JP7587352B2 - Photosensitive composition, cured product, method for producing cured product, and photopolymerizable composition - Google Patents

Description

The present invention relates to a photosensitive composition, a cured product, a method for producing the cured product, and a photopolymerizable composition.

In a display device such as a liquid crystal display device, a material such as an insulating film is provided together with a light source such as a backlight, an electrode layer, a colored layer, etc.

Such insulating films are usually patterned on a substrate. A method for forming a patterned insulating film is known, for example, that uses a negative-type photosensitive composition that contains an alkali-soluble resin having an oxetane ring, a polymerizable polyfunctional compound, and an α-aminoalkylphenone-based photopolymerization initiator (see Patent Document 1).

JP 2012-173678 A

When the dielectric constant of components such as insulating films that make up a display device such as a liquid crystal display device is high, display defects on the display device are likely to occur. For this reason, a photosensitive composition that can form a cured product with a low dielectric constant is desired.

In addition, the cured product obtained by exposing and developing the photosensitive composition may be heated, which may cause the cured product to flow significantly and reach unintended areas.
On the other hand, there are cases where a cured product having a cross-sectional shape that is not rectangular but has gently sloping side faces is desired. Such a cured product can be formed by heating the cured product obtained by exposure and development to flow. In this case, it is necessary for the cured product to flow appropriately when heated.
For this reason, the cured product after exposure and development is required to have a suitable range of thermal flow properties.

The present invention has been made in consideration of the above problems, and aims to provide a photosensitive composition capable of forming a cured product having suitable thermal flow properties and a low dielectric constant, a cured product of the photosensitive composition, a method for producing the cured product, and a photopolymerizable composition that can be blended with the above-mentioned photosensitive composition.

The present inventors have discovered that the above problems can be solved by using a combination of a photopolymerizable compound (B1) and a photopolymerizable compound (B2) having a specific structure as the photopolymerizable compound (B) in a photosensitive composition containing an alkali-soluble resin (A), a photopolymerizable compound (B), and a photopolymerization initiator (C), and by setting the photopolymerizable compound (B2) in a predetermined ratio, thereby completing the present invention. More specifically, the present invention provides the following.

（式（ｂ１－１）中、Ｒ^１ｂ～Ｒ^５ｂは、（メタ）アクリロイル基であり、Ｒ^６ｂは、（メタ）アクリロイルオキシメチル基、炭素原子数２以上５以下のアルケニル基、炭素原子数１以上５以下のアルキル基、炭素原子数１以上５以下のアルコキシ基、炭素原子数２以上５以下のアルコキシメチル基、フェニルオキシ基、フェニルオキシメチル基、炭素原子数２以上５以下のアルカノイルオキシ基、炭素原子数３以上５以下のアルカノイルオキシメチル基、ベンゾイルオキシ基、又はベンゾイルオキシメチル基である。）

（式（ｂ２－１）中、Ｒ^７ｂ～Ｒ^１２ｂは、それぞれ独立に、（メタ）アクリロイルオキシメチル基、又は１以上５以下の酸素原子で中断されてもよく、１以上の炭素原子がオキソ基で置換されていてもよく、１以上の不飽和結合を有していてもよい炭素原子数７以上２０以下の鎖状脂肪族基であり、Ｒ^７ｂ～Ｒ^１２ｂのうちの３つ以上５つ以下が（メタ）アクリロイルオキシメチル基である。） A first aspect of the present invention is a composition comprising an alkali-soluble resin (A), a photopolymerizable compound (B), a photopolymerization initiator (C), and a solvent (S),
the photopolymerizable compound (B) contains a photopolymerizable compound (B1) and a photopolymerizable compound (B2);
The photopolymerizable compound (B1) is a compound represented by the following formula (b1-1):
The photopolymerizable compound (B2) is a compound represented by the following formula (b2-1):
A photosensitive composition, in which the ratio of the mass of the photopolymerizable compound (B2) to the mass of the photopolymerizable compound (B) is 5 mass % or more and 20 mass % or less.

(In formula (b1-1), R ^1b to R ^5b are each a (meth)acryloyl group, and R ^6b is a (meth)acryloyloxymethyl group, an alkenyl group having from 2 to 5 carbon atoms, an alkyl group having from 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, an alkoxymethyl group having from 2 to 5 carbon atoms, a phenyloxy group, a phenyloxymethyl group, an alkanoyloxy group having from 2 to 5 carbon atoms, an alkanoyloxymethyl group having from 3 to 5 carbon atoms, a benzoyloxy group, or a benzoyloxymethyl group.)

(In formula (b2-1), R ^7b to R ^12b each independently represent a (meth)acryloyloxymethyl group or a chain aliphatic group having 7 to 20 carbon atoms which may be interrupted by 1 to 5 oxygen atoms, one or more carbon atoms may be substituted with an oxo group, and which may have one or more unsaturated bonds, and 3 to 5 of R ^7b to R ^12b are (meth)acryloyloxymethyl groups.)

The second aspect of the present invention is a cured product of the photosensitive composition according to the first aspect.

A third aspect of the present invention is a method for forming a coating film by applying the photosensitive composition according to the first aspect;
and exposing the coating film to light.

A fourth aspect of the present invention is a method for forming a coating film by applying the photosensitive composition according to the first aspect;
A step of position-selectively exposing the coating film;
and developing the coating film after exposure.

（式（ｂ１－１）中、Ｒ^１ｂ～Ｒ^５ｂは、（メタ）アクリロイル基であり、Ｒ^６ｂは、（メタ）アクリロイルオキシメチル基、炭素原子数２以上５以下のアルケニル基、炭素原子数１以上５以下のアルキル基、炭素原子数１以上５以下のアルコキシ基、炭素原子数２以上５以下のアルコキシメチル基、フェニルオキシ基、フェニルオキシメチル基、炭素原子数２以上５以下のアルカノイルオキシ基、炭素原子数３以上５以下のアルカノイルオキシメチル基、ベンゾイルオキシ基、又はベンゾイルオキシメチル基である。）

（式（ｂ２－１）中、Ｒ^７ｂ～Ｒ^１２ｂは、それぞれ独立に、（メタ）アクリロイルオキシメチル基、又は１以上５以下の酸素原子で中断されてもよく、１以上の炭素原子がオキソ基で置換されていてもよく、１以上の不飽和結合を有していてもよい炭素原子数７以上２０以下の鎖状脂肪族基であり、Ｒ^７ｂ～Ｒ^１２ｂのうちの３つ以上５つ以下が（メタ）アクリロイルオキシメチル基である。） A fifth aspect of the present invention includes a photopolymerizable compound (B1) and a photopolymerizable compound (B2),
The photopolymerizable compound (B1) is a compound represented by the following formula (b1-1):
The photopolymerizable compound (B2) is a compound represented by the following formula (b2-1):
The content of the photopolymerizable compound (B2) in the photopolymerizable composition is 5% by mass or more and 20% by mass or less.

(In formula (b1-1), R ^1b to R ^5b are each a (meth)acryloyl group, and R ^6b is a (meth)acryloyloxymethyl group, an alkenyl group having from 2 to 5 carbon atoms, an alkyl group having from 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, an alkoxymethyl group having from 2 to 5 carbon atoms, a phenyloxy group, a phenyloxymethyl group, an alkanoyloxy group having from 2 to 5 carbon atoms, an alkanoyloxymethyl group having from 3 to 5 carbon atoms, a benzoyloxy group, or a benzoyloxymethyl group.)

(In formula (b2-1), R ^7b to R ^12b each independently represent a (meth)acryloyloxymethyl group or a chain aliphatic group having 7 to 20 carbon atoms which may be interrupted by 1 to 5 oxygen atoms, one or more carbon atoms may be substituted with an oxo group, and which may have one or more unsaturated bonds, and 3 to 5 of R ^7b to R ^12b are (meth)acryloyloxymethyl groups.)

The present invention provides a photosensitive composition capable of forming a cured product having suitable thermal flow properties and a low dielectric constant, a cured product using the photosensitive composition, a method for producing the cured product, and a photopolymerizable composition that can be blended with the photosensitive composition.

FIG. 4 is a schematic diagram illustrating a method for measuring a taper angle θ.

<Photosensitive composition>
The photosensitive composition contains an alkali-soluble resin (A), a photopolymerizable compound (B), a photopolymerization initiator (C), and a solvent (S).
The photosensitive composition contains, as the photopolymerizable compound (B), a photopolymerizable compound (B1) and a photopolymerizable compound (B2). The photopolymerizable compound (B1) is a compound represented by formula (b1-1). The photopolymerizable compound (B2) is a compound represented by formula (b2-1). The ratio of the mass of the photopolymerizable compound (B2) to the mass of the photopolymerizable compound (B) is 5 mass% or more and 20 mass% or less.
The photosensitive composition contains a combination of the photopolymerizable compound (B1) and a predetermined amount of the photopolymerizable compound (B2), and thus becomes a photosensitive composition that has appropriate thermal flow properties and is capable of forming a cured product having a low dielectric constant.

Below, we will explain the essential and optional components contained in the photosensitive composition and the method for producing the photosensitive composition.

<Alkali-soluble resin (A)>
The photosensitive composition contains an alkali-soluble resin (A). The alkali-soluble resin (A) is not particularly limited and can be appropriately selected from alkali-soluble resins that have been conventionally blended in various photosensitive compositions.
In this specification, the alkali-soluble resin (A) refers to a resin having a functional group (such as a phenolic hydroxyl group, a carboxyl group, or a sulfonic acid group) in the molecule that imparts alkali-solubility.

An example of a resin suitable as the alkali-soluble resin (A) is a resin (a-I) having a cardo structure (hereinafter also referred to as "cardo resin (a-I)").

[Resin having a cardo structure (a-I)]
As the resin (a-I) having a cardo skeleton, a resin having a cardo skeleton in its structure and having a predetermined alkali solubility can be used. A cardo skeleton is a skeleton in which a second ring structure and a third ring structure are bonded to one ring carbon atom constituting a first ring structure. The second ring structure and the third ring structure may be the same structure or different structures.
A representative example of a cardo skeleton is a skeleton in which two aromatic rings (eg, benzene rings) are bonded to the carbon atom at the 9-position of a fluorene ring.

The cardo resin (a-I) is not particularly limited, and any conventionally known resin can be used. Among them, the resin represented by the following formula (a-1) is preferred.

In formula (a-1), ^Xa represents a group represented by the following formula (a-2): m1 represents an integer of 0 or more and 20 or less.

In the above formula (a-2), R ^a1 each independently represents a hydrogen atom, a hydrocarbon group having from 1 to 6 carbon atoms, or a halogen atom, R ^a2 each independently represents a hydrogen atom or a methyl group, R ^a3 each independently represents a linear or branched alkylene group, m2 represents 0 or 1, and W ^a represents a group represented by the following formula (a-3):

In formula (a-2), R ^a3 is preferably an alkylene group having 1 to 20 carbon atoms, more preferably an alkylene group having 1 to 10 carbon atoms, particularly preferably an alkylene group having 1 to 6 carbon atoms, and most preferably an ethane-1,2-diyl group, a propane-1,2-diyl group, or a propane-1,3-diyl group.

Ring A in formula (a-3) represents an aliphatic ring which may be condensed with an aromatic ring and may have a substituent. The aliphatic ring may be an aliphatic hydrocarbon ring or an aliphatic heterocycle.
Examples of the aliphatic ring include a monocycloalkane, a bicycloalkane, a tricycloalkane, and a tetracycloalkane.
Specific examples include monocycloalkanes such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane, as well as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.
The aromatic ring that may be condensed with the aliphatic ring may be an aromatic hydrocarbon ring or an aromatic heterocyclic ring, and is preferably an aromatic hydrocarbon ring, specifically, a benzene ring or a naphthalene ring.

Suitable examples of the divalent group represented by formula (a-3) include the following groups.

The divalent group X ^a in formula (a-1) is introduced into the cardo resin (a-I) by reacting a tetracarboxylic dianhydride giving a residue Z ^a with a diol compound represented by the following formula (a-2a):

In formula (a-2a), R ^a1 , R ^a2 , R ^a3 and m2 are as described for formula (a-2), and ring A in formula (a-2a) is as described for formula (a-3).

The diol compound represented by formula (a-2a) can be produced, for example, by the following method.
First, the hydrogen atom in the phenolic hydroxyl group of a diol compound represented by the following formula (a-2b) is replaced with a group represented by -R ^a3 -OH according to a conventional method, if necessary, and then the resulting compound is glycidylated using epichlorohydrin or the like to obtain an epoxy compound represented by the following formula (a-2c).
Next, the epoxy compound represented by formula (a-2c) is reacted with acrylic acid or methacrylic acid to obtain the diol compound represented by formula (a-2a).
In formulae (a-2b) and (a-2c), R ^a1 , R ^a3 , and m2 are as described for formula (a-2). Ring A in formulae (a-2b) and (a-2c) is as described for formula (a-3).
The method for producing the diol compound represented by formula (a-2a) is not limited to the above method.

Suitable examples of the diol compound represented by formula (a-2b) include the following diol compounds.

In the above formula (a-1), R ^a0 is a hydrogen atom or a group represented by -CO-Y ^a -COOH. Here, Y ^a represents a residue obtained by removing the acid anhydride group (-CO-O-CO-) from a dicarboxylic acid anhydride. Examples of dicarboxylic acid anhydrides include maleic anhydride, succinic anhydride, itaconic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyl-end-methylene-tetrahydrophthalic anhydride, chlorendic anhydride, methyltetrahydrophthalic anhydride, glutaric anhydride, etc.

