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

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

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

[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.

[0002] To protect the circuit pattern on the printed wiring board of a printed circuit board (PCB), 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 for 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 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, or screen printing methods using resist ink or marking ink, which require a screen plate. 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. This poses a problem of prone to curing or ejection failures in inkjet printers. In particular, curable inks are usually heated to reduce the ink viscosity before ejection in order to improve inkjet ejection performance, 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 during the production of ink containing isocyanate groups (see, for example, Patent Document 4). However, the method of keeping the water content at 500 ppm imposes a heavy production load, is difficult to maintain and store, and leads to increased costs, making it a difficult method to implement in practice. Furthermore, this method is based on the premise that the ink will be used immediately after production.

[0006] Japanese Patent No. 06069300 Japanese Patent Application Laid-Open No. 2011-043565 Japanese Patent No. 05969208 Japanese Patent Application Laid-Open No. 2014-201593

[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 provide good ejection properties, stable curing properties, and film performance. Note that, hereinafter, "inkjet ink" may also be simply referred to as "ink."

[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, wherein 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.

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

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

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

[0013] 5. The ink-jet ink according to item 1, wherein the polymerizable monomer having an octanol / water partition coefficient (ClogP) value in the range of 2.0 to 7.0 is contained in an amount of 30% by mass or more relative to the ink-jet ink.

[0014] 6. The ink-jet ink according to item 1, wherein the polymerizable monomer contains at least one polymerizable monomer having a bisphenol A structure.

[0015] 7. The ink-jet ink according to item 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.

[0016] 8. 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, wherein the ink is contained in a container having a capacity within the range of 1 / day·atm.

[0017] 9. A solder resist containing the ink-jet ink according to any one of items 1 to 8.

[0018] 10. A printed wiring board having the solder resist according to claim 9.

[0019] 11. A method for forming a coating film using the inkjet ink according to any one of items 1 to 8, comprising heating the inkjet ink 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] 12. A film forming apparatus comprising the ink-jet ink according to any one of items 1 to 8, the film forming apparatus comprising a means for heating the ink-jet ink to 40° C. or higher in a flow path that supplies the ink-jet ink to an ink-jet head of the film forming apparatus.

[0021] The above-described means of the present invention can suppress the generation of solids in a film-forming apparatus, even when using an ink containing a blocked isocyanate. As a result, it is possible to provide an inkjet ink, solder resist, printed wiring board, film-forming method, and film-forming apparatus that exhibit good ejection properties, stable curing, and film performance. The mechanism of action or manifestation of the effects of the present invention is not clear, but the following is speculated. In inks containing blocked isocyanates, solids are generated by the reaction of the blocked isocyanate with water or hydroxy groups contained in the ink. In particular, heating such ink accelerates the generation of solids. As a result, the generation of solids in a film-forming apparatus can lead to ejection defects. The presumed mechanism of solid generation is that the blocked isocyanate reacts with water or hydroxy 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 bonding site is urea. It is also speculated that the alcohol component generated by hydrolysis of the acrylic monomer reacts with the NCO moiety to polymerize. 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, and the ink ejection properties are good, and stable ink curing and coating performance are obtained.

[0022] FIG. 1 is a diagram illustrating ink flow paths in an inkjet recording device according to an embodiment of the present invention; FIG. 2 is a schematic cross-sectional view of an external circulation type degassing module; FIG. 3 is a schematic cross-sectional view showing the internal configuration of a central tube of an external circulation type degassing module;

[0023] The inkjet ink of the present invention contains 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 or 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 hygroscopicity and enhancing robustness against solid 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 ２It is preferable that the ink is contained in a container that is within the range of 10 ...

[0031] The solder resist of the present invention preferably contains the ink-jet ink, since this improves the coating performance of the solder resist. The printed wiring board of the present invention preferably contains the solder resist, since the circuit pattern of the printed wiring board can be protected by the solder resist with 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 also a coating film forming apparatus equipped with an inkjet ink, and includes 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 water content of the ink is low even when heated to 40°C or higher, the generation of solids due to the reaction of blocked isocyanates in the ink with water, hydroxyl groups, etc. can be suppressed. As a result, the ink has good ejection properties, and stable ink curing and coating performance can be obtained.

[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 the lower limit and upper limit.

[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, as measured by the Karl Fischer method, is in the range of 0.05 to 0.60% by mass, based on 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 radiation in various fields, such as metal processing, electronic circuits, printed circuit boards, plate making, semiconductors, and color filters. 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. In addition to being used as an ink for forming the solder resist pattern described above, the ink can also be used as an adhesive, sealant, or circuit protectant for electronic components. In particular, the ink of 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 of the present invention, its high curability prevents the penetration of oxygen and moisture into the solder resist film. Furthermore, the ink of the present invention improves the adhesion at the interface between the copper foil and the solder resist film on a printed wiring board, preventing copper migration and suppressing a decrease in insulation.

[0037] The ink of the present invention is an ink that can be cured by actinic rays. "Actinic rays (also called "active energy rays")" are rays that can impart energy to the ink to generate reaction initiating species such as active radicals and ions upon irradiation, and include α-rays, γ-rays, X-rays, ultraviolet rays, electron beams, etc. Of these, ultraviolet rays and electron beams are preferred from the viewpoints of curing sensitivity and ease of equipment availability, and ultraviolet rays are more preferred.

[0038] <Water Content> The water content of the ink of the present invention, measured by the Karl Fischer method, is in the range of 0.05 to 0.60% by mass, based on the total mass of the ink, and a range of 0.05 to 0.30% by mass is more preferable from the viewpoints of solid matter generation and ejection properties.

