Radiation-curable ink jet composition and ink jet recording device

Abstract

To provide a radiation-curable inkjet composition excellent in member durability and adhesion.SOLUTION: The radiation-curable inkjet composition is used for an inkjet recording device provided with an inkjet head having a member with an SP value of 7.0-8.0 (J / cm3)1 / 2 in a flow channel and contains a polymerizable monomer A containing: a polymerizable monomer B with an SP value of 7.0 (J / cm3)1 / 2 or less or 8.0 (J / cm3)1 / 2 or more; and a polymerizable monomer C with an SP value of more than 7.0 (J / cm3)1 / 2 and less than 8.0 (J / cm3)1 / 2. The content of the polymerizable monomer B is 20 mass% or more based on the total amount of the ink composition. The content of the polymerizable monomer C is 22.5 mass% or less based on the total amount of the ink composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a radiation-curable ink jet composition and an ink jet recording apparatus. [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. Among these methods, various studies have been conducted on radiation-curable inks. For example, Patent Document 1 discloses an active energy ray-curable composition that exhibits good adhesion to polypropylene substrates and polyethylene terephthalate substrates and can also exhibit high coating strength, and that contains a monofunctional monomer having an alicyclic structure, 10 to 50 parts by weight of a bifunctional monomer having an alicyclic structure relative to 100 parts by weight of the total monomers, chlorinated polypropylene, and a polymer having a polyester structural moiety. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-009074 Summary of the Invention [Problem to be solved by the invention]

[0004] In the examples of Patent Document 1, a monofunctional monomer containing an alicyclic structure that has excellent solubility in chlorinated polypropylene is disclosed, for example, in which isobornyl acrylate is used in a large amount, such as 70% by mass or more. Isobornyl acrylate exhibits good adhesion to non-absorbent substrates such as polypropylene substrates, but on the other hand, depending on the components used inside the inkjet head, it may cause swelling of the components, leading to a decrease in ejection stability. [Means for solving the problem]

[0005] The radiation-curable inkjet composition of the present invention is applied to a flow path with an SP value of 7.0 to 8.0 (J / cm 3 ) 1 / 2 A radiation-curable ink jet composition for use in an ink jet recording apparatus equipped with an ink jet head having the above-mentioned components, which has an SP value of 7.0 (J / cm 3 ) 1 / 2 or less than 8.0 (J / cm 3 ) 1 / 2 and polymerizable monomer B having an SP value of 7.0 (J / cm 3 ) 1 / 2 Excess 8.0(J / cm 3 ) 1 / 2 and polymerizable monomer A including polymerizable monomer C, wherein the content of polymerizable monomer B is 20% by mass or more relative to the total amount of the ink composition, and the content of polymerizable monomer C is 22.5% by mass or less relative to the total amount of the ink composition.

[0006] In addition, the inkjet recording device of the present invention has a flow path with an SP value of 7.0 to 8.0 (J / cm 3 ) 1 / 2 and the radiation-curable ink jet composition according to any one of claims 1 to 8, which is ejected from the ink jet head. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a perspective view showing a serial inkjet device according to an embodiment of the present invention; 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 with reference to the drawings as necessary, but the present invention is not limited to this, and various modifications are possible without departing from the spirit of the present invention. In the drawings, the same elements are given the same reference numerals, and redundant explanations will be omitted. Furthermore, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[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. Radiation-curable inkjet composition The radiation-curable ink jet composition according to this embodiment (hereinafter also simply referred to as "ink composition") is applied to a flow path with an SP value of 7.0 to 8.0 (J / cm 3 ) 1 / 2 A radiation-curable ink jet composition for use in an ink jet recording apparatus equipped with an ink jet head having the above-mentioned components, which has an SP value of 7.0 (J / cm 3 ) 1 / 2 or less than 8.0 (J / cm 3 ) 1 / 2 and polymerizable monomer B having an SP value of 7.0 (J / cm 3 ) 1 / 2 Excess 8.0(J / cm 3 ) 1 / 2 and polymerizable monomer A including polymerizable monomer C, wherein the content of polymerizable monomer B is 20% by mass or more relative to the total amount of the ink composition, and the content of polymerizable monomer C is 22.5% by mass or less relative to the total amount of the ink composition.

[0011] The ink composition of this embodiment contains a predetermined amount of polymerizable monomer B, and thus has an SP value of 7.0 to 8.0 (J / cm 3 ) 1 / 2 Even when recording is performed using an inkjet recording apparatus equipped with an inkjet head having the above-mentioned components, the ink composition passing through the flow path can prevent the components from swelling, etc., and therefore the durability of the components is further improved. Furthermore, the improved durability of the components can also improve the ejection stability.

[0012] Furthermore, the ink composition of this embodiment contains a predetermined amount of polymerizable monomer C, which makes it possible to further improve adhesion to non-absorbent substrates such as polypropylene.

[0013] In addition, the radiation-curable ink jet composition according to this embodiment may contain an oligomer, a polymerization initiator, a polymerization inhibitor, a surfactant, a coloring material, and the like, as needed.

