JP7705267B2 - Curable resin laminates, dry films and cured products, electronic components - Google Patents

Description

The present invention relates to a curable resin laminate useful for producing an interlayer insulating layer in electronic components such as printed wiring boards (hereinafter also simply referred to as "wiring boards"); a dry film having the curable resin laminate; and a cured product of the curable resin laminate obtained using the curable resin laminate or the dry film, and an electronic component.

In recent years, signals from electronic devices have become increasingly high-frequency due to the widespread use of high-capacity, high-speed communications such as those represented by fifth-generation communication systems (5G) and millimeter-wave radar for automotive ADAS (advanced driving systems).

For wiring boards built into such electronic devices, curable resin compositions mainly composed of epoxy resins have been used as insulating materials, but the cured products made from such compositions have high relative dielectric constants (Dk) and dielectric loss tangents (Df), which increase transmission loss for high-frequency signals, causing problems such as signal attenuation and heat generation. For this reason, attention has been focused on polyphenylene ether, which has excellent low dielectric properties.

Non-Patent Document 1 proposes polyphenylene ether with improved heat resistance by introducing allyl groups into the polyphenylene ether molecule to make it a thermosetting resin.

J. Nunoshige, H. Akahoshi, Y. Shibasaki, M. Ueda, J. Polym. Sci. Part A: Polym. Chem. 2008, 46, 5278-3223.

However, when polyphenylene ether is used as an insulating film for wiring boards, for example as an interlayer insulating material sandwiched between upper and lower conductor layers such as copper-clad laminates (CCL), there is a problem in that it does not provide sufficient adhesion to the copper foil used in the conductor layers, i.e., sufficient peel strength.

The object of the present invention is to provide a curable resin laminate that is useful for forming an insulating layer that has low dielectric properties and excellent adhesion (peel strength) to a conductor layer.

The inventors have discovered that the above problems can be solved by providing a multilayer structure in which the thickness of each resin layer is within a specific range, each resin layer containing a polyphenylene ether having a branched structure as a resin component, and each resin layer having a melt viscosity within a specific range, and have thus completed the present invention. That is, the present invention is as follows.

The present invention relates to
A curable resin laminate having a first resin layer and a second resin layer laminated on at least one of the main surfaces of the first resin layer,
the second resin layer has a thickness of 5 to 35% of the total thickness of the first resin layer and the second resin layer;
the first resin layer contains (A1) polyphenylene ether and (B1) a filler,
the second resin layer contains (A2) polyphenylene ether and has a melt viscosity (MV ₂ ) at 140° C. of 40,000 dPa·s or less;
a melt viscosity (MV ₁ ) of the first resin layer at 140° C. and a melt viscosity (MV ₂ ) of the second resin layer at 140° C. have a relationship of MV ₁ >MV ₂ ;
The (A1) polyphenylene ether and the (A2) polyphenylene ether are obtained from raw material phenols containing at least a phenol satisfying condition 1, and are polyphenylene ethers having a slope calculated in a conformation plot of less than 0.6.
(Condition 1)
Contains hydrogen atoms at the ortho and para positions

The present invention may be a dry film having the curable resin laminate.
The present invention may also provide a cured product comprising the curable laminate.
The present invention may also relate to an electronic component having the cured product.

The present invention provides a curable resin laminate that is useful for forming an insulating layer that has low dielectric properties and excellent adhesion (peel strength) to a conductor layer.

The following describes a curable resin laminate, which is a laminate structure including at least two resin layers, but the present invention is not limited to the following in any way.

When isomers exist in the described compounds, all possible isomers are usable in the present invention unless otherwise specified.

In the present invention, phenols that are used as raw materials for polyphenylene ether (PPE) and can become structural units of polyphenylene ether are collectively referred to as "raw material phenols."

In the present invention, when describing the raw material phenols, terms such as "ortho position" and "para position" are used, unless otherwise specified, the position of the phenolic hydroxyl group is taken as the reference (ipso position).

In the present invention, when simply referring to an "ortho position" or the like, it means "at least one of the ortho positions". Therefore, unless there is any particular contradiction, when simply referring to an "ortho position", it may be interpreted as meaning either one of the ortho positions, or as meaning both ortho positions.

In the present invention, polyphenylene ether in which some or all of the functional groups (e.g., hydroxyl groups) of the polyphenylene ether have been modified may be referred to simply as "polyphenylene ether." Therefore, when the term "polyphenylene ether" is used, it includes both unmodified polyphenylene ether and modified polyphenylene ether, unless there is a particular contradiction.

In this specification, monohydric phenols are mainly disclosed as the raw material phenols, but polyhydric phenols may be used as the raw material phenols as long as they do not impair the effects of the present invention.

In this specification, when the upper and lower limits of a numerical range are stated separately, all combinations of each lower limit and each upper limit are essentially stated, provided there is no contradiction.

In this specification, solids are used to mean non-volatile components (components other than volatile components such as solvents).

The following describes the structure and components of the curable resin laminate, the effects of the curable resin laminate, the manufacturing method of the curable resin laminate, and uses of the curable resin laminate.

In the following, there may be cases where no distinction is made between the components contained in the curable composition and the components contained in the curable resin layer, which is the dried coating film of the curable composition.

<<<<<<<Constitution and components of curable resin layer>>>>>>>
The curable resin laminate of the present invention has a first resin layer and a second resin layer laminated (directly) on at least one of the main surfaces of the first resin layer.
The second resin layer has a thickness of 5 to 35% of the total thickness of the first resin layer and the second resin layer.
The first resin layer and the second resin layer contain polyphenylene ether.
The first resin layer essentially contains a filler.
The second resin layer may or may not contain a filler.

The curable resin laminate of the present invention is usually used so that the second resin layer comes into contact with an object to be adhered, such as copper foil (copper circuit). Therefore, when it is a two-layer laminate consisting of a first resin layer and a second resin layer, the first resin layer side of the resin layer is disposed so as to come into contact with a substrate such as a wiring board, and the second resin layer is used so as to come into contact with an object to be adhered, such as copper foil (copper circuit).

In the curable resin laminate of the present invention, a base film made of polyethylene terephthalate, polypropylene, or the like or other resin layer may be laminated on the outer layer of the first resin layer and/or the second resin layer. In addition, two or more base films or other layers may be provided.

The curable resin laminate of the present invention may be any laminate satisfying the above-mentioned constitution, and may be, for example, a laminate consisting of at least three layers laminated in the order of second resin layer/first resin layer/second resin layer. When the curable resin laminate of the present invention has two second resin layers, the thickness, material, etc. of each second resin layer may be the same or different within a range satisfying the following conditions.
(conditions)
The combined thickness of the second resin layer is 10 to 70% of the combined thickness of the first resin layer and the second resin layer, and each resin layer is configured to have a predetermined melt viscosity as a cured product.

<<<<<<Configuration >>>>>>
<<<<<Configuration: First Resin Layer>>>>
The first resin layer of the present invention contains (A1) polyphenylene ether and (B1) a filler.

In other words, the first resin layer is a dry coating film obtained from a first curable composition containing (A1) polyphenylene ether and (B1) a filler.

The content M of the filler ( _B1 ) relative to the total solid content of the first resin layer (or the total solid content of the first curable composition) is preferably 30 mass% or more. From the viewpoint of low thermal expansion, the content M of the filler ( _B1 ) is more preferably 30 to 80 mass%, further preferably 50 to 80 mass%, and particularly preferably 65 to 80 mass%.

The content M _A1 of the polyphenylene ether (A1) relative to the total solid content in the first resin layer (or the total solid content of the first curable composition) is preferably 3 to 40 mass%, more preferably 5 to 30 mass%, even more preferably 7 to 25 mass%, and particularly preferably 9 to 20 mass%.

The first resin layer may also contain other components (C1).

(A1) Polyphenylene ether, (B1) Filler, and (C1) Other components will be described later.

The thickness _T1 of the first resin layer is thicker than the thickness _T2 of the second resin layer, and is, for example, preferably 1 to 50 μm, more preferably 10 to 45 μm, even more preferably 20 to 30 μm, and particularly preferably 24 to 29 μm.

<<<<<Configuration: Second Resin Layer>>>>
The second resin layer of the present invention contains (A2) polyphenylene ether.

In other words, the second resin layer is a dry coating film obtained from a second curable composition containing (A2) polyphenylene ether.

The second resin layer may or may not contain a filler (B2).

When the second resin layer contains a filler (B2), the content (M _B2 ) of the filler (B2) relative to the total solid content of the second resin layer (or the total solid content of the second curable composition) is preferably 40 mass% or less, and more preferably 35 mass% or less. Furthermore, when the second resin layer contains a filler, the content M _B2 of the filler (B2) is preferably 5 to 35 mass%, and more preferably 20 to 35 mass%, in order to achieve an excellent balance between low thermal expansion and adhesion to the conductor layer.

