JP7474592B2 - Curable resin composition, dry film, resin-coated copper foil, cured product, and electronic component - Google Patents

Description

The present invention relates to a curable resin composition, a dry film, a resin-coated copper foil, a cured product, and an electronic component.

Curable resin compositions containing epoxy resins have been used as insulating materials for forming electronic components such as printed wiring boards, and various combinations of curing agents and other components for curable resins such as epoxy resins have been studied to impart various properties to the cured products. For example, Patent Document 1 attempts to improve the adhesion of the cured product of a curable resin composition by using two types of curing agents and additives for epoxy resins.

Patent No. 5396805

However, from the standpoint of reliability and the like, curable resin compositions for forming insulating layers of electronic components are required to be capable of forming cured products with even more excellent heat resistance.
On the other hand, signals from communication devices are becoming increasingly high frequency due to the spread of high-capacity, high-speed communications such as the fifth generation communication system (5G) and millimeter wave radar for automotive ADAS (advanced driving systems). However, unless the relative dielectric constant (Dk) and dielectric loss tangent (Df) are sufficiently low, the higher the frequency, the greater the transmission loss due to dielectric loss, resulting in problems such as signal attenuation and heat generation. Therefore, it is also required to be able to form a cured product with a low dielectric constant and low dielectric loss tangent.
In order to stably manufacture, operate, and maintain the durability of electronic components, it is also important to obtain a cured product that has excellent adhesion to the conductor metals of the electronic components, such as copper. When the adhesion of the cured product is high, the dielectric constant tends to increase.
In view of the above problems, an object of the present invention is to provide a curable resin composition that can give a cured product having high heat resistance, a low dielectric constant, a low dielectric tangent, and excellent adhesion to conductive metals, and a dry film having a resin layer obtained from the composition, a copper foil with a resin, a cured product, and an electronic component.

The object of the present invention is to
(A) an epoxy resin,
(B) a compound having an active ester group,
(C) an inorganic filler, and
(D) polyester additives;
The present inventors have found that this object can be achieved by a curable resin composition comprising the above-mentioned formula (D), wherein the polyester additive is a polymer having a polyalkylene glycol structure and an aliphatic polyester structure.

In the curable resin composition of the present invention, it is preferable that the amount of the polyester additive (D) relative to the total mass of the epoxy resin (A) and the compound having an active ester group (B) is 1 mass% or more and 35 mass% or less.

In addition, it is preferable that the molar ratio of the polyalkylene glycol structure to the aliphatic polyester structure in the polyester additive (D) is in the range of 35-55:65-45.

Furthermore, it is preferable that the ratio of the total amount of epoxy groups in (A) the epoxy resin to the total amount of active ester groups in (B) the compound having an active ester group is 0.2 to 0.9.

（式中、Ｘ_１はそれぞれ独立的にベンゼン環またはナフタレン環を有する基であり、ｋは０または１を表し、ｎは繰り返し単位の平均で０．０５～２．５である。）で表される化合物であることが好ましい。 The compound (B) having an active ester group is represented by the following general formula (1):

(wherein _X1 is each independently a group having a benzene ring or a naphthalene ring, k is 0 or 1, and n is an average of 0.05 to 2.5 in the repeating units).

（式（２）中、Ｘ_２はそれぞれ独立的に下記式（３）：

で表される基または下記式（４）：

で表される基であり、
ｍは１～６の整数であり、ｎはそれぞれ独立的に１～５の整数であり、ｑはそれぞれ独立的に１～６の整数であり、
式（３）中、ｋはそれぞれ独立的に１～５の整数であり、
式（４）中、Ｙは上記式（３）で表される基（ｋはそれぞれ独立的に１～５の整数）であり、ｔはそれぞれ独立的に０～５の整数である）
で表される構造部位を有し、その両末端が一価のアリールオキシ基である構造を有する化合物であることであることが好ましい。 The compound (B) having an active ester group is represented by the following general formula (2):

(In formula (2), _X2 each independently represents the following formula (3):

or a group represented by the following formula (4):

is a group represented by
m is an integer from 1 to 6, each n is independently an integer from 1 to 5, and each q is independently an integer from 1 to 6;
In formula (3), k is independently an integer from 1 to 5,
In formula (4), Y is a group represented by formula (3) above (wherein k is an integer of 1 to 5, and t is an integer of 0 to 5).
and a compound having a structure represented by the following formula (I) and both terminals of which are monovalent aryloxy groups.

Another object of the present invention is to provide a dry film having the above-mentioned curable resin composition as a resin layer.
A resin-coated copper foil having the above-mentioned curable resin composition as a resin layer on a copper foil or a copper foil with a carrier.
The above objects can be achieved by the above-mentioned curable resin composition, the cured product of the resin layer of the dry film or the resin layer of the resin-coated copper foil, and an electronic device having the above-mentioned cured product.

The curable resin composition of the present invention provides a cured product that has high heat resistance, low dielectric constant, low dielectric loss tangent, and excellent adhesion to conductor metals. In addition, a dry film having a resin layer obtained from the curable resin composition of the present invention, a resin-coated copper foil having a resin layer obtained from the curable resin composition of the present invention, the curable resin composition of the present invention, a cured product of the resin layer of the dry film or the resin layer of the resin-coated copper foil, and an electronic component having this cured product each have high heat resistance, low dielectric constant, low dielectric loss tangent, and excellent adhesion to conductor metals.

<Curable resin composition>
The curable resin composition of the present invention comprises:
(A) an epoxy resin (also referred to as component A);
(B) a compound having an active ester group (also referred to as component B),
(C) an inorganic filler (also referred to as component C), and
(D) polyester additive (also referred to as component D);
and (D) the polyester additive is a polymer having a polyalkylene glycol structure and an aliphatic polyester structure.

The components contained in the curable resin composition of the present invention are described below. In this specification, when a numerical range is expressed with "~", it means a range including the numerical values (i.e., from ... to ...).

[(A) Epoxy resin]
The curable resin composition of the present invention contains one or more types of (A) epoxy resins.

As the (A) epoxy resin, any resin having one or more epoxy groups can be used, and preferred examples include bifunctional epoxy resins having two epoxy groups in the molecule, and multifunctional epoxy resins having three or more epoxy groups in the molecule. Hydrogenated epoxy resins may also be used.

Furthermore, it is preferable that the epoxy resin (A) contains at least one of a trifunctional or higher liquid epoxy resin and a trifunctional or higher semi-solid epoxy resin. When a trifunctional or higher liquid epoxy resin or a trifunctional or higher semi-solid epoxy resin is contained, the glass transition temperature can be improved while maintaining a low dielectric tangent.

The epoxy resin (A) may be one or more of solid epoxy resin, semi-solid epoxy resin, and liquid epoxy resin, but preferably contains a solid epoxy resin. Furthermore, it is also preferable to use a liquid or semi-solid epoxy resin in terms of producing a dry film or a resin-coated copper foil.

In this specification, solid epoxy resin refers to an epoxy resin that is solid at 40°C, semi-solid epoxy resin refers to an epoxy resin that is solid at 20°C and liquid at 40°C, and liquid epoxy resin refers to an epoxy resin that is liquid at 20°C. The liquid state is determined in accordance with the "Method of Confirming Liquid State" in Appendix 2 of the Ministerial Ordinance on the Testing and Properties of Hazardous Materials (Ministry of Home Affairs Ordinance No. 1 of 1989). For example, the method described in paragraphs 23 to 25 of JP 2016-079384 A is used.

Examples of solid epoxy resins include naphthalene-type epoxy resins such as EPICLON HP-4700 (naphthalene-type epoxy resin) manufactured by DIC, NC-7000L (naphthalene-skeleton-containing multifunctional solid epoxy resin) manufactured by Nippon Kayaku, and ESN-475V manufactured by Nippon Steel Chemical &Material; epoxidized products of condensation products of phenols and aromatic aldehydes having phenolic hydroxyl groups (trisphenol-type epoxy resins) such as EPPN-502H (trisphenol epoxy resin) manufactured by Nippon Kayaku; dicyclopentadiene aralkyl-type epoxy resins such as EPICLON HP-7200H (dicyclopentadiene-skeleton-containing multifunctional solid epoxy resin) manufactured by DIC; biphenyl aralkyl-type epoxy resins such as NC-3000H and NC-3000L (biphenyl-skeleton-containing multifunctional solid epoxy resin) manufactured by Nippon Kayaku; EPICLON N660 and EPICLON Examples of suitable epoxy resins include novolac epoxy resins such as N690 and EOCN-104S manufactured by Nippon Kayaku Co., Ltd.; biphenyl epoxy resins such as YX-4000 manufactured by Mitsubishi Chemical Corporation; and phosphorus-containing epoxy resins such as TX0712 manufactured by Nippon Steel Chemical & Material Co., Ltd. By including a solid epoxy resin, the glass transition temperature of the cured product becomes higher and the heat resistance becomes excellent. Among solid epoxy resins, epoxy resins having a skeleton in which aromatic compounds and phenols or naphthols are linked by methylene chains, such as ESN-475V and NC3000H, are preferred, since they can produce cured products with higher Tg and lower dielectric tangent.

