Inkjet ink and storage method for inkjet ink

Abstract

The objective is to suppress the generation of solid matter within a coating-forming apparatus even when using inkjet ink containing blocked isocyanate and storing it for a long period of time. As a result, the objective is to provide an inkjet ink and a method for storing inkjet ink that provide good injection properties and stable curing properties. [Solution] The inkjet ink of the present invention is an inkjet ink containing a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator, wherein when stored at a temperature of 30°C and a humidity of 60%RH for one year from the date of manufacture, the water content of the inkjet ink measured by the Karl Fischer method is in the range of 0.05 to 0.80% by mass relative to the total mass.

Description

[Technical Field]

[0001] This invention relates to inkjet inks and methods for storing inkjet inks. In particular, this invention relates to inkjet inks that provide good ejectability and stable curing even when stored for a long period of time using inkjet inks containing blocked isocyanates. [Background technology]

[0002] Traditionally, photolithography and screen printing methods have been used to form etching resists, solder resists, and markings on printed circuit boards. One application of the inkjet method to the manufacturing of printed circuit boards is, for example, using an inkjet ink containing a thermosetting agent on a copper-clad laminate for printed circuit boards. It has already been proposed to form solder resist using an inkjet printer (see, for example, Patent Documents 1-3).

[0003] The aforementioned inkjet method significantly reduces the number of steps and labor involved compared to photolithography, which requires a photomask, and screen printing methods using resist inks or marking inks, which require a screen plate. Furthermore, the inkjet method reduces the amount of consumables such as developers, various inks, and cleaning solvents, and also reduces wastewater, thus contributing to a cleaner environment.

[0004] However, in inks containing the aforementioned thermosetting agent, particularly blocked isocyanates, the blocked isocyanates react with water and hydroxyl groups in the ink to generate solid matter. This leads to problems such as curing or ejection failures in inkjet printers. In particular, with curable inks, heating is usually done to reduce the ink viscosity in order to improve inkjet ejection performance, but heating further accelerates the generation of solid particles.

[0005] Therefore, a method has been proposed to keep the water content low, at 500 ppm, when manufacturing inks containing isocyanate groups (see, for example, Patent Document 4). However, the method of keeping the moisture content at 500 ppm is burdensome to manufacture, difficult to maintain and store, and leads to increased costs. Furthermore, the aforementioned method assumes that the ink will be used immediately after manufacturing, and does not mention the moisture content one year after manufacturing. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 06069300 [Patent Document 2] Japanese Patent Publication No. 2011-043565 [Patent Document 3] Patent No. 05969208 [Patent Document 4] Japanese Patent Publication No. 2014-201593 [Overview of the project] [Problems that the invention aims to solve]

[0007] This invention has been made in view of the above-mentioned problems and circumstances. The problem to be solved by this invention is to suppress the generation of solid matter in a coating device even when an inkjet ink containing blocked isocyanate is stored for a long period of time. As a result, the invention provides an inkjet ink that provides good injection properties and stable curing properties, and a method for storing inkjet ink. In the following, "inkjet ink" will also be simply referred to as "ink." [Means for solving the problem]

[0008] In order to solve the above problems, the inventors, in the process of investigating the causes of the above problems, defined the water content of ink containing blocked isocyanate after one year from the date of manufacture. They found that this suppresses the generation of solid matter in the coating film forming apparatus and provides inkjet inks that have good injection properties and stable curing properties, leading to the present invention. In other words, the above-mentioned problems according to the present invention are solved by the following means.

[0009] 1. An inkjet ink containing a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator, An inkjet ink in which, when stored for one year from the date of manufacture at a temperature of 30°C and a humidity of 60%RH, the water content of the inkjet ink measured by the Karl Fischer method is within the range of 0.05 to 0.80% by mass relative to the total mass.

[0010] 2. Inkjet ink as described in item 1, which is an ink ejected at a temperature of 2.40℃ or higher.

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

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

[0013] 5. The inkjet 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 inkjet ink.

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

[0015] 7. The inkjet ink according to claim 1, wherein the total hydroxyl value of the compound having a hydroxyl group contained in the inkjet ink is 60 mgKOH / g or less.

[0016] 8. A method for storing the inkjet ink according to any one of claims 1 to 7, A method for storing the inkjet ink, which is stored at a temperature of 30°C and a humidity of 60%RH.

Effect of the Invention

[0017] By the above means of the present invention, it is possible to provide an inkjet ink and a storage method thereof that can suppress the generation of solids in the coating film forming apparatus and obtain good injection properties and stable curability even in the ink stored for a long time. Although the expression mechanism or action mechanism of the effect of the present invention is not clear, it is speculated as follows. The ink containing blocked isocyanate reacts with water or hydroxyl groups contained in the ink and the blocked isocyanate to generate solids. In particular, heating such ink accelerates the generation of solids. As a result, when solids are generated in the coating film forming apparatus, it leads to poor injection. As an estimation mechanism of solid generation, water or hydroxyl groups contained in the ink react with the blocked isocyanate, and the blocked isocyanate (NCO) part is hydrolyzed to generate an amine. Further, an amino group reacts with the NCO site to form a multimer in which the bonding site becomes urea. It is also speculated that the alcohol component generated by hydrolysis of the acrylic monomer reacts with the NCO site and polymerizes. Therefore, in the present invention, when stored for one year from the production at a temperature of 30°C and a humidity of 60%RH, the water content of the inkjet ink is within the specific range described above. By reducing the water content over time in this way, the generation of solids in the coating film forming apparatus can be suppressed, the injection property of the ink becomes good, and stable curability of the ink can be obtained.

Modes for Carrying Out the Invention

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

[0019] In embodiments of the present invention, injection at 40°C or higher is preferable because it can lower the viscosity. That is, since monomers with large molecular weights and interactions are used to achieve the desired performance, the viscosity can be adjusted by heating to 40°C or higher before injection.

[0020] The fact that the blocked isocyanate has an aromatic ring structure is preferable in that it can achieve both a high thermal dissociation temperature and good curing performance, and it broadens the robustness against solid formation during heating.

[0021] It is preferable that the blocked isocyanate has an isocyanurate structure, as this provides excellent adhesion of the coating film.

[0022] It is preferable that the polymerizable monomer, having an octanol / water partition coefficient (ClogP) value in the range of 2.0 to 7.0, be contained in an amount of 30% by mass or more relative to the inkjet ink. This reduces hygroscopicity and increases robustness against solid matter generation.

