Radiation-curable ink jet composition and recording method

Abstract

To provide a radiation ray-curable inkjet composition and an inkjet recording method capable of obtaining a coating film which has flexibility, adhesiveness and scratch resistance.SOLUTION: There is provided a radiation ray-curable inkjet composition which comprises a polymerizable compound containing a monofunctional monomer and a polyfunctional monomer, wherein the content of the monofunctional monomer is 90 mass% or more based on the total amount of the polymerizable compound, the weighted average of the glass transition temperature of a homopolymer of each of the polymerizable compounds with the content mass ratio of each of the polymerizable compounds taken as a weight is 42°C or more and the weighted average of an SP value of each of the polymerizable compounds with the content mass ratio of each of the polymerizable compounds taken as a weight is 9.5 to 10.0.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a radiation-curable ink jet composition and a recording method. [Background technology]

[0002] Inkjet recording methods are capable of recording high-resolution images using relatively simple equipment and have been rapidly developing in various fields. In the process, various studies have been conducted on adhesion to substrates, etc. For example, Patent Document 1 discloses that by combining a monofunctional monomer having an SP value of 8.5 or less with a monofunctional monomer having an SP value of 10.3 or more, electrostatic bonding with polar groups on the substrate surface can be formed, thereby achieving strong adhesion while maintaining good affinity with the substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-79383 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of investigations by the present inventors, it has been found that the method described in Patent Document 1 still sometimes results in insufficient adhesion. [Means for solving the problem]

[0005] The radiation-curable inkjet composition of the present invention contains a polymerizable compound containing a monofunctional monomer and a polyfunctional monomer, wherein the content of the monofunctional monomer is 90 mass % or more relative to the total amount of the polymerizable compounds, the weighted average of the glass transition temperatures of homopolymers of the polymerizable compounds, where the content mass ratio of each polymerizable compound is used as a weight, is 42°C or more, and the weighted average of the SP values ​​of the polymerizable compounds, where the content mass ratio of each polymerizable compound is used as a weight, is 9.5 to 10.0.

[0006] The radiation-curable ink jet composition preferably has a weighted average glass transition temperature of 48° C. or higher.

[0007] In the radiation-curable ink jet composition, the content of the polyfunctional monomer is preferably 0.01 to 10% by mass relative to the total amount of the polymerizable compounds.

[0008] In the radiation-curable ink jet composition, the polyfunctional monomer preferably contains a vinyl ether group-containing (meth)acrylic acid ester represented by the following formula (1). CH2=CR 1 -COOR 2 -O-CH=CH-R 3 ··· (1) (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.

[0009] The recording method of the present invention also includes a discharge step of discharging the radiation-curable ink jet composition from an ink jet head and depositing it on a recording medium, and an irradiation step of irradiating the ink composition deposited on the recording medium with radiation.

[0010] Furthermore, the recorded matter of the present invention is a recording medium to which a cured product of the above-mentioned radiation-curable ink jet composition is adhered. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following describes in detail an 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 spirit of the present invention.

[0012] In this specification, "(meth)acryloyl" refers to acryloyl and its corresponding methacryloyl. and "(meth)acrylate" means at least one of acrylate and methacrylate. The term "methacrylate" refers to at least one of the acrylates and the corresponding methacrylates. ) "acrylic" means acrylic and / or its corresponding methacrylic do.

[0013] 1. Radiation-curable inkjet composition The radiation-curable inkjet composition according to this embodiment (hereinafter also simply referred to as "composition") contains polymerizable compounds including a monofunctional monomer and a polyfunctional monomer, and the content of the monofunctional monomer is 90% by mass or more relative to the total amount of the polymerizable compounds. The weighted average of the glass transition temperatures of the homopolymers of the polymerizable compounds, where the content mass ratio of each polymerizable compound is used as a weight, is 42°C or more. The weighted average of the SP values ​​of the polymerizable compounds, where the content mass ratio of each polymerizable compound is used as a weight, is 9.5 to 10.0.

[0014] Thus, in this embodiment, by setting the content of the monofunctional monomer within a predetermined range, the flexibility and adhesion of the coating film can be improved, and by configuring the polymerizable compounds so that the weighted average of the glass transition temperatures of the homopolymers of each polymerizable compound falls within a predetermined range, it is also possible to improve the scratch resistance of the coating film. Furthermore, in such a composition, by adjusting the weighted average of the SP values ​​of each polymerizable compound, it is possible to achieve excellent adhesion to a wide variety of substrates.

[0015] The radiation-curable ink jet composition according to this embodiment is a composition that is ejected from an ink jet head by an ink jet method. Hereinafter, a radiation-curable ink composition will be described as one embodiment of the radiation-curable ink jet composition, but the composition according to this embodiment may be a composition other than an ink composition, for example, a composition used for 3D modeling.

[0016] The radiation-curable inkjet composition of this embodiment is cured by irradiation with radiation. Examples of radiation include ultraviolet light, 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.

[0017] The components that may be contained in the radiation-curable ink jet composition according to this embodiment, its physical properties, and a production method will be described below.

[0018] 1.1. Polymerizable compounds The polymerizable compound includes a monofunctional monomer having one polymerizable functional group and a polyfunctional monomer having multiple polymerizable functional groups, and may optionally include an oligomer having one or multiple polymerizable functional groups. Each polymerizable compound may be used alone or in combination of two or more.

[0019] In this embodiment, the weighted average of the glass transition temperatures of the homopolymers of the polymerizable compounds, where the content mass ratio of each polymerizable compound is used as a weight, is 42°C or higher, preferably 44°C or higher, more preferably 46°C or higher, and even more preferably 48°C or higher. Having a weighted average of the glass transition temperatures of 42°C or higher can improve the scratch resistance of the coating film at room temperature. Furthermore, there is no particular upper limit to the weighted average of the glass transition temperatures, but it is preferably 60°C or lower, more preferably 55°C or lower, and even more preferably 55°C or lower.

