Active ray-curable inkjet resist ink, method for forming cured film, cured film, printed wiring board, and electronic device

Abstract

The active-ray-curable inkjet resist ink according to the present invention comprises an active-ray-polymerizable compound (A), a pigment (B), and a pigment dispersant (C), the pigment (B) comprising a red pigment (B1) having a maximum absorption wavelength of 480-600 nm and a pigment (B2) having a different color from the red pigment (B1), the pigment dispersant (C) having an amine value greater than an acid value, and the pigment dispersant (C) having an acid value greater than that of the red pigment (B1). The inkjet resist ink has a halogen content of 900 ppm or less and does not substantially contain a black inorganic pigment.

Description

Technical Field

[0001] The present invention relates to an active ray-curable inkjet resist ink, a cured film forming method, a cured film, a printed wiring board and an electronic device. Background Art

[0002] Solder resist, one of the resist inks for industrial use, is an insulating film that covers the surface of a printed wiring board to protect the circuit pattern, and can protect the circuit pattern from dust, heat, moisture, etc. In addition, when soldering the substrate, the solder resist can block the solder and prevent the soldering range from expanding too much.

[0003] As industrial resist inks for forming solder resists, inks with reduced halogen content in the inks have been proposed in recent years from the viewpoint of reducing environmental burden. For example, Patent Document 1 proposes an alkali-developable curable resin composition containing a red colorant that does not contain halogen and azo groups. In addition, Patent Document 2 proposes an alkali-developable photoresist ink containing an organic colorant that does not contain halogen in the chemical formula.

[0004] As a method for forming a solder resist, a method using an inkjet printer has been developed. This method is to apply ink on a substrate according to a desired pattern, and to form a solder resist by curing the applied ink with active rays such as ultraviolet rays. Therefore, it is believed that the steps of temporary drying, temporary curing using a photomask, and dissolving the uncured portion with an alkaline aqueous solution can be omitted. Therefore, from the perspective of environmental considerations and reducing the process burden, it is expected to be applied to the formation of solder resist.

[0005] In addition, solder resists are required to protect circuit patterns and have stable color resistance and color visibility even when exposed to high temperature treatment of 200°C or above during the manufacturing process of printed circuit boards or the installation process on printed circuit boards. As the color of solder resists, green is mostly used for reasons such as less burden on human eyes, excellent visibility during visual inspection, and low cost. From the perspective of design and use, various colors such as red, blue, and black are sometimes used.

[0006] However, since the substrate formed with the solder resist (cured film) is subjected to soldering and other processes for mounting electronic components on the substrate, the cured film is required to have quality performance that can withstand high temperature treatment of about 250°C to 290°C. Among them, the color of the cured film is required to be changed in various colors according to customer needs such as ensuring visibility for circuit substrate quality verification, design, and difficulty in interpreting circuit patterns. Therefore, it is hoped that the color change of the cured film will be reduced before and after heat treatment such as the soldering process and the plating process. In addition, it is preferred to form an active ray-curable inkjet ink that can suppress the color change caused by high temperature treatment.

[0007] On the other hand, as an inkjet ink capable of expressing multiple colors, for example, Patent Document 3 proposes a curable inkjet ink for image formation containing a black pigment and at least one color pigment.

[0008] However, in the formation of solder resist, a higher level of ejection stability is required for forming a fine circuit pattern. Therefore, an inkjet ink suitable for forming solder resist is required.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Publication No. 2013-101395

[0012] Patent Document 2: Japanese Patent Application Publication No. 2000-232264

[0013] Patent Document 3: Japanese Patent Application Publication No. 2005-320541 Summary of the invention

[0014] As described above, when forming solder resist by inkjet method, high jetting stability and pigment dispersion stability are required. However, when the photoresist ink technology described in Patent Documents 1 and 2 is applied to inkjet resist ink, the dispersion stability of the pigment after long-term storage is low and insufficient.

[0015] As a method for improving dispersion stability, it is known to use a pigment that has been surface treated (dispersion treated). However, according to research by the inventors, most of the surface treatment agents contain halogen atoms, and the increase in the content of the halogen atoms causes a problem in that the ejection stability of the ink after long-term storage decreases.

[0016] Regarding the demand for multiple colors, unlike the production of images, in the production process of printed circuit boards, there are many heat treatments after film formation, and there is a problem that the pigment fades due to heat and cannot form the desired color. Here, if a pigment with high fading resistance and shielding ability, such as inorganic black pigments such as carbon black, is used, the exposure sensitivity decreases, so there is currently a problem that the adhesion and heat resistance of the solder resist film (cured film) to the substrate cannot be improved.

[0017] On the other hand, it is hoped that the color change of the cured film is small and the quality is stable before and after the heat treatment such as the soldering process and the plating process. When a colorant with high visibility to the human eye and a maximum absorption wavelength of 480nm to 600nm is included, the color change is easy to see. In particular, in the case of black, the color change is easy to see by visual observation. For active ray-curable inkjet inks for inkjet, the visibility of the color of the cured film changes due to the physical properties of the coating and the fading caused by heat before and after the high heat treatment. Therefore, an inkjet resist ink that can suppress the color change caused by high temperature treatment is required.

[0018] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an active radiation curable inkjet resist ink which can improve the dispersion stability of the pigment and the ejection stability of the ink after long-term storage, can suppress the color change of the cured film even after high-temperature treatment, and can improve the adhesion and heat resistance of the cured film to the substrate, a cured film forming method using the same, a cured film, a printed wiring board, and an electronic device.

[0019] One embodiment of the present invention for solving the above-mentioned problems relates to the following active radiation curable inkjet resist inks [1] to

[10] .

[0020] [1] An active radiation curable inkjet resist ink comprising an active radiation polymerizable compound (A), a pigment (B) and a pigment dispersant (C), wherein the pigment (B) comprises a red pigment (B1) having a maximum absorption wavelength of 480 nm to 600 nm and a pigment (B2) of a color different from that of the red pigment (B1), the pigment dispersant (C) having an amine value greater than an acid value, the inkjet resist ink having a halogen content of 900 ppm or less and substantially no black inorganic pigment.

[0021] [2] The active radiation curable inkjet resist ink according to [1], further comprising a synergist (D).

[0022] [3] The active radiation curable inkjet resist ink according to [1] or [2], wherein the content of the black inorganic pigment is less than 0.01% by mass.

[0023] [4] The active radiation curable inkjet resist ink according to any one of [1] to [3], wherein the active radiation polymerizable compound (A) comprises a compound (A1) having a ClogP value of 4.0 to 7.0, and the content of the compound (A1) is 10% by mass to 50% by mass relative to the total mass of the inkjet resist ink.

[0024] [5] The active radiation-curable inkjet resist ink according to [4], wherein the molecular weight of the compound (A1) is 300 to 1500.

[0025] [6] The active radiation-curable inkjet resist ink according to any one of [1] to [5], wherein the active radiation-polymerizable compound (A) comprises a compound having three or more polymerizable groups.

[0026] [7] The active radiation-curable inkjet resist ink according to any one of [1] to [6], wherein the active radiation-polymerizable compound (A) comprises a compound represented by the following general formula (1) or a salt thereof.

[0027] General formula (1)

[0028]

[0029] (In the general formula (1), R1 represents an unsubstituted alkylene group having 1 to 6 carbon atoms, Q represents an oxygen atom or NR2, R2 represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group, and X represents a structure derived from an alcohol or an amine and containing at least one polymerizable group selected from a (meth)acryloyl group, an aryl group, and a vinyl group at the terminal.)

[0030] [8] The active radiation-curable inkjet resist ink according to any one of [1] to [7], further comprising a gelling agent (E).

[0031] [9] The active radiation curable inkjet resist ink according to [8], wherein the viscosity at a temperature of 25° C. is 1.0 Pa·s to 1.0×10 4 Pa·s, and a sol-gel phase transition occurs at a temperature above 40°C and below 100°C.

[0032]

[10] The active radiation curable inkjet resist ink according to any one of [1] to [9], wherein the halogen content in the inkjet resist ink is 300 ppm or less.

[0033] In addition, one embodiment of the present invention for solving the above-mentioned problems relates to the cured film forming method of the following

[11] and

[12] .

[0034]

[11] A method for forming a cured film, comprising the steps of: attaching the active radiation-curable inkjet resist ink described in any one of [1] to

[10] to a printed wiring board; and irradiating the attached inkjet resist ink with active radiation.

[0035]

[12] The cured film forming method according to

[11] , further comprising the step of heating and curing the inkjet resist ink irradiated with the active rays.

[0036] In addition, one embodiment of the present invention for solving the above-mentioned problems relates to a cured film of the following

[13] .

[0037]

[13] A cured film obtained by curing the active radiation-curable inkjet resist ink according to any one of [1] to

[10] .

[0038] In addition, one embodiment of the present invention for solving the above-mentioned problems relates to the printed wiring board of the following

[14] .

[0039]

[14] A printed wiring board comprising the cured film according to

[13] .

[0040] In addition, one embodiment of the present invention for solving the above-mentioned problems relates to the following electronic device

[15] .

[0041]

[15] An electronic device comprising the printed wiring board described in

[14] .

[0042] According to the present invention, there can be provided an active radiation-curable inkjet resist ink which can improve the dispersion stability of the pigment and the ejection stability of the ink after long-term storage, can suppress the color change of the cured film even after high-temperature treatment, and can improve the adhesion and heat resistance of the cured film to the substrate, a cured film forming method using the same, a cured film, a printed wiring board, and an electronic device. DETAILED DESCRIPTION

[0043] The embodiments of the present invention are described in detail below. However, the present invention is not limited to the following embodiments.

[0044] 1. Active ray curable inkjet resist ink

[0045] The active radiation curable inkjet resist ink (hereinafter also referred to as ink) according to the present embodiment comprises an active radiation polymerizable compound (A), a pigment (B) and a pigment dispersant (C), wherein the halogen content in the inkjet resist ink is 900 ppm or less. The ink according to the present embodiment can be used for various resist applications (e.g., solder resist applications).

