JP7599800B2 - Photocurable maleimide resin composition - Google Patents

Description

The present invention relates to a photocurable maleimide resin composition.

Photocurable resins (photosensitive resins), such as UV-curable resins, are already being used in many places. UV-curable resins can be broadly divided into types that cure through radical polymerization of unsaturated double bonds such as acrylic groups, and types that cure through cationic polymerization such as epoxy groups. Generally, they often have functional groups that contain heteroatoms such as oxygen atoms, and the values of the dielectric constant and dielectric tangent of the cured product are large.

In recent years, the next-generation communication system known as 5G has been developed, aiming to realize faster, larger capacity, and lower latency communications than ever before. To achieve this, materials for high frequency bands are required, and reducing transmission loss as a noise countermeasure is essential. For this reason, there is a demand for the development of insulating materials with excellent dielectric properties (low dielectric constant and low dielectric tangent) for use in binder resins for circuit boards, materials for laminating wiring for semiconductors, adhesives, etc.

As mentioned above, many photocurable resins have poor dielectric properties (high dielectric constant and high dielectric tangent), but there have been reports of attempts to solve these problems by using a special colored but transparent maleimide resin (Patent Documents 1 to 5).

However, the special maleimide compound used in the aforementioned report has many linear or branched alkyl groups, and by lowering the crosslink density, it tends to have excellent dielectric properties. On the other hand, it is also known that the disadvantages of low crosslink density include a high coefficient of thermal expansion (CTE) and a low glass transition temperature (Tg).

As a method to solve this problem, the use of a polymeric aromatic maleimide compound has been reported (Patent Document 6). The dielectric properties of the cured product of a composition containing this polymeric aromatic maleimide compound are poorer than other resins (high relative dielectric constant and high dielectric loss tangent), and the composition has poor photocurability to begin with, and it was found that the composition is easily dissolved when exposed to a solvent after being irradiated with light.

International Publication No. WO 2018/56466 JP 2020-33470 A JP 2020-33472 A WO 2020/45489 International Publication No. 2020/262577 JP 2020-33471 A

The present invention therefore aims to provide a photocurable maleimide resin composition with excellent curing properties that has excellent dielectric properties, a high glass transition temperature, and a small thermal expansion coefficient.

As a result of extensive research to solve the above problems, the inventors discovered that the following photocurable maleimide resin composition can achieve the above objective, and thus completed the present invention.

（式（１）中、
Ａは独立して環状構造を有する４価の有機基であり、
Ｂは独立して炭素数６～２００の２価炭化水素基であり、
Ｑは独立して下記式（２）

（式（２）中、Ｒ¹は独立して、水素原子又は炭素数１～５のアルキル基であって、ｘ１及びｘ２はそれぞれ独立に０～４の数である。）
で示されるシクロヘキサン骨格を有する炭素数６～６０の２価の脂環式炭化水素基であり、
ＷはＢ又はＱであり、
Ｂ及びＷの少なくとも１つはダイマー酸骨格由来の炭化水素基であり、
ｎは１～１００であり、ｍは１～２００である。ｎ及びｍで括られた各繰り返し単位の順序は限定されず、結合様式は、交互であっても、ブロックであっても、ランダムであってもよい。）
＜２＞
式（１）中のＡが下記構造式で示される４価の有機基のいずれかである＜１＞に記載の光硬化性マレイミド樹脂組成物。

（上記構造式中の置換基が結合していない結合手は、式（１）において環状イミド構造を形成するカルボニル炭素と結合するものである。）
＜３＞
さらに（Ｃ）成分として、重合禁止剤を含有する＜１＞又は＜２＞に記載の光硬化性マレイミド樹脂組成物。
＜４＞
（Ｂ）成分の光硬化開始剤の含有量が（Ａ）成分１００質量部に対して、０．１～５．０質量部である＜１＞～＜３＞のいずれか１項に記載の光硬化性マレイミド樹脂組成物。
＜５＞
（Ｃ）成分の重合禁止剤の含有量が（Ａ）成分１００質量部に対して、０．０１～０．５０質量部である＜３＞又は＜４＞に記載の光硬化性マレイミド樹脂組成物。
＜６＞
さらに（Ｄ）成分として接着助剤を含有する＜１＞～＜５＞のいずれか１項に記載の光硬化性マレイミド樹脂組成物。
＜７＞
（Ｄ）成分の接着助剤が（Ａ）成分中のマレイミド基と反応しうる官能基を有するものである＜６＞に記載の光硬化性マレイミド樹脂組成物。 ＜1＞
1. A photocurable maleimide resin composition comprising (A) a maleimide compound represented by general formula (1) and (B) a photocuring initiator.

