JP2010024297A - Ink composition, and method for inkjet recording using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based active radiation-curable ink composition curing at high sensitivity even when exposed to a low level radiation, forming an image of high quality, having high storage stability, and causing no nozzle clogging at the time of ejection even when used as inkjet recording ink, and to provide an inkjet recording method using the ink composition. <P>SOLUTION: This ink composition comprises (A) a sensitizing dye represented by general formula (I), (B) a polymerization initiator, (C) a polymerizable compound having an ethylenically unsaturated bond, and (D) water, wherein the (C) polymerizable compound is present in an emulsion state in the ink composition. In the formula (I), X represents O, S, or NR; R represents a hydrogen atom, an alkyl group or an acyl group; n represents 0 or 1, and R<SP>1</SP>to R<SP>8</SP>each independently represents a hydrogen atom or a monovalent substituent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an aqueous ink composition and an ink jet recording method that are suitably used for actinic radiation curable ink jet recording. Specifically, the present invention relates to a photocurable aqueous ink composition that is cured with high sensitivity to irradiation with actinic radiation and has excellent ejection reliability, and an ink jet recording method using the same.

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 method 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. Furthermore, there is little noise and it is excellent as an image recording method.

  Ink compositions that can be cured by irradiation with actinic radiation such as ultraviolet rays (radiation curable ink compositions), such as ink compositions for ink jet recording, can be cured with high sensitivity and form high-quality images. It has been demanded. By achieving high sensitivity, high curability is imparted by irradiation with actinic radiation, so that sufficient curing is achieved in addition to reducing power consumption and extending life by reducing the load on the actinic radiation generator. As a result, there are various advantages such as suppression of volatilization of uncured low molecular weight substances and reduction in the strength of the formed image.

  Among these, water-based actinic radiation curable ink using water as a main medium is suitable for image printing, pretreatment for imparting printability to a recording medium, and post-treatment for protecting / decorating printed images. In addition, since water is the main component, it is highly safe, and since the content of the curable component is small, a high-quality image can be formed. This technology has many excellent features and possibilities, such as being applicable to high-density inkjet recording heads.

  The basic constituent materials of the aqueous actinic radiation curable ink composition are water, a polymerizable substance, a polymerization initiator that generates radicals or the like by actinic radiation to initiate polymerization, and a coloring material (pigment or dye). Among these, the polymerizable substance and the polymerization initiator may be prepared in an emulsion state or may be present in a solution state with water solubility provided by appropriate substituents. An example of actinic radiation curable ink in which the polymerizable compound is present in an emulsion state is, for example, Patent Document 1, and a cured film excellent in color reproducibility, saturation, scratch resistance, glossiness and the like is obtained by light irradiation. Inkjet inks are described.

  Benzyl, benzoin, benzoin ethyl ether, Michler's ketone, anthraquinone, acridine, phenazine, benzophenone, 2-ethylanthraquinone and the like have been generally used as the photopolymerization initiator contained in the curable inkjet ink by ultraviolet light (for example, Non-Patent Document 1). However, when these photopolymerization initiators are used, it takes a long time for image exposure in image formation because the photopolymerizable composition has low curing sensitivity. For this reason, in the case of a fine image, if there is a slight vibration in the operation, an image with good image quality cannot be reproduced, and further, the amount of energy emitted from the light source of the exposure must be increased. It was necessary to consider radiation. In addition, ink used in the ink jet recording system requires various characteristics such as no change in physical properties or precipitation due to storage (solution stability), no clogging of the nozzle (ejection stability), etc. It is.

Generally, the use of various polymerization initiation systems has been disclosed as a method for increasing the sensitivity to radiation in a radiation-curable polymerizable compound (Non-patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4). ,reference). However, there is no example in which a polymerization initiation system satisfying sufficient sensitivity for scanning exposure, storage stability, and ejection stability is employed in an aqueous inkjet recording ink.
For this reason, it can be cured with high sensitivity to low-output radiation, can form high-quality images, and has good storage stability and ejection stability. An ink composition that is suitably used is desired.
JP 2004-285216 A U.S. Pat. No. 4,134,813 JP-A-1-253731 JP-A-6-308727 Bruce M. Monroe (Bruce M. Monroe et al., Chemical Reviews), Vol. 93, (1993), p. 435-448.

  It is an object of the present invention to cure with high sensitivity even when irradiated with low-output radiation, and to form a high-quality image. It is an object of the present invention to provide a water-based actinic radiation curable ink composition that does not cause an ink jet recording method using the ink composition.

In order to solve the above-mentioned problems, the present inventors have conducted extensive studies, and as a result, the polymerizable compound is present in the system in an emulsion state, and a combination of a polymerization initiator and a specific sensitizing dye is used. The present invention was completed by finding out that the extracurricular activities can be solved.
That is, the configuration of the present invention is as follows.
[1] (A) a sensitizing dye represented by the following general formula (I), (B) a polymerization initiator, (C) a polymerizable compound having an ethylenically unsaturated bond, and (D) water. An ink composition comprising the polymerizable compound (C) in an emulsion state in the ink composition.

(In general formula (I), X represents O, S, or NR, R represents a hydrogen atom, an alkyl group, or an acyl group. N represents 0 or 1. R ^{1 to} R ^8. Each independently represents a hydrogen atom or a monovalent substituent, and R ¹ , R ² , R ³ , and R ⁴ may be bonded to each other to form a ring. R ⁵ or R ⁶ and R ⁷ or R ⁸ may be linked to each other to form an aliphatic ring, but they do not form an aromatic ring.
[2] The ink composition according to [1], comprising (B) at least one compound selected from the group consisting of α-aminoketones and acylphosphine oxides as the polymerization initiator.
[3] The ink composition according to [1] or [2], further comprising (E) a pigment as a colorant.
[4] The ink composition according to any one of [1] to [3], which is for inkjet recording.
[5] (a) A step of ejecting the ink composition according to [4] onto a recording medium, and (b) A step of irradiating the ejected ink composition with actinic radiation to cure the ink composition. An ink jet recording method comprising:

Although the action of the compound of the present invention is not clear, it is estimated as follows.
The sensitizing dye represented by the general formula (I) used in the present invention has a high triplet excitation energy and is used in combination with a polymerization initiator, particularly α-aminoketones and acylphosphine used in a preferred embodiment of the present invention. In order to efficiently initiate triplet energy transfer to polymerization initiators such as oxides and generate initiating species with high sensitivity, a polymerizable compound existing in an emulsion state in an aqueous medium is cured with high sensitivity. It is thought that it is possible. In addition, since the crystallinity is lower than that of a thioxanthone compound generally used as a sensitizing dye to be sensitized by such a mechanism and it is difficult to precipitate, the ink composition has excellent stability as a solution, and When the ink composition to be used is used for inkjet recording, it is considered that excellent ejection stability can be obtained.
Thus, in the present invention, it is considered that high sensitivity, solution stability, and ejection stability can be combined.

  According to the present invention, it can be cured with high sensitivity even when irradiated with low-output radiation, and a high-quality image can be formed. It is possible to provide a water-based actinic radiation curable ink composition that does not cause an ink jet recording method using the ink composition.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.
First, the characteristics of the water-based ink composition of the present invention and the actions and effects of image recording by the water-based inkjet method, which is a main application example of the water-based active energy ray-curable ink composition, will be described.
Examples of the actinic radiation that can be used in the present invention include ultraviolet rays and electron beams as will be described in detail below. However, this does not mean that the active energy rays applicable to the present invention are limited to ultraviolet rays.

First, each constituent material of the aqueous active energy ray-curable ink composition of the present invention will be specifically described.
The ink composition of the present invention comprises (A) a sensitizing dye represented by the general formula (I) (hereinafter referred to as a specific sensitizing dye), (B) a polymerization initiator, and (C) an ethylenically unsaturated bond. And (D) water, and the polymerizable compound (C) is present in an emulsion state in the ink composition.

<(B) Polymerization initiator>
The ink composition of the present invention contains a polymerization initiator that is decomposed by actinic radiation to generate radicals and initiate polymerization of the polymerizable compound.
As the polymerization initiator, any compound generally known as a photopolymerization initiator, for example, (i) aromatic ketones, (ii) aromatic onium salt compounds, (iii) organic peroxides, (iv) Hexaarylbiimidazole compounds, (v) ketoxime ester compounds, (vi) borate compounds, (vii) azinium compounds, (viii) metallocene compounds, (ix) active ester compounds, (x) compounds having a carbon halogen bond, etc. It can be appropriately selected and used, but from the viewpoint of curing sensitivity, it preferably contains one or more polymerization initiators selected from the group consisting of α-aminoketones and acylphosphine oxides, and α-aminoketones And acylphosphine oxides are particularly preferred.

  Examples of the α-aminoketone compound preferably used as a polymerization initiator in the present invention include compounds represented by the following general formula (1).

In the general formula (1), Ar is a phenyl group substituted with —SR ¹³ or —N (R ^7E ) (R ^8E ), where R ¹³ represents a hydrogen atom or an alkyl group.
R ^1D and R ^2D are each independently an alkyl group having 1 to 8 carbon atoms. R ^1D and R ^2D may be bonded to each other to form an alkylene group having 2 to 9 carbon atoms. R ^3D and R ^4D are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 2 to 4 carbon atoms substituted with 1 to 4 carbon atoms, or an alkenyl group having 3 to 5 carbon atoms. Represents a group. Here, R ^3D and R ^4D may be bonded to each other to form an alkylene group having 3 to 7 carbon atoms, and the alkylene group is —O— or —N (R ¹² ) — in the alkylene chain. Wherein R ¹² represents an alkyl group having 1 to 4 carbon atoms.
R ^7E and R ^8E each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 2 to 4 carbon atoms substituted with an alkoxy group having 1 to 4 carbon atoms, or an alkenyl group having 3 to 5 carbon atoms. Represents a group. Here, R ^7E and R ^8E may be bonded to each other to form an alkylene group having 3 to 7 carbon atoms, and the alkylene group is —O— or —N (R ¹² ) — in the alkylene chain. May be included. Here, R ¹² has the same meaning as described above.

  Examples of compounds encompassed by α-aminoketones include 2-methyl-1-phenyl-2-morpholinopropan-1-one, 2-methyl-1- [4- (hexyl) phenyl] -2-morpho And linopropan-1-one, 2-ethyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, and the like. Further, Irgacure series manufactured by Ciba Geigy, such as Irgacure 907, Irgacure 369, Irgacure 379, etc., are also available as commercial products, and these are also compounds included in α-aminoketones, and are suitable for the present invention. Can be used.

  Examples of the compound included in the acylphosphine oxides which are polymerization initiators preferably used in the present invention include compounds represented by the following general formula (2) or general formula (3).

