Inkjet ink composition and method for recording inkjet print

Abstract

To provide an inkjet ink composition which is excellent in adhesion to a recording medium and suppresses odor.SOLUTION: The inkjet ink composition contains a monomer and a resin. The monomer does not contain an aromatic group-containing monomer or contains the aromatic group-containing monomer in an amount of less than 35 mass% based on the total amount of the inkjet ink composition. The resin contains at least one of: an acrylic resin (A) having a hydroxy group or a carboxy group; and a resin (B) having one or more structural units selected from the group consisting of predetermined structural units.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ink-jet ink composition and an ink-jet printing method. [Background technology]

[0002] The inkjet recording method is capable of recording high-resolution images using a relatively simple device and has been rapidly developing in various fields. Among these, various studies have been conducted on adhesion and the like. For example, Patent Document 1 discloses an active energy ray-curable ink for inkjet printing containing polymerizable monomers, wherein the polymerizable monomers contain 95 to 99.99 wt % of monofunctional monomers and 0.01 to 5 wt % of polyfunctional monomers relative to the total weight of the polymerizable monomers. It is known that when a 10 μm-thick cured film formed using the active energy ray-curable ink is stretched at a temperature of 170°C and a strain rate of 2 / min, the ductility of the cured film exceeds 120%, thereby providing an active energy ray-curable ink for inkjet printing that has excellent adhesion to plastic substrates that require bendability and stretchability, excellent processability, and excellent abrasion resistance and rub resistance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2007 / 013368 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the ink composition disclosed in Patent Document 1 is applied to a plastic recording medium by inkjet printing, the adhesion between the ink composition coating and the recording medium is still insufficient, and there is room for improvement. In addition, there is also a problem with the odor of the ink composition coating. [Means for solving the problem]

[0005] The inkjet ink composition of the present invention comprises a monomer and a resin, wherein the monomer does not contain an aromatic group-containing monomer, or, if it contains an aromatic group-containing monomer, the content of the aromatic group-containing monomer is less than 35 mass% relative to the total amount of the inkjet ink composition, and the resin comprises at least one of an acrylic resin (A) having either a hydroxy group or a carboxy group, or a resin (B) having one or more structural units selected from the group consisting of structural units represented by the following formulas (1), (2), and (3): [ka]

[0006] The inkjet printing recording method of the present invention includes a discharge step of discharging the inkjet ink composition from an inkjet head and depositing the inkjet ink composition on a non-absorbent recording medium, and a curing step of curing the inkjet ink composition deposited on the non-absorbent recording medium. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a table showing the results of examples. [Figure 2] 10 is a table showing the results of comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. However, the embodiment described here is an example for explaining the present invention, and the present invention is not limited thereto. That is, the technical scope of the present invention should be defined based on the description of the claims, and the present invention can be practiced by arbitrarily modifying the following embodiment within the scope of the gist thereof. In this specification, for example, the expression of a numerical range such as "1 to 100" includes both the lower limit "1" and the upper limit "100". The same applies to the expression of other numerical ranges.

[0009] In this specification, "(meth)acryloyl" means at least one of acryloyl and its corresponding methacryloyl, "(meth)acrylate" means at least one of acrylate and its corresponding methacrylate, and "(meth)acrylic" means at least one of acrylic and its corresponding methacrylic.

[0010] 1. Inkjet ink composition The inkjet ink composition according to this embodiment (hereinafter simply referred to as the "ink composition") contains a monomer and a resin, wherein the monomer does not contain an aromatic group-containing monomer, or, if it contains an aromatic group-containing monomer, the content of the aromatic group-containing monomer is less than 35 mass% relative to the total amount of the ink composition, and the resin contains at least one of an acrylic resin (A) having either a hydroxy group or a carboxy group, or a resin (B) having one or more structural units selected from the group consisting of structural units represented by the following formulas (1), (2), and (3): [ka]

[0011] Increasing the content of the aromatic group-containing monomer in the ink composition tends to result in a noticeable odor in the coating film obtained using the ink composition, while reducing the content of the aromatic group-containing monomer reduces the adhesion of the ink composition to a recording medium.

[0012] In contrast, in this embodiment, low odor control is achieved by reducing the content of aromatic group-containing monomers, and the use of a specific acrylic resin (A) or resin (B) also improves the adhesion of the ink composition to a recording medium. Note that the improvement in adhesion due to the use of a specific resin is thought to be due to the polar groups as described above acting at the interface between the ink composition and the recording medium to improve adhesion, but the mechanism is not limited to this.

[0013] The ink composition according to this embodiment is an ink composition that is ejected from an inkjet head by an inkjet method, and the ink composition may be a radiation-curable inkjet ink composition that is cured by exposure to radiation. Hereinafter, a radiation-curable ink composition will be described as one embodiment of the ink composition, but the composition according to this embodiment may also be a composition other than an ink composition, for example, a composition used for 3D modeling.

[0014] The radiation-curable inkjet composition is cured by irradiation with radiation. Examples of radiation include ultraviolet light, electron beams, infrared light, visible light, and X-rays. As the radiation, ultraviolet light is preferred because radiation sources are readily available and widely used, and materials suitable for curing by ultraviolet radiation are readily available and widely used.

[0015] 1.1.Resin The resin of this embodiment contains at least one of an acrylic resin (A) having either a hydroxy group or a carboxy group, or a resin (B) having one or more structural units selected from the group consisting of structural units represented by the following formulas (1), (2), and (3): [ka]

[0016] The resin may contain at least one of the acrylic resin (A) and the resin (B), and the type thereof is not particularly limited. The resin may contain a resin other than the acrylic resin (A) or the resin (B). The resin may be used alone or in combination of two or more. The use of such a resin can improve the adhesion required when the inkjet ink composition is applied to a recording medium. Adhesion to non-absorbent recording media is particularly improved.

[0017] The weight-average molecular weight (Mw) of the resin is preferably 20,000 or less, 15,000 or less, 10,000 or less, or 5,000 or less. The weight-average molecular weight (Mw) of the resin is preferably 1,000 or more, 2,000 or more, 3,000 or more, or 4,000 or more. When the weight-average molecular weight of the resin is 20,000 or less, the viscosity of the ink composition tends to be low, and the ink composition tends to have excellent ejection properties. Furthermore, when the weight-average molecular weight of the resin is within the above range, the ink composition tends to have excellent adhesion to a recording medium. The weight-average molecular weight (Mw) of the resin can be measured using gel permeation chromatography (GPC). For example, it can be determined using tetrahydrofuran as an eluent and polystyrene as a standard substance.

[0018] The resin content is preferably 10% by mass or less, 8% by mass or less, or 6% by mass or less, relative to the total amount of the ink composition. The resin content is preferably 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. When the resin content is 10% by mass or less, the viscosity of the ink composition can be kept low, which tends to further improve the ejection properties. Furthermore, when the resin content is 1% by mass or more, the adhesion between the ink composition and a recording medium tends to further improve.

[0019] 1.1.1. Acrylic resin (A) The acrylic resin (A) of the present embodiment is not particularly limited as long as it is an acrylic resin having at least one hydroxy group or one carboxy group in one molecule, and may have other functional groups.

[0020] Here, acrylic resin is a general term for polymers obtained by polymerizing at least an acrylic monomer such as (meth)acrylic acid or a (meth)acrylic acid ester as one component, and examples thereof include homopolymers obtained from acrylic monomers, copolymers of acrylic monomers with other monomers, etc. Examples of copolymers of acrylic monomers with other monomers include acrylic-vinyl resins, which are copolymers of acrylic monomers and vinyl monomers.

[0021] The glass transition temperature (Tg) of the acrylic resin (A) is preferably −70 to 140° C., −65 to 110° C., or −60 to 80° C. When the glass transition temperature (Tg) of the acrylic resin (A) is within the above range, adhesion tends to be further improved.

[0022] When the acrylic resin (A) has a hydroxy group, the hydroxyl value (OHV) of the acrylic resin (A) is preferably 1 to 120 KOHmg / g, 5 to 90 KOHmg / g, 10 to 60 KOHmg / g, or 15 to 30 KOHmg / g. When the hydroxyl value (OHV) is within the above range, adhesion tends to be further improved.

[0023] When the acrylic resin (A) has a carboxy group, the acid value (AV) of the acrylic resin (A) is preferably 30 to 250 KOHmg / g, 40 to 200 KOHmg / g, 50 to 150 KOHmg / g, or 60 to 100 KOHmg / g. When the acid value (AV) is within the above range, adhesion tends to be further improved.

[0024] The acid value and hydroxyl value can be measured using potentiometric titration. For example, this can be done based on "JIS K 0070 Testing Methods for Acid Value, Saponification Value, Ester Value, Iodine Value, Hydroxyl Value, and Unsaponifiable Matter of Chemical Products." An example of such a potentiometric titrator is the automatic potentiometric titrator AT610 (manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

[0025] Known examples of commercially available acrylic resins having hydroxy groups include the ARUFON (registered trademark) UH-2000 series (UH-2000, UH-2041, UH-2170, UH-2190) manufactured by Toagosei Co., Ltd.

[0026] Known commercially available acrylic resins having a carboxy group include, for example, ARUFON (registered trademark) UC-3000 series (UC-3000, UC-3080, UC-3510) and UF-5000 series (UF-5080) manufactured by Toagosei Co., Ltd.

[0027] 1.1.2.Resin (B) Resin (B) may have one or more structural units selected from the group consisting of structural units represented by the following formulas (1), (2), and (3), and may have other structural units in addition to these structural units. [ka]

[0028] Such resin (B) is not particularly limited, but examples thereof include polyol resins having a structural unit represented by formula (1) and ketone aldehyde condensation resins having a structural unit represented by formula (2) or (3).

[0029] The glass transition temperature (Tg) of the resin (B) is preferably −70 to 140° C., −30 to 120° C., 0 to 110° C., or 40 to 100° C. When the glass transition temperature (Tg) of the resin (B) is within the above range, adhesion tends to be further improved.

[0030] The hydroxyl value (OHV) of the resin (B) having the structural unit represented by formula (1) is preferably 400 KOHmg / g or less, 350 KOHmg / g or less, 300 KOHmg / g or less, 250 KOHmg / g or less, 200 KOHmg / g or less, 150 KOHmg / g or less, 100 KOHmg / g or less, or 50 KOHmg / g or less. The hydroxyl value (OHV) of the resin (B) having the structural unit represented by formula (1) is preferably 1 KOHmg / g or more, 5 KOHmg / g or more, 10 KOHmg / g or more, 25 KOHmg / g or more, 50 KOHmg / g or more, or 100 KOHmg / g or more.

[0031] Known commercially available resins (B) include, for example, TEGO (registered trademark) Variplus SK, Variplus AP, and Variplus CA manufactured by EVONIK.

[0032] 1.2.Monomer The monomer of this embodiment is not particularly limited and may be a monofunctional monomer having one polymerizable functional group or a polyfunctional monomer having multiple polymerizable functional groups. Each monomer may be used alone or in combination of two or more types.

[0033] Examples of monomers that can be used in the inkjet composition of this embodiment include saturated aliphatic group-containing monomers, nitrogen-containing monomers, oxygen-containing monomers, and hydroxyl group-containing monomers. Aromatic group-containing monomers may be included, but are preferably not included. Furthermore, other monomers may be included as needed, instead of or in addition to these. The other monomers are not particularly limited, but conventionally known monomers having a polymerizable functional group, particularly a polymerizable functional group having a carbon-carbon unsaturated double bond, can be used.

[0034] The content of the monofunctional monomer is preferably 35 to 90 mass %, 45 to 90 mass %, and particularly preferably 70 to 90 mass %, relative to the total amount of monomers. When the content of the monofunctional monomer is 35 mass % or more relative to the total amount of monomers, the curability tends to be excellent, and when it is 90 mass % or less, the odor of the coating film tends to be further reduced.

[0035] The content of the polyfunctional monomer relative to the total amount of monomers is preferably 10 to 65 mass%, 10 to 55 mass%, or 10 to 30 mass%. When the content of the polyfunctional monomer relative to the total amount of monomers is within the above range, the adhesion of the coating film tends to be improved.

[0036] 1.2.1. Aromatic group-containing monomers It is preferable that the ink jet composition does not contain an aromatic group-containing monomer, but if an aromatic group-containing monomer is contained, its content is less than 35% by mass relative to the total amount of the ink jet composition. It is preferable that the content is small. The aromatic group-containing monomer is not particularly limited as long as it has an aromatic group and one or more polymerizable functional groups, and examples thereof include aromatic group-containing monofunctional monomers having one polymerizable functional group and aromatic group-containing polyfunctional monomers having multiple polymerizable functional groups. The aromatic group-containing monomer may be used alone or in combination of two or more.

[0037] The aromatic group-containing monomer is not particularly limited, but examples thereof include phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, alkoxylated 2-phenoxyethyl (meth)acrylate, ethoxylated nonylphenyl (meth)acrylate, alkoxylated nonylphenyl (meth)acrylate, p-cumylphenol EO-modified (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate.

[0038] When an aromatic group-containing monomer is included, the content of the aromatic group-containing monomer is less than 35% by mass, preferably 20% by mass or less, 15% by mass or less, 10% by mass or less, or 5% by mass or less, relative to the total amount of the ink composition. The lower limit of the content of the aromatic group-containing monomer is not particularly limited, and the lower the content, the more preferable, and it may not be included at all (0% by mass). When the content of the aromatic group-containing monomer is less than 35% by mass, the odor of the cured product of the ink composition tends to be suppressed. When the aromatic group-containing monomer is not included, the odor can be further suppressed.

[0039] 1.2.2. Nitrogen-containing monomers The nitrogen-containing monomer is not particularly limited and may be a nitrogen-containing monofunctional monomer having one polymerizable functional group or a nitrogen-containing polyfunctional monomer having multiple polymerizable functional groups. A nitrogen-containing monofunctional monomer is preferred, and a nitrogen-containing monofunctional monomer having a nitrogen-containing heterocyclic structure is more preferred. Here, the nitrogen-containing heterocyclic structure may be a heterocyclic structure further containing an oxygen atom within the nitrogen-containing heterocyclic structure. The nitrogen-containing monomer may be used alone or in combination of two or more.

[0040] Examples of the nitrogen-containing monomer include nitrogen-containing vinyl monomers such as vinylmethyloxazolidinone (VMOX), N-vinylcaprolactam, N-vinylformamide, N-vinylcarbazole, N-vinylacetamide, and N-vinylpyrrolidone; nitrogen-containing acrylate monomers such as acryloylmorpholine; and nitrogen-containing acrylamide monomers such as (meth)acrylamide, N-hydroxymethyl(meth)acrylamide, diacetone acrylamide, N,N-dimethyl(meth)acrylamide, and dimethylaminoethyl acrylate benzyl chloride quaternary salt.

[0041] Among these, it is preferable to contain either a nitrogen-containing vinyl monomer or a nitrogen-containing acrylate monomer, and more preferable are monomers having a nitrogen-containing heterocyclic structure such as vinylmethyloxazolidinone (VMOX), N-vinylcaprolactam, N-vinylcarbazole, N-vinylpyrrolidone, or acryloylmorpholine, and among these, it is more preferable to contain a nitrogen-containing vinyl monomer having an oxazolidine group, and it is particularly preferable to contain vinylmethyloxazolidinone (VMOX).

[0042] The use of such nitrogen-containing monomers tends to further improve the curability of the coating film. Furthermore, nitrogen-containing monofunctional vinyl monomers having a nitrogen-containing heterocyclic structure, such as vinylmethyloxazolidinone (VMOX), tend to further improve the curability of the coating film.

[0043] The content of the nitrogen-containing monomer relative to the total amount of the ink composition is preferably 5 to 50 mass%, 10 to 40 mass%, 15 to 35 mass%, or 20 to 30 mass%. When the content of the nitrogen-containing monomer is within the above range, the adhesion and curability of the coating film tend to be further improved.

[0044] 1.2.3. Hydroxyl-containing monomers The hydroxyl group-containing monomer is not particularly limited and may be a hydroxyl group-containing monofunctional monomer having one polymerizable functional group or a hydroxyl group-containing polyfunctional monomer having multiple polymerizable functional groups, and is preferably a hydroxyl group-containing monofunctional monomer. The hydroxyl group-containing monomer may be used alone or in combination of two or more.

[0045] The hydroxyl group-containing monomer is not particularly limited, but examples thereof include hydroxyalkyl methacrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0046] Among these, 4-hydroxybutyl (meth)acrylate is preferred, and 4-hydroxybutyl acrylate (4-HBA) is particularly preferred. Use of such a hydroxyl group-containing monomer tends to improve the adhesion and curability of the coating film.

[0047] The content of the hydroxyl group-containing monomer relative to the total amount of the ink composition is preferably 3 to 17 mass%, 5 to 15 mass%, or 7 to 13 mass%. When the content of the hydroxyl group-containing monomer is within the above range, the adhesion and curability of the coating film tend to be further improved.

[0048] 1.2.4. Vinyl ether group-containing (meth)acrylates The vinyl ether group-containing (meth)acrylate is not particularly limited, and examples thereof include compounds represented by the following formula (4): By including such a vinyl ether group-containing (meth)acrylate, the viscosity of the composition tends to decrease and the ejection stability tends to be improved. In addition, the curability of the composition is improved, and the improved curability also allows for a higher recording speed. CH2=CR 1 -COOR 2 -O-CH=CH-R 3 (4) (In the formula, R 1 is a hydrogen atom or a methyl group, and 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.

[0049] In the above formula (4), R 2Examples of the divalent organic residue having 2 to 20 carbon atoms and 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 and having an oxygen atom via an ether bond and / or an ester bond in its structure, 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 and having an oxygen atom via an ether bond in its structure, such as an oxyethylene group, an oxy-n-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, a compound having a glycol ether chain in which R2 is an alkylene group having 2 to 9 carbon atoms and having an oxygen atom via an ether bond in the structure, such as an oxyethylene group, an oxy-n-propylene group, an oxyisopropylene group, or an oxybutylene group, is more preferred.

[0050] In the above formula (4), R 3 Suitable examples of the monovalent organic residue having 1 to 11 carbon atoms and represented by the formula (I) 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 methyl or ethyl groups, and aromatic groups having 6 to 8 carbon atoms, such as phenyl and benzyl groups, are preferably used.

[0051] When each of the above organic residues is a group that may be substituted, the substituent is divided into a group containing carbon atoms and a group not containing carbon atoms. First, when the above substituent is a group containing carbon atoms, the carbon atom is counted in the number of carbon atoms of the organic residue. Examples of the group containing carbon atoms include, but are not limited to, a carboxyl group and an alkoxy group. Next, examples of the group not containing carbon atoms include, but are not limited to, a hydroxyl group and a halo group.

[0052] Specific examples of the compound of formula (4) 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-(vinyloxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyethoxy)ethyl (meth)acrylate (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 in that it is easy to balance the curability and viscosity of the composition. In this embodiment, 2-(2-vinyloxyethoxy)ethyl acrylate is also referred to as VEEA.

[0053] The content of the vinyl ether group-containing (meth)acrylate relative to the total amount of the ink composition is preferably 0.1 to 40 mass%, 0.1 to 30 mass%, 1 to 25 mass%, 1 to 20 mass%, or 2 to 15 mass%. When the content of the vinyl ether group-containing (meth)acrylate relative to the total amount of the ink composition is within the above range, the viscosity of the composition tends to decrease, and the ejection stability tends to be further improved.

[0054] 1.2.5. Other monofunctional monomers In the ink composition of this embodiment, examples of other monofunctional monomers include aliphatic group-containing monofunctional monomers and oxygen-containing monofunctional monomers.

[0055] 1.2.5.1. Aliphatic group-containing monofunctional monomers The aliphatic group-containing monofunctional monomer is not particularly limited, but examples thereof include alicyclic group-containing monofunctional monomers such as isobornyl (meth)acrylate (IBXA), tertbutylcyclohexanol acrylate (TBCHA), and 2-(meth)acrylic acid-1,4-dioxaspiro[4,5]dec-2-ylmethyl; linear or branched aliphatic group-containing monofunctional monomers such as isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, isomyristyl (meth)acrylate, isostearyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, butoxyethyl (meth)acrylate, and tetrahydrofurfuryl (meth)acrylate; and lactone-modified flexible (meth)acrylate. Among these, alicyclic group-containing monofunctional monomers are preferred. Use of such an aliphatic group-containing monofunctional monomer tends to further improve the curability of the composition.

[0056] The content of the aliphatic group-containing monofunctional monomer relative to the total amount of the ink composition is preferably 4 to 30 mass%, 6 to 20 mass%, or 8 to 15 mass%. When the content of the aliphatic group-containing monofunctional monomer is within the above range, the adhesion and curability of the coating film tend to be further improved.

[0057] 1.2.5.2. Oxygen-containing monofunctional monomers The oxygen-containing monofunctional monomer is not particularly limited, but may be, for example, a monomer having a cyclic structure containing oxygen. The monomer having a cyclic structure containing oxygen may be an oxygen-containing monomer having a cyclic ether structure. The oxygen-containing monomer having a cyclic ether structure may be cyclic trimethylolpropane formal acrylate (CTFA), cyclic trimethylolpropane formal methacrylate, tetrahydrofurfuryl acrylate (THFA), and (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate (MEDOL-10), among which cyclic trimethylolpropane formal acrylate (CTFA) and (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate (MEDOL-10) are preferred. When using such an oxygen-containing monofunctional monomer having a cyclic ether structure, the adhesion and curability of the coating film tend to be improved.

[0058] The content of the oxygen-containing monofunctional monomer relative to the total amount of the ink composition is preferably 10 to 50 mass%, 15 to 45 mass%, 20 to 40 mass%, or 25 to 35 mass%. When the content of the oxygen-containing monofunctional monomer is within the above range, the adhesion and curability of the coating film tend to be further improved.

[0059] 1.2.6. Other polyfunctional monomers The ink composition of this embodiment may contain other polyfunctional monomers in addition to the above monomers. Examples of other polyfunctional monomers include, but are not limited to, polyfunctional (meth)acrylates.

[0060] 1.2.6.1. Multifunctional (meth)acrylates The polyfunctional (meth)acrylate is not particularly limited, and examples thereof include dipropylene glycol diacrylate (DPGDA), diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol dimethacrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, EO (ethylene oxide) adduct di(meth)acrylate of bisphenol A, and PO (propylene oxide) di(meth)acrylate of bisphenol A. Examples of the acrylate include bifunctional (meth)acrylates such as adduct di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate; and trifunctional or higher polyfunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate (ADPH), ditrimethylolpropane tetra(meth)acrylate, glycerin propoxy tri(meth)acrylate, caprolactone-modified trimethylolpropane tri(meth)acrylate, pentaerythritol ethoxy tetra(meth)acrylate, and caprolactam-modified dipentaerythritol hexa(meth)acrylate (ADPH). In particular, among bifunctional (meth)acrylates, polyfunctional propylene glycol diacrylate is preferred, and dipropylene glycol diacrylate (DPGDA) or tripropylene glycol di(meth)acrylate (TPGDA) is more preferred due to their excellent curability and adhesion.

[0061] The content of the polyfunctional (meth)acrylate relative to the total amount of the ink composition is preferably 1 to 50 mass%, 2.5 to 40 mass%, 5 to 35 mass%, or 7.5 to 30 mass%. When the content of the polyfunctional (meth)acrylate relative to the total amount of the composition is within the above range, the adhesion of the coating film tends to be improved.

[0062] 1.3.Other Ingredients The ink composition according to this embodiment may further contain additives such as an oligomer, a dispersant, a polymerization inhibitor, and a slip agent, as necessary.

[0063] Oligomers The ink composition according to this embodiment may contain an oligomer. Here, an oligomer refers to a polymerizable compound, which is a polymerizable compound having one or more functional groups. The polymerizable compound referred to here is not limited to the polymerizable compounds described above. In this specification, in addition to the above definitions, a polymerizable compound having a molecular weight of 1000 or less is referred to as a monomer, and a polymerizable compound having a molecular weight of more than 1000 is referred to as an oligomer.

[0064] The oligomer is 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 derived from a polymerizable compound having an epoxy group.

[0065] Regarding oligomers, it is preferable that the ink composition does not contain oligomers having aromatic groups, and if it does contain such oligomers, the content of such oligomers is preferably 20% by mass or less, and 10% by mass or less, and particularly preferably no oligomers having aromatic groups are contained, relative to the total amount of the ink composition. By keeping the content within the above range, odor of the coating film tends to be suppressed.

[0066] 1.3.2. Photopolymerization initiator The ink composition according to this embodiment may further contain a photopolymerization initiator. The photopolymerization initiator may be used alone or in combination of two or more types.

[0067] The photopolymerization initiator is not particularly limited as long as it generates active species upon irradiation with radiation, and examples thereof include known photopolymerization initiators such as acylphosphine oxide-based photopolymerization initiators, alkylphenone-based photopolymerization initiators, titanocene-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators. Among these, acylphosphine oxide-based photopolymerization initiators are preferred. Use of such photopolymerization initiators further improves the curability of the ink composition, and in particular tends to further improve the curability in a curing process using UV-LED light.

[0068] The acylphosphine oxide photopolymerization initiator is not particularly limited, but examples thereof include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate.

[0069] Commercially available examples of such acylphosphine oxide photopolymerization initiators include IRGACURE 819 (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide), IRGACURE 1800 (a mixture of bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and 1-hydroxy-cyclohexyl-phenyl ketone in a mass ratio of 25:75), IRGACURE TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide), and IRGACURE TPO-L (ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate) (all manufactured by BASF).

[0070] The thioxanthone-based photopolymerization initiator is not particularly limited, but examples thereof include thioxanthone, 2-methylthioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-chlorothioxanthone, and 2,4-diethylthioxanthone.

[0071] Commercially available thioxanthone-based photopolymerization initiators include, for example, KAYACURE DETX-S (2,4-diethylthioxanthone, trade name of Nippon Kayaku Co., Ltd.), Speedcure DETX (2,4-diethylthioxanthone, trade name of Lambson Co., Ltd.), and KAYACURE ITX (2- / 4-isopropylthioxanthone, trade name of Nippon Kayaku Co., Ltd.).

[0072] The content of the photopolymerization initiator relative to the total amount of the ink composition is preferably 3 to 14 mass%, 5 to 12 mass%, or 7.5 to 10 mass%. When the content of the photopolymerization initiator is within the above range, the curability of the composition and the solubility of the photopolymerization initiator tend to be further improved.

[0073] 1.3.3. Polymerization inhibitors The ink composition according to this embodiment may further contain a polymerization inhibitor. The polymerization inhibitor may be used alone or in combination of two or more.

[0074] Examples of the polymerization inhibitor include, but are not limited to, p-methoxyphenol, hydroquinone monomethyl ether (MEHQ), 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, hydroquinone, cresol, t-butylcatechol, 3,5-di-t-butyl-4-hydroxytoluene, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-butylphenol), and 4,4'-thiobis(3-methyl-6-t-butylphenol), bis(2,2,6,6-tetramethyl-4-piperidyl-1-oxyl) sebacate (bisTEMPO sebacate), and hindered amine compounds.

[0075] The content of the polymerization inhibitor is preferably 0.05 to 1% by mass, and more preferably 0.05 to 0.5% by mass, relative to the total amount of the ink composition.

[0076] 1.3.4.Slip agents The ink composition according to this embodiment may further contain a slip agent. The slip agent may be used alone or in combination of two or more.

[0077] The slip agent is preferably a silicone surfactant, more preferably a polyester-modified silicone or a polyether-modified silicone. Examples of polyester-modified silicones include BYK-347, 348, BYK-UV3500, 3510, and 3530 (all manufactured by BYK Additives & Instruments). Examples of polyether-modified silicones include BYK-3570 (manufactured by BYK Additives & Instruments).

[0078] The content of the slip agent is preferably 0.01 to 2% by mass, and more preferably 0.05 to 1% by mass, based on the total amount of the ink composition.

[0079] Dispersants The ink composition of this embodiment may further contain a dispersant to improve the dispersibility of the colorant, etc. The dispersant may be used alone or in combination of two or more types.

[0080] The dispersant is not particularly limited, but examples thereof include dispersants commonly used in preparing pigment dispersions, such as polymer dispersants, etc. Specific examples thereof include those containing one or more of 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.

[0081] Commercially available polymer dispersants include the Ajisper series manufactured by Ajinomoto Fine-Techno Co., Ltd., the Solsperse series (Solsperse 36000, etc.) available from Avecia and Noveon, the Disperbic series manufactured by BYK Additives & Instruments, and the Disparlon series manufactured by Kusumoto Chemicals Co., Ltd.

[0082] The content of the dispersant is preferably 0.1 to 2 mass %, 0.1 to 1 mass %, or 0.1 to 0.5 mass %, relative to the total amount of the ink composition.

[0083] Colorants The ink composition of this embodiment may further contain a coloring material. The coloring material may be used alone or in combination of two or more types.

[0084] The coloring material is not particularly limited, but examples thereof include pigments and dyes. One type of coloring material may be used alone, or two or more types may be used in combination.

[0085] The content of the colorant relative to the total amount of the ink composition is preferably 0.5 to 15% by mass, more preferably 1.0 to 10% by mass, and even more preferably 2.0 to 7% by mass. When the content of the colorant is within the above range, color development tends to be further improved.

[0086] The ink composition of this embodiment may contain a pigment as a colorant. The pigment is not particularly limited, but examples thereof include organic pigments such as azo pigments (including, for example, azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments), polycyclic pigments (such as phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments), nitro pigments, nitroso pigments, and aniline black; inorganic pigments such as carbon black (such as furnace black, thermal lamp black, acetylene black, and channel black), metal oxides, metal sulfides, and metal chlorides; and extender pigments such as calcium carbonate and talc.

[0087] The pigment may be added to the ink composition as a pigment dispersion obtained by dispersing the pigment in water with a dispersant, or as a pigment dispersion obtained by dispersing a self-dispersing surface-treated pigment in which hydrophilic groups have been introduced to the pigment particle surface using a chemical reaction (hereinafter also referred to as a "self-dispersing pigment") in water, or as a pigment dispersion obtained by dispersing a polymer-coated pigment (hereinafter also referred to as a "resin-dispersed pigment") in water. Among these, it is preferable to include a self-dispersing pigment. The use of a self-dispersing pigment tends to further improve the water repellency of the nozzle plate and the intermittent printing stability.

[0088] The pigment and dispersant constituting the pigment dispersion may each be used alone or in combination of two or more.

[0089] The ink composition of this embodiment may contain a dye as a colorant. The dye is not particularly limited, but examples include acid dyes such as CI Acid Yellow, CI Acid Red, CI Acid Blue, CI Acid Orange, CI Acid Violet, and CI Acid Black; basic dyes such as CI Basic Yellow, CI Basic Red, CI Basic Blue, CI Basic Orange, CI Basic Violet, and CI Basic Black; direct dyes such as CI Direct Yellow, CI Direct Red, CI Direct Blue, CI Direct Orange, CI Direct Violet, and CI Direct Black; reactive dyes such as CI Reactive Yellow, CI Reactive Red, CI Reactive Blue, CI Reactive Orange, CI Reactive Violet, and CI Reactive Black; and disperse dyes such as CI Disperse Yellow, CI Disperse Red, CI Disperse Blue, CI Disperse Orange, CI Disperse Violet, and CI Disperse Black. The dyes may be used alone or in combination.

[0090] 1.4. Recording Media The ink composition according to this embodiment can be suitably used as an ink composition for ejection onto a recording medium in inkjet printing. The recording medium is not particularly limited, but examples thereof include absorbent recording media and non-absorbent recording media. Among these, non-absorbent recording media are preferred.

[0091] Examples of absorbent recording media include plain paper such as electrophotographic paper, inkjet paper, art paper used in general offset printing, coated paper, and cast paper.

[0092] Examples of non-absorbent recording media include plastics such as polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polycarbonate, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, and polyvinyl acetal, as well as plastics with treated surfaces, glass, metal, and wood.

[0093] The form of the recording medium is not particularly limited, and examples thereof include film, board, and cloth.

[0094] Among these recording media, the ink composition according to this embodiment is preferably used on a non-absorbent recording medium, and plastic films are particularly preferred. In particular, polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), and polyolefin (PO) provide excellent coating film adhesion. While the mechanism of this effect is not limited, it is believed that the polar resin in the ink composition interacts with the polar interface of the recording medium to improve adhesion between the ink composition and the recording medium. Polyethylene terephthalate (PET), polypropylene (PP), and polyethylene (PE) are particularly preferred. Furthermore, if the recording medium is a shrink film that shrinks when exposed to heat or other factors, the ink composition provides excellent adhesion and the recording medium's processability is improved.

[0095] Here, non-absorbent or low-absorbent recording media can also be classified by the wettability of the recording surface with water. For example, a recording medium can be characterized by dropping a 0.5 μL droplet of water onto the recording surface of the recording medium and measuring the rate of decrease in contact angle (comparing the contact angle 0.5 milliseconds after impact with the contact angle 5 seconds after impact). More specifically, non-absorbent refers to a rate of decrease of less than 1%, low-absorbent refers to a rate of decrease of 1% or more but less than 5%, and absorbent refers to a rate of decrease of 5% or more. The contact angle can be measured using a portable contact angle meter PCA-1 (manufactured by Kyowa Interface Science Co., Ltd.) or the like.

[0096] 1.5. Method for producing ink composition The production (preparation) of the ink composition is carried out by mixing the components contained in the ink composition and stirring the mixture to ensure a sufficiently uniform mixture. In this embodiment, the preparation of the ink composition preferably includes a step of subjecting a mixture of a photopolymerization initiator and at least a portion of the monomers to at least one of ultrasonic treatment and heating treatment during the preparation process. This reduces the amount of dissolved oxygen in the prepared ink composition, resulting in an ink composition with excellent ejection stability and storage stability. The mixture may contain at least the above components, and may further contain other components contained in the ink composition, or may contain all of the components contained in the ink composition. The monomer contained in the mixture may be at least a portion of the monomers contained in the ink composition.

[0097] 2. Inkjet printing method The inkjet printing recording method according to this embodiment includes a discharge step of discharging the ink composition according to this embodiment using a predetermined inkjet head and depositing it onto a recording medium, and a curing step of irradiating the ink composition deposited on the recording medium with radiation to cure the ink composition.

[0098] 2.1.Corona treatment process The inkjet printing recording method according to this embodiment may further include a corona treatment step in addition to the steps described above. In the corona treatment step, corona treatment is performed on the surface of the recording medium onto which the ink composition will adhere in the subsequent ejection step. By performing corona treatment, adhesion between the corona-treated recording medium and the ink composition in the ejection step is improved. The conditions for performing corona treatment are not particularly limited and may be set appropriately depending on the type of recording medium, etc.

[0099] For example, when a plastic film is used as the recording medium, the adhesion between the recording medium and the ink composition may be insufficient. As a pre-step of the ejection step, the recording medium may be subjected to a corona treatment to modify the surface of the recording medium, thereby improving the adhesion between the ink composition and the recording medium.

[0100] 2.2.Discharge process In the ejection step, the heated ink composition is ejected from a liquid ejection head and deposited on a recording medium. More specifically, a pressure generating means is driven to eject the ink composition filled in the pressure generating chamber of the liquid ejection head from the nozzle. This ejection method is also called an ink jet method. The ejection conditions in the ejection step may be adjusted as appropriate depending on the physical properties of the ink composition.

[0101] The recording medium is not particularly limited and may be any of the above-mentioned recording media. For the ink composition according to this embodiment, a non-absorbent recording medium is preferred, and a plastic film is more preferred.

[0102] 2.3.Curing process In the curing process, the ink composition attached to the recording medium is irradiated with radiation. When irradiated with radiation, a polymerization reaction of the monomers is initiated, curing the composition and forming a coating film. If a photopolymerization initiator is present, it generates active species (initiation species) such as radicals, acids, and bases, and the polymerization reaction of the monomers is accelerated by the function of these initiation species. If a photosensitizer is present, it absorbs radiation and becomes excited, and upon contact with the photopolymerization initiator, it accelerates the decomposition of the photopolymerization initiator, thereby achieving a more rapid curing reaction.

[0103] Examples of the radiation include ultraviolet light, infrared light, visible light, and X-rays. The radiation source is provided downstream of the liquid jet head and irradiates the composition with the radiation. The radiation source is not particularly limited, but examples thereof include ultraviolet light-emitting diodes. Use of such a radiation source can reduce the size and cost of the device. Because ultraviolet light-emitting diodes as an ultraviolet light source are small, they can be installed inside the inkjet device.

[0104] For example, ultraviolet light-emitting diodes can be attached to a carriage (both ends along the medium width direction and / or the medium transport direction side) on which a liquid jet head that ejects the ink composition is mounted. Furthermore, due to the composition of the inkjet composition described above, curing can be achieved at low energy and high speed. The irradiation energy is calculated by multiplying the irradiation time by the irradiation intensity. Therefore, the irradiation time can be shortened, and the printing speed can be increased. On the other hand, the irradiation intensity can also be reduced. This reduces the temperature rise of the printed material, which also leads to a reduced odor of the cured film.

[0105] The thickness of the coating of the ink composition cured in the curing step is not particularly limited, but is preferably 10 μm or less, and particularly preferably 5 μm or less.

[0106] 2.4. Winding process The inkjet printing recording method according to this embodiment may further include a winding step in addition to the steps described above. In the winding step, the ink composition is applied to the recording medium, and the cured recorded matter is wound up by a winding device. The winding device may be a known device such as a roller, and is not particularly limited. [Example]

[0107] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples.

[0108] 1. Preparation of Ink Composition First, the colorant, dispersant, and a portion of each monomer were weighed and placed in a pigment dispersion tank. A 1 mm diameter ceramic bead mill was then placed in the tank and stirred to obtain a pigment dispersion in which the colorant was dispersed in the monomer. Next, the remaining monomer, resin, photopolymerization initiator, polymerization inhibitor, and slip agent were placed in a stainless steel mixing tank, and mixed and stirred to completely dissolve the components, as shown in Figures 1 and 2. The pigment dispersion obtained above was then added, and the mixture was further mixed and stirred at room temperature for an hour. The resulting mixture was then filtered through a 5 μm membrane filter to obtain the ink composition of each example. Note that the numerical values ​​for each component shown in each example in the tables represent mass % unless otherwise specified.

[0109] The abbreviations and product components used in Figures 1 and 2 are as follows:

[0110] <Resin> Resin A-1 (product name "UC-3000", manufactured by Toagosei Co., Ltd., glass transition temperature: 65°C, weight average molecular weight: 10,000) Resin A-2 (product name "UH-2000", manufactured by Toagosei Co., Ltd., glass transition temperature: -55°C, weight average molecular weight: 11,000) Resin A-3 (product name "UP-1000", manufactured by Toagosei Co., Ltd., glass transition temperature: -77°C, weight average molecular weight: 3000) Resin B-1 (product name "Variplus SK, manufactured by EVONIK", glass transition temperature: 90°C, hydroxyl value: 325 mg KOH / g) Resin B-2 (product name "Variplus AP", manufactured by EVONIK, glass transition temperature: 50°C, hydroxyl value: 5 mg KOH / g) Resin B-3 (product name "Variplus CA", manufactured by EVONIK, glass transition temperature: 70°C, hydroxyl value: 110 mg KOH / g) <Monomer> BZA (product name "Viscoat #160, manufactured by Osaka Organic Chemical Industry Ltd., benzyl acrylate") PEA (product name "Viscoat #192, manufactured by Osaka Organic Chemical Industry Co., Ltd., phenoxyethyl 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) 4HBA (Mitsubishi Chemical Corporation, 4-hydroxybutyl acrylate) VMOX (BASF, vinylmethyloxazolidinone) VEEA (2-(2-vinyloxyethoxy)ethyl acrylate, manufactured by Nippon Shokubai Co., Ltd.) DPGDA (product name "SR508", manufactured by Sartomer Corporation, dipropylene glycol diacrylate) ADPH (Shin-Nakamura Chemical Co., Ltd., Pentaerythritol Hexaacrylate) <Photopolymerization initiator> Irg.819 (trade name "IRGACURE 819" manufactured by BASF, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide) TPO-L (trade name "IRGACURE TPO-L", manufactured by BASF, ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate) DETX (trade name "Speedcure DETX", Lambson, 2,4-diethylthioxanthen-9-one) <Polymerization inhibitor> MEHQ (product name "p-methoxyphenol", manufactured by Kanto Chemical Co., Ltd., hydroquinone monomethyl ether) <Slip agent> BYK-UV3500 (BYK Additives & Instruments, polyether-modified polydimethylsiloxane with acryloyl groups) <Dispersant> Solsperse 36000 (Lubrizol polymer dispersant) <Colorant> PB-15:3 (Pigment Blue 15:3)

[0111] 2. Evaluation Method 2.1. Evaluation of 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 composition was rubbed with a cotton swab and the state of the cotton swab was used to determine whether or not it had cured. The irradiation was performed using an LED with a peak wavelength of 395 nm, with an irradiation intensity of 1100 mW / cm. 2 The substrate used was a PET film (PET50A PL Thin [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, and the curability was evaluated according to the following evaluation criteria.

[0112] 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: Irradiation energy is 200mJ / cm 2 The following is the result. A: Irradiation energy is 200mJ / cm 2 Super 300mJ / cm 2 The following is the result. B: Irradiation energy is 300 mJ / cm 2 Super 400mJ / cm 2 The following is the result. C: Irradiation energy is 400 mJ / cm 2 It's super.

[0113] 2.2.Evaluation of 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 the film was irradiated with radiation under the same conditions as those for the curing evaluation until the film was no longer scratched, thereby curing the ink compositions of the Examples and Comparative Examples to produce recorded matter. These recorded matter were evaluated using the cross-cut method in accordance with JIS K5600-5-6.

[0114] More specifically, a cutter was used to make a 10 x 10 grid by placing the blade of a cutting tool perpendicular to the cured film and creating squares with 1 mm spacing between cuts. A transparent adhesive tape (25 mm wide) approximately 75 mm long was attached to the grid, and the tape was rubbed thoroughly with a finger so that the cured film was visible through it. Next, within 5 minutes of application, the tape was firmly peeled off the cured film at an angle close to 60° in 0.5 to 1.0 seconds, and the condition of the grid was visually observed. The evaluation criteria were as follows: A (excellent), B (good), and C (unacceptable) were considered pass / fail. A: No peeling of the cured film was observed. B: Peeling of the cured film was observed in less than 50% of the lattice. C: Peeling of the cured film was observed in more than 50% of the lattice.

[0115] 2.3.Odor evaluation The resulting inkjet compositions were each smelled and evaluated for odor. In order to reduce individual differences in olfaction, 10 people tested the same sample and assigned a score for odor as follows. The average score of the 10 people was calculated, and the odor was evaluated on a four-level scale from A to D based on this average score. A rating of A (excellent), B (good), or C (fair) was considered a pass, and D (poor) was considered a fail. 0: No odor or barely noticeable odor. 1 point: Slight odor is detected. 2 points: The odor is easily detected. 3 points: A strong odor is felt. A: The average score is between 0 and 0.5 points. B: Average score is 0.5 or more and less than 1.5 points C: Average score is 1.5 or more and less than 2.5 points D: Average score is 2.5 or more and less than 3.0 points

[0116] 2.4. Viscosity evaluation Immediately after preparation, the viscosity of each ink composition was measured using a rotational viscometer (product name "Rheometer MCR-301", manufactured by Anton Paar) at 25°C in accordance with JIS Z 8803. The evaluation criteria were as follows: A: Viscosity is less than 20 mPa·s. B: Viscosity is 20 mPa·s or more and less than 40 mPa·s. C: Viscosity is 40 mPa·s or more.

[0117] 3. Evaluation Results The composition and evaluation results of the ink composition used in each example are shown in Figures 1 and 2. As can be seen from Figure 1, the ink compositions of Examples 1 to 16, which did not contain an aromatic group-containing monomer or, if they contained an aromatic group-containing monomer, the content of the aromatic group-containing monomer was less than 35 mass% relative to the total amount of the ink composition, and which contained at least one of an acrylic resin (A) having either a hydroxy group or a carboxy group, or a resin (B) having one or more structural units selected from the group consisting of predetermined structural units, were evaluated to have good levels of both adhesion and odor.

[0118] In detail, when comparing each Example with Comparative Examples 1 to 4 and 6, it is shown that each Example has improved adhesion compared to Comparative Examples 1 to 4, which used a resin that does not have a polar group such as a hydroxy group, a hydroxy group, or a ketone group, and Comparative Example 6, which did not use a resin.

[0119] Furthermore, when comparing each Example with Comparative Example 5, it is shown that each Example has a more suppressed odor than Comparative Example 5, in which the content of aromatic group-containing monomer is 35 mass% or more relative to the ink composition.

Claims

1. a monomer and a resin, the monomers do not include an aromatic group-containing monomer, or if the monomers include an aromatic group-containing monomer, the content of the aromatic group-containing monomer is less than 35% by mass with respect to the total amount of the inkjet ink composition; The resin includes at least one of an acrylic resin (A) having a hydroxy group or a carboxy group, and a resin (B) having one or more structural units selected from the group consisting of structural units represented by the following formulas (1), (2), and (3): Inkjet ink composition. 【Chemical 1】

2. The weight average molecular weight of the resin is 5000 or less. The ink-jet ink composition of claim 1 .

3. the content of the resin is 10% by mass or less relative to the total amount of the inkjet ink composition; The ink-jet ink composition of claim 1 .

4. the monomer comprises vinylmethyloxazolidinone; The ink-jet ink composition of claim 1 .

5. the monomer comprises a monofunctional monomer, The content of the monofunctional monomer is 40 to 90% by mass based on the total amount of the monomers. The ink-jet ink composition of claim 1 .

6. The monomer includes a hydroxyl group-containing monomer. The ink-jet ink composition of claim 1 .

7. The monomer includes a vinyl ether group-containing (meth)acrylate represented by the following formula (4): The ink-jet ink composition of claim 1 . CH 2 =CR 1 -COOR 2 -O-CH=CH-R 3 ・・・(4) (In the formula, R 1 is a hydrogen atom or a methyl group, and 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.

8. the content of the aromatic group-containing monomer is 20% by mass or less relative to the total amount of the inkjet ink composition; The ink-jet ink composition of claim 1 .

9. For printing on non-absorbent recording media, The ink-jet ink composition of claim 1 .

10. an ejection step of ejecting the inkjet ink composition according to any one of claims 1 to 9 from an inkjet head and depositing the ink onto a non-absorbent recording medium; a curing step of curing the inkjet ink composition attached to the non-absorbent recording medium, Inkjet printing method.

11. a winding step of winding up the non-absorbent recording medium to which the ink-jet ink composition adheres after curing, In the curing step, the thickness of the coating film of the cured product of the inkjet ink composition is 10 μm or less. The recording method according to claim 10.

12. a corona treatment step of performing corona treatment on a surface of a non-absorbent recording medium onto which the inkjet ink composition is to be attached, before the ejection step; The recording method according to claim 10.

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