JP2013036020A - Photocurable ink composition for inkjet recording, and inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocurable ink composition for inkjet recording, which has superior curability.SOLUTION: The photocurable ink composition for inkjet recording contains a polymerizable compound and a photopolymerization initiator. The polymerizable compound contains vinyl ether group-containing (meth)acrylic acid esters represented by the following general formula (I): CH=CR-COOR-O-CH=CH-R(wherein Ris hydrogen atom or methyl group, Ris a divalent organic residue having a carbon number of 2-20, and Ris hydrogen atom or monovalent organic residue having a carbon number of 1-11), phenoxy ethyl (meth)acrylates, and a color material.

Description

  The present invention relates to a photocurable ink composition for ink jet recording and an ink jet recording method using the same.

  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 method is an inexpensive device, and ink is ejected only to a required image portion and an image is directly formed 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 ink jet recording methods, photocurable ink compositions that cure when irradiated with light have been used as ink compositions that can provide good water resistance, solvent resistance, and scratch resistance. .

  For example, Patent Document 1 and Patent Document 2 include 2- (vinyloxyethoxy) ethyl (meth) acrylate, at least one of 2- (hydroxyethoxy) ethyl vinyl ether and diethylene glycol divinyl ether, and diethylene glycol di (meth). Ink compositions and reactive diluent compositions containing an acrylate and a photopolymerization initiator are disclosed (Tables 1 to 0114 and 0139 in Patent Document 1, Examples and Tables in Patent Document 2) 1 and Table 4).

  For example, Patent Document 3 discloses 69.82 parts by weight of propoxylated neopentyl glycol diacrylate, 10.0 parts by weight of a bifunctional vinyl ether monomer (a compound having only a vinyl ether group as a substituent), a radical photoinitiator. And an ink-jet ink containing 3.60 parts by weight of a dispersible pigment and having a viscosity at 25 ° C. of 22 mPas is disclosed ([0021] and [0022] of Patent Document 3).

  For example, Patent Document 4 discloses 2- (2-vinyloxyethoxy) ethyl acrylate alone or 2- (2-vinyloxyethoxy) ethyl acrylate and isobornyl acrylate used together with this, and a radical polymerization initiator. And an ink liquid comprising a cationic polymerization initiator, a pigment, a dispersant, and a surfactant are disclosed ([0204] to [0207] of Patent Document 4).

  For example, Patent Document 5 discloses 25.8 wt% hexanediol diacrylate, 4.6 wt% tripropylene glycol diacrylate amine addition compound, 2.3 wt% 2- (2-ethoxyethoxy) ethyl. Acrylate, 2.5 wt% alkoxylated phenoxyethyl acrylate, 3.7 wt% 2-benzyl-2- (dimethylamino) -4'-morpholinobutyrophenone, 3.2 wt% 2-hydroxy-2-methyl Propiophenone, a mixture of 2.8 wt% trimethylbenzophenone and methylbenzophenone, 0.5 wt% isopropylthioxanthone, 27.8 wt% cyan pigment dispersion, and 17.6 wt% 2- (2- Radiation curable inkjet ink containing vinyloxyethoxy) ethyl acrylate opens It is (Patent Document 5 [0208], [0209]).

Japanese Patent No. 3461501 Japanese Patent No. 3544658 JP 2009-62541 A JP 2008-179136 A Special table 2008-507598

  However, any of the compositions and inks disclosed in Patent Documents 1 to 5 have room for improvement in terms of curability. Accordingly, an object of the present invention is to provide a photocurable ink composition for inkjet recording excellent in curability.

The present inventors have intensively studied to solve the above problems. First, the reason why the compositions and inks disclosed in each patent document have room for improvement in terms of curability was examined. Both the composition and the ink contain 2- (vinyloxyethoxy) ethyl (meth) acrylate as a polymerizable compound. Although this (meth) acrylic acid 2- (vinyloxyethoxy) ethyl has a function of improving curability, an ink using only (meth) acrylic acid 2- (vinyloxyethoxy) ethyl as a polymerizable compound is It has been found that the curability is not sufficient. In other words, it has been found that an ink using another compound in combination with 2- (vinyloxyethoxy) ethyl (meth) acrylate as a polymerizable compound may be excellent in curability.
Therefore, the present inventors examined such another type of compound. First, the ink composition and the reactive diluent composition disclosed in Patent Document 1 and Patent Document 2 each contain a compound having only a vinyl ether group and a compound having only a (meth) acrylate group. Although characterized, these compositions have been found to be inferior in curability.

  Moreover, as the said compound disclosed by patent document 3, the bifunctional vinyl ether monomer (compound which has only a vinyl ether group as a substituent) is mentioned. However, a compound having only a vinyl ether group as a substituent reduces the curing rate. Therefore, it has been found that the above-mentioned bifunctional vinyl ether monomer is not suitable as the above-mentioned different kind of compound.

  Moreover, isobornyl acrylate is mentioned as said another kind of compound disclosed by patent document 4. FIG. However, isobornyl acrylate also reduces the cure rate. Therefore, it has been found that the above isobornyl acrylate is not suitable as the above-mentioned different kind of compound.

  Moreover, alkoxylated phenoxyethyl acrylate is mentioned as said another kind of compound disclosed by patent document 5. FIG. However, since the alkoxylated phenoxyethyl acrylate has relatively high viscosity and relatively poor solubility, it can be said that the curing rate of the radiation curable inkjet ink containing the alkoxylated phenoxyethyl acrylate is sufficiently high. Absent. Therefore, it has been found that the above alkoxylated phenoxyethyl acrylate is not suitable as the above different kind of compound.