[0014] 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.

[0015] The radiation-curable inkjet composition of this embodiment 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.

[0016] 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.

[0017] 1.1. Polymerizable Monomer A In this embodiment, those having a polymerizable unsaturated bond are collectively referred to as polymerizable monomer A. When defined from the viewpoint of the number of functional groups of the polymerizable monomer, the polymerizable monomer A may include a monofunctional monomer A1 having one polymerizable functional group and a polyfunctional monomer A2 having multiple polymerizable functional groups. When defined by the SP value obtained using Small's formula, the polymerizable monomer A has an SP value of 7.0 (J / cm 3 ) 1 / 2 or less than 8.0 (J / cm 3 ) 1 / 2 and polymerizable monomer B having an SP value of 7.0 (J / cm 3 ) 1 / 2 Excess 8.0(J / cm 3 ) 1 / 2 and a polymerizable monomer C, which is less than

[0018] In the following, first, the monofunctional monomer A1 and the polyfunctional monomer A2 will be explained, and then the polymerizable monomer B and the polymerizable monomer C will be explained.

[0019] In the present embodiment, the "SP value" is also referred to as the "solubility parameter" and means a value calculated using Small's formula shown below. σ=ρ·(ΣFi) / M (In the above formula, σ represents the SP value, ρ represents the density, Fi represents the molar attractive force constant, and M represents the molecular weight of the repeating unit (monomer) of the polymer.

[0020] The weighted average of the SP values, with the weight being the content mass ratio of each polymerizable monomer A, is preferably 7.5 to 11 (J / cm 3 ) 1 / 2 More preferably, it is 8.0 to 10.5 (J / cm 3 ) 1 / 2 and more preferably 8.5 to 10 (J / cm 3 ) 1 / 2When the weighted average of the glass transition temperatures is within the above range, adhesion and durability of the member tend to be further improved. The weighted average of the SP values ​​can be calculated in the same manner as the method for calculating the weighted average of the glass transition temperatures described below.

[0021] Furthermore, the weighted average of the glass transition temperatures of the homopolymers of polymerizable monomer A, where the content mass ratio of each polymerizable monomer A is used as the weight, is preferably 25 to 40° C., more preferably 27.5 to 37.5° C., and even more preferably 30 to 35° C. When the weighted average of the glass transition temperatures is within the above range, the foldability tends to be further improved.

[0022] The weighted average glass transition temperature of the homopolymer can be adjusted by the glass transition temperature of the homopolymer of the polymerizable monomer used and the content mass ratio of the polymerizable monomer used.

[0023] Here, a method for calculating the weighted average of the glass transition temperatures of the homopolymers of polymerizable monomer A will be described. The weighted average of the glass transition temperatures of the homopolymers is called Tg All , the glass transition temperature of the homopolymer of each polymerizable monomer is Tg N , the content mass ratio of the polymerizable monomer is X N (wt%). N is a number starting from 1 depending on the type of polymerizable compound contained in the radiation-curable inkjet ink composition. For example, when three types of polymerizable compounds are used, Tg1, Tg2, and Tg3 are obtained. The weighted average Tg of the glass transition temperatures of homopolymers All is the glass transition temperature Tg of the homopolymer calculated for each polymerizable monomer. N and the mass ratio X N Therefore, the following equation (1) holds: Tg All =ΣTg N ×X N ···(1)

[0024] The glass transition temperature of a homopolymer of a polymerizable monomer can be measured by differential scanning calorimetry (DSC) in accordance with JIS K 7121. The measuring device used may be, for example, a DSC6220 model manufactured by Seiko Electronics Co., Ltd., and the sample used may be one in which the monomer has been polymerized to such an extent that the glass transition temperature of the homopolymer becomes constant.

[0025] The content of polymerizable monomer A is preferably 75 to 85 mass %, more preferably 70 to 90 mass %, and even more preferably 65 to 95 mass %, relative to the total amount of the ink composition. When the content of polymerizable monomer A is within the above range, adhesion and durability of the member tend to be further improved.

[0026] 1.1.1. Monofunctional Monomer A1 The monofunctional monomer A1 is not particularly limited, but examples thereof include monofunctional monomers having an alicyclic structure, nitrogen-containing monofunctional monomers, aromatic group-containing monofunctional monomers, and urethane acrylates.In addition, other monofunctional monomers may be included as needed instead of or in addition to these.In addition, the monofunctional monomer is 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.

[0027] The content of the monofunctional monomer A1 is preferably 50 to 80% by mass, more preferably 55 to 75% by mass, and even more preferably 60 to 70% by mass, based on the total amount of the polymerizable monomer A. When the content of the monofunctional monomer A1 is 50% by mass or more, adhesion, bending property, and abrasion resistance tend to be further improved. Furthermore, when the content of the monofunctional monomer A1 is 80% by mass or less, blocking resistance and member durability tend to be further improved.

[0028] Examples of monofunctional monomers are shown below, but the monofunctional monomers in this embodiment are not limited to the following.

