JP7184744B2 - Ink set and image recording method - Google Patents

Description

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

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

For example, in Patent Document 1, as step a, an applying step of applying an undercoat composition to a recording medium to form an undercoat layer, and as step b, an image forming step of ejecting ink onto the undercoat layer to form an image. and, as a step c, a curing step of irradiating the undercoat layer and the ink with an actinic ray to cure them in this order, and the undercoat composition comprises a compound having an isocyanate group, a radically polymerizable monomer, and radical polymerization initiation. and an ink containing a radical polymerizable monomer, a radical polymerization initiator, and a colorant.

JP 2016-60049 A

Images recorded using the undercoat composition and ink are sometimes required to have flexibility and curability.

The present disclosure has been made in view of such circumstances, and the problem to be solved by the embodiments of the present invention is an ink set and an image recording method capable of recording an image with excellent flexibility and curability. is to provide

Specific means for solving the above problems include the following aspects.
<1> An undercoat composition containing an isocyanate compound and a radically polymerizable compound, and an ink containing a colorant and a radically polymerizable compound, wherein the monofunctional polymerizable compound accounts for the radically polymerizable compounds 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 converted into a homopolymer.
<3> The ink set according to <1> or <2>, wherein the monofunctional polymerizable compound contained in the undercoat composition has a molecular weight of 140-210.
<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 hydroxyl group-containing monofunctional polymerizable compound.
<5> The ink set according to <4>, wherein the proportion of the hydroxyl group-containing monofunctional polymerizable compound in the radically polymerizable compound contained in the ink is 20% by mass to 50% by mass.
<6> The ratio of the monofunctional polymerizable compound to the radically polymerizable compounds contained in the undercoat composition is defined as A% by mass, and the ratio of the monofunctional polymerizable compound to the radically polymerizable compounds contained in the ink is defined as B% by 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 application step of applying an undercoat composition onto a substrate; A first active energy ray irradiation step of irradiating a ray, an ink application step of applying ink on the undercoat composition irradiated with the first active energy ray by an inkjet recording method, and a second active energy ray applied to the ink. and 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.

According to the present disclosure, an ink set and an image recording method capable of recording an image with excellent flexibility and curability are provided.

The ink set and image recording method of the present disclosure will be described in detail below.

In this specification, the numerical range indicated using "to" means a range including the numerical values before and after "to" as the minimum and maximum values, respectively.
In the numerical ranges described stepwise in this specification, the upper limit or lower limit described in a certain numerical range may be replaced with the upper limit or lower limit of another numerical range described stepwise. Moreover, in the numerical ranges described in this specification, the upper limit or lower limit described in a certain numerical range may be replaced with the values shown in the examples.

As used herein, the amount of each component in the composition refers to the total amount of the multiple substances present in the composition when there are multiple substances corresponding to each component in the composition, unless otherwise specified. means
In the present specification, a combination of two or more preferred aspects is a more preferred aspect.
In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. be

As used herein, the term "image" refers to a general film formed by applying the undercoat composition and the ink in this order, and the term "image recording" refers to the formation of an image (i.e., film). .
The concept of "image" in this specification also includes a solid image.

As used herein, "(meth)acrylate" is a concept that includes both acrylate and methacrylate. Moreover, "(meth)acryl" is a concept that includes both acryl 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. 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 compounds contained in the undercoat composition and the ratio of the monofunctional polymerizable compound to the radically polymerizable compounds contained in the ink are specified. Since it is within the numerical range, the recorded image is excellent in flexibility and curability. On the other hand, in Patent Document 1, specifically, the content of the polyfunctional ethylenically unsaturated compound with respect to the total content of the radically polymerizable monomers in the undercoat composition is 70% by mass or more, and , that the content of the polyfunctional ethylenically unsaturated compound in the ink is 70% by mass or more with respect to the total content of the radically polymerizable monomers. Patent Document 1 describes that the resulting printed material has good adhesion and is excellent in preventing blocking, but does not pay attention to adhesion and curability.

Each component contained in the undercoat composition and the ink constituting the ink set of the present disclosure will be described below.

<Undercoat composition>
In the present disclosure, the primer composition contains 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 is a polyfunctional isocyanate compound having two or more isocyanate groups in one molecule. preferable.

Bifunctional isocyanate compounds having two isocyanate groups in one molecule include, for example, methylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, dipropyl ether diisocyanate, 2,2 - dimethylpentane 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, aliphatic diisocyanates such as thiodihexyl diisocyanate;
m-phenylene diisocyanate, p-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, dimethylbenzene diisocyanate, ethylbenzene diisocyanate, isopropylbenzene diisocyanate, tolidine diisocyanate, 1,4-naphthalene diisocyanate, 1,5 - aromatic diisocyanates such as naphthalene diisocyanate, 2,6-naphthalene diisocyanate, 2,7-naphthalene diisocyanate, meta-xylylene diisocyanate, para-xylylene diisocyanate, tetramethylxylylene diisocyanate; and hydrogenated xylylene diisocyanate, isophorone diisocyanate, dicyclohexyl Alicyclic diisocyanates such as methane 4,4'-diisocyanate can be mentioned.

