Inkjet ink composition, recorded matter, inkjet recording method, and inkjet recording system

Abstract

An inkjet ink composition which is curable by at least active energy rays or heat, and which contains (A) a compound having a structure represented by general formula (1) or a salt thereof, (B) a (meth) acrylic acid ester having a (meth) acrylic acid equivalent in the range of 71-110, and (C) a (meth) acrylic acid ester having a (meth) acrylic acid equivalent in the range of 200-500. General formula (1) # imgabs0 # [In general formula (1), X represents a substituent having at least one group selected from the group consisting of an acryloyl group, a methacryloyl group, an allyl group, a vinyl group, and derivatives thereof at a 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. And R1 represents an unsubstituted alkylene group having 1-6 carbon atoms].

Description

Technical Field

[0001] The present invention relates to an inkjet ink composition, a recorded material, an inkjet recording method, and an inkjet recording system. In particular, the present invention relates to an inkjet ink composition that can produce a cured product having excellent coating properties, adhesion, coating film hardness, and chemical resistance for inkjet use. Background Art

[0002] In order to protect the circuit pattern on the printed wiring board of the printed circuit board, ink is applied and cured to form an insulating film (solder resist). As a method for forming the solder resist, for example, an inkjet method is known. Specifically, inkjet ink (hereinafter also referred to as "ink") is applied, cured with light, and then cured with heat.

[0003] For solder resists formed by inkjet printing, high adhesion to the copper substrate is required. Patent Document 1 discloses an inkjet ink for etching resist containing a photopolymerizable compound having an acidic group. As photopolymerizable compounds having an acidic group, carboxyl groups, phosphoric acid groups, and sulfonic acid groups are used. By using these, high adhesion to the copper substrate can be obtained. However, when photopolymerizable compounds having phosphoric acid groups and sulfonic acid groups are used, the viscosity and particle size of the ink are easily increased due to pigment aggregation. In particular, when the ink bag or inkjet head is retained at high temperature, there is a problem of easy fluctuation in discharge volume and clogging of the inkjet head filter.

[0004] In addition, when using a photopolymerizable compound having a carboxyl group, the viscosity and particle size are less likely to increase compared to a phosphate group or a sulfonic acid group. However, when using a photopolymerizable compound having a carboxyl group, there is a problem that it is difficult to obtain sufficient coating hardness as a resist film.

[0005] Patent Document 2 discloses an inkjet ink using a bifunctional (meth)acrylate compound (a (meth)acrylate compound with a low (meth)acrylate equivalent) having a weight-average molecular weight of less than 500. Inclusion of such a (meth)acrylate compound with a low (meth)acrylate equivalent can achieve sufficient coating film hardness.

[0006] However, there is a problem in that chemical resistance (acid resistance) deteriorates simply by containing such a photopolymerizable compound having a carboxyl group and a (meth)acrylate compound having a low (meth)acrylic acid equivalent.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-37645

[0010] Patent Document 2: Japanese Patent Application Publication No. 2019-167467 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] The present invention has been made in view of the above problems and circumstances, and aims to provide an inkjet ink composition, a recorded material, an inkjet recording method, and an inkjet recording system that can produce a cured product having excellent coating properties, adhesion, coating film hardness, and chemical resistance for inkjet use.

[0013] Means for solving problems

[0014] In order to solve the above-mentioned problems, the present inventors, while studying the causes of the above-mentioned problems, discovered the importance of using a compound (A) having a specific structure having a carboxyl group, a (meth)acrylate (B) with a low (meth)acrylate equivalent, and a (meth)acrylate (C) with a high (meth)acrylate equivalent in combination.

[0015] That is, the above-mentioned problems according to the present invention are solved by the following means.

[0016] 1. An inkjet ink composition that is curable at least by active energy rays or heat, comprising:

[0017] A compound having a structure represented by the following general formula (1) or a salt thereof (A),

[0018] (Meth)acrylate (B) having a (meth)acrylic acid equivalent within a range of 71 to 110,

[0019] (Meth)acrylate (C) having a (meth)acrylic acid equivalent within the range of 200 to 500.

[0020] [Chemistry 1]

[0021] General formula (1)

[0022]

[0023] [In the above general formula (1), X represents a substituent having at least one substituent selected from acryloyl, methacryloyl, allyl, vinyl and derivatives thereof at the terminal.

[0024] 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.

[0025] R1 represents an unsubstituted alkylene group having 1 to 6 carbon atoms.]

[0026] 2. The inkjet ink composition according to item 1, wherein, in the general formula (1), X represents a substituent having at least one substituent selected from derivatives of acryloyl or methacryloyl groups at the terminal.

[0027] 3. The inkjet ink composition according to item 1, wherein, in the above general formula (1), Q represents an oxygen atom.

[0028] 4. The inkjet ink composition according to item 1, wherein, in the general formula (1), R1 represents an unsubstituted alkylene group having 1 or 2 carbon atoms.

[0029] 5. The inkjet ink composition according to item 1, wherein the (meth)acrylate (C) having a (meth)acrylic acid equivalent within a range of 200 to 500 has 7 or less (meth)acryloyl groups.

[0030] 6. The inkjet ink composition according to item 1, wherein the (meth)acrylate (C) having a (meth)acrylic acid equivalent in the range of 200 to 500 has a molecular weight in the range of 200 to 2,000.

[0031] 7. The inkjet ink composition according to item 1, wherein the (meth)acrylate (C) having a (meth)acrylic acid equivalent within a range of 200 to 500 contains any one of an ethylene oxide modified portion, a propylene oxide modified portion, and an ε-caprolactone modified portion.

[0032] 8. The inkjet ink composition according to item 1, wherein the (meth)acrylate (C) having a (meth)acrylic acid equivalent within a range of 200 to 500 is an ε-caprolactone-modified product of erythritol hexaacrylate.

[0033] 9. The inkjet ink composition according to item 1, wherein the (meth)acrylate (B) having a (meth)acrylic acid equivalent within a range of 71 to 110 is erythritol hexaacrylate or dipentaerythritol pentaacrylate.

[0034] 10. The inkjet ink composition according to item 1, further comprising a gelling agent.

[0035] 11. The inkjet ink composition according to item 1, which is used as an inkjet ink for forming a solder resist pattern on a printed circuit board.

[0036] 12. A recorded matter, wherein the inkjet ink composition according to any one of items 1 to 11 is cured by at least active energy rays or heat.

[0037] 13. An inkjet recording method, which is an inkjet recording method using an inkjet ink composition, comprising: using the inkjet ink composition described in any one of items 1 to 11, and discharging the above-mentioned inkjet ink composition from an inkjet head so that it falls on the recording medium; and a process of curing the above-mentioned inkjet ink composition that falls on the above-mentioned recording medium by at least active energy rays or heat.

[0038] 14. An inkjet recording system, which is an inkjet recording system using an inkjet ink composition, comprising: an inkjet head that uses the inkjet ink composition described in any one of items 1 to 11 and discharges the above-mentioned inkjet ink composition; an active energy ray irradiation portion that irradiates active energy rays to at least the above-mentioned inkjet ink composition that falls on a recording medium, or a heating portion that heats the above-mentioned inkjet ink composition.

[0039] Effects of the Invention

[0040] The above-mentioned means of the present invention can provide an inkjet ink composition capable of producing a cured product having excellent coating properties, adhesion, coating film hardness, and chemical resistance for inkjet use. In addition, a recorded article, an inkjet recording method, and an inkjet recording system using the inkjet ink composition can be provided.

[0041] The mechanism of manifestation and action of the effects of the present invention are not yet clear, but are presumed as follows.

[0042] Generally, when a compound having an ester bond (or amide bond) is heated in the presence of water and an acid, it hydrolyzes to produce an alcohol (or amine) and a carboxylic acid. This reaction is an equilibrium reaction.

[0043] The compound or its salt (A) having a structure represented by the general formula (1) in the present invention has a dicarboxylic acid structure. Therefore, by including the compound or its salt (A) in the ink, it coordinates with the metal substrate and can adhere more firmly than general carboxylic acid acrylates.

[0044] The ink of the present invention also contains a (meth)acrylate (B) having a (meth)acrylate equivalent weight of 71 to 110, thereby increasing the crosslinking density and the hardness of the resulting coating film. The lower limit of the (meth)acrylate equivalent weight of the (meth)acrylate (B) being 71 is based on the molecular weight of the acryloyl group (CH2CHCO2). The upper limit of the (meth)acrylate equivalent weight is set to 110 to achieve high hardness.