In the above formula (a-1), Z ^a represents a residue obtained by removing two acid anhydride groups from a tetracarboxylic dianhydride. Examples of the tetracarboxylic dianhydride include the tetracarboxylic dianhydride represented by the following formula (a-4), pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, biphenyl tetracarboxylic dianhydride, and biphenyl ether tetracarboxylic dianhydride.
In the above formula (a-1), m represents an integer of 0 or more and 20 or less.

（式（ａ－４）中、Ｒ^ａ４、Ｒ^ａ５、及びＲ^ａ６は、それぞれ独立に、水素原子、炭素原子数１以上１０以下のアルキル基及びフッ素原子からなる群より選択される１種を示し、ｍ３は、０以上１２以下の整数を示す。）

(In formula (a-4), R ^a4 , R ^a5 , and R ^a6 each independently represent one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, and a fluorine atom, and m3 represents an integer of 0 to 12.)

The alkyl group that can be selected as R ^a4 in formula (a-4) is an alkyl group having 1 to 10 carbon atoms. By setting the number of carbon atoms of the alkyl group within this range, the heat resistance of the resulting carboxylic acid ester can be further improved. When ^{R a4} is an alkyl group, the number of carbon atoms is preferably 1 to 6, more preferably 1 to 5, even more preferably 1 to 4, and particularly preferably 1 to 3, from the viewpoint of easily obtaining a cardo resin having excellent heat resistance.
When R ^a4 is an alkyl group, the alkyl group may be linear or branched.

In terms of facilitating the production of a cardo resin having excellent heat resistance, R ^a4 in formula (a-4) is preferably each independently a hydrogen atom or an alkyl group having from 1 to 10 carbon atoms. R ^a4 in formula (a-4) is more preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group or an isopropyl group, and particularly preferably a hydrogen atom or a methyl group.
In the formula (a-4), a plurality of R ^a4's are preferably the same group, since this facilitates the preparation of a high-purity tetracarboxylic dianhydride.

In formula (a-4), m3 represents an integer of 0 to 12. By setting the value of m3 to 12 or less, purification of the tetracarboxylic dianhydride can be facilitated.
In view of ease of purification of the tetracarboxylic dianhydride, the upper limit of m3 is preferably 5, more preferably 3.
From the viewpoint of chemical stability of the tetracarboxylic dianhydride, the lower limit of m3 is preferably 1, and more preferably 2.
In formula (a-4), m3 is particularly preferably 2 or 3.

In formula (a-4), the alkyl group having 1 to 10 carbon atoms which can be selected as R ^a5 and R ^a6 is the same as the alkyl group having 1 to 10 carbon atoms which can be selected as R ^a4 .
In view of ease of purification of the tetracarboxylic dianhydride, R ^a5 and R ^a6 are preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms (preferably 1 to 6, more preferably 1 to 5, even more preferably 1 to 4, and particularly preferably 1 to 3), and are particularly preferably a hydrogen atom or a methyl group.

Examples of the tetracarboxylic dianhydride represented by formula (a-4) include norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride (also known as "norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride"), methylnorbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-(methylnorbornane)-5,5'',6,6''-tetracarboxylic dianhydride, and norbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride (also known as "norbornane-2-spiro-2'-cyclohex methylnorbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-(methylnorbornane)-5,5'',6,6''-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclopropanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclobutanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride, norbornane-2-spiro-α-cycloheptanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride, norbornane-2-spiro-α- Cyclooctanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclononanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclodecanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride, norbornane-2-spiro-α-cycloundecanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclododecanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride, norbornane-2-spiro-α-cycloto Ridecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclotetradecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclopentadecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride, norbornane-2-spiro-α-(methylcyclopentanone)-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride, norbornane-2-spiro-α-(methylcyclohexanone)-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride, and the like.

The weight average molecular weight of the cardo resin (a-I) is preferably 1,000 to 40,000, more preferably 1,500 to 30,000, and even more preferably 2,000 to 10,000. By setting it within the above range, it is possible to obtain good developability while also obtaining sufficient heat resistance and mechanical strength for the cured film formed using the photosensitive composition.

[Novolak resin (a-II)]
It is also preferable that the alkali-soluble resin (A) contains a novolak resin (a-II) since this makes it easy to form a cured product that does not flow excessively when heated.
As the novolak resin (a-II), various novolak resins that have been conventionally incorporated into photosensitive compositions can be used. As the novolak resin (a-II), those obtained by addition condensation of an aromatic compound having a phenolic hydroxyl group (hereinafter simply referred to as a "phenol") and an aldehyde in the presence of an acid catalyst are preferred.

(Phenols)
Examples of phenols used in preparing the novolak resin (a-II) include phenol; cresols such as o-cresol, m-cresol, and p-cresol; xylenols such as 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, and 3,5-xylenol; ethylphenols such as o-ethylphenol, m-ethylphenol, and p-ethylphenol; 2-isopropylphenol, 3-isopropylphenol, 4-isopropylphenol, o-butylphenol, m-butylphenol, and p-butylphenol. and p-tert-butylphenol; trialkylphenols such as 2,3,5-trimethylphenol and 3,4,5-trimethylphenol; polyhydric phenols such as resorcinol, catechol, hydroquinone, hydroquinone monomethyl ether, pyrogallol, and phloroglucinol; alkyl polyhydric phenols such as alkylresorcinol, alkylcatechol, and alkylhydroquinone (all alkyl groups having 1 to 4 carbon atoms); α-naphthol; β-naphthol; hydroxydiphenyl; and bisphenol A. These phenols may be used alone or in combination of two or more.

Among these phenols, m-cresol and p-cresol are preferred, and it is more preferred to use m-cresol and p-cresol in combination. In this case, by adjusting the mixing ratio of the two, it is possible to adjust various properties such as heat resistance of the cured film formed using the photosensitive composition.
The blending ratio of m-cresol and p-cresol is not particularly limited, but the molar ratio of m-cresol/p-cresol is preferably from 3/7 to 8/2. By using m-cresol and p-cresol in this range, it is easy to obtain a photosensitive composition capable of forming a cured film having excellent heat resistance.

Also preferred is a novolak resin produced by using m-cresol and 2,3,5-trimethylphenol in combination. When such a novolak resin is used, it is particularly easy to obtain a photosensitive composition capable of forming a cured film having excellent heat resistance.
The mixing ratio of m-cresol and 2,3,5-trimethylphenol is not particularly limited, but the molar ratio of m-cresol/2,3,5-trimethylphenol is preferably 70/30 or more and 95/5 or less.

(Aldehydes)
Examples of aldehydes used in preparing the novolac resin (a-II) include formaldehyde, paraformaldehyde, furfural, benzaldehyde, nitrobenzaldehyde, acetaldehyde, etc. These aldehydes may be used alone or in combination of two or more kinds.

(Acid Catalyst)
Examples of the acid catalyst used in preparing the novolak resin (a-II) include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and phosphorous acid, organic acids such as formic acid, oxalic acid, acetic acid, diethylsulfuric acid, and paratoluenesulfonic acid, and metal salts such as zinc acetate, etc. These acid catalysts may be used alone or in combination of two or more kinds.

(Molecular Weight)
The polystyrene-equivalent weight average molecular weight (Mw; hereinafter, also simply referred to as "weight average molecular weight") of the novolak resin (a-II) is, from the viewpoint of heat resistance of a cured film formed using the photosensitive composition, preferably has a lower limit of 2,000, more preferably 5,000, particularly preferably 10,000, further preferably 15,000, and most preferably 20,000; and the upper limit is preferably 50,000, more preferably 45,000, further preferably 40,000, and most preferably 35,000.

As the novolac resin (a-II), at least two types of resins having different weight average molecular weights in terms of polystyrene can be used in combination. By using a combination of resins having different weight average molecular weights, it is possible to achieve a balance between the developability of the photosensitive composition and the heat resistance of the cured film formed using the photosensitive composition.

[Modified Epoxy Resin (a-III)]
The alkali-soluble resin (A) may contain an adduct (a-3) of a polybasic acid anhydride (a-3c) which is a reaction product of an epoxy compound (a-3a) and an unsaturated group-containing carboxylic acid (a-3b). Such an adduct is also referred to as a "modified epoxy resin (a-III)".
In the specification and claims of this application, a compound that meets the above definition but does not fall under the aforementioned resin (a-I) having a cardo structure is referred to as a modified epoxy resin (a-III).

The epoxy compound (a-3a), the unsaturated group-containing carboxylic acid (a-3b), and the polybasic acid anhydride (a-3c) are described below.

<Epoxy compound (a-3a)>
The epoxy compound (a-3a) is not particularly limited as long as it is a compound having an epoxy group, and may be an aromatic epoxy compound having an aromatic group or an aliphatic epoxy compound not containing an aromatic group, and is preferably an aromatic epoxy compound having an aromatic group.
The epoxy compound (a-3a) may be a monofunctional epoxy compound or a di- or higher functional polyfunctional epoxy compound, and is preferably a polyfunctional epoxy compound.

Specific examples of epoxy compounds (a-3a) include bifunctional epoxy resins such as bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AD type epoxy resins, naphthalene type epoxy resins, and biphenyl type epoxy resins; glycidyl ester type epoxy resins such as dimer acid glycidyl ester and triglycidyl ester; glycidyl amine type epoxy resins such as tetraglycidylaminodiphenylmethane, triglycidyl-p-aminophenol, tetraglycidylmeta-xylylenediamine, and tetraglycidylbisaminomethylcyclohexane; heterocyclic epoxy resins such as triglycidyl isocyanurate; phloroglucinol triglycidyl ether, trihydroxybiphenyl triglycidyl trifunctional epoxy resins such as 4-(2,3-epoxypropoxy)phenyl, trihydroxyphenylmethane triglycidyl ether, glycerin triglycidyl ether, 2-[4-(2,3-epoxypropoxy)phenyl]-2-[4-[1,1-bis[4-(2,3-epoxypropoxy)phenyl]ethyl]phenyl]propane, and 1,3-bis[4-[1-[4-(2,3-epoxypropoxy)phenyl]-1-[4-[1-[4-(2,3-epoxypropoxy)phenyl]-1-methylethyl]phenyl]ethyl]phenoxy]-2-propanol; and tetrafunctional epoxy resins such as tetrahydroxyphenylethane tetraglycidyl ether, tetraglycidylbenzophenone, bisresorcinol tetraglycidyl ether, and tetraglycidoxybiphenyl.

As the epoxy compound (a-3a), an epoxy compound having a biphenyl skeleton is preferable.
The epoxy compound having a biphenyl skeleton preferably has at least one biphenyl skeleton represented by the following formula (a-3a-1) in the main chain.
The epoxy compound having a biphenyl skeleton is preferably a polyfunctional epoxy compound having two or more epoxy groups.
By using an epoxy compound having a biphenyl skeleton, it is easy to obtain a photosensitive composition that has an excellent balance between sensitivity and developability and is capable of forming a cured film that has excellent adhesion to a substrate.

（式（ａ－３ａ－１）中、Ｒ^ａ７は、それぞれ独立に、水素原子、炭素原子数１以上１２以下のアルキル基、ハロゲン原子、又は置換基を有してもよいフェニル基であり、ｊは１以上４以下の整数である。）

(In formula (a-3a-1), each R ^a7 independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a halogen atom, or a phenyl group which may have a substituent, and j represents an integer of 1 to 4.)

When R ^a7 is an alkyl group having 1 to 12 carbon atoms, specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an isononyl group, an n-decyl group, an isodecyl group, an n-undecyl group, and an n-dodecyl group.

When R ^a7 is a halogen atom, specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

When R ^a7 is a phenyl group which may have a substituent, the number of the substituents on the phenyl group is not particularly limited. The number of the substituents on the phenyl group is 0 to 5, preferably 0 or 1.
Examples of the substituent include an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an aliphatic acyl group having 2 to 4 carbon atoms, a halogen atom, a cyano group, and a nitro group.

（式（ａ－３ａ－２）中、Ｒ^ａ７及びｊは、式（ａ－３ａ－１）と同様であり、ｋは括弧内の構成単位の平均繰り返し数であって０以上１０以下である。） The epoxy compound (a-3a) having a biphenyl skeleton represented by the above formula (a-3a-1) is not particularly limited, but examples thereof include the epoxy compound represented by the following formula (a-3a-2).

(In formula (a-3a-2), R ^a7 and j are the same as those in formula (a-3a-1), and k is the average repeating number of the structural unit in parentheses and is 0 to 10.)

（式（ａ－３ａ－３）中、ｋは、式（ａ－３ａ－２）と同様である。） Among the epoxy compounds represented by formula (a-3a-2), the compound represented by the following formula (a-3a-3) is preferred because it is particularly easy to obtain a photosensitive composition having an excellent balance between sensitivity and developability.

(In formula (a-3a-3), k is the same as in formula (a-3a-2).)

(Unsaturated group-containing carboxylic acid (a-3b))
In preparing the modified epoxy compound (a-3), an epoxy compound (a-3a) is reacted with an unsaturated group-containing carboxylic acid (a-3b).
As the unsaturated group-containing carboxylic acid (a-3b), a monocarboxylic acid containing a reactive unsaturated double bond such as an acrylic group or a methacrylic group in the molecule is preferable. Examples of the unsaturated group-containing carboxylic acid include acrylic acid, methacrylic acid, β-styrylacrylic acid, β-furfurylacrylic acid, α-cyanocinnamic acid, and cinnamic acid. 3b) may be used alone or in combination of two or more kinds.