Examples of semi-solid epoxy resins include bisphenol A type epoxy resins such as EPICLON 860, EPICLON 900-IM, EPICLON EXA-4816, and EPICLON EXA-4822 manufactured by DIC Corporation, Epotohto YD-134 manufactured by Nippon Steel Chemical & Material Co., Ltd., and jER834 and jER872 manufactured by Mitsubishi Chemical Corporation; naphthalene type epoxy resins such as EPICLON HP-4032 manufactured by DIC Corporation; phenol novolac type epoxy resins such as EPICLON N-740 manufactured by DIC Corporation; and nitrogen-containing epoxy resins such as jER604 manufactured by Mitsubishi Chemical Corporation. By including a semi-solid epoxy resin, the glass transition temperature (Tg) of the cured product becomes high, the coefficient of linear thermal expansion (CTE) becomes low, and the crack resistance becomes excellent. In addition, the inclusion of semi-solid epoxy resin gives the dry film excellent storage stability and prevents cracking and peeling.

Examples of liquid epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenol novolac type epoxy resins, alicyclic epoxy resins, and heterocyclic epoxy resins containing heteroatoms other than nitrogen. By including liquid epoxy resins, the flexibility of the dry film can be improved.

As described above, the epoxy resin (A) may be used alone or in combination of two or more kinds. From the viewpoint of imparting a low dielectric tangent to the cured product of the curable resin composition, the amount of the epoxy resin (A) is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less, when the solid content in the resin composition is taken as 100% by mass. Also, from the viewpoint of the strength of the cured product, the lower limit is preferably 1% by mass or more, and more preferably 3% by mass or more.

The curable resin composition of the present invention may contain a thermosetting resin other than an epoxy resin, as long as the effect of the present invention is not impaired. For example, known and commonly used thermosetting resins such as isocyanate compounds, blocked isocyanate compounds, amino resins, benzoxazine resins, carbodiimide resins, cyclocarbonate compounds, polyfunctional oxetane compounds, episulfide resins, and maleimide resins can be used.

[(B) Compound having an active ester group]
The curable resin composition of the present invention contains (B) a compound having an active ester group as a curing agent for component A.
(B) The compound having an active ester group is a compound having one or more, preferably two or more, active ester groups in one molecule. The compound having an active ester group can generally be obtained by a condensation reaction between a carboxylic acid compound and a hydroxy compound. Among them, a compound having an active ester group obtained by using a phenol compound or a naphthol compound as the hydroxy compound is preferable. Examples of the phenol compound or naphthol compound include hydroquinone, resorcin, bisphenol A, bisphenol F, bisphenol S, phenolphthaline, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, benzenetriol, dicyclopentadienyldiphenol, and phenol novolak. The (B) compound having an active ester group may be a naphthalenediol alkyl/benzoic acid type. The (B) compound having an active ester group may be used alone or in combination of two or more. The (B) compound having an active ester group is preferably one having a benzene, α-naphthol, β-naphthol, or dicyclopentadiene skeleton.

Among the compounds having an active ester group (B), the following compounds having an active ester group (B1) and (B2) can be preferably used.

The compound having an active ester group (B1) has a structure obtained by reacting (b1) a phenolic resin having a molecular structure in which phenols are bonded via an aliphatic cyclic hydrocarbon group, (b2) an aromatic dicarboxylic acid or its halide, and (b3) an aromatic monohydroxy compound. It is preferable that the compound has a structure obtained by reacting in a ratio of 0.05 to 0.75 moles of phenolic hydroxyl groups in the phenolic resin (b1) and 0.25 to 0.95 moles of aromatic monohydroxy compound (b3) per mole of carboxyl groups or acid halide groups in the aromatic dicarboxylic acid (b2) or its halide.

Here, in the (b1) phenolic resin, the molecular structure in which phenols are bonded via an aliphatic cyclic hydrocarbon group includes a structure obtained by polyaddition reaction of an unsaturated aliphatic cyclic hydrocarbon compound containing two double bonds in one molecule with a phenol. Here, examples of the phenol include unsubstituted phenol and substituted phenols in which one or more alkyl groups, alkenyl groups, allyl groups, aryl groups, aralkyl groups, or halogen groups are substituted. Specific examples of the substituted phenol include cresol, xylenol, ethylphenol, isopropylphenol, butylphenol, octylphenol, nonylphenol, vinylphenol, isopropenylphenol, allylphenol, phenylphenol, benzylphenol, chlorophenol, bromophenol, naphthol, and dihydroxynaphthalene, but are not limited to these. Mixtures of these may also be used. Among these, unsubstituted phenol is particularly preferred because of its excellent fluidity and curability.

Specific examples of unsaturated alicyclic hydrocarbon compounds include dicyclopentadiene, tetrahydroindene, 4-vinylcyclohexene, 5-vinylnorbon-2-ene, α-pinene, β-pinene, and limonene. Among these, dicyclopentadiene is preferred in terms of balance of properties, particularly heat resistance and hygroscopicity. Since dicyclopentadiene is contained in petroleum fractions, industrial dicyclopentadiene may contain other aliphatic or aromatic dienes as impurities. However, when considering heat resistance, curability, moldability, and the like, it is desirable for the product to have a dicyclopentadiene purity of 90% by mass or more.

Next, the (b2) aromatic dicarboxylic acid or its halide may be an aromatic dicarboxylic acid such as isophthalic acid, terephthalic acid, 1,4-, 2,3-, or 2,6-naphthalenedicarboxylic acid, or an acid halide such as an acid fluoride, acid chloride, acid bromide, or acid iodide thereof. Among these, acid chlorides of aromatic dicarboxylic acids are preferred because of their particularly good reactivity, and among these, isophthalic acid dichloride and terephthalic acid dichloride are particularly preferred, with isophthalic acid dichloride being particularly preferred.

Next, examples of (b3) aromatic monohydroxy compounds include phenol; alkylphenols such as o-cresol, m-cresol, p-cresol, and 3,5-xylenol; aralkylphenols such as o-phenylphenol, p-phenylphenol, 2-benzylphenol, 4-benzylphenol, and 4-(α-cumyl)phenol; and naphthols such as α-naphthol and β-naphthol. Among these, α-naphthol and β-naphthol are preferred because they lower the dielectric tangent of the cured product.

（式中、Ｘ_１はベンゼン環またはナフタレン環を有する基であり、ｋは０または１を表し、ｎは繰り返し単位の平均値で０．０５～２．５である。）
で表される構造のものがとりわけ硬化物の誘電正接が低く、かつ、有機溶剤に溶解させた際の溶液粘度が低くなる点から好ましい。前記ベンゼン環またはナフタレン環を有する基は、特に限定されず、フェニル基、ナフチル基等でもよく、また、他の原子を介してベンゼン環またはナフタレン環が分子末端に結合していてもよく、置換基を有していてもよい。また、（Ｂ１）活性エステル化合物は、その分子末端にナフタレン環を有するものであることが好ましい。 The active ester compound (B1) has a structure obtained by reacting (b1) a phenol resin, (b2) an aromatic dicarboxylic acid or its halide, and (b3) an aromatic monohydroxy compound. In particular, the active ester compound has a structure represented by the following general formula (1):

(In the formula, _X1 is a group having a benzene ring or a naphthalene ring, k is 0 or 1, and n is the average value of the repeating units and is 0.05 to 2.5.)
The structure represented by the formula (1) is particularly preferred because it provides a low dielectric tangent of the cured product and a low solution viscosity when dissolved in an organic solvent. The group having a benzene ring or a naphthalene ring is not particularly limited and may be a phenyl group, a naphthyl group, or the like, and the benzene ring or the naphthalene ring may be bonded to the molecular end via another atom, or may have a substituent. In addition, it is preferred that the active ester compound (B1) has a naphthalene ring at its molecular end.

In particular, in the above general formula (1), the value of n, i.e., the average value of the repeating units, is in the range of 0.25 to 1.5, which is preferable because it has a low solution viscosity and is easy to manufacture into a dry film for build-up. Also, in the above general formula (1), it is preferable that the value of k is 0 from the viewpoints of high heat resistance and low dielectric tangent.

Here, n in the above general formula (1) can be determined as follows.
[How to determine n in general formula (1)]
By GPC measurement performed under the following conditions, the ratios (β1/α1, β2/α2, β3/α3, β4/α4) of the styrene-equivalent molecular weights (α1, α2, α3, α4) corresponding to n=1, n=2, n=3, and n=4, respectively, to the theoretical molecular weights (β1, β2, β3, β4) corresponding to n=1, n=2, n=3, and n=4, respectively, are determined, and the average value of these (β1/α1 to β4/α4) is determined. The number average molecular weight (Mn) determined by GPC is multiplied by this average value to obtain the average molecular weight. Next, the value of n is calculated by taking the molecular weight of the general formula (1) as the average molecular weight.