In the general formula (2), R ^5D and R ^6D each independently represent an aliphatic group, an aromatic group, an aliphatic oxy group, an aromatic oxy group, or a heterocyclic group, and R ^7D represents an aliphatic group, Represents an aromatic group or a heterocyclic group.

Wherein R ^5D, aliphatic groups which may R ^6D, or R ^7D represents an aliphatic group, for example, an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an alkynyl group, substituted alkynyl group, an aralkyl group, or Examples thereof include a substituted aralkyl group, and among them, an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an aralkyl group, or a substituted aralkyl group are preferable, and an alkyl group and a substituted alkyl group are particularly preferable. The aliphatic group may be a cyclic aliphatic group or a chain aliphatic group. The chain aliphatic group may have a branch.

  Examples of the alkyl group include linear, branched and cyclic alkyl groups, and the number of carbon atoms of the alkyl group is preferably 1 to 30, and more preferably 1 to 20. The preferred range of the number of carbon atoms in the alkyl part of the substituted alkyl group is the same as in the case of the alkyl group. Further, the alkyl group may be either a substituted alkyl group or an unsubstituted alkyl group. Examples of the alkyl group include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group, decyl group, dodecyl group, octadecyl group, cyclohexyl group, cyclopentyl group, neopentyl group, An isopropyl group, an isobutyl group, etc. are mentioned.

Examples of the substituent of the substituted alkyl group include a carboxyl group, a sulfo group, a cyano group, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom), a hydroxy group, and an alkoxycarbonyl group having 30 or less carbon atoms (for example, methoxycarbonyl). Group, ethoxycarbonyl group, benzyloxycarbonyl group), alkylsulfonylaminocarbonyl group having 30 or less carbon atoms, arylsulfonylaminocarbonyl group, alkylsulfonyl group, arylsulfonyl group, acylaminosulfonyl group having 30 or less carbon atoms, carbon number 30 The following alkoxy groups (for example, methoxy group, ethoxy group, benzyloxy group, phenoxyethoxy group, phenethyloxy group, etc.), alkylthio groups having 30 or less carbon atoms (for example, methylthio group, ethylthio group, methylthioethylthioethyl group, etc.) An aryloxy group having 30 or less carbon atoms (for example, phenoxy group, p-tolyloxy group, 1-naphthoxy group, 2-naphthoxy group, etc.), nitro group, alkyl group having 30 or less carbon atoms, alkoxycarbonyloxy group, aryloxy A carbonyloxy group, an acyloxy group having 30 or less carbon atoms (for example, acetyloxy group, propionyloxy group, etc.), an acyl group having 30 or less carbon atoms (for example, acetyl group, propionyl group, benzoyl group, etc.), carbamoyl group (for example, Carbamoyl group, N, N-dimethylcarbamoyl group, morpholinocarbonyl group, piperidinocarbonyl group, etc.), sulfamoyl group (for example, sulfamoyl group, N, N-dimethylsulfamoyl group, morpholinosulfonyl group, piperidinosulfonyl group) Etc.), an aryl group having 30 or less carbon atoms For example, phenyl group, 4-chlorophenyl group, 4-methylphenyl group, α-naphthyl group, etc.), substituted amino group (for example, amino group, alkylamino group, dialkylamino group, arylamino group, diarylamino group, acylamino group) Etc.), substituted ureido groups, substituted phosphono groups, heterocyclic groups and the like. Here, the carboxyl group, the sulfo group, the hydroxy group, and the phosphono group may be in a salt state. At that time, examples of the cation forming the salt include M ⁺ described later.

  Examples of the alkenyl group include linear, branched, and cyclic alkenyl groups. The number of carbon atoms of the alkenyl group is preferably 2 to 30, and more preferably 2 to 20. The alkenyl group may be a substituted alkenyl group having a substituent or an unsubstituted alkenyl group, and the preferred range of the number of carbon atoms in the alkenyl part of the substituted alkenyl group is the same as that of the alkenyl group. . Examples of the substituent of the substituted alkenyl group include the same substituents as those of the substituted alkyl group.

  Examples of the alkynyl group include linear, branched, and cyclic alkynyl groups, and the number of carbon atoms of the alkynyl group is preferably 2 to 30, and more preferably 2 to 20. The alkynyl group may be a substituted alkynyl group having a substituent or an unsubstituted alkynyl group, and the preferred range of the number of carbon atoms in the alkynyl part of the substituted alkynyl group is the same as in the case of the alkynyl group. . Examples of the substituent for the substituted alkynyl group include the same substituents as those for the substituted alkyl group.

  Examples of the aralkyl group include linear, branched, and cyclic aralkyl groups. The number of carbon atoms in the aralkyl group is preferably 7 to 35, and more preferably 7 to 25. The aralkyl group may be a substituted aralkyl group having a substituent or an unsubstituted aralkyl group, and the preferred range of the number of carbon atoms in the aralkyl part of the substituted aralkyl group is the same as in the case of the aralkyl group. . Examples of the substituent for the substituted aralkyl group include the same substituents as those for the substituted alkyl group.

Examples of the aromatic group in the case where R ^5D , R ^6D, or R ^7D represents an aromatic group include an aryl group and a substituted aryl group. As a carbon atom number of an aryl group, 6-30 are preferable and 6-20 are more preferable. The preferable range of the number of carbon atoms in the aryl part of the substituted aryl group is the same as that of the aryl group. Examples of the aryl group include a phenyl group, an α-naphthyl group, a β-naphthyl group, and the like. Examples of the substituent for the substituted aryl group include the same substituents as those for the substituted alkyl group.

The aliphatic oxy group when R ^5D or R ^6D represents an aliphatic oxy group is preferably an alkoxy group having 1 to 30 carbon atoms, for example, a methoxy group, an ethoxy group, a butoxy group, an octyloxy group, a phenoxyethoxy group Groups and the like. However, it is not limited to these.

The aromatic oxy group when R ^5D or R ^6D represents an aromatic oxy group is preferably an aryloxy group having 6 to 30 carbon atoms, such as phenoxy group, methylphenyloxy group, chlorophenyloxy group, methoxyphenyl An oxy group, an octyloxyphenyloxy group, etc. are mentioned. However, it is not limited to these.

The heterocyclic group when R ^5D , R ^6D or R ^7D represents a heterocyclic group is preferably a heterocyclic group containing an N, O or S atom, such as a pyridyl group, a furyl group, a thienyl group, an imidazolyl group. And pyrrolyl group.

R ^8D and R ^10D in the general formula (3) each independently represent an alkyl group, an aryl group, or a heterocyclic group, and R ^9D represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, or a heterocyclic group. Represents. The alkyl group, aryl group, heterocyclic group, alkoxy group and aryloxy group represented by the R ^8D , R ^9D or R ^10D may have a substituent. Examples of the substituent are the same as those in the formula (2).

  The alkyl group, aryl group, heterocyclic group, alkoxy group and aryloxy group in the general formula (3) have the same meaning as in the general formula (2).

  Examples of the acylphosphine oxide compound represented by the general formula (2) or (3) include, for example, Japanese Patent Publication No. 63-40799, Japanese Patent Publication No. 5-29234, Japanese Patent Application Laid-Open No. 10-95788, Japanese Patent Application Laid-Open No. Examples thereof include compounds described in JP-A No. 10-29997.

  Specific examples of the acylphosphine oxide compound include the following compounds (Exemplary compounds (P-1) to (P-26)), but the present invention is not limited to these compounds. Absent.

  Among the exemplified compounds, for example, (P-2) [2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide] is available under the trade name of Darocur TPO (manufactured by Ciba Specialty Chemicals), (P-19) [Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide] is available under the trade name Irgacure 819 (Ciba Specialty Chemicals).

  The content of the polymerization initiator (B) in the ink composition of the present invention is preferably in the range of 0.1 to 30% by mass, and in the range of 0.2 to 20% by mass in terms of solid content. Is more preferable.

In the ink composition of the present invention, the polymerizable compound (C) described later needs to be present as an emulsion in the ink composition, but (B) the polymerization initiator is in the same phase as (C) the polymerizable compound. It may be present in the aqueous phase.
(B) When the polymerization initiator is present in the aqueous phase, the polymerization initiator has hydrophilic properties such as carboxyl groups (including salts thereof), sulfo groups (including salts thereof), ethyleneoxy groups in the molecule. A water-soluble compound having the above substituents may be selected and used.
From the viewpoint of sensitivity, (B) the polymerization initiator is preferably present in the same phase as (C) the polymerizable compound.

The ink composition of the present invention preferably contains at least the specific polymerization initiator as a photopolymerization initiator, but instead of or in addition to the specific polymerization initiator, other than the preferable specific polymerization initiator. Other photopolymerization initiators may be used.
Examples of other polymerization initiators include camphorquinone, benzophenone, benzophenone derivatives, acetophenone, acetophenone derivatives, such as α-hydroxycycloalkylphenyl ketones or 2-hydroxy-2-methyl-1-phenyl-propanone, dialkoxy. Acetophenones, α-hydroxy- or 4-aroyl-1,3-dioxolanes, benzoin alkyl ethers and benzyl ketals, such as benzyl dimethyl ketal, phenyl glyoxalate and its derivatives, dimeric phenyl glyoxalate, perester Such as benzophenone tetracarboxylic acid peresters (eg as described in EP 1126,541), halomethyltriazines such as 2- [2- (4-methoxy-phenyl) Vinyl] -4,6-bis-trichloromethyl [1,3,5] triazine, 2- (4-methoxy-phenyl) -4,6-bis-trichloromethyl [1,3,5] triazine, 2- ( 3,4-dimethoxy-phenyl) -4,6-bis-trichloromethyl [1,3,5] triazine, 2-methyl-4,6-bis-trichloromethyl [1,3,5] triazine, hexaarylbis Imidazole / co-initiator systems such as ortho-chlorohexaphenyl-bisimidazole in combination with 2-mercaptobenzothiazole; ferrocenium compounds or titanocenes such as dicyclopentadienyl-bis (2,6-difluoro -3-pyrrolo-phenyl) titanium; for example, o-a as described in GB 2,339,571 It is also possible to use mixtures of Le oxime ester compound. A boric acid compound can also be used as a co-initiator.

  The content of the polymerization initiator (B) in the ink composition of the present invention is preferably 0.01 to 35 parts by mass with respect to 100 parts by mass of the polymerizable compound (C) having an ethylenically unsaturated bond described later. The content is preferably 0.1 to 30 parts by mass, and more preferably 0.5 to 30 parts by mass. In addition, content of a polymerization initiator here means the total content of the polymerization initiator containing a preferable specific polymerization initiator and another polymerization initiator.