[0023] It is preferable that the polymerizable monomer contains at least one polymerizable monomer having a bisphenol A structure, as this monomer is hydrophobic and has low hygroscopicity.

[0024] It is preferable that the sum of the hydroxy values ​​of the hydroxyl group-containing compounds in the inkjet ink is 60 mgKOH / g or less, as this provides excellent protection against solid buildup and ensures smooth injection.

[0025] The present invention provides a method for storing inkjet inks, which involves storing them at a temperature of 30°C and a humidity of 60%RH. This suppresses the increase in water content even when the ink is stored for a long period of time. As a result, the generation of solid matter in the coating device is suppressed, and good injection properties and stable curing properties are obtained.

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

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

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

[0029] The ink of the present invention functions as an insulating film (solder resist) when applied to a substrate and cured with active light in various fields such as metal processing, electronic circuits, printed circuit boards, plate making, semiconductors, and color filters. Furthermore, since it can be removed with alkali after photocuring, it also functions as an etching resist used when forming etching patterns on a substrate. In addition to being used as an ink for forming solder resist patterns as described above, the ink can also be used as an adhesive, sealant, or circuit protectant for electronic components. In particular, the ink according to the present invention is preferably an ink for forming solder resist patterns used on printed circuit boards. When a solder resist pattern (solder resist film) is formed using the ink according to the present invention, its high curability prevents the penetration of oxygen and moisture into the solder resist film. Furthermore, the ink according to the present invention improves the adhesion between the copper foil and the solder resist film interface on the printed circuit board, preventing copper migration and suppressing a decrease in insulation performance.

[0030] The ink of the present invention is an ink that can be cured by activated light. "Activating light rays" (also called "activating energy rays") are light rays that, upon irradiation, impart energy to generate reaction initiators such as active radicals and ions in the ink, and include alpha rays, gamma rays, X-rays, ultraviolet rays, electron beams, etc. Among these, ultraviolet rays and electron beams are preferred from the viewpoint of curing sensitivity and ease of obtaining equipment, with ultraviolet rays being more preferred.

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

[0032] (Method for measuring moisture content) The moisture content according to the present invention can be measured by known methods such as the Karl Fischer method. The Karl Fischer method for determining water content is a method for quantifying water content in a substance by utilizing the fact that Karl Fischer reagent, which contains iodine, sulfur dioxide, and pyridine, reacts specifically with water in the presence of methanol. In particular, the volumetric titration method involves placing a titration solvent in a titration flask, dissolving the sample in the titration solvent to extract water from the sample, and then titrating with Karl Fischer reagent, which mainly consists of iodine, sulfur dioxide, and a base, to determine the amount of water. Water reacts with iodine and sulfur dioxide in the presence of a base and an alcohol. H20+I2+SO2+CH3OH+3RN → 2RN・HI+RN・HSO4CH3 From the above equation, since H2O and I2 react in a 1:1 ratio, the number of milligrams of water (titer) per 1 ml of Karl Fischer reagent should be determined in advance using water or a water standard substance. Then, the amount of water (mg) is calculated from the titration volume (ml) of Karl Fischer reagent required for the measurement of the sample. Water content (mg) = Karl Fischer reagent titration volume (ml) × titer (mgH2O / ml) Karl Fischer reagent is also known as KF reagent. Then, the water content relative to the total mass of the ink is calculated from the calculated water content. Moisture content (%) = (Amount of water in ink / Total mass of ink) × 100

[0033] Means for controlling the water content to be within the range of 0.05 to 0.80% by mass include controlling the octanol / water partition coefficient (ClogP) of the polymerizable monomer contained in the ink, and controlling the hydroxyl value in the ink. Other means for controlling the water content include heating the ink.

[0034] The ClogP value of the polymerizable monomer is preferably in the range of 2.0 to 7.0. Furthermore, it is preferable, in terms of injection stability, that the polymerizable monomer with a ClogP value in the range of 2.0 to 7.0 is contained in an amount of 30% by mass or more of the total ink. The hydroxyl value in the ink is preferably 60 mg KOH / g or less. To keep the hydroxyl value in the ink within this range, it is preferable to control the composition of the compound having a hydroxyl value contained in the ink or to purify the compound having a hydroxyl value. Examples of the compound having a hydroxyl value include (meth)acrylates.

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

[0036] <Polymerizable monomers> 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 that has one (meth)acrylate group in one molecule. Specific examples of monofunctional (meth)acrylate compounds include glycidyl (meth)acrylate, 3,4-epoxycyclohexyl (meth)acrylate, methylglycidyl (meth)acrylate, 3-methyl-3-(meth)acryloxymethyl oxetane, 3-ethyl-3-(meth)acryloxymethyl oxetane, 3-methyl-3-(meth)acryloxyethyl oxetane, 3-ethyl-3-(meth)acryloxyethyl oxetane, and 2-phenyl-3-(meth)acryloxymethyl oxetane. Xetane, 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 2,6Examples include decanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, phenyl (meth)acrylate, glycerol mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, (meth)acrylate of ethylene oxide adducts of lauryl alcohol, mono[2-(meth)acryloyloxyethyl] succinate, mono[2-(meth)acryloyloxyethyl] maleate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, or 1,4-cyclohexanedimethanol mono(meth)acrylate, n-butyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, isodecyl (meth)acrylate, tridecyl (meth)acrylate, and 2-(2-ethoxyethoxy)ethyl (meth)acrylate.

[0037] In this invention, "polyfunctional monomer" refers to a compound having two or more functional groups. Examples of functional groups that can be cured by radical polymerization include acryloyl groups, methacryloyl groups, allyl groups, vinyl groups, vinyl ester groups, etc., all having ethylenically unsaturated bonds. However, the functional groups are not limited to those mentioned above.

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

[0039] Examples of acrylates with three or more functionalities include trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate, glycerin propoxytriacrylate, and pentaerythritol ethoxytetraacrylate.

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

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

[0042] The acrylate may be a modified form. Examples of modified acrylates include ethylene oxide-modified acrylates such as ethylene oxide-modified trimethylolpropane triacrylate and ethylene oxide-modified pentaerythritol tetraacrylate; propylene oxide-modified acrylates such as propylene oxide-modified trimethylolpropane triacrylate and propylene oxide-modified pentaerythritol tetraacrylate; caprolactone-modified acrylates such as caprolactone-modified trimethylolpropane triacrylate; and caprolactam-modified acrylates such as caprolactam-modified dipentaerythritol hexaacrylate.

