Inkjet ink, solder resist, printed wiring board, coating film forming method and coating film forming device

Abstract

This inkjet ink comprises a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator, and has a water content, as determined by the Karl Fischer method, in the range of 0.05-0.60 mass% with respect to the total mass of the inkjet ink.

Description

[Technical Field]

[0001] The present invention relates to an inkjet ink, a solder resist, a printed wiring board, a coating film forming method, and a coating film forming apparatus. In particular, the present invention relates to an inkjet ink that exhibits good ejection properties, stable curing properties, and coating film performance even when an inkjet ink containing a blocked isocyanate is used. [Background technology]

[0002] In order to protect the circuit patterns on the printed wiring boards of printed circuit boards (PCBs), an insulating film (solder resist film) is formed by applying and curing ink. Conventionally, solder resist has been patterned to match the PCB wiring using silk screen printing, photo development, direct exposure equipment, etc. However, in recent years, methods of applying solder resist film using the inkjet method have been considered in light of material waste and environmental regulations.

[0003] For example, it has already been proposed to form a solder resist on a copper-clad laminate for printed wiring boards by using an inkjet printer with an inkjet ink containing a thermosetting agent (see, for example, Patent Documents 1 to 3). 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 inkjet ejection performance, curable inks are 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 water content to 500 ppm is difficult to achieve in practice because it imposes a heavy manufacturing burden, is difficult to maintain and store, and leads to increased costs. Furthermore, this method is based on the premise that the ink will be used immediately 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 film-forming apparatus when an inkjet ink containing a blocked isocyanate is used. As a result, the present invention aims to provide an inkjet ink, a solder resist, a printed wiring board, a film-forming method, and a film-forming apparatus that exhibit good ejection properties, stable curing properties, and film performance. 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, in the course of investigating the causes of the above-mentioned problems, determined the water content of inkjet inks containing blocked isocyanates, and discovered that this makes it possible to provide inkjet inks and the like that can suppress the generation of cured products and solids in coating film forming equipment and achieve good jetting properties, stable curing properties, and coating film performance, thereby arriving at the present invention.

[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 ink-jet ink has a water content measured by the Karl Fischer method in the range of 0.05 to 0.60% by mass relative to the total mass of the ink-jet ink.

[0010] 2. Ink that is ejected at temperatures above 40°C 2. The inkjet ink according to claim 1.

[0011] 3. The blocked isocyanate has an aromatic ring structure. 2. The inkjet ink according to claim 1.

[0012] 4. The blocked isocyanate has an isocyanurate structure. 2. The inkjet ink according to claim 1.

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

[0015] 6 2. An inkjet ink according to claim 1, wherein the sum of the hydroxy values ​​of compounds having hydroxy groups contained in the inkjet ink is 60 mgKOH / g or less.

[0016] 7Water vapor permeability is 0.05 to 1.50 g / m under conditions of 40°C and 90% RH. 2 2. The ink-jet ink according to claim 1, which is contained in a container having a viscosity within the range of 1000 kJ / day atm.

[0017] 8 .Items 1 to 5 7 A solder resist containing the inkjet ink according to any one of claims 1 to 5.

[0018] 9 .No. 8 A printed wiring board having the solder resist according to item 1.

[0019] 10 .Items 1 to 5 7 Item 1. A method for forming a coating film using the inkjet ink according to any one of items 1 to 5, wherein the inkjet ink is heated to 40°C or higher in a flow path that supplies the inkjet ink to an inkjet head of a coating film forming device.

[0020] 11 .Items 1 to 5 7 A coating film forming apparatus equipped with the ink-jet ink according to any one of claims 1 to 5, A coating film forming apparatus, comprising a means for heating the inkjet ink to 40° C. or higher in a flow path that supplies the inkjet ink to an inkjet head of the coating film forming apparatus. [Effects of the Invention]

[0021] The above-described means of the present invention can suppress the generation of solid matter in a film-forming apparatus even when an ink containing a blocked isocyanate is used, thereby providing an inkjet ink, a solder resist, a printed wiring board, a film-forming method, and a film-forming apparatus that exhibit good jetting properties, stable curing properties, and film performance. 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 ink is set to a range of 0.05 to 0.60% by mass relative to the total mass of the ink. This reduces the reaction of the blocked isocyanate in the ink with water or hydroxy groups. As a result, the generation of solids in the coating film forming device is suppressed, the ink ejection properties are good, and stable ink curing and coating performance are obtained. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram illustrating ink flow paths in an inkjet recording apparatus according to an embodiment of the present invention. [Figure 2] Schematic cross-sectional view of an external reflux type degassing module [Figure 3A] Schematic cross-sectional view showing the internal structure of the central tube of an external circulation type degassing module [Figure 3B] Schematic cross-sectional view showing the internal structure of the central tube of an external circulation type degassing module DETAILED DESCRIPTION OF THE INVENTION

[0023] The inkjet ink of the present invention is an inkjet ink containing a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator, wherein the polymerizable monomer is a polyfunctional (meth)acrylate, and the water content of the inkjet ink measured by the Karl Fischer method is within a range of 0.05 to 0.60% by mass relative to the total mass of the inkjet ink. This feature is a technical feature common to or corresponding to each of the following embodiments.