(In formula (1),
A is independently a tetravalent organic group having a cyclic structure,
B is independently a divalent hydrocarbon group having 6 to 200 carbon atoms;
Q is independently represented by the following formula (2):

(In formula (2), R ¹ is independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and x1 and x2 are each independently a number from 0 to 4.)
is a divalent alicyclic hydrocarbon group having 6 to 60 carbon atoms and a cyclohexane skeleton represented by
W is B or Q;
At least one of B and W is a hydrocarbon group derived from a dimer acid skeleton,
n is 1 to 100, and m is 1 to 200. The order of the repeating units bracketed by n and m is not limited, and the bonding pattern may be alternating, block, or random.
＜2＞
The photocurable maleimide resin composition according to <1>, wherein A in formula (1) is any one of tetravalent organic groups represented by the following structural formulas:

(The bond not bonded to a substituent in the above structural formula is bonded to the carbonyl carbon that forms a cyclic imide structure in formula (1).)
＜3＞
The photocurable maleimide resin composition according to <1> or <2>, further comprising a polymerization inhibitor as a component (C).
＜4＞
<4> The photocurable maleimide resin composition according to any one of <1> to <3>, wherein the content of the photocuring initiator of the component (B) is 0.1 to 5.0 parts by mass per 100 parts by mass of the component (A).
＜5＞
The photocurable maleimide resin composition according to <3> or <4>, wherein the content of the polymerization inhibitor in the component (C) is 0.01 to 0.50 parts by mass per 100 parts by mass of the component (A).
＜6＞
The photocurable maleimide resin composition according to any one of <1> to <5>, further comprising an adhesive assistant as a component (D).
＜７＞
The photocurable maleimide resin composition according to <6>, wherein the adhesive aid of the component (D) has a functional group capable of reacting with the maleimide group in the component (A).

The photocurable maleimide resin composition of the present invention is a photocurable resin composition that produces a cured product having excellent dielectric properties (low relative dielectric constant and low dielectric tangent), a high glass transition temperature, and a small thermal expansion coefficient. Furthermore, the photocurable maleimide resin composition of the present invention has excellent curing properties without dissolving into a solvent after irradiation with light. Therefore, the photocurable maleimide resin composition of the present invention is useful, for example, as a protective film for wiring interlayer insulating layers and solder resists.

The present invention will be explained in more detail below.

（式（１）中、
Ａは独立して環状構造を有する４価の有機基であり、
Ｂは独立して炭素数６～２００の２価炭化水素基であり、
Ｑは独立して下記式（２）

（式（２）中、Ｒ¹は独立して、水素原子又は炭素数１～５のアルキル基であって、ｘ１及びｘ２はそれぞれ独立に０～４の数である。）
で示されるシクロヘキサン骨格を有する炭素数６～６０の２価の脂環式炭化水素基であり、
ＷはＢ又はＱであり、
Ｂ及びＷの少なくとも１つはダイマー酸骨格由来の炭化水素基であり、
ｎは１～１００であり、ｍは１～２００であり、ｎ及びｍで括られた各繰り返し単位の順序は限定されず、結合様式は、交互であっても、ブロックであっても、ランダムであってもよい。） [(A) Maleimide compound having one or more saturated or unsaturated divalent hydrocarbon groups having 6 to 200 carbon atoms per molecule]
The component (A) used in the present invention is a specific maleimide compound represented by the following formula (1), which is a maleimide compound having one or more saturated or unsaturated divalent hydrocarbon groups having 6 to 200 carbon atoms per molecule and at least one dimer acid skeleton per molecule.

(In formula (1),
A is independently a tetravalent organic group having a cyclic structure,
B is independently a divalent hydrocarbon group having 6 to 200 carbon atoms;
Q is independently represented by the following formula (2):

(In formula (2), R ¹ is independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and x1 and x2 are each independently a number from 0 to 4.)
is a divalent alicyclic hydrocarbon group having 6 to 60 carbon atoms and a cyclohexane skeleton represented by
W is B or Q;
At least one of B and W is a hydrocarbon group derived from a dimer acid skeleton,
n is 1 to 100, m is 1 to 200, the order of the repeating units bounded by n and m is not limited, and the bonding pattern may be alternating, block, or random.

When the maleimide compound represented by formula (1) is used, the resulting composition has excellent dielectric properties both before and after curing, strong adhesion to copper foil, and a high Tg, making it highly reliable.

