JP2022042842A - Ink composition and image recording method - Google Patents

Abstract

To provide an ink composition that allows recording of an infrared absorption image having excellent readability after abrasion or stretching, and an image recording method using the ink composition.SOLUTION: An ink composition contains an infrared absorption dye represented by the formula 1, a polymerizable compound, and a polymerization initiator. In the polymerizable compound, the proportion of monofunctional monomers is 70 mass% or more.SELECTED DRAWING: None

Description

The present disclosure relates to ink compositions and image recording methods.

An infrared absorbing dye that does not substantially absorb visible light but absorbs infrared rays has invisibility, and is therefore expected to be applied in the ink field.

For example, Patent Document 1 describes an active energy ray-curable ink containing a specific near-infrared absorber and a polymerizable compound.

Japanese Unexamined Patent Publication No. 2019-99733

Infrared-absorbing images recorded by inks containing infrared-absorbing dyes may be required to be durable against various external forces. In particular, readability after rubbing and readability after stretching may be required.

The present disclosure has been made in view of such circumstances, and the problem to be solved by the embodiment of the present invention is to record an infrared absorption image having excellent readability after rubbing and readability after stretching. It is to provide an ink composition capable of.
Another object to be solved by another embodiment of the present invention is to provide an image recording method capable of recording an infrared absorption image having excellent readability after rubbing and readability after stretching. be.

式１中、Ｒ^１及びＲ^２は、それぞれ独立に、１価の置換基を表す。
Ｒ^３及びＲ^４は、それぞれ独立に、水素原子又はアルキル基を表す。
Ｘ^１及びＸ^２は、それぞれ独立に、酸素原子、又は、－Ｎ（Ｒ^５）－を表す。
Ｒ^５は、水素原子、アルキル基、アリール基又はヘテロアリール基を表す。
Ｘ^３及びＸ^４は、それぞれ独立に、炭素原子、又は、ホウ素原子を表す。
ｔ及びｕは、Ｘ^３及びＸ^４がホウ素原子である場合には１を表し、Ｘ^３及びＸ^４が炭素原子である場合には２を表す。
Ｙ^１、Ｙ^２、Ｙ^３及びＹ^４は、それぞれ独立に、１価の置換基を表す。Ｙ^１とＹ^２、及び、Ｙ^３とＹ^４は、互いに結合して環を形成していてもよい。
Ｙ^１、Ｙ^２、Ｙ^３及びＹ^４は、それぞれ複数存在する場合には、互いに結合して環を形成していてもよい。
ｐ及びｓは、それぞれ独立に０～３の整数を表し、ｑ及びｒは、それぞれ独立に０～２の整数を表す。
＜２＞重合性化合物は、Ｎ－ビニルカプロラクタムを含み、Ｎ－ビニルカプロラクタムの含有量は、重合性化合物の全量に対して１５質量％～３５質量％である、＜１＞に記載のインク組成物。
＜３＞重合性化合物は、分子量が１０００以上の多官能オリゴマーを含む、＜１＞又は＜２＞に記載のインク組成物。
＜４＞多官能オリゴマーは、多官能ウレタン（メタ）アクリレートオリゴマーを含む、＜３＞に記載のインク組成物。
＜５＞多官能ウレタン（メタ）アクリレートオリゴマーの含有量は、インクの全量に対して１質量％～５質量％である、＜４＞に記載のインク組成物。
＜６＞アクリル樹脂をさらに含み、アクリル樹脂の含有量は、インク組成物の全量に対して０．５質量％～２質量％である、＜１＞～＜５＞のいずれか１つに記載のインク組成物。
＜７＞＜１＞～＜６＞のいずれか１つに記載のインク組成物が用いられ、基材上に、インクジェット記録方式を用いてインク組成物を付与するインク付与工程と、基材上に付与されたインク組成物に、活性エネルギー線を照射する活性エネルギー線照射工程と、を含む画像記録方法。
＜８＞活性エネルギー線照射工程は、第１の活性エネルギー線を照射して、基材上に付与されたインク組成物を半硬化させる半硬化工程と、第２の活性エネルギー線を照射して、半硬化したインク組成物を硬化させる本硬化工程と、を含む、＜７＞に記載の画像記録方法。 The disclosure includes the following aspects:
<1> An ink composition containing an infrared absorbing dye represented by the following formula 1, a polymerizable compound, and a polymerization initiator, in which the ratio of the monofunctional monomer to the polymerizable compound is 70% by mass or more.

In Formula 1, R ¹ and R ² each independently represent a monovalent substituent.
R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group.
X ¹ and X ² independently represent an oxygen atom or -N (R ⁵ )-.
R ⁵ represents a hydrogen atom, an alkyl group, an aryl group or a heteroaryl group.
X ³ and X ⁴ independently represent a carbon atom or a boron atom, respectively.
t and u represent 1 when X ³ and X ⁴ are boron atoms, and represent 2 when X ³ and X ⁴ are carbon atoms.
Y ¹ , Y ² , Y ³ and Y ⁴ each independently represent a monovalent substituent. Y ¹ and Y ² and Y ³ and Y ⁴ may be coupled to each other to form a ring.
When a plurality of Y ¹ , Y ² , Y ³ and Y ⁴ are present, they may be bonded to each other to form a ring.
p and s each independently represent an integer of 0 to 3, and q and r each independently represent an integer of 0 to 2.
<2> The ink composition according to <1>, wherein the polymerizable compound contains N-vinylcaprolactam, and the content of N-vinylcaprolactam is 15% by mass to 35% by mass with respect to the total amount of the polymerizable compound. thing.
<3> The ink composition according to <1> or <2>, wherein the polymerizable compound contains a polyfunctional oligomer having a molecular weight of 1000 or more.
<4> The ink composition according to <3>, wherein the polyfunctional oligomer contains a polyfunctional urethane (meth) acrylate oligomer.
<5> The ink composition according to <4>, wherein the content of the polyfunctional urethane (meth) acrylate oligomer is 1% by mass to 5% by mass with respect to the total amount of the ink.
<6> The acrylic resin is further contained, and the content of the acrylic resin is 0.5% by mass to 2% by mass with respect to the total amount of the ink composition, according to any one of <1> to <5>. Ink composition.
<7> The ink composition according to any one of <1> to <6> is used, and an ink applying step of applying the ink composition onto the substrate by using an inkjet recording method and an ink applying step on the substrate. An image recording method comprising an active energy ray irradiation step of irradiating the ink composition applied to the ink composition with an active energy ray.
<8> The active energy ray irradiation step is a semi-curing step of irradiating the first active energy ray to semi-cure the ink composition applied on the substrate, and a second active energy ray irradiation. The image recording method according to <7>, comprising the main curing step of curing the semi-cured ink composition.

According to the present disclosure, there is provided an ink composition capable of recording an infrared absorption image having excellent readability after rubbing and readability after stretching.
Further, the present disclosure provides an image recording method capable of recording an infrared absorption image having excellent readability after rubbing and readability after stretching.

Hereinafter, the ink composition of the present disclosure (hereinafter, also simply referred to as “ink”) and the image recording method will be described in detail.

The numerical range indicated by using "-" in the present specification means a range including the numerical values before and after "-" as the minimum value and the maximum value, respectively.
In the numerical range described in the present specification stepwise, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in another stepwise description. Further, in the numerical range described in the present specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.

In the present specification, the amount of each component in the composition is the total amount of the plurality of substances present in the composition unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition. Means.
In the present specification, a combination of two or more preferred embodiments is a more preferred embodiment.
In the present specification, the term "process" is included in this term not only as an independent process but also as long as the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes. Is done.

As used herein, "image" means film in general, and "image recording" means the formation of an image (ie, film). In addition, the concept of "image" in the present specification also includes a solid image.

As used herein, "(meth) acrylate" is a concept that includes both acrylates and methacrylates. Also, "(meth) acrylic" is a concept that includes both acrylic and methacrylic.

[ink]
The ink according to the present disclosure contains an infrared absorbing dye represented by the formula 1, a polymerizable compound, and a polymerization initiator, and the proportion of the monofunctional monomer in the polymerizable compound is 70% by mass or more.

In recent years, infrared-absorbing dyes have been attracting attention from the viewpoint of invisibility in security applications and the like. For example, Patent Document 1 discloses an ink containing a squarylium dye, but since it contains a compound having 3 to 6 (meth) acryloyl groups in an amount of 30% by mass to 60% by mass with respect to the total amount of the ink. It is considered that the readability is deteriorated by external force such as rubbing and stretching.

On the other hand, in the ink according to the present disclosure, since the ratio of the monofunctional monomer to the polymerizable compound is 70% by mass or more, an infrared absorption image having excellent readability after rubbing and readability after stretching can be obtained. Can be done.

(Infrared absorbing pigment)
The ink according to the present disclosure contains an infrared absorbing dye represented by the formula 1. The infrared absorbing dye contained in the ink may be one kind or two or more kinds.

式１中、Ｒ^１及びＲ^２は、それぞれ独立に、１価の置換基を表す。
Ｒ^３及びＲ^４は、それぞれ独立に、水素原子又はアルキル基を表す。
Ｘ^１及びＸ^２は、それぞれ独立に、酸素原子、又は、－Ｎ（Ｒ^５）－を表す。
Ｒ^５は、水素原子、アルキル基、アリール基又はヘテロアリール基を表す。
Ｘ^３及びＸ^４は、それぞれ独立に、炭素原子、又は、ホウ素原子を表す。
ｔ及びｕは、Ｘ^３及びＸ^４がホウ素原子である場合には１を表し、Ｘ^３及びＸ^４が炭素原子である場合には２を表す。
Ｙ^１、Ｙ^２、Ｙ^３及びＹ^４は、それぞれ独立に、１価の置換基を表す。Ｙ^１とＹ^２、及び、Ｙ^３とＹ^４は、互いに結合して環を形成していてもよい。
Ｙ^１、Ｙ^２、Ｙ^３及びＹ^４は、それぞれ複数存在する場合には、互いに結合して環を形成していてもよい。
ｐ及びｓは、それぞれ独立に０～３の整数を表し、ｑ及びｒは、それぞれ独立に０～２の整数を表す。

In Formula 1, R ¹ and R ² each independently represent a monovalent substituent.
R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group.
X ¹ and X ² independently represent an oxygen atom or -N (R ⁵ )-.
R ⁵ represents a hydrogen atom, an alkyl group, an aryl group or a heteroaryl group.
X ³ and X ⁴ independently represent a carbon atom or a boron atom, respectively.
t and u represent 1 when X ³ and X ⁴ are boron atoms, and represent 2 when X ³ and X ⁴ are carbon atoms.
Y ¹ , Y ² , Y ³ and Y ⁴ each independently represent a monovalent substituent. Y ¹ and Y ² and Y ³ and Y ⁴ may be coupled to each other to form a ring.
When a plurality of Y ¹ , Y ² , Y ³ and Y ⁴ are present, they may be bonded to each other to form a ring.
p and s each independently represent an integer of 0 to 3, and q and r each independently represent an integer of 0 to 2.

[R ¹ and R ² , X ³ and X ⁴ ]
In Equation 1, R ¹ and R ² may be the same or different, but are preferably the same.

