JP6477113B2 - Electron beam curable inkjet ink - Google Patents

Description

  The present invention relates to an electron beam curable inkjet ink.

In recent years, inkjet printing has been able to eject fine droplets at a high frequency due to technological progress of the head. As a result, inkjet printing, which was inferior to existing printing methods in terms of productivity and image quality, has the advantages of digitization such as small lots, short delivery times, and low costs, and is an alternative to existing printing methods in various fields. Is progressing.
In particular, ultraviolet (UV) curable inkjet printing has features such as high-speed curing, high definition, and versatility of base materials compared to other solvent-based and water-based printing systems. Therefore, it can be said that it is suitable for use in packaging materials.

  On the other hand, with the increasing awareness of safety to the human body and the environment, especially for inks used for food and pharmaceutical packaging, it is required to establish safety by reducing the mixing of chemical substances derived from the ink. Especially in the EU market, there is a threshold that regulates the migration of chemical substances into food contents, so it is essential to reduce low-molecular-weight chemical substances that are highly toxic and easily mixed into printed materials. In the Japanese market, there is no threshold, but in actual food packaging applications, it was found that odor repellency is very high, and it is essential to reduce low molecular weight components that are likely to emit odor.

However, as is generally known, many of the low molecular weight components such as initiators and monomers used in the UV curing reaction have become more and more toxic to the human body and the environment. Curing using radical reactions such as is a very complex reaction that proceeds while competing with various substances such as oxygen during the reaction, so a large amount of monomer or initiation is in the cured film after UV irradiation. The agent remains unreacted and remains, causing migration and odor.
In addition, when curing UV ink, the curing speed varies depending on the UV transmittance of the colorant contained in the ink. Especially in black and other low-permeability inks, a large amount of initiator and sensitizer are used. It was necessary to put in. As a result, these dark inks are prone to migration of initiators and sensitizers, and are difficult to use in food and pharmaceutical packaging from the viewpoint of safety.

  On the other hand, the curing or crosslinking technology by electron beam irradiation has been attracting attention as an environmentally friendly process that saves energy and does not release solvents from the viewpoint of environmental problems, which are global problems like UV curing. Consideration has been made. This method is a method of accelerating electrons with a voltage in a vacuum, taking out the accelerated electrons into a normal pressure atmosphere such as air, and irradiating an object with an electron beam.

Advantages of curing and crosslinking by electron beam irradiation include the following.
(1) Since it is not necessary to contain a large amount of an organic solvent as a diluent, it is environmentally friendly.
(2) Fast curing speed, high productivity, and no need for cooling, aging, etc., so post-processing can be performed immediately.
(3) The curing work area is smaller than that of heat drying, and work management is easier than temperature management during heat drying.
(4) There is no thermal damage to the substrate due to room temperature curing.
(5) Since an initiator and a sensitizer are unnecessary, the weather resistance and stability of the cured film are improved, and the odor is low.
(6) Since it can be cured regardless of the pigment concentration, high density and wide color rendering printing is possible.

  It is considered that the advantages of electron beam irradiation as described above can be realized by inkjet printing on food and pharmaceutical packaging. This is because it is possible to eliminate odors and migration derived from initiators and sensitizers contained in UV curable inks, which have been considered a problem in developing inkjet printing on food and pharmaceutical packaging.

  Conventionally, in order to make use of the advantages of such electron beam irradiation, studies have been made on electron beam curable inkjet inks (Patent Documents 1 and 2). However, since these inks contain a large amount of trifunctional or more other functional monomers, they have a three-dimensionally very strong cross-linking structure when cured with an electron beam, and cured films using these inks are hard and flexible. Lack of sex. For this reason, when it is applied to food and pharmaceutical packaging, it does not have the necessary flexibility of cured film at the same time as low odor and low migration, making it difficult to develop into flexible packaging. Furthermore, these inks also have poor ejection properties, which are important as inkjet inks. When high-speed printing is performed, the landing accuracy is lowered and the image quality is lowered. Furthermore, since the pigment concentration was low, only printed matter with low coloring power could be produced.

JP 2004-42465 A JP 1997-314981 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an electron beam curable inkjet ink that can be applied to food / pharmaceutical packaging by realizing both low odor, low migration, flexibility, and high image quality.

That is, the present invention is an electron beam curable inkjet ink containing a colorant and a polymerizable compound,
The polymerizable compound contains a bifunctional monomer;
The bifunctional monomer contains dipropylene glycol diacrylate and 2- (2-vinyloxyethoxy) ethyl acrylate,
The content of 2- (2-vinyloxyethoxy) ethyl acrylate is 10 to 30% by weight based on the total weight of the ink,
The total content of the monofunctional monomer and the bifunctional monomer is 95 to 100% by weight in the total amount of the polymerizable compound,
The viscosity of the ink state, and are following 100mPa · s,
The present invention relates to an electron beam curable ink jet ink characterized by not containing an initiator and a sensitizer .

  The present invention also relates to the above electron beam curable inkjet ink, wherein the amount of the colorant added is higher than 3% by weight in the total amount of the ink.

  Moreover, this invention relates to the printed matter using the said electron beam curable inkjet ink.

  According to the present invention, an electron beam that is compatible with food / pharmaceutical packaging while having low odor, low migration, flexibility, and high image quality while combining low cost with an inkjet system, versatility of base material, and high productivity. A curable inkjet ink could be provided.

  Hereinafter, the active energy ray-curable inkjet ink of this embodiment will be described. Unless otherwise specified, “part” and “%” represent “part by weight” and “% by weight”.

