JP5224824B2 - Ink composition and ink jet recording method using the same - Google Patents

Description

  The present invention relates to an ink composition and an ink jet recording method that are suitably used for ink jet recording. More specifically, the present invention relates to an ink composition suitable for ink jet recording and an ink jet recording method, which is cured with high sensitivity to irradiation with actinic radiation and the cured product has sufficient flexibility even after ink curing.

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 device 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.

  The curable inkjet method using ultraviolet light has been attracting attention in recent years because it has a relatively low odor and can record on a recording medium having no quick drying and no ink absorption. In particular, benzyl, benzoin, benzoin ethyl ether, Michler's ketone, anthraquinone, acridine, phenazine, benzophenone, 2-ethylanthraquinone, and the like have been generally used as photopolymerization initiators (see, 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 1, Patent Document 2, and Patent Document 3). ). However, there is no example in which an ink for ink jet recording employs a polymerization initiating system satisfying sufficient sensitivity for scanning exposure, storage stability, and ejection stability.
For this reason, ink that can be cured with high sensitivity to low-output radiation, can form high-quality images, and has good storage stability and ejection stability, and is suitably used for inkjet recording. Compositions are anxious.
Bruce M. Monroe (Bruce M. Monroe et al., Chemical Reviews), Vol. 93, (1993), p. 435-448. U.S. Pat. No. 4,134,813 JP-A-1-253731 JP-A-6-308727

  The object of the present invention is to cure with high sensitivity even when irradiated with low-output radiation, can form high-quality images, has high storage stability, and is used for inkjet recording. Another object of the present invention is to provide an ink composition that does not cause nozzle clogging during ejection and an ink jet recording method using the ink composition.

In order to solve the above-mentioned problems, the present inventors have made extensive studies, and as a result, a specific sensitizing dye has a high sensitizing effect with respect to a specific initiator, and an ink composition using them as an initiator system is The present invention was completed by finding that it has high sensitivity and good storage stability and ejection stability.
That is, the ink composition of the present invention comprises a polymerization initiator selected from the group consisting of (i) a sensitizing dye represented by the following general formula (I), and (ii) α-amino ketones and acylphosphine oxides. And (iii) a polymerizable compound having an ethylenically unsaturated bond.

In the formula (I), X represents O, S, or NR. n represents 0 or 1. R represents a hydrogen atom, an alkyl group, or an acyl group.
^{R 1, R 2, R 3} , and R ⁴ each independently represent a hydrogen atom, an alkyl group, a halogen atom, or an alkylthio group. R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represents a hydrogen atom or an alkyl group.
Preferably, in the formula (I), the alkyl group represented by R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , and R ⁸ has 1 to 10 carbon atoms. More preferably, in the formula (I), R represents a hydrogen atom or an alkyl group, R ¹ , R ⁴ , and R ⁵ represent a hydrogen atom, and R ² and R ³ each independently represent a hydrogen atom. atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom, or an alkylthio ^group, R 6, ^{R 7,} and ^{R 8} each independently represents a hydrogen atom, or an alkyl group having 1 to 10 carbon atoms.

  When forming a colored image with the ink composition of the present invention, it is preferable that the ink composition further contains a colorant. In addition, the ink composition of the present invention can be cured with high sensitivity by radiation irradiation, and therefore is suitable for inkjet recording.

  The ink jet 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 to form an ink composition. And a step of curing.

Although the operation of the present invention is not clear, it is estimated as follows.
In the present invention, an initiator system in which a polymerization initiator selected from α-aminoketones and acylphosphine oxides and a specific sensitizing dye are used in combination is employed, and the specific sensitizing dye has triplet excitation. Since it has high energy and efficiently causes triplet energy transfer to polymerization initiators such as α-aminoketones and acylphosphine oxides, it is considered that it can be cured with high sensitivity. In addition, the specific sensitizing dye has higher solubility and lower crystallinity than a commonly used thioxanthone compound, and thus has excellent stability as a solution of an ink composition, and an ink composition containing the same When the product is used for inkjet recording, it is considered that excellent ejection stability can be obtained.
Thus, in the present invention, it is considered that both high sensitivity, solution stability, and ejection stability can be achieved.

  According to the present invention, an ink composition that can be cured with high sensitivity even when irradiated with low-output radiation, can form a high-quality image, and has excellent solution stability and ejection stability, and the ink composition An ink jet recording method using the object can be provided.

[Ink composition]
First, the ink composition of the present invention will be described in detail.
The ink composition of the present invention comprises (i) a sensitizing dye represented by the following general formula (I) (hereinafter referred to as a specific sensitizing dye as appropriate), (ii) α-amino ketones and acylphosphine oxides. And (iii) a polymerizable compound having an ethylenically unsaturated bond, and a polymerization initiator selected from the group consisting of:
The ink composition of the present invention can be suitably used for inkjet recording.
Hereinafter, components essential to the ink composition of the present invention will be sequentially described.

