Inkjet ink composition, inkjet recording method, and inkjet recording system

Abstract

The present invention addresses the problem of providing: an inkjet ink composition that provides both flexibility and fastness for recorded matter and that suppresses reductions in the fastness during long-term storage; an inkjet recording method; and an inkjet recording system.　The inkjet ink composition according to the present invention is cured by heat or active-energy radiation, said inkjet ink composition characteristically comprising a polyfunctional compound A and an acrylate oligomer, wherein the degree of resonance stabilization when the polyfunctional compound A has become a radical is the same as or less than that for styrene, and the acrylate oligomer has at least three functional groups.

Description

[Technical Field]

[0001] This invention relates to an inkjet ink composition, an inkjet recording method, and an inkjet recording system. More specifically, it relates to an inkjet ink composition that achieves both flexibility and robustness in recorded materials and suppresses the deterioration of robustness during long-term storage. [Background technology]

[0002] In printed circuit boards, an insulating film (solder resist film) is formed on the printed wiring board by applying and curing ink to protect the circuit pattern. One known method for forming the solder resist film is the inkjet method, which involves applying inkjet ink (hereinafter simply referred to as "ink"), curing it with light, and then curing it with heat.

[0003] Patent Document 1 discloses a technology for an inkjet printing curable composition comprising (A) a highly branched oligomer or polymer having ethylenically unsaturated groups, (B) a photopolymerization initiator, and (C) a thermosetting compound. The cured product of this inkjet printing curable composition exhibits excellent heat resistance, robustness, and adhesion to the substrate, but lacks flexibility, leaving room for improvement for mounting on flexible devices. Furthermore, it has been difficult to suppress the deterioration of the robustness of the cured product during long-term storage.

[0004] Patent Document 2 discloses a technology for an inkjet-curable composition containing a urethane (meth)acrylate, a compound having a cyclic ether group, a photopolymerization initiator, and a thermosetting agent. The cured product of this inkjet-curable composition exhibits excellent storage stability, heat resistance, insulation reliability, wettability to substrates, and migration resistance, but it has been difficult to suppress the deterioration of the robustness of the cured product during long-term storage.

[0005] Furthermore, the inks disclosed in Patent Documents 1 and 2 contain thermosetting compounds, which means that when the ink is ejected at high temperatures, it tends to harden, resulting in a problem where sufficient ejection stability cannot be obtained.

[0006] Patent Document 3 discloses a technology for an active energy ray curable composition containing a monofunctional monomer composition (A) and a polyfunctional (meth)acrylic monomer (B), wherein the ratio of the rate constants is within a specific range. While this active energy ray curable composition exhibits excellent rapid curing properties when using a light-emitting diode (LED) as the light source, curing is achieved only by irradiation with active energy rays. Therefore, there has been a need for further improvement in the robustness of the cured product of this active energy ray curable composition. Furthermore, even with this technology, it has been difficult to suppress the deterioration of the robustness of the cured product during long-term storage. In this specification, "robustness" is used to mean "robustness," "scratch resistance," "abrasion resistance," "friction resistance," etc. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2019-178260 [Patent Document 2] Japanese Patent Publication No. 2016-147970 [Patent Document 3] Japanese Patent Publication No. 2019-104867 [Overview of the project] [Problems that the invention aims to solve]

[0008] This invention has been made in view of the above-mentioned problems and circumstances, and its objective is to provide an inkjet ink composition, an inkjet recording method, and an inkjet recording system that achieve both flexibility and robustness in recorded materials and suppress the deterioration of robustness during long-term storage. [Means for solving the problem]

[0009] In order to solve the above problems, the inventors investigated the causes of the above problems and, as a result, found that in a recording obtained by curing an inkjet ink composition containing a polyfunctional compound A whose resonance stabilization degree when it becomes a radical is equal to or less than that of styrene, and an acrylate oligomer having three or more functional groups, both flexibility and robustness are achieved, and the deterioration of robustness during long-term storage is suppressed, leading to the present invention. In other words, the above-mentioned problems according to the present invention are solved by the following means.

[0010] 1. An inkjet ink composition that hardens with heat, It contains polyfunctional compound A and acrylate oligomer, The polyfunctional compound A is methacrylate or maleimide, The degree of resonance stabilization when the polyfunctional compound A becomes a radical is equal to or less than that of styrene. The acrylate oligomer has three or more functional groups. death, The content of the polyfunctional compound A in the inkjet ink composition is within the range of 1 to 10% by mass. An inkjet ink composition characterized by the following features. 2. Hardens with heat and active energy rays. The inkjet ink composition according to the first claim, characterized by the above.

[0011] 3 The Alfrey-Price Q value of the polyfunctional compound A is in the range of 0.70 to 1.00. The first paragraph characterized by or paragraph 2 The inkjet ink composition described above.

[0012] 4 The shear viscosity of the inkjet ink composition at 25°C and a shear rate of 1000 / sec is in the range of 40 to 400 mPa·s. The first paragraph characterized by from The 3 term any one of the following items The inkjet ink composition described above.

[0014] 5 . When the content rate of the acrylate oligomer in the inkjet ink composition is within the range of 10 to 40% by mass The inkjet ink composition according to any one of claims 1 to 4 any one of the claims up to the claim

[0015] 6 . The acrylate oligomer is a urethane acrylate oligomer The inkjet ink composition according to any one of claims 1 to 5 any one of the claims up to the claim

[0016] 7 . The acrylate oligomer is a hyperbranched acrylate oligomer The inkjet ink composition according to any one of claims 1 to 6 any one of the claims up to the claim

[0017] 8 . Further contains a monomer containing a polyfunctional compound B, The polyfunctional compound B is a monomer other than the polyfunctional compound A among the monomers having two or more functional groups, The content rate of the polyfunctional compound B with respect to the total mass of the monomer is within the range of 90 to 100% by mass The inkjet ink composition according to any one of claims 1 to 7 any one of the claims up to the claim

[0019] 9 . Further contains a gelling agent The inkjet ink composition according to any one of claims 1 to[[ID=四十七]] 8 [[ID=四十八]]any one of the claims up to the claim[[ID=四十九]] [[ID=五十]]

[0020] [[ID=五十一]] [[ID=五十二]]1[[ID=五十三]] 0 [[ID=五十四]]. An inkjet recording method using an inkjet ink composition,[[ID=五十五]] [[ID=五十六]]From claim 1 to claim[[ID=五十七]] 9Using an inkjet ink composition described in any one of the items up to item, The process of ejecting the inkjet ink composition from the inkjet head and depositing it onto a recording medium, and The process includes a step of curing the inkjet ink composition that has landed on the recording medium by heat. An inkjet recording method characterized by the following.

[0021] 1 1 An inkjet recording system using an inkjet ink composition, Articles 1 to 1 9 Using an inkjet ink composition described in any one of the items up to item, An inkjet head for ejecting the aforementioned inkjet ink composition, and The inkjet ink composition has a heating section for heating the inkjet ink composition. An inkjet recording system characterized by the following features. [Effects of the Invention]

[0022] The present invention provides an inkjet ink composition, an inkjet recording method, and an inkjet recording system that achieve both flexibility and robustness in recorded materials and suppress the deterioration of robustness during long-term storage.

[0023] Although the mechanism of action or mechanism of the present invention is not yet clear, it is speculated as follows.

[0024] Generally, active energy ray curable resins contain oligomers and monomers having functional groups, and harden through polymerization and crosslinking by the reaction of radicals and cations generated by irradiation with active energy rays as initiating elements. In the inkjet ink composition of the present invention (hereinafter also simply referred to as "ink"), hardening is thought to occur by a radical polymerization reaction.

[0025] In this invention, "polymerization" refers to a reaction that forms new chemical bonds to create a polymer, and "crosslinking" refers to a reaction that links polymer compounds formed by polymerization reactions together, changing their physical or chemical properties. Active energy ray curable resins harden as polymerization and crosslinking proceed, and the hardness of the cured product of the active energy ray curable resin is improved by increasing the polymerization rate and crosslinking rate.

[0026] The acrylate oligomer according to the present invention has three or more functional groups, and therefore polymerization reactions occur more readily compared to acrylate oligomers having one or two functional groups, forming molecules (polymers) with a high polymerization rate in the initial stages of polymerization. In radical polymerization, as the polymerization rate increases, the viscosity of the system increases and the diffusion rate of growing radicals at the polymer ends decreases, making termination reactions due to collisions between radicals less likely and promoting the growth reaction (gel effect).

[0027] On the other hand, oxygen in the air is highly reactive with radicals and readily reacts with radical-active species to form hydroperoxy radicals. Since these radicals have poor reactivity with monomers, the polymerization reaction is inhibited (polymerization inhibition). However, in this invention, the viscosity of the system increases rapidly, making it difficult for oxygen to react with radical-active species and thus difficult to generate hydroperoxy radicals. Therefore, polymerization inhibition by oxygen is less likely to occur, meaning polymerization proceeds more easily, improving the rapid curing properties of the ink and the robustness of the cured product.

[0028] Furthermore, the polyfunctional compound A according to the present invention exhibits resonance stabilization equal to or less than that of styrene when it becomes a radical. In other words, the functional groups of polyfunctional compound A according to the present invention are relatively unreactive, and some unreacted functional groups remain. As a result, the ink of the present invention undergoes moderate polymerization and crosslinking, achieving both sufficient flexibility and practically acceptable durability in recorded materials.

[0029] Furthermore, the ink of the present invention undergoes polymerization and crosslinking upon heating after irradiation with active energy rays, further improving the robustness of the recorded material. However, as mentioned above, the functional groups of polyfunctional compound A are relatively unreactive, so some unreacted functional groups remain even after the heating reaction.

[0030] Typically, cured products of active energy ray-curable resins have a problem in that their robustness tends to decrease during long-term storage due to hydrolysis and other factors that break down the crosslinked structure. However, in the cured product of the ink of the present invention, while the crosslinked structure is broken down by hydrolysis and other factors, the aforementioned unreacted functional groups form new bonds, thus maintaining the three-dimensional structure and suppressing the deterioration of the robustness of the recorded material. [Modes for carrying out the invention]

[0031] The present invention relates to an inkjet ink composition that is cured by active energy rays or heat, and is characterized by containing a polyfunctional compound A and an acrylate oligomer, wherein the degree of resonance stabilization when the polyfunctional compound A becomes a radical is equal to or less than that of styrene, and the acrylate oligomer has three or more functional groups. This feature is a technical feature common to or corresponding to the embodiments described below.

[0032] In this invention, "recorded material" refers to something recorded on a recording medium using the ink of the present invention by the inkjet recording method described later, and "cured material" simply refers to the ink composition of the present invention that has been cured, but they are essentially synonymous.

