JP2021105139A - Ink set and image recording method - Google Patents

Abstract

To provide an ink set capable of recording an image excellent in flexibility and curability and to provide an image recording method.SOLUTION: There are provided: an ink set which comprises an undercoat composition including an isocyanate compound and a radical polymerizable compound and an ink including a coloring agent and a radical polymerizable compound in which a ratio of a monofunctional polymerizable compound to the radical polymerizable compound included in the undercoat composition is 35 mass% to 70 mass% and a ratio of a monofunctional polymerizable compound to the radical polymerizable compound included in the ink is 30 mass% to 65 mass%; and an image recording method.SELECTED DRAWING: None

Description

The present disclosure relates to an ink set and an image recording method.

Conventionally, when an image is recorded on a base material using ink, a method of forming an undercoat layer on the base material in advance using an undercoat composition has been known.

For example, Patent Document 1 describes a step a of applying an undercoat composition to a recording medium to provide an undercoat layer, and a step b of an image forming step of ejecting ink onto the undercoat layer to form an image. And, as step c, a curing step of irradiating the undercoat layer and the ink with active light to cure the ink is included in this order, and the undercoat composition comprises a compound having an isocyanate group, a radically polymerizable monomer, and radical polymerization initiation. Described is an inkjet recording method comprising an agent and the ink containing a radically polymerizable monomer, a radical polymerization initiator, and a colorant.

Japanese Unexamined Patent Publication No. 2016-60049

Images recorded with an undercoat composition and ink may require flexibility and curability.

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 an ink set and an image recording method capable of recording an image having excellent flexibility and curability. Is to provide.

Specific means for solving the above problems include the following aspects.
<1> A monofunctional polymerizable compound containing an undercoat composition containing an isocyanate compound and a radically polymerizable compound and an ink containing a colorant and a radically polymerizable compound, which is included in the radically polymerizable compound contained in the undercoat composition. An ink set in which the ratio is 35% by mass to 70% by mass, and the ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the ink is 30% by mass to 65% by mass.
<2> The ink set according to <1>, wherein the monofunctional polymerizable compound contained in the undercoat composition has a glass transition temperature of −40 ° C. to 50 ° C. when a homopolymer is used.
<3> The ink set according to <1> or <2>, wherein the monofunctional polymerizable compound contained in the undercoat composition has a molecular weight of 140 to 210.
<4> The ink set according to any one of <1> to <3>, wherein at least one of the monofunctional polymerizable compounds contained in the ink is a hydroxy group-containing monofunctional polymerizable compound.
<5> The ink set according to <4>, wherein the ratio of the hydroxy group-containing monofunctional polymerizable compound to the radically polymerizable compound contained in the ink is 20% by mass to 50% by mass.
<6> The proportion of the monofunctional polymerizable compound in the radically polymerizable compound contained in the undercoat composition is A mass%, and the proportion of the monofunctional polymerizable compound in the radical polymerizable compound contained in the ink is B mass%. The ink set according to any one of <1> to <5>, wherein the absolute value of the difference between A and B is 20 or less.
<7> The ink set according to any one of <1> to <6> is used, and an undercoat composition applying step of applying an undercoat composition on a substrate and a first active energy for the undercoat composition. The first active energy ray irradiation step of irradiating the line, the ink applying step of applying the ink on the undercoat composition irradiated with the first active energy ray by the inkjet recording method, and the second active energy ray irradiating the ink. An image recording method including a second active energy ray irradiation step.
<8> The image recording method according to <7>, wherein in the second active energy ray irradiation step, the second active energy ray is irradiated in a nitrogen atmosphere.

The present disclosure provides an ink set and an image recording method capable of recording an image having excellent flexibility and curability.

Hereinafter, the ink set and the image recording method of the present disclosure 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 stepwise in the present specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. 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 as long as the intended purpose of the process is achieved, not only in an independent process but also in the case where it cannot be clearly distinguished from other processes. Is done.

In the present specification, the "image" means the entire film formed by applying the undercoat composition and the ink in this order, and the "image recording" means the formation of an image (that is, a 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 acrylate and methacrylate. In addition, "(meth) acrylic" is a concept that includes both acrylic and methacryl.

[Ink set]
The ink set of the present disclosure includes an undercoat composition containing an isocyanate compound and a radically polymerizable compound, and an ink containing a colorant and a radically polymerizable compound, and is monofunctional among the radically polymerizable compounds contained in the undercoat composition. The proportion of the polymerizable compound is 35% by mass to 70% by mass, and the proportion of the monofunctional polymerizable compound in the radically polymerizable compound contained in the ink is 30% by mass to 65% by mass.

In the ink set of the present disclosure, the ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the undercoat composition and the ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the ink are specific. Since it is in the numerical range, the recorded image has excellent flexibility and curability. On the other hand, Patent Document 1 specifically states that the content of the polyfunctional ethylenically unsaturated compound is 70% by mass or more with respect to the total content of the radically polymerizable monomer in the undercoat composition. , It is described that the content of the polyfunctional ethylenically unsaturated compound is 70% by mass or more with respect to the total content of the radically polymerizable monomer in the ink. Patent Document 1 describes that the obtained printed matter has good adhesion and is excellent in suppressing blocking, but does not pay attention to adhesion and curability.

Hereinafter, the undercoat composition constituting the ink set of the present disclosure and each component contained in the ink will be described.

<Undercoat composition>
In the present disclosure, the undercoat composition comprises an isocyanate compound and a radically polymerizable compound.

(Isocyanate compound)
The isocyanate compound contained in the undercoat composition is not particularly limited as long as it is a compound having an isocyanate group, but from the viewpoint of improving curability, it may be a polyfunctional isocyanate compound having two or more isocyanate groups in one molecule. preferable.

Examples of the bifunctional isocyanate compound having two isocyanate groups in one molecule include methylene diisocyanis, dimethylene diisocyanis, trimethylene diisocyanis, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, dipropyl ether diisocyanis, 2,2. − Didimethylpentane diisocyanate, 3-methoxyhexane diisocyanate, octamethylene diisocyanate, 2,2,4-trimethylpentane diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, 3-butoxyhexane diisocyanate, 1,4-butylene glycol dipropyl ether diisocyanate, An aliphatic diisocyanate such as thiodihexyl diisocyanate;
m-phenylenediocyanate, p-phenylenediocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, dimethylbenzene diisocyanate, ethylbenzene diisocyanate, isopropylbenzene diisocyanate, trizine diisocyanate, 1,4-naphthalenedi isocyanate, 1,5 Aromatic diisocyanates such as −naphthalenediocyanate, 2,6-naphthalenediocyanate, 2,7-naphthalenediocyanate, metaxylylene diisocyanate, paraxylylene diisocyanate, tetramethylxylylene diisocyanate; and hydrogenated xylylene diisocyanate, isophorone diisocyanate, dicyclohexyl Examples thereof include alicyclic diisocyanates such as methane 4,4'-diisocyanate.

The isocyanate compound may be a biuret form or an isocyanurate form which is a trimeric of a bifunctional isocyanate compound, and is an adduct (that is, an adduct form) of a polyol such as trimethylolpropane and a bifunctional isocyanate compound. It may be an adduct (that is, an allophanate) of an alcohol such as methanol and a bifunctional isocyanate compound.