[0029] 1.1.1.1. Monofunctional monomers with alicyclic structures The monofunctional monomer having an alicyclic structure is not particularly limited, but examples thereof include: Examples of the monomer include monomers having a monocyclic hydrocarbon group such as tert-butylcyclohexanol (meth)acrylate (TBCHA), 3,3,5-trimethylcyclohexyl (meth)acrylate (TMCHA), and 2-(meth)acrylic acid-1,4-dioxaspiro[4,5]dec-2-ylmethyl; monomers having an unsaturated polycyclic hydrocarbon group such as dicyclopentenyl (meth)acrylate and dicyclopentenyloxyethyl (meth)acrylate; and monomers having a saturated polycyclic hydrocarbon group such as dicyclopentanyl (meth)acrylate and isobornyl (meth)acrylate (IBXA).

[0030] Among these, isobornyl (meth)acrylate, tert-butylcyclohexanol acrylate, and trimethylcyclohexyl (meth)acrylate are preferred, and isobornyl acrylate is more preferred. By using such monofunctional monomers having an alicyclic structure, the adhesion, abrasion resistance, bending resistance, and blocking resistance of the coating film tend to be further improved.

[0031] The content of isobornyl (meth)acrylate is preferably 5.0 to 20% by mass, more preferably 10 to 20% by mass, and even more preferably 12.5 to 17.5% by mass, relative to the total amount of the ink composition. When the content of isobornyl (meth)acrylate is 5.0% by mass or more, adhesion tends to be further improved. Furthermore, when the content of isobornyl (meth)acrylate is 20% by mass or less, member durability and blocking resistance tend to be further improved.

[0032] The content of the monofunctional monomer having an alicyclic structure is preferably 5.0 to 20% by mass, more preferably 10 to 20% by mass, and even more preferably 12.5 to 17.5% by mass, relative to the total amount of the ink composition. When the content of the monofunctional monomer having an alicyclic structure is 5.0% by mass or more, adhesion tends to be further improved. When the content of the monofunctional monomer having an alicyclic structure is 20% by mass or less, member durability and blocking resistance tend to be further improved.

[0033] 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, vinylmethyloxazolidinone, and N-vinylpyrrolidone; nitrogen-containing monofunctional acrylate monomers such as acryloylmorpholine (ACMO); 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.

[0034] Among these, it is preferable to contain either a nitrogen-containing monofunctional vinyl monomer or a nitrogen-containing monofunctional acrylate monomer, and more preferable to contain a monomer having a nitrogen-containing heterocyclic structure such as N-vinylcaprolactam, N-vinylcarbazole, N-vinylpyrrolidone, vinylmethyloxazolidinone, or acryloylmorpholine, and even more preferable to contain acryloylmorpholine or vinylmethyloxazolidinone.

[0035] The use of such nitrogen-containing monofunctional monomers tends to further improve the abrasion resistance of the coating film. Furthermore, nitrogen-containing monofunctional acrylate monomers having a nitrogen-containing heterocyclic structure such as acryloylmorpholine tend to further improve the adhesion of the coating film.

[0036] The content of the nitrogen-containing monofunctional monomer is preferably 1.0 to 15 mass %, more preferably 2.0 to 12 mass %, and even more preferably 3.0 to 10 mass %, relative to the total amount of the ink composition. When the content of the nitrogen-containing monofunctional monomer is within the above range, the abrasion resistance and adhesion of the coating film tend to be further improved.

[0037] 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 (PEA), 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] 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. By using such aromatic group-containing monofunctional monomers, the solubility of the polymerization initiator tends to be further improved, and the curability of the ink composition tends to be further improved. In particular, when an acylphosphine oxide-based polymerization initiator or a thioxanthone-based polymerization initiator is used, the solubility tends to be improved.

[0039] The content of the aromatic group-containing monofunctional monomer is preferably 12.5 to 35 mass %, more preferably 15 to 30 mass %, and even more preferably 17.5 to 25 mass %, relative to the total amount of the ink composition. When the content of the aromatic group-containing monofunctional monomer is within the above range, the abrasion resistance and adhesion of the coating film tend to be further improved.

[0040] 1.1.1.4. Urethane acrylate Urethane acrylate is not particularly limited as long as it is a (meth)acrylic acid ester having urethane bond, and for example, (methylcarbamoyloxy) ethyl (meth) acrylate, (ethylcarbamoyloxy) ethyl (meth) acrylate, (propylcarbamoyloxy) ethyl (meth) acrylate, (butylcarbamoyloxy) ethyl (meth) acrylate (MUA), (methylcarbamoyloxy) ethoxyethyl (meth) acrylate, (ethylcarbamoyloxy) ethoxyethyl (meth) acrylate, (propylcarbamoyloxy) ethoxyethyl (meth) acrylate, (butylcarbamoyloxy) ethoxyethyl (meth) acrylate.By using such urethane acrylate, adhesion tends to be further improved.

[0041] The content of the urethane acrylate is preferably 1.0 to 15% by mass, more preferably 2.0 to 12% by mass, and even more preferably 3.0 to 10% by mass, relative to the total amount of the ink composition. When the content of the urethane acrylate is within the above range, adhesion tends to be further improved.