The epoxy compound (a-3a) and the unsaturated group-containing carboxylic acid (a-3b) can be reacted by a known method. A preferred reaction method is, for example, a method in which the epoxy compound (a-3a) and the unsaturated group-containing carboxylic acid (a-3b) are reacted in an organic solvent at a reaction temperature of 50°C to 150°C for several hours to several tens of hours using a tertiary amine such as triethylamine or benzylethylamine, a quaternary ammonium salt such as dodecyltrimethylammonium chloride, tetramethylammonium chloride, tetraethylammonium chloride or benzyltriethylammonium chloride, pyridine, or triphenylphosphine as a catalyst.

The ratio of the amounts of the epoxy compound (a-3a) and the unsaturated group-containing carboxylic acid (a-3b) used in the reaction between them, expressed as the ratio of the epoxy equivalent of the epoxy compound (a-3a) to the carboxylic acid equivalent of the unsaturated group-containing carboxylic acid (a-3b), is usually preferably 1:0.5 to 1:2, more preferably 1:0.8 to 1:1.25, and particularly preferably 1:0.9 to 1:1.1.
When the ratio of the amount of the epoxy compound (a-3a) to the amount of the unsaturated group-containing carboxylic acid (a-3b) is 1:0.5 to 1:2 in terms of the equivalent ratio, the crosslinking efficiency tends to be improved, which is preferable.

(Polybasic acid anhydride (a-3c))
The polybasic acid anhydrides (a-3c) are anhydrides of carboxylic acids having two or more carboxy groups.
The polybasic acid anhydride (a-3c) is not particularly limited, but examples thereof include maleic anhydride, succinic anhydride, itaconic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic dianhydride, 3-methylhexahydrophthalic anhydride, 4-methylhexahydrophthalic anhydride, 3-ethylhexahydrophthalic anhydride, 4-ethylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, 3-methyltetrahydrophthalic anhydride, 4-methyltetrahydrophthalic anhydride, 3-ethyltetrahydrophthalic anhydride, 4-ethyltetrahydrophthalic anhydride, a compound represented by the following formula (a-3c-1), and a compound represented by the following formula (a-3c-2). The polybasic acid anhydrides (a-3c) may be used alone or in combination of two or more kinds.

（式（ａ－３ｃ－２）中、Ｒ^ａ８は、炭素原子数１以上１０以下の置換基を有してもよいアルキレン基を示す。）

(In formula (a-3c-2), R ^a8 represents an alkylene group having 1 to 10 carbon atoms which may have a substituent.)

As the polybasic acid anhydride (a-3c), a compound having two or more benzene rings is preferable because it is easy to obtain a photosensitive composition that has an excellent balance between sensitivity and developability. Furthermore, it is more preferable that the polybasic acid anhydride (a-3c) contains at least one of the compound represented by the above formula (a-3c-1) and the compound represented by the above formula (a-3c-2).

The method for reacting the epoxy compound (a-3a) with the unsaturated group-containing carboxylic acid (a-3b) and then reacting with the polybasic acid anhydride (a-3c) can be appropriately selected from known methods.
The ratio of the amounts used, expressed as the molar ratio of OH groups in the components after the reaction of the epoxy compound (a-3a) with the unsaturated group-containing carboxylic acid (a-3b) to the equivalent ratio of the acid anhydride groups of the polybasic acid anhydride (a-3c), is usually 1:1 to 1:0.1, and preferably 1:0.8 to 1:0.2. By setting the ratio within the above range, a photosensitive composition having good developability is easily obtained.

In addition, the acid value of the modified epoxy resin (a-III) is preferably 10 mgKOH/g or more and 150 mgKOH/g or less, more preferably 70 mgKOH/g or more and 110 mgKOH/g or less, based on the resin solids content. By making the acid value of the resin 10 mgKOH/g or more, sufficient solubility in the developer can be obtained, and by making the acid value 150 mgKOH/g or less, sufficient curability can be obtained, resulting in good surface properties.

The weight average molecular weight of the modified epoxy resin (a-III) is preferably 1,000 or more and 40,000 or less, and more preferably 2,000 or more and 30,000 or less. A weight average molecular weight of 1,000 or more makes it easier to form a cured film with excellent heat resistance and strength. A weight average molecular weight of 40,000 or less makes it easier to obtain a photosensitive composition that exhibits sufficient solubility in a developer.

[Acrylic resin (a-IV)]
The acrylic resin (a-IV) is also preferred as a component constituting the alkali-soluble resin (A). The alkali-soluble resin (A) preferably contains the acrylic resin (a-IV) because it has suitable thermal flow properties and is easy to form a cured product with a low relative dielectric constant.

The ratio of the mass of the acrylic resin (a-IV) to the total mass of the alkali-soluble resin (A) is typically preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 100% by mass.

As the acrylic resin (a-IV), those containing structural units derived from (meth)acrylic acid and/or structural units derived from other monomers such as (meth)acrylic acid esters can be used. (Meth)acrylic acid is acrylic acid or methacrylic acid. As the other monomers, typically, compounds represented by the following formula (a-4-1) are preferably used.

In the above formula (a-4-1), R ^a9 is a hydrogen atom or a methyl group. R ^a10 is a monovalent organic group. This organic group may contain a bond or a substituent other than the hydrocarbon group, such as a heteroatom, in the organic group. In addition, this organic group may be linear, branched, or cyclic. ^{R a11} is a group represented by -O- or -NR ^a12 -. R ^a12 is a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms.

The substituent other than the hydrocarbon group in the organic group of R ^a10 is not particularly limited as long as the effects of the present invention are not impaired, and examples thereof include a halogen atom, a hydroxyl group, a mercapto group, a sulfide group, a cyano group, an isocyano group, a cyanato group, an isocyanato group, a thiocyanato group, an isothiocyanato group, a silyl group, a silanol group, an alkoxy group, an alkoxycarbonyl group, a carbamoyl group, a thiocarbamoyl group, a nitro group, a nitroso group, a carboxy group, a carboxylate group, an acyl group, an acyloxy group, a sulfino group, a sulfo group, a sulfonato group, a phosphino group, a phosphinyl group, a phosphono group, a phosphonato group, a hydroxyimino group, an alkyl ether group, an alkyl thioether group, an aryl ether group, an aryl thioether group, an amino group (-NH ₂ , -NHR, -NRR': R and R' each independently represent a hydrocarbon group), etc. The hydrogen atom contained in the above substituent may be substituted with a hydrocarbon group. The hydrocarbon group contained in the above-mentioned substituent may be any one of straight-chain, branched-chain, and cyclic.

In addition, the organic group represented by R ^a10 may have a reactive functional group such as an acryloyloxy group, a methacryloyloxy group, an epoxy group, or an oxetanyl group.
An acyl group having an unsaturated double bond, such as an acryloyloxy group or a methacryloyloxy group, can be produced, for example, by reacting at least a part of the epoxy groups in an acrylic resin (a-IV) containing a structural unit having an epoxy group with an unsaturated carboxylic acid, such as acrylic acid or methacrylic acid.
It is also possible to react at least a portion of the epoxy groups with an unsaturated carboxylic acid, and then react the groups formed by the reaction with a polybasic acid anhydride.

Specific examples of polybasic acid anhydrides include maleic anhydride, succinic anhydride, itaconic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic dianhydride, 3-methylhexahydrophthalic anhydride, 4-methylhexahydrophthalic anhydride, 3-ethylhexahydrophthalic anhydride, 4-ethylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, 3-methyltetrahydrophthalic anhydride, 4-methyltetrahydrophthalic anhydride, 3-ethyltetrahydrophthalic anhydride, and 4-ethyltetrahydrophthalic anhydride.

As a specific example, when a structural unit derived from glycidyl methacrylate is reacted with acrylic acid, a structural unit having a hydroxyl group is produced as shown in the following reaction formula: When such a structural unit having a hydroxyl group is reacted with a polybasic acid anhydride such as tetrahydrophthalic acid, a structural unit having a carboxyl group and an unsaturated double bond, which imparts alkali solubility to the resin, is produced.

In addition, an unsaturated double bond can be introduced into the acrylic resin (a-IV) by reacting a compound having an epoxy group and an unsaturated double bond with a structural unit derived from an unsaturated carboxylic acid such as acrylic acid or methacrylic acid contained in the acrylic resin (a-IV). As the compound having an epoxy group and an unsaturated double bond, for example, glycidyl (meth)acrylate or compounds represented by the formulae (a-4-1a) to (a-4-1o) described later can be used.

R ^a10 is preferably an alkyl group, an aryl group, a cycloalkyl group, a polycycloalkyl group, a cycloalkylalkyl group, a polycycloalkylalkyl group, an aralkyl group, or a heterocyclic group, and these groups may be substituted with a halogen atom, a hydroxyl group, an alkyl group, or a heterocyclic group, and an oxygen atom may be bonded to these groups to form an epoxy group. When these groups contain an alkylene moiety, the alkylene moiety may be interrupted by an ether bond, a thioether bond, or an ester bond.

When the alkyl group is linear or branched, the number of carbon atoms is preferably 1 to 20, more preferably 1 to 15, and particularly preferably 1 to 10. Examples of suitable alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, tert-pentyl, n-hexyl, n-heptyl, n-octyl, isooctyl, sec-octyl, tert-octyl, n-nonyl, isononyl, n-decyl, and isodecyl.

In the cycloalkyl group, polycycloalkyl group, cycloalkylalkyl group, polycycloalkylalkyl group, and alicyclic group-containing groups other than these groups, suitable examples of the alicyclic group contained in these groups include monocyclic alicyclic groups such as cyclopentyl group and cyclohexyl group, and polycycloalkyl groups such as adamantyl group, norbornyl group, isobornyl group, tricyclononyl group, tricyclodecyl group, tetracyclododecyl group, bicyclo-[2.1.1]-hexyl group, bicyclo-[2.2.1]-heptyl group, bicyclo-[2.2.2]-octyl group, bicyclo-[3.3.0]-octyl group, bicyclo-[4.3.0]-nonyl group, and bicyclo-[4.4.0]-decyl group.

Suitable examples of the compound represented by formula (a4-1) and having a cycloalkyl group, a polycycloalkyl group, a cycloalkylalkyl group, a polycycloalkylalkyl group, or an alicyclic group-containing group other than these groups as R ^a10 include compounds represented by the following formulas (a-4-1a) to (a-4-1h). Among these, in order to achieve appropriate developability, compounds represented by the following formulas (a-4-1c) to (a-4-1h) are preferred, and compounds represented by the following formula (a-4-1c) or (a-4-1d) are more preferred.

In the above formula, R ^a20 represents a hydrogen atom or a methyl group, R ^a21 represents a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 6 carbon atoms, and R ^a22 represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ^a21 is preferably a single bond or a linear or branched alkylene group, such as a methylene group, an ethylene group, a propylene group, a tetramethylene group, an ethylethylene group, a pentamethylene group, or a hexamethylene group. ^{R a22} is preferably, for example, a methyl group or an ethyl group.

The alkali-soluble resin (A) preferably contains an acrylic resin that contains a structural unit (A-1) derived from a polycycloalkyl (meth)acrylate, since this facilitates the formation of a cured product with a low dielectric constant.
In other words, the acrylic resin preferably contains a structural unit derived from a compound represented by any one of the above formulas (a-4-1c) to (a-4-1h) and having a single bond as R ^a21 . It is more preferable that the acrylic resin contains, as the structural unit (A-1), a structural unit derived from a compound represented by formula (a-4-1c), formula (a-4-1d), or formula (a-4-1g) and having a single bond as R ^a21 , because this is particularly likely to form a cured product with a low dielectric constant.

The amount of the structural unit (A-1) in the acrylic resin is not particularly limited as long as it does not impair the object of the present invention. The amount of the structural unit (A-1) in the acrylic resin is preferably 10% by mass or more and 50% by mass or more, more preferably 12% by mass or more and 40% by mass or less, and even more preferably 15% by mass or more and 35% by mass or less, based on the amount of all structural units.

Specific examples of the compound represented by formula (a-4-1) in the case where the compound represented by formula (a-4-1) has a chain group having an epoxy group as R ^a10 include (meth)acrylic acid epoxy alkyl esters such as glycidyl (meth)acrylate, 2-methylglycidyl (meth)acrylate, 3,4-epoxybutyl (meth)acrylate, and 6,7-epoxyheptyl (meth)acrylate.

The compound represented by formula (a-4-1) may also be an alicyclic epoxy group-containing (meth)acrylic acid ester. The alicyclic group constituting the alicyclic epoxy group may be monocyclic or polycyclic. Examples of monocyclic alicyclic groups include cycloalkyl groups such as cyclopentyl and cyclohexyl groups. Examples of polycyclic alicyclic groups include polycycloalkyl groups such as norbornyl, isobornyl, tricyclononyl, tricyclodecyl, and tetracyclododecyl groups.

The alkali-soluble resin (A) preferably contains a structural unit (A-2) derived from a (meth)acrylate containing an alicyclic epoxy group, since this makes it easy to form a cured product with a low dielectric constant.
Specific examples of the compound represented by formula (a-4-1) that is a (meth)acrylate containing an alicyclic epoxy group include compounds represented by the following formulae (a-4-1i) to (a-4-1w). Among these, in order to achieve appropriate developability, the compounds represented by the following formulae (a-4-1i) to (a-4-1m) are preferred, and the compounds represented by the following formulae (a-4-1i) to (a-4-1k) are more preferred.

In the above formula, R ^a23 represents a hydrogen atom or a methyl group, R ^a24 represents a divalent aliphatic saturated hydrocarbon group having from 1 to 6 carbon atoms, R ^a25 represents a divalent hydrocarbon group having from 1 to 10 carbon atoms, and t represents an integer of from 0 to 10. R ^a24 is preferably a linear or branched alkylene group, such as a methylene group, an ethylene group, a propylene group, a tetramethylene group, an ethylethylene group, a pentamethylene group, or a hexamethylene group. R ^a25 is preferably, for example, a methylene group, an ethylene group, a propylene group, a tetramethylene group, an ethylethylene group, a pentamethylene group, a hexamethylene group, a phenylene group, a cyclohexylene group, or -CH ₂ -Ph-CH ₂ - (Ph represents a phenylene group).