Among them, from the viewpoint of adhesion between the substrate and the image, the isocyanate compound is preferably an aliphatic isocyanate compound, and more preferably an aliphatic isocyanate compound having two or more isocyanate groups in one molecule. It is more preferably an aliphatic diisocyanate, an isocyanurate of an aliphatic diisocyanate, an allophanate of an aliphatic diisocyanate and an alcohol, or an adduct of an aliphatic diisocyanate and a polyol, and an aliphatic diisocyanate or an isocyanurate of an aliphatic diisocyanate. It is particularly preferred to be a body.

The isocyanate compound may be a commercially available product on the market. Commercially available products include, for example, bamboo series (manufactured by Mitsui Chemicals, Inc.) such as Takenate D103H, D204, D160N, D170N, D165N, D178NL, D110N, and Coronate HX, HXR, HXL, HXLV, HK, HK-T, HL. , 2096 (manufactured by Nippon Polyurethane Industry Co., Ltd.).

The content of the isocyanate compound in the undercoat composition is preferably 2% by mass to 90% by mass, more preferably 5% by mass to 70% by mass, based on the total mass of the undercoat composition. More preferably, it is by mass% to 50% by mass.

The isocyanate compound may be contained alone or in combination of two or more in the undercoat composition.

(Radical polymerizable compound)
A radically polymerizable compound is a compound having at least one radically polymerizable group in one molecule. The radically polymerizable compound contained in the undercoat composition is composed of a monofunctional polymerizable compound having one radically polymerizable group and a polyfunctional polymerizable compound having two or more radically polymerizable groups. The proportion of the monofunctional polymerizable compound in the radically polymerizable compound contained in the undercoat composition is 35% by mass to 70% by mass. The balance obtained by subtracting the content of the monofunctional polymerizable compound from the total content of the radically polymerizable compound is the polyfunctional polymerizable compound.

In the present disclosure, since the proportion of the monofunctional polymerizable compound in the radically polymerizable compound contained in the undercoat composition is 35% by mass or more, it is possible to record an image having excellent flexibility. On the other hand, since the proportion of the monofunctional polymerizable compound in the radically polymerizable compound contained in the undercoat composition is 70% by mass or less, an image having excellent curability can be recorded. In addition, it is possible to suppress the phenomenon (so-called migration) in which unreacted monomer components are transferred to the outside from the image recording material. In particular, it is excellent in that it can be applied to packaging materials in the food packaging field and the cosmetic packaging field where the safety of the base material is strictly required.

The ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the undercoat composition is preferably 45% by mass to 65% by mass from the viewpoint of improving the flexibility and curability of the recorded image. It is more preferably 50% by mass to 65% by mass.

The content of the radically polymerizable compound in the undercoat composition is preferably 60% by mass to 95% by mass, more preferably 65% by mass to 90% by mass, based on the total mass of the undercoat composition. , 75% by mass to 85% by mass is more preferable.

-Monofunctional polymerizable compound-
The monofunctional polymerizable compound is not particularly limited as long as it is a compound having one radically polymerizable group. The radically polymerizable group is not particularly limited as long as it is a group capable of causing a polymerization reaction, but is preferably an ethylenically unsaturated group from the viewpoint of curability.

Examples of the monofunctional ethylenically unsaturated compound include monofunctional (meth) acrylate, monofunctional (meth) acrylamide, monofunctional aromatic vinyl compound, monofunctional vinyl ether and monofunctional N-vinyl compound.

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. , Tert-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-ethylhexyl diglycol (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, ethyl carbitol (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, 3-hydroxybutyl (meth) Acrylate, 4-hydroxybutyl (meth) acrylate, cyclic trimethylolpropanformal (meth) a Crylate, phenylglycidyl ether (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) acrylate, trimethoxysilylpropyl (meth) acrylate, trimethylsilyl Propyl (meth) acrylate, polyethylene oxide monomethyl ether (meth) acrylate, polyethylene oxide (meth) 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-methacryloyloxyethyl-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 (Meta) acrylate, EO modified -2-ethylhexyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, (3-ethyl-3-3) Examples thereof include oxetanylmethyl) (meth) acrylate and phenoxyethylene glycol (meth) acrylate.

Examples of the monofunctional (meth) acrylamide include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-n-butyl (meth) acrylamide, and the like. N-t-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 Flufuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexylmethylvinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chlorethyl vinyl ether, chlorbutyl vinyl ether, chloroethoxyethyl vinyl ether , Phenylethyl vinyl ether and phenoxypolyethylene glycol vinyl ether.

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

The monofunctional polymerizable compound contained in the undercoat composition is preferably a monofunctional (meth) acrylate from the viewpoint of improving the curability of the recorded image.

The monofunctional polymerizable compound contained in the undercoat composition preferably has a glass transition temperature of −40 ° C. to 90 ° C., more preferably −40 ° C. to 80 ° C., and −40 ° C. when used as a homopolymer. The temperature is more preferably 0 ° C to 50 ° C, and more preferably 0 ° C to 30 ° C. When the glass transition temperature is −40 ° C. or higher, an image having better curability can be recorded. Further, when the glass transition temperature is 90 ° C. or lower, an image having more flexibility can be recorded.

When the undercoat composition contains a plurality of monofunctional polymerizable compounds, it is preferable that the average value of the glass transition temperature in the case of homopolymer is in the above range. That is, for the monofunctional polymerizable compound contained in the undercoat composition, the glass transition temperature when homopolymerized is measured, the average value of the measured values is calculated, and the calculated value is preferably in the above range. ..

The glass transition temperature when the monofunctional polymerizable compound was used as a homopolymer was measured by the following method. First, a homopolymer having a weight average molecular weight of 10,000 to 20,000 is produced using a monofunctional polymerizable compound. The glass transition temperature of the homopolymer produced is measured according to the method described in JIS K7121: 2012. The glass transition temperature is measured using a differential scanning calorimeter, for example, using the product name "DSC-60" manufactured by Shimadzu Corporation. The weight average molecular weight is measured using a gel permeation chromatograph (GPC). For example, HLC-8220GPC (manufactured by Tosoh Corporation) is used as the GPC, three TSKgel and Super Multipore HZ-H (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) are used as columns, and THF (tetrahydrofuran) is used as the eluent. Use. The conditions are a sample concentration of 0.45% by mass, a flow rate of 0.35 ml / min, a sample injection amount of 10 μl, a measurement temperature of 40 ° C., and detection using a differential refractive index (RI) detector. As a standard sample, the calibration curve is a product name "TSK standard polystyrene" manufactured by Tosoh Co., Ltd .: "F-40", "F-20", "F-4", "F-1", "A-5000", It is prepared using 8 samples of "A-2500", "A-1000" and "n-propylbenzene". The glass transition temperature of the homopolymer fluctuates depending on the weight average molecular weight of the homopolymer, but when the weight average molecular weight is 10,000 to 20,000, the fluctuation is negligibly small.

The monofunctional polymerizable compound contained in the undercoat composition preferably has a molecular weight of 140 to 210, more preferably 180 to 210. When the molecular weight is 140 or more, an image having better curability can be recorded. Further, when the molecular weight is 210 or less, an image having more excellent flexibility and curability can be recorded.

The molecular weight is measured using a mass spectrometer, for example, the product name "API3200 System" manufactured by Siex.

The monofunctional polymerizable compound may be contained alone in the undercoat composition, or may be contained in two or more.

-Polyfunctional polymerizable compound-
The polyfunctional polymerizable compound is not particularly limited as long as it is a compound having two or more radically polymerizable groups. The radically polymerizable group is not particularly limited as long as it is a group capable of causing a polymerization reaction, but is preferably an ethylenically unsaturated group from the viewpoint of curability.

Examples of the polyfunctional ethylenically unsaturated compound include a polyfunctional (meth) acrylate compound and a polyfunctional vinyl ether.

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, decandiol 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 and tris (2-acryloyloxyethyl) isocyanurate.

Further, the polyfunctional (meth) acrylate may be a urethane (meth) acrylate which is a reaction product of a bifunctional isocyanate compound and a hydroxyl group-containing polyfunctional (meth) acrylate. Examples of the bifunctional isocyanate compound include the above. Examples of the hydroxyl group-containing polyfunctional (meth) acrylate include phenylglycidyl ether (meth) acrylate, pentaerythritol (meth) triacrylate and dipentaerythritol penta (meth) acrylate.

Further, the polyfunctional (meth) acrylate may be an epoxy (meth) acrylate which is a reaction product of (meth) acrylic acid and an epoxy resin. Examples of the epoxy resin include bisphenol A type epoxy resin and cresol novolac type epoxy resin.

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 trimethylolpropane trivinyl ether, PO-added trimethylolpropanetrivinyl ether, EO-added ditrimethylolpropanetetravinyl 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 polyfunctional polymerizable compound contained in the undercoat composition is preferably a polyfunctional (meth) acrylate from the viewpoint of improving the curability of the recorded image.

In the present disclosure, the undercoat composition may contain components other than the isocyanate compound and the radically polymerizable compound. Other components include polymerization initiators, surfactants and additives.

(Polymerization initiator)
The undercoat composition may contain at least one polymerization initiator. The polymerization initiator is preferably a radical polymerization initiator that generates radicals.

Examples of the radical polymerization initiator include (a) an alkylphenone compound, (b) an acylphosphine oxide compound, (c) an aromatic onium salt compound, (d) an organic peroxide, (e) a thio compound, and (f) a hexaary. Rubiimidazole compound, (g) ketooxime ester compound, (h) borate compound, (i) azinium compound, (j) metallocene compound, (k) active ester compound, (l) compound having carbon halogen bond, and (m) ) Alkylamine compounds can be mentioned.

The radical polymerization initiator is preferably (b) an acylphosphine oxide compound.

Examples of the acylphosphine oxide compound include bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, bis (2,6-dimethylbenzoyl) phenylphosphine oxide, and bis (2,4,6-trimethylbenzoyl) -2-methoxy. Phenylphosphine 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-dipentyloxyphenyl Phosphine oxide, 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide, 2,6-dimethylbenzoylethoxyphenylphosphine oxide, 2,4,6-trimethylbenzoylmethoxyphenylphosphine oxide, bis (2,6-dimethoxybenzoyl)- 2,4,4-trimethylpentylphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,6-dimethylbenzoylmethoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyl (4-pentyloxyphenyl) Examples include phenylphosphine oxide and 2,6-dimethylbenzoyl (4-pentyloxyphenyl) phenylphosphine oxide.

Among them, as the acylphosphine oxide compound, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide are preferable, and bis (2,4,6-trimethylbenzoyl) phenyl. Phosphine oxide is more preferred. Bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide has been introduced under the product name "Omnirad 819" by IGM Resins B. et al. V. It is available from the company.

The content of the polymerization initiator in the undercoat composition is preferably 1.0% by mass to 15.0% by mass, more preferably 1.5% by mass to 10.0% by mass, based on the total mass of the undercoat composition. It is preferable, and more preferably 2.0% by mass to 6.0% by mass.

(Surfactant)
The undercoat composition may contain at least one surfactant from the viewpoint of improving ejection stability when applied using an inkjet recording method.

Examples of the surfactant include those described in JP-A-62-173436 and JP-A-62-183457. Examples of the surfactant include anionic surfactants such as dialkyl sulfosuccinate, alkylnaphthalene sulfonate, and fatty acid salt; polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, acetylene glycol, and polyoxyethylene. -Nonionic surfactants such as polyoxypropylene block copolymers; and cationic surfactants such as alkylamine salts and quaternary ammonium salts. Further, the surfactant may be a fluorine-based surfactant or a silicone-based surfactant.

In the present disclosure, the surfactant is preferably a silicone-based surfactant from the viewpoint of improving the adhesion to the substrate. Examples of the silicone-based surfactant include polysiloxane compounds, and modified polysiloxane compounds in which an organic group is introduced into a part of the methyl group of dimethylpolysiloxane are preferable. Modifications include polyether denaturation, methylstyrene denaturation, alcohol denaturation, alkyl denaturation, aralkyl denaturation, fatty acid ester denaturation, epoxy denaturation, amine denaturation, amino denaturation, and mercapto denaturation. A plurality of types of organic machines may be introduced into a part of the methyl group of dimethylpolysiloxane. Above all, from the viewpoint of discharge stability, the silicone-based surfactant is preferably a polyether-modified polysiloxane compound.

Examples of the polyether-modified polysiloxane compound include SILWET L-7604, SILWET L-7607N, SILWET FZ-2104 and SILWET FZ-2161 (manufactured by Momentive Performance Materials Japan GK); BYK306, BYK307, BYK331, BYK333, BYK347 and BYK348 (manufactured by BYK Chemie); and KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, Examples thereof include KF-643, KF-6020, X-22-6191, X-22-4515, KF-6011, KF-6012, KF-6015 and KF-6017 (manufactured by Shin-Etsu Chemical Co., Ltd.).

The content of the surfactant in the undercoat composition is preferably 0.001% by mass to 4.0% by mass, more preferably 0.01% by mass to 3.0% by mass, based on the total mass of the undercoat composition. It is preferable, and more preferably 0.05% by mass to 2.0% by mass.

(Additive)
The undercoat composition may contain additives such as a cosensitizer, an ultraviolet absorber, an antioxidant, an antioxidant, a conductive salt, a solvent, and a basic compound, if necessary. Further, the undercoat composition may contain a colorant, but it is preferable not to contain it. When the undercoat composition contains a colorant, the colorant is preferably a white colorant. As the colorant, the same colorant as the colorant contained in the ink described later can be used. When the undercoat composition contains a colorant, the content of the colorant in the undercoat composition is preferably 0.01 to 30% by mass with respect to the total mass of the undercoat composition.

(Physical characteristics)
The pH of the undercoat composition is preferably 7 to 10, more preferably 7.5 to 9.5, from the viewpoint of improving ejection stability when applied using an inkjet recording method. The pH is measured at 25 ° C. using a pH meter, and is measured, for example, using a pH meter (model number "HM-31") manufactured by Toa DKK Corporation.

The viscosity of the undercoat composition is preferably 0.5 mPa · s to 30 mPa · s, more preferably 2 mPa · s to 20 mPa · s, preferably 2 mPa · s to 15 mPa · s, and 3 mPa. -It is more preferably s to 10 mPa · s. The viscosity is measured at 25 ° C. using a viscometer, and is measured, for example, using a TV-22 type viscometer manufactured by Toki Sangyo Co., Ltd.

The surface tension of the undercoat composition is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and even more preferably 25 mN / m to 45 mN / m. The surface tension is measured at 25 ° C. using a surface tensiometer, and is measured by a plate method using, for example, an automatic surface tension meter (product name "CBVP-Z") manufactured by Kyowa Surface Science Co., Ltd.

<Ink>
In the present disclosure, the ink comprises a colorant and a radically polymerizable compound.

(Colorant)
Colorants include dyes and pigments. From the viewpoint of durability such as heat resistance, light resistance, and water resistance, the colorant is preferably a pigment.

When a pigment is used as the colorant, the pigment can be contained in the ink as a pigment dispersion liquid. The pigment dispersion liquid is a liquid obtained by dispersing a pigment in a liquid medium using a dispersant, and contains at least a pigment, a dispersant, and a liquid medium. Details of the dispersant will be described later. Further, the liquid medium may be an organic solvent or a radically polymerizable compound described later.

As the pigment, either an organic pigment or an inorganic pigment which is usually commercially available can be used. Examples of pigments include "Dictionary of Pigments" edited by Seijiro Ito (2000), W.A. Herbst, K. et al. Examples thereof include pigments described in Hunger "Industrial Organic Pigments", JP-A-2002-12607, JP-A-2002-1880.25, JP-A-2003-26978, and JP-A-2003-342503.

The content of the colorant in the ink is preferably 0.001% by mass to 15.0% by mass, and preferably 0.01% by mass to 15.0% by mass, based on the total mass of the ink. More preferably, 2.0% by mass to 15.0% by mass is further preferable.

The colorant may be contained alone in the ink, or may be contained in two or more kinds.

(Radical polymerizable compound)
The radically polymerizable compound contained in the ink is composed of a monofunctional polymerizable compound having one radically polymerizable group and a polyfunctional polymerizable compound having two or more radically polymerizable groups. The ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the ink is 30% by mass to 65% by mass. The balance obtained by removing the monofunctional polymerizable compound from the radically polymerizable compound is a polyfunctional polymerizable compound.

In the present disclosure, since the ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the ink is 30% by mass or more, it is possible to record an image having excellent flexibility. On the other hand, since the ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the ink is 65% by mass or less, an image having excellent curability can be recorded. In addition, it is possible to suppress the phenomenon (so-called migration) in which unreacted monomer components are transferred to the outside from the image recording material. In particular, it is excellent in that it can be applied to packaging materials in the food packaging field and the cosmetic packaging field where the safety of the base material is strictly required.

The ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the ink is preferably 35% by mass to 50% by mass, preferably 40% by mass, from the viewpoint of improving the flexibility and curability of the recorded image. It is more preferably% to 50% by mass.

The content of the radically polymerizable compound in the ink is preferably 60% by mass to 98% by mass, more preferably 70% by mass to 95% by mass, and 70% by mass, based on the total mass of the ink. ~ 90% by mass is more preferable.

-Monofunctional polymerizable compound-
The monofunctional polymerizable compound is not particularly limited as long as it is a compound having one radically polymerizable group. The radically polymerizable group is not particularly limited as long as it can cause a radical polymerization reaction, but is preferably an ethylenically unsaturated group from the viewpoint of curability. Specific examples of the monofunctional polymerizable compound contained in the ink are the same as specific examples of the monofunctional polymerizable compound contained in the undercoat composition.

From the viewpoint of improving the curability of the recorded image, at least one of the monofunctional polymerizable compounds contained in the ink is preferably a hydroxy group-containing monofunctional polymerizable compound. In particular, the ratio of the hydroxy group-containing monofunctional polymerizable compound to the radically polymerizable compound contained in the ink is preferably 5% by mass to 70% by mass, more preferably 10% by mass to 60% by mass. It is more preferably 20% by mass to 50% by mass.

The monofunctional polymerizable compound contained in the ink preferably has a glass transition temperature of −40 ° C. to 50 ° C., more preferably 0 ° C. to 30 ° C. when it is homopolymerized. When the glass transition temperature is −40 ° C. or higher, an image having better curability can be recorded. Further, when the glass transition temperature is 50 ° C. or lower, an image having more flexibility can be recorded.

When the ink contains a plurality of monofunctional polymerizable compounds, it is preferable that the average value of the glass transition temperature in the case of homopolymer is in the above range. That is, it is preferable that the glass transition temperature of the monofunctional polymerizable compound contained in the ink is measured as a homopolymer, the average value of the measured values is calculated, and the calculated value is in the above range.

The monofunctional polymerizable compound contained in the ink preferably has a molecular weight of 140 to 210, and more preferably 180 to 210. When the molecular weight is 140 or more, an image having better curability can be recorded. Further, when the molecular weight is 210 or less, an image having more excellent flexibility and curability can be recorded.

In the present disclosure, from the viewpoint of adhesion between the image and the substrate, the ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the undercoat composition is defined as A mass%, and the polymerizable compound contained in the ink radically. When the proportion of the monofunctional polymerizable compound occupying is B mass%, the absolute value of the difference between A and B is preferably 20 or less. The lower limit of the absolute value of the difference between A and B is not particularly limited and may be 0.

-Polyfunctional polymerizable compound-
The polyfunctional polymerizable compound is not particularly limited as long as it is a compound having two or more radically polymerizable groups. The radically polymerizable group is not particularly limited as long as it is a group capable of causing a polymerization reaction, but is preferably an ethylenically unsaturated group from the viewpoint of curability. Specific examples of the polyfunctional polymerizable compound contained in the ink are the same as those of the polyfunctional polymerizable compound contained in the undercoat composition.

In the present disclosure, the ink may contain components other than the colorant and the radically polymerizable compound. Other components include dispersants, polymerization initiators, surfactants and additives.

(Dispersant)
When a pigment is used as the colorant, the pigment can be contained in the ink as a pigment dispersion liquid. The pigment can be dispersed in a liquid medium using a dispersant. As the dispersant, generally known ones can be used. From the viewpoint of dispersion stability, the dispersant is preferably a compound having both a hydrophilic structure and a hydrophobic structure.

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 polyoxy. 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 phosphoric acid 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, DISPERBYK-164. 168, DISPERBYK-170, DISPERBYK-171, DISPERBYK-174, DISPERBYK-182 (all manufactured by BYK Chemie); , SOLSPERSE36000, SOLSPERSE39000, SOLSPERSE41000, SOLSPERSE71000 (all manufactured by Lubrizol)
Can be mentioned.

As a disperser for dispersing the pigment, a known disperser can be used, and examples thereof include a ball mill, a sand mill, a bead mill, a roll mill, a jet mill, a paint shaker, an attritor, an ultrasonic disperser, and a disper.

From the viewpoint of dispersion stability, the content of the dispersant in the ink with respect to the content of the pigment is preferably 0.05 to 1.0 on a mass basis, and more preferably 0.1 to 0.5. preferable.

(Polymerization initiator)
The ink may contain at least one polymerization initiator. The polymerization initiator is preferably a radical polymerization initiator that generates radicals.

Examples of the radical polymerization initiator include (a) an alkylphenone compound, (b) an acylphosphine oxide compound, (c) an aromatic onium salt compound, (d) an organic peroxide, (e) a thio compound, and (f) a hexaary. Rubiimidazole compound, (g) ketooxime ester compound, (h) borate compound, (i) azinium compound, (j) metallocene compound, (k) active ester compound, (l) compound having carbon halogen bond, and (m) ) Alkylamine compounds can be mentioned.

The radical polymerization initiator is preferably at least one selected from the group consisting of (b) an acylphosphine oxide compound and (e) a thio compound. The thio compound is preferably a thioxanthone compound having a thioxanthone skeleton, and more preferably a combination of an acylphosphine oxide compound and a thioxanthone compound as a radical polymerization initiator.

The content of the polymerization initiator in the ink is preferably 1.0% by mass to 15.0% by mass, more preferably 1.5% by mass to 10.0% by mass, based on the total mass of the ink. It is more preferably 0% by mass to 8.0% by mass.

When the acylphosphine oxide compound and the thioxanthone compound are used in combination, the content of the acylphosphine oxide compound in the ink is preferably 0.6% by mass to 9.0% by mass, preferably 1.0% by mass, based on the total mass of the ink. It is more preferably from% by mass to 6.0% by mass, and even more preferably from 2.5% by mass to 5.0% by mass. The content of the thioxanthone compound in the ink is preferably 0.4% by mass to 6.0% by mass, more preferably 0.5% by mass to 4.0% by mass, and 1.5% by mass, based on the total mass of the ink. More preferably, it is from% by mass to 3.0% by mass.

(Surfactant)
The ink may contain at least one surfactant from the viewpoint of improving ejection stability when applied using an inkjet recording method. Specific examples of the surfactant are as described above.

In the present disclosure, the surfactant is preferably a silicone-based surfactant from the viewpoint of improving the adhesion to the substrate. Examples of the silicone-based surfactant include polysiloxane compounds, and modified polysiloxane compounds in which an organic group is introduced into a part of the methyl group of dimethylpolysiloxane are preferable. Modifications include polyether denaturation, methylstyrene denaturation, alcohol denaturation, alkyl denaturation, aralkyl denaturation, fatty acid ester denaturation, epoxy denaturation, amine denaturation, amino denaturation, and mercapto denaturation. A plurality of types of organic machines may be introduced into a part of the methyl group of dimethylpolysiloxane. Above all, from the viewpoint of discharge stability, the silicone-based surfactant is preferably a polyether-modified polysiloxane compound.

The content of the surfactant in the ink is preferably 0.001% by mass to 4.0% by mass, more preferably 0.01% by mass to 3.0% by mass, and 0. It is more preferably 05% by mass to 2.0% by mass.

(Additive)
If necessary, the ink may contain additives such as a cosensitizer, an ultraviolet absorber, an antioxidant, a fading agent, a conductive salt, a solvent, and a basic compound.

(Physical characteristics)
The pH of the ink is preferably 7 to 10 and more preferably 7.5 to 9.5 from the viewpoint of improving ejection stability when the ink is applied by using an inkjet recording method. The pH is measured at 25 ° C. using a pH meter, and is measured, for example, using a pH meter (model number "HM-31") manufactured by Toa DKK Corporation.

The viscosity of the ink is preferably 0.5 mPa · s to 30 mPa · s, more preferably 2 mPa · s to 20 mPa · s, preferably 2 mPa · s to 15 mPa · s, and 3 mPa · s. It is more preferably 10 mPa · s. The viscosity is measured at 25 ° C. using a viscometer, and is measured, for example, using a TV-22 type viscometer manufactured by Toki Sangyo Co., Ltd.

The surface tension of the ink is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and even more preferably 25 mN / m to 45 mN / m. The surface tension is measured at 25 ° C. using a surface tensiometer, and is measured by a plate method using, for example, an automatic surface tension meter (product name "CBVP-Z") manufactured by Kyowa Surface Science Co., Ltd.

[Image recording method]
The image recording method of the present disclosure includes an undercoat composition applying step of applying the undercoat composition contained in the ink set on a substrate, and a first activation energy ray irradiation of irradiating the undercoat composition with a first active energy ray. A step, an ink applying step of applying the ink contained in the ink set on the undercoat composition irradiated with the first active energy ray by an inkjet recording method, and a second activity of irradiating the ink with the second active energy ray. Including an energy ray irradiation step.

(Undercoat composition applying step)
In the undercoat composition applying step, the undercoat composition contained in the ink set is applied onto the base material by an inkjet recording method.

The type of the base material is not particularly limited, and a generally known base material can be used as the base material. When used for printing food packaging packages for flexible packaging, the substrate is preferably transparent. In addition, "transparent" means that the visible light transmittance is 80% or more, and it is preferable that the visible light transmittance is 90% or more. Further, the transparent base material may be colored as long as it is transparent, but it is preferably colorless.

Examples of the base material include glass, quartz, and plastic film. Examples of the resin constituting the plastic film include cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, acrylic resin, chlorinated polyolefin resin, polyether sulfone resin, and polyethylene terephthalate. PET), polyethylene naphthalate, nylon, polyethylene, polystyrene, polypropylene, polycycloolefin resin, polyimide resin, polycarbonate resin, and polyvinyl acetal. The plastic film may be a film containing only one of these resins, or a film in which two or more of these resins are mixed.

The thickness of the base material is not particularly limited, but is preferably 1 μm to 500 μm, more preferably 2 μm to 200 μm, further preferably 5 μm to 100 μm, and particularly preferably 10 μm to 90 μm.

In the undercoat composition applying step, the undercoat composition can be applied by applying a known method such as a coating method, a dipping method, or an inkjet recording method. The application method is, for example, bar coater, extrusion coater, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, etc. This is done using a curtain coater or an extrusion coater.

The undercoat composition is preferably applied to the same region as the ink film formed by applying the ink or to a region wider than the ink film, and is applied so as to cover the entire surface of the region where the ink film is formed. Is preferable.

The thickness of the undercoat layer formed by applying the undercoat composition is preferably 0.5 μm to 6.0 μm, preferably 2.0 μm to 4.0 μm, from the viewpoint of the flexibility of the recorded image. Is more preferable.

(1st active energy ray irradiation step)
In the first active energy ray irradiation step, the undercoat composition is irradiated with the first active energy ray.

In the present disclosure, from the viewpoint of improving the adhesion to the substrate, it is preferable to semi-cure the undercoat composition by irradiation with active energy rays. In the present disclosure, "semi-curing" means a state in which the polymerization rate of the radically polymerizable compound contained in at least one of the undercoat composition and the ink is 80% or less. The polymerization rate is preferably 10% or more. The polymerization rate is calculated by the following method.

After the undercoat composition is applied onto the base material, 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 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 radically 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 radically 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} x 100

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

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.

Exposure amount in irradiation of active energy rays, from the viewpoint of semi-curing the undercoat composition ^is preferably ^{3mJ / cm 2 ~100mJ / cm 2} , more preferably 5mJ / cm ² ~20mJ / cm 2 ..

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 irradiating ultraviolet rays. Among them, 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.

(Ink application process)
In the ink application step, the ink contained in the ink set is applied to the undercoat composition irradiated with the first active energy ray by an inkjet recording method.

The inkjet recording method is not particularly limited as long as it can record an image, and is a known method, for example, a charge control method for ejecting ink by using electrostatic attraction, and a drop using the vibration pressure of a piezo element. The on-demand method (pressure pulse method), the acoustic inkjet method that converts an electric signal into an acoustic beam and irradiates the ink to eject the ink using the radiation pressure, and the acoustic inkjet method that heats the ink to form bubbles and applies the generated pressure. It may be any of the thermal inkjet (bubble jet (registered trademark)) methods to be used.

As an inkjet recording method, in particular, by the method described in JP-A-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, regarding 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. An example is a line method using a line head that has been used.

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 that scans a short head becomes unnecessary.

Further, since the movement of the carriage and the complicated scanning control with the base material are not required and only the base material moves, 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.

When ejecting ink, it is preferable to heat the inkjet head from the viewpoint of ejection stability, and it is preferable to heat the ink jet head to 40 ° C. to 70 ° C.

In the ink applying step, only one type of ink may be applied, or two or more types of ink may be applied. For example, when recording a color image, it is preferable to apply at least each color ink of yellow, cyan, magenta and black, and more preferably to apply each color ink of white, yellow, cyan, magenta and black. Further, each of the above color inks may be applied in combination with a light color ink such as light magenta or light cyan, a special color ink such as orange, green or violet, a clear ink or a metallic ink.

(Second active energy ray irradiation step)
In the second active energy ray irradiation step, the ink is irradiated with the second active energy ray. In the second active energy ray irradiation step, it is preferable to irradiate the second active energy ray in a nitrogen atmosphere from the viewpoint of improving the curability of the recorded image. In a nitrogen atmosphere, the oxygen concentration is preferably 1% or less, more preferably 0.5% or less, and even more preferably 0.3% or less.

In the second active energy ray irradiation step, the undercoat composition and the ink are cured so that the polymerization rate of the radically polymerizable compound in the undercoat composition and the radically polymerizable compound in the ink is more than 80% and 100% or less. Is preferable. The respective polymerization rates are more preferably 85% to 100%, further preferably 90% to 100%.

Examples of the 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.

Exposure amount in irradiation of active energy rays, from the viewpoint of completely curing the undercoat composition and ink ^is preferably ^{50mJ / cm 2 ~1000mJ / cm 2} , is 100mJ / cm ² ~500mJ / cm 2 Is more preferable.

(Other processes)
The image recording method of the present disclosure may include a step other than the undercoat composition applying step, the first active energy ray irradiation step, the ink applying step, and the second active energy ray irradiation step. As another step, for example, a step of semi-curing the ink may be provided after the ink applying step. In particular, when two or more kinds of inks are applied, it is preferable that the first ink is applied, the first ink is semi-cured, and then the next ink is applied. After applying the final ink, it is preferable to proceed to the second active energy ray irradiation step without semi-curing the final ink.

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.

[Preparation of undercoat composition]
The isocyanate compounds, polyfunctional polymerizable compounds, monofunctional polymerizable compounds, polymerization initiators and surfactants listed in the table below were mixed so that each component had the content (mass%) shown in the table. The mixture was stirred with a mixer (product name "L4R", manufactured by Silberson) at 25 ° C. under the condition of 5000 rpm for 20 minutes to obtain an undercoat composition.

[Ink preparation]
First, pigment dispersions of each color were prepared.

-Preparation of cyan pigment dispersion-
300 parts by mass of cyan pigment, 620 parts by mass of "SR9003", and 80 parts by mass of "SOLSPERSE32000" were put into a disperser motor mill M50 (manufactured by Eiger), and zirconia beads having a diameter of 0.65 mm were used to achieve a peripheral speed of 9 m. The dispersion treatment was carried out at / s for 4 hours to obtain a cyan pigment dispersion liquid.

-Preparation of magenta pigment dispersion-
300 parts by mass of magenta pigment, 600 parts by mass of "SR9003", and 100 parts by mass of "SOLSPERSE32000" were put into a disperser motor mill M50 (manufactured by Eiger), and zirconia beads having a diameter of 0.65 mm were used to achieve a peripheral speed of 9 m. The dispersion treatment was carried out at / s for 10 hours to obtain a magenta pigment dispersion liquid.

-Preparation of yellow pigment dispersion-
300 parts by mass of yellow pigment, 600 parts by mass of "SR9003", and 100 parts by mass of "SOLSPERSE32000" were put into a disperser motor mill M50 (manufactured by Eiger), and zirconia beads having a diameter of 0.65 mm were used to achieve a peripheral speed of 9 m. A dispersion treatment was carried out at / s for 10 hours to obtain a yellow pigment dispersion.

-Preparation of black pigment dispersion-
400 parts by mass of black pigment, 520 parts by mass of "SR9003", and 80 parts by mass of "SOLSPERSE32000" were put into a disperser motor mill M50 (manufactured by Eiger), and zirconia beads having a diameter of 0.65 mm were used to achieve a peripheral speed of 9 m. A dispersion treatment was carried out at / s for 7 hours to obtain a black pigment dispersion liquid.

-Preparation of white pigment dispersion-

500 parts by mass of white pigment, 440 parts by mass of "SR9003", and 60 parts by mass of "SOLSPERSE32000" were put into a disperser motor mill M50 (manufactured by Eiger), and zirconia beads having a diameter of 0.65 mm were used for peripheral speed. The dispersion treatment was carried out at 9 m / s for 4 hours to obtain a white pigment dispersion liquid.

Next, the prepared pigment dispersion liquid and the polyfunctional polymerizable compound, the monofunctional polymerizable compound, the polymerization initiator, the polymerization inhibitor and the surfactant described in the table below are contained in each component in the table. It was mixed so as to be (% by mass). The mixture was stirred at 25 ° C. at 5000 rpm for 20 minutes using a mixer (product name "L4R", manufactured by Silberson) to obtain ink.

For the preparation of the ink, Speedcure 7010L (manufactured by Rambson) and Irgastab UV-22 (manufactured by BASF) were used. Speedcure7010L is a mixture of Speedcure7010 and EOTMPTA, and the mixing ratio is 1: 1 on a mass basis. In addition, Irgastab UV-22 is a mixture of a quinone compound and a propoxylated glycerol triacrylate, and the mixing ratio is 15:85 on a mass basis.

Details of each component listed in the table are as follows. In the table, the monofunctional ratio indicates the ratio of the monofunctional polymerizable compound to the radically polymerizable compound. The hydroxy group-containing monofunctional ratio indicates the ratio of the hydroxy group-containing monofunctional polymerizable compound to the radically polymerizable compound. The monofunctional ratio in the undercoat composition was set to A, the monofunctional ratio in the ink was set to B, and the absolute value of the difference between A and B was calculated and described as "| AB |". The unit of the monofunctional ratio and the hydroxy group-containing monofunctional ratio is mass%.

<Isocyanate compound>
-Takenate D160N: Adduct of hexamethylene diisocyanate and trimethylolpropane (manufactured by Mitsui Chemicals, Inc.)
-Takenate D170N: Isocyanurate form of hexamethylene diisocyanate (manufactured by Mitsui Chemicals, Inc.)
-Takenate D178NL: Hexamethylene diisocyanate allophanate (manufactured by Mitsui Chemicals, Inc.)
-Takenate D110N: Adduct of xylylene diisocyanate and trimethylolpropane (manufactured by Mitsui Chemicals, Inc.)

<Radical polymerizable compound>
-Polyfunctional polymerizable compound-
SR341: 3-Methyl-1,5-pentanediol diacrylate (manufactured by Sartomer, bifunctional)
SR344: Polyethylene glycol (400) diacrylate (manufactured by Sartomer, bifunctional)
SR9003: Propoxylation (2) Neopentyl glycol diacrylate (manufactured by Sartomer, bifunctional)
GPTA: Propoxified glycerol triacrylate (trifunctional)
EOTMPTA: Trimethylolpropane EO-added triacrylate (trifunctional)
-DPHA: Dipentaerythritol hexaacrylate (product name "Ethermer265", manufactured by Changxing Materials Industry Co., Ltd., 6-functional)
UV7630B: Urethane acrylate (six-functional, manufactured by Mitsubishi Chemical Corporation), which is a reaction product of dicyclohexylmethane 4,4'-diisocyanate and pentaerythritol tri (meth) acrylate.
-Monofunctional polymerizable compound-
4-HBA: 4-Hydroxybutyl acrylate (molecular weight 144, Tg-32 ° C)
HPA: 2-Hydroxypropyl acrylate (molecular weight 130 ° C, Tg-7 ° C)
CBA: Ethylcarbitol acrylate (molecular weight 188, Tg-67 ° C)
LA: Lauryl acrylate (molecular weight 240, Tg-23 ° C)
CTFA: Cyclic trimethylolpropane formal acrylate (molecular weight 200, Tg 27 ° C)
IBOA: Isobornyl acrylate (molecular weight 208, Tg 96 ° C)

<Colorant>
Cyan pigment: PB15: 4, product name "Heliogen (registered trademark) Blue D 7110 F" (manufactured by BASF)
Magenta pigment: Product name "Cinquasia (registered trademark) Magenta L 4540" (manufactured by BASF)
Yellow pigment: P.I. Y. 120, product name "Novoperm Yellow H2G" (manufactured by Clariant)
Black Pigment: Carbon Black, Product Name "Special Black 250" (Orion Engineered Carbons)
White pigment: Titanium oxide, product name "Typake CR60-2" (manufactured by Ishihara Sangyo Co., Ltd.)

<Dispersant>
-SOLPERSE32000: Polyethyleneimine-based dispersant (manufactured by Lubrizol)

<Polymerization initiator>
Ominirad 819: Bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide (manufactured by IGM Resins BV)
Speedcure 7010: 1,3-di ({α- [1-chloro-9-oxo-9H-thioxanthene-4-yl) oxy] acetylpoly [oxy (1-methylethylene)]} oxy) -2,2 -Bis ({α- [1-methylethylene)]} oxymethyl) propane

<Polymerization inhibitor>
-Quinone compounds: 2,6-bis (1,1-dimethylethyl) -4- (phenylmethylene) -2,5-cyclohexadiene-1-one

<Surfactant>
BYK-307: Polyester-modified polydimethylsiloxane (manufactured by BYK Chemie)

[Image recording]
A roller coating machine was arranged at the most upstream portion of the roll transport system, and an LED light source, an inkjet head, and an LED light source were arranged in this order downstream of the roller coating machine. The LED light source on the downstream side was placed in the blanket.

As the inkjet head, the product name "CA3" manufactured by TOSHIBA TEC Corporation was used. Four inkjet heads were arranged in parallel in a direction intersecting the transport direction of the base material. The prepared ink was filled in the inkjet head. The inkjet head was heated to 45 ° C., the frequency was set so that the amount of droplets dropped was 42 pL, and the output was performed at a resolution of 600 dpi (dots per inch). As an LED light source, a UV LED irradiator with a peak wavelength of 385 nm (product name "G4B", manufactured by Kyocera Corporation) was used. A nitrogen gas generator with a compressor (product name "Maxi-Flow30", manufactured by Inhouse Gas) is connected to the blanket at a pressure of 0.2 MPa · s, and the nitrogen concentration in the blanket is 99% and the oxygen concentration is 0.1%. Nitrogen was flowed at a flow rate of 2 liters / minute to 10 liters / minute so as to be as follows.

As the base material, OPP (stretched polypropylene) film (product name "FOR-AQ25", manufactured by Futamura Chemical Co., Ltd., thickness 25 μm) and PET (polyethylene terephthalate) film (product name "FE2001", manufactured by Futamura Chemical Co., Ltd., thickness). 12 μm) and used. The base material was conveyed at a speed of 30 m / min, and an undercoat composition was applied onto the base material so as to have a film thickness of 2 μm using a roller coating machine. Next, the undercoat composition was semi-cured by irradiating ultraviolet rays with an exposure amount of 10 mJ / cm ^{2 using an LED light source.} Ink was ejected onto the semi-cured undercoat composition and a 100% solid image was recorded. Then, using an LED light source ^{, ultraviolet rays were irradiated at an exposure amount of 200 mJ / cm 2} , and the undercoat composition and the ink were completely cured.

[evaluation]
For each Example and Comparative Example, the flexibility, adhesion and curability were evaluated using the obtained image recordings. The evaluation method is as follows.

<Flexibility>
After repeatedly bending the image recording material using the OPP film as the base material, it was visually observed whether or not the image recording surface had cracks. The number of bends before cracking was recorded. The evaluation criteria are as follows. The rank with the best flexibility is "5".
No cracking occurred even after repeated bending at 5:50 times.
Cracks occurred after 4:41 to 50 bends. Cracks occurred after 3:21 to 40 bends.
2: 2 to 20 times of bending caused cracks.
Cracks occurred after 1: 1 bending.

<Curable>
A6 size paper was placed on the image recording surface of an image recording object using a PET film as a base material. It was held at 40 ° C. for 24 hours with a load of 1 kg / A6 size applied from the top of the paper. After 24 hours, the state of transfer to paper was visually observed. When the image was transferred, the ratio (%) of the area of the image transferred to the paper to the area of the paper was measured. It was evaluated that the smaller the above ratio, the better the curability. The evaluation criteria are as follows. The rank with the best curability is "5".
5: No transcription.
4: The area of the image transferred to the paper is more than 0% and less than 5% of the area of the paper.
3: The area of the image transferred to the paper is 5% or more and less than 25% of the area of the paper.
2: The area of the image transferred to the paper is 25% or more and less than 50% of the area of the paper.
1: The area of the image transferred to the paper is 50 or more of the area of the paper.

<Adhesion>
A 1 cm wide cellophane tape (registered trademark) was attached on the image recording surface of an image recording object using a PET film as a base material. Using IMADA standard type digital force gauge ZTS series, vertical electric measuring stand MX2 series, and 90 ° peeling test jig P90-200N / 200N-EZ film chuck FC series, cellophane tape can be peeled at a peeling speed of 300 mm / min. It was peeled off and the peeling force was measured. It can be judged that the larger the peeling force, the better the adhesion between the base material and the image. The evaluation criteria are as follows. The rank with the best adhesion is "5".
5 No peeling occurs 4 Peeling occurs and the peeling force is 1.0 N or more.
3 Peeling occurs, and the peeling force is 0.4 N or more and less than 1.0 N.
2 Peeling occurs, and the peeling force is 0.1 N or more and less than 0.4 N.
1 Peeling occurs, and the peeling force is less than 0.1N.

The evaluation results are shown in the table below.

As shown in Tables 1 to 4, in Examples 1 to 36, the ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the undercoat composition was 35% by mass to 70% by mass, and the ink The ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the above was 30% by mass to 65% by mass, and it was found that the recorded image was excellent in flexibility, curability and adhesion.

On the other hand, as shown in Table 5, in Comparative Example 1 and Comparative Example 2, it was found that the ink did not contain the monofunctional polymerizable compound, and the recorded image was inferior in flexibility and adhesion.

In Comparative Example 3, it was found that the undercoat composition did not contain an isocyanate compound, and the recorded image was inferior in flexibility and adhesion.

In Comparative Example 4, it was found that the ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the ink was less than 30% by mass, and the recorded image was inferior in flexibility and adhesion.

In Comparative Example 5, it was found that the undercoat composition did not contain the monofunctional polymerizable compound, and the recorded image was inferior in flexibility and adhesion.

In Comparative Example 6, it was found that the ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the undercoat composition was less than 35% by mass, and the recorded image was inferior in flexibility.

In Comparative Example 7, it was found that the ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the undercoat composition was more than 70% by mass, and the recorded image was inferior in curability.

In Comparative Example 8, it was found that the ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the ink was more than 65% by mass, and the recorded image was inferior in curability.

In Example 13, the glass transition temperature when a homopolymer of the monofunctional polymerizable compound contained in the undercoat composition was used was −40 ° C. to 50 ° C., and an image having more flexibility was recorded as compared with Example 18. It turned out to be done.

In Example 13, the glass transition temperature when a homopolymer of the monofunctional polymerizable compound contained in the undercoat composition was used was −40 ° C. to 50 ° C., and an image having better curability was recorded as compared with Example 19. It turned out to be done.

In Example 13, the molecular weight of the monofunctional polymerizable compound contained in the undercoat composition was 140 to 210, and it was found that an image having better flexibility and curability was recorded as compared with Example 17.

In Example 13, the molecular weight of the monofunctional polymerizable compound contained in the undercoat composition was 140 to 210, and it was found that an image having better adhesion and curability was recorded as compared with Example 21.

In Example 3, it was found that the ink contained a hydroxy group-containing monofunctional polymerizable compound, and an image having better curability and adhesion was recorded as compared with Example 6.

In Example 3, the ink contains a hydroxy group-containing monofunctional polymerizable compound, and the ratio of the hydroxy group-containing monofunctional polymerizable compound to the radically polymerizable compound is 20% by mass to 50% by mass, which is compared with Example 5. Then, it was found that an image having better curability and adhesion was recorded.

In Example 13, the ink contains a hydroxy group-containing monofunctional polymerizable compound, and the ratio of the hydroxy group-containing monofunctional polymerizable compound to the radically polymerizable compound is 20% by mass to 50% by mass, which is compared with Example 27. Then, it was found that an image having better curability and adhesion was recorded. Further, it was found that in Example 13, an image having better curability was recorded as compared with Example 30.

In Example 22, the ink contains a hydroxy group-containing monofunctional polymerizable compound, and the ratio of the hydroxy group-containing monofunctional polymerizable compound to the radically polymerizable compound is 20% by mass to 50% by mass, which is compared with Example 7. Then, it was found that an image having better curability and adhesion was recorded. Further, it was found that in Example 22, an image having better curability was recorded as compared with Example 28 and Example 31.

In Example 23, the ink contains a hydroxy group-containing monofunctional polymerizable compound, and the ratio of the hydroxy group-containing monofunctional polymerizable compound to the radical polymerizable compound is 20% by mass to 50% by mass, which is compared with Example 9. Then, it was found that an image having superior flexibility and adhesion was recorded. Further, it was found that in Example 23, an image superior in flexibility and curability was recorded as compared with Example 29. Further, it was found that in Example 23, an image having better curability was recorded as compared with Example 32.

In Example 3, the ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the undercoat composition is A mass%, and the ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the ink is B mass. When% was set, the absolute value of the difference between A and B was 20 or less, and it was found that an image having better curability and adhesion was recorded as compared with Example 2.

Claims (8)

An undercoat composition containing an isocyanate compound and a radically polymerizable compound,
With an ink containing a colorant and a polymerizable compound,
The proportion of the monofunctional polymerizable compound in the radically polymerizable compound contained in the undercoat composition is 35% by mass to 70% by mass.
An ink set in which the proportion of the monofunctional polymerizable compound in the radically polymerizable compound contained in the ink is 30% by mass to 65% by mass. The ink set according to claim 1, wherein the monofunctional polymerizable compound contained in the undercoat composition has a glass transition temperature of −40 ° C. to 50 ° C. when a homopolymer is used. The ink set according to claim 1 or 2, wherein the monofunctional polymerizable compound contained in the undercoat composition has a molecular weight of 140 to 210. The ink set according to any one of claims 1 to 3, wherein at least one of the monofunctional polymerizable compounds contained in the ink is a hydroxy group-containing monofunctional polymerizable compound. The ink set according to claim 4, wherein the ratio of the hydroxy group-containing monofunctional polymerizable compound to the radically polymerizable compound contained in the ink is 20% by mass to 50% by mass. The proportion of the monofunctional polymerizable compound in the radically polymerizable compound contained in the undercoat composition was defined as A mass%, and the proportion of the monofunctional polymerizable compound in the radically polymerizable compound contained in the ink was defined as B mass%. The ink set according to any one of claims 1 to 5, wherein the absolute value of the difference between A and B is 20 or less. The ink set according to any one of claims 1 to 6 is used.
An undercoat composition applying step of applying the undercoat composition onto a base material, and
The first active energy ray irradiation step of irradiating the undercoat composition with the first active energy ray, and
An ink application step of applying the ink to the undercoat composition irradiated with the first active energy ray by an inkjet recording method, and an ink application step.
An image recording method including a second active energy ray irradiation step of irradiating the ink with a second active energy ray. The image recording method according to claim 7, wherein in the second active energy ray irradiation step, the second active energy ray is irradiated in a nitrogen atmosphere.