JP7509162B2 - Method for manufacturing printed wiring board - Google Patents

Description

The present invention relates to a method for manufacturing a printed wiring board.

Printed wiring boards are widely used in various electronic devices. In order to miniaturize electronic devices and improve their functionality, printed wiring boards are required to have finer and denser circuit wiring. Here, a known method for manufacturing printed wiring boards is a build-up method in which insulating layers and conductor layers are alternately stacked on an inner layer substrate. The insulating layer is formed, for example, by forming a resin composition layer containing a resin composition on the inner layer substrate and thermally curing the resin composition layer (Patent Documents 1 and 2).

JP 2002-167427 A JP 2013-75948 A

One method for forming an insulating layer of a printed wiring board is to use a resin sheet. In this method, a resin sheet having a support and a resin composition layer is prepared, the resin composition layer is laminated on an inner layer substrate, and the resin composition layer is thermally cured to obtain an insulating layer. In this method, the resin composition layer is thermally cured while the resin composition layer is in contact with the support, and the support may be peeled off after the thermal curing. For example, in order to prevent the insulating layer from being damaged when a via hole is formed by irradiation with laser light, the resin composition layer may be thermally cured to form an insulating layer, and then a via hole may be formed in the insulating layer, after which the support may be peeled off.

The resin composition layer may be thermally cured in a nitrogen atmosphere. For example, if the resin composition layer is thermally cured in an air atmosphere, the components contained in the resin composition layer may be deteriorated by oxidation. In contrast, if the resin composition layer is thermally cured in a nitrogen atmosphere, the deterioration due to oxidation can be suppressed, and an insulating layer with excellent dielectric and mechanical properties can be formed.

However, when the resin composition layer is thermally cured under a nitrogen atmosphere without peeling off the support, peeling failure may occur between the insulating layer obtained by curing the resin composition layer and the support. As a result of the inventor's investigation, it was found that the above-mentioned peeling failure occurs when the resin composition layer contains an imidazole-based compound and the support has a release layer containing a (meth)acrylic resin.

The present invention was devised in consideration of the above problems, and aims to provide a method for manufacturing a printed wiring board that can produce a printed wiring board while suppressing peeling defects between the insulating layer and the support.

The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result, have found that the above-mentioned problems can be solved when the thermal curing of the resin composition layer includes changing the curing temperature to cure the resin composition layer in stages, thereby completing the present invention.
That is, the present invention includes the following.

[1] (I) A step of laminating a resin sheet including a support having a release layer and a resin composition layer formed on the release layer of the support to an inner layer substrate such that the resin composition layer is bonded to the inner layer substrate;
(II) a step of thermally curing the resin composition layer under a nitrogen atmosphere; and (III) a step of peeling off the support.
A method for producing a printed wiring board, comprising, in this order:
the release layer comprises a (meth)acrylic resin;
the resin composition layer includes a resin composition including an imidazole-based compound;
A method for manufacturing a printed wiring board, wherein the thermal curing of the resin composition layer includes, in this order, subjecting the resin composition layer to a heat treatment in which it is held at a temperature T1, and subjecting it to a heat treatment in which it is held at a temperature T2 higher than the temperature T1.
[2] The method for producing a printed wiring board according to [1], wherein the resin composition contains a thermosetting resin.
[3] The method for producing a printed wiring board according to [2], wherein the thermosetting resin comprises at least one selected from the group consisting of an epoxy resin, a phenolic resin, an active ester resin, a carbodiimide resin, an acid anhydride resin, an amine resin, a benzoxazine resin, a cyanate ester resin, and a thiol resin.
[4] The method for producing a printed wiring board according to any one of [1] to [3], wherein the temperature T2 is 150° C. or higher.
[5] The method for producing a printed wiring board according to any one of [1] to [4], wherein the difference T2-T1 between the temperature T1 and the temperature T2 is 20° C. or more.
[6] The method for producing a printed wiring board according to any one of [1] to [5], wherein the temperature T1 is 50° C. or higher.
[7] The method for producing a printed wiring board according to any one of [1] to [6], wherein the step (II) includes heating the resin composition layer to a temperature T2 at a heating rate of 0.5 ° C./min or more and 30 ° C./min or less.

According to the present invention, it is possible to manufacture a printed wiring board while suppressing peeling defects between the insulating layer and the support.

The present invention will be described below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and may be modified as desired without departing from the scope of the claims and their equivalents.

In the following description, unless otherwise specified, "long" refers to a film or sheet shape having a length 10 or more times its width. The length is preferably 20 or more times its width, and specifically may be long enough to be wound into a roll for storage or transportation. There is no particular upper limit to the length, and it may be, for example, 100,000 or less times its width.

[Outline of the method for manufacturing printed wiring boards]
In a method for producing a printed wiring board according to an embodiment of the present invention, a printed wiring board is produced using a resin sheet including a support having a release layer and a resin composition layer formed on the release layer of the support. Specifically, the method for producing a printed wiring board according to this embodiment includes the following steps:
(I) laminating a resin sheet onto an inner layer substrate such that the resin composition layer is bonded to the inner layer substrate;
(II) a step of thermally curing the resin composition layer under a nitrogen atmosphere; and (III) a step of peeling off the support.
In this method, the insulating layer is formed by curing the resin composition layer, so that a printed wiring board including the insulating layer can be manufactured.

The release layer of the support contains a (meth)acrylic resin. The resin composition layer contains a resin composition containing an imidazole-based compound. The thermal curing of the resin composition layer in step (II) includes subjecting the resin composition layer to a heat treatment in which it is held at a temperature T1, and then subjecting it to a heat treatment in which it is held at a temperature T2 higher than the temperature T1.

Conventionally, when a release layer containing a (meth)acrylic resin was combined with a resin composition containing an imidazole-based compound and then heat-treated under a nitrogen atmosphere, peeling failure occurred between the insulating layer and the support. Specifically, when attempting to peel off the support, adhesion occurred between the insulating layer and the support, and the insulating layer or the support could be damaged. In contrast, when the conditions for thermal curing in step (II) are controlled as in the present embodiment, peeling failure between the insulating layer and the support can be suppressed.

The inventors speculate that the mechanism by which peeling defects can be suppressed as described above is as follows. However, the technical scope of the present invention is not limited to the mechanism described below.

If the resin composition layer is thermally cured in air, the catalytic activity of the imidazole-based compound is suppressed by oxygen and carbon dioxide contained in the air. However, if the resin composition layer is thermally cured in a nitrogen atmosphere, the catalytic activity of the imidazole-based compound is not suppressed. Therefore, in the past, the catalytic activity of the imidazole-based compound caused a reaction between the (meth)acrylic resin contained in the release layer and one or more components contained in the resin composition, which resulted in adhesion between the release layer and the resin composition layer. According to the inventor's investigation, it is presumed that the (meth)acrylic resin in the release layer reacts with the thermosetting resin that may be contained in the resin composition, and in particular reacts significantly with the epoxy resin, phenol resin, and active ester resin. The inventor presumes that this adhesion was one of the causes of the conventional peeling failure.

In contrast, in the method for manufacturing a printed wiring board according to the present embodiment, the temperature is raised stepwise, including holding at temperature T1 and holding at a temperature T2 higher than temperature T1, to cure the resin composition layer stepwise. In such stepwise curing, the reaction between the components contained in the resin composition layer proceeds preferentially over the reaction between the (meth)acrylic resin contained in the release layer and the components contained in the resin composition. For example, as a result of the reaction between the components contained in the resin composition layer proceeding at temperature T1, the amount of reactive components in the resin composition layer decreases. Therefore, at temperature T2, the degree of reaction between the (meth)acrylic resin contained in the release layer and the components contained in the resin composition layer decreases. Therefore, adhesion between the release layer and the resin composition layer can be suppressed, and peeling failure can be suppressed.

[Resin sheet]
The resin sheet used in the method for producing a printed wiring board according to one embodiment of the present invention comprises a support having a release layer, and a resin composition layer provided on the release layer of the support.

- Support -
The support usually comprises a support substrate, and a release layer on the support substrate. Examples of the support substrate include a thermoplastic resin film, a metal foil, and a release paper, and the thermoplastic resin film and the metal foil are preferred.

When a thermoplastic resin film is used as the support substrate, examples of the thermoplastic resin include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), acrylics such as polycarbonate (PC) and polymethyl methacrylate (PMMA), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, polyimide, etc. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, and inexpensive polyethylene terephthalate is particularly preferred.

When a metal foil is used as the support substrate, examples of the metal foil include copper foil and aluminum foil, with copper foil being preferred. As the copper foil, a foil made of a single metal, copper, or an alloy of copper and another metal (e.g., tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.) may be used.

The support substrate may have been subjected to a surface treatment such as matte treatment, corona treatment, or antistatic treatment on the surface on the release layer side.

The thickness of the support substrate is not particularly limited, but is preferably in the range of 5 μm to 75 μm, and more preferably in the range of 10 μm to 60 μm.

The release layer contains a (meth)acrylic resin. In this specification, "(meth)acrylic resin" includes (meth)acrylic compounds and polymers thereof. In addition, "(meth)acrylic compounds" include acrylic compounds containing an acryloyl group, methacryloyl compounds containing a methacryloyl group, and combinations thereof.

In general, the release layer is formed using a release agent. The release agent usually contains a release compound as a compound capable of imparting releasability, and may further contain any resin other than the release compound as necessary. Thus, in one example, the release layer formed using the release agent contains a release compound, and may further contain any resin as necessary. In another example, the release layer formed using the release agent may be formed by bonding some or all of the components contained in the release agent through reactions such as polymerization reactions and crosslinking reactions, and curing the release agent. Thus, in this example, the release layer may contain the release compound and any resin contained in the release agent, as well as their reaction products (e.g., polymers). The (meth)acrylic resin may be contained as a release compound, may be contained as any resin, or may be contained as a reaction product thereof.

The release compound refers to a compound that can exert a function of lowering the surface free energy of the release layer or lowering the static friction coefficient of the release layer. Therefore, the (meth)acrylic resin as the release compound can be a (meth)acrylic resin that can exert the above-mentioned functions.

Examples of (meth)acrylic resins as releasing compounds include (meth)acrylic resins containing long-chain alkyl groups and (meth)acrylic resins containing fluorine atoms.

A long-chain alkyl group generally refers to an alkyl group having 12 or more carbon atoms, preferably 16 or more carbon atoms. A (meth)acrylic resin containing such a long carbon chain in the molecule has high hydrophobicity and can exhibit high releasability. The upper limit of the number of carbon atoms in the long-chain alkyl group can be, for example, 25 or less. Examples of (meth)acrylic resins containing a long-chain alkyl group include long-chain acrylic acrylates such as tetradecyl acrylate and octadecyl acrylate; long-chain acrylic methacrylates such as tetradecyl methacrylate and octadecyl methacrylate; and polymers thereof.

Examples of (meth)acrylic resins containing fluorine atoms include fluoroalkyl acrylates such as trifluoroethyl acrylate; fluoroaryl acrylates such as pentafluorophenyl acrylate; fluoroalkyl methacrylates such as trifluoroethyl methacrylate; fluoroaryl methacrylates such as pentafluorophenyl methacrylate; and polymers of these.

Examples of (meth)acrylic resins as optional resins include acrylic compounds such as acrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, acrylamide, N-methylol acrylamide, and diacetone acrylamide; methacrylic compounds such as methacrylic acid, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, and hydroxypropyl methacrylate; and polymers thereof.

One type of (meth)acrylic resin may be used alone, or two or more types may be used in combination.

The amount of (meth)acrylic resin in the release layer is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, and particularly preferably 90% by mass or more, relative to 100% by mass of the release layer, and is usually 100% by mass or less. Conventionally, when a release layer containing a (meth)acrylic resin is used in this way, a problem of poor peeling between the insulating layer and the support has arisen. According to the manufacturing method described in this embodiment, this problem of poor peeling can be suppressed.

The amount of (meth)acrylic resin in the release agent used to manufacture the release layer is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, particularly preferably 90% by mass or more, and usually 100% by mass or less, based on 100% by mass of the non-volatile components of the release agent. Conventionally, when a release layer formed using a release agent containing a (meth)acrylic resin in this manner is used, a problem of poor peeling between the insulating layer and the support has arisen. According to the manufacturing method described in this embodiment, this problem of poor peeling can be suppressed.

The release layer may further contain any component other than the (meth)acrylic resin in combination with the (meth)acrylic resin. The release agent for forming the release layer may further contain any component other than the (meth)acrylic resin in combination with the (meth)acrylic resin. Examples of the optional component other than the (meth)acrylic resin include releasable compounds other than the (meth)acrylic resin. Examples of the releasable compounds other than the (meth)acrylic resin include long-chain alkyl group-containing resins, olefin resins, fluorine compounds, wax-based compounds, etc.

