JP2012140551A - Ultraviolet-curing inkjet ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet-curing inkjet ink composition that is excellent in curability, scratch resistance, and anti-wrinkle properties when a thick film is cured.SOLUTION: The ultraviolet-curing inkjet ink composition comprises: a monomer A; a (meth)acrylate that has a fluorene skeleton; and a photopolymerization initiator. The monomer A is expressed by the formula (I): CH=CR-COOR-O-CH=CH-R(wherein Ris a hydrogen atom or a methyl group; Ris a 2-20C divalent organic residue; and Ris the hydrogen atom or 1-11C monovalent residue).

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 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 an ultraviolet curable inkjet ink composition containing 2- (2-vinyloxyethoxy) ethyl acrylate, tripropylene glycol diacrylate, an aminoacrylate acrylic resin, and a photopolymerization initiator. ing.

JP 2008-280383 A

  However, the ink composition disclosed in Patent Document 1 has room for improvement in terms of curability, abrasion resistance, and wrinkle suppression during thick film curing.

  Some embodiments according to the present invention provide an ultraviolet curable inkjet ink composition excellent in curability, abrasion resistance, and wrinkle suppression during thick film curing by solving the above-described problems.

  The present inventors have intensively studied to solve the above problems. As a result, the inventors have found that the above problems can be solved by an ultraviolet curable inkjet ink composition containing a predetermined monomer, a (meth) acrylate having a fluorene skeleton, and a photopolymerization initiator, and completed the present invention.

  That is, the present invention is as follows.

[Application Example 1]
The ultraviolet curable inkjet ink composition according to this application example 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 (meth) acrylate having a fluorene skeleton, and a photopolymerization initiator.

  According to the photocurable ink composition described in Application Example 1, an image excellent in curability, light resistance, and wrinkle suppression during thick film curing can be recorded on a recording medium.

[Application Example 2]
Monomer A described in the above application example is preferably 2- (vinyloxyethoxy) ethyl (meth) acrylate.

[Application Example 3]
The monomer A described in the above application example is preferably contained in an amount of 50 to 80% by mass with respect to the total mass of the ink composition.

[Application Example 4]
The (meth) acrylate having a fluorene skeleton described in the application example is preferably a compound represented by the following general formula (II).

[Application Example 5]
The (meth) acrylate having a fluorene skeleton described in the application example is preferably contained in an amount of 0.5 to 30% by mass with respect to the total mass of the ink composition.

[Application Example 6]
In the said application example, it is preferable that 5-35 mass% phenoxyethyl (meth) acrylate is further included.

[Application Example 7]
The photopolymerization initiator described in the application example preferably includes 7% by mass or more of an acylphosphine oxide compound and 0.5% by mass or more of a thioxanthone compound with respect to the total mass of the ink composition.

[Application Example 8]
The ultraviolet ray curable inkjet ink composition described in the application example can be cured by irradiating ultraviolet rays having an emission peak wavelength in a range of 350 to 420 nm with an irradiation energy of 300 mJ / cm ² or less. .

[Application Example 9]
The ultraviolet curable inkjet ink composition described in the above application example can be cured in a thick film state having a thickness of 9 μm or more.

  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, “(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 this specification, “curability” refers to a property of being cured by polymerization in the presence or absence of a photopolymerization initiator by irradiation with light. “Abrasion resistance” refers to the property of scratch resistance of an image recorded on a recording medium. “Wrinkle suppression during thick film curing” refers to the property that wrinkles are less likely to occur when an image having a thickness of 9 μm or more after curing is lowered by light irradiation.

[UV-curable inkjet ink composition]
One embodiment of the present invention relates to an ultraviolet curable inkjet ink composition. The ultraviolet curable inkjet ink composition 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.)
(Meth) acrylic acid ester (henceforth "monomer A") represented by these, (meth) acrylate which has a fluorene skeleton, and a photoinitiator.
Hereinafter, additives (components) contained in or capable of being contained in the ultraviolet curable inkjet ink composition of the present embodiment (hereinafter also simply referred to as “ink composition”) will be described.

(Polymerizable compound)
The polymerizable compound 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 can cure the printed ink.

(Monomer A)
Monomer A, which is an essential polymerizable compound in the present embodiment, is represented by the above general formula (I).

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

In the above general formula (I), the divalent organic residue represented by R ² includes a linear, branched or cyclic alkylene group having 2 to 20 carbon atoms, an ether bond in the structure and / or Or a C2-C20 alkylene group which has an oxygen atom by an ester bond, and a C6-C11 optionally substituted bivalent aromatic group are suitable. 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 said general formula (I), as a C1-C11 monovalent organic residue represented by R < ³ >, a C1-C10 linear, branched or cyclic alkyl group, carbon An optionally substituted aromatic group of formula 6 to 11 is 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 the above organic residue 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. 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-ethyl (meth) acrylate include 2- (2-vinyloxyethoxy) ethyl (meth) acrylate and 2- (1-vinyloxyethoxy) ethyl (meth) acrylate. (Vinyloxyethoxy) ethyl includes 2- (2-vinyloxyethoxy) ethyl acrylate and 2- (1-vinyloxyethoxy) ethyl acrylate.

  The content of the monomer A is preferably 50 to 80% by mass and more preferably 65 to 80% by mass with respect to the total mass (100% by mass) of the ink composition. When the content is within the above range, the curability of the ink can be particularly improved.

  The method for producing the vinyl ether group-containing (meth) acrylic acid ester represented by the general formula (I) is not limited to the following, but is a method for esterifying (meth) acrylic acid and a hydroxyl group-containing vinyl ether (production method). B), a method of esterifying (meth) acrylic acid halide and a hydroxyl group-containing vinyl ether (production method C), a method of esterifying (meth) acrylic anhydride and a hydroxyl group-containing vinyl ether (production method D), ( Method of transesterifying (meth) acrylic acid esters with hydroxyl group-containing vinyl ethers (Production method E), Method of esterifying (meth) acrylic acid and halogen-containing vinyl ethers (Production method F), Alkali (meth) acrylate ( Earth) Method of esterifying metal salt and halogen-containing vinyl ether (Production G), Hydroxyl group (Me ) How to vinyl exchange and vinyl acrylic esters and carboxylic acid (Preparation 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.

((Meth) acrylate having fluorene skeleton)
In the present embodiment, the chemical structure of the (meth) acrylate having a fluorene skeleton, which is an essential polymerizable compound, is particularly limited as long as it has a fluorene skeleton in the molecule and a (meth) acryloyl group. For example, 9,9-bis (di (meth) acryloyloxyphenyl) fluorenes, 9,9-bis (tri (meth) acryloyloxyphenyl) fluorenes, and the corresponding polyhydric alcohols [9,9- (Meth) acrylates of alkylene oxide (C _2-4 alkylene oxide) adducts of bis (di or trihydroxyphenyl) fluorenes] and the like.

The 9,9-bis (di (meth) acryloyloxyphenyl) fluorenes include, for example, 9,9-bis (di (meth) acryloyloxyphenyl) fluorene [9,9-bis (3,4-di (meth) ) Acryloyloxyphenyl) fluorene, 9,9-bis (2,4-di (meth) acryloyloxyphenyl) fluorene, 9,9-bis (2,5-di (meth) acryloyloxyphenyl) fluorene, etc.], substitution 9,9-bis (di (meth) acryloyloxyphenyl) fluorene having a group {eg, 9,9-bis (alkyl-di (meth) acryloyloxyphenyl) fluorene [9,9-bis (3,4-di (Meth) acryloyloxy-5-methylphenyl) fluorene, 9,9-bis (3,4-di (meth) acryloyloxy-6-me 9,9-bis (C _1-4 alkyl-di (meth) acryloyloxyphenyl) fluorene such as tilphenyl) fluorene, 9,9-bis (2,4-di (meth) acryloyloxy-3,6-dimethylphenyl) ) 9,9-bis (diC _1-4 alkyl-di (meth) acryloyloxyphenyl) fluorene etc.], 9,9-bis (alkoxy-di (meth) acryloyloxyphenyl) fluorene [eg 9 9,9-bis (C _1-4 alkoxy-di (meth) acryloyloxyphenyl) fluorene, etc.] such as 9,9-bis (3,4-di (meth) acryloyloxy-5-methoxyphenyl) fluorene], 9, 9-bis (aryl-di (meth) acryloyloxyphenyl) fluorene [eg, 9,9-bis (3,4-di (meth) Acryloyloxy-5-phenylphenyl) fluorene such as 9,9-bis (C _6-8 aryldi (meth) acryloyloxy phenyl) fluorene, etc.], etc.} and the like.

  The 9,9-bis (tri (meth) acryloyloxyphenyl) fluorenes include fluorenes corresponding to the 9,9-bis (di (meth) acryloyloxyphenyl) fluorenes such as 9,9-bis ( 2,4,6- (meth) acryloyloxyphenyl) fluorene, 9,9-bis (2,4,5-tri (meth) acryloyloxyphenyl) fluorene, 9,9-bis (3,4,5-tri 9,9-bis (tri (meth) acryloyloxyphenyl) fluorene such as (meth) acryloyloxyphenyl) fluorene is included.

Examples of the (meth) acrylate of an alkylene oxide adduct of 9,9-bis (dihydroxyphenyl) fluorene include 9,9-bis [3,4-di (2- (meth) acryloyloxyethoxy) phenyl] fluorene. 9,9-bis [di (2- (meth) acryloyloxy C _2-4 alkoxy) phenyl] fluorene (n1 = n2 = 1), 9,9-bis {3,4-di [2- (2 - (meth) acryloyloxy) ethoxy] phenyl} fluorene such as 9,9-bis {di [2- (2- (meth) acryloyloxy C _2-4 alkoxy) C _2-4 alkoxyphenyl] fluorene} (n1 = N2 = 2) and the like.

Examples of the (meth) acrylate of an alkylene oxide adduct of 9,9-bis (trihydroxyphenyl) fluorene include 9,9-bis [3,4,5-tri (2- (meth) acryloyloxyethoxy). 9,9-bis [di (2- (meth) acryloyloxy C _2-4 alkoxy) phenyl] fluorene (n1 = n2 = 1), 9,9-bis {3,4,5-tri, such as phenyl] fluorene 9,9-bis {tri [2- (2- (meth) acryloyloxy C _2-4 alkoxy) C _2-4 alkoxyphenyl such as [2- (2- (meth) acryloyloxyethoxy) ethoxy] phenyl} fluorene ] Fluorene} (n1 = n2 = 2) and the like.

  Among these (meth) acrylates having a fluorene skeleton, a monomer represented by the following general formula (II) is particularly preferable.

Specific examples of the (meth) acrylate having a fluorene skeleton represented by the above general formula (I) are not limited to the following, but 9,9-bis (di (meth) acryloyloxyphenyl) fluorene [9,9 -Bis (3,4-di (meth) acryloyloxyphenyl) fluorene, 9,9-bis (2,4-di (meth) acryloyloxyphenyl) fluorene, 9,9-bis (2,5-di (meta) ) Acryloyloxyphenyl) fluorene, etc.], 9,9-bis (di (meth) acryloyloxyphenyl) fluorene having a substituent {for example, 9,9-bis (alkyl-di (meth) acryloyloxyphenyl) fluorene [9 , 9-bis (3,4-di (meth) acryloyloxy-5-methylphenyl) fluorene, 9,9-bis (3,4-di ( 9,9-bis (C _1-4 alkyl-di (meth) acryloyloxyphenyl) fluorene such as (meth) acryloyloxy-6-methylphenyl) fluorene, 9,9-bis (2,4-di (meth) acryloyl) 9,9-bis (diC _1-4 alkyl-di (meth) acryloyloxyphenyl) fluorene etc.] such as oxy-3,6-dimethylphenyl) fluorene, 9,9-bis (alkoxy-di (meth) acryloyl) Oxyphenyl) fluorene [e.g. 9,9-bis ( _C1-4 alkoxy-di (meth) acryloyloxy such as 9,9-bis (3,4-di (meth) acryloyloxy-5-methoxyphenyl) fluorene] Phenyl) fluorene and the like], 9,9-bis (aryl-di (meth) acryloyloxyphenyl) fluorene [for example 9,9-bis (3,4-di (meth) acryloyloxy-5-phenylphenyl) fluorene, etc.], etc.} and the like.

Among these, 9,9-bis [4- (2- (meth) acryloyloxyethoxy) phenyl] fluorene is more preferable because it has a relatively low viscosity and is excellent in abrasion resistance and wrinkle suppression during thick film curing. Preferably, 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene is more preferable.

  The content of the (meth) acrylate having a fluorene skeleton is preferably 0.5 to 30% by mass, more preferably 1 to 20% by mass with respect to the total mass (100% by mass) of the ink composition. When the content is within the above range, particularly abrasion resistance and wrinkle suppression during thick film curing can be improved.

  Although it does not specifically limit as a manufacturing method of the (meth) acrylate which has a fluorene skeleton of this invention, For example, the method manufactured by making the polyhydric alcohol which has a fluorene skeleton, and (meth) acrylic acid or its derivative (s) react. Is mentioned.

(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, salts or esters thereof, urethane, amide and anhydride thereof, acrylonitrile, styrene, various types 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, oxetane (meth) acrylate, aliphatic urethane (meth) acrylate, and aromatic urethane (meth). Acrylate and polyester (meth) acrylate are mentioned.

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

  Among other polymerizable compounds, an ester of (meth) acrylic acid, that is, (meth) acrylate is preferable.

  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 , Tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, lactone-modifiable Examples include flexible (meth) acrylate, t-butylcyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and dicyclopentenyloxyethyl (meth) acrylate.

  Among the (meth) acrylates, examples of the bifunctional (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 (meth) acrylate, dimethylol-tricyclodecane di (meth) acrylate, EO (ethylene oxide) adduct of bisphenol A di (meth) acrylate, PO of bisphenol A (propylene oxide) De) adduct di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, and polytetramethylene glycol di (meth) acrylate.

  Among the above (meth) acrylates, trifunctional or more polyfunctional (meth) acrylates include, for example, trimethylolpropane tri (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, and pentaerythritol tri (meth) acrylate. , Pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, glycerin propoxytri (meth) acrylate, cowprolactone modified trimethylolpropane tri (meth) acrylate, pentaerythritol Examples include ethoxytetra (meth) acrylate and caprolactam-modified dipentaerythritol hexa (meth) acrylate.

  Among these, other polymerizable compounds preferably include monofunctional (meth) acrylates. In this case, the ink composition has a low viscosity, is excellent in solubility of the photopolymerization initiator and other additives, and is easy to obtain ejection stability during ink jet recording. Furthermore, since the toughness, heat resistance, and chemical resistance of the coating film increase, it is more preferable to use a monofunctional (meth) acrylate and a bifunctional (meth) acrylate in combination.

  Furthermore, the monofunctional (meth) acrylate preferably has one or more skeletons selected from the group consisting of an aromatic ring skeleton, a saturated alicyclic skeleton, and an unsaturated alicyclic skeleton. When the other polymerizable compound is a monofunctional (meth) acrylate having the skeleton, the viscosity of the ink composition can be reduced.

  Examples of the monofunctional (meth) acrylate having an aromatic ring skeleton include phenoxyethyl (meth) acrylate and 2-hydroxy-3-phenoxypropyl (meth) acrylate. Examples of the monofunctional (meth) acrylate having a saturated alicyclic skeleton include isobornyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, and dicyclopentanyl (meth) acrylate. Examples of the monofunctional (meth) acrylate having an unsaturated alicyclic skeleton include dicyclopentenyloxyethyl (meth) acrylate.

  Among these, in order to reduce viscosity and odor, at least one of phenoxyethyl (meth) acrylate and isobornyl (meth) acrylate is preferable, and phenoxyethyl (meth) acrylate is more preferable.

  The content of the polymerizable compound other than the monomer A and the (meth) acrylate having a fluorene skeleton described above is preferably 5 to 50% by mass with respect to the total mass (100% by mass) of the ink composition. In particular, when the ink composition contains the above phenoxyethyl (meth) acrylate, the content of phenoxyethyl (meth) acrylate is preferably 5 to 35% by mass with respect to the total mass (100% by mass) of the ink composition. More preferably, it is 5-30 mass%. When the content is within the above range, viscosity and odor are lowered while maintaining curability.

  Said other polymeric compound may be used individually by 1 type, and may use 2 or more types together.

(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 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, diethyl Oxanthone, 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) (Ciba Japan K.K.), KAYACURE DETX-S (2,4-diethylthioxanthone) (Nippon Kayaku Co.) , Ltd. )), Lucirin TPO, LR8883, LR8970 (above, manufactured by BASF) and Ubekrill P36 (manufactured by UCB).

  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. 5 to 20% by mass is preferable. In particular, as described above, when the photopolymerization initiator contained in the ink composition is an acylphosphine oxide compound and a thioxanthone compound, the acylphosphine oxide compound is preferably used with respect to the total mass (100% by mass) of the ink composition. Is contained in an amount of 7% by mass or more, more preferably 7 to 15% by mass. In addition, the thioxanthone compound is preferably contained in an amount of 0.5% by mass or more, more preferably 0.5 to 5% by mass with respect to the total mass (100% by mass) of the ink composition. In this case, the curability of the ink can be particularly improved.

  In addition, it is possible to omit the addition of a photopolymerization initiator by using a photopolymerizable compound as the polymerizable compound described above, but it is easier to start polymerization by using a photopolymerization initiator. It can be adjusted and is preferred.

[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, 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. 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. (from CABOT JAPAN K. F. C. , 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. And CI Pigment White 6, 18, and 21.

  Examples of pigments used in yellow ink include C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 2, C.I. I. Pigment yellow 3, C.I. I. Pigment yellow 4, C.I. I. Pigment yellow 5, C.I. I. Pigment yellow 6, C.I. I. Pigment yellow 7, C.I. I. Pigment yellow 10, C.I. I. Pigment yellow 11, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 16, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 24, C.I. I. Pigment yellow 34, C.I. I. Pigment yellow 35, C.I. I. Pigment yellow 37, C.I. I. Pigment yellow 53, C.I. I. Pigment yellow 55, C.I. I. Pigment yellow 65, C.I. I. Pigment yellow 73, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 75, C.I. I. Pigment yellow 81, C.I. I. Pigment yellow 83, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 95, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 98, C.I. I. Pigment yellow 99, C.I. I. Pigment yellow 108, C.I. I. Pigment yellow 109, C.I. I. Pigment yellow 110, C.I. I. Pigment yellow 113, C.I. I. Pigment yellow 114, C.I. I. Pigment yellow 117, C.I. I. Pigment yellow 120, C.I. I. Pigment yellow 124, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 129, C.I. I. Pigment yellow 133, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 139, C.I. I. Pigment yellow 147, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 153, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 167, C.I. I. Pigment yellow 172, C.I. I. Pigment yellow 180.

  Examples of pigments used in magenta ink include C.I. I. Pigment Red 1, C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 4, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 8, C.I. I. Pigment Red 9, C.I. I. Pigment red 10, C.I. I. Pigment red 11, C.I. I. Pigment red 12, C.I. I. Pigment red 14, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 17, C.I. I. Pigment red 18, C.I. I. Pigment red 19, C.I. I. Pigment red 21, C.I. I. Pigment red 22, C.I. I. Pigment red 23, C.I. I. Pigment red 30, C.I. I. Pigment red 31, C.I. I. Pigment red 32, C.I. I. Pigment red 37, C.I. I. Pigment red 38, C.I. I. Pigment red 40, C.I. I. Pigment red 41, C.I. I. Pigment red 42, C.I. I. Pigment red 48 (Ca), C.I. I. Pigment red 48 (Mn), C.I. I. Pigment red 57 (Ca), C.I. I. Pigment red 57: 1, C.I. I. Pigment red 88, C.I. I. Pigment red 112, C.I. I. Pigment red 114, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 144, C.I. I. Pigment red 146, C.I. I. Pigment red 149, C.I. I. Pigment red 150, C.I. I. Pigment red 166, C.I. I. Pigment red 168, C.I. I. Pigment red 170, C.I. I. Pigment red 171, C.I. I. Pigment red 175, C.I. I. Pigment red 176, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 179, C.I. I. Pigment red 184, C.I. I. Pigment red 185, C.I. I. Pigment red 187, C.I. I. Pigment red 202, C.I. I. Pigment red 209, C.I. I. Pigment red 219, C.I. I. Pigment red 224, C.I. I. Pigment red 245, or C.I. I. Pigment Violet 19, C.I. I. Pigment violet 23, C.I. I. Pigment violet 32, C.I. I. Pigment violet 33, C.I. I. Pigment violet 36, C.I. I. Pigment violet 38, C.I. I. Pigment violet 43, C.I. I. Pigment Violet 50.

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

  Examples of pigments other than magenta, cyan and yellow include C.I. I. Pigment green 7, C.I. I. Pigment green 10, C.I. I. Pigment brown 3, C.I. I. Pigment brown 5, C.I. I. Pigment brown 25, C.I. I. Pigment brown 26, C.I. I. Pigment orange 1, C.I. I. Pigment orange 2, C.I. I. Pigment orange 5, C.I. I. Pigment orange 7, C.I. I. Pigment orange 13, C.I. I. Pigment orange 14, C.I. I. Pigment orange 15, C.I. I. Pigment orange 16, C.I. I. Pigment orange 24, C.I. I. Pigment orange 34, C.I. I. Pigment orange 36, C.I. I. Pigment orange 38, C.I. I. Pigment orange 40, C.I. I. Pigment orange 43, C.I. I. Pigment orange 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 has preferable 300 nm or less, and 50-200 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, 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.

  Since the excellent concealability and color reproducibility can be obtained, the content of the color material is preferably 1 to 20% by mass with respect to the total 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 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., Ltd., Ajisper series, Solsperse series available from Avecia Co. (Solsperse 36000, etc.), BYK Chemie's Dispervic series, Enomoto Disparon series manufactured by Kasei Co., Ltd. can be listed.

[Slip agent]
The ink composition of the present embodiment may further include a slip agent (surfactant) because an advantageous effect that high abrasion resistance is obtained is obtained. 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-347, BYK-348, BYK-UV3500, 3510, 3530, and 3570 (manufactured by BYK Japan KK).

[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 adjusting 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 an inkjet recording method described later. Examples of the recording medium include an absorptive or non-absorbable recording medium. The ink jet recording method of the present embodiment has various absorption performances from a non-absorbable recording medium in which penetration of the water-soluble ink composition is difficult to an absorbent recording medium in which penetration of the water-soluble ink composition is easy. Widely applicable to recording 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 thereof 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, a plate made of an alloy such as stainless steel or brass.

[Inkjet recording method]
The ultraviolet curable inkjet ink composition of the present embodiment can be used in an inkjet recording method. The inkjet recording method includes a discharge step of discharging the ink composition onto a recording medium, and a curing step of curing the ink composition by irradiating the ink composition discharged in the discharge step with ultraviolet rays. ,including. 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 is preferably 25 mPa · s or less, more preferably 5 to 20 mPa · s. If the viscosity of the ink composition is as described above with the temperature of the ink composition at room temperature or without heating the ink composition, the temperature of the ink composition is at room temperature or without heating the ink composition. Can be discharged. On the other hand, the ink composition may be discharged to a preferable viscosity by heating to a predetermined temperature. In this way, good discharge stability is realized.

  Since the radiation curable ink composition of the present embodiment has a higher viscosity than the water-based ink composition used in ordinary inkjet recording inks, 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 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. 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 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, the emission peak wavelength, preferably in the range of 350 to 420 nm, more preferably ultraviolet rays in the range of 365～405Nm, preferably 300 mJ / cm ² or less, more preferably irradiation energy of 100~250mJ / cm ² It is preferable to use an ultraviolet curable inkjet ink composition that can be cured by irradiation. In this case, curing with low energy and high speed is possible due to the composition of the ink composition in the present embodiment. The irradiation energy is calculated by multiplying the irradiation time by the irradiation intensity. The irradiation time can be shortened by the composition of the ink composition in the present embodiment, 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 a photopolymerization initiator that decomposes upon irradiation with ultraviolet rays in the above wavelength range and / or 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.

  In addition, it is preferable to use an ultraviolet curable inkjet ink composition that can be cured in a thickness of 9 μm, more preferably 9 to 15 μm. In this case, due to the composition of the ink composition in the present embodiment, it is possible to form an image with a thick film, and an effect of suppressing wrinkles during thick film curing can be obtained. Such an ink composition can be obtained by the various methods described above.

  Thus, according to the present embodiment, it is possible to provide an ultraviolet curable inkjet ink composition that is excellent in curability, scratch resistance, and wrinkle suppression during thick film curing.

  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 A]
2- (2-vinyloxyethoxy) ethyl acrylate (VEEA [trade name], manufactured by Nippon Shokubai Co., Ltd.) (abbreviated as VEEA in Tables 1 to 3)
[(Meth) acrylate having fluorene skeleton]
9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene (A-BPEF [trade name], manufactured by Shin-Nakamura Chemical Co., Ltd.) (abbreviated as A-BPEF in Tables 1 to 3)
・ Ogsol EA-F5510 [trade name], manufactured by Osaka Gas Chemical Co. (abbreviated as EA-F5510 in Tables 1 to 3)
[Polymerizable compounds other than the above]
-Phenoxyethyl acrylate biscort # 192 (trade name, manufactured by OSAKA ORGANIC CHEMICAL INDUSTRY LTD., Abbreviated as PEA in Tables 1 to 3)
N-vinylcaprolactam (V-CAP [trade name], manufactured by ISP Japan) (abbreviated as NVC in Tables 1 to 3)
Isobornyl acrylate IBXA (trade name, manufactured by Osaka Organic Chemical Co., Ltd., abbreviated as IBXA in Tables 1 to 3)
Dimethylol tricyclodecane diacrylate (A-DPC [trade name], Shin-Nakamura Chemical Co., Ltd.) (abbreviated as DMTCDDA in Tables 1 to 3)
Pentaerythritol triacrylate) (A-TMM-3LM-N [trade name], Shin-Nakamura Chemical Co., Ltd.) (abbreviated as PETIA in Tables 1 to 3)
(Photopolymerization initiator)
IRGACURE 819 (trade name, manufactured by Ciba Japan, solid content: 100%, abbreviated 819 in Tables 1 to 3)
DAROCURE TPO (trade name manufactured by Ciba Japan, solid content 100%, abbreviated as TPO in Tables 1 to 3)
-KAYACURE DETX-S (trade name, manufactured by Nippon Kayaku Co., Ltd., 100% solid content, abbreviated as DETX-S in Tables 1 to 3)
[Slip agent]
Silicone surface conditioner BYK-UV3500 (trade name, manufactured by BYK, abbreviated as UV3500 in Tables 1 to 3)
[Pigment]
・ C. I. Pigment Black 7 (abbreviated as Pigment Black 7 in Tables 1 to 3)
[Dispersant]
Solsperse 36000 (trade name manufactured by LUBRIZOL, abbreviated as SOL36000 in Tables 1 to 3)

[Examples 1-14, Comparative Examples 1-6]
The components listed in Tables 1 to 3 below were added so as to have the compositions (units: mass%) described in Tables 1 to 3, and this was stirred with a high-speed water-cooled stirrer to obtain a black color. An ultraviolet curable ink composition for inkjet was obtained. In addition, the blank part in Table 1 thru | or Table 3 means no addition.

〔Evaluation item〕
(1. Curability)
Using an ink jet printer PX-G5000 (trade name, manufactured by Seiko Epson Corporation), the photocurable ink composition was filled in each nozzle row. A solid pattern image (recording resolution 720 × 720 dpi) on a PET film (Lumirror 125E20 [trade name], manufactured by Panac Co., Ltd.) at normal temperature and normal pressure so that the dot diameter of the ink is medium and the film thickness of the printed material is 12 μm. with print, from UV-LED in the ultraviolet irradiation apparatus mounted next to the carriage, the irradiation intensity is 60 mW / cm ^2, and wavelength of ultraviolet 200 mJ / cm ² irradiated to the solid pattern image is 395nm Cured. As described above, a recorded matter having a solid pattern image printed on a PET film was produced. A 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.
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 measurement of irradiation intensity was performed using an ultraviolet intensity meter UM-10 and a light receiving unit UM-400 (both manufactured by KONICA MINOLTA SENSING, INC.).
Whether or not it can be said to be tack-free was determined under the following conditions. That is, the determination was made based on whether the ink sticks to the cotton swab or whether the cured ink on the recording medium is scratched. The cotton swab used here was a Johnson swab manufactured by Johnson & Johnson. The number of rubbing was 10 reciprocations and the rubbing strength was 100 g load.
Moreover, the film thickness of the ink coating film (cured film) at the time of sclerosis | hardenability evaluation was 12 micrometers. The evaluation criteria are as follows. Among the evaluation criteria, ○ and Δ are practically acceptable criteria. The evaluation results are shown in Table 4 and Table 5 below.
○: tack-free at the time of irradiation energy 200mJ / cm ² or less △: tack-free at the time of irradiation energy 200mJ / cm ² ultra 300mJ / cm ² or less ×: tack-free at the time of irradiation energy 300mJ / cm ² more than

(2. Abrasion resistance)
Using an inkjet printer PX-G5000 (trade name, manufactured by Seiko Epson Corporation), the photocurable ink composition was filled in each nozzle row. A solid pattern image is printed on a PET label (PET50A PL Thin 11BL [trade name], manufactured by Lintec Corporation) at room temperature and normal pressure so that the dot diameter of the ink is medium and the film thickness after printing is 12 μm. while, the irradiation intensity from UV-LED in the ultraviolet irradiation apparatus mounted next to the carriage by UV radiation 300 mJ / cm ² with a wavelength of 395nm of 1000 mW / cm ² to cure the solid pattern image. As described above, a recorded matter having a solid pattern image printed on a PET film was produced.
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 measurement of irradiation intensity was performed using an ultraviolet intensity meter UM-10 and a light receiving unit UM-400 (both manufactured by KONICA MINOLTA SENSING, INC.).
The rubbing resistance test was conducted using a Gakushin type friction fastness tester manufactured by Tester Sangyo Co., Ltd. according to JIS K5701. In the test method, a gold width was placed on the solid pattern image and rubbed with a load of 500 g, and peeling of the cured surface of the printed matter after the rub was visually compared. The results are shown in Tables 4 and 5.
A: No stain on the gold width / No scratch on the printed surface (good)
B: Dirty on the gold / no scratch on the printed surface (normal)
C: Dirty on the gold width / Scratch on the printed surface (bad)

(2. Wrinkle suppression during thick film curing)
Using an inkjet printer PX-G5000 (trade name, manufactured by Seiko Epson Corporation), the photocurable ink composition was filled in each nozzle row. While printing a solid pattern image on a PET film (Lumirror 125E20 [trade name], manufactured by Panac Co., Ltd.) at normal temperature and normal pressure, the dot diameter of the ink is medium and the printed film has a thickness of 12 μm after curing. and irradiation intensity from UV-LED in the ultraviolet irradiation apparatus mounted next to the carriage by UV radiation 200 mJ / cm ² with a wavelength of 395nm of 1000 mW / cm ² to cure the solid pattern image. As described above, a recorded matter having a solid pattern image printed on a PET film was produced.
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 measurement of irradiation intensity was performed using an ultraviolet intensity meter UM-10 and a light receiving unit UM-400 (both manufactured by KONICA MINOLTA SENSING, INC.).
Whether or not wrinkles during thick film curing was suppressed was judged by visual observation and microscopic observation. Moreover, the film thickness of the ink coating film (cured film) at the time of sclerosis | hardenability evaluation was 12 micrometers. The evaluation criteria are as follows. Among the evaluation criteria, ○ is a practically acceptable criterion. The evaluation results are shown in Table 4 and Table 5 below.
○: No wrinkle can be confirmed by visual observation or microscopic observation.
Δ: Although wrinkles cannot be confirmed by visual observation, wrinkles can be confirmed by microscopic observation.
X: A wrinkle can be confirmed visually.

  From Tables 3 and 4 above, the ultraviolet curable inkjet ink composition containing the predetermined monomer A and (meth) acrylate having a fluorene skeleton exhibits curability, abrasion resistance, and wrinkle suppression during thick film curing. Was found to be good.

Claims (9)

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.)
An ink composition for ultraviolet curable ink jet, comprising a monomer A represented by the formula: (meth) acrylate having a fluorene skeleton, and a photopolymerization initiator.   The ultraviolet curable inkjet ink composition according to claim 1, wherein the monomer A is 2- (vinyloxyethoxy) ethyl (meth) acrylate.   The ultraviolet curable inkjet ink composition according to claim 1 or 2, wherein the monomer A is contained in an amount of 50 to 80% by mass based on the total mass of the ink composition. The ultraviolet curable inkjet ink composition according to any one of claims 1 to 3, wherein the (meth) acrylate having a fluorene skeleton is represented by the following general formula (II).

  The ultraviolet curable inkjet ink according to any one of claims 1 to 4, wherein the (meth) acrylate having a fluorene skeleton is contained in an amount of 0.5 to 35% by mass based on the total mass of the ink composition. Composition.   The ultraviolet curable inkjet ink composition according to any one of claims 1 to 5, further comprising 5-35% by mass of phenoxyethyl (meth) acrylate with respect to the total mass of the ink composition.   The said photoinitiator contains 7 mass% or more of an acyl phosphine oxide compound and 0.5 mass% or more of thioxanthone compounds with respect to the total mass of this ink composition. The ultraviolet curable ink composition for inkjet described. The ultraviolet curable ink jet according to any one of claims 1 to 7, which can be cured by irradiating ultraviolet rays having an emission peak wavelength in a range of 350 to 420 nm with an irradiation energy of 300 mJ / cm ² or less. Ink composition.   The ultraviolet curable inkjet ink composition according to any one of claims 1 to 8, which is curable in a thick film state having a thickness of 9 µm or more.