The isocyanate compound may be a biuret or isocyanurate trimer of a bifunctional isocyanate compound, or an adduct (i.e., an adduct) 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, more preferably an aliphatic isocyanate compound having two or more isocyanate groups in one molecule. More preferably, it is 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. Body is particularly preferred.

The isocyanate compound may be a commercial product on the market. Commercially available products include, for example, Takenate series such as Takenate D103H, D204, D160N, D170N, D165N, D178NL, and D110N (manufactured by Mitsui Chemicals, Inc.), and Coronate HX, HXR, HXL, HXLV, HK, HK-T, and 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. % to 50% by mass is more preferred.

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

(Radical polymerizable compound)
A radically polymerizable compound means a compound having at least one radically polymerizable group in one molecule. The radically polymerizable compound contained in the undercoat composition consists of a monofunctional polymerizable compound having one radically polymerizable group and a polyfunctionally polymerizable compound having two or more radically polymerizable groups. The ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the undercoat composition is 35% by mass to 70% by mass. The balance after 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, an image with excellent flexibility can be recorded. 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 with excellent curability can be recorded. In addition, it is possible to suppress a phenomenon (so-called migration) in which unreacted monomer components are transferred from the image recorded matter to the outside. In particular, it is excellent in that it can be applied to packaging materials in the fields of food packaging and cosmetic packaging, which require strict safety of substrates.

The proportion of the monofunctional polymerizable compound in the radical 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. More preferably, it is 50% by mass to 65% by mass.

The content of the radical 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 are more preferred.

- 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 from the viewpoint of curability, it is preferably an ethylenically unsaturated group.

Monofunctional ethylenically unsaturated compounds include, for example, monofunctional (meth)acrylates, monofunctional (meth)acrylamides, monofunctional aromatic vinyl compounds, monofunctional vinyl ethers and monofunctional N-vinyl compounds.

Examples of monofunctional (meth)acrylates 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 acrylates, 4-n-butylcyclohexyl (meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate, bornyl (meth)acrylate, isobornyl (meth)acrylate, 2-ethylhexyl diglycol (meth)acrylate, butoxyethyl ( meth) 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 Furfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate Acrylate, 4-hydroxybutyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate acrylate, 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-hydroxypropyl phthalate, 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, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, (3-ethyl-3- oxetanylmethyl) (meth)acrylates and phenoxyethylene glycol (meth)acrylates.

Examples of monofunctional (meth)acrylamides include (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, 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 (meth)acrylamide and (meth)acryloylmorpholine.

Examples of monofunctional aromatic vinyl compounds include styrene, dimethylstyrene, trimethylstyrene, isopropylstyrene, chloromethylstyrene, methoxystyrene, acetoxystyrene, chlorostyrene, dichlorostyrene, bromostyrene, vinylbenzoic acid methyl ester, 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-octylstyrene, 3-(2-ethylhexyl)styrene, 4-(2-ethylhexyl)styrene, allylstyrene, isopropenylstyrene, butenylstyrene, octenylstyrene, 4-t-butoxycarbonylstyrene and 4- t-butoxystyrene can be mentioned.

Monofunctional vinyl ethers include, for example, 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, 4-methyl Cyclohexyl methyl 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 Furfuryl 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, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether , phenylethyl vinyl ether and phenoxypolyethylene glycol vinyl ether.

Monofunctional N-vinyl compounds include, for example, 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. when converted into a homopolymer, more preferably −40° C. to 80° C., −40 °C to 50 °C, more preferably 0 °C to 30 °C. When the glass transition temperature is −40° C. or higher, an image having excellent curability can be recorded. Further, when the glass transition temperature is 90° C. or less, an image having excellent flexibility can be recorded.

When the undercoat composition contains a plurality of monofunctional polymerizable compounds, the average value of the glass transition temperatures of homopolymers is preferably within the above range. That is, for the monofunctional polymerizable compound contained in the undercoat composition, the glass transition temperature of each homopolymer is measured, the average value of the measured values is calculated, and the calculated value is preferably within the above range. .

The glass transition temperature when the monofunctional polymerizable compound was 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 produced homopolymer 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. Weight average molecular weights are measured using gel permeation chromatography (GPC). For example, HLC-8220GPC (manufactured by Tosoh Corporation) is used as GPC, TSKgel, Super Multipore HZ-H (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) is used as a column, and THF (tetrahydrofuran) is used as an 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. For the calibration curve, as a standard sample, the product name "TSK standard polystyrene" manufactured by Tosoh Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", Eight samples of "A-2500", "A-1000" and "n-propylbenzene" are used. The glass transition temperature of the homopolymer varies depending on the weight average molecular weight of the homopolymer, but when the weight average molecular weight is 10,000 to 20,000, the variation is negligibly small.

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

Molecular weights are measured using a mass spectrometer, for example, the product name "API3200 system" from Sciex.

The monofunctional polymerizable compound may be contained singly or in combination of two or more in the undercoat composition.

- 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 from the viewpoint of curability, it is preferably an ethylenically unsaturated group.

Polyfunctional ethylenically unsaturated compounds include, for example, polyfunctional (meth)acrylate compounds and polyfunctional vinyl ethers.

Polyfunctional (meth)acrylates include, for example, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth) acrylates, 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 ) 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 Glycol di(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 Ether di(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane EO addition tri(meth)acrylate, pentaerythritol tri (meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tri(meth)acryloyloxyethoxytrimethylolpropane , glycerin polyglycidyl ether poly(meth)acrylate and tris(2-acryloyloxyethyl)isocyanurate.

Moreover, 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 bifunctional isocyanate compounds include those described above. Examples of hydroxyl group-containing polyfunctional (meth)acrylates include phenylglycidyl ether (meth)acrylate, pentaerythritol (meth)triacrylate and dipentaerythritol penta(meth)acrylate.

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

Polyfunctional vinyl ethers include, for example, 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, hexanediol divinyl ether, Vinyl ether, 1,4-cyclohexanedimethanol divinyl ether, bisphenol A alkylene oxide divinyl ether, bisphenol F alkylene oxide divinyl ether, trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerin trivinyl ether, pentaerythritol Tetravinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol hexavinyl ether, EO-added trimethylolpropane trivinyl ether, PO-added trimethylolpropane trivinyl ether, EO-added ditrimethylolpropane tetravinyl ether, PO-added ditrimethylolpropane tetravinyl ether, EO-added penta Erythritol tetravinyl ether, PO-added pentaerythritol tetravinyl ether, EO-added dipentaerythritol hexavinyl ether and PO-added dipentaerythritol hexavinyl ether can be mentioned.

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 ingredients include polymerization initiators, surfactants and additives.

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

Examples of radical polymerization initiators include (a) alkylphenone compounds, (b) acylphosphine oxide compounds, (c) aromatic onium salt compounds, (d) organic peroxides, (e) thio compounds, and (f) hexaaryl rubyimidazole compounds, (g) ketoxime ester compounds, (h) borate compounds, (i) azinium compounds, (j) metallocene compounds, (k) active ester compounds, (l) compounds having a carbon-halogen bond, and (m ) alkylamine compounds.

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

Acylphosphine oxide compounds include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethylbenzoyl)phenylphosphine oxide, 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) phenylphosphine oxide, and 2,6-dimethylbenzoyl(4-pentyloxyphenyl)phenylphosphine oxide.

Among them, the acylphosphine oxide compound is preferably bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenyl Phosphine oxides are more preferred. Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is available from IGM Resins B.V. under the product name "Omnirad 819". V. 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. Preferably, 2.0% by mass to 6.0% by mass is more preferable.

(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 surfactants include those described in JP-A-62-173463 and JP-A-62-183457. Examples of surfactants include anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, and fatty acid salts; polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycol, 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 fluorosurfactant or a silicone surfactant.

In the present disclosure, the surfactant is preferably a silicone-based surfactant from the viewpoint of improving adhesion to the substrate. Examples of silicone-based surfactants include polysiloxane compounds, preferably modified polysiloxane compounds in which organic groups are introduced into some of the methyl groups of dimethylpolysiloxane. Modification includes polyether modification, methylstyrene modification, alcohol modification, alkyl modification, aralkyl modification, fatty acid ester modification, epoxy modification, amine modification, amino modification, and mercapto modification. A plurality of types of organic groups may be introduced into some of the methyl groups of dimethylpolysiloxane. Among them, from the viewpoint of ejection stability, the silicone-based surfactant is preferably a polyether-modified polysiloxane compound.

Examples of polyether-modified polysiloxane compounds include SILWET L-7604, SILWET L-7607N, SILWET FZ-2104 and SILWET FZ-2161 (manufactured by Momentive Performance Materials Japan LLC); BYK306, BYK307, BYK331, BYK333, BYK347 and BYK348 (manufactured by BYK Chemie); 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. Preferably, 0.05% by mass to 2.0% by mass is more preferable.

(Additive)
The undercoat composition may contain additives such as a co-sensitizer, an ultraviolet absorber, an antioxidant, an anti-fading agent, a conductive salt, a solvent, and a basic compound, if necessary. In addition, although the undercoat composition may contain a coloring agent, it is preferable not to contain a coloring agent. When the undercoat composition contains a colorant, the colorant is preferably a white colorant. As the coloring agent, the same coloring agents as those 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 based on the total mass of the undercoat composition.

(physical properties)
The pH of the undercoat composition is preferably from 7 to 10, more preferably from 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, for example, using a pH meter manufactured by DKK Toa (model number “HM-31”).