[0020] The weighted average of the glass transition temperature is calculated as Tg. All The glass transition temperature of the homopolymer of each polymerizable compound is Tg N The content mass ratio of the polymerizable compound is X N(% by mass). N is a number starting from 1 depending on the type of polymerizable compound contained in the radiation-curable inkjet composition. For example, when three types of polymerizable compounds are used, Tg1, Tg2, and Tg3 are obtained. The glass transition temperature of the homopolymer of each polymerizable compound can be obtained from the safety data sheet (SDS) or catalog information of that polymerizable compound. The weighted average Tg of the glass transition temperatures is All is the glass transition temperature Tg calculated for each polymerizable compound. N and content X N Therefore, the following equation (2) holds true. Tg All =ΣTg N ×X N ···(2)

[0021] In this embodiment, the weighted average of the SP values ​​of the polymerizable compounds, where the content mass ratio of each polymerizable compound is used as a weight, is 9.5 to 10.0. By having the weighted average of the SP values ​​within this range, it is possible to improve adhesion to recording media made of various materials. According to the studies of the present inventors, it has been found that even when a polymerizable compound with a high SP value and a polymerizable compound with a low SP value are present, adhesion is poor. Further studies have shown that in order to improve adhesion to recording media made of various materials, it is necessary to set the weighted average of the SP values ​​within a specific numerical range.

[0022] We will explain how to calculate the weighted average of the SP values. All , the SP value of each polymerizable compound is SP N The content mass ratio of the polymerizable compound is X N (% by mass). N is a number starting from 1 depending on the type of polymerizable compound contained in the radiation-curable inkjet composition. For example, when three types of polymerizable compounds are used, SP1, SP2, and SP3 are produced. The SP value of each polymerizable compound can be obtained from the safety data sheet (SDS) or catalog information of that polymerizable compound. The weighted average SP of the SP values ​​is All is the SP calculated for each polymerizable compound. N and content XN Therefore, the following equation (2) holds true. SP All =ΣSP N ×X N ···(2)

[0023] The weighted average of the glass transition temperature and the weighted average of the SP value can be adjusted by the glass transition temperature and the SP value of the polymerizable compound used and the content mass ratio of the polymerizable compound used.

[0024] 1.1.1. Monofunctional Monomers The monofunctional monomer of this embodiment is not particularly limited, but examples thereof include monofunctional acrylates having a polycyclic hydrocarbon group, nitrogen-containing monofunctional monomers, aromatic group-containing monofunctional monomers, and saturated aliphatic group-containing monofunctional monomers. Other monofunctional monomers may also be included as necessary. The other monofunctional monomers are not particularly limited, but conventionally known monofunctional monomers having a polymerizable functional group, particularly a polymerizable functional group having a carbon-carbon unsaturated double bond, can be used.

[0025] The content of the monofunctional monomer is 90% by mass or more, preferably 92% by mass or more, and more preferably 94% by mass or more, relative to the total amount of the polymerizable compounds. When the content of the monofunctional monomer is 90% by mass or more, relative to the total amount of the polymerizable compounds, the flexibility and adhesion of the coating film are further improved. There is no particular upper limit for the content of the monofunctional monomer, but it is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less, relative to the total amount of the polymerizable compounds. When the content of the monofunctional monomer is 99% by mass or less, relative to the total amount of the polymerizable compounds, the abrasion resistance tends to be further improved.

[0026] Furthermore, the content of the monofunctional monomer is preferably 78% by mass or more, more preferably 80% by mass or more, and even more preferably 82% by mass or more, relative to the total amount of the composition. When the content of the monofunctional monomer is 78% by mass or more, relative to the total amount of the composition, the flexibility and adhesion of the coating film tend to be further improved. Furthermore, the upper limit of the content of the monofunctional monomer is preferably 92% by mass or less, more preferably 90% by mass or less, and even more preferably 88% by mass or less, relative to the total amount of the composition. When the content of the monofunctional monomer is 92% by mass or less, relative to the total amount of the composition, the abrasion resistance tends to be further improved.

[0027] Examples of monofunctional monomers are shown below, but the monofunctional monomers in this embodiment are not limited to the following.

[0028] 1.1.1.1. Monofunctional acrylates with polycyclic hydrocarbon groups The monofunctional acrylate having a polycyclic hydrocarbon group is not particularly limited, and examples thereof include acrylates having an unsaturated polycyclic hydrocarbon group such as dicyclopentenyl acrylate and dicyclopentenyloxyethyl acrylate; and acrylates having a saturated polycyclic hydrocarbon group such as dicyclopentanyl acrylate and isobornyl acrylate. Among these, acrylates having an unsaturated polycyclic hydrocarbon group are preferred, and it is more preferred to include at least dicyclopentenyl acrylate. By using such monofunctional acrylates having a polycyclic hydrocarbon group, the scratch resistance of the coating film tends to be further improved.

[0029] The content of the monofunctional acrylate having a polycyclic hydrocarbon group relative to the total amount of the polymerizable compounds is preferably 5 to 45 mass%, more preferably 10 to 40 mass%, and even more preferably 15 to 35 mass%. When the content of the monofunctional acrylate having a polycyclic hydrocarbon group relative to the total amount of the polymerizable compounds is within the above range, the scratch resistance of the coating film tends to be further improved.

[0030] The content of the monofunctional acrylate having a polycyclic hydrocarbon group relative to the total amount of the composition is preferably 5 to 40 mass%, more preferably 10 to 40 mass%, and even more preferably 15 to 35 mass%. When the content of the monofunctional acrylate having a polycyclic hydrocarbon group relative to the total amount of the composition is within the above range, the scratch resistance of the coating film tends to be further improved.