The acrylic resin (a-IV) may also be a polymer of a monomer other than a (meth)acrylic acid ester. Examples of such monomers include (meth)acrylamides, unsaturated carboxylic acids, allyl compounds, vinyl ethers, vinyl esters, and styrenes. These monomers may be used alone or in combination of two or more.

(Meth)acrylamides include (meth)acrylamide, N-alkyl(meth)acrylamide, N-aryl(meth)acrylamide, N,N-dialkyl(meth)acrylamide, N,N-aryl(meth)acrylamide, N-methyl-N-phenyl(meth)acrylamide, and N-hydroxyethyl-N-methyl(meth)acrylamide.

Examples of unsaturated carboxylic acids include monocarboxylic acids such as crotonic acid; dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid; and anhydrides of these dicarboxylic acids.

Allyl compounds include allyl esters such as allyl acetate, allyl caproate, allyl caprylate, allyl laurate, allyl palmitate, allyl stearate, allyl benzoate, allyl acetoacetate, and allyl lactate; allyloxyethanol; and the like.

Examples of vinyl ethers include alkyl vinyl ethers such as hexyl vinyl ether, octyl vinyl ether, decyl vinyl ether, ethylhexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, chloroethyl vinyl ether, 1-methyl-2,2-dimethylpropyl vinyl ether, 2-ethylbutyl vinyl ether, hydroxyethyl vinyl ether, diethylene glycol vinyl ether, dimethylaminoethyl vinyl ether, diethylaminoethyl vinyl ether, butylaminoethyl vinyl ether, benzyl vinyl ether, and tetrahydrofurfuryl vinyl ether; and vinyl aryl ethers such as vinyl phenyl ether, vinyl tolyl ether, vinyl chlorophenyl ether, vinyl-2,4-dichlorophenyl ether, vinyl naphthyl ether, and vinyl anthranyl ether.

Vinyl esters include vinyl butyrate, vinyl isobutyrate, vinyl trimethyl acetate, vinyl diethyl acetate, vinyl valerate, vinyl caproate, vinyl chloroacetate, vinyl dichloroacetate, vinyl methoxyacetate, vinyl butoxyacetate, vinyl phenylacetate, vinyl acetoacetate, vinyl lactate, vinyl-β-phenylbutyrate, vinyl benzoate, vinyl salicylate, vinyl chlorobenzoate, vinyl tetrachlorobenzoate, vinyl naphthoate, etc.

Examples of styrenes include styrene; alkyl styrenes such as methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, isopropylstyrene, butylstyrene, hexylstyrene, cyclohexylstyrene, decylstyrene, benzylstyrene, chloromethylstyrene, trifluoromethylstyrene, ethoxymethylstyrene, and acetoxymethylstyrene; alkoxy styrenes such as methoxystyrene, 4-methoxy-3-methylstyrene, and dimethoxystyrene; and halostyrenes such as chlorostyrene, dichlorostyrene, trichlorostyrene, tetrachlorostyrene, pentachlorostyrene, bromostyrene, dibromostyrene, iodostyrene, fluorostyrene, trifluorostyrene, 2-bromo-4-trifluoromethylstyrene, and 4-fluoro-3-trifluoromethylstyrene.

The amount of the structural unit derived from (meth)acrylic acid and the amount of the structural unit derived from other monomers in the acrylic resin (a-IV) are not particularly limited as long as the object of the present invention is not impaired. The amount of the structural unit derived from (meth)acrylic acid in the acrylic resin (a-IV) is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 30% by mass or less, based on the number of moles of all structural units in the acrylic resin (a-IV).
The amount of the structural unit (A-2) derived from the (meth)acrylate containing an alicyclic epoxy group in the acrylic resin (a-IV) is not particularly limited as long as it does not impair the object of the present invention, but is preferably 30% by mass or more and 75% by mass or less, and more preferably 50% by mass or more and 73% by mass or less. When such a resin is used, it is possible to cause a self-reaction between the carboxyl group contained in the resin and the alicyclic epoxy group. Therefore, when a photosensitive composition containing such a resin is used, the mechanical properties such as the hardness of the film formed can be improved by causing a self-reaction between the carboxyl group and the alicyclic epoxy group using a method such as heating the film.

When the acrylic resin (a-IV) has a structural unit having an unsaturated double bond, the amount of the structural unit having an unsaturated double bond in the acrylic resin (a-IV) is preferably 1 mass % or more and 50 mass % or less, more preferably 1 mass % or more and 30 mass % or more, and particularly preferably 1 mass % or more and 20 mass % or less, based on the number of moles of all structural units of the acrylic resin (a-IV).
When the acrylic resin (a-IV) contains a structural unit having an unsaturated double bond in an amount within the above range, the acrylic resin can be incorporated into a crosslinking reaction within the resist film and uniformized, which is effective in improving the heat resistance and mechanical properties of the cured film.

The weight average molecular weight of the acrylic resin (a-IV) is not particularly limited as long as it does not impair the object of the present invention. The weight average molecular weight of the acrylic resin (a-IV) is preferably 9,000 or more, more preferably 9,000 to 50,000, even more preferably 9,100 to 30,000, even more preferably 9,200 to 20,000, and particularly preferably 9,500 to 15,000. By setting it within the above range, it tends to be easier to balance the film-forming ability of the photosensitive composition and the developability after exposure.

The content of the alkali-soluble resin (A) is preferably 20% by mass or more and 85% by mass or less, and more preferably 25% by mass or more and 75% by mass or less, based on the mass (total solid content) of the photosensitive composition excluding the mass of the organic solvent (S) described below. By setting the content within the above range, it is easy to obtain a photosensitive composition with excellent developability.

（式（ｂ１－１）中、Ｒ^１ｂ～Ｒ^５ｂは、（メタ）アクリロイル基であり、Ｒ^６ｂは、（メタ）アクリロイルオキシメチル基、炭素原子数２以上５以下のアルケニル基、炭素原子数１以上５以下のアルキル基、炭素原子数１以上５以下のアルコキシ基、炭素原子数２以上５以下のアルコキシメチル基、フェニルオキシ基、フェニルオキシメチル基、炭素原子数２以上５以下のアルカノイルオキシ基、炭素原子数３以上５以下のアルカノイルオキシメチル基、ベンゾイルオキシ基、又はベンゾイルオキシメチル基である。）

（式（ｂ２－１）中、Ｒ^７ｂ～Ｒ^１２ｂは、それぞれ独立に、（メタ）アクリロイルオキシメチル基、又は１以上５以下の酸素原子で中断されてもよく、１以上の炭素原子がオキソ基で置換されていてもよく、１以上の不飽和結合を有していてもよい炭素原子数７以上２０以下の鎖状脂肪族基であり、Ｒ^７ｂ～Ｒ^１２ｂのうちの３つ以上５つ以下が（メタ）アクリロイルオキシメチル基である。） <Photopolymerizable compound (B)>
The photosensitive composition contains, as the photopolymerizable compound (B), a photopolymerizable compound (B1) and a photopolymerizable compound (B2), and the photopolymerizable compound (B1) is represented by the following formula (b1-1): The photopolymerizable compound (B2) is a compound represented by the following formula (b2-1).

In formula (b1-1), R ^1b to R ^5b each represent a (meth)acryloyl group, R ^6b represents a (meth)acryloyloxymethyl group, an alkenyl group having from 2 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an alkoxymethyl group having 2 to 5 carbon atoms, a phenyloxy group, a phenyloxymethyl group, an alkanoyloxy group having 2 to 5 carbon atoms, a group, an alkanoyloxymethyl group having 3 to 5 carbon atoms, a benzoyloxy group, or a benzoyloxymethyl group.

In formula (b2-1), R ^7b to R ^12b each independently represent a (meth)acryloyloxymethyl group or a group which may be interrupted by 1 to 5 oxygen atoms, and one or more carbon atoms are each an oxo group. a chain aliphatic group having 7 to 20 carbon atoms which may be substituted with a group and which may have one or more unsaturated bonds, and three or more of R ^7b to R ^12b are At most one of the groups is a (meth)acryloyloxymethyl group.

In this specification, "(meth)acryloyl" means both "acryloyl" and "methacryloyl", and "(meth)acrylic" means both "acrylic" and "methacrylic".

In formula (b1-1), specific examples of the alkenyl group having 2 to 5 carbon atoms as R ^6b include a vinyl group and an allyl group.
Specific examples of the alkyl group having 1 to 5 carbon atoms as R ^6b include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, and a tert-pentyl group.
Specific examples of the alkoxy group having 1 to 5 carbon atoms as R ^6b include a methoxy group, an ethoxy group, an n-propyloxy group, an isopropyloxy group, an n-butyloxy group, an isobutyloxy group, a sec-butyloxy group, a tert-butyloxy group, an n-pentyloxy group, an isopentyloxy group, a sec-pentyloxy group, and a tert-pentyloxy group.
Specific examples of the alkoxymethyl group having from 2 to 5 carbon atoms as R ^6b include a group in which an alkoxy group having from 1 to 4 carbon atoms is bonded to a methylene group.
Specific examples of the alkanoyloxy group having from 2 to 5 carbon atoms as R ^6b include an acetyloxy group, a propanoyloxy group, and a butanoyloxy group.
Specific examples of the alkanoyloxymethyl group having 3 to 5 carbon atoms as R ^6b include a group in which an alkanoyloxy group having 2 to 4 carbon atoms is bonded to a methylene group.
From the viewpoint of ease of synthesis, R ^6b is preferably a (meth)acryloyloxymethyl group.

Specific examples of the compound represented by formula (b1-1) include compounds represented by the following formula: In the following formula, R ^21b each independently represents a hydrogen atom or a methyl group.

（式（ｂ２－２）中、Ｒ^１９ｂ及びＲ^２０ｂは、それぞれ独立に、水素原子又はメチル基である。） In formula (b2-1), examples of the chain aliphatic group having ⁷ to ²⁰ carbon atoms, which may be interrupted by 1 to 5 oxygen atoms, in which one or more carbon atoms may be substituted with an oxo group, and which may have one or more unsaturated bonds, as R 7b to R 12b include groups represented by the following formula (b2-2).

(In formula (b2-2), R ^19b and R ^20b each independently represent a hydrogen atom or a methyl group.)

In formula (b2-1), it is preferable that four or more and five or less of R ^7b to R ^12b are (meth)acryloyloxymethyl groups, and it is more preferable that five of R ^7b to R ^12b are (meth)acryloyloxymethyl groups.

Specific examples of the compound represented by formula (b2-1) include compounds represented by the following formula: In the following formula, R ^21b each independently represents a hydrogen atom or a methyl group.

The photosensitive composition contains, as the photopolymerizable compound (B), a photopolymerizable compound (B1) which is a compound represented by the above formula (b1-1), and a photopolymerizable compound (B2) which is a compound represented by the above formula (b2-1), and the ratio of the mass of the photopolymerizable compound (B2) to the mass of the photopolymerizable compound (B) is 5 mass% or more and 20 mass% or less. Therefore, as shown in the examples described later, a cured product having appropriate thermal flow properties and a low dielectric constant can be formed.
The ratio of the mass of the photopolymerizable compound (B2) to the mass of the photopolymerizable compound (B) is preferably 6 mass% or more and 20 mass% or less, more preferably 8 mass% or more and 17 mass% or less, and even more preferably 9 mass% or more and 15 mass% or less, in terms of thermal flow properties.

（式（ｂ３－１）中、Ｒ^１３ｂ～Ｒ^１７ｂは、（メタ）アクリロイル基であり、Ｒ^１８ｂは、ヒドロキシメチル基である。） The photopolymerizable compound (B) may contain a photopolymerizable compound other than the photopolymerizable compound (B1) and the photopolymerizable compound (B2). The photopolymerizable compound that may be contained in the photopolymerizable compound (B) includes the photopolymerizable compound (B3) represented by the following formula (b3-1). The ratio of the mass of the photopolymerizable compound (B3) represented by the formula (b3-1) to the mass of the photopolymerizable compound (B) is preferably 0% by mass or more and 35% by mass or less, more preferably 0% by mass or more and 30% by mass or less, and particularly preferably 0% by mass or more and 20% by mass or less. When the photopolymerizable compound (B3) is contained in an amount exceeding 0% by mass, the ratio of the mass of the photopolymerizable compound (B2) to the mass of the photopolymerizable compound (B) is preferably 10% by mass or more and 20% by mass or less, more preferably 15% by mass or more and 20% by mass or less. When the photopolymerizable compound (B3) is not contained (0 mass%), the ratio of the mass of the photopolymerizable compound (B2) to the mass of the photopolymerizable compound (B) is more preferably 8 mass% or more and 17 mass% or less, and even more preferably 9 mass% or more and 15 mass% or less.

(In formula (b3-1), R ^13b to R ^17b are (meth)acryloyl groups, and R ^18b is a hydroxymethyl group.)

The compound represented by formula (b1-1), the compound represented by formula (b2-1) and the compound represented by formula (b3-1) can each be synthesized by a conventionally known method.
For example, the compound represented by formula (b1-1) in which R ^6b is a (meth)acryloyloxymethyl group can be obtained by reacting dipentaerythritol with (meth)acrylic acid in the presence of an acid such as sulfuric acid or p-toluenesulfonic acid, and isolating and purifying the resulting product by medium pressure chromatography.
The compound represented by formula (b2-1), in which five of R ^7b to R ^12b are (meth)acryloyloxymethyl groups and the remaining one is a group represented by formula (b2-2), can be obtained by reacting a compound represented by formula (b1-1) in which R ^6b is a (meth)acryloyloxymethyl group with (meth)acrylic acid in the presence of an acid such as sulfuric acid or p-toluenesulfonic acid, and isolating and purifying the resultant product by medium pressure chromatography.
The compound represented by formula (b3-1) can be obtained by reacting dipentaerythritol with a predetermined amount of (meth)acrylic acid in the presence of an acid such as sulfuric acid or p-toluenesulfonic acid, and isolating and purifying the product by medium pressure chromatography.

