Curable composition, solder resist ink, and printed circuit board

Abstract

The present invention provides a curable composition, a solder resist ink, and a printed circuit board, which give a cured product having excellent adhesion and heat resistance and a low relative dielectric constant. The curable composition of the present invention contains a (meth)acrylic monomer as a main component, a photopolymerization initiator, a thermally curable compound, and a gelling agent, and is characterized in that the relative dielectric constant of the cured product thereof at 10 GHz is less than 2.90.

Description

Technical Field

[0001] This invention relates to curable compositions, solder resist inks, and printed circuit boards. More specifically, it relates to curable compositions that provide excellent adhesion and heat resistance, and have a low relative permittivity, solder resist inks, and printed circuit boards using the same. Background Technology

[0002] For materials used in mobile communication devices, a specific dielectric constant at a particular frequency is sometimes required. For example, in organic EL elements used in mobile displays, materials with a dielectric constant specified at 100 kHz have been proposed to suppress erroneous touch sensor operation (Patent Document 1). Furthermore, in high-frequency circuits used in mobile communication devices, transmission losses occur at the junctions of wiring and insulation materials, particularly in the insulation material itself, leading to problems such as heat generation, noise, and power consumption during signal transmission. It has been found that transmission loss is proportional to both frequency and the dielectric loss tangent of the material. With the adoption of 5G mobile communication systems, the demand for materials with low dielectric loss tangents is increasing.

[0003] On the other hand, from the viewpoint of heat resistance and electrical insulation, resin compositions with carboxyl-containing resins, epoxy resins, and other curable resins as the main component, and further containing fillers and other additives, are widely used as interlayer insulation materials and solder resist materials. However, the cured products of these resin compositions contain a large number of polar groups, thus becoming materials with high dielectric constants and dielectric losses, which need to be improved. Photosensitive solder resist materials are mainly based on epoxy acrylate resins. In this regard, negative photoresists that can be developed with alkaline aqueous solutions such as sodium carbonate aqueous solution are the mainstream. Regarding photosensitive solder resists, the patterned photosensitive solder resist is cured and stabilized by heat treatment. Particularly in epoxy acrylate resins, it is known that by this heat treatment, residual carboxylic acids are blocked with epoxy groups, but even after blocking, carboxylic acids remain (Patent Document 2).

[0004] In recent years, research has been ongoing on inkjet printing of solder resist film formation processes. Using this technology, patterns of insulating layers matching the wiring can be directly formed, eliminating the need for a developing process. This technique generates fewer polar groups during the developing process, which is advantageous for achieving a low dielectric constant. In the curable compositions used for inkjet printing, epoxy monomers and acrylic monomers are used as curing components, cured by light irradiation and heat (Patent Document 3). To address the challenges of 5G, it is necessary to further reduce the number of polar groups such as carboxylic acids within the aforementioned curable composition system. Epoxy monomers leave hydroxyl groups during polymerization, and acrylic monomers also generate polar groups due to oxygen hindrance during free radical polymerization, thus posing a problem in achieving a low dielectric constant for 5G applications.

[0005] On the other hand, when using curing compositions that do not generate polar groups during curing to produce solder resist films, there are concerns about reduced adhesion of the cured material to the conductor wiring of the wiring board, especially when considering low dielectric constant. Therefore, the cured material constituting the solder resist film requires heat resistance, low dielectric constant, and good adhesion.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2020-076052

[0009] Patent Document 2: Japanese Patent Application Publication No. 2010-34414

[0010] Patent Document 3: Japanese Patent Application Publication No. 2019-178288 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] The present invention was made in view of the above-mentioned problems and conditions, and its solution is to provide a curable composition that provides a curable material with excellent adhesion and heat resistance and a low relative permittivity, a solder resist ink, and a printed circuit board using the same.

[0013] Methods for solving problems

[0014] In order to solve the above-mentioned problems, the inventors, during the research on the causes of the above problems, discovered that in a curable composition containing a (meth)acrylic acid monomer as the main component, a photopolymerization initiator, a thermosetting compound, and a gelling agent, the cured product has a specific relative permittivity, and thus the present invention was completed.

[0015] That is, the aforementioned problems involved in this invention are solved by the following means.

[0016] 1. A curable composition comprising a (meth)acrylic acid monomer as the main component, a photopolymerization initiator, a thermosetting compound, and a gelling agent, characterized in that the relative permittivity of the cured product of the above-mentioned curable composition at 10 GHz is less than 2.90.

[0017] 2. The curable composition according to claim 1, wherein the content of the thermosetting compound is in the range of 1 to 15% by mass relative to the total amount of the curable composition.

[0018] 3. The curable composition according to claim 1 or 2, wherein 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.

[0019] 4. The curable composition according to any one of claims 1 to 3, wherein the thermosetting compound comprises a multifunctional isocyanate compound in which the isocyanate group is protected with a thermally dissociable blocking agent.

[0020] 5. The curable composition according to any one of items 1 to 4, wherein the viscosity at 25°C is 1 to 1 × 10⁻⁶. 4 It has a phase transition point in the range of Pa·s and above 40℃ but below 100℃.

[0021] 6. Solder resist ink, comprising any one of items 1 to 5.

[0022] 7. A printed circuit board comprising a substrate, a circuit pattern disposed on the surface of the substrate, and a solder resist disposed on the circuit pattern, wherein the solder resist is formed using the solder resist ink described in item 6.

[0023] 8. The printed circuit board according to claim 7, wherein the circuit pattern is composed of copper wiring, and the surface roughness Ra of the copper wiring is in the range of 0.1 to 2.0 μm.

[0024] The effects of the invention

[0025] Through the above-described means of the present invention, it is possible to provide curable compositions that provide excellent adhesion and heat resistance and have a low relative permittivity, solder resist inks, and printed circuit boards using the same.

[0026] The mechanism by which the effects of this invention are manifested or function is not yet clear, but speculations are made as follows.

[0027] In the curable composition of the present invention, by using a photopolymerizable (meth)acrylic acid 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 gel, forming a fine cardhouse structure within the composition. Therefore, it is believed that because the diffusion rate of oxygen and moisture from the outside is slowed down, the generation of polar groups such as carboxylic acids and hydroxyl groups generated during the curing of the curable composition is further suppressed. Moreover, a low dielectric constant (relative dielectric constant of less than 2.90 at 10 GHz) and a low dielectric loss tangent are achieved in the obtained cured product.

[0028] Furthermore, in addition to the above, the curable composition of the present invention also contains a thermosetting compound and is thermally polymerizable. This encapsulates the polar groups generated in trace amounts during photopolymerization and improves adhesion to the circuit board and heat resistance. Detailed Implementation

[0029] The curable composition of the present invention is a curable composition containing (meth)acrylic acid monomers as the main component, as well as a photopolymerization initiator, a thermosetting compound and a gelling agent, characterized in that the relative permittivity of the cured product of the above curable composition at 10 GHz is less than 2.90.

[0030] This feature is a common or corresponding technical feature in the following embodiments.

[0031] As 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, the content of the above-mentioned thermosetting compound is preferably in the range of 1 to 15% by mass relative to the total amount of the above-mentioned curable composition.

[0032] As an embodiment of the curable composition of the present invention, from the viewpoint of improving the solubility stability of the gelling agent in the curable composition, it is preferable that the above-mentioned (meth)acrylic monomer includes a (meth)acrylic monomer with a molecular weight in the range of 200 to 1500 and a ClogP value in the range of 3.5 to 7.0.

[0033] As an embodiment of the curable composition of the present invention, from the viewpoint of obtaining a low relative permittivity of the cured product and improving its resistance to high temperature and high humidity, it is preferable that the above-mentioned thermosetting compound contains a multifunctional isocyanate compound in which the isocyanate group is protected with a thermally dissociable blocking agent.

[0034] As an embodiment of the curable composition of the present invention, from the viewpoint of workability in the production of cured products using the curable composition and the reproducibility of fine lines when drawing with inkjet printing, a viscosity of 1 to 1 × 10⁻⁶ at 25°C is preferred. 4 It has a phase transition point in the range of Pa·s and above 40℃ but below 100℃.

[0035] The solder resist ink of the present invention is characterized in that it contains the curable composition of the present invention.

[0036] The printed circuit board of the present invention comprises a substrate, a circuit pattern disposed on the surface of the substrate, and a solder resist film disposed on the circuit pattern, characterized in that the solder resist film is formed using the solder resist ink of the present invention.

[0037] As an embodiment of the printed circuit board of the present invention, from the viewpoint of the adhesion of the solder mask, it is preferable that the circuit pattern is composed of copper wiring, and the surface roughness Ra of the copper wiring is in the range of 0.1 to 2.0 μm.

[0038] The present invention, its constituent elements, and the forms and methods for carrying out the present invention will be described below. It should be noted that in the present invention, "~" is used to mean the lower limit and upper limit value included in the numerical values ​​listed before and after it.

[0039] [Curing composition]

[0040] The curable composition of the present invention is a curable composition containing (meth)acrylic acid monomers as the main component, as well as a photopolymerization initiator, a thermosetting compound and a gelling agent, characterized in that the relative permittivity of the cured product of the above curable composition at 10 GHz is less than 2.90.

[0041] In this invention, "(meth)acrylic acid" refers to acrylic acid or methacrylic acid, "(meth)acrylate" refers to acrylate or methacrylate, and "(meth)acryloyloxy" refers to acryloyloxy or methacryloyloxy.

[0042] The (meth)acrylic monomers contained in the curable compositions of the present invention refer to compounds that are not thermosetting compounds described later in the context of (meth)acrylic acid and its derivatives. That is, (meth)acrylic compounds that do not have thermosetting functional groups are referred to as (meth)acrylic monomers.

[0043] <(meth)acrylic acid monomers>

[0044] The (meth)acrylic acid monomers involved in this invention are vinyl-based free radical polymerizable compounds derived from (meth)acrylic acid, and are compounds that can undergo free radical polymerization under the action of active energy rays. The curable composition of this invention contains (meth)acrylic acid monomers as a main component. In this specification, a main component refers to a component that accounts for 50% or more by mass relative to the total. Specifically, regarding the content of (meth)acrylic acid monomers in the curable composition, it is preferably 50-95% by mass, more preferably 70-90% by mass relative to the total curable composition.

[0045] By including (meth)acrylate monomers as the main component, the relative permittivity of the resulting cured product can be within the specific range mentioned above. Furthermore, by setting the upper limit of the (meth)acrylate monomer content to the aforementioned value, the content of the thermosetting compound can be sufficiently ensured, easily obtaining a cured product with excellent adhesion to the substrate and heat resistance.

[0046] As (meth)acrylic acid monomers, ester compounds of (meth)acrylic acid, i.e., (meth)acrylates and their derivatives, are preferred. (Meth)acrylates can be monofunctional (meth)acrylates having one (meth)acryloyloxy group, or polyfunctional (meth)acrylates having two or more (meth)acryloyloxy groups. (Meth)acrylic acid monomers may have functional groups other than (meth)acryloyloxy groups (however, not thermosetting functional groups). Examples of functional groups include hydroxyl, carboxyl, imide, alkyl, cycloalkyl, alkoxide, aromatic, and heterocyclic groups. These functional groups are not considered thermosetting functional groups in this invention, but as described later, they can react with thermosetting functional groups in thermosetting compounds through heat to facilitate thermosetting.

[0047] Examples of monofunctional (meth)acrylates include isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomyristyl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyl-diethylene (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, butoxyethyl (meth)acrylate, ethoxydiethylene (meth)acrylate, methoxydiethylene (meth)acrylate, and methoxy polyethylene glycol. (Meth)acrylates, methoxypropylene glycol (meth)acrylates, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl-2-hydroxyethyl-phthalic acid, and tert-butylcyclohexyl (meth)acrylate, etc.

