the photosensitive resin composition. In particular, from the viewpoint of photocurability and developability of the photosensitive resin composition, a photosensitive carboxyl group-containing resin having an ethylenically unsaturated double bond in its molecule is preferred. The ethylenically unsaturated double bond in the molecule constituting the carboxyl group-containing resin is preferably derived from acrylic acid or methacrylic acid or derivatives thereof. When using only a carboxyl group-containing resin that does not have an ethylenically unsaturated double bond, it is necessary to use a compound having multiple ethylenically unsaturated groups in its molecule, i.e., a photopolymerizable monomer, as described later, in order to make the photosensitive resin composition photocurable. Specific examples of carboxyl group-containing resins include the following compounds (which may be either oligomers or polymers).

[0014] (1) A carboxyl group-containing resin obtained by copolymerization of an unsaturated carboxylic acid such as (meth)acrylic acid with an unsaturated group-containing compound such as styrene, α-methylstyrene, lower alkyl (meth)acrylate, or isobutylene.

[0015] (2) A carboxyl group-containing urethane resin obtained by polyaddition reaction of diisocyanates such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates with carboxyl group-containing dialcohol compounds such as dimethylolpropionic acid and dimethylolbutanoic acid, and diol compounds such as polycarbonate polyols, polyether polyols, polyester polyols, polyolefin polyols, acrylic polyols, bisphenol A alkylene oxide adduct diols, and compounds having phenolic hydroxyl groups and alcoholic hydroxyl groups.

[0016] (3) Diisocyanate and a bifunctional epoxy resin such as bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bixylenol type epoxy resin, or biphenol type epoxy resin, and a monocarboxylic acid compound having an ethylenically unsaturated double bond such as (meth)acrylic acid, a partially acid anhydride modified product, a carboxyl group-containing dialcohol compound, and a carboxyl group-containing photosensitive urethane resin obtained by polyaddition reactions of these compounds.

[0017] (4) A carboxyl group-containing photosensitive urethane resin obtained by adding a compound having one hydroxyl group and one or more (meth)acryloyl groups in the molecule, such as hydroxyalkyl (meth)acrylate, to the synthesis of the resin described in (2) or (3) above, and then (meth)acrylizing the terminal (meth)acrylic.

[0018] (5) A carboxyl group-containing photosensitive urethane resin in which a compound having one isocyanate group and one or more (meth)acryloyl groups in the molecule is added to the synthesis of the resin of (2) or (3) described above, and the terminal (meth)acrylic compound is formed by adding such a compound to the end (meth)acrylic compound, such as an equimolar reaction product of isophorone diisocyanate and pentaerythritol triacrylate.

[0019] (6) A carboxyl group-containing photosensitive resin obtained by reacting a bifunctional or polyfunctional (solid) epoxy resin with (meth)acrylic acid and adding a dibasic acid anhydride to the hydroxyl groups present in the side chain.

[0020] (7) A carboxyl group-containing photosensitive resin obtained by reacting a polyfunctional epoxy resin, in which the hydroxyl groups of a bifunctional (solid) epoxy resin are further epoxidized with epichlorohydrin, with (meth)acrylic acid, and then adding a dibasic acid anhydride to the resulting hydroxyl groups.

[0021] (8) A carboxyl group-containing polyester resin obtained by reacting a dicarboxylic acid such as adipic acid, phthalic acid, or hexahydrophthalic acid with a bifunctional oxetane resin, and adding a dibasic acid anhydride such as phthalic anhydride, tetrahydrophthalic anhydride, or hexahydrophthalic anhydride to the resulting primary hydroxyl group.

[0022] (9) A carboxyl group-containing photosensitive resin obtained by reacting an epoxy compound having multiple 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 then reacting the alcoholic hydroxyl group of the reaction product with a polybasic acid anhydride such as maleic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, or adipic anhydride.

[0023] (10) A carboxyl group-containing photosensitive resin obtained by reacting a compound having multiple 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 then reacting the resulting reaction product with a polybasic acid anhydride.

[0024] (11) A carboxyl group-containing photosensitive resin obtained by reacting a reaction product obtained by reacting a compound having multiple phenolic hydroxyl groups in one molecule with a cyclic carbonate compound such as ethylene carbonate or propylene carbonate with an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.

[0025] (12) A carboxyl group-containing photosensitive resin obtained by adding a compound having one epoxy group and one or more (meth)acryloyl groups in one molecule to the resins of (1) to (11) above. In this specification, (meth)acrylate is a general term for acrylate, methacrylate and mixtures thereof, and the same applies to other similar expressions.

[0026] In one embodiment, the carboxyl group-containing resin includes a carboxyl group-containing resin obtained using a phenol compound as a starting material. Examples of carboxyl group-containing resins obtained using a phenol compound as a starting material include a carboxyl group-containing resin obtained by adding a compound having one epoxy group and one or more (meth)acryloyl groups to one molecule of the carboxyl group-containing resin of (10) or (11). By including a carboxyl group-containing resin obtained using a phenol compound as a starting material, the HAST resistance and PCT resistance of the cured product of the photosensitive resin composition can be improved. Furthermore, by combining a carboxyl group-containing resin obtained using a phenol compound as a starting material with an acylphosphine oxide-based photopolymerization initiator having a specific structure described later, the deep curing properties when curing the photosensitive resin composition can be improved, thereby further improving the various resistances of the cured product as described above.

[0027] The carboxyl group-containing resins are not limited to those mentioned above and can be used in any other way. Furthermore, one type of carboxyl group-containing resin may be used alone, or two or more types may be used in combination.

[0028] The acid value of the carboxyl group-containing resin is preferably 30 to 150 mg KOH / g, and more preferably 50 to 120 mg KOH / g. An acid value of 30 mg KOH / g or higher for the carboxyl group-containing resin results in good alkali developability of the photosensitive resin composition. On the other hand, an acid value of 150 mg KOH / g or lower for the carboxyl group-containing resin suppresses the dissolution of the exposed areas by the developer, and further suppresses the dissolution and peeling of the exposed and unexposed areas without distinction, making it easier to draw a good resist pattern.

[0029] The acid value of the carboxyl group-containing resin is preferably 30 to 150 mgKOH / g, and more preferably 50 to 120 mgKOH / g. When the acid value of the carboxyl group-containing resin is 30 mgKOH / g or more, favorable alkali developability can be obtained for the photosensitive resin composition. On the other hand, when the acid value is 150 mgKOH / g or less, dissolution of exposed areas by the developer and consequent undifferentiated dissolution and peeling of exposed areas and unexposed areas can be suppressed, thereby enabling favorable formation of resist patterns.