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. Viscosity is measured at 25° C. using a viscometer, for example, using a TV-22 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, even more preferably 25 mN/m to 45 mN/m. The surface tension is measured at 25° C. using a surface tensiometer, for example, by a plate method using an automatic surface tensiometer manufactured by Kyowa Interface Science Co., Ltd. (product name “CBVP-Z”).

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

(coloring agent)
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. A pigment dispersion 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 may be a radically polymerizable compound to be described later.

As the pigment, both commercially available organic pigments and inorganic pigments can be used. As pigments, for example, Seishiro Ito, "Dictionary of Pigments" (published in 2000); Herbst, K.; Hunger "Industrial Organic Pigments", JP-A-2002-12607, JP-A-2002-188025, JP-A-2003-26978 and JP-A-2003-342503.

The content of the coloring agent in the ink is preferably 0.001% by mass to 15.0% by mass, more preferably 0.01% by mass to 15.0% by mass, relative to the total mass of the ink. More preferably 2.0% by mass to 15.0% by mass.

The colorant may be contained singly or in combination of two or more in the ink.

(Radical polymerizable compound)
The radical polymerizable compound contained in the ink consists of a monofunctional polymerizable compound having one radical polymerizable group and a polyfunctional polymerizable compound having two or more radical 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 remainder of the radically polymerizable compound excluding the monofunctional polymerizable compound is a polyfunctional polymerizable compound.

In the present disclosure, since the proportion of the monofunctional polymerizable compound in the radically polymerizable compound contained in the ink is 30% by mass or more, an image with excellent flexibility can be recorded. On the other hand, since the proportion of the monofunctional polymerizable compound in the radically polymerizable compound contained in the ink is 65% by mass or less, an image with excellent curability can be recorded. In addition, it is possible to suppress a phenomenon (so-called migration) in which unreacted monomer components are transferred from the image recorded matter to the outside. In particular, it is excellent in that it can be applied to packaging materials in the fields of food packaging and cosmetic packaging, which require strict safety of substrates.

The proportion of the monofunctional polymerizable compound in the radically polymerizable compound contained in the ink is preferably 35% by mass to 50% by mass, and 40% by mass, from the viewpoint of improving the flexibility and curability of the recorded image. % to 50 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 with respect to the total mass of the ink. ~90% by mass is more preferred.

- 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 radical polymerization reaction, but from the viewpoint of curability, it is preferably an ethylenically unsaturated group. Specific examples of the monofunctional polymerizable compound contained in the ink are the same as those 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 proportion of the hydroxyl group-containing monofunctional polymerizable compound in 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 converted into a homopolymer. When the glass transition temperature is −40° C. or higher, an image having excellent curability can be recorded. Further, when the glass transition temperature is 50° C. or less, an image having excellent flexibility can be recorded.

When the ink contains a plurality of monofunctional polymerizable compounds, it is preferable that the average glass transition temperature of the homopolymer is within the above range. That is, the glass transition temperature of each 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 preferably within the above range.

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

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

- 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 from the viewpoint of curability, it is preferably an ethylenically unsaturated group. 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 ingredients 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. A pigment can be dispersed in a liquid medium using a dispersing agent. As the dispersant, a commonly known one can be used. From the viewpoint of dispersion stability, the dispersant is preferably a compound having both a hydrophilic structure and a hydrophobic structure.

Dispersants include, for example, higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, alkyl phosphates, polyoxyalkylene alkyl ether phosphates, polyoxy 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.

Dispersants include high molecular weight dispersants having a molecular weight of 1000 or more obtained by copolymerizing hydrophilic monomers and hydrophobic monomers. From the viewpoint of dispersion stability, the hydrophilic monomer is preferably a dissociative group-containing monomer, and preferably a dissociative group-containing monomer having a dissociative group and an ethylenically unsaturated bond. Examples of dissociable group-containing monomers include carboxy group-containing monomers, sulfonic acid group-containing monomers, and phosphoric acid group-containing monomers. 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. Group-containing monomers are preferred. The polymer may be either a random copolymer or a block copolymer.

Dispersants may be commercially available. Commercially available products include, for example,
DISPERBYK-101 DISPERBYK-102 DISPERBYK-103 DISPERBYK-106 DISPERBYK-110 DISPERBYK-111 DISPERBYK-161 DISPERBYK-162 DISPERBYK-163 DISPERBYK-164 １６８、ＤＩＳＰＥＲＢＹＫ－１７０、ＤＩＳＰＥＲＢＹＫ－１７１、ＤＩＳＰＥＲＢＹＫ－１７４、ＤＩＳＰＥＲＢＹＫ－１８２（以上、ＢＹＫケミー社製）；及びＳＯＬＳＰＥＲＳＥ３０００、ＳＯＬＳＰＥＲＳＥ５０００、ＳＯＬＳＰＥＲＳＥ９０００、ＳＯＬＳＰＥＲＳＥ１２０００、ＳＯＬＳＰＥＲＳＥ１３２４０、ＳＯＬＳＰＥＲＳＥ１３９４０、ＳＯＬＳＰＥＲＳＥ１７０００、ＳＯＬＳＰＥＲＳＥ２２０００、ＳＯＬＳＰＥＲＳＥ２４０００、ＳＯＬＳＰＥＲＳＥ２６０００、ＳＯＬＳＰＥＲＳＥ２８０００、ＳＯＬＳＰＥＲＳＥ３２０００ , SOLSPERSE36000, SOLSPERSE39000, SOLSPERSE41000, SOLSPERSE71000 (manufactured by Lubrizol)
is mentioned.