[0042] 1.1.2. Polyfunctional Monomer A2 The polymerizable monomer A may contain a polyfunctional monomer A2. The polyfunctional monomer A2 is not particularly limited, but examples thereof include vinyl group-containing (meth)acrylates and polyfunctional (meth)acrylates. The polyfunctional monomer is not limited to the above.

[0043] The content of the polyfunctional monomer is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and even more preferably 25% by mass or more, relative to the total amount of the ink composition. Furthermore, the content of the polyfunctional monomer is preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less, relative to the total amount of the ink composition. When the content of the polyfunctional monomer is 10% by mass or more, blocking resistance, member durability, and abrasion resistance tend to be further improved. When the content of the polyfunctional monomer is 45% by mass or less, adhesion and bending resistance tend to be further improved.

[0044] Examples of polyfunctional monomers are given below, but the polyfunctional monomers in this embodiment are not limited to the following.

[0045] 1.1.2.1 Vinyl group-containing (meth)acrylates The vinyl group-containing (meth)acrylate is not particularly limited, but examples thereof include compounds represented by the following formula (I): By including such a vinyl group-containing (meth)acrylate, the viscosity of the ink composition tends to decrease and the ejection stability tends to be improved. In addition, the curability of the ink composition is improved, and the improved curability also enables the recording speed to be increased. H2C=CR 1 -CO-OR 2 -O-CH=CH-R 3 (I) (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.

[0046] In the above formula (I), 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 via 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 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 ink composition and further improving the curability of the ink 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.

[0047] In the above formula (I), 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.

[0048] 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.

[0049] Specific examples of the compound of formula (I) 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 because it allows the ink composition to have a good balance between curability and viscosity. In this embodiment, 2-(2-vinyloxyethoxy)ethyl acrylate is also referred to as VEEA.

[0050] The content of the vinyl group-containing (meth)acrylate is preferably 7.5 to 40% by mass or more, more preferably 15 to 35% by mass, and even more preferably 20 to 30% by mass, relative to the total amount of the ink composition. When the content of the vinyl group-containing (meth)acrylate is within the above range, the viscosity of the ink composition tends to decrease, and the ejection stability tends to be further improved.

[0051] 1.1.2.2 Multifunctional (meth)acrylates The polyfunctional (meth)acrylate is not particularly limited, and examples thereof include dipropylene glycol di(meth)acrylate (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, PO (propylene oxide) di(meth)acrylate of bisphenol A, and the like. Examples of the acrylate include bifunctional (meth)acrylates such as ethylene oxide 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, 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.

[0052] Among these, dipropylene glycol diacrylate (DPGDA) is more preferable. By using such a polyfunctional (meth)acrylate, the curability and abrasion resistance tend to be further improved, and the viscosity tends to be further reduced.

[0053] The content of the polyfunctional (meth)acrylate is preferably 1.0 to 12 mass %, more preferably 1.5 to 10 mass %, and even more preferably 2.0 to 8.0 mass %, relative to the total amount of the ink composition. When the content of the polyfunctional (meth)acrylate is within the above range, curability tends to be further improved and viscosity tends to be further reduced.

[0054] 1.1.3. Polymerizable Monomer B The SP value of polymerizable monomer B is 7.0 (J / cm 3 ) 1 / 2 or less than 8.0 (J / cm 3 ) 1 / 2 More preferably, 6.5 (J / cm 3 ) 1 / 2 or less than 8.5 (J / cm 3 ) 1 / 2 More preferably, it is 6.0 (J / cm 3 ) 1 / 2 or less than 9.5 (J / cm 3 ) 1 / 2 When the SP value of the polymerizable monomer B is within the above range, the durability of the member is further improved.

[0055] As the polymerizable monomer B, among the monofunctional monomer A1 and the polyfunctional monomer A2, a monomer having an SP value according to Small's formula of 7.0 (J / cm 3 ) 1 / 2 or less than 8.0 (J / cm 3 ) 1 / 2 The above-mentioned can be used. Among them, nitrogen-containing monofunctional monomers are preferred, and acryloylmorpholine is more preferred. By using such polymerizable monomer B, the scratch resistance and adhesion of the coating film and the durability of the member tend to be further improved.

[0056] The content of polymerizable monomer B is 20% by mass or more, preferably 30 to 80% by mass, more preferably 40 to 75% by mass, and even more preferably 50 to 70% by mass, relative to the total amount of the ink composition. When the content of polymerizable monomer B is 20% by mass or more, the durability of the member is further improved. When the content of polymerizable monomer B is 80% by mass or less, the abrasion resistance and adhesion of the coating film, as well as the durability of the member, tend to be further improved.

[0057] 1.1.4. Polymerizable Monomer C The SP value of polymerizable monomer C is 7.0 (J / cm 3 ) 1 / 2 Excess 8.0(J / cm 3 ) 1 / 2 More preferably, it is less than 7.1 (J / cm 3 ) 1 / 2 More than 7.9(J / cm 3 ) 1 / 2 and more preferably 7.2 (J / cm 3 ) 1 / 2 More than 7.8(J / cm 3 ) 1 / 2 When the SP value of the polymerizable monomer C is within the above range, adhesion and abrasion resistance are further improved.