[0030] The weight average molecular weight of the carboxyl group-containing resin varies depending on the resin skeleton, but is generally preferably 2,000 to 150,000, and more preferably 5,000 to 100,000. When the weight average molecular weight of the carboxyl group-containing resin is 2,000 or more, a decrease in moisture resistance of the coating film of the photosensitive resin composition after exposure and accompanying film thinning during development can be suppressed, and as a result, a decrease in resolution of a cured product of the photosensitive resin composition can be suppressed. On the other hand, when the weight average molecular weight of the carboxyl group-containing resin is 150,000 or less, developability and storage stability of the photosensitive resin composition can be improved. Note that the weight average molecular weight of the carboxyl group-containing resin can be determined from a standard polystyrene conversion value measured by gel permeation chromatography (GPC).

[0031] The content of the carboxyl group-containing resin in the photosensitive resin composition is not particularly limited as long as the effects of the present invention are achieved, but is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, in terms of solid content, relative to the total amount of the photosensitive resin composition. When the content of the carboxyl group-containing resin is 5% by mass or more, the coating film strength of the photosensitive resin composition can be improved. On the other hand, when the content of the carboxyl group-containing resin is 60% by mass or less, the viscosity of the photosensitive resin composition becomes appropriate and processability is improved.

[0032] (Photopolymerization Initiator) The photosensitive resin composition of the present invention comprises an acylphosphine oxide-based photopolymerization initiator having a specific structure. Specifically, the photopolymerization initiator is represented by the following general formula (I): [Wherein, R１ and R ２ each independently represent an aryl group having 7 to 20 carbon atoms which may be substituted with at least one selected from the group consisting of an alkyl group, an alkoxy group and a phenyl group, or an arylcarbonyl group having 7 to 20 carbon atoms which may be substituted with at least one selected from the group consisting of an alkyl group and an alkoxy group; R ３ represents a phenyl group or an aryl group having 7 to 20 carbon atoms which may be substituted with at least one selected from the group consisting of an alkyl group and an alkoxy group.], which is a compound having a partial structure represented by the formula. When the acylphosphine oxide-based photopolymerization initiator having the specific structure described above is contained as a photopolymerization initiator, the photosensitive resin composition can be imparted with good deep-section curability upon exposure, and furthermore, a cured product of the photosensitive resin composition can be imparted with good insulation reliability.

[0033] R １ and R ２is not particularly limited as long as it satisfies the above conditions, and is preferably any group selected from the group consisting of: a phenyl group substituted with one methyl group (e.g., monomethylphenyl groups such as o-tolyl group, m-tolyl group, and p-tolyl group), a phenyl group substituted with one ethyl group (e.g., monoethylphenyl groups such as o-ethylphenyl group, m-ethylphenyl group, and p-ethylphenyl group), a phenyl group substituted with one propyl group (e.g., monopropylphenyl groups such as o-propylphenyl group, m-propylphenyl group, and p-propylphenyl group), a phenyl group substituted with one n-butyl group (e.g., mono(n-butyl)phenyl groups such as o-(n-butyl)phenyl group, m-(n-butyl)phenyl group, and p-(n-butyl)phenyl group), a phenyl group substituted with one tert-butyl group (e.g., mono(tert-butyl)phenyl groups such as o-(tert-butyl)phenyl group, m-(tert-butyl)phenyl group, and p-(tert-butyl)phenyl group), a phenyl group substituted with one n-hexyl group (e.g., mono(n-hexyl)phenyl groups such as o-(n-hexyl)phenyl group, m-(n-hexyl)phenyl group, and p-(n-hexyl)phenyl group), a phenyl group substituted with one n-octyl group (e.g., mono(n-octyl)phenyl groups such as o-(n-octyl)phenyl group, m-(n-octyl)phenyl group, and p-(n-octyl)phenyl group), a phenyl group substituted with one n-dodecyl group (e.g., mono(n-dodecyl)phenyl groups such as o-(n-dodecyl)phenyl group, m-(n-dodecyl)phenyl group, and p-(n-dodecyl)phenyl group), a phenyl group substituted with one phenyl group (e.g., biphenylyl groups such as o-biphenylyl group, m-biphenylyl group, and p-biphenylyl group), and a phenyl group substituted with two methyl groups (e.g., dimethylphenyl groups such as 2,3-dimethylphenyl group, 2,4-dimethylphenyl group, 2,5-dimethylphenyl group, 2,6-dimethylphenyl group, 3,4-dimethylphenyl group, 3,5-dimethylphenyl group, 3,6-dimethylphenyl group, and 4,6-dimethylphenyl group). Among these groups, R １ and R ２It is particularly preferable that R is one of the groups selected from the group consisting of a phenyl group substituted with one methyl group (tolyl group) and a phenyl group substituted with two methyl groups (dimethylphenyl group). １ and R ２ They may be the same or different, but preferably they are the same.

[0034] R ３ The above-mentioned conditions are not particularly limited, but include: a phenyl group substituted with one methyl group (e.g., monomethylphenyl groups such as o-tolyl, m-tolyl, and p-tolyl groups) (together with the carbonyl group (-CO-) of general formula (I) to form a methylbenzoyl group); a phenyl group substituted with two methyl groups (e.g., dimethylphenyl groups such as o-xylyl, m-xylyl, and p-xylyl groups) (together with the carbonyl group (-CO-) of general formula (I) to form a dimethylbenzoyl group); a phenyl group substituted with three methyl groups (e.g., trimethylphenyl groups such as 1,3,5-methylphenyl and 2,4,6-methylphenyl groups) (together with the carbonyl group (-CO-) of general formula (I) to form a trimethylbenzoyl group); and a phenyl group substituted with one butyl group. It is preferable that the group is selected from the group consisting of a tert group (for example, tert-butylphenyl groups such as 2-tert-butylphenyl group, 3-tert-butylphenyl group, 4-tert-butylphenyl group, etc.) (together with the carbonyl group (-CO-) of general formula (I) to form a butylbenzoyl group), or a phenyl group substituted with two methoxy groups (for example, dimethoxyphenyl groups such as 2,3-dimethoxyphenyl group, 2,4-dimethoxyphenyl group, 2,5-dimethoxyphenyl group, 2,6-dimethoxyphenyl group, 3,4-dimethoxyphenyl group, 3,5-dimethoxyphenyl group, 3,6-dimethoxyphenyl group, 4,6-dimethoxyphenyl group, etc.) (together with the carbonyl group (-CO-) of general formula (I) to form a dimethoxybenzoyl group). Among these groups, R ３ It is particularly preferable that the group is one of the groups selected from the group consisting of a phenyl group substituted with one butyl group (butylphenyl group) and a phenyl group substituted with three methyl groups (trimethylphenyl group).