[0046] As described above, when a surface-treated (dispersion-treated) pigment is used in ink in order to improve dispersion stability, there is a problem that the ejection stability of the ink during long-term storage may be reduced depending on the content of the pigment.

[0047] The present inventors studied the reasons for this and found that if the above-mentioned surface-treated pigment is used, the halogen content in the ink tends to increase. It is believed that if the halogen content in the ink increases, metal ions such as calcium ions contained in the ink react with halogen ions during the preparation of the ink to easily precipitate inorganic salts. It is believed that the precipitation of the inorganic salts leads to a decrease in the jetting stability of the ink.

[0048] Therefore, the present inventors conducted intensive research and found that by adjusting the type and amount of the pigment used so that the halogen content is 900 ppm or less and using a pigment dispersant having an amine value greater than the acid value in an ink, the reduction in ejection stability can be suppressed and the dispersion stability can be improved.

[0049] The pigment dispersant is believed to be easy to interact with the pigment. It is believed that by making the ink having a halogen content of 900 ppm or less contain the pigment dispersant, it is possible to inhibit the halogen ions or the inorganic salts in the ink from hindering the adsorption of the pigment dispersant and the pigment, thereby improving the dispersion stability. In addition, the dispersibility of the pigment can be improved after the ink is stored for a long time, and it is believed that the jetting stability of the ink after long-term storage can also be improved.

[0050] Furthermore, the present inventors have found that even when a red pigment with high visibility to the human eye is used, the color change caused by high-temperature treatment or the like can be significantly improved according to the present invention.

[0051] Furthermore, since the ink does not substantially contain a black pigment, it is possible to suppress the absorption of active radiation by the black pigment and promote the polymerization of the active radiation polymerizable compound, thereby improving the adhesion and heat resistance of the cured film to the substrate.

[0052] 1-1. Active radiation polymerizable compound (A)

[0053] The active radiation polymerizable compound (A) contained in the ink according to the present embodiment is a compound that is polymerized and crosslinked by irradiation with active radiation. In the present embodiment, the active radiation polymerizable compound (A) may be a compound that is polymerized and crosslinked by heating.

[0054] Examples of active rays include electron beams, ultraviolet rays, α rays, γ rays, and X-rays, etc. Among these, ultraviolet rays and electron beams are preferred, and ultraviolet rays are more preferred.

[0055] The number of polymerizable groups contained in the active ray polymerizable compound (A) may be 1 (monofunctional) or 2 or more (multifunctional). From the viewpoint of further improving the adhesion between the cured film formed by the active ray curable inkjet resist ink and the substrate and the heat resistance of the cured film, the active ray polymerizable compound (A) preferably contains a compound containing 2 or more polymerizable groups, and more preferably contains a compound containing 3 or more polymerizable groups. The number of polymerizable groups in the active ray polymerizable compound is preferably 30 or less.

[0056] The content of the compound having two polymerizable groups is preferably 15% to 80% by mass relative to the total mass of the active ray polymerizable compound (A). In addition, the content of the compound having three or more polymerizable groups is preferably 5% to 70% by mass relative to the total mass of the active ray polymerizable compound (A).

[0057] The active radiation polymerizable compound (A) is preferably a free radical polymerizable compound. A free radical polymerizable compound is a compound (monomer, oligomer, dendrimer or mixture thereof) having an ethylenically unsaturated bond that can undergo free radical polymerization. The ink may contain only one free radical polymerizable compound or a combination of two or more free radical polymerizable compounds.

[0058] Examples of the radical polymerizable compound include unsaturated carboxylic acid esters and (meth)acrylates. Among these, (meth)acrylates are preferred.

[0059] Examples of the monofunctional (meth)acrylates include isoamyl acrylate, octadecyl acrylate, lauryl acrylate, octyl acrylate, decyl acrylate, isomyristyl acrylate, isooctadecyl acrylate, 2-ethylhexyl diglycol acrylate, 2-acryloyloxyethyl hexahydrophthalate, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, methoxydiethylene glycol acrylate, methoxypolyethylene glycol acrylate, methoxypropylene glycol acrylate, phenoxyethyl acrylate, o-phenylphenol acrylate, nonylphenol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, cumylphenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 2-acryloyloxyethyl succinate, 2-acryloyloxyethyl phthalate, 2-acryloyloxyethyl-2-hydroxyethyl phthalate, and tert-butylcyclohexyl acrylate.

[0060] Among the above-mentioned monofunctional (meth)acrylates, phenoxyethyl acrylate, o-phenylphenol acrylate, and 2-hydroxy-3-phenoxypropyl acrylate are preferred from the viewpoint of suppressing cure shrinkage.

[0061] Examples of difunctional (meth)acrylates include triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, PO adduct di(meth)acrylate of bisphenol A, hydroxypivalic acid neopentyl glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, and tricyclodecane dimethanol di(meth)acrylate.

[0062] Among the above-mentioned bifunctional (meth)acrylates, neopentyl glycol diacrylate, tricyclodecane dimethanol diacrylate, bisphenol A PO adduct diacrylate, and hydroxypivalic acid neopentyl glycol diacrylate are preferred from the viewpoint of accelerating the curing of the ink.

[0063] Examples of trifunctional or higher-functional (meth)acrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, di(trimethylolpropane) tetra(meth)acrylate, glycerol propoxy tri(meth)acrylate, and pentaerythritol ethoxy tetra(meth)acrylate.

[0064] The (meth)acrylate may be a compound modified by an alkylene oxide such as ethylene oxide (EO) or propylene oxide (PO) or caprolactone (modified (meth)acrylate). Examples of the modified (meth)acrylate include o-phenylphenol EO-modified (meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, EO-modified pentaerythritol tetra(meth)acrylate, EO-modified hexanediol di(meth)acrylate, PO-modified trimethylolpropane tri(meth)acrylate, PO-modified pentaerythritol tetra(meth)acrylate, nonylphenol PO-modified (meth)acrylate, propoxylated neopentyl glycol di(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, caprolactone-modified acrylates including caprolactone-modified trimethylolpropane tri(meth)acrylate, and caprolactam-modified dipentaerythritol hexa(meth)acrylate.

[0065] From the viewpoint of further improving the heat resistance of the cured film, the active radiation polymerizable compound preferably contains a compound having a cyclic structure.

[0066] The (meth)acrylate may be a polymerizable oligomer. Examples of the (meth)acrylate as a polymerizable oligomer include epoxy (meth)acrylate oligomers, urethane (meth)acrylate oligomers, polyester (meth)acrylate oligomers, and linear (meth)acrylate oligomers. Among these, the polymerizable oligomer is preferably a urethane (meth)acrylate oligomer.

[0067] According to the findings of the inventors, urethane acrylate oligomers are easily polymerized and easily form cross-linked structures through hydrogen bonds between urethane bonds. Therefore, by including urethane acrylate oligomers in the ink, the firmness of the cured film formed by the ink and the adhesion to the substrate can be further improved.

[0068] The urethane acrylate oligomer is obtained by, for example, reacting isocyanate with an acrylic acid derivative having a hydroxyl group.

[0069] Examples of the isocyanate used as a raw material of the urethane acrylate oligomer include isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, diphenylmethane-4,4′-diisocyanate (MDI), hydrogenated MDI, polymeric MDI, 1,5-naphthalene diisocyanate, norbornane diisocyanate, tolidine diisocyanate, meta-xylylene diisocyanate (XDI), hydrogenated XDI, lysine diisocyanate, triphenylmethane triisocyanate, tris(isocyanatephenyl)phosphorothioate, tetramethylxylene diisocyanate, and 1,6,10-undecane triisocyanate.

[0070] Examples of acrylic acid derivatives having a hydroxyl group that are raw materials for the urethane acrylate oligomer include hydroxyalkyl (methyl) acrylates such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, and 2-hydroxybutyl acrylate; monoacrylates of diols such as ethylene glycol, propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, and polyethylene glycol; monoacrylates or diacrylates of triols such as trimethylolethane, trimethylolpropane, and glycerin; and epoxy acrylates such as bisphenol A epoxy acrylate.

[0071] The above-mentioned polymerizable oligomer can be an acrylate oligomer having a hyperbranched structure or a dendritic polymer structure. Acrylate oligomers are easy to polymerize by having these structures, and are easy to form a cross-linked structure. Therefore, the firmness and heat resistance of the cured film can be further improved.

[0072] Examples of commercially available products of acrylate oligomers having a hyperbranched structure or a dendrimer structure include V#1000 (dendrimer structure, manufactured by Osaka Organic Chemical Industry Co., Ltd.), CN2302, CN2303, and CN2304 (hyperbranched structures, all manufactured by Sartomer), SP1106 (dendrimer structure, manufactured by Miwon), ETERCURE6361-100, and ETERCURE6363 (hyperbranched structures, all manufactured by Eternal Chemical Industry Co., Ltd.). The ink may contain only one of these or two or more of them in combination.

[0073] The active radiation polymerizable compound (A) preferably contains a compound represented by the general formula (1) or a salt thereof.

[0074] General formula (1)

[0075]

[0076] In the general formula (1), R1 represents an unsubstituted alkylene group having 1 to 6 carbon atoms, Q represents an oxygen atom or NR2, R2 represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group, and X represents a structure derived from an alcohol or an amine containing at least one polymerizable group selected from a (meth)acryloyl group, an aryl group, and a vinyl group at the terminal.

[0077] Since the active radiation polymerizable compound represented by the general formula (1) has a structure derived from a dicarboxylic acid, it can improve the affinity between the ink and the substrate, and can further improve the adhesion between the formed cured film and the substrate.

[0078] From the viewpoint of further improving the adhesion between the cured film and the substrate, R1 is preferably an unsubstituted alkylene group having 1 or 2 carbon atoms.

[0079] From the viewpoint of further improving the adhesion between the cured film and the substrate, Q is preferably an oxygen atom.

[0080] From the viewpoint of further improving the adhesion between the cured film and the substrate, the above-mentioned polymerizable group at the end of X preferably includes a (meth)acryloyl group. From the viewpoint of further improving the ejection stability of the ink, the total number of carbon atoms in X is preferably 50 or less, and more preferably 30 or less.