<Sensitizing dye>
The ink composition of the present invention contains a sensitizing dye in order to promote the decomposition of the polymerization initiator by irradiation with actinic rays. To do.
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. The ink composition of the present invention needs to contain one or more specific sensitizing dyes belonging to the following compounds.
[(I) Sensitizing dye represented by formula (I)]

In the formula (I), X is O, S, or represents NR, wherein 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 bonded to R ⁷ and R ^8, and X containing a hetero atom and a carbon atom bonded to R ⁵ and R ⁶ are directly bonded to each other. A 5-membered heterocycle containing

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, a halogen atom.

The alkyl groups ^which may ^R 1 in one general formula ^{(I), R 2, R} 3, R 4, R 5, R 6, R 7 and ^{R 8} represents a monovalent substituent, carbon 1 to 10 Alkyl group is 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.
In the present invention, R ¹ , R ² , R ³ , and R ⁴ each independently represent a hydrogen atom, an alkyl group, a halogen atom, or an alkylthio group. R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represents a hydrogen atom or an alkyl group.
Preferably, in the formula (I), the alkyl group represented by R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , and R ⁸ has 1 to 10 carbon atoms.
More preferably, in the formula (I), R represents a hydrogen atom or an alkyl group, R ¹ , R ⁴ , and R ⁵ represent a hydrogen atom, and R ² and R ³ each independently represent a hydrogen atom. atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom, or an alkylthio ^group, R 6, ^{R 7,} and ^{R 8} each independently represents a hydrogen atom, or an alkyl group having 1 to 10 carbon atoms.

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 ( ^IC ), 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.

Moreover, it is preferable that at least one of R ^1C , R ^2C , R ^3C , R ^4C , R ^5C , R ^6C , R ^7C and R ^8C is a halogen atom. Preferred substitution positions 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.

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, and matching with a light source is good and high sensitivity. .

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.

  The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms, and has 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, an n-butyl group, a sec-butyl group, or a t-butyl group. Are more preferred.

The acyloxy group is preferably an aliphatic acyloxy group having 2 to 10 carbon atoms, and more preferably an aliphatic acyloxy group having 2 to 5 carbon atoms.
As the alkoxycarbonyl group, an aliphatic alkoxycarbonyl group having 2 to 10 carbon atoms 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. .
When the content is described in relation to the polymerization initiator described later, the mass ratio of specific polymerization initiator: specific sensitizing dye is 200: 1 to 1: 200, preferably 50: 1 to 1:50, more preferably. Is preferably included in an amount of 20: 1 to 1: 5.

[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.

The further example of the photosensitizer which can be used together is 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.

<Polymerization initiator>
The ink composition of the present invention contains a polymerization initiator.
The present invention is characterized by containing the specific polymerization initiator described in detail below, but a known polymerization initiator can also be used in combination. As the polymerization initiator in the present invention, a radical polymerization initiator is preferably used.

[(Ii) Polymerization initiator selected from the group consisting of α-aminoketones and acylphosphine oxides]
Hereinafter, the specific polymerization initiator which is a characteristic component of the present invention will be described in detail.
The polymerization initiator suitably used in the present invention is a photopolymerization initiator selected from the group consisting of α-aminoketones and acylphosphine oxides.
The α-aminoketone compound which is a specific polymerization initiator is a compound 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 an alkoxy group having 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 the compounds included in the α-amino ketones include 2-methyl-1-phenyl-2-morpholinopropan-1-one, 2-methyl-1- [4- (hexyl) phenyl] -2- And morpholinopropan-1-one, 2-ethyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, and the like. Further, it is also available as a commercial product such as Irgacure series manufactured by Ciba Geigy, for example, Irgacure 907, Irgacure 369, Irgacure 379, and the like, and these are compounds included in α-amino ketones, which are suitable for the present invention. Can be used.

  The compound included in the acylphosphine oxides is a compound 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.

Examples of the aliphatic group represented by R ^5D , R ^6D, or R ^7D include an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an alkynyl group, a substituted alkynyl group, an aralkyl group, and a substituted aralkyl group. Among them, an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an aralkyl group, or a substituted aralkyl group is 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 (eg, 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,

Acyloxy group having 30 or less carbon atoms (for example, acetyloxy group, propionyloxy group, etc.), 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.), carbon An aryl group having a number of 30 or less (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 urea De group, a substituted phosphono group, and a heterocyclic group. 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 represented by R ^5D , R ^6D or R ^7D 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 represented by R ^5D or R ^6D is preferably an alkoxy group having 1 to 30 carbon atoms, and examples thereof include a methoxy group, an ethoxy group, a butoxy group, an octyloxy group, and a phenoxyethoxy group. . However, it is not limited to these.

The aromatic oxy group represented by R ^5D or R ^6D is preferably an aryloxy group having 6 to 30 carbon atoms, such as a phenoxy group, a methylphenyloxy group, a chlorophenyloxy group, a methoxyphenyloxy group, or an octyloxy group. A phenyloxy group etc. are mentioned. However, it is not limited to these.

The heterocyclic group represented by R ^5D , R ^6D or R ^7D is preferably a heterocyclic group containing an N, O or S atom, for example, a pyridyl group, a furyl group, a thienyl group, an imidazolyl group, a pyrrolyl group or the like. Is mentioned.

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 R ^8D , R ^9D or R ^10D may have a substituent. The same substituents as in the formula (2) can be mentioned.

  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, Examples include compounds described in Kaihei 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 specific polymerization initiator 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. More preferred.