[0024] In an embodiment of the present invention, the ink is preferably ejected at 40° C. or higher, since the viscosity can be reduced. That is, since a monomer with a large molecular weight and high interaction is used to enhance performance, the viscosity can be adjusted by heating to 40° C. or higher before ejection.

[0025] 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.

[0026] The blocked isocyanate preferably has an isocyanurate structure, in that excellent adhesion of the coating film is obtained.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] Water vapor permeability is 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 a container that has a temperature within the range of 1000 ppm / day atm, in that an increase in the water content of the ink can be suppressed.

[0031] The solder resist of the present invention preferably contains the ink-jet ink, in that the coating performance of the solder resist is improved. The printed wiring board of the present invention preferably comprises the solder resist, since the circuit pattern of the printed wiring board can be protected by the solder resist having good coating performance.

[0032] The coating film forming method of the present invention is a coating film forming method using an inkjet ink, in which the inkjet ink is heated to 40° C. or higher in a flow path that supplies the inkjet ink to an inkjet head of a coating film forming apparatus. The coating film forming apparatus of the present invention is a coating film forming apparatus equipped with inkjet ink, and has a means for heating the inkjet ink to 40°C or higher in a flow path that supplies the inkjet ink to an inkjet head of the coating film forming apparatus. This reduces the viscosity of the ink when it is ejected. Furthermore, because the ink's water content is low even when heated to 40°C or higher, the generation of solids due to the blocked isocyanate in the ink reacting with water, hydroxyl groups, etc. is suppressed. As a result, the ink has good ejection properties and stable ink curing and coating performance.

[0033] 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.

[0034] 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 the water content of the inkjet ink measured by the Karl Fischer method is within the range of 0.05 to 0.60% by mass relative to the total mass of the inkjet ink.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] <Moisture content> The ink of the present invention has a water content measured by the Karl Fischer method in the range of 0.05 to 0.60% by mass relative to the total mass of the ink, and preferably in the range of 0.05 to 0.30% by mass from the viewpoints of solid matter generation and ejection properties.

[0039] (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

[0040] The water content can be controlled within the range of 0.05 to 0.60% 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.

[0041] 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 within the range of 0.05 to 60 mgKOH / g. 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.

[0042] 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.

[0043] <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.

[0044] 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. The polymerizable monomer used in the present invention preferably contains a polyfunctional monomer from the viewpoint of the physical properties of the coating film.

[0045] 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.

[0046] 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.

[0047] Of the above acrylates, phenoxyethyl acrylate, o-phenylphenol acrylate, and 2-hydroxy-3-phenoxypropyl acrylate are preferred from the viewpoint of suppressing cure shrinkage.

[0048] 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.

[0049] 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.

[0050] (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.

[0051] Examples of polyfunctional (meth)acrylate monomers having a ClogP value in the range of 2.0 to 7.0 include 1,6-hexanediol diacrylate (ClogP 3.0) (Monomer E described below), EO-modified trimethylolpropane triacrylate (ClogP 4.0), dipropylene glycol diacrylate (ClogP 2.0), propoxylated (2) neopentyl glycol diacrylate (ClogP 4.9), 1,10-decanediol dimethacrylate (ClogP 5.75), tricyclodecane dimethanol diacrylate (ClogP 4.69), and tricyclodecane dimethanol dimethacrylate (ClogP 5.12). Other monomers listed in the examples described below can also be used.

[0052] 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.

[0053] 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 commercially available software package 1 or 2 listed below. 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.

[0054] (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.

[0055] (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.

[0056] 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 value values ​​is defined as the hydroxy value per 1 g of ink.

[0057] 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.

[0058] Examples of epoxy (meth)acrylates include aliphatic alcohol-based epoxy (meth)acrylates, aliphatic polyhydric alcohol-based epoxy (meth)acrylates, and phenol-based epoxy (meth)acrylates. Examples of epoxy (meth)acrylates include polyhydric phenol-based epoxy (meth)acrylates, alicyclic carboxylic acid-based epoxy acrylates, and aromatic carboxylic acid-based epoxy (meth)acrylates. 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.