[0035] The photopolymerization initiator is not particularly limited as long as it is one of the compounds mentioned above, but preferably the following compounds are used. (2,4,6-trimethylbenzoyl)bis(o-tolyl)phosphine oxide (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide (2,4,6-trimethylbenzoyl)bis(2,3-dimethylphenyl)phosphine oxide (2,4,6-trimethylbenzoyl)bis(3,5-dimethylphenyl)phosphine oxide (2,4,6-trimethylbenzoyl)bis(o-ethylphenyl)phosphine oxide (2,4,6-trimethylbenzoyl)bis(p-ethylphenyl)phosphine oxide (2,4,6-trimethylbenzoyl)bis(p-propylphenyl)phosphine oxide (2,4,6-trimethylbenzoyl)bis(p-(n-butyl)phenyl)phosphine oxide (2,4,6-trimethylbenzoyl)bis(p-(tert-butyl)phenyl)phosphine oxide (2,4,6-trimethylbenzoyl)bis(p-(n-hexyl)phenyl)phosphine oxide (2,4,6-trimethylbenzoyl)bis(p-(n-octyl)phenyl)phosphine oxide (2,4,6-trimethylbenzoyl)bis(p-(n-dodecyl)phenyl)phosphine oxide (2,4,6-trimethylbenzoyl)bis(p-biphenyl)phosphine oxide (2,4-dimethylbenzoyl)bis(o-tolyl)phosphine oxide (2,4-dimethylbenzoyl)bis(p-tolyl)phosphine oxide (2,4-dimethylbenzoyl)bis(2,3-dimethylphenyl)phosphine oxide (2,4-dimethylbenzoyl)bis(3,5-dimethylphenyl)phosphine oxide (2,4-dimethylbenzoyl)bis(o-ethylphenyl)phosphine oxide (2,4-dimethylbenzoyl)bis(p-ethylphenyl)phosphine oxide (2,4-dimethylbenzoyl)bis(p-propylphenyl)phosphine oxide (2,4-dimethylbenzoyl)bis(p-(n-butyl)phenyl)phosphine oxide (2,4-dimethylbenzoyl)bis(p-(tert-butyl)phenyl)phosphine oxide (2,4-dimethylbenzoyl)bis(p-(n-hexyl)phenyl)phosphine oxide (2,4-dimethylbenzoyl)bis(p-(n-octyl)phenyl)phosphine oxide (2,4-dimethylbenzoyl)bis(p-(n-dodecyl)phenyl)phosphine oxide (2,4-dimethylbenzoyl)bis(p-biphenyl)phosphine oxide (4-tert-butylbenzoyl)bis(o-tolyl)phosphine oxide (4-tert-butylbenzoyl)bis(p-tolyl)phosphine oxide (4-tert-butylbenzoyl)bis(2,3-dimethylphenyl)phosphine oxide (4-tert-butylbenzoyl)bis(3,5-dimethylphenyl)phosphine oxide (4-tert-butylbenzoyl)bis(o-ethylphenyl)phosphine oxide (4-tert-butylbenzoyl)bis(p-ethylphenyl)phosphine oxide (4-tert-butylbenzoyl)bis(p-propylphenyl)phosphine oxide (4-tert-butylbenzoyl)bis(p-(n-butyl)phenyl)phosphine oxide (4-tert-butylbenzoyl)bis(p-(tert-butyl)phenyl)phosphine oxide (4-tert-butylbenzoyl)bis(p-(n-hexyl)phenyl)phosphine oxide (4-tert-butylbenzoyl)bis(p-(n-octyl)phenyl)phosphine oxide (4-tert-butylbenzoyl)bis(p-(n-dodecyl)phenyl)phosphine oxide (4-tert-butylbenzoyl)bis(p-biphenyl)phosphine oxide (4-methylbenzoyl)bis(o-tolyl)phosphine oxide (4-methylbenzoyl)bis(p-tolyl)phosphine oxide (4-methylbenzoyl)bis(2,3-dimethylphenyl)phosphine oxide (4-methylbenzoyl)bis(3,5-dimethylphenyl)phosphine oxide, (4-methylbenzoyl)bis(o-ethylphenyl)phosphine oxide, (4-methylbenzoyl)bis(p-ethylphenyl)phosphine oxide, (4-methylbenzoyl)bis(p-propylphenyl)phosphine oxide, (4-methylbenzoyl)bis(p-(n-butyl)phenyl)phosphine oxide, (4-methylbenzoyl)bis(p-(tert-butyl)phenyl)phosphine oxide, (4-methylbenzoyl)bis(p-(n-hexyl)phenyl)phosphine oxide, (4-methylbenzoyl)bis(p-(n-octyl)phenyl)phosphine oxide, (4-methylbenzoyl)bis(p-(n-dodecyl)phenyl)phosphine oxide, (4-methylbenzoyl)bis(p-biphenyl)phosphine oxide, (2,6-dimethoxybenzoyl)bis(o-tolyl)phosphine oxide (2,6-dimethoxybenzoyl)bis(p-tolyl)phosphine oxide (2,6-dimethoxybenzoyl)bis(2,3-dimethylphenyl)phosphine oxide (2,6-dimethoxybenzoyl)bis(3,5-dimethylphenyl)phosphine oxide (2,6-dimethoxybenzoyl)bis(o-ethylphenyl)phosphine oxide (2,6-dimethoxybenzoyl)bis(p-ethylphenyl)phosphine oxide (2,6-dimethoxybenzoyl)bis(p-propylphenyl)phosphine oxide (2,6-dimethoxybenzoyl)bis(p-(n-butyl)phenyl)phosphine oxide (2,6-dimethoxybenzoyl)bis(p-(tert-butyl)phenyl)phosphine oxide (2,6-dimethoxybenzoyl)bis(p-(n-hexyl)phenyl)phosphine oxide (2,6-dimethoxybenzoyl)bis(p-(n-octyl)phenyl)phosphine oxide (2,6-dimethoxybenzoyl)bis(p-(n-dodecyl)phenyl)phosphine oxide (2,6-dimethoxybenzoyl)bis(p-biphenyl)phosphine oxide,

[0036] Of the compounds mentioned above, the following compounds are particularly preferred: (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide (2,4,6-trimethylbenzoyl)bis(o-tolyl)phosphine oxide (2,4,6-trimethylbenzoyl)bis(2,3-dimethylphenyl)phosphine oxide (4-tert-butylbenzoyl)bis(o-tolyl)phosphine oxide

[0037] The photopolymerization initiator is not limited to the specific compounds mentioned above. Furthermore, the photopolymerization initiator may be used alone or in combination of two or more compounds.

[0038] In one embodiment, the photopolymerization initiator can be one synthesized using a substituted benzoyl chloride and a phosphine by methods described in Japanese Patent Publications, such as JP-A-58-77890, JP-A-61-130296, and JP-A-5-345790.