The content of the photopolymerizable compound (B) in the photosensitive composition is preferably 1% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 40% by mass or less, based on the mass (total solid content) of the photosensitive composition excluding the mass of the organic solvent (S) described below. By setting the content within the above range, it tends to be easier to balance the sensitivity, developability, and resolution.

The above-mentioned photopolymerizable compound (B) can also be used as a photopolymerizable composition for purposes other than as a component contained in the above-mentioned photosensitive composition.

（式（１）中、Ｒ^ｃ１は水素原子、ニトロ基又は１価の有機基であり、Ｒ^ｃ２及びＲ^ｃ３は、それぞれ、置換基を有してもよい鎖状アルキル基、置換基を有してもよい環状有機基、又は水素原子であり、Ｒ^ｃ２とＲ^ｃ３とは相互に結合して環を形成してもよく、Ｒ^ｃ４は１価の有機基であり、Ｒ^ｃ５は、水素原子、置換基を有してもよい炭素原子数１以上１１以下のアルキル基、又は置換基を有してもよいアリール基であり、ｎ１は０以上４以下の整数であり、ｎ２は０又は１である。） <Photopolymerization initiator (C)>
The photopolymerization initiator (C) is not particularly limited as long as it can cure the above-mentioned photopolymerizable compound (B) by exposure. As the photopolymerization initiator (C), typically, an oxime ester compound can be preferably used. A preferred example of the oxime ester compound is a compound represented by the following formula (1).

(In formula (1), R ^c1 is a hydrogen atom, a nitro group, or a monovalent organic group; R ^c2 and R ^c3 are each a chain alkyl group which may have a substituent, a cyclic organic group which may have a substituent, or a hydrogen atom; R ^c2 and R ^c3 may be bonded to each other to form a ring; R ^c4 is a monovalent organic group; R ^c5 is a hydrogen atom, an alkyl group having 1 to 11 carbon atoms which may have a substituent, or an aryl group which may have a substituent; n1 is an integer of 0 to 4, and n2 is 0 or 1.)

In formula (1), R ^c1 is a hydrogen atom, a nitro group, or a monovalent organic group. R ^c1 is bonded to a 6-membered aromatic ring different from the 6-membered aromatic ring bonded to the group represented by -(CO) _n2 - on the fluorene ring in formula (1). In formula (1), the bonding position of R ^c1 to the fluorene ring is not particularly limited. When the compound represented by formula (1) has one or more R ^c1 , it is preferable that one of the one or more R ^c1 is bonded to the 2-position in the fluorene ring, because the synthesis of the compound represented by formula (1) is easy. When there are multiple R ^c1s , the multiple R ^c1s may be the same or different.

When R ^c1 is an organic group, R ^c1 is not particularly limited as long as it does not impede the object of the present invention, and is appropriately selected from various organic groups. When R ^c1 is an organic group, suitable examples include an alkyl group, an alkoxy group, a cycloalkyl group, a cycloalkoxy group, a saturated aliphatic acyl group, a saturated aliphatic acyloxy group, an alkoxycarbonyl group, a phenyl group which may have a substituent, a phenoxy group which may have a substituent, a benzoyl group which may have a substituent, a phenoxycarbonyl group which may have a substituent, a benzoyloxy group which may have a substituent, a phenylalkyl group which may have a substituent, a naphthyl group which may have a substituent, a naphthoxy group which may have a substituent, a naphthoyl group which may have a substituent, a naphthoxycarbonyl group which may have a substituent, a naphthyloxy group which may have a substituent, a naphthylalkyl group which may have a substituent, a heterocyclyl group which may have a substituent, a heterocyclylcarbonyl group which may have a substituent, an amino group substituted with one or two organic groups, a morpholin-1-yl group, and a piperazin-1-yl group.

When R ^c1 is an alkyl group, the number of carbon atoms of the alkyl group is preferably 1 or more and 20 or less, more preferably 1 or more and 6 or less. When R ^c1 is an alkyl group, it may be a straight chain or a branched chain. Specific examples of when R ^c1 is an alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an isononyl group, an n-decyl group, and an isodecyl group. When R ^c1 is an alkyl group, the alkyl group may contain an ether bond (-O-) in the carbon chain. Examples of the alkyl group having an ether bond in the carbon chain include a methoxyethyl group, an ethoxyethyl group, a methoxyethoxyethyl group, an ethoxyethoxyethyl group, a propyloxyethoxyethyl group, and a methoxypropyl group.

When R ^c1 is an alkoxy group, the number of carbon atoms of the alkoxy group is preferably 1 or more and 20 or less, more preferably 1 or more and 6 or less. When R ^{c1 is an alkoxy group, it may be a straight chain or a branched chain. Specific examples of when R c1 is} an alkoxy group include a methoxy group, an ethoxy group, an n-propyloxy group, an isopropyloxy group, an n-butyloxy group, an isobutyloxy group, a sec-butyloxy group, a tert-butyloxy group, an n-pentyloxy group, an isopentyloxy group, a sec-pentyloxy group, a tert-pentyloxy group, an n-hexyloxy group, an n-heptyloxy group, an n-octyloxy group, an isooctyloxy group, a sec-octyloxy group, a tert-octyloxy group, an n-nonyloxy group, an isononyloxy group, an n-decyloxy group, and an isodecyloxy group. In addition, when R ^c1 is an alkoxy group, the alkoxy group may contain an ether bond (—O—) in the carbon chain. Examples of the alkoxy group having an ether bond in the carbon chain include a methoxyethoxy group, an ethoxyethoxy group, a methoxyethoxyethoxy group, an ethoxyethoxyethoxy group, a propyloxyethoxyethoxy group, and a methoxypropyloxy group.

When R ^{c1 is a cycloalkyl group or a cycloalkoxy group, the number of carbon atoms of the cycloalkyl group or the cycloalkoxy group is preferably 3 to 10, more preferably 3 to 6. Specific examples of when R c1 is} a cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Specific examples of when ^{R c1} is a cycloalkoxy group include a cyclopropyloxy group, a cyclobutyloxy group, a cyclopentyloxy group, a cyclohexyloxy group, a cycloheptyloxy group, and a cyclooctyloxy group.

When R ^c1 is a saturated aliphatic acyl group or a saturated aliphatic acyloxy group, the number of carbon atoms in the saturated aliphatic acyl group or the saturated aliphatic acyloxy group is preferably from 2 to 21, and more preferably from 2 to 7. Specific examples of when ^{R c1} is a saturated aliphatic acyl group include an acetyl group, a propanoyl group, a n-butanoyl group, a 2-methylpropanoyl group, a n-pentanoyl group, a 2,2-dimethylpropanoyl group, a n-hexanoyl group, a n-heptanoyl group, a n-octanoyl group, a n-nonanoyl group, a n-decanoyl group, a n-undecanoyl group, a n-dodecanoyl group, a n-tridecanoyl group, a n-tetradecanoyl group, a n-pentadecanoyl group, and a n-hexadecanoyl group. Specific examples of when R ^c1 is a saturated aliphatic acyloxy group include an acetyloxy group, a propanoyloxy group, a n-butanoyloxy group, a 2-methylpropanoyloxy group, a n-pentanoyloxy group, a 2,2-dimethylpropanoyloxy group, a n-hexanoyloxy group, a n-heptanoyloxy group, a n-octanoyloxy group, a n-nonanoyloxy group, a n-decanoyloxy group, a n-undecanoyloxy group, a n-dodecanoyloxy group, a n-tridecanoyloxy group, a n-tetradecanoyloxy group, a n-pentadecanoyloxy group, and a n-hexadecanoyloxy group.

When R ^c1 is an alkoxycarbonyl group, the alkoxycarbonyl group preferably has 2 or more and 20 or less, and more preferably has 2 or more and 7 or less, carbon atoms. Specific examples of when R ^c1 is an alkoxycarbonyl group include a methoxycarbonyl group, an ethoxycarbonyl group, an n-propyloxycarbonyl group, an isopropyloxycarbonyl group, an n-butyloxycarbonyl group, an isobutyloxycarbonyl group, a sec-butyloxycarbonyl group, a tert-butyloxycarbonyl group, an n-pentyloxycarbonyl group, an isopentyloxycarbonyl group, a sec-pentyloxycarbonyl group, a tert-pentyloxycarbonyl group, an n-hexyloxycarbonyl group, an n-heptyloxycarbonyl group, an n-octyloxycarbonyl group, an isooctyloxycarbonyl group, a sec-octyloxycarbonyl group, a tert-octyloxycarbonyl group, an n-nonyloxycarbonyl group, an isononyloxycarbonyl group, an n-decyloxycarbonyl group, and an isodecyloxycarbonyl group.

When R ^c1 is a phenylalkyl group, the number of carbon atoms of the phenylalkyl group is preferably 7 or more and 20 or less, more preferably 7 or more and 10 or less. When R ^c1 is a naphthylalkyl group, the number of carbon atoms of the naphthylalkyl group is preferably 11 or more and 20 or less, more preferably 11 or more and 14 or less. Specific examples of when ^{R c1} is a phenylalkyl group include a benzyl group, a 2-phenylethyl group, a 3-phenylpropyl group, and a 4-phenylbutyl group. Specific examples of when ^{R c1} is a naphthylalkyl group include an α-naphthylmethyl group, a β-naphthylmethyl group, a 2-(α-naphthyl)ethyl group, and a 2-(β-naphthyl)ethyl group. When R ^c1 is a phenylalkyl group or a naphthylalkyl group, R ^c1 may further have a substituent on the phenyl group or the naphthyl group.

When R ^c1 is a heterocyclyl group, the heterocyclyl group is a 5- or 6-membered monocyclic ring containing one or more N, S, or O, or a heterocyclyl group in which such monocyclic rings are fused to each other or such monocyclic ring is fused to a benzene ring. When the heterocyclyl group is a fused ring, the number of rings of the monocyclic ring constituting the fused ring is 3 or less. The heterocyclyl group may be an aromatic group (heteroaryl group) or a non-aromatic group. Examples of the heterocyclic ring constituting such a heterocyclyl group include furan, thiophene, pyrrole, oxazole, isoxazole, thiazole, thiadiazole, isothiazole, imidazole, pyrazole, triazole, pyridine, pyrazine, pyrimidine, pyridazine, benzofuran, benzothiophene, indole, isoindole, indolizine, benzimidazole, benzotriazole, benzoxazole, benzothiazole, carbazole, purine, quinoline, isoquinoline, quinazoline, phthalazine, cinnoline, quinoxaline, piperidine, piperazine, morpholine, piperidine, tetrahydropyran, and tetrahydrofuran. When ^{R c1} is a heterocyclyl group, the heterocyclyl group may further have a substituent.

When R ^c1 is a heterocyclylcarbonyl group, the heterocyclyl group contained in the heterocyclylcarbonyl group is the same as when R ^c1 is a heterocyclyl group.

When R ^c1 is an amino group substituted with one or two organic groups, suitable examples of the organic group include an alkyl group having from 1 to 20 carbon atoms, a cycloalkyl group having from 3 to 10 carbon atoms, a saturated aliphatic acyl group having from 2 to 21 carbon atoms, a phenyl group which may have a substituent, a benzoyl group which may have a substituent, a phenylalkyl group having from 7 to 20 carbon atoms which may have a substituent, a naphthyl group which may have a substituent, a naphthyl group which may have a substituent, a naphthylalkyl group having from 11 to 20 carbon atoms which may have a substituent, and a heterocyclyl group, etc. Specific examples of these suitable organic groups are the same as those of R ^c1 . Specific examples of the amino group substituted with one or two organic groups include a methylamino group, an ethylamino group, a diethylamino group, an n-propylamino group, a di-n-propylamino group, an isopropylamino group, an n-butylamino group, a di-n-butylamino group, an n-pentylamino group, an n-hexylamino group, an n-heptylamino group, an n-octylamino group, an n-nonylamino group, an n-decylamino group, a phenylamino group, a naphthylamino group, an acetylamino group, a propanoylamino group, an n-butanoylamino group, an n-pentanoylamino group, an n-hexanoylamino group, an n-heptanoylamino group, an n-octanoylamino group, an n-decanoylamino group, a benzoylamino group, an α-naphthoylamino group, and a β-naphthoylamino group.

Examples of the substituent when the phenyl group, naphthyl group, and heterocyclyl group contained in R ^c1 further have a substituent include an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a saturated aliphatic acyl group having 2 to 7 carbon atoms, an alkoxycarbonyl group having 2 to 7 carbon atoms, a saturated aliphatic acyloxy group having 2 to 7 carbon atoms, a monoalkylamino group having an alkyl group having 1 to 6 carbon atoms, a dialkylamino group having an alkyl group having 1 to 6 carbon atoms, a morpholin-1-yl group, a piperazin-1-yl group, a halogen, a nitro group, and a cyano group. When the phenyl group, naphthyl group, and heterocyclyl group contained in R ^c1 further have a substituent, the number of the substituent is not limited as long as it does not impede the object of the present invention, but is preferably 1 to 4. When the phenyl group, naphthyl group, and heterocyclyl group contained in R ^c1 have multiple substituents, the multiple substituents may be the same or different.

Among the groups described above, R ^c1 is preferably a nitro group or a group represented by R ^c10 -CO-, since the sensitivity tends to be improved. R ^c10 is not particularly limited as long as it does not impair the object of the present invention, and can be selected from various organic groups. Examples of groups suitable for R ^c10 include an alkyl group having 1 to 20 carbon atoms, a phenyl group which may have a substituent, a naphthyl group which may have a substituent, and a heterocyclyl group which may have a substituent. Among these groups, a 2-methylphenyl group, a thiophen-2-yl group, and an α-naphthyl group are particularly preferred for R ^c10 .
In addition, when R ^c1 is a hydrogen atom, the transparency tends to be good, which is preferable. Note that when R ^c1 is a hydrogen atom and R ^c4 is a group represented by the formula (1a) or (1b) described later, the transparency tends to be even better.

In formula (1), R ^c2 and R ^c3 are each a chain alkyl group which may have a substituent, a cyclic organic group which may have a substituent, or a hydrogen atom. R ^c2 and R ^c3 may be bonded to each other to form a ring. Among these groups, R ^c2 and R ^c3 are preferably a chain alkyl group which may have a substituent. When R ^c2 and R ^c3 are a chain alkyl group which may have a substituent, the chain alkyl group may be a straight chain alkyl group or a branched chain alkyl group.

When R ^c2 and R ^c3 are chain alkyl groups having no substituents, the number of carbon atoms of the chain alkyl group is preferably 1 or more and 20 or less, more preferably 1 or more and 10 or less, and particularly preferably 1 or more and 6 or less. Specific examples of the chain alkyl group when R ^c2 and R ^c3 are chain alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, sec-pentyl group, tert-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, isooctyl group, sec-octyl group, tert-octyl group, n-nonyl group, isononyl group, n-decyl group, and isodecyl group. In addition, when R ^c2 and R ^c3 are alkyl groups, the alkyl group may contain an ether bond (-O-) in the carbon chain. Examples of the alkyl group having an ether bond in the carbon chain include a methoxyethyl group, an ethoxyethyl group, a methoxyethoxyethyl group, an ethoxyethoxyethyl group, a propyloxyethoxyethyl group, and a methoxypropyl group.

When R ^c2 and R ^c3 are chain alkyl groups having a substituent, the number of carbon atoms in the chain alkyl group is preferably 1 or more and 20 or less, more preferably 1 or more and 10 or less, and particularly preferably 1 or more and 6 or less. In this case, the number of carbon atoms in the substituent is not included in the number of carbon atoms in the chain alkyl group. The chain alkyl group having a substituent is preferably linear.
The substituent that the alkyl group may have is not particularly limited as long as it does not impair the object of the present invention. Suitable examples of the substituent include a cyano group, a halogen atom, a cyclic organic group, and an alkoxycarbonyl group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, a fluorine atom, a chlorine atom, and a bromine atom are preferred. Examples of the cyclic organic group include a cycloalkyl group, an aromatic hydrocarbon group, and a heterocyclyl group. Specific examples of the cycloalkyl group are the same as the suitable examples when R ^c1 is a cycloalkyl group. Specific examples of the aromatic hydrocarbon group include a phenyl group, a naphthyl group, a biphenylyl group, an anthryl group, and a phenanthryl group. Specific examples of the heterocyclyl group are the same as the suitable examples when R ^c1 is a heterocyclyl group. When R ^c1 is an alkoxycarbonyl group, the alkoxy group contained in the alkoxycarbonyl group may be linear or branched, and is preferably linear. The alkoxy group contained in the alkoxycarbonyl group preferably has 1 or more and 10 or less, and more preferably has 1 or more and 6 or less, carbon atoms.

When the chain alkyl group has a substituent, the number of the substituents is not particularly limited. The preferred number of substituents varies depending on the number of carbon atoms in the chain alkyl group. The number of substituents is typically 1 to 20, preferably 1 to 10, and more preferably 1 to 6.

When R ^c2 and R ^c3 are cyclic organic groups, the cyclic organic group may be an alicyclic group or an aromatic group. Examples of the cyclic organic group include an aliphatic cyclic hydrocarbon group, an aromatic hydrocarbon group, and a heterocyclyl group. When R ^c2 and R ^c3 are cyclic organic groups, the substituents that the cyclic organic group may have are the same as those when R ^c2 and R ^c3 are chain alkyl groups.

When R ^c2 and R ^c3 are aromatic hydrocarbon groups, the aromatic hydrocarbon group is preferably a phenyl group, a group formed by bonding multiple benzene rings via carbon-carbon bonds, or a group formed by condensing multiple benzene rings. When the aromatic hydrocarbon group is a phenyl group or a group formed by bonding or condensing multiple benzene rings, the number of benzene rings contained in the aromatic hydrocarbon group is not particularly limited, and is preferably 3 or less, more preferably 2 or less, and particularly preferably 1. Specific preferred examples of the aromatic hydrocarbon group include a phenyl group, a naphthyl group, a biphenylyl group, an anthryl group, and a phenanthryl group.

When R ^c2 and R ^c3 are alicyclic hydrocarbon groups, the alicyclic hydrocarbon group may be monocyclic or polycyclic. The number of carbon atoms of the alicyclic hydrocarbon group is not particularly limited, but is preferably 3 to 20, more preferably 3 to 10. Examples of monocyclic cyclic hydrocarbon groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, norbornyl, isobornyl, tricyclononyl, tricyclodecyl, tetracyclododecyl, and adamantyl.

When R ^c2 and R ^c3 are heterocyclyl groups, the heterocyclyl group is a 5- or 6-membered monocyclic ring containing one or more N, S, or O, or a heterocyclyl group in which such monocyclic rings are fused to each other or such monocyclic ring is fused to a benzene ring. When the heterocyclyl group is a fused ring, the number of rings of the monocyclic ring constituting the fused ring is 3 or less. The heterocyclyl group may be an aromatic group (heteroaryl group) or a non-aromatic group. Examples of heterocycles constituting such heterocyclyl groups include furan, thiophene, pyrrole, oxazole, isoxazole, thiazole, thiadiazole, isothiazole, imidazole, pyrazole, triazole, pyridine, pyrazine, pyrimidine, pyridazine, benzofuran, benzothiophene, indole, isoindole, indolizine, benzimidazole, benzotriazole, benzoxazole, benzothiazole, carbazole, purine, quinoline, isoquinoline, quinazoline, phthalazine, cinnoline, quinoxaline, piperidine, piperazine, morpholine, piperidine, tetrahydropyran, and tetrahydrofuran.

R ^c2 and R ^c3 may be bonded to each other to form a ring. The group consisting of the ring formed by R ^c2 and R ^c3 is preferably a cycloalkylidene group. When R ^c2 and R ^c3 are bonded to form a cycloalkylidene group, the ring constituting the cycloalkylidene group is preferably a 5-membered or 6-membered ring, more preferably a 5-membered ring.

When the group formed by combining ^Rc2 and ^Rc3 is a cycloalkylidene group, the cycloalkylidene group may be fused with one or more other rings. Examples of the ring that may be fused with the cycloalkylidene group include a benzene ring, a naphthalene ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, a furan ring, a thiophene ring, a pyrrole ring, a pyridine ring, a pyrazine ring, and a pyrimidine ring.

Among the above-described R ^c2 and R ^c3 , a suitable example of the group is a group represented by the formula -A ¹ -A ^2. In the formula, A ¹ is a linear alkylene group, and A ² is an alkoxy group, a cyano group, a halogen atom, a halogenated alkyl group, a cyclic organic group, or an alkoxycarbonyl group.

The number of carbon atoms of the linear alkylene group of A ¹ is preferably 1 to 10, more preferably 1 to 6. When A ² is an alkoxy group, the alkoxy group may be linear or branched, and linear is preferred. The number of carbon atoms of the alkoxy group is preferably 1 to 10, and more preferably 1 to 6. When A ^{2 is a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom is preferred, and a fluorine atom, a chlorine atom, or a bromine atom is more preferred. When A 2 is} a halogenated alkyl group, the halogen atom contained in the halogenated alkyl group is preferably a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, and a fluorine atom, a chlorine atom, or a bromine atom is more preferred. The halogenated alkyl group may be linear or branched, and linear is preferred. When ^{A 2} is a cyclic organic group, examples of the cyclic organic group are the same as the cyclic organic groups that R ^c2 and R ^c3 have as substituents. When ^A2 is an alkoxycarbonyl group, examples of the alkoxycarbonyl group are the same as the alkoxycarbonyl groups which ^Rc2 and ^Rc3 have as substituents.

Specific examples of suitable R ^c2 and R ^c3 include alkyl groups such as an ethyl group, an n-propyl group, an n-butyl group, an n-hexyl group, an n-heptyl group, and an n-octyl group; alkoxyalkyl groups such as a 2-methoxyethyl group, a 3-methoxy-n-propyl group, a 4-methoxy-n-butyl group, a 5-methoxy-n-pentyl group, a 6-methoxy-n-hexyl group, a 7-methoxy-n-heptyl group, an 8-methoxy-n-octyl group, a 2-ethoxyethyl group, a 3-ethoxy-n-propyl group, a 4-ethoxy-n-butyl group, a 5-ethoxy-n-pentyl group, a 6-ethoxy-n-hexyl group, a 7-ethoxy-n-heptyl group, and an 8-ethoxy-n-octyl group; cyanoalkyl groups such as 2-phenylethyl group, 3-phenyl-n-propyl group, 4-phenyl-n-butyl group, 5-phenyl-n-pentyl group, 6-phenyl-n-hexyl group, 7-phenyl-n-heptyl group, and 8-phenyl-n-octyl group; phenylalkyl groups such as 2-cyclohexylethyl group, 3-cyclohexyl-n-propyl group, 4-cyclohexyl-n-butyl group, 5-cyclohexyl-n-pentyl group, 6-cyclohexyl-n-hexyl group, 7-cyclohexyl-n-heptyl group, and 8-cyclohexyl-n-octyl group; 2-cyclohexylethyl group, 3-cyclohexyl-n-propyl group, 4-cyclohexyl-n-butyl group, 5-cyclohexyl-n-pentyl group, 6-cyclohexyl-n-hexyl group, 7-cyclohexyl-n-heptyl group, 8-cyclohexyl-n-octyl group, 2-cyclopentylethyl group, 3-cyclopentyl-n-propyl group, cycloalkylalkyl groups such as 4-cyclopentyl-n-butyl group, 5-cyclopentyl-n-pentyl group, 6-cyclopentyl-n-hexyl group, 7-cyclopentyl-n-heptyl group, and 8-cyclopentyl-n-octyl group; 2-methoxycarbonylethyl group, 3-methoxycarbonyl-n-propyl group, 4-methoxycarbonyl-n-butyl group, 5-methoxycarbonyl-n-pentyl group, 6-methoxycarbonyl-n-hexyl group, 7-methoxycarbonyl-n-heptyl group, 8-methoxycarbonyl-n-octyl group, 2-ethoxycarbonylethyl group, 3-ethoxycarbonyl-n-propyl group, 4-ethoxycarbonyl-n-butyl group, 5-ethoxycarbonyl-n-pentyl group, 6-ethoxycarbonyl-n-hexyl group, 7-methoxycarbonyl-n-heptyl group, 8-methoxycarbonyl-n-octyl group, 2-ethoxycarbonylethyl group, 3-ethoxycarbonyl-n-propyl group, 4-ethoxycarbonyl-n-butyl group, 5-ethoxycarbonyl-n-pentyl group, 6-ethoxycarbonyl alkoxycarbonylalkyl groups such as 2-chloroethyl group, 3-chloro-n-propyl group, 4-chloro-n-butyl group, 5-chloro-n-pentyl group, 6-chloro-n-hexyl group, 7-chloro-n-heptyl group, and 8-ethoxycarbonyl-n-octyl group; and halogenated alkyl groups such as 2-chloroethyl group, 3-chloro-n-propyl group, 4-chloro-n-butyl group, 5-chloro-n-pentyl group, 6-chloro-n-hexyl group, 7-chloro-n-heptyl group, 8-chloro-n-octyl group, 2-bromoethyl group, 3-bromo-n-propyl group, 4-bromo-n-butyl group, 5-bromo-n-pentyl group, 6-bromo-n-hexyl group, 7-bromo-n-heptyl group, 8-bromo-n-octyl group, 3,3,3-trifluoropropyl group, and 3,3,4,4,5,5,5-heptafluoro-n-pentyl group.

Among the above, preferred groups for R ^c2 and R ^c3 are an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, a 2-methoxyethyl group, a 2-cyanoethyl group, a 2-phenylethyl group, a 2-cyclohexylethyl group, a 2-methoxycarbonylethyl group, a 2-chloroethyl group, a 2-bromoethyl group, a 3,3,3-trifluoropropyl group, and a 3,3,4,4,5,5,5-heptafluoro-n-pentyl group.

As with R ^c1 , examples of suitable organic groups for R ^c4 include alkyl groups, alkoxy groups, cycloalkyl groups, cycloalkoxy groups, saturated aliphatic acyl groups, alkoxycarbonyl groups, saturated aliphatic acyloxy groups, phenyl groups which may have a substituent, phenoxy groups which may have a substituent, benzoyl groups which may have a substituent, phenoxycarbonyl groups which may have a substituent, benzoyloxy groups which may have a substituent, phenylalkyl groups which may have a substituent, naphthyl groups which may have a substituent, naphthoxy groups which may have a substituent, naphthoyl groups which may have a substituent, naphthoxycarbonyl groups which may have a substituent, naphthoyloxy groups which may have a substituent, naphthylalkyl groups which may have a substituent, heterocyclyl groups which may have a substituent, heterocyclylcarbonyl groups which may have a substituent, amino groups substituted with one or two organic groups, morpholin-1-yl groups, and piperazin-1-yl groups. Specific examples of these groups are the same as those described for R ^c1 . Also preferred as R ^c4 are a cycloalkylalkyl group, a phenoxyalkyl group which may have a substituent on the aromatic ring, and a phenylthioalkyl group which may have a substituent on the aromatic ring. The substituents which the phenoxyalkyl group and the phenylthioalkyl group may have are the same as the substituents which the phenyl group included in R ^c1 may have.