<Sensitizing dye>
The ink composition of the present invention contains a sensitizing dye in order to promote decomposition of the polymerization initiator by irradiation with actinic rays. As the sensitizing dye, a compound represented by the following general formula (I) is an essential component. Contained as.
In general, 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. The generation of active species such as these causes the active species generated here to cause and accelerate the polymerization and curing reaction of the polymerizable compound described later.

As the sensitizing dye, a compound corresponding to the wavelength of actinic radiation that generates an initiating species in the polymerization initiator used in the ink composition may be used, but it should be used for a curing reaction of a general ink composition. In view of the above, examples of preferable sensitizing dyes include those having an absorption wavelength in the 350 nm to 450 nm region.
[(A) Sensitizing dye represented by formula (I)]
The ink composition of the invention is required to contain one or more specific sensitizing dyes belonging to the compound represented by the following general formula (I).

In the formula (I), X represents O, S, or NR, where R represents a hydrogen atom, an alkyl group, or an acyl group. An alkyl group or an acyl group is preferable. n represents 0 or 1.
X is preferably O or S, and more preferably S. Here, when n is 0, there is no carbon atom (CR ⁷ R ⁸ ) bonded to R ⁷ and R ^8, and X containing a hetero atom and carbon atoms bonded to R ⁵ and R ⁶ are Directly bonded to form a 5-membered heterocycle containing X.

R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , and R ⁸ each independently represent a hydrogen atom or a monovalent substituent.
When R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ represent a monovalent substituent, examples of the monovalent substituent include a halogen atom, aliphatic group, aromatic Group, heterocyclic group, cyano group, hydroxy group, nitro group, amino group, alkylamino group, alkoxy group, aryloxy group, amide group, arylamino group, ureido group, sulfamoylamino group, alkylthio group, arylthio Group, alkoxycarbonylamino group, sulfonamido group, carbamoyl group, sulfamoyl group, sulfonyl group, alkoxycarbonyl group, heterocyclic oxy group, azo group, acyloxy group, carbamoyloxy group, silyloxy group, aryloxycarbonyl group, aryloxycarbonyl Amino group, imide group, heterocyclic thio group, sulfinyl group, phosphoryl group, acyl , A carboxyl group or a sulfo group. Among them, preferably, an alkyl group, an alkoxy group, a halogen atom.

In addition, as R < ¹ >, R < ² >, R < ³ >, R < ⁴ >, R < ⁵ >, R < ⁶ >, R < ⁷ > and R < ⁸ > in General Formula (I) represents a monovalent substituent, Ten alkyl groups are preferable, and those having 1 to 4 carbon atoms such as methyl group, ethyl group, propyl group, n-butyl group, sec-butyl group and t-butyl group are more preferable.
Similarly, alkoxy groups include those having 1 to 4 carbon atoms such as methoxy, ethoxy, hydroxyethoxy, propoxy, n-butoxy, isobutoxy, sec-butoxy, and t-butoxy. Preferably mentioned.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

R ¹ , R ² , R ³ , and R ⁴ may be linked to each other, for example, fused together to form a ring.
Examples of the ring structure in the case where these form a ring include a 5- to 6-membered aliphatic ring and an aromatic ring, and may be a heterocyclic ring containing an element other than a carbon atom, or may be formed. The rings may be further combined to form a binuclear ring, for example, a condensed ring. Further, these ring structures may further have a substituent exemplified in the case where R ^{1 to} R ⁸ represent a monovalent substituent in the general formula (I). N, O, and S can be mentioned as an example of a hetero atom in case the formed ring structure is a heterocyclic ring.

When n = 1, R ⁵ or R ⁶ and R ⁷ or R ⁸ may be connected to each other to form an aliphatic ring, but do not form an aromatic ring. The number of ring members of the aliphatic ring is preferably a 3- to 6-membered ring, more preferably a 5-membered ring or a 6-membered ring.

  Examples of sensitizing dyes that can be used more suitably include sensitizing dyes represented by the following general formula (IA).

In the formula (IA), X represents O or S. n represents 0 or 1. R ^1A , R ^2A , R ^3A , R ^4A , R ^5A , R ^6A , R ^7A and R ^8A are each independently a hydrogen atom, alkyl group, halogen atom, hydroxyl group, cyano group, nitro group, amino group, alkylthio group Represents an alkylamino group, an alkoxy group, an alkoxycarbonyl group, an acyloxy group, an acyl group, a carboxyl group or a sulfo group. Two adjacent R ^1A , R ^2A , R ^3A , and R ^4A may be linked (condensed) with each other to form a ring. R ^5A or R ^6A and R ^7A or R ^8A may be linked to each other to form an aliphatic ring, but do not form an aromatic ring.

  Examples of sensitizing dyes that can be used more suitably include sensitizing dyes represented by the following general formula (IB).

In the formula (IB), X represents O or S. R ^1B , R ^2B , R ^3B , R ^4B , R ^5B , R ^6B , R ^7B and R ^8B are each independently a hydrogen atom, alkyl group, halogen atom, hydroxyl group, cyano group, nitro group, amino group, alkylthio group Represents an alkylamino group, an alkoxy group, an alkoxycarbonyl group, an acyloxy group, an acyl group, a carboxyl group or a sulfo group. R ^1B , R ^2B , R ^3B , and R ^4B may be linked (condensed) with each other adjacent two to form a ring. R ^5B or R ^6B and R ^7B or R ^8B may ^combine with each other to form an aliphatic ring, but do not form an aromatic ring.

  Examples of sensitizing dyes that can be used more suitably include sensitizing dyes represented by the following general formula (IC).

In the formula (I-C), R ^1C , R ^2C , R ^3C , R ^4C , R ^5C , R ^6C , R ^7C and R ^8C are each independently a hydrogen atom, alkyl group, halogen atom, hydroxyl group, cyano group Nitro group, amino group, alkylthio group, alkylamino group, alkoxy group, alkoxycarbonyl group, acyloxy group, acyl group, carboxyl group or sulfo group.
R ^1C , R ^2C , R ^3C , and R ^4C may be formed by condensing two adjacent groups to form a 5- to 6-membered aliphatic ring or aromatic ring, and these rings are Heterocycles containing elements other than carbon atoms may be used, and the formed rings may be further combined to form a binuclear ring, for example, a condensed ring. Further, these ring structures are exemplified when R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ represent a monovalent substituent in the general formula (I). Each substituent may be further included. When the ring structure is a heterocyclic ring, examples of heteroatoms include N, O, and S. R ^5C or R ^6C and R ^7C or R ^8C may ^combine with each other to form an aliphatic ring, but do not form an aromatic ring.

In addition, at least one of R ^1C , R ^2C , R ^3C , R ^4C , R ^5C , R ^6C , R ^7C and R ^8C is preferably a halogen atom. Preferred substitution positions for the halogen atom include R ^1C , R ^2C , R ^3C and R ^4C , with R ^2C being most preferred. The number of halogen atoms is preferably one or two, more preferably one.

Further, R ^2C is preferably a substituent other than hydrogen, and among them, an alkyl group, a halogen atom, an acyloxy group, and an alkoxycarbonyl group are preferable, and an alkyl group and a halogen atom are particularly preferable. It is very sensitive.

Either R ^7C or R ^8C is preferably a substituent other than hydrogen, and more preferably both are substituents other than hydrogen. Preferable substituents include an alkyl group, a halogen atom, a carboxyl group, and an alkoxycarbonyl group. Among them, an alkyl group and an alkoxycarbonyl group are preferable, and an alkyl group is most preferable.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and a chlorine atom, a bromine atom and an iodine atom are preferable.

When any of R ^1C , R ^2C , R ^3C , R ^4C , R ^5C , R ^6C , R ^7C , and R ^8C is an alkyl group, the alkyl group includes an alkyl group having 1 to 10 carbon atoms. Preferably, those having 1 to 4 carbon atoms such as methyl group, ethyl group, propyl group, n-butyl group, sec-butyl group and t-butyl group are more preferable.

When any of R ^1C , R ^2C , R ^3C , R ^4C , R ^5C , R ^6C , R ^7C , and R ^8C is an acyloxy group, the acyloxy group includes an aliphatic acyloxy group having 2 to 10 carbon atoms. Group is preferable, and an aliphatic acyloxy group having 2 to 5 carbon atoms is more preferable.
When any of R ^1C , R ^2C , R ^3C , R ^4C , R ^5C , R ^6C , R ^7C , and R ^8C is an alkoxycarbonyl group, the alkoxycarbonyl group is an aliphatic group having 2 to 10 carbon atoms. An alkoxycarbonyl group is preferable, and an alkoxycarbonyl group having 2 to 5 carbon atoms is more preferable.

  Specific examples of the specific sensitizing dye that can be suitably used in the present invention [Exemplary compounds (I-1) to (I-133)] are shown below, but the present invention is not limited thereto.

  Specific sensitizing dyes according to the present invention include, for example, Japanese Patent Application Laid-Open No. 2004-189695, “Tetrahedron” Vol. 49, p939 (1993), “Journal of Organic Chemistry” p893 (1945), and “ Journal of Organic Chemistry "p4939 (1965) and the like.

The content of the specific sensitizing dye in the ink composition of the present invention is preferably about 0.05 to 30% by mass, more preferably 0.1 to 20% by mass in terms of solid content with respect to the ink composition. 0.2 to 10% by mass is more preferable.
In addition, since this specific sensitizing dye hardly absorbs in the visible light region, it has an advantage that there is no concern of affecting the hue of the ink composition even if an amount capable of exhibiting the effect is added. . If content is described in relation to the (B) polymerization initiator, the polymerization initiator (total amount of the specific polymerization initiator and the other polymerization initiator): 200: 1 to 1 by mass ratio of the specific sensitizing dye. : 200, preferably 50: 1 to 1:50, more preferably 20: 1 to 1: 5.

In the ink composition of the present invention, the polymerizable compound (C) described later exists as an emulsion in the ink composition, but (A) the specific sensitizing dye is present in the same phase as the polymerizable compound. Or may be present in the aqueous phase.
(A) When a specific sensitizing dye is present in the aqueous phase, a carboxyl group (including a salt thereof), a sulfo group (including a salt thereof), an ethyleneoxy group, or the like in the molecule of the sensitizing dye What was made water-soluble by introducing a hydrophilic substituent may be used.
In the present invention, it is preferable from the viewpoint of sensitivity that the (A) specific sensitizing dye is present in the same phase as the (C) polymerizable compound.
At this time, the (A) specific sensitizing dye is preferably soluble in the (C) polymerizable compound. Here, being soluble means that (A) the specific sensitizing dye is dissolved at 1% by mass or more in the polymerizable compound (C) at room temperature (25 ° C.), and it is dissolved at 3% by mass or more. Is preferred. From the viewpoint of preventing the precipitation of the (A) specific sensitizing dye, the amount of the (A) specific sensitizing dye used is preferably less than the upper limit of the amount dissolved in the (C) polymerizable compound. More preferably, it is 70 mass% or less.

[Other sensitizing dyes]
In the present invention, in addition to the specific sensitizing dye described above, a known sensitizing dye can be used in combination as long as the effects of the present invention are not impaired. The other sensitizing dye is 1: 5 to 100: 1, preferably 1: 1 to 100: 1, more preferably, in a mass ratio of the specific sensitizing dye to the other sensitizing dye with respect to the specific sensitizing dye. Can be added in an amount of 2: 1 to 100: 1.
Examples of known sensitizing dyes that can be used in combination include benzophenone, thioxanthone, in particular isopropylthioxanthone, anthraquinone and 3-acylcoumarin derivatives, terphenyl, styryl ketone and 3- (aroylmethylene) thiazoline, camphorquinone, eosin, Examples include rhodamine and erythrosine.

Examples of sensitizing dyes that can be used in combination are as follows.
(1) Thioxanthone Thioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-dodecylthioxanthone, 2,4-di-ethylthioxanthone, 2,4-dimethylthioxanthone, 1-methoxycarbonylthioxanthone, 2-ethoxycarbonylthioxanthone, 3 -(2-methoxyethoxycarbonyl) thioxanthone, 4-butoxycarbonylthioxanthone, 3-butoxycarbonyl-7-methylthioxanthone, 1-cyano-3-chlorothioxanthone, 1-ethoxycarbonyl-3-chlorothioxanthone, 1-ethoxycarbonyl- 3-ethoxythioxanthone, 1-ethoxycarbonyl-3-aminothioxanthone, 1-ethoxycarbonyl-3-phenylsulfurylthioxanthone, 3,4- Di- [2- (2-methoxyethoxy) ethoxycarbonyl] thioxanthone, 1-ethoxycarbonyl-3- (1-methyl-1-morpholinoethyl) thioxanthone, 2-methyl-6-dimethoxymethylthioxanthone, 2-methyl-6 -(1,1-dimethoxybenzyl) thioxanthone, 2-morpholinomethylthioxanthone, 2-methyl-6-morpholinomethylthioxanthone, n-allylthioxanthone-3,4-dicarboximide, n-octylthioxanthone-3,4-di Carboximide, N- (1,1,3,3-tetramethylbutyl) thioxanthone-3,4-dicarboximide, 1-phenoxythioxanthone, 6-ethoxycarbonyl-2-methoxythioxanthone, 6-ethoxycarbonyl-2- Methylthioxanthate , Thioxanthone-2-polyethylene glycol ester, 2-hydroxy-3- (3,4-dimethyl-9-oxo -9H- thioxanthone-2-yloxy) -N, N, N-trimethyl-1-propanaminium chloride;

(2) Benzophenone Benzophenone, 4-phenylbenzophenone, 4-methoxybenzophenone, 4,4′-dimethoxybenzophenone, 4,4′-dimethylbenzophenone, 4,4′-dichlorobenzophenone, 4,4′-dimethylaminobenzophenone, 4 , 4'-diethylaminobenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4- (4-methylthiophenyl) benzophenone, 3,3'-dimethyl-4-methoxybenzophenone, methyl-2-benzoylbenzoate 4- (2-hydroxyethylthio) benzophenone, 4- (4-tolylthio) benzophenone, 4-benzoyl-N, N, N-trimethylbenzenemethanaminium chloride, 2-hydroxy-3- (4-benzoylphenoxy) ) -N, N, N-trimethyl-1-propanaminium chloride monohydrate, 4- (13-acryloyl-1,4,7,10,13-pentaoxatridecyl) benzophenone, 4-benzoyl-N , N-dimethyl-N- [2- (1-oxo-2-propenyl) oxy] ethylbenzenemethanaminium chloride;

(3) 3-acylcoumarin 3-benzoylcoumarin, 3-benzoyl-7-methoxycoumarin, 3-benzoyl-5,7-di (propoxy) coumarin, 3-benzoyl-6,8-dichlorocoumarin, 3-benzoyl- 6-chlorocoumarin, 3,3′-carbonylbis [5,7-di (propoxy) coumarin], 3,3′-carbonylbis (7-methoxycoumarin), 3,3′-carbonylbis (7-diethylaminocoumarin) ), 3-isobutyroylcoumarin, 3-benzoyl-5,7-dimethoxycoumarin, 3-benzoyl-5,7-diethoxycoumarin, 3-benzoyl-5,7-dibutoxycoumarin, 3-benzoyl-5 7-di (methoxyethoxy) coumarin, 3-benzoyl-5,7-di (allyloxy) coumarin, 3-benzoyl-7- Dimethylaminocoumarin, 3-benzoyl-7-diethylaminocoumarin, 3-isobutyroyl-7-dimethylaminocoumarin, 5,7-dimethoxy-3- (1-naphthoyl) coumarin, 5,7-dimethoxy-3- (1-naphthoyl) ) Coumarin, 3-benzoylbenzo [f] coumarin, 7-diethylamino-3-thienoylcoumarin, 3- (4-cyanobenzoyl) -5,7-dimethoxycoumarin;

(4) 3- (Aroylmethylene) thiazoline 3-methyl-2-benzoylmethylene-β-naphthothiazoline, 3-methyl-2-benzoylmethylenebenzothiazoline, 3-ethyl-2-propionylmethylene-β-naphthothiazoline;

(5) Anthracene 9,10-dimethoxy-anthracene, 9,10-diethoxy-anthracene, 9,10-dimethoxy-2-ethyl-anthracene,

(6) Other carbonyl compounds Acetophenone, 3-methoxyacetophenone, 4-phenylacetophenone, benzyl, 2-acetylnaphthalene, 2-naphthaldehyde, 9,10-naphtholaquinone, 9-fluorenone, dibenzosuberone, xanthone, 2,5 -Bis (4-diethylaminobenzylidene) cyclopentanone, α- (para-dimethylaminobenzylidene) ketone, such as 2- (4-dimethylaminobenzylidene) indan-1-one or 3- (4-dimethylaminophenyl)- 1-Indan-5-ylpropenone, 3-phenylthiophthalimide, N-methyl-3,5-di (ethylthio) phthalimide.

<(C) Polymerizable compound having an ethylenically unsaturated bond>
The ink composition of the present invention contains (C) a polymerizable compound having an ethylenically unsaturated bond (hereinafter, appropriately referred to as “polymerizable compound”).
One of the characteristics of the present invention is that the polymerizable compound having an ethylenically unsaturated bond is present in an emulsion state in the ink composition. Examples of the polymerizable compound include acryloyl and methacryloyl groups. A compound having at least one ethylenically unsaturated bond capable of radical polymerization in the molecule is used.

These (C) polymerizable compounds according to the present invention are characterized in that they are present substantially in an emulsion state in an aqueous ink composition containing water as a main solvent. That is, it is selected from those having a solid monomer, oligomer or polymer chemical form at room temperature and normal pressure.
In order to form an emulsion state in a solvent containing water as a main component, a polymerizable compound that is solid at ordinary temperature (25 ° C.) and normal pressure, or has lipophilic and hydrophobic properties and does not dissolve in water. It is necessary to select.
In the present invention, “not soluble in water” means that the solubility in water at room temperature (25 ° C.) is less than 5% by mass, and in the present invention, the one having a solubility of less than 2% by mass is used. And more preferably a compound having a solubility of less than 1% by mass.

The presence of these polymerizable compounds in the aqueous ink composition in an emulsion state can be confirmed by, for example, observation with an optical microscope, an electron microscope, or the like, or a method such as a dynamic light scattering method. The emulsion particle size is arbitrary as long as it does not affect the discharge properties, but it is usually preferably in the range of 50 to 500 nm.
As the particle size distribution measurement method of the emulsion in the present invention, optical microscopy, confocal laser microscopy, electron microscopy, atomic force microscopy, static light scattering, laser diffraction, dynamic light scattering, centrifugal sedimentation Methods, electric pulse measurement methods, chromatography methods, ultrasonic attenuation methods, and the like are known, and devices corresponding to the respective principles are commercially available.

  In view of the particle size range and ease of measurement in the present invention, the dynamic light scattering method is preferred for measuring the particle size of the dispersed particles. As a commercially available measuring device using dynamic light scattering, Nanotrac UPA (Nikkiso Co., Ltd.), dynamic light scattering type particle size distribution measuring device LB-550 (Horiba, Ltd.), a concentrated particle size analyzer FPAR-1000 (Otsuka Electronics Co., Ltd.) etc. are mentioned.

  Examples of radically polymerizable compounds capable of forming an emulsion state in an aqueous ink composition include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and salts and esters thereof. , Urethanes, acid amides and acid anhydrides, and further selected from acrylonitrile, styrene derivatives, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, unsaturated polyurethanes, etc., and have the above properties. However, the present invention is not limited to these. Moreover, even if it is a monofunctional compound which has only one ethylenically unsaturated bond in a molecule | numerator, the polyfunctional compound which has this may be sufficient.

  Specific examples of the radical polymerizable compound that can be preferably used in the present invention and can exist in the emulsion state in the aqueous ink composition are listed below, but the present invention is not limited to these compounds.

<Examples of acrylate compounds>
The acrylates suitably used as the polymerizable compound (C) in the ink composition of the present invention may be monofunctional. It may be polyfunctional, and examples thereof include the following compounds.
(Examples of monofunctional alkyl acrylates)
Methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, isobornyl acrylate, cyclohexyl acrylate, dicyclopentenyl acrylate , Dicyclopentenyloxyethyl acrylate, benzyl acrylate.

(Examples of monofunctional hydroxy acrylates)
2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxy-3-chloropropyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxy-3-allyloxypropyl acrylate, 2-acryloyloxyethyl-2 -Hydroxypropyl phthalate.

(Example of monofunctional halogen-containing acrylates)
2,2,2-trifluoroethyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, 1H-hexafluoroisopropyl acrylate, 1H, 1H, 5H-octafluoropentyl acrylate, 1H, 1H, 2H, 2H- Heptadecafluorodecyl acrylate, 2,6-dibromo-4-butylphenyl acrylate, 2,4,6-tribromophenoxyethyl acrylate, 2,4,6-tribromophenol 3EO addition acrylate.

(Examples of monofunctional ether-containing acrylates)
2-methoxyethyl acrylate, 1,3-butylene glycol methyl ether acrylate, butoxyethyl acrylate, methoxytriethylene glycol acrylate, methoxypolyethylene glycol # 400 acrylate, methoxydipropylene glycol acrylate, methoxytripropylene glycol acrylate, methoxypolypropylene glycol acrylate, Ethoxydiethylene glycol acrylate, 2-ethylhexyl carbitol acrylate, tetrahydrofurfuryl acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, phenoxy polyethylene glycol acrylate, cresyl polyethylene glycol acrylate, p-nonylphenoxyethyl acrylate DOO, p- nonylphenoxy polyethylene glycol acrylate, glycidyl acrylate.

(Examples of monofunctional carboxyl acrylates)
β-carboxyethyl acrylate, succinic acid monoacryloyloxyethyl ester, ω-carboxypolycaprolactone monoacrylate, 2-acryloyloxyethyl hydrogen phthalate, 2-acryloyloxypropyl hydrogen phthalate, 2-acryloyloxypropyl hexahydrohydrogen phthalate, 2- Acryloyloxypropyltetrahydrophthalate.

(Examples of other monofunctional acrylates)
N, N-dimethylaminoethyl acrylate, N, N-dimethylaminopropyl acrylate, morpholinoethyl acrylate, trimethylsiloxyethyl acrylate, diphenyl-2-acryloyloxyethyl phosphate, 2-acryloyloxyethyl acid phosphate, caprolactone-modified-2-acryloyl Oxyethyl acid phosphate.

(Example of bifunctional acrylates)
1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol # 200 diacrylate, polyethylene glycol # 300 diacrylate, polyethylene glycol # 400 diacrylate, polyethylene glycol # 600 diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, tetrapropylene glycol diacrylate, polypropylene glycol # 400 diacrylate, polypropylene glycol # 700 diacrylate, neopentyl glycol diacrylate, Neopentyl glycol PO (propylene Oxide) modified diacrylate, hydroxypivalic acid neopentyl glycol ester diacrylate, caprolactone adduct diacrylate of hydroxypivalic acid neopentyl glycol ester, 1,6-hexanediol bis (2-hydroxy-3-acryloyloxypropyl) ether, 1,9-nonanediol diacrylate, pentaerythritol diacrylate, pentaerythritol diacrylate monostearate, pentaerythritol diacrylate monobenzoate, bisphenol A diacrylate, EO (ethylene oxide) modified bisphenol A diacrylate, PO modified bisphenol A di Acrylate, hydrogenated bisphenol A diacrylate, EO-modified hydrogenated bisphenol A diacrylate PO modified hydrogenated bisphenol A diacrylate, bisphenol F diacrylate, EO modified bisphenol F diacrylate, PO modified bisphenol F diacrylate, EO modified tetrabromobisphenol A diacrylate, tricyclodecane dimethylol diacrylate, isocyanuric acid EO Modified diacrylate.

(Example of trifunctional acrylates)
Glycerin PO modified triacrylate, trimethylolpropane triacrylate, trimethylolpropane EO modified triacrylate, trimethylolpropane PO modified triacrylate, isocyanuric acid EO modified triacrylate, isocyanuric acid EO modified ε-caprolactone modified triacrylate, 1,3 5-triacryloylhexahydro-s-triazine, pentaerythritol triacrylate, dipentaerythritol triacrylate tripropionate.

(Examples of tetrafunctional or higher acrylates)
Pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate monopropionate, dipentaerythritol hexaacrylate, tetramethylolmethane tetraacrylate, oligoester tetraacrylate, tris (acryloyloxy) phosphate.

<Examples of methacrylate compounds>
The methacrylates suitably used as the polymerizable compound (C) in the ink composition of the present invention may be monofunctional. It may be polyfunctional, and examples thereof include the following compounds.
(Example of monofunctional alkyl methacrylates)
Methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, lauryl methacrylate, stearyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, dicyclopentenyl methacrylate , Dicyclopentenyloxyethyl methacrylate, benzyl methacrylate.

(Examples of monofunctional hydroxymethacrylates)
2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxy-3-chloropropyl methacrylate, 2-hydroxy-3-phenoxypropyl methacrylate, 2-hydroxy-3-allyloxypropyl methacrylate, 2-methacryloyloxyethyl-2 -Hydroxypropyl phthalate.

(Examples of monofunctional halogenated methacrylates)
2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 1H-hexafluoroisopropyl methacrylate, 1H, 1H, 5H-octafluoropentyl methacrylate, 1H, 1H, 2H, 2H- Heptadecafluorodecyl methacrylate, 2,6-dibromo-4-butylphenyl methacrylate, 2,4,6-tribromophenoxyethyl methacrylate, 2,4,6-tribromophenol 3EO addition methacrylate.

(Examples of monofunctional ether-containing methacrylates)
2-methoxyethyl methacrylate, 1,3-butylene glycol methyl ether methacrylate, butoxyethyl methacrylate, methoxytriethylene glycol methacrylate, methoxypolyethylene glycol # 400 methacrylate, methoxydipropylene glycol methacrylate, methoxytripropylene glycol methacrylate, methoxypolypropylene glycol methacrylate, Ethoxydiethylene glycol methacrylate, 2-ethylhexyl carbitol methacrylate, tetrahydrofurfuryl methacrylate, phenoxyethyl methacrylate, phenoxydiethylene glycol methacrylate, phenoxy polyethylene glycol methacrylate, cresyl polyethylene glycol methacrylate, p- Cycloalkenyl phenoxyethyl methacrylate, p- nonylphenoxy polyethylene glycol methacrylate, glycidyl methacrylate.

(Examples of monofunctional carboxyl-containing methacrylates)
β-carboxyethyl methacrylate, succinic acid monomethacryloyloxyethyl ester, ω-carboxypolycaprolactone monomethacrylate, 2-methacryloyloxyethyl hydrogen phthalate, 2-methacryloyloxypropyl hydrogen phthalate, 2-methacryloyloxypropyl hexahydrohydrogen phthalate, 2- Methacryloyloxypropyl tetrahydrophthalate.

(Examples of other monofunctional methacrylates)
N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminopropyl methacrylate, morpholinoethyl methacrylate, trimethylsiloxyethyl methacrylate, diphenyl-2-methacryloyloxyethyl phosphate, 2-methacryloyloxyethyl acid phosphate, caprolactone-modified-2-methacryloyl Oxyethyl acid phosphate.

(Example of bifunctional methacrylates)
1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol # 200 dimethacrylate, polyethylene glycol # 300 dimethacrylate, polyethylene glycol # 400 dimethacrylate, polyethylene glycol # 600 dimethacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, tetrapropylene glycol dimethacrylate, polypropylene glycol # 400 dimethacrylate, polypropylene glycol # 700 dimethacrylate, neopentyl glycol dimethacrylate, Neope Chilled glycol PO modified dimethacrylate, hydroxypivalic acid neopentyl glycol ester dimethacrylate, caprolactone adduct dihydroxymethacrylate of hydroxypivalic acid neopentyl glycol ester, 1,6-hexanediol bis (2-hydroxy-3-methacryloyloxypropyl) ether 1,9-nonanediol dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol dimethacrylate monostearate, pentaerythritol dimethacrylate monobenzoate, bisphenol A dimethacrylate, EO-modified bisphenol A dimethacrylate, PO-modified bisphenol A dimethacrylate, hydrogen Bisphenol A dimethacrylate, EO-modified hydrogenated bisphenol A dimethacrylate Tacrylate, PO modified hydrogenated bisphenol A dimethacrylate, bisphenol F dimethacrylate, EO modified bisphenol F dimethacrylate, PO modified bisphenol F dimethacrylate, EO modified tetrabromobisphenol A dimethacrylate, tricyclodecane dimethylol dimethacrylate, isocyanuric acid EO Modified dimethacrylate.

(Example of trifunctional methacrylates)
Glycerin PO modified trimethacrylate, trimethylolpropane trimethacrylate, trimethylolpropane EO modified trimethacrylate, trimethylolpropane PO modified trimethacrylate, isocyanuric acid EO modified trimethacrylate, isocyanuric acid EO modified ε-caprolactone modified trimethacrylate, 1, 3, 5-trimethacryloylhexahydro-s-triazine, pentaerythritol trimethacrylate, dipentaerythritol trimethacrylate tripropionate.

(Examples of tetrafunctional or higher methacrylates)
Pentaerythritol tetramethacrylate, dipentaerythritol pentamethacrylate monopropionate, dipentaerythritol hexamethacrylate, tetramethylolmethane tetramethacrylate, oligoester tetramethacrylate, tris (methacryloyloxy) phosphate.

Hereinafter, compounds other than acrylates and methacrylates that are preferably used as the polymerizable compound (C) in the present invention are listed.
<Examples of compounds of arylates>
Allyl glycidyl ether, diallyl phthalate, triallyl trimellitate, isocyanuric acid triarylate.

<Examples of acid amide compounds>
Acrylamide, N-methylolacrylamide, diacetoneacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, N-isopropylacrylamide, acryloylmorpholine, methacrylamide, N-methylolmethacrylamide, diacetone methacrylamide, N, N -Dimethylmethacrylamide, N, N-diethylmethacrylamide, N-isopropylmethacrylamide, methacryloylmorpholine.

<Examples of styrene compounds>
Styrene, p-hydroxystyrene, p-chlorostyrene, p-bromostyrene, p-methylstyrene, p-methoxystyrene, pt-butoxystyrene, pt-butoxycarbonylstyrene, pt-butoxycarbonyloxystyrene 2,4-diphenyl-4-methyl-1-pentene.

<Examples of other vinyl compounds>
Vinyl acetate, vinyl monochloroacetate, vinyl benzoate, vinyl pivalate, vinyl butyrate, vinyl laurate, divinyl adipate, vinyl methacrylate, vinyl crotonate, vinyl 2-ethylhexanoate, N-vinylcarbazole, N-vinylpyrrolidone etc.

  Examples of the polymerizable compound that can exist substantially in an emulsion state in the aqueous ink composition include the following monomer examples and product examples in addition to the above-described exemplary compounds.

  Trifunctional or higher monomer; pentaerythritol tetraacrylate (trade name: M-450 manufactured by Toagosei Co., Ltd.), polyester acrylate (trade name: M-81000 manufactured by Toagosei Co., Ltd.), bifunctional monomer; neopentyl glycol diacrylate ( Product name: NK ester NPG manufactured by Shin-Nakamura Chemical Co., Ltd., urethane acrylate (trade name: M-1210 manufactured by Toagosei Co., Ltd.), polyester acrylate (product name: M-6200 manufactured by Toagosei Co., Ltd.), monofunctional monomer; 2-ethylhexyl Carbitol acrylate (trade name: M-120 manufactured by Toagosei Co., Ltd.), N-vinylpyrrolidone, etc.

