Active energy ray-curable inkjet ink and inkjet recording method

Abstract

An active energy ray-curable inkjet ink according to the present disclosure is cured by an active energy ray, and contains a (meth)acrylate monomer having a cyclic imide group, a polymerizable monomer having an acidic group, and a polymerization initiator.

Description

Active energy ray curable inkjet ink and inkjet recording method

[0001] The present disclosure relates to an actinic ray-curable inkjet ink and an inkjet recording method. In particular, the present disclosure relates to an actinic ray-curable inkjet ink that can simultaneously satisfy etching resistance and strippability, and also has excellent plating resistance, ejection stability, and recyclability.

[0002] Conventionally, photolithography and screen printing have been used to form etching resists, solder resists, and markings on printed circuit boards. Meanwhile, a known method for manufacturing printed circuit boards using an inkjet printer involves drawing a conductor circuit pattern on a copper-clad laminate for printed wiring boards using an inkjet printer. This forms an etching resist, which is then subjected to etching. This method significantly reduces the number of steps and labor required compared to photolithography, which requires a photomask, and screen printing, which requires a screen plate and uses resist ink or marking ink. Furthermore, it can reduce consumables such as developers, various inks, and cleaning solvents, and also reduces wastewater, which is expected to contribute to a cleaner environment.

[0003] For solder resist, forming a cured film using light and heat using an inkjet method has already been proposed. For example, Patent Document 1 discloses an ink containing a (meth)acrylate compound having an imide group as a solder resist ink. While this ink improves etching resistance and resistance to high temperatures and humidity, it is not intended for use in peeling off the formed cured film, and therefore makes no mention of the peelability of the cured film, failing to simultaneously satisfy both etching resistance and peelability. Furthermore, for example, Patent Documents 2 to 4 disclose inks containing photopolymerizable compounds without acidic groups and monomers containing acidic groups. However, they do not disclose compounds containing imide groups as the photopolymerizable compounds without acidic groups. As a result, etching resistance is insufficient due to insufficient adhesion, and it is not possible to simultaneously satisfy both etching resistance and peelability.

[0004] International Publication No. 2021 / 001937 Japanese Patent Application Laid-Open No. 2020-37645 Special Publication No. 2017-537986 Special Publication No. 2005-539391

[0005] The present disclosure has been made in consideration of the above-mentioned problems and circumstances, and an object of the present disclosure is to provide an actinic radiation-curable inkjet ink and an inkjet recording method that can simultaneously satisfy etching resistance and strippability, and also have excellent plating resistance, ejection stability, and recyclability.

[0006] The present inventors have investigated the causes of the above problems in order to solve them. As a result, the present inventors have found that etching resistance and strippability can be simultaneously achieved by using a (meth)acrylate monomer having a cyclic imide group, a polymerizable monomer having an acidic group, and a polymerization initiator in combination. Furthermore, the present inventors have found that the resulting composition also has excellent plating resistance, injection stability, and recyclability. That is, the above problems of the present disclosure can be solved by the following means.

[0007] 1. An actinic energy ray-curable inkjet ink that is cured by actinic energy rays, the actinic energy ray-curable inkjet ink containing: a (meth)acrylate monomer having a cyclic imide group; a polymerizable monomer having an acidic group; and a polymerization initiator.

[0008] 2. The actinic radiation-curable inkjet ink according to item 1, wherein the mass ratio (% by mass) of the content of the (meth)acrylate monomer having a cyclic imide group relative to the entire ink to the content (% by mass) of the polymerizable monomer having an acidic group relative to the entire ink ((meth)acrylate monomer having a cyclic imide group / polymerizable monomer having an acidic group) is within a range of 0.5 to 30.

[0009] 3. The actinic ray-curable ink-jet ink according to item 1, wherein the (meth)acrylate monomer having a cyclic imide group is N-acryloyloxyethylhexahydrophthalimide.

[0010] 4. The actinic ray-curable ink-jet ink according to item 1, wherein the polymerizable monomer having an acidic group is a polymerizable monomer having a carboxyl group.

[0011] 5. The actinic ray-curable ink-jet ink according to item 1, wherein the polymerizable monomer having an acidic group is 2-carboxyethyl acrylate.

[0012] 6. The actinic ray-curable ink-jet ink according to item 1, which contains a polymerizable monomer having an alicyclic structure.

[0013] 7. The actinic ray-curable ink-jet ink according to item 1, which contains a monomer having an acrylamide group.

[0014] 8. The actinic radiation-curable ink-jet ink according to item 7, wherein the monomer having an acrylamide group is acryloylmorpholine.

[0015] 9. The actinic ray-curable ink-jet ink according to item 1, which contains a polyfunctional monomer.

[0016] 10. The actinic ray-curable ink-jet ink according to item 1, which contains a dye.

[0017] 11. The actinic ray-curable ink-jet ink according to item 1, which contains a gelling agent.

[0018] 12. The actinic ray-curable ink-jet ink according to item 1, which is used as an etching resist.

[0019] 13. The actinic ray-curable ink-jet ink according to item 1, which is used as a plating resist.

[0020] 14. An inkjet recording method comprising ejecting an actinic ray-curable inkjet ink onto a substrate and curing the ink with actinic rays, the inkjet recording method comprising using the actinic ray-curable inkjet ink according to any one of items 1 to 13 as the actinic ray-curable inkjet ink.

[0021] The above-described means of the present disclosure provide an actinic radiation-curable inkjet ink and inkjet recording method that simultaneously satisfy etching resistance and releasability, and also exhibit excellent plating resistance, ejection stability, and recyclability. In particular, the present disclosure provides excellent releasability against alkaline solutions. The mechanism of action or manifestation of the effects of the present disclosure is unclear, but the following speculation is made. Conventionally, improving etching resistance requires improving adhesion between the ink and the substrate (the printing medium). However, excessive adhesion can lead to poor releasability. Simply using a (meth)acrylate monomer having a cyclic imide group that has high affinity with the substrate to simultaneously satisfy both etching resistance and releasability is insufficient. Therefore, by using a polymerizable monomer having an acidic group and a polymerization initiator in addition to the (meth)acrylate monomer having a cyclic imide group, the imide group and the acidic monomer are appropriately incorporated into the formed polymerized coating film. As a result, etching resistance and releasability can be simultaneously satisfied. Furthermore, by appropriately incorporating a (meth)acrylate monomer having a cyclic imide group that has high affinity with the substrate, the durability of the coating film is increased and plating resistance can be improved at the same time. Furthermore, the physical properties of viscosity and surface tension of the (meth)acrylate monomer having a cyclic imide group are suitable for inkjet ejection at an ejection temperature of 60°C or higher, so inkjet ejection stability is also improved. Furthermore, since the ink components can be efficiently separated from the substrate while maintaining the durability of the coating film, deinking is favorable and recyclability can be improved.

[0022] FIG. 1 is a diagram illustrating the manufacturing process for a printed circuit board when an ink of the present disclosure is used to form an etching resist. FIG. 2 is a diagram illustrating the manufacturing process for a printed circuit board when an ink of the present disclosure is used to form an etching resist. FIG. 3 is a diagram illustrating the manufacturing process for a printed circuit board when an ink of the present disclosure is used to form an etching resist. FIG. 4 is a diagram illustrating the manufacturing process for a printed circuit board when an ink of the present disclosure is used to form an etching resist. FIG. 5 is a diagram illustrating the manufacturing process for a printed circuit board when an ink of the present disclosure is used to form a plating resist. FIG. 6 is a diagram illustrating the manufacturing process for a printed circuit board when an ink of the present disclosure is used to form a plating resist. FIG. 7 is a diagram illustrating the manufacturing process for a printed circuit board when an ink of the present disclosure is used to form a plating resist.

[0023] The actinic ray-curable inkjet ink of the present disclosure is an actinic ray-curable inkjet ink that is cured by actinic ray, and is characterized by containing a (meth)acrylate monomer having a cyclic imide group, a polymerizable monomer having an acidic group, and a polymerization initiator. This characteristic is a technical characteristic common to or corresponding to each of the following embodiments.