[0043] (Polyfunctional (meth)acrylates with ClogP values ​​in the range of 2.0 to 7.0) The ink of the present invention preferably contains a polymerizable monomer having an octanol / water partition coefficient (ClogP) value in the range of 2.0 to 7.0. That is, the ink of the present invention preferably contains a polyfunctional (meth)acrylate having a ClogP value in the range of 2.0 to 7.0. When the ClogP value is in the range of 2.0 to 7.0, hydrolyzed amines and (meth)acrylates derived from blocked isocyanates, which are hydrolyzed by the water in the ink, react with the components in the ink to form reactants. As a result, the solubility of the formed reactants is improved, which suppresses the elution of cured material and foreign matter as solids, thereby improving injection stability.

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

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

[0046] [ka]

[0047] Furthermore, it is preferable for the ink to contain 30% by mass or more of a polyfunctional (meth)acrylate monomer with a ClogP value in the range of 2.0 to 7.0 relative to the total ink, in terms of injection stability. In particular, it is preferable that the ink of the present invention contains a polyfunctional (meth)acrylate monomer with a ClogP value in the range of 2.0 to 7.0 in an amount of 30% to 50% by mass relative to the total ink.

[0048] In this invention, "ClogP value" refers to the logP value calculated by computation. The ClogP value can be calculated using methods such as the fragment method or the atomic approach. More specifically, to calculate the ClogP value, you can use the fragment method described in the following literature or the commercially available software packages 1 or 2 below. Reference: C. Hansch and A. Leo, “Substituent Constants for Correlation Analysis in Chemistry and Biology” (John Wiley & Sons, New York, 1969) Software Package 1: MedChem Software (Release 3.54, August 1991, Medicinal Chemistry Project, Pomona College, Claremont, CA) Software Package 2: Chem Draw Ultra ver.20.0.0.47 (PerkinElmer Informatics) The ClogP values ​​described in this specification are "ClogP values" calculated using software package 2.

[0049] (Bisphenol A structure) It is preferable that the polyfunctional (meth)acrylate has at least one bisphenol A structure. The polyfunctional (meth)acrylate monomer having a bisphenol A structure is preferably, for example, the PO adduct diacrylate of bisphenol A, EO-modified bisphenol A diacrylate, or bisphenol A type epoxy acrylate.

[0050] (Hydroxy value) As mentioned above, the sum of the hydroxy values ​​of the hydroxyl group-containing compounds in the ink of the present invention is preferably 60 mgKOH / g or less, and from the viewpoint of adhesion, the lower limit is preferably 0.05 mgKOH / g or more. When the hydroxy values ​​are within the above range, the generation of solid matter is suppressed even when the ink is hydrated, resulting in excellent storage stability. Means for setting the hydroxyl value within the range of 0.05 to 60 mgKOH / g include appropriately selecting a compound having a hydroxyl value to be contained in the ink, controlling the composition of the compound having a hydroxyl value, and purifying the compound having a hydroxyl value. In this invention, "hydroxy value" refers to the amount (mg) of potassium hydroxide (KOH) required to neutralize the acetic acid bonded to the hydroxyl group when 1 g of the ink of this invention is acetylated. The hydroxy value can be calculated according to the method described in JIS K0070-1992, or it can be determined from the composition of compounds containing hydroxyl groups in 1 g of ink.

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

[0052] The aforementioned compound having a hydroxyl group is not particularly limited as long as it is a compound that has a hydroxyl 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.

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

[0054] 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, relative to the total mass of the ink. Within this range, the adhesion of the coating film is improved.

[0055] <Blocked Isocyanates> A blocked isocyanate is a compound having an isocyanate group in which the isocyanate group is blocked by a blocking agent. The compound having the isocyanate group will also be referred to as an "isocyanate compound" below. Heating causes the blocking agent to dissociate from the blocked isocyanate, thereby activating the isocyanate group.

[0056] In the ink of the present invention, until it is coated onto a recording medium, the blocked isocyanate has its isocyanate groups sealed and is unreactive, thus the ink has storage stability. After coating, when the ink is heated to a temperature above the temperature at which the blocking agent dissociates, isocyanate groups are generated. These then react with the hydroxyl groups and / or carboxyl groups of the monomers contained in the ink, forming a cured coating film.

[0057] (Isocyanate compounds) 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 its molecule. As polyfunctional isocyanates, specifically, 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), tetramethyl xylylene diisocyanate (TMXDI), tollidine diisocyanate (TODI), and 1,5-naphthalene diisocyanate (NDI); hexamethylene diisocyanate Examples include aliphatic polyisocyanates such as phosphate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, and norbornane diisocyanate methyl (NBDI); alicyclic 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 their bilets, isocyanurates, and carbodiimide modified products. The ink of the present invention may use any one of these isocyanates alone or two or more of them.

[0058] (Blocking agent) As the blocking agent, a known blocking agent can be used. Examples of blocking agents include alcohols such as ethanol, n-propanol, isopropanol, t-butanol, and isobutanol; phenols such as phenol, chlorophenol, cresol, xylenol, and p-nitrophenol; alkylphenols such as pt-butylphenol, psec-butylphenol, psec-aminophenol, p-octylphenol, and p-nonylphenol; basic nitrogen-containing compounds such as 3-hydroxypyridine, 8-hydroxyquinoline, and 8-hydroxyquinaldine; and active compounds such as diethyl malonate, acetate acetate, and acetylacetone. Examples 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, ketone or aldehyde oximes such as acetoxime, methyl ethyl ketone oxime, cyclohexanone oxime, butanone oxime, and acetaldehyde oxime, ethyleneimine, and bisulfites.

[0059] The blocking agent is preferably at least one compound selected from the group consisting of oxime compounds, pyrazole compounds, and active ethylene compounds, in terms of ink preservation and thermal dissociation properties. Examples of oxime compounds include formamide oxime, acetaldehyde oxime, 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.

[0060] Examples of polyfunctional isocyanate compounds having isocyanate groups protected by the blocking agent include 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate. Examples of polyfunctional isocyanate compounds having isocyanate groups protected by the blocking agent include 2-[(3-butylidene)aminooxycarbonylamino]ethyl methacrylate. Examples of polyfunctional isocyanate compounds having isocyanate groups protected by the blocking agent include 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl acrylate. Examples of polyfunctional isocyanate compounds having isocyanate groups protected by the blocking agent include 2-[(3-butylidene)aminooxycarbonylamino]ethyl acrylate.