[0039] The content of the photopolymerization initiator in the photosensitive resin composition is not particularly limited as long as the effects of the present invention are achieved, but is preferably 0.5 to 50 parts by mass, more preferably 1 to 30 parts by mass, in terms of solid content, per 100 parts by mass of the carboxyl group-containing resin described above. When the content of the photopolymerization initiator is 0.5 parts by mass or more per 100 parts by mass of the carboxyl group-containing resin, the photocurability of the photosensitive resin composition on the substrate becomes sufficient, and peeling of the coating film of the photosensitive resin composition and deterioration of coating film properties such as chemical resistance can be suppressed. On the other hand, when the content of the photopolymerization initiator is 50 parts by mass or less per 100 parts by mass of the carboxyl group-containing resin, the light absorption of the photopolymerization initiator on the surface of the resin layer is within an appropriate range, and a decrease in the deep curing properties of the resin layer can be suppressed.

[0040] The photosensitive resin composition of the present invention may be used in combination with the above-mentioned photopolymerization initiator and a photoinitiator or sensitizer. Examples of photoinitiator or sensitizers include benzoin compounds, anthraquinone compounds, thioxanthone compounds, ketal compounds, benzophenone compounds, tertiary amine compounds, and xanthone compounds. In particular, it is preferable to use thioxanthone compounds such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, and 4-isopropylthioxanthone. The inclusion of thioxanthone compounds can improve deep curing properties. These compounds can also be used as photopolymerization initiators, but it is preferable to use them in combination with a photopolymerization initiator. Furthermore, one type of photoinitiator or sensitizer may be used alone, or two or more types may be used in combination.

[0041] These photopolymerization initiators, photoinitiators, and sensitizers absorb specific wavelengths, which can sometimes lead to reduced sensitivity and cause them to function as UV absorbers. However, they are not used solely for the purpose of improving the sensitivity of photosensitive resin compositions. By absorbing light of specific wavelengths as needed, the photoreactivity of the surface can be increased, changing the line shape and apertures of the solder resist layer pattern to vertical, tapered, or reverse tapered shapes, while also improving the accuracy of line width and aperture diameter.

[0042] (Thermosetting component) The photosensitive resin composition of the present invention contains a thermosetting component. By including a thermosetting component in the photosensitive resin composition, an improvement in its heat resistance can be expected. The thermosetting component may be used alone or in combination of two or more types.

[0043] Any known thermosetting component can be used. For example, known thermosetting components such as melamine resin, benzoguanamine resin, melamine derivatives, amino resins such as benzoguanamine derivatives, isocyanate compounds, blocked isocyanate compounds, cyclocarbonate compounds, epoxy compounds, oxetane compounds, episulfide resins, bismaleimide, and carbodiimide resins can be used. Particularly preferred are thermosetting components having multiple cyclic ether groups or cyclic thioether groups (hereinafter abbreviated as cyclic (thio) ether groups) in the molecule.

[0044] The thermosetting components having multiple cyclic (thio) ether groups in the molecule described above are compounds having multiple 3, 4, or 5-membered cyclic (thio) ether groups in the molecule. Examples include compounds having multiple epoxy groups in the molecule, i.e., polyfunctional epoxy compounds; compounds having multiple oxetanyl groups in the molecule, i.e., polyfunctional oxetane compounds; and compounds having multiple thio ether groups in the molecule, i.e., episulfide resins.

[0045] Examples of polyfunctional epoxy compounds include epoxidized vegetable oils; bisphenol A type epoxy resins; hydroquinone type epoxy resins; bisphenol type epoxy resins; thioether type epoxy resins; brominated epoxy resins; novolac type epoxy resins; biphenol novolac type epoxy resins; bisphenol F type epoxy resins; hydrogenated bisphenol A type epoxy resins; glycidylamine type epoxy resins; hydantoin type epoxy resins; alicyclic epoxy resins; trihydroxyphenylmethane type epoxy resins; bixylenol type or biphenol type epoxy resins or mixtures thereof. Examples of epoxy resins include, but are not limited to, bisphenol S type epoxy resins, bisphenol A novolac type epoxy resins, tetraphenyloleethane type epoxy resins, heterocyclic epoxy resins, diglycidyl phthalate resins, tetraglycidyl xylenolethane resins, naphthalene group-containing epoxy resins, epoxy resins having a dicyclopentadiene skeleton, glycidyl methacrylate copolymer epoxy resins, copolymer epoxy resins of cyclohexylmaleimide and glycidyl methacrylate, epoxy-modified polybutadiene rubber derivatives, and CTBN-modified epoxy resins. These epoxy resins can be used individually or in combination of two or more types.

[0046] Examples of polyfunctional oxetane compounds include bis[(3-methyl-3-oxetanylmethoxy)methyl] ether, bis[(3-ethyl-3-oxetanylmethoxy)methyl] ether, 1,4-bis[(3-methyl-3-oxetanylmethoxy)methyl]benzene, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, (3-methyl-3-oxetanyl)methyl acrylate, and (3-ethyl-3-oxetanyl)methyl acrylate. Examples include polyfunctional oxetanes such as relates, (3-methyl-3-oxetanyl)methyl methacrylate, (3-ethyl-3-oxetanyl)methyl methacrylate, and their oligomers or copolymers, as well as ethers of oxetane alcohols with resins having hydroxyl groups such as novolac resins, poly(p-hydroxystyrene), cardo-type bisphenols, calixarenes, calixresorcinarenes, or silsesquioxane. Other examples include copolymers of unsaturated monomers having an oxetane ring with alkyl (meth)acrylates.

[0047] Examples of compounds having multiple cyclic thioether groups in their molecules include bisphenol A type episulfide resins. Furthermore, episulfide resins obtained by replacing the oxygen atoms in the epoxy groups of novolac type epoxy resins with sulfur atoms using a similar synthesis method can also be used.

[0048] Examples of amino resins such as melamine derivatives and benzoguanamine derivatives include methylolmelamine compounds, methylolbenzoguanamine compounds, methylol glycol uryl compounds, and methylol urea compounds.

[0049] Polyisocyanate compounds can be incorporated as isocyanate compounds. Examples of polyisocyanate compounds include aromatic polyisocyanates such as 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, naphthalene-1,5-diisocyanate, o-xylylene diisocyanate, m-xylylene diisocyanate, and 2,4-tolylene dimer; aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, trimethylhexamethylene diisocyanate, 4,4-methylenebis(cyclohexyl isocyanate), and isophorone diisocyanate; alicyclic polyisocyanates such as bicycloheptane triisocyanate; and adducts, biuret compounds, and isocyanurates of the isocyanate compounds mentioned above.

[0050] As the blocked isocyanate compound, the addition reaction product of an isocyanate compound and an isocyanate blocking agent can be used. Examples of isocyanate compounds that can react with an isocyanate blocking agent include the polyisocyanate compounds mentioned above. Examples of isocyanate blocking agents include phenol-based blocking agents, lactam-based blocking agents, activated methylene-based blocking agents, alcohol-based blocking agents, oxime-based blocking agents, mercaptan-based blocking agents, acid amide-based blocking agents, imide-based blocking agents, amine-based blocking agents, imidazole-based blocking agents, and imine-based blocking agents.

