JP5554262B2 - Active energy ray-curable ink composition and image forming method - Google Patents

Description

  The present invention relates to an active energy ray-curable ink composition and an image forming method.

  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. Among these, the ink jet method can be implemented with an inexpensive apparatus, and the ink can be efficiently used because the image is directly formed on the recording medium by ejecting the ink only to the required image portion. Running cost is low.

  As one of the ink jet methods, there is a recording method using an ink for ink jet recording that can be cured by irradiation with active energy rays. According to this method, the productivity of printing can be improved and a sharp image can be formed by irradiating active energy rays immediately after ink ejection or after a certain period of time to cure ink droplets.

  Here, Patent Document 1 discloses an ink composition using a specific compound having an alicyclic group and a polymerization initiator.

JP 2007-138118 A

However, in Patent Document 1, there is still room for improvement in glossiness of recorded images. Therefore, an ink composition having good glossiness of recorded images and good adhesion to a substrate is desired.
The problem to be solved by the present invention is to provide an ink composition excellent in gloss of recorded images and adhesion to a substrate in light of the above circumstances.

Specific means for solving the above problems are as follows.
Item 1. An active energy ray-curable ink composition containing (A) a polymerization initiator and (B) a compound represented by the following general formula (1).

(In the formula, X ¹ represents a tertiary alkyl group, and R ^{1 to} R ¹⁰ each independently represents a hydrogen atom or an alkyl group.)
Item 2. Item 2. The active energy ray-curable ink composition according to Item 1, wherein the tertiary alkyl group in the general formula (1) is the following general formula (1A).

(Wherein R ^1a , R ^2a and R ^3a each independently represents an alkyl group, and at least two of R ^1a , R ^2a and R ^3a may be bonded to each other to form a ring, provided that R ^1a , (The total number of carbon atoms contained in R ^2a and R ^3a is 3 or more and 11 or less. * Represents a bonding position.)
Item 3. Item 3. The active energy ray-curable ink composition according to Item 1 or 2, wherein X ¹ in the general formula (1) is a t-butyl group.
Item 4. Item 4. The active energy ray-curable ink composition according to any one of Items 1 to 3, wherein R ¹ , R ⁸ , R ⁹ and R ¹⁰ in the general formula (1) are hydrogen atoms.
Item 5. Item 5. The item according to any one of Items 1 to 4, wherein the content of the compound represented by the general formula (1) in the active energy ray-curable ink composition is 25 to 60% by mass. An active energy ray-curable ink composition.
Item 6. Item 6. The active energy ray-curable ink composition according to any one of Items 1 to 5, further comprising (C) another polymerizable compound that is a polymerizable compound other than (B).
Item 7. Item 7. The active energy ray-curable ink composition according to Item 6, comprising an N-vinyl compound as the other polymerizable compound (C).
Item 8. Item 8. The active energy ray-curable ink composition according to any one of Items 1 to 7, further comprising (D) a colorant.
Item 9. Item 9. The active energy ray-curable ink composition according to any one of Items 1 to 8, which is for inkjet recording.
Item 10. The step of discharging the active energy ray-curable ink composition according to any one of Items 1 to 9 onto the recording medium, and irradiating the discharged active energy ray-curable ink composition with active energy rays And a step of curing the active energy ray-curable ink composition.
Item 11. Item 11. The image forming method according to Item 10, wherein the step of discharging the active energy ray-curable ink composition is a step of discharging the active energy ray-curable ink composition by an inkjet method.

  As described above, according to the present invention, it is possible to provide an active energy ray-curable ink composition and an image forming method excellent in gloss of recorded images and adhesion to a substrate.

<Active energy ray-curable ink composition>
The active energy ray-curable ink composition of the present invention contains (A) a polymerization initiator and (B) a compound represented by the general formula (1). Hereinafter, the active energy ray-curable ink composition of the present invention may be simply referred to as an ink composition.
The ink composition of the present invention can be suitably used for inkjet recording.
Hereinafter, components essential to the ink composition of the present invention will be sequentially described.

[(B) Compound Represented by General Formula (1)]
The ink composition of the present invention comprises (B) a compound represented by the general formula (1).

(In the formula, X ¹ represents a tertiary alkyl group, and R ^{1 to} R ¹⁰ each independently represents a hydrogen atom or an alkyl group.)

  Hereinafter, (B) the compound represented by the general formula (1) will be described.

X ¹ in the general formula (1) represents a tertiary alkyl group.
The tertiary alkyl group preferably has 4 to 12 carbon atoms, and more preferably 4 to 8 carbon atoms.
Specific examples of the tertiary alkyl group include t-butyl group, t-pentyl group, 1,1,3,3-tetramethylbutyl group, norbornyl group, 1-methylcyclohexyl group, 1-ethylcyclopentyl group, 2 A-(2-methyl) adamantyl group, a 2- (2-ethyl) adamantyl group and the like can be mentioned, more preferably a t-butyl group and a t-pentyl group, and particularly preferably a t-butyl group.
X ¹ may further have a substituent, but it is preferably not substituted, that is, it is preferably a tertiary alkyl group consisting of only a carbon atom and a hydrogen atom.

  The tertiary alkyl group preferably has a structure represented by the following general formula (1A).

In the formula, R ^1a , R ^2a and R ^3a each independently represent an alkyl group, and at least two of R ^1a , R ^2a and R ^3a may be bonded to each other to form a ring. However, the total number of carbon atoms contained in R ^1a , R ^2a and R ^3a is 3 or more and 11 or less. * Represents a bonding position.

The alkyl group of R ^1a , R ^2a and R ^3a may have a linear structure, a branched structure, or a cyclic structure. R ^1a , R ^2a and R ^3a may have a substituent, may not have a substituent, and preferably has no substituent.
Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, isopentyl, neopentyl, 1-ethylpropyl, and hexyl. Group, isohexyl group, 1,1-dimethylbutyl group, 2,2-dimethylbutyl group, 3,3-dimethylbutyl group, 2-ethylbutyl group, heptyl group, octyl group, nonyl group, decyl group, cyclopropyl group, A cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, etc. are mentioned.
The total number of carbon atoms of R ^1a , R ^2a and R ^3a is 3 to 11, more preferably 3 to 7, and particularly preferably 3 to 4.
In the present invention, it is particularly preferable that R ^1a , R ^2a and R ^3a in the general formula (1A) are a methyl group.

When at least two of R ^1a , R ^2a and R ^3a are bonded to each other to form a ring, it is preferable to form a 4- to 7-membered ring, more preferably a 5- to 6-membered ring.

In general formula (1), R ^{1 to} R ¹⁰ each independently represents a hydrogen atom or an alkyl group. The alkyl group may have a linear structure, a branched structure, or a cyclic structure. Further, the alkyl group may have a substituent or may not have a substituent, and preferably has no substituent. That is, an alkyl group consisting of only carbon atoms and hydrogen atoms is preferable.
When R ^{1 to} R ¹⁰ are alkyl groups, specific examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, and pentyl. Group, isopentyl group, neopentyl group, 1-ethylpropyl group, hexyl group, isohexyl group, 1,1-dimethylbutyl group, 2,2-dimethylbutyl group, 3,3-dimethylbutyl group, 2-ethylbutyl group, heptyl Group, octyl group, nonyl group, decyl group and the like.
When R ^{1 to} R ¹⁰ are alkyl groups, the alkyl group preferably has 1 to 12 carbon atoms, more preferably 1 to 4 carbon atoms, and particularly preferably 1.
In the present invention, is ^{R 1,} R 8 in the general formula (1), ^{R 9} and ^{R 10} are hydrogen ^atoms, it is preferred that R 2 to R ⁷ are each independently a hydrogen atom or an alkyl ^{group, R} 1, R ⁸ , R ⁹ and R ¹⁰ are each a hydrogen atom, more preferably 5 or more of R ^{2 to} R ⁷ are hydrogen atoms, and particularly preferably all of R ^{1 to} R ¹⁰ are hydrogen atoms. .

  Specific examples of the compound represented by the general formula (1) that can be suitably used in the present invention are shown below, but the present invention is not limited thereto. Moreover, when stereoisomers exist in each exemplified compound, any of them may be used, and a mixture of stereoisomers may be used.

  As the compound represented by (B) the general formula (1) in the present invention, 1-1, 1-2, 1-3, 1-4 and the like are preferable, and 1-1, 1-2 and the like are particularly preferable.

The content of the component (B) in the ink composition of the present invention is preferably in the range of 25 to 60% by mass and more preferably in the range of 30 to 50% by mass with respect to the total mass of the ink composition.
Moreover, (B) component may be used by 1 type and may use 2 or more types.

[(A) Polymerization initiator]
The ink composition of the present invention contains a polymerization initiator. As a polymerization initiator in this invention, a photoinitiator is mentioned preferably. As the photopolymerization initiator, a known photopolymerization initiator can be appropriately selected and used according to the kind of the polymerizable compound and the purpose of use of the ink composition.
The photopolymerization initiator used in the ink composition of the present invention is a compound that absorbs external energy (light) and generates radicals that are polymerization initiation species. Examples of light include active energy rays, that is, γ rays, β rays, electron beams, ultraviolet rays, visible rays, infrared rays, and the like.

  As the photopolymerization initiator, known compounds can be used. Preferred photopolymerization initiators that can be used in the present invention include (a) aromatic ketones, (b) acylphosphine oxide compounds, and (c) aromatics. Onium salt compound, (d) organic peroxide, (e) thio compound, (f) hexaarylbiimidazole compound, (g) ketoxime ester compound, (h) borate compound, (i) azinium compound, (j) Examples thereof include metallocene compounds, (k) active ester compounds, (l) compounds having a carbon halogen bond, and (m) alkylamine compounds.

  These photopolymerization initiators may use the above compounds (a) to (m) alone or in combination. The photopolymerization initiator in the present invention is preferably used alone or in combination of two or more.

  Preferable examples of (a) aromatic ketones, (b) acylphosphine oxide compounds, and (e) thio compounds include “RADIATION CURING IN POLYMER SCIENCE AND TECHNOLOGY”, J. MoI. P. FOUASSIER, J.A. F. RABEK (1993), pp. Examples include compounds having a benzophenone skeleton or a thioxanthone skeleton described in 77-117. More preferable examples include α-thiobenzophenone compounds described in JP-B-47-6416, benzoin ether compounds described in JP-B-47-3981, α-substituted benzoin compounds described in JP-B-47-22326, Benzoin derivatives described in JP-B-47-23664, aroylphosphonic acid esters described in JP-A-57-30704, dialkoxybenzophenones described in JP-B-60-26483, JP-B-60-26403, JP-A Benzoin ethers described in JP-A-62-81345, JP-B-1-34242, US Pat. No. 4,318,791, α-aminobenzophenones described in European Patent 0284561A1, JP-A-2-21152 P-Di (dimethylaminobenzoyl) benze Thio-substituted aromatic ketones described in JP-A-61-194062, acylphosphine sulfides described in JP-B-2-9597, acylphosphines described in JP-B-2-9596, and JP-B-63-61950 Thioxanthones, and coumarins described in JP-B-59-42864. Moreover, the polymerization initiators described in JP 2008-105379 A and JP 2009-114290 A are also preferable.

  Among these, in the present invention, it is preferable to use an aromatic ketone or an acylphosphine oxide compound as a photopolymerization initiator, and p-phenylbenzophenone (manufactured by Wako Pure Chemical Industries, Ltd.), bis (2,4,6- Trimethylbenzoyl) -phenylphosphine oxide (Irgacure 819: manufactured by BASF Japan), bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphenylphosphine oxide, 2,4,6-trimethylbenzoyl- Diphenyl-phosphine oxide (Darocur TPO: manufactured by BASF Japan Ltd., Lucirin TPO: manufactured by BASF Corp.), 1-hydroxycyclohexyl phenyl ketone (Irgacure 184, manufactured by BASF Japan Ltd.) and the like are preferable.

A polymerization initiator can be used individually by 1 type or in combination of 2 or more types.
The preferable content of the polymerization initiator in the ink composition is preferably in the range of 0.1 to 15% by mass.

In the present invention, the polymerization initiator (A) is polymerized with respect to the total amount of the component (B) or when the component (B) and another polymerizable compound (C) as an optional component are used in combination. Preferably, it is contained in the range of 0.01 to 35% by mass, more preferably 0.1 to 30% by mass, and still more preferably 0.5 to 30% by mass relative to the total amount of the active compound. is there.
In addition, (A) the polymerization initiator is 200: 1 to 1: 200 in a mass ratio of the polymerization initiator to the sensitizing dye with respect to the (E) sensitizing dye that can be used as required later. Preferably, it is contained in the range of 50: 1 to 1:50, more preferably 20: 1 to 1: 5.

The mechanism of the present invention is not clear, but is estimated as follows.
The ink composition of the present invention contains (B) a compound represented by the general formula (1) together with (A) a polymerization initiator. The compound represented by the general formula (1) has a bulky tertiary alkyl group in the vicinity of the polymerizable group. By using the ink composition containing the compound represented by the general formula (1), when the ink composition discharged on the recording medium is cured by irradiation with active energy rays, the polymerization is slightly delayed. It is considered that high gloss is exhibited by combining with the ejected ink composition, and flattening and then curing. In addition, the glass transition temperature of the polymer produced by the rigidity of the cyclohexyl group is considered to be high, and it is considered that high curing sensitivity is expressed. The improvement of the curing sensitivity in the vicinity of the support also contributes to the improvement of adhesion. It is thought that there is.

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

[(C) Other polymerizable compound]
The ink composition of the present invention preferably contains (C) another polymerizable compound other than the compound represented by the general formula (1) in addition to the component (B).
The other polymerizable compound in the present invention may be either a radical polymerizable compound or a cationic polymerizable compound, but in the present invention, a radical polymerizable compound is preferable.

  Hereinafter, other polymerizable compounds applicable to the present invention will be further described.

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

  Examples of polymerizable compounds having an ethylenically unsaturated bond include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, unsaturated carboxylic acid esters, and unsaturated carboxylic acid amides. And radically polymerizable compounds such as salts thereof, anhydrides having an ethylenically unsaturated group, acrylonitrile, styrene, N-vinyl compounds, various unsaturated polyesters, unsaturated polyethers, and unsaturated polyamides.

Specifically, N-vinyl compounds such as N-vinylcaprolactam, N-vinylpyrrolidone, and N-methyl-N-vinylacetamide 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, cyclohexyl acrylate , Tetrahydrofurfuryl acrylate, benzyl acrylate, bis (4-acryloxypolyethoxyphenyl) propane, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, phenoxyethyl acrylate, propoxylated neopentyl glycol diacrylate, ethylene Glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate Acrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, oligoester acrylate, N-methylolacrylamide, di Acrylic acid derivatives such as acetone acrylamide, epoxy acrylate, cyclic trimethylpropane formal acrylate (CTFA), tetrahydrofurfuryl acrylate (THFA),
Methyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate, 1,6-hexanediol dimethacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, Methacryl derivatives such as polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, trimethylolethane trimethacrylate, trimethylolpropane trimethacrylate, 2,2-bis (4-methacryloxypolyethoxyphenyl) propane,
Other examples include derivatives of allyl compounds such as allyl glycidyl ether, diallyl phthalate, and triallyl trimellitate. More specifically, Yamashita Shinzo, “Cross-linking agent handbook” (1981 Taiseisha); Ed., "UV / EB Curing Handbook (raw material)" (1985, Polymer Press Society); Radtech Study Group, "Application and Market of UV / EB Curing Technology", 79 pages, (1989, CMC) Commercially available products described in Eiichiro Takiyama, “Polyester Resin Handbook”, (1988, Nikkan Kogyo Shimbun), etc., or radically polymerizable or crosslinkable monomers, oligomers and polymers known in the industry can be used.

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

The ink composition of the present invention can be used in combination with a cationically polymerizable compound as necessary.
The cationically polymerizable compound used in the present invention is not particularly limited as long as it is a compound that initiates a polymerization reaction with an acid generated from a photoacid generator and cures, and various known cationic polymerizations known as photocationically polymerizable monomers. Sex monomers can be used. Examples of the cationic polymerizable monomer include JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, and 2001-2001. Examples thereof include epoxy compounds, vinyl ether compounds, oxetane compounds and the like described in each publication such as No. 220526.

  In addition, as the cationic polymerizable compound, for example, a polymerizable compound applied to a cationic polymerization type photocurable resin is known, and recently, a photo cationic polymerization type sensitized in a visible light wavelength region of 400 nm or more. Examples of the polymerizable compound applied to the photo-curable resin are disclosed in JP-A-6-43633 and JP-A-8-324137. These can also be applied to the ink composition of the present invention.

  The molecular weight of the other polymerizable compound in the present invention is preferably 130 to 3000, more preferably 130 to 500, as a weight average molecular weight.

In the present invention, it is preferable to contain an N-vinyl compound as component (C) or another polymerizable compound in order to further improve adhesion in addition to glossiness.
The ink composition containing the compound represented by the general formula (1) of the present invention tends to be hydrophobic and may have poor adhesion to a plastic substrate, but this problem is avoided by the N-vinyl compound. Is considered possible.
Specific examples of the N-vinyl compound include N-vinylcaprolactam, N-vinylpyrrolidone, N-methyl-N-vinylacetamide, and N-vinylcaprolactam is particularly preferable.
The added amount of the N-vinyl compound is preferably 3 to 25% by mass, more preferably 5 to 20% by mass, and particularly preferably 10 to 15% by mass with respect to the total amount of the ink composition.

The N-vinyl compound preferably used in the present invention is not particularly limited as long as it has a structure in which an unsaturated ethylene group is bonded to the nitrogen atom of a cyclic or acyclic nitrogen compound.
The N-vinyl compound preferably has a structure represented by the following general formula (2).

In the formula, R ²¹ and R ²² each independently represents an alkyl group or an acyl group. R ²¹ and R ²² may combine with each other to form a ring.

When R ²¹ and R ²² are alkyl groups, the alkyl group may have a linear structure, a branched structure, or a cyclic structure. Further, the alkyl group may have a substituent or may not have a substituent.
Specific examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, s-butyl group, t-butyl group, pentyl group, isopentyl group, neopentyl group, 1-ethylpropyl group. Group, hexyl group, isohexyl group, 1,1-dimethylbutyl group, 2,2-dimethylbutyl group, 3,3-dimethylbutyl group, 2-ethylbutyl group, heptyl group, octyl group, nonyl group, decyl group, etc. Can be mentioned.
The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 7 carbon atoms, and particularly preferably 1 to 5 carbon atoms.

When R ²¹ and R ²² are acyl groups, the acyl group may have a linear structure, a branched structure, or a cyclic structure. The acyl group may have a substituent or may not have a substituent.
Specific examples of the acyl group include formyl group, acetyl group, propionyl group and the like.
The acyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 7 carbon atoms, and particularly preferably 1 to 5 carbon atoms.

When R ²¹ and R ²² are bonded to each other to form a ring, it is preferably a 5- to 10-membered ring, more preferably a 5- to 8-membered ring, and most preferably a 5- to 7-membered ring. .

  The N-vinyl compound more preferably has a structure represented by the following general formula (2-1).

  In the formula, m represents an integer of 2 to 6, m is preferably an integer of 3 to 5, m is more preferably 3 or 5, and m is 5, that is, N-vinylcaprolactam. It is particularly preferred.

  In the present invention, a monofunctional acrylate compound (hereinafter referred to as a specific monofunctional acrylate) that is hydrophobic and has a glass transition temperature of 35 ° C. or lower is used as another polymerizable compound in order to increase gloss and flexibility. It is also preferable to contain. Here, hydrophobic means that the solubility in water at 25 ° C. is 0.5% by mass or less. The glass transition temperature is preferably -85 ° C to 35 ° C, more preferably -70 ° C to 10 ° C, and most preferably -60 ° C to -20 ° C.

  The specific monofunctional acrylate is preferably an acrylate compound having a long-chain alkyl group or a phenyl group. As the long-chain alkyl group, a linear or branched alkyl group having 8 to 20 carbon atoms is preferable, and an alkyl group having 8 to 15 carbon atoms is more preferable. The long chain alkyl group or the phenyl group may have a substituent or may not have a substituent, but preferably has no substituent, that is, only a carbon atom and a hydrogen atom. Preferably it consists of.

  Specific long chain alkyl groups include octyl, isooctyl, nonyl, isononyl, decyl, isodecyl, dodecyl, tridecyl, octadecyl and the like.

  Preferred examples of the monofunctional acrylate include 2-phenoxyethyl acrylate, octyl acrylate, isooctyl acrylate, nonyl acrylate, isodecyl acrylate, lauryl acrylate, tridecyl acrylate, and stearyl acrylate.

  When the specific monofunctional acrylate in the ink composition of the present invention is contained, the content of the monofunctional acrylate with respect to the ink composition is preferably 1% by mass or more and 40% by mass or less, and preferably 3% by mass or more and 30% by mass. % Or less is more preferable, and 5% by mass or more and 25% by mass or less is particularly preferable.

  The ink composition of the present invention can contain a vinyl ether compound for the purpose of improving curability and flexibility. The vinyl ether compound may be a monofunctional, bifunctional, or trifunctional vinyl ether compound, and is preferably a bifunctional vinyl ether compound. Examples of the vinyl ether compound include ethylene glycol monovinyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, trimethylolpropane trivinyl ether, and the like. Among these, triethylene glycol divinyl ether is preferable.

  In the present invention, the total content of the polymerizable compound, that is, the total content of the component (B) and the other polymerizable compound (C) that can be used together with the component (B) is the mass of the entire ink composition of the present invention. It is 45-95 mass% with respect to it, More preferably, it is 50-90 mass%.

  In the ink composition of the present invention, the component (B) is based on the total content of polymerizable compounds contained in the ink composition (that is, the total content of the components (B) and (C)). 25 mass% or more and 95 mass% or less is preferable, 30 mass% or more and 90 mass% or less are more preferable, and 40 mass% or more and 70 mass% or less are still more preferable.

  In the present invention, regarding the selection of the polymerization initiator and the polymerizable compound, in addition to the combination of the cationic polymerizable compound and the cationic polymerization initiator, and the combination of the radical polymerizable compound and the radical polymerization initiator, these It is good also as a radical cation hybrid type curable ink which used together the polymeric compound of this, and a polymerization initiator.

[(D) Colorant]
The ink composition of the present invention is not particularly required to form a colored image, but can contain a colorant when a colored image is to be formed.

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

  A colorant that can be suitably used in the ink composition of the present invention is selected from compounds that do not function as a polymerization inhibitor in a polymerization reaction that is a curing reaction, from the viewpoint of not reducing the sensitivity of the curing reaction by active energy rays. Is preferred.

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

Examples of the red or magenta pigment include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, 53. : 1, 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144 , 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13, 16, 20, 36, and the like.
Examples of the blue or cyan pigment include Pigment Blue 1,15,15: 1,15: 2,15: 3, 15: 4,15: 6,16,17-1,22,27,28,29,36. , 60, and the like.

Examples of the green pigment include Pigment Green 7, 26, 36, 50, and the like.
Examples of the yellow pigment include Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 120. , 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193, and the like, and Pigment Yellow 120, 155, 180 are preferable.
Examples of the black pigment include Pigment Black 7, 28, 26, and the like.
Examples of the white pigment include Pigment White 6, 18, 21, and the like.
These pigments can be appropriately selected and used according to the purpose.

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

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

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

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

Although not limited to the following, preferred specific examples include C.I. I. Solvent Black 3, 7, 27, 29 and 34; C.I. I. Solvent Yellow 14, 16, 19, 29, 30, 56, 82, 93 and 162; C.I. I. Solvent Red 1, 3, 8, 18, 24, 27, 43, 49, 51, 72, 73, 109, 122, 132 and 218; I. Solvent Violet 3; C.I. I. Solvent Blue 2,11,25,35,38,67 and 70; I. Solvent Green 3 and 7; I. Solvent orange 2; and the like.
Among these, particularly preferred are the Black Black PC-0850, Oil Black HBB, Oil Yellow 129, Oil Yellow 105, Oil Pink 312, Oil Red 5B, Oil Scallet 308, Vali Fast Blue 2600e, Orient Chemical Co., Ltd.), Aizen Spillon Blue GNH (Hodogaya Chemical Co., Ltd.), Neopen Yellow 075, Neopen Mazena SE1378, Neopen Blue 808, Neopen FF4012, Neopen FF4012 .

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

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

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

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

  One or more colorants may be appropriately selected according to the intended use of the ink composition.

  In the ink composition of the present invention, when using a colorant such as a pigment that remains in a solid state, the average particle diameter of the colorant particles is preferably 0.005 to 0.5 μm, more preferably. It is preferable to set the colorant, the dispersant, the dispersion medium, the dispersion conditions, and the filtration conditions so as to be 0.01 to 0.45 μm, and more preferably 0.015 to 0.4 μm.

The content of the colorant in the ink composition of the present invention is appropriately selected depending on the purpose of use of the ink composition, but generally considering the ink physical properties and colorability, the content of the colorant is generally based on the total mass of the ink composition. The content is preferably 0.5 to 10% by mass.
In the case where the ink composition of the present invention is a white ink composition having a white pigment such as titanium oxide as a colorant, the content of the colorant is the mass of the entire ink composition in order to ensure concealment. It is preferable that it is 5-30 mass% with respect to it, and it is more preferable that it is 10-25 mass%.

[(E) Sensitizing dye]
<Sensitizing dye>
A sensitizing dye can be added to the ink composition of the present invention in order to promote decomposition of the polymerization initiator by irradiation with active energy rays. A sensitizing dye absorbs specific active energy rays and enters an electronically excited state. Sensitizing dyes in an electronically excited state come into contact with the polymerization initiator and cause actions such as electron transfer, energy transfer, and heat generation, thereby promoting chemical changes of the polymerization initiator, that is, decomposition and generation of radicals. It is something to be made.

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

  Polynuclear aromatics (eg, anthracene, pyrene, perylene, triphenylene), thioxanthones (eg, isopropylthioxanthone), xanthenes (eg, fluorescein, eosin, erythrosine, rhodamine B, rose bengal), cyanines (eg, Thiacarbocyanine, oxacarbocyanine), merocyanines (eg, merocyanine, carbomerocyanine), thiazines (eg, thionine, methylene blue, toluidine blue), acridines (eg, acridine orange, chloroflavin, acriflavine), anthraquinones (For example, anthraquinone), squalium (for example, squalium), coumarins (for example, 7-diethylamino-4-methylcoumarin), and the like. Xanthones may be mentioned as preferred class. Moreover, thiochromanones described in JP-A-2008-195926 can also be preferably used.

[(F) Co-sensitizer]
The ink composition of the present invention can also contain a co-sensitizer. In the present invention, the co-sensitizer has functions such as further improving the sensitivity of the sensitizing dye to the active energy ray or suppressing inhibition of polymerization of the polymerizable compound by oxygen.

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

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

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

[(G) Other ingredients]
Other components can be further added to the ink composition of the present invention as necessary. Examples of other components include a polymerization inhibitor and a solvent.

  A polymerization inhibitor may be added from the viewpoint of enhancing the storage stability. The ink composition of the present invention is preferably discharged in the range of 40 to 80 ° C. by heating and reducing the viscosity, and a polymerization inhibitor is preferably added to prevent clogging of the head due to thermal polymerization. The polymerization inhibitor is preferably added in an amount of 200 to 20,000 ppm based on the total amount of the ink composition of the present invention. Examples of the polymerization inhibitor include hydroquinone, benzoquinone, p-methoxyphenol and the like.

It is preferable that the ink composition of the present invention does not contain a solvent so that the ink composition can react quickly and cure immediately after landing of the ink composition. However, a predetermined solvent can be included as long as the curing rate of the ink composition is not affected. In the present invention, an organic solvent or water can be used as the solvent. In particular, an organic solvent can be added to improve the adhesion with a recording medium (a support such as paper). Suitable solvents include propylene carbonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, and mixtures thereof.
The amount of the organic solvent is, for example, in the range of 0 to 5% by mass, preferably 0.1 to 3% by mass, with respect to the total mass of the ink composition of the present invention.

  The ink composition of the present invention is preferably a non-aqueous ink composition containing substantially no water. Specifically, it is preferably 5% by mass or less, more preferably 1% by mass or less, based on the total amount of the ink composition.

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

[Properties of ink composition]
As described above, the ink composition of the present invention has curability, and there are no particular restrictions on the means for image formation using this ink composition, and it can be applied to general coating methods, transfer methods, inkjet recording methods, and the like. Can be applied. The ink composition of the present invention has a feature that it can be suitably used for inkjet recording.
Hereinafter, preferable physical properties when the ink composition of the present invention is used for inkjet recording will be described.

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

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

<Image forming method>
The image forming method of the present invention and the ink jet recording apparatus applicable to the image forming method will be described below.

The image forming method of the present invention comprises a step of ejecting the ink composition of the present invention onto a recording medium, and a step of curing the ink composition by irradiating the ejected ink composition with active energy rays. It is characterized by including. The ink composition is preferably discharged by an ink jet recording apparatus.
The image forming method of the present invention includes the above steps, whereby an image is formed by the ink composition cured on the recording medium.

  In the step of discharging the ink composition in the image forming method of the present invention, an ink jet recording apparatus described in detail below can be used.

-Inkjet recording device-
There is no restriction | limiting in particular as an inkjet recording device used for the image forming method of this invention, The well-known inkjet recording device which can achieve the target resolution can be selected arbitrarily and can be used.

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

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

  The ejection of the ink composition of the present invention using the above-described ink jet recording apparatus is performed by heating the ink composition to preferably 25 to 60 ° C., more preferably 25 to 50 ° C. Preferably it is performed after lowering to 5 to 30 mPa · s, more preferably 7 to 25 mPa · s.

  In the ink composition of the present invention, it is preferable to keep the temperature of the ink during ejection as constant as possible. Therefore, in the present invention, it is appropriate that the control range of the ink temperature is ± 5 ° C. of the set temperature, preferably ± 2 ° C. of the set temperature, more preferably ± 1 ° C. of the set temperature.

Next, a process of irradiating the discharged ink composition with active energy rays and curing the ink composition will be described.
The ink composition ejected onto the recording medium is cured by irradiating with active energy rays. This is because the polymerization initiator contained in the ink composition of the present invention is decomposed by irradiation with active energy rays to generate radicals and other starting species, and depending on the function of the starting species, a specific heterocyclic compound or, if desired, This is because the polymerization reaction of other polymerizable compounds used in combination occurs and is accelerated. At this time, if the sensitizing dye is present together with the radical polymerization initiator in the ink composition, the sensitizing dye in the system absorbs the active energy ray to be in an excited state and promotes its decomposition by contact with the radical polymerization initiator. And a more sensitive curing reaction can be achieved.

Further, the polymerization initiation system applied to the ink composition of the present invention has sufficient sensitivity even with a low output active energy ray. Therefore, the output of the active energy ray is preferably 2,000 mJ / cm ² or less, more preferably 10 to 2,000 mJ / cm ² , and still more preferably 20 to 1,000 mJ / cm ² . Yes, and particularly preferably 50 to 800 mJ / cm ² .
Further, the active energy rays, the exposure surface illuminance of, for example, 10 to 2,000 mW / cm ^2, preferably, it is suitable to be irradiated at 20 to 1,000 mW / cm ^2.

  Mercury lamps and gas / solid lasers are mainly used as active energy ray sources, and mercury lamps and metal halide lamps are widely known as light sources used for curing active energy ray-curable ink compositions. ing. However, from the viewpoint of environmental protection, mercury-free is strongly desired, and replacement with a GaN-based semiconductor ultraviolet light-emitting device is very useful industrially and environmentally. Furthermore, LED (UV-LED) and LD (UV-LD) are small, have a long life, have high efficiency, and are low in cost, and are expected as light sources for photo-curable ink jets.

  In addition, a light emitting diode (LED) and a laser diode (LD) can be used as an active energy ray source. In particular, when an ultraviolet light source is required, an ultraviolet LED and an ultraviolet LD can be used. For example, Nichia Corporation has introduced a purple LED whose main emission spectrum has a wavelength between 365 nm and 420 nm. When even shorter wavelengths are required, US Pat. No. 6,084,250 discloses an LED that can emit active energy rays centered between 300 nm and 370 nm. Other ultraviolet LEDs are also available and can emit radiation in different ultraviolet bands. 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.

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

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

  Further, curing may be performed by another light source that is not driven. International Publication No. 99/54415 pamphlet discloses a method using an optical fiber or a method of irradiating a recording unit with UV light by applying a collimated light source to a mirror surface provided on the side of the head unit as an irradiation method. Such a curing method can also be applied to the image forming method of the present invention.

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

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited to these examples.
In the following description, “parts” means “parts by mass” unless otherwise specified.

  Of the compounds used in Examples and Comparative Examples, compounds not described by the manufacturer were synthesized by applying known methods or known methods.

The materials of the ink compositions used in the examples and comparative examples are as shown below.
NOVOPERM YELLOW 4G01 (yellow pigment, CI Pigment Yellow 155, manufactured by Clariant Japan Co., Ltd.)
CINQUASIA MAGENTA RT-355D (magenta pigment, mixed crystal of CI Pigment Violet 19 and CI Pigment Red 202, manufactured by BASF Japan Ltd.)
・ IRGALITETE BLUE GLVO (Cyan Pigment, CI Pigment Blue 15: 4, manufactured by BASF Japan Ltd.)
SPECIAL BLACK 250 (black pigment, CI Pigment Black 7, manufactured by Evonik Degussa Japan Co., Ltd.)
・ KRONOS 2300 (white pigment, CI Pigment White 6, manufactured by Kronos)
・ SOLSPERSE22000 (pigment dispersant, manufactured by Nippon Lubrizol Co., Ltd.)
・ SOLPERSE32000 (pigment dispersant, manufactured by Nippon Lubrizol Co., Ltd.)
SOLPERSE 41000 (pigment dispersant, manufactured by Nippon Lubrizol Co., Ltd.)
DISPERBYK-168 (pigment dispersant, solid content 30%, manufactured by Big Chemie Japan Co., Ltd.)
NVC (polymerizable compound, N-vinylcaprolactam, manufactured by BASF Japan Ltd.)
SR395 (polymerizable compound, isodecyl acrylate, manufactured by Sartomer Japan, Inc.)
・ RAPI-CURE DVE-3 (polymerizable compound, triethylene glycol divinyl ether, manufactured by IS Japan Co., Ltd.)
SR339A (polymerizable compound, 2-phenoxyethyl acrylate, manufactured by Sartomer Japan, Inc.)
SR9003 (polymerizable compound, propoxylated (2) neopentyl glycol diacrylate (compound obtained by diacrylate conversion of neopentyl glycol propylene oxide 2-mol adduct), manufactured by Sartomer Japan, Inc.)
SR341 (polymerizable compound, 3-methyl-1,5-pentanediol diacrylate, manufactured by Sartomer Japan, Inc.)
・ Cyclohexyl acrylate (polymerizable compound, manufactured by Wako Pure Chemical Industries, Ltd., compound obtained by removing t-Bu group from compound 1-1 described later)
・ Lucirin TPO (photopolymerization initiator, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, manufactured by BASF Japan Ltd.)
IRGACURE 819 (photopolymerization initiator, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, manufactured by BASF Japan Ltd.)
IRGACURE 184 (photopolymerization initiator, 1-hydroxycyclohexyl phenyl ketone, manufactured by BASF Japan Ltd.)
FIRSTCURE ITX (sensitizing dye, isopropyl thioxanthone, manufactured by ChemFirst Inc.)
FIRSTCURE ST-1 (polymerization inhibitor, manufactured by ChemFirst Inc.)

Compound 1-1 (compound represented by the general formula (1), name 2-t-butylcyclohexyl acrylate)

Production Example <Synthesis of 1-1>
A solution of 78.0 g (0.5 mol) of 2-t-butylcyclohexanol (manufactured by Aldrich Co., Ltd.) in 300 mL of ethyl acetate was cooled to 0 ° C., and 49.5 g of acryloyl chloride (manufactured by Wako Pure Chemical Industries, Ltd.). (0.55 mol) was added. To this solution, a solution of 60.7 g (0.6 mol) of triethylamine (manufactured by Wako Pure Chemical Industries, Ltd.) in 100 mL of ethyl acetate was added dropwise over 30 minutes while keeping the internal temperature in the range of 0 to 10 ° C. And stirred for 1 hour. 300 mL of ethyl acetate was added to the reaction solution, 1 L of water was added for liquid separation, the organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, and the solid was filtered. To this solution, 0.1 g of 4-methoxyphenol (manufactured by Wako Pure Chemical Industries, Ltd.) was added, the ethyl acetate solution was distilled off under reduced pressure, and then purified by distillation under reduced pressure to obtain 67 g of compound 1-1 as a colorless transparent liquid. (0.32 mol) was obtained.

<Preparation of mill base>
Cyan, yellow, magenta, black, and white mill bases were mixed at the composition shown in Table 1 and stirred for 10 minutes at 2500 rpm using a mixer (Silverson L4R). Then, it put into bead mill disperser DISPERMAT LS (made by VMA), and disperse | distributed for 6 hours at 2500 rotation / min using the YTZ ball | bowl (made by Nikkato Co., Ltd.) with a diameter of 0.65 mm.

<Preparation of ink composition>
The components in Table 2 were stirred for 15 minutes at 2500 rpm using a mixer (Silverson L4R). Thereafter, the mixture was filtered using a cartridge filter (product name: Profile II AB01A01014J) manufactured by Nippon Pole Co., Ltd. to obtain ink compositions of each color.

Example 1
Ink set 1 consisting of yellow ink Y1, magenta ink M1, cyan ink C1, black ink K1 and white ink W1 is loaded into Fujifilm's UV inkjet printer LuxelJet UV350GTW and coated in Oji Paper Co., Ltd. in quality mode. A test image was printed on paper (product name: OK Topcoat +), and glossiness evaluation and adhesion evaluation were performed. The results are shown in Table 6.

<Glossiness evaluation>
Glossiness of composite black (yellow, magenta, cyan, black, each density was set to 100%) was measured for 60 ° gloss using a gloss meter (product name GM-60) manufactured by Konica Minolta Sensing Co., Ltd. The higher the value, the higher the gloss and the vivid printed matter. A glossiness of 20 or more is acceptable and is particularly preferably 27 or more.

<Adhesion evaluation>
The adhesion to the recording medium is evaluated by a cross hatch test (EN ISO 2409), and expressed by notations 5B to 1B according to the ASTM method. It is evaluated that 5B is most excellent in adhesion and 3B, 4B, and 5B are at a level having no practical problem. A polyvinyl chloride sheet (Avery, Fasson 400) was used as the recording medium. Practically, it must be 3B or more, preferably 4B or more.

(Comparative Example 1)
Evaluation was carried out in the same manner as in Example 1 except that cyclohexyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd., compound obtained by removing t-Bu group from compound 1-1) was used instead of compound 1-1. It was. The results are shown in Table 6.

(Comparative Example 2)
Of the ink set used in Example 1, for yellow ink, magenta ink, and cyan ink, compound 1-1 was changed to 3,3,5-trimethylcyclohexyl acrylate, NVC was changed to Actilane 421, and SR395 was changed to Photo2017. Evaluation was carried out in the same manner as in Example 1 except that the amount added was changed as shown in Table 3. The results are shown in Table 6.

(Example 2)
Evaluation was performed in the same manner as in Example 1 except that 13.8 parts by mass of NVC was replaced with SR395. The results are shown in Table 6.

(Example 3)
Of the ink set used in Example 1, the ratios of Compound 1-1, NVC, and SR395 were changed as shown in Table 4 for yellow ink, magenta ink, and cyan ink, and the others were the same as in Example 1. Evaluation was performed. The results are shown in Table 6.

(Example 4)
Of the ink set used in Example 1, for yellow ink, magenta ink, and cyan ink, the ratios of Compound 1-1, NVC, and SR395 were changed as shown in Table 5; Evaluation was performed.

(Example 5)
(C) Other polymerizable compounds included in the ink set used in Example 1, SR9003, SR339A (used for mill base adjustment), NVC, SR395, SR341, and DVE3 are all changed to Compound 1-1. Otherwise, the evaluation was performed in the same manner as in Example 1. The results are shown in Table 6.

(Example 6)
Evaluation was performed in the same manner as in Example 1 except that 1-2 was used instead of the compound 1-1. The results are shown in Table 6. Compound 1-2 was synthesized from the corresponding alcohol in the same manner as 1-1.

(Example 7)
Evaluation was performed in the same manner as in Example 1 except that 1-4 was used instead of the compound 1-1. The results are shown in Table 6. Compound 1-4 was synthesized from the corresponding alcohol in the same manner as 1-1.

  In Examples 1-7, both glossiness and adhesiveness were good. Moreover, Example 1, Example 3 and Examples 4, 6, and 7 in which NVC was added to the ink composition had better adhesion than Example 2 in which NVC was not added. It was.

  Furthermore, when sclerosis | hardenability evaluation was performed with the following method about the image obtained in Example 1-7, Example 1- Example 3, Example 5, and Example 6 became "(double-circle)", Example 4 For Example 7 it was “◯”.

<Curability evaluation>
The curability was evaluated according to the following criteria based on the stickiness of the surface of the printed material due to tactile sensation and the presence or absence of transfer of the image area when the printed material was left to stand for 1 day. For practical use, it is necessary to be ◯ or more, and ◎ is preferable.
A: There was no stickiness on the surface of the printed material, and there was no transfer.
○: The printed surface was slightly sticky, but there was no transfer.
(Triangle | delta): There existed stickiness on the printed material surface, and transcription | transfer produced a little.
X: The surface of the printed material was very sticky, and severe transfer occurred.

Claims (11)

(A) a polymerization initiator;
(B) a compound represented by the following general formula (1);
An active energy ray-curable ink composition comprising:

(In the formula, X ¹ represents a tertiary alkyl group, and R ^{1 to} R ¹⁰ each independently represents a hydrogen atom or an alkyl group.) The active energy ray-curable ink composition according to claim 1, wherein the tertiary alkyl group in the general formula (1) is the following general formula (1A).

(Wherein R ^1a , R ^2a and R ^3a each independently represents an alkyl group, and at least two of R ^1a , R ^2a and R ^3a may be bonded to each other to form a ring, provided that R ^1a , (The total number of carbon atoms contained in R ^2a and R ^3a is 3 or more and 11 or less. * Represents a bonding position.) The active energy ray-curable ink composition according to claim 1, wherein X ¹ in the general formula (1) is a t-butyl group. The active energy ray-curable ink composition according to claim ¹ , wherein R ¹ , R ⁸ , R ⁹ and R ¹⁰ in the general formula (1) are hydrogen atoms.   The content of the compound represented by (B) general formula (1) in the active energy ray-curable ink composition is 25 to 60% by mass, according to any one of claims 1 to 4. The active energy ray-curable ink composition as described.   The active energy ray-curable ink composition according to claim 1, further comprising (C) another polymerizable compound that is a polymerizable compound other than (B).   The active energy ray-curable ink composition according to claim 6, comprising (C) an N-vinyl compound as the other polymerizable compound.   The active energy ray-curable ink composition according to any one of claims 1 to 7, further comprising (D) a colorant.   The active energy ray-curable ink composition according to any one of claims 1 to 8, which is for inkjet recording.   A step of ejecting the active energy ray-curable ink composition according to any one of claims 1 to 9 on a recording medium, and an active energy ray to the discharged active energy ray-curable ink composition. A step of irradiating to cure the active energy ray-curable ink composition.   The image forming method according to claim 10, wherein the step of discharging the active energy ray-curable ink composition is a step of discharging the active energy ray-curable ink composition by an inkjet method.