Examples of compounds containing long-chain alkyl groups include compounds other than (meth)acrylic resins that contain long-chain alkyl groups. Specific examples of compounds containing long-chain alkyl groups include the "Ashio Resin" (registered trademark) series, which are long-chain alkyl compounds manufactured by Asio Sangyo Co., Ltd., the "Peiroil" (registered trademark) series, which are long-chain alkyl compounds manufactured by Lion Specialty Chemicals Co., Ltd., and the "Rezem" series, which are aqueous dispersions of long-chain alkyl compounds manufactured by Chukyo Yushi Co., Ltd.

Examples of olefin resins include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene.

Examples of fluorine compounds include compounds other than (meth)acrylic resins that contain fluorine atoms in the molecule. Specific examples of fluorine compounds include perfluoroalkyl group-containing compounds, polymers of olefin compounds that contain fluorine atoms, and aromatic fluorine compounds such as fluorobenzene.

Examples of wax-based compounds include natural waxes, synthetic waxes, and combinations thereof. Natural waxes include vegetable waxes, animal waxes, mineral waxes, and petroleum waxes. Examples of vegetable waxes include candelilla wax, carnauba wax, rice wax, wood wax, and jojoba oil. Examples of animal waxes include beeswax, lanolin, and whale wax. Examples of mineral waxes include montan wax, ozokerite, and ceresin. Examples of petroleum waxes include paraffin wax, microcrystalline wax, and petrolatum. Examples of synthetic waxes include synthetic hydrocarbons, modified waxes, hydrogenated waxes, fatty acids, acid amides, amines, imides, esters, and ketones. Examples of synthetic hydrocarbons include Fischer-Tropsch wax (also known as Sazowar wax) and polyethylene wax. The synthetic hydrocarbon may include low molecular weight polymers (specifically, viscosity average molecular weight of 500 to 20,000) selected from the group consisting of polypropylene, ethylene-acrylic acid copolymer, polyethylene glycol, polypropylene glycol, block conjugates of polyethylene glycol and polypropylene glycol, and graft conjugates of polyethylene glycol and polypropylene glycol. Examples of modified waxes include montan wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives. The derivatives here refer to compounds obtained by any of the following processes, or a combination of these: refining, oxidation, esterification, and saponification. Examples of hydrogenated waxes include hydrogenated castor oil and hydrogenated castor oil derivatives.

Any releasing compound other than the (meth)acrylic resin may be used alone or in combination of two or more types.

The amount of releasing compound in the release agent (the total amount of (meth)acrylic resin as a releasing compound and releasing compounds other than (meth)acrylic resin) is preferably 10% by mass or more, more preferably 15% by mass or more, and particularly preferably 20% by mass or more, based on 100% by mass of the non-volatile components of the release agent, and is preferably 90% by mass or less, more preferably 60% by mass or less, and particularly preferably 40% by mass or less.

The amount of the releasing compound in the release layer (the total of the (meth)acrylic resin as the releasing compound and the releasing compound other than the (meth)acrylic resin) is preferably 10% by mass or more, more preferably 15% by mass or more, and particularly preferably 20% by mass or more, relative to 100% by mass of the release layer, and is preferably 90% by mass or less, more preferably 60% by mass or less, and particularly preferably 40% by mass or less.

Another example of the optional component is any resin other than (meth)acrylic resin. Examples of the optional resin other than (meth)acrylic resin include epoxy resin, melamine resin, oxazoline compound, carbodiimide compound, polyester resin, urethane resin, etc. The optional resin other than (meth)acrylic resin may be used alone or in combination of two or more types.

The amount of optional resins in the release agent (the total of the optional resins, the (meth)acrylic resins, and the optional resins other than the (meth)acrylic resins) is preferably 10% by mass or more, more preferably 20% by mass or more, and particularly preferably 40% by mass or more, based on 100% by mass of the non-volatile components of the release agent, and is preferably 90% by mass or less, more preferably 80% by mass or less, and particularly preferably 60% by mass or less.

The amount of any resin in the release layer (the total of the (meth)acrylic resin as the optional resin and any resin other than the (meth)acrylic resin) is preferably 10% by mass or more, more preferably 20% by mass or more, and particularly preferably 40% by mass or more, relative to 100% by mass of the release layer, and is preferably 90% by mass or less, more preferably 80% by mass or less, and particularly preferably 60% by mass or less.

Further examples of optional components include additives such as lubricants, inorganic particles, organic particles, surfactants, antioxidants, and thermal initiators. These additives may be used alone or in combination of two or more. The amount of additive is not particularly limited, but may be, for example, 0.01% by mass or more and 10% by mass or less relative to 100% by mass of the total of the release compound and optional resin.

The thickness of the release layer is preferably 50 nm or more, more preferably 70 nm or more, and is preferably 400 nm or less, more preferably 200 nm or less, and particularly preferably 130 nm or less.

The support can be manufactured, for example, by a method including applying a release agent to the surface of the support substrate. The release agent may further include a solvent in combination with the non-volatile components, such as the (meth)acrylic resin and any optional components, described above. When the release agent includes a solvent, it is preferable that the method for manufacturing the support includes drying after applying the release agent.

As the solvent, an aqueous solvent is preferable from the viewpoint of suppressing rapid evaporation of the solvent and forming a uniform release layer. Examples of aqueous solvents include water; and mixed solvents of water and a water-soluble organic solvent such as an alcohol solvent, a ketone solvent, or a glycol solvent. The solvent may be used alone or in combination of two or more types. When a solvent is used, the non-volatile component concentration of the release agent is preferably 40% by mass or less from the viewpoint of improving the coatability and forming a uniform release layer.

Methods for applying the release agent include, for example, wire bar coating, reverse coating, gravure coating, die coating, blade coating, dip coating, air knife coating, curtain coating, and roller coating.

There are no particular limitations on the drying temperature of the release agent. In one example, drying may be performed at a temperature range of 80°C or higher and 130°C or lower. In another example, drying may be performed at a temperature range of 160°C or higher and 240°C or lower.

A layer containing the non-volatile components of the release agent can be formed by applying the release agent to the surface of the support substrate and drying it as necessary. This layer may be used as the release layer. The layer containing the non-volatile components of the release agent may be subjected to a curing treatment to obtain a release layer. Examples of the curing treatment include a heating treatment and an ultraviolet irradiation treatment. Usually, the curing treatment promotes a polymerization reaction and a crosslinking reaction of some or all of the components contained in the release agent, thereby curing the release agent, and a release layer made of the cured product of the release agent can be obtained.

The method for manufacturing the support may also include any process, such as a stretching process, as necessary.

--Resin composition layer--
The support has a resin composition layer formed on the release layer of the support. Usually, the resin composition layer is in contact with the release layer of the support, and no other layer is provided between the release layer and the resin composition layer. This resin composition layer contains a resin composition, and preferably contains only the resin composition.

The resin composition contains (A) an imidazole-based compound. (A) The imidazole-based compound typically functions as a curing catalyst in the resin composition. Specifically, the resin composition typically contains (B) a thermosetting resin, and (A) the imidazole-based compound can function as a catalyst that promotes the curing reaction of (B) the thermosetting resin.

(A) Examples of imidazole compounds include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-furan phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1 ')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-furan imidazole compounds such as phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, and 2-phenylimidazoline; and adducts of the above imidazole compounds with epoxy resins.

As the (A) imidazole-based compound, a commercially available product may be used. Examples of commercially available products of the (A) imidazole-based compound include "1B2PZ", "2E4MZ", "2MZA-PW", "2MZ-OK", "2MA-OK", "2MA-OK-PW", "2PHZ", "2PHZ-PW", "Cl1Z", "Cl1Z-CN", "Cl1Z-CNS", and "C11Z-A" manufactured by Shikoku Chemical Industry Co., Ltd.; and "P200-H50" manufactured by Mitsubishi Chemical Corporation. As the (A) imidazole-based compound, one type may be used alone, or two or more types may be used in combination.

The amount of the imidazole compound (A) in the resin composition is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and particularly preferably 0.03% by mass or more, based on 100% by mass of the non-volatile components of the resin composition, and is preferably 1% by mass or less, more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less.

The amount of the (A) imidazole compound in the resin composition is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, particularly preferably 0.1% by mass or more, and is preferably 5% by mass or less, more preferably 2% by mass or less, particularly preferably 1% by mass or less, based on 100% by mass of the resin components of the resin composition. The resin components of the resin composition refer to the non-volatile components of the resin composition excluding the (C) inorganic filler described below.

The resin composition usually contains (B) a thermosetting resin. As the (B) thermosetting resin, a resin that undergoes a reaction when heat is applied to form a bond and harden the resin composition can be used. As the (B) thermosetting resin, for example, epoxy resin, phenol resin, active ester resin, carbodiimide resin, acid anhydride resin, amine resin, benzoxazine resin, cyanate resin, and thiol resin can be mentioned. As the (B) thermoplastic resin, one type may be used alone, or two or more types may be used in any combination.

The epoxy resin can be a resin having epoxy groups. Examples of the epoxy resin include bixylenol type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol AF type epoxy resin, dicyclopentadiene type epoxy resin, trisphenol type epoxy resin, naphthol novolac type epoxy resin, phenol novolac type epoxy resin, tert-butyl-catechol type epoxy resin, naphthalene type epoxy resin, naphthol type epoxy resin, anthracene type epoxy resin, glycidylamine type epoxy resin, glycidyl ester type epoxy resin, cresol novolac type epoxy resin, phenol aralkyl type epoxy resin, biphenyl type epoxy resin, linear aliphatic epoxy resin, epoxy resin having a butadiene structure, alicyclic epoxy resin, heterocyclic epoxy resin, spiro ring-containing epoxy resin, cyclohexane type epoxy resin, cyclohexane dimethanol type epoxy resin, naphthylene ether type epoxy resin, trimethylol type epoxy resin, tetraphenylethane type epoxy resin, isocyanurate type epoxy resin, phenolphthalimidine type epoxy resin, and the like. The epoxy resin may be used alone or in combination of two or more types.

From the viewpoint of obtaining an insulating layer having excellent heat resistance, it is preferable that the epoxy resin contains an epoxy resin containing an aromatic structure. An aromatic structure is a chemical structure generally defined as aromatic, and also includes polycyclic aromatic rings and aromatic heterocycles. Examples of epoxy resins containing an aromatic structure include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AF type epoxy resins, dicyclopentadiene type epoxy resins, trisphenol type epoxy resins, naphthol novolac type epoxy resins, phenol novolac type epoxy resins, tert-butyl-catechol type epoxy resins, naphthalene type epoxy resins, naphthol type epoxy resins, anthracene type epoxy resins, bisxylenol type epoxy resins, glycidylamine type epoxy resins having an aromatic structure, glycidyl ester type epoxy resins having an aromatic structure, cresol novolac type epoxy resins, biphenyl type epoxy resins, linear aliphatic epoxy resins having an aromatic structure, epoxy resins having a butadiene structure having an aromatic structure, alicyclic epoxy resins having an aromatic structure, heterocyclic epoxy resins, spiro ring-containing epoxy resins having an aromatic structure, cyclohexane dimethanol type epoxy resins having an aromatic structure, naphthylene ether type epoxy resins, trimethylol type epoxy resins having an aromatic structure, and tetraphenylethane type epoxy resins having an aromatic structure.

The resin composition preferably contains an epoxy resin having two or more epoxy groups in one molecule. The proportion of the epoxy resin having two or more epoxy groups in one molecule relative to 100% by mass of the non-volatile components of the entire epoxy resin is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

Epoxy resins include epoxy resins that are liquid at a temperature of 20°C (hereinafter sometimes referred to as "liquid epoxy resins") and epoxy resins that are solid at a temperature of 20°C (hereinafter sometimes referred to as "solid epoxy resins"). The resin composition may contain only liquid epoxy resins as the epoxy resin, or may contain only solid epoxy resins, or may contain a combination of liquid epoxy resins and solid epoxy resins.

Preferably, the liquid epoxy resin has two or more epoxy groups in one molecule.

Preferred liquid epoxy resins are bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AF type epoxy resins, naphthalene type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, phenol novolac type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexane type epoxy resins, cyclohexane dimethanol type epoxy resins, and epoxy resins having a butadiene structure.

Specific examples of liquid epoxy resins include DIC's "HP4032", "HP4032D", and "HP4032SS" (naphthalene type epoxy resins); Mitsubishi Chemical's "828US", "828EL", "jER828EL", "825", and "Epicoat 828EL" (bisphenol A type epoxy resins); Mitsubishi Chemical's "jER807" and "1750" (bisphenol F type epoxy resins); Mitsubishi Chemical's "jER152" (phenol novolac type epoxy resin); Mitsubishi Chemical's "630", "630LSD", and "604" (glycidylamine type epoxy resins); ADEKA's "ED-523T" (glycirol type epoxy resin); ADEKA's "EP-3950L" and "EP-3980S" (glycidylamine type epoxy resins); A Examples of such epoxy resins include "EP-4088S" (dicyclopentadiene type epoxy resin) manufactured by DEKA Corporation; "ZX1059" (mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "EX-721" (glycidyl ester type epoxy resin) manufactured by Nagase Chemtex Corporation; "Celloxide 2021P" (alicyclic epoxy resin having an ester skeleton) manufactured by Daicel Corporation; "PB-3600" manufactured by Daicel Corporation, "JP-100" and "JP-200" (epoxy resin having a butadiene structure) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "ZX1658" and "ZX1658GS" (liquid 1,4-glycidylcyclohexane type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; and "YX8000" (hydrogenated bisphenol A type epoxy resin) manufactured by Mitsubishi Chemical Corporation. These may be used alone or in combination of two or more types.