[0039] (Method for Measuring Water Content) The water content according to the present invention can be measured by a known method such as the Karl Fischer method. The water content measurement method by the Karl Fischer method is a method for quantifying the water content in a substance by utilizing the fact that a Karl Fischer reagent containing iodine, sulfur dioxide, and pyridine reacts specifically with water in the presence of methanol. In particular, the volumetric titration method is a method in which a titration solvent is placed in a titration flask, a sample is dissolved in the titration solvent to extract the water content in the sample, and then the water content is determined by titrating with a Karl Fischer reagent containing iodine, sulfur dioxide, and a base as its main components. Water reacts with iodine and sulfur dioxide in the presence of a base and alcohol. H ２ 0+I ２ +SO ２ +CH ３ OH+3RN → 2RN・HI+RN・HSO ４ CH ３ From the above equation, H ２ 0 and I ２ Since this is a 1:1 reaction, the number of milligrams of water (potency) per 1 ml of Karl Fischer reagent is determined in advance using water or a water standard substance. Then, the amount of water (mg) is calculated from the amount of Karl Fischer reagent titer (ml) required to measure the sample. Amount of water (mg) = Karl Fischer reagent titer (ml) × potency (mgH ２ 0 / ml) Karl Fischer reagent is also called KF reagent. Then, the water content relative to the total mass of the ink is calculated from the calculated water content. Water content (%) = (amount of water in ink / total mass of ink) x 100

[0040] The water content can be adjusted to a 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 in the range of 2.0 to 7.0. Furthermore, from the viewpoint of ejection stability, it is preferable that the polymerizable monomer having a ClogP value in the 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 in the range of 0.05 to 60 mgKOH / g. In order to achieve a hydroxy value in the ink within this range, it is preferable to control the charging 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)acrylates.

[0042] 2. Constitution 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, the photopolymerization initiator, and the like 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-mentioned groups. From the viewpoint of the physical properties of the coating film, it is preferable that the polymerizable monomer used in the present invention contains a polyfunctional monomer.

[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 the modified acrylate 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] (Polyfunctional (meth)acrylate with ClogP value in the range of 2.0 to 7.0) The ink of the present invention preferably contains a polymerizable monomer with an octanol / water partition coefficient (ClogP) value in the range of 2.0 to 7.0. That is, the ink of the present invention preferably contains a polyfunctional (meth)acrylate with 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, amines derived from blocked isocyanates hydrolyzed by moisture in the ink and hydrolysates of (meth)acrylates react with components in the ink to form reaction products. Furthermore, the solubility of the reaction product formed is improved, which can prevent the elution of cured products and foreign matter as solids and improves 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 also 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" refers to a logP value calculated by calculation. The ClogP value can be calculated by a fragment method, an atomic approach method, or the like. More specifically, the ClogP value can be calculated using the fragment method described in the following document or the following commercially available software package 1 or 2: Document: C. Hansch and A. Leo, "Substitute 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 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 bisphenol A PO adduct diacrylate, 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 hydroxy groups contained in the ink of the present invention is preferably 60 mgKOH / g or less, with a lower limit of 0.05 mgKOH / g or more being preferable from the viewpoint of adhesion. When the hydroxy value is within this range, the generation of solids is suppressed even when the ink contains water, resulting in excellent storage stability. Methods for achieving the hydroxy value within the range of 0.05 to 60 mgKOH / g include appropriately selecting the compounds having a hydroxy value contained in the ink, controlling the charge composition of the compounds having a hydroxy value, and purifying the compounds having a hydroxy value. In the present invention, the term "hydroxy value" refers to the amount (mg) of potassium hydroxide (KOH) required to neutralize acetic acid bonded to hydroxy groups 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 by calculation from the charge composition of the compounds having hydroxy groups in 1 g of ink.

[0056] The hydroxy value in the present invention is determined from the charge composition of the compound having a hydroxy group in 1 g of ink using the above calculation method. A specific calculation method is as shown in formula (a) below. Hydroxy value [mg KOH / g] = A [mol] × (number of hydroxy groups in the compound having a hydroxy group) × B [mg / mol] (a) In formula (a) above, "A" represents the number of moles of the compound having a hydroxy group in 1 g of ink. Furthermore, "B" represents the molecular weight of 1 mol of potassium hydroxide (56,000 [mg / mol]). When the ink contains multiple types of compounds having a hydroxy group, the hydroxy value is calculated for each compound having a hydroxy group using formula (a) above. The sum of the obtained hydroxy value values ​​is then regarded as the hydroxy value for 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. 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 hydroxyl group-containing compounds can 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 in the range of 40 to 90% by mass, and more preferably in the 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, in which the isocyanate group 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 isocyanate groups are blocked and non-reactive until it is applied to a recording medium. After application, heating the ink at a temperature equal to or higher than the temperature at which the blocking agent dissociates generates isocyanate groups. These groups then react with hydroxyl groups and / or carboxyl groups of the monomers contained in the ink, causing the ink to harden and form a coating film.

[0062] (Isocyanate Compound) From the viewpoint of curability, the isocyanate compound is preferably a polyfunctional isocyanate. 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 the polyfunctional isocyanate 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 may be used.