[Other polymerization initiators]
The ink composition of the present invention is required to contain at least the specific polymerization initiator as a photopolymerization initiator, but other photopolymerization initiators may be used in combination as long as the effects of the present invention are not impaired. Good.
Examples of known polymerization initiators that can be used in combination include camphorquinone, benzophenone, benzophenone derivatives, acetophenone, acetophenone derivatives, such as α-hydroxycycloalkyl phenyl ketones or 2-hydroxy-2-methyl-1-phenyl-propanone. Dialkoxyacetophenones, α-hydroxy- or 4-aroyl-1,3-dioxolanes, benzoin alkyl ethers and benzyl ketals, for example, benzyl dimethyl ketal, phenyl glyoxalate and its derivatives, dimeric phenyl glyoxalate Peresters 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, Hexaarylbisimidazole / 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 described in GB 2,339,571 It is also possible to use mixtures of UNA O- acyloxime ester compound. A boric acid compound can also be used as a co-initiator.

  The content of the polymerization initiator in the ink composition of the present invention is preferably 0.01 to 35 parts by mass with respect to (iii) 100 parts by mass of the polymerizable compound having an ethylenically unsaturated bond, which will be described later. The content is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 30 parts by mass. Here, the content of the polymerization initiator means the total content of the polymerization initiator including the specific polymerization initiator and other polymerization initiators that can be used in combination.

<(Iii) Polymerizable compound having an ethylenically unsaturated bond>
The ink composition of the present invention contains a polymerizable compound. The polymerizable compound that can be suitably used in the present invention is a compound having an ethylenically unsaturated bond capable of radical polymerization, and any compound having at least one ethylenically unsaturated bond capable of radical polymerization in the molecule. Any type may be used, including those having chemical forms such as monomers, oligomers, and polymers.
Only one kind of radically polymerizable compound may be used, or two or more kinds thereof may be used in combination at an arbitrary ratio in order to improve desired properties. It is preferable to use two or more kinds in combination for controlling performance such as reactivity and physical properties.

Examples of the polymerizable compound having an ethylenically unsaturated bond include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid and their salts, and ethylenically unsaturated groups. Examples thereof include radically polymerizable compounds such as anhydrides, acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes.
Specifically, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, bis (4-acryloxypolyethoxyphenyl) propane, neopentyl glycol Diacrylate, 1,6-hexanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, pentaerythritol triacrylate, pentaerythritol Tetraacrylate, dipentaery Acrylic acid derivatives such as lithol tetraacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, oligoester acrylate, N-methylol acrylamide, diacetone acrylamide, epoxy acrylate, methyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate , Lauryl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate, 1,6-hexanediol dimethacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, trimethylol Methacryl derivatives such as tan trimethacrylate, trimethylolpropane trimethacrylate, 2,2-bis (4-methacryloxypolyethoxyphenyl) propane, and other derivatives of allyl compounds such as allyl glycidyl ether, diallyl phthalate, triallyl trimellitate More specifically, Shinzo Yamashita, “Cross-linking agent handbook”, (1981 Taiseisha); Kato Kiyomi, “UV / EB curing handbook (raw material)” (1985, Polymer publication) ); Rad-Tech Study Group, “Application and Market of UV / EB Curing Technology”, p. 79, (1989, CMC); Eiichiro Takiyama, “Polyester Resin Handbook”, (1988, Nikkan Kogyo Shimbun) Commercially available products described in the above, or radically polymerizable or crosslinkable monomers known in the industry, Ligomers and polymers can be used.

  Examples of the radical polymerizable compound are described in JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, JP-A-10-863, JP-A-9-134011 and the like. And a photocurable polymerizable compound used in the photopolymerizable composition.

In order to further improve sensitivity, bleeding, and adhesion to a recording medium, a monoacrylate and a polyfunctional acrylate monomer or a polyfunctional acrylate oligomer having a molecular weight of 400 or more, preferably 500 or more are used in combination as a radical polymerizable compound. Is preferred. In particular, in an ink composition used for recording on a flexible recording medium such as a PET film or a PP film, a combination of a monoacrylate selected from the above compound group and a polyfunctional acrylate monomer or polyfunctional acrylate oligomer is used. It is preferable because the film strength can be increased while the film is flexible to improve adhesion.
Furthermore, an aspect in which at least three kinds of polymerizable compounds of monofunctional, bifunctional, and trifunctional or higher polyfunctional monomers are used in combination further maintains sensitivity, bleeding, and adhesion to a recording medium. This is preferable from the viewpoint of further improvement.

As monoacrylates, stearyl acrylate, isoamyl acrylate, isomystil acrylate, and isostearyl acrylate have high sensitivity and low shrinkage to prevent curling. preferable.
As the oligomer that can be used in combination with the monoacrylate, an epoxy acrylate oligomer and a urethane acrylate oligomer are particularly preferable.
In addition, methacrylate has better skin irritation than acrylate.
Among the above compounds, when alkoxy acrylate is used in an amount of less than 70% by mass and the balance is acrylate, it is preferable because it has good sensitivity, bleeding characteristics, and odor characteristics.