The maleimide compound of component (A) has a divalent aliphatic hydrocarbon group, and each molecule has one hydrocarbon group derived from a dimer acid skeleton.

The dimer acid referred to here is a liquid dibasic acid mainly composed of a dicarboxylic acid having 36 carbon atoms, which is produced by dimerization of an unsaturated fatty acid having 18 carbon atoms, which is made from natural products such as vegetable oils and fats. The dimer acid does not have a single skeleton, but has multiple structures, and there are several types of isomers. Representative dimer acids are classified as linear (a), monocyclic (b), aromatic (c), and polycyclic (d). In this specification, the dimer acid skeleton refers to a group derived from a dimer diamine having a structure in which the carboxy group of such a dimer acid is substituted with a primary aminomethyl group. That is, the dimer acid skeleton of the (A) component is preferably a group in which two carboxy groups are substituted with methylene groups in each of the dimer acids shown below in (a) to (d).
Furthermore, when the maleimide compound of component (A) has a hydrocarbon group derived from a dimer acid skeleton, the hydrocarbon group derived from the dimer acid skeleton preferably has a structure in which the carbon-carbon double bonds in the hydrocarbon group derived from the dimer acid skeleton are reduced by a hydrogenation reaction, from the viewpoint of the heat resistance and reliability of the cured product.

（式（２）中、Ｒ¹は独立して、水素原子又は炭素数１～５のアルキル基であって、ｘ１及びｘ２はそれぞれ独立に０～４の数である。）
で示されるシクロヘキサン骨格を有する炭素数６～６０、好ましくは７～３０、より好ましくは８～２０の２価の脂環式炭化水素基である。 In addition, in the formula (1), Q independently represents the following formula (2):

(In formula (2), R ¹ is independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and x1 and x2 are each independently a number from 0 to 4.)
It is a divalent alicyclic hydrocarbon group having a cyclohexane skeleton and having 6 to 60, preferably 7 to 30, and more preferably 8 to 20 carbon atoms, represented by the following formula:

Specific examples of R ¹ include a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a t-butyl group. Among these, a hydrogen atom and a methyl group are preferable. Each R ¹ may be the same or different.
Moreover, the above x1 and x2 are each independently a number from 0 to 4, and preferably a number from 0 to 2. Note that x1 and x2 may be the same or different.

（上記構造式中の置換基が結合していない結合手は、式（１）において環状イミド構造を形成する窒素原子と結合するものである。） Specific examples of Q include divalent alicyclic hydrocarbon groups represented by the following structural formulas.

(The bond not bonded to a substituent in the above structural formula is bonded to the nitrogen atom that forms a cyclic imide structure in formula (1).)

In the formula (1), W is B or Q. The structural unit W has B or Q is determined by the manufacturing method.

In the formula (1), n is 1 to 100, preferably 1 to 60, and more preferably 2 to 50, and m is 1 to 200, preferably 1 to 50, and more preferably 3 to 40. If n or m is too large, the flowability may decrease, and moldability may be poor.
The order of the repeating units bracketed by n and m is not limited, and the bonding pattern may be alternating, block, or random.

In the formula (1), A independently represents a tetravalent organic group having a cyclic structure, and among these, it is preferable that A is any of the tetravalent organic groups represented by the following structural formulas.

In addition, in the formula (1), B is independently a divalent hydrocarbon group having 6 to 200 carbon atoms, preferably 8 to 100, and more preferably 10 to 50 carbon atoms. Among these, a branched divalent hydrocarbon group in which one or more hydrogen atoms in the divalent hydrocarbon group are substituted with an alkyl or alkenyl group having 6 to 200 carbon atoms, preferably 8 to 100, and more preferably 10 to 50 carbon atoms, is preferred. The branched divalent hydrocarbon group may be either a saturated aliphatic hydrocarbon group or an unsaturated hydrocarbon group, and may have an alicyclic structure or an aromatic ring structure in the middle of the molecular chain.
Specific examples of the branched divalent hydrocarbon group include divalent hydrocarbon groups derived from diamines at both ends, called dimer diamines. Note that dimer diamines are compounds derived from dimers (dimer acids) of unsaturated fatty acids such as oleic acid, and therefore B is particularly preferably a group in which the two carboxy groups in each of the dimer acids (a) to (d) above are each substituted with a methylene group.

