Curable composition, solder resist ink, and printed circuit board

Abstract

The present invention addresses the problem of providing: a curable composition from which a cured product having excellent adhesiveness and heat resistance and a low relative dielectric constant is formed; an ink for solder resist; and a printed circuit board using the same. A curable composition according to the present invention contains a (meth)acrylic monomer as a main component and further contains a photopolymerization initiator, a thermosetting compound, and a gelling agent, the curable composition being characterized in that a cured product of said curable composition has a relative dielectric constant of less than 2.90 at 10 GHz.

Description

[Technical Field]

[0001] The present invention relates to a curable composition, a solder resist ink, and a printed circuit board. More particularly, the present invention relates to a curable composition, a solder resist ink, and a printed circuit board using the same that give a cured product having excellent adhesion and heat resistance and a low dielectric constant. [Background technology]

[0002] Materials used in mobile communication devices may be required to have a dielectric constant at a specific frequency. For example, it has been proposed to use materials with a specified dielectric constant at 100 kHz for organic light-emitting diode (EL) elements used in mobile displays to prevent touch sensor malfunctions (Patent Document 1). Furthermore, in high-frequency circuits used in mobile communication devices, transmission loss occurs between wiring and insulating materials, and transmission loss in insulating materials in particular is a problem, leading to issues such as heat generation, noise, and power consumption during signal transmission. It has been shown that transmission loss is proportional to frequency and the dielectric loss tangent of a material. With the shift to fifth-generation mobile communication systems (5G), there is a growing demand for materials with low dielectric loss tangents.

[0003] On the other hand, from the viewpoint of heat resistance and electrical insulation, resin compositions containing a curable resin such as a carboxyl group-containing resin or an epoxy resin as a main component, and further containing additives such as fillers, are widely used as interlayer insulating materials and solder resist materials. However, the cured products of these resin compositions contain many polar groups, resulting in materials with high dielectric constants and dielectric loss, and improvements have been required. Photosensitive solder resist materials include those primarily made of epoxy acrylate resins. These are mainly negative-type photoresists that can be developed with an alkaline aqueous solution such as a sodium carbonate solution. Photosensitive solder resists are cured and stabilized by heat treatment of patterned photosensitive solder resists. In particular, in epoxy acrylate resins, this heat treatment is known to seal residual carboxylic acids with epoxy groups, etc., but carboxylic acids and other residues remain even after sealing (Patent Document 2).

[0004] In recent years, efforts have been made to develop inkjet printing for the solder resist film formation process. This technology allows for the direct formation of an insulating layer pattern corresponding to the wiring, eliminating the need for a development process. This eliminates the need for a development process, resulting in fewer polar groups being generated during the development process, making it an advantageous technology for achieving low dielectric constants. Curable compositions used in inkjet printing contain epoxy monomers or acrylic monomers as curable components, and are cured by light irradiation or heat (Patent Document 3). To meet the demands of 5G, it is necessary to further reduce the polar groups, such as carboxylic acids, present in the curable composition system. Epoxy monomers leave residual hydroxyl groups during polymerization, and acrylic monomers also generate polar groups due to oxygen inhibition of radical polymerization, posing challenges to achieving low dielectric constants in line with 5G.

[0005] On the other hand, when a curable composition that does not generate polar groups upon curing is used to produce a solder resist film in consideration of a low dielectric constant, there is a concern that the adhesion of the cured product to the conductor wiring of the wiring board will be reduced. Thus, the cured product that constitutes the solder resist film is required to have heat resistance, a low dielectric constant, and adhesion. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-076052 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-34414 [Patent Document 3] Japanese Patent Application Publication No. 2019-178288 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in view of the above problems and circumstances, and an object of the present invention is to provide a curable composition that gives a cured product that has excellent adhesion and heat resistance and a low dielectric constant, a solder resist ink, and a printed circuit board using the same. [Means for solving the problem]

[0008] In the process of investigating the causes of the above problems in order to solve the above problems, the present inventors found that the above problems can be solved when a cured product obtained from a curable composition containing a (meth)acrylic monomer as a main component, a photopolymerization initiator, a thermosetting compound, and a gelling agent has a specific relative dielectric constant, and thus arrived at the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0009] 1. (Meth)acrylic monomer 50~95% by mass and further comprising a photopolymerization initiator, a thermosetting compound, and a gelling agent, the (meth)acrylic monomer contains a (meth)acrylic monomer having a molecular weight in the range of 200 to 1500 and a ClogP value in the range of 3.5 to 7.0, the thermosetting compound contains at least one group selected from an isocyanate group, an epoxy group, and a maleimide group; The gelling agent is a ketone wax, an ester wax, a higher fatty acid, a higher alcohol, or a fatty acid amide, and A curable composition, characterized in that a cured product of the curable composition has a relative dielectric constant at 10 GHz of less than 2.90.

[0010] 2. The curable composition according to item 1, wherein the content of the thermosetting compound is within the range of 1 to 15 mass % based on the total amount of the curable composition.

[0012] 3 Item 1, wherein the thermosetting compound contains a polyfunctional isocyanate compound in which the isocyanate group is protected with a thermally dissociable blocking agent. or No. Section 2 The curable composition according to claim 1.

[0013] 4 Viscosity at 25°C is 1 to 1 x 10 4 The first to third terms have a phase transition temperature in the range of Pa·s and between 40°C and 100°C.3 The curable composition according to any one of claims 1 to 5.

[0014] 5 .Items 1 to 5 4 Item 1. A solder resist ink containing the curable composition according to any one of items 1 to 5.

[0015] 6 A printed circuit board comprising a substrate, a circuit pattern provided on a surface of the substrate, and a solder resist film provided on the circuit pattern, The solder resist film is 5 2. A printed circuit board formed using the solder resist ink according to claim 1.

[0016] 7 The circuit pattern is made of copper wiring, and the surface roughness Ra of the copper wiring is in the range of 0.1 to 2.0 μm. 6 Item 1. The printed circuit board according to item 1. [Effects of the Invention]

[0017] According to the above-mentioned means of the present invention, it is possible to provide a curable composition that gives a cured product that has excellent adhesion and heat resistance and a low relative dielectric constant, a solder resist ink, and a printed circuit board using the same. The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is speculated as follows.

[0018] In the curable composition of the present invention, by using a photopolymerizable (meth)acrylic monomer as the main component, the amount of polar groups in the cured product can be reduced. Furthermore, by including a gelling agent in the curable composition, the components in the curable composition are gelled to form a fine house-of-card structure within the composition. This is thought to slow the diffusion rate of oxygen and moisture entering from the outside, further suppressing the generation of polar groups such as carboxylic acids and hydroxyl groups that are generated when the curable composition cures. This also results in a low dielectric constant (relative dielectric constant at 10 GHz of less than 2.90) and a low dielectric loss tangent for the resulting cured product.

[0019] Furthermore, in addition to the above, the curable composition of the present invention may contain a thermosetting compound and be subjected to thermal polymerization in combination, thereby making it possible to seal polar groups generated in small amounts during photopolymerization and to improve adhesion to circuit boards and heat resistance. DETAILED DESCRIPTION OF THE INVENTION

[0020] The curable composition of the present invention is a curable composition containing a (meth)acrylic monomer as a main component, and further containing a photopolymerization initiator, a thermosetting compound, and a gelling agent, and is characterized in that a cured product of the curable composition has a relative dielectric constant of less than 2.90 at 10 GHz. This feature is a technical feature common to or corresponding to each of the following embodiments.

[0021] In an embodiment of the curable composition of the present invention, from the viewpoint of easily adjusting the amount of polar groups in the obtained cured product, it is preferable that the content of the thermosetting compound is within a range of 1 to 15 mass % relative to the total amount of the curable composition.

[0022] As an embodiment of the curable composition of the present invention, from the viewpoint of enhancing the dissolution stability of the gelling agent in the curable composition, it is preferable that the (meth)acrylic monomer contains a (meth)acrylic monomer having a molecular weight in the range of 200 to 1500 and a ClogP value in the range of 3.5 to 7.0.

[0023] In an embodiment of the curable composition of the present invention, from the viewpoint of reducing the dielectric constant of the obtained cured product and improving the resistance to high temperatures and high humidity, it is preferable that the thermosetting compound contains a polyfunctional isocyanate compound in which an isocyanate group is protected with a thermally dissociable blocking agent.

[0024] In an embodiment of the curable composition of the present invention, from the viewpoint of workability in producing a cured product using the curable composition and from the viewpoint of reproducibility of fine lines when drawing by an inkjet method, the viscosity at 25°C is 1 to 1 × 10 4It is preferable that the viscosity is in the range of Pa·s and that the phase transition point is 40°C or higher and lower than 100°C.

[0025] The ink for a solder resist of the present invention is characterized by containing the curable composition of the present invention.

[0026] The printed circuit board of the present invention is a printed circuit board comprising a substrate, a circuit pattern provided on the surface of the substrate, and a solder resist film provided on the circuit pattern, wherein the solder resist film is formed using the solder resist ink of the present invention.

[0027] In an embodiment of the printed circuit board of the present invention, the circuit pattern is preferably made of copper wiring, and the surface roughness Ra of the copper wiring is preferably within a range of 0.1 to 2.0 μm from the viewpoint of adhesion of the solder resist film.

[0028] The present invention, its components, and embodiments and modes for carrying out the present invention will be described below. In the present invention, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0029] [Curable composition] The curable composition of the present invention is a curable composition containing a (meth)acrylic monomer as a main component, and further containing a photopolymerization initiator, a thermosetting compound, and a gelling agent, and is characterized in that a cured product of the curable composition has a relative dielectric constant of less than 2.90 at 10 GHz.

[0030] In the present invention, "(meth)acrylic" means acrylic or methacrylic, "(meth)acrylate" means acrylate or methacrylate, and "(meth)acryloyloxy group ((meth)acryloyloxy group)" means acryloyloxy group (acryloyloxy group) or methacryloyloxy group (methacryloyloxy group).

[0031] The (meth)acrylic monomer contained in the curable composition of the present invention refers to a compound among (meth)acrylic acid and its derivatives that is not a thermosetting compound, as described below. In other words, a (meth)acrylic compound that does not have a thermosetting functional group is called a (meth)acrylic monomer.

[0032] <(Meth)acrylic monomer> The (meth)acrylic monomer according to the present invention is a radically polymerizable compound having a vinyl group derived from (meth)acrylic acid, and is a compound capable of radical polymerization by the action of active energy rays. The curable composition of the present invention contains the (meth)acrylic monomer as a main component. In this specification, the term "main component" refers to a component that accounts for 50% by mass or more of the entire composition. Specifically, the content of the (meth)acrylic monomer in the curable composition is preferably 50 to 95% by mass, more preferably 70 to 90% by mass, of the entire curable composition.

[0033] By including the (meth)acrylic monomer as the main component, the dielectric constant of the resulting cured product can be set within the above-mentioned specific range. Furthermore, by setting the upper limit of the (meth)acrylic monomer content to the above-mentioned value, the content of the thermosetting compound can be sufficiently ensured, and a cured product having excellent adhesion to the substrate and excellent heat resistance can be easily obtained.

[0034] The (meth)acrylic monomer is preferably an ester compound of (meth)acrylic acid, i.e., (meth)acrylate and its derivatives. The (meth)acrylate may be a monofunctional (meth)acrylate having one (meth)acryloyloxy group, or a polyfunctional (meth)acrylate having two or more (meth)acryloyloxy groups. The (meth)acrylic monomer may have a functional group other than a (meth)acryloyloxy group (but not a thermosetting functional group). Examples of the functional group include a hydroxy group, a carboxy group, an imide group, an alkyl group, a cycloalkyl group, an alkyleneoxy group, an aromatic group, and a heterocyclic group. In the present invention, these functional groups are not considered to be thermosetting functional groups, but as will be described later, they may react with the thermosetting functional group of a thermosetting compound by heat and contribute to thermosetting.