[0063] (Blocking Agent) Known blocking agents can be used as the blocking agent. Examples of the blocking agent 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 p-t-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 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. An example of the polyfunctional isocyanate compound having an isocyanate group protected with a blocking agent is 2-[(3-butylidene)aminooxycarbonylamino]ethyl methacrylate. An example of the polyfunctional isocyanate compound having an isocyanate group protected with a blocking agent is 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl acrylate. An 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. Blocked isocyanates having an aromatic ring are not particularly limited, but examples 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 blocking agents containing a benzene ring and blocking agents containing a heteroaromatic ring are preferred. In particular, it is preferable to contain dimethylpyrazole (DMP) as a blocking agent for the blocked isocyanate containing an aromatic group.

[0067] The blocked isocyanate may contain a polyisocyanate structure. Examples of the polyisocyanate structure include three types: isocyanurate type, biuret type, and adduct type. As the blocked isocyanate of the present invention, from the viewpoints of curability and coating film performance, the isocyanurate type and biuret type are preferred, and the isocyanurate type (having an isocyanurate structure) is particularly preferred.

[0068] The content of the blocked isocyanate is preferably in the range of 0.1 to 20 parts by mass, and more preferably in the range of 1 to 10 parts by mass, per 100 parts by mass of the polymerizable monomer. When the content of the blocked isocyanate is 0.1 part by mass or more, sufficient curing by heat is achieved. When the content 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 Corporation), 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 K.K.).

[0070] <Photopolymerization initiator> When the polymerizable monomer (polyfunctional (meth)acrylate monomer) is a radically polymerizable compound, it is preferable to use a photoradical initiator as the photopolymerization initiator according to the present invention. Furthermore, when the polymerizable monomer is a cationically polymerizable compound, it is preferable to use a photoacid generator as the photopolymerization initiator according to the present invention. The ink of the present invention may contain only one type of photopolymerization initiator, or 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, and 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-based initiators include 2,4,6-trimethylbenzoin diphenylphosphine oxide. Examples of hydrogen abstraction type radical initiators include benzophenone-based initiators, thioxanthone-based initiators, aminobenzophenone-based initiators, and 10-butyl-2-chloroacridone. Furthermore, examples of hydrogen abstraction type radical initiators include 2-ethylanthraquinone, 9,10-phenanthrenequinone, and camphorquinone.

[0074] Examples of benzophenone-based initiators include benzophenone, o-benzoylmethylbenzoate-4-phenylbenzophenone, 4,4'-dichlorobenzophenone, and hydroxybenzophenone. Examples of benzophenone-based initiators include 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-based initiators include 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone. Examples of aminobenzophenone-based initiators include Michler's ketone and 4,4'-diethylaminobenzophenone. Examples of the photoacid generator include the compounds described in "Organic Materials for Imaging," edited by Organic Electronics Materials Research Group, Bunshin Publishing (1993), pp. 187-192.

[0075] The content of the photopolymerization initiator may be within a range that allows the ink to be sufficiently cured, and may be, for example, within a 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). Further, examples of commercially available photopolymerization initiators include 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. By containing a polymerization inhibitor, it is possible to reduce the adhesion between multiple curable compounds. The term "polymerization inhibitor" includes all compounds added to suppress polymerization reactions during the preparation of an ink containing a polymerizable monomer or during storage after preparation.

[0077] In the present invention, various known polymerization inhibitors can be used. As the polymerization inhibitor, it is preferable to contain any one of an N-oxyl-based polymerization inhibitor, a phenol-based polymerization inhibitor containing an o-t-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 a printed wiring board. In the ink of the present invention, the content of the polymerization inhibitor is preferably in the range of 0.05 to 0.5% by mass based on the total mass of the ink.

[0079] (N-oxyl-Based Polymerization Inhibitor) Examples of the N-oxyl-based 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, and Irgastab (registered trademark) UV10 (manufactured by BASF).

[0080] (Phenol-Based Polymerization Inhibitors) Examples of phenol-based polymerization inhibitors include 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, and 2-tert-butyl-4,6-dimethylphenol. Examples of phenol-based polymerization inhibitors include 2,6-di-tert-butyl-4-methylphenol and 2,4,6-tri-tert-butylphenol. Examples of phenol-based 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 quinone-based polymerization inhibitors 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) Examples of other polymerization inhibitors include copper dithiocarbamate-based polymerization inhibitors such as copper dimethyldithiocarbamate, copper diethyldithiocarbamate, and copper dibutyldithiocarbamate.

[0084] These may be contained alone or in combination of two or more. Among these, N-oxyl-based and quinone-based polymerization inhibitors are preferred. As the inhibitor, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) is preferred. 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 Components> (Surfactant) The ink of the present invention may further contain a surfactant, if necessary. Examples of surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, and silicone-based and fluorine-based surfactants. Examples of the anionic surfactants include dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts. Examples of the nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene-polyoxypropylene block copolymers. Examples of the cationic surfactants include alkylamine salts and quaternary ammonium salts.