(GPC measurement conditions)
Measurement equipment: Tosoh Corporation "HLC-8220 GPC"
Column: Tosoh Corporation guard column " _HXL -L"
+ Tosoh Corporation "TSK-GEL G2000HXL"
+ Tosoh Corporation "TSK-GEL G2000HXL"
+ Tosoh Corporation "TSK-GEL G3000HXL"
+ Tosoh Corporation "TSK-GEL G4000HXL"
Detector: RI (differential refractive index)
Data processing: Tosoh Corporation "GPC-8020 Model II Version 4.10"
Measurement conditions: Column temperature 40°C
Developing solvent: tetrahydrofuran Flow rate: 1.0 ml/min Standard: In accordance with the measurement manual for the aforementioned "GPC-8020 Model II Version 4.10," the following monodisperse polystyrene with known molecular weight was used.
(Polystyrene used)
Tosoh Corporation "A-500"
Tosoh Corporation "A-1000"
Tosoh Corporation "A-2500"
Tosoh Corporation "A-5000"
Tosoh "F-1"
Tosoh Corporation "F-2"
Tosoh "F-4"
Tosoh Corporation "F-10"
Tosoh Corporation "F-20"
Tosoh Corporation "F-40"
Tosoh Corporation "F-80"
Tosoh Corporation "F-128"
Sample: A 1.0% by mass tetrahydrofuran solution calculated as resin solid content was filtered through a microfilter (50 μl).

Specifically, the method of reacting (b1) a phenol resin, (b2) an aromatic dicarboxylic acid or its halide, and (b3) an aromatic monohydroxy compound can be such that each of these components is reacted in the presence of an alkali catalyst.
Examples of the alkali catalyst that can be used here include sodium hydroxide, potassium hydroxide, triethylamine, pyridine, etc. Among these, sodium hydroxide and potassium hydroxide are particularly preferred because they can be used in the form of an aqueous solution and provide good productivity.

Specific examples of the reaction include a method in which (b1) phenol resin, (b2) aromatic dicarboxylic acid or its halide, and (b3) aromatic monohydroxy compound are mixed in the presence of an organic solvent, and the reaction is carried out while the alkaline catalyst or its aqueous solution is continuously or intermittently added dropwise. In this case, the concentration of the aqueous alkaline catalyst solution is preferably in the range of 3.0 to 30%. Examples of organic solvents that can be used here include toluene and dichloromethane.

After the reaction is complete, if an aqueous solution of an alkaline catalyst is used, the reaction liquid is allowed to stand and separated, the aqueous layer is removed, and the remaining organic layer is washed until the aqueous layer is nearly neutral, and the desired resin can be obtained.

The compound having an active ester group (B1) thus obtained is usually obtained as a solution in an organic solvent, so when it is used as a varnish for laminates or a dry film for build-up, it can be mixed with other ingredients as is, and the amount of organic solvent can be adjusted appropriately to produce the desired curable resin composition. The active ester compound (B1) is characterized by its low melt viscosity when dissolved in an organic solvent to form a resin solution; specifically, the solution viscosity of the compound having an active ester group in a toluene solution with a solid content of 65% is 300 to 10,000 mPa·s (25°C).

で表される構造部位を有し且つその両末端が一価のアリールオキシ基である構造を有するものである。 The compound having an active ester group of (B2) is represented by the following general formula (2):

and both ends of which are monovalent aryloxy groups.

で表される基または下記式（４）：

で表される基であり、ｍは１～６の整数であり、ｎはそれぞれ独立的に１～５の整数であり、ｑはそれぞれ独立的に０～６の整数であり、式（３）中、ｋはそれぞれ独立的に１～５の整数であり、式（４）中、Ｙは上記式（３）で表される基（ｋはそれぞれ独立的に１～５の整数）であり、ｔはそれぞれ独立的に０～５の整数である） (In formula (2), _X2 each independently represents the following formula (3):

or a group represented by the following formula (4):

wherein m is an integer of 1 to 6, n is each independently an integer of 1 to 5, and q is each independently an integer of 0 to 6; in formula (3), k is each independently an integer of 1 to 5; in formula (4), Y is a group represented by formula (3) above (wherein k is each independently an integer of 1 to 5), and t is each independently an integer of 0 to 5).

で表される部分構造が、水酸基当量が１７０～２００グラム／当量の変性ナフタレン化合物の由来構造であることが好ましい。 The compound (B2) having an active ester group is represented by the general formula (2)

is preferably a structure derived from a modified naphthalene compound having a hydroxyl group equivalent of 170 to 200 g/equivalent.

In order to clarify the relationship between m and n in formula (2), several patterns are shown as examples below, but the compound having an active ester group (B2) is not limited to these.
For example, when m=1, formula (2) represents a structure of formula (2-I) below.

In formula (2-I), n is an integer from 1 to 5, and when n is 2 or more, each q is independently an integer from 0 to 6.

For example, when m = 2, formula (2) represents the structure of formula (2-II) below.

In formula (2-II), n is independently an integer from 1 to 5, and when n is 2 or more, q is independently an integer from 0 to 6.

The compound having an active ester group (B2) has a naphthylene ether structural portion in the molecular backbone, and therefore can impart superior heat resistance and flame retardancy to the cured product. At the same time, since the structural portion is bonded to the structural portion represented by the following formula (5), the cured product can also have superior dielectric properties. In addition, by having aryloxy groups at both ends of the structure of the compound having an active ester group (B2), the thermal decomposition resistance of the cured product can be improved to a sufficient degree even in multilayer printed circuit board applications.

The compound having an active ester group (B2) preferably has a softening point in the range of 100 to 200°C, particularly 100 to 190°C, in order to provide a cured product with excellent heat resistance.

In the compound having an active ester group (B2), m in formula (2) is an integer of 1 to 6. Of these, m is preferably an integer of 1 to 5. Furthermore, n in formula (2) is each independently an integer of 1 to 5. Of these, n is preferably an integer of 1 to 3.
In formula (2), the relationship between m and n is described for confirmation. For example, when m is an integer of 2 or more, n is 2 or more, but in that case, each n is an independent value. That is, as long as it is within the numerical range of n, it may be the same value or different values.

In the compound having an active ester group of (B2), when q in formula (2) is 1 or more, _X2 may be substituted at any position in the naphthalene ring structure.

The aryloxy groups at both ends of the structure may be derived from monohydric phenolic compounds such as phenol, cresol, p-t-butylphenol (para-tertiary butylphenol), 1-naphthol, and 2-naphthol. Among these, from the viewpoint of thermal decomposition resistance of the cured product, a phenoxy group, a tolyloxy group, or a 1-naphthyloxy group is preferred, and a 1-naphthyloxy group is even more preferred.

The method for producing the compound having an active ester group (B2) will be described in detail below.
The method for producing the compound having an active ester group (B2) comprises a step of reacting a dihydroxynaphthalene compound with benzyl alcohol in the presence of an acid catalyst to obtain a benzyl-modified naphthalene compound (hereinafter, this step may be abbreviated as "step 1"), and then a step of reacting the obtained benzyl-modified naphthalene compound with an aromatic dicarboxylic acid chloride and a monohydric phenol compound (hereinafter, this step may be abbreviated as "step 2").

That is, in step 1, the dihydroxynaphthalene compound is reacted with benzyl alcohol in the presence of an acid catalyst to obtain a benzyl-modified naphthalene compound having a naphthylene structure as the main skeleton, phenolic hydroxyl groups at both ends of the main skeleton, and a benzyl group pendantly bonded to the aromatic nucleus of the naphthylene structure. It is worth noting that, in general, when a dihydroxynaphthalene compound is converted into naphthylene ether under an acid catalyst, it is extremely difficult to control the molecular weight, resulting in a high molecular weight product, whereas the above-mentioned production method, by using benzyl alcohol in combination, can suppress such high molecular weight and obtain a resin suitable for electronic material applications.

Furthermore, by adjusting the amount of benzyl alcohol used, it is possible to adjust the content of benzyl groups in the benzyl-modified naphthalene compound, and also to adjust the melt viscosity of the benzyl-modified naphthalene compound itself. That is, the reaction ratio of the dihydroxynaphthalene compound and benzyl alcohol can usually be selected from a range in which the reaction ratio of the dihydroxynaphthalene compound and benzyl alcohol (dihydroxynaphthalene compound)/(benzyl alcohol) is 1/0.1 to 1/10 on a molar basis, but from the perspective of the balance between heat resistance, flame retardancy, dielectric properties, and thermal decomposition resistance, it is preferable that the reaction ratio of the dihydroxynaphthalene compound and benzyl alcohol (dihydroxynaphthalene compound)/(benzyl alcohol) is 1/0.5 to 1/4.0 on a molar basis.

Examples of dihydroxynaphthalene compounds that can be used here include 1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, and 2,7-dihydroxynaphthalene. Among these, 1,6-dihydroxynaphthalene or 2,7-dihydroxynaphthalene is preferred, and 2,7-dihydroxynaphthalene is more preferred, since the flame retardancy of the cured product of the resulting benzyl-modified naphthalene compound is further improved, and the dielectric tangent of the cured product is also lowered, resulting in improved dielectric properties.