(Electron beam curable inkjet ink)
The electron beam curable ink-jet ink of the present invention contains a colorant such as a pigment and a polymerizable compound, and can further contain a pigment dispersant, an additive, and the like (hereinafter referred to as “electron beam curing of this embodiment”). Type ink-jet ink composition "may be referred to as" ink "or" ink composition ". Unlike the ultraviolet curable inkjet ink, the energy of the electron beam is very strong and can excite the polymerizable compound itself, so that the initiator and sensitizer which are essential components of the ultraviolet curable inkjet ink do not have to be included. Hereinafter, first, the electron beam curable inkjet ink of the present invention will be described.

(Polymerizable compound)
As the “polymerizable compound” defined in the present specification, a compound that directly undergoes a polymerization reaction after being irradiated with an electron beam can be used. Hereinafter, the “polymerizable compound” is also simply referred to as “monomer”.

  Specific examples of the polymerizable compound include monofunctional monomers, bifunctional monomers, and trifunctional or higher polyfunctional monomers. Among them, acrylic monomers, vinyl monomers, vinyl ether monomers, vinyl ester monomers, acrylic and vinyl or allyl. Are included in the molecule, such as different monomers, allyl ether monomers, and allyl ester monomers.

  As a polymeric compound in this invention, a monofunctional monomer and / or a bifunctional monomer are contained, and also the polyfunctional monomer more than trifunctional can be contained.

  The monofunctional monomer and the bifunctional monomer can be expected to have the effect of reducing the viscosity of the ink and reducing the residual amount of the cured film.

  In the present invention, monofunctional acrylic monomers, bifunctional acrylic monomers, heterobifunctional monomers including acryl and vinyl in the molecule, heterobifunctional monomers including acryl and allyl in the molecule, and the like are more preferably used.

The monofunctional monomer is a compound having only one polymerizable functional group in the molecule. Specific examples of the compound include benzyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, (ethoxy (or propoxy)) 2-phenoxyethyl (meth) acrylate, dicyclopentenyl (oxyethyl) (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, 2-methoxyethyl (meth) acrylate, methoxytriethylene glycol ( (Meth) acrylate, 2-ethoxyethyl (meth) acrylate, ethoxyethoxyethyl (meth) acrylate, methoxydipropylene glycol (meth) acrylate, dipropylene glycol (meth) acrylate Nonylphenol EO modified acrylate, nonylphenol PO modified acrylate, o-phenylphenol EO modified acrylate, 2-ethylhexyl EO modified acrylate, β-carboxylethyl (meth) acrylate, trimethylolpropane formal (meth) acrylate, isoamyl (meth) Acrylate, cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, norbornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate, 2 -Hydroxy-3-phenoxypropyl (meth) acrylate, 1,4-cyclohexanedimethanol (meth) acrylate, 2- Hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, N-acryloyloxyethyl hexahydrophthalimide, acryloylmorpholine, N-vinylcaprolactam, N-vinylpyrrolidone, N-vinyl Examples include formamide and N-acryloyloxyethyl hexahydrophthalimide. These compounds may be used alone or in combination of two or more.
The monofunctional monomer is preferably 2-phenoxyethyl (meth) acrylate, (ethoxy (or propoxy))-2-phenoxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, acryloylmorpholine, N-acryloyloxyethyl. Hexahydrophthalimide is mentioned.

  A bifunctional monomer is a compound having two polymerizable functional groups in the molecule. Specifically, a bifunctional (meth) acrylate, a bifunctional monomer containing a vinyl group in the molecule, acrylic and vinyl molecules Heterogeneous bifunctional monomers included in the molecule, and heterobifunctional monomers including acrylic and allyl in the molecule.

Examples of specific compounds of bifunctional (meth) acrylates include dimethylol tricyclodecane di (meth) acrylate, (ethoxy (or propoxy)) bisphenol A di (meth) acrylate, cyclohexanedimethanol di (meth) Acrylate, (poly) ethylene glycol di (meth) acrylate, (ethoxy (or propoxy)) 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol acrylate, 1,10-decanediol diacrylate, (Ethoxy (or propoxy)) neopentyl glycol di (meth) acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, (neopentyl glycol modified) tri Chi trimethylolpropane di (meth) acrylate, tripropylene glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate.
Preferred examples of the bifunctional monomer include 1,9-nonanediol acrylate, 1,10-decanediol diacrylate, dipropylene glycol di (meth) acrylate, and (ethoxy (or propoxy)) bisphenol A di (meth) acrylate. It is done.

  Specific examples of the monomer containing a vinyl group in the molecule include butanediol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, cyclohexane dimethanol divinyl ether, and trimethylolpropane divinyl ether. These compounds may be used independently and may be used together 2 or more types.

  As an example of a specific compound of a heterobifunctional monomer that includes acrylic and vinyl in the molecule and a heterobifunctional monomer that includes acrylic and allyl in the molecule, VEEA (2- (2-vinyloxyethoxy) ethyl acrylate) ), VEEM (2- (2-vinyloxyethoxy) methyl acrylate), 2-hydroxy-3-allyloxypropyl acrylate, 2-hydroxy-3-vinyloxypropyl acrylate, 2-hydroxy acrylate -3- (2-vinyloxyethoxy) ethyl and the like.

  Trifunctional or higher polyfunctional monomers include trimethylolpropane tri (meth) acrylate, trimethylolpropane tri (meth) acrylate hydroxypivalate, tri (meth) acrylate ethoxylated, pentaerythritol tri (meth) acrylate, tetra Methylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, caprolactone-modified trimethylolpropane tri (meth) acrylate, propoxylate glyceryl tri (meth) acrylate, trimethylolpropane oligo (meth) acrylate, ethoxylated trimethylol Propane tri (meth) acrylate, propoxylated trimethylolpropane tri (meth) acrylate, ethoxylated isocyanuric acid tri (meth) acrylate , Caprolactone-modified tris- (2-acryloxyethyl) isocyanurate, tri (2-hydroxyethyl isocyanurate) tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, tetramethylolpropane tetra (meth) acrylate, tetra Methylolmethane tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol hydroxypenta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, caprolactone modified dipenta Erythritol hexa (meth) acrylate, ethoxylated dipentaerythritol hexa (meth) acrylate, tripentaerythritol (medium And acrylate).