As a dispersing device for dispersing the pigment, known dispersing devices can be used, such as ball mills, sand mills, bead mills, roll mills, jet mills, paint shakers, attritors, ultrasonic dispersers and dispersers.

In the ink, the content of the dispersant with respect to the content of the pigment is preferably 0.05 to 1.0, more preferably 0.1 to 0.5 on a mass basis, from the viewpoint of dispersion stability. 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 radical polymerization initiators include (a) alkylphenone compounds, (b) acylphosphine oxide compounds, (c) aromatic onium salt compounds, (d) organic peroxides, (e) thio compounds, and (f) hexaaryl rubyimidazole compounds, (g) ketoxime ester compounds, (h) borate compounds, (i) azinium compounds, (j) metallocene compounds, (k) active ester compounds, (l) compounds having a carbon-halogen bond, and (m ) alkylamine compounds.

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

4. 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, relative to the total mass of the ink. 0% by mass to 8.0% by mass is more preferable.

When an acylphosphine oxide compound and a 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, and 1.0% by mass, based on the total mass of the ink. % to 6.0% by mass is more preferred, and 2.5% to 5.0% by mass is even more preferred. 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 with respect to the total mass of the ink. % to 3.0% by mass is more preferred.

(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 surfactants are as described above.

In the present disclosure, the surfactant is preferably a silicone-based surfactant from the viewpoint of improving adhesion to the substrate. Examples of silicone-based surfactants include polysiloxane compounds, preferably modified polysiloxane compounds in which organic groups are introduced into some of the methyl groups of dimethylpolysiloxane. Modification includes polyether modification, methylstyrene modification, alcohol modification, alkyl modification, aralkyl modification, fatty acid ester modification, epoxy modification, amine modification, amino modification, and mercapto modification. A plurality of types of organic groups may be introduced into some of the methyl groups of dimethylpolysiloxane. Among them, from the viewpoint of ejection 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 0.01% by mass to 4.0% by mass, more preferably 0.01% by mass to 3.0% by mass. 05% by mass to 2.0% by mass is more preferable.

(Additive)
The ink may contain additives such as a co-sensitizer, an ultraviolet absorber, an antioxidant, an anti-fading agent, a conductive salt, a solvent, and a basic compound, if necessary.

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

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. More preferably, it is up to 10 mPa·s. Viscosity is measured at 25° C. using a viscometer, for example, using a TV-22 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, even more preferably 25 mN/m to 45 mN/m. The surface tension is measured at 25° C. using a surface tensiometer, for example, by a plate method using an automatic surface tensiometer manufactured by Kyowa Interface Science Co., Ltd. (product name “CBVP-Z”).

[Image recording method]
The image recording method of the present disclosure includes an undercoat composition application step of applying the undercoat composition contained in the ink set onto a substrate, and a first actinic ray irradiation of irradiating the undercoat composition with a first actinic energy ray. an ink application 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 active energy ray of irradiating the ink with the second active energy ray and an energy beam irradiation step.

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

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

Substrates include, for example, glass, quartz, and plastic films. Examples of resins constituting plastic films include cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, acrylic resins, chlorinated polyolefin resins, polyethersulfone resins, 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.

Although the thickness of the substrate is not particularly limited, it is preferably 1 μm to 500 μm, more preferably 2 μm to 200 μm, even more preferably 5 μm to 100 μm, and particularly preferably 10 μm to 90 μm.

In the step of applying the undercoat composition, the application of the undercoat composition can be performed by applying a known method such as a coating method, an immersion method, or an inkjet recording method. Coating methods include, for example, bar coaters, extrusion coaters, air doctor coaters, blade coaters, rod coaters, knife coaters, squeeze coaters, reverse roll coaters, transfer roll coaters, gravure coaters, kiss roll coaters, cast coaters, spray coaters, It is done using a curtain coater or an extrusion coater.

The undercoat composition is preferably applied to the same area as the ink film formed by applying the ink or to a wider area than the ink film, and is applied so as to cover the entire area where the ink film is formed. is preferred.

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

(First 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-cured" 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. A polymerization rate is calculated by the following method.