As the solid epoxy resin, a solid epoxy resin having three or more epoxy groups in one molecule is preferable, and an aromatic solid epoxy resin having three or more epoxy groups in one molecule is more preferable.

Preferred solid epoxy resins are bixylenol type epoxy resins, naphthalene type epoxy resins, naphthalene type tetrafunctional epoxy resins, naphthol novolac type epoxy resins, cresol novolac type epoxy resins, dicyclopentadiene type epoxy resins, trisphenol type epoxy resins, naphthol type epoxy resins, biphenyl type epoxy resins, naphthylene ether type epoxy resins, anthracene type epoxy resins, bisphenol A type epoxy resins, bisphenol AF type epoxy resins, phenol aralkyl type epoxy resins, tetraphenylethane type epoxy resins, and phenolphthalimidine type epoxy resins.

Specific examples of solid epoxy resins include DIC's "HP4032H" (naphthalene type epoxy resin); DIC's "HP-4700" and "HP-4710" (naphthalene type tetrafunctional epoxy resin); DIC's "N-690" (cresol novolac type epoxy resin); DIC's "N-695" (cresol novolac type epoxy resin); DIC's "HP-7200", "HP-7200HH", "HP-7200H", and "HP-7200L" (dicyclopentadiene type epoxy resin); and DIC's "EXA-7311". , "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP6000" (naphthylene ether type epoxy resin); "EPPN-502H" (trisphenol type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; "NC7000L" (naphthol novolac type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; "NC3000H", "NC3000", "NC3000L", "NC3000FH", "NC3100" (biphenyl type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "ESN475V", "ESN4 100V (naphthalene type epoxy resin); "ESN485" (naphthol type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "ESN375" (dihydroxynaphthalene type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX4000H", "YX4000", "YX4000HK", and "YL7890" (bixylenol type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd.; "YL6121" (biphenyl type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd.; "YX8800" (anthracene type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd.; "Y Examples of such epoxy resins include "X7700" (phenol aralkyl type epoxy resin); "PG-100" and "CG-500" manufactured by Osaka Gas Chemicals; "YL7760" (bisphenol AF type epoxy resin) manufactured by Mitsubishi Chemical; "YL7800" (fluorene type epoxy resin) manufactured by Mitsubishi Chemical; "jER1010" (bisphenol A type epoxy resin) manufactured by Mitsubishi Chemical; "jER1031S" (tetraphenylethane type epoxy resin) manufactured by Mitsubishi Chemical; and "WHR991S" (phenolphthalimidine type epoxy resin) manufactured by Nippon Kayaku Co., Ltd. These may be used alone or in combination of two or more types.

When a liquid epoxy resin and a solid epoxy resin are used in combination as the epoxy resin, the mass ratio between them (liquid epoxy resin:solid epoxy resin) is preferably 20:1 to 1:20, more preferably 10:1 to 1:10, and particularly preferably 7:1 to 1:7.

The epoxy equivalent of the epoxy resin is preferably 50 g/eq. to 5,000 g/eq., more preferably 60 g/eq. to 3,000 g/eq., even more preferably 80 g/eq. to 2,000 g/eq., and particularly preferably 110 g/eq. to 1,000 g/eq. The epoxy equivalent represents the mass of the resin per equivalent of epoxy groups. This epoxy equivalent can be measured according to JIS K7236.

The weight average molecular weight (Mw) of the epoxy resin is preferably 100 to 5,000, more preferably 250 to 3,000, and even more preferably 400 to 1,500. The weight average molecular weight of the resin can be measured by gel permeation chromatography (GPC) as a polystyrene-equivalent value.

The amount of epoxy resin in the resin composition is preferably 1% by mass or more, more preferably 5% by mass or more, and particularly preferably 10% by mass or more, based on 100% by mass of the non-volatile components in the resin composition, and is preferably 50% by mass or less, more preferably 40% by mass or less, and particularly preferably 30% by mass or less.

The amount of epoxy resin in the resin composition is preferably 10% by mass or more, more preferably 30% by mass or more, and particularly preferably 50% by mass or more, based on 100% by mass of the resin components in the resin composition, and is preferably 90% by mass or less, more preferably 85% by mass or less, and particularly preferably 80% by mass or less.

The phenolic resin may be a resin having one or more, preferably two or more, hydroxyl groups bonded to an aromatic ring such as a benzene ring or a naphthalene ring in one molecule. From the viewpoint of heat resistance and water resistance, a phenolic resin having a novolac structure is preferred. From the viewpoint of adhesion, a nitrogen-containing phenolic resin is preferred, and a triazine skeleton-containing phenolic resin is more preferred. Among these, from the viewpoint of highly satisfying heat resistance, water resistance, and adhesion, a triazine skeleton-containing phenolic novolac resin is preferred.

Specific examples of phenolic resins include "MEH-7700", "MEH-7810", and "MEH-7851" manufactured by Meiwa Kasei Co., Ltd., "NHN", "CBN", and "GPH" manufactured by Nippon Kayaku Co., Ltd., "SN-170", "SN-180", "SN-190", "SN-475", "SN-485", "SN-495", "SN-375", and "SN-395" manufactured by Nippon Steel Chemical & Material Co., Ltd., and "LA-7052", "LA-7054", "LA-3018", "LA-3018-50P", "LA-1356", "TD2090", and "TD-2090-60M" manufactured by DIC Corporation. One type of phenolic resin may be used alone, or two or more types may be used in combination.

The amount of phenolic resin in the resin composition is preferably 0.1% by mass or more, preferably 0.5% by mass or more, particularly preferably 1% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, particularly preferably 30% by mass or less, based on 100% by mass of non-volatile components in the resin composition.

The amount of phenolic resin in the resin composition is preferably 0.1% by mass or more, preferably 1% by mass or more, particularly preferably 3% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less, particularly preferably 40% by mass or less, based on 100% by mass of the resin components in the resin composition.

The active ester resin may be a resin having one or more active ester groups in one molecule. The active ester group may be an ester bond directly bonded to an aromatic ring. As the active ester resin, generally, a compound having two or more highly reactive active ester groups in one molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds, is preferred. The active ester resin is preferably one obtained by a condensation reaction between a carboxylic acid compound and/or a thiocarboxylic acid compound and a hydroxy compound and/or a thiol compound. In particular, from the viewpoint of improving heat resistance, an active ester resin obtained from a carboxylic acid compound and a hydroxy compound is preferred, and an active ester resin obtained from a carboxylic acid compound and a phenol compound and/or a naphthol compound is more preferred. Examples of the carboxylic acid compound include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid. Examples of phenol compounds or naphthol compounds 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, dicyclopentadiene-type diphenol compounds, and phenol novolak. Here, "dicyclopentadiene-type diphenol compounds" refer to diphenol compounds obtained by condensing one molecule of dicyclopentadiene with two molecules of phenol.

Specifically, the active ester resin is preferably a dicyclopentadiene type active ester resin, a naphthalene type active ester resin containing a naphthalene structure, an active ester resin containing an acetylated product of phenol novolac, or an active ester resin containing a benzoylated product of phenol novolac, and among these, at least one selected from a dicyclopentadiene type active ester resin and a naphthalene type active ester resin is more preferable. As the dicyclopentadiene type active ester resin, an active ester resin containing a dicyclopentadiene type diphenol structure is preferable.

Commercially available active ester resins include, for example, active ester resins containing a dicyclopentadiene-type diphenol structure such as "EXB9451", "EXB9460", "EXB9460S", "EXB-8000L", "EXB-8000L-65M", "EXB-8000L-65TM", "HPC-8000L-65TM", "HPC-8000", "HPC-8000-65T", "HPC-8000H", and "HPC-8000H-65TM" (manufactured by DIC Corporation); active ester resins containing a naphthalene structure such as "HP-B-8151-62T", "EXB-8100L-65T", "EXB-8150-60T", and "EXB-815 0-62T", "EXB-9416-70BK", "HPC-8150-60T", "HPC-8150-62T", "EXB-8" (manufactured by DIC Corporation); phosphorus-containing active ester resin, "EXB9401" (manufactured by DIC Corporation); active ester resin which is an acetylated product of phenol novolac, "DC808" (manufactured by Mitsubishi Chemical Corporation); active ester resin which is a benzoylated product of phenol novolac, "YLH1026", "YLH1030", "YLH1048" (manufactured by Mitsubishi Chemical Corporation); active ester resin containing a styryl group and a naphthalene structure, "PC1300-02-65MA" (manufactured by Air Water Inc.), etc. can be used. One type of active ester resin may be used alone, or two or more types may be used in combination.

The amount of active ester resin in the resin composition is preferably 0.1% by mass or more, preferably 0.5% by mass or more, particularly preferably 1% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, particularly preferably 30% by mass or less, based on 100% by mass of non-volatile components in the resin composition.

The amount of active ester resin in the resin composition is preferably 0.1% by mass or more, preferably 1% by mass or more, particularly preferably 3% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less, particularly preferably 40% by mass or less, based on 100% by mass of the resin components in the resin composition.

The carbodiimide resin may be a resin having one or more, preferably two or more, carbodiimide structures in one molecule. Examples of carbodiimide resins include biscarbodiimide and polycarbodiimide. Specific examples of biscarbodiimide include aliphatic biscarbodiimides such as tetramethylene-bis(t-butylcarbodiimide) and cyclohexane-bis(methylene-t-butylcarbodiimide); and aromatic biscarbodiimides such as phenylene-bis(xylylcarbodiimide). Specific examples of polycarbodiimides include aliphatic polycarbodiimides such as polyhexamethylenecarbodiimide, polytrimethylhexamethylenecarbodiimide, polycyclohexylenecarbodiimide, poly(methylenebiscyclohexylenecarbodiimide), and poly(isophoronecarbodiimide); and aromatic polycarbodiimides such as poly(phenylenecarbodiimide), poly(naphthylenecarbodiimide), poly(tolylenecarbodiimide), poly(methyldiisopropylphenylenecarbodiimide), poly(triethylphenylenecarbodiimide), poly(diethylphenylenecarbodiimide), poly(triisopropylphenylenecarbodiimide), poly(diisopropylphenylenecarbodiimide), poly(xylylenecarbodiimide), poly(tetramethylxylylenecarbodiimide), poly(methylenediphenylenecarbodiimide), and poly[methylenebis(methylphenylene)carbodiimide]. Commercially available carbodiimide resins include, for example, "Carbodilite V-02B", "Carbodilite V-03", "Carbodilite V-04K", "Carbodilite V-07" and "Carbodilite V-09" manufactured by Nisshinbo Chemical Co., Ltd.; and "Stavaxol P", "Stavaxol P400" and "Hi-Kasil 510" manufactured by Rhein Chemie. One type of carbodiimide resin may be used alone, or two or more types may be used in combination.

The acid anhydride resin may be a resin having one or more acid anhydride groups in one molecule, and preferably has two or more acid anhydride groups in one molecule. Specific examples of acid anhydride resins include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic dianhydride, and benzophenone tetracarboxylic dianhydride. Examples of the acid anhydride include polymeric acid anhydrides such as water, biphenyltetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride, oxydiphthalic dianhydride, 3,3'-4,4'-diphenylsulfonetetracarboxylic dianhydride, 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-C]furan-1,3-dione, ethylene glycol bis(anhydrotrimellitate), and styrene-maleic acid resin in which styrene and maleic acid are copolymerized. Examples of commercially available acid anhydride resins include "HNA-100", "MH-700", "MTA-15", "DDSA", and "OSA" manufactured by New Japan Chemical Co., Ltd.; "YH-306" and "YH-307" manufactured by Mitsubishi Chemical Corporation; "HN-2200" and "HN-5500" manufactured by Hitachi Chemical Co., Ltd.; and "EF-30", "EF-40", "EF-60", and "EF-80" manufactured by Clay Valley. One type of acid anhydride resin may be used alone, or two or more types may be used in combination.