The number average molecular weight of the maleimide compound of component (A) is not particularly limited, but from the viewpoint of the handleability of the composition, it is preferably from 800 to 50,000, and more preferably from 900 to 30,000. Furthermore, component (A) may be used alone or in combination of two or more types.
The number average molecular weight referred to in this specification refers to the number average molecular weight measured by gel permeation chromatography (GPC) under the following conditions using polystyrene as a standard substance.

[Measurement conditions]
Developing solvent: tetrahydrofuran (THF)
Flow rate: 0.35mL/min
Detector: Refractive index detector (RI)
Column: TSK Guard column Super H-L
TSKgel SuperHZ4000 (4.6mm I.D. x 15cm x 1)
TSKgel SuperHZ3000 (4.6mm I.D. x 15cm x 1)
TSKgel SuperHZ2000 (4.6mm I.D. x 15cm x 2)
(Both manufactured by Tosoh Corporation)
Column temperature: 40°C
Sample injection volume: 5 μL (THF solution with a concentration of 0.2% by mass)

[(B) Photocuring initiator]
The photocuring initiator (B) is added to promote the crosslinking reaction of the maleimide compound (A) or the crosslinking reaction with a reactive group capable of reacting with the maleimide group in component (A). A photosensitizer such as an amine compound, a urea compound, a sulfur-containing compound, a phosphorus-containing compound, or a nitrile compound may also be used in combination.

There are no particular limitations on the photocuring initiator as long as it initiates a reaction by light. Examples of photocuring initiators include aromatic ketones such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-methyl-1-(4-(methylthio)phenyl)-2-morpholinopropanone-1, 2,4-diethylthioxanthone, 2-ethylanthraquinone, and phenanthrenequinone; benzyl dimethyl ketal; Benzyl derivatives; 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-di(m-methoxyphenyl)imidazole dimer, 2-(o-fluorophenyl)-4,5-phenylimidazole dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer, 2,4-di(p-methoxyphenyl)-5-phenylimidazole 2,4,5-triarylimidazole dimers such as 2-(2,4-dimethoxyphenyl)-4,5-diphenylimidazole dimer; acridine derivatives such as 9-phenylacridine and 1,7-bis(9,9'-acridinyl)heptane; bisacylphosphine oxadiazines such as bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; ides; alkylphenone compounds such as 1-hydroxy-cyclohexyl-phenyl-ketone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone; acylphosphine oxide compounds such as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, benzophenone compounds, etc.

The content of the photocuring initiator, component (B), relative to 100 parts by mass of component (A) is preferably 0.1 to 5.0 parts by mass, more preferably 0.2 to 4.5 parts by mass, and even more preferably 0.5 to 4.0 parts by mass.
Furthermore, when the composition of the present invention contains a photocurable resin having a reactive group capable of reacting with a maleimide group other than the component (A) described below, the content of the component (B) is preferably 0.1 to 7.0 parts by mass, more preferably 0.2 to 6.0 parts by mass, and even more preferably 0.5 to 5.0 parts by mass relative to 100 parts by mass of the sum of the component (A) and the photocurable resins having a reactive group capable of reacting with a maleimide group other than the component (A) (hereinafter, both components may be collectively referred to simply as the "photocurable resin component").
When the amount of the (B) component is less than 0.1 parts by mass per 100 parts by mass of the (A) component, the photocuring may proceed slowly. When the amount of the (B) component is more than 5.0 parts by mass, the composition may lack storage stability even if a polymerization inhibitor described below is added.
The component (B) may be used alone or in combination of two or more.

The photocurable maleimide resin composition of the present invention may further contain various additives as necessary, provided that the effects of the present invention are not impaired. Examples of other additives are given below.

[(C) Polymerization inhibitor]
The photocurable maleimide resin composition of the present invention may contain a polymerization inhibitor as component (C). The polymerization inhibitor is added to improve the storage stability of the photocurable resin composition of the present invention, and is not particularly limited as long as it can improve the storage stability.

Examples of polymerization inhibitors include commonly used ones such as catechol, resorcinol, and 1,4-hydroquinone, as well as 2-methylcatechol, 3-methylcatechol, 4-methylcatechol, 2-ethylcatechol, 3-ethylcatechol, 4-ethylcatechol, 2-propylcatechol, 3-propylcatechol, 4-propylcatechol, 2-n-butylcatechol, 3-n-butylcatechol, 4-n-butylcatechol, 2-tert-butylcatechol, and 3-tert-butylcatechol. alkyl catechol compounds such as catechol, 4-tert-butylcatechol, and 3,5-di-tert-butylcatechol; alkyl resorcinol compounds such as 2-methylresorcinol, 4-methylresorcinol, 2-ethylresorcinol, 4-ethylresorcinol, 2-propylresorcinol, 4-propylresorcinol, 2-n-butylresorcinol, 4-n-butylresorcinol, 2-tert-butylresorcinol, and 4-tert-butylresorcinol; methylhydroquinone compounds such as methylhydroquinone, methylhydroquinone, and methylhydroquinone; alkylhydroquinone compounds such as ethylhydroquinone, propylhydroquinone, and tert-butylhydroquinone; phosphine compounds such as tributylphosphine, trioctylphosphine, tricyclohexylphosphine, and triphenylphosphine; phosphine oxide compounds such as trioctylphosphine oxide and triphenylphosphine oxide; phosphite compounds such as triphenylphosphine and trisnonylphenylphosphite; 2,2,6,6-tetramethylpiperidine-1 -oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, and other hindered amine compounds; naphthalene compounds such as 1,4-dihydroxy-2-naphthalenesulfonate ammonium, 4-methoxy-1-naphthol, and other naphthoquinone compounds such as 1,4-naphthoquinone, 2-hydroxy-1,4-naphthoquinone, and anthrone; and phenolic antioxidants such as pyrogallol, phloroglucin, and 4,4'-butylidene-bis(6-tert-butyl-m-cresol).

The content of the polymerization inhibitor as component (C) is preferably 0.01 to 0.50 parts by mass, more preferably 0.02 to 0.45 parts by mass, and even more preferably 0.03 to 0.40 parts by mass, per 100 parts by mass of component (A).
Furthermore, when the composition of the present invention contains a photocurable resin having a reactive group capable of reacting with a maleimide group other than the component (A) described below, the amount is preferably 0.01 to 0.70 parts by mass, more preferably 0.02 to 0.60 parts by mass, and even more preferably 0.03 to 0.50 parts by mass, relative to 100 parts by mass of the photocurable resin component.
When the amount of the (C) component is less than 0.01 part by mass per 100 parts by mass of the (A) component, the polymerization inhibiting effect may be weakened. When the amount is more than 0.50 parts by mass, the effect reaches a plateau, and not only is it difficult to expect significant improvement in storage stability, but curability may also be affected.
The component (C) may be used alone or in combination of two or more types.

[(D) Adhesive assistant]
The photocurable maleimide resin composition of the present invention may contain an adhesive aid as component (D). The adhesive aid is added to improve the adhesive strength of the photocurable resin composition of the present invention. The maleimide compound of component (A) has strong adhesive strength to metals, and by adding component (D), the adhesive strength of the composition to some substances such as glass can be further improved.

Examples of adhesive aids include silane coupling agents, triazole-based compounds, and tetrazole-based compounds.

There is no particular restriction on the type of adhesive aid, but it is preferable that it has a functional group that can react with the maleimide group in component (A). Examples of functional groups that can react with the maleimide group include maleimide groups, epoxy groups, (meth)acrylic groups, vinyl groups, allyl groups, phenolic hydroxyl groups, and amino groups. Among these, those that have at least one of maleimide groups and (meth)acrylic groups, which have excellent photocuring properties, are preferred.

Examples of the silane coupling agent include epoxy group-containing alkoxysilanes such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-methacryloxypropylmethyldiethoxysilane; Examples of alkoxysilanes include (meth)acrylic group-containing alkoxysilanes such as vinyltrimethoxysilane and vinyltriethoxysilane; alkenyl group-containing alkoxysilanes such as vinyltrimethoxysilane and vinyltriethoxysilane; and amino group-containing alkoxysilanes such as N-2-(aminoethyl)3-aminopropyltrimethoxysilane, N-2-(aminoethyl)3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane.
Examples of triazole compounds include 1,2,3-triazole, 1,2,4-triazole, benzotriazole, and N-trimethylsilyl-benzotriazole.
Examples of the tetrazole compounds include 1H-tetrazole, 5-amino-1H-tetrazole, 5-phenyl-1H-tetrazole, and 1-phenyl-5-mercapto-1H-tetrazole.

The content of the adhesive aid of the component (D) is preferably 0.01 to 10.0 parts by mass, more preferably 0.05 to 8.0 parts by mass, and even more preferably 0.1 to 5.0 parts by mass, per 100 parts by mass of the component (A).
Furthermore, when the composition of the present invention contains a photocurable resin having a reactive group capable of reacting with a maleimide group other than the component (A) described below, the content of the component (D) is preferably 0.01 to 12.0 parts by mass, more preferably 0.05 to 10.0 parts by mass, and even more preferably 0.1 to 8.0 parts by mass, relative to 100 parts by mass of the photocurable resin component.
The component (D) may be used alone or in combination of two or more types.

