JP7319506B1 - Active energy ray-curable ink composition and printed matter - Google Patents

Abstract

Kind Code: A1 An active energy ray-curable ink in which the resulting printed matter has excellent workability that can be used for DR cans and has anti-blocking properties that allow it to be laid flat without applying varnish. Compositions and printed matter are provided. The composition comprises a pigment, a polyester resin, an acrylate monomer and a photopolymerization initiator, wherein the acrylate monomer comprises an acrylate monomer having an isocyanurate ring, a bifunctional acrylate and a monofunctional acrylate, and has an isocyanurate ring. The content of the acrylate monomer is 25 to 50% by mass based on the total amount of the acrylate monomer, and the content of the monofunctional acrylate is 8 to 30% by mass based on the total amount of the acrylate monomer. An active energy ray-curable ink composition, wherein the total content of bifunctional acrylate is 30 to 75% by mass based on the total amount of acrylate monomers. [Selection figure] None

Description

TECHNICAL FIELD The present invention relates to an active energy ray-curable ink composition and printed matter. More specifically, the present invention provides that the resulting printed matter has excellent workability that can be used for DR cans, and has blocking resistance that allows it to be laid flat without applying varnish. The present invention relates to active energy ray-curable ink compositions and printed matter.

The surface of a metal container such as a food can is provided with an indication of the contents, a decoration, or the like. A DR can is produced by printing a display or the like on a metal base material and punching the metal base material. DR cans are subjected to retort treatment after food is placed and sealed. Patent Literature 1 proposes an active energy ray-curable printing ink composition that is resistant to whitening in retort treatment after printing.

Japanese Patent No. 6514836

DR cans are prone to cracks during punching. The generated cracks are further enlarged by the subsequent retort treatment. As a result, conventional DR cans tend to lose gloss. When the gloss is lowered, the luster of the surface of the can is lost, and the commercial value tends to be lowered. Therefore, the ink composition is required to have excellent workability so as not to generate cracks during punching. In some cases, metal substrates on which indications and the like are printed are stored flat without being coated with varnish before being punched. In this case, the printed indicia are reflected on the back side of another metal substrate. In the DR can, the back surface of the metal substrate is the surface that comes into direct contact with food and the like. Therefore, from a hygienic point of view, excellent anti-blocking properties are required to prevent set-off. The active energy ray-curable printing ink composition described in Patent Document 1 cannot achieve both of these workability and blocking resistance.

The present invention has been made in view of such circumstances, and the resulting printed matter has excellent workability that can be used for DR cans, and can be laid flat without applying varnish. It is an object of the present invention to provide an active energy ray-curable ink composition and a printed matter having a high blocking resistance.

The active energy ray-curable ink composition and printed matter of the present invention for solving the above problems mainly include the following configurations.

(1) containing a pigment, a polyester resin, an acrylate monomer, and a photopolymerization initiator, wherein the acrylate monomer contains an acrylate monomer having an isocyanurate ring, a bifunctional acrylate, and a monofunctional acrylate; The content of the acrylate monomer having the isocyanurate ring is 25 to 50% by mass based on the total amount of the acrylate monomer, and the content of the monofunctional acrylate is 8 to 30% by mass based on the total amount of the acrylate monomer. An active energy ray-curable ink composition, wherein the sum of the monofunctional acrylate content and the bifunctional acrylate content is 30 to 75% by mass based on the total amount of acrylate monomers.

According to such a configuration, the printed matter obtained using the active energy ray-curable ink composition has excellent workability that can be used for DR cans, and can be laid flat without applying varnish. It has blocking resistance that can be

(2) The active energy ray-curable ink composition according to (1), wherein the polyester resin has an excess hydroxyl group ratio of 1.0 or more.

According to such a configuration, the printed matter obtained using the active energy ray-curable ink composition has more excellent hot water retort resistance. As a result, the resulting DR can is more resistant to whitening and loss of gloss.

(3) The active energy ray-curable ink composition according to (1) or (2), which is for metal printing.

According to such a configuration, the printed matter obtained using the active energy ray-curable ink composition is particularly suitable for use in DR cans.

(4) A printed matter in which the active energy ray-curable ink composition according to any one of (1) to (3) is printed on a substrate.

With such a configuration, the printed matter has excellent workability that can be used for DR cans, and has anti-blocking properties that allow it to be laid flat without applying varnish.

According to the present invention, the resulting printed matter has excellent workability that can be used for DR cans, and has blocking resistance that allows it to be laid flat without applying varnish. Curable ink compositions and printed matter can be provided.

<Active energy ray-curable ink composition>
An active energy ray-curable ink composition (hereinafter also referred to as an ink composition) of one embodiment of the present invention contains a pigment, a polyester resin, an acrylate monomer, and a photopolymerization initiator. Acrylate monomers include acrylate monomers having an isocyanurate ring, bifunctional acrylates, and monofunctional acrylates. The content of the acrylate monomer having an isocyanurate ring is 25-50% by mass in the total amount of the acrylate monomer. The content of monofunctional acrylate is 8 to 30% by mass based on the total amount of acrylate monomers. The sum of the content of monofunctional acrylate and the content of bifunctional acrylate is 30 to 75% by mass based on the total amount of acrylate monomers. Each of these will be described below.

(pigment)
Pigments are not particularly limited. By way of example, the pigments are various inorganic or organic pigments.

Inorganic pigments and organic pigments preferably have heat resistance, light resistance, and retort resistance. Inorganic pigments include titanium oxide, silica, carbon black, and the like. Organic pigments include phthalocyanine-based pigments, azo-based pigments, quinacridone-based pigments, diketopyrrolopyrrole-based pigments, quinophthalone-based pigments, and the like.

The content of the pigment is appropriately adjusted depending on the type and purpose. For example, the pigment content is preferably 10% by mass or more in the ink composition. Moreover, the content of the pigment is preferably 60% by mass or less in the ink composition. When the content of the pigment is within the above range, the ink composition has excellent dispersion stability, and in terms of film physical properties, it is possible to avoid adverse effects due to a high pigment concentration.

(polyester resin)
The polyester resin is a polyester composed of an acid component containing a polybasic acid and a polyhydric alcohol component. In the polyester resin, the acid component containing polybasic acid is preferably a divalent acid, and the polyhydric alcohol component is preferably a divalent alcohol. As a result, the obtained film has excellent hot water retort resistance. In addition, the obtained film has better adhesion and anti-blocking properties to metal substrates.

The polybasic acid contained in the acid component is not particularly limited. A polybasic acid is a compound having a plurality of carboxyl groups, and is a component for condensation polymerization with a polyhydric alcohol component to increase the molecular weight. Compounds such as aromatic polybasic acids, aliphatic polybasic acids, alicyclic polybasic acids, and α,β-unsaturated dicarboxylic acids can be used as polybasic acids. Among these, the acid component containing a polybasic acid is selected from the group consisting of an alicyclic polybasic acid, an alicyclic polybasic acid anhydride, an aromatic polybasic acid, and an aromatic polybasic acid anhydride. It is preferable to include at least one selected. The compound having multiple carboxy groups has two or more carboxy groups and may be acid anhydrides thereof. Also, since an acid anhydride group is formed by dehydration from two carboxy groups, one acid anhydride group corresponds to two carboxy groups in this embodiment.

Examples of aromatic polybasic acids include orthophthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, trimellitic acid, pyromellitic acid and biphenyldicarboxylic acid. Examples of aliphatic polybasic acids include succinic acid, azelaic acid, dodecanedioic acid, and dimer acid. Alicyclic polybasic acids include, for example, 1,2,3,6-tetrahydrophthalic acid, hexahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. α,β-unsaturated dicarboxylic acids include, for example, fumaric acid, maleic acid, itaconic acid, citraconic acid and the like. Alkyl esters and acid anhydrides of these compounds can also be used. Among these, the acid component preferably contains at least one selected from the group consisting of alicyclic polybasic acids or anhydrides thereof, aromatic polybasic acids or anhydrides thereof, tetrahydrophthalic anhydride, It is more preferable to contain at least one selected from the group consisting of hexahydrophthalic anhydride, phthalic anhydride, and isophthalic acid, and at least one selected from the group consisting of tetrahydrophthalic anhydride and hexahydrophthalic anhydride. is more preferable. Thereby, the ink composition has better hot water retort resistance.

Polyhydric alcohol components include ethylene glycol, 1,4-butanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, xylylene glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, poly(ethyleneoxy)glycol, poly(tetramethyleneoxy)glycol, alkylene oxide adduct of bisphenol A, alkylene oxide adduct of hydrogenated bisphenol A, and the like. Among these, the polyhydric alcohol component preferably contains at least one selected from the group consisting of hydrogenated bisphenol A, 1,6-hexanediol, cyclohexanedimethanol, and diethylene glycol. Thereby, the ink composition has better hot water retort resistance.

The weight average molecular weight of the polyester resin of the present embodiment is preferably 1000 or more, more preferably 1300 or more. Moreover, the weight average molecular weight of the polyester resin is preferably 5,000 or less, more preferably 3,000 or less. By setting the polymerization average molecular weight of the polyester resin within the above range, the film obtained using the ink composition of the present embodiment has superior adhesion and blocking resistance to metal substrates. The weight-average molecular weight of the polyester resin of the present embodiment can be obtained as a polystyrene-equivalent weight-average molecular weight by gel permeation chromatography (GPC), for example.

The excess hydroxyl group ratio of the polyester resin of the present embodiment is preferably 1.0 or more, more preferably 1.15 or more. Also, the excess hydroxyl group is preferably 2.0 or less, more preferably 1.90 or less. If the hydroxyl excess ratio is less than 1.0, the resulting ink composition has poor hot water retort resistance.

In the present embodiment, the excess hydroxyl group ratio (OH amount/COOH amount), which is the molar ratio of the hydroxyl group to the carboxy group, is based on the blending of the monomers used, and the OH amount and the COOH amount are calculated by the following formula. It can be obtained by calculating the amount/amount of COOH.
OH amount = number of moles of each monomer used in compounding x valence Amount of COOH = number of moles of each monomer used in compounding x valence

The acid value of the polyester resin is not particularly limited. For example, the polyester resin preferably has an acid value of 0.1 mgKOH/g or more. Moreover, the acid value of the polyester resin is preferably 35 mgKOH/g or less. When the acid value of the polyester resin is within the above range, the ink composition has better hot water retort resistance. In addition, in this embodiment, an acid value can be calculated by the neutralization titration method, for example.

The content of the polyester resin is preferably 10% by mass or more in the ink composition. Moreover, the content of the polyester resin is preferably 40% by mass or less in the ink composition. When the content of the polyester resin is within the above range, the film obtained using the ink composition of the present embodiment has superior adhesion to metal substrates and anti-blocking properties.

In addition to the above polyester resin, conventionally used ink resins may be used in combination. Ink resins include petroleum resins, epoxy resins, allyl resins, ketone resins, and the like.

(acrylate monomer)
Acrylate monomers include acrylate monomers having an isocyanurate ring, bifunctional acrylates, and monofunctional acrylates.

Acrylate Monomer Having Isocyanurate Ring The acrylate monomer having an isocyanurate ring is not particularly limited. Examples of acrylate monomers having an isocyanurate ring include isocyanurate EO-modified triacrylate, isocyanurate EO-modified diacrylate, and isocyanurate ε-caprolactone-modified triacrylate. Among these, the acrylate monomer having an isocyanurate ring is preferably an isocyanuric acid EO-modified triacrylate or an isocyanuric acid EO-modified diacrylate from the viewpoint of excellent blocking resistance of the printed matter obtained using the ink composition.

The content of the acrylate monomer having an isocyanurate ring should be 25% by mass or more, preferably 30% by mass or more, based on the total amount of the acrylate monomer. Moreover, the content of the acrylate monomer having an isocyanurate ring may be 50% by mass or less, preferably 45% by mass or less, in the total amount of the acrylate monomer. When the content of the acrylate monomer having an isocyanurate ring is less than 25% by mass, the printed matter obtained using the ink composition has poor workability in DR can applications. On the other hand, when the content of the acrylate monomer having an isocyanurate ring exceeds 50% by mass, the acrylate monomer having an isocyanurate ring precipitates, making the ink composition unsuitable.

- Bifunctional acrylate The bifunctional acrylate is not particularly limited. Examples of bifunctional acrylates include 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 3-methyl -1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,9- nonanediol di(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate Acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate, neopentyl glycol EO modified di(meth)acrylate, neopentyl glycol PO Modified di(meth)acrylate, bisphenol A (EO-modified) di(meth)acrylate, bisphenol A (PO-modified) di(meth)acrylate, trimethylolpropane EO-modified di(meth)acrylate, trimethylolpropane PO-modified di(meth)acrylate ) acrylates and the like.

The content of the bifunctional acrylate is preferably 5% by mass or more, more preferably 10% by mass or more, based on the total amount of the acrylate monomer. Also, the content of the bifunctional acrylate is preferably 65% by mass or less, more preferably 50% by mass or less, in the total amount of the acrylate monomer. When the content of the bifunctional acrylate is within the above range, the printed matter obtained using the ink composition has excellent processability.

- Monofunctional acrylate The monofunctional acrylate is not particularly limited. By way of example, monofunctional acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, cyclohexyl (meth)acrylate, methoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, phenol EO-modified (meth)acrylate, nonylphenol EO-modified (meth)acrylate, glycidyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate , dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, Benzyl (meth)acrylate, phenylbenzyl (meth)acrylate, mono(2-acryloyloxyethyl) succinate, N-[2-(acryloyloxy)ethyl]phthalimide, N-[2-(acryloyloxy)ethyl]tetrahydrophthalimide etc.

The content of the monofunctional acrylate should be 8% by mass or more, preferably 10% by mass or more, based on the total amount of the acrylate monomers. Moreover, the content of the monofunctional acrylate may be 30% by mass or less, preferably 25% by mass or less, in the total amount of the acrylate monomer. If the content of the monofunctional acrylate is less than 8% by mass, the printed matter obtained using the ink composition has poor processability for use in DR cans. On the other hand, when the content of the monofunctional acrylate exceeds 30% by mass, the printed matter obtained using the ink composition has poor blocking resistance.

Returning to the description of the entire acrylate monomer, the total content of the monofunctional acrylate and the bifunctional acrylate may be 30% by mass or more, preferably 40% by mass or more, of the total amount of the acrylate monomer. preferable. In addition, the sum of the monofunctional acrylate content and the bifunctional acrylate content may be 75% by mass or less, preferably 65% by mass or less, based on the total amount of the acrylate monomers. When the sum of the content of monofunctional acrylate and the content of difunctional acrylate is less than 30% by mass, the printed matter obtained using the ink composition has poor processability for use in DR cans. On the other hand, when the sum of the monofunctional acrylate content and the bifunctional acrylate content exceeds 75% by mass, the printed matter obtained using the ink composition has poor blocking resistance.

In addition, the acrylate monomer may include other acrylate monomers in addition to the above-described acrylate monomer having an isocyanurate ring, bifunctional acrylate and monofunctional acrylate. Other acrylate monomers are not particularly limited. For example, other acrylate monomers may be trifunctional acrylates, tetrafunctional acrylates, pentafunctional acrylates, hexafunctional acrylates, etc., and two hydroxyl groups of a diol compound are substituted with (meth)acryloyloxy groups. A (meth)acrylate monomer, a di- or tri(meth)acrylate monomer in which two or three hydroxyl groups of a triol compound are substituted with (meth)acryloyloxy groups, and the like may be used.

Trifunctional acrylates are not particularly limited. Examples of trifunctional acrylates include trimethylolpropane tri(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and EO- and PO-modified products thereof.

Tetrafunctional acrylate is not particularly limited. Examples of tetrafunctional acrylates include ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, and the like.

The pentafunctional acrylate is not particularly limited. For example, the pentafunctional acrylate is dipentaerythritol penta(meth)acrylate and the like.

A hexafunctional acrylate is not particularly limited. For example, the hexafunctional acrylate is dipentaerythritol hexa(meth)acrylate and the like.

Alternatively, the polyfunctional acrylate may be a poly(meth)acrylate in which multiple hydroxyl groups of dipentaerythritol, such as dipentaerythritol hexa(meth)acrylate, are substituted with (meth)acryloyloxy groups.

The content of the acrylate monomer is preferably 15% by mass or more, more preferably 20% by mass or more, in the ink composition. Moreover, the content of the acrylate monomer is preferably 55% by mass or less, more preferably 50% by mass or less, in the ink composition. When the content of the acrylate monomer is within the above range, the ink composition has better adhesion to metal substrates and blocking resistance.

(Photoinitiator)
A photopolymerization initiator is a component that generates radicals upon irradiation with active energy rays, and is blended to cure the ink composition.

A photoinitiator is not specifically limited. By way of example, photoinitiators include benzophenone, diethylthioxanthone, 2-methyl-1-(4-methylthio)phenyl-2-morpholinopropan-1-one, 4-benzoyl-4′-methyldiphenyl sulfide, 1-chloro-4-propoxythioxanthone, isopropylthioxanthone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenylketone, bis-2,6-dimethoxybenzoyl-2,4,4 -trimethylpentylphosphine oxide, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2,2-dimethyl-2-hydroxyacetophenone, 2 , 2-dimethoxy-2-phenylacetophenone, 2,4,6-trimethylbenzyl-diphenylphosphine oxide, 2-benzyl-2-dimethylamino-1-(morpholinophenyl)-butan-1-one and the like.

The content of the photopolymerization initiator is not particularly limited. For example, the content of the photopolymerization initiator in the ink composition is preferably 1% by mass or more, more preferably 2% by mass or more. Moreover, the content of the photopolymerization initiator is preferably 20% by mass or less, more preferably 15% by mass or less, in the ink composition. When the content of the photopolymerization initiator is within the above range, the ink composition is sufficiently curable.

(Optional component)
The ink composition of the present embodiment may contain optional components such as an extender pigment, wax, a polymerization inhibitor and a dispersant, in addition to the pigment, polyester resin, acrylate monomer and photopolymerization initiator described above.

Extender pigments are preferably included in order to impart viscoelasticity to the ink composition, adjust fluidity, prevent misting, and the like.

The extender pigment is not particularly limited. Examples of extender pigments include clay, talc, mica, kaolinite (kaolin), barium sulfate, magnesium sulfate, calcium carbonate, silicon oxide, aluminum oxide, bentonite, ground calcium carbonate, barium carbonate, zirconia, alumina, and the like. is.

When an extender is included, the content of the extender is not particularly limited. For example, the content of the extender pigment is preferably more than 0% by mass, more preferably 1% by mass or more, in the ink composition. The content of the extender pigment is preferably 30% by mass or less, more preferably 15% by mass or less, in the ink composition. When the content of the extender is within the above range, the viscoelasticity and fluidity of the ink composition are easily adjusted, and misting is easily prevented.

Wax is not particularly limited. As an example, waxes include waxes such as polyethylene wax, olefin wax, and Fischer-Tropsch wax.

When wax is included, the content of wax is not particularly limited. For example, the wax content in the ink composition is preferably more than 0% by mass, more preferably 1% by mass or more. Also, the content of the wax is preferably 30% by mass or less, more preferably 15% by mass or less, in the ink composition.

A polymerization inhibitor is not specifically limited. Examples of polymerization inhibitors include phenolic compounds such as butylhydroxytoluene, tocopherol acetate, nitrosamines, benzotriazole, hindered amines, and the like.

When a polymerization inhibitor is included, the content of the polymerization inhibitor is not particularly limited. For example, the content of the polymerization inhibitor in the ink composition is preferably more than 0% by mass, more preferably 0.1% by mass or more. Moreover, the content of the polymerization inhibitor is preferably 10% by mass or less, more preferably 5% by mass or less, in the ink composition.

Dispersants are not particularly limited. Examples of dispersants include carbodiimide-based dispersants, polyesteramine-based dispersants, fatty acid amine-based dispersants, modified polyacrylate-based dispersants, modified polyurethane-based dispersants, polychain polymer nonionic dispersants, and polyionic activators.

When a dispersant is included, the content of the dispersant is not particularly limited. For example, the content of the dispersant is preferably 1 to 200% by mass when the colorant is 100% by mass.

The method for preparing the ink composition of this embodiment is not particularly limited. To give an example, the ink composition can be prepared by a conventional method using a roll mill, ball mill, bead mill, or the like.

<Printed Matter>
A printed matter of one embodiment of the present invention is a printed matter in which the active energy ray-curable ink composition of the above embodiment is printed on a substrate. As an example, a printed matter comprising a film formed by printing the ink composition described above on a metal plate or a metal substrate provided with a base coat layer will be described below.

The ink composition of the above embodiment is printed on a substrate such as a metal substrate to form a film. The metal substrate is not particularly limited. For example, the metal plate is a metal substrate such as stainless steel, aluminum, tin-plated steel plate, tin-free steel, or a metal base plate obtained by providing a base coat (primer) layer on these metal substrates. . For forming the base coat layer, for example, a base coat composition such as a size paint or a white coating generally used in metal printing may be used. Also, the metal substrate may be laminated with a PET film.

A method for printing the ink composition of the present embodiment on a metal substrate is not particularly limited. For example, the printing method is a normal printing method such as an offset method using dampening water or a dry offset method.

The thickness of the ink film to be obtained is not particularly limited. For example, the thickness of the ink film is 0.1 to 6 μm.

Conditions for curing the ink composition are not particularly limited. The active energy rays used for the active energy ray curing reaction are ultraviolet rays, electron beams, and the like. Ultraviolet light sources include xenon lamps, high-pressure mercury lamps, metal halide lamps, gallium lamps, ultraviolet light emitting diodes (UV-LED), ultraviolet laser diodes (UV-LD), etc., and ultraviolet irradiation devices having these light sources are used. can. Incidentally, the amount of light, the arrangement of the light source, the transport speed, etc. can be adjusted as necessary. When a high pressure mercury lamp is used, it is preferable to carry out curing at a conveying speed of about 2 to 100 m/min for one lamp having a light quantity of about 80 to 160 W/cm. On the other hand, in the case of electron beams, it is preferable to cure by an electron beam accelerator having an accelerating voltage of about 10 to 300 kV under conditions of a conveying speed of about 5 to 50 m/min.

A thermosetting topcoat varnish layer may be formed on the ink layer. The thermosetting topcoat varnish layer can be exemplified by any water-based or solvent-based thermosetting topcoat varnish. Commercially available solvent-based thermosetting topcoat varnishes include polyester/amino-based topcoat varnishes manufactured by Toyochem Co., Ltd., and the like.

The printed matter of the present embodiment is formed with a film made of the ink composition described above. Therefore, even when the printed matter is laid flat without such a varnish layer, the film is less likely to be transferred to the back surface of another printed matter, and the anti-blocking property is excellent.

The method of forming the varnish layer is not particularly limited. For example, the varnish layer is coated with a roll coater and then dried by heating at 150° C. to 250° C. for 5 seconds to 15 minutes to form a coating film excellent in appearance, hardness, workability, and retort resistance. be able to.

When a varnish layer is formed, the thickness of the varnish layer is not particularly limited. For example, the thickness of the varnish layer is preferably 3 μm or more. Also, the thickness of the varnish layer is preferably 10 μm or less. When the thickness of the varnish layer is within the above range, cracks are less likely to occur in the printed material during punching or the like when manufacturing DR cans, and whitening after retort treatment is suppressed.

As described above, the ink composition of the above-described embodiment has excellent processability when producing DR cans, and is less prone to cracks and whitening after hot water retort treatment. Therefore, it is suitable for metal printing, and particularly suitable for metal printing on DR cans.

As described above, according to the ink composition of the present embodiment, the resulting printed matter has excellent workability that can be used for DR cans, and can be stacked flat without applying varnish. have sex.

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples. The invention is not limited to these examples. Each numerical value in the table is based on mass%.

The raw materials used are as follows.
<Pigment>
LIONOL BLUE FG-7351: Pigment Blue 15:3, manufactured by Toyocolor Co., Ltd. <Acid and alcohol for polyester resin synthesis>
Tetrahydrophthalic anhydride: Rikacid TH, 152 g/mol, valence 2, manufactured by Shin Nippon Rika Co., Ltd. Hydrogenated bisphenol A: Rikabinol HB, 240 g/mol, valence 2, manufactured by Shin Nippon Rika Co., Ltd. 1,6 hexane Diol: 1,6 hexanediol, 118 g/mol, valence 2, manufactured by UBE <Acrylate Monomer>
Aronix M-408: ditrimethylolpropane tetraacrylate, tetrafunctional acrylate, manufactured by Toagosei Co., Ltd. OTA480: glycerin PO-modified triacrylate, trifunctional acrylate, manufactured by Daicel Ornex Co., Ltd. Laromer LR 8863: trimethylolpropane EO-modified tri Acrylate, trifunctional acrylate, BASF MIRAMER M370: isocyanuric acid EO-modified triacrylate (>99.9%), acrylate monomer having an isocyanurate ring, MIWON SPECIALTY CHEMICAL Aronix M-315: isocyanuric acid EO-modified triacrylate and diacrylate (diacrylate ratio: 3 to 13%), acrylate monomer having an isocyanurate ring, MIRAMER M216 manufactured by Toagosei Co., Ltd.: neopentyl glycol PO-modified diacrylate, bifunctional acrylate, KAYARAD HX220 manufactured by MIWON SPECIALTY CHEMICAL : Caprolactone-modified hydroxypivalic acid neopentyl glycol ester diacrylate, difunctional acrylate, Nippon Kayaku Co., Ltd. Iupimer UV SA-1002N: Tricyclodecane dimethanol diacrylate, difunctional acrylate, Mitsubishi Chemical Co., Ltd. Aronix M -101A: Phenol EO-modified acrylate, monofunctional acrylate, Toagosei Co., Ltd. MIRAMER M1140: Isobornyl acrylate, monofunctional acrylate, MIWON SPECIALTY CHEMICAL MIRAMER M150: Tetrahydrofurfuryl acrylate, monofunctional acrylate, MIWON SPECIALTY CHEMICAL <Photoinitiator>
Omnirad 379: 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, manufactured by IGM Resins Omnirad EMK: 4,4- Bis (diethylamino) benzophenone, Omnirad DETX manufactured by IGM Resins: 2,4-diethylthioxanthone, manufactured by IGM Resins <Additive>
SST-3T1-RC: polytetrafluoroethylene, manufactured by Shamrock

<Preparation of Resin 1>
Tetrahydrophthalic anhydride: 34.5% by weight, hydrogenated bisphenol A: 60.3% by weight, 1,6 hexanediol: 5.2% by mass was charged and esterified by a conventional method at 220° C. while blowing nitrogen gas to obtain a polyester resin (resin 1) having an acid value of 15.1 and a weight average molecular weight of 1834. The hydroxyl group excess ratio of the obtained resin 1 was 1.3.
<Preparation of Resin 2>
Tetrahydrophthalic anhydride: 28.7% by weight, hydrogenated bisphenol A: 65.6% by weight, 1,6 hexanediol: 5.7% by mass was charged and esterified by a conventional method at 220° C. while blowing nitrogen gas to obtain a polyester resin (resin 2) having an acid value of 12.5 and a weight average molecular weight of 1,069. The hydroxyl group excess ratio of the obtained Resin 2 was 1.7.
<Preparation of Resin 3>
Tetrahydrophthalic anhydride: 43.3% by weight, hydrogenated bisphenol A: 52.2% by weight, 1,6 hexanediol: 4.5% by mass was charged and esterified by a conventional method at 220° C. while blowing nitrogen gas to obtain a polyester resin (resin 1) having an acid value of 65.0 and a weight average molecular weight of 2767. The excess hydroxyl group ratio of Resin 3 obtained was 0.9.

<Example 1>
The ink composition of Example 1 was prepared by mixing each component according to the formulation shown in Table 1 and then kneading the mixture with a three-roll mill heated to 40°C. The obtained ink composition was evaluated for workability, blocking resistance, presence or absence of precipitation, and presence or absence of whitening by the following evaluation methods. Table 1 shows the results.

<Examples 2 to 16, Comparative Examples 1 to 16>
Ink compositions were prepared and evaluated in the same manner as in Example 1, except that the formulations were changed to those shown in Tables 1 and 2. The results are shown in Tables 1 and 2.

As a metal plate used for evaluation, an electric tin plate (ET2.8/2.8 T2.5B manufactured by Nippon Steel & Sumikin Co., Ltd.) was coated with a polyester/amino base coating (manufactured by Toyochem Co., Ltd.) in an amount of 140 mg. A metal plate provided with a base coat layer coated at 100 cm ² and baked at 180° C. for 10 minutes was prepared. The resulting ink was spread on the base coat layer of the metal plate using an RI tester (manufactured by Tester Sangyo Co., Ltd.) to a film thickness of 1.5 μm. Using a 120 W/cm irradiation device manufactured by Su Co., Ltd., the printed matter was irradiated with ultraviolet rays at a distance of 11 cm from the printed matter and at a conveyor speed of 30 m/min to cure the ink. Also, after printing twice under the same printing conditions, a polyester/amino-based top coating (manufactured by Toyochem Co., Ltd.) was applied at a coating amount of 70 mg/100 cm ² and baked at 180 ° C. for 10 minutes to prepare test sample B. . Using the obtained test samples A and B, evaluation was performed by the following method. The RI tester is a tester that spreads ink on a recording medium, and can adjust the transfer amount of ink and printing pressure.

<Workability>
A cylinder having a diameter of 80 mm and a height of 50 mm was punched out from the test sample B prepared by the above method to obtain a processed product. The processed product thus obtained was sterilized for 90 minutes while being immersed in hot water at 125° C., and then the decrease in gloss on the side surface of the processed product was visually evaluated according to the following criteria. ○△ or more was judged to be a practical level.
(Evaluation criteria)
◯: The decrease in gloss was very small.
◯Δ: A decrease in gloss was observed, but some gloss remained.
Δ: Significant decrease in glossiness.
x: The decrease in gloss was very large.
-: Evaluation was not possible due to precipitation.

<Blocking resistance>
The test sample A prepared by the above method was cut into a size of 3 cm x 5 cm, an electric tin plate cut into the same size was placed on the opposite side of the ink film, and a blocking tester (manufactured by Tester Sangyo Co., Ltd. ⁾ It was left for 1 hour in an electric oven at 40° C. with a load applied, and then taken out. ○△ or more was judged to be a practical level.
(Evaluation criteria)
◯: No set-off occurred.
○△: Set-off was slightly confirmed.
(triangle|delta): Clear transfer was confirmed.
x: Clear set-off was confirmed, and peeling of the ink film was confirmed.
-: Evaluation was not possible due to precipitation.

<Presence or absence of precipitation>
The prepared ink was allowed to stand at 10° C. for 240 hours, and then the presence or absence of precipitates in the ink was visually evaluated according to the following criteria.
(Evaluation criteria)
◯: No precipitate was found.
x: Precipitates were found.

<Presence or absence of whitening>
The test sample B prepared by the above method was sterilized for 90 minutes while immersed in hot water at 125°C, and then the degree of whitening of the coating film surface was visually evaluated according to the following criteria. ○△ or more was judged to be a practical level.
(Evaluation criteria)
◯: No whitening occurred.
◯Δ: There was slight whitening.
Δ: Obvious whitening was confirmed.
x: The entire coating film was completely whitened.
-: Evaluation was not possible due to precipitation.

As shown in Tables 1-2, the ink compositions of Examples 1-16 of the present invention did not precipitate. In addition, the printed matter using the ink composition had workability suitable for use in DR cans, and was less likely to whiten even when subjected to hot water retort treatment. Furthermore, the printed matter did not show through even when laid flat, and had excellent blocking resistance.

Claims (4)

including a pigment, a polyester resin, an acrylate monomer, and a photoinitiator;
The acrylate monomer includes an acrylate monomer having an isocyanurate ring, a bifunctional acrylate, and a monofunctional acrylate,
The content of the acrylate monomer having the isocyanurate ring is 25 to 50% by mass in the total amount of the acrylate monomer,
The content of the monofunctional acrylate is 8 to 30% by mass in the total amount of acrylate monomers,
An active energy ray-curable ink composition, wherein the sum of the content of the monofunctional acrylate and the content of the bifunctional acrylate is 30 to 75% by mass based on the total amount of the acrylate monomer. 2. The active energy ray-curable ink composition according to claim 1, wherein the polyester resin has an excess hydroxyl group ratio of 1.0 or more. 3. The active energy ray-curable ink composition according to claim 1, which is for metal printing. 3. A printed matter in which the active energy ray-curable ink composition according to claim 1 or 2 is printed on a substrate.