[0048] Among multifunctional (meth)acrylates, difunctional (meth)acrylates include, for example, di(meth)acrylates containing 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 oxoalkylene group as a repeating unit. Examples of repeating units, i.e., oxoalkylene groups, include those with 1 to 4 carbon atoms. The oxoalkylene group can be linear or branched. For example, the propylene group can be any one of -(CH2)3-, -CH(CH3)-CH2-, and -CH(CH2CH3)-. The number of repetitions of the oxoalkylene group (hereinafter denoted by "n") can be 2 to 20, preferably 3 to 14, and more preferably 3 to 10.

[0049] As di(meth)acrylates having a polyoxyalkylene group, specifically, as compounds with an oxyethylene alkylene group, examples include polyethylene glycol di(meth)acrylates such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate. As compounds with a propyleneene alkylene group, examples include polypropylene glycol di(meth)acrylates such as dipropylene glycol di(meth)acrylate and tripropylene glycol di(meth)acrylate. Additionally, compounds with an oxyalkylene group having four carbon atoms as a repeating unit, such as polytetramethylene glycol di(meth)acrylate, can also be listed.

[0050] Other difunctional (meth)acrylates include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tricyclodecanediethanol di(meth)acrylate, bisphenol A propylene oxide (hereinafter sometimes represented by "PO") or ethylene oxide (hereinafter sometimes represented by "EO") adduct di(meth)acrylate, bisphenol F PO or EO adduct di(meth)acrylate, and neopentyl glycol di(meth)acrylate of hydroxypentanoic acid, etc.

[0051] Examples of trimethylolpropane trimethacrylates include, for example, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol pentamethacrylate, dipentaerythritol hexamethacrylate, di(trimethylolpropane)tetramethacrylate, glycerol propoxytrimethacrylate, and pentaerythritol ethoxytetramethacrylate.

[0052] (Meth)acrylates can be modified. Examples of (meth)acrylates as modifiers include ethylene oxide (EO) modified or propylene oxide (PO) modified (meth)acrylates. Examples of EO-modified 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, EO or PO-modified 1,6-hexanediol di(meth)acrylate, etc. The number of EOs or POs in the EO-modified or PO-modified (meth)acrylate corresponds to the repetition number n of the oxyalkylene group in the above-mentioned polyoxyalkylene group, preferably about 1 to 5, more preferably 2 to 4.

[0053] Examples of (meth)acrylates as modifiers include: caprolactone-modified (meth)acrylates containing caprolactone-modified trimethylolpropane tri(meth)acrylate, and caprolactam-modified (meth)acrylates containing caprolactam-modified dipentaerythritol hexa(meth)acrylate.

[0054] (Meth)acrylates can be polymerizable oligomers. Examples of (meth)acrylates that are polymerizable oligomers include epoxy (meth)acrylate oligomers, aliphatic urethane (meth)acrylate oligomers, aromatic urethane (meth)acrylate oligomers, polyester (meth)acrylate oligomers, and linear (meth)acrylate oligomers.

[0055] (Meth)acrylates can be (meth)acrylate compounds containing imide groups. Using (meth)acrylates containing imide groups can improve the high-temperature and high-humidity resistance of the cured product. Furthermore, in the case of (meth)acrylates containing imide groups, due to the high polarity of the imide groups, the cured product exhibits strong metal adhesion; for example, in the case of solder mask fabrication, improved adhesion to the circuit board can be expected. Additionally, due to its strong cohesiveness, the impact on metal adhesion is minimal even under high humidity conditions.

[0056] Examples of (meth)acrylates having an imide group include imide acrylates or imide methacrylates described in Japanese Patent Application Publication No. 10-36462 and Japanese Patent Application Publication No. 11-21470.

[0057] In this invention, one of the (meth)acrylates may be used alone, or two or more may be used together. There is no particular limitation on the molecular weight of the (meth)acrylate, but from the viewpoint of jetting stability in inkjet printing, a molecular weight of 200 to 1500 is preferred, and more preferably 300 to 1200.

[0058] Regarding the relative permittivity, the solubility stability of the gelling agent, and the jetting stability in inkjet printing, the curable composition of the present invention preferably contains a (meth)acrylic monomer with a molecular weight in the range of 200 to 1500 and a ClogP value in the range of 3.5 to 7.0. Hereinafter, the (meth)acrylic monomer with a molecular weight in the range of 200 to 1500 and a ClogP value in the range of 3.5 to 7.0 will be referred to as (meth)acrylic monomer (Al).

[0059] (Meth)acrylic acid monomers (Al) with a molecular weight range of 200-1500 possess the aforementioned advantages. Furthermore, with a ClogP of 3.5 or higher, a large number of hydrophobic structures are present, making it difficult for water to penetrate during polymerization and upon solidification. This suppresses the presence of polar groups in the solidified product, thus improving the relative dielectric constant. (Meth)acrylic acid monomers (Al) with a ClogP of 7.0 or lower exhibit improved solubility stability in the gelling agent, enabling the formation of the desired card-cell structure. This suppresses the generation of polar groups caused by oxygen and water during polymerization, further improving the relative dielectric constant.

[0060] As the (meth)acrylate monomer (A1), a (meth)acrylate with a molecular weight in the range of 200 to 1500 and a ClogP value in the range of 3.5 to 7.0 is preferred. As the ClogP value of the (meth)acrylate monomer (A1), a range of 4.0 to 6.0 is more preferred. Furthermore, the (meth)acrylate monomer (A1) can be a (meth)acrylate having a polyoxyalkylene group (e.g., n = 2 to 10) as a repeating unit selected from oxyethylene and oxypropylene groups.

[0061] Examples of (meth)acrylic acid monomers (A1) include, for example, 1,10-decanediol dimethacrylate (molecular weight: 310, ClogP: 5.8), tricyclodecanediethanol diacrylate (molecular weight: 304, ClogP: 4.7), tricyclodecanediethanol dimethacrylate (molecular weight: 332, ClogP: 5.3), 3PO modified trimethylolpropane triacrylate (molecular weight: 470, ClogP: 4.0–5.0), dipentaerythritol pentaacrylate (molecular weight: 524, ClogP: 3.8), 6EO modified trimethylolpropane triacrylate (molecular weight: 560, ClogP: 3.6), bisphenol A3EO modified diacrylate (molecular weight: 468, ClogP: 5.9), and bisphenol F4EO modified diacrylate (molecular weight: 499, ClogP: 5.0–5.2).

[0062] Furthermore, regarding spray stability and the solubility stability of the gelling agent, it is preferable that the curable composition contains (meth)acrylate (A1) in the range of 50-95% by mass, more preferably in the range of 70-90% by mass. As (meth)acrylate (A1), one type may be used alone, or two or more may be used in combination. The curable composition may contain only (meth)acrylate monomer (A1), or it may be a combination of (meth)acrylate monomer (A1) and other (meth)acrylate monomers besides (meth)acrylate monomer (A1). Examples of other (meth)acrylate monomers include (meth)acrylates with a molecular weight in the range of 200-1500 and a ClogP value outside the range of 3.5-7.0.

[0063] Here, the "logP value" referred to in this invention is a coefficient representing the affinity of organic compounds for water and 1-octanol. The 1-octanol / water partition coefficient P is the distribution equilibrium when a trace amount of the compound is dissolved as a solute in a two-liquid solvent of 1-octanol and water, and is the ratio of the equilibrium concentrations of the compound in each solvent, expressed as logP relative to the base 10. That is, the "logP value" is the logarithm of the 1-octanol / water partition coefficient P, which is known to be an important parameter representing the hydrophilicity or hydrophobicity of a molecule.

[0064] The “ClogP value” is the logP value calculated through computation. The ClogP value can be calculated using methods such as fragmentation and atomic proximity. More specifically, to calculate the ClogP value, one can use the fragmentation method described in the literature (C. Hansc H and A. Leo, “Substituent Constants for Correlation Analysis in Chemistry and Biology” (Jo Hn Wiley & Sons, New York, 1969)) or the commercially available software packages 1 or 2 described below.

[0065] Software package 1: MedChem Software (Release 3.54, August 1991, Medicinal Chemistry Project, Pomona College, Claremont, CA)

[0066] Package 2: Chem Draw Professional 16.0 (Perkin Elmer)

[0067] The ClogP values ​​described in this manual are "ClogP values" calculated using software package 2.

[0068] As other (meth)acrylate monomers used in conjunction with (meth)acrylate monomers (A1), those with a molecular weight in the range of 200 to 1500 and having 3 to 14 repeating units of oxoethylene represented by (-CH2-CH2-O-) within the molecule, and (meth)acrylates with a molecular weight in the range of 200 to 1500 and having 2 to 14 repeating units of oxopropylene within the molecule (however, ClogP values ​​outside the range of 3.5 to 7.0) are preferred in terms of spray stability, gelling agent solubility, and curing shrinkage (adhesion). (Meth)acrylates with polyoxyalkylene groups that meet the above conditions will also be referred to as (meth)acrylate monomers (A2).

[0069] Examples of (meth)acrylic monomers (A2) include, for example, polyethylene glycol diacrylate (n=9, molecular weight; 508, ClogP; 0.2-0.5), 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).

[0070] (Meth)acrylic monomers (A2) can be used alone or in combination of two or more. It should be noted that (meth)acrylic monomer (A2) can constitute the (meth)acrylic monomer contained in the curable composition on its own, or it can be used together with other (meth)acrylic monomers. In this case, (meth)acrylic monomer (A2) is preferably used in combination with (meth)acrylic monomer (A1), but it can also be used in combination with other (meth)acrylic monomers besides (A1).

[0071] When using (meth)acrylate monomer (A2), regarding the curing shrinkage (adhesion) of the cured product, it is preferable that the content of (meth)acrylate monomer (A2) is in the range of 30 to 70% by mass relative to the total cured composition. Furthermore, when (meth)acrylate monomer (A1) and (meth)acrylate monomer (A2) are used together, the content of (meth)acrylate monomer (A2) relative to the total cured composition is preferably 1.5 to 60% by mass, more preferably 5 to 30% by mass, and even more preferably 10 to 20% by mass. In this case, the content of (meth)acrylate monomer (A1) relative to the total cured composition is preferably 30 to 90% by mass, more preferably 70 to 90% by mass.

[0072] (Meth)acrylate monomers may contain other (meth)acrylate monomers besides (meth)acrylate monomer (A1) and (meth)acrylate monomer (A2). Preferably, the molecular weight of these other (meth)acrylate monomers is in the range of 200 to 1500; examples include dicyclopentyl acrylate (molecular weight: 206, ClogP: 3.1).

[0073] The curable composition may contain (meth)acrylate monomers consisting solely of other (meth)acrylate monomers, but these other (meth)acrylate monomers are preferably used in combination with (meth)acrylate monomer (A1) or (meth)acrylate monomer (A2). In this case, the content of the other (meth)acrylate monomers relative to the total curable composition is preferably 5-30% by mass, more preferably 10-20% by mass.

[0074] <Other photopolymerizable compounds>

[0075] The curable composition of this invention may contain other photopolymerizable compounds besides (meth)acrylic acid monomers. These other photopolymerizable compounds are any compounds that undergo polymerization or crosslinking reactions through irradiation with active energy rays and have the function of curing the curable composition. Examples of other photopolymerizable compounds include free radical polymerizable compounds other than (meth)acrylic acid monomers and cationic polymerizable compounds. These other photopolymerizable compounds can be any of monomers, polymerizable oligomers, prepolymers, or mixtures thereof. The curable composition may contain only one or more of these other photopolymerizable compounds. The cationic polymerizable compounds can be epoxy compounds, vinyl ether compounds, and oxetane compounds, etc. The curable composition may contain only one or more of these cationic polymerizable compounds.