  In the present invention, the total content of the monofunctional monomer and the bifunctional monomer is 95 to 100% by weight in the total amount of the polymerizable compound.

  The monomer content in the ink is preferably 50 to 97% by weight based on the total amount of ink from the viewpoints of curability and ejection stability. More preferably, it is 60-97 weight%, More preferably, it is 70-97 weight%.

As the monomer, it is preferable to use an acrylate having a skeleton of EO (ethylene oxide) or PO (propylene oxide) from the viewpoint of curability.
In addition, phenoxyethyl acrylate, (ethoxy (or propoxy)) 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, 2- (2-vinyloxyethoxy) ethyl acrylate, from the viewpoint of achieving both low residue and flexibility. , Dipropylene glycol diacrylate, 2-hydroxy-3-allyloxypropyl acrylate, 2-hydroxy-3-vinyloxypropyl acrylate, 2-hydroxy-3- (2-vinyloxyethoxy) ethyl acrylate Is preferred.
In particular, a monomer selected from PEA (phenoxyethyl acrylate), VEEA (2- (2-vinyloxyethoxy) ethyl acrylate), and DPGDA (dipropylene glycol diacrylate) is preferable. Since these monomers easily propagate radicals, it seems that the reaction speed between the monomers is improved, and by using them alone or in combination, the residual amount of the monomer in the cured film can be reduced even in high-speed printing.

  The amount of the monomer having EO or PO as the main skeleton is preferably 40 to 100% by weight, particularly preferably 50 to 100% by weight, based on the monomer component in the ink, from the viewpoint of low viscosity and low residual amount.

  The amount of the monomer having EO or PO as the main skeleton is preferably 10% by weight or more, more preferably 20 to 95% by weight, and further preferably 40 to 95% by weight based on the total weight of the ink.

  In particular, when VEEA is used as the monomer, the reactivity is greatly improved, so that the conveyance speed can be increased, and the residual rate in the cured film is also reduced. The amount of VEEA added is preferably 10 to 60% by weight, more preferably 10 to 45% by weight, and particularly preferably 10 to 30% by weight in the ink.

  In addition, vinyl monomers or allyl monomers are extremely effective for lowering viscosity because of their low intermolecular force, and can be used, but acrylic monomers and vinyl monomers or allyl monomers coexist in the ink, and When a large amount of vinyl monomer or allyl monomer is present, the rate of radical propagation from the acrylic monomer to the vinyl monomer or allyl monomer is slow, so that a large amount of monomer may remain in the cured film after irradiation with active energy rays. Therefore, the compounding amount of the vinyl monomer or allyl monomer is preferably 30% by weight or less, more preferably 10% by weight or less in the ink.

  In addition to the above-mentioned monomers, oligomers and prepolymers can be used for the ink composition, but for reasons such as ink viscosity and residual amount in the cured film, the ink composition contains 15% by weight or less, further 5% by weight or less. More preferably.

(Ink viscosity)
The viscosity at 25 ° C. of the ink used in the present invention is 100 mPa · s or less, preferably 40 mPa · s or less. Ink-jet ink ejects droplets and draws an image, so that the minute droplets must be ejected from the nozzle by a minute pressure. Although the ink viscosity is temporarily lowered by heating at the time of discharge, this discharge is made possible. However, by setting the viscosity to 100 mPa · s or less, the ink can be stably discharged. In addition, by controlling the ink viscosity to 40 mPa · s or less, the discharge speed can be increased and the landing system can be enhanced. This improves beading (fusion between dots) caused by poor landing and improves image quality. It can be greatly improved. Furthermore, it is preferable that the viscosity in 25 degreeC is 5-30 mPa * s. If it is 5 mPa · s or more, the discharge is stable, and if it is 30 mPa · s or less, the discharge accuracy is excellent and the image quality is excellent.
The viscosity can be measured by reading the viscosity under a 25 ° C. environment using a TVE25L viscometer manufactured by Toki Sangyo Co., Ltd.

(Coloring agent)
As the colorant, generally known solubility or salt increasing dyes or pigments can be used. Among them, a pigment can be suitably selected from the suppression of the coloration itself and durability. Furthermore, as a pigment, the pigment generally used for the ink composition of a printing use and a coating use can be used. Specifically, inorganic pigments or organic pigments such as carbon black, titanium oxide, and calcium carbonate can be used.

In particular, as a pigment component that achieves both non-migration and color reproducibility, for example, as a colorant used for magenta ink, C.I. I. Pigment violet 19, C.I. I. Pigment red 81 series, C.I. I. Pigment red 122, 176, 185, 169, 202, 269, etc.
For example, as a colorant used for yellow ink, C.I. I. Pigment yellow 120, 139, 150, 151, 155, 180, 185, etc.
For example, as a colorant used for cyan ink, C.I. I. Pigment Blue 15: 3, 15: 4,
For example, as a colorant used for other color inks, C.I. I. Pigment green 7, 36, C.I. I. Pigment orange 43, C.I. I. Pigment violet 23,
Further, as a colorant used for other inks, C.I. I. Pigment black 7, surface-treated titanium oxide, and carbon black can be preferably used.

  The addition amount of the colorant is preferably 1% by weight or more based on the total amount of the ink because it exhibits a desired color developability when used as a packaging material for foods and pharmaceuticals. For example, in a food / pharmaceutical packaging application that may be used for a very thin substrate of about 20 μm, the thickness of the cured film may be excessively increased in order to increase color development. In this case, since the ink cured film layer which occupies for printed matter becomes very high, there is a problem that the entire packaging material becomes inflexible and the cured film breaks. If the added amount of the colorant is higher than 3% by weight in the ink, the cured film can be made thin while providing sufficient color development properties. It is preferable without cracking.