[0035] Examples of monofunctional (meth)acrylates include isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomylstyryl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth), ) acrylate, methoxypropylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl-phthalate, and t-butylcyclohexyl (meth)acrylate.

[0036] Among the polyfunctional (meth)acrylates, difunctional (meth)acrylates include, for example, di(meth)acrylates having a (meth)acryloyloxy group at the carbon atom end of the polyoxyalkylene group and a (meth)acryloyl group at the oxygen atom end. The polyoxyalkylene group is a divalent group having an oxyalkylene group as a repeating unit. Examples of the oxyalkylene group as a repeating unit include oxyalkylene groups having 1 to 4 carbon atoms. The alkylene group of the oxyalkylene group may be linear or branched. For example, the propylene group may be any of -(CH2)3-, -CH(CH3)-CH2-, and -CH(CH2CH3)-. The repeat number of the oxyalkylene group (hereinafter referred to as "n") may be 2 to 20, preferably 3 to 14, and more preferably 3 to 10.

[0037] Specific examples of di(meth)acrylates having a polyoxyalkylene group include polyethylene glycol di(meth)acrylates such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate, which are compounds in which the oxyalkylene group is an oxyethylene group. Examples of compounds in which the alkylene group is a propylene group include polypropylene glycol di(meth)acrylates such as dipropylene glycol di(meth)acrylate and tripropylene glycol di(meth)acrylate. Further examples include compounds having a repeating unit of a C4 oxyalkylene group, such as polytetramethylene glycol di(meth)acrylate.

[0038] Other examples of bifunctional (meth)acrylates include 1,4-butanediol di(meth)acrylate, in which (meth)acrylic acid is ester-bonded to a diol, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, propylene oxide (hereinafter sometimes referred to as "PO") or ethylene oxide (hereinafter sometimes referred to as "EO") adduct di(meth)acrylate of bisphenol A, PO or EO adduct di(meth)acrylate of bisphenol F, and hydroxypivalic acid neopentyl glycol di(meth)acrylate.

[0039] Examples of trifunctional or higher functional (meth)acrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerin propoxy tri(meth)acrylate, and pentaerythritol ethoxy tetra(meth)acrylate.

[0040] The (meth)acrylate may be a modified product. Examples of modified (meth)acrylates include ethylene oxide (EO)- or propylene oxide (PO)-modified (meth)acrylates. Examples of EO- or PO-modified (meth)acrylates include EO- or PO-modified trimethylolpropane tri(meth)acrylate, EO- or PO-modified pentaerythritol tetra(meth)acrylate, EO- or PO-modified neopentyl glycol di(meth)acrylate, and EO- or PO-modified 1,6-hexanediol di(meth)acrylate. The number of EO or PO in the EO- or PO-modified (meth)acrylate corresponds to the number of repeating oxyalkylene groups, n, in the polyoxyalkylene group, and is preferably about 1 to 5, and more preferably 2 to 4.

[0041] Examples of modified (meth)acrylates also include caprolactone-modified (meth)acrylates such as caprolactone-modified trimethylolpropane tri(meth)acrylate, and caprolactam-modified (meth)acrylates such as caprolactam-modified dipentaerythritol hexa(meth)acrylate.

[0042] The (meth)acrylate may be a polymerizable oligomer. Examples of the (meth)acrylate that is a polymerizable oligomer include an epoxy (meth)acrylate oligomer, an aliphatic urethane (meth)acrylate oligomer, an aromatic urethane (meth)acrylate oligomer, a polyester (meth)acrylate oligomer, and a linear (meth)acrylic oligomer.

[0043] The (meth)acrylate may be a (meth)acrylate compound having an imide group. Use of a (meth)acrylate having an imide group is expected to improve the high temperature and high humidity resistance of the cured product. In addition, in the case of a (meth)acrylate having an imide group, the imide group has high polarity, so the cured product has strong metal adhesion, and when used to prepare a solder resist film, for example, improved adhesion to a circuit board can be expected. In addition, since the compound itself has strong cohesion, it has little effect on metal adhesion even under high humidity conditions.

[0044] Examples of the (meth)acrylate having an imide group include the imide acrylates and imide methacrylates described in JP-A Nos. 10-36462 and 11-21470.

[0045] In the present invention, the (meth)acrylate may be used alone or in combination of two or more of them. The molecular weight of the (meth)acrylate is not particularly limited, but from the viewpoint of ejection stability in inkjet, the molecular weight is preferably 200 to 1500, more preferably 300 to 1200.

[0046] The curable composition of the present invention preferably contains, as the (meth)acrylic monomer, a (meth)acrylic monomer having a molecular weight within the range of 200 to 1500 and a ClogP value within the range of 3.5 to 7.0 from the viewpoints of the dielectric constant, the dissolution stability of the gelling agent, and the ejection stability in inkjet printing. Hereinafter, the (meth)acrylic monomer having a molecular weight within the range of 200 to 1500 and a ClogP value within the range of 3.5 to 7.0 will also be referred to as (meth)acrylic monomer (A1).

[0047] The (meth)acrylic monomer (A1) has the above advantages due to its molecular weight being in the range of 200 to 1500. Furthermore, a ClogP of 3.5 or greater results in the presence of many hydrophobic structures, making it difficult for water to penetrate during polymerization or when the cured product is formed. This reduces the amount of polar groups present in the cured product, improving the dielectric constant. The (meth)acrylic monomer (A1) has a ClogP of 7.0 or less, improving the dissolution stability of the gelling agent and enabling the formation of the desired house-of-cards structure. This reduces the generation of polar groups due to oxygen or water during polymerization, improving the dielectric constant.

[0048] The (meth)acrylic monomer (A1) is preferably a (meth)acrylate having a molecular weight in the range of 200 to 1500 and a ClogP value in the range of 3.5 to 7.0. The ClogP value of the (meth)acrylic monomer (A1) is more preferably in the range of 4.0 to 6.0. The (meth)acrylic monomer (A1) may also be a (meth)acrylate having a polyoxyalkylene group (e.g., n=2 to 10) with a repeating unit of an oxyalkylene group selected from an oxyethylene group and an oxypropylene group.

[0049] Examples of the (meth)acrylic monomer (A1) include 1,10-decanediol dimethacrylate (molecular weight: 310, ClogP: 5.8), tricyclodecane dimethanol diacrylate (molecular weight: 304, ClogP: 4.7), tricyclodecane dimethanol dimethacrylate (molecular weight: 332, ClogP: 5.3), 3PO-modified trimethylolpropane triacrylate (molecular weight: 470, ClogP: 4.0 to 5.0), dipentaerythritol pentaacrylate (molecular weight: 524, ClogP: 3.8), 6EO-modified trimethylolpropane triacrylate (molecular weight: 560, ClogP: 3.6), bisphenol A 3EO-modified diacrylate (molecular weight: 468, ClogP: 5.9), and bisphenol F 4EO-modified diacrylate (molecular weight: 499, ClogP: 5.0 to 5.2).

[0050] In addition, the (meth)acrylate (A1) is preferably contained in an amount of 50 to 95% by mass, more preferably 70 to 90% by mass, based on the total mass of the curable composition, in terms of injection stability and dissolution stability of the gelling agent. As the (meth)acrylate (A1), one of these may be used alone, or two or more may be used in combination. The (meth)acrylic monomer contained in the curable composition may consist solely of the (meth)acrylic monomer (A1), or may be a combination of the (meth)acrylic monomer (A1) and a (meth)acrylic monomer other than the (meth)acrylic monomer (A1). Examples of other (meth)acrylic monomers include (meth)acrylates having a molecular weight of 200 to 1500 and a ClogP value outside the range of 3.5 to 7.0.

[0051] Here, the "logP value" referred to in the present invention is a coefficient indicating the affinity of an organic compound for water and 1-octanol. The 1-octanol / water partition coefficient P is the partition equilibrium when a trace amount of a compound is dissolved as a solute in a two-phase solvent consisting of 1-octanol and water, and is the ratio of the equilibrium concentrations of the compound in each solvent, and is expressed as their logarithm logP to the base 10. In other words, the "logP value" is the logarithm of the 1-octanol / water partition coefficient P, and is known as an important parameter indicating the hydrophilicity or hydrophobicity of a molecule.

[0052] The "ClogP value" refers to a logP value calculated by calculation. The ClogP value can be calculated by the fragment method, the atomic approach method, or the like. More specifically, the ClogP value can be calculated using the fragment method described in the literature (C. Hansch and A. Leo, "Substituent Constants for Correlation Analysis in Chemistry and Biology" (John Wiley & Sons, New York, 1969)) or the commercially available software package 1 or 2 listed below.

[0053] Software package 1: MedChem Software (Release 3.54, August 1991, Medicinal Chemistry Project, Pomona College, Claremont, CA), Software Package 2: ChemDraw Professional 16.0 (Perkin Elmer) The numerical ClogP values ​​given herein are "ClogP values" calculated using software package 2.

[0054] Other (meth)acrylic monomers used in combination with (meth)acrylic monomer (A1) are preferably (meth)acrylates having a polyoxyalkylene group selected from (meth)acrylates having a molecular weight of 200 to 1500 and 3 to 14 repeating oxyethylene groups represented by (-CH2-CH2-O-) in the molecule and (meth)acrylates having a molecular weight of 200 to 1500 and 2 to 14 repeating oxypropylene groups in the molecule (provided that the ClogP value is outside the range of 3.5 to 7.0). In terms of injection stability, gelling agent dissolution stability, and cure shrinkage (adhesion), (meth)acrylates having a polyoxyalkylene group that satisfy the above conditions will hereinafter also be referred to as (meth)acrylic monomer (A2).

[0055] Examples of the (meth)acrylic monomer (A2) include polyethylene glycol diacrylate (n=9, molecular weight: 508, ClogP: 0.2 to 0.5), 4EO-modified hexanediol diacrylate (molecular weight: 358, ClogP: 2.5), 4EO-modified pentaerythritol tetraacrylate (molecular weight: 528, ClogP: 2.3), nonylphenol 2PO-modified acrylate (molecular weight: 390, ClogP: 7.6), and dipropylene glycol diacrylate (molecular weight: 242, ClogP: 2.0).

[0056] The (meth)acrylic monomer (A2) may be used alone or in combination of two or more. The (meth)acrylic monomer (A2) may constitute the (meth)acrylic monomer contained in the curable composition alone, or may constitute the (meth)acrylic monomer together with another (meth)acrylic monomer. In this case, the (meth)acrylic monomer (A2) is preferably used in combination with the (meth)acrylic monomer (A1), but may also be used in combination with other (meth)acrylic monomers other than the (meth)acrylic monomer (A1).

[0057] When the (meth)acrylic monomer (A2) is used, the content of the (meth)acrylic monomer (A2) is preferably within a range of 30 to 70 mass% based on the total curable composition in terms of cure shrinkage (adhesion) of the cured product. Furthermore, when the (meth)acrylic monomer (A1) and the (meth)acrylic monomer (A2) are used in combination, the content of the (meth)acrylic monomer (A2) is preferably 1.5 to 60 mass% based on the total curable composition, more preferably 5 to 30 mass%, and even more preferably 10 to 20 mass%. In this case, the content of the (meth)acrylic monomer (A1) is preferably 30 to 90 mass%, more preferably 70 to 90 mass%, based on the total curable composition.

[0058] The (meth)acrylic monomer may contain other (meth)acrylic monomers other than the (meth)acrylic monomer (A1) and the (meth)acrylic monomer (A2). The other (meth)acrylic monomers preferably have a molecular weight in the range of 200 to 1500, and examples thereof include dicyclopentanyl acrylate (molecular weight: 206, ClogP: 3.1).

[0059] The (meth)acrylic monomer contained in the curable composition may be composed solely of the other (meth)acrylic monomer, but the other (meth)acrylic monomer is preferably used in combination with the (meth)acrylic monomer (A1) or the (meth)acrylic monomer (A2). In this case, the content of the other (meth)acrylic monomer is preferably 5 to 30 mass %, more preferably 10 to 20 mass %, based on the total mass of the curable composition.