[0061] The aforementioned blocked isocyanate is preferably having an aromatic ring structure from the viewpoint of ink storage and coating film performance. There are no particular restrictions on the blocked isocyanates having aromatic rings, 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), tetramethyl xylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI), and 1,5-naphthalene diisocyanate (NDI). Furthermore, 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 include dimethylpyrazole (DMP) as the blocking agent for the blocked isocyanate containing an aromatic group.

[0062] The aforementioned blocked isocyanate may contain the structure of a polyisocyanate. Polyisocyanates can be categorized into three types: isocyanurate type, biuret type, and adduct type. In the present invention, the block isocyanurate type and biuret type are preferred from the viewpoint of curability and coating film performance, with the isocyanurate type (having an isocyanurate structure) being particularly preferred.

[0063] 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 polymerizable monomer. When the amount of blocked isocyanate is 0.1 parts by mass or more, sufficient curing by heat is achieved. When the amount of blocked isocyanate is 20 parts by mass or less, excellent ink storage properties are achieved at high temperatures.

[0064] The above-mentioned blocking agents may be used individually, in combination of two or more types, or multiple types of blocked isocyanates blocked by one or more blocking agents may be used. Examples of commercially available blocked isocyanates include BI7774, BI7779, BI7950, BI7960, BI7961, BI7981, BI7982, BI7991, BI7992 (all manufactured by LANXESS), MFK60X (manufactured by Asahi Kasei Chemicals), VPLS2253, BL4265SN (both manufactured by Sumika Bayer Urethanes), PU5211, PU5210 (both manufactured by Leeson Polyurethanes), Karenz MOI-BP (2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate), Karenz MOI-BM (2-(0-[1′-methylpropyleneneamino]carboxyamino)ethyl methacrylate) (both manufactured by Showa Denko Corporation), etc.

[0065] <Photopolymerization initiator> In the photopolymerization initiator according to the present invention, when the polymerizable monomer (polyfunctional (meth)acrylate monomer) is a radical polymerizable compound, it is preferable to use a photoradical initiator. Furthermore, in the photopolymerization initiator according to the present invention, when the polymerizable monomer is a cationic polymerizable compound, it is preferable to use a photoacid generator. The photopolymerization initiator may be present in the ink of the present invention as a single agent or as a combination of two or more agents. The photopolymerization initiator may also be a combination of both a photoradical initiator and a photoacid generator.

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

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

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

[0069] Examples of benzophenone initiators include benzophenone, o-benzoylmethyl-4-phenylbenzophenone, 4,4′-dichlorobenzophenone, and hydroxybenzophenone. Other examples of benzophenone initiators include 4-benzoyl-4′-methyl-diphenyl sulfide, acrylic benzophenone, 3,3′,4,4′-tetra(t-butylperoxycarbonyl)benzophenone, and 3,3′-dimethyl-4-methoxybenzophenone. Examples of thioxanthone initiators include 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone. Examples of aminobenzophenone initiators include Michler's ketone and 4,4′-diethylaminobenzophenone. Examples of photoacid generators include compounds listed on pages 187-192 of "Organic Materials for Imaging," edited by the Organic Electronic Materials Research Group, Bunshin Publishing (1993).

[0070] The amount of photopolymerization initiator should be within a range that allows the ink to cure sufficiently, for example, it can be in the range of 0.01 to 10% by mass relative to the total mass of the ink of the present invention. Examples of commercially available photoinitiators include Omnirad TPO, Omnirad 379, and Omnirad TPO (all manufactured by IGM). Other examples of commercially available photoinitiators include Speedgure ITX (manufactured by Sartomer) and Speedcure EPD (manufactured by Sartomer).

[0071] <Polymerization inhibitors> The ink of the present invention preferably further contains a polymerization inhibitor. By including a polymerization inhibitor, the adhesion between multiple curable compounds can be reduced. "Polymerization inhibitors" include all compounds added to suppress polymerization reactions during the preparation or storage of inks containing polymerizable monomers.

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

[0073] Furthermore, among these, the inclusion of an N-oxyl polymerization inhibitor is even more preferable from the viewpoint of adhesion to printed circuit boards. 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 relative to the total mass of the ink.

[0074] (N-oxyl polymerization inhibitor) Examples of N-oxyl polymerization inhibitors include, for example, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-methoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, and Irgastab® UV10 (manufactured by BASF).

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

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

[0077] (Amine-based polymerization inhibitors) Examples of amine polymerization inhibitors include alkylated diphenylamine, N,N′-diphenyl-p-phenylenediamine, and phenothiazine.

[0078] (Other polymerization inhibitors) Other polymerization inhibitors include copper dithiocarbamate-based polymerization inhibitors such as copper dimethyldithiocarbamate, copper diethyldithiocarbamate, and copper dibutyldithiocarbamate.

[0079] These may contain only one type, or two or more types. Among these, N-oxyl and quinone-based polymerization inhibitors are preferred. 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) is preferred as the inhibitor. Also preferred as the inhibitor are 2,6-di-t-butyl-p-cresol (butylated hydroxytoluene: BHT) and 2,4-di-tert-butylphenol. Naphthoquinone and the like are preferred polymerization inhibitors having two or more aromatic rings.

[0080] <Other ingredients> (Surfactants) The ink of the present invention may further contain a surfactant as needed. Examples of surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, and silicone-based and fluorine-based surfactants. Examples of the aforementioned anionic surfactants include dialkyl sulfosuccinates, alkylnaphthalene 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 surfactant include alkylamine salts and quaternary ammonium salts.

[0081] (Coloring agent) The ink of the present invention may further contain a colorant as needed. The coloring agent may be a pigment or a dye, but it is preferable to use a pigment because it has good dispersibility with the components of the ink and excellent weather resistance. The pigments are not particularly limited, and examples include organic or inorganic pigments with the following numbers listed in the color index.

[0082] In the ink of the present invention, only one coloring agent may be contained, or two or more coloring agents may be contained, and the desired color may be achieved. The colorant content is preferably in the range of 0.1 to 20% by mass, and more preferably in the range of 0.2 to 10% by mass, relative to the total mass of the ink.

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

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

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

[0086] Yellow pigment Examples of yellow pigments include pigments selected from Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138, 139, 147, 153, 154, 155, 157, 166, 167, 168, 180, 185, and 193, or mixtures thereof.