Examples of the monovalent substituent represented by R ¹ and R ² include a halogen atom, a cyano group, a nitro group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an aralkyl group, and −OR ¹⁰ . , -COR ¹¹ , -COOR ¹² , -OCOR ¹³ , -NR ¹⁴ R ¹⁵ , -NHCOR ¹⁶ , -CONR ¹⁷ R ¹⁸ , -NHCONR ¹⁹ R ²⁰ , -NHCOOR ²¹ , -SR ²² , -SO ₂ R ²³ ,- Included are SO ₂ OR ²⁴ , -NHSO ₂ R ²⁵ , and SO ₂ NR ²⁶ R ²⁷ . R ¹⁰ to R ²⁷ each independently represent a hydrogen atom, an aliphatic group, an aromatic group, or a heterocyclic group.

When R ¹² of −COOR ¹² is a hydrogen atom (that is, a carboxyl group), the hydrogen atom may be dissociated (that is, a carbonate group) or may be in a salt state. Further, when R ²⁴ of —SO ₂ OR ²⁴ is a hydrogen atom (that is, a sulfo group), the hydrogen atom may be dissociated (that is, a sulfonate group) or may be in a salt state.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

The number of carbon atoms of the alkyl group is preferably 1 to 20, more preferably 1 to 15, and even more preferably 1 to 8. The alkyl group may be a linear alkyl group, a branched chain alkyl group, or a cyclic alkyl group, but a linear alkyl group or a branched chain alkyl group is preferable.

The alkenyl group preferably has 2 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, and particularly preferably 2 to 8 carbon atoms. The alkenyl group may be a linear alkenyl group, a branched chain alkenyl group, or a cyclic alkenyl group, but a linear alkenyl group or a branched alkenyl group is preferable.

The carbon number of the alkynyl group is preferably 2 to 40, more preferably 2 to 30, and particularly preferably 2 to 25. The alkynyl group may be a linear alkynyl group, a branched alkynyl group, or a cyclic alkynyl group, but a linear alkynyl group or a branched alkynyl group is preferable.

The aryl group preferably has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, and even more preferably 6 to 12 carbon atoms.

The alkyl moiety of the aralkyl group is the same as the above alkyl group. The aryl moiety of the aralkyl group is the same as the above aryl group. The carbon number of the aralkyl group is preferably 7 to 40, more preferably 7 to 30, and even more preferably 7 to 25.

The heteroaryl group is preferably a monocyclic ring or a condensed ring, preferably a monocyclic ring or a condensed ring having a condensed number of 2 to 8, and more preferably a monocyclic ring or a condensed ring having a condensed number of condensed rings of 2 to 4. The number of heteroatoms constituting the ring of the heteroaryl group is preferably 1 to 3. The hetero atom constituting the ring of the heteroaryl group is preferably a nitrogen atom, an oxygen atom or a sulfur atom. The heteroaryl group is preferably a 5-membered ring or a 6-membered ring. The number of carbon atoms constituting the ring of the heteroaryl group is preferably 3 to 30, more preferably 3 to 18, and even more preferably 3 to 12. Examples of heteroaryl groups include pyridine ring, piperidine ring, furan ring group, flufuran ring, thiophene ring, pyrrole ring, quinoline ring, morpholine ring, indole ring, imidazole ring, pyrazole ring, carbazole ring, phenothiazine ring, phenoxazine. Examples thereof include a ring, an indole ring, a thiazole ring, a pyrazole ring, a thiadiazine ring, a benzoquinoline ring, and a thiazylazole ring.

The alkyl group, alkenyl group, alkynyl group, aralkyl group, aryl group, and heteroaryl group may have a substituent or may be unsubstituted.

Examples of the substituent include the substituents described in paragraph No. 0030 of JP-A-2018-154672. Among them, the substituents are an alkyl group, an aryl group, an amino group, an alkoxy group, an aryloxy group, an aromatic heterocyclic oxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, an acylamino group and an alkoxycarbonylamino. Group, aryloxycarbonylamino group, sulfonylamino group, alkylthio group, arylthio group, aromatic heterocyclic thio group, sulfonyl group, hydroxy group, mercapto group, halogen atom, cyano group, sulfo group, or carboxy group. Preferably, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an aromatic heterocyclic oxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, an alkylthio group, an arylthio group, an aromatic heterocyclic thio group, More preferably, it is a sulfonyl group, a hydroxy group, a mercapto group, a halogen atom, a cyano group, a sulfo group, or a carboxy group.

The "carbon number" of the substituent means the "total carbon number" of the substituent.

For details of each substituent, refer to paragraph Nos. 0031 to 0 of JP-A-2018-154672.
You can refer to the substituents described in 035.

In formula 1, X ³ is preferably a carbon atom, and the two R ^1s are preferably bonded to each other to form a ring. X ⁴ is preferably a carbon atom, and the two R ^2s are preferably bonded to each other to form a ring.

The ring formed by bonding ^{two R1s} or two R2s to each other may be a monocyclic ring or a condensed ring. Examples of the ring formed by bonding two R ^1s or two R ^2s to each other include a benzene ring, a naphthalene ring, a pentalene ring, an inden ring, an azulene ring, a heptalene ring, an indecene ring, a perylene ring, and a pentacene ring. Acenaphthene ring, phenanthrene ring, anthracene ring, naphthalene ring, lysene ring, triphenylene ring, fluorene ring, biphenyl ring, pyrrole ring, furan ring, thiophene ring, imidazole ring, oxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyridine ring. , Pyridazine ring, indolidine ring, indole ring, benzofuran ring, benzothiophene ring, isobenzofuran ring, quinolysin ring, quinoline ring, phthalazine ring, naphthylidine ring, quinoxalin ring, quinoxazoline ring, isoquinoline ring, carbazole ring, phenanthrene ring. , Aclysin ring, phenanthrene ring, thianthrene ring, chromen ring, xanthene ring, phenoxatiin ring, phenothiazine ring, and phenazine ring. Above all, the ring formed by bonding ^{two R1s} or two R2s to each other is preferably a fluorene ring.

The ring formed by bonding ^{two R1s} or two R2s to each other may have a substituent. Examples of the substituent having the ring include the same substituents as the monovalent substituent represented by R ¹ and R ² .

The ring formed by bonding ^{two R1s} or two R2s to each other is preferably a ring represented by the following formula 2.

In formula 2, A ¹ to A ⁸ are independently hydrogen atom, alkyl group, alkenyl group, aryl group, aralkyl group, alkoxy group, aryloxy group, hydroxy group, amino group, -NR ⁶ R ⁷ , sulfo. Represents a group, -SO ₂ NR ⁸ R ⁹ , -COOR ¹⁰ , -CONR ¹¹ R ¹² , a nitro group, a cyano group, or a halogen atom. A ¹ to A ⁸ may be combined with each other to form a ring. R ⁶ to R ¹² independently represent a hydrogen atom, an alkyl group, an aryl group, an acyl group, or a pyridyl group. R ⁶ and R ⁷ , R ⁸ and R ⁹ , and R ¹¹ and R ¹² may be coupled to each other to form a ring. ^Q1 to ^Q4 independently represent a carbon atom or a nitrogen atom, and when ^Q1 to ^Q4 are nitrogen atoms, ^A1 , ^A4 , ^A5 and ^A8 do not exist. The two * indicate the binding site of the nitrogen atom and X ¹ that binds to X ³ in the formula 1 or the binding site of the nitrogen atom and X ² that binds to X ⁴ in the formula 1.

In the formula 2, the alkyl group represented by A ¹ to A ⁸ may be a linear alkyl group, a branched chain alkyl group, or a cyclic alkyl group. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a tert-butyl group, an isobutyl group, a tert-amyl group, a 2-ethylhexyl group, a stearyl group, a cyclopentyl group, and a cyclohexyl group. The alkyl group may have a substituent. Examples of the substituent include a halogen atom, an alkyl group, an alkoxy group, an amino group and a nitro group. Examples of the alkyl group having a substituent include a chloromethyl group, a trichloromethyl group, a trifluoromethyl group, a 2-methoxyethyl group, a 2-chloroethyl group, a 2-nitroethyl group, and a dimethylcyclohexyl group. Among them, the alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, and more preferably a methyl group or an ethyl group from the viewpoint of manufacturing suitability.

The alkenyl group represented by A ¹ to A ⁸ may be a linear alkenyl group, a branched chain alkenyl group, or a cyclic alkenyl group. Examples of the alkenyl group include a vinyl group, a 1-propenyl group, an allyl group, a 2-butenyl group, a 3-butenyl group, an isopropenyl group, an isobutenyl group, a 1-pentenyl group, a 2-pentenyl group, a 3-pentenyl group and a 4- Examples thereof include a pentenyl group, a 1-hexenyl group, a 2-hexenyl group, a 3-hexenyl group, a 4-hexenyl group, and a 5-hexenyl group. The alkyl group may have a substituent. Examples of the substituent include those similar to those of the substituent of the alkyl group. Among them, the alkenyl group is preferably an alkenyl group having 1 to 4 carbon atoms, and more preferably a vinyl group or an allyl group from the viewpoint of production suitability.

Examples of the aryl group represented by A ¹ to A ⁸ include a phenyl group and a naphthyl group. The aryl group may have a substituent. Examples of the substituent include those similar to those of the substituent of the alkyl group. Examples of the aryl group having a substituent include 4-methylphenyl group, 3,5-dimethylphenyl group, pentafluorophenyl group, 4-bromophenyl group, 2-methoxyphenyl group, 4-diethylaminophenyl group and 3-nitrophenyl group. Groups and 4-cyanophenyl groups are mentioned. Above all, the aryl group is preferably a phenyl group from the viewpoint of production suitability.

Examples of the aralkyl group represented by A ¹ to A ⁸ include a benzyl group, a phenethyl group, a phenylpropyl group, and a naphthylmethyl group. The aralkyl group may have a substituent. Examples of the substituent include those similar to those of the substituent of the alkyl group. Above all, the aralkyl group is preferably a benzyl group from the viewpoint of manufacturing aptitude.

The alkoxy group represented by A ¹ to A ⁸ may be a linear alkoxy group, a branched chain alkoxy group, or a cyclic alkoxy group. Examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an n-octyloxy group, a 2-ethylhexyloxy group, a cyclohexyloxy group, and a stearyloxy group. The alkoxy group may have a substituent. Examples of the substituent include those similar to those of the substituent of the alkyl group. Examples of the alkoxy group having a substituent include a trifluoromethoxy group and a 2- (diethylamino) ethoxy group.

Examples of the aryloxy group represented by A ¹ to A ⁸ include a phenoxy group and a naphthyloxy group. The aryloxy group may have a substituent. Examples of the substituent include those similar to those of the substituent of the alkyl group. Examples of the aryloxy group having a substituent include 4-methylphenyloxy group, 3,5-chlorophenyloxy group, 4-chloro-2-methylphenyloxy group, 4-tert-butylphenyloxy group and 4-methoxyphenyloxy group. Groups include 4-diethylaminophenyloxy groups, and 4-nitrophenyloxy groups.

Examples of the halogen atom represented by A ¹ to A ⁸ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

Examples of the alkyl group represented by R ⁶ to R ¹² include the same as the alkyl group represented by A ¹ to A ⁸ .

Examples of the aryl group represented by R ⁶ to R ¹² include the same aryl groups represented by A ¹ to A ⁸ .

Examples of the acyl group represented by R ⁶ to R ¹² include an acetyl group, a propionyl group, and a benzoyl group. The acyl group may have a substituent. Examples of the substituent include those similar to those of the substituent of the alkyl group. Examples of the acyl group having a substituent include a trifluoroacetyl group.

Examples of the pyridinyl group represented by R ⁶ to R ¹² include a 2-pyridinyl group, a 3-pyridinyl group, and a 4-pyridinyl group. The pyridinyl group may have a substituent. Examples of the substituent include those similar to those of the substituent of the alkyl group. Examples of the pyridinyl group having a substituent include a 2-methyl-4-pyridinyl group.

In Equation 2, Q ¹ to Q ⁴ independently represent a carbon atom or a nitrogen atom. It is preferable that all of ^Q1 to ^Q4 are carbon atoms.

Hereinafter, a specific example of the ring represented by the formula 2 will be shown.

[Y ¹ , Y ² , Y ³ , and Y ⁴ ]
Examples of the monovalent substituent represented by Y ¹ , Y ² , Y ³ and Y ⁴ in the formula 1 include the same monovalent substituent as R ¹ and R ² .

[P, q, r, and s]
In Equation 1, p, q, r, and s are preferably 0. That is, it is preferable that Y ¹ , Y ² , Y ³ and Y ⁴ do not exist in the formula 1.

[X ¹ and X ² ]
In Equation 1, X ¹ and X ² may be the same or different, but are preferably the same. X ¹ and X ² are preferably −N ⁽ R5) −.

The alkyl group, aryl group, and heteroaryl group represented by ^R5 may be unsubstituted or have a monovalent substituent. Examples of the monovalent substituent include monovalent substituents similar to those of R ¹ and R ² .

The number of carbon atoms of the alkyl group is preferably 1 to 20, more preferably 1 to 10, further preferably 1 to 4, and particularly preferably 1 to 2. The alkyl group may be linear or branched.

The aryl group preferably has 6 to 20 carbon atoms, more preferably 6 to 12 carbon atoms.

The heteroaryl group may be monocyclic or polycyclic. The number of heteroatoms constituting the ring of the heteroaryl group is preferably 1 to 3. The hetero atom constituting the ring of the heteroaryl group is preferably a nitrogen atom, an oxygen atom or a sulfur atom. The number of carbon atoms constituting the ring of the heteroaryl group is preferably 3 to 30, more preferably 3 to 18, and even more preferably 3 to 12.

R ⁵ is preferably a hydrogen atom, a methyl group, or an ethyl group, more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom.

[R ³ and R ⁴ ]
In Equation 1, R ³ and R ⁴ may be the same or different, but are preferably the same. The number of carbon atoms of the alkyl group represented by R ³ and R ⁴ is preferably 1 to 4, and more preferably 1 or 2. The alkyl group may be linear or branched. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and an isobutyl group. R ³ and R ⁴ are each independently preferably a hydrogen atom, a methyl group, or an ethyl group, more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom.

Specifically, the infrared absorbing dye represented by the formula 1 is preferably the infrared absorbing dye represented by the formula 3.

In formula 3, Z ¹ to Z ⁵ independently represent a hydrogen atom, a sulfo group, −SO ^-3- M ⁺ or a halogen atom, and M ⁺ represents a metal ion or an organic cation. A1 to ^A8 and ^Q1 to ^Q4 in Equation ³ are synonymous with A1 to ^A8 and ^Q1 to ^Q4 in Equation ¹ .

Examples of the halogen atom represented by Z ¹ to Z ⁵ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

Examples of the metal ion represented by M ⁺ include alkali metal cations (for example, sodium cation and potassium cation) and alkaline earth metal cations (for example, calcium cation).

Examples of the organic cation represented by M ⁺ include ammonium cation, pyridinium cation, imidazolium cation, phosphonium cation, and sulfonium cation.

In Formula 3, it is preferable that all of Z ¹ to Z ⁵ are hydrogen atoms from the viewpoint of robustness.

The infrared absorbing dye represented by the formula 1 is described in detail in Japanese Patent Application Laid-Open No. 2011-2080101, and the compound described here can be suitably used as the near infrared absorbing dye in the present disclosure.

Hereinafter, specific examples of the infrared absorbing dye represented by the formula 1 will be shown. However, the infrared absorbing dye represented by the formula 1 is not limited to the specific examples shown below. In the formula, "Me" represents a methyl group and "Ph" represents a phenyl group.

From the viewpoint of readability after rubbing and readability after stretching, the squarylium dye represented by the formula 1 includes Specific Examples B-1, B-3, B-4, B-6, B-9, and B-11. , B-21, B-22, B-24, B-25, B-26, B-27, or B-28.

The near-infrared absorbing dye represented by the formula 1 is preferably dispersed in the ink in the form of particles. From the viewpoint of light resistance, the average particle size of the near-infrared absorbing dye represented by the formula 1 is preferably 10 nm or more, more preferably 15 nm or more, further preferably 20 nm or more, and particularly preferably 50 nm or more. The average particle size of the squarylium dye represented by the formula 1 is preferably 400 nm or less, more preferably 300 nm or less, still more preferably 200 nm or less, from the viewpoint of dispersibility and ejection property.

The average particle size of the near-infrared absorbing dye represented by the formula 1 is the average particle size in the coated state when the near-infrared absorbing dye represented by the formula 1 is coated with a dispersant or the like. Point to.

The average particle size is the average particle size of scattered light measured by a dynamic light scattering method, and is measured using a particle size distribution measuring device. The average particle size is measured using, for example, a particle size distribution measuring device (product name “Zetasizer Nano ZS”, manufactured by Malvern Panasonic).

The molecular weight of the near-infrared absorbing dye represented by the formula 1 is preferably 100 to 2000, more preferably 150 to 1000. The molecular weight is calculated from the type and number of atoms constituting the near-infrared absorbing dye represented by the formula 1.

The content of the infrared absorbing dye represented by the formula 1 is preferably 0.2% by mass to 5% by mass, more preferably 0.5% by mass to 2% by mass, based on the total amount of the ink. preferable.

(Polymerizable compound)
The ink according to the present disclosure contains a polymerizable compound. The polymerizable compound contained in the ink may be one kind or two or more kinds.

Examples of the polymerizable compound include a photopolymerizable compound in which the polymerization reaction proceeds by irradiation with light, and a thermopolymerizable compound in which the polymerization reaction proceeds by heating or irradiation with infrared rays. Examples of the photopolymerizable compound include a polymerizable compound having a radically polymerizable group (that is, a radically polymerizable compound) and a polymerizable compound having a cationically polymerizable cationically polymerizable group (that is, a cationically polymerizable compound). ). Among them, the polymerizable compound is preferably a photopolymerizable compound, and more preferably a radically polymerizable compound.

The radically polymerizable compound is preferably an ethylenically unsaturated compound having an ethylenically unsaturated group. Examples of the ethylenically unsaturated compound include a monofunctional ethylenically unsaturated compound and a polyfunctional ethylenically unsaturated compound.

The monofunctional ethylenically unsaturated compound is a compound having one ethylenically unsaturated group, for example, monofunctional (meth) acrylate, monofunctional (meth) acrylamide, monofunctional aromatic vinyl compound, monofunctional vinyl ether and Examples include monofunctional N-vinyl compounds.

Examples of the monofunctional (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, hexyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. , Butyl-octyl (meth) acrylate, isoamyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) Acrylate, 4-n-Butylcyclohexyl (meth) acrylate, 4-tert-Butylcyclohexyl (meth) acrylate, Bornyl (meth) acrylate, Isobornyl (meth) acrylate, 2-ethylhexyldiglycol (meth) acrylate, Butoxyethyl ( Meta) acrylate, 2-chloroethyl (meth) acrylate, 4-bromobutyl (meth) acrylate, cyanoethyl (meth) acrylate, benzyl (meth) acrylate, butoxymethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, 2- (2-methoxyethoxy) ethyl (meth) acrylate, 2- (2-butoxyethoxy) ethyl (meth) acrylate, ethylcarbitol (meth) acrylate, 2,2,2-tetrafluoroethyl (meth) acrylate, 1H, 1H, 2H, 2H-perfluorodecyl (meth) acrylate, 4-butylphenyl (meth) acrylate, phenyl (meth) acrylate, 2,4,5-tetramethylphenyl (meth) acrylate, 4-chlorophenyl (meth) acrylate , 2-Phenoxymethyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, glycidyl (meth) acrylate, glycidyloxybutyl (meth) acrylate, glycidyloxyethyl (meth) acrylate, glycidyloxypropyl (meth) acrylate, tetrahydro Flufuryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) Acrylate, 3-hydroxybutyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, die Chilaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) acrylate, trimethoxysilylpropyl (meth) acrylate, trimethylsilylpropyl (meth) acrylate, polyethylene oxide monomethyl ether (meth) acrylate, polyethylene oxide (Meta) acrylate, polyethylene oxide monoalkyl ether (meth) acrylate, dipropylene glycol (meth) acrylate, polypropylene oxide monoalkyl ether (meth) acrylate, 2-methacryloyloxyethyl succinic acid, 2-methacryloyloxyhexahydrophthalic acid, 2-Methylloyloxyethyl-2-hydroxypropylphthalate, butoxydiethylene glycol (meth) acrylate, trifluoroethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, ethylene oxide (EO) modified phenol (meth) acrylate, EO modified cresol (meth) acrylate, EO modified nonylphenol (meth) acrylate, propylene oxide (PO) modified nonylphenol (meth) acrylate, EO modified -2-ethylhexyl (meth) acrylate, di Cyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, (3-ethyl-3-oxetanylmethyl) (meth) acrylate, phenoxyethylene glycol (meth) acrylate, and Cyclic trimethylol propanformal (meth) acrylate can be mentioned.

Examples of the monofunctional (meth) acrylamide include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, and Nn-butyl (meth) acrylamide. Nt-butyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl Examples include (meth) acrylamide and (meth) acryloylmorpholin.

Examples of the monofunctional aromatic vinyl compound include styrene, dimethylstyrene, trimethylstyrene, isopropylstyrene, chloromethylstyrene, methoxystyrene, acetoxystyrene, chlorostyrene, dichlorostyrene, bromostyrene, vinyl benzoic acid methyl ester, and 3-methyl. Styrene, 4-methylstyrene, 3-ethylstyrene, 4-ethylstyrene, 3-propylstyrene, 4-propylstyrene, 3-butylstyrene, 4-butylstyrene, 3-hexylstyrene, 4-hexylstyrene,3-octyl Styrene, 4-octyl styrene, 3- (2-ethylhexyl) styrene, 4- (2-ethylhexyl) styrene, allyl styrene, isopropenyl styrene, butenyl styrene, octenyl styrene, 4-t-butoxycarbonyl styrene and 4- Included is t-butoxystyrene.

Examples of the monofunctional vinyl ether include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, cyclohexylmethyl vinyl ether and 4-methyl. Cyclohexylmethyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl ether, tetrahydro Full frill vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexylmethyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chlorethyl vinyl ether, chlorbutyl vinyl ether, chlorethoxyethyl vinyl ether , Phenylethyl vinyl ether and phenoxypolyethylene glycol vinyl ether.

Examples of the monofunctional N-vinyl compound include N-vinylcaprolactam and N-vinylpyrrolidone.

The ink of the present disclosure preferably contains N-vinyl-ε-caprolactam from the viewpoint of making it difficult for the polymerization to be inhibited by oxygen.

The content of N-vinyl-ε-caprolactam is preferably 15% by mass to 35% by mass, more preferably 18% by mass to 30% by mass, based on the total amount of the polymerizable compound. When the content of N-vinyl-ε-caprolactam is 15% by mass to 35% by mass, an infrared absorption image having better readability after rubbing can be obtained.

The polyfunctional ethylenically unsaturated compound is a compound having two or more ethylenically unsaturated groups, and examples thereof include polyfunctional (meth) acrylates and polyfunctional vinyl ethers.

Examples of the polyfunctional (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, and dipropylene glycol di (meth). Acrylate, Tripropylene glycol di (meth) acrylate, Polyethylene glycol di (meth) acrylate, Polypropylene glycol di (meth) acrylate, Butylene glycol di (meth) acrylate, Tetraethylene glycol di (meth) acrylate, Neopentyl glycol di (meth) ) Acrylate, 3-Methyl-1,5-pentanediol di (meth) acrylate, hexanediol di (meth) acrylate, heptanediol di (meth) acrylate, EO-modified neopentyl glycol di (meth) acrylate, PO-modified neopentyl Glycoldi (meth) acrylate, EO-modified hexanediol di (meth) acrylate, PO-modified hexanediol di (meth) acrylate, octanediol di (meth) acrylate, nonanediol di (meth) acrylate, decanediol di (meth) acrylate , Dodecanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, glycerin di (meth) acrylate, pentaerythritol di (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl Etherdi (meth) acrylate, tricyclodecanedimethanol di (meth) acrylate, trimethylol ethanetri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane EO-added tri (meth) acrylate, pentaerythritol tri (Meta) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tri (meth) acryloyloxyethoxytrimethylol propane , Glycerin polyglycidyl ether poly (meth) acrylate, tris (2-acryloyloxyethyl) isocyanurate and 2- (2-vinyloxyethoxy) ethyl (meth) acrylate.

Examples of the polyfunctional vinyl ether include 1,4-butanediol divinyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, butylene glycol divinyl ether, and hexanediol di. Vinyl ether, 1,4-cyclohexanedimethanol divinyl ether, bisphenol A alkylene oxide divinyl ether, bisphenol F alkylene oxide divinyl ether, trimethylol ethane trivinyl ether, trimethylol propanetrivinyl ether, ditrimethylol propanetetravinyl ether, glycerin trivinyl ether, pentaerythritol Tetravinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol hexavinyl ether, EO-added trimethylol propanetrivinyl ether, PO-added trimethylolpropanetrivinyl ether, EO-added ditrimethylolpropane tetravinyl ether, PO-added ditrimethylolpropanetetravinyl ether, EO-added penta Examples thereof include erythritol tetravinyl ether, PO-added pentaerythritol tetravinyl ether, EO-added dipentaerythritol hexavinyl ether and PO-added dipentaerythritol hexavinyl ether.

The polymerizable compounds are Shinzo Yamashita, "Handbook of Crosslinking Agents" (1981, Taiseisha); Kiyomi Kato, "UV / EB Curing Handbook (Raw Materials)" (1985, Polymer Publishing Association); Ed., Radtech Study Group, "Application and Market of UV / EB Curing Technology", p. 79, (1989, CMC); Eiichiro Takiyama, "Polyester Resin Handbook", (1988, Nikkan Kogyo Shimbun), etc. It may be a commercially available product of.

In the ink according to the present disclosure, the ratio of the monofunctional monomer to the polymerizable compound is 70% by mass or more. When the ratio of the monofunctional monomer to the polymerizable compound is 70% by mass or more, an infrared absorption image having excellent readability after rubbing and excellent readability after stretching can be obtained. The ratio of the monofunctional monomer to the polymerizable compound is preferably 90% by mass or more, more preferably 95% by mass or more. The upper limit of the ratio of the monofunctional monomer to the polymerizable compound is not particularly limited, and is, for example, 100% by mass.

In the present disclosure, "monomer" means a compound having a molecular weight of less than 1000. That is, the "monofunctional monomer" means a compound having one polymerizable group and having a molecular weight of less than 1000. The molecular weight of a compound having a molecular weight of less than 1000 can be calculated based on the type and number of atoms constituting the compound after specifying the chemical structure of the compound by, for example, nuclear magnetic resonance (NMR).

The ink according to the present disclosure preferably contains a polyfunctional oligomer having a molecular weight of 1000 or more. When the ink contains a polyfunctional oligomer, the crosslink density is increased and the strength of the ink film is increased, so that an infrared absorption image having better readability after rubbing can be obtained.

The polyfunctional oligomer means a polymer having a molecular weight of less than 5000, and is distinguished from a so-called polymer (resin) in this respect. Further, the polyfunctional oligomer in the present disclosure does not include a dispersant described later (including a high molecular weight dispersant having a molecular weight of 1000 or more) in that it contains a polymerizable group.

The molecular weight of the polyfunctional oligomer is preferably 500 or more, more preferably 1000 or more. The molecular weight of the polyfunctional oligomer is preferably 5000 or less, and more preferably 3000 or less, from the viewpoint of ejection performance when the ink is ejected by the inkjet recording method.

A molecular weight having a molecular weight of 1000 or more is obtained, for example, as a weight average molecular weight. Weight average molecular weight means a value measured by gel permeation chromatography (GPC). For the measurement by GPC, HLC (registered trademark) -8020GPC (manufactured by Tosoh) was used as the measuring device, and TSKgel (registered trademark) Super Multipore HZ-H (4.6 mm ID x 15 cm, manufactured by Tosoh) was used as the column. In this use, THF (tetrahydrofuran) is used as the eluent. The measurement is performed using an RI detector with a sample concentration of 0.45% by mass, a flow rate of 0.35 ml / min, a sample injection amount of 10 μL, and a measurement temperature of 40 ° C. The calibration curve is "Standard sample TSK standard, polystyrene" manufactured by Tosoh Co., Ltd .: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-" It is made from 8 samples of "2500", "A-1000", and "n-propylbenzene".

Examples of the polyfunctional oligomer include a polyfunctional urethane (meth) acrylate oligomer, a polyfunctional polyester (meth) acrylate oligomer, a polyfunctional epoxy (meth) acrylate oligomer, and a polyfunctional silicon (meth) acrylate oligomer.

The polyfunctional urethane (meth) acrylate oligomer is a compound having a urethane structure and having two or more (meth) acryloyl groups. Urethane structures are usually formed of polyisocyanates and polyols.

Examples of the polyisocyanate for forming a urethane structure include aliphatic polyisocyanates and aromatic polyisocyanates. Above all, the polyisocyanate is preferably an aliphatic polyisocyanate from the viewpoint of improving the readability of the infrared absorption image after stretching. Examples of the polyol for forming a urethane structure include polyester polyols, polyether polyols, and polycarbonate polyols. Above all, the polyol is preferably a polyester polyol from the viewpoint of improving the readability of the infrared absorption image after scraping.

That is, the urethane structure of the polyfunctional urethane (meth) acrylate oligomer is preferably a structure derived from an aliphatic polyisocyanate and a polyester polyol.

The number of (meth) acryloyl groups in the polyfunctional urethane (meth) acrylate oligomer is 2 or more, preferably 2 to 6, and more preferably 2 to 4.

The polyfunctional polyester (meth) acrylate oligomer is a compound having an ester structure and having two or more (meth) acryloyl groups. The polyfunctional polyester (meth) acrylate oligomer does not contain a urethane structure. The polyfunctional polyester (meth) acrylate oligomer is produced, for example, by reacting a polyester polyol with (meth) acrylic acid.

The polyfunctional epoxy (meth) acrylate oligomer is a compound having a structure derived from an epoxy compound and having two or more (meth) acryloyl groups.

The polyfunctional silicon (meth) acrylate oligomer is a compound having a siloxane structure and having two or more (meth) acryloyl groups.

The polyfunctional oligomer preferably contains a polyfunctional urethane (meth) acrylate oligomer from the viewpoint of improving the readability of the infrared absorption image after scraping.

The content of the polyfunctional urethane (meth) acrylate oligomer is preferably 1% by mass to 5% by mass, preferably 2% by mass, based on the total amount of the ink, from the viewpoint of improving the readability of the infrared absorption image after rubbing. It is more preferably to 4% by mass.

When the content of the monofunctional monomer is 100 parts by mass, the content of the polyfunctional urethane (meth) acrylate oligomer is 2.0 parts by mass to 7 parts by mass from the viewpoint of improving the readability of the infrared absorption image after rubbing. It is preferably 5 parts by mass, more preferably 2 parts by mass to 5 parts by mass.

Further, the polyfunctional oligomer preferably contains a polyfunctional silicon (meth) acrylate oligomer from the viewpoint of improving the strength of the ink film.

The content of the polyfunctional silicon (meth) acrylate oligomer is preferably 0.5% by mass to 4% by mass, preferably 0.5% by mass, based on the total amount of the ink, from the viewpoint of improving the strength of the ink film. It is more preferably about 2% by mass.

(Dispersant)
The ink according to the present disclosure preferably contains at least one dispersant. For example, the infrared absorbing dye represented by the formula 1 and the dispersant are mixed to prepare a pigment dispersion liquid, and then the pigment dispersion liquid and other components are mixed to prepare the infrared absorbing dye represented by the formula 1. Can be contained in the ink. The dispersant referred to here is a compound having no polymerizable group, and the dispersant does not contain the polyfunctional oligomer.

As the dispersant, generally known ones can be used. The dispersant is preferably a compound having both a hydrophilic structure and a hydrophobic structure from the viewpoint of dispersion stability.

Examples of the dispersant include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, alkyl phosphates, polyoxyalkylene alkyl ether phosphates, and polyoxys. Examples thereof include low molecular weight dispersants having a molecular weight of less than 1000, such as alkylene alkylphenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin fatty acid ester, sorbitan fatty acid ester, polyoxyethylene fatty acid amide, and amine oxide.

Moreover, as a dispersant, a high molecular weight dispersant having a molecular weight of 1000 or more obtained by copolymerizing a hydrophilic monomer and a hydrophobic monomer can be mentioned. From the viewpoint of dispersion stability, the hydrophilic monomer is preferably a dissociative group-containing monomer, and is preferably a dissociative group-containing monomer having a dissociative group and an ethylenically unsaturated bond. Examples of the dissociable group-containing monomer include a carboxy group-containing monomer, a sulfonic acid group-containing monomer, and a phosphate group-containing monomer. From the viewpoint of dispersion stability, the hydrophobic monomer is an aromatic group-containing monomer having an aromatic group and an ethylenically unsaturated bond, or an aliphatic hydrocarbon having an aliphatic hydrocarbon group and an ethylenically unsaturated bond. It is preferably a group-containing monomer. The polymer may be either a random copolymer or a block copolymer.

The dispersant may be a commercially available product. As a commercial product, for example
DISPERBYK-101, DISPERBYK-102, DISPERBYK-103, DISPERBYK-106, DISPERBYK-110, DISPERBYK-111, DISPERBYK-161, DISPERBYK-162, DISPERBYK-163, DISPERBYK-164, DISPERBYK-164 168, DISPERBYK-170, DISPERBYK-171, DISPERBYK-174, and DISPERBYK-182 (manufactured by BYK Chemie);
SOLSPERSE3000, SOLSPERSE5000, SOLSPERSE9000, SOLSPERSE12000, SOLSPERSE13240, SOLSPERSE13940, SOLSPERSE17000, SOLSPERSE22000, SOLSPERSE24000, SOLSPERSE26000, SOLSPERSE28000, SOLSPERSE32000, SOLSPERSE35000, (manufactured by Lubrizol Corporation) SOLSPERSE36000, SOLSPERSE39000, SOLSPERSE41000, and SOLSPERSE71000;
TEGO® Dispers series (eg, TEGO Dispers 610, 610S, 630, 651, 655, 750W, and 755W) (Evonik);
Disparon® series (eg DA-375 and DA-1200) (manufactured by Kusumoto Kasei);
Floren series (eg, WK-13E, G-700, G-900, GW-1500, GW-1640, and WK-13E) (manufactured by Kyoei Chemical Industry Co., Ltd.);
EFKA® series (eg, EFKA PX 4701, EFKA PX 4731, and EFKA PX 4732) (manufactured by BASF) can be mentioned.

As a dispersion device for dispersing the infrared absorbing dye represented by the formula 1, a known dispersion device can be used, for example, a ball mill, a sand mill, a bead mill, a roll mill, a jet mill, a paint shaker, an attritor, and an ultrasonic wave. Dispersers and dispersers are included.

The ratio of the content of the dispersant to the content of the infrared absorbing dye represented by the formula 1 in the ink (that is, the content of the dispersant / the content of the infrared absorbing dye) is based on the mass from the viewpoint of dispersion stability. It is preferably 0.05 to 2.0, and more preferably 0.1 to 1.0.

(Polymer initiator)
The ink preferably contains at least one polymerization initiator. Examples of the polymerization initiator include a radical polymerization initiator that generates a radical, a cationic polymerization initiator, and an acid generator that generates an acid. Above all, the polymerization initiator is preferably a radical polymerization initiator.

Examples of the radical polymerization initiator include a hydroxyalkylphenone-based polymerization initiator, an acetophenone-based polymerization initiator, a benzophenone-based polymerization initiator, a benzoin-based polymerization initiator, a benzoin ether-based polymerization initiator, and an aminoalkylphenone-based polymerization initiator. Examples thereof include an oxime-based polymerization initiator, a thioxanthone-based polymerization initiator, and an acylphosphine oxide-based polymerization initiator.

Examples of the hydroxyalkylphenone-based polymerization initiator include 1-hydroxycyclohexylphenyl ketone and 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane-1-one.

Examples of the acetophenone-based polymerization initiator include acetophenone, 2,2-diethoxyacetophenone and p-dimethylaminoacetophenone.

Examples of the benzophenone-based polymerization initiator include benzophenone, 2-chlorobenzophenone, p, p'-dichlorobenzophenone, p, p'-bisdichloromethanebenzophenone, and Michler ketone.

Examples of the benzoin-based polymerization initiator and the benzoin ether-based polymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-propyl ether, benzoin isobutyl ether and benzoin n-butyl ether.

Oxime-based polymerization initiators include 1- [4- (phenylthio) phenyl] -1,2-octanedione-2- (O-benzoyloxime) and 1- [9-ethyl-6- (2-methylbenzoyl). ) -9H-carbazole-3-yl] etanone-1- (O-acetyloxime).

Examples of the thioxanthone-based polymerization initiator include thioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dichlorothioxanthone, 2-dodecylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dimethylthioxanthone. , 1-methoxycarbonylthioxanthone, 2-ethoxycarbonylthioxanthone, 3- (2-methoxyethoxycarbonyl) thioxanthone, 4-butoxycarbonylthioxanthone, 3-butoxycarbonyl-7-methylthioxanthone, 1-cyano-3-chlorothioxanthone, 1 -Ethoxycarbonyl-3-chlorothioxanthone, 1-ethoxycarbonyl-3-ethoxythioxanthone, 1-ethoxycarbonyl-3-aminothioxanthone, 1-ethoxycarbonyl-3-phenylsulfylthioxanthone, 3,4-di [2- (2) -Methoxyethoxy) ethoxycarbonyl] thioxanthone, 1-ethoxycarbonyl-3- (1-methyl-1-morpholinoethyl) thioxanthone, 2-methyl-6-dimethoxymethylthioxanthone, 2-methyl-6- (1,1-dimethoxy) Benzyl) thioxanthone, 2-morpholinomethylthioxanthone, 2-methyl-6-morpholinomethylthioxanthone, n-allylthioxanthone-3,4-dicarboxyimide, n-octylthioxanthone-3,4-dicarboxyimide, N- (1) , 1,3,3-Tetramethylbutyl) thioxanthone-3,4-dicarboxyimide, 1-phenoxythioxanthone, 6-ethoxycarbonyl-2-methoxythioxanthone, 6-ethoxycarbonyl-2-methylthioxanthone, thioxanthone-2- Examples include polyethylene glycol ester and 2-hydroxy-3- (3,4-dimethyl-9-oxo-9H-thioxanthone-2-yloxy) -N, N, N-trimethyl-1-propaneaminium chloride.

The thioxanthone-based polymerization initiator may be a commercially available product. Examples of commercially available products include SPEEDCURE series manufactured by Rambson (eg, SPEEDCURE 7010, SPEEDCURE CPTX, SPEEDCURE ITX, etc.).

Examples of the acylphosphine oxide-based polymerization initiator include bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, bis (2,6-dimethylbenzoyl) phenylphosphine oxide, and bis (2,4,6-trimethylbenzoyl)-. 2-methoxyphenylphosphine oxide, bis (2,6-dimethylbenzoyl) -2-methoxyphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,4-dimethoxyphenylphosphine oxide, bis (2,6) -Dimethylbenzoyl) -2,4-dimethoxyphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,4-dipentyloxyphenylphosphine oxide, bis (2,6-dimethylbenzoyl) -2,4- Dipentyloxyphenylphosphine oxide, 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide, 2,6-dimethylbenzoylethoxyphenylphosphine oxide, 2,4,6-trimethylbenzoylmethoxyphenylphosphine oxide, bis (2,6-dimethoxy) Benzoyl) -2,4,4-trimethylpentylphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,6-dimethylbenzoylmethoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyl (4-pentyl) Oxyphenyl) phenylphosphine oxide and 2,6-dimethylbenzoyl (4-pentyloxyphenyl) phenylphosphine oxide can be mentioned.

Among them, the acylphosphine oxide compound is preferably bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide or 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis (2,4,6-trimethylbenzoyl) phenylphosphine. Oxides are more preferred. The bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide is referred to as the product name "Omnirad 819" by IGM Resins B.I. V. It is available from the company. 2,4,6-trimethylbenzoyldiphenylphosphine oxide is referred to as the product name "Omnirad TPO H" by IGM Resins B.I. V. It is available from the company.

From the viewpoint of curability, the polymerization initiator preferably contains a thioxanthone-based polymerization initiator, contains a thioxanthone-based polymerization initiator, and comprises a hydroxyalkylphenone-based polymerization initiator and an acylphosphine oxide-based polymerization initiator. More preferably, it is at least one selected from the group.

The content of the polymerization initiator is preferably 3% by mass to 20% by mass, more preferably 5% by mass to 15% by mass, based on the total amount of the ink.

(resin)
The ink according to the present disclosure preferably contains a resin. When the ink contains a resin, an infrared absorption image having better readability after rubbing can be obtained. The resin referred to here does not have an action of dispersing the infrared absorbing dye represented by the formula 1, and is distinguished from the above-mentioned dispersant. Further, the resin referred to here does not have a polymerizable group and is distinguished from the above-mentioned polymerizable compound.

Examples of the resin include acrylic resin, cellulose derivative, epoxy resin, polyester, polyurethane, polyamide, polyvinyl chloride, polyimide, phenol resin, and silicone resin.

Above all, the resin is preferably an acrylic resin from the viewpoint of dispersion stability. That is, the ink according to the present disclosure preferably contains an acrylic resin. In the present disclosure, the "acrylic resin" refers to a polymer containing a structural unit derived from a (meth) acrylic compound.

The (meth) acrylic compound is a compound having an acryloyl group (CH ₂ = CH—C (= O) −) or a methacryloyl group (CH ₂ = C (CH ₃ ) −C (= O) −). Examples of the (meth) acrylic compound include (meth) acrylic acid, (meth) acrylic acid ester, and (meth) acrylamide.

The acrylic resin is preferably a polymer containing structural units derived from (meth) acrylic acid ester, more preferably a polymer containing structural units derived from methyl (meth) acrylate, and methyl poly (meth) acrylate. Is more preferable.

The content of the acrylic resin is preferably 0.5% by mass to 2% by mass with respect to the total amount of the ink from the viewpoint of improving the readability of the infrared absorption image after rubbing.

When the content of the monofunctional monomer is 100 parts by mass, the content of the acrylic resin is 0.75 parts by mass to 3.0 parts by mass from the viewpoint of improving the readability of the infrared absorption image after rubbing. Is preferable.

The weight average molecular weight of the resin is preferably 5,000 to 100,000, more preferably 10,000 to 50,000, from the viewpoint of ejection performance when the ink is ejected by the inkjet recording method.

The weight average molecular weight of the resin means a value measured by gel permeation chromatography (GPC). For the measurement by GPC, HLC (registered trademark) -8020GPC (manufactured by Tosoh Corporation) is used as a measuring device, and TSKgel (registered trademark) Super Multipore HZ-H (4.6 mm ID × 15 cm, manufactured by Tosoh Co., Ltd.) is used as a column. In this use, THF (tetrahydrofuran) is used as the eluent. The measurement is performed using an RI detector with a sample concentration of 0.45% by mass, a flow rate of 0.35 ml / min, a sample injection amount of 10 μL, and a measurement temperature of 40 ° C. The calibration curve is "Standard sample TSK standard, polystyrene" manufactured by Tosoh Co., Ltd .: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-" It is made from 8 samples of "2500", "A-1000", and "n-propylbenzene".

(Other ingredients)
In addition to the above components, the ink may be, for example, a polymerization inhibitor, a solid wetting agent, a wax, a surfactant, an anti-fading agent, an emulsion stabilizer, a penetration accelerator, an ultraviolet absorber, an antiseptic, and an antifungal agent. Other additives such as molds, pH regulators, viscosity regulators and the like may be included.

(Physical characteristics)
The pH of the ink is preferably 6.0 to 11.0, more preferably 7.0 to 10.0, and 7.0 to 9.0 from the viewpoint of storage stability of the ink. Is even more preferable.

The pH is measured at 25 ° C. using a pH meter, and is measured, for example, using a desktop pH meter (product name: LAQUAF-74S, manufactured by HORIBA, Ltd.).

The viscosity of the ink is preferably 1.0 mPa · s to 15.0 mPa · s, more preferably 2.0 mPa · s to 10.0 mPa · s, from the viewpoint of ink ejection property. It is more preferably 0 mPa · s to 8.0 mPa · s.

The viscosity is measured at 30 ° C. using a viscometer, and is measured, for example, using a viscometer (product name “TVB-22L”, manufactured by Toki Sangyo Co., Ltd.).

The surface tension of the ink is preferably 20 mN / m to 60 mN / m, more preferably 25 mN / m to 45 mN / m, from the viewpoint of ink ejection property.

The surface tension is measured at 25 ° C. using a surface tension meter, and is measured by a plate method using, for example, an automatic surface tension meter (product name “DY-300”, manufactured by Kyowa Surface Science Co., Ltd.).

[Ink set]
The ink according to the present disclosure may be combined with an undercoat composition to form an ink set. The ink set according to the present disclosure preferably includes the above ink and an undercoat composition containing an infrared reflective material.

The infrared reflective material contained in the undercoat composition is not particularly limited as long as it is a material having a function of reflecting infrared rays. The infrared reflective material is preferably at least one selected from the group consisting of titanium oxide, silver, aluminum, and indium from the viewpoint of improving the readability of the infrared absorbing image, and is preferably titanium oxide, silver, aluminum, or. Indium is more preferred, and titanium oxide or aluminum is even more preferred.

The content of the infrared reflective material is preferably 1% by mass to 10% by mass with respect to the total amount of the undercoat composition from the viewpoint of improving the readability of the infrared absorbing image.

The undercoat composition preferably contains at least one selected from the group consisting of a resin, a solvent, and a polymerizable compound as a component other than the infrared reflective material.

Further, the ink set according to the present disclosure may further include a topcoat composition. The topcoat composition is preferably a colorless and transparent clear ink.

The topcoat composition preferably contains a polymerizable compound and a polymerization initiator from the viewpoint of improving the readability of the infrared absorption image after scraping.

[Image recording]
The image recording material according to the present disclosure preferably includes a base material and an ink layer which is a solidified product of the ink provided on the base material. Further, the image recording material according to the present disclosure includes a base material, an undercoat layer containing an infrared reflective material provided on the base material, and an ink layer provided on the undercoat layer, which is a solidified form of the ink. , Are more preferred. Further, the image recording material according to the present disclosure preferably includes a base material, an ink layer which is a solidified product of the ink provided on the base material, and a top coat layer provided on the ink layer. ..

The solidified product contains a dried product of the ink and a cured product obtained by polymerizing the polymerizable compound in the ink.

When the undercoat layer containing the infrared reflective material is provided, the readability of the infrared absorbing image is improved.

When the topcoat layer is provided, the readability of the infrared absorption image after rubbing is improved.

(Base material)
The type of the base material is not particularly limited, and examples thereof include paper, cloth, wood, metal, and plastic.

The type of paper is not particularly limited, and examples thereof include general printing paper such as high-quality paper, coated paper, and art paper, and inkjet recording paper.

The substrate may be a non-permeable substrate. "Non-permeable" means that the amount of water absorbed is small or does not absorb water, and specifically, the amount of water absorbed is 10.0 g / m ² or less.

Examples of the impermeable substrate include metals (eg, aluminum) and plastics (eg, polyvinyl chloride resin, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate. , Polyethylene, Polystyrene, Polypropylene, Polycarbonate and Polyvinyl Acetal), and Glass. Among them, the base material is preferably polycarbonate or polyethylene terephthalate.

The impermeable substrate may be surface-treated.

Examples of the surface treatment include corona treatment, plasma treatment, frame treatment, heat treatment, wear treatment, light irradiation treatment (UV treatment), and flame treatment. Preliminarily applying corona treatment to the surface of the impermeable substrate increases the surface energy of the impermeable substrate, promotes the wetting of the surface of the impermeable substrate and the adhesion of ink to the impermeable substrate. To. The corona treatment can be performed using, for example, a corona master (manufactured by Shinko Electric Meter Co., Ltd., PS-10S). The conditions for the corona treatment may be appropriately selected according to the type of the impermeable substrate, the composition of the ink, and the like. For example, the following processing conditions can be mentioned.
-Processing voltage: 10 kV to 15.6 kV
-Processing speed: 30 mm / s to 100 mm / s

The thickness of the base material is not particularly limited, and is, for example, 25 μm to 500 μm.

(Undercoat layer)
The undercoat layer can be formed by applying the undercoat composition to the substrate. By using the undercoat composition containing the infrared reflective material, the undercoat layer containing the infrared reflective material can be formed.

The thickness of the undercoat layer is preferably 1 μm to 20 μm from the viewpoint of flexibility.

The undercoat layer may be provided on the entire base material or may be provided only on a part of the base material.

The undercoat layer may be provided as an image in the same manner as the ink layer described later.

(Ink layer)
The ink layer can be formed by applying the above ink on the base material or the undercoat layer.

The ink layer may be provided on the entire base material or the undercoat layer, or may be provided only on a part of the base material or the undercoat layer. When the undercoat layer is provided, it is preferable that the undercoat layer and the ink layer are provided so as to overlap each other at the same location on the substrate.

The ink layer is preferably provided as an image. The image is preferably a code image, and the code image is preferably a barcode, QR code (registered trademark) or dot code. A barcode is, for example, an image in which a plurality of lines having different thicknesses are arranged in a striped pattern. The QR code is, for example, an image in which a plurality of squares of different sizes are formed in a vertical and horizontal mosaic pattern. The dot code is, for example, an image in which extremely small points are arranged in a range of about 2 mm square. The dot code is provided as a "screen code" by Apollo Japan.

The thickness of the ink layer is preferably 5 μm to 20 μm from the viewpoint of ensuring the durability of the ink film. Further, when the undercoat layer is provided on the substrate, the ratio of the thickness of the ink layer to the thickness of the undercoat layer (that is, the thickness of the ink layer / the thickness of the undercoat layer) ensures the durability of the ink film. From the viewpoint of the above, it is preferably 0.5 to 2.

(Top coat layer)
The topcoat layer can be formed by applying the topcoat composition on the ink layer.

The thickness of the topcoat layer is preferably 5 μm to 20 μm from the viewpoint of ensuring the durability of the ink film.

The topcoat layer may be provided on the entire ink layer, or may be provided only on a part of the ink layer.

The topcoat layer may be provided as an image in the same manner as the ink layer.

[Image recording method]
In the image recording method according to the present disclosure, the above ink is used, and an ink applying step of applying ink to the base material by using an inkjet recording method and irradiation of the ink applied onto the base material with active energy rays. It is preferable to include an active energy ray irradiation step.

(Ink application process)
The ink applying step is a step of applying ink to the substrate by using an inkjet recording method.

The ink ejection method in the inkjet recording method is not particularly limited, and is a known method, for example, a charge control method for ejecting ink by using an electrostatic attraction force, or a drop-on-demand method (pressure) using the vibration pressure of a piezo element. (Pulse method), an acoustic inkjet method that converts an electric signal into an acoustic beam and irradiates the ink to eject the ink using radiation pressure, and a thermal inkjet method that heats the ink to form bubbles and uses the generated pressure. Any of the bubble jet (registered trademark) method may be used.

As an inkjet recording method, in particular, by the method described in Japanese Patent Application Laid-Open No. 54-59936, the ink subjected to the action of heat energy causes a rapid volume change, and the ink is ejected from the nozzle by the acting force due to this state change. The inkjet recording method for ejecting can be effectively used.

Further, for the inkjet recording method, the method described in paragraphs 093 to 0105 of JP-A-2003-306623 can also be referred to.

As the inkjet head used in the inkjet recording method, a short serial head is used, and a shuttle method in which recording is performed while scanning the head in the width direction of the base material and a recording element are arranged corresponding to the entire area of one side of the base material. A line method using a line head that has been used can be mentioned.

In the line method, a pattern can be formed on the entire surface of the base material by scanning the base material in a direction intersecting the arrangement direction of the recording elements, and a transport system such as a carriage for scanning a short head is not required.

In addition, the movement of the carriage and the complicated scanning control with the base material are not required, and only the base material moves, so that the recording speed can be increased as compared with the shuttle method.

The amount of ink ejected from the inkjet head is preferably 1 pL (picolitre) to 100 pL, more preferably 3 pL to 80 pL, and even more preferably 3 pL to 50 pL.

(Active energy ray irradiation process)
The active energy ray irradiation step is a step of irradiating the ink applied on the substrate with the active energy ray. The active energy ray irradiation step is a semi-curing step of irradiating the first active energy ray to semi-curing the ink applied on the substrate and a second semi-curing step from the viewpoint of improving the readability of the infrared absorption image. It is preferable to include a main curing step of irradiating with active energy rays to cure the semi-cured ink.

-Semi-curing process-
In the semi-curing step, the ink applied on the substrate is irradiated with the first active energy ray.
In the present disclosure, "semi-curing" means a state in which the polymerization rate of the polymerizable compound contained in the ink is 80% or less. The polymerization rate is preferably 10% or more. The polymerization rate is calculated by the following method.

After applying ink on the substrate, a sample piece having a size of 20 mm × 50 mm (hereinafter referred to as a sample piece after irradiation) is cut out from the film formed by irradiating the substrate with active energy rays. The cut out sample piece after irradiation is immersed in 10 mL of THF (tetrahydrofuran) for 24 hours to obtain an eluate in which the undercoat composition is eluted. With respect to the obtained eluate, the amount of the polymerizable compound (hereinafter referred to as "X1") is measured by high performance liquid chromatography.
Separately, after applying the undercoat composition on the substrate, the same operation as above is carried out except that the active energy rays are not irradiated, and the amount of the polymerizable compound (hereinafter referred to as “X2”) is measured. Using X1 and X2, the polymerization rate is calculated from the following formula.
Polymerization rate (%) = {(X2-X1) / X2} × 100

Examples of the first active energy ray include ultraviolet rays, visible rays and electron beams. Among them, the active energy rays are preferably ultraviolet rays (hereinafter, also referred to as “UV”).

The peak wavelength of ultraviolet rays is, for example, preferably 200 nm to 405 nm, more preferably 250 nm to 400 nm, and even more preferably 300 nm to 400 nm.

The exposure amount in the irradiation of the first active energy ray is preferably 3 mJ / cm ² to 100 mJ / cm ² and more preferably 5 mJ / cm ² to 20 mJ / cm ² from the viewpoint of semi-curing the ink. preferable.

As a light source for irradiating ultraviolet rays, a mercury lamp, a gas laser and a solid-state laser are mainly used, and a mercury lamp, a metal halide lamp and an ultraviolet fluorescent lamp are widely known. Further, UV-LED (light emitting diode) and UV-LD (laser diode) are small in size, have a long life, are highly efficient, and are low in cost, and are expected as light sources for ultraviolet irradiation. Above all, the light source for ultraviolet irradiation is preferably a metal halide lamp, a high-pressure mercury lamp, a medium-pressure mercury lamp, a low-pressure mercury lamp, or a UV-LED.

-Main curing process-
In this curing step, the semi-cured ink is irradiated with a second active energy ray.

In this curing step, it is preferable to cure the ink so that the polymerization rate of the polymerizable compound contained in the ink is more than 80% and 100% or less. The polymerization rate is more preferably 85% to 100%, still more preferably 90% to 100%.

Examples of the second active energy ray include ultraviolet rays, visible rays and electron beams, and among them, ultraviolet rays are preferable. Examples of the light source for irradiating ultraviolet rays include the above.

The peak wavelength of ultraviolet rays is, for example, preferably 200 nm to 405 nm, more preferably 250 nm to 400 nm, and even more preferably 300 nm to 400 nm.

The exposure amount in the irradiation of the second active energy ray is preferably 50 mJ / cm ² to 1000 mJ / cm ² and preferably 100 mJ / cm ² to 500 mJ / cm ² from the viewpoint of completely curing the ink. More preferred.

(Other processes)
The image recording method of the present disclosure may include a step other than the ink applying step and the active energy ray irradiation step.

The image recording method of the present disclosure may include, as another step, a step of applying the undercoat composition on the substrate and a step of irradiating the undercoat composition applied on the substrate with active energy rays. .. The step of irradiating the active energy ray may include a step of semi-curing the undercoat composition and a step of main-curing the semi-cured undercoat composition.

When the step of applying the undercoat composition on the base material is included, in the above ink applying step, the above ink is applied onto the base material to which the undercoat composition is applied.

Further, the image recording method of the present disclosure may include, as another step, a step of applying the topcoat composition after the above-mentioned ink applying step and the above-mentioned active energy ray irradiation step.

Hereinafter, the present disclosure will be described in more detail with reference to Examples, but the present disclosure is not limited to the following Examples as long as the gist of the present disclosure is not exceeded.

The details of the infrared absorbing dye, the polymerizable compound, the polymerization initiator, the dispersant, the resin, and the polymerization inhibitor used in Examples and Comparative Examples are shown below. In addition, FLORSTAB UV12 (manufactured by Kromachem) was used for the preparation of the ink. FLORSTAB UV12 is a mixture of N-nitroso-N-phenylhydroxylamine aluminum salt and PEA, and the content of PEA is 90% or more. Since the N-nitroso-N-phenylhydroxylamine aluminum salt is a polymerization inhibitor and PEA is a monofunctional polymerizable monomer, it is described separately in the columns of the polymerization inhibitor and the monofunctional polymerizable monomer in the table. For example, when the content of FLORSTAB UV12 contained in the ink was 0.2% by mass, PEA was 0.185% by mass and N-nitroso-N-phenylhydroxylamine aluminum salt was 0.015% by mass.

[Infrared absorbent dye]
B-24 to B-28, A-1 ... Compounds with the following structure

[Polymerizable compound]
<Monofunctional monomer>
-Isobornyl acrylate: Product name "SR506NS", manufactured by Sartmer, "IBOA" in the table.
-N-vinyl caprolactam ... Product name "V-CAP", manufactured by Ashland, "NVC" in the table
-Cyclic trimethylolpropane formal acrylate ... Product name "SR531", manufactured by Sartmer, "CTFA" in the table
-Phenoxyethyl acrylate ... Product name "SR339", manufactured by Sartmer, "PEA" in the table
The prepared ink includes PEA contained in FLORSTAB UV12 (manufactured by Kromachem) and PEA added as SR339.
<Bifunctional monomer>
-3-Methyl-1,5-pentadiol diacrylate ... Product name "SR341", manufactured by Sartmer, "3MPDDA" in the table
-Polyethylene glycol (600) diacrylate ... Product name "SR610", manufactured by Sartmer, "PEGDA" in the table
<Trifunctional monomer>
-Ethoxylation (3) Trimethylolpropane Triacrylate ... Product name "SR454 NS, manufactured by Sartmer," EOTMPTA "in the table)
-Trimethylolpropane triacrylate ... Product name "TMPTA", manufactured by Osaka Organic Chemical Industry Co., Ltd., "TMPTA" in the table
<6 functional monomers>
・ Dipentaerythritol hexaacrylate ... Product name "KAYARAD DPHA", manufactured by Nippon Kayaku Co., Ltd., "DPHA" in the table
<Polyfunctional oligomer>
-Urethane acrylate oligomer: Product name "CN964", manufactured by Sartmer, average number of functional groups 2, weight average molecular weight 3800, in the table, "urethane acrylate"
-Polyester acrylate oligomer: Product name "CN2302", manufactured by Sartmer, average number of functional groups 16, weight average molecular weight 1270, "polyester acrylate" in the table.
-Silicone acrylate oligomer: Product name "TEGORAD2100", "Silicon acrylate" in the table

[Polymer initiator]
1-Hydroxycyclohexylphenylketone ... Product name "Omnirad 184", IGM Resins B.I. V. Manufactured by isopropylthioxanthone ... Product name "Speedcure ITX", manufactured by LAMBSON, "ITX" in Table 2
-Bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide ... Product name "Omnirad 819", IGM Resins B. V. 2,4,6-trimethylbenzoyldiphenylphosphine oxide manufactured by IGM Resins B. product name "Omnirad TPO H". V. Made by the company

[Dispersant]
-Solspec 35000 (manufactured by Lubrizol)

[resin]
・ Acrylic resin: Product name "Dianal BR-113", manufactured by Mitsubishi Chemical Corporation, polymethyl methacrylate

[Polymerization inhibitor]
-Tris (N-nitroso-N-phenylhydroxylamine) aluminum salt ... "Nitroso compound" in the table contained in "FLORSTAB UV12" (manufactured by Kromachem)

<Example 1>
10 parts by mass of infrared absorbing dye S-1, 85 parts by mass of PEA, and 5 parts by mass of SOLPERSE35000 were mixed. Using a batch type bead mill (manufactured by AIMEX), the mixture was dispersed with zirconia beads having a diameter of 0.5 mm until the average particle size became 250 nm or less to obtain a dispersion liquid. The remaining components were mixed with this dispersion so as to have the composition shown in Table 1. An ink was prepared by stirring at room temperature (25 ° C.) at 5,000 rpm for 20 minutes using a mixer (product name "L4R", manufactured by Silberson).

<Examples 2 to 19 and Comparative Examples 1 to 3>
Inks were prepared in the same manner as in Example 1 except that the amount of each component charged was changed so as to have the compositions shown in Tables 1 and 2.

In Examples 2 to 19 and Comparative Examples 1 to 3, image recording was performed under the image recording conditions 1-1 to obtain an image recorded object. The details of the image description condition 1-1 are as follows.

<Image recording condition 1-1>
The prepared ink was introduced into the white throttle of an inkjet recording device (product name "Acity LED 1600R", manufactured by FUJIFILM Corporation). As a base material, PC (polycarbonate) film (trade name "Panlite" film thickness 500 μm, manufactured by Teijin Chemicals Ltd.), PET (polyethylene terephthalate) film (product name "Viewful UV TP-188", film thickness 188 μm, manufactured by Kimoto Co., Ltd.) ) Was prepared. A QR code (registered trademark) image, a dot image with a halftone dot ratio of 4%, and a solid image (Solid image) with a halftone dot ratio of 100% were recorded on the substrate. After recording the image, it was exposed. The resolution was 1200 dpi (dot per inch) × 1200 dpi, the number of passes was 48, and image recording was performed under the conditions of bidirectional printing. In the lampwork of the inkjet recording device, a pinning light source and a curing light source (main curing light source) were used, and it was set to perform two-step exposure. The time from the time of ink landing to the semi-curing exposure was 0.1 seconds, and the time from the time of ink landing to the main curing exposure was 2 seconds.

Using the obtained image recording material, the readability after rubbing and the readability after stretching were evaluated. The evaluation method is as follows. The evaluation results are shown in Tables 1 and 2. In the table, "ratio of monofunctional monomer" means the ratio of monofunctional monomer to the polymerizable compound. The "NVC content" means the content of NVC with respect to the total amount of the polymerizable compound.

(Readability after rubbing)
A friction test of 15 reciprocations was carried out using a gold cloth with a load of 200 g on the portion where the image recorded on the PET film was recorded. As the friction tester, a Gakushin type friction tester (product name "AB-301", manufactured by Tester Sangyo Co., Ltd.) was used. A reading test was performed on the portion where the dots were recorded after the friction test was performed. Ten locations were arbitrarily selected, and it was determined whether or not they could be read while irradiating IR-LED light using a HANDY Sope manufactured by Spectracorp. The evaluation criteria are as follows. In the following evaluation criteria, the rank with the best readability after scraping is "6".
6: 9 or 10 places were read.
5: 7 or 8 places were read.
4: 5 or 6 places were read.
3: 3 or 4 places were read.
2: 1 or 2 locations were read.
1: I couldn't read at all.

(Readability after stretching)
A heat stretching test was performed on the QR code image recorded on the PC film. The testing machine and stretching conditions are as follows.
Testing machine: Tensilon (manufactured by Shimadzu Corporation)
Stretching conditions: Image samples having a temperature of 180 ° C. and a tensile speed of 50 mm / min and a heating and stretching ratio of 140% and 40% were prepared.
The heat-stretching ratio is based on the length of the sample before heat-stretching (hereinafter referred to as "X1"; specifically, 5 cm) and the length of the sample after heat-stretching (hereinafter referred to as "X2"). , Calculated.
Heat stretching rate (%) = {(X2-X1) / X1} × 100
For example, when X2 is 15 cm, the heat stretching ratio is calculated to be 200%.
A reading test was performed on each of the prepared image samples. In the reading test, HANDY Scope manufactured by Spectracorp was used to determine whether or not the reading was possible. The evaluation criteria are as follows. In the following evaluation criteria, the rank with the best readability after stretching is "A".
A: All the image samples were read.
B: It could not be read in the image sample having a heat stretching ratio of 140%, but it could be read in the image sample having a heating stretching ratio of 40%.
C: None of the image samples could be read.

As shown in Tables 1 and 2, in Examples 1 to 19, the ink contains an infrared absorbing dye represented by the formula 1, a polymerizable compound, and a polymerization initiator, and is a simple compound among the polymerizable compounds. It was found that the ratio of the functional monomer was 70% by mass or more, and an infrared absorption image having excellent readability after rubbing and readability after stretching could be obtained.

On the other hand, in Comparative Example 1, it was found that the obtained infrared absorbing image was inferior in readability after rubbing because the infrared absorbing dye contained in the ink was not the infrared absorbing dye represented by the formula 1.

On the other hand, in Comparative Example 2 and Comparative Example 3, since the ratio of the monofunctional monomer to the polymerizable compound was less than 70% by mass, it was found that the obtained infrared absorption image was inferior in readability after stretching.

Example 7 is compared with Example 6 in which the content of N-vinylcaprolactam is 15% by mass to 35% by mass with respect to the total amount of the polymerizable compound, and the content of N-vinylcaprolactam is less than 15% by mass. Therefore, it was found that the readability of the infrared absorption image after scraping was excellent. It was found that Example 7 was superior in readability of the infrared absorption image after scraping as compared with Example 8 in which the content of N-vinylcaprolactam was more than 35% by mass.

Since Examples 9 and 10 contain a polyfunctional oligomer, it was found that the infrared absorption image is excellent in readability after rubbing as compared with claim 4 which does not contain the polyfunctional oligomer.

Since Example 10 contains a polyfunctional urethane (meth) acrylate oligomer, it was found that the readability of the infrared absorption image after rubbing is superior to that of Example 9 which does not contain the polyfunctional urethane (meth) acrylate oligomer. rice field.

In Example 10, since the content of the polyfunctional urethane (meth) acrylate oligomer is 1% by mass to 5% by mass, the content of Example 11 is less than 1% by mass, and the content is 5% by mass. It was found that the readability of the infrared absorption image after rubbing was excellent as compared with Example 12, which was more than%.

It was found that Examples 1 to 3 were superior in readability of the infrared absorption image after rubbing as compared with Example 4 containing the acrylic resin and not containing the acrylic resin.

Further, in Examples 1 and 2, the content of the acrylic resin is 0.5% by mass to 2% by mass with respect to the total amount of the ink, and the content of the acrylic resin is more than 2% by mass. It was found that the readability of the infrared absorption image after rubbing was excellent as compared with No. 3.

