JP6134090B2 - UV curable ink composition for inkjet - Google Patents

Description

  The present invention relates to an ultraviolet curable inkjet ink composition.

Conventionally, various methods have been used as a recording method for forming an image on a recording medium 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.

In recent years, in order to form good images such as water resistance, solvent resistance, and abrasion resistance on the surface of a recording medium, an ultraviolet curable inkjet ink composition that cures when irradiated with ultraviolet rays in an inkjet recording method. Is used.

For example, Patent Document 1 is substantially free of water or volatile organic solvents and contains 69.82 parts propoxylated neopentyl glycol diacrylate, 1.56 parts wettable resin, 3
. 6 parts pigment, 1.25 parts pigment dispersant, 0.12 parts stabilizer, 10.0 parts triethylene glycol divinyl ether, 13.6 parts photoinitiator, 0.05 Ink for printing formed by mixing a part of the antifoaming agent is disclosed.

Further, for example, in Patent Document 2, 2.2 parts of pigment, 0.5 part of pigment dispersant, 2.5 parts of pentaerythritol tetraacrylate as a polymerizable monomer, 32.7 parts of diethylene glycol Monovinyl ether acrylate, 22.7 parts tetraethylene glycol diacrylate, 6 parts isobornyl acrylate, and 24.6 parts N-vinyl pyrrolidone and 8.7 parts photopolymerization initiator were mixed. An active energy ray curable ink for inkjet printing is disclosed.

JP-T-2004-526820 JP 2009-96910 A

However, the techniques disclosed in Patent Documents 1 and 2 cause high ink viscosity, causing poor ink ejection, poor ink adhesion to a recording medium, or shrinkage in a printed matter after ink curing. The problem of standing out arises.

Accordingly, an object of the present invention is to provide an ultraviolet curable ink composition having low viscosity, excellent adhesion, and suppressed shrinkage.

The present inventors have intensively studied to solve the above problems. As a result, a compound having both a vinyl group and a (meth) acryl group in the molecule, and a polymerizable compound having another specific structure,
UV curable ink composition for inkjet (hereinafter, also simply referred to as “ink composition”)
It has been found that an ink composition having a reduced viscosity, excellent adhesion, and suppressed shrinkage can be obtained by containing a predetermined amount in each of the above.

That is, the present invention is as follows.
[1]
An ultraviolet curable ink composition for inkjet, which is 20 to 70 mass% of the following general formula (I) with respect to the total mass of the ink composition:
_{^{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.)
At least of the polymerizable compound having an alicyclic structure in the molecule and the polymerizable compound having a cyclic ether structure in the molecule, and 10 to 20% by mass relative to the total mass of the ink composition An ultraviolet curable inkjet ink composition comprising any of the above.
[2]
The ultraviolet ray according to [1], wherein the polymerizable compound having an alicyclic structure in the molecule is at least one selected from the group consisting of tricyclodecane dimethanol diacrylate, adamantyl acrylate, and cyclohexane dimethanol monoacrylate. A curable inkjet ink composition.
[3]
The polymerizable compound having a cyclic ether structure in the molecule is one or more selected from the group consisting of tetrahydrofurfuryl acrylate, γ-butyrolactone acrylate, dioxolane acrylate, and dioxane glycol diacrylate, [1] or [2
] The ultraviolet curable ink composition for inkjet.
[4]
The ultraviolet curable inkjet according to any one of [1] to [3], comprising both a polymerizable compound having an alicyclic structure in the molecule and a polymerizable compound having a cyclic ether structure in the molecule. Ink composition.
[5]
The polymerizable compound having an alicyclic structure in the molecule is contained in an amount of 5% by mass or more based on the total mass of the ink composition, and the polymerizable compound having a cyclic ether structure in the molecule is the ink composition. The ultraviolet curable inkjet ink composition according to [4], which is contained in an amount of 5% by mass or more based on the total mass of the product.
[6]
At least one of the polymerizable compound having an alicyclic structure in the molecule and the polymerizable compound having a cyclic ether structure in the molecule is a (meth) acrylate compound, [1
] The ultraviolet curable inkjet ink composition as described in any one of [5] to [5].
[7]
The ultraviolet curable inkjet ink composition according to any one of [1] to [6], wherein the viscosity at 20 ° C. is 30 mPa · s or less.
[8]
The ultraviolet curable inkjet ink composition according to any one of [1] to [7], wherein the compound represented by the general formula (I) is 2- (vinyloxyethoxy) ethyl acrylate.

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. “Adhesion” refers to the property that the coating film is difficult to peel off from the substrate. In particular, in the examples, the property is obtained when a right-angle lattice pattern is cut into the cured product and penetrates to the substrate of the recording medium. . “Shrinkage” refers to the property that the degree of lifting is large at the edge of a recorded material obtained by adhering and curing the ink composition on the recording medium.

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.

[UV-curable inkjet ink composition]
An ultraviolet curable inkjet ink composition according to an embodiment of the present invention has 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.)
And a compound represented by the formula (hereinafter referred to as “monomer A”), and at least one of a polymerizable compound having an alicyclic structure in the molecule and a polymerizable compound having a cyclic ether structure in the molecule, respectively. Including by content.

Hereinafter, additives (components) that are contained in the ink composition of the present embodiment or that can be optionally contained will be described.