Among the organic groups, R ^c4 is preferably an alkyl group, a cycloalkyl group, a phenyl group which may have a substituent, or a cycloalkylalkyl group, or a phenylthioalkyl group which may have a substituent on the aromatic ring. As the alkyl group, an alkyl group having 1 to 20 carbon atoms is preferred, an alkyl group having 1 to 8 carbon atoms is more preferred, an alkyl group having 1 to 4 carbon atoms is particularly preferred, and a methyl group is most preferred. Among the phenyl groups which may have a substituent, a methylphenyl group is preferred, and a 2-methylphenyl group is more preferred. The number of carbon atoms in the cycloalkylalkyl group contained in the cycloalkylalkyl group is preferably 5 to 10, more preferably 5 to 8, and particularly preferably 5 or 6. The number of carbon atoms in the alkylene group contained in the cycloalkylalkyl group is preferably 1 to 8, more preferably 1 to 4, and particularly preferably 2. Among the cycloalkylalkyl groups, a cyclopentylethyl group is preferred. The number of carbon atoms in the alkylene group contained in the phenylthioalkyl group which may have a substituent on the aromatic ring is preferably 1 to 8, more preferably 1 to 4, and particularly preferably 2. Among the phenylthioalkyl groups which may have a substituent on the aromatic ring, a 2-(4-chlorophenylthio)ethyl group is preferred.

Also preferred as R ^c4 is a group represented by -A ³ -CO-O-A ^{4. A 3} is a divalent organic group, preferably a divalent hydrocarbon group, and preferably an alkylene group. ^{A 4} is a monovalent organic group, preferably a monovalent hydrocarbon group.

When ^A3 is an alkylene group, the alkylene group may be linear or branched, and is preferably linear. When ^A3 is an alkylene group, the number of carbon atoms in the alkylene group is preferably 1 to 10, more preferably 1 to 6, and particularly preferably 1 to 4.

Suitable examples of ^A4 include an alkyl group having from 1 to 10 carbon atoms, an aralkyl group having from 7 to 20 carbon atoms, and an aromatic hydrocarbon group having from 6 to 20 carbon atoms. Suitable specific examples of ^A4 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, a phenyl group, a naphthyl group, a benzyl group, a phenethyl group, an α-naphthylmethyl group, and a β-naphthylmethyl group.

Specific preferred examples of the group represented by -A ³ -CO-O-A ⁴ include a 2-methoxycarbonylethyl group, a 2-ethoxycarbonylethyl group, a 2-n-propyloxycarbonylethyl group, a 2-n-butyloxycarbonylethyl group, a 2-n-pentyloxycarbonylethyl group, a 2-n-hexyloxycarbonylethyl group, a 2-benzyloxycarbonylethyl group, a 2-phenoxycarbonylethyl group, a 3-methoxycarbonyl-n-propyl group, a 3-ethoxycarbonyl-n-propyl group, a 3-n-propyloxycarbonyl-n-propyl group, a 3-n-butyloxycarbonyl-n-propyl group, a 3-n-pentyloxycarbonyl-n-propyl group, a 3-n-hexyloxycarbonyl-n-propyl group, a 3-benzyloxycarbonyl-n-propyl group, and a 3-phenoxycarbonyl-n-propyl group.

（式（１ａ）及び式（１ｂ）中、Ｒ^ｃ７及びＲ^ｃ８はそれぞれ有機基であり、ｎ３は０以上４以下の整数であり、Ｒ^ｃ７及びＲ^ｃ８がベンゼン環上の隣接する位置に存在する場合、Ｒ^ｃ７とＲ^ｃ８とが互いに結合して環を形成してもよく、ｎ４は１以上８以下の整数であり、ｎ５は１以上５以下の整数であり、ｎ６は０以上（ｎ５＋３）以下の整数であり、Ｒ^ｃ９は有機基である。） R ^c4 has been described above. As R ^c4 , a group represented by the following formula (1a) or (1b) is preferable.

(In formula (1a) and formula (1b), R ^c7 and R ^c8 each represent an organic group, n3 represents an integer of 0 to 4, when R ^c7 and R ^c8 are present at adjacent positions on the benzene ring, R ^c7 and R ^c8 may be bonded to each other to form a ring, n4 represents an integer of 1 to 8, n5 represents an integer of 1 to 5, n6 represents an integer of 0 to (n5+3), and R ^c9 represents an organic group.)

Examples of organic groups for R ^c7 and R ^c8 in formula (1a) are the same as those for R ^c1 . R ^c7 is preferably an alkyl group or a phenyl group. When R ^c7 is an alkyl group, the number of carbon atoms is preferably 1 or more and 10 or less, more preferably 1 or more and 5 or less, particularly preferably 1 or more and 3 or less, and most preferably 1. That is, R ^c7 is most preferably a methyl group. When R ^c7 and R ^c8 are bonded to form a ring, the ring may be an aromatic ring or an aliphatic ring. Suitable examples of the group represented by formula (1a) in which R ^c7 and R ^c8 form a ring include a naphthalene-1-yl group and a 1,2,3,4-tetrahydronaphthalene-5-yl group. In the above formula (1a), n3 is an integer of 0 to 4, preferably 0 or 1, and more preferably 0.

In the above formula (1b), R ^c9 is an organic group. Examples of the organic group include the same groups as those described for R ^c1 . Among the organic groups, an alkyl group is preferable. The alkyl group may be linear or branched. The number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 5, and particularly preferably 1 to 3. Preferred examples of R ^c9 include a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group, and among these, a methyl group is more preferable.

In the above formula (1b), n5 is an integer of 1 to 5, preferably an integer of 1 to 3, and more preferably 1 or 2. In the above formula (1b), n6 is an integer of 0 to (n5+3), preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and particularly preferably 0. In the above formula (1b), n4 is an integer of 1 to 8, preferably an integer of 1 to 5, more preferably an integer of 1 to 3, and particularly preferably 1 or 2.

In formula (1), R ^c5 is a hydrogen atom, an alkyl group having 1 to 11 carbon atoms which may have a substituent, or an aryl group which may have a substituent. When R ^c5 is an alkyl group, preferred examples of the substituent that may be substituted include a phenyl group and a naphthyl group. When R ^c1 is an aryl group, preferred examples of the substituent that may be substituted include an alkyl group having 1 to 5 carbon atoms, an alkoxy group, and a halogen atom.

In formula (1), preferred examples of R ^c5 include a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a phenyl group, a benzyl group, a methylphenyl group, and a naphthyl group. Among these, a methyl group or a phenyl group is more preferred.

Specific preferred examples of the compound represented by formula (1) include the following PI-1 to PI-41.

Suitable examples of the photopolymerization initiator (C) other than the compound represented by the above formula (1) include oxime ester compounds having a structure not corresponding to the above formula (C1), such as 2-(benzoyloxyimino)-1-[4-(phenylthio)phenyl]-1-octanone (for example, commercially available as OXE-01 (manufactured by BASF)), and O-acetyl-1-[6-(2-methylbenzoyl)-9-ethyl-9H-carbazol-3-yl]ethanone oxime (for example, commercially available as OXE-02 (manufactured by BASF)); -2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-dimethylaminophenyl)butan-1-one, 2-(4-methylbenzyl)-2-diethylamino-1-(4-morpholinophenyl)butan-1-one, 2-methyl-1-phenyl-2-morpholinopropan-1-one, 2-methyl-1-[4-(hexyl)phenyl]-2-morpholinopropan-1-o α-aminoketone compounds such as 1-phenyl-2-hydroxy-2-methylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, and 1-hydroxycyclohexyl phenyl ketone; α-hydroxyketone photopolymerization initiators such as benzoin, benzoin methyl ether, and benzoin ethyl ether. benzoin-based photopolymerization initiators such as benzoin ether, benzoin propyl ether, and benzyl methyl ketal; benzophenone-based photopolymerization initiators such as benzophenone, benzoylbenzoic acid, benzoylbenzoic acid methyl, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl, 4'-methyldiphenyl sulfide, and 4,4'-bisdiethylaminobenzophenone; thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diiso ... Thioxanthone-based photopolymerization initiators such as pyrthioxanthone; 2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine, 2-pipenyl-4.6-bis(trichloromethyl)-s-triazine, 2,4-bis(trichloromethyl)-6-styryl-s-triazine, 2-(naphth-1-yl)-4,6-biphenyl-s-triazine, triazine-based photopolymerization initiators such as 2-(4-methoxy-naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-(piperonyl)-6-triazine, 2,4-trichloromethyl-(4'-methoxystyryl)-6-triazine, and 2-[4-(4-methoxystyryl)phenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine; carbazole-based photopolymerization initiators; 2,2'-bis(2-chlorophenyl)-4,4',5,5 '-Tetrakis(4-ethoxycarbonylphenyl)-1,2'-biimidazole, 2,2'-bis(2-bromophenyl)-4,4',5,5'-tetrakis(4-ethoxycarbonylphenyl)-1,2'-biimidazole, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2,4-dichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2,4,6-trichlorophenyl)-4,4' , 5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2-bromophenyl)-4,4,5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2,4-dibromophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2,4,6-tribromophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, and other biimidazole-based photopolymerization initiators; and benzimidazoline-based photopolymerization initiators as represented by the following formula.

Other suitable specific examples of the compound represented by formula (1) include the following compounds:

The ratio of the mass of the compound represented by the above formula (1) to the mass of the photopolymerization initiator (C) is not particularly limited as long as it does not impair the object of the present invention. The ratio of the compound represented by the above formula (1) to the mass of the photopolymerization initiator (C) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass.

The content of the photopolymerization initiator (C) is preferably 0.1% by mass or more and 30% by mass or less, and more preferably 0.5% by mass or more and 20% by mass or less, based on the total mass of the solid content of the photosensitive composition. By using an amount of the photopolymerization initiator (C) within this range, it is easy to obtain the desired effect of using the photopolymerization initiator (C).

<Organic Solvent (S)>
The photosensitive composition contains an organic solvent (S). Examples of the organic solvent (S) include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol-n-propyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-n-butyl ether, (poly)alkylene glycol monoalkyl ethers such as dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, tripropylene glycol monomethyl ether, and tripropylene glycol monoethyl ether; (poly)alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; ) Alkylene glycol monoalkyl ether acetates; other ethers such as diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, and tetrahydrofuran; ketones such as methyl ethyl ketone, cyclohexanone, 2-heptanone, and 3-heptanone; alkyl esters of lactate such as methyl 2-hydroxypropionate and ethyl 2-hydroxypropionate; ethyl 2-hydroxy-2-methylpropionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, and 2-hydroxy-3-methyl Examples of the solvent include methyl butyrate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, 3-methyl-3-methoxybutyl propionate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl formate, isopentyl acetate, n-butyl propionate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, n-butyl butyrate, methyl pyruvate, ethyl pyruvate, n-propyl pyruvate, methyl acetoacetate, ethyl acetoacetate, and other esters such as ethyl 2-oxobutanoate; aromatic hydrocarbons such as toluene and xylene; and amides such as N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide. These solvents may be used alone or in combination of two or more.

The amount of organic solvent (S) used can be appropriately determined depending on the application of the photosensitive composition. One example of the amount of organic solvent (S) used is an amount that results in a solids concentration of the photosensitive composition in the range of 1% by mass or more and 50% by mass or less.

<Other ingredients>
The photosensitive composition may contain various other additives as necessary, such as a dispersing aid, a bulking agent, a filler, an adhesion promoter, an antioxidant, an ultraviolet absorber, an anti-aggregation agent, a thermal polymerization inhibitor, an antifoaming agent, a surfactant, etc.

Examples of thermal polymerization inhibitors used in photosensitive compositions include hydroquinone and hydroquinone monoethyl ether. Examples of antifoaming agents include silicone-based and fluorine-based compounds, and examples of surfactants include anionic, cationic, and nonionic compounds.

<Method of preparing photosensitive composition>
The photosensitive composition is prepared by uniformly mixing the above-mentioned components in the desired amounts. If the prepared photosensitive composition does not contain insoluble components such as pigments, the photosensitive composition may be filtered using a filter to make the photosensitive composition uniform.

<Production method of cured product>
By using the photosensitive composition described above, a cured product can be formed.
Specifically, the method for producing a cured product includes a step of applying the above-mentioned photosensitive composition to form a coating film, and a step of exposing the coating film to light.
The cured product is preferably patterned. A method for producing a patterned cured product includes the steps of applying the above-mentioned photosensitive composition to form a coating film, position-selectively exposing the coating film, and developing the exposed coating film.

By using the above-mentioned photosensitive composition, a cured film (cured product) having a low relative dielectric constant can be produced. Therefore, the produced cured product can be used in applications requiring a low dielectric constant, such as an insulating film. In addition, when the alkali-soluble resin (A) is an acrylic resin, the produced cured product has high transparency, and is therefore useful for display devices such as OLED, organic EL, or liquid crystal, and can be suitably used for planarizing films, interlayer insulating films, protective films for color filters, spacers for maintaining a constant thickness of the liquid crystal layer in liquid crystal display devices, or microlenses in solid-state imaging devices.
The cured product produced preferably exhibits a relative dielectric constant of 3.05 or less, more preferably 2.98 or less, and even more preferably 2.90 or less.