[0076] From the viewpoint of controlling dielectric constant, the curable composition of the present invention is mainly composed of (meth)acrylic acid monomers. Therefore, it is preferable to contain 0 to 2 other photopolymerizable compounds, more preferably 1 or less, and most preferably none. The content of other photopolymerizable compounds in the curable composition relative to the total amount of the curable composition can be, for example, set to 10% by mass or less, preferably 5% by mass or less, and particularly preferably 0% by mass.

[0077] Photopolymerization initiators

[0078] The photopolymerization initiator involved in this invention is an essential component contained in a curable composition for photopolymerizing (meth)acrylic acid monomers. As a photopolymerization initiator, a photoradical initiator is preferred. It should be noted that when a cationic polymerizable compound is used as another photopolymerizable compound in addition to the (meth)acrylic acid monomer, a photoacid-generating agent is preferably used in addition to the photoradical initiator.

[0079] The photopolymerization initiator in the curable composition of the present invention may contain only one type or two or more types. The photopolymerization initiator may be a combination of a photoradical initiator and a photoacid-producing agent.

[0080] Photoradical initiators include cleavage-type free radical initiators and hydrogen-abstraction-type free radical initiators. Examples of cleavage-type free radical initiators include acetophenone-based initiators, benzoin-based initiators, acylphosphine oxide-based initiators, benzoin, and methyl phenylacetalate.

[0081] Examples of acetophenone-based initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, benzoyladium dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)one, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-methylthiophenyl)propane-1-one, 2-benzyl-2-di-methylamino-1-(4-morpholinophenyl)butanone, and 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholino-4-yl-phenyl)butane-1-one.

[0082] Examples of benzoin-based initiators include benzoin, benzoin methyl ether, and benzoin isopropyl ether.

[0083] Examples of acylphosphine oxide initiators include 2,4,6-trimethylbenzoyl diphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0084] Examples of hydrogen-abstracting free radical initiators include benzophenone-based initiators, thioxanthone-based initiators, aminobenzophenone-based initiators, 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-phenanthroquinone, and camphorquinone.

[0085] Examples of benzophenone-based initiators include benzophenone, o-benzoylbenzoic acid methyl-4-phenylbenzophenone, 4,4′-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4′-methyl-diphenyl sulfide, acrylated benzophenone, 3,3′,4,4′-tetra(tert-butylperoxycarbonyl)benzophenone, and 3,3′-dimethyl-4-methoxybenzophenone.

[0086] Examples of thioxanthone-based initiators include 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone. Examples of aminobenzophenone-based initiators include michalcone and 4,4′-diethylaminobenzophenone.

[0087] Examples of photoacid-generating agents include compounds described in "Organic Materials for Imaging," published by the Organic Electronics Materials Research Association (1993), pages 187-192.

[0088] The content of the photopolymerization initiator can be set within a range that allows the curable composition to cure sufficiently. For example, it can be set to 0.01% to 10% by mass relative to the total mass of the curable composition of the present invention, preferably 0.1% to 5% by mass.

[0089] Photopolymerization initiators can be used in combination of two photopolymerization initiators with different wavelengths of absorption sensitivity. Examples of photopolymerization initiator combinations include combinations of acylphosphine oxide-based initiators and thioxanthone-based initiators, and combinations of peroxide-based initiators and thioxanthone-based initiators.

[0090] Examples of commercially available photopolymerization initiators include Omnirad TPO H (manufactured by IGM, 2,4,6-trimethylbenzoyl diphenylphosphine 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)-butane-1-one), and Omnirad ITX (manufactured by IGM, 2-isopropylthioxanthone).

[0091] The curable composition of the present invention may further include photopolymerization initiator auxiliaries as needed. The photopolymerization initiator auxiliaries may be tertiary amine compounds, preferably aromatic tertiary amine compounds. Examples of aromatic tertiary amine compounds include N,N-dimethylaniline, N,N-diethylaniline, N,N-dimethyl-p-toluidine, ethyl N,N-dimethylamino-p-benzoate, isopentyl ethyl N,N-dimethylamino-p-benzoate, N,N-dihydroxyethylaniline, triethylamine, and N,N-dimethylhexylamine. Among these, ethyl N,N-dimethylamino-p-benzoate and isopentyl ethyl N,N-dimethylamino-p-benzoate are preferred. These compounds may be used alone or in combination of two or more.

[0092] Commercially available photopolymerization initiator additives include Genocure EPD (manufactured by Rahn AG, N,N-dimethylamino-p-benzoate ethyl ester), etc.

[0093] <Thermosetting Compounds>

[0094] Regarding the curable composition of the present invention, as a free radical polymerizable compound, it contains a (meth)acrylic acid monomer as the main component, and also contains a thermosetting compound that is cured by heat. The curable composition of the present invention, by containing a thermosetting compound, results in a cured product with improved adhesion to circuit boards and heat resistance. The (meth)acrylic acid monomer of the curable composition of the present invention reacts and cures with active energy rays and the thermosetting compound by heating to form a cured product.

[0095] The content of the thermosetting compound in the curable composition is the amount by which the curable composition can contain (meth)acrylate monomers as the main component, preferably 1 to 15% by mass relative to the total curable composition, more preferably 2 to 10% by mass. If the content of the thermosetting compound is less than 1% by mass, the adhesion and heat resistance may be insufficient. If the content of the thermosetting compound exceeds 15% by mass, the thermal stability may decrease above the gelation temperature. In addition, unreacted thermosetting compounds may sometimes react with water to generate polar groups.

[0096] The thermosetting compounds involved in this invention refer to compounds having thermosetting functional groups. Examples of thermosetting functional groups include those described in reviews such as "Refinement of Thermosetting Polymers" (Tsuyoshi Endo, CMC Corporation, 1986), Chapter II-I of "Handbook of Latest Adhesive Technologies" (Yuji Harasaki, Comprehensive Technical Center, 1985), "Synthesis, Design, and Development of New Applications of Acrylic Resins" (Takayuki Otsu, Chubu Business Development Center Publishing Department, 1985), and "Functional Acrylic Resins" (Eizo Omori, Technosystem, 1985). Specifically, regarding thermosetting properties, it is preferable that the aforementioned thermosetting functional group is at least one selected from isocyanate groups, epoxy groups, and maleimide groups.

[0097] The thermosetting compounds of the present invention may contain a (meth)acrylate structure, and (meth)acrylates having thermosetting functional groups are treated as thermosetting compounds. Thermosetting in the thermosetting compounds of the present invention can be carried out through reactions between the thermosetting functional groups of the thermosetting compound, or through reactions between the thermosetting functional groups of the thermosetting compound and the aforementioned functional groups contained in the (meth)acrylate, which is the main component. The thermosetting compounds will be described below according to the types of thermosetting functional groups they possess.

[0098] (Isocyanate group)

[0099] Examples of thermosetting compounds having isocyanate groups include polyfunctional isocyanate compounds having two or more isocyanate groups in the molecule.

[0100] As polyfunctional isocyanate compounds, specific examples include 2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI), 4,4′-diphenylmethane diisocyanate (4,4′-MDI), 2,4′-diphenylmethane diisocyanate (2,4′-MDI), 1,4-phenylene diisocyanate, phenylenediamine diisocyanate (XDI), tetramethylphenylenediamine diisocyanate (TMXDI), toluidine diisocyanate (TODI), and 1,5-naphthalene diisocyanate. Aromatic polyisocyanates such as NDI; aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, and norbornene diisocyanate methyl ester (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.

[0101] These polyfunctional isocyanate compounds can be polymerized; examples of polymers include biuret esters and isocyanurate esters, both of which are trimers. Furthermore, polyfunctional isocyanate compounds can be modified by carbodiimide modifiers, etc.

[0102] As a thermosetting compound having an isocyanate group, it can be a (meth)acrylate compound having an isocyanate group. As a (meth)acrylate compound having an isocyanate group, it is only necessary to have an isocyanate group and a (meth)acryloyloxy group within the molecule; examples include 2-(meth)acryloyloxyethyl isocyanate, 2-isocyanoethyl (meth)acrylate, and 3-isocyanopropyl (meth)acrylate. Furthermore, products of the reaction between hydroxyalkyl (meth)acrylates such as hydroxyethyl (meth)acrylate and polyisocyanates such as toluene diisocyanate can also be used.

[0103] As thermosetting compounds containing isocyanate groups, blocked isocyanate compounds (thermally dissociable blocked isocyanate compounds) are preferred in terms of reducing the relative permittivity of the cured product and improving its resistance to high temperature and humidity. These compounds suppress the reactivity of the isocyanate groups through the protection of the blocking agent at temperatures below the dissociation temperature of the blocking agent, thus resulting in curable compositions containing them exhibiting high thermal stability. Furthermore, by heating to above the dissociation temperature, the blocking agent dissociates, thereby making the isocyanate groups reactive.

[0104] Preferred blocked isocyanate compounds are thermally dissociable blocked isocyanate compounds that are polyfunctional isocyanates. In the case of polyfunctional blocked isocyanate compounds with isocyanate groups protected by a blocking agent, the isocyanurate rings formed by the trimerization reaction of isocyanates exhibit higher bonding thermal stability and superior heat resistance compared to urethane bonds, urea bonds, etc. Furthermore, when polyfunctional blocked isocyanate compounds are used, a network structure with isocyanurate rings is further formed, further improving heat resistance and reducing susceptibility to humidity effects at high temperatures.

[0105] Regarding the preservation and thermal dissociation properties of the curable composition, the thermally dissociative blocking agent is preferably a compound selected from at least one of oxime compounds, pyrazole compounds, and active ethylidene compounds.

[0106] Examples of oxime compounds include formamide oxime, acetaldehyde oxime, acetone oxime, methyl ethyl ketone oxime (MEKO), and cyclohexanone oxime.

[0107] Examples of pyrazole compounds include pyrazole, 3-methylpyrazole, and 3,5-dimethylpyrazole (DMP).

[0108] Examples of active ethylidene compounds include dimethyl malonate, diethyl malonate (DEM), methyl acetoacetate, ethyl acetoacetate, and acetylacetone.

[0109] As a blocking agent for thermal dissociation, caprolactams such as ε-caprolactam can also be used.

[0110] Examples of blocked isocyanate compounds having isocyanate groups protected by the aforementioned blocking agents include ethyl (meth)acrylate 2-[(3,5-dimethylpyrazolyl)carbonylamino] (Carlium MOI-BP, Showa Denko Corporation), ethyl (meth)acrylate 2-[(3-butylene)aminooxycarbonylamino], and ethyl (meth)acrylate 2-(O-[1′-methylpropyleneamino]carboxylamino) (Carlium MOI-BM, Showa Denko Corporation). It should be noted that the parentheses following the compound name indicate a commercially available substitute (product name and manufacturer). The same applies to the following polyfunctional blocked isocyanate compounds having isocyanate groups protected by blocking agents.

[0111] Examples of multifunctional isocyanate compounds with isocyanate groups protected by the aforementioned blocking agents include HDI biuret blocked with DMP (Trixene BI7961, manufactured by LANXESS), HDI trimer blocked with DMP (Trixene BI7982, manufactured by LANXESS), HDI trimer blocked with DMP and DEM (Trixene BI7992, manufactured by LANXESS), HDI trimer blocked with MEKO (PU5211, manufactured by Leeson Polyurethanes), and multifunctional isocyanate blocked with ε-caprolactam (VESTANATB1186A, manufactured by Evonik).