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

[0088] Examples of commercially available pigments Examples of commercially available pigments include Black Pigment (Mikuni), Chromofine Yellow 2080, 5900, 5930, AF-1300, 2700L, Chromofine Orange 3700L, 6730, Chromofine Scarlet 6750, Chromofine Magenta 6880, 6886, 6891N, 6790, 6887, Chromofine Violet RE, Chromofine Red 6820, 6830, Chromofine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5000P, and Chromofine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Chromofine Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400(B), 2500, 2600, ZAY-260, 2700(B), 2770, Seika Fast Red 8 040, C405(F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seika Fast Carmine 6B1476T-7, 1483LT, 3840, 3870, Seika Fast Bordeaux 10B-430, Seika Light Rose R40, Seika Light Violet B800, 7805, Seika Fast Maroon 460N, Seika Fast Orange 900, 2900, Seika Light Blue C718, A612, Cyanine Blue 4933M, 4933GN-EP, 4940, 4973 (all manufactured by Dainichi Seika Kogyo Co., Ltd.; "Chromofine" is a registered trademark of the company); KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118, 124, KET Green 201 (manufactured by DIC);Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T-13, T-05, Pigment Yellow1705, Colortex Orange 202, Colortex Red101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, 105C, USN, Colortex Maroon601, Colortex BrownB610N, Colortex Violet600, Pigment Red 122, Colortex Blue516, 517, 518, 519, A818, P-908, 510, Colortex Green 402, 403, Colortex Black 702, U905 (all manufactured by Sanyo Pigment Co., Ltd., "Colortex" and "Finecol" are registered trademarks of the company); Lionol Yellow 1405G, Lionol Blue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (all manufactured by Toyo Ink Co., Ltd., "Lionol" is a registered trademark of the company), Toner Magenta E02, Permanent Rubin F6B, Toner Yellow HG, Permanent Yellow GG-02, Hostapean Blue B2G (all manufactured by Hoechst Industries); Novoperm P-HG, Hostapean Pink E, Hostapean Blue Examples include B2G (all manufactured by Clariant; "Novoperm" and "Hostaperm" are registered trademarks of the company); carbon black #2600, #2400, #2350, #2200, #1000, #990, #980, #970, #960, #950, #850, MCF88, #750, #650, MA600, MA7, MA8, MA11, MA100, MA100R, MA77, #52, #50, #47, #45, #45L, #40, #33, #32, #30, #25, #20, #10, #5, #44, CF9 (all manufactured by Mitsubishi Chemical), etc.

[0089] Pigment dispersion Pigment dispersion can be carried out using, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, and paint shaker.

[0090] The pigment dispersion is preferably carried out so that the volume-average particle size of the pigment particles is preferably in the range of 0.08 to 0.5 μm. Furthermore, the pigment dispersion is preferably carried out so that the maximum particle size of the pigment particles is preferably in the range of 0.3 to 10 μm, more preferably in the range of 0.3 to 3 μm. The dispersion of pigments is controlled by selecting the pigment, dispersant, and dispersion medium, as well as by adjusting the dispersion conditions and filtration conditions.

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

[0092] Dispersing agent The ink of the present invention may further contain a dispersion aid as needed. The dispersing agent should be selected according to the pigment. The total content of dispersants and dispersing aids is preferably in the range of 1 to 50% by mass relative to the total mass of the pigment.

[0093] 《Dispersion medium》 The ink of the present invention may further contain a dispersion medium for dispersing pigments, if necessary. The ink of the present invention may contain a solvent as a dispersion medium, but it is preferable to use the aforementioned monomer as the dispersion medium in order to suppress the residue of solvent in the formed image. Among the aforementioned monomers, monomers with particularly low viscosity are recommended.

[0094] Furthermore, when a solvent is used as a dispersion medium, the solvent tends to evaporate easily when the ink is heated, reducing the dispersibility of the pigment, which is detrimental to injection stability. However, by using the aforementioned polyfunctional (meth)acrylate monomer, the reduction in pigment dispersibility can be suppressed.

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

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

[0097] 《Hardening accelerator》 In the present invention, a curing accelerator may be included as needed. As a curing accelerator, there are no particular restrictions on what can be used as long as it promotes the thermal curing of the resin components. Examples of curing accelerators include imidazoles, dicyandiamide derivatives, dicarboxylic acid dihydrazides, triphenylphosphine, and tetraphenylphosphonium tetraphenylborate. Other examples of curing accelerators include 2-ethyl-4-methylimidazole-tetraphenylborate and 1,8-diazabicyclo[5.4.0]undecene-7-tetraphenylborate.

[0098] Ion scavenger In the present invention, an ion scavenger may be included as needed. The inclusion of an ion scavenger offers advantages such as the adsorption of ionic impurities and improved insulation properties under conditions where the cured film is humid. Examples of ion scavenging agents include inorganic ion adsorbents such as triazine thiol compounds, bisphenol-based reducing agents, zirconium compounds, and antimony-bismuth-based magnesium-aluminum compounds.

[0099] Flame retardant In this invention, a flame retardant may be included as needed. As flame retardants, hydrated metal-based compounds such as aluminum hydroxide and magnesium hydroxide, red phosphorus, ammonium phosphate, ammonium carbonate, zinc borate, zinc stannate, molybdenum compounds, bromine compounds, and chlorine compounds can be used. In addition, as flame retardants, phosphate esters, phosphate-containing polyols, phosphate-containing amines, melamine cyanurates, melamine compounds, triazine compounds, guanidine compounds, and silicone polymers can be used.

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

[0101] 3. Method for manufacturing inkjet ink The ink of the present invention can be prepared by mixing the aforementioned polymerizable monomer, a blocked isocyanate, a photopolymerization initiator, and any other component. It is also 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 the polymerizable monomer, and then mix the pigment dispersion with the other components. The pigment dispersion may further contain a dispersant.

[0102] The aforementioned pigment dispersion can be prepared by dispersing a pigment in a polymerizable compound. Pigment dispersion can be performed using, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, or paint shaker. A dispersant may be added at this time.

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

[0104] [Ink container] The ink according to the present invention has a water vapor transmission rate of 0.05 to 1.50 g / m² under conditions of 40°C and 90% RH. 2 It is preferable that the ink is contained in an ink container that is within the range of day / atm. Hereinafter, the ink container will also be simply referred to as "container". In this invention, the water vapor transmission rate is a value measured by a method in accordance with JIS K7129 (40℃, 90%RH).

[0105] The container is a component that is filled with ink and substantially holds the ink. The containers used in this invention are not limited to the following, but examples include ink cartridges, packs, bottles, tanks, jars, and cans. Among these, ink cartridges, packs, bottles, and tanks are preferred, and packs are more preferred, because they are widely used and allow for easy control of the water vapor transmission rate to a desired value. In addition, the ink used in this invention can be stored in a bottle and then further stored in a pack.

[0106] The pack is a container made of flexible film. The pack is preferable because it is lightweight, easy to place into a box-shaped container, its volume can easily change in response to the amount of ink remaining, and the film can be heat-sealed to form a bag.

[0107] The following (A) to (C) are at least possible uses of the containment in this embodiment. (A) A separate component from the inkjet recording device (coating device), which is attached to the recording device and sequentially supplies the composition to the recording device in the form of an ink cartridge or the like. (B) It is separate from the recording device, and when ink is used, only the ink is transferred from the container to the recording device. (C) Forms of tanks etc. containing ink that are pre-installed in the recording device

[0108] The above (A) and (B) can be described as ink containers from the time they are shipped until just before the ink is supplied (transferred) to the recording device. The above (C) can be defined as the ink container from the time the recording device is shipped until the first time the ink is used in the recording device. Furthermore, (A) and (C) above can be described as ink containers that perform printing on the recording device, in which ink is supplied from the container to the recording device via a connection part such as an ink tube. Furthermore, (B) above can be described as an ink container into which ink is transferred to a recording device, and then used for printing by the recording device. In (B), the object to which the ink is transferred includes a tank or the like installed in the recording device.

[0109] Examples of materials that can be used to construct 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. Furthermore, the container may be constructed by mixing the above materials in appropriate ratios or by layering multiple types of the above materials. In the case of film, the container may be obtained by lamination. When layering multiple types of film, it is not necessary for all of the multiple types of film to be the above-mentioned films; some of the films may be made of other materials, such as metals and metal compounds.

[0110] Furthermore, from the viewpoint of increasing the flexibility of the container, a plasticizer may be included 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 due to their versatility as plasticizers. Examples of fatty acid esters include phthalate esters, adipic acid esters, trimellitic acid esters, and citrate esters. Fatty acid esters can be used individually or in combination of two or more.

[0111] The container may be agitated during storage and transport to release the sedimentation of components contained in the ink. This is because, if a long period of time passes after the components in the ink have settled, the settled material may cake and become difficult to release. Furthermore, when supplying ink from the container to a recording device, it is preferable to agitate the container to release the sedimentation.

[0112] When the contents are contained in a flexible film container (pack), durability is particularly important to prevent cracking or tearing during agitation. Suitable film materials with good durability include, for example, plastic films such as polyethylene terephthalate (PET), polypropylene, polyethylene, ethylene vinyl acetate copolymer, ethylene vinyl alcohol copolymer, and polystyrene. More preferably, the film material is ethylene vinyl acetate copolymer. Preferred films include stretched plastic films such as high-density, low-density, or linearly low-density polyethylene, polypropylene, ethylene-vinyl alcohol copolymer, and polystyrene. Laminated films formed by bonding multiple layers of film may also be used.

[0113] If the container is the pack described above, if the components in the ink settle, the pack may be shaken from side to side to agitate the ink and restore its balance. In such cases, to prevent cracking or tearing of the pack, a plasticizer may be included as a component of the pack. Any of the above-mentioned plasticizers will suffice, with fatty acid esters being preferred.

[0114] If the container is the aforementioned pack, the water vapor transmission rate of the film constituting the pack is 0.05 to 1.50 g / m² under conditions of 40°C and 90% RH. 2 It is preferable that the temperature is within the range of day·atm. Furthermore, the water vapor transmission rate is 0.05 to 1.00 g / m³. 2 It is even more preferable that it be within the range of day·atm, specifically 0.05~0.5g / m². 2 It is especially preferable that the price is within the range of daily ATMs. Water vapor transmission rate is 0.05 to 1.50 g / m³ 2 By using a film within the range of 'day·atm', it is possible to suppress the increase in moisture content in the ink filled inside the pack, even when the pack is stored for a long period of time. Water vapor transmission rate of 1.50 g / m 2 To keep the temperature below 1 / day·atm, for example, one can select materials that make up the film, or provide the film with a layer composed of at least one of a metal and a metal compound.

[0115] In this context, 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. Preferred metal compounds are metal oxides, such as alumina, silica, titania, and zirconia. These can be used individually or in combination of two or more. In this specification, metal oxides include silica.

[0116] The thickness of the film constituting the pack is preferably in 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. If the film is a laminated film consisting of multiple layers, the film thickness refers to the total thickness. A film thickness within the above range is preferable in terms of the durability and flexibility of the film.

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

[0118] 5. Solder resist and printed circuit boards It is preferable that the solder resist used is the ink of the present invention as described above. As a method for forming a solder resist pattern, first, a conductive oxide film such as copper or zinc, formed on a substrate, is patterned using inkjet printing with the ink according to the present invention. Next, the ink is 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, by removing the resist film covering the oxide film with alkali, intricate circuits and patterns can be formed. In this way, a printed circuit board having solder resist is formed.

[0119] 6.Coating film formation method The method for forming a coating film using the ink of the present invention preferably includes the following steps (1) to (5). (1) Ink heating process (2) Ink degassing process (3) The process of ejecting heated ink from the nozzle of the inkjet head and landing it on a printed circuit board with a circuit formed on it. (4) A process of partially curing the ink by irradiating the impacted ink with activated light. (5) After partial curing, the ink is heated to complete curing. In the following, as an example of a coating film formation method, we will explain the method for forming a resist film.

[0120] <(1) Step> Step (1) is the process of heating the ink. Heating allows the ink droplets to be ejected from the inkjet head in a heated state. This improves ejection stability. The ink temperature at injection is preferably 40°C or higher, and preferably 100°C or lower. To further improve injection stability, the ink temperature at injection is more preferably in the range of 40 to 90°C. In particular, it is preferable to perform injection at an ink temperature such that the ink viscosity is in the range of 7 to 15 mPa·s, more preferably 8 to 13 mPa·s.

[0121] The preferred method for heating the ink is to heat the ink in the 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. As for the heating method, it is preferable to heat at least one of the following by an ink heating unit: the ink supply system including the ink tank of the head carriage, the supply pipe and the pre-chamber ink tank immediately before the head, the filtered piping, and the inkjet head. In particular, in the present invention, it is preferable to perform the heating process multiple times before injection. Specifically, it is preferable to heat the first sub-tank that stores the ink in the ink supply system. In addition to heating in the first sub-tank, it is preferable to heat the second sub-tank immediately before injection after degassing (described later) or to heat within the inkjet head, in order to improve injection performance.

[0122] For the ink heating section, a panel heater, rubber heater, ribbon heater, or warm water can be used.

[0123] <(2) Step> Step (2) is a degassing process to remove air bubbles from the ink. For the degassing method, it is preferable to use, for example, hollow fibers or ultrasound. When using hollow fibers, it is preferable to use an external recirculation type hollow fiber membrane degassing module in which the inside of the hollow fiber membrane is degassed and ink flows to the outside of the hollow fiber membrane. As such an external recirculation type hollow fiber membrane degassing module, for example, the one described in International Publication No. 2022 / 102058 can be used. Furthermore, while an external recirculation type hollow fiber membrane degassing module is preferred from the viewpoint of degassing efficiency and processing flow rate, it is not limited to this, and other types of degassing modules, such as an internal recirculation type, may also be used.

[0124] <(3) Step> In step (3), ink droplets are ejected from the inkjet head and landed on a recording medium, such as a printed circuit board, at a position corresponding to the resist film to be formed, thereby performing patterning. The inkjet head can use either an on-demand or continuous ejection method. The on-demand inkjet head may be any of the following: electromechanical conversion methods such as single-cavity type, double-cavity type, bender type, piston type, shear-mode type, and shared-wall type, as well as electro-thermal conversion methods such as thermal inkjet type and bubble jet (registered trademark) (bubble jet is a registered trademark of Canon Inc.). The amount of ink droplets ejected is preferably in the range of 2 to 20 pL, considering the recording speed and image quality.

[0125] The printed circuit board is not particularly limited, but preferably it is made of materials such as paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / nonwoven epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, copper-clad laminates for high-frequency circuits using fluorine, polyethylene, PPO, cyanate ester, etc., and is available in all grades (FR-4, etc.), as well as polyimide film, PET film, glass substrate, ceramic substrate, wafer plate, stainless steel plate, etc.

[0126] In order to improve adhesion with the ink, it is preferable to perform a fine roughening treatment on the printed circuit board to increase the contact area with the ink. When applying ink using an inkjet method, the viscosity of the ink needs to be low in order to be ejected by the inkjet head. Therefore, the ink used before application is mainly composed of polymerizable monomers and hardens with active light after application. Such inks tend to shrink during curing after application, resulting in poor adhesion between the ink and the printed circuit board. Therefore, it is necessary to perform a fine roughening treatment on the circuit board to increase the contact area with the circuit board. In addition, due to the low viscosity of the ink, there is a problem of bleeding on the roughened circuit board. Therefore, it is preferable to perform a treatment to adjust the contact angle after roughening the circuit board. Therefore, when applying the ink of the present invention to the above-mentioned applications, it is preferable to perform a roughening treatment or a treatment to prevent bleeding as a pretreatment of the wiring substrate.

[0127] One method of roughening is to create a rough surface on the surface of the wiring board by forming irregularities using methods such as buffing or scrubbing (physical polishing). Other roughening methods include chemical polishing using copper chloride-based, persulfate-based, sulfuric acid / hydrogen peroxide-based, formic acid-based, and organic acid-based polishing. As a method of roughening, chemical polishing is preferred from the viewpoint of adhesion, and organic acid-based treatment is even more preferred.

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

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

[0130] <(4) Step> In the step (4), the ink landed in the step (3) is irradiated with actinic rays to temporarily cure the ink. The actinic rays can be selected, for example, from electron beams, ultraviolet rays, alpha rays, gamma rays, X-rays, etc., but ultraviolet rays are preferred. Irradiation with ultraviolet rays can be performed, for example, using a water-cooled LED manufactured by Phoseon Technology under the condition of a wavelength of 300 to 420 nm.

[0131] Irradiation with ultraviolet rays is preferably performed such that the peak illuminance on the surface of the resist film of ultraviolet rays having a wavelength within the range of 300 to 420 nm is within the range of 0.5 to 10 W / cm 2 . More preferably, the irradiation with ultraviolet rays is performed such that the peak illuminance on the surface of the resist film of the ultraviolet rays is within the range of 1 to 5 W / cm 2 . From the viewpoint of suppressing the irradiation of radiant heat to the ink, the light amount irradiated to the resist film is preferably less than 1000 mJ / cm 2 . Irradiation with actinic rays is preferably performed within 0.001 to 300 seconds after the ink lands, and more preferably within 0.001 to 60 seconds in order to form a high-definition resist film.

[0132] <(Step (5))> In the step (5), after the temporary curing in the step (4), the ink is further heated to be fully cured. The heating method is preferably, for example, to put it into an oven set within the range of 110 to 180 °C for 10 to 60 minutes.

[0133] 7. Coating film forming apparatus The ink of the present invention is suitably used in a coating film forming apparatus. Examples of the coating film forming apparatus include an inkjet recording apparatus provided with an inkjet head. The inkjet recording device preferably has an ink heating unit, a degassing unit, and an inkjet head. Furthermore, the inkjet recording device preferably has an active light irradiation unit (UV irradiation unit) that irradiates the ink that has landed on the recording medium with active light.

[0134] As described above, the ink heating section preferably heats the ink in the flow path that supplies ink to the inkjet head so that the ink temperature at the time of ejection is 40°C or higher. The ink heating section is preferably provided in at least one of the following: the ink supply system, such as the ink tank of the head carriage, the supply pipe and the pre-chamber ink tank immediately before the head, the filtered piping, and the inkjet head. In particular, in the present invention, it is preferable that the ink heating section be provided in the ink supply system, such as in the first sub-tank for storing ink, the second sub-tank after degassing and immediately before injection, or inside the inkjet head. For the ink heating section, a panel heater, rubber heater, ribbon heater, or warm water can be used.

[0135] The degassing device preferably has a configuration using hollow fibers, for example. When using hollow fibers, it is preferable to have an external recirculation type hollow fiber membrane degassing module in which the inside of the hollow fiber membrane is degassed and ink flows to the outside of the hollow fiber membrane. The degassing device may also include an ink heating section.

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

[0137] Examples of fluorescent tubes that emit ultraviolet light include low-pressure mercury lamps and mercury lamps with an operating pressure of several hundred Pa to approximately 1 MPa. Other 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 emit ultraviolet light at a higher intensity and consume less power (e.g., light-emitting diodes) are more desirable. Furthermore, the energy rays are not limited to ultraviolet light; any energy ray that has the property of curing ink depending on the properties of the ink is acceptable, and the light source can be replaced according to the wavelength of the energy ray.

[0138] From the viewpoint of injection stability and printing accuracy, the recording method of an inkjet recording device is preferably a scanning method.