The amine resin may be a resin having one or more, preferably two or more, amino groups in one molecule. Examples of the amine resin include aliphatic amines, polyether amines, alicyclic amines, aromatic amines, etc., and among these, aromatic amines are preferred. The amine resin is preferably a primary amine or a secondary amine, and more preferably a primary amine. Specific examples of the amine resin include 4,4'-methylenebis(2,6-dimethylaniline), 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, m-phenylenediamine, m-xylylenediamine, diethyltoluenediamine, 4,4'-diaminodiphenylether, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxybenzidine, 2,2-bis(3-amino-4-hydroxyphenyl)propionate, and the like. Pan, 3,3-dimethyl-5,5-diethyl-4,4-diphenylmethanediamine, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, bis(4-(4-aminophenoxy)phenyl)sulfone, bis(4-(3-aminophenoxy)phenyl)sulfone, and the like. Commercially available amine resins include, for example, "SEIKACURE-S" manufactured by Seika Corporation; "KAYABOND C-200S", "KAYABOND C-100", "KAYAHARD A-A", "KAYAHARD A-B", and "KAYAHARD A-S" manufactured by Nippon Kayaku Co., Ltd.; "Epicure W" manufactured by Mitsubishi Chemical Corporation; and "DTDA" manufactured by Sumitomo Seika Chemicals Co., Ltd. One type of amine resin may be used alone, or two or more types may be used in combination.

Specific examples of benzoxazine resins include "JBZ-OP100D" and "ODA-BOZ" manufactured by JFE Chemical Corporation; "HFB2006M" manufactured by Showa Polymer Co., Ltd.; and "P-d" and "F-a" manufactured by Shikoku Chemical Industry Co., Ltd. The benzoxazine resins may be used alone or in combination of two or more types.

The cyanate resin may be a resin having one or more, preferably two or more, cyanate groups in one molecule. Examples of the cyanate ester resin include bifunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate (oligo(3-methylene-1,5-phenylene cyanate)), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanate phenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanate phenyl-1-(methylethylidene))benzene, bis(4-cyanate phenyl)thioether, and bis(4-cyanate phenyl)ether; polyfunctional cyanate resins derived from phenol novolac and cresol novolac; and prepolymers in which these cyanate resins are partially converted to triazine. Specific examples of cyanate ester resins include "PT30" and "PT60" (both of which are phenol novolac-type multifunctional cyanate ester resins) manufactured by Lonza Japan Co., Ltd., "BA230" and "BA230S75" (prepolymers in which part or all of bisphenol A dicyanate is triazine-converted to form a trimer). One type of cyanate ester resin may be used alone, or two or more types may be used in combination.

Examples of thiol resins include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), tris(3-mercaptopropyl)isocyanurate, etc. The thiol resins may be used alone or in combination of two or more types.

In a preferred embodiment, the thermosetting resin (B) includes an epoxy resin. In a more preferred embodiment, the thermosetting resin (B) includes a combination of an epoxy resin and a resin capable of reacting with the epoxy resin to cure the resin composition. The resin capable of reacting with the epoxy resin to cure the resin composition may be referred to as an "epoxy curing agent" hereinafter. Examples of epoxy curing agents include phenolic resins, active ester resins, carbodiimide resins, acid anhydride resins, amine resins, benzoxazine resins, cyanate ester resins, and thiol resins. Among the epoxy curing agents, phenolic resins and active ester resins are preferred. The epoxy curing agents may be used alone or in combination of two or more types.

The active group equivalent of the epoxy curing agent is preferably 50 g/eq. to 3000 g/eq., more preferably 100 g/eq. to 1000 g/eq., even more preferably 100 g/eq. to 500 g/eq., and particularly preferably 100 g/eq. to 300 g/eq. The active group equivalent represents the mass of the epoxy curing agent per equivalent of active group.

When an epoxy resin and an epoxy curing agent are used in combination, it is preferable that the ratio of the number of epoxy groups in the epoxy resin to the number of active groups in the epoxy curing agent ("number of active groups in the epoxy curing agent"/"number of epoxy groups in the epoxy resin") is within a specific range. Specifically, the ratio ("number of active groups in the epoxy curing agent"/"number of epoxy groups in the epoxy resin") is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.3 or more, and is preferably 5.0 or less, more preferably 3.0 or less, and particularly preferably 1.5 or less. The "number of epoxy groups in the epoxy resin" refers to the total value obtained by dividing the mass of the non-volatile components of the epoxy resin present in the resin composition by the epoxy equivalent. The "number of active groups in the epoxy curing agent" refers to the total value obtained by dividing the mass of the non-volatile components of the epoxy curing agent present in the resin composition by the active group equivalent of the epoxy curing agent.

The amount of (B) thermosetting resin in the resin composition is preferably 5% by mass or more, more preferably 10% by mass or more, and particularly preferably 20% by mass or more, based on 100% by mass of the non-volatile components of the resin composition, and is preferably 70% by mass or less, more preferably 60% by mass or less, and particularly preferably 50% by mass or less.

The amount of (B) thermosetting resin in the resin composition is preferably 60% by mass or more, more preferably 70% by mass or more, and particularly preferably 80% by mass or more, based on 100% by mass of the resin components of the resin composition, and is preferably 99.9% by mass or less, and more preferably 99% by mass or less.

The mass ratio of the (A) imidazole compound to the (B) thermosetting resin in the resin composition ((B) thermosetting resin/(A) imidazole compound) is preferably 100 or more, more preferably 200 or more, even more preferably 300 or more, particularly preferably 400 or more, and is preferably 1000 or less, more preferably 900 or less, even more preferably 800 or less, particularly preferably 700 or less.

The resin composition may further contain (C) an inorganic filler. (C) The inorganic filler is usually contained in the resin composition in the form of particles.

(C) An inorganic compound is used as the material for the inorganic filler. (C) Examples of the material for the inorganic filler include silica, alumina, glass, cordierite, silicon oxide, barium sulfate, barium carbonate, talc, clay, mica powder, zinc oxide, hydrotalcite, boehmite, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, boron nitride, aluminum nitride, manganese nitride, aluminum borate, strontium carbonate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, titanium oxide, zirconium oxide, barium titanate, barium zirconate titanate, barium zirconate, calcium zirconate, zirconium phosphate, and zirconium tungstate phosphate. Among these, silica and alumina are preferred, and silica is particularly preferred. Examples of silica include amorphous silica, fused silica, crystalline silica, synthetic silica, and hollow silica. In addition, spherical silica is preferred as the silica. (C) The inorganic filler may be used alone or in combination of two or more types.

(C) Commercially available inorganic fillers include, for example, "SP60-05" and "SP507-05" manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YC100C", "YA050C", "YA050C-MJE", "YA010C", "SC2500SQ", "SO-C4", "SO-C2", "SO-C1", and "SC2050-SXF" manufactured by Admatechs Co., Ltd.; "UFP-30" manufactured by Denka Co., Ltd.; and "Silfil NSS-3N", "Silfil NSS-4N", and "Silfil NSS-5N" manufactured by Tokuyama Corporation.

The average particle size of the inorganic filler (C) is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 0.1 μm or more, particularly preferably 0.2 μm or more, and is preferably 10 μm or less, more preferably 5 μm or less, even more preferably 2 μm or less, particularly preferably 1 μm or less.

(C) The average particle size of the inorganic filler can be measured by a laser diffraction/scattering method based on the Mie scattering theory. Specifically, a particle size distribution of the inorganic filler is created on a volume basis using a laser diffraction/scattering particle size distribution measuring device, and the median diameter is used as the average particle size. The measurement sample can be prepared by weighing 100 mg of inorganic filler and 10 g of methyl ethyl ketone into a vial and dispersing the mixture ultrasonically for 10 minutes. The measurement sample is measured using a laser diffraction particle size distribution measuring device with blue and red light source wavelengths, and the volume-based particle size distribution of the inorganic filler is measured using a flow cell method, and the average particle size can be calculated as the median diameter from the particle size distribution obtained. An example of a laser diffraction particle size distribution measuring device is the "LA-960" manufactured by Horiba, Ltd.

The specific surface area of the inorganic filler (C) is preferably 0.1 m ² /g or more, more preferably 0.5 m ² /g or more, even more preferably 1 m ² /g or more, particularly preferably 3 m ² /g or more, and is preferably 100 m ² /g or less, more preferably 70 m ² /g or less, even more preferably 50 m ² /g or less, particularly preferably 40 m ² /g or less. The specific surface area of the inorganic filler can be measured according to the BET method by adsorbing nitrogen gas onto the sample surface using a specific surface area measuring device (Macsorb HM-1210 manufactured by Mountech Co., Ltd.) and calculating the specific surface area using the BET multipoint method.

(C) The inorganic filler is preferably treated with a surface treatment agent from the viewpoint of improving moisture resistance and dispersibility. Examples of the surface treatment agent include fluorine-containing silane coupling agents, aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, alkoxysilanes, organosilazane compounds, titanate coupling agents, etc. One type of surface treatment agent may be used alone, or two or more types may be used in any combination.

Examples of commercially available surface treatment agents include Shin-Etsu Chemical's "KBM403" (3-glycidoxypropyltrimethoxysilane), Shin-Etsu Chemical's "KBM803" (3-mercaptopropyltrimethoxysilane), Shin-Etsu Chemical's "KBE903" (3-aminopropyltriethoxysilane), Shin-Etsu Chemical's "KBM573" (N-phenyl-3-aminopropyltrimethoxysilane), Shin-Etsu Chemical's "SZ-31" (hexamethyldisilazane), Shin-Etsu Chemical's "KBM103" (phenyltrimethoxysilane), Shin-Etsu Chemical's "KBM-4803" (long-chain epoxy-type silane coupling agent), and Shin-Etsu Chemical's "KBM-7103" (3,3,3-trifluoropropyltrimethoxysilane).

From the viewpoint of improving the dispersibility of the inorganic filler, it is preferable that the degree of surface treatment with the surface treatment agent falls within a specific range. Specifically, it is preferable that 100% by mass of the inorganic filler is surface-treated with 0.2% to 5% by mass of the surface treatment agent, more preferably with 0.2% to 3% by mass of the surface treatment agent, and even more preferably with 0.3% to 2% by mass of the surface treatment agent.

The degree of surface treatment by the surface treatment agent can be evaluated by the amount of carbon per unit surface area of the inorganic filler. From the viewpoint of improving the dispersibility of the inorganic filler, the amount of carbon per unit surface area of the inorganic filler is preferably 0.02 mg/m ² or more, more preferably 0.1 mg/m ² or more, and even more preferably 0.2 mg/m ² or more. On the other hand, from the viewpoint of preventing an increase in the melt viscosity of the resin composition, it is preferably 1.0 mg/m ² or less, more preferably 0.8 mg/m ² or less, and even more preferably 0.5 mg/m ² or less.

(C) The amount of carbon per unit surface area of the inorganic filler can be measured after the surface-treated inorganic filler is washed with a solvent (e.g., methyl ethyl ketone (MEK)). Specifically, a sufficient amount of MEK as a solvent is added to the inorganic filler that has been surface-treated with a surface treatment agent, and ultrasonic cleaning is performed at 25°C for 5 minutes. After removing the supernatant and drying the solids, the amount of carbon per unit surface area of the inorganic filler can be measured using a carbon analyzer. An example of a carbon analyzer that can be used is the "EMIA-320V" manufactured by Horiba, Ltd.

The amount of (C) inorganic filler in the resin composition is preferably 20% by mass or more, more preferably 40% by mass or more, and particularly preferably 60% by mass or more, based on 100% by mass of the non-volatile components in the resin composition, and is preferably 90% by mass or less, more preferably 85% by mass or less, and particularly preferably 80% by mass or less.

The resin composition may further contain (D) a thermoplastic resin. This (D) thermoplastic resin does not include (A) an imidazole compound, (B) a thermosetting resin, or (C) an inorganic filler.

(D) Examples of thermoplastic resins include phenoxy resins, polyimide resins, polyvinyl acetal resins, polyolefin resins, polybutadiene resins, polyamideimide resins, polyetherimide resins, polysulfone resins, polyethersulfone resins, polyphenylene ether resins, polycarbonate resins, polyetheretherketone resins, and polyester resins. (D) Thermoplastic resins may be used alone or in combination of two or more.

Examples of the phenoxy resin include phenoxy resins having one or more skeletons selected from the group consisting of bisphenol A skeleton, bisphenol F skeleton, bisphenol S skeleton, bisphenolacetophenone skeleton, novolac skeleton, biphenyl skeleton, fluorene skeleton, dicyclopentadiene skeleton, norbornene skeleton, naphthalene skeleton, anthracene skeleton, adamantane skeleton, terpene skeleton, and trimethylcyclohexane skeleton. The terminal of the phenoxy resin may be any functional group such as a phenolic hydroxyl group or an epoxy group. Specific examples of phenoxy resins include "1256" and "4250" manufactured by Mitsubishi Chemical Corporation (both phenoxy resins containing a bisphenol A skeleton); "YX8100" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol S skeleton); "YX6954" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol acetophenone skeleton); "FX280" and "FX293" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.; "YL7500BH30", "YX6954BH30", "YX7553", "YX7553BH30", "YL7769BH30", "YL6794", "YL7213", "YL7290", "YL7482" and "YL7891BH30" manufactured by Mitsubishi Chemical Corporation; and the like.