[0060] <Other photopolymerizable compounds> The curable composition of the present invention may contain other photopolymerizable compounds in addition to the (meth)acrylic monomer. The other photopolymerizable compounds may be compounds that undergo a polymerization or crosslinking reaction upon irradiation with active energy rays, thereby polymerizing or crosslinking and curing the curable composition. Examples of other photopolymerizable compounds include radically polymerizable compounds and cationically polymerizable compounds other than (meth)acrylic monomers. The other photopolymerizable compounds may be monomers, polymerizable oligomers, prepolymers, or mixtures thereof. The curable composition may contain only one type of other photopolymerizable compound, or two or more types. The cationically polymerizable compounds may be epoxy compounds, vinyl ether compounds, oxetane compounds, etc. The curable composition may contain only one type of cationically polymerizable compound, or two or more types.

[0061] From the viewpoint of controlling the dielectric constant, the curable composition according to the present invention is mainly composed of a (meth)acrylic monomer, and therefore preferably contains 0 to 2 types of other photopolymerizable compounds, more preferably 1 or less types, and most preferably contains no other photopolymerizable compounds. The content of the other photopolymerizable compounds in the curable composition can be, for example, 10% by mass or less, preferably 5% by mass or less, and particularly preferably 0% by mass, based on the total amount of the curable composition.

[0062] <Photopolymerization initiator> The photopolymerization initiator according to the present invention is an essential component contained in the curable composition for photopolymerizing the (meth)acrylic monomer. As the photopolymerization initiator, a photoradical initiator is preferred. When a cationically polymerizable compound is used as another photopolymerizable compound in addition to the (meth)acrylic monomer, it is preferred to use a photoacid generator in addition to the photoradical initiator.

[0063] The curable composition of the present invention may contain only one type of photopolymerization initiator, or may contain two or more types of photopolymerization initiators. The photopolymerization initiator may be a combination of both a photoradical initiator and a photoacid generator.

[0064] Photoradical initiators include cleavage-type radical initiators and hydrogen abstraction-type radical initiators. Examples of cleavage-type radical initiators include acetophenone-based initiators, benzoin-based initiators, acylphosphine oxide-based initiators, and benzyl and methylphenyl glyoxyesters.

[0065] Examples of acetophenone-based initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone, and 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one.

[0066] Examples of benzoin-based initiators include benzoin, benzoin methyl ether, and benzoin isopropyl ether.

[0067] Examples of the acylphosphine oxide initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0068] Examples of the hydrogen abstraction type radical initiator include benzophenone-based initiators, thioxanthone-based initiators, aminobenzophenone-based initiators, 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-phenanthrenequinone, and camphorquinone.

[0069] Examples of benzophenone-based initiators include benzophenone, o-benzoylmethylbenzoate-4-phenylbenzophenone, 4,4′-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4′-methyl-diphenyl sulfide, acrylated benzophenone, 3,3′,4,4′-tetra(t-butylperoxycarbonyl)benzophenone, and 3,3′-dimethyl-4-methoxybenzophenone.

[0070] Examples of thioxanthone initiators include 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone. Examples of aminobenzophenone initiators include Michler's ketone and 4,4'-diethylaminobenzophenone.

[0071] Examples of photoacid generators include the compounds described in Organic Electronics Materials Research Group, "Imaging Organic Materials," Bunshin Publishing (1993), pp. 187-192.

[0072] The content of the photopolymerization initiator may be within a range that allows the curable composition to be sufficiently cured, and may be, for example, within a range of 0.01 to 10 mass % relative to the total mass of the curable composition of the present invention, and preferably 0.1 to 5 mass %.

[0073] The photopolymerization initiator may be a combination of two types of photopolymerization initiators with different absorption sensitivity wavelengths. Examples of such combinations of photopolymerization initiators include a combination of an acylphosphine oxide initiator and a thioxanthone initiator, and a combination of a peroxide initiator and a thioxanthone initiator.

[0074] Examples of commercially available photopolymerization initiators include Omnirad TPO H (manufactured by IGM, 2,4,6-trimethylbenzoyldiphenylphosphine oxide), Omnirad 819 (manufactured by IGM, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide), Omnirad 379 (manufactured by IGM, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one), and Omnirad ITX (manufactured by IGM, 2-isopropylthioxanthone).

[0075] The curable composition of the present invention may further contain a photopolymerization initiator aid, etc., as needed. The photopolymerization initiator aid may be a tertiary amine compound, preferably an aromatic tertiary amine compound. Examples of aromatic tertiary amine compounds include N,N-dimethylaniline, N,N-diethylaniline, N,N-dimethyl-p-toluidine, N,N-dimethylamino-p-benzoic acid ethyl ester, N,N-dimethylamino-p-benzoic acid isoamyl ethyl ester, N,N-dihydroxyethylaniline, triethylamine, and N,N-dimethylhexylamine. Among these, N,N-dimethylamino-p-benzoic acid ethyl ester and N,N-dimethylamino-p-benzoic acid isoamyl ethyl ester are preferred. These compounds may be used alone or in combination of two or more.

[0076] Commercially available photopolymerization initiator aids include Genocure EPD (manufactured by Rahn AG, N,N-dimethylamino-p-benzoic acid ethyl ester).

[0077] <Thermosetting compounds> The curable composition of the present invention contains a (meth)acrylic monomer as a radically polymerizable compound as a main component, and further contains a thermosetting compound that is cured by heat. By containing the thermosetting compound, the curable composition of the present invention can improve the adhesion to a circuit board and heat resistance of the obtained cured product. The curable composition of the present invention cures by reacting the (meth)acrylic monomer upon irradiation with active energy rays and the thermosetting compound upon heating to form a cured product.

[0078] The content of the thermosetting compound in the curable composition is an amount that allows the curable composition to contain a (meth)acrylic monomer as a main component, and is preferably 1 to 15 mass % and more preferably 2 to 10 mass % relative to the total curable composition. If the content of the thermosetting compound is less than 1 mass %, the adhesion and heat resistance may be insufficient. If the content of the thermosetting compound exceeds 15 mass %, the thermal stability may decrease when the temperature is raised above the gelation temperature. Furthermore, unreacted thermosetting compound may react with water to generate polar groups.

[0079] The thermosetting compound according to the present invention refers to a compound having a thermosetting functional group. Examples of the thermosetting functional group include those cited in reviews such as "Refining Thermosetting Polymers" (by Tsuyoshi Endo, published by CMC Corporation, 1986), "Latest Binder Technology Handbook" Chapter II-I (by Yuji Harasaki, published by the General Technology Center, 1985), "Synthesis, Design, and New Application Development of Acrylic Resins" (by Takayuki Otsu, published by the Chubu Management Development Center Publishing Department, 1985), and "Functional Acrylic Resins" (by Eizo Omori, published by Techno System, 1985). Specifically, from the standpoint of thermosetting properties, the thermosetting functional group is preferably at least one selected from the group consisting of an isocyanate group, an epoxy group, and a maleimide group.

[0080] The thermosetting compound according to the present invention may contain a (meth)acrylate structure, and a (meth)acrylate having a thermosetting functional group is considered a thermosetting compound. The thermosetting of the thermosetting compound according to the present invention may be achieved by a reaction between the thermosetting functional groups of the thermosetting compound, or by a reaction between the thermosetting functional group of the thermosetting compound and the functional group contained in the (meth)acrylate, which is the main component. Below, thermosetting compounds are described according to the type of thermosetting functional group they have.

[0081] (isocyanate group) Examples of thermosetting compounds having an isocyanate group include polyfunctional isocyanate compounds having two or more isocyanate groups in the molecule.

[0082] Specific examples of polyfunctional isocyanate compounds include aromatic isocyanates such as 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI), and 1,5-naphthalene diisocyanate (NDI). Polyisocyanates include aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, and norbornane diisocyanate methyl (NBDI); alicyclic polyisocyanates such as transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6XDI (hydrogenated XDI), H12MDI (hydrogenated MDI), and H6TDI (hydrogenated TDI); and polyisocyanates such as polymethylene polyphenylene polyisocyanate.

[0083] These polyfunctional isocyanate compounds may be polymerized, and examples of the polymerized compounds include biuret and isocyanurate trimers. The polyfunctional isocyanate compounds may also be modified, for example, into carbodiimide-modified compounds.

[0084] The thermosetting compound having an isocyanate group may be a (meth)acrylate compound having an isocyanate group. The (meth)acrylate compound having an isocyanate group may be any compound having an isocyanate group and a (meth)acryloyloxy group in the molecule, such as 2-(meth)acryloyloxyethyl isocyanate, 2-isocyanatoethyl (meth)acrylate, 3-isocyanatopropyl (meth)acrylate, etc. Other examples include reaction products of hydroxyalkyl (meth)acrylates such as hydroxyethyl (meth)acrylate with polyisocyanates such as tolylene diisocyanate.

[0085] As a thermosetting compound having an isocyanate group, a blocked isocyanate compound (thermally dissociable blocked isocyanate compound) having an isocyanate group protected with a thermally dissociable blocking agent is preferred in terms of lowering the dielectric constant of the cured product and improving resistance to high temperatures and high humidity. In a thermally dissociable blocked isocyanate compound, the reactivity of the isocyanate group is suppressed by protection by the blocking agent below the dissociation temperature of the blocking agent, so that a curable composition containing this compound has high thermal stability. Furthermore, the blocking agent dissociates when heated to a temperature above the dissociation temperature, making the isocyanate group reactive.

[0086] The blocked isocyanate compound is preferably a thermally dissociable blocked isocyanate compound of a polyfunctional isocyanate compound. In the case of a polyfunctional blocked isocyanate compound having an isocyanate group protected with a blocking agent, the isocyanurate ring formed by the trimerization reaction of the isocyanate has higher thermal stability of the bond than urethane or urea bonds, and is excellent in heat resistance. Furthermore, when a polyfunctional blocked isocyanate compound is used, a network structure having an isocyanurate ring is formed, which further improves heat resistance and makes the compound less susceptible to the effects of humidity at high temperatures.

[0087] The thermally dissociable blocking agent is preferably at least one compound selected from the group consisting of oxime compounds, pyrazole compounds, and active ethylene compounds, in terms of the storage stability and thermal dissociability of the curable composition.

[0088] Examples of oxime compounds include formamide oxime, acetaldoxime, acetoxime, methyl ethyl ketone oxime (MEKO), and cyclohexanone oxime.

[0089] Examples of pyrazole compounds include pyrazole, 3-methylpyrazole, and 3,5-dimethylpyrazole (DMP).

[0090] Examples of active ethylene compounds include dimethyl malonate, diethyl malonate (DEM), methyl acetoacetate, ethyl acetoacetate, and acetylacetone.

[0091] As the thermally dissociable blocking agent, caprolactam such as ε-caprolactam can also be used.

[0092] Examples of blocked isocyanate compounds having an isocyanate group protected with a blocking agent include 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl (meth)acrylate (Karenz MOI-BP, manufactured by Showa Denko K.K.), 2-[(3-butylidene)aminooxycarbonylamino]ethyl (meth)acrylate, and 2-(0-[1'-methylpropylideneamino]carboxyamino)ethyl (meth)acrylate (Karenz MOI-BM, manufactured by Showa Denko K.K.). Substitute commercially available products (product names and manufacturers) are listed in parentheses after the compound names. The same applies to the following multifunctional blocked isocyanate compounds having an isocyanate group protected with a blocking agent.

[0093] Examples of the polyfunctional blocked isocyanate compound having an isocyanate group protected with a blocking agent include a DMP-blocked HDI biuret (Trixene BI7961, manufactured by LANXESS), a DMP-blocked HDI trimer (Trixene BI7982, manufactured by LANXESS), a DMP- and DEM-blocked HDI trimer (Trixene BI7992, manufactured by LANXESS), a MEKO-blocked HDI trimer (PU5211, manufactured by Leeson Polyurethanes), and an ε-caprolactam-blocked polyfunctional isocyanate (VESTANATB1186A, manufactured by Evonik).