Here, the relationship between the content (M _B1 ) of the (B1) filler and the content (M _B2 ) of the (B2) filler is preferably M _B1 >M _B2 . More specifically, the ratio (M B2 /M _{B1 ) of the content (M B1} ) of the (B1) filler to the total solid content in the first curable composition and the content (M _B2 ) of the ( _B2 ) filler to the total solid content in the _second curable composition is more preferably 50% or less, even more preferably 45% or less, and even more preferably 15% or less, from the viewpoint of low dielectric properties.

The content M _A2 of the polyphenylene ether (A2) relative to the total solid content in the second resin layer (or the total solid content of the second curable composition) is preferably 10 to 50 mass %, more preferably 30 to 50 mass %.

The second resin layer may also contain other components (C2).

(A2) Polyphenylene ether, (B2) filler, and (C2) other components will be described later.

The ratio (T2/(T1 _{+ T2} )) of the thickness _T2 of the second resin layer to the total thickness ( _T1 + _T2 ) of the thickness of the first resin layer ( _T1 ) and the thickness of the _second resin layer ( _T2 ) is 5-35%, preferably 10-25%, and more preferably 15-25%. When _the ratio of the thickness _T2 of the second resin layer is within the above range, stable adhesion to the conductor layer can be obtained.

The thickness _T2 of the second resin layer is thinner than the thickness _T1 of the first resin layer, and is, for example, preferably 0.5 to 40 μm, more preferably 0.7 to 30 μm, even more preferably 1 to 20 μm, and particularly preferably 3 to 10 μm.

<<<<<Composition: Other layers>>>>>
Examples of the other layers include a base film made of polyethylene terephthalate, polypropylene, etc., and a cover film for protecting the surface of the curable resin layer.

<<<<<<Physical Properties>>>>>>
<<<<Melt Viscosity>>>>
The first resin layer preferably has a melt viscosity (MV ₁ ) of more than 20,000 dPa·s at 140° C., more preferably more than 25,000 dPa·s, and particularly preferably more than 30,000 dPa·s. The upper limit of the melt viscosity (MV ₁ ) is not particularly limited, but is, for example, 500,000 dPa·s.

The second resin layer has a melt viscosity (MV ₂ ) of 40,000 dPa·s or less at 140° C. The lower limit of the melt viscosity (MV ₂ ) is not particularly limited, but is, for example, 10,000 dPa·s.

Further, the relationship between the melt viscosity (MV ₁ ) of the first resin layer at 140° C. and the melt viscosity (MV ₂ ) of the second resin layer is MV ₁ >MV ₂ .

More specifically, the melt viscosity difference (MV ₁ -MV ₂ ) between the melt viscosity (MV ₁ ) of the first resin layer at 140° C. and the melt viscosity (MV ₂ ) of the second resin layer at 140° C. is preferably 2,000 dPa·s or more, more preferably 5,000 dPa·s or more. The upper limit of the melt viscosity difference (MV ₁ -MV ₂ ) is not particularly limited, and is, for example, 450,000 dPa·s, 400,000 dPa·s, or 300,000 dPa·s.

The melt viscosity of the resin layer at 140°C can be adjusted by changing the molecular structure, molecular weight, and content of the resin component (polyphenylene ether), or by changing the content of the filler component. Specifically, increasing the filler content in the resin layer tends to increase the melt viscosity at 140°C.

The melt viscosity of each of the first resin layer and the second resin layer can be measured by the following method.
Each individual resin layer (for example, a dry film having an individual resin layer with a thickness of 25 μm) is repeatedly laminated to a thickness of 500 μm using a vacuum laminator MVLP-500 manufactured by Meiki Seisakusho Co., Ltd. to prepare a test piece for melt viscosity measurement. This test piece is placed in a melt viscosity measuring device, and the melt viscosity at 140° C. [unit: dPa s] is measured.
The melt viscosity is measured using a rheometer (MARS 40) manufactured by HAAKE Corp. under the following conditions: oscillation temperature rise method (5° C./min.), measurement temperature range: 70 to 200° C., frequency: 1 Hz, stress control: 2.5 N, parallel plate: diameter 20 mm, gap: 450 μm, sample size: 2.5×2.5 cm.

<<<<<<Ingredients>>>>>>
The components of the first resin layer and the second resin layer, that is, (A1) polyphenylene ether, (A2) polyphenylene ether, (B1) filler, (B2) filler, (C1) other components, and (C2) other components, will be described.

<<<<<Components: Polyphenylene ether (A1) and (A2)>>>>
The polyphenylene ether (A1) contained in the first curable composition and the resin layer and the polyphenylene ether (A2) contained in the second curable composition and the resin layer may be the same or different components. Here, the polyphenylene ether (A1) and the polyphenylene ether (A2) are collectively referred to as polyphenylene ether (predetermined polyphenylene ether) and will be described.

<<<<Polyphenylene ether (prescribed polyphenylene ether)>>>
The polyphenylene ether of the present invention is obtained from raw material phenols containing phenols that at least satisfy condition 1, and is a polyphenylene ether having a branched structure obtained from raw material phenols containing phenols that at least satisfy condition 1. Such a polyphenylene ether is referred to as a predetermined polyphenylene ether.
(Condition 1)
Contains hydrogen atoms at the ortho and para positions

Phenols that satisfy condition 1 (for example, phenols (A) and (B) described below) have hydrogen atoms at the ortho position, so when they are oxidatively polymerized with phenols, ether bonds can be formed not only at the ipso and para positions but also at the ortho position, making it possible to form a branched chain structure.

In this way, polyphenylene ethers having a branched structure may be referred to as "predetermined polyphenylene ether branched polyphenylene ether."

In this way, a part of the structure of the specified polyphenylene ether is branched by benzene rings ether-bonded at least at the ipso, ortho, and para positions. This specified polyphenylene ether is considered to be, for example, a polyphenylene ether compound having a branched structure in the skeleton as shown in at least formula (i).

In formula (i), R _a to R _k each represent a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms (preferably 1 to 12 carbon atoms).

Here, the raw material phenols constituting the specified polyphenylene ether may contain other phenols that do not satisfy condition 1, as long as the effects of the present invention are not impaired.

Examples of such other phenols include phenols (C) and (D) described below, and phenols that do not have a hydrogen atom at the para position. In particular, phenols (C) and (D) described below form ether bonds at the ipso and para positions during oxidative polymerization, and are polymerized in a linear chain. Therefore, in order to increase the molecular weight of polyphenylene ether, it is preferable to further include phenols (C) and (D) as raw phenols.

The polyphenylene ether may also have a functional group containing an unsaturated carbon bond. The presence of such a functional group provides crosslinkability and excellent reactivity, resulting in improved properties of the cured product.
In the present invention, unless otherwise specified, the term "unsaturated carbon bond" refers to an ethylenic or acetylenic carbon-carbon multiple bond (double bond or triple bond).
The functional group containing such an unsaturated carbon bond is not particularly limited, but is preferably an alkenyl group (e.g., a vinyl group, an allyl group), an alkynyl group (e.g., an ethynyl group), or a (meth)acryloyl group, more preferably a vinyl group, an allyl group, or a (meth)acryloyl group from the viewpoint of excellent curability, and even more preferably an allyl group from the viewpoint of excellent low dielectric properties. The number of carbon atoms in these functional groups having an unsaturated carbon bond can be, for example, 15 or less, 10 or less, 8 or less, 5 or less, 3 or less, etc.
The method for introducing such a functional group containing an unsaturated carbon bond into a given polyphenylene ether is not particularly limited, but includes the following [Method 1] or [Method 2].

[Method 1]
Method 1 is
As raw phenols,
This method comprises adding a phenol (A) which satisfies at least both the following condition 1 and the following condition 2 (mode 1), or adding a mixture of a phenol (B) which satisfies at least the following condition 1 but does not satisfy the following condition 2, and a phenol (C) which does not satisfy the following condition 1 but satisfies the following condition 2 (mode 2).
(Condition 1)
Having hydrogen atoms at the ortho and para positions (condition 2)
It has a hydrogen atom at the para position and a functional group containing an unsaturated carbon bond.

According to method 1, it is possible to obtain a specific polyphenylene ether having a functional group containing an unsaturated carbon bond derived from the raw material phenol.

[Method 2]
Method 2 is
In this method, the terminal hydroxyl groups of a branched polyphenylene ether are modified with functional groups containing unsaturated carbon bonds to obtain a terminal-modified polyphenylene ether.

According to method 2, even if the raw material phenol does not have a functional group containing an unsaturated carbon bond, it is possible to obtain a specified polyphenylene ether into which a functional group containing an unsaturated carbon bond has been introduced.

Method 1 and Method 2 may be performed simultaneously.