[0086] (Colorant) 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 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, based on 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, 257, and Pigment Violet. 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, and 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 Co., Ltd.), Chromofine Yellow 2080, 5900, 5930, AF-1300, 2700L, Chromofine Orange 3700L, 6730, Chromofine Scarlet 6750, Chromofine Magenta 6880, 6886, 6891N, 6790, 6887, and 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, 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, Seikafast Carmine 6B1476T-7, 1483LT, 3840, 3870, Seikafast Bordeaux 10B-430, Seikalite Rose R40, Seikalite Violet B800, 7805, Seikafast Maroon 460N, Seikafast Orange 900, 2900, Seikalite Blue C718, A612, Cyanine Blue 4933M, 4933GN-EP, 4940, 4973 (all manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.; "Chromofine" is a registered trademark of the company); KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118, 124, KET Green 201 (manufactured by DIC);Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T-13, T-05, Pigment Yellow1705, Colortex Orange 202, Colortex Red101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, 105C, USN, Colortex Maroon601, Colortex 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 Dye Co., Ltd.; "Colortex" and "Finecol" are registered trademarks of the company); Lionol Yellow 1405G, Lionol Blue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (all manufactured by Toyo Ink Co., Ltd.; "Lionol" is a registered trademark of the company), Toner Magenta E02, Permanent Rubin F6B, Toner Yellow HG, Permanent Yellow GG-02, Hostaperm 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] <<Dispersion of Pigment>> 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 the range of 0.08 to 0.5 μm. The pigment is also preferably dispersed so that the maximum particle size of the pigment particles is preferably within the range of 0.3 to 10 μm, more preferably within the range of 0.3 to 3 μm. The pigment dispersion is adjusted by selecting the pigment, dispersant, and dispersion medium, dispersing conditions, filtration conditions, etc.

[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, naphthalenesulfonic acid-formalin condensate salts, aromatic sulfonic acid-formalin condensate salts, polyoxyethylene alkyl phosphate esters, polyoxyethylene nonylphenyl ether, and stearylamine acetate. Examples of commercially available 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 dispersion aid, if necessary. The dispersion 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 the dispersion medium, but in order to suppress the solvent from remaining in the formed image, it is preferable to use the above-mentioned monomer as the dispersion medium. The above-mentioned monomer may particularly be a monomer having a low viscosity.

[0099] Furthermore, when 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 above-mentioned 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, and the like, if necessary.

[0101] Coupling Agent: The ink of the present invention may further contain various coupling agents as needed. The inclusion of a coupling agent can improve adhesion to a printed wiring board. 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 included 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, and tetraphenylphosphonium tetraphenylborate. Other examples of the curing accelerator include 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 included as needed. The inclusion of an ion scavenger has advantages such as adsorbing ionic impurities and improving the insulating properties of the cured film under hygroscopic conditions. Examples of the ion scavenger include inorganic ion adsorbents such as triazine thiol compounds, bisphenol-based reducing agents, zirconium compounds, and antimony-bismuth-based magnesium aluminum compounds.

[0104] <<Flame Retardant>> 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. 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 a solvent may be added to adjust the ink viscosity.

[0106] 3. Method for Producing Inkjet Ink The ink of the present invention can be prepared by mixing the above-mentioned 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, or the like. A dispersant may be added at this time.

[0108] 4. Method for storing inkjet ink The method for storing ink according to the present invention is the same as the method for storing the ink of the present invention described above, and preferably involves storing 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 the container for storing the ink of the present invention.

[0109] [Ink Container] The ink of the present invention has a water vapor permeability of 0.05 to 1.50 g / m under conditions of 40° C. and 90% RH. ２ It is preferable that the ink is contained in a container that is within the range of 10 ...

[0110] The container is a member that is filled with ink and substantially retains the ink. The container according to the present invention may be, but is not limited to, an ink cartridge, a pack, a bottle, a tank, a glass bottle, or a can. Among these, ink cartridges, packs, bottles, and tanks are preferred, with packs being more preferred, because they are widely used and allow for easy control of the water vapor transmission rate to a desired value. Furthermore, the ink of the present invention may be contained in a bottle and then further contained in a pack.

[0111] A pack is a container made of a flexible film, and is preferable because it is lightweight, can be easily placed in a box-shaped container, the volume of the container easily changes 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 forms (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 such as a tank that is separate from the recording device and transfers only the ink from the container to the recording device when the ink is used; and (C) a form such as a tank that is pre-installed in the recording device and contains the ink.

[0113] The above (A) and (B) can be said to be ink containers from the time the container is shipped until just before ink is supplied (transferred) to the recording device. The above (C) can be said to be ink containers from the time the recording device is shipped until the recording device starts using ink for the first time. Note that the above (A) and (C) can be said to be ink containers that perform printing with the recording device while ink is being supplied to the recording device from a container via a connection such as an ink tube. Also, the above (B) can be said to be an ink container that performs printing with the recording device after ink has been transferred from the container to the recording device. Note that the object to which ink is transferred in (B) can be a tank or the like attached to the recording device.

[0114] Examples of materials constituting 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 made by blending the above materials in an appropriate ratio or by layering multiple types of the above materials. In the case of a film, the container may be obtained by laminating the materials. When multiple types of films are layered, it is not necessary for all of the multiple films to be the above-mentioned films; a portion of the film may be made of another material, such as a metal or a metal compound.

[0115] Furthermore, from the viewpoint of increasing the flexibility of the container, a plasticizer may be contained as a constituent material of the container. 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 phthalate esters, adipic acid esters, trimellitic acid esters, and citrate esters. 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 flexible film, durability is particularly required to prevent cracks or tears from occurring during stirring. Durable film materials include, for example, plastic films such as polyethylene terephthalate (PET), polypropylene, polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, and polystyrene. Ethylene-vinyl acetate copolymer is a more preferred 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 made by bonding multiple layers of film 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 permeability 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 preferable that the water vapor transmission rate is in the range of 0.05 to 1.50 g / m. ２By using a film within the range of 1.50 g / m², it is possible to suppress the increase in the moisture content of the ink filled in the pack even when the pack is stored for a long period of time. ２ To achieve a value of 1.5·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, from the viewpoint of high versatility, it is preferable to provide a layer composed of at least one of a metal and a metal compound. Examples of metals include Al and Ti. Examples of metal compounds include metal oxides, such as alumina, silica, titania, and zirconia. These are 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. The film thickness is the total thickness when the film is a laminated film consisting of multiple layers. A film thickness within the above range is preferable 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 Board The ink of the present invention described above is used for the solder resist. To form a solder resist pattern, first, a conductive oxide film of copper, zinc, or the like formed on a substrate is patterned by inkjet printing with the ink of the present invention. The ink is then cured with light to form a resist film. Next, the oxide film in the areas not covered by the resist film is removed with an acid etching solution. Furthermore, the resist film covering the oxide film is removed with alkali, thereby forming a precise circuit or pattern. In this way, a printed wiring board having a solder resist is formed.