Methods for applying the photosensitive composition include methods using contact transfer type application devices such as roll coaters, reverse coaters, and bar coaters, and non-contact type application devices such as spinners (rotary application devices) and curtain flow coaters. The photosensitive composition can also be applied in the form of a film by printing methods such as the inkjet method.

There is no particular limitation on the thickness of the coating film. The thickness of the coating film is preferably 0.05 μm or more, more preferably 1 μm or more. The thickness of the coating film may be, for example, 7 μm or more, or 10 μm or more. There is no particular upper limit to the thickness of the coating film, but it may be, for example, 50 μm or less, or 20 μm or less. The thickness of the coating film is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 2 μm or less.
The thickness of the coating film is preferably in the range of 0.05 μm to 10 μm, more preferably 1 μm to 5 μm, and even more preferably 1 μm to 2 μm.

The coating film is then dried as necessary. There are no particular limitations on the drying method. Examples of drying methods include (1) drying on a hot plate at a temperature of 80°C to 120°C, preferably 90°C to 100°C, for 60 to 120 seconds, (2) leaving the film at room temperature for several hours to several days, and (3) placing the film in a hot air heater or infrared heater for several tens of minutes to several hours to remove the solvent.

By exposing the coating film to light, a cured film is formed.

The light source for exposure is not particularly limited, and examples thereof include a high pressure mercury lamp, an ultra-high pressure mercury lamp, a xenon lamp, a carbon arc lamp, an LED, etc. Using such a light source, the coating film can be exposed by irradiating the coating film with radiation such as an ArF excimer laser, a KrF excimer laser, an _F2 excimer laser, extreme ultraviolet light (EUV), vacuum ultraviolet light (VUV), an electron beam, an X-ray, a soft X-ray, a g-ray, an i-ray, an h-ray, a j-ray, or a k-ray, or with electromagnetic waves.

The exposure dose varies depending on the composition of the photosensitive composition, but is preferably, for example, from 10 mJ/cm ² to 2000 mJ/cm ² , more preferably from 100 mJ/cm ² to 1500 mJ/cm ² , and even more preferably from 200 mJ/cm ² to 1200 mJ/cm ^2. The exposure illuminance varies depending on the composition of the photosensitive composition, but is preferably in the range of from 1 mW/cm ² to 50 mW/cm ² .

The cured film cured by exposure is typically heated. The heating temperature is not particularly limited, and is preferably from 180°C to 280°C, more preferably from 200°C to 260°C, and particularly preferably from 220°C to 250°C. The heating time is typically from 1 minute to 60 minutes, more preferably from 10 minutes to 50 minutes, and particularly preferably from 20 minutes to 40 minutes.

On the other hand, the coating film may be exposed to light in a selective manner. In this case, the coating film is exposed to light in a selective manner through a negative mask having a light-transmitting portion having a shape corresponding to the pattern shape of the cured film.
Except for using a negative mask, the exposure method is the same as the above-mentioned exposure method.

The exposed coating film is then developed with a developer to form a patterned cured film. The development method is not particularly limited, and for example, a dipping method, a spray method, etc. can be used. Examples of the developer include organic ones such as monoethanolamine, diethanolamine, and triethanolamine, and aqueous solutions of sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia, and quaternary ammonium salts.

The patterned cured film obtained after development may be heated in the same manner as the exposure method for the patterned coating film described above.

The cured product of the above-mentioned photosensitive composition has moderate thermal flow properties. Therefore, when heated after exposure and development, the cured product obtained by exposure and development does not flow significantly and reach unintended areas. In addition, when heated after exposure and development, the cured product flows moderately, so that a cured product can be obtained whose cross-sectional shape has side surfaces that are more gently inclined than a rectangle.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[Synthesis of Photopolymerizable Compound B-1 (Photopolymerizable Compound (B1))]
50.00 g of dipentaerythritol, 150 mL of toluene, 0.25 g of 4-methoxyphenol, and 0.96 g of concentrated sulfuric acid were placed in a four-neck flask.
Also, 84.68 g of acrylic acid was dissolved in 85 mL of toluene and charged into the dropping funnel.
This toluene solution of acrylic acid was added dropwise to a four-neck flask, and the temperature was raised to 110° C. and the mixture was aged for 3 hours.
Thereafter, the mixture was cooled to room temperature, and washing with water, washing with _{a NaHCO3} solution, and washing with ion-exchanged water were carried out in this order.
Next, 0.25 g of 4-methoxyphenol was added, and the mixture was concentrated using a rotary evaporator. The mixture was then separated using a medium pressure column (manufactured by Yamazen Corporation) to obtain 81.14 g of the following photopolymerizable compound B-1 (yield 72.2%, purity 100%).

[Synthesis of Photopolymerizable Compound B-2 (Photopolymerizable Compound (B2))]
15.00 g of the photopolymerizable compound B-1, 45 mL of toluene, 0.08 g of 4-methoxyphenol, and 0.13 g of concentrated sulfuric acid were placed in a four-neck flask.
Also, 1.86 g of acrylic acid was dissolved in 1.86 mL of toluene and added to the dropping funnel.
This toluene solution of acrylic acid was added dropwise to a four-neck flask, and the temperature was raised to 110° C. and the mixture was aged for 3 hours.
Thereafter, the mixture was cooled to room temperature, and washing with water, washing with _{a NaHCO3} solution, and washing with ion-exchanged water were carried out in this order.
Next, 0.08 g of 4-methoxyphenol was added, and the mixture was concentrated using a rotary evaporator. The mixture was then separated using a medium pressure column (manufactured by Yamazen Corporation) to obtain 15.54 g of the following photopolymerizable compound B-2 (yield 92.1%, purity 100%).

[Synthesis of Photopolymerizable Compound B-3 (Photopolymerizable Compound (B3))]
50.00 g of dipentaerythritol, 150 mL of toluene, 0.25 g of 4-methoxyphenol, and 0.96 g of concentrated sulfuric acid were placed in a four-neck flask.
Also, 70.56 g of acrylic acid was dissolved in 71 mL of toluene and charged into the dropping funnel.
This toluene solution of acrylic acid was added dropwise to a four-neck flask, and the temperature was raised to 110° C. and the mixture was aged for 3 hours.
Thereafter, the mixture was cooled to room temperature, and washing with water, washing with _{a NaHCO3} solution, and washing with ion-exchanged water were carried out in this order.
Next, 0.25 g of 4-methoxyphenol was added, and the mixture was concentrated using a rotary evaporator. The mixture was then separated using a medium pressure column (manufactured by Yamazen Corporation) to obtain 55.28 g of the following photopolymerizable compound B-3 (yield: 53.6%, purity: 100%).

[Examples 1 to 6, Comparative Examples 1 to 7]
In the examples and comparative examples, an acrylic resin P1 having the following structure was used as the alkali-soluble resin (A). The numerical values in the parentheses in the following formula are the contents (mass%) of each structural unit in the resin. The weight average molecular weight of resin P1 in terms of polystyrene is 10,000.

In the examples and comparative examples, the above-mentioned photopolymerizable compounds B-1 to B-3 were used as the photopolymerizable compound (B).

In the examples and comparative examples, the following C-1 was used as the photopolymerization initiator (C).

13.9 parts by mass of acrylic resin P1 as alkali-soluble resin (A), 6.9 parts by mass of photopolymerizable compound (B) (component (B)), 0.8 parts by mass of compound C-1 as photopolymerizable compound (C), 31.2 parts by mass of diethylene glycol methyl ethyl ether, 46.7 parts by mass of propylene glycol monomethyl ether acetate, 0.2 parts by mass of 3-glycidyloxypropyltrimethoxysilane, 0.2 parts by mass of surfactant (BYK-310, manufactured by BYK-Chemie), and 0.1 parts by mass of antioxidant (Irganox 1010, manufactured by BASF Japan) were mixed to obtain photosensitive compositions of each example and each comparative example. The amounts (mass%) of photopolymerizable compounds B-1 to B-3 in the photopolymerizable compound (B) (component (B)) are shown in Table 1.

The obtained photosensitive composition was used to evaluate the dielectric constant and thermal flow properties according to the following methods. The evaluation results are shown in Table 1.

<Measurement of relative permittivity>
The dielectric constant was measured by the mercury probe method. SSM-495 (manufactured by Nippon Semilab) was used as the dielectric constant measuring device using the mercury probe method. A film-like cured product having a thickness of 1 μm was formed using the composition of each of the Examples and Comparative Examples by the following steps 1) to 4). The dielectric constant of the formed cured product was then measured.
1) A photosensitive composition is applied onto a substrate (silicon wafer) to form a coating film.
2) The formed coating film is heated at 100° C. for 120 seconds.
3) The coating film is exposed to light at an exposure dose of 1 J/ ^cm2 .
4) The exposed coating film is heated at 230° C. for 20 minutes.

<Heat flow properties (taper angle θ)>
The photosensitive composition was applied onto a glass substrate using a spin coater and heated at 100°C for 120 seconds to form a coating film. Next, a proximity exposure machine (product name: TME-150RTO, manufactured by Topcon Corporation) was used to irradiate the coating film with ultraviolet light (i-line) at an exposure dose of 50 mJ/ ^cm2 through a negative mask for forming a line pattern having a width of 10 μm. The coating film after exposure was developed with a 2.38 mass% TMAH aqueous solution at 25°C for 50 seconds, and then post-baked at 230°C for 20 minutes to form a line pattern having a thickness of 3 μm and a width of 10 μm.
The taper angle of the cross section of the obtained line pattern was evaluated. The taper angle θ was measured by observing the cross section of the line portion 1 of the line pattern in the width direction with a scanning electron microscope, and was determined as the junction angle between the side surface of the line portion 1 and the substrate 2, as shown in FIG.
The taper angle (pattern cross-sectional shape) was evaluated according to the following criteria.
A: The measurement angle (taper angle) θ is 60 degrees or more and 70 degrees or less. B: The measurement angle θ is 71 degrees or more and 80 degrees or less, or 45 degrees or more and 59 degrees or less. C: The measurement angle θ is 81 degrees or more and 90 degrees or less, or 30 degrees or more and 44 degrees or less. D: The measurement angle θ is less than 30 degrees.

The technical significance of the taper angle θ will be further explained below.
When the pattern has a rectangular shape (that is, the taper angle θ is about 90°), when another layer is laminated on the pattern, depending on the material of the upper layer, the wettability may be poor, and the pattern may not be covered neatly.
On the other hand, when the taper angle θ is small, the cured material flows significantly when heated and reaches unintended areas. This reduces the position selectivity of the cured material. In addition, when the taper angle θ is small, the pattern has thick and thin areas, so when the pattern is processed by etching, some areas are insufficiently etched, and the pattern has an effect on the underlying material.
Therefore, it is desirable that the taper angle θ of the pattern is an appropriate angle (45 to 80°) that is neither near 90° nor too small.

According to Table 1, it can be seen that the photosensitive composition of the example containing an alkali-soluble resin (A), a photopolymerizable compound (B1) which is a compound represented by the above-mentioned formula (b1-1), and a photopolymerizable compound (B2) which is a compound represented by the above-mentioned formula (b2-1) in addition to the alkali-soluble resin (A) and the photopolymerization initiator (C), and in which the photopolymerizable compound (B2) is in a predetermined ratio, can form a cured product having appropriate thermal flow properties and a low relative dielectric constant.
On the other hand, even when a photosensitive composition of a comparative example was used that did not contain at least one of the photopolymerizable compound (B1) and the photopolymerizable compound (B2), or that contained the photopolymerizable compound (B1) and the photopolymerizable compound (B2) but not in the specified ratio, a cured product having appropriate thermal flow properties and a low dielectric constant could not be formed.

Claims (4)

Contains an alkali-soluble resin (A), a photopolymerizable compound (B), a photopolymerization initiator (C), and a solvent (S),
The photopolymerizable compound (B) consists of only the photopolymerizable compound (B1) and the photopolymerizable compound (B2), or
the photopolymerizable compound (B) is composed only of a photopolymerizable compound (B1), a photopolymerizable compound (B2), and a photopolymerizable compound (B3);
The photopolymerizable compound (B1) is a compound represented by the following formula (b1-1):
The photopolymerizable compound (B2) is a compound represented by the following formula (b2-1):
The photopolymerizable compound (B3) is a compound represented by the following formula (b3-1):
a ratio of the mass of the photopolymerizable compound (B1) to the mass of the photopolymerizable compound (B) is 60 mass% or more and 94 mass% or less;
a ratio of the mass of the photopolymerizable compound (B2) to the mass of the photopolymerizable compound (B) is 6 mass% or more and 20 mass% or less;
A photosensitive composition, wherein a ratio of the mass of the photopolymerizable compound (B3) to the mass of the photopolymerizable compound (B) is 0 mass % or more and 30 mass % or less.

(In formula (b1-1), R ^1b to R ^5b are (meth)acryloyl groups, and R ^6b is a (meth)acryloyloxymethyl group.)

(In formula (b2-1), R ^7b to R ^11b each independently represent a (meth)acryloyloxymethyl group, and R ^12b represents a group represented by the following formula (b2-2).)

(In formula (b2-2), R ^19b and R ^20b each independently represent a hydrogen atom or a methyl group.)

(In formula (b3-1), R ^13b to R ^17b are (meth)acryloyl groups, and R ^18b is a hydroxymethyl group.) A cured product of the photosensitive composition according to claim 1. A step of applying the photosensitive composition according to claim 1 to form a coating film;
and exposing the coating film to light. A step of applying the photosensitive composition according to claim 1 to form a coating film;
A step of position-selectively exposing the coating film;
and developing the coating film after exposure.

Images