[0112] The above-mentioned sealing agents can be used alone or in combination with two or more. One or more thermally dissociable isocyanate compounds sealed by one or more sealing agents can be used as thermosetting compounds.

[0113] In addition to the above, other examples of commercially available products among thermally dissociable blocked isocyanate compounds include MF-K60X (manufactured by Asahi Kasei Chemicals), VPLS2253, and BL4265SN (both manufactured by Sumitomo Chemical Bayer Polyurethanes).

[0114] (Epoxy group)

[0115] Examples of thermosetting compounds containing epoxy groups include various monomers containing chain epoxy groups (e.g., glycidyl (meth)acrylate, β-methyl glycidyl (meth)acrylate, glycidyl vinyl ether, allyl glycidyl ether, etc.), various vinyl monomers containing (2-oxo-1,3-dioxacyclopentane) groups (e.g., methyl (2-oxo-1,3-dioxacyclopentane)acrylate, etc.), various vinyl monomers containing alicyclic epoxy groups (e.g., 3,4-epoxycyclohexyl (meth)acrylate, methyl 3,4-epoxycyclohexyl (meth)acrylate, ethyl 3,4-epoxycyclohexyl (meth)acrylate, etc.), bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, and brominated bisphenol A diglycidyl ether. Bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ethers, polypropylene glycol diglycidyl ethers; polyglycidyl ethers of polyether polyols obtained by adding one or more olefin oxides to aliphatic polyols such as ethylene glycol, propylene glycol, and glycerol; diglycidyl esters of aliphatic long-chain dicarboxylic acids; monoglycidyl ethers of aliphatic higher alcohols; monoglycidyl ethers of polyether alcohols obtained by adding olefin oxides to phenol, cresol, butylphenol, or the like; and glycidyl esters of higher fatty acids, etc.

[0116] Furthermore, examples of thermosetting compounds having epoxy groups include compounds having (meth)acryloyloxy and epoxy groups, and partially (meth)acryloylated forms of epoxy compounds. Examples of such compounds having (meth)acryloyloxy and epoxy groups include glycidyl methacrylate and 4-hydroxybutyl (meth)acrylate glycidyl ether.

[0117] The partial (meth)acrylamide of the aforementioned epoxy compound is obtained by reacting the epoxy compound with (meth)acrylic acid in the presence of a catalyst using conventional methods. Examples of epoxy compounds that can be used as partial (meth)acrylamides of the aforementioned epoxy compound include phenolic varnish-type epoxy compounds and bisphenol-type epoxy compounds.

[0118] Examples of phenolic varnish-type epoxy compounds include phenolic varnish-type epoxy compounds, cresol varnish-type epoxy compounds, biphenyl varnish-type epoxy compounds, triphenol varnish-type epoxy compounds, and dicyclopentadiene varnish-type epoxy compounds. Examples of bisphenol-type epoxy compounds include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, 2,2′-diallyl bisphenol A type epoxy compounds, hydrogenated bisphenol type epoxy compounds, and polyoxypropylene bisphenol A type epoxy compounds. By appropriately changing the amount of the epoxy compound and (meth)acrylic acid, epoxy compounds with the desired acrylamide ratio can be obtained.

[0119] (maleimide group)

[0120] Examples of thermosetting compounds containing maleimide groups include N-methylmaleimide, N-ethylmaleimide, N-hexylmaleimide, N-propylmaleimide, N-butylmaleimide, N-octylmaleimide, N-dodecylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-p-carboxyphenylmaleimide, N-p-hydroxyphenylmaleimide, and N-p-chlorobenzene. N-tolyl maleimide, N-p-tolyl maleimide, N-p-xylmethyl maleimide, N-o-chlorophenyl maleimide, N-o-tolyl maleimide, N-benzyl maleimide, N-2,5-diethylphenyl maleimide, N-2,5-dimethylphenyl maleimide, N-m-tolyl maleimide, N-α-naphthyl maleimide, N-o-xylmethyl maleimide, N-m-xylmethyl maleimide 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′ -Dimaleimide-bis(3-ethylphenyl)methane, 4,4′-bismaleimide-bis(3-methyl-5-ethyl-phenyl)methane, N,N′-(2,2-bis-(4-phenoxyphenyl)propane)dimaleimide, N,N′-2,4-toluenedimaleimide, N,N′-2,6-toluenedimaleimide, N,N′-m-phenylenedimethylenedimaleimide, bisphenol A diphenyl ether bismaleimide, etc.

[0121] (Other thermosetting functional groups)

[0122] Examples of thermosetting compounds include those with functional groups other than the aforementioned thermosetting functional groups, such as oxacyclobutyl and oxazoline groups.

[0123] Examples of thermosetting compounds containing oxetane groups include oxetane (meth)acrylates. Commercially available examples of such compounds include those manufactured by Osaka Organic Chemicals Co., Ltd. under trade names such as OXE-10 and OXE-30.

[0124] Examples of thermosetting compounds containing 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 substituents on the oxazoline group of these monomers containing an oxazoline group.

[0125] <Gelting Agent>

[0126] The curable composition of the present invention contains a gelling agent as an essential component. By containing a gelling agent, the curable composition of the present invention suppresses the generation of polar groups during curing by light and heat, as described above, thereby achieving a low relative permittivity of the resulting cured product. Furthermore, the presence of a gelling agent in the resulting cured product prevents the penetration of oxygen and moisture into the cured product. From this viewpoint, it is preferable that the gelling agent is maintained in a state of uniform dispersion within the cured product.

[0127] As a gelling agent, there are no particular limitations as long as it is a compound capable of gelling the curable composition. From the viewpoint of improving the above-mentioned effects, ketone waxes, ester waxes, higher fatty acids, higher alcohols and fatty acid amides are preferred, ketone waxes and ester waxes are more preferred, and ketone waxes represented by the following general formula (G1) and ester waxes represented by the following general formula (G2) are even more preferred.

[0128] In addition, gelling agents described in Japanese Patent Application Publication Nos. 2018-506594, 2015-509996, 2006-193745, and 2011-225876 can also be used.

[0129] In terms of dispersion in the cured product (cured film) without hindering the curing property of the curable composition, the gelling agent involved in this invention is preferably a compound of at least one of the compounds represented by the following general formula (G1) or (G2). Furthermore, in inkjet printing using the curable composition as ink, it is preferred to have good pinning properties, be able to draw fine lines while taking into account film thickness, and have excellent fine line reproduction.

[0130] General formula (G1): R1-CO-R2

[0131] General formula (G2): R3-COO-R4

[0132] [In the formula, R1 to R4 each independently represent a straight-chain portion having 12 or more carbon atoms, and may be branched aliphatic hydrocarbon groups.]

[0133] The compound represented by the above general formula (G1) is a ketone wax with R1 and R2 bonded to both sides of the carbonyl group (-C(=O)-). The compound represented by the above general formula (G2) is an ester wax with R3 and R4 bonded to both sides of the ester group (-C(=O)O-). Because R1 and R2, or R3 and R4, are each independently branched aliphatic hydrocarbon groups with a straight chain portion having 12 or more carbon atoms, the crystallinity of the gelling agent is further improved, its water resistance is enhanced, and more sufficient space is generated in the card chamber structure. Therefore, it is easier to fully encapsulate each component in the curable composition within the aforementioned space, further improving its pinning properties when used as an ink.

[0134] R1 to R4, as long as they have the above-described structure, can be either saturated or unsaturated aliphatic hydrocarbon groups. The number of carbon atoms in each of R1 to R4 is preferably 26 or less. If the number of carbon atoms in R1 to R4 is 26 or less, the melting point of the gelling agent will not be excessively increased, and therefore, when the curable composition is ejected as ink, it is not necessary to excessively heat the ink. From the above perspective, R1 and R2, or R3 and R4, are particularly preferably straight-chain aliphatic hydrocarbon groups with 12 or more but less than 23 carbon atoms.

[0135] Furthermore, from the viewpoint of increasing the gelation temperature of the curable composition and enabling the ink to gel more rapidly upon bounce when the curable composition is used as ink, it is preferable that either R1 or R2, or either R3 or R4, is a saturated alkyl group with 12 or more but less than 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 with 12 or more but less than 23 carbon atoms.

[0136] Examples of ketone waxes represented by the above general formula (G1) include di(tetracosyl)one (C24-C24), di(eicosyl)one (C22-C22), distearate ketone (C18-C18), di(eicosyl)one (C20-C20), dipalmitoyl ketone (C16-C16), dimyristyl ketone (C14-C14), dilauryl ketone (C12-C12), and lauryl ketone. Myristyl ketone (C12-C14), lauryl palmityl ketone (C12-C16), myristyl palmityl ketone (C14-C16), myristyl stearyl ketone (C14-C18), myristyl docosyl ketone (C14-C22), palmyl stearyl ketone (C16-C18), palmyl docosyl ketone (C16-C22), stearyl docosyl ketone (C18-C22). It should be noted that the number of carbon atoms in parentheses above indicates the number of carbon atoms in each of the two hydrocarbon groups that are broken by the carbonyl group.

[0137] Examples of commercially available ketone waxes represented by the general formula (G1) include Stearonne (manufactured by Alfa Aeser), 18-Pentatriacontanon (manufactured by Alfa Aeser), Henriacontan-16-on (manufactured by Alfa Aeser), and KAOWAX T-1 (manufactured by Kao Corporation).

[0138] Examples of ester waxes represented by the general formula (G2) include docosyl docosanoate (C21-C22), eicosyl eicosanoate (C19-C20), stearyl stearate (C17-C18), palmitate stearate (C17-C16), lauryl stearate (C17-C12), cetyl palmitate (C15-C16), stearyl palmitate (C15-C18), myristyl myristate (C13-C14), cetyl myristate (C13-C16), octyl dodecyl myristate (C13-C20), stearyl oleate (C17-C18), stearyl erucate (C21-C18), stearyl linoleate (C17-C18), docosyl oleate (C18-C22), and eicosyl linoleate (C17-C20). It should be noted that the number of carbon atoms in the parentheses above represents the number of carbon atoms in each of the two hydrocarbon groups separated by the ester group.

[0139] Examples of commercially available ester waxes represented by the general formula (G2) include Unistar M-2222SL and Spamacechi, manufactured by Nippon Yushu Corporation (“Unistar” is a registered trademark of the company), Ecosepal SS and Ecosepal MY-M, manufactured by Kao Corporation (“Ekisepal” is a registered trademark of the company), EMLEX CC-18 and EMLEX CC-10, manufactured by Nippon Emulsion Corporation (“EMALEX” is a registered trademark of the company), and Ammreps PC, manufactured by Advanced Alcohol Industries Co., Ltd. (“Ammreps” is a registered trademark of the company).

[0140] These commercially available products are mostly mixtures of two or more types, and therefore can be separated and purified as needed to contain them in the curable composition. When the curable composition contains two or more types of ketone waxes selected from general formula (G1) and ester waxes selected from general formula (G2), it is preferable to contain a combination of ketone waxes and ester waxes.

[0141] Regarding the content of the gelling agent involved in this invention, it is preferably in the range of 0.5 to 5.0% by mass relative to the total mass of the curing composition. By setting the content of the gelling agent within the above range, the solubility and pinning effect of the gelling agent in the curing composition become good, thereby improving the water resistance when the cured product (cured film) is formed. Furthermore, from the above viewpoint, it is more preferable that the content of the gelling agent in the curing composition is in the range of 0.5 to 2.5% by mass.

