JP5613042B2 - Ink set for inkjet recording and inkjet recording method - Google Patents

Description

  The present invention relates to an ink set for ink jet recording and an ink jet recording 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.
The ink jet method is an ink composition because the printing apparatus is inexpensive and 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. Can be used efficiently, especially in the case of small lot production. Furthermore, it has low noise and is excellent as an image recording method, and has attracted attention in recent years.
In particular, an ink composition for ink jet recording (a radiation curable ink composition for ink jet recording) that can be cured by irradiation with radiation such as ultraviolet rays is cured by irradiation with radiation such as ultraviolet rays, and most of the components of the ink composition are cured. Compared with the solvent-based ink composition, it is excellent in terms of drying and is difficult to bleed, so that it can be printed on various recording media.
In the ink jet recording method, various methods have been proposed as a method for irradiating the ink composition with radiation such as ultraviolet rays (see, for example, Patent Document 1).

JP 2008-208190 A

  The problem to be solved by the present invention is an ink jet recording which is excellent in productivity (curing sensitivity), excellent in stretchability of the obtained cured film, excellent in hue, and having a high quality image with reduced graininess. An ink set is provided. Furthermore, another object of the present invention is to provide an ink jet recording method using the ink set for ink jet recording.

The above problems have been solved by the following means (1) and (10). It is listed together with preferred embodiments (2) to (9).
(1) It contains at least one pair of dark ink and light ink having the same hue, and both the dark ink and the light ink are (component A) radical polymerizable compound, (component B) photopolymerization initiator, And (Component C) a pigment, which contains a monofunctional monomer and a polyfunctional monomer as the radical polymerizable compound, and the weight ratio of monofunctional monomer / polyfunctional monomer in the dark ink An ink set for inkjet recording, wherein the weight ratio (Y) of the monofunctional monomer / polyfunctional monomer in the light-colored ink (X) satisfies the relationship X>Y;
(2) The ink set for inkjet recording according to (1), wherein X / Y is 1.2 or more and 5 or less,
(3) The ink set for ink jet recording according to (1) or (2), wherein the ink composition comprises (Component B-1) a thioxanthone-based photopolymerization initiator as (Component B) a photopolymerization initiator,
(4) The ink set for ink jet recording according to (3), wherein the concentration of the thioxanthone photopolymerization initiator in the dark ink is greater than the concentration of the thioxanthone photopolymerization initiator in the light ink.
(5) The dark color ink and the light color ink are both (component B) photopolymerization initiator, (component B-2) α-aminoalkylphenone compound and / or (component B-3) acylphosphine. An ink set for inkjet recording according to (3) or (4), comprising a compound;
(6) In any one of (1) to (5), the concentration of the (component C) pigment in the dark ink is at least three times the concentration of the (component C) pigment in the light ink. Ink set for ink-jet recording as described,
(7) The inkjet ink set according to any one of (1) to (6), which contains N-vinylcaprolactam as the monofunctional monomer,
(8) The ink set for inkjet recording according to any one of (1) to (7), comprising (meth) acrylate having an alkylene oxide group as the polyfunctional monomer,
(9) The ink set for inkjet recording according to any one of (1) to (8), which is for curing an LED having an emission peak wavelength in a wavelength region of 380 nm to 420 nm,
(10) A step of printing with the ink set for ink jet recording according to any one of (1) to (8), and a step of curing the ink with an LED having an emission peak wavelength in a wavelength region of 380 nm to 420 nm. An ink jet recording method comprising:

  According to the present invention, there is provided an ink set for ink jet recording capable of obtaining a high-quality image having excellent productivity (curing sensitivity), excellent stretchability of the obtained cured film, excellent hue, and reduced granularity. Could be provided.

(1) Ink set for ink jet recording The ink set for ink jet recording of the present invention contains at least one pair of dark color ink and light color ink having the same hue, and both the dark color ink and the light color ink (component A) ) A radical polymerizable compound, (Component B) a photopolymerization initiator, and (Component C) a pigment, which contains a monofunctional monomer and a polyfunctional monomer as the radical polymerizable compound, The weight ratio (X) of the monofunctional monomer / polyfunctional monomer in the dark ink and the weight ratio (Y) of the monofunctional monomer / polyfunctional monomer in the light ink satisfy the relationship of X> Y. To do.
The hue of the cured film may be changed by an initiator or a decomposition product thereof, and the influence becomes more noticeable when a light color ink is used. By satisfying the above relationship, the amount of initiator in the light-color ink can be reduced without impairing the curability. Further, by using the above-described dark and light inks together, excellent stretchability and granularity can be ensured.
The present invention is described in detail below.

(Ink composition)
First, the ink composition constituting the ink set for inkjet recording of the present invention will be described.
The ink composition constituting the ink set for ink jet recording of the present invention contains at least one pair of dark ink and light ink having the same hue. Here, “the same hue” means that the hues of the ink compositions used when performing multicolor ink jet recording are the same. That is, the color of the subtractive three color inks consisting of cyan (C), magenta (M), and yellow (Y), the hue of special color inks such as orange, green, and violet, or the black (B) ink that is an achromatic color. This means that the hues are the same, and the colors may be substantially the same. Further, a pair of dark black ink and substantially achromatic gray ink may be used. White ink is not a target for a pair of ink compositions having the same hue.
The hue of a pair of ink compositions composed of dark color ink and light color ink is preferably selected from CMYB, in which graininess is conspicuous when an image is formed. More preferably, it is M.
The ink set of the present invention contains at least two types of dark ink and light color ink having the same hue and different pigment concentrations as a pair. You may contain 3 or more types of ink compositions from which a density | concentration differs.
Ink sets for ink jet recording containing an ink composition having a normal concentration are preferably used even for inks of hues that do not constitute a pair of dark ink and light ink. In particular, in order to form a full-color image, an ink set including four colors of CMYB is preferable.

Both the dark color ink and the light color ink of the same color contain a radical polymerizable compound. The radical polymerizable compound is a compound that undergoes addition polymerization in a chain manner with a polymerization initiating radical. Radical polymerizable compounds are roughly classified into monomers having a molecular weight of 1,000 or less (also referred to as “low molecule”) and oligomers / polymers exceeding 1,000 (also referred to as “polymer”). It is roughly classified into a monofunctional monomer having only one radical polymerizable group in one molecule and a polyfunctional monomer having two or more radical polymerizable groups in one molecule. The molecular weight of the polymerizable monomer is preferably 750 or less. Therefore, the “monofunctional monomer” means a low molecular compound having only one radical polymerizable group in the molecule, and the polyfunctional monomer is a low molecular compound having two or more radical polymerizable groups in the molecule. Say.
The ink composition used in the present invention contains, as the radical polymerizable compound, a low-molecular monofunctional monomer and a low-molecular polyfunctional monomer as essential components. The total of the monofunctional monomer and the polyfunctional monomer is preferably 80% by weight or more of the radical polymerizable compound, and more preferably 90% by weight.

The ink composition used in the present invention preferably contains a radical polymerizable oligomer or polymer as an optional component, and more preferably contains a polyfunctional oligomer. Here, “oligomer” refers to a compound having a molecular weight of more than 1,000 and 10,000 or less.
Specific examples of the monofunctional monomer and the polyfunctional monomer will be described in detail later.

The weight ratio (X) of monofunctional monomer / polyfunctional monomer in the dark color ink and the weight ratio (Y) of monofunctional monomer / polyfunctional monomer in the light color ink satisfy the relationship of X> Y.
X / Y is preferably 1.2 or more, and more preferably 1.2 or more and 5 or less.

(Component A) Radical polymerizable compound The ink composition contained in the ink set for ink jet recording of the present invention contains a polymerizable compound (hereinafter also referred to as “component A”). Component A contains a radically polymerizable monofunctional monomer (also referred to as “component Am”) and a polyfunctional monomer (also referred to as “component Ap”).
The monofunctional monomer is preferably selected from monomers having only one ethylenically unsaturated group in the molecule and a molecular weight of 1,000 or less. The monofunctional monomer (component Am) includes cyclic maleic anhydride and acyclic (meth) acrylic acid ester. Preferred examples of component Am include (component Am1) N-vinyl compound and (component Am2) monofunctional (meth) acrylate compound having an aromatic group.

The total content of the radically polymerizable compound in the ink composition is 40 to 98% by weight based on the total weight of the ink composition (synonymous with “in the ink composition” or “in the ink”). Is preferable, and it is more preferable that it is 50 to 95 weight%.
Hereinafter, the monofunctional monomer and the polyfunctional monomer will be described.

(Component Am) Radical polymerizable monofunctional monomer The ink composition of the present invention contains a radical polymerizable monofunctional monomer (hereinafter, also simply referred to as “monofunctional monomer”, also referred to as “component Am”). This monofunctional radically polymerizable monomer is preferably a compound having only one ethylenically unsaturated bond in the molecule.
Only one type of monofunctional monomer may be used, or two or more types may be used in combination at any ratio in order to achieve the desired properties.

  Component Am preferably contains a monofunctional monomer selected from the group consisting of acrylates, methacrylates, vinyloxy compounds, N-vinyl compounds, ethylenically unsaturated carboxylic acid compounds, acrylamides and methacrylamides, It is more preferable to contain a monofunctional monomer selected from the group consisting of acrylates, methacrylates, cyclic compounds having an N-vinyl group, ethylenically unsaturated carboxylic acid compounds, and acrylamides and methacrylamides. In addition, when referring to both or one of “acrylate” and “methacrylate”, it is described as “(meth) acrylate”, and when referring to both or one of “acryl” and “methacryl”, “(meth) acryl” May be described.

(Compound having an N-vinyl group and a group having a cyclic structure)
In the present invention, it is preferable to use a compound having an N-vinyl group and a group having a cyclic structure as component Am (radical polymerizable monofunctional monomer). Among these, N-vinylcarbazole, 1-vinylimidazole, and N-vinyl lactams are preferably used, and N-vinyl lactams are more preferably used.
Preferable examples of N-vinyl lactams that can be used in the present invention include compounds represented by the following formula (Am1).