[0124] 6. Coating Film Formation Method The coating film formation method of the present invention is a coating film formation method 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 formation method includes a step of heating the ink. Furthermore, the coating film formation method preferably includes the following steps (2) to (5) in addition to (1) the step of heating the ink: (1) a step of heating the ink; (2) a step of degassing the ink; (3) a step of ejecting the heated ink from the nozzles of the inkjet head and causing it to land on a printed wiring board on which a circuit has been formed; (4) a step of irradiating the landed ink with actinic light rays to provisionally cure the ink; and (5) a step of heating the ink after provisional curing to fully cure the ink. Below, a method of forming a resist film will be described as an example of the coating film formation method.

[0125] <Step (1)> Step (1) is a step of heating the ink. By heating, ink droplets can be ejected from the inkjet head in a heated state. This can improve ejection stability. The temperature of the ink at the time of ejection is preferably 40°C or higher, with the upper limit being preferably 100°C or lower. In order to further improve ejection stability, the temperature of the ink at the time of 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 ink to the inkjet head so that the temperature of the ink at the time of ejection is 40°C or higher. For example, the heating method preferably involves heating at least one of an ink supply system, such as an ink tank in the head carriage, a supply pipe, and an anterior ink tank immediately before the head, a pipe with a filter, and the inkjet head, using an ink heater. In particular, in the present invention, the heating step is preferably performed multiple times before ejection. Specifically, it is preferable to heat the ink in the first sub-tank that stores the ink in the ink supply system. In addition to heating in the first sub-tank, it is also preferable to heat the ink in the second sub-tank immediately before ejection after degassing (described later) or in 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 step of degassing to remove air bubbles from the ink. The degassing method preferably uses, for example, hollow fibers or ultrasound. When hollow fibers are used, an external reflux type hollow fiber membrane degassing module is preferably used, in which the inside of the hollow fiber membrane is degassed and the ink flows to the outside of the hollow fiber membrane. As such an external reflux type hollow fiber membrane degassing module, for example, the one described in International Publication No. 2022 / 102058 can be used. 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. The degassing module may be of another type, such as an internal reflux type.

[0129] <Step (3)> In 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. On-demand inkjet heads may be electro-mechanical conversion types such as single-cavity, double-cavity, bender, piston, shear-mode, and shared-wall types, or electro-thermal conversion types such as thermal inkjet and Bubble Jet (registered trademark) types (Bubble Jet is a registered trademark of Canon Inc.). The volume 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, etc., 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 and improve adhesion to the ink. When coating ink using an inkjet method, the viscosity of the ink must be low so that it can be ejected from an inkjet head. Therefore, inks containing polymerizable monomers as the main component before coating and cured by actinic radiation after coating are used. Such inks tend to shrink upon curing after coating, resulting in poor adhesion between the ink and the printed wiring board. Therefore, a fine roughening treatment must be performed on the wiring board to increase the contact area with the wiring board. Furthermore, the low viscosity of the ink can cause bleeding on a roughened wiring board. Therefore, a treatment to adjust the contact angle is preferably performed after roughening the wiring board. Therefore, when using the ink of the present invention for the above-mentioned applications, it is preferable to perform a roughening treatment or a treatment to prevent bleeding as a pretreatment for the wiring board.

[0132] Examples of roughening treatment methods include physical polishing, which involves forming irregularities on the surface of the wiring board using a buff, scrub, or the like to form a rough surface. Other roughening treatment methods include chemical polishing treatments such as copper chloride-based, persulfate-based, sulfuric acid / hydrogen peroxide-based, formic acid-based, and organic acid-based. From the viewpoint of adhesion, chemical polishing is preferred as a roughening treatment method, and organic acid-based treatments are more preferred.

[0133] Specific examples of chemical polishing treatments include MacDermid's MultiPrep 200 copper chloride system, MacDermid's Microclean, ME-301, and PR-820 persulfate system, and Shikoku Kasei's GB1000F / 1400, G200, GB3100, and GB4300 sulfuric acid / hydrogen peroxide system, and MacDermid's Metex G-5 and Metex Examples of organic acid-based paints include G-6, ME-501, ME-602, ME-605, ME-709, BTH-2066 from BOARDTEC Corporation, CPE-900, EMR-5000, and EMR-7000 from Mitsubishi Gas Chemical Company, and CZ8100, CZ8101, and CZ8202 from MEC Corporation, and BTH-2083 and BTH-2085 from BOARDTEC Corporation. From the viewpoint of adhesion, sulfuric acid / hydrogen peroxide-based paints and organic acid-based paints are preferred, and organic acid-based paints are more preferred. As a treatment for preventing bleeding, MEC Corporation's CZ8300 series and BOARDTEC Corporation's BTH-3066 are preferred.