[0059] 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.

[0060] <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.

[0061] 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.

[0062] (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.

[0063] (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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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).

[0070] <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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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).

[0076] <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.

[0077] 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.

[0078] 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.

[0079] (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.

[0080] (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.

[0081] (Quinone-based polymerization inhibitor) Examples of the quinone polymerization inhibitor include hydroquinone, methoxyhydroquinone, benzoquinone, 1,4-naphthoquinone, and p-tert-butylcatechol.

[0082] (amine-based polymerization inhibitor) Examples of the amine-based polymerization inhibitor include alkylated diphenylamine, N,N'-diphenyl-p-phenylenediamine, and phenothiazine.

[0083] (Other polymerization inhibitors) Other examples of the polymerization inhibitor include copper dithiocarbamate polymerization inhibitors such as copper dimethyldithiocarbamate, copper diethyldithiocarbamate, and copper dibutyldithiocarbamate.

[0084] 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.

[0085] <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.

[0086] (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.

[0087] 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.

[0088] (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.

[0089] 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.

[0090] Green Pigment Examples of green pigments include pigments selected from Pigment Green 7, 26, 36, and 50, and mixtures thereof.

[0091] 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.

[0092] Black pigment Examples of black pigments include pigments selected from Pigment Black 7, 28, and 26, and mixtures thereof.

[0093] <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 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 Pigment 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).

[0094] 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.

[0095] 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.

[0096] <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.

[0097] <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.

[0098] 《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.

[0099] 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.

[0100] (Other additives) The ink of the present invention may further contain a coupling agent, a solvent, etc., as required.

[0101] 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.

[0102] <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.

[0103] <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.

[0104] 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.

[0105] "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.

[0106] 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.

[0107] 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.

[0108] 4. How to store inkjet ink The method for storing the ink according to the present invention is the same as the method for storing the ink according to the present invention described above, and it is preferable to store the ink at a temperature within the range of -15 to 40°C and at a humidity of 60% RH or less. 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.

[0109] [Ink container] The ink of 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 temperature is kept within the range of 100°C / day atm. Hereinafter, the ink container will also be simply referred to as the "container."

[0110] 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.

[0111] 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.

[0112] 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

[0113] 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 part 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 5. Solder resist and printed wiring boards The solder resist 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.

[0124] 6.Coating film formation method The coating film forming method of the present invention is a method for forming a coating film using the inkjet ink, in which the ink is heated to 40°C or higher in a flow channel that supplies the ink to an inkjet head of a coating film forming device. That is, the coating film forming method includes a step of heating the ink. Furthermore, the coating film forming method preferably includes the following steps (2) to (5) in addition to the step (1) of heating the ink. (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.

[0125] <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.

[0126] 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.

[0127] The ink heating section may be a panel heater, a rubber heater, a ribbon heater, or a heater for retaining heat.

[0128] <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.

[0129] <Step (3)> In the step (3), ink droplets are ejected from an inkjet head and landed 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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, MEC's ​​CZ8300 series and BOARDTEC's BTH-3066 are preferred.

[0134] 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.

[0135] <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.

[0136] 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.

[0137] <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.

[0138] 7.Coating film forming equipment The coating film forming apparatus of the present invention is a coating film forming apparatus equipped with the inkjet ink, and has a means (ink heating unit) for heating the ink to 40° C. or higher in a flow path that supplies the ink to an inkjet head. The film forming apparatus of the present invention will be described in detail below with reference to the drawings. However, the scope of the present invention is not limited to the illustrated examples. In the following description, components having the same functions and configurations are designated by the same reference numerals, and their description will be omitted.

[0139] An example of the coating film forming device is an inkjet recording device equipped with an inkjet head. The inkjet recording apparatus preferably has an ink heating unit, a degassing unit, and an inkjet head. Furthermore, the inkjet recording apparatus preferably has an actinic ray irradiation unit (UV irradiation unit) that irradiates the ink that has landed on the recording medium with actinic rays.

[0140] FIG. 1 is a diagram illustrating the ink flow path in an inkjet recording apparatus. In the inkjet recording apparatus 1, ink is pumped out from an ink tank 51 of an ink supply unit 50 by a supply pump 53 and supplied to each recording head 24a via an ink flow path 24b. The inkjet recording apparatus 1 is also configured to be able to return ink that was not ejected from each recording head 24a to the ink flow path 24b as needed.

[0141] A first sub-tank 241, a degassing device 280, a liquid feed pump 243, a check valve 244, a second sub-tank 245, and the like are provided on the ink flow path 24b. The recording head 24a, the ink flow path 24b, and each component part located on the ink flow path 24b are heated and kept warm by an ink heating unit (ink heating means) 270, so that the ink temperature is maintained at an appropriate temperature. Specifically, the ink heating unit 270 heats the recording head 24a, the ink flow path 24b, and each component part located on the ink flow path 24b so that the ink ejection temperature is 40°C or higher.