[0094] The blocking agent may be used alone or in combination of two or more types. One or more thermally dissociable blocked isocyanate compounds blocked with a single blocking agent or two or more types of blocking agents can be used as the thermosetting compound.

[0095] In addition to the above, other commercially available product names of thermally dissociable blocked isocyanate compounds include MF-K60X (manufactured by Asahi Kasei Chemicals Corporation), VPLS2253, and BL4265SN (all manufactured by Sumika Bayer Urethane Co., Ltd.).

[0096] (epoxy group) Examples of thermosetting compounds having an epoxy group include various chain epoxy group-containing monomers (e.g., glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, glycidyl vinyl ether, allyl glycidyl ether, etc.), various (2-oxo-1,3-oxolane) group-containing vinyl monomers (e.g., (2-oxo-1,3-oxolane)methyl (meth)acrylate, etc.), various alicyclic epoxy group-containing vinyl monomers (e.g., 3,4-epoxycyclo hexyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, etc.), bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, brominated bisphenol S diglycidyl ether, hydrogenated bisphenol A diglycidyl ether glycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ethers, polypropylene glycol diglycidyl ethers; polyglycidyl ethers of polyether polyols obtained by adding one or more alkylene oxides to aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, and glycerin; diglycidyl esters of aliphatic long-chain dibasic acids; monoglycidyl ethers of aliphatic higher alcohols; monoglycidyl ethers of polyether alcohols obtained by adding phenol, cresol, butylphenol, or these with alkylene oxides; and glycidyl esters of higher fatty acids.

[0097] Furthermore, examples of thermosetting compounds having an epoxy group include compounds having a (meth)acryloyloxy group and an epoxy group, partial (meth)acrylates of epoxy compounds, etc. Examples of the compounds having a (meth)acryloyloxy group and an epoxy group include glycidyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate glycidyl ether, etc.

[0098] The partially (meth)acrylated epoxy compound can be obtained by reacting an epoxy compound with (meth)acrylic acid in the presence of a catalyst according to a conventional method. Examples of epoxy compounds that can be used for the partially (meth)acrylated epoxy compound include novolac epoxy compounds and bisphenol epoxy compounds.

[0099] Examples of the novolac epoxy compounds include phenol novolac epoxy compounds, cresol novolac epoxy compounds, biphenyl novolac epoxy compounds, trisphenol novolac epoxy compounds, and dicyclopentadiene novolac epoxy compounds. Examples of the bisphenol epoxy compounds include bisphenol A epoxy compounds, bisphenol F epoxy compounds, 2,2'-diallyl bisphenol A epoxy compounds, hydrogenated bisphenol epoxy compounds, and polyoxypropylene bisphenol A epoxy compounds. By appropriately changing the amounts of the epoxy compound and (meth)acrylic acid, it is possible to obtain an epoxy compound with a desired acrylate ratio.

[0100] (maleimide group) Examples of the thermosetting compound having a maleimide group include N-methylmaleimide, N-ethylmaleimide, N-hexylmaleimide, N-propylmaleimide, N-butylmaleimide, N-octylmaleimide, N-dodecylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, Np-carboxyphenylmaleimide, Np-hydroxyphenylmaleimide, Np-chlorophenylmaleimide, Np-tolylmaleimide, Np-xylylmaleimide, No-chlorophenylmaleimide, No-tolylmaleimide, N-benzylmaleimide, N-2,5-diethylphenylmaleimide, N-2,5-dimethylphenylmaleimide, Nm-tolylmaleimide, N-α-naphthylmaleimide, No-xylylmaleimide, and Nm-xylyl Examples of the dimaleimide include maleimide, bismaleimide methane, 1,2-bismaleimide ethane, 1,6-bismaleimide hexane, bismaleimide dodecane, N,N'-m-phenylene dimaleimide, N,N'-p-phenylene dimaleimide, 4,4' bismaleimide diphenyl ether, 4,4'-bismaleimide diphenylmethane, 4,4'-bismaleimide-di(3-methylphenyl)methane, 4,4'-bismaleimide-di(3-ethylphenyl)methane, 4,4'-bismaleimide-di(3-methyl-5-ethyl-phenyl)methane, N,N'-(2,2-bis-(4-phenoxyphenyl)propane)dimaleimide, N,N'-2,4-tolylene dimaleimide, N,N'-2,6-tolylene dimaleimide, N,N'-m-xylylene dimaleimide, and bisphenol A diphenyl ether bismaleimide.

[0101] (Other thermosetting functional groups) Examples of the thermosetting compound include a thermosetting compound having a functional group other than the above-mentioned thermosetting functional group, such as an oxetanyl group or an oxazoline group.

[0102] Examples of thermosetting compounds having an oxetanyl group include oxetane (meth)acrylate, etc. Commercially available products of such compounds include OXE-10 and OXE-30, both of which are manufactured by Osaka Organic Chemical Industry Co., Ltd.

[0103] Examples of thermosetting compounds having an oxazoline group include 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, and monomers having a substituent on the oxazoline group of these oxazoline group-containing monomers.

[0104] <Gelling agent> The curable composition of the present invention contains a gelling agent as an essential component. By including a gelling agent in the curable composition of the present invention, the generation of polar groups is suppressed when the curable composition is cured by light and heat, as described above, and the resulting cured product has a low dielectric constant. Furthermore, the presence of a gelling agent in the resulting cured product can prevent oxygen and moisture from penetrating into the cured product. From this perspective, it is preferable that the gelling agent be maintained in a uniformly dispersed state in the cured product.

[0105] The gelling agent is not particularly limited as long as it is a compound that can gel the curable composition. From the viewpoint of further enhancing the above-mentioned effect, ketone wax, ester wax, higher fatty acid, higher alcohol, and fatty acid amide are preferred, ketone wax and ester wax are more preferred, and ketone wax represented by the following general formula (G1) and ester wax represented by the following general formula (G2) are even more preferred.

[0106] In addition, the gelling agents described in JP-A-2018-506594, JP-A-2015-509996, JP-A-2006-193745, and JP-A-2011-225876 can also be used.

[0107] The gelling agent according to the present invention is preferably at least one compound selected from the compounds represented by the following general formula (G1) or (G2), in that it can be dispersed in the cured product (cured film) without inhibiting the curability of the curable composition. Furthermore, in inkjet printing using the curable composition as an ink, it is preferable in that it has good pinning properties, can achieve both fine lines and a thick film, and has excellent fine line reproducibility.

[0108] General formula (G1): R1-CO-R2 General formula (G2): R3-COO-R4 [In the formula, R1 to R4 each independently represent an aliphatic hydrocarbon group having 12 or more carbon atoms and a linear portion, which may be branched.]

[0109] The compound represented by the general formula (G1) above is a ketone wax in which R1 and R2 are bonded to both sides of a carbonyl group (-C(=O)-). The compound represented by the general formula (G2) above is an ester wax in which R3 and R4 are bonded to both sides of an ester group (-C(=O)O-). In the ketone wax represented by the general formula (G1) above or the ester wax represented by the general formula (G2) above, R1 and R2, or R3 and R4, are each independently an optionally branched aliphatic hydrocarbon group having a linear portion with 12 or more carbon atoms. This increases the crystallinity of the gelling agent, improves water resistance, and creates more space in the house-of-card structure. This makes it easier for each component in the curable composition to be fully enclosed within the space, resulting in improved pinning properties when used as an ink.

[0110] R1 to R4 may be either a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group, so long as they have the above structure. It is preferable that R1 to R4 each independently have 26 or fewer carbon atoms. When R1 to R4 each have 26 or fewer carbon atoms, the melting point of the gelling agent does not become excessively high, and therefore it is not necessary to excessively heat the ink when the curable composition is ejected as ink. From the above viewpoint, it is particularly preferable that R1 and R2, or R3 and R4, each independently be a linear aliphatic hydrocarbon group having from 12 to 23 carbon atoms.

[0111] Furthermore, from the viewpoint of increasing the gelling temperature of the curable composition and gelling the ink more rapidly after impact when the curable composition is used as an ink, it is preferable that either R1 or R2, or either R3 or R4, is a saturated alkyl group having from 12 to 23 carbon atoms. From the above viewpoint, it is more preferable that both R1 and R2, or both R3 and R4, are saturated alkyl groups having from 12 to 23 carbon atoms.

[0112] Examples of ketone waxes represented by the general formula (G1) include dilignoceryl ketone (C24-C24), dibehenyl ketone (C22-C22), distearyl ketone (C18-C18), dieicosyl ketone (C20-C20), dipalmityl ketone (C16-C16), dimyristyl ketone (C14-C14), dilauryl ketone (C12-C12), lauryl myristyl ketone ( These include: lauryl palmityl ketone (C12-C14), lauryl palmityl ketone (C12-C16), myristyl palmityl ketone (C14-C16), myristyl stearyl ketone (C14-C18), myristyl behenyl ketone (C14-C22), palmityl stearyl ketone (C16-C18), palmityl behenyl ketone (C16-C22), and stearyl behenyl ketone (C18-C22). Note that the number of carbon atoms in the parentheses above indicates the number of carbon atoms in each of the two hydrocarbon groups separated by the carbonyl group.

[0113] Commercially available examples of the ketone wax represented by general formula (G1) include Stearonne (manufactured by Alfa Aeser; Stearon), 18-Pentatriacontanone (manufactured by Alfa Aeser), Hentriacontan-16-one (manufactured by Alfa Aeser), and Kaowax T-1 (manufactured by Kao Corporation).

[0114] Examples of the ester wax represented by the general formula (G2) include behenyl behenate (C21-C22), icosanoic acid icosyl (C19-C20), stearyl stearate (C17-C18), palmityl stearate (C17-C16), lauryl stearate (C17-C12), cetyl palmitate (C15-C16), stearyl palmitate (C15-C18), These include myristyl myristate (C13-C14), cetyl myristate (C13-C16), octyldodecyl myristate (C13-C20), stearyl oleate (C17-C18), stearyl erucate (C21-C18), stearyl linoleate (C17-C18), behenyl oleate (C18-C22), and arachidyl linoleate (C17-C20). Note that the number of carbon atoms in the parentheses above indicates the number of carbon atoms in each of the two hydrocarbon groups separated by the ester group.

[0115] Commercially available examples of the ester wax represented by general formula (G2) include Unistar M-2222SL and Sperm Acetate, manufactured by NOF Corporation ("Unistar" is a registered trademark of the company), Exepar SS and Exepar MY-M, manufactured by Kao Corporation ("Exepar" is a registered trademark of the company), EMALEX CC-18 and EMALEX CC-10, manufactured by Nippon Emulsion Co., Ltd. ("EMALEX" is a registered trademark of the company), and Amuleps PC, manufactured by Kokyu Alcohol Kogyo Co., Ltd. ("Amuleps" is a registered trademark of the company).

[0116] These commercially available products are often mixtures of two or more types, and may be separated and purified as necessary before being incorporated into the curable composition. When the curable composition contains two or more types selected from the ketone wax represented by general formula (G1) and the ester wax represented by general formula (G2), it is preferable to contain a combination of the ketone wax and the ester wax.

[0117] The content of the gelling agent according to the present invention is preferably within the range of 0.5 to 5.0% by mass relative to the total mass of the curable composition. By setting the content of the gelling agent within this range, the solubility and pinning effect of the gelling agent in the curable composition are improved, and further, the water resistance of the cured product (cured film) is improved. From the above viewpoint, the content of the gelling agent in the curable composition is more preferably within the range of 0.5 to 2.5% by mass.

[0118] Furthermore, from the following viewpoint, it is preferable that the gelling agent crystallizes in the curable composition at a temperature equal to or lower than the gelation temperature of the curable composition. The gelation temperature refers to the temperature at which the gelling agent undergoes a phase transition from sol to gel and the viscosity of the curable composition suddenly changes when the curable composition that has been solated or liquefied by heating is cooled. Specifically, the solated or liquefied curable composition is cooled while measuring its viscosity with a viscoelasticity measuring device (e.g., MCR300, manufactured by Physica), and the temperature at which the viscosity suddenly increases can be determined to be the gelation temperature of the curable composition.