Specific examples of polyimide resins include "SLK-6100" manufactured by Shin-Etsu Chemical Co., Ltd., and "Rikacoat SN20" and "Rikacoat PN20" manufactured by New Japan Chemical Co., Ltd. Specific examples of polyimide resins include modified polyimides such as linear polyimides obtained by reacting bifunctional hydroxyl-terminated polybutadiene, a diisocyanate compound, and a tetrabasic acid anhydride (polyimides described in JP-A-2006-37083), and polysiloxane skeleton-containing polyimides (polyimides described in JP-A-2002-12667 and JP-A-2000-319386, etc.).

Examples of polyvinyl acetal resins include polyvinyl formal resins and polyvinyl butyral resins, with polyvinyl butyral resins being preferred. Specific examples of polyvinyl acetal resins include Denka Butyral 4000-2, Denka Butyral 5000-A, Denka Butyral 6000-C, and Denka Butyral 6000-EP manufactured by Denki Kagaku Kogyo Co., Ltd.; and S-LEC BH series, BX series (e.g. BX-5Z), KS series (e.g. KS-1), BL series, and BM series manufactured by Sekisui Chemical Co., Ltd.

Examples of polyolefin resins include ethylene-based copolymer resins such as low-density polyethylene, very low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methyl acrylate copolymer; polyolefin-based polymers such as polypropylene and ethylene-propylene block copolymer.

Examples of polybutadiene resins include hydrogenated polybutadiene skeleton-containing resins, hydroxyl group-containing polybutadiene resins, phenolic hydroxyl group-containing polybutadiene resins, carboxyl group-containing polybutadiene resins, acid anhydride group-containing polybutadiene resins, epoxy group-containing polybutadiene resins, isocyanate group-containing polybutadiene resins, urethane group-containing polybutadiene resins, polyphenylene ether-polybutadiene resins, etc.

Specific examples of polyamide-imide resins include "Viromax HR11NN" and "Viromax HR16NN" manufactured by Toyobo Co., Ltd. Specific examples of polyamide-imide resins include modified polyamide-imides such as "KS9100" and "KS9300" (polyamide-imide containing a polysiloxane skeleton) manufactured by Hitachi Chemical Co., Ltd.

An example of a polyethersulfone resin is "PES5003P" manufactured by Sumitomo Chemical Co., Ltd.

Specific examples of polysulfone resins include polysulfones "P1700" and "P3500" manufactured by Solvay Advanced Polymers.

A specific example of a polyphenylene ether resin is NORYL SA90 manufactured by SABIC. A specific example of a polyetherimide resin is ULTEM manufactured by GE.

Examples of polycarbonate resins include hydroxyl group-containing carbonate resins, phenolic hydroxyl group-containing carbonate resins, carboxyl group-containing carbonate resins, acid anhydride group-containing carbonate resins, isocyanate group-containing carbonate resins, and urethane group-containing carbonate resins. Specific examples of polycarbonate resins include "FPC0220" manufactured by Mitsubishi Gas Chemical Co., Ltd., "T6002" and "T6001" (polycarbonate diols) manufactured by Asahi Kasei Chemicals Corporation, and "C-1090", "C-2090", and "C-3090" (polycarbonate diols) manufactured by Kuraray Co., Ltd. Specific examples of polyether ether ketone resins include "Sumiploy K" manufactured by Sumitomo Chemical Co., Ltd.

Examples of polyester resins include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polytrimethylene terephthalate resin, polytrimethylene naphthalate resin, and polycyclohexane dimethyl terephthalate resin.

The weight average molecular weight (Mw) of the (D) thermoplastic resin is preferably greater than 5,000, more preferably 8,000 or more, even more preferably 10,000 or more, and particularly preferably 20,000 or more, and is preferably 100,000 or less, more preferably 70,000 or less, even more preferably 60,000 or less, and particularly preferably 50,000 or less.

The amount of (D) thermoplastic resin in the resin composition is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and particularly preferably 0.2% by mass or more, based on 100% by mass of non-volatile components in the resin composition, and is preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less.

The amount of (D) thermoplastic resin in the resin composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more, based on 100% by mass of the resin components in the resin composition, and is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less.

The resin composition may further contain (E) a flame retardant. (E) Flame retardants do not include those corresponding to the above-mentioned (A) imidazole-based compounds, (B) thermosetting resins, (C) inorganic fillers, or (D) thermoplastic resins. (E) Flame retardants include, for example, phosphazene compounds, organic phosphorus-based flame retardants, organic nitrogen-containing phosphorus compounds, nitrogen compounds, silicone-based flame retardants, metal hydroxides, etc. One type of flame retardant may be used alone, or two or more types may be used in combination.

Examples of flame retardants include "SPH-100", "SPS-100", "SPB-100", and "SPE-100" (phosphazenes) manufactured by Otsuka Chemical Co., Ltd.; "FP-100", "FP-110", "FP-300", and "FP-400" (phosphazenes) manufactured by Fushimi Pharmaceutical Co., Ltd.; "HCA-NQ", "HCA-HQ", and "HCA-HQ-HST" (phosphinic acid esters (containing phenolic hydroxyl groups)) manufactured by Sankosha; and "PX-200", "PX-201", "PX-202", "CR-733S", "CR-741", and "CR-747" (phosphate esters) manufactured by Daihachi Chemical Industry Co., Ltd.

The amount of the flame retardant (E) in the resin composition is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, based on 100% by mass of the non-volatile components in the resin composition. The upper limit is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

The resin composition may further contain (F) an optional additive. (F) Optional additives include, for example, a curing catalyst other than an imidazole-based compound; a radically polymerizable compound; an organometallic compound such as an organic copper compound, an organic zinc compound, or an organic cobalt compound; a colorant such as phthalocyanine blue, phthalocyanine green, iodine green, diazo yellow, crystal violet, titanium oxide, or carbon black; a polymerization inhibitor such as hydroquinone, catechol, pyrogallol, or phenothiazine; a leveling agent such as a silicone-based leveling agent or an acrylic polymer-based leveling agent; a thickener such as bentone or montmorillonite; an antifoaming agent such as a silicone-based antifoaming agent, an acrylic-based antifoaming agent, a fluorine-based antifoaming agent, or a vinyl resin-based antifoaming agent; an ultraviolet absorber such as a benzotriazole-based ultraviolet absorber; an adhesion improver such as urea silane; a triazo Examples of the adhesiveness imparting agent include adhesion imparting agents such as tetrazole-based adhesion imparting agents and triazine-based adhesion imparting agents; antioxidants such as hindered phenol-based antioxidants; fluorescent brighteners such as stilbene derivatives; surfactants such as fluorine-based surfactants and silicone-based surfactants; dispersants such as phosphate ester-based dispersing agents, polyoxyalkylene-based dispersing agents, acetylene-based dispersing agents, silicone-based dispersing agents, anionic dispersing agents, and cationic dispersing agents; stabilizers such as borate-based stabilizers, titanate-based stabilizers, aluminate-based stabilizers, zirconate-based stabilizers, isocyanate-based stabilizers, carboxylic acid-based stabilizers, and carboxylic anhydride-based stabilizers; photopolymerization initiator assistants such as tertiary amines; photosensitizers such as pyrarizones, anthracenes, coumarins, xanthones, and thioxanthones. (F) The optional additives may be used alone or in combination of two or more.

The resin composition may further contain (G) a solvent as an optional volatile component in addition to the non-volatile components such as the above-mentioned (A) imidazole-based compound, (B) thermosetting resin, (C) inorganic filler, (D) thermoplastic resin, (E) flame retardant, and (F) optional additives. As the (G) solvent, an organic solvent is usually used. Examples of organic solvents include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone; ether-based solvents such as tetrahydropyran, tetrahydrofuran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, diphenyl ether, and anisole; alcohol-based solvents such as methanol, ethanol, propanol, butanol, and ethylene glycol; 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diglycol acetate, γ-butyrolactone, and methyl methoxypropionate. Examples of the solvent include ether ester solvents such as ethyl acetate, ester alcohol solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate, ether alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether (butylcarbitol), amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone, sulfoxide solvents such as dimethyl sulfoxide, nitrile solvents such as acetonitrile and propionitrile, aliphatic hydrocarbon solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane, and aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and trimethylbenzene. The (G) solvent may be used alone or in combination of two or more.

(G) The amount of the solvent is not particularly limited, but when all components in the resin composition are taken as 100% by mass, it can be, for example, 60% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 15% by mass or less, 10% by mass or less, or it can be 0% by mass.

From the viewpoint of making the printed wiring board thinner, the thickness of the resin composition layer is preferably 100 μm or less, more preferably 80 μm or less, and more preferably 50 μm or less. The lower limit of the thickness of the resin composition layer is not particularly limited, but may be 5 μm or more, 10 μm or more, etc.

-Method of manufacturing resin sheet-
The method for producing the resin sheet is not particularly limited. The resin sheet can be produced, for example, by a method including coating the resin composition on the release layer of the support. When a liquid (varnish) resin composition is used, the resin composition may be directly coated on the release layer of the support. In addition, a liquid (varnish) resin composition may be prepared by mixing a solvent and a non-volatile component of the resin composition, and this may be coated on the release layer. Examples of the solvent include the same as the (G) solvent described as a component of the resin composition. Coating may be performed using a coating device such as a die coater.

The method for producing a resin sheet may include drying the applied resin composition as necessary. Drying may be performed by a drying method such as heating or blowing hot air. The drying conditions are not particularly limited, but the resin composition layer is usually dried so that the solvent content is 10% by mass or less, preferably 5% by mass or less. Although this may vary depending on the boiling point of the solvent in the resin composition, for example, when a resin composition containing 30% by mass to 60% by mass of solvent is used, the resin composition layer can be formed by drying at 50°C to 150°C for 3 to 10 minutes.

The method for producing a resin sheet may further include any step. For example, the method for producing a resin sheet may include laminating a resin composition layer and a protective film conforming to the support. The thickness of the protective film is not particularly limited, but is, for example, 1 μm to 40 μm. When the protective film is laminated, adhesion of dirt and scratches to the surface of the resin composition layer can be suppressed. Usually, the protective film is removed before laminating the resin sheet and the inner layer substrate in step (I).

[Step (I): Lamination of resin sheet and inner layer substrate]
The method for producing a printed wiring board according to one embodiment of the present invention includes a step (I) of laminating a resin sheet on an inner layer substrate so that the resin composition layer is bonded to the inner layer substrate. The "inner layer substrate" used in the step (I) is a member that becomes the substrate of the printed wiring board, and examples thereof include a glass epoxy substrate, a metal substrate, a polyester substrate, a polyimide substrate, a BT resin substrate, and a thermosetting polyphenylene ether substrate. The substrate may have a conductor layer on one or both sides, and the conductor layer may be patterned. An inner layer substrate having a conductor layer (circuit) formed on one or both sides of the substrate may be called an "inner layer circuit substrate". In addition, an intermediate product on which an insulating layer and/or a conductor layer is to be formed during the production of a printed wiring board is also included in the above-mentioned "inner layer substrate". When the printed wiring board is a circuit board with built-in components, an inner layer substrate with built-in components may be used.

The inner layer substrate and the resin sheet can be laminated, for example, by heat-pressing the resin sheet to the inner layer substrate from the support side. Examples of the member for heat-pressing the resin sheet to the inner layer substrate (hereinafter also referred to as the "heat-pressing member") include a heated metal plate (such as a SUS panel) or a metal roll (such as a SUS roll). Note that rather than pressing the heat-pressing member directly onto the resin sheet, it is preferable to press it via an elastic material such as heat-resistant rubber so that the resin sheet can sufficiently follow the surface irregularities of the inner layer substrate.

The lamination of the inner layer substrate and the resin sheet may be performed by a vacuum lamination method. In the vacuum lamination method, the heat-pressure bonding temperature is preferably in the range of 60°C to 160°C, more preferably in the range of 80°C to 140°C, the heat-pressure bonding pressure is preferably in the range of 0.098MPa to 1.77MPa, more preferably in the range of 0.29MPa to 1.47MPa, and the heat-pressure bonding time is preferably in the range of 20 seconds to 400 seconds, more preferably in the range of 30 seconds to 300 seconds. The lamination is preferably performed under reduced pressure conditions of 26.7hPa or less.

Lamination can be performed using a commercially available vacuum laminator. Examples of commercially available vacuum laminators include a vacuum pressure laminator manufactured by Meiki Seisakusho Co., Ltd., a vacuum applicator manufactured by Nikko Materials Co., Ltd., and a batch-type vacuum pressure laminator.

After lamination, the laminated resin sheets may be smoothed under normal pressure (atmospheric pressure), for example by pressing a heat-pressure bonding member from the support side. The pressing conditions for the smoothing treatment may be the same as the heat-pressure bonding conditions for the lamination. The smoothing treatment may be performed using a commercially available laminator. Note that lamination and smoothing treatment may be performed consecutively using the commercially available vacuum laminator.

[Step (II): Thermal curing of resin composition layer]
The method for producing a printed wiring board according to one embodiment of the present invention includes a step (II) of thermally curing the resin composition layer under a nitrogen atmosphere after the step (I). By thermally curing the resin composition layer, an insulating layer can be formed. The formed insulating layer contains a cured product of the resin composition, and preferably contains only the cured product of the resin composition.

