Inkjet curable composition for metal-containing substrate, solder resist and inkjet recording method

Abstract

To provide an inkjet curable composition for metal-containing substrates, which is capable of suppressing changes in viscosity, particle size and discoloration prevention property over time at high temperatures, and to provide a solder resist capable of improving adhesion, hardness, solder heat resistance and plating resistance over time at high temperatures by using the inkjet curable composition for metal-containing substrates, and an inkjet recording method.SOLUTION: An inkjet curable composition for metal-containing substrates according to the present invention contains a polymerizable compound, a polymerization initiator, and a pigment, and is curable upon irradiation with active light, the inkjet curable composition for metal-containing substrates containing a nitrogen-containing aromatic heterocyclic compound with a tertiary amine.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a curable composition for inkjet for metal-containing substrates, a solder resist, and an inkjet recording method.The present invention particularly relates to a curable composition for inkjet for metal-containing substrates that can suppress changes in viscosity, particle size, and discoloration prevention performance over time at high temperatures, and a solder resist having excellent coating film physical properties. [Background technology]

[0002] As disclosed in Patent Document 1, a technique is known in which an alkali-developable photoresist contains a nitrogen-containing aromatic heterocyclic compound such as melamine, benzotriazole, or triazole. This technique can promote adhesion of the photoresist to a substrate (e.g., copper) and suppress discoloration of the substrate.

[0003] On the other hand, it is known that an insulating film (solder resist) is formed by applying and curing ink to a printed wiring board in a printed circuit board for the purpose of protecting a circuit pattern by an inkjet method. More specifically, inkjet ink (hereinafter also simply referred to as "ink") is applied, cured by actinic radiation, and then cured by heat. Patent Document 2 discloses a technique for promoting adhesion to copper by adding a nitrogen-containing aromatic heterocyclic compound to such a solder resist ink.

[0004] However, the ink for solder resist described in Patent Document 2 has a problem in that it does not sufficiently prevent discoloration of the coating film or the substrate beneath the coating film during the curing process or soldering process. In addition, in order to obtain suitable ejection properties, inkjet inks are often used after being heated to reduce their viscosity. Therefore, it is desired that the viscosity and particle size of the ink, as well as the coating properties including adhesion and hardness required for a solder resist, and discoloration prevention performance do not change over time at high temperatures. However, it has been even more difficult to achieve such performance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2014 / 167671 [Patent Document 2] Patent No. 5986701 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above problems and circumstances. The problem to be solved by the present invention is to provide a curable composition for inkjet for metal-containing substrates, which can suppress changes in viscosity and particle size over time at high temperatures, and changes in discoloration prevention performance of the coating film and the substrate under the coating film. Another problem to be solved by the present invention is to improve coating adhesion, hardness, heat resistance, and plating resistance over time at high temperatures in a solder resist and an inkjet recording method using the curable composition for inkjet for metal-containing substrates. [Means for solving the problem]

[0007] The present inventors have investigated the causes of the above problems in order to solve the above problems. The present inventors have found that by incorporating a polymerizable compound, a polymerization initiator, a pigment, and a nitrogen-containing aromatic heterocyclic compound having a tertiary amine in a curable composition for inkjet for metal-containing substrates, it is possible to suppress changes in viscosity, particle size, and discoloration prevention performance of the coating film and the substrate under the coating film over time at high temperatures. In addition, the present inventors have found that a solder resist using such a curable composition for inkjet for metal-containing substrates can improve adhesion, hardness, heat resistance, and plating resistance even over time at high temperatures. That is, the above-mentioned problems of the present invention are solved by the following means.

[0008] 1. A curable composition for inkjet printing on a metal-containing substrate, which contains a polymerizable compound, a polymerization initiator, and a pigment, and is cured by exposure to actinic radiation, Contains nitrogen-containing aromatic heterocyclic compounds having tertiary amines 1. A curable inkjet curable composition for a metal-containing substrate, comprising:

[0009] 2. The curable composition for inkjet according to item 1, wherein the nitrogen-containing aromatic heterocyclic compound is an aromatic heterocyclic compound not directly condensed with a benzene ring.

[0010] 3. The polymerizable compound is a polymerizable compound having a carboxy group, a hydroxy group, or an epoxy group. 2. The curable composition for inkjet for metal-containing substrates according to claim 1,

[0011] 4. The nitrogen-containing aromatic heterocyclic compound contains a 5-membered nitrogen-containing aromatic heterocyclic compound. 2. The curable composition for inkjet for metal-containing substrates according to claim 1,

[0012] 5. The nitrogen-containing aromatic heterocyclic compound contains a triazole compound. 2. The curable composition for inkjet for metal-containing substrates according to claim 1,

[0013] 6. The triazole compound has a structure represented by the following general formula (a): 6. The curable composition for inkjet for metal-containing substrates according to item 5, [ka] [In the general formula (a), Ra and Rb each represent an alkyl group having 1 to 20 carbon atoms.]

[0014] 7. The polymerizable compound having a carboxy group has a structure represented by the following general formula (1): 4. The curable composition for inkjet for metal-containing substrates according to claim 3. [ka] In the general formula (1), X represents a substituent having at least one group selected from an acryloyl group, a methacryloyl group, an allyl group, a vinyl group, and derivatives thereof at its terminal. Q represents an oxygen atom or NR4, and R4 represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. R1 represents an unsubstituted alkylene group having 1 to 6 carbon atoms.]

[0015] 8. The polymerizable compound having a hydroxy group is an epoxy acrylate obtained by reacting (meth)acrylic acid with an epoxy compound. 4. The curable composition for inkjet for metal-containing substrates according to claim 3.

[0016] 9. The polymerizable compound having a carboxy group, a hydroxy group, or an epoxy group has a bisphenol structure, a cresol novolac structure, or a phenol novolac structure. 4. The curable composition for inkjet for metal-containing substrates according to claim 3.

[0017] 10. The polymerization initiator contains thioxanthone. 2. The curable composition for inkjet for metal-containing substrates according to claim 1,

[0018] 11. Contains N-oxyls or nitrosamines as polymerization inhibitors 2. The curable composition for inkjet for metal-containing substrates according to claim 1,

[0019] 12. A curable ink composition for inkjet printing on a metal-containing substrate according to any one of items 1 to 11. A solder resist comprising:

[0020] 13. An inkjet recording method in which an inkjet curable composition is discharged onto a substrate and cured by actinic radiation, Item 12. The curable composition for inkjet for a metal-containing substrate according to any one of items 1 to 11 is used as the curable composition for inkjet, A metal-containing substrate is used as the substrate. 1. An ink-jet recording method comprising:

[0021] 14. Heating the substrate to 140° C. or higher 14. The ink jet recording method according to item 13,

[0022] 15. A process for heating the curable composition for inkjet for metal-containing substrates to 40° C. or higher in an inkjet head. 14. The ink jet recording method according to item 13, Effect of the Invention

[0023] The above-mentioned means of the present invention can provide a curable composition for inkjet for metal-containing substrates that can suppress changes in viscosity, particle size, and discoloration prevention performance over time at high temperatures. Also, a solder resist and an inkjet recording method using the curable composition for inkjet for metal-containing substrates that can improve adhesion, hardness, heat resistance, and plating resistance over time at high temperatures can be provided. Although the mechanism by which the effects of the present invention are manifested or the mechanism by which the effects of the present invention are acted upon has not been clearly understood, it is speculated as follows.

[0024] (Nitrogen-containing aromatic heterocyclic compound has a tertiary amine) If the aromatic heterocyclic compound does not have a tertiary amine, the aromatic heterocyclic compound (e.g., melamine or benzotriazole) will adsorb to the pigment or dispersant, inhibiting the dispersant from adsorbing to the pigment. This will cause the pigment to aggregate, increasing the viscosity and particle size of the ink. In addition, the amount of aromatic heterocyclic rings that interact with the substrate will decrease, and discoloration prevention and adhesion will not be achieved. In contrast, as in the present invention, the nitrogen-containing aromatic heterocyclic compound has a tertiary amine, and the nitrogen-containing aromatic heterocycle is less likely to interact with the pigment due to the steric hindrance of the tertiary amine. This suppresses pigment aggregation, and prevents the ink viscosity and particle size from increasing. In addition, the aromatic heterocycle that interacts with the substrate is not reduced, and discoloration can be prevented. In particular, the ink viscosity and particle size can be prevented from increasing over time at high temperatures, and when the compound is used as a cured film such as a solder resist, the heat resistance and plating resistance can be improved, and the adhesion and hardness to the substrate can be improved. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The curable composition for inkjet for metal-containing substrates of the present invention contains a polymerizable compound, a polymerization initiator, and a pigment, and is cured by exposure to actinic rays. The curable composition for inkjet for metal-containing substrates of the present invention is characterized in that it contains a nitrogen-containing aromatic heterocyclic compound having a tertiary amine. This feature is a technical feature common to or corresponding to each of the following embodiments.

[0026] As an embodiment of the present invention, it is preferable that the polymerizable compound is a polymerizable compound having a carboxy group, a hydroxy group or an epoxy group, in that adhesion between a cured film such as a solder resist and a substrate is improved.

[0027] It is preferable that the nitrogen-containing aromatic heterocyclic compound contains a five-membered nitrogen-containing aromatic heterocyclic compound, since this improves the ability to prevent discoloration over time at high temperatures.

[0028] It is preferable that the nitrogen-containing aromatic heterocyclic compound contains a triazole compound, since this improves the ability to prevent discoloration over time at high temperatures.

[0029] The triazole compound preferably has a structure represented by the following general formula (a) in that when it is made into a cured film such as a solder resist, it has excellent plating resistance.

[0030] [ka] [In the above general formula (a), Ra and Rb each represent an alkyl group having 1 to 20 carbon atoms.

[0031] It is preferable that the polymerizable compound having a carboxy group has a structure represented by the following general formula (1), since the compound has a dicarboxylic acid, the adhesion between the solder resist and the copper substrate is improved. [ka] In the general formula (1), X represents a substituent having at least one group selected from an acryloyl group, a methacryloyl group, an allyl group, a vinyl group, and derivatives thereof at its terminal. Q represents an oxygen atom or NR4, and R4 represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. R1 represents an unsubstituted alkylene group having 1 to 6 carbon atoms.]

[0032] The polymerizable compound having a hydroxy group is preferably an epoxy acrylate obtained by reacting (meth)acrylic acid with an epoxy compound, in that the adhesion between the solder resist and the substrate is improved.

[0033] The polymerizable compound having a carboxy group, a hydroxy group or an epoxy group preferably has any one of a bisphenol structure, a cresol novolac structure or a phenol novolac structure in terms of improving the heat resistance of the solder resist.

[0034] It is preferable that the polymerization initiator contains thioxanthone, since this improves the plating resistance of the cured film of the curable composition for inkjet after aging at high temperatures.

[0035] It is preferable that the polymerization inhibitor contains N-oxyls or nitrosamines in order to improve the storage stability of the ink.

[0036] The curable composition for inkjet for a metal-containing substrate of the present invention is suitably used for a solder resist.

[0037] The inkjet recording method of the present invention is an inkjet recording method in which an inkjet curable composition is discharged onto a substrate and cured by actinic radiation, and is characterized in that the inkjet curable composition of the present invention for inkjet use on a metal-containing substrate is used as the inkjet curable composition, and a substrate containing a metal is used as the substrate. This makes it possible to improve the physical properties of the solder resist made from the inkjet curable composition for a metal-containing substrate.

[0038] It is preferable to include a step of heating the base material at 140° C. or higher in order to improve the hardness of the solder resist.

[0039] It is preferable to include a step of heating the curable composition for inkjet for a metal-containing substrate to 40° C. or higher in an inkjet head, since this can further improve the ejection properties from an inkjet head.

[0040] The present invention, its components, and embodiments for carrying out the present invention will be described below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after the symbol "to" are included as lower and upper limits.

[0041] [Curable composition for inkjet] The curable composition for inkjet for metal-containing substrate of the present invention contains a polymerizable compound, a polymerization initiator, and a pigment, and is cured by exposure to actinic rays. The curable composition for inkjet contains a nitrogen-containing aromatic heterocyclic compound having a tertiary amine. Hereinafter, the curable composition for inkjet for a metal-containing substrate of the present invention will also be referred to simply as "curable composition for inkjet," "curable composition," or "ink."

[0042] <Nitrogen-containing aromatic heterocyclic compound containing a tertiary amine>

[0043] In the present invention, the term "nitrogen-containing aromatic heterocyclic compound" refers to a nitrogen-containing aromatic heterocycle or nitrogen-containing heteroaryl, and is a compound having an aromatic heterocycle containing at least one nitrogen atom as a ring-constituting atom. The atoms constituting the aromatic heterocycle may include heteroatoms such as oxygen atoms and sulfur atoms in addition to carbon and nitrogen.

[0044] Specific examples of nitrogen-containing aromatic heterocycles include azoles having a five-membered ring and azines having a six-membered ring. Specific examples of the azole include pyrrole, isoxazole, and isothiazole, each of which has one nitrogen atom, pyrazole, imidazole, oxadiazole, and thiadiazole, each of which has two nitrogen atoms, and 1,2,3-triazole and 1,2,4-triazole, each of which has three nitrogen atoms, and tetrazole, each of which has four nitrogen atoms. Specific examples of azines include pyridine having one nitrogen atom, pyrimidine, pyrazine, and pyridazine having two nitrogen atoms, and triazine having three nitrogen atoms.

[0045] The nitrogen-containing aromatic heterocycle is preferably a 5-membered nitrogen-containing aromatic heterocycle, since this improves the ability to prevent discoloration over time at high temperatures. In the present invention, it is preferable that the nitrogen-containing aromatic heterocycle is not directly condensed with a benzene ring. Examples of the nitrogen-containing aromatic heterocycle directly condensed with a benzene ring include quinoline, isoquinoline, indole, benzotriazole, and benzimidazole.

[0046] Examples of the tertiary amine include trimethylamine, triethylamine, N,N-dimethylethylamine, N-methyldi-n-octylamine, bis(2-ethylhexyl)aminomethyl, N,N-bis(2-ethylhexyl)methylamine, and 1-methylpiperazine.

[0047] The nitrogen-containing aromatic heterocyclic compound having a tertiary amine according to the present invention preferably contains a five-membered nitrogen-containing aromatic heterocyclic compound, and in particular, it is preferred that the compound contains a triazole compound, since this improves the discoloration prevention performance over time at high temperatures.

[0048] Moreover, it is preferable that the triazole compound has a structure represented by the following general formula (a) in that the solder resist has excellent plating resistance.

[0049] [ka]

[0050] In the general formula (a), Ra and Rb each represent an alkyl group having 1 to 20 carbon atoms. Ra is preferably an alkyl group having 1 to 10 carbon atoms. Rb is preferably an alkyl group having 1 to 10 carbon atoms.

[0051] Examples of the nitrogen-containing aromatic heterocyclic compound having a tertiary amine according to the present invention include the following compounds, but the present invention is not limited thereto. As the nitrogen-containing aromatic heterocyclic compound having a tertiary amine, the following compounds B-1 to B-7, in which a benzene ring is not directly condensed to the nitrogen-containing aromatic heterocycle, are preferred.

[0052] [ka]

[0053] The content of the nitrogen-containing aromatic heterocyclic compound having a tertiary amine is preferably within a range of 0.05 to 5 mass %, more preferably within a range of 0.1 to 2.5 mass %, based on the total mass of the curable composition for inkjet. By setting the content of the nitrogen-containing aromatic heterocyclic compound having a tertiary amine within the above range, it is possible to suppress changes in viscosity, particle size, and discoloration prevention performance over time at high temperatures.

[0054] <Polymerizable compound> The polymerizable compound according to the present invention is a compound that undergoes polymerization and crosslinking upon irradiation with actinic rays. The polymerizable compound may be a compound that undergoes further polymerization and crosslinking upon heating after irradiation with actinic rays.

[0055] Examples of actinic rays include electron beams, ultraviolet rays, α rays, γ rays, X-rays, etc. Among these, ultraviolet rays and electron beams are preferred, and ultraviolet rays are more preferred.

[0056] The polymerizable compound may be a cationic polymerizable compound or a radical polymerizable compound, but is preferably a radical polymerizable compound. The radical polymerizable compound is a compound having an ethylenically unsaturated bond capable of radical polymerization.

[0057] The polymerizable compound according to the present invention is preferably a polymerizable compound having a carboxy group, a hydroxy group or an epoxy group, in that this improves the adhesion between the solder resist and the base material and further enhances the effect of inhibiting discoloration before and after soldering. Although the reason why the above effect is exhibited is unclear, it is speculated that the effect is due to the fact that the carboxy group, hydroxy group, or epoxy group also interacts with the substrate, resulting in a more dense coating of the substrate.

[0058] (Polymerizable compound having a carboxy group) The polymerizable compound having a carboxy group is preferably a radically polymerizable compound. The ink may contain only one type of radically polymerizable compound, or may contain a combination of two or more types.

[0059] Examples of the radical polymerizable compound having a carboxy group include (meth)acrylic acid, carboxyethyl (meth)acrylate, 2-acryloyloxyethyl-phthalic acid, 2-acryloyloxyethylhexahydrophthalic acid, etc. Among these, the radical polymerizable compound is preferably (meth)acrylic acid or carboxyethyl acrylate (also referred to as "carboxy group-containing polymerizable compound A-10" described in the examples). In this specification, "(meth)acrylate" means acrylate or methacrylate, and "(meth)acrylic" means acrylic or methacrylic.

[0060] The polymerizable compound having a carboxy group may be monofunctional or polyfunctional. In order to prevent the deterioration of adhesion caused by cure shrinkage of the solder resist, the polymerizable compound having a carboxy group is preferably a compound having 5 or less functional groups.

[0061] Furthermore, it is preferable that the polymerizable compound having a carboxy group has a structure represented by the following general formula (1), since the polymerizable compound has a carboxylic acid, the adhesion between the solder resist and the substrate is improved.

[0062] [ka]

[0063] In the general formula (1), X represents a substituent having at least one group selected from an acryloyl group, a methacryloyl group, an allyl group, a vinyl group, and derivatives thereof at its terminal. Q represents an oxygen atom or NR4, and R4 represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. R1 represents an unsubstituted alkylene group having 1 to 6 carbon atoms.

[0064] The compound having the structure represented by the general formula (1) has two carbonyl groups (C(=O)) in the molecule via an unsubstituted alkylene group, which allows the two oxygen atoms contained in the two carbonyl groups to form coordinate bonds with a metal atom, thereby enabling the adhesion to the substrate to be more sufficiently increased.

[0065] From the viewpoint of stabilizing the coordinate bond between the two oxygen atoms and the metal atom and more sufficiently enhancing the adhesion to the substrate, R1 is preferably an unsubstituted alkylene group having 1 to 6 carbon atoms. From the viewpoint of further enhancing the adhesion, R1 is preferably an unsubstituted alkylene group having 1 or 2 carbon atoms. As a result, when the coordinate bond is formed, a ring structure is formed by the metal atom, the two oxygen atoms, and R1 (alkylene group), and the coordinate bond is more stabilized. From the same viewpoint, Q is preferably an oxygen atom.

[0066] In addition, the polymerizable group at the end of X is preferably a (meth)acryloyl group. Since the (meth)acryloyl group is highly reactive, it is easily polymerized and incorporated into the coating film. Therefore, a compound having a (meth)acryloyl group as a polymerizable group can fully exert the effect of improving adhesion due to the carboxyl group.

[0067] Examples of the compound having the structure represented by the general formula (1) include the compounds shown below, but the present invention is not limited to these.

[0068] [ka]

[0069] [ka]

[0070] The polymerizable compound having a carboxy group may be a monomer or an oligomer, but is preferably a monomer. In this specification, the term "monomer" refers to a polymerizable compound that is a monomer having a molecular weight of less than 700. The molecular weight can be measured by gel permeation chromatography.

[0071] (Polymerizable compound having a hydroxy group) The polymerizable compound having a hydroxyl group is not particularly limited as long as it is a compound having a hydroxyl group in its structure. Specific examples of the polymerizable compound having a hydroxyl group include hydroxyalkyl(meth)acrylate and hydroxy(meth)acrylate having an alicyclic structure. Examples of hydroxyalkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate (hydroxy group-containing polymerizable compound A-11 below). Moreover, examples of hydroxy(meth)acrylates having an alicyclic structure include 1,4-cyclohexanedimethanol mono(meth)acrylate. The polymerizable compound having a hydroxyl group may be an epoxy acrylate obtained by reacting (meth)acrylic acid with an epoxy compound. As the epoxy acrylate, a commercially available product may be used. Examples of the commercially available product include Epoxy Ester 70PA (manufactured by Kyoeisha Chemical Co., Ltd.) (hydroxyl group-containing polymerizable compound A-12 below), Epoxy Ester 200PA (manufactured by Kyoeisha Chemical Co., Ltd.), and DENACOL ACRYLATE DA-111 (manufactured by Nagase Chemtex Co., Ltd.). Among these, epoxy acrylate is preferred. Epoxy acrylate is preferred in that it provides better adhesion between the solder resist and the substrate.

[0072] [ka]

[0073] (Polymerizable compound having an epoxy group) The polymerizable compound having an epoxy group is not particularly limited as long as it is a compound having an epoxy group in its structure. Specific examples of the polymerizable compound having an epoxy group include an aliphatic alcohol-based epoxy, an aliphatic polyhydric alcohol-based epoxy, and a phenol-based epoxy.

[0074] Other examples of epoxy (meth)acrylates include the following: [ka]

[0075] The polymerizable compound having a carboxy group, a hydroxy group or an epoxy group preferably has any one of a bisphenol structure, a cresol novolac structure or a phenol novolac structure in terms of improving the heat resistance of a cured film such as a solder resist. Examples of the bisphenol structure include a bisphenol A type structure and a bisphenol F type structure.

[0076] Examples of the polymerizable compound having any one of a bisphenol structure, a cresol novolac structure, and a phenol novolac structure include the following compounds in addition to the above-mentioned epoxy group-containing polymerizable compound A-22.

[0077] [ka]

[0078] The content of the polymerizable compound is preferably in the range of 20 to 99% by mass, more preferably in the range of 30 to 95% by mass, based on the total mass of the curable composition for inkjet. By setting the content of the polymerizable compound within the above range, the coating adhesion and hardness can be improved in the solder resist and the inkjet recording method.

[0079] <Polymerization initiator> The polymerization initiator according to the present invention is a compound that initiates polymerization and crosslinking of the polymerizable compound by irradiation with actinic rays.

[0080] The polymerization initiator may be a radical polymerization initiator when the ink contains a radically polymerizable compound, and may be a cationic polymerization initiator when the ink contains a cationic polymerizable compound. Examples of the radical polymerization initiator include intramolecular bond cleavage type radical polymerization initiators and hydrogen abstraction type radical polymerization initiators.

[0081] Examples of the intramolecular bond cleavage type radical polymerization initiator include acetophenone-based initiators such as diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-methylthiophenyl)propan-1-one, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone; benzoin-based initiators such as benzoin, benzoin methyl ether, and benzoin isopropyl ether; acylphosphine oxide-based initiators such as bis-2,4,6-trimethylbenzoin diphenylphosphine oxide, benzyl, and methylphenyl glyoxyesters.

[0082] Commercially available acetophenone initiators include, for example, Omnirad 907 (manufactured by IGM) (molecular weight 279) and Omnirad 379 (manufactured by IGM) (molecular weight 381). Commercially available acylphosphine initiators include, for example, Omnirad TPO H (manufactured by IGM) (molecular weight 348), Omnirad 819 (manufactured by IGM) (molecular weight 419), and the like.

[0083] Examples of the hydrogen abstraction type radical polymerization initiator include benzophenone-based initiators such as benzophenone, o-benzoylmethylbenzoate, 4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylated benzophenone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone-based initiators such as 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone; aminobenzophenone-based initiators such as Michler's ketone and 4,4'-diethylaminobenzophenone; 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-phenanthrenequinone, and camphorquinone.

[0084] Commercially available thioxanthone initiators include 2-isopropylthioxanthone (Speedcure ITX (manufactured by Sartomer Corporation) (molecular weight 254)) and 2,4-diethylthioxanthone (Speedcure DETX (manufactured by Sartomer Corporation) (molecular weight 268)).

[0085] Examples of the cationic polymerization initiator include a photoacid generator. Examples of photoacid generators include aromatic onium compounds, such as diazonium, ammonium, iodonium, sulfonium, and phosphonium, such as B(C6F5)4. - , PF6 - , AsF6 - , SbF6 - , CF3SO3 - These include salts, sulfonates which generate sulfonic acids, halides which photogenerate hydrogen halides, and iron-allene complexes.

[0086] The polymerization initiator according to the present invention preferably contains thioxanthone in that the plating resistance of the solder resist is improved.

[0087] The content of the polymerization initiator is preferably within a range from 1 to 10% by mass, and more preferably within a range from 2 to 8% by mass, based on the total mass of the curable composition for inkjet.

[0088] <Gelling agent> The curable composition for inkjet of the present invention may contain a gelling agent.

[0089] The gelling agent causes the ink to become a sol when heated and to become a gel when it is at room temperature. This allows the ink to be ejected from the inkjet head and then landed on a recording medium, where the gelled ink is cooled and temporarily solidified, improving the pinning ability of the ink. This prevents the ink from spreading and makes it difficult for adjacent dots to become identical, allowing for the formation of a more precise pattern.

[0090] Furthermore, since the curable composition for inkjet contains a gelling agent, the hydrophobicity of the formed solder resist is increased, and the water absorption of the solder resist can be further suppressed, thereby further suppressing the occurrence of ion migration in a high humidity environment and sufficiently suppressing the deterioration of the insulating properties of the solder resist.

[0091] The gelling agent is preferably a compound that dissolves in the polymerizable compound contained in the ink at a temperature higher than the gelling temperature of the ink, and that crystallizes in the ink at a temperature equal to or lower than the gelling temperature of the ink. Here, the term "gelation temperature" refers to the temperature at which the ink undergoes a phase transition from sol to gel when the ink, which has been sol- or liquefied by heating, is cooled, and the viscosity of the ink changes suddenly. Specifically, the ink that has been solated or liquefied is cooled while its viscosity is measured using a rheometer (e.g., MCR300 manufactured by Anton Paar), and the temperature at which the viscosity increases suddenly can be determined as the gelation temperature of the ink.

[0092] The gelling agent preferably crystallizes in the ink at a temperature equal to or lower than the gelling temperature of the ink, and forms a structure in which the radical polymerizable compound is encapsulated in a three-dimensional space formed by the gelling agent crystallized into a plate shape. Such a structure is hereinafter referred to as a "house of cards structure." When a house of cards structure is formed, the liquid actinic radiation polymerizable compound is held in the space. Therefore, dots formed by the ink adhering to the recording medium are less likely to wet and spread, and the pinning property of the ink is further improved. As a result, dots formed by the ink adhering to the recording medium are less likely to coalesce with each other.

[0093] Examples of gelling agents that can facilitate the formation of a card house structure by crystallization include aliphatic ketones, aliphatic esters, petroleum waxes, vegetable waxes, animal waxes, and mineral waxes. Examples of the gelling agents include hydrogenated castor oil, modified waxes, higher fatty acids, higher alcohols, hydroxystearic acid, fatty acid amides including N-substituted fatty acid amides and special fatty acid amides. Examples of the gelling agents include higher amines, sucrose fatty acid esters, synthetic waxes, dibenzylidene sorbitol, dimer acid, and dimer diol.

[0094] Examples of aliphatic ketones include dilignoceryl ketone, dibehenyl ketone, distearyl ketone, dieicosyl ketone, dipalmityl ketone, dilauryl ketone, dimyristyl ketone, myristyl palmityl ketone, and palmityl stearyl ketone.

[0095] Examples of fatty esters include fatty acid esters of monoalcohols such as behenyl behenate, icosanoic acid ethyl ester, stearyl stearate, palmityl stearate, myristyl myristate, cetyl myristate, and oleyl palmitate; and fatty acid esters of polyhydric alcohols such as glycerin fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, ethylene glycol fatty acid esters, and polyoxyethylene fatty acid esters.

[0096] Examples of commercially available products of the above aliphatic esters include the EMALEX series (manufactured by Nippon Emulsion Co., Ltd. ("EMALEX" is a registered trademark of the company)), the Rikemal series, and the Poem series (manufactured by Riken Vitamin Co., Ltd.). Both "Rikemal" and "Poem" are registered trademarks of Riken Vitamin Co., Ltd.

[0097] Examples of higher fatty acids include behenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, and erucic acid.

[0098] Examples of higher alcohols include stearyl alcohol and behenyl alcohol.

[0099] Among these, from the viewpoint of further improving the pinning property, the gelling agent is preferably an aliphatic ketone, an aliphatic ester, a higher fatty acid, or a higher alcohol. The gelling agent is more preferably an aliphatic ketone represented by the following general formula (G1) or an aliphatic ester represented by the following general formula (G2). Only one type of gelling agent may be contained, or two or more types may be contained in combination.

[0100] General formula (G1):R a -CO-R b General formula (G2):R c -COO-R d

[0101] In general formula (G1), R a and R b each independently represents a linear hydrocarbon group having 12 to 26 carbon atoms, which may have a branched chain. In general formula (G2), R c and R d each independently represents a linear hydrocarbon group having 12 to 26 carbon atoms, which may have a branched chain.

[0102] In general formulae (G1) and (G2), R a ~R dWhen the number of carbon atoms is 12 or more, the crystallinity of the gelling agent represented by the general formulas (G1) and (G2) is further increased. Furthermore, more sufficient space is generated in the house of cards structure. Therefore, the polymerizable compound is easily and sufficiently enclosed in the space, and the pinning property of the ink is improved.

[0103] Also, R a ~R d By making the number of carbon atoms in the group equal to or less than 26, the melting point of the gelling agent represented by general formula (G1) and general formula (G2) can be prevented from rising excessively, and the ink can be discharged by lowering the heating temperature of the ink without increasing the solation temperature of the ink containing the gelling agent too much.

[0104] Examples of aliphatic ketones represented by general formula (G1) include dilignoceryl ketone (carbon number: 23-24), dibehenyl ketone (carbon number: 21-22), distearyl ketone (carbon number: 17-18), dieicosyl ketone (carbon number: 19-20), dipalmityl ketone (carbon number: 15-16), dimyristyl ketone (carbon number: 13-14), dilauryl ketone (carbon number: 11-12), lauryl ketone (carbon number: 13-14), and glyceryl ketone (carbon number: 14-16). These include lauryl palmityl ketone (carbon number: 11-14), lauryl palmityl ketone (11-16), myristyl palmityl ketone (13-16), myristyl stearyl ketone (13-18), myristyl behenyl ketone (13-22), palmityl stearyl ketone (15-18), palmityl behenyl ketone (15-22) and stearyl behenyl ketone (17-22). The number of carbon atoms in the parentheses above indicates the number of carbon atoms in each of the two hydrocarbon groups separated by the carbonyl group.

[0105] Examples of commercially available products of the compound represented by general formula (G1) include 18-Pentatriacontanone and Hentriacontan-16-one (both manufactured by Alfa Aeser), and Kaowax T1 (manufactured by Kao Corporation).

[0106] Examples of the aliphatic ester represented by the general formula (G2) include behenyl behenate (carbon number: 21-22), icosanoic acid icosyl (carbon number: 19-20), stearyl stearate (carbon number: 17-18), palmityl stearate (carbon number: 17-16), lauryl stearate (carbon number: 17-12), cetyl palmitate (carbon number: 15-16), stearyl palmitate (carbon number: 15-18), myristyl Myristyl phosphate (carbon number: 13-14), cetyl myristate (carbon number: 13-16), octyldodecyl myristate (carbon number: 13-20), stearyl oleate (carbon number: 17-18), stearyl erucate (carbon number: 21-18), stearyl linoleate (carbon number: 17-18), behenyl oleate (carbon number: 18-22), and arachidyl linoleate (carbon number: 17-20). The number of carbons in the parentheses above indicates the number of carbons in each of the two hydrocarbon groups separated by the ester group.

[0107] Commercially available examples of aliphatic esters represented by general formula (G2) include Unistar M-2222SL, Sperm Acetate, Nissan Electol WEP-2 and Nissan Electol WEP-3 (all manufactured by NOF Corporation, "Unistar" and "Nissan Electol" are registered trademarks of the company), Exepar SS and Exepar MY-M (all manufactured by Kao Corporation, "Exepar" is a registered trademark of the company), EMALEX CC-18 and EMALEX CC-10 (manufactured by Nippon Emulsion Co., Ltd., "EMALEX" is a registered trademark of the company), and Amureps PC (manufactured by Kokyu Alcohol Kogyo Co., Ltd., "Amureps" is a registered trademark of the company). These commercially available products are often mixtures of two or more types, so If necessary, the compound may be separated and purified before being added to the ink.

[0108] The content of the gelling agent is preferably 1 to 10% by mass, more preferably 1 to 5% by mass, based on the total mass of the curable composition for inkjet. When the content is 1% by mass or more, the water absorption of the solder resist can be further suppressed, and the deterioration of the insulating properties in a high humidity environment can be further suppressed. When the content is 10% by mass or less, the solubility of the gelling agent in the polymerizable compound can be further increased.

[0109] <Other> The curable composition for inkjet of the present invention contains a pigment as a colorant within a range in which the effects of the present invention can be achieved.

[0110] (Coloring agent) The colorant may be a dye or a pigment, with pigments being preferred from the viewpoints of increasing the heat resistance of the colorant and preventing discoloration of the cured film of the composition after aging at high temperatures. The pigment can be selected from, for example, a yellow pigment, a red pigment, a blue pigment, a black pigment, and a white pigment depending on the color of the image to be formed.

[0111] Examples of yellow pigments include Pigment Yellow (PY) 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, and 193. Of these, PY185 and PY150 are preferred from the viewpoints of increasing the heat resistance of the pigment and preventing discoloration of the cured film.

[0112] Examples of red pigments include Pigment Red (PR) 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 (PV) 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange (PO) 13, 16, 20, 36, etc. Among these, PR122 and PV19 are preferred from the viewpoint of increasing the heat resistance of the pigment and preventing discoloration of the cured film.

[0113] Examples of blue pigments include Pigment Blue (PB) 1, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17:1, 22, 27, 28, 29, 36, and 60. Of these, PB15:3 and PB15:4 are preferred from the viewpoints of increasing the heat resistance of the pigment and preventing discoloration of the cured film.

[0114] Examples of green pigments include CI Pigment Green (hereinafter also simply referred to as "PG") 7, PG26, PG36, and PG50.

[0115] Examples of black pigments include CI Pigment Black (hereinafter also simply referred to as "PBk") 7, PBk26, and PBk28.

[0116] The white pigment may be any pigment that imparts a white color to the cured film formed by curing the white ink. Examples of the white pigment include inorganic pigments such as titanium oxide, zinc oxide, calcium carbonate, barium sulfate, and aluminum hydroxide. Among these, titanium oxide is preferred.

[0117] The crystal form of the titanium oxide may be any of rutile, anatase and brookite. However, from the viewpoint of facilitating the formation of a smaller particle size of the white pigment, the anatase type having a smaller specific gravity is preferred. From the viewpoint of further improving the concealing property of the formed image, the rutile type having a large refractive index in the visible light region is preferred as the crystal form.

[0118] The content of the colorant is preferably 0.1 to 10 mass % and more preferably 0.3 to 5 mass % based on the total mass of the curable composition. When the colorant is a pigment, from the viewpoint of reducing the amount of impurities in the curable composition, the content of the pigment is preferably 20 mass % or less and more preferably 10 mass % or less based on the total mass of the curable composition.

[0119] (Synergist) The curable composition for inkjet of the present invention may contain a synergist. A synergist is a compound that has an anchor part that adsorbs to a pigment and a polar part that adsorbs to a pigment dispersant. In the ink, the anchor part of the synergist adsorbs to the pigment, and the polar part adsorbs to the pigment dispersant. Therefore, the pigment dispersant can adhere to the pigment via the synergist and is less likely to dissociate from the pigment. This can further improve the dispersion stability of the ink.

[0120] Furthermore, as a result of the inventors' investigations, it was found that when the amine value of the pigment dispersant contained in the ink is higher than the acid value, the dispersion stability of the ink can be significantly improved by adding a synergist.

[0121] Examples of synergists include pigment derivatives. Pigment derivatives are compounds in which a polar group is introduced into a pigment core. In other words, in pigment derivatives, the pigment core serves as the anchor portion, and the polar group serves as the polar portion.

[0122] Examples of the polar group include a chlorine group, a sulfonyl group, a sulfonylamido group, a carboxy group, a carboxylamido group, an amino group, an amido group, an aminomethyl group, an imido group, an imidomethyl group, a phthalimido group, a phthalimidomethyl group, a nitro group, a cyano group, a phosphate group, etc. Among these, the carboxy group, the sulfonyl group, the nitro group, the phosphate group, the amino group, and the amido group are preferred.

[0123] Examples of pigment derivatives include azo derivatives, quinoline derivatives, pyrazole derivatives, and the like.

[0124] The method for synthesizing the pigment derivative is not particularly limited. For example, when a sulfonyl group is introduced as a polar group into an azo pigment, fuming sulfuric acid, concentrated sulfuric acid, or the like is added to a solution in which the pigment is dispersed, and the solution is heated to a range of 60 to 200°C and stirred. Then, the volatile components are removed to obtain a pigment in which a sulfonyl group is introduced into the azo pigment.

[0125] Examples of commercially available pigment derivatives include Solsperse 5000S, Solsperse 12000S, and Solsperse 22000 (manufactured by Lubrizol).

[0126] The synergist may be a water-based dye having an acidic or basic group. Examples of the acidic group include a carboxy group, a sulfonyl group, and a phosphate group, etc. Among these, the sulfonyl group is preferred. Examples of the basic group include an amino group and an imino group.

[0127] Examples of such water-based dyes include CI Acid Yellow 3, CI Acid Yellow 11, CI Acid Yellow 23, Direct Red 21, and the like.

[0128] The content of the synergist is preferably in the range of 1 to 10% by mass, more preferably in the range of 2 to 8% by mass, based on the total mass of the pigment. When it is 1% by mass or more, the dispersion stability of the ink can be further improved. When it is 10% by mass or less, the proportion of the pigment can be increased, and color variation of the cured film can be further suppressed.

[0129] (Pigment dispersant) When the inks of the present invention contain a pigment, the ink may also contain a pigment dispersant.

[0130] Examples of the pigment dispersant include carboxylate esters having a hydroxy group, salts of long-chain polyaminoamides and high molecular weight acid esters, salts of high molecular weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, high molecular weight unsaturated acid esters, polymer copolymers, modified polyurethanes, modified polyacrylates, polyether ester-type anionic surfactants, naphthalenesulfonic acid formalin condensate salts, aromatic sulfonic acid formalin condensate salts, polyoxyethylene alkyl phosphate esters, polyoxyethylene nonylphenyl ether, and stearylamine acetate. Examples of commercially available pigment dispersants include the Solsperse® series manufactured by Avecia and the PB series manufactured by Ajinomoto Fine-Techno Co., Ltd.

[0131] The content of the pigment dispersant is preferably within a range of 1 to 50% by mass relative to the mass of the pigment.

[0132] The pigment dispersant may have an acid value or an amine value. In particular, the amine value is greater than the acid value, and the acid value is preferably 20 mg / KOH or less. The pigment dispersant can improve the dispersion stability of the ink.

[0133] Pigment dispersants having an amine value greater than the acid value include BYK-JET-9151 (manufactured by BYK-Chemie), EFKA7701 (manufactured by BASF), etc. The pigment dispersants may be contained in the ink alone or in combination of two or more kinds.

[0134] The acid value of the pigment dispersant is preferably 20 mg / KOH or less, and more preferably 10 mg / KOH or less. The lower limit of the acid value is not particularly limited, and can be 0 mg / KOH or more.

[0135] The amine value of the pigment dispersant should be larger than the acid value, but from the viewpoint of further improving the dispersion stability of the ink, it is preferably 10 mg / KOH or more, and more preferably 20 mg / KOH or more. The upper limit of the amine value is not particularly limited, but can be, for example, 60 mg / KOH or less.

[0136] From the viewpoint of further improving the dispersion stability of the ink, the difference between the amine value and the acid value of the pigment dispersant is preferably within the range of 1 to 40 mg / KOH, and more preferably within the range of 10 to 40 mg / KOH.

[0137] The acid value and amine value can be measured by potentiometric titration, for example, by the method described in Journal of the Color Materials Association 61,

[12] 692-698 (1988).

[0138] The acid value is determined from the amount of the above solution required for neutralization when a solution prepared by dissolving 1 g of the pigment dispersant in 100 mL of methyl isobutyl ketone (MIBK) is subjected to potentiometric titration with a 0.01 mol / L solution of potassium methoxide-methyl isobutyl ketone / methanol (volume ratio 4:1).

[0139] The amine value can be determined from the amount of perchloric acid MIBK solution required for neutralization when a solution prepared by dissolving 1 g of the pigment dispersant in 100 mL of MIBK is subjected to potentiometric titration with a 0.01 mol / L perchloric acid MIBK solution.

[0140] (Surfactant) The curable composition for inkjet of the present invention may contain a surfactant. Examples of the surfactant include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts. Examples of the surfactant include nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene-polyoxypropylene block copolymers. Examples of the surfactant include cationic surfactants such as alkylamine salts and quaternary ammonium salts, as well as silicone-based and fluorine-based surfactants.

[0141] Commercially available examples of silicone surfactants include Tego rad 2250 (Evonik), KF-351A, KF-352A, KF-642, and X-22-4272, (Shin-Etsu Chemical Co., Ltd.), BYK307, BYK345, BYK347, and BYK348 (BYK-Chemie ("BYK" is a registered trademark of the company)), and TSF4452 (Momentive Performance Materials).

[0142] Examples of commercially available fluorosurfactants include Megafac F (manufactured by DIC Corporation ("Megafac" is a registered trademark of the company)), Surflon (manufactured by AGC Sei Chemical Co., Ltd. ("Surflon" is a registered trademark of the company)), Fluorad FC (manufactured by 3M Corporation ("Fluorad" is a registered trademark of the company)), Monflor (manufactured by Imperial Chemical Industries Co., Ltd.), Zonyls (manufactured by E.I. duPont Nemelas and Company), Licowet VPF (manufactured by Lubeberke-Hoechst), and FTERGENT (manufactured by NEOS Corporation ("FTERGENT" is a registered trademark of the company)).

[0143] The content of the surfactant relative to the total mass of the curable composition is not particularly limited as long as the effects of the present invention are achieved, but can be, for example, 0.001% by mass or more and less than 1.0% by mass.

[0144] (Polymerization inhibitor) From the viewpoint of storage stability, the inkjet curable composition of the present invention preferably further contains a radical polymerization inhibitor.

[0145] Examples of the radical polymerization inhibitor include phenolic hydroxy group-containing compounds, quinones or hydroquinones, phenothiazines, N-oxyls, nitrosamines, and the like. From the viewpoint of improving storage stability at higher temperatures and discoloration prevention performance, the radical polymerization inhibitor is preferably an N-oxyl or a nitrosamine.

[0146] Examples of the phenolic hydroxy group-containing compound include 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, 2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,4,6-tri-tert-butylphenol, 2,6-di-t-butyl-p-cresol (butylated hydroxytoluene: BHT), 4-methoxyphenol, and 2-methoxy-4-methylphenol.

[0147] Examples of the quinones or hydroquinones include hydroquinone, methoxyhydroquinone, benzoquinone, 1,4-naphthoquinone, p-tert-butylcatechol, and hydroquinone. Monomethyl ether (MEHQ) is included.

[0148] The N-oxyls (nitroxyl- or N-oxyl-groups, compounds having at least one >NO·-group) are, for example, piperidine N-oxyl compounds, preferably piperidine N-oxyl free radical compounds.

[0149] Examples of the N-oxyls include 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-methoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 2,2,6,6-tetramethyl-piperidine-N-oxyl, BASF Aktiengesellschaft Uvinul 4040P, 4,4',4"-tris-(2,2,6,6-tetramethyl-piperidine-N-oxyl)phosphite, 3-oxo-2,2,5,5-tetramethyl-pyrrolidine-N-oxyl, 1-oxyl-2,2,6,6-tetramethyl-4-methoxypiperidine, 1-oxyl-2,2,6,6-tetramethyl-4-trimethylsilyloxypiperidine, 1-oxyl-2,2,6,6-tetramethyl-4-trimethylsilyloxypiperidine, tetramethylpiperidin-4-yl-2-ethylhexanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-sebacate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-stearate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-benzoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-(4-t-butyl)benzoate, Bis-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) succinate, bis-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) adipate, 1,10-decanedioic acid-bis-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) ester, bis-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) n-butyl malonate, bis-(1-oxy N,N'-bis-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)phthalate, bis-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)isophthalate, bis-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)terephthalate, bis-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)hexahydroterephthalate, N,N'-bis-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) adipamide, N-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) caprolactam, N-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) dodecyl succinimide, 2,4,6-tris-[N-butyl-N-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl] triazine, N,N'-bis-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-N,N'-bis-formyl-1,6-diaminohexane, 4,4'-ethylene-bis-(1-oxyl-2,2,6,6-tetramethylpiperazin-3-one) are preferred. An example of a commercially available N-oxyl product is Irgastab UV-10 (manufactured by BASF Japan).

[0150] Examples of the nitrosamines include salts of N-nitrosophenylhydroxylamine. Examples of the salt of N-nitrosophenylhydroxylamine include N-nitrosophenylhydroxylamine ammonium salt, N-nitroso-N-phenylhydroxylamine aluminum (NPHA), and the like.

[0151] The amount of each polymerization inhibitor is not particularly limited, and the content of each polymerization inhibitor is preferably within the range of 0.01 to 1 mass % in 100 mass % of the curable composition for inkjet.

[0152] (Antioxidants) The curable composition for inkjet of the present invention may contain an antioxidant in order to further enhance the effect of preventing discoloration of the coating film. The antioxidants include n-octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)-propionate, n-octadecyl-3-(3'-methyl-5'-t-butyl-4'-hydroxyphenyl)-propionate, n-tetradecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)-propionate, 1,6-hexanediol-bis-(3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate), 1,4-butanediol-bis-(3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate), phenyl)-propionate), triethylene glycol-bis-(3-(3-t-butyl-5-methyl-4-hydroxyphenyl)-propionate), tetrakis-(methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate methane, 3,9-bis(2-(3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)2,4,8,10-tetraoxaspiro(5,5)undecane, N,N'-bis-3-(3'5'-di-t-butyl-4-hydroxyphenoxy) hindered phenols such as N,N'-bis(3-(3,5-di-t-butyl-4-hydroxyphenol)propionyl)hydrazine, N-salicyloyl-N'-salicylidenehydrazine, 3-(N-salicyloyl)amino-1,2,4-triazole, and N,N'-bis(2-(3-(3,5-dibutyl-4-hydroxyphenyl)propionyloxy)ethyl)oxyamide. compounds, didodecyl-3,3'-thiodipropionate, ditetradecyl-3,3'-thiodipropionate, dioctadecyl-3,3'-thiodipropionate, ditridecyl-3,3'-thiodipropionate, pentaerythrityl tetrakis(3-dodecylthiopropionate), pentaerythrityl tetrakis(3-tetradecylthiopropionate), pentaerythrityl tetrakis(3-tridecylthiopropionate), dilauryl-3,3-thiodipropionate, dimyristyl-3,3-thiodipropionate, distearyl-3,3-thiodipropionate, pentaerythrityl tetrakis(3-lauryl thiodipropionate, 2-mercaptobenzimidazole, lauryl stearyl thiodipropionate, zinc salt of 2-mercaptomethylbenzimidazole, zinc salt of 2-mercaptomethylbenzimidazole, 2-mercaptomethylbenzimidazole, zinc dibutylthiocarbamate and other sulfur-based antioxidants, triphenyl phosphite, tris(methylphenyl) phosphite, tris(methylphenyl) phosphite, Triisooctyl phosphite, tridecyl phosphite, tris(2-ethylhexyl) phosphite, tris(nonylphenyl) phosphite, tris(octylphenyl) phosphite, tris[decylpoly(oxyethylene)phosphite, tris(cyclohexylphenyl) phosphite, tricyclohexyl phosphite, tri(decyl)thiophosphite, triisodecylthiophosphite, phenyl bis(2-ethylhexyl) phosphite , phosphorus-based antioxidants such as phenyl diisodecyl phosphite, tetradecyl poly(oxyethylene) bis(ethylphenyl) phosphite, phenyl dicyclohexyl phosphite, phenyl diisooctyl phosphite, phenyl di(tridecyl) phosphite, diphenyl cyclohexyl phosphite, diphenyl isooctyl phosphite, diphenyl 2-ethylhexyl phosphite, diphenyl isodecyl phosphite, diphenyl cyclohexyl phenyl phosphite, and diphenyl (tridecyl) thiophosphite; aromatic amine-based antioxidants such as phenylnaphthylamine, 4,4'-dimethoxydiphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, di-tert-butyldiphenylamine, N,N'-di(octylphenyl)amine, 4-isopropoxydiphenylamine, and N,N'-di(2-naphthyl)-p-phenylenediamine.

[0153] These antioxidants can be used alone or in combination. Among them, hindered phenol compounds are preferred because they have a high discoloration suppressing effect. Trade names of hindered phenol compound antioxidants include Irganox 245, Irganox 259, Irganox 565, Irganox 1010, Irganox 1035, Irganox 1076, Irganox 1081, Irganox 1098, Irganox 1222, Irganox 1330, and Irganox 1425WL (all manufactured by BASF).

[0154] The amount of the antioxidant is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass, per 100 parts by mass of ink. When the amount of the antioxidant is 0.1 part by mass or more per 100 parts by mass of ink, the effect of preventing discoloration of the coating film is large. When the amount of the antioxidant is 5 parts by mass or less per 100 parts by mass of ink, the storage stability of the ink and the adhesion of the coating film are good.

[0155] (Deodorants, fragrances) The curable composition for inkjet of the present invention preferably further contains a deodorant and a fragrance from the viewpoint of suppressing the odor of the ink and the odor generated when the cured film is heated.

[0156] There is no particular limitation on the deodorant that can be used in the present invention, but deodorants that chemically bond with amines or aldehydes are preferred. Examples of deodorants that chemically bond with amines include sarcosine-based compounds such as N-oleoyl sarcosine, etc. Examples of deodorants that chemically bond with aldehydes include hydrazide-based compounds such as ChemCatch P-9600 and ChemCatch T-6900 (Otsuka Chemical).

[0157] The following fragrances can be used in the present invention: (1) Essential oils such as grapefruit oil, orange oil, lemon oil, lime oil, nutmeg oil, cassia oil, lavender oil, cypress oil, fennel oil, ylang-ylang oil, chamomile oil, jasmine oil, hiba oil, peppermint oil, lavender oil, and rosemary oil.

[0158] (2) Alcohols such as hexyl alcohol, phenylethyl alcohol (rose P), furfuryl alcohol, cyclotene, geraniol, linalool, linalool, 1-menthol, borneol, lambasulol, hexyl alcohol, cyclotene, maltol, eugenol, and α-phenylethanol.

[0159] (3) Aldehydes such as tetradecanal, hexadecanal, octadecanal, benzaldehyde, and furfural.

[0160] (4) Aldehydes such as ethyl acetoacetate, propyl acetate, amyl acetate, linalyl acetate, benzyl acetate, dimethylbenzylcarbinyl acetate, benzyl propionate, heptanal, octanal, dodecanal, citral, lyral, cyclamen aldehyde, and vanillin.

[0161] (5) Nootkatone, ethylpyrazine, lemon turpeneless, orange turpeneless, vanillin, ethyl vanillin, furfuryl mercaptan, borneol, and aromatic compounds such as heliotrope, vanillin, and ethyl vanillin.

[0162] (6) Esters such as ethyl acetate, propyl acetate, amyl acetate, linalyl acetate, benzyl acetate, dimethylbenzyl carbinil acetate, benzyl propionate, and geranyl acetate. Among these, linalool, vanillin, and ethyl vanillin are preferred.

[0163] In the present invention, various blended flavors can be formulated and used by suitably combining the above-mentioned flavors, for example, banana flavor, blueberry flavor, vanilla flavor, mint flavor, apple flavor, peach flavor, melon flavor, pineapple flavor, grape flavor, lilac flavor, jasmine flavor, and the like. In addition, various commercially available formulated blended flavors, such as vanilla flavor (vanilla BVK-3359 (manufactured by Takasago International Corporation)), mint flavor (mint THP-8148 (manufactured by Hasegawa International Corporation)), banana flavor (banana T-1510 (manufactured by Yamamoto International Corporation)), blueberry flavor (blueberry V-647 (manufactured by Yamamoto International Corporation)), and fennel oil N-3707 (manufactured by Takasago International Corporation) can also be used.

[0164] The content of these fragrances is in the range of 0.01 to 10% by mass, preferably 0.01 to 5% by mass, based on the total amount of the ink. If the content of these fragrances is 0.01% by mass or more, the fragrance can be felt, and if it is 10% by mass or less, the curing property is not affected, which is preferable.

[0165] [Physical Properties] When the inkjet curable composition does not contain a gelling agent, the viscosity of the curable composition at 40° C. is preferably 7 to 15 mPa s, and more preferably 8 to 13 mPa s. When the viscosity is within the above range, the ejection stability of the ink can be further improved.

[0166] When the curable composition contains a gelling agent, from the viewpoint of further improving the ejection property from an inkjet head, the viscosity of the curable composition at 80°C is preferably from 3 to 20 mPa s, and more preferably from 7 to 9 mPa s.

[0167] When the curable composition contains a gelling agent, the curable composition preferably undergoes a sol-gel phase transition at a temperature of 40°C or higher and lower than 100°C. The gelling temperature of the curable composition is preferably 40 to 70° C. When the gelling temperature of the curable composition is 40° C. or higher, the ink quickly gels after landing on a recording medium, resulting in higher pinning properties. When the gelling temperature of the ink is 70° C. or lower, the ink is less likely to gel when ejected from an inkjet head, where the ink temperature is usually about 80° C., and the ink can be ejected more stably.

[0168] The viscosity of the ink at 40° C., the viscosity at 80° C., and the gelation temperature can be determined by measuring the temperature change of the dynamic viscoelasticity of the ink using a rheometer. Examples of the rheometer include the stress-controlled rheometer Physica MCR series (manufactured by Anton Paar). Specifically, the ink is heated to 100°C and cooled to 25°C under conditions of a shear rate of 11.7 (1 / s) and a cooling rate of 0.1°C / s, and a viscosity temperature curve is obtained. The viscosities at 40°C and 80°C can then be determined by reading the viscosities at 40°C and 80°C, respectively, on the viscosity temperature curve. The gelation temperature can be determined as the temperature at which the viscosity becomes 200 mPa s on the viscosity temperature curve.

[0169] [Method of preparing inkjet curable composition] The inkjet curable composition according to the present invention can be prepared by mixing the above-mentioned components. At this time, it is preferable to mix the components while heating them in order to increase the solubility of each component.

[0170] Alternatively, a pigment dispersion containing the pigment and the pigment dispersant may be prepared in advance, and the remaining components may be added and mixed therein. In this case, the pigment may be dispersed using, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, or a paint shaker.

[0171] The inkjet curable composition can be used to form a solder resist (insulating film) for electronic components. Therefore, the curable composition can be used, for example, as a solder resist ink for forming a solder resist on a printed wiring board, or an ink for forming a solder resist on a semiconductor / IC package and an RFID antenna. The curable composition can also be used as an ink for a semiconductor sealant, an ink for an underfill material, an ink for a die bonding material, an ink for a black matrix of an LED or an image display device, an ink for a multilayer board prepreg, and the like.

[0172] [Inkjet recording method] The inkjet recording method of the present invention is an inkjet recording method in which a curable composition for inkjet is discharged onto a substrate and cured by actinic rays, and is characterized in that the curable composition for inkjet of the present invention is used and a substrate containing a metal is used as the substrate.

[0173] Specifically, the inkjet recording method of the present invention includes a step of applying the above-mentioned inkjet curable composition to the surface of a substrate, and a step of irradiating the applied curable composition with actinic rays to cure the curable composition.

[0174] (1) Applying ink In this step, the curable composition for inkjet of the present invention is applied to a substrate by an inkjet method.

[0175] The ejection method from the inkjet head may be either an on-demand method or a continuous method. The on-demand inkjet head may be of any of the following types: electro-mechanical conversion type, such as single cavity type, double cavity type, bender type, piston type, shear mode type, and shared wall type; and electro-thermal conversion type, such as thermal inkjet type and bubble jet type ("Bubble Jet" is a registered trademark of Canon Inc.).

[0176] The ink is preferably heated so that the temperature of the ink when filled into the inkjet head is 40° C. or higher. In particular, the temperature of the ink is preferably set to 40 to 100° C., and more preferably set to 40 to 90° C. By setting the ink temperature in the above range, the ejection properties from the inkjet head can be further improved.

[0177] In particular, when the ink contains a gelling agent, the ink droplets are ejected from the inkjet head in a heated, solubilized state, and therefore it is preferable to set the temperature of the ink when filled in the inkjet head to a gelling temperature of the ink +10°C or higher and a gelling temperature of the ink +30°C or lower. When the temperature of the actinic radiation curable ink in the inkjet head is equal to or higher than the gelling temperature + 10°C, the ink is less likely to gel inside the inkjet head or on the nozzle surface, resulting in a decrease in ejection performance. On the other hand, when the temperature of the ink in the inkjet head is equal to or lower than the gelling temperature + 30°C, the components are less likely to deteriorate due to high temperatures.

[0178] The method of heating the ink is not particularly limited. Examples of the heating method include heating the ink by using a head cap. At least one of the ink supply system such as the ink tank, supply pipe, and front chamber ink tank immediately before the head that constitute the ridge, the piping with filter, and the piezo head can be heated by a panel heater, ribbon heater, warm water, or the like.

[0179] The amount of ink droplets ejected is preferably 3.0 to 9.0 pL from the viewpoint of increasing the pattern formation speed and forming a finer pattern.

[0180] Examples of electronic components include printed wiring boards, semiconductor / IC packages, mini / micro LEDs, etc. Examples of the substrate, which is the metal portion of the electronic component, may contain nickel, aluminum, etc. in addition to copper.

[0181] (2) A step of irradiating with actinic rays In this step, the ink applied to the surface of the substrate is irradiated with actinic radiation to cure the ink.

[0182] The actinic radiation can be selected from, for example, electron beams, ultraviolet rays, α rays, γ rays, and X-rays, and is preferably ultraviolet rays or electron beams. The ultraviolet light is preferably light having a peak wavelength of 360 to 410 nm. The ultraviolet light is preferably irradiated from an LED light source. LEDs emit less radiant heat than conventional light sources (such as metal halide lamps). Therefore, by using LEDs, the ink is less likely to melt when exposed to actinic rays, and uneven gloss is less likely to occur.

[0183] (3) Heating process The inkjet recording method of the present invention may further include a step of heating the substrate to 140° C. or higher. By carrying out this heating step, the hardness of the solder resist is improved. The heating temperature of the substrate is preferably 140 to 180° C. The heating time is preferably 30 to 120 minutes, and more preferably 30 to 60 minutes.

[0184] [Solder resist] The solder resist of the present invention is characterized by containing the above-mentioned curable composition for inkjet. That is, the solder resist of the present invention is formed by irradiating the above-mentioned curable composition for inkjet with actinic rays. The above-mentioned solder resist can be formed by the above-mentioned inkjet recording method.

[0185] The electrical resistance of the solder resist is 1.0×10 8 The electrical resistance is 1.0×10 8 ~1.0×10 18 Ω is preferred, and 1.0×10 10 ~1.0×10 18 More preferably, the electrical resistance is 1.0×10 11~1.0×10 18 It is preferably Ω.

[0186] [Printed wiring board] The printed wiring board according to the present invention has the above-mentioned solder resist on a base material (substrate).

[0187] The substrate on which the solder resist is formed may be a base substrate having a conductive film such as copper foil formed thereon. Examples of the base substrate include a rigid substrate and a flexible substrate. Examples of resin substrates include paper phenol substrates, paper epoxy substrates, glass epoxy substrates, and glass These include glass polyimide substrates, Teflon (registered trademark) substrates, PPO substrates, composite substrate epoxy substrates, etc. Examples of materials for the flexible substrate include PET film and polyimide film. EXAMPLES

[0188] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In the following examples, unless otherwise specified, the operations were performed at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

[0189] [Preparing materials] <Polymerizable compound> As the polymerizable compound, the following compound was used.

[0190] [ka]

[0191] · Dipentaerythritol hexaacrylate (6 functional groups) Propoxylated (3) Trimethylolpropane triacrylate (3 functional) Dipropylene glycol diacrylate (bifunctional)

[0192] <Nitrogen-containing aromatic heterocyclic compounds having tertiary amines> As the nitrogen-containing aromatic heterocyclic compounds having a tertiary amine, the following B-1 to B-10 were used.

[0193] [ka]

[0194] [ka]

[0195] <Other nitrogen-containing aromatic heterocyclic compounds> As other nitrogen-containing aromatic heterocyclic compounds, the following were used.

[0196] [ka]

[0197] <Polymerization initiator> As the polymerization initiator, the following initiators 1 to 3 were used. Initiator 1: Omnirad907 (IGM Resins BV) (acetophenone-based initiator, intramolecular cleavage type, α-aminoalkylphenone) Initiator 2: Omnirad819 (IGM Resins BV) (acylphosphine initiator, intramolecular cleavage type, bis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide) Initiator 3: Speedcure ITX (manufactured by Sartomer) (thioxanthone-based initiator, hydrogen abstraction type, 2-isopropylthioxanthone)

[0198] <Polymerization inhibitor> As the polymerization inhibitor, the following was used. ·MEHQ (hydroquinone monomethyl ether) Irgastab UV-10 (BASF Japan, N-oxyl) ·NPHA (N-nitroso-N-phenylhydroxylamine aluminum, nitrosamines)

[0199] <Preparation of pigment dispersion> (Preparation of Yellow Pigment Dispersion) The following materials were placed in a stainless steel beaker, heated on a hot plate at 65°C for 1 hour, stirred and dissolved, and then cooled to room temperature. Then, 15.0 parts by mass of yellow pigment PY185 (Paliotol Yellow D1155, manufactured by BASF) was added to the stainless steel beaker. Then, the mixture in the stainless steel beaker and 200 g of zirconia beads (diameter 0.5 mm) were placed in a glass bottle and sealed. This was dispersed in a paint shaker (5400, manufactured by Red Devil) until the desired particle size was reached, and the zirconia beads were removed to prepare a yellow pigment dispersion. Pigment dispersant 1 (EFKA PX4701, manufactured by BASF) 11.2 parts by mass Synergist 1 (Solsperse 22000, Lubrizol) 3.0 parts by mass Dispersion medium: Dipropylene glycol diacrylate 70.8 parts by mass

[0200] (Preparation of Cyan Pigment Dispersion) A cyan pigment dispersion was prepared in the same manner as the yellow pigment dispersion, except that the amount of dispersant used and the amount of dispersion medium were changed as follows, the pigment added was changed to 23.0 parts by mass of cyan pigment PB15:4 (Chromofine Blue 6332JC, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), and Synergist 1 was not added. Note that the cyan pigment PB15:4 is a pigment that has been treated with a synergist. Pigment dispersant 1 (EFKA PX4701, manufactured by BASF) 7.0 parts by mass Dispersion medium: Dipropylene glycol diacrylate 70.0 parts by mass

[0201] The above-mentioned yellow pigment and cyan pigment are pigments that have been subjected to a water washing treatment to reduce the amount of impurities (conductive substances and ionic impurities).

[0202] <dye> The following dyes were used: Solvent Blue 35

[0203] [Preparation of Inkjet Ink] <Preparation of Inkjet Ink 1> 3.0 parts by mass of the yellow pigment dispersion liquid and 3.0 parts by mass of the cyan pigment dispersion liquid were mixed, and the following materials were added to the resulting mixture while stirring, to prepare an inkjet ink. (polymerizable compound) Carboxy group-containing polymerizable compound 1 10.0 parts by mass Dipentaerythritol hexaacrylate 10.0 parts by mass Propoxylated (3) trimethylolpropane triacrylate 30.0 parts by mass Dipropylene glycol diacrylate 37.9 parts by weight (Polymerization initiator) Initiator 2 3.0 parts by weight Initiator 3 3.0 parts by weight (Polymerization inhibitor) Irgastab UV-10 (BASF) 0.1 parts by weight

[0204] The resulting ink composition was filtered through a 3.0 μm membrane filter (manufactured by ADVANTECH Corporation) to obtain inkjet ink 1.

[0205] <Preparation of Inkjet Inks 2 to 24> Inkjet inks 2 to 24 were obtained in the same manner as in the preparation of the inkjet ink 1, except that the materials and amounts used were changed so as to obtain the ink compositions shown in Tables I to III below.

[0206] [Table 1]

[0207] [Table 2]

[0208] [Table 3]

[0209] [Formation of hardened film] Each prepared ink was loaded into an inkjet recording device having an inkjet recording head equipped with a piezoelectric inkjet nozzle. Then, a voltage was applied to the inkjet recording head so that the droplet discharge amount was 6.0 pL. Then, a solid pattern of 20 mm x 50 mm and 30 μm thick, and a comb-like fine line pattern of 100 μm line and space and 30 μm thick were formed on a copper-clad laminate for printed wiring boards (FR-4, thickness 1.6 mm, size 150 mm x 95 mm). During pattern formation, the ink in the inkjet recording head was heated by a built-in heater of the recording head so that the temperature was 80°C.

[0210] The printed pattern was irradiated with an LED lamp (Fire Jet™ FJ100, manufactured by Phoseon Technology, wavelength 395 nm) at an intensity of 500 mJ / cm 2 The ink layer was cured by irradiating it with ultraviolet light so that the ink layer became Thereafter, the copper-clad laminate on which the pattern was formed was placed in an oven set at 150° C. and heated for 60 minutes to further cure the ink layer, thereby obtaining a cured film. The cured films were formed under three conditions: immediately after preparing the ink, after storing the ink at 85°C for four days, and after storing the ink at 85°C for eight days.

[0211] [evaluation] <Discoloration> In the above [Formation of a cured film], the solid pattern cured film before being placed in the oven was measured for L by reflected light measurement using a fluorescent spectrodensitometer FD-7 (Konica Minolta) under the following conditions. * a * b * was measured. Illumination conditions: M0(A), observation light source: D50, observation conditions: 2° field of view After heating in an oven at 150°C for 60 minutes, the cured film was subjected to the same L * a * b * was measured. After heating in a 150°C oven for 60 minutes, the cured film was immersed in a 260°C solder bath for 10 seconds three times, and then subjected to the same L * a * b * was measured. The ΔE before and after 60 minutes at 150°C and before and after soldering was calculated using the following formula, and evaluated based on the following criteria, with "A", "B" and "C" being deemed acceptable for practical use. The cured films formed under three conditions were measured immediately after the ink was prepared, after the ink was stored at 85°C for 4 days, and after the ink was stored at 85°C for 8 days. * a * b * was measured. ΔE = [(ΔL * ) 2 +(Δa * ) 2 +(Δb * ) 2 〕 1 / 2 (standard) A: ΔE≦6 B: 6<ΔE≦10 C:10<ΔE≦15 D:15<ΔE

[0212] <Adhesion> In the obtained solid pattern cured film, a checkerboard-like cut was made according to the cross-cut method of JIS K5600-5-6:1999, and an adhesive tape was attached. The adhesive tape was peeled off, and the peeling state of the cured film from the substrate was observed, and the adhesion residual rate was obtained. Here, the adhesion residual rate refers to the ratio of the number of squares in which the cured film remains after the tape is peeled off to the number of squares created by the above-mentioned cuts. The adhesion residual rate was calculated for each of the cured films formed under three conditions: immediately after preparing the ink, after storing the ink at 85°C for 4 days, and after storing the ink at 85°C for 8 days. Based on each adhesion residual rate, the adhesion was evaluated according to the following evaluation criteria. "A", "B", and "C" were determined to be acceptable for practical use. (standard) A: The adhesion residual rate is 100%. B: The adhesion residual rate is 80% or more but less than 100%. C: Adhesion residual rate is 60% or more but less than 80% D: The adhesion residual rate is less than 60%.

[0213] <Pencil hardness> For each of the prepared cured film samples, the pencil hardness of the surface was measured using a Hi-Uni (registered trademark) made by Mitsubishi Pencil Co., Ltd. in accordance with the method described in "JIS Standard K-5400." Specifically, the wood of the pencil was scraped off and the lead was 5-6 mm long. The tip of the lead was polished smoothly with abrasive paper to give a circular cross section. The pencil was held at a 45 degree angle to the sample surface, and a load of 1 kg was applied to the sample surface, and the cured film was scratched at a 45 degree angle. The pencil hardness was measured for the cured films formed under three conditions: immediately after the ink was prepared, after the ink was stored at 85°C for 4 days, and after the ink was stored at 85°C for 8 days. The maximum pencil hardness at which the cured film did not reach the recording medium was evaluated. A maximum pencil hardness of 4H or more was considered to be within the range of no practical problem.

[0214] <Solder heat resistance> As a method for evaluating the heat resistance of the cured film, the following solder heat resistance was evaluated. The solid pattern print sample was immersed in a 260°C solder bath for 10 seconds three times, and then the adhesion residual rate was calculated in the same manner as in the "adhesion" above, and the peeling state of the cured film was evaluated according to the following criteria. The adhesion residual rate was calculated for each of the cured films formed under three conditions: immediately after the ink was prepared, after the ink was stored at 85°C for 4 days, and after the ink was stored at 85°C for 8 days. In the following criteria, "A" and "B" were defined as ranges that are acceptable for practical use. (standard) A: Adhesion remaining rate is 90% or more (100%) B: Adhesion residual rate is 90% or more but less than 100% C: Adhesion residual rate is 70% or more but less than 90% D: Adhesion remaining rate is less than 70%

[0215] <Plating resistance> Each sample of the cured film obtained above was plated with nickel 0.5 μm and gold 0.03 μm using a commercially available electroless nickel plating bath and electroless gold plating bath, and a cross-cut tape peel test was performed. The number of remaining grids out of 100 was counted for the cured films formed under three conditions: immediately after the ink was prepared, after the ink was stored at 85°C for 4 days, and after the ink was stored at 85°C for 8 days, and the results were evaluated based on the following criteria. In the following criteria, "A" and "B" were defined as ranges that are acceptable for practical use. (standard) A: 100 out of 100 remaining units B: The remaining number is 80 to 99 out of 100 C: The remaining number is 60 to 79 out of 100 D: The number of remaining units is 59 or less out of 100 units.

[0216] <Viscosity fluctuation> The 80°C viscosity of each ink prepared was measured using a Physica MCR301 (manufactured by Anton Paar) with a shear rate of 1000 (1 / s). Measurements were taken immediately after the ink was prepared, after storage at 85°C for 4 days, and after 8 days at 85°C. The difference in viscosity (viscosity change) between the ink immediately after preparation and after storage at 85°C for 4 days, and the difference in viscosity (viscosity change) between the ink immediately after preparation and after storage at 85°C for 8 days were calculated, and the results were evaluated according to the following criteria. In the following criteria, "A", "B", and "C" were defined as ranges that are acceptable for practical use. (standard) A: Viscosity fluctuation is less than 0.3 mPa s B: Viscosity fluctuation is 0.3 mPa s or more but less than 0.7 mPa s C: Viscosity fluctuation is 0.7 mPa s or more but less than 1.0 mPa s D: Viscosity fluctuation is 1.0 mPa s or more

[0217] <Average particle size variation> The average particle size (Z-average) of each ink prepared was measured by dynamic light scattering using a Datasizer Nano ZSP (Malvern). The ink was diluted 200 times before measurement. The measurement temperature was 25°C. Measurements were performed immediately after the ink was prepared, after storage at 85°C for 4 days, and after storage at 85°C for 8 days. The difference between the average particle size immediately after the ink was prepared and the average particle size after storage at 85°C for 4 days (average particle size variation), and the difference between the average particle size immediately after the ink was prepared and the average particle size after storage at 85°C for 8 days (average particle size variation) were calculated, and evaluation was performed according to the following criteria. In the following criteria, "A" and "B" were determined to be in the range that does not cause problems in practical use. (standard) A: Average particle size variation is less than 15 nm B: Average particle size fluctuation is 15 nm or more and less than 30 nm C: Average particle size fluctuation is 30 nm or more and less than 50 nm D: Average particle size fluctuation is 50 nm or more

[0218] [Table 4]

[0219] [Table 5]

[0220] [Table 6]

[0221] As shown by the above results, the ink of the present invention can suppress the change in viscosity, particle size, and discoloration prevention performance over time at high temperatures compared to the ink of the comparative example. Furthermore, it is recognized that the cured film formed using the ink of the present invention has better adhesion, hardness, solder heat resistance, and plating resistance over time at high temperatures compared to the cured film formed using the ink of the comparative example.

Claims

1. A curable composition for inkjet for metal-containing substrates, which contains a polymerizable compound, a polymerization initiator, and a pigment, and is cured by irradiation with actinic radiation, Contains a nitrogen-containing aromatic heterocyclic compound having a tertiary amine 1. A curable inkjet curable composition for a metal-containing substrate.

2. The curable composition for inkjet according to claim 1 , wherein the nitrogen-containing aromatic heterocyclic compound has an aromatic heterocycle to which a benzene ring is not directly condensed.

3. The polymerizable compound is a polymerizable compound having a carboxy group, a hydroxy group, or an epoxy group. The curable composition for inkjet for metal-containing substrates according to claim 1 .

4. The nitrogen-containing aromatic heterocyclic compound contains a 5-membered nitrogen-containing aromatic heterocyclic compound. The curable composition for inkjet for metal-containing substrates according to claim 1 .

5. The nitrogen-containing aromatic heterocyclic compound contains a triazole compound. The curable composition for inkjet for metal-containing substrates according to claim 1 .

6. The triazole compound has a structure represented by the following general formula (a): The curable composition for inkjet for metal-containing substrates according to claim 5 . 【Chemistry 1】 [In the general formula (a), Ra and Rb each represent an alkyl group having 1 to 20 carbon atoms.]

7. The polymerizable compound having a carboxy group has a structure represented by the following general formula (1): The curable composition for inkjet for metal-containing substrates according to claim 3 . 【Chemistry 2】 In the general formula (1), X represents a substituent having at least one group selected from an acryloyl group, a methacryloyl group, an allyl group, a vinyl group, and derivatives thereof at its terminal. Q is an oxygen atom or NR ４ represents R ４ represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. R １ represents an unsubstituted alkylene group having 1 to 6 carbon atoms.

8. The polymerizable compound having a hydroxy group is an epoxy acrylate obtained by reacting (meth)acrylic acid with an epoxy compound. The curable composition for inkjet for metal-containing substrates according to claim 3 .

9. The polymerizable compound having a carboxy group, a hydroxy group, or an epoxy group has a bisphenol structure, a cresol novolac structure, or a phenol novolac structure. The curable composition for inkjet for metal-containing substrates according to claim 3 .

10. The polymerization initiator contains thioxanthone. The curable composition for inkjet for metal-containing substrates according to claim 1 .

11. Contains N-oxyls or nitrosamines as polymerization inhibitors The curable composition for inkjet for metal-containing substrates according to claim 1 .

12. A solder resist comprising the curable composition for inkjet for a metal-containing substrate according to claim 1 .

13. An inkjet recording method comprising discharging a curable composition for inkjet recording onto a substrate and curing the composition with actinic radiation, The curable composition for inkjet for a metal-containing substrate according to any one of claims 1 to 11 is used as the curable composition for inkjet, A metal-containing substrate is used as the substrate.

1. An ink-jet recording method comprising:

14. Heating the substrate at 140° C. or higher The inkjet recording method according to claim 13 .

15. The curable composition for inkjet for metal-containing substrates is heated to 40° C. or higher in an inkjet head. The inkjet recording method according to claim 13 .

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