[0081] The content of the compound represented by the general formula (1) is preferably 1 to 50% by mass, more preferably 3 to 20% by mass, relative to the total mass of the ink. When the vapor content is within the above range, the adhesion between the cured film and the substrate can be further improved.

[0082] Examples of the compound represented by the general formula (1) include the compounds shown below.

[0083]

[0084]

[0085] In the present embodiment, the active radiation polymerizable compound (A) preferably includes a compound (A1) having a ClogP value of 4.0 to 7.0. The compound (A1) is preferably a monomer and does not contain an oligomer or a dendrimer.

[0086] The "logP value" is an index indicating the hydrophobicity (hydrophilicity) of a compound. Specifically, it is the logarithmic value of the 1-octanol / water partition coefficient P. That is, the larger the logP value, the more likely the compound is to become hydrophobic.

[0087] Furthermore, the "CLogP value" is an estimated value of the LogP value calculated by calculation using the fragment method, etc. More specifically, the CLogP value can be calculated using the fragment method described in the literature (C. Hansch and A. Leo, "Substituent Constants for Correlation Analysis in Chemistry and Biology" (John Wiley & Sons, New York, 1969)) or the following commercially available software packages 1 or 2.

[0088] Software package 1: MedChem Software (Release 3.54, August 1991, Medicinal Chemistry Project, Pomona College, Claremont, CA)

[0089] Software package 2: Chem Draw Ultra ver. 8.0. (April 2003, CambridgeSoft Corporation, USA)

[0090] The ClogP values ​​described in this specification are values ​​calculated using the above-mentioned software package 2.

[0091] By making the ClogP value of the compound (A1) 4.0 or more, the compound (A1) becomes more hydrophobic, and the water resistance of the formed cured film is further improved. In addition, according to the findings of the present inventors, by making the ClogP value of the compound (A1) 7.0 or less, it is possible to suppress the excessive hydrophobicity of the ink, suppress the precipitation of inorganic salts caused by halogen, and further improve the ejection stability.

[0092] Examples of the compound (A1) having a ClogP value of 4.0 to 7.0 include propoxylated (3) neopentyl glycol diacrylate (molecular weight: 470, ClogP value: 4.90), 1,10-decanediol dimethacrylate (molecular weight: 310, ClogP value: 5.75), tricyclodecane dimethanol diacrylate (molecular weight: 304, ClogP value: 4.69), tricyclodecane dimethanol dimethacrylate (molecular weight: 332, ClogP value: 5.12), dipentaerythritol hexaacrylate (molecular weight: 578, ClogP value: 5.08), etc. The active radiation polymerizable compound (A) may contain only one compound (A1) or a combination of two or more compounds.

[0093] The molecular weight of the compound (A1) is preferably 300 to 1500. By making the molecular weight of the compound (A1) greater than 300, the liquid component of the ink is less likely to volatilize. As a result, the drying of the ink attached to the nozzle of the nozzle can be further suppressed, and the non-volatile components such as the pigment contained in the ink are fixed to the nozzle, and the ejection stability decreases. By being less than 1500, the viscosity of the ink can be suppressed from being too high, and the decrease in ejection stability can be suppressed. From this point of view, the molecular weight is more preferably 300 to 1000, and more preferably 300 to 800.

[0094] When the active radiation polymerizable compound (A) includes the compound (A1), the content of the compound (A1) is 10% to 50% by mass, more preferably 15% to 45% by mass, relative to the total mass of the ink. By setting the content within the above range, the water resistance and ejection stability of the cured film can be further improved.

[0095] From the viewpoint of further suppressing a decrease in ejection stability, the content of the compound having a ClogP value of 7.0 or higher is preferably less than 30% by mass, more preferably less than 10% by mass, and even more preferably less than 1% by mass relative to the total mass of the ink.

[0096] In the present specification, the content of the compound having two polymerizable groups, the content of the compound having three or more polymerizable groups, the content of the compound represented by the general formula (1), and the content of the compound (A1) are independent amounts.

[0097] The content of the active radiation polymerizable compound (A) may be, for example, 1 to 99% by mass, preferably 30 to 99% by mass, and more preferably 50 to 95% by mass, based on the total mass of the ink.

[0098] 1-2. Pigment (B)

[0099] The pigment (B) contained in the ink according to the present embodiment includes a red pigment (B1) having a maximum absorption wavelength of 480 nm to 600 nm and a pigment (B2) having a color different from that of the red pigment (B1).

[0100] 1-2-1. Red pigment (B1)

[0101] The red pigment (B1) is a pigment having a maximum absorption wavelength of 480 nm to 600 nm. As described above, the ink according to the present embodiment can suppress changes in the visibility of the color of the cured film by including the red pigment (B1).

[0102] Examples of the red pigment (B1) include Pigment Red (PR) 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 (PV) 3, 19, 23, 29, 30, 37, 50, 88, and Pigment Orange (PO) 13, 16, 20, 36. The red pigment (B1) may be a mixture thereof.

[0103] Among these, PR 122, PV 19, and PR 149 are preferred from the viewpoint of easily adjusting the halogen content in the ink to the above range. The content of these pigments is preferably 85 to 100% by mass, more preferably 95 to 100% by mass, relative to the total mass of the red pigment (B1).

[0104] From the viewpoint of further suppressing the color change of the cured film, the content of the red pigment (B1) may be, for example, 0.1% to 20% by mass, preferably 1.0% to 15.0% by mass, and more preferably 1.0% to 10.0% by mass, relative to the total mass of the ink.

[0105] 1-2-2. Pigment of a different color from red pigment (B2)

[0106] Pigment (B2) is a pigment of a different color from red pigment. In this specification, "a color different from red pigment" refers to a pigment with a maximum absorption wavelength outside the range of 480nm to 600nm. Pigment (B2) is preferably a pigment with a clear peak of absorbance in the visible light region outside the range of 480nm to 600nm. Examples of pigment (B2) include yellow pigments, blue pigments, etc. Pigment (B2) may include only one of these pigments, or may include two or more in combination.

[0107] Examples of the yellow pigment include Pigment Yellow (PY) 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193, etc. The yellow pigment may be a mixture thereof.

[0108] Examples of blue pigments include Pigment Blue (PB) 1, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17:1, 22, 27, 28, 29, 36, 60, etc. The blue pigment may be a mixture thereof. According to the knowledge of the present inventors, blue pigments are more easily dispersed in ink.

[0109] The content of the pigment (B2) may be, for example, 0.1% by mass to 20% by mass.

[0110] The total content of the red pigment (B1) and the pigment (B2) is preferably 0.1% to 20% by mass relative to the total mass of the ink. The red pigment (B1) may be contained in an amount of 0.1% to 19.9% ​​by mass relative to the total mass of the ink, and the pigment (B2) may be contained in an amount of 0.1% to 19.9% ​​by mass relative to the total mass of the ink.

[0111] The ink involved in this embodiment does not substantially contain black pigment. In this specification, "substantially does not contain black inorganic pigment" means that the content of black pigment relative to the total mass of the ink is less than 0.01 mass %. The content of black inorganic pigment is preferably less than 0.001 mass %, more preferably less than 0.0001 mass % relative to the total mass of the ink.

[0112] According to the knowledge of the inventors, when a solder resist pattern is formed using ink containing a black inorganic pigment, discoloration is not likely to occur even when heat is applied to the cured film. However, on the other hand, when the ink is cured, the black inorganic pigment absorbs active rays, and the polymerization of the active ray polymerizable compound in the ink cannot be fully carried out, and the adhesion and heat resistance of the cured film are likely to decrease. Therefore, if the content of the black inorganic pigment is less than 0.01% by mass, the decrease in the adhesion and heat resistance of the cured film can be suppressed.

[0113] In the ink involved in this embodiment, the volume average particle size of the pigment (B) is not particularly limited, and is preferably 0.08 μm to 0.5 μm. The particle size of the above-mentioned pigment particles refers to the particle size of the pigment particles in the state of attachment of the pigment dispersant (C) described later. By making the above-mentioned volume average particle size within the above-mentioned range, the dispersibility of the pigment can be further improved, and the jetting stability can be further improved. The above-mentioned volume average particle size can be obtained by using a known particle size measuring instrument using a dynamic light scattering method or an electrophoresis method.

[0114] 1-3. Pigment dispersant (C)

[0115] The pigment dispersant (C) included in the ink according to the present embodiment has an amine value greater than an acid value, and the acid value is 20 mg / KOH or less. As described above, by using such a pigment dispersant (C), the dispersion stability of the ink can be improved.

[0116] Examples of the pigment dispersant (C) include BYK-JET-9151 (manufactured by BYK-Chemie) and EFKA7701 (manufactured by BASF). The pigment dispersant (C) may be contained in the ink alone or in combination of two or more.

[0117] The acid value of the pigment dispersant (C) is preferably 20 mg / KOH or less, and more preferably 10 mg / KOH or less. The lower limit of the acid value is not particularly limited, and may be 0 mg / KOH or more.

[0118] The amine value of the pigment dispersant (C) only needs to be greater than the acid value, but from the viewpoint of further improving the dispersion stability of the ink, the amine value is preferably 10 mg / KOH or more, more preferably 20 mg / KOH or more. The upper limit of the amine value is not particularly limited, and may be, for example, 60 mg / KOH or less.

[0119] From the viewpoint of further improving the dispersion stability of the ink, the difference between the amine value and the acid value of the pigment dispersant (C) is preferably 1 to 40 mg / KOH, more preferably 10 to 40 mg / KOH.

[0120] The acid value and amine value can be measured by potentiometric titration, for example, by the method described in Journal of the Color Society 61,

[12] 692-698 (1988).

[0121] The acid value can be determined by dissolving 1 g of the pigment dispersant (C) in 100 mL of methyl isobutyl ketone (MIBK) and performing potentiometric titration with a 0.01 mol / L potassium methoxide-methyl isobutyl ketone / methanol (volume ratio 4:1) solution to determine the acid value from the amount of the solution required for neutralization.