The thermal curing of the resin composition layer in step (II) is carried out in a nitrogen atmosphere. The nitrogen atmosphere is filled with nitrogen gas, so the oxygen concentration in the nitrogen atmosphere is low. The range of the oxygen concentration in the nitrogen atmosphere is preferably 5% by mass or less, more preferably 3% by mass or less, particularly preferably 1% by mass or less, and ideally 0% by mass.

The pressure condition of the nitrogen atmosphere in which step (II) is carried out may be normal pressure or reduced pressure. In one example, the specific pressure condition range of the nitrogen atmosphere is preferably 0.075 mmHg (0.1 hPa) or more, more preferably 1 mmHg (1.3 hPa) or more, and preferably 3751 mmHg (5000 hPa) or less, more preferably 1875 mmHg (2500 hPa) or less.

The thermal curing of the resin composition layer in the step (II) is
(II-2) subjecting the resin composition layer to a heat treatment at a temperature T1;
(II-4) subjecting the resin composition layer to a heat treatment in which the resin composition layer is maintained at a temperature T2 higher than the temperature T1;
Hereinafter, the heat treatment step of maintaining the temperature T1 may be referred to as a "pre-cure step (II-2)." Also, the heat treatment step of maintaining the temperature T2 may be referred to as a "post-cure step (II-4)."

Usually, before the pre-cure step (II-2), the resin composition layer is at a temperature rise start temperature T0, which is lower than the temperature T1. The temperature rise start temperature T0 can be, for example, room temperature. Thus, the step (II) can include a step (II-1) of raising the temperature of the resin composition layer from the temperature rise start temperature T0 to the temperature T1 before the pre-cure step (II-2). From the viewpoint of obtaining the effects of the present invention significantly, the range of the temperature rise rate in this step (II-1) is preferably 0.5°C/min or more, more preferably 1°C/min or more, even more preferably 1.5°C/min or more, even more preferably 2°C/min or more, particularly preferably 2.5°C/min or more, and is preferably 30°C/min or less, more preferably 25°C/min or less, even more preferably 20°C/min or less, even more preferably 15°C/min or less, and particularly preferably 10°C/min or less. The temperature rise rate in the step (II-1) may be constant or may be changed.

In the pre-cure step (II-2), the resin composition layer is subjected to a heat treatment in which it is held at a temperature T1. The heating temperature T1 in this pre-cure step (II-2) is set in a temperature range that is higher than room temperature and lower than the temperature T2. The specific range of the heating temperature T1 is preferably 50°C or higher, more preferably 60°C or higher, even more preferably 70°C or higher, and particularly preferably 80°C or higher, from the viewpoint of obtaining the effects of the present invention significantly, and is preferably less than 150°C, more preferably 140°C or lower, and even more preferably 130°C or lower. In the pre-cure step (II-2), holding the resin composition layer at a temperature T1 includes not only maintaining the temperature of the resin composition layer at a constant temperature, but also fluctuating the temperature of the resin composition layer within a range that does not significantly impair the effects of the present invention. For example, the temperature of the resin composition layer in the pre-cure step (II-2) may fluctuate within a range of ±10°C, ±8°C, or ±5°C. However, even if the temperature of the resin composition layer fluctuates in this manner, it is preferable that the temperature of the resin composition layer in the pre-cure step (II-2) is within the above-mentioned preferred range, for example, in the range of 50°C or higher and lower than 150°C. In particular, it is particularly preferable that the temperature of the resin composition layer does not fluctuate and is constant in the pre-cure step (II-2).

The time range for which the resin composition layer is held at the heating temperature T1 in the pre-cure step (II-2) depends on the composition of the resin composition and the value of the heating temperature T1, but from the viewpoint of obtaining a significant effect of the present invention, it is preferably 10 minutes or more, more preferably 15 minutes or more, and particularly preferably 20 minutes or more, and is preferably 150 minutes or less, more preferably 120 minutes or less, and particularly preferably 120 minutes or less.

Usually, before the post-cure step (II-4), the resin composition layer is at a temperature lower than the temperature T2. Therefore, step (II) may include step (II-3) of raising the temperature of the resin composition layer to the temperature T2 after the pre-cure step (II-2) and before the post-cure step (II-4). From the viewpoint of obtaining the effects of the present invention significantly, the range of the temperature rise rate in this step (II-3) is preferably 0.5°C/min or more, more preferably 1°C/min or more, even more preferably 1.5°C/min or more, even more preferably 2°C/min or more, particularly preferably 2.5°C/min or more, and preferably 30°C/min or less, more preferably 25°C/min or less, even more preferably 20°C/min or less, even more preferably 15°C/min or less, particularly preferably 10°C/min or less. The temperature rise rate in step (II-3) may be constant or may be changed.

In the post-cure step (II-4), the resin composition layer is subjected to a heat treatment in which it is maintained at a temperature T2. The heating temperature T2 in the post-cure step (II-4) is set to a temperature higher than the temperature T1. From the viewpoint of obtaining the effects of the present invention significantly, the specific range of the heating temperature T2 is preferably 150°C or higher, more preferably 155°C or higher, even more preferably 160°C or higher, particularly preferably 170°C or higher, and preferably 250°C or lower, more preferably 230°C or lower, even more preferably 220°C or lower, even more preferably 210°C or lower, and particularly preferably 200°C or lower. In the post-cure step (II-4), maintaining the resin composition layer at a temperature T2 includes not only maintaining the temperature of the resin composition layer at a constant temperature, but also fluctuating the temperature of the resin composition layer within a range that does not significantly impair the effects of the present invention. For example, the temperature of the resin composition layer in the post-cure step (II-4) may fluctuate within a range of ±10°C, ±8°C, or ±5°C. However, even if the temperature of the resin composition layer fluctuates in this way, it is preferable that the temperature of the resin composition layer in the post-cure step (II-4) is within the above-mentioned preferred range, for example, in the range of 150°C or higher and 250°C or lower. In particular, it is particularly preferable that the temperature of the resin composition layer does not fluctuate and is constant in the post-cure step (II-4).

From the viewpoint of obtaining the effects of the present invention more clearly, it is preferable that the difference T2-T1 between the heating temperature T1 in the precure step (II-2) and the heating temperature T2 in the postcure step (II-4) is within a specific range. Specifically, the difference T2-T1 is preferably 20°C or more, more preferably 30°C or more, particularly preferably 40°C or more, and preferably 150°C or less, more preferably 140°C or less, even more preferably 130°C or less, particularly preferably 120°C or less. When the temperature of the resin composition layer fluctuates in the precure step (II-2) and/or the postcure step (II-4), it is preferable that the difference between the median temperature of the resin composition in the precure step (II-2) and the median temperature of the resin composition in the postcure step (II-4) is within the above range.

The time range for holding the resin composition layer at the heating temperature T2 in the post-cure step (II-4) depends on the composition of the resin composition and the value of the heating temperature T2, but from the viewpoint of obtaining a significant effect of the present invention, it is preferably 10 minutes or more, more preferably 15 minutes or more, particularly preferably 20 minutes or more, and is preferably 150 minutes or less, more preferably 120 minutes or less.

After the heat treatment at temperature T1 in the precure step (II-2), the resin composition layer may be cooled once and then subjected to heat treatment at heating temperature T2 in the postcure step (II-4). Alternatively, after the heat treatment at temperature T1 in the precure step (II-2), the resin composition layer may be subjected to heat treatment at temperature T2 in the precure step (II-4) without being cooled.

The heat treatment in the precure step (II-2) and the heat treatment in the postcure step (II-4) may be performed using the same heat treatment device. Alternatively, the heat treatment in the precure step (II-2) may be performed using a first heat treatment device, and the heat treatment in the postcure step (II-4) may be performed using a second heat treatment device different from the first heat treatment device. The heat treatment device is not particularly limited as long as it can thermally cure the resin composition layer. For example, an oven, a hot press, or the like may be used as the heat treatment device. For example, after the heat treatment in the precure step (II-2) is performed using an oven adjusted to a temperature T1, the inner layer substrate and the resin sheet may be transferred to an oven adjusted to a temperature T2, and the heat treatment in the postcure step (II-4) may be performed. Alternatively, after the heat treatment in the precure step (II-2) is performed using a heat treatment device capable of being temperature programmed, the temperature may be increased from T1 to T2, and the heat treatment in the postcure step (II-4) may be performed.

Step (II) may further include any step in combination with the above-mentioned steps (II-1) to (II-4). For example, step (II) may include a step of subjecting the resin composition layer to a heat treatment in which the layer is held at a heating temperature other than the temperatures T1 and T2. That is, step (II) is not limited to a two-step heat treatment, and may include three or more steps of heat treatment.

[Step (III): Peeling off the support]
The method for producing a printed wiring board according to one embodiment of the present invention includes a step (III) of peeling off the support after the step (II). According to this embodiment, the support and the insulating layer as the cured resin composition layer can be prevented from adhering to each other. Therefore, peeling failure can be suppressed, and the support can be peeled off smoothly.

Typically, the support is peeled off by pulling it relative to the insulating layer. For example, the support may be fixed while the insulating layer and inner layer substrate are transported and the support peeled off. For example, the support may be fixed while the insulating layer and inner layer substrate are pulled and the support peeled off. For example, the support may be pulled while the insulating layer and inner layer substrate are transported and the support peeled off.

Typically, the support is pulled relatively in a peeling direction that forms a specific angle with respect to the surface of the insulating layer, thereby achieving peeling of the support. There is no particular limit to the range of the angle that the peeling direction forms with respect to the surface of the insulating layer. From the viewpoint of smoothly peeling the support, the range of the angle is preferably 0° or more, and preferably 70° or less, more preferably 60° or less, even more preferably 50° or less, even more preferably 40° or less, even more preferably 30° or less, even more preferably 20° or less, and particularly preferably 10° or less.

The temperature conditions for peeling off the support are not particularly limited. From the viewpoint of reducing the energy required for manufacturing the printed wiring board, peeling off the support is usually performed at room temperature or a temperature close to room temperature. Therefore, usually, after the above-mentioned step (II), the inner layer substrate, the insulating layer, and the support are cooled, and then the support is peeled off. The specific temperature range for peeling off the support is preferably in the range of 10°C or more and 40°C. In addition, the cooling rate in the step of cooling from temperature T2 is not particularly limited, but is preferably 0.5°C/min or more, more preferably 1°C/min or more, even more preferably 1.5°C/min or more, even more preferably 2°C/min or more, particularly preferably 2.5°C/min or more, and preferably 30°C/min or less, more preferably 25°C/min or less, even more preferably 20°C/min or less, even more preferably 15°C/min or less, and particularly preferably 10°C/min or less.

In the method for producing a printed wiring board according to this embodiment, peeling failure between the insulating layer and the support is suppressed, so that it is possible to increase the peeling speed of the support. From the viewpoint of contributing to an improvement in the production speed of the printed wiring board, a fast peeling speed is preferable. The specific peeling speed range is preferably 1 m/min or more, more preferably 2 m/min or more, even more preferably 3 m/min or more, even more preferably 4 m/min or more, and particularly preferably 5 m/min or more. There is no particular upper limit, and it can be, for example, 20 m/min or less, 10 m/min or less, etc.

[Step (IV): Drilling]
The method for producing a printed wiring board according to an embodiment of the present invention may further include any step. For example, the method for producing a printed wiring board according to the present embodiment may include a step (IV) of drilling holes in the insulating layer. This step (IV) may be performed before or after the step (III).

Step (IV) involves forming via holes and through holes in the insulating layer. The holes may be formed using, for example, a drill, a laser, or plasma, depending on the composition of the resin composition used to form the insulating layer. The dimensions and shape of the holes may be appropriately determined depending on the design of the printed wiring board.

[Step (V): Roughening treatment]
The method for producing a printed wiring board according to one embodiment of the present invention may include a step (V) of roughening the insulating layer. This step (V) is usually performed after the step (III), but may be performed before the step (III). In addition, the step (V) is preferably performed after the step (IV). For example, after forming a hole in the insulating layer in the step (IV) and performing the step (V) of roughening, the step (III) of peeling off the support may be performed. When the step (V) is performed after the formation of the hole in the step (IV), it is possible to remove the resin residue (smear) that may remain in the hole.

The procedure and conditions for the roughening treatment are not particularly limited, and known procedures and conditions used in forming an insulating layer for a printed wiring board may be adopted. For example, the insulating layer may be roughened by carrying out a swelling treatment using a swelling liquid, a roughening treatment using an oxidizing agent, and a neutralization treatment using a neutralizing liquid in this order.

