Nonaqueous ink jet ink composition and ink jet recording apparatus

Abstract

To provide an ink jet ink composition or the like that can reduce nozzle missing in the head.SOLUTION: The present invention provides a nonaqueous ink jet ink composition for use in a recording method which involves long-term printing operation without a step of taking measures against nozzle missing, wherein the nonaqueous ink jet ink composition includes a polymerizable monomer and a liquid photoinitiator in the form of liquid at 20°C, wherein the content of a solid photoinitiator in the form of solid at 20°C is 1.5 mass% or less with respect to the total mass of the nonaqueous inkjet ink composition.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a non-aqueous ink-jet ink composition and an ink-jet recording apparatus. [Background technology]

[0002] Inkjet recording methods are capable of recording high-definition images with a relatively simple device, and have been rapidly developed in various fields. In the process, various studies have been conducted on continuous discharge stability, etc. For example, Patent Document 1 discloses a radiation-curable inkjet composition that contains a bifunctional or higher acylphosphine oxide-based photopolymerization initiator that is solid by itself at room temperature and a polymerizable compound, the composition has a dissolved oxygen content of 0 to 8.0 kPa, and is contained in a composition container. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-199817 A Summary of the Invention [Problem to be solved by the invention]

[0004] As disclosed in Patent Document 1, when preparing an inkjet composition containing a photopolymerization initiator that is solid at room temperature, ultrasonic treatment is performed to dissolve fine particles of the photopolymerization initiator, to remove dissolved oxygen contained in the inkjet composition, and to cause air bubbles remaining inside or on the surface of the photopolymerization initiator particles to detach from the photopolymerization initiator and be released into the composition, thereby removing the fine air bubbles. However, if ultrasonic treatment is not performed, fine air bubbles remain in the ink, which causes a problem of increased nozzle dropout in the head when recording is performed continuously for a long period of time.

[0005] As described above, by subjecting the inkjet composition to an ultrasonic treatment process, minute air bubbles can be removed, but when an ultrasonic treatment process is performed, restrictions are imposed on the location, configuration, etc. of the inkjet composition production device, and the production process becomes long. Therefore, a method for preparing an ink that allows long-term continuous recording without ultrasonic treatment is desired. [Means for solving the problem]

[0006] The present invention relates to a non-aqueous inkjet ink composition used in a recording method for long-term printing without performing a process to prevent nozzle clogging, the non-aqueous inkjet ink composition comprising a polymerizable monomer and a liquid photoinitiator that is liquid at 20°C, wherein the content of the solid photoinitiator that is solid at 20°C is 1.5 mass% or less relative to the total amount of the non-aqueous inkjet ink composition. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic cross-sectional view of a line-type printer. [Diagram 2] 1 is a table showing the results of the examples. [Diagram 3] 1 is a table showing the results of the examples. [Figure 4] 1 is a table showing the results of the examples. [Diagram 5] 1 is a table showing the results of the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Below, we will explain in detail the embodiment of the present invention (hereinafter referred to as the "present embodiment"); however, the present invention is not limited to this embodiment, and various modifications are possible without departing from the gist of the present invention.

[0009] 1. Non-aqueous inkjet ink composition The non-aqueous inkjet ink composition according to this embodiment (hereinafter also simply referred to as the "ink composition") is a non-aqueous inkjet ink composition used in a recording method for long-term printing without performing any step to prevent nozzle clogging, and contains a polymerizable monomer and a liquid photoinitiator that is liquid at 20°C, and the content of the solid photoinitiator that is solid at 20°C is 1.5 mass% or less relative to the total amount of the non-aqueous inkjet ink composition.

[0010] Conventional inkjet inks containing photoinitiators tend to increase the number of nozzles missing from the head unless they are subjected to an ultrasonic treatment process. The cause of this is thought to be as follows. Conventional inkjet inks containing photoinitiators use solid photoinitiators as photoinitiators from the viewpoint of curability, so that minute bubbles are generated in the inkjet ink during ink preparation. If the inkjet ink containing these minute bubbles is not subjected to an ultrasonic treatment process, the inkjet ink is discharged from the inkjet head with the minute bubbles remaining, which is thought to result in an increase in nozzles missing from the head. Nozzle missing refers to a situation in which the ink is not properly discharged due to the presence of bubbles in the ink near the nozzles, resulting in the appearance of nozzles that do not print properly. However, the cause of the increase in nozzles missing from the head is not limited to this.

[0011] In particular, when printing for a long period of time without implementing any countermeasures against clogged nozzles, there was a tendency for the increase in clogged nozzles in the head to be significant. This is thought to be because when printing for a long period of time without implementing any countermeasures against clogged nozzles, minute air bubbles remaining in the inkjet ink tend to accumulate in the head. However, the cause of the significant increase in clogged nozzles in the head is not limited to this.

[0012] Furthermore, if an ink-jet ink containing a conventional solid photoinitiator is subjected to an ultrasonic treatment step in order to suppress the above-mentioned missing nozzles in the head, it becomes necessary to install equipment for the ultrasonic treatment step, which limits the degree of freedom in terms of the location, configuration, etc. of the ink-jet ink production apparatus and tends to lengthen the production time of the ink-jet ink.

[0013] Therefore, in this embodiment, by using a liquid photoinitiator that is liquid at 20°C under 1 atmosphere as the photoinitiator, it is possible to suppress nozzle missing in the head without subjecting the ink composition to ultrasonic treatment or performing a process to prevent nozzle missing. It is believed that the use of the liquid photoinitiator makes it difficult for minute bubbles to be generated when preparing the ink composition, but the reason why nozzle missing in the head can be suppressed is not limited to this. In addition, since an ultrasonic treatment process is not required when preparing the ink composition as in the case of using a solid photoinitiator, the freedom of the location and configuration of the ink composition production device can be improved, and the production time of the ink composition can be shortened.

[0014] Furthermore, the ink composition of the present embodiment tends to be able to suppress missing nozzles in a head even when printing for a long time without subjecting the ink composition to an ultrasonic treatment step and without carrying out a step to prevent missing nozzles. This is thought to be because minute air bubbles are less likely to be generated when the ink composition is prepared, but the reason why missing nozzles in a head can be suppressed even when printing for a long time without subjecting the ink composition to an ultrasonic treatment step and without carrying out a step to prevent missing nozzles is not limited to this.

[0015] The viscosity of the ink composition at 25° C. is preferably less than 40 mPa·s, less than 30 mPa·s, less than 20 mPa·s, 3 to 40 mPa·s, 4 to 30 mPa·s, 5 to 25 mPa·s, or 10 to 20 mPa·s. When the viscosity of the ink composition is within the above range, the ink composition tends to be suitable for inkjet recording methods.

[0016] The viscosity of the ink composition at 25° C. can be measured by a method in accordance with JIS Z 8803. The viscosity of the ink composition can be adjusted by changing the type and / or content of the photoinitiator, changing the type and / or content of the polymerizable monomer, changing the type and / or content of the oligomer, changing the type and / or content of the colorant, changing the type and / or content of the surfactant, adding a viscosity adjuster as an additional component described later, or the like.

[0017] Each component of the ink composition of this embodiment will be described in detail below.

[0018] 1.1. Photoinitiators In this specification, the term "photoinitiator" includes not only a photopolymerization initiator, but also a sensitizer and a fluorescent brightener used in conjunction with the photoinitiator. When the ink composition contains a photoinitiator, the photoinitiator generates active species (initiation species) such as radicals, acids, and bases when irradiated with radiation, and the polymerization reaction of the polymerizable monomer described below is promoted by the function of the initiation species.

[0019] The photoinitiator of the present embodiment includes a liquid photoinitiator that is liquid at 20° C. under 1 atmosphere (hereinafter, also simply referred to as “liquid photoinitiator”) and a solid photoinitiator that is solid at 20° C. under 1 atmosphere (hereinafter, also simply referred to as “solid photoinitiator”). The photoinitiator is not particularly limited, but examples thereof include aromatic ketones, hydroxyketones, acylphosphine compounds, aromatic onium salt compounds, organic peroxides, thioxanthones, thio compounds such as thiophenes, hexaarylbisimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having carbon-halogen bonds, and alkylamine compounds. These photoinitiators are used alone or in combination of two or more. Further, examples of the photoinitiator of the present invention that is classified as a fluorescent whitening agent include naphthalene benzoxazoyl derivatives, thiophene benzoxazoyl derivatives, stilbene benzoxazoyl derivatives, coumarin derivatives, styrene biphenyl derivatives, pyrazolone derivatives, stilbene derivatives, styryl derivatives of benzene and biphenyl, bis(benzazol-2-yl) derivatives, carbostyril, naphthalimide, dibenzothiophene-5,5'-dioxide derivatives, pyrene derivatives, and pyridotriazole.

[0020] 1.1.1. Liquid photoinitiators The ink composition of the present embodiment includes a liquid photoinitiator. In addition to a liquid photopolymerization initiator, examples of the liquid photoinitiator include a liquid sensitizer and a liquid fluorescent brightener, and are not particularly limited. Examples of the liquid photoinitiator include aromatic ketones, hydroxyketones, acylphosphine compounds, aromatic onium salt compounds, organic peroxides, thioxanthone-based compounds, thio compounds such as thiophene, hexaarylbisimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon-halogen bond, and alkylamine compounds. Among these, it is preferable to use one or more selected from the group consisting of acylphosphine-based initiators and thioxanthone-based initiators, it is more preferable to use an acylphosphine-based initiator, and it is even more preferable to use an acylphosphine-based initiator and a thioxanthone-based initiator in combination. These liquid photoinitiators are used alone or in combination of two or more.

[0021] The content of the liquid photoinitiator is preferably 5.0 to 25.0 mass%, 7.0 to 22.5 mass%, 8.5 to 20.0 mass%, or 10.0 to 17.5 mass% relative to the total amount of the ink composition. When the content of the liquid photoinitiator is within the above range, there is a tendency for the curability and suppression of missing nozzles in the head to be excellent.

[0022] The content of the liquid photoinitiator is preferably 80.0 to 99.9 mass%, 82.5 to 99.9 mass%, or 85.0 to 99.9 mass% based on the total amount of the photoinitiator. Alternatively, the content of the liquid photoinitiator may be 100 mass% based on the total amount of the photoinitiator. By having the content of the liquid photoinitiator within the above range, there is a tendency for the curability and the suppression of missing nozzles in the head to be more excellent.

[0023] 1.1.1.1. Acylphosphine initiators The ink composition of the present embodiment may contain an acylphosphine-based initiator, which is an acylphosphine compound, among the liquid photoinitiators. The acylphosphine-based initiator is not particularly limited, but examples thereof include ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (hereinafter also referred to as "TPO-L") or an oligomer thereof. Among these, ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate is preferred.

[0024] The content of the acylphosphine initiator is preferably 3.0 to 20.0 mass%, 5.0 to 15.0 mass%, 6.0 to 12.5 mass%, or 6.5 to 11.0 mass% relative to the total amount of the ink composition. When the content of the acylphosphine initiator is within the above range, there is a tendency for the curability and suppression of missing nozzles in the head to be more excellent.

[0025] The content of the acylphosphine initiator is preferably 30.0 to 99.0 mass%, 40.0 to 95.0 mass%, 45.0 to 90.0 mass%, 50.0 to 85.0 mass%, or 55.0 to 82.5 mass% relative to the total amount of the photoinitiator. By having the content of the acylphosphine initiator within the above range, there is a tendency for curability and suppression of missing nozzles in the head to be more excellent.

[0026] The content of TPO-L is preferably 7.0% by mass or more, 7.0 to 20.0% by mass, 7.2 to 15.0% by mass, or 7.4 to 12.5% ​​by mass, relative to the total amount of the ink composition. When the content of TPO-L is within the above range, the curability tends to be more excellent.

[0027] 1.1.1.2. Thioxanthone initiators The ink composition of the present embodiment may contain a thioxanthone-based initiator, which is a thio compound, among the liquid photoinitiators. The thioxanthone-based initiator is not particularly limited, but examples thereof include polybutylene glycol bis(9-oxo-9H-thioxanthenyloxy)acetate (CAS No. 813452-37-8), Poly[oxy(methyl-1,2-ethanediyl)], α-hydro-ω-[[2-[(1-chloro-9-oxo-9H-thioxanthen-4-yl)oxy]acetyl]oxy]-, ether with 2,2-bis(hydroxymethyl)-1,3-propanediyl (4:1) (CAS No. 1003567-83-6). These thioxanthone-based initiators may be used alone or in combination of two or more.

[0028] The content of the thioxanthone initiator is preferably 0.1 to 10.0 mass%, 0.5 to 7.5 mass%, or 1.0 to 5.0 mass% relative to the total amount of the ink composition. When the content of the thioxanthone initiator is within the above range, there is a tendency for the curability and the suppression of missing nozzles in the head to be excellent.

[0029] Furthermore, when the ink composition is a clear ink composition described below, the content of the thioxanthone initiator is preferably 3.0% by mass or less, 0.1 to 3.0% by mass, 0.1 to 2.0% by mass, or 0.1 to 1.0% by mass relative to the total amount of the clear ink composition. By having the content of the thioxanthone initiator within the above range, there is a tendency for the curability and the suppression of yellowing of the coating film to be more excellent.

[0030] The content of the thioxanthone initiator is preferably 1.0 to 40.0 mass%, 5.0 to 35.0 mass%, or 10.0 to 30.0 mass% relative to the total amount of the photoinitiator. When the content of the thioxanthone initiator is within the above range, there is a tendency for curability and suppression of missing nozzles in the head to be more excellent.

[0031] Furthermore, when the ink composition is a clear ink composition described below, the content of the thioxanthone initiator is preferably 30.0 mass% or less, 1.0 to 30.0 mass%, 1.0 to 20.0 mass%, or 1.0 to 10.0 mass% relative to the total amount of the photoinitiator. By having the content of the thioxanthone initiator within the above range, there is a tendency for the curability, suppression of nozzle dropout in the head, and suppression of yellowing of the coating film to be excellent.

[0032] 1.1.1.3. Other liquid photoinitiators Other liquid photoinitiators include hydroxyketone-based photoinitiators, such as, but not limited to, 2-hydroxy-2-methyl-1[4-(1-methylvinyl)phenyl]propanone or an oligomer thereof.

[0033] The content of the other liquid photoinitiator relative to the total amount of the ink composition is not particularly limited, but is, for example, 0.1 to 10.0 mass%, 0.5 to 8.0 mass%, or 1.0 to 6.0 mass%, and may not contain the other liquid photoinitiator.

[0034] The content of the other liquid photoinitiator relative to the total amount of the photoinitiator is not particularly limited, but is, for example, 0.1 to 40.0 mass%, 0.5 to 39.0 mass%, or 1.0 to 38.0 mass%, and may not contain the other liquid photoinitiator.

[0035] 1.1.2. Solid photoinitiators Examples of the solid photoinitiator include a solid photopolymerization initiator, a solid sensitizer, and a solid fluorescent brightener, and are not particularly limited. Examples of the solid photoinitiator include aromatic ketones, hydroxyketones, acylphosphine compounds, aromatic onium salt compounds, organic peroxides, thioxanthones, thio compounds such as thiophene, hexaarylbisimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon-halogen bond, and alkylamine compounds. These solid photoinitiators may be used alone or in combination of two or more.

[0036] Among the solid photoinitiators, the acylphosphine-based solid photoinitiator, which is an acylphosphine compound, is not particularly limited, and examples thereof include phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and diphenyl-2,4,6-trimethylbenzoylphosphine oxide (hereinafter also referred to as "TPO"). These acylphosphine-based solid photoinitiators are used alone or in combination of two or more.

[0037] Among the solid photoinitiators, examples of thioxanthone-based solid photoinitiators that are thio compounds include, but are not limited to, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propane.

[0038] In the ink composition of this embodiment, the content of the solid photoinitiator is 1.50% by mass or less, preferably 0.50% by mass or less, 0.01 to 1.50% by mass, 0.01 to 1.00% by mass, 0.01 to 0.75% by mass, 0.01 to 0.50% by mass, 0.01 to 0.25% by mass, or 0.01 to 0.10% by mass, based on the total amount of the ink composition. Alternatively, the ink composition of this embodiment may not contain a solid photoinitiator. By having the content of the solid photoinitiator within the above range, there is a tendency for the suppression of nozzle missing of the head to be more excellent.

[0039] The content of the solid photoinitiator is preferably 0.1 to 20.0 mass%, 0.1 to 15.0 mass%, 0.1 to 12.5 mass%, or 0.1 to 10.0 mass% based on the total amount of the photoinitiator. Alternatively, the ink composition of the present embodiment may not contain a solid photoinitiator. When the content of the solid photoinitiator is within the above range, there is a tendency for the ink composition to be more excellent in suppressing missing nozzles in the head.

[0040] 1.1.3. Photoinitiator The photopolymerization initiator of the present embodiment generates active species (initiation species) such as radicals, acids, and bases when irradiated with radiation, and promotes the polymerization reaction of the monomers by the function of the initiation species.

[0041] The liquid or solid photopolymerization initiator is not particularly limited, but examples thereof include ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate, 2-hydroxy-2-methyl-1[4-(1-methylvinyl)phenyl]propanone or its oligomer, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and diphenyl-2,4,6-trimethylbenzoylphosphine oxide. The photopolymerization initiator may be either a liquid photoinitiator or a solid photoinitiator. The photopolymerization initiator may be used alone or in combination of two or more kinds.

[0042] The content of the photopolymerization initiator relative to the total amount of the ink composition is not particularly limited, and is, for example, 2.0 to 25.0 mass %, 3.0 to 20.0 mass %, 4.0 to 17.5 mass %, or 5.0 to 15.0 mass %.

[0043] The content of the photopolymerization initiator relative to the total amount of the photoinitiator is not particularly limited, and is, for example, 60.0 to 100.0 mass %, 65.0 to 97.5 mass %, or 70.0 to 95.0 mass %.

[0044] 1.1.4.Fluorescent whitening agents The ink composition of this embodiment may contain a fluorescent brightening agent as a photoinitiator. The fluorescent brightening agent of this embodiment has a function of absorbing ultraviolet light and emitting pale fluorescence. Furthermore, when combined with another photoinitiator, it exhibits a sensitizing effect, and therefore, by including a fluorescent brightening agent, the ink composition tends to have better curability than when only a photoinitiator is included.

[0045] Examples of liquid or solid fluorescent whitening agents include, but are not limited to, naphthalene benzoxazoyl derivatives, thiophene benzoxazoyl derivatives, stilbene benzoxazoyl derivatives, coumarin derivatives, styrene biphenyl derivatives, pyrazolone derivatives, stilbene derivatives, styryl derivatives of benzene and biphenyl, bis(benzazol-2-yl) derivatives, carbostyril, naphthalimide, derivatives of dibenzothiophene-5,5'-dioxide, pyrene derivatives, and pyridotriazole. These fluorescent whitening agents may be used alone or in combination of two or more.

[0046] More specifically, the fluorescent whitening agent is not particularly limited, but may be, for example, 1,4-bis(2-benzoxazolyl)naphthalene or 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene. The fluorescent whitening agent may be a liquid photoinitiator or a solid photoinitiator. The fluorescent whitening agent may be used alone or in combination of two or more kinds.

[0047] The content of the fluorescent brightening agent is preferably 1.00% by mass or less, 0.50% by mass or less, 0.01 to 1.00% by mass, 0.03 to 0.75% by mass, or 0.05 to 0.50% by mass, relative to the total amount of the ink composition. When the content of the fluorescent brightening agent is within the above range, the curability and low-temperature deposition property tend to be more excellent.

[0048] The content of the fluorescent brightening agent is preferably 0.1 to 10.0 mass%, 0.3 to 7.5 mass%, or 0.5 to 5.0 mass%, relative to the total amount of the photoinitiator. When the content of the fluorescent brightening agent is within the above range, the curability tends to be more excellent.

[0049] 1.1.5. Sensitizers The sensitizer of the present embodiment absorbs radiation to become excited, and has the function of accelerating the decomposition of the photopolymerization initiator by contacting the photopolymerization initiator, thereby further accelerating the polymerization reaction of the monomer.

[0050] Examples of liquid or solid sensitizers include, but are not limited to, amine compounds (aliphatic amines, amines containing an aromatic ring, piperidine, reaction products of epoxy resins and amines, triethanolamine triacrylate, etc.), urea compounds (allylthiourea, o-tolylthiourea, etc.), sulfur compounds (2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propane, sodium diethyldithiophosphate, soluble salts of aromatic sulfinic acids, etc.), nitrile compounds (N,N-diethyl-p-aminobenzonitrile, etc.), phosphorus compounds (tri-n-butylphosphine, sodium diethyldithiophosphide, etc.), nitrogen compounds (Michler's ketone, N-nitrisohydroxylamine derivatives, oxazolidine compounds, tetrahydro-1,3-oxazine compounds, condensates of formaldehyde or acetaldehyde with diamines, etc.), and chlorine compounds (carbon tetrachloride, hexachloroethane, etc.). These fluorescent whitening agents are used alone or in combination of two or more. The sensitizer may be a liquid photoinitiator or a solid photoinitiator. The sensitizer may be used alone or in combination of two or more.

[0051] The content of the sensitizer relative to the total amount of the ink composition is not particularly limited, but is, for example, 0.5 to 10.0 mass%, 1.0 to 8.0 mass%, or 2.0 to 6.0 mass%, or the ink composition may not contain a sensitizer.

[0052] The content of the sensitizer relative to the total amount of the photoinitiator is not particularly limited, but is, for example, 1.0 to 40.0 mass%, 5.0 to 35.0 mass%, or 10.0 to 30.0 mass%, or the sensitizer may not be included.

[0053] 1.2. Polymerizable monomers The ink composition of the present embodiment contains a polymerizable monomer. The polymerizable monomer is not particularly limited, but is, for example, a photopolymerizable compound that polymerizes and solidifies when irradiated with light such as ultraviolet light. Examples of the polymerizable monomer include monofunctional monomers, bifunctional monomers, and polyfunctional monomers having three or more functional groups. The polymerizable monomers may be used alone or in combination of two or more types.

[0054] The content of the polymerizable monomer is preferably 60.0 to 95.0 mass%, 62.5 to 92.5 mass%, 65.0 to 90.0 mass%, or 67.5 to 87.5 mass% relative to the total amount of the ink composition. When the content of the polymerizable monomer is within the above range, flexibility, adhesion, and curability tend to be more excellent.

[0055] 1.2.1. Monofunctional monomers The monofunctional monomer is not particularly limited, but examples thereof include benzyl (meth)acrylate, isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomyristyl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and the like. Examples of the monofunctional monomer include tert-butylcyclohexyl (meth)acrylate, methoxypropylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, lactone-modified flexible (meth)acrylate, t-butylcyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and vinylmethyloxazolidinone. Among these, vinylmethyloxazolidinone is preferred from the viewpoint of improving adhesion and curing properties. These monofunctional monomers may be used alone or in combination of two or more.

[0056] The content of the monofunctional monomer is preferably 25.0 to 557.5 mass%, 27.5 to 55.0 mass%, or 30.0 to 52.5 mass%, relative to the total amount of the ink composition. When the content of the monofunctional monomer is within the above range, adhesion and curability tend to be better.

[0057] The content of the monofunctional monomer is preferably 25.0 to 70.0 mass%, 27.5 to 67.5 mass%, or 30.0 to 65.0 mass%, based on the total amount of the polymerizable monomers. When the content of the monofunctional monomer is within the above range, adhesion and curability tend to be more excellent.

[0058] In addition, the ink composition of the present embodiment preferably contains 30% by mass or less of phenoxyethyl (meth)acrylate as a monofunctional monomer relative to the total amount of the ink composition. The ink composition preferably contains 25% by mass or less of phenoxyethyl (meth)acrylate, preferably 15% by mass or less, preferably 10% by mass or less, and preferably 5% by mass or less. Phenoxyethyl (meth)acrylate may not be contained. The lower limit of the content of phenoxyethyl (meth)acrylate is not particularly limited, but is, for example, 1% by mass or more, 2% by mass or more, or 3% by mass or more relative to the total amount of the ink composition. By containing 30% by mass or less of phenoxyethyl (meth)acrylate or not containing phenoxyethyl (meth)acrylate, there is a tendency for the ink composition to have excellent continuous printing stability and low-temperature precipitation properties. In addition, the ink composition tends to prevent the coating film from yellowing, lower the viscosity of the inkjet ink composition, and have excellent discharge stability.

[0059] The content of vinylmethyloxazolidinone is preferably 5.0 to 30.0 mass%, 7.5 to 27.5 mass%, or 10.0 to 25.0 mass% relative to the total amount of the ink composition. When the content of vinylmethyloxazolidinone is 5.0 mass% or more, adhesion tends to be excellent, and when it is 30.0 mass% or less, curability tends to be excellent.

[0060] 1.2.2. Bifunctional monomers The bifunctional monomer is not particularly limited, but examples thereof include diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonyl di(meth)acrylate, 1,2-nonyl di(meth)acrylate, 1,3-nonyl di(meth)acrylate, 1,4-nonyl di(meth)acrylate, 1,5-nonyl di(meth)acrylate, 1,6-nonyl di(meth)acrylate, 1,7-nonyl di(meth)acrylate, 1,8-nonyl di(meth)acrylate, 1,9-nonyl di(meth)acrylate, 1,8-nonyl di(meth)acrylate, 1,9-nonyl di(meth)acrylate, 1,2-nonyl di(meth)acrylate, 1,3-nonyl di(meth)acrylate, 1,4-nonyl di(meth)acrylate, 1,5-nonyl di(meth)acrylate, 1,6-nonyl di(meth)acrylate, 1,7 ...3-nonyl di(meth)acrylate, 1,4-nonyl di(meth)acrylate, 1,5-nonyl di(meth)acrylate, 1,5-nonyl di(meth)acrylate, 1, Examples of the difunctional monomer include nandiol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, EO (ethylene oxide) adduct di(meth)acrylate of bisphenol A, PO (propylene oxide) adduct di(meth)acrylate of bisphenol A, hydroxypivalic acid neopentyl glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate, and vinyl ether group-containing (meth)acrylate represented by the following formula (1). Among these, from the viewpoint of improving viscosity characteristics, flexibility and curability, vinyl ether group-containing (meth)acrylate represented by the following formula (1) is preferred. These bifunctional monomers may be used alone or in combination of two or more. H2C=CR 1 -CO-OR 2 -O-CH=CH-R 3 (1) (In the formula, R 1 is a hydrogen atom or a methyl group, R 2 is a divalent organic residue having 2 to 20 carbon atoms, and R 3 is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms.

[0061] In the above formula (1), R 2Examples of the divalent organic residue having 2 to 20 carbon atoms represented by the formula (I) include a linear, branched or cyclic alkylene group having 2 to 20 carbon atoms, which may be substituted, an alkylene group having 2 to 20 carbon atoms, which has an oxygen atom due to an ether bond and / or an ester bond in the structure, which may be substituted, and a divalent aromatic group having 6 to 11 carbon atoms, which may be substituted. Among these, alkylene groups having 2 to 6 carbon atoms, such as an ethylene group, an n-propylene group, an isopropylene group, and a butylene group, and alkylene groups having 2 to 9 carbon atoms, which have an oxygen atom due to an ether bond in the structure, such as an oxyethylene group, an oxyn-propylene group, an oxyisopropylene group, and an oxybutylene group, are preferred. Furthermore, from the viewpoint of further reducing the viscosity of the composition and further improving the curability of the composition, R 2 is an alkylene group having 2 to 9 carbon atoms and having an oxygen atom by an ether bond in the structure, such as an oxyethylene group, an oxyn-propylene group, an oxyisopropylene group, or an oxybutylene group, is more preferred.

[0062] In the above formula (1), R 3 Preferred examples of the monovalent organic residue having 1 to 11 carbon atoms and represented by the formula (1) are linear, branched or cyclic alkyl groups having 1 to 10 carbon atoms which may be substituted, and aromatic groups having 6 to 11 carbon atoms which may be substituted. Among these, alkyl groups having 1 to 2 carbon atoms, such as a methyl group or an ethyl group, and aromatic groups having 6 to 8 carbon atoms, such as a phenyl group and a benzyl group, are preferably used.

[0063] When each of the organic residues is a group that may be substituted, the substituent is divided into a group that contains carbon atoms and a group that does not contain carbon atoms.First, when the substituent is a group that contains carbon atoms, the carbon atom is counted in the number of carbon atoms of the organic residue.As the group that contains carbon atoms, but is not limited to the following, for example, a carboxyl group and an alkoxy group can be mentioned.Next, as the group that does not contain carbon atoms, but is not limited to the following, for example, a hydroxyl group and a halo group can be mentioned.

[0064] Specific examples of the compound of formula (1) include, but are not limited to, 2-vinyloxyethyl (meth)acrylate, 3-vinyloxypropyl (meth)acrylate, 1-methyl-2-vinyloxyethyl (meth)acrylate, 2-vinyloxypropyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, 1-methyl-3-vinyloxypropyl (meth)acrylate, 1-vinyloxymethylpropyl (meth)acrylate, 2-methyl-3-vinyloxypropyl (meth)acrylate, 1,1-dimethyl-2-vinyloxyethyl (meth)acrylate, ) 3-vinyloxybutyl acrylate, 1-methyl-2-vinyloxypropyl (meth)acrylate, 2-vinyloxybutyl (meth)acrylate, 4-vinyloxycyclohexyl (meth)acrylate, 6-vinyloxyhexyl (meth)acrylate, 4-vinyloxymethylcyclohexylmethyl (meth)acrylate, 3-vinyloxymethylcyclohexylmethyl (meth)acrylate, 2-vinyloxymethylcyclohexylmethyl (meth)acrylate, p-vinyloxymethylphenylmethyl (meth)acrylate, m-vinyloxymethylphenyl (meth)acrylate Methyl, o-vinyloxymethylphenylmethyl (meth)acrylate, 2-(2-vinyloxyethoxy)ethyl (meth)acrylate, 2-(2-vinyloxyethoxy)ethyl acrylate, 2-(vinyloxyisopropoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxy)propyl (meth)acrylate, 2-(vinyloxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxy)propyl (meth)acrylate, 2-(vinyloxyisopropoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxy)isopropyl (meth)acrylate, 2-(vinyloxyeth (meth)acrylate 2-(vinyloxyethoxyisopropoxy)ethyl, (meth)acrylate 2-(vinyloxyisopropoxyethoxy)ethyl, (meth)acrylate 2-(vinyloxyisopropoxyisopropoxy)ethyl, (meth)acrylate 2-(vinyloxyethoxyethoxy)propyl, (meth)acrylate 2-(vinyloxyethoxyisopropoxy)propyl, (meth)acrylate 2-(vinyloxyisopropoxyethoxy)propyl, (meth)acrylate 2-(vinyloxyisopropoxyisopropoxy)propyl, (meth)acrylate 2-(vinyloxyisopropoxyisopropoxy)propyl,2-(vinyloxyethoxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyethoxyisopropoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxyisopropoxy)isopropyl (meth)acrylate, 2-(vinyloxyethoxyethoxyethoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxyethoxyethoxyethoxy)ethyl (meth)acrylate ethyl, 2-(isopropenoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxyethoxy)ethyl (meth)acrylate, polyethylene glycol monovinyl ether (meth)acrylate, and polypropylene glycol monovinyl ether (meth)acrylate. Of these specific examples, 2-(2-vinyloxyethoxy)ethyl acrylate is particularly preferred from the viewpoints of viscosity characteristics, flexibility, and curability. In this embodiment, 2-(2-vinyloxyethoxy)ethyl acrylate is sometimes referred to as VEEA.

[0065] The content of the bifunctional monomer is preferably 20.0 to 65.0 mass%, 25.0 to 62.5 mass%, or 30.0 to 60.0 mass% relative to the total amount of the ink composition. When the content of the bifunctional monomer is within the above range, the viscosity characteristics, flexibility, and curability tend to be more excellent.

[0066] The content of the bifunctional monomer is preferably 25.0 to 75.0 mass%, 30.0 to 72.5 mass%, or 35.0 to 70.0 mass% based on the total amount of the polymerizable monomers. When the content of the bifunctional monomer is within the above range, the viscosity characteristics, flexibility, and curability tend to be more excellent.

[0067] The content of 2-(2-vinyloxyethoxy)ethyl acrylate is preferably 10.0 to 40.0 mass%, 12.5 to 37.5 mass%, or 15.0 to 35.0 mass% relative to the total amount of the ink composition. When the content of 2-(2-vinyloxyethoxy)ethyl acrylate is 10.0 mass% or more, the viscosity characteristics and curability tend to be more excellent, and when it is 40.0 mass% or less, the flexibility tends to be more excellent.

[0068] 1.2.3. Multifunctional Monomers The trifunctional or higher polyfunctional monomer is not particularly limited, but examples thereof include trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerin propoxy tri(meth)acrylate, cowprolactone-modified trimethylolpropane tri(meth)acrylate, pentaerythritol ethoxy tetra(meth)acrylate, and caprolactam-modified dipentaerythritol hexa(meth)acrylate. These polyfunctional monomers can be used alone or in combination of two or more.

[0069] The content of the polyfunctional monomer is preferably 1.0 to 10.0 mass%, 2.0 to 7.5 mass%, or 3.0 to 5.0 mass% relative to the total amount of the ink composition. When the content of the polyfunctional monomer is within the above range, the viscosity characteristics tend to be more excellent.

[0070] The content of the polyfunctional monomer is preferably 1.0 to 10.0 mass%, 2.0 to 9.0 mass%, or 3.0 to 8.0 mass% relative to the total amount of the polymerizable monomers. When the content of the polyfunctional monomer is within the above range, the viscosity characteristics tend to be more excellent.

[0071] 1.3.Oligomers The ink composition of the present embodiment may contain an oligomer. The oligomer of the present embodiment refers to a compound that is a multimer such as a dimer or trimer, which contains a polymerizable compound as a constituent, and has one or more polymerizable functional groups. Note that the polymerizable compound referred to here is not limited to the above-mentioned monofunctional monomer, bifunctional monomer, and polyfunctional monomer.

[0072] Such oligomers are not particularly limited, but examples thereof include urethane acrylate oligomers in which the repeating unit is a urethane, polyester acrylate oligomers in which the repeating unit is an ester, and epoxy acrylate oligomers in which the repeating unit is an epoxy.

[0073] Among these, urethane acrylate oligomers are preferred, aliphatic urethane acrylate oligomers and aromatic urethane acrylate oligomers are more preferred, and aliphatic urethane acrylate oligomers are even more preferred. The urethane acrylate oligomer is preferably a urethane acrylate oligomer having 4 or less functional groups, and more preferably a urethane acrylate oligomer having 2 functional groups. The functionality refers to the number of (meth)acryloyl groups.

[0074] The urethane acrylate oligomer is not particularly limited, but examples thereof include polyether-based urethane acrylate oligomers having a urethane bond and an ether bond, polyester-based urethane acrylate oligomers having a urethane bond and an ester bond, and polycarbonate-based urethane acrylate oligomers having a urethane bond and a carbonate bond.

[0075] Commercially available urethane oligomers include, but are not limited to, CN929 (polyester-based aliphatic urethane acrylate, functional group number 3), CN962 (polyester-based aliphatic urethane acrylate, functional group number 2), CN963 (polyester-based aliphatic urethane acrylate, functional group number 2), CN964 (polyester-based aliphatic urethane acrylate, functional group number 2), CN965 (polyester-based aliphatic urethane acrylate, functional group number 2), CN968 (polyester-based aliphatic urethane acrylate, functional group number 6), CN980 (polyether-based aliphatic urethane acrylate, functional group number 2), CN981 (polyester (polyether-based aliphatic urethane acrylate, functional group 2), CN982 (polyester-based aliphatic urethane acrylate, functional group 2), CN983 (polyester-based aliphatic urethane acrylate, functional group 2), CN996 (polyether-based aliphatic urethane acrylate, functional group 2), CN9001 (polyester-based aliphatic urethane acrylate, functional group 2), CN9002 (polyester-based aliphatic urethane acrylate, functional group 2), CN9788 (polyester-based aliphatic urethane acrylate, functional group 2), CN9893 (polyether-based aliphatic urethane acrylate, functional group 2) (all from Sartomer Corporation) Company) product name), EBECRYL 230 (number of functional groups 2), 270 (number of functional groups 2), 5129 (number of functional groups 6), 8210 (number of functional groups 4), 8301 (number of functional groups 6), 8311 (number of functional groups 3), 8402 (number of functional groups 2), 8405 (4 functional groups), 8701 (3 functional groups), 8804 (2 functional groups), 8807 (2 functional groups), 9260 (3 functional groups), 9270 (2 functional groups), KRM 8200 (number of functional groups: 6), 8296 (number of functional groups: 3), 8452 (number of functional groups: 10) (DAICEL-CYTEC Company LTD.) and other aliphatic urethane acrylate oligomers, as well as aromatic urethane acrylate oligomers such as CN971 (polyester-based aromatic urethane acrylate, functional group number 3), CN972 (polyester-based aromatic urethane acrylate, functional group number 3), CN975 (polyester-based aromatic urethane acrylate, functional group number 6), CN978 (polyester-based aromatic urethane acrylate, functional group number 2), CN9782 (polyester-based aromatic urethane acrylate, functional group number 2), CN9783 (polyester-based aromatic urethane acrylate, functional group number 2) (all of which are product names manufactured by Sartomer Corporation), EBECRYL 210 (functional group number 2), 220 (functional group number 6) (all of which are product names manufactured by Daicel-Cytec Corporation).

[0076] The content of the oligomer relative to the total amount of the ink composition is not particularly limited, but is, for example, 0.1 to 10.0 mass %, 0.5 to 7.5 mass %, or 1.0 to 7.0 mass %.

[0077] 1.4.Colorants The ink composition of the present embodiment may or may not contain a coloring material. When the ink composition contains a coloring material, examples of the coloring material include dyes and pigments.

[0078] The dye is not particularly limited, but examples thereof include acid dyes, direct dyes, reactive dyes, and basic dyes. Specific examples of the dye include CI Acid Yellow 17, 23, 42, 44, 79, 142, CI Acid Red 52, 80, 82, 249, 254, 289, CI Acid Blue 9, 45, 249, CI Acid Black 1, 2, 24, 94, CI Food Black 1, 2, CI Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 1 44, 173, CI Direct Red 1, 4, 9, 80, 81, 225, 227, CI Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, CI Direct Black 19, 38, 51, 71, 154, 168, 171, 195, CI Reactive Red 14, 32, 55, 79, 249, CI Reactive Black 3, 4, 35. These dyes may be used alone or in combination of two or more.

[0079] Examples of pigments include, but are not limited to, inorganic pigments and organic pigments. Examples of inorganic pigments include, but are not limited to, carbon blacks such as furnace black, lamp black, acetylene black, and channel black, iron oxide, and titanium oxide. Examples of organic pigments include azo pigments such as insoluble azo pigments, condensed azo pigments, azo lakes, and chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, and polycyclic pigments such as quinophthalone pigments, dye chelates, dye lakes, nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments. These pigments may be used alone or in combination of two or more.

[0080] The carbon black is not particularly limited, and examples thereof include No. 2300, No. 900, MCF88, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, No. 2200B, etc. (all manufactured by Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (all manufactured by Carbon Columbia), Rega1 400R, Rega1 330R, Rega1 660R, Mogul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. (manufactured by Cabot Corporation). Examples of such inks include Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Special Black 5, Special Black 4A, and Special Black 4 (all manufactured by Degussa).

[0081] The white pigment is not particularly limited, but examples thereof include CI Pigment White 6, 18, and 21.

[0082] The yellow pigment is not particularly limited, but examples thereof include CI Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 16, 17, 24, 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108, 109, 110, 113, 114, 117, 120, 124, 128, 129, 133, 138, 139, 147, 151, 153, 154, 155, 167, 172, and 180.

[0083] The magenta pigment is not particularly limited, but examples thereof include CI Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48(Ca), 48(Mn), 57(Ca), 57:1, 88, 112, 114, 122, 123, 144, 146, 149, 150, 166, 168, 170, 171, 175, 176, 177, 178, 179, 184, 185, 187, 202, 209, 219, 224, and 245, and CI Pigment Violet. 19, 23, 32, 33, 36, 38, 43, and 50.

[0084] Examples of cyan pigments include, but are not limited to, CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:34, 15:4, 16, 18, 22, 25, 60, 65, and 66, and CI Vat Blue 4 and 60.

[0085] In addition, pigments other than magenta, cyan, and yellow are not particularly limited, but examples thereof include CI Pigment Green 7, 10, CI Pigment Brown 3, 5, 25, and 26, and CI Pigment Orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, and 63.

[0086] The content of the coloring material is not particularly limited to the total amount of the ink composition, but is, for example, 1.0 to 5.0% by mass.

[0087] Alternatively, the ink composition of the present embodiment may be a clear ink composition. A clear ink composition is an ink composition that does not contain or substantially does not contain a colorant. In the present embodiment, the term "substantially does not contain a colorant" is not particularly limited, but may mean, for example, that the content of the colorant relative to the total amount of the ink composition is 0.50% by mass or less, 0.25% by mass or less, 0.10% by mass or less, 0.05% by mass or less, 0.01% by mass or less, 0.001 to 0.500% by mass, 0.001 to 0.250% by mass, 0.001 to 0.100% by mass, 0.001 to 0.050% by mass, or 0.001 to 0.010% by mass.

[0088] When the ink composition of this embodiment is a clear ink composition, by containing the thioxanthone-based initiator, which is the liquid photoinitiator described above, and a fluorescent brightening agent, it is possible to improve the curability while suppressing yellowing of the coating film.

[0089] Dispersants The dispersant for dispersing the pigment is not particularly limited, and examples thereof include polyoxyalkylene polyalkylene polyamines, vinyl polymers and copolymers, acrylic polymers and copolymers, polyesters, polyamides, polyimides, polyurethanes, amino polymers, silicon-containing polymers, sulfur-containing polymers, fluorine-containing polymers, and epoxy resins as the main component. Commercially available dispersants include the Ajisper series manufactured by Ajinomoto Fine-Techno Co., Ltd., the Solsperse series available from Avecia Co. (Solsperse 36000 (acid value 45), Solsperse 32000 (amine value 35), etc.), the Disperbyk series manufactured by BYK Chemie (DISPERBYK 168, 180, etc.), and the Disparlon series manufactured by Kusumoto Chemicals Co., Ltd. These dispersants may be used alone or in combination of two or more.

[0090] The content of the dispersant relative to the total amount of the ink composition is not particularly limited, but is, for example, 0.1 to 3.0% by mass.

[0091] 1.5.Surfactants The surfactant is not particularly limited, but examples thereof include acetylene glycol-based surfactants, fluorine-based surfactants, and silicone-based surfactants. From the viewpoint of more effectively and reliably achieving the effects of the present invention, silicone-based surfactants are preferred.

[0092] Examples of silicone surfactants include, but are not limited to, BYK-UV3500, UV3570, and BYK350 (trade names manufactured by BYK Japan KK).

[0093] The content of the surfactant relative to the total amount of the ink composition is not particularly limited, but may be, for example, 0.1 to 1.0% by mass.

[0094] 1.6. Polymerization inhibitors The polymerization inhibitor is not particularly limited, but examples thereof include hydroquinones such as hydroquinone, hydroquinone monomethyl ether (MEHQ), 1-o-2,3,5-trimethylhydroquinone, and 2-tert-butylhydroquinone; catechols such as catechol, 4-methylcatechol, and 4-tert-butylcatechol; phenol, butylhydroxytoluene, butylhydroxyanisole, p-methoxyphenol, cresol, pyrogallol, 3,5-di-t-butyl-4-hydroxytoluene, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2' phenols such as methylenebis(4-ethyl-6-butylphenol) and 4,4'-thiobis(3-methyl-6-t-butylphenol); compounds having a 2,2,6,6-tetramethylpiperidine-N-oxyl skeleton such as 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, compounds having a 2,2,6,6-tetramethylpiperidine skeleton, compounds having a 2,2,6,6-tetramethylpiperidine-N-alkyl skeleton, and hindered amines such as compounds having a 2,2,6,6-tetramethylpiperidine-N-acyl skeleton. These polymerization inhibitors can be used alone or in combination of two or more.

[0095] The content of the polymerization inhibitor relative to the total amount of the ink composition is not particularly limited, but may be, for example, 0.05 to 1.0 mass %. When the content of the polymerization inhibitor is within the above range, the storage stability of the ink tends to be superior.

[0096] 1.7.Water The non-aqueous inkjet ink composition according to this embodiment does not contain water or does not substantially contain water. In this embodiment, the term "substantially does not contain water" is not particularly limited, but for example, the water content is 0.50 mass% or less, 0.25 mass% or less, 0.10 mass% or less, 0.05 mass% or less, or 0.01 mass% or less, relative to the total amount of the ink composition. In addition, it is not particularly limited, but for example, the water content is 0.001 to 0.500 mass%, 0.001 to 0.250 mass%, 0.001 to 0.100 mass%, 0.001 to 0.050 mass%, or 0.001 to 0.010 mass%.

[0097] In addition, in this specification, when the term "water" is used simply, it is not particularly limited, but examples thereof include ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water.

[0098] 1.8.Other Ingredients In addition to the above-mentioned components, the ink composition of the present embodiment may contain other known components that can be used in conventional ink compositions. The other components are not particularly limited, but may include, for example, slip agents, dissolution aids, viscosity adjusters, pH adjusters, antioxidants, preservatives, and corrosion inhibitors. These other components may be used alone or in combination of two or more.

[0099] 2. Method for producing non-aqueous inkjet ink composition The method for producing the non-aqueous inkjet ink composition of this embodiment is not particularly limited, and may, for example, involve mixing the above-mentioned components. In addition, in the method for producing the ink composition of this embodiment, a colorant dispersion liquid may be prepared by dispersing a pigment, which is a colorant, and a dispersant in a monomer, and the obtained colorant dispersion liquid may be mixed with the other components described above. The monomer is not limited to the above-mentioned polymerizable monomer.

[0100] The colorant dispersion liquid may be prepared in advance before preparing the ink composition, or may be prepared by mixing and dispersing the colorant dispersion liquid together with other components when preparing the ink composition.

[0101] 3. Recording medium The recording medium used for recording with the ink composition of this embodiment is not particularly limited, but examples thereof include absorbent recording media, low absorbent recording media, and non-absorbent recording media.

[0102] Examples of absorbent recording media include, but are not limited to, plain paper such as electrophotographic paper that has high ink permeability, inkjet paper (paper specifically for inkjet printers that has an ink absorbing layer made of silica particles or alumina particles, or an ink absorbing layer made of a hydrophilic polymer such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP)), fabrics, and the like.

[0103] The low-absorbency recording medium is not particularly limited, but examples thereof include art paper, coated paper, cast paper, and the like, which are used in general offset printing and have relatively low ink permeability.

[0104] Non-absorbent recording media are not particularly limited, but examples include plastic films and plates such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, polyurethane, etc.; metal plates such as iron, silver, copper, aluminum, etc.; or metal plates and plastic films produced by vapor deposition of these various metals, alloy plates such as stainless steel and brass, and recording media in which a plastic film such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, polyurethane, etc. is adhered (coated) to a paper substrate.

[0105] 4. Inkjet recording method The inkjet recording method of this embodiment (hereinafter also simply referred to as "recording method") includes an ink deposition step of ejecting the ink composition of this embodiment from an inkjet head and depositing it on a recording medium, and an irradiation step of irradiating the ink composition deposited on the recording medium with radiation, and may also include other steps, as necessary, such as a transport step of transporting the recording medium. Furthermore, the recording method of this embodiment does not include a nozzle clogging countermeasure step for preventing nozzle clogging of the head.

[0106] The recording method of the ink composition of the present embodiment is a method of printing for a long time without performing a process for preventing nozzle clogging. When a normal ink containing a solid photoinitiator is used, it is possible to efficiently produce a large amount of recorded material by printing for a long time without performing a process for preventing nozzle clogging, but there is a tendency for the increase in nozzle clogging in the head to be significant. However, by using the ink composition of the present embodiment, when printing for a long time without performing a process for preventing nozzle clogging, there is a tendency for the nozzle clogging in the head to be suppressed while efficiently producing a large amount of recorded material.

[0107] Note that "long period of time" here does not mean, for example, to exclude short period of printing, such as printing for a few minutes or seconds, going through a process to prevent dropped nozzles, and then printing for a few minutes or seconds again. The purpose of defining "long period of time" is to define, for example, a case where a line printer performs printing for a long period of time while transporting the recording medium without performing a process to prevent dropped nozzles, or a case where a serial printer performs printing for a long period of time when the carriage carrying the head moves to the edge of the recording medium without performing a process to prevent dropped nozzles.

[0108] In light of this, if a "long time" is defined numerically in this embodiment, it means 10 minutes or more. In addition, 20 minutes or more is preferable, 30 minutes or more is more preferable, 40 minutes or more is more preferable, and 50 minutes or more is even more preferable. The upper limit is not particularly limited, but is 24 hours or less, 18 hours or less, 12 hours or less, 6 hours or less, or 3 hours or less.

[0109] In addition, the term "printing without performing a nozzle missing countermeasure process" is not particularly limited, but may refer to, for example, printing without performing a nozzle missing countermeasure process such as pressurized nozzle cleaning, suction nozzle cleaning, or flushing during printing. By printing without performing a nozzle missing countermeasure process, it is possible to efficiently produce a large amount of recorded material, but there is a tendency for the nozzle missing of the head to increase significantly. However, by using the ink composition of the present embodiment, when printing without performing a nozzle missing countermeasure process, there is a tendency for the nozzle missing of the head to be suppressed while efficiently producing a large amount of recorded material.

[0110] 4.1.Ink application process In the ink deposition step, the ink composition of the present embodiment is ejected from an inkjet head and deposited on a recording medium. More specifically, a pressure generating means provided in the inkjet head is driven to eject the ink composition filled in the pressure generating chamber of the inkjet head from a nozzle.

[0111] Inkjet heads used in the ink application step include line heads that perform recording by a line method and serial heads that perform recording by a serial method.

[0112] In the line method using a line head, for example, an inkjet head having a width equal to or greater than the recording width of the recording medium is fixed to a recording device. Then, the recording medium and the inkjet head are moved relatively in the sub-scanning direction (the conveying direction of the recording medium, i.e., the direction perpendicular to the width direction of the recording medium), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with this movement to record an image on the recording medium.

[0113] In the serial method using a serial head, for example, the inkjet head is mounted on a carriage that can move in the width direction of the recording medium. The carriage is then moved in the main scanning direction (width direction of the recording medium), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with this movement to record an image on the recording medium.

[0114] The ink application process of the present embodiment may be carried out for a long period of time without carrying out a process for preventing missing nozzles. In this case, the term "long period of time" is not particularly limited, but is, for example, the same as that defined in the recording method of the ink composition of the present embodiment.

[0115] Furthermore, the term "performing the ink application process without carrying out a process for preventing missing nozzles" is not particularly limited, but for example, means applying an ink composition to a recording medium without carrying out a process for preventing missing nozzles.

[0116] During the ink application process, a process of lowering the oxygen concentration by introducing nitrogen may be included. By including this process, the curing property of the ink composition is improved, and the adhesion and resistance to wear of the recorded matter tend to be improved and odors tend to be reduced. In addition, it also tends to be possible to reduce the amount of photoinitiator added to the ink composition.

[0117] 4.2.Irradiation process In the irradiation step, the ink composition attached to the recording medium is irradiated with radiation. When irradiated with radiation, a polymerization reaction of the monomer is initiated, curing the composition and forming a coating film. If a photoinitiator is present at this time, it generates active species (initiation species) such as radicals, acids, and bases, and the polymerization reaction of the monomer is promoted by the function of the initiation species.

[0118] Here, examples of the radiation include ultraviolet rays, infrared rays, visible light, and X-rays. The radiation source is provided downstream of the inkjet head and irradiates the composition with the radiation. The radiation source is not particularly limited, but may be, for example, a UV-LED. By using such a radiation source, the device can be made smaller and the cost reduced. The UV-LED as the ultraviolet ray source is small, so it can be installed in the inkjet recording device.

[0119] 4.3.Measures to prevent missing nozzles The recording method of this embodiment does not include a step of preventing clogged nozzles. By using the ink composition of this embodiment, there is a tendency that clogged nozzles in a head can be suppressed even in the absence of a step of preventing clogged nozzles.

[0120] The nozzle clogging prevention process is not particularly limited, but examples thereof include pressurized nozzle cleaning, suction nozzle cleaning, and flushing. Air bubbles present in the vicinity of the nozzles can be discharged or removed from the vicinity of the nozzles to prevent nozzle clogging. Wiping, or other processes that wipe the ink ejection surface of the nozzles, are not included in the nozzle clogging prevention process because they are unlikely to be effective in preventing nozzle clogging.

[0121] 4.4.Transportation process The recording method of the present embodiment may include a conveying step. In the conveying step, the recording medium is conveyed in a predetermined direction in the recording device. More specifically, the recording medium is conveyed from the paper feed section to the paper discharge section of the recording device using a conveying roller or a conveying belt provided in the recording device. In the conveying process, the ink composition discharged from the inkjet head adheres to the recording medium, forming a recorded matter. The order and timing of the ink adhesion step, the irradiation step, the nozzle missing prevention step, and the conveying step are not particularly limited, and for example, the four steps may be performed simultaneously or alternately. In addition, some of the four steps may be performed simultaneously, and the remaining steps may be performed separately.

[0122] 5. Recording Equipment The inkjet recording apparatus of the present embodiment is not particularly limited, but may be, for example, a serial printer. In the case of a serial printer, an inkjet head having a length smaller than the width of the recording medium is provided, and the head moves to perform recording in multiple passes. In addition, in a serial printer, the head is mounted on a carriage that moves in a predetermined direction, and the ink composition is ejected onto the recording medium by moving the head in conjunction with the movement of the carriage. In this way, recording is performed in two or more passes. A pass is also called a main scan. A sub-scan is performed between passes to transport the recording medium. In other words, main scans and sub-scans are performed alternately.

[0123] The inkjet recording apparatus of the present embodiment is not particularly limited, but may be, for example, a line-type printer. Fig. 1 shows a schematic cross-sectional view of a line-type printer. As shown in Fig. 1, the line printer 1 includes a recording medium feed section 110, a conveying section 120, a recording section 130, a drying section 140, and a discharge section 150.

[0124] Here, the feeding section 110 feeds the recording medium F to the transport section 120, and the transport section 120 transports the recording medium F sent from the feeding section 110 to the recording section 130, the drying section 140, and the discharging section 150. Specifically, the transport section 120 has each feed roller, and transports the sent recording medium F in the feed direction Y.

[0125] The recording unit 130 also includes an inkjet head 131 that ejects a radiation-curable composition onto the recording medium F sent from the transport unit 120, and light sources 132, 133 that irradiate the deposited composition with radiation. In the case of a line-type printer, for example, the inkjet head 131 is provided as a line head having a length equal to or greater than the width of the recording medium, and the head is fixed without (almost) moving, and recording is performed in one pass (single pass). A pass is also called a scan.

[0126] In this embodiment, the transport speed of the recording medium and the distance between the inkjet head 131 and the light source 132 are adjusted so that the above recording method is possible. Although one inkjet head is shown in Fig. 1, the present invention is not limited to this, and multiple inkjet heads may be provided depending on the type of composition.

[0127] The drying section 140 is used to dry the composition attached to the recording medium as necessary, and has a drying section 141 (platen heater) provided opposite the recording section 130, and a drying section 142 provided downstream of the recording section 130. Furthermore, the discharge section 150 is provided so that the recorded matter can be discharged to the outside of the line printer 1. This may not be necessary if drying is not required.

[0128] In addition, the inkjet recording device of the present embodiment is not limited to the serial printer, and may be the line printer. The line printer has, for example, a line head, which is an inkjet head having a length equal to or greater than the recording width of the recording medium, and a moving mechanism for relatively moving the recording medium and the inkjet head in a direction perpendicular to the width direction of the recording medium, and performs recording on the recording medium in one scan. Line printers print continuously for a long period of time compared to serial printers, so that it is possible to efficiently produce a large amount of recorded matter, but there is a tendency for the increase in nozzle clogging of the head to be significant. However, by using the ink composition of the present embodiment, there is a tendency for nozzle clogging of the head to be suppressed while efficiently producing a large amount of recorded matter when printing continuously for a long period of time.

[0129] The inkjet recording apparatus of this embodiment may further include a control unit that executes a recording method for printing for a long period of time (for example, 10 minutes or more) without performing a process to prevent missing nozzles. EXAMPLES

[0130] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited to the following examples. In addition, unless otherwise specified, the experiments were carried out at room temperature (25°C) and 1 atm.

[0131] 1. Preparation of Non-Aqueous Inkjet Ink Composition First, the colorant, dispersant, and base monomer were weighed and placed in a pigment dispersion tank, and a ceramic bead mill with a diameter of 1 mm was placed in the tank and stirred to obtain a colorant dispersion liquid in which the colorant was dispersed in the base monomer. Next, the colorant dispersion liquid and the remaining components were placed in a stainless steel container for mixing in a mixing tank, and mixed and stirred at 25°C for 2 hours to obtain the composition shown in Figures 2 to 5, and further filtered through a 5 μm membrane filter to obtain non-aqueous inkjet ink compositions of Examples and Comparative Examples. The numerical values ​​of each component shown in each example in the figures represent the content (mass%) unless otherwise specified.

[0132] The abbreviations and product components used in Figures 2 to 5 are as follows. Note that blank spaces in Figures 2 to 5 indicate that the component was not used. Also, "-" in Figures 2 to 5 indicates that the evaluation was not performed. PB15:3 (CI Pigment Blue 15:3) Carbon black (product name "MA-100", manufactured by Mitsubishi Chemical Corporation) Dispersant 1 (product name "Solsperse36000", manufactured by Avecia) Dispersant 2 (product name "Solsperse32000", manufactured by Avecia) PEA (product name "Viscoat #192", manufactured by Osaka Organic Chemical Industry Co., Ltd., phenoxyethyl acrylate) BZA (product name "Viscoat #160", manufactured by Osaka Organic Chemical Industry Ltd., benzyl acrylate) IBXA (Osaka Organic Chemical Industry, Ltd., isobornyl acrylate) CTFA (product name "Viscoat #200", manufactured by Osaka Organic Chemical Industry Co., Ltd., cyclic trimethylolpropane formal acrylate) · VMOX (BASF, vinylmethyloxazolidinone) 4-HBA (Osaka Organic Chemical Industry Co., Ltd., 4-hydroxybutyl acrylate) · VEEA (2-(2-vinyloxyethoxy)ethyl acrylate, manufactured by Nippon Shokubai Co., Ltd.) DPGDA (product name "Viscoat #310HP", manufactured by Osaka Organic Chemical Industry Ltd., tripropylene glycol diacrylate) 16HDDA (product name "Viscoat #230", manufactured by Osaka Organic Chemical Industry Co., Ltd., 1,6-hexanediol diacrylate) A-DPH (Dipentaerythritol hexaacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.) CN9893 (Sartomer, bifunctional urethane acrylate oligomer) Omnirad TPO-L (manufactured by IGM Resins BV, ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate: acylphosphine type) ·ESACURE KIP 150 (manufactured by IGM Resins BV, oligomer of 2-hydroxy-2-methyl-1[4-(1-methylvinyl)phenyl]propanone: hydroxyketone type) Speedcure 7010 (manufactured by Sartomer, CAS No. 1003567-83-6: thioxanthone type) Omnipol TX (manufactured by IGM Resins BV, CAS No. 813452-37-8: thioxanthone type) Omnirad 819 (IGM Resins BV, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide: acylphosphine type) Omnirad TPO (manufactured by IGM Resins BV, diphenyl-2,4,6-trimethylbenzoylphosphine oxide: acylphosphine type) Speedcure DETX (Sartomer, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propane: thioxanthone type) TELALUX KCB (Clariant Japan, 1,4-bis(2-benzoxazolyl)naphthalene: solid at 20°C under 1 atmosphere) TELALUX OB (Clariant Japan, 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene: solid at 20°C under 1 atmosphere) BYK-UV3500 (BYK Additives & Instruments, polyether-modified polydimethylsiloxane with acryloyl groups) ·LA-7RD (ADEKA, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl) MEHQ (product name "p-methoxyphenol", manufactured by Kanto Chemical Co., Ltd., hydroquinone monomethyl ether)

[0133] 2. Evaluation Method In Figures 2 to 5, the evaluation marked with "-" indicates that the evaluation was not performed.

[0134] 2.1. Viscosity characteristics (initial ink viscosity) Using a rotational viscometer (product name "Rheometer MCR-301", manufactured by Anton Paar), the viscosity of the ink compositions of the Examples and Comparative Examples immediately after preparation was measured at room temperature (25° C.) in accordance with JIS Z 8803. [Evaluation Criteria] A: The viscosity is less than 20 mPa·s. B: Viscosity is 20 mPa·s or more and less than 30 mPa·s. C: Viscosity is 30 mPa·s or more and less than 40 mPa·s. D: Viscosity is 40 mPa·s or more.

[0135] 2.2.Continuous printing stability A line-type inkjet printer was prepared with an inkjet head having a nozzle diameter of 20 μm, a drive frequency of 15 kHz, and an ink ejection volume of 7 ng per ejection, with 360 nozzles per head. Continuous ejection was performed from this head (360 nozzles) at the above ejection frequency. Inspection was performed every 5 minutes to see if ink was being ejected from all nozzles, and continuous ejection was performed for a maximum of 50 minutes in total. Nozzle cleaning or flushing was performed during this time. [Evaluation Criteria] A: There are no non-discharge nozzles after 50 minutes of continuous discharge. B: No non-discharge nozzles after 20 minutes of continuous discharge. C: There is a non-discharge nozzle during continuous discharge for less than 20 minutes.

[0136] 2.3. Curability The ink compositions of the examples and comparative examples were applied to a substrate in an amount that would result in a film thickness of 8 μm (film thickness after curing), and the curing energy required for curing was confirmed. The ink compositions were rubbed with a cotton swab and judged from the state of the cotton swab whether or not they had cured. Irradiation was performed using an LED with a peak wavelength of 395 nm, with an irradiation intensity of 1100 mW / cm. 2 The substrate was a PET film (PET50A PL Shin [product name], manufactured by Lintec Corporation). The irradiated coating film (composition film) was rubbed 10 times with a cotton swab under a load of 100 g, and the curing energy (irradiation energy) at which the film was no longer scratched was determined.

[0137] The irradiation energy [mJ / cm 2 ] is the irradiance [mW / cm ] on the irradiated surface irradiated by the light source 2 The irradiation intensity was measured using a UV intensity meter UM-10 and a light receiving unit UM-400 (both manufactured by KONICA MINOLTA SENSING, INC.). [Evaluation Criteria] AA: The curing energy at which the film no longer scratches is 200 mJ / cm 2 The following is the result. A: The curing energy at which the surface no longer scratches is 200 mJ / cm 2 Super 300mJ / cm 2 The following is the result. B: The curing energy at which the surface no longer scratches is 300 mJ / cm 2 Super 400mJ / cm 2 The following is the result. C: The curing energy at which the surface no longer scratches is 400 mJ / cm 2 It's super.

[0138] 2.4.Flexibility The ink compositions of the examples and comparative examples were applied to a PET film (PET50A PL Shin [product name], manufactured by Lintec Corporation) in an amount that resulted in a film thickness of 8 μm (film thickness after curing), and were irradiated with radiation under the same conditions as those for the curing evaluation until the ink composition of the examples and comparative examples was no longer scratched, thereby curing the ink compositions of the examples and comparative examples to produce a cured film on the PET film. The cured film was peeled off from the PET film and cut into a strip of 1 cm width and 8 cm length to produce a test piece. The elongation of the test piece was evaluated using a tensile tester (TENSILON, manufactured by ORIENTEC Corporation). The elongation was the value at the time when a crack occurred when pulled at 5 mm / min. The value was calculated from {(length at crack-length before stretching) / length before stretching×100}. [Evaluation Criteria] A: The elongation rate is 100% or more. B: The elongation rate is 50% or more and less than 100%. C: The elongation rate is less than 50%.

[0139] 2.5.Adhesion The ink compositions of the examples and comparative examples were applied to a PET film (PET50A PL Thin [product name], manufactured by Lintec Corporation) in an amount to give a film thickness of 8 μm (film thickness after curing), and were irradiated with radiation under the same conditions as those for the curing evaluation until the ink composition was no longer scratched, thereby curing the ink compositions of the examples and comparative examples to produce a recorded product. Evaluation of the recorded product was performed using the cross-cut method in accordance with JIS K5600-5-6.

[0140] More specifically, the blade of a cutting tool was applied perpendicular to the coating film with a cutter, and a grid of 10 x 10 grids was created with a grid of 1 mm spacing between the cuts. A transparent adhesive tape (25 mm wide) of about 75 mm in length was applied to the grid, and the tape was rubbed with a finger sufficiently so that the cured film could be seen through. Next, within 5 minutes of applying the tape, the tape was peeled off from the cured film at an angle close to 60° in 0.5 to 1.0 seconds, and the state of the grid was visually observed. The evaluation criteria are as follows. [Evaluation Criteria] A: There is no peeling in the 10x10 grid section. B: Of the 10x10 grid, squares 1 to 10 are peeled off. C: Of the 10x10 grid, 11 to 50 squares are peeled off. D: More than 51 squares of the 10x10 grid are peeled off.

[0141] 2.6.Low temperature precipitation 40 g of the ink compositions of the Examples and Comparative Examples were placed in a 50 mL glass bottle and left to stand at -20°C for 48 hours, then returned to room temperature (25°C) and filtered through a 10 µm filter, and any foreign matter on the filter was visually inspected. [Evaluation Criteria] A: There are a lot of foreign objects on the filter. B: There is a small amount of foreign matter on the filter. C: There is no foreign matter on the filter.

[0142] 2.7. Color Tone Evaluation of Clear Ink Composition A 10 μm coating of the ink composition of the example was prepared using a bar coater, and cured by irradiating radiation so that the energy of the curing was twice the energy at which the coating was no longer scratched in the curability evaluation. The color of the cured coating was measured using a GretagMacbeth colorimeter "Spectrolino" and evaluated based on the measured b*. The larger the b*, the more yellowing the coating has become. [Evaluation Criteria] A: b*<1. B: 1≦b*<2. C: 2≦b*.

[0143] 3. Evaluation results 2 to 5, it was found that the ink compositions of the examples all suppressed missing nozzles in the head and were excellent in continuous printing stability, compared to the ink compositions of the comparative examples. [Explanation of symbols]

[0144] 1... line printer, 110... feeding section, 120... conveying section, 130... recording section, 131... inkjet head, 132... light source, 133... light source, 140... drying section, 141... drying section, 142... drying section, 150... discharge section, F... recording medium, Y... feed direction

Claims

1. A non-aqueous inkjet ink composition for use in a recording method for long-term printing without performing a process for preventing nozzle clogging, comprising: a polymerizable monomer and a liquid photoinitiator that is liquid at 20° C.; the content of a solid photoinitiator that is solid at 20° C. is 1.5% by mass or less based on the total amount of the non-aqueous inkjet ink composition; A non-aqueous ink-jet ink composition.

2. the content of the solid photoinitiator is 0.5% by mass or less based on the total amount of the non-aqueous ink-jet ink composition; The non-aqueous ink-jet ink composition of claim 1.

3. the solid photoinitiator contains a fluorescent brightening agent, and the content of the fluorescent brightening agent is 0.5% by mass or less based on the total amount of the non-aqueous ink-jet ink composition; The non-aqueous ink-jet ink composition of claim 1.

4. The liquid photoinitiator comprises an acylphosphine-based initiator; The non-aqueous ink-jet ink composition of claim 1.

5. The acylphosphine initiator comprises ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate; The non-aqueous ink-jet ink composition of claim 4.

6. the content of the ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate is 7% by mass or more based on the total amount of the non-aqueous ink-jet ink composition; The non-aqueous ink-jet ink composition of claim 5.

7. the liquid photoinitiator further comprises a thioxanthone-based initiator; The non-aqueous ink-jet ink composition of claim 4.

8. the polymerizable monomer comprises 2-(2-vinyloxyethoxy)ethyl acrylate; the content of the 2-(2-vinyloxyethoxy)ethyl acrylate is 10 to 40% by mass based on the total amount of the non-aqueous ink-jet ink composition; The non-aqueous ink-jet ink composition of claim 1.

9. the polymerizable monomer comprises vinylmethyloxazolidinone, the content of the vinylmethyloxazolidinone is 5 to 30% by mass based on the total amount of the non-aqueous inkjet ink composition; The non-aqueous ink-jet ink composition of claim 1.

10. A clear ink composition, The non-aqueous ink-jet ink composition of claim 1.

11. an inkjet head having a width equal to or greater than the recording width of a recording medium; a moving mechanism that moves the recording medium and the inkjet head relatively in a direction perpendicular to a width direction of the recording medium, The inkjet head ejects the nonaqueous inkjet ink composition according to any one of claims 1 to 11 onto the recording medium. Inkjet recording device.

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