JP2017137369A - Active energy ray-curable inkjet ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide active energy ray-curable inkjet ink which has extremely high curability and discharge stability, and has not only adhesion to various substrates but also excellent designability such as glossiness and image formation capability.SOLUTION: Active energy ray-curable inkjet ink contains 5 wt.% or more and 50 wt.% or less of at least acrylic acid 2-(2-vinyloxyethoxy)ethyl in ink, and contains 0.1 wt.% or more and 5 wt.% or less of a resin having an acid value in the ink.SELECTED DRAWING: None

Description

  The present invention relates to an active energy ray-curable ink jet ink having very high curability and ejection stability and having adhesion to various substrates.

  The ink jet printing method is a printing method in which fine droplets of ink are ejected and landed from an ink jet head on a substrate to be printed to form images and characters on the substrate. A wide variety of inks such as solvent-based, water-based, and oil-based inks have been used for inkjet printing. However, in recent years, the demand for active energy ray-curable inkjet ink has increased. This is because the active energy ray-curable ink-jet ink can be applied to non-absorbing base materials such as plastic and glass, and the environmental load can be reduced by suppressing the volatilization amount of the solvent. Especially in industrial printing, in addition to the above advantages, from the viewpoint of water resistance of printed matter, ink drying energy, and adhesion of ink components to the head due to ink drying, active energy ray curable type from solvent system or water system Is expected to be replaced with inkjet ink.

  In recent years, with the improvement of the performance of inkjet heads, application of inkjet printing methods to the existing printing market using offset printing or the like is expected. In the existing printing market, productivity is very important. However, in the conventional sign market, a multi-pass printing method is used, and it is difficult to realize desired productivity by such a printing method. For this reason, in the existing printing market, it is desirable to use a single-pass printing method capable of high-speed printing in order to realize productivity that cannot be obtained by the multi-pass printing method using the inkjet printing method.

  In addition, many of the substrates used in the sign market are vinyl chloride sheets. However, in the existing printing market, various substrates such as various coated papers and various films are used. In particular, in label printing, where the market has grown significantly in the single-pass printing method, plastic substrates such as PP and PE are often used. In order to be able to apply the same ink to a variety of substrates, it is necessary to ensure that the print image quality and adhesion to various substrates can be secured at a certain level or higher for any substrate. I must.

  In a single-pass printing method capable of high-speed printing, it is preferable to design in an optimum viscosity range with a low viscosity in order to smoothly eject ink from an inkjet head and obtain a good print image quality. Therefore, it is common to design inks using low viscosity polymerizable monomers. However, low-viscosity polymerizable monomers have strong skin irritation, so the types and amounts that can be suitably used are extremely limited.

  Therefore, Patent Document 1 discloses that the viscosity is reduced by adding an organic solvent to the composition of the active energy ray-curable inkjet ink. However, the printing described in Patent Document 1 requires a drying step of the organic solvent by heating. Therefore, there is a problem that advantages such as high-speed curability and reduced drying cost in the active energy ray-curable inkjet ink are reduced.

In Patent Document 2, an ink containing 2- (2-vinyloxyethoxy) ethyl acrylate, a photosensitive monomer as a reactive diluent, and an acrylic resin for imparting adhesion and light resistance to various substrates. Is disclosed. However, in the ink described in Patent Document 2, curability is inhibited by the resin present in excess and the vinyl monomer 2- (2-vinyloxyethoxy) ethyl acrylate. The image quality and adhesion were not fully exhibited. Furthermore, due to the excessive resin, the discharge response at high speed (discharge performance at a high frequency) is poor, and printing stability such as continuous printability is lacking for high-speed printing applications. Moreover, in the coating film hardened | cured at low speed, gloss (gloss) was nonuniform | heterogenous by resin which exists excessively, and it was inferior to the designability.

Special table 2013-502479 gazette JP 2008-280383 A

  The object of the present invention is an active energy ray curable type having very high curability and ejection stability, and having excellent design properties such as glossiness as well as adhesion to various substrates and image forming ability. It relates to providing an inkjet ink.

  That is, the present invention includes at least 2- (2-vinyloxyethoxy) ethyl acrylate in the ink in an amount of 5% by weight to 50% by weight and a resin having an acid value in the ink of 0.1% by weight to 5% by weight. The present invention relates to an active energy ray-curable ink-jet ink comprising:

  The present invention also relates to the above active energy ray-curable ink-jet ink, wherein the acid value of the resin is 50 mgKOH / g or more.

  The present invention also relates to the above-mentioned active energy ray-curable ink-jet ink, which does not contain a monofunctional monomer or contains 50% by weight or less in the ink when a monofunctional monomer is contained.

  The present invention also relates to the above active energy ray-curable inkjet ink, wherein the resin having an acid value has a weight average molecular weight of 7,000 or less.

The present invention also relates to a method for producing a printed matter, wherein the active energy ray-curable inkjet ink is printed by a single pass printing method with a printing speed of 35 m / min or more and a printing resolution of 90000 dots / inch ² or more.

  Moreover, this invention relates to the manufacturing method of the said printed matter whose printing base material is the base material which surface corona-treated.

According to the present invention, an active energy ray-curable inkjet ink having excellent curability, high ejection stability, excellent adhesion to various substrates, and good glossiness can be provided.

  In one embodiment of the ink of the present invention, 2- (2-vinyloxyethoxy) ethyl acrylate is 5% by weight to 50% by weight and a resin having an acid value is 0.1% by weight to 5% by weight. As a result, it is possible to form an image having good gloss as well as good curability and adhesion that have not been realized in high-speed printing applications.

  Hereinafter, the active energy ray-curable inkjet ink of the present invention will be described in detail. In the following description, unless otherwise specified, the term “ink” means “active energy ray-curable inkjet ink”, and the term “monomer” means “polymerizable monomer”. “Part” means “part by weight” and “%” means “% by weight”.

<2- (2-vinyloxyethoxy) ethyl acrylate>
The ink of the present invention contains 2- (2-vinyloxyethoxy) ethyl acrylate as a polymerizable monomer. 2- (2-vinyloxyethoxy) ethyl acrylate is commercially available, for example, as “VEEA” and “VEEA-AI” manufactured by Nippon Shokubai Co., Ltd.

2- (2-Vinyloxyethoxy) ethyl acrylate is a vinyl ether group-containing acrylic ester and a polymerizable monomer having a vinyl ether group and an acryloyl group. This polymerizable monomer has a low viscosity and a high reactivity. Therefore, it is excellent as a material for producing a low-viscosity and high-sensitivity ink. The content of 2- (2-vinyloxyethoxy) ethyl acrylate is 5 to 50% by weight, preferably 5 to 35% by weight, more preferably 10 to 30% by weight, based on the total weight of the ink. .
If it is in the said range, the viscosity of an ink will become a suitable range. Moreover, the polymerization reactivity of 2- (2-vinyloxyethoxy) ethyl acrylate and other polymerizable monomers is improved, and good curability is exhibited. Furthermore, even when the printing speed is high, the ejection is stable and sufficient curability can be obtained.
Although the principle is not clear, 2- (2-vinyloxyethoxy) ethyl acrylate containing a vinyl ether group and an acryloyl group improves the polymerization reactivity between the vinyl ether group and the acrylic group, but the vinyl ether group and the vinyl ether group The polymerization reaction is characterized by being very slow. Therefore, a suitable range exists for the composition ratio of 2- (2-vinyloxyethoxy) ethyl acrylate and other monomers.
That is, when 2- (2-vinyloxyethoxy) ethyl acrylate is present in the above range or more, the curability is inferior and the physical properties of the coating such as gloss are deteriorated.