[0142] Furthermore, from the viewpoint that the gelling agent preferably crystallizes in the curing composition at a temperature below the gelation temperature of the curing composition, the gelling agent transitions from the sol to the gel phase and the viscosity of the curing composition changes drastically when the curing composition, which has been sol-gelled or liquefied by heating, is cooled, is specifically, the gelation temperature of the curing composition can be taken as the temperature at which the viscosity rises sharply when the sol-gelled or liquefied curing composition is cooled while measuring its viscosity using a viscoelasticity measuring device (e.g., MCR300, manufactured by Physica).

[0143] The curable composition of the present invention contains a (meth)acrylic acid monomer as a main component and other photopolymerizable compounds and photopolymerization initiators as needed, and further contains a thermosetting compound and a gelling agent. The curable composition of the present invention is cured by irradiation with active energy rays, causing the photopolymerizable compound containing the (meth)acrylic acid monomer to react (hereinafter also referred to as "photocuring"). Alternatively, it is cured by heating, causing the thermosetting compound to react (hereinafter also referred to as "thermal curing"). There is no limitation on the order of photocuring and thermal curing. For example, when the curable composition of the present invention is applied to a substrate, and the coating liquid is temporarily cured by photocuring under active energy rays, and then heated for primary curing by thermal curing, the presence of a gelling agent can suppress the wetting and spreading of the coating liquid after temporary curing, enabling the formation of highly precise patterns.

[0144] <Optional Ingredients>

[0145] The curable composition of the present invention may contain a colorant as an optional component. Furthermore, within the scope of achieving the effects of the present invention, other optional components may include polymerization inhibitors, surfactants, curing accelerators, coupling agents, ion scavengers, etc. Other optional components may be contained in only one type or in two or more types in the curable composition of the present invention.

[0146] (Coloring agent)

[0147] The curable composition of the present invention may further contain colorants as needed.

[0148] The colorant can be a dye or a pigment. Pigments are preferred due to their good dispersibility with the components of the curable composition and excellent weather resistance. There are no particular limitations on the pigment; for example, organic or inorganic pigments listed in the Excellence Index can be included.

[0149] Examples of red or magenta pigments include pigments or mixtures thereof selected from 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, Pigment Orange 13, 16, 20, 36.

[0150] In the example of blue or cyan pigments, there are pigments or mixtures thereof selected from Pigment Blue 1, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17-1, 22, 27, 28, 29, 36, 60.

[0151] In the example of green pigment, it contains pigments selected from Pigment Green 7, 26, 36, 50, or mixtures thereof.

[0152] In the example of yellow pigment, it includes pigments or mixtures thereof 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, 193.

[0153] In the case of black pigments, pigments selected from Pigment Black 7, 28, 26 or mixtures thereof are included.

[0154] 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, Chromofine VioletRE, Chromofine Red 6820, 6830, and 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, Seikafast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400(B), 2500, 2600, ZAY-260, 2700(B), 2770, Seikafast Red 8040, C405(F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seikafast Carmine 6B1476T-7, 1483LT, 3840, 3870, Seikafast Bordeaux 10B-430, Seikalight Rose R40, Seikalight Violet B800, 7805, Seikafast Maroon 460N, Seikafast Orange 900, 2900, Seikalight Blue C718, A612, Cyanine Blue 4933M, 4933GN-EP, 4940, 4973 (manufactured by Dainippon Seika Kogyo Co., Ltd.);KETYellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange501, 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 (made by DIC Corporation); 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 Red 101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, 105C, USN, Colortex Maroon 601, Colortex Brown B610N, Colortex Violet 600, Pigment Red 122, Colortex Blue 516, 517, 518, 519, A818, P-908, 510, Colortex Green 402, 403, Colortex Black 702, U905 (manufactured by Sanyo Pigment Co., Ltd.); Lionol Yellow 1405G, Lionol Blue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (manufactured by Toyo Ink Co., Ltd.), Toner Magenta EO2, Permanent Rubin F6B, Toner Yellow HG, Permanent Yellow GG-02, Hostapem Blue B2G (manufactured by Hearst Industries); Novoperm P-HG, Hostapem Pink E, Hostapem 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, CF9 (Made by Mitsubishi Chemical), etc.

[0155] Pigments can be dispersed using methods such as ball mills, sand mills, grinding mills, roller mills, agitators, Henschel mixers, colloid mills, ultrasonic homogenizers, bead mills, wet spray mills, and paint vibrators.

[0156] The pigment is preferably dispersed in such a way that the volume average particle size of the pigment particles is preferably in the range of 0.08 to 0.5 μm, the maximum particle size is preferably in the range of 0.3 to 10 μm, and more preferably in the range of 0.3 to 3 μm.

[0157] The dispersion of pigments is adjusted by the selection of pigments, dispersants and dispersion media, dispersion conditions and filtration conditions.

[0158] To improve the dispersibility of pigments, the curable composition of the present invention may further include a dispersant.

[0159] Examples of dispersants include carboxylic acid esters with hydroxyl groups, 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, formalin condensate salts of naphthalene sulfonate, formalin condensate salts of aromatic sulfonate, polyoxyethylene alkyl phosphates, polyoxyethylene nonylphenyl ethers, and stearamine acetates, etc.

[0160] Examples of commercially available dispersants include EFKA7701 (manufactured by BASF), Solsperse 22000 and other Solsperse series (manufactured by Nippon Rouble), and Ajinomoto Finetechno's PB series, etc.

[0161] The curable composition of the present invention may further include a dispersing agent if desired. The dispersing agent may be selected according to the pigment.

[0162] Regarding the total amount of dispersant and dispersing aid, it is preferably in the range of 1 to 50% by mass relative to the pigment.

[0163] The curable composition of the present invention may, as needed, further include a dispersion medium for dispersing the pigment. As a dispersion medium, the curable composition may contain a solvent; to suppress solvent residue in the formed image, it is preferable to use the aforementioned photopolymerizable compound (particularly a low-viscosity monomer) as the dispersion medium. When using a photopolymerizable compound such as a (meth)acrylate monomer, the amount of the dispersion medium is added to the content of the aforementioned photopolymerizable compound such as the (meth)acrylate monomer.

[0164] Examples of dyes include oil-soluble dyes.

[0165] Regarding oil-soluble dyes, the following types of dyes can be listed. Examples of magenta dyes include MS Magenta VP, MS Magenta HM-1450, MS Magenta HSo-147 (all manufactured by Mitsui Chemicals), AIZENSOT Red-1, AIZEN SOT Red-2, AIZEN SOT Red-3, AIZEN SOT Pink-1, SPIRON Red GEHSPECIAL (all manufactured by Hodogaya Chemicals), RESOLIN Red FB 200%, MACROLEX Red Violet R, MACROLEX ROT5B (all manufactured by Bayer Japan), KAYASET Red B, KAYASET Red 130, KAYASETRed 802 (all manufactured by Nippon Kayaku Co., Ltd.), PHLOXIN, ROSE BENGAL, ACID Red (all manufactured by Daiwa Kasei Co., Ltd.), HSR-31, DIARESIN Red K (all manufactured by Mitsubishi Chemicals), and Oil Red (manufactured by BASF Japan).

[0166] Examples of cyan dyes include MS Cyan HM-1238, MS Cyan HSo-16, Cyan HSo-144, MSCyan VPG (all manufactured by Mitsui Chemicals), AIZEN SOT Blue-4 (manufactured by Hodogaya Chemicals), RESOLINBR.BlueBGLN 200%, MACROLEX Blue RR, CERES Blue GN, SIRIUS SUPRATURQ.Blue Z-BGL, SIRIUS SUPRA TURQ.Blue FB-LL 330% (manufactured by Bayer Japan), KAYASET Blue FR, KAYASET Blue N, KAYASET Blue 814, Turq.Blue GL-5 200, Light Blue BGL-5 200 (manufactured by Nippon Kayaku Co., Ltd.), DAIWA Blue 7000, Oleosol Fast Blue GL (manufactured by Daiwa Kasei Co., Ltd.), and DIARESIN Blue. P (Mitsubishi Chemical Corporation), SUDAN Blue 670, NEOPEN Blue 808, ZAPON Blue 806 (all manufactured by BASF Japan), etc.

[0167] Examples of yellow dyes include MS Yellow HSm-41, Yellow KX-7, Yellow EX-27 (manufactured by Mitsui Chemicals), AIZEN SOT Yellow-1, AIZEN SOT Yellow-3, AIZEN SOT Yellow-6 (manufactured by Hodogaya Chemicals), MACROLEX Yellow 6G, MACROLEX FLUOR.Yellow 10GN (manufactured by Bayer Japan), KAYASET Yellow SF-G, KAYASET Yellow 2G, KAYASET Yellow AG, KAYASETYYellow EG (manufactured by Nippon Kayaku Co., Ltd.), DAIWA Yellow 330HB (manufactured by Daiwa Kasei Co., Ltd.), HSY-68 (manufactured by Mitsubishi Chemicals), SUDAN Yellow 146, NEOPEN Yellow 075 (manufactured by BASF Japan), etc.

[0168] Examples of black dyes include MS Black VPC (manufactured by Mitsui Chemicals), AIZENSOT Black-1, AIZEN SOT Black-5 (manufactured by Hodogaya Chemicals), RESORIN Black GSN 200%, RESOLINBlackBS (manufactured by Bayer Japan), KAYASET Black AN (manufactured by Nippon Kayaku Co., Ltd.), DAIWA BlackMSC (manufactured by Daiwa Kasei Co., Ltd.), HSB-202 (manufactured by Mitsubishi Chemicals), NEPTUNE Black X60, and NEOPENBlack X58 (manufactured by BASF Japan).

[0169] The colorant is included in one or more types in the curable composition of the present invention, and can be tinted to the desired color. The content of the colorant is preferably in the range of 0.1 to 20% by mass relative to the total amount of the curable composition, and more preferably in the range of 0.4 to 10% by mass.

[0170] (polymerization inhibitor)

[0171] Examples of polymerization inhibitors include (alkyl)phenol, hydroquinone, catechol, resorcinol, p-methoxyphenol, tert-butylcatechol, tert-butylhydroquinone, pyrogallol, 1,1-picrylhydrazide, phenothiazine, p-benzoquinone, nitrosobenzene, 2,5-di-tert-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, copper ferroin, N-nitrosophenylhydroxylamine aluminum, tri-p-nitrophenylmethyl, N-(3-hydroxyanilino-1,3-dimethylbutylene)aniline oxide, dibutylcresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraldehyde oxime, methyl ethyl ketone oxime, and cyclohexanone oxime.

[0172] Examples of commercially available polymerization inhibitors include Irgastab UV10 (manufactured by BASF) and Genorad 18 (manufactured by Rahn AG).

[0173] The amount of polymerization inhibitor can be set arbitrarily within the range that achieves the effects of the present invention. The amount of polymerization inhibitor, relative to the total mass of the curable composition, can, for example, be set to 0.001% by mass or more but less than 1.0% by mass.

[0174] (surfactant)

[0175] 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, alkynyl glycols, and polyoxyethylene-polyoxypropylene block copolymers; cationic surfactants such as alkylamine salts and quaternary ammonium salts; and silicone-based and fluorinated surfactants.

[0176] Examples of organosilicon-based surfactants include polyether-modified polysiloxane compounds, specifically including 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 Chemical Co., Ltd. (“BYK” is a registered trademark of the company), and TSF4452, manufactured by Mobile Products & Products Materia Medica.

[0177] Fluorinated surfactants refer to products in which the hydrogen atom bonded to carbon in the hydrophobic group of a conventional surfactant is partially or completely replaced by fluorine. Examples of fluorinated surfactants include Megafac F, manufactured by DIC (“Megafac” is a registered trademark of the company), Surflon, manufactured by AGC semichemical Co., Ltd. (“Surflon” is a registered trademark of the company), Fluorad FC, manufactured by 3M (“Fluorad” is a registered trademark of the company), Monflor, manufactured by Teikoku Chemical Industry Co., Ltd., Zonyls, manufactured by I-E-D-Y-Pon-Nemelas-And-Cappani, Licowet VPF, manufactured by Lubeberuke Heist, and FTERGENT, manufactured by Neos (“FTERGENT” is a registered trademark of the company).

[0178] The amount of surfactant can be set arbitrarily within the range that achieves the effects of the present invention. The amount of surfactant, relative to the total mass of the curable composition, can, for example, be set to 0.001% by mass or more but less than 1.0% by mass.

[0179] (Curing accelerator)

[0180] The curable composition of the present invention may include a curing accelerator as needed. As a curing accelerator, it can be used without particular limitation as long as it promotes the thermal curing of thermosetting compounds, etc.

[0181] Examples of curing accelerators include imidazoles, dicyandiamide derivatives, dicarboxylic acid dihydrazide, triphenylphosphine, tetraphenylphosphonium tetraphenylborate, 2-ethyl-4-methylimidazolium-tetraphenylborate, and 1,8-diazabicyclo[5.4.0]undecene-7-tetraphenylborate.

[0182] (Coupled agent)

[0183] The curable composition of the present invention may contain various coupling agents as needed. By including a coupling agent, the adhesion to copper foil can be improved. Examples of various coupling agents include silane-based, titanium-based, and aluminum-based coupling agents.

[0184] (ion scavenger)

[0185] The curable composition of the present invention may include an ion scavenger if necessary. By including an ion scavenger, it has advantages such as adsorption of ionic impurities and improved insulation under conditions of moisture absorption in the cured film.

[0186] Examples of inorganic ion scavengers include triazine thiols, bisphenol-based reducing agents, zirconium compounds, and antimony-bismuth magnesium-aluminum compounds.

[0187] The amounts of the curing accelerator, coupling agent, and ion trap can be arbitrarily set within the range that achieves the effects of the present invention. The amounts of these components, relative to the total mass of the curable composition, can each be set, for example, to be 0.001% by mass or more and less than 1.0% by mass.

[0188] From the viewpoint of curability, the curable composition of the present invention is preferably used directly for applications such as inks without dilution with a solvent. That is, the curable composition of the present invention is preferably used in a solvent-free state. However, in order to adjust the viscosity, a solvent may be added as needed, and the curable composition may be used in a diluted solution state.

[0189] [Physical Properties of Curing Compositions]

[0190] The physical properties of the cured product of the curable composition and the physical properties of the curable composition are described.

[0191] <Relative permittivity of the cured material>

[0192] The cured product of the curable composition of the present invention preferably has a relative permittivity of less than 3.0 at 1 MHz. More preferably, the relative permittivity of the cured product at 1 MHz is 2.95 or less, and even more preferably 2.90 or less.

[0193] The relative permittivity of the cured composition of the present invention at 10 GHz is less than 2.90. Preferably, the relative permittivity of the cured composition at 10 GHz is 2.80 or less, more preferably 2.70 or less.

[0194] Therefore, the curable composition of the present invention can be used, for example, to form solder resist films with low dielectric constants suitable for 5G applications. Furthermore, the curable composition of the present invention, for example, can be used to form solder resist films for high-performance devices.

[0195] It should be noted that the relative permittivity of the cured material at 1 MHz and at 10 GHz can be determined, for example, by the following methods.

[0196] (Methods for determining relative permittivity)

[0197] The cured material used for determining the relative permittivity was prepared as follows. First, the curable composition was inkjet-coated onto a substrate for curing the material in a solid pattern of 70 mm × 70 mm and 23 μm thick. The resulting coating was then irradiated with ultraviolet light (395 nm) using an LED lamp to achieve a concentration of 500 mJ / cm². 2 After photocuring (temporary curing) of the curable composition by applying a certain amount of irradiation, it is then placed in an oven set at 150°C for 60 minutes to achieve thermal curing (primary curing). The cured material (film) is peeled off from the substrate used for preparing the cured material and cut out a square piece of approximately 5 cm as the test sample.

[0198] (Relative permittivity at 1MHz)

[0199] The relative permittivity at 1 MHz was determined, for example, using an LCR meter. In this case, a tin foil with a main electrode diameter of 1.8 cm was attached to the sample obtained above to form an electrode, and the relative permittivity was measured. The measurement was conducted at room temperature (23±2℃ / 50±5%RH) as the test atmosphere. For thickness measurement, a micrometer was used, and the average value of 5 points was calculated. As the measuring apparatus, for example, an LCR meter; HP4284A (manufactured by Agilent Technologies); a thermostat; TO-19 (manufactured by Ando Electric Co., Ltd.); and a solid electrode; SE-70 (manufactured by Ando Electric Co., Ltd.) can be used.

[0200] (Relative permittivity at 10 GHz)

[0201] The relative permittivity at 10 GHz was determined using the void resonator method. In the void resonator method, the sample obtained above was used directly as is. Measurements were taken at room temperature (23±2℃ / 50±5%RH) as the test atmosphere. For thickness measurement, a micrometer was used, and the average value of 5 points was calculated. The measuring apparatus included a Censor Speedster 8340B (manufactured by YHP Corporation), a Network Analyzer 8510B (manufactured by YHP Corporation), a cylindrical void resonator (TE mode, near 10 GHz) (material: copper, internal mirror finish), and a semi-rigid cable for signal transmission.

[0202] (Viscosity and phase transition point of the curing composition)

[0203] For example, when used as inkjet ink, in terms of ensuring sufficient gelation and good pinning properties of the ink upon drop and cooling to room temperature, it is preferable that the viscosity of the curable composition of the present invention at 25°C is 1 to 1 × 10⁻⁶. 4 The viscosity of the curable composition of the present invention is preferably in the range of 3 to 20 mPa·s, more preferably in the range of 7 to 9 mPa·s, from the viewpoint of further improving the ejection performance from the inkjet head, when used as an inkjet ink.

[0204] The curable composition of the present invention preferably has a phase transition point in the range of 40°C or higher and less 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) rapidly gels after the recording medium bounces off, thus further improving pinning properties. Therefore, it becomes possible to form high-resolution images and patterns. In addition, if the phase transition point is less than 100°C, the processability of the curable composition becomes good, and the jetting stability is improved. Similarly, when the curable composition is used as an inkjet ink, the ink (curable composition) can be discharged at a lower temperature. From the viewpoint of reducing the load on the image forming apparatus, the phase transition point of the curable composition of the present invention is more preferably in the range of 40 to 60°C.

[0205] 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.

[0206] Using a viscoelasticity measuring device, such as an 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 were determined at a shear rate of 1000 (1 / s). The phase transition point is defined as the temperature at which the complex viscosity coefficient (complex viscosity ratio) reaches 1 Pa in a viscoelastic curve obtained by changing the temperature at a cooling rate of 0.1°C / s, a strain of 5%, an angular frequency of 10 radians / s, and a cooling rate of 0.1°C / s.

[0207] When using a curable composition as an inkjet ink, from the viewpoint of further improving ejection from the inkjet head, it is preferable that the average dispersed particle size of the pigment particles involved in this invention is in the range of 50 to 150 nm, and the maximum particle size is in the range of 300 to 1000 nm. More preferably, the average dispersed particle size is in the range of 80 to 130 nm.

[0208] The average dispersed particle size of the pigment particles in this invention refers to the value obtained using a Data Siennano ZSP, manufactured by Malvern Corporation, and determined by dynamic light scattering. It should be noted that the ink containing the colorant has a high concentration, and light would not be able to pass through this measuring device; therefore, the ink (curing composition) was diluted 200 times before measurement. The measurement temperature was room temperature (25°C).

[0209] The curable composition of the present invention is used by curing it after being applied to a substrate. There are no particular limitations on the method of applying the curable composition to the substrate; any known coating method may be used. However, inkjet coating, as described above, is preferred as it further enhances the effects of the present invention.

[0210] The curing of the curable composition of the present invention is performed as described above, by combining light curing and heat curing. There is no limitation on the order of light curing and heat curing; however, from the viewpoint of workability, a method of performing heat curing after light curing is preferred. The relative permittivity of the cured product of the curable composition of the present invention at 10 GHz is less than 2.90. Furthermore, the cured product, thanks to the action of a gelling agent, can suppress the intrusion of oxygen and moisture from the outside.

[0211] Considering the above characteristics, the curable composition of the present invention is particularly advantageous for use as an ink for solder resist. Furthermore, in addition to being used as an ink for solder resist patterning, the curable composition of the present invention can also be used as an adhesive, sealant, circuit protectant, etc., for electronic components.

[0212] [Solder resist ink]

[0213] The solder resist ink of the present invention is characterized by containing the curable composition of the present invention. The solder resist ink may contain only the curable composition of the present invention, or may contain other components besides the curable composition as needed. Examples of other components include the solvents described above. Preferably, the solder resist ink of the present invention is composed of the curable composition of the present invention.

[0214] Solder resist ink is used for forming solder resist films on printed circuit boards. The solder resist ink of the present invention, by containing the curable composition of the present invention, prevents oxygen and moisture from penetrating into the solder resist film during the formation of the solder resist pattern (solder resist film) through the card chamber structure formed by the gelling agent. As a result, the generation of polar groups is reduced, thus enabling a lower dielectric constant. Furthermore, the adhesion between the circuit pattern (conductor pattern), such as copper wiring, and the solder resist film interface in the printed circuit board becomes better, thereby preventing the migration of conductors, such as copper, and suppressing the reduction of insulation.

[0215] Printed Circuit Board

[0216] The printed circuit board of the present invention comprises a substrate, a circuit pattern disposed on the surface of the substrate, and a solder resist film disposed on the circuit pattern, characterized in that the solder resist film is formed using the solder resist ink of the present invention.

[0217] The printed circuit board of the present invention, except for the solder resist film, can be configured to have the same structure as known printed circuit boards.

[0218] For example, the substrate used in a printed circuit board is not particularly limited, and can be made of known materials such as phenolic paper, epoxy paper, epoxy glass cloth, polyimide glass, epoxy glass cloth / non-woven fabric, epoxy glass cloth / paper, epoxy synthetic fibers, fluoropolymer-polyphenylene oxide (PPO)-cyanate, polyimide, polyethylene terephthalate (PET), glass, ceramics, and other insulating materials. Alternatively, the substrate can be made of semiconductors such as wafers, or metals such as stainless steel, copper, or aluminum.

[0219] In the case of printed circuit boards (PCBs), the surface of the board has a circuit pattern (conductor pattern) that conforms to the design, such as leaving only contacts for external electrical connection by soldering, and a solder resist film is formed on the circuit pattern. The solder resist film can be formed according to the design pattern of the PCB. In addition, the thickness of the solder resist film depends on the type and application of the PCB, and can be set to about 10 to 60 μm, preferably 15 to 40 μm.

[0220] In a printed circuit board, wiring conductors can be formed as circuit patterns (conductor patterns) on one or both surfaces of the board. Alternatively, the substrate can be a multilayer board or a laminated board where wiring conductors are formed not only on the surface but also inside the board. In the printed circuit board of the present invention, the circuit pattern (conductor pattern) is preferably composed of copper wiring. For example, substrates using materials such as copper-clad laminates for high-frequency circuits can be used as the substrate for the printed circuit board; that is, copper-clad laminates of all grades (FR-4, etc.). In such substrates, the copper wiring is formed by etching or other processing of the copper layer (copper foil) present on the surface.