[0119] The curable composition of the present invention contains a (meth)acrylic monomer as a main component, and optionally other photopolymerizable compounds and photopolymerization initiators, and further contains a thermosetting compound and a gelling agent. The curable composition of the present invention undergoes a reaction of the photopolymerizable compound containing the (meth)acrylic monomer upon irradiation with active energy rays, resulting in curing (hereinafter also referred to as "photocuring"). Furthermore, the thermosetting compound undergoes a reaction of the thermosetting compound upon heating, resulting in curing (hereinafter also referred to as "thermocuring"). The order of photocuring and thermocuring does not matter. For example, when the curable composition of the present invention is applied to a substrate, the applied coating liquid is pre-cured by photocuring upon irradiation with active energy rays, and then heated for full curing by thermocuring, the inclusion of a gelling agent can suppress the wetting and spreading of the coating liquid after pre-curing, allowing for the formation of highly accurate patterns.

[0120] <Optional ingredients> The curable composition of the present invention may contain a colorant as an optional component. Furthermore, as long as the effects of the present invention are obtained, other optional components such as a polymerization inhibitor, a surfactant, a curing accelerator, a coupling agent, and an ion scavenger may be contained. The curable composition of the present invention may contain only one type of other optional component, or two or more types.

[0121] (coloring agent) The curable composition of the present invention may further contain a colorant, if necessary. The colorant may be a dye or a pigment, but is preferably a pigment because it has good dispersibility in the components of the curable composition and excellent weather resistance. The pigment is not particularly limited, but examples thereof include organic pigments or inorganic pigments with the following numbers listed in the Color Index.

[0122] Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 53:1, 57:1, 57:2, 58:4, 63:1, 81, 81:1, 81:2, 81:3, 81:4, 88, 104, 108, 112, 122, 123, 144, 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, and Pigment Orange. 13, 16, 20, 36 or a mixture thereof.

[0123] Examples of blue or cyan pigments include pigments selected from Pigment Blue 1, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17-1, 22, 27, 28, 29, 36, and 60, or mixtures thereof.

[0124] Examples of green pigments include pigments selected from Pigment Green 7, 26, 36, 50, or mixtures thereof.

[0125] Examples of yellow pigments include pigments selected from Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, and 193, or mixtures thereof.

[0126] Examples of black pigments include pigments selected from Pigment Black 7, 28, and 26, or mixtures thereof.

[0127] Examples of commercially available pigments include Black Pigment (manufactured by Mikuni), Chromofine Yellow 2080, 5900, 5930, AF-1300, 2700L, Chromofine Orange 3700L, 6730, Chromofine Scarlet 6750, Chromofine Magenta 6880, 6886, 6891N, 6790, 6887, and Chromofine Violet. RE, Chromofine Red 6820, 6830, Chromofine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5000P, Chromofine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Chromofine Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400(B), 2500, 2600, ZAY-260, 2700(B), 2770 Seika Fast Red 8040, C405(F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seika Fast Carmine 6B1476T-7, 1483LT, 3840, 3870, Seika Fast Bordeaux 10B-430, Seika Light Rose R40, Seika Light Violet B800, 7805, Seika Fast Maroon 460N, Seika Fast Orange 900, 2900, Seika Light Blue C718, A612, Cyanine Blue 4933M, 4933GN-EP, 4940, 4973 (manufactured by Dainichi Seika Color & Chemicals Mfg. Co., Ltd.); KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118, 124, KET Green 201 (manufactured by DIC);Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T-13, T-05, Pigment Yellow1705, Colortex Orange 202, Colortex Red101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, 105C, USN, Colortex Maroon601, Colortex BrownB610N, Colortex Violet600, Pigment Red 122, Colortex Blue516, 517, 518, 519, A818, P-908, 510, Colortex Green 402, 403, Colortex Black 702, U905 (manufactured by Sanyo Dye Co., Ltd.); Lionol Yellow 1405G, Lionol Blue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (manufactured by Toyo Ink Co., Ltd.); Toner Magenta E02, Permanent Rubin F6B, Toner Yellow HG, Permanent Yellow GG-02, Hostapearm Blue B2G (manufactured by Hoechst Industries); Novoperm P-HG, Hostaperm Pink E, Hostaperm Blue B2G (manufactured by Clariant); carbon black #2600, #2400, #2350, #2200, #1000, #990, #980, #970, #960, #950, #850, MCF88, #750, #650, MA600, MA7, MA8, MA11, MA100, MA100R, MA77, #52, #50, #47, #45, #45L, #40, #33, #32, #30, #25, #20, #10, #5, #44, and CF9 (manufactured by Mitsubishi Chemical Corporation) are examples.

[0128] The pigment can be dispersed using, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like.

[0129] The pigment is preferably dispersed so that the volume average particle size of the pigment particles is preferably within a range of 0.08 to 0.5 μm, and the maximum particle size is preferably within a range of 0.3 to 10 μm, more preferably within a range of 0.3 to 3 μm. The dispersion of the pigment is adjusted by selecting the pigment, dispersant, and dispersion medium, and by adjusting the dispersion conditions and filtration conditions.

[0130] The curable composition of the present invention may further contain a dispersant to enhance the dispersibility of the pigment. Examples of the dispersant include carboxylic acid esters having a hydroxy group, salts of long-chain polyaminoamides and high-molecular-weight acid esters, salts of high-molecular-weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, high-molecular-weight unsaturated acid esters, polymer copolymers, modified polyurethanes, modified polyacrylates, polyether ester-type anionic surfactants, naphthalenesulfonic acid formalin condensate salts, aromatic sulfonic acid formalin condensate salts, polyoxyethylene alkyl phosphate esters, polyoxyethylene nonylphenyl ether, and stearylamine acetate.

[0131] Examples of commercially available dispersants include EFKA7701 (manufactured by BASF), the Solsperse series such as Solsperse 22000 (manufactured by Lubrizol Japan), and the PB series from Ajinomoto Fine-Techno Co., Ltd.

[0132] The curable composition of the present invention may further contain a dispersing aid, if necessary, which may be selected depending on the pigment.

[0133] The total amount of the dispersant and dispersion aid is preferably within the range of 1 to 50% by mass relative to the pigment.

[0134] The curable composition of the present invention may further contain a dispersion medium for dispersing the pigment, if necessary. A solvent may be contained in the curable composition as the dispersion medium. However, in order to prevent the solvent from remaining in the formed image, it is preferable to use a photopolymerizable compound (particularly a monomer with low viscosity) as the dispersion medium. When a photopolymerizable compound such as a (meth)acrylic monomer is used as the dispersion medium, the amount of the dispersion medium is added to the content of the photopolymerizable compound such as the (meth)acrylic monomer.

[0135] The dye may be an oil-soluble dye. Examples of oil-soluble dyes include the following various dyes: Examples of magenta dyes include MS Magenta VP, MS Magenta HM-1450, MS Magenta HSo-147 (all manufactured by Mitsui Chemicals, Inc.), AIZEN SOT Red-1, AIZEN SOT Red-2, AIZEN SOTRed-3, AIZEN SOT Pink-1, SPIRON Red GEH SPECIAL (all manufactured by Hodogaya Chemical Co., Ltd.), RESOLIN Red FB 200%, MACROLEX Red Violet R, MACROLEX ROT5B (all manufactured by Bayer Japan Ltd.), KAYASET Red B, KAYASET Red 130, KAYASET Red 802 (all manufactured by Nippon Kayaku Co., Ltd.), PHLOXIN, ROSE BENGAL, ACID Red (all manufactured by Daiwa Chemical Industry Co., Ltd.), HSR-31, DIARESIN Red K (all manufactured by Mitsubishi Chemical Corporation), and Oil Red (manufactured by BASF Japan Ltd.).

[0136] Examples of cyan dyes include MS Cyan HM-1238, MS Cyan HSo-16, Cyan HSo-144, and MS Cyan VPG (all manufactured by Mitsui Chemicals, Inc.), AIZEN SOT Blue-4 (manufactured by Hodogaya Chemical Co., Ltd.), RESOLIN BR.Blue BGLN 200%, MACROLEX Blue RR, CERES Blue GN, SIRIUS SUPRATURQ.Blue Z-BGL, and SIRIUS SUPRA TURQ.Blue FB-LL 330% (all manufactured by Bayer Japan KK), KAYASET Blue FR, KAYASET Blue N, KAYASET Blue 814, Turq.Blue GL-5 200, and Light Blue BGL-5200 (all manufactured by Nippon Kayaku Co., Ltd.), DAIWA Blue 7000 and OleosolFast Blue GL (all manufactured by Daiwa Chemical Industry Co., Ltd.), DIARESIN Blue P (manufactured by Mitsubishi Chemical Corporation), and SUDAN Blue 670, NEOPEN Blue 808, ZAPON Blue 806 (all manufactured by BASF Japan Ltd.), etc.

[0137] Examples of yellow dyes include MS Yellow HSm-41, Yellow KX-7, Yellow EX-27 (manufactured by Mitsui Chemicals, Inc.), AIZEN SOT Yellow-1, AIZEN SOT Yellow-3, AIZEN SOT Yellow-6 (all manufactured by Hodogaya Chemical Co., Ltd.), MACROLEX Yellow 6G, MACROLEX FLUOR. Yellow 10GN (all manufactured by Bayer Japan KK), KAYASETYellow SF-G, KAYASET Yellow 2G, KAYASET Yellow AG, KAYASET Yellow EG (all manufactured by Nippon Kayaku Co., Ltd.), DAIWA Yellow 330HB (manufactured by Daiwa Chemical Industry Co., Ltd.), HSY-68 (manufactured by Mitsubishi Chemical Corporation), SUDAN Yellow 146, NEOPEN Yellow 075 (all manufactured by BASF Japan Ltd.), and the like.

[0138] Examples of black dyes include MS Black VPC (manufactured by Mitsui Chemicals, Inc.), AIZEN SOT Black-1, AIZEN SOT Black-5 (all manufactured by Hodogaya Chemical Co., Ltd.), RESOLIN Black GSN 200%, RESOLIN Black BS (all manufactured by Bayer Japan KK), KAYASET Black AN (manufactured by Nippon Kayaku Co., Ltd.), DAIWA Black MSC (manufactured by Daiwa Chemical Industry Co., Ltd.), HSB-202 (manufactured by Mitsubishi Chemical Corporation), NEPTUNE Black X60, NEOPEN Black X58 (all manufactured by BASF Japan KK), and the like.

[0139] The curable composition of the present invention may contain one or more colorants to be toned to a desired color. The content of the colorant is preferably within a range of 0.1 to 20% by mass, more preferably within a range of 0.4 to 10% by mass, based on the total amount of the curable composition.

[0140] (polymerization inhibitor) Examples of the polymerization inhibitor include (alkyl)phenols, hydroquinone, catechol, resorcinol, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiazine, p-benzoquinone, nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, cupferron, aluminum N-nitrosophenylhydroxyamine, tri-p-nitrophenylmethyl, N-(3-oxyanilino-1,3-dimethylbutylidene)aniline oxide, dibutyl cresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraldoxime, methyl ethyl ketoxime, and cyclohexanone oxime.

[0141] Examples of commercially available polymerization inhibitors include Irgastab UV10 (manufactured by BASF) and Genorad 18 (manufactured by Rahn AG).

[0142] The amount of the polymerization inhibitor can be set arbitrarily as long as the effects of the present invention are obtained. The amount of the polymerization inhibitor can be, for example, 0.001% by mass or more and less than 1.0% by mass relative to the total mass of the curable composition.

[0143] (surfactant) Examples of surfactants include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene-polyoxypropylene block copolymers; cationic surfactants such as alkylamine salts and quaternary ammonium salts; and silicone-based and fluorine-based surfactants.

[0144] Examples of silicone surfactants include polyether-modified polysiloxane compounds, specifically Tego rad 2250 manufactured by Evonik, KF-351A, KF-352A, KF-642, and X-22-4272 manufactured by Shin-Etsu Chemical Co., Ltd., BYK307, BYK345, BYK347, and BYK348 manufactured by BYK-Chemie ("BYK" is a registered trademark of the company), and TSF4452 manufactured by Momentive Performance Materials.

[0145] Fluorine-based surfactants refer to surfactants in which some or all of the hydrogen atoms bonded to the carbon atoms of the hydrophobic group of a typical surfactant have been replaced with fluorine. Examples of fluorine-based surfactants include Megafac F (manufactured by DIC Corporation; "Megafac" is a registered trademark of DIC), Surflon (manufactured by AGC Seimi Chemical Co., Ltd.; "Surflon" is a registered trademark of AGC Seimi Chemical Co., Ltd.), Fluorad FC (manufactured by 3M Corporation; "Fluorad" is a registered trademark of 3M), Monflor (manufactured by Imperial Chemical Industries, Ltd.), Zonyls (manufactured by E.I. duPont Nemerus & Co., Ltd.), Licowet VPF (manufactured by Lubbewerke-Hoechst), and FTERGENT (manufactured by Neos Corporation; "FTERGENT" is a registered trademark of 3M).

[0146] The amount of the surfactant can be set arbitrarily as long as the effects of the present invention are obtained, and can be, for example, 0.001% by mass or more and less than 1.0% by mass relative to the total mass of the curable composition.

[0147] (curing accelerator) The curable composition of the present invention may contain a curing accelerator as needed. The curing accelerator is not particularly limited as long as it accelerates the thermal curing of a thermosetting compound or the like.

[0148] Examples of the curing accelerator include imidazoles, dicyandiamide derivatives, dicarboxylic acid dihydrazide, triphenylphosphine, tetraphenylphosphonium tetraphenylborate, 2-ethyl-4-methylimidazole-tetraphenylborate, and 1,8-diazabicyclo[5.4.0]undecene-7-tetraphenylborate.

[0149] (coupling agent) The curable composition of the present invention may contain various coupling agents as needed. The inclusion of a coupling agent can improve adhesion to copper foil. Examples of various coupling agents include silane-based, titanium-based, and aluminum-based coupling agents.

[0150] (ion scavenger) The curable composition of the present invention may contain an ion scavenger as needed. The inclusion of an ion scavenger has advantages such as adsorbing ionic impurities and improving the insulating properties of the cured film under hygroscopic conditions. Examples of the ion trapping agent include inorganic ion adsorbents such as triazine thiol compounds, bisphenol-based reducing agents, zirconium compounds, and antimony-bismuth-based magnesium aluminum compounds.

[0151] The amounts of the curing accelerator, coupling agent, and ion scavenger can be set as desired within the range in which the effects of the present invention are obtained. The amount of each of these components can be, for example, 0.001% by mass or more and less than 1.0% by mass relative to the total mass of the curable composition.

[0152] From the viewpoint of curability, it is preferable that the curable composition of the present invention is used as is for applications such as ink without diluting with a solvent. That is, it is preferable that the curable composition of the present invention is used without a solvent. However, in order to adjust the viscosity, a solvent may be added as needed to use the curable composition in the form of a diluted solution.

[0153] [Physical Properties of Curable Composition] The physical properties of the cured product of the curable composition and the physical properties of the curable composition will be described below.

[0154] <Relative dielectric constant of the cured product> The cured product of the curable composition of the present invention preferably has a relative dielectric constant at 1 MHz of less than 3.0, more preferably 2.95 or less, and even more preferably 2.90 or less.

[0155] The cured product of the curable composition of the present invention has a relative dielectric constant at 10 GHz of less than 2.90.The relative dielectric constant at 10 GHz of the cured product is preferably 2.80 or less, and more preferably 2.70 or less.

[0156] As a result, the curable composition of the present invention can be used, for example, to form a solder resist film with a low dielectric constant that is compatible with 5G. Furthermore, when the curable composition of the present invention is used to form a solder resist film, it becomes compatible with higher performance devices.

[0157] The dielectric constant at 1 MHz and the dielectric constant at 10 GHz of the cured product can be measured, for example, by the following method.

[0158] (Method for measuring relative permittivity) The cured product used for measuring the relative dielectric constant is prepared, for example, as follows: First, the curable composition is ink-jet coated onto a substrate for preparing the cured product in a solid pattern of 70 mm × 70 mm and 23 μm thick. The resulting coating layer is irradiated with ultraviolet light (395 nm) at 500 mJ / cm using an LED lamp. 2 The curable composition is photocured (pre-cured) by irradiating it with light at an irradiation dose of 1000 kJ / min, and then thermally cured (mainly cured) by placing it in an oven set at 150°C for 60 minutes. The cured product (film) is peeled off from the substrate used for producing the cured product and cut into a piece approximately 5 cm square to be used as a measurement sample.

[0159] (relative permittivity at 1MHz) The dielectric constant at 1 MHz is measured, for example, by the LCR meter method. In this case, a tin foil with a main electrode diameter of 1.8 cm is attached to the measurement sample obtained above to form an electrode, and then the dielectric constant is measured. The measurement is performed at room temperature (23±2°C / 50±5%RH). The thickness is measured with a micrometer and the average value of five points is calculated. Examples of measurement equipment that can be used include an LCR meter HP4284A (Agilent Technologies), a thermostatic bath TO-19 (Ando Electric), and a solid electrode SE-70 (Ando Electric).

[0160] (relative permittivity at 10GHz) The relative permittivity at 10 GHz is measured using the cavity resonator method. In the cavity resonator method, the measurement sample obtained above is used as is. The measurement is performed in a test atmosphere at room temperature (23±2°C / 50±5%RH), and the thickness is measured using a micrometer, with the average value of five points calculated. The measurement equipment used is a Synthesized Sweeper 8340B (YHP), a Network Analyzer 8510B (YHP), a cylindrical cavity resonator: TE mode near 10 GHz (material: copper, internal mirror finish), and a semi-rigid cable for signal transmission.

[0161] (Viscosity and phase transition point of curable composition) The viscosity of the curable composition of the present invention at 25°C is 1 to 1 × 10 4A viscosity in the range of Pa·s is preferable, for example, because when used as an inkjet ink, the ink is sufficiently gelled when cooled to room temperature after landing, resulting in good pinning properties. Furthermore, from the viewpoint of further improving the ejection properties from an inkjet head when used as an inkjet ink, the viscosity of the curable composition of the present invention at 80°C is preferably in the range of 3 to 20 mPa·s, and more preferably in the range of 7 to 9 mPa·s.

[0162] The curable composition of the present invention preferably has a phase transition point in the range of 40°C or higher and lower than 100°C. If the phase transition point is 40°C or higher, for example, when used as an inkjet ink, the ink (curable composition) quickly gels after landing on a recording medium, thereby improving pinning properties. This makes it possible to form high-definition images and patterns. Furthermore, if the phase transition point is lower than 100°C, the curable composition has good handleability and high ejection stability. Similarly, from the viewpoint of enabling the ink (curable composition) to be ejected at a lower temperature and reducing the load on an image-forming apparatus when the curable composition is used as an inkjet ink, the phase transition point of the curable composition of the present invention is more preferably in the range of 40 to 60°C.

[0163] The viscosity at 25° C., viscosity at 80° C., and phase transition point of the curable composition of the present invention are values ​​obtained using a viscoelasticity measuring device according to the following method.

[0164] Using a viscoelasticity measuring device such as MCR300 (manufactured by Physica), the viscosity at 25°C, the viscosity at 80°C, and the phase transition point of the curable composition of the present invention are measured at a shear rate of 1000 (1 / s). Here, the phase transition point refers to the temperature at which the complex viscosity becomes 1 Pa in a viscoelasticity curve obtained by changing the temperature at a cooling rate of 0.1°C / s, a strain of 5%, an angular frequency of 10 radian / s, and a cooling rate of 0.1°C / s.

[0165] In order to improve the ejection properties of the curable composition from an inkjet head when used as an inkjet ink, the average dispersed particle size of the pigment particles according to the present invention is preferably within a range of 50 to 150 nm and the maximum particle size is preferably within a range of 300 to 1000 nm, and more preferably within a range of 80 to 130 nm.

[0166] The average dispersed particle size of pigment particles in the present invention refers to a value determined by dynamic light scattering using a Datasizer Nano ZSP (manufactured by Malvern). Note that inks containing colorants are highly concentrated, and light does not pass through this measuring device. Therefore, the ink (curable composition) is diluted 200 times before measurement. The measurement temperature is room temperature (25°C).

[0167] The curable composition of the present invention is used by applying it to an object to be coated and curing it. The method for applying the curable composition to an object to be coated is not particularly limited, and any known application method can be applied, but as described above, the effect of the present invention can be more effectively exhibited when the curable composition is applied by the inkjet method, which is preferred.

[0168] As described above, the curable composition of the present invention is cured by a combination of photocuring and heat curing. The order of photocuring and heat curing is not important, but from the viewpoint of workability and the like, a method in which photocuring is followed by heat curing is preferred. The cured product of the curable composition of the present invention has a relative dielectric constant of less than 2.90 at 10 GHz. Furthermore, the cured product can suppress the intrusion of oxygen and moisture from the outside due to the action of the gelling agent.

[0169] In consideration of the above-mentioned properties, the curable composition of the present invention is particularly advantageous when used as an ink for a solder resist. In addition to being used as an ink for forming a solder resist pattern, the curable composition of the present invention can also be used as an adhesive, sealant, circuit protectant, etc. for electronic components.

[0170] [Solder resist ink] The solder resist ink of the present invention is characterized by containing the curable composition of the present invention. The solder resist ink may consist solely of the curable composition of the present invention, or may contain other components in addition to the curable composition as necessary. Examples of other components include the above-mentioned solvents. The solder resist ink of the present invention preferably consists of the curable composition of the present invention.

[0171] A solder resist ink is an ink for forming a solder resist film used on a printed circuit board. By containing the curable composition of the present invention, the solder resist ink of the present invention can prevent oxygen and moisture from penetrating into the solder resist film when a solder resist pattern (solder resist film) is formed due to the card-house structure formed by the gelling agent, thereby reducing the generation of polar groups and enabling a low dielectric constant. Furthermore, the solder resist ink of the present invention improves the adhesion between the circuit pattern (conductor pattern) on the printed circuit board, for example, the copper wiring, and the solder resist film interface, and further prevents migration of the conductor, for example, copper, thereby suppressing a decrease in insulation properties.

[0172] [Printed circuit board] The printed circuit board of the present invention is a printed circuit board comprising a substrate, a circuit pattern provided on the surface of the substrate, and a solder resist film provided on the circuit pattern, wherein the solder resist film is formed using the solder resist ink of the present invention.

[0173] The printed circuit board of the present invention may have the same configuration as known printed circuit boards, except for the solder resist film.

[0174] For example, the substrate for a printed circuit board is not particularly limited, and may be made of a known insulating material such as paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / non-woven cloth epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, fluorine-polyethylene-polyphenylene oxide (PPO)-cyanate ester, polyimide, polyethylene terephthalate (PET), glass, ceramic, etc. The substrate may also be made of a semiconductor such as a wafer, or a metal such as stainless steel, copper, or aluminum.

[0175] A printed circuit board has a circuit pattern (conductor pattern) according to a design on the surface of the board, and a solder resist film is provided on the circuit pattern, leaving only contact points that are electrically connected to the outside by soldering or the like. The solder resist film may be patterned and formed according to the design of the printed circuit board. The thickness of the solder resist film depends on the type and application of the printed circuit board, but can be, for example, about 10 to 60 μm, and preferably 15 to 40 μm.