[0051] The amount of thermosetting component is such that, based on solid content, the number of functional groups of the thermosetting component that react is preferably 0.5 to 2.5 moles, more preferably 0.8 to 2.0 moles, per mole of carboxyl groups contained in the carboxyl group-containing resin.

[0052] Furthermore, the photosensitive resin composition may also contain a thermosetting catalyst in addition to the thermosetting component described above. Examples of thermosetting catalysts include imidazole derivatives such as imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, and 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole; amine compounds such as dicyandiamide, benzyldimethylamine, 4-(dimethylamino)-N,N-dimethylbenzylamine, 4-methoxy-N,N-dimethylbenzylamine, and 4-methyl-N,N-dimethylbenzylamine; hydrazine compounds such as adipic acid dihydrazide and sebacate acid dihydrazide; and phosphorus compounds such as triphenylphosphine. In particular, the catalyst is not limited to these, and any catalyst that promotes the reaction between the epoxy group and the carboxyl group is acceptable. One catalyst may be used alone, or two or more may be used in combination.

[0053] Furthermore, S-triazine derivatives such as guanamine, acetoguanamine, benzoguanamine, 2,4-diamino-6-methacryloyloxyethyl-S-triazine, 2-vinyl-2,4-diamino-S-triazine, 2-vinyl-4,6-diamino-S-triazine isocyanuric acid adduct, and 2,4-diamino-6-methacryloyloxyethyl-S-triazine isocyanuric acid adduct can also be used, and preferably these compounds that also function as adhesion imparters are used in combination with the thermosetting catalyst. The thermosetting catalyst may be used alone or in combination of two or more types.

[0054] The thermosetting catalyst may also include materials other than those mentioned above, such as phenolic resins, polycarboxylic acids and their acid anhydrides, cyanate ester resins, and activated ester resins.

[0055] (Fillers) The photosensitive resin composition of the present invention may also contain fillers in addition to the components described above. By including fillers in the photosensitive resin composition, the elastic modulus of the solder resist layer can be adjusted. Known inorganic or organic fillers can be used as fillers, but inorganic fillers such as barium sulfate, spherical silica, hydrotalcite, and talc are particularly preferred. Furthermore, metal oxides such as metal oxides and aluminum hydroxide can be used as extender pigment fillers to obtain flame retardancy.

[0056] The filler content is not particularly limited as long as the effects of the present invention are achieved, but is preferably 10 to 70% by mass, more preferably 20 to 65% by mass, on a solid content basis, relative to the total amount of the photosensitive resin composition.

[0057] The filler may be surface-treated to improve its dispersibility in the photosensitive resin composition. Using a surface-treated filler can suppress aggregation. The surface treatment method is not particularly limited, and any known and conventional method may be used, but it is preferable to treat the surface of the inorganic filler with a surface treatment agent having a curable reactive group, for example, a coupling agent having a curable reactive group as an organic group.

[0058] As coupling agents, silane-based, titanate-based, aluminate-based, and zircoaluminate-based coupling agents can be used. Among these, silane-based coupling agents are preferred. Examples of such silane-based coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, N-(2-aminomethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-anilinopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane. The coupling agent may be used alone or in combination of two or more. It is preferable that these silane-based coupling agents are pre-immobilized on the surface of the filler by adsorption or reaction. Here, the amount of coupling agent treated per 100 parts by mass of spherical silica is preferably 0.5 to 10 parts by mass.

[0059] (Photopolymerizable monomers) The photosensitive resin composition of the present invention may also contain photopolymerizable monomers in addition to the components described above. Photopolymerizable monomers are monomers having an ethylenically unsaturated double bond. Examples of such photopolymerizable monomers include conventionally known polyester (meth)acrylates, polyether (meth)acrylates, urethane (meth)acrylates, carbonate (meth)acrylates, epoxy (meth)acrylates, and the like. Specifically, alkyl acrylates such as 2-ethylhexyl acrylate and cyclohexyl acrylate; hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; mono- or diacrylates of alkylene oxide derivatives such as ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol; acrylamides such as N,N-dimethylacrylamide, N-methylolacrylamide, and N,N-dimethylaminopropylacrylamide; aminoalkyl acrylates such as N,N-dimethylaminoethyl acrylate and N,N-dimethylaminopropyl acrylate; polyhydric alcohols such as hexanediol, trimethylolpropane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, and trishydroxyethyl isocyanurate. Polyvalent acrylates derived from ethanol or its alkylene oxide adducts or ε-caprolactone adducts, etc.; polyvalent acrylates such as phenoxyacrylate, bisphenol A diacrylate, and other phenols or their alkylene oxide adducts; acrylates derived from glycidyl ethers such as glycerin diglycidyl ether, trimethylolpropane triglycidyl ether, and triglycidyl isocyanurate; and, not limited to the above, acrylates obtained by directly acrylateting polyols such as polyether polyols, polycarbonate diols, hydroxyl-terminated polybutadienes, and polyester polyols, or by urethane acrylates via diisocyanates, as well as melamine acrylate and at least one of each methacrylate corresponding to the acrylates, can be appropriately selected and used. Such photopolymerizable monomers can also be used as reactive diluents.

[0060] Epoxy acrylate resins, obtained by reacting a polyfunctional epoxy resin such as a cresol novolac type epoxy resin with acrylic acid, or epoxy urethane acrylate compounds, obtained by reacting the hydroxyl groups of the epoxy acrylate resin with a half-urethane compound of a hydroxyacrylate such as pentaerythritol triacrylate and a diisocyanate such as isophorone diisocyanate, may be used as photopolymerizable monomers. Such epoxy acrylate resins can improve photocurability without reducing touch-drying properties.

[0061] The content of the photopolymerizable monomer is not particularly limited as long as the effects of the present invention are achieved, but is preferably 0.2 to 60 parts by mass, more preferably 0.5 to 50 parts by mass, in terms of solid content, per 100 parts by mass of the carboxyl group-containing resin. By having a photopolymerizable monomer content of 0.2 parts by mass or more per 100 parts by mass of the carboxyl group-containing resin, the photocurability of the photosensitive resin composition can be improved. On the other hand, by having a photopolymerizable monomer content of 60 parts by mass or less per 100 parts by mass of the carboxyl group-containing resin, the surface hardness of the solder resist layer can be improved.

[0062] (Organic solvents) In addition, the photosensitive resin composition may contain organic solvents from the viewpoint of ease of preparation and applicability. As organic solvents, known and commonly used organic solvents can be used, such as ketones like methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons like toluene, xylene, and tetramethylbenzene; glycol ethers like cellosolve, methyl cellosolve, butyl cellosolve, 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 like ethyl acetate, butyl acetate, butyl lactate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and propylene carbonate; aliphatic hydrocarbons like octane and decane; and petroleum-based solvents such as petroleum ether, petroleum naphtha, and solvent naphtha. Organic solvents may be used individually or in combination of two or more types.