[0033] In embodiments of the present invention, from the viewpoint of achieving the desired effect, it is preferable that the Alfrey-Price Q value of the polyfunctional compound A is in the range of 0.70 to 1.00.

[0034] From the viewpoint of obtaining sufficient ejection stability at 80°C and improving the robustness of the recorded material, it is preferable that the shear viscosity of the inkjet ink composition at 25°C and a shear rate of 1000 / sec is in the range of 40 to 400 mPa·s.

[0035] From the viewpoint of improving the flexibility of the recorded material and its durability during long-term storage, it is preferable that the content of the polyfunctional compound A in the inkjet ink composition is within the range of 1 to 15% by mass.

[0036] From the viewpoint of improving the robustness of the recorded material, it is preferable that the content of the acrylate oligomer in the inkjet ink composition is in the range of 10 to 40% by mass.

[0037] From the viewpoint of improving the robustness of the recorded material, it is preferable that the acrylate oligomer is a urethane acrylate oligomer.

[0038] From the viewpoint of improving the robustness of the recorded material, it is preferable that the acrylate oligomer is a hyperbranched acrylate oligomer.

[0039] From the viewpoint of improving the robustness of the recorded material, it is preferable that the material further contains monomers, and that the content of polyfunctional compound B relative to the total mass of the monomers is in the range of 90 to 100% by mass.

[0040] From the viewpoint of improving the flexibility of the recorded material and its robustness during long-term storage, it is preferable that the polyfunctional compound A is a methacrylate compound.

[0041] From the viewpoint of improving the pinning properties of the ink and the robustness of the recorded material, it is preferable to further include a gelling agent.

[0042] Furthermore, the inkjet recording method of the present invention is characterized by using the inkjet ink composition of the present invention, and comprising the steps of ejecting the inkjet ink composition from an inkjet head and depositing it onto a recording medium, and curing the inkjet ink composition deposited on the recording medium with active energy rays and heat.

[0043] The inkjet recording system of the present invention is characterized by using the inkjet ink composition of the present invention and having an inkjet head for ejecting the inkjet ink composition, an active energy ray irradiation unit for irradiating the inkjet ink composition that has landed on a recording medium with active energy rays, and a heating unit for heating the inkjet ink composition that has been irradiated with active energy rays.

[0044] The present invention, its components, and embodiments and models for carrying out the present invention will be described in detail below. In this application, "~" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0045] <Summary of the inkjet ink composition of the present invention> The inkjet ink composition of the present invention (hereinafter also simply referred to as "ink") is an inkjet ink composition that is cured by active energy rays or heat, and contains a polyfunctional compound A and an acrylate oligomer, wherein the degree of resonance stabilization when the polyfunctional compound A becomes a radical is equal to or less than that of styrene, and the acrylate oligomer has three or more functional groups.

[0046] "Hardening by active energy rays or heat" means hardening by irradiation with active energy rays or heating. In the ink of the present invention, the robustness of the recorded material is improved by hardening by irradiation with active energy rays and then further hardening by heating. The ink of the present invention can be hardened by irradiation with active energy rays alone or by heating alone, but it is preferable to irradiate with active energy rays at least, and further heating is more preferable from the viewpoint of improving the robustness of the recorded material.

[0047] Generally, active energy ray curable resins harden upon irradiation with active energy rays. More specifically, radicals and cations generated by irradiation with active energy rays act as initiators, reacting with oligomers and monomers having polymerizable functional groups, resulting in polymerization and crosslinking, which leads to hardening. Furthermore, active energy ray curable resins containing thermosetting agents also harden upon heating, thus improving the pencil hardness of the cured product.

[0048] In particular, when using active energy ray-curable resins as solder resist inks, in addition to robustness, adhesion to printed circuit boards and heat resistance are required, making it effective for the ink to contain a thermosetting agent. However, inks containing thermosetting agents have high viscosity at high temperatures, and under the temperature conditions during ink ejection in inkjet methods, there has been a problem in that sufficient ink ejection stability cannot be obtained.

[0049] The ink of the present invention contains a polyfunctional compound A (monomer) and an acrylate oligomer. It is believed that the polyfunctional compound A and the acrylate oligomer are polymerized by radical polymerization, and further cured by forming a crosslinked structure. The reaction mechanism of radical polymerization is as follows: a monomer (or oligomer) reacts with a radical active species generated from a small amount of polymerization initiator to produce monomer (or oligomer) radicals (initiation reaction), and this reaction occurs continuously (growth reaction) to form a polymer. The radical active species attacks the ethylenically unsaturated bonds of the monomer (or oligomer) to initiate polymerization.

[0050] Furthermore, the ink of the present invention undergoes polymerization and crosslinking upon further heating. However, this polymerization reaction requires relatively high temperatures and prolonged heating, and is unlikely to occur under the conditions of ink ejection. Therefore, the viscosity of the ink does not increase, and sufficient ejection stability can be obtained.

[0051] <<Composition of the inkjet ink composition of the present invention>> [1 Polyfunctional compound A] The ink of the present invention contains a polyfunctional compound A whose resonance stabilization degree when it becomes a radical is equal to or less than that of styrene, thereby suppressing the deterioration of the robustness of recorded materials during long-term storage.

[0052] In the present invention, "polyfunctional compound" refers to a compound having two or more functional groups, and in the present invention, "functional group" refers to an atom or group of atoms that causes the reactivity of the compound. Furthermore, in this invention, the "degree of resonance stabilization when radicalized" is used as an indicator of the degree of reactivity in the polymerization reaction of polyfunctional compounds. Here, "resonance stabilization when a radical is formed" refers to the degree to which a conjugated π-electron system is stabilized at a lower energy level compared to an isolated π-electron system due to the contribution of resonance structures. This can be determined through various analytical experiments, such as measurements of radical lifetime and generation rate using electron spin resonance (ESR) devices, measurements of bond dissociation energy during radical generation, and theoretical calculations.

[0053] In this invention, the degree of resonance stabilization can be quantified as the Alfrey-Price Q value (hereinafter also simply referred to as "Q value"), and the Q value of polyfunctional compound A is 1 or less. In this invention, the Q value of polyfunctional compound A is preferably in the range of 0.70 to 1.00, and more preferably in the range of 0.70 to 0.80. Details of the Q value will be described later.

[0054] The polyfunctional compound A according to the present invention is a monomer and has a weight-average molecular weight of less than 1000. In this invention, when two or more polyfunctional compounds with different Q values ​​are used in combination, the polyfunctional compound with the highest Q value among those with a Q value of 1 or less will be designated as "Polyfunctional Compound A," and other polyfunctional compounds with a Q value lower than that of Polyfunctional Compound A will be designated as "Polyfunctional Compound B." A detailed explanation of Polyfunctional Compound B will be given later.

[0055] Since curing is thought to occur by radical polymerization, it is preferable that the above functional groups have ethylenically unsaturated bonds. Examples of functional groups include acryloyl groups, methacryloyl groups, and maleimide groups. It is preferable that at least one of the functional groups of polyfunctional compound A according to the present invention is a methacryloyl group or a maleimide group, with a methacryloyl group being the most preferred.

[0056] In the ink of the present invention, the content of polyfunctional compound A is preferably in the range of 1 to 15% by mass, and more preferably in the range of 2 to 10% by mass, relative to the total mass of the ink. Within this range, the flexibility of the recorded material and its durability during long-term storage can be improved.

[0057] [1.1 Alfrey-Price Q-value] The Q value according to the present invention is an empirical parameter in Alfrey-Price's Q,e theory, with styrene (Q value: 1.0, e value: -0.8) as the reference. The Q,e theory is described in general textbooks on polymer chemistry, for example, "Chemistry of Polymer Synthesis" by Takayuki Otsu (Kagaku Dojin, 1979), pp. 116-120; "Polymer Synthesis Chemistry" by Shohei Inoue (Shokabo, 2011), pp. 89-91; "Polymer Synthesis (Vol. 1)" by Tsuyoshi Endo (Kodansha, 2010), pp. 69-71; "Basic Master Polymer Chemistry" edited by Tadaomi Nishikubo (Ohmsha, 2011), p. 182; and "Free Radical Copolymerization Reactivity Ratios" in Polymer Handbook 4th Edition, edited by J. Brandrup, E. H. Mimmergut, and E. A. Grulke, etc., where the Q and e values ​​of various monomers are determined based on styrene. Therefore, "equivalent to or less than styrene" means that the Q-factor is 1 or less.

[0058] The Q value is an indicator of how well a radical can stabilize a monomer when it is added; a higher value indicates a greater resonance stabilization effect. The e value, which indicates the polarity effect, is used as a measure of the electron density of the ethylenically unsaturated bond; if the substituent is electron-withdrawing, it will show a negative value, and the larger the absolute value of the negative value, the lower the electron density of the ethylenically unsaturated bond that can be radically polymerized.

[0059] Therefore, the Q value can be adjusted by appropriately selecting the type of functional group and the molecular structure of the compound. In inks, from the viewpoint of achieving both sufficient flexibility and practically acceptable robustness in the recorded material through appropriate polymerization and crosslinking, the Q value of polyfunctional compound A is preferably in the range of 0.70 to 1.00, and more preferably in the range of 0.70 to 0.80.

[0060] If the Q value of polyfunctional compound A is 0.70 or higher, the radical reactivity of polyfunctional compound A is relatively lower than that of compounds with a Q value of less than 0.70. Therefore, during the polymerization of oligomers, polyfunctional compound A is less likely to be incorporated into the polymerization chain, and unreacted functional groups tend to remain after film formation. On the other hand, if the Q value is 1.00 or lower, the reactivity of polyfunctional compound A is relatively higher than that of polyfunctional compounds with a Q value greater than 1.00. Although unreacted functional groups remain, their high reactivity allows them to form new bonds during long-term storage, thus maintaining a three-dimensional structure in the cured product and improving the robustness of the recorded material.

[0061] The Q value according to the present invention can be determined by theoretical calculation. When theoretically calculating the Q and e values, it is necessary to calculate computational parameters obtained by optimizing the molecular structure of each monomer. The calculation parameters were determined based on Xinliang Yu, Xueye Wang & Bo Li. Prediction of the Qe parameters from radical structures. Colloid and Polymer Science. 2010 vol. 288, p. 951-958.

[0062] Table 1 of the above-mentioned document contains the calculation results of the quantum chemical descriptors for each compound (monomer) when calculating the Q value. Using the same method as in the above-mentioned document, the quantum chemical descriptors for each compound were calculated using DFT (Density Functional Theory), and the descriptors (q) for each compound listed in Table 1 are shown below. MC2 Q AC2 ΔE βg The corresponding values ​​were determined and substituted into Equation 4 in the literature to calculate the Q value, which was found to be consistent with the calculation results in Table 1. Then, this calculation method was applied to each compound in this study to calculate the Q value. Note that if a molecule had two or more functional groups, only one of them was considered a radical for the calculation.

[0063] Introduction to the Q-flow and e-processing of the Gaussian distribution of Gaussian16 (Revision B.01, MJ Frisch, GW Trucks, HB Schlegel, GE Scuseria, MA Robb, JR Cheeseman, G. Scalmani, 1999). [ PubMed ] Barone V, Petersson GA, Nakatsuji H, Li, M Caricato, AV Marenich, J Bloino, Janesko BG, Gomperts R, Mennucci, Hratchian HP, Ortiz JV, Izmaylov AF, Sonnenberg JL, Williams-Young D, Ding F, Lipparini F, Egidi F, Goings J, B Peng, A. Petrone, T. Henderson, D. Ranasinghe, VG Zakrzewski, J. Gao, N. Rega, G. Zheng, W. Liang, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, K.S. Throssell, JA Montgomery, Jr, Peralta JE, Ogliaro F, Bearpark MJ, Heyd, EN Brothers, Kudin KN, Staroverov VN, Keith TA, Kobayashi R, Normand J, Raghavachari K, Rendell AP, Burant JC, Iyengar SS, Tomasi JC, Cossi M, Millam JM. Klene , C Adamo , R Cammi , JW Ochterski , RL Martin , K Morokuma , O Farkas , J .(B. Foresman, and DJ Fox, Gaussian, Inc., Wallingford CT, 2016.) Software can be used. In this invention, the calculation method is DFT calculation (density functional theory), using UB3LYP as the functional and 6-31G(d) as the basis function.

[0064] The polyfunctional compound A according to the present invention is not particularly limited as long as its Q value is 1 or less, but it is preferably a methacrylate or maleimide. Furthermore, in the relationship of the Q values ​​of "polyfunctional compound A" and "polyfunctional compound B" described above, if it corresponds to "polyfunctional compound A", it may be an acrylate as described later as a specific example of "polyfunctional compound B". The following describes methacrylates and maleimides that are preferably used in the present invention.

[0065] [1.2 Methacrylate] The polyfunctional compound A according to the present invention is preferably a methacrylate having a methacryloyl group. Being a methacrylate allows the ink of the present invention to polymerize and crosslink appropriately, achieving both sufficient flexibility and practically acceptable durability for the recorded material. Furthermore, during long-term storage, unreacted functional groups form new bonds, maintaining the three-dimensional structure and suppressing a decrease in the durability of the recorded material.

[0066] Examples of polyfunctional methacrylates are given below. Of these, those with a Q value of 1 or less correspond to polyfunctional compound A in the present invention, and those with a Q value in the range of 0.70 to 1.00 are more preferred. Furthermore, in the present invention, when two or more polyfunctional compounds with different Q values ​​are used in combination, the polyfunctional compound with the highest Q value among those with a Q value of 1 or less corresponds to polyfunctional compound A, and the other polyfunctional compounds correspond to polyfunctional compound B described later.

[0067] The polyfunctional methacrylate is not particularly limited as long as its Q value is within the above range. Examples of polyfunctional methacrylates include triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, tripropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, neopentyl glycol dimethacrylate, tricyclodecanedimethanol dimethacrylate, bisphenol A PO adduct dimethacrylate, hydroxypivalate neopentyl glycol dimethacrylate, polytetramethylene glycol dimethacrylate, and tricyclodecanedimethanol dimethacrylate, among other bifunctional methacrylates.

[0068] Furthermore, examples include polyfunctional methacrylates containing three or more functional methacrylates such as trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol hexamethacrylate, ditrimethylolpropane tetramethacrylate, glycerin propoxytrimethacrylate, and pentaerythritol ethoxytetramethacrylate.

[0069] The methacrylate may be a modified form. Examples of modified methacrylates include ethylene oxide-modified trimethylolpropane trimethacrylate, ethylene oxide-modified pentaerythritol tetramethacrylate, caprolactone-modified methacrylate, caprolactone-modified trimethylolpropane trimethacrylate, and caprolactam-modified methacrylate, including caprolactam-modified dipentaerythritol hexamethacrylate.

[0070] Examples of commercially available methacrylates with a Q value in the range of 0.70 to 1.00 include DCP, HD-N, 4G, M-40G, and 3PG from Shin Nakamura Chemical Industry Co., Ltd., and M301 from Miwon Corporation.

[0071] [1.3 Maleimide] The polyfunctional compound A according to the present invention is preferably maleimide. Being maleimide allows the ink of the present invention to polymerize and crosslink appropriately, achieving both sufficient flexibility and practically acceptable fastness for the recorded material.

[0072] Examples of polyfunctional maleimides are given below. Of these, those with a Q value of 1 or less correspond to polyfunctional compound A in the present invention, and those with a Q value in the range of 0.70 to 1.00 are more preferred. Furthermore, in the present invention, when two or more polyfunctional compounds with different Q values ​​are used in combination, the polyfunctional compound with the highest Q value among those with a Q value of 1 or less corresponds to polyfunctional compound A, and the other polyfunctional compounds correspond to polyfunctional compound B described later.

[0073] Examples of polyfunctional maleimides include 4,4'-diphenylmethanebismaleimide, phenylmethanemaleimide, bisphenol A bisphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethanebismaleimide, and 1,6-bismaleimide-(2,2,4-trimethyl)hexane.

[0074] Examples of commercially available products include BMI-1000, BMI-2300, BMI-4000, BMI-5100, and BMI-YMH manufactured by Yamato Kasei Kogyo Co., Ltd., and BMI-70 and BMI-80 manufactured by K.I. Kasei Co., Ltd.

[0075] [2 Acrylate oligomers] The acrylate oligomer according to the present invention has three or more functional groups, which facilitates polymerization and improves the robustness of the recorded material. The acryloyl groups contained in the acrylate oligomer have ethylenically unsaturated bonds and harden by radical polymerization.

[0076] The acrylate oligomer according to the present invention has three or more functional groups, and one of these functional groups is an acryloyl group. All of the functional groups may be acryloyl groups, or some may be different functional groups. The different functional groups are not particularly limited, but from the viewpoint of facilitating polymerization and improving the robustness of the recorded material, methacryloyl groups are preferred.

[0077] The number of functional groups in a single molecule is not particularly limited as long as it is three or more, but it is preferably in the range of 4 to 30. Being within this range facilitates polymerization and improves the robustness of the recorded material.

[0078] In this invention, "oligomer" refers to a compound in which the number of monomer bonds (degree of polymerization) is in the range of 2 to 10, and the weight-average molecular weight is in the range of 1000 to 15000. The acrylate oligomer may contain only one type, or two or more types.

[0079] In the ink of the present invention, the acrylate oligomer content is preferably in the range of 10 to 40% by mass, and more preferably in the range of 10 to 30% by mass, relative to the total mass of the ink. Within this range, flexibility and durability are further improved.

[0080] The acrylate oligomer is not particularly limited as long as it has three or more functional groups. Examples of acrylate oligomers include urethane acrylate oligomers, polyester acrylate oligomers, and epoxy acrylate oligomers. Additionally, hyperbranched acrylate oligomers with distinctive structures are also mentioned.

[0081] [2.1 Urethane acrylate oligomer] The acrylate oligomer according to the present invention is preferably a urethane acrylate oligomer. Because urethane acrylate oligomers have a relatively high viscosity, polymerization proceeds easily, and a cross-linked structure is readily formed by hydrogen bonding between urethane bonds. In addition, depending on the type of urethane acrylate oligomer, the robustness of the recorded material may be improved.

[0082] The urethane acrylate oligomer according to the present invention has a urethane bond formed by an addition reaction between an isocyanate group and a hydroxyl group, and an acryloyl group. The urethane acrylate may contain only one type, or two or more types.

[0083] Urethane acrylate oligomers can be obtained, for example, by reacting an isocyanate with an acrylic acid derivative having a hydroxyl group.

[0084] Examples of isocyanates used as raw materials for urethane acrylate oligomers include isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), hydrogenated MDI, polymeric MDI, 1,5-naphthalene diisocyanate, norbornane diisocyanate, tolidine diisocyanate, xylylene diisocyanate (XDI), hydrogenated XDI, lysine diisocyanate, triphenylmethane triisocyanate, tris(isocyanatephenyl)thiophosphate, tetramethylxylene diisocyanate, and 1,6,10-undecane triisocyanate.

[0085] As the isocyanate used as a raw material for urethane acrylate oligomers, chain-extended isocyanate compounds obtained by reacting polyols such as ethylene glycol, glycerin, sorbitol, trimethylolpropane, propylene glycol, carbonate diol, polyether diol, polyester diol, and polycaprolactone diol with an excess of isocyanate may be used.

[0086] Examples of acrylic acid derivatives having a hydroxyl group that can be used as raw materials for urethane acrylate oligomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, and 2-hydroxybutyl acrylate; monoacrylates of dihydric alcohols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and polyethylene glycol; monoacrylates or diacrylates of trihydric alcohols such as trimethylolethane, trimethylolpropane, and glycerin; and epoxy acrylates such as bisphenol A type epoxy acrylate.

[0087] It is preferable that the urethane acrylate oligomer does not have a carboxyl group. By using a urethane acrylate oligomer that does not have a carboxyl group, the insulating properties of the recorded material are improved.

[0088] The number of acryloyl functional groups contained in one molecule of a urethane acrylate oligomer is not particularly limited as long as it is three or more, but is preferably in the range of 3 to 20, more preferably in the range of 3 to 15, and even more preferably in the range of 3 to 10.

[0089] The weight-average molecular weight of the urethane acrylate oligomer is preferably in the range of 1,000 to 15,000. Being within this range ensures sufficient discharge stability in the ink of the present invention.

[0090] Furthermore, in the production of the ink of the present invention, the urethane acrylate oligomer may contain a diluent. The type of diluent is not particularly limited and examples include acrylate monomers and solvents, but acrylate monomers are preferred from the viewpoint of reducing volatile organic compounds (VOCs).

[0091] Examples of commercially available urethane acrylate oligomers include M-1100, M-1200, M-1210, M-1600 (all manufactured by Toagosei Co., Ltd.), EBECRYL 230, EBECRYL 270, EBECRYL 4858, EBECRYL 8402, EBECRYL 8804, EBECRYL 8803, EBECRYL 8807, EBECRYL 9260, EBECRYL 1290, EBECRYL 5129, EBECRYL 4842, EBECRYL 210, EBECRYL 4827, EBECRYL 6700, EBECRYL 220, and EBECRYL 2220 (all manufactured by Daicel Ornex Co., Ltd., "EBECRYL" is a registered trademark of the company), Art Resin UN-9000H, Art Resin UN-9000A, Art Resin UN-7100, Art Resin UN-1255, Art Resin UN-330, Art Resin UN-3320HB, Art Resin UN-1200TPK, Art Resin SH-500B (and others) (Manufactured by Negami Kogyo Co., Ltd., "Art Resin" is a registered trademark of the company), U-122P, U-108A, U-340P, U-4HA, U-6HA, U-324A, U-15HA, UA-5201P, UA-W2A, U-1084A, U-6LPA, U-2HA, U-2PHA, UA-4100, UA-7100, UA-4200, UA-4400, UA-340P, U -3HA, UA-7200, U-2061BA, U-10H, U-122A, U-340A, U-108, U-6H, UA-4000 (all manufactured by Shin Nakamura Chemical Industry Co., Ltd.), and AH-600, AT-600, UA-306H, AI-600, UA-101T, UA-101I, UA-306T, UA-306I (all manufactured by Kyoeisha Chemical Co., Ltd.), CN959, CN96 Examples include 9NS, CN996NS, CN2920, CN9009, CN9011, CN8885, CN8885NS, CN989, CN989NS, CN9023, CN9290, CN968NS, CN972, CN975NS, CN992 (all manufactured by Sartomer), BR-144B, BR-771F, BRC-843 (all manufactured by DYMAX), etc.

[0092] In the present invention, the content of urethane acrylate oligomer is not particularly limited, but is preferably in the range of 1 to 40% by mass, more preferably in the range of 5 to 30% by mass, and even more preferably in the range of 10 to 20% by mass, relative to the total mass of the ink.

[0093] [2.2 Hyperbranched acrylate oligomers] The acrylic oligomer according to the present invention is preferably a hyperbranched acrylate oligomer. Having a hyperbranched structure facilitates polymerization and the formation of crosslinked structures, thereby improving the robustness of the recorded material.

[0094] In the present invention, "hyperbranch structure" refers to a dendritic compound having a large number of branching points within a single molecule. For example, it can be synthesized by the self-condensation of AB2 type molecules having a total of three or more substituents of two types within a single molecule, or by the A2+B3 method, which is a condensation reaction between two molecules (A2 type and B3 type).

[0095] Therefore, the hyperbranch structure in the present invention includes dendrimer structures (tree-like structures), star structures, and graft structures.

[0096] Examples of commercially available hyperbranched acrylate oligomers include V#1000 (manufactured by Osaka Organic Chemical Industry Co., Ltd.), CN2302, CN2303, CN2304 (all manufactured by Sartomer), SP1106 (all manufactured by Miwon), 6361-100, 6363 (manufactured by Choko Kagaku Kogyo Co., Ltd.), etc. These may be used individually or in combination of two or more types.

[0097] [3 monomers] The ink of the present invention preferably further contains a monomer. The monomer according to the present invention may be any monomer that undergoes polymerization or crosslinking reactions upon irradiation with active energy rays. It may also be a compound that exhibits polymerization reactions upon heating, but it is preferable to include it in an amount sufficient to obtain adequate ink discharge stability. The monomer preferably contains both monofunctional and polyfunctional compounds. The content of polyfunctional compound B relative to the total mass of the monomer is preferably in the range of 90 to 100% by mass, and more preferably 100% by mass. Increasing the content of polyfunctional compound B further improves the robustness of the recorded material.

[0098] In the present invention, "monomer" refers to a monomer, that is, a compound that serves as a starting material when forming a polymer in a polymerization reaction, and has a weight-average molecular weight of less than 1000, and includes "monofunctional compounds" and "polyfunctional compound B". Therefore, the monomer according to the present invention does not include polyfunctional compound A. Note that monofunctional compounds and polyfunctional compound B may each be contained as one type or as two or more types.

[0099] In the present invention, "monofuncular compound" refers to a compound having one functional group among the above monomers. Since monofunctional compounds can be used as reactive diluents, the viscosity of the ink of the present invention can be adjusted by including a relatively low-viscosity monofunctional compound.

[0100] Furthermore, in the present invention, "polyfunctional compound B" refers to a compound having two or more functional groups among the above monomers. Also, in cases where the ink of the present invention uses two or more polyfunctional compounds with different Q values, it refers to the other polyfunctional compounds excluding the polyfunctional compound with the highest Q value (polyfunctional compound A) that has a Q value of 1 or less.

[0101] In particular, the ink of the present invention further contains a polyfunctional compound B that has a lower Q value compared to the aforementioned polyfunctional compound A, i.e., a higher reactivity compound, which allows polymerization and crosslinking to proceed appropriately, thereby improving the rapid curing properties of the ink and the robustness of the recorded material.

[0102] The functional groups are not particularly limited, but from the viewpoint of curing by radical polymerization, examples include acryloyl groups, methacryloyl groups, allyl groups, vinyl groups, vinyl ester groups, etc., that have ethylenically unsaturated bonds.

[0103] The monofunctional and polyfunctional compounds B having the above-mentioned functional groups are preferably unsaturated carboxylic acid ester compounds, and more preferably acrylates.

[0104] Examples of monofunctional acrylates include isoamyl acrylate, stearyl acrylate, lauryl acrylate, octyl acrylate, decyl acrylate, isomirsutyl acrylate, isostearyl acrylate, 2-ethylhexyl diglycol acrylate, 2-hydroxybutyl acrylate, 2-acryloyloxyethylhexahydrophthalic acid, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, methoxydiethylene glycol acrylate, methoxypolyethylene glycol acrylate, methoxypropylene glycol acrylate, Examples include phenoxyethyl acrylate, o-phenylphenol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, cumylphenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl-2-hydroxyethyl phthalic acid, and t-butylcyclohexyl acrylate.

[0105] Examples of polyfunctional acrylates are given below. In the ink of the present invention, the polyfunctional compound with a Q value of 1 or less and the highest Q value compared to other polyfunctional compounds used in combination corresponds to polyfunctional compound A, while the other polyfunctional compounds correspond to polyfunctional compound B. Examples of bifunctional acrylates include triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, neopentyl glycol diacrylate, bisphenol A PO adduct diacrylate, hydroxypivalate neopentyl glycol diacrylate, polytetramethylene glycol diacrylate, and tricyclodecanedimethanol diacrylate.

[0106] Examples of acrylates with three or more functionalities include trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate, glycerin propoxytriacrylate, and pentaerythritol ethoxytetraacrylate.

[0107] Of the above acrylates, phenoxyethyl acrylate, o-phenylphenol acrylate, and 2-hydroxy-3-phenoxypropyl acrylate are preferred from the viewpoint of suppressing curing shrinkage.

[0108] From the viewpoint of rapid curing, neopentyl glycol diacrylate, tricyclodecanedimethanol diacrylate, bisphenol A PO adduct diacrylate, and hydroxypivalic acid neopentyl glycol diacrylate are preferred.

[0109] Furthermore, the acrylate may be a modified form. Examples of modified acrylates include ethylene oxide-modified acrylates such as ethylene oxide-modified trimethylolpropane triacrylate and ethylene oxide-modified pentaerythritol tetraacrylate; propylene oxide-modified acrylates such as propylene oxide-modified trimethylolpropane triacrylate and propylene oxide-modified pentaerythritol tetraacrylate; caprolactone-modified acrylates such as caprolactone-modified trimethylolpropane triacrylate; and caprolactam-modified acrylates such as caprolactam-modified dipentaerythritol hexaacrylate.

[0110] In the ink of the present invention, the monomer content is preferably in the range of 40 to 90% by mass, and more preferably in the range of 60 to 85% by mass, relative to the total mass of the ink. Discharge stability can be obtained by being within the above range.

[0111] Of these, the content of polyfunctional compound B is preferably in the range of 90 to 100% by mass, and more preferably 100% by mass, relative to the total mass of the monomer (i.e., the total mass of the monofunctional compound and polyfunctional compound B). By having a content of polyfunctional compound B, which has a lower Q value compared to the aforementioned polyfunctional compound A, i.e., is highly reactive, within the above range, the robustness of the recorded material is further improved.

[0112] [4 Polymerization initiators] The ink of the present invention can be cured by radical polymerization or ionic polymerization, but in the present invention, it is preferable to use a radical polymerization initiator as the polymerization initiator. The polymerization initiator may be contained in the ink of the present invention by one type only, or by two or more types.

[0113] Examples of radical polymerization initiators include α-cleavage type radical polymerization initiators (also known as "Norish type I polymerization initiators") and hydrogen abstraction type radical polymerization initiators (also known as "Norish type II polymerization initiators").

[0114] The content of the α-cleavage type radical polymerization initiator is preferably in the range of 0.3 to 6% by mass relative to the total mass of the ink of the present invention. Furthermore, the content of the hydrogen abstraction type radical polymerization initiator is preferably in the range of 0.5 to 10% by mass relative to the total mass of the ink of the present invention.

[0115] α-cleavage type radical polymerization initiators are initiators that cleave after photoexcitation and directly provide an initiation radical. Furthermore, hydrogen abstraction-type radical polymerization initiators are photopolymerization initiators that are activated by active energy rays (e.g., ultraviolet light) and generate free radicals by abstracting hydrogen from a second compound, with the second compound becoming the actual initiating free radical. This second compound is called a polymerization synergist or co-initiator. Both α-cleavage type radical polymerization initiators and hydrogen abstraction type radical polymerization initiators can be used individually or in combination in the present invention.

[0116] Examples of α-cleavage type radical polymerization initiators include acetophenone-based initiators, benzoin-based initiators, acylphosphine oxide-based initiators, benzyl, and methylphenylglyoxyesters.

[0117] Examples of acetophenone-based initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethylketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone.

[0118] Examples of benzoin-based initiators include benzoin, benzoin methyl ether, and benzoin isopropyl ether. Examples of acylphosphine oxide initiators include 2,4,6-trimethylbenzoindiphenylphosphine oxide and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0119] Examples of hydrogen abstraction radical initiators include benzophenone-based initiators, thioxanthone-based initiators, aminobenzophenone-based initiators, 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-phenanthrenequinone, and camphorquinone.

[0120] Examples of benzophenone-based initiators include benzophenone, o-benzoylmethyl-4-phenylbenzophenone, 4,4′-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4′-methyl-diphenyl sulfide, acrylic benzophenone, 3,3′,4,4′-tetra(t-butylperoxycarbonyl)benzophenone, and 3,3′-dimethyl-4-methoxybenzophenone. Examples of thioxanthone initiators include 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone.

[0121] Examples of aminobenzophenone initiators include Michler's ketone and 4,4′-diethylaminobenzophenone.

[0122] [5 Polymerization inhibitors] The ink of the present invention preferably further contains a polymerization inhibitor. By including a polymerization inhibitor, the adhesion between multiple curable compounds can be reduced. In the present invention, "polymerization inhibitor" includes all compounds added to suppress polymerization reactions during the preparation or storage of an ink containing a polymerizable compound.

[0123] In the present invention, various conventionally known polymerization inhibitors can be used, but from the viewpoint of achieving the desired effect, it is more preferable to include a polymerization inhibitor that is one of the following: an N-oxyl polymerization inhibitor, a phenol polymerization inhibitor containing an ot-butyl group, or a polymerization inhibitor having two or more aromatic rings.

[0124] Furthermore, among these, the inclusion of an N-oxyl polymerization inhibitor is even more preferable from the viewpoint of adhesion to printed circuit boards. In the ink of the present invention, the content of the polymerization inhibitor is preferably in the range of 0.05 to 0.5% by mass relative to the total mass of the ink.

[0125] [5.1 N-oxyl polymerization inhibitors] Examples of N-oxyl polymerization inhibitors include 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-methoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, and Irgastab® UV10 (manufactured by BASF).

[0126] [5.2 Phenolic polymerization inhibitors] Examples of phenolic polymerization inhibitors 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-t-butyl-p-cresol (butylated hydroxytoluene: BHT), 4-methoxyphenol, and 2-methoxy-4-methylphenol.

[0127] [5.3 Quinone-based polymerization inhibitors] Examples of quinone polymerization inhibitors include hydroquinone, methoxyhydroquinone, benzoquinone, 1,4-naphthoquinone, and p-tert-butylcatechol.

[0128] [5.4 Amine-based polymerization inhibitors] Examples of amine polymerization inhibitors include alkylated diphenylamine, N,N′-diphenyl-p-phenylenediamine, and phenothiazine.

[0129] [5.5 Other polymerization inhibitors] Other examples include copper dithiocarbamate-based polymerization inhibitors such as copper dimethyldithiocarbamate, copper diethyldithiocarbamate, and copper dibutyldithiocarbamate.

[0130] These may contain only one type, or two or more types. Among these, N-oxyl and quinone-based polymerization inhibitors are preferred, with 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), 2,6-di-t-butyl-p-cresol (butylated hydroxytoluene: BHT), 2,4-di-tert-butylphenol, and, as polymerization inhibitors having two or more aromatic rings, naphthoquinone being preferred.

[0131] [6 Gelling agent] The ink of the present invention preferably further contains a gelling agent. By including a gelling agent, the ink on the recording medium can be temporarily fixed (pinned) in a gel state, suppressing the spreading of the ink. This also improves the robustness of the recorded material.

[0132] It is preferable that the gelling agent crystallizes at a temperature below the gelling temperature of the ink. "Gellation temperature" refers to the temperature at which, when a composition that has been solified or liquefied by heating is cooled, the gelling agent undergoes a phase transition from sol to gel, causing a rapid change in the viscosity of the composition. Specifically, a sol- or liquefied composition can be cooled while measuring its viscosity using a viscoelasticity measuring device (e.g., MCR300, manufactured by Anton Paar), and the temperature at which the viscosity rapidly increases can be defined as the gelation temperature of the composition.

[0133] In the present invention, when the gelling agent crystallizes in the ink, a structure is formed in which polymerizable compounds (polymerizing compounds such as polyfunctional compound A, acrylate oligomers, and monomers) are encapsulated in the three-dimensional space formed by the plate-like crystallized gelling agent, a structure known as a cardhouse structure. To form this cardhouse structure, it is preferable that the polymerizable compounds dissolved in the ink and the gelling agent are compatible.

[0134] Examples of gelling agents suitable for forming cardhouse structures 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, fatty acid amides including N-substituted fatty acid amides and special fatty acid amides, higher amines, esters of sucrose fatty acids, synthetic waxes, dibenzylidene sorbitol, dimer acids, and dimer ols.

[0135] In particular, from the viewpoint of improving pinning properties, it is preferable that the hydrocarbon group has a number of carbon atoms in the range of 9 to 25, and is an aliphatic ketone, aliphatic ester, higher fatty acid, or higher alcohol. The gelling agent may contain only one type, or it may contain two or more types.

[0136] [6.1 Faliphatic Ketones] Examples of aliphatic ketones include dilignoseryl ketone, dibehenyl ketone, distearyl ketone, dieicosyl ketone, dipalmityl ketone, dilauryl ketone, dimyristyl ketone, myristylpalmityl ketone, and palmitylstearyl ketone.

[0137] [6.2 Aliphatic esters] Examples of aliphatic esters include fatty acid esters of monoalcohols such as behenyl behenate, eicosyl eicosanoate, 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.

[0138] Examples of commercially available aliphatic esters include the EMALEX® series from Nippon Emulsion Co., Ltd., and the Rikemar® series and Poem® series from Riken Vitamin Co., Ltd.

[0139] [6.3 Higher fatty acids] Examples of higher fatty acids include behenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, and erucic acid.

[0140] [6.4 Higher Alcohols] Examples of higher alcohols include stearyl alcohol and behenyl alcohol.

[0141] [6.5 Suitable gelling agents] In the present invention, the gelling agent is particularly preferably an aliphatic ketone represented by the following general formula (G1) or an aliphatic ester represented by the following general formula (G2).

[0142] General formula (G1): R1-CO-R2

[0143] (In general formula (G1), R1 and R2 each independently represent an alkyl group containing a straight chain portion with 12 to 26 carbon atoms, and which may also contain branching. R1 and R2 may be the same or different.)

[0144] General formula (G2): R3-COO-R4

[0145] (In general formula (G2), R3 and R4 each independently represent an alkyl group containing a linear portion with 12 to 26 carbon atoms, and which may also contain branching. R3 and R4 may be the same or different.)

[0146] In general formulas (G1) and (G2), having 12 or more carbon atoms in the linear or branched hydrocarbon group increases the crystallinity of the aliphatic ketone represented by general formula (G1) and the aliphatic ester represented by general formula (G2), and also creates more space in the cardhouse structure. As a result, polymerizable compounds are more easily encapsulated within this space, improving the pinning properties of the ink.

[0147] Furthermore, because the number of carbon atoms in the linear or branched hydrocarbon group is 26 or less, the melting point of the aliphatic ketone represented by general formula (G1) and the aliphatic ester represented by general formula (G2) does not rise excessively, meaning that the melting point can be set to a temperature that is easy to handle, and there is no need to excessively heat the ink when ejecting it.

[0148] Examples of aliphatic ketones represented by general formula (G1) include dilignoseryl ketone (23,24 carbon atoms), dibehenyl ketone (21,22 carbon atoms), distearyl ketone (17,18 carbon atoms), dieicosyl ketone (19,20 carbon atoms), dipalmityl ketone (15,16 carbon atoms), dimyristyl ketone (13,14 carbon atoms), dilauryl ketone (11,12 carbon atoms), and lauryl myristyl ketone (carbon atoms). Examples include carbon 11, 14), lauryl palmityl ketone (carbon count: 11, 16), myristyl palmityl ketone (carbon count: 13, 16), myristyl stearyl ketone (carbon count: 13, 18), myristyl behenyl ketone (carbon count: 13, 22), palmityl stearyl ketone (carbon count: 15, 18), palmityl behenyl ketone (carbon count: 15, 22), and stearyl behenyl ketone (carbon count: 17, 22). The carbon counts in parentheses represent the carbon counts of the two hydrocarbon groups separated by the carbonyl group.

[0149] Examples of commercially available aliphatic ketones represented by general formula (G1) include 18-Pentatriacontanon and Hentriacontan-16-one from Alfa Aeser, and Kao Wax T-1 from Kao Corporation.

[0150] Examples of aliphatic esters represented by general formula (G2) include behenyl behenate (21,22 carbon atoms), eicosyl eicosanoate (19,20 carbon atoms), stearyl stearate (17,18 carbon atoms), palmityl stearate (16,17 carbon atoms), lauryl stearate (12,17 carbon atoms), cetyl palmitate (6,15 carbon atoms), stearyl palmitate (15,18 carbon atoms), and myris. Examples include myristyl tinate (13,14 carbon atoms), cetyl myristate (13,16 carbon atoms), octyldodecyl myristate (13,20 carbon atoms), stearyl oleate (17,18 carbon atoms), stearyl erucate (18,21 carbon atoms), stearyl linoleate (17,18 carbon atoms), behenyl oleate (18,22 carbon atoms), and arachidyl linoleate (17,20 carbon atoms). The carbon numbers in parentheses represent the carbon atoms of the two hydrocarbon groups separated by the ester group.

[0151] Examples of commercially available aliphatic esters represented by general formula (G2) include Unistar® M-2222SL and Sperm Acetate from NOF Corporation, Exepearl® SS and Exepearl® MY-M from Kao Corporation, EMALEX® CC-18 and EMALEX® CC-10 from Nippon Emulsion Co., Ltd., and Amlepus® PC from Higher Alcohol Industry Co., Ltd.

[0152] [6.6 Gelling agent content] In the present invention, the gelling agent content is preferably in the range of 1 to 10% by mass relative to the total mass of the ink.

[0153] [7 Other ingredients] [7.1 Surfactants] The ink of the present invention may further contain a surfactant as needed. 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.

[0154] [7.2 Colorants] The ink of the present invention may further contain a colorant as needed. The coloring agent may be a pigment or a dye, but it is preferable to use a pigment because it has good dispersibility with the components of the ink and excellent weather resistance. The pigments are not particularly limited, and examples include organic or inorganic pigments with the following numbers listed in the color index.

[0155] In the ink of the present invention, only one coloring agent may be contained, or two or more coloring agents may be contained, and the desired color may be achieved. The colorant content is preferably in the range of 0.1 to 20% by mass, and more preferably in the range of 0.2 to 10% by mass, relative to the total mass of the ink.

[0156] (Pigment) Red or magenta pigment Examples of red or magenta pigments include: Pigment Red 3, 5, 19, 22, 31, 38, 43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 53:1, 57:1, 57:2, 58:4, 63:1, 81, 81:1, 81:2, 81:3, 81:4, 88, 104, 108, 112, 122, 123, 144, 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257; Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88; Pigment Orange Examples include pigments or mixtures thereof selected from 13, 16, 20, and 36.

[0157] Blue or cyan pigment Examples of blue or cyan pigments include pigments selected from Pigment Blue 1, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17:1, 22, 27, 28, 29, 36, and 60, or mixtures thereof.

[0158] Green pigment Examples of green pigments include pigments selected from Pigment Green 7, 26, 36, and 50, or mixtures thereof.

[0159] Yellow pigment Examples of yellow pigments include pigments selected from Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, and 193, or mixtures thereof.

[0160] Black pigment Examples of black pigments include pigments selected from Pigment Black 7, 28, and 26, or mixtures thereof.

[0161] Examples of commercially available pigments Examples of commercially available pigments include Black Pigment (Mikuni), Chromofine Yellow 2080, 5900, 5930, AF-1300, 2700L, Chromofine Orange 3700L, 6730, Chromofine Scarlet 6750, Chromofine Magenta 6880, 6886, 6891N, 6790, 6887, Chromofine Violet RE, Chromofine Red 6820, 6830, Chromofine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5000P, and Chromofine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Chromofine Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400(B), 2500, 2600, ZAY-260, 2700(B), 2770, Seika Fast Red 8 040, C405(F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seika Fast Carmine 6B1476T-7, 1483LT, 3840, 3870, Seika Fast Bordeaux 10B-430, Seika Light Rose R40, Seika Light Violet B800, 7805, Seika Fast Maroon 460N, Seika Fast Orange 900, 2900, Seika Light Blue C718, A612, Cyanine Blue 4933M, 4933GN-EP, 4940, 4973 (all manufactured by Dainichi Seika Kogyo Co., Ltd.; "Chromofine" is a registered trademark of the company); KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118, 124, KET Green 201 (manufactured by DIC);Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T-13, T-05, Pigment Yellow1705, Colortex Orange 202, Colortex Red101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, 105C, USN, Colortex Maroon601, Colortex BrownB610N, Colortex Violet600, Pigment Red 122, Colortex Blue516, 517, 518, 519, A818, P-908, 510, Colortex Green 402, 403, Colortex Black 702, U905 (all manufactured by Sanyo Pigment Co., Ltd., "Colortex" and "Finecol" are registered trademarks of the company); Lionol Yellow 1405G, Lionol Blue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (all manufactured by Toyo Ink Co., Ltd., "Lionol" is a registered trademark of the company), Toner Magenta E02, Permanent Rubin F6B, Toner Yellow HG, Permanent Yellow GG-02, Hostapean Blue B2G (all manufactured by Hoechst Industries); Novoperm P-HG, Hostapean Pink E, Hostapean Blue Examples include B2G (all manufactured by Clariant; "Novoperm" and "Hostaperm" are registered trademarks of the company); carbon black #2600, #2400, #2350, #2200, #1000, #990, #980, #970, #960, #950, #850, MCF88, #750, #650, MA600, MA7, MA8, MA11, MA100, MA100R, MA77, #52, #50, #47, #45, #45L, #40, #33, #32, #30, #25, #20, #10, #5, #44, CF9 (all manufactured by Mitsubishi Chemical), etc.

[0162] Pigment dispersion Pigment dispersion can be performed using, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, and paint shaker.

[0163] The pigment dispersion is preferably carried out such that the volume-average particle size of the pigment particles is preferably in the range of 0.08 to 0.5 μm, the maximum particle size is preferably in the range of 0.3 to 10 μm, and more preferably in the range of 0.3 to 3 μm. The dispersion of pigments is controlled by selecting the pigment, dispersant, and dispersion medium, as well as by adjusting the dispersion conditions and filtration conditions.

[0164] Dispersant The ink of the present invention may further contain a dispersant to improve the dispersibility of the pigment. Examples of dispersants include hydroxyl group-containing carboxylic acid esters, salts of long-chain polyaminoamides and high molecular weight acid esters, salts of high molecular weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, high molecular weight unsaturated acid esters, polymer copolymers, modified polyurethanes, modified polyacrylates, polyether ester-type anionic surfactants, naphthalene sulfonic acid formalin condensate salts, aromatic sulfonic acid formalin condensate salts, polyoxyethylene alkyl phosphate esters, polyoxyethylene nonylphenyl ether, and stearylamine acetate. Examples of commercially available dispersants include the Solsperse® series from Avecia and the PB series from Ajinomoto Fine Techno.

[0165] Dispersing agent The ink of the present invention may further contain a dispersion aid as needed. The dispersing agent should be selected according to the pigment. The total content of dispersants and dispersing aids is preferably in the range of 1 to 50% by mass relative to the total mass of the pigment.

[0166] 《Dispersion medium》 The ink of the present invention may further contain a dispersion medium for dispersing pigments, if necessary. The ink of the present invention may contain a solvent as a dispersion medium, but in order to suppress the residue of solvent in the formed image, it is preferable to use the aforementioned monomer (particularly a monomer with low viscosity) as the dispersion medium.

[0167] Furthermore, when a solvent is used as a dispersion medium, the solvent tends to evaporate easily when the ink is heated, reducing the dispersibility of the pigment. However, by using the aforementioned polyfunctional compound B, the decrease in pigment dispersibility can be suppressed.

[0168] [7.3 Other Additives] The ink of the present invention may further contain a coupling agent, a solvent, etc., as needed.

[0169] (Coupling agent) The ink of the present invention may further contain various coupling agents as needed. The inclusion of coupling agents can improve adhesion to printed circuit boards. Examples of various coupling agents include silane-based, titanium-based, and aluminum-based coupling agents.

[0170] (solvent) The ink of the present invention is preferably solvent-free from the viewpoint of rapid curing and discharge stability, but solvents may be added to adjust the ink viscosity.

[0171] ≪Physical Properties of the Inkjet Ink Composition of the Present Invention≫

[0172] [1. Viscosity at shear rate] The viscosity of the ink of the present invention at 25°C and a shear rate of 1000 / sec (hereinafter also referred to as "shear rate viscosity (1000 / sec)") is preferably in the range of 40 to 400 mPa·s, and more preferably in the range of 50 to 250 mPa·s. By being within this range, the viscosity at 80°C can be adjusted to the range of 3 to 20 mPa·s, and sufficient discharge stability can be obtained.

[0173] Furthermore, because it falls within the above range, the shear rate viscosity at 25°C (1000 / sec) is higher compared to conventional inkjet ink compositions where the ink ejection temperature is 40-60°C. In other words, because a compound with high viscosity and a large molecular weight is added, the gel effect occurs relatively early, which suppresses polymerization inhibition by oxygen and improves durability.

[0174] In the present invention, the viscosity at a shear rate (1000 / sec) is a value obtained by the following method. The ink of the present invention is heated to 25°C and measured using a stress-controlled rheometer Physica MCR301 (cone plate diameter: 75 mm, cone angle: 1.0°, manufactured by Anton Paar) under conditions of a shear rate of 1000 / sec.

[0175] Furthermore, from the viewpoint of obtaining sufficient ejection stability from the inkjet head, the shear rate viscosity of the ink of the present invention in the range of 70 to 90°C is preferably in the range of 7 to 15 mPa·s, more preferably in the range of 8 to 13 mPa·s, and even more preferably in the range of 9 to 12 mPa·s.

[0176] [2. Viscosity under shear strain] The ink of the present invention preferably has its properties, such as viscosity, optimized or appropriate depending on the intended use and conditions, and the viscosity at 25°C and with a shear strain of 5% and an angular frequency of 10 radians / s (hereinafter also referred to as "shear strain viscosity") is 1 to 1 × 10 4 It is preferable that it be within the range of Pa·s. Also, 1 to 1 × 10 2The Pa·s range is more preferably within the Pa·s range, and even more preferably within the range of 1 to 1 × 10⁻⁶ Pa·s. Being within this range improves the pinning properties when the ink is applied to a recording medium and cooled to room temperature, resulting in sufficient robustness of the recorded material. Furthermore, because sufficient pinning properties are achieved, the ink of the present invention can be cured in a single batch. Single-batch curing will be described later. Furthermore, by incorporating the aforementioned gelling agent into the ink of the present invention, the shear strain viscosity can be adjusted to within the above range.

[0177] [3 Phase transition point] The ink of the present invention preferably has a phase transition point in the range of 40 to 100°C. Because the phase transition temperature is above 40°C, the ink gels rapidly after landing on the recording medium, improving pinning performance. Furthermore, having a phase transition temperature of 100°C or lower allows for both easy handling and stable ink ejection. The phase transition point of the ink of the present invention is more preferably in the range of 40 to 60°C. Being within this range allows the ink to be ejected at a relatively low temperature, thereby reducing the temperature-related load on the recording device.

[0178] [4. Methods for measuring and determining viscosity and phase transition point in shear strain] The ink of the present invention is heated to 100°C, and the ink is cooled to 20°C using a stress-controlled rheometer Physica MCR301 (cone plate diameter: 75 mm, cone angle: 1.0°, manufactured by Anton Paar) under conditions of a cooling rate of 0.1°C / s, strain of 5%, and angular frequency of 10 radians / s to obtain a viscosity temperature dependence curve.

[0179] The viscosity at 80°C and 25°C can be determined by reading the viscosity values ​​at 80°C and 25°C, respectively, from the viscosity temperature dependence curve. The phase transition point can be determined from the viscosity temperature dependence curve as the temperature at which the viscosity becomes 200 mPa·s.

[0180] ≪Method for producing the inkjet ink composition of the present invention≫ The ink of the present invention can be prepared by mixing the aforementioned polymerizable compound with any other component under heating. It is also preferable to filter the resulting mixture with a predetermined filter. When preparing an ink containing a pigment, it is preferable to prepare a pigment dispersion containing the pigment and the polymerizable compound, and then mix the pigment dispersion with the other component. The pigment dispersion may further contain a dispersant.

[0181] The above-mentioned pigment dispersion can be prepared by dispersing a pigment in a polymerizable compound. Pigment dispersion can be performed using, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, or paint shaker. A dispersant may also be added at this time.

[0182] ≪Inkjet recording method of the present invention≫ The inkjet recording method of the present invention is characterized by using the inkjet ink composition of the present invention, and comprising the steps of ejecting the inkjet ink composition from an inkjet head and depositing it onto a recording medium, and curing the inkjet ink composition deposited on the recording medium with active energy rays or heat.

[0183] In the inkjet method, ink is ejected from an inkjet head and deposited onto a recording medium. Because the inkjet method makes it easy to apply ink only to the necessary areas, it is particularly suitable for forming solder resist patterns and printing characters.

[0184] In the curing process using activated energy rays, the curing may be performed immediately after the ink placement process, or all at once after the placement process is completed. The ink of the present invention has a relatively high viscosity at room temperature (25°C) and does not easily spread after landing on a recording medium. Therefore, it is not necessary to cure the ink immediately after it lands on the recording medium. Instead, the ink can be ejected within a certain range, landed on the recording medium, and then cured all at once. By curing all at once, ejection failures due to light leakage can be reduced.

[0185] In the present invention, "simultaneous irradiation," "simultaneous heating," and "simultaneous curing" refer to the process of ejecting multiple ink droplets within a certain predetermined range and landing them on a recording medium, and then simultaneously curing all of the multiple ink droplets that have landed within that range by irradiating them with active energy rays or heating them. In other words, instead of curing each ink droplet that lands on the recording medium, the process involves landing the ink, irradiating or heating it with active energy rays, and curing it all at once within a certain predetermined range (for example, landing all the ink necessary to form a predetermined image (pattern)).

[0186] Furthermore, it is preferable to form a solder resist film used in printed circuit boards using the inkjet recording method of the present invention.

[0187] The inkjet recording method of the present invention will be described below. The inkjet recording method of the present invention comprises (1) the step of ejecting the ink of the present invention from an inkjet head and depositing it onto a recording medium, and (2) the step of curing the ink deposited on the recording medium with active energy rays or heat.

[0188] [Step (1)] In step (1), the ink of the present invention is ejected from the nozzle of the inkjet head and deposited onto the recording medium. The recording medium is not particularly limited, but it is preferably a printed circuit board.

[0189] The inkjet head can use either an on-demand or continuous ejection method. On-demand inkjet heads may be either electromechanical conversion methods such as single-cavity type, double-cavity type, bender type, piston type, shear-mode type, and shared-wall type, or electro-thermal conversion methods such as thermal inkjet type and bubble jet (registered trademark) (bubble jet is a registered trademark of Canon Inc.).

[0190] Discharge stability is achieved by discharging ink droplets from the inkjet head while they are heated. The temperature of the ink when it is filled into the inkjet head is preferably in the range of 40 to 100°C, and more preferably in the range of 40 to 90°C from the viewpoint of further improving discharge stability. In addition, the viscosity of the ink at the discharge temperature is preferably in the range of 7 to 15 mPa·s, and more preferably in the range of 8 to 13 mPa·s.

[0191] When using a sol-gel phase transition type ink containing a gelling agent, it is preferable that the temperature of the ink when it is filled into the inkjet head be within the range of (gelling temperature + 10) to (gelling temperature + 30)°C. A temperature of (gelling temperature + 10)°C or higher in the inkjet head prevents the ink from gelling inside the head or on the nozzle surface, ensuring sufficient ejection stability. Furthermore, a temperature of (gelling temperature + 30)°C or lower prevents the deterioration of each component in the ink due to temperature changes.

[0192] The method of heating the ink is not particularly limited. For example, at least one of the ink supply system, such as the ink tank, supply pipe, and pre-chamber ink tank immediately before the head, which constitute the head carriage, as well as the filtered piping and the piezo head, can be heated by a panel heater, ribbon heater, or warm water.

[0193] From the viewpoint of recording speed and image quality, the amount of ink droplets ejected is preferably in the range of 2 to 20 pL.

[0194] The printed circuit board, which is the recording medium, is not particularly limited, but is preferably made of materials such as paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / nonwoven epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, copper-clad laminates for high-frequency circuits using fluorine, polyethylene, PPO, cyanate ester, etc., and is preferably copper-clad laminates of all grades (FR-4, etc.), as well as polyimide film, PET film, glass substrate, ceramic substrate, wafer plate, stainless steel plate, etc.

[0195] [Step (2)] In step (2), the ink that has landed on the recording medium is cured by active energy rays or heat. The ink of the present invention can be cured by irradiation with active energy rays alone or by heating alone, but it is preferable to irradiate with active energy rays at least, and it is even more preferable to heat.

[0196] Examples of active energy rays include electron beams, ultraviolet rays, alpha rays, gamma rays, and X-rays, but ultraviolet rays are preferred. Ultraviolet irradiation can be performed using, for example, a water-cooled LED manufactured by Phoseon Technology, under conditions of a wavelength of 395 nm. By using an LED as the light source, it is possible to suppress ink curing failures caused by the ink melting due to the radiant heat of the light source.

[0197] The peak irradiance on the surface of the solder resist film with ultraviolet light having a wavelength in the range of 370-410 nm is 0.5-10 W / cm². 2 It is preferably within the range of 1 to 5 W / cm². 2 It is more preferable that the light intensity be within the specified range, and ultraviolet irradiation is performed so that it falls within the above range. From the viewpoint of suppressing the irradiation of radiant heat to the ink, the amount of light irradiated onto the solder resist film is 1000 mJ / cm². 2 It is preferable that it be less than [a certain value].

[0198] Irradiation with active energy rays is preferably performed between 0.001 and 300 seconds after the ink hits the surface, and more preferably between 0.001 and 60 seconds in order to form a high-resolution solder resist film.

[0199] From the viewpoint of suppressing polymerization inhibition by oxygen, it is preferable to cure the ink by irradiating the deposited ink with active energy rays in an atmosphere with an oxygen concentration in the range of 0.1 to 10.0 volume%. Furthermore, from the viewpoint of making blooming less likely, it is more preferable that the oxygen concentration be in the range of 0.5 to 8.0 volume%, and even more preferable that it be in the range of 0.5 to 6.0 volume%.

[0200] The preferred heating method is, for example, to place the product in an oven set to a temperature within the range of 110 to 180°C for 10 to 90 minutes.

[0201] ≪Inkjet Recording System of the Present Invention≫ The inkjet recording system of the present invention is characterized by using the inkjet ink composition of the present invention and having an inkjet head for ejecting the inkjet ink composition, an active energy ray irradiation unit for irradiating the inkjet ink composition that has landed on a recording medium with active energy rays, and a heating unit for heating the inkjet ink composition that has been irradiated with the active energy rays.

[0202] In other words, the system of the present invention uses a recording device having an inkjet head for ejecting an inkjet ink composition, an active energy ray irradiation unit for irradiating the inkjet ink composition that has landed on a recording medium with active energy rays, and a heating unit for heating the inkjet ink composition that has been irradiated with the active energy rays, and the ink of the present invention.

[0203] Furthermore, from the viewpoint of ejection stability and printing accuracy, the recording method of the inkjet recording device is preferably a scanning method.

[0204] The inkjet recording apparatus used in the present invention comprises an inkjet head for ejecting the ink of the present invention onto a recording medium, an active energy ray irradiation unit for curing the ink of the present invention by irradiating the ink that has landed on the recording medium with active energy rays (for example, ultraviolet rays), and a heating unit for further curing by heating.

[0205] Types of inkjet recording devices (printers) include single-pass printers and serial printers. A single-pass printer has a line head with a length corresponding to the width of the recording medium (recording medium width), and the head is fixed without (almost) moving, allowing printing to be performed in one pass (single pass).

[0206] On the other hand, serial printers typically print in two or more passes (multipass) with the print head moving back and forth (shuttle movement) in a direction perpendicular to the transport direction of the recording medium.

[0207] In single-pass printers, multiple inkjet heads must be arranged to form a line head, requiring a relatively large number of inkjet heads. In contrast, serial printers can be configured with only a small number of recording heads.

[0208] In this invention, either type of printer can be used, and preferably, a serial printer can be used. [Examples]

[0209] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the examples, the units "parts" or "%" are used, and unless otherwise specified, they represent "parts by mass" or "mass%". Furthermore, in the following examples, the operations were carried out at room temperature (25°C) unless otherwise specified.

[0210] [Example 1] <Preparation of yellow pigment dispersion Y> Dispersant 1 and Dispersant 2, along with the dispersion medium, were placed in a stainless steel beaker and heated on a 65°C hot plate for 1 hour while stirring until dissolved. After cooling to room temperature, the pigments listed below were added, and the mixture was placed in a glass bottle with 200g of 0.5mm diameter zirconia beads and sealed tightly. This was dispersed using a paint shaker until the desired particle size was achieved, after which the zirconia beads were removed.

[0211] Dispersant 1: PX4701 (BASF) 6.0 parts by mass Dispersant 2: Solsperse 22000 (manufactured by Lubrizol Japan Co., Ltd.) 0.3 parts by mass Dispersion medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 61.5 parts by mass Pigment: PY185 (BASF, Paliotol Yellow D1155) 10.2 parts by mass

[0212] <Preparation of Cyanide Pigment Dispersion C> The yellow pigment dispersion was prepared in the same manner as dispersion Y, except that the dispersant, dispersion medium, and pigment were changed as shown below.

[0213] Dispersant: PX4701 (BASF) 7.0 parts by mass Dispersion medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 70 parts by mass Pigment: PB15:4 (manufactured by Dainichi Seika, Chromofine® Blue 6332JC) 23 parts by mass

[0214] In this experiment, the following compounds were used as polyfunctional compound A, acrylate oligomer, monomer, polymerization initiator, polymerization inhibitor, and gelling agent.

[0215] <Polyfunctional compound A> Maleimide A: BMI-5100, manufactured by Yamato Chemical Industries Co., Ltd. Maleimide B: BMI-1000, manufactured by Yamato Chemical Industries Co., Ltd. Maleimide C:N-phenylmaleimide, manufactured by Tokyo Chemical Industry Co., Ltd. Methacrylate A:DCP, manufactured by Shin-Nakamura Chemical Industry Co., Ltd. Methacrylate B:HD-N, manufactured by Shin-Nakamura Chemical Industry Co., Ltd. Methacrylate C:4G, manufactured by Shin-Nakamura Chemical Industry Co., Ltd. Methacrylate D:M301, manufactured by Miwon Corporation. Methacrylate E:M-40G, manufactured by Shin-Nakamura Chemical Industry Co., Ltd. Methacrylate F: EM310, manufactured by Choko Chemical Industry Co., Ltd. Methacrylate G: M1131, manufactured by Miwon Corporation.

[0216] <Acrylate oligomer> Urethane acrylate oligomer A: CN8885, manufactured by Sartomer. Urethane acrylate oligomer B: CN989, manufactured by Sartomer. Urethane acrylate oligomer C: CN972, manufactured by Sartomer. Urethane acrylate oligomer D: CN975NS, manufactured by Sartomer. Urethane acrylate oligomer E: CN992, manufactured by Sartomer. Acrylate oligomer A (hyperbranched structure): CN2304, manufactured by Sartomer. Acrylate oligomer B (hyperbranched structure): SP1106, manufactured by Miwon. Acrylate oligomer C (hyperbranched structure): 6361-100, manufactured by Choko Chemical Industry Co., Ltd. Polyester acrylate oligomer: CN2259, manufactured by Sartomer.

[0217] <Monomer> [Monofunctional compound] Acrylate a:M150, manufactured by Miwon. Acrylate b: 4-HBA, manufactured by Osaka Organic Chemical Industry Co., Ltd. [Polyfunctional compound B] Acrylate c: M222, manufactured by Miwon Acrylate d: SR259, manufactured by Sartomer Acrylate e: A-DCP, manufactured by Shin-Nakamura Chemical Co., Ltd. Acrylate f: SR492, manufactured by Sartomer

[0218] <Polymerization initiator> Type I (Nourish Type I) A: Omnirad (registered trademark) 907, manufactured by IGM Resins B.V. Type I (Nourish Type I) B: Omnirad (registered trademark) 819, manufactured by IGM Resins B.V. Type II (Nourish Type II): Speedcure (registered trademark) ITX, manufactured by Lambson

[0219] <Polymerization inhibitor> Irgastab (registered trademark) UV-10, manufactured by BASF

[0220] <Gelling agent> Gelling agent A: Kao Wax T1, manufactured by Kao Corporation Gelling agent B: Exceparl SS, manufactured by Kao Corporation Gelling agent C: Amreps PC, manufactured by Kodo Alcohol Industry Co., Ltd.

[0221] <Preparation of ink> The following components were mixed and filtered through a TEFLON (registered trademark) 3 μm membrane filter manufactured by ADVATEC to prepare Ink 1.

[0222] <Polyfunctional compound A> 3.0 parts by mass of maleimide A <Acrylic oligomer> 15.0 parts by mass of urethane acrylate oligomer A <Monomer> 10.0 parts by mass of acrylate b 36.7 parts by mass of acrylate c 20.0 parts by mass of acrylate d 10.0 parts by mass of acrylate f <Polymerization initiator> 1.0 part by mass of Type I A 1.0 part by mass of Type I B 2.0 parts by mass of Type II <Polymerization inhibitor> 0.1 part by mass of Irgastab (registered trademark) UV-10 <Pigment dispersion> 0.7 part by mass of Dispersion Y 0.5 part by mass of Dispersion C

[0223] Inks 2 to 38 were prepared in the same manner except that the types and addition amounts of the polyfunctional compound A, acrylate oligomer, monomer and gelling agent were changed to those described in Tables I to VII.

[0224] <Formation of an ink cured film by an inkjet method (Sample A)> Each of the prepared inks was loaded into an inkjet recording apparatus having an inkjet recording head equipped with a piezo-type inkjet nozzle. Using this apparatus, an ink cured film was formed on a polyimide film having a thickness of 100 μm.

[0225] The ink supply system consists of an ink tank, an ink flow path, a sub-ink tank immediately before the inkjet recording head, a pipe with a metal filter, and a piezo head. The ink is heated to 80 °C from the ink tank to the head portion. A heater is also built into the piezo head to heat the ink temperature inside the recording head to 80 °C. The piezo head has nozzles with a diameter of 22 μm, and the nozzles with a resolution of 360 dpi are arranged in a staggered pattern to form a nozzle array with a resolution of 720 dpi.

[0226] Using this inkjet device, a voltage was applied so that dots with a droplet volume of 6.0 pL were formed, and a solid pattern of 20 mm × 50 mm was printed on the substrate to a thickness of 20 μm each. Then, a LED lamp (395 nm, 8W / cm 2 , water cooled unit) manufactured by Phoseon Technology was irradiated at 1W / cm 2 to 500 mJ / cm 2 to cure the coating film. Thereafter, it was put into an oven set at 150 °C for 60 minutes for curing, and Sample A was obtained.

[0227] [Formation of solder resist pattern by inkjet method (Sample B)] Similarly, a solder resist pattern was formed on a copper-clad laminate for printed wiring boards (FR-4, thickness 1.6 mm, size 150 mm × 95 mm), and Sample B was obtained.

[0228] [Evaluation]

[0229] [Flexibility] For the fabricated Sample A, a flexural resistance test was conducted according to the description method of "JIS standard K-5600-5-1". Specifically, using a cylindrical mandrel flexure tester and mandrels with diameters of 2, 3, 4, 5, 6, 7, and 8 mm, the mandrel diameter at which cracks in the ink cured film were visually confirmed was measured. The evaluation was conducted according to the following criteria. Δ or above was defined as the range without practical problems. [Criteria] ◎: No cracks were confirmed for all mandrels. 〇: Cracks were confirmed for mandrels with a diameter of 4 mm or less, and not confirmed for mandrels with a diameter of 5 mm or more. △: Cracks were confirmed for mandrels with a diameter of 7 mm or less, and not confirmed for mandrels with a diameter of 8 mm. ×: Cracks were confirmed for mandrels with a diameter of 8 mm.

[0230] [Fastness (pencil hardness)] For the prepared sample B, in accordance with the description method of "JIS Standard K-5400", using Hi-Uni (registered trademark) manufactured by Mitsubishi Pencil Co., Ltd., the surface pencil hardness was measured as an evaluation of the fastness, that is, "scratch resistance".

[0231] Specifically, the wooden part of the pencil was shaved off, and the core was made to a length of 5 to 6 mm. A pencil with a circular cross-section obtained by smoothly polishing the tip of the core with abrasive paper was used. This pencil was held at an angle of 45 degrees with respect to the sample surface, and the coating film was scratched at an angle of 45 degrees with a weight of 1 kg applied to the sample surface. The maximum hardness of the pencil for which the coating film did not reach the substrate was evaluated.

[0232] The evaluation was carried out according to the following criteria. △ or higher was regarded as the range without practical problems. (Criteria) ◎: Pencil hardness 6H or higher. 〇: Pencil hardness 5H. △: Pencil hardness 3H or 4H. ×: Pencil hardness less than 3H.

[0233] <Fastness (pencil hardness) in long-term storage> The prepared sample B was left for 1 month under the conditions of 85 °C and 85% relative humidity, and then the pencil hardness was measured in the same manner as above. The evaluation was carried out according to the following criteria. △ or higher was regarded as the range without practical problems. (Criteria) ◎: Pencil hardness 6H or higher. 〇: Pencil hardness 5H. △: Pencil hardness 3H or 4H. ×: Pencil hardness less than 3H.

[0234] The addition amounts of the components in each ink and the evaluation results are shown in Tables I to VII below. Note that "-" indicates that it does not apply or has not been measured. In particular, for the addition amount, it indicates that it was not added. Also, "monofunctional" indicates a monofunctional compound.

[0235]

Table 1

[0236] [Table 2]

[0237] [Table 3]

[0238] [Table 4]

[0239] [Table 5]

[0240] [Table 1]

[0241] [Table 7]

[0242] From the above results, it was found that the ink of the present invention can achieve both flexibility and robustness in the resulting recorded material, and that sufficient robustness can be obtained even during long-term storage, while suppressing the deterioration of robustness. Furthermore, it was found that by appropriately selecting polyfunctional compound A, acrylate oligomer, monomer, and gelling agent, the flexibility, robustness, and long-term storage robustness of the recorded material can be further improved.

[0243] [Example 2] <Ink preparation> Inks 39-45 were prepared in the same manner as described in Table VII, except that the types and amounts of polyfunctional compound A, acrylate oligomer, monomer, and gelling agent were changed.

[0244] (Measurement of shear rate viscosity) Then, viscosity was measured using a stress-controlled rheometer, Physica MCR301 (cone plate diameter: 75 mm, cone angle: 1.0°, manufactured by Anton Paar), under conditions of a shear rate of 1000 / sec.

[0245] (Measurement of shear strain viscosity) Furthermore, the ink of the present invention was heated to 100°C, and the ink was cooled to 20°C using a stress-controlled rheometer Physica MCR301 (cone plate diameter: 75 mm, cone angle: 1.0°, manufactured by Anton Paar) under conditions of a cooling rate of 0.1°C / s, strain of 5%, and angular frequency of 10 radians / s to obtain a viscosity temperature dependence curve. The viscosity at 25°C was then determined by reading from the viscosity temperature dependence curve.

[0246] Then, the same evaluation as in Example 1 was performed. The amount of components added and the evaluation results for each ink are shown in Table VIII below. Note that "-" indicates that it is not applicable or not measured. In particular, for the amount added, it indicates that it was not added. Also, "monofunctional" refers to a monofunctional compound.

[0247] [Table 8]

[0248] From the above results, it was found that by setting the shear viscosity of the present invention at 25°C and a shear rate of 1000 / sec within the range of 40 to 400 mPa·s, ink ejection stability is achieved, and the flexibility and robustness of the recorded material are further improved. By setting it within the range of 50 to 250 mPa·s, it is possible to achieve a better balance between flexibility and robustness in the recorded material.

[0249] Furthermore, it was found that by setting the viscosity at 25°C, a shear strain of 5%, and an angular frequency of 10 radians / s to 1 Pa·s or higher, the pinning properties when the ink is applied to the recording medium and cooled to room temperature are improved, and sufficient robustness of the recorded material can be obtained. [Industrial applicability]

[0250] By recording using the inkjet ink composition of the present invention, it is possible to achieve both flexibility and robustness in the resulting recorded material and suppress the deterioration of robustness during long-term storage. Therefore, it can be suitably used as a solder resist ink to protect circuit patterns on printed wiring boards.

Claims

1. A heat-curing inkjet ink composition, It contains polyfunctional compound A and acrylate oligomer, The polyfunctional compound A is methacrylate or maleimide, The degree of resonance stabilization when the polyfunctional compound A becomes a radical is equal to or less than that of styrene. The acrylate oligomer has three or more functional groups, The content of the polyfunctional compound A in the inkjet ink composition is within the range of 1 to 10% by mass. An inkjet ink composition characterized by the following features.

2. It hardens with heat and active energy rays. The inkjet ink composition according to feature 1.

3. The Alfrey-Price Q value of the polyfunctional compound A is in the range of 0.70 to 1.

00. The inkjet ink composition according to claim 1 or 2.

4. The shear viscosity of the inkjet ink composition at 25°C and a shear rate of 1000 / sec is in the range of 40 to 400 mPa·s. The inkjet ink composition according to any one of claims 1 to 3.

5. The content of the acrylate oligomer in the inkjet ink composition is within the range of 10 to 40% by mass. The inkjet ink composition according to any one of claims 1 to 4.

6. The acrylate oligomer is a urethane acrylate oligomer. An inkjet ink composition according to any one of claims 1 to 5.

7. The acrylate oligomer is a hyperbranched acrylate oligomer. The inkjet ink composition according to any one of claims 1 to 6.

8. It further contains a monomer containing polyfunctional compound B, The polyfunctional compound B is a monomer having two or more functional groups, other than the polyfunctional compound A. The content of polyfunctional compound B relative to the total mass of the monomer is in the range of 90 to 100% by mass. The inkjet ink composition according to any one of claims 1 to 7.

9. It further contains a gelling agent. The inkjet ink composition according to any one of claims 1 to 8.

10. An inkjet recording method using an inkjet ink composition, Using the inkjet ink composition described in any one of claims 1 to 9, The process of ejecting the inkjet ink composition from the inkjet head and depositing it onto a recording medium, and The process includes a step of curing the inkjet ink composition that has landed on the recording medium by heat. An inkjet recording method characterized by the following.

11. An inkjet recording system using an inkjet ink composition, Using the inkjet ink composition described in any one of claims 1 to 9, An inkjet head for ejecting the aforementioned inkjet ink composition, and The inkjet ink composition has a heating section for heating the inkjet ink composition. An inkjet recording system characterized by the following features.

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