[0024] In an embodiment of the present disclosure, it is preferred that the mass ratio (% by mass) of the content of the (meth)acrylate monomer having a cyclic imide group relative to the entire ink to the content (% by mass) of the polymerizable monomer having an acidic group relative to the entire ink ((meth)acrylate monomer having a cyclic imide group / polymerizable monomer having an acidic group) be within a range of 0.5 to 30. This allows the cyclic imide group and the acidic monomer to be suitably incorporated into the formed coating film, improving etching resistance, plating resistance, and removability.

[0025] The (meth)acrylate monomer having a cyclic imide group is preferably N-acryloyloxyethylhexahydrophthalimide, since this further improves etching resistance and plating resistance.

[0026] In terms of releasability, it is preferable that the polymerizable monomer having an acidic group contains a polymerizable monomer having a carboxyl group.In terms of releasability and recyclability, it is preferable that the polymerizable monomer having an acidic group contains 2-carboxyethyl acrylate.

[0027] The ink of the present disclosure preferably contains a polymerizable monomer having an alicyclic structure in terms of etching resistance and plating resistance.

[0028] It is preferable that the composition contains a monomer having an acrylamide group in terms of plating resistance, and it is particularly preferable that the composition contains acryloylmorpholine as the monomer having an acrylamide group in terms of plating resistance and etching resistance.

[0029] The ink of the present disclosure preferably contains a polyfunctional monomer, which further improves recyclability, etching resistance, and plating resistance. The ink of the present disclosure preferably contains a dye, which further improves etching resistance and plating resistance. Furthermore, the ink of the present disclosure preferably contains a gelling agent, which further improves etching resistance. The gelling agent can also fix (pin) ink droplets that land on a recording medium, preventing the droplets from coalescing, thereby enabling the formation of high-resolution images. The ink of the present disclosure is suitable for use as an etching resist or plating resist.

[0030] The inkjet recording method of the present disclosure is an inkjet recording method in which an actinic ray-curable inkjet ink is ejected onto a substrate and cured by actinic rays, and is characterized in that the actinic ray-curable inkjet ink of the present disclosure is used as the actinic ray-curable inkjet ink. This makes it possible to simultaneously satisfy etching resistance and plating resistance as substrate adhesion, and releasability, and also provides excellent ejection stability and recyclability.

[0031] The present disclosure, its components, and modes and aspects for carrying out the disclosure will be described below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0032] [Active Energy Ray-Curable Inkjet Ink] The active energy ray-curable inkjet ink of the present disclosure is an active energy ray-curable inkjet ink that is cured by active energy rays. The active energy ray-curable inkjet ink contains a (meth)acrylate monomer having a cyclic imide group, a polymerizable monomer having an acidic group, and a polymerization initiator. In the present disclosure, the term "active energy ray-curable inkjet ink" refers to an inkjet ink that is cured by irradiation with active energy rays. In this specification, it is also simply referred to as "ink."

[0033] "Active energy rays" refer to radiation that acts physically and chemically on a polymerization initiator or a polymerizable compound to promote a crosslinking reaction and a polymerization reaction. Specific examples of active energy rays include visible light, ultraviolet light, X-rays, electron beams, α-rays, β-rays, and γ-rays. In this specification, "(meth)acrylate" is a general term for "acrylate" and "methacrylate," and refers to either or both of them.

[0034] The ink of the present disclosure may contain, in addition to the (meth)acrylate monomer having a cyclic imide group, the polymerizable monomer having an acidic group, and the polymerization initiator, a polymerizable monomer having an alicyclic structure, an aromatic monomer, a monomer having an acrylamide group, a polyfunctional monomer, a dye, or a gelling agent, as necessary. Each of the components of the ink will be described below.

[0035] <(Meth)acrylate Monomer Having a Cyclic Imide Group> Examples of the (meth)acrylate monomer having a cyclic imide group include a monomer having a structure represented by the following general formula (1) and a monomer having a structure represented by the following general formula (2).

[0036] In the general formulas (1) and (2), R represents a hydrogen atom or a methyl group. An example of a compound in which R represents a hydrogen atom in the general formula (1) is N-acryloyloxyethylhexahydrophthalimide. Commercially available N-acryloyloxyethylhexahydrophthalimide products include Aronix M-140 (manufactured by Toagosei Co., Ltd.) and Miramer M1088 (manufactured by Miwon Co., Ltd.).

[0037] The content of the (meth)acrylate monomer having a cyclic imide group is preferably within a range of 10 to 60% by mass, and more preferably within a range of 20 to 50% by mass, based on the total mass of the ink. In particular, the content of the (meth)acrylate monomer having a cyclic imide group is preferably greater than 30% by mass, based on the total mass of the ink. By ensuring that the content of the (meth)acrylate monomer having a cyclic imide group falls within the above range, etching resistance, plating resistance, and recyclability are improved.

[0038] <Polymerizable Monomer Having an Acidic Group> The polymerizable monomer having an acidic group is preferably a polymerizable monomer having an acidic group such as a carboxy group, a phosphate group, a sulfonic acid group, or a hydroxy group in its molecule. A phosphate group is also called a phospho group, and a sulfonic acid group is also called a sulfo group. In particular, the polymerizable monomer having an acidic group is preferably a (meth)acrylate compound having a carboxy group.

[0039] Examples of the (meth)acrylate compound having a carboxy group include (meth)acrylate compounds having a hydroxy group and (meth)acrylates obtained by adding an acid anhydride to an oligomer of these compounds. Examples of the acid anhydride include phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, himic anhydride, maleic anhydride, trimellitic anhydride, methylcyclohexene tricarboxylic anhydride, and pyromellitic anhydride. Examples of the acid anhydride include 2-carboxyethyl acrylate, 4-(meth)acryloyloxyethoxycarbonylphthalic acid, 4-(meth)acryloyloxybutoxycarbonylphthalic acid, 4-(meth)acryloyloxyhexyloxycarbonylphthalic acid, and 4-(meth)acryloyloxydecanoic anhydride. Examples of the (meth)acryloyloxyalkoxycarbonyl phthalic acids include siloxycarbonyl phthalic acid, (meth)acryloyloxyalkoxyalkoxycarbonyl phthalic acids such as 4-(meth)acryloyloxyethoxyethoxycarbonyl phthalic acid, mono-2-(acryloyloxy)ethyl succinate, 2,2-bis(acryloylamido)acetic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, etc. As the (meth)acrylate compound having a carboxy group, 2-carboxyethyl acrylate is particularly preferred.

[0040] Examples of (meth)acrylate compounds having a phosphate group include bis(2-(meth)acryloyloxyethyl)phosphate ester, 2-hydroxyethyl(meth)acrylate acid phosphate, ethyl(meth)acrylate acid phosphate, 3-chloro-2-acidphosphooxypropyl(meth)acrylate, polyoxyethylene glycol(meth)acrylate acid phosphate, 2-(meth)acryloyloxyethyl caproate acid phosphate, and mono-2-(methacryloyloxy)ethyl phosphate. Further, examples of (meth)acrylate compounds having a phosphate group include the following compounds: (meth)acryloyloxyalkyl phosphates such as 2-(meth)acryloyloxyethyl phosphate (meaning 2-acryloyloxyethyl phosphate or 2-methacryloyloxyethyl phosphate, hereinafter abbreviated as such), 2- or 3-(meth)acryloyloxypropyl phosphate, 4-(meth)acryloyloxybutyl phosphate, 6-(meth)acryloyloxyhexyl phosphate, 8-(meth)acryloyloxyoctyl phosphate, 10-(meth)acryloyloxydecyl phosphate, 12-(meth)acryloyloxylauryl phosphate, 16-(meth)acryloyloxycetyl phosphate, 18-(meth)acryloyloxystearyl phosphate, and 20-(meth)acryloyloxyeicosyl phosphate; di(meth)acryloyloxyalkyl phosphates such as 1,3-di(meth)acryloyloxypropyl-2-phosphate; (meth)acryloyloxyalkylaryl phosphate esters such as 2-(meth)acryloyloxyethyl phenyl phosphate ester, 2-(meth)acryloyloxyethyl anisyl phosphate ester, and 2-(meth)acryloyloxyethyl tolyl phosphate ester; (meth)acryloyloxyalkylaryl phosphonic acids such as 2-(meth)acryloyloxyethyl phenylphosphonic acid;(Meth)acryloyloxyalkyl thiophosphates such as 2-(meth)acryloyloxyethyl thiophosphate, 2- or 3-(meth)acryloyloxypropyl thiophosphate, 4-(meth)acryloyloxybutyl thiophosphate, 6-(meth)acryloyloxyhexyl thiophosphate, 8-(meth)acryloyloxyoctyl thiophosphate, 10-(meth)acryloyloxydecyl thiophosphate, 12-(meth)acryloyloxylauryl thiophosphate, 16-(meth)acryloyloxycetyl thiophosphate, 18-(meth)acryloyloxystearyl thiophosphate, and 20-(meth)acryloyloxyeicosyl thiophosphate; di(meth)acryloyloxyalkyl thiophosphates such as 1,3-di(meth)acryloyloxypropyl-2-thiophosphate; (meth)acryloyloxyalkylaryl thiophosphates such as 2-(meth)acryloyloxyethyl phenyl thiophosphate, 2-(meth)acryloyloxyethyl anisyl thiophosphate, and 2-(meth)acryloyloxyethyl tolyl thiophosphate; (meth)acryloyloxyalkylaryl thiophosphonic acids such as 2-(meth)acryloyloxyethyl phenyl thiophosphonic acid;