  The content of the polymerizable compound (C) in the ink composition of the present invention may be appropriately determined based on the content of the (B) polymerization initiator and a preferred mass ratio thereof. Usually, however, in terms of solid content, The range is preferably 2 to 70% by mass, more preferably 3 to 30% by mass, and particularly preferably 5 to 20% by mass.

<(D) Water>
The ink composition of the present invention contains water as a main solvent.
As water, it is preferable to use ion-exchanged water, distilled water or the like that does not contain impurities.
The water content in the ink composition of the present invention is preferably 10 to 97% by mass, and in the case of an ink composition for inkjet recording, it is preferably 30 to 95% by mass, and 50 More preferably, it is -95 mass%.

<Water-soluble organic solvent>
The water-based ink composition of the present invention contains water as a main solvent, but it is preferable to further use a water-soluble organic solvent in the solvent depending on the purpose.
Examples of the water-soluble organic solvent that can be used in the present invention include alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl). Alcohol), polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol Etc.), polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether, ethylene glycol) Ether monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether , Triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, mole) Phosphorus, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N , N-dimethylacetamide, etc.), heterocyclic rings (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides ( For example, dimethyl sulfoxide etc.), sulfones (for example, sulfolane etc.), urea, acetonitrile, acetone etc. are mentioned. Preferable water-soluble organic solvents include polyhydric alcohols. Furthermore, it is particularly preferable to use a polyhydric alcohol and a polyhydric alcohol ether in combination.

  The water-soluble organic solvent may be used alone or in combination. The total amount of the water-soluble organic solvent in the ink composition is 5 to 60% by mass, preferably 10 to 35% by mass.

<(E) Colorant>
When the ink composition of the present invention is applied to uses such as the formation of an image portion of a lithographic printing plate, it is not essential to form a colored image. Is not necessary, but a colorant can be contained in order to improve the visibility of the image portion formed by the ink composition or when a colored image is to be formed using the ink composition.

  The colorant that can be used in the present invention is not particularly limited. However, since the polymerizable compound (C) is present in an emulsion in water in the ink composition, the colorant is used in the form of (1) A mode in which a pigment is used as a colorant and dispersed in an aqueous medium, (2) A mode in which an oil-soluble dye is used as a colorant, dissolved in a polymerizable compound and present in an emulsion phase formed by the polymerizable compound, (3) A water-soluble dye can be used as a colorant, and any of the modes of dissolving this in an aqueous phase can be used. These can also be used in combination, but generally the pigment is weather resistant to the dye. Therefore, it is preferable to use a pigment as the colorant.

(Pigment)
As the pigment that can be used as the colorant (E) in the present invention, conventionally known colored organic or colored inorganic pigments can be used.
For example, azo pigments such as azo lake, insoluble azo pigment, condensed azo pigment, chelate azo pigment, phthalocyanine pigment, perylene and perylene pigment, anthraquinone pigment, quinacridone pigment, dioxazine pigment, thioindigo pigment, isoindolinone pigment, quinophthalone pigment, etc. Examples include polycyclic pigments, dye lakes such as basic dye lakes, and acid dye lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments, and inorganic pigments such as carbon black.

  Examples of magenta or red pigments include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 170, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 194, C.I. I. Pigment red 209, C.I. I. Pigment red 222, C.I. I. And CI Pigment Red 224.

  Examples of orange or yellow pigments include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 138, pigment yellow 180, and the like.

  Examples of green or cyan pigments include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment green 7, C.I. I. And CI Pigment Green 36.

  Examples of the pigment for black include carbon black. Examples of the white pigment include Pigment White 6, 18, 21, and the like.

  For these pigments, a pigment dispersant may be used as necessary when preparing pigment particles. Examples of the pigment dispersant that can be used include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates. Salt, alkyl sulfonate, sulfosuccinate, naphthalene sulfonate, alkyl phosphate, polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester , Activators such as polyoxyethylene fatty acid amides, amine oxides, or styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid Block copolymers of two or more monomers selected from derivatives, random copolymers and can be exemplified salts thereof.

  A self-dispersing pigment can also be used in the ink composition of the present invention. The self-dispersing pigment as used in the present invention refers to a pigment that can be dispersed without a dispersant, and particularly preferably pigment particles having a polar group on the surface.

The pigment particles having a polar group on the surface as used in the present invention are a pigment whose surface is directly modified with a polar group, or an organic substance having an organic pigment mother nucleus, which is bonded directly or via a joint. (Hereinafter referred to as pigment derivative).
Examples of the polar group include a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a boric acid group, and a hydroxyl group, preferably a sulfonic acid group and a carboxylic acid group, and more preferably a sulfonic acid group.

  Examples of a method for obtaining pigment particles having a polar group on the surface include, for example, WO 97/48769, JP-A-10-110129, JP-A-11-246807, JP-A-11-57458, 11-189739, JP-A-11-323232, JP-A-2000-265094, etc., oxidize the pigment particle surface with an appropriate oxidizing agent, so that at least a part of the pigment surface has a sulfonic acid group or The method of introduce | transducing polar groups, such as the salt, is mentioned. Specifically, it is prepared by oxidizing carbon black with concentrated nitric acid or, in the case of color pigments, by oxidizing with sulfamic acid, sulfonated pyridine salt, amidosulfuric acid, etc. in sulfolane or N-methyl-2-pyrrolidone. can do. In these reactions, the pigment dispersion can be obtained by removing and purifying the substance that has been excessively oxidized and becomes water-soluble. Moreover, when a sulfonic acid group is introduced onto the surface by oxidation, the acidic group may be neutralized with a basic compound as necessary.

  As other methods for obtaining pigment particles having polar groups on the surface, the pigment particles described in JP-A-11-49974, JP-A-2000-273383, JP-A-2000-303014, etc. are treated with a treatment such as milling. Examples include a method of adsorbing to the surface, a method of dissolving the pigment described in Japanese Patent Application Nos. 2000-377068, 2001-1495, and 2001-234966 in a solvent together with a pigment derivative, and crystallizing in a poor solvent. In any method, pigment particles having a polar group on the surface can be easily obtained.

  The polar group on the surface of the pigment may be free or in a salt state, or may have a counter salt. Examples of the counter salt include inorganic salts (lithium, sodium, potassium, magnesium, calcium, aluminum, nickel, ammonium) and organic salts (triethylammonium, diethylammonium, pyridinium, triethanolammonium, etc.), preferably 1 A counter salt having a valence.

  As a method for dispersing the pigment, for example, various dispersing machines 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, and a paint shaker can be used. It is also preferable to use a centrifugal separator or a filter for the purpose of removing the coarse particles of the pigment dispersion.

(Oil-soluble dye)
As described above, the ink composition of the present invention may contain an oil-soluble dye as a colorant.
The oil-soluble dye that can be used in the present invention will be described.
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; Examples include methine dyes such as benzylidene dyes and monomethine oxonol dyes; quinone dyes such as naphthoquinone dyes and anthraquinone dyes; and other dye species such as quinophthalone dyes, nitro / nitroso dyes, Examples include acridine dyes and acridinone dyes.

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, oxonol dyes Methine dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes; quinone dyes such as naphthoquinone, anthraquinone, anthrapyridone; condensed polycyclic dyes such as dioxazine dyes, etc. Can be mentioned.

  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; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes Phthalocyanine dyes; anthraquinone dyes; for example, 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, and 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 Chemical 2606e, Oil 2606e (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.

In the present invention, the oil-soluble dye may be used alone or in combination of several kinds.
Further, when an oil-soluble dye is used as a colorant, other water-soluble dyes, disperse dyes, pigments, and other colorants can be used in combination as long as the effects of the present invention are not impaired. .

(Water-soluble dye)
The water-soluble dye that can be used in the ink composition of the present invention will be described.
When a dye is used as a coloring material, unlike the case of using the pigment, it is difficult to use the dye without any fading due to active energy ray irradiation, and there is some fading. For this reason, when a dye is applied as the coloring material of the ink, it is preferable to use a so-called azo metal-containing dye in which a complex is formed with metal ions because discoloration is small.

  Examples of water-soluble black dyes include monoazo complexes, disazo complexes coordinated with polyvalent metals such as Cr, Cu, Mn, Al, Zn, and Fe, and non-complex azo black dyes such as Direct Black 17 and Direct Black 19, direct black 51, direct black 154, direct black 174, direct black 195, and the like can be suitably used.

  Examples of water-soluble yellow dyes include Acid Yellow 11, Acid Yellow 17, Acid Yellow 23, Acid Yellow 25, Acid Yellow 29, Acid Yellow 42, Acid Yellow 49, Acid Yellow 61, Acid Yellow 71, Direct Yellow 12, Direct yellow 24, direct yellow 26, direct yellow 44, direct yellow 86, direct yellow 87, direct yellow 98, direct yellow 100, direct yellow 130, direct yellow 132, direct yellow 142, and the like.

  Examples of the water-soluble magenta dye include Acid Red 1, Acid Red 6, Acid Red 8, Acid Red 32, Acid Red 35, Acid Red 37, Acid Red 51, Acid Red 52, Acid Red 80, Acid Red 85, Acid Red 87, Acid Red 92, Acid Red 94, Acid Red 115, Acid Red 180, Acid Red 254, Acid Red 256, Acid Red 289, Acid Red 315, Acid Red 317, Direct Red 1, Direct Red 4, Direct Red 13, Direct Red 17, Direct Red 23, Direct Red 28, Direct Red 31, Direct Red 62, Direct Red 79, Direct Red 81, Die Kutoreddo 83, Direct Red 89, Direct Red 227, Direct Red 240, such as Direct Red 242 and Direct Red 243, and the like.

  Examples of water-soluble cyan dyes include Acid Blue 9, Acid Blue 22, Acid Blue 40, Acid Blue 59, Acid Blue 93, Acid Blue 102, Acid Blue 104, Acid Blue 113, Acid Blue 117, Acid Blue 120, Acid Blue 167, Acid Blue 229, Acid Blue 234, Acid Blue 254, Direct Blue 6, Direct Blue 22, Direct Blue 25, Direct Blue 71, Direct Blue 78, Direct Blue 86, Direct Blue 90, Direct Blue 106 and Direct Blue 199 etc. are mentioned.

  When the oil-soluble dye or the water-soluble dye is used as a colorant, the preferred content (total amount of dye) in the ink composition is 0.1 to 10% on a mass basis with respect to the total amount of the ink composition. It is a range. The ink composition having a low dye concentration is suitably applied to, for example, a so-called light-color ink of density-modulated ink.

<Other additives>
In addition to the essential components (A) to (D) and (E) the colorant, the ink composition of the present invention is used with known additives as long as the effects of the present invention are not impaired. be able to. Hereinafter, additives that can be used in the ink composition will be described.