[0176] In a printed circuit board, the wiring conductors can be formed as a circuit pattern (conductor pattern) on one or both surfaces of the board. Furthermore, the board may be a multilayer board or a build-up board in which wiring conductors are formed inside the board as well as on the surface. In the printed circuit board of the present invention, the circuit pattern (conductor pattern) is preferably composed of copper wiring. For example, the printed circuit board may be made of a material such as a copper-clad laminate for high-frequency circuits, and copper-clad laminates of all grades (e.g., FR-4) can be used. In such a board, the copper wiring can be formed by processing the copper layer (copper foil) on the surface by etching or the like.

[0177] In the printed circuit board of the present invention, the solder resist film is formed using the solder resist ink of the present invention, and therefore has a relative dielectric constant of less than 2.90 at 10 GHz and is excellent in adhesion and heat resistance. In forming the solder resist film on copper wiring, the copper wiring preferably has a surface roughness Ra in the range of 0.1 to 2.0 μm to further improve adhesion. A surface roughness Ra in this range improves adhesion of the solder resist film to the copper wiring when the solder resist ink is applied.

[0178] In order to adjust the surface roughness Ra of the conductor wiring, it is preferable to roughen the conductor layer serving as a circuit pattern (conductor pattern) of copper wiring or to perform a pretreatment to prevent bleeding. Roughening methods include physical polishing, which involves forming irregularities on the surface of the conductor layer by means of buffing or scrubbing to form a rough surface, and chemical polishing using a chemical polishing agent such as a copper chloride-based, persulfate-based, sulfuric acid / hydrogen peroxide-based, formic acid-based, or organic acid-based chemical polishing agent.

[0179] As the pretreatment, from the viewpoint of improving adhesion, chemical polishing treatment or treatment for improving adhesion is preferable, and in the case of chemical polishing treatment, treatment with an organic acid is more preferable. Specific examples of chemical polishing treatments include copper chloride-based treatments such as MacDermid's MultiPrep 200, persulfate-based treatments such as MacDermid's Microclean, ME-301, and PR-820, sulfuric acid / hydrogen peroxide-based treatments such as Shikoku Chemicals' GB1000F / 1400, G200, GB3100, and GB4300, MacDermid's Multibond 100, Multibond 150, Multibond MP, Metex G-5, Metex G-6, ME-501, ME-602, ME-605, and ME-709, BOARDTEC's BTH-2066, and Mitsubishi Gas Chemical's CPE-900, EMR-5000, and EMR-7000, and organic acid-based treatments such as MEC's ​​CZ8100, CZ8101, and CZ8201, and BOARDTEC's BTH-2085. Examples of treatments that improve adhesion include the GT process by MEC and GliCAP by Shikoku Kasei.

[0180] From the viewpoint of improving adhesion, sulfuric acid / hydrogen peroxide-based and organic acid-based solvents are preferred, and organic acid-based solvents are more preferred. A liquid-repellent treatment may be carried out to prevent bleeding.

[0181] The surface roughness Ra of the circuit pattern (conductor pattern) such as copper wiring roughened by the above pretreatment is preferably 0.1 to 2.0 μm, more preferably 0.1 to 1.5 μm, even more preferably 0.2 to 1.3 μm, and most preferably 0.3 to 1.1 μm. If the surface roughness Ra is 0.1 μm or more, adhesion is further improved, and if it is 2.0 μm or less, bleeding and transmission loss at 10 GHz are further suppressed.

[0182] The thickness of the circuit pattern (conductor pattern) such as copper wiring roughened by the pretreatment agent is preferably 0.1 to 3.0 μm, more preferably 0.3 to 2.0 μm, and even more preferably 0.5 to 1.5 μm. If the roughening thickness is 0.1 μm or more, the anchor effect improves adhesion, while if it is 3.0 μm or less, the conductor such as copper is not unnecessarily roughened or densified, improving adhesion.

[0183] Surface roughness Ra can be controlled by adjusting conditions such as the type of pretreatment agent, treatment temperature, and time. Surface roughness Ra is the arithmetic mean roughness measured in accordance with JIS B 0601. Specifically, surface roughness Ra can be measured using a scanning probe microscope (SPM), a non-contact interference microscope (WYKO), a laser microscope, or surface roughness (contact stylus method).

[0184] [Method for forming solder resist film] A method for forming a solder resist film using the solder resist ink of the present invention (hereinafter also simply referred to as "ink") preferably includes the steps of: (1) ejecting the ink of the present invention from the nozzles of an inkjet head and causing it to land on a circuit pattern of a printed circuit board on which a circuit pattern has been formed; (2) irradiating the landed ink with active energy rays to photo-cure (pre-cure) the ink; and (3) heating the ink to thermally cure (mainly cure).

[0185] <Step (1)> In step (1), droplets of the ink of the present invention are ejected from an inkjet head and landed on regions on a printed circuit board where a solder resist film is to be formed, including a circuit pattern. The ejection method from the inkjet head may be either an on-demand method or a continuous method.

[0186] The on-demand inkjet head may be of any of the following types: electro-mechanical conversion type, such as single cavity type, double cavity type, bender type, piston type, shear mode type, and shared wall type; and electro-thermal conversion type, such as thermal inkjet type and Bubble Jet (registered trademark) type (Bubble Jet is a registered trademark of Canon Inc.).

[0187] Discharging ink droplets from an inkjet head in a heated state can improve discharge stability. The ink temperature during discharge is preferably in the range of 40 to 100°C, and more preferably in the range of 40 to 90°C to further improve discharge stability. In particular, it is preferable to perform discharge at an ink temperature that results in an ink viscosity in the range of 7 to 15 mPa·s, more preferably in the range of 8 to 13 mPa·s.

[0188] In order to improve the ejection properties of sol-gel phase transition ink from the inkjet head, it is preferable that the temperature of the ink when filled into the inkjet head be set to between (gelation temperature (phase transition point) + 10)°C and (gelation temperature (phase transition point) + 30)°C. If the temperature of the ink inside the inkjet head is below (gelation temperature + 10)°C, the ink will gel inside the inkjet head or on the nozzle surface, which will likely result in a decrease in ink ejection properties. On the other hand, if the temperature of the ink inside the inkjet head exceeds (gelation temperature + 30)°C, the ink will become too hot and the ink components may deteriorate.

[0189] The method for heating the ink is not particularly limited. For example, at least one of the ink supply system, such as the ink tank constituting the head carriage, the supply pipe, and the anterior ink tank immediately before the head, the piping with a filter, and the piezo head, can be heated by a panel heater, a ribbon heater, or heated water.

[0190] The amount of ink droplets ejected is preferably within the range of 2 to 20 pL from the viewpoints of work efficiency, a thickness that can protect the circuit pattern in the resulting solder resist film, and ensuring fine line reproducibility of the circuit pattern.

[0191] <Step (2)> In step (2), the ink deposited in step (1) is irradiated with active energy rays to temporarily cure the ink. The active energy rays can be selected from, for example, electron beams, ultraviolet rays, α rays, γ rays, and X-rays, but ultraviolet rays are preferred.

[0192] The ultraviolet light can be irradiated at a wavelength of 395 nm using, for example, a water-cooled LED manufactured by Phoseon Technology Co., Ltd. Using an LED as the light source can prevent ink from being melted by the radiant heat of the light source, which can lead to poor ink curing.

[0193] The ultraviolet irradiation is carried out such that the peak irradiance of ultraviolet light having a wavelength in the range of 370 to 410 nm on the ink coating surface is preferably 0.5 to 10 W / cm 2 in the range of 1 to 5 W / cm 2 From the viewpoint of suppressing the radiation heat from being irradiated onto the ink, the amount of light irradiated onto the ink coating is set to 1000 mJ / cm 2 The irradiation of active energy rays is preferably carried out within 0.001 to 300 seconds after the ink has landed, and more preferably within 0.001 to 60 seconds in order to form a highly precise solder resist film.

[0194] <Step (3)> In step (3), after the temporary curing in step (2), the ink coating film is further heated to fully cure it. The heating method is preferably, for example, placing it in an oven set to a temperature in the range of 110 to 180°C for 10 to 60 minutes. [Example]

[0195] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, operations were carried out at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass," respectively.

[0196] <Components of the curable composition> The (meth)acrylic monomers, thermosetting compounds, photopolymerization initiators, and gelling agents used in the curable compositions of the following Examples and Comparative Examples were commercially available products or compounds shown in Table I. The molecular weight, ClogP, and classification of the (meth)acrylic monomers are also shown.

[0197] [Table 1]

[0198] <Preparation of Colorant Dispersion> The pigment dispersions incorporated into the curable compositions were prepared as follows.

[0199] (E-1: Preparation of Yellow Pigment Dispersion) Dispersant 1 and Dispersant 2 shown below and the dispersion medium were placed in a stainless steel beaker, heated on a hot plate at 62°C for 55 minutes while stirring and dissolving, and then cooled to room temperature. The pigment shown below was added to this, and the mixture was placed in a glass bottle together with 200 g of zirconia beads with a diameter of 0.5 mm and sealed. This was dispersed in a paint shaker until the desired particle size was reached, after which the zirconia beads were removed.

[0200] Dispersant 1: EFKA7701 (manufactured by BASF) 6.2 parts by mass Dispersant 2: Solsperse 22000 (manufactured by Lubrizol Japan) 0.5 parts by mass Dispersion medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 82.3 parts by mass Pigment: PY185 (BASF, Paliotol Yellow D1155) 13.8 parts by mass

[0201] (E-2: Preparation of cyan pigment dispersion) The yellow pigment dispersion was prepared in the same manner as in the preparation of the yellow pigment dispersion, except that the dispersant, dispersion medium, and pigment were changed as shown below.

[0202] Dispersant: EFKA7701 (BASF) 6.7 parts by mass Dispersion medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 72 parts by mass Pigment: PB15:4 (Dainichi Seika Chemicals, Chromofine Blue 6332JC) 21 parts by mass

[0203] [Preparation of Curable Composition (Inkjet Ink)] Each component was mixed according to the ink composition (parts by mass) shown in Tables II to IV below, and filtered through a 3 μm Teflon (registered trademark) membrane filter manufactured by ADVATEC Corporation to obtain curable compositions (inkjet inks, hereinafter also simply referred to as "inks") AA-1 to AA-16, AB-1 to AB-6 (Tables II and III), and BB-1 to BB-11 (Table IV).

[0204] In Tables II to IV, the total amount (parts by mass) of dipropylene glycol diacrylate contained in the blended pigment dispersions E-1 and E-2 and the amount of M222 (dipropylene glycol diacrylate) blended as the (meth)acrylic monomer A-5 is shown in the column for (meth)acrylic monomer A-5. In addition, the amount blended as pigment dispersions E-1 and E-2, i.e., the amount including dipropylene glycol diacrylate as a dispersion medium, is shown directly in the column for pigment dispersion.

[0205] Specifically, for Ink AA-1 in Table II, 54 parts by mass of (meth)acrylic monomers A-9 and A-8 were used, respectively, along with 34 parts by mass of pigment dispersions E-1 and E-2, and 1 part by mass of each of pigment dispersions E-1 and E-2. Since pigment dispersions E-1 and E-2 contain dipropylene glycol diacrylate, the amounts of dipropylene glycol diacrylate contained in the above proportions in pigment dispersions E-1 and E-2 per part by mass of each of pigment dispersions E-1 and E-2 were calculated, and the total amount, 1.5 parts by mass, was entered in the (meth)acrylic monomer A-5 column in Table II. The same procedure was followed for the other inks in Tables II to IV.

[0206] In all inks shown in Tables II to IV, pigment dispersions E-1 and E-2 are used in amounts of 1 part by mass each, and therefore the amount of (meth)acrylic monomer A-5 derived from the pigment dispersions is 1.5 parts by mass. In Table IV, there are inks containing more than 1.5 parts by mass of (meth)acrylic monomer A-5. In these inks, M222 (dipropylene glycol diacrylate) was used in an amount obtained by subtracting 1.5 parts by mass from the amount of (meth)acrylic monomer A-5 shown in Table IV during preparation. In Tables II to IV, blank spaces indicate that the content of the corresponding component is "0" parts by mass.