  Further, the ink of the present invention has flexibility even when the thickness of the ink cured film is 2 to 20 μm.

(Pigment dispersant)
The pigment dispersant is roughly classified into a pigment dispersion aid and a resin-type pigment dispersant.

  The pigment dispersing aid is a compound obtained by introducing an organic pigment as a base skeleton and introducing a substituent such as a sulfonic acid, a sulfonamide group, an aminomethyl group, or a phthalimidomethyl group into a side chain, or a metal salt compound.

  The main chain skeleton of the resin-type pigment dispersant is not particularly limited, and examples thereof include a polyurethane skeleton, a polyacryl skeleton, a polyester skeleton, a polyamide skeleton, a polyimide skeleton, and a polyurea skeleton. Among these, a polyurethane skeleton, a polyacryl skeleton, and a polyester skeleton are preferable from the viewpoint of storage stability of the ink composition. The structure is not particularly limited, and examples include a random structure, a block structure, a comb structure, a star structure, etc., and a block structure or a comb structure in terms of reducing the viscosity of the ink and storage stability. Is preferred.

  Among those exemplified, a resin-type pigment dispersant having a basic functional group is preferable, and a commercially available product may be used. Examples that can be used with a resin-type pigment dispersant having a basic functional group include Solsperse 24000GR, 32000, 33000, 35000, 39000, 41000, 53000, and J180 manufactured by Lubrizol. Further, Ajisper PB821, 822, 824, 827, and 711 manufactured by Ajinomoto Fine Techno Co. can be mentioned.

  The addition amount of the resin-type pigment dispersant is arbitrarily selected in order to ensure the desired stability. The fluidity of the ink is excellent when the effective component of the resin-type pigment dispersant (that is, the solid content (nonvolatile content) of the resin-type pigment dispersant is 20 to 150% by weight with respect to 100% by weight of the pigment. Within the range, the dispersion stability of the ink is good, and the quality is equivalent to the initial value even after a long period of time. Dispersion becomes very stable, and stable discharge property is exhibited even in a high frequency region of 20 kHz or higher, so that high accuracy and high productivity can be realized, and more preferably 30% by weight to 70% by weight.

(Additive)
You may add an additive to the ink of this embodiment as needed. Examples of the additive include a resin, an inhibitor, a surface tension adjuster, and an organic solvent.

(resin)
The ink of the present invention may contain a resin. It is preferable to use a resin having an acid value of 50 or more and a weight average molecular weight (Mw) of 1000 or more and 20000 or less.
Here, the resin means a resin other than those used as the resin-type dispersion resin and the surface tension adjusting agent.

The weight average molecular weight of the resin is preferably 1000 or more and 15000 or less, more preferably 2000 or more and 12000 or less, and further preferably 3000 or more and 10,000 or less.
Mw is determined as a styrene equivalent molecular weight by general gel permeation chromatography (hereinafter referred to as GPC).
Specifically, it is a molecular weight in terms of polystyrene when a tskgel column (manufactured by Tosoh Corporation) is used and GMF equipped with an RI detector (manufactured by Tosoh Corporation, HLC-8320GPC) uses DMF as a developing solvent.

The acid value of the resin is preferably 50 to 250, and more preferably 50 to 150.
Here, the “acid value” represents an acid value per 1 g of the solid content of the dispersant, and is determined by potentiometric titration according to JIS K 0070.

  A resin having an acid value of 50 or more has an electrostatic bond between the polar group on the surface of the printing substrate and the polar portion of the resin, and improves the adhesion to the substrate. In particular, adhesion to PP or PET is improved by adding a resin having an acid value of 50 or more. PP and PET have many non-polar parts and express adhesiveness by bonding with polar parts generated by corona treatment, etc., so that stronger adhesiveness can be expressed by adding a resin having an acid value. . Further, when a resin having a molecular weight of more than 20000 is contained, the injection characteristics are deteriorated.

As the resin in the present invention, acrylic acid resin, styrene acrylic acid copolymer resin, styrene maleic acid copolymer resin, vinyl chloride vinyl acetate copolymer resin, vinyl chloride vinyl acetate maleate copolymer resin, polyester resin, polypropylene resin, polylactic acid Examples thereof include a resin, a cellulose resin, a cellulose acetate resin, and a butyral resin.
From the viewpoint of good solubility with the monomer and / or oligomer contained in the ink, it is preferable to use an acrylic acid resin, a styrene acrylic acid copolymer resin, a styrene maleic acid copolymer resin, or a polyester resin.

  Examples of the resin include “Johncrill 586, 611 (styrene acrylic resin”) manufactured by BASF, and “SMA 2625P (styrene maleic acid resin)” manufactured by Elf Atchem Japan.

  When the resin is included, the content is preferably 1 to 9.5% by weight, more preferably 1 to 7% by weight based on the total weight of the ink.

  Adhesion is improved by containing 1% by weight or more of a resin having an acid value of 50 or more in the total amount of ink. Moreover, when it contains more than 9.5%, the ratio of the resin component in a cured film will become high, solvent resistance will deteriorate, and the discharge stability of ink will deteriorate.

(Banner)
Inhibitors are preferably used in order to increase the viscosity stability of the ink over time, the ejection properties after the time, and the on-machine viscosity stability in the recording apparatus. As the inhibitor, hindered phenol compounds, phenothiazine compounds, hindered amine compounds, and phosphorus compounds are particularly preferably used.

  Among these, in terms of solubility in ink and the color of the inhibitor itself, as a hindered phenol compound, Seiko Chemical Co., Ltd. “BHT Swanox”, “Nonflex Alba”, Honshu Chemical Co., Ltd. “H-BHT”, “Phenothiazine” manufactured by Seiko Chemical Co., Ltd., “phenothiazine” manufactured by Sakai Chemical Industry, “HO-TEMPO” manufactured by Evonik Degussa, and “Triphenylphosphine” manufactured by BASF as the phosphorus compound are suitable. Selected. These inhibitors may be used alone or in combination of two or more as required.

  The amount of the inhibitor added is preferably 0.1 to 2.0% by weight in the ink, more preferably 0.1 to 1.5% by weight, and particularly preferably 0.1 to 1% by weight. Within the above range, it is possible to achieve both the storage stability of the ink, the curability during high-speed printing, and the migration reduction of the inhibitor.

(Surface tension regulator)
In order to improve the uniform wetting and spreading property to the substrate, it is preferable to add a surface tension adjusting agent. The surface tension adjusting agent is preferably a silicone type or an acrylic type from the viewpoint of prevention of flipping due to compatibility. More preferably, an acrylic surface tension modifier is used in an electron beam irradiation apparatus that does not perform temporary curing from the viewpoint of suppressing bleeding between inks due to excessive spreading of ink onto a substrate. More preferably, the residual rate of a cured film can be reduced by using the surface tension regulator which has reactivity, such as an acryloyl group.

  The amount of the surface tension modifier added is preferably 0.01 to 5% by weight in the ink, more preferably 0.01 to 3% by weight, and particularly preferably 0.1 to 2% by weight. If it is 0.01% by weight or more, the wetting and spreading of the ink can be made uniform, and if it is 5% by weight or less, the surface tension adjusting agent is sufficiently oriented at the ink interface and exhibits a sufficient effect. One or more surface tension modifiers may be used as necessary.

(Organic solvent)
Although it does not specifically limit as an organic solvent, The glycol monoacetates, glycol diacetates, glycols, glycol ethers, lactic acid esters, etc. which are generally used with a solvent-type inkjet ink can be mix | blended. However, since the organic solvent is likely to remain in the cured film and the risk of migration increases, the blending amount is preferably 10% by weight or less, more preferably 3% by weight or less in the ink, and 0.5% or less. Further preferred. These organic solvents may be used alone or in combination of two or more as required.

  Organic solvents include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl Ether acetate, ethylene glycol monomethyl ether propionate, ethylene glycol monoethyl ether propionate, ethylene glycol monobutyl ether propionate, diethyl diglycol, diethylene glycol dialkyl ether, tetraethylene glycol dialkyl Ether, diethylene glycol monomethyl ether propionate, diethylene glycol monoethyl ether propionate, diethylene glycol monobutyl ether propionate, propylene glycol monomethyl ether propionate, dipropylene glycol monomethyl ether propionate, ethylene glycol monomethyl ether butyrate, ethylene glycol Monoethyl ether butyrate, ethylene glycol monobutyl ether butyrate, diethylene glycol monomethyl ether butyrate, diethylene glycol monoethyl ether butyrate, diethylene glycol monobutyl ether butyrate, propylene glycol monomethyl ether butyrate, dipropylene glycol monomethyl ether Glycol mono acetates such as Chireto,

  Ethylene glycol diacetate, diethylene glycol diacetate, propylene glycol diacetate, dipropylene glycol diacetate, ethylene glycol acetate propionate, ethylene glycol acetate butyrate, ethylene glycol propionate butyrate, ethylene glycol dipropionate, ethylene glycol acetate Dibutyrate, diethylene glycol acetate propionate, diethylene glycol acetate butyrate, diethylene glycol propionate butyrate, diethylene glycol dipropionate, diethylene glycol acetate dibutyrate, propylene glycol acetate propionate, propylene glycol acetate butyrate, propylene glycol Lopionate butyrate, propylene glycol dipropionate, propylene glycol acetate dibutyrate, dipropylene glycol acetate propionate, dipropylene glycol acetate butyrate, dipropylene glycol propionate butyrate, dipropylene glycol dipropionate, di Glycol diacetates such as propylene glycol acetate dibutyrate,

  Glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol,

  Ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, propylene glycol n-propyl ether, Triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, ethylene glycol diethyl ether, ethylene glycol dimethyl ether, ethylene glycol ethyl methyl ether, diethylene glycol Ethyl methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether Glycol ethers such as

  Examples thereof include lactic acid esters such as methyl lactate, ethyl lactate, propyl lactate, and butyl lactate.

Among the organic solvents, glycol ethers are preferable, and tetraethylene glycol dialkyl ether, ethylene glycol monobutyl ether acetate, and diethylene glycol diethyl ether are particularly preferable.
The (poly) ethylene glycol and (poly) propylene glycol skeletons of glycol ethers improve the reactivity of the polymerizable monomer, the curability of the coating film is excellent, and the residual amount is reduced. Further, the ink viscosity becomes low, the discharge stability is excellent, and a good image quality is obtained.

  The boiling point of the organic solvent is preferably from 100 to 300 ° C, more preferably from 150 to 250 ° C, from the viewpoint of ejection stability.

(Moisture management)
The present invention is characterized by containing substantially no water. “Substantially no water” means that water is not intentionally contained in the ink, and does not exclude a trace amount of water contained in each compounding component. When water is contained in the ink, radicals generated during electron beam irradiation are trapped, the polymerization reaction does not proceed efficiently, and the residual ratio of the polymerizable compound in the cured film tends to increase.

  In addition to intentionally not adding water, the water content in the ink is preferably 1.0% by weight or less, and is controlled by controlling the raw materials and manufacturing process so that it is 0.5% by weight or less. It is preferred that

(Ink production method)
The ink is preferably prepared by adding a polymerizable compound and other additives to a pigment dispersion in which a polymerizable compound, a pigment dispersant, and a pigment are dispersed using an ordinary dispersing machine such as a sand mill. By this method, it is possible to sufficiently disperse using a normal disperser, so that excessive dispersion energy is not applied and a large dispersion time is not required. For this reason, it is possible to prepare an ink that hardly deteriorates during dispersion of the ink component and is excellent in stability.

  As the conditions for preparing the pigment dispersion, it is preferable to use fine beads. Specifically, it is preferable to use fine beads of 0.1 mm to 2 mm in order to produce a stable dispersion with low viscosity. Furthermore, it is preferable to use fine beads having a size of 0.1 mm to 1 mm because a dispersion with improved productivity and good ink jet discharge can be produced.

  The ink is preferably filtered through a filter after being dispersed by a disperser. From the viewpoint of inkjet discharge stability, the pore size of the filter is preferably 3 μm or less, more preferably 1 μm or less.

(Electron beam curing method)
The “electron beam” in the present invention is to artificially accelerate electrons and use them as a beam. A high voltage is applied to accelerate, but if this acceleration voltage is too high, the thermoelectrons will pass through the ink coating and reach the underlying substrate, causing the substrate to deteriorate and further decomposing the components in the substrate. May cause harmful low-molecular components and lead to odor and migration. Therefore, the acceleration voltage of the electron beam used in the present invention is preferably 10 to 150 kV. Further, 60 to 100 kV is more preferable because the ink coating film can be sufficiently cured while preventing decomposition of the base material, and odor and migration can be minimized.

(Oxygen concentration during curing)
When used in the atmosphere, electron beams decompose oxygen and generate a large amount of ozone. Therefore, electron beam devices are usually used under low oxygen concentrations. Therefore, the oxygen concentration at the time of curing of the present invention is preferably 1000 ppm or less. Furthermore, if the oxygen concentration is 50 to 500 ppm, the ink can be sufficiently cured and a sufficient printing speed can be maintained, which is more preferable from the viewpoint of quality and productivity.

(Printing substrate)
In this invention, the film (PP, OPP, BOPP, PE, PET) generally used for a packaging material and a paper base material can be used. Although it is possible to use a base material having a function of blocking gas and liquid, such as an aluminum vapor deposition film, the purpose of the present invention is to reduce the residual rate of the ink raw material. In particular, it can be used effectively for general coated papers and films that are likely to be mixed.
Since the ink of the present invention has good flexibility after curing, the film thickness of the substrate can be used even at 2 to 20 μm.

  In order to control the permeability of the ink, it is also effective to modify the surface of the base material such as anchor coating or corona treatment. In particular, corona treatment tends to be considered to promote penetration because the surface of the base material is generally polarized to improve the wettability of the ink. However, in practice, changing only the surface state can be suitably used because it is possible to modify only the surface of the coating layer and to suppress the permeation if it is a substrate having a coating layer.

  As a result of evaluating the printed materials for food packaging according to EUPIA guidance (EuPIA Guideline on Printing Inks applied to the non-food contact surface of food packaging materials and articles), the migration value into the food substitute evaluation liquid In order to fall below the lower limit of the above, it is known that the standard is satisfied by setting the residual amount of the monomer and initiator remaining in the cured product to a certain value or less. From the result, in the present invention, the monomer residual ratio is preferably 1% or less, and the initiator residual ratio is preferably 2% or less. At this level, the odor is not a concern at all. Furthermore, the monomer residual ratio is preferably 0.5% or less, and the initiator residual ratio is more preferably 1% or less from the viewpoint of safety.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, the aspect of this invention is not limited to these examples.

1. Preparation of Pigment Dispersion Prior to the preparation of the ink composition, various pigment dispersions were prepared as follows (Table 1). In addition, the compounding quantity of the component described in the table | surface is all "weight part."

(Preparation of pigment dispersion 1)
The following materials were stirred with a high speed mixer or the like until uniform, and then the obtained mill base was dispersed with a horizontal sand mill for about 1 hour to prepare pigment dispersion 1.

Pigment: Phthalocyanine pigment (Toyocolor)
"LIONOL BLUE FG-7400-G" 20.0 parts Pigment dispersant: Solsperse 32000 (manufactured by Lubrizol) 10.0 parts Monomer: 70.0 parts of dipropylene glycol acrylate (DPGDA)

(Preparation of pigment dispersion 2)
Similar to Pigment Dispersion 1, Pigment Dispersion 2 having the following composition was prepared.

Pigment: Quinacridone pigment (manufactured by Clariant)
“Inkjet Magenta E5B02” 20.0 parts Pigment dispersant: Solsperse 32000 (manufactured by Lubrizol) 10.0 parts Monomer: 70.0 parts dipropylene glycol diacrylate

(Preparation of pigment dispersion 3)
Similar to pigment dispersion 1, pigment dispersion 3 having the following composition was prepared.

Pigment: Benzimidazolone pigment (manufactured by Clariant)
“Noveperm Yellow P-HG” 20.0 parts Pigment dispersant: Solsperse 32000 (manufactured by Lubrizol) 10.0 parts Monomer: 70.0 parts of dipropylene glycol diacrylate

(Preparation of pigment dispersion 4)
Similar to Pigment Dispersion 1, Pigment Dispersion 4 having the following composition was prepared.

Pigment: Carbon black pigment (Degussa)
“Special Black 350” 20.0 parts Pigment Dispersant: Solsperse 32000 (manufactured by Lubrizol) 10.0 parts Monomer: Dipropylene glycol diacrylate 70.0 parts

(Preparation of pigment dispersion 5)
Similar to Pigment Dispersion 1, Pigment Dispersion 5 having the following composition was prepared.