Examples of the swelling liquid used in the roughening treatment include an alkaline solution, a surfactant solution, etc., and an alkaline solution is preferred. As the alkaline solution, a sodium hydroxide solution and a potassium hydroxide solution are more preferred. Examples of commercially available swelling liquids include "Swelling Dip Securigans P" and "Swelling Dip Securigans SBU" manufactured by Atotech Japan. The swelling treatment using a swelling liquid can be performed, for example, by immersing the insulating layer in a swelling liquid at 30°C to 90°C for 1 to 20 minutes. From the viewpoint of suppressing the swelling of the resin of the insulating layer to an appropriate level, it is preferable to immerse the insulating layer in a swelling liquid at 40°C to 80°C for 5 to 15 minutes.

The oxidizing agent used in the roughening treatment may be, for example, an alkaline permanganate solution in which potassium permanganate or sodium permanganate is dissolved in an aqueous solution of sodium hydroxide. The roughening treatment using an oxidizing agent such as an alkaline permanganate solution is preferably carried out by immersing the insulating layer in an oxidizing agent solution heated to 60°C to 100°C for 10 to 30 minutes. The concentration of permanganate in the alkaline permanganate solution is preferably 5% by mass to 10% by mass. Commercially available oxidizing agents include, for example, alkaline permanganate solutions such as "Concentrate Compact CP" and "Dosing Solution Securigans P" manufactured by Atotech Japan.

The neutralizing solution used in the roughening treatment is preferably an acidic aqueous solution, and a commercially available product is, for example, "Reduction Solution Securigant P" manufactured by Atotech Japan. Treatment with a neutralizing solution can be carried out, for example, by immersing the treated surface that has been roughened with an oxidizing agent in a neutralizing solution at 30°C to 80°C for 5 to 30 minutes. From the standpoint of workability, etc., a method in which the object that has been roughened with an oxidizing agent is immersed in a neutralizing solution at 40°C to 70°C for 5 to 20 minutes is preferred.

In one example, the arithmetic mean roughness (Ra) of the surface of the insulating layer after the roughening treatment is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. There is no particular limit to the lower limit, and it may be, for example, 1 nm or more, 2 nm or more, etc. In addition, the root mean square roughness (Rq) of the surface of the insulating layer after the roughening treatment is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. There is no particular limit to the lower limit, and it may be, for example, 1 nm or more, 2 nm or more, etc. The arithmetic mean roughness (Ra) and root mean square roughness (Rq) of the surface of the insulating layer can be measured using a non-contact surface roughness meter.

[Step (VI): Formation of Conductive Layer]
The method for producing a printed wiring board according to an embodiment of the present invention may include a step (VI) of forming a conductor layer. In this step (VI), a conductor layer is usually formed on an insulating layer. Therefore, the step (VI) is usually performed after the step (III). In a preferred embodiment, the steps (IV), (V) and (VI) are performed in this order.

The conductor material used for the conductor layer is not particularly limited. In a preferred embodiment, the conductor layer contains one or more metals selected from the group consisting of gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin and indium. The conductor layer may be a single metal layer or an alloy layer. Examples of the alloy layer include layers formed from an alloy of two or more metals selected from the above group (e.g., nickel-chromium alloy, copper-nickel alloy and copper-titanium alloy). Among them, from the viewpoints of versatility of the conductor layer formation, cost, ease of patterning, etc., a single metal layer of chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver or copper, or an alloy layer of a nickel-chromium alloy, a copper-nickel alloy, or a copper-titanium alloy is preferred, a single metal layer of chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver or copper, or an alloy layer of a nickel-chromium alloy is more preferred, and a single metal layer of copper is even more preferred.

The conductor layer may be a single-layer structure, or a multi-layer structure in which two or more single metal layers or alloy layers made of different types of metals or alloys are laminated. When the conductor layer has a multi-layer structure, the layer in contact with the insulating layer is preferably a single metal layer of chromium, zinc, or titanium, or an alloy layer of a nickel-chromium alloy.

The thickness of the conductor layer depends on the desired printed wiring board design, but is generally between 3 μm and 35 μm, preferably between 5 μm and 30 μm.

The conductor layer may be formed, for example, by plating. As a specific example, a conductor layer having a desired wiring pattern can be formed by plating the surface of the insulating layer using a conventionally known technique such as a semi-additive method or a full-additive method. From the viewpoint of ease of production, the semi-additive method is preferred. Below, an example of forming a conductor layer by a semi-additive method is shown.

First, a plating seed layer is formed on the surface of the insulating layer by electroless plating. Next, a mask pattern is formed on the formed plating seed layer to expose a portion of the plating seed layer corresponding to the desired wiring pattern. A metal layer is formed on the exposed plating seed layer by electrolytic plating, and the mask pattern is then removed. Thereafter, unnecessary plating seed layer is removed by a removal method such as etching, and a conductor layer having the desired wiring pattern can be formed.

If necessary, the formation of the insulating layer and the conductor layer in steps (I) to (VI) may be repeated to manufacture a multilayer printed wiring board.

[Other steps]
The method for producing a printed wiring board according to one embodiment of the present invention may further include any optional steps in combination with the steps described above.

For example, a long resin sheet that is continuously transported in the longitudinal direction may be used. In this case, the resin sheet is usually pulled out from a roll of the resin sheet, and the pulled out resin sheet is supplied onto the inner layer substrate. In this case, the method for manufacturing a printed wiring board may include a step of cutting the long resin sheet to an appropriate size. The resin sheet may be cut before or after step (I).

For example, a resin sheet having a protective film for protecting the resin composition layer may be used. The protective film is usually provided on the side of the resin composition layer opposite the support. In this case, the method for producing a printed wiring board may include a step of removing the protective film. Usually, the protective film is removed before step (I).

[Applications of printed wiring boards]
The printed wiring board manufactured by the manufacturing method according to one embodiment of the present invention can be used in a wide range of applications, for example, it can be applied to a semiconductor device. This semiconductor device includes the above-mentioned printed wiring board. Specific examples of the semiconductor device include various semiconductor devices used in electrical products (e.g., computers, mobile phones, digital cameras, televisions, etc.) and vehicles (e.g., motorcycles, automobiles, trains, ships, aircraft, etc.). However, the printed wiring board may be applied to applications other than those mentioned above.

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the following examples. In the following description, the terms "parts" and "%" used to indicate amounts refer to "parts by mass" and "% by mass", respectively, unless otherwise specified. Furthermore, the operations described below were carried out in an atmospheric environment at room temperature and normal pressure (25°C, 1 atm), unless otherwise specified.

<Production Example 1: Production of Support 1 Having a Release Layer Containing Acrylic Resin>
(Production of acrylic resin (A1))
In a temperature-controllable reactor equipped with a stirrer, a thermometer, and a condenser, 500 parts by mass of toluene, 80 parts by mass of stearyl methacrylate (18 carbon atoms in the alkyl chain), 15 parts by mass of methacrylic acid, 5 parts by mass of 2-hydroxyethyl methacrylate, and 1 part of azobisisobutyronitrile were dropped using a dropper at a reaction temperature of 85°C for 4 hours to carry out a polymerization reaction. The mixture was then aged at the same temperature for 2 hours to complete the reaction, thereby obtaining an acrylic resin (A). This acrylic resin (A) was dissolved in water containing 5% by mass of isopropyl alcohol and 5% by mass of n-butyl cellosolve, to obtain a resin solution containing an acrylic resin (A1) as a mold-releasing compound.

(Preparation of acrylic resin (B1))
Methyl methacrylate (a), hydroxyethyl methacrylate (b), and an aromatic urethane acrylate oligomer (EBECRYL 220 manufactured by Daicel Allnex Corporation, having 6 acryloyl groups) (c) were charged in a mass ratio of (a)/(b)/(c) = 94/1/5 into a stainless steel reaction vessel. Furthermore, 2 parts by mass of sodium dodecylbenzenesulfonate was added as an emulsifier to the reaction vessel with respect to a total of 100 parts by mass of (a) + (b) + (c), and the mixture was stirred to prepare a mixed solution (1).

Next, a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a dropping funnel was prepared. 60 parts by mass of the above mixed liquid (1), 200 parts by mass of isopropyl alcohol, and 5 parts by mass of potassium persulfate as a polymerization initiator were added to the reaction apparatus and heated to 60°C to prepare mixed liquid (2). Mixed liquid (2) was kept heated at 60°C for 20 minutes.

Next, a mixed solution (3) consisting of 40 parts by mass of mixed solution (1), 50 parts by mass of isopropyl alcohol, and 5 parts by mass of potassium persulfate was prepared. Mixed solution (3) was added dropwise to mixed solution (2) over a period of 2 hours using a dropping funnel to prepare mixed solution (4).

Then, the mixed liquid (4) was heated to 60°C and kept for 2 hours. The obtained mixed liquid (4) was cooled to below 50°C and then transferred to a container equipped with a stirrer and a pressure reducing device. 60 parts by mass of 25% ammonia water and 900 parts by mass of pure water were added to this container, and isopropyl alcohol and unreacted monomers were recovered under reduced pressure while heating to 60°C, to obtain a composition containing acrylic resin (B1) as an optional resin dispersed in pure water.

(Preparation of release agent (1))
An intermediate composition was obtained by mixing a resin solution containing an acrylic resin (A1) and a composition containing an acrylic resin (B1) such that the mass ratio (solid content mass ratio) of the acrylic resin (A1) and the acrylic resin (B1) was (A1)/(B1)=20/80. Furthermore, a fluorine-based surfactant ("Pluscoat (registered trademark) RY-2" manufactured by GOO Chemical Industry Co., Ltd.) was added to this intermediate composition in an amount of 0.1 part by mass relative to 100 parts by mass of the entire intermediate composition, thereby obtaining a release agent (1) as a liquid acrylic resin composition.

(Production of Support 1)
A PET film (Toray Industries, Inc. "T60" (thickness 38 μm)) was prepared as a support substrate. A release agent (1) was applied to one side of the support substrate using a gravure coater and dried to form a release layer having a thickness of 0.1 μm. By the above operations, a support 1 including a support substrate and a release layer containing an acrylic resin was obtained.

<Production Example 2: Production of Support 2 Having a Release Layer Containing No Acrylic Resin>
(Preparation of polyolefin resin (C1))
280 g of a propylene-ethylene copolymer (propylene/ethylene=99/1 (mass ratio)) was heated and melted in a nitrogen atmosphere in a four-neck flask. Thereafter, 5.5 g of dicumyl peroxide as a radical generator was added over 1 hour with stirring while maintaining the temperature in the system at 170° C. Then, the reaction was allowed to proceed for 1 hour. After completion of the reaction, the obtained reaction product was poured into a large amount of acetone to precipitate a resin. This resin was further washed several times with acetone to remove unreacted monomers. The resin was then dried under reduced pressure in a vacuum dryer to obtain polyolefin resin (C1).

(Preparation of Aqueous Dispersion of Polyolefin Resin (C1))
A stirrer equipped with a 1-liter pressure-resistant glass container with a heater was prepared. 60 g of polyolefin resin (C1), 45.0 g of ethylene glycol-n-butyl ether (boiling point 171 ° C.), and 188.1 g of distilled water were charged into the glass container of this stirrer, and the stirring blade was set to a rotation speed of 300 rpm and stirred. After 10 minutes, the mixture was heated, and the temperature in the system was kept at 140 ° C. and stirred for another 60 minutes. Thereafter, the mixture was cooled to room temperature (about 25 ° C.) by air cooling while stirring at a rotation speed of 300 rpm. The contents of the glass container were pressure-filtered (air pressure 0.2 MPa) with a 300 mesh stainless steel filter (wire diameter 0.035 mm, plain weave) to obtain an aqueous dispersion of polyolefin resin (C1) (non-volatile component concentration 25% by mass).

(Preparation of release agent (2))
100 parts by mass of the aqueous dispersion of polyolefin resin (C1) calculated as nonvolatile components and 300 parts by mass of an aqueous polyvinyl alcohol solution ("JT-05" manufactured by Japan Vinyl Acetate & Poval Co., Ltd., saponification rate 94.5%, polymerization degree 500, nonvolatile component concentration 8% by mass) calculated as nonvolatile components were mixed, and water was further added to adjust the final nonvolatile component concentration to 6.0% by mass, thereby obtaining a release agent (2) as a liquid polyolefin resin composition.

(Production of Support 2)
A PET film (Toray Industries, Inc. "T60" (thickness 38 μm)) was prepared as a support substrate. A release agent (2) was applied to one side of the support substrate using a gravure coater, and dried to form a release layer having a thickness of 0.1 μm. By the above operations, a support substrate 2 including a support substrate and a release layer not including an acrylic resin was obtained.