[0139] Types of inkjet recording devices include single-pass printers and serial printers. A single-pass printer has a line head with a length (recording medium width) corresponding to the width of the recording medium. In a single-pass printer, the head is fixed (almost) without moving, and printing is performed in one pass (single pass).

[0140] On the other hand, serial printers typically print in two or more passes (multipass) with the print head moving back and forth (shuttle movement) in a direction perpendicular to the transport direction of the recording medium.

[0141] Single-pass printers require a relatively large number of inkjet heads because multiple inkjet heads must be arranged to form a line head. In contrast, serial printers can be configured with only a small number of recording heads. [Examples]

[0142] 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, the operations were carried out at room temperature (25°C). Unless otherwise specified, "%" and "parts" mean "mass%" and "parts by mass," respectively.

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

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

[0145] <Blocked Isocyanates> The blocked isocyanates used were those shown in Table I below. In Table III and beyond, "Trixene BI7982," "Trixene BI7992," and "Trixene BI7961" are abbreviated as "BI7982," "BI7992," and "BI7961," respectively. Also, "Kalenz MOI-BP" and "Kalenz MOI-BM" are abbreviated as "MOI-BP" and "MOI-BM," respectively.

[0146] [Table 1]

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

[0148] [Table 2]

[0149] <Photopolymerization initiator> The following substances were used as photopolymerization initiators. • Omnirad 379EG (manufactured by IGM) • Omnirad TPO H (manufactured by IGM) • Speedcure 2-ITX (manufactured by Sartomer, 2-isopropylthioxanthone)

[0150] <Other additives> ·melamine

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

[0152] [Table 3]

[0153] [Table 4]

[0154] [Table 5]

[0155] [Table 6]

[0156] [Table 7]

[0157] <Ink water content> The water content of the ink, stored in a storage container for one year from the date of manufacture in an environment of 30°C and 60%RH, was measured using a Karl Fischer moisture meter (MKV-710, manufactured by Kyoto Electronics Manufacturing Co., Ltd.). Details of the calculation method for water content are as described above. The storage container had a water vapor transmission rate of 15 g / m². 2 A general polyethylene flexible packaging material with a water vapor content of 0.15°C was used, and the ink was sealed in this packaging material. The water vapor transmission rate was measured according to the method conforming to JIS K7129 (40°C, 90%RH). The reason for using a general flexible packaging material as a storage container was to demonstrate that the water content of the present invention can be reduced even when using general packaging materials.

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

[0159] <Processing of copper substrates> A copper-clad laminate for printed circuit boards (FR-4, 1.6 mm thick, 150 mm x 95 mm) was treated with MEC's ​​CZ-8100 treatment solution. This resulted in the fabrication of a pre-treated copper substrate with a surface roughness Ra of 1.5 μm and a treatment depth of 1 μm.

[0160] <Pattern formation using inkjet technology> Each ink, after being stored in the aforementioned storage container for one year from the date of manufacture in an environment of 30°C and 60%RH humidity, was loaded into an inkjet recording device having an inkjet recording head equipped with a piezo-type inkjet nozzle. Using this device, a pattern was formed on a copper-clad laminate for printed circuit boards (FR-4, 1.6 mm thick, 150 mm x 95 mm in size) that had undergone the aforementioned pretreatment. The ink supply system of the aforementioned device consists of an ink tank, an ink flow path, a sub-ink tank located directly in front of the inkjet recording head, piping with a metal filter, and a piezo head. The ink from the ink tank to the print head was heated to 60°C. Next, a heater was built into the piezo print head, and the ink temperature inside the piezo print head was heated to 55°C. The piezo print head used was a Konica Minolta KM1800i-SHC. Using this inkjet recording device, a voltage was applied to create dots with a droplet size of 3.5 pl. Then, a 70 mm x 70 mm solid pattern and a comb-type pattern with lines and spaces of 100 μm were printed on the substrate, each with a thickness of 30 μm. After that, a Phoseon Technology LED lamp (365 nm) was used to apply a voltage of 1000 mJ / cm². 2 The ink layer was partially cured by irradiating it to a certain degree. Then, it was placed in an oven set to 150°C for 60 minutes to fully cure it, and further cured with a mercury lamp at 2000 mJ / cm². 2 The material was irradiated, and a printed sample was obtained.

[0161] [evaluation] <Amount of solid matter generated> Each ink was stored in the aforementioned storage container for one year from the date of manufacture in an environment of 30°C and 60% RH. After being stored at injection temperature (60°C) for one day, 300 ml of the ink was pressure filtered using a 5 μm PTFE filter (2 mm diameter). The 5 μm PTFE filter was then removed, washed with ethanol, and examined using an optical microscope to check for the presence or absence of solid matter, and evaluated according to the following criteria. Criteria "A" and "B" below are considered to be without practical problems. (standard) A: There are no solid objects on the entire surface of the filter. B: Solid matter is present in an area of ​​less than 1% of the filter surface area. C: Solid matter is present in the range of 1% to less than 10% of the filter area. D: Solid matter is present in an area of ​​10% or more of the filter surface.

[0162] <Ink injection stability> Using the aforementioned piezo head, ink was continuously ejected (driven) under the conditions of droplet volume of 3.5 pl, droplet velocity of 7 m / sec, ejection frequency of 40 kHz, and print coverage of 100%. The number of nozzles that were not ejecting ink was counted after 1 minute, 5 minutes, and 10 minutes from the start of operation, and evaluated according to the following criteria. Criteria "A" and "B" below are considered to be acceptable for practical use. (standard) A: The number of missing nozzles is less than two. B: The number of missing nozzles is 2 or more but less than 10. C: The number of defective nozzles is between 10 and 50. D: The number of missing nozzles is 50 or more.

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

[0164] [Table 8]

[0165] As shown in the results above, the ink of the present invention suppresses the generation of solid matter even after long-term storage, has good injection properties, and exhibits excellent adhesion to the substrate, compared to the ink of the comparative example. [Industrial applicability]

[0166] The present invention can be used in inkjet inks and the like that can be stored for a long period of time using inkjet inks containing blocked isocyanates to obtain good injection properties and stable curing properties.

Claims

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

2. The inkjet ink according to claim 1, wherein the ink is ejected at a temperature of 40°C or higher.

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

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

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

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

7. The inkjet ink according to claim 1, wherein the total hydroxyl value of the hydroxyl group-containing compounds contained in the inkjet ink is 60 mg KOH / g or less.

8. A method for storing inkjet ink according to any one of claims 1 to 7, Storage method for inkjet inks: Store at a temperature of 30°C and a humidity of 60% RH.

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