<<Prescribed polyphenylene ether obtained by method 1>>
The specified polyphenylene ether obtained by method 1 has at least crosslinkability due to a hydrocarbon group containing an unsaturated carbon bond, since at least a phenol satisfying condition 2 (for example, either phenol (A) or phenol (C)) is used as a phenol raw material. When the specified polyphenylene ether has such a hydrocarbon group containing an unsaturated carbon bond, it is also possible to carry out modification such as epoxidation using a compound which reacts with the hydrocarbon group and has a reactive functional group such as an epoxy group.

That is, the predetermined polyphenylene ether obtained by method 1 is, for example, a polyphenylene ether having at least a branched structure as represented by formula (i) in the skeleton, and is considered to be a compound having a hydrocarbon group containing at least one unsaturated carbon bond as a functional group. Specifically, it is considered to be a compound in which at least one of R _a to R _k in the above formula (i) is a hydrocarbon group having an unsaturated carbon bond.

In particular, in the above embodiment 2, from an industrial and economical point of view, it is preferable that the phenol (B) is at least one of o-cresol, 2-phenylphenol, 2-dodecylphenol, and phenol, and the phenol (C) is 2-allyl-6-methylphenol.

The phenols (A) to (D) are described in more detail below.

As described above, the phenol (A) is a phenol that satisfies both conditions 1 and 2, i.e., a phenol that has hydrogen atoms at the ortho and para positions and has a functional group that contains an unsaturated carbon bond, and is preferably a phenol (a) represented by the following formula (1).

In formula (1), R ₁ to R ₃ are hydrogen atoms or hydrocarbon groups having 1 to 15 carbon atoms. However, at least one of R ₁ to R ₃ is a hydrocarbon group having an unsaturated carbon bond. From the viewpoint of facilitating polymerization by oxidative polymerization, the hydrocarbon group preferably has 1 to 12 carbon atoms.

Examples of phenols (a) represented by formula (1) include o-vinylphenol, m-vinylphenol, o-allylphenol, m-allylphenol, 3-vinyl-6-methylphenol, 3-vinyl-6-ethylphenol, 3-vinyl-5-methylphenol, 3-vinyl-5-ethylphenol, 3-allyl-6-methylphenol, 3-allyl-6-ethylphenol, 3-allyl-5-methylphenol, and 3-allyl-5-ethylphenol. Only one type of phenol represented by formula (1) may be used, or two or more types may be used.

As described above, phenol (B) is a phenol that satisfies condition 1 but does not satisfy condition 2, i.e., a phenol that has hydrogen atoms at the ortho and para positions and does not have a functional group containing an unsaturated carbon bond, and is preferably a phenol (b) represented by the following formula (2).

In formula (2), R ₄ to R ₆ are hydrogen atoms or hydrocarbon groups having 1 to 15 carbon atoms. However, R ₄ to R ₆ do not have an unsaturated carbon bond. From the viewpoint of facilitating polymerization by oxidative polymerization, the hydrocarbon group preferably has 1 to 12 carbon atoms.

Examples of phenols (b) represented by formula (2) include phenol, o-cresol, m-cresol, o-ethylphenol, m-ethylphenol, 2,3-xylenol, 2,5-xylenol, 3,5-xylenol, o-tert-butylphenol, m-tert-butylphenol, o-phenylphenol, m-phenylphenol, and 2-dodecylphenol. Only one type of phenol represented by formula (2) may be used, or two or more types may be used.

As described above, the phenol (C) is a phenol that does not satisfy condition 1 but satisfies condition 2, i.e., a phenol that has a hydrogen atom at the para position, does not have a hydrogen atom at the ortho position, and has a functional group that contains an unsaturated carbon bond, and is preferably a phenol (c) represented by the following formula (3).

In formula (3), R ₇ and R ₁₀ are hydrocarbon groups having 1 to 15 carbon atoms, and R ₈ and R ₉ are hydrogen atoms or hydrocarbon groups having 1 to 15 carbon atoms, provided that at least one of R ₇ to R ₁₀ is a hydrocarbon group having an unsaturated carbon bond. From the viewpoint of facilitating polymerization by oxidative polymerization, the hydrocarbon group preferably has 1 to 12 carbon atoms.

Examples of phenols (c) represented by formula (3) include 2-allyl-6-methylphenol, 2-allyl-6-ethylphenol, 2-allyl-6-phenylphenol, 2-allyl-6-styrylphenol, 2,6-divinylphenol, 2,6-diallylphenol, 2,6-diisopropenylphenol, 2,6-dibutenylphenol, 2,6-diisobutenylphenol, 2,6-diisopentenylphenol, 2-methyl-6-styrylphenol, 2-vinyl-6-methylphenol, and 2-vinyl-6-ethylphenol. Only one type of phenol represented by formula (3) may be used, or two or more types may be used.

As described above, the phenol (D) is a phenol having a hydrogen atom at the para position, no hydrogen atom at the ortho position, and no functional group containing an unsaturated carbon bond, and is preferably a phenol (d) represented by the following formula (4).

In formula (4), R ₁₁ and R ₁₄ are hydrocarbon groups having 1 to 15 carbon atoms and no unsaturated carbon bonds, and R ₁₂ and R ₁₃ are hydrogen atoms or hydrocarbon groups having 1 to 15 carbon atoms and no unsaturated carbon bonds. From the viewpoint of facilitating polymerization by oxidative polymerization, the hydrocarbon group preferably has 1 to 12 carbon atoms.

Examples of phenols (d) represented by formula (4) include 2,6-dimethylphenol, 2,3,6-trimethylphenol, 2-methyl-6-ethylphenol, 2-ethyl-6-n-propylphenol, 2-methyl-6-n-butylphenol, 2-methyl-6-phenylphenol, 2,6-diphenylphenol, and 2,6-ditolylphenol. Only one type of phenol represented by formula (4) may be used, or two or more types may be used.

Here, in the present invention, examples of the hydrocarbon group include an alkyl group, a cycloalkyl group, an aryl group, an alkenyl group, and an alkynyl group, and preferably an alkyl group, an aryl group, and an alkenyl group. Examples of the hydrocarbon group having an unsaturated carbon bond include an alkenyl group and an alkynyl group. These hydrocarbon groups may be linear or branched.

<<Prescribed polyphenylene ether obtained by method 2>>
The polyphenylene ether obtained by method 2 is a terminal-modified branched polyphenylene ether.

Since such terminally modified branched polyphenylene ether has a branched structure and the terminal hydroxyl groups are modified, it is possible to obtain a cured product that is soluble in various solvents and has further reduced low dielectric properties. Furthermore, since the terminally modified branched polyphenylene ether has unsaturated carbon bonds at the terminal positions, it has extremely good reactivity and the performance of the resulting cured product is even better.

When a terminal hydroxyl group is modified with a modifying compound, an ether bond or an ester bond is usually formed between the terminal hydroxyl group and the modifying compound.

Here, the modifying compound is not particularly limited as long as it contains a functional group having an unsaturated carbon bond and can react with a phenolic hydroxyl group in the presence or absence of a catalyst.

A suitable example of the modifying compound is an organic compound represented by the following formula (11):

In formula (11), _R , _R , and _R are each independently a hydrogen atom or a hydrocarbon group having 1 to 9 carbon atoms, _R is a hydrocarbon group having 1 to 9 carbon atoms, and X is a group capable of reacting with a phenolic hydroxyl group, such as F, Cl, Br, I, or CN.

From another perspective, a suitable example of a modifying compound is an organic compound represented by the following formula (11-1):

In formula (11-1), R is a vinyl group, an allyl group, or a (meth)acryloyl group, and X is a group capable of reacting with a phenolic hydroxyl group, such as F, Cl, Br, or I.

The modification of the terminal hydroxyl groups of the branched polyphenylene ether can be confirmed by comparing the hydroxyl value of the branched polyphenylene ether with that of the terminally modified branched polyphenylene ether. Note that the terminally modified branched polyphenylene ether may have some hydroxyl groups that remain unmodified.

The reaction temperature, reaction time, the presence or absence of a catalyst, and the type of catalyst during modification can be designed as appropriate. Two or more types of compounds may be used as modification compounds.

When the specific polyphenylene ethers described above are used as components of a curable composition, they may be used alone or in combination of two or more types.

The ratio of phenols satisfying condition 1 to the total amount of raw phenols used in the synthesis of a given polyphenylene ether is preferably 1 to 50 mol %.

It is not necessary to use phenols that satisfy condition 2 above, but if they are used, the ratio of phenols that satisfy condition 2 to the total amount of raw material phenols is preferably 0.5 to 99 mol%, and more preferably 1 to 99 mol%.

<<Physical properties and characteristics of specific polyphenylene ethers>>
<Degree of branching>
The branched structure (degree of branching) of a given polyphenylene ether can be confirmed based on the following analytical procedure.

