JP2009067963A - Ink composition for ink-jet recording, and ink-jet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition for ink-jet recording, which has high sensitivity to the irradiation of active radiations, can form images excellent in curability, gives cured images having high adhesiveness to recording media, and has excellent discharging stability, when applied to ink-jet devices, and to provide an ink-jet recording method using the ink composition. <P>SOLUTION: Provided is the ink composition for the ink-jet recording, characterized by comprising (A) a compound represented by general formula (I) (wherein, R<SP>1</SP>and R<SP>2</SP>are each independently H or an alkyl group), (B) a radically polymerizable compound, and (C) a radical polymerization initiator. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink composition used for inkjet recording, and an inkjet recording method using the ink composition.

As an image recording method for forming an image on a recording medium such as paper based on an image data signal, there are an electrophotographic method, a sublimation type and a melt type thermal transfer method, an ink jet method and the like. The electrophotographic system requires a process of forming an electrostatic latent image on a photosensitive drum by charging and exposure, and there is a problem that the system becomes complicated and consequently the manufacturing cost becomes high. In addition, although the thermal transfer system is inexpensive, there are problems such as high running costs and waste materials due to the use of ink ribbons.
On the other hand, the ink jet system is an inexpensive apparatus and ejects ink 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. Further, the ink jet method has less noise and is excellent as an image recording method.

  As an ink composition (radiation curable ink composition) that can be used for ink jet recording ink compositions and can be cured by irradiation with actinic radiation such as ultraviolet rays, it can be cured with high sensitivity to form a high-quality image. Is required.

  By achieving high sensitivity of the radiation curable ink composition, high curability can be obtained by irradiation with actinic radiation, which reduces power consumption and extends the life of equipment by reducing the load on the actinic radiation generator. In addition to the advantages, it also has various advantages such as suppression of volatilization of uncured low-molecular substances and suppression of a decrease in formed image strength. Further, the improvement of the cured film strength by increasing the sensitivity of the radiation curable ink composition brings high strength and durability to the image area formed by this ink composition.

  As an ultraviolet curable ink composition, for example, an ink composition that uses a combination of monomers having different functional groups among monofunctional monomers or polyfunctional monomers has been proposed (for example, see Patent Document 1). . Moreover, the composition containing polyfunctional acrylate is proposed as a radiation-curable composition (for example, refer patent document 2). Although these ink compositions are excellent in curing speed and can form images without bleeding, since polyfunctional acrylate is used as the main component of the curable composition, the problem that flexibility after curing decreases, There has been a problem that the adhesiveness (adhesion) with the recording medium is reduced due to volume shrinkage during curing.

  In addition, regarding the adhesiveness to the recording medium in the ultraviolet curable ink composition, a radiation curable inkjet using N-vinyl lactam as a component for promoting the adhesiveness to the recording medium and the flexibility after curing. An ink composition is disclosed (for example, see Patent Document 3). However, N-vinyl lactams typified by N-vinylcaprolactam are sticky to the image surface after curing due to low copolymerization with general-purpose radically polymerizable monomers such as acrylate. In some cases, leaching of molecular components may be a problem, and when N-vinyl lactams are added alone, the storage stability of the ink may be lowered.

As described above, there is a demand for an ink composition having excellent ejection stability when used in an inkjet apparatus while maintaining excellent curing sensitivity and image strength while being excellent in adhesiveness with a recording medium. The current situation is that it has not been provided yet.
Japanese Patent Laid-Open No. 5-214280 JP-A-8-41133 JP-T-2004-514014

An object of the present invention is to form an image with high sensitivity to irradiation with actinic radiation and excellent curability, and the image after curing has high adhesiveness with a recording medium and is used in an ink jet apparatus. Another object of the present invention is to provide an ink composition for ink jet recording having excellent ejection stability.
Furthermore, it is providing the inkjet recording method using this ink composition.

  As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by using a specific sulfur-containing compound in the ink composition, and completing the ink composition for inkjet recording of the present invention. It came.

That is, the present invention is as follows.
<1> (A) a compound represented by the following general formula (I), (B) a radical polymerizable compound,
(C) A radical polymerization initiator, and an ink composition for ink jet recording.

In general formula (I), R ¹ and R ² each independently represent a hydrogen atom or an alkyl group.

  <2> The ink composition for ink jet recording according to <1>, wherein the (B) radical polymerizable compound is a compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule.

<3> (i-1) a step of discharging the ink composition for inkjet recording according to <1> or <2> onto a recording medium; and
(I-2) a step of irradiating the discharged ink composition for inkjet recording with active radiation to cure the ink composition;
An ink jet recording method comprising:

  According to the present invention, an image having high sensitivity to irradiation with actinic radiation and excellent curability can be formed, and the image after curing has high adhesiveness with a recording medium and is used in an ink jet apparatus. It is possible to provide an ink composition for ink jet recording excellent in ejection stability at the time. Furthermore, an ink jet recording method using the ink composition can be provided.

[Ink composition for inkjet recording]
The ink composition for ink jet recording of the present invention (hereinafter sometimes simply referred to as “ink composition”) includes (A) a compound represented by the general formula (I) and (B) a radically polymerizable compound. And (C) a radical polymerization initiator.
Hereinafter, components essential to the ink composition for ink jet recording of the present invention will be described.

<(A) Compound represented by Formula (I)>
The ink composition for ink-jet recording of the present invention contains (A) a compound represented by the following general formula (I) [hereinafter, appropriately referred to as (A) a specific sulfur-containing compound] in the composition. Features.
As the specific sulfur-containing compound (A) that can be used in the present invention, any compound represented by the following general formula (I) can be used.

In the formula, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group, and from the viewpoint of solubility in the ink composition, it is preferable that either R ¹ or R ² is an alkyl group, More preferably, both R ¹ and R ² are alkyl groups. Moreover, it is more preferable that R ¹ and R ² are the same alkyl group from the viewpoint of production suitability and availability.

  Examples of the alkyl group include linear, branched, and cyclic alkyl groups. From the viewpoints of viscosity of the ink composition, solubility in the ink composition, availability, and the like, linear and branched alkyl groups are included. Group is more preferable, and a linear alkyl group is still more preferable.

  The alkyl group is preferably an alkyl group having about 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 18 carbon atoms, and still more preferably an alkyl group having about 8 to 14 carbon atoms. Specifically, for example, a methyl group, an ethyl group, a 2-ethylhexyl group, a dodecyl group, a tridecyl group, a tetradecyl group, and an octadecyl group are preferable.

The alkyl group may further have a substituent, and preferred substituents include an aryl group, a hydroxyl group, and a halogen atom.
Specifically, for example, an unsubstituted or substituted alkyl group having 8 to 18 carbon atoms is preferably an alkyl group having a substituent such as a hydroxyl group or an aryl group. When the substituent is used, the aryl group may further have a substituent such as an alkyl group or a hydroxyl group.

  Specific examples of the specific sulfur-containing compound (A) are listed below, but the present invention is not limited thereto.

  Among these, (A-4), (A-6) and (A-8) are preferable, and (A-6) is more preferable.