<Other polymerizable monomers>
The ink of the present invention may contain other polymerizable monomer in addition to 2- (2-vinyloxyethoxy) ethyl acrylate. Other polymerizable monomers can be selected from conventionally known monofunctional monomers and / or polyfunctional monomers.

  Here, in the present specification, descriptions such as “(meth) acryloyl”, “(meth) acrylic acid”, “(meth) acrylate”, and “(meth) acryloyloxy”, respectively, unless otherwise specified, It means “acryloyl and / or methacryloyl”, “acrylic acid and / or methacrylic acid”, “acrylate and / or methacrylate”, and “acryloyloxy and / or methacryloyloxy”.

The monofunctional monomer includes a compound having only one polymerizable functional group in the molecule.
Examples of the monofunctional monomer include a monofunctional acrylic monomer and a monofunctional vinyl monomer.
Examples of specific compounds 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 Relate, 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, isoboronyl (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, acrylic Acryloyl morpholine, and N- acrylate or monofunctional acrylic monomers such as acryloyloxyethyl hexahydrophthalimide,
And monofunctional vinyl monomers such as N-vinylcaprolactam, N-vinylpyrrolidone, and N-vinylformamide.
These compounds may be used alone or in combination of two or more.

The polyfunctional monomer includes a compound having two or more polymerizable functional groups in the molecule. Examples thereof include polyfunctional acrylic monomers other than 2- (2-vinyloxyethoxy) ethyl acrylate, vinyl monomers, and the like.
Examples of specific compounds include dimethylol tricyclodecane di (meth) acrylate, ethoxylated bisphenol A di (meth) acrylate, propoxylated 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) trimethylo Rupropane di (meth) acrylate, tripropylene glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, pentaerythritol tri (or tetra) (meth) acrylate, trimethylolpropane tri (or tetra) (meth) acrylate, Examples include tetramethylol methane tri (or tetra) (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like.
Another example of the polyfunctional monomer is a polyfunctional vinyl monomer containing a plurality of vinyl groups in the molecule. Examples of specific compounds include butanediol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, cyclohexane dimethanol divinyl ether, trimethylolpropane divinyl ether, pentaerythritol tri (or tetra) vinyl ether, trimethylolpropane diallyl ether, Examples include pentaerythritol tri (or tetra) allyl ether. These compounds may be used independently and may be used together 2 or more types.
“EO modification” represents ethylene oxide modification, and “PO modification” represents propylene oxide modification.

  When using a monofunctional monomer as one embodiment, the content of the monofunctional monomer is 50% by weight or less, preferably 40% by weight or less, and more preferably 30% by weight or less, based on the total weight of the ink. By setting the content of the monofunctional monomer within the above range, it becomes easy to suppress the odor of the ink, suppress the skin sensitization, and obtain excellent curability.

  When a polyfunctional monomer other than 2- (2-vinyloxyethoxy) ethyl acrylate is used in combination, the blending amount is preferably 10% by weight or more, more preferably 30% by weight or more, based on the total weight of the ink, 50 More preferably by weight.

  Among these, it is preferable to contain a monofunctional and / or polyfunctional acrylic monomer from the viewpoint of curability and adhesion. As described above, the vinyl ether group of 2- (2-vinyloxyethoxy) ethyl acrylate significantly improves the polymerization reaction with the acryloyl group, so that better curability can be obtained and the resin having an acid value can be obtained. When used in combination, adhesion and gloss are also excellent.

  The total content of 2- (2-vinyloxyethoxy) ethyl acrylate and monofunctional and polyfunctional acrylic monomers is preferably 80% by weight or more, more preferably 90% by weight or more, based on the total weight of the polymerizable monomers. 100% by weight is more preferable.

  Among the above embodiments, from the viewpoint of curability, it is preferable to contain a polymerizable monomer having an EO (ethylene oxide) or PO (propylene oxide) skeleton as the other polymerizable monomer. The polymerizable monomer having an EO or PO skeleton includes the EO or PO modified monomer of the specific example, and an ethoxy or propoxylated monomer. Although details are not clear, the oxygen atom present in the EO or PO skeleton attracts electrons in the molecule, and thus the dipole moment in the molecule is biased, and 2- (2-vinyloxyethoxy) ethyl acrylate or It is presumed that the intermolecular distance is reduced because the resin having an acid value attracts each other, and the polymerization reaction proceeds efficiently.

Among them, it is preferable to include a monofunctional and / or polyfunctional acrylic monomer having an EO or PO skeleton.
For example, 2-phenoxyethyl (meth) acrylate, ethoxylated 2-phenoxyethyl (meth) acrylate, propoxylated 2-phenoxyethyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, methoxy Monofunctional acrylic monomers such as dipropylene glycol (meth) acrylate, dipropylene glycol (meth) acrylate, nonylphenol EO modified acrylate, nonylphenol PO modified acrylate; ethoxylated bisphenol A di (meth) acrylate, propoxylated bisphenol A di (meth) Acrylate, (ethoxy (or propoxy)) neopentyl glycol di (meth) acrylate, dipropylene glycol di (meth) Group) consisting of polyfunctional acrylic monomers such as (tri) acrylate, (neopentyl glycol modified) trimethylolpropane di (meth) acrylate, tripropylene glycol di (meth) acrylate, trimethylolpropane tri (or tetra) (meth) acrylate It is preferable to include at least one compound selected from.
Especially, it is preferable that at least one of 2-phenoxyethyl acrylate and dipropylene glycol diacrylate is included, and it is more preferable that dipropylene glycol diacrylate is included.

  The total content of monofunctional and polyfunctional acrylic monomers having an EO / PO-modified skeleton is preferably 15 to 85% by weight, more preferably 20 to 80% by weight, and more preferably 30 to 75% by weight based on the total weight of the ink. % Is more preferable.

Among these, as the other polymerizable monomer used in combination with 2- (2-vinyloxyethoxy) ethyl acrylate, a polyfunctional acrylic monomer having an EO / PO-modified skeleton is preferably included.
The total content of 2- (2-vinyloxyethoxy) ethyl acrylate and polyfunctional acrylic monomer having an EO / PO-modified skeleton is preferably 70% by weight or more based on the total weight of the polymerizable monomers, and is 80% by weight or more. Is more preferable, and 90% by weight or more is still more preferable.

  In one embodiment, the content of the polymerizable monomer in the ink is preferably 65 to 95% by weight, more preferably 75 to 95% by weight, and still more preferably 80 to 92% by weight, based on the total weight of the ink.

  In a preferred embodiment of the ink of the present invention, the polymerizable monomer includes 2- (2-vinyloxyethoxy) ethyl acrylate and other polyfunctional monomers. In a more preferred embodiment, the polymerizable monomer includes 2- (2-vinyloxyethoxy) ethyl acrylate and a polyfunctional polymerizable monomer having an EO / PO skeleton. In a more preferred embodiment, the polymerizable monomer comprises 2- (2-vinyloxyethoxy) ethyl acrylate, dipropylene glycol di (meth) acrylate, (neopentyl glycol modified) trimethylolpropane di (meth) acrylate, And at least one selected from the group consisting of propylene glycol di (meth) acrylate and EO-modified bisphenol A diacrylate.

  In particular, a combination of 2- (2-vinyloxyethoxy) ethyl acrylate and dipropylene glycol di (meth) acrylate is preferable in terms of ink viscosity, odor, and high curability. In one embodiment, when 2- (2-vinyloxyethoxy) ethyl acrylate, dipropylene glycol di (meth) acrylate, and other polymerizable monomers other than these are used as the polymerizable monomer, the polymerizable The content of the other polymerizable monomer with respect to the total weight of the monomer is preferably 5 to 50% by weight, more preferably 10 to 50% by weight, and even more preferably 20 to 40% by weight.