  Based on the above knowledge, as a result of repeated further studies by the present inventors, a polymerizable compound containing vinyl ether group-containing (meth) acrylic acid esters having a predetermined structure and phenoxyethyl (meth) acrylate, and photopolymerization The present invention has been completed by finding that the above-mentioned problems can be solved by a photocurable ink composition for inkjet recording containing an initiator.

That is, the present invention is as follows.
[1]
A photocurable inkjet recording ink composition comprising a polymerizable compound and a photopolymerization initiator, wherein the polymerizable compound is represented by the following general formula (I):
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (I)
Wherein R ¹ is a hydrogen atom or a methyl group, R ² is a divalent organic residue having 2 to 20 carbon atoms, and R ³ is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms. Group.)
A photocurable ink composition for inkjet recording, comprising a vinyl ether group-containing (meth) acrylic acid ester represented by the formula: phenoxyethyl (meth) acrylate, and a coloring material.

[2]
The photocurable ink jet recording ink composition according to [1], wherein the content of the phenoxyethyl (meth) acrylate is 9 to 60% by mass with respect to the total mass of the ink composition.

[3]
The photopolymerization initiator according to [1] or [2], wherein the photopolymerization initiator contains an acyl phosphine oxide compound in an amount of 7% by mass or more based on the total mass of the ink composition.

[4]
The photocurable initiator, the photocurable ink composition for ink jet recording according to [1] or [2], comprising 7 to 15% by mass of an acylphosphine oxide compound based on the total mass of the ink composition. .

[5]
The photopolymerization initiator includes the photocurable ink jet recording ink composition according to [1] or [2], wherein the photopolymerization initiator includes 10 to 15% by mass of an acylphosphine oxide compound based on a total mass of the ink composition. .

[6]
The photocurable inkjet recording ink composition according to any one of [1] to [5], wherein the vinyl ether group-containing (meth) acrylic acid ester is 2- (vinyloxyethoxy) ethyl (meth) acrylate. object.

[7]
Content of the said vinyl ether group containing (meth) acrylic acid ester is 10-60 mass% with respect to the gross mass of this ink composition, The photocurable type | mold in any one of [1]-[6] Ink composition for inkjet recording.

[8]
For photocurable ink jet recording according to any one of [1] to [7], wherein ultraviolet rays having an emission peak wavelength in the range of 350 to 420 nm are cured by irradiation with an irradiation energy of 300 mJ / cm ² or less. Ink composition.

[9]
[1] to [8] A photocurable ink jet recording ink composition ejected onto the recording medium, and a photocurable ink jet recording ink composition ejected by the ejecting process. And a curing step of curing the photocurable ink composition for inkjet recording by irradiating with ultraviolet rays.

  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, “curing” means that when an ink containing a polymerizable compound is irradiated with radiation, the polymerizable compound is polymerized and the ink is solidified. “Curable” refers to the property of curing in response to light. “Adhesion” refers to the property of the coating film being difficult to peel off from the substrate. “Abrasion resistance” refers to the property that when the cured product is scratched, the cured product is difficult to peel off from 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.

  In this specification, “recorded material” refers to a material in which ink is recorded on a recording medium to form a cured product. In addition, the hardened | cured material in this specification means the hardened | cured substance containing the cured film and coating film of an ink.

[Photocurable ink composition for inkjet recording]
The photocurable ink composition for ink jet recording according to an embodiment of the present invention (hereinafter also simply referred to as “ink composition”) contains a polymerizable compound and a photopolymerization initiator. And the said polymeric compound is the following general formula (I):
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (I)
Wherein R ¹ is a hydrogen atom or a methyl group, R ² is a divalent organic residue having 2 to 20 carbon atoms, and R ³ is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms. Group.)
The vinyl ether group containing (meth) acrylic acid ester represented by these, phenoxyethyl (meth) acrylate, and a coloring material are included.
Hereinafter, additives (components) that are or can be included in the ink composition of the present embodiment will be described.

(Polymerizable compound)
The polymerizable compound contained in the ink composition of the present embodiment can be polymerized at the time of ultraviolet irradiation by the action of a photopolymerization initiator described later, and the printed ink can be cured.

(Vinyl ether group-containing (meth) acrylic acid esters)
The vinyl ether group-containing (meth) acrylic acid ester, which is an essential polymerizable compound in the present embodiment, is represented by the general formula (I).

When the ink composition contains the above-mentioned vinyl ether group-containing (meth) acrylic acid esters in combination with phenoxyethyl (meth) acrylate described later, the viscosity of the ink can be reduced, and the curability and abrasion resistance can be reduced. , Adhesion, and solubility of the photopolymerization initiator can all be excellent. Here, the reason why the photopolymerization initiator is excellent in solubility is that the compatibility between the polymerizable compound and additives such as the photopolymerization initiator is improved.
Furthermore, rather than using a compound having a vinyl ether group and a compound having a (meth) acrylic acid ester group (a kind of radical polymerizable group) separately, the vinyl ether group and the (meth) acrylic acid ester group are contained in one molecule. It is preferable to use a compound having both of these in order to further improve the curability of the ink.