  In the formula (Am1), n represents an integer of 2 to 6, and n is 3 to 5 from the viewpoint of flexibility after the ink composition is cured, adhesion to the support, and availability of raw materials. It is preferably an integer, more preferably n is 3 or 5, and particularly preferably n is 5, that is, N-vinylcaprolactam. N-vinylcaprolactam is preferable because it is excellent in safety, is generally available and can be obtained at a relatively low price, and provides particularly good ink curability and adhesion of a cured film to a support.

The N-vinyllactams may have a substituent such as an alkyl group or an aryl group on the lactam ring, and may be linked with a saturated or unsaturated ring structure.
The N-vinyl lactams may be contained in the ink composition alone or in a plurality of kinds.
The ink composition of the present invention preferably contains 5 to 40% by weight of N-vinyl lactam in the ink, and more preferably 15 to 35% by weight.

(Component Am2) Monofunctional (meth) acrylate compound having an aromatic group As another monofunctional monomer that can be used in the present invention, a monofunctional (meth) acrylate compound having an aromatic group represented by the following formula (Am2) Is mentioned.

In the formula (Am2), R ¹ represents a hydrogen atom or a methyl group.
X ¹ in the formula (Am2) represents (—C (O) O—) or (—C (O) NH— bonded to the ethylenically unsaturated double bond represented by the formula (Am2) at the carbon atom of the carbonyl group. ), And the divalent linking group further includes an ether bond (—O—), an ester bond (—C (O) O— or —OC (O) —), an amide bond ( -C (O) NH- or -NHC (O)-), a carbonyl bond (-C (O)-), an optionally substituted alkylene group having 20 or less carbon atoms, or a combination thereof May be combined.
The divalent linking group is -C (O) O-, -C (O) NH-, or -C (O) O- or -C (O) NH- and an ether bond, an ester bond or a carbon number. It is more preferably a group in which 20 or less alkylene groups and a group in which two or more of these are combined are linked.
R ² in Formula (Am2) is a group having at least one cyclic structure that does not have an ethylenically unsaturated group, and includes an aromatic group including a monocyclic aromatic group and / or a polycyclic aromatic group; And an alicyclic hydrocarbon group having a cycloalkane skeleton, an adamantane skeleton and a norbornane skeleton. Further, the aromatic structure and the cyclic structure of the alicyclic hydrocarbon group may contain heteroatoms such as O, N, and S.

Preferred examples of the aromatic group represented by R ² in the formula (Am2) include a monocyclic aromatic phenyl group and a polycyclic aromatic group having 2 to 4 rings.
Specific examples of the polycyclic aromatic group include naphthyl group, anthryl group, 1H-indenyl group, 9H-fluorenyl group, 1H-phenenyl group, phenanthrenyl group, triphenylenyl group, pyrenyl group, naphthacenyl group, tetraphenyl group, Preferred examples include biphenylenyl group, as-indacenyl group, s-indacenyl group, acenaphthylenyl group, fluoranthenyl group, acephenanthrenyl group, aceanthrylenyl group, chrysenyl group, and preadenyl group.

These aromatic groups may be aromatic heterocyclic groups containing heteroatoms such as O, N, and S. Specifically, furyl group, thienyl group, 1H-pyrrolyl group, 2H-pyrrolyl group, 1H-pyrazolyl group, 1H-imidazolyl group, isoxazolyl group, isothiazolyl group, pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazoyl group And monocyclic aromatic heterocyclic groups such as a tetrazoyl group.
In addition, thiantenyl group, benzofuranyl group, isobenzofuranyl group, chromenyl group, isochromenyl group, xanthenyl group, phenoxathiinyl group, indolizinyl group, isoindolyl group, indolyl group, indazolyl group, purinyl group, quinolidinyl group, isoquinolyl group, Quinolyl group, phthalazinyl group, naphthyridinyl group, quinoxalinyl group, quinazolinyl group, cinnolinyl group, pteridinyl group, carbazolyl group, β-carboliyl group, phenanthridinyl group, acridinyl group, perimidinyl group, phenanthrolinyl group, phenazinyl group, Examples thereof include polycyclic aromatic heterocyclic groups such as a phenothiazinyl group, a phenoxazinyl group, and a pyrrolidinyl group.
The aromatic group may have one or more substituents such as a halogen atom, a hydroxyl group, an amino group, a mercapto group, a siloxane group, and a hydrocarbon group having 30 or less carbon atoms. For example, you may form the cyclic structure containing hetero atoms, such as O, N, and S, by two or more substituents which an aromatic group has like phthalic anhydride and phthalimide anhydride.

R ² in the formula (Am2) may be an alicyclic hydrocarbon group. Moreover, the group which has an alicyclic hydrocarbon group containing hetero atoms, such as O, N, and S, may be sufficient.
The alicyclic hydrocarbon group may be a 3 to 12-membered cycloalkane or a group having a ring structure in which two or more of these cycloalkanes are condensed. Among these, cyclohexyl group, cyclopentyl group, cycloheptyl group, isobornyl group, norbornyl group, adamantyl group, dicyclopentanyl group, dicyclopentenyl group, tricyclodecanyl group and the like can be preferably exemplified.
Specific examples of the alicyclic hydrocarbon group containing a heteroatom such as O, N, and S include a tetrahydrofuryl group, a pyrrolidinyl group, a pyrazolidinyl group, an imidazolidinyl group, an isoxazolidinyl group, and a pyranyl group. Thiopyranyl group, isothiazolidinyl group, piperidinyl group, piperazinyl group, morpholino group, thiomorpholino group and the like.
These alicyclic hydrocarbon groups and alicyclic hydrocarbon groups having a heteromonocycle are a halogen atom, a hydroxyl group, an amino group, a mercapto group, a siloxane group, and a total carbon number that may further have a substituent. It is preferably a hydrocarbon group of 30 or less, a heterocyclic group containing a heteroatom such as O, N, or S, or an oxy group (═O) as a divalent substituent.

R ² in the formula (Am2) may be a group having an adamantane skeleton represented by the following formula (I) or an alicyclic hydrocarbon group having a norbornane skeleton represented by the formula (II).

R ³ and R ⁴ in formula (I) or formula (II) each independently represent a substituent, and can be bonded at any position on each alicyclic hydrocarbon structure. Further, q R ³ and r R ⁴ may be the same or different.
R ³ present in q and R ⁴ present in r may each independently be a monovalent or polyvalent substituent, and as a monovalent substituent, a hydrogen atom, a hydroxyl group, substituted or unsubstituted An amino group, a mercapto group, a siloxane group, a hydrocarbon group or a heterocyclic group having a total carbon number of 30 or less which may have a substituent, or an oxy group (= O) as a divalent substituent. It is preferable.
The substitution number q of R ³ represents an integer of 0 to 5, and the substitution number r of R ⁴ represents an integer of 0 to 5.
Further, one carbon atom in the adamantane skeleton in the formula (I) may be substituted with a carbonyl bond (—C (O) —) and / or an ester bond (—C (O) O—). One carbon atom in the norbornane skeleton may be substituted with an ether bond (—O—) and / or an ester bond (—C (O) O—).

  The norbornane skeleton represented by the formula (II) may have a cyclic hydrocarbon structure as represented by the formula (III). N in the formula (III) represents a cyclic hydrocarbon structure, and both ends thereof may be substituted at any position of the norbornane skeleton, and may be a monocyclic structure or a polycyclic structure. In addition to the hydrocarbon bond, the cyclic hydrocarbon structure may contain a carbonyl bond (—C (O) —) and / or an ester bond (—C (O) O—).

  The cyclic structure represented by the formula (III) is preferably a structure represented by the formula (IV), the formula (V) or the formula (VI).

In formula (IV), formula (V) and formula (VI), R ⁵ , R ⁶ and R ⁷ each independently represent a substituent, s, t and u each independently represent an integer of 0 to 5; Further, s R ⁵ , t R ⁶ , and u R ⁷ may be the same or different.
X ^{1 in} formula (Am2) can be bonded at any position on each alicyclic hydrocarbon structure shown below in formula (IV), formula (V), or formula (VI).
R ⁵ , R ⁶ and R ⁷ in formula (IV), formula (V) or formula (VI) each independently represent a substituent, and each of the following fats in formula (IV), formula (V) or formula (VI) The bond can be made at any position on the cyclic hydrocarbon structure. The substituents in R ⁵ , R ⁶ and R ⁷ are synonymous with the substituents in R ³ and R ⁴ in formulas (I) to (III), and the preferred ranges are also the same.

  In the present invention, the monofunctional radical polymerizable monomer includes phenyl group, naphthyl group, anthracenyl group, pyridinyl group, tetrahydrofurfuryl group, piperidinyl group, cyclohexyl group, cyclopentyl group, cycloheptyl group, isobornyl group, tricyclodecanyl. What has group which has cyclic structures, such as group, is mentioned preferably.

  The monofunctional monomer that can be used in the present invention is preferably norbornyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, cyclopentyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) ) Acrylate, cyclodecyl (meth) acrylate, dicyclodecyl (meth) acrylate, trimethylcyclohexyl (meth) acrylate, 4-t-butylcyclohexyl (meth) acrylate, acryloylmorpholine, 2-benzyl (meth) acrylate, phenoxyethyl (meth) Acrylate, phenoxydiethylene glycol (meth) acrylate, phenoxytriethylene glycol (meth) acrylate, ethylene oxide (EO Modified cresol (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, caprolactone modified tetrahydrofurfuryl acrylate, nonylphenoxy polyethylene glycol (meth) acrylate, neopentyl glycol benzoate (meth) acrylate, paracumylphenoxyethylene glycol (meth) acrylate, N-phthalimidoethyl (meth) acrylate, pentamethylpiperidyl (meth) acrylate, tetramethylpiperidyl (meth) acrylate, N-cyclohexylacrylamide, N- (1,1-dimethyl-2-phenyl) ethylacrylamide, N-diphenylmethyl Acrylamide, N-phthalimidomethylacrylamide, N- (1,1′-dimethyl-3- (1,2,4-triazol) 1-yl)) propyl acrylamide, 5- (meth) acryloyloxy-methyl-5-ethyl-1,3-dioxacyclohexane, acrylic acid, it can be exemplified methacrylate. Among these, phenoxyethyl (meth) acrylate and isobornyl (meth) acrylate can be preferably exemplified.