The ink composition of the present invention contains the components (i) to (iii) as essential components, but other known components can be used in combination as additives of the ink composition depending on the purpose. Hereinafter, these optional components will be described.
<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, but (1) pigments and (2) oil-soluble dyes that are excellent in weather resistance and rich in color reproducibility are preferable. The known colorant can be selected and used. The colorant that can be suitably used in the ink composition of the present invention or the ink composition for inkjet recording functions as a polymerization inhibitor in a polymerization reaction that is a curing reaction from the viewpoint of not reducing the sensitivity of the curing reaction by actinic radiation. It is preferred to select compounds that do not.

(1) Pigment The pigment that can be used in the present invention is not particularly limited. For example, organic or inorganic pigments having the following numbers described in the color index can be used.
Examples of the red or magenta pigment include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, and 53. : 1, 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13, 16, 20, 36, and the like.
Examples of the blue or cyan pigment include Pigment Blue 1, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17-1, 22, 27, 28, 29, 36. , 60, and the like.
Examples of the green pigment include Pigment Green 7, 26, 36, 50, and the like.
Examples of the yellow pigment include Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, and 137. 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193, and the like.
Examples of the black pigment include Pigment Black 7, 28, 26, and the like.
Examples of the white pigment include Pigment White 6, 18, 21, and the like.
These pigments can be appropriately selected and used according to the purpose.

(2) Oil-soluble dye The oil-soluble dye that can be used in the present invention is described below.
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 and xanthene dyes; quinone dyes such as naphthoquinone, anthraquinone and 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 Spillon 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. .

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

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

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

  In preparing the ink composition of the present invention, the colorant may be added by adding directly with each component. However, in order to improve dispersibility, a solvent or a specific monofunctional (meth) acrylic acid derivative according to the present invention is used in advance. Alternatively, it may be added to a dispersion medium such as other polymerizable compound used in combination as desired, and uniformly dispersed or dissolved, and then blended.

  In the present invention, in order to avoid the problem of deterioration of the solvent resistance of the image portion over time and the problem of VOC (Volatile Organic Compound) of the remaining solvent, which is a concern when the solvent remains in the cured image. The colorant is preferably added in advance to any one of a polymerizable compound containing a specific monofunctional (meth) acrylic acid derivative or a mixture thereof and blended. In consideration of only dispersibility, it is preferable to select a monomer having the lowest viscosity as the polymerizable compound used for the addition of the colorant.

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

  The content of the colorant in the ink composition of the present invention is appropriately selected depending on the purpose of use. However, in consideration of the ink physical properties and colorability, generally, the content of the colorant is 1 with respect to the total mass of the ink composition. It is preferable that it is -10 mass%, and it is more preferable to contain 2-8 mass%.

<Other ingredients>
If necessary, other components can be added to the ink composition of the present invention. Examples of other components include a polymerization inhibitor and a solvent.
A polymerization inhibitor may be added from the viewpoint of enhancing the storage stability. Further, when the ink composition of the present invention is used as an ink composition for ink jet recording, it is preferably discharged at a temperature in the range of 40 to 80 ° C. with a reduced viscosity, and also for preventing head clogging due to thermal polymerization. It is preferable to add a polymerization inhibitor. The polymerization inhibitor is preferably added in an amount of 200 to 20,000 ppm based on the total amount of the ink composition of the present invention. Examples of the polymerization inhibitor include hydroquinone, benzoquinone, p-methoxyphenol, TEMPO, TEMPOL, and cuperon Al.

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

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

-Properties of ink composition-
As described above, the ink composition of the present invention needs to contain a polymerization initiator and a specific monofunctional (meth) acrylic acid derivative, and as other optional components, other polymerizable compounds, colorants, and the like. It contains.
These components are preferably 1 to 10% by mass, more preferably 2 to 8% by mass of the colorant based on the total mass of the ink composition, and an acidic group-containing monofunctional (meth) acrylic acid derivative or basic. The total polymerizable compound including the group-containing monofunctional (meth) acrylic acid derivative is preferably 5 to 97% by mass, and more preferably 30 to 95% by mass. The amount of the polymerization initiator is preferably 0.01 to 35% by mass, more preferably 0.1 to 30% by mass, and more preferably 0.1 to 30% by mass, based on the total polymerizable compound including the specific monofunctional (meth) acrylic acid derivative. It is suitable to contain so that it may become 0.5-30 mass% preferably.

The ink composition of the present invention can be suitably used as an ink for inkjet recording. The preferred physical properties in the usage mode as the ink for inkjet recording will be described.
When the ink composition is used as an ink for ink jet recording, the viscosity is preferably 7 to 30 mPa at the temperature at the time of ejection (for example, 40 to 80 ° C., preferably 25 to 50 ° C.) in consideration of the ejectability. · S, more preferably 7 to 25 mPa · s. For example, the viscosity of the ink composition of the present invention at room temperature (25 to 30 ° C.) is preferably 35 to 500 mPa · s, more preferably 35 to 200 mPa · s.
It is preferable that the composition ratio of the ink composition of the present invention is appropriately adjusted so that the viscosity is in the above range. By setting the viscosity at room temperature high, even when a porous recording medium is used, ink penetration into the recording medium can be avoided, and uncured monomers and odors can be reduced. Furthermore, ink bleeding at the time of ink droplet landing can be suppressed, and as a result, the image quality is improved.