Pigment: Rutile titanium oxide (Ishihara Sangyo Co., Ltd.)
“PF-740” 60.0 parts Pigment dispersant: Solsperse 32000 (manufactured by Lubrizol) 6.0 parts Monomer: 34.0 parts dipropylene glycol diacrylate

(Preparation of pigment dispersion 6)
Similar to the pigment dispersion 1, a pigment dispersion 6 having the following composition was prepared.

Pigment: Phthalocyanine pigment (Toyocolor)
“LIONOL BLUE FG-7400-G” 20.0 parts Pigment dispersant: Solsperse 32000 (manufactured by Lubrizol) 10.0 parts Monomer: 1,6-hexanediol diacrylate (HDDA) 70.0 parts

Table 1

2. Preparation of ink composition Using each of the pigment dispersions 1 to 6 prepared earlier, a monomer, a stabilizer and a surface conditioner were sequentially added while stirring so that the ink formulation shown in Table 2 was obtained. Gently mixed until uniform. Then, it filtered with the 1 micrometer membrane filter about the obtained liquid mixture, and obtained the inkjet ink composition by removing a coarse particle.

  The raw material components of the ink described in Table 2 are as follows.

・ IBXA: Isobornyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.)
Aronix M-140: N-acryloyloxyethyl hexahydrophthalimide (manufactured by Toa Gosei Co., Ltd.)
・ Biscoat # 192: Phenoxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.)
・ VCAP / RC: N-vinylcaprolactam (manufactured by ASP Japan)
・ DPGDA: Dipropylene glycol diacrylate (manufactured by BASF)
VEEA: 2- (2-vinyloxyethoxy) ethyl acrylate (manufactured by Nippon Shokubai Co., Ltd.)
・ Biscoat # 230: 1,6-hexanediol diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.)
・ EBECRYL600: Bisphenol A type epoxy acrylate (manufactured by Daicel Ornex)
KAYARAD HX220: Caprolactone-modified hydroxypivalate neopentyl glycol diacrylate (manufactured by Nippon Kayaku Co., Ltd.)
・ TMPTA: Trimethylolpropane triacrylate (manufactured by Daicel Ornex)
DPHA: Dipentaerythritol hexaacrylate (manufactured by Toagosei Co., Ltd.)
Irgacure 127: 2-Hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one (manufactured by BASF)
・ Lucirin TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide (manufactured by BASF)
・ Johncrill 586: Styrene-acrylic resin (BASF)
・ DEDG: Diethyl diglycol (Nippon Emulsifier Co., Ltd.)
・ MEK: Methyl ethyl ketone (Maruzen Petrochemical Co., Ltd.)
・ Phenothiazine: Phenothiazine (Seiko Chemical Co., Ltd.)
BYK-UV3510: polyether-modified polydimethylsiloxane (manufactured by BYK Chemie)
BYK361N: Acrylic polymer (manufactured by BYK Chemie)

(Viscosity measurement)
The viscosity of the prepared ink was a TVE25L viscometer manufactured by Toki Sangyo Co., Ltd. The measurement conditions are as follows: rotation speed suitable for measurement in a circulating chiller environment of 25 ° C. (20 mPa · s or less ink is 20 rpm, 20 to 60 mPa · s ink is 10 rpm, 60 mPa · s or higher viscosity) The ink was adjusted to 5 rpm), and the measured value after 3 minutes was used as the viscosity.

(Examples 1 to 20 and Comparative Examples 1 to 9)
3. Inkjet printing Next, using the inkjet ink composition prepared above, the inkjet discharge device loaded with the head (CA3) manufactured by TOSHIBA TEC CO., LTD., Frequency 5 kHz, head temperature 40 ° C., ink droplet amount 42 pl, 150 × The ink composition was discharged onto Pronovilm RC60 manufactured by Innovia under a printing condition of 150 dpi.
After ink landing, electron beam / ultraviolet curing was performed using one of the following lamps to obtain a cured film.
EB: Using an electron beam irradiation apparatus manufactured by Iwasaki Electric Co., Ltd., an electron beam was cured at an acceleration voltage of 80 kV and a dose of 50 kGy at a conveyor speed of 25 m / min and 1 Pass.
UV: Using a metal halide lamp manufactured by Harrison Toshiba Lighting, UV curing was performed at an output of 160 W / cm, a conveyor speed of 25 m / min, and 1 Pass.

4). In addition to the evaluation of the cured film, various evaluations were performed on the cured film according to the method described below. The evaluation results are shown in Table 2.

(Flexibility)
The cured film on which the above printing was performed was bent 90 ° / 180 ° together with the substrate, and visually evaluated whether the cured film was broken. The evaluation criteria are as follows.
○: The cured film does not crack even if the substrate is folded 180 °. Δ: The cured film does not crack even if the substrate is folded 90 °. X: The cured film cracks when the substrate is folded 90 °.

(Residual rate)
The cured film (10 cm × 10 cm) on which the above printing has been performed is cut into 1 cm squares together with the base material, and immersed in 100 ml of methyl ethyl ketone in a sealed container for 3 days at 60 ° C., whereby low molecular residual components in the cured film The residual rate of was extracted. Two days later, methyl ethyl ketone stirred and homogenized was taken out of the container, and the extracted components were identified by GCMS (GCMS-QP2010 Plus manufactured by Shimadzu Corporation) and HPLC (manufactured by Shimadzu Corporation). An amount of unreacted monomer / initiator remaining in the cured film was calculated by preparing a calibration curve of the detected compound and quantifying each compound.