Furthermore, preferred specific examples of monofunctional monomers that can be used in the present invention are shown in the following M-1 to M-55.
In some of the following exemplary compounds, the hydrocarbon chain is described by a simplified structural formula in which symbols of carbon (C) and hydrogen (H) are omitted. Me represents a methyl group.

(Component Am3) Compound Represented by Formula (Am3) The ink composition of the invention preferably contains a monofunctional monomer represented by Formula (Am3) as (Component Am3).
(Component Am3) By containing the compound represented by the formula (Am3), the adhesion between the recording medium (particularly polyvinyl chloride, polyethylene terephthalate (PET), acrylic resin) and the image is excellent.

（式（Ａｍ３）中、Ｒ¹、Ｒ²及びＲ³はそれぞれ独立に、水素原子、メチル基、又は、エチル基を表し、Ｘ²は単結合、又は、二価の連結基を表す。）

(In formula (Am3), R ¹ , R ² and R ³ each independently represents a hydrogen atom, a methyl group or an ethyl group, and X ² represents a single bond or a divalent linking group.)

R ¹ is preferably a hydrogen atom or a methyl group, more preferably a hydrogen atom.
R ² and R ³ are each independently preferably a hydrogen atom, a methyl group, or an ethyl group, more preferably a hydrogen atom, and still more preferably R ² and R ³ are both hydrogen atoms.
The divalent linking group for X ² is not particularly limited as long as it does not significantly impair the effects of the present invention, but is a divalent hydrocarbon group or a divalent group in which a hydrocarbon group and an ether bond are combined. It is preferably a divalent hydrocarbon group, a poly (alkyleneoxy) group, or a poly (alkyleneoxy) alkyl group. Moreover, it is preferable that carbon number of the said bivalent coupling group is 1-60, and it is more preferable that it is 1-20.
X ² is preferably a single bond, a divalent hydrocarbon group, or a divalent group in which a hydrocarbon group and an ether bond are combined, and is a divalent hydrocarbon group having 1 to 20 carbon atoms. More preferably, it is a C1-C8 divalent hydrocarbon group, more preferably a methylene group.

  Although the specific example of component Am3 is given to the following, it is not limited to these compounds. In the following specific examples, R represents a hydrogen atom or a methyl group.

Among these, cyclic trimethylolpropane formal (meth) acrylate is preferable, and cyclic trimethylolpropane formal acrylate is particularly preferable.
Component Am3 may be a commercially available product, and a specific example of a commercially available product is SR531 (manufactured by SARTOMER).

  From the viewpoint of the adhesion between the recording medium and the image and the curability of the ink composition, the content of the component Am3 is preferably 1 to 50% by weight, preferably 5 to 40% by weight, based on the total weight of the ink composition. Is more preferable, and 5-35 weight% is still more preferable.

  Monofunctional monomers other than Component Am1, Component Am2 and Component Am3 may be used. Specific examples include isoamyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and stearyl (meth) acrylate. , Lauryl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, isoamylstil (meth) acrylate, isostearyl (meth) acrylate, 2-ethylhexyl diglycol (meth) acrylate, 2-hydroxybutyl (meth) Acrylate, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate Methoxypropylene glycol (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2- (meth) acryloxyethyl succinic acid, 2- (meta And monofunctional monomers such as acryloyloxyethyl-2-hydroxyethylphthalic acid and t-butylcyclohexyl (meth) acrylate.

  Furthermore, it is also preferable to use a monofunctional vinyloxy compound as the monofunctional monomer. Suitable monofunctional vinyloxy compounds include, for example, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, Examples thereof include monovinyl ether compounds such as isopropyl vinyl ether, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

Examples of (meth) acrylamide compounds include N, N-dimethyl (meth) acrylamide, N-cyclohexyl (meth) acrylamide, N- (1,1-dimethyl-2-phenyl) ethyl (meth) acrylamide, and N-diphenyl. Methyl (meth) acrylamide, N-phthalimidomethyl (meth) acrylamide, N- (1,1′-dimethyl-3- (1,2,4-triazol-1-yl)) propyl (meth) acrylamide, N-methylol (Meth) acrylamide, diacetone (meth) acrylamide, etc. can be illustrated.
Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and salts thereof.

  Also, specifically, Junzo Yamashita “Cross-linking agent handbook” (1981, Taiseisha); Kato Kiyosumi “UV / EB curing handbook (raw material)” (1985, Polymer publication society); Articles on the application and market of UV / EB curing technology, p. 79 (1989, CMC); Eiichiro Takiyama's “Polyester Resin Handbook” (1988, Nikkan Kogyo Shimbun), etc. These radically polymerizable monomers can be used.

Among these, as component Am, phenoxyethyl (meth) acrylate, N-vinylcaprolactam, tetrahydrofurfuryl (meth) acrylate, 2- (2-ethoxyethoxy) ethyl (meth) acrylate, and N, N-dimethyl (Meth) acrylamide can be preferably exemplified, and phenoxyethyl (meth) acrylate, N-vinylcaprolactam and isobornyl (meth) acrylate can be more preferably exemplified, and phenoxyethyl acrylate and N-vinylcaprolactam can be further exemplified.
The molecular weight of the monofunctional radically polymerizable monomer is 80 to 1,000, and preferably 80 to 750.
One type of monofunctional radically polymerizable monomer may be included in the ink composition, or a plurality of types may be included.

  The total content of component Am in the ink composition of the present invention is preferably 30 to 98 parts by weight, more preferably 40 to 95 parts by weight with respect to 100 parts by weight of the ink composition, and 50 More preferably, it is -90 weight part. Within the above range, the curability is excellent and the viscosity is moderate.

(Component Ap) Multifunctional monomer In addition to the monofunctional monomer (component Am), the ink composition used in the present invention is a radical polymerizable polyfunctional monomer (also simply referred to as “polyfunctional monomer”, also labeled “component Ap”). Contain). The component Ap, like the component Am, is a low molecule having a molecular weight of 1,000 or less, and preferably has a molecular weight of 200 to 750.

The polyfunctional monomer as component Ap will be described.
Examples of the polyfunctional monomer that can be used in the present invention include an acrylicoxy group, a methacryloxy group, a vinyloxy group, an N-vinyl group, an ethylenically unsaturated carboxylic acid residue, an acrylamide group, and a methacrylamide group. Preferred examples include polyfunctional radical polymerizable monomers having two or more groups having an ethylenically unsaturated double bond selected. By containing a polyfunctional monomer, an ink composition having high cured film strength can be obtained. However, the ratio of the polyfunctional monomer to the entire ink composition is preferably 20% by weight or less, more preferably 3 to 15% by weight, from the viewpoint of maintaining a cured film stretchability suitable for molding. .
A polyfunctional monomer may be used individually by 1 type, and may be used in combination of 2 or more type as appropriate.

  Specific examples of the polyfunctional monomer include bis (4-acryloxypolyethoxyphenyl) propane, neopentyl glycol di (meth) acrylate, 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, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) ) Acrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, trimethylolpropane triacrylate, tetra Chi roll methane tetraacrylate, tetramethylolmethane triacrylate, dimethylol tricyclodecane diacrylate, modified glycerol triacrylate, modified bisphenol A diacrylate, dipentaerythritol hexaacrylate, and caprolactone-modified dipentaerythritol hexaacrylate.

It is preferable to contain poly (meth) acrylate having an alkylene oxide group as a polyfunctional monomer. Here, “poly (meth) acrylate” means that the molecule has two or more (meth) acrylic acid ester residues, and preferably has 2 to 4 residues. More preferably, it has a (meth) acrylic acid ester residue. Moreover, as an alkylene oxide, ethylene oxide and / or propylene oxide are preferable. The added mole number of the alkylene oxide group is 1 to 10, and preferably 1 to 6. This polyfunctional monomer can be obtained by adding an alkylene oxide to glycols to obtain a polyester of (meth) acrylic acid.
Specific examples of the (meth) acrylate having an alkylene oxide group include PO adduct diacrylate of bisphenol A, EO adduct diacrylate of bisphenol A, and propoxylated neopentyl glycol diacrylate.

(Radical polymerizable oligomer)
The ink composition of the present invention may contain a radical polymerizable oligomer as an optional component in addition to the component Am and the component Ap, and preferably contains a radical polymerizable oligomer. Here, as already mentioned, the oligomer is a radically polymerizable compound having a molecular weight exceeding 1,000, preferably containing a plurality of ethylenically unsaturated groups, and containing 2 to 4 polyfunctional oligomers. It is preferable that The polyfunctional oligomer preferably has an ethylenically unsaturated group at the molecular end or molecular side chain of an addition polymer having a finite number (generally 5 to 100) structural units, and the weight average molecular weight is 1, It is preferably more than 1,000 and 10,000 or less, more preferably 1,000 to 5,000.
The radical polymerizable oligomer preferably has a plurality of (meth) acryloxy groups.

  As the radically polymerizable oligomer as an optional component, any monomer may be used as its constituent unit, for example, olefin-based (ethylene oligomer, propylene oligomer butene oligomer, etc.), vinyl-based (styrene oligomer, vinyl alcohol oligomer, Vinylpyrrolidone oligomer acrylate oligomer, methacrylate oligomer, etc.), diene (butadiene oligomer, chloroprene rubber, pentadiene oligomer, etc.), ring-opening polymerization (di-, tri-, tetraethylene glycol, polyethylene glycol, polyethylimine, etc.), heavy Addition system (oligoester acrylate, polyamide oligomer, polyisocyanate oligomer), addition condensation oligomer (phenol resin, amino resin, xylene resin, ketone resin, etc.), etc. It can be mentioned. In this, oligoester (meth) acrylate is preferable, in which urethane (meth) acrylate, polyester (meth) acrylate, and epoxy (meth) acrylate are more preferable, and urethane (meth) acrylate is more preferable.

Preferred examples of the urethane (meth) acrylate include aliphatic urethane (meth) acrylates and aromatic urethane (meth) acrylates, and more preferred are aliphatic urethane (meth) acrylates.
The urethane (meth) acrylate is preferably a bifunctional to tetrafunctional urethane (meth) acrylate, and more preferably a bifunctional urethane (meth) acrylate.
By containing urethane (meth) acrylate, an ink composition having excellent adhesion to a recording medium and excellent curability can be obtained.
The content of the radical polymerizable oligomer is preferably less than 10% by weight in the ink composition, preferably 5% by weight or less, and particularly preferably 0 to 5% by weight.
Regarding the radically polymerizable oligomer, an oligomer handbook (supervised by Junji Yoshikawa, Chemical Industry Daily Co., Ltd.) can also be referred to.

Examples of commercially available radical polymerizable oligomers include urethane (meth) acrylates such as R1204, R1211, R1213, R1217, R1218, R1301, R1302, R1303, R1304, R1306, and R1308 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. , R1901, R1150, etc., and EBECRYL series (for example, EBECRYL230, 270, 4858, 8402, 8804, 8807, 8803, 9260, 1290, 1290K, 5129, 4842, 8210, 210, 4827, manufactured by Daicel Cytec Co., Ltd. 6700, 4450, 220), NK Oligos U-4HA, U-6HA, U-15HA, U-108A, U200AX, etc. manufactured by Shin-Nakamura Chemical Co., Ltd., Aronix M-110 manufactured by Toagosei Co., Ltd. , M-1200, M-1210, M-1310, M-1600, M-1960, include the CN964 such as manufactured by Sartomer Japan (Ltd.).
Examples of the polyester (meth) acrylate include EBECRYL series (for example, EBECRYL770, IRR467, 81, 84, 83, 80, 675, 800, 810, 812, 1657, 1810, IRR302, 450, manufactured by Daicel Cytec Co., Ltd. 670, 830, 870, 1830, 1870, 2870, IRR267, 813, IRR483, 811 etc.), Aronix M-6100, M-6200, M-6250, M-6500, M-7100, manufactured by Toagosei Co., Ltd. M-8030, M-8060, M-8100, M-8530, M-8560, M-9050, etc. are mentioned.
Moreover, as epoxy (meth) acrylate, for example, EBECRYL series (for example, EBECRYL600, 860, 2958, 3411, 3600, 3605, 3700, 3701, 3703, 3702, 3708, RDX63182, 6040, etc. manufactured by Daicel Cytec Co., Ltd. ) And the like.

(Component B) Photopolymerization Initiator The ink composition of the present invention contains (Component B) a photopolymerization initiator.
The polymerization initiator that can be used in the present invention is a compound that absorbs external energy and generates a polymerization initiating species. External energy used for initiating polymerization is roughly divided into heat and active energy rays, and a thermal polymerization initiator and a photopolymerization initiator are used, respectively. Examples of active energy rays include γ rays, β rays, electron beams, ultraviolet rays, visible rays, and infrared rays.
The photopolymerization initiator used in the present invention is preferably a radical polymerization initiator, and a known radical photopolymerization initiator can be used.

  The radical polymerization initiator that can be used in the present invention includes (a) aromatic ketones, (b) acylphosphine compounds, (c) aromatic onium salt compounds, (d) organic peroxides, and (e) thio compounds. (F) hexaarylbiimidazole compound, (g) ketoxime ester compound, (h) borate compound, (i) azinium compound, (j) metallocene compound, (k) active ester compound, and (l) carbon halogen Examples thereof include a compound having a bond. These radical polymerization initiators may be used alone or in combination with the above compounds (a) to (l). The radical polymerization initiator in the present invention is suitably used alone or in combination of two or more.

The ink composition of the present invention contains (Component B) a photopolymerization initiator, contains (Component B-1) a thioxanthone compound as Component B, and the content of the thioxanthone compound is based on the total weight of the ink composition. On the other hand, it is preferably 0.03 to 5.0% by weight. Further, as Component B, it is preferable to further contain (Component B-2) an α-aminoalkylphenone compound and / or (Component B-3) an acylphosphine compound. The content of Component B-2 is preferably 1 to 15% by weight based on the total weight of the ink composition. The content of the (Component B-3) acylphosphine compound is preferably 1 to 15% by weight with respect to the total weight of the ink composition.
The (component B) photopolymerization initiator in the present invention absorbs external energy such as the active radiation to generate a polymerization initiating species, and also absorbs specific active energy rays to decompose the polymerization initiator. Accelerating compounds (so-called sensitizers) are also included.
(Component B) The photopolymerization initiator is preferably a radical polymerization initiator because Component A is a radically polymerizable compound.
In addition, the ink composition of the present invention includes (Component B-1) a thioxanthone compound, (Component B-2) an α-aminoalkylphenone compound, and (Component B) from the viewpoint of curability and hue of a cured film. More preferably, component B-3) a monoacylphosphine compound is contained.

(Component B-1) Thioxanthone Compound The ink composition of the present invention preferably contains (Component B-1) a thioxanthone compound in an amount of 0.03 to 5.0% by weight based on the total weight of the ink composition.
The thioxanthone compound is preferably a compound represented by the formula (b-1).

（式（ｂ−１）中、Ｒ¹〜Ｒ⁸はそれぞれ独立に、水素原子、アルキル基、ハロゲン原子、ヒドロキシ基、シアノ基、ニトロ基、アミノ基、アルキルチオ基、アルキルアミノ基（一置換及び二置換の場合を含む。）、アルコキシ基、アルコキシカルボニル基、アシルオキシ基、アシル基、カルボキシ基又はスルホ基を表す。）

(In formula (b-1), R ^{1 to} R ⁸ are each independently a hydrogen atom, an alkyl group, a halogen atom, a hydroxy group, a cyano group, a nitro group, an amino group, an alkylthio group, an alkylamino group (monosubstituted and Including a case of disubstitution.), An alkoxy group, an alkoxycarbonyl group, an acyloxy group, an acyl group, a carboxy group or a sulfo group.

The alkyl group, alkylthio group, alkylamino group, alkoxy group, alkoxycarbonyl group, acyloxy group, and the alkyl moiety in the acyl group preferably have 1 to 20 carbon atoms, more preferably 1 to 8 carbon atoms. Preferably, it is 1-4.
Two adjacent R ^{1 to} R ⁸ may be connected to each other to form a ring. Examples of the ring structure in the case where these form a ring include a 5- or 6-membered aliphatic ring, an aromatic ring, etc., and may be a heterocyclic ring containing an element other than a carbon atom. The rings may be further combined to form a binuclear ring, for example, a condensed ring. These ring structures may further have a substituent. Examples of the substituent include a halogen atom, a hydroxy group, a cyano group, a nitro group, an amino group, an alkylthio group, an alkylamino group, an alkoxy group, an alkoxycarbonyl group, an acyloxy group, an acyl group, a carboxy group, and a sulfo group. N, O, and S can be mentioned as an example of a hetero atom in case the formed ring structure is a heterocyclic ring.

Examples of thioxanthone compounds include thioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-chlorothioxanthone, 2-dodecylthioxanthone, 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, 1-methoxycarbonylthioxanthone, 2-ethoxy. Carbonylthioxanthone, 3- (2-methoxyethoxycarbonyl) thioxanthone, 4-butoxycarbonylthioxanthone, 3-butoxycarbonyl-7-methylthioxanthone, 1-cyano-3-chlorothioxanthone, 1-ethoxycarbonyl-3-chlorothioxanthone, 1 -Ethoxycarbonyl-3-ethoxythioxanthone, 1-ethoxycarbonyl-3-aminothioxanthone, 1-ethoxycarbonyl-3-phenyl Nylsulfurylthioxanthone, 3,4-di [2- (2-methoxyethoxy) ethoxycarbonyl] thioxanthone, 1-ethoxycarbonyl-3- (1-methyl-1-morpholinoethyl) thioxanthone, 2-methyl-6-dimethoxymethyl Thioxanthone, 2-methyl-6- (1,1-dimethoxybenzyl) thioxanthone, 2-morpholinomethylthioxanthone, 2-methyl-6-morpholinomethylthioxanthone, n-allylthioxanthone-3,4-dicarboximide, n-octyl Thioxanthone-3,4-dicarboximide, N- (1,1,3,3-tetramethylbutyl) thioxanthone-3,4-dicarboximide, 1-phenoxythioxanthone, 6-ethoxycarbonyl-2-methoxythioxanthone, 6-et Cycarbonyl-2-methylthioxanthone, thioxanthone-2-polyethylene glycol ester, 2-hydroxy-3- (3,4-dimethyl-9-oxo-9H-thioxanthone-2-yloxy) -N, N, N-trimethyl- An example is 1-propanaminium chloride.
Among these, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, and 4-isopropylthioxanthone are more preferable, and 2,4-diethylthioxanthone is particularly preferable from the viewpoints of availability and curability.

  The content of the thioxanthone compound is 0.03 to 5.0% by weight with respect to the total weight of the ink composition, and 0.03 to 3.0% by weight from the viewpoint of the hue of the cured film. Is preferable, 0.05 to 2.0% by weight is more preferable, and from the viewpoint of curing sensitivity, it is preferably more than 0.3% by weight and 5.0% by weight or less, 0.4 More preferably, it is -5.0 weight%.

(Component B-2) α-aminoalkylphenone compound The ink composition of the invention preferably further contains (Component B-2) an α-aminoalkylphenone compound from the viewpoint of curability.
Component B-2 is preferably a compound represented by Formula (b-2-1).

In formula (b-3-1), R ¹ , R ² and R ³ are each independently a hydroxy group, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, Or, it represents an amino group which may have a substituent, and X represents a hydrogen atom, an amino group which may have a substituent, an alkylthio group which may have a substituent, or a substituent. It represents an alkyl group that may have. The substituents in the case where R ¹ , R ² , R ³ and X are amino groups may be bonded to each other to form a heterocyclic group. Examples of the substituent include an alkyl group having 1 to 10 carbon atoms.

  Component B-2 is preferably a compound represented by Formula (b-2-2) or Formula (b-2-3).

In formula (b-2-2), R ⁴ , R ⁵ , R ⁶ and R ⁷ each independently represents an alkyl group which may have a substituent, and R ⁴ , R ⁵ and R ⁶ And R ⁷ may be bonded to each other to form a heterocyclic group. R ¹ , R ² , and a substituent in formula (b-2-2) have the same meaning as in formula (b-2-1).

In formula (b-2-3), R ⁸ represents an alkyl group which may have a substituent.
R ^1, R ² in formula (b-2-3), and the substituents, R ^1, R ² in formula (b-2-1), and has the same meaning as the substituent, the formula (b-2 R ⁴ and R ⁵ in -3) has the same meaning as R ⁴ and R ⁵ in the formula (b-2-2).
There is no restriction | limiting in particular as said heterocyclic group, Although it can select suitably, For example, a morpholino group is preferable.

Preferred examples of the α-aminoalkylphenone compound include IRGACURE 369 (manufactured by Ciba Specialty Chemicals) and IRGACURE 907 (manufactured by Ciba Specialty Chemicals) as commercially available products.
Among these, the α-aminoalkylphenone compound is particularly preferably 2- [4- (methylthio) benzoyl] -2- (4-morpholinyl) propane (IRGACURE 907).

  From the viewpoint of curability, the content of (Component B-2) α-aminoalkylphenone compound is preferably from 1 to 15% by weight, more preferably from 1 to 10% by weight, based on the total weight of the ink composition. More preferred is ˜5% by weight.

(Component B-3) Acylphosphine Compound The ink composition of the present invention preferably contains (Component B-3) an acylphosphine compound, and the content of the acylphosphine compound is the total amount of the ink composition. It is preferable that it is 1 to 15 weight% with respect to a weight.
The (Component B-3) acylphosphine compound in the ink composition of the present invention preferably contains a monoacylphosphine compound, more preferably only a monoacylphosphine compound, from the viewpoint of the hue of the cured film. .
(Component B-3) The acylphosphine compound is not particularly limited and known compounds can be used, but the acylphosphine oxide compounds described in paragraphs 0080 to 0098 of JP-A-2009-96985 are preferred. Among them, those having a structure represented by formula (b-3-1) or formula (b-3-2) in the structure of the compound are preferable.

（式中、波線部分は他の構造との結合位置を表す。）

(In the formula, the wavy line represents the coupling position with another structure.)

  In particular, as the acylphosphine oxide compound, a compound represented by the formula (b-3-3) or the formula (b-3-4) is particularly preferable.

（式（ｂ−３−３）中、Ｒ⁶、Ｒ⁷及びＲ⁸はそれぞれ独立に、メチル基又はエチル基を置換基として有していてもよい芳香族炭化水素基を表す。）

(In formula (b-3-3), R ⁶ , R ⁷ and R ⁸ each independently represents an aromatic hydrocarbon group optionally having a methyl group or an ethyl group as a substituent.)

As a monoacyl phosphine oxide compound represented by the formula (b-3-3), R ^{6 to} R ⁸ are preferably a phenyl group which may have a methyl group as a substituent, and R ⁷ And R ⁸ is a phenyl group, and R ⁶ is more preferably a phenyl group having 1 to 3 methyl groups.
Among them, as the monoacylphosphine oxide compound represented by the formula (b-3-3), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (DAROCUR TPO: manufactured by Ciba Specialty Chemicals, LUCIRIN TPO: BASF) is preferred.

（式（ｂ−３−４）中、Ｒ⁹、Ｒ¹⁰及びＲ¹¹はそれぞれ独立に、メチル基又はエチル基を置換基として有していてもよい芳香族炭化水素基を表す。）

(In formula (b-3-4), R ⁹ , R ¹⁰ and R ¹¹ each independently represents an aromatic hydrocarbon group which may have a methyl group or an ethyl group as a substituent.)

In the bisacylphosphine oxide compound represented by the formula (b-3-4), R ^{9 to} R ¹¹ are preferably a phenyl group which may have a methyl group as a substituent, and R ¹¹ Is more preferably a phenyl group, and R ⁹ and R ¹⁰ are more preferably a phenyl group having 1 to 3 methyl groups.
Among them, as the bisacylphosphine oxide compound represented by the formula (b-3-4), bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide (IRGACURE 819, manufactured by Ciba Specialty Chemicals) Is preferred.

  From the viewpoint of curability, the content of (Component B-3) acylphosphine compound in the ink composition of the present invention is preferably 1 to 15% by weight, and preferably 5 to 15% by weight based on the total weight of the ink composition. % Is more preferable, and 4 to 8% by weight is still more preferable.

<Other polymerization initiators>
The ink composition of the present invention may contain a polymerization initiator other than Component B-1 to Component B-3.
Other polymerization initiators include, for example, aromatic ketones, aromatic onium salt compounds, organic peroxides, thio compounds, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, activity Examples include ester compounds and compounds having a carbon halogen bond.
As the other polymerization initiator, a known polymerization initiator other than Component B-1 to Component B-3, preferably a radical polymerization initiator, can be used. For example, paragraph 0090 of JP2009-185186A To those described in ˜0116.
Further, as other polymerization initiators, thiochromanone compounds may be used, and examples thereof include compounds described in paragraphs 0064 to 0068 of JP 2010-126644 A.

The content of the (component B) photopolymerization initiator in the ink composition of the present invention is 1.5 to 25% by weight with respect to the total weight of the ink composition from the viewpoints of curability and hue of the cured film. It is preferably 2 to 20% by weight, more preferably 5 to 18% by weight, and particularly preferably 5 to 15% by weight.
The ink composition of the present invention contains, as Component B, (Component B-1) a thioxanthone compound, (Component B-2) an α-aminoalkylphenone compound, and (Component B-3) an acyl phosphine compound. When it does, from a viewpoint of sclerosis | hardenability and the hue of a cured film, content (B1) of component B-3, content (B2) of component B-2, and content (B3) of component B-3 are (B2). It is preferable to satisfy the relationship of + (B3)> (B1).
The ink composition of the present invention contains, as Component B, (Component B-3) an acylphosphine compound, (Component B-2) an α-aminoalkylphenone compound, and (Component B-1) a thioxanthone compound. When it does, from a viewpoint of sclerosis | hardenability and the hue of a cured film, content (B1) of component B-1, content (B2) of component B-2, and content (B3) of component B-3 are (B3). It is preferable to satisfy the relationship of ≧ (B2)> (B1).

(Component C) Pigment In the present invention, the ink composition contains (Component C) a pigment.
The pigment generally means a colorant that is hardly soluble in various solvents (organic solvent, water), and has a solubility of 1% by weight or less in the ink composition.
There is no restriction | limiting in particular as a pigment which can be used for this invention, A well-known pigment can be used. As the pigment that can be used in the present invention, it is preferable to select a compound that does not function as a polymerization inhibitor in a polymerization reaction that is a curing reaction, from the viewpoint of not reducing the sensitivity of the curing reaction by actinic radiation.

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 red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 42, 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,
Pigment Blue 1,15,15: 1,15: 2,15: 3,15: 4,15: 6,16,17-1,22,27,28,29,36,60 as a blue or cyan pigment ,
As a green pigment, Pigment Green 7, 26, 36, 50,
Examples of yellow pigments include Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 120, and 137. , 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193,
As the black pigment, Pigment Black 7, 28, 26,
As a white pigment, Pigment White 6, 18, 21
Etc. can be used according to the purpose.
Specific examples of pigments that can be used in the present invention include IRGALITETE BLUE GLVO (cyan pigment, manufactured by Ciba Specialty Chemicals), CINQUASIA MAGENTA RT-355 D (magenta pigment, Ciba Specialty Chemicals). NOVOPERM YELLOW H2G (yellow pigment, manufactured by Clariant), SPECIAL BLACK 250 (black pigment, manufactured by Ciba Specialty Chemicals), KRONOS 2300 (white pigment, manufactured by KRONOS), and Taipei CR60-2 (white) Preferred examples include pigments and Ishihara Sangyo Co., Ltd.

  The pigment that can be used in the present invention is mixed with a dispersant and dispersed in (Component A) a radical polymerizable compound (polymerizable monomer), or the pigment is dispersed after mixing the polymerizable compound and the dispersant. It is preferable to do. For the dispersion of the pigment, 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.

In preparing the ink composition, the pigment may be blended directly with each component, but in order to improve dispersibility, it is added in advance to a dispersion medium such as a solvent or a radical polymerizable compound used in the present invention, It can also be blended after being uniformly dispersed or dissolved.
In the present invention, in order to avoid the deterioration of solvent resistance when the solvent remains in the cured image and the problem of VOC (Volatile Organic Compound) of the remaining solvent, the pigment is not a polymerizable monomer. It is preferable to add to a dispersion medium in advance and mix. In consideration of only the dispersion suitability, it is preferable to select a monomer having a low viscosity as the polymerizable compound (polymerizable monomer) used for adding the pigment.

  These pigments may be used by appropriately selecting one type or two or more types according to the purpose of use of the ink composition.

  In addition, when using the pigment which exists as a solid in the ink composition, the average particle diameter of the pigment particles is preferably 0.005 to 0.5 μm, more preferably 0.01 to 0.45 μm, and further It is preferable to set the pigment, the dispersant, the dispersion medium, the dispersion conditions, and the filtration conditions so that the thickness is preferably 0.015 to 0.4 μm. This particle size control is preferable because clogging of the head nozzle can be suppressed and the storage stability, transparency, and curing sensitivity of the ink composition can be maintained.

In order to make dark ink and light ink having the same hue, it is preferable that both inks contain substantially the same pigment. The pigment content in the light color ink is preferably 1 to 80% by weight, more preferably 2 to 60% by weight, and more preferably 3 to 50% by weight of the pigment content in the dark color ink. More preferred is 5 to 33% by weight.
In the ink composition having at least one pair of hues of the same color, it is preferable that the pigment concentration in the dark color ink is an ink jet ink set that is 3 times or more the pigment concentration in the light color ink. Is preferably 3 to 50 times, more preferably 3 to 33 times, and particularly preferably 3 to 20 times.

In the present invention, the content of the pigment in the dark ink composition is preferably 0.5 to 20% by weight, more preferably 1.0 to 15% by weight, based on the whole ink composition. More preferably, it is 10 weight%.
The content of the colorant in the ink composition is appropriately selected depending on the color and purpose of use, but is preferably 0.01 to 30% by weight with respect to the weight of the whole ink composition.

(Component D) Dispersant The ink composition preferably contains (Component D) a dispersant. In particular, when a pigment is used, a dispersant is preferably contained in order to stably disperse the pigment in the ink composition. As the dispersant, a polymer dispersant is preferable. In the present invention, the “polymer dispersant” means a dispersant having a weight average molecular weight of 1,000 or more.

As the polymer dispersant, DISPERBYK-101, 102, 103, 106, 111, 161, 162, 163, 164, 166, 167, 168, 170, 171, 174, 182 (manufactured by BYK Chemie); EFKA 4010, 4046 4080, 5010, 5207, 5244, 6745, 6750, 7414, 745, 7462, 7500, 7570, 7575, 7580 (manufactured by Fuka Additive); Disperse Aid 6, 8, 15, 9100 (manufactured by San Nopco) ); SOLSPERSE 3000, 5000, 9000, 12000, 13240, 13940, 17000, 22000, 24000, 26000, 28000, 32000, 36000, 39000, 41000, 71000, etc. Sparse dispersant (Noveon); Adeka Pluronic L31, F38, L42, L44, L61, L64, F68, L72, P95, F77, P84, F87, P94, L101, P103, F108, L121, P-123 (( ADEKA Co., Ltd.), Ionette S-20 (manufactured by Sanyo Chemical Industries, Ltd.); Disparon KS-860, 873SN, 874 (polymer dispersing agent), # 2150 (aliphatic polycarboxylic acid), # 7004 (poly) Ether ester type) (manufactured by Enomoto Kasei Co., Ltd.).
The content of the dispersant in the ink composition is appropriately selected depending on the purpose of use, but is preferably 0.05 to 15% by weight with respect to the total weight of the ink composition.

(Component E) Amine Compound The ink composition of the present invention preferably contains an amine compound from the viewpoint of the hue of the cured film.
As the amine compound that can be used in the present invention, any conventionally known amine compound can be used without particular limitation.
The amine compound may be a compound having one amine moiety in the molecule or a compound having two or more amine moieties in the molecule, and may be an alkyl group, an alkenyl group, an alkynyl group. , Halogen atoms (—F, —Br, —Cl, —I), hydroxy groups, alkoxy groups, aryloxy groups, alkylthio groups, arylthio groups, acyl groups, acyloxy groups, alkoxycarbonyl groups, aryloxycarbonyl groups, etc. You may have.

  From the viewpoint of safety, the amine compound that can be used in the present invention preferably has a boiling point of 120 ° C. or higher at standard atmospheric pressure, more preferably 150 ° C. or higher, and further preferably 180 ° C. or higher. preferable.

In addition, the amine compound that can be used in the present invention may be any of primary, secondary, and tertiary amine compounds, but from the viewpoint of suppressing side reactions and discoloration reactions with polymerizable compounds, tertiary amine compounds. Alternatively, it is preferable to use a hindered amine compound.
The amine compound may be an aliphatic amine compound or an aromatic amine compound, but is preferably an aliphatic amine compound from the viewpoint of acid scavenging ability.
Furthermore, the amine compound mentioned above is also contained as an amine compound. However, in the content in the ink composition of the present invention, when the amine oligomer has a polymerizable group, it is not handled as an amine compound but as a polymerizable compound.

Although the specific example of the amine compound which can be used for this invention is shown, this invention is not limited to these.
n-hexylamine, n-octylamine, di-n-butylamine, tri-n-hexylamine, cyclohexylamine, dicyclohexylamine, 3- (di-n-butylamino) propylamine, 3-amino-1-phenylbutane N-t-butylpyrrolidine, 2,6-dimethylpiperidine, decahydroquinoline, decahydroisoquinoline, tropine, 2,2,6,6-tetramethyl-4-piperidone, 1- (2-pyridyl) piperazine, N , N′-dimethylpiperazine, 1,4-diazabicyclo [2.2.2] octane, 4-pyrrolidinopyridine, cumylamine, 3-butoxypropylamine, 3-methylthiopropylamine, bis (3-aminopropyl) ether, N, N-di-n-propylaniline, N, N-bis (3-aminopropyl L) Methylamine, N- (3-aminopropyl) morpholine, N-benzyl-2-methyl-1,3-propanediamine, hexamethylenetetramine, hexahydro-1,3,5-triphenyl-1,3,5 -Triazine, 1,4,7-trimethyl-1,4,7-triazacyclononane, 1,4,7,10-tetraazacyclododecane, tris (3-aminopropyl) amine, N, N-dimethylaniline 1-ethylpyrrole, 2,5-dimethylpyrrole, 4- (dimethylamino) pyridine, 2,6-dichloropyridine, 2,6-diaminopyridine, 2,6-dimethyl-4-hydroxypyridine, 2,6- Diethyl pyridinedicarboxylate, 2,4,6-trimethylpyridine, 4-vinylpyridine, 3-acetylpyridine, 2-benzoylpyridy , Methyl nicotinate, 2,2′-bipyridyl, 2,2 ′: 6 ′, 2 ″ -terpyridine, quinoline, isoquinoline, 8-quinolinol, acridine, 5-aminoindole, carbazole, phenanthridine, 9 (10H ) -Acridone, 1,6-naphthyridine, 1,8-naphthyridine, 1,10-phenanthroline, quinacridone, 1H-pyrrolo [2,3-b] pyridine and the like.

  As the amine compound that can be used in the present invention, a hindered amine compound can be particularly preferably exemplified, and a hindered amine compound having no nucleophilic site in the molecule is most preferred.

  Commercially available light stabilizers HALS (manufactured by Ciba Specialty Chemicals Co., Ltd.) and Sanol (manufactured by Sankyo Co., Ltd.) have an ester structure which is a nucleophilic site in the molecule. It is not included in the hindered amine compound which has.

  Preferred examples of component E include compounds represented by the following formula (e-1).

（式中、Ｒはそれぞれ独立に、水素原子又は炭素数１〜６のアルキル基を表し、ｎは１〜１０の整数を表す。）

(In the formula, each R independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 1 to 10).

R in formula (e-1) is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and more preferably a hydrogen atom or a methyl group.
Moreover, it is preferable that four R which are not directly couple | bonding with a nitrogen atom among R in Formula (e-1) is a C1-C6 alkyl group each independently.
The alkyl group in R may be a linear alkyl group or a branched alkyl group.
N in the formula (e-1) is preferably an integer of 4 to 10, more preferably an integer of 7 to 9, and particularly preferably 8.

  The ink composition of the present invention may contain only one type of component E, or may contain two or more types.

  In addition, as component E on the market, CN371 (amine-modified acrylate oligomer, manufactured by Sartomer), CN550 (amine-modified polyether acrylate oligomer, manufactured by Sartomer), bis (1,2,2,6,6-pentamethyl) -4-piperidyl) sebacate (sold by Ciba Specialty Chemicals under the name "Tinvin 765" and Sankyo Co., Ltd. under the name "Sanol LS-765"), bis (2,2,6,6) A preferred example is 6-tetramethyl-4-piperidyl) sebacate (sold under the name “Tinuvin 770DF” by Ciba Specialty Chemicals, Inc., and Sanyo Co., Ltd. under the name “Sanol LS-770”).

  The amount of (Component E) amine compound added to the ink composition of the present invention is preferably 0.01 to 10% by weight, and preferably 0.1 to 5% by weight, based on the total weight of the ink composition. More preferred. When it is in the above range, an ink composition having excellent sensitivity and capable of obtaining a high-quality printed material can be obtained.

(Component F) Polymerization inhibitor The ink composition of the present invention preferably contains (Component F) a polymerization inhibitor from the viewpoint of storage stability of the ink composition.
Examples of the polymerization inhibitor include nitroso polymerization inhibitors, hindered amine polymerization inhibitors, hindered phenol polymerization inhibitors, hydroquinone, benzoquinone, p-methoxyphenol, 2,2,6,6-tetramethylpiperidine- 1-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL), tris (N-nitroso-N-phenylhydroxylamine) aluminum salt (cuperon Al), etc. Can be mentioned.
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.

<Other ingredients>
The ink composition of the present invention may contain an ultraviolet absorber, an antioxidant, an anti-fading agent, a conductive salt, a surfactant, a basic compound and the like as necessary. These can be exemplified by those described in JP-A-2009-221416, and can be suitably used in the present invention.
The ink composition of the present invention may contain a surfactant, but does not contain a surfactant or the content of the surfactant is 0 with respect to the total weight of the ink composition. 0.05% by weight or less, and more preferably no surfactant is contained.

[Ink properties]
In the present invention, it is preferable to use an ink composition having a viscosity at 25 ° C. of 40 mPa · s or less in consideration of ejection properties. More preferably, it is 5-40 mPa * s, More preferably, it is 7-30 mPa * s. Moreover, it is preferable that the viscosity in discharge temperature (Preferably 25-80 degreeC, More preferably, 25-50 degreeC) is 3-15 mPa * s, and it is more preferable that it is 3-13 mPa * s. It is preferable that the composition ratio of the ink composition of the present invention is appropriately adjusted so that the viscosity is in the above range. By setting the viscosity at room temperature high, even when a porous recording medium is used, penetration of the ink composition into the recording medium can be avoided and uncured monomers can be reduced. Furthermore, ink bleeding at the time of landing of the ink composition droplets can be suppressed, and as a result, the image quality is improved, which is preferable.

  The surface tension of the ink composition of the present invention at 25 ° C. is preferably 20 to 35 mN / m, and more preferably 23 to 33 mN / m. When recording on various recording media such as polyolefin, PET, coated paper, and non-coated paper, 20 mN / m or more is preferable from the viewpoint of bleeding and penetration, and 35 mN / m or less is preferable in terms of wettability.

(2) Inkjet recording method, inkjet recording apparatus and printed material The ink composition of the present invention can be suitably used for inkjet recording.
In the inkjet recording method of the present invention, the ink composition of the present invention is ejected onto a recording medium (support, recording material, etc.) for inkjet recording, and actinic radiation is applied to the ink composition ejected onto the recording medium. It is a method of forming an image by irradiating and curing the ink.

More specifically, the inkjet recording method of the present invention comprises (a ¹ ) an image forming step of forming an image on a recording medium by ejecting the ink composition of the present invention by an inkjet method, and (b ¹ ). It is preferable to include a curing step of irradiating the obtained image with actinic radiation to cure the ink composition to obtain a printed material having a cured image on the recording medium.
By including the steps (a ¹ ) and (b ¹ ), the ink jet recording method of the present invention forms an image with the ink composition cured on the recording medium.
The printed matter of the present invention is a printed matter recorded by the inkjet recording method of the present invention.
The discharge amount per droplet of the ink composition in the image forming step is preferably in the range of 3 to 42 pL.

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

  In the present invention, the recording medium is not particularly limited, and a known recording medium can be used as a support or a recording material. For example, paper, paper laminated with plastic (eg, polyethylene, polypropylene, polystyrene, etc.), metal plate (eg, aluminum, zinc, copper, etc.), plastic film (eg, cellulose diacetate, cellulose triacetate, cellulose propionate) Cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc.), paper or plastic film on which the above-mentioned metal is laminated or deposited. In addition, as the recording medium in the present invention, a non-absorbable recording medium can be preferably used.

In the case of molding, it is preferable to use a support as the recording medium.
The support that can be used in the present invention is not particularly limited, and a known recording medium described below can be used.
Specific examples of the support material include polyethylene, polypropylene, polymethylpentene, polybutene, polyolefin resins such as olefinic thermoplastic elastomer, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, terephthalic acid-isophthalic acid-ethylene glycol Copolymer, terephthalic acid-ethylene glycol-1,4 cyclohexanedimethanol copolymer, polyester resin such as polyester thermoplastic elastomer, nylon resin such as nylon 6, nylon 9, nylon 6, 6, etc., polyvinyl fluoride, polyfluoride Fluorine resin such as vinylidene fluoride, poly (vinylidene trifluoride), ethylene-tetrafluoroethylene copolymer, polytetrafluoroethylene, acrylic resin, polyvinyl chloride, polystyrene, poly It can be exemplified Boneto resin. Examples of the acrylic resin include polymethyl (meth) acrylate, polyethyl (meth) acrylate, polybutyl (meth) acrylate, methyl (meth) acrylate-butyl (meth) acrylate copolymer, ethyl (meth) acrylate-butyl (meth) ) A resin such as an acrylate copolymer or a methyl (meth) acrylate-styrene copolymer can be used alone or in a mixture of two or more. Among them, polyethylene terephthalate, polycarbonate resin, or a resin sheet obtained by blending a polycarbonate resin with another resin is preferably used because it is easy to perform decorative printing and has excellent resistance to the finished molded product.
Although there is no restriction | limiting in particular as a shape of a support body, When performing a shaping | molding process especially, it is preferable that it is a sheet form.

Moreover, as a support body, the sheet | seat (thermoplastic resin sheet) of a thermoplastic resin as mentioned above can be used conveniently.
Among thermoplastic resin sheets, high gloss areas, low gloss areas, and embossing suitability for imparting thin sheet thickness, and when forming and processing such as vacuum forming by heat-softening the molded printed matter Is appropriately selected in consideration of compatibility between molding suitability by heat during the molding process and durability of embossing (preventing disappearance of embossing). The layer structure of the transparent resin substrate sheet may be either a single layer or a laminate in which two or more layers of different kinds of resins are laminated.

  Additives can be appropriately added to the thermoplastic resin sheet as necessary. Appropriate amounts of various additives can be added as long as they do not hinder the thermal behavior such as surface gloss and melting point. For example, UV stabilizers such as benzotriazole and benzophenone, light stabilizers such as hindered amine radical scavengers, lubricants such as silicone resins and waxes, colorants, plasticizers, heat stabilizers, antibacterial agents, antifungal agents , Antistatic agents and the like.

  In the present invention, the thickness of the support (total thickness in the case of a laminate structure) is not particularly limited, but is preferably a resin sheet having a thickness within a range that allows molding, more preferably 50 to 2,000 μm. Preferably, the thing of 100-1,500 micrometers is still more preferable, and the thing of 150-1,000 micrometers is especially preferable.

There is no restriction | limiting in particular as an inkjet recording device used for the inkjet recording method of this invention, The well-known inkjet recording device which can achieve the target resolution can be selected arbitrarily and can be used. That is, any known ink jet recording apparatus including a commercially available product may be used to discharge the ink composition onto the recording medium (support) in the step (a ¹ ) of the ink jet recording method of the present invention. it can.
Examples of the ink jet recording apparatus that can be used in the present invention include an apparatus including an ink supply system, a temperature sensor, and an actinic radiation source.
The ink supply system includes, for example, an original tank containing the ink composition of the present invention, a supply pipe, an ink composition supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head. The piezo-type inkjet head is preferably 1 to 100 pL, more preferably 3 to 42 pL, still more preferably 8 to 30 pL, preferably 320 × 320 to 4,000 × 4,000 dpi, more preferably 400. It can be driven so that it can discharge at a resolution of × 400 to 1,600 × 1,600 dpi, more preferably 720 × 720 dpi. In the present invention, dpi represents the number of dots per 2.54 cm.

  As described above, since the radiation curable ink composition such as the ink composition of the present invention preferably has a constant temperature for the ejected ink, the ink composition supply tank to the inkjet head portion are insulated. And warming can be performed. The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors in each piping portion and perform heating control according to the flow rate of the ink composition and the environmental temperature. The temperature sensor can be provided near the ink composition 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.

Using the above inkjet recording apparatus, the ink composition of the present invention is ejected by heating the ink composition to preferably 25 to 80 ° C., more preferably 25 to 50 ° C. Preferably it is performed after lowering to 3 to 15 mPa · s, more preferably 3 to 13 mPa · s. In particular, it is preferable to use an ink composition having a viscosity of 50 mPa · s or less at 25 ° C. as the ink composition of the present invention, since it can be discharged satisfactorily. By using this method, high ejection stability can be realized.
A radiation curable ink composition such as the ink composition of the present invention generally has a higher viscosity than a water-based ink composition usually used in an ink composition for ink jet recording, and therefore has a large viscosity fluctuation due to temperature fluctuations during ejection. Viscosity fluctuation of the ink composition has a great influence on the change of the droplet size and the change of the droplet discharge speed, and thus causes the image quality deterioration. Therefore, it is necessary to keep the temperature of the ink composition during ejection as constant as possible. Therefore, in the present invention, the control range of the ink temperature is preferably ± 5 ° C. of the set temperature, more preferably ± 2 ° C. of the set temperature, and further preferably ± 1 ° C. of the set temperature. .

Next, (b ¹ ) a curing process in which the obtained image is irradiated with actinic radiation to cure the ink composition to obtain a printed material having a cured image on the recording medium will be described.
The ink composition ejected on the recording medium is cured by irradiation with actinic radiation. This is because the photopolymerization initiator contained in the ink composition of the present invention is decomposed by irradiation with actinic radiation to generate a polymerization initiating species such as a radical, and the polymerization reaction of the radical polymerizable monomer is a function of the initiating species. This is because it is created and promoted. At this time, if a sensitizer is present together with the polymerization initiator in the ink composition, the sensitizer in the system absorbs actinic radiation to be in an excited state, and promotes decomposition of the polymerization initiator by contacting with the polymerization initiator. And a more sensitive curing reaction can be achieved.

  Here, as the active radiation used, α rays, γ rays, electron beams, X rays, ultraviolet rays, visible light, infrared rays, or the like are used.

For curing the ink composition of the present invention, it is preferable to use an ultraviolet light emitting diode (UV-LED) as a radiation source for irradiating ultraviolet rays, and generate ultraviolet rays having an emission peak wavelength in the range of 300 to 420 nm. More preferably, a light emitting diode is used.
As a UV-LED, for example, Nichia Corporation has launched a purple LED whose main emission spectrum has a wavelength between 365 nm and 420 nm. Other ultraviolet LEDs are also available and can emit radiation in different ultraviolet bands.
The emission peak wavelength of ultraviolet rays used for curing the ink composition of the present invention is preferably from 300 to 420 nm, more preferably from 350 to 420 nm, depending on the absorption characteristics of the sensitizer from the viewpoint of curability. Preferably, 360 to 420 nm is more preferable.

Since the ink composition of the present invention has sufficient sensitivity, it can be cured sufficiently even with low output actinic radiation. Specifically, the maximum illuminance on the surface of the recording medium is preferably 10 to 2,000 mW / cm ² , more preferably 650 to 1,500 mW / cm ² from the viewpoint of image quality and productivity, and 700 to 1,400 mW / cm ² is more preferable.

The ink composition of the present invention is appropriately irradiated with such actinic radiation for 0.01 to 120 seconds, more preferably 0.01 to 90 seconds, and still more preferably 0.01 to 10 seconds. is there.
In the inkjet recording method of the present invention, the ink composition is irradiated with actinic radiation at an exposure surface illuminance of 2,000 mW / cm ² or less within 0.01 to 10 seconds after the ink composition is discharged. Is preferably cured.
Actinic radiation irradiation conditions and a basic irradiation method are disclosed in JP-A-60-132767. Specifically, the light source is provided on both sides of the head unit including the ink composition discharge device, and the head unit and the light source are scanned by a so-called shuttle method. Irradiation with actinic radiation is performed for a certain period of time (preferably 0.01 to 0.5 seconds, more preferably 0.01 to 0.3 seconds, still more preferably 0.01 to 0.15 seconds) after the ink composition has landed. ). In this way, by controlling the time from landing to irradiation of the ink composition to an extremely short time, it is possible to prevent the ink composition that has landed on the recording medium from spreading before curing. In addition, since the ink composition can be exposed to a porous recording medium before the ink composition penetrates to a deep part where the light source does not reach, it is preferable because residual unreacted monomers can be suppressed.
Further, the curing may be completed 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 ink jet recording method of the present invention.

By adopting the ink jet recording method as described above, the dot diameter of the landed ink composition can be kept constant even for various recording media (supports) having different surface wettability. Will improve. 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 ink compositions in order of low lightness, it becomes easy for the irradiation rays to reach the lower ink composition, and good curing sensitivity, reduction of residual monomers, and improvement in adhesion can be expected. In addition, irradiation can be performed by discharging all colors and collectively exposing, but exposure for each color is preferable from the viewpoint of promoting curing.
Thus, the ink composition of the present invention can form an image on the surface of a recording medium by being cured with high sensitivity by irradiation with actinic radiation.

The ink jet recording method of the present invention may be used as an ink set including at least seven colors, ie, light cyan and light magenta light-color ink compositions and cyan, magenta, black, white and yellow dark ink compositions. In this case, it is preferable to apply the recording medium in the order of white → light cyan → light magenta → yellow → cyan → magenta → black.
Thus, the ink composition of the present invention can form an image on the surface of a recording medium by being cured with high sensitivity by irradiation with actinic radiation.

When using the ink set of the present invention, an ink set comprising at least one of the dark and light ink compositions of the present invention and an ink composition having a normal pigment concentration having a hue other than the hue of the dark and light ink composition of the present invention It is preferable that The combination of hues is not particularly limited, but an ink composition containing cyan, magenta, yellow, black, light magenta, and light cyan is preferable.
The ink set of the present invention can be suitably used for the ink jet recording method of the present invention.
In order to obtain a full-color image using the ink composition of the present invention, the ink set of the present invention is an ink set including at least four dark ink compositions consisting of yellow, cyan, magenta, and black. Preferably, the ink set is a combination of five color ink compositions consisting of yellow, cyan, magenta, black and white, and more preferably 5 consisting of yellow, cyan, magenta, black and white. More preferably, the ink set is a combination of a dark color ink composition and a two-color ink composition comprising light cyan and light magenta.

  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, “part” means “part by weight” unless otherwise specified, and “%” means “% by weight”.

(Preparation of cyan mill base)
300 parts by weight of IRGALITETE BLUE GLVO, 600 parts by weight of Actilane 421 (propoxylated neopentyl glycol diacrylate) (manufactured by Akcros), and 100 parts by weight of Solsperse 32000 were mixed with stirring to obtain a pigment mill base. The pigment mill base was prepared in a disperser motor mill M50 (manufactured by Eiger) and dispersed for 4 hours at a peripheral speed of 9 m / s using zirconia beads having a diameter of 0.65 mm.

(Preparation of magenta mill base)
300 parts by weight of CINQUASIA MAGENTA RT-355 D, 600 parts by weight of Actilane 421, and 100 parts by weight of Solsperse 32000 were stirred and mixed to obtain a pigment mill base. The pigment mill base was prepared in a disperser motor mill M50 (manufactured by Eiger) and dispersed for 10 hours at a peripheral speed of 9 m / s using zirconia beads having a diameter of 0.65 mm.

(Examples 1 to 10 and Comparative Examples 1 to 3)
<Method for producing ink composition>
Each ink composition was obtained by mixing and stirring the materials described in Tables 1 and 2. In addition, the numerical value in a table | surface represents the compounding quantity (part by weight) of each component.

Each component in the table is as follows.
NVC: N-vinylcaprolactam (V-CAP, manufactured by ISP)
PEA: Phenoxyethyl acrylate (SR339, manufactured by Sartomer)
IBOA: Isobornyl acrylate (SR506, manufactured by Sartomer)
DPGDA: Dipropylene glycol diacrylate (SR508, manufactured by Sartomer)
TMPTA: trimethylolpropane triacrylate (SR351, manufactured by Sartomer)
CN964A85: urethane acrylate oligomer, average number of functional groups 2, Irg907 manufactured by Sartomer Japan, Inc .: 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one (IRGACURE 907, Ciba Specialty) (Chemicals)
Irg819: Bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide (IRGACURE 819, manufactured by Ciba Specialty Chemicals)
DETX: 2,4-diethylthioxanthone (KAYACURE DETX, manufactured by Nippon Kayaku Co., Ltd.)
ST-1: FIRSTCURE ST-1 (polymerization inhibitor, manufactured by Chem First)
Tinuvin 770DF: bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate (TINUVIN 770DF, manufactured by Ciba Specialty Chemicals)

<Inkjet recording method>
Recording was performed on a recording medium using an ink jet recording experimental apparatus having a piezoelectric ink jet nozzle. The ink jet recording apparatus has a total of eight ink supply systems, and the ink supply systems are independent for each ink supply meter. Each of the ink supply systems is an original tank, a supply pipe, an ink supply tank immediately before the ink jet head, a filter, and a piezo type. It consists of an inkjet head. The prepared ink was filled in an ink tank, and the ink supply tank to the inkjet head part were insulated and heated.
The eight piezo-type inkjet heads were arranged in parallel, and were driven simultaneously so that 10-30 pl multi-size dots could be ejected at a resolution of 600 × 400 dpi. After landing, UV light is condensed to an exposure surface illuminance (maximum illuminance on the surface of the recording medium) of 800 mW / cm ² , so that irradiation starts 0.1 seconds to 0.3 seconds after ink landing on the recording medium. The exposure system, main scanning speed and injection frequency were adjusted. Further, the integrated light amount irradiated to the image was set to 500 mJ / cm ² .
As the ultraviolet lamp, an ultraviolet light emitting diode (NC4U134 manufactured by Nichia Corporation) that emits ultraviolet light having a wavelength of 385 nm was used.
In the present invention, dpi represents the number of dots per 2.54 cm. An image was created using a polyvinyl chloride sheet as the recording medium.

In the following evaluation, a 12 μm solid film was prepared according to the printing method and used for the evaluation.
[Productivity (curing sensitivity) evaluation]
Productivity (curing sensitivity) was evaluated based on the exposure energy that eliminates color transfer and stickiness on the surface after printing.
The presence or absence of stickiness on the surface after printing was determined by palpation, and color transfer was judged by pressing plain paper (Fuji Xerox Co., Ltd. copy paper C2) immediately after printing. It was evaluated that the sensitivity was so high that there was no color transfer or stickiness, and the grade was evaluated according to the following criteria.
A: No color transfer, no stickiness
○: No color transfer and almost no stickiness.
X: There is color transfer and there is stickiness.

[Evaluation of hue (yellowing)]
Using the printing method described above, a halftone image having 16 gradations for each color was created, and the hue of the middle density portion (40%) was measured. Here, the hue was measured using a spectrophotometer (Spectraeye, manufactured by Gretag Macbeth Co., Ltd.), and L ^* a ^* b ^* was measured under the conditions of a light source F8 and a viewing angle of 2 degrees. A sample prepared with an ink containing no thioxanthone compound was defined as _ΔE0 and evaluated according to the following evaluation criteria.
A: ΔE <2 Yellowing is hardly recognized ○: 2 ≦ ΔE <3 Yellowing is recognized but not so noticeable ×: ΔE ≧ 3 Yellowing is conspicuous D is a level that can be visually recognized and has a practical problem.
In addition, it is thought that said yellowing has arisen by absorption by the long wave side of a polymerization initiator, or decomposition | disassembly and structural change of a polymerization initiator.

(Graininess evaluation)
A halftone image of 16 gradations for each color was created using the above printing method, and the graininess of the highlight portion (10 to 40%) was evaluated. The evaluation was performed by visual evaluation by 15 general evaluators and judged according to the following criteria.
◎: 12 or more people who evaluated that the image does not feel rough ○: 8 or more people who evaluated that the image does not feel rough ×: People who evaluated that the image does not feel rough The evaluation results obtained for 7 or less are shown in Tables 1 and 2 together with the ink formulation.

[Elongation evaluation]
A cured film was prepared in the same manner as the curing sensitivity except that Fasson PE (Fason Polyethylene film: film thickness 100 μm) was used as the support. The obtained cured film is cut into an axial length of 5 cm and a width of 2.5 cm, and stretched at a speed of 30 cm / min using a tensile tester (manufactured by Shimadzu Corporation), and the elongation at which the cured film breaks is measured. did. The state of elongation from the initial length to twice the length was defined as 100% elongation.
◎: Elongation rate 120% or more ○: Elongation rate 100% or more and less than 120% ×: Elongation rate less than 100%

Claims (11)

Containing at least one pair of dark and light inks having the same hue;
Each of the dark color ink and the light color ink is an ink composition containing (Component A) a radical polymerizable compound, (Component B) a photopolymerization initiator, and (Component C) a pigment.
As the radical polymerizable compound, containing a monofunctional monomer and a polyfunctional monomer,
Monofunctional monomer / polyfunctional monomer weight ratio of (X) and the weight ratio of the monofunctional monomer / polyfunctional monomer of the light color ink in the dark ink (Y), meets the relationship of X> Y,
The dark color ink and the light color ink are both (component B) photopolymerization initiator, (component B-1) thioxanthone photopolymerization initiator, (component B-2) α-aminoalkylphenone compound, and (Component B-3) containing an acylphosphine compound,
An ink set for ink jet recording, wherein the concentration of the thioxanthone photopolymerization initiator in the dark color ink is greater than the concentration of the thioxanthone photopolymerization initiator in the light color ink .   The ink set for inkjet recording according to claim 1, wherein X / Y is 1.2 or more and 5 or less.   The ink set for inkjet recording according to claim 1, wherein each of the dark color ink and the light color ink includes urethane (meth) acrylate as the polyfunctional monomer.   In both the dark color ink and the light color ink, the content (B1) of the component B-1, the content (B2) of the component B-2, and the content (B3) of the component B-3 are (B3) ≧ ( The ink set for inkjet recording according to any one of claims 1 to 3, which satisfies a relationship of B2)> (B1). (Component C) concentration of the pigment in the dark in the ink, the at light ink in the (Component C) of the concentration of the pigment 3 times or more, for ink jet recording according to any one of claims 1-4 Ink set. The ink set for inkjet recording according to any one of claims 1 to 5 , wherein each of the dark color ink and the light color ink contains N-vinylcaprolactam as the monofunctional monomer. The ink set for inkjet recording according to any one of claims 1 to 6 , wherein each of the dark color ink and the light color ink contains a (meth) acrylate having an alkylene oxide group as the polyfunctional monomer. The ink set for inkjet recording according to any one of claims 1 to 7 , which is for curing an LED having an emission peak wavelength in a wavelength region of 360 nm or more and 420 nm.   The ink set for inkjet recording according to any one of claims 1 to 8, wherein each of the dark color ink and the light color ink includes (Component E) an amine compound.   The ink set for inkjet recording according to claim 9, wherein each of the dark color ink and the light color ink includes a compound represented by the following formula (e-1) as the (Component E) amine compound.

(In the formula, each R independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 1 to 10). It includes the step of printing with the ink set for inkjet recording according to any one of claims 1 to 10 , and the step of curing the ink with an LED having an emission peak wavelength in a wavelength region of 360 nm or more and 420 nm. An inkjet recording method.