[0063] The content of the organic solvent is not particularly limited and can be appropriately set according to the desired viscosity, etc., to facilitate the preparation of the photosensitive resin composition.

[0064] (Other Components) In addition to the components described above, the photosensitive resin composition may also contain components such as colorants, elastomers, mercapto compounds, urethane catalysts, thixonating agents, adhesion promoters, block copolymers, chain transfer agents, polymerization inhibitors, copper damage inhibitors, antioxidants, rust inhibitors, thickeners such as organic bentonite and montmorillonite, defoaming agents and leveling agents such as silicone-based, fluorine-based, and polymer-based agents, and flame retardants such as phosphinates, phosphate ester derivatives, and phosphazene compounds. These components may be those known in the field of electronic materials.

[0065] (Dry Film) According to another aspect of the present invention, a dry film (hereinafter also referred to as "the dry film of the present invention") is provided, comprising a first film and a resin layer formed from the photosensitive resin composition of the present invention laminated on the first film. The first film in the dry film of the present invention refers to a film that is at least adhered to the resin layer when laminating the layer of the photosensitive resin composition (resin layer) constituting the dry film onto a substrate. The first film may be peeled off from the resin layer in a process after lamination. In particular, in the present invention, it is preferable to peel it off from the resin layer in a process after exposure. When making a dry film of the photosensitive resin composition of the present invention, the photosensitive resin composition of the present invention is diluted with an organic solvent to adjust to an appropriate viscosity, and applied to the first film to a uniform thickness using a comma coater, blade coater, lip coater, rod coater, squeeze coater, reverse coater, transfer roll coater, gravure coater, spray coater, etc., and the resin layer can usually be obtained by drying at a temperature of 50 to 130°C for 1 to 30 minutes. There are no particular restrictions on the thickness (film thickness) when applying the photosensitive resin composition, but generally, the film thickness after drying is appropriately selected within the range of 1 to 150 μm, preferably 10 to 60 μm.

[0066] The first film is not particularly limited as long as it is a known film, and 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 can be suitably used. Among these, polyester films are preferably used from the viewpoint of heat resistance, mechanical strength, and handling. Laminates of these films can also be used as the first film.

[0067] Furthermore, from the viewpoint of improving mechanical strength, the thermoplastic resin film described above is preferably a film stretched in one or two axes.

[0068] The thickness of the first film is not particularly limited, but can be, for example, 10 μm to 150 μm.

[0069] After forming a layer (resin layer) of the photosensitive resin composition of the present invention on the first film, it is preferable to further laminate a peelable second film onto the surface of the resin layer for purposes such as preventing dust from adhering to the surface of the resin layer. The second film is a film that is peeled off from the resin layer before lamination when the resin layer constituting the dry film is laminated onto a substrate. As the second film, for example, polyethylene film, polytetrafluoroethylene film, polypropylene film, surface-treated paper, etc., should be such that the adhesive force between the resin layer and the second film is less than the adhesive force between the resin layer and the first film when the second film is peeled off.

[0070] The thickness of the second film is not particularly limited, but can be, for example, 10 μm to 150 μm.

[0071] Furthermore, the dry film of the present invention may also be obtained by forming a resin layer on the second film described above by applying and drying the photosensitive resin composition of the present invention, and then laminating the first film on its surface. In other words, the film on which the photosensitive resin composition of the present invention is applied when manufacturing the dry film of the present invention may be either the first film or the second film.

[0072] (Cured product) According to another aspect of the present invention, a cured product (hereinafter also referred to as "cured product of the present invention") is provided, which is formed by curing the photosensitive resin composition of the present invention or the resin layer of the dry film of the present invention. Since the cured product of the present invention is a cured product of the photosensitive resin composition of the present invention, it has good deep curing properties and adhesion to the substrate, and furthermore, good insulation reliability.

[0073] The conditions for curing the resin layer of the photosensitive resin composition or dry film of the present invention are not particularly limited as long as they are general conditions used for curing resin compositions, and can be appropriately set depending on the type of radical polymerization initiator contained in the photosensitive resin composition, for example. In one embodiment, the conditions for curing the resin layer of the photosensitive resin composition or dry film of the present invention can be the conditions described later for printed circuit boards.

[0074] (Printed Wiring Board) According to another aspect of the present invention, a printed wiring board (hereinafter also referred to as "the printed wiring board of the present invention") is provided that comprises the cured product of the present invention described above. That is, the printed wiring board of the present invention has a cured product obtained from the photosensitive resin composition of the present invention or from the resin layer of the dry film of the present invention. As a method for manufacturing the printed wiring board of the present invention, for example, the photosensitive resin composition of the present invention is adjusted to a viscosity suitable for the coating method using an organic solvent, and is applied to a substrate by a method such as dip coating, flow coating, roll coating, bar coating, screen printing, or curtain coating, and then the organic solvent contained in the photosensitive resin composition is evaporated and dried (pre-dried) at a temperature of 60 to 100°C to form a tack-free resin layer. In the case of a dry film, the resin layer is formed on the substrate by laminating it onto the substrate using a laminator or the like so that the resin layer is in contact with the substrate.

[0075] Examples of substrates constituting the printed circuit board of the present invention include printed circuit boards and flexible printed circuit boards with circuits pre-formed using copper or the like, copper-clad laminates using materials such as paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / nonwoven fabric epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, fluororesin / polyethylene / polyphenylene ether, polyphenylene oxide / cyanate, metal substrates, polyimide films, polyethylene terephthalate films, polyethylene naphthalate (PEN) films, glass substrates, ceramic substrates, and wafers.

[0076] The bonding of the dry film to the resin layer on the substrate is preferably performed under pressure and heat using a vacuum laminator or the like. By using such a vacuum laminator, even if the surface of the circuit board is uneven when a circuit-formed substrate is used, the dry film adheres closely to the circuit board, preventing the inclusion of air bubbles and improving the ability to fill in depressions on the substrate surface. The pressure is preferably around 0.1 to 2.0 MPa, and the heating is preferably around 40 to 120°C.

[0077] The volatilization drying performed after forming the resin layer of the present invention on the substrate can be carried out using a hot air circulation drying oven, an IR oven, a hot plate, a convection oven, or the like.

[0078] Next, the resin layer formed on the substrate is selectively exposed to active energy rays through a photomask with a predetermined pattern, and the unexposed areas are developed with a dilute alkaline aqueous solution (for example, a 0.3 to 3% by mass sodium carbonate aqueous solution) to form a pattern on the cured product. In the case of a dry film, after exposure, the first film is peeled off from the dry film and developed to form a patterned cured product on the substrate. However, within a range that does not impair the properties, the first film may be peeled off from the dry film before exposure, and the exposed resin layer may be exposed and developed. Furthermore, by irradiating the cured product with active energy rays and then heat curing it (for example, 100 to 220°C), or irradiating it with active energy rays after heat curing, or by performing final finishing curing (main curing) with heat curing alone, a cured film with excellent properties such as adhesion and hardness is formed.