(Polymerizable compound)
The polymerizable compound contained in the ink composition of the present embodiment can be polymerized at the time of light irradiation alone or by the action of a photopolymerization initiator described later to cure the printed ink.

(Monomer A)
In this embodiment, the monomer A, which is an essential polymerizable compound, contains a vinyl group and (
A compound having both a (meth) acrylic group and represented by the above general formula (I). This monomer A can be rephrased as vinyl ether group-containing (meth) acrylic acid esters.

When the ink composition contains the monomer A, the ink curability and the like can be improved.

In the above general formula (I), the divalent organic residue represented by R ^{2 has 2} to 2 carbon atoms.
0 linear, branched or cyclic optionally substituted alkylene group, optionally substituted alkylene having 2 to 20 carbon atoms having an oxygen atom by at least one of an ether bond and an ester bond Preferred is a group or a divalent aromatic group having 6 to 11 carbon atoms which may be substituted. 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, 6 or more carbon atoms such as an alkyl group having 1 or 2 carbon atoms that is a methyl group or an ethyl group, a phenyl group, and a benzyl group.
˜8 aromatic groups are preferably used.

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. As a group containing a carbon atom,
Although not limited to the following, for example, a carboxyl group and an alkoxy group can be mentioned. 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 monomer A represented by the general formula (I) are not limited to the following,
(Meth) acrylic acid 2-vinyloxyethyl, (meth) acrylic acid 3-vinyloxypropyl, (meth) acrylic acid 1-methyl-2-vinyloxyethyl, (meth) acrylic acid 2-vinyloxypropyl, (meth) acrylic acid 4 -Vinyloxybutyl, 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 (meth) acrylate, 1-methyl-2-vinyl (meth) acrylate Roxypropyl, 2-vinyloxybutyl (meth) acrylate, 6-vinyloxyhexyl (meth) acrylate, p-vinyloxymethylphenylmethyl (meth) acrylate, m-vinyloxymethylphenylmethyl (meth) acrylate, ( (Meth) acrylic acid o-vinyloxymethylphenylmethyl, (meth) acrylic acid 2- (vinyloxyethoxy) ethyl, (meth) acrylic acid 2- (vinyloxyisopropoxy) ethyl, (
2- (vinyloxyethoxy) propyl (meth) acrylate, 2- (vinyloxyethoxy) isopropyl (meth) acrylate, 2- (vinyloxyisopropoxy) (meth) acrylate
Propyl, 2- (vinyloxyisopropoxy) isopropyl (meth) acrylate, 2- (vinyloxyethoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxyisopropoxy) ethyl (meth) acrylate, (meth ) 2- (vinyloxyisopropoxyethoxy) ethyl acrylate, 2- (vinyloxyisopropoxyisopropoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxyethoxy) propyl (meth) acrylate,
(Meth) acrylic acid 2- (vinyloxyethoxyisopropoxy) propyl, (meth) acrylic acid 2- (vinyloxyisopropoxyethoxy) propyl, (meth) acrylic acid 2- (
Vinyloxyisopropoxyisopropoxy) propyl, 2- (vinyloxyethoxyethoxy) isopropyl (meth) acrylate, 2- (vinyloxyethoxyisopropoxy) isopropyl (meth) acrylate, 2- (vinyloxy) (meth) acrylate Isopropoxyethoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyisopropoxyisopropoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyethoxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (vinyloxyethoxy) Ethoxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (isopropenoxyethoxy) ethyl, (meth) acrylic acid 2
-(Isopropenoxyethoxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (isopropenoxyethoxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (isopropenoxyethoxyethoxyethoxyethoxy) ethyl, (meth) acrylic acid Examples thereof include polyethylene glycol monovinyl ether 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, (
(Meth) acrylic acid 2-vinyloxypropyl, (meth) acrylic acid 4-vinyloxybutyl,
(Meth) acrylic acid 5-vinyloxypentyl, (meth) acrylic acid 6-vinyloxyhexyl, (meth) acrylic acid 4-vinyloxymethylcyclohexylmethyl, (meth) acrylic acid p-vinyloxymethylphenylmethyl, (meta Preference is given to 2- (vinyloxyethoxy) ethyl acrylate, 2- (vinyloxyethoxyethoxy) ethyl (meth) acrylate, and 2- (vinyloxyethoxyethoxyethoxy) ethyl (meth) acrylate.

Of these, 2- (vinyloxyethoxy) ethyl (meth) acrylate is preferred because of its low viscosity, high flash point, and excellent curability, and it also has low odor and suppresses irritation to the skin. In addition, 2- (vinyloxyethoxy) ethyl acrylate is more preferable because it is excellent in reactivity and adhesion.

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 and 2- (1-vinyloxyethoxy) ethyl acrylate.

  Monomer A may be used individually by 1 type, and may be used in combination of 2 or more type.

Monomer A is contained in an amount of 20 to 70% by mass, preferably 20 to 40% by mass, based on the total mass (100% by mass) of the ink composition. When the content is 20% by mass or more, the viscosity of the ink can be reduced. Moreover, adhesiveness can be made favorable as content is 70 mass% or less.

The production method of the monomer A represented by the general formula (I) is not limited to the following,
A method of esterifying (meth) acrylic acid and a hydroxyl group-containing vinyl ether (production method B),
Method of esterifying (meth) acrylic acid halide and hydroxyl group-containing vinyl ethers (Production method C), Method of esterifying (meth) acrylic anhydride and hydroxyl group-containing vinyl ethers (Production method D), (Meth) acrylic Method of transesterifying acid ester with hydroxyl group-containing vinyl ether (Production method E), Method of esterifying (meth) acrylic acid and halogen-containing vinyl ether (Production method F), Alkali (meth) acrylate (earth) Method of esterifying metal salt and halogen-containing vinyl ether (production method G), method of exchanging hydroxyl-containing (meth) acrylic acid esters with vinyl carboxylate (production method H), hydroxyl-containing (meth) acrylic acid ester And a method of exchanging ethers with alkyl vinyl ethers (Production Method I).

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

(Polymerizable compound having an alicyclic structure in the molecule)
The ink composition of this embodiment may contain a polymerizable compound having an alicyclic structure in the molecule.

Examples of the polymerizable compound having an alicyclic structure in the molecule include, but are not limited to, tricyclodecane dimethanol di (meth) acrylate, adamantyl (meth) acrylate, cyclohexanedimethanol mono (meth) acrylate, cyclohexane Dimethanol di (meth) acrylate, trimethylcyclohexyl (meth) acrylate, isobornyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and dicyclopentenyloxyethyl (meth) acrylate Can be mentioned.

Since the polymerizable compound having an alicyclic structure in the molecule can increase the curing rate, (meth)
An acrylate compound is preferred.

Among these, since rigidity is imparted, it is preferably one or more selected from the group consisting of tricyclodecane dimethanol diacrylate, adamantyl acrylate, and cyclohexane dimethanol monoacrylate.

The polymerizable compound having an alicyclic structure in the molecule may be used alone or in combination of two or more.

  The content of the polymerizable compound having an alicyclic structure in the molecule will be described later.

(Polymerizable compound having a cyclic ether structure in the molecule)
The ink composition of this embodiment may contain a polymerizable compound having a cyclic ether structure in the molecule.

Examples of the polymerizable compound having a cyclic ether structure in the molecule include, but are not limited to, tetrahydrofurfuryl (meth) acrylate and γ-butyrolactone (meth).
Examples include acrylate, dioxolane (meth) acrylate, dioxane glycol di (meth) acrylate, oxetane (meth) acrylate, and cyclic trimethylolpropane formal (meth) acrylate. In the present specification, “cyclic ether structure”
It is assumed that a cyclic ester structure is also included, and the cyclic ether structure may have a plurality of ether moieties.

Since the polymerizable compound having a cyclic ether structure in the molecule can increase the curing rate,
A (meth) acrylate compound is preferred.

Among the above, tetrahydrofurfuryl acrylate, because adhesion becomes better,
It is preferably one or more selected from the group consisting of γ-butyrolactone acrylate and dioxane glycol diacrylate.

The polymerizable compound having a cyclic ether structure in the molecule may be used alone,
Two or more kinds may be used in combination.

The ink composition preferably includes a polymerizable compound having an alicyclic structure in the molecule and a polymerizable compound having a cyclic ether structure in the molecule. In this case, the adhesiveness can be further improved, and the shrinkage can be further suppressed.

The content of the polymerizable compound having a cyclic ether structure in the molecule differs depending on the content of the polymerizable compound having an alicyclic structure in the molecule. That is, the total content of the polymerizable compound having an alicyclic structure in the molecule and the polymerizable compound having a cyclic ether structure in the molecule is 10 to 20% by mass with respect to the total mass (100% by mass) of the ink composition. %. When the total content is 10% by mass or more, the adhesiveness can be excellent, and the shrinkage can be suppressed. Speaking in more detail about the shrinkage, if the total content is 10% by mass or more, the polymerizable compound has a cyclic skeleton, so that the effect of reducing the shrinkage during curing is sufficiently exerted. Therefore, shrinkage is suppressed.
Further, when the total content is 20% by mass or less, the viscosity of the ink can be reduced.

Therefore, when a polymerizable compound having an alicyclic structure is included in the molecule and a polymerizable compound having a cyclic ether structure is not included in the molecule, the content of the polymerizable compound having an alicyclic structure in the molecule is 10-20 mass% is preferable with respect to the total mass (100 mass%) of a composition, and 12-17 mass% is more preferable. In addition, when a polymerizable compound having a cyclic ether structure is included in the molecule and a polymerizable compound having an alicyclic structure is not included in the molecule, the content of the polymerizable compound having a cyclic ether structure in the molecule is Total mass of composition (100% by mass)
On the other hand, 10-20 mass% is preferable and 12-17 mass% is more preferable.

Further, when the ink composition contains both a polymerizable compound having an alicyclic structure in the molecule and a polymerizable compound having a cyclic ether structure in the molecule, the content of each polymerizable compound is determined as follows. 5 mass% or more is preferable with respect to the total mass (100 mass%), and 7-15 mass% is more preferable. When the content is within the above range, the adhesiveness can be further improved, and the shrinkage can be further suppressed.

(Polymerizable compounds other than the above)
As the polymerizable compound other than the above (hereinafter, referred to as “other polymerizable compound”), conventionally known various monomers and oligomers such as monofunctional, bifunctional, and trifunctional or more polyfunctional can be used. . Examples of the monomer include unsaturated carboxylic acids such as (meth) acrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid, and salts or esters thereof, urethane, amide and anhydride thereof, acrylonitrile, styrene. , Various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes. Examples of the oligomer include oligomers formed from the above monomers such as linear acrylic oligomers, epoxy (meth) acrylate, aliphatic urethane (meth) acrylate, aromatic urethane (meth) acrylate, and polyester (meta). ) Acrylates.

Moreover, an N-vinyl compound may be included as another monofunctional monomer or polyfunctional monomer. Examples of such N-vinyl compounds include N-vinylcaprolactam, N-vinylformamide, N-vinylcarbazole, N-vinylacetamide, N-vinylpyrrolidone, and acryloylmorpholine, and derivatives thereof.

Among other polymerizable compounds, an ester of (meth) acrylic acid, that is, (meth) acrylate is preferable, polyfunctional (meth) acrylate having 2 or more functions is more preferable, and polyfunctional acrylate is more preferable. In particular, the ink composition of the present embodiment includes at least one of the predetermined amount of monomer A, a polymerizable compound having an alicyclic structure in the molecule, and a polymerizable compound having a cyclic ether structure in the molecule as the polymerizable compound. In addition to the heel, the adhesiveness is further improved by including a polyfunctional acrylate.

Among the above (meth) acrylates, monofunctional (meth) acrylates include, for example, isoamyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, iso Myristyl (meth) acrylate, isostearyl (meth) acrylate, 2-ethylhexyl-diglycol (meth) acrylate, 2-hydroxybutyl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol ( (Meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate DOO, 2-hydroxyethyl (meth) acrylate, 2-
Examples include hydroxypropyl (meth) acrylate and 2-hydroxy-3-phenoxypropyl (meth) acrylate.

Among the (meth) acrylates, examples of the polyfunctional (meth) acrylate include triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and 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 (
Bifunctional (meth) acrylates such as (meth) acrylate, di (meth) acrylate of bisphenol A, neopentyl glycol di (meth) acrylate, and polytetramethylene glycol di (meth) acrylate, and trimethylolpropane tri (Meth) acrylate, glycerin propoxytri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, sorbitol penta (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, and pentaerythritol ethoxytetra (Meth) acrylate having a pentaerythritol skeleton such as (meth) acrylate, dipentaerythritol hexa (meth) acrylate And dipentaerythritol penta (meth) having a dipentaerythritol skeleton of acrylate (meth) acrylate, propionic acid-modified tripentaerythritol penta (meth) acrylate, tripentaerythritol hexa (
(Meth) acrylate, tripentaerythritol hepta (meth) acrylate, and (pentaerythritol octa (meth) acrylate) and other (meth) acrylates having a tripentaerythritol skeleton, tetrapentaerythritol penta (meth) acrylate, tetrapentaerythritol hexa (meta) ) Acrylate, tetrapentaerythritol hepta (meth) acrylate, tetrapentaerythritol octa (meth) acrylate, tetrapentaerythritol nona (meth) acrylate, tetrapentaerythritol nona (meth) acrylate, tetrapentaerythritol deca (meth) acrylate, etc. (Meth) acrylate with tetrapentaerythritol skeleton, pentapentaerythritol undeca (meta With acrylate and pentaerythritol pentaerythritol skeleton such as pentaerythritol and pentaerythritol dodeca (meth) acrylate (meth) acrylate,
In addition, trifunctional or higher functional (meth) acrylates such as at least one of these ethylene oxide (EO) adducts and propylene oxide (PO) adducts may be mentioned.

Among these, it is preferable that another polymeric compound contains polyfunctional (meth) acrylate as above-mentioned. Among the polyfunctional (meth) acrylates, the polyfunctional (meth) acrylate having the pentaerythritol skeleton is preferable, and at least one of pentaerythritol tri (meth) acrylate and pentaerythritol tetra (meth) acrylate is more preferable. At least one of erythritol triacrylate and pentaerythritol tetraacrylate is more preferable. In the above case, the viscosity of the ink is further reduced, and the crosslink density in the ink is increased, so that the adhesion is further improved.

The said other polymeric compound may be used individually by 1 type, and may use 2 or more types together.
The other polymerizable compound is 50 to 50% based on the total mass (100% by mass) of the ink composition.
It is good to contain 85 mass%.

(Polymerization inhibitor)
The ink composition of this embodiment may contain a polymerization inhibitor. Examples of the polymerization inhibitor include, but are not limited to, p-methoxyphenol, cresol, t-butylcatechol, di-t-butylparacresol, hydroquinone monomethyl ether, α-naphthol,
3,5-di-tert-butyl-4-hydroxytoluene, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-butylphenol), and Phenol compounds such as 4,4′-thiobis (3-methyl-6-tert-butylphenol), p-benzoquinone, anthraquinone, naphthoquinone, phenanthraquinone, p-xyloquinone, p-toluquinone, 2,6-dichloroquinone, 2,5-diphenyl-p-benzoquinone, 2,5-diacetoxy-p-benzoquinone, 2,5-dicaproxy-p-benzoquinone, 2,5-diacyloxy-p-benzoquinone, hydroquinone, 2,5
-Dibutylhydroquinone, mono-t-butylhydroquinone, monomethylhydroquinone,
And quinone compounds such as 2,5-di-t-amylhydroquinone, phenyl-β-naphthylamine, p-benzylaminophenol, di-β-naphthylparaphenylenediamine, dibenzylhydroxylamine, phenylhydroxylamine, and diethylhydroxylamine Amine compounds such as dinitrobenzene, trinitrotoluene, and picric acid, oxime compounds such as quinonedioxime and cyclohexanone oxime, and sulfur compounds such as phenothiazine.

(Photopolymerization initiator)
The ink composition of this embodiment preferably contains a photopolymerization initiator. By using a photopolymerizable compound as the above-described polymerizable compound, it is possible to omit the addition of a photopolymerization initiator. However, it is preferable to use a photopolymerization initiator because the start of polymerization can be easily adjusted.

The photopolymerization initiator is used to form an image by curing ink present on the surface of a recording medium by photopolymerization by irradiation with ultraviolet rays. The photopolymerization initiator is not limited as long as it generates active species such as radicals and cations by the energy of light and initiates the polymerization of the polymerizable compound. A polymerization initiator can be used, and among these, it is preferable to use a radical photopolymerization initiator.

Examples of the photo radical polymerization initiator include aromatic ketones, acyl phosphine oxide compounds, aromatic onium salt compounds, organic peroxides, thio compounds (thioxanthone compounds, thiophenyl group-containing compounds, etc.), hexaarylbiphenyls, and the like. Examples include imidazole 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 can be particularly improved, at least one of the acylphosphine oxide compound and the thioxanthone compound is preferable,
An acylphosphine oxide compound is 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 radical photopolymerization 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 2
959 (1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-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-morpholinopropan-1-one), IRGACURE 3
69 (2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1), IRGACURE 379 (2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone), DA
ROCUR 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)]), I
RGAURE OXE 02 (ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (O-acetyloxime)), IRG
ACURE 754 (mixture of oxyphenylacetic acid, 2- [2-oxo-2-phenylacetoxyethoxy] ethyl ester and oxyphenylacetic acid, 2- (2-hydroxyethoxy) ethyl ester) (above, manufactured by BASF), Speedcure TPO (Lambso
n), KAYACURE DETX-S (2,4-diethylthioxanthone) (manufactured by Nippon Kayaku Co., Ltd.), Lucirin TPO, LR8883, L
R8970 (above, manufactured by BASF), Ubekrill P36 (manufactured by 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.

Since the photopolymerization initiator can increase the curing rate, the total mass (100% by mass) of the ink composition
It is preferable that 5-20 mass% is contained with respect to.

[Color material]
The ink composition of the present embodiment preferably further includes 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 coloring 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. In addition, as a commercial item of titanium oxide, for example, CR60
-2 (trade name made by ISHIHARA SANGYO KAISHA, LTD.).

Organic pigments include insoluble azo pigments, condensed azo pigments, azo lakes, chelate azo pigments, etc., 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. 23
00, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52,
MA7, MA8, MA100, No. 2200B, etc. (above, Mitsubishi Chemical Corporation (Mitsubishi Che
mical Corporation), Raven 5750, Raven 5250, Raven
5000, Raven 3500, Raven 1255, Raven 700, etc. (above, Columbia Carbon), Rega1 400R, Rega
1 330R, Rega1 660R, Mogul L, Monarch 700, Mo
narch 800, Monarch 880, Monarch 900, Monarc
h 1000, Monarch 1100, Monarch 1300, Monarch
1400 etc. (manufactured by CABOT JAPAN K.K.), Color Black F
W1, Color Black FW2, Color Black FW2V, Colo
r Black FW18, Color Black FW200, Color B1a
ck S150, Color Black S160, Color Black S17
0, Printex 35, Printex U, Printex V, Printex
140U, Special Black 6, Special Black 5, Sp
special Black 4A, Special Black 4 (Degussa (De
gussa)).

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, 3
7, 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, 2
1, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48 (Ca), 4
8 (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
Or 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, 1
5, 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, 3
8, 40, 43, 63.

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

When the above pigment is used, the average particle size is preferably 300 nm or less, and 50 to 25
0 nm is more preferable. When the average particle diameter is in the above range, the ink composition is more excellent in reliability such as ejection stability 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, 3
3, 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, 35
Is 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 20% by mass with respect to the total mass (100% by mass) of the ink composition.

[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 in preparing pigment dispersions, 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's Ajisper series, LUBRIZOL's Solsper's series (Solsperse 36000, etc.), BYK's Dispervic series, and Enomoto Kasei's Disparon series. It is done.

[Slip agent]
The ink composition of the present embodiment may further include a slip agent (surfactant). The slip agent is not particularly limited. For example, polyester-modified silicone or polyether-modified silicone can be used as a silicone-based surfactant, and polyether-modified polydimethylsiloxane or polyester-modified polydimethylsiloxane is particularly used. preferable. Specific examples include BYK-377, BYK-UV3500 (above, BYK
And KF-615A (manufactured by Shin-Etsu Chemical Co., Ltd.).

[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 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, pH adjusters, and thickeners can be mentioned.

[Recording medium]
The recording medium refers to an object to be ejected by using the inkjet recording method described later, with which the ultraviolet curable inkjet ink composition of the present embodiment is used. Examples of the recording medium include an absorptive or non-absorbable recording medium. The ink jet recording method described below is a recording medium having various absorption performances, from a non-absorbing recording medium in which the water-soluble ink composition is difficult to penetrate to an absorbent recording medium in which the water-soluble ink composition is easy to penetrate. Widely applicable to media. 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 having high water-based ink permeability, ink jet paper (an ink absorbing layer composed of silica particles or alumina particles, or polyvinyl alcohol). Art paper and coats used for general offset printing with relatively low permeability of water-based ink from (PVA) and inkjet pyrrole (PVP) and other ink-absorbing layers composed of hydrophilic polymers such as polyvinylpyrrolidone (PVP). Examples include 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, and a plate made of an alloy such as stainless steel or brass.

[Inkjet recording method]
The inkjet recording method uses the ultraviolet curable inkjet ink composition of the present embodiment. In the inkjet recording method, the ink composition of the embodiment is ejected onto a recording medium, and the ink composition ejected in the ejection process is irradiated with ultraviolet rays to cure the ink composition. A curing step. 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 ink jet recording apparatus can be used.
When discharging the ink composition, the viscosity of the ink composition at 20 ° C. is preferably 30 mPa
・ S or less, more preferably 10 to 20 mPa · s. If the viscosity at 20 ° C. of the ink composition is within the above range, ejection failure can be prevented even if the ink composition is discharged at room temperature or without heating the ink composition. .

Since the ultraviolet curable ink composition of the present embodiment has a higher viscosity than the water-based ink composition used in ordinary ink jet recording ink, the viscosity fluctuation due to temperature fluctuation 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 discharged onto the recording medium is subjected to ultraviolet rays (
It is cured by irradiation with 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. It is because it is promoted by. Or it is because the polymerization reaction of a photopolymerizable compound starts by irradiation of an ultraviolet-ray. 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 ultraviolet rays to be in an excited state and contacts the photopolymerization initiator to decompose the photopolymerization initiator. 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 preferable as a light source for ultraviolet curable ink jet. Among these, UV-LED is particularly preferable.

Here, the emission peak wavelength is preferably in the range of 360 to 420 nm, more preferably 3
The ultraviolet ray is preferably in the range of 85 to 405 nm. In this case, curing with low energy and high speed is possible due to the composition of the ink composition in the present embodiment.
In the above case, the irradiation energy is preferably 500 mJ / cm ² or less, 300 to 1
00 mJ / cm ² is more preferable. The irradiation energy is calculated by multiplying the irradiation time by the irradiation intensity.

According to this embodiment, the irradiation time can be shortened by the composition of the ink composition, and in this case, the printing speed is increased. On the other hand, the irradiation intensity can be reduced by the composition of the ink composition in the present embodiment, and in that case, the apparatus can be downsized and the cost can be reduced. In this case, UV-LED is preferably used for 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 above wavelength range and a polymerizable compound that initiates polymerization upon irradiation with ultraviolet rays in the above wavelength range. . 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.

As described above, according to this embodiment, it is possible to provide an ultraviolet curable ink composition having a low viscosity, excellent adhesion, and suppressed shrinkage.

Hereinafter, the embodiments of the present invention will be described more specifically by way of examples. However, the embodiments are not limited to these examples.

[Raw materials]
The raw materials used in the following examples and comparative examples are as follows.
(Polymerizable compound)
2- (2-vinyloxyethoxy) ethyl acrylate (VEEA [trade name], trade name by Nippon Shokubai Co., Ltd., hereinafter abbreviated as “VEEA”)
Tripropylene glycol diacrylate (APG-200 [trade name], manufactured by SHIN-NAKAMURA CHEMICAL CO., LTD., Abbreviated as “TPGDA” in Tables 1 to 4)
Dipropylene glycol diacrylate (APG-100 [trade name], manufactured by Shin-Nakamura Chemical Co., Ltd., abbreviated as “DPGDA” in Tables 1 to 4)
・ Cyclohexanedimethanol diacrylate (CD406 [trade name], manufactured by SARTOMER,
In Tables 1 to 4, “CHDMDA” was abbreviated. )
Trimethylcyclohexyl acrylate (CD420 [trade name], manufactured by SARTOMER, Table 1
In -4, it abbreviated as "TMCHA". )
Tetrahydrofurfuryl methacrylate (SR230 [trade name], manufactured by SARTOMER, Table 1
-4 was abbreviated as "THFMA". )
・ Isobornyl acrylate (IBXA [trade name], OSAKA ORGANI
C CHEMICAL INDUSTRY LTD.) And abbreviated as “IBXA” in Tables 1 to 4. )
Tricyclodecane dimethanol diacrylate (SR833 [trade name], manufactured by SARTOMER, abbreviated as “TCDDMDA” in Tables 1 to 4)
・ Adamantyl acrylate (adamantate HA [trade name], Idemitsu Kosan Co., Ltd. (Idemitsu K
(Osan Co., Ltd.) and in Tables 1-4, abbreviated as “AdA”. )
Cyclohexane dimethanol monoacrylate (CHDMMA [trade name], manufactured by Nippon Kasei Co., Ltd., abbreviated as “CHDMMA” in Tables 1 to 4)
Tetrahydrofurfuryl acrylate (V # 150 [trade name], manufactured by Osaka Organic Chemical Industry Co., Ltd., abbreviated as “THFA” in Tables 1 to 4)
Γ-butyrolactone acrylate (GBLA [trade name], manufactured by Osaka Organic Chemical Industry Co., Ltd., Table 1
In -4, it abbreviated as "GBLA". )
Dioxolane acrylate (MEDOL-10 [trade name], manufactured by Osaka Organic Chemical Industry Co., Ltd., abbreviated as “DOLA” in Tables 1 to 4)
Dioxane glycol diacrylate (SR508 [trade name], manufactured by SARTOMER, Table 1
4 was abbreviated as “DOGDA”. )
Oxetane acrylate (OXE-10 [trade name], manufactured by Osaka Organic Chemical Industry Co., Ltd., Tables 1 to 4
Then, it was abbreviated as “OXE-10”. )
・ Cyclic trimethylolpropane formal acrylate (SR531 [trade name], SARTOM
In Tables 1 to 4, manufactured by ER, abbreviated as “CTFA”. )
(Photopolymerization initiator)
IRGACURE 819 (trade name, manufactured by BASF, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, solid content: 100%, abbreviated as “819” in Tables 1 to 4)
DAROCURE TPO (trade name manufactured by BASF, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, solid content 100%, abbreviated as “TPO” in Tables 1 to 4)
[Slip agent]
Silicone surface conditioner BYK-UV3500 (polydimethylsiloxane having a polyether-modified acrylic group, trade name of BYK, abbreviated as “UV3500” in Tables 1 to 4)
(Polymerization inhibitor)
P-methoxyphenol (trade name, manufactured by Kanto Chemical Co., Ltd., abbreviated as “MEHQ” in Tables 1 to 4)
[Pigment]
・ CR60-2 (titanium oxide, product name made by ISHIHARA SANGYO KAISHA, LTD.,
Hereinafter, it is abbreviated as “oxidized Ti”. )
[Dispersant]
・ Solsperse 36000 (trade name, manufactured by LUBRIZOL, hereinafter “Sol 36000
". )

[Examples 1 to 27, Comparative Examples 1 to 11]
(Preparation of pigment dispersion)
Prior to the preparation of the ink composition, a pigment dispersion was prepared. 60% by mass of pigment (oxidized Ti)
, 5% by mass of dispersant (Sol 36000), 35% by mass of VEEA as a polymerizable compound
Were mixed with each other and stirred with a stirrer for 1 hour. The mixed liquid after stirring was dispersed with a bead mill to obtain a pigment dispersion. The dispersion conditions were such that zirconia beads having a diameter of 0.65 mm were filled at a filling rate of 70%, the peripheral speed was 9 m / s, and the dispersion time was 2 to 4 hours.

[Preparation of ink composition]
The components described in Tables 1 to 4 below were added so as to have the compositions (units: mass%) described in Tables 1 to 4 (in Tables 1 to 4, the pigment and a part of VEEA are the above pigment dispersions) This was mixed and stirred at room temperature for 1 hour to be completely dissolved. This was further filtered through a 5 μm membrane filter to obtain each ultraviolet curable ink composition for inkjet.

In Tables 1 to 4, the dispersant in the pigment dispersion is not described because the composition can be calculated based on the solid content of the pigment and VEEA. In addition, “VEE” in Tables 1 to 4
The column “A” shows VEEA added at the time of preparing the pigment dispersion and v added at the time of preparing the ink composition.
It is the total value with EEA. In Tables 1 to 4, “other monomer” means other polymerizable compound, “alicyclic monomer” means a polymerizable compound having an alicyclic structure in the molecule, and “ether cyclic monomer” means molecular It means a polymerizable compound having a cyclic ether structure.

[Evaluation item]
About the ultraviolet curable inkjet ink composition prepared in each Example and Comparative Example,
Viscosity, adhesion and shrinkage were evaluated by the following methods. The following solid printing uses a modified ink jet printer (Seiko Epson) with a recording resolution of 720
Application was carried out at dpi × 720 dpi and an application thickness (final film thickness after curing) of 10 μm.

〔viscosity〕
The viscosity of each ink composition was 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. ○ is a practically acceptable evaluation standard. The evaluation results are shown in Table 5.
○: 20 mPa · s or less,
×: Over 20 mPa · s.

[Adhesion]
According to JIS K-5600-5-6 (ISO 2409) (Coating General Test Method-Part 5: Mechanical Properties of Coating Film-Section 6: Adhesiveness (Cross Cut Method)), PET5 which is a recording medium
The adhesion between 0A (Pin film manufactured by Lintec Corporation) and an image formed by solid printing was evaluated. Here, the cross-cut method will be described.
As a cutting tool, a single blade cutting tool (a cutter that is generally commercially available) and a guide for cutting at equal intervals using a single blade cutting tool were prepared.
First, the cutting tool blade was applied so as to be perpendicular to the coating film, and six cuts were made in the recorded matter. After making these six cuts, the direction of 90 ° was changed, and another six cuts were made so as to be perpendicular to the cuts already made.
Next, take out the transparent adhesive tape (width 25 ± 1 mm) so that the length is about 75 mm, attach the tape to the grid-cut portion formed on the coating film, and finger enough to see through the coating film. I rubbed the tape. Next, within 5 minutes of adhesion, it was reliably pulled apart at an angle close to 60 ° in 0.5 to 1.0 seconds.
The evaluation criteria are as follows. ◎ and ○ are practically acceptable evaluation criteria. The evaluation results are shown in Table 5.
A: Peeling is hardly seen in any lattice eye (rank 0 or rank 1 in JIS K-5600-5-6).
○: Peeling is observed in part of the lattice (less than 50%) (rank 2 or rank 3 in JIS K-5600-5-6).
X: Peeling is observed in 50% or more of the lattice (rank 4 or rank 5 in JIS K-5600-5-6).

[Shrinkage]
Shrinkage evaluation (curl test) was performed. Lumirror (registered trademark) E20 as a recording medium
# 125 (trade name, manufactured by Toray Industries, Inc., biaxially stretched polyester (PET
) A test piece having a width of 7 mm and a length of 44 mm was prepared from a film, a white grade, and a thickness of 125 μm. Solid printing was performed on the center of the test piece within a range of 5 mm in width and 40 mm in length. Thereafter, the ink was cured by irradiating with ultraviolet rays under the following conditions. The ultraviolet irradiation conditions were a wavelength of 395 nm, an irradiation intensity of 1,000 mW / cm ² , and a maximum integrated irradiation dose of 500.
mJ / cm ² .
Shrinkage was evaluated by measuring the degree of lifting (curl) at the end of the test piece after curing. The evaluation criteria are as follows. ◎ and ○ are practically acceptable evaluation criteria. The evaluation results are shown in Table 5.
A: Less than 5 mm
○: 5 mm or more and less than 10 mm,
X: 10 mm or more.

From Table 5 above, first, when the content of the monomer A is 20 to 70% by mass, the viscosity is lowered as compared with the case where the content is less than 20% by mass, and compared with the case where the content is more than 70% by mass. It was found that the adhesion was excellent.

Moreover, content of the polymeric compound (alicyclic monomer) which has an alicyclic structure in a molecule | numerator is 10-20.
In the case of mass%, it was found that the shrinkage was suppressed as compared with the case where the content was less than 10 mass%, and the viscosity was reduced as compared with the case where the content was more than 20 mass%.

In addition, when the content of the polymerizable compound (ether cyclic monomer) having a cyclic ether structure in the molecule is 10 to 20% by mass, the adhesiveness is excellent as compared with the case where the content is less than 10% by mass. It was found that the viscosity was reduced as compared with the case where the amount was more than 20% by mass.

Furthermore, when the ink composition contains both an alicyclic monomer and an ether cyclic monomer, each content is 5% by mass or more and the total content is 10 to 20% by mass. Compared with the case where the content is less than 5% by mass, the adhesiveness is excellent and the shrinkage is suppressed, and each content is 5% by mass or more, but the total content is more than 20% by mass. It was found that the viscosity decreased.

Claims (8)

An ultraviolet curable inkjet ink composition comprising:
20 to 70% by mass of the following general formula (I) with respect to the total mass of the ink composition:
_{^{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.)
A compound represented by
As a polymerizable compound having a cyclic ether structure in the molecule of 10 to 20% by mass based on the total mass of the ink composition, tetrahydrofurfuryl acrylate, γ-butyrolactone acrylate, dioxolane acrylate, and dioxane glycol diacrylate are included. One or more selected from the group, and an ultraviolet curable inkjet ink composition. An ultraviolet curable inkjet ink composition comprising:
20 to 70% by mass of the following general formula (I) with respect to the total mass of the ink composition:
_{^{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.)
A compound represented in,
Comprising a polymerizable compound having an alicyclic structure in the molecule and (meth) acrylates, a polymerizable compound having a ring-like ether structure in the molecule and (meth) acrylates, and,
The total content of (meth) acrylates which are polymerizable compounds having an alicyclic structure in the molecule and (meth) acrylates which are polymerizable compounds having a cyclic ether structure in the molecule is the ink composition. The ultraviolet curable ink-jet ink composition is 10 to 20% by mass based on the total mass of the ink. (Meth) acrylates, which are polymerizable compounds having an alicyclic structure in the molecule, are contained in an amount of 5% by mass or more based on the total mass of the ink composition, and
The ultraviolet curable inkjet ink according to claim 2, wherein (meth) acrylates, which are polymerizable compounds having a cyclic ether structure in the molecule, are contained in an amount of 5% by mass or more based on the total mass of the ink composition. Composition. (Meth) acrylates, which are polymerizable compounds having an alicyclic structure in the molecule, The ultraviolet curing according to claim 2 or 3, which is contained in an amount of 5 to 15% by mass based on the total mass of the composition. Ink jet ink composition. (Meth) acrylates which are polymerizable compounds having a cyclic ether structure in the molecule And 5 to 15% by mass based on the total mass of the ink composition. An ultraviolet curable ink composition for inkjet according to the item 1. As (meth) acrylates which are polymerizable compounds having an alicyclic structure in the molecule, Licyclodecane dimethanol di (meth) acrylate, adamantyl (meth) acrylate , Cyclohexanedimethanol mono (meth) acrylate, cyclohexanedimethano Rudi (meth) acrylate, trimethylcyclohexyl (meth) acrylate, isovol Nyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, dicyclo Pentanyl (meth) acrylate and dicyclopentenyloxyethyl (meth) acrylate The ultraviolet curable ink according to any one of claims 2 to 5, comprising at least one of the rates. An ink composition for a kjet. As (meth) acrylates which are polymerizable compounds having the cyclic ether structure, Torahydrofurfuryl (meth) acrylate, γ-butyrolactone (meth) acrylate , Dioxolane (meth) acrylate, dioxane glycol di (meth) acrylate, Oxetane (meth) acrylate, cyclic trimethylolpropane formal (meth) acrylic The ultraviolet curable ink according to any one of claims 2 to 6, comprising at least one of the rates. An ink composition for a kjet. The ultraviolet curable inkjet ink composition according to any one of claims 1 to 7 , wherein the compound represented by the general formula (I) is 2- (vinyloxyethoxy) ethyl acrylate.