JP2017125194A - Recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a UV-curable inkjet ink composition giving excellent durability of an inkjet head and having excellent discharge reliability.SOLUTION: The UV-curable inkjet ink composition comprises a monomer and a photopolymerization initiator, and the composition contains a monomer, which satisfies a condition where an SP value (σ) calculated by Small's formula is presented by |σ-10.5|≥1.0, by 20 mass% or more with respect to the total mass of the ink composition and a monomer, which satisfies a condition where the SP value (σ) is represented by 0.5≤|σ-10.5|<1.0, by 20 mass% or more with respect to the total mass of the ink composition. When the composition contains a monomer, which satisfies a condition where the SP value (σ) is represented by |σ-10.5|<0.5, the monomer is included by 20 mass% or less with respect to the total mass of the ink composition. The UV-curable inkjet composition is discharged from an inkjet head using an epoxy-based adhesive.SELECTED DRAWING: None

Description

  The present invention relates to an ultraviolet curable inkjet ink composition and a recording method.

  Conventionally, various methods have been used as a recording method for forming an image on a recording medium such as paper based on an image data signal. Among these, the ink jet system is an inexpensive apparatus, and ink is ejected only to a required image portion to form an image directly on a recording medium. Therefore, the ink can be used efficiently, and the running cost is low. Furthermore, the inkjet method is excellent as a recording method because of its low noise.

  In recent years, in order to form a print having high water resistance, solvent resistance, scratch resistance, and the like on the surface of a recording medium, an ultraviolet curable inkjet ink composition that is cured when irradiated with ultraviolet rays in an inkjet recording method. Is used.

  For example, Patent Document 1 discloses that a pigment, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, or trimethylolpropane triacrylate, which is a compound containing two or more ethylenic double bonds, has a molecular weight. 2-phenoxyethyl acrylate, acryloylmorpholine, or isobornyl acrylate, which is a compound containing one ethylenic double bond of 90 to 210, and 2-benzyl-2-dimethylamino-1- ( An active energy ray-curable inkjet ink containing 4-morpholinophenyl) -butanone-1 and acylphosphine oxides is disclosed.

JP 2002-241647 A

  However, when the inkjet ink disclosed in Patent Document 1 is to be ejected from the inkjet head, there is a problem that the adhesive used in the inkjet head swells and the inkjet head may have poor durability. For this reason, there is a strong demand for ink-jet inks that are excellent in ink-jet ink characteristics and that have excellent durability of the ink-jet head even after repeated ejection. On the other hand, an ink composition having excellent head durability is often inferior in solubility of the photopolymerization initiator, and thus inferior in ejection reliability. Therefore, it is required to satisfy both the durability of the head and the ejection reliability.

  Therefore, an object of the present invention is to provide an ultraviolet curable ink composition for inkjet which is excellent in durability of an inkjet head and is also excellent in ejection reliability.

  The present inventors have intensively studied to solve the above problems. As a result, in order to obtain an ink having excellent durability of the inkjet head, it has been conceived that an ink composition that does not swell the adhesive used in the inkjet head may be used. As the adhesive, an epoxy adhesive, an acrylic adhesive, a silicon adhesive, or the like is used. Therefore, in the case of using an epoxy-based adhesive among these, further intensive investigations were made on the composition of an ultraviolet curable ink jet ink excellent in ink characteristics.

  As a result, the inventors found that the above problems can be solved by an ultraviolet curable inkjet ink composition containing a predetermined amount of a monomer having an SP value calculated by the Small formula in a predetermined range, and completed the present invention.

That is, the present invention is as follows.
[1]
A UV curable inkjet ink composition comprising a monomer and a photopolymerization initiator, wherein the SP value (σ) calculated by the Small formula is represented by | σ-10.5 | ≧ 1.0 In the range of 20% by mass or more with respect to the total mass of the ink composition, and the SP value (σ) is represented by 0.5 ≦ | σ−10.5 | <1.0. The monomer satisfying the above conditions is contained in the range of 20% by mass or more with respect to the total mass of the ink composition, and the SP value (σ) is represented by | σ−10.5 | <0.5. Is contained in a range of 20% by mass or less with respect to the total mass of the ink composition, and is discharged from an inkjet head using an epoxy adhesive. Ink jet ink composition.
[2]
Monomers satisfying the condition that the SP value (σ) is expressed as 0.5 ≦ | σ−10.5 | <1.0 are 20% by mass or more and 65% by mass with respect to the total mass of the ink composition. The ultraviolet curable inkjet ink composition according to [1], which is contained in the following range.
[3]
A monomer satisfying the condition that the SP value (σ) is represented by | σ-10.5 | ≧ 1.0 is within a range of 20% by mass to 70% by mass with respect to the total mass of the ink composition. The ultraviolet curable inkjet ink composition according to [1] or [2].
[4]
A monomer satisfying the condition that the SP value (σ) is represented by | σ-10.5 | ≧ 1.0 is represented by the following general formula (I):
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (I)
Wherein R ¹ is a hydrogen atom or a methyl group, R ² is a divalent organic residue having 2 to 20 carbon atoms, and R ³ is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms. Group.)
The ultraviolet curable inkjet ink composition according to any one of [1] to [3], which is a vinyl ether group-containing (meth) acrylic acid ester represented by:
[5]
The ultraviolet curable inkjet ink according to [4], wherein the vinyl ether group-containing (meth) acrylic acid ester represented by the general formula (I) is 2- (vinyloxyethoxy) ethyl (meth) acrylate. Composition.
[6]
[1] A recording method comprising an ejection step of ejecting the ultraviolet curable inkjet ink composition according to any one of [5] from an inkjet head using an epoxy adhesive onto a recording medium.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. In addition, this invention is not restrict | limited to the following embodiment, A various deformation | transformation can be implemented within the range of the summary.

  In this specification, “curability” refers to a property of curing in response to light.

  In this specification, “(meth) acrylate” means at least one of acrylate and its corresponding methacrylate, and “(meth) acryl” means at least one of acryl and its corresponding methacryl.

In the present specification, the “SP value” is also referred to as a solubilization parameter (Solubility Parameter) and means a value calculated using the Small 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.)

[UV-curable inkjet ink composition]
An ultraviolet curable ink composition for inkjet according to an embodiment of the present invention (hereinafter also simply referred to as “ink composition”) is ejected from an inkjet head using an epoxy adhesive and is small. The monomer satisfying the condition that the SP value (σ) calculated by the formula of | σ-10.5 | ≧ 1.0 is 20 relative to the total mass (100% by mass) of the ink composition. A monomer that satisfies the condition represented by 0.5 ≦ | σ-10.5 | <1.0 in a range of not less than mass% is 20 with respect to the total mass (100 mass%) of the ink composition. In the case where a monomer that is included in a range of at least mass% and satisfies the condition represented by | σ−10.5 | <0.5 is included, the monomer is added to the total mass (100 mass% of the ink composition). ) In a range of 20% by mass or less.

As described above, the monomer contained in the ink composition of the present embodiment has a value in a predetermined range derived from a specific formula using the SP value (σ) calculated by the Small formula.
Here, the above “10.5” is a numerical value derived from experiments, but it is presumed that it is close to the SP value of the epoxy resin that is a constituent component of the epoxy adhesive. The monomer having the SP value close to 10.5 is likely to penetrate the epoxy adhesive, that is, the epoxy resin which is a thermosetting resin, and as a result, the epoxy adhesive becomes softer. It will swell. In other words, as the value of | σ-10.5 | increases, the attack to the epoxy resin, that is, the penetration into the resin having a hydroxyl group generated by epoxy group ring-opening polymerization can be prevented.

  On the other hand, as the value of | σ-10.5 | is smaller, it has an aromatic ring such as bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide (for example, IRGACURE 819 manufactured by BASF). It has been found that the solubility of the photopolymerization initiator tends to be excellent. In this way, the ink composition contains more monomer that does not have a too large or too small value of | σ-10.5 |, and is thus ejected from an inkjet head using an epoxy adhesive. The present inventor has found that a suitable ink can be obtained.

  Hereinafter, additives (components) contained in or capable of being contained in the ultraviolet curable inkjet ink of the present embodiment will be described.

〔monomer〕
The monomer contained in the ink composition of the present embodiment is polymerized at the time of light irradiation by the action of a photopolymerization initiator described later, and the printed ink composition can be cured.

(1. Monomer with SP value (σ) satisfying | σ-10.5 | ≧ 1.0)
The monomer satisfying | σ-10.5 | ≧ 1.0 as the SP value (σ) contained in the ink composition of the present embodiment is not limited to the following, but for example, isobornyl acrylate (SP value of 7. 24), isostearyl acrylate (SP value 8.23), isodecyl acrylate (SP value 8.36), lauryl acrylate (SP value 8.36), isooctyl acrylate (SP value 8.42), MEDOL-10 ( OSAKA ORGANIC CHEMICAL INDUSTRY LTD. Trade name, (2-methyl-2-ethyl-1,3-dioxolan-4-yl) methyl acrylate, SP value 8.59), diethylene glycol divinyl ether (SP Value 9.07), 1,9-nonanediol diacrylate (SP value 9.08), dipentaerythritol hexaacrylate (SP Value 9.31), 1,6-hexanediol diacrylate (SP value 9.31), ethyl carbitol acrylate (SP value 9.37), acroylmorpholine (SP value 11.55), V # 150D (n = 5) (trade name, SP value 11.58 made by Osaka Organic Chemical Co., Ltd.), DA-141 (trade name made by Nagase Chemtex Corporation, SP value 11.83), and hydroxyethylacrylamide (SP value) 15.63), and a monomer satisfying an SP value (σ) of | σ-10.5 | ≧ 1.0 among vinyl ether group-containing (meth) acrylic acid esters represented by the following general formula (I) (for example, , 2- (2-vinyloxyethoxy) ethyl acrylate having an SP value of 9.41).
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (I)
Wherein R ¹ is a hydrogen atom or a methyl group, R ² is a divalent organic residue having 2 to 20 carbon atoms, and R ³ is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms. Group.)

  Among these, since the curability of the ink can be improved, among the vinyl ether group-containing (meth) acrylic acid esters, the SP value (σ) is | σ-10.5 | ≧ 1.0. A monomer that fills is preferred. Hereinafter, the vinyl ether group-containing (meth) acrylic acid esters will be described in detail, but only those having an SP value (σ) of | σ-10.5 | ≧ 1.0 correspond to the monomers. .

In the above general formula (I), the divalent organic residue represented by R ² may be a linear, branched or cyclic alkylene group having 2 to 20 carbon atoms and a structure. An optionally substituted alkylene group having 2 to 20 carbon atoms and an optionally substituted divalent aromatic group having 6 to 11 carbon atoms having an oxygen atom by at least one of an ether bond and an ester bond Is preferred. Among these, C2-C6 alkylene groups such as ethylene group, n-propylene group, isopropylene group, and butylene group, oxyethylene group, oxy n-propylene group, oxyisopropylene group, and oxybutylene group An alkylene group having 2 to 9 carbon atoms having an oxygen atom due to an ether bond in the structure is preferably used.

In the general formula (I), the monovalent organic residue having 1 to 11 carbon atoms represented by R ³ is a linear, branched or cyclic substituted group having 1 to 10 carbon atoms. Suitable alkyl groups and optionally substituted aromatic groups having 6 to 11 carbon atoms are preferred. Among these, C6-C2 aromatic groups, such as a C1-C2 alkyl group which is a methyl group or an ethyl group, a phenyl group, and a benzyl group, are used suitably.

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

  Specific examples of the vinyl ether group-containing (meth) acrylic acid ester represented by the general formula (I) are not limited to the following, but include 2-vinyloxyethyl (meth) acrylate and 3-vinyl (meth) acrylate. Roxypropyl, 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, (meth) acrylic acid 3- Vinyloxybutyl, 1-methyl-2-vinyloxypropyl (meth) acrylate, 2-vinyl (meth) acrylate Xylbutyl, 4-vinyloxycyclohexyl (meth) acrylate, 6-vinyloxyhexyl (meth) acrylate, 4-vinyloxymethylcyclohexylmethyl (meth) acrylate, 3-vinyloxymethylcyclohexylmethyl (meth) acrylate, (Meth) acrylic acid 2-vinyloxymethylcyclohexylmethyl, (meth) acrylic acid p-vinyloxymethylphenylmethyl, (meth) acrylic acid m-vinyloxymethylphenylmethyl, (meth) acrylic acid o-vinyloxymethylphenyl Methyl, 2- (vinyloxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyisopropoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxy) propyl (meth) acrylate, (meth) acrylic acid 2- (Vinyloxyethoxy) isopropyl (Meth) acrylic acid 2- (vinyloxyisopropoxy) propyl, (meth) acrylic acid 2- (vinyloxyisopropoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (vinyloxyethoxyisopropoxy) ethyl, 2- (vinyloxyisopropoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyisopropoxyisopropoxy) ethyl (meth) acrylate, (meth) acrylic acid 2 -(Vinyloxyethoxyethoxy) propyl, (meth) acrylic acid 2- (vinyloxyethoxyisopropoxy) propyl, (meth) acrylic acid 2- (vinyloxyisopropoxyethoxy) propyl, (meth) acrylic acid 2- (vinyl) Loxyisopropoxyisopropoxy) propyl, (meta ) Acrylic acid 2- (vinyloxyethoxyethoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyethoxyisopropoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyisopropoxyethoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyisopropoxyisopropoxy) isopropyl, 2- (vinyloxyethoxyethoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxyethoxyethoxyethoxy) ethyl (meth) acrylate, (meth) acrylic acid 2- (isopropenoxyethoxy) ethyl, (meth) acrylic acid 2- (isopropenoxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (isopropenoxyethoxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (Isopropenoxye Ethoxy ethoxy) ethyl, and (meth) Polyethylene glycol monovinyl ether acrylate, and (meth) acrylic acid polypropylene glycol monovinyl ether.

  Among those described above, 2-vinyloxyethyl (meth) acrylate, 3-vinyloxypropyl (meth) acrylate, 1-methyl-2-vinyloxyethyl (meth) acrylate, 2-vinyloxypropyl (meth) acrylate, ( 4-vinyloxybutyl (meth) acrylate, 4-vinyloxycyclohexyl (meth) acrylate, 5-vinyloxypentyl (meth) acrylate, 6-vinyloxyhexyl (meth) acrylate, 4-vinyloxy (meth) acrylate Methylcyclohexylmethyl, p-vinyloxymethylphenylmethyl (meth) acrylate, 2- (vinyloxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxyethoxy) ethyl (meth) acrylate, (meth) acrylic The acid 2- (vinyloxyethoxyethoxyethoxy) ethyl is preferred Arbitrariness.

  Of these, 2- (vinyloxyethoxy) ethyl (meth) acrylate is more preferred, and 2- (vinyloxyethoxy) ethyl acrylate is further preferred because of its low viscosity, high flash point, and excellent curability. preferable. Examples of 2- (vinyloxyethoxy) ethyl (meth) acrylate include 2- (2-vinyloxyethoxy) ethyl (meth) acrylate and 2- (1-vinyloxyethoxy) ethyl (meth) acrylate. Examples of 2- (vinyloxyethoxy) ethyl acrylate include 2- (2-vinyloxyethoxy) ethyl acrylate (SP value 9.41) and 2- (1-vinyloxyethoxy) ethyl acrylate.

  The content of the vinyl ether group-containing (meth) acrylic acid esters is preferably 20 to 70% by mass with respect to the total mass (100% by mass) of the ink composition. When the content is within the above range, particularly the curability of the ink and the reliability of the head can be satisfactorily achieved.

  The method for producing the vinyl ether group-containing (meth) acrylic acid esters is not limited to the following, but is a method of esterifying (meth) acrylic acid and a hydroxyl group-containing vinyl ether (Production Method B), (meth) acrylic acid halogen Method of esterifying a compound and a hydroxyl group-containing vinyl ether (Production method C), Method of esterifying (meth) acrylic anhydride and a hydroxyl group-containing vinyl ether (Production method D), (Meth) acrylic acid ester and a hydroxyl group Method of transesterifying vinyl ethers (production method E), Method of esterifying (meth) acrylic acid and halogen-containing vinyl ethers (production method F), alkali (earth) metal salt of (meth) acrylic acid and halogen-containing vinyl ether Esterification method (Production G), hydroxyl group-containing (meth) acrylic acid ester And a method of a carboxylic acid vinyl for vinyl exchange (Procedure H), hydroxyl group-containing (meth) How to ether exchange and acrylic acid esters and alkyl vinyl ethers (formula I).

  Among these, since the desired effect can be further exhibited in this embodiment, the production method E is preferable.

  Monomers satisfying the above | σ-10.5 | ≧ 1.0 may be used alone or in combination of two or more.

  The content of the monomer satisfying the above | σ-10.5 | ≧ 1.0 is in a range of 20% by mass or more with respect to the total mass (100% by mass) of the ink composition, and is 20 to 70% by mass. Is preferred. When the content is within the above range, the swelling of the adhesive used in the inkjet head can be effectively prevented, so that the durability of the inkjet head for discharging the ink composition is excellent.

(2. Monomer satisfying SP value (σ) of 0.5 ≦ | σ-10.5 | <1.0)
The monomer satisfying the SP value (σ) contained in the ink composition of the present embodiment satisfying 0.5 ≦ | σ−10.5 | <1.0 is not limited to the following. For example, tripropylene glycol diacrylate (SP value 9.49), dipropylene glycol diacrylate (SP value 9.55), tetraethylene glycol diacrylate (SP value 9.95), tetrahydrofurfuryl acrylate (SP value 9.97), phenoxyethyl acrylate ( SP value 9.99), benzyl acrylate (SP value 10.00), N-vinylformamide (SP value 11.01), and 4-hydroxybutyl acrylate (SP value 11.31).

  Monomers satisfying the above 0.5 ≦ | σ-10.5 | <1.0 may be used alone or in combination of two or more.

  The content of the monomer satisfying the above 0.5 ≦ | σ−10.5 | <1.0 is in the range of 20% by mass or more with respect to the total mass (100% by mass) of the ink composition. The range of -65 mass% is preferable, and 20-50 mass% is more preferable. It is excellent in the solubility of a photoinitiator as content is 20 mass% or more. Further, when the upper limit of the content is 65% by mass, the adhesive swelling rate is lowered, and thus the durability of the inkjet head is excellent.

(3. Monomer with SP value (σ) satisfying | σ-10.5 | <0.5)
A monomer having an SP value (σ) satisfying | σ-10.5 | <0.5 is an optional component. Examples of the monomer include, but are not limited to, PHE-2 (Dai-ichi Kogyo Seiyaku Co., Ltd., trade name, phenoxydiethylene glycol acrylate, SP value of 10.1), ME -4S (trade name, methoxytetraethylene glycol acrylate (EO-modified type), SP value 10.15), pentaerythritol triacrylate (SP value 10.25), dicyclopentanyl dimethylene diacrylate (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) SP value 10.34), FA513AS (trade name, manufactured by Hitachi Chemical Co., Ltd., dicyclopentanyloxyacrylate, SP value 10.35), FA512AS (trade name, manufactured by Hitachi Chemical Co., Ltd.) Dicyclopentenyloxyethyl acrylate, SP value 10.44), FA511AS (Hitachi Chemical) Gosha trade name, cyclohexyl acrylate, SP value 10.54), and N- vinylcaprolactam (SP value 10.65) and the like.

  Monomers satisfying the above | σ-10.5 | <0.5 may be used singly or in combination of two or more.

  When a monomer satisfying | σ-10.5 | <0.5 is included in the ink composition, the content of the monomer is 20% by mass or less with respect to the total mass (100% by mass) of the ink composition. And is preferably 10% by mass or less. When the content is within the above range, swelling of the adhesive used in the ink jet head can be effectively prevented, so that the ink jet head for discharging the ink composition has excellent durability.

(Photopolymerization initiator)
The photopolymerization initiator contained in the ink composition of the present embodiment is used to form a print by curing the ink present on the surface of the recording medium by photopolymerization by ultraviolet irradiation. By using ultraviolet rays (UV) among the radiation, the safety is excellent and the cost of the light source lamp can be suppressed. There is no limitation as long as it generates active species such as radicals and cations by the energy of light (ultraviolet rays) and initiates the polymerization of the polymerizable compound. However, a photo radical polymerization initiator or a photo cationic polymerization initiator may be used. Among them, it is preferable to use a radical photopolymerization initiator.

  Examples of the photo radical polymerization initiator include aromatic ketones, acylphosphine oxide compounds, aromatic onium salt compounds, organic peroxides, thio compounds (thioxanthone compounds, thiophenyl group-containing compounds, etc.), hexaarylbiimidazoles, and the like. Examples include compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon halogen bond, and alkylamine compounds.

  Among these, since the curability of the ink composition can be particularly improved, at least one of an acylphosphine oxide compound and a thioxanthone compound is preferable, and an acylphosphine oxide compound and a thioxanthone compound are more preferable.

  Specific examples of the photo radical polymerization initiator include acetophenone, acetophenone benzyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine. , Carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4′-dimethoxybenzophenone, 4,4′-diaminobenzophenone, Michler's ketone, benzoin propyl ether, benzoin ethyl ether, benzyldimethyl ketal, 1- (4-isopropylphenyl) ) -2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, thioxanthone, diethylthio Xanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, bis (2,4,6-trimethylbenzoyl) -phenyl Phosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2,4-diethylthioxanthone, and bis- (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide Can be mentioned.

  Examples of commercially available photo radical polymerization initiators include IRGACURE 651 (2,2-dimethoxy-1,2-diphenylethane-1-one), IRGACURE 184 (1-hydroxy-cyclohexyl-phenyl-ketone), DAROCUR 1173. (2-hydroxy-2-methyl-1-phenyl-propan-1-one), IRGACURE 2959 (1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane- 1-one), IRGACURE 127 (2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl] -2-methyl-propan-1-one}, IRGACURE 907 (2-Methyl-1- (4-methylthiophenyl) -2-morphol Linopropan-1-one), IRGACURE 369 (2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1), IRGACURE 379 (2- (dimethylamino) -2-[(4- Methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone), DAROCUR TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide), IRGACURE 819 (bis (2, 4,6-trimethylbenzoyl) -phenylphosphine oxide), IRGACURE 784 (bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrole-1-) Yl) -phenyl) titanium), IRGACURE OXE 01 (1.2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)]), IRGACURE OXE 02 (ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (O-acetyloxime)), IRGACURE 754 (oxyphenylacetic acid, 2- [2-oxo-2-phenylacetoxyethoxy] ethyl ester and oxyphenylacetic acid, 2- (Mixture of (2-hydroxyethoxy) ethyl ester) (manufactured by BASF), KAYACURE DETX-S (2,4-diethylthioxanthone) (manufactured by Nippon Kayaku Co., Ltd.), Lucirin TPO LR8883, LR8970 (manufactured by BASF), Ubekrill P36 (UCB), and the like.

  The said photoinitiator may be used individually by 1 type, and may be used in combination of 2 or more type.

  The photopolymerization initiator sufficiently exhibits the ultraviolet curing rate, and avoids undissolved photopolymerization initiator and coloring derived from the photopolymerization initiator, so that the total mass (100% by mass) of the ink composition is used. 3 to 15% by mass is preferable.

[Color material]
The ink composition of the present embodiment may further include a color material. As the color material, at least one of a pigment and a dye can be used.

(Pigment)
In this embodiment, the light resistance of the ink composition can be improved by using a pigment as the color material. As the pigment, both inorganic pigments and organic pigments can be used.

  As the inorganic pigment, carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black and channel black, iron oxide, and titanium oxide can be used.

  Organic pigments include insoluble azo pigments, condensed azo pigments, azo lakes and chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc. Polycyclic pigments, dye chelates (eg basic dye chelates, acid dye chelates, etc.), dye rakes (basic dye rakes, acid dye rakes), nitro pigments, nitroso pigments, aniline black, daylight A fluorescent pigment is mentioned.

  More specifically, as carbon black used as black ink, No. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, no. 2200B and the like (manufactured by Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (and above, manufactured by Columbia Columbia), Regal 400R, Rega1 330R, Rega1 660R, Mogul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. (CABOT JAPAN K. F. manufactured by CABOT JAPANB. , Color Black FW2, Color Black FW2V, Color Black FW 18, Color Black FW200, Color B1ack S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Sep, Special Black 6, Sep, Color Black S170, Color Black S170, Color Black S170, Color Black S170, Color Black S170, Color Black S170, Color Black S170, Color Black S170 (Degussa)).

  Examples of pigments used in white ink include C.I. I. Pigment white 6,18,21.

  Examples of pigments used in yellow ink include C.I. I. 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, 154 167, 172, 180.

  Examples of pigments used in magenta ink include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 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, C.I. I. Pigment violet 19, 23, 32, 33, 36, 38, 43, 50.

  Examples of pigments used for cyan ink include C.I. I. Pigment Blue 1, 2, 3, 15, 15: 1, 15: 2, 15: 3, 15:34, 15: 4, 16, 18, 22, 25, 60, 65, 66, C.I. I. Bat Blue 4,60.

  Examples of pigments other than magenta, cyan, and yellow include C.I. I. Pigment green 7,10, C.I. I. Pigment brown 3, 5, 25, 26, C.I. I. Pigment orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 63.

  The said pigment may be used individually by 1 type, and may use 2 or more types together.

  When using said pigment, the average particle diameter is although it does not specifically limit, It should just be 300 nm or less, and about 50-200 nm is preferable. When the average particle diameter is in the above range, the ink composition is more excellent in reliability such as ejection reliability and dispersion stability, and an image with excellent image quality can be formed. Here, the average particle diameter in the present specification is measured by a dynamic light scattering method.

(dye)
In the present embodiment, a dye can be used as the color material. The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used. Examples of the dye include C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. I. Acid Red 52, 80, 82, 249, 254, 289, C.I. I. Acid Blue 9, 45, 249, C.I. I. Acid Black 1, 2, 24, 94, C.I. I. Food Black 1, 2, C.I. I. Direct Yellow 1,12,24,33,50,55,58,86,132,142,144,173, C.I. I. Direct Red 1,4,9,80,81,225,227, C.I. I. Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, C.I. I. Directed Black 19, 38, 51, 71, 154, 168, 171, 195, C.I. I. Reactive Red 14, 32, 55, 79, 249, C.I. I. Reactive black 3, 4, and 35 are mentioned.

  The said dye may be used individually by 1 type, and may use 2 or more types together.

  The content of the color material is preferably 2 to 6% by mass with respect to the total mass (100% by mass) of the ink composition because the viscosity is low and excellent concealability and color reproducibility are obtained.

[Dispersant]
When the ink composition of this embodiment contains a pigment, it may further contain a dispersant in order to improve pigment dispersibility. Although it does not specifically limit as a dispersing agent, For example, the dispersing agent currently used for preparing pigment dispersion liquids, such as a polymer dispersing agent, is mentioned. Specific examples include polyoxyalkylene polyalkylene polyamines, vinyl polymers and copolymers, acrylic polymers and copolymers, polyesters, polyamides, polyimides, polyurethanes, amino polymers, silicon-containing polymers, sulfur-containing polymers, fluorine-containing polymers, and epoxies. The thing which has 1 or more types of resin as a main component is mentioned. Commercially available polymer dispersants include Ajinomoto Fine Techno Co., Ajisper series, Solsperse series (Solsperse 36000, etc.) available from Avecia Co., BYK Chemie Dispersic series, Enomoto Kasei Co., Ltd. Disparon series made by the company.

[Other additives]
The ink composition of the present embodiment may include additives (components) other than the additives listed above. Such components are not particularly limited, and may include, for example, conventionally known slip agents (surfactants), polymerization accelerators, penetration enhancers, wetting agents (humectants), and other additives. Examples of the other additives include conventionally known fixing agents, antifungal agents, preservatives, antioxidants, ultraviolet absorbers, chelating agents, and thickeners.

[Recording medium]
The ultraviolet curable inkjet ink composition of the present embodiment can be recorded by being ejected onto a recording medium by a recording method described later. Examples of the recording medium include an absorptive or non-absorbable recording medium. The above recording method can be widely applied to recording media having various absorption performances, from non-absorbing recording media in which water-soluble ink penetration is difficult to absorbent recording media in which water-soluble ink penetration is easy. However, when the ink composition is applied to a non-absorbable recording medium, it may be necessary to provide a drying step after being cured by irradiation with ultraviolet rays.

  The absorbent recording medium is not particularly limited. For example, plain paper such as electrophotographic paper excellent in water-based ink permeability, inkjet paper (an ink absorbing layer composed of silica particles or alumina particles, or polyvinyl chloride). Art paper used for general offset printing in which water-based ink has relatively low permeability from an ink-dedicated paper having an ink absorbing layer composed of a hydrophilic polymer such as alcohol (PVA) or polyvinylpyrrolidone (PVP), Examples thereof include coated paper and cast paper.

  The non-absorbable recording medium is not particularly limited. For example, films and plates of plastics such as polyvinyl chloride, polyethylene, polypropylene, and polyethylene terephthalate (PET), and metals such as iron, silver, copper, and aluminum are used. Examples thereof include a plate, a metal plate produced by vapor deposition of these various metals, a plastic film, a plate made of an alloy such as stainless steel or brass.

[Recording method]
The ultraviolet curable inkjet ink composition of the present embodiment can be used in a recording method. The recording method includes a discharge step of discharging the ink composition onto a recording medium. In addition, the recording method may include a curing step of curing the ink composition by irradiating the ink composition ejected in the ejection step with ultraviolet rays. In this way, a coating film (cured film) is formed by the ink composition cured on the recording medium.

[Discharge process]
In the ejection step, a conventionally known inkjet recording apparatus can be used, and the ink composition is ejected from an inkjet head included in the inkjet recording apparatus toward a recording medium. The inkjet head includes a head (made of a cured product of an epoxy adhesive) that uses the above-described epoxy adhesive in at least a part of a portion that comes into contact with the ink composition such as the inside or the surface of the head. It is preferable to do. Although it does not specifically limit as the said epoxy-type adhesive agent, For example, the conventionally well-known adhesive agent which hardens the main ingredient containing the compound which has an epoxy group with a hardening | curing agent is mentioned. The compound having an epoxy group contained in the main agent is not particularly limited. For example, bisphenol type epoxy such as bisphenol A type and bisphenol F type, novolak type epoxy such as phenol novolak type and cresol novolak type, and epoxy polyol type Epoxy, urethane-modified epoxy, chelate-modified epoxy, and rubber-modified epoxy can be used. Although it does not specifically limit as said hardening | curing agent, For example, amines, such as an amine and a polyamine, acid anhydrides, amides, such as an amide and a polyamide, imidazoles, and a polymercaptan can be used. Of these, bisphenol type epoxy as the main agent and amines as the curing agent are particularly preferable. The mixing ratio of the main agent and the curing agent (main agent: curing agent) is preferably 10: 1 to 1:10.
When discharging the ink composition, the viscosity of the ink composition is preferably less than 40 mPa · s, and more preferably less than 15 mPa · s. If the viscosity of the ink composition is within the above range, the ink composition can be discharged at room temperature, for example, without heating. On the other hand, the ink composition may be discharged at a lower temperature by heating the ink composition to a predetermined temperature. If the ink composition is heated, good ejection reliability is realized.

  Since the ink composition of the present embodiment has a higher viscosity than the water-based ink used in a normal inkjet recording ink, the viscosity variation due to temperature variation during ejection is large. Such fluctuations in the viscosity of the ink have a great influence on the change in the droplet size and the change in the droplet discharge speed, which can cause image quality deterioration. Therefore, it is preferable to keep the temperature of the ink during ejection as constant as possible.

[Curing process]
Next, in the curing step, the ink composition ejected on the recording medium is cured by irradiation with ultraviolet rays (light). This is because the photopolymerization initiator contained in the ink composition is decomposed by irradiation with ultraviolet rays to generate starting species such as radicals, acids, and bases, and the polymerization reaction of the photopolymerizable compound functions as the starting species. This is because the polymerization reaction of the photopolymerizable compound is started by the irradiation of ultraviolet rays. At this time, if a sensitizing dye is present together with the photopolymerization initiator in the ink composition, the sensitizing dye in the system absorbs actinic radiation to be in an excited state and comes into contact with the photopolymerization initiator. Degradation can be accelerated and a more sensitive curing reaction can be achieved.

  Mercury lamps and gas / solid lasers are mainly used as ultraviolet sources, and mercury lamps and metal halide lamps are widely known as light sources used for curing ultraviolet curable ink-jet ink compositions. . On the other hand, there is a strong demand for mercury-free from the viewpoint of environmental protection, and replacement with a GaN-based semiconductor ultraviolet light-emitting device is very useful industrially and environmentally. Furthermore, an ultraviolet light emitting diode (UV-LED) and an ultraviolet laser diode (UV-LD) are small, have a long lifetime, high efficiency, and low cost, and are expected as light sources for ultraviolet curable ink jets. Among these, UV-LED is preferable.

Here, as the ultraviolet light source, an ultraviolet light having an emission peak wavelength of preferably in the range of 350 to 420 nm, more preferably in the range of 365 to 405 nm, preferably less than 400 mJ / cm ² , more preferably less than 200 mJ / cm ^2. It is possible to irradiate with the irradiation energy. According to the ink composition of the present embodiment, by adjusting the composition, curing at low energy and high speed is possible, irradiation time can be shortened, and printing speed can be increased. is there. The irradiation energy is calculated by multiplying the irradiation time by the irradiation intensity. Further, the emission peak wavelength may be one or plural within the above wavelength range. Even in the case where there are a plurality, the total irradiation energy of the ultraviolet rays having the emission peak wavelength is set as the irradiation energy.
On the other hand, the irradiation intensity of the ink composition of the present embodiment can be reduced by adjusting the composition. If the irradiation intensity can be reduced, the apparatus can be downsized and the cost can be reduced. It is preferable to use a UV-LED for such low-energy ultraviolet irradiation. Such an ink composition can be obtained by including at least one of a photopolymerization initiator that decomposes upon irradiation with ultraviolet rays in the wavelength range and a polymerizable compound that starts polymerization upon irradiation with ultraviolet rays in the wavelength range.

  As described above, according to the present embodiment, since the viscosity is low, the curability and the solubility of the photopolymerization initiator are excellent, and the adhesive swelling rate is low, the adhesive swelling can be effectively prevented. It is possible to provide an ultraviolet curable inkjet ink composition which is excellent in both durability and ejection reliability of the head.

  Hereinafter, the embodiments of the present invention will be described more specifically with reference to examples and comparative examples. However, the present embodiment is not limited to only these examples.

[Use ingredients]
The components used in the following examples and comparative examples are as follows.
[Monomer with SP value (σ) satisfying | σ-10.5 | ≧ 1.0]
1,9-nonanediol diacrylate (V # 260 [trade name], Osaka Organic Chemical Co., Ltd., SP value 9.08, hereinafter abbreviated as NDDA)
1,6-hexanediol diacrylate (V # 230 [trade name], manufactured by Osaka Organic Chemical Co., Ltd., SP value of 9.31, hereinafter abbreviated as HDDA)
2- (2-vinyloxyethoxy) ethyl acrylate (VEEA [trade name], manufactured by Nippon Shokubai Co., Ltd., SP value 9.41, hereinafter abbreviated as VEEA)
[Monomer satisfying SP value (σ) of 0.5 ≦ | σ-10.5 | <1.0]
Phenoxyethyl acrylate V # 192 (trade name, Osaka Organic Chemical Co., Ltd., SP value 9.99, hereinafter abbreviated as PEA)
4-Hydroxybutyl acrylate (Biscoat 4-HBA [trade name], Osaka Organic Chemical Co., Ltd., SP value 11.3, hereinafter abbreviated 4HBA)
[Monomer with SP value (σ) satisfying | σ-10.5 | <0.5]
N-vinylcaprolactam (V-CAP [trade name], manufactured by ISP Japan, SP value 10.65, hereinafter abbreviated as NVC)
(Photopolymerization initiator)
IRGACURE 819 (trade name, manufactured by BASF, solid content: 100%, hereinafter abbreviated as 819)
DAROCURE TPO (trade name, manufactured by BASF, solid content: 100%, hereinafter abbreviated as TPO)
[Pigment]
・ C. I. Pigment Blue 15: 3 (manufactured by Toyo Ink Manufacturing Co., Ltd., abbreviated as blue below)

[Examples 1-7, Comparative Examples 1-9]
The components described in Table 1 and Table 2 below were added so as to have the composition (unit: mass%) described in Table 1 and Table 2, and this was stirred with a high-speed water-cooled stirrer, An ultraviolet curable ink composition for inkjet was obtained.

〔Evaluation item〕
(1. Swelling rate of adhesive)
About 0.2 g of epoxy adhesive (a mixture of EPIKOTE 828, which is an epoxy resin manufactured by shell), and VERSAMID 125, which is a curing agent manufactured by COGNIS, is cured by about 0.2 g. The weight was prepared and measured. Thereafter, the adhesive piece was dipped in the ink placed in the screw tube, capped, and left in a 60 ° C. environment for 7 days. After leaving, the adhesive piece was taken out and the ink was washed thoroughly, and the weight was measured. And the swelling rate was computed from the following formula | equation.
Weight change rate (%) = {(weight after charging−weight before charging) / weight before charging} × 100
The evaluation criteria are as follows. The evaluation results are shown in Tables 3 and 4 below.
AA: less than 50%,
A: 50% or more and less than 60%,
B: 60% or more.

(2. Curability)
Using a modified inkjet printer PX-G5000 (trade name, manufactured by Seiko Epson Corporation), each of the nozzle arrays was filled with the above-described ultraviolet curable inkjet ink composition. A solid pattern image is printed on a PET film PET50 (K2411) PA-T1 8LK (trade name, manufactured by Lintec Corporation) at room temperature and normal pressure under the conditions of a recording resolution of 720 dpi × 720 dpi and a droplet weight of 7 ng. Printed. Note that this solid pattern image is an image in which dots are recorded for all of the pixels that are the minimum recording unit area defined by the recording resolution.
Along with the printing described above, a solid pattern image is obtained by irradiating UV light having an irradiation intensity of 400 mW / cm ² and a wavelength of 395 nm with 600 mJ / cm ² from the UV-LED in the UV irradiation device mounted on the side of the carriage. Cured. In addition, it was judged that it was hardened | cured when the tackiness of the image (coating film surface) disappeared by the finger touch test.

Evaluation was performed by calculating the irradiation energy of ultraviolet rays required for curing. The irradiation energy [mJ / cm ² ] was determined from the product of the irradiation intensity [mW / cm ² ] on the irradiated surface irradiated from the light source and the irradiation duration [s]. The irradiation intensity was measured using an ultraviolet intensity meter UM-10 and a light receiving unit UM-400 (both manufactured by KONICA MINOLTA SENSING, INC.).
The evaluation criteria are as follows. The evaluation results are shown in Tables 3 and 4 below.
AA: Cured with an irradiation energy of less than 200 mJ / cm ² .
A: Cured with an irradiation energy of 200 mJ / cm ² or more and less than 400 mJ / cm ² .

(3. Viscosity)
Viscosity of the above UV curable ink composition for inkjet is measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.) at a temperature of 20 ° C. and a rotation speed of 10 rpm. did. The evaluation results are shown in Tables 3 and 4 below.
AA: less than 15 mPa · s,
A: 15 mPa · s or more and less than 40 mPa · s.

(4. Photopolymerization initiator solubility)
Start when the UV curable ink-jet ink composition is stored at 0 ° C. for 1 day and then filtered through a membrane filter (Millipore Corporation, polytetrafluoroethylene (PTFE) hydrophobic, pore size 10 μm) The precipitation of the agent was visually confirmed.
The evaluation results are shown in Tables 3 and 4 below.
○: There was no undissolved residue.
X: There was undissolved residue.

From Table 3 and Table 4, the ultraviolet curable inkjet ink composition discharged from the inkjet head using an epoxy adhesive contains 20% by mass or more of a monomer satisfying | σ-10.5 | ≧ 1.0. And an ink composition (Example) containing 20% by mass or more of a monomer satisfying 0.5 ≦ | σ−10.5 | <1.0 has low viscosity, is curable, and dissolves a photopolymerization initiator. It was found that the durability of the ink jet head was also excellent because of its low adhesive swelling ratio. Specifically, when the ink composition contains 20% by mass or more of a monomer satisfying | σ-10.5 | ≧ 1.0, the ink composition is compared with other ink compositions (Comparative Examples 1 to 4 and 7). Thus, it was found that the durability of the inkjet head is excellent because the adhesive swelling rate is remarkably low. In addition, the ink composition contains 20% by mass or more of a monomer satisfying 0.5 ≦ | σ−10.5 | <1.0, and compared with other ink compositions (Comparative Examples 5 and 9), It was found that the photopolymerization initiator was excellent in solubility.
If the photopolymerization initiator is excellent in solubility (initiator solubility), the photopolymerization initiator hardly precipitates even at a low temperature, so that the ejection reliability is excellent.

In addition to this, when a monomer satisfying the SP value (σ) of | σ−10.5 | <0.5 is included in the ink composition, the monomer is included in a range of 20% by mass or less. Thus, it was found that the swelling rate of the adhesive can be suppressed to a low level as compared with ink compositions other than that (particularly Comparative Examples 6 and 8).
Note that when the ink is prepared with a composition that does not cause precipitation of the photopolymerization initiator even at a low temperature, the addition amount (content) of the photopolymerization initiator is reduced, and thus the curability is poor. I have confirmed that.

Claims (6)

An ultraviolet curable inkjet ink composition comprising a monomer and a photopolymerization initiator,
A monomer satisfying the condition that the SP value (σ) calculated by the Small formula is represented by | σ-10.5 | ≧ 1.0 is 20% by mass or more based on the total mass of the ink composition. Including in scope,
A monomer satisfying the condition that the SP value (σ) is expressed as 0.5 ≦ | σ−10.5 | <1.0 is within a range of 20% by mass or more based on the total mass of the ink composition. Including
When the SP value (σ) includes a monomer satisfying the condition represented by | σ−10.5 | <0.5, the monomer is contained in an amount of 20% by mass or less based on the total mass of the ink composition. And in the range of
An ultraviolet curable ink composition for inkjet, which is ejected from an inkjet head using an epoxy adhesive.   Monomers satisfying the condition that the SP value (σ) is expressed as 0.5 ≦ | σ−10.5 | <1.0 are 20% by mass or more and 65% by mass with respect to the total mass of the ink composition. The ultraviolet curable inkjet ink composition according to claim 1, which is contained in the following range.   A monomer satisfying the condition that the SP value (σ) is represented by | σ-10.5 | ≧ 1.0 is within a range of 20% by mass to 70% by mass with respect to the total mass of the ink composition. The ultraviolet curable ink-jet ink composition according to claim 1, comprising: A monomer satisfying the condition that the SP value (σ) is represented by | σ-10.5 | ≧ 1.0 is represented by the following general formula (I):
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (I)
Wherein R ¹ is a hydrogen atom or a methyl group, R ² is a divalent organic residue having 2 to 20 carbon atoms, and R ³ is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms. Group.)
The ultraviolet curable inkjet ink composition according to any one of claims 1 to 3, which is a vinyl ether group-containing (meth) acrylic acid ester represented by:   The ultraviolet curable inkjet ink according to claim 4, wherein the vinyl ether group-containing (meth) acrylic acid ester represented by the general formula (I) is 2- (vinyloxyethoxy) ethyl (meth) acrylate. Composition.   An ultraviolet curable inkjet ink comprising a discharge step of discharging the ultraviolet curable inkjet ink composition according to any one of claims 1 to 5 from an inkjet head using an epoxy adhesive to a recording medium. Composition recording method.