(Analysis Procedure)
After preparing polyphenylene ether chloroform solutions at intervals of 0.1, 0.15, 0.2, and 0.25 mg/mL, a graph of refractive index difference and concentration is created while feeding at 0.5 mL/min, and the refractive index increment dn/dc is calculated from the slope. Next, the absolute molecular weight is measured under the following device operating conditions. With reference to the chromatogram of the RI detector and the chromatogram of the MALS detector, a regression line is obtained by the least squares method from a logarithmic graph (conformation plot) of molecular weight and radius of gyration, and the slope is calculated.

(Measurement conditions)
Equipment name: HLC8320GPC
Mobile phase: Chloroform Column: TOSOH TSKguard column HHR-H
+ TSKgelGMHHR-H (2 bottles)
+TSKgelG2500HHR
Flow rate: 0.6mL/min.
Detector: DAWN HELEOS (MALS detector)
+ Optilab rEX (RI detector, wavelength 254 nm)
Sample concentration: 0.5 mg/mL
Sample solvent: Same as mobile phase. 5 mg of sample dissolved in 10 mL of mobile phase. Injection volume: 200 μL
Filter: 0.45 μm
STD Reagent: Standard polystyrene Mw 37,900
STD concentration: 1.5mg/mL
STD solvent: Same as mobile phase. 15 mg of sample is dissolved in 10 mL of mobile phase. Analysis time: 100 min.

For resins with the same absolute molecular weight, the more branching of the polymer chain progresses, the smaller the distance from the center of gravity to each segment (radius of gyration). Therefore, the slope of the logarithmic plot of absolute molecular weight and radius of gyration obtained by GPC-MALS indicates the degree of branching, with a smaller slope indicating a greater degree of branching. In the present invention, a smaller slope calculated from the above conformation plot indicates a greater amount of branching in the polyphenylene ether, and a larger slope indicates a lesser amount of branching in the polyphenylene ether.

In the specific polyphenylene ether constituting the curable composition of the present invention, the above slope is preferably less than 0.6, and is preferably 0.55 or less, 0.50 or less, 0.45 or less, 0.40 or less, or 0.35 or less. When the above slope is within this range, the polyphenylene ether is considered to have sufficient branching. The lower limit of the above slope is not particularly limited, but is, for example, 0.05 or more, 0.10 or more, 0.15 or more, or 0.20 or more.

The slope of the conformation plot can be adjusted by changing the temperature, amount of catalyst, stirring speed, reaction time, amount of oxygen supplied, and amount of solvent during the synthesis of polyphenylene ether. More specifically, by increasing the temperature, increasing the amount of catalyst, increasing the stirring speed, lengthening the reaction time, increasing the amount of oxygen supplied, and/or decreasing the amount of solvent, the slope of the conformation plot tends to become lower (the polyphenylene ether becomes more easily branched).

<Molecular weight of specific polyphenylene ether>
The predetermined polyphenylene ether constituting the curable composition of the present invention preferably has a number average molecular weight of 2,000 to 30,000, more preferably 5,000 to 30,000, even more preferably 8,000 to 30,000, and particularly preferably 8,000 to 25,000. By setting the molecular weight within such a range, it is possible to improve the film-forming property of the curable composition while maintaining the solubility in a solvent. Furthermore, the predetermined polyphenylene ether constituting the curable composition of the present invention preferably has a polydispersity index (PDI: weight average molecular weight/number average molecular weight) of 1.5 to 20.

In the present invention, the number average molecular weight and weight average molecular weight are measured by gel permeation chromatography (GPC) and converted using a calibration curve prepared using standard polystyrene.

<Hydroxyl value of specified polyphenylene ether>
The hydroxyl value of the predetermined polyphenylene ether constituting the curable composition of the present invention is preferably 15.0 or less, more preferably 2 or more and 10 or less, and further preferably 3 or more and 8 or less, when the number average molecular weight (Mn) is in the range of 2,000 to 30,000.

However, when the specified polyphenylene ether is a specified polyphenylene ether obtained by method 2, the hydroxyl value may be lower than the above value.

Solvent Solubility of Certain Polyphenylene Ethers
The specific polyphenylene ether constituting the curable composition of the present invention is preferably soluble in 100 g of cyclohexanone (more preferably 100 g of cyclohexanone, DMF and PMA) at 25° C. The solubility of 1 g of polyphenylene ether in 100 g of a solvent (e.g., cyclohexanone) means that when 1 g of polyphenylene ether is mixed with 100 g of a solvent, no turbidity or precipitation can be visually confirmed. It is more preferable that the specific polyphenylene ether is soluble in 1 g or more of cyclohexanone at 25° C. in 100 g of cyclohexanone.

The specific polyphenylene ether constituting the curable composition of the present invention has a branched structure, which improves the solubility in various solvents and the dispersibility and compatibility of the components in the composition. This allows each component of the composition to be uniformly dissolved or dispersed, making it possible to obtain a uniform cured product. As a result, the mechanical properties and other properties of the cured product are extremely excellent. In particular, the specific polyphenylene ethers can be crosslinked with each other. As a result, the mechanical properties and low thermal expansion properties of the obtained cured product are improved.

<<Method of Producing Prescribed Polyphenylene Ether>>
The specified polyphenylene ether constituting the curable composition of the present invention can be produced by applying a conventionally known method for synthesizing polyphenylene ether (polymerization conditions, the presence or absence of a catalyst, the type of catalyst, and the like), except for using a specific phenol as a raw material.

Next, an example of a method for producing this specific polyphenylene ether will be described.

A specific polyphenylene ether can be produced, for example, by preparing a polymerization solution containing a specific phenol, a catalyst, and a solvent (polymerization solution preparation step), passing oxygen through at least the solvent (oxygen supply step), and oxidatively polymerizing the phenol in the oxygen-containing polymerization solution (polymerization step).

The polymerization solution preparation step, oxygen supply step, and polymerization step are described below. Each step may be performed continuously, or a part or all of one step may be performed simultaneously with a part or all of another step, or a step may be interrupted and another step may be performed during that time. For example, an oxygen supply step may be performed during the polymerization solution preparation step or the polymerization step. In addition, the method for producing polyphenylene ether of the present invention may include other steps as necessary. Examples of other steps include a step of extracting the polyphenylene ether obtained by the polymerization step (for example, a step of performing reprecipitation, filtration, and drying), the above-mentioned modification step, etc.

<Polymerization solution preparation process>
The polymerization solution preparation step is a step of preparing a polymerization solution by mixing raw materials including phenols to be polymerized in the polymerization step described below. The raw materials for the polymerization solution include raw phenols, a catalyst, and a solvent.

(catalyst)
The catalyst is not particularly limited, and any suitable catalyst used in the oxidative polymerization of polyphenylene ether may be used.

Examples of catalysts include amine compounds and metal amine compounds consisting of a heavy metal compound such as copper, manganese, or cobalt and an amine compound such as tetramethylethylenediamine. In particular, to obtain a copolymer with a sufficient molecular weight, it is preferable to use a copper-amine compound in which a copper compound is coordinated to an amine compound. Only one type of catalyst may be used, or two or more types may be used.

The amount of catalyst contained is not particularly limited, but may be 0.1 to 0.6 mol % relative to the total amount of raw phenols in the polymerization solution.

Such catalysts may be dissolved in advance in a suitable solvent.

(solvent)
The solvent is not particularly limited, and may be any suitable solvent used in the oxidative polymerization of polyphenylene ether. It is preferable to use a solvent capable of dissolving or dispersing the phenolic compound and the catalyst.

Specific examples of the solvent include aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; halogenated aromatic hydrocarbons such as chloroform, methylene chloride, chlorobenzene, dichlorobenzene, and trichlorobenzene; nitro compounds such as nitrobenzene; methyl ethyl ketone (MEK), cyclohexanone, tetrahydrofuran, ethyl acetate, N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), propylene glycol monomethyl ether acetate (PMA), and diethylene glycol monoethyl ether acetate (CA). Only one type of solvent may be used, or two or more types may be used.

The solvent may include water or a solvent that is compatible with water.

The amount of solvent in the polymerization solution is not particularly limited and may be adjusted as appropriate.

(Other ingredients)
The polymerization solution may contain other raw materials as long as the effects of the present invention are not impaired.

<Oxygen supply step>
The oxygen supplying step is a step of bubbling an oxygen-containing gas into the polymerization solution.

The time for which oxygen gas is passed through and the oxygen concentration in the oxygen-containing gas used can be changed as appropriate depending on the air pressure, temperature, etc.

<Polymerization process>
The polymerization step is a step in which phenols in a polymerization solution are oxidatively polymerized under conditions in which oxygen is supplied to the polymerization solution.

Specific polymerization conditions are not particularly limited, but for example, the mixture may be stirred at 25 to 100°C for 2 to 24 hours.

When producing a specific polyphenylene ether through the steps described above, a specific method for introducing a functional group containing an unsaturated carbon bond into a branched polyphenylene ether can be understood by referring to the above-mentioned methods 1 and 2. That is, a specific polyphenylene ether having a functional group containing an unsaturated carbon bond can be obtained by using a specific type of raw material phenol or by further providing a step of modifying the terminal hydroxyl group (modification step) after the polymerization step.