[0041] Examples of (meth)acrylate compounds having a sulfonic acid group include methallylsulfonic acid, bis(3-sulfopropyl)itaconic acid, 2-(sulfoxy)ethyl methacrylic acid, and 2-acrylamido-2-methyl-1-propanesulfonic acid. Examples of (meth)acrylate compounds having a sulfonic acid group include 3-sulfopropylacrylic acid, 3-sulfopropylmethacrylic acid, and acrylamido-2-methyl-2-propanesulfonic acid.

[0042] Examples of the (meth)acrylate compound having a monofunctional hydroxy group include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 1-methyl-2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxymethylcyclohexylmethyl (meth)acrylate, and p-hydroxymethylphenylmethyl (meth)acrylate. 2-(hydroxyethoxy)ethyl (meth)acrylate, 2-(hydroxyethoxyethoxy)ethyl (meth)acrylate, 2-(hydroxyethoxyethoxy)ethyl (meth)acrylate, 2-(hydroxyethoxyethoxy)ethyl (meth)acrylate, methyl α-hydroxymethylacrylate, ethyl α-hydroxymethylacrylate, hydroxyalkyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl acrylate, and the like.

[0043] Of the (meth)acrylates, the polymerizable monomer having an acidic group is preferably 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl hexahydrophthalic acid, 2-methacryloyloxyethyl succinic acid, 2-methacryloyloxyethyl acid phosphate, 2-hydroxyethyl methacrylate acid phosphate, mono-2-(acryloyloxy)ethyl succinate, 2-methacryloyloxyethyl succinate, 2-methacryloyloxyethyl phthalic acid, 2-carboxyethyl acrylate, etc. The polymerizable monomer having an acidic group is most preferably 2-carboxyethyl acrylate.

[0044] Commercially available examples of the polymerizable monomer having an acidic group include Light Ester HO-MS(N) (manufactured by Kyoeisha Chemical Co., Ltd.), CN146 (manufactured by Sartomer Inc.), CN147 (manufactured by Sartomer Inc.), EM213 (manufactured by ETERNAL MATERIALS Inc.), Miramer CEA (manufactured by Miwon Co., Ltd.), etc. Examples of 2-carboxyethyl acrylate include EM213 (manufactured by ETERNAL MATERIALS Inc.) and Miramer CEA (manufactured by Miwon Co., Ltd.).

[0045] The content of the polymerizable monomer having an acidic group is preferably in the range of 1 to 30% by mass based on the total mass of the ink, in order to obtain excellent durability of the resist film and excellent dissolution and strippability in alkali, and the content of the polymerizable monomer having an acidic group is more preferably 1.5 to 10%.

[0046] The mass ratio ((meth)acrylate monomer having a cyclic imide group / polymerizable monomer having an acidic group) of the content (% by mass) of the (meth)acrylate monomer having a cyclic imide group relative to the total ink content in the ink to the content (% by mass) of the polymerizable monomer having an acidic group relative to the total ink content is preferably within a range of 0.5 to 30. It is more preferable that the mass ratio is within a range of 2.0 to 10.0.

[0047] <Polymerization initiator> The polymerization initiator is preferably a radical polymerization initiator. Examples of radical polymerization initiators include intramolecular cleavage-type photopolymerization initiators and hydrogen abstraction-type polymerization initiators. In the present disclosure, it is more preferable to use a hydrogen abstraction-type polymerization initiator. By using a hydrogen abstraction-type polymerization initiator, gradual crosslinking of polymer chains due to hydrogen abstraction proceeds in the formed coating film, making it possible to improve etching resistance and plating resistance without reducing releasability. The ink may contain only one type of photopolymerization initiator, or two or more types in combination.

[0048] Examples of the intramolecular cleavage type photopolymerization initiator include acetophenone-based initiators such as 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzil dimethyl ketal, 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; and acylphosphine oxide-based initiators such as 2,4,6-trimethylbenzoin diphenylphosphine oxide and bis(2,4,6-trimethylbenzoin)phenylphosphine oxide.

[0049] Commercially available examples of intramolecular cleavage type photopolymerization initiators include Omnirad 127, Omnirad 184, Omnirad 651, Omnirad 2959, Omnirad 819, Omnirad 907, Esacure One (manufactured by IGM Resins), and SPEEDCURE 73 (manufactured by Sartomer).

[0050] Examples of the hydrogen abstraction type photopolymerization initiator include benzophenone-based initiators such as benzophenone, methyl o-benzoylbenzoate, 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; and thioxanthone-based initiators such as 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone.

[0051] Examples of commercially available hydrogen abstraction photopolymerization initiators include SpeedCure 2-ITX, SpeedCure 7010, and SpeedCure BP.

[0052] The content of the polymerization initiator is preferably in the range of 1 to 10% by mass, and more preferably in the range of 1.5 to 8% by mass, based on the total mass of the ink.

[0053] <Alicyclic Monomer> A polymerizable monomer having an alicyclic structure is also referred to as an alicyclic monomer. The alicyclic monomer may be a monofunctional monomer (alicyclic monofunctional monomer) or a polyfunctional monomer having an alicyclic structure (alicyclic polyfunctional monomer), but is preferably an alicyclic monofunctional monomer. The alicyclic monomer is preferably an alicyclic monofunctional monomer having a molecular weight in the range of 200 to 300. Furthermore, the alicyclic monomer is preferably an alicyclic (meth)acrylate monomer. Note that when a (meth)acrylate having a cyclic imide group has an alicyclic structure, the amount added is calculated as a (meth)acrylate having a cyclic imide group, not as an alicyclic monomer. Examples of alicyclic monofunctional monomers include isobornyl acrylate, 3,5,5-trimethylcyclohexyl acrylate, 4-tert-butylcyclohexyl acrylate, dicyclopentenyloxyethyl acrylate, dicyclopentenyl acrylate, and dicyclopentanyl acrylate. These alicyclic monofunctional monomers are preferred in that they have excellent dilution properties and improve the tack-free properties of the resulting cured coating. Examples of alicyclic polyfunctional monomers include cyclohexanedimethanol di(meth)acrylate and tricyclodecane dimethanol diacrylate. These alicyclic polyfunctional monomers are preferred in that they improve the strength of the cured coating. Commercially available alicyclic monomers include Miramer M1130 (manufactured by Miwon), Miramer M1140 (manufactured by Miwon), FA-511AS (manufactured by Resonac), FA-513AS (manufactured by Resonac), and FA-512AS (manufactured by Resonac). The content of the alicyclic monofunctional monomer and alicyclic polyfunctional monomer is preferably within the range of 5 to 40% by mass of the total ink.

[0054] The mass ratio of the content (mass%) of the (meth)acrylate monomer having a cyclic imide group to the content (mass%) of the alicyclic monomer ((meth)acrylate monomer having a cyclic imide group / alicyclic monomer) is within a range of 0.25 to 8.00. Preferably, the mass ratio is within a range of 1.00 to 5.00.