<resin>
As described above, in one embodiment of the ink of the present invention, 2- (2-vinyloxyethoxy) ethyl acrylate and a resin having an acid value are 0.1 wt% or more and 5 wt% or less based on the total weight of the ink. Including. A resin having an acid value can exhibit good adhesion due to the interaction with a polar surface such as a hydroxyl group, a carbonyl group or a carboxyl group present on the surface of a plastic or coated paper as a recording medium.

In one embodiment, the acid value of the resin is preferably 20 mgKOH / g or more, more preferably 50 mgKOH / g or more, and still more preferably 80 mgKOH / g or more. Moreover, 400 mg / KOH or less is preferable, 300 mg / KOH or less is more preferable, and 250 mg KOH / g or less is still more preferable.
Within the above range, not only the adhesion is excellent, but also the stability of the ink can be maintained. If the acid component is present in excess, it will react with the vinyl group of the polymerizable monomer contained in the ink and storage stability will be reduced.

  The acid value is the number of mg of potassium hydroxide required to neutralize the acid group contained in 1 g of resin solids, and the measurement can be performed according to JIS K0070.

  Generally, the resin is added in order to develop good adhesion. In order to develop good adhesion to various base materials, a method of increasing the amount of resin added can be considered. However, in that method, excessive resin prevents curing and cannot be sufficiently cured during high-speed printing. Further, the excessively existing resin causes a decrease in gloss of the cured film, uneven gloss, and poor adhesion. In addition, it causes a discharge failure during high-speed printing.

  In one embodiment of the present invention, the resin having an acid value is preferably contained in the ink in an amount of 0.1 wt% to 5 wt%, and preferably 0.3 wt% to 3 wt%.

In particular, 2- (2-vinyloxyethoxy) ethyl acrylate has high solubility, and particularly excellent compatibility with a resin having an acid value.
Although the principle is not clear, since the resin having an acid value and 2- (2-vinyloxyethoxy) ethyl acrylate have good compatibility, the resin and the ink cured film are uniformly dispersed in the cured film during curing. A uniform film surface is formed without segregation on the surface of the cured film. Thereby, curability is promoted and, at the same time, good gloss and adhesion can be obtained.

In addition, if a resin having a too high molecular weight is used, a problem arises in the ejection properties of the ink jet. In one embodiment of the present invention, the weight average molecular weight (Mw) is preferably 10,000 or less, more preferably 7000 or less, and even more preferably 5000 or less.
Further, Mw is preferably 1000 or more, and more preferably 1500 or more.
When the Mw is 1000 or more and 7000 or less, not only ink jetting properties at high speed printing are improved, but also ink wetting and spreading, image quality and gloss are improved, and adhesion to a substrate is also excellent.

  Mw can be measured using, for example, GPC (gel permeation chromatography) “HPC-8020” manufactured by Tosoh Corporation, and the solvent can be measured in terms of tetrahydrofuran and polystyrene.

  From the viewpoint of ejection properties, the resin molecular weight dispersity (Mw / Mn) is preferably 4 or less, more preferably 3 or less, and even more preferably 2 or less. Mn is the number average molecular weight.

  Examples of the resin of the present invention include a non-reactive resin having no reactive functional group and a curable resin having a reactive functional group.

From the viewpoint of adhesion, a non-reactive resin is preferable. The non-reactive resin is oriented at the substrate / ink-cured film interface when the ink is cured, so that stronger adhesion can be obtained.
In particular, when 2- (2-vinyloxyethoxy) ethyl acrylate having high solubility is used in combination, excellent ejection stability can be realized due to good compatibility with the resin during ink ejection. Moreover, at the time of hardening, the speed | rate which orientates to the base material / ink cured film interface of a non-reactive resin is accelerated | stimulated, and it can make high glossiness and adhesiveness compatible.

  From the viewpoint of curability and high gloss, a curable resin is preferable. Since the curable resin is incorporated into the ink cured film together with other monomers at the time of curing, it can exhibit high glossiness. In particular, by using 2- (2-vinyloxyethoxy) ethyl acrylate, low reactivity, which is a demerit of the curable resin, can be compensated and good curability can be realized.

(Non-reactive resin)
Examples of the non-reactive resin used in one embodiment of the present invention include thermoplastic resins.
For example, acrylic resins such as polyacrylic acid resin, styrene acrylic acid copolymer resin, and butadiene-acrylonitrile copolymer resin; styrene maleic acid copolymer resin, polyvinyl chloride resin, vinyl chloride vinyl acetate copolymer resin, and vinyl chloride Vinyl chloride resins such as vinyl acetate maleic acid copolymer resin; polyvinyl resins such as polyvinyl acetal resin, polyvinyl butyral resin, polyvinyl pyrrolidone resin;
Examples include polyurethane resins, polyketone resins, polyester resins, polypropylene resins, polylactic acid resins, cellulose resins, cellulose acetate resins, and butyral resins.

  From the viewpoint of compatibility with 2- (2-vinyloxyethoxy) ethyl acrylate, it is preferable to use acrylic resins such as polyacrylic acid resins and styrene acrylic acid copolymer resins, and styrene maleic acid copolymer resins. More preferably, polyacrylic acid resin or styrene acrylic acid copolymer resin is used. Since these resins are particularly excellent in compatibility with 2- (2-vinyloxyethoxy) ethyl acrylate, they have excellent ejection properties and high gloss and exhibit better adhesion.

  The polyacrylic acid resin is, for example, a homopolymer of (meth) acrylic acid or (meth) acrylic acid alkyl ester, or a copolymer of (meth) acrylic acid and (meth) acrylic acid alkyl ester. The styrene acrylic acid copolymer resin is, for example, a copolymer of (meth) acrylic acid and / or (meth) acrylic acid alkyl ester and a styrene monomer.

Polyacrylic acid resins and styrene acrylic acid copolymers are commercially available in the form of flakes, aqueous solutions or water dispersions (emulsions). From the standpoint of cured film resistance and ink stability, flakes are available. Preferably used.
Specific examples of commercially available products include Joncryl (registered trademark) acrylic resin manufactured by BASF, for example, Joncryl 586 (acid value 110, Mw 4500, Tg 66 ° C.), Joncryl 611 (acid value 52, Mw 8150, Tg 60 ° C.), Joncryl 678 (acid number 216, Mw 8500, Tg 101 ° C.), Joncryl 680 (acid number 215, Mw 4500, Tg 91 ° C.), Joncryl 682 (acid number 238, Mw 1750, Tg 57 ° C.), Joncryl 690 (acid number 240, g 105 ° C., Mw 16500) ), Joncryl ECO675 (acid value 222, Mw5800, Tg95 ° C.), Joncryl ECO684 (acid value 244, Mw1800, Tg88 ° C), Joncryl ECO694 (acid value 200, Mw13750) Tg 101 ° C.), Joncryl 815 (acid value 38, Mw 10000, Tg 55 ° C.), Joncry 817 (acid value 55, Mw 14000, Tg 68 ° C.), Joncryl 819/820 (acid value 75, Mw 15000, Tg 57 ° C.), Joncryl 821/822 Acid value 70, Mw 10500, Tg 62 ° C.), Joncryl 843 (acid value 204, Mw 6100, Tg 86 ° C.), Joncryl 845 (acid value 240, Mw 2400, Tg 78 ° C.), Joncryl 848 (acid value 215, Mw 4500, Tg 67 ° C.);
As an ARUFON (registered trademark) series acrylic resin manufactured by Toa Gosei Co., Ltd., for example, UC-3000 (acid value 74, Mw 10000, Tg 65 ° C.), UC-3080 (acid value 230, Mw 14000, Tg 133 ° C.), UC-3900 ( Acid value 100, Mw 4600, Tg 60 ° C.), UC-3910 (acid value 200, Mw 8500, Tg 85 ° C.), UC-3920 (acid value 240, Mw 15500, Tg 102 ° C.), UC-3510 (acid value 70, Mw 2000, Tg— 50 ° C.), UF-5022 (acid value 235, Mw 14000, Tg 75 ° C.), UH-2000 (acid value 0, Mw 11000, Tg-55 ° C.) and the like;
As a styrene maleic acid copolymer resin of Cray Valley USA, for example, SMA 1000 (acid value 465-495, Mw 5500, Tg 155 ° C.), SMA 2000 (acid value 335-375, Mw 7500, Tg 135 ° C.), SMA 3000 (acid) 265-305, Mw 9500, Tg 125 ° C.), SMA EF30 (acid value 275-285, Mw 9500, Tg 125 ° C.), SMA EF40 (acid value 195-235, Mw 11000, Tg 115 ° C.), SMA EF60 (acid value 141-171, Mw 11500, Tg 106 ° C.), SMA EF80 (acid value 105 to 135, Mw 14400, Tg 104 ° C.), SMA 1440 (acid value 165 to 205, Mw 7000, Tg 60 ° C.), SMA 17352 (acid value 255 to 285, Mw 7000) Tg125 ℃), SMA 2625 (acid value 200~240, Mw9000, Tg110 ℃), SMA3840 (acid value 95~120, Mw10500, Tg75 ℃);
However, it is not limited to this.
In addition, Tg in a parenthesis is a glass transition temperature.

The glass transition temperature (Tg) of the resin is preferably -20 to 150 ° C, more preferably 0 to 120 ° C, still more preferably 20 to 80 ° C.
In the case of the said range, the blocking resistance of ink and the adhesiveness to a base material are excellent, and favorable gloss can be obtained. Moreover, in the said range, resin can be easily dissolved at low temperature at the time of ink production, and it is excellent in productivity.

As the glass transition temperature (Tg) of the resin, a measured Tg obtained by actual measurement is applied. Specifically, as the measurement Tg, a value measured under normal measurement conditions using a differential scanning calorimeter (DSC) EXSTAR 6220 manufactured by SII Nanotechnology, Inc. can be used.
However, when measurement is difficult due to decomposition of the resin or the like, calculation Tg calculated by the following calculation formula is applied. The calculation Tg is calculated by the following formula (T).
1 / Tg = Σ (Xi / Tgi) (T)
Here, it is assumed that n types of monomer components from i = 1 to n are copolymerized in the polymer to be calculated. Xi is the weight fraction of the i-th monomer (ΣXi = 1), and Tgi is the glass transition temperature (absolute temperature) of the homopolymer of the i-th monomer. However, Σ is the sum from i = 1 to n. In addition, the value (Tgi) of the homopolymer glass transition temperature of each monomer employ | adopts the value of Polymer Handbook (3rd Edition) (J. Brandrup, EHImmergut (Wiley-Interscience, 1989)).

  The resin is preferably solid at room temperature. The softening point of the resin is preferably 30 to 200 ° C, more preferably 70 to 150 ° C, and still more preferably 100 to 200 ° C, from the viewpoint of adhesion to various base materials. In the case of the said range, the blocking resistance of ink and the adhesiveness to a base material are excellent, and favorable gloss can be obtained. The softening point refers to a temperature at which a solid substance begins to soften and become deformed.

(Curable resin)
Examples of the curable resin having a reactive group include a thermosetting resin, a photocurable resin, and an oxidative polymerizable resin. Examples of the reactive group include an acryloyl group, a methylol group, an alkylmethylol group, an isocyanate group, a masked isocyanate group, and an epoxy group.

  Examples of the photocurable resin include energy ray curable resins (photosensitive resins) such as ultraviolet rays and electron beams. Specific examples thereof include, for example, photosensitive cyclized rubber resins, photosensitive phenol resins, photosensitive polyacrylate resins, photosensitive polyamide resins, photosensitive polyimide resins, and unsaturated polyester resins and polyesters. Examples include acrylate resins, polyepoxy acrylate resins, polyurethane acrylate resins, polyether acrylate resins, polyol acrylate resins, and the like.

  As the resin used in the present invention, a photosensitive polyacrylate resin is preferred from a store compatible with 2- (2-vinyloxyethoxy) ethyl acrylate.

  In addition, oligomers and monomers are used depending on the application, and a cross-linking agent such as a methylol melamine-based, isocyanate-based, or epoxy-based cross-linking agent is also used in combination.

  The resin having an acid value of the present invention does not include a pigment dispersion resin described later.

<Photopolymerization initiator>
In one embodiment of the present invention, a photopolymerization initiator is blended in the ink from the viewpoint of curing the ink using an active energy ray such as ultraviolet rays. The photopolymerization initiator that can be used in the present invention may be a known photopolymerization initiator. For example, it is preferable to use a photopolymerization initiator that generates radicals in a molecular cleavage type or a hydrogen abstraction type. In this invention, a photoinitiator may be used independently and may use 2 or more types together. Further, a photopolymerization initiator that generates radicals and a photopolymerization initiator that generates cations may be used in combination.

Specific examples of the photopolymerization initiator include 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy)- Phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] -phenyl} -2 Α-hydroxyalkylphenone compounds such as methyl-propan-1-one and phenylglyoxylic acid methyl ester;
2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, 2- Dimethylamino-2- (4-methyl-benzyl) -1- (4-morpholin-4-yl-phenyl) -butanone-1-one, 2- (dimethylamino) -2-[(4-methylphenyl) Α-aminoalkylphenone compounds such as methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone;
Acylphosphine oxide compounds such as bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide;
1,2-octanedione, 1- [4- (phenylthio) -2- (O-benzoyloxime)], ethanone 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl ] Oxime ester compounds such as 1- (O-acetyloxime);
Benzophenone compounds such as benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4′-methyl-diphenyl sulfide;
Etc.

  Among these, a photopolymerization initiator selected from the group consisting of α-aminoalkylphenone compounds, acylphosphine oxide compounds, and benzophenone compounds is preferable from the viewpoint of curability and storage stability. Further, from the viewpoint of curability and adhesion, it is preferable to include an α-aminoalkylphenone compound, an acyl phosphine oxide compound, and a benzophenone compound.

As α-aminoalkylphenone compounds, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1; As acylphosphine oxide compounds, bis (2,4,6-trimethylbenzoyl) ) -Phenylphosphine oxide and / or 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide; as benzophenone compounds, from 4-phenylbenzophenone and / or 4-benzoyl-4'-methyl-diphenyl sulfide At least one selected from the group is preferably used.
Further, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-trimethylbenzoyl At least one selected from the group consisting of -diphenyl-phosphine oxide, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide is preferably used.

  Moreover, you may use the sensitizer with respect to the said photoinitiator. Examples of sensitizers include amine compounds and thioxanthone compounds that do not cause an addition reaction with a polymerizable monomer. Examples of such compounds include trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, N-dimethylbenzylamine, ethyl- Tertiary amine compounds such as 4-dimethylaminobenzoate and 4,4′-bis (diethylamino) benzophenone and ethylhexyl-4-dimethylaminobenzoate; thioxanthones such as thioxanthone, 2,4-diethylthioxanthone and 2-isopropylthioxanthone System compounds. Of these, ethyl-4-dimethylaminobenzoate, 4,4′-bis (diethylamino) benzophenone, and 2-isopropylthioxanthone are particularly preferably used.

  The content of the photopolymerization initiator and the sensitizer is preferably 2 to 30% by weight, more preferably 2 to 20% by weight, and still more preferably 5 to 15% by weight with respect to the total weight of the polymerizable monomer. When the content of the photopolymerization initiator is 2% by weight or more, it is easy to obtain good curability. On the other hand, when the content is 20% by weight or less, the curing rate can be efficiently increased, and the undissolved component of the photopolymerization initiator is not generated even at a low temperature. Easy to get.

<Other components>
The inkjet ink of the present invention may contain a pigment, a pigment dispersant, a surface conditioner, and various additives in addition to the polymerizable monomer and the photopolymerization initiator. Specific examples of the additive include a solvent, a polymerization inhibitor, an antifoaming agent, and an antioxidant.

  One embodiment of the ink of the present invention may be a clear ink composed of the above-described components. Moreover, in another embodiment, the color ink comprised by adding a coloring agent to the above-mentioned structural component may be sufficient. Hereinafter, embodiments of the color ink will be described.

<Pigment>
In one embodiment of the inkjet ink of the present invention, a pigment can be used as a colorant. The usable pigment may be a pigment generally used for printing and paint inks, and an appropriate pigment should be selected from these pigments according to the required application such as color development and light resistance. Can do. The pigment may be either an inorganic pigment or an organic pigment.

  Inorganic pigments include, for example, alkaline earth metal sulfates such as barium sulfate, alkaline earth metal carbonates such as calcium carbonate, silicas such as finely divided silicic acid and synthetic silicates, calcium silicate, alumina, alumina Examples include achromatic (white) pigments such as hydrate, titanium oxide, zinc oxide, talc, and clay. Among these, achromatic (white) pigments of titanium oxide and calcium carbonate are preferable.

  The average particle diameter of the inorganic pigment is preferably 500 nm or less, preferably 400 nm or less, more preferably 300 nm or less, from the viewpoint of ink ejection stability. The average particle diameter is D50, and can be measured, for example, by diluting the ink 200 to 1000 times with ethyl acetate and using Microtrac UPA150 (Nikkiso Co., Ltd.).

An example of the organic pigment that can be used in the present invention is as follows. When these pigments are used, it is preferable in that a color ink having excellent light resistance can be obtained.
Magenta pigments-C.I. I. Pigment Violet 19, C.I. I. Pigment Red 122, 176, 185, 202, 266, 269.
Yellow pigment-C.I. I. Pigment Yellow 120, 139, 150, 151, 155, 180, 185.
Cyan pigments-C.I. I. Pigment Blue 15: 3, 15: 4.
Green pigment-C.I. I. Pigment Green 7, 36.
Orange pigment-C.I. I. Pigment Orange 43, 64.
Violet pigments-C.I. I. Pigment Violet 23.
Black pigment-C.I. I. Pigment Black7.

In the present invention, the ink is not limited to the pigment described above, and the ink may be formed using other pigments. That is, it is also possible to use a color other than the above-mentioned orange, green and violet pigments, and a toned color ink having a color tone other than those described above or using two or more pigments. As one embodiment of the present invention, an ink set can be configured by appropriately combining various color inks, toning color inks, white inks, and clear inks not containing pigments.
In the embodiment of the color ink, the pigment content is preferably 0.1 to 20% by weight, more preferably 2 to 10% by weight, based on the total weight of the ink. By setting the pigment content within the above range, it becomes easy to obtain good results in terms of color density and light resistance of the printed matter.
In the embodiment of the white ink, the content of the pigment is preferably 3 to 50% by weight, more preferably 5 to 40% by weight, and further preferably 7 to 20% by weight based on the total weight of the white ink. By setting the pigment content within the above range, it becomes easy to obtain good results in terms of storage stability and hiding properties of the ink.

<Pigment dispersant>
When constituting an ink containing a pigment as an embodiment of the present invention, it is preferable to use a pigment dispersant in order to improve the dispersibility of the pigment and the storage stability of the ink. Conventionally known compounds can be used as the pigment dispersant. Among these, a resin type dispersant having a basic functional group, and a resin type dispersant having a urethane skeleton are preferable.
Use of a resin-type dispersant having a urethane skeleton is preferable because a pigment dispersion having excellent high frequency characteristics and good storage stability can be easily obtained.
Examples of basic functional groups include primary, secondary, or tertiary amino groups, nitrogen-containing heterocycles such as pyridine, pyrimidine, and pyrazine. In particular, fatty acid amine dispersants can be preferably used.
Specific examples of such a resin-type pigment dispersant (hereinafter referred to as “pigment dispersion resin”) include Solsperse 32000, 76400, 76500, J100, and J180 manufactured by Lubrizol; and Disperbyk-161, 162, 163 164, 165, 166, 167, 168 and the like.

  The resin having an acid value of the present invention does not contain a pigment dispersion resin.

  The addition amount of the pigment dispersion resin is arbitrarily selected in order to ensure the desired stability. In one embodiment, the fluidity of the ink is excellent when the pigment dispersion resin is 25 to 150 parts by weight with respect to 100 parts by weight of the organic pigment. Use of a pigment-dispersed resin within this range is preferable because the dispersion stability of the ink becomes good and tends to exhibit quality equivalent to the initial value even after a long period of time. Furthermore, when the pigment dispersion resin is 40 to 100 parts by weight with respect to 100 parts by weight of the organic pigment, it is preferable from the viewpoint of both the dispersibility of the ink and the discharge property.

The addition amount of the pigment dispersion resin can be arbitrarily selected according to the type of pigment used. In one embodiment, when carbon black is used as a pigment, the pigment-dispersed resin is preferably 25 to 150 parts by weight, more preferably 40 to 100 parts by weight with respect to 100 parts by weight of carbon black.
In another embodiment, when an inorganic pigment having no glitter such as titanium oxide is used as the pigment, the pigment dispersion resin is preferably 2 to 20 parts by weight with respect to 100 parts by weight of the pigment. Part is more preferable, and 4 to 7 parts by weight is more preferable.

<Surface conditioner>
The surface conditioner described in the present specification means a substance that reduces the surface tension of ink by addition.
Examples of the surface conditioner include a silicone-based surface conditioner, a fluorine-based surface conditioner, an acrylic surface conditioner, and an acetylene glycol-based surface conditioner.
From the viewpoint of the ability to lower the surface tension and the compatibility with the polymerizable monomer, it is preferable to use a silicone-based surface preparation agent.

  Specific examples of silicone-based surface conditioners include modified dimethylsiloxane skeletons. Of these, a polyether-modified siloxane-based surface conditioner is preferable. The polyether may be, for example, polyethylene oxide and polypropylene oxide. In one embodiment of the present invention, a commercially available polyether-modified silicone surfactant can be used. Examples of representative products that can be preferably used include polyether-modified siloxanes such as BYK®-378, 348, and 349 from BYK Chemie; and polyether-modified polydimethylsiloxanes such as BYK-UV3500 and UV3510. It is done. Also, polyether-modified siloxane copolymers such as TEGO® GLIDE 450, 440, 435, 432, 410, 406, 130, 110, and 100 from Evonik Degussa. Among these, polyether-modified silicone-based surface conditioners such as BYK-331, 378, 348, UV3510, TEGO GLIDE 450, 440, 432, and 410 are preferable from the viewpoint of good image quality formation.

  The content of the silicone-based surface conditioner is preferably in the range of 0.1% by weight or more and less than 5.0% by weight with respect to the total weight of the ink. By making the content 0.1% by weight or more, the wettability of the ink to the substrate can be easily improved. On the other hand, by making the content less than 5.0% by weight, it becomes easy to ensure the storage stability of the ink.

<Polymerization inhibitor>
A polymerization inhibitor can be used in order to increase the viscosity stability of the ink over time, the discharge stability after the time, and the viscosity stability in the ink jet recording apparatus. As the polymerization inhibitor, hindered phenol compounds, phenothiazine compounds, hindered amine compounds, and phosphorus compounds are particularly preferably used. Specific examples include 4-methoxyphenol, hydroquinone, methylhydroquinone, t-butylhydroquinone, 2,6-di-t-butyl-4-methylphenol, phenothiazine, and an aluminum salt of N-nitrosophenylhydroxylamine. . From the viewpoint of improving the aging stability while maintaining curability, it is preferably blended at a ratio of 0.01 to 2% by weight with respect to the entire ink.

<Organic solvent>
In addition, an organic solvent or water may be contained in the ink in order to reduce the viscosity of the ink and to improve the wetting and spreading property to the substrate. The boiling point of the organic solvent is preferably 120 ° C to 300 ° C, more preferably 140 to 270 ° C, and further preferably 160 to 260 ° C.

Preferred organic solvents include glycol compounds such as monoacetates, diacetates, diols, monoalkyl ethers, dialkyl ethers, and lactic acid esters. Of these, monoacetates, monoalkyl ethers, and dialkyl ethers of glycol compounds are preferable.
More specifically, tetraethylene glycol dialkyl ether, ethylene glycol monobutyl ether acetate, and diethylene glycol diethyl ether are preferable.

  The amount of the organic solvent or water added is preferably 0.1 to 10% by weight based on the total weight of the ink. By making the addition amount of the organic solvent within the above range, it becomes easy to obtain good results with respect to the respective characteristics of curability, ejection stability and adhesion. From the viewpoint of curability, the amount of the organic solvent added is more preferably 0.2 to 5% by weight based on the total weight of the ink. Further, from the viewpoint of ejection stability, 0.5 to 4% by weight is more preferable.

<Printing method>
Since the ink of the present invention is excellent in curability, it can be used in a single pass printing method.
The single pass printing method is, for example, an ink ejection mechanism having one or more inkjet heads, a mechanism for transporting a substrate on which ink has landed at a desired speed, and subsequently irradiating active energy rays such as a UV lamp and an electron beam. Have a continuous mechanism to cure the ink.

The resolution (nozzle density) of the single-pass printing type inkjet head is preferably 90,00 dots / inch ² (150 × 600 dpi) or more, more preferably 180,000 dots / inch ² (300 × 600 dpi) or more, 360,000 dots / Inch ² (600 × 600 dpi) or more is more preferable.

In the single pass printing method, the printing speed (substrate conveyance speed) is at least 35 m / min, more preferably at least 50 m / min, and even more preferably 75 m / min.
In the mechanism irradiated with the UV lamp, the time from the ink landing on the substrate to the irradiation with the UV lamp is preferably 20 to 5000 ms, and more preferably 40 to 1000 ms.

The optimum ink film thickness is preferably 2 μm or more and 30 μm or less, more preferably 4 μm or more and 25 μm or less, and still more preferably 6 μm or more and 20 μm or less. Within the above range, excellent color developability and curability are excellent.

<Curing method>
As a typical ink curing method, there are a pin cure type and a pin cureless type. In the pin cure type, generally, active energy rays are irradiated between the heads, and the ink ejected on the printing substrate is fixed each time it is ejected. On the other hand, in the pin cureless type, the ink ejected from a plurality of heads is simultaneously cured without fixing the ink each time it is ejected. The pin cure type requires, for example, at least four lamps in four-color printing. Accordingly, the cost of the apparatus is increased and the apparatus is increased in size, so that there are many cases where the use is limited and it is difficult to spread. However, according to the present invention, since the ink has excellent curability, it can be suitably applied to a pin cureless type printer. According to the present invention, it is possible to easily obtain a high-quality printed matter particularly in a pin cureless type printer.
In the case of the pin cure type, the time from the ink landing on the substrate to the irradiation with the UV lamp is preferably 20 to 500 ms, and more preferably 40 to 300 ms.

  The active energy ray for curing the ink may be an energy ray that affects the electron orbit of the irradiated object and can induce polymerization reaction of radicals, cations, anions and the like. Although it does not specifically limit, an electron beam, an ultraviolet-ray, and infrared rays are mentioned as a specific example. In the present invention, ultraviolet rays are preferably used.

  Specific examples that can be used as an ultraviolet light source include high pressure mercury lamps, metal halide lamps, low pressure mercury lamps, ultra high pressure mercury lamps, ultraviolet lasers, LEDs, and sunlight. From the viewpoint of convenience and price, it is preferable to use a high-pressure mercury lamp, a metal halide lamp, an LED, or the like. The emission maximum wavelength is preferably 200 to 600 nm, more preferably 300 to 450 nm, still more preferably 320 to 420 nm, and particularly preferably ultraviolet light in the range of 340 to 400 nm.

<Material printing base>
Examples of printing substrates to which the ink of the present invention can be applied include plastic substrates made of materials such as polycarbonate, hard vinyl chloride, soft vinyl chloride, polystyrene, polystyrene foam, acrylic (PMMA, etc.), polypropylene, polyethylene, and polyethylene terephthalate (PET). Paper substrates such as high-quality paper, art-coated paper, semi-gloss coated paper, cast-coated paper; glass substrates; metal substrates such as stainless steel and aluminum-deposited paper.
These printing substrates may have a smooth surface or an uneven shape. Various base materials may be transparent, translucent, or opaque. In addition, the printing substrate may be a laminate of two or more of the above-mentioned various substrates. Furthermore, the printing substrate may have a functional layer such as a peeling adhesive layer on the opposite side of the printing surface. In another embodiment of the printing substrate, a functional layer such as an adhesive layer may be provided on the printing surface after printing.

  In particular, the printing substrate used in the ink of the present invention is preferably a non-absorbing or hardly absorbing substrate such as polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), or coated paper.

  2-100 micrometers is preferable and, as for the thickness of a plastic base material, 6-50 micrometers is more preferable.

The surface of the plastic substrate or coated paper is preferably subjected to surface treatment such as corona discharge treatment or easy adhesion treatment.
For example, due to corona discharge treatment, molecular bonds on the substrate surface are broken, and polar functional groups such as hydroxyl, carbonyl, and carboxyl groups are introduced by reacting with oxygen radicals and ozone in the atmosphere generated by corona discharge. Is done. Good adhesion and gloss can be expressed by the interaction between the polar group and the resin having an acid value contained in the ink.

Corona treatment amount in the present invention is preferably carried out at 20W · min / m ² or more 1500W · min / m ² or so, more preferably 50W · min / m ² or more ^{1200W · min / m 2, 100W} · min / m ² or more and 1000 W · min / m ² are more preferable.
If it is said range, there is little damage to a base material, and the outstanding glossiness can be expressed by the favorable adhesiveness and the improvement of wetting spread of ink. Moreover, if it is said range, the effect outstanding with respect to hard-to-bond base materials, such as PE, PP, and coated paper especially will be expressed.

  According to the present invention, adhesion to various substrates can be improved by containing 2- (2-vinyloxyethoxy) ethyl acrylate and a resin having an acid value. In addition, since the ink is excellent in curability and ejection stability, it becomes easy to efficiently form high-quality images on various printing substrates.

  Hereinafter, the present invention will be described in more detail, but the following examples do not limit the scope of the right of the present invention. In addition, the description of “parts” in Examples represents “parts by weight”.

1. Preparation of ink (Examples 1 to 3, 5 to 13 and Comparative Examples 1 to 6) Preparation of black ink Black pigment 15 parts by weight, pigment dispersant 7.5 parts by weight, dipropylene glycol diacrylate 77.5 parts by weight Stir until uniform with a high speed mixer. Next, the obtained mill base was subjected to a dispersion treatment in a horizontal sand mill for about 1 hour to prepare a pigment dispersion A.
A mixed liquid of a polymerizable monomer, a photopolymerization initiator, and a polymerization inhibitor was slowly added to the previously prepared pigment dispersion so as to have the composition shown in Table 1, and the resulting mixed liquid was stirred. Next, after adding a surface tension adjusting agent to the mixed solution, the mixture was shaken with a shaker for 6 hours to prepare a black ink. The obtained black ink was filtered through a PTFE filter having a pore diameter of 0.5 microns to remove dust and coarse particles, and used as an evaluation ink. In addition, the addition and mixing of the raw material for obtaining the said liquid mixture may be random.

(Example 4) Preparation of white ink 50 parts by weight of a white pigment, 2.5 parts by weight of a pigment dispersant, and 47.5 parts by weight of dipropylene glycol diacrylate (DPGDA) were stirred with a high-speed mixer or the like until uniform. Next, the obtained mill base was subjected to a dispersion treatment in a horizontal sand mill for about 2 hours to prepare a pigment dispersion B.
A mixed liquid of a polymerizable monomer, a photopolymerization initiator, and a polymerization inhibitor was slowly added to the previously prepared pigment dispersion so as to have the composition shown in Table 1, and the resulting mixed liquid was stirred. Next, after adding a surface tension adjusting agent to the mixed solution, the mixture was shaken for 6 hours to produce a white ink. The obtained white ink was filtered through a membrane filter having a pore diameter of 1 micron to remove dust and coarse particles, and used as an evaluation ink. In addition, the addition and mixing of the raw material for obtaining the said liquid mixture may be random.

Details of the raw materials used in each experimental example are as follows.
<Pigment>
Black pigment: Carbon black (“Special Black 350” manufactured by Evonik Degussa)
・ White pigment: Titanium oxide (“Taipec CR-60 (aluminum-treated titanium oxide, primary particle size 210 nm)” manufactured by Ishihara Sangyo Co., Ltd.)
<Pigment dispersant>
-Basic pigment dispersion resin “Solsperse 32000 (acid value 24.8 mmgKOH / g, amine value 27.1 mmgKOH / g)” manufactured by Lubrizol
<monomer>
VEEA: 2- (2-vinyloxyethoxy) ethyl acrylate, “VEEA-AI” manufactured by Nippon Shokubai Co., Ltd.
-PEA: Phenoxyethyl acrylate, "SR339" manufactured by Sartomer
DPGDA: Dipropylene glycol diacrylate, manufactured by BASF “Laromer DPGDA”
<resin>
J-682: BASF styrene acrylic acid copolymer resin “Joncry 682”, acid value 238, Mw 1750
J-ECO 675: BASF styrene acrylic acid copolymer resin “Joncry ECO 675”, acid value 222, Mw 5800
J-ECO611: Styrene acrylic acid copolymer resin "Joncry ECO611" manufactured by BASF, acid value 53, Mw8150
J-815: BASF styrene acrylic acid copolymer resin “Joncry 815”, acid value 40, Mw 10000
SMA 2625P: manufactured by Cray Valley USA, styrene maleic acid copolymer resin “SMA 2625P”, acid value 50, Mw 5000
A-UC-3900: Toa Gosei Co., Ltd. acrylic resin “ARUFON UC-3900”, acid value 100, Mw4600
A-UH-2000: Toa Gosei Co., Ltd. acrylic resin “ARUFON UH-2000”, acid value 0, Mw 11000
<Stabilizer>
・ BHT: “H-BHT” manufactured by Honshu Chemical
・ Phenothiazine: Seiko Chemical Co., Ltd., “Phenothiazine”
<Surface conditioner>
BYK-UV3510: polyether modified polydimethylsiloxane <stabilizer> manufactured by BYK Chemie
・ Irgacure 819: Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide manufactured by BASF ・ DAROCUR TPO: manufactured by BASF 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide ・ Irgacure 369: BASF 2-Benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1
KAYACURE BMS: 4-Benzoyl-4'-methyl-diphenyl sulfide manufactured by Nippon Kayaku Co., Ltd.

2. Ink Evaluation Method Evaluation inks prepared in each of the examples and comparative examples are an ink jet ejection mechanism equipped with a Kyocera head (KJ4A), a mechanism for transporting the ink landed substrate at a desired speed, and a UV lamp. Using a single-pass inkjet printer (One Pass Jet, manufactured by Tritech Co., Ltd.), which has a mechanism that emits light at an ink droplet, printing is performed under printing conditions of an ink droplet amount of 14 pl and 600 × 600 dpi, and various characteristics are evaluated. did.
As a UV lamp, a UV lamp (240 W) manufactured by GEW was used, and a sample of a cured film was prepared under the condition of an integrated light quantity of 200 mJ / cm ² . The printing speed and printed image were changed in each performance evaluation.

(Adhesion)
Samples of cured films were prepared by printing 100% of the evaluation ink with an inkjet printer on various substrates. The conveyor speed was 35 m / min. The obtained cured film was cut into 6 pieces each in length and width at intervals of 2.5 mm. In addition, a cellophane adhesive tape is applied to the cured film, scraped with an eraser from the top, and the cellophane adhesive tape is sufficiently adhered to the coated surface, and then peeled off at 90 °. Judged from the degree of close contact with. The evaluation criteria are as follows. A value of ◯ or higher is considered to be good adhesion.
◎: Tape peeling area less than 5% ○: Tape peeling area from 5% to less than 25% △: Tape peeling area from 25% to less than 50% ×: Tape peeling area of 50% or more Also used for adhesion test The finished substrate is as follows.
-PP: PP TOP WHITE manufactured by UPM Raflatac
・ PE: PE GLOSS WHITE made by UPM Raflatac
・ Coated paper: Raflacoat manufactured by UPM Rafratac

(Curable)
On a PET base material (PET50 K2411 manufactured by Lintec Corporation), 100% solid printing was performed using the inkjet printer. The conveyor speed was changed from 20 to 75 m / min for printing. The degree of curability was judged from the printing speed at which a 100% solid print portion was cured at 1 Pass. The printed matter was palpated to determine that the ink was not on the hand. The evaluation criteria are as follows, and ◯ or higher is considered as good curability.
◎: Cured at 50 m / min or more ○: Cured at 35 m / min or more and less than 50 m / min Δ: Cured at 20 m / min or more and less than 35 m / min ×: Not cured at 20 m / min

(gross)
An evaluation ink was printed on a base material PET50 K2411 manufactured by Lintec Corporation with an inkjet printer to obtain a sample of a cured film. The conveyor speed was 35 m / min.
The 60 ° gloss on the printed surface was measured with a gloss meter (Micro-TRI-Gloss) manufactured by BYK Gardner. The evaluation criteria are as follows.
◎: 60 ° gloss is 70 or more ◯: 60 ° gloss is 60 or more and less than 70 Δ: 60 ° gloss is 50 or more and less than 60 ×: 60 ° gloss is less than 50