[0079] The exposure machine used for active energy ray irradiation can be any device that irradiates ultraviolet light in the range of 350 to 450 nm, equipped with a high-pressure mercury lamp, ultra-high-pressure mercury lamp, metal halide lamp, mercury short-arc lamp, etc. Furthermore, a direct writing device (for example, a laser direct imaging device that directly draws images with a laser using CAD data from a computer) can also be used. The lamp light source or laser light source of the direct writing device can have a maximum wavelength in the range of 350 to 450 nm. The exposure amount for image formation varies depending on the film thickness, etc., but is generally 10 to 1000 mJ / cm ２ Preferably 20 to 800 mJ / cm² ２ It can be within the range of

[0080] The development methods described above can include dipping, showering, spraying, and brushing, and alkaline aqueous solutions such as potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia, and amines can be used as the developing solution.

[0081] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, the numerical values ​​for each component all refer to parts by mass unless otherwise specified.

[0082] (Synthesis of Carboxyl Group-Containing Resin A-1) 220 parts of cresol novolac type epoxy resin (DIC Corporation, EPICLON® N-695, epoxy equivalent: 220) were placed in a four-necked flask equipped with a stirrer and reflux condenser, and 214 parts of carbitol acetate were added and heated until dissolved. Next, 0.1 parts of hydroquinone as a polymerization inhibitor and 2.0 parts of dimethylbenzylamine as a reaction catalyst were added. The resulting mixture was heated to 95-105°C, and 72 parts of acrylic acid were gradually added dropwise, and the mixture was reacted for 16 hours. The resulting reaction product was cooled to 80-90°C, 106 parts of tetrahydrophthalic anhydride were added, the mixture was reacted for 8 hours, and then cooled. In this way, a solid solution of carboxyl group-containing resin A-1 with an acid value of 100 mg KOH / g and a solid content of 65% was obtained.

[0083] (Synthesis of Carboxyl Group-Containing Resin A-2) In an autoclave equipped with a thermometer, a nitrogen introduction device / alkylene oxide introduction device, and a stirring device, 119.4 g of novolac-type cresol resin (manufactured by Aica Kogyo Co., Ltd., Showol CRG951, OH equivalent: 119.4), 1.19 g of potassium hydroxide, and 119.4 g of toluene were placed, and the system was heated and the temperature increased while stirring and purging with nitrogen. Then, 63.8 g of propylene oxide was gradually added dropwise at 125-132°C and 0-4.8 kg / cm³. ２ The mixture was reacted for 16 hours. Next, the reaction solution was cooled to room temperature, and 1.56 g of 89% phosphoric acid was added and mixed to neutralize the potassium hydroxide, yielding a propylene oxide reaction solution of novolac-type cresol resin with a non-volatile content of 62.1% and a hydroxyl value of 182.2 g / eq. (i.e., an alkylene oxide reaction solution of novolac-type cresol resin in which 1.08 moles of alkylene oxide were added per equivalent of phenolic hydroxyl groups). 293.0 g of the obtained alkylene oxide reaction solution of novolac-type cresol resin, 43.2 g of acrylic acid, 11.53 g of methanesulfonic acid, 0.18 g of methylhydroquinone, and 252.9 g of toluene were placed in a reactor equipped with a stirrer, thermometer, and air blowing tube, and the mixture was reacted at 110°C for 12 hours while blowing air at a rate of 10 ml / min and stirring. The water produced by the reaction was distilled off as an azeotropic mixture with toluene, with 12.6 g of water being distilled off. The reaction solution was then cooled to room temperature, neutralized with 35.35 g of 15% sodium hydroxide aqueous solution, and then washed with water. Next, using an evaporator, toluene was removed by distillation while substituting with 118.1 g of diethylene glycol monoethyl ether acetate to obtain a novolac-type acrylate resin solution. Then, 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, thermometer, and air blowing tube, and 60.8 g of tetrahydrophthalic anhydride was gradually added while stirring and blowing air at a rate of 10 ml / min, and the reaction was carried out at 95-101°C for 6 hours. In this way, a solution of solid carboxyl group-containing resin A-2 with an acid value of 88 mg KOH / g and a solid content of 71% was obtained.

[0084] (Preparation of photopolymerization initiator B-1) PhiCure TMO ((2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide) manufactured by Diroid Materials Co., Ltd. was prepared as photopolymerization initiator B-1. Photopolymerization initiator B-1 is a compound that satisfies general formula (I).

[0085] (Synthesis of Photopolymerization Initiator B-2) Using 2,4,6-trimethylbenzoyl chloride, bis(o-tolyl)phosphine, and hydrogen peroxide as the main raw materials, photopolymerization initiator B-2 ((2,4,6-trimethylbenzoyl)bis(o-tolyl)phosphine oxide) was synthesized in accordance with the synthesis method described in Japanese Patent Application Publication No. 5-345790. Photopolymerization initiator B-2 is a compound that satisfies general formula (I).

[0086] (Synthesis of Photopolymerization Initiator B-3) Using 2,4,6-trimethylbenzoyl chloride, bis(2,3-dimethylphenyl)phosphine, and hydrogen peroxide as the main raw materials, photopolymerization initiator B-3 ((2,4,6-trimethylbenzoyl)bis(2,3-dimethylphenyl)phosphine oxide) was synthesized in accordance with the synthesis method described in Japanese Patent Application Publication No. 5-345790. Photopolymerization initiator B-3 is a compound that satisfies general formula (I).

[0087] (Synthesis of Photopolymerization Initiator B-4) Using 4-tert-butylbenzoyl chloride, bis(o-tolyl)phosphine, and hydrogen peroxide as the main raw materials, the photopolymerization initiator B-4 ((4-tert-butylbenzoyl)bis(o-tolyl)phosphine oxide) was synthesized in accordance with the synthesis method described in Japanese Patent Application Publication No. 5-345790. Photopolymerization initiator B-4 is a compound that satisfies general formula (I).

[0088] (Preparation of photopolymerization initiator B-5) Omnirad TPO N (2,4,6-trimethylbenzoyldiphenylphosphine oxide) manufactured by IGM Resins was prepared as photopolymerization initiator B-5. Note that photopolymerization initiator B-5 is a compound that does not satisfy general formula (I).

[0089] (Preparation of photopolymerization initiator B-6) Omnirad 907 (2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one) from IGM Resins was prepared as photopolymerization initiator B-6. Note that photopolymerization initiator B-6 is a compound that does not satisfy general formula (I).