[0055] The total content of the (meth)acrylate monomer having a cyclic imide group and the alicyclic monomer is preferably 30% by mass or more, and more preferably in the range of 30 to 70% by mass, based on the total mass of the ink.

[0056] <Aromatic Monomer> The aromatic monomer is a monomer having an aromatic ring. The aromatic monomer is preferably a monomer having a molecular weight in the range of 200 to 300. Examples of aromatic monomers include 2-phenoxyethyl (meth)acrylate, bisphenol A diacrylate, o-phenylphenoxyethyl (meth)acrylate, and m-phenoxybenzyl (meth)acrylate. Examples of aromatic monomers include ethoxylated phenoxy (meth)acrylate, alkoxylated phenol (meth)acrylate, and 2-hydroxy-o-phenylphenolpropyl (meth)acrylate. Examples of commercially available aromatic monomers include Miramer M1182 (manufactured by Miwon), Miramer M142 (manufactured by Miwon), Miramer M1142 (manufactured by Miwon), and SR339NS (manufactured by Sartomer). The content of the aromatic monomer is preferably within a range of 0 to 40% by mass based on the total mass of the ink.

[0057] <Monomers Having an Acrylamide Group> Examples of monomers having an acrylamide group include N,N-dimethylacrylamide, N-hydroxyethylacrylamide, acryloylmorpholine, N,N-diethylacrylamide, N-isopropylacrylamide, diacetone acrylamide, etc. Commercially available monomers having an acrylamide group include DMAA, HEAA, ACMO, DEAA, NIPAM, and DAAM manufactured by KJ Chemicals, etc. The ink does not necessarily contain a monomer having an acrylamide group, and the content of the monomer having an acrylamide group is preferably in the range of 0 to 30% by mass, and more preferably in the range of 5 to 25% by mass, based on the total mass of the ink.

[0058] <Polyfunctional Monomer> The polyfunctional monomer may be any monomer having two or more functional groups in the molecule. The polyfunctional monomer is preferably a bifunctional or trifunctional or higher functional (meth)acrylate monomer. The polyfunctional monomer may be the above-mentioned polyfunctional polymerizable monomer having an acidic group, or the above-mentioned alicyclic polyfunctional monomer.

[0059] Examples of bifunctional (meth)acrylate monomers include triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, bisphenol A PO adduct di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate.

[0060] Examples of trifunctional or higher functional (meth)acrylate monomers include tricyclodecane dimethanol diacrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerin propoxy tri(meth)acrylate, and pentaerythritol ethoxy tetra(meth)acrylate.

[0061] The (meth)acrylate monomer may be a modified product. Examples of the modified product include ethylene oxide-modified (meth)acrylate compounds such as ethylene oxide-modified trimethylolpropane tri(meth)acrylate and ethylene oxide-modified pentaerythritol tetraacrylate. Examples of the modified product include caprolactone-modified (meth)acrylate compounds such as caprolactone-modified trimethylolpropane tri(meth)acrylate. Examples of the modified product include caprolactam-modified (meth)acrylate compounds such as caprolactam-modified dipentaerythritol hexa(meth)acrylate. These may be used alone or in combination of two or more.

[0062] Commercially available examples of the polyfunctional monomer include M222 (bifunctional acrylate monomer having a propylene oxide skeleton, manufactured by Miwon), M210 (bifunctional acrylate monomer, neopentyl glycol hydroxypivalic acid ester diacrylate, manufactured by Miwon), A-DOG (dioxane glycol diacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd., molecular weight 326), A-DCP (tricyclodecane dimethanol diacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd., molecular weight 304), SR444 (trifunctional acrylate monomer, manufactured by Sartomer), and M262 (bifunctional acrylate monomer having a cyclic structure, manufactured by Miwon).

[0063] The ink does not necessarily contain a polyfunctional monomer, and the content of the polyfunctional monomer is preferably within a range of 0 to 30% by mass, and more preferably within a range of 2 to 30% by mass, relative to the total mass of the ink, from the viewpoint of the hardness of the coating film.

[0064] <Other Monomers> The ink of the present disclosure may contain other monomers in addition to the above-described monomers. Examples of the other monomers include (meth)acrylates such as caprolactone (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, isooctyl (meth)acrylate, lauryl (meth)acrylate, isodecyl (meth)acrylate, tetrahydrofurfuryl acrylate, and stearyl (meth)acrylate, and methoxypolyethylene glycol (meth)acrylate. Monomers having an ethylene glycol moiety are particularly preferred from the viewpoint of reducing cure shrinkage. Examples of commercially available products of the other monomers include Miramer M1110 (manufactured by Miwon), Miramer M150 (manufactured by Miwon), and SR551 (manufactured by Sartomer). Compounds having an ethylene oxide moiety are particularly preferred.

[0065] <Dye> The ink of the present disclosure may contain a colorant as needed. The colorant may be a dye or a pigment, but a dye is preferred because it has excellent etching resistance and plating resistance. By containing a dye in the ink, the ink colored by the dye is cured to form a coating film, making the resist pattern clear.

[0066] The dye is not particularly limited, but it is preferable to contain at least one dye selected from, for example, a dye having an anthraquinone skeleton and an amino group, a dye having a naphthalene skeleton and an amino group, and a dye having a phthalocyanine skeleton. These dyes are preferred because they have a relatively rigid skeleton and therefore have a high effect of suppressing color fading.

[0067] Examples of dyes having an anthraquinone skeleton and an amino group include Solvent Red 122 and Solvent Blue 35.

[0068] The structural formula of Solvent Red 122 is shown below.

[0069] The structural formula of Solvent Blue 35 is shown below.

[0070] Examples of dyes having a naphthalene skeleton and an amino group include Solvent Blue 5 and Basic Blue 7.

[0071] The structural formula of Solvent Blue 5 is shown below.

[0072] The structural formula of Basic Blue 7 is shown below.

[0073] An example of a dye having a phthalocyanine skeleton is Direct Blue 87.

[0074] The structural formula of Direct Blue 87 is shown below.

[0075] The dye content of the ink is preferably in the range of 0.01 to 3 mass %, more preferably 0.03 to 2 mass %, and even more preferably 0.05 to 1.5 mass %. When the dye content is in this range, a well-colored cured film can be obtained and etching resistance can be improved.

[0076] The dye may be a dye other than a dye having an anthraquinone skeleton and an amino group, a dye having a naphthalene skeleton and an amino group, a dye having a triarylmethane structure, and a dye having a phthalocyanine skeleton. However, it is preferable that the dye having an anthraquinone skeleton and an amino group, the dye having a naphthalene skeleton and an amino group, and the dye having a phthalocyanine skeleton are contained in a larger amount than the other dyes. One type of dye may be used alone, or multiple types may be used in combination.

[0077] <Gelling Agent> The gelling agent can gel ink droplets that have landed on the oxide film and temporarily fix them (pin them). When the ink is pinned in a gel state, the ink is prevented from wetting and spreading, making it difficult for adjacent dots to coalesce, allowing for the formation of images with higher resolution. The ink of the present disclosure may contain only one type of gelling agent, or two or more types.

[0078] Examples of gelling agents include dialkyl ketones, fatty acid esters, fatty acid amides, oil gelling agents, etc., but the gelling agents used in the present disclosure preferably do not have acidic groups such as -OH or -COOH at the end of the alkyl chain. In other words, a gelling agent that does not have an acidic group does not necessarily mean a 100% pure gelling agent that is composed only of those that do not have acidic groups. A gelling agent that does not have an acidic group also includes cases in which a gelling agent that has an acidic group is contained as an impurity to the extent that the intended effect of the present invention is not impaired, and it is sufficient that the gelling agent has an acid value of 10 mgKOH / g or less.

[0079] Particularly preferred gelling agents include at least one compound selected from compounds having structures represented by the following general formulas (G1) and (G2): General formula (G1): R １ -CO-R ２ General formula (G2): R ３ -COO-R ４ [In the formula, R １ ~R ４ each independently represents an alkyl chain having 12 or more carbon atoms, which has a linear portion and may be branched.