(Surfactant)
A surfactant can be added to the ink composition of the present invention. As the surfactant preferably used, anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, Nonionic surfactants such as polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. In particular, an anionic surfactant and a nonionic surfactant can be preferably used.

  In the present invention, a polymeric surfactant can also be used, and the following water-soluble resins are mentioned as preferred polymeric surfactants from the viewpoint of ejection stability. As the water-soluble resin, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid copolymer are preferably used. Polymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer Etc.

(latex)
Latex can be added to the ink composition of the present invention. Examples of the latex that can be used in the present invention include styrene-butadiene copolymer, polystyrene, acrylonitrile-butadiene copolymer, acrylic acid ester copolymer, polyurethane, silicon-acrylic copolymer, and acrylic-modified fluorine-fatting. Latex. The latex may be a polymer particle dispersed using an emulsifier, or a so-called soap-free latex dispersed without using an emulsifier. A surfactant is often used as an emulsifier, but a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group (for example, a polymer in which a solubilizing group is graft-bonded, a single group having a solubilizing group). It is also preferable to use a polymer obtained from a monomer and a monomer having an insoluble part.

  Soap-free latex is a latex that does not use an emulsifier and a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group (for example, a polymer in which a solubilizing group is graft-bonded, a solubilizing group) A polymer obtained from a monomer having an insoluble part and a monomer having an insoluble part).

  In recent years, as latex polymer particles, there are latexes in which core-shell type polymer particles with different compositions at the center and outer edge of the particles are dispersed, in addition to latex in which polymer particles that are uniform throughout the particle are dispersed. This type of latex can also be preferably used.

  The average particle size of the polymer particles in the latex used in the ink composition of the present invention is preferably 10 nm or more and 300 nm or less, and more preferably 10 nm or more and 100 nm or less. When the average particle size of the latex in the ink composition is in the above range, the glossiness of the image, the water resistance and the scratch resistance can be improved. The average particle size of the polymer particles in the latex can be determined by a commercially available particle size measuring instrument using a light scattering method, an electrophoresis method, or a laser Doppler method.

  In the ink composition of the present invention, when latex is used, the addition amount is preferably 0.1% by mass or more and 20% by mass or less in terms of solid content, and the addition of solid content in latex The amount is particularly preferably 0.5% by mass or more and 10% by mass or less. When the solid content of the latex is 0.1% by mass or more, the effect of improving water resistance can be exhibited. When the latex content is 20% by mass or less, the ink viscosity increases with time, the pigment dispersion particle size increases, etc. Thus, good ink storage stability can be maintained without causing problems caused by the effect of latex.

(Aqueous polymer)
An aqueous polymer can be added to the ink composition of the present invention.
Preferable examples of the aqueous polymer include natural polymers, and specific examples thereof include proteins such as glue, gelatin, casein, or albumin, natural rubbers such as gum arabic or gum tragacanth, and glucosides such as saponin. And alginic acid and propylene glycol alginate, triethanolamine alginate, or alginic acid derivatives such as ammonium alginate, and cellulose derivatives such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, or ethylhydroxylcellulose.

  Other preferable examples of the aqueous polymer include synthetic polymers such as polyvinyl alcohols, polyvinylpyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer, potassium acrylate-acrylonitrile copolymer, Acrylic resin such as vinyl acetate-acrylic acid ester copolymer or acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester Styrene acrylic resin such as copolymer, styrene-α-methylstyrene-acrylic acid copolymer, or styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, styrene-maleic acid copolymer, styrene -Maleic anhydride copolymer, vinyl naphth Talen-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-croton Examples include acid copolymers, vinyl acetate copolymers such as vinyl acetate-acrylic acid copolymers, and salts thereof. Among these, polyvinylpyrrolidones are particularly preferable examples.

  The molecular weight of the water-soluble polymer that can be used in the present invention is preferably 1,000 or more and 200,000 or less. Furthermore, 3,000 or more and 20,000 or less are more preferable. If it is less than 1,000, the effect of suppressing the growth and aggregation of pigment particles is reduced, and if it exceeds 200,000, problems such as an increase in viscosity and poor dissolution tend to occur.

  The addition amount of the water-soluble polymer is preferably 10% by mass or more and 1,000% by mass or less with respect to the dissolved pigment. Furthermore, 50 mass% or more and 200 mass% or less are more preferable. If it is less than 10% by mass, the effect of suppressing the growth and aggregation of the pigment particles is reduced, and if it exceeds 1000% by mass, problems such as an increase in viscosity and poor dissolution tend to occur.

  In addition to the above-described components, the ink according to the present invention is used for the purpose of improving ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances as necessary. According to various known additives, for example, viscosity modifiers, surface tension modifiers, specific resistance modifiers, film forming agents, dispersants, surfactants, ultraviolet absorbers, antioxidants, antifading agents, anticorrosives Agents, rust preventives and the like can be appropriately selected and used. For example, oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, JP-A-57-74193 and 57-87988. And UV absorbers described in JP-A Nos. 62-261476, JP-A-57-74192, JP-A-57-87989, JP-A-60-72785, JP-A-61-146591, JP-A-1-146591. No. 5091 and 3-13376, etc., JP 59-42993, 59-52689, 62-280069, 61-242871, and JP 4-219266. And the like, such as fluorescent brighteners, sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate and other pH adjusters described in the above.

(Method for preparing ink composition)
The ink composition of the present invention is characterized in that the polymerizable compound (C) is present in an emulsion state in the ink composition. To prepare such an ink composition, first, a non-aqueous composition is used. An emulsion may be prepared by preparing a phase and dispersing it in an aqueous medium by a conventional method.
Here, the non-aqueous phase preferably contains at least a polymerizable compound, and further contains a polymerization initiator, a specific sensitizing dye, and the like that are compatible with the non-aqueous phase to form a uniform phase.
In addition, the aqueous medium (aqueous phase) preferably contains a water-soluble polymer, a surfactant and the like in order to improve dispersion stability.
A pre-prepared composition for forming a non-aqueous phase is dispersed in an aqueous solvent to bring the polymerizable compound into an emulsion state. The emulsion can be formed using a known method or apparatus, and ultrasonic dispersion For example, an ultrasonic dispersion apparatus, a micromixer, or a microreactor can be used as appropriate.
The particle size of the emulsion can be adjusted by appropriately adjusting the stirring conditions (shearing force / temperature / pressure) during emulsification, the use conditions of the dispersing device, the ratio of the non-aqueous phase to the aqueous medium phase, and the like. .

Since the ink composition of the present invention has the above-described configuration, it is cured with high sensitivity by actinic radiation, and thus can be suitably used for various ink applications.
Among these, the ink composition of the present invention, which is excellent in storage stability and has a relatively low viscosity with water as a main component, can be said to have a remarkable effect when used for inkjet recording applications.

As an advantage of using the aqueous actinic radiation curable ink composition of the present invention for image formation using an aqueous ink jet method, an excellent component is obtained by adding a component relating to polymerization and curing to an aqueous medium in an ink composition. The point which can achieve discharge stability is mentioned.
That is, in order to use the aqueous ink composition of the present invention in an ink jet system, the viscosity is maintained in an appropriate range by the aqueous solvent, and the surface tension is also optimized. Furthermore, from the viewpoint of ejection stability, in a preferred embodiment of the present invention, since a polymerizable compound present in an emulsion state, a polymerization initiator and a sensitizing dye coexist in the same phase, good ejection characteristics are achieved. Unlike the case where such a compound is dissolved in a water-soluble solvent, there is also an advantage that there is no concern about a decrease in dischargeability due to precipitation of components involved in curing in the solvent.

The ink composition according to the invention preferably has a viscosity at 50 ° C. of 15 mPa · s or less, more preferably 5 to 15 mPa · s.
The ink viscosity (mPa · s) in the present invention is not particularly limited as long as it is tested with a standard solution for calibration of a viscometer specified in JIS Z 8809, and is a viscosity measured at 50 ° C. according to a known method. As the viscosity measuring device, a rotary, vibration or capillary type viscometer can be used, for example, a Saybolt viscometer, a Redwood viscometer, etc., for example, a cone plate type manufactured by Tokimec E type viscometer, E Type Viscometer (rotary viscometer) manufactured by Toki Sangyo Co., Ltd., B type viscometer BL manufactured by Tokyo Keiki Co., Ltd., FVM-80A manufactured by Yamaichi Electronics Co., Ltd., Viscoliner manufactured by Nametore Industries Co., Ltd., Yamaichi VISCO MATE MODEL VM-1A, DD-1 manufactured by Denki Co., Ltd. can be exemplified.

The ink composition of the present invention preferably has a surface tension of 35 mN / m or less, more preferably 20 to 35 mN / m.
Here, the surface tension (mN / m) of the ink composition is a value measured by a surface tension measured at 50 ° C., and is described in general interface chemistry and colloid chemistry reference books. Laboratory Chemistry Volume 18 (Interface and Colloid), The Chemical Society of Japan, published by Maruzen Co., Ltd. 68 to 117 can be referred to, and specifically, it can be determined by using the ring method (Dunoi method) or the platinum plate method (Wilhelmy method), but in the present invention, it was measured by the platinum plate method. It can be measured by using a surface tension meter CBVP-Z manufactured by Kyowa Interface Science.

  In the ink composition, the viscosity or surface tension specified above is not particularly limited, but the type and concentration of the pigment, the type and concentration of the polymerizable compound, the type and concentration of the surfactant, and the like are appropriately adjusted. Thus, it can be adjusted to a desired value.

Next, an inkjet recording medium that can be used in the present invention will be described.
The recording medium used in the present invention is a metal such as aluminum, iron or copper, vinyl chloride, acrylic, polycarbonate, polyethylene terephthalate, acrylonitrile butadiene styrene copolymer, polyethylene or polypropylene, ceramics such as glass, wood or paper. , Printing paper, fiber etc.

A preferable recording medium to which the ink composition of the present invention is applied is a non-absorbing ink that is not absorbed by the recording medium from the viewpoint that the polymerizable compound contributing to image formation can be present on the surface of the recording medium without being absorbed. Absorbent recording media may be mentioned.
The base material of such a recording medium is also preferably non-ink-absorbing. Here, “non-ink-absorbing” means that the ink is absorbed by a fibrous material such as paper, or that a resin that swells by absorbing ink is used as an ink absorbing layer on the film, or a filler or resin particles are used. It means that it does not have an ink absorption layer in which a void is provided in the layer. Specifically, what is generally used as a flexible packaging material is preferable. The material of the flexible packaging material is polyester, polyolefin, polyamide, polyesteramide, polyether, polyimide, polyamideimide, polystyrene, polycarbonate, poly-p-phenylene sulfide, polyetherester, polyvinyl chloride, poly (meth) acrylic acid Esters, polyethylene, polypropylene and nylon are preferred. Moreover, these copolymers and blends, and also those crosslinked can be used. Among them, stretched polyethylene terephthalate, polystyrene, polypropylene, and nylon are preferable in terms of transparency, dimensional stability, rigidity, environmental load, and cost. The thickness of the film is 2 to 100 μm, preferably 6 to 45 μm, and more preferably 10 to 30 μm.