[0058] As the polymerizable monomer C, among the monofunctional monomer A1 and the polyfunctional monomer A2, a monomer having an SP value of 7.0 (J / cm) according to Small's formula is used. 3 ) 1 / 2 Excess 8.0(J / cm 3 ) 1 / 2 Those having a molecular weight of less than 10 ...

[0059] The content of polymerizable monomer C is 22.5% by mass or less, preferably 5.0 to 20% by mass, and more preferably 10 to 17.5% by mass, relative to the total amount of the ink composition. When the content of polymerizable monomer C is 22.5% by mass or less, the durability of the member is further improved. Furthermore, when the content of polymerizable monomer C is 5.0% by mass or more, the adhesion and abrasion resistance tend to be further improved.

[0060] The ratio of the content of polymerizable monomer C to the content of polymerizable monomer B is preferably 2.0 to 8.0, more preferably 2.5 to 7.5, and even more preferably 3.0 to 7.0. When the ratio of the content of polymerizable monomer C to the content of polymerizable monomer B is within the above range, adhesion, abrasion resistance, and member durability tend to be further improved.

[0061] 1.2.Oligomers The ink of this embodiment may further contain an oligomer. An oligomer is a polymer containing a polymerizable compound as a constituent component, and refers to a compound having one or more polymerizable functional groups. Note that the polymerizable compound referred to here is not limited to the monofunctional monomers and polyfunctional monomers described above. In this embodiment, an oligomer is defined as one having a molecular weight of 1000 or more, and a monomer is defined as one having a molecular weight of 1000 or less.

[0062] 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.

[0063] Among these, urethane acrylate oligomers are preferred, aliphatic urethane acrylate oligomers and aromatic urethane acrylate oligomers are more preferred, and aliphatic urethane acrylate oligomers are even more preferred. Furthermore, the urethane acrylate oligomer is preferably a tetrafunctional or lower urethane acrylate oligomer, and more preferably a difunctional urethane acrylate oligomer. By using such an oligomer, the viscosity tends to be further reduced, and curability and adhesion tend to be further improved.

[0064] The content of the oligomer is preferably 1 to 15% by mass, more preferably 1 to 10% by mass, and even more preferably 2 to 7% by mass, relative to the total amount of the ink composition. When the content of the oligomer relative to the total amount of the ink is within the above range, the viscosity tends to be further reduced, and the curability and adhesion tend to be further improved.

[0065] 1.3. Polymerization initiator The polymerization initiator is not particularly limited as long as it is a photopolymerization initiator that generates active species upon irradiation with radiation, 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 and thioxanthone-based polymerization initiators are preferred, with acylphosphine oxide-based polymerization initiators being more preferred. Use of such polymerization initiators tends to further improve the curability of the composition, particularly the curability in a curing process using UV-LED light. The polymerization initiators may be used alone or in combination of two or more.

[0066] The content of the polymerization initiator is preferably 3 to 15 mass %, more preferably 5 to 12 mass %, and even more preferably 7 to 10 mass %, relative to the total amount of the ink 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.

[0067] 1.3.1. Acylphosphine oxide polymerization initiators 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.

[0068] Commercially available acylphosphine oxide polymerization initiators such as these are not particularly limited, but examples thereof include Omnirad 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 Speedcure TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide).

[0069] The content of the acylphosphine oxide polymerization initiator is preferably 3 to 15 mass %, more preferably 5 to 12 mass %, and even more preferably 7 to 10 mass %, relative to the total amount of the ink composition. When the content of the acylphosphine oxide polymerization initiator is within the above range, the curability of the composition and the solubility of the polymerization initiator tend to be further improved.

[0070] 1.3.2. Thioxanthone polymerization initiators The thioxanthone-based polymerization initiator is not particularly limited, but examples thereof include thioxanthone, diethylthioxanthone, isopropylthioxanthone, and chlorothioxanthone.

[0071] Commercially available thioxanthone polymerization initiators include, but are not limited to, Speedcure DETX (2,4-diethylthioxanthen-9-one), Speedcure ITX (2-isopropylthioxanthone) (both manufactured by Lambson Chemical), and KAYACURE DETX-S (2,4-diethylthioxanthone) (manufactured by Nippon Kayaku Co., Ltd.).

[0072] 1.4.Polymerization inhibitors 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), hindered amine compounds, 2,2,6,6-tetramethylpiperidinyl-1-oxyl, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl (LA-7RD), and derivatives of 2,2,6,6-tetramethylpiperidinyl-1-oxyl.

[0073] The content of the polymerization inhibitor is preferably 0.1 to 0.5% by mass, and more preferably 0.1 to 0.3% by mass, relative to the total amount of the ink composition. When the content of the polymerization inhibitor is within the above range, the storage stability of the ink composition tends to be further improved.

[0074] 1.5.Surfactants The surfactant is not particularly limited, but examples thereof include acetylene glycol surfactants, fluorine-based surfactants, and silicone-based surfactants.

[0075] The acetylene glycol surfactant is not particularly limited, but examples thereof include alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and alkylene oxide adducts of 2,4-dimethyl-5-decyne-4-ol and 2,4-dimethyl-5-decyne-4-ol.

[0076] The fluorine-based surfactant is not particularly limited, but examples thereof include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines, and perfluoroalkyl amine oxide compounds.

[0077] Examples of silicone surfactants include polysiloxane compounds, polyester-modified silicones, and polyether-modified organosiloxanes. 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 surfactant is preferably 0.1 to 1 mass %, more preferably 0.2 to 0.8 mass %, relative to the total mass of the composition. When the content of the surfactant is within the above range, the wettability of the ink composition tends to be further improved.

[0079] 1.6.Colorants The ink composition according to this embodiment may further contain a coloring material. By containing a coloring material, the ink composition according to this embodiment can be used as a colored ink composition. The coloring material can be at least one of a pigment and a dye.

[0080] 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.

[0081] 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.

[0082] Although this can be changed appropriately depending on the type of ink desired, the total content of coloring materials is preferably 0.5 to 15% by mass, more preferably 1.0 to 10% by mass, and even more preferably 1.5 to 5.0% by mass, relative to the total amount of ink composition. Note that the ink 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).

[0083] The dye is not particularly limited, but examples thereof 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 above dyes may be used alone or in combination of two or more.

[0084] 1.7.Other Ingredients The radiation-curable ink jet composition according to this embodiment may further contain additives such as coloring materials such as pigments and dyes, and dispersants for pigments and the like, as needed.

[0085] 2. Inkjet method In the inkjet method according to this embodiment, the flow path is filled with an ink having an SP value of 7.0 to 8.0 (J / cm 3 ) 1 / 2 and an irradiation step of irradiating the radiation-curable ink jet composition adhered to the recording medium with radiation.

[0086] 2.1.Discharge process In the ejection step, the heated composition is ejected from an inkjet head and attached to 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.

[0087] The inkjet head 10 used in the ejection step includes a line head that performs recording by a line method and a serial head that performs recording by a serial method.

[0088] 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 inkjet 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.

[0089] 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.

[0090] 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.

[0091] Examples of the radiation include ultraviolet light, infrared light, visible light, and X-rays. The radiation source is provided downstream of the inkjet head and irradiates the ink 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.

[0092] 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 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, 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 reduction in the odor of the cured film.

[0093] 3. Inkjet device The inkjet device of this embodiment uses a flow path with an SP value of 7.0 to 8.0 (J / cm 3 ) 1 / 2 and the radiation-curable ink jet composition according to any one of claims 1 to 8, which is ejected from the ink jet head. The ink jet apparatus may further include a radiation source that irradiates the ink composition with radiation.

[0094] The inkjet head has a flow path with an SP value of 7.0 to 8.0 (J / cm 3 ) 1 / 2 Here, the "flow path" refers to a path through which the ink composition is transported within the inkjet head, and a part of the path has an SP value according to Small's formula of 7.0 to 8.0 (J / cm 3 ) 1 / 2Examples of materials that can achieve such an SP value include silicone adhesives that bond inkjet head components together and ethylene propylene diene rubber that forms rubber bushings.

[0095] As an example of an inkjet device, a perspective view of a serial printer is shown in Fig. 1. As shown in Fig. 1, the serial printer 20 includes a conveying unit 220 and a recording unit 230. The conveying unit 220 conveys the recording medium F fed to the serial printer to the recording unit 230, and ejects the recording medium after recording outside the serial printer. Specifically, the conveying unit 220 has feed rollers and conveys the fed recording medium F in the sub-scanning direction T1.

[0096] The recording unit 230 also includes an inkjet head 231 that ejects a composition onto the recording medium F sent from the conveying unit 220, a radiation source 232 that irradiates the deposited ink composition with radiation, a carriage 234 that carries these, and a carriage movement mechanism 235 that moves the carriage 234 in the main scanning directions S1 and S2 of the recording medium F.

[0097] In the case of a serial printer, an inkjet head 231 having a length smaller than the width of the recording medium is provided, and the head moves to perform recording in multiple passes (multi-pass). In addition, in a serial printer, the head 231 and radiation source 232 are mounted on a carriage 234 that moves in a predetermined direction, and the head moves in conjunction with the movement of the carriage, thereby ejecting the composition onto the recording medium. In this way, recording is performed in two or more passes (multi-pass). A pass is also called a main scan. A sub-scan is performed to transport the recording medium between passes. In other words, main scans and sub-scans are performed alternately.

[0098] Although FIG. 1 shows an embodiment in which the radiation source is mounted on a carriage, the present invention is not limited to this, and the radiation source may be one that is not mounted on a carriage.

[0099] Furthermore, the inkjet device of this embodiment is not limited to the serial printer, but may be the line printer described above.

[0100] 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 stretchability 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.

[0101] 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. [Example]

[0102] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0103] 1. Preparation of ink composition The ink compositions of each example were obtained by placing the components in a mixing tank, mixing and stirring, and filtering through a 5 μm membrane filter so as to obtain the composition shown in Table 1. The numerical values ​​for each component shown in each example in the table represent wt % unless otherwise specified.

[0104] [Table 1]

[0105] The abbreviations and product ingredients used in Table 1 are as follows: [Dispersion] PB15:3: Pigment blue 15:3 Dispersant: Solsperse 36000 (Lubrizol, polymer dispersant) [Monofunctional Monomer A1] (Polymerizable monomer B) IBXA (Osaka Organic Chemical Industry, Ltd., isobornyl acrylate) TMCHA (product name "Viscoat #196", manufactured by Osaka Organic Chemical Industry Ltd., 3,3,5-trimethylcyclohexyl acrylate) TBCHA (product name "SR217", manufactured by Sartomer Corporation, tert-butylcyclohexanol acrylate) (Polymerizable Monomer C) PEA (product name "Viscoat #192", manufactured by Osaka Organic Chemical Industry Ltd., phenoxyethyl acrylate) ACMO (KJ Chemicals Co., Ltd., acryloylmorpholine) MUA (Tokyo Chemical Industry Co., Ltd., 2-(butylcarbamoyloxy)ethyl acrylate) [Polyfunctional Monomer A2] (Polymerizable Monomer C) VEEA (Nippon Shokubai Co., Ltd., 2-(2-vinyloxyethoxy)ethyl acrylate) DPGDA (product name "SR508", manufactured by Sartomer Corporation, dipropylene glycol diacrylate) [Oligomer] CN9893 (polyether-based aliphatic urethane acrylate oligomer, functional group number 2, (Product name manufactured by Sartomer) [Polymerization initiator] Speedcure TPO (product name "Speedcure TPO", LAMBSON) (2,4,6-trimethylbenzoyldiphenylphosphine oxide) Omnirad 819 (Product name "Omnirad 819" IGM Resins Co., Ltd. Manufactured by bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide) Speedcure DETX (Product name "Speedcure DETX", LAMB SON, 2,4-diethylthioxanthen-9-one) [Surfactant] BYK-UV3500 (BYK Additives & Instruments, silicone surfactant) [Polymerization inhibitor] LA-7RD (ADEKA Corporation trade name, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl) MEHQ (product name "p-methoxyphenol", manufactured by Kanto Chemical Co., Ltd., hydroquinone monomethyl ether)

[0106] 2. Evaluation Method 2.1.Component durability Ethylene propylene diene rubber (EB270N-1-1000-100, manufactured by Akitsu Industries, SP value: 7.9-8.0), which is a component constituting the flow path of an inkjet head, was cut to a size of 30 mm x 30 mm, and 0.2 g of silicone adhesive (KE-4897-W, manufactured by Shin-Etsu Chemical Co., Ltd., SP value: 7.3-7.6) was cured for 7 days at 25°C and 50% RH to prepare adhesive test pieces. The adhesive test pieces were immersed in each ink composition at 60°C for 7 days, and the weight change rate of the adhesive test pieces before and after immersion was calculated. The component durability was evaluated according to the following evaluation criteria. Weight change rate (wt%) = {(weight after insertion - weight before insertion) / weight before insertion} x 100 (Evaluation criteria) A: Weight change rate is less than 20% by weight B: Weight change rate is 20% by weight or more and less than 40% by weight C: Weight change rate is 40% or more by weight

[0107] 2.2. Blocking resistance Each radiation-curable inkjet composition was applied to a polyvinyl chloride film, which was a recording medium, using a bar coater to a coating thickness of 12 μm, and the UV irradiance was 1000 mW / cm 2The cumulative energy is 250mJ / cm 2 The recording medium was then irradiated with ultraviolet light so that the ink film was uniformly irradiated. An LED with a peak wavelength of 395 nm was used as the light source. The back side of the recording medium was then placed on the printed surface of the resulting recording material with the ink coating film, and the recording material was left for 24 hours under a load of 600 g in an environment of 20-25°C / 40-60% RH. After leaving the recording material, the recording material was visually observed for image sticking and blocking marks, and the blocking resistance was evaluated according to the following evaluation criteria. (Evaluation criteria) A: No sticking B: Sticking, no blocking marks C: Sticking, blocking marks

[0108] 2.3.Bending test The ink coating film obtained in the above-mentioned blocking resistance test was subjected to a bending test in accordance with JIS K5400 using a coating film bending tester PI-801 manufactured by Tester Sangyo Co., Ltd. The mandrel diameter used was φ2 mm. The bending test results for the obtained printed matter were evaluated based on the following criteria. (Evaluation criteria) A: No cracks when bent at 180° B: No cracks when bent at 130°C, cracks when bent at 180°C C: Cracks when bent at 90°