[0045] Furthermore, the ink of the present invention contains a (meth)acrylate (C) with a (meth)acrylate equivalent weight within the range of 200 to 500, thereby reducing reactivity and providing excellent chemical resistance when formed into a coating film. The lower limit of the (meth)acrylate equivalent weight of the (meth)acrylate (C) is set at 200 for chemical resistance purposes. Furthermore, the upper limit of the (meth)acrylate equivalent weight is set at 500, as excessively high (meth)acrylate equivalent weights result in reduced hardness. DETAILED DESCRIPTION

[0046] The inkjet ink composition of the present invention is an inkjet ink composition that is cured by at least active energy rays or heat, and contains: a compound having a structure represented by the following general formula (1) or a salt thereof (A); a (meth)acrylate (B) having a (meth)acrylate equivalent in the range of 71 to 110; and a (meth)acrylate (C) having a (meth)acrylate equivalent in the range of 200 to 500.

[0047] [Chemistry 2]

[0048] General formula (1)

[0049]

[0050] [In the above general formula (1), X represents a substituent having at least one substituent selected from acryloyl, methacryloyl, allyl, vinyl and derivatives thereof at the terminal.

[0051] 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.

[0052] R1 represents an unsubstituted alkylene group having 1 to 6 carbon atoms.]

[0053] This feature is a common or corresponding technical feature of the following embodiments.

[0054] As an embodiment of the present invention, preferably, in the general formula (1), X represents a terminal substituent having at least one substituent selected from derivatives of acryloyl or methacryloyl groups. This can enhance the reactivity of the compound (A) having a structure represented by the general formula (1) or its salt (A), thereby improving adhesion.

[0055] In the general formula (1), Q preferably represents an oxygen atom in order to improve adhesion.

[0056] Furthermore, in the general formula (1), it is preferred that R1 represents an unsubstituted alkylene group having 1 or 2 carbon atoms in order to improve adhesion.

[0057] In terms of chemical resistance, the (meth)acrylate having a (meth)acrylic acid equivalent within the range of 200 to 500 preferably has 7 or less (meth)acryloyl groups.

[0058] The molecular weight of the (meth)acrylate having a (meth)acrylic acid equivalent of 200 to 500 is preferably 200 to 2000. When the molecular weight is within the above range, the ink viscosity is within an appropriate range, inkjet discharge is stable, and coating properties are excellent.

[0059] The (meth)acrylates having a (meth)acrylic acid equivalent of 200 to 500 preferably contain any one of an ethylene oxide-modified moiety, a propylene oxide-modified moiety, and an ε-caprolactone-modified moiety. This provides the (meth)acrylates with a (meth)acrylic acid equivalent of 71 to 110, resulting in improved compatibility.

[0060] In particular, the (meth)acrylate having a (meth)acrylic acid equivalent within a range of 200 to 500 is preferably an ε-caprolactone-modified product of erythritol hexaacrylate.

[0061] The (meth)acrylate having a (meth)acrylic acid equivalent of 71 to 110 is preferably erythritol hexaacrylate or dipentaerythritol pentaacrylate, thereby achieving high coating film hardness.

[0062] In order to temporarily fix the ink on the recording medium in a gelled state and suppress the wetting and spreading of the ink, it is preferable to further contain a gelling agent. Furthermore, by reducing the water absorption of the ink, the hydrolysis of the compound having the structure represented by the general formula (1) or its salt (A) can be suppressed. As a result, the generation of precipitates can be suppressed, and the ejection performance of the inkjet can be improved.

[0063] The inkjet ink composition of the present invention is preferably used as an inkjet ink for forming a solder resist pattern used in a printed circuit board. Furthermore, the inkjet ink composition of the present invention is preferably used for a recorded material that is cured by at least active energy rays or heat.

[0064] The inkjet recording method of the present invention is an inkjet recording method using an inkjet ink composition, comprising: a process of using the above-mentioned inkjet ink composition and discharging the above-mentioned inkjet ink composition from an inkjet head so that it falls on a recording medium; and a process of curing the inkjet ink composition that falls on the recording medium by at least active energy rays or heat.

[0065] This makes it possible to obtain a cured product (recorded material) that is excellent in coating properties, adhesion, coating film hardness, and chemical resistance for inkjet printing.

[0066] The inkjet recording system of the present invention is an inkjet recording system using an inkjet ink composition, comprising: an inkjet head that uses the above-mentioned inkjet ink composition and discharges the above-mentioned inkjet ink composition; an active energy ray irradiation part that irradiates active energy rays to the above-mentioned inkjet ink composition that falls on a recording medium, or a heating part that heats the inkjet ink composition.

[0067] This makes it possible to obtain a cured product (recorded material) that is excellent in coating properties, adhesion, coating film hardness, and chemical resistance for inkjet printing.

[0068] Hereinafter, the present invention and its constituent elements and forms and modes for carrying out the present invention will be described. It should be noted that in this application, "to" is used to mean that the numerical values described before and after it are included as the lower limit and the upper limit.

[0069] [Inkjet ink composition of the present invention]

[0070] The inkjet ink composition of the present invention is an inkjet ink composition that is cured by at least active energy rays or heat, and contains:

[0071] A compound having a structure represented by the following general formula (1) or a salt thereof (A),

[0072] (Meth)acrylate (B) having a (meth)acrylic acid equivalent within a range of 71 to 110, and

[0073] (Meth)acrylate (C) having a (meth)acrylic acid equivalent within the range of 200 to 500.

[0074] [Chemistry 3]

[0075] General formula (1)

[0076]

[0077] [In the above general formula (1), X represents a substituent having at least one substituent selected from acryloyl, methacryloyl, allyl, vinyl and derivatives thereof at the terminal.

[0078] 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.

[0079] R1 represents an unsubstituted alkylene group having 1 to 6 carbon atoms.]

[0080] The inkjet ink composition of the present invention functions in various fields, such as metalworking, electronic circuits, printed circuit boards, platemaking, semiconductors, and color filters, by forming an insulating film (solder resist) after application to a substrate and curing with light or heat. Furthermore, since the photocuring layer can be removed with alkali, it also functions as an etching resist used when forming etching patterns on substrates.

[0081] Specifically, the inkjet ink composition of the present invention is used to pattern a conductive oxide film of copper, zinc, or other materials formed on a substrate by inkjet printing, and then cured with light to form a resist film. Subsequently, an acidic etching solution is used to remove the oxide film from the portions not covered by the resist film, and an alkali is used to remove the resist film covering the oxide film, thereby forming a fine circuit or pattern.

[0082] In addition to the above-mentioned applications, it can be preferably used mainly for the purpose of patterning a film having both adhesion and hardness on a substrate having an inorganic surface such as metal or glass.

[0083] The inkjet ink composition of the present invention is curable by at least active energy rays or heat. The inkjet ink composition may be curable solely by active energy rays, solely by heat, or by both active energy rays and heat.

[0084] "Active energy rays" are radiation (electromagnetic waves and particle rays) that impart energy to reaction initiating species that generate polymerization reactions, etc., in the ink composition upon irradiation. These radiations include α-rays, γ-rays, X-rays, ultraviolet rays, electron beams, and the like. Among these, ultraviolet rays and electron beams are preferred, with ultraviolet rays being more preferred, from the perspectives of curing sensitivity and availability of equipment.

[0085] [1. Compound having a structure represented by general formula (1) or a salt thereof (A)]

[0086] The inkjet ink composition of the present invention (hereinafter also referred to as "ink") contains a compound having a structure represented by the above-mentioned general formula (1) or a salt thereof (A), thereby achieving high adhesion as a recorded object and suppressing fluctuations in viscosity and particle size during long-term storage and retention.

[0087] In the general formula (1), from the perspective of improving the reactivity of the compound having the structure represented by the general formula (1) or its salt (A) and improving the adhesion, X preferably represents a substituent having at least one substituent selected from derivatives of acryloyl or methacryloyl groups at the terminal.

[0088] Furthermore, in terms of reducing the viscosity of the ink and improving inkjet suitability, the substituent represented by X preferably has a total carbon number of 50 or less, more preferably 30 or less.

[0089] In the above general formula (1), Q preferably represents an oxygen atom in order to improve adhesion.

[0090] In the general formula (1), it is preferred that R1 represents an unsubstituted alkylene group having 1 or 2 carbon atoms in order to improve adhesion.

[0091] In addition, the compound having the structure represented by the general formula (1) is preferably not a salt in terms of improving compatibility with other monomers and the hydrophobicity of the ink and inhibiting hydrolysis of the compound having the structure represented by the general formula (1) or its salt (A).