[0122] The amine value can be determined by dissolving 1 g of the pigment dispersant (C) in 100 mL of methyl isobutyl ketone (MIBK), and then potentiometrically titrating the solution with a 0.01 mol / L perchloric acid MIBK solution to determine the amine value from the amount of perchloric acid MIBK solution required for neutralization.

[0123] For example, the content of the pigment dispersant (C) can be 1% to 95% by mass, preferably 10% to 70% by mass, and more preferably 30% to 45% by mass relative to the total mass of the pigment (B). By making the above content of the pigment dispersant (C) 10% by mass or more, the dispersion stability of the ink can be further improved.

[0124] 1-4. Synergist (D)

[0125] The ink according to this embodiment may contain a synergist (D).

[0126] The synergist (D) is a compound having an anchoring portion adsorbed on the pigment (B) and a polar portion adsorbed on the pigment dispersant. In the ink, the anchoring portion of the synergist (D) is adsorbed on the pigment, and the polar portion is adsorbed on the pigment dispersant (C). Therefore, the pigment dispersant (C) can be attached to the pigment via the synergist (D) and is not easy to dissociate from the pigment. Thus, the dispersion stability of the ink can be further improved. In particular, when B2 is a Y pigment, if a synergist is used for dispersion, the dispersion stability of the ink can be further improved.

[0127] Furthermore, according to the results of the present inventors' studies, when the amine value of the pigment dispersant (C) contained in the ink is larger than the acid value, the dispersion stability of the ink can be significantly improved by including the synergist (D).

[0128] Examples of synergists include pigment derivatives. Pigment derivatives are compounds in which polar groups are introduced into a pigment serving as a parent core. That is, in the pigment derivative, the pigment serving as a parent core becomes an anchor portion, and the polar group becomes a polar portion.

[0129] Examples of the polar group include chloro, sulfonyl, sulfonamide, carboxyl, carboxyamide, amino, amide, aminomethyl, imido, imidomethyl, phthalimido, phthalimidomethyl, nitro, cyano, phosphoric acid, etc. Among these, carboxyl, sulfonyl, nitro, phosphoric acid, amino, amide, aminomethyl, imido, imidomethyl, phthalimido, phthalimidomethyl, nitro, cyano, phosphoric acid, etc. are preferred.

[0130] Examples of the pigment derivative include azo derivatives, quinoline derivatives, pyrazole derivatives, and the like.

[0131] The method for synthesizing the pigment derivative is not particularly limited. For example, when introducing a sulfonyl group as a polar group into an azo pigment, fuming sulfuric acid, concentrated sulfuric acid, etc. can be added to a solution in which the pigment is dispersed, heated to 60° C. to 200° C. and stirred, and then volatile components are removed to obtain a pigment having a sulfonyl group introduced into the azo pigment.

[0132] Examples of commercially available products of the pigment derivative include Solsperse 5000S, Solsperse 12000S, and Solsperse 22000 (manufactured by Lubrizol).

[0133] The synergist (D) may be an aqueous dye having an acidic group or a basic group.

[0134] Examples of the acidic group include a carboxyl group, a sulfonyl group, a phosphoric acid group, etc. Among these, a sulfonyl group is preferred.

[0135] Examples of the above-mentioned basic group include an amino group, an imino group, and the like.

[0136] Examples of the aqueous dye include CI Acid Yellow 3, CI Acid Yellow 11, CI Acid Yellow 23, Direct Red 21, and the like.

[0137] The content of the synergist (D) is preferably 1% to 10% by mass, more preferably 2% to 8% by mass, relative to the total mass of the pigment (B). If it is 1% by mass or more, the dispersion stability of the ink can be further improved. If it is 10% by mass or less, the proportion of the pigment can be increased, further suppressing the color change of the cured film.

[0138] 1-5. Gel (E)

[0139] The ink according to this embodiment may contain a gelling agent (E).

[0140] The gelling agent (E) makes the ink sol under heating and gel at room temperature. Specifically, the gelling agent can make the ink sol when the ink temperature is 80°C and gel at 25°C. Thus, the heated and sol-gelled ink can be ejected from the nozzle, and the ink that falls on the recording medium and is cooled and gelled can be temporarily solidified, thereby improving the fixation of the ink. If the ink that falls on the recording medium is gelled and fixed, the wetting and diffusion of the ink can be suppressed, adjacent dots are less likely to be the same, and a higher-precision pattern can be formed on the circuit substrate.

[0141] The gelling agent (E) is preferably a compound that dissolves in the active radiation polymerizable compound contained in the ink at a temperature higher than the gelling temperature of the ink and crystallizes in the ink at a temperature below the gelling temperature of the ink. Here, the "gelling temperature" refers to the temperature at which the ink changes from a sol phase to a gel when the above-mentioned ink that has been solified or liquefied by heating is cooled, and the viscosity of the ink changes rapidly. Specifically, when the solified or liquefied ink is cooled while measuring the viscosity with a rheometer (e.g., MCR300 manufactured by Anton Paar), the temperature at which the viscosity rises rapidly can be taken as the gelling temperature of the ink.

[0142] The gelling agent (E) preferably crystallizes in the ink at a temperature below the gelling temperature of the ink, and forms a structure in which a radical polymerizable compound is contained in a three-dimensional space formed by the crystallized plate-like gelling agent (hereinafter referred to as a "card house structure"). When the card house structure is formed, the liquid active radiation polymerizable compound is retained in the above space, so that the dots formed by the ink attached to the recording medium are less likely to be wetted and spread, and the fixation of the ink is further improved. As a result, the dots formed by the ink attached to the recording medium are less likely to be fused together.

[0143] In addition, according to the new findings of the present inventors, when an active radiation polymerizable compound having a ClogP value of 4 to 7 is used in combination with a gelling agent, color changes caused by environmental changes of the cured film can be suppressed. This is believed to be because the dissolution stability of the gelling agent is improved by setting the ClpgP value to 4 to 7, and a desired cascade structure can be formed, so that the active radiation polymerizable compound is retained in the cascade structure.

[0144] From the viewpoint of making it easier to form a house-of-cards structure, the active radiation polymerizable compound dissolved in the ink is preferably compatible with the gelling agent (E).

[0145] Examples of gelling agents that can more easily form a house-of-cards structure by crystallization include aliphatic ketones, aliphatic esters, petroleum waxes, plant waxes, animal waxes, mineral waxes, hydrogenated castor oil, modified waxes, higher fatty acids, higher alcohols, hydroxystearic acid, N-substituted fatty acid amides and fatty acid amides including special fatty acid amides, higher amines, esters of sucrose fatty acids, synthetic waxes, dibenzylidene sorbitol, dimer acids and dimer diols.

[0146] Examples of the aliphatic ketones include dimylinuryl ketone, dibehenyl ketone, distearyl ketone, diarachidyl ketone, dipalmityl ketone, dilauryl ketone, dimyristyl ketone, myristylpalmityl ketone and palmitylstearyl ketone.

[0147] Examples of aliphatic esters include fatty acid esters of monohydric alcohols such as behenyl behenate, arachidyl arachidate, stearyl stearate, cetyl stearate, myristyl myristate, cetyl myristate, and oleyl palmitate; and fatty acid esters of polyhydric alcohols such as glycerol fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, ethylene glycol fatty acid esters, and polyoxyethylene fatty acid esters.

[0148] Examples of commercially available products of the aliphatic esters include Emalex series (manufactured by NIHON EMULSION CO., LTD. ("Emalex" is a registered trademark of the company)), RIKEMAL series, and Poem series (manufactured by RIKEN VITAMIN CO., LTD. ("RIKEMAL" and "Poem" are registered trademarks of the company)).

[0149] Examples of higher fatty acids include behenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, and erucic acid.

[0150] Examples of the higher alcohols include stearyl alcohol and behenyl alcohol.

[0151] Among these, from the viewpoint of further improving the fixation, the gelling agent is preferably an aliphatic ketone, an aliphatic ester, a higher fatty acid and a higher alcohol, and more preferably an aliphatic ketone represented by the following general formula (G1) or an aliphatic ester represented by the following general formula (G2). The gelling agent (E) may contain only one kind or a combination of two or more kinds.

[0152] General formula (G1): R a -CO-R b

[0153] General formula (G2): R c -COO-R d

[0154] In the general formula (G1), R a and R bindependently represent a linear hydrocarbon group having 12 to 26 carbon atoms which may have a branch. In the general formula (G2), R c and R d Each of the groups independently represents an optionally branched linear hydrocarbon group having 12 to 26 carbon atoms.

[0155] In the general formulas (G1) and (G2), by making R a ~R d The number of carbon atoms in the general formula (G1) and the general formula (G2) is 12 or more, thereby further improving the crystallinity of the gelling agent represented by the general formula (G1) and the general formula (G2), and generating more sufficient space in the above-mentioned house-of-cards structure. Therefore, the active radiation polymerizable compound (A) is easily and fully enclosed in the above-mentioned space, and the fixation of the ink is improved.

[0156] In addition, by making R a ~R d The carbon number of the compound is 26 or less, which can prevent the melting point of the gelling agent represented by the general formula (G1) and the general formula (G2) from rising too much. As a result, the solubilization temperature of the ink containing the gelling agent will not be too high, and the heating temperature of the ink can be reduced to eject the ink.

[0157] Examples of the aliphatic ketone represented by the general formula (G1) include dimylindole ketone (carbon number: 23-24), dibehenyl ketone (carbon number: 21-22), distearyl ketone (carbon number: 17-18), di(eicosyl) ketone (carbon number: 19-20), dipalmityl ketone (carbon number: 15-16), dimyristyl ketone (carbon number: 13-14), dilauryl ketone (carbon number: 1 The carbon number in the parentheses indicates the carbon number of each of the two hydrocarbon groups separated by the carbonyl group.

[0158] Examples of commercially available products of the compound represented by the general formula (G1) include 18-pentatriacontanon and Hentriacontan-16-on (both manufactured by Alfa Aeser), and Kao Wax T1 (manufactured by Kao Corporation).

