JP6318111B2 - Photopolymerization initiator and ink composition, ink set and image forming method using the same - Google Patents

Description

  The present invention relates to a compound useful as a photopolymerization initiator. The present invention also relates to an ink composition and an ink set containing the compound. Furthermore, the present invention relates to an image forming method using this ink composition or ink set.

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 ink jet method does not require a plate at the time of printing, and the ink composition is ejected only on the required image portion to form an image directly on the recording medium. Therefore, the ink composition can be used efficiently, and the running cost is low. cheap. Furthermore, the ink jet system has a cheap printing apparatus and low noise. As described above, the inkjet method has various advantages as compared with other image recording methods.
A radiation curable ink composition is known as an ink composition used for an ink jet system. Since this radiation curable ink composition is polymerized and cured by irradiation of radiation such as ultraviolet rays, a radiation non-curable ink composition (solvent ink composition) was used. There are advantages such as that the image is less likely to bleed compared to the case.

  In recent years, from the viewpoint of energy saving and space saving, it is desired to use a light emitting diode (LED) as an ultraviolet (UV) light source for curing a radiation curable ink composition.

  In addition, from the viewpoint of environmental protection and safety, reduction of volatile organic compounds (VOC) that have been widely used as a solvent or the like has been demanded. For this reason, water-based photocuring systems that can reduce the amount of VOC used have attracted attention. Also in the field of printing inks, various water-based photocurable inks using a water-soluble organic solvent such as water or alcohol as a medium have been proposed and applied to an ink jet recording system.

  A water-soluble photopolymerization initiator is used for such a water-based photocurable ink jet recording ink. However, among currently available photopolymerization initiators, those that can be used in an aqueous system are very limited, such as α-hydroxyacetophenone (for example, Patent Documents 1 and 2). .

JP 2009-173879 A International Publication No. 86/05778

Patent Document 1 discloses an α-hydroxyacetophenone type photoinitiator having an anionic group composed of carboxylic acid, sulfonic acid, sulfuric acid or a salt thereof as a pendant. However, the α-hydroxyacetophenone type photoinitiator disclosed in Patent Document 1 has a problem that its synthesis and purification are not easy and are difficult to obtain. Further, when the ink using this photoinitiator is stored at a low temperature, there is a concern that the photoinitiator is precipitated.
Patent Document 2 discloses an α-hydroxyacetophenone type photoinitiator having a water-soluble group at the para position relative to the ketone group. However, the 2-hydroxyacetophenone type photopolymerization initiator disclosed in Patent Document 2 does not have sufficient water solubility, and is not suitable for energy rays from a UV-LED light source (around 365 nm) in terms of the maximum absorption wavelength. There was the difficulty of not having sufficient absorption.

An object of the present invention is to provide a compound that has both high sensitivity to ultraviolet light and high solubility in water and is useful as a water-soluble photopolymerization initiator. In particular, this compound has high absorption in light having a wavelength near 365 nm, and is suitable as an initiator for a photopolymerization reaction using a UV-LED light source.
Moreover, this invention makes it a subject to provide the ink composition excellent in sclerosis | hardenability which mix | blended this compound as a photoinitiator. Furthermore, an object of the present invention is to provide an ink set using the ink composition and an image recording method.

  The present inventors have conducted intensive studies in view of the above problems. As a result, the α-hydroxyacetophenone compound having a specific structure has high water solubility and excellent absorption with respect to light in the ultraviolet region, and the ink composition using this compound has an ultraviolet light source, particularly UV. -It discovered that favorable curability was shown by active energy ray irradiation using LED light source. The present invention has been completed based on these findings.

That is, the said subject was solved by the following means.
[1]
A compound represented by the following general formula (1).

In general formula (1), R ^{1 to} R ⁴ each independently represents a hydrogen atom or an alkyl group having 6 or less carbon atoms. However, one or two of R ^{1 to} R ⁴ are groups represented by the following general formula (2) or (3). R ⁵ represents a hydrogen atom or an alkyl group having 6 or less carbon atoms. R ⁶ and R ⁷ each independently represents an alkyl group or an aryl group. R ⁶ and R ⁷ may combine with each other to form a 5- or 6-membered ring.

In the general formulas (2) and (3), R ⁸ represents an alkylene group which may contain a hetero atom. R ⁹ represents a hydrogen atom or an alkyl group having 6 or less carbon atoms. R ¹⁰ has the same meaning as R ⁸ and R ¹¹ has the same meaning as R ⁹ . * Represents a bonding site with a benzene ring .
[2 ]
R ¹ to R ⁴ of one or two is a group represented by the general formula (2), compounds described in [1].
[ 3 ]
The compound according to [1] or [2] , wherein R ⁸ is a group represented by the following general formula (4).

In general formula (4), n represents the integer of 0-5.
[ 4 ]
The compound according to any one of [1] to [ 3 ], wherein R ³ is a group represented by the general formula (2).
[5]
R ¹ , R ² , and R ⁴ are hydrogen atoms or methyl groups, R ⁶ and R ⁷ are alkyl groups, and R ⁸ is a C 1-6 alkylene group having one oxygen atom, The compound according to [4], wherein R ⁹ is a hydrogen atom, a methyl group or an ethyl group.
[6]
The compound according to any one of [1] to [5], wherein R ⁶ and R ⁷ are methyl groups.
[ 7 ]
An ink composition comprising a photopolymerization initiator composed of the compound according to any one of [1] to [ 6 ], a polymerizable compound, and an aqueous medium.
[ 8 ]
An ink application step of applying the ink composition according to [ 7 ] on a recording medium;
And an active energy ray irradiating step of irradiating the ink composition applied on the recording medium with an active energy ray.
[ 9 ]
The image forming method according to [ 8 ], wherein the peak wavelength of the active energy ray is 300 to 450 nm.
[ 10 ]
The image formation according to [ 8 ] or [ 9 ], which includes a treatment agent application step of applying a treatment agent containing an aggregating component onto a recording medium, and the treatment agent application step is performed before the ink application step. Method.
[ 11 ]
The image forming method according to any one of [ 8 ] to [ 10 ], wherein the ink application step is a step of applying ink by an inkjet recording method.
[ 12 ]
[ 7 ] An ink set comprising the ink composition according to [ 7 ] and a treatment agent containing an aggregating component.

In this specification, unless otherwise specified, when there are a plurality of substituents, linking groups, ligands, repeating units, etc. (hereinafter referred to as substituents) represented by specific symbols, or a plurality of substituents, etc. Are defined simultaneously or alternatively, the respective substituents and the like may be the same as or different from each other. The same applies to the definition of the number of substituents and the like.
In the present specification, the “group” of each group described as an example of each substituent is used to include both an unsubstituted form and a form having a substituent. For example, “alkyl group” means an alkyl group which may have a substituent.
In the present invention, “(meth) acrylate” represents both and / or acrylate and methacrylate, and “(meth) acrylamide” represents both and / or acrylamide and methacrylamide.
In the present invention, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  The compound of the present invention has high sensitivity to ultraviolet rays and is useful as a water-soluble photopolymerization initiator. The ink composition and ink set of the present invention are excellent in curability because the compound of the present invention is blended as a photopolymerization initiator. Furthermore, according to the image forming method of the present invention, the image quality (rubbing resistance, blocking resistance, etc.) can be improved.

  The compound of the present invention is represented by the following general formula (1).

In general formula (1), R ^{1 to} R ⁴ each independently represents a hydrogen atom or an alkyl group having 6 or less carbon atoms. However, at least one of R ^{1 to} R ⁴ is a group represented by the following general formula (2) or (3). R ⁵ represents a hydrogen atom or an alkyl group having 6 or less carbon atoms. R ⁶ and R ⁷ each independently represents an alkyl group or an aryl group. R ⁶ and R ⁷ may combine with each other to form a 5- or 6-membered ring.

The alkyl group having 6 or less carbon atoms that can be adopted as R ^{1 to} R ⁴ is preferably a linear or branched alkyl group having 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms. Examples of the alkyl group having 6 or less carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, 3-ethylpentyl, and hexyl.
Among them, R ^{1 to} R ⁴ are preferably a hydrogen atom, methyl or ethyl, more preferably a hydrogen atom or methyl, and still more preferably a hydrogen atom.

In the general formula (1), at least one of R ^{1 to} R ⁴ is a group represented by the following general formula (2) or (3).

In General Formulas (2) and (3), R ⁸ represents a divalent hydrocarbon group that may contain a hetero atom. R ⁹ represents a hydrogen atom or an alkyl group having 6 or less carbon atoms. R ¹⁰ has the same meaning as R ⁸ and R ¹¹ has the same meaning as R ⁹ . * Represents a bonding site with a benzene ring.
Here, “a divalent hydrocarbon group which may contain a hetero atom” means that a part of the carbon-carbon bond of the divalent hydrocarbon group may be interrupted by a hetero atom.

The divalent hydrocarbon group which may contain a hetero atom and may be adopted as R ⁸ is preferably an arylene group or an alkylene group which may contain a hetero atom.
The above-mentioned alkylene group (when it does not contain a heteroatom) that can be adopted as R ⁸ may be linear or branched. When the said alkylene group is linear, the carbon number becomes like this. Preferably it is 1-4, More preferably, it is 1-3. Moreover, when the said alkylene group has a branch, the carbon number becomes like this. Preferably it is 3-7, More preferably, it is 3-6.
The arylene group that can be taken as R ⁸ is preferably phenylene or naphthylene, more preferably phenylene. The arylene group may have a substituent, and examples of the substituent on the arylene group include an alkyl group having 1 to 3 carbon atoms.
When the group represented by R ⁸ is a hydrocarbon group containing a hetero atom, examples of the hetero atom contained in the hydrocarbon group include an oxygen atom, a nitrogen atom, a sulfur atom, and a silicon atom. Especially, the form which has -O- and -S- in the carbon-carbon bond of a hydrocarbon group is preferable, and the form which has -O- is more preferable.
The alkylene group containing a hetero atom which R ⁸ can take is preferably a straight chain containing at least one hetero atom having 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, and still more preferably 1 to 4 carbon atoms. Or it is a branched alkylene group.
R ⁸ is preferably an alkylene group or an alkylene group containing an oxygen atom.

R ⁸ is particularly preferably a group represented by the following general formula (4) from the viewpoint of solubility in water.

  In general formula (4), n represents the integer of 0-5. n is preferably 1 to 5, and more preferably 1 or 2.