[0090] [Preparation of Photosensitive Resin Compositions] The photosensitive resin compositions of Examples 1 to 12 and Comparative Examples 1 to 4 were prepared by mixing each component shown in Table 1 in the amounts (solid content) shown in the same table. Specifically, each component shown in Table 1 was pre-mixed in a stirrer and then kneaded in a three-roll mill to obtain the photosensitive resin compositions of Examples 1 to 12 and Comparative Examples 1 to 3. The carboxyl group-containing resins and photopolymerization initiators in Table 1 are carboxyl group-containing resins A-1 to A-2 and photopolymerization initiators B-1 to B-6, respectively, which were synthesized or prepared according to the procedure described above. The components other than the carboxyl group-containing resins and photopolymerization initiators in Table 1 are as follows. Thermosetting component: Phenol novolac type epoxy resin (N-740, manufactured by DIC Corporation) Thermosetting catalyst: Melamine Inorganic filler: Silica (AdmaFine SO-E2, manufactured by Admatex Co., Ltd.) Photopolymerizable monomer: Dipentaerythritol hexaacrylate (DPHA, manufactured by Nippon Kayaku Co., Ltd.)

[0091]

[0092] The insulating reliability of the cured products of each photosensitive resin composition in the examples and comparative examples was evaluated based on crack resistance and HAST (Highly Accelerated Stress Test System) resistance on the substrate.

[0093] (Evaluation of crack resistance on substrate) The crack resistance of the cured photosensitive resin compositions on the substrate was evaluated according to the following procedure. First, each photosensitive resin composition was applied to a first film (polyethylene terephthalate film) using an applicator to a dry film thickness of 30 μm, and dried at 80°C for 20 minutes to produce a dry film having a layer (resin layer) of each photosensitive resin composition. Next, the resin layers of each dry film were bonded to a laminate from which the copper foil had been removed, and laminated using a vacuum laminator (CVP-300: manufactured by Nikko Materials Co., Ltd.) in the first chamber at 90°C under conditions of vacuum pressure of 3 hPa and vacuum time of 30 seconds, followed by pressing under conditions of press pressure of 0.5 MPa and press time of 30 seconds. Next, the film was exposed at the optimal exposure amount using a high-pressure mercury lamp exposure apparatus, and the first film was peeled off from the dry film. ２ CO ３ Aqueous solution sprayed at a pressure of 2 kg / cm² ２ The material was sprayed under these conditions and developed for 60 seconds to form a 0.3 mm square pattern. Furthermore, it was subjected to an integrated exposure of 1000 mJ / cm² in a UV conveyor oven. ２ After UV irradiation under the specified conditions, the substrates were heated at 160°C for 60 minutes to fully cure them and obtain evaluation substrates. The evaluation substrates were placed in a cold-heat cycle machine that performed temperature cycles between -55°C and 150°C. The appearance was visually inspected after 2000 cycles, and the crack resistance of the cured product of each photosensitive resin composition on the substrate was evaluated according to the following criteria. The evaluation results are shown in Table 1. The optimal exposure amount was determined when exposure was performed via a step tablet (Stouffer 41 steps), and the number of step tablets remaining after development was 8. ○: No cracks were observed in the cured product after 2000 cycles, indicating good crack resistance. ×: Cracks were observed in the cured product after 2000 cycles, indicating poor crack resistance.

[0094] (HAST Resistance) The HAST resistance of the cured photosensitive resin compositions was evaluated according to the following procedure. First, each photosensitive resin composition was applied to a first film (polyethylene terephthalate film) using an applicator to a dry film thickness of 25 μm, and dried at 80°C for 20 minutes to produce a dry film having a layer (resin layer) of each photosensitive resin composition. Next, the resin layers of each dry film were bonded to a printed circuit board with an L / S = 5 / 5 comb-tooth pattern, and laminated in the first chamber at 90°C under conditions of a vacuum pressure of 3 hPa and a vacuum time of 30 seconds using a vacuum laminator (CVP-300: manufactured by Nikko Materials Co., Ltd.), followed by pressing under conditions of a press pressure of 0.5 MPa and a press time of 30 seconds. Next, the film was exposed at the optimal exposure amount using a high-pressure mercury lamp exposure apparatus, and the first film was peeled off from the dry film. ２ CO ３ Aqueous solution sprayed at a pressure of 2 kg / cm² ２ The film was sprayed under these conditions and developed for 60 seconds. Furthermore, it was subjected to an integrated exposure of 1000 mJ / cm² in a UV conveyor oven. ２ After UV irradiation under these conditions, the substrate was heated at 160°C for 60 minutes to fully cure it, and an evaluation substrate was obtained. Electrodes were connected to the evaluation substrate, and the substrate was placed in a high-temperature, high-humidity chamber at 130°C and 85% humidity, and a HAST test was performed at a voltage of 5V. From the start of the test, the electrical insulation was 1 × 10⁻⁶. ６ The time until the electrical insulation resistance fell below Ω was measured, and the HAST resistance of the cured product of each photosensitive resin composition was evaluated according to the following criteria. The evaluation results are shown in Table 1. ○: Electrical insulation resistance from the start of the test was 1 × 10⁻⁶ ６ The time it takes for the resistance to drop below Ω is 500 hours or more, indicating extremely good HAST resistance. △: Electrical insulation performance from the start of the test is 1 × 10⁻⁶ ６ The time it takes for the resistance to fall below Ω is between 200 and 500 hours, indicating good HAST resistance. ×: Electrical insulation is 1 × 10⁻¹⁶ from the start of the test. ６ The time it takes to fall below Ω is less than 200 hours, indicating poor HAST resistance.

[0095] From the evaluation results shown in Table 1, it can be seen that the cured products of each photosensitive resin composition in Examples 1 to 12 have excellent crack resistance and HAST resistance on the substrate and possess good insulation reliability. Therefore, it can be seen that each photosensitive resin composition in Examples 1 to 12 can form cured products with good insulation reliability. On the other hand, it can be seen that the cured products of each photosensitive resin composition in Comparative Examples 1 to 3 have poor crack resistance and HAST resistance on the substrate and do not possess good insulation reliability.

Claims

1. A carboxyl group-containing resin, a photopolymerization initiator, and a thermosetting component, wherein the photopolymerization initiator is of the following general formula (I): [In the formula, R １ and R ２ Each independently represents an aryl group having 7 to 20 carbon atoms, which may be substituted with at least one of an alkyl group, an alkoxy group, and a phenyl group, or an arylcarbonyl group having 7 to 20 carbon atoms, which may be substituted with at least one of an alkyl group and an alkoxy group, R ３ A photosensitive resin composition characterized by having a substructure represented by ].

2. The photosensitive resin composition according to claim 1, wherein the carboxyl group-containing resin includes a carboxyl group-containing resin obtained using a phenol compound as a starting material.

3. A dry film comprising a first film and a resin layer formed from the photosensitive resin composition according to claim 1, laminated on at least one surface of the first film.

4. A cured product obtained by curing the resin layer of the photosensitive resin composition according to claim 1, or the dry film according to claim 3.

5. A printed circuit board comprising the cured product described in claim 4.

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