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

[Inkjet recording method]
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 that the radiation curable ink has 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 starting species such as radicals, acids, bases, etc. 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 or a method of irradiating a recording unit with UV light by applying a collimated light source to a mirror surface provided on the side of the head unit 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.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to the form in these Examples. The following examples relate to UV ink jet ink compositions for each color. Further, in the following description, unless otherwise specified, “parts” means “parts by mass”.

[Example 1]
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink composition.
(White ink composition)
Light acrylate LA 17.4 parts [Lauryl acrylate: monofunctional acrylate]
Actylane 421 (Akcros acrylate monomer) 25.0 parts [propoxylated neopentyl glycol diacrylate: bifunctional acrylate]
-Photomer 2017 (UV diluent manufactured by EChem) 15.0 parts-Solsperse 36000 (dispersant made by Noveon) 2.0 parts-15.0 parts-MICROLITH WHITE R-A (pigment manufactured by Ciba Specialty Chemicals)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 parts-Rapi-Cure DVE-3 8.0 parts (vinyl ether manufactured by ISP Europe)
Specific sensitizing dye [Compound I-4 (the following structure)] 4.0 parts Darocur TPO [specific polymerization initiator (P-2)] 8.5 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
・ Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts

<Evaluation of ink composition>
The obtained ink composition was printed on a sheet made of polyvinyl chloride, and the desired integrated exposure (described in Tables 1 and ² ) under the light of an iron-doped ultraviolet lamp (power 120 W / cm ² ). The ink was cured by changing the transport speed so as to pass through to cure the ink, and a printed matter was obtained. Tables 1 and 2 show 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 accumulated 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 matter. If the color liquid is transferred immediately after printing, press the plain paper (Fuji Xerox Co., Ltd. copy paper C2). It was good.

−Discharge stability−
After storing the obtained ink composition at room temperature for 4 weeks, using a commercially available ink jet recording apparatus having a piezo ink jet nozzle, recording on a recording medium is performed, and dot missing when continuously printed at room temperature for 48 hours. In addition, the presence or absence of ink scattering was visually observed and evaluated according to the following criteria. The results are shown in Table 1 below.
○: Dot drop or ink splatter does not occur or occurs 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 ink jet recording apparatus used for the evaluation consists of the original tank, supply pipe, ink supply tank immediately before the ink jet head, filter, and piezo ink jet head. The ink supply tank to the ink jet head part are insulated and heated. 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.

[Example 2]
The following components were stirred with a high-speed water-cooled stirrer to obtain a cyan UV inkjet ink composition.
(Cyan ink composition)
Light acrylate LA 21.4 parts Actylene 421 (Akcros acrylate monomer) 30.0 parts Photomer 2017 (EChem UV diluent) 20.0 parts Solsperse 32000 (Noveon dispersant) 0 .4 parts ・ Irgalite Blue GLVO 3.6 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 part-Rapi-Cure DVE-3 (vinyl ether manufactured by ISP Europe)
8.0 parts Specific sensitizing dye [Compound I-4 (the above structure)] 4.0 parts Darocur TPO 8.5 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

Example 3
The following components were stirred with a high-speed water-cooled stirrer to obtain a magenta UV inkjet ink composition.
(Magenta ink composition)
Light acrylate L-A 15.4 parts Actylene 421 (Akcros acrylate monomer) 36.0 parts Photomer 2017 (EChem UV diluent) 20.0 parts Solsperse 32000 (Noveon dispersant) 0 .4 parts-Cinquasia Magenta RT-355 D
(Ciba Specialty Chemicals Pigment) 3.6 parts Genorad 16 (Rahn Stabilizer) 0.05 parts Rapid-Cure DVE-3 8.0 parts (ISP Europe Vinyl Ether)
Specific sensitizing dye [Compound I-4 (the above structure)] 4.0 parts Darocur TPO 8.5 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
・ Irgacure 907 [specific polymerization initiator] 4.0 parts (Ciba Specialty Chemicals photoinitiator)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

Example 4
The following components were stirred with a high-speed water-cooled stirrer to obtain a yellow UV inkjet ink composition.
(Yellow color ink composition)
Light acrylate LA 10.0 parts Actylene 421 (Akcros acrylate monomer) 45.4 parts Photomer 2017 (EChem UV diluent) 20.0 parts Solsperse 32000 (Noveon dispersant) 0 .4 parts · Chromophthalal Yellow LA 3.6 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 parts-Rapi-Cure DVE-3 4.0 parts (vinyl ether manufactured by ISP Europe)
Specific sensitizing dye [Compound I-4 (the above structure)] 4.0 parts Darocur TPO 8.5 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

Example 5
The following components were stirred with a high-speed water-cooled stirrer to obtain a black UV inkjet ink composition.
(Black ink composition)
Light acrylate LA 24.4 parts Actylene 421 (Akcros acrylate monomer) 31.0 parts Photomer 2017 (EChem UV diluent) 20.0 parts Solsperse 32000 (Noveon dispersant) 0 .4 parts Microlith Black C-K 2.6 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 part-Rapi-Cure DVE-3 5.0 parts (vinyl ether manufactured by ISP Europe)
Specific sensitizing dye [Compound I-4 (the above structure)] 4.0 parts Darocur TPO 8.5 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

Example 6
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink composition.
(White ink composition)
・ Phenoxyethyl acrylate 25.0 parts ・ N-vinylcaprolactam 15.0 parts ・ FA-512A [the following structure] 17.4 parts ・ Solsperse 36000 (a dispersant manufactured by Noveon) 2.0 parts ・ MICROLITH WHITE R-A 15 0.0 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 parts-Rapi-Cure DVE-3 8.0 parts (vinyl ether manufactured by ISP Europe)
Specific sensitizing dye [Compound I-4 (the above structure)] 4.0 parts Darocur TPO 8.5 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

[Comparative Example 1]
The following components were stirred with a high-speed water-cooled stirrer to obtain a comparative cyan UV inkjet ink composition.
(Comparative cyan ink composition)
Light acrylate LA 21.4 parts Actylene 421 (Akcros acrylate monomer) 30.0 parts Photomer 2017 (EChem UV diluent) 20.0 parts Solsperse 32000 (Noveon dispersant) 0 .4 parts ・ Irgalite Blue GLVO 3.6 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 part-Rapi-Cure DVE-3 (vinyl ether manufactured by ISP Europe)
8.0 parts ・ Lucirin TPO (photopolymerization initiator manufactured by BASF) 8.5 parts ・ Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

[Comparative Example 2]
The following components were stirred with a high-speed water-cooled stirrer to obtain a cyan UV inkjet ink composition.
(Cyan ink composition)
Light acrylate LA 21.4 parts Actylene 421 (Akcros acrylate monomer) 30.0 parts Photomer 2017 (EChem UV diluent) 20.0 parts Solsperse 32000 (Noveon dispersant) 0 .4 parts ・ Irgalite Blue GLVO 3.6 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 part-Rapi-Cure DVE-3 (vinyl ether manufactured by ISP Europe)
8.0 parts, 2-chlorothioxanthone 4.0 parts, Lucirin TPO (photopolymerization initiator manufactured by BASF) 8.5 parts, Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization manufactured by Ciba Specialty Chemicals) Initiator)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

[Comparative Example 3]
The following components were stirred with a high-speed water-cooled stirrer to obtain a cyan UV inkjet ink composition.
(Cyan ink composition)
Light acrylate LA 21.4 parts Actylene 421 (Akcros acrylate monomer) 30.0 parts Photomer 2017 (EChem UV diluent) 20.0 parts Solsperse 32000 (Noveon dispersant) 0 .4 parts ・ Irgalite Blue GLVO 3.6 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 part-Rapi-Cure DVE-3 (vinyl ether manufactured by ISP Europe)
8.0 parts, 2,4-diethylthioxanthone 4.0 parts, Lucirin TPO (photopolymerization initiator manufactured by BASF) 8.5 parts, Irgacure 907 [specific polymerization initiator] 4.0 parts (produced by Ciba Specialty Chemicals) Photopolymerization initiator)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

[Comparative Example 4]
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink composition.
(White ink composition)
・ Phenoxyethyl acrylate 25.0 parts ・ N-vinylcaprolactam 15.0 parts ・ FA-512A [above structure] 17.4 parts ・ Solsperse 36000 (Noveon dispersant) 2.0 parts ・ MICROLITH WHITE R-A 15 0.0 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 parts-Rapi-Cure DVE-3 8.0 parts (vinyl ether manufactured by ISP Europe)
・ 4.0 parts of 2,4-diethylthioxanthone 8.5 parts of Darocur TPO (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

  From Table 1, Examples 1-6 using the sensitizing dye 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, and other than the present invention. It can be seen that the ejection stability is better than Comparative Examples 2 to 4 using a sensitizing dye.

Example 7
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink composition.
(White ink composition)
-Light acrylate LA 15.4 parts [Acrylic lauryl ester: monofunctional acrylate]
Actylane 421 (Akcros acrylate monomer) 23.0 parts [propoxylated neopentyl glycol diacrylate: bifunctional acrylate]
-Photomer 2017 (UV diluent manufactured by EChem) 15.0 parts-Solsperse 36000 (dispersant made by Noveon) 2.0 parts-15.0 parts-MICROLITH WHITE R-A (pigment manufactured by Ciba Specialty Chemicals)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 parts-Rapi-Cure DVE-3 8.0 parts (vinyl ether manufactured by ISP Europe)
Specific sensitizing dye [Compound I-4 (the above structure)] 8.0 parts Darocur TPO [Specific polymerization initiator (P-2)] 8.5 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

Example 8
In Example 1, an ink composition was prepared in the same manner as in Example 1 except that the sensitizing dye I-4 was replaced with the specific sensitizing dye I-14 (the following structure). The obtained ink composition was evaluated in the same manner as in Example 1.

[Example 9] to [Example 12]
In Example 7, an ink composition was prepared in the same manner as in Example 1 except that the sensitizing dye I-4 was replaced with the compound (specific sensitizing dye) shown in Table 2, and evaluated in the same manner as in Example 1. did.
The structure of the specific sensitizing dye is the structure described above.