After applying the undercoat composition to the substrate, a sample piece having a size of 20 mm×50 mm (hereinafter referred to as a post-irradiation sample piece) is cut out from the film formed by irradiating the active energy ray. The cut 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. The obtained eluate is subjected to high performance liquid chromatography to measure the amount of the radically polymerizable compound (hereinafter referred to as “X1”).
Separately, after applying the undercoat composition on the substrate, the same operation as above is performed except that the active energy ray is not irradiated, and the amount of the radically polymerizable compound (hereinafter referred to as “X2”) is measured. Using X1 and X2, the conversion is calculated from the following formula.
Polymerization rate (%) = {(X2-X1)/X2} x 100

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

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

From the viewpoint of semi-curing the undercoat composition, the exposure amount in irradiation with active energy rays is preferably 3 mJ/cm ² to 100 mJ/cm ² , more preferably 5 mJ/cm ² to 20 mJ/cm ² . .

Mercury lamps, gas lasers and solid-state lasers are mainly used as light sources for ultraviolet irradiation, and mercury lamps, metal halide lamps and ultraviolet fluorescent lamps are widely known. UV-LEDs (light-emitting diodes) and UV-LDs (laser diodes) are small, have a long life, are highly efficient, and are low-cost, and are expected to serve as light sources for ultraviolet irradiation. 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 by an inkjet recording method onto the undercoat composition irradiated with the first active energy ray.

The inkjet recording method is not particularly limited as long as it can record an image, and known methods include, for example, a charge control method that ejects ink using electrostatic attraction, and a drop method that uses vibration pressure of a piezoelectric element. An on-demand method (pressure pulse method), an acoustic inkjet method that converts an electrical signal into an acoustic beam and irradiates it onto the ink to use radiation pressure to eject the ink, and a method that heats the ink to form air bubbles and uses the pressure generated Any thermal ink jet (bubble jet (registered trademark)) system may be used.

As an ink jet recording method, in particular, the method described in Japanese Patent Laid-Open No. 59936/1989 causes a sudden change in volume of the ink under the action of thermal energy, and the acting force due to this change in state causes the ink to be ejected from the nozzle. It is possible to effectively use an ink jet recording method for discharging.

As for the inkjet recording method, the method described in paragraphs 0093 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 the shuttle method performs recording while scanning the head in the width direction of the substrate, and the recording elements are arranged corresponding to the entire side of the substrate. and a line method using a line head that has been developed.

In the line method, a pattern can be formed on the entire surface of the substrate by scanning the substrate in a direction that intersects the direction in which the printing elements are arranged, and a conveying system such as a carriage for scanning a short head is not required.

In addition, complicated scanning control of the movement of the carriage and the base material is not required, and only the base material is moved, so that the recording speed can be increased compared to the shuttle system.

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

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

In the ink application step, only one type of ink may be applied, or two or more types 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 it is more preferable to apply each color ink of white, yellow, cyan, magenta and black. Moreover, each color ink described above may be applied in combination with light color ink such as light magenta and light cyan, special color ink such as orange, green and violet, clear ink, or 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, even more preferably 0.3% or less.

In the second active energy ray irradiation step, the undercoat composition and the ink are cured such 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 not more than 100%. is preferred. Each polymerization rate is more preferably 85% to 100%, more preferably 90% to 100%.

Examples of active energy rays include ultraviolet rays, visible rays, and electron beams, with ultraviolet rays being preferred. Examples of the light source for ultraviolet irradiation include those described above.

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

The exposure amount in irradiation with active energy rays is preferably 50 mJ/cm ^{2 to 1000 mJ/cm 2 and more preferably 100 mJ/cm 2 to 500 mJ/cm 2 from the} viewpoint of completely curing the undercoat composition and ink. is more preferred.

(Other processes)
The image recording method of the present disclosure may include steps 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 types of ink are applied, it is preferable to semi-harden the first ink after applying the first ink, and then apply the next ink. After applying the last ink, it is preferable to proceed to the second active energy ray irradiation step without semi-curing the last ink.

EXAMPLES 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 thereof is not exceeded.

[Preparation of Undercoat Composition]
The isocyanate compound, polyfunctional polymerizable compound, monofunctional polymerizable compound, polymerization initiator and surfactant shown in the table below were mixed so that the content (% by mass) of each component was shown in the table. The mixture was stirred for 20 minutes at 25° C. and 5000 rpm using a mixer (product name “L4R”, manufactured by Silverson) to obtain an undercoat composition.

[Ink preparation]
First, a pigment dispersion liquid for each color was prepared.

-Preparation of cyan pigment dispersion-
300 parts by mass of a cyan pigment, 620 parts by mass of "SR9003", and 80 parts by mass of "SOLSPERSE32000" are put into a dispersing machine Motor Mill M50 (manufactured by Eiger), and zirconia beads with a diameter of 0.65 mm are used, and the peripheral speed is 9 m. /s for 4 hours to obtain a cyan pigment dispersion.

-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" are put into a dispersing machine Motor Mill M50 (manufactured by Eiger), and zirconia beads with a diameter of 0.65 mm are used, and the peripheral speed is 9 m. /s for 10 hours to obtain a magenta pigment dispersion.

-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" are put into a dispersing machine Motor Mill M50 (manufactured by Eiger), and zirconia beads with a diameter of 0.65 mm are used, and the peripheral speed is 9 m. /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" are put into a dispersing machine Motor Mill M50 (manufactured by Eiger), and zirconia beads with a diameter of 0.65 mm are used at a peripheral speed of 9 m. /s for 7 hours to obtain a black pigment dispersion.

-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" are put into a dispersing machine Motor Mill M50 (manufactured by Eiger), and zirconia beads with a diameter of 0.65 mm are used, and the peripheral speed is Dispersion treatment was performed at 9 m/s for 4 hours to obtain a white pigment dispersion.

Next, the prepared pigment dispersion, the polyfunctional polymerizable compound, the monofunctional polymerizable compound, the polymerization initiator, the polymerization inhibitor and the surfactant described in the table below are mixed with each component in the content described in the table. (% by mass). The mixture was stirred for 20 minutes at 25° C. and 5000 rpm using a mixer (product name “L4R”, manufactured by Silverson) to obtain an ink.

Speedcure 7010L (manufactured by Lambson) and Irgastab UV-22 (manufactured by BASF) were used for ink preparation. Speedcure 7010L is a mixture of Speedcure 7010 and EOTMPTA with a mixing ratio of 1:1 on a mass basis. Irgastab UV-22 is a mixture of a quinone compound and 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 hydroxyl group-containing monofunctional ratio indicates the ratio of the hydroxyl group-containing monofunctional polymerizable compound to the radically polymerizable compound. Letting A be the monofunctional ratio in the undercoat composition and B be the monofunctional ratio in the ink, the absolute value of the difference between A and B was calculated and described as "|AB|". The unit of the monofunctional ratio and the hydroxyl group-containing monofunctional ratio is % by mass.

<Isocyanate compound>
Takenate D160N: an 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: allophanate form of hexamethylene diisocyanate (manufactured by Mitsui Chemicals, Inc.)
Takenate D110N: an 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: propoxylated (2) neopentyl glycol diacrylate (manufactured by Sartomer, bifunctional)
・GPTA: propoxylated glycerol triacrylate (trifunctional)
EOTMPTA: trimethylolpropane EO added triacrylate (trifunctional)
・ DPHA: dipentaerythritol hexaacrylate (product name “Etermer265”, manufactured by Eternal Materials Co., Ltd., hexafunctional)
UV7630B: urethane acrylate that is a reaction product of dicyclohexylmethane 4,4'-diisocyanate and pentaerythritol tri(meth)acrylate (manufactured by Mitsubishi Chemical Corporation, hexafunctional)
- 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: Ethyl carbitol 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 “Tipaque CR60-2” (manufactured by Ishihara Sangyo Co., Ltd.)

<Dispersant>
・SOLSPERSE32000: polyethyleneimine-based dispersant (manufactured by Lubrizol)

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

<Polymerization inhibitor>
・Quinone compound: 2,6-bis(1,1-dimethylethyl)-4-(phenylmethylene)-2,5-cyclohexadien-1-one

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

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

As an inkjet head, a product name "CA3" manufactured by Toshiba Tech Co., Ltd. was used. Four inkjet heads were arranged in parallel in a direction intersecting the conveying direction of the substrate. An inkjet head was filled with the prepared ink. The inkjet head was heated to 45° C., the frequency was set so that the droplet ejection volume 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) was connected to the blanket at a pressure of 0.2 MPa s, and the nitrogen concentration in the blanket was 99%, and the oxygen concentration was 0.1%. Nitrogen was flowed at a flow rate of 2 liters/minute to 10 liters/minute such that:

As a base material, OPP (oriented polypropylene) film (product name “FOR-AQ25”, Futamura Chemical Co., Ltd., thickness 25 μm) and PET (polyethylene terephthalate) film (product name “FE2001”, Futamura Chemical Co., Ltd., thickness 12 μm) was used. The substrate was conveyed at a speed of 30 m/min, and the undercoat composition was applied onto the substrate using a roller coating machine so as to have a film thickness of 2 μm. Next, an LED light source was used to irradiate ultraviolet rays at an exposure amount of 10 mJ/cm ² to semi-cure the undercoat composition. Ink was ejected onto the semi-cured undercoat composition to record a 100% solid image. Thereafter, an LED light source was used to irradiate ultraviolet rays at an exposure amount of 200 mJ/cm ² to completely cure the undercoat composition and ink.

[evaluation]
For each example and comparative example, the obtained image recorded matter was used to evaluate flexibility, adhesion and curability. The evaluation method is as follows.