[0080] The ketone wax represented by the general formula (G1) or the ester wax represented by the general formula (G2) has a linear or branched hydrocarbon group (alkyl chain) with 12 or more carbon atoms. This further enhances the crystallinity of the gelling agent, and creates more sufficient space in the house-of-card structure described below. As a result, ink media such as solvents and photopolymerizable compounds are more easily contained within the space, and the ink pinning ability is further enhanced. Furthermore, it is preferable that the linear or branched hydrocarbon group (alkyl chain) has 26 or less carbon atoms. When the carbon number is 26 or less, the melting point of the gelling agent does not increase excessively, and therefore there is no need to excessively heat the ink when ejecting the ink. From the above viewpoint, R １ and R ２ , or R ３ and R ４ It is particularly preferable that R is a linear hydrocarbon group having 12 to 23 carbon atoms. From the viewpoint of increasing the gelling temperature of the ink and gelling the ink more rapidly after landing, it is preferable that R １ Or R ２ Either or R ３ Or R ４ From the above viewpoint, it is preferable that either one of R is a saturated hydrocarbon group having 12 to 23 carbon atoms. １ and R ２ Both of these, or R ３ and R ４ It is more preferable that both of the groups are saturated hydrocarbon groups having 11 or more but less than 23 carbon atoms.

[0081] Examples of the ketone wax represented by the general formula (G1) include dilignoceryl ketone (C24-C24), dibehenyl ketone (C22-C22), distearyl ketone (C18-C18), dieicosyl ketone (C20-C20), dipalmityl ketone (C16-C16), dimyristyl ketone (C14-C14), dilauryl ketone (C12-C12), lauryl myristyl ketone ( Examples of ketones include lauryl palmityl ketone (C12-C14), lauryl palmityl ketone (C12-C16), myristyl palmityl ketone (C14-C16), myristyl stearyl ketone (C14-C18), myristyl behenyl ketone (C14-C22), palmityl stearyl ketone (C16-C18), palmityl behenyl ketone (C16-C22), and stearyl behenyl ketone (C18-C22). The number of carbon atoms in the parentheses indicates the number of carbon atoms in each of the two hydrocarbon groups separated by the carbonyl group.

[0082] Commercially available examples of the ketone wax represented by general formula (G1) include Stearonne (manufactured by Alfa Aeser; Stearon) and 18-Pentatriacontanon (manufactured by Alfa Aeser), as well as Hentriacontan-16-on (manufactured by Alfa Aeser) and Kaowax T-1 (manufactured by Kao Corporation).

[0083] Examples of fatty acids or ester waxes represented by general formula (G2) include behenyl behenate (C21-C22), icosanoic acid icosyl (C19-C20), stearyl stearate (C17-C18), palmityl stearate (C17-C16), lauryl stearate (C17-C12), cetyl palmitate (C15-C16), stearyl palmitate (C15-C18), and the like. ), myristyl myristate (C13-C14), cetyl myristate (C13-C16), octyldodecyl myristate (C13-C20), stearyl oleate (C17-C18), stearyl erucate (C21-C18), stearyl linoleate (C17-C18), behenyl oleate (C18-C22), and arachidyl linoleate (C17-C20). The number of carbon atoms in the parentheses indicates the number of carbon atoms in each of the two hydrocarbon groups separated by the ester group.

[0084] Commercially available ester waxes represented by general formula (G2) include Unistar M-2222SL and Sperm Acetate, manufactured by NOF Corporation ("Unistar" is a registered trademark of the company), Exseparl SS, and Exseparl MY-M. Commercially available ester waxes include EMALEX CC-18 and EMALEX CC-10, manufactured by Kao Corporation ("Exseparl" is a registered trademark of the company). Commercially available ester waxes include Nippon Emulsion Co., Ltd. ("EMALEX" is a registered trademark of the company), Amreps PC, and Kokyu Alcohol Kogyo Co., Ltd. ("Amreps" is a registered trademark of the company). Since these commercially available products are often mixtures of two or more types, they may be separated and purified as necessary before being incorporated into the ink. Of these gelling agents, ketone waxes, ester waxes, higher fatty acids, higher alcohols, and fatty acid amides are preferred from the viewpoint of enhancing pinning properties.

[0085] The content of the gelling agent is preferably within a range of 0.5 to 5.0% by mass relative to the total mass of the ink. By setting the content of the gelling agent within this range, excellent etching resistance and plating resistance are achieved, and the solubility of the gelling agent in the solvent component and pinning effect are improved. From the above viewpoint, the content of the gelling agent in the inkjet ink is more preferably within a range of 0.5 to 2.5% by mass.

[0086] Furthermore, from the following viewpoint, it is preferable that the gelling agent crystallizes in the ink at a temperature equal to or lower than the gelling temperature of the ink. The gelling temperature is the temperature at which the gelling agent undergoes a phase transition from sol to gel and the viscosity of the ink suddenly changes when the ink that has been solated or liquefied by heating is cooled. Specifically, the solated or liquefied ink is cooled while its viscosity is measured using a viscoelasticity measuring device (e.g., MCR300, manufactured by Physica), and the temperature at which the viscosity suddenly increases can be determined to be the gelling temperature of the ink.

[0087] When a gelling agent crystallizes in an ink, a structure may be formed in which the ink medium, such as a solvent or a photopolymerizable compound, is encapsulated in a three-dimensional space formed by the gelling agent crystallized into a plate-like shape. This structure is hereinafter referred to as a "house of card structure." When a house of card structure is formed, the liquid ink medium is retained within the space, making it more difficult for ink droplets to wet and spread, thereby enhancing the pinning ability of the ink. Enhanced ink pinning ability reduces the likelihood of ink droplets landing on a recording medium coalescing, allowing for the formation of higher-resolution images. To form a house of card structure, it is preferable that the ink medium, such as the solvent or photopolymerizable compound in the ink, and the gelling agent are compatible. However, if the ink medium, such as the solvent or photopolymerizable compound in the ink, and the gelling agent are phase-separated, it may be difficult to form a house of card structure.

[0088] <Other Components> The ink of the present disclosure may further contain other components, including a polymerization inhibitor and a surfactant, as long as the effects of the present disclosure are obtained. Only one type of these components may be contained in the ink of the present disclosure, or two or more types may be contained.

[0089] (Polymerization Inhibitor) Examples of the polymerization inhibitor include (alkyl)phenols, hydroquinone, catechol, resorcinol, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiazine, p-benzoquinone, nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, cupferron, aluminum N-nitrosophenylhydroxyamine, tri-p-nitrophenylmethyl, N-(3-oxyanilino-1,3-dimethylbutylidene)aniline oxide, dibutyl cresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraldoxime, methyl ethyl ketoxime, and cyclohexanone oxime. Examples of commercially available polymerization inhibitors include Irgastab UV-10 (manufactured by BASF) and Genorad 18 (manufactured by Rahn AG).

[0090] The amount of the polymerization inhibitor can be set arbitrarily as long as the effects of the present disclosure can be obtained. The amount of the polymerization inhibitor can be, for example, 0.001% by mass or more and less than 1.0% by mass of the total ink.

[0091] (Surfactant) Examples of surfactants include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene-polyoxypropylene block copolymers; cationic surfactants such as alkylamine salts and quaternary ammonium salts; and silicone-based and fluorine-based surfactants.

[0092] Examples of silicone surfactants include polyether-modified polysiloxane compounds, specifically Tego Rad 2250 manufactured by Evonik, KF-351A, KF-352A, KF-642, and X-22-4272 manufactured by Shin-Etsu Chemical Co., Ltd., BYK307, BYK345, BYK347, and BYK348 manufactured by BYK ("BYK" is a registered trademark of the company), and TSF4452 manufactured by Momentive Performance Materials.

[0093] Fluorine-based surfactants refer to surfactants in which some or all of the hydrogen atoms bonded to the carbon atoms of the hydrophobic groups in ordinary surfactants have been substituted with fluorine. Examples of fluorine-based surfactants include Megafac F (manufactured by DIC Corporation) ("Megafac" is a registered trademark of DIC), Surflon (manufactured by AGC Sei Chemical Co., Ltd.) ("Surflon" is a registered trademark of AGC Sei Chemical Co., Ltd.), Fluorad FC (manufactured by 3M Corporation) ("Fluorad" is a registered trademark of 3M), Monflor (manufactured by Imperial Chemical Industries, Ltd.), Zonyls (manufactured by E.I. duPont Nemelas & Co., Ltd.), Licowet VPF (manufactured by Lubewerke-Hoechst), and FTERGENT (manufactured by Neos Corporation) ("FTERGENT" is a registered trademark of 3M).

[0094] The amount of surfactant can be set arbitrarily as long as the effects of the present disclosure can be obtained. The amount of surfactant can be, for example, 0.001% by mass or more and less than 1.0% by mass of the total ink.

[0095] <Physical Properties> When the ink of the present disclosure contains a gelling agent, it preferably has a phase transition point in the range of 40°C or higher and lower than 100°C. If the phase transition point is 40°C or higher, the ink quickly gels after landing on a recording medium, thereby improving pinning properties. Furthermore, if the phase transition point is lower than 100°C, the ink is easier to handle and has higher ejection stability. From the viewpoint of enabling the ink to be ejected at lower temperatures and reducing the load on the image forming apparatus, it is more preferable that the phase transition point of the ink of the present disclosure is in the range of 40 to 60°C.

[0096] The viscosity and phase transition point of the ink of the present disclosure at 40 to 90°C can be determined by measuring the temperature change of the dynamic viscoelasticity of the ink using a rheometer. In the present disclosure, these viscosity and phase transition points are values ​​obtained by the following method.

[0097] The ink of the present disclosure is heated to 100°C, and the viscosity is measured using a Physica MCR301 (manufactured by Anton Paar) at a shear rate of 1000 (1 / s). The ink is then cooled to 20°C under conditions of a shear rate of 11.7 (1 / s) and a temperature decrease rate of 0.1°C / s, to obtain a viscosity temperature curve. The viscosity at 40 to 90°C can be determined by reading the viscosities at 40 to 90°C from the viscosity temperature curve. The phase transition point can be determined as the temperature at which the viscosity reaches 200 mPa s from the viscosity temperature curve.

[0098] <Applications> The ink of the present disclosure can be used to form insulating films, protective films, etching resists, and plating resists in various fields, such as metal processing, electronic circuits, printed circuit boards, plate making, semiconductors, and color filters. In particular, the ink of the present disclosure is preferably used as an etching resist or plating resist, and is particularly preferably used as an etching resist because of its good removability to alkaline solutions. In order to be used to form an etching resist, the cured film formed by the ink needs to be configured to be removable with an alkaline solution or the like. In order to be used to form a plating resist, the cured film formed by the ink may be removed with a stripper containing an organic solvent or the like.

[0099] <Inkjet Recording Method> The inkjet recording method of the present disclosure is an inkjet recording method in which an actinic ray-curable inkjet ink is ejected onto a substrate and cured by actinic rays, and the actinic ray-curable inkjet ink of the present disclosure described above is used as the inkjet curable composition. Specifically, the inkjet recording method preferably includes: (1) a step of ejecting the ink of the present disclosure from a nozzle of an inkjet head and causing it to land on an oxide film on a substrate; and (2) a step of irradiating the ink that has landed on the oxide film with actinic rays to cure the ink. Hereinafter, a method for manufacturing a printed circuit board using the ink of the present disclosure to form an etching resist will be described as an example. FIGS. 1 to 4 are diagrams illustrating the process for manufacturing a printed circuit board using the ink of the present disclosure to form an etching resist.

[0100] <Step (1)> In FIG. 1, a conductive oxide film 2 is formed on a substrate 1, which is a recording medium. Droplets of ink are ejected from an inkjet head 5 onto the oxide film 2 shown in FIG. 1 and land at positions corresponding to the etching resist film 3 to be formed, thereby forming a pattern (see FIG. 2). The ejection method from the inkjet head may be either an on-demand method or a continuous method. On-demand inkjet heads may be electro-mechanical conversion types such as single-cavity type, double-cavity type, bender type, piston type, shear mode type, and shared wall type, or electro-thermal conversion types such as thermal inkjet type and bubble jet (registered trademark) type. Bubble jet is a registered trademark of Canon Inc.

[0101] Discharging ink droplets from an inkjet head in a heated state can improve discharge stability. The temperature of the ink when discharged is preferably within a range of 40 to 100°C, and more preferably within a range of 60 to 90°C to further improve discharge stability. In particular, it is preferable to discharge the ink at an ink temperature such that the viscosity of the ink is within a range of 8 to 15 mPa·s, more preferably within a range of 8 to 13 mPa·s.

[0102] In order to improve the ejection properties of the sol-gel phase transition ink from the inkjet head, it is preferable that the temperature of the ink when filled into the inkjet head be set to (gelation temperature + 10)°C to (gelation temperature + 30)°C of the ink. If the temperature of the ink inside the inkjet head is less than (gelation temperature + 10)°C, the ink will gel inside the inkjet head or on the nozzle surface, and the ejection properties of the ink will likely decrease. On the other hand, if the temperature of the ink inside the inkjet head exceeds (gelation temperature + 30)°C, the ink will become too hot, which may cause the ink components to deteriorate.

[0103] The method for heating the ink is not particularly limited. For example, at least one of the ink supply system, such as the ink tank constituting the head carriage, the supply pipe, and the anterior ink tank immediately before the head, the piping with a filter, and the piezo head can be heated by a panel heater, a ribbon heater, or heated water. From the viewpoints of printing speed and image quality, the volume of ink droplets when ejected is preferably within the range of 2 to 20 pL.

[0104] The substrate is not particularly limited, but examples thereof include copper-clad laminates of all grades (e.g., FR-4) made of materials such as paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / non-woven cloth epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, copper-clad laminates for high-frequency circuits using materials such as fluorine, polyethylene, PPO, cyanate ester, etc., as well as polyimide films, PET films, glass substrates, ceramic substrates, wafer plates, stainless steel plates, aluminum substrates, etc. Copper-clad laminates and aluminum substrates are particularly preferred. Examples of conductive oxide films include copper, gold, silver, aluminum, nickel, and ITO.

[0105] <Step (2)> In step (2), the ink that has been deposited on the oxide film in step (1) is irradiated with actinic rays to harden the ink and form an etching resist film. The actinic rays can be selected from, for example, electron beams, ultraviolet rays, α rays, γ rays, and X-rays, but ultraviolet rays are preferred. The ultraviolet rays can be irradiated at a wavelength of 395 nm using, for example, a water-cooled LED manufactured by Phoseon Technology. Using an LED as the light source can prevent poor ink curing due to the ink melting due to the radiant heat of the light source.

[0106] The ultraviolet irradiation is carried out such that the peak irradiance of ultraviolet light having a wavelength in the range of 360 to 410 nm on the surface of the resist film is preferably 0.5 to 10 W / cm ２ in the range of 1 to 5 W / cm ２ From the viewpoint of suppressing the radiation heat from being irradiated onto the ink, the amount of light irradiated onto the resist film is set to be in the range of 350 to 3000 mJ / cm.２ The irradiation with actinic rays can be carried out within 0.001 to 60 seconds after the ink has landed. The irradiation with actinic rays is preferably carried out within 0.001 to 1.0 seconds after the ink has landed, and more preferably within 0.001 to 0.5 seconds in order to form a highly precise resist film.

[0107] The irradiation of actinic rays may be carried out in two stages. First, the ink is pre-cured by irradiating it with actinic rays for 0.001 to 2.0 seconds after it lands, and then after all printing is completed, the ink is further cured by irradiating it with actinic rays. By dividing the irradiation of actinic rays into two stages, shrinkage of the recording material that occurs when the ink is cured is less likely to occur. As described above, an etching resist film is formed by the inkjet method. After the etching resist film is formed, a resist pattern such as a circuit, pattern, characters, or image is obtained on the substrate by etching.