[0134] The surface roughness of the copper plate roughened by the 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. An Ra of 0.1 μm or more improves adhesion, while an Ra of 1.5 μm or less suppresses bleeding. The thickness of the copper plate roughened by 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. A roughened thickness of 0.1 μm or more improves adhesion due to the anchor effect, while a roughened thickness of 3.0 μm or less improves adhesion because the copper is not unnecessarily coarsened or densified. Surface roughness can be controlled by adjusting conditions such as the type of pretreatment agent and the treatment temperature and time. Surface roughness can be measured using a laser microscope, 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 provisionally cure the ink. The actinic rays can be selected from, for example, electron beams, ultraviolet rays, α rays, γ rays, and X-rays, but ultraviolet rays are preferred. The ultraviolet rays can be irradiated 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 ultraviolet light having a wavelength in the range of 300 to 420 nm on the surface of the resist film 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 From the viewpoint of suppressing the radiation heat from being irradiated onto the ink, the amount of light irradiated onto the resist film is set to be within the range of 1000 mJ / cm. ２ The irradiation with 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 temporary curing in step (4), the ink is further heated to fully cure it. The heating method is preferably, for example, placing the ink in an oven set to a temperature in the range of 110 to 180°C for 10 to 60 minutes.

[0138] 7. Film-forming device The film-forming device of the present invention is a film-forming device 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 device 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, parts having the same functions and configurations will be given the same reference numerals, and their description will be omitted.

[0139] The coating film forming device may be an inkjet recording device equipped with an inkjet head. The inkjet recording device preferably has an ink heating unit, a degassing unit, and an inkjet head. The inkjet recording device also 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] 1 is a diagram illustrating the ink flow paths 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 necessary.

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

[0142] <Ink Heating Unit> The ink heating unit 270 is preferably provided 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 recording head 24a and 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 solids due to heating, the ink heating unit 270 is preferably provided between the first sub-tank 241 and the degassing device 280. Furthermore, although the ink may be ejected from the recording head 24a immediately after being degassed, it is preferable to further provide the ink heating unit 270 between the degassing device 280 and the recording head 24a to ensure more stable ejection and prevent an increase in pressure loss. In the following explanation, we will explain the case where the ink heating unit 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 unit 270 is composed of a heater and a heat transfer member that transfers heat from the heater. The ink heating unit 270 may also be composed of warm water. The heater may be, for example, an electric heating wire that generates Joule heat when energized. Examples of such heaters include a panel heater, a ribbon heater, and a rubber heater. The heat transfer member is a member with high thermal conductivity, such as a heat conduction plate made of various metals (alloys). The heater or heat transfer member is 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 or the second sub-tank 245.

[0144] <First Sub-Tank> The first sub-tank 241 is an ink chamber with a smaller volume than the 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, allowing the viscosity of the ink to be adjusted 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 first sub-tank 241 to a temperature of 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] A control unit (not shown) controls the temperature of the ink heating unit 270. 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 configured to use a hollow fiber membrane or ultrasonic waves. Below, we will explain degassing devices that use hollow fiber membranes.

[0148] (Degassing Apparatus Using Hollow Fiber Membrane) The degassing apparatus 280 is composed of a degassing module 242, a vacuum pump 249, a vacuum path 250, a pressure sensor 251, an atmosphere release valve 252, and the like. The degassing module 242 is an external reflux type degassing module having a hollow fiber membrane 2426 therein as a gas permeable membrane that is permeable to gas dissolved in a liquid. The degassing module 242 is also connected to a vacuum pump 249, a vacuum path 250, a pressure sensor 251, and an atmosphere release valve 252. The vacuum pump 249 reduces the air pressure inside the degassing module 242. The vacuum path 250 connects the vacuum pump 249 and the degassing module 242. The pressure sensor 251 measures the air pressure inside 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 . The example shown in FIG. 2 illustrates an external reflux type degassing module 242. The degassing module 242 is formed, for example, in a cylindrical shape, removes dissolved gases (degasses) from the ink that flows in, and discharges the degassed ink. The degassing module 242 is configured such that, inside an outer shell (chamber) 2421, a central tube 2424 is surrounded by a number of hollow fiber membranes (gas-permeable membranes) 2426. One end of the central tube 2424 is connected to an ink inlet 2422, and the other end is sealed with a plug 2424a. The outer wall of the central tube 2424 is provided with numerous fine holes (holes) 2424b (perforations). Ink that flows in through the ink inlet 2422 flows out through these fine holes 2424b to the surrounding area and then out through an ink outlet 2423. 2, the ink outlet 2423 is provided facing horizontally, 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 facing 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 has a structure of many hollow fine fibers with one end closed, and the 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 reflux-type degassing module. FIG. 3B is a cross-sectional view of the plane taken along line IVB-IVB in FIG. 3A . The degassing module 252 preferably includes a heating unit 2427 (ink heating unit) inside the central tube 2424. The heating unit 2427 is configured, for example, by a stainless steel rod-shaped member having a heating wire and a thermocouple inside. By locating the heating unit 2427 in the center of the degassing module 242, the ink in the degassing module 242 can be uniformly and efficiently heated, allowing the ink to reach the desired temperature in a short time. Furthermore, since the entire ink in the degassing module 242 can be uniformly heated, it is possible to prevent localized unheated ink areas in the corners of the degassing module 242. By uniformly and efficiently heating the ink, the degassing efficiency and ink delivery rate can be improved, and the ink viscosity can be sufficiently reduced, suppressing ink ejection failures.

[0152] The temperature of the heating unit 2427 is controlled by a 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 2422 and control the heating temperature. As described above, the shape and configuration of the heating unit 2427 may also be configured so that the heating unit 2427 itself generates heat. The heating unit 2427 may be configured, for example, so that a heating element itself is provided outside the degassing module 2422 and heats the inside of the degassing module 242 by transferring heat from the heating element to the heating unit 2427.

