JP2016160334A - Ink composition for inkjet recording and inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink composition for inkjet recording, which has excellent curability and gives a printed matter with suppressed odor, and an inkjet recording method using the ink composition for inkjet recording.SOLUTION: The ink composition for inkjet recording comprises: as component A, (A-1) a (meth)acrylate compound having two or more functional groups and (A-2) a vinyl ether compound having two or more functional groups and/or a compound having a (meth)acryloyloxy group and a vinyl ether group, by more than 75 wt.% with respect to the total mass of the ink composition; a compound having a molecular weight of 1,000 or more and two or more maleimide structures in the molecule, as component B, by 1 to 10 mass% with respect to the total mass of the ink composition; a photosensitizer having a molecular weight of 1,000 or more as component C, by 0.5 to 10 mass% with respect to the whole mass of the ink composition; and substantially no photopolymerization initiator having a molecular weight of less than 1,000.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ink composition 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. It is an excellent method in that it can be printed on various recording media because it is excellent in drying properties and difficult to blur images as compared with solvent-based ink compositions.

Until now, soft packaging printing has been performed mainly by conventional printing methods such as gravure printing and flexographic printing. However, in recent years, digital printing capable of responding to the increase in small lot printing has also attracted attention in the flexible packaging field. In the case of digital printing, there is no need to create a plate and color matching is not required, so it is possible to reduce costs, especially when printing small lots, and to shorten the printing time because preparation time can be reduced. It also leads to.
Examples of conventional inkjet recording methods include the methods described in Patent Documents 1 and 2.

Patent Document 1 discloses an electron-accepting monomer (A) having an unsaturated bond a and a maximum charge of a carbon atom constituting the unsaturated bond a being −0.30 or more, and an unsaturated bond d. And an electron donating monomer (D) having a minimum charge of carbon atoms constituting the unsaturated bond d of −0.50 or less, and a polymerizable monomer (X) having a (meth) acrylic acid ester group ), The electron donating monomer (D) contains vinyl ether, and the electron accepting monomer with respect to the total amount of the electron accepting monomer (A), the electron donating monomer (D), and the polymerizable monomer (X). The ratio of the total amount of the electron-donating monomer (A) and the electron-donating monomer (D) is 25 to 90% by weight, and the electron-accepting monomer (A) with respect to the number of functional groups of the electron-donating monomer (D) The ratio of the number of functional groups (A / (D) is a 70 / 30-35 / 65, actinic radiation curable inkjet ink is described.
Patent Document 2 discloses a pigment, a polymer dispersant, a surfactant, a polymerizable compound A having an electron-deficient unsaturated double bond, and a polymerizable compound B having an electron-rich unsaturated double bond. An active energy ray-curable inkjet ink containing the polymerizable compound B1 represented by the general formula (b1) as the polymerizable compound B, and having a static surface tension of 25 mN / m or more and 40 mN / m. An active energy ray-curable ink-jet ink having a dynamic surface tension of 40 mN / m or more and 55 mN / m or less in 50 milliseconds is described below.

JP 2014-24980 A JP 2014-118454 A

  The problem to be solved by the present invention is to provide an ink composition for ink jet recording which is excellent in curability and suppresses the odor of the obtained printed matter, and an ink jet recording method using the ink composition for ink jet recording. It is to be.

The above-described problems of the present invention have been solved by the means described in <1> or <6> below. It is described below together with <2> to <5>, <7> and <8> which are preferred embodiments.
<1> As component A, A-1: a bifunctional or higher functional (meth) acrylate compound, and A-2: a bifunctional or higher functional vinyl ether compound and / or a compound having a (meth) acryloyloxy group and a vinyl ether group, A compound containing more than 75% by mass with respect to the total mass of the ink composition and having a molecular weight of 1,000 or more and having two or more maleimide structures in the molecule as component B is 1 A photopolymerization initiator containing 0.5 to 10% by mass of a photosensitizer having a molecular weight of 1,000 or more as component C and 0.5 to 10% by mass with respect to the total mass of the ink composition. An ink composition for ink jet recording, characterized by being substantially free of
<2> The ink composition for inkjet recording according to <1>, wherein the component C includes a compound having a skeleton represented by the formula C-1 in the molecule;

式Ｃ−１中、Ｒ¹及びＲ²は、それぞれ独立に、炭素数１〜５のアルキル基、又は、ハロゲン原子を表し、ｉは２〜４の整数を表し、ｊは０〜４の整数を表し、ｋは０〜３の整数を表し、Ｘ¹はエーテル結合（−Ｏ−）及び／又はエステル結合（−（Ｃ＝Ｏ）−Ｏ−）を含んでいてもよい炭素数２〜３００のｉ価の炭化水素基を表す、
＜３＞ 上記Ａ−１を、インク組成物全質量に対して３５質量％以上含有し、かつ、上記Ａ−２を、インク組成物全質量に対して５〜４０質量％含有する、＜１＞又は＜２＞に記載のインクジェット記録用インク組成物、
＜４＞ インクジェット記録用インク組成物中の、水及び揮発性溶剤の含有量が、インク組成物全質量に対して１質量％未満である、＜１＞〜＜３＞のいずれか１つに記載のインクジェット記録用インク組成物、
＜５＞ インクジェット記録用インク組成物中の、単官能重合性化合物の含有量が、インク組成物中に含まれる重合性化合物の総質量に対して、０．５質量％未満である、＜１＞〜＜４＞のいずれか１つに記載のインクジェット記録用インク組成物、
＜６＞ ＜１＞〜＜５＞のいずれか１つに記載のインクジェット記録用インク組成物を被記録媒体へ吐出する吐出工程、及び、被記録媒体上のインク組成物に活性エネルギー線を照射して硬化する硬化工程を含むことを特徴とするインクジェット記録方法、
＜７＞ 上記硬化工程が、酸素濃度１体積％以下の雰囲気中で行われる、＜６＞に記載のインクジェット記録方法、
＜８＞ 上記硬化工程における活性エネルギー線の照射に用いられる光源が、発光ダイオード及び／又はレーザーダイオードである、＜６＞又は＜７＞に記載のインクジェット記録方法ト記録方法。

In formula C-1, R ¹ and R ² each independently represents an alkyl group having 1 to 5 carbon atoms or a halogen atom, i represents an integer of 2 to 4, and j represents an integer of 0 to 4 K represents an integer of 0 to 3, and X ¹ has 2 to 300 carbon atoms which may contain an ether bond (—O—) and / or an ester bond (— (C═O) —O—). Represents an i-valent hydrocarbon group of
<3> The A-1 is contained in an amount of 35% by mass or more with respect to the total mass of the ink composition, and the A-2 is contained in an amount of 5 to 40% by mass with respect to the total mass of the ink composition. > Or <2>, an ink composition for ink jet recording,
<4> In any one of <1> to <3>, the content of water and a volatile solvent in the ink composition for inkjet recording is less than 1% by mass with respect to the total mass of the ink composition. The ink composition for ink jet recording according to the description,
<5> The content of the monofunctional polymerizable compound in the ink composition for inkjet recording is less than 0.5% by mass with respect to the total mass of the polymerizable compound contained in the ink composition, <1 >-<4> The ink composition for ink-jet recording according to any one of
<6> An ejection step of ejecting the ink composition for inkjet recording according to any one of <1> to <5> onto a recording medium, and irradiating the ink composition on the recording medium with active energy rays An ink jet recording method comprising a curing step of curing by heating,
<7> The inkjet recording method according to <6>, wherein the curing step is performed in an atmosphere having an oxygen concentration of 1% by volume or less.
<8> The inkjet recording method and the recording method according to <6> or <7>, wherein the light source used for the irradiation of active energy rays in the curing step is a light emitting diode and / or a laser diode.

  ADVANTAGE OF THE INVENTION According to this invention, the ink composition for inkjet recording which is excellent in sclerosis | hardenability, and the odor of the obtained printed matter is suppressed, and the inkjet recording method using the said ink composition for inkjet recording can be provided. It was.

It is a schematic diagram which shows an example of the inkjet recording device used suitably for this invention.

Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the specification of the present application, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.
In the description of the group (atomic group) in this specification, the description which does not describe substitution and non-substitution includes what does not have a substituent and what has a substituent. For example, the “alkyl group” includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).
In the present specification, “(meth) acrylate” represents acrylate and methacrylate, “(meth) acryl” represents acryl and methacryl, and “(meth) acryloyl” represents acryloyl and methacryloyl.
In the present invention, “mass%” and “wt%” are synonymous, and “part by mass” and “part by weight” are synonymous.
In the present invention, a combination of two or more preferred embodiments is a more preferred embodiment.

In the present invention, in the case of a compound having a distribution in molecular weight, the molecular weight means a weight average molecular weight.
In the present invention, the weight average molecular weight is determined by measuring by GPC method (gel permeation chromatography) and converting to standard polystyrene. For example, GLC uses HLC-8220GPC (manufactured by Tosoh Corp.) and elution using three columns of TSKgeL SuperHZM-H, TSKgeL SuperHZ4000, TSKgeL SuperHZ2000 (manufactured by Tosoh Corp., 4.6 mmID × 15 cm). THF (tetrahydrofuran) is used as the liquid. As conditions, the sample concentration is 0.35% by mass, the flow rate is 0.35 ml / min, the sample injection amount is 10 μl, the measurement temperature is 40 ° C., and an IR detector is used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It is prepared from 8 samples of “A-2500”, “A-1000”, “n-propylbenzene”.

(Ink composition for inkjet recording)
The ink composition for ink-jet recording of the present invention (hereinafter also simply referred to as “ink composition”) includes, as Component A, A-1: a bifunctional or higher (meth) acrylate compound, and A-2: bifunctional. The above vinyl ether compound and / or the compound having a (meth) acryloyloxy group and vinyl ether group in the molecule is contained in an amount of more than 75% by mass with respect to the total mass of the ink composition, and the component B has a molecular weight of 1,000 or more. Yes, containing 1 to 10% by mass of a compound having two or more maleimide structures in the molecule with respect to the total mass of the ink composition, and as component C, a photosensitizer having a molecular weight of 1,000 or more is 0.5 to It is characterized by containing 10% by mass and substantially free of a photopolymerization initiator having a molecular weight of less than 1,000.
In the ink using the ink composition described in Patent Document 1 or Patent Document 2, the present inventors include a low molecular weight polymerization initiator in order to increase curability. It has been found that there is a problem that the agent remains and causes odor.
On the other hand, as an ink composition that does not contain a low molecular weight polymerization initiator, an ink composition containing a maleimide compound described in JP-A-2000-144033 has been studied. The ink was found to have problems that the curability is low and the film quality is not good.
Accordingly, the present inventors have found that by using the ink composition for ink jet recording of the present invention, both curability and suppression of odor of printed matter can be achieved.
Moreover, the ink composition for inkjet recording of the present invention is suitable for package printing, and particularly suitable for package printing for food packaging.

<Component A>
In the ink composition of the present invention, as component A, A-1: a bifunctional or higher functional (meth) acrylate compound (hereinafter also referred to as “compound A-1”), and A-2: a bifunctional or higher functional vinyl ether. Compound (hereinafter also referred to as “Compound A-2-1”) and / or a compound having a (meth) acryloyloxy group and a vinyl ether group in the molecule (hereinafter also referred to as “Compound A-2-2”, Compound A 2-1 and Compound A-2-2 are also referred to as “Compound A-2”) in an amount of more than 75 mass% with respect to the total mass of the ink composition.
The ink composition of the present invention preferably contains Compound A-1 and Compound A-2-1 as Component A.

[A-1: Bifunctional or higher functional (meth) acrylate compound]
As compound A-1 used for this invention, the di (meth) acrylic acid ester (bifunctional (meth) acrylate compound) of a C6-C12 aliphatic hydrocarbon diol is illustrated preferably. The hydrocarbon diol may be any of a linear hydrocarbon diol, a branched hydrocarbon diol and a cyclic hydrocarbon diol, and a linear hydrocarbon diol and a branched hydrocarbon diol are preferably exemplified.
Moreover, it is preferable that compound A-1 does not have a vinyl ether group.
Di (meth) acrylic acid esters of aliphatic hydrocarbon diols having 6 to 12 carbon atoms are preferred because of their low viscosity and their relatively low odor.
Examples of the di (meth) acrylic acid ester of an aliphatic hydrocarbon diol having 6 to 12 carbon atoms include 1,6-hexanediol di (meth) acrylate, 1,7-heptanediol di (meth) acrylate, 1,8- Octanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, 1,12-dodecanediol di (meth) acrylate, 3-methyl-1, 5-pentanediol di (meth) acrylate, 2-n-butyl-2-ethyl-1,3-propanediol di (meth) acrylate, cyclohexanedimethanol di (meth) acrylate, tricyclodecane dimethanol di (meth) Acrylate is preferably exemplified.
Among these, decanediol diacrylate, dodecanediol diacrylate, and 3-methyl-1,5-pentanediol dimethacrylate are more preferable, and 3-methyl-1,5-pentanediol diacrylate is more preferable.
In the present invention, the bifunctional or higher functional (meth) acrylate compound contains at least one (meth) acryloyloxy group in the molecule and has a viscosity at room temperature (25 ° C.) of less than 0.1 Pa · s. Means a compound of When the viscosity is within the above range, it is possible to achieve both migration of printed matter and suppression of odor and reactivity.

  Specific examples of other bifunctional (meth) acrylate compounds include dipropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and ethylene oxide (EO) modification. Neopentyl glycol di (meth) acrylate, propylene oxide (PO) modified neopentyl glycol di (meth) acrylate, EO modified hexanediol di (meth) acrylate, PO modified hexanediol di (meth) acrylate, tripropylene glycol di (meth) ) Acrylate and triethylene glycol di (meth) acrylate are preferred.

  Trifunctional or higher functional (meth) acrylate compounds include pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, trimethylolethane tri (meth) acrylate, and trimethylol. Examples include propane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, and oligoester (meth) acrylate.

[A-2: Bifunctional or higher vinyl ether compound and / or compound having (meth) acryloyloxy group and vinyl ether group]
-A-2-1: Bifunctional or higher vinyl ether compound-
The compound A-2-1 used in the present invention is preferably a bifunctional or trifunctional vinyl ether compound.
Moreover, it is preferable that compound A-2-1 does not have a (meth) acryloyloxy group.
As the vinyl ether compound, divinyl ether of alkylene glycol or polyalkylene glycol and trivinyl ether of trimethylolpropane are preferably used.
Examples of the compound A-2-1 preferably used in the present invention include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether. Bifunctional or trifunctional vinyl ether compounds such as vinyl ether, cyclohexanedimethanol divinyl ether, and trimethylolpropane trivinyl ether can be exemplified.
In particular, a bifunctional vinyl ether compound having an ethylene glycol chain is preferable. In this case, the cured film has excellent curability and image gloss. Preferred examples include diethylene glycol divinyl ether, triethylene glycol divinyl ether, and tetraethylene glycol divinyl ether, and more preferred examples include triethylene glycol divinyl ether.

-A-2-2: Compound having (meth) acryloyloxy group and vinyl ether group-
The compound A-2-2 used in the present invention is not limited as long as it has a (meth) acryloyloxy group and a vinyl ether group, but one (meth) acryloyloxy group and one vinyl ether group. The compound which has each is preferable.
Compound A-2-2 is preferably a compound in which one hydroxy group of alkylene glycol or polyalkylene glycol forms a (meth) acrylic acid ester and the other hydroxy group forms a vinyl ether.
As compound A-2-2 suitably used in the present invention, 2- (2-vinyloxyethoxy) ethyl acrylate and 2- (2-vinyloxyethoxy) ethyl methacrylate are preferable, and 2- (2 -Vinyloxyethoxy) ethyl is more preferable.

[Content of Component A]
The ink composition of the present invention contains Component A in an amount of more than 75% by mass and preferably 76 to 95% by mass with respect to the total mass of the ink composition.
The compound A-1, compound A-2-2, and compound A-2-1 may be used alone or in combination of two or more. The content of the component A is as follows: , Compound A-1, Compound A-2-2, and Compound A-2-1.
Further, the ink composition of the present invention preferably contains 35% by mass or more, more preferably 35 to 95% by mass, and more preferably 40 to 80% by mass of Compound A-1 with respect to the total mass of the ink composition. More preferably.
The ink composition of the present invention preferably contains 5 to 40% by mass of compound A-2, more preferably 15 to 40% by mass, based on the total mass of the ink composition.

<Component B>
The ink composition of the present invention contains, as Component B, 1 to 10% by mass of a compound having a molecular weight of 1,000 or more and having two or more maleimide structures in the molecule based on the total mass of the ink composition.

Component B preferably has a poly (alkyleneoxy) group in the molecule from the viewpoint of adhesion of the cured ink composition. The number of carbon atoms of the alkylene group in the poly (alkyleneoxy) group is preferably 1 to 6, and more preferably 2 to 3.
Component B is preferably a compound represented by the following formula B-1.

In Formula B-1, L ^B1 is a divalent linking group, and X ^B1 is an ether bond (—O—), an ester bond (— (C═O) —O—), a thioether bond, a thioester bond, or a urethane bond. Or a carbonate group, Q ^B1 represents a single bond or a divalent hydrocarbon group, m represents an integer of 1 or more, n represents an integer of 2 or more, and Z ^B1 represents an n-valent linking group. .

From the viewpoint of the curing sensitivity of the ink composition and the adhesion of the ink composition after curing, L ^B1 is a single bond, a linear or branched alkylene group, an ether bond (—O—), an ester bond ( A group represented by-(C = O) -O-), a carbonyl group or a combination thereof is preferable, and a group in which a carbonyl group and an alkylene group are bonded is more preferable.
The group in which the carbonyl group and the alkylene group are bonded is preferably a group represented by the following formula B-1-2.

In Formula B-1-2, R ^B2 is an alkylene group having 1 to 4 carbon atoms, and a methylene group is preferable.
The wavy line portion is preferably bonded to X ^B1 in the formula B-1, and the * portion is preferably bonded to a nitrogen atom in the maleimide structure. For the embodiments, X ^B1 that binds wavy portion is preferably an ether bond (-O-).

Q ^B1 is preferably a single bond or a linear or branched alkylene group having 1 to 6 carbon atoms.
X ^B1 represents an ether bond (—O—), an ester bond (— (C═O) —O—) or a carbonate group, and an ether bond (—O—) is particularly preferable.
From the viewpoint of solubility in the ink component and adhesion of the ink composition after curing, Z ^B1 represents an aliphatic group, an ether bond (—O—), an ester bond (— (C═O) —O—), amino It is preferably an n-valent linking group comprising a group and a combination thereof.
From the viewpoints of solubility in ink components and ejection properties, n is preferably an integer of 2 to 6, and more preferably an integer of 2 to 4.
From the viewpoint of safety, the molecular weight of Component B is 1,000 or more, preferably 1,000 to 5,000.

  Examples of component B include the following compounds.

[Method for producing component B]
Component B includes, for example, a method obtained by esterifying maleimide carboxylic acid produced by a known method with a polyhydric alcohol compound.
As an example of the manufacturing method of the said maleimide carboxylic acid, the method of making it dry after making maleic anhydride and glycine react in acetic acid is mentioned.

  Moreover, it is also possible to use a commercially available compound as Component B, and BMI1500 and BMI3000 (both manufactured by Designer Moleculars) are preferably mentioned.

[Content of Component B]
The ink composition of the present invention contains Component B in an amount of 1 to 10% by mass, preferably 2 to 9% by mass, more preferably 5 to 8% by mass, based on the total mass of the ink composition.
Moreover, the component B may be used individually by 1 type, or may use 2 or more types.

<Component C>
The ink composition of the present invention contains, as Component C, 0.5 to 10% by mass of a photosensitizer having a molecular weight of 1,000 or more.
Examples of component C include polynuclear aromatics (eg, pyrene, perylene, triphenylene, 2-ethyl-9,10-dimethoxyanthracene), xanthenes (eg, fluorescein, eosin, erythrosine, rhodamine B, rose). Bengal, etc.), cyanines (eg, thiacarbocyanine, oxacarbocyanine, etc.), merocyanines (eg, merocyanine, carbomerocyanine, etc.), thiazines (eg, thionine, methylene blue, toluidine blue, etc.), acridines (eg, Acridine orange, chloroflavin, acriflavine, etc.), anthraquinones (eg, anthraquinone, etc.), squaliums (eg, squalium), coumarins (eg, 7-diethylamino-4-methylcoumarin, etc.), thioxanthate Photosensitizers which are high molecular weight having at least one skeleton selected from the class are preferred. Among them, a compound having a thioxanthone skeleton in the molecule is preferable, and a skeleton represented by the formula C-1 is preferably included in the molecule.

In formula C-1, R ¹ and R ² each independently represents an alkyl group having 1 to 5 carbon atoms or a halogen atom, i represents an integer of 2 to 4, and j represents an integer of 0 to 4 K represents an integer of 0 to 3, and X ¹ has 2 to 300 carbon atoms which may contain an ether bond (—O—) and / or an ester bond (— (C═O) —O—). Represents an i-valent hydrocarbon group.

In Formula C-1, R ¹ and R ² each independently represents an alkyl group having 1 to 5 carbon atoms or a halogen atom, and the alkyl group having 1 to 5 carbon atoms is linear or branched. It may be either a ring or a ring, but is preferably linear or branched, preferably an alkyl group having 1 to 4 carbon atoms, and more preferably an alkyl group having 2 to 3 carbon atoms. More preferably, they are an ethyl group or an isopropyl group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and a chlorine atom is preferable. R ¹ and R ² are particularly preferably each independently an ethyl group, an isopropyl group or a chlorine atom.
In formula C-1, j represents an integer of 0 to 4, preferably 0 to 2, and more preferably 0 or 1. When j is an integer of 2 or more, a plurality of R ¹ may be the same or different.
In formula C-1, k represents an integer of 0 to 3, preferably 0 to 2, more preferably 0 or 1, and still more preferably 0. When k is an integer of 2 or more, a plurality of R ² may be the same or different.
In formula C-1, i represents an integer of 2 to 4, more preferably 3 or 4, and still more preferably 4.
In formula C-1, X ¹ is an i-valent hydrocarbon group having 2 to 300 carbon atoms which may contain an ether bond (—O—) and / or an ester bond (— (C═O) —O—). Represents.
In Formula C-1, a plurality of (i) thioxanthone structures (structures represented by [] in Formula C-1) excluding X ¹ as a linking group are present, but they are the same as each other. However, they may be different and are not particularly limited. From the viewpoint of synthesis, they are preferably the same.

  In the compound represented by the formula C-1, the substitution position to the thioxanthone structure is represented as follows.

The substitution position of X ¹ is the 1-4 position, preferably the 2-position, the 3-position or the 4-position, more preferably the 2-position or the 4-position, and even more preferably the 4-position.
The substitution position of R ¹ is 5 to 8 positions, preferably 6 positions and 7 positions, and more preferably 6 positions.
The substitution position of R ² is 1 to 4, and is preferably 1 position, 2 position or 3 position, and more preferably 1 position.
Specific examples are shown below, but the present invention is not limited to the following compounds.

A commercially available compound can also be used as the compound represented by the formula C-1.
Specifically, Speedcure 7010 (produced by Lambson, 1,3-di ({α- [1-chloro-9-oxo-9H-thioxanthen-4-yl] oxy} acetylpoly [oxy (1-methylethylene)]) oxy) -2,2-bis ({α- [1-chloro-9-oxo-9H-thioxanthen-4-yl] oxy} acetylpoly [oxy (1-methylethylene)]) oxymethyl) propane, CAS No. 100367-83-6) is exemplified.

[Method for producing component C]
In addition, the compound represented by the formula C-1 can be produced by a known reaction, and is not particularly limited. Can do.

[Content of Component C]
The ink composition of the present invention contains Component C in an amount of 0.5 to 10% by mass and preferably 1 to 5% by mass with respect to the total mass of the ink composition.
Component C may be used alone or in combination of two or more.

<Other ingredients>
The ink composition of the present invention may contain a colorant, a polymerization inhibitor, a dispersant, a surfactant, and other components as other components.
Details of each optional component will be described below.

[Colorant]
In the present invention, the ink composition preferably contains a colorant in order to improve the visibility of the formed image portion.
Although there is no restriction | limiting in particular as a coloring agent, The pigment and oil-soluble dye which were excellent in weather resistance and were rich in color reproducibility are preferable, and it can select and use arbitrarily from well-known coloring agents, such as a soluble dye. As the colorant, it is preferable to select a compound that does not function as a polymerization inhibitor 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, blue or cyan pigments include Pigment Blue 1,15,15: 1,15: 2,15: 3,15: 4,15: 6,16,1 -1, 22, 27, 28, 29, 36, 60, Pigment Green 7, 26, 36, 50 as a green pigment, and Pigment Yellow 1, 3, 12, 13, 14, 17, 34 as a yellow pigment , 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 120, 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180 185, 193, Pigment Black 7, 28, 26 as the black pigment, and Pigment White 6, 18, 21, etc. as the white pigment according to the purpose.
In the present invention, a disperse dye can be used as long as it is soluble in a water-immiscible organic solvent. The disperse dye generally includes a water-soluble dye, but in the present invention, the disperse dye is preferably used as long as it is soluble in a water-immiscible organic solvent.
Preferable specific examples of the disperse dye include C.I. I. Disperse Yellow 5,42,54,64,79,82,83,93,99,100,119,122,124,126,160,184: 1,186,198,199,201,204,224 and 237 C. I. Disperse Orange 13, 29, 31: 1, 33, 49, 54, 55, 66, 73, 118, 119 and 163; I. Disperse Red 54, 60, 72, 73, 86, 88, 91, 92, 93, 111, 126, 127, 134, 135, 143, 145, 152, 153, 154, 159, 164, 167: 1,177 , 181, 204, 206, 207, 221, 239, 240, 258, 277, 278, 283, 311, 323, 343, 348, 356 and 362; I. Disperse Violet 33; C.I. I. Disperse Blue 56, 60, 73, 87, 113, 128, 143, 148, 154, 158, 165, 165: 1, 165: 2, 176, 183, 185, 197, 198, 201, 214, 224, 225 , 257, 266, 267, 287, 354, 358, 365 and 368; I. Disperse Green 6: 1 and 9;

  The colorant is preferably added to the ink composition and then moderately dispersed in the ink composition. For dispersing the colorant, for example, a dispersion device such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, or a paint shaker can be used.

The colorant may be directly added together with each component when preparing the ink composition. Further, in order to improve dispersibility, it may be added to a dispersion medium such as a solvent or component A in advance and uniformly dispersed or dissolved, and then blended.
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 colorant contains component A. It is preferable to add and mix in advance in such a dispersion medium. In consideration of only dispersibility, it is preferable to select a monomer having a low viscosity as the component A used for adding the colorant. One or more colorants may be appropriately selected and used according to the purpose of use of the ink composition.

When using a colorant such as a pigment that remains solid in the ink composition, the average particle diameter of the colorant particles is preferably 0.005 to 0.5 μm, more preferably 0.01 to It is preferable to set the colorant, the dispersant, the dispersion medium, the dispersion conditions, and the filtration conditions so as to be 0.45 μm, more 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.
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 mass with respect to the total mass of the ink composition.

(Polymerization inhibitor)
The ink composition of the present invention may contain a polymerization inhibitor from the viewpoints of storage stability and suppression of head clogging.
Examples of the polymerization inhibitor include nitroso polymerization inhibitors, hindered amine polymerization inhibitors, hydroquinone, benzoquinone, p-methoxyphenol, TEMPO, TEMPOL, and cuperon Al.
The content of the polymerization inhibitor is preferably 0.02 to 2% by mass with respect to the total mass of the ink composition.

[Dispersant]
In the present invention, the ink composition may contain a dispersant.
In particular, when the ink composition contains the colorant, it is preferable to include a dispersant for dispersing the colorant.
As the dispersant, a polymer dispersant is preferable. The “polymer dispersing agent” in the present invention means a dispersing agent having a weight average molecular weight of 1,000 or more.

Examples of the polymer dispersant include DISPERBYK-101, DISPERBYK-102, DISPERBYK-103, DISPERBYK-106, DISPERBYK-111, DISPERBYK-161, DISPERBYK-162, DISPERBYK-163, DISPERBYK-164, DISPERBYK-166, DISPERBYK-166, and DISPERBYK-166. , DISPERBYK-168, DISPERBYK-170, DISPERBYK-171, DISPERBYK-174, DISPERBYK-182 (manufactured by BYK Chemie); EFKA7462, EFKA7500, EFKA7570, EFKA7575, EFKA7580 (manufactured by Efka Additive); Disperse Aid 6, Disperse Aid 8, Disperse Aid 15, Disperse Aid 9100 (manufactured by Sannopco); Solsperse (SOLSPERSE) 3000 Various Solsperse dispersants (manufactured by Noveon) such as 5000, 9000, 12000, 13240, 13940, 17000, 22000, 24000, 26000, 28000, 32000, 36000, 39000, 41000, 71000; Adeka Pluronic L31, F38, L42, L44 , L61, L64, F68, L72, P95, F77, P84, F87, P94, L101, P103, F108, L121, -123 (manufactured by ADEKA Corporation), Ionette S-20 (manufactured by Sanyo Chemical Industries, Ltd.); Disparon KS-860, 873SN, 874 (polymer dispersing agent), # 2150 (aliphatic polycarboxylic acid), # 7004 (polyether 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 mass with respect to the total mass of the ink composition.

[Surfactant]
A surfactant may be added to the ink composition in order to impart stable ejection properties for a long time.
Examples of the surfactant include those described in JP-A Nos. 62-173463 and 62-183457. For example, anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene blocks Nonionic surfactants such as copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. Moreover, you may use a fluorine-type surfactant (for example, organic fluoro compound etc.) and silicone type surfactant (for example, polysiloxane compound etc.) as said surfactant. The organic fluoro compound is preferably hydrophobic. Examples of the organic fluoro compound include fluorine surfactants, oily fluorine compounds (eg, fluorine oil) and solid fluorine compound resins (eg, tetrafluoroethylene resin). No. (columns 8 to 17) and those described in JP-A Nos. 62-135826.

The polysiloxane compound is preferably a modified polysiloxane compound in which an organic group is introduced into a part of the methyl group of dimethylpolysiloxane. Examples of modification include polyether modification, methylstyrene modification, alcohol modification, alkyl modification, aralkyl modification, fatty acid ester modification, epoxy modification, amine modification, amino modification, mercapto modification, etc. is not. These modification methods may be used in combination. Of these, polyether-modified polysiloxane compounds are preferred from the viewpoint of improving ejection stability in inkjet.
Examples of the polyether-modified polysiloxane compound include, for example, SILWET L-7604, SILWET L-7607N, SILWET FZ-2104, SILWET FZ-2161 (manufactured by Nihon Unicar Co., Ltd.), BYK306, BYK307, BYK331, BYK333, BYK347. , BYK348 and the like (manufactured by BYK Chemie), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, Examples thereof include KF-6020, X-22-6191, X-22-4515, KF-6011, KF-6012, KF-6015, and KF-6017 (manufactured by Shin-Etsu Chemical Co., Ltd.).
Among these, a silicone-based surfactant is preferably used as the surfactant.
The content of the surfactant in the ink composition is appropriately selected depending on the purpose of use, but is preferably 0.0001 to 5% by mass, and 0.001 to 2% by mass with respect to the total mass of the ink composition. More preferably.

[Other ingredients]
In the present invention, the ink composition may contain a co-sensitizer, an ultraviolet absorber, an antioxidant, an anti-fading agent, a conductive salt, a solvent, a polymer compound, and a basic compound, if necessary, in addition to the above components. Etc. may be included. As these other components, known components can be used, for example, those described in JP-A-2009-22214.

[Physical properties of ink composition]
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 5-30 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 is appropriately adjusted so that the viscosity is in the above range. By setting the viscosity at room temperature (25 ° C.) high, even when a porous recording medium (support) is used, penetration of the ink composition into the recording medium is avoided, and uncured components A can be reduced. Further, it is preferable because ink bleeding at the time of landing of the ink composition droplets can be suppressed, and as a result, the image quality is improved.

  The surface tension of the ink composition at 25 ° C. is preferably 18 mN / m or more and 40 mN / m or less, more preferably 18 mN / m or more and 35.0 mN / m or less, and more preferably 20 mN / m or more and 30.0 mN / m or less. m or less is more preferable, and 20 mN / m or more and 28.0 mN / m or less is particularly preferable. When the content is in the above range, a printed matter excellent in blocking inhibition can be obtained.

  In addition, although a well-known method can be used as a measuring method of the surface tension at 25 degreeC in this invention, It is preferable to measure by the suspension ring method or the Wilhelmy method. For example, a method of measuring using an automatic surface tension meter CBVP-Z manufactured by Kyowa Interface Science Co., Ltd. or a method of measuring using SIGMA 702 manufactured by KSV INSTRUMENTS LTD is preferred.

[Composition of ink composition]
The ink composition of the present invention contains Component A in an amount of more than 75% by mass, preferably 76 to 95% by mass, more preferably 80 to 92% by mass, and more preferably Component B. 1 to 10% by weight, preferably 2 to 9% by weight, more preferably 4 to 8% by weight, more preferably 4 to 8% by weight based on the total weight of the ink composition. It is preferable to contain 0.5-10 mass% and 1-2 mass%.
In addition, the ink composition of the present invention preferably includes 80 to 100% by mass, and preferably 80 to 98% by mass, based on the total mass of the ink composition, of Component A, Component B and Component C. Is more preferable, and it is still more preferable that 84-98 mass% is included.

The content of the colorant in the ink composition is preferably 0 to 20% by mass with respect to the total mass of the ink composition, and the content of the polymerization inhibitor is 0 to 0 with respect to the total mass of the ink composition. The content of the dispersant is preferably 0% by mass to 10% by mass with respect to the total mass of the ink composition, and the content of the surfactant is based on the mass of the entire composition. 0 to 5% by mass is preferable.
In addition, the ink composition of the present invention is composed of the components A, B, C, colorant, polymerization inhibitor, dispersant, and surfactant in a total amount of 95 to 95% based on the total mass of the ink composition. The content is preferably 100% by mass, more preferably 98 to 100% by mass, and even more preferably 99 to 100% by mass.

The ink composition of the present invention is substantially free of a photopolymerization initiator having a molecular weight of less than 1,000. In the present invention, “substantially free of a photopolymerization initiator having a molecular weight of less than 1,000” means that the content of the photopolymerization initiator having a molecular weight of less than 1,000 is 1 mass relative to the total mass of the ink composition. % Or less. The content of the photopolymerization initiator having a molecular weight of less than 1,000 is preferably 0.5% by mass or less and more preferably 0.1% by mass or less with respect to the total mass of the ink composition.
The photopolymerization initiator includes a compound that absorbs external energy such as actinic rays to generate radical polymerization initiating species, and a compound that absorbs actinic rays and promotes decomposition of the radical polymerization initiator (so-called sensitizers). ).
According to the said aspect, generation | occurrence | production of the odor after hardening an ink composition is suppressed.
The ink composition of the present invention is an actinic ray curable ink composition and is different from a water-based ink composition or a solvent ink composition.
The content of water and volatile solvent in the ink composition of the present invention is preferably less than 1% by mass, more preferably 0.5% by mass or less, based on the total mass of the ink composition. More preferably, it is 0.1 mass% or less.
The volatile solvent in the present invention is a solvent having a boiling point of 150 ° C. or lower.
Further, from the viewpoint of odor prevention, the content of the monofunctional polymerizable compound in the ink composition of the present invention is preferably less than 1% by mass with respect to the total mass of the ink composition, and is 0.5% by mass. More preferably, it is more preferably 0.1% by mass or less.
In the present invention, the polymerizable compound refers to a compound having a polymerizable group in the molecule, and the monofunctional polymerizable compound refers to a compound having only one polymerizable group in the molecule.
Examples of the polymerizable group include a radical polymerizable group or a cationic polymerizable group.
Monofunctional polymerizable compounds having a radical polymerizable group include monofunctional (meth) acrylate compounds, monofunctional (meth) acrylamide compounds, monofunctional aromatic vinyl compounds, monofunctional vinyl ether compounds (such as triethylene glycol divinyl ether), And monofunctional N-vinyl compounds (N-vinylcaprolactam and the like).
The above-described photopolymerization initiator, volatile solvent, and monofunctional polymerizable compound content described as "mass% or less" and "less than mass%" are not included in the embodiment at all, That is, 0 mass% is included.

(Inkjet recording method)
The ink jet recording method of the present invention includes a discharge step of discharging the ink composition for ink jet recording of the present invention to a recording medium, and a curing step of curing the ink composition on the recording medium by irradiating with ultraviolet rays. It is characterized by.
The ink jet recording method of the present invention is suitable for package printing, and is particularly suitable for package printing for food packaging.
Hereinafter, each process will be described.

<Discharge process>
The discharge process in the present invention is not particularly limited as long as it is a discharge process for discharging an ink composition onto a recording medium, and is a process for discharging the ink composition of the present invention onto a recording medium by an inkjet method.

[Recording medium]
The recording medium (base material, support, recording material, etc.) used in the inkjet recording method of the present invention is not particularly limited, and any known recording medium can be used.
Among these, a transparent recording medium is preferable for printing food packaging packages for soft packaging.
In the present invention, “transparent” means that the visible light transmittance is 80% or more, and the visible light transmittance is preferably 90% or more. The transparent recording medium may be colored as long as it is transparent, but is preferably a colorless recording medium.
Specific examples of the recording medium include glass, quartz, and plastic films (for example, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, acrylic resin, chlorinated polyolefin resin, Polyethersulfone resin, polyethylene terephthalate (PET), polyethylene naphthalate, nylon, polyethylene, polystyrene, polypropylene, polycycloolefin resin, polyimide resin, polycarbonate resin, polyvinyl acetal, etc.).
The transparent recording medium may be a mixture of two or more of these resins, or a laminate of two or more of these resins.

Among them, the recording medium is preferably a recording medium having an image forming surface made of at least one resin selected from the group consisting of polyolefin resin, polyester resin and polyamide resin, polyethylene terephthalate, polyethylene, More preferably, it is a recording medium having an image forming surface made of at least one resin selected from the group consisting of polypropylene and nylon, and at least one selected from the group consisting of polyethylene terephthalate, polyethylene, polypropylene and nylon. More preferably, the recording medium is made of a seed resin.
As polyethylene, LDPE (low density polyethylene), MDPE (medium density polyethylene), HDPE (high density polyethylene), and polypropylene as CPP (unstretched polypropylene), OPP (biaxially stretched polypropylene), KOP (polyvinylidene chloride coating) As the OPP), AOP (PVA-coated OPP), and polyethylene terephthalate, biaxially stretched polyester and nylon are preferably ON (stretched nylon), KON (stretched nylon), and CN (unstretched nylon).
In addition, EVA (ethylene / vinyl acetate copolymer film), PVA (vinylon), EVOH (polyvinyl alcohol), PVC (polyvinyl chloride), PVDC (polyvinylidene chloride, saran), cellophane (PT, MST, K cello), It is also preferable to use a combination with ZX (Zecron (polyacrylonitrile, PAN)) and PS (polystyrene, styrene).
An optimum material is selected depending on the application of the package, and a film having a combination of the characteristics of each material can be produced by forming a multilayer film.
Moreover, AL (aluminum foil), VM film (aluminum vapor-deposited film, transparent vapor-deposited film), etc. can be incorporated in the multilayer structure for the purpose of improving the strength of the package and blocking oxygen.
In recent years, a co-extruded film in which a resin is extruded from two or more parallel slits to form a film and laminate at the same time is also preferably used. Even films as thin as a few μm that cannot be made into a film can be laminated up to 5 to 7 layers, so films with various performances and applications have been made.

  Although there is no restriction | limiting in particular as thickness of the said recording medium, It is preferable that it is 1-500 micrometers, It is more preferable that it is 2-200 micrometers, It is further more preferable that it is 5-100 micrometers, It is 10-90 micrometers. It is particularly preferred.

(Discharge means)
In the discharging step, the ink composition of the present invention is discharged by an ink jet method.
As a means for ejecting the ink composition by the ink jet method, it is preferable to use an ink jet head. As an inkjet head, for example, a charge control method that ejects ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses the vibration pressure of a piezo element, and an electrical signal is converted into an acoustic beam into ink A head such as an acoustic ink jet system that irradiates and discharges ink using radiation pressure, or a thermal ink jet (bubble jet (registered trademark)) system that uses ink to form bubbles by heating the ink is suitable. is there.

  There is no restriction | limiting in particular as an inkjet recording device which can be 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 can discharge the ink composition onto the recording medium in the discharging step of the ink jet recording method of the present invention.

Examples of the ink jet recording apparatus that can be used in the present invention include an apparatus including an ink supply system, a temperature sensor, and an active energy ray source.
The ink supply system includes, for example, an original tank containing an ink composition, a supply pipe, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head. The piezo-type inkjet head preferably has a multi-size dot of 1 to 100 pl, more preferably 8 to 30 pl, preferably 320 × 320 to 4,000 × 4,000 dpi, more preferably 400 × 400 to 1,600 ×. It can be driven so that it can discharge at a resolution of 1,600 dpi, more preferably 1,200 × 1,200 dpi. In the present invention, dpi represents the number of dots per 2.54 cm.

When only one kind is used as the ink composition, the total droplet ejection amount per unit area of the ink composition is preferably 0.001 to 10 g / m ² , and 0.01 to 9 g / m 2. ² is more preferable, and 0.5 to 8 g / m ² is particularly preferable.
When two or more kinds of ink compositions are used, the total droplet ejection amount per unit area of the ink composition is preferably 0.001 to 10 g / m ² , and 0.01 to 9 g / m 2. ² is more preferable, and 0.5 to 8 g / m ² is particularly preferable.

Since the ink composition preferably has a constant temperature for the ejected ink composition, the ink jet recording apparatus preferably includes a means for stabilizing the ink composition temperature. The parts to be kept at a constant temperature are all the piping systems and members from the ink tank (intermediate tank if there is an intermediate tank) to the nozzle ejection surface. That is, heat insulation and heating can be performed from the ink supply tank to the inkjet head portion.
The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors at each piping site and perform heating control according to the ink flow rate and the environmental temperature. The temperature sensor can be provided near the ink supply tank and the nozzle of the inkjet head. Moreover, it is preferable that the head unit to be heated is thermally shielded or insulated so that the apparatus main body is not affected by the temperature from the outside air. In order to shorten the printer start-up time required for heating or to reduce the loss of heat energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

  It is preferable to keep the temperature of the ink composition at the time of ejection as constant as possible. Therefore, in the present invention, the temperature control range of the ink composition is preferably set to ± 5 ° C. of the set temperature, more preferably ± 2 ° C. of the set temperature, and further preferably set temperature ± 1 ° C. .

  In addition, when an undercoating process described later is performed before the ejection process, the droplet ejection interval from the application of the undercoating composition to the first droplet ejection of the ink composition is 5 μs or more and 10 seconds. Or less, more preferably 10 μs or more and 5 seconds or less, and particularly preferably 20 μs or more and 5 seconds or less.

In the ink jet recording method of the present invention, the ink composition of the present invention may be used alone or in combination of two or more.
For example, when forming a color image, it is preferable to use at least each color ink composition of yellow, cyan, magenta, and black, and more preferable to use each color ink composition of white, yellow, cyan, magenta, and black. preferable.
Further, a light color ink composition such as light magenta or light cyan, a special color ink composition such as orange, green and violet, a clear ink composition, a metallic ink composition, or the like may be used.

In the ink jet recording method of the present invention, when two or more ink compositions are ejected, after ejecting one ink composition, before ejecting the next other one ink composition, the ejected above It is preferable to include a step of semi-curing the ink composition. That is, the inkjet recording method of the present invention includes a step of ejecting the ink composition for each ink composition to be used, and a step of semi-curing the ejected ink composition by irradiation with active energy rays. It is preferable. The effect of this invention can be exhibited more as it is the said aspect.
In addition, the process of semi-hardening by irradiation of the said active energy ray is contained in the hardening process mentioned later.

  In the ink jet recording method of the present invention, the order of the ink compositions to be ejected is not particularly limited, but is preferably applied to the recording medium from an ink composition having a low brightness, and yellow, cyan, magenta, When black is used, it is preferably applied on the recording medium in the order of black → magenta → cyan → yellow. In addition, when white is added to this, it is preferable to apply it on the recording medium in the order of black → magenta → cyan → yellow → white. Further, the present invention is not limited to this, and an ink set including at least a total of seven colors including yellow, light cyan, light magenta, cyan, magenta, black, and white ink compositions can be preferably used. For example, black, magenta, cyan, yellow, light magenta, light cyan, and white are preferably applied on the recording medium in this order.

<Curing process>
The ink jet recording method of the present invention includes a curing step of curing the ink composition by irradiating the ink composition ejected in the ejection step with an active energy ray.
The ink composition of the present invention discharged onto a recording medium is cured by irradiation with active energy rays. This is because the component B contained in the ink composition generates radicals that are polymerization initiation species upon irradiation with active energy rays, and the polymerization reaction of a polymerizable compound such as component A or the like in component B and component A. This is because an alternating copolymerization reaction with a vinyl ether group and a polymerization reaction of component B occur and are accelerated. At this time, if the component C is present together with the polymerization initiator in the ink composition, the sensitizer in the system absorbs the active energy ray and enters an excited state, and contact with the component B generates radicals by the component B, The polymerization reaction of the polymerizable compound such as component A can be promoted, and a more sensitive curing reaction can be achieved.

Here, the active energy ray used may be ultraviolet light, visible light, infrared light, or the like. Although the peak wavelength of the active energy ray depends on the absorption characteristics of the sensitizer, for example, it is preferably 200 to 600 nm, more preferably 300 to 450 nm, still more preferably 300 to 420 nm, The active energy ray is particularly preferably ultraviolet light having a peak wavelength of 400 nm or less.
In addition, the polymerization initiation system of the ink composition of the present invention has sufficient sensitivity even with a low output active energy ray. Even if the light source used for irradiation is a light emitting diode and / or a laser diode, sufficient curing characteristics can be obtained. The exposure surface illuminance is preferably 10 to 4,000 mW / cm ² , more preferably 20 to 2,500 mW / cm ² .

As an ultraviolet ray source, a mercury lamp and a metal halide lamp are widely known. However, from the viewpoint of environmental protection, mercury-free is strongly desired, and replacement with a GaN-based semiconductor ultraviolet light-emitting device is very useful industrially and environmentally. Furthermore, ultraviolet light-emitting diodes (UV-LEDs) and ultraviolet laser diodes (UV-LDs) are small, have a long lifetime, high efficiency, and are low in cost, and are expected as light sources for photo-curable ink jets.
In the present invention, the light source used for irradiation with actinic rays is preferably a light emitting diode and / or a laser diode, and more preferably an ultraviolet light emitting diode and / or an ultraviolet laser diode.
For example, Nichia Corporation has introduced a purple LED whose main emission spectrum has a wavelength between 365 nm and 420 nm. When even shorter wavelengths are required, US Pat. No. 6,084,250 discloses an LED that can emit ultraviolet light centered between 300 nm and 370 nm.
Other ultraviolet light emitting LEDs are also available and can radiate radiation in different ultraviolet bands. A preferred ultraviolet source in the present invention is a UV-LED or UV-LD, and a particularly preferred ultraviolet source is a UV-LED.
The maximum illumination intensity of the LED on a recording medium is preferably 10 to 2,000 mW / cm ^2, more preferably 20 to 1,000 mW / cm ^2, at 50 to 800 mW / cm ² It is particularly preferred.
The ink jet recording method of the present invention is suitable for soft packaging package printing. In the soft packaging package, as described above, it is preferable to use a recording medium having a relatively thin film thickness. In this case, it is preferable to use an LED because deformation and shrinkage of the recording medium due to heat are suppressed.

In the curing step, it is preferable to irradiate the ink composition with active energy rays, preferably for 0.01 to 120 seconds, and more preferably for 0.1 to 90 seconds.
The irradiation conditions of active energy rays and the basic irradiation method are disclosed in JP-A-60-132767. Specifically, the light source is provided on both sides of the head unit including the ink composition discharge device, and the head unit and the light source are scanned by a so-called shuttle method. The irradiation with the active energy ray is performed for a certain period of time after the ink composition has landed (preferably 0.01 to 0.5 seconds, more preferably 0.01 to 0.3 seconds, and still more preferably 0.01 to 0.15). Seconds). 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 it 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 above-described aspect, the dot diameter of the landed ink composition can be kept constant even on various recording media having different surface wettability, and the image quality is improved. In addition, in order to obtain a color image, it is preferable to superimpose in order from the color with the highest brightness. By superimposing the ink compositions in order from the 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.

The atmosphere for irradiating the active energy ray is not particularly limited, but the oxygen concentration is preferably 2% by volume or less, more preferably 1% by volume or less, and the oxygen concentration is 300 ppm or less. Further preferred. It is excellent in sclerosis | hardenability as it is the said range, especially surface curability.
The oxygen concentration is preferably adjusted by nitrogen purge.

More preferably, the curing step includes a semi-curing step of irradiating an active energy ray to the image formed by the discharged ink composition and semi-curing.
In addition, when two or more ink compositions are ejected in the ejection step, the ejected ink composition is ejected after ejecting one ink composition and before ejecting the next one other ink composition. It is preferable to include a step of irradiating an active energy ray to an image formed by an object and semi-curing the image.
Further, after the last ink composition is ejected, an image formed with the ejected ink composition may or may not be subjected to a semi-curing step by irradiating active energy rays. Is preferred.
In the inkjet recording method of the present invention, the method for semi-curing the ink composition is not particularly limited, but the following methods can be preferably exemplified.
In the present invention, “semi-cured” means partially cured (partially cured) and refers to a state where the ink composition is partially cured but not completely cured. When another ink composition ejected on the ink composition applied on the recording medium (base material) is semi-cured, the degree of curing may be non-uniform. For example, it is preferable that the ink composition is cured in the depth direction.

Examples of the method for semi-curing the ink composition include known thickening methods such as a method for causing the ink composition to undergo ultraviolet curing to cause a curing reaction.
The method of causing a semi-curing reaction by applying ultraviolet rays is a method in which the polymerization reaction of the polymerizable compound on the surface of the ink composition applied to the recording medium is insufficient.

  In the case where the ink composition of the present invention is polymerized in an atmosphere containing a large amount of oxygen, such as in the air or air partially substituted with an inert gas, the oxygen composition on the recording medium is suppressed due to the radical polymerization inhibiting action of oxygen. There is a tendency that radical polymerization is inhibited on the surface of the droplet of the ink composition applied to (hereinafter also referred to as ink composition droplet). As a result, the semi-curing becomes non-uniform, the curing proceeds more inside the ink composition droplets, and the surface curing tends to be delayed.

When the ink composition of the present invention is partially photocured in the presence of oxygen that inhibits radical polymerization, the curing of the ink composition proceeds more internally than externally.
In particular, on the surface of the ink composition, the polymerization reaction is more likely to be inhibited due to the influence of oxygen in the air compared to the inside. Therefore, the ink composition can be semi-cured by controlling the application conditions of active energy rays or heat.
The peak wavelength of the active energy ray to be irradiated is, for example, preferably 200 to 600 nm, and more preferably 250 to 400 nm.

The amount of energy required for semi-curing the ink composition varies depending on the type and content of Component B, but is preferably 1 to 500 mJ / cm ² .

The application of active energy rays promotes the generation of active species due to the decomposition of component B, and the increase in active species and the temperature increase cause polymerization reaction due to the active species or curing reaction due to polymerization or cross-linking of the crosslinkable material. Promoted.
Moreover, thickening (viscosity increase) can also be suitably performed by irradiation with actinic light.

  The unpolymerization rate of the ink composition of the present invention can be quantitatively measured by the reaction rate of ethylenically unsaturated groups (described later).

  When the semi-cured state of the ink composition is realized by a polymerization reaction of a polymerizable compound that starts polymerization by irradiation with active energy rays or heating, from the viewpoint of improving the scratch resistance of the printed matter, the unpolymerized rate (A (after polymerization) ) / A (before polymerization)) is preferably 0.2 or more and 0.9 or less, more preferably 0.3 or more and 0.9 or less, and 0.5 or more and 0.9 or less. Is particularly preferred.

Here, A (after polymerization) is the absorbance of the infrared absorption peak due to the polymerizable group after the polymerization reaction, and A (before polymerization) is the absorbance of the infrared absorption peak due to the polymerizable group before the polymerization reaction. . For example, when the polymerizable compound contained in the ink composition is an acrylate monomer or a methacrylate monomer, an absorption peak based on a polymerizable group (acryloyloxy group, methacryloyloxy group) can be observed in the vicinity of 810 cm ⁻¹ . It is preferable to define the unpolymerized rate by absorbance. Further, when the polymerizable compound is an oxetane compound, an absorption peak based on a polymerizable group (oxetanyl group) can be observed in the vicinity of 986 cm ⁻¹ , and it is preferable to define the unpolymerization rate based on the absorbance of the peak. When the polymerizable compound is an epoxy compound, an absorption peak based on a polymerizable group (epoxy group) can be observed in the vicinity of 750 cm ⁻¹ , and the unpolymerization rate is preferably defined by the absorbance of the peak.
Moreover, as a means for measuring an infrared absorption spectrum, a commercially available infrared spectrophotometer can be used, which may be either a transmission type or a reflection type, and is preferably selected as appropriate in the form of a sample. For example, it can be measured using an infrared spectrophotometer FTS-6000 manufactured by BIO-RAD.

[Complete curing process]
Moreover, when the said semi-hardening process is performed, it is preferable that a hardening process includes the complete hardening process which irradiates an active energy ray to the said image, and completes hardening.
In the present invention, “fully cured” refers to a state in which the inside and surface of the undercoat liquid and ink composition on the recording medium are completely cured. Specifically, plain paper (for example, copy paper C2 manufactured by Fuji Xerox Co., Ltd., product code V436) is pressed to a uniform force (a constant value within a range of 500 to 1,000 mN / cm ² ), It can be judged by whether or not the liquid surface has been transferred to the paper. That is, the case where no transfer is performed is called a completely cured state.

  In the inkjet recording method of the present invention, the recording medium conveyance speed, that is, the printing speed is preferably 15 m / min to 300 m / min, more preferably 20 m / min to 200 m / min. More preferably, it is 25 m / min-100 m / min.

<Undercoating process>
The ink jet recording method of the present invention may include an undercoat step of forming an undercoat layer on the recording medium before the ejection step.
There is no restriction | limiting in particular as an undercoat composition which forms the said undercoat layer, Although a well-known thing can be used, It is preferable to use the undercoat composition mentioned later.
In the ink jet recording method of the present invention, as a means for applying the undercoat composition onto the recording medium, a coating apparatus or an ink jet nozzle can be used, and a coating apparatus is preferably used.
There is no restriction | limiting in particular as said coating device, According to the objective etc., it can select suitably according to the objective etc., for example, an air doctor coater, a blade coater, a lot coater, a knife coater, a squeeze coater, an impregnation coater , Reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater and extrusion coater. For details, see Yuji Harasaki's “Coating Engineering”.
Among these, from the viewpoint of apparatus cost, the application of the undercoat composition onto the recording medium is preferably performed using a relatively inexpensive bar coater or spin coater.

The undercoat composition is preferably applied to the same area as the image formed by ejecting the ink composition on the recording medium in the ejection process or to a wider area than the image, so as to cover the entire area where the image can be formed. It is preferable to be given to.
Application amount of the undercoat composition (mass per unit area) is preferably 0.05-5 g / m ^2, and more preferably 0.06~3g / m ^2. When the application amount of the undercoat composition is within the above range, a sufficient adhesion improving effect can be obtained and a printed matter having excellent flexibility can be obtained.
Further, the application amount (mass ratio per unit area) of the undercoat composition is within a range of 0.05 to 5 when the maximum application amount (per color) of the ink composition per unit area is 1. It is preferable that it is within the range of 0.07 to 4, more preferably within the range of 0.1 to 3.

The ink jet recording method of the present invention preferably includes a step of semi-curing the undercoat layer before the discharging step.
The method of semi-curing the undercoat layer is not particularly limited, and includes a method of semi-curing with heat or actinic light, but a method of irradiating the undercoat layer with ultraviolet light, that is, causing a curing reaction by ultraviolet exposure is preferable. It can be illustrated.
The amount of energy required for semi-curing the undercoat layer varies depending on the composition, particularly the type and content of the polymerization initiator, but is preferably ¹ to 500 mJ / cm ² .
In addition, the semi-curing of the undercoat layer can be performed in the same manner as the semi-curing of the ink composition, and the exposure apparatus used, the exposure conditions, and the preferred mode are also the same.
In addition, when a step of semi-curing the undercoat layer is included, it is preferable to completely cure the undercoat layer by irradiation with ultraviolet rays in the curing step.

(Undercoat composition)
In the ink jet recording method of the present invention, the undercoat composition used for forming the undercoat layer preferably contains a compound having an isocyanate group, a polymerizable compound, and a polymerization initiator.
The undercoat composition used in the present invention is preferably an oily liquid composition curable by ultraviolet rays.
As the polymerizable compound and the polymerization initiator used in the undercoat composition, Component A and Component B in the ink composition are also used, but it is preferable to use a polymerizable compound and a polymerizable initiator described later.
The undercoat composition preferably contains 70% by mass or more of the polyfunctional polymerizable compound with respect to the total content of the polymerizable compound. When the amount is in the above range, the amount of residual monomer in the obtained printed matter can be further reduced.
The content of the polymerizable compound in the undercoat composition is preferably 5 to 95% by mass, and 5 to 50% by mass with respect to the total mass of the undercoat composition, from the viewpoint of cohesion and blocking inhibition. It is preferably 10 to 40% by mass.
The content of the polymerization initiator is preferably 1.0 to 15% by mass, more preferably 1.5 to 10% by mass, and more preferably 2.0 to 8% by mass with respect to the total mass of the undercoat composition. It is more preferable that it is 0 mass%, and it is especially preferable that it is 2.0-5.0 mass%. It is excellent in curability as it is the said range.

-Polymerizable compound-
The undercoat composition used in the present invention contains a polymerizable compound (also referred to as “monomer”).
The polymerizable compound used in the undercoat composition may be a radical polymerizable compound or a cationic polymerizable compound, but is preferably a radical polymerizable compound.
The cationic polymerizable compound is not particularly limited, and a known cationic polymerizable compound can be used. From the viewpoint of curability and scratch resistance, a compound having an epoxy ring, a compound having an oxetane ring, and a vinyl ether compound are preferable. More preferred are compounds having an epoxy ring and compounds having an oxetane ring.
There is no restriction | limiting in particular as a radically polymerizable compound, A well-known ethylenically unsaturated compound can be used, A (meth) acrylate compound, a vinyl ether compound, an allyl compound, an N-vinyl compound, unsaturated carboxylic acids etc. can be illustrated. . For example, the radically polymerizable monomer described in JP2009-22214A, the polymerizable compound described in JP2009-209289A, and the ethylenically unsaturated compound described in JP2009-191183A can be mentioned.

As the polymerizable compound used in the undercoat composition, an ethylenically unsaturated compound is preferable, and a compound having a (meth) acryloyl group is more preferable.
The polymerizable compound in the undercoat composition preferably contains a polyfunctional polymerizable compound, more preferably contains a polyfunctional polymerizable compound having one or more (meth) acryloyl groups in the molecule, and one or more in the molecule. It is more preferable to include a bifunctional polymerizable compound having a (meth) acryloyl group.
Further, the undercoat composition preferably contains, as a polymerizable compound, 75% by mass or more of a polyfunctional polymerizable compound having one or more (meth) acryloyl groups in the molecule with respect to the total mass of the undercoat composition. The bifunctional polymerizable compound having one or more (meth) acryloyl groups in the molecule is more preferably contained in an amount of 75% by mass or more based on the total mass of the undercoat composition.

Examples of the polyfunctional polymerizable compound having one or more (meth) acryloyl groups in the molecule include di (meth) acrylic acid esters (bifunctional (meth) acrylate compounds) of aliphatic hydrocarbon diols having 6 to 12 carbon atoms. Preferably exemplified. The hydrocarbon diol may be any of a linear hydrocarbon diol, a branched hydrocarbon diol and a cyclic hydrocarbon diol, and a linear hydrocarbon diol and a branched hydrocarbon diol are preferably exemplified.
A di (meth) acrylic acid ester of an aliphatic hydrocarbon diol having 6 to 12 carbon atoms is preferable because of its low viscosity.
Examples of the di (meth) acrylic acid ester of an aliphatic hydrocarbon diol having 6 to 12 carbon atoms include 1,6-hexanediol di (meth) acrylate, 1,7-heptanediol di (meth) acrylate, 1,8- Octanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, 1,12-dodecanediol di (meth) acrylate, 3-methyl-1, 5-pentanediol di (meth) acrylate, 2-n-butyl-2-ethyl-1,3-propanediol di (meth) acrylate, cyclohexanedimethanol di (meth) acrylate, tricyclodecane dimethanol di (meth) Acrylate is preferably exemplified.
Among these, decanediol diacrylate, dodecanediol diacrylate, and 3-methyl-1,5-pentanediol dimethacrylate are more preferable, and 3-methyl-1,5-pentanediol diacrylate is more preferable.

  Specific examples of the polyfunctional polymerizable compound having one or more (meth) acryloyl groups in the molecule include dipropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and neopentyl glycol diester. (Meth) acrylate, ethylene oxide (EO) modified neopentyl glycol di (meth) acrylate, propylene oxide (PO) modified neopentyl glycol di (meth) acrylate, EO modified hexanediol di (meth) acrylate, PO modified hexanediol di (Meth) acrylate, tripropylene glycol di (meth) acrylate, and triethylene glycol di (meth) acrylate are preferred.

  More specifically, the polymerizable compound used in the undercoat composition is more specifically, Yamashita Junzo “Crosslinker Handbook” (1981, Taiseisha); Kato Kiyomi “UV / EB Curing Handbook (raw material)” (1985) Radtech Research Group, “Application and Market of UV / EB Curing Technology”, p. 79 (1989, CMC Publishing Co., Ltd.); “Polyester Resin Handbook” by Eiichiro Takiyama (1988) Commercially available products described in Nikkan Kogyo Shimbun Co., Ltd., etc., or radically polymerizable or crosslinkable monomers, oligomers and polymers known in the industry can be used.

The polymerizable compound used in the undercoat composition may be used alone or in combination of two or more.
The content of the polymerizable compound in the undercoat composition is preferably 10 to 95% by mass, and 50 to 90% by mass with respect to the total mass of the undercoat composition, from the viewpoint of compatibility between adhesion and blocking inhibition. It is preferably 70 to 85% by mass.

-Polymerization initiator-
The undercoat composition preferably contains a polymerization initiator, and when it contains a radical polymerizable compound, it contains a radical polymerizable initiator, and when it contains a cationic polymerizable compound, it contains a cationic polymerization initiator. It is more preferable. Especially, as a polymerization initiator, a radical polymerization initiator is preferable.
The polymerization initiator used in the undercoat composition is preferably a photopolymerization initiator, and more preferably a photoradical polymerization initiator.
The cationic polymerization initiator or radical polymerization initiator used in the undercoat composition undergoes a chemical change through the action of light or the interaction with the electronically excited state of the sensitizing dye to generate radicals, acids or bases. Among these, the above photo radical generator or photo acid generator is preferable from the viewpoint that polymerization can be initiated by a simple means of exposure.

  In the undercoat composition, a cationic polymerization initiator or a radical polymerization initiator is appropriately selected from the polymerization initiators described in detail below in consideration of the relationship with the cationic polymerizable compound or radical polymerizable compound used in combination. You can select and use.

As the specific photopolymerization initiator, those known to those skilled in the art can be used without limitation, and specifically, for example, Bruce M. et al. Monroe et al., Chemical Reviews, 93, 435 (1993). R. S. By Davidson, Journal of Photochemistry and biologic A: Chemistry, 73.81 (1993). J. P. Faussier “Photoinitiated Polymerization—Theory and Applications”: Rapra Review vol. 9, Report, Rapra Technology (1998). M. Tsunooka et al. , Prog. Polym. Sci. , 21, 1 (1996). Many are described.
In addition, a large number of chemical amplification type photoresists and compounds used for photocationic polymerization are described in (Organic Electronics Materials Study Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), pages 187 to 192). ing. Further, F.I. D. Saeva, Topics in Current Chemistry, 156, 59 (1990). G. G. Maslak, Topics in Current Chemistry, 168, 1 (1993); B. Shuster et al. , J .; Am. Chem. Soc. 112, 6329 (1990); D. F. Eaton et al. , J .; Am. Chem. Soc. , 102, 3298 (1980), and the like, a group of compounds that undergo oxidative or reductive bond cleavage through interaction with the electronically excited state of the sensitizer is also known.

As a cationic polymerization initiator (preferably a photoacid generator), an onium salt compound such as diazonium salt, phosphonium salt, sulfonium salt, iodonium salt, imide sulfonate, oxime sulfonate, which generates an acid upon decomposition by irradiation with ultraviolet rays, Preferred examples include sulfonate compounds such as diazodisulfone, disulfone, and o-nitrobenzyl sulfonate.
The cationic polymerization initiator is preferably an aromatic onium salt, more preferably an iodonium salt or a sulfonium salt, and particularly preferably an iodonium PF ₆ salt or a sulfonium salt PF ₆ salt from the viewpoint of curability. .

The radical polymerization initiator is more preferably a radical photopolymerization initiator.
Examples of radical polymerization initiators include (a) aromatic ketones, (b) acylphosphine compounds, (c) aromatic onium salt compounds, (d) organic peroxides, (e) thio compounds, and (f) hexaary. A rubiimidazole compound, (g) a ketoxime ester compound, (h) a borate compound, (i) an azinium compound, (j) a metallocene compound, (k) an active ester compound, (l) a compound having a carbon halogen bond, and (m ) Alkylamine compounds and the like. These radical polymerization initiators may use the above compounds (a) to (m) alone or in combination. Details of the radical polymerization initiator are described in, for example, paragraphs 0090 to 0116 of JP2009-185186A and paragraphs 0024 to 0080 of JP2014-43010A. The thing can be illustrated.

-Compound having an isocyanate group-
The undercoat composition preferably contains a compound having an isocyanate group.
It does not specifically limit as a compound which has an isocyanate group used for undercoat composition, A well-known isocyanate compound can be used.
The compound having an isocyanate group may be either aliphatic or aromatic isocyanate, but aliphatic isocyanate is preferred from the viewpoint of safety and stability.
Moreover, the product marketed can also be used as a compound which has an isocyanate group. For example, Takenate series such as Takenate D103H, D204, D160N, D170N, D165N, D178NL, D110N (Mitsui Chemicals), Coronate HX, HXR, HXL, HXLV, HK, HK-T, HL, 2096 (Japan) Polyurethane Industry Co., Ltd.) is preferable.
Also, TM-550 and CAT-RT-37-2K (manufactured by Toyo Morton Co., Ltd.), X series solvent-free adhesives such as XC233-2 and XA126-1 (manufactured by Dainichi Seika Kogyo Co., Ltd.) A commercially available two-component mixed adhesive of an isocyanate compound and a polyol compound described later can also be used.

The compound which has an isocyanate group may be used individually by 1 type, or may use 2 or more types together.
The content of the compound having an isocyanate group is preferably 2 to 90% by mass, more preferably 5 to 80% by mass, and still more preferably 10 to 75% by mass with respect to the total mass of the undercoat composition. .

-Polyol compound-
The undercoat composition may contain a polyol compound.
As the polyol compound, a diol compound is preferable.
Although it does not specifically limit as a polyol compound, When an isocyanate compound is TM-550, when CAT-RT-37-2K (made by Toyo Morton Co., Ltd.) and an isocyanate compound are XC233-2, It is possible to use products that are commercially available as two-component mixed adhesives of isocyanate compounds and polyol compounds, such as X series useless adhesives such as XA126-1 (manufactured by Dainichi Seika Kogyo Co., Ltd.). .
A polyol compound may be used individually by 1 type, or may use 2 or more types together.
When the undercoat composition used in the present invention contains a polyol compound, the content of the polyol compound is preferably 5 to 50% by mass, and 10 to 40% by mass with respect to the total mass of the undercoat composition. It is more preferable.

-Binder polymer-
The primer composition may include a binder polymer. As the binder polymer, an inactive resin having no polymerizable group is preferable.
As the binder polymer, known binder polymers such as polyester resins, polyurethane resins, vinyl resins, acrylic resins, rubber resins can be used, but acrylic resins are preferable, and inert methyl methacrylate homopolymer and / or copolymer. A polymer is more preferred. For example, polymethyl methacrylate (molecular weight 10,000, catalog number 81497; molecular weight 20,000, catalog number 81498; molecular weight 50,000, catalog number 81501), methyl methacrylate / n-butyl methacrylate copolymer (mass) 85/15, molecular weight 75,000; catalog number 474029), etc .; ELVACITE 2013 (methyl methacrylate / n-butyl methacrylate copolymer, mass ratio 36/64, molecular weight 37,000), 2021, 614, manufactured by Lucite International 4025, 4026, 4028, etc .; Paramid DM55, B66, etc. manufactured by Rohm and Haas; BR113, 115, etc., manufactured by Diana America

The weight average molecular weight (Mw) of the binder polymer is preferably 1,000 or more, more preferably 1,000 to 1,000,000, and still more preferably 5,000 to 200,000. 8,000 to 100,000 is particularly preferable.
A binder polymer may be used individually by 1 type, or may use 2 or more types together.
The content of the binder polymer is preferably 0.2 to 15% by mass and more preferably 1 to 10% by mass with respect to the total mass of the undercoat composition.
When the content of the binder polymer is within the above range, a printed matter excellent in blocking inhibition can be obtained.

-Colorant-
The undercoat composition that can be used in the present invention may contain a colorant, but preferably contains or does not contain a white colorant, and more preferably does not contain it.
As the white pigment, Pigment White 6, 18, 21 or the like can be used depending on the purpose.
Further, when the undercoat composition contains a colorant, the content of the colorant is appropriately selected depending on the color and purpose of use, but is 0.01 to 30% by mass with respect to the total mass of the undercoat composition. It is preferable.

-Other ingredients-
The undercoat composition used in the present invention may contain a dispersant, a surfactant, a polymerization inhibitor, and other components.
The dispersant, surfactant, polymerization inhibitor, and other components used in the undercoat composition include the dispersant, surfactant, polymerization inhibitor, and other components in the ink composition of the present invention described above. Can be suitably used, and preferred embodiments are the same.

-Physical properties of the undercoat composition-
In the present invention, when the undercoat layer is provided by an ink jet method, the viscosity at 25 ° C. of the undercoat composition is preferably 40 mPa · s or less, more preferably 5 to 40 mPa · s, and even more preferably 7 in consideration of dischargeability. ˜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 to adjust the composition ratio of the undercoat composition appropriately so that the viscosity falls within the above range. By setting the viscosity at room temperature (25 ° C.) high, even when a porous recording medium (support) is used, penetration of the undercoat composition into the recording medium is avoided, and Reduction is possible.
The surface tension of the undercoat composition at 25 ° C. is preferably 15 mN / m to 40 mN / m, more preferably 20 mN / m to 35 mN / m, and further preferably 20 mN / m to 30 mN / m. preferable.

-Preparation of undercoat composition-
The undercoating composition can be prepared by stirring and mixing the components.
Here, when preparing the undercoat composition, all the components contained in the undercoat composition may be stirred and mixed at the same time, or the composition obtained by stirring and mixing the components other than the isocyanate compound and / or the radical polymerization initiator is stored. In addition, an undercoat composition may be prepared by adding an isocyanate compound and / or a radical polymerization initiator before use.
The undercoating composition is preferably applied to a recording medium within one day after preparation from the viewpoint of applicability.

<Lamination process>
The ink jet recording method of the present invention preferably further includes a laminating step of forming at least an adhesive layer and a laminating film on the image after the curing step.
The laminating step is more preferably a laminating step in which an adhesive layer and a laminate film are formed on the entire surface of the recording medium on the image side.
By laminating, elution and blocking of the ink composition components from the printed matter, and volatilization and elution of the residual monomer can be suppressed, and can be preferably used particularly for food packaging.
The adhesive layer is not particularly limited, and can be formed by applying a known adhesive by a known method.
As the laminate film, a resin film is preferably used, and examples thereof include a polyethylene terephthalate film, a polypropylene film, a nylon film, a polyvinyl chloride film, a polyethylene film, and a triacetyl cellulose film. Moreover, those films may be biaxially stretched.
In the laminating process, the laminate film may be bonded after the adhesive layer is formed on the image, or may be bonded on the image after the adhesive layer is first applied to the laminate film.
As a method for laminating, a known method can be used without any particular limitation, and dry lamination can be exemplified.
When a resin film is used as the base material, it is preferable to use a resin film having high adhesiveness with the resin film used on the surface on which the base material is laminated, although it depends on the laminating method selected. .

(Inkjet recording device)
The ink jet recording apparatus preferably used in the present invention will be further described in detail.
An ink jet recording apparatus suitably used in the present invention includes a transport unit that transports a recording medium, an applying unit that applies an undercoat composition onto the recording medium, and an ink jet ink composition onto the undercoat composition. It is preferable to have discharge means for discharging and ultraviolet irradiation means for irradiating ultraviolet rays.
The ink jet recording apparatus used in the present invention is preferably a so-called single pass ink jet recording apparatus.
FIG. 1 is a schematic diagram showing an example of an ink jet recording apparatus preferably used in the present invention. In addition, although the following apparatus has the exposure light source 17 for undercoating composition semi-hardening, even if it is an apparatus which does not have such a semi-hardening light source, it can be used conveniently for this invention.
The recording medium 12 stretched by the feeding roller 24 and the take-up roller 26 which is a conveying means of the recording medium 12 is conveyed in the direction of arrow A, and the undercoat composition is applied by the undercoat composition application roller 14. . Subsequently, the undercoating composition is semi-cured by the undercoating composition semi-curing exposure light source 17. Subsequently, the ink compositions of the respective colors (K: black, Y: yellow, M: magenta, C: cyan, W: white) are ejected by the inkjet heads 18K, 18C, 18M, 18Y, and 18W that discharge the ink compositions of the respective colors. ) Are ejected, and the ejected black, yellow, magenta and cyan ink compositions are semi-cured by the semi-curing exposure light sources 20K, 20C, 20M and 20Y installed immediately after the inkjet heads 18K, 18C, 18M and 18Y. Is done. The semi-curing exposure light sources 17, 20K, 20C, 20M, and 20Y are all ultraviolet exposure light sources. Finally, the recording medium is exposed in a poor oxygen atmosphere by the nitrogen purge ultraviolet exposure light source unit 22, and the whole of the undercoat composition and the ink composition that have been semi-cured are cured.
In the nitrogen purge ultraviolet exposure light source unit 22, for example, the ultraviolet light source is surrounded by an inert gas blanket, and is connected to an inert gas generator via an inert gas pipe to operate the inert gas generator. And the aspect by which the air in a blanket is substituted by an inert gas is mentioned preferably. As described above, nitrogen or the like can be used as the inert gas.
In FIG. 1, a nip roll 28 is provided to improve the conveyance accuracy. When the nip roll is used, more accurate transportability is realized, and registration deviation (landing position deviation) is suppressed. The nip roll 28 is not essential, and an ink jet recording apparatus that does not have a nip roll may be used.

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

The materials used in the present invention are as shown below.
<Colorant>
IRGALITE RED D3773 (CI Pigment Red 48: 4, magenta pigment, manufactured by BASF)
・ IRGALITE BLUE GLVO (Cyan pigment, manufactured by BASF Japan Ltd.)
・ NOVOPERM YELLOW H2G (yellow pigment, manufactured by Clariant)
・ SPECIAL BLACK 250 (black pigment, manufactured by BASF Japan)
・ Taipeke CR60-2 (white pigment, manufactured by Ishihara Sangyo Co., Ltd.)
<Dispersant>
・ EFKA7701 (BASF)
・ SOLSPERSE 32000 (Lubrizol)
<Component A>
SR341: 3-methyl-1,5-pentanediol diacrylate (Sartomer)
VEEA: 2- (2-vinyloxyethoxy) ethyl acrylate (manufactured by Nippon Shokubai Co., Ltd.)
DVE-3: triethylene glycol divinyl ether (BASF)
SR9003: propoxylation (2) neopentyl glycol diacrylate (Sartomer)
<Component B>
IRGACURE 819 (bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide (manufactured by BASF, molecular weight 419)
MI-3: (synthetic product, compound having the following structure, weight average molecular weight 1,270)
BMI 1500, long-chain alkyl bismaleimide oligomer (Designer Moleculars, compound with the following structure, molecular weight of about 1,500)
<Component C>
Speedcure 7010 (manufactured by Lambson, molecular weight 1,899)
<Polymerization inhibitor>
UV-22 (Irgastab (registered trademark) UV-22, Poly [oxy (methyl-1,2-ethanediyl)]-α, α ′, α ”-1,2,3-propanetriyltris [-[(1-oxo -2-propen-1-yl) oxy] -2,6-bis (1,1-dimethylethyl) -4- (phenylenemethylene) cyclohexa-2,5-dien-1-one], manufactured by BASF
<Surfactant>
BYK-307 (silicone surfactant, polyether-modified polydimethylsiloxane, manufactured by BYK Chemie)

[Synthesis of MI-3]
-Synthesis of maleimidoacetic acid-
A three-necked flask equipped with a condenser and a stirrer was charged with 30.0 g of glycine, 39.2 g of maleic anhydride and 500 ml of acetic acid, reacted at room temperature for 2 hours, and then reacted in an oil bath at 130 ° C. for 4 hours. Went. Acetic acid was distilled off under reduced pressure, and the resulting crude product was stirred in a mixed solvent of 500 mL of acetone and 1 L of toluene. After removing insolubles by filtration, the solvent was distilled off under reduced pressure, and ethyl acetate and water were added to carry out a liquid separation operation. The organic layer was dried over magnesium sulfate, the solvent was distilled off under reduced pressure, and recrystallization from ethyl acetate was performed to obtain 16.3 g of maleimidoacetic acid.

-Synthesis of maleimide compound (MI-3)-
In a three-necked flask, poly (propylene glycol) manufactured by Aldrich (polystyrene conversion value by GPC: number average molecular weight 950, weight average molecular weight 1,000) 5.0 g, maleimidoacetic acid 2.33 g, N, N-dimethyl-4 -After adding 0.03 g of aminopyridine and 50 mL of dehydrated THF and dissolving at room temperature, 3.1 g of N, N'-dicyclohexylcarbodiimide was added and reacted at room temperature for 4 hours. After evaporating the solvent under reduced pressure, the residue was purified by silica gel column chromatography using ethyl acetate as a developing solvent to obtain 2.50 g of the desired maleimide compound (MI-3). (Polystyrene conversion value by GPC: number average molecular weight 1,150, weight average molecular weight 1,270)

<Preparation of pigment dispersion (magenta)>
300 parts by mass of IRGALITE RED D3773, 1,050 parts by mass of SR341, and 150 parts by mass of EFKA7701 were stirred and mixed to obtain a magenta pigment dispersion. The magenta pigment dispersion 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 ink composition>
In the ratio shown in Table 1, each material was stirred and mixed for 20 minutes at 4,000 rpm at room temperature (25 ° C.) using a mixer (Silverson L4R). Examples 1 to 7 and Comparative Examples The ink compositions used in 1 to 3 were prepared. The numerical value of each component shown in Table 1 represents the content, and the unit is parts by mass. Moreover, the description of "-" in a table | surface means that the component is not contained.

<Curability evaluation>
The obtained ink composition was solid-printed on a PET (thickness 12 um) to a thickness of 6 μm with a Toshiba inkjet head (CA3), and then a nitrogen purge exposure machine (GS Yuasa Corporation). Manufactured by CSNT-40, light source: metal halide lamp), in an atmosphere having an oxygen concentration of 0.5 vol%, and the exposure is performed under the condition that the integrated exposure amount is 1,000 mJ / cm ² per exposure. A printed matter having a cured film thereon was obtained. The exposure was repeated until the cured film was touched with a finger and there was no stickiness. If the evaluation is A or B, there is no practical problem.
After creating the printed material, the curability was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1.
A: 1 time B: 2 times or more and 3 times or less C: 4 times or more and 6 times or less D: 7 times or more

<Odor evaluation>
A printed material produced by the same method as the evaluation of curability was cut into 5 cm squares, enclosed in a 10 cm × 10 cm plastic bag with a zip, and allowed to stand at room temperature (25 ° C.) for 24 hours. Thereafter, the zip was released, and the odor was evaluated according to the following evaluation criteria. If the evaluation is A or B, there is no practical problem. This evaluation was performed on a cured film that had been exposed six times. The evaluation results are shown in Table 1.
A: Almost odorless.
B: Although there is a certain odor, it is not an unpleasant level.
C: There is a very strong odor.

<Adhesion evaluation>
In accordance with the ink jet recording method, a solid image having an average film thickness of 12 μm was drawn on the evaluation substrate using the ink compositions of Examples and Comparative Examples, the ink image was cut into 5 cm × 2 cm, and JIS K5600-5-6: Evaluated according to the adhesion of the coating film (cross-cut method). As an evaluation base material, untreated polyethylene terephthalate (PET) (manufactured by Toray Industries, Inc., Lumirror T60) was used.
The evaluation criteria are shown below.
A: 1 or 0 in the evaluation described in JIS 5600-5-6
B: Either 2 or 3 in the evaluation described in JIS 5600-5-6 C: 4 or 5 in the evaluation described in JIS 5600-5-6
In addition, if it is evaluation A or B, it is an allowable range which does not have a problem practically.

As is clear from the results of Examples 1 to 7 and Comparative Examples 1 to 3, the molecular weight is 1,000 or more, the compound having two or more maleimide structures in the molecule and the molecular weight of 1,000 or more. By using a photosensitizer, a printed matter having a low odor and good adhesion was obtained. From the comparison between Example 1 and Examples 3 to 5 and Comparative Example 3, by including both Compound A-1 and Compound A-2, the ink was excellent in curability and excellent in odor and adhesion after curing. It can be seen that a composition was obtained.
As can be seen from the comparison between Example 1 and Example 2, the compound containing a (meth) acryloyloxy group and a vinyl ether group in the molecule (compound (compound)) contains a bifunctional or higher vinyl ether compound (compound A-2-1). The curability was better than that containing the same amount of A-2-2).
As shown by the comparison between Example 1 and Examples 3 to 5, the curability was excellent when the content of the bifunctional or higher vinyl ether compound (Compound A-2-1) was 5 to 40% by mass.

(Example 8)
A printed material was prepared in the same manner as in Example 6 except that an LED light source having a peak at 385 nm was used as the exposure light source and exposure was performed so that the integrated exposure amount was 2,000 mJ / cm ² . The cured sample was not sticky even when touched with a finger and was almost odorless.

Example 9
A printed matter was produced in the same manner as in Example 6 except that the exposure was performed in an atmosphere having an oxygen concentration of 1.5% by volume, and the curability, odor, and adhesion were evaluated.
The result of the curability evaluation was B, the result of the odor evaluation was B, and the result of the adhesion evaluation was C.

<Examples 10 to 13>
Similarly to the pigment dispersion (magenta), a pigment dispersion (yellow), a pigment dispersion (cyan), a pigment dispersion (black), and a pigment dispersion (white) were prepared under the composition and dispersion conditions shown in Table 2. .
As described in Table 3, except that the pigment dispersion (magenta) was changed to the pigment dispersion (yellow), pigment dispersion (cyan), pigment dispersion (black), or pigment dispersion (white), Ink compositions and printed materials were prepared in the same manner as in Example 6 and evaluated for curability, odor, and adhesion (Examples 10 to 13). The results of curable evaluation, odor evaluation, and adhesion evaluation in Examples 10 to 13 are shown in Table 3.

From the results shown in Table 3, the ink composition of the present invention containing a cyan pigment, yellow pigment, black pigment or white pigment is also excellent in curability, and the cured ink composition is excellent in odor and adhesion. It was.
From the results of Tables 1 and 3, the ink composition of the present invention, the magenta ink, the cyan ink, the yellow ink, the black ink, or the white ink, is excellent in curability, and excellent in odor and adhesion after curing. You can see that

<Example 14>
PET (thickness: 12 μm) was used with an inkjet head (CA3) manufactured by Toshiba Corporation using the ink compositions containing magenta, cyan, yellow, black, and white pigments prepared in Example 6 and Examples 10 to 13, respectively. A full-color image was formed on the top so as to have a thickness of 6 μm to 12 μm. Using a nitrogen purge exposure machine (manufactured by GS Yuasa Corporation, CSNT-40, light source: metal halide lamp), the integrated exposure amount is 1,000 mJ / per exposure in an atmosphere with an oxygen concentration of 0.5 vol%. Exposure was performed under the conditions of cm ² to obtain a printed material having a cured film on the substrate. The exposure was repeated until the cured film was touched with a finger and there was no stickiness.

  12: Recording medium, 14: Undercoating composition application roller, 17: Undercoating composition semi-curing exposure light source, 18K, 18C, 18M, 18Y, 18W: Inkjet head, 20K, 20C, 20M, 20Y: Semi-curing exposure Light source, 22: nitrogen purge exposure light source unit, 24: delivery roller, 26: take-up roller, 28: nip roll

Claims (8)

As component A, A-1: a bifunctional or higher functional (meth) acrylate compound, and A-2: a bifunctional or higher functional vinyl ether compound and / or a compound having a (meth) acryloyloxy group and a vinyl ether group, an ink composition Containing more than 75% by weight with respect to the total weight,
Component B contains 1 to 10% by mass of a compound having a molecular weight of 1,000 or more and having two or more maleimide structures in the molecule, based on the total mass of the ink composition,
As component C, a photosensitizer having a molecular weight of 1,000 or more is contained in an amount of 0.5 to 10% by mass based on the total mass of the ink composition,
An ink composition for ink jet recording, which is substantially free of a photopolymerization initiator having a molecular weight of less than 1,000. The ink composition for inkjet recording according to claim 1, wherein Component C comprises a compound having a skeleton represented by Formula C-1 in the molecule.

In formula C-1, R ¹ and R ² each independently represents an alkyl group having 1 to 5 carbon atoms or a halogen atom, i represents an integer of 2 to 4, and j represents an integer of 0 to 4 K represents an integer of 0 to 3, and X ¹ has 2 to 300 carbon atoms which may contain an ether bond (—O—) and / or an ester bond (— (C═O) —O—). Represents an i-valent hydrocarbon group.   The A-1 is contained at 35% by mass or more with respect to the total mass of the ink composition, and the A-2 is contained at 5 to 40% by mass with respect to the total mass of the ink composition. An ink composition for ink jet recording described in 1.   The inkjet recording ink composition according to any one of claims 1 to 3, wherein the content of water and a volatile solvent in the inkjet recording ink composition is less than 1 mass% with respect to the total mass of the ink composition. Ink composition.   The content of the monofunctional polymerizable compound in the ink composition for inkjet recording is less than 0.5% by mass with respect to the total mass of the polymerizable compound contained in the ink composition. The ink composition for inkjet recording according to any one of the above. A discharge step of discharging the ink composition for inkjet recording according to any one of claims 1 to 5 to a recording medium; and
An ink jet recording method comprising a curing step of irradiating and curing an active energy ray on an ink composition on a recording medium.   The ink jet recording method according to claim 6, wherein the curing step is performed in an atmosphere having an oxygen concentration of 1% by volume or less.   The inkjet recording method according to claim 6 or 7, wherein a light source used for irradiation of active energy rays in the curing step is a light emitting diode and / or a laser diode.

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