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

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

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

  Examples of the vinyl ether group-containing (meth) acrylic acid esters include, but are not limited to, for example, 2-vinyloxyethyl (meth) acrylate, 3-vinyloxypropyl (meth) acrylate, and 1-methyl (meth) acrylate. 2-vinyloxyethyl, 2-vinyloxypropyl (meth) acrylate, 4-vinyloxybutyl (meth) acrylate, 1-methyl-3-vinyloxypropyl (meth) acrylate, 1-vinyloxymethyl (meth) acrylate Propyl, 2-methyl-3-vinyloxypropyl (meth) acrylate, 1,1-dimethyl-2-vinyloxyethyl (meth) acrylate, 3-vinyloxybutyl (meth) acrylate, 1-methyl- (meth) acrylate 2-vinyloxypropyl, 2-vinyloxybutyl (meth) acrylate, (meth) a 4-vinyloxycyclohexyl silylate, 6-vinyloxyhexyl (meth) acrylate, 4-vinyloxymethylcyclohexylmethyl (meth) acrylate, 3-vinyloxymethylcyclohexylmethyl (meth) acrylate, (meth) acrylic acid 2-vinyloxymethylcyclohexylmethyl, p-vinyloxymethylphenylmethyl (meth) acrylate, m-vinyloxymethylphenylmethyl (meth) acrylate, o-vinyloxymethylphenylmethyl (meth) acrylate, (meth) 2- (vinyloxyethoxy) ethyl acrylate, 2- (vinyloxyisopropoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxy) propyl (meth) acrylate, 2- (vinyloxy) (meth) acrylate Ethoxy) isopropyl, (meth) acrylic acid 2- Vinyloxyisopropoxy) propyl, 2- (vinyloxyisopropoxy) isopropyl (meth) acrylate, 2- (vinyloxyethoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxyisopropoxy) (meth) acrylate ) Ethyl, 2- (vinyloxyisopropoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyisopropoxyisopropoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxyethoxy) propyl (meth) acrylate 2- (vinyloxyethoxyisopropoxy) propyl (meth) acrylate, 2- (vinyloxyisopropoxyethoxy) propyl (meth) acrylate, 2- (vinyloxyisopropoxyisopropoxy) propyl (meth) acrylate, (Meth) acrylic acid 2- (vinylo) Xylethoxyethoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyethoxyisopropoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyisopropoxyethoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyisopropoxy) Isopropoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyethoxyethoxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (vinyloxyethoxyethoxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (isopropenoxyethoxy) ) Ethyl, (meth) acrylic acid 2- (isopropenoxyethoxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (isopropenoxyethoxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (isopropenoxyethoxyethoxyethoxy) D ) Ethyl, and (meth) Polyethylene glycol monovinyl ether acrylate, and (meth) acrylic acid polypropylene glycol monovinyl ether.

  Among these, when used in combination with phenoxyethyl (meth) acrylate described later, the viscosity of the ink can be further reduced, the flash point is high, and the curability of the ink is further improved. Vinyloxyethoxy) ethyl, that is, at least one of 2- (vinyloxyethoxy) ethyl acrylate and 2- (vinyloxyethoxy) ethyl methacrylate is preferred, and 2- (vinyloxyethoxy) ethyl acrylate is more preferred . In particular, 2- (vinyloxyethoxy) ethyl acrylate and 2- (vinyloxyethoxy) ethyl methacrylate each have a simple structure and a small molecular weight, so that the viscosity of the ink can be further reduced. 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. Incidentally, 2- (vinyloxyethoxy) ethyl acrylate is superior in terms of curability compared to 2- (vinyloxyethoxy) ethyl methacrylate.

  A vinyl ether group containing (meth) acrylic acid ester may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the vinyl ether group-containing (meth) acrylic acid esters is preferably 10 to 60% by mass in order to further improve curability with respect to the total mass (100% by mass) of the ink composition. In addition to curability, the abrasion resistance and adhesion are further improved, so that the content is more preferably 10 to 30% by mass, and further preferably 20 to 30% by mass. On the other hand, when the ink composition is particularly excellent in curability, it is more preferably 20 to 60% by mass, and further preferably 30 to 60% by mass.

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

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

(Phenoxyethyl (meth) acrylate)
The ink composition of this embodiment contains phenoxyethyl (meth) acrylate as a polymerizable compound. When the ink composition contains a phenoxyethyl (meth) acrylate as a polymerizable compound in addition to the vinyl ether group-containing (meth) acrylic acid ester, the viscosity of the ink can be reduced and curability is increased. In addition, the rub resistance, adhesion, and solubility of the photopolymerization initiator can all be excellent.

  The content of phenoxyethyl (meth) acrylate is preferably 9 to 60% by mass and more preferably 10 to 50% by mass in order to further improve the curability with respect to the total mass (100% by mass) of the ink composition. % Is more preferable, and 10 to 40% by mass is even more preferable. When the content is not less than the above lower limit (especially 10% by mass), the solubility of the photopolymerization initiator is further improved in addition to the curability. On the other hand, when the content is not more than the above upper limit (particularly 50% by mass), in addition to curability, the adhesion is further improved.

(Monofunctional (meth) acrylate)
The ink composition of this embodiment may further contain monofunctional (meth) acrylate (excluding phenoxyethyl (meth) acrylate) as a polymerizable compound. Examples of the monofunctional (meth) acrylate include, but are not limited to, isoamyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, and isomyristyl. (Meth) acrylate, isostearyl (meth) acrylate, 2-ethylhexyl-diglycol (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (Meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate , Tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, lactone-modified flexible (Meth) acrylate, t-butylcyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, benzyl (meth) acrylate, ethoxylated nonylphenyl (meth) acrylate, alkoxy Nonylphenyl (meth) acrylate, and p-cumylphenol EO-modified (meth) acrylate.

  The said monofunctional (meth) acrylate may be used individually by 1 type, and may be used in combination of 2 or more type.

  The monofunctional (meth) acrylate may be contained in the ink composition as long as the desired effects of the present embodiment are not impaired. The content of the monofunctional (meth) acrylate is preferably 50% by mass or less with respect to the total mass (100% by mass) of the ink composition.

(Multifunctional (meth) acrylate)
The ink composition of this embodiment may further contain polyfunctional (meth) acrylate as a polymerizable compound. Among the polyfunctional (meth) acrylates, bifunctional (meth) acrylates (excluding the above-mentioned predetermined vinyl ether group-containing (meth) acrylic acid esters) are not limited to the following, for example, triethylene glycol Di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, 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 trisi Rhodecane di (meth) acrylate, EO (ethylene oxide) adduct di (meth) acrylate of bisphenol A, PO (propylene oxide) adduct di (meth) acrylate of bisphenol A, neopentyl glycol di (meth) acrylate hydroxypivalate, And polytetramethylene glycol di (meth) acrylate. Among these, at least one of dipropylene glycol diacrylate and tripropylene glycol diacrylate is preferable because of its fast curability and easy viscosity reduction of the ink.

  Among polyfunctional (meth) acrylates, trifunctional or higher (meth) acrylates are not limited to the following, but include, for example, trimethylolpropane tri (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, pentaerythritol. Tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, glycerin propoxytri (meth) acrylate, cowprolactone modified trimethylolpropane tri (meth) ) Acrylate, pentaerythritol ethoxytetra (meth) acrylate, and caprolactam-modified dipentaerythritol hexa (meth) acrylate.

  A polyfunctional (meth) acrylate may be used individually by 1 type, and may be used in combination of 2 or more type.

The polyfunctional (meth) acrylate may be contained in the ink composition as long as the desired effect of the present embodiment is not impaired. The content of the polyfunctional (meth) acrylate is preferably 40% by mass or less with respect to the total mass (100% by mass) of the ink composition.
When the content of the polyfunctional (meth) acrylate is within the above range, it is possible to prevent the viscosity of the ink from being increased and to ensure good flexibility of the recorded matter.

(Polymerizable compounds other than the above)
In addition to the above-mentioned vinyl ether group-containing (meth) acrylic acid esters, monofunctional (meth) acrylates, and polyfunctional (meth) acrylates, various conventionally known monofunctional and polyfunctional monomers and oligomers are also used. It is possible (hereinafter referred to as “other polymerizable compounds”). Examples of the monomer include unsaturated carboxylic acids such as itaconic acid, crotonic acid, isocrotonic acid and maleic acid, salts or esters thereof, urethanes, amides and anhydrides thereof, acrylonitrile, styrene, various unsaturated polyesters, unsaturated monomers. Examples include saturated polyethers, unsaturated polyamides, and unsaturated urethanes. Moreover, as said oligomer, the oligomer formed from said monomer is mentioned, for example.

  Another polymeric compound may be used individually by 1 type, and may be used in combination of 2 or more type.

  Other polymerizable compounds may be contained in the ink composition as long as the desired effects of the present embodiment are not impaired. The content of the other polymerizable compound is preferably 10% by mass or less with respect to the total mass (100% by mass) of the ink composition.

(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, 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 it is possible to further improve the curability of the ink, it is preferable to use at least one of an acyl phosphine oxide compound and a thioxanthone compound, and it is more preferable to use an acyl phosphine oxide compound. More preferably, an acylphosphine oxide compound and a thioxanthone compound are used in combination.

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

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

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

  The content of the photopolymerization initiator can improve the ultraviolet curing rate and have excellent curability, and in order to avoid undissolved photopolymerization initiator and coloring derived from the photopolymerization initiator, The content is preferably 8 to 20% by mass with respect to the total mass (100% by mass) of the ink composition.

  In particular, when the photopolymerization initiator includes an acylphosphine oxide compound, the content thereof is preferably 7% by mass or more, and 7 to 15% by mass with respect to the total mass (100% by mass) of the ink composition. % Is more preferable, 10 to 15% by mass is particularly preferable, and 10 to 14% by mass is further preferable. When the content is not less than the above lower limit (particularly 10% by mass), the curability is further improved. More specifically, the curability is further improved because a sufficient curing speed can be obtained particularly when curing with an LED (preferable emission peak wavelength: 350 nm to 420 nm). On the other hand, when the content is not more than the above upper limit (particularly 14% by mass), the solubility of the photopolymerization initiator is further improved.

  Further, when the content of the acyl phosphine oxide compound is in the above range, the acyl phosphine oxide compound is preferably 4% by mass or more, more preferably based on the total mass (100% by mass) of the ink composition. May contain 6% by mass or more of a bisacylphosphine oxide compound. When the bisacylphosphine oxide compound is contained in the lower limit (especially 6% by mass) or more, the curability is further improved. Furthermore, since the upper limit of the content of the bisacylphosphine oxide compound is further excellent in initiator solubility, it is preferably 10% by mass or less with respect to the total mass (100% by mass) of the ink composition. It is more preferable that it is 8 mass% or less.

  Moreover, when content of an acyl phosphine oxide compound is said range, the said acyl phosphine oxide compound is preferably 53 mass% or more with respect to the total mass (100 mass%) of the acyl phosphine oxide compound. More preferably, 55 mass% or more of bisacylphosphine oxide compounds may be included. When the bisacylphosphine oxide compound is contained in the lower limit (especially 55% by mass) or more, the curability is further improved. Furthermore, since the upper limit of the content of the bisacylphosphine oxide compound is more excellent in initiator solubility, it is 90% by mass or less based on the total mass (100% by mass) of the acylphosphine oxide compound. Preferably, it is 80 mass% or less.

  Examples of the bisacylphosphine oxide compound include, but are not limited to, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis- (2,6-dimethoxybenzoyl) -2,4, 4-trimethylpentylphosphine oxide is mentioned. On the other hand, examples of the acylphosphine oxide compound other than the bisacylphosphine oxide compound include, but are not limited to, a monoacylphosphine oxide compound. Examples of the monoacylphosphine oxide compound include, but are not limited to, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide.

  If the content of the phenoxyethyl (meth) acrylate is within the above-mentioned preferable range, the solubility of the acylphosphine oxide compound is further improved. Therefore, the content of the acylphosphine oxide compound is set to the above-mentioned preferable range. can do. Thus, there is a correlation between the content of phenoxyethyl (meth) acrylate and the content of the acylphosphine oxide compound.

  Moreover, when a photoinitiator contains a thioxanthone compound, it is preferable that the content is 1-5 mass% with respect to the total mass (100 mass%) of an ink composition.

[Color material]
The ink composition of the present embodiment further includes a color material. As the color material, at least one of a pigment and a dye can be used. A pigment is preferable in terms of excellent light resistance.

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

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

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

  More specifically, as carbon black used as black ink, No. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, no. 2200B and the like (trade names manufactured by Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700 and the like (trade names manufactured by Columbia Columbia) , Rega 1 400R, Rega 1 330R, Rega 1 660R, Mogul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch K 1400, etc. Name), Color Black FW1, Color Black FW2, Color Black FW2V, Colo Black FW18, Color Black FW200, Color B1ack S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Beck Degussa brand name).

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

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

  Examples of pigments used in magenta ink include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 88, 112, 114, 122, 123, 144, 146, 149, 150, 166, 168 170, 171, 175, 176, 177, 178, 179, 184, 185, 187, 202, 209, 219, 224, 245, 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, 15, 15: 1, 15: 2, 15: 3, 15:34, 15: 4, 16, 18, 22, 25, 60, 65, 66, or C.I. I. Bat Blue 4,60.

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

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

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

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

  The content of the color material has a good color developability and can reduce the inhibition of curing of the coating film due to light absorption of the color material itself. Mass% is preferred. The photocurable ink composition containing a color material has poor curability and inferior adhesion and scratch resistance of a recorded product as compared with an ink composition containing no color material, but the photocurable ink of this embodiment If it is a composition, it can be set as the ink composition which is excellent in sclerosis | hardenability, adhesiveness, and abrasion resistance, and can be used for image recording.

[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 (trade name), Solsperse series available from Avecia Co. (Solsperse 32000, 36000, etc. [above, trade name]) , BYK Chemie's Disperbic series (trade name) and Enomoto Kasei's Disparon series (trade name).

  A dispersing agent may be used individually by 1 type, and may be used in combination of 2 or more type. The content of the dispersant is not particularly limited, and a preferable amount may be added as appropriate.

(Polymerization inhibitor)
The ink composition of this embodiment may further contain a polymerization inhibitor. When the ink composition contains a polymerization inhibitor, the polymerization reaction of the polymerizable compound before curing can be prevented.

  Although it does not restrict | limit especially as a polymerization inhibitor, For example, a phenol type polymerization inhibitor is mentioned. Examples of the phenol-based polymerization inhibitor include, but are not limited to, for example, p-methoxyphenol, cresol, t-butylcatechol, di-t-butylparacresol, hydroquinone monomethyl ether, α-naphthol, 3,5-di- t-butyl-4-hydroxytoluene, 2,6-di-t-butyl-4-methylphenol, 2,2'-methylene-bis (4-methyl-6-t-butylphenol), 2,2'-methylene -Bis (4-ethyl-6-butylphenol) and 4,4'-thio-bis (3-methyl-6-tert-butylphenol).

  Examples of commercially available phenolic polymerization inhibitors include p-methoxyphenol (trade name, p-methoxyphenol, manufactured by Tokyo Chemical Industry Co., Ltd.), non-flex MBP (Seiko Chemical Co., Ltd. ( Seiko Chemical Co., Ltd., trade name, 2,2′-methylene-bis (4-methyl-6-tert-butylphenol)), BHT Swanox (trade name, 2,6-di-t, manufactured by Seiko Chemical Co., Ltd.) -Butyl-4-methylphenol).

  A polymerization inhibitor may be used individually by 1 type, and may be used in combination of 2 or more type. The content of the polymerization inhibitor is not particularly limited, and a preferable amount may be added as appropriate.

[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, as the silicone surfactant, polyester-modified silicone or polyether-modified silicone can be used, and polyether-modified polydimethylsiloxane or polyester-modified polydimethylsiloxane is particularly used. preferable. Examples of commercially available slip agents include BYK-347, BYK-348, BYK-UV3500, 3510, 3530, and 3570 (manufactured by BYK).
A slip agent may be used individually by 1 type, and may be used in combination of 2 or more type. The content of the slip agent is not particularly limited, and a preferable amount may be added as appropriate.

[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.

[Characteristics of Photocurable Inkjet Recording Ink Composition]
The viscosity at 25 ° C. of the ink composition is preferably less than 35 mPa · s, and preferably 25 mPa · s or less, in order to improve the ink ejection stability and to further improve the ink curability. More preferred.

  The ink composition is preferably cured by irradiation with ultraviolet rays having an emission peak wavelength in the range of 350 to 420 nm. When the ink composition of the present embodiment can be cured at the emission peak wavelength within the above range, it can be cured at a low energy and at a high speed due to the composition of the ink composition. In particular, it is preferable to be able to cure with low energy because a light emitting diode (LED) which has been attracting attention in recent years from the environmental viewpoint can be used as an ultraviolet irradiation source. That is, the ink composition of this embodiment is excellent in curability by the LED.

Further, an ink composition that cures with an irradiation energy of ultraviolet rays of 300 mJ / cm ² or less is preferable, and an ink composition that cures with an irradiation energy of ultraviolet rays of 200 mJ / cm ² or less is more preferable. By using such an ink composition, an image can be formed at low cost. The irradiation energy is calculated by multiplying the irradiation time by the irradiation intensity.

  As described above, according to the present embodiment, light having excellent curability, low viscosity, excellent image (cured product) adhesion and abrasion resistance, and photopolymerization initiator solubility. A curable ink composition for inkjet recording can be provided.

[Recording medium]
The 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 embodiment described below is widely used for recording media having various absorption performances from non-absorbing recording media in which water-based ink penetration is difficult to absorbent recording media in which water-based ink penetration is easy. Applicable. However, when the above 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, sheets and plates of plastics such as polyvinyl chloride (PVC), polyethylene, polypropylene, polyethylene terephthalate (PET), iron, silver, copper, Examples thereof include a metal plate such as aluminum, 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]
One embodiment of the present invention relates to an inkjet recording method. The photocurable ink composition for ink jet recording of the above embodiment can be suitably used for the ink jet recording method of the present embodiment. 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, an image, that is, an ink coating film (cured film) is formed by the ink composition cured on the recording medium. Another embodiment of the present invention is a photocurable ink jet recording ink composition which is the above-described embodiment of the present invention used in the ink jet recording method according to an embodiment of the present invention. Here, the photocurable ink composition for ink jet recording which is an embodiment of the present invention used in the ink jet recording method which is an embodiment of the present invention performs recording by the ink jet recording method which is an embodiment of the present invention. It means a photocurable ink jet recording ink composition which is an embodiment of the present invention sold for a recording apparatus.

[Discharge process]
In the ejection step, the ink composition is ejected onto the recording medium, and the ink composition adheres to the recording medium. The viscosity of the ink composition during ejection is preferably 3 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. In that case, it is preferable that the temperature of the ink at the time of discharge is 20-30 degreeC. 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 photocurable ink composition for ink jet recording of the present embodiment has a higher viscosity than a normal aqueous ink composition, the viscosity fluctuation due to temperature fluctuation at the time of ejection is large. Such a variation in the viscosity of the ink has a great influence on the change in the droplet size and the change in the droplet ejection speed, and can cause image quality degradation. 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 and adhered onto the recording medium is cured by irradiation with light (ultraviolet rays). 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 polymerizable compound depends on the function of the starting species. It is to be promoted. Or it is because the polymerization reaction of a polymeric 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 photocurable ink compositions for inkjet recording. Yes. 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, ultraviolet light-emitting diodes (UV-LEDs) and ultraviolet laser diodes (UV-LDs) are small, have a long life, have high efficiency, and are low in cost, and are expected as light sources for photo-curable ink jets. Among these, UV-LED is preferable.

Here, since it is easy to increase the output of the LED, it is preferable to use a UV-LED whose emission peak wavelength is preferably in the range of 350 to 420 nm, and is preferably a photocurable inkjet recording that can be cured with an irradiation energy of 300 mJ / cm ² or less. It is preferable to use the ink composition for ink jet recording. In this case, low cost printing and high printing speed can be realized. Such an ink composition can be obtained by including at least one of a photopolymerization initiator that decomposes upon irradiation with ultraviolet rays in the wavelength range and a polymerizable compound that starts polymerization upon irradiation with ultraviolet rays in the wavelength range.
Moreover, as LED irradiation intensity | strength, it is preferable to harden | cure using UV-LED with a peak intensity of 800 mW / cm < ² > or more, and it is more preferable that it is a peak intensity of 800-2000 mW / cm < ² >. In this case, the curability of the ink composition can be further improved, and the appearance of the recorded matter can be improved.

  As described above, according to the present embodiment, the photocuring is excellent in curability, and further has low viscosity, and is excellent in the adhesion and abrasion resistance of the image (cured product) and the solubility of the photopolymerization initiator. A suitable inkjet recording method using the ink composition for type inkjet recording can be provided.

  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.

[Use ingredients]
The components used in the following examples and comparative examples are as follows.

[Pigment]
IRGALITE BLUE GLVO (Cyan pigment (CI Pigment Blue 15: 4), trade name manufactured by BASF, hereinafter abbreviated as “BLUE GLVO”)

[Dispersant]
Solsperse 32000 (trade name manufactured by LUBRIZOL, abbreviated as “SOL32000” below)

[Vinyl ether group-containing (meth) acrylic acid esters]
VEEA (2- (2-vinyloxyethoxy) ethyl acrylate, trade name of Nippon Shokubai Co., Ltd., hereinafter abbreviated as “VEEA”)
In the table, vinyl ether group-containing (meth) acrylic acid esters are described as “acrylic / vinyl-containing monomers”.

[Monofunctional (meth) acrylate]
Biscoat # 192 (phenoxyethyl acrylate, trade name of OSAKA ORGANIC CHEMICAL INDUSTRY LTD., Hereinafter abbreviated as “PEA”)
IBXA (Isobornyl acrylate, trade name of Osaka Organic Chemical Co., Ltd., hereinafter abbreviated as “IBXA”)

[Multifunctional (meth) acrylate]
-NK ester APG-100 (dipropylene glycol diacrylate, trade name of SHIN-NAKAMURA CHEMICAL CO., LTD., Hereinafter abbreviated as "DPGDA")
NK ester APG-200 (Tripropylene glycol diacrylate, trade name of Shin-Nakamura Chemical Co., Ltd., hereinafter abbreviated as “TPGDA”)

(Photopolymerization initiator)
IRGACURE 819 (trade name, manufactured by BASF, solid content: 100%, hereinafter abbreviated as “819”)
Speedcure TPO (trade name, manufactured by Lambson, solid content: 100%, hereinafter abbreviated as “TPO”)
Speedcure DETX (trade name, manufactured by Lambson, solid content: 100%, hereinafter abbreviated as “DETX”)

(Polymerization inhibitor)
P-methoxyphenol (trade name, p-methoxyphenol, manufactured by Tokyo Chemical Industry Co., Ltd., abbreviated as “MEHQ” below)

[Slip agent]
BYK-UV3500 (trade name manufactured by BYK, abbreviated as “UV3500” below)

[Examples 1 to 16, Comparative Examples 1 to 6]
(Preparation of pigment dispersion)
Prior to the preparation of the ink composition, a pigment dispersion was prepared. The pigment, the dispersant, and the polymerizable compound described in the “dispersion-derived monomer” column in Tables 1 and 2 below are mixed so as to have the composition (unit: mass%) described in Tables 1 and 2 below. Stir 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 Table 1 and Table 2 below were added and mixed so as to have the composition (unit: mass%) described in Table 1 and Table 2 (in Tables 1 and 2, the pigment, the dispersant, The polymerizable compound described in the “Liquid-derived monomer” column was added as the above-mentioned pigment dispersion.) By stirring this with a high-speed water-cooled stirrer, a cyan photocurable ink composition for inkjet recording was prepared. did.

[Evaluation item]
About the photocurable ink composition for inkjet recording prepared in each Example and each comparative example, the viscosity, the solubility of a photoinitiator, sclerosis | hardenability, adhesiveness, and abrasion resistance were evaluated with the following method.

(1. Viscosity)
The viscosity of the ink composition of each example and each comparative example was measured using a DVM-E type rotational viscometer (manufactured by TOKYO KEIKI INC) under the conditions of a temperature of 25 ° C. and a rotational speed of 10 rpm. . The evaluation criteria are as follows. The evaluation results are shown in Tables 3 and 4 below.
A: 25 mPa · s or less,
B: More than 25 mPa · s and less than 35 mPa · s,
C: 35 mPa · s or more.

(2. Solubility of photopolymerization initiator)
Using components other than the pigment and the pigment dispersant, an ink composition without pigment was prepared in the same manner as in the above Examples and Comparative Examples, and each ink composition was prepared by sufficiently stirring. Thereafter, it was visually observed whether or not the photopolymerization initiator remained undissolved. Then, the ink composition having no undissolved photopolymerization initiator is put in a thermostatic bath at 0 ° C., taken out after 24 hours and returned to room temperature, and then visually checked again whether the photopolymerization initiator is precipitated. Observed.
The evaluation criteria are as follows. The evaluation results are shown in Tables 3 and 4 below. In addition, this evaluation name in Table 3 and Table 4 was abbreviated as "initiator solubility".
A: After stirring at room temperature and after storage at 0 ° C., no undissolved residue or precipitation of the photopolymerization initiator was observed.
B: Although there was no undissolved residue of the photopolymerization initiator after stirring at room temperature, precipitation of the photopolymerization initiator was observed after storage at 0 ° C.
C: The undissolved residue of the photopolymerization initiator was observed after stirring at room temperature.

(3. Curability)
Using an ink jet recording apparatus provided with a piezo ink jet nozzle, each nozzle row was filled with the ink composition of each example and each comparative example. A solid pattern image (printed material) having a thickness of 10 μm on a PVC sheet (Frontlite Glossy 120 g [trade name], manufactured by Cooley) at room temperature and normal pressure while adjusting the ink discharge amount. A recording resolution of 720 × 720 dpi) was printed. At this time, the dischargeability of each ink composition was good. In addition, the UV-LED in the UV irradiation device mounted on the side of the carriage is irradiated with UV light having an irradiation intensity of 1 W / cm ² and a peak wavelength of 395 nm at an irradiation condition of 100 mJ / cm ² per pass. The solid pattern image was cured by adding the number of passes until tack-free. As described above, a recorded matter in which a solid pattern image was printed on a PVC sheet was produced.
Note that the “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 “number of passes” means the number of times the head moves relative to the recorded matter and the coating film is irradiated with ultraviolet rays from the ultraviolet irradiation device mounted on the head. The irradiation energy [mJ / cm ² ] was obtained from the product of the irradiation intensity [mW / cm ² ] on the irradiated surface irradiated from the light source and the irradiation duration [s]. The irradiation intensity was measured using an ultraviolet intensity meter UM-10 and a light receiving unit UM-400 (both manufactured by KONICA MINOLTA SENSING, INC.).
Here, the curability relating to the coating film was evaluated using the irradiation energy at the time of tack-free as an index. Here, whether or not it can be said to be tack-free was determined under the following conditions. That is, it is determined whether ink adheres to the swab or whether the ink cured product on the recording medium is scratched. The ink does not adhere to the cotton swab and the ink cured product on the recording medium The case where no scratches were made was considered tack-free. 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.
The evaluation criteria are as follows. The evaluation results are shown in Tables 3 and 4 below.
A: 200 mJ / cm ² or less,
B: More than 200 mJ / cm ^{2 and} 300 mJ / cm ² or less,
C: More than 300 mJ / cm ² .

(4. Adhesiveness)
In the above-mentioned “3. Curability” test, a recorded material that was cured by irradiation with ultraviolet rays until tack-free was used. 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)) Cross-cut was performed, and the adhesion was evaluated based on the following ranks A to E from the results of the peel test using a cellophane tape. 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. Each rank value is obtained by rounding off the first decimal place of the value obtained by calculating the peeling rate. The evaluation results are shown in Tables 3 and 4 below.
A: Hagarage rate 0-5%,
B: Hagaret rate 6-15%,
C: Hagarage rate 16-35%,
D: Hagaret rate 36-65%,
E: Haggare rate 66-100%.

(5. Abrasion resistance)
In accordance with JIS K5701 (ISO 11628) (specifying methods for testing inks, color developed samples, and printed materials used for lithographic printing), the Gakushin friction fastness tester (TESTER SANGYO CO., LTD.) Was used to evaluate the abrasion resistance. The evaluation method is that the surface of the recorded material obtained in the “3. Curability” test is placed with a gold width, rubbed under a load of 500 g, and the cured surface of the recorded material is peeled off visually. Compared.
The evaluation criteria are as follows. The evaluation results are shown in Tables 3 and 4 below.
A: There is no dirt on the gold width, and there is no peeling or scratching of the recording surface.
B: The gold width is dirty, and the recording surface is not peeled or scratched.
C: The gold band was dirty, and the recording surface was slightly peeled or scratched in a linear shape.
D: The gold width was dirty, and the recording surface was largely peeled or scratched on the surface.

From the above results, photocuring containing a polymerizable compound containing a vinyl ether group-containing (meth) acrylic acid ester represented by the above general formula (I) and phenoxyethyl (meth) acrylate, and a photopolymerization initiator. Type ink-jet recording ink compositions (each example) are superior in curability and lower in viscosity than other ink compositions (each comparative example), and are soluble in photopolymerization initiators. It was also found that the adhesiveness and the abrasion resistance were also excellent. Comparative Examples 5 and 6 are ink compositions obtained by removing the coloring material and the dispersing material from the ink compositions of Comparative Examples 2 and 4, respectively. However, the curability is good, and Comparative Examples 2 and 4 and In comparison, the adhesion and abrasion resistance were improved, but the ink composition did not contain a coloring material and could not be used for image recording. Furthermore, although not described in the table, the irradiation energy per pass was made the same as that in the above example by setting the irradiation intensity of the UV-LED to 500 mW / cm ² and increasing the irradiation time per pass. The curability was evaluated under the same conditions as in Example 1 except that the curability was evaluated as B, and wrinkles were observed on the surface of the solid pattern.

Claims (9)

A photocurable inkjet recording ink composition comprising a polymerizable compound and a photopolymerization initiator,
The polymerizable compound 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.)
A vinyl ether group-containing (meth) acrylic acid ester represented by:
A photocurable inkjet recording ink composition comprising phenoxyethyl (meth) acrylate and a coloring material.   2. The photocurable ink composition for ink jet recording according to claim 1, wherein the content of the phenoxyethyl (meth) acrylate is 9 to 60% by mass with respect to the total mass of the ink composition.   3. The photocurable ink composition for ink jet recording according to claim 1, wherein the photopolymerization initiator contains 7% by mass or more of an acyl phosphine oxide compound based on the total mass of the ink composition.   3. The photocurable ink composition for ink jet recording according to claim 1, wherein the photopolymerization initiator contains 7 to 15% by mass of an acylphosphine oxide compound based on the total mass of the ink composition.   3. The photocurable ink composition for ink jet recording according to claim 1, wherein the photopolymerization initiator includes 10 to 15% by mass of an acyl phosphine oxide compound based on a total mass of the ink composition.   The photocurable inkjet recording ink composition according to any one of claims 1 to 5, wherein the vinyl ether group-containing (meth) acrylic acid ester is 2- (vinyloxyethoxy) ethyl (meth) acrylate. object.   The content of the said vinyl ether group containing (meth) acrylic acid ester is 10-60 mass% with respect to the total mass of this ink composition, The photocurable type of any one of Claims 1-6. Ink composition for inkjet recording. The photocurable ink jet recording according to any one of claims 1 to 7, wherein the ultraviolet ray having an emission peak wavelength in a range of 350 to 420 nm is cured by irradiation with an irradiation energy of 300 mJ / cm ² or less. Ink composition. A discharge step of discharging the photocurable ink jet recording ink composition according to any one of claims 1 to 8 onto a recording medium;
A curing step of curing the photocurable ink jet recording ink composition by irradiating the photocurable ink jet recording ink composition ejected in the ejection step with ultraviolet rays.