<Example 20 to Example 23>
Inks were prepared in the same manner as in Example 1 except that the amount of each component charged was changed so as to have the composition shown in Table 3.

In Examples 20 to 23, image recording was performed under the image recording condition 1-2 or the image recording condition 1-3 to obtain an image recorded object. The details of the image recording condition 1-2 and the image recording condition 1-3 are as follows.

<Image recording condition 1-2>
Under the image recording condition 1-2, the image recording and the exposure were performed by the same method as the image recording condition 1-1 except that the lampwork of the inkjet recording device was set to perform one-step exposure. The time from the time when the ink landed to the final curing exposure was 0.1 seconds.

<Image recording conditions 1-3>
In image recording conditions 1-3, image recording and exposure were performed in the same manner as in image recording conditions 1-1, except that the lampwork of the inkjet recording device was set to perform one-step exposure. The time from the time when the ink landed to the final curing exposure was 2 seconds.

Using the obtained image recording material, the readability after rubbing and the readability after stretching were evaluated. The evaluation results are shown in Table 3.

As shown in Table 3, it was found that in Example 1, the readability of the infrared absorption image after rubbing was superior to that of Examples 20 and 21 in which two-step exposure was performed and one-step exposure was performed. rice field. Similarly, in Example 17, it was found that the readability of the infrared absorption image after rubbing was excellent as compared with Examples 22 and 23 in which the two-step exposure was performed and the one-step exposure was performed.

<Examples 24 to 42>
A dispersion was prepared using CTFA instead of PEA in Example 1. Then, the ink was prepared by the same method as in Example 1 except that the amount of each component charged was changed so as to have the compositions shown in Tables 4 to 6.

In Examples 24 to 42, image recording was performed under any of the image recording conditions 2-1 to 2-6, and an image recorded object was obtained. The details of the image recording conditions 2-1 to 2-6 are as follows.

<Image recording condition 2-1>
In the image recording condition 2-1 in the same manner as in the image recording condition 1-1, except that the base material is changed to a white polyester film (product name "white coat 50-SN", manufactured by Nissei Shinka Co., Ltd.). , Image recording and exposure were performed.

<Image recording condition 2-2>
Under the image recording condition 2-2, the image recording and the exposure were performed by the same method as the image recording condition 2-1 except that the lampwork of the inkjet recording apparatus was set to perform one-step exposure. The time from the time when the ink landed to the final curing exposure was 0.1 seconds.

<Image recording conditions 2-3>
In the image recording condition 2-3, the image recording and the exposure were performed by the same method as the image recording condition 2-1 except that the lampwork of the inkjet recording device was set to perform one-step exposure. The time from the time when the ink landed to the final curing exposure was 2 seconds.

<Image recording conditions 2-4>
Under the image recording condition 2-4, after image recording and exposure are performed by the same method as the image recording condition 2-1, clear ink (product name “LL391”, FUJIFILM) is used as a topcoat composition on the recorded image. A solid image (solid image) with a halftone dot ratio of 100% was recorded using (manufactured by the company). After recording the image, it was exposed. Image recording and exposure using clear ink were performed under the same conditions as image recording condition 2-1.

<Image recording conditions 2-5>
Under the image recording condition 2-5, after image recording and exposure are performed by the same method as the image recording condition 2-2, clear ink (product name “LL391”, Fujifilm) is used as a topcoat composition on the recorded image. A solid image (solid image) with a halftone dot ratio of 100% was recorded using (manufactured by the company). After recording the image, it was exposed. Image recording and exposure using clear ink were performed under the same conditions as image recording condition 2-1.

<Image recording conditions 2-6>
In the image recording condition 2-6, after image recording and exposure are performed in the same manner as in the image recording condition 2-3, clear ink (product name "LL391", Fujifilm) is used as a topcoat composition on the recorded image. A solid image (solid image) with a halftone dot ratio of 100% was recorded using (manufactured by the company). After recording the image, it was exposed. Image recording and exposure using clear ink were performed under the same conditions as image recording condition 2-1.

Using the obtained image recording material, the readability after rubbing and the readability after stretching were evaluated. The evaluation results are shown in Tables 4 to 6.

As shown in Tables 4 to 6, in Examples 24 to 42, the ink contains an infrared absorbing dye represented by the formula 1, a polymerizable compound, and a polymerization initiator, and is a simple compound among the polymerizable compounds. It was found that the ratio of the functional monomer was 70% by mass or more, and an infrared absorption image having excellent readability after rubbing and readability after stretching could be obtained.

It was found that Example 24 was superior in readability of the infrared absorption image after rubbing as compared with Example 30 containing the polyfunctional urethane acrylate oligomer and not containing the polyfunctional urethane acrylate oligomer.

<Example 43 and Example 44>
An ink having the same composition as in Example 24 was prepared. In Example 43, the image was recorded under the image recording method condition 3-1 to obtain an image recorded object. In Example 44, the image was recorded under the image recording method condition 3-2, and an image recorded object was obtained. The details of the image recording condition 3-1 and the image recording condition 3-2 are as follows.

<Image recording condition 3-1>
The prepared ink was introduced into the yellow throttle of an inkjet recording device (product name "Acity LED 1600R", manufactured by FUJIFILM Corporation). As the white ink, UV curable ink for an inkjet printer (product name "LL021", manufactured by FUJIFILM Corporation) was used. As a base material, a polyethylene terephthalate film (product name "Viewful UV TP-188", manufactured by Kimoto Co., Ltd.) was prepared. A QR code (registered trademark) image and a 2-point line image were recorded on the substrate using white ink. After recording the image, it was exposed. Next, a QR code (registered trademark) image and a 2-point line image were superimposed and recorded on the recorded image using the prepared ink. After recording the image, it was exposed. The resolution was 1200 dpi (dot per inch) × 1200 dpi, the number of passes was 48, and image recording was performed under the conditions of bidirectional printing. In the lampwork of the inkjet recording device, a pinning light source and a curing light source (main curing light source) were used, and it was set to perform two-step exposure. The time from the time of landing of the white ink to the semi-curing exposure was 0.1 seconds, and the time from the time of landing of the prepared ink to the main curing exposure was 2 seconds.

<Image recording condition 3-2>
Under the image recording condition 3-2, the image is recorded by the same method as the image recording condition 3-1 except that the white ink used in the image recording condition 3-1 is changed to the metallic ink A containing aluminum. rice field.
(Preparation of metallic ink A)
The following components were mixed and stirred to prepare metallic ink A. Stirring was performed using a mixer (product name "L4R", manufactured by Silberson) at room temperature (25 ° C.) at 5,000 rpm for 20 minutes.
-Indium particle dispersion ... 12.5 parts by mass-3-Methyl-1,5-pentanediol diacrylate (product name "SR341", manufactured by Sartmer) ... 48.6 parts by mass-Isobornyl acrylate ... 10 parts by mass -N-vinylcaprolactum ... 20.7 parts by mass-2,4,6-trimethylbenzoyldiphenylphosphine oxide (product name "Omnirad TPO H", manufactured by IGM Resins B.V.) ... 2.0 parts by mass-bis ( 2,4,6-trimethylbenzoyl) phenylphosphine oxide (product name "Omnirad 819", manufactured by IGM Resins B.V.) ... 4.0 parts by mass, isopropylthioxanthone (product name "Speedcure ITX", manufactured by LAMBSON) … 2.0 parts by mass ・ Mixture of Tris (N-nitroso-N-phenylhydroxylamine) aluminum salt and PEA, PEA content is 90% or more (Product name “FLORSTAB UV12”, manufactured by Kromachem)… 0.2 Part by mass The above indium particle dispersion is obtained by concentrating "Leaf powder (registered trademark) 49CJ-1120" manufactured by Oike Kogyo Co., Ltd. (containing 20% by mass of indium particles (solid content) which are peeled pieces of an indium film). This is a dispersion liquid in which the dispersion liquid having an indium particle content of 60% by mass is replaced with PEA by decantation. The indium particle dispersion liquid contains 16% by mass of indium particles (solid content) which are stripped pieces of the indium film, the dispersion medium is mainly PEA, and PGME (propylene glycol monomethyl ether) is contained in the entire dispersion liquid. On the other hand, 1% by mass remains.

Using the obtained image recording material, the readability after rubbing was evaluated.

In Examples 43 and 44, the ink contains an infrared absorbing dye represented by the formula 1, a polymerizable compound, and a polymerization initiator, and the ratio of the monofunctional monomer to the polymerizable compound is 70% by mass or more. It was found that an infrared absorption image with excellent readability after rubbing can be obtained.

Examples 43 and 44 have an infrared absorbing image after scraping as compared to Example 24, which has an undercoat layer containing an infrared reflective material (ie, a layer formed of white ink) and no undercoat layer. It was found that the readability of the ink was excellent.

Claims (8)

It contains an infrared absorbing dye represented by the following formula 1, a polymerizable compound, and a polymerization initiator.
An ink composition in which the proportion of the monofunctional monomer in the polymerizable compound is 70% by mass or more.

In Formula 1, R ¹ and R ² each independently represent a monovalent substituent.
R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group.
X ¹ and X ² independently represent an oxygen atom or -N (R ⁵ )-.
^R5 represents a hydrogen atom, an alkyl group, an aryl group or a heteroaryl group.
X ³ and X ⁴ independently represent a carbon atom or a boron atom, respectively.
t and u represent 1 when X ³ and X ⁴ are boron atoms, and represent 2 when X ³ and X ⁴ are carbon atoms.
Y ¹ , Y ² , Y ³ and Y ⁴ each independently represent a monovalent substituent. Y ¹ and Y ² and Y ³ and Y ⁴ may be coupled to each other to form a ring.
When a plurality of Y ¹ , Y ² , Y ³ and Y ⁴ are present, they may be bonded to each other to form a ring.
p and s each independently represent an integer of 0 to 3, and q and r each independently represent an integer of 0 to 2. The polymerizable compound contains N-vinylcaprolactam.
The ink composition according to claim 1, wherein the content of the N-vinylcaprolactam is 15% by mass to 35% by mass with respect to the total amount of the polymerizable compound. The ink composition according to claim 1 or 2, wherein the polymerizable compound contains a polyfunctional oligomer having a molecular weight of 1000 or more. The ink composition according to claim 3, wherein the polyfunctional oligomer contains a polyfunctional urethane (meth) acrylate oligomer. The ink composition according to claim 4, wherein the content of the polyfunctional urethane (meth) acrylate oligomer is 1% by mass to 5% by mass with respect to the total amount of the ink composition. Contains more acrylic resin,
The ink composition according to any one of claims 1 to 5, wherein the content of the acrylic resin is 0.5% by mass to 2% by mass with respect to the total amount of the ink composition. The ink composition according to any one of claims 1 to 6 is used.
An ink applying step of applying the ink composition onto a substrate using an inkjet recording method,
An active energy ray irradiation step of irradiating the ink composition applied on the substrate with an active energy ray,
Image recording method including. The active energy ray irradiation step is
A semi-curing step of irradiating the first active energy ray to semi-curing the ink composition applied onto the substrate, and a semi-curing step.
The main curing step of irradiating the second active energy ray to cure the semi-cured ink composition, and
7. The image recording method according to claim 7.