[0159] Examples of the aliphatic esters represented by the general formula (G2) include behenyl behenate (carbon number: 21-22), arachidyl eicosyl ester (carbon number: 19-20), stearyl stearate (carbon number: 17-18), hexadecanol stearate (carbon number: 17-16), lauryl stearate (carbon number: 17-12), hexadecanol palmitate (carbon number: 15-16), stearyl palmitate (carbon number: 15-18), and myristyl alcohol. Myristyl myristate (carbon number: 13-14), cetyl myristate (carbon number: 13-16), octyldodecyl myristate (carbon number: 13-20), stearyl oleate (carbon number: 17-18), stearyl erucate (carbon number: 21-18), stearyl linoleate (carbon number: 17-18), behenyl oleate (carbon number: 18-22), and eicosyl linoleate (carbon number: 17-20). The carbon number in the parentheses indicates the carbon number of each of the two hydrocarbon groups separated by the ester group.

[0160] Examples of commercially available products of the aliphatic ester represented by the general formula (G2) include UNISTER M-2222SL, SPERMACETI, NISSAN ELECTOL WEP-2 and NISSAN ELECTOL WEP-3 (all manufactured by NOF Corporation, "UNISTER" and "NISSAN ELECTOL" are registered trademarks of the company), EXCEPARL SS and EXCEPARL MY-M (both manufactured by Kao Corporation, "EXCEPARL" is a registered trademark of the company), EMALEX CC-18 and EMALEX CC-10 (manufactured by NIHON EMULSION Co., Ltd., "EMALEX" is a registered trademark of the company), and AMREPS PC (manufactured by KOKYUALCOHOL KOGYO Co., Ltd., "AMREPS" is a registered trademark of the company). Most of these commercially available products are mixtures of two or more types, and therefore, they can be separated and purified as needed and then included in the ink.

[0161] The content of the gelling agent (E) is preferably 1% to 10% by mass, preferably 2% to 8% by mass, and more preferably 3% to 7% by mass relative to the total mass of the ink. When the content is 1% by mass or more, the fixation of the ink can be further improved, and when the content is 10% by mass or less, the solubility in the active radiation polymerizable compound can be further improved.

[0162] 1-6. Polymerization initiator (F)

[0163] In this embodiment, the ink may contain a polymerization initiator.

[0164] The polymerization initiator is a compound that initiates polymerization and crosslinking of the above-mentioned active radiation polymerizable compound by irradiation with active radiation. In addition, when the ink is cured by irradiation with electron beams, the polymerization and crosslinking of the above-mentioned active radiation polymerizable compound can be initiated even without a polymerization initiator, and the ink may not contain a polymerization initiator.

[0165] When the ink contains a radical polymerizable compound, the polymerization initiator (F) may be a radical polymerization initiator. Examples of the radical polymerization initiator include an intramolecular bond cleavage type radical polymerization initiator and an intramolecular hydrogen abstraction type radical polymerization initiator.

[0166] Examples of the intramolecular bond cleavage type free radical polymerization initiator include acetophenone-based initiators such as diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, benzil dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-methylthiophenyl)propane-1-one and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone; benzoin-based initiators such as benzoin, benzoin methyl ether and benzoin isopropyl ether; acylphosphine oxide-based initiators such as 2,4,6-trimethylbenzoin diphenylphosphine oxide; benzil and methylphenyl glyoxylates, etc.

[0167] Examples of the intramolecular hydrogen abstraction type radical polymerization initiator include benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylated benzophenone, 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone, and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone initiators such as 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone; aminobenzophenone initiators such as Michler's ketone and 4,4'-diethylaminobenzophenone; 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-phenanthrenequinone, and camphorquinone.

[0168] The content of the polymerization initiator (F) is preferably 1% by mass to 10% by mass, more preferably 2% by mass to 8% by mass, relative to the total mass of the ink.

[0169] 1-7. Others

[0170] The ink according to the present embodiment may further contain other components such as a surfactant, a polymerization inhibitor, and a moisturizing agent within a range in which the effects of the present invention are exhibited.

[0171] Examples of surfactants include anionic surfactants such as dialkyl sulfosuccinates, alkylnaphthalene sulfonates, and fatty acid salts, nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene / polyoxypropylene block copolymers, cationic surfactants such as alkylamine salts and quaternary ammonium salts, and silicone-based and fluorine-based surfactants.

[0172] Examples of commercially available silicone surfactants include Tego rad 2250 (manufactured by Evonik), KF-351A, KF-352A, KF-642, and X-22-4272 (manufactured by Shin-Etsu Chemical Co., Ltd.), BYK307, BYK345, BYK347, and BYK348 (manufactured by BYK-Chemie ("BYK" is a registered trademark of the company)), and TSF4452 (manufactured by Momentive Performance Materials).

[0173] Examples of commercially available fluorine-based surfactants include Megafac F (manufactured by DIC Corporation ("Megafac" is a registered trademark of the company)), Surflon (manufactured by AGC Seimi Chemical Co., Ltd. ("Surflon" is a registered trademark of the company)), Fluorad FC (manufactured by 3M Company ("Fluorad" is a registered trademark of the company)), Monflor (manufactured by Imperial Chemical Industries), Zonyls (manufactured by EI du Pont de Nemours and Company), Licowet VPF (manufactured by Rubberge-Hoechst), and FTERGENT (manufactured by NEOS Corporation ("FTERGENT" is a registered trademark of the company)).

[0174] The content of the surfactant relative to the total mass of the ink is not particularly limited within a range in which the effects of the present invention are exhibited, and may be, for example, 0.001 mass % or more and less than 1.0 mass %.

[0175] Examples of the polymerization inhibitor include N-oxyl radical polymerization inhibitors, phenol polymerization inhibitors, quinone polymerization inhibitors, amine polymerization inhibitors, copper dithiocarbamate polymerization inhibitors, etc. The polymerization inhibitor may be contained in the ink alone or in combination of two or more.

[0176] Examples of the N-oxyl radical polymerization inhibitor include 4-hydroxy-2,2,6,6-tetramethylpiperidin-N-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethyl-piperidin-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidin-N-oxyl, 4-methoxy-2,2,6,6-tetramethyl-piperidin-N-oxyl, 4-acetoxy-2,2,6,6-tetramethyl-piperidin-N-oxyl, etc. Examples of commercial products of the N-oxyl radical polymerization inhibitor include Irgastab UV10 (manufactured by BASF ("Irgastab" is a registered trademark of the company)).

[0177] Examples of the phenolic polymerization inhibitor include 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, 2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,4,6-tri-tert-butylphenol, 2,6-di-tert-butyl-p-cresol (butylated hydroxytoluene: BHT), 4-methoxyphenol, and 2-methoxy-4-methylphenol.

[0178] Examples of the quinone-based polymerization inhibitor include hydroquinone, methoxyhydroquinone, benzoquinone, 1,4-naphthoquinone, and p-tert-butylcatechol.

[0179] Examples of the amine-based polymerization inhibitor include alkylated diphenylamine, N,N′-diphenyl-p-phenylenediamine, and phenothiazine.

[0180] Examples of the copper dithiocarbamate-based polymerization inhibitor include copper dimethyl dithiocarbamate, copper diethyl dithiocarbamate, and copper dibutyl dithiocarbamate.

[0181] The content of the polymerization inhibitor is not particularly limited within the range in which the effects of the present invention are exerted. For example,

[0182] 1-8.Physical properties

[0183] The ink according to the present embodiment has a halogen content of 900 ppm or less. In the present specification, the "halogen content" refers to the content of the halogen element in the ink measured by the flask combustion method.

[0184] As described above, by making the halogen content in the ink 900ppm or less, the precipitation of inorganic salts in the ink can be suppressed, and the decline in ejection stability can be suppressed. From such a viewpoint, the halogen content is preferably 750ppm or less, more preferably 500ppm or less, further preferably 300ppm or less, and particularly preferably 200ppm or less. The upper limit of the halogen content is not particularly limited, and can be 0ppm or more.

[0185] The measurement by the flask combustion method can be performed, for example, by placing the inkjet resist ink in a combustion flask and burning the ink sample. Then, the gas generated by the combustion is absorbed by an absorption liquid (hydrogen peroxide). The absorption liquid is analyzed by ion chromatography to determine the halogen content [ppm].

[0186] The above halogen content can be adjusted according to the types and amounts of the pigment, pigment dispersant, and synergist contained in the ink.

[0187] When the ink does not contain a gelling agent, the viscosity of the ink at 40° C. is preferably 7 to 15 mPa·s, more preferably 8 to 13 mPa·s. By setting the viscosity within the above range, the ejection stability of the ink can be further improved.

[0188] When the ink contains a gelling agent, the viscosity of the ink at 80°C is preferably 3 mPa·s to 20 mPa·s, more preferably 7 to 9 mPa·s, from the viewpoint of further improving the ejection performance from the nozzle. In addition, from the viewpoint of fully gelling the ink when the temperature drops to room temperature after falling, the viscosity of the inkjet resist ink at 25°C is preferably 1.0 Pa·s to 1.0×10 4 Pa·s.

[0189] When the ink contains a gelling agent, the ink preferably undergoes a sol-gel phase transition at a temperature of 40°C or higher and lower than 100°C. In addition, the gelling temperature of the ink is preferably 40°C to 70°C. If the gelling temperature of the ink is 40°C or higher, the ink quickly gels after falling on the recording medium, so the fixation is further improved. If the gelling temperature of the ink is 70°C or lower, the ink is not easy to gel when the inkjet resist ink is ejected from a nozzle whose ink temperature is generally around 80°C, so the ink can be ejected more stably.

[0190] The viscosity at 80°C, the viscosity at 25°C and the gelation temperature of the inkjet resist ink can be obtained by measuring the temperature change of the dynamic viscoelasticity of the ink using a rheometer (for example, a stress-controlled rheometer Physica MCR series, manufactured by Anton Paar). Specifically, the ink is heated to 100°C and cooled to 25°C under the conditions of a shear rate of 11.7 (1 / s) and a cooling rate of 0.1°C / s to obtain a temperature change curve of the viscosity. Then, the viscosity at 80°C and the viscosity at 25°C can be obtained by reading the viscosities at 80°C and 25°C, respectively, in the temperature change curve of the viscosity. The gelation temperature can be obtained as the temperature at which the viscosity becomes 200mPa·s in the temperature change curve of the viscosity.