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

<Curability>
A sheet of A6 size paper was placed on the image recording surface of the image recording material using the PET film as the base material. The paper was held at 40° C. for 24 hours while a load of 1 kg/A6 size was applied from above. 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 ratio, the better the curability. Evaluation criteria are as follows. The most excellent rank for curability is "5".
5: No transfer.
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 cellotape (registered trademark) with a width of 1 cm was attached to the image recording surface of the image recording material using the PET film as the base material. Using IMADA's 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 was applied at a peeling speed of 300mm/min. It was peeled off and the peel force was measured. It can be judged that the greater the peeling force, the better the adhesion between the substrate and the image. Evaluation criteria are as follows. The most excellent rank for adhesion is "5".
5 Peeling does not occur 4 Peeling occurs and the peeling force is 1.0 N or more.
3 Peeling occurs, and the peel force is 0.4N or more and less than 1.0N.
2 Peeling occurs, and the peel force is 0.1N or more and less than 0.4N.
1 Peeling occurs and the peel 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 proportion of the monofunctional polymerizable compound in the radical polymerizable compound contained in the undercoat composition was 35% by mass to 70% by mass, and the ink It was found that the ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in is 30% by mass to 65% by mass, and the recorded image is excellent in flexibility, curability and adhesion.

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

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

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

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

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

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

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

Example 13 has a glass transition temperature of −40° C. to 50° C. when the homopolymer of the monofunctional polymerizable compound contained in the undercoat composition is used. It turns out that it will be.

Example 13 has a glass transition temperature of −40° C. to 50° C. when the homopolymer of the monofunctional polymerizable compound contained in the undercoat composition is used. It turns out that it will be.

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

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

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

In Example 3, the ink contains a hydroxyl group-containing monofunctional polymerizable compound, and the proportion of the hydroxyl group-containing monofunctional polymerizable compound in the radically polymerizable compound is 20% by mass to 50% by mass, compared with Example 5. As a result, it was found that an image having excellent curability and adhesion was recorded.

In Example 13, the ink contains a hydroxy group-containing monofunctional polymerizable compound, and the proportion of the hydroxy group-containing monofunctional polymerizable compound in the radically polymerizable compound is 20% by mass to 50% by mass, compared with Example 27. As a result, it was found that an image having excellent curability and adhesion was recorded. In addition, it was found that Example 13 recorded an image with better curability than Example 30.

In Example 22, the ink contains a hydroxyl group-containing monofunctional polymerizable compound, and the ratio of the hydroxyl group-containing monofunctional polymerizable compound to the radically polymerizable compound is 20% by mass to 50% by mass, compared with Example 7. As a result, it was found that an image having excellent curability and adhesion was recorded. In addition, it was found that Example 22 recorded an image having better curability than Example 28 and Example 31.

In Example 23, the ink contains a hydroxy group-containing monofunctional polymerizable compound, and the proportion of the hydroxy group-containing monofunctional polymerizable compound in the radically polymerizable compound is 20% by mass to 50% by mass, compared with Example 9. As a result, it was found that an image having excellent flexibility and adhesion was recorded. In addition, it was found that Example 23 recorded an image with more excellent flexibility and curability than Example 29. In addition, it was found that Example 23 recorded an image with better curability than Example 32.

In Example 3, the proportion of the monofunctional polymerizable compound in the radically polymerizable compound contained in the undercoat composition was A mass %, and the proportion of the monofunctional polymerizable compound in the radically polymerizable compound contained in the ink was B mass. %, the absolute value of the difference between A and B was 20 or less.

Claims (8)

an undercoat composition containing an isocyanate compound and a radically polymerizable compound;
and an ink containing a colorant and a polymerizable compound,
The ratio of the monofunctional polymerizable compound to the radically polymerizable compound contained in the undercoat composition is 35% by mass to 70% by mass,
The ink set, wherein 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 converted into a homopolymer. 3. The ink set according to claim 1, wherein the monofunctional polymerizable compound contained in the undercoat composition has a molecular weight of 140-210. <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 hydroxyl group-containing monofunctional polymerizable compound. 5. The ink set according to claim 4, wherein the proportion of the hydroxyl group-containing monofunctional polymerizable compound in the radically polymerizable compound contained in the ink is 20% by mass to 50% by mass. The ratio of the monofunctional polymerizable compound to the radically polymerizable compounds contained in the undercoat composition was defined as A% by mass, and the ratio of the monofunctional polymerizable compound to the radically polymerizable compounds contained in the ink was defined as B% by mass. 6. The ink set according to claim 1, 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 substrate;
a first active energy ray irradiation step of irradiating the undercoat composition with a first active energy ray;
An ink application step of applying the ink by an inkjet recording method onto the undercoat composition irradiated with the first active energy ray;
and a second active energy ray irradiation step of irradiating the ink with a second active energy ray. 8. The image recording method according to claim 7, wherein in said second active energy ray irradiation step, said second active energy ray is irradiated in a nitrogen atmosphere.