[Photocurable resin having a reactive group capable of reacting with a maleimide group]
In the present invention, a photocurable resin (A') having a reactive group capable of reacting with a maleimide group other than the component (A) may also be added.
The photocurable resin is not limited to a specific type, and examples thereof include various resins other than component (A), such as epoxy resins, phenolic resins, melamine resins, silicone resins, cyclic imide resins including maleimide compounds other than component (A), urea resins, thermosetting polyimide resins, modified polyphenylene ether resins, thermosetting acrylic resins, epoxy-silicone hybrid resins, etc. Examples of reactive groups that can react with maleimide groups include epoxy groups, maleimide groups, hydroxyl groups, acid anhydride groups, alkenyl groups such as allyl groups and vinyl groups, (meth)acrylic groups, and thiol groups.

From the viewpoint of reactivity, the reactive group of the photocurable resin is preferably a maleimide group or a (meth)acrylic group. However, the amount of the photocurable resin having a reactive group capable of reacting with a maleimide group is 0 to 50 mass % of the total amount of the photocurable resin.

[Inorganic filler]
In the present invention, an inorganic filler may be further added. It may be blended for the purpose of increasing the strength or rigidity of the cured product of the photocurable maleimide resin composition of the present invention, or adjusting the thermal expansion coefficient or dimensional stability of the cured product. As the inorganic filler, those usually blended in epoxy resin compositions or silicone resin compositions can be used. For example, silicas such as spherical silica, fused silica, and crystalline silica, alumina, silicon nitride, aluminum nitride, boron nitride, barium sulfate, talc, clay, aluminum hydroxide, magnesium hydroxide, calcium carbonate, glass fiber, and glass particles may be mentioned. Furthermore, fluorine-containing resins, coating fillers, and/or hollow particles may be added to improve the dielectric properties. The inorganic filler may be used alone or in combination of two or more types.

The average particle size and shape of the inorganic filler are not particularly limited, but spherical silica having an average particle size of 0.5 to 5 μm is preferably used. The average particle size is determined as the mass average value D ₅₀ (or median diameter) in particle size distribution measurement by laser light diffraction method.

Furthermore, in order to improve the properties of the inorganic filler, it is preferable that the inorganic filler is surface-treated with a silane coupling agent having an organic group capable of reacting with a maleimide group. Examples of such silane coupling agents include epoxy group-containing alkoxysilane, amino group-containing alkoxysilane, (meth)acrylic group-containing alkoxysilane, and alkenyl group-containing alkoxysilane.
As the silane coupling agent, a (meth)acrylic group- and/or amino group-containing alkoxysilane is suitably used, and specific examples thereof include 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and 3-aminopropyltrimethoxysilane.

The amount of inorganic filler to be mixed is 0 to 70 mass % of the total photocurable resin from the viewpoint of light transmittance.

[others]
In addition to the above, non-functional silicone oil, thermoplastic resin, thermoplastic elastomer, organic synthetic rubber, light stabilizer, flame retardant, pigment, dye, etc. may be blended.

[Production method]
The photocurable maleimide resin composition of the present invention can be produced by mixing the above-mentioned components.
The photocurable maleimide resin composition of the present invention can be dissolved in an organic solvent and treated as a varnish, and the photocurable maleimide resin composition can be produced as a varnish by mixing each of the above-mentioned components with an organic solvent. Any organic solvent can be used without limitation as long as it dissolves the photocurable resin having a reactive group capable of reacting with the maleimide group as component (A) and other additives, and examples of the organic solvent include anisole, xylene, toluene, tetrahydrofuran (THF), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetonitrile, etc. These may be used alone or in combination of two or more.

Alternatively, when component (A) is liquid at room temperature, the individual components can be blended and mixed using a planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.) or a mixer such as a THINKY CONDITIONING MIXER (manufactured by Thinky Corporation).
Alternatively, the components may be premixed and extruded into a sheet or film using a melt kneader, and then used as is. Furthermore, the sheet or film may be processed into granules or tablets.

[Application]
The photocurable maleimide resin composition of the present invention can be used for applications requiring an insulating resin composition, and is not particularly limited, but as long as it is a resin composition that can be formed into a film at room temperature, it can be used for applications such as photosensitive films, photosensitive films with supports, insulating resin sheets such as prepregs, circuit boards (for laminates, multilayer printed wiring boards, etc.), solder resists, underfill materials, die bonding materials, semiconductor encapsulants, hole filling resins, component embedding resins, and adhesives for bonding metals to metals. Among these, it can be suitably used as a resin composition for insulating layers of multilayer printed wiring boards or as a solder resist. On the other hand, when it is liquid at room temperature, it is suitably used as an adhesive, particularly an adhesive for use in areas where little heat can be applied.

The photocurable maleimide resin composition of the present invention is cured by irradiation with light under the usual conditions of wavelength, illuminance, time, etc., as the curing conditions for photocurable resins. For example, it is cured by irradiation with UV light of 365 nm or the like. Depending on the application, after photocuring under the above conditions, it may be combined with thermal curing under conditions such as 180°C for 1 hour.

The present invention will be specifically explained below with examples and comparative examples, but the present invention is not limited to the following examples.

－Ｃ₃₆Ｈ₇₂－はダイマー酸骨格由来の構造を示す。
ｎ≒５（平均値）、ｍ≒１（平均値）
（Ａ－２）：下記式で示される直鎖アルキレン基含有ビスマレイミド化合物（商品名：ＢＭＩ－２５００、Ｄｅｓｉｇｎｅｒ Ｍｏｌｅｃｕｌｅ Ｉｎｃ．製）

－Ｃ₃₆Ｈ₇₂－はダイマー酸骨格由来の構造を示す。
ｎ≒５（平均値）、ｍ≒１（平均値） [(A) Maleimide compound]
(A-1): A linear alkylene group-containing bismaleimide compound represented by the following formula (product name: X-45-2600, manufactured by Shin-Etsu Chemical Co., Ltd.)

--C ₃₆ H ₇₂ -- represents a structure derived from a dimer acid skeleton.
n ≒ 5 (average value), m ≒ 1 (average value)
(A-2): A linear alkylene group-containing bismaleimide compound represented by the following formula (product name: BMI-2500, manufactured by Designer Molecules Inc.)

--C ₃₆ H ₇₂ -- represents a structure derived from a dimer acid skeleton.
n ≒ 5 (average value), m ≒ 1 (average value)

－Ｃ₃₆Ｈ₇₂－はダイマー酸骨格由来の構造を示す。
ｎ≒５（平均値）
（Ａ－４）：下記構造の芳香族マレイミド（商品名：ＢＭＩ－６１００、Ｄｅｓｉｇｎｅｒ Ｍｏｌｅｃｕｌｅｓ Ｉｎｃ．製）

ｎ≒８（平均値）、ｍ≒１（平均値）
（Ａ－５）：４，４’－ジフェニルメタンビスマレイミド（商品名：ＢＭＩ－１０００、大和化成工業（株）製）
（Ａ－６）：ビスフェノールＡ－ジフェニルエーテルビスマレイミド（商品名：ＢＭＩ－４０００、大和化成工業（株）） [(A') Photocurable resin having a reactive group capable of reacting with a maleimide group (maleimide compound other than component (A)]
(A-3): A linear alkylene group-containing bismaleimide compound represented by the following formula (product name: BMI-3000, manufactured by Designer Molecules Inc.)

--C ₃₆ H ₇₂ -- represents a structure derived from a dimer acid skeleton.
n ≒ 5 (average value)
(A-4): Aromatic maleimide having the following structure (product name: BMI-6100, manufactured by Designer Molecules Inc.)

n ≒ 8 (average value), m ≒ 1 (average value)
(A-5): 4,4'-diphenylmethane bismaleimide (product name: BMI-1000, manufactured by Daiwa Chemical Industry Co., Ltd.)
(A-6): Bisphenol A-diphenyl ether bismaleimide (product name: BMI-4000, Daiwa Chemical Industry Co., Ltd.)

[(B) Photocuring initiator]
(B-1): Bis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide (product name: Ominirad 819, manufactured by iGM Resins)

[(C) Polymerization inhibitor]
(C-1) 4,4'-butylidene-bis(6-tert-butyl-m-cresol) (product name: ANTAGE W-300, manufactured by Kawaguchi Chemical Industry Co., Ltd.)

[(D) Adhesive assistant]
(D-1): 3-methacryloxypropyltrimethoxysilane (product name: KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.)

[Examples 1 to 3, Comparative Examples 1 to 7]
<Preparation of varnish>
The components shown in Tables 1 and 2 were added to a 500 mL four-neck flask equipped with a Dimroth condenser and a stirrer, and the mixture was stirred at 50° C. for 2 hours to obtain a varnish-like resin composition.

<Dielectric constant, dielectric tangent, glass transition temperature, thermal expansion coefficient, hardening>
The varnish-like photocurable cyclic imide resin composition prepared by the above method was applied to a 38 μm-thick PET film using a roller coater, and an uncured resin film having a thickness of 50 μm was obtained by drying for 10 minutes at 100° C. for Examples and Comparative Examples 1 to 3, and for 10 minutes at 180° C. for Comparative Examples 4 to 7. Next, the uncured resin film obtained was irradiated with 2000 mJ/ ^cm2 UV for 3 seconds to photocure the film, and a cured resin film was obtained.
Using this cured resin film, a network analyzer (manufactured by Keysight, product name: E5063-2D5) and a strip line (manufactured by Keycom Corporation) were connected to measure the relative dielectric constant and dielectric loss tangent of the cured resin film at a frequency of 10 GHz.
The glass transition temperature (Tg) and coefficient of thermal expansion (CTE, 0 to 40° C.) of the cured resin film were measured using a DMA-800 manufactured by TA Instruments.
Furthermore, the photocured resin film was immersed in anisole for 6 hours, and the curability was evaluated by assigning a weight change of 0.3% or less to the initial weight as "good" and a weight change of more than 0.3% as "bad."

<Adhesion to copper foil>
The varnish-like photocurable cyclic imide resin composition prepared by the above method was applied to a copper foil (trade name: TQ-M4-VLP, Mitsui Metal Co., Ltd.) having a thickness of 18 μm and Rz = 0.6 μm with a roller coater, and dried at 100 ° C for 10 minutes to prepare an uncured resin film having a thickness of 50 μm on the copper foil. A slide glass (trade name: S1111, Matsunami Glass Industry Co., Ltd.) was laminated on the surface on which the uncured resin film was formed on the copper foil using a vacuum press (Nikko Materials Co., Ltd., product name: V-130) under conditions of 100 ° C, 0.3 MPa pressure, and 60 seconds. It was irradiated with 2000 mJ / cm ² UV from the slide glass side for 3 seconds, photocured, and additionally thermally cured at 180 ° C for 1 hour.
In order to evaluate the adhesion, the 90° peel adhesion strength (kN/m) was measured when peeling the copper foil of the adhesive test piece from the slide glass at a temperature of 23° C. and a tensile speed of 50 mm/min in accordance with JIS-C-6481 "Test methods for copper-clad laminates for printed wiring boards."

＊１：外観不良あり、分離傾向が確認された。
＊２：ＴＭＡカーブに変曲点が２つ観測された。

*1: Poor appearance and tendency to separate were observed.
*2: Two inflection points were observed in the TMA curve.

From the above, the photocurable maleimide resin composition of the present invention has excellent dielectric properties (low dielectric constant and low dielectric tangent), a high glass transition temperature, and a small thermal expansion coefficient in the cured product, and therefore it has been confirmed that it is useful as a protective film for wiring interlayer insulation layers and solder resists, etc.

Claims (2)

(A) a maleimide compound represented by general formula (1),
(B) 0.1 to 5.0 parts by mass of a photocuring initiator relative to 100 parts by mass of the (A) component;
(C) 0.01 to 0.50 parts by mass of a polymerization inhibitor relative to 100 parts by mass of the component (A), and (D) 0.1 to 5.0 parts by mass of an adhesive aid having a functional group capable of reacting with the maleimide group in the component (A), selected from a maleimide group, an epoxy group, a (meth)acrylic group, a vinyl group, an allyl group, a phenolic hydroxyl group, and an amino group, relative to 100 parts by mass of the component (A) .
A photocurable maleimide resin composition comprising:

(In formula (1),
A is independently a tetravalent organic group having a cyclic structure,
B is independently a divalent hydrocarbon group having 6 to 200 carbon atoms;
Q is independently represented by the following formula (2):

(In formula (2), R ¹ is independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and x1 and x2 are each independently a number from 0 to 4.)
is a divalent alicyclic hydrocarbon group having 6 to 60 carbon atoms and a cyclohexane skeleton represented by
W is B or Q;
At least one of B and W is a hydrocarbon group derived from a dimer acid skeleton,
n is 1 to 100, and m is 1 to 200. The order of the repeating units bracketed by n and m is not limited, and the bonding pattern may be alternating, block, or random. 2. The photocurable maleimide resin composition according to claim 1, wherein A in formula (1) is any one of tetravalent organic groups represented by the following structural formulas:

(The bond not bonded to a substituent in the above structural formula is bonded to the carbonyl carbon that forms a cyclic imide structure in formula (1).)