[0153] Furthermore, a second heating unit 2428 (ink heating unit) that heats the liquid inside the degassing module 242 is provided on the outer surface of the degassing module 242. That is, the second heating unit 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. For example, a rubber heater or the like is used as this second heating unit 2428. The second heating unit 2428 is provided with a temperature sensor such as a thermistor (not shown), and is controlled to turn on and off by a control unit in the same way as the heating unit 2427. By providing this second heating unit 2428, the ink inside the degassing module can be heated to the target temperature in an even shorter time.

[0154] The vacuum pump 249 shown in Figure 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 and contracts. The pump chamber includes an intake port with a check valve that only allows fluid to flow in from the outside, and an exhaust port 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 has flowed 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, and prevents the ink that has been sent to the second sub-tank 245 from flowing back.

[0158] The above-described 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 this is not limiting and other types, such as an internal reflux type, may also be used. Furthermore, commercially available products can also be used as external reflux type hollow fiber degassing modules. Examples of commercially available products include SEPAREL EF-002A-P and SEPAREL EF-004P from Dainippon Ink and Chemicals, Inc.

[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 this is not particularly limited. The ink in the second sub-tank 245 is connected to the inlets 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 liquid level detection data from 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, allowing the viscosity of the ink to be adjusted 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 to a temperature of 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 control unit controls the temperature of the ink heating unit 270. The control unit detects the temperature of the ink heating unit 270 using a thermocouple built into the ink heating unit 270, for example, 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), ROM (Read Only Memory), RAM (Random Access Memory), etc. The control unit reads out various processing programs, such as a system program, stored in the ROM and loads them into the RAM, and the programs loaded into the RAM are executed by the CPU. This allows various control processes, such as image formation processing and the above-mentioned temperature control, to be executed.

[0164] In the inkjet recording apparatus having the above-described configuration, the ink in the ink path 24b is heated and kept warm by the ink heating unit 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. The ink heating unit 270 may also be provided by incorporating a heater in the recording head 24a. In addition, the degassing device 280 is provided after the first sub-tank 241 and degasses after heating, but this is not limiting and the ink heating unit 270 may be provided in front of the first sub-tank 241 and degassses before heating.

[0166] The ink ejected from the nozzle is irradiated with actinic rays by an actinic ray irradiation unit. The actinic ray irradiation unit has, for example, a fluorescent tube such as a low-pressure mercury lamp, and causes the fluorescent tube to emit light to irradiate energy rays such as ultraviolet rays. Examples of fluorescent tubes that emit ultraviolet rays include low-pressure mercury lamps and mercury lamps with operating pressures of approximately 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 lower power consumption (e.g., light-emitting diodes) are more desirable. Furthermore, the energy rays are not limited to ultraviolet rays, and any energy rays that have the property of curing the ink depending on the properties of the ink may be used, and the light source may be selected depending on the wavelength of the energy rays, etc.

[0167] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. 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 to this, and the mixture was placed in a glass bottle together with 200 g of zirconia beads having a diameter of 0.5 mm and sealed. The mixture was dispersed using a paint shaker until the desired particle size was reached, and the zirconia beads were then 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) (Oracet® Yellow 140 manufactured by BASF) 12.2 parts by mass

[0169] <Preparation of Cyan Pigment Dispersion> This cyan 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 (manufactured by 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) (manufactured by Dainichiseika Color & Chemicals Co., Ltd., Chromofine Blue 6332JC) 21 parts by mass

[0170] <Blocked Isocyanate> The blocked isocyanates shown in Table I below were used. In Table I, "HDI Trimer" refers to C ２４ H ３６ N ６ O ６ and has an isocyanurate structure. The isocyanate compound "TDI" is toluene isocyanate, an aromatic diisocyanate. The isocyanate compound "IPDI" is isophorone diisocyanate, and "IPDI Adduct" refers to an adduct, which is a bifunctional or higher isocyanate compound obtained by reacting an isocyanate monomer with a bifunctional 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, which 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]

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

[0173]

[0174]

[0175] <Photopolymerization initiator> The following photopolymerization initiators were used: Omnirad 379EG (manufactured by IGM) Omnirad TPO H (manufactured by IGM) Speedcure 2-ITX (2-isopropylthioxanthone, manufactured by Sartomer)

[0176] <Other additives> - Melamine

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

[0178] <Water Content of Ink> For the prepared inks, the water content of inks 1 to 21 and 101 to 107 was measured 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, the inks were stored in an environment of 30°C and 90% humidity for several days, and then adjusted to the water content shown in the table below. The water 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 water content are as described above.

[0179]

[0180]

[0181]

[0182]

[0183]

[0184]

[0185]

[0186] <Treatment of Copper Substrate> 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, thereby producing 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 equipped with an inkjet recording head equipped with a piezo-type inkjet nozzle. Using this device, patterns were formed on a copper-clad laminate for printed wiring boards (FR-4, 1.6 mm thick, 150 mm x 95 mm) that had undergone the copper pretreatment described above. The ink supply system of the device consisted of an ink tank, an ink flow path, a sub-ink tank installed immediately before the inkjet 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 installed in the piezo head, and the ink temperature inside the piezo head was heated to 55°C. A Konica Minolta KM1800i-SHC piezo head was used. Using this inkjet recording device, voltage was applied to form dots with a droplet volume of 3.5 pl. Then, a 70 mm × 70 mm solid pattern and a comb-shaped pattern with a line and space of 100 μm were printed on the substrate so that each had a thickness of 30 μm. Each pass was irradiated with 200 mJ / cm using an LED lamp (365 nm) manufactured by Phoseon Technology. ２ The ink layer was then temporarily cured by irradiating it with 2000 mJ / cm irradiated with a mercury lamp 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 charge 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 [mg KOH / g] = A [mol] × (number of hydroxy groups in the compound having a hydroxy group) × 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. Furthermore, "B" represents the molecular weight of 1 mol of potassium hydroxide (56,000 [mg / mol]). Note that when an ink contains multiple types of compounds having a hydroxy group, the hydroxy value of each compound having a hydroxy group is calculated using the above formula (a). The sum of the obtained hydroxy value values ​​is then regarded as the hydroxy value in 1 g of ink. The obtained hydroxy values ​​were ranked according to the following criteria. (Criteria) A: 30 mg KOH / g or less B: More than 30 mg KOH / g and 45 mg KOH / g or less C: More than 45 mg KOH / g and 60 mg KOH / g or less D: More than 60 mg KOH / g

[0189] [Evaluation] <Amount of solid matter generated> 300 ml of each ink, with the water content adjusted, was pressure filtered using a PTFE filter (diameter 2 mm) with a pore size of 5 μm. The PTFE filter with a pore size of 5 μm was then removed and washed with ethanol, and the presence or absence of solid matter generation was confirmed using an optical microscope. The amount of solid matter generation was evaluated according to the following criteria. The following criteria, "A," "B," and "C," were deemed acceptable for practical use. (Criteria) A: No solid matter was present on the entire filter surface. B: Solid matter was present within an area of ​​less than 1% of the filter area. C: Solid matter was present within an area of ​​1% to less than 5% of the filter area. D: Solid matter was present within an area of ​​5% or more of the filter area.

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

[0191] <Adhesion to substrate> For the solid pattern print sample 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 adhesion to the substrate was evaluated according to the following criteria. "A" and "B" in the following criteria were determined to be acceptable for practical use. A: The residual adhesion rate was 100%. B: The residual adhesion rate was 80% or more and less than 100%. C: The residual adhesion rate was 60% or more and less than 80%. D: The residual adhesion rate was 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, washed with water, and dried. Thereafter, 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 acid resistance was evaluated according to the following criteria. "A" and "B" in the following criteria were determined to be acceptable for practical use. A: The residual adhesion rate was 100%. B: The residual adhesion rate was 80% or more and less than 100%. C: The residual adhesion rate was 60% or more and less than 80%. D: The residual adhesion rate was less than 60%.

[0193]

[0194]

[0195]

[0196]

[0197]

[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 Preparation of Inks Ink compositions shown in Tables XV and XVI below were mixed. The mixed solution was heated to 40°C and filtered through a 3 μm pore size Teflon membrane filter (manufactured by ADVATEC) to prepare inks 201 to 211. The water content of ink 201 was measured after preparation. Inks 202 to 211 were adjusted to the water content shown in the tables below by storing them in an environment of 30°C and 90% RH for several days after preparation. The water content was measured as described above.

[0200]

[0201]

[0202] [Evaluation] <Storage in container> 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 three months, and then the ink after six months of storage was evaluated as described in Tables XVII and XVIII. The water vapor transmission rates of the containers shown in the tables below were values ​​measured under conditions of 40°C and 90% RH. (Containers) a: GX-P-F (manufactured by Toppan Publishing Co., Ltd.) b: GL-ARH (manufactured by Toppan Publishing Co., Ltd.) c: Barrierox® Coat Type 1011 HGCW (manufactured by Toray Advanced Film Co., Ltd.) d: A-OP AG #30 (manufactured by Mitsui Chemicals Tocello Inc.) e: Barrierox® Coat Type 1011 HGCR (manufactured by Toray Advanced Film Co., Ltd.)

[0203]

[0204]

[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 It can be seen that by storing the ink in a container that is within the range of 1000 ppm / day 1000 ppm, the generation of solid matter is suppressed even when stored for a long period of time, and the ink has excellent ejection properties, substrate adhesion, and acid resistance.

[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.

[0207] DESCRIPTION OF SYMBOLS 1 Inkjet recording apparatus (film forming apparatus) 24a Recording head 24b Ink flow path 50 Ink supply section 51 Ink tank 53 Supply pump 241 First sub-tank 241a First float sensor 242 Degassing module 243 Liquid feed pump 244 Check valve 245 Second sub-tank 245a Second float sensor 249 Vacuum pump 270 Ink heating section (heating means according to the present invention) 280 Degassing device 2421 Outer shell (chamber) 2424 Central tube 2424b Spherical hole (hole) 2426 Hollow fiber membrane (gas permeable membrane) 2427 Heating section (heating means according to the present invention) 2428 Second heating section (heating means according to the present invention)

Claims

1. An inkjet ink containing a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator, wherein the water content of the inkjet ink, as 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.

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

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

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

5. The ink-jet ink according to claim 1, wherein the polymerizable monomer having an octanol / water partition coefficient (ClogP) value within the range of 2.0 to 7.0 is contained in an amount of 30% by mass or more relative to the ink-jet ink.

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

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

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

9. A solder resist comprising the inkjet ink according to any one of claims 1 to 8.

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

11. A method for forming a coating film using the inkjet ink according to any one of claims 1 to 8, comprising heating the inkjet ink to 40°C or higher in a flow path that supplies the inkjet ink to an inkjet head of a coating film forming device.

12. A coating film forming apparatus comprising the inkjet ink according to any one of claims 1 to 8, the 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.

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