[0092] Specific examples of the compound having a structure represented by the above-mentioned general formula (1) or a salt thereof are shown below, but the present invention is not limited thereto.

[0093] [Chemistry 4]

[0094]

[0095] [Chemistry 5]

[0096]

[0097] A higher content of the compound having a structure represented by the general formula (1) or its salt (A) contributes to better adhesion. However, if the content is too high, it acts as an acid catalyst and promotes its own hydrolysis. Therefore, the content is preferably within the range of 1 to 50% by mass, more preferably within the range of 3 to 20% by mass, relative to the total mass of the ink.

[0098] [2. (Meth)acrylate (B) having a (meth)acrylic acid equivalent within a range of 71 to 110]

[0099] The ink of the present invention contains a (meth)acrylate (B) having a (meth)acrylate equivalent of 71 to 110 (hereinafter also referred to as "low (meth)acrylate equivalent (meth)acrylate (B)") to increase the crosslinking density and improve the coating film hardness.

[0100] In the present invention, the "(meth)acrylic acid equivalent" is a value obtained by dividing the molecular weight of the (meth)acrylate monomer by the number of functional groups.

[0101] Therefore, monomers with lower acrylic acid equivalents have more crosslinking points in the molecule and are more reactive. Conversely, monomers with higher acrylic acid equivalents have lower reactivity and higher molecular weight, which tends to increase viscosity.

[0102] In the present invention, the “low (meth)acrylic acid equivalent” refers to a (meth)acrylate having a (meth)acrylic acid equivalent within the range of 71 to 110.

[0103] The (meth)acrylate (B) with a low (meth)acrylic acid equivalent according to the present invention can be a wide variety of known (meth)acrylates. The (meth)acrylate (B) with a low (meth)acrylic acid equivalent preferably has 3 to 6 (meth)acryloyl groups.

[0104] The (meth)acrylate (B) having a low (meth)acrylic acid equivalent may be used alone or in combination with the ink of the present invention.

[0105] Examples of the (meth)acrylate (B) with a low (meth)acrylic acid equivalent according to the present invention include (meth)acrylates having three (meth)acryloyl groups (also referred to as "trifunctional (meth)acrylates") such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate.

[0106] Examples of the (meth)acrylate having four (meth)acryloyl groups (also referred to as "tetrafunctional (meth)acrylate") include pentaerythritol tetra(meth)acrylate.

[0107] Examples of the (meth)acrylate having five (meth)acryloyl groups (also referred to as "pentafunctional (meth)acrylate") include dipentaerythritol penta(meth)acrylate.

[0108] Examples of the (meth)acrylate having six (meth)acryloyl groups (also referred to as “hexafunctional (meth)acrylate”) include dipentaerythritol hexa(meth)acrylate.

[0109] Among the above, the (meth)acrylate (B) with low (meth)acrylate equivalent according to the present invention is preferably erythritol hexaacrylate or dipentaerythritol pentaacrylate. Erythritol hexaacrylate and dipentaerythritol pentaacrylate have a high number of functional groups and a low (meth)acrylate equivalent, thereby improving the coating hardness.

[0110] Examples of commercially available products of the (meth)acrylate (B) having a low (meth)acrylic acid equivalent include M500 (DPPA, pentafunctional acrylate, manufactured by Sartomer), M600 (DPHA, hexafunctional acrylate, manufactured by Sartomer), EM235 (PET3A, trifunctional acrylate, manufactured by Changxing Chemical Co., Ltd.), EM241 (PET4A, quadrifunctional acrylate, manufactured by Changxing Chemical Co., Ltd.), and SR351 (TMPTA, trifunctional acrylate, manufactured by Sartomer).

[0111] In addition, the molecular weight and (meth)acrylic acid equivalent of these commercial products are described in the table of the examples mentioned later.

[0112] The content of the low (meth)acrylic acid equivalent (meth)acrylate (B) is preferably in the range of 0.1 to 20% by mass, more preferably 5 to 15% by mass, relative to the total ink. By adjusting the content within this range, the ink has an appropriate viscosity, which is more preferable from the perspective of inkjet coating properties.

[0113] [3. (Meth)acrylate (C) having a (meth)acrylic acid equivalent within a range of 200 to 500]

[0114] The ink of the present invention contains a (meth)acrylate (C) having a (meth)acrylate equivalent weight of 200 to 500 (hereinafter also referred to as a "high (meth)acrylate equivalent weight (meth)acrylate (C)"), which reduces the number of functional groups and lowers reactivity. As a result, a coating film with excellent chemical resistance (acid resistance) can be formed.

[0115] In the present invention, "high (meth)acrylic acid equivalent" refers to (meth)acrylates having a (meth)acrylic acid equivalent of 200 to 500. Preferably, the (meth)acrylic acid equivalent is within the range of 200 to 400, more preferably within the range of 200 to 300, and even more preferably within the range of 200 to 250. If the (meth)acrylic acid equivalent is below the lower limit, chemical resistance decreases. If the (meth)acrylic acid equivalent is exceeded, coating film hardness decreases.

[0116] The (meth)acrylate (C) having a high (meth)acrylic acid equivalent preferably has 7 or less (meth)acryloyl groups, thereby achieving high chemical resistance.

[0117] Furthermore, the molecular weight of the (meth)acrylate having a high (meth)acrylic acid equivalent is preferably within a range of 200 to 2000. This allows the ink to have an appropriate viscosity and improves inkjet coating properties.

[0118] Furthermore, the (meth)acrylate (C) having a high (meth)acrylic acid equivalent may be a modified product.

[0119] Examples of modified (meth)acrylates include ethylene oxide-modified (9 or 15) trimethylolpropane tri(meth)acrylate, propylene oxide-modified (meth)acrylates including propylene oxide-modified nonylphenol acrylate, and caprolactam-modified (meth)acrylates including caprolactam-modified dipentaerythritol hexa(meth)acrylate.

[0120] The (meth)acrylate as the modified product preferably contains any one of an ethylene oxide modified portion, a propylene oxide modified portion, and an ε-caprolactone modified portion.

[0121] Specifically, as the (meth)acrylate (C) having a high (meth)acrylic acid equivalent, an ε-caprolactone-modified product of erythritol hexaacrylate is preferred.

[0122] Examples of commercially available products of caprolactam-modified dipentaerythritol hexaacrylate include DPCA60 and DPCA120 (both hexafunctional acrylates, manufactured by Nippon Kayaku Co., Ltd.).

[0123] Examples of commercially available products of the (meth)acrylate (C) having a high (meth)acrylic acid equivalent include preferably DPCA60 (DP6CAHA, CA-modified, hexafunctional acrylate, manufactured by Nippon Kayaku Co., Ltd.), DPCA120 (DP12CAHA, CA-modified, hexafunctional acrylate, manufactured by Nippon Kayaku Co., Ltd.), EM2382 (TMP(EO)9TA, EO-modified, trifunctional acrylate, manufactured by Changxing Chemical Co., Ltd.), SR9035 (TMP(EO)15TA, EO-modified, trifunctional acrylate, manufactured by Sartomer Co., Ltd.), M1602 (NP(PO)2A, PO-modified, monofunctional acrylate, manufactured by Miwon Co., Ltd.), M280 (PEG400DA, bifunctional acrylate, manufactured by Miwon Co., Ltd.), and M2200 (BPA(EO)20DA, EO-modified, bifunctional acrylate, manufactured by Miwon Co., Ltd.).

[0124] In addition, the molecular weight and (meth)acrylic acid equivalent of these commercial products are described in the table of the examples mentioned later.

[0125] The content of the high (meth)acrylic acid equivalent (meth)acrylate (C) is preferably in the range of 0.1 to 20% by mass, more preferably 5 to 15% by mass, relative to the total ink. By adjusting the content within this range, the ink has an appropriate viscosity, which is more preferable from the perspective of inkjet coating properties.

[0126] [4. Polymerization initiator]

[0127] The ink of the present invention can be cured by radical polymerization or ionic polymerization. In the present invention, a radical polymerization initiator is preferably used as the polymerization initiator.

[0128] The ink of the present invention may contain only one type of polymerization initiator or two or more types of polymerization initiators.

[0129] Examples of the radical polymerization initiator include an α-cleavage type radical polymerization initiator (also referred to as a “Norishū I type polymerization initiator”) and a hydrogen abstraction type radical polymerization initiator (also referred to as a “Norishū II type polymerization initiator”).

[0130] The content of the α-cleavage radical polymerization initiator is preferably within a range of 0.3 to 6% by mass relative to the total mass of the ink of the present invention. Furthermore, the content of the hydrogen abstraction radical polymerization initiator is preferably within a range of 0.5 to 10% by mass relative to the total mass of the ink of the present invention.