<<<<<Components: Fillers (B1 and (B2)>>>>
The (B1) filler contained in the first curable composition and the resin layer of the present invention and the (B2) filler contained in the second curable composition and the resin layer of the present invention may be the same component or different components. Here, the (B1) filler and the (B2) filler will be collectively described as a filler.

Examples of the filler include inorganic fillers and organic fillers.
Examples of inorganic fillers that can be used include metal oxides such as silica, alumina, and titanium oxide; metal hydroxides such as aluminum hydroxide and magnesium hydroxide; clay minerals such as talc and mica; fillers having a ferovskite crystal structure such as barium titanate and strontium titanate; boron nitride, aluminum borate, barium sulfate, and calcium carbonate.
Examples of the organic filler that can be used include fluororesin fillers such as polytetrafluoroethylene (PTFE), tetrafluoroethylene/ethylene copolymer (ETFE), tetrafluoroethylene/perfluoroalkylvinyl ether copolymer (PFA), tetrafluoroethylene/hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), and polyvinyl fluoride (PVF); and hydrocarbon resin fillers such as cycloolefin polymer (COP) and cycloolefin copolymer (COC).

Among these, the filler component is preferably silica, taking into consideration low dielectric tangent and low thermal expansion. Below, we will explain silica, which is a preferred form of the filler component.

<<Silica>>
The average particle size of the silica is preferably 0.01 to 10 μm, more preferably 0.1 to 3 μm. Here, the average particle size can be determined as the median diameter (d50, volume basis) based on cumulative distribution from the measured particle size distribution value by a laser diffraction/scattering method using a commercially available laser diffraction/scattering particle size distribution measuring device.

It is also possible to use silica with different average particle sizes in combination. If you want to increase the silica loading, you can use silica with an average particle size of 1 μm or more in combination with nano-sized silica with an average particle size of less than 1 μm.

The silica may be surface-treated with a coupling agent. By treating the surface with a silane coupling agent, the dispersibility with polyphenylene ether can be improved. The affinity with organic solvents can also be improved.

As the silane coupling agent, for example, an epoxy silane coupling agent, a mercapto silane coupling agent, a vinyl silane coupling agent, etc. can be used. As the epoxy silane coupling agent, for example, γ-glycidoxypropyl trimethoxy silane, γ-glycidoxypropyl methyl dimethoxy silane, etc. can be used. As the mercapto silane coupling agent, for example, γ-mercaptopropyl triethoxy silane, etc. can be used. As the vinyl silane coupling agent, for example, vinyl triethoxy silane, etc. can be used.

The amount of silane coupling agent used may be, for example, 0.1 to 5 parts by mass, or 0.5 to 3 parts by mass, per 100 parts by mass of silica.

<<<<<Components: Other components (C1 and (C2)>>>>
The first curable composition and the resin layer may contain the other component (C1), and the second curable composition and the resin layer may contain the other component (C2). The other component (C1) and the other component (C2) may be the same or different. Here, the other component (C1) and the other component (C2) are collectively described as the other components.

Other components include conventionally known additives that can be blended into the first curable composition and the second curable composition. More specifically, it is preferable to include peroxides, crosslinking curing agents, elastomers, maleimide compounds, etc.

Furthermore, the other components may include, within a range that does not impair the effects of the present invention, components such as a flame retardancy improver (such as a phosphorus-based compound), cellulose nanofibers, polymer components (such as resin components such as cyanate ester resins, epoxy resins, and phenol novolac resins, and organic polymers such as unbranched polyphenylene ethers, polyimides, and polyamides), dispersants, thermosetting catalysts, thickeners, defoamers, antioxidants, rust inhibitors, and adhesion promoters.
These may be used alone or in combination of two or more.

<<<Peroxide>>>
When the above-mentioned specific polyphenylene ether has an unsaturated carbon bond, the curable composition or the curable resin laminate preferably contains a peroxide.

Peroxides include methyl ethyl ketone peroxide, methyl acetoacetate peroxide, acetylacetonate peroxide, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)butane, t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, di-t-butyl hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, 2,5-di Examples of peroxides include methyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-butene, acetyl peroxide, octanoyl peroxide, lauroyl peroxide, benzoyl peroxide, m-toluyl peroxide, diisopropyl peroxydicarbonate, t-butylene peroxybenzoate, di-t-butyl peroxide, t-butylperoxyisopropyl monocarbonate, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, etc. Only one type of peroxide may be used, or two or more types may be used.

Among these, peroxides with a one-minute half-life temperature of 130°C to 180°C are preferred from the standpoint of ease of handling and reactivity. Such peroxides have a relatively high reaction initiation temperature, so they are unlikely to promote curing when curing is not required, such as during drying, and do not impair the storage stability of the curable composition containing polyphenylene ether. In addition, they have low volatility, so they do not volatilize during drying or storage, and have good stability.

The content of the peroxide in the curable composition or the curable resin laminate is preferably 0.01 to 20 mass %, more preferably 0.05 to 10 mass %, and particularly preferably 0.1 to 10 mass %, of the total solid content of the curable composition or the curable resin laminate in terms of the total amount of peroxide. By keeping the total amount of peroxide within this range, it is possible to prevent deterioration of the film quality when formed into a coating film while ensuring sufficient effect at low temperatures.

If necessary, it may also contain azo compounds such as azobisisobutyronitrile and azobisisovaleronitrile, or radical initiators such as dicumyl and 2,3-diphenylbutane.

<<<Crosslinking curing agent>>>
When the predetermined polyphenylene ether has an unsaturated carbon bond, the curable composition or the curable resin laminate preferably contains a crosslinking type curing agent.

As the crosslinking type curing agent, one having good compatibility with polyphenylene ether is used, and examples thereof include polyfunctional vinyl compounds such as divinylbenzene, divinylnaphthalene, and divinylbiphenyl; vinylbenzyl ether compounds synthesized by the reaction of phenol with vinylbenzyl chloride; allyl ether compounds synthesized by the reaction of styrene monomer, phenol with allyl chloride; and further, trialkenyl isocyanurate. As the crosslinking type curing agent, trialkenyl isocyanurate, which has particularly good compatibility with polyphenylene ether, is preferred, and specifically, triallyl isocyanurate (hereinafter, TAIC (registered trademark)) and triallyl cyanurate (hereinafter, TAC) are preferred. These exhibit low dielectric properties and can increase heat resistance. In particular, TAIC (registered trademark) is preferred because of its excellent compatibility with polyphenylene ether.

As the crosslinking curing agent, a (meth)acrylate compound (methacrylate compound and acrylate compound) may be used. In particular, it is preferable to use a trifunctional to pentafunctional (meth)acrylate compound. As the trifunctional to pentafunctional methacrylate compound, trimethylolpropane trimethacrylate or the like may be used, while as the trifunctional to pentafunctional acrylate compound, trimethylolpropane triacrylate or the like may be used. The use of these crosslinking curing agents can improve heat resistance. Only one type of crosslinking curing agent may be used, or two or more types may be used.

When the components in the curable composition or curable resin laminate containing a specific polyphenylene ether contain a hydrocarbon group having an unsaturated carbon bond, it is possible to obtain a cured product with excellent dielectric properties, particularly by curing with a crosslinking curing agent.

In the curable composition or curable resin laminate, the blending ratio of the specific polyphenylene ether to the cross-linking curing agent (e.g., trialkenyl isocyanurate) is preferably 20:80 to 90:10, more preferably 30:70 to 90:10, in terms of solids ratio (specific polyphenylene ether:cross-linking curing agent). By setting the ratio in this range, a cured product with low dielectric properties and excellent heat resistance can be obtained.

<<<Maleimide compounds>>>
The maleimide compound is not particularly limited as long as it contains at least one maleimide group in one molecule.

The maleimide compound is
(1) monofunctional aliphatic/alicyclic maleimides,
(2) monofunctional aromatic maleimides,
(3) polyfunctional aliphatic/alicyclic maleimide,
(4) polyfunctional aromatic maleimides,
Examples include:

<<(1) Monofunctional Aliphatic/Alicyclic Maleimide>>
Examples of the monofunctional aliphatic/alicyclic maleimide (1) include N-methylmaleimide, N-ethylmaleimide, and the reaction product of maleimide carboxylic acid with tetrahydrofurfuryl alcohol disclosed in JP-A-11-302278.

<<(2) Monofunctional aromatic maleimide>>
Examples of the monofunctional aromatic maleimide (2) include N-phenylmaleimide and N-(2-methylphenyl)maleimide.

<<(3) Polyfunctional aliphatic/alicyclic maleimide>>
Examples of the polyfunctional aliphatic/alicyclic maleimide (3) include isocyanurate-skeleton polymaleimides such as N,N'-methylene bismaleimide, N,N'-ethylene bismaleimide, maleimide ester compounds having an isocyanurate skeleton obtained by dehydrating and esterifying tris(hydroxyethyl)isocyanurate with aliphatic/alicyclic maleimide carboxylic acid, and maleimide urethane compounds having an isocyanurate skeleton obtained by urethanizing tris(carbamate hexyl)isocyanurate with aliphatic/alicyclic maleimide alcohol, isophorone bisurethane bis(N-ethylmaleimide), triethylene glycol bis(maleimide ethyl carbamide), and the like. Examples of such compounds include aliphatic/alicyclic maleimide ester compounds obtained by dehydrating esterification of aliphatic/alicyclic maleimide carboxylic acids with various aliphatic/alicyclic polyols, or by transesterification of aliphatic/alicyclic maleimide carboxylic acid esters with various aliphatic/alicyclic polyols, aliphatic/alicyclic polymaleimide ester compounds obtained by subjecting aliphatic/alicyclic maleimide carboxylic acids to an ether ring-opening reaction with various aliphatic/alicyclic polyepoxides, and aliphatic/alicyclic polymaleimide urethane compounds obtained by subjecting aliphatic/alicyclic maleimide alcohols to a urethanization reaction with various aliphatic/alicyclic polyisocyanates.

Specific examples include aliphatic bismaleimide compounds represented by the following general formulas (X1) and (X2), which are obtained by subjecting maleimide alkyl carboxylic acid or maleimide alkyl carboxylic acid ester having an alkyl group having 1 to 6 carbon atoms, more preferably a linear alkyl group, to a dehydration esterification reaction or an ester exchange reaction with polyethylene glycol having a number average molecular weight of 100 to 1000 and/or polypropylene glycol having a number average molecular weight of 100 to 1000 and/or polytetramethylene glycol having a number average molecular weight of 100 to 1000.

(In the formula, m is an integer of 1 to 6, n is a value of 2 to 23, and R1 represents a hydrogen atom or a methyl group.)

(In the formula, m represents an integer of 1 to 6, and p represents a value of 2 to 14.)

<<(4) Polyfunctional aromatic maleimide>>
Examples of the polyfunctional aromatic maleimide (4) include N,N'-(4,4'-diphenylmethane)bismaleimide, bis-(3-ethyl-5-methyl-4-maleimidophenyl)methane, 2,2'-bis-(4-(4-maleimidophenoxy)propane, N,N'-(4,4'-diphenyloxy)bismaleimide, N,N'-p-phenylene bismaleimide, N,N'-m-phenylene bismaleimide, N,N'-2,4-tolylene bismaleimide, and N,N'-2,6-tolylene bismaleimide. Examples of such compounds include aromatic polymaleimide ester compounds obtained by dehydrating esterification of maleimide carboxylic acid with various aromatic polyols, or by transesterification reaction of maleimide carboxylic acid esters with various aromatic polyols; aromatic polymaleimide ester compounds obtained by ring-opening reaction of maleimide carboxylic acid with various aromatic polyepoxides; and aromatic polymaleimide urethane compounds obtained by urethanization reaction of maleimide alcohol with various aromatic polyisocyanates.

Among these, it is preferable that the maleimide compound is polyfunctional. It is preferable that the maleimide compound has a bismaleimide skeleton. The maleimide compounds can be used alone or in combination of two or more.

The weight average molecular weight of the maleimide compound is not particularly limited, but can be 100 or more, 200 or more, 500 or more, 750 or more, 1,000 or more, 2000 or more, or 100,000 or less, 50,000 or less, 10,000 or less, 5,000 or less, 4,000 or less, or 3,500 or less.

The content of the maleimide compound can typically be 0.5 to 50 mass %, 1 to 40 mass %, or 1.5 to 30 mass % based on the total solid content in the curable composition or the curable resin laminate.
From another viewpoint, the blending ratio of the predetermined polyphenylene ether to the maleimide compound in the curable composition or the curable resin laminate can be, in terms of solid content ratio, 9:91 to 99:1, 17:83 to 95:5, or 25:75 to 90:10.
Furthermore, when the curable composition or the curable resin laminate contains a maleimide compound and a cross-linking curing agent, the blending ratio of the maleimide compound to the cross-linking curing agent, expressed as a solids ratio (maleimide compound:cross-linking curing agent), is preferably 80:20 to 10:90, and more preferably 70:30 to 20:80. By setting the ratio within such a range, a cured product having low dielectric properties and excellent heat resistance can be obtained.

<<<Elastomer>>>
Examples of the elastomer include diene-based synthetic rubbers such as polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, polychloroprene rubber, nitrile rubber, and ethylene-propylene rubber; non-diene-based synthetic rubbers such as ethylene-propylene rubber, butyl rubber, acrylic rubber, polyurethane rubber, fluororubber, silicone rubber, and epichlorohydrin rubber; natural rubber, styrene-based elastomers, olefin-based elastomers, urethane-based elastomers, polyester-based elastomers, polyamide-based elastomers, acrylic elastomers, and silicone-based elastomers.

From the viewpoint of compatibility with polyphenylene ether and dielectric properties, at least a part of the elastomer is preferably a styrene-based elastomer. Examples of styrene-based elastomers include styrene-butadiene copolymers such as styrene-butadiene-styrene block copolymer and styrene-butadiene-butylene-styrene block copolymer; styrene-isoprene copolymers such as styrene-isoprene-styrene block copolymer; styrene-ethylene-butylene-styrene block copolymer and styrene-ethylene-propylene-styrene block copolymer. Styrene-based elastomers that do not have unsaturated carbon bonds, such as styrene-ethylene-butylene-styrene block copolymer, are preferred because the dielectric properties of the resulting cured product are particularly good.

The content ratio of the styrene block in the styrene-based elastomer is preferably 10 to 70 mass %, 30 to 60 mass %, or 40 to 50 mass %. The content ratio of the styrene block can be determined from the integral ratio of the spectrum measured by ¹ H-NMR.

Here, the raw material monomers for styrene-based elastomers include not only styrene but also styrene derivatives such as α-methylstyrene, 3-methylstyrene, 4-propylstyrene, and 4-cyclohexylstyrene.

The content of styrene-based elastomer in 100% by weight of elastomer may be, for example, 10% by weight or more, 20% by weight or more, 30% by weight or more, 40% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, or 100% by weight.

The elastomer may have functional groups (including bonds) that react with other components.

For example, the reactive functional group may have an unsaturated carbon bond. By configuring the elastomer in this way, it is possible to crosslink the unsaturated carbon bonds (for example, the unsaturated carbon bonds of branched polyphenylene ether), which has the effect of reducing the risk of bleed-out.

The elastomer may be modified with (meth)acrylic acid, maleic acid, or anhydrides or esters thereof. It may also be obtained by adding water to the remaining unsaturated bonds of a diene-based elastomer.

The number average molecular weight of the elastomer may be 1,000 to 150,000. If the number average molecular weight is equal to or greater than the lower limit, the elastomer has excellent low thermal expansion properties, and if the number average molecular weight is equal to or less than the upper limit, the elastomer has excellent compatibility with other components.

The content of the elastomer in the curable composition or curable resin laminate may be 10 to 300 parts by mass per 100 parts by mass of the specified polyphenylene ether. Alternatively, the content of the elastomer may be 3 to 65% by mass based on the total solid content in the curable composition or curable resin laminate. When the content is within the above range, a good balance of good tensile properties, adhesion, and heat resistance can be achieved.

<<<<<<<Effects of curable resin laminate>>>>>>>
The curable resin laminate of the present invention is placed on an object to be adhered (such as copper foil) so that the second resin layer and the object to be adhered are in contact with each other, and then heated and pressed, so that the second resin layer fills the uneven parts of the object to be adhered (such as copper foil) without any gaps. The curable resin laminate is then cured, whereby a crosslinking reaction occurs at the interfaces between the first resin layer, the second resin layer, and the resin layers, and the object to be adhered and the curable resin laminate are firmly adhered to each other, resulting in excellent peel strength.

<<<<<<<Method for producing curable resin laminate>>>>>>>
<<<<<<Raw materials>>>>>
The curable resin laminate can be obtained by diluting the above-mentioned first curable composition and second curable composition with a solvent or the like as necessary to form a solution, applying the solution onto a base film or a substrate, and drying the solution.

The amount of solvent used to dilute the curable composition is not particularly limited and can be adjusted as appropriate depending on the application and desired viscosity of the curable composition.

<<<<<Solvent>>>>
Examples of solvents that can be used in the curable composition of the present invention include conventionally usable solvents such as chloroform, methylene chloride, and toluene, as well as relatively safe solvents such as N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), cyclohexanone, propylene glycol monomethyl ether acetate (PMA), diethylene glycol monoethyl ether acetate (CA), methyl ethyl ketone, and ethyl acetate. The solvent may be N,N-dimethylformamide (DMF). Only one type of solvent may be used, or two or more types may be used.

＜＜＜＜＜Manufacturing process＞＞＞＞＞
An example of a process for producing the curable resin laminate will be described below.

<<<<< Dry film >>>>>
The dry film of the present invention is characterized in that at least one surface of the curable resin laminate is supported or protected by a film.

The film (substrate film) that serves as the support is not particularly limited, and can be a metal foil such as copper foil, a polyimide film, a polyester film, a polyethylene naphthalate (PEN) film, or other film. These films can also be used as a support or cover film for a dry film.

A method for producing a dry film can be, for example, to apply a solution of the second curable composition onto a base film using an applicator or the like, and dry the solution to form a second resin layer, and then apply a solution of the first curable composition onto the second resin layer, and dry the solution to form a first resin layer, thereby forming a dry film having a two-layer curable resin laminate in which the second resin layer and the first resin layer are laminated in sequence on the base film.
Furthermore, by further forming a second resin layer on the first resin layer of the two-layer curable resin laminate, a dry film having a three-layer curable resin structure having the second resin layer on both sides of the first resin layer can be formed.

After forming the resin layer, a process of providing other layers (e.g., a cover film) may be carried out as necessary.

Instead of laminating resin layers in order on the substrate film as described above, a dry film having a curable resin laminate can be produced by first preparing a first dry film having a first resin layer and/or a second dry film having a second resin layer, bonding these together, and then peeling off the substrate film and bonding them together to produce a dry film having a structure in which the two-layer curable resin laminate or the three-layer curable resin laminate is sandwiched between substrate films.

The application and drying of the curable composition can be carried out by known methods and conditions. For example, a curable composition of uniform thickness can be obtained by known application methods such as a comma coater, blade coater, lip coater, rod coater, squeeze coater, reverse coater, transfer roll coater, gravure coater, spray coater, etc.

The coating of the curable composition obtained by coating is then dried by heating at a temperature of 60 to 130°C for 1 to 30 minutes to form a resin layer consisting of a dried coating. Heat drying can be carried out by known heating means such as a hot air circulation drying oven, an IR oven, a hot plate, or a convection oven.

The thickness of the resin layer can be adjusted by changing the coating conditions and the viscosity of the curable composition.

<<<<<<<<Method and applications of curable resin laminate>>>>>>>
As an example, the curable resin laminate of the present invention is formed on a suitable substrate so that the second resin layer is the surface layer side, and then a conductor layer (such as copper foil) is pressure-bonded to the second resin layer. As a method for forming the curable resin laminate on a substrate, the first curable composition and the second curable composition may be applied to the substrate and dried, or the curable resin laminate may be formed on the substrate in the form of the above-mentioned dry film.

As for substrates, in addition to printed wiring boards and flexible printed wiring boards with pre-formed circuits, other substrates that can be used include paper-phenolic resin, paper-epoxy resin, glass cloth-epoxy resin, glass-polyimide, glass cloth/non-woven cloth-epoxy resin, glass cloth/paper-epoxy resin, synthetic fiber-epoxy resin, copper-clad laminates of all grades (such as FR-4) using composite materials such as fluororesin, polyethylene, PPO, and cyanate ester, polyimide film, PET film, glass substrates, ceramic substrates, and wafer plates.

When forming on a substrate by coating and drying, for example, a solution of a first curable composition is coated on a substrate and dried to form a first resin layer, and then a solution of a second curable composition is coated on the first resin layer and dried to form a second resin layer, thereby forming a curable resin laminate in which the first resin layer and the second resin layer are laminated in this order on the substrate.

Coating and drying on the substrate can be carried out by known methods and conditions, and the same coating and drying methods as those used in the dry film manufacturing method described above can be used.

When forming on a substrate in the form of a dry film, for example, in the case of a dry film having two layers of a curable resin laminate sandwiched between base films, the base film in contact with the first resin layer is peeled off, and then the first resin layer is placed so as to be in contact with the substrate. Next, using a vacuum laminator or the like, the dry film is laminated on the substrate by heating and pressurizing from the side of the base film in contact with the second resin layer, and after cooling to room temperature, the surface base film is peeled off, thereby forming a curable resin laminate in which the first resin layer and the second resin layer are laminated on the substrate in this order.

The lamination of the dry film onto the substrate can be carried out by known methods and conditions. Among them, it is preferable to use a vacuum laminator because it does not generate voids, etc., and lamination can be performed at a temperature of 80 to 160°C for a time of 10 to 120 seconds.

Then, a coating object such as copper foil is placed on the second resin layer, which is the surface layer of the curable resin laminate, and a conductor layer is formed on the second resin layer by applying heat and pressure using a vacuum laminator or vacuum press. The curable resin laminate is then thermally cured by an appropriate method.

In the heat curing process, for example, the curable resin laminate is heated in a hot air circulating drying oven at 100 to 220°C for 30 to 120 minutes, causing a heat curing reaction and forming a cured product.

The curable resin laminate and dry film of the present invention are suitable for use in forming an insulating film on a circuit board, and are suitable for forming an interlayer adhesive, an electromagnetic wave shielding layer, or an interlayer insulating layer.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following in any way.

<<Synthesis of PPE resin>>
<Synthesis of PPE-1 (branched PPE resin)>
In a 3L two-necked flask, 2.6 g of di-μ-hydroxo-bis[(N,N,N',N'-tetramethylethylenediamine)copper(II)] chloride (Cu/TMEDA) and 3.18 mL of tetramethylethylenediamine (TMEDA) were added and thoroughly dissolved, and oxygen was supplied at 10 ml/min. A raw material solution was prepared by dissolving 105 g of 2,6-dimethylphenol and 13 g of 2-allylphenol, which are raw material phenols, in 1.5 L of toluene. This raw material solution was dropped into the flask and reacted at 40°C for 6 hours while stirring at a rotation speed of 600 rpm. After the reaction was completed, the product was reprecipitated in a mixture of 20 L of methanol and 22 mL of concentrated hydrochloric acid, filtered, and dried at 80°C for 24 hours to obtain PPE-1, a branched PPE resin.

The number average molecular weight of PPE-1 was 20,000 and the weight average molecular weight was 60,000.

The slope of the conformational plot of PPE-1 was 0.31.

<Synthesis of PPE-2 (branched PPE resin)>
2.6 g of di-μ-hydroxo-bis[(N,N,N',N'-tetramethylethylenediamine)copper(II)] chloride (Cu/TMEDA) and 3.18 mL of tetramethylethylenediamine (TMEDA) were added to a 3 L two-necked flask and thoroughly dissolved, and oxygen was supplied at 10 ml/min. 105 g of 2,6-dimethylphenol and 4.89 g of orthocresol, which are raw material phenols, were dissolved in 1.5 L of toluene to prepare a raw material solution. This raw material solution was dropped into the flask and reacted at 40°C for 6 hours while stirring at a rotation speed of 600 rpm. After the reaction was completed, the product was reprecipitated in a mixture of 20 L of methanol and 22 mL of concentrated hydrochloric acid, filtered, and dried at 80°C for 24 hours to obtain a branched PPE resin.

50 g of branched PPE resin, 4.8 g of allyl bromide as a modifying compound, and 300 mL of NMP were added to a 1 L two-necked flask equipped with a dropping funnel and stirred at 60°C. 5 mL of 5 M NaOH aqueous solution was added dropwise to the solution. After that, it was further stirred at 60°C for 5 hours. Next, the reaction solution was neutralized with hydrochloric acid, and then reprecipitated in 5 L of methanol and filtered. It was washed three times with a mixture of methanol and water in a mass ratio of 80:20, and then dried at 80°C for 24 hours to obtain PPE-2, a branched PPE resin.

The number average molecular weight of PPE-2 was 19,000 and the weight average molecular weight was 66,500.

The slope of the conformational plot of PPE-2 was 0.33.

The number average molecular weight (Mn) and weight average molecular weight (Mw) of each PPE resin were determined by gel permeation chromatography (GPC). In GPC, Shodex K-805L was used as the column, the column temperature was 40°C, the flow rate was 1 mL/min, the eluent was chloroform, and the standard substance was polystyrene.

<Solubility of PPE resin in solvent>
The solvent solubility of each PPE resin was confirmed.

Branched PPE resins 1 and 2 were soluble in cyclohexanone.
<<<Preparation of Curable Composition/Creation of Dry Film>>>
Varnishes and dry films of the curable compositions according to the respective Examples and Comparative Examples were obtained as follows.
<<Example 1>>
<Preparation of curable composition for first resin layer>
PPE-1: 100 parts by mass and styrene elastomer (Asahi Kasei Corporation: product name "H1051"): 49 parts by mass were mixed and stirred at 40 ° C for 30 minutes to completely dissolve. TAIC (manufactured by Mitsubishi Chemical Corporation): 60 parts by mass as a crosslinking curing agent, spherical silica filler (manufactured by Admatechs Co., Ltd.: product name "SC2500-SVJ"): 534 parts by mass, and maleimide resin (manufactured by Designer Molecules: product name "BMI-3000J", Mw = 3,000): 16 parts by mass were added to the PPE resin solution obtained by this, and mixed, and then dispersed with a three-roll mill. Finally, 3 parts by mass of α,α'-bis(t-butylperoxy-m-isopropyl)benzene (manufactured by NOF Corporation: product name "Perbutyl P-40"), which is a peroxide, was added and stirred with a magnetic stirrer. In this manner, a varnish of the curable composition for the first resin layer of Example 1 was obtained.

<Preparation of First Resin Layer (Dry Film Having First Resin Layer)>
Next, the varnish of the curable composition for the first resin layer of Example 1 was applied with an applicator onto a 100 μm thick PET film (manufactured by Toyobo Co., Ltd.: product name "TN-200") so that the thickness of the resin layer after drying would be 29 μm, and then dried at 90° C. for 5 minutes to prepare a dry film including the first resin layer of Example 1. In addition, for melt viscosity measurement, a dry film was prepared under the same conditions as above so that the thickness of the resin layer after drying would be 25 μm.

<Measurement of Melt Viscosity of First Resin Layer>
20 dry films each having a thickness of 25 μm of the first resin layer of Example 1 described above were prepared, and using a vacuum laminator MVLP-500 manufactured by Meiki Seisakusho, lamination was performed so that the resin layers were in contact with each other, and the PET film was repeatedly peeled off to prepare a melt viscosity measurement test piece having a resin layer thickness of 500 μm. The melt viscosity at 140 ° C. was measured using this test piece with a rheometer (MARS 40) manufactured by HAAKE under the conditions of oscillation heating method (5 ° C. / min.), measurement temperature range: 70 to 200 ° C., frequency: 1 Hz, stress control: 3 Pa, parallel plate: 20 mm, gap: 450 μm, sample size: 2.5 × 2.5 cm.

<Preparation of curable composition for second resin layer>
A varnish of the curable composition for the second resin layer of Example 1 was obtained in the same manner as in the above-mentioned first resin layer curable composition, except that the content of the spherical silica filler was 0 parts by mass.

<Preparation of second resin layer (dry film having second resin layer)>
Next, the varnish of the curable composition for the second resin layer of Example 1 was applied to a PET film having a thickness of 100 μm with an applicator so that the thickness of the resin layer after drying was 2 μm, and then dried at 90° C. for 5 minutes to prepare a dry film having the second resin layer of Example 1. In addition, for melt viscosity measurement, a dry film was prepared under the same conditions as above so that the thickness of the resin layer after drying was 25 μm.

<Measurement of Melt Viscosity of Second Resin Layer>
Twenty dry films each having the second resin layer of Example 1 with a thickness of 25 μm were prepared, and the melt viscosity at 140° C. was measured in the same manner as in the melt viscosity measurement of the first resin layer described above.

<Preparation of Curable Resin Laminate (Dry Film Having First Resin Layer and Second Resin Layer)>
A dry film having the above-mentioned first resin layer with a thickness of 29 μm and a dry film having the second resin layer with a thickness of 2 μm were arranged so that the resin layers were in contact with each other, and were bonded together using a vacuum laminator MVLP-500 manufactured by Meiki Seisakusho to obtain the dry film of Example 1.

<<Examples 2-13, Comparative Examples 1-5>>
Curable compositions for the first and second resin layers were prepared in the same manner as in Example 1, except that the components and contents were set to the values shown in the table. The melt viscosities of the first and second resin layers according to Examples 2-13 and Comparative Examples 1-5 were measured, and dry films each including a first resin layer and a second resin layer were produced.

<<Example 14>>
After bonding a dry film having a first resin layer and a dry film having a second resin layer, the PET film on the first resin layer side was peeled off, and a dry film having a second resin layer was further bonded to produce the dry film of Example 14.

<<Comparative Example 6-12>>
A dry film including a first resin layer was produced, and the melt viscosity of each of Comparative Examples 6 to 12 was measured. A PET film was attached to the resin layer so as to be in contact with the dry film, and a dry film according to Comparative Example 6 to 12 was produced.

<<<Preparation of cured product>>>
After peeling off the PET film on the first resin layer side of each dry film of the Examples and Comparative Examples, the dry film was placed so that the first resin layer was in contact with the glossy side of a low-roughness copper foil (FV-WS (manufactured by Furukawa Electric Co., Ltd.): Rz = 1.2 μm), and laminated with a vacuum laminator. Next, after peeling off the remaining PET film, the oven was completely filled with nitrogen using an inert oven, and the temperature was raised to 200°C and cured for 60 minutes to obtain each cured film of the Examples and Comparative Examples.

It was not possible to produce a cured film using the dry film of Comparative Example 3.

<<<<Evaluation>>>
The cured films of the above-mentioned cured products were evaluated as follows.

<<CTE: Coefficient of thermal expansion>>
The cured film was cut into a length of 3 cm and a width of 0.3 cm, and measured using a TMA (Thermomechanical Analysis) Q400 manufactured by TA Instruments in tension mode with a chuck distance of 16 mm, a load of 30 mN, and in a nitrogen atmosphere, by raising the temperature from 20 to 250° C. at a rate of 5° C./min, and then lowering the temperature from 250 to 20° C. at a rate of 5° C./min. The average thermal expansion coefficient from 100° C. to 50° C. during the temperature decrease was determined.

<<Young's modulus and breaking strain>>
The cured film was cut into a piece 8 cm long and 0.5 cm wide, and the Young's modulus and breaking strain were measured under the following conditions.
The Young's modulus was determined from the slope of the strain at a stress range of 5 MPa to 10 MPa in the obtained stress-strain diagram.
[Measurement conditions]
Testing machine: Tensile testing machine EZ-SX (manufactured by Shimadzu Corporation)
Distance between chucks: 50 mm
Test speed: 1 mm/min
Elongation calculation: (tensile movement amount/chuck distance) x 100

<<Dielectric constant>>
The relative dielectric constant Dk and the dielectric loss tangent Df were measured according to the following method.
The cured film was cut into a length of 80 mm and a width of 45 mm and used as a test piece for measurement by the SPDR (Split Post Dielectric Resonator) resonator method. The measurement equipment used was a vector network analyzer E5071C manufactured by Keysight Technologies, LLC, an SPDR resonator, and a calculation program manufactured by QWED. The conditions were a frequency of 10 GHz and a measurement temperature of 25°C.

<<Peel strength>>
The surface of the copper-clad laminate of solid copper (whole copper foil) was pretreated with CZ-8100 manufactured by MEC. Next, the PET film on the first resin layer side of the dry film of Example 1-13 and Comparative Example 1-3, and the PET film on one side of Example 14 and Comparative Example 4-10 were peeled off, and the exposed resin layer and the treated surface were bonded together with a vacuum laminator so that they were in contact with each other. Thereafter, the remaining PET film was peeled off, and the rough surface of the low-roughness copper foil (FV-WS (manufactured by Furukawa Electric Co., Ltd.): Rz = 1.2 μm) was bonded to the exposed resin layer with a vacuum laminator so that it was in contact with the exposed resin layer. The substrate was then completely filled with nitrogen using an inert oven, heated to 200 ° C., and cured for 60 minutes to prepare a peel strength evaluation substrate.
A cut 10 mm wide and 100 mm long was made in the low-roughness copper foil portion of the above-mentioned peel strength evaluation substrate, one end of which was peeled off and gripped with a gripper, and 90° peel strength was measured under the following conditions.
[Measurement conditions]
Testing machine: Tensile testing machine EZ-SX (manufactured by Shimadzu Corporation)
Test speed: 1 mm/min

Claims (4)

A curable resin laminate having a first resin layer and a second resin layer laminated on at least one of the main surfaces of the first resin layer,
the second resin layer has a thickness of 5 to 35% of the total thickness of the first resin layer and the second resin layer;
the first resin layer contains (A1) polyphenylene ether and (B1) a filler,
the second resin layer contains (A2) polyphenylene ether and has a melt viscosity (MV ₂ ) at 140° C. of 40,000 dPa·s or less;
a melt viscosity (MV ₁ ) of the first resin layer at 140° C. and a melt viscosity (MV ₂ ) of the second resin layer at 140° C. have a relationship of MV ₁ >MV ₂ ;
The curable resin laminate, wherein the (A1) polyphenylene ether and the (A2) polyphenylene ether are obtained from raw material phenols containing at least a phenol satisfying condition 1, and are polyphenylene ethers having a slope calculated in a conformation plot of less than 0.6.
(Condition 1)
Contains hydrogen atoms at the ortho and para positions A dry film having the curable resin laminate according to claim 1. A cured product obtained by curing the curable resin laminate according to claim 1 or the curable resin laminate of the dry film according to claim 2 . An electronic component having the cured product of claim 3.