[0221] In the printed circuit board of the present invention, the solder resist film is formed using the solder resist ink of the present invention described above, therefore, the relative permittivity at 10 GHz is less than 2.90, and it exhibits excellent adhesion and heat resistance. It should be noted that, in order to form the solder resist film on the copper wiring and further improve the adhesion, the surface roughness Ra of the copper wiring is preferably in the range of 0.1 to 2.0 μm. If the surface roughness Ra is within the above range, the adhesion between the solder resist film and the copper wiring is improved when the solder resist ink is applied.

[0222] To adjust the surface roughness Ra of conductor wiring, it is preferable to roughen the conductor layer, such as copper wiring, which serves as a circuit pattern (conductor pattern), as a pretreatment to prevent leakage. Examples of roughening methods include physical abrasive treatment (creating a rough surface by polishing, wiping, etc.) and chemical abrasive treatment using chemical abrasives such as copper chloride-based, persulfate-based, sulfuric acid / hydrogen peroxide-based, formic acid-based, and organic acid-based abrasives.

[0223] As a pretreatment, from the viewpoint of improving adhesion, chemical polishing is preferred, and among chemical polishing treatments, treatments that improve adhesion are more preferred. Specific examples of chemical polishing treatments include: MacDermid's MultiPrep 200 for copper chloride systems; MacDermid's MicroClean, ME-301, and PR-820 for persulfate systems; Shikoku Kasei's GB1000F / 1400, G200, GB3100, and GB4300 for sulfuric acid / hydrogen peroxide systems; MacDermid's MultiBond 100, MultiBond 150, MultiBond MP, Metex G-5, and Metex... Treatments used include G-6, ME-501, ME-602, ME-605, ME-709, BOARDTEC's BTH-2066, Mitsubishi Gas Chemical's CPE-900, EMR-5000, and EMR-7000. For organic acid systems, MEC's ​​CZ8100, CZ8101, and CZ8201, and BOARDTEC's BTH-2085, among others, were employed. Additionally, for treatments to improve airtightness, MEC's ​​GT process and Shikoku Chemical's GliCAP process were cited.

[0224] From the perspective of improving sealing, sulfuric acid / hydrogen peroxide-based systems and organic acid-based systems are preferred, with organic acid-based systems being more preferred. To prevent leakage, liquid-repellent treatment can be performed.

[0225] The surface roughness Ra of the circuit pattern (conductor pattern) such as copper wiring, which has been 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, the sealing performance is further improved; if it is 2.0 μm or less, leakage and transmission loss at 10 GHz are further suppressed.

[0226] The thickness of the circuit pattern (conductor pattern) such as copper wiring that is roughened by the aforementioned 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 roughened thickness is 0.1 μm or more, the sealing performance is improved due to the anchoring effect; if it is 3.0 μm or less, the conductor such as copper will not be excessively roughened, thus improving the sealing performance.

[0227] Surface roughness Ra can be controlled by adjusting the type of pretreatment agent, treatment temperature, time, and other conditions. Surface roughness Ra is the arithmetic mean roughness measured based on JIS B 0601. Specifically, surface roughness Ra can be measured using scanning probe microscopy (SPM), non-contact interference microscopy (WYKO), laser microscopy, and surface roughness (contact needle method).

[0228] [Methods for forming solder resist film]

[0229] The method for forming a solder resist film using the solder resist ink of the present invention (hereinafter also referred to as "ink") preferably includes: (1) a step of ejecting the ink of the present invention from the nozzle of an inkjet head and dropping it onto the circuit pattern of a printed circuit board on which the circuit pattern has been formed; (2) a step of irradiating the dropped ink with active energy rays to light-cur the ink (temporary curing); and (3) a step of heating the ink and performing thermal curing (primary curing).

[0230] <(1) process>

[0231] In step (1), droplets of the ink of the present invention are ejected from the inkjet head, causing them to bounce off and pattern in the area containing the circuit pattern on the printed circuit board where a solder resist film should be formed. The ejection method from the inkjet head can be either on-demand or continuous.

[0232] On-demand inkjet heads can be any of the following: single-chamber, dual-chamber, supplier, piston, shared-mode, and shared-wall electromechanical conversion types, as well as thermal inkjet and Bubble-Jet (a registered trademark of Canon) electro-thermal conversion types.

[0233] By ejecting ink droplets from the inkjet head while they are heated, ejection stability can be improved. The ink temperature at ejection is preferably in the range of 40 to 100°C, and more preferably in the range of 40 to 90°C to further improve ejection stability. It is particularly preferred to perform the ejection at an ink temperature in which the ink viscosity is in the range of 7 to 15 mPa·s, and more preferably in the range of 8 to 13 mPa·s.

[0234] For sol-gel phase transition inks, to improve ink ejection from the printhead, it is preferable to set the ink temperature when filling the printhead to (gelation temperature (phase transition point) + 10) °C to (gelation temperature (phase transition point) + 30) °C. If the ink temperature inside the printhead is below (gelation temperature + 10) °C, the ink will gel inside the printhead or on the nozzle surface, easily reducing ink ejection. On the other hand, if the ink temperature inside the printhead exceeds (gelation temperature + 30) °C, the ink becomes excessively hot, sometimes leading to ink composition deterioration.

[0235] There are no particular restrictions on the method of heating the ink. For example, at least one of the ink supply system, such as the ink tank that makes up the head holder, the supply pipe and the front chamber ink tank in front of the head, the piping with the filter, and the piezoelectric head, can be heated by a panel heater, a strip heater or insulated water.

[0236] Regarding the amount of ink droplets discharged, from the viewpoint of ensuring operational efficiency and protecting the thickness of the circuit pattern in the obtained solder resist film as well as the reproducibility of the fine lines of the circuit pattern, it is preferably in the range of 2 to 20 pL.

[0237] <(2) process>

[0238] In step (2), the ink that was ejected in step (1) is irradiated with active energy rays to temporarily solidify the ink. The active energy rays can be selected from, for example, electron beams, ultraviolet rays, alpha rays, gamma rays, and X-rays, with ultraviolet rays being preferred.

[0239] Regarding ultraviolet irradiation, for example, water-cooled LEDs manufactured by Phoseon Technology can be used at a wavelength of 395nm. By using LEDs as the light source, it is possible to suppress poor ink curing caused by the ink melting due to the radiant heat of the light source.

[0240] The ink coating is irradiated with ultraviolet light so that the peak illuminance at the surface of the ink coating with ultraviolet light wavelengths in the range of 370–410 nm is preferably 0.5–10 W / cm². 2 Within the range, it is more preferable to be 1 to 5 W / cm 2 Within a certain range. From the viewpoint of suppressing radiant heat from irradiating the ink, it is preferable that the amount of light irradiating the ink coating film is less than 1000 mJ / cm. 2 The irradiation with active energy rays is preferably carried out within a period of 0.001 to 300 seconds after the ink bomb falls, and more preferably within a period of 0.001 to 60 seconds in order to form a high-precision solder resist film.

[0241] <(3) process>

[0242] In step (3), after the temporary curing in (2), the ink coating is then heated for primary curing. The preferred heating method is, for example, immersing the coating in an oven set in the range of 110 to 180°C for 10 to 60 minutes.

[0243] Example

[0244] The present invention is specifically illustrated below with examples, but the invention is not limited thereto. It should be noted that, unless otherwise specified, the operation is performed at room temperature (25°C) in the following examples. Furthermore, unless otherwise specified, "%" and "parts" refer to "mass %" and "parts by mass," respectively.

[0245] <Components of the Curing Composition>

[0246] The components of the curable compositions used in the following examples and comparative examples, namely (meth)acrylic monomers, thermosetting compounds, photopolymerization initiators, and gelling agents, were commercially available products or compounds as shown in Table I. For (meth)acrylic monomers, molecular weight, ClogP, and classification are described together.

[0247] [Table 1]

[0248]

[0249] <Preparation of colorant dispersions>

[0250] The pigment dispersion prepared as described below is used in a curable composition.

[0251] (E-1: Preparation of Yellow Pigment Dispersion)

[0252] Dispersant 1 and Dispersant 2, along with the dispersion medium, were placed in a stainless steel beaker and heated on a hot plate at 62°C with stirring for 55 minutes to dissolve. After cooling to room temperature, the pigment was added, and 200g of 0.5mm diameter zirconia beads were placed in a glass bottle and stoppered. The mixture was then dispersed using a paint vibrator until the desired particle size was achieved, after which the zirconia beads were removed.

[0253]

[0254] (E-2: Preparation of Cyan Pigment Dispersion)

[0255] In the preparation of the above-mentioned yellow pigment dispersion, the dispersant, dispersion medium and pigment were changed as shown below, and otherwise the same preparation was carried out.

[0256] Dispersant: EFKA7701 (manufactured by BASF) 6.7 parts by weight

[0257] Dispersion medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 72 parts by weight

[0258] Pigment: PB15: 4 (Dainichi Seika Co., Ltd., Konan Fluoride 6332JC) 21 parts by mass

[0259] [Preparation of Curable Composition (Inkjet Ink)]

[0260] According to the ink compositions (parts by mass) listed in Tables II to IV below, the components were mixed and filtered using a 3μm Teflon membrane filter manufactured by ADVATEC (registered trademark) to obtain curable compositions (inkjet ink, hereinafter also referred to as "ink") AA-1 to AA-16, AB-1 to AB-6 (Tables II and III) and BB-1 to BB-11 (Table IV).

[0261] It should be noted that in Tables II to IV, the total amount (parts by mass) of dipropylene glycol diacrylate contained in pigment dispersions E-1 and E-2, plus the amount of M222 (dipropylene glycol diacrylate) incorporated as a (meth)acrylic monomer A-5, is recorded in the column for (meth)acrylic monomer A-5. Furthermore, in the column for pigment dispersions, the amount of dipropylene glycol diacrylate contained as a dispersion medium in pigment dispersions E-1 and E-2 is recorded directly as is.

[0262] Specifically, in ink AA-1 of Table II, 54 parts by mass and 34 parts by mass of (meth)acrylic monomers A-9 and A-8 were used respectively, along with 1 part by mass each of pigment dispersions E-1 and E-2. However, since pigment dispersions E-1 and E-2 contain dipropylene glycol diacrylate, the amount of dipropylene glycol diacrylate contained in pigment dispersions E-1 and E-2 in the above-mentioned proportions is calculated, and the total amount of 1.5 parts by mass is recorded in column A-5 of Table II for (meth)acrylic monomers. The same procedure is followed for other inks in Tables II to IV.

[0263] It should be noted that in all the inks shown in Tables II to IV, 1 part by mass each of pigment dispersions E-1 and E-2 was used, therefore the amount of (meth)acrylate monomer A-5 from the pigment dispersions was 1.5 parts by mass. In Table IV, there are inks where the amount of (meth)acrylate monomer A-5 exceeds 1.5 parts by mass. In these inks, M222 (dipropylene glycol diacrylate) was used in preparation, calculated by subtracting 1.5 parts by mass from the amount of (meth)acrylate monomer A-5 shown in Table IV. In Tables II to IV, blank columns indicate that the content of this component is "0" parts by mass.

[0264] In addition, Tables II to IV show the proportions [mass %] of (meth)acrylic monomers (A1), (A2) and others.