[0191] When the ink contains a gelling agent, the viscosity of the ink at 25°C, a strain of 5% as a shear strain, and an angular frequency of 10 radian / s (hereinafter also referred to as "shear strain viscosity") is preferably 1.0 Pa·s to 1.0×10 4 Pa·s, more preferably 1.0 Pa·s to 1.0×10 2 Pa·s, more preferably 1.0 Pa·s to 1.0×10 Pa·s. By setting the value to 1.0 Pa·s or more, the fixation of the ink can be further improved. By setting the value to 1.0×10 4 Pa·s or less, the ejection stability can be further improved.

[0192] The shear strain viscosity can be measured by changing the shear rate of 11.7 (1 / s) to a strain of 5% and an angular frequency of 10 radian / s in the above-mentioned method for measuring the viscosity of the inkjet resist ink.

[0193] 1-8. Preparation method of inkjet resist ink

[0194] The ink according to the present embodiment can be prepared by mixing the above-mentioned components. In order to improve the solubility of each component, it is preferable to mix them while heating.

[0195] It should be noted that a pigment dispersion containing a pigment and a pigment dispersant may be prepared in advance, and the remaining components may be added thereto and mixed. In this case, in order to improve the solubility of the pigment dispersant, etc., it is preferred to prepare the pigment dispersion while heating the pigment and the dispersant, etc. while mixing.

[0196] 2. Cured film formation method

[0197] The cured film forming method according to the present embodiment comprises the steps of: attaching the above-mentioned active radiation curable inkjet resist ink to a printed wiring board; and irradiating the attached inkjet resist ink with active radiation.

[0198] 2-1. Ink adhesion process

[0199] In this step, the above-mentioned inkjet resist ink is applied to the position where a pattern is to be formed on the printed wiring board by an inkjet method.

[0200] The ejection method from the nozzle can be any of an on-demand method and a continuous method. The on-demand method nozzle can be any of an electromechanical conversion method such as a single-chamber type, a dual-chamber type, a curved type, a piston type, a shared pattern type, and a shared wall type, and a thermoelectric conversion method such as a thermal inkjet type and a bubble jet ("bubble jet" is a registered trademark of Canon Inc.) type.

[0201] From the viewpoint of further improving the discharge performance from the head, the temperature of the ink when the ink is filled into the head is preferably set to 40°C to 100°C, more preferably 40°C to 90°C.

[0202] In particular, when the ink contains a gelling agent, in order to eject the ink droplets from the nozzle in a heated and solubilized state, the temperature of the ink when filling the nozzle is preferably set to be equal to or higher than the gelling temperature of the ink + 10°C and equal to or lower than the gelling temperature + 30°C. If the temperature of the above-mentioned active radiation curable ink in the nozzle is equal to or higher than the gelling temperature + 10°C, the ejection performance is unlikely to be reduced due to the gelling of the ink in the nozzle or on the nozzle surface. On the other hand, if the temperature of the ink in the nozzle is equal to or lower than the gelling temperature + 30°C, the components are unlikely to be degraded due to high temperature.

[0203] The method for heating the ink is not particularly limited. For example, at least one of the ink supply system such as the ink cartridge constituting the print head carriage, the supply pipe and the front chamber ink cartridge just in front of the nozzle, the pipe with a filter, and the piezoelectric head can be heated by a plate heater, a belt heater, and warm water.

[0204] From the viewpoint of increasing the pattern forming speed and forming a finer pattern, the amount of ink droplets discharged is preferably 3.0 pL to 9.0 pL.

[0205] The printed wiring board to which the ink is attached can be a board in which a conductive film such as copper foil is formed on a base board. The base board includes a rigid board and a flexible board.

[0206] Examples of the rigid substrate include a paper phenolic substrate, a paper epoxy substrate, a glass epoxy substrate, a glass polyimide substrate, a Teflon (registered trademark) substrate, a PPO substrate, a composite base epoxy substrate, and the like.

[0207] Examples of the material of the flexible substrate include a PET film, a polyimide film, and the like.

[0208] 2-2. Step of irradiating with active rays

[0209] In this step, the ink attached to the substrate is irradiated with active rays to cure the ink.

[0210] The active rays can be selected from, for example, electron beams, ultraviolet rays, α rays, γ rays, and X-rays, preferably ultraviolet rays or electron beams. The ultraviolet rays are preferably light having a peak wavelength of 360 nm to 410 nm. In addition, the ultraviolet rays are preferably irradiated by an LED light source. LEDs have less heat radiation than existing light sources (such as metal halide lamps), so by using LEDs, the ink is not easily melted when irradiated with active rays, and uneven gloss is not easily generated.

[0211] It should be noted that when the cured film forming method involved in this embodiment further has a heat curing step described later, this step may stop at the stage of temporarily curing the ink by irradiation with active rays. Here, "temporary curing" means partially curing the ink to the extent that the ink droplets attached to the substrate do not move or deform.

[0212] 2-3. Heating and curing process

[0213] The cured film forming method according to the present embodiment may further include a step of heating the ink irradiated with the active ray to cure it. In this step, after the step of irradiating with the active ray, the ink on the substrate is heated to further cure the ink.

[0214] This step can further improve the curability of the formed cured film, thereby further improving the adhesion and heat resistance between the cured film and the printed wiring board.

[0215] The method of heating the ink on the substrate is not particularly limited, and for example, an oven may be used.

[0216] The heating temperature of the ink is not particularly limited as long as the ink can be thermally cured, but is preferably 140° C. to 180° C. The heating time of the ink is preferably 30 to 120 minutes, more preferably 30 to 60 minutes.

[0217] 3. Cured film

[0218] The cured film according to the present embodiment is obtained by curing the above-mentioned active radiation-curable inkjet resist ink.

[0219] The above-mentioned cured film can be formed by the above-mentioned cured film forming method.

[0220] The color of the cured film is not particularly limited as long as it is a color formed using a red pigment, and is, for example, red, blue, green, orange, purple, black, etc. From the viewpoint of suppressing color change of the cured film after high temperature treatment, the color is preferably black.

[0221] 4. Printed wiring board

[0222] The printed wiring board according to the present embodiment has the above-mentioned cured film on the board.

[0223] The type of the printed wiring board on which the cured film is to be formed may be the same as the board described in the method for forming the cured film.

[0224] 5. Electronic devices

[0225] An electronic device according to the present embodiment includes the above-mentioned printed wiring board.

[0226] Examples of the above-mentioned electronic devices include information devices such as mobile phones, computers, and smartphones, household appliances such as refrigerators, washing machines, and microwave ovens, medical equipment, industrial robots, etc.

[0227] Example

[0228] The present invention will be described in detail below with reference to examples, but the scope of the present invention is not limited to the description of the examples.

[0229] 1. Preparation of inkjet resist inks AA1 to AA11

[0230] 1-1. Preparation of pigment dispersion

[0231] 7.0 parts by mass of pigment dispersant C-1 (BYK-JET-9151, manufactured by BYK) and 77.0 parts by mass of dipropylene glycol diacrylate as a dispersion medium were added to a stainless steel beaker, and the mixture was stirred for 1 hour on a hot plate set at 65°C, and then cooled to room temperature. 16.0 parts by mass of magenta pigment B-M1 (InkJet Magenta E5B02, manufactured by Craliant) were heated in the cooled beaker. Next, the solution in the beaker was placed in a glass bottle with 200 g of zirconia beads having a diameter of 0.5 mm, and the bottle was covered tightly, and a paint shaker (5400, manufactured by Red Devil) was used for dispersion. Thereafter, the zirconia beads were removed to prepare pigment dispersion M1.

[0232] Pigment dispersions M2 to M6, pigment dispersions Y1, Y2, pigment dispersions Cy1 to Cy3, and pigment dispersion K were prepared in the same manner as pigment dispersion M1, except that the type and amount of the pigment, the type and amount of the pigment dispersant, and the amount of the synergist added were changed as shown in Table 1. The numerical values ​​of the compositions in Table 1 represent parts by mass.

[0233] The types of the pigment and the pigment dispersant used in the preparation of the pigment dispersion are as follows.

[0234] (pigment)

[0235] B-M1: Magenta pigment PV19 (Ink Jet Magenta E5B02, manufactured by Craliant)

[0236] B-M2: Magenta pigment PV19 (FASTOGEN SUPER RED BRZ, manufactured by DIC Corporation)

[0237] B-M3: Magenta pigment PV19 / PR122 (Cinquasia Magenta D4500J, manufactured by BASF)

[0238] BY: Yellow pigment PY185 (PALIOTOL YELLOW D1155, manufactured by BASF)

[0239] BC: Cyan pigment PB15:4 (Chromofine Blue 6332JC, Dainichi Seika Industries, Ltd.)

[0240] BK: Black pigment PB7 (Mitsubishi Carbon Black MA-7, manufactured by Mitsubishi Chemical Corporation)

[0241] (Pigment dispersant)

[0242] C-1: BYK-JET-9151 (manufactured by BYK-Chemie, acid value: 8 mg / KOH, amine value: 18 mg / KOH)

[0243] C-2: EFKA7701 (manufactured by BASF, acid value: —, amine value: 40 mg / KOH)

[0244] C-3: Solsperse 36000 (manufactured by Lubrizol, acid value: 45 mg / KOH, amine value: -)

[0245] The acid value and amine value of the pigment dispersants C-1 to C-3 were measured by the following method.

[0246] (Acid value)

[0247] A solution of 1 g of the pigment dispersant dissolved in 100 mL of methyl isobutyl ketone (MIBK) was potentiometrically titrated with a 0.01 mol / L potassium methoxide-methyl isobutyl ketone / methanol (volume ratio 4:1) solution. The amount of the solution required for neutralization was then converted to a unit to determine the acid value of the pigment dispersant. It should be noted that the potentiometric titration was performed using an automatic titrator (COM-1500, manufactured by HIRANUMA Co., Ltd.).