Examples of acid catalysts that can be used in the reaction of the dihydroxynaphthalene compound with benzyl alcohol in step 1 include inorganic acids such as phosphoric acid, sulfuric acid, and hydrochloric acid; organic acids such as oxalic acid, benzenesulfonic acid, toluenesulfonic acid, methanesulfonic acid, and fluoromethanesulfonic acid; and Friedel-Crafts catalysts such as aluminum chloride, zinc chloride, stannous chloride, ferric chloride, and diethyl sulfate.

The amount of the acid catalyst used can be appropriately selected depending on the target modification rate, etc. For example, in the case of inorganic acids or organic acids, the amount is in the range of 0.001 to 5.0 parts by mass, preferably 0.01 to 3.0 parts by mass, per 100 parts by mass of the dihydroxynaphthalene compound, and in the case of Friedel-Crafts catalysts, the amount is in the range of 0.2 to 3.0 moles, preferably 0.5 to 2.0 moles, per 1 mole of the dihydroxynaphthalene compound.

The reaction of the dihydroxynaphthalene compound with benzyl alcohol in step 1 can be carried out without a solvent, or in the presence of a solvent to increase the homogeneity of the reaction system. Examples of such solvents include mono- or di-ethers of ethylene glycol and diethylene glycol, such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, and diethylene glycol monobutyl ether; non-polar aromatic solvents such as benzene, toluene, and xylene; aprotic polar solvents such as dimethylformamide and dimethylsulfoxide; and chlorobenzene.

The specific method for carrying out the reaction in step 1 is to dissolve the dihydroxynaphthalene compound, benzyl alcohol and the acid catalyst in the absence of a solvent or in the presence of the solvent, and carry out the reaction under temperature conditions of 60 to 180°C, preferably 80 to 160°C. The reaction time is not particularly limited, but is preferably 1 to 10 hours. Thus, the reaction can be carried out by maintaining the temperature for 1 to 10 hours. In addition, it is preferable to distill off the water produced during the reaction from the system using a fractionating tube or the like, since this allows the reaction to proceed quickly and improves productivity.

If the resulting benzyl-modified naphthalene compound is significantly colored, an antioxidant or reducing agent may be added to the reaction system to suppress coloration. Examples of antioxidants include hindered phenol compounds such as 2,6-dialkylphenol derivatives, divalent sulfur compounds, and phosphite ester compounds containing a trivalent phosphorus atom. Examples of reducing agents include hypophosphorous acid, phosphorous acid, thiosulfuric acid, sulfurous acid, hydrosulfite, or salts of these.

After the reaction is complete, the acid catalyst is removed by neutralization, water washing, or decomposition, and the desired resin having phenolic hydroxyl groups can be separated by common procedures such as extraction and distillation. The neutralization and water washing can be carried out according to conventional methods, and basic substances such as sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia, triethylenetetramine, and aniline can be used as neutralizing agents.

Specific examples of the aromatic dicarboxylic acid chloride include acid chlorides of phthalic acid, isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid. Among these, isophthalic acid chloride and terephthalic acid chloride are preferred from the viewpoint of the balance between solvent solubility and heat resistance.

Specific examples of the monohydric phenol compound include phenol, cresol, p-t-butylphenol, 1-naphthol, and 2-naphthol. Among them, phenol, cresol, and 1-naphthol are preferred because of their good reactivity with carboxylic acid chloride, and 1-naphthol is even more preferred because of its good thermal decomposition resistance.

Here, the method for reacting the benzyl-modified naphthalene compound, aromatic dicarboxylic acid chloride, and monohydric phenol compound can specifically involve reacting each of these components in the presence of an alkali catalyst.

Examples of alkali catalysts that can be used here include sodium hydroxide, potassium hydroxide, triethylamine, pyridine, etc. Among these, sodium hydroxide and potassium hydroxide are particularly preferred because they can be used in the form of an aqueous solution and provide good productivity.

Specifically, the reaction can be carried out by mixing the above-mentioned components in the presence of an organic solvent and continuously or intermittently dropping in the alkaline catalyst or its aqueous solution. In this case, the concentration of the aqueous alkaline catalyst solution is preferably in the range of 3.0 to 30% by mass. Examples of organic solvents that can be used here include toluene, dichloromethane, and chloroform.

After the reaction is complete, if an aqueous solution of an alkaline catalyst is used, the reaction liquid is allowed to stand and separated, the aqueous layer is removed, and the remaining organic layer is washed until the aqueous layer is nearly neutral, and the desired resin can be obtained.

The compound having an active ester group (B2) obtained in this manner preferably has a softening point of 100 to 200°C, since this increases its solubility in organic solvents.

The amount of the compound having an active ester group (B) is preferably 50% by mass or less, more preferably 40% by mass or less, and particularly preferably 30% by mass or less, in terms of the strength of the cured product, when the solid content in the resin composition is 100% by mass. In addition, the lower limit is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, in order to obtain a cured product with a lower dielectric loss tangent.
Conventionally, it was thought that the heat resistance would deteriorate if a large amount of a compound having an active ester group was blended as a curing agent, but unexpectedly, it is possible to obtain a cured product with a high glass transition temperature (Tg), low dielectric tangent, and low linear thermal expansion coefficient. Although the detailed mechanism is not clear, it is considered that by increasing the ratio of a compound having an active ester group, preferably a compound having an active ester group having the structure of the above general formula (1) or (2), the volume ratio of the active ester structure, i.e., an aromatic ester structure that is rigid and has high molecular orientation, increases, thereby controlling the movement of the chain portion between the crosslinking points, thereby improving the glass transition temperature.

In order to obtain a cured product having both high heat resistance and low dielectric tangent from the curable resin composition of the present invention, the ratio of the total amount of epoxy groups in the epoxy resin (A) to the total amount of ester groups in the compound having an active ester group (B) is preferably 0.2 to 0.9, more preferably 0.2 to 0.8, even more preferably 0.2 to 0.6, and particularly preferably 0.2 to 0.4.
The total amount of epoxy groups mentioned above can be determined by dividing the amount of the epoxy resin (A) contained in the composition by the epoxy equivalent of the epoxy resin (A). The total amount of active ester groups of the compound having an active ester group (B) can be determined by dividing the amount of the compound having an active ester group (B) contained in the composition by the active ester equivalent of the compound having an active ester group (B).
Incidentally, each of component A and component B may contain a plurality of types of compounds as described below. In such a case, the amount of each compound is divided by the epoxy equivalent or active ester equivalent to determine the total amount of epoxy groups or the total amount of ester groups.
The curable resin composition of the present invention may contain a curing agent other than the compound having an active ester group (B) within a range that does not impair the effects of the present invention. Examples of the curing agent include a compound having a phenolic hydroxyl group, a polycarboxylic acid and an acid anhydride thereof, a compound having a cyanate ester group, and an alicyclic olefin polymer.

[(C) Inorganic filler]
The curable resin composition of the present invention contains an inorganic filler (C). By containing an inorganic filler (C), the curing shrinkage of the obtained cured product is suppressed, the CTE becomes lower, and the thermal properties such as adhesion, hardness, and crack resistance can be improved by matching the thermal strength with a conductor layer such as copper around the insulating layer. As the inorganic filler (C), a conventionally known inorganic filler can be used, and is not limited to a specific one. For example, extender pigments such as barium sulfate, barium titanate, amorphous silica, crystalline silica, fused silica, and spherical silica, talc, clay, Neuburg silica particles, boehmite, magnesium carbonate, calcium carbonate, titanium oxide, aluminum oxide, aluminum hydroxide, silicon nitride, aluminum nitride, and calcium zirconate, and metal powders such as copper, tin, zinc, nickel, silver, palladium, aluminum, iron, cobalt, gold, and platinum can be mentioned. The inorganic filler (C) is preferably a spherical particle. Among them, silica is preferred, since it suppresses the cure shrinkage of the cured product of the curable resin composition, lowers the CTE, and improves properties such as adhesion and hardness. The average particle size (median size, D50) of the (C) inorganic filler is preferably 0.01 to 10 μm. As the (C) inorganic filler, silica having an average particle size of 0.01 to 3 μm is preferred. In this specification, the average particle size of the (C) inorganic filler is the average particle size including not only the particle size of the primary particles but also the particle size of the secondary particles (aggregates). The average particle size can be determined by a laser diffraction type particle size distribution measuring device. An example of a measuring device using the laser diffraction method is Microtrack MT3000II manufactured by Microtrack Bell.

The inorganic filler (C) is preferably a surface-treated inorganic filler. The surface treatment may be a surface treatment using a coupling agent or a surface treatment that does not introduce an organic group, such as an alumina treatment. The method for treating the surface of the inorganic filler (C) is not particularly limited, and any known, commonly used method may be used, and the surface of the inorganic filler (C) may be treated with a surface treatment agent having a curable reactive group, such as a coupling agent having a curable reactive group.

(C) The surface treatment of the inorganic filler is preferably a surface treatment with a coupling agent. As the coupling agent, silane-based, titanate-based, aluminate-based, zircoaluminate-based, and other coupling agents can be used. Among them, silane-based coupling agents are preferred. Examples of such silane-based coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, N-(2-aminomethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-anilinopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane, which can be used alone or in combination. It is preferable that these silane coupling agents are immobilized in advance on the surface of the inorganic filler by adsorption or reaction. Here, the amount of coupling agent to be treated per 100 parts by mass of inorganic filler is, for example, 0.1 to 10 parts by mass, preferably 0.5 to 10 parts by mass.

The curable reactive group is preferably a thermosetting reactive group. Examples of the thermosetting reactive group include a hydroxyl group, a carboxyl group, an isocyanate group, an amino group, an imino group, an epoxy group, an oxetanyl group, a mercapto group, a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, an ethoxyethyl group, and an oxazoline group. Among these, at least one of an amino group and an epoxy group is preferable. The surface-treated inorganic filler may have a photocurable reactive group in addition to the thermosetting reactive group.

The surface-treated inorganic filler may be contained in the resin layer from the curable resin composition in a surface-treated state. The inorganic filler and the surface treatment agent may be separately blended into the curable resin composition forming the resin layer to surface-treat the inorganic filler in the composition, but it is preferable to blend an inorganic filler that has been surface-treated in advance. By blending an inorganic filler that has been surface-treated in advance, it is possible to prevent a decrease in crack resistance, etc. due to the surface treatment agent that was not consumed in the surface treatment, which may remain when blended separately. When performing surface treatment in advance, it is preferable to blend a pre-dispersion in which the inorganic filler is pre-dispersed in a solvent or curable resin. It is more preferable to pre-disperse the surface-treated inorganic filler in a solvent and blend the pre-dispersion into the composition, or to pre-disperse the surface-untreated inorganic filler in a solvent, perform sufficient surface treatment, and then blend the pre-dispersion into the composition.

(C) The inorganic filler may be mixed with the epoxy resin etc. in a powder or solid state, or may be mixed with a solvent or dispersant to form a slurry and then mixed with the epoxy resin etc.

(C) The inorganic filler may be used alone or in a mixture of two or more kinds. The amount of (C) inorganic filler is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 65% by mass or more, from the viewpoint of low CTE, assuming that the solid content in the resin composition is 100% by mass. Also, from the viewpoint of toughness of the cured film, it is preferably 90% by mass or less, more preferably 80% by mass or less, and particularly preferably 75% by mass or less.

[(D) Polyester Additives]
The curable resin composition of the present invention further contains (D) a polyester additive in addition to the above-mentioned components A to C. The polyester additive (D) is a polymer having a polyalkylene glycol structure and an aliphatic polyester structure. By using such a polyester-based additive having a specific structure in combination with components A to C, it is possible to obtain a cured product having high heat resistance, low dielectric constant, low dielectric loss tangent, and excellent adhesion to conductive metals.

Specific examples of the polyester additive (D) include copolymers including a diblock copolymer of formula (D-1) or a triblock copolymer of formula (D-2).
Xn-Ym (D-1)
Ym1-Xn-Ym2 (D-2)
In formula (D-1), n:m is in the range of 35 to 55:65 to 45, preferably 40 to 50:60 to 50,
In formula (D-2), n:m1+m2 is in the range of 35-55:65-45, preferably 40-50:60-50.
Further, in the formulas (D-1) and (D-2),
X is a unit derived from polyalkylene glycol (represented by the general formula HO-(RO) _p -H, where R is an alkylene having 1 to 6 carbon atoms, preferably 2 to 5 carbon atoms, and p is, for example, 2 to 1000, preferably 2 to 200);
Y is a unit derived from an aliphatic polyester (represented by the general formula -(OR' _q CO)r-, where R' is methylene, q is, for example, 2 to 8, preferably 5 to 7, and r is, for example, 2 to 100, preferably 2 to 50), particularly polycaprolactone ((CH ₂ ) ₅ CO ₂ )r'(r' is, for example, 2 to 40). Excellent adhesion can be obtained when derived from polycaprolactone.
A curable resin composition containing the compound of the above formula (D-1) or (D-2) as the component D has particularly improved adhesion to conductive metals.

The compound represented by formula (D-1) or (D-2) can be produced by a conventional method for producing a block copolymer. For example, a polyalkylene glycol is synthesized by condensation polymerization of an alkylene oxide and water or anionic ring-opening polymerization of an alkylene oxide, and then a compound represented by formula (D-1) or (D-2) can be produced by ring-opening polymerization of caprolactone to the hydroxyl group of the polyalkylene glycol.

In addition, as the polyester additive (D), a compound containing a block copolymer represented by the above formula (D-1) or (D-2), or both, as part of the molecule can also be used.

(D) As the polyester additive, regardless of its specific structure, for example, a compound having a mass average molecular weight Mw (measured by GPC using a styrene standard) of 5,000 to 15,000, preferably 7,000 to 12,000, and more preferably 8,000 to 1,000 is used.

Furthermore, (D) polyester additive usually has a hydroxyl value of 8 to 17 mgKOH/g, preferably 10 to 15 KOH/g, is solid at room temperature (25°C), for example has a melting point of 40°C to 70°C, and has a viscosity at 75°C of usually 3,000 to 10,000 mPa·s, preferably 3,500 to 9,000 mPa·s, which greatly contributes to performance such as adhesion to conductor metals.

A composition containing components A, B and C can provide a cured product with a high glass transition temperature and a low dielectric tangent. However, even if component D is further added, a cured product with a high glass transition temperature and a low dielectric tangent can be obtained, which has increased adhesion to conductive metals and a low dielectric constant.
The polyester additive (D) may be used alone or in a mixture of two or more kinds. The amount of the polyester additive (D) is preferably 2% by mass or more, more preferably 2.5% by mass or more, from the viewpoint of adhesion, when the total mass of the solid content of the epoxy resin (A) and the compound having an active ester group (B) is taken as 100% by mass. In addition, from the viewpoint of low dielectric constant and low dielectric loss tangent of the cured film, it is preferably 25% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less.

[Thermoplastic resin]
The curable resin composition of the present invention may further contain a thermoplastic resin in order to improve the mechanical strength of the resulting cured film. The thermoplastic resin is preferably soluble in a solvent. When the thermoplastic resin is soluble in a solvent, it improves flexibility when made into a dry film, and can suppress the occurrence of cracks and powder fall. Examples of the thermoplastic resin include thermoplastic polyhydroxypolyether resins, phenoxy resins which are condensates of epichlorohydrin and various bifunctional phenolic compounds, or phenoxy resins in which the hydroxyl group of the hydroxyether moiety present in the skeleton is esterified using various acid anhydrides or acid chlorides, polyvinyl acetal resins, polyamide resins, polyamideimide resins, and the like. The thermoplastic resins may be used alone or in combination of two or more. Among these thermoplastic resins, phenoxy resins are preferred because they can improve the glass transition temperature while maintaining a low dielectric tangent.

Polyvinyl acetal resin can be obtained, for example, by acetalizing polyvinyl alcohol resin with an aldehyde. The aldehyde used is not particularly limited, and examples include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, amylaldehyde, hexylaldehyde, heptylaldehyde, 2-ethylhexylaldehyde, cyclohexylaldehyde, furfural, benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, and β-phenylpropionaldehyde, with butyraldehyde being preferred.

Specific examples of phenoxy resins include FX280S and FX293 manufactured by Nippon Steel Chemical & Material Co., Ltd., jER (registered trademark) YX8100BH30, jER (registered trademark) YX6954BH30, YL6954, YL6974, and jER (registered trademark) YX7200B35 manufactured by Mitsubishi Chemical Corporation. Specific examples of polyvinyl acetal resins include the S-LEC KS series manufactured by Sekisui Chemical Co., Ltd., polyamide resins include the KS5000 series manufactured by Hitachi Chemical Co., Ltd., and the BP series manufactured by Nippon Kayaku Co., Ltd., and polyamide-imide resins include the KS9000 series manufactured by Hitachi Chemical Co., Ltd.

The amount of the thermoplastic resin is preferably 0.1% by mass or more, and more preferably 0.3% by mass or more, from the viewpoint of the mechanical strength of the resulting cured film, when the total of (A) the epoxy resin and (B) the compound having an active ester group in the resin composition is taken as 100% by mass. Also, from the viewpoint of the dielectric properties of the cured film, the amount is preferably 20% by mass or less, and more preferably 15% by mass or less.

[Curing accelerator]
The curable resin composition of the present invention may contain a curing accelerator. The curing accelerator accelerates the thermosetting reaction and is used to further improve properties such as adhesion, chemical resistance, and heat resistance.

In the present invention, the curing accelerator can be used mainly to accelerate the reaction of (A) the epoxy resin and (B) the compound having an active ester group.

Specific examples of the curing accelerator for the curing reaction with (A) an epoxy resin and (B) a compound having an active ester group include imidazole and its derivatives; guanamines such as acetoguanamine and benzoguanamine; polyamines such as diaminodiphenylmethane, m-phenylenediamine, m-xylylenediamine, diaminodiphenylsulfone, dicyandiamide, urea, urea derivatives, melamine, and polybasic hydrazides; organic acid salts and/or epoxy adducts thereof; amine complexes of boron trifluoride; triazine derivatives such as ethyldiamino-S-triazine, 2,4-diamino-S-triazine, and 2,4-diamino-6-xylyl-S-triazine; amines such as trimethylamine, triethanolamine, N,N-dimethyloctylamine, N-benzyldimethylamine, pyridine, dimethylaminopyridine, N-methylmorpholine, hexa(N-methyl)melamine, 2,4,6-tris(dimethylaminophenol), tetramethylguanidine, and m-aminophenol; polyvinylphenol, poly Examples of the curing accelerator include polyphenols such as vinylphenol bromide, phenol novolac, and alkylphenol novolac; organic phosphines such as tributylphosphine, triphenylphosphine, and tris-2-cyanoethylphosphine; phosphonium salts such as tri-n-butyl(2,5-dihydroxyphenyl)phosphonium bromide and hexadecyltributylphosphonium chloride; quaternary ammonium salts such as benzyltrimethylammonium chloride and phenyltributylammonium chloride; the polybasic acid anhydrides; photocationic polymerization catalysts such as diphenyliodonium tetrafluoroborate, triphenylsulfonium hexafluoroantimonate, and 2,4,6-triphenylthiopyrylium hexafluorophosphate; styrene-maleic anhydride resin; equimolar reactants of phenylisocyanate and dimethylamine, equimolar reactants of organic polyisocyanates such as tolylene diisocyanate and isophorone diisocyanate and dimethylamine, and metal catalysts. Among the curing accelerators, imidazole and its derivatives, and dimethylaminopyridine are preferred.

The curing accelerator can be used alone or in combination of two or more. When the curing accelerator is blended in the curable resin composition of the present invention, the blending amount is preferably 5% by mass or less, and more preferably 3% by mass or less, from the viewpoint of storage stability of the resin composition before the thermal curing reaction, when the total amount of solids of components A and B is taken as 100% by mass, and is preferably 0.01% by mass or more, and more preferably 0.1% by mass or more, from the viewpoint of curability.

[Rubber particles]
The curable resin composition may contain rubber particles as necessary. Examples of such rubber particles include polybutadiene rubber, polyisopropylene rubber, urethane-modified polybutadiene rubber, epoxy-modified polybutadiene rubber, acrylonitrile-modified polybutadiene rubber, carboxyl-modified polybutadiene rubber, acrylonitrile-butadiene rubber modified with carboxyl or hydroxyl groups, and crosslinked rubber particles thereof, core-shell type rubber particles, etc., and one type may be used alone or two or more types may be used in combination. These rubber particles are added to improve the flexibility of the obtained cured film, improve crack resistance, enable surface roughening treatment with an oxidizing agent, and improve adhesion strength with copper foil, etc.

The average particle size of the rubber-like particles is preferably in the range of 0.005 to 1 μm, and more preferably in the range of 0.2 to 1 μm. The average particle size of the rubber-like particles in the present invention can be determined by a laser diffraction particle size distribution measuring device. For example, the rubber-like particles are uniformly dispersed in a suitable organic solvent by ultrasonic waves or the like, and a particle size distribution of the rubber-like particles is created on a mass basis using a Nanotrac wave manufactured by Microtrac Bell, and the median diameter is taken as the average particle size.

[Flame retardants]
The curable resin composition of the present invention may contain a flame retardant. Examples of the flame retardant include hydrated metals such as aluminum hydroxide and magnesium hydroxide, red phosphorus, ammonium phosphate, ammonium carbonate, zinc borate, zinc stannate, molybdenum compounds, bromine compounds, chlorine compounds, phosphoric acid esters, phosphorus-containing polyols, phosphorus-containing amines, melamine cyanurate, melamine compounds, triazine compounds, guanidine compounds, and silicon polymers. The flame retardants may be used alone or in combination of two or more.

[Organic solvent]
The organic solvent is not particularly limited, and examples thereof include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, petroleum-based solvents, etc. More specifically, ketones such as methyl ethyl ketone, cyclohexanone, methyl butyl ketone, and methyl isobutyl ketone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; glycol ethers such as cellosolve, methyl cellosolve, butyl cellosolve, carbitol, methyl carbitol, butyl carbitol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, and triethylene glycol monoethyl ether; ethyl acetate, butyl acetate, isobutyl acetate, ethyl Examples of the solvent include esters such as ethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, and propylene glycol butyl ether acetate; alcohols such as ethanol, propanol, 2-methoxypropanol, n-butanol, isobutyl alcohol, isopentyl alcohol, ethylene glycol, and propylene glycol; aliphatic hydrocarbons such as octane and decane; petroleum solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha, as well as N,N-dimethylformamide (DMF), tetrachloroethylene, and turpentine. In addition, organic solvents such as Swazol 1000 and Swazol 1500 manufactured by Maruzen Petrochemical Co., Ltd., Solvent #100 and Solvent #150 manufactured by Sankyo Chemical Co., Ltd., Shellsol A100 and Shellsol A150 manufactured by Shell Chemicals Japan Ltd., and Ipzol No. 100 and Ipzol No. 150 manufactured by Idemitsu Kosan Co., Ltd. may be used. The organic solvents may be used alone or in combination of two or more.

When made into a dry film, it is preferable that the amount of residual solvent in the resin layer is 0.1 to 10.0% by mass. If the residual solvent is 10.0% by mass or less, bumping during thermal curing is suppressed and the surface flatness is improved. In addition, it is possible to prevent the melt viscosity from dropping too low and causing the resin to flow, resulting in good flatness. If the residual solvent is 0.1% by mass or more, and particularly 0.5% or more, the flowability during lamination is good, and the flatness and embeddability are improved.

[Other ingredients]
The curable resin composition of the present invention may further contain, as necessary, organic fillers such as silicon powder, fluorine powder, and nylon powder; conventionally known colorants such as phthalocyanine blue, phthalocyanine green, iodine green, disazo yellow, crystal violet, titanium oxide, carbon black, and naphthalene black; conventionally known thickeners such as asbestos, orben, bentone, and finely powdered silica; silicone-based, fluorine-based, and polymer-based defoamers and/or leveling agents; adhesion imparting agents such as thiazole-based, triazole-based, and silane coupling agents; and conventionally known titanate-based and aluminum-based additives.

In this specification, solids refers to the components excluding organic solvents.

The curable resin composition of the present invention may be used in the form of a dry film or in liquid form. When used in liquid form, it may be one-component or two-component or more, but from the viewpoint of storage stability, it is preferable to use two-component or more.

<Dry film>
The dry film of the present invention can be produced by applying the curable resin composition of the present invention onto a carrier film and drying it to form a resin layer as a dried coating film.
If necessary, a protective film can be laminated on the resin layer.

The carrier film plays a role of supporting the resin layer of the dry film, and is a film onto which a curable resin composition is applied when forming the resin layer. Examples of the carrier film include polyester films such as polyethylene terephthalate and polyethylene naphthalate, films made of thermoplastic resins such as polyimide films, polyamideimide films, polyethylene films, polytetrafluoroethylene films, polypropylene films, and polystyrene films, and surface-treated paper. Among these, polyester films are preferably used from the viewpoints of heat resistance, mechanical strength, and ease of handling. The thickness of the carrier film is not particularly limited, but is appropriately selected from the range of approximately 10 to 150 μm depending on the application. The surface of the carrier film on which the resin layer is provided may be subjected to a release treatment. In addition, sputtering or copper foil may be formed on the surface of the carrier film on which the resin layer is provided.

The protective film is provided on the side of the resin layer opposite the carrier film in order to prevent dust and the like from adhering to the surface of the resin layer of the dry film and to improve handling. For example, the protective film may be a film made of a thermoplastic resin exemplified as the carrier film above, or surface-treated paper, among which polyester film, polyethylene film, and polypropylene film are preferred. The thickness of the protective film is not particularly limited, but is appropriately selected from the range of approximately 10 to 150 μm depending on the application. The surface of the protective film on which the resin layer is provided may be subjected to a release treatment.

<Copper foil with resin>
The resin-coated copper foil of the present invention has a resin layer obtained by applying the curable resin composition of the present invention to the copper foil surface of a copper foil or a copper foil with a carrier, and drying the composition.

[Copper foil with carrier]
The copper foil with a carrier may be formed by laminating a resin layer made of the curable resin composition of the present invention so as to be in contact with the copper foil in this order. It is preferable to use an ultra-thin copper foil as the copper foil.