[0265] [The physical properties of ink]

[0266] (Viscosity and phase transition point)

[0267] The viscosity and phase transition point at 25°C of the obtained inks AA-1~AA-16, AB-1~AB-6 and BB-1~BB-11 were determined using the method described above.

[0268] The viscosity of the ink of this invention at 25°C is 1 to 1 × 10⁻⁶. 4 Pa·s, while the comparative examples of gelling agent-free inks all had a gel phase transition temperature of less than 1 Pa·s. Furthermore, the gel phase transition temperatures of the inks of the present invention were all between 40 and 100°C, while no gel phase transition phenomenon was observed in the comparative examples of gelling agent-free inks.

[0269] (Relative permittivity of ink-cured material)

[0270] Using the obtained inks AA-1~AA-16, AB-1~AB-6 and BB-1~BB-11, solid patterns were printed on polypropylene films using the inkjet recording device shown below, and the films were cured to produce test samples of the cured films.

[0271] Specifically, ink was sprayed onto a polypropylene film in a solid pattern of 70mm × 70mm and 23μm thickness. The resulting ink layer was then tested using an LED lamp (395nm, 8W / cm²) manufactured by Phoseon Technology. 2 Water-cooled unit), irradiated with ultraviolet light (395nm) to achieve 500mJ / cm². 2 After being irradiated to a certain amount to achieve photocuring (temporary curing), the cured material (film) was peeled off from the polypropylene film and placed in an oven set at 150°C for 60 minutes to achieve thermal curing (primary curing). Approximately 5 cm square samples were cut out to prepare the test samples, and the relative permittivity at 1 MHz and 10 GHz was determined using the method described above. The results are shown in Tables II to IV.

[0272] [Rating 1]

[0273] The following method was used to evaluate the adhesion and heat resistance of the cured ink film to the copper layer of the copper-clad laminate. The results are shown in Tables II to IV.

[0274] (1) Evaluation of the preparation of stacked samples

[0275] <Processing of Copper Clad Laminates>

[0276] A pretreated copper-clad laminate substrate with a copper surface roughness Ra of 1.5 μm was fabricated by treating the copper layer on the surface of a copper-clad laminate (FR-4; 1.6 mm thick, 150 mm × 95 μm) for printed wiring boards using MEC's ​​CZ-8100 treatment solution. It should be noted that the surface roughness Ra is the arithmetic mean roughness measured using a laser microscope.

[0277] <Pattern formation using inkjet printing>

[0278] The inks prepared above are loaded into an inkjet recording device having an inkjet recording head equipped with piezoelectric inkjet nozzles. Using this device, a pattern is formed on a copper-clad laminate (FR-4, 1.6 mm thick, 150 mm × 95 mm in size) for printed wiring boards that has undergone the above-described copper pretreatment.

[0279] The ink supply system consists of an ink tank, ink flow path, a sub-ink tank in front of the inkjet head, piping with a metal filter, and a piezoelectric head. From the ink tank to the head, the ink is heated to 80°C. A heater is also built into the piezoelectric head to heat the ink inside to 75°C. The piezoelectric head used is the Konica Minolta KM1800i-SHC.

[0280] Using this inkjet device, voltage was applied at a droplet volume of 3.5 p1 to form a solid ink layer of 70 mm × 70 mm and a comb-shaped pattern with lines and gaps of 100 μm on a substrate, resulting in a thickness of 23 μm. The substrate was then illuminated with an LED lamp (395 nm, 8 W / cm²) manufactured by Phoseon Technology. 2 (Water-cooled unit) thus reaching 500mJ / cm 2 The ink layer is temporarily cured. Then, it is placed in an oven set at 150°C for 60 minutes for primary curing, resulting in a laminated sample with a cured film pattern formed on the pretreated copper layer of the copper-clad laminate.

[0281] (2) Evaluation of stacked samples

[0282] <Substrate Adhesion>

[0283] For the aforementioned solid patterned laminated samples, checkerboard-like cuts were made in the cured film using the cross-cutting method according to JIS K5600. Adhesive tape was then applied, peeled off, and the peeling state of the cured film was observed. The adhesion residue rate was calculated using the following method and evaluated according to the following criteria. The adhesion residue rate was calculated by using the number of grids created by the cuts as the denominator and the number of grids remaining after tape peeling as the numerator.

[0284] (Benchmark)

[0285] 5: Adhesion residue rate 100%

[0286] 4: Adhesion residue rate is above 80% but less than 100%.

[0287] 3: Adhesion residue rate is above 60% but less than 80%.

[0288] 2: Adhesion residue rate is above 50% but less than 60%.

[0289] 1. Adhesion residue rate is less than 50%.

[0290] Solder heat resistance

[0291] For the above-mentioned solid patterned laminated samples, after immersing in a solder bath at 260°C for 10 seconds three times, the above-mentioned adhesion retention rate was evaluated, and the peeling state of the cured film was observed.

[0292]

[0293]

[0294]

[0295] As shown in the results above, the curable composition of the present invention is superior to the curable composition of the comparative examples in terms of relative permittivity, substrate adhesion, and solder heat resistance. Furthermore, the following aspects of heat and moisture resistance, solvent resistance, acid resistance, alkali resistance, and insulation reliability were also evaluated, confirming that there are no problems in practical application.

[0296] In addition, using a comb pattern with lines and gaps of 100 μm, the reproducibility of fine lines was evaluated using the following method. As a result, for the sample of the present invention, lines and gaps of 100 μm could be drawn, but for the comparative example sample without gelling agent, lines and gaps could not be drawn at 100 μm, the gaps were filled with ink, or became lines with a thickness of more than 100 μm.

[0297] <Heat and moisture resistance>

[0298] The solid patterned laminated samples were placed at 85°C and 85% relative humidity for 500 hours. Then, the substrate adhesion was evaluated, and the peeling state of the cured film was observed.

[0299] Solvent resistance

[0300] For the above-mentioned solid patterned laminated samples, after immersion in propylene glycol monomethyl ether acetate at 20°C for 20 minutes, followed by washing and drying, the substrate adhesion was evaluated, and the peeling state of the cured film was observed.

[0301] <Acid Resistance>

[0302] For the above-mentioned solid patterned laminated samples, after immersion in a 10% by mass sulfuric acid aqueous solution at 20°C for 20 minutes, followed by washing and drying, the above-mentioned substrate adhesion was evaluated, and the peeling state of the cured film was observed.

[0303] <Alkali resistance>

[0304] For the above-mentioned solid patterned laminated samples, after immersion in a 10% by mass sodium hydroxide aqueous solution at 20°C for 20 minutes, followed by washing and drying, the substrate adhesion was evaluated as described above, and the peeling state of the cured film was observed.

[0305] <Insulation Reliability>

[0306] On a copper-clad laminate (FR-4; 1.6 mm thick, 150 mm × 95 mm) for printed wiring boards, a conductive comb-shaped wiring pattern with 75 μm lines and gaps was fabricated. A solid pattern was then formed by inkjet printing using prepared inks to completely cover the comb-shaped wiring pattern. The insulation performance of the resulting samples was evaluated for up to 1000 hours at 85°C, 85% RH, and an applied voltage of 100 V.

[0307] (Benchmark)

[0308] ◎: After 1000 hours, there was no significant decrease in resistance or short circuit; the insulation resistance value was 10. 8 Ω and above

[0309] ○: After 500 hours, there was no significant decrease in resistance or short circuit; the insulation resistance value was 10. 8 Ω and above

[0310] △: After 250 hours, there was no significant decrease in resistance or short circuit; the insulation resistance was 10. 8 Ω and above

[0311] ×: The insulation resistance value was less than 10 after 250 hours. 8 Ω

[0312] <Reproducibility of fine lines>

[0313] The comb-shaped pattern with lines and gaps of 100 μm was observed using an optical microscope.

[0314] [Rating 2]

[0315] Using the BB-4 ink obtained above, the differences in adhesion, heat resistance, and exudation caused by different pretreatments of the copper layer in copper-clad laminates were evaluated. The results are shown in Table V.

[0316] (1) Evaluation of the preparation of stacked samples

[0317] <Processing of Copper Clad Laminates>

[0318] By treating the copper layer on the surface of a copper-clad laminate (FR-4; 1.6 mm thick, 150 mm × 95 mm) for printed wiring boards under adjusted conditions using MEC's ​​CZ-8100, CZ8101, and CZ8201 treatment solutions, copper-clad laminate substrates with different surface roughness Ra were fabricated, ranging from CC-2 to CC-11. An untreated copper-clad laminate was used as CC-1.

[0319] <Pattern formation using inkjet printing>

[0320] Using ink BB-4, similar to Evaluation 1 above, laminated samples were obtained in which a solid film pattern (70mm×70mm, 23μm thick) was formed on the copper layer of copper-clad laminates CC-1 to CC-11.

[0321] (2) Evaluation of stacked samples

[0322] For the laminated samples with the solid pattern described above, the substrate adhesion and solder heat resistance were evaluated in the same manner as in Evaluation 1 above. Additionally, the spalling was evaluated using the following method.

[0323] <Evaluation of Leakage>

[0324] The following benchmark was used to evaluate the distance of the solid image typed (cured film pattern) from the 70mm×70mm area onto the copper plate that is the non-typed area, which was visually confirmed.

[0325] (Benchmark)

[0326] 5: The exudate is less than 1mm

[0327] 4: Exudate size is 1mm or more but less than 2mm

[0328] 3: Exudate size is 2mm or larger but less than 3mm

[0329] 2: Exudate size is 3mm or larger but less than 4mm

[0330] 1: Exudate size is 4mm or larger

[0331]

[0332] In addition, by adjusting the processing conditions using other pretreatment agents (Shikoku Chemical's GB1000F / 1400, G200, GB3100, GB4300; MacDermid's MultiBond 100, MultiBond 150, MultiBond MP, MultiPrep 200; BOARDTEC's BTH-2066, BTH-2085) as described in the instruction manual, substrates with Ra values ​​of 0.1 to 2.0 μm were prepared and evaluated in the same manner. The results corresponded to the Ra values ​​described in Table V above.

[0333] Furthermore, it was confirmed that even when using MEC's ​​GT process as a pretreatment to improve adhesion, and Shikoku Chemical's GliCAP process, there were no problems in practical applications regarding substrate adhesion, solder heat resistance, heat and moisture resistance, solvent resistance, acid resistance, alkali resistance, insulation reliability, and leakage evaluation.

[0334] Industrial availability

[0335] According to the present invention, it is possible to provide a curable composition that provides excellent adhesion and heat resistance and has a low relative permittivity, a solder resist ink, and a printed circuit board using the same.

Claims

1. A curable composition, which is a curable composition containing 50 to 95 mass% of a (meth) acrylic monomer having no thermally curable functional group, further containing a photopolymerization initiator, a thermally curable compound, and a gelling agent, characterized in that, a cured product of the curable composition has a relative dielectric constant of less than 2.90 at 10 GHz, the (meth)acrylic monomer includes 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.

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

3. The curable composition according to claim 1 or 2, wherein, The thermally curable compound includes a polyfunctional isocyanate compound in which an isocyanate group is protected with a blocking agent that is thermally dissociable.

4. The curable composition according to claim 1 or 2, wherein, viscosity at 25°C is in the range of 1 to 1 x 10 4 in the range of 1 to 1 x 10 5. The curable composition according to claim 3, wherein, viscosity at 25°C is in the range of 1 to 1 x 10 4 in the range of 1 to 1 x 10 6. An ink for solder resist containing the curable composition according to any one of claims 1 to 5.

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

8. The printed circuit substrate of claim 7, wherein, the circuit pattern is composed of a copper wiring having a surface roughness Ra in the range of 0.1 to 2.0 μm.

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