[0031] 1.1.1.2. Nitrogen-containing monofunctional monomers The nitrogen-containing monofunctional monomer is not particularly limited, and examples thereof include nitrogen-containing monofunctional vinyl monomers such as N-vinylcaprolactam, N-vinylformamide, N-vinylcarbazole, N-vinylacetamide, and N-vinylpyrrolidone; nitrogen-containing monofunctional acrylate monomers such as acryloylmorpholine; and nitrogen-containing monofunctional acrylamide monomers such as (meth)acrylamide, N-hydroxymethyl(meth)acrylamide, diacetone acrylamide, N,N-dimethyl(meth)acrylamide, and dimethylaminoethyl acrylate benzyl chloride quaternary salt.

[0032] Among these, it is preferable to contain either a nitrogen-containing monofunctional vinyl monomer or a nitrogen-containing monofunctional acrylate monomer, more preferably a monomer having a nitrogen-containing heterocyclic structure such as N-vinylcaprolactam, N-vinylcarbazole, N-vinylpyrrolidone, or acryloylmorpholine, and even more preferably to contain either N-vinylcaprolactam or acryloylmorpholine.

[0033] The use of such nitrogen-containing monofunctional monomers tends to further improve the scratch resistance of the coating film.Furthermore, nitrogen-containing monofunctional vinyl monomers having a nitrogen-containing heterocyclic structure such as n-vinylcaprolactam tend to further improve the flexibility of the coating film, and nitrogen-containing monofunctional acrylate monomers having a nitrogen-containing heterocyclic structure such as acryloylmorpholine tend to further reduce the odor of the composition.

[0034] The content of the nitrogen-containing monofunctional monomer is preferably 5 to 40 mass %, more preferably 5 to 35 mass %, and even more preferably 5 to 30 mass %, relative to the total amount of polymerizable compounds. When the content of the nitrogen-containing monofunctional monomer is 5 mass % or more relative to the total amount of polymerizable compounds, the abrasion resistance of the coating film tends to be further improved. Furthermore, when the content of the nitrogen-containing monofunctional monomer is 40 mass % or less relative to the total amount of polymerizable compounds, the adhesion tends to be further improved.

[0035] The content of the nitrogen-containing monofunctional monomer is preferably 5 to 40 mass %, more preferably 5 to 35 mass %, and even more preferably 5 to 30 mass %, relative to the total amount of the composition. When the content of the nitrogen-containing monofunctional monomer is 5 mass % or more relative to the total amount of the composition, the scratch resistance of the coating film tends to be further improved. Furthermore, when the content of the nitrogen-containing monofunctional monomer is 40 mass % or less relative to the total amount of the composition, the adhesion tends to be further improved.

[0036] 1.1.1.3. Aromatic group-containing monofunctional monomers The aromatic group-containing monofunctional 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. Among these, phenoxyethyl (meth)acrylate and benzyl (meth)acrylate are preferred, phenoxyethyl (meth)acrylate is more preferred, and phenoxyethyl acrylate (PEA) is even more preferred. The use of such aromatic group-containing monofunctional monomers tends to further improve the solubility of the polymerization initiator and further improve the curability of the composition. In particular, when using an acylphosphine oxide-based polymerization initiator or a thioxanthone-based polymerization initiator, the solubility tends to be improved. Furthermore, the use of phenoxyethyl (meth)acrylate tends to further reduce odor.

[0037] In this embodiment, the aromatic group-containing monofunctional monomer is not a compound having a polycyclic hydrocarbon group.

[0038] Other examples of aromatic group-containing monofunctional monomers include compounds represented by the following general formula (3) and general formula (4).

[0039] CH2=CR 4 -COOR 5 -Ar···(3) CH2=CR 4 -COO-Ar ···(4) (In the above formulas (3) and (4), R 4 In the above formula (3), Ar representing the aromatic ring skeleton has at least one aryl group, and the carbon atoms constituting the aryl group are R 5and R5 is a divalent organic residue having 1 to 4 carbon atoms. In the above formula (4), Ar representing the aromatic ring skeleton is a monovalent organic residue having at least one aryl group, and a carbon atom constituting the aryl group is bonded to -COO- in the formula.

[0040] In the above general formula (3), R 5 Preferred examples of the group represented by the formula (I) include linear, branched, or cyclic alkylene groups having 1 to 4 carbon atoms, which may be substituted, and alkylene groups having 1 to 4 carbon atoms and which have an oxygen atom via an ether bond and / or an ester bond in their structure. Among these, alkylene groups having 1 to 4 carbon atoms, such as ethylene, n-propylene, isopropylene, and butylene, and alkylene groups having 1 to 4 carbon atoms and which have an oxygen atom via an ether bond in their structure, such as oxyethylene, oxy-n-propylene, oxyisopropylene, and oxybutylene, are preferably used. When the organic residue is an optionally substituted group, the substituent is not particularly limited, and examples include a carboxyl group, an alkoxy group, a hydroxyl group, and a halo group. When the substituent is a group containing a carbon atom, the carbon atom is counted as part of the carbon number of the organic residue.

[0041] In the above general formulas (3) and (4), examples of the aryl group contained in at least one Ar (aryl) (aromatic ring skeleton) include, but are not limited to, a phenyl group and a naphthyl group. The number of aryl groups is 1 or more, preferably 1 or 2. The aryl group may be substituted on any carbon atom constituting the group, except for the carbon atom bonded to the organic residue represented by R5 in formula (3), the carbon atom bonded to -COO- in formula (4), and the carbon atom connecting the aryl groups when multiple aryl groups are present. When substituted, the number of substitutions per aryl group is 1 or more, preferably 1 or 2. The substituent is not particularly limited, but examples include linear, branched, or cyclic alkyl and alkoxy groups having 1 to 10 carbon atoms, carboxyl groups, halo groups, and hydroxyl groups.