[0131] An α-cleavage type free radical polymerization initiator is an initiator that cleaves upon photoexcitation and directly gives an initiating free radical.

[0132] In addition, hydrogen abstraction-type free radical polymerization initiators are activated by active energy rays (e.g., ultraviolet rays). Furthermore, they are photopolymerization initiators that generate free radicals by abstracting hydrogen from a second compound, with the second compound being the actual initiating free radical. This second compound is called a polymerization synergist or coinitiator.

[0133] In the present invention, both the α-cleavage type radical polymerization initiator and the hydrogen abstraction type radical polymerization initiator can be used alone or in combination.

[0134] Examples of the α-cleavage type radical polymerization initiator include acetophenone-based initiators, benzoin-based initiators, acylphosphine oxide-based initiators, benzil, and methylphenylglyoxylate.

[0135] Examples of acetophenone-based initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-methylthiophenyl)propane-1-one, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone.

[0136] Examples of the benzoin-based initiator include benzoin, benzoin methyl ether, and benzoin isopropyl ether.

[0137] Examples of the acylphosphine oxide-based initiator include 2,4,6-trimethylbenzoindiphenylphosphine oxide and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0138] Examples of the hydrogen abstraction type radical initiator include benzophenone-based initiators, thioxanthone-based initiators, aminobenzophenone-based initiators, 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-phenanthrenequinone, and camphorquinone.

[0139] Examples of benzophenone-based initiators include benzophenone, methyl-4-phenyl benzophenone o-benzoylbenzoate, 4,4′-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4′-methyl-diphenyl sulfide, acrylated benzophenone, 3,3′,4,4′-tetrakis(tert-butylperoxycarbonyl)benzophenone, and 3,3′-dimethyl-4-methoxybenzophenone.

[0140] Examples of the thioxanthone-based initiator include 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone.

[0141] Examples of aminobenzophenone-based initiators include Michler's ketone and 4,4'-diethylaminobenzophenone.

[0142] [5. Inhibitor]

[0143] The ink of the present invention preferably further contains a polymerization inhibitor. By containing a polymerization inhibitor, the adhesion between a plurality of curable compounds can be reduced.

[0144] In the present invention, the term "polymerization inhibitor" encompasses all compounds added to inhibit a polymerization reaction during the preparation of an ink containing a polymerizable compound or during storage after the preparation.

[0145] In the present invention, various conventionally known polymerization inhibitors can be used. From the viewpoint of the effect, the polymerization inhibitor is preferably an N-oxyl-based polymerization inhibitor, an o-tert-butyl group-containing phenolic polymerization inhibitor, or a polymerization inhibitor having two or more aromatic rings.

[0146] Moreover, among these, it is more preferable to contain an N-oxyl-based polymerization inhibitor from the viewpoint of adhesion to a printed wiring board.

[0147] In the ink of the present invention, the content of the polymerization inhibitor is preferably within a range of 0.05 to 0.5% by mass relative to the total mass of the ink.

[0148] [5-1. N-oxyl-based polymerization inhibitors]

[0149] Examples of N-oxyl-based polymerization inhibitors include 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethyl-piperidinyl-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidinyl-N-oxyl, 4-methoxy-2,2,6,6-tetramethyl-piperidinyl-N-oxyl, 4-acetoxy-2,2,6,6-tetramethyl-piperidinyl-N-oxyl, and Irgastab (registered trademark) UV10 (manufactured by BASF).

[0150] [5-2. Phenolic polymerization inhibitor]

[0151] Examples of phenolic polymerization inhibitors 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-tert-butyl-p-cresol (butylated hydroxytoluene: BHT), 4-methoxyphenol, and 2-methoxy-4-methylphenol.

[0152] [5-3. Quinone-based polymerization inhibitors]

[0153] Examples of the quinone-based polymerization inhibitor include hydroquinone, methoxyhydroquinone, benzoquinone, 1,4-naphthoquinone, and p-tert-butylcatechol.

[0154] [5-4. Amine-based polymerization inhibitors]

[0155] Examples of the amine-based polymerization inhibitor include alkylated diphenylamine, N,N'-diphenyl-p-phenylenediamine, and phenothiazine.

[0156] [5-5. Other polymerization inhibitors]

[0157] Other examples include copper dithiocarbamate-based polymerization inhibitors such as copper dimethyldithiocarbamate, copper diethyldithiocarbamate, and copper dibutyldithiocarbamate.

[0158] Among these, only one type may be contained, or two or more types may be contained.

[0159] Among these, N-oxyl-based and quinone-based polymerization inhibitors are preferred, with 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO), 2,6-di-tert-butyl-p-cresol (butylated hydroxytoluene: BHT), and 2,4-di-tert-butylphenol being preferred. As polymerization inhibitors having two or more aromatic rings, naphthoquinone and the like are preferred.

[0160] [6. Gelling agent]

[0161] The ink of the present invention preferably further contains a gelling agent.

[0162] The inclusion of a gelling agent allows the ink on the recording medium to be temporarily fixed (pinned) in a gel state, thereby suppressing the wetting and spreading of the ink. Furthermore, by reducing the water absorption of the ink, the hydrolysis of the compound having the structure represented by the above-mentioned general formula (1) or its salt (A) can be suppressed.

[0163] The gelling agent preferably crystallizes at a temperature lower than the gelling temperature of the ink.

[0164] The "gelling temperature" refers to the temperature at which, when a composition that has been solubilized or liquidized by heating is cooled, the gelling agent changes phase from a sol to a gel, and the viscosity of the composition changes suddenly.

[0165] Specifically, the composition in a solubilized or liquid state is cooled while measuring the viscosity using a viscoelasticity measuring apparatus (e.g., MCR300, manufactured by Antron Pal Co., Ltd.) The temperature at which the viscosity rises sharply can be taken as the gelation temperature of the composition.

[0166] In the present invention, when the gelling agent crystallizes in the ink, a structure is formed in which a polymerizable compound (compounds participating in polymerization, such as the compound having a structure represented by the above-mentioned general formula (1) or its salt (A), a (meth)acrylate ester with a low (meth)acrylic acid equivalent (B), and a (meth)acrylate ester with a high (meth)acrylic acid equivalent (C)) is enclosed in the three-dimensional space formed by the crystallized plate-like gelling agent, a so-called card-cell structure. To form this card-cell structure, the polymerizable compound dissolved in the ink is preferably compatible with the gelling agent.

[0167] Examples of gelling agents suitable for forming a cell-cell structure include aliphatic ketones, aliphatic esters, petroleum waxes, plant waxes, animal waxes, mineral waxes, hardened 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, higher amines, esters of sucrose fatty acids, synthetic waxes, dibenzylidene sorbitol, dimer acids, and dimer alcohols.

[0168] Among them, from the viewpoint of improving the pinning property, preferred are aliphatic ketones, aliphatic esters, higher fatty acids, and higher alcohols having a hydrocarbon group with a carbon number of 9 to 25.

[0169] The gelling agent may be contained alone or in combination of two or more.

[0170] [6-1. Aliphatic Ketones]

[0171] Examples of the aliphatic ketone include ditetracosyl ketone, dibehenyl ketone, distearyl ketone, dieicosyl ketone, dipalmityl ketone, dilauryl ketone, dimyristyl ketone, myristylpalmityl ketone, and palmitylstearyl ketone.

[0172] [6-2. Aliphatic esters]

[0173] Examples of the aliphatic ester include fatty acid esters of monohydric alcohols such as behenyl behenate, eicosyl eicosate, and oleyl palmitate; and fatty acid esters of polyhydric alcohols such as glycerol fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, ethylene glycol fatty acid esters, and polyoxyethylene fatty acid esters.

[0174] Examples of commercially available products of the aliphatic esters include the Emalex (registered trademark) series manufactured by Japan Emal Dioxide Co., Ltd., and the Riken Biomin Co., Ltd. (registered trademark) series and the Poem (registered trademark) series.

[0175] [6-3. Higher fatty acids]

[0176] Examples of higher fatty acids include behenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, and erucic acid.

[0177] [6-4. Higher alcohols]

[0178] Examples of higher alcohols include stearyl alcohol and behenyl alcohol.

[0179] [6-5. Preferred Gelling Agents]

[0180] In the present invention, the gelling agent is particularly preferably an aliphatic ketone represented by the following general formula (G1) or an aliphatic ester represented by the following general formula (G2).

[0181] General formula (G1): R1-CO-R2

[0182] (In general formula (G1), R1 and R2 each independently represent an alkyl group containing a linear portion having 12 to 26 carbon atoms and optionally containing a branch. R1 and R2 may be the same or different.)

[0183] General formula (G2): R3-COO-R4

[0184] (In general formula (G2), R3 and R4 each independently represent an alkyl group containing a linear portion having 12 to 26 carbon atoms and optionally containing a branch. R3 and R4 may be the same or different.)

[0185] In general formulas (G1) and (G2), the fact that the linear or branched hydrocarbon group has 12 or more carbon atoms further enhances the crystallinity of the aliphatic ketone represented by general formula (G1) and the aliphatic ester represented by general formula (G2), and creates more ample spaces within the aforementioned card-cell structure. Consequently, the polymerizable compound can be readily enclosed within these spaces, improving the ink's pinning properties.

[0186] In addition, since the number of carbon atoms of the straight-chain or branched hydrocarbon group is 26 or less, the melting point of the aliphatic ketone represented by the general formula (G1) and the aliphatic ester represented by the general formula (G2) will not rise excessively, that is, the melting point can be made into a temperature that is easy to handle, and the ink does not need to be excessively heated when the ink is discharged.

[0187] Examples of the aliphatic ketone represented by the general formula (G1) include di(tetracosyl)ketone (carbon number: 23, 24), di(docosyl)ketone (carbon number: 21, 22), distearyl ketone (carbon number: 17, 18), di(eicosyl)ketone (carbon number: 19, 20), dipalmityl ketone (carbon number: 15, 16), dimyristyl ketone (carbon number: 13, 14), dilauryl ketone (carbon number: 11, 12), Laurylmyristyl ketone (carbon numbers: 11, 14), laurylpalmityl ketone (carbon numbers: 11, 16), myristylpalmityl ketone (carbon numbers: 13, 16), myristylstearyl ketone (carbon numbers: 13, 18), myristylbehenyl ketone (carbon numbers: 13, 22), palmitylstearyl ketone (carbon numbers: 15, 18), palmitylbehenyl ketone (carbon numbers: 15, 22), and stearylbehenyl ketone (carbon numbers: 17, 22). The carbon number in parentheses indicates the carbon number of each of the two hydrocarbon groups separated by the carbonyl group.

[0188] Examples of commercially available products of the aliphatic ketone represented by the general formula (G1) include 18-pentatriacontanon and Hentriacontan-16-on manufactured by Alfa Aeser, and Kaowax T-1 manufactured by Kao Corporation.

[0189] Examples of the aliphatic ester represented by the general formula (G2) include behenyl behenate (carbon number: 21, 22), eicosyl eicosate (carbon number: 19, 20), stearyl stearate (carbon number: 17, 18), palmityl stearate (carbon number: 16, 17), lauryl stearate (carbon number: 12, 17), cetyl palmitate (carbon number: 6, 15), and stearyl palmitate (carbon number: 15, 18). , myristyl myristate (carbon numbers: 13, 14), cetyl myristate (carbon numbers: 13, 16), octyldodecyl myristate (carbon numbers: 13, 20), stearyl oleate (carbon numbers: 17, 18), stearyl erucate (carbon numbers: 18, 21), stearyl linoleate (carbon numbers: 17, 18), behenyl oleate (carbon numbers: 18, 22), and eicosyl linoleate (carbon numbers: 17, 20). The carbon numbers in parentheses represent the carbon numbers of the two hydrocarbon groups separated by the ester group.

[0190] Examples of commercially available products of the aliphatic ester represented by the general formula (G2) include UNISTAR (registered trademark) M-2222SL and SPAM ACETY manufactured by NOF Corporation, EKICEPAL (registered trademark) SS and EKICEPAL (registered trademark) MY-M manufactured by Kao Corporation, EMALEX (registered trademark) CC-18 and EMALEX (registered trademark) CC-10 manufactured by Nippon Emal Corporation, and AMREPULS (registered trademark) PC manufactured by Alcore Industries, Ltd.

[0191] In the present invention, the content of the gelling agent is preferably within a range of 1 to 10% by mass relative to the total mass of the ink.

[0192] [7. Other ingredients]

[0193] [7-1. Surfactants]

[0194] The ink of the present invention may further contain a surfactant as needed.

[0195] Examples of surfactants include anionic surfactants such as dialkyl sulfosuccinates, alkylnaphthalenesulfonates, 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.

[0196] [7-2. Colorant]

[0197] The ink of the present invention may further contain a colorant as needed.

[0198] The colorant may be a pigment or a dye, and is preferably a pigment from the viewpoint of good dispersibility in the constituent components of the ink and excellent weather resistance.

[0199] The pigment is not particularly limited, and examples thereof include organic pigments or inorganic pigments having the following numbers described in the quality index.

[0200] The ink of the present invention may contain only one colorant or two or more colorants, and the color can be adjusted to a desired color.

[0201] The content of the colorant is preferably within a range of 0.1 to 20% by mass, more preferably within a range of 0.2 to 10% by mass, relative to the total mass of the ink.

[0202] (pigment)

[0203] Red or Magenta Pigment

[0204] Examples of red or magenta pigments include pigments selected from Pigment Red 3, 5, 19, 22, 31, 38, 43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 53:1, 57:1, 57:2, 58:4, 63:1, 81, 81:1, 81:2, 81:3, 81:4, 88, 104, 108, 112, 122, 123, 144, 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, and 257; Pigment Violet 3, 19, 23, 29, 30, 37, 50, and 88; and Pigment Orange 13, 16, 20, and 36; and mixtures thereof.

[0205] Cyan or Blue Pigment

[0206] Examples of cyan or blue pigments include pigments selected from Pigment Blue 1, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17:1, 22, 27, 28, 29, 36, and 60, or mixtures thereof.

[0207] Green Paint

[0208] Examples of green pigments include pigments selected from Pigment Green 7, 26, 36, and 50, or mixtures thereof.

[0209] Yellow Pigment

[0210] Examples of yellow pigments include pigments selected from Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, and 193, or mixtures thereof.

[0211] Black Pigment

[0212] Examples of black pigments include pigments selected from Pigment Black 7, 28, and 26, or mixtures thereof.

[0213] 《Examples of Commercially Available Pigments》

[0214] Examples of commercially available products as pigments include Black Pigment (manufactured by Mikuni Corporation), Chromophine Yellow 2080, 5900, 5930, AF-1300, 2700L, Chromophine Orange 3700L, 6730, Chromophine Scarlet 6750, Chromophine Magenta 6880, 6886, 6891N, 6790, 6887, Chromophine Violet RE, Chromophine Red 6820, 6830, Chromophine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5000P, Chromophine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Chromophine Black A-1103, Seikafast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400(B), 2500, 2600, ZAY-260, 2700(B), 2770, Seikafast Red 8040, C405(F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seikafast Carmine 6B1476T-7, 1483LT, 3840, 3870, Seikafast Bordeaux 10B-430, Seika Light Rose Red R40, Seika Light Purple B800, 7805, Seikafast Brown Red 460N, Seikafast Orange 900, 2900, Seika Light Blue C718, A612, Cyanine Blue 4933M, 4933GN-EP, 4940, 4973 (all manufactured by Dainichi Seika Kogyo Co., Ltd. It should be noted that "Chromophine" is a registered trademark of this company); KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118, 124, KET Green 201 (all manufactured by DIC Corporation);Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T-13, T-05, Pigment Yellow 1705, Colortex Orange 202, Colortex Red 101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, 105C, USN, Colortex Maroon 601, Colortex Brown B610N, Colortex Violet 600, Pigment Red 122, Colortex Blue 516, 517, 518, 519, A818, P-908, 510, Colortex Green 402, 403, Colortex Black 702, U905 (all manufactured by Sanyo Color Co., Ltd.; "Colortex" and "Finecol" are registered trademarks of the company); Lionol Yellow 1405G, Lionol Blue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (all manufactured by Toyo Ink Co., Ltd.; "Lionol" is a registered trademark of the company); Toner Magenta E02, Permanent Rubin F6B, Toner Yellow HG, Permanent Yellow GG-02, Hostapem Blue B2G (all manufactured by Hoechst Industries); Novoperm P-HG, Hostaperm Pink E, Hostaperm Blue B2G (all manufactured by Clariant; "Novoperm" and "Hostaperm" are registered trademarks of the company); carbon black #2600, #2400, #2350, #2200, #1000, #990, #980, #970, #960, #950, #850, MCF88, #750, #650, MA600, MA7, MA8, MA11, MA100, MA100R, MA77, #52, #50, #47, #45, #45L, #40, #33, #32, #30, #25, #20, #10, #5, #44, CF9 (all manufactured by Mitsubishi Chemical), etc.

[0215] Dispersion of Pigments

[0216] The pigment can be dispersed using, for example, a ball mill, a sand mill, an attritor, a roll mill, a stirrer, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a bead mill, a wet jet mill, or a paint shaker.

[0217] The pigment is preferably dispersed so that the volume average particle size of the pigment particles is preferably within the range of 0.08 to 0.5 μm. Furthermore, the pigment particles are preferably dispersed so that the maximum particle size is preferably within the range of 0.3 to 10 μm, more preferably within the range of 0.3 to 3 μm.

[0218] The dispersion of the pigment is adjusted by the selection of the pigment, dispersant and dispersion medium, the dispersion conditions, the filtration conditions, etc.

[0219] Dispersants

[0220] The ink of the present invention may further contain a dispersant in order to improve the dispersibility of the pigment.

[0221] As the example of dispersant, can list carboxylate, long-chain polyaminoamide and the salt of high molecular weight acid ester, the salt of high molecular weight polycarboxylic acid, the salt of long-chain polyaminoamide and polar acid ester, high molecular weight unsaturated acid ester, high molecular weight copolymer, modified polyurethane, modified polyacrylate, polyether ester type anion system active agent, naphthalenesulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate, polyoxyethylene nonylphenyl ether and stearylamine acetate etc. as the example of commercially available product of dispersant, can list Solsperse (registered trademark) series of Avecia company system, PB series of Ajinomoto ファインテクノ company system etc.

[0222] Dispersing Agents

[0223] The ink of the present invention may further contain a dispersing aid as necessary.

[0224] The dispersing aid can be selected according to the pigment.

[0225] The total content of the dispersant and the dispersing aid is preferably within a range of 1 to 50% by mass relative to the total mass of the pigment.

[0226] Dispersion Medium

[0227] The ink of the present invention may further contain a dispersion medium for dispersing the pigment, as necessary.

[0228] The ink of the present invention may contain a solvent as a dispersion medium.

[0229] [7-3. Other additives]

[0230] The ink of the present invention may further contain a coupling agent, a solvent, and the like, as necessary.

[0231] (Coupling agent)

[0232] The ink of the present invention may further contain various coupling agents as needed. By containing a coupling agent, the adhesion to the printed wiring board can be improved.

[0233] Examples of various coupling agents include silane-based, titanium-based, and aluminum-based coupling agents.

[0234] (Solvent)

[0235] The ink of the present invention is preferably solvent-free from the viewpoint of rapid curing and discharge stability, but solvent may be added to adjust the viscosity of the ink.

[0236] [Method for producing inkjet ink composition]

[0237] The method for producing the inkjet ink composition of the present invention can be prepared by mixing the compound having a structure represented by the above-mentioned general formula (1) or its salt (A), the above-mentioned (meth)acrylate with a low (meth)acrylic acid equivalent (B), and the above-mentioned (meth)acrylate with a high (meth)acrylic acid equivalent (C) under heating.

[0238] The resulting mixed solution is preferably filtered using a specified filter. When preparing an ink containing a pigment, it is preferred to prepare a pigment dispersion containing the pigment and a polymerizable compound, and then mix the pigment dispersion with the other components. The pigment dispersion may further contain a dispersant.

[0239] The pigment dispersion can be prepared by dispersing the pigment in a polymerizable compound. The pigment can be dispersed using, for example, a ball mill, sand mill, attritor, roll mill, stirrer, Henschel mixer, colloid mill, ultrasonic homogenizer, bead mill, wet jet mill, paint shaker, or the like. A dispersant may be added.

[0240] [Record of the present invention]

[0241] In the recorded matter of the present invention, the above-mentioned inkjet ink composition of the present invention is cured at least by active energy rays or heat.

[0242] Specifically, the recorded article of the present invention refers to a product recorded on a recording medium using the inkjet ink composition of the present invention using the inkjet recording method described below. Furthermore, the term "cured article" as used herein refers to a product obtained by curing the inkjet ink composition of the present invention, and is essentially synonymous with the aforementioned recorded article.

[0243] [Inkjet recording method of the present invention]

[0244] The inkjet recording method of the present invention comprises: a step of using the inkjet ink composition of the present invention and discharging the inkjet ink composition from an inkjet head so that it lands on a recording medium; and a step of curing the inkjet ink composition that has landed on the recording medium by at least active energy rays or heat.

[0245] In the inkjet method, ink is ejected from an inkjet head and lands on a recording medium. The inkjet method is particularly suitable for forming solder resist patterns and printing text because it is easy to apply ink only to the desired area.

[0246] In the step of curing by irradiation with active energy rays, the ink may be cured immediately after the step of dropping the ink, or may be cured all at once after the step of dropping the ink.

[0247] The ink of the present invention has a relatively high viscosity at room temperature (25°C), making it difficult to wet and spread onto the recording medium after being ejected. Therefore, the ink does not need to be cured immediately after landing on the recording medium. Instead, the ink can be discharged within a certain, predetermined range and cured simultaneously after landing on the recording medium. This simultaneous curing can reduce ejection defects caused by light leakage.

[0248] In the present invention, the so-called "simultaneous irradiation", "simultaneous heating" and "simultaneous curing" mean that first a plurality of ink droplets are discharged in a certain specified range and fall on the recording medium, and then the plurality of ink droplets that fall in the certain range are simultaneously irradiated or heated with active energy rays, thereby curing.

[0249] In other words, it is not about solidifying each drop of ink that lands on the recording medium. Instead, it is about performing concentrated ink landing, active energy ray irradiation or heating, and solidification in a certain or specified area (for example, landing all the ink required to form a specified image (pattern)).

[0250] Furthermore, by the inkjet recording method of the present invention, a solder resist film for a printed wiring board is preferably formed.

[0251] The inkjet recording method of the present invention is described below. The inkjet recording method of the present invention comprises: (1) a step of discharging the ink of the present invention from an inkjet head and landing it on a recording medium; and (2) a step of curing the ink landed on the recording medium using active energy rays or heat.

[0252] [Process (1)]

[0253] In step (1), the ink of the present invention is discharged from the nozzles of the inkjet head and lands on a recording medium. The recording medium is not particularly limited, but is preferably a printed circuit board.

[0254] The discharge method from the inkjet head may be either an on-demand method or a continuous method.

[0255] On-demand inkjet heads can be any of the electro-mechanical conversion types such as single-chamber type, dual-chamber type, bender type, piston type, shared pattern type and shared wall type, as well as electro-thermal conversion types such as thermal inkjet type and Bubble Jet (registered trademark) (Bubble Jet is a registered trademark of Canon Inc.) type.

[0256] Discharge stability is achieved by discharging ink droplets from the inkjet head while they are heated. The ink temperature when filling the inkjet head is preferably between 40 and 100°C. Furthermore, to further improve discharge stability, it is more preferably between 40 and 90°C. Furthermore, the ink viscosity at the discharge temperature is preferably between 7 and 15 mPa·s, and more preferably between 8 and 13 mPa·s.

[0257] When a sol-gel phase change ink containing a gelling agent is used, the temperature of the ink in the inkjet head is preferably (gelling temperature + 10) to (gelling temperature + 30)°C of the ink.

[0258] By keeping the ink temperature within the inkjet head at (gelling temperature + 10)°C or higher, the ink does not gel inside the inkjet head or on the nozzle surface, achieving sufficient discharge stability. Furthermore, by keeping the ink temperature at (gelling temperature + 30)°C or lower, the degradation of the ink components due to temperature is prevented.

[0259] There are no particular limitations on the method for heating the ink. For example, a panel heater, a tape heater, or heated water can be used to heat at least one of the ink supply system, including the ink tanks that make up the printhead carriage, the supply pipes, the ink tanks in the front chamber in front of the head, the piping with the filter, and the piezoelectric head.

[0260] The amount of ink droplets during discharge is preferably within a range of 2 to 20 pL from the viewpoint of recording speed and image quality.

[0261] The recording medium is not particularly limited, and various metals, glass, ceramics, polyimide films, PET films, etc. can be used. From the perspective of improving adhesion, it is preferred that an inorganic substance such as metal or glass be contained on the surface.

[0262] As metal, for example, copper, aluminum, iron, their oxides etc. can be listed. In addition, it is particularly preferred to be used for printed circuit boards containing inorganic substances such as metals and glass on the surface. As the example of printed circuit boards, it is preferably possible to use copper-clad laminates of all grades (FR-4 etc.) of materials such as copper-clad laminates for high-frequency circuits utilizing glass cloth epoxy, glass polyimide, glass cloth / non-woven epoxy, glass cloth / paper epoxy etc.