(Cured film weight)
The cured film weight was calculated as follows.
Cured film weight = printed material after printing (cured film + base material) weight−base material weight before printing

(Initiator residual rate)
The residual ratio of unreacted initiator remaining in the cured film was calculated as follows.
Initiator residual ratio = total amount of extracted initiator (g) / weight of cured film (g)
(Residual ratio of components other than initiator)
The residual ratio of components other than the initiator such as unreacted monomers and additives remaining in the cured film was calculated as follows.
Residual ratio of components other than initiator = total amount of components other than extracted initiator (g) / weight of cured film (g)

As a result of evaluating the printed materials for food packaging according to EUPIA guidance (EuPIA Guideline on Printing Inks applied to the non-food contact surface of food packaging materials and articles), the migration value into the food substitute evaluation liquid In order to fall below the lower limit of the above, it is known that the standard is satisfied by setting the residual amount of the monomer and initiator remaining in the cured product to a certain value or less. From the results, the present invention was evaluated as follows. △ or more is considered good.
○: Residual rate of initiator is less than 1%, and residual rate of components other than initiators such as monomers and additives is less than 0.5%.
Δ: Initiator residual ratio is 1% to less than 2%, and the residual ratio of components other than initiators such as monomers and additives is 0.5% to less than 1%, which is a residual practical level.
X: The residual ratio of the initiator is 2% or more, and the residual ratio of components other than the initiators such as monomers and additives is 1% or more, which may impair the taste and flavor of the food due to odor.

(Solvent resistance)
The cured film subjected to the above printing was rubbed with a cotton swab soaked in 95% ethanol to evaluate the solvent resistance. The evaluation criteria are as follows.
○: The swab is not colored, and the cured film surface is not marked. Δ: The swab is not colored, but the cured film surface is slightly marked. ×: The swab is colored, and the cured film surface is marked.

(Dischargeability)
The ejectability was evaluated by observing the state of ink being ejected with a stroboscope using a head (CA3) manufactured by Toshiba Tec Corporation. For the waveform, Fire1 mode was selected. The point of evaluation was to observe the state of droplet breakup at the start of discharge when the frequency was 20 kHz and after 10 minutes of continuous discharge at 1 mm and 2 mm after discharge. It is preferable that droplet breakup does not occur and is stable. The evaluation criteria are as follows.
○: Continuous up to 2 mm without breaking into droplets. It is stable.
Δ: Split at 1 mm, but droplets coalesce at 2 mm.
Or the state of fracture has changed greatly from the beginning.
X: Split at 1 mm, and droplets do not coalesce even at 2 mm.
An ejection failure has occurred at the beginning or after 10 minutes.

(concentration)
For CYAN / MAGENTA / YELLOW / BLACK inks, the cured film on which the above printing has been performed is measured using a spectrophotometer (manufactured by X-rite), and the color reproduction area in the L * a * b * color space is plotted. Thus, the concentration was evaluated. The obtained color reproduction region was compared with the magenta hue defined by Japan Color 2007 for sheet-fed printing, and it was evaluated whether the magenta of Japan Color 2007 was reproducible. The evaluation criteria are as follows.
◯: A color gamut equivalent to or better than Japan color △: A color gamut equivalent to Japan color is shown ×: For WHITE ink showing a color gamut narrower than Japan color, the cured film on which the above printing was performed is Macbeth By measuring the transmission density with a TR-924 densitometer, the concealability was evaluated and the density was evaluated. The evaluation criteria are as follows.
○: Transmission density is 0.6 or more Δ: Transmission density is 0.45 or more and less than 0.6 ×: Transmission density is less than 0.45

Table 2

(Example 1 to Example 20)
As shown in Table 2, in Examples 1 to 20, the total amount of monofunctional and bifunctional monomers is 95 to 100% by weight in the polymerizable compound, and achieves both flexibility and low residual properties, dischargeability, etc. Meets practical grade for use in food and pharmaceutical packaging. Among them, Examples 1, 2, 4, 9, 13, 15, 17, 18, and 19 have good flexibility, low residual rate, and good discharge properties, and sufficient concentration and sufficient solvent resistance of the coating film. Therefore, it can be said that it is more preferable as a food / pharmaceutical packaging ink.

(Comparative Examples 1 to 9)
On the other hand, as shown in Table 2, in Comparative Examples 1 and 2, the UV-cured coating film is not flexible and the coating film is broken when bent, and in Comparative Example 1, the monomer is contained in the Comparative Example. In No. 2, a large amount of the initiator remained, and it could not be used for food and pharmaceutical packaging. Further, in Comparative Examples 3 to 6, and 8, the electron beam cured coating film was not flexible, and the coating film was broken when it was bent, so that it could not be a practical grade for use in flexible packaging of foods and pharmaceuticals. In Comparative Example 7, the electron beam-cured coating film was not flexible and would be broken when bent, and also had a high viscosity and could not be stably ejected as an inkjet ink. In Comparative Example 9, the ink viscosity was low by containing a large amount of the solvent, but the solvent remained in the coating film in a large amount, so that it could not be a practical grade for use in food / pharmaceutical packaging.

  From the above, it was proved that the electron beam curable inkjet ink of the present invention is an electron beam curable inkjet ink that has both low odor, low migration, flexibility, and high image quality and can be used for food and pharmaceutical packaging. .

Claims (3)

An electron beam curable inkjet ink containing a colorant and a polymerizable compound,
The polymerizable compound contains a bifunctional monomer;
The bifunctional monomer contains dipropylene glycol diacrylate and 2- (2-vinyloxyethoxy) ethyl acrylate,
The content of 2- (2-vinyloxyethoxy) ethyl acrylate is 10 to 30% by weight based on the total weight of the ink,
The total content of the monofunctional monomer and the bifunctional monomer is 95 to 100% by weight in the total amount of the polymerizable compound,
The viscosity of the ink state, and are following 100mPa · s,
An electron beam curable inkjet ink characterized by not containing an initiator and a sensitizer . The addition amount of the colorant, being greater than 3 wt% in the total amount of the ink composition, an electron beam-curable inkjet ink according to claim 1, wherein. Claim 1 or printed matter using an electron beam-curable inkjet ink 2 described.