  Separately, an ink composition in which only the pigment was removed from the compositions of Examples 7, 9, and 10 was separately prepared. Under severe storage conditions, when the ink composition was stored at 60 ° C. for 4 weeks, the ink composition of Example 7 showed gelation, whereas the ink composition of Example 9 had a slight viscosity. Although an increase was observed, gelation did not occur. Further, the ink composition of Example 10 hardly changed. Although it is a result on severe storage conditions, it turns out that the number of hydrogen atoms is smaller in the carbon atom adjacent to the S atom from the viewpoint of thermal stability.

Example 13
The following components were stirred with a high-speed water-cooled stirrer to obtain a cyan UV inkjet ink composition.
(Cyan ink composition)
Light acrylate L-A 19.4 parts Actylane 421 (Akcros acrylate monomer) 28.0 parts Photomer 2017 (EChem UV diluent) 20.0 parts Solsperse 32000 (Noveon dispersant) 0 .4 parts ・ Irgalite Blue GLVO 3.6 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 part-Rapi-Cure DVE-3 (vinyl ether manufactured by ISP Europe)
8.0 parts-Specific sensitizing dye [Compound I-14 (Structure)] 8.0 parts-Darocur TPO 8.5 parts (Ciba Specialty Chemicals photopolymerization initiator)
Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

Example 14
The following components were stirred with a high-speed water-cooled stirrer to obtain a magenta UV inkjet ink composition.
(Magenta ink composition)
Light acrylate L-A 13.4 parts Actylane 421 (Akcros acrylate monomer) 34.0 parts Photomer 2017 (EChem UV diluent) 20.0 parts Solsperse 32000 (Noveon dispersant) 0 .4 parts-Cinquasia Magenta RT-355 D
(Ciba Specialty Chemicals Pigment) 3.6 parts Genorad 16 (Rahn Stabilizer) 0.05 parts Rapid-Cure DVE-3 8.0 parts (ISP Europe Vinyl Ether)
Specific sensitizing dye [Compound I-14 (the above structure)] 8.0 parts Darocur TPO 8.5 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
・ Irgacure 907 [specific polymerization initiator] 4.0 parts (Ciba Specialty Chemicals photoinitiator)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

Example 15
The following components were stirred with a high-speed water-cooled stirrer to obtain a yellow UV inkjet ink composition.
(Yellow color ink composition)
Light acrylate L-A 8.0 parts Actylene 421 (Akcros acrylate monomer) 43.4 parts Photomer 2017 (EChem UV diluent) 20.0 parts Solsperse 32000 (Noveon dispersant) 0 .4 parts · Chromophthalal Yellow LA 3.6 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 parts-Rapi-Cure DVE-3 4.0 parts (vinyl ether manufactured by ISP Europe)
Specific sensitizing dye [Compound I-14 (the above structure)] 8.0 parts Darocur TPO 8.5 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

Example 16
The following components were stirred with a high-speed water-cooled stirrer to obtain a black UV inkjet ink composition.
(Black ink composition)
Light acrylate LA 22.4 parts Actylene 421 (Akcros acrylate monomer) 29.0 parts Photomer 2017 (EChem UV diluent) 20.0 parts Solsperse 32000 (Noveon dispersant) 0 .4 parts Microlith Black C-K 2.6 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 part-Rapi-Cure DVE-3 5.0 parts (vinyl ether manufactured by ISP Europe)
Specific sensitizing dye [Compound I-14 (the above structure)] 8.0 parts Darocur TPO 8.5 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

Example 17
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink composition.
(White ink composition)
・ Phenoxyethyl acrylate 25.0 parts ・ N-vinylcaprolactam 15.0 parts ・ FA-512A [above structure] 13.4 parts ・ Solsperse 36000 (Noveon dispersant) 2.0 parts ・ MICROLITH WHITE R-A 15 0.0 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 parts-Rapi-Cure DVE-3 8.0 parts (vinyl ether manufactured by ISP Europe)
Specific sensitizing dye [Compound I-14 (the above structure)] 8.0 parts Darocur TPO 8.5 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

Example 18
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink composition.
(White ink composition)
・ Phenoxyethyl acrylate 25.0 parts ・ N-vinylcaprolactam 15.0 parts ・ FA-512A [above structure] 19.4 parts ・ Solsperse 36000 (Noveon dispersant) 2.0 parts ・ MICROLITH WHITE R-A 15 0.0 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 part-2.0 parts of Rapi-Cure DVE-3 (vinyl ether manufactured by ISP Europe)
Specific sensitizing dye [Compound I-14 (the above structure)] 8.0 parts Darocur TPO 8.5 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

Example 19
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink composition.
(White ink composition)
・ Phenoxyethyl acrylate 25.0 parts ・ N-vinylcaprolactam 15.0 parts ・ FA-512A [above structure] 13.4 parts ・ Solsperse 36000 (Noveon dispersant) 2.0 parts ・ MICROLITH WHITE R-A 15 0.0 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 parts-Rapi-Cure DVE-3 8.0 parts (vinyl ether manufactured by ISP Europe)
Specific sensitizing dye [Compound I-17 (following structure)] 8.0 parts Darocur TPO 8.5 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