[0263] [(2) process]

[0264] In step (2), the ink that has landed on the recording medium is cured by active energy rays or heat. The ink of the present invention can be cured by either irradiation with active energy rays or heating alone, preferably by at least irradiation with active energy rays. Furthermore, heating is more preferably performed.

[0265] Examples of active energy rays include electron beams, ultraviolet rays, α rays, γ rays, and X-rays, and ultraviolet rays are preferred.

[0266] Ultraviolet irradiation can be performed using, for example, a water-cooled LED manufactured by Phoseon Technology Co., Ltd. at a wavelength of 395 nm. Using an LED as a light source can suppress poor curing of the ink caused by melting of the ink by radiant heat from the light source.

[0267] The peak illuminance of the solder resist surface due to ultraviolet rays having a wavelength in the range of 370 to 410 nm is preferably 0.5 to 10 W / cm 2 In addition, it is more preferably 1 to 5 W / cm 2 The amount of light irradiated to the solder resist is preferably less than 1000 mJ / cm2 from the viewpoint of suppressing radiant heat from being irradiated to the ink. 2 .

[0268] The irradiation with the active energy ray is preferably performed within 0.001 to 300 seconds after the ink is ejected, and more preferably within 0.001 to 60 seconds in order to form a high-definition solder resist film.

[0269] From the perspective of suppressing polymerization inhibition caused by oxygen, it is preferred to cure the ink by irradiating the dropped ink with active energy rays in an atmosphere having an oxygen concentration within the range of 0.1 to 10.0% by volume. Furthermore, from the perspective of minimizing the occurrence of blurring, the oxygen concentration is more preferably within the range of 0.5 to 8.0% by volume, and even more preferably within the range of 0.5 to 6.0% by volume.

[0270] As a heating method, for example, it is preferable to place the mixture in an oven set at a temperature within a range of 110 to 180° C. for 10 to 90 minutes.

[0271] [Inkjet recording system of the present invention]

[0272] The inkjet recording system of the present invention comprises: an inkjet head that uses the inkjet ink composition of the present invention and discharges the inkjet ink composition; and an active energy ray irradiation unit that irradiates the inkjet ink composition that lands on a recording medium with at least active energy rays, or a heating unit that heats the inkjet ink composition.

[0273] That is, in the system of the present invention, a recording device having an inkjet head for discharging an inkjet ink composition, an active energy ray irradiation unit for irradiating active energy rays to the inkjet ink composition that lands on a recording medium, or a heating unit for heating the inkjet ink composition irradiated with the active energy rays, and the ink of the present invention are used.

[0274] In addition, as a recording method of the inkjet recording apparatus, a scanning method is preferable from the viewpoint of discharge stability and printing accuracy.

[0275] Types of inkjet recording devices (printers) include single-pass printers and serial printers. Single-pass printers have a lint head with a length corresponding to the width of the recording medium (the width of the recording medium). The lint head is fixed (substantially) immobile, and printing is performed in a single pass.

[0276] On the other hand, a serial printer generally performs printing in two or more passes (multi-pass) while the head reciprocates (reciprocates) in a direction perpendicular to the conveyance direction of the recording medium.

[0277] In a single-pass printer, a plurality of inkjet heads must be arranged in parallel to form a line head, requiring a relatively large number of inkjet heads. On the other hand, a serial printer can be constructed with only a small number of recording heads.

[0278] In the present invention, any type of printer can be used, and preferably, a serial printer can be used.

[0279] Example

[0280] The present invention is described in detail below using 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" refer to "mass %" and "mass parts," respectively.

[0281] <Preparation of Yellow Pigment Dispersion Y>

[0282] Dispersants 1 and 2, along with the dispersion medium, were placed in a stainless steel beaker and heated on a 65°C hot plate while stirring to dissolve for 1 hour. The mixture was then cooled to room temperature. The pigments listed below were then added to the mixture, along with 200g of 0.5mm diameter zirconium oxide beads, and placed in a glass bottle, which was then sealed.

[0283] After the particles were dispersed using a paint shaker until they had a desired particle size, the zirconium oxide beads were removed.

[0284]

[0285] <Preparation of Cyan Pigment Dispersion C>

[0286] In the preparation of the yellow pigment dispersion Y, the same method as that of the dispersion Y was carried out except that the dispersant, dispersion medium, and pigment were changed as shown below.

[0287] Dispersant: PX4701 (manufactured by BASF) 7.0 parts by mass Dispersing medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 70 parts by mass

[0288] Pigment: PB15:4 (manufactured by Dainichi Seika Co., Ltd., Cromofine (registered trademark) Blue 6332JC) 23 parts by mass

[0289] The compound having a structure represented by the general formula (1) or its salt (A), the (meth)acrylate with a low (meth)acrylic acid equivalent (B), the (meth)acrylate with a high (meth)acrylic acid equivalent (C), the polymerization initiator, the polymerization inhibitor, the gelling agent, other monomers, etc. used in the preparation of the ink described below are as follows.

[0290] <Compound having a structure represented by general formula (1) or a salt thereof (A)>

[0291] A-1: The above-mentioned exemplary compound A-1

[0292] A-2: The above-mentioned exemplary compound A-2

[0293] A-3: The above-mentioned exemplary compound A-3

[0294] <(Meth)acrylate (B) with low (meth)acrylic acid equivalent>

[0295] DPHA: M600 (manufactured by Miwon Co., Ltd.) (hexafunctional (meth)acrylate: dipentaerythritol hexaacrylate)

[0296] DPPA: M500 (manufactured by Miwon Co., Ltd.) (pentafunctional (meth)acrylate: dipentaerythritol pentaacrylate)

[0297] PET3A: EM235 (manufactured by Changxing Chemical Co., Ltd.) (trifunctional (meth)acrylate: pentaerythritol triacrylate)

[0298] PET4A: EM241 (manufactured by Changxing Chemical Co., Ltd.) (tetrafunctional (meth)acrylate: pentaerythritol tetraacrylate)

[0299] TMPTA: SR351 (manufactured by Sartomer) (trifunctional (meth)acrylate: trimethylolpropane triacrylate)

[0300] <(Meth)acrylate (C) with high (meth)acrylic acid equivalent>

[0301] DP6CAHA: DPCA60 (manufactured by Nippon Kayaku Co., Ltd.) (CA modified, (hexafunctional (meth)acrylate: caprolactam-modified dipentaerythritol hexaacrylate)

[0302] DP12CAHA: DPCA120 (manufactured by Nippon Kayaku Co., Ltd.) (CA-modified, hexafunctional (meth)acrylate: caprolactam-modified dipentaerythritol hexaacrylate)

[0303] TMP(EO)9TA: EM2382 (manufactured by Changxing Chemical Co., Ltd.) (EO modified, trifunctional (meth)acrylate: trimethylolpropane triacrylate)

[0304] TMP(EO)15TA: SR9035 (manufactured by Sartomer) (EO modified, trifunctional (meth)acrylate: trimethylolpropane triacrylate)

[0305] NP(PO)2A: M1602 (manufactured by Miwon) (PO modified, monofunctional (meth)acrylate: nonylphenol acrylate)

[0306] PEG400DA: M280 (manufactured by Miwon) (bifunctional (meth)acrylate: polyethylene glycol 200 diacrylate)

[0307] BPA(EO)20DA: M2200 (manufactured by Miwon) (EO modified, bifunctional (meth)acrylate: bisphenol A diacrylate)

[0308] <Other monomers>

[0309] DPGDA: M222 (manufactured by Miwon) (dipropylene glycol diacrylate)

[0310] <Gelling agent>

[0311] Gelling agent A: Eki Separ SS (manufactured by Kao Corporation) (aliphatic ester represented by the above general formula (G2))

[0312] <Polymerization initiator>

[0313] Type I type (ノリッシュ type) A:

[0314] Omnirad (registered trademark) 907, IGM Resins (manufactured by BV)

[0315] Type I type (ノリッシュ type) B:

[0316] Omnirad (registered trademark) 819, IGM Resins (manufactured by BV)

[0317] TypeII type (ノリッシュII type):

[0318] Speedcure (registered trademark) ITX (manufactured by Lambson)

[0319] <Polymerization inhibitor>

[0320] UV-10 Irgastab (registered trademark) (manufactured by BASF)

[0321] <Ink Preparation>

[0322] The following components were mixed and filtered using a 3 μm Teflon (registered trademark) membrane filter manufactured by ADVATEC to prepare Ink 1.

[0323] <<Compound having a structure represented by general formula (1) or its salt (A)>>

[0324] A-3 10.0 parts by mass

[0325] 《(Meth)acrylate (B) with low (meth)acrylic acid equivalent》

[0326] DPPA 10.0 parts by mass

[0327] 《(Meth)acrylate (C) with high (meth)acrylic acid equivalent》

[0328] DP6CAHA 10.0 parts by mass

[0329] Other Monomers

[0330] DPGDA 60.7 parts by mass

[0331] Polymerization Initiator

[0332] Omnirad 907 3.0 parts by mass

[0333] OmnirAd 819 3.0 parts by mass

[0334] Speedcure ITX 2.0 parts by mass

[0335] Inhibitors

[0336] Irgastab (registered trademark) UV-10 0.1 parts by mass

[0337] Pigment dispersion

[0338] Dispersion liquid Y 0.7 parts by mass

[0339] Dispersion liquid C 0.5 parts by mass

[0340] In the preparation of ink 1, each ink was prepared in the same manner except that the types and addition amounts of the compound or its salt (A), the (meth)acrylate with a low (meth)acrylic acid equivalent (B), the (meth)acrylate with a high (meth)acrylic acid equivalent (C), other monomers, gelling agents, polymerization initiators, polymerization inhibitors, and pigment dispersions were changed to those shown in Tables I to V.

[0341] <Ink Cured Film Formation Using the Inkjet Method>

[0342] Each prepared ink was loaded into an inkjet recording apparatus equipped with an inkjet recording head equipped with a piezoelectric inkjet nozzle. Using this apparatus, a solder resist pattern was formed on a copper-clad laminate for a printed wiring board (FR-4, 1.6 mm thick, 150 mm x 95 mm in size) to obtain a cured film (or cured product).

[0343] The ink supply system consists of an ink tank, ink flow path, a sub-tank in front of the inkjet recording head, piping with a metal filter, and a piezoelectric head. The ink is heated to 80°C from the tank to the head. The piezoelectric head also has a built-in heater to keep the ink temperature within the recording head at 80°C. The piezoelectric head has nozzles with a 22μm diameter and a nozzle resolution of 360dpi, arranged in a zigzag pattern, creating a nozzle array with a resolution of 720dpi.

[0344] Using this inkjet device, a voltage was applied so that the droplet volume became 6.0 pL. A solid pattern (ベタパターン) of 20 mm × 50 mm was printed on the substrate so that each pattern had a thickness of 20 μm. The substrate was then irradiated with an LED lamp (395 nm, 8 W / cm 2 , water cooled unit) to make it 1W / cm 2 , 500mJ / cm 2 Then, the coating was cured by placing it in an oven set at 150° C. for 60 minutes to obtain a cured film.

[0345] [evaluate]

[0346] <Adhesion>

[0347] The solid pattern print samples were cut in a checkerboard pattern using the cross-cut method of JIS standard K5600. Tape was then applied and peeled off to observe the peeling state of the cured film. In the following criteria, "AAA," "AA," and "A" indicate no practical problems.

[0348] (Benchmark)

[0349] AAA: The adhesion residual rate is 100%.

[0350] AA: The adhesion residual rate is 80% or more and less than 100%.

[0351] A: The adhesion residual rate is 60% or more and less than 80%.

[0352] B: The adhesion residual rate is less than 60%.

[0353] Pencil hardness

[0354] The surface pencil hardness of the printed sample of the solid pattern was measured according to the method described in JIS standard K-5400. A pencil hardness of 5H or higher was considered to be no problem in practical use.

[0355] <Acid resistance (chemical resistance)>

[0356] The solid pattern was immersed in a 10% HCl aqueous solution at 25°C for 30 minutes, then rinsed with pure water. The water was wiped off and evaluated using the following criteria: "AAAA," "AAA," "AA," and "A" were considered to indicate no practical problems.

[0357] (Benchmark)

[0358] AAAA: The adhesion residual rate is 100%.

[0359] AAA: The adhesion residual rate is 90% or more and less than 100%.

[0360] AA: The adhesion residual rate is 80% or more and less than 90%.

[0361] A: The adhesion residual rate is 60% or more and less than 80%.

[0362] B: The adhesion residual rate is less than 60%.

[0363] <Applicability (viscosity)>

[0364] The viscosity of each prepared ink at 80° C. was measured using Physica MCR301 (manufactured by Anton Paar) at a shear rate of 1000 (1 / s). In the following criteria, if the ink is rated “A”, discharge from the inkjet head is stable and coating properties are excellent.

[0365] (Benchmark)

[0366] A: The viscosity is within the range of 7 to 15 mPa·s.

[0367] B: The viscosity is less than 7 mPa·s or greater than 15 mPa·s.

[0368] [Table 1]

[0369] Table I

[0370]

[0371] [Table 2]

[0372] Table II

[0373]

[0374] [Table 3]

[0375] Table III

[0376]

[0377] [Table 4]

[0378] Table IV

[0379]

[0380] [Table 5]

[0381] Table V

[0382]

[0383] As shown in the above results, it was confirmed that the ink of the present invention produced a cured product having excellent adhesion, coating hardness, and acid resistance compared to the ink of the comparative example. Furthermore, the ink of the present invention also had good coating properties.

[0384] Industrial applicability

[0385] The present invention can be utilized in an inkjet ink composition, recorded matter, inkjet recording method, and inkjet recording system capable of obtaining a cured product having excellent coating properties, adhesion, coating film hardness, and chemical resistance for inkjet use.

Claims

1. An inkjet ink composition that is curable at least by active energy rays or heat, comprising: A compound having a structure represented by the following general formula (1) or a salt thereof (A), (Meth)acrylate (B) having a (meth)acrylic acid equivalent within a range of 71 to 110, and (Meth)acrylate (C) having a (meth)acrylic acid equivalent within the range of 200 to 500, General formula (1) In the above general formula (1), X represents a terminal substituent having at least one substituent selected from acryloyl, methacryloyl, allyl, vinyl, and derivatives thereof, Q represents an oxygen atom or NR4, 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.

2. The inkjet ink composition according to claim 1, wherein In the general formula (1), X represents a substituent having at least one substituent selected from derivatives of acryloyl or methacryloyl groups at the terminal.

3. The inkjet ink composition according to claim 1, wherein In the general formula (1), Q represents an oxygen atom.

4. The inkjet ink composition according to claim 1, wherein In the general formula (1), R1 represents an unsubstituted alkylene group having 1 or 2 carbon atoms.

5. The inkjet ink composition according to claim 1, wherein The (meth)acrylate (C) having a (meth)acrylic acid equivalent within the range of 200 to 500 has 7 or less (meth)acryloyl groups.

6. The inkjet ink composition according to claim 1, wherein The molecular weight of the (meth)acrylate (C) having a (meth)acrylic acid equivalent within the range of 200 to 500 is within the range of 200 to 2,000.

7. The inkjet ink composition according to claim 1, wherein The (meth)acrylate (C) having a (meth)acrylic acid equivalent within a range of 200 to 500 contains any one of an ethylene oxide modified portion, a propylene oxide modified portion, and an ε-caprolactone modified portion.

8. The inkjet ink composition according to claim 1, wherein The (meth)acrylate (C) having a (meth)acrylic acid equivalent within a range of 200 to 500 is an ε-caprolactone-modified product of erythritol hexaacrylate.

9. The inkjet ink composition according to claim 1, wherein The (meth)acrylate (B) having a (meth)acrylic acid equivalent of 71 to 110 is erythritol hexaacrylate or dipentaerythritol pentaacrylate.

10. The inkjet ink composition according to claim 1, further comprising a gelling agent. 11 . The inkjet ink composition according to claim 1 , which is used as an inkjet ink for forming a solder resist pattern on a printed circuit board. 12 . A recorded object obtained by curing the inkjet ink composition according to claim 1 by at least active energy rays or heat.

13. An inkjet recording method using an inkjet ink composition, comprising: A step of using the inkjet ink composition according to any one of claims 1 to 11, and discharging the inkjet ink composition from an inkjet head to drop it onto a recording medium; and A step of curing the inkjet ink composition that has landed on the recording medium by at least active energy rays or heat.

14. An inkjet recording system using an inkjet ink composition, comprising: An inkjet head that uses the inkjet ink composition according to any one of claims 1 to 11 and discharges the inkjet ink composition; and At least an active energy ray irradiation portion irradiates the inkjet ink composition that lands on a recording medium with active energy rays, or a heating portion heats the inkjet ink composition.

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