(Discharge stability)
The prepared ink-jet ink was printed with a nozzle check pattern with an ink-jet printer. After printing 100,000 shots, the nozzle check pattern was printed again, and the ejection performance was evaluated by the number of missing nozzles. The evaluation criteria are as follows. A value of ◯ or higher is regarded as good ejection stability. The conveyor speed was 35 m / min.
◎: No nozzle missing after 100,000 printing ○: Nozzle missing 1-2 after 100,000 printing △: Nozzle missing 3-5 after 100,000 printing ×: Nozzle missing 6 or more after 100,000 printing

(Storage stability)
After the prepared ink was placed in a screw tube bottle (capacity: about 7 mL) and sealed, the viscosity measured after standing for 7 days in an environment of 60 ° C. was compared with the initial viscosity immediately after preparation, so that Evaluation was performed. To measure the viscosity, a TVE25L viscometer manufactured by Toki Sangyo Co., Ltd. was used. In addition, the evaluation criteria at this time are as follows.
A: Increase in viscosity after aging test is less than 5% compared to initial viscosity B: Increase in viscosity after aging test is 5% or more and less than 10% compared to initial viscosity △: Increase in viscosity after aging test , 10% or more and less than 15% compared to the initial viscosity X: Increase in viscosity after the aging test is 15% or more compared to the initial viscosity

(Adhesion and gloss evaluation on corona-treated substrates)
In Examples 14 to 19 and Comparative Examples 7 to 10, the presence or absence of corona treatment in each substrate was compared. The corona treatment was carried out using a corona treatment machine (Multidyne 1 manufactured by Navidas, output 800 W, distance 5 mm from the electrode) and surface treatment of the substrate under the condition of a discharge amount of 200 W · min / m ² . The evaluation method for adhesion is evaluated in the same manner as in Examples 1 to 13 and Comparative Examples 1 to 6, and the gloss evaluation method is different from those in Examples 1 to 13 and Comparative Examples 1 to 6, Each material was evaluated. In Examples 14-16, the ink prepared in Example 3 was used, and in Examples 17-19, the ink prepared in Example 11 was used. In Comparative Examples 7 and 8, the ink prepared in Comparative Example 1 was used, and in Comparative Examples 9 and 10, the ink prepared in Comparative Example 5 was used. The evaluation results are shown in Table 2.

(Resolution and image quality evaluation)
In Examples 20 to 27 and Comparative Examples 11 to 18, the curability, bleeding, and OD value were evaluated at each resolution. The evaluation method of sclerosis | hardenability was implemented by the method similar to Examples 1-13 and Comparative Examples 1-6. As the ink, the inks prepared in Example 1, Example 12, Comparative Example 3, and Comparative Example 4 were used. The evaluation results are shown in Table 3.

(Smear)
A text image having a character size of 6 pt was printed on a PP substrate (PP TOP WHITE manufactured by UPM Raflatac) using the inkjet printer, and the obtained image was observed. Printing was performed under printing conditions of 600 × 600 dpi, and the conveyor speed was 35 m / min.
◎: Better ink with almost no ink bleed ○: Slight ink bleed △: Ink bleed ×: Large ink bleed

(OD value)
On a PP substrate (PP TOP WHITE manufactured by UPM Raflatac), 100% solid printing was performed using the inkjet printer, and the OD value was measured. Printing was performed under printing conditions of 600 × 600 dpi, and the conveyor speed was 35 m / min.
◎: OD value of printed material is 1.8 or more ◯: OD value is 1.5 or more and 1.8 or more △: OD value is 1.3 or more and 1.5 or less ×: OD value is less than 1.3

From Examples 1 to 19 in Tables 1 and 2, according to the embodiment of the present invention, it has very high curability and ejection stability, has good adhesion to various substrates, and is good It can be seen that an ink can be provided that forms an image having a gloss.
From the comparison between Examples and Comparative Examples 1 and 2, it can be seen that adhesion is greatly improved when a resin having an acid value is contained.
Similarly, it can be seen from the comparison between Examples and Comparative Examples 4 to 6 that the adhesion is greatly improved when 5- (2-vinyloxyethoxy) ethyl acrylate is contained in an amount of 5 to 50% by weight.
In addition, from comparison between Examples 1 to 4 and Comparative Example 3, when an acid resin is excessively present, not only ejection failure occurs, but also curing inhibition by the resin occurs, and adhesion due to decrease in curability. And loss of gloss occurs. The excess acid component reacts with the vinyl group of the polymerizable monomer contained in the ink, the ink is thickened and discharge failure occurs, and the storage stability of the ink also decreases.
From the comparison between Example 5 and Comparative Example 4, when 2- (2-vinyloxyethoxy) ethyl acrylate is excessively present in the ink composition, curability is remarkably lowered, and adhesion and gloss are lowered. This is probably because the reaction efficiency between vinyl ether groups of 2- (2-vinyloxyethoxy) ethyl acrylate is poor.

From the comparison of Examples 6 to 8, it can be seen that when the monofunctional monomer is contained, the monofunctional monomer has excellent curability and adhesion when it is 50% by weight or less in the ink.
From comparison between Example 9 and Example 10, it can be seen that the discharge stability is excellent when the weight average molecular weight of the resin having an acid value is 7000 or less.
A comparison between Example 10 and Example 11 shows that the adhesion is more excellent when the acid value of the resin is 50 mgKOH / g or more.
A comparison of Examples 1, 2, 13 and Example 12 shows that styrene acrylic acid resin and acrylic acid resin have good compatibility with the monomer, and further improve curability, adhesion, gloss, and dischargeability. .
In comparison between Examples 14-19 and Comparative Examples 7-10, the combination of 2- (2-vinyloxyethoxy) ethyl acrylate and the optimal amount of resin having an acid value is based on the substrate after corona treatment. It can be seen that not only the excellent adhesion is exhibited, but the gloss is greatly improved by improving the spread of the ink.

In the comparison between Examples 20 to 27 and Comparative Examples 11 to 18, the optimum combination of 2- (2-vinyloxyethoxy) ethyl acrylate and resin having an acid value is a printing speed of 35 m / min or more and printing. It can be seen that when printing by a single pass printing method with a resolution of 90000 dots / inch ² or more, more excellent curability and image forming ability are exhibited.

As described above, the active energy ray-curable inkjet ink of the present invention has excellent curability, high ejection stability, excellent adhesion to various substrates, and good gloss.

Claims (6)

At least 2- (2-vinyloxyethoxy) ethyl acrylate is contained in the ink in an amount of 5% by weight to 50% by weight and a resin having an acid value is contained in the ink of 0.1% by weight to 5% by weight. A characteristic active energy ray-curable inkjet ink.
2. The active energy ray-curable inkjet ink according to claim 1, wherein the acid value of the resin is 50 mgKOH / g or more.
3. The active energy ray-curable inkjet ink according to claim 1, wherein the ink does not contain a monofunctional monomer or contains 50% by weight or less in the ink when a monofunctional monomer is contained.
The active energy ray-curable inkjet ink according to any one of claims 1 to 3, wherein the resin having an acid value has a weight average molecular weight of 7,000 or less.
The active energy ray-curable inkjet ink according to any one of claims 1 to 4 is printed by a single pass printing method having a printing speed of 35 m / min or more and a printing resolution of 90000 dots / inch ² or more. Method.
The method for producing a printed material according to claim 5, wherein the printing substrate is a substrate having a corona-treated surface.