<Inkjet recording method>
Next, an ink jet recording method of the present invention and an ink jet recording apparatus applicable to the method will be described.
In the inkjet recording method of the present invention, the ink composition of the present invention is ejected onto a recording medium (support, recording material, etc.) for inkjet recording, and the ink composition ejected onto the recording medium is active. In this method, an image is formed by irradiating radiation and curing the ink.

That is, the inkjet recording method of the present invention comprises: (a) a step of ejecting the ink composition of the present invention onto a recording medium; and (b) irradiating the ejected ink composition with actinic radiation, And a step of curing the composition.
By including the steps (a) and (b), the ink jet recording method of the present invention forms an image with the ink composition cured on the recording medium.

In the step (a) in the ink jet recording method of the present invention, an ink jet recording apparatus described in detail below can be used.
<Inkjet recording apparatus>
There is no restriction | limiting in particular as an inkjet recording device used for the 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 (a) 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 × 720 dpi. It can drive so that it can discharge with the resolution of. In the present invention, dpi represents the number of dots per 2.54 cm.

  As described above, since it is desirable for the radiation curable ink to have a constant temperature for the ejected ink, heat insulation and heating can be performed from the ink supply tank to the inkjet head portion. 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 thermal energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

Next, (b) the 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 polymerization initiator contained in the ink composition of the present invention is decomposed by irradiation with actinic radiation to generate radicals, acids, bases and other starting species, and the function of the starting species causes a specific monofunctionality ( This is because the polymerization reaction of the (meth) acrylic acid derivative and other polymerizable compound used in combination as required occurs and is accelerated, and the ink composition is cured. At this time, if a sensitizing dye is present together with the polymerization initiator in the ink composition, the sensitizing dye in the system absorbs actinic radiation to be in an excited state and promotes decomposition of the polymerization initiator by contacting with the polymerization initiator. And achieve a more sensitive curing reaction.

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. 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 further more preferable that it is 350-420 nm.
In the present invention, the polymerization initiating system has sufficient sensitivity even with low-power 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 .
The active radiation, the illumination intensity on the exposed surface is, for example, 10 to 2,000 mW / cm ^2, preferably, it is suitable to 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 photocurable 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.
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 of the present invention is suitably irradiated with such actinic radiation for, for example, 0.01 to 120 seconds, preferably 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 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, the irradiation line can easily reach the lower ink, and good curing sensitivity, reduction of residual monomers, reduction of odor, and improvement of adhesion 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.
In this way, the ink composition of the present invention is cured with high sensitivity by irradiation with actinic radiation, and forms a hydrophobic image on the surface of the recording medium.

Here, the actinic radiation source used for curing the ink or preferred irradiation conditions thereof are also the same as those described in the ink jet recording method.
The ink composition of the present invention is cured with high sensitivity by actinic radiation, and can form a hydrophobic region excellent in adhesion to the support and film quality. For this reason, in addition to the formation of colored images, marking, etc., it can also be used, for example, for the formation of the image portion of a lithographic printing plate. By applying to this application, a lithographic plate having high image quality and excellent printing durability. It is also possible to obtain a printed version.
The ink composition of the present invention is excellent for ink jet recording for the reasons described above, but it is needless to say that it is also useful as a commonly used ink composition.

Since the water-based ink composition of the present invention is a water-based ink using water as a medium, a drying step can be provided after the curing step by irradiation with actinic rays.
The drying method is not particularly limited, and a known drying means can be appropriately selected and used. For example, a method of blowing warm air with controlled temperature and humidity, a method of conveying on a heat plate, and a heater inside. The method etc. which pass between heating rolls can be mentioned. By performing such a drying step, removal of the solvent and curing are promoted, and image formation can be performed quickly.

  Since the ink composition of the present invention has the above-described configuration, the ink composition has excellent ejection stability and is cured with high sensitivity. Therefore, an image formed by this ink composition using the ink jet recording method has high image quality.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these.
[Preparation of yellow ink composition]
<Preparation of pigment dispersion 1>
After mixing the following compounds, the mixture was dispersed using a horizontal bead mill (System Zeta Mini, manufactured by Ashizawa) filled with zirconia beads having a diameter of 0.3 mm at a volume ratio of 60%. Next, after dilution with ion-exchanged water until the pigment concentration became 5% by mass, impurities were removed by ultrafiltration. Next, ion exchange treatment was performed, and the particle size was made uniform by centrifugation to prepare pigment dispersion 1.
(Pigment dispersion 1 composition)
C. I. Pigment Yellow 128 166g
・ High molecular dispersant (styrene / 2-ethylhexyl acrylate / n-butyl acrylate / styrene sulfonic acid = 64/16/15/5) 32 g
・ Diethylene glycol 180g
・ Ion exchange water 1000g

<Preparation of photopolymerization compound dispersion 1>
100 g of polyester diacrylate (bifunctional acid value of 10 or less), 2.0 g of Irgacure 907 (manufactured by Ciba Specialty Chemicals Co., Ltd.), and 1.0 g of Exemplified Compound I-14 were dissolved in 200 g of ethyl acetate. Thereafter, 500 ml of water and 5 g of sodium dodecyl sulfate were added, and ultrasonic dispersion was performed. Next, after evaporating and removing ethyl acetate from the obtained polymerizable compound dispersion using an evaporator, purification and particle size distribution are adjusted by centrifugation and ultrafiltration to prepare a polymerizable compound dispersion 1. did. The presence of the emulsion in the polymerizable compound dispersion was confirmed by observing the dispersion with an optical microscope. The particle size of the emulsion was 0.14 μm as measured by Nikkiso Co., Ltd. Nanotrac UPA-EX150, which is a dynamic light scattering particle size measuring device.

<Preparation of ink composition>
The prepared pigment dispersion 1 corresponds to 30 g in solid content, 330 g of the prepared polymerizable compound dispersion 1, 100 g of ethylene glycol, glycerin as a viscosity modifier, sodium dodecyl sulfate as a surface tension adjuster, pH adjuster Ammonia was added as appropriate, and the remainder was made up to 1 liter with water to prepare a yellow ink composition in which the polymerizable compound was present in an emulsion state.
Met.

<Evaluation of ink composition>
The obtained ink composition is printed on a sheet made of polyvinyl chloride, and becomes a desired integrated exposure amount (described in Table 2) under the light of an iron-doped ultraviolet lamp (power 120 W / cm ² ). In this way, irradiation was carried out by changing the transport speed to pass the ink, and the ink was cured to obtain a printed matter. Table 2 shows the evaluation results of the ink composition and the printed material.

-Sensitivity-
The exposure energy in curing was measured with a light quantity integrator (UV PowerMAP manufactured by EIT). As a result, the cumulative exposure amount of ultraviolet rays on the sheet was about 330 mJ / cm ² , and it was confirmed that the sheet was cured with high sensitivity. The curability is determined by the presence or absence of stickiness on the surface of the printed material. Immediately after printing, plain paper (Fuji Xerox Co., Ltd., copy paper C2) is pressed. It was good.

−Discharge stability−
The obtained ink composition was stored at room temperature for 4 weeks, then recorded on a recording medium using an ink jet recording apparatus having a piezo type ink jet nozzle, and when missing dots and ink were printed continuously at room temperature for 48 hours. The presence or absence of scattering was visually observed and evaluated according to the following criteria. The results are shown in Table 2 below.
○: Dot drop or ink splatter does not occur or occurs 3 times or less △: Dot drop or ink splatter occurs 4 to 10 times ×: Dot drop or ink splatter occurs 11 times or more

  The ink supply system of the inkjet recording device used for the evaluation consists of the original tank, supply pipe, ink supply tank immediately before the inkjet head, filter, and piezo-type inkjet head. Went. Temperature sensors were provided near the ink supply tank and the nozzles of the ink jet head, respectively, and temperature control was performed so that the nozzle portions were always 40 ° C. ± 2 ° C. The piezo-type inkjet head was driven so that 8 to 30 pl multi-size dots could be ejected at a resolution of 720 × 720 dpi. In the present invention, dpi represents the number of dots per 2.54 cm.

[Examples 2-4, Comparative Examples 1-2]
The composition of the photopolymerizable compound dispersion used in Example 1 was changed to the composition shown in Table 1 below, and the pigment dispersion and the ink composition were adjusted in the same manner as in Example 1 to obtain respective ink compositions.
Table 1 shows the evaluation results of the ink composition and the printed matter, which were obtained in the same manner as in Example 1.

比較化合物１

Comparative compound 1

  As shown in Table 1, it can be seen that Examples 1 to 4 which are ink compositions of the present invention have good curability even at a low exposure amount as compared with Comparative Example 1 in which no sensitizing dye is used. Moreover, although the comparative example 2 using the thioxanthone compound generally used as a sensitizing dye shows improvement in sclerosis | hardenability, when it uses for inkjet recording, it turns out that there is a problem in discharge stability. Further, by comparing Example 1 and Example 2, it can be seen that the use of a sensitizing dye having a halogen atom in the molecule as the specific sensitizing dye is superior in curability.

Claims (5)

(A) a sensitizing dye represented by the following general formula (I), (B) a polymerization initiator, (C) a polymerizable compound having an ethylenically unsaturated bond, and (D) water, The ink composition, wherein the polymerizable compound (C) is present in an emulsion state in the ink composition.

(In general formula (I), X represents O, S, or NR, R represents a hydrogen atom, an alkyl group, or an acyl group. N represents 0 or 1. R ^{1 to} R ^8. Each independently represents a hydrogen atom or a monovalent substituent, and R ¹ , R ² , R ³ , and R ⁴ may be bonded to each other to form a ring. R ⁵ or R ⁶ and R ⁷ or R ⁸ may be linked to each other to form an aliphatic ring, but they do not form an aromatic ring.   The ink composition according to claim 1, wherein (B) the polymerization initiator includes one or more compounds selected from the group consisting of α-aminoketones and acylphosphine oxides.   The ink composition according to claim 1, further comprising (E) a pigment as a colorant.   The ink composition according to any one of claims 1 to 3, which is for inkjet recording.   (A) a step of ejecting the ink composition according to claim 4 onto a recording medium; and (b) a step of irradiating the ejected ink composition with actinic radiation to cure the ink composition. An ink jet recording method comprising: