Inkjet ink and storage method for inkjet ink

Abstract

The inkjet ink of the present invention is an inkjet ink containing a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator, and when stored at a temperature of 30°C and a humidity of 60% RH for one year from the date of production, the water content of the inkjet ink measured by the Karl Fischer method is within the range of 0.05 to 0.80% by mass relative to the total mass.

Description

[Technical Field]

[0001] The present invention relates to an inkjet ink and a method for storing the inkjet ink, and in particular to an inkjet ink containing a blocked isocyanate that exhibits good ejection properties and stable curing properties even when stored for a long period of time. [Background technology]

[0002] Conventionally, photolithography and screen printing methods have been used to form etching resists, solder resists, and markings on printed wiring boards. As a method for utilizing the inkjet method in the production of printed wiring boards, for example, it has already been proposed to use inkjet ink containing a thermosetting agent on a copper-clad laminate for printed wiring boards, and then form a solder resist using an inkjet printer (see, for example, Patent Documents 1 to 3).

[0003] The inkjet method can significantly reduce the number of steps and labor compared to photolithography, which requires a photomask, and screen printing methods using resist ink or marking ink, which require a screen. Furthermore, the inkjet method can reduce consumables such as developers, various inks, and cleaning solvents, and can also reduce wastewater, which is expected to contribute to a cleaner environment.

[0004] However, in inks containing the above-mentioned heat curing agent, particularly blocked isocyanate, the blocked isocyanate reacts with water or hydroxy groups contained in the ink to generate solids, which can easily cause curing or ejection defects in inkjet printers. In particular, in order to improve the inkjet ejection performance of curable inks, the ink is usually heated to reduce the ink viscosity before ejection, but heating further accelerates the generation of solids.

[0005] Therefore, a method has been proposed in which the water content is kept low at 500 ppm when producing ink containing an isocyanate group (see, for example, Patent Document 4). However, the method of limiting the moisture content to 500 ppm imposes a heavy manufacturing burden, is difficult to maintain and store, and leads to increased costs. Furthermore, the method assumes that the ink will be used immediately after production, and does not mention the moisture content one year after production. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 06069300 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-043565 [Patent Document 3] Patent No. 05969208 [Patent Document 4] Japanese Patent Application Laid-Open No. 2014-201593 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above problems and circumstances. The problem to be solved by the present invention is to suppress the generation of solid matter in a coating film forming apparatus even when an inkjet ink containing a blocked isocyanate is used and stored for a long period of time. As a result, the present invention aims to provide an inkjet ink and a method for storing an inkjet ink that can achieve good ejection properties and stable curing properties. In the following description, "inkjet ink" will also be simply referred to as "ink." [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present inventors investigated the causes of the above-mentioned problems and determined the water content of inkjet ink containing a blocked isocyanate and one year after production, and found that this can suppress the generation of solids in a coating film forming device and provide inkjet inks and the like that have good ejection properties and stable curing properties, which led to the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0009] 1. An inkjet ink containing a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator, the ink-jet ink contains 30% by mass or more of the polymerizable monomer having an octanol / water partition coefficient (ClogP) value in the range of 2.0 to 7.0; the sum of the hydroxy values ​​of the compounds having a hydroxy group contained in the inkjet ink is 0.05mgKOH / g or more 60 mg KOH / g or less, and An inkjet ink whose water content, measured by the Karl Fischer method, is within the range of 0.05 to 0.80% by mass relative to the total mass when stored for one year at a temperature of 30°C and a humidity of 60% RH from the date of manufacture.

[0010] 2. The ink-jet ink according to item 1, which is an ink that is ejected at 40°C or higher.

[0011] 3. The ink-jet ink according to item 1, wherein the blocked isocyanate has an aromatic ring structure.

[0012] 4. The ink-jet ink according to item 1, wherein the blocked isocyanate has an isocyanurate structure.

[0014] 5 .An inkjet ink described in item 1, wherein the polymerizable monomer contains at least one polymerizable monomer having a bisphenol A structure.

[0016] 6 .Items 1 to 5 5 A method for storing the ink-jet ink according to any one of claims 1 to 5, comprising: Inkjet ink storage method: Store at a temperature of 30°C and a humidity of 60% RH. [Effects of the Invention]

[0017] The above-described means of the present invention can provide an inkjet ink and a storage method thereof that can suppress the generation of solid matter in a coating film forming apparatus and provide good ejection properties and stable curing properties even when the ink has been stored for a long period of time. The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is speculated as follows. Ink containing blocked isocyanate generates solids when the blocked isocyanate reacts with the water and hydroxyl groups in the ink. In particular, heating such ink accelerates the generation of solids. As a result, if solids are generated in the coating film forming equipment, it can lead to ejection failure. The estimated mechanism for solid formation is that the blocked isocyanate reacts with the water and hydroxyl groups contained in the ink, hydrolyzing the blocked isocyanate (NCO) moiety and generating an amine. Furthermore, the amino group reacts with the NCO moiety to form a polymer in which the bond site becomes urea. It is also speculated that the alcohol component generated by the hydrolysis of the acrylic monomer reacts with the NCO moiety and polymerizes. Therefore, in the present invention, the water content of the inkjet ink when stored for one year from the date of manufacture at a temperature of 30°C and a humidity of 60% RH is set to be within the above-mentioned specific range. By reducing the water content over time in this way, it is possible to suppress the generation of solid matter in the coating film forming apparatus, improve the ink ejection properties, and obtain stable ink curing properties. DETAILED DESCRIPTION OF THE INVENTION

[0018] The inkjet ink of the present invention is an inkjet ink containing a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator, and when stored at a temperature of 30°C and a humidity of 60% RH for one year from the date of production, the water content of the inkjet ink measured by the Karl Fischer method is within the range of 0.05 to 0.80% by mass relative to the total mass. This feature is a technical feature common to or corresponding to each of the following embodiments.

[0019] In an embodiment of the present invention, injection at 40°C or higher is preferred because it allows for lowering the viscosity. That is, since monomers with large molecular weights and interactions are used to achieve high performance, the viscosity can be adjusted by heating to 40°C or higher before injection.

[0020] The blocked isocyanate preferably has an aromatic ring structure, since this allows both the thermal decomposition temperature and the curing performance to be satisfied, and increases the robustness of the solid matter generation during heating.

[0021] The blocked isocyanate preferably has an isocyanurate structure, in that excellent adhesion of the coating film is obtained.

[0022] The inkjet ink preferably contains 30% by mass or more of the polymerizable monomer having an octanol / water partition coefficient (ClogP) value in the range of 2.0 to 7.0, thereby reducing moisture absorption and increasing the robustness of solid matter generation.

[0023] The polymerizable monomer preferably contains at least one polymerizable monomer having a bisphenol A structure, since the polymerizable monomer is a hydrophobic monomer and has low moisture absorption.

[0024] The sum of the hydroxy values ​​of the compounds having a hydroxy group contained in the inkjet ink is preferably 60 mgKOH / g or less, in terms of preventing the generation of solid matter and providing excellent ejection properties.

[0025] The inkjet ink of the present invention is stored at a temperature of 30°C and a humidity of 60% RH. This prevents the increase in water content even when the ink is stored for a long period of time. As a result, the generation of solids in the coating film forming device is suppressed, and good ejection properties and stable curing properties are achieved.

[0026] The present invention, its components, and embodiments and modes for carrying out the present invention will be described below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits.

[0027] 1. Overview of the inkjet ink of the present invention The inkjet ink of the present invention is an inkjet ink containing a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator, and when stored at a temperature of 30°C and a humidity of 60% RH for one year from the date of production, the water content of the inkjet ink measured by the Karl Fischer method is within the range of 0.05 to 0.80% by mass relative to the total mass.

[0028] In the present invention, "(meth)acrylate" means acrylate or methacrylate, "(meth)acryloyl group" means acryloyl group or methacryloyl group, and "(meth)acrylic" means acrylic or methacrylic.

[0029] The ink of the present invention functions as an insulating film (solder resist) when applied to a substrate and cured with actinic rays in various fields, such as metal processing, electronic circuits, printed circuit boards, plate making, semiconductors, color filters, etc. Furthermore, since the ink can be removed with alkali after photocuring, it also functions as an etching resist used when forming an etching pattern on a substrate. The ink can be used not only as an ink for forming the solder resist pattern described above, but also as an adhesive, a sealant, a circuit protectant, etc. for electronic components. In particular, the ink according to the present invention is preferably an ink for forming a solder resist pattern used on a printed wiring board. When a solder resist pattern (solder resist film) is formed using the ink according to the present invention, the ink has high curing properties, making it possible to prevent the penetration of oxygen and moisture into the solder resist film. Furthermore, the ink according to the present invention improves the adhesion between the copper foil and the solder resist film interface on the printed wiring board, preventing copper migration and suppressing a decrease in insulation properties.

[0030] The ink of the present invention is an ink that can be cured by actinic radiation. "Actinic rays (also referred to as "active energy rays")" are rays that can impart energy to the ink by irradiation, generating reaction initiating species such as active radicals and ions, and include α-rays, γ-rays, X-rays, ultraviolet rays, electron beams, etc. Of these, ultraviolet rays and electron beams are preferred from the viewpoint of curing sensitivity and ease of equipment availability, with ultraviolet rays being more preferred.

[0031] <Moisture content> When the ink of the present invention is stored at a temperature of 30°C and a humidity of 60% RH for one year after production, the water content of the ink measured by the Karl Fischer method is within the range of 0.05 to 0.80% by mass relative to the total mass. The water content of the ink is preferably within a range of 0.10 to 0.60% by mass. Here, "when stored for one year from the date of manufacture" refers to when the ink has been stored for one year from the end of the ink manufacturing process. Furthermore, "at the end of the ink manufacturing process" refers to a point within 30 minutes immediately before the end of the ink preparation process. In the present invention, the "water content of the ink when stored for one year after production" refers to the water content when stored for one year in an environment at a temperature of 30°C and a humidity of 60% RH.

[0032] (Method for measuring moisture content) The water content according to the present invention can be measured by a known method such as the Karl Fischer method. The Karl Fischer method for determining water content in a substance utilizes the specific reaction of the Karl Fischer reagent, which contains iodine, sulfur dioxide, and pyridine, with water in the presence of methanol. In particular, volumetric titration involves placing a titration solvent in a titration flask, dissolving the sample in the titration solvent, extracting the water from the sample, and then titrating the sample with the Karl Fischer reagent, whose main components are iodine, sulfur dioxide, and a base, to determine the water content. Water reacts with iodine and sulfur dioxide in the presence of a base and an alcohol. H20+I2+SO2+CH3OH+3RN → 2RN・HI+RN・HSO4CH3 From the above equation, since the reaction ratio between H20 and I2 is 1:1, the number of milligrams of water (titer) per 1 ml of Karl Fischer reagent is determined in advance using water or a water standard substance, etc. Then, the amount of water (mg) is calculated from the titer (ml) of Karl Fischer reagent required to measure the sample. Water content (mg) = Karl Fischer reagent titer (ml) x titer (mgH2O / ml) Karl Fischer reagent is also called KF reagent. Then, the moisture content relative to the total mass of the ink is calculated from the calculated moisture amount. Water content (%) = (amount of water in ink / total mass of ink) x 100

[0033] The water content can be controlled within the range of 0.05 to 0.80% by mass by controlling the octanol / water partition coefficient (ClogP) of the polymerizable monomer contained in the ink, controlling the hydroxyl value in the ink, etc. Another method for controlling the water content is to heat the ink.

[0034] The ClogP value of the polymerizable monomer is preferably within a range of 2.0 to 7.0. From the viewpoint of ejection stability, it is also preferable that the polymerizable monomer having a ClogP value within a range of 2.0 to 7.0 is contained in an amount of 30% by mass or more relative to the total ink. The hydroxy value in the ink is preferably 60 mgKOH / g or less. In order to keep the hydroxy value in the ink within this range, it is preferable to control the composition of the compound having a hydroxy value contained in the ink or to purify the compound having a hydroxy value. Examples of the compound having a hydroxy value include (meth)acrylate.

[0035] 2. Composition of inkjet ink The ink of the present invention contains a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator. The polymerizable monomer, the blocked isocyanate, and the photopolymerization initiator will be described below.

[0036] <Polymerizable monomer> The polymerizable monomer according to the present invention is a monofunctional (meth)acrylate or a polyfunctional (meth)acrylate. A monofunctional (meth)acrylate compound is a compound having one (meth)acrylate group in one molecule. Specific examples of the monofunctional (meth)acrylate compound include glycidyl (meth)acrylate, 3,4-epoxycyclohexyl (meth)acrylate, methylglycidyl (meth)acrylate, 3-methyl-3-(meth)acryloxymethyloxetane, 3-ethyl-3-(meth)acryloxymethyloxetane, 3-methyl-3-(meth)acryloxyethyloxetane, 3-ethyl-3-(meth)acryloxyethyloxetane, 2-phenyl-3-(meth)acryloxymethyl ... Oxetane, 2-trifluoromethyl-3-(meth)acryloxymethyloxetane, 4-trifluoromethyl-2-(meth)acryloxymethyloxetane, (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, iso-butyl (meth)acrylate, t-butyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, tricyclo[5.2.1.0 2,6]decanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, phenyl (meth)acrylate, glycerol mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, (meth)acrylate of an ethylene oxide adduct of lauryl alcohol, succinic acid mono[2-(meth)acryloyloxyethyl], maleic acid mono[2-(meth)acryloyloxyethyl], 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, or 1,4-cyclohexanedimethanol mono(meth)acrylate, n-butyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, isodecyl (meth)acrylate, tridecyl (meth)acrylate, and 2-(2-ethoxyethoxy)ethyl (meth)acrylate.

[0037] In the present invention, the term "polyfunctional monomer" refers to a compound having two or more functional groups. From the viewpoint of curing by radical polymerization, examples of the functional group include an ethylenically unsaturated bond-containing acryloyl group, methacryloyl group, allyl group, vinyl group, vinyl ester group, etc. However, the functional group is not limited to the above.

[0038] Examples of bifunctional acrylates include triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate, polypropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, neopentyl glycol diacrylate, bisphenol A PO (propylene oxide) adduct diacrylate, hydroxypivalic acid neopentyl glycol diacrylate, polytetramethylene glycol diacrylate, tricyclodecane dimethanol dimethacrylate, and tricyclodecane dimethanol diacrylate.

[0039] Examples of tri- or higher functional acrylates include trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate, glycerin propoxy triacrylate, and pentaerythritol ethoxy tetraacrylate.

[0040] Of the above acrylates, phenoxyethyl acrylate, o-phenylphenol acrylate, and 2-hydroxy-3-phenoxypropyl acrylate are preferred from the viewpoint of suppressing cure shrinkage.

[0041] From the viewpoint of rapid curing, neopentyl glycol diacrylate, tricyclodecane dimethanol diacrylate, bisphenol A PO adduct diacrylate, and hydroxypivalic acid neopentyl glycol diacrylate are preferred.

[0042] The acrylate may be a modified product. Examples of modified acrylates include ethylene oxide-modified acrylates including ethylene oxide-modified trimethylolpropane triacrylate and ethylene oxide-modified pentaerythritol tetraacrylate, propylene oxide-modified acrylates including propylene oxide-modified trimethylolpropane triacrylate and propylene oxide-modified pentaerythritol tetraacrylate, caprolactone-modified acrylates including caprolactone-modified trimethylolpropane triacrylate, and caprolactam-modified acrylates including caprolactam-modified dipentaerythritol hexaacrylate.

[0043] (Multifunctional (meth)acrylate with a ClogP value in the range of 2.0 to 7.0) The ink of the present invention preferably contains a polymerizable monomer having an octanol / water partition coefficient (ClogP) value in the range of 2.0 to 7.0, i.e., a polyfunctional (meth)acrylate having a ClogP value in the range of 2.0 to 7.0. When the ClogP value is in the range of 2.0 to 7.0, the amines derived from the blocked isocyanates hydrolyzed by the water content in the ink and the hydrolyzates of the (meth)acrylates react with the components in the ink to form reaction products. The solubility of the reaction products thus formed is improved, which prevents the elution of solids such as cured products and foreign matter, improving ejection stability.

[0044] Examples of polyfunctional (meth)acrylate monomers having a ClogP value in the range of 2.0 to 7.0 include EO-modified trimethylolpropane triacrylate (ClogP 4.0), dipropylene glycol diacrylate (ClogP 2.0), 1,10-decanediol dimethacrylate (ClogP 5.75), tricyclodecane dimethanol diacrylate (ClogP 4.69), and tricyclodecane dimethanol dimethacrylate (ClogP 5.12).

[0045] Furthermore, as the polyfunctional (meth)acrylate according to the present invention, the polyfunctional (meth)acrylates shown below can also be used.

[0046] [ka]

[0047] From the viewpoint of ejection stability, it is preferable that the ink contains 30% by mass or more of a polyfunctional (meth)acrylate monomer having a ClogP value in the range of 2.0 to 7.0, based on the total mass of the ink. In particular, it is preferable that the ink of the present invention contains 30 to 50% by mass of a polyfunctional (meth)acrylate monomer having a ClogP value in the range of 2.0 to 7.0, based on the total mass of the ink.

[0048] In the present invention, the "ClogP value" is a logP value calculated by calculation. The ClogP value can be calculated by the fragment method, the atomic approach method, etc. More specifically, the ClogP value can be calculated using the fragment method described in the following document or the following commercially available software package 1 or 2. Reference: C. Hansch and A. Leo, "Substituent Constants for Correlation Analysis in Chemistry and Biology" (John Wiley & Sons, New York, 1969) Software package 1: MedChem Software (Release 3.54, August 1991, Medicinal Chemistry Project, Pomona College, Claremont, CA), Software package 2: ChemDraw Ultra ver.20.0.0.47 (PerkinElmer Informatics) The numerical values ​​of the ClogP values ​​described in the present specification and elsewhere are "ClogP values" calculated using Software Package 2.

[0049] (bisphenol A structure) The polyfunctional (meth)acrylate preferably has at least one type of bisphenol A structure. Preferred examples of the polyfunctional (meth)acrylate monomer having a bisphenol A structure include the above-mentioned PO adduct diacrylate of bisphenol A, EO-modified bisphenol A diacrylate, and bisphenol A-type epoxy acrylate.

[0050] (hydroxy value) As described above, the sum of the hydroxy values ​​of the compounds having a hydroxy group contained in the ink of the present invention is preferably 60 mgKOH / g or less, and the lower limit is preferably 0.05 mgKOH / g or more from the viewpoint of adhesion. When the hydroxy value is within the above range, the generation of solids is suppressed even when the ink contains water, and the storage stability is excellent. Examples of means for adjusting the hydroxy value to be within the range of 0.05 to 60 mgKOH / g include appropriately selecting the compound having a hydroxy value contained in the ink, controlling the charging composition of the compound having a hydroxy value, and purifying the compound having a hydroxy value. In the present invention, the "hydroxy value" refers to the amount (mg) of potassium hydroxide (KOH) required to neutralize the acetic acid bonded to the hydroxy group when 1 g of the ink of the present invention is acetylated. The hydroxy value can be calculated according to the method described in JIS K0070-1992, or can be calculated from the charged composition of the compound having a hydroxy group in 1 g of ink.

[0051] The hydroxy value in the present invention is determined from the composition of the compound having a hydroxy group in 1 g of ink, among the above calculation methods. The specific calculation method is as shown in the following formula (a). Hydroxy value [mgKOH / g] = A [mol] × (number of hydroxyl groups in the compound with hydroxyl groups) × B [mg / mol] (a) In the above formula (a), "A" represents the number of moles of the compound having a hydroxy group in 1 g of ink, and "B" represents the molecular weight of 1 mole of potassium hydroxide (56,000 mg / mol). If the ink contains multiple types of compounds with hydroxy groups, the hydroxy value is calculated for each compound with a hydroxy group using the above formula (a), and the sum of the obtained hydroxy values ​​is taken as the hydroxy value per 1 g of ink.

[0052] The compound having a hydroxy group is not particularly limited as long as it has a hydroxy group in its structure. Examples of hydroxyalkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Furthermore, examples of hydroxy(meth)acrylates having an alicyclic structure include 1,4-cyclohexanedimethanol mono(meth)acrylate.

[0053] Examples of epoxy (meth)acrylates include aliphatic alcohol-based epoxy (meth)acrylates. ) acrylate, aliphatic polyhydric alcohol-based epoxy (meth)acrylate, phenol-based epoxy (meth)acrylate, etc. Furthermore, examples of the epoxy (meth)acrylate include polyhydric phenol-based epoxy (meth)acrylate, alicyclic carboxylic acid-based epoxy acrylate, aromatic carboxylic acid-based epoxy (meth)acrylate, etc. Commercially available epoxy (meth)acrylates can be used. Examples of such commercially available products include DENACOL ACRYLATE DA-111, DA-141, DA-212, DA-250, DA-314, DA-721, DA-722, DA-911M, DA-920, and DA-931. All of these commercially available products are manufactured by Nagase ChemteX Corporation. These compounds having a hydroxy group may be used alone or in combination of two or more.

[0054] In the ink of the present invention, the content of the polymerizable monomer is preferably within a range of 40 to 90% by mass, and more preferably within a range of 60 to 85% by mass, based on the total mass of the ink. By keeping the content within this range, coating adhesion is improved.

[0055] <Blocked isocyanate> A blocked isocyanate is a compound having an isocyanate group, the isocyanate group of which is blocked with a blocking agent. Hereinafter, the compound having an isocyanate group will also be referred to as an "isocyanate compound." Heating dissociates the blocking agent from the blocked isocyanate, activating the isocyanate group.

[0056] The ink of the present invention has storage stability because the blocked isocyanate has blocked isocyanate groups and is non-reactive until it is applied to a recording medium. After application, heating the ink to a temperature above the temperature at which the blocking agent dissociates generates isocyanate groups. These groups then react with hydroxyl and / or carboxyl groups of the monomer contained in the ink, causing the ink to harden and form a coating film.

[0057] (Isocyanate compounds) The isocyanate compound is preferably a polyfunctional isocyanate from the viewpoint of curability. The polyfunctional isocyanate is not particularly limited as long as it is a compound having two or more isocyanate groups in the molecule. Specific examples of polyfunctional isocyanates include aromatic polyisocyanates such as 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI), and 1,5-naphthalene diisocyanate (NDI); hexamethylene diisocyanate; aliphatic polyisocyanates such as transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6XDI (hydrogenated XDI), H12MDI (hydrogenated MDI), and H6TDI (hydrogenated TDI); polyisocyanates such as polymethylene polyphenylene polyisocyanate; and biuret, isocyanurate, and carbodiimide-modified products thereof. The ink of the present invention may use any one of these isocyanates alone or two or more of them in combination.

[0058] (blocking agent) As the blocking agent, known blocking agents can be used. Examples of blocking agents include alcohols such as ethanol, n-propanol, isopropanol, t-butanol, and isobutanol; phenols such as phenol, chlorophenol, cresol, xylenol, and p-nitrophenol; alkylphenols such as pt-butylphenol, psec-butylphenol, p-sec-aminophenol, p-octylphenol, and p-nonylphenol; basic nitrogen-containing compounds such as 3-hydroxypyridine, 8-hydroxyquinoline, and 8-hydroxyquinaldine; and active metal ions such as diethyl malonate, ethyl acetoacetate, and acetylacetone. Examples of suitable amines include ethylene compounds, acid amides such as acetamide, acrylamide, and acetanilide, acid imides such as succinimide and maleimide, imidazoles such as 2-ethylimidazole and 2-ethyl-4-methylimidazole, pyrazoles such as pyrazole, 3-methylpyrazole, and 3,5-dimethylpyrazole, lactams such as 2-pyrrolidone and ε-caprolactam, oximes of ketones or aldehydes such as acetoxime, methyl ethyl ketone oxime, cyclohexanone oxime, butanone oxime, and acetaldoxime, ethyleneimine, and bisulfites.

[0059] The blocking agent is preferably at least one compound selected from the group consisting of oxime compounds, pyrazole compounds, and active ethylene compounds, in terms of ink storage stability and thermal dissociation properties. Examples of oxime compounds include formamide oxime, acetaldoxime, acetoxime, methyl ethyl ketone oxime, cyclohexanone oxime, and butanone oxime (MEKO). Examples of the pyrazole compounds include pyrazole, 3-methylpyrazole, and 3,5-dimethylpyrazole. Examples of active ethylene compounds include dimethyl malonate, diethyl malonate (DEM), methyl acetoacetate, ethyl acetoacetate, and acetylacetone.

[0060] An example of the polyfunctional isocyanate compound having an isocyanate group protected with a blocking agent is 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate. Another example of the polyfunctional isocyanate compound having an isocyanate group protected with a blocking agent is 2-[(3-butylidene)aminooxycarbonylamino]ethyl methacrylate. Another example of the polyfunctional isocyanate compound having an isocyanate group protected with a blocking agent is 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl acrylate. Another example of the polyfunctional isocyanate compound having an isocyanate group protected with a blocking agent is 2-[(3-butylidene)aminooxycarbonylamino]ethyl acrylate.

[0061] The blocked isocyanate preferably has an aromatic ring structure from the viewpoint of ink storage stability and coating film performance. The blocked isocyanate having an aromatic ring is not particularly limited, but examples thereof include aromatic polyisocyanates such as 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI), and 1,5-naphthalene diisocyanate (NDI). The blocking agent for the blocked isocyanate may contain an aromatic group, and a blocking agent containing a benzene ring or a blocking agent containing a heteroaromatic ring is preferred. Dimethylpyrazole (DMP) is particularly preferred as a blocking agent for the blocked isocyanate containing an aromatic group.

[0062] The blocked isocyanate may contain a polyisocyanate structure. The polyisocyanate structure may be of three types: isocyanurate, biuret, and adduct. As the blocked isocyanate of the present invention, from the viewpoints of curability and coating film performance, the isocyanurate and biuret types are preferred, and the isocyanurate type (having an isocyanurate structure) is particularly preferred.

[0063] The content of the blocked isocyanate is preferably within a range of 0.1 to 20 parts by mass, and more preferably within a range of 1 to 10 parts by mass, per 100 parts by mass of the polymerizable monomer. When the amount of the blocked isocyanate is 0.1 parts by mass or more, the ink is sufficiently cured by heat, and when the amount of the blocked isocyanate is 20 parts by mass or less, the ink has excellent storage stability at high temperatures.

[0064] The blocking agent may be used alone or in combination of two or more kinds. Alternatively, a plurality of blocked isocyanates blocked with a single blocking agent or two or more kinds of blocking agents may be used. Examples of commercially available blocked isocyanates include BI7774, BI7779, BI7950, BI7960, BI7961, BI7981, BI7982, BI7991, and BI7992 (all manufactured by LANXESS), MFK60X (manufactured by Asahi Kasei Chemicals Corporation), VPLS2253 and BL4265SN (both manufactured by Sumika Bayer Urethane Co., Ltd.), PU5211 and PU5210 (both manufactured by Leeson Polyurethanes), Karenz MOI-BP (2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate), and Karenz MOI-BM (2-(0-[1′-methylpropylideneamino]carboxyamino)ethyl methacrylate) (both manufactured by Showa Denko KK).

[0065] <Photopolymerization initiator> When the polymerizable monomer (polyfunctional (meth)acrylate monomer) is a radical polymerizable compound, the photopolymerization initiator according to the present invention preferably uses a photoradical initiator. When the polymerizable monomer is a cationically polymerizable compound, the photopolymerization initiator according to the present invention preferably uses a photoacid generator. The ink of the present invention may contain only one type of photopolymerization initiator, or may contain two or more types of photopolymerization initiators. The photopolymerization initiator may be a combination of both a photoradical initiator and a photoacid generator.

[0066] Photoradical initiators include cleavage-type radical initiators and hydrogen abstraction-type radical initiators. Examples of cleavage-type radical initiators include acetophenone-based initiators, benzoin-based initiators, acylphosphine oxide-based initiators, benzyl and methylphenyl glyoxyesters.

[0067] Examples of acetophenone-based initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzil dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone.

[0068] Examples of benzoin-based initiators include benzoin, benzoin methyl ether, and benzoin isopropyl ether. Examples of acylphosphine oxide initiators include 2,4,6-trimethylbenzoindiphenylphosphine oxide. Examples of hydrogen abstraction radical initiators include benzophenone-based initiators, thioxanthone-based initiators, aminobenzophenone-based initiators, and 10-butyl-2-chloroacridone, and examples of hydrogen abstraction radical initiators include 2-ethylanthraquinone, 9,10-phenanthrenequinone, and camphorquinone.

[0069] Examples of benzophenone initiators include benzophenone, o-benzoylmethylbenzoate-4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylated benzophenone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, and 3,3'-dimethyl-4-methoxybenzophenone. Examples of thioxanthone initiators include 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone. Examples of aminobenzophenone initiators include Michler's ketone and 4,4'-diethylaminobenzophenone. Examples of photoacid generators include the compounds described in Organic Electronics Materials Research Group, "Imaging Organic Materials," Bunshin Publishing (1993), pp. 187-192.

[0070] The content of the photopolymerization initiator may be in a range that allows the ink to be sufficiently cured, and may be, for example, in the range of 0.01 to 10% by mass relative to the total mass of the ink of the present invention. Examples of commercially available photopolymerization initiators include Omnirad TPO, Omnirad 379, and Omnirad TPO (all manufactured by IGM), and Speedgure ITX (manufactured by Sartomer) and Speedcure EPD (manufactured by Sartomer).

[0071] <Polymerization inhibitor> The ink of the present invention preferably further contains a polymerization inhibitor, which can reduce the adhesiveness between multiple curable compounds. The term "polymerization inhibitor" includes all compounds added to inhibit polymerization reactions during preparation of ink containing polymerizable monomers or during storage after preparation.

[0072] In the present invention, various conventionally known polymerization inhibitors can be used. The polymerization inhibitor preferably contains any one of an N-oxyl-based polymerization inhibitor, a phenol-based polymerization inhibitor containing an ot-butyl group, or a polymerization inhibitor having two or more aromatic rings.

[0073] Among these, it is more preferable to contain an N-oxyl-based polymerization inhibitor from the viewpoint of adhesion to printed wiring boards. In the ink of the present invention, the content of the polymerization inhibitor is preferably within the range of 0.05 to 0.5% by mass relative to the total mass of the ink.

[0074] (N-oxyl polymerization inhibitor) Examples of the N-oxyl polymerization inhibitor include 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-methoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, Irgastab (registered trademark) UV10 (manufactured by BASF), and the like.

[0075] (Phenol-based polymerization inhibitor) Examples of phenolic polymerization inhibitors include 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, and 2-tert-butyl-4,6-dimethylphenol. Examples of phenolic polymerization inhibitors include 2,6-di-tert-butyl-4-methylphenol and 2,4,6-tri-tert-butylphenol. Examples of phenolic polymerization inhibitors include 2,6-di-t-butyl-p-cresol (butylated hydroxytoluene: BHT), 4-methoxyphenol, and 2-methoxy-4-methylphenol.

[0076] (Quinone-based polymerization inhibitor) Examples of the quinone polymerization inhibitor include hydroquinone, methoxyhydroquinone, benzoquinone, 1,4-naphthoquinone, and p-tert-butylcatechol.

[0077] (amine-based polymerization inhibitor) Examples of the amine-based polymerization inhibitor include alkylated diphenylamine, N,N'-diphenyl-p-phenylenediamine, and phenothiazine.

[0078] (Other polymerization inhibitors) Other examples of the polymerization inhibitor include copper dithiocarbamate polymerization inhibitors such as copper dimethyldithiocarbamate, copper diethyldithiocarbamate, and copper dibutyldithiocarbamate.

[0079] Only one of these may be contained, or two or more of them may be contained. Among these, N-oxyl and quinone polymerization inhibitors are preferred. As the inhibitor, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) is preferred. Furthermore, as the inhibitor, 2,6-di-t-butyl-p-cresol (butylated hydroxytoluene: BHT) and 2,4-di-tert-butylphenol are preferred. As a polymerization inhibitor having two or more aromatic rings, naphthoquinone and the like are preferred.

[0080] <Other ingredients> (surfactant) The ink of the present invention may further contain a surfactant, if necessary. Examples of surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, as well as silicone-based and fluorine-based surfactants. Examples of the anionic surfactant include dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts. Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene-polyoxypropylene block copolymers. Examples of the cationic surfactant include alkylamine salts and quaternary ammonium salts.

[0081] (coloring agent) The ink of the present invention may further contain a colorant, if necessary. The colorant may be a pigment or a dye, but is preferably a pigment from the viewpoints of having good dispersibility in the constituent components of the ink and excellent weather resistance. The pigment is not particularly limited, and examples thereof include organic pigments or inorganic pigments having the following numbers listed in the Color Index.

[0082] The ink of the present invention may contain only one type of colorant, or may contain two or more types of colorants, and may be toned to a desired color. The content of the colorant is preferably within a range of 0.1 to 20% by mass, and more preferably within a range of 0.2 to 10% by mass, relative to the total mass of the ink.

[0083] (pigment) Red or magenta pigment Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 53:1, 57:1, 57:2, 58:4, 63:1, 81, 81:1, 81:2, 81:3, 81:4, 88, 104, 108, 112, 122, 123, 144, 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, and 257; Pigment Violet 3, 19, 23, 29, 30, 37, 50, and 88; and Pigment Orange. 13, 16, 20, 36 or a mixture thereof.

[0084] Blue or cyan pigment Examples of blue or cyan pigments include pigments selected from Pigment Blue 1, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17:1, 22, 27, 28, 29, 36, and 60, or mixtures thereof.

[0085] Green Pigment Examples of green pigments include pigments selected from Pigment Green 7, 26, 36, and 50, and mixtures thereof.

[0086] Yellow pigment 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, 147, 153, 154, 155, 157, 166, 167, 168, 180, 185, and 193, or mixtures thereof.

[0087] Black pigment Examples of black pigments include pigments selected from Pigment Black 7, 28, and 26, and mixtures thereof.

[0088] <Examples of commercially available pigments> Examples of commercially available pigments include Black Pigment (manufactured by Mikuni), Chromofine Yellow 2080, 5900, 5930, AF-1300, 2700L, Chromofine Orange 3700L, 6730, Chromofine Scarlet 6750, Chromofine Magenta 6880, 6886, 6891N, 6790, 6887, Chromofine Violet RE, Chromofine Red 6820, 6830, Chromofine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5000P, and Chromofine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Chromofine Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400(B), 2500, 2600, ZAY-260, 2700(B), 2770, Seika Fast Red 8 040, C405(F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seika Fast Carmine 6B 1476T-7, 1483LT, 3840, 3870, Seika Fast Bordeaux 10B-430, Seika Light Rose R40, Seika Light Violet B 800, 7805, Seika Fast Maroon 460N, Seika Fast Orange 900, 2900, Seika Light Blue C718, A612, Cyanine Blue 4933M, 4933GN-EP, 4940, 4973 (all manufactured by Dainichi Seika Color & Chemicals Mfg. Co., Ltd.; "Chromofine" is a registered trademark of the 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 (manufactured by DIC);Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T-13, T-05, Pigment Yellow1705, Colortex Orange 202, Colortex Red101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, 105C, USN, Colortex Maroon601, Colortex BrownB610N, Colortex Violet600, Pigment Red 122, Colortex Blue516, 517, 518, 519, A818, P-908, 510, Colortex Green 402, 403, Colortex Black 702, U905 (all manufactured by Sanyo Dye 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, Hostapearm 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, and CF9 (all manufactured by Mitsubishi Chemical);

[0089] Pigment Dispersion The pigment can be dispersed using, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like.

[0090] The pigment is preferably dispersed so that the volume average particle size of the pigment particles is preferably within a range of 0.08 to 0.5 μm, and the maximum particle size of the pigment particles is preferably within a range of 0.3 to 10 μm, more preferably within a range of 0.3 to 3 μm. The dispersion of the pigment is adjusted by selecting the pigment, dispersant and dispersion medium, dispersing conditions, filtering conditions, and the like.

[0091] <Dispersant> The ink of the present invention may further contain a dispersant to improve the dispersibility of the pigment. Examples of dispersants include carboxylic acid esters having a hydroxy group, salts of long-chain polyaminoamides and high-molecular-weight acid esters, salts of high-molecular-weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, high-molecular-weight unsaturated acid esters, polymer copolymers, modified polyurethanes, modified polyacrylates, polyether ester-type anionic surfactants, naphthalene sulfonic acid formalin condensate salts, aromatic sulfonic acid formalin condensate salts, polyoxyethylene alkyl phosphate esters, polyoxyethylene nonylphenyl ether, and stearylamine acetate. Examples of commercially available dispersants include the Solsperse (registered trademark) series manufactured by Avecia and the PB series manufactured by Ajinomoto Fine-Techno Co., Ltd.

[0092] <Dispersion aid> The ink of the present invention may further contain a dispersing aid, if necessary. The dispersing aid may be selected depending on the pigment. The total content of the dispersant and dispersion aid is preferably within the range of 1 to 50% by mass relative to the total mass of the pigment.

[0093] 《Dispersion medium》 The ink of the present invention may further contain a dispersion medium for dispersing the pigment, if necessary. The ink of the present invention may contain a solvent as a dispersion medium, but in order to prevent the solvent from remaining in the formed image, it is preferable to use the above-mentioned monomer as the dispersion medium. As the above-mentioned monomer, a monomer having a particularly low viscosity can be used.

[0094] Furthermore, if a solvent is used as a dispersion medium, the solvent is likely to volatilize when the ink is heated, which is a problem from the viewpoint of ejection stability, and the dispersibility of the pigment is likely to decrease. However, by using the aforementioned polyfunctional (meth)acrylate monomer, the decrease in dispersibility of the pigment can be suppressed.

[0095] (Other additives) The ink of the present invention may further contain a coupling agent, a solvent, etc., as required.

[0096] Coupling Agents The ink of the present invention may further contain various coupling agents as needed, which can improve adhesion to printed wiring boards. Examples of various coupling agents include silane-based, titanium-based, and aluminum-based coupling agents.

[0097] <Curing accelerator> In the present invention, a curing accelerator may be contained as needed. The curing accelerator is not particularly limited as long as it accelerates the thermal curing of the resin component. Examples of the curing accelerator include imidazoles, dicyandiamide derivatives, dicarboxylic acid dihydrazides, triphenylphosphine, tetraphenylphosphonium tetraphenylborate, 2-ethyl-4-methylimidazole-tetraphenylborate, and 1,8-diazabicyclo[5.4.0]undecene-7-tetraphenylborate.

[0098] <Ion scavenger> In the present invention, an ion scavenger may be contained as needed. The inclusion of an ion scavenger has the advantage that ionic impurities are adsorbed, improving the insulating properties of the cured film when it absorbs moisture. Examples of the ion trapping agent include inorganic ion adsorbents such as triazine thiol compounds, bisphenol-based reducing agents, zirconium compounds, and antimony-bismuth-based magnesium aluminum compounds.

[0099] Flame retardants In the present invention, a flame retardant may be contained as needed. Examples of flame retardants that can be used include hydrated metals such as aluminum hydroxide and magnesium hydroxide, red phosphorus, ammonium phosphate, ammonium carbonate, zinc borate, zinc stannate, molybdenum compounds, bromine compounds, and chlorine compounds.Furthermore, examples of flame retardants that can be used include phosphate esters, phosphorus-containing polyols, phosphorus-containing amines, melamine cyanurate, melamine compounds, triazine compounds, guanidine compounds, and silicone polymers.

[0100] "solvent" The ink of the present invention is preferably solvent-free from the viewpoint of rapid curing and ejection stability, but solvents may be added to adjust the ink viscosity.

[0101] 3. Inkjet ink manufacturing method The ink of the present invention can be prepared by mixing the aforementioned polymerizable monomer, blocked isocyanate, photopolymerization initiator, and any other components. It is preferable to filter the resulting mixture through a predetermined filter. When preparing an ink containing a pigment, it is preferable to prepare a pigment dispersion containing the pigment and polymerizable monomer, and then mix the pigment dispersion with other components. The pigment dispersion may further contain a dispersant.

[0102] The pigment dispersion can be prepared by dispersing a pigment in a polymerizable compound. The pigment can be dispersed using, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, etc. In this case, a dispersant may be added.

[0103] 4. How to store inkjet ink The method for storing the ink of the present invention is the same as the method for storing the ink of the present invention described above, in which the ink is stored at a temperature of 30° C. and a humidity of 60% RH. Specifically, in order to store the ink within the above temperature and humidity ranges, it is preferable to use the following ink container as a container for containing the ink of the present invention.

[0104] [Ink container] The ink according to the present invention has a water vapor transmission rate of 0.05 to 1.50 g / m under conditions of 40°C and 90% RH. 2 It is preferable that the ink is contained in an ink container having a moisture permeability within the range of 1000 ppm / day / atm. Hereinafter, the ink container may be simply referred to as a "container." In the present invention, the water vapor permeability is a value measured using a method in accordance with JIS K7129 (40°C, 90% RH).

[0105] The container is a member that is filled with ink and substantially holds the ink. The form of the container in the present invention is not limited to the following, but examples include an ink cartridge, a pack, a bottle, a tank, a vial, and a can. Among these, ink cartridges, packs, bottles, and tanks are preferred, and packs are more preferred, because they are widely used and the water vapor transmission rate can be easily controlled to a desired value. Furthermore, the ink in the present invention can be contained in a bottle and then further contained in a pack.

[0106] A pack is a container made of flexible film. A pack is preferable because it is lightweight, can be easily placed in a box-shaped container, the volume of the container changes easily according to the amount of ink remaining, and the film can be heat-sealed to form a bag.

[0107] The container of this embodiment can be used in at least the following modes (A) to (C). (A) A form such as an ink cartridge that is separate from the inkjet recording device (film-coating device) and is attached to the recording device to sequentially supply the composition to the recording device. (B) A form that is separate from the recording device, and when ink is used, only the ink is transferred from the container to the recording device (C) A form such as a tank that is pre-installed in the recording device and contains ink

[0108] The above (A) and (B) can be said to be ink containers from the time of shipping until just before supplying (transferring) ink to the recording device. The above (C) can be said to be an ink container from the time the recording apparatus is shipped until the recording apparatus starts using ink for the first time. The above (A) and (C) can be said to be ink containers that perform printing in the recording device while ink is being supplied from the container to the recording device via a connection such as an ink tube. Furthermore, the above (B) can be said to be an ink container that transfers ink from the container to a recording device and then prints with the recording device. The object to which the ink is transferred in (B) can be a tank or the like attached to the recording device.

[0109] Examples of materials that can be used to form the container include polyethylene terephthalate (PET), polypropylene (PP), polyethylene, ethylene vinyl acetate copolymer, ethylene vinyl alcohol copolymer (EVOH), and polystyrene. The container may also be a film made of these materials. The container may also be constructed by blending the above materials in an appropriate ratio or by stacking multiple materials. In the case of a film, the container may be obtained by laminating. When multiple types of films are stacked, it is not necessary for all of the multiple films to be the above-mentioned films, and a portion of the films may be made of other materials, such as metals and metal compounds.

[0110] In order to increase the flexibility of the container, the container may contain a plasticizer as a constituent material. Examples of plasticizers include fatty acid esters, epoxy compounds, and polyester compounds. Among these, fatty acid esters are preferred in terms of versatility as plasticizers. Examples of fatty acid esters include phthalates, adipates, trimellitates, and citrates. The fatty acid esters may be used alone or in combination of two or more.

[0111] During storage and transportation, the container may be agitated to release the sedimentation of components contained in the ink. This is because, if the sedimentation of components contained in the ink continues for a long period of time, the sediment may turn into cake, making it difficult to release. Furthermore, when supplying ink from the container to a recording device, it is preferable to agitate the container to release the sedimentation.

[0112] When the container is a container (pack) made of a flexible film, durability is particularly required so that cracks and tears do not occur during the stirring operation. Preferred examples of durable film materials include plastic films such as polyethylene terephthalate (PET), polypropylene, polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polystyrene, etc. Ethylene-vinyl acetate copolymer is more preferred as the film material. Preferred examples of the film include stretched plastic films such as high-density, low-density, or linear low-density polyethylene, polypropylene, ethylene-vinyl alcohol copolymer, and polystyrene. A laminated film in which multiple layers of films are bonded together may also be used.

[0113] When the container is the above-mentioned pack, if the components contained in the ink settle, the pack may be shaken left and right to agitate the ink and restore the ink. In this case, in order to prevent the pack from cracking or breaking, a plasticizer may be contained as a constituent material of the pack. The plasticizer may be any of those listed above, and fatty acid esters are preferred.

[0114] When the container is the above-mentioned pack, the water vapor transmission rate of the film constituting the pack is 0.05 to 1.50 g / m under conditions of 40°C and 90% RH. 2 The water vapor transmission rate is preferably in the range of 0.05 to 1.00 g / m. 2 It is more preferable that the range is 0.05 to 0.5 g / m 2 It is particularly preferred that the temperature is in the range of 1000 kJ / day atm. Water vapor permeability of 0.05 to 1.50 g / m 2 By using a film within the range of 1000 ppm / day, it is possible to prevent the moisture content of the ink filled in the pack from increasing even when the pack is stored for a long period of time. Water vapor permeability of 1.50g / m 2 To achieve a value of 1.000 sq m / day atm or less, for example, the material constituting the film may be selected appropriately, or a layer composed of at least one of a metal and a metal compound may be provided on the film.

[0115] Among these, it is preferable to provide a layer made of at least one of a metal and a metal compound from the viewpoint of high versatility. Examples of metals include Al and Ti. Metal compounds are preferably metal oxides, such as alumina, silica, titania, and zirconia. These may be used alone or in combination of two or more. In this specification, metal oxides include silica.

[0116] The thickness of the film constituting the pack is preferably within the range of 50 to 200 μm. The lower limit of the film thickness is more preferably 70 μm or more, and even more preferably 80 μm or more. The upper limit of the film thickness is preferably 150 μm or less, and even more preferably 130 μm or less. When the film is a laminated film consisting of multiple layers, the film thickness is the total thickness. A film thickness within the above range is preferred in terms of the durability and flexibility of the film.

[0117] The volume of ink that can be stored in the container is not limited to the following, but is preferably in the range of 100 to 5000 mL. The lower limit of the ink volume is preferably 200 mL or more, and more preferably 500 mL or more. The upper limit of the ink volume is preferably 3000 mL or less, more preferably 2000 mL or less, and even more preferably 1000 mL or less. When the volume is within the above range, the curing property, storage stability, and ejection stability can all be further improved.

[0118] 5. Solder resist and printed wiring boards The solder resist preferably uses the ink of the present invention described above. The method for forming the solder resist pattern involves first patterning an oxide film of conductive material such as copper or zinc formed on a substrate by inkjet printing using the ink according to the present invention. The ink is then cured with light to form a resist film. Next, the oxide film in the portion not covered with the resist film is removed with an acid etching solution. Furthermore, by removing the resist film covering the oxide film with alkali, it is possible to form precise circuits and patterns. In this way, a printed wiring board having a solder resist is formed.

[0119] 6.Coating film formation method The method for forming a coating film using the ink of the present invention preferably includes the following steps (1) to (5). (1) Ink heating process (2) Ink degassing process (3) A process in which heated ink is ejected from the nozzle of an inkjet head and landed on a printed wiring board on which a circuit has been formed. (4) A process in which the ink is temporarily hardened by irradiating it with actinic rays. (5) After the temporary curing, the ink is heated to fully cure it. In the following, a method for forming a resist film will be described as an example of a method for forming a coating film.

[0120] <Step (1)> Step (1) is the process of heating the ink. By heating, the ink droplets can be ejected from the inkjet head in a heated state, which improves ejection stability. The temperature of the ink during ejection is preferably 40°C or higher, with the upper limit being preferably 100°C or lower. To further improve ejection stability, the temperature of the ink during ejection is more preferably within the range of 40 to 90°C. In particular, it is preferable to eject the ink at an ink temperature such that the viscosity of the ink is within the range of 7 to 15 mPa·s, more preferably within the range of 8 to 13 mPa·s.

[0121] The ink is preferably heated in a flow path that supplies the ink to the inkjet head so that the ink temperature at the time of ejection is 40° C. or higher. As the heating method, it is preferable to heat at least one of an ink supply system such as an ink tank of a head carriage, a supply pipe and a front chamber ink tank immediately before the head, a pipe with a filter, and an inkjet head by an ink heater. In particular, in the present invention, it is preferable to perform the heating process multiple times before ejection. Specifically, it is preferable to heat the first sub-tank that stores the ink in the ink supply system. In addition to heating the first sub-tank, it is also preferable to heat the second sub-tank immediately before ejection after degassing, as described below, or to heat the ink inside the inkjet head, in order to improve ejection performance.

[0122] The ink heating section may be a panel heater, a rubber heater, a ribbon heater, or a heater for retaining heat.

[0123] <Step (2)> Step (2) is a degassing step to remove air bubbles from the ink. The degassing method preferably uses, for example, hollow fibers or ultrasonic waves. When hollow fibers are used, an external reflux type hollow fiber membrane degassing module is preferred, in which the inside of the hollow fiber membrane is degassed and ink flows to the outside of the hollow fiber membrane. For example, the module described in International Publication No. 2022 / 102058 can be used as such an external reflux type hollow fiber membrane degassing module. Furthermore, an external reflux type hollow fiber membrane degassing module is preferred from the viewpoint of degassing efficiency and processing flow rate, but is not limited thereto. Other types of degassing modules, such as an internal reflux type, may also be used.

[0124] <Step (3)> In the step (3), ink droplets are ejected from an inkjet head and land on a recording medium, such as a printed wiring board, at positions corresponding to the resist film to be formed, thereby forming a pattern. The ejection method from the inkjet head may be either an on-demand method or a continuous method. The on-demand inkjet head may be of any of the following types: electro-mechanical conversion type, such as single cavity type, double cavity type, bender type, piston type, shear mode type, and shared wall type; and electro-thermal conversion type, such as thermal inkjet type and Bubble Jet (registered trademark) type (Bubble Jet is a registered trademark of Canon Inc.). The amount of ink droplets ejected is preferably within the range of 2 to 20 pL in terms of recording speed and image quality.

[0125] The printed wiring board is not particularly limited, but examples thereof include copper-clad laminates of all grades (FR-4, etc.) 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 made of fluorine-polyethylene-PPO-cyanate ester, and other materials, as well as polyimide films, PET films, glass substrates, ceramic substrates, wafer plates, stainless steel plates, etc.

[0126] The printed wiring board is preferably subjected to a fine roughening treatment to increase the contact area with the ink in order to improve adhesion with the ink. When coating ink using the inkjet method, the viscosity of the ink must be low so that it can be ejected from an inkjet head. Therefore, inks that are primarily composed of polymerizable monomers before coating and that are cured by actinic radiation after coating are used. Such inks tend to shrink upon curing after coating, which can lead to poor adhesion between the ink and the printed wiring board. Therefore, in order to increase the contact area with the wiring board, it is necessary to perform a fine roughening treatment on the wiring board. Furthermore, because the ink has a low viscosity, there is a problem of bleeding occurring on the roughened wiring board. Therefore, it is preferable to perform a treatment to adjust the contact angle after roughening the wiring board. Therefore, when the ink of the present invention is used for the above-mentioned purposes, it is preferable to perform a roughening treatment or a treatment to prevent bleeding as a pretreatment for the wiring substrate.

[0127] Examples of roughening treatment methods include physical polishing, which involves forming irregularities on the surface of the wiring board using means such as buffing or scrubbing to form a rough surface. Other roughening treatment methods include chemical polishing treatments such as those based on copper chloride, persulfate, sulfuric acid / hydrogen peroxide, formic acid, and organic acids. As a roughening treatment method, from the viewpoint of adhesion, chemical polishing treatment is preferred, and organic acid treatment is more preferred.

[0128] Specific examples of chemical polishing treatments include copper chloride-based products such as MacDermid's MultiPrep 200, persulfate-based products such as MacDermid's Microclean, ME-301, and PR-820, sulfuric acid / hydrogen peroxide-based products such as Shikoku Kasei's GB1000F / 1400, G200, GB3100, and GB4300, MacDermid's Metex G-5, Metex G-6, ME-501, ME-602, ME-605, and ME-709, BOARDTEC's BTH-2066, and Mitsubishi Gas Chemical Company's CPE-900, EMR-5000, and EMR-7000, and organic acid-based products such as MEC's ​​CZ8100, CZ8101, and CZ8202, and BOARDTEC's BTH-2083 and BTH-2085. From the viewpoint of adhesion, sulfuric acid / hydrogen peroxide-based and organic acid-based compounds are preferred, and organic acid-based compounds are more preferred. As a treatment for preventing bleeding, CL8300 series from MEC and BTH-3066 from BOARDTEC are preferred.

[0129] The surface roughness of the copper plate roughened by the above pretreatment is preferably Ra 0.1 to 1.5 μm, more preferably 0.3 to 1.3 μm, and most preferably 0.4 to 1.1 μm. If Ra is 0.1 μm or more, adhesion is improved, and if it is 1.5 μm or less, bleeding is suppressed. The thickness of the copper plate roughened with the pretreatment agent is preferably 0.1 to 3.0 μm, more preferably 0.3 to 2.0 μm, and even more preferably 0.5 to 1.5 μm. If the roughening thickness is 0.1 μm or more, adhesion is improved due to the anchor effect, and if it is 3.0 μm or less, copper is not unnecessarily roughened or densified, thereby improving adhesion. The surface roughness can be controlled by adjusting the conditions such as the type of pretreatment agent, the treatment temperature, and the treatment time. The surface roughness can be measured using a laser microscope, a white light interference microscope, or the like.

[0130] <Step (4)> In step (4), the ink deposited in step (3) is irradiated with actinic rays to temporarily cure the ink. The actinic ray can be selected from, for example, electron beams, ultraviolet rays, α rays, γ rays, and X-rays, and is preferably ultraviolet rays. The ultraviolet light can be irradiated using, for example, a water-cooled LED manufactured by Phoseon Technology under conditions of a wavelength of 300 to 420 nm.

[0131] The ultraviolet irradiation is carried out such that the peak irradiance of the ultraviolet light on the surface of the resist film having a wavelength in the range of 300 to 420 nm is preferably 0.5 to 10 W / cm. 2 The irradiation of ultraviolet light is more preferably carried out so that the peak irradiance of the ultraviolet light on the surface of the resist film is in the range of 1 to 5 W / cm. 2 The measurement should be carried out so that it is within the range of 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 1000 mJ / cm 2 It is preferable that it is less than 10 ... The irradiation of actinic rays is preferably carried out within 0.001 to 300 seconds after the ink has landed, and more preferably within 0.001 to 60 seconds in order to form a highly precise resist film.

[0132] <Step (5)> In step (5), after the preliminary curing in step (4), the ink is further heated to fully cure it. The heating method is preferably, for example, placing the product in an oven set to a temperature in the range of 110 to 180° C. for 10 to 60 minutes.

[0133] 7.Coating film forming device The ink of the present invention is suitably used in a coating film forming apparatus, such as an inkjet recording apparatus equipped with an inkjet head. The inkjet recording apparatus preferably includes an ink heating unit, a degassing unit, and an inkjet head, and also preferably includes an actinic ray irradiation unit (UV irradiation unit) that irradiates the ink that has landed on the recording medium with actinic rays.

[0134] As described above, the ink heating section preferably heats the ink in the flow path that supplies ink to the inkjet head so that the ink temperature at the time of ejection is 40° C. or higher. The ink heating section is preferably provided in at least one of an ink supply system such as an ink tank on the head carriage, a supply pipe, and a front chamber ink tank immediately before the head, a pipe with a filter, and an inkjet head. In particular, in the present invention, the ink heating unit is preferably provided in the ink supply system, in the first sub-tank that stores ink, in the second sub-tank immediately before ejection after degassing, or in the inkjet head. The ink heating section may be a panel heater, a rubber heater, a ribbon heater, or a heater for retaining heat.

[0135] The degassing device preferably has a configuration using hollow fibers, for example. When hollow fibers are used, an external reflux type hollow fiber membrane degassing module is preferred, in which the inside of the hollow fiber membrane is degassed and ink is circulated to the outside of the hollow fiber membrane. The degassing device may include an ink heating unit.

[0136] The actinic ray irradiation unit irradiates the ink with energy rays to cure the ink after the ink has been ejected onto the recording medium. The actinic ray irradiation unit has, for example, a fluorescent tube such as a low-pressure mercury lamp, and irradiates the ink with energy rays such as ultraviolet light by causing the fluorescent tube to emit light.

[0137] Examples of fluorescent tubes that emit ultraviolet rays include low-pressure mercury lamps and mercury lamps with operating pressures of several hundred Pa to 1 MPa. Examples of such fluorescent tubes include light sources that can be used as germicidal lamps, cold cathode tubes, ultraviolet laser light sources, metal halide lamps, and light-emitting diodes. Among these, light sources that can irradiate ultraviolet rays with higher illuminance and consume less power (such as light-emitting diodes) are more desirable. The energy rays are not limited to ultraviolet rays, and any energy rays that have the property of curing ink depending on the properties of the ink may be used, and the light source may be changed depending on the wavelength of the energy rays, etc.

[0138] The recording method of the inkjet recording apparatus is preferably a scanning method from the viewpoint of ejection stability and printing accuracy.

[0139] Types of inkjet recording devices include single-pass printers and serial printers. Single-pass printers are equipped with a line head having a length equivalent to the width of the recording medium (recording medium width). In single-pass printers, the head is fixed and does not move (almost) at all, and printing is performed in one pass (single pass).

[0140] On the other hand, in a serial printer, printing is usually performed in two or more passes (multi-pass) while the head moves back and forth (shuttle movement) in a direction perpendicular to the conveyance direction of the recording medium.

[0141] Single-pass printers require a relatively large number of inkjet heads because they need to line up multiple inkjet heads, whereas serial printers can be configured with only a small number of recording heads. [Example]

[0142] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, operations were carried out at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass," respectively.

[0143] <Preparation of Yellow Pigment Dispersion (Y Dispersion)> Dispersant 1 and Dispersant 2 shown below and the dispersion medium were placed in a stainless steel beaker, heated on a hot plate at 65°C for 1 hour while stirring and dissolving, and then cooled to room temperature. The pigment shown below was then added, and the mixture was placed in a glass bottle together with 200 g of 0.5 mm diameter zirconia beads and sealed. The mixture was dispersed in a paint shaker until the desired particle size was reached, after which the zirconia beads were removed. Dispersant 1: EFKA7701 (manufactured by BASF) 5.6 parts by mass Dispersant 2: Solsperse 22000 (manufactured by Lubrizol Japan) 0.4 parts by mass Dispersion medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 80.6 parts by mass Pigment: PY147 (pigment yellow 147) (BASF Oracet® Yellow 140) 13.4 parts by mass

[0144] <Preparation of cyan pigment dispersion (C dispersion)> The yellow pigment dispersion was prepared in the same manner as in the preparation of the yellow pigment dispersion, except that the dispersant, dispersion medium, and pigment were changed as shown below. Dispersant: EFKA7701 (BASF) 7 parts by mass Dispersion medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 70 parts by mass Pigment: PB15:4 (pigment blue 15:4) (Dainichi Seika Chemicals, Chromofine Blue 6332JC) 23 parts by mass

[0145] <Blocked isocyanate> The blocked isocyanates used were those shown in Table I below. Note that in Table III and onward, "Trixene BI7982," "Trixene BI7992," and "Trixene BI7961" are abbreviated as "BI7982," "BI7992," and "BI7961," respectively. Furthermore, "Karenz MOI-BP" and "Karenz MOI-BM" are abbreviated as "MOI-BP" and "MOI-BM," respectively.

[0146] [Table 1]

[0147] <Polymerizable monomer> The polymerizable monomers used were those shown in Table II below.

[0148] [Table 2]

[0149] <Photopolymerization initiator> The photopolymerization initiator used was as follows: Omnirad 379EG (IGM) Omnirad TPO H (IGM) Speedcure 2-ITX (Sartomer, 2-isopropylthioxanthone)

[0150] <Other additives> ·melamine

[0151] <Preparation of Inkjet Ink> The ingredients were mixed according to the ink compositions shown in Tables III to VII below, and the mixture was filtered through a 3 μm Teflon (registered trademark) membrane filter manufactured by ADVANTEC while being heated to 60° C., to obtain inks 1 to 25.

[0152] [Table 3]

[0153] [Table 4]

[0154] [Table 5]

[0155] [Table 6]

[0156] [Table 7]

[0157] <Water content of ink> The moisture content of the ink stored in a storage container for one year after manufacture in an environment of 30°C temperature and 60% RH was measured using a Karl Fischer moisture meter (MKV-710, manufactured by Kyoto Electronics Manufacturing Co., Ltd.). The details of the method for calculating the moisture content are as described above. The storage container used was a container with a water vapor transmission rate of 15 g / m 2 A general polyethylene flexible packaging material with a temperature of 100°C / day atm was used, and the ink was sealed in this flexible packaging material. The water vapor transmission rate was measured using a method in accordance with JIS K7129 (40°C, 90% RH). The reason for using a general flexible packaging material as a storage container is to demonstrate that the water content can be reduced with the ink of the present invention even when using a general packaging material.

[0158] <Hydroxy value in ink> The hydroxy value in each ink was calculated from the charged composition of the compound having a hydroxy group in 1 g of ink. The specific calculation method is as shown in the following formula (a). Hydroxy value [mgKOH / g] = A [mol] × (number of hydroxyl groups in the compound with hydroxyl groups) × B [mg / mol] (a) In the above formula (a), "A" represents the number of moles of the compound having a hydroxy group in 1 g of ink, and "B" represents the molecular weight of 1 mole of potassium hydroxide (56,000 mg / mol). If the ink contains multiple types of compounds with hydroxy groups, the hydroxy value is calculated for each compound with a hydroxy group using the above formula (a), and the sum of the obtained hydroxy values ​​is taken as the hydroxy value per 1 g of ink.

[0159] <Copper substrate processing> A copper-clad laminate for printed wiring boards (FR-4, thickness 1.6 mm, size 150 mm × 95 mm) was treated with MEC's ​​CZ-8100 treatment solution. This produced a pretreated copper substrate with a surface roughness Ra of 1.5 μm and a treatment depth of 1 μm.

[0160] <Inkjet pattern formation> After storing each ink in the storage container for one year at a temperature of 30°C and a humidity of 60%RH, the ink was loaded into an inkjet recording device having an inkjet recording head equipped with a piezoelectric inkjet nozzle. Using this device, a pattern was formed on a copper-clad laminate for printed wiring boards (FR-4, thickness 1.6 mm, size 150 mm × 95 mm) that had been pretreated as described above. The ink supply system of the device comprises an ink tank, an ink flow path, a sub-ink tank provided immediately before the ink jet recording head, piping with a metal filter, and a piezo head. The ink from the ink tank to the head was heated to 60°C. Next, a heater was also installed in the piezo head, and the ink temperature inside the piezo head was heated to 55°C. The piezo head used was a KM1800i-SHC manufactured by Konica Minolta. Using this inkjet recording device, voltage was applied so that the droplet volume would be 3.5 pL. Then, a 70 mm x 70 mm solid pattern and a comb-shaped pattern with 100 μm lines and spaces were printed on the substrate, each with a thickness of 30 μm. After that, an LED lamp (365 nm) manufactured by Phoseon Technology was used to print the pattern at 1000 mJ / cm. 2 The ink layer was then temporarily cured by irradiating it with light at a rate of 2000 mJ / cm 2 in an oven set at 150°C for 60 minutes. 2 After irradiation, a print sample was obtained.

[0161] [evaluation] <Solid matter generation amount> Each ink was stored in the storage container at a temperature of 30°C and a humidity of 60%RH for one year from the date of manufacture, and then stored at the injection temperature (60°C) for one day. 300 ml of the ink was then pressure-filtered using a 5 μm PTFE filter (2 mm diameter). The 5 μm PTFE filter was then removed and washed with ethanol. The presence or absence of solid matter was checked using an optical microscope and evaluated according to the following criteria. "A" and "B" in the following criteria are considered to be acceptable for practical use. (standard) A: No solid matter is present on the entire surface of the filter. B: Solids are present within less than 1% of the filter area. C: Solid matter is present in an area of ​​1% or more but less than 10% of the filter area. D: Solid matter is present over 10% or more of the filter area.

[0162] <Ink ejection stability> Using the piezo head, ink was continuously ejected (driven) under conditions of droplet volume of 3.5 pL, droplet speed of 7 m / sec, ejection frequency of 40 kHz, and printing rate of 100%. The number of nozzles that were not ejecting was counted 1 minute, 5 minutes, and 10 minutes after the start of driving, and evaluated according to the following criteria. "A" and "B" in the following criteria are considered to be no problem in practical use. (standard) A: The number of missing nozzles is less than two. B: The number of missing nozzles is 2 or more and less than 10. C: The number of missing nozzles is 10 or more and less than 50. D: The number of missing nozzles is 50 or more.

[0163] <Substrate adhesion> For solid pattern print samples, grid-shaped cuts were made in the cured film according to the cross-cut method of JIS K5600, adhesive tape was applied, and the tape was peeled off to observe the peeling state of the cured film. Here, the residual adhesion rate was calculated by taking the number of squares made by the cuts as the denominator and the number of squares remaining after tape peeling as the numerator. The calculated residual adhesion rate was evaluated according to the following criteria. "A" and "B" in the following criteria are considered to be acceptable for practical use. (standard) A: The adhesion residual rate is 100%. B: The residual adhesion rate is 80% or more and less than 100%. C: The residual adhesion rate is 60% or more and less than 80%. D: The residual adhesion rate is less than 60%.

[0164] [Table 8]

[0165] As shown by the above results, the ink of the present invention suppresses the generation of solid matter even when stored for a long period of time, has good ejection properties, and is excellent in adhesion to the substrate, compared to the ink of the comparative example. [Industrial Applicability]

[0166] The present invention can be used for ink-jet inks containing blocked isocyanates, which can provide good ejection properties and stable curing properties even when stored for a long period of time.

Claims

1. An inkjet ink containing a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator, the ink-jet ink contains 30% by mass or more of the polymerizable monomer having an octanol / water partition coefficient (ClogP) value in the range of 2.0 to 7.0; the sum of the hydroxy values ​​of the compounds having a hydroxy group contained in the inkjet ink is 0.05 mgKOH / g or more and 60 mgKOH / g or less, and An inkjet ink, wherein the water content of the inkjet ink, measured by the Karl Fischer method, is within the range of 0.05 to 0.80% by mass relative to the total mass when stored at a temperature of 30°C and a humidity of 60% RH for one year from the date of manufacture.

2. 2. The ink-jet ink according to claim 1, which is ejected at a temperature of 40[deg.] C. or higher.

3. 2. The ink-jet ink according to claim 1, wherein the blocked isocyanate has an aromatic ring structure.

4. 2. The ink-jet ink according to claim 1, wherein the blocked isocyanate has an isocyanurate structure.

5. 2. The ink-jet ink according to claim 1, wherein the polymerizable monomer comprises at least one polymerizable monomer having a bisphenol A structure.

6. A method for storing the inkjet ink according to any one of claims 1 to 5, comprising the steps of: Inkjet ink storage method: Store at a temperature of 30°C and a humidity of 60% RH.

Images