[0248] (Amine value)

[0249] A solution prepared by dissolving 1 g of the pigment dispersant in 100 mL of methyl isobutyl ketone (MIBK) was potentiometrically titrated with a 0.01 mol / L perchloric acid MIBK solution. The amount of perchloric acid MIBK solution required for neutralization was then converted to a unit to determine the amine value of the pigment dispersant. It should be noted that the potentiometric titration used the same apparatus as that used in the method for determining the acid value.

[0250] (Synergizer)

[0251] D: Solsperse 22000 (manufactured by Lubrizol)

[0252]

[0253] 1-2. Preparation of inkjet resist ink

[0254] While stirring 2.2 parts by mass of the pigment dispersion M1 and 1.8 parts by mass of the pigment dispersion Y1, 20.0 parts by mass of the active ray polymerizable compound A-1, 38.9 parts by mass of the active ray polymerizable compound A-3, 33.0 parts by mass of the active ray polymerizable compound A-4, 1.0 parts by mass of the photopolymerization initiator 1 (Irgacure TPO, manufactured by BASF), 3.0 parts by mass of the photopolymerization initiator 2 (Genocure ITX, manufactured by Rahn AG) and 0.1 parts by mass of the polymerization inhibitor (Irgastab UV10, manufactured by BASF) were added to prepare an ink composition. The obtained ink composition was filtered with a 3.0 μm membrane filter (manufactured by ADVANTECH) to obtain an inkjet resist ink AA1.

[0255] Inkjet resist inks AA2 to AA11 were obtained in the same manner as inkjet resist ink AA1 except that the type and amount of the pigment dispersion liquid used were changed as shown in Table 2. The numerical values ​​of the compositions in Table 2 represent parts by mass.

[0256] The types of the active radiation polymerizable compound used in the preparation of the inkjet resist inks AA2 to AA11 are as follows.

[0257] A-1: o-phenylphenol EO acrylate (monofunctional, molecular weight: 268, ClogP value: 3.89)

[0258] A-2: dipropylene glycol diacrylate (difunctional, molecular weight: 242, ClogP value: 2.04)

[0259] A-3: Tricyclodecane dimethanol diacrylate (difunctional, molecular weight: 304, ClogP value: 4.69)

[0260] A-4: Isobornyl acrylate (monofunctional, molecular weight: 208, ClogP value: 4.66)

[0261] 1-3. Evaluation

[0262] (Ink color)

[0263] The colors of the obtained inkjet resist inks AA1 to AA11 were visually observed and judged.

[0264] (Halogen content)

[0265] Inkjet resist ink AA1 was placed in a combustion flask to burn the ink sample. The generated gas was absorbed by hydrogen peroxide, and the absorption liquid was analyzed by ion chromatography to determine the halogen content [ppm]. The same method was used to determine the halogen content of inkjet resist inks AA2 to AA11.

[0266] (Particle size)

[0267] The average particle diameter of the pigment particles contained in the inkjet resist inks AA1 to AA11 was measured by a dynamic light scattering method using a particle size distribution analyzer (Zetasizer Nano ZSP, manufactured by Malvern).

[0268] (Pigment dispersion stability)

[0269] The inkjet resist inks AA1 to AA11 were collected in separate heat-resistant tubes and stored in a thermostatic chamber at 60°C for 1 month. The average particle size of the pigment particles contained in the inkjet resist ink after storage was measured in the same manner as described above. The difference (PB-PA) between the average particle size (PA) of the pigment particles before storage in the thermostatic chamber and the average particle size (PB) of the pigment particles after storage was calculated, and the pigment dispersion stability was evaluated according to the following criteria.

[0270] ○The difference in average particle size before and after storage is less than 7nm

[0271] △The difference in average particle size before and after storage is 7nm or more and less than 15nm

[0272] ×The difference in average particle size before and after storage is 15 nm or more

[0273] (Ink jetting stability)

[0274] The inkjet resist inks AA1 to AA11 were collected in separate containers and stored in a thermostatic chamber at 25°C for 2 months. The stored inkjet resist inks AA to AA11 were loaded into an inkjet recording device having an inkjet recording head. The inkjet recording head was equipped with a piezoelectric inkjet (KM1800iSHC-C: manufactured by Konica Minolta, Inc.: resolution 600 dpi). Using the above-mentioned piezoelectric head, continuous ejection (driving) was performed under the conditions of a droplet volume of 3.5 pL, a droplet velocity of 7 m / s, an ejection frequency of 440 kHz, and a printing rate of 100%, and the number of nozzles that did not eject after 1 minute, 5 minutes, and 10 minutes from the start of the drive was counted.

[0275] ○: The number of defective nozzles is less than 5.

[0276] △: The number of defective nozzles is 5 or more and less than 20.

[0277] ×: The number of defective nozzles is 20 or more.

[0278] The evaluation results are summarized in Table 2.

[0279]

[0280] In inks AA1 to AA9, the dispersion stability and ejection stability of the pigments are good. This is believed to be because the amine value of the pigment dispersant contained in the ink is higher than the acid value, so the interaction between the pigment dispersant and the pigment is high, and the dispersion stability of the pigment is high. In addition, it is believed that by setting the halogen content of the ink to 900 ppm or less, the precipitation of inorganic salts with metal ions in the ink can be suppressed, and the ejection stability is high.

[0281] Inks AA2, AA3, AA6, and AA7 have higher dispersion stability. This is considered to be because the inks contain a synergist.

[0282] Ink AA1 has better ejection stability than ink AA9. This is probably because the molecular weight of the compound with a ClogP value of 4 to 7 contained in the ink is 300 to 1500, and thus the adhesion of non-volatile components to the nozzles due to volatilization of the liquid components of the ink can be suppressed.

[0283] On the other hand, in inks AA10 and AA12 in which the amine value of the dispersant was lower than the acid value, the dispersion stability and ejection stability were not improved. In addition, in ink AA11 in which the halogen content of the ink was greater than 900 ppm, the ejection stability was not improved.

[0284] 2. Preparation of inkjet resist inks BB1 to BB20

[0285] 2-1. Pigment dispersion

[0286] Pigment dispersions M1 to M6, pigment dispersions Y1 and Y2, pigment dispersion C1, and pigment dispersion K shown in Table 1 were used.

[0287] 2-2. Preparation of inkjet resist ink

[0288] While stirring 2.2 parts by mass of the pigment dispersion M1 and 1.8 parts by mass of the pigment dispersion Y1, 30.0 parts by mass of the active ray polymerizable compound A-1, 16.9 parts by mass of the active ray polymerizable compound A-2, 25.0 parts by mass of the active ray polymerizable compound A-6, 20.0 parts by mass of the active ray polymerizable compound A-7, 1.0 parts by mass of the photopolymerization initiator 1 (Irgacure TPO, manufactured by BASF), 3.0 parts by mass of the photopolymerization initiator 2 (Genocure ITX, manufactured by Rahn AG) and 0.1 parts by mass of the polymerization inhibitor (Irgastab UV10, manufactured by BASF) were added to prepare an ink composition. The obtained ink composition was filtered with a 3.0 μm membrane filter (manufactured by ADVANTECH) to obtain an inkjet resist ink B1.

[0289] Inkjet resist inks BB2 to BB20 were obtained in the same manner as inkjet resist ink BB1 except that the type and amount of the pigment dispersion and the type and amount of the active radiation polymerizable compound were changed as shown in Tables 3 to 6. The numerical values ​​of the compositions in Tables 3 to 6 represent parts by mass.

[0290] The types of the active radiation polymerizable compound and the gelling agent used in the preparation of the inkjet resist inks BB1 to BB20 are as follows.

[0291] (Active radiation polymerizable compound)

[0292] A-1: o-phenylphenol EO acrylate (monofunctional, molecular weight: 268, ClogP value: 3.89)

[0293] A-2: dipropylene glycol diacrylate (difunctional, molecular weight: 242, ClogP value: 2.04)

[0294] A-3: Tricyclodecane dimethanol diacrylate (difunctional, molecular weight: 304, ClogP value: 4.69)

[0295] A-5: Nonylphenol 2PO modified acrylate (monofunctional, molecular weight: 390, ClogP value: 2.04)

[0296] A-6: Propoxylated (3) neopentyl glycol diacrylate (difunctional, molecular weight: 328, ClogP value: 3.33)

[0297] A-7: 4EO modified hexanediol diacrylate (difunctional, molecular weight: 358, ClogP value: 2.49)

[0298] A-8: Dipentaerythritol hexaacrylate (hexafunctional, molecular weight: 578, ClogP value: 5.08)

[0299] A-9: Aliphatic urethane acrylate oligomer (trifunctional, CN989, manufactured by Sartomer)

[0300] A-10: Acrylate dendrimer, SP1106, manufactured by Miwon (octadecanoic acid, molecular weight: 1630)

[0301] A-11: Compound represented by the following formula (a) (trifunctional, molecular weight: 398, ClogP value: 2.98)

[0302]

[0303] The viscosity and sol-gel phase transition temperature of the prepared inkjet resist inks BB12 to BB18 at 25° C. were measured by the following method.

[0304] The ink was heated to 100°C using a stress-controlled rheometer (Physica MCR series, manufactured by Anton Paar), and cooled to 25°C under the conditions of a shear rate of 11.7 (1 / s) and a cooling rate of 0.1°C / s to obtain a viscosity temperature change curve. The viscosity at 80°C and the viscosity at 25°C were then obtained by reading the viscosity at 25°C from the viscosity temperature change curve. The sol-gel phase transition temperature was obtained as the temperature at which the viscosity reached 200 mPa·s in the viscosity temperature change curve.

[0305] [Table 3]

[0306]

[0307] [Table 4]

[0308]

[0309] [Table 5]

[0310]

[0311] [Table 6]

[0312]

[0313] 2-3. Patterning using inkjet resist ink

[0314] Two independently driven heads of a piezoelectric nozzle (KM1800iSHC-C, manufactured by Konica Minolta, with a resolution of 600 dpi) were arranged so that the nozzles were alternately arranged to produce an inkjet recording head with a nozzle array of 1200 dpi. Inkjet resist ink BB1 was filled into the head module from an ink cartridge storing the inkjet resist ink BB1 through an ink flow path.

[0315] Next, a voltage was applied to the inkjet recording head so that the droplet discharge amount became 6.0 pL, and a solid pattern of 20 mm × 50 mm and 30 μm thick and a fine line pattern of 100 μm line and space and 30 μm thick were printed on a copper-clad laminate for printed wiring boards (FR4, thickness 1.6 mm, size 150 mm × 95 mm). During printing, the ink in the recording head was heated by a built-in heater of the recording head so that it became 80°C.

[0316] For the printed pattern, the intensity is 500mJ / cm 2 The ink layer was temporarily cured by irradiating with LED light (Fire Jet(TM) FJ100, manufactured by Phoseon Technology, wavelength 395 nm). Thereafter, the substrate was placed in an oven and heated at 150° C. for 60 minutes to obtain a printed sample.

[0317] The same operation was performed for inkjet resist inks BB2 to BB20.

[0318] 2-4. Evaluation

[0319] (Pigment dispersion stability)

[0320] Inkjet resist inks BB1 to BB20 were collected in separate heat-resistant tubes and stored in a thermostatic chamber at 60°C for 1 month. The average particle size of the pigment particles contained in the inkjet resist ink after storage was measured in the same manner as described above. The difference (PB-PA) between the average particle size (PA) of the pigment particles before storage in the thermostatic chamber and the average particle size (PB) of the pigment particles after storage was calculated, and the pigment dispersion stability was evaluated according to the following criteria.

[0321] ○The difference in average particle size before and after storage is less than 7nm

[0322] △The difference in average particle size before and after storage is 7nm or more and less than 15nm

[0323] ×The difference in average particle size before and after storage is 15 nm or more

[0324] (Coating color)

[0325] The color of the coating film of the formed solid pattern was visually observed and judged.

[0326] (Halogen content)

[0327] The halogen contents in the inkjet resist inks BB1 to BB20 were measured in the same manner as described above.

[0328] (Ink jetting stability)

[0329] Using the above-mentioned piezoelectric head, continuous ejection (drive) is performed under the conditions of droplet volume 3.5pl, droplet velocity 7m / s, ejection frequency 40kHz, and printing rate 100%, and the number of nozzles that do not eject after 1 minute, 5 minutes, and 10 minutes from the start of driving is counted.

[0330] ○: The number of defective nozzles is less than 5.

[0331] △: The number of defective nozzles is 5 or more and less than 20.

[0332] ×: The number of defective nozzles is 20 or more.

[0333] (Thin line reproducibility)

[0334] The formed thin line pattern was observed at 500 times magnification using a microscope (VHX-5000, manufactured by KEYENCE CORPORATION), and the thin line reproducibility was evaluated based on the following criteria.

[0335] ◎The line is sharp, the error of line width and line spacing is reproduced within ±10μm, and there is no scattering of satellite droplets, etc.

[0336] ○ The line is slightly thick or thin, and the error in line width and line spacing is greater than ±10μm and can be reproduced within ±20μm

[0337] △The line thickness or thinness is observed, and the error in line width and line spacing is greater than ±20μm and can be reproduced within ±30μm

[0338] × Observe that the line is uneven, the line width and line spacing error is greater than ±30μm, or observe that the line is deformed and the line spacing is filled

[0339] (Solder heat resistance)

[0340] After the substrate formed with the above solid pattern was immersed in a solder bath at 260°C for 10 seconds three times, a checkerboard-shaped cut was made in the cured film according to the cross-cut method of JIS K5600-5-6:1999, and an adhesive tape was attached. The adhesive tape was peeled off, and the peeled-off state of the cured film after peeling off from the substrate was observed to determine the adhesion residual rate. Here, the adhesion residual rate refers to the ratio of the number of squares remaining in the cured film after the tape is peeled off to the number of squares made by cutting the above cut. Based on the adhesion residual rate, the solder heat resistance was evaluated according to the following evaluation criteria.

[0341] ◎The adhesion residual rate is 100%

[0342] ○ The adhesion residual rate is 90% or more and less than 100%

[0343] △The adhesion residual rate is 70% or more and less than 90%

[0344] × Adhesion residual rate is less than 70%

[0345] (Changes in color tone of coating film after high temperature treatment)

[0346] The substrate having the solid pattern formed thereon was further placed in an oven and heated for 60 minutes at 140° C. The cured film of the solid pattern before and after heating was measured with a colorimeter and visually observed, and the change in color tone was evaluated according to the following criteria.

[0347] ◎Color difference ΔE * Less than 2, no color change is seen when visually observed

[0348] ○Color difference ΔE * 2 or more and less than 3, and the color tone changes slightly when visually observed

[0349] △ Color difference ΔE * 3 or more and less than 5, color tone changes are seen when visually observed

[0350] × Color difference ΔE * 5 or above, the color tone is obviously different

[0351] (Adhesion of coating film to substrate after high temperature treatment)

[0352] The substrate formed with the above-mentioned solid pattern is further placed in an oven and heated at 140°C for 60 minutes. According to the cross-cutting method of JIS K5600-5-6:1999, a checkerboard-shaped cut is made into the heated cured film, and an adhesive tape is attached. The adhesive tape is peeled off, and the peeled-off state of the cured film after peeling off from the substrate is observed to determine the adhesion residual rate. The adhesion residual rate can be determined in the same way as the evaluation of solder heat resistance. Based on the adhesion residual rate, the evaluation of substrate adhesion is performed according to the following criteria.

[0353] ◎The adhesion residual rate is 100%

[0354] ○ The adhesion residual rate is 80% or more and less than 100%

[0355] △ The adhesion residual rate is more than 60% and less than 80%

[0356] × Adhesion residual rate is less than 60%

[0357] The evaluation results are summarized in Table 7.

[0358]

[0359] In inks BB1 to BB18, the dispersion stability and ejection stability of the pigments are good. This is believed to be because the amine value of the pigment dispersant contained in the ink is higher than the acid value, so the interaction between the pigment dispersant and the pigment is high, and the dispersion stability of the pigment is high. In addition, it is believed that by setting the halogen content of the ink to 900 ppm or less, the precipitation of inorganic salts with metal ions in the ink can be suppressed, and the ejection stability is high.

[0360] Furthermore, it was confirmed that even if the ink contained a red pigment, the color change of the cured film could be suppressed.

[0361] In inks BB6 to BB18 in which the active radiation polymerizable compound in the ink includes a compound having three or more polymerizable groups, solder resistance is improved.

[0362] This application claims priority based on Japanese Patent Application No. 2022-087986 filed on May 30, 2022. The contents described in the specification and drawings of that application are incorporated herein by reference in their entirety.

[0363] Industrial Applicability

[0364] The active radiation curable inkjet resist ink of the present invention can improve the dispersion stability of the pigment and the jetting stability of the ink after long-term storage, can suppress the color change of the cured film even after high-temperature treatment, and can improve the adhesion and heat resistance of the cured film to the substrate. Therefore, the resist ink is useful in, for example, the production of wiring boards.

Claims

1. An active ray-curable inkjet resist ink comprising an active ray-polymerizable compound A, a pigment B and a pigment dispersant C, The pigment B comprises a red pigment B1 having a maximum absorption wavelength of 480 nm to 600 nm, and a pigment B2 having a color different from that of the red pigment B1. The amine value of the pigment dispersant C is greater than the acid value, The inkjet resist ink has a halogen content of 900 ppm or less and substantially contains no black inorganic pigment.

2. The active radiation curable inkjet resist ink according to claim 1, wherein Further comprising a synergist D.

3. The active radiation curable inkjet resist ink according to claim 1 or 2, wherein: The content of the black inorganic pigment is less than 0.01 mass %.

4. The active radiation curable inkjet resist ink according to claim 1 or 2, wherein: The active radiation polymerizable compound A comprises a compound A1 having a ClogP value of 4.0 to 7.0, The content of the compound A1 is 10% by mass to 50% by mass relative to the total mass of the inkjet resist ink.

5. The active radiation curable inkjet resist ink according to claim 4, wherein The molecular weight of the compound A1 is 300-1500.

6. The active radiation curable inkjet resist ink according to claim 1 or 2, wherein: The active radiation polymerizable compound A includes a compound having three or more polymerizable groups.

7. The active radiation curable inkjet resist ink according to claim 1 or 2, wherein: The active radiation polymerizable compound A comprises a compound represented by the following general formula (1) or a salt thereof: General formula (1) In the general formula (1), R1 represents an unsubstituted alkylene group having 1 to 6 carbon atoms, Q represents an oxygen atom or NR2, R2 represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group, and X represents a structure derived from an alcohol or an amine containing at least one polymerizable group selected from a (meth)acryloyl group, an aryl group, and a vinyl group at the terminal.

8. The active radiation curable inkjet resist ink according to claim 1 or 2, wherein The invention further comprises a gelling agent E.

9. The active radiation curable inkjet resist ink according to claim 8, wherein The viscosity at 25°C is 1.0 Pa·s~1.0×10 4 Pa·s, and a sol-gel phase transition occurs at a temperature above 40°C and below 100°C.

10. The active radiation curable inkjet resist ink according to claim 1 or 2, wherein The halogen content in the inkjet resist ink is 300 ppm or less.

11. A method for forming a cured film, comprising the following steps: A step of attaching the active radiation curable inkjet resist ink according to claim 1 or 2 to a substrate, and A step of irradiating the adhered inkjet resist ink with active rays.

12. The cured film forming method according to claim 11, wherein The method further comprises the step of heating and curing the active radiation-curable inkjet resist ink irradiated with the active radiation.

13. A cured film obtained by curing the active radiation curable inkjet resist ink according to claim 1 or 2. 14 . A printed wiring board comprising the cured film according to claim 13 . 15 . An electronic device comprising the printed wiring board according to claim 14 .

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