[0042] The content of the aromatic group-containing monofunctional monomer relative to the total amount of polymerizable compounds is preferably 30 to 55 mass%, more preferably 35 to 50 mass%, and even more preferably 40 to 45 mass%. When the content of the aromatic group-containing monofunctional monomer relative to the total amount of polymerizable compounds is within the above range, the scratch resistance of the coating film tends to be further improved.

[0043] The content of the aromatic group-containing monofunctional monomer relative to the total amount of the composition is preferably 20 to 50 mass %, more preferably 25 to 45 mass %, and even more preferably 30 to 40 mass %. When the content of the aromatic group-containing monofunctional monomer relative to the total amount of the composition is within the above range, the scratch resistance of the coating film tends to be further improved.

[0044] 1.1.1.3. Monofunctional monomers containing saturated aliphatic groups One example of the other monofunctional monomers is a saturated aliphatic group-containing monofunctional monomer. In this embodiment, the saturated aliphatic group-containing monofunctional monomer is not a compound having a polycyclic hydrocarbon group.

[0045] The saturated aliphatic group-containing monofunctional monomer is not particularly limited, and examples thereof include alicyclic group-containing monofunctional monomers such as tert-butylcyclohexanol acrylate (TBCHA) and 2-(meth)acrylate-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, tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate; and lactone-modified flexible (meth)acrylates. Among these, alicyclic group-containing monofunctional monomers are preferred, as the use of such saturated aliphatic group-containing monofunctional monomers tends to further improve the curability of the composition.

[0046] The content of the saturated aliphatic group-containing monofunctional monomer is preferably 1 to 17.5 mass% relative to the total amount of polymerizable compounds, more preferably 3 to 15 mass%, and even more preferably 5 to 12.5 mass%. When the content of the saturated aliphatic group-containing monofunctional monomer is 1 mass% or more relative to the total amount of polymerizable compounds, the flexibility and adhesion of the coating film tend to be further improved. Furthermore, when the content of the saturated aliphatic group-containing monofunctional monomer is 17.5 mass% or less relative to the total amount of polymerizable compounds, the abrasion resistance of the coating film tends to be further improved.

[0047] The content of the saturated aliphatic group-containing monofunctional monomer is preferably 1 to 15 mass %, more preferably 3 to 12.5 mass %, and even more preferably 5 to 10 mass %, relative to the total amount of the composition. When the content of the saturated aliphatic group-containing monofunctional monomer is 1 mass % or more relative to the total amount of the composition, the flexibility and adhesion of the coating film tend to be further improved. Furthermore, when the content of the saturated aliphatic group-containing monofunctional monomer is 15 mass % or less relative to the total amount of the composition, the abrasion resistance of the coating film tends to be further improved.

[0048] Other In addition to the above, other monofunctional monomers that may be used include, for example, unsaturated carboxylic acids such as (meth)acrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid; salts of the unsaturated carboxylic acids; esters, urethanes, amides, and anhydrides of unsaturated carboxylic acids; acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes.

[0049] 1.1.2. Multifunctional Monomers Examples of the polyfunctional monomer of this embodiment include vinyl ether group-containing (meth)acrylate, bifunctional (meth)acrylate, and trifunctional or higher polyfunctional (meth)acrylate. However, the polyfunctional monomer is not limited to the above.

[0050] The content of the polyfunctional monomer is preferably 0.01% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, relative to the total amount of the polymerizable compounds. When the content of the polyfunctional monomer is 1% by mass or more, relative to the total amount of the polymerizable compounds, the abrasion resistance tends to be further improved. Furthermore, the upper limit of the content of the polyfunctional monomer is preferably 10% by mass or less, more preferably 7.5% by mass or less, and even more preferably 6% by mass or less, relative to the total amount of the polymerizable compounds. When the content of the polyfunctional monomer is 10% by mass or less, relative to the total amount of the polymerizable compounds, the flexibility and adhesion of the coating film tend to be further improved.

[0051] The content of the polyfunctional monomer is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, relative to the total amount of the composition. When the content of the polyfunctional monomer is 1% by mass or more, relative to the total amount of the composition, the abrasion resistance tends to be further improved. Furthermore, the upper limit of the content of the polyfunctional monomer is preferably 10% by mass or less, more preferably 7.5% by mass or less, and even more preferably 5% by mass or less, relative to the total amount of the composition. When the content of the polyfunctional monomer is 10% by mass or less, relative to the total amount of the composition, the flexibility and adhesion of the coating film tend to be further improved.

[0052] Examples of polyfunctional monomers are given below, but the polyfunctional monomers in this embodiment are not limited to the following.

[0053] 1.1.2.1 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 (1): 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. Furthermore, the curability of the composition is improved, and the improved curability also allows for faster recording speeds. CH2=CR 1 -COOR 2 -O-CH=CH-R 3 ··· (1) (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.

[0054] 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 and having an oxygen atom due to an ether bond and / or an ester bond in its 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 and having an oxygen atom due to 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, 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 oxy-n-propylene group, an oxyisopropylene group, or an oxybutylene group, and more preferred are compounds having a glycol ether chain.

[0055] In the above formula (1), R 3 Suitable monovalent organic residues 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.

[0056] 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.

[0057] 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, p) 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 methacrylate, 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 Examples of suitable acrylates include ethyl (meth)acrylate, 2-(isopropenoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxyethoxy)ethyl (meth)acrylate, polyethylene glycol monovinyl ether (meth)acrylate, and polypropylene glycol monovinyl ether (meth)acrylate. Among 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.

[0058] The content of the vinyl ether group-containing (meth)acrylate relative to the total amount of polymerizable compounds is preferably 0.5 to 10 mass %, more preferably 0.75 to 8 mass %, and even more preferably 1 to 6 mass %. When the content of the vinyl ether group-containing (meth)acrylate relative to the total amount of polymerizable compounds is within the above range, the viscosity of the composition tends to decrease, and the ejection stability tends to be further improved.

[0059] The content of the vinyl ether group-containing (meth)acrylate relative to the total amount of the composition is preferably 0.5 to 10 mass %, more preferably 0.75 to 8 mass %, and even more preferably 1 to 6 mass %. When the content of the vinyl ether group-containing (meth)acrylate relative to the total amount of polymerizable compounds is within the above range, the viscosity of the composition tends to decrease, and the ejection stability tends to be further improved.

[0060] 1.1.2.2 Difunctional (meth)acrylates The bifunctional (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, and 1,4-butanediol di(meth)acrylate. Examples of the di(meth)acrylates include 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, PO (propylene oxide) adduct di(meth)acrylate of bisphenol A, hydroxypivalic acid neopentyl glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate.

[0061] 1.1.2.3 Trifunctional or higher polyfunctional (meth)acrylates The tri- or higher functional polyfunctional (meth)acrylate is not particularly limited, and 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, caprolactone-modified trimethylolpropane tri(meth)acrylate, pentaerythritol ethoxy tetra(meth)acrylate, and caprolactam-modified dipentaerythritol hexa(meth)acrylate.

[0062] Oligomers The oligomer of this embodiment refers to a compound that is a multimer such as a dimer or trimer containing a polymerizable compound as a constituent component and has one or more polymerizable functional groups. The polymerizable compound referred to here is not limited to the monofunctional monomers and polyfunctional monomers described above. In this embodiment, a compound having a molecular weight of 1000 or more is defined as an oligomer, and a compound having a molecular weight of less than 1000 is defined as a monomer.

[0063] 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.

[0064] Among these, urethane acrylate oligomers are preferred, with aliphatic urethane acrylate oligomers and aromatic urethane acrylate oligomers being more preferred, and aliphatic urethane acrylate oligomers being even more preferred. The urethane acrylate oligomer is preferably a tetrafunctional or lower functional urethane acrylate oligomer, and more preferably a difunctional urethane acrylate oligomer.

[0065] Use of such an oligomer tends to further improve the storage stability and abrasion resistance of the composition.

[0066] The content of the oligomer is preferably 0.5 to 10 mass %, more preferably 1 to 7.5 mass %, and even more preferably 1.5 to 5 mass %, relative to the total amount of the polymerizable compounds. When the content of the oligomer relative to the total amount of the polymerizable compounds is within the above range, the storage stability of the composition tends to be further improved, and the scratch resistance of the coating film tends to be further improved.

[0067] The content of the oligomer is preferably 0.5 to 10 mass %, more preferably 1 to 7.5 mass %, and even more preferably 1.5 to 5 mass %, relative to the total amount of the composition. When the content of the oligomer relative to the total amount of the composition is within the above range, the storage stability of the composition is further improved, and the scratch resistance of the coating film tends to be further improved.

[0068] 1.2. Polymerization initiator The radiation-curable inkjet composition according to this embodiment preferably contains a polymerization initiator that generates active species upon irradiation with radiation. The polymerization initiator may be used alone or in combination of two or more.

[0069] The polymerization initiator is not particularly limited, and examples thereof include known polymerization initiators such as acylphosphine oxide-based polymerization initiators, alkylphenone-based polymerization initiators, titanocene-based polymerization initiators, and thioxanthone-based polymerization initiators. Among these, acylphosphine oxide-based polymerization initiators are preferred. Use of such a polymerization initiator tends to further improve the curability of the composition, particularly the curability in a curing process using UV-LED light.

[0070] The acylphosphine oxide polymerization initiator is not particularly limited, but examples thereof include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

[0071] Commercially available examples of such acylphosphine oxide polymerization 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-hydroxycyclohexylphenyl ketone in a mass ratio of 25:75), and IRGACURE TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide) (all manufactured by BASF).

[0072] The content of the polymerization initiator is preferably 1 to 20 mass %, more preferably 3 to 15 mass %, even more preferably 5 to 10 mass %, and particularly preferably 7 to 9 mass %, relative to the total amount of the composition. When the content of the polymerization initiator is within the above range, the curability of the composition and the solubility of the polymerization initiator tend to be further improved.

[0073] 1.3. Other additives The radiation-curable ink jet composition according to this embodiment may further contain additives such as a colorant, a dispersant, a polymerization inhibitor, a slip agent, a photosensitizer, and a polymerization inhibitor, as needed.

[0074] 1.3.1.Colorants The radiation-curable ink jet composition according to this embodiment may further contain a coloring material. By containing a coloring material, the radiation-curable ink jet composition according to this embodiment can be used as a colored radiation-curable ink jet composition. The coloring material can be at least one of a pigment and a dye.

[0075] The total content of coloring materials is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 2 to 10% by mass, relative to the total amount of the composition. The radiation-curable inkjet composition according to this embodiment may be a clear ink that does not contain coloring materials or that contains coloring materials to an extent that coloring is not intended (for example, 0.1% by mass or less).

[0076] 1.3.1.1. Pigments By using a pigment as a coloring material, the light resistance of the radiation-curable ink jet composition can be improved. Both inorganic and organic pigments can be used as the pigment. One type of pigment may be used alone, or two or more types may be used in combination.

[0077] As inorganic pigments, carbon blacks (CI (Colour Index Generic Name) Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black, iron oxide, and titanium oxide can be used.

[0078] Examples of organic pigments include azo pigments such as insoluble azo pigments, condensed azo pigments, azo lakes, and chelate azo pigments; polycyclic pigments such as phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments; dye chelates (for example, basic dye chelates, acid dye chelates, etc.); dye lakes (basic dye lakes, acid dye lakes), nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments.

[0079] More specifically, carbon blacks used for the black 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 (manufactured by Cabot Corporation (CABOTJAPAN KK)), 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, Special Black 4 (all manufactured by Degussa).

[0080] The pigments used for white are CI Pigment White 6, 18, and 21. Examples include:

[0081] Pigments used for yellow 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.

[0082] Pigments used for magenta 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, 245, and CI Pigment Violet. Examples include 19, 23, 32, 33, 36, 38, 43, and 50.

[0083] Pigments used for cyan include CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:34, 15:4, 16, 18, 22, 25, 60, 65, 66, and CI Vat Blue 4 and 60.

[0084] Examples of pigments other than magenta, cyan, and yellow include CI Pigment Green 7 and 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.

[0085] The content of the pigment is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 2 to 10% by mass, relative to the total amount of the composition.

[0086] 1.3.1.2.Dye A dye can be used as the coloring material. The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used. The dyes can be used alone or in combination of two or more.

[0087] The dye is not particularly limited, and examples thereof 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, 14 2, 144, 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.

[0088] Dispersants When the radiation-curable inkjet composition contains a pigment, it may further contain a dispersant to improve the pigment dispersibility. The dispersant may be used alone or in combination of two or more types.

[0089] The dispersant is not particularly limited, but examples thereof include dispersants commonly used in preparing pigment dispersions, such as polymer dispersants, and 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.

[0090] 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.

[0091] The content of the dispersant is preferably 0.1 to 2 mass %, more preferably 0.1 to 1 mass %, and even more preferably 0.1 to 0.5 mass %, relative to the total amount of the composition.

[0092] 1.3.3. Polymerization inhibitors The radiation-curable inkjet 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.

[0093] 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), 4,4'-thiobis(3-methyl-6-t-butylphenol), and hindered amine compounds.

[0094] The content of the polymerization inhibitor is preferably 0.05 to 1 mass %, more preferably 0.05 to 0.5 mass %, relative to the total amount of the composition.

[0095] 1.3.4.Slip agents The radiation-curable inkjet 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.

[0096] The slip agent is preferably a silicone surfactant, more preferably a polyester-modified silicone or a polyether-modified silicone. Examples of polyether-modified silicones include BYK-378, 3455, BYK-UV3500, 3510, and 3530 (all manufactured by BYK Additives & Instruments). Examples of polyester-modified silicones include BYK-3570 (manufactured by BYK Additives & Instruments).

[0097] The content of the slip agent is preferably 0.01 to 2 mass %, more preferably 0.05 to 1 mass %, relative to the total amount of the composition.

[0098] Photosensitizers The radiation-curable inkjet composition according to this embodiment may further contain a photosensitizer. Examples of the photosensitizer include amine compounds (aliphatic amines, amines containing an aromatic group, piperidine, reaction products of epoxy resins and amines, triethanolamine triacrylate, etc.), urea compounds (allylthiourea, o-tolylthiourea, etc.), sulfur compounds (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.).

[0099] 1.4.Physical Properties The viscosity of the radiation-curable inkjet composition according to this embodiment at 20°C is preferably 25 mPa·s or less, and more preferably 5 mPa·s to 25 mPa·s. When the viscosity of the composition at 20°C is within this range, an appropriate amount of the composition is ejected from the nozzle, and deflection and scattering of the composition can be further reduced, making the composition suitable for use in inkjet recording devices. The viscosity can be measured using a viscoelasticity tester MCR-300 (manufactured by Pysica) at 20°C by increasing the shear rate from 10 to 1000 and reading the viscosity at a shear rate of 200.

[0100] The surface tension of the radiation-curable inkjet composition according to this embodiment at 20°C is preferably 20 mN / m or more and 40 mN / m or less. When the surface tension of the radiation-curable inkjet composition at 20°C is within this range, the composition is less likely to wet a nozzle surface that has been treated with a liquid repellent. This allows the composition to be ejected normally and in an appropriate amount from the nozzle, further reducing deflection and scattering of the composition, making the composition suitable for use in inkjet recording devices. The surface tension can be measured by wetting a platinum plate with the radiation-curable inkjet composition at 20°C using an automatic surface tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

[0101] 1.5. Method for producing the composition The production (preparation) of the radiation-curable ink jet composition is carried out by mixing the components contained in the composition and stirring the mixture to ensure a sufficient homogeneous mixture. In this embodiment, the preparation of the radiation-curable ink jet composition preferably includes a step of subjecting a mixture of a polymerization 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 composition, resulting in a radiation-curable ink jet composition with excellent ejection stability and storage stability. The mixture may contain at least the components described above, and may further contain other components contained in the radiation-curable ink jet composition, or may contain all of the components contained in the radiation-curable ink jet composition. The monomer contained in the mixture may be at least a portion of the monomers contained in the radiation-curable ink jet composition.

[0102] 2. Inkjet recording method The inkjet recording method according to this embodiment includes a discharge step of discharging the radiation-curable inkjet composition from an inkjet head and depositing it on a recording medium, and an irradiation step of irradiating the radiation-curable inkjet composition deposited on the recording medium with radiation. This allows a coating film to be formed at the location on the recording medium where the radiation-curable inkjet composition has been applied. Each step will be described in detail below.

[0103] 2.1.Discharge process In the ejection step, the composition is ejected from an inkjet head and deposited on a recording medium. More specifically, a pressure generating means is driven to eject the composition filled in a pressure generating chamber of the inkjet head from a nozzle. This ejection method is also called an inkjet method.

[0104] Inkjet heads used in the ejection step include a line head that performs recording by a line method and a serial head that performs recording by a serial method.

[0105] 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 the recording device. The recording medium is then moved in the sub-scanning direction (the longitudinal direction of the recording medium, the transport direction), 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.

[0106] In the serial method using a serial head, for example, an 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 (the horizontal or width direction of the recording medium), and ink droplets are ejected from the nozzle openings of the head in conjunction with this movement, thereby recording an image on the recording medium.

[0107] 2.2.Irradiation process In the irradiation step, the radiation-curable inkjet 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 polymerization initiator is present, it generates active species (initiation species) such as radicals, acids, and bases, and the polymerization reaction of the monomers is promoted by the function of the initiation species. Furthermore, if a photosensitizer is present, it absorbs radiation and becomes excited, and upon contact with the polymerization initiator, it promotes the decomposition of the polymerization initiator, thereby achieving a more rapid curing reaction.

[0108] Examples of the radiation include ultraviolet light, infrared light, visible light, and X-rays. The radiation source is installed downstream of the inkjet head and irradiates the composition. The radiation source is not particularly limited, but examples include UV-LEDs. Use of such a radiation source can reduce the size and cost of the device. UV-LEDs as an ultraviolet light source are small and can be installed inside the inkjet recording device.

[0109] For example, it can be attached to a carriage (either at both ends along the width direction of the medium and / or on the side in the medium transport direction) on which an inkjet head that ejects the radiation-curable inkjet composition is mounted. Furthermore, due to the composition of the radiation-curable inkjet composition described above, it is possible to achieve low-energy, high-speed curing. 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 reduction in the odor of the cured film.

[0110] 4. Records The recorded matter of this embodiment is obtained by adhering the radiation-curable inkjet composition to a recording medium and curing it. The composition has good flexibility and adhesion, which can prevent cracking or chipping of the coating film when post-processing such as cutting or bending is performed. Therefore, the recorded matter of this embodiment can be suitably used for signage and the like.

[0111] The material of the recording medium is not particularly limited, but examples include plastics such as polyvinyl chloride, polyethylene terephthalate, polypropylene, polyethylene, polycarbonate, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, and polyvinyl acetal, as well as plastics with treated surfaces, glass, paper, metal, and wood.

[0112] Among these, polyvinyl chloride with an SP value of 9.5 to 9.7, polyethylene terephthalate with an SP value of 12, polypropylene with an SP value of 8.0, and polyethylene with an SP value of 7.9 are preferred. When such recording media with an SP value of approximately 9.5 to 10 are used, the effects of the composition of this embodiment are particularly readily exhibited, resulting in excellent coating film adhesion and effectively suppressing cracking and chipping of the coating film during post-processing. Furthermore, by narrowing the SP value of the composition to a limited range of 9.5 to 10.0, good adhesion and abrasion resistance can be achieved for a variety of recording media with SP values ​​in the range of 7 to 13.

[0113] The form of the recording medium is not particularly limited, and examples include film, board, cloth, etc. [Example]

[0114] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples.

[0115] 1. Preparation of Inkjet 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 monomers, polymerization initiator, and polymerization inhibitor were placed in a stainless steel mixing tank so as to obtain the composition shown in Table 1, and mixed and stirred to completely dissolve. After that, the pigment dispersion obtained above was added, and the mixture was further mixed and stirred at room temperature for an hour, and then filtered through a 5 μm membrane filter to obtain the radiation-curable inkjet composition of each example. Note that the numerical values ​​for each component shown in each example in the table represent mass %.

[0116] [Table 1]

[0117] The abbreviations and product ingredients used in Table 1 are as follows:

[0118] <Monofunctional monomer> PEA (product name "Viscoat #192, manufactured by Osaka Organic Chemical Industry Co., Ltd., phenoxyethyl acrylate") NVC (N-vinylcaprolactam, manufactured by ISP Japan Co., Ltd.) ACMO (Acryloylmorpholine, manufactured by KJ Chemicals Co., Ltd.) IBXA (Osaka Organic Chemical Industry, Ltd., isobornyl acrylate) DCPA (Dicyclopentenyl acrylate, manufactured by Hitachi Chemical Co., Ltd.) TBCHA (product name "SR217", manufactured by Sartomer Corporation, tert-butyl cyclohexanol acrylate) <Polyfunctional Monomer> VEEA (2-(2-vinyloxyethoxy)ethyl acrylate, manufactured by Nippon Shokubai Co., Ltd.) <Oligomer> CN991 (Sartomer Corporation, bifunctional urethane acrylate oligomer) <Polymerization initiator> Irg.819 (trade name "IRGACURE 819" manufactured by BASF, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide) TPO (product name "IRGACURE TPO", manufactured by BASF, 2,4,6-trimethylbenzoyldiphenylphosphine oxide) <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) <Coloring materials (pigments)> Carbon black (product name "MA-100", manufactured by Mitsubishi Chemical Corporation) <Dispersant> Solsperse 36000 (polymer dispersant, manufactured by Lubrizol).

[0119] 2. Evaluation Method 2.1. Flexibility Assessment Each radiation-curable inkjet composition was applied to a vinyl chloride film (JT5829R, manufactured by MACtac) using a bar coater to a thickness of 10 μm. Then, a metal halide lamp (manufactured by iGraphics) was used to apply the composition to the film at 400 mJ / cm. 2 The coating was cured with an energy of 100 keV to form a coating film. The release paper was peeled off from the PVC film on which the coating was formed, and the film was cut into a strip of 1 cm wide and 8 cm long to prepare a test piece. The elongation percentage, which indicates flexibility, was measured for each test piece using a tensile tester (TENSILON, manufactured by ORIENTEC). The elongation percentage was the value at which a crack occurred when pulled at 5 mm / min. The value was calculated by {(length at crack - length before stretching) / length before stretching × 100}. The evaluation criteria are as follows: (Evaluation criteria) A: 300% or more B: 250% or more but less than 300% C: 200% or more but less than 250% D: Less than 200%

[0120] 2.2. Evaluation of PP adhesion Each radiation-curable inkjet composition was applied to a polypropylene board (manufactured by Coroplast) using a bar coater to a thickness of 10 μm. Then, a metal halide lamp (manufactured by Eye Graphics) was used to apply the inkjet composition to the polypropylene board at 400 mJ / cm 2 . 2 The resulting coating film was cured with an energy of 1000 kJ / s to form a coating film. The resulting coating film was evaluated by a cross-cut test in accordance with JIS K5600-5-6.

[0121] More specifically, a cutter blade was placed perpendicular to the coating film, and squares were cut with 1 mm spacing between each square to create a 10 x 10 grid. A piece of 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 are as follows: (Evaluation criteria) A: No peeling of the cured film was observed on the lattice. B: Peeling of the cured film was observed in less than 10% of the lattice. C: Peeling of the cured film was observed in 10% or more but less than 50% of the lattice. D: Peeling of the cured film was observed in more than 50% of the lattice.

[0122] 2.3. Evaluation of PET adhesion Adhesion to polyethylene terephthalate film was evaluated in the same manner as above, except that a polyethylene terephthalate film (manufactured by Toray Industries, Inc.) was used as the recording medium instead of a polypropylene board (manufactured by Coroplast). (Evaluation criteria) A: No peeling of the cured film was observed on the lattice. B: Peeling of the cured film was observed in less than 10% of the lattice. C: Peeling of the cured film was observed in 10% or more but less than 50% of the lattice. D: Peeling of the cured film was observed in more than 50% of the lattice.

[0123] 2.3. Evaluation of abrasion resistance The cured coating film prepared in the flexibility evaluation above was subjected to a micro-scratch test in accordance with JIS R3255. For the measurement, an ultra-thin film scratch tester (CSR-5000, manufactured by Nanotec Co., Ltd.) was used to measure the load capacity as a measure of abrasion resistance. The load capacity was determined by micro-scratching while applying a load, and the load was measured when the stylus reached the media surface. The measurement was performed with a stylus diameter of 15 μm, an amplitude of 100 μm, and a scratch speed of 10 μm / sec. The evaluation criteria were as follows: (Evaluation criteria) A: 30mN / cm 2 End B: 25 mN / cm 2 More than 30mN / cm 2 less than C: 20mN / cm 2 More than 25mN / cm 2 less than D: 20 mN / cm 2 less than

[0124] 3. Evaluation Results The composition and evaluation results of the radiation-curable inkjet composition used in each example are shown in Table 1. As can be seen from Table 1, the radiation-curable inkjet compositions of Examples 1 to 7, which contained 90 mass % or more of monofunctional monomers relative to the total amount of polymerizable compounds, had a weighted average of the glass transition temperatures of the homopolymers of the polymerizable compounds of 42°C or higher, with the weights being the content mass ratios of the polymerizable compounds, and had a weighted average of the SP values ​​of the polymerizable compounds of 9.5 to 10.0, with the content mass ratios of the polymerizable compounds being weights, were all good, with flexibility, adhesion, and abrasion resistance all achieving a grade of B or higher.

[0125] Specifically, comparing each Example with Comparative Example 1, it is found that abrasion resistance is further improved when the weighted average of the glass transition temperatures of the homopolymers of each polymerizable compound is 42°C or higher. Furthermore, comparing each Example with Comparative Examples 2 and 3, it is found that adhesion is improved when the weighted average of the SP values ​​of each polymerizable compound, where the content mass ratio of each polymerizable compound is used as a weight, is within the range of 9.5 to 10.0. Furthermore, comparing each Example with Comparative Example 4, it is found that flexibility and adhesion are improved when the proportion of monofunctional monomers is 90 mass% or higher relative to the total polymerizable compounds.

Claims

1. The polymerizable compound contains a monofunctional monomer (excluding acrylamide, acrylamide derivative monomers, and acrylamide-based monomers) and a polyfunctional monomer, the content of the monofunctional monomer is 90% by mass or more based on the total amount of the polymerizable compound; a weighted average of glass transition temperatures of homopolymers of the polymerizable compounds, the weight being determined by the content mass ratio of the polymerizable compounds, of 42°C or higher and 51°C or lower; a weighted average of the SP values ​​of the polymerizable compounds, where the content mass ratio of each polymerizable compound is used as a weight, is 9.5 to 10.0; Radiation-curable inkjet compositions.

2. The weighted average of the glass transition temperatures is 48°C or higher. The radiation-curable ink jet composition according to claim 1 .

3. the content of the polyfunctional monomer is 0.01 to 10% by mass with respect to the total amount of the polymerizable compound; The radiation-curable ink jet composition according to claim 1 or 2.

4. The polyfunctional monomer includes a vinyl ether group-containing (meth)acrylic acid ester represented by the following formula (1): The radiation-curable ink jet composition according to any one of claims 1 to 3. CH 2 =CR 1 -COOR 2 -O-CH=CH-R 3 ・・・ (1) (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.

5. a discharge step of discharging the radiation-curable ink jet composition according to any one of claims 1 to 4 from an ink jet head and depositing it on a recording medium; an irradiation step of irradiating the radiation-curable inkjet composition adhered to the recording medium with radiation, Recording method.

6. A cured product of the radiation-curable ink jet composition according to any one of claims 1 to 4 adhered to a recording medium. Recorded material.

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