[0142] <Ink heating unit> The ink heating unit 270 is preferably provided at least between the first sub-tank 241 and the degassing device 280 (degassing module 242) or between the degassing device 280 and the recording head 24a, among the components on the ink flow path 24b. The ink heating unit 270 may also be provided in the degassing device 280. From the viewpoint of preventing the formation of solid matter due to heating, it is preferable that the ink heating unit 270 be provided between the first sub-tank 241 and the degassing device 280. In addition, the ink may be ejected from the recording head 24a immediately after being degassed, but in order to eject the ink more stably from the standpoint of preventing an increase in pressure loss, it is preferable to further provide an ink heating section 270 between the degassing device 280 and the recording head 24a. In the following explanation, we will explain the case where the ink heating section 270 is provided in the first sub-tank 241, the second tank 247 between the first sub-tank 241 and the degassing device 280, and the degassing device 280, but this is not limited to this.

[0143] The ink heating section 270 is configured by a heater, a heat transfer member that transfers heat from the heater, etc. The ink heating section 270 may also be configured using warm water. The heater may be, for example, an electric heating wire, which generates Joule heat when energized. Examples of such heaters include panel heaters, ribbon heaters, and rubber heaters. The heat transfer member may be a member with high thermal conductivity, such as a heat conduction plate made of various metals (alloys). The heater and heat transfer member are provided, for example, to cover the piping of the ink flow path 24b or to be in contact with the side walls of the first sub-tank 241 and the second sub-tank 245.

[0144] <First sub-tank> The first sub-tank 241 is an ink chamber having a smaller volume than one or more ink tanks 51 that store ink. A first float sensor 241a is provided in the first sub-tank 241. A control unit (not shown) operates the supply pump 53 based on detection data of the liquid level position by the first float sensor 241a, thereby storing a predetermined amount of ink in the first sub-tank 241.

[0145] The first sub-tank 241 is preferably provided with an ink heating section 270. The ink in the first sub-tank 241 is heated by the ink heating section 270, so that the viscosity of the ink at the time of ejection can be adjusted. The ink heating section 270 preferably heats the ink so that the temperature of the ink when ejected is 40°C or higher, and preferably heats the ink in the first sub-tank 241 so that the temperature is 40 to 60°C. The ink heating section 270 is preferably provided in contact with the side wall, bottom wall, etc. of the first sub-tank 241.

[0146] The temperature of the ink heating unit 270 is controlled by a control unit (not shown). The control unit detects the temperature of the ink heating unit 270 using, for example, a thermocouple built into the ink heating unit 270, and performs on / off control using a target temperature that is set appropriately depending on the type of liquid.

[0147] <Degassing device> The degassing device 280 performs a degassing process to remove gases such as air from the ink that has flowed in, and then discharges the degassed ink. The degassing device is preferably one that uses a hollow fiber membrane or ultrasonic waves. Degassing devices that use a hollow fiber membrane will be described below.

[0148] (Degassing device using hollow fiber membrane) The degassing device 280 is composed of a degassing module 242, a vacuum pump 249, a vacuum path 250, a pressure sensor 251, an air release valve 252, and the like. The degassing module 242 is an external reflux type degassing module having therein a hollow fiber membrane 2426 as a gas permeable membrane that allows the permeation of gas dissolved in the liquid. Furthermore, a vacuum pump 249 , a vacuum path 250 , a pressure sensor 251 , and an air release valve 252 are connected to the degassing module 242 . The vacuum pump 249 reduces the air pressure inside the degassing module 242 . A vacuum line 250 connects the vacuum pump 249 with the degassing module 242 . The pressure sensor 251 measures the air pressure in the vacuum path 250 . The atmosphere release valve 252 is a valve that can switch the inside of the vacuum path 250 between an airtight state and an atmosphere open state.

[0149] The degassing module 242 of the degassing device 280 will be described in detail with reference to Fig. 2. In the example shown in Fig. 2, an external reflux type degassing module 242 is shown. The degassing module 242 is formed, for example, in a cylindrical shape, removes (degasses) dissolved gases from the ink that has flowed in, and discharges the degassed ink. The degassing module 242 is configured such that a large number of hollow fiber membranes (gas permeable membranes) 2426 are arranged around a central tube 2424 inside an outer shell (chamber) 2421. One end of the central tube 2424 is connected to an ink inlet 2422, and the other end is sealed with a plug 2424a. Numerous fine holes (holes) 2424b (perforations) are provided on the outer wall of the central tube 2424. Ink flowing in from the ink inlet 2422 flows out from these fine holes 2424b to the surrounding area and then flows out from the ink outlet 2423. 2, the ink outlet 2423 is provided in a horizontal direction, and is configured so that ink flows out to the side of the degassing module 242. However, this configuration is not limited thereto, and the ink outlet 2423 may be provided in any direction, and the ink may be configured to flow out in any direction. Furthermore, it is preferable to provide the ink outlet 2423 at a position corresponding to the upper end of the hollow fiber membrane 2426 as shown in FIG. 2, because this prevents air from pooling in the chamber.

[0150] The hollow fiber membrane 2426 is a structure of many hollow fine fibers with one end closed, and its membrane surface is gas permeable. The other end of the fine fiber structure of the hollow fiber membrane 2426 is connected to a gas outlet 2425 to which a vacuum path 250 is connected. The pressure inside the hollow fiber membrane 2426 is reduced by suction with a vacuum pump 249. In this state, ink comes into contact with the membrane surface of the hollow fiber membrane 2426, and only the dissolved gas in the ink selectively permeates the membrane surface, degassing the ink. The dissolved gas that has passed through the hollow fiber membrane 2426 flows down the vacuum path 250.

[0151] Fig. 3A is a schematic cross-sectional view showing the internal configuration of the central tube of an external circulation type degassing module, and Fig. 3B is a cross-sectional view taken along line IVB-IVB in Fig. 3A. The degassing module 252 preferably has a heating section 2427 (ink heating section) inside the central tube 2424 . The heating unit 2427 is configured by having a heating wire and a thermocouple inside a rod-shaped member made of, for example, SUS. In this way, by arranging the heating unit 2427 in the center of the degassing module 242, the ink in the degassing module 242 can be heated uniformly and efficiently, and the ink can be heated to the target temperature in a short time. Furthermore, because the entire ink in the degassing module 242 can be heated uniformly, it is possible to prevent localized areas of unheated ink from occurring in the corners of the degassing module 242. In this way, because the ink can be heated uniformly and efficiently, it is possible to improve the degassing efficiency and the amount of ink sent, and to sufficiently reduce the viscosity of the ink, thereby suppressing the occurrence of ink non-ejection.

[0152] The temperature of the heating unit 2427 is controlled by the control unit. The control unit detects the temperature of the heating unit 2427 using, for example, a thermocouple built into the heating unit 2427, and performs on / off control using a target temperature that is set appropriately depending on the type of liquid. The shape and configuration of the heating unit 2427 may be any shape and configuration as long as it can heat the ink in the degassing module 242 and control the heating temperature. Furthermore, the shape and configuration of the heating unit 2427 may be configured so that the heating unit 2427 itself generates heat, as described above. The heating unit 2427 may be configured, for example, so that a heating element itself is provided outside the degassing module 242, and heat from the heating element is transferred to the heating unit 2427 to heat the inside of the degassing module 242.

[0153] Furthermore, on the outer surface of the degassing module 242, a second heating section 2428 (ink heating section) that heats the liquid inside the degassing module 242 is provided. That is, the second heating part 2428 is formed in a flat shape and is provided so as to cover the outer peripheral surface of the outer shell 2421 of the degassing module 242. As such second heating part 2428, for example, a rubber heater or the like is used. The second heating section 2428 is provided with a temperature sensor such as a thermistor (not shown), and is controlled to turn on and off by a control section in the same manner as the heating section 2427. By providing such a second heating section 2428, the ink in the degassing module can be heated to the target temperature in an even shorter time.

[0154] The vacuum pump 249 shown in FIG. 1 is a diaphragm pump that includes a pump chamber and a drive source. The pump chamber includes an expandable diaphragm. The drive source operates the diaphragm so that the volume of the pump chamber expands or contracts. The pump chamber is provided with an intake port equipped with a check valve that only allows fluid to flow in from the outside, and an outlet port equipped with a check valve that only allows fluid to flow out from the inside.

[0155] The pressure sensor 251 detects the air pressure in the vacuum path 250 and outputs the result to the control unit. The control unit controls the driving of the vacuum pump 249 based on the detection result from the pressure sensor 251.

[0156] The atmosphere release valve 252 is an electromagnetic valve that can switch the vacuum path 250 between an airtight state and an atmosphere-open state in accordance with an operation command from the control unit.

[0157] The liquid feed pump 243 sends the ink that flows out from the ink outlet 2423 of the degassing module 242 to the second sub-tank 245. A check valve 244 is provided between the liquid feed pump 243 and the second sub-tank 245 to prevent the ink that has been sent to the second sub-tank 245 from flowing back.

[0158] The above-mentioned degassing module 242 is an external reflux type hollow fiber membrane degassing module from the viewpoint of preferable degassing efficiency and processing flow rate, but is not limited to this and other types such as an internal reflux type may also be used. Commercially available products such as SEPAREL EF-002A-P and SEPAREL EF-004P from Dainippon Ink and Chemicals, Inc. can also be used as the external reflux type hollow fiber degassing module.

[0159] <Second sub-tank> The second sub-tank 245 is a small ink chamber that temporarily stores ink that has been degassed by the degassing device 280. The second sub-tank has approximately the same capacity as the first sub-tank 241, although there is no particular limitation. The ink in the second sub-tank 245 is connected to the inlet 240a of each recording head 24a, and ink is supplied to each recording head 24a in an amount corresponding to the amount of ink ejected from the nozzles. A second float sensor 245a is provided in the second sub-tank 245. Based on the detection data of the liquid level position by the second float sensor 245a, the control unit operates the liquid feed pump 243 to store a predetermined amount of ink.

[0160] The second sub-tank 245 is preferably provided with an ink heating section 270, similar to the first sub-tank 241. The ink in the second sub-tank 247 is heated by the ink heating section 270, making it possible to adjust the viscosity of the ink when ejected. The ink heating section 270 preferably heats the ink so that the temperature of the ink when ejected is 40°C or higher, and preferably heats the ink in the second sub-tank 247 so that the temperature is 40 to 60°C. The ink heating section 270 is preferably provided in contact with the side wall, bottom wall, etc. of the second sub-tank 247.

[0161] The temperature of the ink heating unit 270 is controlled by the control unit. The control unit detects the temperature of the ink heating unit 270 using, for example, a thermocouple built into the ink heating unit 270, and performs on / off control using a target temperature that is set appropriately depending on the type of liquid.

[0162] Ink that is not ejected from the nozzles of the recording head 24a can be returned from the outlet 240b via the recovery path 241b and the valve 241c to the first sub-tank 241. For example, when it is necessary to drain ink from the ink flow path 24b during maintenance of the recording head 24a, the valve 241c can be opened to recover the ink from the recording head 24a without discarding it.

[0163] The control unit controls the operation of each unit of the inkjet recording apparatus 1 and supervises the overall operation. The control unit includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. In the control unit, various processing programs such as the system program stored in the ROM are read and loaded into the RAM, and the programs loaded into the RAM are executed by the CPU, thereby executing various control processes such as the image formation process and the temperature control described above.

[0164] In the inkjet recording apparatus having the above configuration, the ink in the ink path 24b is heated and kept warm by the ink heater 270, and is set so that the ink temperature is 40° C. or higher when ejected from the recording head.

[0165] In the inkjet recording apparatus 1 described above, the ink heating unit 270 is provided in the first sub-tank 241, the second sub-tank 247, and the degassing module 242, but this is not limiting and the ink heating unit 270 may be provided in front of the first sub-tank 241. In addition, the ink heating unit 270 may be provided by incorporating a heater in the recording head 24a. Furthermore, the degassing device 280 is provided after the first sub-tank 241 and performs degassing after heating, but this is not limiting, and the device may be provided before the first sub-tank 241 and perform degassing before heating.

[0166] The ink ejected from the nozzle is irradiated with actinic rays by an actinic ray irradiating unit. The actinic ray irradiating section has, for example, a fluorescent tube such as a low-pressure mercury lamp, and irradiates energy rays such as ultraviolet rays by causing the fluorescent tube to emit light. 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. [Example]

[0167] 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.

[0168] <Preparation of Yellow Pigment 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 63°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) 5.5 parts by mass Dispersant 2: Solsperse 22000 (manufactured by Lubrizol Japan) 0.35 parts by mass Dispersion medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 78.6 parts by mass Pigment: PY147 (pigment yellow 147) (BASF Oracet® Yellow 140) 12.2 parts by mass

[0169] <Preparation of Cyan Pigment 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) 7.2 parts by mass Dispersion medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 73 parts by mass Pigment: PB15:4 (pigment blue 15:4) (Dainichi Seika Chemicals, Chromofine Blue 6332JC) 21 parts by mass

[0170] <Blocked isocyanate> The blocked isocyanates used were those shown in Table I below. In Table I, "HDI Trimmer" is C 24 H 36 It is N6O6 and has an isocyanurate structure. The "TDI" in the isocyanate compound is toluene isocyanate, an aromatic diisocyanate. The isocyanate compound "IPDI" stands for isophorone diisocyanate, and "IPDI Adduct" refers to an adduct, which is a difunctional or higher isocyanate compound obtained by reacting an isocyanate monomer with a difunctional or higher low-molecular-weight active hydrogen-containing compound (such as an alcohol). The blocking agent "Cashew oil" is a phenolic blocking agent derived from cashew oil. The blocking agent "DMP" is dimethylpyrazole and has an aromatic ring structure. The blocking agent "ε-Cap" is ε-caprolactam. In Table III and subsequent tables below, "Trixene BI7774," "Trixene BI7981," "Trixene BI7960," "Trixene BI7982," and "Trixene BI7950" are abbreviated as "BI7774," "BI7981," "BI7960," "BI7982," and "BI7950," respectively.

[0171] [Table 1]

[0172] <Photopolymerizable monomer> As the photopolymerizable monomers, those shown in Table II below and the following monomers A to G were used.

[0173] [Table 2]

[0174] [ka]

[0175] <Photopolymerization initiator> The photopolymerization initiator used was as follows: Omnirad 379EG (IGM) Omnirad TPO H (IGM) Speedcure 2-ITX (Sartomer, 2-isopropylthioxanthone)

[0176] <Other additives> ·melamine

[0177] <Preparation of Inkjet Ink> The ink compositions shown in Tables III to IX below were mixed. The mixed liquid was heated to 40°C and filtered through a 3 μm pore size Teflon (registered trademark) membrane filter (manufactured by ADVATEC Corporation) to prepare inks 1 to 29 and inks 101 to 107.

[0178] <Water content of ink> For the inks prepared, inks 1 to 21 and 101 to 107 were measured for their water content after preparation. For ink 22, the water content was measured after preparation, dehydration with magnesium sulfate, filtration, and then measurement. For inks 23 to 29, after preparation, they were stored in an environment of 30°C and 90% humidity for several days to adjust the water content to the values ​​listed in the table below. The moisture content was measured using a Karl Fischer moisture meter (MKV-710, manufactured by Kyoto Electronics Manufacturing Co., Ltd.) Details of the method for calculating the moisture content are as described above.

[0179] [Table 3]

[0180] [Table 4]

[0181] [Table 5]

[0182] [Table 6]

[0183] [Table 7]

[0184] [Table 8]

[0185] [Table 9]

[0186] <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.

[0187] <Inkjet pattern formation> Each inkjet ink with adjusted water content 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. An LED lamp (365 nm) manufactured by Phoseon Technology was used for each pass, at 200 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.

[0188] <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 value values ​​is defined as the hydroxy value per 1 g of ink. The obtained hydroxyl values ​​were ranked according to the following criteria. (standard) A: 30mgKOH / g or less B: More than 30mgKOH / g and less than 45mgKOH / g C: More than 45 mgKOH / g and less than 60 mgKOH / g D: Greater than 60 mg KOH / g

[0189] [evaluation] <Solid matter generation amount> 300 ml of each ink with adjusted water content was pressure filtered through a 5 μm pore size PTFE filter (2 mm diameter). The 5 μm pore size PTFE filter was then removed and washed with ethanol, after which the presence or absence of solid matter was confirmed using an optical microscope. The amount of solid matter generated was evaluated according to the following criteria. "A," "B," and "C" were deemed 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 5% of the filter area. D: Solid matter is present in an area of ​​5% or more of the filter area.

[0190] <Ink ejection stability> (Number of missing nozzles after 200kg of ink is ejected) Using the piezo head, continuous ejection (driving) was performed under the conditions of droplet volume 3.5 pL, droplet speed 7 m / sec, ejection frequency 20 kHz, and printing rate 100%, and the number of nozzles that were not ejecting after ejecting 200 kg of ink was counted. "A", "B", and "C" on the following criteria were determined to be acceptable for practical use. A: The number of missing nozzles is 0. B: The number of missing nozzles is 1 or more and less than 3. C: The number of missing nozzles is 3 or more but less than 5. D: The number of missing nozzles is 5 or more and less than 10. E: The number of missing nozzles is 10 or more.

[0191] <Substrate adhesion> For the solid pattern print samples obtained above, grid-shaped cuts were made in the cured film according to the cross-cut method of JIS K5600, and adhesive tape was attached and peeled off. The peeling state of the cured film was observed, and the substrate adhesion was evaluated according to the following criteria. "A" and "B" in the following criteria were considered to be acceptable for practical use. 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%.

[0192] <Acid resistance> For the solid pattern print sample obtained above, the cured film was immersed in 10% hydrochloric acid for 30 minutes, then washed with water and dried. Then, a grid-like cut was made in the cured film according to the cross-cut method of JIS K5600, and adhesive tape was attached and peeled off. The peeling state of the cured film was observed, and the acid resistance was evaluated according to the following criteria. "A" and "B" in the following criteria were considered to be acceptable for practical use. 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%.

[0193] [Table 10]

[0194] [Table 11]

[0195] [Table 12]

[0196] [Table 13]

[0197] [Table 14]

[0198] As shown by the above results, the ink of the present invention suppresses the generation of solid matter and is superior in jetting property, substrate adhesion, and acid resistance compared to the ink of the comparative example. Therefore, it is evident that good jetting property, stable curing property, and coating film performance can be obtained even when an ink containing a blocked isocyanate is used.

[0199] [Example 2] <Ink Preparation> The ingredients were mixed according to the ink compositions shown in Tables XV and XVI below. While the mixed liquid was heated to 40°C, it was filtered through a Teflon membrane filter (manufactured by ADVATEC) with a pore size of 3 μm to prepare inks 201 to 211. The water content of ink 201 was measured after preparation. Inks 202 to 211 were prepared and then stored in an environment of 30°C and 90% RH for several days to adjust to the water content shown in the table below. The water content was measured as described above.

[0200] [Table 15]

[0201] [Table 16]

[0202] [evaluation] <Storage in containment unit> The following containers were processed to a size capable of holding 5 kg of ink. The processed containers were filled with ink and stored in an environment of 35°C and 90% RH for 3 months and then for 6 months. The ink was evaluated as described in Tables XVII and XVIII. The water vapor transmission rates of the containers shown in the table below were measured under conditions of 40°C and 90% RH. (Containment Unit) a: GX-PF (manufactured by Toppan Co., Ltd.) b: GL-ARH (manufactured by Toppan Co., Ltd.) c: Barrierox® Coat Type 1011 HGCW (Toray Advanced Film Co., Ltd.) d: A-OP AG #30 (Mitsui Chemicals Tohcello Co., Ltd.) e: Barrierox® Coat Type 1011 HGCR (Toray Advanced Film Co., Ltd.)

[0203] [Table 17]

[0204] [Table 18]

[0205] As shown in the above results, the water vapor permeability is 0.05 to 1.50 g / m under conditions of 40°C and 90% RH. 2 By storing the ink in a container that satisfies the temperature range of 100°C / day atm, it is possible to suppress the generation of solid matter even when stored for a long period of time, and it is clear that the ink has excellent ejection properties, substrate adhesion, and acid resistance. [Industrial Applicability]

[0206] The present invention can be used in an inkjet ink, a solder resist, a printed wiring board, a coating film forming method, and a coating film forming apparatus that can provide good ejection properties, stable curing properties, and coating film performance even when an inkjet ink containing a blocked isocyanate is used. [Explanation of symbols]

[0207] 1. Inkjet recording device (film forming device) 24a recording head 24b Ink flow path 50 Ink supply unit 51 Ink Tank 53 Supply Pump 241 First Subtank 241a No. 1 float sensor 242 Degassing Module 243 Liquid transfer pump 244 Check valve 245 Second Subtank 245a Second float sensor 249 Vacuum Pump 270 Ink heating unit (heating means according to the present invention) 280 Degassing device 2421 Shell (Chamber) 2424 Central tube 2424b Small hole (hole) 2426 Hollow fiber membrane (gas permeable membrane) 2427 Heating unit (heating means according to the present invention) 2428 Second heating unit (heating means according to the present invention)

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 ink-jet ink has a water content measured by the Karl Fischer method in the range of 0.05 to 0.60% by mass relative to the total mass of the ink-jet ink.

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 contains at least one polymerizable monomer having a bisphenol A structure.

6. 2. The ink-jet ink according to claim 1, wherein the sum of the hydroxy values ​​of the compounds having a hydroxy group contained in the ink-jet ink is 60 mgKOH / g or less.

7. Water vapor permeability is 0.05 to 1.50 g / m under conditions of 40°C and 90% RH ２ 2. The ink-jet ink according to claim 1, which is contained in a container having a temperature within the range of 1 / day 1 / atm.

8. A solder resist comprising the ink-jet ink according to any one of claims 1 to 7.

9. A printed wiring board having the solder resist according to claim 8.

10. A method for forming a coating film using the inkjet ink according to any one of claims 1 to 7, wherein the inkjet ink is heated to 40°C or higher in a flow path that supplies the inkjet ink to an inkjet head of a coating film forming device.

11. A coating film forming apparatus comprising the ink-jet ink according to any one of claims 1 to 7, A coating film forming apparatus, comprising a means for heating the ink-jet ink to 40° C. or higher in a flow path for supplying the ink-jet ink to an ink-jet head of the coating film forming apparatus.

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