Among these, R ⁸ is preferably an alkylene group having 1 to 3 carbon atoms or a group represented by the general formula (4) where n is 1 or 2.

R ¹⁰ has the same meaning as R ⁸ , and the preferred range is also the same. R ¹⁰ and R ⁸ may be the same or different.

In general formulas (2) and (3), R ⁹ represents a hydrogen atom or an alkyl group having 6 or less carbon atoms.
The alkyl group having 6 or less carbon atoms that can be employed as R ⁹ is preferably a linear or branched alkyl group having 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms. Examples of the alkyl group having 6 or less carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, 3-ethylpentyl, and hexyl.
Among them, R ⁹ is preferably a hydrogen atom, methyl or ethyl, more preferably a hydrogen atom or methyl, and still more preferably a hydrogen atom.

R ¹¹ has the same meaning as R ⁹ , and the preferred range is also the same. R ¹¹ and R ⁹ may be the same or different.

  The compound represented by the general formula (1) preferably has one or two groups represented by the general formula (2) or (3), and preferably has one.

In the general formula (1), R ⁵ has the same meaning as R ⁹ , and the preferred form is also the same.

The alkyl group that can be adopted as R ⁶ and R ⁷ is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, and butyl.
The aryl group that can be adopted as R ⁶ and R ⁷ is preferably an aryl group having 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms. Examples of the aryl group include phenyl and naphthyl. The aryl group may have a substituent, and examples of the substituent on the aryl group include methyl, ethyl, propyl, isopropyl, and butyl.
The 5- or 6-membered ring formed by combining R ⁶ and R ⁷ is preferably an alicyclic hydrocarbon ring, and is preferably cyclohexane.
The R ⁶ and ^{R 7,} preferably even if the methyl or phenyl are preferred, also a cyclohexyl bonded ^{R 6} and ^{R 7.} Further, from the viewpoint of solubility in water, R ⁶ and R ⁷ are particularly preferably methyl.

In the compound represented by the general formula (1) of the present invention, the group represented by the general formula (2) or (3) is substituted at the meta position with respect to the carbon atom to which the carbonyl group is bonded. It is preferable that it is a compound. That is, in the general formula (1), R ³ or R ⁴ is preferably a group represented by the general formula (2) or (3).
When a plurality of groups represented by the general formula (2) or (3) are included in the general formula (1), the plurality of R ⁸ , R ⁹ , R ¹⁰ , and R ¹¹ may be the same or different. They may be the same.

From the viewpoint of blocking resistance, it is preferable that at least one of R ^{1 to} R ⁴ is a group represented by the general formula (2). Among these, it is preferable that one of R ^{1 to} R ⁴ is a group represented by the general formula (2). Furthermore, from the viewpoint of abrasion resistance, R ³ is particularly preferably a group represented by the above general formula (2). In this case, R ^{1 to} R ^{4 that} are not groups represented by the general formula (2) are preferably hydrogen atoms.

Specific examples of the compound represented by the general formula (1) (hereinafter collectively referred to as “the compound of the present invention”) are shown below, but the present invention is not limited thereto.
In the following, Me represents methyl, Et represents ethyl, and Ph represents phenyl.

  The compounds of the present invention can be synthesized by reaction of Grignard reagent prepared from aryl bromide with acid chloride. Also, Organic Letters, 2013, vol. 15, ISSUE 23 p. It can be synthesized with reference to 6086-6089.

The compound of this invention shows favorable solubility with respect to water-soluble organic solvents, such as water and alcohol, as demonstrated in the below-mentioned Example. The solubility of the compound of the present invention is not particularly limited, but the solubility in water at 20 ° C. is preferably 2% by mass or more, more preferably 2.5% by mass or more, and 3% by mass or more. It is particularly preferred.
Further, the compound of the present invention exhibits high sensitivity to light in the ultraviolet region, particularly light around 365 nm, and generates radicals. The generated radical polymerizes the polymerizable compound by a radical reaction. Due to these characteristics, the compound of the present invention can be suitably used as a water-soluble photopolymerization initiator. As a use mode of the compound of the present invention as a photopolymerization initiator, a photocurable water-based ink composition described below can be exemplified.

[Use of photopolymerization initiator]
The photopolymerization initiator of the present invention can be used for various materials.
For example, paints, adhesives, adhesives, inks, functional coatings, various films, various films, optical materials, printing plate materials, semiconductor materials, recording materials, tissue culture dishes, paper additives, medical materials, plastics , Water retaining agents, water absorbing agents, hydrophilic members and the like.
More specifically, various film antireflection layers, various film undercoat adhesive layers, various film coating layers, resists, printing plates, color filters, endoscope coating agents, ion exchange membranes, reverse osmosis membranes, conductive coatings. Examples thereof include membranes, medical adhesives, proton conductive membranes, and microporous membranes.

  For example, as the pressure-sensitive adhesive, a radiation curable type for an optical member is preferable by combining the polyfunctional acrylate described in International Publication No. 10/092995, International Publication No. 10/092988 pamphlet and the photopolymerization initiator of the present invention. An adhesive composition can be obtained.

  As an optical film, a preferable optical film can be produced by combining the polyfunctional acrylate described in JP-A-2008-165205, JP-A-2012-150428, and the photopolymerization initiator of the present invention.

  As a printing plate material, a preferred resin printing plate precursor for laser engraving can be prepared by combining a polyfunctional acrylate described in JP 2009-226946 A and the photopolymerization initiator of the present invention.

  As a solder resist material, each photosensitive film is produced by combining the polyfunctional acrylate described in JP-A No. 2009-217040, etc. and the photopolymerization initiator of the present invention, and a copper-clad laminate is produced using this photosensitive film. Can be stacked.

  As a metal material, a metal material can be made by combining the polyfunctional acrylate described in JP 2009-263707 A and the like and the photopolymerization initiator of the present invention.

  Each lens can be made by combining a polyfunctional acrylate described in JP 2011-072341 A and the photopolymerization initiator of the present invention. Medical materials described in JP 2011-072341 A (eye lens, endoscope, catheter, infusion tube, gas transport tube, stent, sheath, cuff, tube connector, access port, drainage bag, blood circuit, It is also useful as a wound dressing and drug carrier.

  Hereinafter, the ink composition which is a more preferable application will be described in detail.

<Ink composition>
The ink composition of the present invention contains at least the compound of the present invention represented by the general formula (1) as a photopolymerization initiator, and further contains a polymerizable compound and an aqueous medium. By including a photopolymerization initiator comprising the compound of the present invention and a polymerizable compound, an ink composition having excellent curability (curing reaction sensitivity) can be obtained, and an image can be formed on a recording medium using this ink composition. After the formation, an image having excellent abrasion resistance and blocking resistance can be formed by irradiating active energy rays such as light. Further, since the photopolymerization initiator comprising the compound of the present invention is water-soluble, it is suitable for an aqueous ink composition using water or a water-soluble organic solvent as a medium.
The ink composition of the present invention can be a clear ink (colorless ink) composition that does not contain a colorant (coloring material) or an ink composition that contains a colorant, but contains a colorant. It is preferable.
In addition, the ink composition of the present invention can be suitably used particularly as an inkjet ink.
The dose of the active energy ray for curing the ink composition of the present invention, when employing ultraviolet light, usually, the irradiation intensity (light output) 5~100mW / cm ^2, be a dose 100~3000mJ / cm ² As a result, the ink composition is usually cured in 1 second to 20 seconds.
Hereinafter, each component of the ink composition of the present invention will be described.

[Photopolymerization initiator]
The photopolymerization initiator used in the ink composition of the present invention is the compound of the present invention represented by the general formula (1) (hereinafter also referred to as “photopolymerization initiator of the present invention”). As the photopolymerization initiator, the compound of the present invention may be used alone or in combination of two or more.
The content of the photopolymerization initiator in the ink composition is preferably 0.1 to 40% by mass, more preferably 1 to 30% by mass, and more preferably 5 to 20% with respect to the total amount of solid components. More preferably, it is mass%.
In the present specification, “total amount of solid components” or “total solid content” refers to the total mass of components excluding water and organic solvent from the total composition of the composition.
Moreover, it is preferable to use 0.1-100 mass parts of photoinitiators with respect to 100 mass parts of polymeric compounds, It is more preferable to use 1-75 mass parts, It is more preferable to use 10-50 mass parts. .
This photopolymerization initiator suppresses the decomposition until the polymerization reaction starts by shielding light.

[Polymerizable compound]
The polymerizable compound used in the ink composition of the present invention is not particularly limited as long as it is a compound capable of initiating a polymerization reaction by the photopolymerization initiator of the present invention, and at least an ethylenically unsaturated bond capable of radical polymerization in the molecule. A compound having one or the like can be used. The polymerizable compound may be any of a monomer, an oligomer, a polymer and the like.
The polymerizable compound is preferably a water-soluble compound from the viewpoint of ejection stability of the ink composition. The solubility of the polymerizable compound is not particularly limited, but the solubility in water at 25 ° C. is preferably 2% by mass or more, more preferably 5% by mass or more, and further preferably 10% by mass or more. It is particularly preferably 20% by mass or more, and most preferably uniformly mixed with water at an arbitrary ratio.

Specific examples of such polymerizable compounds include (meth) acrylamide compounds, (meth) acrylate compounds, vinyl compounds, maleimide compounds, vinylsulfone compounds, N-vinylamide compounds, and derivatives thereof. These compounds are more preferably bifunctional or more. More preferred are (meth) acrylamide compounds, (meth) acrylate compounds and vinyl compounds, and particularly preferred are bifunctional or higher functional (meth) acrylamide compounds. In the ink composition of the present invention, these polymerizable compounds may be used alone or in combination of two or more. When two or more types are used in combination, two or more types selected from (meth) acrylamide compounds, (meth) acrylate compounds, vinyl compounds, maleimide compounds, vinylsulfone compounds, and N-vinylamide compounds may be used in combination. Preferably, at least one of them is a (meth) acrylamide compound.
The polymerizable compound has a poly (ethyleneoxy) chain, a poly (propyleneoxy) chain, an ionic group (for example, a carboxyl group, a sulfo group, etc.), a hydroxyl group, etc. in the molecule from the viewpoint of improving water solubility. It may be.

  As the (meth) acrylamide compound, any of a monofunctional (meth) acrylamide compound and a polyfunctional (meth) acrylamide compound can be used, and a polyfunctional (meth) acrylamide compound is preferable. Specific examples of the monofunctional (meth) acrylamide compound and the polyfunctional (meth) acrylamide compound are shown below, but the present invention is not limited thereto.