Examples of the carrier foil include copper foil, aluminum foil, stainless steel (SUS) foil, and resin film with a metal-coated surface, with copper foil being preferred. The copper foil may be electrolytic copper foil or rolled copper foil. The thickness of the carrier foil is usually 250 μm or less, and preferably 9 to 200 μm. If necessary, a release layer may be formed between the carrier foil and the copper foil.

The method for forming the copper foil is not particularly limited, but it is preferable to use an ultra-thin copper foil, which can be formed by wet film formation methods such as electroless copper plating and electrolytic copper plating, dry film formation methods such as sputtering and chemical vapor deposition, or a combination of these. The thickness of the ultra-thin copper foil is preferably 0.1 to 7.0 μm, more preferably 0.5 to 5.0 μm, and even more preferably 1.0 to 3.0 μm.

<Cured Product>
The cured product of the present invention can be obtained by curing the curable resin composition of the present invention, the resin layer of the dry film of the present invention, or the resin layer of the resin-coated copper foil of the present invention.

The curing method is not particularly limited, and may be a conventionally known method, for example, curing by heating at 150 to 230°C. As a method for producing a printed wiring board using a curable resin composition, for example, in the case of a three-layered dry film in which a resin layer is sandwiched between a carrier film and a protective film, a printed wiring board can be produced by the following method. Either the carrier film or the protective film is peeled off from the dry film, and the dry film is heat-laminated to a circuit board on which a circuit pattern is formed, and then heat-cured. Heat curing may be performed in an oven or by hot plate pressing. When laminating or hot plate pressing the dry film of the present invention to the circuit board, copper foil or a circuit board can be laminated at the same time. A pattern or a via hole is formed by laser irradiation or a drill at a position corresponding to a predetermined position on the circuit board, and the circuit wiring is exposed, thereby producing a printed wiring board. At this time, if there is a component (smear) that has not been completely removed and remains on the circuit wiring in the pattern or via hole, a desmear treatment is performed. The remaining carrier film or protective film can be peeled off after lamination, heat curing, laser processing, or desmearing.

When a printed wiring board is manufactured using the resin-coated copper foil of the present invention, a resin layer may be laminated on a circuit board, and a circuit may be formed by a modified semi-additive process (MSAP) method using the copper foil as all or part of the wiring layer to manufacture a build-up wiring board. A build-up wiring board may also be manufactured in which the copper foil is removed and a circuit is formed by a semi-additive process (SAP) method. A printed wiring board may also be manufactured by direct build-up on a wafer, in which lamination of resin-coated copper foil and circuit formation are alternately repeated on a semiconductor integrated circuit. A coreless build-up method may also be used in which resin layers and conductor layers are alternately laminated without using a core substrate.

<Electronic Components>
The electronic device of the present invention has the cured product of the present invention, that is, the curable resin composition of the present invention, the resin layer of the dry film of the present invention, or the cured product of the resin layer of the resin-coated copper foil of the present invention.
Examples of electronic components include permanent protective films for printed wiring boards, such as solder resist layers, interlayer insulating layers, and coverlays for flexible printed wiring boards. Electronic components also include passive components such as inductors for applications other than printed wiring boards.

In addition to the above-mentioned applications, the curable resin composition of the present invention can also be suitably used for permanently filling holes in printed wiring boards, such as through holes and via holes. It can also be used as an encapsulant for semiconductor chips, and as a material for copper clad laminates (CCL) and prepregs.

In addition, since the cured product of the curable resin composition of the present invention has excellent dielectric properties, its use also provides good transmission quality in high-frequency applications. Specific examples of high-frequency applications include substrates for millimeter-wave radar and millimeter-wave sensors for autonomous driving, motherboards for mobile devices compatible with high-speed communication, SLP (Substrate-Like PCB) circuits formed by the modified semi-additive process (MSAP) method, application processors (AP) for mobile devices and personal computers, highly multilayer substrates for base station servers and routers, substrates for antennas, and semiconductor encapsulation materials.

Furthermore, a wiring board may be formed by bonding wiring using the dry film of the present invention.

The circuit-forming material using the curable resin composition of the present invention may be in the form of a resin-coated copper foil (RCC: Resin-Coated-Copper) compatible with the modified semi-additive process (MSAP) or a build-up film compatible with the semi-additive process (SAP).

According to the present invention, it is possible to obtain a cured product having a low dielectric tangent, for example, less than 0.010, or even less than 0.006 at a frequency of 10 GHz and 23°C.
Furthermore, according to the present invention, it is possible to obtain a cured product having a low dielectric constant; for example, it is possible to achieve a dielectric constant of less than 3.2, or even less than 3.0, at a frequency of 10 GHz and 23°C.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the following, unless otherwise specified, "parts" and "%" refer to parts by mass and % by mass.

(B) Synthesis of Compound Having Active Ester Group)
[Synthesis Example 1]
In a flask equipped with a thermometer, a dropping funnel, a cooling tube, a fractionating tube, and a stirrer, 203.0 g of isophthalic acid chloride (molar number of acid chloride groups: 2.0 mol) and 1338 g of toluene were charged, and the system was purged with nitrogen under reduced pressure to dissolve. Next, 96.0 g (0.67 mol) of α-naphthol and 220 g of dicyclopentadiene phenol resin (molar number of phenolic hydroxyl groups: 1.33 mol) were charged, and the system was purged with nitrogen under reduced pressure to dissolve. Thereafter, 1.12 g of tetrabutylammonium bromide was dissolved, and while purging with nitrogen gas, the system was controlled to 60°C or less, and 400 g of 20% aqueous sodium hydroxide solution was dropped over 3 hours.
Stirring was then continued under these conditions for 1.0 hour. After the reaction was completed, the mixture was allowed to stand and separated, and the aqueous layer was removed. Water was then added to the toluene phase in which the reactants were dissolved, and the mixture was stirred and mixed for about 15 minutes, and the mixture was allowed to stand and separated, and the aqueous layer was removed. This operation was repeated until the pH of the aqueous layer reached 7. Thereafter, water was removed by decanting, and a compound (B-1) having an active ester group was obtained in a toluene solution state with a solid content of 65%.
The ester group equivalent of the obtained compound (B-1) having an active ester group was 223 g/mol calculated on solid content basis.

[Synthesis Example 2]
In a flask equipped with a thermometer, a dropping funnel, a cooling tube, a fractionating tube, and a stirrer, 320 g (2.0 mol) of 2,7-dihydroxynaphthalene, 184 g (1.7 mol) of benzyl alcohol, and 5.0 g of paratoluenesulfonic acid monohydrate were charged, and stirred at room temperature while blowing in nitrogen. The temperature was then raised to 150°C, and the mixture was stirred for 4 hours while distilling off the water produced. After the reaction was completed, 900 g of methyl isobutyl ketone and 5.4 g of a 20% aqueous sodium hydroxide solution were added for neutralization, and the aqueous layer was removed by separation, and the mixture was washed three times with 280 g of water. The methyl isobutyl ketone was removed under reduced pressure to obtain 460 g of a benzyl-modified naphthalene compound (intermediate of B-2). The obtained benzyl-modified naphthalene compound (intermediate of B-2) was a black solid, and had a hydroxyl equivalent of 180 g/equivalent.
Next, in another flask equipped with a thermometer, a dropping funnel, a cooling tube, a fractionating tube, and a stirrer, 203.0 g of isophthalic acid chloride (molar number of acid chloride groups: 2.0 mol) and 1400 g of toluene were charged, and the inside of the system was substituted with nitrogen under reduced pressure to dissolve. Next, 96.0 g (0.67 mol) of α-naphthol and 240 g (molar number of phenolic hydroxyl groups: 1.33 mol) of a benzyl-modified naphthalene compound (intermediate of B-2) were charged, and the inside of the system was substituted with nitrogen under reduced pressure to dissolve. Thereafter, 0.70 g of tetrabutylammonium bromide was dissolved, and while applying a nitrogen gas purge, the inside of the system was controlled to 60°C or less, and 400 g of a 20% aqueous sodium hydroxide solution was dropped over 3 hours. Then, stirring was continued under these conditions for 1.0 hour. After the reaction was completed, the mixture was left to stand for liquid separation, and the aqueous layer was removed. Further, water was added to the toluene layer in which the reactant was dissolved, and the mixture was stirred and mixed for 15 minutes, and then the mixture was allowed to stand and separated to remove the aqueous layer. This operation was repeated until the pH of the aqueous layer reached 7. Thereafter, water was removed by decanting to obtain a compound (B-2) having an active ester group in a toluene solution state with a solid content of 65 mass %. The ester group equivalent of the obtained compound (B-2) having an active ester group was 230 g/mol in terms of solid content.

<1. Preparation of Curable Resin Composition>
Various components shown in the following Table 1 were kneaded and mixed in the ratios (parts by mass) shown in Table 1 to prepare curable resin compositions for producing films after curing in Examples 1 to 9 and Comparative Examples 1 and 2. The values in Table 1 indicate parts by mass or % by mass (solid content equivalent).
For each of the curable resin compositions, test samples were prepared as described below, and the glass transition temperature (Tg), dielectric constant, dielectric loss tangent, and peel strength were measured and evaluated. The results are shown in Table 1.

2. Preparation of cured film
The curable resin composition of each of the Examples and Comparative Examples obtained above was applied onto the glossy surface of a copper foil (F2-WS manufactured by Furukawa Electric Co., Ltd., 18 μm thick) using a film applicator, and then dried in a hot air circulation drying oven at 90° C. for 10 minutes and subsequently cured at 200° C. for 60 minutes. The copper foil was then peeled off to prepare cured films (cured films) of Examples 1 to 9 and Comparative Examples 1 and 2 each having a thickness of about 40 μm.

<3. Measurement of glass transition temperature (Tg)>
The sample obtained in <2. Preparation of cured film> above was cut to a measurement size (3 mm x 10 mm), and the glass transition temperature (Tg) was measured using a TMA Q400EM manufactured by TA Instruments Co., Ltd. The temperature was raised from room temperature at a heating rate of 10°C/min, and measurements were taken twice in succession, and the glass transition temperature (Tg) at the intersection of two tangents with different linear thermal expansion coefficients in the second measurement was evaluated.

The glass transition temperature was evaluated according to the following criteria.
◎: 175℃ or higher 〇: Less than 175℃ 170℃ or higher ×: Less than 170℃

<4. Measurement of dielectric constant (Dk) and dielectric loss tangent (Df)>
The sample obtained in the above <Preparation of Cured Film> was cut to a measurement size (50 mm x 60 mm), and the dielectric constant and dielectric loss tangent at 10 GHz at 23°C were measured using an SPDR dielectric resonator and a network analyzer (both manufactured by Agilent Technologies).
The dielectric constant (10 GHz) was evaluated according to the following criteria.
⊚: Less than 3.0 ◯: 3.0 or more and less than 3.2 ×: 3.2 or more The dielectric loss tangent (10 GHz) was evaluated according to the following criteria.
◎: Less than 0.006 〇: 0.006 or more to less than 0.010 ×: 0.010 or more

<5. Preparation of samples for measuring peel strength>
(1) Roughening Treatment of Laminate Both sides of a glass cloth-based epoxy resin double-sided copper-clad laminate [copper foil thickness 18 μm, substrate thickness 0.3 mm, Panasonic R5715ES] having an inner layer circuit formed thereon was immersed in CZ8100 manufactured by MEC Co., Ltd. to roughen the copper surface (etching amount: about 1 μm).
(2) Preparation of resin-coated copper foil Using a film applicator, the curable resin composition of each of the Examples and Comparative Examples obtained in <1. Preparation of curable resin composition> was applied onto the ultra-thin copper foil surface of an ultra-thin copper foil with a carrier (MT18Ex manufactured by Mitsui Kinzoku, ultra-thin copper foil with a thickness of 3 μm), and dried at 90° C. for 10 minutes in a hot air circulation drying oven to obtain a resin-coated copper foil with a resin layer thickness of about 40 μm.
(3) Lamination of resin-coated copper foil Using a batch-type vacuum pressure laminator MVLP-500 (manufactured by Meiki Seisakusho Co., Ltd.), the resin composition-coated surface of the resin-coated copper foil (2) was laminated on both sides of the laminated plate that had been roughened in the roughening treatment (1). The lamination was performed by reducing the pressure for 30 seconds to 13 hPa or less, and then pressing for 30 seconds at 80°C and a pressure of 0.5 MPa.
(4) Curing of Resin Composition The laminate (3) having the resin-coated copper foil laminated thereon was cured in a hot air circulating drying oven at 170° C. for 30 minutes.
(5) Electrolytic Copper Plating After curing, the carrier copper foil was peeled off from both sides of the laminate, and the ultra-thin copper foil (3 μm) on both sides was electrolytically plated to a thickness of about 25 μm.
(6) Annealing Treatment The laminated sheet after electrolytic copper plating was subjected to annealing treatment at 200° C. for 60 minutes in a hot air circulation drying oven.

<Peel Strength Measurement>
The samples prepared by the above method were measured in accordance with JIS C6481 and evaluated according to the following criteria. The results are shown in Table 4.
◎: 0.55 kN/m or more ○: Less than 0.55 kN/m 0.4 kN/m or more ×: Less than 0.4 kN/m

Details of the components in Table 1 are as follows:
EPICLON (registered trademark) EXA-835LV (DIC Corporation, mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin, liquid, epoxy equivalent: 165 g/eq)
NC-3000H (manufactured by Nippon Kayaku Co., Ltd., biphenyl novolac type epoxy resin, solid, epoxy equivalent: 290 g/eq)
B-1: Produced by Synthesis Example 1 (active ester equivalent: 223 g/eq)
B-2: Produced by Synthesis Example 2 (active ester equivalent: 230 g/eq)
SO-C2: Phenylaminosilane-treated spherical silica (average particle size: 0.5 μm, carbon content per unit mass: 0.18) (manufactured by Admatechs Co., Ltd.)
Exp. BC10: (manufactured by DIC Corporation, a block copolymer obtained from polypropylene glycol and polycaprolactone (molar ratio of about 49:51), mass average molecular weight Mw (measured by GPC using a polyethylene standard) of about 9,000, melting point of about 58°C, hydroxyl value of 11 to 14 mgKOH/g, viscosity of 4,000 mPa.s (75°C))
Exp. BC20: (manufactured by DIC Corporation, a block copolymer obtained from polytetramethylene glycol and polycaprolactone (molar ratio of about 44:56), mass average molecular weight Mw (measured by GPC using a polyethylene standard) of about 9,000, melting point of about 58°C, hydroxyl value of 11 to 14 mgKOH/g, viscosity of 4,000 mPa.s (75°C))
Polypropylene glycol 3000: (manufactured by Junsei Chemical Co., Ltd., molecular weight 3,000)
Plaxel 240: (manufactured by Daicel Corporation, polycaprolactone diol, molecular weight 4,000)
2E4MZ: 2-ethyl-4-methylimidazole *1: Ratio of the total amount of epoxy groups in the epoxy resin (A) in the composition to the total amount of active ester groups in the compound having an active ester group (B)

Examples 1 to 9 demonstrate that the curable resin composition of the present invention can produce a cured product that has high heat resistance, low dielectric constant, low dielectric tangent, and excellent adhesion.

Claims (9)

(A) an epoxy resin,
(B) a compound having an active ester group,
(C) an inorganic filler, and
(D) polyester additives;
The polyester additive (D) is a polymer having a polyalkylene glycol structure and an aliphatic polyester structure, and is a diblock copolymer represented by the following formula (D-1) or a triblock copolymer represented by the following formula (D-2).
Xn-Ym (D-1)
Ym1-Xn-Ym2 (D-2)
(In formula (D-1), n:m is in the range of 40 to 50:60 to 50,
In formula (D-2), n:m1+m2 is in the range of 40 to 50:60 to 50;
X is a unit derived from a polyalkylene glycol (represented by the general formula HO-(RO) _p -H, where R is an alkylene having 2 to 5 carbon atoms and p is 2 to 200),
Y is a unit derived from polycaprolactone ((CH ₂ ) ₅ CO ₂ )r'(r' is 2 to 40). The curable resin composition according to claim 1, wherein the blending amount of the polyester additive (D) is 1% by mass or more and 35% by mass or less relative to the total mass of the epoxy resin (A) and the compound having an active ester group (B). The curable resin composition according to claim 1 or 2 , wherein a ratio of a total amount of epoxy groups in the epoxy resin (A) to a total amount of active ester groups in the compound (B) having an active ester group is 0.2 to 0.9. The compound (B) having an active ester group is represented by the following general formula (1):

(wherein _X1 is each independently a group having a benzene ring or a naphthalene ring, k is 0 or 1, and n is an average of 0.05 to 2.5 of the repeating units). The curable resin composition according to any one of claims 1 to 3 , The compound (B) having an active ester group is represented by the following general formula (2):

(In formula (2), _X2 each independently represents the following formula (3):

or a group represented by the following formula (4):

is a group represented by
m is an integer from 1 to 6, each n is independently an integer from 1 to 5, and each q is independently an integer from 1 to 6;
In formula (3), k is independently an integer from 1 to 5,
In formula (4), Y is a group represented by formula (3) above (wherein k is an integer of 1 to 5, and t is an integer of 0 to 5).
The curable resin composition according to any one of claims 1 to 3 , wherein the compound has a structure represented by the following formula (1): A dry film comprising the curable resin composition according to any one of claims 1 to 5 as a resin layer. A resin-coated copper foil comprising a copper foil or a carrier-coated copper foil having the curable resin composition according to any one of claims 1 to 5 as a resin layer thereon. A curable resin composition according to any one of claims 1 to 5 , a resin layer of a dry film according to claim 6 , or a cured product of the resin layer of a resin-coated copper foil according to claim 7 . An electronic part comprising the cured product according to claim 8 .