[0207] Tables II to IV also show the proportions [mass %] of the (meth)acrylic monomers (A1), (A2) and others in the (meth)acrylic monomers.

[0208] [Ink properties] (Viscosity, phase transition point) The viscosity and phase transition point at 25° C. of the resulting inks AA-1 to AA-16, AB-1 to AB-6, and BB-1 to BB-11 were measured by the methods described above.

[0209] The viscosity of the ink of the present invention at 25°C is 1 to 1 × 10 4 The gel phase transition temperature of the inks of the present invention was 40 to 100°C, whereas the gel phase transition phenomenon was not observed in the comparative inks that did not contain a gelling agent.

[0210] (Relative dielectric constant of cured ink) Using the resulting inks AA-1 to AA-16, AB-1 to AB-6, and BB-1 to BB-11, solid patterns were printed on polypropylene film using the inkjet recording device shown below, and the resulting film was cured to prepare a measurement sample of the cured product (film).

[0211] Specifically, the ink was applied by inkjet printing to a propylene film in a solid pattern of 70 mm x 70 mm and 23 μm thick. The resulting ink layer was irradiated with an LED lamp (395 nm, 8 W / cm) manufactured by Phoseon Technology. 2 UV light (395 nm) was applied at 500 mJ / cm using a water-cooled unit. 2 The ink was photocured (pre-cured) by irradiating it with light at a dose of 1000 kJ / cm, and then the cured product (film) was peeled off the propylene film and placed in an oven set at 150°C for 60 minutes for thermal curing (main curing). Measurement samples were cut into approximately 5 cm squares, and the dielectric constants at 1 MHz and 10 GHz were measured using the method described above. The results are also shown in Tables II to IV.

[0212] [Rating 1] The cured ink film was evaluated for adhesion to the copper layer of the copper-clad laminate and heat resistance using the following methods, and the results are shown in Tables II to IV.

[0213] (1) Preparation of laminated samples for evaluation <Processing of copper clad laminate> The copper layer on the surface of a copper-clad laminate for printed wiring boards (FR-4; thickness 1.6 mm, size 150 mm x 95 mm) was treated with MEC's ​​CZ-8100 treatment solution to produce a pretreated copper-clad laminate with a copper layer surface roughness Ra of 1.5 μm. The surface roughness Ra is the arithmetic mean roughness measured using a laser microscope.

[0214] <Inkjet pattern formation> Each inkjet ink prepared above was loaded into an inkjet recording apparatus having an inkjet recording head equipped with a piezoelectric inkjet nozzle. Using this apparatus, a pattern was formed on a copper-clad laminate for printed wiring boards (FR-4, thickness 1.6 mm, size 150 mm × 95 mm) that had been subjected to the copper pretreatment described above.

[0215] The ink supply system consists of an ink tank, ink flow path, a sub-ink tank just before the inkjet recording head, piping with a metal filter, and a piezo head. The ink is heated to 80°C from the ink tank to the head. A heater is also built into the piezo head, and the ink temperature inside the piezo head is heated to 75°C. The piezo head used was the KM1800i-SHC manufactured by Konica Minolta.

[0216] Using this inkjet device, a voltage was applied so that the droplet volume would be 3.5 pL, and a 70 mm × 70 mm solid ink layer and a comb-shaped pattern with a line and space of 100 μm were formed on the substrate, each with a thickness of 23 μm. After that, an LED lamp (395 nm, 8 W / cm) manufactured by Phoseon Technology was used to form the ink. 2 , water cooled unit) at 500mJ / cm 2 The ink layer was pre-cured by irradiating the ink so that the ink layer was irradiated to a temperature of 150°C for 60 minutes, and then fully cured, to obtain a laminate sample in which a cured film pattern was formed on the pretreated copper layer of the copper-clad laminate.

[0217] (2) Evaluation of laminated samples <Substrate adhesion> For the solid pattern laminated sample, grid-like cuts were made in the cured film according to the cross-cut method of JIS K5600, adhesive tape was applied and peeled off, and the peeling state of the cured film was observed, and the residual adhesion rate was determined by the following method and evaluated according to the following criteria. Here, the residual adhesion rate is calculated by using the number of squares made by the cuts as the denominator and the number of squares remaining after tape peeling as the numerator.

[0218] (standard) 5: 100% adhesion remaining rate 4: Adhesion residual rate: 80% or more but less than 100% 3: Adhesion residual rate 60% or more but less than 80% 2: Adhesion residual rate 50% or more but less than 60% 1: Less than 50% residual adhesion

[0219] <Solder heat resistance> The solid pattern laminate sample was immersed in a 260° C. solder bath for 10 seconds three times, and then the residual adhesion rate was evaluated as described above, and the peeling state of the cured film was observed.

[0220] [Table 2]

[0221] [Table 3]

[0222] [Table 4]

[0223] As shown in the above results, the curable composition of the present invention is superior to the curable composition of the comparative example in terms of dielectric constant, substrate adhesion, and solder heat resistance. In addition, the following heat and moisture resistance, solvent resistance, acid resistance, alkali resistance, and insulation reliability were also evaluated, and it was confirmed that there are no problems in practical use.

[0224] Furthermore, the reproducibility of fine lines was evaluated using the following method using a comb pattern with lines and spaces of 100 μm. As a result, the samples of the present invention were able to draw lines and spaces of 100 μm, but the comparative sample, which did not contain a gelling agent, was unable to draw lines and spaces of 100 μm, and the spaces were filled with ink or the lines were thicker than 100 μm.

[0225] <Heat and moisture resistance> The solid pattern laminate sample was left to stand for 500 hours under conditions of 85° C. and 85% relative humidity, after which the substrate adhesion was evaluated as described above, and the state of peeling of the cured film was observed.

[0226] <Solvent resistance> The solid pattern laminate sample was immersed in propylene glycol monomethyl acetate at 20° C. for 20 minutes, washed with water and dried, and then the substrate adhesion was evaluated as described above, and the peeling state of the cured film was observed.

[0227] <Acid resistance> The solid pattern laminate sample was immersed in a 10% by mass aqueous sulfuric acid solution at 20° C. for 20 minutes, then washed with water and dried, and the substrate adhesion was evaluated as described above, and the peeling state of the cured film was observed.

[0228] <Alkali resistance> The solid pattern laminate sample was immersed in a 10% by mass aqueous solution of sodium hydroxide at 20° C. for 20 minutes, then washed with water and dried, and the substrate adhesion was evaluated as described above, and the peeling state of the cured film was observed.

[0229] <Insulation reliability> A conductive comb-shaped wiring pattern with 75 μm lines and spaces was prepared on a copper-clad laminate (FR-4; thickness 1.6 mm, size 150 mm × 95 mm) for printed wiring boards, and a solid pattern was formed by inkjet printing using each inkjet ink prepared so as to cover the entire comb-shaped wiring pattern. The insulation properties of the obtained samples were evaluated for up to 1000 hours under conditions of 85°C, 85% RH, and 100 V applied.

[0230] (standard) ◎: After 1000 hours, there is no significant decrease in resistance or short circuit, and the insulation resistance is 10 8 Ω or more ○: After 500 hours, there is no significant decrease in resistance or short circuit, and the insulation resistance is 10 8 Ω or more △: After 250 hours, there is no significant decrease in resistance or short circuit, and the insulation resistance is 10 8 Ω or more ×: The insulation resistance value is 10 before 250 hours have elapsed. 8 Less than Ω

[0231] <Fine line reproducibility> The comb-shaped pattern with lines and spaces of 100 μm was observed under an optical microscope.

[0232] [Rating 2] Using the ink BB-4 obtained above, differences in adhesion, heat resistance, and bleeding due to differences in pretreatment of the copper layer of a copper-clad laminate were evaluated. The results are shown in Table V.

[0233] (1) Preparation of laminated samples for evaluation <Processing of copper clad laminate> Copper clad laminates CC-2 to CC-11 with different surface roughness Ra were fabricated by treating the copper layer on the surface of a copper clad laminate (FR-4; 1.6 mm thick, 150 mm x 95 mm) for printed wiring boards using MEC's ​​CZ-8100, CZ8101, and CZ8201 treatment solutions under adjusted conditions. An untreated copper clad laminate was used as CC-1.

[0234] <Inkjet pattern formation> Using ink BB-4, laminate samples were obtained in the same manner as in Evaluation 1 above, in which a cured film pattern (70 mm × 70 mm, 23 μm thick solid pattern) was formed on the copper layer of copper-clad laminate substrates CC-1 to CC-11.

[0235] (2) Evaluation of laminated samples The solid pattern laminated sample was evaluated for substrate adhesion and solder heat resistance in the same manner as in Evaluation 1. In addition, bleeding was evaluated by the following method.

[0236] <Evaluation of bleeding> The distance of bleeding from the 70 mm x 70 mm solid image printed (cured film pattern) area onto the non-printed area of ​​the copper plate was visually confirmed and evaluated according to the following criteria. (standard) 5: Bleeding component is less than 1 mm 4: The bleeding component is 1mm or more but less than 2mm 3: The bleeding component is 2mm or more but less than 3mm 2: The bleeding component is 3mm or more but less than 4mm 1: Bleeding component is 4mm or more

[0237] [Table 5]

[0238] In addition, by adjusting the treatment conditions using other pretreatment agents described in the specification (GB1000F / 1400, G200, GB3100, GB4300 from Shikoku Chemicals; Multibond 100, Multibond 150, Multibond MP, MultiPrep200 from MacDermid; BTH-2066, BTH-2085 from BOARDTEC), substrates with Ra ranging from 0.1 to 2.0 μm were prepared and similar evaluations were performed. The evaluation results corresponded to the Ra values ​​listed in Table V above.

[0239] Furthermore, it was confirmed that even when using the GT process by MEC Corporation or the GliCAP process by Shikoku Kasei Corporation, which are pretreatments for improving adhesion, there are no problems in practical use in terms of substrate adhesion, solder heat resistance, heat and moisture resistance, solvent resistance, acid resistance, alkali resistance, insulation reliability, and bleeding. [Industrial Applicability]

[0240] According to the present invention, it is possible to provide a curable composition that gives a cured product that has excellent adhesion and heat resistance and a low relative dielectric constant, a solder resist ink, and a printed circuit board using the same.

Claims

1. A curable composition containing 50 to 95% by mass of a (meth)acrylic monomer, and further containing a photopolymerization initiator, a thermosetting compound, and a gelling agent, the (meth)acrylic monomer comprises a (meth)acrylic monomer having a molecular weight in the range of 200 to 1500 and a ClogP value in the range of 3.5 to 7.0; the thermosetting compound contains at least one selected from an isocyanate group, an epoxy group, and a maleimide group; The gelling agent is a ketone wax, an ester wax, a higher fatty acid, a higher alcohol, or a fatty acid amide, and A curable composition, characterized in that a cured product of the curable composition has a relative dielectric constant at 10 GHz of less than 2.

90.

2. The curable composition according to claim 1, wherein the content of the thermosetting compound is in the range of 1 to 15 mass % based on the total amount of the curable composition.

3. 3. The curable composition according to claim 1, wherein the thermosetting compound comprises a polyfunctional isocyanate compound in which an isocyanate group is protected with a thermally dissociable blocking agent.

4. Viscosity at 25°C is 1 to 1 x 10 ４ The curable composition according to claim 1 , having a viscosity in the range of Pa·s and a phase transition point of 40° C. or higher but lower than 100° C.

5. A solder resist ink comprising the curable composition according to claim 1 .

6. A printed circuit board comprising a substrate, a circuit pattern provided on a surface of the substrate, and a solder resist film provided on the circuit pattern, A printed circuit board, wherein the solder resist film is formed using the solder resist ink according to claim 5.

7. 7. The printed circuit board according to claim 6, wherein the circuit pattern is made of copper wiring, and the surface roughness Ra of the copper wiring is in the range of 0.1 to 2.0 μm.

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