<Production Example 3: Production of Resin Varnish A1>
A mixture was obtained by dissolving 6 parts of a bisphenol-type epoxy resin ("ZX1059" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., epoxy equivalent of about 169 g/eq., a 1:1 mixture of bisphenol A type and bisphenol F type), 9 parts of a bixylenol-type epoxy resin ("YX4000HK" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent of about 185 g/eq.), 21 parts of a biphenyl-type epoxy resin ("NC3000L" manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent of 288 g/eq.), and 10 parts of a phenoxy resin ("YX7553BH30" manufactured by Mitsubishi Chemical Corporation, a 1:1 solution of cyclohexanone:methyl ethyl ketone (MEK) with a non-volatile component of 30% by mass) in a mixed solvent of 20 parts of solvent naphtha and 5 parts of cyclohexanone with heating and stirring. After cooling to room temperature, 6 parts of a triazine skeleton-containing cresol novolak-based curing agent (hydroxyl group equivalent of 151 g/eq., DIC Corporation's "LA-3018-50P", a 2-methoxypropanol solution containing 50% nonvolatile components), 20 parts of an active ester-based curing agent (DIC Corporation's "HPC-8000-65T", a toluene solution containing 65% nonvolatile components by weight, a weight average molecular weight of about 2700, and an active group equivalent of about 223 g/eq.) were added to the mixture. 1 part, 2 parts of an imidazole-based curing accelerator ("1-benzyl-2-phenylimidazole" manufactured by Shikoku Kasei Co., Ltd., MEK solution containing 5% by mass of non-volatile components), 2 parts of a flame retardant ("HCA-HQ" manufactured by Sankosha Co., Ltd., 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide, average particle size 2 μm), and 170 parts of an inorganic filler were mixed and uniformly dispersed in a high-speed rotating mixer. After that, this mixture was filtered with a cartridge filter ("SHP050" manufactured by ROKITECHNO Co., Ltd.) to prepare resin varnish A1. As the inorganic filler, spherical silica ("SOC2" manufactured by Admatechs Co., Ltd., average particle size 0.5 μm, specific surface area 5.8 m ² /g) surface-treated with an aminosilane coupling agent ("KBM573" manufactured by Shin-Etsu Chemical Co., Ltd.) was used.

<Production Example 4: Production of Resin Varnish A2>
A mixture was obtained by heating and dissolving, with stirring, 30 parts of a biphenyl type epoxy resin (epoxy equivalent of about 290 g/eq., "NC3000H" manufactured by Nippon Kayaku Co., Ltd.), 5 parts of a naphthalene type tetrafunctional epoxy resin (epoxy equivalent of 162 g/eq., "HP-4700" manufactured by DIC Corporation), 15 parts of a liquid bisphenol A type epoxy resin (epoxy equivalent of 180 g/eq., "jER828EL" manufactured by Mitsubishi Chemical Corporation), and 2 parts of a phenoxy resin (weight average molecular weight of 35,000, "YX7553BH30" manufactured by Mitsubishi Chemical Corporation, a methyl ethyl ketone (MEK) solution containing 30% by mass of non-volatile components) in a mixed solvent of 8 parts of MEK and 8 parts of cyclohexanone. To this mixture, 32 parts of a triazine skeleton-containing phenol novolac-based curing agent (phenolic hydroxyl group equivalent of about 124 g/eq., DIC Corporation's "LA-7054", MEK solution with 60% by mass of non-volatile components), 2 parts of an imidazole-based curing accelerator (Shikoku Kasei Corporation's "1-benzyl-2-phenylimidazole", MEK solution with 5% by mass of non-volatile components), 160 parts of an inorganic filler, and 2 parts of a polyvinyl butyral resin solution (weight average molecular weight 27000, glass transition temperature 105°C, Sekisui Chemical Co., Ltd.'s "KS-1", a mixed solution of 15% by mass of ethanol and toluene in a mass ratio of 1:1) were mixed and uniformly dispersed using a high-speed rotating mixer to prepare resin varnish A2. As the inorganic filler, spherical silica ("SOC2" manufactured by Admatechs Co., Ltd., average particle size 0.5 μm, specific surface area 5.8 m ² /g) surface-treated with an aminosilane coupling agent ("KBM573" manufactured by Shin-Etsu Chemical Co., Ltd.) was used.

<Production Example 5: Production of Resin Varnish B1>
Resin varnish B1 was prepared in the same manner as in Production Example 3, except that 2 parts of the imidazole-based curing accelerator ("1-benzyl-2-phenylimidazole" manufactured by Shikoku Chemical Industry Co., Ltd., MEK solution containing 5% by mass of non-volatile components) was changed to 2 parts of a phosphorus-based curing accelerator ("tetrabutylphosphonium decanoate" manufactured by Hokko Chemical Industry Co., Ltd., MEK solution containing 5% by mass of non-volatile components).

[Example 1]
(Production of resin sheets)
Resin varnish A1 was uniformly applied to the release layer side surface of the support 1 obtained in Production Example 1 using a die coater, and dried for 6 minutes at 80°C to 120°C (average 100°C) to obtain a resin sheet having a support substrate, a release layer, and a resin composition layer in this order. The thickness of the resin composition layer of the resin sheet was 40 μm.

(Lamination of resin sheet onto inner layer circuit board)
Both sides of a glass cloth-based epoxy resin double-sided copper-clad laminate (copper foil thickness 18 μm, substrate thickness 0.8 mm, Panasonic Electric Works "R1515A") were immersed in an etching agent (Mech "CZ8100") to roughen the copper surface, and an inner layer circuit board was obtained. A resin sheet was laminated on both sides of this inner layer circuit board using a batch-type vacuum pressure laminator (Nichigo-Morton two-stage build-up laminator "CVP700"). This lamination was performed so that the resin composition layer of the resin sheet was bonded to the inner layer circuit board. In addition, this lamination was performed by decompressing for 30 seconds to an atmospheric pressure of 13 hPa or less, and then pressing under press conditions of 100 ° C., pressure 0.74 MPa, and 30 seconds. By the above lamination, a sample laminate having a support, a resin composition layer, an inner layer circuit board, a resin composition layer, and a support in this order was obtained.

(Curing of Resin Composition Layer)
After lamination of the resin composition layer and the inner layer circuit board, the sample laminate was placed in a nitrogen oven with the support attached. After placing, the door was closed and nitrogen was circulated until the oxygen concentration in the oven reached 0.5%. After confirming that the oxygen concentration in the oven reached 0.5%, the resin composition layer was thermally cured under the following curing conditions. Specifically, in the curing conditions of this Example 1, the temperature in the oven was raised from 30°C to 130°C at 10°C/min, and then thermal curing was allowed to proceed at 130°C for 30 minutes, and then the temperature was raised to 170°C at 10°C/min, and then thermal curing was allowed to proceed for 30 minutes at 170°C. Thereafter, the temperature was lowered to 30°C at 5°C/min, and the sample laminate was removed from the nitrogen oven. The resin composition layer was thermally cured to form an insulating layer, and an evaluation sample was obtained that had a support, an insulating layer, an inner layer circuit board, an insulating layer, and a support in this order. The thickness of the insulating layer on the inner layer circuit was 40 μm.

(Removal of Support)
The evaluation sample was cooled to room temperature (about 25° C.), and then the support was peeled off. The peeling was excellent, and the support was peeled off without damaging the support and the insulating layer. As a result of the peeling, a printed wiring board with an insulating layer and a support peeled off from the insulating layer were obtained.

[Example 2]
Except for changing the resin varnish A1 to the resin varnish A2, a resin sheet, an evaluation sample, and a printed wiring board were produced in the same manner as in Example 1. In the step of peeling off the support, the peelability was good, and the support and the insulating layer were not damaged, and the support was peeled off.

[Comparative Example 1]
A resin sheet and an evaluation sample were produced in the same manner as in Example 1, except that the curing conditions in the step of thermally curing the resin composition layer were changed as follows. In the curing conditions of this Comparative Example 1, after confirming that the oxygen concentration in the oven was 0.5%, the temperature in the oven was raised from 30° C. to 200° C. at 10° C./min, and then thermal curing was allowed to proceed at 200° C. for 90 minutes. Thereafter, the temperature was lowered to 30° C. at 5° C./min, and the sample laminate was removed from the nitrogen oven to obtain an evaluation sample.

The evaluation sample was cooled to room temperature (approximately 25°C), and then an attempt was made to peel off the support. However, the insulating layer and the support were stuck together, making peeling difficult. Furthermore, when an attempt was made to peel it off forcefully, the support was destroyed.

[Comparative Example 2]
A resin sheet and an evaluation sample were manufactured in the same manner as in Comparative Example 1, except that the resin varnish A1 was changed to the resin varnish A2. The evaluation sample was cooled to room temperature (about 25°C), and then an attempt was made to peel off the support. However, the insulating layer and the support were stuck together, making peeling difficult. Furthermore, when the insulating layer and the support were forcibly peeled off, the support was destroyed.

[Reference Example 1]
A resin sheet and an evaluation sample were produced in the same manner as in Comparative Example 1, except that the resin varnish A1 was replaced with the resin varnish B. The evaluation sample was cooled to room temperature (about 25°C), and then the support was peeled off. The peeling was good, and the support was peeled off without damaging the support and the insulating layer. As a result of the peeling, a printed wiring board having an insulating layer and a support peeled off from the insulating layer were obtained.

[Reference Example 2]
A resin sheet and an evaluation sample were manufactured in the same manner as in Comparative Example 1, except that the support 1 was changed to the support 2. The evaluation sample was cooled to room temperature (about 25°C), and then the support was peeled off. The peeling property was good, and the support was peeled off without damaging the support and the insulating layer. As a result of the peeling, a printed wiring board having an insulating layer and a support peeled off from the insulating layer were obtained.

[Reference Example 3]
A resin sheet and an evaluation sample were manufactured in the same manner as in Comparative Example 1, except that the support 1 was changed to a PET film with a silicone release layer (Toyobo Co., Ltd. "E7004", thickness 38 μm). The evaluation sample was cooled to room temperature (about 25° C.), and then the support was peeled off. The peeling was good, and the support was peeled off without damaging the support and the insulating layer. As a result of the peeling, a printed wiring board with an insulating layer and a support peeled off from the insulating layer were obtained.

[Reference Example 4]
After the sample laminate was put into the nitrogen oven, the resin sheet and the evaluation sample were produced in the same manner as in Comparative Example 1, except that the resin composition layer was thermally cured in an air atmosphere without circulating nitrogen. The evaluation sample was cooled to room temperature (about 25°C), and then the support was peeled off. The peelability was good, and the support was peeled off without damaging the support and the insulating layer. As a result of the peeling, a printed wiring board having an insulating layer and a support peeled off from the insulating layer were obtained.

[result]
The results of the above-mentioned Examples, Comparative Examples and Reference Examples are shown in the following table. The meanings of the abbreviations in the "Determination" column in the following table are as follows.
"OK": The support was peeled off without damaging the support or the insulating layer.
"NG": Peel failure occurred, with the support or insulating layer being destroyed.

[Consider]
From the results of Comparative Examples 1 and 2, it can be seen that peeling failure has occurred between the support and the resin composition layer in the past. Moreover, from the results of Reference Examples 1 to 4, it can be seen that the above-mentioned peeling failure is a specific problem that occurs when all of the following conditions are satisfied: the release agent contains a (meth)acrylic resin, the resin composition layer contains a resin composition containing an imidazole compound, and the thermal curing is performed in a nitrogen atmosphere. From Examples 1 and 2, it was confirmed that the above-mentioned specific problem can be solved by the manufacturing method of the present invention.

Claims (8)

(I) a step of laminating a resin sheet comprising a support having a release layer and a resin composition layer formed on the release layer of the support, onto an inner layer substrate such that the resin composition layer is bonded to the inner layer substrate;
(II) a step of thermally curing the resin composition layer under a nitrogen atmosphere; and (III) a step of peeling off the support at a peeling speed of 1 m/min or more .
A method for producing a printed wiring board, comprising, in this order:
the release layer comprises a (meth)acrylic resin;
the resin composition layer includes a resin composition including an imidazole-based compound;
A method for manufacturing a printed wiring board, wherein the thermal curing of the resin composition layer includes, in this order, subjecting the resin composition layer to a heat treatment in which it is held at a temperature T1, and subjecting it to a heat treatment in which it is held at a temperature T2 higher than the temperature T1. The method for producing a printed wiring board according to claim 1, wherein the resin composition contains a thermosetting resin. The method for producing a printed wiring board according to claim 2, wherein the thermosetting resin comprises one or more selected from the group consisting of epoxy resins, phenolic resins, active ester resins, carbodiimide resins, acid anhydride resins, amine resins, benzoxazine resins, cyanate ester resins, and thiol resins. The method for manufacturing a printed wiring board according to any one of claims 1 to 3, wherein the temperature T2 is 150°C or higher. The method for manufacturing a printed wiring board according to any one of claims 1 to 4, wherein the difference T2-T1 between temperature T1 and temperature T2 is 20°C or more. The method for manufacturing a printed wiring board according to any one of claims 1 to 5, wherein the temperature T1 is 50°C or higher. The method for producing a printed wiring board according to any one of claims 1 to 6, wherein step (II) includes heating the resin composition layer to a temperature T2 at a heating rate of 0.5°C/min or more and 30°C/min or less. The method for manufacturing a printed wiring board according to any one of claims 1 to 7, wherein the amount of (meth)acrylic resin in the release layer is 30% by mass or more relative to 100% by mass of the release layer.