[0109] 2.4.Adhesion The ink coating film obtained in the above-mentioned blocking resistance test was evaluated by a cross-cut test in accordance with JIS K5600-5-6. More specifically, the blade of a cutter was placed perpendicular to the ink coating film, and squares with 1 mm spacing between the cuts were created to create a 10 x 10 grid. 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 the tape. Next, within 5 minutes of application, the tape was firmly peeled off from the cured film at an angle close to 60° in 0.5 to 1.0 seconds, and the state of the grid was visually observed. (Evaluation criteria) A: Peeling is less than 10% of the grid B: Peeling is 10% or more but less than 35% of the grid. C: Peeling of 35% or more of the grid

[0110] 2.5. Scratch resistance The ink coating film obtained in the above-mentioned blocking resistance test was rubbed with a Gakushin-type rub fastness tester AB-301 (trade name, manufactured by Tester Sangyo Co., Ltd.) equipped with a white cotton cloth (compliant with JIS L 0803) at a load of 200 g, either until the recorded matter peeled off or 20 times back and forth. The recording medium was then visually inspected for peeling of the recorded matter, and the rub resistance was evaluated according to the following evaluation criteria. (Evaluation criteria) A: The load when the stylus reaches the media surface is 30mN or more and less than 35mN B: The load when the stylus reaches the media surface is 25 mN or more and less than 30 mN C: The load when the stylus reaches the media surface is 20 mN or more but less than 25 mN D: The load when the stylus reaches the media surface is less than 20 mN

[0111] 3. Evaluation Results As shown in Table 1, according to the present invention, the flow path has an SP value of 7.0 to 8.0 (J / cm 3 ) 1 / 2 It can be seen that even when used in an inkjet recording apparatus equipped with an inkjet head having the above-mentioned components, by using predetermined amounts of polymerizable monomers B and C, it is possible to provide a radiation-curable inkjet composition that is excellent in both component durability and adhesion. [Explanation of symbols]

[0112] 20... serial printer, 220... transport unit, 230... recording unit, 231... inkjet head, 232... radiation source, 234... carriage, 235... carriage moving mechanism, F... recording medium, S1, S2... main scanning direction, T1... sub-scanning direction

Claims

1. The flow path has an SP value of 7.0 to 8.0 (J / cm 3 ) 1 / 2 An inkjet head having the above components A radiation-curable inkjet composition for use in an inkjet recording apparatus comprising: SP value 7.0 (J / cm 3 ) 1 / 2 or less than 8.0 (J / cm 3 ) 1 / 2 The polymerizable mono mer B and SP value 7.0 (J / cm 3 ) 1 / 2 Excess 8.0 (J / cm 3 ) 1 / 2 Polymerizable and a polymerizable monomer A containing a monomer C, The content of the polymerizable monomer A is 65% by mass or more relative to the total amount of the ink composition. 、 The content of the polymerizable monomer B is 20% by mass or more relative to the total amount of the ink composition. the law of nature, The content of the polymerizable monomer C is 22.5% by mass or less with respect to the total amount of the ink composition. and The weight of the content mass ratio of each polymerizable monomer A is used as a weight. the weighted average glass transition temperature of the polymer is 40°C or less; the polymerizable monomer A includes a monofunctional monomer A1, The content of the monofunctional monomer A1 is 80 mass% based on the total amount of the polymerizable monomer A. Below is the Radiation-curable inkjet compositions.

2. the polymerizable monomer B includes a nitrogen-containing monofunctional monomer; The radiation-curable ink jet composition according to claim 1 .

3. The polymerizable monomer B includes acryloylmorpholine. The radiation-curable ink jet composition according to claim 2 .

4. the polymerizable monomer C includes a monofunctional monomer having an alicyclic structure, The radiation-curable ink jet composition according to claim 1 .

5. the polymerizable monomer C includes isobornyl (meth)acrylate, The content of the isobornyl (meth)acrylate is 5% by weight based on the total amount of the ink composition. 0 to 20% by mass, The radiation-curable ink jet composition according to claim 4.

6. The weight of the content mass ratio of each polymerizable monomer A is used as a weight. The weighted average glass transition temperature of the polymer is 25 to 40°C. The radiation-curable ink jet composition according to any one of claims 1 to 5.

7. the polymerizable monomer A includes a monofunctional monomer A1, The content of the monofunctional monomer A1 is 50 to 80% based on the total amount of the polymerizable monomer A. is mass %; The radiation-curable ink jet composition according to any one of claims 1 to 6.

8. the polymerizable monomer A includes a polyfunctional monomer A2, The polyfunctional monomer A2 is a vinyl group-containing (meth)acrylate represented by the following general formula (I): Including The radiation-curable ink jet composition according to any one of claims 1 to 7. H 2 C=CR 1 -CO-OR 2 -O-CH=CH-R 3 ・・・ (I) (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 Ri, R 3 is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms.

9. The content of the polyfunctional monomer A2 is 20% by mass or more with respect to the total amount of the ink composition. be, The radiation-curable ink jet composition according to claim 8.

10. an inkjet head having a member with an SP value of 7.0 to 8.0 in a flow path; The radiation according to any one of claims 1 to 8, which is ejected from the inkjet head. comprising a curable inkjet composition; Inkjet recording device.

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