The content of the specific sulfur-containing compound (A) in the ink composition of the present invention is in the range of 0.01 to 3% by mass in the total solid content of the ink composition from the viewpoint of curing speed and ink jet suitability of the ink composition. It is preferable that the range is 0.1 to 2% by mass, and more preferably 0.1 to 1.5% by mass.
Moreover, (A) specific sulfur-containing compound may be used by 1 type, and may use 2 or more types.

<(B) Radical polymerizable compound>
The ink composition of the present invention contains (B) a radical polymerizable compound.
The radical polymerizable compound applicable to the present invention will be described.
The radical polymerizable compound is a compound having an ethylenically unsaturated bond capable of radical polymerization, and may be any compound as long as it has at least one ethylenically unsaturated bond capable of radical polymerization in the molecule. , Oligomers, polymers and the like having a chemical form. Only one kind of radically polymerizable compound may be used, or two or more kinds thereof may be used in combination at an arbitrary ratio in order to improve desired properties. It is preferable to use two or more kinds in combination for controlling performance such as reactivity and physical properties.

  Examples of the polymerizable compound having an ethylenically unsaturated bond capable of radical polymerization include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and salts thereof, Examples thereof include radically polymerizable compounds such as anhydrides having a saturated group, acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes.

  Specifically, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, tridecyl acrylate, 2-phenoxyethyl acrylate, bis (4-acryloxypolyethoxyphenyl) Propane, polyethylene glycol diacrylate, polypropylene glycol diacrylate, dipentaerythritol tetraacrylate, trimethylolpropane triacrylate, oligoester acrylate, N-methylolacrylamide, diacetone acrylamide, epoxy acrylate, isobornyl acrylate, dicyclopentenyl acrylate, Dicyclopentenyloxyethyl acrylate, Acrylic acid derivatives such as cyclopentanyl acrylate; methyl methacrylate, n-butyl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2-bis (4- Methacryl derivatives such as methacryloxypolyethoxyphenyl) propane; and other derivatives of allyl compounds such as allyl glycidyl ether, diallyl phthalate, and triallyl trimellitate. More specifically, Shinzo Yamashita, “Crosslinker Handbook”, (1981 Taiseisha); Kato Kiyosumi, “UV / EB Curing Handbook (Materials)” (1985, Polymer Publications); Radtech Study Group, “Application and Market of UV / EB Curing Technology”, p. 79, (1989, CMC); Eiichiro Takiyama, “Polyester Resin Handbook”, (1988, Nikkan Kogyo Shimbun) Commercially available products or radically polymerizable or crosslinkable monomers, oligomers and polymers known in the industry can be used.

  Among these acrylates and methacrylates, alcohol acrylates having an ether oxygen atom such as tetrahydrofurfuryl acrylate and 2-phenoxyethyl acrylate are preferable from the viewpoints of curability and film properties after curing. For the same reason, an acrylate of an alcohol having an alicyclic structure is also preferable, and a bicyclo ring structure or a tricyclo ring structure such as isobornyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, dicyclopentanyl acrylate, etc. Specific examples of preferable acrylates include dicyclopentenyl acrylate and dicyclopentenyloxyethyl acrylate having a double bond in the alicyclic structure.

  Examples of the radically polymerizable compound include JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, JP-A-10-863, JP-A-9-134011, and JP-T-2004. There are known photocurable polymerizable compounds used in the photopolymerizable composition described in each publication such as JP-A-514014, and these can also be applied to the ink composition for inkjet recording of the present invention.

Furthermore, it is preferable to use a vinyl ether compound as the radical polymerizable compound. Suitable vinyl ether compounds include, for example, ethylene glycol divinyl ether, ethylene glycol monovinyl ether, diethylene glycol divinyl ether, triethylene glycol monovinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol. Di- or trivinyl ether compounds such as divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, hydroxyethyl monovinyl ether, hydroxynonyl monovinyl ether, trimethylolpropane trivinyl ether; ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octade Monovinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-O-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl vinyl ether, etc. Examples include vinyl ether compounds.
Commercially available products such as Rapi-Cure DVE-3 and Rapi-Cure DVE-2 (both manufactured by ISP Europe) can be used as the vinyl ether compound.

  Of these vinyl ether compounds, divinyl ether compounds and trivinyl ether compounds are preferable from the viewpoints of curability, adhesiveness, and surface hardness, and divinyl ether compounds are particularly preferable. A vinyl ether compound may be used individually by 1 type, and may be used in combination of 2 or more type as appropriate.

  Other polymerizable compounds include (meth) acrylic monomers or prepolymers, (meth) acrylic acid esters such as epoxy monomers or prepolymers, urethane monomers or prepolymers (hereinafter referred to as acrylate compounds as appropriate). .) May be used, and the compounds shown below are listed as compound examples.

  That is, 2-ethylhexyl-diglycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxybutyl acrylate, hydroxypivalate neopentyl glycol diacrylate, 2-acryloyloxyethyl phthalate, methoxy-polyethylene glycol acrylate, Tetramethylol methane triacrylate, 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, dimethylol tricyclodecane diacrylate, ethoxylated phenyl acrylate, 2-acryloyloxyethyl succinic acid, nonylphenol EO adduct acrylate, modified glycerin Triacrylate, bisphenol A diglycidyl ether acrylic acid adduct, modified bisphenol A diacrylate, phenoxy-poly Tylene glycol acrylate, 2-acryloyloxyethylhexahydrophthalic acid, PO adduct diacrylate of bisphenol A, EO adduct diacrylate of bisphenol A, dipentaerythritol hexaacrylate, pentaerythritol triacrylate tolylene diisocyanate urethane prepolymer Lactone-modified flexible acrylate, butoxyethyl acrylate, propylene glycol diglycidyl ether acrylic acid adduct, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, 2-hydroxyethyl acrylate, methoxydipropylene glycol acrylate, ditrimethylolpropane Tetraacrylate, pentaerythritol triacrylate hexamethyl Nji diisocyanate urethane prepolymer, stearyl acrylate, isoamyl acrylate, isomyristyl acrylate, isostearyl acrylate, lactone-modified acrylate, and the like.

These acrylate compounds are polymerizable compounds that have been used in UV curable inks, have low skin irritation and sensitization (ease of rashes), and have relatively low viscosity and stable ink ejection properties. It is preferable because the sensitivity and adhesiveness with the recording medium are good.
The monomers listed here as other polymerizable compounds are low in sensitization even with a low molecular weight, have high reactivity, low viscosity, and excellent adhesion to a recording medium.

  In order to further improve the sensitivity, bleeding, and adhesion to the recording medium, as other polymerizable compound components, monoacrylate and a polyfunctional acrylate monomer or polyfunctional acrylate oligomer having a molecular weight of 400 or more, preferably 500 or more are used. It is a preferable aspect to use together.

  In particular, in an ink composition used for recording on a flexible recording medium such as a PET film or a PP film, a monoacrylate selected from the above compound group, and one kind selected from the above-mentioned specific heterocyclic compound, The combined use with a polyfunctional acrylate monomer or polyfunctional acrylate oligomer selected from other polymerizable compounds is preferable because the film strength can be increased while the film is made flexible to enhance the adhesion.