Among the monomers exemplified above, monomers 21, 27, 28, 41, 43 and 48 are preferable from the viewpoints of curability and solubility.
These (meth) acrylamide compounds can be synthesized using a general method for synthesizing acrylamide compounds (for example, Journal of the American Chemical Society, 1979, 101, 5383 as a reference).

  As the (meth) acrylate compound, any of a monofunctional (meth) acrylate compound (a compound having one (meth) acryloyl group) and a polyfunctional (meth) acrylate compound can be used, and preferably a polyfunctional (meth). It is an acrylate compound.

  Specifically, as a monofunctional (meth) acrylate compound, isoamyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, Isostearyl (meth) acrylate, 2-ethylhexyl diglycol (meth) acrylate, 2-hydroxybutyl (meth) acrylate, butoxyethyl (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene Glycol (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate 2-hydroxypropyl (meth) acrylate, 2- (meth) acryloxyethyl succinic acid, 2- (meth) acryloxyethyl-2-hydroxyethylphthalic acid, lactone-modified flexible (meth) acrylate, Examples thereof include t-butylcyclohexyl (meth) acrylate, 2- (2-ethoxyethoxy) ethyl acrylate, cyclopentenyl acrylate, cyclopentenyloxyethyl acrylate, and dicyclopentanyl acrylate.

  Polyfunctional (meth) acrylate compounds include bis (4-acryloxypolyethoxyphenyl) propane, neopentyl glycol di (meth) acrylate, ethoxylated (2) neopentyl glycol di (meth) acrylate (neopentyl glycol ethylene oxide) 2 mol adduct diacrylated compound), propoxylation (2) neopentylglycol di (meth) acrylate (nepentylglycol propylene oxide 2 mol adduct diacrylated), 1,6-hexanediol di (Meth) acrylate, 1,9-nonanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, Raethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetrapropylene glycol di (meth) acrylate, polypropylene glycol di (meth) Acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethanetetra (meth) acrylate, tetramethylolmethanetri ( (Meth) acrylate, dimethylol tricyclodecane di (meth) acrylate, modified glycerin tri (meth) acrylate, Bisphenol A di (meth) acrylate, propylene oxide (PO) adduct di (meth) acrylate of bisphenol A, ethylene oxide (EO) adduct di (meth) acrylate of bisphenol A, dipentaerythritol hexa (meth) acrylate, caprolactone Examples thereof include modified dipentaerythritol hexa (meth) acrylate.

  Specific examples of the vinyl compound include divinylbenzene, N-vinyl-ε-caprolactam, styrene, N-vinylpyrrolidone, N-vinylcarbazole, N-vinylimidazole, N-vinylformamide, vinyl alcohol, acrolein, and 2-vinyl. Crotonaldehyde, 2-vinyl furan, 3-vinyl furan, methyl vinyl ether, ethyl vinyl ether, decyl vinyl ether, isobutyl vinyl ether, butyl vinyl ether, divinyl ether, phenyl vinyl ether, 3-methyl phenyl ether, vinyl amine, acrylonitrile, vinyl benzyl alcohol, vinyl benzyl Amine, vinyl acetate, vinyl sulfonic acid, vinyl propionate, vinyl butyrate, vinyl stearate, vinyl laurate, cyclohexane cal Nsan vinyl, vinyl pivalate, vinyl monochloroacetate, vinyl adipate, vinyl methacrylate and vinyl sorbate and the like.

  The content of the polymerizable compound in the ink composition is preferably 5 to 80% by mass, more preferably 30 to 70% by mass, and 40 to 60% by mass with respect to the total amount of the solid components. More preferably it is.

[Aqueous medium]
The ink composition of the present invention contains an aqueous medium. The aqueous medium contains at least water, and optionally contains at least one organic solvent.
The water used for the aqueous medium is preferably water containing no ionic impurities, such as ion-exchanged water and distilled water.
The water content in the ink composition can be appropriately selected according to the purpose, but is usually preferably 10 to 95% by mass, and preferably 30 to 90% by mass with respect to the total mass of the ink composition. % Is more preferable.

-Organic solvent-
The aqueous medium preferably contains a water-soluble organic solvent. By containing the water-soluble organic solvent, the effect of preventing drying, wetting or promoting penetration can be obtained. In order to prevent drying, the ink adheres to and drys at the ink discharge port of the ejection nozzle and is used as an anti-drying agent to prevent clogging. For drying prevention and wetting, the vapor pressure is lower than that of water. A water-soluble organic solvent is preferred. Further, for penetration promotion, it can be used as a penetration enhancer that enhances ink permeability to paper.
A water-soluble organic solvent may be used individually by 1 type, or may be used in mixture of 2 or more types.
The content of the water-soluble organic solvent in the ink composition is preferably 1 to 60% by mass and more preferably 5 to 40% by mass with respect to the total mass of the ink composition.

  Examples of water-soluble organic solvents include, for example, glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol and other alkanediols (polyhydric alcohols); sugar alcohols; ethanol, methanol, C1-C4 alkyl alcohols such as butanol, propanol, isopropanol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono -N-propyl ether, ethylene glycol mono-isopropyl ether, diethylene glycol No-isopropyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monoethyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene Glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-isopropyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono N-propyl ether, dipropylene glycol mono-isopropyl ether , Glycol ethers such as tripropylene glycol monomethyl ether, and the like. These can be used individually by 1 type or in combination of 2 or more types.

  For the purpose of preventing drying and wetting, polyhydric alcohols are useful. For example, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-butanediol, 2 , 3-butanediol and the like. These may be used individually by 1 type and may use 2 or more types together.

  For the purpose of promoting penetration, polyol compounds are preferred, and aliphatic diols are preferred. Examples of the aliphatic diol include 2-ethyl-2-methyl-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, 2,2-diethyl-1,3-propanediol, -Ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol and the like. Among these, preferred examples include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.

  The water-soluble organic solvent used in the present invention can also contain at least one compound represented by the structural formula (I) of JP2013-199433A from the viewpoint of curling generation in the recording medium.

[Colorant]
The ink composition of the present invention preferably contains a colorant.
The ink composition of the present invention (hereinafter sometimes simply referred to as “ink”) can be used not only for the formation of a single color image but also for the formation of a multicolor image (for example, a full color image). Two or more colors can be selected to form an image. When forming a full color image, the ink composition can be used as, for example, a magenta color ink, a cyan color ink, and a yellow color ink. Further, in order to adjust the color tone, it may be used as a black color ink.

In addition, the ink composition of the present invention is an ink having a color tone of red (R), green (G), blue (B), and white (W) other than the color tone of yellow (Y), magenta (M), and cyan (C). It can be used as a composition or an ink composition having a special color in the so-called printing field.
The ink composition of each color tone can be prepared by changing the hue of a colorant (for example, a pigment) as desired.

  In the ink composition of the present invention, known dyes, pigments and the like can be used without particular limitation as the colorant. From the viewpoint of ink colorability, a colorant that is almost insoluble or hardly soluble in water is preferable. Specifically, various pigments, disperse dyes, oil-soluble dyes, dyes forming J aggregates, and the like can be mentioned. In consideration of light resistance, pigments are more preferable.

There is no restriction | limiting in particular in the kind of pigment used for the ink composition of this invention, A normal organic and inorganic pigment can be used.
Examples of organic pigments include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments and polycyclic pigments are more preferable. Examples of the azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments. Examples of the polycyclic pigment include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. Examples of dye chelates include basic dye chelates and acid dye chelates.

  Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black. Among these, carbon black is particularly preferable. In addition, as carbon black, what was manufactured by well-known methods, such as a contact method, a furnace method, a thermal method, is mentioned, for example.

  Specific examples of the pigment that can be used in the present invention include pigments described in paragraph numbers [0142] to [0145] of JP2007-100071A.

Moreover, when using a dye as a coloring component in this invention, what hold | maintained the dye to the water-insoluble support | carrier can be used as a coloring agent. As the dye, known dyes can be used without particular limitation. For example, the dyes described in JP-A-2001-115066, JP-A-2001-335714, JP-A-2002-249677 and the like can be used in the present invention. It can be used suitably. The carrier is not particularly limited as long as it is insoluble in water or hardly soluble in water, and inorganic materials, organic materials, and composite materials thereof can be used. Specifically, the carriers described in JP-A-2001-181549, JP-A-2007-169418, etc. can be suitably used in the present invention.
The carrier holding the dye (colorant) can be used as it is or in combination with a dispersant as required. As the dispersant, a dispersant described later can be suitably used.

The above colorants may be used alone or in combination of the above plural types.
The content of the colorant (particularly the pigment) in the ink composition is 0.05 to 10% by mass with respect to the total mass of the ink composition from the viewpoint of color density, granularity, ink stability, and ejection reliability. Is preferable, and 0.1 to 5 mass% is more preferable.

[Dispersant]
When the colorant used in the ink composition of the present invention is a pigment, it is preferable to form colored particles (hereinafter simply referred to as “colored particles”) dispersed in an aqueous solvent by a dispersant.
The dispersant may be a polymer dispersant or a low molecular surfactant type dispersant. The polymer dispersant may be either a water-soluble polymer dispersant or a water-insoluble polymer dispersant. In the present invention, a water-insoluble polymer dispersant is preferable from the viewpoint of dispersion stability and dischargeability when applied to an ink jet system.

-Water-insoluble polymer dispersant-
The water-insoluble polymer dispersant in the present invention (hereinafter sometimes simply referred to as “dispersant”) is a water-insoluble polymer and is not particularly limited as long as the pigment can be dispersed. A dispersant can be used. The water-insoluble polymer dispersant can be constituted by including, for example, both a hydrophobic structural unit and a hydrophilic structural unit.

Examples of the monomer constituting the hydrophobic structural unit include styrene monomers, alkyl (meth) acrylates, aromatic group-containing (meth) acrylates, and the like.
Moreover, as a monomer which comprises a hydrophilic structural unit, if it is a monomer containing a hydrophilic group, there will be no restriction | limiting in particular. Examples of hydrophilic groups include nonionic groups, carboxyl groups, sulfonic acid groups, and phosphoric acid groups. Examples of the nonionic group include a hydroxyl group, an amide group (nitrogen atom is unsubstituted), a group derived from an alkylene oxide polymer (for example, polyethylene oxide, polypropylene oxide, etc.), a group derived from a sugar alcohol, and the like. .
From the viewpoint of dispersion stability, the hydrophilic structural unit in the present invention preferably contains at least a carboxyl group, and preferably includes a nonionic group and a carboxyl group.

Specific examples of the water-insoluble polymer dispersant in the present invention include a styrene- (meth) acrylic acid copolymer, a styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, and a (meth) acrylic acid ester. -(Meth) acrylic acid copolymer, polyethylene glycol (meth) acrylate- (meth) acrylic acid copolymer, styrene-maleic acid copolymer and the like.
Here, “(meth) acrylic acid” means acrylic acid or methacrylic acid.

  The water-insoluble polymer dispersant used in the present invention is preferably a vinyl polymer containing a carboxyl group from the viewpoint of dispersion stability of the pigment, and a structural unit derived from at least an aromatic group-containing monomer as a hydrophobic structural unit. And a vinyl polymer having a structural unit containing a carboxyl group as a hydrophilic structural unit.

  The weight average molecular weight of the water-insoluble polymer dispersant is preferably 3,000 to 200,000, more preferably 5,000 to 100,000, and still more preferably 5,000, from the viewpoint of pigment dispersion stability. -80,000, particularly preferably 10,000-60,000.

The content of the dispersant in the colored particles in the present invention is preferably 10 to 90 parts by mass of the dispersant with respect to 100 parts by mass of the pigment from the viewpoint of the dispersibility of the pigment, the ink colorability, and the dispersion stability. 20-70 mass parts is more preferable, and 30-50 mass parts is especially preferable.
When the content of the dispersant in the colored particles is within the above range, the pigment is preferably coated with an appropriate amount of the dispersant, and it tends to be easy to obtain colored particles having a small particle size and excellent stability over time.

  The colored particles in the present invention may contain other dispersants in addition to the water-insoluble polymer dispersant. For example, a conventionally known water-soluble low molecular dispersant, water-soluble polymer, or the like can be used. The content of the dispersant other than the water-insoluble polymer dispersant can be used within the range of the content of the dispersant.

  The colored particles in the present invention are preferably configured to contain a pigment and a water-insoluble polymer dispersant from the viewpoint of dispersion stability and dischargeability, and at least a part of the surface of the pigment is coated with the water-insoluble polymer dispersant. It is preferable that it is comprised. Such colored particles can be obtained as a colored particle dispersion by, for example, dispersing a mixture containing a pigment, a dispersant, and, if necessary, a solvent (preferably an organic solvent) with a disperser.

  For example, the colored particle dispersion is prepared by adding an aqueous solution containing a basic substance to a mixture of a pigment, a water-insoluble polymer dispersant, and an organic solvent in which the dispersant is dissolved or dispersed (mixing / hydration step), A process for removing the solvent (solvent removal process) may be provided to produce the dispersion. Thereby, the colorant is finely dispersed, and a dispersion of colored particles having excellent storage stability can be produced.

  The organic solvent needs to be able to dissolve or disperse the dispersant, but in addition to this, it is preferable that the organic solvent has a certain degree of affinity for water. Specifically, those having a solubility in water at 20 ° C. of 10 to 50% by mass or less are preferable.

More specifically, the dispersion of colored particles can be produced by a production method including the following step (1) and step (2), but is not limited thereto.
Step (1): A step of dispersing a mixture containing a pigment, a dispersant, and an organic solvent that dissolves or disperses the dispersant, a basic substance, and a solution containing water as a main component. Step (2): Dispersion Removing at least part of the organic solvent from the treated mixture

  In step (1), first, a dispersant is dissolved or dispersed in an organic solvent to obtain a mixture (mixing step). Next, a solution containing a colorant and a basic substance and containing water as a main component, water, and, if necessary, a surfactant and the like are added to the mixture and mixed and dispersed to obtain an oil-in-water dispersion. obtain.

  The basic substance is used for neutralization of an anionic group (preferably a carboxyl group) that the polymer may have. There is no particular limitation on the degree of neutralization of the anionic group. Usually, the liquid property of the finally obtained dispersion of colored particles is preferably such that the pH is 4.5 to 10, for example. The pH can also be determined by the desired degree of neutralization of the polymer.

  Preferable examples of the organic solvent include alcohol solvents, ketone solvents, and ether solvents. Among these, examples of alcohol solvents include ethanol, isopropanol, n-butanol, tertiary butanol, isobutanol, and diacetone alcohol. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of the ether solvent include dibutyl ether, tetrahydrofuran, dioxane and the like. Among these solvents, isopropanol, acetone and methyl ethyl ketone are preferable, and methyl ethyl ketone is particularly preferable. The organic solvent may be used alone or in combination.

In the production of a dispersion of colored particles, a strong shearing force is applied using a two-roll, three-roll, ball mill, tron mill, disper, kneader, kneader, homogenizer, blender, single-screw or twin-screw extruder, etc. The kneading and dispersing process can be carried out. For details on kneading and dispersing, see T.W. C. “Paint Flow and Pigment Dispersion” by Patton (published by John Wiley and Sons, 1964) and the like.
If necessary, use a vertical or horizontal sand grinder, pin mill, slit mill, ultrasonic disperser, etc., and fine dispersion using beads made of glass having a particle diameter of 0.01 to 1 mm, zirconia, etc. It can be obtained by performing processing.

  The removal of the organic solvent in the method for producing a colored particle dispersion in the present invention is not particularly limited, and can be removed by a known method such as vacuum distillation.

The colored particles in the colored particle dispersion thus obtained maintain a good dispersion state, and the obtained colored particle dispersion has excellent temporal stability.
In the ink composition of the present invention, the colored particles may be used singly or in combination of two or more.

In the present invention, the volume average particle diameter of the colorant (or colored particles) is preferably 10 to 200 nm, more preferably 10 to 150 nm, and still more preferably 10 to 100 nm. When the volume average particle size is 200 nm or less, the color reproducibility is good, and in the case of the ink jet method, the droplet ejection characteristics are good. Moreover, light resistance becomes favorable because a volume average particle diameter is 10 nm or more.
Moreover, there is no restriction | limiting in particular regarding the particle size distribution of a coloring agent (or colored particle | grains), Either a wide particle size distribution or a monodispersed particle size distribution may be sufficient. Further, two or more colorants having a monodispersed particle size distribution may be mixed and used.
The volume average particle size and particle size distribution of the colorant (or colored particles) can be measured using, for example, a light scattering method.

[Other polymerization initiators]
The ink composition of the present invention may contain an arbitrary amount of a polymerization initiator other than the compound of the present invention (hereinafter referred to as “other polymerization initiator”).
As another polymerization initiator, a radical polymerization initiator is preferable. Specific examples of the radical polymerization initiator include (a) aromatic ketones, (b) acylphosphine compounds, (c) aromatic onium salt compounds, (d) organic peroxides, (e) thio compounds, ( f) hexaarylbiimidazole compound, (g) ketoxime ester compound, (h) borate compound, (i) azinium compound, (j) metallocene compound, (k) active ester compound, (l) compound having carbon halogen bond And (m) alkylamine compounds and the like. More specifically, polymerization initiators described in pages 65 to 148 of “Ultraviolet curing system” written by Kiyosuke Kato (published by General Technology Center Co., Ltd .: 1989) can be given.

The other polymerization initiator may be either a water-insoluble initiator dispersed in water or a water-soluble initiator, but is preferably a water-soluble polymerization initiator. The term “water-soluble” as used herein means that 0.5% by mass or more dissolves in water at 25 ° C. The water-soluble initiator is preferably dissolved in water at 1% by mass or more at 25 ° C., more preferably 3% by mass or more.
Another polymerization initiator may be used individually by 1 type, and may use 2 or more types together.

[Resin particles]
The ink composition of the present invention is disclosed in JP-A-2013-199433, [0086] to [0089], from the viewpoint of improving the fixing property of the ink composition to a recording medium, image abrasion resistance, and blocking resistance. The resin fine particles described can also be contained.

[Surfactant]
The ink composition of the present invention may contain a surfactant as necessary. The surfactant can be used as a surface tension adjusting agent.
As a surface tension modifier, a compound having a structure having both a hydrophilic part and a hydrophobic part in the molecule can be used effectively. Anionic surfactant, cationic surfactant, amphoteric surfactant, nonionic surfactant Either a surfactant or a betaine surfactant can be used. Furthermore, you may use said dispersing agent (polymer dispersing agent) as surfactant.
In the present invention, a nonionic surfactant is preferable from the viewpoint of suppression of ink droplet ejection interference, and an acetylene glycol derivative is more preferable.

When the ink composition of the present invention is used in an ink jet recording system, a surfactant (surface tension adjusting agent) is used so that the surface tension of the ink composition is 20 to 60 mN / m from the viewpoint of favorably discharging the ink composition. The amount is preferably adjusted to 20 to 45 mN / m, more preferably 25 to 40 mN / m.
The content of the surfactant in the ink composition is not particularly limited, except that the above range of the surface tension is preferable, and is preferably 1% by mass or more, more preferably based on the total mass of the ink composition. It is 1-10 mass%, More preferably, it is 1-3 mass%.

[Other ingredients]
In addition to the above components, the ink composition may further contain conventional components, for example, various additives as necessary.
Various additives include, for example, ultraviolet absorbers, antifading agents, antifungal agents, pH adjusters, rust inhibitors, antioxidants, emulsion stabilizers, preservatives, antifoaming agents, viscosity modifiers, and dispersion stabilizers. Known additives such as agents, chelating agents, solid wetting agents and the like can be mentioned.

  Examples of the UV absorber include benzophenone UV absorbers, benzotriazole UV absorbers, salicylate UV absorbers, cyanoacrylate UV absorbers, nickel complex salt UV absorbers, and the like.

  As the antifading agent, various organic and metal complex antifading agents can be used. Examples of organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, heterocycles, and metal complexes. There are nickel complex, zinc complex and the like.

Examples of the antifungal agent include, for example, sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, ethyl p-hydroxybenzoate, 1,2-benzisothiazolin-3-one, sodium sorbate, pentachlorophenol Sodium etc. are mentioned.
The content of the antifungal agent in the ink composition is preferably in the range of 0.02 to 1.00% by mass with respect to the total mass of the ink composition.

  The pH adjuster is not particularly limited as long as it can adjust the pH to a desired value without adversely affecting the ink composition to be prepared, and can be appropriately selected according to the purpose. For example, alcohol amines (for example, diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol, etc.), alkali metal hydroxides (for example, lithium hydroxide, sodium hydroxide, potassium hydroxide) Etc.), ammonium hydroxide (for example, ammonium hydroxide, quaternary ammonium hydroxide, etc.), phosphonium hydroxide, alkali metal carbonate and the like.

  Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

  Examples of the antioxidant include phenol antioxidants (including hindered phenol antioxidants), amine antioxidants, sulfur antioxidants, phosphorus antioxidants, and the like.

  Examples of the chelating agent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate and the like.

[Physical properties of ink composition]
The surface tension (25 ° C.) of the ink composition of the present invention is preferably 20 mN / m or more and 60 mN / m or less. More preferably, it is 20 mN or more and 45 mN / m or less, More preferably, it is 25 mN / m or more and 40 mN / m or less.
The surface tension is measured using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) under the condition of 25 ° C.

The viscosity of the ink composition of the present invention at 25 ° C. is preferably 1.2 mPa · s or more and 15.0 mPa · s or less, more preferably 2 mPa · s or more and less than 13 mPa · s, and further preferably Is 2.5 mPa · s or more and less than 10 mPa · s.
The viscosity is measured using a VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD) under conditions of 25 ° C.

  The pH of the ink composition is preferably pH 6 to 11 from the viewpoint of the stability of the ink composition. When the ink set described later is used, it is preferable that the ink composition is aggregated at a high speed by contact with the treatment agent.

<Ink set>
The ink set of the present invention includes the above-described ink composition of the present invention and a treatment agent containing an aggregating component capable of forming an aggregate upon contact with the ink composition.
By forming an image using an ink composition containing a polymerizable compound and the photopolymerization initiator of the present invention and a processing agent containing an aggregating component, the image has good image quality, high scratch resistance, and anti-blocking properties. An image having excellent properties can be formed.
Hereinafter, the treatment agent of the ink set will be described.

<Treatment agent>
The treating agent constituting the ink set of the present invention contains a component (aggregating component) capable of forming an aggregate containing the pigment in the ink composition by contacting with the ink composition of the present invention. Examples of the aggregating component include components selected from acidic compounds, polyvalent metal salts, and cationic polymers, and the aggregating component is preferably an acidic compound. The treatment agent may contain other components as necessary in addition to the aggregation component.
The treatment agent constituting the ink set of the present invention is usually in the form of an aqueous solution.

− Acidic compounds −
The acidic compound is capable of aggregating (fixing) the ink composition by contact with the ink composition on the recording medium, and functions as a fixing agent. For example, if the ink composition is deposited on a recording medium (preferably coated paper) applied with a treatment agent containing an acidic compound, the components in the ink composition can be aggregated. The ink composition can be fixed on the recording medium.

Examples of acidic compounds include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, and tartaric acid. , Lactic acid, sulfonic acid, orthophosphoric acid, metaphosphoric acid, pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, oxalic acid, acetic acid, benzoic acid Can be mentioned. From the viewpoint of achieving both suppression of volatilization and solubility in a solvent, the acidic compound is preferably an acid having a molecular weight of 35 to 1,000, more preferably an acid having a molecular weight of 50 to 500, and particularly preferably an acid having a molecular weight of 50 to 200. The pKa (in H ₂ O, 25 ° C.) is preferably from −10 to 7 acids, more preferably from 1 to 7 acids, more preferably from 1 to 7 from the viewpoint of achieving both ink bleeding prevention and photocurability. An acid of 5 or less is particularly preferred.
pKa is a value calculated by Advanced Chemistry Development (ACD / Labs) Software V11.02 (1994-2014 ACD / Labs) or a literature value (for example, described in J. Phys. Chem. A 2011, 115, 6641-6645). A value can be used.

Among these, acidic compounds with high water solubility are preferable. Further, from the viewpoint of fixing the whole ink by reacting with the ink composition, a trivalent or less acidic compound is preferable, and a divalent or trivalent acidic compound is particularly preferable.
As the treatment agent, an acidic compound may be used alone or in combination of two or more.

  When the treating agent is an aqueous solution containing an acidic compound, the pH (25 ° C.) of the treating agent is preferably 0.1 to 6.8, more preferably 0.1 to 6.0, and 0 More preferably, it is 1 to 5.0.

  When the treatment agent contains an acidic compound as an aggregating component, the content of the acidic compound in the treatment agent is preferably 40% by mass or less, more preferably 15 to 40% by mass, further preferably 15% to 35% by mass, 20 mass%-30 mass% is especially preferable. By setting the content of the acidic compound in the treatment agent to 15 to 40% by mass, the components in the ink composition can be more efficiently fixed.

When the treatment agent contains an acidic compound as an aggregating component, the amount of the treatment agent applied to the recording medium is not particularly limited as long as it is an amount sufficient to cause the ink composition to agglomerate, but it is easy to fix the ink composition. from the viewpoint, it is preferable that the application amount of the acidic compound to impart processing agent so as to ^{0.5g / m 2 ~4.0g / m 2} , and 0.9g / ^{m 2} ~3.75g / m 2 It is preferable to apply a treatment agent.

<Image forming method>
The image forming method of the present invention includes an ink application process in which an ink composition is applied onto a recording medium to form an image, and an active energy beam irradiation that irradiates the ink composition applied on the recording medium with an active energy beam. Including at least a process, and further including other processes as necessary.

[recoding media]
The recording medium used in the image forming method of the present invention is not particularly limited, but general printing paper mainly composed of cellulose, such as so-called high-quality paper, coated paper, and art paper, used for general offset printing or the like is used. Can do. General printing paper mainly composed of cellulose is relatively slow in ink absorption and drying in image recording by a general ink jet method using water-based ink, and color material movement is likely to occur after droplet ejection, and image quality is likely to deteriorate. However, according to the ink jet recording method of the present invention, it is possible to record a high-quality image excellent in color density and hue by suppressing the movement of the color material.

  As the recording medium, commercially available media can be used. For example, “OK Prince Quality” manufactured by Oji Paper Co., Ltd., “Shiraoi” manufactured by Nippon Paper Industries Co., Ltd., and Nippon Paper Industries Co., Ltd. ) "New NPI fine quality" fine paper (A), Nippon Paper Industries' "Silver Diamond" quality coated paper, Oji Paper's "OK Everlight Coat" and Nippon Paper Industries ( Light-weight coated paper (A3) such as “Aurora S” manufactured by Co., Ltd., “OK Coat L” manufactured by Oji Paper Co., Ltd. and “Aurora L” manufactured by Nippon Paper Industries Co., Ltd., Oji Paper Co., Ltd. Coated paper (A2, B2) such as “OK Top Coat +” manufactured by Nippon Paper Industries Co., Ltd. and “Aurora Coat” manufactured by Nippon Paper Industries Co., Ltd. “OK Kanto +” manufactured by Oji Paper Co., Ltd., Mitsubishi Paper Industries Co., Ltd. ) Art paper (A1) such as “Tokuhishi Art” made by Nippon Steel, Ltd. Light, and the like. It is also possible to use various photographic papers for ink jet recording.

  Among the recording media, so-called coated paper used for general offset printing is preferable. The coated paper is obtained by applying a coating material to the surface of high-quality paper, neutral paper, or the like that is mainly surface-treated with cellulose as a main component and is not surface-treated. The coated paper tends to cause quality problems such as image gloss and scratch resistance in image formation by ordinary aqueous inkjet, but in the inkjet recording method of the present invention, gloss unevenness is suppressed and gloss and resistance are reduced. An image having good rubbing properties can be obtained. In particular, it is preferable to use a coated paper having a base paper and a coat layer containing kaolin and / or calcium bicarbonate. More specifically, art paper, coated paper, lightweight coated paper, or finely coated paper is more preferable.

Among these, from the viewpoint of obtaining a high-quality image having a large color material movement suppression effect and better color density and hue than before, the water absorption coefficient Ka is preferably 0.05 to 0.5. a recording medium mL ^/ m 2 ^{· ms 1/2,} more preferably recording medium 0.1~0.4mL ^/ m 2 ^{· ms 1/2,} more preferably 0.2-0.3 ml / It is a recording medium of m ² · ms ^1/2 .

  The water absorption coefficient Ka is synonymous with that described in JAPAN TAPPI paper pulp test method No. 51: 2000 (issued by Japan Paper Pulp Technology Association). Specifically, the absorption coefficient Ka is an automatic scanning absorption meter. It is calculated from the difference in the amount of water transferred between the contact time of 100 ms and the contact time of 900 ms using KM500Win (manufactured by Kumagai Riki Co.).

[Processing agent application step]
In the treatment agent application step, a treatment agent containing an aggregating component contained in the ink set is applied on the recording medium. For applying the treatment agent to the recording medium, a known liquid application method can be used without particular limitation, and any method such as spray application, application using an application roller, application by an inkjet method, immersion, etc. can be selected. .

  Specifically, for example, a size press method represented by a horizontal size press method, a roll coater method, a calendar size press method, etc .; a knife coater method represented by an air knife coater method; a transfer roll such as a gate roll coater method Roll coater method represented by coater method, direct roll coater method, reverse roll coater method, squeeze roll coater method, etc .; bill blade coater method, short duel coater method; blade coater method represented by two stream coater method; rod Bar coater method represented by bar coater method, etc .; Bar coater method represented by rod bar coater method, etc .; Cast coater method; Gravure coater method; Curtain coater method; Die coater method; Brush coater method; Etc., and the like.

  Moreover, the method of apply | coating by controlling a coating amount by using the coating device provided with the liquid quantity limiting member like the coating device of Unexamined-Japanese-Patent No. 10-230201 may be used.

  The region to which the treatment agent is applied may be the entire surface application to the entire recording medium or the partial application to be partially applied to the region to which the ink is applied in the ink application process. In the present invention, from the viewpoint of uniformly adjusting the amount of treatment agent applied, uniformly recording fine lines and fine image portions, etc., and suppressing density unevenness such as image unevenness, a recording medium is applied by application using an application roller or the like. The entire surface is preferably applied to the entire surface.

  Examples of a method for applying the treatment agent while controlling the amount of the treatment agent to be applied in a predetermined region include a method using an anilox roller. An anilox roller is a roller with a ceramic-sprayed roller surface processed with a laser to give it a pyramid shape, a diagonal line, a turtle shell shape, or the like. The treatment agent enters the dent portion formed on the roller surface and is transferred when it comes into contact with the paper surface, and is applied in a coating amount controlled by the dent of the anilox roller.

[Ink application process]
In the ink application process, the ink composition contained in the ink set is applied onto the recording medium. The ink composition application method is not particularly limited as long as the ink composition can be applied in a desired image-like manner, and a known ink application method can be used. For example, a method of applying an ink composition onto a recording medium by means of an ink jet method, a copying method, a printing method, or the like can be given. Among these, the step of applying the ink composition by an ink jet method is preferable from the viewpoint of compactness of the recording apparatus and high-speed recording properties.

[Inkjet method]
In image formation by an ink jet method, by supplying energy, an ink composition is discharged onto a recording medium to form a colored image. As a preferable ink jet recording method for the present invention, the method described in paragraph Nos. 0093 to 0105 of JP-A No. 2003-306623 can be applied.

The inkjet method is not particularly limited, and is a known method, for example, a charge control method that discharges ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses vibration pressure of a piezoelectric element, Any of an acoustic ink jet method in which an electric signal is converted into an acoustic beam, irradiated onto ink, and ink is ejected using radiation pressure may be used.
The ink jet head used in the ink jet method may be an on-demand method or a continuous method. Further, there are no particular limitations on the ink nozzles used when recording by the ink jet method, and the ink nozzles can be appropriately selected according to the purpose.
Inkjet methods include a method of ejecting many low-density inks called photo inks in a small volume, a method of improving the image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent inks. The method used is included.

  Also, as an ink jet system, a short serial head is used, a shuttle system that performs recording while scanning the head in the width direction of the recording medium, and a line head in which recording elements are arranged corresponding to the entire area of one side of the recording medium There is a line system using. In the line method, an image can be recorded on the entire surface of the recording medium by scanning the recording medium in a direction orthogonal to the arrangement direction of the recording elements, and a carriage system such as a carriage for scanning a short head is not necessary. Further, since complicated scanning control of the carriage movement and the recording medium is not required, and only the recording medium is moved, the recording speed can be increased as compared with the shuttle system.

  In the present invention, the order of performing the treatment agent application step and the ink application step is not particularly limited, but from the viewpoint of image quality, it is preferable that the ink application step is performed after the treatment agent application step. That is, the ink application step is preferably a step of applying the ink composition onto the recording medium to which the treatment agent has been applied.

[Active energy ray irradiation process]
The image forming method of the present invention preferably includes a step of irradiating the ink composition applied on the recording medium with active energy rays. By irradiating active energy rays, the polymerizable compound contained in the ink composition is polymerized to form a cured film containing a colorant. Thereby, the abrasion resistance and blocking resistance of the image are more effectively improved.

The ink composition applied onto the recording medium undergoes a curing reaction when irradiated with active energy rays. In this reaction, the photopolymerization initiator of the present invention contained in the ink composition is decomposed by irradiation with active energy rays to generate radicals, whereby the polymerization reaction of the polymerizable compound is initiated and accelerated, and the ink composition. Is a reaction that cures.
When an acidic compound is contained in the processing agent, the ink composition is further agglomerated (fixed) by the acid supplied from the acidic compound upon irradiation with the active energy ray, and image quality (rubbing resistance / blocking resistance) Etc.).

In the present invention, α-rays, γ-rays, electron beams, X-rays, ultraviolet rays, visible light, infrared light, and the like can be used as active energy rays. As described above, the photopolymerization initiator of the present invention has particularly high absorption for light in the ultraviolet region, and from this viewpoint, the wavelength of the active energy ray is preferably 200 to 600 nm, It is more preferably 300 to 450 nm, and further preferably 350 to 420 nm.
The irradiation amount of the active energy ray, is preferably 5000 mJ / cm ² or less, more preferably 10~4000mJ / cm ^2, more preferably from 20~3000mJ / cm ^2, 100~3000mJ / Particularly preferred is cm ² .

Mercury lamps and gas / solid lasers are mainly used as active energy ray sources, and mercury lamps and metal halide lamps are widely known as light sources used for curing UV photocurable ink jet recording inks. ing. However, at present, mercury-free is strongly desired from the viewpoint of environmental protection, and replacement with a GaN-based semiconductor ultraviolet light-emitting device is very useful industrially and environmentally. In addition, LEDs and laser diodes (LDs) are small, have a long life, have high efficiency, and are low in cost, and are expected as light sources for photocurable ink jets.
In the present invention, it is possible to use LEDs and LDs as active energy ray sources. In particular, UV-LEDs and UV-LDs can be used as ultraviolet sources. For example, Nichia Corporation has introduced a purple LED whose main emission spectrum has a wavelength between 365 nm and 420 nm.
A particularly preferable active energy ray source in the present invention is a UV-LED, and a UV-LED having a peak wavelength of 350 to 420 nm is particularly preferable.

[Ink drying process]
The image forming method of the present invention may include an ink drying step for drying and removing a solvent (for example, water, the above-described aqueous medium) in the ink composition applied onto the recording medium, if necessary. Good. The ink drying step is not particularly limited as long as at least a part of the ink solvent can be removed, and a commonly used method can be applied.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples. Unless otherwise specified, “part” and “%” representing the composition are based on mass.

Example I.1. Synthesis and Evaluation of Compound Represented by General Formula (1) As specific examples of the compound represented by the general formula (1) (photopolymerization initiator), the compounds A-1, A-3, A-6, A -7, A-9, A-10, A-14, A-15, A-16, and A-17 were synthesized by the following method.

[Synthesis of Compound A-1]
Synthesized according to Scheme 1 below.
10.0 g (53.0 mmol) of m-bromobenzenethiol and 8.8 g (63.0 mmol) of potassium carbonate were stirred in 70 ml of ethanol (EtOH). To the obtained solution, 7.9 g (63.0 mmol) of ethylene glycol mono-2-chloroethyl ether dissolved in 40 ml of ethanol was added dropwise, and after completion of the addition, the mixture was heated at an internal temperature of 50 ° C. for 2.5 hours. The obtained liquid was allowed to cool to room temperature, subjected to liquid separation extraction with sodium hydrogen carbonate, concentrated, and then subjected to silica gel column chromatography to obtain 10.7 g (yield 73%) of a thioether.

  10.7 g (38.7 mmol) of the thioether compound and 5.3 g (77.3 mmol) of imidazole were stirred in 26 ml of tetrahydrofuran (THF). The resulting solution was cooled with an ice bath. To the cooled liquid, 7.6 g (50.2 mmol) of tert-butyldimethylchlorosilane (TBSCl) dissolved in 52 ml of tetrahydrofuran was added dropwise, and after completion of the dropwise addition, the mixture was heated at an internal temperature of 50 ° C. for 3.5 hours. The obtained liquid was allowed to cool to room temperature, subjected to liquid separation extraction with ammonium chloride, concentrated, and then subjected to silica gel column chromatography to obtain 13.3 g (yield 88%) of a TBS protector.

  Magnesium (1.0 g, 40.8 mmol) and ethylene bromide (3 drops) were stirred in 12 ml of tetrahydrofuran under heating and reflux conditions. A solution obtained by dissolving 13.3 g (34.0 mmol) of the above TBS protector in 24 ml of tetrahydrofuran was added dropwise to the resulting solution. The obtained mixture was heated at an internal temperature of 60 ° C. for 0.5 hours to prepare a Grignard reagent. To the obtained Grignard reagent, 0.7 g (3.5 mmol) of copper iodide dissolved in 12 ml of tetrahydrofuran was dropped at room temperature and stirred at room temperature for 0.5 hour. The obtained solution was added dropwise at room temperature to a solution in which 4.4 g (40.8 mmol) of isobutyryl chloride was dissolved in 24 ml of tetrahydrofuran, and stirred for 4 hours. Liquid separation extraction was performed with water, and after concentration, 3.5 g (yield 27%) of a ketone body was obtained by silica gel column chromatography.

  A ketone body (3.5 g, 9.2 mmol) is reacted with 1.5 g (9.6 mmol) of bromine to obtain a bromo body, and then reacted with 1.8 g (46.0 mmol) of NaOH to obtain 1 of compound A-1. 0.2 g (yield 46%) was obtained.

The obtained compound was identified using ¹ H NMR. From the following results, it was confirmed to be Compound A-1.
¹ H NMR (400 MHz, CDCl ₃ ): 8.05 (s, 1H), 7.82 (d, 1H), 7.52 (d, 1H), 7.36 (m, 1H), 3.70 ( m, 5H), 3.56 (m, 2H), 3.17 (t, 2H), 2.04 (s, 1H), 1.60 (s, 6H)

[Synthesis of Compounds A-3, A-6, A-7, A-9, A-10, A-14, A-15, and A-16]
Compounds A-3, A-6, A-7, A-9, A-10, A-14, A-15, and A-16 were obtained in the same manner as in the synthesis of A-1.
The obtained compound was identified using ¹ H NMR. From the following results, it was confirmed that they were compounds A-3, A-6, A-7, A-9, A-10, A-14, A-15, and A-16.

A-3
¹ H NMR (400 MHz, CDCl ₃ ): 8.06 (s, 1H), 7.78 (d, 1H), 7.51 (d, 1H), 7.39 (m, 1H), 3.75 ( m, 9H), 3.51 (m, 2H), 3.17 (t, 2H), 2.05 (s, 1H), 1.62 (s, 6H)

A-6
¹ H NMR (400 MHz, CDCl ₃ ): 8.07 (s, 1H), 7.82 (d, 1H), 7.29 (d, 1H), 3.71 (m, 5H), 3.56 ( m, 2H), 3.20 (t, 2H), 2.29 (s, 3H), 2.04 (s, 1H), 1.61 (s, 6H)

A-7
¹ H NMR (400 MHz, CDCl ₃ ): 8.05 (s, 1H), 7.75 (d, 1H), 7.52 (d, 1H), 7.36 (m, 1H), 3.66 ( m, 4H), 3.39 (t, 2H), 3.16 (s, 3H), 3.07 (t, 2H), 2.01 (s, 1H), 1.60 (s, 6H)

A-9
¹ H NMR (400 MHz, CDCl ₃ ): 7.84 (d, 1H), 7.59 (m, 2H), 7.41 (m, 1H), 3.75 (m, 5H), 3.59 ( m, 2H), 3.14 (t, 2H), 2.05 (s, 1H), 1.64 (s, 6H)

A-10
¹ H NMR (400 MHz, CDCl ₃ ): 8.01 (s, 2H), 7.57 (s, 1H), 3.59 (m, 6H), 3.32 (m, 4H), 2.09 ( s, 1H), 1.67 (s, 6H)

A-14
¹ H NMR (400 MHz, CDCl ₃ ): 8.08 (s, 1H), 7.84 (d, 1H), 7.34 (d, 1H), 7.22 (m, 1H), 3.64 ( m, 5H), 3.15 (m, 2H), 2.07 (s, 1H), 1.55 (s, 6H), 1.23 (d, 3H), 1.10 (d, 3H)

A-15
¹ H NMR (400 MHz, CDCl ₃ ): 8.10 (s, 1H), 7.85 (d, 1H), 7.52 (d, 1H), 7.40 (m, 1H), 3.70 ( m, 5H), 3.61 (m, 2H), 3.17 (t, 2H), 2.04 (s, 1H), 1.52 (m, 10H)

A-16
¹ H NMR (400 MHz, CDCl ₃ ): 8.10 (s, 1H), 7.85 (d, 1H), 7.51 (m, 11H), 7.30 (m, 1H), 3.68 ( m, 5H), 3.55 (m, 2H), 3.17 (t, 2H), 2.07 (s, 1H)

[Synthesis of Compound A-17]
Synthesized according to Scheme 2 below.
10.0 g (58.1 mmol) of m-bromoaniline and 9.3 g (69.7 mmol) of potassium carbonate were stirred in 70 ml of ethanol (EtOH). To the obtained solution, 11.2 g (139.4 mmol) of 2-chloroethanol dissolved in 40 ml of ethanol was added dropwise, and after completion of the addition, the mixture was heated at an internal temperature of 50 ° C. for 5 hours. The obtained liquid was allowed to cool to room temperature, subjected to liquid separation extraction with sodium hydrogen carbonate, concentrated, and then subjected to silica gel column chromatography to obtain 10.3 g (yield 68%) of the trisubstituted product.
10.3 g (39.5 mmol) of the trisubstituted product and 6.7 g (96.8 mmol) of imidazole were stirred in 39 ml of tetrahydrofuran. The resulting solution was cooled with an ice bath. To the cooled liquid, 15.5 g (102.7 mmol) of tert-butyldimethylchlorosilane (TBSCl) dissolved in 78 ml of tetrahydrofuran was added dropwise, and after completion of the dropwise addition, the mixture was heated at an internal temperature of 50 ° C. for 7 hours. The obtained liquid was allowed to cool to room temperature, subjected to liquid separation extraction with ammonium chloride, concentrated, and then subjected to silica gel column chromatography to obtain 16.6 g (yield 86%) of a TBS protector.

  Magnesium (1.0 g, 40.8 mmol) and ethylene bromide (3 drops) were stirred in 12 ml of tetrahydrofuran under heating and refluxing conditions. A solution obtained by dissolving 16.6 g (34.0 mmol) of the above TBS protector in 24 ml of tetrahydrofuran was dropped into the obtained solution. The Grignard reagent was prepared by heating the obtained liquid at an internal temperature of 60 ° C. for 0.5 hour. To the obtained Grignard reagent, 0.7 g (3.5 mmol) of copper iodide dissolved in 12 ml of tetrahydrofuran was dropped at room temperature and stirred at room temperature for 0.5 hour. The obtained solution was added dropwise at room temperature to a solution in which 4.4 g (40.8 mmol) of isobutyryl chloride was dissolved in 24 ml of tetrahydrofuran, and stirred for 4 hours. Liquid separation extraction was performed with water, and after concentration, 5.6 g (yield 34%) of a ketone body was obtained by performing silica gel column chromatography.

  A ketone body 5.6 g (11.6 mmol) is reacted with 1.9 g (12.1 mmol) of bromine to obtain a bromo body, and then reacted with 2.3 g (57.9 mmol) of NaOH to obtain 1. 3 g (yield 42%) was obtained.

The obtained compound was identified using ¹ H NMR. From the following results, it was confirmed that it was Compound A-17.
¹ H NMR (400 MHz, CDCl ₃ ): 7.86 (s, 1H), 7.73 (d, 1H), 7.43 (d, 1H), 7.32 (m, 1H), 3.81 ( t, 4H), 3.65 (m, 4H), 2.31 (s, 2H), 2.02 (s, 1H), 1.63 (s, 6H)

[Comparative compounds B-1 to B-5]
The following B-1 to B-5 were prepared as comparative compounds.
IRGACURE 2959 (trade name, manufactured by BASF) was prepared as B-1.
B-2 to B-5 were synthesized by the same method as the synthesis of A-1.

[Evaluation]
About each said compound, the maximum absorption wavelength and solubility were measured.

[Maximum absorption wavelength]
Each of the obtained compounds was dissolved in acetonitrile so that the concentration was 0.02 g / L. The maximum absorption wavelength (λmax) detected in the range of 250 to 450 nm was measured using an ultraviolet-visible spectrophotometer UV2550 (manufactured by Shimadzu Corporation). The results are shown in Table 1.

[Solubility in water]
About each obtained compound, the solubility (mass%) in 20 degreeC water was calculated | required. The results are shown in Table 1.

Example II. Preparation of colorant-containing ink composition and evaluation of sensitivity [synthesis of polymerizable compound M-1]
In a 1 L three-necked flask equipped with a stirrer, 40.0 g (182 mmol) of 4,7,10-trioxa-1,13-tridecanediamine, 37.8 g (450 mmol) of sodium hydrogen carbonate, 100 g of water, and 200 g of tetrahydrofuran And 35.2 g (389 mmol) of acrylic acid chloride was added dropwise over 20 minutes in an ice bath. After dropping, the mixture was stirred at room temperature for 5 hours, and then tetrahydrofuran was distilled off from the obtained reaction mixture under reduced pressure. Next, the aqueous layer was extracted four times with 200 ml of ethyl acetate, and the obtained organic layer was dried over magnesium sulfate, filtered, and the solvent was distilled off under reduced pressure to obtain 35 of the target polymerizable compound M-1 solid. 0.0 g (107 mmol, 59% yield) was obtained.

[Synthesis of Polymer Dispersant P-1]
To a 1000 ml three-necked flask equipped with a stirrer and a condenser tube, 88 g of methyl ethyl ketone was added and heated to 72 ° C. under a nitrogen atmosphere. Here, 50 g of methyl ethyl ketone was mixed with 0.85 g of dimethyl 2,2′-azobisisobutyrate and benzyl methacrylate. A solution in which 60 g, 10 g of methacrylic acid and 30 g of methyl methacrylate were dissolved was dropped over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution of 0.42 g of dimethyl 2,2′-azobisisobutyrate in 2 g of methyl ethyl ketone was added, heated to 78 ° C. and heated for 4 hours. The obtained reaction solution was reprecipitated twice in a large excess amount of hexane, and the precipitated resin was dried to obtain 96 g of a polymer dispersant P-1.
The composition of the obtained resin was confirmed by ¹ H-NMR, and the weight average molecular weight (Mw) determined by GPC was 44,600. Furthermore, when the acid value was calculated | required by the method as described in JIS specification (JISK0070: 1992), it was 65.2 mgKOH / g.

[Preparation of dispersion of resin-coated pigment]
-Resin-coated cyan pigment dispersion-
Pigment Blue 15: 3 (phthalocyanine blue A220, manufactured by Dainichi Seika Co., Ltd.), 5 parts of the above polymer dispersant P-1, 42 parts of methyl ethyl ketone, 5.5 parts of 1 mol / L NaOH aqueous solution, Then, 87.2 parts of ion-exchanged water was mixed and dispersed with a bead mill for 4 hours using 0.1 mmφ zirconia beads.
By removing methyl ethyl ketone from the obtained dispersion at 55 ° C. under reduced pressure and further removing a part of water, a dispersion (colored particles) of a resin-coated cyan pigment having a pigment concentration of 10.2% by mass was obtained. It was.

-Resin-coated magenta pigment dispersion-
In the preparation of the resin-coated cyan pigment dispersion, the resin coating was carried out in the same manner as above except that Chromathal Jet Magenta DMQ (Pigment Red 122, manufactured by BASF Japan Ltd.) was used instead of phthalocyanine blue A220 used as the pigment. A magenta pigment dispersion (colored particles) was obtained.

-Resin-coated yellow pigment dispersion-
Resin-coated yellow was prepared in the same manner as described above except that Irgalite Yellow GS (Pigment Yellow 74, manufactured by BASF Japan Ltd.) was used instead of phthalocyanine blue A220 used as a pigment in the preparation of the resin-coated cyan pigment dispersion. A pigment dispersion (colored particles) was obtained.

-Resin-coated black pigment dispersion-
The resin-coated cyan pigment dispersion was prepared in the same manner as above except that the pigment dispersion CAB-O-JET ™ 200 (carbon black, manufactured by CABOT) was used instead of the phthalocyanine blue A220 used as the pigment. A dispersion (colored particles) of the coated black pigment was obtained.

Example 1-1: Preparation of ink set 1 [Preparation of ink set 1]
The cyan ink composition (C1), the magenta ink composition (M1), the yellow ink composition (Y1), the black ink composition (K1), and the treating agent 1 of the ink formulation 1 were prepared as follows. As a result, an ink set 1 comprising these ink composition and the treatment agent 1 was obtained.

[Ink Formula 1]
(Preparation of cyan ink composition C1)
Using the above dispersion of resin-coated cyan pigment, the resin-coated cyan pigment dispersion, ion-exchanged water, photopolymerization initiator, polymerizable compound, and surfactant are mixed so that the following ink formulation 1 is obtained. A cyan ink composition C1 of ink formulation 1 was prepared by filtration through a 5 μm membrane filter (PVDF membrane, pore size 5 μm, manufactured by Millipore).
-Ink formula 1
・ Resin-coated cyan pigment dispersion: 6%
Compound A-1 (photopolymerization initiator) 3%
・ Polymerizable compound M-1 10%
・ Orphine E1010 ... 1%
(Nissin Chemical Co., Ltd .; surfactant)
・ Ion-exchanged water: added to 100% overall.
When the pH (25 ° C.) of the cyan pigment ink C1 was measured using a pH meter WM-50EG (manufactured by Toa DKK), the pH value was 8.5.

(Preparation of magenta ink composition (M1))
In the preparation of the cyan ink composition (C1), a magenta ink composition of ink formulation 1 (in the same manner as above except that a resin-coated magenta pigment dispersion was used instead of the resin-coated cyan pigment dispersion ( M1) was prepared. The pH value was 8.5.

(Preparation of yellow ink composition (Y1))
In the preparation of the cyan ink composition (C1), a yellow ink composition (ink formulation 1) of the ink formulation 1 was prepared in the same manner as described above except that a resin-coated yellow pigment dispersion was used instead of the resin-coated cyan pigment dispersion. Y1) was prepared. The pH value was 8.5.

(Preparation of black ink composition (K1))
In the preparation of the cyan ink composition (C1), a black ink composition (K1) of ink formulation 1 was prepared in the same manner as described above except that a resin-coated black pigment dispersion was used instead of the resin-coated cyan pigment dispersion. ) Was prepared. The pH value was 8.5.

[Preparation of Treatment Agent 1]
The processing agent 1 was produced by mixing the following materials. It was 1.0 when pH (25 degreeC) of the processing agent 1 was measured with Toa DKK Co., Ltd. pH meter WM-50EG.
-Treatment agent composition-
・ Malonic acid 25.0%
・ Tripropylene glycol monomethyl ether (water-soluble organic solvent)
5.0%
・ Ion exchange water 70.0%

Examples 1-2 to 1-10: Preparation of ink sets 2 to 10 In ink set 1, in place of compound A-1, compounds A-3, A-6, A-7, A-9, A-10, Cyan ink compositions C2 to C10, magenta ink compositions M2 to M10, yellow ink composition in the same manner as ink set 1 except that the same mass of A-14, A-15, A-16, or A-17 was used. Articles Y2 to Y10 and black ink compositions K2 to K10 were prepared. Here, an ink set composed of the ink compositions C1, M1, Y1, and K1 is defined as an ink set 1, and similarly, an ink set composed of the ink compositions C2 to C10, M2 to M10, Y2 to Y10, and K2 to K10. Were set to ink sets 2 to 10, respectively.

Comparative Examples 1-1 to 1-5: Preparation of Comparative Ink Sets 11 to 15 Ink set 1 except that the same amount of compounds B-1 to B-5 was used instead of compound A-1 in ink set 1. In the same manner, ink sets 11 to 15 were obtained.

[Inkjet recording]
As a recording medium (coated paper), Tokishi Art Double Sided N (Mitsubishi Paper) (basis weight: 104.7 g / m ² ) was prepared, and an image was formed as shown below. The following evaluation was performed.

Using the ink sets 1 to 15 prepared above, solid images were formed by four-color single-pass recording.
The solid image was formed by discharging the ink composition over the entire surface of a sample obtained by cutting the recording medium into A5 size.
The conditions for recording are as follows.

(1) Treatment agent application process The entire surface of the recording medium is processed with a roll coater whose application amount is controlled by an anilox roller (number of lines: 100 to 300 / inch) so that the application amount is 1.4 g / m ^2. Agent 1 was applied.
(2) Treatment Agent Drying / Penetration Processing Step Next, the recording medium coated with the treatment agent 1 was subjected to a drying treatment and a penetration treatment under the following conditions.
・ Wind speed: 10m / s
Temperature: Heated with a contact type flat heater from the opposite side (back side) of the recording medium application surface so that the surface temperature of the recording medium on which the treatment agent is applied (application surface) side is 60 ° C. did.
(3) Ink application process The ink composition was ejected by the inkjet method on the application surface of the recording medium under the following conditions to form a line image and a solid image, respectively.
・ Printer head: 1,200 dpi / 20 inch wide piezo full line head for 4 colors ・ Discharged droplet volume: 2.0 pL
・ Drive frequency: 30kHz
(4) Ink drying step Next, the recording medium provided with the ink composition was dried under the following conditions.
・ Drying method: blow drying ・ wind speed: 15m / s
-Temperature: Heated by a contact type flat heater from the opposite side (back side) of the recording surface of the recording medium so that the surface temperature of the recording surface of the recording medium was 60 ° C.
(5) Active energy ray irradiation (immobilization) step Next, using a UV-LED light source (trade name: NCSU275U365, peak wavelength: 365 nm, light output: 148 mW / cm ² ) manufactured by Nichia Corporation, The recorded image was irradiated with ultraviolet rays as active energy rays under the condition that the irradiation amount was 1000 mJ / cm ² to obtain an image recorded matter (image sample).

[Evaluation]
The obtained image sample was subjected to an image abrasion resistance test and an anti-blocking test as follows. In addition, a discharge stability test was performed on the obtained ink composition. The results are shown in Table 1.

(Abrasion resistance)
An unrecorded recording medium (Tokuhishi Art Double Side N, manufactured by Mitsubishi Paper Industries) is wrapped around a paperweight (weight 470 g, size 15 mm × 30 mm × 120 mm) (the area where the unrecorded recording medium and the image sample for evaluation are in contact is 150 mm) ² ) The solid image sample obtained above was rubbed 3 times (corresponding to a load of 260 kg / m ² ). The recorded surface after rubbing was visually observed and evaluated according to the following evaluation criteria.
-Evaluation criteria-
A: No peeling of the image (coloring material) was visible on the recording surface.
B: Slight peeling of the image (coloring material) was observed on the recording surface.
C: The peeling of the image (coloring material) can be visually recognized on the recording surface, which is a level that causes a practical problem.

(Blocking resistance)
Immediately after irradiating the solid energy sample of 2 cm square of the solid image sample with an active energy ray, an unrecorded recording medium (Tokuhishi art double-sided N (Mitsubishi Paper)) was stacked and a load of 350 kg / m ² was applied to the solid image sample at 60 ° C. The ink was allowed to stand for 24 hours under an environmental condition of 30% RH, and the degree of ink transfer to the white background of an unrecorded recording medium was visually observed and evaluated according to the following evaluation criteria.
-Evaluation criteria-
A: There was no transfer of ink.
B: Ink transfer was hardly noticeable.
C: Some transfer of ink was observed, which was a practically acceptable limit level.
D: Ink transfer was remarkable.

(Discharge stability)
The black ink composition obtained above was stored for 14 days under a low temperature condition of −5 ° C., and the supernatant was collected. The storage tank connected to the printer head was filled with the obtained ink composition (supernatant part) and discharged. After confirming that the filled ink composition was ejected from all 96 nozzles of the printer head at the start of ejection, the ink composition was continuously ejected for 45 minutes. Then, after 45 minutes of continuous discharge, the number of nozzles that could be discharged to the end (the number of discharge nozzles after 45 minutes of continuous discharge) was counted. Using this number of discharge nozzles, the ink discharge rate was calculated by the following formula, and the discharge stability of the ink composition was evaluated according to the following evaluation criteria.
In addition, what is practically acceptable is classified into A and B.
Ink ejection rate (%) = (number of ejection nozzles after 45 minutes of continuous ejection) / (total number of nozzles) × 100

-Evaluation criteria-
A: The ink discharge rate after completion of continuous discharge for 45 minutes is 98% or more.
B: The ink discharge rate after 45 minutes of continuous discharge is 95% or more and less than 98%.
C: The ink discharge rate after completion of continuous discharge for 45 minutes is 90% or more and less than 95%.
D: The ink discharge rate after completion of continuous discharge for 45 minutes is less than 90%.

Compounds A-1, A-3, A-6, A-7, A-9, A-10, A-14, A-15, A-16, and A-17 of the present invention are comparative compounds B- Compared with 1-B-5, the maximum absorption wavelength was on the long wavelength side in the ultraviolet region, and the solubility in water was high.
In addition, the ink composition using the photopolymerization initiator shown in this example had better ejection stability than the ink composition using the comparative compound.
Furthermore, the image formed using the photopolymerization initiator shown in the present example is more resistant to abrasion and blocking than images formed using Comparative Compounds B-1 to B-5. It was good. The fact that the rubbing resistance was good even when a UV-LED light source was used contributed to the fact that the absorption of the compound of the present invention was shifted to the long wavelength side as a whole.

Claims (12)

A compound represented by the following general formula (1).

In general formula (1), R ^{1 to} R ⁴ each independently represents a hydrogen atom or an alkyl group having 6 or less carbon atoms. However, one or two of R ^{1 to} R ⁴ are groups represented by the following general formula (2) or (3). R ⁵ represents a hydrogen atom or an alkyl group having 6 or less carbon atoms. R ⁶ and R ⁷ each independently represents an alkyl group or an aryl group. R ⁶ and R ⁷ may combine with each other to form a 5- or 6-membered ring.

In the general formulas (2) and (3), R ⁸ represents an alkylene group which may contain a hetero atom. R ⁹ represents a hydrogen atom or an alkyl group having 6 or less carbon atoms. R ¹⁰ has the same meaning as R ⁸ and R ¹¹ has the same meaning as R ⁹ . * Represents a bonding site with a benzene ring. R ¹ to R ⁴ of one or two is a group represented by the general formula (2) A compound according to claim 1. The compound of Claim 1 or 2 whose R < ⁸ > is group represented by following General formula (4).

In general formula (4), n represents the integer of 0-5. The compound according to any one of claims 1 to 3 , wherein R ³ is a group represented by the general formula (2). R ¹ , R ² And R ⁴ Is a hydrogen atom or a methyl group, R ⁶ And R ⁷ Is an alkyl group and R ⁸ Is an alkylene group having 1 to 6 carbon atoms having one oxygen atom, R ⁹ The compound of Claim 4 whose is a hydrogen atom, a methyl group, or an ethyl group. The compound according to any one of claims 1 to 5 , wherein R ⁶ and R ⁷ are methyl groups. The ink composition containing the photoinitiator which consists of a compound of any one of Claims 1-6, a polymeric compound, and an aqueous medium. An ink application step of applying the ink composition according to claim 7 on a recording medium;
And an active energy ray irradiating step of irradiating the ink composition applied on the recording medium with an active energy ray. The image forming method according to claim 8 , wherein a peak wavelength of a source of the active energy ray is 300 to 450 nm. The image according to claim 8 or 9 , further comprising a treatment agent application step of applying a treatment agent containing an aggregating component onto the recording medium, wherein the treatment agent application step is performed prior to the ink application step. Forming method. The ink application step, the image forming method according to any one of claims 8-10 is a step of applying an ink by an ink-jet recording system. An ink set comprising the ink composition according to claim 7 and a treatment agent containing an aggregating agent.