[0108] (Etching Treatment) In the etching treatment, first, the oxide film 2 not covered by the etching resist film 3 is removed with an acid etching solution (see FIG. 3). The etching resist film 3 covering the oxide film 2 is then stripped with an alkaline solution, thereby obtaining fine, highly accurate line drawings such as circuits, patterns, letters, and images (see FIG. 4). The reaction mechanism of wet etching using a liquid is to corrode and remove the substrate. For example, in the case of a metal substrate, etching is performed by forcibly corroding the metal by oxidizing and dissolving it. In other words, etching resistance refers to a protective function that inhibits corrosion of the substrate. A cured film produced using the ink of the present disclosure can inhibit corrosion of the substrate in the area where the cured film is applied, thereby imparting etching resistance. Examples of etching solutions include aqueous ferric chloride solutions, aqueous cupric chloride solutions, aqueous ammonia copper solutions, highly concentrated aqueous sodium hydroxide solutions, highly concentrated hydrochloric acid, hydrogen fluoride water, and aqueous ferric nitrate solutions. The etching solutions exemplified above may be used alone or in combination. The etching treatment can be carried out, for example, under conditions of 40 to 60° C. For example, it is preferable to mainly use an aqueous ferric chloride solution for etching copper. When copper is immersed in the aqueous ferric chloride solution, the copper dissolves in the aqueous ferric chloride solution, and the iron is replaced by copper to generate copper chloride, which progresses the etching of the copper substrate.

[0109] Examples of the alkaline solution include an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, an aqueous solution of tetramethylammonium hydroxide, and an aqueous solution of sodium (meta)silicate.

[0110] The ink of the present disclosure can also be used to form a plating resist. Figures 5 to 8 are diagrams illustrating the manufacturing process for a printed circuit board when the ink of the present disclosure is used to form a plating resist. Similar to the formation of the etching resist described above, ink droplets are ejected from an inkjet head 5 onto a substrate 1, which is a recording medium (see Figure 5). Then, the ink is allowed to land at positions corresponding to the plating resist film 3a to be formed, thereby forming a pattern (see Figure 6). The landed ink is then irradiated with actinic light rays, and the ink is cured to form a plating resist film 3a. After the plating resist film 3a is formed, a plating layer 4 is formed on the substrate 1 by performing the following plating process, as shown in Figure 7.

[0111] (Plating Treatment) For the plating treatment, any of electrolytic plating, electroless plating in an acidic bath, a neutral bath, and an alkaline bath can be suitably used. As the plating treatment, electroless plating is preferred, and an acidic bath is also preferred. By plating, a plating layer is formed on the portion of the metal layer exposed on the surface of the substrate (the portion other than the plating resist film). The plating layer is formed of metals such as, but not limited to, gold, silver, platinum, rhodium, palladium, copper, and nickel. The plating treatment process preferably includes a nickel plating process or a gold plating process. The nickel plating process is preferred from the viewpoint of protecting the copper and being suitable for the soldering process. The gold plating process is preferred from the viewpoint of the long-term stability of the nickel plating layer. Specifically, the plating treatment process preferably includes a degreasing process using a weak alkaline solution, an acid cleaning process, a palladium activation process, a nickel plating process, a gold plating process, etc. The plating process includes immersion in an acid solution and immersion at high temperatures of about 60 to 90°C, and therefore forms a plating layer that simultaneously has acid resistance and heat resistance as coating film properties, thereby improving plating resistance.

[0112] After the plating layer 4 is formed, the plating resist film 3a other than the plating layer 4 is stripped off with an organic solvent or a water-based stripping solution containing an organic solvent, as shown in Fig. 8. Usable organic solvents include not only solvents that are readily soluble in water, but also poorly soluble or water-insoluble organic solvents.Specific examples of organic solvents include linear, branched, secondary, or polyhydric alcohols such as ethanol, propanol, 2-propanol, butanol, 2-butanol, hexanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, trimethylolpropane, neopentyl glycol, glycerin, 1,2,4-butanetriol, 1,2-butanediol, 1,4-butanediol, and diacetone alcohol; ethylene glycol alkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether; polyethylene glycol alkyl ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and triethylene glycol monomethyl ether; propylene glycol alkyl ethers such as propylene glycol monomethyl ether; polypropylene glycol alkyl ethers such as dipropylene glycol monomethyl ether; ethylene glycol monomethyl ether acetate; Acetate esters such as glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, glycerin monoacetate, glycerin diacetate, etc.; lactic acid esters such as ethyl lactate, butyl lactate, etc.; adipic acid esters such as diethyl adipate, dibutyl adipate, etc.; phthalate esters such as diethyl phthalate, dibutyl phthalate, etc.; dialkyl glycol ethers such as diethylene glycol diethyl ether; ketones such as methyl ethyl ketone, cyclohexanone, isophorone, etc. aromatic hydrocarbons such as benzene, toluene, and xylene; aromatic alcohols such as benzyl alcohol; petroleum-based aromatic mixed solvents such as the Swazol series (manufactured by Maruzen Petrochemical Co., Ltd.) and the Solvesso series (manufactured by Exxon Chemical Co.); or n-hexane, cyclohexane, tetrahydrofuran, 1-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone), methyl ethyl ketone, 2-pyrrolidone, γ-butyrolactone, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, and dimethylacetamide.These organic solvents may be used alone or in combination of two or more.

[0113] Among the above organic solvents, aromatic alcohols such as benzyl alcohol, 1-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone), 2-pyrrolidone, γ-butyrolactone, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, methyl ethyl ketone, and dimethylacetamide are preferred. Organic solvents that can be preferably used are aromatic alcohols such as benzyl alcohol, 1-methyl-2-pyrrolidone, and 2-pyrrolidone, which are preferred because of their high permeability to UV-curable inks containing (meth)acrylate monomers having a cyclic imide group. Particularly preferred organic solvents are aromatic alcohols such as benzyl alcohol. It is preferred that the mass ratio (% by mass) of the content of the (meth)acrylate monomer having a cyclic imide group to the content (% by mass) of the polymerizable monomer having an acidic group ((meth)acrylate monomer having a cyclic imide group / polymerizable monomer having an acidic group) be within a range of 0.5 to 30, as this provides particularly high permeability. As long as the stripping liquid contains an aromatic alcohol, it may be either a water-based stripping liquid or an organic solvent-based stripping liquid.

[0114] The etching resist film after the etching treatment is stripped off with an alkaline solution, or the plating resist film after the plating treatment is stripped off with a stripper containing an organic solvent, can be stripped off by an immersion method, a spray stripping method, or an immersion and ultrasonic irradiation method. When stripping is performed by an immersion method, for example, the substrate may be immersed in an alkaline solution or a stripper containing an organic solvent at 40 to 60°C for 1 to 60 minutes. This operation may be performed only once, or the same operation may be performed multiple times. Furthermore, after the stripping step, the substrate may be washed with the alkaline solution, organic solvent, or other solvent used in the stripping step.

[0115] The present disclosure will be specifically described below using examples, but the present disclosure is not limited thereto. In the following examples, unless otherwise specified, operations were performed at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

[0116] [Inkjet Ink Materials] The following materials were used for the inkjet ink.

[0117]

[0118]

[0119] [Preparation of Ink] The ink components shown in the table below were mixed, and the mixture was filtered through a 3 μm Teflon (registered trademark) membrane filter manufactured by ADVANTEC while being heated to 80° C., to obtain inks 1 to 43.

[0120]

[0121]

[0122]

[0123]

[0124]

[0125]

[0126] [Inkjet Pattern Formation] The prepared ink was loaded into an inkjet recording device equipped with an inkjet recording head equipped with piezo-type inkjet nozzles. The inkjet recording head used was a KM1800iSHC-C (manufactured by Konica Minolta, Inc.). Using this device, a pattern was formed on a copper-clad laminate for printed wiring boards (FR-4, 1.6 mm thick, 150 mm x 95 mm). The ink supply system consisted of an ink tank, an ink flow path, a sub-ink tank immediately before the inkjet recording head, piping with a metal filter, and a piezo-electric head. The ink was heated to 80°C from the ink tank to the head. The ink temperature inside the inkjet head was heated to 80°C using an inkjet recording device, with a droplet volume of 6.0 pL. A 20 mm x 50 mm solid pattern was printed on the substrate to a thickness of 20 μm. Thereafter, a Fire Jet™ FJ100 (manufactured by Phoseon Technology, wavelength 395 nm) was used at 2 W / cm ２ , 3000mJ / cm ２ The ink layer was cured by irradiation so as to obtain a cured film.

[0127] [Evaluation] <Etching Resistance> A sample of the cured film was immersed in an aqueous solution of ferric chloride at 60°C for 30 minutes, then rinsed with water and dried. After that, adhesive tape was applied and peeled off to observe the peeling state of the cured film. The etching resistance was evaluated according to the following criteria. Criteria A, B, and C below were determined to be acceptable for practical use. (Criteria) A: No peeling occurred. B: No peeling occurred, but some discoloration occurred. C: Slight peeling occurred at the edges, but the coating film remained for the most part and no peeling occurred. D: Peeling occurred over the entire surface.

[0128] <Alkali Removal Properties> A sample of the cured film was immersed in a 3% aqueous sodium hydroxide solution at 40°C, rinsed with water, dried, and then visually observed for dissolution and removability of the cured film. The alkali removability was evaluated according to the following criteria. Criteria A, B, and C below were deemed acceptable for practical use. (Criteria) A: Peeled within 1 minute. B: Peeled in 1 to 2 minutes. C: Peeled in 2 to 3 minutes. D: No peeling even after immersion for 3 minutes.

[0129] <Plating Resistance> The cured film sample was treated in the following five steps to obtain a plated sample. (First Step) The sample was immersed in a 0.5% aqueous solution of ACL-009 (manufactured by Uemura Kogyo Co., Ltd.) as a weak alkaline cleaner for 5 minutes at 50°C, followed by rinsing with pure water for 3 minutes. (Second Step) The sample was immersed in a 50 mL / L aqueous sulfuric acid solution at room temperature for 3 minutes, followed by rinsing with pure water for 3 minutes. (Third Step) The sample was immersed in the prepared activation solution for 2 minutes at 25°C, followed by rinsing with pure water for 2 minutes. The activation solution was prepared as follows: 30 mL of 62.5% by mass diluted sulfuric acid was slowly mixed with 700 mL of ion-exchanged water while stirring. After confirming that the liquid temperature was 40°C or below, 100 mL of Accemalta MNK-4-M (manufactured by Uemura Kogyo Co., Ltd.) was added and stirred, and 170 mL of ion-exchanged water was added to prepare the activation solution. (Fourth Step) The specimen was immersed in the prepared nickel plating solution at 80°C for 10 minutes with stirring, and then rinsed with pure water for 3 minutes. The nickel plating solution was prepared as follows: 150 mL of NPR-4-M (manufactured by Uemura Kogyo Co., Ltd.) and 45 mL of NPR-4-A (manufactured by Uemura Kogyo Co., Ltd.) were added to 500 mL of ion-exchanged water, and 305 mL of ion-exchanged water was added and heated to 80°C with stirring. Then, 3 mL of NPR-4-D (manufactured by Uemura Kogyo Co., Ltd.) was added and stirred to prepare a nickel plating solution. (Fifth Step) The specimen was immersed in the prepared gold plating solution at 80°C for 3 minutes with stirring, and then rinsed with pure water for 3 minutes to obtain a plated sample. The gold plating solution was prepared as follows. To 500 mL of ion-exchanged water, 75 mL of TAM-LCM-75 (manufactured by Uemura Kogyo Co., Ltd.) and 45 mL of TAM-LCR (manufactured by Uemura Kogyo Co., Ltd.) were added and stirred. Then, 0.5 mL of a potassium cyanide aqueous solution (100 g / L concentration) was added and stirred, 10 mL of a separately prepared gold-containing solution was added and stirred, and 350 mL of ion-exchanged water was added. The pH of the prepared gold plating solution was adjusted to 5.2. The gold-containing solution was prepared by dissolving 0.5 g of KCN and 147 g of potassium aurous cyanide in 1000 mL of ion-exchanged water. A cross-cut tape peel test was performed on the resulting plated samples. The number of remaining cross-cuts out of 100 was counted, and plating resistance was evaluated according to the following criteria. Criteria A, B, and C below were considered acceptable for practical use.(Criteria) A: The remaining number is 100 out of 100. B: The remaining number is 90 to 99 out of 100. C: The remaining number is 70 to 89 out of 100. D: The remaining number is 69 or less out of 100.

[0130] <Ejection Stability> Using an inkjet recording device equipped with a piezoelectric inkjet head (KM1800iSHC-C, manufactured by Konica Minolta, Inc.), continuous ejection (driving) was performed while circulating ink using the piezoelectric inkjet head under conditions of a droplet volume of 3.5 pL, a droplet speed of 7 m / s, an ejection frequency of 40 kHz, and a printing rate of 100%. 10 minutes after the start of driving, the number of nozzles that had ejection problems was counted. Ejection stability was evaluated according to the following criteria. Criteria A, B, and C below were considered acceptable for practical use. (Criteria) A: The number of nozzles that had ejection problems was 0 or more but less than 2 nozzles. B: The number of nozzles that had ejection problems was 2 or more but less than 5 nozzles. C: The number of nozzles that had ejection problems was 5 or more but less than 20 nozzles. D: The number of nozzles that had ejection problems was 20 or more nozzles.

[0131] <Recyclability> Instead of the copper-clad laminate for printed wiring boards, a 20 μm thick cured film was formed using a corona-equipped PP sheet for carriers manufactured by Okamoto Corporation in the same manner as in the inkjet pattern formation described above. The obtained cured film was then immersed in a 10% NaOH aqueous solution, and recyclability was evaluated according to the following criteria. Criteria A, B, and C below were determined to be acceptable for practical use. (Criteria) A: The cured film peeled from the PP sheet within 1 minute. B: The cured film peeled from the PP sheet in 1 minute or more but less than 2 minutes. C: The cured film peeled from the PP sheet in 2 minutes or more but less than 3 minutes. D: The cured film did not peel from the PP sheet even after immersion for 3 minutes.

[0132]

[0133] As shown by the above results, the ink of the present disclosure is superior to the ink of the comparative example in terms of etching resistance, alkali strippability, plating resistance, ejection stability, and recyclability.

[0134] The present disclosure can be used for an actinic ray-curable inkjet ink and inkjet recording method that can simultaneously satisfy etching resistance and strippability, and also has excellent plating resistance, ejection stability, and recyclability.

[0135] REFERENCE SIGNS LIST 1 substrate 2 oxide film 3 etching resist film 3a plating resist film 4 plating layer 5 inkjet head

Claims

1. An actinic energy ray-curable inkjet ink that is cured by actinic energy rays, the actinic energy ray-curable inkjet ink containing: a (meth)acrylate monomer having a cyclic imide group; a polymerizable monomer having an acidic group; and a polymerization initiator.

2. The actinic radiation-curable inkjet ink according to claim 1, wherein the mass ratio (% by mass) of the content of the (meth)acrylate monomer having a cyclic imide group relative to the entire ink to the content (% by mass) of the polymerizable monomer having an acidic group relative to the entire ink ((meth)acrylate monomer having a cyclic imide group / polymerizable monomer having an acidic group) is within a range of 0.5 to 30.

3. The actinic ray-curable ink-jet ink according to claim 1, wherein the (meth)acrylate monomer having a cyclic imide group is N-acryloyloxyethylhexahydrophthalimide.

4. The actinic ray-curable ink-jet ink according to claim 1, wherein the polymerizable monomer having an acidic group contains a polymerizable monomer having a carboxyl group.

5. The actinic ray-curable ink-jet ink according to claim 1, wherein the polymerizable monomer having an acidic group is 2-carboxyethyl acrylate.

6. The actinic radiation curable inkjet ink according to claim 1, which contains a polymerizable monomer having an alicyclic structure.

7. The actinic ray-curable ink-jet ink according to claim 1, which contains a monomer having an acrylamide group.

8. The actinic radiation curable inkjet ink according to claim 7, wherein the monomer having an acrylamide group is acryloylmorpholine.

9. The actinic ray-curable ink-jet ink according to claim 1, which contains a polyfunctional monomer.

10. The actinic radiation curable ink-jet ink according to claim 1, which contains a dye.

11. The actinic radiation curable ink-jet ink according to claim 1, which contains a gelling agent.

12. The actinic ray-curable ink-jet ink according to claim 1, which is used as an etching resist.

13. The actinic ray-curable ink-jet ink according to claim 1, which is used as a plating resist.

14. An inkjet recording method comprising ejecting an actinic ray-curable inkjet ink onto a substrate and curing the ink with actinic rays, wherein the actinic ray-curable inkjet ink according to any one of claims 1 to 13 is used as the actinic ray-curable inkjet ink.

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