Example 20
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink composition.
(White ink composition)
・ Phenoxyethyl acrylate 25.0 parts ・ N-vinylcaprolactam 15.0 parts ・ FA-512A [above structure] 13.4 parts ・ Solsperse 36000 (Noveon dispersant) 2.0 parts ・ MICROLITH WHITE R-A 15 0.0 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 parts-Rapi-Cure DVE-3 8.0 parts (vinyl ether manufactured by ISP Europe)
Specific sensitizing dye [Compound I-129 (the following structure)] 8.0 parts Darocur TPO 8.5 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
・ Irgacure 2959 (IR2959) 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

Example 21
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink composition.
・ Phenoxyethyl acrylate 25.0 parts ・ N-vinylcaprolactam 15.0 parts ・ FA-512A [above structure] 13.4 parts ・ Solsperse 36000 (Noveon dispersant) 2.0 parts ・ MICROLITH WHITE R-A 15 0.0 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 parts-Rapi-Cure DVE-3 8.0 parts (vinyl ether manufactured by ISP Europe)
Specific sensitizing dye [Compound I-71 (the following structure)] 8.0 parts Irgacure 819 [Specific polymerization initiator (P-19)] 8.5 parts (Ciba Specialty Chemicals photopolymerization initiator)
・ Irgacure 2959 4.0 parts (Photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

[Example 22]
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink composition.
(White ink composition)
・ Phenoxyethyl acrylate 25.0 parts ・ N-vinylcaprolactam 15.0 parts ・ FA-512A [above structure] 13.4 parts ・ Solsperse 36000 (Noveon dispersant) 2.0 parts ・ MICROLITH WHITE R-A 15 0.0 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 part-Rapi-Cure DVE-3 (vinyl ether manufactured by ISP Europe)
8.0 parts / specific sensitizing dye [compound I-116 (the following structure)] 8.0 parts / Irgacure 819 8.5 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
・ Irgacure 369 [specific polymerization initiator] 4.0 parts (Ciba Specialty Chemicals photopolymerization initiator)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

[Comparative Example 5]
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink composition.
(White ink composition)
・ Phenoxyethyl acrylate 23.0 parts ・ N-vinylcaprolactam 15.0 parts ・ FA-512A [above structure] 17.4 parts ・ Solsperse 36000 (Noveon dispersant) 2.0 parts ・ MICROLITH WHITE R-A 15 .0 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (stabilizer manufactured by Rahn) 0.05 parts-Rapi-Cure DVE-3 8.0 parts (vinyl ether manufactured by ISP Europe)
• 2,4-diethylthioxanthone 8.0 parts • Darocur TPO 8.5 parts (Ciba Specialty Chemicals photopolymerization initiator)
Irgacure 907 [specific polymerization initiator] 4.0 parts (photopolymerization initiator manufactured by Ciba Specialty Chemicals)
Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts This ink composition was evaluated in the same manner as in Example 1.

As is apparent from Table 2, even if the sensitizing dye of the present invention is changed or the colorant is changed, the ink compositions of Examples 7 to 22 of the present invention are all cured with high sensitivity and discharged. It was excellent in stability. When compared with Comparative Example 1 in Table 1, it can be clearly seen that the sensitivity is particularly high.
In addition, since the images formed on the printed materials in Examples 1, 6, 7 to 12, and 17 to 22 have a good white color, the ink composition of the present invention is excellent in sensitivity and ejection stability. Further, it can be seen that a white ink excellent in color reproducibility can be obtained.
On the other hand, the ink composition of Comparative Example 5 in which the sensitizing dye is not the specific sensitizing dye of the present invention has good curability but has insufficient ejection stability. Since the white ink of Comparative Example 5 was yellow-colored presumably due to the comparative sensitizing dye 2,4-diethylthioxanthone, the color reproducibility of the white image was not good.

Claims (6)

(I) a sensitizing dye represented by the following general formula (I); (ii) a polymerization initiator selected from the group consisting of α-aminoketones and acylphosphine oxides; and (iii) an ethylenically unsaturated bond. And an ink composition containing the polymerizable compound.

In the formula (I), X represents O, S, or NR. n represents 0 or 1. R represents a hydrogen atom, an alkyl group, or an acyl group.
^{R 1, R 2, R 3} , and R ⁴ each independently represent a hydrogen atom, an alkyl group, a halogen atom, or an alkylthio group. R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represents a hydrogen atom or an alkyl group. In the formula (I), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ And R ⁸ The ink composition according to claim 1, wherein the alkyl group represented by formula (1) has 1 to 10 carbon atoms. In the formula (I), R represents a hydrogen atom or an alkyl group, and R ¹ , R ⁴ And R ⁵ Represents a hydrogen atom and R ² And R ³ Each independently represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom, or an alkylthio group; ⁶ , R ⁷ And R ⁸ The ink composition according to claim 1, wherein each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. The ink composition according to any one of claims 1 to 3, comprising a colorant. The ink composition according to any one of claims 1 to 4, which is for inkjet recording. (A) a step of discharging the ink composition according to any one of claims 1 to 5 onto a recording medium; and (b) irradiating the discharged ink composition with actinic radiation, curing the ink composition, the containing inaction inkjet recording method.