  In addition, the embodiment in which at least three kinds of polymerizable compounds of monofunctional, bifunctional, and trifunctional or higher polyfunctional monomers are used in combination improves sensitivity, bleeding, and adhesiveness to the recording medium while maintaining safety. From the viewpoint that it can be further improved, it is mentioned as a preferred embodiment.

  As monoacrylates, stearyl acrylate, isoamyl acrylate, isomystil acrylate, and isostearyl acrylate have high sensitivity and low shrinkage to prevent curling, and are preferable in terms of prevention of bleeding, odor of printed matter, and cost reduction of irradiation apparatus. .

As the oligomer that can be used in combination with the monoacrylate, an epoxy acrylate oligomer and a urethane acrylate oligomer are particularly preferable.
In addition, methacrylate has better skin irritation than acrylate.
Among the above compounds, when alkoxy acrylate is used in an amount of 70% by mass or less and the balance is acrylate, it is preferable because it has good sensitivity, bleeding characteristics, and odor characteristics.

  The radically polymerizable compound used in the present invention is preferably a compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule from the viewpoint of curing speed, flexibility after curing, and adhesion to a recording medium. It is preferably at least one selected from (meth) acrylates containing atoms or N-vinyl lactams.

  The compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule that can be used in the present invention includes "an amide group or lactam ring in the molecule, and the nitrogen atom of the amide group or lactam ring is a vinyl group. And compounds selected from “N-vinylamides having a structure substituted by”, “compounds having an amide group in the molecule”, and “(meth) acrylates having a tertiary amine structure in the molecule”.

  As the compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule, from the viewpoint of physical properties of the cured film after curing and adhesion between the cured film and the recording medium, the nitrogen atom of the amide group or lactam ring is vinyl. N-vinylamides having a structure substituted with a group are preferred. Among N-vinylamides, N-vinyllactams having a structure in which a nitrogen atom of a lactam ring is substituted with a vinyl group are more preferable from the viewpoint of safety and availability.

  When the compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule is an N-vinyl lactam, the N-vinyl lactam has a number of lactam rings which is determined by the stability of the compound and the ink composition. From the viewpoint of solubility, availability, etc., it is preferably 5-7. Specifically, such N-vinyl lactams are preferably N-vinyl pyrrolidone having a 5-membered ring structure or N-vinyl caprolactam having a 7-membered ring structure, and particularly preferably N-vinyl caprolactam.

  Other examples of N-vinylamides that can be used as compounds having a nitrogen atom and a polymerizable unsaturated bond in the molecule include N-vinylacetamide, N-vinylformamide, N-methyl-N-vinylacetamide, N -Methyl-N-vinylformamide and the like.

  On the other hand, as a (meth) acrylate having a tertiary amine structure in the molecule that can be used as a compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule, for example, 1,2,2,6,6-pentamethyl- Preferred examples include 4-methacryloxypiperidine (FA-711MM manufactured by Hitachi Chemical Co., Ltd.) and amine-modified acrylates (for example, CN2100, CN501, CN550, CN551 manufactured by Sartomer).

  Examples of the compound having an amide group in the molecule that can be used as a compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule include 4-acryloylmorpholine, diacetone acrylamide, and diisopropyl acrylamide.

  In the ink composition of the present invention, the content of the compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule depends on the curing speed, the adhesion between the cured film and the recording medium, and the film of the cured film after curing. From the viewpoint of physical properties, it is preferably in the range of 1 to 35% by mass, more preferably in the range of 3 to 30% by mass, and still more preferably in the range of 5 to 26% by mass with respect to the mass of the entire ink composition.

  Moreover, (B) radically polymerizable compound may be used by 1 type, and may use 2 or more types together.

  The content of the radically polymerizable compound (B) in the ink composition of the present invention is the total solid content of the ink composition from the viewpoints of curing speed, adhesion of the cured film to the recording medium, and film properties after curing. Among them, the range is preferably 5 to 35% by mass, more preferably 10 to 30% by mass, and still more preferably 12 to 26% by mass.

<(C) Radical polymerization initiator>
The ink composition of the present invention contains a radical polymerization initiator.
As the radical polymerization initiator, a known polymerization initiator can be appropriately selected and used according to the kind of the polymerizable compound used in combination and the purpose of use of the ink composition.
The radical polymerization initiator used in the ink composition of the present invention is a compound that absorbs external energy and generates a polymerization initiating species. External energy used for initiating polymerization is roughly divided into heat and radiation, and a thermal polymerization initiator and a photopolymerization initiator are used, respectively. Examples of radiation include γ rays, β rays, electron beams, ultraviolet rays, visible rays, and infrared rays.
Known compounds can be used as the thermal polymerization initiator and the photopolymerization initiator.

Preferred radical polymerization initiators that can be used in the present invention include (a) aromatic ketones, (b) acylphosphine oxide compounds, (c) aromatic onium salt compounds, (d) organic peroxides, (e) thios. Compound, (f) hexaarylbiimidazole compound, (g) ketoxime ester compound, (h) borate compound, (i) azinium compound, (j) metallocene compound, (k) active ester compound, (l) carbon halogen bond And (m) an alkylamine compound.
In the present invention, the radical polymerization initiator may be used alone or in combination. From the viewpoint of the effect, it is preferable to use two or more radical polymerization initiators in combination.

  Specific examples of the radical polymerization initiator used in the present invention include benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-benzyl. 2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, bis (2,4,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, 1,2- And octanedione, 1- (4- (phenylthio) -2,2- (O-benzoyloxime)) and the like. Furthermore, as other molecular cleavage type polymerization initiators, 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyl dimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4- Isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, and the like may be used in combination. Furthermore, hydrogen abstraction type photopolymerization initiators such as benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4′-methyl-diphenyl sulfide and the like can be used in combination.

  The radical polymerization initiator in the present invention has a range of 1 to 50% by mass based on the total amount of (A) the compound represented by the general formula (I), (B) the radical polymerizable compound and the colorant described later. Preferably, the range of 2-40 mass% is more preferable, and the range of 5-35 mass% is still more preferable.

  In addition, the radical polymerization initiator is in a mass ratio of polymerization initiator: sensitizing dye to the sensitizing dye that can be used as necessary, which will be described later, and is 200: 1 to 1: 200, preferably 50: It is appropriate that it is included in the range of 1: 1 to 50, more preferably 20: 1 to 1: 5.

In the ink composition for ink jet recording of the present invention, in addition to the essential components, other components can be used in combination for the purpose of improving physical properties, as long as the effects of the present invention are not impaired.
Hereinafter, these optional components will be described below.

<Colorant>
The ink composition for inkjet recording of the present invention can form a colored image by containing a colorant.

  There is no restriction | limiting in particular as a coloring agent which can be used for this invention, It can select and use from arbitrary well-known coloring agents, such as a pigment, an oil-soluble dye, a water-soluble dye, a disperse dye. Among these, as the colorant, pigments and oil-soluble dyes that are excellent in weather resistance and rich in color reproducibility are preferable, and pigments are more preferable.

  A colorant that can be suitably used in the ink composition for ink jet recording of the present invention is selected from compounds that do not function as a polymerization inhibitor in a polymerization reaction that is a curing reaction, from the viewpoint of not reducing the sensitivity of the curing reaction by actinic radiation. It is preferable to do.

-Pigment-
Although it does not necessarily limit as a pigment which can be used for this invention, For example, the organic or inorganic pigment of the following number described in a color index can be used.

Examples of the red or magenta pigment include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, 53. : 1, 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144 , 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13, 16, 20, 36, and the like.
Examples of the blue or cyan pigment include Pigment Blue 1,15,15: 1,15: 2,15: 3, 15: 4,15: 6,16,17-1,22,27,28,29,36. , 60, and the like.
Examples of the green pigment include Pigment Green 7, 26, 36, 50, and the like.
Examples of the yellow pigment include Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, and 137. , 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193, and the like.
Examples of the black pigment include Pigment Black 7, 28, 26, and the like.
Examples of the white pigment include Pigment White 6, 18, 21, and the like.
These pigments can be appropriately selected and used according to the purpose.

-Oil-soluble dye-
Below, the oil-soluble dye which can be used by this invention is demonstrated.
The oil-soluble dye that can be used in the present invention means a dye that is substantially insoluble in water. Specifically, the solubility in water at 25 ° C. (the mass of the dye that can be dissolved in 100 g of water) is 1 g or less, preferably 0.5 g or less, more preferably 0.1 g or less. Accordingly, the oil-soluble dye means a so-called water-insoluble pigment or oil-soluble dye, and among these, an oil-soluble dye is preferable.

  Among the oil-soluble dyes that can be used in the present invention, any yellow dye can be used. For example, phenols, naphthols, anilines, pyrazolones, pyridones, aryl or heteryl azo dyes having open-chain active methylene compounds as coupling components; for example, azomethine dyes having open-chain active methylene compounds as coupling components For example, methine dyes such as benzylidene dyes and monomethine oxonol dyes; for example, quinone dyes such as naphthoquinone dyes and anthraquinone dyes; and other dye species such as quinophthalone dyes, nitro Examples thereof include nitroso dyes, acridine dyes, acridinone dyes and the like.

  Among the oil-soluble dyes that can be used in the present invention, any magenta dye can be used. For example, aryl or heteryl azo dyes having phenols, naphthols, anilines as coupling components; for example, azomethine dyes having pyrazolones, pyrazolotriazoles as coupling components; for example, arylidene dyes, styryl dyes, merocyanine dyes, Methine dyes such as oxonol dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes and xanthene dyes; quinone dyes such as naphthoquinone, anthraquinone and anthrapyridone; A ring dye; and the like.

  Of the oil-soluble dyes applicable to the present invention, any cyan dye can be used. For example, indoaniline dyes, indophenol dyes or azomethine dyes having pyrrolotriazoles as coupling components; polymethine dyes such as cyanine dyes, oxonol dyes, merocyanine dyes; carboniums such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes Examples include dyes; phthalocyanine dyes; anthraquinone dyes; aryl or heteryl azo dyes having phenols, naphthols, and anilines as coupling components; indigo / thioindigo dyes;

  Each of the above dyes may exhibit yellow, magenta, and cyan colors only after a part of chromophore (chromogenic atomic group) is dissociated. In this case, the counter cation may be an alkali metal or ammonium. Such inorganic cations may be used, and organic cations such as pyridinium and quaternary ammonium salts may be used. Furthermore, polymer cations having such a structure may be used.

Although not limited to the following, preferred specific examples include C.I. I. Solvent Black 3, 7, 27, 29 and 34; C.I. I. Solvent Yellow 14, 16, 19, 29, 30, 56, 82, 93 and 162; C.I. I. Solvent Red 1, 3, 8, 18, 24, 27, 43, 49, 51, 72, 73, 109, 122, 132 and 218; I. Solvent Violet 3; C.I. I. Solvent Blue 2,11,25,35,38,67 and 70; I. Solvent Green 3 and 7; I. Solvent orange 2; and the like.
Particularly preferred among these are: Nubian Black PC-0850, Oil Black HBB, Oil Yellow 129, Oil Yellow 105, Oil Pink 312, Oil Red 5B, Oil Scallet 308, Vali Fast Blue chemistry 2606e B2 (Manufactured by Co., Ltd.), Aizen Spiron Blue GNH (manufactured by Hodogaya Chemical Co., Ltd.), Neopen Yellow 075, Neopen Magenta SE1378, Neopen Blue 808, Neopen Blue FF4012, and Neo42 Cy FF4012.

-Disperse dye-
In the present invention, a disperse dye can be used as long as it is soluble in a water-immiscible organic solvent. The disperse dye generally includes a water-soluble dye, but in the present invention, the disperse dye is preferably used as long as it is soluble in a water-immiscible organic solvent.
Preferable specific examples of the disperse dye include C.I. I. Disperse Yellow 5,42,54,64,79,82,83,93,99,100,119,122,124,126,160,184: 1,186,198,199,201,204,224 and 237 C. I. Disperse Orange 13, 29, 31: 1, 33, 49, 54, 55, 66, 73, 118, 119 and 163; I. Disperse Red 54, 60, 72, 73, 86, 88, 91, 92, 93, 111, 126, 127, 134, 135, 143, 145, 152, 153, 154, 159, 164, 167: 1,177 , 181, 204, 206, 207, 221, 239, 240, 258, 277, 278, 283, 311, 323, 343, 348, 356 and 362; I. Disperse Violet 33; C.I. I. Disperse Blue 56, 60, 73, 87, 113, 128, 143, 148, 154, 158, 165, 165: 1, 165: 2, 176, 183, 185, 197, 198, 201, 214, 224, 225 , 257, 266, 267, 287, 354, 358, 365 and 368; I. Disperse Green 6: 1 and 9;

  The colorant that can be used in the present invention is preferably appropriately dispersed in the ink after being added to the ink composition for ink jet recording of the present invention. For dispersing the colorant, for example, a dispersion device such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, or a paint shaker can be used.

  It is also possible to add a dispersant when dispersing the colorant. The type of the dispersant is not particularly limited, but a polymer dispersant is preferably used, and examples of the polymer dispersant include Solsperse series manufactured by Zeneca. Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. In the present invention, these dispersant and dispersion aid are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the colorant.

  In preparing the ink composition for ink jet recording of the present invention, the colorant may be blended by adding directly with each component. However, in order to improve dispersibility, the solvent or the (B) radical polymerizable compound in the present invention is used in advance. It can also be added after being dispersed in a dispersion medium such as

In the present invention, in order to avoid the deterioration of the solvent resistance when the solvent remains in the cured image and the problem of VOC (Volatile Organic Compound) of the remaining solvent, the colorant is (B) a radical. It is preferable to add and mix any one of the polymerizable compounds or a mixture thereof in advance.
In consideration of only dispersibility, it is preferable to select a monomer having the lowest viscosity as the polymerizable compound used for the addition of the colorant.

  One or more colorants may be appropriately selected and used depending on the intended use of the ink composition for ink jet recording.

  In the ink composition for inkjet recording of the present invention, when using a colorant such as a pigment that remains in a solid state, the average particle diameter of the colorant particles is preferably 0.005 to 0.5 μm, It is preferable to set the colorant, the dispersant, the dispersion medium, the dispersion conditions, and the filtration conditions so as to be more preferably 0.01 to 0.45 μm, and still more preferably 0.015 to 0.4 μm. This particle size control is preferable because clogging of the head nozzle can be suppressed and ink storage stability, ink transparency, and curing sensitivity can be maintained.

The content of the colorant in the ink composition for ink jet recording of the present invention is appropriately selected depending on the intended use of the ink composition, but generally considering the ink physical properties and colorability, generally the total amount of the ink composition. On the other hand, it is preferable that it is 0.5-10 mass%, and it is more preferable that it is 1-8 mass%.
In the case where the ink composition for ink jet recording of the present invention is a white ink composition having a white pigment such as titanium oxide as a colorant, the content of the colorant is an ink composition in order to ensure concealment. It is preferable that it is 5-30 mass% with respect to the whole mass, and it is more preferable that it is 10-25 mass%.

<Sensitizing dye>
A sensitizing dye can be added to the ink composition of the present invention in order to promote decomposition of the radical polymerization initiator by irradiation with actinic rays. A sensitizing dye absorbs specific actinic radiation and enters an electronically excited state. The sensitizing dye in an electronically excited state is brought into contact with the polymerization initiator to cause actions such as electron transfer, energy transfer, and heat generation, thereby causing a chemical change of the polymerization initiator, that is, decomposition, radical, acid or base. It promotes the generation of.

  As the sensitizing dye, a compound corresponding to the wavelength of actinic radiation that generates an initiation species in the radical polymerization initiator used in the ink composition may be used. Considering that it is used for a curing reaction of a general ink composition, examples of preferable sensitizing dyes include those belonging to the following compounds and having an absorption wavelength in the 350 nm to 450 nm region. Can be mentioned.

  Polynuclear aromatics (eg, anthracene, pyrene, perylene, triphenylene), thioxanthones (eg, isopropylthioxanthone), xanthenes (eg, fluorescein, eosin, erythrosine, rhodamine B, rose bengal), cyanines (eg, Thiacarbocyanine, oxacarbocyanine), merocyanines (eg, merocyanine, carbomerocyanine), thiazines (eg, thionine, methylene blue, toluidine blue), acridines (eg, acridine orange, chloroflavin, acriflavine), anthraquinones (For example, anthraquinone), squalium (for example, squalium), coumarins (for example, 7-diethylamino-4-methylcoumarin), and the like. Xanthones may be mentioned as preferred class.

<Co-sensitizer>
The ink composition for inkjet recording of the present invention can also contain a co-sensitizer. In the present invention, the co-sensitizer has functions such as further improving the sensitivity of the sensitizing dye to actinic radiation or suppressing polymerization inhibition of the polymerizable compound by oxygen.

  Examples of co-sensitizers include amines such as M.I. R. Sander et al., “Journal of Polymer Society”, Vol. 10, 3173 (1972), Japanese Patent Publication No. 44-20189, Japanese Patent Publication No. 51-82102, Japanese Patent Publication No. 52-134692, Japanese Patent Publication No. 59-138205. No. 60-84305, JP-A 62-18537, JP-A 64-33104, Research Disclosure 33825, and the like. Specific examples include triethanolamine. P-dimethylaminobenzoic acid ethyl ester, p-formyldimethylaniline, p-methylthiodimethylaniline and the like.

  Other examples of co-sensitizers include thiols and sulfides such as thiol compounds described in JP-A-53-702, JP-B-55-500806, JP-A-5-142772, No. 56-75643, such as 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzimidazole, 2-mercapto-4 (3H) -quinazoline, β-mercapto. And naphthalene.

  Other examples of co-sensitizers include amino acid compounds (eg, N-phenylglycine), organometallic compounds described in Japanese Patent Publication No. 48-42965 (eg, tributyltin acetate), Japanese Patent Publication No. 55-34414. Hydrogen donors described in JP-A-6-308727, sulfur compounds (e.g., trithiane) described in JP-A-6-308727, phosphorus compounds (such as diethyl phosphite) described in JP-A-6-250387, JP-A-8-65779 Examples include Si—H and Ge—H compounds.

<Other ingredients>
If necessary, other components can be added to the ink composition for ink jet recording of the present invention. Examples of other components include a polymerization inhibitor and a solvent.

  A polymerization inhibitor may be added from the viewpoint of enhancing the storage stability. In addition, the ink composition for ink jet recording of the present invention is preferably discharged in the range of 40 to 80 ° C. with heating and low viscosity, and a polymerization inhibitor may be added to prevent clogging of the head due to thermal polymerization. preferable. The polymerization inhibitor is preferably added in an amount of 200 to 20,000 ppm based on the total amount of the ink composition of the present invention. Examples of the polymerization inhibitor include hydroquinone, benzoquinone, p-methoxyphenol, TEMPO, TEMPOL, and cuperon Al.

In view of the fact that the ink composition for ink jet recording of the present invention is a radiation curable ink composition, it is preferable that no solvent is contained so that the ink composition can react quickly and be cured immediately after landing of the ink composition. However, a predetermined solvent can be included as long as the curing rate of the ink composition is not affected. In the present invention, an organic solvent or water can be used as the solvent. In particular, an organic solvent can be added in order to improve adhesiveness with a recording medium (a support such as paper). The addition of an organic solvent is effective because the VOC problem can be avoided.
The amount of the organic solvent is, for example, 0.1 to 5% by mass, preferably 0.1 to 3% by mass with respect to the mass of the entire ink composition of the present invention.

  In addition, a known compound can be added to the ink jet recording ink composition of the present invention, if necessary. For example, surfactants, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, waxes and the like are appropriately selected and added. be able to. In order to improve the adhesion to a recording medium such as polyolefin or PET, it is also preferable to include a tackifier that does not inhibit the polymerization. Specifically, a high molecular weight adhesive polymer described in JP-A-2001-49200, pages 5 to 6 (for example, (meth) acrylic acid and an alcohol having an alkyl group having 1 to 20 carbon atoms). An ester, a copolymer of (meth) acrylic acid and an alicyclic alcohol having 3 to 14 carbon atoms, a copolymer of an ester of (meth) acrylic acid and an aromatic alcohol having 6 to 14 carbon atoms), and polymerizability. Examples thereof include a low molecular weight tackifying resin having an unsaturated bond.

[Properties of ink composition for inkjet recording]
The preferred physical properties of the ink composition for ink jet recording of the present invention will be described.
The ink composition for ink jet recording of the present invention has a viscosity of preferably 7 to 30 mPa · s at a temperature at the time of ejection (for example, 40 to 80 ° C., preferably 25 to 50 ° C.) in consideration of ejectability. More preferably, it is 7 to 25 mPa · s. For example, the viscosity of the ink composition for inkjet recording of the present invention at room temperature (25 to 30 ° C.) is preferably 10 to 50 mPa · s, more preferably 12 to 40 mPa · s.

  The composition ratio of the ink composition for ink-jet recording of the present invention is preferably adjusted as appropriate so that the viscosity is in the above range. By setting the viscosity at room temperature high, even when a porous recording medium is used, ink penetration into the recording medium can be avoided, and uncured monomers and odors can be reduced. Furthermore, ink bleeding at the time of ink droplet landing can be suppressed, and as a result, the image quality is improved.

  The surface tension of the ink composition for inkjet recording of the present invention is preferably 20 to 30 mN / m, more preferably 23 to 28 mN / m. When recording on various recording media such as polyolefin, PET, coated paper, and non-coated paper, 20 mN / m or more is preferable from the viewpoint of bleeding and penetration, and the wettability is preferably 30 mN / m or less.

[Inkjet recording method]
The ink jet recording method of the present invention and the ink jet recording apparatus applicable to the ink jet recording method will be described below.

The inkjet recording method of the present invention comprises (i-1) a step of ejecting the inkjet recording ink composition of the present invention onto a recording medium, and (i-2) the ejected inkjet recording ink composition. Irradiating actinic radiation to cure the ink composition.
By including the steps (i-1) and (i-2), the ink jet recording method of the present invention forms an image with the ink composition cured on the recording medium.

  In the step (i-1) of the ink jet recording method of the present invention, an ink jet recording apparatus described in detail below can be used.

-Inkjet recording device-
There is no restriction | limiting in particular as an inkjet recording device used for the inkjet recording method of this invention, The well-known inkjet recording device which can achieve the target resolution can be selected arbitrarily and can be used. That is, any known inkjet recording apparatus including a commercially available product can eject ink onto a recording medium in step (i-1) of the inkjet recording method of the present invention.

Examples of the ink jet recording apparatus that can be used in the present invention include an apparatus including an ink supply system, a temperature sensor, and an actinic radiation source.
The ink supply system includes, for example, an original tank containing the ink composition of the present invention, a supply pipe, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head. The piezo-type inkjet head has a multi-size dot of 1 to 100 pl, preferably 8 to 30 pl, for example, 320 × 320 to 4000 × 4000 dpi, preferably 400 × 400 to 1600 × 1600 dpi, and more preferably 720 ×. It can drive so that it can discharge with a resolution of 720 dpi. In the present invention, dpi represents the number of dots per 2.54 cm.

  In the radiation curable ink such as the ink composition for ink jet recording of the present invention, it is desirable that the ejected ink is kept at a constant temperature. Therefore, heat insulation and heating are performed from the ink supply tank to the ink jet head portion. Can do. The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors at each piping site and perform heating control according to the ink flow rate and the environmental temperature. The temperature sensor can be provided near the ink supply tank and the nozzle of the inkjet head. Moreover, it is preferable that the head unit to be heated is thermally shielded or insulated so that the apparatus main body is not affected by the temperature from the outside air. In order to shorten the printer start-up time required for heating or to reduce the loss of heat energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

  The ink composition for ink jet recording of the present invention using the above ink jet recording apparatus is preferably heated at 40 to 80 ° C., more preferably 25 to 50 ° C. It is preferably performed after the viscosity is lowered to preferably 7 to 30 mPa · s, more preferably 7 to 25 mPa · s. In particular, it is preferable to use an ink composition for ink-jet recording of the present invention having an ink viscosity at 25 ° C. of 35 to 500 mPa · s because a great effect can be obtained. By using this method, high ejection stability can be realized.

  A radiation curable ink composition such as the ink composition for ink jet recording of the present invention generally has a viscosity higher than that of a water-based ink generally used for ink jet recording ink, and therefore has a large viscosity fluctuation due to temperature fluctuations during ejection. The ink viscosity fluctuation has a great influence on the change of the droplet size and the change of the droplet discharge speed, and causes the image quality deterioration. Therefore, it is necessary to keep the temperature of the ink at the time of ejection as constant as possible. Therefore, in the present invention, it is appropriate that the control range of the ink temperature is ± 5 ° C. of the set temperature, preferably ± 2 ° C. of the set temperature, more preferably ± 1 ° C. of the set temperature.

Next, (i-2) a step of irradiating the discharged ink composition with actinic radiation to cure the ink composition will be described.
The ink composition ejected on the recording medium is cured by irradiation with actinic radiation. This is because the radical polymerization initiator contained in the ink composition of the present invention decomposes upon irradiation with actinic radiation to generate radicals and other starting species, and depending on the function of the starting species, a specific polymerizable compound or optionally used in combination. This is because the polymerization reaction of other polymerizable compounds is caused and accelerated. At this time, if a sensitizing dye is present together with the radical polymerization initiator in the ink composition, the sensitizing dye in the system absorbs actinic radiation to be in an excited state and promotes its decomposition by contacting with the radical polymerization initiator. A more sensitive curing reaction can be achieved.

  Here, α rays, γ rays, electron beams, X rays, ultraviolet rays, visible light, infrared rays, or the like can be used as the active radiation used. In particular, any one of electron beam, ultraviolet light, and visible light is preferable. Although the peak wavelength of actinic radiation is based also on the absorption characteristic of a sensitizing dye, it is preferable that it is 200-600 nm, for example, it is more preferable that it is 300-450 nm, and it is still more preferable that it is 350-420 nm.

Further, the polymerization initiation system applied to the ink composition for ink jet recording of the present invention has sufficient sensitivity even with a low output actinic radiation. Thus, the output of the active radiation is preferably 2,000 mJ / cm ² or less, more preferably from 10 to 2,000 mJ / cm ^2, more preferably be 20 to 1,000 mJ / cm ² Particularly preferably, it is 50 to 800 mJ / cm ² .
Furthermore, the actinic radiation is, the exposure surface illuminance of, for example, 10 to 2,000 mW / cm ^2, preferably, suitably be irradiated at 20 to 1,000 mW / cm ^2.

  Mercury lamps and gas / solid lasers are mainly used as actinic radiation sources, and mercury lamps and metal halide lamps are widely known as light sources used for curing UV photocurable ink jet recording inks. Yes. However, from the viewpoint of environmental protection, mercury-free is strongly desired, and replacement with a GaN-based semiconductor ultraviolet light-emitting device is very useful industrially and environmentally. Furthermore, LED (UV-LED) and LD (UV-LD) 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.

  Further, a light emitting diode (LED) and a laser diode (LD) can be used as the active radiation source. In particular, when an ultraviolet light source is required, an ultraviolet LED and an ultraviolet LD can be used. For example, Nichia Corporation has introduced a purple LED whose main emission spectrum has a wavelength between 365 nm and 420 nm. When even shorter wavelengths are required, US Pat. No. 6,084,250 discloses an LED that can emit actinic radiation centered between 300 nm and 370 nm. Other ultraviolet LEDs are also available and can emit radiation in different ultraviolet bands. The actinic radiation source particularly preferred in the present invention is a UV-LED, particularly preferably a UV-LED having a peak wavelength at 350 to 420 nm.

Incidentally, it is preferable that maximum illumination intensity of the LED on a recording medium is 10 to 2,000 mW / cm ^2, more preferably 20 to 1,000 mW / cm ^2, particularly preferably 50 to 800 mW / cm ² .

The ink composition for ink jet recording of the present invention is appropriately irradiated with such actinic radiation, for example, for 0.01 to 120 seconds, preferably for 0.1 to 90 seconds.
Actinic radiation irradiation conditions and a basic irradiation method are disclosed in JP-A-60-132767. Specifically, the light source is provided on both sides of the head unit including the ink ejection device, and the head unit and the light source are scanned by a so-called shuttle method. Irradiation with actinic radiation takes a certain time (for example, 0.01 to 0.5 seconds, preferably 0.01 to 0.3 seconds, more preferably 0.01 to 0.15 seconds) after ink landing. Will be done. In this way, by controlling the time from ink landing to irradiation to an extremely short time, it is possible to prevent the ink that has landed on the recording medium from spreading before curing. Further, since the ink can be exposed to the porous recording medium before the ink penetrates to a deep part where the light source does not reach, the residual unreacted monomer can be suppressed, and as a result, the odor can be reduced. .

  Further, the curing may be completed by another light source that is not driven. WO99 / 54415 pamphlet discloses a method using an optical fiber and a method of applying a collimated light source to a mirror surface provided on the side surface of the head unit and irradiating the recording unit with UV light as an irradiation method. The curing method can also be applied to the ink jet recording method of the present invention.

  By adopting the ink jet recording method as described above, the dot diameter of the landed ink can be kept constant even on various recording media having different surface wettability, and the image quality is improved. In addition, in order to obtain a color image, it is preferable to superimpose in order from the color with the lowest brightness. By superimposing the inks in the order of low lightness, it becomes easy for the irradiation line to reach the lower ink, and good curing sensitivity, reduction of residual monomers, reduction of odor, and improvement of adhesiveness can be expected. In addition, irradiation can be performed by discharging all colors and collectively exposing, but exposure for each color is preferable from the viewpoint of promoting curing.

Thus, the ink composition for ink jet recording of the present invention can be cured with high sensitivity by irradiation with actinic radiation, whereby a high-definition and high-strength image can be formed on the surface of the recording medium. In addition, an image excellent in adhesiveness with a recording medium can be formed.
Furthermore, the ink composition for ink jet recording of the present invention is an ink composition excellent in ejection stability without causing precipitation of contained components around the ink jet head or the like when applied to an ink jet apparatus. Therefore, stable image formation can be performed.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the embodiments in these examples. The following examples relate to UV ink jet recording ink of each color. Further, in the following description, unless otherwise specified, “parts” means “parts by mass”.

[Example 1]
The following components were stirred with a high-speed water-cooled stirrer to obtain a cyan UV inkjet ink.
(Cyan ink composition)
Specific sulfur-containing compound [Exemplary compound (A-6): Component (A)] 0.2 parts (Sumitomo Chemical Industries, Sumilizer TPL-R)
-N-vinyl caprolactam: (B) component 26.0 parts (the product made by IPS Japan, V-CAP)
Monofunctional acrylate: 37.0 parts of component (B) (Sartomer, SR339)
Monofunctional acrylate: component (B) 19.0 parts (Sartomer, SR506)
-Polyfunctional acrylate: Component (B) 6.0 parts (Sartomer, SR399)
・ Solsperse 32000 (manufactured by Noveon, dispersing agent) 1.2 parts ・ Irgalite Blue GLVO 3.0 parts (manufactured by Ciba Specialty Chemicals, pigment)
-Firstcure ST-1 0.05 part (manufactured by ChemFirst, polymerization inhibitor)
・ Lucirin TPO (manufactured by BASF, photoinitiator): (C) component 5.5 parts ・ Irgacure 369: (C) component 0.5 part (manufactured by Ciba Specialty Chemicals, photoinitiator)
4-phenylbenzophenone: (C) component 1.0 part (Tokyo Chemical Industry Co., Ltd., photoinitiator)
Darocur ITX: 0.5 part of component (C) (Ciba Specialty Chemicals, photoinitiator)
・ Byk 307 (by anti-foaming agent manufactured by BYK Chemie) 0.05 parts

(Evaluation of ink)
Recording was performed on a sheet made of polyvinyl chloride using an ink jet recording apparatus having the obtained cyan ink composition and a piezo type ink jet head (CA3 head manufactured by Toshiba Tec). The ink supply system is composed of an original tank, supply piping, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head, and temperature control is performed so that the nozzle portion is always 45 ° C. ± 3 ° C. (100% Print coated image). After discharging the ink composition, irradiation was performed by passing it under a light beam of an iron-doped ultraviolet lamp (power 120 W / cm) at a stepped rate to cure the ink and obtain a printed matter. .
At this time, the following evaluation was performed.

<Curing sensitivity>
The obtained printed matter was evaluated by palpation, and the minimum exposure amount when the tackiness completely disappeared was measured with a light amount accumulator (manufactured by EIT, UV PowerMAP). It is evaluated that the smaller this value is, the higher the sensitivity is. As a result, it was confirmed that the ink composition of Example 1 was cured with high sensitivity because the cumulative exposure amount of ultraviolet rays on the sheet was about 400 mJ / cm ² .

<Adhesion with recording medium>
Adhesiveness with a recording medium when the cumulative exposure amount of ultraviolet rays on the sheet is about 400 mJ / cm ² is evaluated by a cross-hatch test (EN ISO 2409), and represented by notations 5B to 1B by the ASTM method. It is evaluated that 5B has the most excellent adhesiveness, and 3B or more is a level having no practical problem.
As a result, the ink composition of Example 1 had high adhesiveness, and the value thereof was 4B as expressed by the ASTM method. The results are shown in Table 1 below.

<Discharge stability>
When the obtained ink composition was stored at 40 ° C. for 8 weeks, the recording was performed on the recording medium using the above-described inkjet recording apparatus having the piezoelectric inkjet nozzle, and the dots were printed continuously for 1 hour at room temperature. The presence or absence of omission and ink scattering was visually observed and evaluated according to the following criteria. The results are shown in Table 1 below.
○: Dot drop or ink splatter does not occur or occurs 5 times or less △: Dot drop or ink splatter occurs 6 to 20 times ×: Dot drop or ink splatter occurs 21 times or more

[Example 2]
The following components were stirred with a high-speed water-cooled stirrer to obtain a magenta UV inkjet ink.
(Magenta ink composition)
Specific sulfur-containing compound [Exemplary compound (A-6): Component (A)] 0.4 parts (Sumitomo Chemical Industries, Sumilizer TPL-R)
-N-vinylcaprolactam: 25.0 parts of (B) component (the V-CAP made by IPS Japan Ltd.)
-Bifunctional acrylate: 13.2 parts of component (B) (Sartomer, SR9045)
Monofunctional acrylate: Component (B) 44.0 parts (Sartomer, SR339)
Polyfunctional acrylate: 1.0 part of component (B) (Sartomer, SR399)
-Rapi-Cure DVE-3: (B) component 4.0 part (The vinyl ether compound made by ISP Europe)
Solsperse 32000 (Noveon, dispersant) 1.2 parts Cinquasia Magenta RT-355D 3.6 parts (Ciba Specialty Chemicals, pigment)
-Firstcure ST-1 0.05 part (manufactured by ChemFirst, polymerization inhibitor)
・ Lucirin TPO (manufactured by BASF, photoinitiator): (C) component 5.0 parts ・ Irgacure 369: (C) component 0.5 part (manufactured by Ciba Specialty Chemicals, photoinitiator)
4-phenylbenzophenone: (C) component 1.0 part (Tokyo Chemical Industry Co., Ltd., photoinitiator)
Darocur ITX: 1.0 part of component (C) (manufactured by Ciba Specialty Chemicals, photoinitiator)
・ Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts

  The obtained magenta color ink was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured. The printed matter with this ink was evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

Example 3
The following components were stirred with a high-speed water-cooled stirrer to obtain a black UV inkjet ink.
(Black ink composition)
Specific sulfur-containing compound [Exemplary compound (A-6): (A) component] 0.1 part (Sumitomo Chemical Industries, Sumilizer TPL-R)
Specific sulfur-containing compound [Exemplary compound (A-8): Component (A)] 0.1 part (Sumitomo Chemical Industries, Sumilizer TPM)
-N-vinylcaprolactam: 24.0 parts of (B) component (the product made by IPS Japan, V-CAP)
Monofunctional acrylate: 50.0 parts of component (B) (Sartomer, SR339)
Monofunctional acrylate: Component (B) 5.0 parts (Sartomer, SR489)
-Polyfunctional acrylate: Component (B) 6.0 parts (Sartomer, SR399)
-Rapi-Cure DVE-3: (B) component 4.0 part (The vinyl ether compound made by ISP Europe)
Solsperse 32000 (Noveon, dispersant) 1.2 parts Microlith Black CK 2.6 parts (Ciba Specialty Chemicals, pigment)
-Firstcure ST-1 0.05 part (manufactured by ChemFirst, polymerization inhibitor)
・ Lucirin TPO (manufactured by BASF, photoinitiator): (C) component 4.4 parts ・ Irgacure 369: (C) component 0.5 part (manufactured by Ciba Specialty Chemicals, photoinitiator)
4-phenylbenzophenone: (C) component 1.0 part (Tokyo Chemical Industry Co., Ltd., photoinitiator)
Darocur ITX: 1.0 part of component (C) (manufactured by Ciba Specialty Chemicals, photoinitiator)
・ Byk 307 (by anti-foaming agent manufactured by BYK Chemie) 0.05 parts

  The obtained black ink was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured. The printed matter with this ink was evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

Example 4
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink.
(White ink composition)
Specific sulfur-containing compound [Exemplary compound (A-6): Component (A)] 0.3 part (Sumitomo Chemical Industries, Sumilizer TPL-R)
-N-vinylcaprolactam: (B) component 16.0 parts (the product made by IPS Japan, V-CAP)
-Bifunctional acrylate: Component (B) 14.0 parts (Sartomer, SR9045)
Monofunctional acrylate: component (B) 42.0 parts (SR339, manufactured by Sartomer)
Polyfunctional acrylate: (B) component 3.0 parts (Sartomer, SR399)
Solsperse 36000 (manufactured by Noveon, dispersing agent) 2.4 parts MICROLITE WHITE RA 16.0 parts (manufactured by Ciba Specialty Chemicals, pigment)
-Firstcure ST-1 0.05 part (manufactured by ChemFirst, polymerization inhibitor)
・ Lucirin TPO (manufactured by BASF, photoinitiator): (C) component 4.5 parts ・ Irgacure 369: (C) component 0.5 part (manufactured by Ciba Specialty Chemicals, photoinitiator)
4-phenylbenzophenone: (C) component 1.0 part (Tokyo Chemical Industry Co., Ltd., photoinitiator)
Darocur ITX: 0.2 part of component (C) (manufactured by Ciba Specialty Chemicals, photoinitiator)
・ Byk 307 (by anti-foaming agent manufactured by BYK Chemie) 0.05 parts

  The obtained white ink was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured. The printed matter with this ink was evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

Example 5
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink.
(White ink composition)
Specific sulfur-containing compound [Exemplary compound (A-6): Component (A)] 0.3 part (Sumitomo Chemical Industries, Sumilizer TPL-R)
-Bifunctional acrylate: 16.0 parts of component (B) (Sartomer, SR9045)
Monofunctional acrylate: component (B) 40.0 parts (Sartomer SR339)
Monofunctional acrylate: (B) component 15.0 parts (Sartomer SR531)
Polyfunctional acrylate: (B) component 4.0 parts (Sartomer, SR399)
Solsperse 36000 (manufactured by Noveon, dispersing agent) 2.4 parts MICROLITE WHITE RA 16.0 parts (manufactured by Ciba Specialty Chemicals, pigment)
-Firstcure ST-1 0.05 part (manufactured by ChemFirst, polymerization inhibitor)
・ Lucirin TPO (manufactured by BASF, photoinitiator): (C) component 4.4 parts ・ Irgacure 369: (C) component 0.5 part (manufactured by Ciba Specialty Chemicals, photoinitiator)
4-phenylbenzophenone: (C) component 1.0 part (Tokyo Chemical Industry Co., Ltd., photoinitiator)
・ Darocur ITX: 0.3 part of component (C) (manufactured by Ciba Specialty Chemicals, photoinitiator)
・ Byk 307 (by anti-foaming agent manufactured by BYK Chemie) 0.05 parts

  The obtained white ink was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured. The printed matter with this ink was evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

[Comparative Example 1]
The following components were stirred with a high-speed water-cooled stirrer to obtain a cyan UV inkjet ink.
(Cyan ink composition)
-N-vinylcaprolactam: 26.2 parts of component (B) (manufactured by ASP Japan, V-CAP)
Monofunctional acrylate: 37.0 parts of component (B) (Sartomer, SR339)
Monofunctional acrylate: component (B) 19.0 parts (Sartomer, SR506)
-Polyfunctional acrylate: Component (B) 6.0 parts (Sartomer, SR399)
・ Solsperse 32000 (manufactured by Noveon, dispersing agent) 1.2 parts ・ Irgalite Blue GLVO 3.0 parts (manufactured by Ciba Specialty Chemicals, pigment)
-Firstcure ST-1 0.05 part (manufactured by ChemFirst, polymerization inhibitor)
・ Lucirin TPO (manufactured by BASF, photoinitiator): (C) component 5.5 parts ・ Irgacure 369: (C) component 0.5 part (manufactured by Ciba Specialty Chemicals, photoinitiator)
4-phenylbenzophenone: (C) component 1.0 part (Tokyo Chemical Industry Co., Ltd., photoinitiator)
Darocur ITX: 0.5 part of component (C) (Ciba Specialty Chemicals, photoinitiator)
・ Byk 307 (by anti-foaming agent manufactured by BYK Chemie) 0.05 parts

  The obtained cyan ink was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured. The printed matter with this ink was evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

As is apparent from Table 1, the ink compositions of Examples 1 to 5 are all cured with high sensitivity, and are excellent in all items of adhesion to the recording medium and ejection stability.
On the other hand, it can be seen that (A) the ink composition of Comparative Example 1 containing no specific sulfur-containing compound is inferior in ejection stability.

Claims (3)

(A) a compound represented by the following general formula (I);
(B) a radically polymerizable compound;
(C) a radical polymerization initiator;
An ink composition for ink-jet recording, comprising:

In general formula (I), R ¹ and R ² each independently represent a hydrogen atom or an alkyl group.   2. The ink composition for ink jet recording according to claim 1, wherein the radically polymerizable compound (B) is a compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule. (I-1) a step of discharging the ink composition for ink jet recording according to claim 1 or 2 onto a recording medium; and
(I-2) a step of irradiating the discharged ink composition for inkjet recording with active radiation to cure the ink composition;
An ink jet recording method comprising: